53.4“, Geological Survey Professional Paper SYNOPSIS 0F GEOLOGIC RESULTS Geological Survey fl: Q}; Research 1960 Synopsis of Geologic Results AA Z(y'EOLOGICAL SURVEY IROFESSIONAL PAPER 400—A ,04 \/: V4323 EARTH SCIENCES LiBRARy 4’44 ////?fl/«l/ W8 Geological Survey Research 1960 THOMAS B. NOLAN, Director GEOLOGICAL SURVEY PROFESSIONAL PAPER 400 14 Ayaopyz's of geologic rem/ts, accompanied éy s/zon‘ papers in t/ze geological scz'eacey. Pao/z's/zea' yeparate/y as c/zapters fl and-B 1 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960 n 621375 PL v. 4M EARTH ssztracas , LscaARY FOREWORD The activities of the United States Geological Survey encompass projects that span the full range of the geological sciences. The volume and complexity of such a research program make it difficult to review, coordinate, and release the results of the work as quickly as is de- sirable; as a result considerable time normally elapses between the completion of many in- vestigations and the publication of the final reports. And yet this same volume and com- plexity make it the more essential that some means be found to digest and make available to all the new ideas and new discoveries that have been achieved. In an effort to help solve this problem the present volume has been prepared; it sum- marizes the results of the recent work of the Geologic Division of the Survey. The report consists of two main parts: Chapter A, “Synopsis of Geologic Results,” is primarily a summary of important new findings, either as yet unpublished or published during the fiscal year 1960—the 12 months ending June 30, 1960. It also includes a list of investigations in progress during that period, along with the names and headquarters of those in charge of each, and a list of reports published or otherwise made available to the public during the same period. Chapter B, “Short Papers in the Geological Sciences,” consists of 232 papers, generally less than 1,000 words in length. These are of two kinds. Some papers are primarily announce- ments of new discoveries or observations on problems of limited scope, regarding which more detailed and comprehensive reports may or may not be published later. Others summarize the conclusions drawn from extensive investigations that have been in progress for some time; these conclusions in large part will be embodied in much longer reports that will be published later. This report is frankly an experiment. Although both chapters in this volume deal largely with the work of the Geologic Division, it is hoped to expand the scope of the report in future years to include results obtained by other Divisions of the Geological Survey, and to issue it annually. But whether this is done, and Whether future issues will be in the same form as this one, depends on how well this volume achieves the purposes described above. Comments and suggestions from those who use the volume will be appreciated and will help determine the content of the future ones. Cgvvm 4‘ M THOMAS B. NOLAN, Director. III .199 PREFACE The main activities of the Geologic Division of the Geological Survey may be grouped into three main categories, defined by the immediate objectives that motivate them: (a) economic geology; (c) regional geology; and (b) research on geological processes and principles. The work in the field of economic geology is aimed primarily at developing information that will be useful in the search for usable deposits of minerals and fuels, or help to solve problems connected with engineering works, such as the construction of high- ways and dams. It also provides the nation with an appraisal of its known and potential mineral resources. The regional studies determine the structure, composi- tion, history, and distribution of the rocks that under— lie the United States and other areas. Because this work is essentially exploratory in nature, its underly- ing purpose is also mainly economic, for it provides the basis for the broad appraisal of the potential min- eral resources of undeveloped areas. The research on geologic processes and principles consists of observa- tional, experimental, or theoretical investigations in the field and in the laboratory, aimed at improving our understanding of geologic processes and principles and hence developing and extending the usefulness of the geologic sciences. In addition, an important part of the Division’s work consists of services to other Fed— eral agencies that either do not have geologic staffs of their own or that require some of the special skills of the Division’s scientists. Nearly all of the Division’s activities yield new data and principles valuable in the development or appli— cation of the geologic sciences, and it is the purpose of chapter A to summarize the highlights of important findings that have come to the fore during fiscal year 1960. Some of these have been published or placed on open file during the year, some are published in chap- ter B of this volume, and some have not yet been pub- published elsewhere at all. Only a part of the results released during this period can be reported here, even in summary fashion, and the reader who needs more complete and detailed information will wish to con- sult the publications listed on pages A107—A127 and the papers in chapter B. A comprehensive list of investigations in progress is given on pages A76—A106, with the names and addresses of those in charge of them, in the hope that it may prove helpful to those interested in work in progress in various areas or topics. The results summarized here are presented in sev— eral categories based on the immediate objectives of the work or its applicability to some special field. Those results that have mainly to do with economic problems are described on pages Al-A26; results that. bear mainly on the geology of specific regions are given on pages A26—A54; and those that deal mainly with principles, processes, and methods of general in- terest are discussed on pages A54—A73. Although this classification of subject matter is a familiar one, it is nevertheless overlapping—an investigation stimu- lated by economic objectives may also yield important results in the fields of regional and theoretical geology, and so on. Limitations of both space and time pre- vent us from including an index to chapter A, but gen- eral cross-references are given at appropriate places in the text. We hope that these, together with the table of contents, will guide the reader to the topic in which he is most interested. The short papers of chapter B are arranged topically and in addition are accompanied by a short index. During fiscal year 1960, the Geologic Division’s serv- ices were utilized by and financially supported to some extent by the following organizations: Federal Agencies: Air Force—Cambridge Research Center Air Force—Technical Application Center Army—Corps of Engineers Army Engineer Research and Development Labo- ratory Army—Waterways Experiment Station Atomic Energy Commission—Division of Biology and Medicine Atomic Energy Commission—Division of Reactor Development Atomic Energy Commission—Military Applica- tion Division Atomic Energy Commission—Raw Materials Di- vision Atomic Energy Commission—Research Division- Atomic Energy Commission—Special Projects Di- vision VI PREFACE Bureau of Indian Affairs Bureau of Mines Bureau of Land Management Bureau of Public Roads Bureau of Reclamation Department of Agriculture International Cooperation Administration National Institutes of Health—Cancer Institute National Park Service National Science Foundation Navy—Bureau of Docks Navy—Office of Naval Research Ofiice of Minerals Exploration Ofl‘ice of Minerals Mobilization State Agencies: Arkansas Geological and Conservation Commis- Slon California Department of Natural Resources, Di- vision of Mines Colorado State Metal Mining Fund Board Connecticut Geological and Natural History Sur— vey Commission of Public Lands, Hawaii State Geological Survey of Kansas, University of Kansas Kentucky Geological Survey, University of Ken- tucky Massachusetts Department of Public Works Department of Conservation, Geological Survey Division, State of Michigan New Hampshire State Planning and Develop- ment Commission Nevada Bureau of Mines, University of Nevada North Carolina Department of Conservation and Development Bureau of Topographic and Geologic Survey, De- partment of Internal Affairs, Commonwealth of Pennsylvania State of Rhode Island and Providence Plantations Washington Department of Conservation, Divi- sion of Mines and Geology Wisconsin Geological and Natural History Sur— vey, University of Wisconsin Geological Survey of Wyoming Commonwealth : Puerto Rico Economic Development Administra- tion In addition to the agencies named above, the Geo— logic Division has cooperated from time to time with other organizations, and some of the results described in the following pages stem from work supported in previous years by agencies not listed above. All co- operating agencies are identified where appropriate in the individual papers of chapter B, and they are men- tioned in connection with some of the larger programs in chapter A. Space limitations make it impossible to identify their contributions in connection with many of the short statements in the following pages but it is a pleasure to acknowledge here the financial support and splendid technical cooperation we have received from all of them. Nearly everyone in- the Geologic Division contrib- uted directly or indirectly to this report, which was prepared between March and June 1960, but the chief responsibilities for it were held as follows: V. E. McKelvey planned and directed all phases of the prep- aration of the report, and assembled chapter A from information supplied by many project chiefs and pro- gram leaders. R. A. Weeks and R. L. Boardman com- piled the list of investigations in progress, and David Gallagher compiled the list of publications and the index to chapter B. Doris I. Kniffin managed the ‘ clerical aspects of the project. J. P. Albers and A. B. Griggs helped process the papers of chapter B, and F. C. Calkins critically reviewed nearly all of both chapters and vastly improved their style and expres- sion. I am deeply grateful to these people and to the members of the Division as a whole for their enthu- siastic support of this undertaking. WQQ~M CHARLES A. ANDERSON, Chief Geologist. Synopsis of Geologic Results Prepared by members of the Geologic Division under the direction of V. E. MCKELVEY GEOLOGICAL SURVEY RESEARCH 1960 GEOLOGICAL SURVEY PROFESSIOJNAL PAPER 400—A 14 summary of important results recent/y oétaz'nea', accompanied a} a list of reports released in fiscal 1960, and a list of z'flvestz'gatz'om in progress ‘ UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, US. Government Printing Office Washington 25, D.C. - Price $1 (paper cover) CONTENTS Mineral resource investigations ________________________ Heavy metals ___________________________________ District and regional studies __________________ Michigan iron districts ___________________ Sedimentary iron ore in the Christmas area, Arizona ______________________________ Manganiferous zone of the Butte district, Montana _____________________________ Manganese deposits near Philipsburg, Montana _____________________________ Michigan copper district _________________ Pima copper district, Arizona _____________ Upper Mississippi Valley zinc-lead district- - East Tintic silver-lead district, Utah _______ Coeur d’Alene lead-zinc-silver district, Idaho ________________________________ The Colorado mineral belt ________________ Base and precious metal deposits in north- central Nevada _______________________ Rhenium and molybdenum in the Runge mine, South Dakota ___________________ Other districts in Western United States- _ - - Metalliferous deposits in Alaska ___________ Commodity studies __________________________ Topical studies ______________________________ Light metals and industrial minerals ________________ District and regional studies __________________ Mount Wheeler beryllium deposit, Nevada- Beryllium in the Lake George district, Colorado ----------------------------- Beryllium in tin districts of the Seward Peninsula, Alaska --------------------- Beryllium and fluorspar in the Thomas Range, Utah _________________________ Black Hills pegmatites, South Dakota ______ Talc and asbestos deposits ________________ Phosphate deposits in Montana and Wyoming ____________________________ Phosphate in northern Florida and South Carolina _____________________________ High calcium limestone in southeastern Alaska _______________________________ Clay deposits in Maryland _______________ Clay deposits in Kentucky _______________ Green River saline deposits, Wyoming ----- Carlsbad potash district, New Mexico ------ Box-ate deposits of southwestern United States _______________________________ Commodity and topical studies _______________ Beryllium ______________________________ Selenium _______________________________ Marine phosphorites _____________________ Page A1 1 1 1 NNNNI—I H 0303 01010114383ka 03 0| ‘1 GGDO‘ OI wusiqq WWWWQ Mineral resource inyestigations—Continued Radioactive minerals ____________________________ District and regional studies _________________ Colorado Plateau _______________________ Gila County, Arizona ____________________ Crooks Gap area, Wyoming -------------- Baggs area, Wyoming ___________________ Gas Hills district, Wyoming ______________ Black Hills, South Dakota --------------- Palangana salt dome, Texas ______________ Uran‘iferous phosphorite in Eocene rocks, Wyoming ____________________________ Uraniferous lignite in the Williston basin, Montana and North Dakota ___________ Chattanooga shale, Tennessee and Alabama- Commodity and topical studies _______________ Distribution of epigenetic uranium de- posits in the United States _____________ Urailium in sandstone-type deposits _______ Uranium in petroleum ___________________ Ura‘nium in coal ________________________ Uraniferous black shale and phosphorite__ - Thorium in monazite ____________________ Fuels ------ l ___________________________________ Petroleum and natural gas ___________________ McAlester basin, Oklahoma -------------- Wilson County, Kansas __________________ Hdrseshoe atoll, Midland basin, Texas _____ Williston basin, Montana, North Dakota, and South Dakota ____________________ Utah and southwestern Wyoming _________ Al‘aska ________________________________ Origin of helium and nitrogen in natural gas- Coal _ _\ ____________________________________ Geology of specific coal fields _____________ Nsational coal resources __________________ Distribution of minor elements in coal _____ Oil shale ___________________________________ Development qi exploration and mapping techniques__ __ Geochemical and botanical exploration ____________ New analytical techniques ___________________ Prospecting techniques ______________________ Application of isotope geology to exploration _______ Isotope geology of lead ______________________ Oxygen isotopes in ore and gangue minerals_-_- Geophysical exploration ------------------------- Aeroinagnetic methods ---------------------- Aerial radioactivity surveys ------------------ Electrical methods __________________________ Grav‘ity methods --------------------------- Geologic mapping _______________________________ Photogeology _______________________________ Scribing techniques _________________________ 1 IX 10 10 10 11 11 11 11 11 12 12 12 12 12 12 12 12 13 13 l3 13 13 l4 14 14 14 14 14 15 15 15 16 16 l7 l7 17 18 18 18 18 Geology applied to problems in the fields of engineering and public health _________________________________ Construction problems ___________________________ Damsite location and sewage system construc- tion _____________________________________ Highway and bridge construction _____________ Emergency aircraft landing sites ______________ Problems related to permafrost or frost heaving- Problems related to erosion __________________ Engineering problems related to rock failure ________ Coal “bumps” ______________________________ Deformation of rock by nuclear explosions _____ Earthquakes and earthquake-triggered land- slides ____________________________________ Other landslides and mudflows ________________ Selection of sites for nuclear tests and evaluation of effects of underground nuclear explosions ________ Project Chariot _____________________________ Project Gnome _____________________________ Nevada Test Site ___________________________ Radioactive waste disposal investigations __________ Geochemical studies _________________________ Sedimentary basin studies ___________________ Geophysical studies _________________________ Measurement of background radiation _____________ Distribution of elements as related to health ________ Regional geology ___________________ . _________________ Synthesis of geologic data on maps of large regions__ Tectonic map of the United States ____________ Paleotectonic maps of the Triassic and Permian systems __________________________________ Epigenetic uranium deposits in the United States- New England and eastern New York _____________ Regional geologic mapping ___________________ Stratigraphic and lithofacies studies in Vermont and Maine _______________________________ Tectonic studies in Connecticut and Vermont--- Geophysical surveys _______________________ Ages of intrusions in the northern Appalachians- The Appalachians Stratigraphic and geomorphic studies in the Valley and Ridge province _________________ Structural studies in eastern Pennsylvania and New Jersey _______________________________ Geologic results of aeromagnetic surveys ______ Geologic mapping in North and South Carolina- Atlantic Coastal Plain __________________________ Interpretation of aeromagnetic measurements on the Atlantic Continental shelf and in Florida- Aerial radiological surveys ___________________ Paleontologic and stratigraphic studies _________ Eastern plateaus ________________________________ Interpretation of geophysical surveys __________ Geologic mapping in western Kentucky ________ Stratigraphy of Upper Devonian rocks in western New York ________________________________ Quaternary geology in Pennsylvania and the Ohio Valley ______________________________ Shield area and upper Mississippi Valley ___________ Remanent magnetization in the Lake Superior region ___________________________________ Interpretation of geophysical data in central Wisconsin ________________________________ CONTENTS Page A18 19 19 19 19 20 20 20 21 21 21 22 22 22 22 23 24 24 25 25 25 25 26 26 27 27 28 28 28 28 29 29 29 29 29 30 30 30 31 31 31 31 32 32 32 32 32 33 33 33 Regional geology—Continued Shield area and upper Mississippi Valley—Continued Geologic studies in northern Michigan and Wisconsin ________________________________ Age of some Pleistocene sediments ____________ Gulf Coastal Plain and Mississippi embayment _____ Mesozoic stratigraphy of the eastern Gulf Coastal Plain _____________________________ Lithofacies and origin of Tertiary sediments in the Coastal Plain of southern Texas ________ Buried igneous masses in Missouri and Arkansas- Ozark region and Eastern Plains _________________ Geology of northwestern Arkansas ___________ Aeromagnetic studies in southeastern Missouri-- Permian stratigraphy in southeastern New Mexico __________________________________ Northern Rockies and plains _____________________ Geology of parts of northeastern Washington and northern Idaho ----------------------- Stratigraphy of the Belt series in western Montana and adjacent areas _______________ Geology of areas in the vicinity of the Idaho batholith _________________________________ Geology of parts of western Montana ---------- Coral zones in Mississippian rocks _____________ Geology of parts of western Wyoming, south- eastern Idaho, and northeastern Utah _______ Geology of the Wind River basin, Wyoming---_ Geologic and geophysical studies in parts of the Black Hills, South Dakota ----------------- Devonian rocks in eastern Montana and western North Dakota ____________________ Lithofacies and thickness of the Pierre shale in South Dakota ____________________________ Geology of the Bearpaw Mountains, Montana-_ Glaciation in the vicinity of Glacier National Park, Montana --------------------------- Southern Rockies and plains --------------------- Precambrian rocks and structures in the Front Range and Sawatch Range, Colorado ______ Geology of volcanic terranes in Colorado and New Mexico _____________________________ Geology of North Park, Colorado _____________ Age of deformation in the Raton basin, Colorado- Colorado Plateau _______________________________ History of salt anticlines in the Paradox basin_ - Structure in the vicinity of the Carrizo Moun- tains ____________________________________ Stratigraphic and paleontologic studies of Meso- zoic rocks ________________________________ Basin and Range province _______________________ Thrust faults in Nevada _____________________ Cenozoic rocks and structures in the western Mojave Desert, California _________________ Geology of the Sierra Diablo, Texas ----------- New information on the age of strata ---------- Crustal structure and block faulting ----------- Quaternary history __________________________ Columbia Plateau and Snake River Plains --------- Geology of parts of John Day area, Oregon____ Petrology and remanent magnetism of Snake River lavas ______________________________ Page A33 34 34 34 34 34 34 35 35 35 35 35 36 36 36 37 37 37 37 37 38 38 38 38 38 38 39 39 39 39 39 39 4O 40 40 40 40 41 41 41 41 42 CONTENTS Regional geology—Continued Columbia Plateau and Snake River Plains—Continued Structure and history of the western Snake River plain ______________________________ Aeroradioactivity in the vicinity of the National Reactor Test Station area, Idaho __________ Cenozoic volcanic rocks and structure in north- central Nevada ___________________________ Pacific Coast region _____________________________ Geology of the Sierra Nevada batholith ________ Structure and Jurassic fauna of the western foothills metamorphic belt of the Sierra Nevada __________________________________ Igneous rocks of the Cascade Range __________ Stratigraphy and structure of the Klamath Mountains and Coast Ranges, northern California ________________________________ Geology of major sedimentary basins __________ Alaska ________________________________________ Geology of the southern part of the Brooks Range ___________________________________ Cretaceous rocks of the Koyukuk basin ______ Geology of the Tofty-Eureka district __________ Stratigraphy of the Matanuska formation ______ Geology of the eastern part of the Chugach Mountains _______________________________ Geology of Admiralty Island _________________ Reconnaissance aeromagnetic surveys of sedi— mentary basins ___________________________ Tectonic provinces of Alaska _________________ Glacial history and distribution of surficial de- posits in Alaska __________________________ Hawaii ________________________________________ Alumina-rich soil and clay __________________ Ultramafic differentiates in the Kaupulehu flow- Recent volcanic activity at Kilauea-Iki and Kapoho _________________________________ Puerto Rico and the Canal Zone __________________ , Western Pacific Islands __________________________ Geologic contrasts between the island arcs and islands of the western Pacific basin ________ Regional stratigraphic and paleontologic studies- Origin of tropical soils and bauxite on the higher islands __________________________________ Antarctica _____________________________________ Extraterrestrial studies __________________________ Geologic investigations in foreign nations ______________ Chromite deposits in the Philippines ______________ Coal in Pakistan ________________________________ Iron deposits in Brazil ___________________________ Mineral and fossil fuel potential of Southern Peru" Metalliferous deposits in Chile_____‘ _______________ Investigations of geologic processes and principles____ _ _ _ Paleontology ___________________________________ Geomorphology and plant ecology ________________ Development of karst features ________________ Dynamic equilibrium in the development of landscape ________________________________ Formation of beaches and bars _______________ Plant ecology ______________________________ World vegetation classification ________________ Page A42 42 42 42 42 43 43 43 43 44 44 44 44 44 44 46 46 46 46 47 47 47 47 47 48 48 48 Investigations of geologic processes and principles—Con. Geophysics _____________________________________ Physical properties of rocks __________________ Mechanical properties ___________________ Electrical properties _____________________ Magnetic properties _____________________ Mass properties ________________________ Phosphorescence and thermoluminescence__ Thermal properties ______________________ Thermodynamic properties _______________ Permafrost studies _________________________ Areal diflerences in character of permafrost- Interpretation of temperature data ________ Rock deformation ___________________________ Contraction cracks ______________________ Tectonic fracturing and faulting __________ Rock fragmentation and mixing due to volcanism and to strong shock __________ Paleomagnetism ____________________________ Studies of the thickness and composition of the crust ____________________________________ Mineralogy, geochemistry, and petrology __________ Mineralogy and crystal chemistry _____________ Description of new minerals ______________ Synthesis of minerals ____________________ Crystal chemistry _______________________ Experimental geochemistry ___________________ Silicate systems _________________________ Reactions of minerals in hydrothermal solutions _____________________________ Dry sulfide systems _____________________ Geochemical distribution of the elements ______ Revision of Clarke’s “ Data of Geochem- istry” _______________________________ Chemical composition of sedimentary rocks ________________________________ Distribution of minor elements ___________ Organic geochemistry _______________________ Structure and geochemical relations of carbonaceous substances _______________ Biogeochemical processes in isotope frac- tionation ____________________________ Petrology __________________________________ Origin of granitic rocks __________________ Origin of ultramafic rocks and related gab— bros _________________________________ Origin of welded tufls ___________________ Fluidity of lava _________________________ Source of some volcanic magmas __________ Role of fluids in low temperature alteration of volcanic glass ______________________ Origin of propylitic alteration ____________ Metamorphism of manganese minerals _____ Steatization as a product of regional meta- morphism ____________________________ Origin of jadeite and rodingite in serpentine _ Migration of elements during metamor- phism _______________________________ Origin of evaporite deposits ______________ . Transformation of aragonite mud to apha— nitic limestone ________________________ Origin of chert _________________________ XI Page A55 56 56 56 56 56 56 57 57 57 57 57 57 58 58 58 58 59 59 59 60 60 60 61 61 61 61 62 62 62 64 65 65 65 65 65 66 66 66 66 66 67 67 67 67 67 67 68 68 XII Investigations of geologic processes and principles—Con. Isotope and nuclear studies ______________________ Deuterium and tritium in natural fluids _______ Differences in the isotopic composition of meteoric, connate, and thermal waters-_ Deuterium content of ocean and terrestrial waters _______________________________ Tritium and deuterium content of atmos- pheric hydrogen ______________________ Deuterium in liquid inclusions ____________ Measurement of alpha activity _______________ Geochronology _____________________________ Refinement of the geologic time scale ______ Age of some uranium ores ________________ A geochronologic method based on mag- netic properties of crystals damaged by radiation ____________________________ A geochemical method for dating obsidian artifacts _____________________________ Carbon—14 dates applied to the study of Pleistocene glaciation ___________________ Analytical and other laboratory techniques _____________ Analytical chemistry ____________________________ Zirconium in small amounts __________________ Niobium and tantalum ______________________ Flame photometry __________________________ Analysis of liquid inclusions __________________ Fluorine in phosphate rock and chlorine in silicate rock _____________________________________ Small amounts of magnesium _________________ Uranium ___________________________________ Analysis of chromite ________________________ Ferrous iron ________ , _______________________ Zinc in silicate rocks ________________________ CONTENTS Page A68 68 68 68 68 69 69 69 69 70 70 70 70 70 70 70 70 71 71 71 71 71 71 71 71 Analytical and other laboratory techniques—Continued Analytical chemistry—Continued Combined gravimetric and spectrographic anal- ysis of silicates ___________________________ Accuracy and precision of silicate analyses _____ Spectroscopy ___________________________________ Concentration of rhenium for analysis _________ Determination of lead in zircon _______________ Use of special standards in spectrochemical analysis _________________________________ Use of gas jet in reducing cyanogen band inter- ference __________________________________ A constant feed direct-current arc ____________ Development and use of the electron micro— probe analyzer ___________________________ X-ray fluorescence analysis of sphalerite _______ Mineralogic and petrographic techniques ___________ New techniques and tools in microscopy _______ Mineral separation methods __________________ Staining and autoradiographic methods ________ Methods for studying liquid inclusions ________ Methods in experimental geochemistry ________ Geologic Division offices _____________________________ Main centers ___________________________________ Field offices in the United States and Puerto Rico__ Offices in foreign countries _______________________ Investigations in progress in the Geologic Division during fiscal year 1960 ___________________________________ - Regional investigations __________________________ Topical investigations ___________________________ Geologic Division publications in fiscal year 1960 _______ List of publications _____________________________ Subject classification of publications _______________ ILLUSTRATIONS Page FIGURE 1. Index map of the United States, exclusive of Alaska and Hawaii ______________________ A27 2. Map of Alaska showing the location of areas where available geologic maps meet recon- naissance standards _____________________ 45 3. Index map of Western Pacific Islands _______ 49 4. Index map of Antarctica ____________________ 51 Page A71 72 72 72 72 72 72 72 72 73 73 73 73 73 73 74 74 74 75 77 77 94 107 107 127 GEOLOGICAL SURVEY RESEARCH I960 SYNOPSIS OF GEOLOGIC RESULTS MINERAL RESOURCE INVESTIGATIONS Most of the investigations of mineral resources (in- cluding fuels) made by the Geological Survey can be grouped into (a) district and regional studies and (b) commodity and topical studies. The district and regional studies are focused on areas known or thought to contain mineral resources; their purpose is to establish guides useful in the search for concealed deposits, define areas favorable for exploration, and appraise known and potential resources. Most stud- ies of this kind involve geologic mapping and many of them ultimately help to develop general principles of wide application. The commodity and topical stud- ies deal with the appraisal of national resources of various minerals, synthesis of empirical data on ore habits that help to define environments favorable for the occurrence of useful minerals, and experimental and theoretical studies of the origin and distribution of such minerals. The long—range aims of both groups of studies are to obtain data on field relations and on theoretical principles that will provide a foundation from which private industry can extend its search for usable raw materials and that will provide the nation as a whole with a continuing appraisal of its mineral wealth. Important new findings in the fields of heavy metals, light metals and industrial minerals, radioactive min- erals, and fuels are summarized in the following pages. HEAVY METALS DISTRICT AND REGIONAL STUDIES Michigan iron districts Geologic mapping and magnetic surveying of the Michigan iron districts, in cooperation with the Mich- igan Geological Survey Division, have established in considerable detail the distribution of iron-formations of several areas, notably the Iron River—Crystal Falls district (James and others, 1960) and the adjoining Lake Mary quadrangle (Bayley, 1959a) ; in the latter area, the work contributed to the discovery of a Pre- cambrian iron-formation, about 200 feet thick, in sees. 24 and 25, T. 43 N., R. 31 W., Iron County, and sec. 30, T. 43 N., R. 30 W, Dickinson- County. The for- mation is concealed by Pleistocene deposits and has now been explored by drilling. Sedimentary iron ore in the Christmas area, Arizona A deposit of sedimentary iron ore has been discov- ered in the Christmas quadrangle, Arizona by Will— den (Art. 111). It is in a bed 5 to 7 feet thick near the top of the Martin formation, of Devonian age. As it contains only about 37 percent iron, it probably is not minable now, but the occurrence suggests that other sedimentary iron deposits may be found in rocks of this age in Arizona. Manganiferous zone of the Butte district, Montana As a part of a regional study of the Boulder batho- lith, Montana, Smedes (Art. 12) has found that more than 6,000 feet of volcanic rocks lie uncomformably on the batholith and older rocks. Block faulting oc- curred repeatedly, at one time producing a graben west of Butte. Gravity surveys by W. T. Kinoshita indicate that the floor of this graben lies at a depth of about 1,000 feet beneath welded tuff, and Smedes believes that quartz monzonite beneath the floor may contain unexplored, truncated segments of metallif— erous quartz veins of the manganiferous zone of the Butte district. Manganese deposits near Philipsburg, Montana Deposits of oxidized rhodochrosite near Philipsburg have been the only consistent source of battery-grade manganese ore in the United States. Detailed study by W. J. Prinz has shown that the primary rhodo- chrosite replacement deposits contain abundant zinc in the southern part of the district, but none in the north- ern part. They consist of both bedding replacements at bed-vein intersections, and of near-vertical pipes that swell in favorable host beds. The depth of oxi- dation of the primary deposits is shallow where the host rock consists of impure limestone, and deep where the host rock is marble. 1Article 11 in Professional Paper 400—B. Similar references to pa- pers in chapter B are given in the same style. A1 ‘A2 Michigan copper district The Michigan copper district has been studied by many geologists for more than a century, and its ma- jor geologic features are well known, but recent in- tensified study of certain aspects of its geologic set- ting has yielded results useful in looking for new deposits. R. E. Stoiber and E. S. Davidson (1959), for example, have shown that the major copper de- posits occur in a relatively restricted zone that is roughly defined by the regional distribution of the minerals contained in the amygdules of basalts. White (1960a) has discussed evidence that copper at the base of the Nonesuch shale (White Pine mine) extends over a wide area and that it was deposited mostly if not entirely before the shale was deformed. The search for new deposits, therefore, need not be con— fined to areas near major faults, as might have been inferred from prior studies, and it has in fact been profitably extended, during the last few years, into areas that were formerly overlooked or considered un- favorable. Pima copper district, Arizona In the Twin Buttes quadrangle, Arizona, clues to the location of concealed copper ore bodies have been found by Cooper (1960) in a study of the geologic setting of the Pima mining district. Two orogenic episodes followed the deposition of the Cretaceous rocks that underlie part of the district, one earlier than the ore and the other later. The earlier episode resulted in complex folds and faults that trend north- west; the other resulted in the rotation of a large ill- defined structural block around an axis trending north- east, and also involved thrust faulting on a large scale. From the geologic relations indicated by the field data, Cooper estimates that the thrust plate moved about 61/2 miles to the north-northwest. If this esti- mate is correct, the roots of several major ore bodies are in part of the district that has not yet been ex- plored. Upper Mississippi Valley zinc-lead district Long range geologic studies of the upper Missis- sippi Valley lead-zinc district, in part in cooperation with the Wisconsin Geological and Natural History Survey and the Iowa Geological Survey, have re— cently culminated in a report by Heyl and others (1960) that describes structural and stratigraphic con— trols useful in prospecting. The principal structural features in this district are three first-order anticlines that trend westerly; their north limbs dip more steeply than their south limbs and reverse faults occur 10— cally along the north limbs. The associated folds decrease in abundance and magnitude northward. GEOLOGICAL SURVEY RESEARCH lQBO—SYNOPSIS 0F GEOLOGIC RESULTS Minor reverse and bedding-plane faults associated with second- and third-order folds, whose trends form a rhombic pattern, control the location of most zinc ore bodies. The lead ore deposits, many of which were formerly important, are controlled either by a group of joints resulting from tension, or a pair re- sulting from shear. Studies made by J. W. Alling- ham, J. E. Carlson, Harry Klemic, T. E. Mullens, and J. W. Whitlow after completion of Professional Paper 309 indicate that many of the second— and third— order folds and associated faults are probably the result, rather than the cause, of the emplacement of the ore bodies; i.e. they formed by compaction and subsidence in areas where mineralizing fluids dis- solved limestone. This interpretation does not invali- date the prospecting techniques outlined in the pro- fessional paper, but it sets rough limits to the areas in which ores of lead and zinc are likely to be found. East Tintic silver-lead district, Utah On the basis of published results of a long-range study by Lovering, Morris, and others in the East Tintic district, Utah, the Bear Creek Mining Com- pany has recently made important new discoveries of ore. Large, high-grade silver-lead replacement ore bodies there are found in places where steep north- northeasterly fissures cut west—dipping thrust faults that involve sedimentary. rocks of early Paleozoic age. The sedimentary rocks are largely overlain by lavas, which were altered by hydrothermal solutions but which do not contain ore bodies. In an effort to aid in the search for concealed ore bodies of the East Tintic type, Lovering and his co-workers (1960) made detailed studies to establish the relations be- tween the hydrothermally altered zones in the lavas and known ore bodies in the underlying sedimentary rocks. During the course of this study they also found primary geochemical anomalies in the altered rocks up-rake from ore-localizing structures. In or- der to test the validity of the techniques developed, a hole was drilled in an area that showed the same type of late stage alteration as that over the known Tintic Standard ore body and that also contained an encouraging geochemical anomaly. This hole pene- trated low-grade ore; and, what was even more im- portant, it cut rocks much younger than were ex- pected at this depth. An analysis of the general geologic structure of the East Tintic Mountains, and of the detailed structure of the East Tintic district, led to the conclusion that a concealed west-dipping thrust fault lay between the drill hole and old mine workings about 1,400 feet to the west. The occur- rence even of low-grade ore near a large unprospected fault, in an area that showed favorable late-stage HEAVY altered zones and a geochemical anomaly at the sur— face, strongly indicated the presence nearby of a con- cealed ore center.» The Bear Creek Mining Company therefore sunk the Burgin exploration shaft and drove west on the 1050 level. They found the thrust fault. near its expected position, and by further exploration found three ore zones, one of which may be compara- ble in size and grade to the largest previously known ore deposit in the district. This discovery has opened entirely new ground to exploration, and has aroused interest in the techniques developed, which should be applicable elsewhere. Coeur d’Alene lead-zinc-silver district, Idaho In the Coeur d’Alene district S. W. Hobbs, A. B. Griggs, R. E. Wallace, and A. B. Campbell have amassed evidence that confirms major post-ore strike slip on the Osburn fault, which extends across the district (see Wallace and others, Art. 13), and the alinement of the major ore bodies along a series of well-defined zones or belts. With these interpretations as guides, it should be possible to concentrate future exploratiOn on the most promising areas. From stud- ies of the mineralogy of the Coeur d’Alene district V. C. Fryklund (Art. 15) has concluded that three different sources may have contributed to the main period of mineralization. R. G. Coleman, R. G. Arnold, and V. C. Fryklund, in a study of ores from the Highland Surprise mine in the Coeur d’Alene district, have shown that the estimated temperature of formation ranged from 3700 to 492° C for pyrrho- tite in 62 samples, and from 375° and 490° for spha- lerite coexisting with pyrrhotite in 14 samples. There appears to be no systematic relation between depth and temperature, although the samples represent a vertical range of 1,600 feet. The Colorado mineral belt Nearly all of the major mining districts of Colo- rado are in the narrow so-called “Colorado mineral belt,” which extends southwestward from central Col- orado to the San Juan Mountains. This belt is char- acterized by intrusive porphyries and associated ore deposits of Laramide age. Tweto and Sims (Art. 4) have found evidence that it extends along an ancient zone of weakness defined by northeast—trending shear zones of Precambrian age. Intermittent movement took place in this zone from early in the Precambrian to the Tertiary, and during Laramide time magmatic activity occurred throughout its length. Tweto (Art. 5) has also found that most of the faults that appear to displace ore bodies in the Leadville district were actually in existence when porphyries of several varie- ties were emplaced. As the porphyries are pre-ore, the METALS A3 faults are also pre-ore, although post-ore movement has occurred on many of them. Base and precious metal deposits in north-central Nevada An analysis of the regional structure and distri- bution of ores in north-central Nevada by Roberts (Art. 9) indicates that many of the mining districts occur within northwest-trending zones of structural weakness. Doming along these zones has formed belts of windows in- the upper plate of the Roberts Moun- tain thrust, which expose favorable carbonate host rocks in the lower plate. Carbonate rocks in the lower part of the sequence—for example, the Eldorado and Hamburg dolomites—may contain lead-zinc—silver de- posits in favorable structural settings, such as fault intersections. The more siliceous rocks in the upper plate close to the thrust may contain minable bodies of gold ore and barite, especially near intrusives. Rhenium and molybdenum in the Runge mine, South Dakota In the Runge mine, South Dakota, water-soluble rhenium and molybdenum have been found during routine spectrographic analysis in a sandstone-type uranium-vanadium deposit (Myers and others, Art. 20). Six of the 27 samples analyzed contained 30 to 700 ppm rhenium and 24 contained 3 to 3,000 ppm molybdenum. Much of the rhenium is water soluble, and its concentration in residues obtained by leaching samples with distilled water and then evaporating is 10 to 25 times greater than the concentration in the samples themselves. The water—soluble rhenium and molybdenum are most abundant in the oxidized and partly oxidized ore that contains paramontroseite, nearly amorphous uraninite, haggite, and minor car- notite. This ore is found only in the upper part of the deposit and along fractures that cut sandstone containing uraninite, coffinite, and montroseite, and it probably makes up less than 10 percent, by volume, of the deposit. Other districts in Western United States During regional studies of the Idaho batholith, B. F. Leonard has found that wide parts of the Johnson Creek-Quartz Creek silicified zone are favorable sites for tungsten and gold mineralization. In the northern Cascades of Washington, F. W. Cater has observed that the important ore deposits are restricted to northwest-trending shears in the Cloudy Pass batholith, to breccias related to it, and to replacement zones in the gneisses peripheral to it. The area may contain undiscovered ore deposits in similar relations to other batholiths. In the Loon Lake area of northern Washington A. B. Campbell has found that many of the lead—zinc, copper, talc, and barite A4 deposits are related spatially to a northeasterly trend- ing zone of faults and dikes. Mineralogic studies of samples from a prospect in the Lone Mountain area, near Tonapah, Nevada, Show that it contains manganoan hedenbergite, andradite, zincian nontronite, sphalerite, galena, magnetite and calcite (Gulbrandsen and Gielow, Art. 10)——a min- eral assemblage characteristic of a number of pyro- metasomatic deposits being mined elsewhere. The deposit from which these samples came apparently does not contain amounts of ore large enough to be minable, but the mineral assemblage suggests that minable deposits of this type may be feund at Lone Mountain. In the Rosita district of the West Mountains, Colo- rado, Q. D. Singewald and M. R. Brock have found that the location of major deposits of base and pre- cious metals in the Tertiary volcanic rocks is controlled by northwest-trending faults in the underlying Pre— cambrian crystalline rocks. Metalliferous deposits in Alaska Near Nome, Alaska, Hummel (Art. 17) has iden- tified two structural systems in the bedrock. Lode and placer deposits of the Nome goldfields are closely associated with some of the folds and faults of the younger system. Concentrations of Cu, Zn, Bi, and M0 in the sediments of Thompson Creek in the Kig- luaik Mountains are evidence that metalliferous lodes exist in a part of the area not formerly known to con- tain them (Hummel and Chapman, Art. 16). Sainsbury and MacKevett (Art. 18) have studied quicksilver deposits in the southwestern part of Alaska and find that their localization is structurally con- trolled. The quicksilver is associated with antimony in these deposits, and is probably of Tertiary age. The mercury was deposited mainly as cinnabar in open fractures in competent rocks, but each deposit has important individual structural controls that af- fected ore deposition and may guide further explo- ration. COMMODITY STUDIES In the field of commodity studies, maps showing the distribution of known deposits of useful minerals in the United States have been prepared during the past year to record and analyze the distribution of mineral deposits. This is a first step toward the prep— aration of metallogen-ic maps that will relate the dis- tribution of mineral deposits to tectonic and petrologic provinces and to tectonic history. Also in the field of commodity studies, Heyl and Bozion (Art. 2) have investigated the distribution of oxidized zinc deposits in the United States. They find that most of them have directly replaced sulfide de- GEOLOGICAL SURVEY RESEARCH limo—SYNOPSIS 0F GEOLOGIC RESULTS posits, and that they showed a markedly varied pat- tern, dependent on (a) pH, rainfall, and climatic fac- tors; and (b) wall rocks and geologic variations be- tween metallogenic provinces. For many elements in the United States, the ton- nage of minable reserves in short tons has been found to be equal to crustal abundance of the element in percent (A) times 109 to 101° (McKelvey, 1960). This relation is useful in forecasting reserves in large seg- ments of the earth’s crust. For estimating world re- serves of many not yet actively sought elements, a fig- ure of A x 1010 to 1011 will probably give the right order of magnitude. TOPICAL STUDIES A broad-scale attack on the origin and physico- chemical characteristics of ore-depositing solutions in the Creede district, Colorado, is getting well under way. The geologic setting of the OH vein, a base- metal deposit selected for this study, has been studied in detail by Steven and Ratté (Art. 8), who have shown that the vein was deposited in a shallow vol- canic environment adjacent to a large volcanic caldera. The ores are localized along faults in a complex graben that extends outward from the caldera; movement on these faults occurred many times while the caldera was subsiding, but mineralization did not take place until the last main period of fault movement. Several new tools and techniques have been developed by Edwin Roedder for study of fluid inclusions in the OH vein (see p. A73), and they have already yielded some pre- liminary results. For example, the absence'of opaque specks within fluid inclusions seems to indicate that the ore was deposited from a solution that contained only small amounts of the ore metals, perhaps as lit- tle as 10 ppm (Roedder, 1959). Preliminary data obtained by E. Roedder, B. Ingram, and M. Toulmin from strongly zoned sphalerite crystals at Creede sug- gest that they were deposited from a rather concen- trated brine, high in Na and Cl and lower in K, Ca, Mg, B, and SO.” diluted at times to various degrees by ground water or water from other sources. The D/H isotope ratios in the inclusions determined by Wayne Hall and Irving Friedman are lower than those in sea water but higher than those in meteoric waters in similar environments. Mackin and Ingerson (Art. 1) have proposed a “deuteric release” hypothesis for the origin of mag— matic ore—forming fluids. The classical view is that metals not accepted in rock-forming minerals become concentrated in late—stage fluids, which may escape from the magma and deposit ores. According to the “deuteric release” theory, iron and other metals are incorporated in early-formed biotite and hornblende LIGHT METALS AND INDUSTRIAL MINERALS that crystallize at depth; if the magma was intruded only to a shallow depth, deuteric alteration could re- lease the metals to the escaping interstitial fluid. Chemical criteria for recognition of possible ore- depositing mineral waters of different types have been developed by White (Art. 206) through the study of existing waters. D. F. Hewett and Michael Fleischer (1960) have studied the mineralogy of more than 250 specimens of manganese oxide minerals collected throughout the United States and interpreted their origin. Of the 27 manganese oxide minerals identified, one group of 10 is persistently supergene; another group of 9 is persistently hypogene and a third group of 8 includes those that are supergene in some places and hypogene in others. Hewett has also found that minor amounts of several metals, alkalies, and alkaline earths are pres- ent in the oxides of one mode of origin and absent in others. Tungsten nearly always occurs in hydrother- mal vein oxides and in those deposited in the aprons of hot springs, but it is sporadic and very low or absent in the supergene oxides. Most of the minor elements in the supergene oxides are those known to exist in the unweathered minerals from which the ox- ides were derived. Fleischer (1959, 1960a) has reviewed the geochem— istry of rhenium, with special reference to its occur- rence in molybdenite. Rhenium is most abundant in porphyry copper ores, but the factors controlling its concentration are not yet understood. LIGHT METALS AND INDUSTRIAL MINERALS DISTRICT AND REGIONAL STUDIES Mount Wheeler beryllium deposit, Nevada Stager (Art. 33) has studied a new association of beryllium that has been found in the Mount Wheeler mine, Nevada, where phenacite, bertrandite, and beryl, intimately associated with scheelite and fluorite, re— place the lowest limestone bed along vertical quartz veins in the Pioche shale of Cambrian age. The beryl- lium minerals probably were deposited by hydrother— mal solutions originating in a nearby granitic intru- sion, and it seems likely that similar deposits of these easily overlooked beryllium minerals may be found in the surrounding area. Beryllium in the Lake George district, Colorado In the Lake George district, Colorado, Sharp and Hawley (Art. 35) have recognized bertrandite-bearing greisen as a new type of beryllium ore. Similar grei— sen may exist elsewhere unrecognized, as the beryllium silicate, bertrandite, is difficult to distinguish from feldspar. The Lake George district is crossed by pre- 557328 0 - 60 - 2 A5 mineralization lineaments that at least locally contain greisen with small amounts of bertrandite (Hawley and others, Art. 34). Beryllium in tin districts of the Seward Peninsula, Alaska A review of all available geologic information has shown that the tin districts of the Seward Peninsula, Alaska, contain promising amounts of beryllium. Beryllium was identified originally in 1940 by George Steiger in samples collected by J. B. Mertie, Jr., and R. R. Coats, from bedrock sources at the Lost River tin mine, and at the Ear Mountain and Cape Mountain tin areas. Spectrographic analyses by Shrock in 1943 of samples of banded tactite collected by A. Knopf from Tin Creek, about 2 miles from Lost River, showed beryllium in the range of 0.016—0.08 percent. Drill cores obtained by the Bureau of Mines at the Lost River mine in 1943—44 (US. Bureau of Mines Report of Investigations 3902) also contained detecta- ble beryllium as beryl and phenacite, and Coats and P. L. Killeen identified beryl in surface veinlets in metasomatized marble at the Lost River mine. Steiger found that the idocrase in samples collected by Coats from the same region is consistently high in beryllium, and deeper holes drilled by the US. Tin Corporation in 1955 showed that parts of the underlying granite are abnormally rich in beryllium. Phenacite was found to be present in one core sample by C. L. Sains- bury. Tin placer concentrates from DMEA projects at Cape Mountain and at Earl Mountain, which were analyzed spectroscopically by the US. Bureau of Mines, and tin placer concentrates from Bureau of Mines tin exploration near Earl Mountain and Cape Mountain (US. Bureau of Mines Report of Investiga- tions 5493 and 7878) contain amounts of beryllium that are generally higher than samples of stream sediments from beryllium—rich provinces elsewhere in the United States. Additiohal detailed work may well outline deposits of economic importance at any or all of the above localities, as well as in other tin- rich areas for which information on beryllium is lack- ing at present. Beryllium and fluorspar in the Thomas Range, Utah In the spring of 1960, prospectors discovered an extensive and new type of beryllium deposit in the vicinity of Spors Mountain inthe Thomas Range dis; trict, Juab County, Utah. This area has just been mapped by Staatz and Osterwald (1956) in connec- tion with a study of its fluorspar and uranium de- posits, so it is possible to make a preliminary inter- pretation of the geology of the beryllium deposits that may be helpful in their further exploration. The A6 account here is based on that mapping, supplemented by a recent field examination by Staatz and W. R. Griflitts. The beryllium deposits are in rhyolitic tufl’ on the lower slopes of Spors Mountain, where, because of its friable character, the tufl’ breaks down and is con- cealed by slope wash and younger deposits. The tufl' is a part of a sequence of faulted and tilted Miocene volcanics, which is overlain by only slightly faulted and imperceptibly tilted Pliocene volcanics and Quat- ernary lake beds. The only beryllium—bearing mineral thus far iden- tified is bertrandite, found by E. J. Young and E. C. T. Chao by X—ray analysis. Other epigenetic minerals include opal, montmorillonite, fluorite, and calcite. Bertrandite and other replacement minerals are most abundant in elliptical nodules that range from 0.5 to at least 8 inches in length. Five samples of the tufi from two of the occurrences were determined by beryl- ometer measurements to carry 0.25 to 1.5 percent BeO; nodules from these same tufl’s contain 1.8 to 10.7 per- cent BeO respectively. The beryllium-rich layers, which are not everywhere at the same horizon in the tufl', may be several yards thick, but contain erratically distributed barren areas. The bertrandite, like the fluorspar, probably was deposited in Pliocene time during the waning stages of the younger period of volcanism. Plate 1 of Bulletin 1069 by Staatz and Osterwald shows the general distribution of the volcanics (vt on the Plate 1 explanation) that contain the beryllium- bearing tufl', and exploration by mining companies has disclosed a number of localities, over an area of sev- eral square miles, where the bed is mineralized. Be— cause of the extensive distribution of the favorable tufl' and its repetition by faulting, which has brought it close to the surface at numerous places, opportuni- ties for further discoveries are promising, and the re- serves of beryllium in the area could be very large. Black Hills pegmatites, South Dakota In the southern Black Hills, pegmatites—which are mined for feldspar, mica, lithium minerals, and beryl —are in medium- to high-grade metamorphic rocks intruded by the so-called granite of Harney Peak. Detailed studies have helped to define areas favorable for prospecting and have led to increased knowledge of the structure, mineral zoning, and origin of the zoned pegmatites. The Hugo pegmatite, for example, near Keystone, has been found by Norton (Art. 32) to consist of seven zones and two replacement bodies. Most of it crystallized from a magma that became increasingly silicic as crystallization proceeded; the core and the replacement bodies, however, which are GEOLOGICAL SURVEY RESEARCH l960—-SYNOPSIS 0F GEOLOGIC RESULTS rich in alumina and the alkalies, were probably de- posited from a water-rich fluid that separated from the silicate rest liquid. In the Fourmile quadrangle J. A. Redden has found that the zoned pegmatites occur in metamorphic rocks several miles from any large body of granite. The high temperatures that prevailed in and near the major intrusive bodies fa- vored the formation of numerous un-zoned quartz- feldspar pegmatites, but not the larger and more valuable zoned pegmatites. Talc and asbestos deposits From a study of the petrology and geochemistry of certain talc—bearing ultramafic rocks and adjacent country rocks in Vermont, A. H. Chidester has con- cluded that the talc was formed by regional meta- morphism unrelated to serpentinization (see p. A67). A. F. Shride has shown that the principal asbestos- producing areas of east-central Arizona are in a struc- tural setting typical of the Colorado Plateau province, rather than of the Basin and Range province as pre- viously thought, and that the geologic structures and extensive bodies of intrusive diabase which favored the formation of asbestos are of Precambrian rather than post—Paleozoic age. Phosphate deposits in Montana and Wyoming The phosphate resources of parts of Montana and Wyoming have recently been estimated as a part of a long range study of the distribution, resources, and origin of the Permian Phosphoria formation. In southwestern Montana and a small part of adjacent Idaho, Swanson (Art. 31) estimated that the phos- phatic shales contain 450 million tons of phosphate rock in units that are more than 3 feet thick and that average more than 31 percent P205; and 6 billion tons averaging more than 24 percent P205. Corresponding contents of uranium in the two grade categories are 35,000 and 420,000 tons. The same rocks also contain 2.5 to 3 percent fluorine. These shales also contain more than 2.2 billion tons of rock in units that are more than 3 feet thick and that average more than 18 percent P205. R. P. Sheldon estimates that the phosphatic shales in Wyoming and a small part of eastern Idaho contain 1.4 billion tons of phosphate rock in units more than 3 feet thick and averaging more than 31 percent P205; 6.5 billion tons containing more than 24 percent P205; and 19 billion tons containing more than 18 percent P205. He also estimates that the phosphatic shales contain 5.5 billion tons of phosphate rock averaging more than 0.010 percent. uranium and 13.5 billion tons averaging more than 0.005 percent uranium. LIGHT METALS AND INDUSTRIAL MINERALS Phosphate in northern Florida and South Carolina In the northern part of the Florida Peninsula, recon- naissance by G. E. Espenshade and Charles Spencer indicate that phosphatic dolomite and phosphorite are widespread in the Miocene Hawthorne formation. The apatite is locally altered to aluminum phosphate, as in the Land Pebble field farther south. In the Charleston, South Carolina area, Malde (1955a) has shown that phosphate nodules in the upper part of the Oligocene Cooper marl were formed by replacement of calcium carbonate and were later reworked to form the basal part of the Pleistocene Ladson formation. High calcium limestone in southeastern Alaska The Heceta-Tuxekan Islands area, southeastern Alaska, contains a thick sequence of relatively pure Silurian limestone, associated with marine high-rank graywacke. Chemical analyses of 56 composite samples of the limestone collected by G. D. Eberlein over a stratigraphic interval of 8,800 feet indicate that most of it contains more than 90 percent of CaCOa, and less than 1 percent of MgO, 0.8 percent of R203, 0.1 percent of combined alkalies, 0.2 percent. of total S, 0.02 percent P205 and 5 percent acid insolubles (mostly SiOZ). In samples from a zone approximately 1,000 feet thick near the middle of the sequence, the rock is nearly pure calcite, suitable for metallurgical uses. Clay deposits in Maryland In a cooperative investigation with the Maryland Department of Geology and the US. Bureau of Mines, M. M. Knechtel, J. W. Hosterman, and H. P. Hamlin have found that much nonmarine clay of Cretaceous age in Maryland is suitable for fire clay. They have also found that large deposits of marine “bloating” clay of Tertiary age appear to constitute excellent raw mate- rial for the manufacture of light-weight concrete ag- gregate (Knechtel, Hosterman, and Hamlin, 1959; see also Art. 29). Thick deposits of this clay underlie extensive areas that include many potential strip-mining sites. Clay deposits in Kentucky A cooperative study, with the Kentucky Geological Survey, has shown that the valuable deposits of flint clay in northeastern Kentucky were formed by sub- aqueous leaching of normal plastic clays in swamp deposits of Early Pennsylvanian age, immediately above an erosion surface cut on sedimentary rocks of Mississip- pian age (Huddle and Patterson, 1959; Patterson and Hosterman, 1960). The Lee formation, which contains the clay beds, grades laterally from very clean quartz sandstone into muddy sandstone, siltstone, shale, and claystone. A7 Green River saline deposits, Wyoming During the course of a long-range study of the stratigraphy, mineralogy and origin of the Green River formation, which contains vast reserves of trona (3Na20°4C02'5H20), Milton and others (1959, 1960) have recently summarized information on the mineral assemblages present in these remarkable deposits. Car- bonates, of which the trona is one, not only make up the bulk of the chemically precipitated minerals, but are present in great variety also—in fact, the Green River contains about one-fourth of all known. species of carbonates. The beds also contain 12 species of sili- cate minerals, including authigenic amphibole magne- sioriebeckite, the pyroxene acmite, and the boron pla- gioclase reedmergnerite. Carlsbad potash district, New Mexico Field studies of the Carlsbad potash deposits by C. L. Jones, H. C. Rainey, and B. M. Madsen have developed the concept that late-stage solutions effected widespread metasomatic replacement in localized parts of favorable beds of previously precipitated salts (Jones, 1959) . These solutions introduced K, Mg, and 801 and removed Na, Ca, and C1 or precipitated them elsewhere. There is evidence that the late-stage replacement was struc- turally controlled. Borate deposits of southwestern United States Studies of the borate deposits of the Mojave Desert and adjacent parts of California and western Nevada continue to yield new information about their mineral- ogy, origin, geologic setting, and resources. R. C. Erd has shown that the Kramer district contains a unique assemblage of nearly 50 minerals; the list now includes 18 species found there during his study. Among them are four black ferromagnetic iron sulfides, some locally abundant, which have x-ray powder patterns distinct from those of previously known iron sulfides. Erd has also shown that at Kramer layers of pyroclastic material have been altered to analcime, clinoptilolite, phillipsite, searlesite, and authigenic adularia and albite. Samples from 10 playas in California and Nevada pro- vided new occurrences of burkeite (Na6(C03) (8002) and searlesite, and one contained an unidentified hydrous sodium calcium sulfate. Three rare borate minerals, hydroboracite, inderite, and kurnakovite, were found in the Eagle Borax deposit in Death Valley. During examination of the Kramer ore body, W. C. Smith found evidence that underground solution has removed much borax, particularly along faults. Peculiar features of the ore body, now believed to be effects of solution, include its abrupt, blunt edges, certain valley- like depressions in the top of the ore, and a hanging wall which in places consists of slumped insoluble A8 residue containing secondary magnesium and calcium borates An improved understanding of the geologic history of Searles Lake, and of the probable source of its boron, has resulted from G. I. Smith’s study of regional as well as local evidence. The study confirms Gale’s gen- eral picture of Searles Lake basin as the third in a chain of basins that received water from the Owens River during the wet periods of the Pleistocene and that partially or totally dried up during ensuing dry periods. Drill cores from the basins (see US. Geological Survey Bulletins 1045—A and 1045—E) show that Searles Lake was an evaporating pan intermittently throughout much of Quaternary time, yet only during the last two major dry periods and only in Searles Lake basin did desiccation produce salt layers that are commer- cially valuable by present standards. From the inter- stitial brines in these upper salts at Searles Lake commercial plants recover sodium, potassium, lithium, carbonate, sulfate, phosphate, and bromine, as well as borate products. Smith concludes that although Searles Lake had a long history as an evaporating pan, boron and other valuable constituents were present in the Owens River system only after their introduc- tion about 50,000 to 60,000 years ago by an episode of volcanic and hot spring activity in the Owens River drainage. Because Searles Lake ceased overflowing about the same time, it concentrated most of the valu- able elements subsequently brought to it by the Owens River. COMMODITY AND TOPICAL STUDIES Beryllium The supply of beryllium obtained from pegmatites throughout the world is so small that hope for any great increase in production rests mainly on the possi- bility of finding major beryllium deposits in non- pegmatitic rocks. Available data on the distribution of beryllium in rocks show that certain types of quartz- gold and quartz—tungsten veins, certain manganese veins, tactites, and some other varieties of rock warrant further investigation (Warner and others, 1959, and Norton and others, 1958 2). The recent discoveries al- ready mentioned (see p. A5) encourage the belief that minable nonpegmatitic deposits can be found. Griffitts and Oda (Art. 44) have found that the beryl- lium content of soils and alluvium can be used in geochemical prospecting for beryllium deposits. De— velopment of beryllium detectors, based on the gamma- neutron reaction, has contributed to beryllium ex- 2Norton, J. J., Griflitts, W. R., and Wllmarth, V. IL, 1958, Geology and resources of beryllium in the U.S.: U.N. Internat. Conf. on Peaceful Uses of Atomic Energy, 2d, Geneva, 1958, Proc., v. 2, p. 21—34. GEOLOGICAL SURVEY RESEARCH limo—SYNOPSIS OF GEOLOGIC RESULTS ploration by providing a rapid means of analysis (Vaughn and others, 1960). Selenium A study of the geology and geochemistry of selenium indicates that this element is markedly concentrated in epithermal antimony and silver deposits (Davidson, 1960). In volcanic rocks, it is concentrated in ash and in rocks composed of ash, rather than in flow rocks (Davidson and Powers, 1959). Selenium has also been found in low grade concentrations in some phosphor- ites and black shales of the Permian Phosphoria for- mation and higher grade concentrations are associated with sandstone-type uranium deposits and some large sulfide deposits. Marine phosphorites Continued studies of the phosphorites in the Permian Phosphoria formation show that they are part of an assemblage of lithofacies that formed synchronously along the western edge of a shoaling land mass of low relief. The lateral sequence of facies, in a shoalward direction, is typically (a) carbonaceous mudstone, (b) phosphorite, (c) chert, (d) light colored carbonate rock and sandstone, (e) saline rocks, (f) greenish— gray mudstone, and (g) red beds (McKelvey and others, 1959). This sequence is reproduced, in whole or part, in both the same order and reverse order in vertical sections, where the facies intertongue as the result of the lateral shifting of environments with transgressions and regressions of the sea. Petrographic studies by R. A. Gulbrandsen, E. R. Cressman, R. P. Sheldon, and T. M. Cheney indicate that much of the phospliorite was formed by direct precipitation from sea water or interstitial water. The lateral sequence of chemical sediments suggests that a salinity gradient existed in the Phosphoria sea, and Gulbrandsen has shown that the succession of chemical sediments might have resulted from phase precipitation in a shoalward moving current. Information on the origin of the phosphorite as- semblage of sediments, gained as the result of the ob- servations of previous workers (notably Kazakov and Brongersma-Sanders) A as well as by studies of the distribution of ancient and modern sediments, provides clues helpful in the search for oil as well as phos- phorite (McKelvey, 1959). Phosphorites in the mod— ern ocean form where cold waters rich in P, N, and Si upwell. These waters become saturated with phos- phates as the temperature rises with decreasing depth, and they may also become successively saturated with carbonates and saline minerals as they move shore- ward. The exceptionally rich nutrient content of these waters support lush growths of organisms, which RADIOACTIVE MINERALS produce important accumulations of carbonaceous mat— ter in the sediments. Sulfides and petroleum form under the reducing conditions that prevail where large amounts of carbonaceous matter are deposited; the petroleum often accumulates in stratigraphic traps that result from synchronous deposition of both reser— voir beds and sealing beds in other parts of the same environment. These relations indicate the following guides to the search for phosphorite and oil: (a) both phosphorite and oil are likely to occur in lateral or vertical asso- ciation with bedded chert, black shale, and marine evaporites; (b) accumulations of oil are likely to occur in stratigraphic traps (such as carbonate rocks sealed by black shale, red beds, or evaporites) whose location can be predicted from the lateral and vertical sequence of lithofacies characteristic of this environment; and (c) as the main ocean currents and continental mar- gins have not shifted much since the Cretaceous, up- welling occurred during the deposition of coastal plain formations in many of the same general areas in which it is occurring now. Coastal-plain sediments adjacent to areas of modern upwelling, then, are favor- able for the occurrence of both phosphorite and oil. RADIOACTIVE MINERALS DISTRICT AND REGIONAL STUDIES Colorado Plateau A compilation of some twenty reports recently pub- lished on the geochemistry and mineralogy of the Colorado Plateau ores (Garrels and Larsen, 1959) documents two important conclusions: (a) the ores that occur in rocks saturated with water consist of low- valent minerals (chiefly vanadium clays, uraninite, coflinite, and montroesite), but those in unsaturated rocks consist partly or wholly of higher valent min- erals, such as carnotite; and (b) the ore minerals in the unsaturated rocks were emplaced in a reducing en- vironment, in Late Cretaceous or early Tertiary time, before regional deformation or during its early stages, so that movement of the transporting fluids was chiefly controlled by sedimentary structures in virtually unde- formed rocks. These conclusions, resulting from years of work by many people both in government and in private industry, provide a sound basis for prospecting for uranium ores, not only on the Colorado Plateau, but in many other areas. In the Slick Rock district, Colorado, Archbold (1959) has found that carbonate-rich zones in sand stone of the Salt Wash member of the Morrison forma- tion are associated with ore deposits, and therefore can serve as guides to ore. A9 On evidence derived mainly from the relations be— tween ores and penecontemporaneous structures, R. H. Moench and J. S. Schlee have concluded that the uranium deposits of the Laguna district in New Mex- ico were probably deposited under near-surface condi- tions prior to deep burial and regional tilting. The paragenesis of uranium ores in the Todilto limestone near Grants, N. Mex., indicates that the limestone is locally replaced by minerals of uranium, vanadium, and to a lesser extent by minerals of fluorine, iron, lead, manganese, molybdenum, and selenium (Trues- dell and Weeks, 1959). Colloform uraninite formed after the early recrystallized calcite, pyrite, fluorite, montroseite, haggite, and vanadium clay; it was ac- companied or closely followed by coffinite, galena, and calcite, and was followed by late calcite, pyrite, mar- casite, haggite, and hematite. Pitchblende has been identified as a secondary mineral in the Ambrosia Lake district, New Mexico (Granger, Art. 26) Where it probably was deposited from ground water that dissolved uranium from oxidizing coifinite. Studies by I. A. Breger indicate that the carbonaceous substances coating the sand grains in the Ambrosia Lake ore are humic substances derived by alkaline ex- traction of low-rank coalified woody debris, and that they are not related to petroleum. Gila County, Arizona In Gila County, Arizona, uranium deposits occur in a potassic siltstone of the Precambrian Apache group. The uranium was probably derived from nearby in- trusive diabase of about the same age (Neuerburg and Granger, 1960). Differentiation of the diabase magma, involving extensive reactions with aqueous fluids, re- sulted in ordinary diabase, diabase pegmatite, deu- terically altered diabase enriched in potassium, syenite, aplite, and deuteric veinlets. The deuteric veinlets were deposited in contraction fractures by rest fluids as they drained from the magma. The distribution of uranium and copper in the differentiates indicates that these fluids removed most of the uranium, but little of the copper, that was originally contained in the magma. Crooks Gap area, Wyoming In the Crooks Gap area, Fremont County, Wyo- ming, J. G. Stephens found that the uranium is mainly in conglomeratic arkose beds of the Wasatch formation (Eocene?). Analyses of springs and seeps in the area show that water from Miocene tufl'aceous rocks contains several times as much uranium as water from Eocene rocks, which suggests that the Miocene rocks may have been the source of the uranium. A10 Baggs area, Wyoming In the Poison basin in the Baggs area of Wyoming, G. E. Prichard has recognized secondary ore minerals in an oxidized zone 20 to 70 feet below the surface in the Browns Park formation of Miocene(?) age; underlying tabular bodies of unoxidized ore appear to be parallel to the base of the zone of oxidation. Gas Hills district, Wyoming Most of the important deposits in the Gas Hills district, Wyoming, studied by H. D. Zeller, P. E. Soister, and D. L. Norton, are in coarse-grained arkosic sandstones of the upper part of the Wind River forma- tion. Unoxidized uranium ores are enriched in molyb- denum, arsenic, and selenium. R. C. Coleman has found that the mineral associations are largely con- trolled by the oxidation state of the ore zones. Urani— nite, coflinite, iron sulfides, jorisite(?), calcium car— bonates and sulfates are the minerals in the dark unoxidized ores. Uranyl carbonates and hydroxides form in the early stage of oxidation and are accom- panied by the blue molybdenum bloom ilsemannite. The change from U(IV) to U(VI) compounds takes place much earlier than the oxidation of iron sulfides. As the iron sulfides begin to oxidize, the uranyl car— bonates dissolve in the acid solutions and the uranyl ions then form complex ions with (PO4)‘3 or (A50...)—3 to produce more stable oxidation products. Some sec- ondary enrichment takes place in sulfide rich zones, where uranium is reprecipitated by reduction. Geo- chemical evidence suggests that the metals in these - deposits were leached from tufl's and arkose by alkaline solutions that accumulated in the Wind River basin. The fluids became progressively enriched in U, M0, Se, As, and P by evaporation, dissolution, or base ex- change. When the basin was tilted, the ore fluids moved into zones where HZS had accumulated, and the ore metals were precipitated by reduction. Black Hills, South Dakota G. B. Gott and associates have found evidence in the southern Black Hills to indicate that carbonate- rich uranium-bearing water migrated vertically through breccia pipes and possibly fault zones, and laterally through permeable channel sandstones. Geochemical control of uranium deposition appears to have con- sisted principally of acidification and reduction of uranium-bearing solutions. This has been accom- plished in at least one place by the intermingling of uranium-bearing bicarbonate solutions with sulfate waters derived from highly carbonaceous pyritic silt- stone. In the northern edge of the Black Hills, R. E. Davis and G. A. Izett found that ore deposition was chiefly controlled by composition of the host rock and GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS its geochemical environment, along with sedimentary structures; tectonic control in less important in this area than previously supposed. Palangana salt dome, Texas Weeks and Eargle (Art. 24) determined that the uranium deposit at Palangana salt dome is in Pliocene and Miocene sands at a depth of about 325 feet. They believe that the uranium was leached by alkaline carbonate ground water from tufl’aceous sediments up dip, and was precipitated by reduction with HZS emanating from the sulfurous caprock of the salt dome. Uraniferous phosphorite in Eocene rocks, Wyoming Although small quantities of phosphate, mostly in the mineral bradleyite (NasMg(PO4)C03), have been known to occur in the Eocene Green River formation and similar deposits, calcium phosphate deposits have been unknown in saline-bearing lacustrine rocks. Re- cently, however, Love and Milton (1959) found some thin apatite-bearing layers of dolomitic siltstone and oil shale intertonguing with trona-bearing beds in the Green River formation near Green River, Wyo. Se- lected samples contain, on the average, 0.05 percent uranium and 6.5 percent P205. Similar uraniferous phosphatic strata were found in the Lysite Mountain area in lacustrine tufiaceous siltstone in the Eocene Tepee Trail formation. As the known phosphatic beds are only a few inches thick, they are not minable, but their discovery opens up the possibility that thicker uraniferous phosphorites may be found in these or similar lacustrine deposits. Uraniferous lig‘nite in the Williston basin, Montana and North Dakota In the Williston basin of Montana and North Dakota, N. M. Denson, J. R. Gill, and W. A. Chisholm have found that present-day ground waters from Oligocene and Miocene tufl's contain more uranium than those from other rocks, and they are also rela— tively high in V, Si02, Mo, Sr, As, and Se, which are all associated with the uranium deposits. From this evidence, they conclude that in the Williston basin, as in many other areas, the uranium in the lignite has been derived from the leaching of Oligocene and Miocene tufls. Chattanooga shale, Tennessee and Alabama L. C. Conant and V. E. Swanson have described the geology, origin, trace elements, and orgarl‘ic material of the Chattanooga shale in central Tennessee and adjacent States. The Chattanooga is only about 35 feet thick in this area, but it has been divided into several units each fairly uniform in lithology and uranium content, that can be traced over thousands of square miles. The shale accumulated slowly in a RADIOACTIVE NIINERALS shallow sea that gradually spread over an area of low relief, and it thins to extinction by overlap on older units in central Alabama and northeastern Mississippi, and also on the margins of the Hohenwald platform, a Devonian island in south—central Tennessee. COMMbDrrY AND TOPICAL smms Distribution of epigenetic uranium deposits in the United States Three maps on a scale of 1 :5,000,000 have been pub- lished recently that show the relation of epigenetic uranium deposits to continental sedimentary rocks, to crystalline rocks older than Late Cretaceous, and to igneous rocks of Late Cretaceous and younger age (Finch and others, 1959). These maps provide a basis for analyzing the relation of the distribution of various types of deposits to the composition and age of the host rocks in which they were deposited, and they should help define areas and rocks favorable for pros- pecting. Uranium in sandstone-type deposits The previously mentioned investigation of the geo- chemistry and mineralogy of Colorado Plateau ores (Garrels and Larsen, 1959) has yielded many results of broad application. For example, Evans (1959) has defined the structure and fields of stability of the vanadium minerals in terms of Eh and pH. The trivalent oxide, montroseite, is converted by weather- ing to tetravalent and pentavalent minerals, but what species are formed depends on the Eh and pH pre- vailing in the environment. The primary tetravalent uranium minerals, which are almost insoluble under reducing conditions, also readily break down under oxidizing conditions (Garrels and Christ, 1959). Many of the higher-valent minerals formed on weathering are water—soluble and are deposited only through evaporation, but hexavalent uranium may be fixed in the zone of weathering if arsenic, phosphorus, or vanadium are available, because these elements form relatively insoluble compounds with uranium. Ex— perimental determinations of the reducing effect of woody materials show that the amounts present in many rocks are adequate to reduce and precipitate uranium and vanadium brought to the environment in oxidized form (Garrels and Pommer, 1959). Using radioactive daughter products as tracers, Rosholt (Art. 21) finds that it is possible to identify the process by which uranium migrates in sandstones and to estimate the time at which the migration took place. Studies of some ore deposits in sandstone show that copper deposits are mainly in first-cycle arkosic sand- stones, vanadium deposits are dominantly in second— cycle sandstones, and uranium deposits are either in All first- or second-cycle sandstones (Fischer and Stewart, Art. 22). This distribution may be related to the geochemistry of these metals in the igneous environ- ment. Much of the copper and uranium in igneous rocks and hydrothermal veins is in a readily oxidizable form, and thus available to circulate in first—cycle sediments. Vanadium in igneous rocks, on the other hand, is in a less available and less concentrated form, and forms clay minerals on weathering; diagenetic reactions and a second cycle of weathering may be required to mobilize it. Uranium in petroleum From an investigation of the association of uranium with petroleum and petroliferous rocks, K. G. Bell has concluded that petroleums do not contain signifi— cant quantities of uranium, and that petroleum does not act as ore-transporting fluids for uranium. He estimates that the average uranium content of crude oils is approximately one part per billion. Breger and Deul (1959) have also concluded that crude oil plays no part in the emplacement of uranium ore; they point out, however, that since migrating oil may pick up small quantities of uranium, the uranium con- tent of oil may have some value as a guide to pros— pecting. This is partly confirmed by H. J. Hyden, who has found by experiments that crude oil can leach uranium from sandstone host rocks. Hyden also finds that the vanadium and nickel contents are related to the organic composition of the petroleum, but that the uranium content as well as the content of other metals is not. Uranium in coal The Geological Survey has recently published a group of ten reports (Bulletin 1055) that describe the occurrence of uranium in coal in northwestern South Dakota and adjacent areas in Montana and North Dakota, the Red Desert area of Wyoming, the Goose Creek and Fall Creek areas of Idaho, and the La Ventura Mesa area of New Mexico. The uranium content of the coal in these areas generally ranges from 0.003 to 0.1 percent, although in the Cave Hills area of South Dakota large tonnages average 0.7 per- cent. Most of the uranium-bearing coals are of low rank and contain more ash than nonuraniferous coals. The regional occurrence of uranium in coals that underlie Tertiary rocks containing volcanic materials, coupled with the fact that the uranium in individual coal beds generally increases toward fractures, perme- able layers, or other structures that probably served as conduits for ground water, indicate that the uran- ium in these coals was deposited by circulating ground water that leached uranium from volcanic materials. A12 Several of the uranium-bearing lignites mentioned above were found by applying this theory to known information in the distribution of both coal and vol- canic materials. In Bulletin 1055 Denson (1959) has used it also to indicate additional areas favorable for the occurrence of uraniferous lignite. Uraniferous black shale and phosphorite Investigations by V. E. Swanson of uranium in black shales show that uranium and distillable oil are quan— titatively related in some shales, but not in others. The major factors controlling the oil yield and uran- ium content of these shales appear to be amount of organic matter, proportion of humic to sapropelic types of organic matter, the amount of phosphate, and depositional environment. R. P. Sheldon (1959a, b) has found that phosphatic sediments of the Phosphoria formation deposited in an environment of low Eh are relatively rich in uranium, whereas those deposited in an environment of high Eh are relatively poor in uranium. He concludes that the low Eh of the depositional environment increases the concentration of uranium in apatite in one or both of two ways: (a) it converts uranium to the U+4 ion and thereby more U(IV) is substituted for calcium in the apatite lattice, or (b) the carbonaceous matter that accumulates in environments of low Eh inhibits the growth of apatite crystallites, allowing more U(VI) to be absorbed on crystallite surfaces. Thorium in monazite From the available thorium analyses of monazite, Overstreet (Art. 27) finds that monazite is rare in the greenschist facies, rare to sparse in the epidote- amphibolite facies, sparse to common in the amphi- bolite facies, and common to abundant in the granulite facies; this indicates that detrital monazite in pelitic sediments decomposes during low-grade regional meta- morphism, but is stable in high-grade metamorphism. The Th02 content in monazite from pelitic metasedi- ments rises from about 0.5 percent in the greenschist facies to 10 percent in the granulite facies. A similar relation to temperature and pressure seems to exist in igneous rocks and hydrothermal veins: monazite in granites that crystallized at shallow depth is less abundant and poorer in thorium than monazite in plutonic granites; and monazite in low-temperature veins is thorium-poor, whereas that from high-tem- perature veins is thorium-rich. FUELS PE'I'ROLEUM AND NATURAL GAS Although the Geological Survey does not participate in petroleum exploration, it facilitates private enter- GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS prize by gathering and publishing data on the areal geology and stratigraphy of sedimentary basins. Many of the results of this work are described under re— gional headings on pages A26—A54 but some of the findings that have to do directly with the search for oil and gas are reported here (see page A9 for a de- scription of the relation of marine upwelling to the origin and occurrence of petroleum). McAlester basin, Oklahoma Subsurface stratigraphic studies by S. E. Frezon along the northern edge of the McAlester basin in- dicate that the upper part of the Simpson group thins from south-central to northeastern Oklahoma. North of the Arbuckle Mountains in south-central Oklahoma the equivalent of the Fite limestone of northeastern Oklahoma (Corbin Ranch) rests on the Bromide formation. Northeastward from this area the Bromide and the underlying McLish formation are truncated and in northeastern Oklahoma the Fite rests on rocks of pre-McLish age. Wilson County, Kansas Preliminary results of part of a continuing co- operative fuels resources program with the State of Kansas indicate that in Wilson County a close rela- tionship exists between gas accumulation and the tops of structures. Oil, however, accumulated generally in lenticular sandstones of Pennsylvanian age; where the control is stratigraphic, oil occurs on the flanks and in the lower parts of structures as well as on their crests. Horseshoe atoll, Midland basin, Texas The occurrence of oil in the Horseshoe atoll, in the northern part of the Midland basin of West Texas, has been described by Stafford (1959) and Burnside (1959). The Horseshoe atoll is an arcuate, reef-like accumulation of fossiliferous limestone, 70 to 90 miles across, that lies more than 6,000 feet below the surface in rocks of Pennsylvanian age. The limestone was extensively reworked and brecciated during deposition. It has an average porosity of about 6 percent, de- veloped primarily by leaching after deposition. Oil is contained in porous zones within the atoll, and in “knolls” on its top which are capped by impervious shale. The Horseshoe atoll is believed to be one of the larger oil reservoirs in the world. Williston basin, Montana, North Dakota, and South Dakota A map showing structure contours on the subsurface Piper formation, of Middle Jurassic age, in the Wil~ liston basin of Montana, North Dakota, and South Dakota, has been prepared by D. T. Sandberg (1959) in conjunction with a study of well cuttings. This map FUELS shows the relations between producing oil fields and major structural features, including the Nesson and Cedar Creek anticlines, Bowdoin and Poplar domes, and the central Montana and Bighorn Mountains up- lifts. It also shows many anticlines and other struc— tural features with which oil may be associated. Utah and southwestern Wyoming In the southern Kolob Terrace coal field, Utah, geologic mapping by W. B. Cashion indicates that sandstones at the base of the Cretaceous are lenticular and lie in a stratigraphic setting that is favorable for the entrapment of oil and gas. In the northwestern part of the Uinta basin of Utah, he finds that in some areas fluvial beds wedge out up dip between impervi- ous lacustrine beds, and hence provide an environment favorable for the accumulation of oil and gas. One of the areas in which the concepts concerning the relation of the occurrence of oil to phosphorite facies (see p. A9) may help in defining ground favorable for oil exploration is the fringe area of the Phosphoria formation. In the Bighorn basin of Wyoming, oil derived from offshore deposits of black shale and phosphorite is trapped in porous carbonate rocks and sealed by impervious green and red shales and evaporites. Cheney and Sheldon (1959) have recognized these same facies relations in southwestern Wyoming and northern Utah, and believe that areas within that general region are also favorable for the occurrence of oil. Alaska The petroleum possibilities of Alaska have been recently summarized by Miller, Payne, and Gryc (1959). In southern Alaska, six possible petroleum provinces have been delineated. The most promising of these are the Cook Inlet Mesozoic province and the Gulf of Alaska Tertiary province. In these two prov— inces, which form an are extending along the southern margin of Alaska from the base of the Alaska Penin- sula to the southeastern Alaska panhandle, the geology is comparable to that of the Coast Ranges of Wash- ington, Oregon, and California. Most of the current search for oil and gas in Alaska is concentrated in this belt. Central Alaska, a region of approximately 275,000 square miles between the Brooks Range and the Alaska Range, is geologically complex and similar to that of the area between the Rocky Mountains and Sierra— Cascade belts of the conterminous United States. Al- though no deposits of petroleum are known in the region, three pre-Cenozoic provinces (the Yukon— Koyukuk, the Kobuk, and the Kandik) and several large Cenozoic basin provinces deserve further study. A13 A large area north of the Brooks Range, including the Arctic foothills and the Arctic coastal plain, has good possibilities for petroleum production. Most of the exposed rocks in the area are of late Paleozoic, Mesozoic, and Cenozoic age. In the Arctic foothills these rocks are folded and faulted, and they dip gently seaward, with minor undulations, under the coastal plain. Part of the area is included in Naval Petroleum Reserve No. 4, in which extensive geologic mapping and exploration were carried out in the period 1944 to 1953 in cooperation with the Office of Naval Petro- leum and Oil Shale Reserves. The results of this work are being published in Geological Survey Professional Papers. Origin of helium and nitrogen in natural gas Analysis of published data shows that all gas fields contain some helium, and that the helium content of natural gas tends to increase systematically with the geologic age of the reservoir rock. Calculations made by Pierce (Art. 37) indicate that the observed rate of increase in helium content with age of the reservoir rock in most gas fields is about what would be expected if the helium were derived from decay of trace amounts of uranium and thorium in the surrounding rocks. Pierce also considers that nitrogen, which in many fields parallels helium in its increase with the age of the reservoir rocks, could be derived from the slow radioactive decay of carbonaceous matter in surround— ing rocks. COAL Coal studies in progress are of three main types: (a) geologic mapping and stratigraphic studies of specific coal fields; (b) appraisal of coal resources on a state and national basis; and (c) investigation of the petrography and composition of coal. Geology of specific coal fields A recently published report by Harbour and Dixon (1955) on the Trinidad-Aguilar area of the Trinidad coal field, Huerfano and Las Animas Counties, Colo., is the sixth in a series on the Trinidad field, which is one of the most important sources of coking coal in the western United States. The Trinidad-Aguilar area has yielded 80 million tons of coal, and still contains nearly 3 billion tons, most of which is suitable for making coke. More than 3 million tons of high volatile C bitumin— ous coal are present in the Mesa Verde area, La Plata and Montezuma Counties, 0010., according to a recent estimate by Wanek (1959). In the Square Buttes coal field of western North Dakota more than 3 billion tons of lignite have been mapped by Johnson and Kunkel (1959). A14 Areal mapping of the southern Kolob Terrace coal field, Utah, by W. B. Cashion, shows that the two productive zones in that field contain 3.5 billion tons of coal. Preliminary results of a cooperative investiga- tion with the State of Washington indicate that the southwestern Washington area contains 3.5 billion tons of subbituminous coal (Beikman and Gower, 1959). In the Homer district of the Kenai coal field, Alaska, Barnes and Cobb (1969) have mapped 30 coal beds 3 to 7 feet in thickness. This coal ranges in rank from lignite to subbituminous B. Indicated reserves total about 400 million tons. National coal resources A new estimate of United States coal reserves, in— corporating data from many sources, is summarized by Averitt (Art. 39). The tonnage remaining in the ground in the United States on January 1, 1960, totals about 1,660 billion tons, of which 830 billion tons are assumed to be recoverable. Distribution of minor elements in coal Zubovic and others (Art. 42), after compiling nu- merous determinations of the quantities of minor elements in coals, conclude that there are no marked difl’erences in the minor-element content of coals from different areas in the United States. Analyses of sink-float fractions of several coals indicate that the elements whose ions are small and highly charged— Be, B, Ti, V, Ge, and to a lesser extent Ga—are gen- erally associated with the organic fraction of the coal, whereas those whose ions are large—Zn, La, and Sn— are associated with the inorganic fraction. In pairs of chemically similar elements, such as Co—Ni and Y—La, those with the smaller ions (Ni and Y) gen- erally show the greater association with the organic fraction. These findings'indicate that the elements abundant in the organic fraction are present as or- ganic complexes—a conclusion strengthened by the fact that the smaller, more highly charged ions gen- erally produce stable metallic-organic complexes (Zubovic and others, Art. 41). OIL SHALE Field studies of the oil shale of the Green River formation in Naval Oil-Shale Reserve No. 2, north— eastern Utah, show that the principal oil shale zones in the northeastern part thin and intertongue with sandstone in the southwestern part of the Reserve (Cashion, 1959). Estimates of the potential yield of selected oil shale zones 15 feet or more thick in the 140 square mile area of the Reserve, range from 800 million barrels for parts of the deposits yielding 30 gallons of oil per ton, to 3.8 billion barrels for parts GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS of the deposits yielding 15 gallons per ton. A re- gional study of the geology and oil shale resources of a 1,900 square mile area in the eastern part of the Uinta Basin, Utah, indicates a similar general de— crease in the thickness of the oil shale zones from the center of the basin toward its south and east flanks. Similar facies changes have also been found by J. R. Donnell in the Green River formation in a 1,400 square mile area of the Piceance Creek Basin, western Colorado. The oil shale deposits there are about 2,000 feet thick in the central part of the basin, and they thin and intertongue with sandstone facies along the northeast and southwest flanks of the basin. Con- tinuing studies of subsurface data from the same area by D. C. Duncan indicate that a large but incompletely} outlined area in north central part of the Basin con- tains a sequence of oil shale more than 100 feet thick, with an oil content of 25 gallons or more per ton. DEVELOPMENT OF EXPLORATION AND MAPPING TECHNIQUES In connection with its work on mineral deposits, the Geological Survey does considerable research on the development of new methods and tools for geo- chemical, botanical, and geophysical exploration. Be- cause geologic mapping constitutes a large part of its activity, the Survey also experiments with new meth- ods of mapping and preparing maps for publication. Some of the new developments in these fields are de- scribed in the following sections. Reference to others will be found in the list of publications on p. A107—A127. GEOCHEMICAL AND BOTANICAL EXPLORATION Since 1946 the Geological Survey has been investi- gating geochemical methods on the premise that diag- nostic chemical patterns exist in the rocks, soils, water, and vegetation in the vicinity of concealed mineral deposits. A major goal of the Survey’s work has been to develop rapid methods of chemical analysis suitable for detecting traces of various metals in the field. Some of the methods now available for field determi- nation of metals in soil and rock are listed on the fol- lowing page. New analytical and prospecting tech— niques are discussed in subsequent paragraphs. New analytical techniques A resin-collection technique has been developed by Canney and Hawkins (Art. 43) for concentrating the ionic constituents of natural waters at the sample site. Its advantages include (a) a much lower limit of de- tection (fractions of 1 part per billion) than can be obtained with most direct analytical methods, and (b) EXPLORATION AND MAPPING TECHNIQUES elimination of the shipment and storage of bulky samples and of possible losses of trace metals from solution prior to analysis. Sensitivity (in parts per million) of field methods for determination of metals in soil and rock Sensitivity Element Method (ppm) Antimony _______ rhodamine-B ___________________ 1 Arsenic _________ mercuric chloride _______________ 10 Bismuth ________ diethyldithiocarbamate __________ 5 Chromium ______ (oxidation to chromate) _________ 100 Cobalt _________ 2-nitroso-1-naphthol ____________ 10 Copper _________ 2,2’—biquinoline ________________ 10 Germanium _____ phenylfluorone _________________ 4 Lead ___________ dithizone ______________________ 20 Manganese ______ (oxidation to permanganate) _____ 50 Mercury ________ dithizone ______________________ 1 Molybdenum- _ _ - potassium thiocyanate __________ 1 Nickel __________ a-furildioxime __________________ 10 Niobium ________ potassium thiocyanate __________ 100 Selenium _______ (reduction to elemental selenium)- 50 Tin ____________ 4,5-dihydroxyfluorescein (gallein) _ 10 Titanium _______ tiron __________________________ 150 Tungsten _______ potassium thiocyanate __________ 20 Uranium- _ _ _ _ _ _ _ potassium ferrocyanide __________ 4 Vanadium ______ phosphoric acid & sodium 50 tungstate. Zinc ____________ dithizone ______________________ 20 Molybdenum is particularly useful as an indicator in geochemical prospecting because it is associated with many base metal ores, is readily oxidized during weathering, and in the oxidized form is soluble in waters of widely differing pH. To make better use of molybdenum as an indicator of other metals, a method has been devised that can determine as little as a few tenths of a part per billion of molybdenum in water (Nakagawa and Ward, 1960). In this method, the molybdenum is first collected by a resin, leached, and then determined as the amber-colored molybdenum thiocyanate. To facilitate botanical prospecting for volatile ele- ments, such as antimony, mercury, and arsenic, F. N. Ward has devised methods for determining traces of these elements in vegetation. Using the reaction of beryllium with morin, he has also developed a modified fluorometric procedure for determining 1 to 10 ppm of beryllium in rocks. Plastic artificial standards have been developed to replace cumbersome and often unstable liquid stand- ards in field tests for a variety of elements (Hawkins and others, 1959). Prospecting techniques In reconnaissance of large areas by geochemical methods based on chemical analysis of the fine-grained fraction of stream sediments, it is usually difficult to distinguish enrichments of metal that are now taking A15 place in streams from enrichments that are related to ore-forming processes. Field studies in Maine by F. C. Canney suggest that many of the false anomalies, at least in glaciated areas, are caused by the scavenging action of the black manganese oxides that coat the pebbles and boulders in many stream courses. Sur- prisingly large quantities of some trace metals have been found concentrated in these coatings. This scavenging action is being investigated to see if it can be utilized in- geochemical surveys. Chemical analysis of igneous rocks has shown that much of the ore metals in stocks associated with ore deposits was introduced into the rocks and affixed to the surface of dark minerals without inducing any recognizable alteration; a large part can be removed by dilute acids. The content of metals is directly related to the abundance of the metals in- the ore de- posits themselves (Griflitts and Nakagawa, Art. 45). A high content of copper and zinc in igneous rocks may mark hypogene dispersion halos that extend sev- eral miles from centers of mineralization, and these halos may be used in the search for such centers. Roach (Art. 50) finds that the thermoluminescence of the host rocks decreases and the porosity increases with distance away from the base-metal replacement deposits in the Eagle Mine, Gilman, Colo. If further work shows that these relations occur in other dis— tricts, they will clearly be helpful in the search for ore deposits. A prospecting tool that offers considerable promise of being effective in the Basin and Range province is comparison of the metal content of caliche on pedi- ments with that of the alluvium (Erickson and Mar- ranzino, Art. 47). APPLICATION OF ISOTOPE GEOLOGY T0 EXPLORATION Investigations of the isotopic compositions of lead, oxygen, and sulfur in minerals are leading to conclu- sions and concepts that bear directly on problems of origin, age, size, and position of ore deposits. Other isotope investigations, bearing less directly on these problems, deal with hydrogen (see p. A68) and the “emanation” isotopes (radon, thoron, actinon) (for ex- ample, Tanner, Art. 51), and with age determination (p. A69) by the K/Ar, Rb/ Sr, and Pb/U methods. Isotope geology of lead An- analysis of all available lead-isotope data has been completed by R. S. Cannon, A. P. Pierce, J. C. Antweiler, and K. L. Buck (Cannon and others, 1959). In terms of Pb206, Pb2°7, and Pb208, about 75 percent A16 of all measured compositions fall within the bounds of an evolution curve predicted from an- assumed primordial composition of lead, together with the esti- mated contributions of radiogenic szoe, Pb207, and Pb208 from breakdown of uranium and thorium. Ex- cept for the highly anomalous “J -type,” the composi— tion of lead from major base-metal districts is strik— ingly concordant with the predicted values—so much so that if the ore in a mineral prospect contains lead of divergent composition, there is little probability that the prospect is in a major deposit. There is a close correspondence between leads from ore deposits and those from rocks, which may mean that many, if not most, ore deposits are formed by concentration of elements from sources within the crust, rather than from a deeper—seated source. The data also show, when analyzed for “model” ages, distinct groupings that suggest major metallogenic epochs at 3,000 my (million years), 1,500—2,000 my, and 0—500 m.y. The “J -type” leads, most of which are from deposits in the central United States, have highly anomalous com— positions, very different from those of leads from otherwise similar deposits of the Mississippi Valley type on other continents, as if the “J—type” leads owed their composition to some provincial phenome— non, as yet unidentified. Uraniferous districts, such as Blind River, Ontario, and the Colorado Plateau, are characterized by leads enriched in Pb206 and Pb207, a fact that could serve to guide prospecting for ura- nium in undeveloped areas.3 Oxygen isotopes in ore and gangue minerals A geologic thermometer that may be of great range and precision, has been tentatively established by R. N. Clayton (of the University of Chicago and the US. Geological Survey) and H. L. James. It uses the 018/016 ratios of iron oxides, calcite, and quartz, and is based on the following considerations: (a) the ex- perimentally determined isotopic equilibrium in the system CaCOa—H20; (b) the relative isotopic fraction- ation between calcite and quartz, as determined by measurements of equilibrium pairs from natural en- vironments; and (c) the assumption, based on measure- ments of materials from many geological environ— ments, that magnetite and hematite undergo little if any isotopic fractionation relative to the solutions from which they are deposited. The isotopic com- positions of magnetite-specularite-calcite-quartz as- semblages from a number of districts have been meas— 3Cannon, R. 8., Stiefl, L. R., and Stern, T. W., 1958, Radiogenic lead in nonradioactive minerals—A clue in the search for uranium and thorium: U.N. Internat. Conf. on Peaceful Uses of Atomic Energy, 2d, Geneva, 1958, Proc., v. 2, p. 215—223. GEOLOGICAL SURVEY RESEARCH l960—SYNOPSIS OF GEOLOGIC RESULTS ured. Examples of temperatures estimated from these measurements are as follows: Iron River, Michigan ________________________ 80°C Balmat, N.Y. (post—ore supergene mineralization) ___________________________ 110°C Coeur d’Alene district, Idaho _________________ 200°C Iron Mountain, Missouri _____________________ 340°C Iron Springs, Utah __________________________ 700°C Data from the Lake Superior region, though incom- plete, suggest that the iron oxides of the main ore bodies were formed from solutions isotopically similar to present-day fresh water. T. S. Lovering, J. H. McCarthy, Jr., and H. W. Lakin are working on a method for indirect determi- nation of oxygen isotopes in carbonate rocks. The oxygen is released from the carbonate by reaction with phosphoric acid, and, as carbon dioxide, is reacted with hydrogen gas to produce water. The density of the water, which is a function of the 013/ 016 ratio, is then measured by the rate at which it falls through a liquid of nearly the same density. With the apparatus now developed, standardized waters differ- ing in density by one part in four million can be distinguished. It is hoped that the “falling drop” technique will ultimately afford a rapid and inexpen- sive means of obtaining oxygen isotope data on car- bonate rocks, so as to facilitate the search for hydro— thermal zoning patterns such as those that surround the ore deposits in the Leadville limestone.4 GEOPHYSICAL EXPLORATION A significant development in the use of geophysics by the Geological Survey during recent years has been the trend towards studying large areas rather than individual features or anomalies. The immediate ob- jective of these regional studies is generally to aid in mapping geology in areas of poor exposures, where mapping by the older methods is diflicult, or to deter- mine the depth or configuration of basement rocks or deeply buried magnetic masses. Although the direct search for ore bodies has received less emphasis, it is likely that a study of the geophysical and geological framework to which anomalies must be referred will ultimately result in easier and more certain geophysi- cal exploration for ore bodies. Information on the development and application of aeromagnetic, radiometric, electrical, and gravity methods follows. New data on the physical properties of rocks, some of which may be useful in exploration, are described on page A56. 4Engel, A. E. J., Clayton, R. N., and Epstein. S., 1958. Variations in isotopic composition of oxygen and carbon in Leadville limestone (Mississippian of Colorado) and in its hydrothermal and metamorphic phases: Jour. Geology, v. 66, p. 374—393. EXPLORATION AND MAPPING TECELNIQUES Aeromagnetic methods The greatest advances in exploration geophysics in recent years have been made in the application of aeromagnetic methods to geologic mapping problems. Practical methods have been developed for calculating second derivatives, and for the upward or downward continuation of magnetic field measurements, and pro- grams have been prepared by Roland Henderson (1960) for making these calculations on high-speed computers; tedious computations, therefore, are no longer a deterrent to the quantitative interpretation of magnetic maps. Magnetic field patterns about prismatic models of geologic structures with a wide variety of dimensions have been determined experi— mentally and analytically, and catalogs of the results have been compiled. Three-dimensional polar charts for calculating the magnetic effects of a rock mass of arbitrary shape have been developed (Henderson, Art. 52). These interpretation aids have combined to make possible a highly quantitative evaluation of many magnetic field maps. Magnetic methods can be used for tracing relief and structure in rocks that differ widely in magnetic sus- ceptibility (see Arts. 54, 79, 85, 88, 95, 102, 114, and 158 for discussions of recent fieldwork). Where the mag- netic contrasts arise from differences in the magnetic properties of basement rocks, the thickness of sedimen- tary cover over the basement can be calculated with an error of only 10 to 15 percent. Recent drilling and seismic surveys at three places in Indiana have con— firmed the predictions of depth. to Precambrian base— ment rocks made by Zietz and others and recorded on a contour map of the Precambrian surface in Professional Paper 316—B, published in 1958. As this map was pre- pared almost wholly on the basis of aeromagnetic data, the new information strengthens confidence in depth determinations made by these methods. Magnetic methods can also be used to trace structure in layered rocks in which magnetic contrasts exist, and were, in fact, used to a large extent in making the recently pub— lished geologic map of the Iron River-Crystal Falls district of Michigan (James and others, 1960). The application of magnetic methods for this purpose has been extended by the development of a graphical meth- od that makes it possible to determine the dip of a buried geologic structure when the depth to the top of the structure is known (Andreasen and Zietz, Art. 107). Aerial radioactivity surveys Recent studies indicate that aerial radioactivity sur- veys will be a valuable aid in mapping areas of poor exposures and low relief in which the rocks difl'er moderately in their content of radioactive minerals A17 (Moxham, 1960; Guillou and Schmidt, Art. 55). It has been found that felsic rocks and shales are gen- erally more radioactive than mafic and carbonate rocks. Some of the results of recent field measure- ments are described on pages A29, A31—A33, and A42. Electrical methods Electromagnetic methods and galvanic-electric tech— niques have been used on a limited scale in Minnesota, Wisconsin, and Maine to determine the structure of metamorphic rocks under alluvial or glacial cover (Frischknecht and Ekren, Art. 56; Anderson, Art. 57 ). Continuous conductive zones, whose conductivity is probably caused by the presence of a few percent of graphite or carbon, are common in metamorphosed shales and slates, and serve as horizon markers in mapping. In Maine, galvanic-electric methods for measuring resistivity and induced polarization have also shown promise for mapping resistant horizon markers. C. J. Zablocki has applied an induction logging technique to the measurement of magnetic suscepti— bility in diamond-drill holes. Susceptibility logs have been run during the past two years in about forty drill holes penetrating magnetite ores in the Lake Superior region, southeastern Missouri, and California. The susceptibilities measured in the holes agreed closely with those calculated from magnetite content. Sus- ceptibility logs generally give a better picture of magnetic distribution than core assays, which must be averaged over several feet of sample. G. V. Keller has shown that induced electrical polarization is of considerable value in the search for low-grade metallic ores that are not sufiiciently con- centrated to cause any magnetic, gravity, or electrical conductivity anomaly (see also p. A56). In favorable circumstances, such as those existing in the copper de- posits in the Nonesuch shale at White Pine, Michigan, and in the disseminated copper deposits of southern Arizona, induced electrical polarization measurements may be used not only to locate ore bodies but also to estimate their grade. Keller has also developed a sys- tem for measuring induced electric polarization con- tinuously by lowering a probe in a drill hole. This method uses an electrode array similar to that nor- mally used in resistivity logging. Current is applied to the electrodes in short pulses, and the transient voltages between pulses are averaged and recorded. The method has been used for logging drill holes in several districts, including the native copper district of northern Michigan, the southern Arizona porphyry copper district, and the eastern Tennessee zinc district. It is useful in determining whether or not ores in a A18 particular district may be located by surface induced— polarization surveys. Gravity methods High-speed electronic computers are also being used in calculating the otherwise time-consuming terrain corrections required in gravity surveys (Kane, Art. 59). Gravity measurements are effectively used to determine the depths and configurations of intermon- tane basins filled with low-density sediments (for ex— ample Mabey, 1960), and Davis, Jackson, and Richter (Art. 60) have also used them to delineate areas favor- able for the occurrence of chromite in Camagiiey Province, Cuba. The accuracy required to measure the small gravity differences that are significant in chromite exploration is attained by using gravimeters that have low scale constants and by frequently check— ing instrumental drift. GEOLOGIC MAPPING The most important advances in geologic mapping techniques have come in the fields of photogrammetry, photogeology, and map drafting. Most Geological Survey research in photogrammetry is done by the Topographic Division and is not discussed here, ex- cept to say that the Topographic Division’s orthopho- toscope has now been brought to a high level of devel- opment. Orthophotographs (photographs having a uniform scale as contrasted to the conventional aerial photographs) produced with this instrument are prov- ing to be a fine base for geologic mapping in areas where topographic maps are not available, and they will undoubtedly be used extensively in the future. Photogeology Inspection of stereoscopically paired aerial photo— graphs, supplemented by techniques that permit quan- titative measurement of relief and of the dip of in- clined strata, has been used widely in recent years for reconnaissance geologic mapping. Photogeologic map- ping, carefully controlled by field work, is also coming into Wider use as a time—saving supplement to field methods in the preparation of standard, all purpose geologic maps. The detail and accuracy with which geometric measurements can be made from aerial photos also make photogeologic methods especially useful in research on certain quantitative geomorphic problems, such as the density, length, and orientation of drainage features in different types of terrane (Ray and Fischer, 1960). Spectrophotometric research on photos shows that the tonal difference between various rock types can be emphasized by using selected parts of the spectrum in taking aerial photographs (Fischer, Art. 61). This GEOLOGICAL SURVEY RESEARCH l960—SYNOPSIS OF GEOLOGIC RESULTS result can be obtained also by rephotographing color photographs through selected filters that emphasize specific lithologic features. Quantitative measure- ments of photographic tone, determined either from optical density of the negative or light reflectance from a paper print, also may be useful in identifying and evaluating lithologic and geomorphic features. Although color aerial photographs cannot yet be used in simple plotting systems, Minard (1960) has found them a valuable tool in mapping poorly exposed formations in the coastal plain in New Jersey. Scribing techniques The drafting of geologic maps, especially for rapid field compilation and preliminary publication, has been greatly facilitated by the development of scribing techniques—work in which the map-making agencies of the Federal government, including the Topographic Division of the Survey, played a leading role. In these techniques, lines are engraved on coated trans- parent but actinically opaque (that is opaque to light waves that affect photographic film) dimensionally stable materials. Scribing offers several advantages over pen and ink drafting for the geologist: it is faster and neater; the lines made by the scribing tool are of uniform width; the line placements are more accurate because the lines need not be redrafted by an illus— trator for preliminary publication; corrections can be easily made by applying acetate ink or some other material that can be rescribed; and a preliminary map on which geologic boundaries and symbols have been scribed by the geologist in the field can be published with minimum delay. Materials and instruments used in scribing can now be obtained from many commer- cial distributors of drafting supplies. GEOLOGY APPLIED TO PROBLEMS IN THE FIELDS OF ENGINEERING AND PUBLIC HEALTH A few decades ago, the science of geology was used mainly in- the search for deposits of usable minerals, but today it is also used to help solve a wide variety of problems related to engineering works, public safety, and public health. Any good geologic map at a scale of a mile to the inch or larger contains infor- mation that can be used in selecting, planning, and designing sites for engineering structures or in evalu- ating the hazards that natural features offer various kinds of human activities. The geologic mapping undertaken by the Survey thus yields much informa- tion of present or future value to engineering. The Survey also conducts many investigations to help solve specific problems met in connection with construction, damage caused by earthquakes, landslides or related GEOLOGY IN THE FIELDS OF ENGINEERING AND PUBLIC HEALTH phenomena, underground testing of nuclear explosives, radioactive waste disposal, and other problems in the field of public health. Results of these studies are described in the following sections. CONSTRUCTION PROBLEMS Most of the Survey’s work on construction problems is intended to provide information that will aid in the design or construction of a specific highway, air- port, dam, or other features. Some of these activities are described here as examples of the use made of geology in construction projects. Damsite location and sewage system construction At the request of the Bureau of Reclamation, Reu- ben Kachadoorian investigated a proposed damsite at Devil Canyon, approximately 125 miles north of Anchorage, Alaska, where the Susitna River flows through a gorge about 600 feet deep and 1,200 feet wide. The foundation of the proposed damsite con- sists of phyllite cut by numerous steeply dipping shear zones that cross the river approximately normal to its course. The proposed spillway site, located about 1,000 feet south of the river, is a V-shaped valley, originally about 85 feet deep, but now filled by outwash overlain by a thin veneer of morainal debris deposited by an advancing glacier. As a re— sult of the study, the proposed damsite was moved 100 feet upstream from its original location to avoid a large shear zone and the spillway site was also relocated to reduce excavation costs. In the Puget Sound area, Washington, which in- cludes Seattle and several nearby communities, geo- logic information developed by H. H. Waldron, D. R. Mullineaux, D. R. Crandell, and L. M. Gard should significantly reduce the cost of constructing a major sewage disposal system. For example, these geol- ogists found that a certain landslide area contains a kame of sand and gravel, and advised that the kame be trenched instead of tunneled as originally planned. Metro engineers estimate that trenching would cost between $100,000 and $200,000 less than tunnelling. The geologists also warned that the valley floor de- posits of the Cedar River probably contain “shoe- string” channel gravels, which might cause heavy flows of water where the trenches intersected them. Since it would be virtually impossible to outline all the gravel-filled channels in advance, the engineers have tentatively decided to spend less than they had intended on exploratory drilling, and to write specifi— cations that allow for additional payment for any channel gravels intersected by the trenches. A19 Highway and bridge construction As a part of a cooperative project with the Massa- chusetts Department of Public Works, the Survey provides geologic information about the sites of pro- posed road cuts. Two examples are typical. The first was connected with plans for a cut 100 feet deep along route 495 in Haverhill. From surface mapping and seismic exploration, C. R. Tuttle and R. N. Oldale found that this cut would be entirely in a drumlin. Seismic velocities and previous experience indicated that the material to be removed was a tough, compact till, diflicult to excavate, and also that it contained a large proportion of silt, so that after excavation it would be subject to massive solifluction. Several borings were therefore recommended to enable the en- gineers to design the slope for maximum stability and minimum maintenance. In the second example a 60-foot cut was proposed for a segment of Route 138 in Fall River. A housing development rested at the top of the planned slope. Preliminary seismic trav- erses showed that the proposed slope would intersect two layers of material that differed in composition and were likely to have different engineering charac— teristics. Drive sample and core borings were made in order to identify the materials in these layers, and thus to obtain information that would be useful in designing a retaining wall. These studies, made in collaboration with the highway engineers, showed that the upper layer contained weathered carbonaceous to graphitic phyllite that would readily slide, so the engineers recommended a gravity wall with a shear key and a benched slope above the wall. Detailed geologic studies by Reuben Kachadoorian and Clyde Wahrhaftig, made at the request of the Bureau of Public Roads, have shown that it is feasi— ble to construct a highway through Nenana Gorge in Central Alaska where numerous landslide areas exist, and have led to several recommendations that would protect both the proposed highway and the present grade of the Alaska Railroad. As an example, one recommendation relates to the construction of a bridge across the Nenana River at Moody, Alaska. The west bank of the gorge is underlain by highly fractured and sheared Birch Creek schist, locally overlain by lake clay beds that are highly susceptible to land sliding. Geologic mapping revealed the presence of a large block of relatively unfractured schist suitable for the support of a bridge foundation and so situated as to be in minimum danger from landslides in the adjacent clay beds. Emergency aircraft landing sites For 5 years W. E. Davies, G. E. Stoertz, and J. H. Hartshorn have been helping the Air Force Cambridge A20 Research Center locate natural emergency landing sites for heavy cargo aircraft in the north polar re- gions. More than 50 sites suitable for the safe land- ing of the largest aircraft have been identified and 2 of the sites have been tested by aircraft landings. Sites selected for testing are on soils ranging from hard packed clay to gravel. The unique combination of the arid climate and permafrost gives rise to an active thaw zone at the surface which, unlike most active zones, has low moisture content and great bear- ing strength. Where such soils are on flat outwash plains, flood plains, former lake or lagoon bottoms, and on river terraces they form natural runways that require very little preparation for use by heavy air- craft. Problems related to permafrost or frost heaving Mapping of the general distribution of permafrost in Alaska, coupled with other geologic studies, has delineated numerous areas in which highway, bridge, or damsite construction and related activity either will not affect the permafrost or where, when thawed, permafrost will not cause destruction or damage to the structure. A direct contribution to engineering has been made by a study of the frost heaving of piles (Péwé and Paige, 1959). Many of the wooden pile bridges on the Alaska Railroad are displaced every year by frost heaving, as are many other structures set on piles. Geologic studies of the several factors that influence frost action led to the discovery of better methods for placing piles. It was shown, for example, that piles firmly anchored in permafrost are rarely dis- placed by frost heave. Moreover, the practice of steam-thawing the holes made for piles delays re- freezing and permits seasonal frost action. In some places it was found necessary to insulate the pile footings to inhibit formation of ice. Some of the principles used in these studies will be applicable to construction work in other parts of the United States where frost penetration is deep. At the request of the Alaska Railroad the Survey examined the foundations of Riley Creek Bridge, near McKinley Park Station, Alaska, to learn the cause of horizontal and vertical movements of the bridge piers. R. Kachadoorian and A. H. Lachenbruch found that the movement was due to the formation of ice lenses beneath the piers as a result of the dissipation of heat more rapidly from the exposed parts of the piers than through the ground surrounding them. They recommended insulating the exposed lateral sur- faces of the piers—a relatively inexpensive solution to the problem. GEOLOGICAL SURVEY RESEARCH lQGO—SYNOPSIS 0F GEOLOGIC RESULTS Analysis of thermal measurements made under build- ings and roadways shows that the minimum thickness of gravel fill necessary to maintain a perennially frozen sub-grade is strongly influenced by the thermal properties of the sub-grade. Except under favorable conditions, the amount of material required to pre- serve permafrost by a single layer of fill is too great for practical use. A theory developed for periodic heat flow in a three—layer medium showed that a thin layer of material with relatively low contact coefficient, such as logs or pumice, placed between the fill and subgrade, would greatly reduce the amount of fill re- quired (Lachenbruch, 1959c). In a cooperative study with the Bureau of Public Roads near Glennallen, Alaska, Green, Lachenbruch, and Brewer (Art. 63) have found that settlement and heaving of roads built on permafrost is caused by the change in the natural heat exchange brought about by the road surface itself. The road surface increases the seasonal range of temperature and hence increases the seasonal depth of thaw. Subsidence results where water from the thawed ground can drain off, and heaving occurs where water, trapped in basins beneath the roadway, refreezes. Problems related to erosion C. A. Kaye is studying the geologic factors that influence the pattern, rate, and mechanics of sea-cliff erosion in New England for the purpose of predicting erosion and recommending control measures. He finds that at Gay Head, on Martha’s Vineyard, Mass, the cliffs of Pleistocene, Tertiary, and Cretaceous sedi— mentary rocks are receding 1 to 5 feet a year, largely by landsliding; but cliffs of compact till at Long Island in Boston Harbor recede only a few inches 8. year; and in hard gabbro along a tidal channel at Nahant, Mass, the rate of abrasion appears to be only a few thousandths of an inch per year. ENGINEERING PROBLEMS RELATED TO BOOK FAILURE The failure of rocks when they are stressed, either naturally or artificially, beyond their elastic limit results in a wide variety of phenomena that affect en- gineering works and other human activities. These phenomena include such things as coal bumps (the bursting of coal seams, part of whose lateral support has been removed in mining), landslides, and earth— quakes that result from failure of large segments of the earth’s crust. Studies of these phenomena that are directly concerned with engineering problems are described here. Results of investigations of rock deformation that have more general application are described on pages A57—A58. GEOLOGY IN THE FIELDS OF ENGINEERING AND PUBLIC HEALTH Coal “bumps” The response of coal and adjacent strata to stresses induced by mining is being studied by Osterwald and Brodsky (Art. 64), in cooperation with the US. Bureau of‘Mines, in the Book Cliffs coal fields of east-central Utah. Surface and underground mapping at the Sunnyside No. 1 mine has shown that the ori- entation, relative to the direction of an adit, of the dominant sets of fractures that existed prior to min- ing determines whether “bumps” are frequent but non— violent or infrequent and violent. This concept is now being applied in actual mining operations. Deformation of rocks by nuclear explosions Surface and underground cracks, faults, and crushed zones produced in bedded volcanic tufl' of the Oak Spring formation by conventional as well as nuclear explosives at the Nevada Test Site are being studied in cooperation with the Atomic Energy Commission to determine their relation to lithology and original structures. The effects of conventional and of nuclear explosives cannot be directly compared at small dis- tances from the charge centers because the volume and mass of ordinary explosives and of their gaseous products are much greater than those of nuclear ex- plosives that liberate an equivalent amount of energy. Farther out, the effects are more easily compared, and in some respects they are similar in kind: for both types the extent of fracturing is assymetric; the strongest displacements commonly follow pre-existing beddingplanes, joint systems, and, faults; and the arrangement of soft and hard tufl' beds affects the transmission of seismic energy (McKeown and Dickey, Art. 190). The maximum radial distance from the explosion chambers of fractures in tufi's of the Oak Spring formation scales empirically as the 0.4 power of the energy yield in tons of the explosion for both nuclear and high-explosive tests (Wilmarth and Mc- Keown, Art. 191). Earthquakes and earthquake-triggered landslides Mass movement, earthquakes, and subsidence are often unrelated to one another, but in some circum- stances they are casually related. Such a relation is strikingly demonstrated by the earthquake that oc- curred on August 17, 1959, Hebgen Lake, Mont. (Wit- kin'd, 1959), which triggered the Madison Canyon landslide—a rockfall avalanche involving some 35 million cubic yards of schist, gneiss, and dolomite (Hadley, 1959a). During this earthquake, an area 27 miles long and 14 miles wide subsided de- tectably. The maximum subsidence was 19 feet and a tract of about 50 square miles dropped more than 10 feet (W. B. Myers, written communication, 1960). 557328 0 - 60 -3 A21 There was almost no elevation above previous levels. The changes of altitude of bench marks as determined by releveling, the tilting of lake shores, and the formation of new fault scarps appear to define a broad basin that plunges gently eastward across the Madison Valley and Madison Range to Hebgen Lake. The subsidence and tilting terminate abruptly northeast of Hebgen Lake, against fault scarps up to 20 feet high, most of which follow faults upon which dis- placement had occurred earlier in Quaternary time. The two major scarps are on faults controlled by the attitude of bedding in Paleozoic rocks,,so the surface fault pattern does not directly indicate the pattern of deep deformation. The rockfall avalanche that occurred at Frank, Alberta, in 1903 was a similar response to earthquake movements, and recent mapping shows that other rockfall avalanches took place in prehistoric times in the seismically active Northern Rockies. For example, M. R. Mudge has found a rockfall avalanche along .the front of the Sawtooth Range in northwestern Montana that involved about 800 million cubic yards of rock. Betty Skipp has found a smaller one in the Maudlow quadrangle, Montana, and W. G. Pierce has identified the natural dam of Deep Lake, Montana, as a rock avalanche that filled the canyon there to a height of about 800 feet. Giant waves that have repeatedly devastated the shores of Lituya Bay, Alaska, have been found by D. J. Miller (1960a, 1960b) to have been caused by earthquake-triggered rockfall avalanches. Such an avalanche plunged into deep water at the head of this T-shaped tidal inlet on July 9, 1958, generating a gravity wave that swept» 7 miles to the mouth of the bay, at a speed of about 100 miles per hour. Trees on the shore of the bay were removed up to a sharp trimline over a total area of 4 square miles and to a maximum height of 1,720 feet, about 4 times greater than the height of any wave swash previously re- ported. Other trimlines record the heights of earlier waves of this kind: one in 1936 reached 490 feet, one about 1874 at least 80 feet, and one in 1853 or 1854, 395 feet. The frequent occurrence of slides causing giant waves in Lituya Bay is attributed to the com- bined effect of recently glaciated steep slopes, highly fractured rocks and deep water in the active fault zone at the head of the bay, heavy rainfall, and fre- quent freezing and thawing. In View of the destruc- tive capacity of these waves and of similar landslide- generated waves in other parts of the world that have been tabulated (Miller, 1960a), it is necessary to con- sider this potential hazard in any future use of Lituya A22 Bay or other lakes and bays that adjoin steep, un- stable slopes in seismically active areas. Other landslides and mudflows In the San Francisco South quadrangle, Bonilla (Art. 66) has mapped and analyzed the origin of landslides as a sample of those that occur in the Cali- fornia Coast Ranges. He finds that 13 of the 16 types recognized in the classification of the Highway Research Board are present in this area; debris slides and earthflows are most numerous, but complex land- slides have affected a greater area. More than one- third of the slides have occurred on slopes of 20° to 25°, and about one-sixth on slopes of about 40°. A preliminary map prepared by McGill (1959) shows all the known active and inactive landslides in the Pacific Palisades area of Los Angeles, where slides have caused considerable damage to houses and inter- ruption of traffic along the Pacific Coast Highway. In the Puget Sound Basin in Washington, D. R. Crandell and others have recognized many previously unidentified volcanic mudflows of Miocene, Pleistocene, and Recent age; one of these, the 60-mile long Osceola mudflow, was previously regarded as a mass of glacial till. In southwestern Colorado, Crandell and D. J. Varnes have found that the Slumgullion earth flow, which is about 5 miles long, is 700 years old, and that its upper half is still active and moving at a maximum rate of 17 to 19 feet per year. SELECTION OF SITES FOR NUCLEAR TESTS AND EVALUATION OF EFFECTS OF UNDERGROUND NUCLEAR EXPLOSIONS Sites for underground nuclear explosions have been selected by the Atomic Energy Commission partly on the basis of studies by the Geologic and Water 'Re— sources Divisions of the Geological Survey (Eckel and others, 1959; Péwé and others, 1959; Kacha- doorian, 1960). These studies have involved geologic mapping and the collecting of relevant facts about the rocks surrounding the point of explosion (Keller, Art. 183). They have also dealt with such problems as containment of the explosions, distribution of the seismic energy liberated by them (Byerly and others, 1960; Diment, Stewart, and Roller, Art. 70), and the extent to which they contaminated water resources (Clebsch and others, 1959). The Survey has also made numerous special studies of the geologic and hydrologic effects of contained underground detona- tions of both nuclear and conventional explosives. Some of the results of these studies are summarized here. GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS Project Chariot Project Chariot, which is a part of the Atomic Energy Commission’s Plowshare Program, is a pro- posed experiment to determine whether harbors can be excavated by means of nuclear explosives. The Chariot site, on the northwest coast of Alaska near the mouth of Ogotoruk Creek (Kachadoorian and others, 1959 and 1960), was selected by the Commis- sion after it had considered other possible sites (Péwé, Hopkins, and Lachenbruch, 1959). Geologic mapping and other studies undertaken to plan the experiment and evaluate its affects show that the rocks of the Ogotoruk Creek area are folded and slightly meta- morphosed sandstone, limestone, chert, argillite, mud— stone, siltstone, and graywacke of Early Mississippian (Campbell, Art. 156) to Cretaceous age. The material to be excavated is largely mudstone, siltstone, and sandstone of the Tiglukpuk formation of Late Juras- sic age. Permafrost in the vicinity of the site extends 800 to 1,200 feet below the surface, and all material to be excavated is in the permafrost zone. The moisture content of the rock is estimated to be about 10 percent. Seismic refraction measurements indicate velocities from 11,500 to 14,500 fps, averaging about 13,500 fps. There may be a layer between the depths of 1,000 to 1,750 feet in which the velocity is higher. The beach at the Chariot site is in a steady-state condition. During ice-free periods the beach sediments are normally transported southeastward along the shore at the rate of about five cubic yards an hour. During heavy storms, however, the rate may exceed 1,000 cubic yards an hour, so that jetties may be re- quired to protect the harbor channel from the material moved during storms. Unconsolidated material at the site contains shallow aquifers, which during the summer depend upon recharge from surface water. Deep aquifers that re- ceive water from distant sources are present at the site. The volume of suspended sediment that will be carried into the harbor by Ogotoruk Creek is very small compared with the size of the proposed excava- tion. During the winter season (mid-October to mid— May) Ogotoruk Creek is frozen and its flow is negli- gible. Project Gnome Project Gnome, also part of the Plowshare Program, is a proposed experiment to determine whether ther- mal energy and valuable isotopes can be recovered from a nuclear explosion completely contained within a homogeneous salt medium. The explosion will be set off near Carlsbad, Eddy County, N. Mex., 1,200 feet below the surface, in thick salt beds of the Salado GEOLOGY IN THE FIELDS OF ENGINEERING formation. Surface and subsurface geologic mapping and other studies made to plan and evaluate this ex- periment show that in the vicinity of the Gnome site, gravel, sand, and silt» of Quaternary age overlie evapo- rites, sandstone, limestone, dolomite, and redbeds of Triassic and late Permian age (Vine, 1960b). The Permian evaporite sequence consists, in ascending or- der, of the Castile, Salado, and Rustler formations (Moore, 1959a; C. L. Jones, 1960; Baltz, 1960). No water is known to be moving through the salt of the Salado formation, but there are extensive aquifers, some of which contain brine, in the Salado and Rustler residuum, in the Rustler formation, in the Triassic rocks, and in the unconsolidated Quaternary deposits (Hale and Clebsch, 1959). Early in 1959 three scaling shots, using 190, 760, and 6,250 pounds of high explosive, were detonated at the Gnome site 1,200 feet below the surface to provide data for calculating motion at various dis— tances from a 9 kiloton (KT) explosion (Roller and others, 1959). The seismic waves generated from these tests and from six routine mine blasts in the Duval Sulphur and Potash Company mine were recorded at the surface at distances of 0.45, 1.8, 3.9, and 9.7 miles from ground zero. Byerly and others (1960) have calculated from these data that the particle displace- ment, velocity, and acceleration produced in the potash mines near Carlsbad by a 9 KT explosion of TNT at the Gnome site—a distance of 46,000 feet from the nearest potash mine—would not exceed: Displacement _______________ 0.1 _0,2 cm Velocity ____________________ 1.5 —3.0 cm per sec at 2 cps 2.5 —5.0 cm per sec at 4 cps Acceleration ________________ 0.02—0.04 g at 2 cps 0.06—0.12 g at 4 cps These motions are less than those recorded at a distance of 90 feet from a routine 75-pound dynamite blast in a potash mine. Nevada Test Site The Nevada Test Site is the continental testing fa- cility of the Atomic Energy Commission where per- formance of nuclear explosives has been studied during past test operations and where experimental nuclear reactors are being studied. The Geological Survey advises the Commission on three essential points— selection of sites for contained underground tests, seismic effects both on and off the test site (Diment, Stewart, and Roller, Art. 70), and ground-water con- tamination problems (Clebsch and others, 1959). In carrying out these responsibilities, extensive surface and underground geologic mapping (Wilmarth and McKeown, Art. 191), geophysical surveys (Diment, Healey, and Roller, Art. 69), and hydrologic studies AND PUBLIC HEALTH A23 have been conducted both before and after explosions, and have been correlated with numerous measurements of chemical, petrographic, mineralogic, and physical properties (Wilmarth, Botinelly, and Wilcox, Art. 67). All contained underground tests of conventional and nuclear explosives have been in the bedded volcanic tufi' of the Oak Spring formation, which is several thousand feet thick, relatively uniform, and easily tunneled (Keller, Art. 183). The Rainier underground nuclear explosion was equivalent to 1.7 KT of con- ventional explosives, and was at a depth of 900 feet below the surface. The explosion formed a breccia zone 140 feet in diameter in the horizontal plane. The breccia contains radioactive glass, angular to subrounded phenocrysts, and xenoliths 0.3 to 3 feet across in a fine—grained matrix of comminuted tufl’. The matrix is characterized by an abundance of hairline fractures, which generally do not cross the phenocrysts or xenoliths, thus indicating that most of the deformation was taken up by the soft matrix. The glass and the radioactivity are mostly confined to the breccia zone, and gamma radiation surveys of the drill holes and mapping in the exploratory tunnel driven after the explosions have shown that they are very irregularly distributed (Bunker, Diment, and Wilmarth, Art. 68). Most of the radioactivity is several tens of feet below and to the northwest of the point of detonation. Fracturing both in the Rainier tunnel and on the surface, and spalling in the tunnel were observed at considerable distances outside the breccia zone. The tunnel collapsed to a distance of 200 feet from the explosion chamber. Severe spalling occurred in the tunnel at distances of 200 to 400 feet, and several new fractures were produced at distances. as great as 1,100 feet. Four inches of movement were observed on a pre-existing fault 1,400 feet from the explosion. The only surface efl’ects were small fractures, largely along pre-explosion joints, and rock falls along the steep topographic scarp beneath which the explosion was detonated (Wilmarth and McKeown, Art. 191). As a result of the Rainier explosion, the rocks adja- cent to the chamber were brecciated. Their porosity increased about 30 percent, and their permeability increased an undetermined amount, while the percent- age of water saturation decreased about 30 percent, the acoustic velocity about 70 percent, and the com- pressive strength more than 50 percent. The decrease in water saturation is approximately equal to the in- crease in porosity, which suggests that little water was driven out by the explosion. The rocks surrounding the breccia zone, out to about 110 feet from the explo- sion, are highly fractured and have low compressive A24 strength, low dilatational velocities, and high per- meability. The hydrologic effects of the Rainier, Logan, and Blanca underground nuclear explosions are due to changes in rock characteristics that directly or in- directly control (a) volume of water in storage, (b) rate and direction of ground—water movement, and (0) chemical and radiochemical equilibrium between the rock and its contained water. The radius of effect is small compared to the probable extent of the perched water zones below each explosion. Water samples from the zone affected by the Logan explosion, to- gether with leaching experiments on slightly radio— active rock from near the Rainier explosion, indicate that some radioisotopes are taken into solution by percolating ground water. Movement of contamina— tion from the nuclear explosions would probably be retarded by a slow rate of groundwater movement, low solubility of the explosion-produced glass containing most of the radioisotopes, and ion exchange of radio- isotopes between ground water and rocks. The position and movement of ground water may be partly controlled by the configuration of the buried Paleozoic bedrock surface under Yucca Valley, where the water table is about 1,500 feet below the surface (Diment, Healey, and Roller, 1959). Gravity and seismic data indicate that the alluvium and tufi' over- lying the bedrock are thickest in a narrow north— trending trough in the eastern part of Yucca Valley, and that they are there more than 3,500 feet thick. A series of gravity highs, bordering the trough on the west, together with refraction seismic measurements, indicate a buried bedrock ridge whose top is locally within 100 feet of the surface, and two drill holes have confirmed this. Gravity, seismic, and magnetic surveys have helped define the configuration. of the buried Paleozoic bed- rock surface under Yucca Valley. This surface may partly control the position and movement of ground water (Diment, Healey, and Roller, 1959). RADIOACTIVE WASTE DISPOSAL INVESTIGATIONS Studies by the Geologic Division bearing on the dis- posal of radioactive wastes deal with the physical chemistry of ion exchange, specific sorption of stron- tium or cesium by certain minerals, and ion exchange and other properties of soils and rocks near reactor sites. In addition, wells or drill holes at radioactive waste disposal sites are being studied by gamma-ray logging techniques. Geologic information is being compiled on sedimentary basins that might be suitable for underground storage of radioactive liquids. Other GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS investigations of waste disposal are being undertaken by the Water Resources Division of the Geological Sur— vey, but these are not reported here. Geochemical studies The ion—exchange (or scavenging) properties of crandallite (CaAlg(PO4)2(OH)5H20) with respect to strontium were investigated by Irving May during the past year. Strontium solutions “spiked” with radioactive Sr89 were passed through columns of crandallite and crandallite-sand mixtures, to determine the effects of Sr concentration, pH, temperature of the influent solution, and the texture (mixture with sand) of the column packing. Crandallite was found to sorb strontium fairly readily from solutions more basic than pH 5. Studies of the ion-exchange characteristics of Ameri— can and South African vermiculites made by C. R. N aeser and Marian Schnepfe (Art. 71) show that ver- miculite sorbs cesium and holds it firmly at pH values above 3. This reaction is reversed when pH values are less than 1. Aluminum causes virtually no inter- ference in sodium-saturated vermiculite at pH 12.6. Hydrogen forms of montmorillonite were titrated with NaOH as a part of a general study by Dorothy Carroll and A. M. Pommer (Arts. 198 and 199) of the mechanisms of ion exchange. The potentiometric titrations gave strong evidence that the ions are placed in the octahedral and tetrahedral positions of the layered structures. Similar studies were extended to “illite,” kaolinite, halloysite, and NH4—saturated ver- miculite. Information on ion exchange and related character- istics of the soils and near—surface bed rocks of the Oak Ridge, Tennessee area, compiled by Dorothy Carroll, indicate that the ion-exchange capacities of soils derived from the limestones, shales, and sand- stones of Cambrian and Ordovician age range from 3 to 15 meq per 100 g, and those of the rocks from which the soils were derived from 5 to 28 meq per 100 g. Most of the ion—exchange capacity of these soils is due to vermiculite, “illite,” and kaolinite. Clarence S. Ross has identified the cause of localiza- tion of a radioactive material in Bandelier rhyolite tufl’ of Smith (1937) that had been treated with liquid waste. He found by a combined petrographic, auto- radiographic technique that the small areas of higher radioactivity were not in the original constituents of the tufi' but in materials that had been picked up by the tuffs. Fragments of these alien materials had been oxidized and limonite had formed within or around them. GEOLOGY IN THE FIELDS OF ENGINEERING AND PUBLIC HEALTH Sedimentary basin studies Storage or disposal of radioactive wastes at depth in salt deposits and permeable beds in deep sedimen- tary basins is considered potentially feasible. In the San Juan Basin, according to C. A. Repen- ning (1959), there are four types of reservoir rocks that might be used for storage of wastes: gypsum, limestone, shale, and sandstone. Gypsum appears to be most useful for disposal of sintered waste. Lime— stone could be suitable for storage of liquid waste, but may prove to be leaky. Shale, in which reservoirs could be constructed by hydraulic fracturing or deep- seated explosions, would be relatively leak-proof. Sandstone would have the advantage in respect to heat control. As a result of an analysis of the geology of the Cen- tral Valley of California, Repenning concludes that the eastern side, as far south as Fresno, appears to be the most promising area for the selection of a waste- disposal site. South of the Stockton arch, sandstone beds tongue out westward into impermeable shale units; in some places along the eastern side of the valley they are warped upward and are truncated and sealed by younger shale. North of the arch the west- ward—thinning sandstone tongues are less abundant and have not been warped and truncated. A study of hydrologic conditions might reveal places where east- ward migration would be slow enough to stay within safe limits. Geophysical studies Carl Bunker, using newly modified and calibrated instruments, has made gamma—ray logs of drill holes at the Nevada Test Site before and after injection of radioisotopes. His results show little horizontal or lateral leakage of the injected radioisotopes into the surrounding rock from a specially designed and in- stalled tile field. The radioactivity was too weak to enable him to make gamma-ray spectral measurements of the waste. Two models of pressure apparatus have been built by E. C. Robertson and R. Raspet to test cylindrical rock samples under biaxial loading by applying pres- sure hydrostatically to the sides but not the ends of the sample. Biaxial tests show the actual, higher strength and elasticity of rock in place and give more uniform numerical results than the more commonly used uni- axial tests. They thus help to measure the physical properties of host rocks for radioactive wastedisposal in natural environments—properties that determine, for example, the host rock’s ability to confine wastes under the elevated pressures and temperatures that may develop after injection of radioactive materials. A25 MEASUREMENT or BACKGROUND RADIATION Owing to the increased use of nuclear power and processing facilities, and to the proposed use of nu- clear energy for harbor construction and other ex- perimental purposes, it has become necessary as a precautionary measure to determine the natural back— ground radioactivity in the many areas. In July, 1958 the Geological Survey, on behalf of the US. Atomic Energy Commission, began a nationwide pro- gram of aerial radiological monitoring surveys (ARMS). The purpose of the program is to obtain data for appraising changes in environmental levels of radiation brought about by nuclear testing pro- grams, by operation of reactors and other nuclear fa- cilities, and by radiation accidents. Most of the ARMS work has consisted of surveying the area extending about 50 miles outward from the center of several reactor and major production facilities. Be- tween July 1958 and January 1960 about 96,000 trav- erse miles were flown, surveying about 110,000 square miles in 11 areas in the United States. Some of the results of ARMS surveys that are of interest in area] geology are described on pages A29, A31—A33, and A42. DISTRIBUTION OF ELEMENTS AS RELATED TO HEALTH Although medical researchers have long been study- ing the physiological effects of a few elements in the geologic environment—iodine, selenium, and fluorine, for example—the work done hitherto in this general field has not been extensive, and few geologic studies have been undertaken for the specific purpose of analyzing such problems. One such study, however, was begun in 1956 in Washington County, Maryland, on behalf of the National Cancer Institute, which, in cooperation with the Washington County Health De- partment, is making an intensive study to relate en— vironmental conditions to incidence of cancer. The geologic part of this study consisted of aerial and ground radioactivity surveys to measure gamma-radia- tion intensities emitted by various rocks, and of bo- tanical and geochemical studies to learn whether the soils and plants contain excesses or deficiencies of elements that might be related to the incidence of cancer. These surveys show relatively small but dis- tinct local differences in radiation intensity that can be correlated with the geology, and an unusual dis- tribution of elements that appears to be related to soil type. Some soils, for example, apparently contain unusually large amounts of titanium, chromium, and lead, and unusually small amounts of iron, zinc, and barium. Nitrates, also, are highly concentrated in A26 some of the ground water and vegetation. The sig- nificance of these findings with respect to cancer incidence is being assessed by the National Cancer Institute. During the past year, Fleischer and Robinson sum- marized for the US. Public Health Service the avail- able data on the geochemistry of fluorine. Of special interest is a map they have prepared showing the maximum reported fluorine content of ground water in each county of the United States. These range from less than 0.1 to 38 ppm. Waters containing more than 1.5 ppm F are generally considered to cause mottling of teeth; such waters occur in more than half the counties of the United States. Recent work by H. A. Powers suggests that in many western and central States there is a connection between high— fluorine waters and the distribution of volcanic ash, which averages about 1100 ppm F. Attention should be called to the fact that extensive data on the chemical composition of rocks, minerals, and waters are already available and could serve as the basis for other studies of the physiologic effects or hazards of the distribution of elements. Aluminum, sodium, and manganese are among the elements most susceptible to neutron-induced radio- activity resulting from use of nuclear weapons or devices. At the request of the US. Army Corps of Engineers, Burns (Art. 73), has examined means of predicting geographic variations in the, content of these elements in rocks when direct sampling is im— practicable. As a first step, he has defined the range in the content of aluminum, sodium, and manganese in several groups of common rocks. The results in- dicate that the aluminum and sodium content of rocks of igneous origin can be predicted from simple lith- ologic descriptions with at least 80 percent probability of correctness within a factor of 2. Predictions of the manganese content of these rocks, and of the sodium and aluminum of rocks of sedimentary origin, would be of intermediate reliability. Predictions of manganese in rocks of sedimentary origin would have only a low degree of reliability—at least 70 percent probability of correctness within a factor of ,5. An interesting by-product of one of the Survey’s investigations came as the result of Frank Senftle’s development of a sensitive device to measure magnetic susceptibility in rocks (see p. A56). Using this in- strument, he has made magnetic measurements on cancerous tissue specimens for the National Cancer Institute. Two rats of the same species were selected for the experiments. A cancer was induced in one of the animals and was allowed to grow for about four weeks. Before the cancer was allowed to affect GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS the normal activity of this animal, the livers of both animals were removed, together with some of the cancerous tissue. These materials were then immedi- ately quick-frozen in liquid nitrogen to prevent decay of the cells. Magnetic measurements were then made at liquid-nitrogen temperatures to preserve the sam- ples throughout the measuring period and also to enhance, if possible, their magnetic susceptibility. The liver from the cancerous rat showed a definite ferro- magnetic effect, while that from the normal rat showed none. The cancerous tissue itself, however, is non- ferromagnetic and is more diamagnetic than the healthy tissue, which seems to indicate a depletion of iron. REGIONAL GEOLOGY The field studies described in the preceding pages are undertaken to solve known problems of economic importance, but most of the Geologic Division’s field work has the broader purpose of defining the com— position, structure, history, and origin of the rocks that compose the earth’s crust in the United States. It is these studies that often provide the first clue to the location of new mineral districts, that make it possible to search intelligently for concealed deposits and appraise the potential mineral resources of vari- ous parts of the country, and that provide background information useful in choosing construction and test sites and in planning new highways and other en— gineering works. The chief method used by the Survey to achieve these objectives is geologic mapping, mostly on scales of 124,000, 1:62,500, and 1:250,000. Regional geo— physical, geochemical, stratigraphic, and paleontologic studies, however, also play an important part. Some of the important results obtained during fiscal 1960 in this program are described in the following pages for the country as a whole and for its major regions (see fig. 1). SYNTHESIS OF GEOLOGIC DATA ON MAPS 0F LARGE REGIONS Utilizing information generously furnished by State surveys, private companies, and universities as well as its own data, the Geological Survey compiles and publishes several kinds of maps on a national or larger scale. It also collaborates with scientific socie- ties in preparing, and sometimes publishing, maps of this type. Several such maps, described below, reached advanced stages of compilation or were completed during the year. Others in progress include: 1. Geologic map of North America, scale 125,000,- 000. This map is being compiled by a committee of GEOLOGY OF THE UNITED STATES A27 FIGURE 1.—Index map of the United States, exclusive of Alaska and Hawaii, showing the boundaries of regions referred to on pages A28—A44. the Geological Society of America, E. N. Goddard, University of Michigan, Chairman. 2. Basement rock map of North America from 20° to 60° N. latitude, scale 1:5,000,000. This map is be- ing compiled by a committee of the American Asso- ciation of Petroleum Geologists, P. T. Flawn, Uni- versity of Texas, Bureau of Economic Geology, Chair- man. 3. Coal fields of the United States, by James Trum- bull. Scale 115,000,000. 4. Mineral distribution maps, scale 122,500,000. Compiled, under the direction of P. W. Guild and T. P. Thayer, for 34 metals and industrial minerals. 5. Paleotectonic maps of the Pennsylvanian system, by E. D. McKee and others. 6. Absolute gravity map of the United States, scale 1 :2,500,000. This map is being compiled by the Amer- ican Geophysical Union Committee for Geophysical and Geological Study of the Continents, G. P. VVool- lard, University of Wisconsin, Chairman. Tectonic map of the United States A new tectonic map of the United States’, exclusive .of Alaska and Hawaii, on a scale 12,500,000 is nearly completed. It was prepared as a joint undertaking by the American Association of Petroleum Geologists and the Geological Survey under the direction of G. V. Cohee and replaces the tectonic map published by the Association in 1944. Two examples will suggest the scope of advances since the previous version. Struc- ture in thousands of square miles in the Pacific Coast states, the Great Basin, the Lake Superior region, and northern New England that, for lack of information, had to be omitted or sketched diagrammatically in 1944, is now reasonably well portrayed. Buried struc- tures in such areas as the Colorado Plateau, the Mid- Continent region, and the Appalachian basin, which in 1944 had to be contoured piecemeal and on as many as four datum. surfaces, are each now contoured on a single datum. Paleotectonic maps of the Triassic and Permian systems The long-term program for preparing paleotectonic maps of each of the systems has been underway since 1953. The first folio, on the Jurassic system, was pub- lished in 1956. The second, on the Triassic, was is- sued in 1960 (McKee and others); a few of the con-- A28 clusions from this study may be mentioned to indicate its scope. In Early Triassic time a miogeosyncline extended from southern California through the eastern Great Basin into western Wyoming. East of the miogeo- syncline, normal marine shelf deposits are well repre- sented; evidence for a eugeosyncline west of the mio— geosyncline is lacking. During Middle and Late Triassic time, on the other hand, a eugeosyncline be- came established in the Cordilleran region; the area bordering the major marine depositional trough on the east was uplifted, and numerous elliptical basins were filled with continental sediments of Late Triassic age. In eastern United States several large struc- tural troughs developed. Maps and text for the Permian system were com- pleted by E. D. McKee and others in 1960 and are now in review. Major tectonic elements evident from this study include a prominent eugeosyncline in the western Cordillera during much of Permian time. An adjacent miogeosyncline on the east was separated from the eugeosyncline by a narrow belt of intermit- tently positive areas in central Nevada and northern Idaho; ocean currents flowing southward along the miogeosynclinal belt furnished upwelling cold waters along its eastern margin from which were deposited phosphorite, chert, and carbonate in western Wyo- ming and adjacent states. Much of the Western Inte- rior during Permian time, from the Dakotas to Texas, was a relatively stable shelf on which warm marine to supersaline waters deposited red beds, extensive carbonate beds, and, in isolated basins, thick evaporite sequences. The southernmost part of the shelf, how- ever, passed abruptly into deep marine basins and embayments in Texas and New Mexico; thick bio- stromal and reef limestones were deposited along the margins of these basins. The shelf was bordered on the east and north by broad, low to moderately high positive areas. The moderately high ancestral Rocky Mountains and Uncompaghre Uplift were active in Colorado and shed coarse detritus. Along the south— ern margin of the country, tectonic activity of the Ouachita orogenic belt, greatest during Pennsylva- nian time, continued into early Permian time and con- tributed to the thick detrital sequence present in the Val Verde trough. In the eastern United States only lowest Permian rocks are now preserved in the Dun- kard basin, where drainage was to the northeast, rather than to the west as it had been in Pennsyl— vanian time. Epigenetic uranium deposits in the United States Three maps, on a scale of 1:5,000,000 have been published recently showing the distribution of epigene- GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS tic uranium deposits in relation to a) continental sedi- mentary rocks, b) pre-Late Cretaceous crystalline rocks, and c) Late Cretaceous and younger igneous rocks (Finch and others, 1959; see also p. A11). NEW ENGLAND AND EASTERN NEW YORK Major geologic mapping programs are underway in cooperation with the Commonwealth of Massachusetts, and the States of Rhode Island, and Connecticut, and field studies related to investigations of mineral deposits are in progress in Maine, Vermont, and eastern New York. Some of the findings of these studies that con- tribute to knowledge of the regional geology are de- scribed below (see p. A6 for information on talc, and asbestos deposits and p. A67 for information on re- gional metamorphism). Regional geologic mapping A geologic map of north-central Vermont compiled by W. M. Cady covers an area of about 1,800 square miles that straddles the axis of the north-trending Green Mountain anticlinorium, and includes the zone of lateral transition from rocks of carbonate-quartz- ite assemblage, in the Cambrian of the Champlain Valley, to metamorphic rocks originally of graywacke- shale assemblage, in the Cambrian in and east of the Green Mountains. A. J. Boucot and others (1960) have compiled a map of an area of 12,000 square miles in northern Maine. This map includes the Moose River syn- clinorium and shows the distribution of rocks of Cam- brian through Devonian age; it includes a compila- tion of aeromagnetic surveys. P. M. Hanshaw and P. R. Barnett (Art. 76) have found that volcanic units in the Triassic of Connec- ticut contain more boron than do the intrusive rocks and that their chromium and nickel contents are use- ful in identifying individual basalts in mapping. Stratigraphic and lithofacies studies in Vermont and Maine Cady (1960), collaborating with P. H. Osberg of the University of Maine, has made a stratigraphic correlation between the unmetamorphosed rocks of the miogeosynclinal zone west of the Green Mountains and the metamorphosed rocks in the eugeosynclinal zone farther east on the basis of a few distinctive lithologic units in the graywacke-shale assemblage (Cady, 1960, p. 548). The stratigraphic succession in northern Maine has been established chiefly through the studies of A. J. Boucot in and near the Moose River synclinorium, which contains about 10,000 feet of upper Lower Devonian strata, chiefly dark sandstone and slate with subordinate amounts of rhyolite. These are underlain GEOLOGY OF THE UNITED STATES on the flanks of the synclinorium by ancient erosional remnants of Cambrian through lower Lower Devonian formations. The Cambrian and Ordovician rocks are chiefly slate and graywacke but are interbedded with volcanic rocks of various kinds and unknown thick- ness. Some of the granitic rocks in this area are also Ordovician (Neuman, Art. 74). The Silurian and lowest Devonian rocks, which are as much as 4,000 feet thick, consist of calcareous sandstone and silt- stone, arkose and arkosic conglomerate, and limestone and limestone conglomerate. Rocks west and south- west of Jackman, along the international boundary, that had previously been assigned to the Cambrian or Ordovician or both, have been found by A. L. Albee to rest on an unconformity that is older than Late Silurian age. These rocks are intruded by in- trusive rhyolitic rocks of Early Devonian age and by granitic rocks that are younger than Early Devonian. Tectonic studies in Connecticut and Vermont C. E. Fritts has found a fault contact along the western boundary of the Triassic rocks of the Con- necticut Valley, where an east-dipping “pre-Triassic peneplain” was mapped by W. M. Davis. The relief on the “pre-Triassic” surface is as much as 1,000 feet in a horizontal distance of 1 mile, which supports the growing belief that Davis’ interpretation was incor- rect. Restored sections constructed transverse to the belt of early and middle Paleozoic rocks of the Appa- lachian geosyncline in northern Vermont show east- ward ofl’lap of both the graywacke-shale assemblage and volcanic rocks. The western margin of the lon- gitudinal zone of greatest mobility (eugeosynclinal zone) must therefore have moved eastward across the geosyncline (Cady, 1960, p. 557, pl. 2). This infer- ence is confirmed by the ultramafic rocks, which are of Ordovician age in the western part of the geo- synclinal belt, but which include some younger than Ordovician in the eastern part. Geophysical surveys Aerial radiological surveys in southern New Eng- land and adjacent parts of New York show a good correlation between radioactivity and bedrock ge- ology. According to Peter Popenoe, the highest radio- activity was recorded over the Hudson Highlands in New York, the Hartland formation south of Water- bury, Connecticut, granitic gneisses in Connecticut and Rhode Island, and the cores of gneiss-capped domes in Connecticut. Much aeromagnetic mapping has been done in the Adirondack Mountains of New York (where, accord- ing to J. R. Balsley, seven iron ore deposits have been A29 discovered by aeromagnetic surveys), New Hampshire, and northern Maine. In Maine, the aeromagnetic data are a valuable aid in geologic mapping, for the major geologic units there have different magnetic properties. For ex- ample the magnetic susceptibility of argillite, slate, and sandstone is usually negligible; that of granite, rhyolite, and pyrrhotitic slate is usually less than 1X10'3 cgs; and that of diorite, diabase, greenstone, gabbro, and serpentine is generally greater than 1X10‘3 cgs (Allingham, Art. 54). Electromagnetic methods are also being used in Maine for mapping structure in areas that contain conductive shales (gen- erally graphitic or pyritic) (Frischknecht and Ekren, Art. 56). Ages of intrusions in the northern Appalachians Potassium-argon and rubidium-strontium age stud- ies by H. Faul in cooperation with a number of other geologists indicate that there were at least six distinct cycles of intrusion (or metamorphism) in the north- ern Appalachians, tentatively dated as follows: Millions of years ago 460 Represented in Maine by a single body of gabbro south of Katahdin. 400 Recorded in the granites of the Chiputneticook Lakes, the Calais area, Mt. Desert Island and Vinalhaven. 360 Encountered in a widespread network of samples from New England, Nova Scotia and the mid-Atlantic states. 310 Represented by still fragmentary data from the New Hampshire magma series and the pegmatites of southern Vermont and New Hampshire. 260 Connecticut pegmatites. 190 White Mountain magma series. If the episodic character of these events in the north- ern Appalachians can be clearly established and cor— related, the information should increase understanding of the tectonic history of the eastern margins of the North American continent. THE APPALACHIANS Geologic work in the Appalachian region is in prog- ress in several areas in the Valley and Ridge, Blue Ridge, and Piedmont provinces. Salient results of current studies are as follows: Stratigraphic and geomorphic studies in the Valley and Ridge province The surface of unconformity that separates Lower and Middle Ordovician rocks in southwestern Vir- ginia and eastern Tennessee has been found by Har- ris (Art. 83) to have as much as 170 feet of relief. Studies in progress by Helmuth Wedow, Jr., in the Tennessee zinc districts suggest that solution chan- A30 nels below this unconformity are controlled by pre- Middle Ordovician structures and that the uncon— formity is one of minor discordance. Englund and Smith have found that Lower Penn— sylvanian strata in the basal beds of the Lee forma— tion and Upper Mississippian beds of the Pennington formation intertongue in eastern Kentucky and south- western Virginia. This suggests that the faunas of Late Mississippian age (Chester) and the floras of Early Pennsylvanian age (Pottsville) overlap and are partial time equivalents. Similar intertonguing of Upper Mississippian and Lower Pennsylvanian strata has been found in the Anthracite region of eastern Pennsylvania. Hack and Young (1959) have demonstrated that the intrenched meanders of the North Fork of the Shenandoah River are caused by strong planar and prismatic structures in the Martinsburg shale that favor northwest-southeast differential erosion. These meanders indicate long-continued deep erosion in the Valley and Ridge province instead of the multiple erosion cycles widely assumed heretofore (see also p. A55). Structural studies in eastern Pennsylvania and New Jersey Structural studies in the valley of the Delaware River of New Jersey and eastern Pennsylvania by Drake and others (Art. 80) show that at many locali— ties Paleozoic rocks are separated from Precambrian rocks by decollements. Arndt and Wood (Art. 81) have recognized five structural stages in the Appalachian orogeny in the Anthracite region of eastern Pennsylvania. They in— fer from the southeastward increase in structural com- plexity of the Valley and Ridge province that the orogeny progressed northwestwardly across the region. If this is true, the Appalachian orogeny probably was progressive elsewhere, for structural complexity in- creases southeastward throughout the Valley and Ridge, Blue Ridge, and Piedmont provinces. Geologic results of aeromagnetic surveys Aeromagnetic surveys made in cooperation with the Pennsylvania Topographic and Geologic Survey have traced local magnetic facies in the metamorphic and igneous rocks of the Piedmont between outcrops, un— der heavy soil, under less magnetic metamorphic rocks, and under Cambrian, Ordovician, and Triassic sedi- mentary rocks. In the vicinity of Allentown, Penn- sylvania, the magnetic data indicate that the Precam- brian rocks exposed at some localities do not extend to great depth (Bromery, 1959). Near Buckingham, about 25 miles southeast of Allentown, the magnetic data show that the Triassic basin is only 7,000 feet GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS deep—considerably less than previously thought (Zietz and Gray, Art. 78). Aeromagnetic anomalies in southwestern Virginia and eastern Tennessee indicate that depth to basement increases southeastward and averages about 17,000 feet (King and Zietz, Art. 88). Geologic mapping in North and South Carolina Overstreet and Bell (Art. 87) have found a belt of low-rank metasedimentary and metavolcanic rocks ex- tending across South Carolina into Georgia that is probably equivalent to the Kings Mountain belt far— ther northeast. They also found several small granite plutons of uncertain age in the eastern Piedmont, where earlier maps showed batholiths elongated north- eastward. Similar granite bodies have been found in the Concord quadrangle of North Carolina by geo- logic mapping (Bell, Art. 84), supported by aero- magnetic and aeroradiometric surveying (Johnson and Bates, Art. 85). Within this quadrangle is a large circular intrusion which was formerly thought to be a ring—dike but has now been found to consist at the surface of two disconnected masses of syenite that partly enclose a mass of gabbroic rocks. Overstreet and Bell (Art. 87) have discovered other similar cir- cular and ring-shaped intrusions of syenite(?) and gabbro in western South Carolina. Two distinct pe- riods of mineralization have been recognized in the Concord area (Bell, Art. 84): the earlier one, asso- ciated with the granite plutons, deposited chiefly gold, tungsten and base metals, and the later one, related to the syenite-gabbro complex, chiefly zinc. In the so-called “slate belt” of the North Carolina Piedmont, A. A. Stromquist, who is mapping the Denton quadrangle, and J. F. Conley of the North Carolina Division of Mineral Resources, who is map- ping the adjacent Albermarle quadrangle, have for the first time established a stratigraphic sequence for the “volcanic slates” (Stromquist and Conley, 1959). A major unconformity separates an upper volcanic unit from an underlying more folded volcanic and sedimentary unit of higher metamorphic grade. In the Grandfather Mountain area of North Caro— lina, detailed quadrangle mapping by Bryant and Reed (1959) shows this area to be a window in an overriding plate of crystalline rocks. The window exposes not only the basement rocks, but also the Chilhowee group of Early Cambrian and Cambrian( ?) age, and the Ocoee group, of Precambrian age. Le- sure’s (1959) studies west of this area indicate that the mica pegmatites of the Spruce Pine district were emplaced before the thrusting. East of the window Reed and Bryant (Art. 86) have found a belt of retro- gressively metamorphosed rocks along a topographic GEOLOGY OF THE UNITED STATES lineament in line with the Brevard belt of low-grade metasediments to the southwest. The lineament ap- pears to mark a major fault of undetermined nature, which separates the rocks of the Inner Piedmont from those of the Blue Ridge. ATLANTIC COASTAL PLAIN Because the bedrock of the Atlantic Coastal Plain is poorly exposed, geophysical methods are especially useful there, and most of the new information on the geology of the Coastal Plain stems from their use. Results that add to our understanding of the geology of the coastal plain are described below. Information on clay and phosphate deposits is given on page A7. Interpretation of aeromagnetic measurements on the Atlantic Continental shelf and in Florida Aeromagnetic profiles over the continental shelf and continental slope between Bermuda and the east coast of North America, flown in cooperation with the Of- fice of Naval Research, and a set of six 400-mile pro- files southeast of Chincoteague Bay, Maryland, show a prominent and more or less continuous magnetic anomaly of 300 to 500 gammas parallel to the outer edge of the continental shelf (King and others, 1960). Large gravity anomalies of comparable width have been observed in the same area by the Lamont Geo- logical Observatory, but these can be accounted for by crustal thinning and may be only indirectly related to the magnetic anomaly. A basement ridge also parallels the outer edge of the continental shelf, ac- cording to Lamont seismic data, but calculations Show that the basement rocks must have a higher-than— average susceptibility to produce a magnetic anom- aly of the observed size from topography alone. Therefore the anomaly may be at least partly the ex- pression of a mass or series of masses of more mag- netic rock, perhaps intrusives, along the outer edge of the continental shelf. Estimates of depth to basement made from aeromagnetic data at selected points on the profiles agree well with depths previously found from seismic measurements. A regional magnetic map of Florida recently com- piled by King (1959a) indicates that, beneath the sedimentary rocks of the Coastal Plain, Florida is divided into two tectonic provinces, separated by a zone of intrusive rocks. The northern province, in the northeastern part of the State, has well-defined northeasterly magnetic trends parallel to those of the Appalachian system, whereas the southern province is characterized by northwesterly trends. The southern province appears to be a continuation of the Ouachita system, which has been traced by other means he- A31 neath the Gulf Coastal Plain to within 60 miles of the subsurface extension of the Appalachian system in Mississippi, where the two systems also appear to be discordant. Depth estimates from Florida aero- magnetic data suggest that faulting may be a factor in the profound downwarp and accumulation of sedi- ments in the southern province. The zone of intru- sive rocks inferred from the magnetic map checks well with the location of the area of crystalline rocks previously delineated by P. L. Applin on the basis of well samples. Aerial radiological surveys Aerial radioactivity measurements, made on behalf of the Atomic Energy Commission within a radius of 50 miles of several nuclear facilities to provide a datum to which changes in background radioactivity can be compared, show a good correlation with the local geol- ogy. For example, preliminary study of the radio- activity over Long Island, which ranges from 500 to 700 counts per second, indicates a difference of about 100 counts per second in- the radioactivity of different glacial units. In the Fort Belvoir area, in Maryland and Virginia, highs and lows on radiation profiles over Cretaceous strata correspond to the location of outcrop bands of marine and nonmarine sediments, respectively; both are less radioactive than the Pied- mont rocks. In the Georgia-South Carolina area, also (Schmidt, 1959; Guillou and Schmidt, Art. 55), the coastal plain sediments are less radioactive than the rocks of the Piedmont, and the Cretaceous and E0- cene rocks, which are apparently derived in- part from nearby granite and gneiss, are more radioactive than the younger coastal plain strata. Flood-plains of streams heading in the Piedmont and older coastal plain formations are more radioactive than those of streams that drain areas underlain by post-Eocene sediments. Paleontologic and stratigraphic studies In Florida and Georgia Schopf (1959b) has ex- tracted a rich assemblage of small microfossils from well samples of dark fissile shales of Ordovician and Silurian age. They include chitinozoans, hystrichos- phaerids, and numerous sporelike forms, some of which may represent chitinous envelopes of testacean proto- zoans. Pyrite and abundant carbonaceous material indicate an environment of restricted circulation, and the microfaunal assemblage probably represents a sar- gassoid biocoenosis. An exhaustive report on Cenozoic echinoids of the eastern United States by Cooke (1959) describes 144 species within- 60 genera. Nearly all the species are A32 restricted to single time units, and hence form good horizon markers. Fossils indicate that the late Oligocene sea was cool in South Carolina (Malde, 1959a), whereas it was of a tropical nature in central Georgia (E. R. Applin, Art. 90). In New York, the landward but non-outcropping edge of a previously unknown glauconitic formation has been recognized by Ruth Todd and N. M. Perl- mutter from shallow wells along the barrier beach on the south side of Long Island. Foraminifera in this unit seem to be related to Cretaceous assemblages known in the New Jersey Coastal Plain and in the walls of a submarine canyon at the outer edge of Georges Bank, east of Cape Cod. In New Jersey progressive changes in strike of successively younger formations, together with other evidence, indicate that differential uplift and subsidence of the Coastal Plain took place during much of its history (Minard and Owens, Art. 82). Altschuler and Young (Art. 89) have concluded that the sand mantle in the higher area of eastern Hillsborough and western Polk Counties, Florida, is principally a residual sand plain formed by lateritic weathering of the Pliocene Bone Valley formation, rather than a succession of Pleistocene marine ter- races. EASTERN PLATEAUS Interpretation of geophysical surveys The Eastern Plateaus are underlain by nearly flat- lying Paleozoic rocks, which are gently folded in the Cincinnati and Nashville domes, the Allegheny syn- clinorium, and the Eastern Interior Basin. Geophysical studies in this region have thrown much light on regional geologic structure and on the com— position of basement rocks. Interpretation of aero- magnetic profiles (King and Zietz, Art. 88) shows that the wedge of sediments east of the Cincinnati arch is 8,000 to 10,000 feet thick in eastern Kentucky and Tennessee and thickens northeastward to more than 17,000 feet in West Virginia, Pennsylvania, and New York. In the region as a whole the magnetic anom- alies generally trend northeastward, approximately parallel to Appalachian structures. The anomaly pat— tern indicates sharp contrasts in the crystalline base- ment rocks, and in some areas it appears possible to define characteristics of the Precambrian basement. Near the axis of the Cincinnati arch, for example, where the Paleozoic rocks are thin, the magnetic data indicate the presence of about 15,000 feet of sedimen- tary rocks, probably in large part Precambrian. Aerial radiological monitoring in the vicinity of nuclear facilities, undertaken on behalf of the Atomic GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Energy Commission, shows a well—defined radioactiv- ity anomaly parallel to the Pine Mountain fault in the Cumberland Plateau; the general radioactivity: ranges from 300 to 800 cps. Elsewhere on the plateau a radioactivity units are less distinct. Used in conjunc- , tion with aeromagnetic measurements, these data may aid in the interpretation of bedrock geology. Geologic mapping in western Kentucky Mapping in the fluorspar district of western Ken- tucky by R. D. Trace has delineated several previ- ously unmapped faults of the northeast-trending fault system, which controls the fluorspar deposition. Movement along these faults appears to have been : vertical, for they do not offset older dikes. By detailed study of drill logs, it has been found that the total thickness of the Osage series and the Warsaw, Salem, and Saint Louis formations is 1,500 feet, and that the formations in the Chester series are more uniform in thickness and lithology than previously thought. Much of the reported variation was due to mistakes in correlation across unrecognized small faults. Stratigraphy of Upper Devonian rocks in western New York Detailed mapping and correlation of key beds in the cyclically deposited Upper Devonian rocks in western New York show that the redefined Genesee formation is an eastward-coarsening wedge of marine rocks which thicken from 91/2 feet of dark shale and thin-bedded Stylioh'na-bearing limestone at Lake Erie to more than 900 feet of intercalated sandstone, silt- stone, and black and gray shale near Ithaca (de Witt and Colton, 1959b). The Genesee thickens most abruptly in the 30 miles between Penn Yan and Ithaca, where the Sherburne flagstone member and the Ithaca member tongue in from the east. Previous workers failed to recognize the extent of the tongues west of Ithaca and miscorrelated the Ithaca member with younger rocks in the Sonyea formation. Cono- dont studies by Hass (1959) suggest that the Geneseo shale member, the basal black shale facies of the Genesee formation, is predominantly Middle Devonian in age, and that the boundary between the Middle and Upper Devonian rocks in the Finger Lakes district is near the base of the Orbiculz'odea lodiemis zone about 10 feet below the top of the Geneseo. Correlation of many of the members of the Genesee formation was corroborated by Hass’ condont studies. Quaternary geology in Pennsylvania and the Ohio Valley Reconnaissance mapping of the Quaternary geol— ogy and soils of the Elmira, New York-Williamsport, Pennsylvania area by C. S. Denny in company with W. H. Lyford, soil scientist with the US. Soil Con- servation Service, has shown that the soils on Wis- \ GEOLOGY OF THE UNITED STATES consin drift do not show the effects of deep weather- ing and that differences in them are related prima- rily to lithologic differences in the drift. Drift of pre-Wisconsin age, however, is strongly weathered to depths of more than 30 feet, and supports Red Yel- low Podzolic soils, which are not found on adjacent weakly weathered Wisconsin drift or on Recent col- luvium. The weathered drift contains considerably more kaolinite than the unweathered drift, from which it also differs in containing a little gibbsite. Collu- vial deposits within the area underlain by Wiscon- sin drift are thicker and more extensive south of the Valley Heads moraine than north of it, suggesting that many of these deposits were formed not later than the building of this moraine. Evidently the erosive processes that form volluvium have not been as active in post—Valley Heads time as they were in early Wisconsin time. Four Quaternary loess deposits have been mapped along the Ohio River between its mouth and Louis- ville, Kentucky (Ray, Art. 92). The oldest, of Kan- san age, is overlain by the Loveland loess, of Illinoian age; the two younger are of Wisconsin age. Each was derived from glacial drift deposited about Louisville, and each in turn was the source of alluviation down- stream. Remnants of terraces formed during the last two periods of aggradation can still be observed along the valley. Petrographic studies of loess formation in the Ohio Valley by P. D. Blackmon confirm ear- lier findings that stratigraphic correlations can be made by size analysis and clay mineral composition. SHIELD AREA AND UPPER MISSISSIPPI VALLEY Results of recent geophysical, geologic, and geo- chronologic studies in the Shield area and upper Mis— sissippi Valley are described in the following para— graphs. Additional information on zinc-lead and iron deposits is given on pages A1 and A2. Remanent magnetization in the Lake Superior region Geophysical studies by Gordon Bath in northern Minnesota, done in cooperation with the Minnesota Geological Survey, and in adjacent parts of Wiscon— sin have explained many unusual and unexpected mag— netic anomalies. Contrary to previous theory, the amplitude of the anomalies is not entirely controlled by the induced magnetization of the magnetite in the rocks. For example, a strong remanent magnetiza— tion is required to explain the magnetic anomaly over the Keweenawan lava flows (Art. 93). In addition, there are strong lows over magnetite-rich formations of the East Mesabi district and pronounced highs over magnetite-poor formations of the Vermilion district, A33 which indicate that the rocks show the efl'ects of de- magnetization and remanent magnetization, as well as of the induced magnetization of the magnetite. The basic igneous rocks of the Duluth gabbro yield mag- netic lows explainable only by a remanent magnetiza- tion at right angles to the induced magnetization. Interpretation of geophysical data in central Wisconsin Aerial magnetic and radioactivity data, interpreted by J. W. Allingham and R. G. Bates, helped in 'map- ping the geology of an area of about 250 square miles near Wausau, Wisconsin. The extensive cover of re- sidual soil and glacial drift is there underlain by vol- canic and sedimentary Precambrian rocks, which have been metamorphosed to the greenschist and amphibo- lite facies and intruded by various kinds of igneous rocks. Areas of granite, diorite, hornblende gabbro, and diabase have been delineated by their distinctive magnetic patterns, and an area of syenite has been outlined from radioactivity profiles. Pendants of quartzite and chlorite schist that are remnants of a large fold have been defined by an arcuate pattern of magnetic anomalies related to skarn and diorite. Geologic studies in northern Michigan and Wisconsin In the copper-bearing Keweenaw Peninsula of Michigan, the rate of thickening of the lava series toward the center of the Superior structural basin as determined by W. S. White indicates that the lavas need not have extended much beyond their present areal limits. It is therefore unnecessary to suppose that a great thickness of lavas beyond these limits was eroded away (White, 1960b). Filling of the basin with vast horizontal lava sheets nearly kept pace with subsidence, but there were pauses in the influx of lavas, during which continued subsidence locally re- versed slopes, so that streams carried sand and gravel into the basin to form elastic deposits interbedded with lavas. Zoning of amygdule minerals in the lavas of the Keweenaw Peninsula crosses stratigraphic units and was probably controlled by temperature. The similarity in mineralogy of the flow tops throughout the Lake Superior region indicates that the mineral zones are of region-a1 extent (Stoiber and Davidson, 1959). In the Iron River-Crystal Falls district, Michigan, studied in cooperation with the Michigan Geological Survey Division, a new group of formations of mid- dle Precambrian age was established, a succession ap- proximately 6,500 feet thick was defined, and several reliable stratigraphic markers were recognized. The major structure is a triangular basin. The apical areas of this basin are faulted and intricately folded, and a typical system of westward-plunging folds mod- A34 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS ifies the southerly trend of the east limb of the basin (James and others, 1960). The Lake Mary quadrangle in Michigan, also in- vestigated in cooperation with the Michigan Geologi- cal Survey Division, is underlain by lower and mid- dle Precambrian metavolcanic rocks, dolomite, slate, and iron formation, cut by dikes and sills of meta- gabbro (Bayley, 1959a). One of the sills, which is about a mile thick and is now nearly vertical, has been shown by Bayley to have been originally a dif- ferentiated sheet, with an ultramafic zone near the base and a granophyric zone near the top; the original pyrogenic minerals, however, have been almost en- tirely altered to metamorphic minerals of the green- schist facies (Bayley, 1959c). The regional metamor- phic grade rises to a maximum in the southern part of the area around a small syntectonic complex of igneous rocks ranging from metagabbro to granite. The major structure is the Holmes Lake anticline, but the rocks are cut by faults that dislocate the isofacies. Detailed mapping of rocks of middle Precambrian age by C. E. Dutton in Florence County, Wisconsin —done in cooperation with the Wisconsin Geological and Natural History Survey—has shown that strata of late Animikie age near Florence are folded and faulted at the southeast apex of a triangular basin that extends northwestward into Michigan. The se~ quence of late Animikie along the northeastern flank of the basin is incomplete because the two lowest for- mations pinch out as a result of nondeposition or truncation. The sequence of late Animikie age along the southwest flank occurs in Wisconsin only in a small syncline in a graben. The area between the graben and the apex of the basin and a similar area southwest of the graben are underlain by uplifted, much less complexly folded strata of older Animikie age extending from the southeast. Age of some Pleistocene sediments Several samples of Pleistocene sediments from the upper Mississippi Valley have recently been dated by Meyer Rubin. Snail shells collected by John Frye of the Illinois Geological Survey from loess in Illinois proved to be older than the Farmdale substage, pre— viously found to be about 25,000 years old, and younger than the Sangamon interglacial stage. These and other dates determined by the Survey’s C14 laboratory have been used by Frye and Willman of the Illinois Survey to revise the chronology of the Wisconsin stage of glaciation. A sample of wood collected near Gilbert, Minne- sota, was found to be 11,330 years old. It is there- fore of the same age as the Two Creeks Forest wood, which was covered by the Valders advance in Wis— consin, and it shows that this advance must have ex- tended into the Lake Superior basin. Six samples of wood from the till of Iowan age in Iowa gives ages of more than 30,000 years. These ages differ widely from the 21,000«22,000 year ages of samples of loess in Illinois previously assigned to the Iowan substage and indicate that the loess is probably an advance eolian deposit of the Tazewell substage rather than of the Iowan. GULF COASTAL PLAIN AND MISSISSIPPI EMBAYMENT Mesozoic stratigraphy of the eastern Gulf Coastal Plain Data from well samples are being used by Paul and Esther Applin to compile maps on a scale of 1 :1,000,- 000 and cross sections showing the subsurface geology of Mesozoic rocks in parts of Florida, Georgia, Ala- bama, and Mississippi. During the course of this work, the subsurface contact between the Comanche and Gulf series has been delineated in western Flor— ida; limestone of Trinity (Comanche) age has been identified in Lamar‘County, Alabama, and rocks of Late Jurassic age in Madison and Rankin Counties, Mississippi, and Washington County, Alabama. Fos- sils found in Harrison County, Mississippi, make it possible to distinguish beds of Fredericksburg age in the Comanche series; and fossils in the Comanche series in Walthall and Hancock Counties, Mississippi, show that the beds containing them are roughly equiv- alent to rocks of Trinity age in Florida. Lithofacies and origin of Tertiary sediments in the coastal plain of southern Texas The origin and geologic environment of uranium deposits in Tertiary sediments of the central and southern Texas coastal plain have been investigated by Eargle (1959a, b) (see also p. A10). He has found that the Jackson group (Eocene) near its outcrop con- sists of deltaic and lagoonal deposits, but that these grade down-dip into offshore bar and marine deposits. Deposition was influenced by structural activity, for the sediments grow coarser near faults, thin over posi— tive structural features, and thicken over negative ones. Buried igneous masses in Missouri and Arkansas Aeromagnetic mapping shows anomalies in Stoddard County, Missouri, and near Walnut Ridge and New- port, Arkansas, that are ascribed to buried igneous masses, some of which are ridges 3,000 to 6,000 feet below the surface. OZARK REGION AND EASTERN PLAINS In addition to the information reported in previ- ous sections on fuels, potash, and nuclear test sites A . GEOLOGY OF THE UNITED STATES (see p. A7, and A12), recent work in northwestern Arkansas and southeastern New Mexico has contrib- uted to knowledge of regional geologic relations, as follows. Geology of northwestern Arkansas Rocks of Ordovician to Early Pennsylvanian age that crop out in the Ozark region of Arkansas have been found to dip and generally thicken southward under a thick cover of Atoka and younger Pennsyl- vanian rocks in the Arkansas Valley (Frezon and Glick, 1959). The base of the Boone formation (Mis- sissippian) has a regional dip of only about 10 feet per mile in the northern part of Arkansas, but its dip is as much as 500 feet per mile along the northern edge of the Arkansas Valley, where the deepening of the basin was partly a result of faulting. Nearly all the formations of Ordovician to Pennsylvanian age exhibit thickness and facies changes that indicate that while these formations were being deposited the north- ern and western part of the Ozark region in Arkan- sas was covered by shallower water, and subsided less, than the southern and eastern part. In the southeastern part of the Ozone quadrangle in Johnson County, Arkansas, just southwest of the west- ernmost edge of a large structurally high area in the Ozarks, the Mulberry fault, which separates the Ozark uplift on the north from the downdropped Arkansas Valley on the south, has been found by E. E. Glick, B. R. Haley, and E. A. Merewether to split eastward into a complicated fault system. The rocks dip west- ward from the structurally high area, and descend 1,000 feet in 5 miles into a basin, illustrating that considerable local structural relief is superimposed on the regional southward dip in the southern Ozark area. The Atoka formation thickens from about 3,500 feet on the north side of the Arkansas Valley to per- haps as much as 20,000 feet on the south side. The northward convergence of individually mapped beds in the northern part of the area suggests that dias— tems may account in part for the wedge shape of the unit. Aeromagnetic studies in southeastern Missouri Allingham (Art. 95) has found that aeromagnetic measurements are a valuable aid in interpreting the geology of Precambrian basement rocks where they are buried by later sediments along the southeastern flank of the Ozark uplift. Not only is it possible to recognize buried topographic features in the basement, including some that are due to faulting, but it is also possible to differentiate granitic rocks, volcanic rocks, and magnetite-rich iron deposits. A35 Permian stratigraphy in southeastern New Mexico In the southwestern part of Eddy County, New Mexico, Hayes (1959) has investigated the strati- graphic relations of Permian shelf rocks to those of the Delaware basin. He has found exposures in Last Chance Canyon that clearly display intertonguing be- tween the upper part of the San Andres limestone (Permian) and the sandstone tongue of the Cherry Canyon formation (middle Guadalupe series). These two units unconformably overlie rocks of latest Leon- ard or earliest Guadalupe age, or both, that are cor— related with the lower part of the San Andres of areas on the north and west. In the Big Dog Canyon scarp a few miles west, rocks of Cherry Canyon age are apparently separated from rocks of latest Leonard .or earliest Guadalupe age by more than 580 feet of carbonate rocks that are considered equivalent in age to the Brushy Canyon formation (early Guadalupe) of the Delaware basin. The sequence within the San Andres limestone in Big Dog Canyon may therefore represent nearly continuous deposition from latest Leonard or earliest Guadalupe time into Cherry Can— yon time. The San Andres limestone is overlain by the Gray- burg formation. The Grayburg and the overlying Queen formation pass laterally into the Goat Seep limestone and are thus of middle Guadalupe age. NORTHERN ROCKIES AND PLAINS Preliminary findings of some of the numerous field investigations in progress in the northern Rocky Mountains and plains are described in the following paragraphs. Results of recent work on mineral de- posits in this region are described on pages A1—A14, and landslides related to block faulting are described on page A21. Geology of parts of northeastern Washington and northern Idaho The Hunters quadrangle, northeastern Washington, straddles the border between miogeosynclinal sedi- ments and eugeosynclinal sediments and volcanics. A. B. Campbell believes that the contact between these two rock assemblages is a high-angle normal fault in an overthrust sheet. The thrusting moved eugeosyn- clinal rocks eastward over miogeosynclinal rocks. The Northport district, according to R. G. Yates, lies on the boundary between miogeosynclinal rocks of early Paleozoic age and eugeosynclinal rocks of late Paleo- zoic and Mesozoic age. Cambrian and Ordovician time is represented by two contrasting assemblages of miogeosynclinal rocks, whose adjacency is interpreted to have resulted from large scale horizontal shorten- ing. In the Republic area, M. H. Staatz (Art. 141), A36 R. L. Parker, J. A. Calkins, and S. J. Muessig have mapped a large graben that cuts metamorphosed sedi- ments and batholithic intrusives of probable Jurassic age. The graben formed in early or middle Tertiary time as the result of collapse and subsidence associ- ated with volcanic activity. In the Mount Spokane quadrangle, rocks formerly thought to be Late Juras- sic or Early Cretaceous intrusions have been found by A. E. Weissenborn to be gneisses and schists that are probably metamorphosed correlatives of sediments of the Belt series that lie east of the Purcell trench. In the Pend Oreille area of Idaho, aeromagnetic data can be used to locate surface and near-surface plutons, such as those at Packsaddle Mountain and Granite Point, according to a preliminary interpreta- tion by E. R. King. The Hope fault divides the area into a northern highly magnetic section and a south— ern one of low magnetic gradients in which the anom- alies due to the plutons stand out sharply. Stratigraphy of the. Belt series in western Montana and adjacent areas In western Montana, northern Idaho, and north— eastern Washington exposures of slightly metamor- phosed Precambrian sedimentary rocks, referred to the Belt series, are widespread. The series is as much as 45,000 feet thick. According to C. P. Ross, who has completed a regional study of these rocks, the groups that make up the series can be recognized throughout the region. The groups, named in strati- graphic descending order, are the Missoula, Piegan, Ravalli, and pre-Ravalli groups. They are being sub- divided locally into formations and members, but these lesser subdivisions cannot now be correlated from area to area. Geology of areas in the vicinity of the Idaho batholith At the northwest margin of the Idaho batholith, Anna Hietanen—Makela has delineated three struc- tural trends, along each of which folding or refolding has occurred; each phase of the deformation was fol— lowed by faulting and intrusion. During the geologic mapping of the Yellow Pine quadrangle, Idaho—part of a program to obtain a geologic cross section of the Idaho batholith—B. F. Leonard has found large re- cumbent folds in highly metamorphosed “Belt” rocks previously thought to be nearly flat lying. The folds generally trend northwest, but locally they are inter— rupted by others that trend east—northeast. In the Riggins area, Idaho, Hamilton (Art. 103) finds that the metamorphic grade of volcanic and sedimentary rocks increases eastward toward a broad complex of intrusive and metamorphic gneisses that are marginal to the Idaho batholith. Two post-metamorphic, west- GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS directed thrust faults have an aggregate displacement of about 10 miles. In the Leesburg quadrangle, W. H. Nelson has found that rocks of the Belt series were metamorphosed to the biotite grade and locally to the garnet grade of dynamothermal metamorphism during the emplacement of the Idaho batholith. E. T. Ruppel finds that the Lemhi Range, in the southern part of the Leadore quadrangle, is underlain princi- pally by Precambrian and early Paleozoic sedimentary rocks, which have been folded into folds that trend about N. 25° W. These rocks are cut by early high angle faults that trend northwest, by later ones that trend northeast, and by nearly flat overthrust faults of uncertain relations. Geology of parts of western Montana In the Sun River Canyon area, M. R. Mudge has found fossils that show that the Devils Glen dolomite is of Late Cambrian age. The Morrison formation (Jurassic) in this area changes in facies along the Sun River from gray and olive drab mudstones and interbedded sandstone and fresh water limestone east of the Gibson dam to red-brown fine- to coarse-grained cross bedded sandstone and interbedded mudstone west of the dam. The two facies are in thrust contact near the dam. In the Willis quadrangle of southwestern Montana, W. B. Myers has shown that Middle and Upper Cam- brian strata overlap a truncated erosion surface on faulted strata of the Belt series—relations that indi- cate deformation in Precambrian or Early Cambrian time. A similar deformation is inferred for the High- land Mountains by M. R. Klepper and H. W. Smedes, where thick coarse breccias of very limited extent, pos- sibly reflecting block faulting, occupy the stratigraphic position of the Cambrian Flathead or Wolsey forma- tions in that area. Geologic mapping by Myers also indicates that thrust faults in the Willis quadrangle are essentially bedding-plane glide surfaces. They originated during the early stage of folding and were active until folding ceased; consequently they are strongly folded. In the Livingston—Trail Creek area, A. E. Roberts has found evidence for at least two pulses of thrusting toward the south and southwest. During the early one, an anticline composed of Paleozoic rocks was thrust onto a syncline of Cretaceous rocks. During the later episode, Precambrian rocks were thrust over Cretaceous rocks. In the Maudlow area, Betty Skipp has mapped an imbricate Laramide thrust zone, with throws up to about 1,700 feet, in overturned Paleo- zoic and Mesozoic beds along the front of the Horse- shoe Hills. GEOLOGY OF THE UNITED STATES According to Zietz (Art. 102), aeromagnetic pro- files across a pluton near Three Forks indicate that the pluton is bottomed at a depth of several thousand feet; this strengthens evidence from the mapping of G. D. Robinson which suggests that the pluton was cut off by the nearby Lombard thrust. Coral zones in Mississippian rocks W. J. Sando (Art. 100) has recognized five coral zones in the Madison and correlative rocks of Mis- sissippian age in the northern Cordilleran region that are useful in regional correlation. The zones indicate that the Brazer, Mission Canyon, and Charles forma- tions are partly equivalent in age. Geology of parts of western Wyoming, southeastern Idaho, and northeastern Utah In the Clark Fork area, Wyoming, W. G. Pierce (Art. 106) has found that the breakaway point of the Heart Mountain detachment fault is near the north- east corner of Yellowstone Park. From this point, horizontal displacement of individual blocks increases southeastward to about 30 miles at the most southeast- erly limit, 65 miles way. The Meridian Ridge or Wyoming anticline, where studied by S. S. Oriel, is a complex structure, rather than a simple anticline as heretofore believed. He found that the Thaynes limestone of Triassic age was earlier mistaken for the Twin Creek limestone of Jurassic age along the east side of the structure as previously mapped, accounting for much of the erro- neous closure. Furthermore, the west side of the structure is cut by steeply dipping faults whereas the east side is complicated by numerous local structures which may be subsidiary to a major fault that lies further east and is covered by Tertiary rocks. In the Green River basin and in Jackson Hole, Wyoming, J. D. Love found proof of pre-Tertiary tilting and erosion. In both areas successively older Cretaceous strata are exposed from east to west, and are overlapped by 5,000 to 15,000 feet of Paleocene strata. Love has also mapped many late Pliocene and Quaternary normal faults, several having displace- ments of from 10,000 to more than 20,000 feet, and in the Jackson Hole area he has collected Pliocene in- vertebrates that demonstrate folding of Pliocene or later age. In the vicinity of Bear Lake Valley, Idaho, F. C. Armstrong and E. R. Cressman find that post- Laramide deformation consists of normal faulting and tilting, with only minor folding. In the Wasatch Mountains of Utah, consistent lead- alpha ages had indicated that the Little Cottonwood stock was Eocene. Recent mapping by M. D. Crit- tenden, J r., however, has shown that it is cut by the 557328 0 - 60 - 4 A37 Charleston thrust, elsewhere known to be of Creta- ceous age. The granite mylonite, a product of this thrusting, is cut by normal faults of middle Tertiary age, as well as by the Wasatch fault of probable Plio— cene and Pleistocene age. Geology of the Wind River basin, Wyoming In the Wind River basin area, W. R. Keefer and J. D. Love have found evidence that during early Ter- tiary time central Wyoming was invaded by a sea, or occupied by a large lake, in which 2,000 feet of dark gray and black shale was deposited. They have shown also that structures along the margins of the basin began to develop locally in Late Cretaceous time and continued to form through the Paleocene (Keefer, Art. 105). One of the largest and most varied Paleo- cene mammal faunas known in central Wyoming was found by Keefer in the Shotgun Butte area. Al— though this collection has not been fully studied, it is known to contain several hundred mammal teeth and abundant shark teeth. Geologic and geophysical studies in parts of the Black Hills, South Dakota In the southern part of the Black Hills, G. B. Gott and others have found that mild structural deforma- tion occurred prior to Fall River time (Early Cre- taceous) ; this probably localized the fluvial sandstones in the Lakota formation, and may have been the be- ginning of the Black Hills uplift. Deposits of fluvial sandstone in both the Lakota and Fall River forma- tions are elongate in a northwestward direction and cross beds dip northwest, suggesting a southeastern source area for most of the sediments of the Inyan Kara group. In the Newcastle area, on the west side of the Black Hills, W. J. Mapel inferred from the orientation of cross beds that the streams that de- posited the Cretaceous Lakota formation flowed north- ward. Throughout the southern Black Hills, solu- tion of nearly 250 feet of calcium sulfate from the Pennsylvanian Minnelusa formation and the subse- quent calcium carbonate recementation of collapse breccias began in early Tertiary time and is continu- mg. Gravity measurements made by R. M. Hazlewood show gravity highs and lows that trend parallel to the eastern flank of the Black Hills uplift. His data also indicate that a steep gravity gradient extends all the way along the west flank of the Black Hills. Devonian rocks in eastern Montana and western North Dakota Widespread subdivisions of the J efl'erson and Three- forks formations, both of Devonian age, have been recognized by C. A. Sandberg in eastern Montana and western North Dakota. He has also found that the A38 Beartooth Butte formation, of Early Devonian age, is more extensive than supposed and may be equivalent to the lower part of the Maywood formation. Lithofacies and thickness of the Pierre shale in South Dakota In a comprehensive study of the Cretaceous Pierre shale (see also p. A64 and Art. 205), H. A. Tourtelot, L. G. Schultz, and J. R. Gill have found that along the Missouri River in central South Dakota it con- sists of clayey rocks with a carbonate-rich unit in- the upper part and several thin beds of marlstone in the lower part. In the Black Hills region, it contains lit- tle carbonate and more silt and sand. The thickness of the Pierre increases from about 500 feet in south- eastern South Dakota to more than 3,000 feet on the southwestern flank of the Black Hills. Geology of the Bearpaw Mountains, Montana In the Bearpaw Mountains, W. T. Pecora and B. C. Hearne, Jr. have found that the complexly faulted border zone surrounding the mountains narrows east- ward and is characterized by steep normal faults. This zone contains down—faulted blocks of volcanic rocks and Tertiary and Upper Cretaceous formations, which have depressed the surrounding formations. Data on remanent magnetism obtained by K. G. Books indi- cate that before deformation the volcanic rocks gen- erally dipped northwest in the northern volcanic field and southeast in the southern volcanic field. Glaciation in the vicinity of Glacier National Park, Montana East of Glacier Park, G. M. Richmond, R. W. Lemke, and E. Dobrovolny determined the strati— graphic relation between continental glacial deposits and the Alpine-piedmont deposits of Bull Lake and Pinedale age. In the Glacier Park area itself, Rich- mond (Art. 98) found evidence of three Wisconsin glaciations, two ice advances in Bull Lake time, three in Pinedale time, two in early Recent time, and two in late Recent time. SOUTHERN ROCKIES AND PLAINS Geologic field investigations in the Southern Rockies and plains in 1960 yielded important results in the study of Precambrian basement rocks, volcanics of Cenozoic age, and sedimentary rocks of Mesozoic and younger age as described below (see p. A3—A5 and A13 for information on mineral deposits in this region). Precambrian rocks and structures in the Front Range and Sawatch Range, Colorado Geologic mapping has recently been started in the Front Range of Colorado to obtain a geologic cross— section of the range at about mid-length, and a longi— tudinal section of the east-central foothills. This work GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS has already shown, among other things, that the oldest Precambrian rocks, a thick series of metasediments which T. S. Lovering and E. N. Goddard had pre- viously grouped mainly in the Idaho Springs and Swandyke formations, can be subdivided into several mappable units of wide areal extent (see Koschmann and Bergendahl, Art. 113). J. D. Wells and D. M. Sheridan have found that the quartzite at Coal Creek, previously regarded by Lovering and Goddard as younger than the biotite gneisses of the Idaho Springs formation, grades into that gneiss. Sims and others (1959) showed that the rocks in the central Front Range were deformed during at least two periods in Precambrian time. Many faults, including the brec- cia reefs that were previously thought to be of Lara- mide age, originated in Precambrian time according to evidence presented by P. K. Sims and G. R. ScOtt. Ogden Tweto and R. C. Pearson, on the basis of comprehensive work in the northern Sawatch Range, have delineated an elongate swarm of metamorphosed lamprophyre dikes within a great Precambrian shear zone. These dikes record almost the latest Precam- brian event in the region, for they are younger than the plutonic granites and the regional metamorphism, yet they themselves are metamorphosed, approximately to the amphibolite facies (Pearson, 1959). An important outgrowth of studies of the Precam- brian in the Front Range and Sawatch Range is the recognition that the Colorado Mineral Belt, defined by Laramide intrusive rocks and ore deposits, is co- extensive with and localized by a zone of intense Pre- cambrian shearing (Tweto and Sims, Art. 4). Geology of volcanic terranes in Colorado and New Mexico In studying the classic volcanic terrane of the San Juan Mountains, Colo., Luedke and Burbank (Art. 7) mapped several ring-fracture zones, associated with ring dikes related to a late intrusion within the well- known Silverton caldera in the western San Juans. Steven and Ratté (Art. 8) discovered a major caldera near Creede, in the central San J uans, and related its subsidence to voluminuous ash flow eruptions. The veins in the Creede district were deposited on the north margin of the caldera along faults extending outward from it; many of these faults were active throughout the subsidence of the caldera, but no sig- nificant mineralization took place until after the last major period of fault movement (see p. A4). Map- ping in the Spanish Peaks area of south-central Colo- rado by Ross B. Johnson has shown that the radial dikes around West Spanish Peak and Dike Mountain occupy a joint complex that resulted mainly from in- termittent orogen-ic stresses caused by the formation of the LaVeta syncline, which occurred before the GEOLOGY OF THE UNITED STATES magma was emplaced. Earlier workers generally at- tributed the radial fissuring to doming of the sedimen- tary rocks by the emplacement of the stocks. Studies by C. S. Ross, R. L. Smith, and R. A. Bailey in the Valles Mountains area, New Mexico, have led to the recognition of zones and zonal variations in ash flow tufl's that should be widely applicable. Geology of North Park, Colorado In North Park, a structural and topographic basin between the Park Range and Front Range, it has been found that the widespread Coalmont formation is of Paleocene and Eocene age (Hail and Leopold, Art. 117) and that the North Park formation is probably of late Miocene age (Hail and Lewis, Art. 116). Geo— logic mapping in the basin by D. M. Kinney and W. J. Hail, Jr. indicates that folding and high—angle thrust- ing related to the Laramide orogeny began before deposition of the Coalmont formation and continued throughout its deposition. A conspicuous unconform— ity in the Coalmont between the Paleocene and the Eocene shows that marked uplift took place locally along the basin margins. Age of deformation in the Raton basin, Colorado Johnson (1960) and others have concluded, from the results of geologic mapping, that the Laramide Revo— lution began in the Raton basin of south-central Colo- rado with epeirogenic movements in late Montana (Late Cretaceous) time. These epeirogenic movements were followed by at least seven orogenic episodes of decreasing magnitude, which extended into Miocene time, and by normal faulting in late Tertiary. COLORADO PLATEAU Most of the geologic studies on the Colorado Plateau have been undertaken to aid the search for uranium and fuels (see p. A9, A11, and A13), but they are also making important contributions to an understanding of the regional geology and history of the area. Some of the new findings are summarized below. History of salt anticlines in the Paradox basin Studies of the salt anticlines in Paradox Valley, Gypsum Valley, Fisher Valley and other areas by D. P. Elston, E. R. Landis and E. M. Shoemaker Show that the salt cores were formed in Late Pennsylvanian and Permian time and continued to grow from Tri— assic to Early Cretaceous time (Art. 118). Subsequent solution of salt and redistribution of salt by plastic flow has resulted in the collapse of Mesozoic rocks deposited over the salt cores; this movement has con- tinued through late Pleistocene time. In the eastern part of the Paradox basin, the dis- tribution of subsurface formations suggests that the I A39 northwesterly trend of the salt anticlines was inher- ited from structures formed before the deposition of salt of the Paradox member of the Hermosa forma- tiqn in Middle Pennsylvanian time. This conclusion is reinforced by the geophysical findings of H. R. Joesting and P. E. Byerly (Byerly and Joesting, 1959; J oesting and Case, Art. 114). Magnetic and/or gravity anomalies are associated with all larger uplifts, basins, salt anticlines, and laccoliths of the central Colorado Plateau. Regional anomalies, associated with the large salt anticlines and with at least some of the laccoliths, relate to structures in the Precambrian base- ment rocks, and perhaps to structures in pre-Missis- sippian formations. In many areas, however, the con- fi uration of the surface of the basement is not re- flected in post-Mississippian rocks. Structure in the vicinity of the Carrizo Mountains A discordance in structure in the Carrizo Mountains has been brought out through the subsurface studies of J. D. Strobell. Well data indicate that an old land mass in the Carrizo Mountains area was lapped by Cambrian sandstone and overstepped by limestones of the Devonian Elbert and Ouray formations. On the Precambrian highland just west of the Carrizos the hiississippian Leadville and Redwall limestones also 1 p out on markedly thinned Devonian beds. The basal Pennsylvanian Molas formation extends across the eroded complex. Accumulations of oil and nod tably high concentrations of helium in nitrogenous natural gas occur below the relatively impermeable Molas formation in solution cavities near the top of the Leadville and Redwall limestones and in porous crystalline zones in the lower part of this limestone. Stratigraphic and paleontologic studies of Mesozoic rocks The results of a stratigraphic study of the San Rafael group by J. C. Wright show that the connec- tion between the shallow Utah basin of deposition and the open ocean to the west was restricted in Jurassic time. This basin was probably saline, as indicated by the meagre fauna and prevailing red color of the San Rafael group in the basin as well as by the saline precipitates that it contains. In eastern Utah substan- tial but locally erratic erosion of the underlying Nav- ajo sandstone took place not only on salt structures but also in other areas. R. A. Scott reports that collections from the Chinle formation of five localities widely separated on the Colorado Plateau have yielded rich assemblages of ollen and spores. Pollen of E phedm were identified, End also pollen and spores comparable to those in the Juropean Keuper. In the Uinta Basin of the northeastern part of the Colorado Plateau, Zapp and Cobban (Art. 112) have A40 been able to map and date the landward extent of marine wedges and the seaward extent of non-marine wedges for five major transgressive cycles in rocks of post-Eagle (Cretaceous) age. BASIN AND RANGE PROVINCE Noteworthy advances in our understanding of the geology of the Basin and Range province have been made recently in regard to: (a) thrust faults in Ne- vada; (b) geology of the Mojave Desert; (0) geology of the Sierra Diablo area, Texas; ((1) dating of strata; (e) crustal structure and block faulting; and (f) Quaternary history (see pages AQ—A8 for new information on mineral deposits in this region). Thrust faults in Nevada In the Osgood Mountains, P. E. Hotz and Ronald Willden have found rocks transitional between the eugeosynclinal elastic and volcanic facies typical of western Nevada and the miogeosynclinal carbonate facies typical of eastern Nevada. Since the Osgood Mountains are 90 miles west of the eastern trace of the Roberts Mountains thrust, and since the overrid- ing plate of the Roberts Mountains thrust contains rocks of the eugeosynclinal facies along its eastern margin, those rocks must have originated west of the Osgood Mountains, and have been- moved more than 90 miles eastward to reach their present position. In the northern part of the Shoshone Range, Gilluly (Art. 119) and others have found that the Roberts Mountains thrust is folded into a tight overturn and is cut .by younger thrusts. In the Snake Range, Nevada, mapping of complex structures by D. H. Whitebread has shown that the thrust faults consistently show younger rocks thrust over older rocks. Within the upper plates of the thrust faults are numerous northward-trending faults with predominantly strike-slip movement. In the Schell Creek Range, Drewes found that the Paleo- zoic rocks east of Connors Pass are thrust on several bedding-plane faults that removed tens to thousands of feet of an otherwise normal sequence (Art. 122). Cenozoic rocks and structures in the western Mojave Desert, California Geologic mapping by T. W. Dibblee, Jr., G. I. Smith, and others, and concurrent geophysical sur- veys by D. R. Mabey, undertaken as a part of borate investigations (see p. A7), have shown that in the western Mojave Desert the surface alluvium of some basins conceals extensive and thick accumulations of Cenozoic sedimentary and volcanic rocks. Whereas actual exposures of the Tertiary and Pleistocene rocks make up only about 10 percent of the area, about 30 GEOLOGICAL SURVEY RESEARCH l960—SYNOPSIS OF GEOLOGIC RESULTS percent more of the area is probably underlain by Tertiary and Pleistocene fill. The greatest thickness of fill, about 10,000 feet, is in basins that are near the Garlock and San Andreas faults. Structure within the concealed fill is largely unknown; little of it has been explored by test drilling. The mapping of ex- posed Cenozoic rocks has shown, however, that they are much faulted and that they are sharply folded in many places, particularly near the steep northwest- trending faults that characterize the Mojave Desert. Geology of the Sierra Diablo, Texas Structures of Basin and Range type extend south- eastward into the northwestern trans-Pecos area of Texas, where a long intermontane depression, the Salt Basin, is bordered on- its eastern and western sides by fault-block ranges. The Guadalupe Mountains, one of the ranges on the east, was previously described by P. B. King, and he is now preparing a report on the Sierra Diablo, a range on the west. The Sierro Diablo fault block had a considerable prior history as a posi- tive area, dating back to a period of folding and faulting near the close of Pennsylvanian time. De- formed Pennsylvanian and older rocks are overlain by a mass of Permian carbonate rocks of Wolfcamp and Leonard age several thousand feet thick which compose the main part of the range. They were formed on a submarine platform at the southwestern edge of the Delaware basin, and the Leonard series at the margin of the platform is a complex of bank, reef, and fore-reef deposits. Knowledge of the Wolf- camp and Leonard series of the Sierra Diablo sup— plements knowledge of the Guadalupe series in the nearby Guadalupe Mountains, making the composite sequence of the two areas one of the standards of ref- erence for the marine Permian in North America. New information on the age of strata Geologic mapping by H. R. Cornwall and F. J. Kleinhampl in the southern Grapevine Mountains of Nevada indicates that olenellid-bearing shales of late Early Cambrian age, previously discovered by J. F. McAllister, belong to the Johnnie formation. This is the lowest known occurrence of fossils in the strati- graphic column in the Great Basin. Research on Great Basin graptolites by R. J. Ross, J r., and W. B. Berry indicates that the entire span of the Ordovician is present in the Great Basin in both eugeosynclinal and miogeosynclinal facies. These studies make possible fairly precise correlations be- tween the two facies, and also with graptolite-bear— ing rocks of New York, Texas, Australia, and Great Britain. J. G. Moore (Art. 131) has found from a review of all fossil evidence that the metavolcanic GEOLOGY or THE mijTED STATES A41 rocks in roof pendants of intrusive bodies related to the Sierra Nevada batholith in western Nevada are of Late Triassic and Early Jurassic age. Crustal structure and block faulting Gravity studies (see Mabey, Art. 130) in the Basin and Range province have revealed an inverse corre— lation between the Bouguer anomaly values and re- gional topography, suggesting that regional isostatic compensation exists throughout the region. The grav- ity data indicate that several basins are underlain by over two miles of Cenozoic rock, and the pre-Tertiary rock surface under some of these basins is as much as two miles below sea level. From an analysis of the block faulting that char— acterizes the Basin and Range province, Moore has found that blocks tend to be tilted toward regional topographic highs, and that many of the major range— front faults are arcuate in plan, concave toward the down—thrown block (Art. 188; see also p. A58). Tiltmeter observations by Greene and Hunt in the Death Valley area indicate that tilting is going on there at the present time (Art. 124). The amount and direction of tilting differs from one station to another, and the rate of tilting at a given station varies from time to time. Geophysical studies along the eastern front of the Sierra Nevada suggest that Mono Basin and Long Valley are volcano-tectonic depressions (Pakiser and others, 1960). Pakiser (1960a; see also Art. 189) has suggested that volcanic rocks in this region were erupted from regions of relative tension or stress re- lief in offsets of major left-lateral en echelon shear zones. Quaternary history From a study of ancient soils'and other surficial deposits, R. B. Morrison believes it possible to cor— relate the later Quaternary stratigraphic units of the Carson Desert with those of the Bonneville Basin, Rocky Mountains, and Sierra Nevada. His tentative correlations confirm earlier suggestions that Lakes Lahontan and Bonneville fluctuated synchronously, and that both lakes were high when the glaciers were extensive in the Sierra Nevada and the Rocky Moun- tains. The intricate stratigraphic record related to the fluctuations of Lake Lahontan not only provides evidence on which to base a detailed history of the Carson Desert, but also gives indirect evidence of gla- cial oscillations not yet recognized in the mountains. In the Little Cottonwood area, Utah, G. M. Rich- mond and R. B. Morrison determined by detailed stratigraphic mapping of the Quaternary deposits that there were five lake cycles of Lake Bonneville, with maxima (earliest to youngest) at about 5100, 51 5, 4770, 4470 and 4410 feet above sea level. COLUMBIA PLATEAU AND SNAKE RIVER PLAINS Current detailed mapping in the Columbia Plateau and Snake River Plains is centered in three areas: the John Day country in north-central Oregon, north- central Nevada, and the Snake River Plain of south- ern Idaho. Geology of parts of John Day area, Oregon In the John Day area, T. P. Thayer finds two gen- er tions of layering in a gabbro—peridotite complex that contains chromite deposits, and believes that this layering resulted from magmatic deformation of semi- solid rocks during their emplacement, which took place in Early and Middle Triassic time. Fifty thou- sand feet of graywacke and volcanic rocks deposited in this area in late Triassic time show major intra- formational unconformities, abrupt facies changes, and local thickening, all of which indicate contemporane- ous deformation (Thayer and Brown, Art. 139). Met— a orphism of these rocks to zeolitic facies, and locally t actinolite—albite facies, has been related to intru- s' n of granodiorite and related rocks (accompanied b gold mineralization) in Late Cretaceous time. Fischer and Wilcox (Art. 140) report that the beds of the John Day formation near Monument, Oreg. were largely wind—laid on a subaerial surface of mod- erate relief. Flows of Columbia River basalt subse- quently filled depressions on the surface of the John Day formation, and eventually blanketed the whole region. The youngest of these flows differ from the older ones in texture and in mineral and chemical c‘ mposition. In Lake County, Oregon, G. W. Walker ( rt. 138) has mapped volcanic rock formations that alre similar to those of Central Oregon in general stratigraphy, and contain a related vertebrate fauna of Miocene age. Petrology and remanent magnetism of Snake River lavas Powers (Art. 137) has found that basaltic rocks of the Snake River valley in southern Idaho differ from ther basalts in the northwestern United States in t eir low content of silica compared to total iron and a esia, and that some basalt—like rocks are alkalic Art. 136). Measurement of remanent magnetism by A. V. Cox n a suite of 800 samples from the basaltic lavas shows that, regardless of differences in mineralogy, the mag- netic polarity of basalt of late Pleistocene and Recent age is north—seeking, whereas the polarity of basalt of middle and early Pleistocene age is south-seeking. Moreover, within each of these groups, smaller difl'er— A42 ences in directions of magnetization can be used to correlate isolated outcrops of individual flows. Structure and history of the western Snake River plain Malde (1959b) has shown that the northwest-trend- ing reach of the Snake River Plain in southwestern Idaho developed by major subsidence along faults that cross the trend of Basin and Range faulting. During subsidence of this graben, clastic sediments and sub- ordinate amounts of interbedded basaltic lava and siliceous volcanic ash, which total at least a mile in thickness, were deposited intermittently from early Pliocene to Recent time. Pliocene and lower Pleisto- cene deposits fill broad basins, whereas the middle Pleistocene and younger deposits are confined to nar- row ancient canyons nearly congruent with the pres— ent canyon of the Snake River. Malde (Art. 135) relates the youngest deposits to the overflow of Lake Bonneville into the Snake River. The graben of the western Snake River Plain in Idaho is a region of high gravity in which three large positive anomalies are arranged en echelon parallel to the regional northwesterly structural trend (Pakiser, 1960b). Simple Bouguer values of about —70 mgals (milligals) at the gravity highs, by comparison with values of about —125 mgals at the basin borders, are interpreted by Baldwin and Hill (1960) to indicate a buried section of basaltic lava somewhere between the limits 81/2 to 24 km in thickness. A elastic deposit several thousand feet thick in the western Snake River Plain, dated as late Pliocene and early Pleistocene, contains a very large fresh-water molluscan fauna in which D. W. Taylor recognizes 109 species, many of which are new. In degree of endemism, in the variety of species and genera, and in the great variety of individual forms, this fauna is similar to that now living in Lake Ohrid, Yugoslavia, and in Lakes Tanganyika and Nyassa, Africa. It is also similar in these respects to the fossil faunas from the former Pontian, Dacian, and Levantine basins of southeastern Europe. Aeroradioactivity in the vicinity of the National Reactor Test Station area, Idaho , According to R. G. Bates, aerial radiological sur- veys (ARMS program) in the vicinity of the Na- tional Reactor Test Station area show that the high- est natural aeroradioactivity levels, 1,000 to 1,900 cps (counts per second), are found in or near areas of rhyolite and related rocks along the northwest and southeast boundaries of the Snake River Plain and in three areas within the plain. A basaltic lava flow southwest of Idaho Falls has a uniformly low radio- activity of 300 to 400 cps. The aeroradioactivity of GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS aa lava is generally about 50 to 150 cps higher than that of pahoehoe lava, perhaps because the aa has a greater surface area per unit volume, and therefore has a larger effective gamma emitting surface than the pahoehoe. The highest aeroradioactivity levels, up to 1,100 cps, over basaltic lava flows were those recorded over serrate flows in the northeast corner of the Craters of the Moon National Monument. Cenozoic volcanic rocks and structure in north-central Nevada In north-central Nevada, R. R. Coats has distin- guished several formations of siliceous volcanic rocks alternating with formations of basaltic lavas. Some of the rocks are mineralized with gold, and all are broken by block faults structurally allied with the Basin and Range province. Fossil mammals, mol- lusks, leaves, and diatoms date the gold mineraliza- tion as late Miocene and the subsequent block faulting as latest Miocene or earliest Pliocene. PACIFIC COAST REGION Geologic investigations in the Pacific Coast region are grouped for discussion into the following cate- gories: (a) the Sierra Nevada batholith, (b) western foothills metamorphic belt, (0) the Cascade Range, (d) Klamath Mountains and the Coast Ranges of northern California, and (e) major sedimentary basins. Geology of the Sierra Nevada batholith The principal objectives of the work in the Sierra Nevada, part of which is being done in cooperation with the State of California, are to determine the spa- tial and temporal relations and the structure, compo- sition, and mode of emplacement of the plutons that constitute the Sierra Nevada batholith; the strati- graphy and structure of the associated Paleozoic and Mesozoic strata; and the factors that controlled the localization of deposits of tungsten, copper, and gold that characterize the range. The first. phase of this investigation is to prepare a reliable geologic map of a strip about 85 miles wide across the central part of the range. This map is being synthesized from all available mapping but it is based main-1y on large- scale geologic mapping of critical areas and recon- naissance mapping of intervening areas by P. C. Bate- man, L. D. Clark, C. D. Rinehart, D. C. Ross, and others. This mapping, supplemented by stratigraphic and paleontologic studies (Rinehart and others, 1959), shows that the top directions of strata of Paleozoic and Mesozoic age, which form the wall rock and roof pendants, are toward the central part of the range, indicating that the batholith was emplaced along the GEOLOGY OF THE UNITED STATES axial part of a synclinorium. New data confirm and extend certain earlier concepts, namely that the Si- erra Nevada batholith is composed of many discrete plutons of granitic rock, which were in general em- placed successively from west to east and show an eastward increase in silica and potassium content. Mapping and petrographic studies by J. G. Moore and P. C. Bateman indicate that most of the individual plutons are concentrically zoned and that quartz and K—feldspar increase toward the core. In the Mount Pinchot quadrangle a swarm of lamprophyric dikes mapped by Moore cuts some of the plutons and in places is cut by others, a fact that helps determine the relative ages of the plutons. Structure and Jurassic fauna of the western foothills metamorphic belt of the Sierra Nevada In the western foothills metamorphic belt, L. D. Clark (1960; see also Art. 148) has identified a ma- jor system of steeply dipping faults and recognized two distinct stages of deformation. The foothills fault system, which trends northwestward and has been traced for about 200 miles, is a zone of shearing thousands of feet wide; displacement may be meas- urable in miles. R. W. Imlay has found that Late Jurassic faunas in this area have a strong boreal aspect, and that they also have affinities with Mexican and Cuban faunas. The Late Jurassic seas in California must therefore have been connected freely northward with Alaska and southward with the Tethyan region. Igneous rocks of the Cascade Range As a part of the cooperative program to prepare a State Geologic Map of Oregon, Peck’s mapping in the Cascade Range has established the stratigraphic sequence of 15,000 feet of Cenozoic volcanic rocks, ranging in composition from rhyodacite to olivine ba- salt, and the relations of the lower part of this se- quence t0 the marine Tertiary strata that interfinger with it from the west (Peck, 1960). He has also shown that these volcanic rocks were extruded from vents alined in northward-trending belts, which in general shifted progressively eastward with time (Peck, Art. 144). In the Holden quadrangle, in the northern Cas- cade Mountains of Washington, Cater has found that the post-Eocene Cloudy Pass batholith reached an exceptionally high level in the earth’s crust. In so doing it developed chilled porphyritic borders and gave rise to hypabyssal porphyry plugs, intrusive brec- cias, and a volcanic neck (Art. 213). A43 Stratigraphy and structure of the Klamath Mountains and Coast Ranges, northern California In the southern part of the Klamath Mountains, geologic mapping of the Weaverville quadrangle, done by Irwin (Art. 147) in cooperation with the State of California, indicates that a belt of metamorphic rocks in that area has a synclinorial structure, and that the Abrams mica schist is probably younger than the Salmon hornblende schist, rather than older as thought by earlier workers. In the Coast Ranges of northern California geologic mapping has been hampered by lack of fossils and of distinct lithologic units in the thick and structurally complex sequence of Upper Jurassic to Upper Cre- taceous graywacke that constitutes much of the ter- ane. The use of stain techniques (Bailey and Ste- vens, 1960) to determine the distribution of the feld- spar content of these rocks may prove to be the clue needed to unravel this geology. Results to date indi— cate that the Upper Jurassic to Upper Cretaceous rocks on the west side of the Sacramento Valley in— crease in K-feldspar content with decreasing age, whereas the rocks of the Franciscan formation gen- erally contain no K—feldspar (Bailey and Irwin, 1959). Geology of major sedimentary basins In the Los Angeles basin surface and subsurface mapping by J. E. Schoellhamer, A. O. Woodford, J. G. Vedder, R. F. .Yerkes, D. L. Durham, T. H. McCulloh, and P. J. Smith, when integrated with the results of density determinations on more than 2,000 samples, made it possible to construct a compartmen- talized lithodensity model of the basin. A gravity map, prepared by subtracting the gravitational ef- fects shown by this model from the Bouguer anomaly values, indicates a steep northeastward—sloping resid— ual regional gravity gradient, which is ascribed to landward thickening of the crust (McCulloh, Art. 150). The position of the boundary between Lower and Upper Cretaceous rocks on the west side of the Sacra- mento Valley was clarified recently by Brown and Rich (Art. 149) when they recognized an extensive zone of Upper Cretaceous slump deposits that contain blocks with Lower Cretaceous fossils. In the central part of the Oregon Coast Range ba- sin, P. D. Snavely, Jr. has tentatively concluded from his study of the sedimentary structures and the dis- tribution of lithofacies in the middle Eocene Tyee formation that these rhythmically bedded sandstones were deposited by turbidity currents flowing along the axis of a eugeosyncline about parallel to the pres- A44 ent range. In the Juan de Fuca basin and on the northern slopes of the Olympic Mountains, geologic mapping and stratigraphic studies by Brown and oth- ers (1960) together with studies of Foraminifera by W. W. Rau, established the stratigraphic sequence of more than 30,000 feet of marine sedimentary and vol- canic rocks of early Eocene to middle Miocene age. H. D. Gower has mapped a heretofore unrecognized major structural feature, the northwestward-trending Calawah River fault zone, in the Pysht quadrangle, Washington. He believes that this fault has a left- lateral displacement measured in tens of miles. Gravity studies by D. J. Stuart in western Wash- ington show a close correlation between gravity highs and thick sequences of Eocene volcanic rocks. In west-central Oregon, R. W. Bromery and P. D. Snavely have inferred from correlation of surface ge- ology with offsets of aeromagnetic patterns, that a fault with a left-lateral separation of about 3 miles extends from the town of Siletz eastward across the poorly exposed rocks in the central part of the Ore- gon Coast Ranges. ALASKA Our understanding of the geology of Alaska is still at an early stage. Large parts of the State have not been mapped at all and our geologic maps of other large parts are not up to the standards now set even for reconnaissance mapping (fig. 2). Some of the mapping now being done is in areas of special economic interest on scales of 1:63,360 or larger, but most of the mapping in progress elsewhere is being done on a scale of 1:250,000, in order to cover the region as quickly as possible. Apart from studies related to mineral and engineering problems (see pages A4—A14 and pages A19—A22, respectively), the principal areas of geologic field work during the past year were in the Brooks Range, the Koyukuk Cretaceous basin, the Tofty- Eureka district, the Matanuska Valley, the Copper River basin, the eastern Chugach Range, and south- eastern Alaska. Geology of the southern part of the Brooks Range As a part of reconnaissance mapping of the south half of the Brooks Range, Brosgé and Reiser completed a geologic map of the Wiseman quadrangle and mapped much of the Chandalar quadrangle. The rocks in this area consist largely of metamorphosed Pale- ozoic sedimentary rocks intruded by granite and basic rocks. Metal prospects occur near granite masses and on strike with them, and copper is associated with a few of the basic intrusives (Art. 161). GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Cretaceous rocks of the Koyukuk basin Reconnaissance mapping and stratigraphic studies by W. W. Patton in the Koyukuk Cretaceous basin of western Alaska, which may contain much petroleum (Miller and others, 1959), shows that late Early Cretaceous rocks in the Kateel River quadrangle are bounded on the north by the folded Early Cretaceous and older volcanic rocks of the Hogatza Arch. Both the volcanics and sediments are capped by Quaternary flows as much as 700 feet thick, but the northern and eastern limits of the Cretaceous sediments beneath these flows and the alluvium are clearly shown by several aeromagnetic profiles that cross the basin (Zietz and others, 1959). Geology of the Tofty-Eureka district In the Tofty-Eureka district in central Alaska, D. M. Hopkins and Bond Taber found that the northern limit of outcrop of a sequence of rocks many thousands of feet thick, consisting of basal orthoquartzite that grades upward to graywacke, coincides approximately with the northern limit of the Early Cretaceous geosyncline in which the sequence was deposited. They distin- guished intrusive rocks of two ages, one probably of Early Cretaceous and the other of Late Cretaceous age, and found that tin is associated with the earlier intrusives and gold with the later. They also found that the gentle valley slopes underlying the placers in the area, at first thought to be pediments carved by minor tributaries, were formed instead by trunk streams flowing east or west, which during most of Pleistocene time were cutting into their south banks and simultaneously deepening their valleys. Stratigraphy of the Matanuska. formation The rocks that make up the Matanuska formation in the Matanuska Valley, Nelchina area, and Copper River lowlands were found by Grantz and Jones (Art. 159) to range in age from Albian to Late Maestrich- tian and to be separated at three stratigraphic levels by unconformities. Although the gross stratigraphic succession is similar in all these areas, the details of the succession change significantly between the Nel- china area and the Matanuska Valley. The formation is more highly deformed in the Matanuska Valley than in the other areas. Geology of the eastern part of the Chugach Mountains The lithologic character and general structural pat— tern of complexly folded sedimentary, volcanic, and metamorphic rocks have been determined by Earl Brabb and D. J. Miller in a strip crossing the previ— ously unknown eastern part of the Chugach Mountains. They discovered that the argillite-graywacke sequence exposed on Barkley Ridge in the southern part of the A45 GEOLOGY OF THE UNITED STATES .mvuavnaum oonammfiaqoog $2: 39: 3m2oom 03333» 9855 maven no ”Sweden: one @5265 Sada .8 maglfi mmbwnh o a... $b cox—£090 I co q 0 0:0 / H 1 5.0:; \ 00 ¢ ..\.. 5295 Lo owmfimw; *0 Boom c an. E 389.: cmmn o>oz mucgfl 05:669. 9: . 63%.: 230326 cows +0: w>cc 3:22 GoEEfimow wot: mfmmwaco‘fioac 52mm; 58 9: c_ 39: :o be owmhmm; we Boom o . .6 umaaoE :wwn w>oc wtmoawc 65:5». .86 _ x0968 :1me 9: E 5.6% $522 we 05822 83$; 3 28m 838... 3 28m 800.08; .5253 3:25 5 000.00: 3 23m 800.com”. 52:3 3:95 a 80.00: 8 28m b km<4< kb 3 You on o no o 92.3: 286 :2...» ... a a... _ ¢ \ K \ kqbw qu a. :14 Eu 3.09.5340 22:2“. acoz mF_mOn_wD |_<_U_mm_3m xoomomm “.0 mn_<2 .mkwkm “gunk 096%“ o .._o 252 . 022%. a o f n i . a concoo on k coma” oaAV no one a an a one o co no can; ayo zozaz<4mxm o .uawu ,noomoo or %wu.ow — ca a oooohoauaaoaoo a o co cacao-0o 000 a O < Ax ‘ m V [W U Q 26:5 0 _ H o I 3.. .mb A46 area is of Late Cretaceous or Paleocene age. Some copper and gold mineralization is associated with dioritic intrusives. They found evidence of two major glaciations, both presumably Wisconsin in age, and they also found evidence of late Wisconsin and Recent uplift. Geology of Admiralty Island The work of E. H. Lathram and others has shown that the metamorphic rocks forming the backbone and western side of Admiralty Island (including the Retreat group, previously thought to be of Triassic to Cretaceous age) are Silurian and Devonian. There is evidence for three periods of folding, all of which may be later than Early Cretaceous. Most of the folds are overturned to the southwest, but a few are overturned to the northeast. The rocks are intruded by many small stocks and by a batholith having an area of at least 150 square miles. Migmatites related to two of the stocks show signs of mineralization (Berg, Art. 19). Reconnaissance aeromagnetic surveys of sedimentary basins Analysis of aeromagnetic profiles across the Yukon Flats indicates that magnetic “basement” underlies most of the area at no great depth (Zietz and others, Art. 36). Only in relatively small parts of the area have low magnetic gradients been found that might indicate possible thick sequences of sedimentary rock. Aeromagnetic traverses across the Bethel lowland show that it is not a simple structural basin but is underlain by four northeast-trending belts, two where magnetic rocks are relatively near the surface, and two where magnetic rocks lie at considerable depth. East-west aeromagnetic lines flown across the Cook Inlet-Susitna lowland between Chelatna Lake and Seldovia, show a line of abrupt change in magnetic pattern that crosses the Susitna and Beluga lowlands and coincides in part with the Castle Mountain fault (Grantz and others, unpublished data). Great thicknesses of sedimentary rocks probably do not occur north or northwest of this line. South of this line, however, thick sections may underlie part of the Beluga lowlands and are known to be present southeast of the line in the Cook Inlet area. A total intensity aeromagnetic contour map and a gravity survey indicate that in places within the southern half of the Copper River basin sedimen- tary rocks are thick enough to have oil possibilities (Andreasen and others, unpublished data). Tectonic provinces of Alaska A tectonic map on a scale of 112,500,000, compiled by George Gryc and others, shows that Alaska is made up of a series of arcuate geosynclinal and geanti- clinal belts that, except for the Brooks Range geanti- GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS cline, are approximately parallel to the coast of the southern part of Alaska. These major tectonic belts are similar to those known further south on the North American continent. The Arctic Coastal Plain and the floor of the Arctic Ocean off Alaska, like the cen- tral interior of the United States and Canada, was probably a platform or shield until the beginning of Cretaceous time. The Brooks Range compares tecton- ically to the Rocky Mountains, the Central Plateau region of interior Alaska to the Basin and Range province, the Alaska Range and associated Talkeetna Mountains to the Sierra-Cascade province, the Cook Inlet—Matanuska Valley lowland to the Great Valley of California, and the Chugach and St. Elias Ranges and the Kenai Mountains to the California and Oregon Coast Ranges. Glacial history and distribution of surficial deposits in Alaska Coulter, Hopkins, Karlstrom, Péwé, Wahrhaftig, and Williams have compiled a map on a scale of 122,500,000, which shows the limits of past ice advances of post-Altithermal or Recent, post-Illinoian, pre- Altithermal, Illinoian, and pre-Illinoian ages through- out Alaska. One of the interesting things brought out by this compilation is that during each advance glaciers have been most extensive on the south side of moun- tain ranges and most restricted on the north sides—a rain shadow effect demonstrating that precipitation sources lay to the south and southwest in the Pacific Ocean and perhaps the Bering Sea during at least the last half of Pleistocene time. Another map of Alaska on a scale of 11,584,000 compiled by Karlstrom and others (Art. 154) shows the distribution of surficial deposits (including glacial deposits, loess, alluvium, coastal sediments, and volcanic deposits) and also the location of ice fields and glaciers, and major faults that have displaced surficial deposits. It should be of considerable use in state-wide planning of engineering projects. In the Johnson River area on the northeast side of the Alaska Range, G. W. Holmes (1959d) has recognized three major glacial advances in his summary of the Quaternary history of the area. In the Cook Inlet area Karlstrom (1959 and Art. 153) has established a Qua- ternary chronology of 5 major glaciations and has correlated this glacial sequence with that of the mid- continent area of the United States. In the upper Kuskokwim region, Fernald (1959) has differentiated and mapped the extent of two ice advances. Other recent observations on the extent, age, and origin of surficial deposits are reported in papers by Coulter (Art. 160), Lewis (1959a,b), Nichols (Art. 162), Wil- liams (1959 and Art. 152), and Williams, Péwé, and Paige (1959). GEOLOGY OF THE UNITED STATES HAWAII The Geologic Division’s current work in Hawaii is mainly concerned with investigations of alumina—rich soils, and with observations on the Hawaiian volcanoes. Alumina-rich soil and clay Alumina—rich soils developed on basaltic rocks in the Hawaiian Islands are being investigated by S. H. Patterson to determine both their economic significance and the geologic factors influencing their distributions. This work, which is being done mainly in Kauai, is an extension of earlier reconnaissance investigations by J. B. Cathcart of the Geological Survey and Professors G. D. Sherman and A. T. Abbott of the University of Hawaii. Kauai, as one of the geologically older island volcanos of the Hawaiian group, is more deeply weathered than the younger islands. Work to date by Patterson indicates the Kauai deposits are sub- marginal as bauxite ore. On the island of Hawaii G. D. Fraser (Art. 163) has mapped an extensive and deeply weathered pyro- ' elastic deposit known as the Pahala ash. This bed, locally several feet thick, is now known to be a unique horizon marker in the Mauna Loa-Kilauea lava se- quence and is believed by Fraser to have emanated from Kilauea as phreatomagmatic explosions. Com- posed largely of pumiceous material, its weathering to high-alumina clay has proceded more rapidly, geo— logically, than weathering of basalt. Ultramafic difl’erentiates in the Kaupulehu flow A remarkable “boulder bed” composed essentially of ultramafic inclusions has been exposed by a new road cut in the 1801 Kaupulehu flow on Hualalai Volcano. Locally this “conglomerate” contains less than one percent lava matrix and is up to 9 feet thick. The mineral and chemical composition of the olivine— rich and pyroxene-rich nodules are being studied in great detail by D. H. Richter and K. J. Murata for their significance in magmatic differentiation of pri- mary basaltic magma. Recent volcanic activity at Kilauea-Iki and Kapoho Recent volcanic activity on the island of Hawaii, beginning with a summit eruption at Kilauea-Iki in November 1959 and ending with a flank eruption at Kapoho in February 1960, was observed and analyzed by geologists D. H. Richter and C. K. Wentworth, geochemists K. J. Murata and W. U. Ault, and geo- physicists J. P. Eaton and H. L. Krivoy of the Geo- logical Survey’s Hawaiian Volcano Observatory. The recent series of eruptions at Kilauea were presaged by a swelling of the volcano from October 1958 to February 1959, measured by the Survey’s newly developed portable tiltmeter. The swelling A47 subsided until August when, accompanied by a series of earthquakes, it commenced again. During the next few months the rate of swelling increased and the series of earthquakes, originally centered 35 miles below the surface, became shallower and more numerous. A great flurry of tiny, near-surface earthquakes centered on the edge of the crater heralded the violent summit eruptions at Kilauea—Iki from November 14 to Decem— ber 20, 1959. Although the swelling subsided slightly during the eruptions, it continued at an increasing rate until January 13, 1960 when an eruption occurred on the flank of the volcano at Kapoho 24 miles away, an event also foreshadowed by a flurry of local earth- quakes. The volcano then settled dramatically as the magma reservoir was drained, and activity cul- minated in a series of small collapses of the crater floor. Sixteen phases of the eruption in the summit crater were recorded in the period November 14 to Decem- ber 18, 1959, each manifested by geyser-like action with fountains up to 1,900 feet high. The lava temperature reached a maximum of 1190° C. The depth of the lava lake exceeded 400 feet and the thickness of the ash fall at the crater rim exceeded 100 feet. The crust on the lava lake has been penetrated by drilling, and devices installed in the hole for geothermal studies have recorded a thermal gradient of 100° C per foot in 7 feet of crust. The lava from the summit eruption contains 46.3 to 49.5 percent Si02. Among the gases identified in the eruption, 802 reached concentrations of one percent within the high— temperature interior of the newly—formed pumice cone, and in Hilo, 22 miles distant, the 802 content of the air reached 2 ppm. The ratio of COz/SOZ ranged from 0.6 to 2,000 at different gas-venting localities. CuClg emission was detected in volcano flames during eruption. The flank eruption at Kapoho was predicted by seismic station monitoring, and public warnings were issued after the Kapoho graben sank three feet. Erup- tion began on January 13, 1960 and ingress of ground water caused violent steam emission coincident with lava eruption. Flows rapidly changed from pahoehoe to aa. The lava that issued from Kapoho was more viscous, reached a lower maximum temperature, and contained more silica (50.2 percent SiOg), plagi- oclase, and pyroxene and less olivine than the lava that came from the summit eruption. The Kapoho eruption is interpreted as a more advanced differen- tiate of the Hawaiian primary magma. PUEBTO RICO AND THE CANAL ZONE The US. Geological Survey has been studying the geology of Puerto Rico in cooperation with the Eco- A48 nomic Development Administration of the Common- wealth of Puerto Rico. The project was started in 1952, and its purpose then was only to investigate the mineral resources, but in 1955 its aims were enlarged to include mapping the entire island on a scale of 1:20,000. The mountainous central part of the island is made up of rocks of Late Cretaceous and early Tertiary age in a complexly faulted northwest-trending anticlinor- ium. Most of the stratigraphic units are lenticular and consist of volcanic rocks or of sedimentary rocks containing volcanic fragments (Berryhill, Briggs, and Glover, 1960). These units are cut by several large bodies of intrusive rock. The coastal border of the island is underlain by gently dipping younger rocks of Tertiary age. In the east-central part of the central mountainous area, graben and horst structures occur in a zone of complex faults (Briggs and Pease, Art. 167), and in south-central Puerto Rico small thrust faults have been recognized by Glover and Mattson (Art. 166). In the north half of the mountainous area hydro- thermally‘altered rocks containing quartz, pyrophyl- lite, alunite, and kaolin group clays occur at several places along a northwest trending belt (Hildebrand, 1959; Pease, Art. 165). In the Canal Zone and adjacent parts of Panama, geologic studies have been carried on intermittently by W. P. Woodring since 1947., The principal ob- jectives have been to determine the geolo 'c history of the land bridge, but geologic mapping b the Geo- logical Section of the Special Engineerin Division of the Canal Zone has been compiled and 's included in Chapter A of Professional Paper 306 on he geology and Tertiary molluks, published in 1957. The de- scription of the Tertiary mollusks is co tinued in Chapter B (Woodring, 1959a). WESTERN PACIFIC ISLANDS The scattered islands and the island groups of the Western Pacific (fig. 3) represent the exposed re— gional geology of an area greater than that of the continental United States. Up to 1946, little detailed geologic information about this area was available; today, as the result of geologic studies supported or done in cooperation with several agencies f the De- partment of Defense, with the US. Atomi Commis- sion, and with the National Research Cou cil, it is abundant. Some of the islands, indeed, a among the most intensely studied places on earth. 1 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS Geologic contrasts between the island arcs and islands of the western Pacific basin The contrasting geologic nature of islands situated on the two major island arc systems bounding the western side of the northern Pacific Basin are illus- trated by differences in the stratigraphic successions of the rocks of Okinawa and Ishigaki in the Ryukyu Islands and of Guam in the southern Mariana Islands and Yap in the western Caroline Islands. On Okin- awa, an island of the western arc, raised late Tertiary and Quaternary reef limestones and associated sedi- ments overlie a thick sequence of tilted Miocene marls and complexly folded and faulted low-grade meta- morphic geosynclinal deposits mostly of late Paleozoic age (Flint, Saplis, and Corwin, 1959); those of Ishi— gaki rest on faulted Eocene limestones, conglomerates and volcanic rocks, and on probable late Paleozoic intermediate-grade metamorphic geosynclinal sedi- ments that have been intruded by granites of late Mesozoic or early Tertiary age (Foster, Art. 170). On Guam, an island of the eastern arc, uplifted reef limestones and argillaceous equivalents overlie a thick sequence of Eocene and Miocene volcanic rocks and associated sediments, most of which were de- posted at or below sea level but are now raiSed to elevations of as much as 1,300 feet and more above sea level (Tracey and others, 1959). At Yap, late Tertiary and Pleistocene reef limestones are lacking; the basement rocks include Miocene volcanic rocks, a. breccia of undetermined Miocene or Oligocene age, and older undated metavolcanic deposits that have been intruded by ultramatic rocks (Cole, Todd, and Johnson, 1960). Whereas basement rocks in both arcs are now ex- posed above sea level, basement rocks in the Northern Marshall Islands, a group in the western Pacific basin east of the arcs, now lie at appreciable depths below sea level. At Eniwetok, Quaternary reef lime- stones rest on thick Miocene and Eocene reef lime— stones that. in turn overlie a flow of olivine alkali basalt at depths of more than 4,000 feet below sea level (S. O. Schlanger and G. A. MacDonald, un- published data). Regional stratigraphic and paleontologic studies Large paleontologic collections, especially of micro- fossils and Mollusca, have made it possible to correlate the Tertiary limestones throughout. the Western Pa- cific. W. Storrs Cole reports a comparable sequence of larger Formaminifera, ranging in age from Eocene to Recent, at widely separated localities in the Fiji Islands, the deep drill holes at Bikini and Eniwetok, and the raised limestones of Saipan, Guam, and the Palau Islands. The sequence can also be correlated A49 WESTERN PACIFIC ISLANDS $3.5m #33280 05 ha "5»deng 303 9:323 2533 ummodm 5383 mo Qua xvfiglé mxbwum can scan .05 .Omn .9: .02 now." 3:: com com 00¢ CON o :2500 sugaomwm Enosmz ES ”8“on :< .m .3 6.320 umaoo .m .D Ezra .w .3 comfiwnm 05 «o mambo 8m .mocawficcouwh oWMofioww can 863m 0328M ESEEwEasm IIIII =85on Minnufi omm£oow Sufism w .Ebmfigm .«melodd h av . . w02<4w_ . em m0_I_n_m n3 (am—200%— 0 wDZdJm_ .curmmmnzmu now now “8:52 533%; was .mzom .ofiofiowu “go—ESQ ... . . . / . . m0 Z \S/ ../\om<>§. .. >\ V n |B \/ 3:4: VI . / . . MO «52228» wa<3- (Ya—Yb} For example, the adjusted mean for K20 is )(2.49— 1.37) = 186 Chemical composition of clay and limestone in Colorado, Kansas, Montana, Nebraska, North Dakota, South Dakota, and Wyoming A. Clay (712 samples, but except for Sl02, not all constituents were determined in all samples) Xa 8a Xe XI) 81: X- 8102 ___________________________ 65. 10 10. 58 65. 10 H20 ___________________________ 7. 13 4. 18 3. 05 A1203 __________________________ 15. 51 5. 67 15. 33 T102 ___________________________ . 87 - 48 - 67 F6203 __________________________ 3. 60 1. 81 3. 53 P205 ___________________________ 1. 78 2. 95 . 83 F60 ___________________________ l. 47 l. 88 . 55 2 ___________________________ 7. 48 9. 90 3. 10 MgO __________________________ 1. 40 1. 34 1. 18 $03 ____________________________ 1. 05 1. 95 . 47 C30 ___________________________ 3. 32 6. 44 2. 85 Organic matter __________________ 2. 94 3. 18 1. 08 N820 __________________________ 1. 50 1. 04 1. 03 K20 ___________________________ 1. 86 1. 01 1. 23 Total ____________________ 115. 01 ________ 100. 00 B. Limestone (751 samples, but except for CnO, not all constituents were determined in all samples) Xu 5a X: X1: ’- X1: 8102 ___________________________ 6. 74 7. 14 6. 74 H20 ___________________________ 1. 63 2. 69 1. 61 A1203 __________________________ 1. 49 1. 62 1. 48 Tio2 ___________________________ . 21 . 18 . 20 F6203 __________________________ 1. 21 1. 09 1. 20 P2 5 ___________________________ . l5 . 83 - 14 FeO ___________________________ ' . 63 . 50 . 62 CO: ___________________________ 36. 06 7. 94 35- 64 MgO __________________________ 2. 22 3. 99 2. 22 803 ____________________________ . 22 . 34 - 21 030 ___________________________ 48. 19 1 7. 21 48. 19 Organic matter __________________ 1. 23 1. 53 1- 22 No.20 __________________________ . 18 . 23 . 17 K20 ___________________________ . 37 . 44 . 36 Total ____________________ 100. 53 ________ 100. 00 A64 Two of the interesting relations that have emerged from this first compilation are: (a) cumulative fre— quency curves prepared for of each constituent suggest that major constituents tend to have a normal statisti- cal distribution and minor constituents a log-normal distribution; and (b) with increasing geologic age the percentage of K20 appears to increase in clays and shale but to decrease in carbonate rocks, sug- gesting that the potassium in interstitial waters may tend to become fixed in clay minerals with lapse of time. Distribution of minor elements During the past year the weighty mass of data on the uranium content of various magma series through- out the world obtained by Esper S. Larsen, Jr. and David Gottfried was augmented by analyses on many oceanic and continental basaltic suites. The results show that the oceanic basalts have consistently less uranium than their continental equivalents. The usual trend, in which uranium rises with SiOz, is reversed in one such oceanic suite, the alkalic Honolulu vol- canic series; this is the first such reversal encountered in the Survey’s studies. Results of several hundred precise thorium analyses by newly developed colorimetric methods do not bear out the generalization, recently published by Whitfield, Rogers, and Adams,5 that the Th/U ratio rises with SiO2 in granitic rocks as a result of loss of part of the uranium to late stage volatiles and solutions; in- stead the Th/U ratios in specific comagmatic series of known chemical composition, in contrast to the Th/U ratios on collected igneous rocks of diverse origins, average about 4.0 in all the differentiates. The one notable exception is the porphyry series in the Colorado Front Range studied by George Phair. In the Central City District a late-stage loss of uran- ium is indicated by the formation of pitchblende deposits. The late—stage differentiates (quartz boston- ites) are remarkable for their high Th/U ratios (maximum 7.5), content of uranium (up to 130 ppm) and thorium (up to 300 ppm), and for their low content of CaO, (which is almost absent in some samples). They are about as close in composition to the experimental system Ab—Or—quartz studied by Tut— tlc and Bowen6 as any rocks yet found in nature. But the high U and Th content of the residual magmas from which they crystallized is not an exotic late stage development; it was an end result of a frac- 5 Whitfield, J. M. Rogers, J. J. W., and Adams, J. A. S., 1959, The relationship between the petrology and the thorium and uranium con- tents of some granitic rocks: Geochlm. et Cosmochim. A.cta., vol. 17, nos. 3/4 p. 248—271. 6Tuttle, O. F., and Bowen, N. L., 1958, The origin of granite in the light of experimental studies: Geol. Soc. America Mem. 74. GEOLOGICAL SURVEY RESEARCH l96‘0—SYNOPSIS 0F GEOLOGIC RESULTS tionation process that can be traced backward in time through a series of earlier differentiates. These data for Th and U in large measure independently confirm the subdivision of the major Laramide petrographic provinces into subprovinces, and these in turn into separate centers of intrusion as delineated by plotting the major oxides on variation diagrams using the results of 70 standard rock analyses by rapid methods. Phair and Gottfried have extended the Colorado Front Range studies to include the Boulder Creek intrusion, a small but complex Precambrian batholith, in order to assess the mobility of minor elements under conditions of (a) magmatic differentiation plus as- similation, (b) crushing and recrystallization, (c) hy- drothermal alteration, and (d) reheating by later intrusions. Their data indicate that the general result of all post-solidification processes was to reduce the uranium content. Under conditions of crushing plus recrystallization, both uranium and lead are commonly removed from zircon, but the lead is removed more rapidly than the uranium, resulting in discrepant “low” ages. The low—age zirconsvfrom this batholith are commonly characterized by fresh, recrystallized rims. A detailed survey of data on the abundance of zir- conium in volcanic rocks made by Chao and Fleischer shows that Within a given region, the zirconium con- tent generally increases regularly with increasing con- tent, of silica and alkalies. There are marked regional variations, however, that are not yet explained. For example, basalts of Palau and Guam contain an aver— age of 20 ppm Zr,-those of the Aleutians and Japan about 50 ppm, and those of the Sierra Nevada of California close to 200 ppm Zr. During the course of developing a method for analyzing zinc in silicate rocks, Rader and others (Art. 216), found that the zinc content of 159 samples of basalt from Widely scattered areas ranges from 0.0048 to 0.018 percent and averages 0.0094 percent. Compared with other constituents, the zinc content of these basalts generally increases as the total iron increases and the silica decreases. From analyses of minor metals in the rocks of the Pierre shale, Tourtelot and others (Art. 205) have found that bentonite seems to have the highest mean contents of zirconium and lead; shale and claystone with more than 1.0 percent organic carbon have the highest mean contents of vanadium, copper, arsenic, selenium, molybdenum, and uranium, and they tend to have the highest mean contents of boron, chromium and probably zinc. Marlstones have the highest mean contents of strontium and manganese. Zubovic and others (Art. 41; also p. A14) report that the elements most closely associated with carbonaceous matter in MINERALOGY, GEOCI—IEMISTRY, AND PETROLOGY coal are beryllium, boron, titanium, vanadium, and germanium. ORGANIC GEOCHEMISTRY Research in organic geochemistry, described here, relates to the structure and geochemical relations of naturally occurring organic substances, and to bio- geochemical processes in isotope fractionation. In- formation on the minor metal content of certain fuels is discussed on pages A3 and A14, and the application of concentrator plants to studies of the incidence of dis- ease and to geochemical prospecting are discussed on p. A25 and in Article 46, respectively. ‘ Structure and geochemical relations of carbonaceous substances A. M. Pommer and I. A. Breger have concluded from potentiometric titrations and infrared analyses of humic acid that in alkaline solution humic acid increases with time in its apparent equivalent weight While undergoing loss of carbonyl groups and con- version of aliphatic structures into polynuclear ring systems. Independent studies by I. A. Breger and by James Schopf indicate that much of the solid carbonaceous matter in Paleozoic and younger shales is similar to coal or lignite, but that one can dis— tinguish between fractions of marine and nonmarine origin. Breger has also found that neutron irradia- tion induces the formation of free radicals and high reactivity in high-rank coals, and that it can convert humic acid in peat to a product. resembling high-rank lignite. His studies of the structure of organic matter associated with Colorado Plateau uranium ores have led him to conclude that the ores are associated with humic substances related to coal rather than to oil. Infrared spectrophotometric analyses by F. D. Sisler of a piece of the Murray meteorite from the Smith- sonian Institution collections indicate that it contains nitrile and other structurally “organic” components, as well as amorphous carbon. Biogeochemical processes in isotope fractionation The mechanisms by which hydrogen isotopes are fractionated by microorganisms and the divergent metabolic pathways of and biologic tolerances to protium, deuterium, and tritium are also being in— vestigated by Sisler in an effort to evaluate ecologic and diagenetic effects and the possible significance of the process in producing heavy water. Laboratory cultures of a bacterium from the Bahama Banks gen- erate protium-enriched gas during carbohydrate fer- mentation in normal media, and in those enriched in deuterium or tritium, but the fate of the heavy iso- topes after fermentation is not yet clear. Experiments in progress with tritium—enriched glucose, in collabora~ A65 tion with Drs. Micah Krichevsky and Benjamin Prescott of the National Institutes of Health, suggest, however, that. the heavy isotopes are bound within polysaccharide molecules and then excreted. D. E. White (Art. 206), from his study of natural waters, infers a biogenic origin for the relatively high nitrogen and iodine content of connate and meta- morphic waters and also for the high C02 content and relatively low 013/012 ratios of ground waters. Equipment for mass spectrometric determination of C13/C12 and 018/016 ratios has been installed under the direction of Irving Friedman and is now being used. Radiocarbon studies by Meyer Rubin show no detectable uptake of old carbonate by grasses growing on caliche and no evident fractionation of carbon isotopes in wood buried in an alkali soil. PETROLO GY Information on rock-forming processes and on the source of the materials of which rocks of various types are composed is gathered during most field and many. laboratory investigations, and has already been discussed in several parts of this report (see espe— cially the sections on mineral resources, regional ge- ology and experimental petrology). Some studies, however, are concerned primarily with these subjects and are yielding results of wide application. These are reported in the following paragraphs. Origin of granitic rocks P. C. Bateman, L. D. Clark, N. K. Huber, J. G. Moore, and C. D. Rinehart have concluded that the granitic rocks of the Sierra Nevada are in discrete plutons, emplaced successively over a period of at least 12 million years. Many of the plutons are com- positionally zoned, both laterally and concentrically, probably as a result of crystallization-differentiation. The plutons were emplaced by pushing the wall rocks aside and upward; piecemeal stoping was quantita- tively unimportant. Granitization and assimilation effects are conspicuous, on a small scale, where granitic magma came in contact with mafic rocks, and the reactions that took place accord with Bowen’s reaction series. Toulmin (1959) has also called upon magmatic processes to explain the origin of a syenite body near Salem, Mass. He suggests that the syenite is an accumulated “shower” of feldspar crystals resulting from periodic release of volatiles from a granitic magma through volcanism. Crowder (1959), on the other hand, has concluded that a quartz—diorite com- plex in the Northern Cascade Mountains was formed by granitization of gneisses and schists. Locally the rocks were rendered plastic and mobile during granit— A66 ization, and, in places, were fusedlto produce anatectic magmas that differentiated to form potassium-rich pegmatites and local granodiorite masses. Origin of ultramafic rocks and related gabbros E. D. Jackson has applied many of the techniques of sedimentary petrology to the layered rocks of the Ultramafic zone of the Stillwater complex, and has found that primary precipitate crystals are not only present in these rocks but that they obeyed the laws that control gravity stratification. From studies of the shape, distribution, and grain-size and size-dis— tribution, orientation, and packing density of the settled crystals, and of the distribution and order of crystallization of the interprecipitate material, he has concluded that the rocks formed during crystallization of a single saturated basalt magma by accumulation of early crystal products on the floor of the magma chamber and that these crystals were enlarged or ce- mented after deposition by the magma from which they crystallized. Jackson believes that crystallization took place near the floor of the magma chamber, that the layered rocks directly reflect changing composition of the magma with time, and that the textures, mineral associations, and cyclical rock distributions in the ultramafic part of the complex can best be explained by a mechanism involving continuous but variable- depth convection that caused periodic refreshment of magma crystallizing in the lower part of the intrusion. T. P. Thayer has compared the petrologic features of stratiform peridotite-gabbro complexes, like the Stillwater complex, with those of Alpine-type intru— sions. He concludes that the stratiform complexes originated by crystallization of molten magma in place with little or no disturbance, whereas Alpine-type com- plexes were intruded as already differentiated crystal mushes and that mixing of gabbro and peridotite commonly occurred during emplacement. Origin of welded tuffs C. S. Ross and R. L. Smith have demonstrated the abundance of welded tuffs (ash flows) in the geologic record and the significance of fluids trapped within ash particles in maintaining an extensive subaerial flow of the dense pyroclastic clouds. R. J. Roberts and D. W. Peterson have shown that two major types of welded tufl's—welded ash tufl's and welded crystal tufl's—can be distinguished on the basis of composition and texture. Eruptions yielding welded ash tuffs are generally characterized by higher silica content and higher volatile content than those yielding welded crystal tufl's. They conclude that the source magmas of the welded ash tuifs are more highly differentiated than those of the welded crystal tufl's. GEOLOGICAL SURVEY RESEARCH l960—SYNOPSIS OF GEOLOGIC RESULTS Fluidity of lava The problem of the fluidity of Precambrian basaltic lavas in the Lake Superior region has been considered by White (1960b), who has concluded that the typical thinning in the direction of flow, the absence of lava tunnels and of true aa, and the characteristic differen- tiation in the Keweenawan flood basalts can be ascribed to the great volume of the flows alone, rather than to greater fluidity of the basalts as has been suggested previously. Powers (Art. 136), on the other hand, has called attention to the exceptionally high fluidity of some alkalic lava in the Snake River plain. Source of volcanic magmas Several deductions have been made recently as to the source of specific volcanic magmas. In Bulletin 1028—H Snyder reported that chemical variations and extrusive sequences of the lavas of Little Sitkin Island _ in the Aleutian Islands of Alaska are inconsistent with the Bowen reaction series, and that they were produced by magmatic melting in a zone where continental and oceanic rocks had previously been mixed by tectonic processes. From the compositional trends and age relations of lavas on Semisopochnoi Island in the same area, Coats (1959) has suggested that, although the chemical trends can best be explained by differentia- tion, the differences between early and late extrusive rocks mean that magma was mixed with its earlier differentiates. Peck (1960) believes that the Cenozoic volcanic rocks of the Cascade Range in Oregon were derived from five or six successive magmas, mostly of andesitic composition, that formed by partial or complete fusion of parts of the underlying crust during periods of crustal stress. Differentiation of these magmas, prob- ably in large part by crystal fractionation, yielded volcanic rocks ranging from olivine basalt to rhyoda- cite. R. L. Smith, who studied the volcanic rocks of the Lava Mountains, Calif, found that earlier volcanic products in the area resulted from explosive activity, whereas the later ones were effusives. The frequency of eruption increased with time, but no systematic compositional change occurred. According to Smith, the volcanic magma probably formed by the complete melting of crustal quartz monzonitic rocks, and did not differentiate after eruptions began. See page A47 for a description of recent observa- tions at the Hawaiian Volcano Observatory. Role of fluids in low-temperature alteration of volcanic glass A. B. Gibbons, and others (Art. 214), from a study of volcanic rocks in southern Nevada, have suggested that mildly alkaline ground water moving through MINERALOGY, GEOCHEMISTRY, AND PETROLOGY permeable tufl' layers altered volcanic glass to zeolites at near—surface temperatures. R. L. Smith and coworkers have recently shown that perlite, long considered a product of hydrothermal alteration of rhyolitic glass, is instead a surficial alteration produced by meteoric water; this conclusion is based partly on the similarity in isotopic composi- tion of oxygen and hydrogen in the perlite to that of ground waters of the area in which it occurs. Origin of propylitic alteration In the San Juan Mountains, Colo., W. S. Burbank (Art. 6) has found that the propylitic or quartz- carbon-ate-chlorite type of alteration has affected many cubic miles of volcanic rocks throughout and beyond the Silverton caldera. Field relations and other data have led him to conclude that this type of alteration takes place after volcanic eruption has ceased as the result of evolution of gas, rich in C02, during crystal- lization and differentiation of deep-seated gabbroic and granodiorite magma. The process consists of (a) condensation of gases in locally adsorbed water films; (b) partial solution of silicate minerals by the con- densates; (c) mixing of saturated condensates with other patches of liquid forced along by gas pressures; and (d) reaction in these mixtures causing precipita- tion of new minerals. Propylitized rocks are prob- ably an arrested stage of this process; if it is long continued it probably forms carbonatized and chlori- tized rocks. Metamorphism of maganese minerals D. F. Hewett. has found that the manganese ortho- silicate, tephroite is widespread in manganese deposits in the Jurassic metavolcanic rocks of the western Sierra Nevada of California. Although tephroite is commonly regarded as of hydrothermal origin, Hewett believes that in the Sierra it is a product of the ther- mal metamorphism of original manganiferous car— bonate in an environment of connate water. Pavlides (Art. 211) has found that tightly folded beds in Aroostook County, Maine, containing braunite (3Mn2030MnSi03) and hematite, have been metamor- phosed to magnetite-bearing rocks that contain no braunite. The recrystallization of the iron oxide and the migration of the manganese is most pronounced in areas of tight folds, which appear to have been local thermal nodes. Steatitization as a product of regional metamorphism In a recently completed study of the Vermont talc area, A. H. Chidester has found that the steatite was formed by regional metamorphism in two stages, both unrelated to earlier alteration of the ultramafic rocks A67 to serpentine. In the first stage, serpentine was altered to talc—carbonate rock by addition of C02 and loss of H20. In the second, metamorphic differentiation in the contact zone between serpentinite and country rock formed steatite and “black wall” chlorite. Origin of jadeite and rodingite in serpentine Coleman (1959b) finds that jadeite in the California serpentine masses is stable in the glaucophane-schist facies and believes it formed by‘ the desilication of quartz-keratophyres in a serpentine environment at pressures less than 5,000 bars and temperatures less than 300°C. In the San Francisco Bay area J. G. Schlocker has noted that alteration of sandstone to jadeite in the Franciscan formation is local, which in- dicates that the process was not controlled by condi- tions of regional extent, as formerly supposed. He also believes that the rodingites in the serpentines of the Franciscan formation are tectonic inclusions of calcium-enriched volcanic and other rocks (see Art. 145). Migration of elements during metamorphism The progressive metamorphism of basalt, graywacke, and siliceous magnesium limestone in the Adirondack Mountains of New York has been studied by Engel and Engel (Art. 212). They have found the meta- morphism at 500° to 600°C was accompanied by emis- sion of water and COz-rich fluids containing alkali silicates, Pb, Ba, and Mn. A different group of elements—mainly Ca, Mg, A1, and Fe—migrated during the metamorphism of rocks in the Orofino area on the northwestern side of the Idaho batholith, according to Anna Hietanen-Makela. The temperatures attained during metamorphism there appear to have been 400° to 500°C. Mrs. Makela is using the aluminum silicates andalusite, kyanite, and sillimanite as a key to the temperature and pressure that prevailed during metamorphism. Origin of evaporite deposits E—an- Zen (Art. 209) has applied the Gibbs Phase Rule to the precipitation of salts from a moving body of water and proposes that many mono-mineralic evaporite deposits form as a result of fractional crys- tallization from an ocean current (see also p. A8). Petrographic studies by C. L. Jones of a core from salt in the Permian Hutchinson salt member of the Wellington formation in Reno County, Kansas, and of salts from several western fields show that magne- site and dolomite pervasively replace calcite, and that calcite is the main primary carbonate deposited in evaporite environments. A68 Transformation of aragonite mud to aphanitic limestone Using electron microscopy techniques, J. C. Hatha- way has shown that aragonite muds can be changed in a relatively short time to aphanitic limestone at low temperatures and pressures. In this transforma- tion, the mud changes progressively from a mass of needle-shaped particles, to a mass of rounded and coalescing particles, to a final rock stage of mosaic texture and fracture surfaces typical of aphanitic limestone. Origin of chert The relation between type and chemical composition of chert has been studied by E. R. Cressman from data compiled from the literature. He plotted the Si02 content of each analysis against the ratio SiOZ/ A1203, and compared the distribution of the plotted analyses with the lines representing the theoretical change in composition that would result from the addition of Si02 to the average pelagic clay, the aver- age sandstone, and the average limestone. Analyses of radiolarian chert and shale fall in a well-defined trend that coincides with the line plotted from the composition of the average shale. - Analyses of spicular cherts fall along the line plotted from the average sandstone. Analyses of chert nodules from lime- stone and dolomite are widely scattered, and all analyses fall to the left of the curve plotted from the composition of the average limestone; however, a curve representing the change in composition that would result from volume-for-volume replacement of calcite of the average limestone by quartz falls in the midst of the points, supporting the hypothesis that most nodular chert is of replacement origin. From an analysis of the spatial relations of fos- sils and chert in the Redwall limestone (Early Mis— sissippian) in Arizona, E. D. McKee (Art. 210) has suggested that layers containing abundant fossils were layers of maximum permeability and therefore espe- cially susceptible to chertification. Dolomite in» the same formation probably formed by the replacement of calcium carbonate on or beneath the sea floor be- fore lithification, but a comparison of the preservation of fossils in dolomite and chert suggests that the chert formed before the dolomite. ISOTOPE AND NUCLEAR STUDIES Isotope and nuclear studies are being made in con- nection with many diverse problems, ranging from methods of.ore finding to the study of paleotempera- ture. Only those studies having to do with the dis- tribution of deuterium and tritium in natural fluids, measurement of alpha activity, and geochronology are GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS described here. Results of other isotope and nuclear studies are discussed in the sections on beryllium (p. A8), uranium (p. A11), exploration methods (p. . A15), and organic geochemistry (p. A65). DEUTERIUM AND TRITIUM IN NATURAL FLUIDS Differences in the isotopic composition of meteoric, connate, and thermal waters Harmon Craig of the University of California, La Jolla, and Donald E. White have found that near Steamboat Springs, Nev., hot springs and surface wa- ters differ significantly in D/H, 013/016 and C13/C12 ratios, depending on‘ details of origin and evapora- tional history (White and Craig, 1959). Preliminary data indicate that connate, magmatic, and metamor- phic waters difl'er chemically (White, Art. 206) as well as isotopically (if both oxygen and hydrogen are considered together) from ordinary surface waters and that isotopic differences in surface waters are related to distance from the oceans, latitude, and evapora- tional history.7 Deuterium content of ocean and terrestrial waters Preliminary results of a study of the deuterium variations in ocean waters being carried out by Irv- ing Friedman, in cooperation with A. O. Redfield of Woods Hole Oceanographic Institution, indicate that in general the waters originating in the Antarctic con— tain as much as 1 percent less deuterium than other ocean waters, and can therefore be traced long dis- tances northward. Deuterium analyses of the surface waters of the United States show that the areas where deuterium is highest are mostly in the Gulf Coast region and in coastal Southern- California (Friedman, unpublished data). Lower values are found further north on the Atlantic Coast and the Pacific Coast. The deuterium content decreases inland with increasing altitude and is especially low in the lee of high mountains. In a study of the deuterium content of Arctic sea ice, Friedman, B. Schoen, and J. Harris found evi- dence for the existence of a layer of water derived from melted snow on the surface of parts of the Arctic ocean in summer. Tritium and deuterium content of atmospheric hydrogen The tritium and deuterium content of atmospheric hydrogen gas has been determined by Frederick Bege- mann of the Max-Planck Institut fiir Chemie, Mainz, Germany and Irving Friedman. Although the tritium is enriched by a factor of 104 to 105 over that in rain, 7Craig, Harmon, Boato, G., and White, D. E., 1956, Isotopic geo- chemistry of thermal waters: Proc. Second Conf. on Nuclear Processes in Geologic Settings, Pub. 400, Nat. Acad. Sci-Natl. Research Coun- cil, p. 29—38. MINERALOGY, GEOCHEMISTRY, AND PETROLOGY the deuterium content is similar to that in rain. In samples collected in Buffalo, New York from Janu— ary 1954 to October 1956, the tritium and deuterium contents show a linear relation to each other. A simi- lar relation was found for samples collected in Ger- many by B. Gonsior, of the University of Heidelberg, who also made the tritium determinations on them. Deuterium in liquid inclusions Wayne Hall and Irving Friedman have found that the deuterium content of water extracted from liquid inclusions in minerals from the Cave-in-Rock fluorite district of southern Illinois show differences that are related to the paragenesis. Fluid inclusions from the early minerals have a deuterium content and salinity similar to that of local connate water. Fluid inclu- sions from later minerals are progressively depleted in deuterium. MEASUREMENT OF ALPHA ACTIVITY A method has been developed by A. Hoyte and F. Senftle for determining the absolute alpha activity of thick powdered mineral samples without using a stand- ard sample. To measure alpha spectra with better resolution, Martinez and Senftle (1960) have studied the effect of crystal thickness and geometry on alpha particle resolution, using cesium iodide as a scintilla- tor. As a result of these investigations, they have been able to obtain a resolution of 1.8 percent for P0210 alpha particles, which is considerably better than has ever been reported for crystal scintillators. The effects of alpha-particle radiation damage on the magnetic properties of crystals has been critically examined by Senftle and Pankey, and they have de— vised a theoretical model which explains the heating curves for some uranium—bearing minerals such as zir- con, coffinite, and uraninite. A new method of age determination based on this work has been outlined A69 (see p. A70), and efforts are currently being made to develop its details. GEOCHRONOLOGY Many age determinations based on C“, potassium- argon, strontium-rubidium, and uranium-lead methods have been made by the Geological Survey to help in solving geologic problems. Most of the recent age determinations that bear mainly on problems of local or regional geology are discussed in other parts of this report, but some results of wider interest. are reported here, along with work on new methods. Refinement of the geologic time scale The age of mica from several stratigraphically well- defined rocks that could serve as tie points in the geo— logic time scale was measured by Henry Faul and Herman Thomas by potassium—argon and strontium- rubidium methods. The results are listed here in or- der of increasing age: Millions of Middle or late Eocene (Rocky Boy Stock, years Bearpaw Mtns. Montana) ________________________ 50 Early Permian or later (Oslo region) ______________ 260 Post-Westphalian (younger than Late Carboniferous) (Dartmoor granite, Cornwall) ____________________ 290 Dinantian, pre-Visean (early Carboniferous) (Vosges granites, France) _______________________ 320 Late Devonian (Chattanooga shale, Tennessee)___ 340—385 Post-Middle Devonian (Hog Island, Jackman, Maine) 360 Between Late Silurian, Late Devonian (Calais granite of Foyles and Richardson, 1929, Maine) ____________________________________ 405 Middle Ordovician (Alabama bentonites) _______ 420—450 No useful tie points are yet known below the Middle Ordovician, so the length of Cambrian time can only be surmised; the above results indicate, however, that the total length of time since the Precambrian is greater than previously thought. Some zircon concentrates from stratigraphically closely bracketed rocks were studied by Thomas Stern and Harry Rose, who obtained the following results: Age (mil- Locality and sample a/mg-hr Pb(ppm) lions of years) Geologic age given in the literature San Vincente, Baja California, SV—l ________ 152 6. 1 100i10 Early Late Cretaceous (post-Albian pre-Maestr- (6. O, 6. 2) ichtian). Talkeetna Mountains Alaska, GG—l _________ 68 3. 4 125 i 15 Post late Early Jurassic, pre-middle Late Jurassic. ‘ (3. 4, 3. 4) Talkeetna Mountains Alaska, GG—2 _________ 103 5. 7 135 :i; 15 Post late Early Jurassic, pre-middle Late Jurassic. (6. 1, 5. 3) Martinsburg shale, near Strasburg, Va. VA—2- 144 24. 5 410145 Middle and Late Ordovician. (24. 5, 24. 5) Martinsburg shale, near Strasburg, Va. 137 23. 5 410445 Middle and Late Ordovician. FMB—l. The above ages were calculated from the formulas and constants given by Gottfried and others (1959, p. 16—19). The errors given above are due only to uncertainties in analytical techniques. These analy- 557328 0 - 60 - 6 ses indicate that the lead-alpha age method yields results which are consistent with the lengthened time scale suggested. by other workers. A70 Age of some uranium ores According to Stiefi' and Stern the Pb/U ratios of uraninite samples from the Urgeirica and Lenteiros mines in Portugal indicate that the age of the ore in both mines is about 83:8 m.y. Algebraic and graphical methods have been devel- oped for evaluating discordant lead-uranium ages (Stern and others, Art. 23). Applying these meth- ods, Stern and others have concluded that the ura- ium deposits in Carbon County, Pennsylvania, were emplaced during Late Jurassic or Early Cretaceous time. A geochronologic method based on magnetic properties of crystals damaged by radiation Sentfle and Pankey have found that the iron impur— ity in crystals damaged by natural radiation is in a reduced nonmagnetic state in the damaged regions. On heating for a limited time in an oxygen deficient atmosphere the crystals at first become magnetic due to diffusion of oxygen into the damaged regions and the subsequent oxidation of the iron to magnetite (Fe304). On further heating the crystals again be- come non-magnetic due to the oxidation of the Fe304 to non-magnetic a hematite (Fe203). The maximum magnetization measured during the heating cycle is proportional to the number of Fe304 molecules formed, and this in turn is related to the total radiation dam— age. As the damage is a function of the age of the crystal, the technique promises to be useful in age determinations. Preliminary measurements have yielded ages that in most cases are close to the age as measured by isotopic methods. A geochemical method for dating obsidian artifacts Friedman and Smith (1960) have developed a new dating technique that depends upon the rate of dif— fusion of water from the atmosphere into freshly worked obsidian artifacts. The useful range of the method is from about 100 years well into the Pleis- tocene. The age of the obsidian is related to the thick- ness of the hydrated layer, as measured with the petrographic microscope, and seems to follow the dif- fusion law .90 = lava where a: = thickness of the hy- drated layer, t= time, and k is a constant which de- pends on the temperature of hydration and the composition of the glass, but seems to be relatively independent of the humidity of the environment. Carbon-14 dates applied to the study of Pleistocene glaciation Carbon-14 measurements on samples from many parts of the world show that glaciations were syn- chronous in both the northern and southern hemi- spheres. According to Meyer Rubin, this indicates that glacial pulsations were not caused by local GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS changes in the pattern of precipitation, as has been proposed recently by Ewing and others, but resulted instead from world—wide cooling. The carbon-14 data have confirmed the concept that changes of sea level during the Pleistocene corre— sponded to glacial pulsations. They have also dem- onstrated the rapidity with which climatic changes took place, and have shown that the time since the last continental glaciation was only about half as long as previously supposed. ANALYTICAL AND OTHER LABORATORY TECHNIQUES Much of the research already discussed in this re- port is an outgrowth of or depends in one way or an- other on chemical, spectrographic, and other analyses performed by the Survey’s analytical laboratories, so that a large part of the results of their work has al- ready been described. In addition to making such analyses, however, the laboratories also investigate new methods of analysis and other laboratory tech- niques so as to improve their accuracy, precision, and efficiency. Methods applicable to geochemical pros- pecting and nuclear studies are described on pages A14 and A16. Some of the other important results of this research are summarized in the sections that follow on analytical chemistry, spectroscopy, and min- eralogic techniques. ANALYTICAL CHEMISTRY Zirconium in small amounts The properties of the dye 5-sulfonic acid-2-hydrox- benzene-azo resorcinol and its use as a reagent for the determination of microgram amounts of zirconium have been studied by Mary H. Fletcher. The four acidic groups of this dye dissociate in solution to give equilibrium mixtures of four anionic species each hav- ing a characteristic absorption spectrum. Spectral data were used to deduce the dissociation constants of these species, and the same approach was used to de- termine the equilibrium constants of the two zir— conium complexes that this dye forms. It was found that zirconium in pure solution can be determined over a wide range of conditions, which gives great flexibil- ity in overcoming interference. The methods used in this study should be useful in determining the com— ponents of other multi-component colored systems. Niobium and tantalum Grimaldi and Schnepfe (1959) have found that se— lenous acid can be used to separate Ta and Nb from relatively large amounts of the elements usually asso- ciated with them in their ores, and to determine total Ta and Nb or either element. The procedure has been used for analyses of 50 to 75 mg samples of ANALYTICAL columbite and tantalite ores in- which the Ta and Nb are present in amounts ranging from 0.2 to 30 mg. Grimaldi (1960) has also designed a method for de- termining the niobium content of rocks in the parts per million range. Interfering elements, such as Re, W, M0, and V, are separated from Nb by simple so- dium hydroxide fusion and leach. The determination is completed spectrophotometrically by a modified thi- ocyanate procedure. Flame photometry Two approaches were studied to overcome matrix effects in flame photometry. In one (Grimaldi, Art. 225) matrix effects are largely overcome by dilution of the sample; those that remain are corrected for by an addition technique. In the other approach, an extraneous element is added to release the normal emis- sion of a given element. Releasing agents and tech- niques were examined by J. I. Dinnin, who found that Sr, La, Nd, Sm, and Y completely release Ca from quenching by Al, S044, and P044, While Mg, Be, Ba, and Sc do so to a large extent. The use of praseodymium as a releasing agent permits the deter- mination of calcium in chromite, hitherto impossible to do by flame photometry. Analysis of liquid inclusions Methods have been devised by B. L. Ingram for determining microgram amounts of Cl‘, 804—2, and Mg in liquid inclusions. Chloride is determined in- directly through its release of thiocyanate ion from mercuric thiocyanate, the released thiocyanate being converted to a colored ferric thiocyanate complex. Magnesium is directly determined spectrophotomet— rically with Magnon. Sulfate is reduced to sulfide with a mixture of hydriodic, hypophosphorous, and formic acids, and determined spectrophotometrically as methylene blue. Fluorine in phosphate rock and chlorine in silicate rock A rapid method for the determination of fluorine in phosphate rock has been described by Shapiro (1960). The sample is dissolved in dilute nitric acid, the solution is passed through a cation-exchange resin column, and the fluorine in the effluent is determined by its bleaching action on the red aluminum-alizarin complex. A method for determining chlorine in sili- cate rock by titration with mercuric nitrate, using so- dium nitroprusside as the indicator, has been devised by Peck and Tomasi (1959). Small amounts of magnesium Investigations of new methods for determining small amounts of magnesium have proved fruitful. Bissalicylidene-ethylenediamine makes it possible to CHEMISTRY A71 determine magnesium photometrically or fluorimet- rically (Cuttitta and White, 1959; White and Cut- titta, 1959); and by using thiazole yellow, it is pos- sible to determine it photometrically in rocks, without prior separations (Shapiro, 1959). Uranium Stevens and others (1959) have developed an auto- matic machine for preparing reproducible phosphors in the fluorimetric determination of uranium. Analysis of chromite ‘ Improved procedures were developed or adapted for determining Al, Ca, Si, total Fe, Cr, and ferrous iron in chromite. To determine total iron, for example, the chromite is dissolved in a mixture of phosphoric and sulfuric acids; the iron is then reduced with a silver reductor, and finally determined by titration with dichromate (Dinnin, Art. 215). Ferrous iron Two new methods for determining ferrous iron in rocks and minerals have been developed. In one, the sample is decomposed with a mixture of hydrofluoric and sulfuric acids in the presence of dichromate in excess over the ferrous iron; the excess dichromate is then titrated with standard ferrous sulfate (Reichen, L. E., and Fahey, J. J ., written communication). In the other, the sample is decomposed with the same acids, but in the presence of an excess of o-phen-an- throline to complex the released ferrous iron; the de- termination is then completed colorimetrically by measuring the absorbance of the orthophenanthroline— ferrous complex (Shapiro, Art. 226). Both methods avoid errors in conventional procedures resulting from air oxidation of ferrous iron during decomposition of the sample. Zinc in silicate rocks A spectrophotometric method for determining small amounts of zinc in silicate rocks has been devised by Rader and others (Art. 216); zinc is isolated by anion exchange and carbamate extraction, and then measured colorimetrically with zincon. Combined gravimetric and spectrographic analysis of silicates A method that combines gravimetric and spectro~ graphic procedures for the analysis of silicate rocks and minerals has been studied by Stevens and others (Art. 228). Its essential features are that major con- stituents are chemically separated and weighed; all precipitates and residues are then analyzed spectro— graphically to make corrections for gains, losses, and impurities, and to determine minor constituents. Al- though the method has promising advantages over conventional procedures, it is so time consuming that A72 it is suitable only for special analyses that require unusual accuracy and precision. Accuracy and precision of silicate analyses A second report on the accuracy and precision of silicate analyses has been prepared by Stevens, Niles, Chodos, Filby, Leininger, Flanagan, Ahrens, and Fleischer (1960) as Bulletin 1113. It summarizes the results of over 30 new analyses of samples G—l (gran- ite) and W—l (diabase) from laboratories throughout the world, discusses the limitations of standard rock analysis, and points out areas where improved meth- ods are needed. The study indicates that, of the pro- cedures in use, those for determining silica and alu- mina are least accurate; the results for SiO2 are gen- erally too low, and those for A1203 are generally too high. SPECTROSCOPY Concentration of rhenium for analysis As a part of a study of the distribution of rhenium, Myers and others (Art. 20) extended the limit of de- tection of water-soluble rhenium from about 50 ppm to about 0.1 ppm by employing a concentration tech- nique. In this method, rhenium is leached from a 50 gram sample with distilled water; the dried extract is then added to a definite proportion of powdered quartz and analyzed spectrochemically by means of the do carbon arc. Determination of lead in zircon A synthetic zircon-baddeleyite-glass mixture con— taining lead has been prepared by H. Rose and T. Stern for determining lead (1 to 500 ppm) in zircon for lead—alpha age measurements by a d-c arc tech- nique. Fifteen milligram samples are mixed with 35 mg of sodium carbonate and arced at 15 amps for 90 seconds. Analysis of 20 zircons indicates an overall 5 percent average deviation from isotope—dilution and chemical values. The new standard and procedure replaces the opal—glass standard previously used, which was shown to be inadequate by comparison of analyses made by independent methods. Use of special standards in spectrochemical analysis Because of the large variety of materials submitted for analysis, special standards are frequently required for quantitative measurement of various elements. For example, during the analysis of some water residues, Mrs. N. Sheffey found that the analytical lines for Fe, Al, Zn, V, and Cr were depressed by high sulfate ion concentrations. This difficulty was overcome by diluting the samples with the same matrix as used for the standards. GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Use of gas jet in reducing cyanogen band interference A relatively simple gas jet surrounding the carbon are used for spectrochemical analysis has been found effective in reducing the cyanogen bands (Annell and Helz, Art. 227). Argon flowing at a rate of 16 cu ft hr and mixing with oxygen at 4 cu ft hr, was found most suitable for suppressing the bands, stabilizing the arc, reducing sample consumption, and intensify- ing lines. Controlling the arc atmosphere in this man- ner makes it possible to analyze several elements that have diagnostic lines in the cyanogen region, such as Ce, La, Sm, Pr, Nd, Eu, Tm, Tl, W, Ru, and Ti. A constant feed direct-current arc A method has also been developed by Annell and Helz for continuously vaporizing successive increments of powdered rock and mineral samples into a 10-am— pere d-c arc. In this procedure graphite electrodes, 0.092 inch in outer diameter and containing a bore 1.5 inches deep and 0.046 inches in diameter, are used as sample anodes. Elements such as Ti, Al, Si, Cu, Ga, As, and Pb are concomitantly vaporized and excited by gradually moving the electrode into the are through a channel in a brass, water-cooled collar. A controlled atmosphere, consisting of a mixture of argon, flowing at the rate of 14 cu'ft hr, and oxygen, flowing 7 cu ft hr, suppresses cyanogen band interference in the spec- tra and stabilizes the arc. Graphite and lithium tetra— borate are mixed with the powdered rock samples to obtain an optimum rate of burning in the arc, selec- tive volatilization, enhancement of desirable lines, and minimum matrix interference. Development and use of the electron microprobe analyzer The electron microprobe analyzer, designed by Isi- dore Adler, is now completed and in operation. This device uses a focused beam of electrons to excite X-rays from samples of the order of several cubic microns in volume. The resulting X-rays may then be analyzed either to identify the elements in the microscopic phase or to give the actual concentration. The sample to be analyzed is located by means of a reflecting-type microscope that is coaxial with the objective magnetic lens and is in the vacuum system. This microscope has a reflecting objective, perforated to permit the electron beam to reach the sample. The X—rays are analyzed by means of two X-ray spectro- graphs mounted in vacuum chambers. The electron microprobe is now being used for study— ing the distribution of minor elements in galena and sphalerite. A tentative procedure has been established for mounting small grains in clear cold-setting plas— tic. By using small brass rings 1/8-inch in diameter, as many as 12 different specimens can be mounted in MINERALOGIC AND PETROGRAPHIC TECHNIQUES a one inch disk and analyzed without opening the vacuum sample chamber. The cold-setting plastic, moreover, quickly forms a small dark spot where bom- barded by the electron beam, which makes it possible to position the desired area readily. Techniques have been worked out for analyzing non- conducting mineral grains by vacuum—coating them with optically transparent films of aluminum in- order to make the surface electrically and thermally con- ducting. This is necessary in order to minimize sur- face charging and heating. X-ray fluorescence analysis of sphalerite An X-ray fluorescence method has been developed by Adler for determining minor constituents in spha- lerites when gross samples are available. Results for cadmium, iron, and manganese agree with the chemi- cal figures to within about 5 percent of the amount present. MINERALOGIC AN'D PETROGRAPHIC TECHNIQUES New techniques and tools in microscopy Wilcox (1959 b, c) has designed two devices for optical determination on single mineral grains. One is a rugged spindle stage, attached to a petrographic microscope, on which crystals can be mounted and their principal indices of refraction and optical sign determined by rotating the spindle. He has also de- signed a simplified universal stage accessory for de- termining the three principal ind-ices of refraction in biaxial crystals. B. F. Leonard, III has perfected a method for quantitatively measuring the reflectivity of opaque minerals with a Hallimond visual micropho- tometer. New immersion liquids with indices of re— fraction between 1.7 and 2.1 have been developed by R. Meyrowitz and H. Westley. Mineral separation methods The principle of asymmetric vibration has been adapted to separate micas and to serve as an improved feeding device for the Frantz separator (Faul and Davis, 1959). Frost (1959) has developed a constant flow elutriating tube for separating high density sul- fides from light silicate gangue. Meyrowitz and oth- ers (1959) have found that dimethyl sulfoxide is a more stable diluent for bromoform than acetone and F. Cuttitta, R. Meyrowitz, B. Levin, and N. Hickling A73 report that dimethyl—formamide shows promise as a diluent for bromoform or methylene iodide. Staining and autoradiographic methods Staining techniques for the modal analysis of feld- spars in thin sections, grain mounts, and polished sec— tions have been improved by E. H. Bailey and R. E. Stevens; they stain potassium feldspar yellow with cobaltin‘itrite and plagioclase red with barium rhodi- zonate. R. F. Gantier and J. A. Thomas have exam- ined many dyes and reagents for staining feldspars and have found that malachite green, methyl red, and methyl violet are the most satisfactory. In a different approach to the same problem, Wayne Mountjoy and L. B. Riley have used the radioactivity of potassium to determine the distribution of potassium feldspar by means of photographic prints. Methods for studying liquid inclusions Apparatus and techniques have been developed by E. W. Roedder and Irving Friedman for vacuum crushing, extraction, and limited analysis of the solu— ble salts in solution from single selected fluid inclu— sions less than a millimeter in diameter. With slightly larger inclusions, H20, C02, H/D isotope ratio, and concentration of dissolved salts can also be determined. A new and improved heating and cooling microscope stage has been developed for studies of liquid-gas in— clusions, which permits determination of the tempera- ture of filling on heating, and depression of the freez- ing point on cooling. The freezing point may be used to estimate the concentration of soluble salts in a sin- gle fluid inclusion whose volume may be as small as a billionth of a milliliter. Methods in experimental geochemistry E. Roseboom has achieved promising results toward solving the difficult experimental problem of measur- ing total pressure of very reactive sulfur- and arsenic- bearing systems; he uses low-melting alkali halides as manometer liquids. Brian J. Skinner has put into operation an inex- pensive mullite stage for the X-ray difl'ractometer that allows measurements to be made at temperatures up to 1400°C under vacuum or controlled atmospheres. Gulbrandsen (Art. 230) has found that the solubil- ity depressant efl'ect of ethyl alcohol on saline solu- tions is an effective means of controlling and studying the precipitation of evaporites. GEOLOGIC DIVISION OFFICES MAIN CENTERS U.S. Geological Survey, Main Office, General Services Building, F St., between 18th and 19th Streets, N.W., Washington 25, D.C., Republic 7—1820. U.S. Geological Survey, Rocky Mountain Center, Federal Center, Denver 2, Colorado, Belmont 3—3611. U.S. Geological Survey, Pacific Coast Center, 345 Middlefield Road, Menlo Park, California, Davenport 5—6761. FIELD OFFICES IN THE UNITED STATES AND PUERTO RICO [Temporary offices not included] Location Geologist in charge and telephone number Address Alaska, College Troy L. Péwé (3263) P0. Box 4004, Brooks Memorial Building. Arizona, Globe N. P. Peterson (964) PO. Box 1211. California, Los Angeles John T. McGill (Granite 3—0971, ext. Geology Building, University of California. 547) Hawaii, Hawaii National Park K. J. Murata Hawaiian Volcano Observatory. Hawaii, Honolulu Charles G. Johnson (81011 ext. 66—3161) District Building 96, Fort Armstrong. Kansas, Lawrence Wm. D. Johnson, Jr. (Viking 3—2700) c/o State Geological Survey, Lindley Hall, Uni- versity of Kansas. Maryland, Beltsville Allen V. Heyl (Tower 9—6430, ext. 468) U.S. Geological Survey, Department of Agriculture Research Center Building. Massachusetts, Boston L. W. Currier (Kenmore 6—1444) 270 Dartmouth Street, Room 1. Michigan, Iron Mountain K. L. Wier (1736) PO. Box 45. Mississippi, Jackson Paul L. Applin (Fleetwood 5—3223) 1202176 North State Street. New Mexico Charles B. Read (Chapel 7—0311, ext. PO. Box 4083, Station A, Geology Building, Uni- 483) versity of New Mexico. Ohio, Columbus J. M. Schopf (Axminster 4—1810) Orton Hall, Ohio State University, 155 South Oval Drive. Ohio, New Philadelphia James F. Pepper (4—2353) PO. Box 272, Muskingum Watershed, Conserva- tion Building, 1319 Third Street, NW. Pennsylvania, Mt. Carmel Thomas M. Kehn (1535) 56 West 2d Street. Puerto Rico, Roosevelt Watson H. Monroe (San Juan 6-5340) P.O. Box 803. Tennessee, Knoxville R. A. Laurence (2—7787) 11 Post Office Building. Utah, Salt Lake City Lowell S. Hilpert (Empire 4—2552) 506 Federal Building. Vermont, Montpelier W. M. Cady (Capitol 3—5311) 43 Liberty Street. Washington, Spokane A. E. Weissenborn (Temple 8—2084) South 157 Howard Street. Wisconsin, Madison C. E. Dutton (Alpine 5—3371, ext. 2128) 222 Science Hall, University of Wisconsin. Wyoming, Laramie W. R. Keefer (Franklin 5-4495) Geology Hall, University of Wyoming. A74 Location Brazil, Belo Horizonte Brazil, Porto Alegre Brazil, Rio de Janeiro Brazil, Rio de Janeiro Brazil, Sao Paulo Chile, Santiago India, Calcutta Indonesia, Bandung Libya, Tripoli Mexico, Mexico, D. F. Pakistan, Quetta Philippines, Manila Taiwan, Taipei (Formosa) Thailand, Bangkok Turkey, Istanbul GEOLOGIC DIVISION OFFICES OFFICES IN FOREIGN COUNTRIES [Temporary field offices not included] Geologic! in charge J. V. N. Dorr, II A. J. Bodenlos C. T. Pierson A. J. Bodenlos A. J. Bodenlos W. D. Carter Lawrence Blade David A. Andrews Gus Goudarzi Ralph Miller John A. Reinemund Joseph F. Harrington Samuel Rosenblum Louis S. Gardner Quentin D. Singewald Mailing address Caixa Postal 17, Belo Horizonte, Minas Gerais, Brazil. c/o American Embassy, APO 676, New York, New York. US. Geological Survey, c/o American Embassy, APO 676, New York, New York. US. Geological Survey, 0/0 American Embassy, APO 676, New York, New York. US. Geological Survey, c/o American Consulate General S.P., APO 676, New York, New York. US. Geological Survey, 0/0 American Embassy, Santiago, Chile. US. Geological Survey, 0/0 American Consulate General, 5/1 Harrington Street, Calcutta 16, India. U.S. Geological Survey, USOM to Indonesia, 0/0 American Embassy, Djakarta, Indonesia. US. Geological Survey, USOM, APO 231, 0/0 Postmaster, New York, New York. U.S. Geological Survey, USOM American Embassy, Mexico, D. F., Mexico. U.S. Geological Survey, USOM American Embassy, APO 27], New York, New York. US. Geological Survey, 0/0 American Embassy, APO 928, San Francisco, California. U.S. Geological Survey, ICA/MSM/China, APO 63, San Francisco, California. US. Geological Survey, c/o American Embassy, APO 146, Box B, San Francisco, California. US. Geological Survey/ICA, 0/0 American Embassy, APO 380, New York, New York. A75 INVESTIGATIONS IN PROGRESS IN THE GEOLOGIC DIVISION DURING FISCAL YEAR 1960 Investigations in progress in the Geologic Division during fiscal year 1960 are listed below, together with the names and headquarters of the individuals in charge of each. Not all of the investigations listed were active during fiscal year 1960; for example, many are completed except for publication of final reports, and some have been temporarily recessed. Headquarters for major offices are indicated by the initials (W) for Washington, D.C., (D) for Denver, 0010., and (M) for Menlo Park, Calif. Headquarters in all other cities are indicated by name; see list of offices on preceding pages for addresses. Projects that include a significant element of geo- logic mapping are indicated by asterisks. One aster- isk (*) indicates projects that involve geologic map- ping at a scale of a mile to the inch or larger; two asterisks (**) indicate projects that involve geologic mapping at a scale smaller than a mile to the inch. Because many of those interested in work in progress are concerned with a specific political area, the investigations are classified by State or similar unit, and titles are repeated as necessary to show work in progress in a given area (investigations, however, that deal with more than four States are listed only under the heading “Studies of large regions of the United States”). Investigations concerned with min- eral resources, engineering problems, methods, or geo- logic processes are listed under geographic headings if they involve a specific area, but they are also listed under topical headings. They are not repeated within the topical groups, however, even though they may deal with more than one subject. The assignment of investigations by subject has been determined by the dominant activity or objective of each. Titles of these investigations are listed only under the topic that represents the dominant activity or objective of each; individual titles are not repeated under other topical headings, even though the investigation may deal with more than one subject. The reader interested in work in progress in, for example, mineralogy, will wish to examine titles of investigations underway in related fields, such as experimental geochemistry, waste dis- posal, and mineral resource investigations. REGIONAL INVESTIGATIONS Large regions of the United States : Geologic map of the United States P. B. King (M) Paleotectonic maps of the Pennsylvanian and Permian E. D. McKee (D) Synthesis of geologic data on Atlantic Coastal Plain and Continental Shelf J. E. Johnston (W) Coal fields of the United States J. Trumbull (W) Granites and related rocks of the Southeastern States, with emphasis on monazite and xenotime J. B. Mertie, Jr. (W) Igneous rocks of Southeastern United States C. Milton (W) Geology of the Piedmont region of the Southeastern States, with emphasis on the origin and distribution of monazite W. C. Overstreet (W) Investigation of sea—level changes in New England M. Rubin (W) Lower Paleozoic stratigraphic paleontology, Eastern United States R. B. Neuman (W) Large regions of the United States—Continued Ordovician stratigraphic paleontology of the Great Basin and Rocky Mountains R. J. Ross, Jr. (D) Silurian and Devonian stratigraphic paleontology of the Great Basin and Pacific Coast 0. W. Merriam (W) Midcontinent Devonian investigations E. R. Landis (D) Upper Paleozoic stratigraphic paleontology, Western United States and Alaska J. T. Dutro, Jr. (W) Mesozoic stratigraphic paleontology, Pacific coast D. L. Jones (M) Mesozoic stratigraphic paleontology, coasts N. F. Sohl (W) Cordilleran Triassic stratigraphy N. J. Silberling (M) Jurassic stratigraphic paleontology of North America R. W. Imlay (W) Cretaceous stratigraphy and paleontology, western interior United States W. A. Cobban (D) Atlantic and Gulf A77 A78 Large regions of the United States—Continued Middle and Late Tertiary history of parts of the Northern Rocky Mountains and Great Plains N. M. Denson (D) Gravity map of the United States H. R. Joesting (W) Cross-country aeromagnetic profiles E. R. King (W) Aeromagnetic profiles over the Atlantic Continental Shelf and Slope E. R. King (W) Geophysical studies of Appalachian structure E. R. King (W) Aerial radiological monitoring surveys, Northeastern United States P. Popenoe (W) Alabama : Clinton iron ores of the southern Appalachians R. P. Sheldon (D) Coal resources W. C. Culbertson (D) *Warrior quadrangle, (coal) W. C. Culbertson (D) Pre-Selma Cretaceous rocks of Alabama and adjacent States L. C. Conant (Tripoli, Libya) Mesozoic rocks of Florida and eastern Gulf coast P. L. Applin (Jackson, Miss.) Alaska : General geology: Index of literature on Alaskan geology E. H. Cobb (M) Tectonic map G. Gryc (W) Physiographic divisions C. Wahrhaftig (M) Glacial map T. N. V. Karlstrom (W) Surficial deposits T. N. V. Karlstrom (W) Compilation of geologic maps, 1:250,000 quadrangles W. H. Condon (M) Cenozoic geology of western Alaska D. M. Hopkins (M) *Petrology and volcanism, Katmai National Monument G. H. Curtis (M) Windy-Curry area R. Kachadoorian (M) *Mount Michelson area E. G. Sable (Ann Arbor, Mich.) “Eastern Chugach Mountains traverse D. J. Miller (M) MLower Yukon-Norton Sound region J. M. Hoare (M) *Eastern Aleutian Islands G. D. Fraser (D) *VWestern Aleutian Islands G. D. Fraser (D) Mineral resources: Metallogenic provinces C. L. Sainsbury (M) Geochemical prospecting techniques R. M. Chapman (D) GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS Alaska—Continued Mineral resources—Continued *‘Klukwan iron district E. C. Robertson (W) "Southern Brooks Range (copper, precious metals) W. P. Brosgé (M) "Regional geology and mineral resources, Alaska E. H. Lathram (M) Quicksilver deposits, southwestern Alaska E. M. MacKevett, Jr. (M) ’Nome C—1 and D—1 quadrangles (gold) C. L. Hummel (M) *Tofty placer district (gold, tin) D. M. Hopkins (M) Seward Peninsula tin investigations P. L. Killeen (W) "Lower Kuskokwim-Brlstol Bay region (mercury, antimony, zinc) J . M. Hoare (M) ‘Heceta-Tuxekan area (high-calcium limestone) G. D. Eberlein (M) Uranium-thorium reconnaissance E. M. MacKevett, Jr. (M) Map of coal fields F. F. Barnes (M) *Matanuska coal field F. F. Barnes (M) Tertiary history of the Yukon-Tanana Upland (coal) D. M. Hopkins (M) ‘Nenana coal investigations C. Wahrhaftig (M) Matanuska stratigraphic studies (coal) A. Grantz (M) ”Stratigraphic and structural studies of the Lower Yukon- Koyukuk area (petroleum) W. W. Patton, Jr. (M) "Nelchina area (petroleum) A. Grantz (M) ‘Iniskin-Tuxedni region (petroleum) R. L. Detterman (M) "Buckland and Huslia Rivers area, west-central Alaska W. W. Patton, Jr. (M) “Gulf of Alaska province (petroleum) D. J. Miller (M) "Northern Alaska petroleum investigations G. Gryc (W) Engineering geology and permafrost: ‘Nuclear test site evaluation, Chariot G. D. Eberlein (M) *Nuclear test site evaluation, Katalla G. D. Eberlein (M) Arctic ice and permafrost studies A. H. Lachenbruch (M) Origin and stratigraphy of ground ice in central Alaska T. L. Péwé (College, Alaska) Ground ice and permafrost, Point Barrow R. F. Black (Madison, Wis.) ‘Lituya Bay giant-wave investigation D. J. Miller (M) *Anchorage and vicinity (construction-site planning) R. D. Miller (D) southeastern REGIONAL INVESTIGATIONS IN PROGRESS Alaska—Continued Engineering geology and permafrost—Continued *Mt. Hayes D—3 and D—4 quadrangles (construction-site planning) T. L. Péwé (College, Alaska) *Engineering geology of Talkeetna-McGrath highway T. L. Péwé (College, Alaska) ‘Surflcial and engineering geology studies and construction materials sources T. L. Péwé (College, Alaska) Galena area (construction-site planning) T. L. P-éwé (College, Alaska) *Surficial geology of the southwestern Copper River basin (construction—site planning) J. R. Williams (W) *Surficial geology of the southeastern Copper River basin, (construction-site planning) D. R. Nichols (W) *Surficial geology of the northeastern Copper River basin (construction-site planning) 0. J. Ferrians, Jr. (Glennallen, Alaska) *Surficial geology and permafrost of the Johnson River district G. W. Holmes (W) "Surficial geology of the Upper Kuskokwim region (con— struction-site planning) A. T. Fernald (W) *‘Surflcial geology of the Kobuk River valley (construction- site planning) A. T. Fernald (W) "Surficial geology of the Kenai lowland (construction-site planning) T. N. V. Karlstrom (\V) *Surficial geology of the Big Delta area (construction-site planning) G. W. Holmes (W) *Surficial geology of (the Barter Island—Mt. Chamberlin area (construction-site planning) G. W. Holmes (W) "Surficial geology of the Yukon Flats district (construc- tion-site planning) J. R. Williams (W) *Surficial geology of the ValdezTiekel belt (construction-site planning) H. W. Coulter (W) *Surflcial geology of the Upper Tanana River valley (con- struction-site planning) A. T. Fernald (W) *Surflcial geology of the Susitna-Maclaren River area (con— struction-site planning) D. R. Nichols (W) *Surficial geology of the Slana-Tok area (construction-site planning) H. R. Schmoll (W) ‘Surficial geology of the Seward-Portage Railroad belt (con- struction-site planning) T. N. V. Karlstrom (W) Surficial geology of the Arctic Slope region H. W. Coulter (W) Paleontology : Upper Paleozoic stratigraphic paleontology, United States and Alaska J. T. Dutro, Jr. (W) Western A79 Alaska—Continued Paleontology—Continued Cretaceous Foraminifera of the Neichina area H. R. Bergquist (W) Cenozoic mollusks F. S. MacNeil (M) Geophysical studies: Geophysical studies, ground surveys D. F. Barnes (M) Geophysical studies, airborne surveys G. E. Andreasen (W) Yukon Flats-Kandik aeromagnetic survey G. E. Andreasen (XV) Koyukuk aeromagnetic studies G. E. Andreasen (W) Copper River basin geophysical studies G. E. Andreasen (W) Cook Inlet aeromagnetic survey G. E. Andreasen (W) Aerial radiological monitoring surveys, Chariot site R. G. Bates (W) Arizona: General geology: Arizona state geologic map J. R. Cooper (D) Devonian rocks and paleogeography of central Arizona C. Teichert (D) Diatremes, Navajo and Hopi Indian Reservations E. M. Shoemaker (M) Permian stratigraphy, northeastern Arizona C. B. Read (Albuquerque, NM.) History of Supai-Hermit formations E. D. McKee (D) Stratigraphy of the Redwall limestone E. D. McKee (D) *Holy Joe Peak quadrangle M. H. Krieger (M) *Eastern Mogollon Rim area E. J. McKay (D) "Paleozoic and Cenozoic rocks in the Alpine-Nutrioso area, Apache County C. T. Wrucke (D) *Elgin quadrangle R. B. Raup (M) *Upper Gila River basin, Arizona, New Mexico R. B. Morrison (D) ‘Geology of southern Cochise County P. T. Hayes (D) Mineral resources: Geochemical halos of mineral deposits, Basin and Range province L. C. Huff (D) *Christmas quadrangle (copper, iron) C. R. Willden (M) *Geology and copper deposits of the Twin Buttes areas (copper) J. R. Cooper (D) *Prescott—Paulden area (copper) M. H. Krieger (M) ‘Mammoth quadrangle (copper) S. C. Creasey (M) Contact-metamorphic deposits of the Little Dragoons area (copper) J. R. Cooper (D) A80 Arizona—Continued Mineral resources—Continued ‘Klondyke quadrangle (copper) F. S. Simons (D) *Globe—Miami area (copper) N. P. Peterson (Globe, Ariz.) *Bradshaw Mountains (copper) C. A. Anderson (W) *MacFadden Peak quadrangle and adjacent areas (asbestos) A. F. Shride (D) Clay studies, Colorado Plateau L. G. Schultz (D) WCompilation of Colorado Plateau geologic maps (uranium, vanadium) D. G. Wyant (D) Relative concentrations of chemical elements in rocks and ore deposits of the Colorado Plateau (uranium, vanadium, copper) A. T. Miesch (D) Uranium-vanadium deposits in sandstone, with emphasis on the Colorado Plateau R. P. Fischer (D) Formation and redistribution of uranium deposits of the Colorado Plateau and Wyoming K. G. Bell (D) Colorado Plateau botanical prospecting studies F. J Kleinhampl (M) Relation of fossil wood to uranium deposits, with empha- sis on the Colorado Plateau R. A. Scott (D) Colorado Plateau ground-water studies (uranium) D. J obin (D) Stratigraphic studies, Colorado Plateau (uranium, vana- dium) L. C. Craig (D) San Rafael group stratigraphy, Colorado Plateau (ura- nium) J. C. Wright (D) Triassic stratigraphy and lithology of the Colorado Plateau (uranium, copper) J. H. Stewart (D) Carrizo Mountains area, Arizona-New Mexico (uranium) J. D. Strobell (D) East Vermillion Cliffs area (uranium, vanadium) R. G. Peterson (Boston, Mass.) Uranium deposits of the Dripping Spring quartzite of southeastern Arizona H. C. Granger (D) Studies of uranium deposits R. B. Raup (D) *Fuels potential of the Navajo Reservation, Arizona and Utah R. B. O’Sullivan (D) Engineering and geophysical studies: Great Basin geophysical studies D. R. Mabey (M) Colorado Plateau regional geophysical studies H. R. Joesting (W) Arkansas: Magnet Cove niobium investigations L. V. Blade (D) Aeromagnetic studies in the Newport, Arkansas, and Ozark bauxite areas A. Jespersen (W) GEOLOGICAL SURVEY RESEARCH l960—SYNOPSIS OF GEOLOGIC RESULTS Arkansas—Continued Barite deposits D. A. Brobst (D) *Northern Arkansas oil and gas investigations E. E. Glick (D) "Ft. Smith district, Arkansas and Oklahoma (coal and gas) T. A Hendricks (D) *Arkansas Basin coal investigations B. R. Haley (D) California: General geology: *Big Maria Mountain's quadrangle W. B. Hamilton (D) *Funeral Peak quadrangle H. D. Drewes (D) Death Valley C. B. Hunt (D) *Ash Meadows quadrangle, California-Nevada C. S. Denny (W) *Mt. Pinchot quadrangle J. G. Moore (M) *Independence quadrangle D. 0. Ross (M) *Blanco Mountain quadrangle C. A. Nelson (Los Angeles, Calif.) Glaciation in the San Joaquin Basin F. M. Fryxell (Rock Island, 111.) *Salinas Valley D. L. Durham (M) ‘San Andreas fault L. F. Noble (Valyermo, Calif.) *Merced Peak quadrangle D. L. Peck (M) *Petrology of the Burney area G. A. Macdonald (Honolulu, Hawaii) *Investigation of the Coast Range ultramaflc rocks E. H. Bailey (M) Glaucophane schist terrane within the Franciscan forma- tion R. G. Coleman (M) ‘Weaverville, French Gulch, and Hayfork quadrangles, southern Klamath Mountains W. P. Irwin (M) Mineral resources: Lateritic nickel deposits of the Klamath Mountains, Ore- gon-California P. E. Hotz (M) *Geologic study of the Sierra Nevada batholith (tungsten, gold, base metals) P. C. Bateman (M) *Bishop tungsten district P. C. Bateman (M) ‘Eastern Sierra tungsten area: Devil’s Postpile, Mt. Mor- rison, and Casa Diablo quadrangles (tungsten, base metals) C. D Rinehart (M) Structural geology of the Sierra foothills mineral belt (cop- per, zinc, gold, chromite) L. D. Clark (M) *Panamint Butte quadrangle including special geochemical studies (lead-silver) W. E. Hall (W) REGIONAL INVESTIGATIONS IN PROGRESS California—Continued Mineral resources—Continued *Cerro Gordo quadrangle (lead, zinc) W. C. Smith (M) *Mt. Diablo area (quicksilver, copper, gold, silver) E. H. Pampeyan (M) ‘Geology and origin of the saline deposits of Searles Lake (boron) G. I. Smith (M) Origin of the borate-bearing marsh deposits of California, Oregon, and Nevada (boron) W. C. Smith (M) *Western Mojave Desert (boron) T. W. Dibblee, Jr (M) *Furnace Creek area (boron) J. F. McAllister (M) *Eastern L0s Angeles basin (petroleum) J. E. Schoellhamer (M) Rocks and structures of the Los Angeles basin, and their gravitational effects (petroleum) T. H. McCulloh (Riverside, Calif.) *Southeastern Ventura basin (petroleum) E. L. Winterer (Los Angeles, Calif.) *Northwest Sacramento Valley (petroleum) R. D. Brown, Jr. (M) Engineering geology: ‘Surficial geology of the Beverly Hills, Venice, and Topanga quadrangles, Los Angeles (urban geology) J T. McGill (Los Angeles, Calif.) *San Francisco Bay area, San Francisco South quadrangle (urban geology) M. G.Boni11a (M) *San Francisco Bay area, San Francisco North quadrangle (urban geology) J. Schlocker (M) ‘Oakland East guadrangle (urban geology) D. H. Radbruch (M) Geophysical studies: Volcanism and crustal deformation L. C. Pakister (D) Great Basin geophysical studies D. R. Mabey (M) Geophysical study of major crustal units, Sierra Nevada H. W. Oliver (W) Geophysical studies of relation of ore deposits to batholithic intrusions, Sierra Nevada area H. W. Oliver (W) Aerial radiological monitoring surveys, San Francisco J. A. Pitkin (W) Aerial radiological monitoring surveys, Los Angeles R. B. Guillou (W) Paleontology : Cenozoic Foraminifera, Colorado Desert P. J. Smith (M) *Geology and paleontology of San Nicolas Island J. G. Vedder (M) Geology and paleontology of the Cuyama Valley area J. G. Vedder (M) Foraminifera of the Lodo formation, central California M. C. Israelsky (M) Colorado: General geology : Age determinations: rocks in Colorado H. Faul (W) A81 Colorado—Continued General geology—Continued Significance of lead-alpha age variation in batholiths of the Colorado Front Range E. S. Larsen, 3d (W) Petrology and geochemistry of the Laramide intrusives in the Colorado Front Range E. S. Larsen, 3d (W) Petrology and geochemistry of the Boulder Creek batholith, Colorado Front Range E. S. Larsen, 3d (W) *Metamorphism and structure of Precambrian quartzite and associated rocks, Coal Creek area J. D. Wells (D) *Upper South Platte River, North Fork G. R. Scott (D) *Mountain Front recharge area G. R. Scott (D) ‘Glenwood Springs quadrangle N. W. Bass (D) Devonian stratigraphy of the middle Rocky Mountain area, Colorado and adjacent States V. E. Swanson (D) Pennsylvanian and Permian stratigraphy, Rocky Mountain Front Range, Colorado and Wyoming E. K. Maughan (D) Investigation of Jurassic stratigraphy, south-central Wyo- ming and northwestern Colorado G. N. Pipiringos (D) Upper Cretaceous stratigraphy, northwestern Colorado and northeastern Utah A. D. Zapp (D) Paleontology and stratigraphy of the Pierre shale, Front Range W. A. Cobban (D) Mineral resources: Ore deposition at Creede E. W. Roedder (W) *Creede and Summitville districts (base and precious metals, and fluorspar) T. A. Steven (D) ‘Tenmile Range, including the Kokomo mining district (base and precious metals) A. H. Koschmann (D) *Central City~Georgetown area, including studies of the Precambrian history of the Front Range (base, precious, and radioactive metals) P. K. Sims (D) *San Juan mining area, including detailed study of the Silverton Caldera (lead, zinc, silver, gold, copper) R. G. Luedke (W) *Holy Cross quadrangle and the Colorado mineral belt (lead, zinc, silver, copper gold) 0. Tweto (D) ‘Rico district (lead, zinc, silver) E. T. McKnight (W) *Minturn quadrangle (zinc, silver, copper, lead, gold) T. S. Lovering (D) *Lake George district (beryllium) C. C. Hawley (D) *Poncha Springs and Saguache quadrangles (fluorspar) R. E. Van Alstine (W) Clay studies, Colorado Plateau L. G. Schultz (D) A82 Colorado—Continued Mineral resources—Continued Wallrock alteration and its relation to thorium deposition in the Wet Mountains E. S. Larsen, 3d (W) *Wet Mountains (thorium, base and precious metals) M. R. Brock (W) *Powderhorn area, Gunnison County (thorium) J. C. Olson (D) *Maybell-Lay area, Mofiat County (uranium) M. J. Bergin (W) "Compilation of Colorado Plateau geologic maps (uranium, vanadium) D. G. Wyant (D) Uranium-vanadium deposits in standstone, with emphasis on the Colorado Plateau R. P. Fischer (D) Formation and redistribution of uranium deposits of the Colorado Plateau and Wyoming K. G. Bell (D) Relative concentrations of chemical elements in rocks and ore deposits of the Colorado Plateau (uranium, vanadium, copper) A. T. Miesch (D) Relation of fossil wood to uranium deposits, with emphasis on the Colorado Plateau R. A. Scott (D) Colorado Plateau botanical prospecting studies. F. J. Kleinhampl (M) Colorado Plateau ground-water studies (uranium) D. Jobin (D) Stratigraphic studies, Colorado Plateau (uranium, vana- dium) L. C. Craig (D) Triassic stratigraphy and lithology of the Colorado Plateau (uranium, copper) J. H. Stewart (D) San Rafael group stratigraphy, Colorado Plateau (uranium) J. C. Wright (D) *Ralston Buttes (uranium) D. M. Sheridan (D) *Klondike Ridge area (uranium, copper, manganese, salines) J. D. Vogel (D) *Western San Juan Mountains (uranium, vanadium, gold) C. S. Bromfield (D) *Baggs area, Wyoming and Colorado (uranium) G. E. Prichard (D) *La Sal area, Utah-Colorado (uranium, vanadium) W. D. Carter (Santiago, Chile) *Lisbon Valley area, Utah-Colorado (uranium, vanadium, copper) G. W. Weir (M) Uravan district (vanadium, uranium) R. L. Boardman (W) *Slick Rock district (uranium, vanadium) D. R. Shawe (D) Exploration for uranium deposits in the Gypsum Valley district C. F. Withington (W) *Bull Canyon district (vanadium, uranium) D. Elston (D) *Ute Mountains (uranium, vanadium) E. B. Ekren (D) GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Colorado—Continued Mineral resources—Continued Subsurface geology of the Dakota sandstone, Colorado and Nebraska ( oil and gas) N. W. Bass (D) *Animas River area, Colorado and New Mexico (coal, oil, and gas) H. Barnes (D) *North Park (coal, oil, and gas) D. M. Kinney (W) *Western North Park (coal, oil, and gas) W. J. Hail (D) *Trinidad coal field R. B. Johnson (D) *Carbondale coal field J. R. Donnell (D) “Oil shale investigations D. C. Duncan (W) Oil shale resources, northwestern Colorado J. R. Donnell (D) ‘Grand-Battlement Mesa oil shale J. R. Donnell (D) Engineering geology and geophysical studies: *Upper Green River valley (construction-site planning) W. R. Hansen (D) *Denver and vicinity; Golden and Morrison quadrangles (urban geology) R. Van Horn (D) Black Canyon of the Gunnison River (construction-site planning) W. R. Hansen (D) *Air Force Academy (construction-site planning) D. J. Varnes (D) Colorado Plateau regional geophysical studies H. R. Joesting (W) Salt anticlines, Paradox Basin, Colorado and Utah (test- site evaluation) D. P. Elston (D) ' Salt anticline studies, Colorado and Utah (test-site evalu- ation) E. M. Shoemaker (M) Connecticut: *Ansonia, Mount Carmel, and Southington quadrangles; bedrock geologic mapping C. E. Fritts (D) *Ashaway quadrangle, Rhode Island-Connecticut; bedrock geologic mapping G. T. Feininger (Boston, Mass.) *Avon and New Hartford quadrangles; bedrock and sur- ficial—geologic mapping R. W. Schnabel (D) *Bristol and New Britain quadrangles; bedrock and sur- flcial geologic mapping H. E. Simpson (D) *Broadbrook, Manchester, and Windsor Locks quadrangles; surficial geologic mapping R. B. Colton (D) *Carolina, Quonochontaug, Narragansett Pier, and Wick- ford quadrangles, RI. and Ashaway and Watch Hill quadrangles, Connecticut-Rhode Island, sur- ficial geologic mapping J. P. Schafer (Boston, Mass.) REGIONAL INVESTIGATIONS IN PROGRESS Connecticut—Continued ‘Columbia, Fitchville, Norwich, Marlboro, and Willia- mantic quadrangles; bedrock geologic mapping G. L. Snyder (D) *Coventry Center and Kingston quadrangles, Rhode Island and Watch Hill quadrangle, Connecticut-Rhode Island; bedrock geologic mapping G. E. Moore, Jr. (Columbus, Ohio) ‘Durham quadrangle; surflcial geologic mapping H. E. Simpson (D) ‘Fitchville and Norwich quadrangles; mapping P. M. Hanshaw (D) *Hampton, Plainfleld, and Scotland quadrangles; bedrock geologic mapping H. R. Dixon (D) *Meriden quadrangle; bedrock and surflcial geologic map- ping P. M. Hanshaw (D) *Montville, New London, Niantic, and Uncasville quad- rangles; bedrock and surflcial geologic mapping R. Goldsmith (D) *Mystic and Old Mystic quadrangles; bedrock geologic mapping R. Goldsmith (D) ‘Springfield South quadrangle, Massachusetts and Connecti- cut; bedrock and surflcial geologic mapping J. H. Hartshorn (Boston, Mass.) *Tarrifville and Windsor Lake quadrangles; bedrock geo- logic mapping R. W. Schnabel (D) Delaware: Correlation of aeromagnetic studies and areal geology, Fall Zone R. W. Bromery (W) Florida: Phosphate deposits of northern Florida G. H. Espenshade (W) ‘Land-pebble phosphate deposits J. B. Cathcart (D) Mesozoic rocks of Florida and eastern Gulf Coast P. L. Applin (Jackson, Miss.) Georgia: Pre-Selma Cretaceous rocks of Alabama and adjacent States L. C. Conant (Tripoli, Libya) Mesozoic rocks of Florida and eastern Gulf Coast P. L. Applin (Jackson, Miss.) Clinton iron ores of the southern Appalachians R. P. Sheldon (D) Massive sulfide deposits of the Ducktown district, Tennes- see and adjacent areas (copper, iron, sulfur) R. M. Hernon (D) Aerial radiological monitoring surveys, Georgia Nuclear Aircraft Laboratory J. A. MacKallor (W) Aerial radiological monitoring surveys, Savannah River Plant, Georgia and South Carolina R. G. Schmidt (W) Hawaii: Distribution and origin of the Kauai bauxite deposits S. H. Patterson (Lihue, Kauai, Hawaii) surflcial geologic A83 Hawaii—Continued Geological, geochemical and geophysical studies of Hawai- ian volcanology K. J. Murata (Hawaii) Pahala Ash studies K. J. Murata (Hawaii) Idaho: General geology: "South Central Idaho C. P. Ross (D) ‘Cross-section of the Idaho batholith; quadrangle B. F. Leonard (D) *Owyhee and Mt. City quadrangles, Nevada-Idaho R. R. Coats (M) Petrology of volcanic rocks, Snake River valley, H. A. Powers (D) ‘Snake River valley, western region H. A. Powers (D) ‘Snake River valley, American Falls region H. A. Powers (D) "Regional geology and structure, Snake River valley H. A. Powers (D) "Mackay quadrangle C. P. Ross (D) 'Leadore, Gilmore, and Patterson quadrangles E. T. Ruppel (D) *Metamorphism of the Oroflno area A. Hietanen-Makela (M) *Leesburg quadrangle W. H. Nelson (D) ‘Sedimentary petrology and geochemistry of the Belt series; Elmira, Mt. Pend Oreille, Packsaddle Mountains, and Clark Fork quadrangles, Idaho-Montana J. E. Harrison (D) Mineral resources: *General geology of the Coeur d’Alene mining district (lead, zinc, silver) A. B. Griggs (M) Ore deposits of the Coeur d’Alene mining district (lead, zinc, silver) V. C. Fryklund, Jr. (Spokane, Wash.) ‘Thunder Mountain niobium area, Montana-Idaho R. L. Parker (D) ‘Blackbird Mountain area (cobalt) J. S. Vhay (Spokane, Wash.) ‘Greenacres quadrangle, Wash-Idaho (high-alumina clays) P. L. Weis (Spokane, Wash.) Geochemistry and petrology of western phosphate deposits R. A. Gulbrandsen (M) Stratigraphy and resources of the Phosphoria formation (phosphate, minor elements) V. E. McKelvey (M) *Soda Springs quadrangle, including studies of the Bannock thrust zone (phosphate) F. C. Armstrong (Spokane, Wash.) ‘Morrison Lake quadrangle, Idaho-Montana (phosphate) E. R. Cressman (M) "Irwin quadrangle, Caribou Mountains (phosphate, oil and gaS) L. S. Gardner (Bangkok, Thailand) *Aspen RangeDry Ridge area (phosphate) T. M. Cheney (M) Yellow Pine A84 Idaho—Continued Mineral resources—Continued ‘Radioactive placer deposits of central Idaho D. L. Schmidt (Seattle, Wash.) Geophysical studies : Pacific Northwest geophysical studies D. J. Stuart (M) Volcanism and crustal deformation geophysical studies L. C. Pakiser (D) Correlation of aeromagnetic studies and areal geology, Pend Oreille area E. R. King (W) Aerial radiological monitoring surveys, National Reactor Testing Station R. G. Bates (W) Illinois: ‘Stratigraphy of the lead-zinc district near Dubuque J. W. Whitlow (W) 'Wisconsin zinc-lead mining district '1‘. E. Mullens (D) Aerial radiological monitoring surveys, Chicago R B. Guillou (W) *Geologic development of the Ohio River valley L. L. Ray (W) Lower Pennsylvanian floras of Illinois and adjacent States C. B. Read (Albuquerque, N. Mex.) Indiana: ‘Geology and coal deposits, Terra Haute and Dennison quad- tangles P. Averitt (D) Aerial radiological monitoring surveys, Chicago R. B. Guillou (W) Lower Pennsylvanian floras of Illinois and adjacent States 0. B. Read (Albuquerque, N. Mex) *Quaternary geology of the Owensboro quadrangle, Ken- tucky-Indiana L. L. Ray (W) *Geologic development of the Ohio River valley L. L Ray (W) Iowa: *Stratigraphy of the lead-zinc district near Dubuque J. W. Whitlow (W) 'Wisconsin zinc-lead mining district T. E. Mullens (D) *Omaha-Council Bluffs and vicinity, Nebraska and Iowa (urban geology) R. D. Miller (D) Lower Pennsylvanian floras of Illinois and adjacent States 0. B. Read (Albuquerque, N. Mex.) Kansas: ‘Tri-State lead-zinc district, Oklahoma, Missouri, Kansas E. T. McKnight (W) Trace elements in rocks of Pennsylvanian age, Oklahoma, Kansas, Missouri (uranium, phosphate) W. Danilchik (Quetta, Pakistan) *Wilson County (oil and gas) W. D. Johnson, Jr. (Lawrence, Kans.) Paleozoic stratigraphy of the Sedgwick Basin (oil and gas) W. L. Adkison (Lawrence, Kans.) *Shawnee County (oil and gas) W. D. Johnson, Jr. (Lawrence, Kans.) GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Kentucky: *Geology of the southern Appalachian folded belt, Ken- tucky, Tennessee, and Virginia L. D. Harris (W) Fluorspar deposits of northwestern Kentucky R. D. Trace (W) *Salem quadrangle (fluorspar) R. D. Trace (W) Clay deposits of the Olive Hill bed of eastern Kentucky J. W. Hosterman (W) *Quaternary geology of the Owensboro quadrangle, Ken- tucky-Indiana L. L. Ray (W) *Petroleum geology of Duflield, Stickleyville, Keokee, 01in- ger, and Pennington Gap quadrangles, Virginia and Kentucky L. D. Harris (W) *Eastern Kentucky coal investigations J. W. Huddle (W) Aeromagnetic studies, Middlesboro-Morristown area, Ten- nessee-Kentucky-Virginia R. W. Johnson, Jr. (Knoxville, Tenn.) Aerial radiological monitoring surveys, Oak Ridge Na- tional Laboratory R. G. Bates (W) *Geologic development of the Ohio River valley L. L. Ray (W) Stratigraphy of cavern fills, Mammoth Cave W. E. Davies (W) Vertebrate paleontology, Big Bone Lick F. C. Whitmore, Jr. (W) Maine: Age determinations : granites of Maine H. Faul‘ (W) *Greenville quadrangle G. H. Espenshade (W) *Bedrock geology of. the Danforth, Forest, and Vanceboro quadrangles D. M. Larrabee (W) *Attean quadrangle A. L. Albee (Pasadena, Calif.) *Hydrogeochemical prospecting in the Forks quadrangle F. C. Canney (D) *Bridgewater quadrangle (manganese) L. Pavlides (W) *Electromagnetic and geologic mapping in Island Falls quad- rangle E. B. Ekren (D) *Aeromagnetic and areal geology studies of the Stratton quadrangle A. Griscom (W) Aeromagnetic surveys J. W. Allingham (W) Gravity studies M. F. Kane (W) Maryland: *Potomac Basin studies, Maryland, Virginia, and West Virginia J. T. Hack (W) Clay deposits M. M. Knechtel (W) *Allegany County (coal) ‘W. de Witt, Jr. (W) REGIONAL INVESTIGATIONS IN PROGRESS Maryland—Continued Aerial radiological monitoring surveys, Belvoir area, Vir- ginia and Maryland R. B. Guillou (W) Airborne radioactivity and environmental studies, Washing- ton County R. M. Moxham (W) *Correlation of aeromagnetic studies and areal geology, Montgomery County A. Griscom (W) Massachusetts : *Assawompsett Pond quadrangle; surficial geologic map- ping C. Kotefi.’ (Boston, Mass.) *Athol quadrangle; bedrock and surflcial geologic mapping D. F. Eschman (Ann Arbor, Mich.) *Ayer quadrangle ; bedrock geologic mapping R. H. J ahns (University Park, Pa.) *Billerica, Lowell, Tyngsboro, and Westford Quadrangles; bedrock and surficial geologic mapping R. H. J ahns (University Park, Pa.) *Brldgewater and Taunton quadrangles; surficial geologic mapping J. H. Hartshorn (Boston, Mass.) *Clinton and Shrewsbury quadrangles; bedrock geologic mapping R. F. Novotny (Boston, Mass.) *Concord and Georgetown quadrangles; bedrock and sur- flcial geologic mapping N. P. Cuppels (Boston, Mass.) *Duxbury and Scituate quadrangles and Fresh Pond-Mystic Lake area; surficial geologic mapping N. E. Chute (Syracuse, N. Y.) *Greenfield quadrangle, surficial geologic mapping R. H. J ahns (University Park, Pa.) I'Lawrence, Reading, South Groveland, and Wilmington quadrangles; bedrock geologic mapping R. 0. Castle (Los Angeles, Calif.) *North Adams quadrangle; bedrock geologic mapping N. Herz (Belo Horizonte, Brazil) *Norwood quadrangle; bedrock and surflcial geologic map- ping. N. E. Chute (Syracuse, N. Y.) *Reading and Salem quadrangles; surficial geologic mapping. R. N. Oldale (Boston, Mass.) *Salem quadrangle; bedrock geologic mapping P. Toulmin, 111 (W) *Springfield South quadrangle, Massachusetts and Connecti- cut; bedrock and surficial geologic mapping J. H. Hartshorn (Boston, Mass.) *Dennis and Harwich quadrangles; surflcial geologic map- ping and special seismic studies of engineering problems L. W. Currier (W) Research and application of geology and seismology to Pub- lic Works planning L. W. Currier (W) Sea—clifl erosion studies C. A. Kaye (Boston, Mass.) Vertebrate faunas, Martha’s Vineyard F. C. Whitmore, Jr. (W) Michigan: *Iron River-Crystal Falls district (iron) H. L. James (M) 557328 0 - 60 - 7 A85 Michigan-Continued *East Marquette district (iron) J. E. Gair (D) ‘Southern Dickinson County (iron) R. W. Bayley (M) *Eastern Iron County (iron) K. L. Wier (Iron Mountain, Mich.) ‘Michigan copper district W. S. White (W) Geophysical studies in the Lake Superior region G. D. Bath (M) *Lake Algonquin drainage J. T. Hack (W) Minnesota: ‘Cuyuna North Range (iron) R. G. Schmidt (W) Geophysical studies in the Lake Superior region G. D. Bath (M) Mississippi : PreSelma Cretaceous rocks of Alabama and adjacent States L. C. Conant (Tripoli, Libya) Oligocene gastropods and pelecypods F. S. MacNeil (M) Missouri: *Tri-State lead-zinc district, Oklahoma, Missouri, Kansas E. T. McKnight (W) Aeromagnetic studies in the Newport, Arkansas, and Ozark bauxite areas A. Jesperson (W) ~ Trace elements in rocks of Pennsylvanian age, Oklahoma, Kansas, Missouri (uranium, phospate) W. Danilchik (Quetta, Pakistan) Correlation of aeromagnetic studies and areal geology, southeast Missouri J. W. Allingham (W) Montana: General geology: Stratigraphy of the Belt series C. P. Ross (D) Mesozoic stratigraphic paleontology W. A. Cobban (D) Northern Great Plains Pleistocene reconnaissance, Mon- tana and North Dakota R. B. Colton (D) Carbonatite deposits W. T. Pecora (W) *Petrology of the Bearpaw Mountains W. T. Pecora (W) *Petrology of the Wolf Creek area R. G. Schmidt (W) *Sedimentary petrology and geochemistry of the Belt series; Elmira, Mt. Pend Oreille, Packsaddle Mountains, and Clark Fork quadrangles, Idaho—Montana J. E. Harrison (D) Chemical and physical properties of the Pierre shale, Mon- tana, North Dakota, South Dakota, Wyoming and Nebraska H. A. Tourtelot (D) *Alice Dome—Sumatra area H. R. Smith (D) *Quaternary geology of the Browning area and the east slope of Glacier National Park G. M. Richmond (D) A86 Montana—Continued General geology—Continued ‘Bedrock and surficial geology, Big Sandy Creek area R. M. Lindvall (1)) *Geology of the Livingston-Trail Creek area (coal) A. E. Roberts (D) ‘Maudlow quadrangle B. Skipp (D) ‘Duck Creek Pass quadrangle W. H. Nelson (1)) *South Gallatin Range I. J. “'itkind (D) *Gravelly Range-Madison Range J. B. Hadley (1)) *Three Forks quadrangle G. 1). Robinson (D) *Toston quadrangle G. 1). Robinson (1)) ’Holter Lake quadrangle G. 1). Robinson (1)) *Willis quadrangle W. B. Myers (D) Mineral resources: Manganese deposits of the Philipsburg area (manganese and base metals) W. C. Prinz (Spokane, Wash.) Chromite resources and petrography of the ultramatic complex E. D. Jackson (M) *Thunder Mountain niobium area, Montana-Idaho R. L. Parker (D) - *General geology of the Coeur d’Alene mining district (lead, zinc, silver) A. B. Griggs (M) Ore deposits of the Coeur d’Alene mining district (lead, zinc, silver) V. C. Fryklund. Jr. (Spokane, Wash.) ‘Bou-lder batholith area (base, precious, and radioactive metals) M. R. Klepper (W) *Morrison Lake quadrangle, Idaho-Montana (phosphate) E. R. Cressman (M) Stratigraphy and resources of Permian rocks in western Montana (phosphate, minor elements) R. W. Swanson (Spokane, Wash.) Stratigraphy and resources of Permian rocks in southwest- ern Montana (phosphate, minor elements) E. R. Cressman (M) *Geology of the Winnett-Mosby area (oil and gas) W. D. Johnson. Jr. (Lawrence, Kans.) Williston Basin oil and gas studies, Wyoming, Montana, North Dakota and South Dakota C. A. Sandberg (D) Reconnaissance geology of the Burney-Broadus coalfield, Wyoming and Montana W. W. Olive (W) Geology of uranium in lignites, Montana, North Dakota, and South Dakota N. M. Denson (D) Engineering geology: Earthquake investigations, Hebgen Lake J. B. Hadley (D) *Sun River Canyon area M. R. Mudge (D) Stillwater GEOLOGICAL SURVEY RESEARCH lQGO—SYNOPSIS 0F GEOLOGIC RESULTS Montana—~00ntinued Engineering geology—Continued ‘Wolf Point area (construction-site planning) R. B. Colton (D) *Great Falls area (urban geology and construction-site planning) R. W. Lemke (D) *Fort Peck area (construction-site planning) H. D. Varnes (D) Geophysical studies: Pacific Northwest geophysical studies D. J. Stuart (M) Aeromagnetic studies, Three Forks area I. Zietz (W) ' Correlation of aeromagnetic studies and areal geology, Pend Oreille area E. R. King (W) Correlation of aeromagnetic studies and areal geology, Bearpaw Mountains K. G. Books (W) Magnetic studies of Montana laccoliths R. G. Henderson (W) Nebraska: Devonian stratigraphy of the middle Rocky Mountain area, Colorado and adjacent States V. E. Swanson (D) Chemical and physical properties of the Pierre shale, Mon- tana, North Dakota, South Dakotaé Wyoming, and Nebraska H. A. Tourtelot (D) *Lower South Platte River R. D. Miller (D) *Lower Republican River R. D. Miller (D) Subsurface geology of Dakota sandstone, Colorado and Nebraska (oil and gas) N. W. Bass (D) Oil and gas investigations, céntral Nebraska basin G. E. Prichard (D) Omaha-Council Bluffs and vicinity, Nebraska and Iowa (urban geology) R. D. Miller (D) Nevada: General geology: *Schell Creek Range H. D. Drewes (D) *Owyhee and Mt. City quadrangles, Nevada-Idaho R. R. Coats (M) *Jarbidge area R. R. Coats (M) *Geology and paleontology of Kobeh Valley T. B. Nolan (W) *Railroad District, and the Dixie Flats, Pine Valley, and Robinson Mountain quadrangles J. F Smith, Jr. (D) *Horse Creek Valley quadrangle H. Masursky (D) *Mt. Lewis and Crescent Valley quadrangles J. Gilluly (D) *Frenchie Creek quadrangle L. J. P. Muflier (D) Cortez quadrangle H. Masursky (D) REGIONAL INVESTIGATIONS IN PROGRESS Nevada—Continued General geology—Continued *Fallon area R. B. Morrison (D) *Ash Meadows quadrangle, California-Nevada C. S. Denny (W) "Humboldt County C. R. Willden (M) "Mineral County D. C Ross (M) "Lincoln County 0. M. Tschanz (M) *Las Vegas-Lake Mead area C. R. Longwell (M) Mineral resources: Geochemical halos of mineral deposits, Basin and Range province L. C. Huff (D) Iron ore deposits R. G. Reeves (M) ‘Unionville and Buffalo Mountain quadrangles, Humboldt Range (iron, tungsten, silver, quicksilver) R. E. Wallace (M) ‘Osgood Mountains quadrangle (tungsten, quicksilver) P. E. Hotz (M) ‘ ’Wheeler Peak and Garrison quadrangles, Snake Range, Nevada-Utah (tungsten) D. H Whitebread (M) *Lyon, Douglas, and Ormsby Counties (copper) J. G. Moore (M) *Regional geologic setting of the Ely district (copper, lead, zinc) A. L. Brokaw (D) Ione quadrangle (lead, quicksilver, tungsten) C. J. Vitaliano (Bloomington, Ind.) ‘Eureka area (zinc, lead, silver, gold) T. B. Nolan (W) "Eureka County (base and precious metals) R. J. Roberts (M) *Antler Peak quadrangle (base and precious metals) R. J. Roberts (M) *Geology and ore deposits of Bullfrog and Bear Mountain quadrangles (fluorite, bentonite, gold, silver) H. R. Cornwall (M) Origin of the borate-bearing marsh deposits of California, Oregon, and Nevada (boron) W. C. Smith (M) Geochemistry and petrology of western phosphate deposits R. A. Gulbrandsen (M) Stratigraphy and resources of the Phosphoria and Park City formations in Utah and Nevada (phosphate, minor elements) T. M. Cheney (M) Engineering geology and geophysical studies : *Engineering geology of the Nevada Test Site area V. R. Wilmarth (D) Geophysical studies at the Nevada Test Site W. H. Diment (D) Great Basin geophysical studies D. R. Mabey (M) Aerial radiological monitoring surveys, Nevada Test Site J. L. Meuschke (W) A87 New Hampshire: Correlation of aeromagnetic studies and areal geology R. W. Bromery (W) New Jersey: ‘Lower Delaware River basin, New Jersey-Pennsylvania J. P. Owens (W) *Middle Delaware River basin, New Jersey-Pennsylvania A. A. Drake, Jr. (W) ‘Selected iron deposits of the Northeastern States A. F. Buddington (Princeton, NJ.) Selected studies of uranium and rare-earth deposits in Pennsylvania and New Jersey H. Klemic (W) Correlation of aeromagnetic studies and areal geology, New York-New Jersey Highlands (iron) A. Jesperson (W) Correlation of aeromagnetic studies and areal geology, Delaware Fall Zone R. W. Bromery (W) New Mexico: General geology: New Mexico geologic map C. H. Dane (W) Southeastern New Mexico stratigraphic investigations P. T. Hayes (D) Stratigraphic significance of the genus Tempskya in south- western New Mexico C. B. Read (Albuquerque, N. Mex.) Diatremes, Navajo and Hopi Indian Reservations E. M. Shoemaker (M) / *Petrology of the Valles Mountains R. L. Smith (W) *Upper Gila River basins, Arizona-New Mexico R. B. Morrison (D) ‘Southern Oscura, northern San Andres Mountains G. O. Bachman (D) *Southern Peloncillo Mountains and Cedar Mountain area C. T. Wrucke (D) *Philmont Ranch quadrangle G. D. Robinson (D) Mineral resources: Geochemical halos of mineral deposits, Basin and Range province L. C. Huff (D) *Central district (copper, zinc) W. R. Jones (D) Clay studies, Colorado Plateau L. G. Schultz (D) Potash and other saline deposits of the Carlsbad area C. L. Jones (M) "Compilation of Colorado Plateau geologic maps (uranium, vanadium) D. G. Wyant (D) Uranium-vanadium deposits in sandstone, with emphasis on the Colorado Plateau R. P. Fischer (D) Formation and redistribution of uranium deposits of the Colorado Plateau and Wyoming K. G. Bell (D) Relative concentrations of chemical elements in different rocks and ore deposits of the Colorado Plateau p (uranium, vanadium, copper) A. T. Miesch (D) A88 New Mexicd—Continued Mineral resources—Continued Colorado Plateau ground-water studies D. J‘obin (D) Relation of fossil wood to uranium deposits, with emphasis on the Colorado Plateau R. A. Scott (D) ’ Colorado Plateau botanical, exploration studies F. J. Kleinhampl (M) Stratigraphic studies, Colorado Plateau (uranium, vana- dium) L. C. Craig (D) San Rafael group stratigraphy, Colorado Plateau (uranium) J. C. Wright (D) , Triassic stratigraphy and lithology of the Colorado Plateau (uranium, copper) J. H. Stewart (D) Mineralogy of uranium-bearing rocks in the Grants area A. D. Weeks (W) Regional relationship of .the uranium deposits of north- western New Mexico L. S. Hilpert (Salt Lake City, Utah) *Laguna district (uranium) R. H. Moench (D) *Grants area (uranium) R. E. Thaden (D) Ambrosia Lake district (uranium) H. C. Granger (D) *Carrizo Mountains area, Arizona-New Mexico (uranium) J. D. Strobell (D) *Tucumcari-Sabinoso area (uranium) R. L. Griggs (D) Oil and gas fields D. C. Duncan (W) *Stratigraphy, northern Franklin Mountains, west Texas (petroleum) R. L. Harbour (D) *Animas River area, Colorado and New Mexico (coal, oil and gas) H. Barnes (D) *East side San Juan Basin (coal, oil, gas) C. H. Dane (W) *Raton Basin coking coal A. A. Wanek (M) Engineering geology and geophysical studies: *Engineering geology of Gnome Test Site V. R. Wilmarth (D) *Nash Draw quadrangle (test-site evaluation) J. D. Vine (M) Seismic studies, southern Eddy County (test-site evalua- tion) P. E. Byerly (D) Colorado Plateau regional geophysical studies H. R. J oesting (XV) Aerial radiological monitoring surveys, Gnome site R. B. Guillou (W) Geophysical studies in the Rowe-Mora area G. E. Andreasen (W) New York: *Glacial geology of the Elmira-Williamsport area, New York, Pennsylvania C. S. Denny (W) Cretaceous Foraminifera N. F. Soh (W) GEOLOGICAL SURVEY RESEARCH 1960-—SYNOPSIS OF GEOLOGIC RESULTS New York—Continued ‘Richville quadrangle H. M. Bannermau (W) *Selected iron deposits of the Northeastern States A. F. Buddington (Princeton, N. J.) Metamorphism and origin of mineral deposits, Gouverneur area A. E. J. Engel (Pasadena, Calif.) Correlation of aeromagnetic studies and areal geology, New York-New Jersey Highlands (iron) A. Jespersen (W) Correlation of aeromagnetic studies and areal geology, Adirondacks area (iron) J. R. Balsley (W) ‘Gouverneur district (talc) A. E. J. Engel (Pasadena, Calif.) Stratigraphy of the Dunkirk and related beds W. de Witt, Jr. (W) I‘Stratigraphy of the Dunkirk and related beds in the Penn Yan and Keuka Lake quadrangles (oil and gas) M. J. Bergin (W) ‘Stratigraphy of the Dunkirk and related beds, in the Bath and Woodhull quadrangles (oil and gas) I. F. Pepper (New Philadelphia, Ohio) North Carolina : *Great Smoky Mountains, Tennessee and North Carolina J. B. Hadley (D) ‘Grandfather Mountain B. H. Bryant (D) ‘Investigations of the Volcanic Slate series A. A. Stromquist (W) *Central Piedmont H. Bell (W) ‘Hamme tungsten deposit J. M. Park, III (Raleigh, N.C.) Massive sulfide deposits of the Ducktown district, Tennes- see andiadjacent areas (copper, iron, sulfur) R. M. Hernon (D) *Swain County copper district G. H. Espenshade (W) Pegmatites of the Spruce Pine and Franklin-Sylva districts F. G. Lesure (Knoxville, Tenn.) ‘Geologic setting of the Spruce Pine pegmatite district (mica, feldspar) D. A. Brobst (D) *Shelby quadrangle (monazite) W. C. Overstreet (W) Central and western North Carolina regional aeromagnetic survey R. W. Johnson, Jr. (Knoxville, Tenn.) Airborne geophysical studies, Concord-Denton area R. W. Johnson, Jr. (Knoxville, Tenn.) North Dakota: Chemical and physical properties of the Pierre shale, Mon- tana, North Dakota, South Dakota, Wyoming, and Nebraska H. A. Tourtelot (D) Northern Great Plains Pleistocene reconnaissance, Montana and North Dakota R. B. Colton (D) Geology of uranium in lignites, Montana, North Dakota, and South Dakota N. M. Denson (D) REGIONAL INVESTIGATIONS IN PROGRESS North Dakota—Continued Williston Basin oil and gas studies, Wyoming, Montana, North Dakota, and South Dakota C. A. Sandberg (D) Ohio: *Geology and coal resources of Belmont County H. L. Berryhill, Jr. (D) Oklahoma: *Tri-State lead-zinc district, Oklahoma, Missouri, Kansas E. T. McKnight (W) Trace elements in rocks of Pennsylvanian age Oklahoma, Kansas, Missouri (uranium, phosphate) W. Danilchik (Quetta, Pakistan) Anadarko Basin, Oklahoma and Texas, oil and gas studies W. L. Adkison. (Lawrence, Kans.) *Ft. Smith district, Arkansas and Oklahoma (coal and gas) T. A. Hendricks (D) McAlester Basin (oil and gas) S. E. Frezon (D) Experimental aeromagnetic survey in northeast Oklahoma 1. Zietz (W) Oregon: Oregon state geologic map G. W. Walker (M) . Foraminiferal studies of the Pacific Northwest W. W. Rau (M) Miocene mollusks E. J. Trumbull (M) Oligocene mollusks E. J. Trumbull (M) *Lower Umpqua River area E. M. Baldwin (Eugene, Oreg.) *Monument quadrangle R. E. Wilcox (D) *Gabbroic and associated intrusive rocks in the central part of the Oregon Coast Ranges P. D. Snavely (M) Lateritic nickel deposits of the Klamath Mountains, Ore- gon-California P. E. Hotz (M) *Ochoco Reservation, Lookout Mountain, Eagle Rock, and Post quadrangles (quicksilver) A. C. Waters (Baltimore, Md.) *Newport embayment (oil and gas) P. D. Snavely, Jr. (M) *Anlauf and Drain quadrangles (oil and gas) L. Hoover (W) ‘John Day area (chromite) T. P. Thayer (W) Origin of the borate-bearing marsh deposits of California, Oregon, and Nevada (boron) W. C. Smith (M) *Portland industrial area, Oregon and Washington (urban geology) ‘ D. E. Trimble (D) Pacific Northwest geophysical studies D. J. Stuart (M) Correlation between geologic and geophysical data, west— central Oregon P. D. Snavely, Jr. (M) Aerial radiological monitoring surveys, Hanford R. G. Schmidt (W) Geophysical studies, west-central Oregon R. W. Bromery (W) A89 Pennsylvania : *Glacial geology of the Elmira-Williamsport area, New York, Pennsylvania C. S. Denny (W) *Middle Delaware River basin, New Jersey-Pennsylvania A. A. Drake, Jr. (W) *Lower Delaware River basin, New J ersey-Pennsylvania J. P. Owens (W) *Investigations of the Lower Cambrian of the Philadelphia district J. H. Wallace (W) *Lehighton quadrangle (uranium) H. Klemic (W) Selected studies of uranium and rare—earth deposits in Pennsylvania and New Jersey H. Klemic (W) *Bituminous coal resources E. D. Patterson (W) *Western middle anthracite coal field H. Arndt (W) *Southern anthracite field G. H. Wood, Jr. (W) *Geology in the vicinity of anthracite mine drainage projects T. M. Kehn (Mt. Carmel, Pa.) Correlation of aeromagnetic studies and areal geology, Tri- assic R. W. Bromery (W) Correlation of aeromagnetic studies and areal geology, Fall Zone R. W. Bromery (W) Rhode Island: *Wickford quadrangle; bedrock geologic mapping R. B. Williams (Providence, RI.) *North Scituate quadrangle; surficial geologic mapping C. S. Robinson (D) *Kingston quadrangle; surficial geologic mapping C. A. Kaye (Boston, Mass.) *Hope Valley quadrangle; surflcial geologic mapping G. T. Feininger (Boston, Mass.) ‘Chepachet, Crompton, and Tiverton quadrangles; bedrock geologic mapping A. Quinn (Providence, RI.) *Coventry Center and Kingston quadrangles; and Watch Hill quadrangle, Connecticut-Rhode Island, bedrock geo- logic mapping G. E. Moore, Jr. (Columbus, Ohio) *Carolina, Quonochontaug, Narragansett Pier, and Wickford quadrangles, Rhode Island, and Ashaway and Watch Hill quadrangles, Connecticut-Rhode Island, surflcial geologic mapping J. P. Schafer (Boston, Mass.) *Ashaway quadrangle, Rhode Island-Connecticut, bedrock geologic mapping G. T. Feininger (Boston, Mass.) South Carolina: Aerial radiological monitoring surveys, Savannah River Plant, Georgia and South Carolina R. G. Schmidt (W) South Dakota: Devonian stratigraphy of the middle Rocky Mountain area, Colorado and adjacent States V. E. Swanson (D) ‘ A90 South Dakota—«Continued Chemical and physical properties of the Pierre shale, Mon- tana, North Dakota, South Dakota, Wyoming and Nebraska H. A. Tourtelot (D) *Southern Black Hills (pegmatite minerals) J. J. Norton (D) *Regional stratigraphic study of the Inyan Kara group, Black Hills (uranium) W. J. Mapel (D) *Southern Black Hills (uranium) G. B. Gott (D) *Harding County, South Dakota and adjacent areas (ura- niferous lignite) G. N. Pipiringos (D) Geology of uranium in lignites, Montana, North Dakota, and South Dakota N. M. Denson (D) Geophysical studies in uranium geology R. M. Hazlewood (D) Williston Basin oil and gas studies, Wyoming, Montana, North Dakota, and South Dakota C. A. Sandberg (D) Landslide studies in the Fort Randall Reservoir area D. J. Varnes (D) Tennessee: *Great Smoky Mountains, Tennessee and North Carolina J. B. Hadley (D) *Geology of the southern Appalachian folded belt, Kentucky, Tennessee, and Virginia L. D. Harris (W) Clinton iron ores of the southern Appalachians R. P. Sheldon (D) Massive sulfide deposits of the Ducktown district, Tennes- see and adjacent areas (copper, iron, sulfur) R. M. Hernon (D) Origin and depositional control of some Tennessee and Virginia zinc deposits H. Wedow, Jr. (Knoxville, Tenn.) East Tennessee zinc studies A. L. Brokaw (D) *Ivydell, Pioneer, J ellico West, and Ketchen quadrangles (coal) K. J. Englund (W) *Knoxville and vicinity (urban geology) J. M. Cattermole (D) Aeromagnetic studies, Middlesboro-Morristown area, Ten- nessee, Kentucky, and Virginia R. W. Johnson, Jr. (Knoxville, Tenn.) Aerial radiological monitoring surveys, Oak Ridge National Laboratory R. G. Bates (W) Central and western North Carolina regional aeromagnetic survey ' R. W. Johnson, Jr. (Knoxville, Tenn.) Texas: *Del Rio area V. L. Freeman (D) *Sierra Blanca area J. F. Smith, Jr. (D) *Sierra Diablo region P. B. King (M) GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS Texas—Continued , Mineralogy of uranium-bearing rocks in Karnes and Duval Counties A. D. Weeks (W) Anadarko Basin, Oklahoma and Texas (Oil and gas) W. L. Adkison (Lawrence, Kans.) ‘Pennsylvanian oil and gas investigations D. A. Myers (D) ‘Stratigraphy, northern Franklin Mountains, west Texas (petroleum) R. L. Harbour (D) ‘Texas coastal plain geophysical and geological studies D. H. Eargle (Austin, Tex.) Aerial radiological monitoring surveys, Gnome site R. B. Guillou (W) Aerial radiological monitoring surveys, Killeen J. A. Pitkin (W) Radon and helium studies A. B. Tanner (Salt Lake City, Utah) Aerial radiological monitoring surveys, Fort Worth J. A. Pitkin (W) Utah: General geology: Southwestern Utah geologic map P. Averitt (D) Upper Cretaceous stratigraphy, northwestern Colorado and northeastern Utah A. D. Zapp (D) *South half, Utah Valley H. J. Bissell (Provo, Utah) *Strawberry Valley and Wasatch Mountains A. A. Baker (W) ‘Little Cottonwood area G. M. Richmond (D) *Confusion Range R. K. Hose (M) *Northern Bonneville Basin J. S. Williams (Provo, Utah) Mineral resources: Geochemical halos of mineral deposits, Basin and Range province L. C. Huff (D) *Wheeler Peak and Garrison quadrangles, Snake Range, Nevada-Utah (tungsten) D. H. Whitebread (M) *San Francisco Mountains (tungsten, copper) D. M. Lemmon (M) ‘Regional geologic setting of the Bingham Canyon district (copper) R. J. Roberts (M) *Alta quadrangle (lead, silver, phosphate rock) M. D. Crittenden, Jr. (M) *East Tintic lead-zinc district, including extensive geochemi- cal studies H. T. Morris (M) ‘Marysvale district (alunite) R. L. Parker (D) ‘Thomas and Dugway Ranges (fluorspar, beryllium) M. H. Staatz (D) Clay studies, Colorado Plateau L. G. Schultz (D) Geochemistry and petrology of western phosphate deposits R. A. Gulbrandsen (M) REGIONAL INVESTIGATIONS IN PROGRESS Utah—Continued Mineral resources—-Continued Stratigraphy and resources of the Phosphoria and Park City formations in Utah and Nevada (phosphate, minor elements) T. M. Cheney (M) “Compilation of Colorado Plateau geologic maps (uranium, vanadium) D. G. Wyant (D) Uranium-vanadium deposits in sandstone, with emphasis on the Colorado Plateau R. P. Fischer (D) Formation and redistribution of uranium deposits of the Colorado Plateau and Wyoming K. G. Bell (D) Stratigraphic studies, vanadium) L. C. Craig (D) San Rafael group (uranium) J. C. Wright (D) Triassic stratigraphy and lithology of the Colorado Plateau (uranium, copper) J. H. Stewart (D) Colorado Plateau botanical exploration studies F. J. Kleinhampl (M) Relative concentrations of chemical elements in different rocks and ore deposits of the Colorada Plateau (uranium, vanadium, copper) A. T. Miesch (D) Colorado Plateau ground-water studies (uranium) D. Jobin (D) Relation of fossil wood to uranium deposits, emphasis on the Colorado Plateau R. A. Scott (D) *La Sal area, Utah-Colorado (uranium, vanadium) W. D. Carter (Santiago, Chile) *Moab-Interriver area, east-central Utah (uranium) E. N. Hinrichs (D) Uranium ore controls of the San Rafael Swell C. C. Hawley (D) ‘Elk Ridge area (uranium) R. Q. Lewis (D) *Deer Flat area, White Canyon district (uranium, copper) T. L. Finnell (D) *White Canyon area (uranium, copper) R. E. Thaden (D) *Abajo Mountains (uranium, vanadium) I. J. Witkind (D) *Sage Plain area (uranium and vanadium) L. C. Huff (D) *Orange Cliffs area (uranium) F. A. McKeown (D) *Lisbon Valley area, Utah-Colorado (uranium, vanadium, copper) G. W. Weir (M) ‘,Circle Cliffs area (uranium) E. S. Davidson (Tucson, Ariz.) *Fuels potential of the Navajo Reservation, Arizona and Utah R. B. O’Sullivan (D) *Cedar Mountain quadrangle, Iron County (coal) P. Averitt (D) Colorado Plateau (uranium, stratigraphy, Colorado Plateau with A91 Utah—Continued Mineral resources—Continued *Southern Kolob Terrace coal field W. B. Cashion (D) *Unita Basin oil shale W. B. Cashion (D) Engineering geology and geophysical studies: ‘Geologic factors related to coal mine bumps F. W. Osterwald (D) ‘Upper Green River Valley (construction-site planning) W. R. Hansen (D) *Surflcial geology of the Oak City area (construction-site planning) D. J. Varnes (D) Salt anticlines, Paradox Basin, Colorado and Utah (test-site evaluation) D. P. Elston (D) Salt anticline studies, evaluation) E. M. Shoemaker (M) Colorado Plateau regional geophysical studies H. R. Joesting (W) Great Basin geophysical studies D. R. Mabey (M) Vermont: *Talc and asbestos deposits of north-central Vermont W. M. Cady (Montpelier, Vt.) ' Correlation of aeromagnetic studies and areal geology R. W. Bromery (\V) Virginia: *Petrology of the Manassas quadrangle C. Milton (W) *Potomac Basin Studies, Virginia J. T. Hack (W) *Geology of the southern Appalachian folded belt, Ken- tucky, Tennessee and Virginia L. D. Harris (W) Origin and depositional control of some Tennessee and Virginia zinc deposits H. Wedow, Jr. (Knoxville, Tenn.) Massive sulfide deposits of the Ducktown district, Ten- nessee and adjacent areas (copper, iron, sulfur) R. M. Hernon (D) *Petroleum geology of Dufl‘ield, Stickleyville, Keokee, Olinger, and Pennington Gap quadrangles, Vir- ginia and Kentucky ‘ L. D. Harris (W) *Herndon quadrangle (construction-site planning) R. E. Eggleton (D) Aerial radiological monitoring surveys, Belvoir area, Vir- ginia and Maryland R. B. Guillou (W) Aeromagnetic studies, Middlesboro-Morristown area, Ten- nessee, Kentucky, and Virginia R. W. Johnson, Jr. (Knoxville, Tenn.) Aeromagnetic studies of Shenandoah Valley dikes R. W. Johnson (Knoxville, Tenn.) Washington : Foraminiferal studies of the Pacific Northwest W. W. Rau (M) *Republic quadrangle R. L. Parker (D) Colorado and Utah (test-site Maryland, Virginia, and West A92 GEOLOGICAL Washington— Continued *Bald Knob quadrangle M. H. Staatz (D) *Grays Harbor basin H. D. Gower (M) *Northern Olympic Peninsula R. D. Brown, Jr. (M) *Holden and Lucerne quadrangles, Northern Cascade Moun- tains (copper) F. W. Cater (D) Metaline lead-zinc district M. G. Dings (D) *Stevens County lead-zinc district R. G. Yates (M) *Greenacres quadrangle, ‘Vashington-Idaho (high-alumina clays) P. L. Weis (Spokane, Wash.) *Hunter quadrangle (magnesite, tungsten, base metals, and barite) A. B. Campbell (D) *Chewelah area ( magnesite) Ian Campbell (San Francisco, Calif.) *Mt. Spokane quadrangle (uranium) A. E. Weissenborn (Spokane, Wash.) *Turtle Lake quadrangle (uranium) G. E. Becraft (W) Coal resources H. D. Gower (M) *Maple Valley, Hobart, and Cumberland quadrangles, King County (coal) A. A. Wanek (M) *Puget Sound Basin (urban geology and construction-site planning) D. R. Crandell (D) Osceola mudflow studies D. R. Crandell (D) *Portland industrial area, Oregon and Washington (urban geology) D. E. Trimble (D) Aerial radiological monitoring surveys, Hanford R. G. Schmidt (W) Pacific Northwest geophysical studies D. J. Stuart (M) West Virginia: ‘Potomac Basin studies, Virginia J. T. Hack (W) Aerial radiological monitoring surveys, Belvoir area, Vir- ginia and Maryland R. B. Guillou (W) Wisconsin: ‘Florence County (iron) C. E. Dutton (Madison, Wis.) ‘Wisconsin zinc-lead mining district ’1‘. E. Mullens (D) '“Stratigraphy of the lead-zinc district near Dubuque J. W. Whitlow (W) Geophysical studies in the Lake Superior region G. D. Bath (M) Correlation of aeromagnetic studies and areal geology, Flor- ence County R. W. Johnson, Jr. (Knoxville, Tenn.) Maryland, Virginia, and West SURVEY RESEARCH l960—SYNOPSIS OF GEOLOGIC RESULTS Wisconsin—Continued Correlation of aeromagnetic studies and areal geology near Wausau J. W. Allingham (W) Wyoming: General geology and engineering geology: Devonian stratigraphy of the middle Rocky Mountain area, Colorado and adjacent States V. E. Swanson (D) Pennsylvanian and Permian stratigraphy, Roeky Mountain Front Range, Colorado and Wyoming E. K. Maughan (D) Investigation of Jurassic stratigraphy, south-central Wy- oming and northwestern Colorado G. N. Pipiringos (D) Regional marine-nonmarine Upper Cretaceous facies rela- tionships J. F. Murphy (D) Chemical and physical properties of the Pierre shale, Mon- tana, North Dakota, South Dakota, Wyoming and Nebraska H. A. Tourtelot (D) *Quaternary geology of the Wind River Mountains G. M. Richmond (D) Structural significance of Reef Creek and Heart Mountain detachment faults W. G. Pierce (M) *Clark Fork area W. G. Pierce (M) *Geology of Grand Teton National Park J. D. Love (Laramie, Wyo.) *Cokeville quadrangle W. W. Rubey (W) Fossil Basin, southwest Wyoming J. J. Tracey, Jr. (W) *Fort Hill quadrangle S. S. Oriel (D) Geology and paleolimnology of the Green River formation W. H. Bradley (W) Mineralogy and geochemistry of the Green River formation 0. Milton (W) *Storm Hill quadrangle G. A. Izett (D) *Upper Green River valley (construction-site planning) W. R. Hansen (D) Mineral resources : ‘Atlantic City district (iron, gold) R. W. Bayley (M) Titaniferous black sands in Upper Cretaceous rocks R. S. Houston (Laramie, Wyo.) Geochemistry and petrology of western phosphate deposits R. A. Gulbrandsen (M) Stratigraphy and resources of Permian rocks in western Wyoming (phosphate, minor elements) R. P. Sheldon (D) Williston Basin oil and gas studies, Wyoming, Montana, North Dakota, and South Dakota C. A. Sandberg (D) *Shotgun Butte (oil and gas) W. R. Keefer (Laramie, Wyo.) *Crowheart Butte area (oil and gas) J. F. Murphy (D) REGIONAL INVESTIGATIONS Wyoming—Continued Mineral resources—Continued *Beaver Divide area (oil and gas) F. B. Van Houten (Princeton, NJ.) Regional geology of the Wind River Basin (oil and gas) W. R. Keefer (Laramie, Wyo.) *Whalen-Wheatland area (oil and gas) L. W. McGrew (Laramie, Wyo.) Reconnaissance geology of the Burney-Broadus coal field, Wyoming and Montana W. W. Olive (W) *Buffalo-Lake de Smet area (coal) W. J. Mapel (D) *Green River formation, Sweetwater County (oil shale, salines) W. C. Culbertson (D) Geophysical studies in uranium geology R. M. Hazlewood (D) Formation and redistribution of uranium deposits of the Colorado Plateau and Wyoming K. G. Bell (D) . *Baggs area, Wyoming and Colorado (uranium) G. E. Prichard (D) Uranium and phosphate in the Green River formation W. R. Keefer (Laramie, Wyo.) *Strawberry Hill quadrangle (uranium) R. E. Davis (D) Shirley basin area (uranium) E. N. Harshman (D) *Western Red Desert area (uranium in coal) G. N. Pipiringos (D) *Gas Hills district (uranium) H. D. Zeller (D) *Southern Powder River Basin (uranium) W. N. Sharp (D) *Pumpkin Buttes area, Powder River Basin (uranium) W. N. Sharp (D) *Crooks Gap area. Fremont County (uranium) J. G. Stephens (D) *Hulett Creek area (uranium) C. S. Robinson (D) *Hiland-Clarkson Hills area (uranium) E. I. Rich (M) ‘Regional stratigraphic study of the Inyan Kara group, Black Hills (uranium) W. J. Mapel (D) Puerto Rico and Canal Zone: Cenozoic faunas, Caribbean area W. P. Woodring (W) Recent Foraminifera, Central America P. J. Smith (M) ‘Geology and mineral resources W. H. Monroe (San Juan, Puerto Rico) Western Pacific Islands: Thermal and seismic studies in the South Pacific J. H. Swartz (W) Pacific Islands vegetation F. R. Fosberg (W) Cenozoic invertebrates, Pacific Islands M. R. Todd (W) Cenozoic invertebrates, mollusks, Pacific Islands H. S. Ladd (W) IN PROGRESS A93 Western Pacific Islands—Continued Oligocene gastropods and pelecypods, Pacific Islands F. S. MacNeil (M) Vertebrate faunas, Ishigaki, Ryukyu Islands F. C. Whitmore, J r., (W) Ecologic studies on Onotoa Atoll P. E. Cloud (W) *Tinian D. B. Doan (W) *Truk J. ’1‘. Stark (Recife, Brazil) *Yap and Caroline Islands C. G. Johnson (Honolulu, Hawaii) *Palau Islands G. Corwin (W) *Pagan Island G. Corwin (W) ’Okinawa G. Corwin (W) *Miyako Archipelago, Ryukyu Islands D. B. Doan (W) ‘Ishigaki, Ryukyu Islands H. L. Foster (W) ‘Guam J. I. Tracey, Jr. (W) *Saipan P. E. Cloud (W) *Bikini and nearby atolls H. S. Ladd (W) Antarctica: Geology of Antarctica E. L. Boudette (W) Foreign: Argentina—development of government geological services (training) W. W. Olive (W) Brazil—geological education A. J. Bodenlos (Rio de J aneiro, Brazil) *Brazil—iron and manganese resources, Minas Gerais J. V. N. Dorr II (Belo Horizonte, Brazil) *Brazil——-base-meta1 resources A. J. Bodenlos (Rio de J‘aneiro, Brazil) Brazil—uranium resources (training) C. T. Pierson (Rio de J aneiro, Brazil) Bolivia—mineral resources and geologic mapping (advisory and training) T. H. Kiilsgaard (W) ”Chile—mineral resources and national geologic mapping W. D. Carter (Santiago, Chile) "Surflcial geology, eastern Greenland planning) W. E. Davies (W) India—mineral resources (advisory) L. V. Blade (Calcutta, India) Indonesia—economic and engineering geology (advisory and training) D. A. Andrews (Bandung, Indonesia) J ordan—mineral resources development (advisory) V. E. McKelvey (M) "Libya—industrial minerals and national geologic map G. H. Goudarzi (Tripoli, Libya) ( construction-site A94 Foreign—Continued Mexico—regional geologic mapping (training) R. L. Miller (Mexico D. F., Mex.) Pakistan—mineral resources development (advisory and training) J. A. Reinemund (Quetta, Pakistan) Peru—economic geology, Southern provinces (advisory) W. W. Olive (W) ”Philippines—iron, chromite and non—metallic mineral re- sources J. F. Harrington (Manila, P. I.) “Saudi Arabia—national geologic map G. F. Brown (J idda, Saudi Arabia) GEOLOGICAL SURVEY RESEARCH HMO—SYNOPSIS OF GEOLOGIC RESULTS Foreign—Continued Thailand—economic geology and mineral industry expan- sion (advisory) L. S. Gardner (Bangkok, Thailand) *Taiwan—economic geology (training) S. Rosenblum (Taipei, Taiwan) Turkey—University of Istanbul (training) Q. D. Singewald (Istanbul, Turkey) Extraterrestrial : Investigations of lunar craters E. M. Shoemaker (M) Photogeology of the moon R. J. Hackman (W) TOPICAL INVESTIGATIONS Heavy metals: District studies: Ferrous and ferro-alloy metals: *Selected iron deposits of the Northeastern States A. F. Buddington (Princeton, NJ.) Correlation of aeromagnetic studies and areal geology, Adirondacks area, New York (iron) J. R. Balsley (W) Correlation of aeromagnetic studies and areal geology, New York-New Jersey Highlands (iron) A. Jespersen (W) Clinton iron ores of the Southern Appalachians R. P. Sheldon (D) ‘Iron River-Crystal Falls district, Michigan (iron) H. L. James (M) *Eastern Iron County, Michigan (iron) K. L. Wier (Iron Mountain, Mich.) *Southern Dickinson County, Michigan (iron) R. W. Bayley (M) *East Marquette district, Michigan (iron) J. E. Gair (D) *Florence County, Wisconsin (iron) C. E. Dutton (Madison, Wis.) *Cuyuna North Range, Minnesota (iron) R. G. Schmidt (W) Iron ore deposits of Nevada R. G. Reeves (M) *Atlantic City district, Wyoming (iron, gold) R. W. Bayley (M) ‘Unionville and Buffalo Mountain quadrangles, Humbolt Range, Nevada (iron, tungsten, silver, quicksilver) R. E. Wallace (M) ”Klukwan iron district, Alaska E. C. Robertson (W) *Bridgewater quadrangle, Maine (manganese) L. Pavlides (W) Manganese deposits of the Philipsburg area, Montana (manganese and base metals) W. C. Prinz (Spokane, Wash.) *John Day area, Oregon (chromite) T. P. Thayer (W) Lateritic nickel deposits of the Klamath Mountains, Oregon-California. P. E. Hotz (M) ‘Hamme tungsten deposit, North Carolina J. M. Parker III (Raleigh, N.C.) Heavy metals—Continued District studies—Continued Ferrous and ferro-alloy metals—Continued *San Francisco Mountains, Utah (tungsten, copper) D. M. Lemmon (M) *Wheeler Peak and Garrison quadrangles, Snake Range, Nevada-Utah (tungsten, beryllium) D. H. Whitebread (M) ‘Osgood Mountains quadrangle, Nevada (tungsten, quick- silver) P. E. Hotz (M) *Bishop tungsten district, California P. C. Bateman (M) *Eastern Sierra tungsten area, California; Devil’s Post- pile, Mt. Morrison, and Casa Diablo quadrangles (tungsten, base metals) C. D. Rinehart (M) *Geologic study of the Sierra Nevada batholith, California (tungsten, gold, base metals) P. C. Bateman (M) ‘Blackbird Mountain area, Idaho (cobalt) J. S. Vhay (Spokane, Wash.) *Thunder Mountain niobium area, Montana-Idaho R. L. Parker (D) Magnet Cove niobium investigations, Arkansas L. V. Blade (D) Base and precious metals: *Swain County copper district, North Carolina G. H. Espenshade (W) Massive sulfide deposits of the Ducktown district, Ten- nessee and adjacent areas (copper, iron, sulfur) R. M. Hernon (D) *Michigan copper district W. S. White (W) *Central district, New Mexico (copper, zinc) W. R. Jones (D) *Klondyke quadrangle, Arizona (copper) F. S. Simons (D) *Bradshaw Mountains, Arizona (copper) C. A. Anderson (W) *Christmas quadrangle, Arizona (copper, iron) C. R. Willden (M) *Globe-Miami area, Arizona (copper) N. P. Peterson (Globe, Ariz.) *Prescott-Paulden area, Arizona (copper) M. H. Krieger (M) *Mammoth quadrangle, Arizona (copper) S. C. Creasey (M) TOPICAL INVESTIGATIONS IN PROGRESS Heavy metals—Continued District studies—Continued Base and precious metals—Continued *Twin Buttes, area, Arizona (copper) J. R. Cooper (D) *Contact-metamorphic deposits of the Little Dragoons area, Arizona (copper) J. R. Cooper (D) Structural geology of the Sierra foothills mineral belt, California (copper, zinc, gold, chromite) L. D. Clark (M) "Holden and Lucerne quadrangles, Northern Cascade Mountains, Washington (copper) F. W. Cater (D) *Regional geologic setting of the Bingham Canyon dis- trict, Utah (copper) R. J. Roberts (M) *Lyon, Douglas, and Ormsby Counties, Nevada (copper) J. G. Moore (M) *Regional geologic setting of the Ely district, Nevada (copper, lead, zinc) A. L. Brokaw (D) "Southern Brooks Range, Alaska (copper, precious metals) W. P. Brosgé (M) *Antler Peak quadrangle, Nevada (base and precious metals) R. J. Roberts (M) *Eureka County, Nevada (base and precious metals) R. J. Roberts (M) ‘Creede and Summitville districts, Colorado (base and precious metals, and fluorspar) T. A. Steven (D) ‘East Tennessee zinc studies A. L. Brokaw (D) Origin and depositional control of some Tennessee and Virginia zinc deposits H. Wedow, Jr. (Knoxville, Tenn.) *Wisconsin zinc-lead mining district T. E. Mullens (D) *Stratigraphy of the lead-zinc district near Dubuque, Iowa J. W. Whitlow (W) *Tri-State lead-zinc district, Oklahoma, Missouri, Kansas E. T. McKnight (XV) *Holy Cross quadrangle, Colorado, and the Colorado min- eral belt (lead, zinc, silver, copper, gold) 0. Tweto (D) ’Tenmile Range, including the Kokomo mining district, Colorado (base and precious metals) A. H. Koschmann (D) *Central City-Georgetown area, Colorado, including stud- ies of the Precambrian history of the Front Range (base, precious, and radioactive metals) P. K. Sims (D) *Minturn quadrangle, Colorado (zinc, silver, copper, lead, gold) T. S. Lovering (D) *Rico district, Colorado (lead, zinc, silver) E. T. McKnight (W) ‘San Juan mining area, Colorado, including detailed study of the Silverton Caldera (lead, zinc, silver, gold, copper) R. G. Luedke (W) *Alta quadrangle, Utah (lead, silver, phosphate rock) M. D. Crittenden, Jr. (M) A95 Heavy metals—Continued District studies—Continued Base and precious metals—Continued ‘East Tintic lead-zinc district, Utah, including extensive geochemical studies H. T. Morris (M) *Eureka area, Nevada (zinc, lead, silver, gold) T. B. Nolan (W) Ione quadrangle, Nevada (lead, quicksilver, tungsten) C. J. Vitaliano (Bloomington, Ind.) ‘Boulder batholith area, Montana (base, precious, and radioactive metals) M. R. Klepper (W) Ore deposits of the Coeur d’Alene mining district, Idaho (lead, zinc, silver) V. C. Fryklund, Jr. (Spokane, Wash.) ‘General geology of the Coeur d’Alene mining district, Idaho (lead, zinc, silver) A. B. Griggs (M) *Cerro Gordo quadrangle, California (lead, zinc) W. C. Smith (M) *Panamint Butte quadrangle, California, including spe- cial geochemical studies (lead-silver) W. E. Hall (W) ‘Metaline lead-zinc district, Washington M. G. Dings (D) *Stevens County, Washington, lead-zinc district R. G. Yates (M) *Mt. Diablo area, California (quicksilver, copper, gold, silver) E. H. Pampeyan (M) *Ochoco Reservation, Lookout Mountain, Eagle Rock, and Post quadrangles, Oregon (quicksilver) A. C. Waters (Baltimore, Md.) "Lower Kuskokwim-Bristol Bay region, Alaska (quick- silver, antimony, zinc) J. M. Hoare (M) Quicksilver deposits, southwestern Alaska E. M. MacKevett, Jr. (M) *Nome C—1 and- D—1 quadrangles, Alaska (gold) C. L. Hummel (M) *Tofty placer district, Alaska (gold, tin) D. M. Hopkins (M) “Regional geology and mineral resources, southeastern Alaska E. H. Lathram (M) Seward Peninsula tin investigations, Alaska P. L. Killeen (W) Commodity and topical studies : Resource study and appraisal of ferrous and ferro—alloy metals T. P. Thayer (W) Tungsten resource studies 0. Tweto (D) Cobalt resource studies J. S. Vhay (Spokane, Wash.) Resources and geochemistry of rare-earth elements of the Western States J. W. Adams (D) Resource study and appraisal of base and precious metals A. R. Kinkel, Jr. (W) Lead-zinc-silver resource studies E. T. McKnight (W) Gold resource studies A. H. Koschmann (D) 4"” A96 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Heavy metals—Continued Commodity and topical studies—Continued Ore deposition at Creede, Colorado E. W. Roedder (W) Origin of the Mississippi Valley type ore deposits A. V. Heyl (W) Western oxidized zinc deposits A. V. Heyl (W) Geophysical studies of relation of ore deposits to meta- morphism A. Griscom (W) Alaskan metallogenic provinces C. L. Sainsbury (M) Light metals and industrial minerals: District studies: Titaniferous black sands in Upper Cretaceous rocks, Wyoming R. S. Houston (Laramie, Wyo.) Distribution and origin of the Kauai bauxite deposits, Hawaii S. H. Patterson (Lihue, Kauai, Hawaii) Bauxite deposits of the Southeastern States E. F. Overstreet (W) Aeromagnetic studies in the Newport, Arkansas, and Ozark bauxite areas A. Jespersen (W) *Marysvale district, Utah (alunite) R. L. Parker (D) *Greenacres quadrangle, Washington-Idaho (high-alumina clays) P. L. Weis (Spokane, Wash.) ‘Hunter quadrangle, Washington (magnes te, tungsten, base metals, barite) A. B. Campbell (D) *Chewelah area, Washington (magnesite) Ian Campbell (San Francisco, Calif.) *Lake George district, Colorado (beryllium) , C. C. Hawley (D) / Pegmatites of the Spruce Pine and Franklin-Sylva dis- tricts, North Carolina F. G. Lesure (Knoville, Tenn.) *Geologic setting of the Spruce Pine pegmatite district, North Carolina (mica, feldspar) D. A. Brobst (D) ‘Southern Black Hills, South Dakota (pegmatite minerals) J‘. J. Norton (D) Fluorspar deposits of northwestern Kentucky R. D. Trace (W) *Salem quadrangle, Kentucky (fluorspar) R. D. Trace (W) *Poncha Springs and Saguache quadrangles, Colorado (fluorspar) R. E. Van Alstine (W) ‘Thomas and Dugway Ranges, Utah (fluorspar, uranium, beryllium) M. H. Staatz (D) ‘Geology and ore deposits of Bullfrog, and Bear Mountain quadrangles, Nevada (fluorspar, bentonite, gold, silver) H. R. Cornwall (M) *Talc and asbestos deposits of north-central Vermont W. M. Cady (Montpelier, Vt.) "Gouverneur district, New York (tale) A. E. J. Engel (Pasadena, Calif.) Light metals and industrial minerals—Continued District studies—Continued ‘MacFadden Peak quadrangle and adjacent areas, Arizona (asbestos) A. F. Shride (D) Barite deposits of Arkansas D. A. Brobst (D) Clay deposits of Maryland M. M. Knechtel (W) Clay deposits of the Olive Hill bed of eastern Kentucky J. W. Hosterman (W) Clay studies, Colorado Plateau L. G. Schultz (D) *Western Mojave Desert, California (boron) T. W. Dibblee, Jr. (M) *Furnace Creek area, California (boron) J. F. McAllister (M) Origin of the borate-bearing marsh deposits of California, Oregon, and Nevada (boron) W. C. Smith (M) *Geology and origin of the saline deposits of Searles Lake, California G. I. Smith (M) Potash and other saline deposits of the Carlsbad area, New Mexico C. L. Jones (M) Phosphate deposits of northern Florida G. H. Espenshade (W) ‘Florida land-pebble phosphate deposits J. B. Cathcart (D) Stratigraphy and resources of Permian rocks in western Montana (phosphate, minor elements) R. W. Swanson (Spokane, Wash.) Stratigraphy and resources of Permian rocks in south- western Montana (phosphate, minor elements) E. R. Cressman (M) *Morrison Lake quadrangle, Idaho-Montana (phosphate) E. R. Cressman (M) Stratigraphy and resources of Permian rocks in western Wyoming (phosphate, minor elements) R. P. Sheldon (D) *Irwin quadrangle, Caribou Mountains, Idaho (phosphate) L. S. Gardner (Bangkok, Thailand) *Soda Springs quadrangle, Idaho, including studies of the Bannock thrust zone (phosphate) F. C. Armstrong (Spokane Wash.) *Aspen Range-Dry Ridge area, Idaho (phosphate) T. M. Cheney (M) Stratigraphy and resources of the Phosphoria formation in Idaho (phosphate, minor elements) V. E. McKelvey (M) Stratigraphy and resources of the Phosphoria and Park City formations in Utah and Nevada (phosphate, minor elements) T. M. Cheney (W) ‘Heceta-Tuxekan area, Alaska (high-calcium limestone) G. D. Eberlein (M) Commodity and topical studies: Resources and geochemistry of selenium in the United States D. F. Davidson (D) Resource study and appraisal of igneous and metamor- phic minerals and light metals T. P. Thayer (W) TOPICAL INVESTIGATIONS IN PROGRESS A97 Light metals and industrial minerals—Continued Commodity and! topical studies—Continued Pegmatite-mineral resource studies J. J. Norton (D) Resource study and appraisals of sedimentary nonmetallic minerals C. L. Rogers (W) Phosphate reserves, Southeastern United States J. B. Cathcart (D) Geochemistry and petrology of western phosphate deposits R. A. Gulbrandsen (M) Phosphate deposits of south-central Montana R. W. Swanson (Spokane, Wash.) Radioactive minerals : District studies : Granites and related rocks of the Southeastern States, with emphasis on monazite and xenotime J. B. Mertie, Jr. (W) Geology of the Piedmont region of the Southeastern States; with emphasis on the origin and distribu- tion of monazite W. C. Overstreet (W) ‘Western San Juan Mountains, Colorado (uranium, vana- dium, gold) C. S. Bromfleld (D) Selected studies of uranium and rare-earth deposits in Pennsylvania and New Jersey H. Klemic (W) *Lehighton quadrangle, Pennsylvania (uranium) H. Klemic (W) ‘Shelby quadrangle, North Carolina (monazite) W. C. Overstreet (W) . Mineralogy of uranium-bearing rocks in Karnes and Duval Counties, Texas A. D. Weeks (W) 'Harding County, South Dakota, and adjacent areas (uraniferous lignite) G. N. Pipiringos (D) *Southern'Black Hills, South Dakota (uranium) G. B. Gott (D) Regional gravity studies in uranium geology, Black Hills area R. M. Hazlewood (D) *Regional stratigraphic study of the Inyan Kara group, Black Hills, Wyoming (uranium) W. J. Mapel (D) *Hulett Creek area, Wyoming (uranium) C. S. Robinson (D) ‘Hiland-Clarkson Hills area, Wyoming (uranium) E. 1. Rich (M) ‘Pumpkin Buttes area, Powder River Basin, Wyoming (uranium) W. N. Sharp (D) *Southern Powder River Basin, Wyoming (uranium) W. N. Sharp (D) "Strawberry Hill quadrangle, \Vyoming (uranium) R. E. Davis (D) Shirley basin area, Wyoming (uranium) E. N. Harshman (D) ‘Gas Hills district, Wyoming (uranium) H. D. Zeller (D) ‘Crooks Gap area, Fremont County, Wyoming (uranium) J. G. Stephens (D) Radioactive minerals—Continued District studies—Continued ‘Western Red Desert area, Wyoming (uranium in coal) G. N. PipiringOs (D) Uranium and phosphate in the Green River formation, Wyoming W. R. Keefer (Laramie, Wyo.) *Baggs area, Wyoming and Colorado (uranium) G. E. Prichard (D) *Powderhorn area, Gunnison County, Colorado (thorium) J. C. Olson (D) *Wet Mountains, Colorado (thorium, base and precious metals) M. R. Brock (W) ‘Maybell—Lay area, Moffat County, Colorado (uranium) M. J. Bergin (W) ' ‘Compilation of Colorado Plateau geologic maps (ura- nium, vanadium) D. G. Wyant (D) Stratigraphic studies, Colorado Plateau (uranium, vanadium) L. C. Craig (D) San Rafael group stratigraphy, Colorado Plateau (ura- nium) J. C. Wright (D) Triassic stratigraphy and lithology of the Colorado Plateau (uranium, copper) J. H. Stewart (D) Relative concentrations of chemical elements in rocks and ore deposits of the Colorado Plateau (ura- nium, vanadium, copper) A. T. Miesch (D) ColoradoPlateau botanical prospecting studies F. J. Kleinhampl (M) Colorado Plateau ground-water studies (uranium) D. Jobin (D) *La Sal area, Utah-Colorado (uranium, vanadium) W. D. Carter (Santiago, Chile) *Lisbon Valley area, Utah-Colorado (uranium, vanadium, copper) G. W. Weir (M) ‘Ralston Buttes, Colorado (uranium) D. M. Sheridan (D) *Klondike Ridge area, Colorado (uranium, copper, man- ganese, salines) J. D. Vogel (D) Uravan district, Colorado (vanadium, uranium) R. L. Boardman (W) Wallrock alteration and its relation to thorium deposi- tion in the Wet Mountains, Colorado E. S. Larsen, 3d (W) *Slick Rock district, Colorado (uranium, vanadium) D. R. Shawe (D) Exploration for uranium deposits in the Gypsum Val- ley district, Colorado C. F. Withington (W) *Bull Canyon district, Colorado (vanadium, uranium) D. Elston (D) *Ute Mountains, Colorado (uranium, vanadium) E. B. Ekren (D) *Abajo Mountains, Utah (uranium, vanadium) I. J. Witkind (D) *White Canyon area, Utah (uranium, copper) R. E. Thaden (D) A98 Radioactive minerals—Continued District studies—Continued ‘Deer Flat area, White Canyon district, Utah (uranium, copper) T. L. Finnel (D) *Elk Ridge area, Utah (uranium) R. Q. Lewis (D) Uranium ore controls of the San Rafael Swell, Utah C. C. Hawley (D) *Sage Plain area, Utah (uranium and vanadium) L. C. Huff (D) ‘Orange Cliffs area, Utah (uranium) F. A. McKeown (D) *Moab-Interriver area, east-central Utah (uranium) E. N. Hinrichs (D) — *Circle Cliffs area, Utah (uranium) E. S. Davidson (Tucson, Ariz.) Regional relations of the uranium deposits of northwest- ern New Mexico L. S. Hilpert (Salt Lake City, Utah) Mineralogy of uranium—bearing rocks in the Grants area, New Mexico A. D. Weeks (W) ‘Grants area, New Mexico (uranium) R. E. Thaden (D) "Laguna district, New Mexico (uranium) R. H. Moench (D) Ambrosia Lake district, New Mexico (uranium) H. C. Granger (D) *Tucumcari-Sabinoso area, New Mexico (uranium) R. L. Griggs (D) *Carrizo Mountains area, Arizona-New Mexico (uranium) J. D. Strobell (D) Studies of uranium deposits in Arizona R. B. Raup (D) *East Vermillion Cliffs area, Arizona (uranium, vana- dium) R. G. Peterson (Boston, Mass.) Uranium deposits of the Dripping Spring quartzite of southeastern Arizona H. C. Granger (D) *Radioactive placer deposits of central Idaho D. L. Schmidt (Seattle, Wash.) "Mt. Spokane quadrangle, Washington (uranium) A. E. )Veissenborn (Spokane, Wash.) *Turtle Lake quadrangle, W'ashington (uranium) G. E. Becraft (W) Commodity and topical studies: Resource studies and appraisals of uranium and thorium deposits A. P. Butler (D) Uranium in natural waters P. W. Fix (W) Geology of uranium in coaly rocks in the United States J. D. Vine (M) Distribution of metals in asphaltite and petroleum (ura- nium) W. J. Hail (D) Relation of fossil wood to uranium deposits, with em- phasis on the Colorado Plateau R. A. Scott (D) ' Formation and redistribution of uranium deposits of the Colorado Plateau and Wyoming K. G. Bell (D) GEOLOGICAL SURVEY RESEARCH l960—SYNOPSIS OF GEOLOGIC RESULTS Radioactive minerals—Continued Commodity and topical studies—Continued Uranium-vanadium deposits in sandstone, with emphasis on the Colorado Plateau R. P. Fischer (D) Geology of uranium in lignites, Montana, North Dakota, and South Dakota N. M. Denson (D) Trace elements in rocks of Pennsylvanian age, Oklahoma, Kansas, Missouri (uranium, phosphate) \V. Danilchik (Quetta, Pakistan) Uranium—thorium reconnaissance, Alaska E. M. MacKevett, Jr. (M) Fuels: District studies: Petroleum and natural gas: *Stratigraphy of the Dunkirk and related beds in the Penn Yan and Keuka Lake quadrangles, New York (oil and gas) M. J. Bergin (W) ‘Stratigraphy of the Dunkirk and related beds, in the Bath and Woodhull quadrangles, New York (oil and gas) J. F. Pepper (New Philadelphia, Ohio) *Petroleum geology of Duflield, Stickleyville, Keokee, Olinger, and Pennington Gap quadrangles, Vir- ginia and Kentucky L. D. Harris (W) ‘Northern Arkansas oil and gas investigations, Arkansas E. E. Glick (D) Anadarko Basin, Oklahoma and Texas (oil and gas) W. L. Adkison (Lawrence, Kans.) McAlester Basin, Oklahoma (oil and gas) S. E. Frezon (D) Central Nebraska basin (oil and gas) G. E. Prichard (D) Subsurface geology of Dakota sandstone, Colorado and Nebraska (oil and gas) N. W. Bass (D) Paleozoic stratigraphy of the Sedgwick Basin, Kansas (oil and gas) W. L. Adkison (Lawrence, Kans.) ‘Wilson County, Kansas (oil and gas) W. D. Johnson, Jr. (Lawrence, Kans.) *Shawnee County, Kansas (oil and gas) W. D. Johnson, Jr. (Lawrence, Kans.) ‘Pennsylvanian oil and gas investigation, Texas D. A. Myers (D) *Stratigraphy, Northern Franklin Mountains, west Texas (petroleum) R. L. Harbour (D) Oil and gas fields, New Mexico D. C. Duncan (W) ‘Fuels potential of the Navajo Reservation, Arizona and Utah R. B. O’Sullivan (D) *Geology of the Winnett-Mosby area, Montana (oil and gaS) W. D. Johnson, Jr. (Lawrence, Kans.) Williston Basin oil and gas studies, Wyoming, Montana, North Dakota and South Dakota C. A. Sandberg (D) *Beaver Divide area, Wyoming (oil and gas) F. B. Van Houten (Princeton, NJ.) TOPICAL INVESTIGATIONS IN PROGRESS A99 Fuels—Continued Fuels—Continued District studies—Continued Petroleum and] natural gaFContinued *Crowheart Butte area, Wyoming (oil and gas) J. F. Murphy (D) *Shotgun Butte, Wyoming (oil and gas) W. R. Keefer (Laramie, Wyo.) *Whalen-Wheatland area, Wyoming (oil and gas) L.W. McGrew (Laramie, Wyo.) Regional geology of the Wind River Basin, Wyoming (oil and gas) W. R. Keefer (Laramie, Wyo.) ‘Eastern Los Angeles basin, California (petroleum) J. E. Schoellhamer (M) Rocks and structures of the Los Angeles basin and their gravitational effects T. H. McCulloh (Riverside, Calif.) *Southeastern Ventura Basin, California (petroleum) E. L. Winterer (Los Angeles, Calif.) *Northwest Sacramento Valley, California (petroleum) R. D. Brown, Jr. (M) *Newport embayment, Oregon (oil and gas) P. D. Snavely, Jr. (M) *Anlauf and Drain quadrangles, Oregon (oil and gas) L. Hoover (W) “Nelchina area, Alaska (petroleum) A. Grantz (M) *Iniskin-Tuxedni region, Alaska (petroleum) R. L. Detterman (M) "Gulf of Alaska province, Alaska (petroleum) D. J. Miller (M) "Buckland and Huslia Rivers area, west-central Alaska W. W. Patton, Jr. (M) “Stratigraphic and structural studies of the Lower Yukon- Koyukuk area, Alaska (petroleum) W. W. Patton, Jr. (M) “Northern Alaska petroleum investigations G. Gryc (W) Coal: *Western middle anthracite coal field, Pennsylvania H. H. Arndt (W) *Southern anthracite field, Pennsylvania G. H. \Vood, Jr. (W) *Geology in the vicinity of anthracite mine drainage projects, Pennsylvania T. M. Kehn (Mt. Carmel, Pa.) *Allegany County, Maryland (coal) W. de Witt, Jr. (W) *Warrior quadrangle, Alabama (coal) W. C. Culbertson (D) *Geology and coal resources of Belmont County, Ohio H. L. Berryhill, Jr. (D) *Eastern Kentucky coal investigations J. W. Huddle (W) *Ivydell, Pioneer, Jellico West, and Ketchen quadrangles Tennessee (coal) K. J. Englund (W) *Geology and coal deposits, Terre Haute and Dennison quadrangles, Indiana P. Averitt (D) ‘Arkansas Basin (coal) B. R. Haley (D) District studies—Continued Coal—«Continued *Ft. Smith District, Arkansas and Oklahoma (coal an gas) , T. A. Hendricks (D) *Geology of the Livingston-Trail Creek area, Montana (coal) A. E. Roberts (D) Reconnaissance geology of the Burney-Broadus coal field, Wyoming and Montana W. W. Olive (\V) *Buffalo—Lake de Smet area, Wyoming (coal) W. J.Mapel (D) . *North Park, Colorado (coal, oil, and gas) D. M. Kinney (W) *Western North Park, Colorado (coal, oil, and gas) W. J. Hail (D) ‘Carbondale coal field, Colorado J. R. Donnell (D) *Trinidad coal field, Colorado R. B. Johnson (D) *Animas River area, Colorado and New Mexico (coal, oil, and gas) H. Barnes (D) *Raton Basin coking coal, New Mexico A. A. Wanek (M) *East side San Juan Basin, New Mexico (coal, oil and gas) C. H. Dane (W) *Cedar Mountain quadrangle, Iron County, Utah (coal) P. Averitt (D) *Southern Kolob Terrace coal field, Utah W. B. Cashion (D) *Maple Valley, Hobart and Cumberland quadrangles, King County, Washington (coal) A. A. Wanek (M) Matanuska stratigraphic studies, Alaska (coal) A. Grantz (M) *Matanuska coal field, Alaska F. F. Barnes (M) Tertiary history of the Yukon-Tanana Upland, Alaska (coal) D. M. Hopkins (M) *Nenana coal investigations, Alaska 0. Wahrhaftig (M) Oil shale: Oil shale investigations, eastern United States L. C. Conant (Tripoli, Libya) *Green River formation, Sweetwater County, Wyoming (oil shale, salines) W. C. Culbertson (D) ”Oil shale investigations in Colorado D. C. Duncan (W) Oil shale resources, northwest Colorado J. R. Donnell (D) *Grand—Battlement Mesa oil-shale, Colorado J‘. R. Donnell (D) *Uinta Basin oil shale, Utah W. B. Cashion (D) Resource studies : Fuel resource studies D. C. Duncan (W) Geology of the continental shelves J. F. Pepper (New Philadelphia, Ohio) A100 Fuels—Continued Resource studies—Continued Synthesis of geologic data on Atlantic Coastal Plain and Continental Shelf J. E. Johnston (W) Coal resources of the United States P. Averitt (D) Coal fields of the United States J. Trumbull (W) *Bituminous coal resources of Pennsylvania E. D. Patterson (W) Coal resources of Alabama W. C. Culbertson (D) Coal resources of Washington H. D. Gower (M) Map of coal fields of Alaska F. F. Barnes (M) Geochemical and botanical exploration methods: Dispersion pattern of minor elements related to igneous intrusions W. R. Griffitts (D) Hydrogeochemical prospecting F. C. Canney (D) Geochemical halos of mineral deposits, Basin and Range province L. C. Hufl (D) Geochemical prospecting techniques, Alaska R. M. Chapman (D) Botanical exploration and research H. L. Cannon (D) Isotope geology in exploration 2 Studies of isotope geology of lead R. S. Cannon, Jr. (D) Radon and helium studies A. B. Tanner (Salt Lake City, Utah) Isotopic fractionation of sulfur in geochemical processes W. U. Ault (Hawaii) Geophysical exploration methods : Correlation of airborne radioactivity data and areal geology R. B. Guillou (W) Development of seismic and acoustic methods W. H. Jackson (D) Seismic noise and model studies W. H. Jackson (D) Magnetic model studies I. Zietz (W) Polar charts for 3-dimensiona1 magnetic anomalies R. G. Henderson (W) Experimental aeromagnetic survey in northeast Oklahoma 1. Zietz (W) Geophysical interpretation aids 1. Roman (W) Downward continuation of magnetic and gravity anom- alies R. G. Henderson (W) Telluric currents investigation F. C. Frischknecht (D) Development of electromagnetic methods F. C. Frischknecht (D) Electronics laboratory \V. W. Vaughn (D) GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Geophysical exploration methods—Continued Geophysical instrument shop R. Raspet (W) Exploration and mapping techniques : Photogeology research W. A. Fischer (W) Photogeology training C. L. Pillmore (W) Photogeology service R. G. Ray (W) Geology applied to construction and terrain problems: Research and application of geology and seismology to public works planning, Massachusetts L.W. Currier (W) ‘Dennis and Harwich quadrangles, Massachusetts, sur- ficial geologic mapping and special seismic studies of engineering problems. L. W. Currier (W) Sea-cliff erosion studies C. A. Kaye (Boston, Mass.) *Herndon quadrangle, Virginia (construction-site plan- ning) R. E. Eggleton (D) *Knoxville and vicinity, Tennessee (urban geology) J. M. Cattermole (D) *Omaha-Council Bluffs and vicinity, Nebraska and Iowa (urban geology) R. D. Miller (D) *Great Falls area, Montana (urban geology and construc- tion-site planning) R. W. Lemke (D) *Fort Peck area, Montana (construction-site planning) H. D. Varnes (D) *VVolf Point area, Montana (construction-site planning) R. B. Colton (D) ‘Denver and vicinity; Golden and Morrison quadrangles, Colorado (urban geology) R. Van Horn (D) ‘Air Force Academy, Colorado (construction-site plan- ning) D. J. Varnes (D) *Black Canyon of the Gunnison River, Colorado (con- struction-site planning) \V. R. Hansen (D) *Upper Green River Valley, planning) W. R. Hansen (D) *Surficial geology of the Oak City area, Utah (construc- tion-site planning) D. J. Varnes (D) *Surficial geology of the Beverly Hills, Venice, and T0- panga quadrangles, Los Angeles, California (urban geology) J. T. McGill (Los Angeles, Calif.) *San Francisco Bay area; San Francisco South quad- rangle, California (urban geology) M. G. Bonilla (M) *San Francisco Bay area; San Francisco l'orth quad- rangle, California (urban geology) J. Schlocker (M) *Oakland East quadrangle, California (urban geology) D. H. Radbruch (M) Utah (construction-site TOPICAL INVESTIGATIONS IN PROGRESS Geology applied! to construction and terrain problems—Con. *Portland industrial area, Oregon and Washington (urban geology) D. E. Trimble (D) ‘Puget Sound Basin, \Vashington (urban geology and construction-site planning) D. R. Crandell (D) *Anchorage and vicinity, Alaska (construction-site plan- ning) R. D. Miller (D) *Mt. Hayes D—3 and D—4 quadrangles, Alaska (construc- tion-site planning) T. L. Péwé (College, Alaska) *Surficial and engineering geology studies and construction materials sources, Alaska T. L. Péwé (College, Alaska) *Engineering geology of Talkeetna-McGrath highway, Alaska T. L. Péwé (College, Alaska) Engineering geology laboratory T. C. Nichols, Jr. (D) Engineering problems related to rock failure: Landslide studies in the Fort Randall Reservoir area, South Dakota H. D. Varnes (D) Earthquake investigations, Hebgen Lake, Montana J. B. Hadley (D) *Geologic factors related to coal mine bumps, Utah F. W. Osterwald (D) Osceola mudflow studies, Washington D. R. Crandell (D) *Lituya Bay giant-wave investigation, Alaska D. J. Miller (M) Literature study of geologic factors involved in sub- sidence / A. S. Allen (W) Nuclear test-site studies: *Engineering geology of AEC Gnome Test Site, New Mexico V. R. Wilmarth (D) *Nash Draw quadrangle, New Mexico (test-site evalua- tion) J. D. Vine (M) Seismic studies, southern Eddy County, New Mexico (test-site evaluation) P. E. B‘yerly (D) Salt anticline studies, Colorado and Utah (test-site evalu- ation) E. M. Shoemaker (M) Salt anticlines, Paradox Basin, Colorado and Utah (test- site evaluation) D. P. Elston (D) Geophysical studies at the Nevada Test Site W. H. Diment (D) *Engineering geology of the AEC Nevada Test Site area V. R. Wilmarth (D) *Nuclear test-site evaluation, Chariot, Alaska G. D. Eberlein (M) *Nuclear test-site evaluation, Katalla, Alaska G. D. Eberlein (M) Radioactive waste disposal investigations: Geochemical problems of radioactive waste disposal H. H. Waesche (W) 557328 0 - 60 - 8 A101 Radioactive waste disposal investigations—Continued Rock salt deposits of the United States W. G. Pierce (M) ‘ Geology of the Appalachian Basin with reference to dis- posal of high-level radioactive wastes G.W. C‘olton (W) Geology of the Michigan Basin with reference to disposal of high-level radioactive wastes W. deWitt (W) Geology of the San Juan and Central Valley Basins with reference to disposal of high—level radioactive wastes C. A. Repenning (M) Measurement of background radiation : Aerial radiological monitoring United States , P. Popenoe (W) Aerial radiological monitoring surveys, Belvoir area, Virginia and Maryland R. B. Guillou (W) Aerial radiological monitoring surveys, Georgia Nuclear Aircraft Laboratory J. A. MacKallor (W) Aerial radiological monitoring surveys, Savannah River Plant, Georgia and South Carolina R. G. Schmidt (W) Aerial radiological monitoring surveys, Oak Ridge Na- tional Laboratory, Tennessee R. G. Bates (W) Aerial radiological monitoring surveys, Chicago, Illinois R. B. Guillou (W) Aerial radiological monitoring surveys, Fort Worth, Texas J. A. Pitkin (W) Aerial radiological monitoring surveys, Killeen, Texas J. A. Pitkin (W) Aerial radiological monitoring surveys, Gnome site, New Mexico R. B. Guillou (W) Aerial radiological monitoring surveys, Nevada Test Site J. L. Meuschke (W) Aerial radiological monitoring surveys, National Reac- tor Testing Station, Idaho R. G. Bates (W) Aerial radiological monitoring surveys, Los Angeles, California R. B. Guillou (W) Aerial radiological monitoring surveys, San Francisco, California J. A. Pitkin (W) Aerial radiological monitoring surveys, Hanford, Wash- ington R. G. Schmidt (W) Aerial radiological monitoring surveys, Chariot site, Alaska R. G. Bates (W) Distribution of elements as related to health: Airborne radioactivity and environmental studies, Wash- ington County, Maryland R. M. Moxham (W) Magnetic susceptibility studies of cancerous tissues F. E. Senftle (W) Geochemistry of fluorine as related to its physiological efiects M. Fleischer (W) surveys, Northeastern A102 GEOLOGICAL SURVEY RESEARCH HMO—SYNOPSIS 0F GEOLOGIC RESULTS Paleontology : Systematic paleontology: Fossil wood and general paleobotany R. A. Scott (D) Paleozoic paleobotany S. H. Mamay (W) Coal lithology and paleobotany J. M. Schopf (Columbus, Ohio) Lower Pennsylvania floras of Illinois and adjacent States C. B. Read (Albuquerque, N. Mex.) Palynology G. 0. W. Kremp (D) Post-Paleozoic pollen and spores E. B. Leopold (D) Charophytes and nonmarine ostracodes R. E. Peck (W) Diatom studies K. E. Lohman (W) Recent Foraminifera, Central America P. J. Smith (M) Cenozoic Foraminifera, Colorado Desert P. J. Smith (M) Foraminiferal studies of the Pacific Northwest W. W. Rau (M) Foraminifera of the Lodo formation, central California M. C. Israelsky (M) Cretaceous Foraminifera of the Nelchina area, Alaska H. R. Bergquist (W) Cretaceous Foraminifera, New York N. F. Sohl (W) Upper Paleozoic fusulines L. G. Henbest (W) Post Paleozoic larger Foraminifera R. C. Douglass (W) Lower Paleozoic corals W. A. Oliver, Jr. (W) Upper Paleozoic corals W. J. Sando (W) Bryozoans and corals, Western United States and Alaska H. Duncan (\V) Cenozoic nonmarine mollusks D. W. Taylor (W) Cenozoic mollusks, Atlantic coast D. Wilson (W) Cenozoic mollusks, Atlantic and Gulf Coastal Plains D. Wilson (W) Cenozoic mollusks, Oregon, Miocene E. J. Trumbull (M) Cenozoic mollusks, Oregon, Oligocene E. J. Trumbull (M) Cenozoic mollusks, Alaska F. S. MacNeil (M) Cenozoic faunas, Caribbean area W. P. Woodring (W) Cenozoic invertebrates, Pacific Islands M. R. Todd (W) Cenozoic mollusks, Pacific Islands H. S. Ladd (W) Oligocene gastropods and pelecypods, Mississippi F. S. MacNeil (M) Oligocene gastropods and pelecypods, Pacific Islands F. S. MacNeil (M) Paleontology—Continued Systematic paleontology—Continued Upper Paleozoic gastropods E. L. Yochelson (W) Ostracodes, Upper Paleozoic and younger I. G. Sohn (W) Lower Paleozoic ostracodes J. M. Berdan (W) Vertebrate paleontologic studies G. E. Lewis (D) Vertebrate faunas, Martha’s Vineyard, Massachusetts F. C. Whitmore, Jr. (W) Vertebrate paleontology, Big Bone Lick, Kentucky F. C. Whitmore, Jr. (W) Vertebrate faunas, lshigaki, Ryukyu Islands F. C. Whitmore, Jr. (W) Stratigraphic paleontology: Lower Paleozoic stratigraphic paleontology, Eastern United States R. B. Neuman (W) Cambrian faunas and stratigraphy A. R. Palmer (W) Ordovician stratigraphic paleontology of the Great Basin and Rocky Mountains R. J. Ross, Jr. (D) Silurian and Devonian stratigraphic paleontology of the Great Basin and Pacific Coast 0. W. Merriam (W) Upper Paleozoic stratigraphic paleontology, Western United States and Alaska J. T. Dutro, Jr. (W) Permian stratigraphy, northeastern Arizona C. B. Read (Albuquerque, N. Mex.) Mesozoic stratigraphic paleontology, Atlantic and Gulf Coasts N. F. Sohl (W) Mesozoic stratigraphic paleontology northwestern Mon- tana W. A. Cobban (D) Mesozoic stratigraphic paleontology, Pacific Coast D. L. Jones (M) Cordilleran Triassic stratigraphy N. J. Silberling (M) Jurassic stratigraphic paleontology of North America R. W. Imlay (W) Cretaceous stratigraphy and paleontology, western inte- rior United States W. A. Cobban (D) Stratigraphic significance of the genus Tempskya in southwestern New Mexico C. B. Read (Albuquerque, N. Mex.) Paleontology and stratigraphy of the Pierre shale, Front Range, Colorado W. A. Cobban (D) Geology and paleontology of the Cuyama Valley area, California J. G. Vedder (M) Cenozoic stratigraphic paleontology D. Wilson (W) Ecologic studies on Onotoa Atoll P. E. Cloud (W) Geomorphology and plant ecology: Sedimentation laboratory for flume experiments E. D. McKee (D) TOPICAL INVESTIGATIONS IN. PROGRESS Geomorphology and plant ecology—Continued Pacific Islands vegetation F. R. Fosberg (W) ‘Potomac Basin studies, Maryland, Virginia, and West Virginia J. T. Hack (W) Physical properties of rocks : Investigations of thermodynamic properties of ore and rock minerals R. A. Robie (W) Investigation of deformation, elasticity, equilibria of rocks E. C. Robertson (W) Investigation of elastic and anelastic properties of earth materials L. Peselnick (W) Investigations of electrical and thermal properties of rocks . G. V. Keller (D) Measurement of magnetic properties of rocks W. E. Huff (W) Magnetic susceptibility of minerals F. E. Senftle (W) Infrared and ultraviolet radiation studies R. M. Moxham (W) Permafrost studies: Arctic ice and permafrost studies, Alaska A. H. Lachenbruch (M) Thermistor studies C. H. Sandberg (M) Ground ice and permafrost, Point Barrow, Alaska R. F. Black (Madison, Wis.) *Surficial geology and permafrost of Johnson River dis‘ trict, Alaska G. W. Holmes (W) Origin and stratigraphy of ground ice in central Alaska T. L. Péwé (College, Alaska) Rock deformation: Analysis of fault patterns D. J. Varnes (D) Diatremes, Navajo and Hopi Indian Reservations E. M. Shoemaker (M) ’ Paleomagnetism : Investigation of remanent magnetization of rocks R. R. Doell (M) Crustal studies: Thermal studies (earth temperatures) H. C. Spicer (W) Volcanism and crustal deformation L. C. Pakiser (D) Gravity map of the United States H. R. Joesting (W) Cross-country aeromagnetic profiles E. R. King (W) Maine aeromagnetic surveys J. W. Allingham (W) Maine gravity studies M. F. Kane (W) Geophysical studies of Appalachian structure E. R. King (W) Central and Western North Carolina regional aeromag- netic survey R. W. Johnson, Jr. (Knoxville, Tenn.) and mineral A103 Crustal studies—Continued Aeromagnetic studies, Middlesboro—Morristown area, Tennessee-Kentucky-Virginia R. W. Johnson, Jr. (Knoxville, Tenn.) Aeromagnetic profiles over the Atlantic Continental Shelf and Slope E. R. King (W) Geophysical studies in the Rowe-Mora area, New Mexico G. E. Andreasen (W) Colorado Plateau regional geophysical studies H. R. Joesting (W) Great Basin geophysical studies D. R. Mabey (M) Pacific Northwest geophysical studies D. J. Stuart (M) Cook Inlet aeromagnetic survey, Alaska G. E. Andreasen (W) Geophysical studies, airborne surveys, Alaska G. E. Andreasen (W) Geophysical studies on Ice Island T—3 G. V. Keller (D) Mineralogy and crystal chemistry : Rock-forming silicate minerals H. T. Evans (W) Serpentine and related silicate minerals H. T. Evans (W) Rock-forming phosphate minerals H. T. Evans (W) Uranium and vanadium minerals H. T. Evans (W) Mineralogy and geochemistry of the Green River forma- tion, )Vyoming C. Milton (W) Mineralogic services and research, Denver T. Botinelly (D) Mineralogic services and research, Menlo Park R. G. Coleman (M) Mineralogic services and research, Washington, DC. A. D. Weeks (W) Thin and polished sections F. Reed (W) Thin and polished sections M. C. Cochran (D) Thin and polished sections R. G. Coleman (M) Experimental geochemistry: Solution chemistry of ore-fluids transport E. W. Roedder (W) Fluid inclusions in minerals E. W. Roedder (W) Application of phase equilibria to geologic thermometry B. J. Skinner (W) Experimental studies on rock alteration J. Heinley (D) Hydrothermal solubility G. \V. Morey (W) Thermophysical properties of sulfides and silicates B. J. Skinner (W) Thermodynamic properties of sulfides and sulfosalts E. IV. Roedder (\V) Hydrothermal silicate and carbonate systems B. J. Skinner (W) Metallic sulfide and arsenide systems B. J. Skinner (W) A104 Experimental geochemistry—Continued Sulfide and sulfosalt systems E. W. Roedder (W) The system NaCl—K:SO.—MgS04—CaSO‘ G. W. Morey (W) The system UOx—HzO G. W. Morey (\V) Mineral equilibria of rocks: system MgO—Alea—Si02 F. Barker (W) Evaporite mineral equilibria: liquidus relations in the system NaCl—CaSOi—Hao at ‘low temperature E-an Zen (W) Geochemistry of borate minerals H. T. Evans (W) Geochemical distribution of the elements: Geochemical distribution of elements M. Fleischer (W) Geochemical compilation of rock analysis M. Hooker (W) Chemical analyses of sedimentary rocks T. P. Hill (W) Trace element distribution among coexisting minerals E. W. Roedder (W) Geochemistry of minor elements E. S. Larsen, 3d (W) Uranium and thorium in magmatic difierentiation E. S. Larsen, 3d (W) Organic geochemistry: Geochemistry of naturally substances F. S. Grimaldi (W) Special studies of organisms F. D. Sisler (W) Petrology: Origin and characteristics of thermal and mineral waters D. E. White (W) Sedimentary petrology and clay mineral studies J. C. Hathaway (D) Studies of welded tuff R. L. Smith (W) Metamorphism and origin of mineral deposits, Gouver- neur area, New York A. E. J. Engel (Pasadena, Calif.) Igneous rocks of southeastern United States C. Milton (W) *Petrology of the Manassas quadrangle, Virginia C. Milton (W) *Petrology of the Valles Mountains, New Mexico R. L. Smith (W) Chemical and physical properties of the Pierre shale, Montana, North Dakota, South Dakota, Wyoming and Nebraska H. A. Tourtelot (1)) Geology and paleolimnology of the Green River forma- tion, Wyoming W. H. Bradley (W) *Petrology of the Bearpaw Mountains, Montana W. T. Pecora (W) Carbonatite deposits, Montana W. T. Pecora (W) ‘Petrology of the Wolf Creek area, Montana R. G. Schmidt ()V) occurring carbonaceous isotope fractionation in living GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS Petrology—Continued Chromite resources and petrology of the Stillwater ultra- maflc complex, Montana E. D. Jackson (M) *Sedimentary petrology and geochemistry of the Belt series; Elmira, Mt. Pend Oreille, Packsaddle Mountains, and Clark Fork quadrangles, Idaho- Montana J. E. Harrison (D) ’Metamorphism of the Orofino area, Idaho A. Hietanen-Makela (W) Petrology and geochemistry of the Boulder Creek bath- olith, Colorado Front Range E. S. Larsen, 3d (W) Petrology and geochemistry of the Laramide intrusives in the Colorado Front Range _ E. S. Larsen, 3d (\V) Petrology of volcanic rocks, Snake River Valley, Idaho H. A. Powers (D) Glaucophane schist terranes within the Franciscan for- mation, California R. G. Coleman (M) *Petrology and volcanism, Katmai National Monument, Alaska G. H. Curtis (M) Geological, geochemical, and geophysical studies of Ha- waiian volcanology K. J. Murata (Hawaii) Petrological services and research 0. Milton (W) Isotope and nuclear studies: Isotope ratios in rocks and minerals I. Friedman (W) Investigation of sea-level changes in New England M. Rubin (W) Geochronology: carbon-14 method M. Rubin (W) Geochronology: lead-uranium ages of mineral deposits L. R. Stieff (W) Geochronology: lead-alpha ages of rocks T. W. Stern (W) Significance of lead-alpha age variation in batholiths of the Colorado Front Range E. S. Larsen, 3d (W) Geochronology: potassium-argon method H. Faul (W) Age determinations: rocks in Colorado H. Faul (W) Age determinations: granites of Maine H. Faul (W) Nuclear irradiation C. M. Bunker (D) Radioactive nuclides in minerals F. E. Senftle (W) Analytical chemistry: Rock and mineral chemical analysis J. J. Fahey (W) General rock chemical analysis L. C. Peck (D) Research on trace analysis methods F. N. Ward (D) Trace analysis and research J. H. McCarthy, Jr. (D) TOPICAL INVESTIGATIONS IN PROGRESS A105 Analytical chemistry—Continued Analytical services and research, Washington, DC. F. S. Grimaldi (\V) Analytical services and research, Denver L. F. Rader, Jr. (D) Analytical services and research, Menlo Park R. E. Stevens (M) Rapid rock chemical analysis W. W. Brannock (W) Petroleum geology laboratory H. A. Tourtelot (D) Spectroscopy : X~ray spectroscopy of ore minerals I. Adler (W) Spectroscopy—Continued Spectrographic services and research, Washington, DC. A. W. Helz (W) Spectrographic services and research, Denver A. T. Myers (D) General bibliographies and handbooks: Bibliography of North American geology M. Cooper (W) Geophysical abstracts J. W. Clarke (W) Geochemical exploration abstracts and information H. W. Lakin (D) Statistics handbook T. G. Lovering (D) GEOLOGIC DIVISION PUBLICATIONS IN FISCAL YEAR 1960 Listed below are the citations of the Geologic Divi- sion’s technical reports published or otherwise released to the public during fiscal year 1960. The list does not include all publications that bear dates between July 1959 and June 1960 because publication of periodicals is sometimes delayed for several months. Neither does the list include a full year’s publications for journal articles bearing dates prior to July 1959 have not been included, even though they may have been actually released during the fiscal year. The reports are listed alphabetically by author in the bibliography. In addition, a subject classification of the reports is given on pages A127—A136. The topics listed there are those discussed in the main sec- tion of the previous part of this report, and they are arranged in the same way. LIST 0]? PUBLICATIONS Adkison, W. L., 1960, Subsurface cross section of Paleozoic rocks from Barber County, Kansas, to Caddo County, Okla- homa: U.S. Geol. Survey Oil and Gas Inv. Map 00-61. Adler, Isidore, 1959, Application of X-ray and electron probes in mineralogical investigations [abs]: Jour. Geophys. Re- search, v. 64, no. 8, p. 1093. Amos, D. H. 1959, DMEA project blossoms into best U.'S. mica mine: Mining World, v. 21, no. 11, p. 30—34, Oct. 1959. Anderson, C. A., 1959, Preliminary geologic map of the NW1/4 Mayer quadrangle, Yavapai Count’y, Arizona: US. Geol. Survey Mineral Inv. Field Studies Map MF—228. 1960, Mining geology: Mining Cong. Jour., v. 46, no. 2, p. 38—41. Anderson, D. G., 1959, Ellesmere Ice Shelf investigations in Bushnell, V. 0. (ed), Proc. 2d Ann. Arctic Planning Conf., Oct. 1959, Air Force Cambridge Research Center, Geophys. Research Directorate, Research Notes, no. 29, AFCRC—TN— 59—661, p. 78—86. Archbold, N. L., 1959, Relationship of carbonate cement to lith- ology and vanadium-uranium deposits in the Morrison formation in southwestern Colorado: Econ. Geology, v. 54, no. 4, p. 666—682. Arndt, H. H., Conlin, R. R., Kehn, ’1‘. M., Miller, J. T., and Wood, G. H., J r., 1959, Structure and stratigraphy in cen- tral Pennsylvania and the anthracite region: Geol. Soc. America Guidebook series. Guidebook for field trips, Pitts- burgh meeting, p. 1—60. Arnold, R. G., Coleman, R. G., and Fryklund, V. C., 1959, Temperatures of formation of coexisting pyrrhotite-sphale- rite, and pyrite from Highland Surprise Mine, Idaho: Car- negie Inst. Washington Year Book, no. 58, p. 156—157. Bachman, G. 0., Vine, J. B., Read, C. B., and Moore, G. W., 1959, Uranium-bearing coal and carbonaceous shale in the La Ventana Mesa area, Sandoval County, New Mexico chap. J in Uranium in coal in the western United States: U.S. Geol. Survey Bull. 1055, p. 295—307, pls. 53—59, fig. 44. Bailey, E. H., 1959, Resources, in Mercury materials survey: US. Bureau of Mines Inf. Circ. 7941. of eugeosynclinal deposition [abs]: Geol. Soc. America, Cordilleran Sec. mtg, May 5—9, 1960, Vancouver, B. C., program, p. 12. 1960, Franciscan formation of California as an example ' Bailey, E. H., Christ, C. L., Fahey, J. J., and Hildebrand, F. A., 1959, Schuetteite, a new supergene mercury mineral: Am. Mineralogist, v. 44, nos. 8—9, p. 1026—1038. Bailey, E. H., and Irwin, W. P., 1959, K—feldspar content of Jurassic and Cretaceous graywackes of the northern Coast Ranges and Sacramento Valley, California : Am. Assoc. Pet- roleum Geologists Bull., v. 43, no. 12, p. 2797—2809. Bailey, E. H., and Stevens, R. E., 1960, Selective staining of plagioclase and K Feldspar on rock slabs and thin sections [abs] : Geol. Soc. America, Cordilleran Sec. mtg, May 5-9, 1960, Vancouver, B. C., program, p. 12. Bailey, R. A., 1959, Contact fusion of argillaceous and arkosic sediments by an andesite intrusion, Valles Mountains, New Mexico [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1565. Baker, A. A., 1959, Faults in the Wasatch Range near Provo, Utah: Intermountain Assoc. Petroleum Geologists, Guide- book 10th Ann. Field Conf., p. 153-158. Baldwin, H. L., J r., and Hill, D. P., 1960, Gravity survey in part of the Snake River Plain, Idaho—.a preliminary report: U.S. Geol. Survey open-file report, 21 p., 3 figs. Balsley, J. R., Bromery, R. W., Remington, E. W., and others, 1960, Aeromagnetic map of the Kerby and part of the Grants Pass quadrangles, Josephine and Curry Counties, Oregon: US. Geol. Survey Geophys. Inv. Map GP—197. Balsley, J. R., and Buddington, A. F., 1960, Magnetic suscepti- bility, anisotropy, and fabric of some Adirondack granites and orthogneisses: Am. Jour. Sci., v. 258—A, p. 6—20. Balsley, J. R., Buddington, A. F., and others, 1959a, Aeromag- netic and geologic map of the Santa Clara quadrangle and part of the St. Regis quadrangle, Franklin County, New York: US. Geol. Survey Geophys. Inv. Map GP—190. 1959b, Aeromagnetic and geologic map of the Oswegat- chie quadrangle, St. Lawrence, Herkimer, and Lewis Coun- ties, New York: U.S. Geol. Survey Geophys. Inv. Map GP—192. 1959c, Aeromagnetic and geologic map of the Tupper Lake quadrangle, St. Lawrence, Hamilton, and Franklin Counties, New York: US. Geol. Survey Geophys. Inv. Map GP-193. A107 A108 Balsley. J. R., Postel, A. W., and others, 1959, Aeromagnetic and geologic map of the Loon Lake quadrangle and part of the Chateaugay quadrangle, Franklin County, New York : U.S. Geol. Survey Geophys. Inv. Map GP—191. Baltz, E. H., 1960, Diagram showing relations of Permian rocks in part of Eddy County, New Mexico: U.S. Geol. Survey TEM—1035, open-file report, 1 chart. Barnes, D. F, 1959, Preliminary report on Lake Peters, Alaska, ice studies, in Bushnell, V. (J., (ed), Free. 2d Ann. Arctic Planning Conf., Oct. 1959, Air Force Cambridge Research Center, Geophys. Research Directorate, Research Notes, no. 29, AFCRC—TN—59—661, p. 102—110. Barnes, F. F., 1960, Coal fields of Alaska: US. Geol. Survey open-file report, 4 p., 1 pl. Barnes, F. F., and Cobb, E. H., 1959, Geology and coal resources of the Homer district, Kenai coal field, Alaska: US. Geol. Survey Bull. 1058—F, p. 217—260, pls. 17—28, fig. 43. Barton, P. B., Jr., and Bethke, P. M., 1960, Thermodynamic properties of some synthetic zinc and copper minerals: , ‘Am. Jour. Sci., v. 258—A, 1121—34. Barton, P. B., Jr., and Toulmin, Priestley III, 1959, Electrum- tarnish method for determining the chemical potential of sulfur in laboratory sulfide systems [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1567. Bayley, R. W., 1959a, Geology of the Lake Mary quadrangle, Iron County, Michigan: US. Geol. Survey Bull. 1077, 112 p., 7 pls., 33 figs. 1959b, Iron-bearing rocks of the Atlantic mining dis- trict, Wyoming—a progress report [abs] : Geol. Soc. Amer- ica Bull., v. 70, no. 12, pt. 2, p. 1774. 1959c, A metamorphosed differentiated sill in northern Michigan: Am. Jour. Sci., v. 257, no. 6, p. 408—430. Begemann, Frederick, and Friedman, Irving, 1959, Tritium and deuterium content of atmospheric hydrogen: Zeitschr. Natiirforschuxng, v. 14A, no. 12, p. 1024—1031. Behre, C. H., Jr., and Heyl, A. V., Jr., 1959, Ervorkommen vom Typus “Mississippi-Tal” in der Vereinigten Staaten: Deutche geol. Gessell. Zeitschr., v. 110, pt. 3, p. 514—558. Beikman, H. M., and Gower, H. D., 1959, Coal resources of southwestern Washington: US. Geol. Survey open-file re- port, 54 p. Bell, Henry, 1959, Relations among some dikes in Cabarrus County, North Carolina: South Carolina Division of Geol- ogy, Geologic Notes, v. 3, no. 2, p. 1—5. Benninghofl, W. S., and Holmes, G. W., 1900, Preliminary report on Upper Cenozoic carbonaceous deposits in the Johnson River area, Alaska Range [abs]: Internat. Symposium on Arctic Geology, 1st, Calgary, Jan. 11—13, 1960, Abstracts of Papers [unnumbered]. Berdan, Jean M., 1960, Revision of the Ostracode family Beecherellidae and redes-cription of Ulrich’s types of Beecherella: Jour. Paleontology, v. 34, no. 3, p. 467—478, pl. 66. . Berg, H. C., and MacKevett, E. M., Jr., 1959, Structural con- trol of quicksilver ore at the Red Devil mine, Alaska [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1708, and 1793. Berryhill, H. L., Jr., 1959, Pattern of regional transcurrent faulting in Puerto Rico [abs]: Geol. Soc; America Bull., v. 70, no. 12, pt. 2, p. 1569. Berryhill, H. L., Jr., Briggs, R. P., and Glover, Lynn III, 1960, Stratigraphy, sedimentation, and structure of Late Creta- ceous rocks in eastern Puerto Rico—Preliminary report: Am. Assoc. Petroleum Geologists Bull., v. 44, p. 137—155. GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Bergquist, H. R., 1960, Occurrence of Foraminifera and cone- donts in upper Paleozoic and Triassic rocks, northern Alaska : J our. Paleontology, v. 34, no. 3, p. 596—601, 1 text fig. Bethke, P. M., and Barton, P. B., Jr., 1959, Trace-element dis- tribution as an indicator of pressure and temperature of ore deposition [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p‘. 1569. Birks, L. 8., Brooks, E. J., Adler, Isidore, and Milton, Charles, 1959, Electron probe analysis of minute inclusions of a copper-iron mineral: Am. Mineralogist, v. 44, nos. 9—10, p. 974—978. Bonilla, M. G., 1959, Geologic observations in the epicentral area of the San Francisco earthquake of March 22, 1957: Calif. Div. Mines Spec. Rept. 57, p. 25—37. 1960, Landslides in the San Francisco South quadran- gle: U.S. Geol. Survey open-file report, 44 p., 10 figs., 1 table. Botjnelly, Theodore, and Fischer, R. P., 1959, Mineralogy and geology of the Rifle and Garfield mines, Garfield County, Colorado, in Garrels, R. M., and Larsen, E. S. 3d, Geo- chemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 213—218 Boucot, A. J. and Arndt, Robert, 1960, Fossils of the Littleton formation (Lower Devonian) of New Hampshire: US. Geol. Survey Prof. Paper 334—B, p. 41—51, pls. 1—3, figs. 3—4. Boucot, A. J ., Griscom, Andrew, Allingham, J. W., and Dempsey, W. J., 1960, Geologic and aeromagnetic map of northern Maine: U.S. Geol. Survey open-file report. Bowles, C. G., and Braddock, W. A., 1960, Solution breccias in the upper part of the Minnelusa sandstone, South Dakota and Wyoming: Geol. Soc. American, Rocky Mtn. Sec., 13th mtg, Rapid City, South Dakota, Apr. 28—30, 1960, program, 1). 6. Bramkamp, R. A., and Ramirez, L. F., 1959a, Geographic map of the Wadi a1 Batin quadrangle, Kingdom of Saudi Arabia : U.S. Geol. Survey Misc. Geol. Inv. Map I—203 B. 1959b, Geographic map of the central Persian Gulf quad- rangle, Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol. Inv. Map I—209 B. 19590, Geographic map of the northeastern Rubi a1 Khali quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol. Inv. Map I—214 B. 1960, Geologic map of the Wadi a1 Batin quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol. Inv. Map I—203 A. Breger, I. A., and Chandler, J. C., 1959, Extractability of humic substances from coalified logs as a guide to temperatures in Colorado Plateau sediments [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1574. Breger, I. A., and Ben], Maurice, 1959, Association of uranium with carbonaceous materials, with special reference to the Temple Mountain region, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 139—149. Brobst, D. A., 1960, Barium minerals, in Gillson, J. L., Indus- trial minerals and rocks, 3d ed.: New York, Am. Inst. Mining Metall. Petroleum Engineers, p. 55—64. Bromery, R. W., 1959, Interpretation of aeromagnetic data across the Reading prong, Pennsylvania [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1574. LIST OF PUBLICATIONS Bromery, R. W., Bennett, B. L., and others, 1959a, Aeromag- netic map of the Malvern quadrangle, Chester County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP— 202. 1959b, Aeromagnetic map of the Phoenixville quadran- gle, Chester and Montgomery Counties, Pennsylvania»: US. Geol. Survey Geophys. Inv. Map GP—209. 1959c, Aeromagnetc map of the Allentown quadrangle, Northampton, Lehigh, and Bucks Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—213. Bromery, R. W., Emery, R. 0., and Balsley, J. R., Jr., 1960, Reconnaissance airborne magnetometer survey off south- ern California: US. G‘eol. Survey Geophys. Inv. Map GP—211. Bromery, R. “7., Henderson, J. R., Jr., Bennett, B. L., and others, 1959, Aeromagnetic map of parts of the Lambert- ville and Stockton quadrangles, Bucks County, Pennsyl— vania, and Hunterdon and Mercer Counties, New Jersey: US. Geol. Survey Geophys. Inv. Map GP—216. Bromery, R. W., Henderson, J. R., Jr., Zandle, G. L., and others, 1959a, Aeromagnetic map of the Buckingham quad- rangle, Bucks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—215. 1959b, Aeromagnetic map of the Elverson quadrangle, Berks and Chester Counties, Pennsylvania: US. Geol. Sur- vey Geophys. Inv. Map GP—221. 1960a, Aeromagnetic map of the Wagontown quadrangle, Chester County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—223. 1960b, Aeromagnetic map of part of the Coatesville quadrangle, Chester County, Pennsylvania: US. Geol. Sur- vey Geophys. Inv. Map GP—225. 1960c, Aeromagnetic map of the Temple quadrangle, Berks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—227. 1960a, Aeromagnetic map of the Fleetwood quadrangle, Berks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—228. 1960e, Aeromagnetic map of the Reading quadrangle, Berks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—230. 1960f, Aeromagnetic map of the Birdsboro quadrangle, Berks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—231. 1960g, Aeromagnetic map of the Honey Brook quad- rangle, Chester and Lancaster Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—233. 1960b, Aeromagnetic map of the Parkesburg quadrangle, Chester and Lancaster Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—234. 1960i, Aeromagnetic map of part of the Easton quad- rangle, Northampton County, Pennsylvania, and Warren County, New Jersey: US. Geol. Survey Geophys. Inv. Map GP—235. 1960j, Aeromagnetic map of part of the Riegelsville quadrangle, Bucks and Northampton Counties, Pennsyl— vania, and Hunterdon and Warren Counties, New Jersey: US. Geol. Survey Geophys. Inv. Map GP—236. 1960k, Aeromagnetic map of part of the Hatboro quad- rangle, Bucks, Montgomery, and Philadelphia Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP— 237. A109 Bromery, R. W., Henderson, J. R., Jr., Zandle, G. L., and others, 19601, Aeromagnetic map of the Langhorne quad- rangle, Bucks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP-238. Bromery, R. W., Zandle, G. L., and others, 1959a, Aeromagnetic map of the Valley Forge quadrangle, Chester, Montgomery, and Delaware Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—200. 1959b, Aeromagnetic map of part of the Norristown quadrangle, Philadelphia, Chester, Delaware, and Mont- gomery Counties, Pennsylvania : U.S. Geol. Survey Geophys. Inv. Map GP—201. 1959c, Aeromagnetic map of part of the West Chester quadrangle, Chester and Delaware Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—203. 1959d, Aeromagnetic map of part of the Media quad- rangle, Chester and Delaware Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—204. 1959e, Aeromagnetic map of East Greenville quadrangle, Berks, Lehigh, and Montgomery Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—205. 1959f, Aeromagnetic map of the Milford Square quad- rangle, Bucks, Lehigh, and Montgomery Counties, Pennsyl- vania: U.S. Geol. Survey Geophys. Inv. Map GP—206. 1959g, Aeromagnetic map of the Sassamansville quad- rangle, Montgomery and Berks Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—207. 1959b, Aeromagnetic map of the Perkiomenville quad- rangle, Montgomery and Bucks Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—208. 1959i, Aeromagnetic map of the Quakertown quadrangle, Bucks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—214. —— 1959j, Aeromagnetic map of the Safe Harbor quadrangle, Lancaster and York Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—217. 1959k, Aeromagnetic map of the Conestoga quadrangle, Lancaster County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—218. 19591, Aeromagnetic map of the Quarryville quadrangle, Lancaster County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—219. 1959m, Aeromagnetic map of the Morgantown quadrangle, Berks, Lancaster, and Chester Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—220. 1960a, Aeromagnetic map of the Pottstown quadrangle, Berks, Chester, and Montgomery Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—222. 1960b, Aeromagnetic map of the Dowington quadrangle, Chester County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—224. 19600, Aeromagnetic map of part of the Unionville quad- rangle, Chester County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—226. 1960a, Aeromagnetic map of the Manatawny quadrangle, Berks County, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP-229. 1960e, Aeromagnetic map of the Boyertown quadrangle, Berks and Montgomery Counties, Pennsylvania: US. Geol. Survey Geophys. Inv. Map GP—232. Brown, R. D., Gower, H. D., and Snavely, P. D., Jr., 1960, Geol- ogy of the Port Angeles-Lake Crescent area, Washington: US. Geol. Survey Oil and Gas Inv. Map 0M--203. A110 Brown, R. W., 1959, Age of wood from excavations in the District of Columbia: Columbia Hist. Soc. Rec., v. 53—56, p. 353—355. Bryant, Bruce, and Reed, J. 0., Jr., 1959, Structural features of the Grandfather Mountain area, northwestern North Carolina [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1757. Bunker, C. M., and Ohm, J. M., 1959, Fishing tools for retrieving gamma-ray logging components: Mining Eng, v. 214, p. 1045—1046. Burnside, R. J ., 1959, Geology of part of the Horseshoe atoll in Borden and Howard Counties, Texas: U.S. Geol. Survey Prof. Paper 315—B, p. 21—35, pls. 10—14, figs. 6—8. Bush, A. L., Marsh, 0. T., and Taylor, R. B., 1959, Preliminary geologic map of the Little Cone quadrangle, San Miguel County, Colorado: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—223. . Byerly, P. E., and Joesting, H. R., 1959, Regional geophysical investigations of the Lisbon Valley area, Utah and Colo- rado: U.S. Geol. Survey Prof. Paper 316—0, p. 39—50, pls. 6—9, figs. 17-21. Byerly, P. E., Stewart, S. W., and Roller, J. C., 1960, Seis- mic measurements by the U.S. Geological Survey during the pre-Gnome high-explosive tests near Carlsbad, New Mexico—Final report: U.S. Geol.-Survey TEI—761, open-file report, 40 p., 9 figs. Byers, F. M., 1960, Geology of Umnak and Bogoslof Islands, Aleutian Islands, Alaska: U.S. Geol. Survey Bull. 1028—L, p. 267—369, pls. 39—51, figs. 49—54. Cadigan, R. A., 1959a, Characteristics of the host rock in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 13—24. 1959b, Stratigraphy of Triassic and associated forma- tions in part of the Colorado Plateau region: U.S. Geol. Survey Bull. 1046—Q. Cady, W. M., 1959, Geotectonic relations in northern Vermont and southern Quebec [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1577. 1960, Stratigraphic and geotectonic relationships in northern Vermont and southern Quebec: Geol. Soc. Amer- ica Bull., v. 71, no. 5, p. 531—576. Calkins, J. A., Parker, R. L., and Disbrow, A. E., 1959, Geo- logic map of the Curlew quadrangle, Washington: U.S. Geol. Survey open-file report. Campbell, A. B., 1959, Precambrian—Cambrian unconformity in northwestern Montana and northern Idaho [abs]: Geol. Soc. America Bull., v.70, no. 12, pt. 2, p. 1776. Cannon, H. L., 1959, Biogeochemical relations in the Thompson district, Grand County, Utah [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1578. Cannon, R. S., Jr., Pierce, A. P., and Antweiler, J. C., 1959, Significance of lead isotopes to problems of ore genesis [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1578. Carr, M. S., and Dutton, C. E., 1959, Iron-ore resources of the United States including Alaska and Puerto Rico, 1955: US. Geol. Survey Bull. 1082—0, p. 61—134, pl. 2, fig. 7. Carr, W. J., and Alverson, D. C., 1959, Stratigraphy of middle Tertiary rocks in part of west-central Florida: U.S. Geol. Survey Bull. 1092, 111 p., 3 pls., 16 figs. Carroll, Dorothy, 1959a, Mineral indicators of environment in sediments of part of the Maryland coastal plain [abs]: Virginia Acad. Sci. Proc., v. 10, no. 4, p. 293—294. GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS Carroll, Dorothy, 1959b, Petrography of Paleozoic sandstones and shales from borings in Florida [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1759. 1960, Ilmenite alteration under reducing conditions in unconsolidated sediments: Econ. Geology, v. 55, no. 3, p. 618—619. Carroll, Dorothy, and Pommer, A. M., 1960, Acidic properties of some clay minerals [abs]: Am. Ceramic Soc. Bull., v. 39, p. 239. Carroll, Dorothy, and Starkey, H. C., 1960, The effect of sea water on clay minerals, in Natl. Conf. on Clays and Clay Minerals Proc., 7th, Washington, D.C., 1958: Pergamon Press, New York, N.Y., p. 80—101. Cashion, W. B., Jr., 1959, Geology and oil-shale resources of Naval Oil Shale Reserve No. 2, Uintah and Carbon Coun- ties, Utah: U.S. Geol. Survey Bull. 1072—0, p. 753—793, pls. 54—57, figs. 34—42. Cass, J. T., 1959a, Reconnaissance geologic map of the Norton Bay quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map I—286. 1959b, Reconnaissance geologic map of the Candle quad- rangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map I—287. 1959c, Reconnaissance geologic map of the Unalakleet quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1—288. 1959d, Reconnaissance geologic map of the Ruby quad- rangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map I—289. 1959c, Reconnaissance geologic map of the Melozitna quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map I—290. 1959f, Reconnaissance geologic map of the Nulato quad- rangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map I—291. Castle, R. 0., 1959, 'Surficial geology of the Wilmington quad- rangle, Massachusetts: U.S. Geol. Survey Geol. Quad. Map GQ—122. Cathcart, J. B., and McGreevy, L. J., 1959, Results of geologic exploration by core drilling, 1953, land-pebble phosphate district, Florida: U.S. Geol. Survey Bull. 1046—K, p. 221— 298, pls. 16—34, fig. 26. Cattermole, J. M., 1960, Geology of the Bearden quadrangle, Tennessee: U.S. Geol. Survey Geol. Quad. Map GQ—126. Chao, E.C.T., and Fleischer, Michael, 1959, Abundance of zir- conium in igneous rocks [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1579. Cheney, T. M., and Sheldon, R. P., 1959, Permian stratigraphy and oil potential, Wyoming and Utah: Intermountain As- soc. Petroleum Geologists, Guidebook 10th Ann. Field Cont, p. 90-100. Chisholm, W. A., 1959, Described sections of rocks of Chester and Morrow age in Newton and Searcy Counties, Arkan- sas: U.S. Geol. Survey open—file report, 67 p. Christ, C. L., 1960, Crystal chemistry and systematic classifica- tion of hydrated borate minerals: Am. Mineralogist, v. 45, nos. 3—4, p. 334—340. Christ, C. L., and Clark, J. R., 1960, X-ray crystallography and crystal chemistry of gowerite, Ca0-3B203'5H20: Am. Min- eralogist, v. 45, nos. 1—2, p. 230—234. Christ, C. L., and Garrels, R. M., 1959, Relations among sodium borate hydrates at the Kramer deposit, Boron, California: Am. Jour. Sci., v. 257 no. 7, p. 516—528. LIST OF PUBLICATIONS Christman, R. A., Brock, M. R., Pearson, R. C., and Singewald, Q. D., 1960, Geology and thorium deposits of the Wet Mountains, Colorado; a progress report: U.S. Geol. Sur- vey Bull. 1072—H, p. 491—535, pls. 15—16, figs. 18—20. Clark, J. R., 1960, X-ray study of alteration in the uranium mineral wyartite: Am. Mineralogist, v. 45, nos. 1-2, p. 200—208. Clark, J. R., and Christ, C. L., 1959a, Studies of borate min- erals (5) ; Reinvestigation of the X-ray crystallography of ulexite and probertite: Am. Mineralogist, v. 44, nos. 7—8, p. 712—719. 1959b, Studies of borate minerals (7) ; X-ray studies of ammoniohorite, larderellite, and the potassium and am- monium pentaborate tetrahydrates: Am. Mineralogist, v. 44, nos. 11—12, p. 1150—1158. 1959c, Studies of borate minerals (8) : The crystal struc- ture of CaBaOs(OH)5'2HaO: Zeitschr. Kristallographie, v. 112, p. 213—233. Clark, J. R., Mrose, M. E., Perloff, Alvin, and Burley, Gordon, 1959, Studies of borate minerals (6); Investigation of veatchite: Am. Mineralogist, v. 44, no. 11—12, p. 1141—1149. Clark, L. D., 1960, Foothills fault system, western Sierra Ne- vada, California: Geol. Soc. America Bull., v. 71, p. 483—496. Clebsch, Alfred, J r., and others, 1959, Ground water in the Oak Spring formation and hydrologic effects of underground nuclear explosions at the Nevada Test Site [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1581. Cloud, P. E., Jr., 1959, Paleoecology—retrospect and prospect: Jour. Paleontology, v. 33, no. 5, p. 926—962, figs. 1—16. 1960, Gas as a sedimentary and diagenetic agent: Am. J our. Sci., v. 258—A, p. 35—45. Cloud, P. E., J r., and Palmer, A. R., 1959, Paleontologic data and age evaluation for individual wells, Pre—Simpson Paleozoic rocks, in Barnes, V. E., Stratigraphy of the Pre-Simpson Paleozoic subsurface rocks of Texas and southeast New Mexico: Texas Univ. Pub. no. 5924, v. 1, pt. 2, p. 73—85. Coats, R. R., 1959, Geologic reconnaissance of Semisopochnoi Island, western Aleutian Islands, Alaska: U.S. Geol. ‘Sur— vey Bull. 1028—0, p. 477—519, pls. 59—68, figs. 73—76. 1960, Stereoscopic-pair projection of aerial photographs in map compilation: Geol. Soc. America Bull., v. 71, no. 5, p. 629—630. Cobb, E. H., 1959a, Antimony, bismuth, and mercury occur- rences in Alaska: U.S. Geol. Survey Mineral Inv. Resource Map MR—ll. 1959b, Chromite, cobalt, nickel, and platinum occur- rences in Alaska: U.S. Geol. Survey Mineral Inv. Resource Map MR—8. 1959c, Copper, lead, and zinc occurrences in Alaska: U.S. Geol. Survey Mineral Inv. Resource Map MR—9. 1959d, Molybdenum, tin, and tungsten occurrences in Alaska: U.S. Geol. Survey Mineral Inv. Resource Map MR—10. Cobban, W. A., Erdmann, C. E., Lemke, R. W., and Maughan, E. K., 1959a, Colorado group on Sweetgrass Arch, Montana, in Billings Geol. Soc. Guidebook 10th Ann. Field Cont: p. 89—92. 1959b, Revision of Colorado group on Sweetgrass Arch, Montana: Am. Assoc. Petroleum Geologists Bull., v. 43, no. 12, p. 2786—2796. Cole, W. S., Todd, Ruth, and Johnson, C. G., 1960, Conflicting age determinations suggested by Foraminifera on Yap, Caroline Islands: Bull. Am. Paleontology, v. 41, no. 186, p. 73—112, pls. 11—13. A111 Coleman, R. G., 1959a, New occurrences of ferroselite (FeSez) : Geochim. et Cosmochim. Acta, v. 16, p. 296—301. 1959b, Genesis of jadeite from San Benito County, Cali- fornia [abs.] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1583. Colton, R. B., 1959, Additional evidence oflglacial Lake Mussel- shell, Montana [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1776. Colton, G. W., and de Witt, Wallace, Jr., 1959, Current-oriented structures in some Upper Devonian rocks in western New York [abs]: Geol. Soc. America Bull., v. 70. no. 12, pt. 2, p. 1759. Cooke, C. W., 1959, Cenozoic echinoids of eastern United States: U.S. Geol. Survey Prof. Paper 321, 106 p., 43 pls. Cooper, J. R., 1959a, Some geologic features of the Dragoon quadrangle: Arizona Geol. Soc., southern Arizona Guide- book II, p. 139—145. 1959b, Reconnaisance geologic map of southeastern Cochise County, Arizona: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—213. 1960, Some gedlogic features of the Pima mining district, Pima County, Arizona: U.S. Geol. Survey Bull. 1112—C, p. 63—103, pls. 1—5, figs. 15, 16. Cornwall, H. R., and Kleinhampl, F. J., 1959, Stratigraphy and structure of Bare Mountain, Nevada [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1714. Cox, Allan, 1960, Variations in the direction of the dipole component of the earth’s magnetic field [abs] : Am. Geophys. Union, 41st Ann. Mtg., Apr. 27—30, 1960, Program, p. 47. Cox, Allan, and Doell, R. R., 1960, Review of paleomagnetism: Geol. Soc. America Bull., v. 71, no. 6, p. 645—768. Craig, L. 0., and others, 1959, Measured sections of the Morrison and adjacent formations: U.S. Geol. Survey open-file re- port, 700 p. Crandell, D. R., and Gard, L. M., Jr., 1959, Geology of the Buckley quadrangle, Washington: U.S. Geol. Survey Geol. Quad. Map GQ—125. Crittenden, M. D., 1959, Mississippian stratigraphy of the central Wasatch and western Uinta Mountains, Utah, in Guidebook to the geology of the Wasatch and Uinta Moun- tains, transition area: Intermountain Assoc. Petroleum Geologists, 10th Ann. Field Conf. Guidebook, p. 63—74. C‘rowder, D. F., 1959, Granitization, migmatization, and fusion in the northern Entiat Mountains, Washington: Geol. Soc. America Bull., v. 70, no. 7, p. 827—878. Currier, L. W., 1960, Geologic appraisal of dimension-stone deposits: U.S. Geol. Survey Bull. 1109, 78 p., 7 pls., 2 figs. Cuttitta, Frank, and White, C. -E., 1959, Spectrophotometric study of the n1agnesium-bissalicylidene-ethylenediaxnine system: Anal. Chemistry, v. 31, no. 12, p. 2087—2090. Dane, C. H., 1959, Historical background of the type locality of the Tres Hermanos sandstone, in Guidebook, 10th Ann. Field Conf. : New Mexico Geol. Soc., p. 85-91. 1960, The boundary between rocks of Carlile and Niobrara age in San Juan Basin, New Mexico and Colorado: Am. Jour. Sci., v. 258—A, p. 46—56. Danilchik, Walter, and Tahirkheli, R. A. K., 1960, Contents of uranium and other elements in sand, Indus, Gilgit, and Hunza Rivers, Gilgit Agency, West Pakistan: Pakistan Geol. Survey Inf. Release No. 11, 7 p., 2 tables, 1 fig. Davidson, D. F., 1960, Selenium in some epithermal deposits of antimony, mercury, and silver and gold: U.S. Geol. Survey Bull. 1112—A, p. 1—15, figs. 1—2. A112 Davidson, D. F., and Powers, H. A., 1959, Selenium content of some volcanic rocks from western United States and Hawaiian Islands: US. Geol. Survey Bull. 1084—0, p. 69—81, figs. 9—11. Davies, W. E., 1959a, Origin of caves in folded limestone [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1802. 1959b, Geologic investigations, in Bushnell, V. 0. (ed.), Proc. 2d Ann. Arctic Planning Cont, Oct. 1959, Air Force Cambridge Research Center, Geophys. Research Directorate, Research Notes, no. 29, AFCR—TN—59—661, p. 51—54. 1960a, Surface features of permafrost in arid areas [abs] : Internat. Symposium on Arctic Geology, 1st, Calgary, Jan. 11—13, 1960, Abstracts of Papers [unnumbered]. 1960b, Origin of caves in folded limestone: Natl, Speleo- logical Soc. Bull., V. 22, pt. 1, p. 3—16. Dean, B. G., 1960, Selected annotated bibliography of the geol- ogy of uranium-bearing veins in the United States: US. Geol. Survey Bull. 1059—G, p. 327—440, pl. 4. Denson, N. M., 1959, Introduction, chap. A in Uranium in coal in the western United States: US. Geol. Survey Bull. 1055, p. 1—10, figs. 1—2. Denson, N. M., Bachman, G. 0., and Zeller, H. D., 1959, Uranium-bearing lignite in northwestern South Dakota and adjacent states, chap. B in Uranium in coal in the western United States: US. Geol. Survey Bull. 1055, p. 11—57, pls. 1—16, figs. 3—8. Departamento Nacional de Producao Mineral and US. Geo- logical Survey, 1959, Geologic map of Quadrilatero Ferri- fero, Minas Gerais, Brazil: Rio de Janeiro, Brazil. de Witt, Wallace, Jr., and Colton, G. W., 1959a, Revised cor- relations of lower Upper Devonian rocks in western and central New York: Am. Assoc. Petroleum Geologists Bull., v. 43, no. 12, p. 2810—2828. 1959b, Correlation of lower Upper Devonian rocks in central New York [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1761. Dibblee, T. W., Jr., 1959a, Geologic map of the Inyokern quadrangle, California: US. Geol. Survey open-file report. 1959b, Geologic map of the Alpine Butte quadrangle, California: US. Geol. Survey Mineral Inv. Field Studies Map MF—222. 1959c, Preliminary geologic map of the Mojave quad- rangle, California: US. Geol. Survey Mineral Inv. Field Studies Map MF—219. 1960a, Geologic map of the Hawes quadrangle, San Bernardino County, California: US. Geol. Survey Mineral Inv. Field Studies Map MF—226. 1960b, Preliminary geologic map of the Shadow Moun- tains quadrangle, Los Angeles and San Bernardino Coun- ties, California: US. Geol. Survey Mineral Inv. Field Studies Map MF—227. 1960c, Preliminary geologic map of the Victorville quadrangle, California: US. Geol. Survey Mineral Inv. Field Studies Map MF—229. 1960d, Preliminary geologic map of the Apple Valley quadrangle, California: US. Geol. Survey Mineral Inv. Field Studies Map MF—232. Dickey, D. D., and McKeown, F. A., 1960, Geology of Dolomite Hill, Nevada Test Site, Nevada: US. Geol. Survey TEI— 755, open-file report, 64 p. GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Diment, W. H., Healey, D. L., and Roller, J. C., 1959, Gravity and seismic exploration in Yucca Valley, Nevada Test Site: US. Geol. Survey TEI—545, open-file report, 41 p. Diment, W. H., and others, 1959a, Geological Survey investi- gations in the U12b.03 and U12b.04 tunnels, Nevada Test Site: U.S. Geol. Survey TEM—996, open-file report, 75 p. 1959b, Geological Survey investigations in the U12e.05 tunnel, Nevada Test Site: US. Geol. Survey TEM—997, open-file report, 55 p. 1959c, Geological Survey investigations in the U12b.01 Tunnel, Nevada Test Site: US. Geol. Survey, TEM—998, open-file report, 39 p. 1959d, Maximum accelerations caused by underground nuclear explosions in the Oak Spring formation at the Nevada Test Site [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1589. Dinnin, J. 1., Massoni, C. J., Curtis, E. L., and Brannock. W. W., 1959, Holder for four, 5-cm rectangular spectro— protometer cells: Chemist-Analyst, v.48, p. 79. Dobrovolny, Ernest, 1960, Parque Central, Santa Barbara, Villa Pabon landslide area, La Paz, Bolivia: Geol. Soc. Amer- ican, Rocky Mtn. Sec., 13th mtg., Rapid City, South Dakota, Apr. 28—30, 1960, program, p. 7. Doell, R. R., and Cox, Allan, 1959, Analysis of paleomagnetic data [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1590. Donnell, J. R., 1959, Mesaverde stratigraphy in the Carbondale area, northwestern Colorado, in Rocky Mountain Assoc. of Geologists, Guidebook, 11th Ann. Field Cont; Symposium on Cretaceous rocks of Colorado and adjacent areas: p. 76—77. Dorr, J. V. N. 11, 1959, A talk on geological research: Revista Mineira de Engenharia (cociedad Miniera de Engenherios), Ano 21, no. 79, p. 25—29. Dorr, J. V. N. II, Simmons, G. C., and Barbosa, A. L. M., 1959, Estratigrafla do Quadrilatero Ferrlfero de Minas Gerais: Engenharia, Mineracao e Metalurgia, v. 29, no. 170, p. 75—79. Douglass, R. C., 1960, The foraminiferal genus Orbitolimt in North America: US. Geol. Survey Prof. Paper 333, p. 1—52, pls. 1—17, figs. 1—32. Drewes, Harald, 1959, Turtleback faults of Death Valley, Cal- ifornia; A reinterpretation: Geol. Soc. America Bull., v. 70, no. 12, pt. 1, p. 1497—1508. ’ Droste, J. B., Rubin, Meyer, and White, G. W., 1959, Age of marginal Wisconsin drift at Corry, northwestern Penn- sylvania : Science, v. 130, no. 3391, p. 1760. Durham, J. W., and Jones, D. L., 1959, Fossil occurrences bearing on the Franciscan problem in central California [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1716. Dutro, J. T., Jr., 1960a, Correlation of Paleozoic rocks in Alaska [abs] : Internat. Symposium on Arctic Geology, 1st, Calgary, Jan. 11—13, 1960, Abstracts of Papers [unnum- bered]. 1960b, Correlation chart of Paleozoic rocks in Alaska: US. Geol. Survey open-file report. Eargle, I). H., 1959a, Geology of the Karnes County uranium area, south-central Texas: Engineering-Science News (Bal- cones Research Center), v. 7, no. 4, p. 1—4. LIST OF PUBLICATIONS Eargle, D. H., 1959b, Stratigraphy of Jackson group (Eocene), . south-central Texas: Am. Assoc. Petroleum Geologists Bull., 43, no. 11, p. 2623—2635. 1959c, Sedimentation and structure, Jackson group, south- central Texas: Gulf Coast Assoc. Geol. Societies Trans, V. 9, p. 31—39. 1960a, Uranium find heralds Texas wildcat action: Oil and Gas J0ur., v. 58, no. 10, p. 148—158. 1960b, Stratigraphy of Pennsylvanian and Lower Permian rocks in Brown and Coleman Counties, Texas: U.S. Geol. Survey Prof. Paper 315—1), 1). 55—77, pls. 27—30, figs. 11, 12. Eaton, J. P., 1959, A portable water-tub tiltmeter: Seismol. Soc. America Bull., v. 49, no. 4, p. 301—316. Eaton, J. P., and Richter, l). H., 1960, The 1959 eruption of Kilauea : GeoTimes, v. 4, no. 5, p. 24—27, 45. Eaton, J. P., and Takasaki, K. J., 1959, Seismological inter- pretation of earthquake induced water-level fluctuations in wells: Seismol. Soc. America Bull., V. 49, no. 3, p. 227—245. Eckel, E. B., and others, 1959, Geology applied to underground nuclear tests [abs]: Geol. Soc. America Bull., v, 70, no. 12, pt. 2, p. 1595. Eckhart, R. A., and Plafker, George, 1959, Haydite raw material in the Kings River, Sutton, and Lawing areas, Alaska: U.S. Geol. Survey Bull. 1039—0, p. 33—65, pls. 7—10, figs. 9—12. Ekren, E. B., and Houser, F. N., 1959a, Preliminary geologic map of the Cortez SW quadrangle, Montezuma County, Colorado: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—217. 1959b, Preliminary geologic map of the Moqui SE quadrangle, Montezuma County, Colorado: U.S. Geol. Sur- vey Mineral Inv. Field Studies Map MF—221. 1959c, Preliminary geologic map of the Sentinel Peak NE quadrangle, Montezuma County, Colorado: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—224. Elston, D. P., and Botinelly, Theodore, 1959, Geology and min- eralogy 0f the J. J. mine, Montrose County, Colorado, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p, 203—211. Engel, A. E. J., 1959, Review and evaluation of studies of the Om/O16 ratio in mineral deposits [abs]: Geol. Soc. Ameri- ca Bu11., v. 70, no. 12, pt. 2, p. 1597. Engel, A. E. J., and Engel, C. G., 1960, Progressive metamor- phism and granitization of the major paragneiss, north- western Adirondack Mountains, New York: Geol. Soc. America Bull., v. 71, no. 1, p. 1—58. Engel, C. G., 1959, Igneous rocks and constituent hornblendes of the Henry Mountains, Utah: Geol. Soc. America Bull., v. 70, no. 8, p. 951—980. Epprecht, W. Th., Schaller, W. T., and Vlisidis, A. C., 1959, Uber Wiserit, Sussexit und ein weiteres Mineral aus den Manganerzen vom Ganzen (bei Sargans): Scheizerische Mineralogische und Petrographische Mitt, v. 39, nos. 1—2 p. 85—104. Erd, R. C., McAllister, J. F., and Almond, Hy, 1959, Gowerite, a new hydrous calcium borate from the Death Valley region, California: Am. Mineralogist, v. 44, nos. 9—10, p. 911—919. Ergun, Salbri, Donaldson, W. F., and Breger, I. A., 1960, Some physical and chemical properties of vitrains associated with uranium: Fuel, v. 39, p. 71—7 7. A113 Eugster, H. P., and McIver, N. L., 1959, Boron analogues of alkali feldspars and related silicates [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1598. Evans, H. T., Jr., 1959, The crystal chemistry and mineralogy of vanadium, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 91—102. Evans, H. 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W., 1959, Age of the Fen carbonatite (Norway) and its relation to the intrusives of the Oslo region: Geochim. et Cosmochim. Acta, v. 17, nos. 1—2, p. 153—156. Faul, Henry, and Thomas, Herman, 1959, Argon ages of the Great Ash bed from the Ordovician of Alabama and of the Bentonite Marker in the Chattanooga shale from Tennessee [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1600. Fellows, R. E., and others, 1959, Mineral resources of Alaska: U .S. Geol. Survey open-file report, 141 p., 13 figs. Fernald, A. T., 1959, Geomorphology of the Upper Kuskokwim region, Alaska: U.S. Geol. Survey Bull. 1071—G [1960]. Finch, W. I., 1959a, Peneconcordant uranium deposit—a pro- posed term : Econ. Geol., v. 54, no. 5, p. 944—946. -1959b, Geology of uranium deposits in Triassic rocks of the Colorado Plateau region: U.S. Geol. Survey Bull. 1074—D, p. 125—164, pls. 6—10, figs. 6—7. Finch, W. I., Parrish, I. S., and Walker, G. W., 1959, Epigenetic uranium deposits in the United States: U.S. Geol. Survey Misc. Geol. Inv. Map I—299, [1960]. Fischer, R. P., 1959, Vanadium and uranium in rocks and ore deposits, in Garrels, R. M., and Larsen, E. S. 3d, Geochemis- try and mineralogy of the Colorado Plateau uranium ore-s: U.S. Geol. Survey Prof. Paper 320, p. 219—230. Fischer, W. A., and Ray, R. G., 1960, Quantitative photography— a research tool: Photogrammetric Engineering, v. 26, no. 1, p. 143—160. Fisher, D. J., Erdmann, C. E., and Reeside, J. B., Jr., 1960, Cretaceous and Tertiary formations of the Book Cliffs, Carbon, Emery, and Grand Counties, Utah, and Garfield and Mesa Counties, Colorado: U.S. Geol. Survey Prof. Paper 332, 80 p., 12 pls., 1 fig. Fleischer, Michael, 1959, The geochemistry of rhenium, with special reference to its occurrence in molybdenite: Econ. Geology, v. 54, no. 8, p. 1406—1413. 1960a, The geochemistry of rhenium—addendum: Econ. Geology, v. 55, no. 3, p. 607—609. 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Sec., 13th mtg, Rapid City, South Dakota, Apr. 28—30, 1960, program, p. 8 Fraser, G. D., and Snyder, G. L., 1960, Geology of southern Adak Island and Kagalaska Island, Alaska: U.S. Geol. Survey Bull. 1028—M, p. 371—408, pls. 52-53, figs. 55—61. Frezon, S. E., and Glick, E. E., 1959, Pre—Atoka rocks of north- ern Arkansas: U.S. Geol. Survey Prof. Paper 314—H, p. 171— 189, pls. 20—31, fig. 37. Friedel, R. A., and Breger, I. A., 1959, Free-radical concentra- tions and other properties of pile-irradiated coals: Science. v. 130, no. 3391, p. 1762—1763. Friedman, Irving, and Smith, R. L., 1960, A possible new dating method using obsidian. I. Development of the method: American Antiquity (in press) Friedman, Irving, Thorpe, A. N., and Senftle, Frank, 1960, Tektites and glasses from melted terrestrial rocks [abs] : Am. Geophys. Union, 41st Ann. Mtg, Apr. 27—30, 1960, Program, p. 60. I Friedman, J. D., 1959a, SM/S‘“ isotopic-abundance ratios and genesis of sulfide ore bodies at Summitville and Ellenville, New York [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1606. 1959b, Development of geologic thought Ulster County, New York: Washington Acad. Sci. Jour., v. 49, no. 7, p. 252—255. concerning GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Frischknecht, F. C., 1959, Scandinavian electromagnetic pros- pecting: Mining Eng, v. 11, no. 9, p. 932—937. Frost, I. C., 1959, An elutriating tube for the specific gravity separation of minerals: Am. Mineralogist, v. 44, nos. 7—8, p. 886—890. Gardner, L. S., 1959, Geologic map of the Lewistown area, Fergus County, Montana: U.S. Geol. Survey Oil and Gas Inv. Map 0M-199. Garrels, R. M., and Christ, C. L., 1959, Behavior of uranium minerals during oxidation, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 81—89. — Garrels, R. M., and Larsen, E. S. 3d, 1959, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, 236 p., 8 pls., 69 figs. Garrels, R. M., Larsen, E. S., 3d, Pommer, A. M., and Coleman, R. G., 1959, Detailed chemical and mineralogical relations in two vanadium-uranuim ores, m Garrels, R. M., and Lar- sen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 165—184. Garrels, R. M., and Ponnner, A. M., 1959, Some quantitative aspects of the oxidation and reduction of the ores, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranuim ores: U.S. Geol. Survey Prof. Paper 320, p. 157—164. Gates, G. 0., 1959, U.S. Geological Survey aids development: Fairbanks News-Miner, Progress Edition, Nov. 11, 1959, p. 122. Gates, R. M., 1960, Bedrock geology of the Roxbury quadrangle, Connecticut: U.S. Geol. Survey Geol. Quad. Map GQ—121. Gibbons, A. B., 1960, Geologic effects of the Ranier underground test—Preliminary report: U.S. Geol. Survey TEI—718, open- file report, 35 p. Gibbons, A. B., Hinrichs, E. N., Hansen, W. R., and Lemke, R. W., 1960, Preliminary geologic map of the Tippipah Spring NW quadrangle, Nye County, Nevada: U.S. Geol. Survey TEI—754, open-file report, 1 map. Gill, J. R., 1959, Reconnaissance for uranium in the Ekalaka lignite field, Carter County, Montana, chap. F in Uranium in coal in the western United States: U.S. Geol. Survey Bull. 1055, p. 167—179, pls. 33—35, figs. 28—29. Gill, J. R., Schultz, L. G., and Tourtelot, H. A., 1960, Correla- tion of units in the lower part of the Pierre shale, Great Plains region: Geol. Soc. America, Rocky Mtn. Sec., 13th mtg, Rapid City, South Dakota, Apr. 28—30, 1960, program, p. 8. Gill, J. R., Zeller, H. D., and Schopf, J. M., 1959, Core drilling for uranium-bearing lignite, Mendenhall area, Harding County, South Dakota, chap. D in Uranium in coal in the western United States: U.S. Geol. Survey Bull. 1055, p. 97—146, pls. 22—29, figs. 13—18. Gilluly, James, 1960, A folded thrust in Nevada—inferences as to time relations between folding and faulting: Am. J our. Sci., v. 258—A, p. 68—79. Glover, Lynn, 1959, Stratigraphy and uranium content of the Chattanooga shale in northeastern Alabama, northwestern Georgia, and eastern Tennessee: U.S. Geol. Survey Bull. 1087—E, p. 133—168, pls. 14—18, figs. 16-20. LIST OF PUBLICATIONS Gordon, Mackenzie, Jr., 1960, Some American midcontinent Carboniferous cephalopods: Jour. Paleontology, v. 34, no. 1, p. 133—151. Gott, G. B., Braddock, W. A., and Post, E. V., 1960, Uranium deposits of the southwestern Black Hills: Geol. Soc. Amer- ica, Rocky Mtn. Sec., 13th mtg., Rapid City, South Dakota, Apr. 28—30, program, p. 9. Gottfried, David, Jaffee. H. W., and Senftle, F. E., 1959, Eval- uation of the lead-alpha (Larsen) method for determining ages of igneous rocks: U.S. Geol. Survey Bull. 1097—A, p. 1—63, pl. 1, figs. 1—6. Goudarzi, Gus, 1959, A summary of the geologic history of Libya: U.S. Geol. Survey open-file report. [011 file in the Office of the Petroleum Committee, Ministry of the Natl. Economy, Tripoli, Libya, and U.S. Geol. Survey Library, Washington, DC, 61 p., 1 p1.] Grantz, Arthur, 1960a, Geologic map of Talkeetna Mountains (A—2) quadrangle,_Alaska, and the contiguous area to the north and northwest: U.S. Geol. Survey Misc. Geol. Inv. Map 1—313. 1960b, Geologic map of Talkeetna Mountains (A—1) quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map I—314. 1960c, Generalized geologic map of the Nelchina area, Alaska, showing igneous rocks and larger faults: U.S. Geol. Survey Misc. Geol. Inv. Map 1—312. Griflitts, W. R., 1959, Non-pegmatitic deposits of beryllium in the United States, [abs.]: Mining Eng, v. 11, no. 12, p. 1227. Grimaldi, F. S., 1960, Determination of niobium in the parts per million range in rocks: Anal. Chemistry, v. 32, no. 1. p. 119—121. Grimaldi, F. S., and Schnepfe, N. M., 1959, Semimicro determin- ation of combined tantalum and niobium with selenous acid : Anal. Chemistry, v. 31, no. 7, p. 1270—1272. Griscom, Andrew, 1959, Martic line in Pennsylvania—an aero- magnetic interpretation [abs.]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1612. Gryc, George, 1959, Alaska’s possible future petroleum re- sources: Fairbanks News-Miner, Sec. 11, p. 122, 124, Nov. 11, 1959. 1960, Progress report—A study of of tectonics of Alaska, [abs.]: Internat. Symposium on Arctic Geology, 1st, Cal- gary, Jan. 11-13, 1960, Abstracts of Papers [unnumbered]. Hack, J. T., 1960, Interpretation of erosional topography in humid temperate regions: Am. Jour. Sci, v. 258—A, p. 80—97. Hack, J. T., and Young, R. S., 1959, Intrenched meanders of the North Fork of the Shenandoah River, Virginia: U.S. Geol. Survey Prof. Paper 354—A, p. 1—10, pl. 1, figs. 1—5. Hadley, J. B., 1959a, The Madison Canyon landslide: Geo- Tinies, v.4, no. 3, p. 14—17. 1959b, Structure of the north part of the Gravelly Range, Madison County, Montana [abs.]: Geol. Soc. American Bull., v. 70, no. 12, pt. 2, p. 1778. Hale, W. E., and Clebsch, Alfred, Jr., 1959, Preliminary ap- praisal of ground-water conditions in southeastern Eddy County and southwestern Lea County, New Mexico: U.S. Geol. Survey TERI—1045, open-file report, 29 p. Hall, C. A., Jones, D. L., and Brooks, S. A., 1959, Pigeon Point formation ,of Late Cretaceous age in San Mateo County, California: Am. Assoc. Petroleum Geologists Bull., v. 43, no. 12, p. 2855—2859. A115 Hall, W. E., 1959, Geochemical study of lead—silver-zinc ore from the Darwin mine, Inyo County, California: Mining Eng. v. 11, no. 9, p. 940. Hallgarth, W. E., 1960, Stratigraphy of Paleozoic rocks in northwestern Colorado: U.S. Geol. Survey Oil and Gas Inv. Map 00—59. Hamilton, Warren, 1959, Chemistry of granophyres from Wichita Mountains, Oklahoma: Geol. Soc. America Bull., v. 70, no. 8, p. 1119—1126. 1960a, Origin of the Gulf of California [abs.]: Am. Geophys. Union, 41st Ann. Mtg., Apr. 27—30, 1960, Pro- gram, p. 75. 1960b, Antarctic tectonics and continental drift: Am. Assoc. Petroleum Geologists and Soc. Econ. Paleontologists and Mineralogists, joint meeting, Atlantic City, New Jersey, April 25—28, 1960, program, p. 72. 1960c, Motion pictures of geologic field work in the Antarctic [abs.]: Am. Geophys. Union, 41st Ann. Mtg, Apr. 27—30, 1960, Program, p. 76. Hamilton, Warren, and Hayes, P. T., 1959a, U.S. Geological Survey work in south Victoria Land in 1958—1959: Polar- Record, v. 9, no. 63, p. 575. 1959b, Cover picture showing the Taylor glacier, south Victoria Land with a short description of movement in the glacier: GeoTimes, v. 4, no. 1. Hansen, W. R., 1960, An improved Jacob staff for measuring inclined stratigraphic intervals: Am. ASSOC. Petroleum Geologists Bull., v. 44, no. 2, p. 252—254. Harbour, R. L., and Dixon, G. H., 1959, Coal resources of Trinidad-Aguilar area, Las Animas and Huerfano Counties, Colorado: U.S. Geol. Survey Bull. 1072—G, p. 445—489, pls. 10—14, fig. 17. Hartshorn, J. H., 1959, Groundhog 1959—East Greenland, in Bushnell, V. 0., ed., Proc. 2d Ann. Arctic Planning Conf., Oct. 1959, Air Force Cambridge Research Center, Geophys. Research Directorate, Research Notes, no. 29, AFCRC—TN- 59—661, p. 61—67. Hass, W. H., 1959, Conodont faunas from the Devonian of New York and Pennsylvania [abs.]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1615. Hathaway, J. G., 1959, Mixed-layered structures in vanadium clays, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 133—138. Hawkins, D. B., Canney, F. C., and Ward, F. N., 1959, Plastic standards for geochemical prospecting: Econ. Geology, v. 54, no. 4, p. 738—744. Hayes, P. T., 1959, San Andres limestone and related Permian rocks in Last Chance Canyon and vicinity, southeastern New Mexico: Am. Assoc. Petroleum Geologists Bull., v. 43, no. 9, p. 2197—2213. Hemphill, W. -R., 1959, Photogeologic map of the Notom—l quadrangle, Wayne County, Utah: U.S. Geol. Survey Misc. Geol. Inv. Map I—294. Henbest, L. G., 1960, Reclassification, living habits, and shell mineralogy of certain Late Paleozoic sedentary foramini- fera: Am. Assoc. Petroleum Geologists and Soc. Econ. Paleontologists and Mineralogists, joint meeting, Atlantic City, New Jersey, April 25—28, 1960, program, p. 82. Henderson, R. G., 1960, A comprehensive system of automatic computation in magnetic and gravity interpretation: Geo- physics, V. 25, no. 3, p. 569—585. Hewett, D. F., and Fleischer, Michael, 1960, Deposits of the manganese oxides: Econ. Geology, v. 55, no. 1, p. 1—55. A116 Heyl, A. V., Jr., Agnew, A. F., Lyons, E. J., and Behre, C. B., Jr., 1960, The geology of the upper Mississippi Valley zinc-lead district: U.S. Geol. Survey Prof. Paper 309, 310 p., 24 Dis, 101 figs. Heyl, A. V., Jr., Milton, Charles, and Axelrod, J. M., 1959, Nickel minerals from near Linden, Iowa County, Wiscon- sin: Am. Mineralogist, v. 4-4, nos. 9—10, p. 995—1009. Hildebrand, F. A., 1959, Zones of hydrothermally altered rocks in eastern Puerto Rico: San Juan, P.R., Dept. Indus. Inv., Adm. Govt. Econ., Informes Tecnicos, p. 82—96 [in Spanish]. Hilpert, L. S., and Moench, R. H., 1960, Uranium deposits of the southern part of the San Juan Basin, New Mexico: Econ. Geology, v. 55, no. 3, 429—464. Hoare, J. M., and Coonrad, W. L., 1960a, Geology of the Rus- sian Mission quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1—292. 1960b, Geology of the Bethel quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map I—285. Holmes, C. D., and Colton, R. B., 1960, Patterned ground near Dundas (Thule Air Force Base), Greenland: Meddelelser Om Gr¢nland, v. 158, no. 6, 15 1). Holmes, G. W., 1959a, The Mt. Chamberlin-Barter Island project, 1959, program and operations, in Bushnell, V. C., ed., Proc. 2d Ann. Arctic Planning Cont, Oct. 1959, Air Force Cambridge Research Center, Geophys. Research Directorate, Research Notes, no. 29, AFCRC—TN—59—661, p. 94. 1959b, Glacial geology of the Mt. Michelson B—2 quadran- gle, Alaska, in U.S. Geol. Survey, Military Geology Branch, Preliminary report of the Mt. Chamberlin—Barter Island project, Alaska: prepared for Air Force Cambridge Re— search Center, USAF, under Contract C 50—58—38, AFCRC— TN—59—650, p. 47—60. 1959c, Introduction, in U.S. Geol. Survey, Military Geol- ogy Branch, Preliminary report of the Mt. Chamberlin- Barter Island project, Alaska: prepared for Air Force )ambridge Research Center, USAF, under Contract C 50— 58—38, AFCRCeTN—59—650, p. 1—5. 1959a, Glaciation in the Johnson River-Tok area, Alas- ka Range [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1620. Holmes, G. W., and Lewis, C. R., 1960, Glacial geology of the Mt. C‘hamberlin area, Brooks Range, Alaska [abs] : Inter- nat. Symposium on Arctic Geology, 1st, Calgary, Jan. 11—13, 1960, Abstracts of Papers [unnumbered]. Hopkins, D. M., 1959a, Some characteristics of the climate in forest and tundra regions of Alaska: Arctic, v. 12, no. 4, p. 215—220. 1959b, History of Imuruk Lake, Seward Peninsula, Alaska: Geol. Soc. America Bull., v. 70, no. 8, p. 1033—1046. Hopkins, D. M., and Benninghoff, W. S., 1960, Upper Tertiary sediments in Alaska and northwestern Canada [abs] : In- ternat. Symposium on Arctic Geology, 1st, Calgary, Jan. 11—13, 1960, Abstracts of Papers [unnumbered]. Hose, R. K., and Repenning, C. A., 1959, Stratigraphy of Pennsylvanian, Permian and Lower Triassic rocks of Con- fusion Range, west—central Utah: Amer. Assoc. Petroleum Geologists Bull., v. 43, no. 9, p. 2167—2196. Houser, F. N., and Ekren, E. B., 1959a, Preliminary geologic map of the Moqui SW quadrangle, Montezuma County, Colorado: U.S. Geol. Survey Mineral Inv. Field Studies Map RIF—216. GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Houser, F. N., and Ekren, E. B., 19591), Cretaceous strata of the‘ Ute Mountains area of southwestern Colorado, in Rocky Mountain Assoc. of Geologists, Guidebook, 11th Ann. Field Conf., Symposium on Cretaceous rocks of Colorado and! ad» jacent areas, p. 145—152. Houser, F. N., and Poole, F. G., 1959a, Granite exploration hole, area 15 Nevada Test Site, Nye County, Nevada—Interim report, Part A, Structural, petrographic and chemical data: U.S. Geol. Survey TEM—836, open-file report, 58 p. 1959b, Lithologic log and drill information for the Mar- ble exploration hole 3, U15 area, Nevada Test Site, Nye County, Nevada: U.S. Geol. Survey TEM—1031, open-file report, 22 p. 1960, Primary structures in pyroclastic rocks of the Oak Spring formation (Tertiary), northeastern Nevada Test Site, Nye County, Nevada [abs]: Geol. Soc. America, Cordilleran Sec. mtg., May 5—9, 1960, Vancouver, BC. _ program, p. 28. Hubbert, M. K., and Rubey, W. W., 1960, Role of fluid pres- sure in mechanics of overthrust faulting; a reply: Geol. Soc. America Bull., v. 71, no. 5, p. 617—628. Huddle, J. W., and Patterson, S. H., 1959, Recent ideas on the origin of underclay seat earths [abs]: Geol. Soc. Amer- ica Bull., v. 70, no. 12, pt. 2, p. 1621. Hummel, C. L., 1960. Structural geology and structural con- trol of mineral deposits in an area near Nome, Alaska [abs]: Geol. Soc. America, Cordilleran Sec. mtg., May 5—9, 1960, Vancouver, BC, program, p. 29. Hunt, C. B., 1960, Geologic mapping by helicopter: GeoTimes, v. 4, no. 7, p. 1244,4041. Hurley, P. M., Boucot, A. J., Albee, A. L., F‘aul, Henry, Pinson, W. H., and Fairbairn, H. W., 1959, Minimum age of the Lower Devonian slate near Jackson, Maine: Geol. Soc. America Bull., v. 70, no. 7, p. 947—950. Imlay, R. W., Dole, H. M., Wells, F. G., and Peck, D. L., 1959, Relations of certain Upper Jurassic and Lower Cretaceous formations in southwestern Oregon: Am. Assoc. Petroleum Geologists Bull., v.43, no. 12, p. 2770—2785. Izett, G. A., Mapel, W. J., and Pilmore, C. L., 1960, Early Cretaceous folding on the west flank of the Black Hills, Wyoming: Geol. Soc. America, Rocky Mtn. Sec, 13th mtg, Rapid City, South Dakota, Apr. 28—30, program, p. 10. Jackson, W. H., and Warrick, R. E., 1959, Acoustic velocities and elastic parameters of salt and potash ore from measure- ments in the United States Potash Company mine, in Roller, J. 0., and others, Seismic measurements by the U.S. Geo logical Survey during the pre-Gnome high-explosive tests; a preliminary summary: U.S. Geol. Survey TEM—774, open- file report, p. 26-32. V Jaffe, H. W., Gottfried, David, Waring, C. L., and Worthing, H. W., 1959, Lead-alpha age determinations of accessory minerals of igneous rocks (1953—1957) : U.S. Geol. Survey Bull. 1097—B, p. 65—148. Jager, Emilie, and Faul, Henry, 1959, Age measurements on some granites and gneisses from the Alps: Geol. Soc. Amer- ica Bull., v. 70, no. 12, pt. 1, p. 1553—1558. James, H. L., 1959, General features of stable-isotope research, as applied to problems of ore deposits: Introduction [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1623. 1960, Problems of stratigraphy and correlation of Pre- cambrian rocks, with particular reference to the Lake Superior region: Am. J our. Sci., v. 258—A, p. 104—114. LIST OF PUBLICATIONS James, H. L., Dutton, C. E., Pettijohn, F. J., and Wier, K. L., 1960, Geologic map of the Iron River-Crystal Falls dis- trict, Michigan: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—225. Jones, C. L., 1959, Potash deposits in the Carlsbad district, southeastern New Mexico [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1625. ' 1960, Thickness, character, and structure of upper Per- mian evaporites in part of Eddy County, New Mexico: U.S. Geol. Survey TEM—1033, open-file report, 19 p. Jones, C. L., and Madsen, B. M., 1959, Observations on igneous intrusions in late Permian evaporites, southeastern New Mexico [abs.] : Geol. Soc, America Bull., v. 70, no. 12, pt. 2, p. 1625. Jones, D. L., 1959, Stratigraphy of Upper Cretaceous rocks in Yreka-Hornbrook area, northern California [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1726. 1960a, Lower Cretaceous (Albian) fossils from south- western Oregon and their paleogeographic significance: J our. Paleontology, v.34, no. 1, p. 152—160. 1960b, Pelecypods of the genus Pterotm‘gonm from the west coast of North America: Jour. Paleontology, v. 34, no. 3, p. 433—439 [pl. 59, 60; 2 text figs]. Jones, W. R., Peoples, J. W., and Howland, A. L., 1960, Igneous and tectonic structures of the Stillwater complex, Mon- tana: U.S. Geol. Survey Bull. 1071—H, p. 281—340, pls. 23—25, figs. 38~45. Johnson, H. S., Jr., 1959a, Uranium resources of the Cedar Mountain area, Emery County, Utah, a regional synthesis: U.S. Geol. Survey Bull. 1087—B, p. 23—58, figs. 3—8. 1959b, Uranium resources of the Green River and Henry Mountains districts, Utah, a regional synthesis: U.S. Geol. Survey Bull. 1087—0, p. 59—104, pls. 6—9, fig. 9. Johnson, R. B., 1960, Geology of the Huerfano Park area, Huer- fano and Custer Counties, Colorado: U.S. Geol. Survey Bull. 1071—D, p. 87—119, pls. 4—9, fig. 11. Johnson, R. W., Jr., 1959, Aeromagnetic survey of a mica peri- dotite body in Union County, Tennessee [abs] ; Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1764. Johnson, W. B., Jr., and Kunkel, R. P., 1959, The Square But- tes coal field, Oliver and Mercer Counties, North Dakota: U.S. Geol. Survey Bull. 1076, 91 p., 7 pls., 4 figs. Johnston, J. E., Trumbull, James, and Eaton, G. P., 1959, Will we find natural gas near northeast markets?: Gas Age, v. 124, no. 4, p. 25—31; and The petroleum potential of the emerged and submerged Atlantic Coastal Plain of the United States: World Petroleum Cong, 5th, New York, 1959, Proc., v. 1, p. 435—445 [1960]. Kachadoorian, Reuben, 1960, Engineering geology bearing on harbor site selection along the Gulf of Alaska from Point Whitshed to Cape Yakataga, Alaska: U.S. Geol. Survey TEI—642, open-file report, 32 p. Kachadoorian, Reuben, Campbell, R. H., Sainsbury, C. L., and Scholl, D. W., 1959, Geology of the Ogotoruk Creek area, northwestern Alaska: U.S. Geol. Survey TEM—976, open-file report, 43 p., 3 pls., 3 figs, 7 tables. Kachadoorian, Reuben, and others, 1960, Geologic investiga- tions in support of Project Chariot in vicinity of Cape Thompson, northwestern Alaska—preliminary report: U.S. Geol. Survey TEI—753, open-file report, 94 p. 557328 0 - 60 — 9 A117 Kachadoorian, Reuben, Sainsbury, C. L., and Campbell, R. H., 1959, Geologic factors affecting proposed nuclear test near Cape Thompson, northwest Alaska [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1795. Karlstrom, T. N. V., 1959, Reassessment of radiocarbon dating and correlations of standard late Pleistocene chronologies [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1627. 1960, Pleistocene physical and biologic environments of Pacific Coastal southcentral and southwestern Alaski [abs]: Internat. Symposium on Arctic Geology, 1st, Cal- gary, Jan. 11—13, 1960, Abstracts of Papers [unnumbered]. Karlstrom, T. N. V., and others, 1959, Surficial deposits map of Alaska : U.S. Geol. Survey open-file map. Kaye, C. A., 1959a, Geology of the San Juan metropolitan area, Puerto Rico: U.S. Geol. Survey Prof. Payer 317—A, p. 1—48, pls. 1—9, figs. 1—5. 1959b, Shoreline features and Quaternary shoreline changes, Puerto Rico: U .S. Geol. Survey Prof. Paper 317—B, p. 49—140, pls. 1, 10—11, figs. 6—63. 19590, Geology of Isla Mona, Puerto Rico, and notes on age of Mona Passage, with a section on The petrography of the phosphorites, by Z. S. Altschuler: U.S. Geol. Survey Prof. Paper 317—0, p. 141—178, pls. 12—13, figs. 1, 64—69. Keller, A. S., and Reiser, H. N., 1959, Geology of the Mount Katmai area, Alaska: U.S. Geol. Survey Bull. 1058—G, p. 261—298, pls. 29—32, figs. 44—46. Keller, G. V., 1959a, Electrical properties of sandstones of the Morrison formation: U.S. Geol. Survey Bull. 1052—J, p. 307—344, pls. 12—13, figs. 95—108. 1959b, Directional resistivity measurements in explora- tion for uranium deposits on the Colorado Plateau: U.S. Geol. Survey Bull. 1083—B, p. 37—7 2, figs. 9—28. Keller, G. V., and Frischknecht, F. C., 1960, Electrical resistivity studies on the Athabasca glacier, Alberta, Canada [abs]: Internat. Symposium on Arctic Geology, 1st, Calgary, Jan. 11—13, 1960, Abstracts of Papers [unnumbered]. Keller, G. V., and Licastro, P. H., 1959, Dielectric constant and electrical resistivity of natural—state cores: U.S. Geol. Survey Bull. 1052—H, p. 257—285, figs. 68—88. Keller, G. V., and others, 1959, Character of the Oak Spring formation (Tertiary) [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1628. Keller, G. V., and Plouff, Donald, 1959, Geophysical investiga- tions at Fletcher’s Ice Island, in Bushnell, V. 0., ed., Proc. 2d Ann. Arctic Planning Conf., Oct. 1959, Air Force Cam- bridge Research Center, Geophys. Research Directorate, Research Notes, no. 29, AFCRC-TN—59—661, p. 102—110. Keller, W. D., 1959, Clay minerals in the mudstones of the ore- bearing formations, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 113— 119. Kepferle, R. C., 1959, Uranium in Sharon Springs member of Pierre shale, South Dakota and northeastern Nebraska: U.S. Geol. Survey Bull. 1046—R, p. 577—604, pls. 50—53, figs. 85—92. Ketner, K. B., and McGreevy, L. J ., 1959, Stratigraphy of the area between Hernando and Hardee Counties, Florida: U.S. Geol. Survey Bull. 1074—0, p. 49—124, pls. 3-5, figs. 3—5. King, E. R., 1959a, Regional magnetic map of Florida: Am. Assoc. Petroleum Geologists Bull., v. 43, no. 12, p. 2844— 2854. A118 King, E. R., 1959b, Two aeromagnetic profiles across western Kansas, in Symposium on geophysics in Kansas: Kansas Geol. Survey Bull, 137, p. 135—141. King, E. R., and Zietz, Isidore, 1960, Thickness of the sedimen- tary section in the Appalachian basin: Am. Assoc. Petro- leum Geologists and Soc. Econ. Paleontologists and Mineralogists, joint meeting, Atlantic City, New Jersey, April 25—28, 1960, program, p. 66. King, E. R., Zietz, Isidore, and Dempsey, W. J ., 1960, Aeromag- netic profiles over the Atlantic continental shelf and slope: Am. Assoc. Petroleum Geologists and Soc. Econ. Paleontolo- gists and Mineralogists, joint meeting, Atlantic City, New Jersey, April 25—28, 1960, program, p. 36. King, P. B., 1960, The anatomy and habitat of low-angle thrust faults : Am. Jour. Sci., v. 258—A, p. 115-125. King, R. R., Jussen, V. M., Loud, E. S., and Conant, G. D., 1960, Bibliography of North American geology, 1957: US. Geol. 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Survey Prof. Paper 320, p. 151—156. Stern, T. W., Stieff, L. R., Klemic, H., and Delevaux, N. H., 1959, Lead—isotope age studies in Carbon County, Pennsylva- nia [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1680. Steven, T. A., and Ratté, J. C., 1959, Caldera subsidence in the Creede area, San Juan Mountains, Colorado [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1788. Stevens, R. E., Neil, S. T., and Roberson, (‘. E., 1960, Gravi- metric conversion factors, and other data used in inter- preting analyses of rocks, minerals and waters: GeoTimes, v. 4, no. 7, p. 41. Stevens, R. E., and others, 1960, Second report on a cooperative investigation of the composition of two silicate rocks: U.S. Geol. Survey Bull. 1113, 126 p., 8 figs. Stevens, R. E., Wood, W. H., Goetz, K. G., and Horr, C. A., 1959, Machine for preparing phosphors for the fluorimetric determination of urainum: Anal. Chemistry, v. 31, p. 962. Stewart, J. H., 1959, Stratigraphic relations of Hoskinnini member (Triassic?) of Moenkopi formation on Colorado Plateau: Am. Assoc. Petroleum Geologists Bull., v. 43, no. 8, p. 1835—1851. Stewart, J. H., Williams, G. A., Albee, H. F., and Raup, O. B., 1959, Stratigraphy of Triassic and associated formations in part of the Colorado Plateau region with a section on Sedi- mentary petrology by R. A. Cadigan: U.S. Geol. Survey Bull. 1046—62, p. 487—576, pl. 49, figs. 70—84. Stieff, L. R., and Stern, T. W., 1959, New graphical and alge— braic methods for the evaluation of discordant lead- uranium ages [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1681. Stoertz, G. E., 1959, Investigations in the Storely area, East Greenland, in Bushnell, V. C., ed., Proceedings: 2d Ann. Arctic Planning Cont, Oct. 1959, ‘Air Force Cambridge Research Center, Geophys. Research Directorate, Research Notes, no. 29, AFCRC—TN—59—661, p. 68—76. Stoiber, R. E., and Davidson, E. S., 1959, Amygdule mineral zoning in the Portage Lake lava series, Michigan copper district: Econ. Geology, v. 54, no. 7, p. 1250—1277; no. 8, p. 1444—1460. Stromquist, A. A., and Conley, J. F., Geology of the Albemarle and Denton quadrangles, North Carolina: Carolina Geol. Soc. Field Trip Guidebook, Oct. 24, 1959. Swanson, V. E., 1960, Oil yield and uranium content of black shales: U.S. Geol. Survey Prof.- Paper 356—A, p. 1—44, figs. 1—21. Tanner, A. B., 1959, Meteorological influence on radon concen- tration in drill holes: Mining Eng., v. 11, no. 7, p. 706—708. LIST OF PUBLICATIONS Tappan, Helen, 1960, Cretaceous biostratigraphy of northern Alaska: Am. Assoc. Petroleum Geologists Bull., v. 44, no. 3, pt. 1, p. 273—297. Tatlock, D. B., Wallace, R. E., and Silberling, N. J., 1960, Alkali metasomatism, Humboldt range, Nevada [abs]: Geol. Soc. America, Cordilleran Sec. mtg., May 5—9, 1960, Vancouver, B. C., program, p. 45. Taylor, A. R., 1960, Victoria Land traverse, Antarctica: U.S. Antarctic Projects Oflice Bull., v. 1, no. 6, p. 15—18. Taylor, D. W., 1960, Distribution of the freshwater clam Pisi‘d- tum ultramo‘ntanum; a paleozoogeographic inquiry: Am. J our. Sci., v. 258—A, p. 325—334. Teichert, Curt, 1959, Evaluation of bathymetric evidence fur- nished by marine fossilsiabsj, in Preprints, International Oceanographic Congress, [1st] New York 1959: Washing- ton, D.C., Am. Assoc. Adv. Sci., p. 291—292. Terriere, R. T., 1960, Geology of Grosvenor quadrangle, Texas, and petrology of some of its Pennsylvanian limestones: U.S. Geol. Survey open-file report, 171 p., 38 illus. Thompson, C. E. and Nakagawa, H. M., 1960, Spectrophoto- metric determination of traces of lead in igneous rocks: U.S. Geol. Survey Bull. 1084—F, p. 151—164, figs. 22—27. Thorpe, A. N., and Senftle, F. E., 1959, Absolute method of measuring magnetic susceptibility: Rev. Sci. Instruments, v. 30, no. 11, p. 1006—1008. Toulmin, Priestley, 3d, 1959, Composition of feldspars and crystallization history of the granite-synenite complex near Salem, Essex County, Massachusetts [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1689. Toulmin, Priestley 3d, and Barton, P. B., Jr., 1960, Formation of tarnish on gold-silver solid solutions as a measure of chemical potential of sulfur [abs.]: Am. Chem. Soc., Ab- stracts of papers presented at 137th meeting, Cleveland, p. 33M—34M. Tourtelot, H. A., 1960, Origin and use of the word “shale”: Am. J our. Sci., v. 258—A, p. 335—343. Tracey, J. 1., Jr., and Oriel, S. S., 1959, Uppermost Cretaceous and lower Tertiary rocks of the Fossil Basin, in. Inter- mountain Association of Petroleum Geologists, Guidebook to the geology of the Wasatch and Uinta Mts.: Inter- mountain Assoc. Petroleum Geologists 10th Ann. Field Cont, p. 126—130. Tracey, J. 1., Jr., and others, 1959, Military geology of Guam, Mariana Islands—Part I, Description of terrain and envi- ronment; Part II, engineering aspects of geology and soils: U.S. Army, Chief Engineers, Intelligence Div., Ofl‘ice Engi- neers, U.S. Army Pacific, 282 p. [includes maps]. Trites, A. F., Jr., Chew, R. T. 3d, and Lovering, T. G., 1959, Mineralogy of the uranium deposit at the Happy Jack mine, San Juan County, Utah, in Garrels, R. M., and Larsen E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 185—195. Truesdell, A. H., and Weeks, A. D., 1959, Relation of the Todilto limestone uranium deposits to Colorado Plateau uranium deposits in sandstone [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1689. Trumbull, James, and Johnston, J. E., 1960, The continental shelf of the east coast as 'a possible future petroleum producing province: Am. Assoc. Petroleum Geologists and Soc. Econ. Paleontologists and Mineralogists, joint meeting, Atlantic City, New Jersey, April 25—28, 1960, program p. 31. A125 Tschanz, C. M., 1959, Thrust faults in southeastern Lincoln County, Nevada [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1753. Tschanz, C. M., and Pampeyan, E. H., 1960, Geologic map of Lincoln County, Nevada [abs]: Geol. Soc. America, Cor- dilleran Sec. mtg., May 5—9, 1960, Vancouver, B. 0., pro- gram, p. 46. Tweto, Ogden, 1959, Differences in the Pliocene-Pleistocene histories of the Upper Arkansas and the Eagle River valleys, Colorado [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1789. U.S. Geological Survey, 1959a, Non~renewable natural resources in Africa south of the Sahara, Appendix 4 of Recommenda- tions for strengthening science and technology in selected areas of Africa south of the Sahara: Washington, DC. National Academy of Sciences—National Research Council. 1959b, Geologic investigations of radioactive deposits-— Semiannual progress report, Dec. 1, 1958, to May 31, 1959: U.S. Geol. Survey TISE version of (PEI-751. 1960a, Staff report on mineral fuels, in Mineral and water resources of Wyoming: U.S. 86th Cong, 2d sess., Senate Document 76. 1960b, Geologic investigations of radioactive deposits— Semiannual progress report, June 1 to Nov. 30, 1959: U.S. Geol. Survey TISE version of TEI—752. Varnes, D. J., Finnell, T. L., and Post, E. V., 1959 Graphic- locator method in geologic mapping, U.S. Geol, Survey Bull. 1081—A, p. 1—10. Vaughn, W. W., Wilson, E. E., and Ohm, J. M., 1960, A field instrument for quantitative determination of beryllium by activation analysis: U.S. Geol. Survey Circ. 427, 9 p., 8 figs. Vergara, J. F., and Spencer, F. D., 1959, Geology and coal resources of Bislig-Lingig region, Surigao, 1957: Philip- pines Bureau of Mines, Special Projects Series Pub. No. 14, 62 p., 5 pls. Vhay, J. S., 1960, Preliminary report on the copper-cobalt de- posits of the Quartzburg district, Grant County, Oregon: U.S. Geol. Survey open-file report, 20 p., 3 pl. Vine, J. D., 1959a, Dopplerite from Cretaceous rocks in Wyo- ming [abs.]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1691. 1959b, Geology and uranium deposits in carbonaceous rocks of the Fall Creek area, Bonneville County, Idaho, chap. I in Uranium in coal in the western United States: U.S. Geol. Survey Bull. 1055, p. 255—294, pls. 51—52, figs. 39—43. 1960, Geologic map of the Nash Draw quadrangle, Eddy County, New Mexico: U.S. Geol. Survey TEM—830, open- file report. Vine, J. D., and Prichard, G. E., 1960, Geology and uranium occurrences in the Miller Hill area, Carbon County, Wyo- ming: U.S. Geol. Survey Bull. 1074—F, p. 201—239, pls. 14—20, figs. 10—14. Vitaliano, D. B., 1959, Foreign languages for geologists: J our. Geol. Education, v. 7, no. 2, p. 49—53. Vitaliano, D. B., and. others, 1959, Index to geophysical ab- stracts 172—175, 1958: U.S. Geol. Survey Bull. 1086—E, p. 467—551. 1960, Index to geophysical abstracts 176—179, 1959: U.S. Geol. Survey Bull. 1106—13, p. 533—621. Vitaliano, D. B., Vesselowsky, S. T., and others, 1959a, Geo- physical abstracts 177, April—June 1959: U.S. Geol. Survey Bull. 1106—B, p. 129—259. 1959b, Geophysical abstracts 178, July—September 1959: U.S. Geol. Survey Bull. 1106—C, p. 261—406. Al26 Vitaliano, D. B., Vesselowsky, S. T., and; others, 1960, Geo- physical abstracts 179, October-December 1959: U.S. Geol. Survey Bull. 1106—D, p. 407—531. Waage, K. M., 1959a, Stratigraphy of the Inyan Kara group in the Black Hills: U.S. Geol. Survey Bull. 1081—B, p. 11—90, pl. 2, figs. ‘5—9. 1959b, Dakota stratigraphy along the Colorado Front Range: Rocky Mtn. Assoc. Geologists, Guidebook 11th Ann. Field Cont, p. 115—123. Waesche, H. H., 1960, Quartz crystals and optical calcite, in Industrial minerals and rocks: Am. Inst. Mining Metall. Petroleum Engineers, New York, 3d ed., p. 687—698. Wahrhaftig, Clyde, 1960, The physiographic provinces of Alas- ka : U.S. Geol. Survey open-file report. Wallace, R. E., 1959, Graphic solution of some earth satellite problems by use of the stereographic net: British Inter- planetary Soc. J0ur., v. 17, p. 120—123. Wallace, R. E., Silberling, N. J., Irwin, W. P., and Tatlock, D. B., 1959, Preliminary geologic map of the Buflalo Mountain quadrangle, Nevada: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—220. Wallace, R. E., Silberling, N. J., and Tatlock, D. B., 1960, Structural features of the Humboldt range, Nevada [abs] : Geol. Soc. America, Cordilleran Sec. mtg., May 5—9, 1960, Vancouver, B. C., program, p. 46. ' \Vallace, R. M., de Mello, N. M. P., Sallant‘ien, B., and Pares, M. S., 1959, Geology of a part of the Serra de Moeda, Marinho de Serra quadrangle, Minas Gerais, Brazil: Geol. Soc. Brazil Bull., v. 8, no. 2, p. 41-96. Wanek, A. A., 1959, Geology and fuel resources of the Mesa Verde area, Montezuma and La Plata Counties, Colorado: U.S. Geol. Survey Bull. 1072—M, p. 667—721, pls. 39—51, fig. 31. Warner, L. A., Holser, W. T., Wilmarth, V. T., andCameron, E. N., 1959, Occurrence of nonpegmatite beryllium in the United States: U.S. Geol. Survey Prof. Paper 318, 198 p., 5 pls., 60 figs. Warrick, R. E., and Winslow, J. D., 1960, Application of seismic methods to a ground-water problem in northeastern Ohio: Geophysics, v. 25, no. 2, p. 505-519. Weeks, A. D., Coleman, R. G., and Thompson, M. E., 1959, Summary of the ore mineralogy, m Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 65—79. Weeks, A. D., and Eargle, I). H., 1959, Deposition of uranium at Palangana Salt Dome, Duval County, Texas [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1695. Weeks, A. D., and Garrels, R. M., 1959, Geologic setting of the Colorado Plateau ores, in Garrels, R. M., and Larsen, E. S. 3d, Geochemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 3—11. Weis, P. L., 1959, Lower Cambrian and Precambrian rocks in northeastern Washington [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1790. Welch, S. W., 1960, Mississippian rocks of the northern part of the Black Warrior basin, Alabama and Mississippi: U. S. Geol. Survey Oil and Gas Inv. Map OC—62. Weld, B. A., Asselstine, E. S., and Johnson, Arthur, 1959, Reports and maps of the Geological Survey released only in the open files, 1958: U.S. Geol. Survey Circ. 412, 10 p. GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Weld, B. A., Asselstine, E. S., and Johnson, Arthur, 1960, Re- ports and maps of the Geological Survey released only in the open files, 1959: U.S. Geol. Survey Circ. 428, 10 p. Wells, J. D., 1959, Preliminary geologic map of the House Rock Spring SE quadrangle, Coconino County, Arizona: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—189. White, C. E., and Cuttitta, Frank, 1959, Fluorometric study of magnesium-bissalicylidene-ethylenediamine system: Anal. Chemistry, v. 31, p. no. 12, p. 2083—2087. White, D. E., and Craig, Harmon, 1959, Isotope geology of the Steamboat Springs area, Nevada [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1696. White, W. S., 1960a, The White Pine copper deposit—Discus- sion: Econ. Geology, v. 55, no. 2, p. 402—409. —— 1960b, The Keweenawan lavas of Lake Superior, an example of flood basalts: Am. Jour. Sci., v. 258—A, p. 367—374. Whitmore, F. 0., Jr., 1960, Terrain intelligence and current military concepts: Am. Jour. Sci., v. 258—A, p. 375—387. Wilcox, R. E., 1959a, Some effects of recent volcanic ash falls, with especial reference to Alaska: U.S. Geol. Survey Bull. 1028—N, p. 409—476, pls. 54—58, figs. 62—72. 1959b, Use of the spindle stage for determination of principal indices of refraction of crystal fragments: Am. Mineralogist, v. 44, nos. 11—12, p. 1272—1293. 1959c, Universal stage accessory for direct determina- tions of the three principal indices of refraction: Am. Mineralogist, v. 44, nos. 9—10, p. 1064—1070. Williams, J. R., 1959, Geology of the western part of the Big Delta (D—6) quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-297. Williams, J. R., Péwé, T. L., and Paige, R. A., 1959, Geology of the Fairbanks (D—l) quadrangle, Alaska: U.S. Geol. Survey Geol. Quad. Map GQ—124. Williams, P. L., 1960, A stained slice method for rapid determi- nation of phenocryst composition of volcanic rocks: Am. J our. Sci., v. 258, p. 148—152. Wilmarth, V. R., 1959, Geology of the Garo uranium-vanadium- copper deposit, Park County, Colorado: U.S. Geol. Survey Bull. 1087—A, p. 1-21, pls. 1—5, figs. 1—2. 1960, Some effects of underground nuclear explosions on tuft: U.S. Geol. Survey TEI—756, pub. ‘by U.S. Atomic Energy Comm., Tech. Inf. Service, Oak Ridge, Tenn, 34 p., 19 figs. ‘ Wilmarth, V. R., and others, 1959, Efl’ects of underground nuclear explosions on tuff at Nevada Test Site [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1700. Wilpolt, R. H., and Marden, D. W., 1960, Geology and oil and gas possibilities of Upper Mississippian rocks of south— western Virginia, southern West Virginia, and eastern Kentucky: U.S. Geol. Survey Bull. 1072—K, p. 587—655, pls. 27—29, flgs. 24—30. Wilson, Druid, Keroher, G. C., and Hansen, B. E., 1959, Index to the geologic names of North America : U.S. Geol. Survey Bull. 1056—B, p. 407—622. Wilson, R. F., and Stewart, J. H., 1959, Correlation of Upper Triassic and Lower Jurassic formations between {south- western Utah and southern Nevada [abs]: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1755. Withington, C. F., and Jaster, M.C., 1960, Selected annotated bibliography of gypsum and anhydrite in the United States and Puerto Rico: U.S. Geol. Survey Bull. 1105, 126 p. SUBJECT CLASSIFICATION OF PUBLICATIONS Witkind, I. J ., 1959, The Hebgen Lake earthquake: Geo’l‘imes, v. 4, no. 3, p. 13—14. Wolcott, D. E., and Gott, G. B., 1960, Stratigraphy of the Inyan Kara group in the southern Black Hills, South Dakota and Wyoming: Geol. Soc. America Rocky Mtn. Sec, 13th mtg., Rapid City, South Dakota, Apr. 28—30, program, p. 17. Wood, G. H., Jr., Arndt, H. H., and Kehn, T. M., 1959, Struc- tural features of the anthracite region of Pennsylvania [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1770. Woodland, M. V., 1959, Data of rock analyses; Part VI; Bibli- ography and index of rock analyses in the periodical and serial literature of Scotland: Geochim. et Cosmochim. Acta, v. 17, nos. 1—2, p. 136447. Woodring, W. P., 1959a, Geology and paleontology of Canal Zone and adjoining parts of Panama. Description of Tertiary mollusks (gastropods: Vermetidae to Thaididae) : U.S. Geol. Survey Prof. Paper 306—B, p. 147—239, pls. 24—37. 1959b, Tertiary Caribbean lnolluscan faunal province [abs], in. Preprints, International Oceanographic Congress, [1st] New York 1959: Am. Assoc. Adv. Sci., Washington, DC, p. 299—300. 1960, Paleoecologic dissonance; Astarte and Nipa in the early Eocene \London clay: Am. Jour. Sci., v. 258—A, p. 418—419. A127 ' \Vright, F. G., and Wright, 0. W., 1960, The Glacier Bay National Monument in southwestern Alaska—its glaciers and geology: U.S. Geol. Survey open-file report, 224 p., 99 pls. Yates, Robert G. and Thompson, George A., 1960, Geology and quicksilver deposits of the Terlingua district, Texas: US. Geol. Survey Prof. Paper 312, 114 p., 22 pls, 25 figs. Yochelson, E. L., and Dutro, J. T., Jr., 1960, Late Paleozoic Gastropoda from northern Alaska: US. Geol. Survey Prof. Paper 334—D, p. 111—147, pls, 12—14, figs. 23—29. Zeller, H. D., and Schopf, J. M., 1959, Core drilling for uranium- bearing lignite in Harding and Perkins Counties, South Dakota, and Bowman County, North Dakota, chap. C m Uranium in coal in the western United States: US. Geol. Survey Bull. 1055, p. 59—95, pls. 17—21, figs. 9—12. Zietz, Isidore, and Gray, Carlyle, 1959, Geophysical and geo- logical interpretation of a Triassic structure in eastern Pennsylvania [abs.] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1705. Zietz, Isidore, and others, 1959, Regional geologic interpretation of aeromagnetic profiles in the Yukon-Kandik and Koyukuk areas, Alaska [abs] : Geophysics, v. 24, no. 5, p. 1136—37. Zietz, Isidore, Patton, W. W., Jr., and Dempsey, W. J., 1959, Preliminary interpretation of total-intensity aeromagnetic profiles of the Koyukuk area, Alaska: US. Geol. Survey open-file report, 6 p. SUBJECT CLASSIFICATION OF PUBLICATIONS [The publications listed on p. A107—A127 are classified below in the same categories and in the same order as the subjects discussed on p. A1—A73.] Bibliographies: King, R. R., J ussen, Loud, and Conant, 1960 King, R. R., and others, 1959 Soister and Conklin, 1959 Vitaliano and others, 1960 Weld, Asselstine, and Johnson, 1959, 1960 Wilson, Druid, 1959 Heavy metals: Anderson, C. A., 1959, 1960 Arnold, Coleman and Frykland, 1959 Bailey, E. H., 1959 Bailey, E. H., and Irwin, 1959 Barton and Bethke, 1960 Bayley, 1959 a, b Behre and Heyl, 1959 Berg and MacKevett, 1959 Bethke and Barton, 1959 Birks, Brooks, Adler, and Milton, 1959 Calkins, Parker, and Disbrow, 1959 Cannon, R. S., Pierce, and Antweiler, 1959 Carr, M. S., and Dutton, 1959 Cobb, 1959a—d Cooper, 1959a, b, 1960 Departam‘ento Nacional de Producao Mineral and US. Geological Survey, 1959 Epprecht, Schaller, and Vlisidis, 1959 Evans, 1959 Evans and McKnight, 1959a, b Fellows and others, 1959 Fischer, R. P., 1959 Fleischer, 1959; 1960a, b Friedman, J. D., 1959a Gates, G. 0., 1959 Heavy metals—Continued Hall, W. E., 1959 Hathaway, 1959 Hewett and Fleischer, 1960 Heyl, Milton, and Axelrod, 1959 Heyl, Agnew, Lyons, and Behre, 1960 Hulnmel, 1960 James, 1959 James, Dutton, Pettijohn, and Wier, 1960 Lovering and others, 1960 Lovering and Shepard, 1960 Luedke, Wrucke, and Graham, 1959 McKelvey, 1960 Marvin and Magin, 1959 Muessig and Quinlan, 1959 Petersen, Hamilton, and Myers, 1959 Plan Regional Para e1 Desarrollo del Sur del Peru, 1959 Roedder, 1959 Rossman, 1960 Sims, Moench, and Harrison, 1959 Skinner, 1959 Skinner, Barton, and Kullerud, 1959 ‘Stoiber and Davidson, 1959 U.S. Geological Survey, 1959b Vhay, 1960 White, D. E., and Craig, 1959 White, W. S., 1960a Wilmarth, 1959 Yates and Thompson, 1960 Light metals and industrial minerals : Amos, 1959 Brobst, 1960 Carroll and Pommer, 1960 A128 Light metals and: industrial minerals—Continued Cathcart and McGreevy, 1959 Christ, 1960 Christ and Clark, J. R., 1960 Christ and Garrels, 1959 Clark, J. R., and Christ, 1959a—c Clark, J. R., Mrose, Perloff, and Burley, 1959 Coleman, 1959a Currier, 1960 Davidson, 1960 Davidson and Powers, 1959 Dibblee, 1959a—c; 1960a—d Eckhart and Plafker, 1959 Erd, McAllister, and Almond, 1959 Eugster and McIver, 1959 Fellows and others, 1959 Gates, G. 0., 1959 Gildersleeve, 1959 Griffitts, 1959 Huddle and Patterson, 1959 Jones, C. L., 1959, 1960 Jones, C. L., and Madsen, 1959 Kaye, 1959a—c Knechtel, Hosternlan, and Hamlin, 1959 Laurence, 1960 Lesure, 1959 Love and Milton, 1959 Luedke, Wrucke, and Graham, 1959 Mabey and others, 1959 McKelvey, 1959 McKelvey and others, 1959 Malde, 1959a Mertie, 1960 Milton and Eugster, 1959 Milton and Fahey, 1960 Moxham, Eckhart, and Cobb, 1960 Mudge, Walters, and Skoog, 1959 Murphy, 1960 Olson and Hinrichs, 1960 Overstreet, Theobald, and Whitlow, 1959 Owens and Minard, 1960 Patterson, 1960 Patterson and Hosterman, 1960 Patton and Matzko, 1959 Pierce and Rich, 1959 Redden, 1959 Sheldon, 1959a, b Skinner and Evans, 1960 Smith, G. I., 1959 Smith, W. C., 1960 Smith, W. L., Stone, Ross, and Levine, 1960 Staatz and Osterwald, 1959 US. Geological Survey, 1959a Vaughn, Wilson, and Ohm, 1960 Waesche, 1960 Warner, Holser, Wilmarth, and Cameron, 1959‘ Withington and J aster, 1960 Radioactive minerals : Archbold, 1959 Bachman, Vine, Read, and Moore, 1959 Bell, 1959 Botinelly and Fischer, 1959 Breger and Chandler, 1959 Breger and Deul, 1959 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Radioactive minerals—Continued Bush, Marsh, and Taylor, 1959 Byerly and J oesting, 1959 Cadigan, 1959a, b Cannon, H. L., 1959 Christman, Brock, Pearson, and Singewald, 1960 Clarke, J. R., 1960 Craig, Holmes, Freeman, Mullens, and others, 1959 Danilchik and Tahirkheli, 1960 Dean, 1960 Benson, 1959 Denson, Bachman, and Zeller, 1959 Eargle, 1959a, 1960a Ekren and Houser, 1959a-c Elston and Botinelly, 1959 Ergun, Donaldson, and Breger, 1960 Evans, 1959 Fellows and others, 1959 Finch, 1959a, b Finch and others, 1959 Fischer, R. P., 1959 Foster, 1959a Garrels and Christ, 1959 Garrels and Larsen, 1959 Garrels, Larsen, Pommer, and Coleman, 1959 Garrels and Pommer, 1959 Gates, G. 0., 1959 Gill, 1959 Gill, Zeller, and Schopf, 1959 Glover, 1959 Gott, Braddock, and Post, 1960 Hathaway, 1959 Hilpert and Moench, 1960 Houser and Ekren, 1959a Johnson, H. S., Jr., 1959a, b Keller, G. V., 1959a, b Keller, W. D., 1959 Kepferle, 1959 Landis, 1960 Larsen and Gottfried, 1960 Leo, 1960 Lewis, R. Q., and Trimble, 1960 Love and Milton, 1959 MacKevett, 1959a, b Mapel and Gott, 1959 Mapel and Hail, 1959 Marvin and Magin, 1959 Masursky and Pipiringos, 1959 Mertie, 1960 Moore, Melin, and Kepferle, 1959 Neuerburg and Granger, 1960 Newman and Elston, 1959 Outerbridge, Staatz, Meyrowitz, and Pommer, 1960 Overstreet, Theobald, and Whitlow, 1959 Petersen, 1959, 1960 Petersen, Hamilton, and Myers, 1959 Petersen and Phoenix, 1959 Phoenix, 1959 Post, 1959 Roach and Thompson, 1959 Schlee, 1959 Schlee and Moench, 1960 Sheldon, 19593, b Shoemaker, Miesch, Newman, and Riley, 1959 SUBJECT CLASSIFICATION OF PUBLICATIONS . Al29 Radioactive minerals—Continued Shoemaker and Newman, 1959 Sims, Moench, and Harrison, 1959 Soister and Conklin, 1959 Staatz and Osterwald, 1959 Stern and Stieff, 1959 Stern, Stieff, Klemic, and Delevaux, 1959 Stewart, 1959 Stewart, Williams, Albee, and Raup, 1959 Swanson, 1960 Tanner, 1959 Trites, Chew, and Levering, 1959 Truesdell and Weeks, 1959 U.S. Geological Survey, 1959b, 1960b Vine, 1959b Vine and Prichard, 1960 Waage, 1959a Weeks, Coleman, and Thompson, 1959 Weeks and Eargle, 1959 Weeks and Garrels, 1959 Wells, 1959 Wilmarth, 1959 Wolcott and Gott, 1960 Zeller and Schopf, 1959 Fuels : Adkison, 1960 Arndt, Conlin, Kehn, Miller, and Wood, 1959 Bachman, Vine, Read, and Moore, 1959 Barnes, F. F., 1960 Barnes, F. F., and Cobb, 1959 Beikman and Gower, 1959 Brown, Gower, and ‘Snavely, 1960 Burnside, 1959 Cashion, 1959 Cheney and Sheldon, 1959 Cloud, 1960 , Cloud and Palmer, 1959 Benson, 1959 Denson, Bachman, and Zeller, 1959 Donnell, 1959 Dutro, 1960a, b Ergun, Donaldson, and Breger, 1960 Friedel and Breger, 1959 Gardner, 1959 Gates, G. 0., 1959 Gill, 1959 Gill, Zeller, and Schopf, 1959 Glover, 1959 Gryc, 1959 Hallgrath, 1960 Harbour and Dixon, 1959 Johnson, W. 1)., Jr., and Kunkel, 1959 Johnston, Trumbull, and Eaton, 1959 Kottlowski, 1960a, b Kremp, Kovar, and Riegel, 1959 Landis, 1959 McKelvey, 1959 Mapel and Hail, 1959 Masursky and I’ipiringos, 1959 Miller, D. J ., MacNeil, and Wahrhaftig, 1960 Miller, D. J ., Payne, and Gryc, 1959 Moore, Melin, and Kepferle, 1959 Fuels—Continued Plan Regional Para el Desarrollo del Sur del Peru, 1959 Sandberg, C. A., 1960 Sandberg, D. T., 1959 Stafford, 1959 Swanson, 1960 Trumbull and Johnston, 1960 U.S. Geological Survey, 1960a Vine, 1959b Wanek, 1959 Wilpolt and Marden, 1960 Wood, Arndt, and Kehn, 1959 Zeller and Schopf, 1959 Geochemical and botanical exploration methods: Anderson, C. A., 1960 Bell, 1959 Cannon, H. L., 1959 Davies, 1959b Hawkins, Canney, and Ward, 1959 Levering and others, 1960 Nakagawa and Ward, 1960 Sigafoos, 1959 Isotope geology in exploration: Cannon, R. 8., Pierce, and Antweiler, 1959 Friedman, J. D., 1959a James, 1959 Tanner, 1959 White, D. E., and Craig, 1959 Geophysical exploration methods: Anderson, C. A., 1960 Bunker and Ohm, 1959 Frischknecht, 1959 Henderson, 1960 Johnson, R. W., Jr., 1959 Keller, G. V., 1959a, b King, E. R., and Zietz, 1960 Kinoshita and Kent, 1960 Mabey and others, 1959 Moxham, 1960 Roman, 1959 Warrick and Winslow, 1960 Geologic mapping and field methods 2 Anderson, C. A., 1959, 1960 Coats, 1960 Fischer, W. A., and Ray, 1960 Hansen, 1960 Hunt, 1960 Minard, 1960 Ray and Fischer, 1960 Stoertz, 1959 Varnes, Finnell, and Post, 1959 Geology applied to construction problems : Bonilla, 1960 Cattermole, 1960 Crandell and Gard, 1959 Flint, Saplis, and Corwin, 1959 Hartshorn, 1959 Holmes, G. W., 1959a, c Kaye, 1959a Lachenbruch, 1959b, 0 Lachenbruch and Greene, 1960 Lewis, G. R., 1959a, b McGill, 1959 Miller, R. D., and Dobrovolny, 1960 A130 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Geology applied to construction problems—Continued Péwé and Paige, 1959 Tracey and others, 1959 \‘Vhitmore, 1960 Engineering problems related to rock failure: Bonilla, 1959, 1960 Byerly, Stewart, and Roller, 1960 Dobrovolny, 1960 Hadley, 1959a McGill, 1959 Miller, D. J ., 1960a, b Myers, 1960 Witkind, 1959 Nuclear test-site studies: Baltz, 1960 Byerly, Stewart, and Roller, 1960 Clebsch and others, 1959 Dickey and McKeown, 1960 Diment, Healey, and Roller, 1959 Diment and others, 1959a—d lckel and others, 1959 Gibbons, 1960 Gibbons, Hinrichs, Hansen, and Lemke, 1960 Hale and Clebsch, 1959 Houser and Poole, 1959a, b; 1960 Jackson and Warrick, 1959 Jones, C. L., 1960 Kachadoorian, 1960 Kachadoorian, Campbell, Sainsbury, and Scholl, 1959 Kachadoorian and others, 1960 Kachadoorian, Sainsbury, and Campbell, 1959 Keller, G. V., and others, 1959 Lachenbruch, 1959b Lachenbruch and Green, 1960 McKeown and others, 1959 McKeown and Wilmarth, 1959 Moore, 1959a Péwé, Hopkins, and Lachenbruch, 1959 Poole and Roller, 1960 Price, 1960 Roller, Stewart, Jackson, Warrick, and Byerly, 1959 Scholl and Sainsbury, 1960a Vine, 1960 Wilmarth, 1960 Wilmarth and others, 1959 Radioactive waste disposal investigations: Carroll and Pommer, 1960 Carroll and Starkey, 1960 Pierce and Rich, 1959 Pommer and Carroll, 1960 Repenning, 1959 Ross, C. S., 1960 Schnepfe, 1960 Measurement of background radiation: Moxharn, 1960 Schmidt, 1959 Distribution of elements as related to health : Moxham, 1960 Synthesis of geologic data on large regions: Bailey, E. H., 1959a Brobst, 1960 Carr, M. S., and Dutton, 1959 Dean, 1960 Denson, 1959 Synthesis of geologic data on large regions—Continued Finch and others, 1959 Griffitts, 1959 King, R. R., Jussen, Loud, and Conant, 1960 King, R. R., and others, 1959 McKee and others, 1960 Pierce and Rich, 1959 Soister and Conklin, 1959 Warner, Holser, Wilmarth, and Cameron, 1959 Weld, Asselstine, and Johnson, 1959, 1960 Wilson, Druid, 1959 Withington and J aster, 1960 Eastern New York and New England: Balsley and Buddington, 1960 Balsley, Buddington, and others, 1959a—c Balsley, Postel, and others, 1959 Boucot and Arndt, 1960 Boucot, Griscom, Allingham, and Dempsey, 1960 Cady, 1959, 1960 Castle, 1959 Engel, A. E. J., and Engel, C. G., 1960 Gates, R. M., 1960 Hurley, Boucot, Albee, Faul, Pinson, and Fairbairn, 1959 Leonard and Vlisidis, 1960 Luedke, Wrucke, and Graham, 1959 Postel, Nelson, and Wiesnet, 1959 Smysor, 1959a Toulmin, 1959 Appalachians : Amos, 1959 Arndt, Conlin, Kuhn, Miller, and Wood, 1959 Bell, 1959 Bromery, 1959 Bromery, Bennett, and others, 1959a—c Bromery, Henderson, and Bennett, 1959 Bromery, Henderson, Zandle, and others, 1959a, b; 1960a—l Bromery, Zandle, and others, 1959a—m, 1960a—e Bryant and Reed, 1959 Cattermole, 1960 Friedman, J. 15., 1959b Glover, 1959 ' Griscom, 1959 Hack, 1960 Hack and Young, 1959 Johnson, R, W., Jr., 1959 King, E. R., and Zietz, 1960 Laurence, 1960 Lesure, 1959 Luedke, Wrucke, and Graham, 1959 Murphy, 1960 Neuman, 1960 Overstreet, Theobald, and Whitlow, 1959 Sando, 1960 Smith, W. L., Stone, Ross, and Levine, 1960 Smysor, 1959b Stern, Stieff, Klemic, and Delevaux, 1959 Stromquist and Conley, 1959 Wilpolt and Marden, 1960 Wood, Arndt, and Kehn, 1959 Zietz and Gray, 1959 Atlantic Coastal Plain 2 Brown, 1959 Carr, W. J ., and Alverson, 1959 Carroll, 1959a, b SUBJECT CLASSIFICATION OF PUBLICATIONS A131 Atlantic Coastal Plain—Continued Cathcart and McGreevy, 1959 Cooke, 1959 Johnston, Trumbull, and Eaton, 1959 Ketner, 1959 King, E. R., 1959a King, E. R., Zietz, and Dempsey, 1960 Knechtel, Hosterman, and Hamlin, 1959 Malde, 1959a Minard, 1960 Murphy, 1960 Owens and Minard, 1960 Schmidt, 1959 Schopf, 1959b Smysor, 1959b. Trumbull and Johnston, 1960 Eastern Plateaus : Colton, G. W., and de Witt, 1959 de Witt and Colton, G. W., 1959a, b Droste, Rubin, and White, G. W., 1959 Faul and Thomas, 1959 Friedman, J. D., 1959b Glover, 1959 Hass, 1959 King, E. R., and Zietz, 1960 Luedke, Wrucke, and Graham, 1959 Marcher, 1959 Oliver, 1960 Patterson and Hosterman, 1960 Wilpolt and Marden, 1960 Shield area and upper Mississippi Valley: Bayley, 1959a, c Behre and Heyl, 1959 Gill, Schultz, and Tourtelot, 1960 Heyl, Agnew, Lyons, and Behre, 1960 Heyl, Milton, and Axelrod, 1959 James, 1960 James, Dutton, Pettijohn, and Wier, 1960 Kepferle, 1959 Kottlowski, 1960a, b Mudge, Walters, and Skoog, 1959 Stoiber, and Davidson,»1959 Warrick and Winslow, 1960 White, W. 'S., 1960a, b Gulf Coastal Plain and Mississippi Embayment: Eargle, 1959a—c; 1960a Evans and McKnight, 1959a, b Weeks and Eargle, 1959 Welch, 1960 Ozark region and eastern plains: Adkison, 1960 Baltz, 1960 Burnside, 1959 Byerly, Stewart, and Roller, 1960 Chisholm, 1959 Cloud and Palmer, 1959 Dane, 1959 Eargle, 1960b Frezon and Glick, 1959 Hale and Clebsch, 1959 Hamilton, 1959 Hayes, 1959 Jackson and Warrick, 1959 Jones, C. L., 1959, 1960 Ozark region and eastern plains—Continued Jones, C. L., and Madsen, 1959 Landis, 1960 Mamay, 1959 Moore, 1959a, b Motts, 1959 Madge and Burton, 1959 Roller, Stewart, Jackson, Warrick, and Byerly, 1959 Stafford, 1959 Terriere, 1960 Vine, 1960 Yates and Thompson, 1960 Northern Rockies and plains: Arnold, Coleman, and Fryklund, 1959 Baker, 1959 Bayley, 1959b Bowles and Braddock, 1960 Calkins, Parker, and Disbrow, 1959 Campbell, 1959 Cheney and Sheldon, 1959 Cobhan, Erdmann, Lemke, and Maughan, 1959a, b Colton, R. B., 1959 Crittenden, 1959 Denson, Bachman, and Zeller, 1959 Fraser, 1960 Gardner, 1959 Gildersleeve, 1959 Gill, 1959 Gill, Schultz, and Tourtelot, 1960 Gill, Zeller, and Schopf, 1959 Gott, Braddock, and Post, 1960 Hadley, 1959a, b Hallgarth, 1960 Izett, Mapel, and Fillmore, 1960 Johnson, W. D., J r., and Kunkel, 1959 Jones, W. R., Peoples, and Howland, 1960 Kinoshita and Kent, 1960 Klepper and Smedes, 1959 Land‘is, 1960 Leo, 1960 Love, 1959, 1960 Love and Milton, 1959 McKelvey and others, 1959 Mapel and Gott, 1959 Marshall, 1960a—c Masursky and Pipiringos, 1959 Milton, Chao, Axelrod, and Grimaldi, 1960 Milton and Eugster, 1959 Milton and Fahey, 1960 Milton, Mrose, Chao, and Fahey,1959 Moore, Melin, and Kepferle, 1959 Mudge, 1959 Mudge and Dobrovolny, 1959 Muessig and Quinlan, 1959 Myers, 1960 Nelson, 1959 Olson, 1960 Post, 1959 Redden, 1959 Robinson, C. S., 1960 Robinson, G. D., 1959a, b Ross, C. P., 1960 Ross, C. P., and Rezak, 1959 Ross, R. J., Jr., 1959 A132 Northern Rockies and plains—Continued Sandberg, C. A., 1960 Sandberg, D. T., 1959 Sando, Dutro, and Gere, 1959 Schultz, Tourtelot, and Gill, 1960 Sheldon, 1959a, b Smith, J. F., Jr., Witkind, and Trimble, 1960 Tracey and Oriel, 1959 US. Geological Survey, 1960a Vine, 1959a, 1959b Vine and Prichard, 1960 Waage, 1959a Weis, 1959 Witkind, 1959 Wolcott and Gott, 1960 Zeller and Schopf, 1959 Southern Rockies and plains: Bailey, R. A., 1959 Christman, Brock, Pearson, and Singewald, 1960 Dane, 1959 Donnell, 1959 Gildersleeve, 1959 Gill, Schultz, and Tourtelot, 1960 Harbour and Dixon, 1959 Johnson, R. B., 1960 King, E. R., 1959b Kinney and Hail, 1959 Landis, 1959, 1960 Pearson, 1959 Ratté and Steven, 1959 Scott, G. R., Iand Cobban, 1959 Sims, Moench, and Harrison, 1959 Steven and Ratté, 1959 Tweto, 1959 US. Geological Survey, 1960a ‘Vaage, 1959b VVilmarth, 1959 Colorado Plateau : Archbold, 1959 Bachman, Vine, Read, and Moore, 1. 59 Botinelly and Fischer, 1959 Bush, Marsh, and Taylor, 1959 Byerly and J oesting, 1959 Cadigan, 1959a, b Cannon, H. L., 1959 Cashion, 1959 Craig, Holmes, Freeman, Mullens, and others, 1959 Dane, 1959, 1960 Ekren and Houser, 1959a—c Elston and Botinelly, 1959 Engel, C. G., 1959 Finch, 1959b Fischer, R. P., 1959 Fisher, Erdmann, and Reeside, 1960 Foster, 1959a Garrels and Christ, 1959 Garrels and Larsen, 1959 Garrels, Larsen, Pommer, and Coleman, 1959 Hemphill, 1959 Hilpert and Moench, 1960 Houser and Ekren, 1959a, b Johnson, H. S., Jr., 1959a, b Keller, G. V., 1959a, b Keller, W. D., 1959 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Colorado Plateau—Continued Kinney, Hansen, and Good, 1959 Krieger, 1959 Landis, 1959 Lewis, R. Q., and Trimble, 1960 Marshall, 1959 Newman and Elston, 1959 Petersen, 1959, 1960 Petersen, Hamilton, and Myers, 1959 Petersen and Phoenix, 1959 Phoenix, 1959 Repenning, 1959 Roach and Thompson, 1959 Schlee, 1959 Schlee and Moench, 1960 Shoemaker, 1959a, b Shoemaker, Miesch, Newman, and Riley, 1959 Shoemaker and Newman, 1959 Stern and Stieff, 1959 Stewart, 1959 Stewart, Williams, Albee, and Raup, 1959 Trites, Chew, and Lovering, 1959 Truesdell and Weeks, 1959 Wanek, 1959 Weeks, Coleman, and Thompson, 1959 Weeks and Garrels, 1959 Wells, 1959 Basin and Range province: Anderson, C. A., 1959 Christ and Garrels, 1959 Clebsch and others, 1959 Cooper, 1959a, b; 1960 Cornwall and Kleinhampl, 1959 Dane, 1959 Dibblee, 1959a—c; 1960a—d Dickey and McKeown, 1960 Diment, Healey, and Roller, 1959 Diment and others, 1959a—d Drewes, 1959 Erd, McAllister, and Almond, 1959 Gibbons, 1960 Gibbons, Hinrichs, Hansen, and Lemke, 1960 Gilluly, 1960 Hall, W. E., 1959 Hose and Repenning, 1959 Houser and Poole, 1959a, b ; 1960 Keller, G. V., and others, 1959 Longwell, 1960 Lovering and others, 1960 Levering and Shepard, 1960 Mabey, 1960 Mabey and others, 1959 McClymonds, 1959 McKelvey and others, 1959 McKeown and others, 1959 McKeown and Wilmarth, 1959 Mapel and Hail, 1959 Neuerburg and Granger, 1960 Olson and Hinrichs, 1960 Outerbridge, Staatz, Meyrowitz, and Pommer, 1960 Palmer, 1960a, 0 Peterson, 1959 Pomeroy, 1959 Poole and Roller, 1960 SUBJECT CLASSIFICATION OF PUBLICATIONS A133 Basin and Range province—Continued Price, 1960 Ross, C. P., 1960 Silberling, 1960 Smith, G. I., 1959 Staatz and Osterwald, 1959 Tatlock, Wallace, and Silberling, 1960 Tschanz, 1959 Tschanz and Pampeyan, 1960 Wallace, Silberling, Irwin, and Tatlock, 1959 Wallace, Silberling, and Tatlock, 1960 White, D. E., and Craig, 1959 Wilmarth, 1960 Wilmarth and others, 1959 Wilson, R. F., and Stewart, 1959 Columbia Plateau and Snake River Plains : Baldwin and Hill, 1960 Kinoshita and Kent, 1960 McKelvey and others, 1959 Malde, 1959b Mapel and Hail, 1959 Pakiser, 1960b Ross, C. P., 1960 Vhay, 1960 Pacific Coast: Bailey, E. H., 1960 Bailey, E. H., Christ, Fahey, and Hildebrand, 1959 Bailey, E. H., and Irwin, 1959 Balsley, Bromery, Remington, and others, 1960 Beikman and Gower, 1959 Bonilla, 1959, 1960 Bromery, Emery, and Balsley, 1960 Brown, Gower, and Snavely, 1960 Clark, L. D., 1960 Coleman, 1959b Crandell and Gard, 1959 Crowder, 1959 Durham and Jones, 1959 Hall, C. A., Jones, D. L., and Brooks, 1959 Imlay, Dole, Wells, and Peck, 1959 Jones, D. L., 1959a, 1960a, b Kinoshita and Kent, 1960 McGill, 1959 Mallory, 1959 Pakiser, 1960a, b Pakiser, Press, and Kane, 1960 Peck, D. L., 1960 Radbru-ch, 1959 Rinehart, 1959 Rinehart, Ross, and Huber, 1959 Smith, P. B., 1960 Alaska : Barnes, D. F., 1959 Barnes, F. F., and Cobb, 1959 Benninghoff and Holmes, 1960 Berg and )IacKevett, 1959 Berquist, 1960 Byers, 1960 Carr, M. S., and Dutton, 1959 Cass, 19593—f Coats, 1959 Cobb, 1959a—d Dutro, 1960a, b Alaska—Continued Eckhart and Plafker, 1959 Fellows and others, 1959 Fernald, 1959 Fraser and Snyder, 1960 Gates, G. 0., 1959 Grantz, 1960a—c Gryc, 1959, 1960 Hoare and Coonrad, 1960a, b Holmes, G. W., 1959a—d Holmes, G. W., and Lewis, C. R., 1960 Hopkins, 1959a, b Hopkins and Benninghoff, 1960 Hummel, 1960 Kachadoorian, 1960 Kachadoorian, Campbell, Sainsbury, and Scholl, 1959 Kachadoorian and others, 1960 Kachadoorian, Sainsbury, and Campbell, 1959 Karlstrom, 1960 Karlstrom and others, 1959 Keller, A. S., and Reiser, 1959 Keller, G. V., and Frischknecht, 1960 Keller, G. V., and Plouff, 1959a, b Lachenbruch, 1959b Lachenbruch and Brewer, 1959 Lachenbruch and Greene, 1960 Lathram, 1960 Lathram, Loney, Condon, and Berg, 1959 Lewis, G. R., 1959a, 1) Lewis, R. Q., Nelson, and Powers, 1960 MacKevett, 1959a, b Miller, D. J., 1960a, b Miller, D. J ., MacNeil, and Wahrhaftig, 1960 Miller, D. J ., Payne, and Gryc, 1959 Miller, R. D., and Dobrovolny, 1960 Moxham, Eckhart, and Cobb, 1960 Nichols and Yehle, 1960 Patton, 1959 Patton and Matzko, 1959 Péwé, 1959c , Péwé, Hopkins, and Lachenbruch, 1959 Péwé and Paige, 1959 Powers, Coats, and Nelson, 1960 Rossman, 1960 Sable, 1959 Sainsbury and Campbell, 1959 Scholl and Sainsbury, 1960a, b Tappan, 1960 Wahrhaftig, 1960 Wilcox, 1959a Williams, J, R., 1959 Williams, J. R., Péwé, and Paige, 1959 Wright and Wright, 1960 Yochelson and Dutro, 1960 Zietz and others, 1959 Zietz, Patton, and Dempsey, 1959 Hawaii : Davidson and Powers, 1959 Eaton and Richter, 1960 Patterson, 1960 Richter and Eaton, 1960 Robertson, 1959 Puerto Rico and the Canal Zone: Berryhill, 1959 A134 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS 0F GEOLOGIC RESULTS Puerto Rico and! the Canal Zone—Continued Berryhill, Briggs, and Glover, 1960 Carr, M. S., and Dutton, 1959 Hildebrand, 1959 Kaye, 1959a, b, c Withington and J aster, 1960 Woodring, 1959a Western Pacific Islands: Cole, Todd, and Johnson, C. G., 1960 Flint, Saplis, and Corwin, 1959 Fosberg, 1960a, b Ladd, 1960 McKee, 1959 Taylor, A. R., 1960 Tracey and others, 1959 Antarctica : Hamilton, 1960b, c Hamilton and Hayes, 1959a, b Péwé, 1959a, b Péwé, Rivard, and Llano, 1959a, b Extraterrestrial studies: Friedman, Irving, Thorpe, and Senftle, 1960 Mason, Elias, Hackman, and Olson, 1959, 1960 Senftle and Thorpe, 1959a, b Wallace, 1959 Geologic investigations in foreign areas : Anderson, D. G., 1959 Bramkamp, 1960 B‘ramkamp and Ramirez, 1959a—c Danilchik and Tahirkheli, 1960 Departamento Nacional de Producfio Mineral and U.S. Geo- logical Survey, 1959 Dobrovolny, 1960 Dorr, 1959 Dorr, Simmons, and Barbosa, 1959 Goudarzi, 1959 Hamilton, 1960a Holmes, 0. D., and Colton, R. B., 1960 Krinsley, 1960 Plan Regional e1 Desarrollo del Sur del Peru, 1959 Pomerene, 1959 Pratt, 1959 Rezak, 1959 Rosenblum, 1960 Rossman, Fernadez, Fontanos, and Zepeda, 1959 Sachet, 1959 Segerstrom, 1959a, b Segerstrom and Parker, 1959 Spencer and Vergara, 1959 IRS. Geological Survey, 1959a Stoertz, 1959 Vergara and Spencer, 1959 Vitaliano, 1959 Wallace, de Mello, Sallantien. and I’ares, 1959 Paleontology : Berdan, 1960 Boucot and Arndt, 1960 Cloud, 1959 Cloud and Palmer, 1959 Cole, Todd, and Johnson, C. G., 1960 Cooke, 1959 Dean, 1960 Douglas, 1960 Durham and Jones, D. L., 1959 Paleontology—Continued Flower and Gordon, 1959 Gordon, 1960 Hass, 1959 Henbest, 1960 Jones, D. L., 1960a, b Kremp, Ames, and Frederiksen, 1959 Kremp, Kovar, and Riegel, 1959 Ladd, 1959, 1960 Lohman, 1960a, b Mallory, 1959 Mamay, 1959 Oliver, 1960 Palmer, 1960a, b, c Péwé, Rivard, and Llano, 1959a, b Rezak, 1959 Rinehart, Ross, and Huber, 1959 Ross, R. J., Jr., 1959 Schopf, 1959a, b; 1960 Scott, R. A., Barghoorn, and Leopold, 1960 Silberling, 1960 Smith, P. B., 1960 Sohn and Berdan, 1960 Tappan, 1960 Taylor, D. W., 1960 Teichert, 1959 Woodring, 1959a, b; 1960 Yochelson and Dutro, 1960 Geomorphology and plant ecology : Davies, 1959a, 1960b Droste, Rubin, and White, G. W., 1959 Fernald, 1959 Fosberg, 1959a, b; 1960a, b Hack, 1960 Hack and Young, 1959 Hopkins, 1959a Karlstrom, 1960 Karlstrom and others, 1959 Kaye, 1959b Krinsley, 1960 McKee, 1960b Motts, 1959 Péwé, 1959a Sachet, 1959 Sigafoos, 1959 Tweto, 1959 Wahrhaftig, 1960 Physical properties of rocks: Anderson, D. G., 1959 Baldwin, 1960 Barnes, D. F., 1959 Barton and Bethke, 1960 Keller, G. V., 1959a Keller, G. V., and Frischknecht, 1960 Keller, G. V., and Licastro, 1959 Pankey and Senftle, 1959 Plouff, Keller, Frischknecht, and Wahl, 1960 Robertson, 1959, 1960 Senftle and Thorpe, 1959a, b Thorpe and Senftle, 1959 Vitaliano, and others, 1959, 1960 Vitaliano, Vesselowsky, and others, 1959a, b; 1960 Permafrost studies: Davies, 1959b, 1960a SUBJECT CLASSIFICATION OF PUBLICATIONS A135 Permafrost studies—Continued Garrels, 1959a Hartshorn, 1959 Holmes, C. D., and Colton, R. B., 1960 Lachenbruch, 1959a—d; 1960 Lachenbruch and Brewer, 1959 Lachenbruch and Greene, 1960 Péwé and Paige, 1959 Williams, J. R., 1959 Williams, J. R., Péwé, and Paige, 1959 Rock deformation: Eaton, 1959 Eaton and Takasaki, 1959 Fraser, 1960 Gilluly, 1960 Gryc, 1960 Hamilton, 1960a, b Hubbert and Ru‘bey, 1960 King, P. B., 1960 Lachenbruch, 1959a, d; 1960 Lesure, 1959 Myers, 1960 Pakiser, 1960a Péwé, 1959b Robertson, 1960 Shoemaker, 1959a, b Steven and Ra‘tté, 1959 Paleonlagnetism : Balsley and Buddington, 1960a Cox, 1960 Cox and Doell, 1960 Doell and Cox, 1959 Crustal studies: Baldwin and Hill, 1960 Byerly and J oesting, 1959 Eaton and Takasaki, 1959 Keller, G. V., and Plouff, 1959a, b King, E. B., 1959a King, E. R., and Zietz, 1960 Mabey, 1960 Pakiser, 1960b Mineralogy and crystal chemistry : Bailey, E. B., Christ, Fahey, and Hildebrand, 1959 Birks, Brooks, Adler, and Milton, 1959 Botinelly and Fischer, 1959 Carroll, 1960 Carroll and Pommer, 1960 Carroll and Starkey, 1960 Christ, 1960 Christ and Clark, J. R., 1960 Christ and Carrels, 1959 Clark, J. B., 1960 Clark, J. R., and Christ, 1959a-c Clark, J. R., Mrose, Perloff, and Burley, 1959 Coleman, 1959a Elston and Botinelly, 1959 Epprecht, Schaller, and Vlisidis, 1959 Erd, McAllister, and Almond, 1959 Eugster and McIver, 1959 Evans, 1959 Evans and Lonsdale, 1959 Evans and McKnight, 1959a, b Fahey, Ross, and Axelrod, 1960 Mineralogy and crystal chemistry—Continued Fleischer, 1960b Foster, 1959a, b; 1960 Garrels and Christ, 1959 Garrels and Larsen, 1959 Carrels, Larsen, Pommer, and Coleman, 1959 Garrels and Pommer, 1959 Hall, W. E., 1959 Hath-away, 1959 Hewett and Fleischer, 1960 Heyl, Milton, and Axelrod, 1959 Keller, W. D., 1959 Leo, 1960 Leonard and Vlisidis, 1960 Lindberg and Christ, 1959a, b Marvin and Magin, 1959 Milton, Chao, Axelrod, and Grimaldi, 1960 Milton and Eugster, 1959 Milton and Fahey, 1960 Milton and Ingram, 1959 Milton, Mrose, Chao, and Fahey, 1959 Mrose and von Knorring, 1959 Mrose and Wappner, 1959 Outerbridge, Staatz, Meyrowitz, and Pommer, 1960 Pankey and Senftle, 1959 Petersen, Hamilton, and Myers, 1959 Pommer, 1959 Pommer and Carroll, 1960 Redden, 1959 Ross, C. S., 1960 Ross and Evans, 1959, 1960 'Schnepfe, 1960 Skinner, Barton, and Kullerud, 1959 Skinner and Evans, 1960 Smith, W. L., Stone, Ross, and Levine, 1960 Trites, Chew, and Lovering, 1959 Vine, 1959a Weeks, Coleman, and Thompson, 1959 Experimental geochemistry : Arnold, Coleman, and Fryklund, 1959 Barton and Bethke, 1960 Barton and Toulmin, 1959 Bethke and Barton, 1959 Breger and Chandler, 1959 Ergun, Donaldson, and Breger, 1960 Marvin and Magin, 1959 Pommer and Carroll 1960 Roedder, 1959 Schnepfe, 1960 Skinner, 1959 Skinner, Barton, and Kullerud, 1959 Toulmin and Barton, 1960 Geochemical distribution of the elements: Begemann and Friedman, 1959 Chao and Fleischer, 1959 Davidson, 1960 Davidson and Powers, 1959 Fleischer, 1959, 1960a Fleischer and Chao, 1959 Larsen and Gottfried, 1960 McKelvey, 1960 Neuerburg and Granger, 1960 Shoemaker, Miesch, Newman, and Riley, 1959 A136 Geochemical dlistribution Organic geochemistry : the elements—Continued, Shoemaker and Newman, Woodland, 1959 Breger and Chandler, 1959 Breger and Deul, 1959 Cannon, H. L., 1959 Ergun, Donaldson, and Breger, 1960 Friedel and Breger, 1959 Sisler, 1959 Petrology : Bailey, E. H., 1960 Bailey, E. H., and Irwin, 1959 Bailey, R. A., 1959 Balsley and Buddington, 1960a Bayley, 19590 Bowles, 1960 Cadigan, 1959a, b Carroll, 1959a Cloud, 1960 Coats, 1959 Coleman, 1959b C‘rowder, 1959 , Davidson and Powers, 1959 Eaton and Richter, 1960 Engel, C. G., 1959 Engel, A. E. J., and Engel, C. G., 1960 Faul, Elmore, and Brannock, 1959 Fraser and Snyder, 1960 Hamilton, 1959 Huddle and Patterson, 1959 J affe, Gottfried, Waring, and Worthing, 1959 Jones, W. R., Peoples, and Howland, 1960 Keller, A. S., and Reiser, 1959 Klepper and Smedes, 1959 Larsen and Gottfried, 1960 Lewis, R. Q., Nelson, and Powers, 1960 Lovering and Shepard, 1960 McKee, 1959, 1960a McKelvey, 1959 McKelvey and others, 1959 Moore, 1959b Murata, 1960 Nichols and Yehle, 1960 Pakiser, 1960a, b Pakiser, Press, and Kane, 1960 Pearson, 1959 Peterson, 1959 Powers, Coats, and Nelson, 1960 Ratté and Steven, 1959 Rose and Stern, 1960 Smith, G. 1., 1959 Stewart, Williams, Albee, and Raup, 1959 Tatlock, Wallace, and Silberling, 1960 Terriere, 1960 ‘ Toulmin, 1959 Tourtelot, 1960 White, W. S., 1960b Wilcox, 1959a Woodland, 1959 GEOLOGICAL SURVEY RESEARCH 1960—SYNOPSIS OF GEOLOGIC RESULTS Isotope and nuclear studies : Begemann and Friedman, 1959 Cannon, R. 8., Pierce, and Antweiler, 1959 Droste, Rubin, and White, G. W., 1959 Engel, A. E. J., 1959 Fan], 1959, 1960 Faul and Thomas, 1959 Fan], Elmore, and Brannock, 1959 Friedman, J. D., 1959a Friedman and Smith, 1960 Gottfried, J affee, and Senftle, 1959 Hurley, Boucot, Albee, Faul, Pinson, and Fairbairn, 1959 J ager and Faul, 1959 James, 1959 Karlstrom, 1959 Martinez and Senftle, 1960 Rubin and Alexander, 1960 Sakakura, Lindberg, and Faul, 1959 Senftle, Stern, and Alekna, 1959 Sisler, 1959 Stern and Stieff, 1959 Stern, Stieff, Klemic, and Delevaux, 1959 Stieif and Stern, 1959 Vaughn, Wilson, and Ohm, 1960 White, D. E., and Craig, 1959 Analytical chemistry: Breger and Deul, 1959 Garrels, Larsen, Pommer, and Coleman, 1959 Garrels and Pommer, 1959 Grimaldi, 1960 Grimaldi and Schnepfe, 1959 Hawkins, Canney, and Ward, 1959 Kinser, 1959 Milton and Ingram, 1959 Nakagawa and Ward, 1960 Peck, L. C., and Tomasi, 1959 Pommer and Abell, 1959 Shapiro, 1959, 1960 Shapiro and Brannock, 1959 Stevens and others, 1960 Stevens, Wood, Goetz, and Horr, 1959 White, C. E., and Cuttitta, 1959 Spectroscopy: Adler, 1959 Birks, Brooks, Adler, and Milton, 1959 Cuttitta, and White, 1959 Dinnin, Massoni, Curtis, and Brannock, 1959 Rose and Stern, 1960 Thompson and Nakagawa, 1960 Mineralogic and petrographic methods : Adler, 1959 Bailey, E. H., and Stevens, 1960 Evans and Lonsdale, 1959 Faul and Davis, 1959 Frost, 1959 Martinez and Senftle, 1960 Meyrowi-tz, Cuttitta, and Hickling, 1959 Murata, 1960 Pommer and Carroll, 1960 Stevens, Neil, and Robertson, 1960 Wilcox, 1959b, 0 Williams, P. L., 1960 LLS. GOVERNMENT PRINTING OFFICE: I960 0—557320 W/ (fl eoldgical SurVey Research 1960 Short Papers 1n the Geological Sciences /// I .GEOVLOGICAL SURVEMY/PROFESSIONAL PAPER 400- B gmgfifi‘i’ M 3:23:71 , Short Papers in the Geological Sciences Geological Survey Research 1960 GEOLOGICAL SURVEY PROFESSIONAL PAPER 400—B Scientific notes anaI summaries of investigations prepared 5} mentoers of t/ze Geologic Division in t/zefie/a’s ofgeo/ogy ana’ a/[ieaI sciences UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960 UNITED STATES DEPARTMENT OF THE INTERIOR ' FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, US. Government Printing Oflice Washington 25, D.C. - Price $4.25 (Paper cover) CONTENTS Foreword (see chapter A) Preface (see chapter A) Geolo 1. ooflcacnqswm 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27 Geolo 28 29. 30. 31. 32. 33. 34. 35. gy of metalliferous deposits An hypothesis for origin of ore—forming fluid, by J. Hoover Mackin and Earl Ingerson ___________________________ . Varieties of supergene zinc deposits in the United States, by A. V. Heyl, Jr., and C. N. Bozion ____________________ . Lithofacies of the Copper Harbor conglomerate, northern Michigan, by Walter S. White and James C. Wright ______ . Relation of the Colorado mineral belt to Precambrian structure, by Ogden Tweto and P. K. Sims _________________ . Pre-ore age of faults at Leadville, Colorado, by Ogden Tweto _________________________________________________ . Pre-ore propylitization, Silverton caldera, Colorado, by Wilbur S. Burbank _____________________________________ . Ring-fractured bodies in the Silverton caldera, Colorado, by Robert G. Luedke and Wilbur S. Burbank _____________ . Relation of mineralization to caldera subsidence in the Creede district, San Juan Mountains, Colorado, by Thomas A. Steven and James C. Ratté __________________________________________________________________________ Alinement of mining districts in north-central Nevada, by Ralph J. Roberts ____________________________________ Mineral assemblage of a pyrometasomatic deposit near Tonopah, Nevada, by R. A. Gulbrandsen and D. G. Gielow- Sedimentary iron-formation in the Devonian Martin formation, Christmas quadrangle, Arizona, by Ronald Willden- Early Tertiary volcanic geology of an area north and west of Butte, Montana, by Harry W. Smedes _______________ Tectonic setting of the Coeur d’Alene district, Idaho, by Robert E. Wallace, Allan B. Griggs, Arthur B. Campbell, and S. Warren Hobbs __________________________________________________________________________________ Bleaching in the Coeur d’Alene district, Idaho, by P. L. Weis _________________________________________________ Origin of the Main period veins, Coeur d’Alene district, Idaho, by Verne C. Fryklund, Jr _________________________ Geologic and economic significance of some geochemical results obtained from stream sediment samples near Nome, Alaska, by C. L. Hummel and Robert M. Chapman _______________________________________________________ Structural geology and structural control of mineral deposits near Nome, Alaska, by C. L. Hummel _______________ Structural control in five quicksilver deposits in southwestern Alaska, by C. L. Sainsbury and E. M. MacKevett, Jr-_ Three areas of possible mineral resource potential in southeastern Alaska, by Henry C. Belg ______________________ A study of rhenium and molybdenum in uranium ore from the Runge mine, Fall River County, South Dakota, by means of a spectrographic and concentration method, by A. T. MyerS, J. C. Hamilton, and V. R. Wilmarth _____________ A study of uranium migration in sandstone-type ore deposits, by John N. Rosholt, Jr _____________________________ Distribution and lithologic characteristics of sandstone beds that contain deposits of copper, vanadium, and uranium, by R. P. Fischer and J. H. Stewart ______________________________________________________________________ Lead-isotope age studies in Carbon County, Pennsylvania, by T. W. Stern, L. R. Stieif, Harry Klemic, and M. H. Delevaux ____________________________________________________________________________________________ Uranium at Palangana salt dome, Duval County, Texas, by Alice D. Weeks and D. Hoye Eargle __________________ Paragenesis of uranium ores in Todilto limestone near Grants, New Mexico, by Alfred H. Truesdell and Alice D. Weeks _______________________________________________________________________________________________ Pitchblende identified in a sandstone-type uranium deposit in the central part of the Ambrosia Lake district, New Mexico, by Harry C. Granger _________________________________________________________________________ . Metamorphic grade and the abundance of ThOz in monazite, by William C. Overstreet ___________________________ gy of light metals and industrial minerals . Concentrations of “ilmenite” in the Miocene and post-Miocene formations near Trenton, New Jersey, by James P. Owens, James P. Minard, Donald R. Wiesnet, and Frank J. Markewicz ______________________________________ Bloating ‘clay in Miocene strata of Maryland, New Jersey, and Virginia, by Maxwell M. Knechtel and John W. Hosterman __________________________________________________________________________________________ Significance of unusual mineral occurrence at Hicks Dome, Hardin County, Illinois, by Robert D. Trace ____________ Phosphate and associated resources in Permian rocks of southwestern Montana, by Roger W. Swanson _____________ Hugo pegmatite, Keystone, South Dakota, by J. J. Norton __________________________________________________ A new beryllium deposit at the Mount Wheeler mine, White Pine County, Nevada, by H. K. Stager ................ Pre-mineralization faulting in the Lake George area, Park County, Colorado, by C. C. Hawley, W. N. Sharp, and W. R. Griffitts _________________________________________________________________________________________ Bertrandite-bearing greisen, a new beryllium ore, in the Lake George district, Colorado, by W. N. Sharp and C. C. Hawley ______________________________________________________________________________________________ Geology of fuels 36. Regional aeromagnetic surveys of possible petroleum provinces in Alaska, by Isidore Zietz, G. E. Andreasen, and Arthur Grantz ________________________________________________________________________________________ III Page B1 2 5 8 10 12 13 14 17 20 21 23 25 27 29 30 33 35 38 39 41 42 45 48 52 54 55 73 75 IV CONTENTS Geology of fuels—Continued 37. 38. 39. 40. 41. 42. Studies of helium and associated natural gases, by Arthur P. Pierce ____________________________________________ The interpretation of Tertiary swamp types in brown coal, by Gerhard O. W. Kremp and Anton J. Kovar _________ Coal reserves of the United States, January 1, 1960, by Paul Averitt __________________________________________ Relation of the minor element content of coal to possible source rocks, by Peter Zubovic, Taisia Stadnichenko, and Nola B. Shefl'ey _______________________________________________________________________________________ The association of some minor elements with organic and inorganic phases of coal, by Peter Zubovic, Taisia Stad— nichenko, and Nola B. Sheffey __________________________________________________________________________ Comparative abundance of the minor elements in coals from different parts of the United States, by Peter Zubovic, Taisia Stadnichenko, and Nola B. Shefiey ________________________________________________________________ Exploration and mapping techniques 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. t 53. 54. 55. - 56. 57. 58. 59. 60. 61. 62. Field application of ion-exchange resins in hydrogeochemical prospecting, by F. C. Canney and D. B. Hawkins ______ Geochemical prospecting for beryllium, by Wallace R. Griflitts and U. Oda _____________________________________ Variations in base-metal contents of monzonitic intrusives, by Wallace R. Grifiitts and H. M. Nakagawa ____________ Geochemistry of sandstones and related vegetation in the Yellow Cat area of the Thompson district, Grand County, Utah, by Helen L. Cannon ______________________________________________________________________________ Geochemical prospecting for copper in the Rocky Range, Beaver County, Utah, by R. L. Erickson and A. P. Marranzino ___________________________________________________________________________________________ Soil and plant sampling at the Mahoney Creek lead-zinc deposit, Revillagigedo Island, southeastern Alaska, by Hansford T. Shacklette ________________________________________________________________________________ Geochemical exploration in Alaska, by Robert M. Chapman and Hansford T. Shacklette _________________________ Thermoluminescence and porosity of host rocks at the Eagle mine, Gilman, Colorado, by Carl H. Roach ____________ Usefulness of the emanation method in geologic exploration, by Allan B. Tanner- - - _ _ _ - _ _ _ - _ _ _ _ _ _ _ ; _____________ Polar charts for evaluating magnetic anomalies of three-dimensional bodies, by Roland G. Henderson _________________ Magnetic evidence for the attitude of a buried magnetic mass, by Gordon E. Andreasen and Isidore Zietz ______________ Use of aeromagnetic data to determine geologic structure in northern Maine, by John W. Allingham _______________ Correlation of aeroradioactivity data and areal geology, by Robert B. Guillou and Robert G. Schmidt ______________ Mapping conductive strata by electromagnetic methods, by F. C. Frischknecht and E. B. Ekren __________________ Electrical properties of sulfide ores in igneous and metamorphic rocks near East Union, Maine, by L. A. Anderson _______ Electrical properties of zinc-bearing rocks in Jefferson County, Tennessee, by G. V. Keller ________________________ Terrain corrections using an electronic digital computer, by Martin F. Kane ____________________________________ Application of gravity surveys to chromite exploration in Camagiiey Province, Cuba, by W. E. Davis, W. H. Jackson, and D. H. Richter _____________________________________________________________________________________ Spectral reflectance measurements as a basis for film-filter selection for photographic differentiation of rock units, by William A. Fischer _____________________________________________________________________________________ Technique for viewing moon photographs stereoscopically, by Robert J. Hackman _______________________________ Geology applied to engineering and public health 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. Some thermal effects of a roadway on permafrost, by Gordon W. Greene, Arthur H. Lachenbruch, and Max C. Brewer- _ Tentative correlation between coal bumps and orientation of mine workings in the Sunnyside No. 1 mine, Utah, by Frank W. Osterwald and Harold Brodsky _________________________________________________________________ Review of the causes of subsidence, by Alice S. Allen _________________________________________________________ A sample of California Coast Range landslides, by M. G. Bonilla ________________________________________ , ______ Alteration of tuffs by Rainier underground nuclear explosion, Nevada Test Site, Nye County, Nevada, by V. R. Wil- marth, Theodore Botinelly, and R. E. Wilcox _____________________________________________________________ Distribution of gamma radioactivity, radioactive glass, and temperature surrounding the site of the Rainier under: ground nuclear explosion, Nevada, by C. M. Bunker, W. H. Diment, and V. R. Wilmarth ________________________ Gravity and seismic exploration at the Nevada Test Site, by W. H. Diment, D. L. Healey, and J. C. Roller ________ Maximum ground accelerations caused by nuclear explosions at distances of 5 to 300 kilometers, by W. H. Diment, S. W. Stewart, and J. C. Roller _________________________________________________________________________ Cation exchange with vermiculite, by Marian M. Schnepfe ___________________________________________________ Preparation of stable gelatin-montmorillonite clay extrusions, by Irving May ___________________________________ Variation of aluminum, sodium, and manganese in common rocks, by James R. Burns- , , , _ _ _ , _ _ _ , _ _ _ - A _ _ _ _ A _ 7 _ _ _ Geology of Eastern United States 74. 75. 76. 77. 78. 79. Pre-Silurian stratigraphy in the Shin Pond and Stacyville quadrangles, Maine, by Robert B. Neuman .............. A comparison of two estimates of the thorium content of the Conway granite, New Hampshire, by F. J. Flanagan, W. L. Smith, and A. M. Sherwood ________________________________________________________________________ Possible use of boron, chromium, and nickel content in correlating Triassic igneous rocks in Connecticut, by P. M. Hanshaw and P. R. Barnett ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ._ ______ Coral faunas in the Onondaga limestone of New York, by William A. Oliver, Jr _________________________________ Geophysical and geological interpretation of a Triassic structure in easternPennsylvania, by Isidore Zietz and Carlyle Bromery _____________________________________________________________________________________________ Page B 77 79 8 1 82 84 87 89 90 93 96 98 102 104 107 111 112 114 117 119 121 125 128 132 133 136 139 141' 144 147 149 149 151 156 160 161 163 164 166 168 170 172 174 178 CONTENTS Geology of Eastern United States—Continued 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. Taconic and post-Taconic folds in eastern Pennsylvania and western New Jersey, by Avery A. Drake, Jr., Robert E. Davis, and Donald C. Alvord ___________________________________________________________________________ Late Paleozoic orogeny in eastern Pennsylvania consists of five progressive stages, by Harold H. Arndt and Gordon H. Wood, Jr _________________________________________________________________________________________ Differential subsidence of the southern part of the New Jersey Coastal Plain since early Late Cretaceous time, by James P. Minard and James P. Owens ___________________________________________________________________ Drowned valley topography at beginning of Middle Ordovician deposition in southwest Virginia and northern Tennes- see, by Leonard D. Harris ______________________________________________________________________________ A synthesis of geologic work in the Concord area, North Carolina, by Henry Bell III ____________________________ Aeromagnetic and aeroradioactivity survey of the Concord quadrangle, North Carolina, by Robert W. Johnson, Jr., and Robert G. Bates ___________________________________________________________________________________ A major topographic lineament in western North Carolina and its possible structural significance, by John C. Reed, Jr. ., and Bruce H. Bryant __________________________________________________________________________________ Geologic relations inferred from the provisional geologic map of the crystalline rocks of South Carolina, by William C Overstreet and Henry Bell III __________________________________________________________________________ Determination of structure in the Appalachian basin by geophysical methods, by Elizabeth R. King and Isidore Zietz- _ Residual origin of the “Pleistocene” sand mantle in central Florida Uplands and its bearing on marine terraces and Cenozoic uplift, by Z. S. Altschuler and E. J. Young _______________________________________________________ A tropical sea in central Georgia in late Oligocene time, by Esther R. Applin ___________________________________ Significance of changes in thickness and lithofacies of the Sunniland limestone, Collier County, Florida, by Paul L. Applin _______________________________________________________________________________________________ Significance of loess deposits along the Ohio River valley, by Louis L. Ray _____________________________________ Magnetization of volcanic rocks in the Lake Superior geosyncline, by Gordon D. Bath ___________________________ Geology of Western Conterminous United States 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. \ 108.‘ 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. Measurements of electrical properties of rocks in southeast Missouri, by C. J. Zablocki ____________________________ Interpretation of aeromagnetic anomalies in southeast Missouri, by John W. Allingham __________________________ Some aftershocks of the Hebgen Lake, Montana, earthquake of August 1959, by S. W. Stewart, R. B. Hofmann, and W. H. Diment ________________________________________________________________________________________ Depth soundings in Hebgen Lake, Montana, after the earthquake of August 17, 1959, by W. H. Jackson ___________ Correlation of alpine and continental glacial deposits of Glacier National Park and adjacent .high plains, Montana, by Gerald M. Richmond _______________________________________________________________________________ The late Quaternary age of obsidian-rhyolite flows in the western part of Yellowstone National Park, Wyoming, by Gerald M. Richmond and Warren Hamilton ______________________________________________________________ Distribution of corals 1n the Madison group and correlative strata in Montana, western Wyoming, and northeastern Utah, by William J. Sando _____________________________________________________________________________ Middle Tertiary unconformity in southwestern Montana, by G. D. Robinson ___________________________________ Configuration of the 10N pluton, Three Forks, Montana, by Isidore Zietz ______________________________________ Metamorphism and thrust faulting in the Riggins quadrangle, Idaho, by Warren Hamilton _______________________ Diverse interfingering Carboniferous strata in the Mackay quadrangle, Idaho, by Clyde P. Ross __________________ Progressive growth of anticlines during Late Cretaceous and Paleocene time in central Wyoming, by William R. Keefer _______________________________________________________________________________________________ The “break-away” point of Heart Mountain detachment fault in northwestern Wyoming, by William G. Pierce____ Regional geologic interpretation of aeromagnetic and gravity data for the Rowe-Mora area, New Mexico, by Gordon E. Andreasen, Martin F. Kane, and Isidore Zietz __________________________________________________________ Southwestern edge of late Paleozoic landmass in New Mexico, by George 0. Bachman ___________________________ New information on the areal extent of some Upper Cretaceous units in northwestern New Mexico, by Calle H. Dane- _ Lithologic subdivisions of the Redwall limestone in northern Arizona—their paleogeographic and economic significance, by Edwin D. McKee __________________________________________________________________________________ Pliocene sediments near Salida, Chaffee County, Colorado, by Ralph E. Van Alstine, and G. Edward Lewis ________ Some Late Cretaceous strand lines in northwestern Colorado and northeastern Utah, by A. D. Zapp and W. A. Cobban_ Stratigraphy and structure of the Precambrian metamorphic rocks in the Tenmile Range, Colorado, by A. H. Kosch- mann and M. H. Bergendahl ___________________________________________________________________________ Salt anticlines and deep-seated structures in the Paradox basin, Colorado and Utah, by H. R. Joesting and J. E. Case- - Distribution and physiographic significance of the Browns Park formation, Flaming Gorge and Red Canyon areas, Utah- Colorado, by Wallace R. Hansen, Douglas M. Kinney, and John M. Good ______________________________ Probable late Miocene age of the North Park formation in the North Park area, Colorado, by W. J. Hail, Jr., and G. E. Lewis __________________________________________________________________________________________ Paleocene and Eocene age of the Coalmont formation, North Park, Colorado, by W. J. Hail, Jr., and Estella B. Leopold ______________________________________________________________________________________________ Pre-Cutler unconformities and early growth of the Paradox Valley and Gypsum Valley salt anticlines, Colorado, by D. P. Elston and E. R. Landis __________________________________________________________________________ V Page B 180 182 184 186 189 192 195 197 199 202 207 209 211 212 214 216 219 221 223 224 225 227 229 230 232 233 236 238 239 241 243 245 246 __..m 249 252 257 259 260 261 265 VI CONTENTS Geology of Western Conterminous United States—Continued Page 120. Structural features of pyroclastic rocks of the Oak Spring formation at the Nevada Test Site, Nye County, Nevada, as related to the topography of the underlying surface, by F. N. Houser and F. G. Poole ___________________________ B266 121. Origin of the Amargosa thrust fault, Death Valley area, California: a result of strike-slip faulting in Tertiary time, by Harald Drewes ______________________________________________________________________________________ 268 122. Bedding—plane thrust faults east of Connors Pass, Schell Creek Range, eastern Nevada, by Harald Drewes __________ 270 123. Possible interbasin circulation of ground water in the southern part of the Great Basin, by Charles B. Hunt and T. W. Robinson _______________________________________________________________________________________ 273 124. Observations of current tilting of the earth’s surface in the Death Valley, California, area, by Gordon W. Greene and Charles B. Hunt ______________________________________________________________________________________ 275 12.5. Pliocene(?) sediments of salt water origin near Blythe, southeastern California, by Warren Hamilton ________________ 276 126. Structure in the Big Maria Mountains of southeastern California, by Warren Hamilton __________________________ 277 127. Fossil Foraminifera from the southeastern California deserts, by Patsy Beckstead Smith _________________________ 278 128. Time of the last displacement on the middle part of the Garlock fault, California, by George I. Smith ______________ 280 129. Welded tuffs in the northern Toiyabe Range, Nevada, by Harold Masursky ____________________________________ 281 130. Regional gravity survey of part of the Basin and Range province, by Don R. Mabey ____________________________ 283 , 131. Mesozoic age of roof pendants in west-central Nevada, by James G. Moore _____________________________________ 285 132. Identification of the Dunderberg shale of Late Cambrian age in the eastern Great Basin, by Allison R. Palmer ______ 289 133. Intrusive rocks of Permian and Triassic age in the Humboldt Range, Nevada, by Robert E. Wallace, Donald B. Tatlock, and Norman J. Silberling _______________________________________________________________________ 291 134. Regional significance of some lacustrine limestones in Lincoln County, Nevada, recently dated as Miocene, by Charles M. Tschanz ___________________________________________________________________________________ 293 135. Evidence in the Snake River Plain, Idaho, of a catastrophic flood from Pleistocene Lake Bonneville, by Harold E. Malde _______________________________________________________________________________________________ 295 136. Alkalic lava flow, with fluidity of basalt, in the Snake River Plain, Idaho, by Howard A. Powers ____________________ 297 137. A distinctive chemical characteristic of Snake River basalts of Idaho, by Howard A. Powers ______________________ 298 138. Age and correlation of some unnamed volcanic rocks in south-central Oregon, by George W. Walker _______________ 298 139. Upper Triassic graywackes and associated rocks in the Aldrich Mountains, Oregon, by T. P. Thayer and C. E. Brown- 300 140. The John Day formation in the Monument quadrangle, Oregon, by Richard V. Fisher and Ray E. Wilcox _________ 302 141. The Republic graben, a major structure in northeastern Washington, by Mortimer H. Staatz _____________________ 304 142. Suggested source of Miocene volcanic detritus flanking the central Cascade Range, Washington, by Leonard M. Gard, Jr __________ ' ___________________________________________________________________________________ 306 143. Late Recent age of Mount St. Helens volcano, Washington, by D. R. Mullineaux and D. R. Crandell _____________ 307 144. Cenozoic volcanism in the Oregon Cascades, by Dallas L. Peck _______________________________________________ 308 145. Rodingite from Angel Island, San Francisco Bay, California, by Julius Schlocker ________________________________ 311 146. Gravity anomalies at Mount Whitney, California, by H. W. Oliver ____________________________________________ 313 147. Relations between Abrams mica schist and Salmon hornblende schist in Weaverville quadrangle, California, by William P. Irwin ______________________________________________________________________________________ 315 148. Evidence for two stages of deformation in the western Sierra Nevada metamorphic belt, California, by Lorin D. Clark- 316 r 149. Early Cretaceous fossils in submarine slump deposits of Late Cretaceous age, northern Sacramento Valley, California, by Robert D. Brown, Jr., and Ernest I. Rich _____________________________________________________________ 318 150. Gravity variations and the geology of the Los Angeles Basin of California, by Thane H. McCulloh ________________ 320 151. Previously unreported Pliocene Mollusca from the southeastern Los Angeles Basin, by J. G. Vedder _______________ 326 Geology of Alaska 152. Cenozoic sediments beneath the central Yukon Flats, Alaska, by John R. Williams ______________________________ 329 ,153’. The Cook Inlet, Alaska, glacial record and Quaternary classification, by Thor N. V. Karlstrom ___________________ 330 154. .Surflcial deposits of Alaska, by Thor N. V. Karlstrom ________________________________________________________ 333 155. Recent eustatic sea-level fluctuations recorded by Arctic beach ridges, by G. W. Moore __________________________ 335 156. Generalized stratigraphic section of the Lisburne group in the Point Hope A—2 quadrangle, northwestern Alaska, by Russell H. Campbell ___________________________________________________________________________________ 337 157. A marine fauna probably of late Pliocene age near Kivalina, Alaska, by D. M. Hopkins and F. S. MacNeil ________ 339 158. Possible significance of broad magnetic highs over belts of moderately deformed sedimentary rocks in Alaska and California, by Arthur Grantz and Isidore Zietz ____________________________________________________________ 342 159. Stratigraphy and age of the Matanuska formation, south-central Alaska, by Arthur Grantz and David L. Jones____ 347 160. Radiocarbon dates relating to the Gubik formation, northern Alaska, by Henry W. Coulter, Keith M. Hussey, and John B. O’Sullivan ____________________________________________________________________________________ 350 161. Metasedimentary rocks in the south-central Brooks Range, Alaska, by William P. Brosgé ______________________ 351 , 162. Slump structures in Pleistocene lake sediments, Copper River Basin, Alaska, by Donald R. Nichols ______________ 353 Geology of Hawaii, Puerto Rico, Pacific Islands, and Antarctica 163. Pahala ash—an unusual deposit from Kilauea Volcano, Hawaii, by George D. Fraser ____________________________ 354 ‘ 164. Sinkholes and towers in the karst area of north-central Puerto Rico, by Watson H. Monroe ...................... 356 165. Structural control of hydrothermal alteration in some volcanic rocks in Puerto Rico, by M. H. Pease, Jr ........... 360 CONTENTS Geology of Hawaii, Puerto Rico, Pacific Islands, and Antarctica—Continued 166. 167. 168. 169. 170. 171. 172. 173. 174. Successive thrust and transcurrent faulting during the early Tertiary in south-central l’uerto Rico, by Lynn Glover III and Peter H. Mattson _________________________________________________________________________________ Compressional graben and horst structures in east- central Puerto Rico, by R. P. Briggs and M. H. Pease, Jr _______ Stratigraphic distribution of detrital quartz in pre- -Oligocene rocks' in south- central Puerto Rico, by Peter H. Mattson and Lynn Glover III __________________________________________________________________________________ Occurrences of bauxitic clay in the karst area of north- central Puerto Rico, by Fred A. Hildebrand-_____-__; ______ The stratigraphy of Ishigaki-shima, Ryl‘ikyfi-rettfi, by Helen L. Foster _________________________________________ Fossil mammals from Ishigaki—shima, Ryfikyu-rettfi, by Frank C. Whitmore, Jr _________________________________ Distribution of molluscan faunas in the Pacific islands during the Cenozoic, by Harry S. Ladd ____________________ Geology of Taylor Glacier-Taylor Dry Valley region, South Victoria Land, Antarctica, by Warren Hamilton and Philip T. Hayes _______________________________________________________________________________________ New interpretation of Antarctic tectonics, by Warren Hamilton _______________________________________________ Paleontology, geomorphology, and plant ecology 175. Gigantopteridaceae in Permian floras of the Southwestern United States, by Sergius H. Mamay ___________________ 176. Upper Paleozoic floral zones of the United States, by Charles B. Read and Sergius H. Mamay ____________________ 177. Fossil spoor and their environmental significance in Morrow and Atoka series, Pennsylvanian, Washington County, Arkansas, by Lloyd G. Henbest _________________________________________________________________________ 178. Paleontologic significance of shell composition and diagenesis of certain late Paleozoic sedentary Foraminifera, by Lloyd G. Henbest _____________________________________________________________________________________ 179. Relation of solution features to chemical character of water in the Shenandoah Valley, Virginia, by John T. Hack--- 180. Some examples of geologic factors in plant distribution, by Charles B. Hunt ____________________________________ Geophysics 181. Rate of melting at the bottom of floating ice, by David F. Barnes and John E. Hobbie ___________________________ 182. Internal friction and rigidity modulus of Solenhofen limestone over a wide frequency range, by L. Peselnick and W. F. Outerbridge _____________________________________________________________________________________ 183. Physical properties of tuffs of the Oak Spring formation, Nevada, by George V. Keller ___________________________ 184. Magnetic susceptibility and thermoluminescence of calcite, by Frank E. Senftle, Arthur Thorpe, and Francis J. Flanagan _____________________________________________________________________________________________ 185. Salt features that simulate ground patterns formed in cold climates, by Charles B. Hunt and A. L. Washburn ______ 186. Thermal contraction cracks and ice wedges in permafrost, by Arthur H. Lachenbruch ____________________________ 187. Contraction-crack polygons, by Arthur H. Lachenbruch ______________________________________________________ 188. Curvature of normal faults in the Basin and Range province of the Western United States, by James G. Moore _____ 189. Volcanism in eastern California—a proposed eruption mechanism, by L. C. Pakiser ______________________________ 190. Some relationships between geology and effects of underground nuclear explosions at Nevada Test Site, Nye County, Nevada, by F. A. McKeown and D. D. Dickey ___________________________________________________________ 191. Structural effects of Rainier, Logan, and Blanca underground nuclear explosions, Nevada Test Site, Nye County, Nevada, by V. R. Wilmarth and F. A. McKeown _________________________________________________________ 192. Brecciation and mixing of rock by strong shock, by Eugene M. Shoemaker _____________________________________ 193. Paleomagnetism, polar wandering, and continental drift, by Richard R. Doell and Allan V. Cox ___________________ 194. Preparation of an accurate equal-area projection, by Richard R. Doell and Robert E. Altenhofen _________________ Mineralogy, geochemistry, and petrology 195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207. 208. Crystal habit of frondelite, Sapucaia pegmatite mine, Minas Gerais, Brazil, by Marie Louise Lindberg _____________ Some characteristics of glauconite from the coastal plain formations of New Jersey, by James P. Owens and James P. Minard ______________________________________________________________________________________________ X-ray determinative curve for natural olivine of composition Foso—m, by Everett D. Jackson- _ - - - - - - - _ - _ - _ _ - _ - - - - L g": Acidic properties of Fithian “illite”, by Dorothy Carroll and Alfred M. Pommer ________________________________ Carbon dioxide and alumina in the potentiometric titration of H-montmorillonite, by Dorothy Carroll _____________ Changes in thermogravimetric curves of calcium sulfate dihydrate with variations in the heating rate, by Charles A. Kinser _______________________________________________________________________________________________ Synthetic bayleyite, by Robert Meyrowitz and Marie Louise Lindberg _________________________________________ Synthetic hydrous boron micas, by Hans P. Eugster and Thomas L. Wright _____________________________________ Recent developments in the crystal chemistry of vanadium oxide minerals, by Howard T. Evans, Jr _______________ Authigenic rhodochrosite spherules from Gardner Creek, Kentucky, by E. C. T. Chao and William E. Davies ______ Stratigraphic variations in mineralogy and chemical composition of the Pierre shale in South Dakota and adjacent parts of North Dakota, Nebraska, Wyoming, and Montana, by Harry A. Tourtelot, Leonard G. Schultz, and James R. Gill _________________________________________________________________________________________ Summary of chemical characteristics of some waters of deep origin, by Donald E. White ________________________ .- Geochemical investigation of molybdenum at Nevares Spring in Death Valley, California, by F. N. Ward, H. M. Nakagawa, and Charles B. Hunt ________________________________ , _______________________________________ The Death Valley salt pan, 3. study of evaporites, by Charles B. Hunt __________________________________________ VII Page B363 365 367 368 372 372 374 376 379 380 381 383 386 387 390 392 395’ 396 401 403 404 406 409 411 415 418 423 426 427 429 430 432 434 436 438 440 441 443 446 447 452 454 456 ‘23:. VIII CONTENTS Mineralogy, geochemistry, and petrology—Continued 209. 210. 211. 212. 213. 214. Early stages of evaporite deposition, by E-an Zen ___________________________________________________________ Spatial relations of fossils and bedded cherts in the Redwall limestone, Arizona, by E. D. McKee _________________ Structurally localized metamorphism of manganese deposits in Aroostook County, Maine, by Louis Pavlides _______ Migration of elements during metamorphism in the northwest Adirondack Mountains, New York, by A. E. J. Engel and Celeste G. Engel _____________________ ' _____________________________________________________________ Chilled contacts and volcanic phenomena associated with the Cloudy Pass batholith,Washingt0n, by Fred W. Cater, Jr- The role of impermeable rocks in controlling zeolitic alteration of tuff, by A. B. Gibbons, E. N. Hinrichs, and Theodore Botinelly _____________________________________________________________________________________________ Analytical and petrographic methods 215. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. Index- Determination of total iron in chromite and chrome ore, by Joseph I. Dinnin ___________________________________ Determination of zinc in basalts and other rocks, by L. F. Rader, W. C. Swadley, H. H. Lipp, and Claude Huffman, Jr- Comparison of three methods for the determination of total and organic carbon in geochemical studies, by I. C. Frost- The determination of lead in iron-bearing materials, by Jesse J. Warr and Frank Cuttitta ________________________ Determination of lead in pyrites, by Frank Cuttitta and Jesse J. Warr _________________________________________ Determination of lead in zircon with dithizone, by Frank Cuttitta and Jesse J. Warr ____________________________ Preparation of lead iodide for mass spectrometry, by Frank Cuttitta and Jesse J. Warr __________________________ Determination of small quantities of oxygen adsorbed on anatase, by Frank Cuttitta ____________________________ Preliminary tests of isotopic fractionation of copper adsorbed on quartz and sphalerite, by Frank Cuttitta, F. E. Senftle, and E. C. Walker ______________________________________________________________________________ Water—soluble boron in sample containers, by Claude Hufl’man, Jr --------------------------------------------- Dilution—addition method for flame spectrophotometry, by F. S. Grimaldi ______________________________________ A spectrophotometric method for the determination of FeO in rocks, by Leonard Shapiro ________________________ Spectrochemical analysis using controlled atmospheres with a simple gas jet, by C. S. Annell and A. W. Helz _______ Combination of gravimetric and spectrographic methods in the analysis of silicates, by Rollin E. Stevens, Arthur A. Chodos, Raymond G. Havens, Elizabeth Godijn, and Sarah T. Neil _________________________________________ Sodium—sensitive glass electrodes in clay titrations, by Alfred M. Pommer -------------------------------------- Precipitation of salts from solution by ethyl alcohol as an aid to the study of evaporites, by R. A. Gulbrandsen _____ A gamma-ray absorption method for the determination of uranium in ores, by Alfred F. I-loyte ___________________ Method of grinding cesium iodide crystals, by Prudencio Martinez ____________________________________________ Page B458 461 463 465 471 473 476 477 480 483 485 486 487 488 491 493 495 496 497 499 502 504 504 507 509 GEOLOGICAL SURVEY RESEARCH I960 SHORT PAPERS IN THE GEOLOGICAL SCIENCES GEOLOGY 0F METALLIFEROUS DEPOSITS 1. AN HYPOTHESIS FOR THE ORIGIN OF ORE-FORMING FLUID By J. HOOVER MACKIN and EARL INGERSON, University of Washington, Seattle, Wash, and University of Texas, Austin, Tex. It is generally agreed that primary metalliferous veins are genetically related to intrusive igneous bodies, but in most mining districts the field relations demon- strate only that both the magma and the ore-forming fluid originated below the present surface, and it is therefore not possible to determine the nature of the genetic relationship by direct observation. The classi- cal view, based largely on theoretical considerations, holds that “metals and mineralizers,” present in minute proportions in the orginal melt, are concentrated in a rest liquid by fractional crystallization of rock-form- ing minerals devoid of those substances, and that during a late stage in the solidification of the intrusion the rest liquid escapes to form ore deposits. The different hypothesis outlined in this note is based on studies in the Iron Springs district, in southwestern Utah. In the Iron Springs district replacement ore bodies of magnetite and hematite occur in Jurassic limestone around the borders of early Teritiary laccoliths of granodiorite porphyry. The present erosion surface cuts the laccoliths at a favorable level, and it is possible to prove that the iron in the ore bodies was derived from the immediately adjacent porphyry. Several lines of evidence indicate that the iron was originally incorpo- rated in biotite and hornblende that crystallized in the melt in depth prior to the emplacement of the laccoliths. The outermost part of the typical Iron Springs lacco- lith—a “peripheral shell” 100 to 200 feet thick—con- solidated so rapidly that there was little deuteric altera- tion; the biotite and hornblende phenocrysts in the peripheral shell rock are fresh, and the field relations indicate that this rock yielded no ore. In the interior of the laccoliths, on the other hand, the. biotite and horn- blende phenocrysts were largely or completely destroyed by deuteric alteration, and the iron contained in them was released into the interstitial fluid of a slowly con- solidating crystal mush. This fluid escaped only from those parts of the laccoliths where renewed intrusion caused outbulging that opened gaping tension joints in the semisolid mush within the peripheral shell. The tension joints are bordered by bleached—appearing “selvages” as much as three or four inches in width; the selvage rock contains about 30 percent less iron than the rock midway between them. The faces of the selvaged joints are encrusted with magnetite and other minerals, and the joint fillings are in a merely descrip- tive sense fissure veins; they differ in origin from ordi- nary fissure veins, which are, if we may use a medieval analogy, the branches or leaves of the “mineral tree”, whereas the selvaged joints in the Iron Springs lacco- liths are the roots of the “mineral tree.” It is possible to walk across ledge outcrops from the deep interior of the laccoliths, where the interstitial fluid was all re- tained, upward and outward through the selvaged joint zone, where the iron of the ore deposits originated, and thence along magnetite-impregnated breccias formed by late-intrusive faults, that served as conduits for move- ment of the ore-forming fluid through the peripheral shell, and finally reach the replacement ore bodies at the contact. This theory implies that the replacement ore bodies of the Iron Springs district should occur only adjacent to parts of the laccoliths where there are selvaged joints, and, conversely, that the selvaged joints should be present only where there was late-intrusive distension. Ore bodies should therefore be restricted to segments of the contact that are convex outward in section, or in plan, or both; Where the contact is planar there should be no selvaged joints in the intrusive rock and no re- placement ore in the adjacent limestone. These im- plications are borne out by the actual distribution of the iron ore bodies. B1 B2 Crystalline hematite was deposited in cracks in the upper part of a silicic ignimbrite sheet formed by a nueé ardente eruption in the Iron Springs district just prior to emplacement of the laccoliths. As the ignim- brite sheet is almost identical in composition with the intrusions, one can reasonably assume that it was de- rived from the same magmatic source. The biotite and hornblende phenocrysts in a layer of Vitrophyre at the base of the ignimbrite sheet are perfectly fresh, but those in the middle part, where the matrix is stony— textured, are largely or wholly destroyed by deuteric alteration. The mechanics of origin of the ignimbrite sheet virtually rule out the possibility that the fluid which deposited the fumarolic hematite in its upper part was a magmatic rest liquid, enriched in “metals and mineralizers” by fractional crystallization; the re- lations indicate rather that the iron was released by deuteric alteration of intratelluric hornblende and bio- tite while the ignimbrite was consolidating at the surface. The “deuteric release” hypothesis of origin of the ore—forming fluid in the Iron Springs district has thus far been applied only in that district, and its validity depends entirely on specific lines of evidence developed there, but it is worthwhile to consider its possible appli- cation to a larger, long—standing geologic problem: Why is it that ore deposits tend to cluster around stocks and other hypabyssal intrusions consisting of porphyry, while the border zones and roof pendants of the great batholiths tend to be relatively barren? This relation- ship does not comport with the View that the ore metals are concentrated in a rest liquid by fractional crystalli- zation. Slow and complete crystallization in batho- lithic bodies should be much more favorable for such concentration than the conditions under which hypa— byssal bodies consolidate. The poverty of deep-seated bodies as compared with hypabyssal bodies is, on the GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S other hand, a direct and necessary consequence of the “deuteric” release hypothesis, not considered when that hypothesis was being formulated in the Iron Springs district. Iron is an integral constituent of some rock—forming minerals, and many of the other ore metals are readily accepted into the lattices of many of the rock—forming minerals, particularly biotite. If these minerals crys- tallize in a batholithic chamber and if the magma con- solidates completely in that same chamber, the metals locked up in the rock-forming minerals will not be available to form ore bodies. But if, during the period of crystallization, a phenocryst-bearing magma moves upward from the batholithic chamber to form a hypa- byssal body, deuteric decay of those phenocrysts that are unstable under the new conditions will release the metals to the interstitial fluid in the interior of the con- solidating body. A second requirement for the produc- tion of ore is continued growth of the hypabyssal body, or a renewed upsurging of magma which causes disten- sion in convex parts of the chamber at a time when the crystal mush in those parts is stiff enough to crack but is still chemically reactive; the gaping primary tension joints which will then penetrate into the semisolid mush can become the “roots of the mineral tree”. A general prerequisite is, of course, that the original melt shall contain all the substances needed for making ore; we have only iron oxide ore in Iron Springs because the magmas there happen to have been nearly devoid of sulfur, which is a constituent of most ores of other metals. The “deuteric release” hypothesis is useful because its consequences are readily deducible and very specific, and serve as a basis for diagnostic tests that can be applied Wherever the present erosion surface or mine workings cut an intrusive body at the level at which ore was released. 52‘ 2. VARIETIES OF SUPERGENE ZINC DEPOSITS IN THE UNITED STATES By A. V. HEYL, JR., and C. N. BOZION, Beltsville, Md., and Washington, DC. Deposits of oxidized zinc minerals are widely dis— tributed throughout the United States, especially in the general region of the Rocky Mountains and Basin and Range provinces, in the principal Mississippi Valley districts, in the Valley and Ridge province, and in the New Jersey Highlands and western Adirondacks. Most supergene zinc deposits can be classified into three main types in order of their abundance: (a) di- rect-replacement deposits (fig. 2.1), (c) wallrock de— posits (fig. 2.2),and (b) saprolitic (weathered in place) and residual (essentially in place, but compacted) ac- cumulations (fig. 2.3). A few supergene wurtzite de- METALLIFEROUS DEPOSITS K Clay and saprolite posits are known (for example, Horn Silver mine in Utah, Butler, 1913), also placer (Heyl and others, 1959, p. 131), bog (Cannon, 1955), and cave accumulations. Many deposits are combinations of several types. Fault with gouge ‘ Clay l‘ll Eocene imestone l (I l / xidize Zinc \ ore §)/ s Jurassic red shale O 5 FEET w FIGURE 2.1.—Direct-replacement deposit of zinc sulfide vein by oxidized zine minerals, Redmond, Utah. \ . \‘ Fissure s“ \. \“a xx \\\\§\\§/2/}\\\§§§\§~ \\\\\¥ /‘§\\\\~ \Ms \////,\\\\ FIGURE 2.2.—Wallrock deposits of oxidized zinc ore (after Loughlin, 1914), Tintic district, Utah. B3 Clay and saprolite igpre Sha y dolomite with issemin ta 5 aleri e ,< W FIGURE 2.3.—Saprolitic and residual accumulation of oxidized zinc ore (after Watson, 1905, fig. 16), Bertha, Va. DIRECT-REPLACEMENT DEPOSITS Deposits directly replacing hypogene sulfides are the most abundant. They retain the shape of the original ore bodies, although the metals are redistributed. In areas of slow oxidation and near—neutral conditions (pH 7—8), such as the upper Mississippi Valley (Heyl and others, 1959, p. 164—165), pseudomorphs of smith- sonite after sulfides are common; but in areas of deep and rapid oxidation zinc, copper, and iron tend to mi- grate towards the margins of the deposit where they reconcentrate as smithsonite, hemimorphite, malachite- azurite, and limonite casings, or as kidney—shaped, con- centric-shelled masses within the original ore body. Lead, silver, and gold migrate somewhat but redeposit nearly in place as supergene compounds and native gold and silver. Galena, completely replaced by cerus- site, anglesite, and plumbojarosite, is typical. Sphaler- ite is replaced by smithsonite and hemimorphite, and less commonly by hydrozincite, willemite, descloizite, and adamite. Outcrops are leached to a porous gossan of limonite, jasperoid, calcite, and less abundantly cerussite, plumbojarosite, cerargyrite, hemimorphite, and gold. Although many discussions of zinc oxidation state that supergene zinc deposits of commercial size in rocks lean in carbonate are rare or nonexistent, at least 24 are known. All are in the West, and some are rich and large, such as those in the Warm Springs district, Idaho (Umpleby and others, 1930), Clifton-Morenci (Lind— gren, 1905), Globe-Miami (Peterson, 1950, p. 98—112), Silver-Eureka (Wilson, 1951, , p. 83—97) districts of Arizona, and the Sedalia mine (Lindgren, 1908, p. 161— 166), Salida, Colorado. The “rule” that zinc is usually dispersed in solutions when deposits in noncarbonate rocks are oxidized obviously has many exceptions. The wall rocks include metasedimentary and clastic sedi- mentary rocks, gneisses, mafic and felsic igneous rocks, and calcareous quartzites. Most districts have under- B4 gone deep and intense oxidation, usually in areas of arid climate where supergene solutions are so sparse that most metals are redeposited within the original ore bodies as the solutions descend and evaporate. Descloizite, mottramite, and vanadinite are common as main or accessory minerals throughout the southern part of the Basin and Range province of the United States and Mexico. The source of the vanadium has been attributed by some (Kelly and others, 1958, p. 1596; Fischer, 1959, p. 222—223) to adjacent limestones. Newhouse (1934, p. 209—219) attributed the vanadium to traces in hypogene deposits. The present study shows that vanadium minerals are found in a wide variety of geologic environments throughout metallogenetic prov- inces irrespective of wallrocks, be they felsic or mafic igneous rocks, gneisses, amphibolites, limestones, or elastic rocks of different ages. Only one of several oxi- dized zinc deposits in the vanadium-bearing Colorado Plateau province contains vanadium minerals, which supports the ideas of Newhouse. VVillemite is a supergene mineral locally abundant in the West, and mined in at least nine localities; nearly all are in deeply oxidized districts of the Basin and Range province. For reasons unclear, it is restricted to certain deposits within districts. WALLROCK DEPOSITS Wallrock deposits (fig. 2.2) are common in the West, but uncommon in the East, except for very small pockets in walls of direct—replacement and saprolitic deposits and a single large supergene willemite ore body at Balmat, N.Y. (Brown, 1936). Wallrock pockets, casings, blankets, veins, and pipes of supergene zinc ores in carbonate rocks below and adjacent to leached sulfide bodies comprise some of the largest and richest deposits in the “rest, such as Lead- Ville, Colo. (Loughlin, 1918); Magdalena, N. Mex. (Loughlin and Koschmann, 1942) ; Goodsprings, Nev. (Hewett, 1931) ; and Cerro Gordo, Calif. (Knopf, 1918). The main minerals in these bodies commonly are smithsonite, hemimorphite, limonite, calcite, and jasperoid in massive, lamellar, and vuggy masses re- placing barren limestones (fig. 2.2). Chalcophanite, hydrohetaerolite, and sauconite are also abundant where manganese and silica are present, as at Leadville, Colo., and Tintic, Utah (Loughlin, 1914). In the Basin and Range province, where oxidation and leach- ing have been deep and intense over long periods, hydrozincite and aurichalcite occur in commercial quantities; for reasons unknown, hydrozincite is nearly restricted to the northern parts of that province. Wall— rock deposits contain very little of the gold, silver, lead, vanadium, molybdenum, antimony, and arsenic typical GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES of direct—replacement deposits. Where leached to a gossan, vuggy and concentrically banded limonite and jasperoid contain a little hemimorphite. SAPROLITIC ACCUMULATIONS AND RESIDUAL DEPOSITS Saprolitic accumulations (fig. 2.3) and residual de- posits are restricted to the East—the former to the warm and humid Ridge and Valley province. Sapro- litic accumulations include residual as well as rede- posited masses of smithsonite, hemimorphite, and locally, sauconite collected partly in saprolite and in compacted clay-filled solution pockets between buried pinnacles of unweathered limestone. The supergene minerals are derived from lean disseminated or mas— sive sphalerite in unweathered limestone pinnacles, such as at .Austinville and Bertha, Va. (Watson, 1905, p. 7 8—92). The unfractured sulfide-bearing limestone in the warm, wet climate is rapidly dissolved into pin— nacles and pockets by abundant vadose waters (pH 4—5) ; along fractures residual limestone solution-clay slumps into pockets, intermingled with limestone saprolite still in place. Smithsonite replaces part of the sphalerite and remains as residual masses embedded in the clayey pockets. Some zinc dissolves in vadose wa- ters but is redeposited as smithsonite, hemimorphite, and sauconite near the bottoms of the pockets when accumulated solutions become saturated in zinc. CONCLUSIONS The study shows that supergene zinc deposit-s most commonly directly replace the sulfide deposits, and they show regional patterns of geology dependent on (a) pH, rainfall, and climatic factors; (b) wallrocks and geologic variations between metallogenetic prov- inces. Deposits in noncarbonate wall rocks are fairly common, and many western deposits contain complex minerals previously thought to be uncommon. REFERENCES Brown, J. S., 1936, Supergene sphalerite, galena, and willemite at Balmat, N.Y.: Econ. Geology, v. 31, p. 331—354. Butler, B. S., 1913, Geology and ore deposits of the San Fran- cisco and adjacent districts: U.S. Geol. Survey Prof. Paper 80. Cannon, H. L., 19155, Geochemical relations of zinc—bearing peat to the Lockport dolomite, Orleans County, N.Y.: US. Geol. Survey Bull. 1000—D, p. 119—185. Fischer, R. P., 1959, Vanadium and uranium in rocks and ore deposits, in Garrels, R. M., and Larsen, E. S., 3d, Geo— chemistry and mineralogy of Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 219—230. Hewett, D. F., 1931, Geology and ore deposits of the Good- springs quadrangle, Nevada: US. Geol. Survey Prof. Paper 162, 172 p. ' METALLIFEROUS DEPOSITS Heyl, A. V., and others, 1959, The geology of the upper Missis- sippi Valley zinc-lead district: U.S. Geol. Survey Prof. Paper 309, p. 131, p. 164—165. Kelly, W. 0., and others, 1958, Progress in studies on leached outcrops [abs]: Geol. Soc. America Bull., v. 69, p. 1596. Knopf, Adolph, 1918, A geologic reconnaissance of the Inyo Range and the eastern slope of the Sierra Nevada, Calif: U.S. Geol. Survey Prof. Paper 110. Lingren, ‘Valdemar, 1905, The copper deposits of the Clifton- Morenci district, Ariz.: U.S. Geol. Survey Prof. Paper 43, 375 p. 1908, Notes on copper deposits in Chaffee, Fremont, and Jefferson Counties, 0010.: U.S. Geol. Survey Bull. 340, part 1, p. 161-166. Loughlin, G. F., 1914, The oxidized zinc deposits of the Tintic district: Econ. Geology, v. 9, no. 1, p. 1—19. 1918, The oxidized zinc ores of Leadville, 0010.: U.S. Geol. Survey Bull. 681. B5 Loughlin, G. F., and Koschmann, 1942, Geology and ore deposits of the Magdalena mining district, N. Mex.: U.S. Geol. Survey Prof. Paper 200. Newhouse, W. H., 1934, The source of vanadium, molybdenum, tungsten, and chromium in oxidized lead deposits: Am. Mineralogist, v. 19, no. 5, p. 209. Peterson, N. P., 1950, Arizona zinc and lead deposits; Lead and zinc deposits in the Globe-Miami district, Arizona: Arizona Bur. Mines Bull. 156, Geol. Ser. 18, p. 98~112. Umpleby, J. B., and others, 1930, Geology and ore deposits of the Wood River region, Idaho: U.S. Geol. Survey Bull. 814. Watson, T. L., 1905, Lead and zinc deposits of Virginia: Vir- ginia Geol. Survey Bull. 1, p. 78—92, fig. 16. Wilson, E. D., 1951, Silver and Eureka districts, Chap. 9 of Arizona zinc and lead deposits, Pt. 2: Arizona Bur. Mines Bull. 158, Geol. Ser. no. 19, p. 83—97. 3. LITHOFACIES OF THE COPPER HARBOR CONGLOMERATE, NORTHERN MICHIGAN . By IVALTER S. W'HITE and JAMES C. WRIGHT, Beltsville, Md., and Denver, Colo. The Copper Harbor conglomerate of northern Michi- gan crops out along the south limb of the Lake Su- perior syncline from Keweenaw County westward through Gogebic County, Mich. (fig. 3.1), and along its north limb on Isle Royale. The formation, which is of late Keweenawan age, is underlain by the Portage Lake lava series, a thick sequence of flood basalts of middle Keweenawan age, and overlain by the Nonesuch shale and the Freda sandstone of late Keweenawan age. The formation interfingers slightly with both the overlying shale and the underlying lava. The Copper Harbor conglomerate consists chiefly of red to brown arkosic conglomerate and sandstone, ce- mented with calcite and laumontite; most of its pebbles are of rhyolite, a few are of mafic lava, and other types are rare. Locally it contains interbedded groups of mafic and rhyolitic lava flows, and a very little red shale and volcanic ash. The ash, which contains mont- morillonite and tiny books of biotite, was observed in only seven beds in a series of holes drilled through the formation at Calumet. The distribution of the principal rock types in the formation is portrayed in figure 3.2. East of Houghton the contacts are based on detailed mapping (much of it by H. R. Cornwall), supported by airborne magne- tometer traverses in areas under Lake Superior. The relative proportions of sandstone and conglomerate are not known everywhere east of Houghton, but con- glomerate predominates where no pattern is used. The persistent sandstone unit shown in the lower part of the formation throughout Keweenaw County is based on a few outcrops and on prominent topographic expression (Cornwall, 1954). West of Houghton, exposures are generally poor and only a few small areas have been mapped in detail. The thickness of the formation and of its subdivisions at various places has been determined from breadth of outcrop. Our own field data are supplemented by scat— tered observations recorded in many published reports, and by the results of an airborne magnetometer survey of part of the area by the U.S. Geological Survey. The Copper Harbor conglomerate thins markedly at Houghton, where the formation appears to lap up on a. ridge of the underlying lavas. This ridge is the product of differential uplift, most of which occurred during the first. half of Copper Harbor time; the base of the formation is parallel with the two persistent con- glomerate beds in the underlying lava series, but its top is not (see fig. 3.2). Most of the thick accumulation of rhyolite that makes up a large part of the formation in western Ontonagon County is believed to consist of rhyolite flows that piled up close to their source. The area in which the rhyolite is thick and the overlying conglom- erate is thin (as little as 500 feet thick in places) is roughly outlined by a dashed line in figure 3.1 ; just out- B6 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 90° 48° 89° 88° /7 57/0 9 2 Southwestern . partof Manitou 'Isle Royale Island 89° KEWEENAW BAY 95$ 1 x) 0 47° 88 /o / 3414?- Jr' E1 \5 6 4 3 /0 ‘ Ontonagon HOUGHTONj 59 :: '_"’ 1 4 ' OWhite Pine $ “— I o ''''' ~ \>‘ ' '....> ! LAnse 3 K 7 'F_ | -_ ! IBAlééGA E 4 ,, -\ 8 ONTONAGON co 1 l O 10 20 30 4O 50 60 MILES i....:....1 1 l | J FIGURE 3.1.—Distribution of Copper Harbor conglomerate and its oriented sedimentary structures. 1, Jacobs ville sandstone; 2, Nonesuch shale and Freda sandstone; 3, Copper Harbor conglomerate; 4, Portage Lake lava series and lavas in lower part of Copper Harbor conglomerate; 5, average direction of current flow shown by crossbeds in conglomeratic sandstone; number beside each arrow gives the number of individ- ual observations included in average; 6, average direction of current flow shown by crossbeds in “red facies”; 7, direction of current flow indicated by imbrication of pebbles; 8, limit of thick mass of extrusive rhyolite. side this area, the conglomerate is 2,000 to 3,000 feet thick. The directions of the currents that deposited the con- glomerate were determined from the attitudes of cross- beds, and, at one place near Houghton, from that of im- bricated pebbles. Though many of the samplings of attitudes are small, and some are known to be biased because of the nature of the exposures, the measured directions indicate clearly, when taken together, that the conglomerate was deposited by northward flowing currents, in contrast with the rocks to be described next. A separate facies of the Copper Harbor conglomer- ate, here designated the “red facies,” is exposed in at least the western third of the area shown in figure 3.1. The dominant rock of this facies is platy fine- to me- dium-grained sandstone, redder than the rocks of the formation as a whole. This red sandstone occurs in thick sequences with very little interbedded conglomer- ate, and its statigraphic position is not everywhere the same. In Gogebic County it occurs only in the upper- most 200 to 500 feet of the formation (fig. 3.2), but at the Mendenhall location 250 feet or more of red platy sandstone underlies 500 feet of conglomerate and coarse brownish-red sandstone. North of White Pine, north of the line of figure 3.2, rocks of the red facies occur from 300 to at least 1,000 feet below the top of the formation. The currents that deposited the rocks of the red facies flowed southward, as indicated in figure 3.1 by arrows with dashed-line shafts. The Lake Superior basin was at least 60 or 70 miles across in late Keweenawan time. The conglomerate facies is interpreted as a piedmont fan, deposited by northward-flowing streams at the foot of hills along the southern margin of this basin. The great central expanse of the basin presumably had a more nearly hor- izontal surface, covered by finer grained sediments de- posited on flood plains or in standing water. The red facies is interpreted as a flood-plain deposit, trans- ported by currents that locally, at least, flowed south- ward on this broad alluvial plain to deposit material against the toe of the fan. We have suggested previously (White, 1960) that the copper in the base of the Nonesuch shale at White Pine and elsewhere (White and Wright, 1954, p. 715—716) B7 METALLIFEROUS DEPOSITS .wQEwm «>5 93A owfihom 3 con Swaaofiwnoo udwumwmaoa .u Cumin—m onwamwfieww .3 van—doofi $32 Efimmwn mo 303:8 .w muwuaflseouwufi. .3292: was “Ewan .m ”32??? JV ”5:2 05393 rm ”98% 65a .N mfiwuwfiofiwqoo .H .5550 nowmdsqo 53mm? 5 “3.595 Mina mo 55% $1.5 NH 3 m mm: 5503 we was .2me £95932 HO $43 E SPEQ d8 :33. MEEOE dwwEfiE 955.8: ga$§3wn8 Spam Enaco 23 go nomagwlwwcb oEafinguw'Nw 593% ooom 000m 000? OOOm OOON 000 H bmmm .MZ _ _ ...:143 _ mud: Om Om Ow Om ON OH o ... EH ml WE wE ”BEEN _ _ \ x a. n. . #53 $6. 8.3 owmtom .c./ Mn / / JJI w> ‘ // .... > a “M ..... II 1/ / >1,” ‘ / 79‘ 0/ I . / :[ug #W/J/ : \ / .n 1.] 3, //l U / /. I \\\\ / . .H... . BSmEewcou .831“. L880 .. m.» \\ .V .’ l ...:l .... . nu > > \ .00. N1» mu 1 .-...§ E . ..k 0—0 2me 0—0 Losmmcoz _ _ 0% _ _ _ _ _ _ pow _ c_c _ pmr mam d r r r. n T H n r r k m m m mam m mm 3 mm @mm mfi q. a a R NTm g TG 3mm dm GERRC H_m I H H e E-Hflnw W H.A n donw. mm A—Gk k ..w . C S u r m 10.5 E G H G N o m c n m N Oh M n. 1.1 o W E a U U_0 WMm OE OGela M.W H. p a E W 0 O T ) T W B M n 0 E E H H N h N 8 a C K 0 n 0 w M 0 P .>>W B8 may have been deposited from connate water, squeezed out of the Keweenawan sedimentary rocks during com- paction and diagenesis. This source of water would be very large and suitably located if the coarse-grained facies of the Copper Harbor conglomerate does indeed give way to fine-grained sediments in the central part of the Lake Superior basin, far down the dip from the copper deposits. The thick pile of rhyolite outlined by the dashed line in figure 3.1 may have acted like a buried hill to intensify the flow of water up into the Nonesuch shale; this mechanism could help explain the GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES unusual concentrations of copper close to the border of the thick mass of rhyolite. REFERENCES Cornwall, H. R., 1954, Bedrock geology of the Lake Medora quadrangle, Michigan: U.S. Geol. Survey Geol. Quad. Map GQ—52. White, W. S., 1960, The White Pine copper deposit: Econ. Geology, v. 55, p. 402—410. White, W. S., and Wright, J. C., 1954, e White Pine copper deposit, Ontonagon County, Michig n: Econ. Geology, v. 49, p. 675—716. 6% 4. RELATION OF' THE COLORADO MINERAL BELT TO PRECAMBRIAN STRUCTURE By OGDEN TWETO and P. K. SIMS, Denver, Colo. Work done in cooperation with Colorado State Metal Mining Fund Boa/rd The narrow northeast—trending Colorado mineral belt is characterized by intrusive porphyries and asso- ciated ore deposits of Laramide age, and in some places by fissures and faults of northeasterly trend. All the major mining districts of Colorado, except the uranium districts of southwestern Colorado and a few mining districts associated with isolated volcanic centers, such as Cripple Creek, are in this belt. The mineral belt extends diagonally across the gen- erally north-trending mountain ranges of the State for a distance of 250 miles—from the Front Range in cen- tral Colorado southwestward across the Park and Sawatch Ranges to the San Juan Mountains (fig. 4.1). It thus cuts indiscriminantly across the geologic grain of the State, occupies several different geologic environ— ments, and seems to be independent of the present mountain structure. Although the most conspicuous features of the min— eral belt are of Laramide age, the belt follows an ancient zone of weakness defined by northeast-trend- ing shear zones of Precambrian age, which form an echelon pattern in a strip that is nearly coextensive with the mineral belt. Many of these zones have not yet been fully mapped, but major shear zones of this group have been studied in detail in two areas—on the eastern flank of the Front Range (Moench, Har- rison, and Sims, 1954, 1958; Sims, Moench, and Har- rison, 1959; Harrison and Wells, 1959; J. D. Wells and D. M. Sheridan, oral communication, 1959) and in the northern part of the Sawatch Range (Tweto and Pearson, 1958). In the eastern part of the Front Range is the Idaho Springs-Ralston shear zone, marked by cataclasis and related small-scale cross folds, which lies along the southeastern side of the mineral belt (fig. 4.1). In the Sawatch Range, there is the composite Homestake shear zone which comprises: dozens of individual shear zones in a belt 7 or 8 miles wide. In the Park Range, which lies between the Front j and Sawatch Ranges, the northeast-trending line of shearing is interrupted by a major cross-trending shear zone, of Precambrian age, which localized the Gore and Mosquito faults in Laramide time. Lesser cross faults‘ of northwest trend are numerous in the Front Range, where they are known as breccia reefs (Lovering and Goddard, 1950). These faults originated in Precamo brian time but are in general younger than the north- east-trending shear zones, and many of them were re- activated during the Laramide. Intermittent movement. has occurred in the shear zones through most of the geologic time recorded in the region. Primary folds in the oldest metamorphic rocks, some of them oriented in stress fields confined to the shear zones, indicate that the shear zones existed at the stage of deformation by plastic flow. At a later stage, when pressure was less intense and temperature lower, shearing took place by fracturing and locally by minor cross-folding. Early fracturing occurred be- fore the metamorphic environment had permanently METALLIFEROUS DEPOSITS B9 Hot Sulphur Springs 0 l i %,Outlne l I #407000 0 LORADO' l | I ) Colorado Mineral Belt 15 MlLES I 106°OO’ MIDDLE , . E X P LA N AT | O N ff - : Stocks .Dikes Groups of sills Laramide intrusive rocks -o—o—o— Sedimentary rocks and surficnal deposits Precambrian rocks _ - - High-angle fault Dashed where inferred H Thrust fault Saw teeth on upper plate _‘~.,- v-v” Precambrian shear zone Outline of mineral belt FIGURE 4.1—Geologic setting of Precambrian shear zones and northeastern part of Colorado mineral belt. disappeared, and rocks formed at this stage are reor- ganized and recrystallized gneisses. Later shearing yielded cataclastic gneisses, mylonite, broad granulated zones, and locally pseudotachylyte. Still later, but still in the Precambrian, gouge, breccia, and fault zones were formed, partly by the degradation of earlier shear products of higher rank. Differential movements in parts of the regional zone of shearing continued intermittently through Paleozoic and Mesozoic time, mostly on a minor scale, as recorded by thinning, wedgeouts, and changes in facies of several sedimentary formations along the shear zone. In some places the shear zones formed a sharp border between the persistent positive and nega- tive areas that existed in Colorado during Paleozoic and Mesozoic time. 557753 0—60—2 With the onset of the Laramide orogeny, magma in- vaded the regional zone of shearing and imparted to it the conspicuous features that characterize the mineral belt—intrusive igneous bodies and ore deposits. Fault movement took place along the zone at this stage also but was in general on a smaller scale than it had been previously. Reasons for the appearance of magma in the ancient zone of weakness at this time, and the proc- esses by which it yielded a large family of porphyries and a remarkable variety of ore deposits, are major problems remaining for investigation. REFERENCES Harrison, J. E., and Wells, J. D., 1959, Geology and ore de- posits of the Chicago Creek area, Clear Creek County, Colorado: U.S. Geol. Survey Prof. Paper 319. B10 Lovering, T. S., and Goddard, E. N., 1950, Geology and ore deposits of the Front Range, Colorado: U.S. Geol. Survey Prof. Paper 223. Moench, R. H., Harrison, J. E., and Sims, P. K., 1954, Precam- brian structures in the vicinity of Idaho Springs, Front Range, Colorado [abs] : Geol. Soc. America Bull., v. 65, p. 1383-1384. 1958, Precambrian folding in the central part of the GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Front Range mineral belt, Colorado [abs]: Geol. Soc. America Bull., v. 69, p. 1737. Sims, P. K., Moench, R. H., and Harrison, J. E., 1959, Rela— tion of Front Range Mineral Belt to ancient Precambrian structures [abs]: Geol. Soc. America Bull., v. 70, p. 1749. Tweto, Ogden, and Pearson, R. C., 1958, Great Precambrian shear zone, Sawatch Range, Colorado [abs]: Geol. Soc. America Bull., v. 69, p. 1748. 5% .5. PRE-ORE AGE OF' FAULTS AT LEADVILLE, COLORADO By OGDEN TWETO, Denver, Colo. Work done in cooperation with Colorado State Metal M fining Fund Boa/rd In the Leadville mining district, Colorado, sedimen- tary rocks of Paleozoic age dip gently eastward and are broken by many faults, most of which are upthrown to the east. Porphyries of Laramide age form sills, dikes, and irregular bodies that cut the sedimentary rocks in an intricate pattern. Although the porphyries—pre- sumably derived from the same source as the ores— are all older than the ores, they are in general only weakly mineralized; the ore deposits are largely re— stricted to the sedimentary rocks in layers and blocks between bodies of porphyry. Faults displace many ore bodies, and for this reason many major faults of the district have been regarded as younger than the ores (Emmons, 1886; Emmons, Irving, and Loughlin, 1927). Recent studies within the Leadville district and north of it have revealed, however, that practically all the faults originated before the ore, although many un- derwent renewed movement during a post—ore stage. O 32' we 2395?? ’3?5?o§® v 0. :32: A." \ ' I. .k‘ d H c V v ' V V V v v ' o: ’03” 9‘0’3'0’ ’9 9} o o o o . 29292939320292. c b a FIGURE 5.1.——Cross-section sketches of relations between porphyry bodies and faults in the Leadville district, Colorado. Igne- ous rocks patterned and numbered; sedimentary rock units blank and lettered. METALLIFEROUS DEPOSITS The faults are dated by their relations to intrusive porphyries. Some 25 or 30 distinct varieties of por- phyry are recognized in the area, and about 15 of these show clear-cut age relations with respect to one another and hence can be fitted into an age sequence. Mem- bers of this sequence show many different kinds of re- lations to faults. Some varieties of porphyry are dis- placed by some faults but not by others; others are dis- placed by almost every fault they intersect, and still others by very few. Similarly, individual faults dis- place some porphyries but guided the emplacement of others and are cut by still others. Relations such as those sketched in figure 5.1 indicate that many of the faults existed at the time certain porphyries were em- placed, and that movement recurred on some faults dur- ing the period of porphyry emplacement. Clearly, both the faults and the porphyry bodies of the areas are products of the same general phase of the Laramide orogeny, and the porphyry sequence can thus be used as a time scale both to determine relative ages of faults and to trace evolution of the fault pattern. Results of such dating are shown in simplified form in figure 5.2 which illustrates the extent of faulting at four different stages during the period of porphyry em- placement. Some of the faults might be older than the ages assigned them, as they are dated only by relatively young members of the porphyry sequence, but they can— not be younger. On the other hand, the age of many of the faults is closly bracketed; the faults displace cer- tain porphyries but guided the emplacement of other, younger ones. Except as simplified because of scale, the fault pattern shown in the top diagram of figure 5.2 is the one that exists today. Yet the pattern was achieved before the period of porphyry intrusion came to an end, for some of the youngest porphyries locally obliterate the faults. These youngest porphyries, like the others, are hydro- thermally altered and weakly mineralized; they are clearly older than the ore. This being so, the faults all originated before the ore, although many have a his- tory of movement that extends virtually to the present. Faults that existed at the ore—depositing stage could afi'ect the original distribution of ore, as many obvious— ly did, and yet the resulting ore bodies could later have been displaced by renewed movement on these same faults. REFERENCES Emmons, S. F., 1886, Geology and mining industry of Leadville, Colorado: U.S. Geol. Survey Mon. 12. Emmons, S. F., Irving, J. D., and Loughlin, G. F., 1927, Geology and ore deposits of the Leadville mining district, Colo rado: U.S. Geol. Survey Prof. Paper 148. 6% B11 Faults in existence (Generalized pattern) Stage in porphyry— ore sequence By the time of the ore stage, a few faults in next diagram below had been locally obliterated by the latest porphyries Ore stage Younger porphyries Eagle River porphyry Syenodiorite Lincoln porphyry Rhyolite porphyry Johnson Gulch porphyry Evans Gulch porphyry Sacramento porphyry Elk Mountain porphyry Successively later stages within Laramide orogeny Pando porphyry includes White porphyry and Mt Zion porphyry \ I ll ll/ LeadviiieVL’ ,9 5 MILES FIGURE 5.2.—Fault pattern in the Leadville district, Colorado, at; successive stages defined by the sequence of porphyries. B12 GEOLOGICAL SURVEY RESEARCH 19 6 0— SHORT PAPERS IN THE GEOLOGICAL SCIENCES 6. PRE-ORE PROPYLITIZATION, SILVERTON CALDERA, COLORADO By WILBUR S. BURBANK, Exeter, N.H. Work done in cooperation with the Colorado State Metal M tntng Fund Board Several types of rock alteration, such as argillization, sericitization, and silicification that are closely related to ore deposition (Ransome, 1901; Burbank, 1941 and 1950), have been recognized in the Silverton caldera and surrounding area, northwestern San Juan Mountains, Colorado. Some alteration of the layered succession of calc-alkaline lavas and related pyroclastic rocks of late Tertiary age undoubtedly occurred during the period of eruptions. However, of principal concern here is the propylitic or quartz-carbonate—chlorite type of altera— tion that took place mostly prior to, but in part during, the period of ore deposition. This type of alteration becomes more pronounced with depth in certain parts of the caldera, and grades to a quartz—carbonate-albite- epidote-chlorite type analogous to the albite-epidote hornfels facies of low-grade contact metamorphism. Carbonate is locally either absent or a minor constituent in the albitic type. Pyrite is present in small quantities in much of the propylitized rocks. Problems involved in the alteration include: (a) the depth and source of the altering agents, (b) the reasons for its post-volcanic and pre-ore position in the sequence of events, and (c) the mechanism of pervasive penetra- tion of altering agents in the pores of many massive rocks whose initial permeability to liquid solutions must have been vanishingly low. Diffusion processes in a static medium occupying the rock pores are tentatively ruled out because of the extreme slowness of such proc— esses, the highly pervasive nature of the alteration, and the belief that except in near-surface positions the pores of the heated volcanic rocks nearby and within' the caldera could not have been initially saturated with aqueous liquids. Propylitic alteration has affected many cubic miles of volcanic rocks throughout and beyond the caldera. Carbon dioxide is believed to have been a major con— stituent of the agents of rock alteration although other gases undoubtedly were present. Estimates of carbon- ate formed range from 2 to 5 percent (equivalent to 100 to 250 feet of limestone per mile of rock); this amount is far greater than can be accounted for by ther— mal metamorphism of any known basement rocks. During Volcanism the gases tended to become dissi— pated rather than entrapped due to the highly explosive nature of many of the eruptions. Injections of clastic dikes composed of Precambrian rock fragments are in- dicative that gas pressures in the basement rocks tended to reach culmination during earlier stages of propylitic alteration. Intense propylitic alteration, following ces- sation of volcanic eruptions, may be attributed in part to final sealing of the vents. The occurrence of a partly carbonatized and mineralized breccia pipe at the edge of a gabbroic and granodioritic stock northwest of the Sil- verton caldera suggests that the primitive magmas were of similar composition, and that the propylitization was related to deep-seated crystallization and differen— titation of such magmas. The amounts of H20, 002, and 82 in basaltic magmas and in their siliceous differentiates suggest that gases rich in CO2 would be expelled during crystallization (Sheperd, 1938; Rubey, 1951, p. 1136, fig. 4). The ex- pulsion of CO2 also is suggested by the work of Morey and Fleischer (1940) on the system COz—H20~K20— SiOz, which shows that the solubility of C02 in alkali silicate solutions decreases much more rapidly than that _ of H20 as the silica content of the solution increases. They concluded (1940, p. 1056) that this process prob- ably would apply to more complex silicate mixtures. Garrels and Richter (1955) presented data to support the possibility that carbon dioxide could exist as a sep- arate phase in comparatively shallow environments be- cause of the low mutual solubilities of C02 and H20. It is postulated that the evolved gases invaded the deeper parts of the caldera and surrounding ground through previously heated rocks deficient in uncom- bined water, and that the gradients of pressure were es- tablished in a pervasive gas phase composed mainly of carbon dioxide. Alteration is inferred to have taken place in an open system by a series of coupled conden— sations and vaporizations in rock pores under osmotic conditions and under control of physical and chemical adsorption in capillary and sub-capillary spaces. Re— current actions are interpreted to consist of: (a) con- densation of gases in locally adsorbed water films; (b) partial solution of silicate minerals by the condensates; (c) mixing of saturated condensates with other droplets of liquid forced along by gas pressures; and ((1) re- action in these mixtures causing precipitation of new METALLIFEROUS DEPOSITS minerals. Continuous attack by new condensates of the active gases would maintain a certain degree of per- meability by solution of country rock and re-solution of precipitated material which would allow egress of solutions saturated with products of rock decomposi— tion. These solutions were forced by expanding gases into newly fractured rock and reopened fissure systems in numerous and repetitive stages of adjustment throughout this period of late activity. The resulting reactions between the gases, liquid con- densates, and solids could have caused widespread and highly pervasive propylitic alteration. Most of the pro— pylitized rocks are considered as an arrested stage of development in this reaction. The carbonatized and chloritized breccia pipe possibly represents the end stage of development—the result of long continued and concentrated passage of altering agents within a restricted volume of rock. B13 REFERENCES Burbank, W. S., 1941, Structural control of ore deposition in the Red Mountain, Sneffels, and Telluride districts of the San Juan Mountains, Colorado: Colorado Sci. Soc. Proc., v. 14, no. 5, p. 141—261. 1950, Problems of wall-rock alteration in shallow v01- canic environments: Colorado School of Mines Quart, v. 45, no. 18, p. 287—319. Garrels, R. M., and Richter, D. H., 1955, Is carbon dioxide an ore-forming fluid under shallow-earth conditions?: Econ. Geology, v. 50, p. 447—458. Morey, G. W., and Fleischer, Michael, 1940, Equilibrium between vapor and liquid phases in the system 002—H20—K20—Si0'2: Geol. Soc. America Bull., v. 51, p. 1035—1058. Ransome, F. L., 1901, A report on the economic geology of the Silverton quadrangle, Colorado: US. Geol. Survey Bull. 182, 265 p. Rubey, W. W., 1951, Geologic history of sea water: Geol. Soc. America Bull., v. 62, p. 1111—1147. Shepherd, E. S., 1938, The gases in rocks and some related prob- lems: Am. Jour. Sci., 5th ser., v. 35A, p. 311—351. 7. RING-FRACTURED BODIES IN THE SILVERTON CALDERA, COLORADO By ROBERT G. LUEDKE and WILBUR S. BURBANK, Washington, DC. and Exeter, NH. Work done in cooperation with the Colorado State Metal Mining Fund Board The Silverton caldera, in the northwestern part of the San Juan Mountains, Colorado, is a nearly circular volcanic center about 12 miles in diameter, filled with a layered succession over a mile thick of calc—alkaline lavas and related pyroclastic rocks of late Tertiary age. These rocks were complexly faulted and tilted by re— peated upthrust and collapse during and after subsi- dence of the main caldera floor. Within the margin of the caldera is a great zone of ring faults, as much as two miles wide, into which many pipelike bodies of quartz latite, rhyolite, and breccia were intruded, after the main episodes of extrusive activity. The intrusion of these rocks was followed by alteration and mineral- ization. Several smaller bodies of ring—fractured rock, each about a mile in diameter, are located in an apparently random fashion within the northern part of the cal- dera. Discontinuous ring fractures and faults around each of these bodies are superimposed upon pre—exist- ing structural features of the caldera without greatly disturbing them, though some early—formed shear zones and tilted blocks are slightly offset by the faults. Planar flow structures of the volcanic rocks within some of the tilted blocks locally dip inward from the arcuate breaks. Many of the veins and altered zones cross these ring-fractured bodies with little or no deflec- tion in trend. These ring—fractured bodies are neither volcanic vents nor intrusive plugs; they are cylindrical columns of the country .rock that were pushed up by magma, and that collapsed when magma was withdrawn and up— ward pressure released. The net downward displace- ment of the layered volcanic rocks amounted to as much as 200 feet. Their collapse was accompanied locally by minor injections of quartz latite and rhyolite into ring fractures and other fissures. A possible cause for the inferred withdrawal of magma might have been the intrusion of the pipelike bodies into the major ring-fault zone of the caldera. 6% B14 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 8. RELATION OF MINERALIZAT‘ION TO CALDERA SUBSIDENCE IN THE CREEDE DISTRICT, SAN JUAN MOUNTAINS, COLORADO By THOMAS A. STEVEN and JAMES C. RA'I'I‘E, Denver, Colo. Work done in cooperation with the Colorado State Metal M int/rig Fund Board and US. Atomic Energy Commission Detailed study of the volcanic rocks in the central San Juan Mountains has defined a subcircular caldera about 10 miles in diameter, which we have called the Creede caldera after the nearby town and mining dis— trict. The ores in the Creede district are localized along faults in a complex graben that extends outward from the caldera; these faults were active many times while the caldera area was subsiding but mineralization did not take place until the last main period of fault movement. The volcanic rocks exposed in this area include the upper units of the Potosi volcanic series of Larsen and Cross (1956, p. 30—167), and the younger Fisher quartz latite and Creede formation. The volcanic sequence we have determined, however, differs considerably from that defined previously in the San J uans, and in this paper informal local names are applied to most of the units. The oldest rocks exposed near Creede formed prior to any known caldera subsidence, and they record con- current accumulation from several volcanic centers. We have no knowledge of the original extent of any of these formations; only those parts of these and the suc- ceeding formations that we know or can reasonably extrapolate are shown by pattern on figure 8.1. The accumulation centering on Bachelor Mountain (fig. 8.1A) is more than 3,500 feet thick, and consists of welded rhyolite tufl grading up into non-welded pumi— ce us tuff. To the northeast, the Bachelor Mountain rocks intertongue with a great sequence of quartz latitic welded tuffs more than 4,000 feet thick. To the weft, Bachelor Mountain rocks overlie a local rhyolitic ac umulation, and intertongue with quartz latitic lava flows and breccias derived from a source west of the Creede district. The pumiceous eruptions of the Bachelor Mountain volcano culminated in the collapse of the probable vent area and in the development of several north~northwest trending normal faults (fig. 8.13). The exposed mar- gin of this early caldera is characterized by pervasively brecciated rock passing outward into strongly sheeted rock. The early caldera stage was followed by renewed eruptions of rhyolitic magma that deposited great sheets of welded ash flows over most of the Creede area (fig. 8.10). These rocks have a maximum aggregate thickness exceeding 2,500 feet. Southeast of Creede they are interlayered with quartz latitic lava flows and southwest of Creede are intertongued with dacitic flows and breccias. The main Creede caldera probably origi- nated as a result of these rhyolitic eruptions, as some faults along the eastern margin of the caldera were active at this time. Great volumes of quartz latitic ash (fig. 8.11?) were erupted following the rhyolitic intracaldera stage. Outside the main Creede caldera, the quartz latites form widespread sheets of tuff and welded tufl:' more than a thousand feet thick. Within the caldera, at least 6,000 feet of quartz latitic welded tuff is exposed, and the total thickness may be much greater. Intertongued landslide and talus breccia from the caldera walls indi- cate that at least the upper several thousand feet, and perhaps all of the observed caldera fill is younger than the welded tuffs of the rhyolitic intracaldera stage. Caldera subsidence stopped sometime following the quartz latitic eruptions, leaving a broad, flat-floored caldera with outward extending grabens (fig. 8.1E). Breccias derived by avalanching from the caldera walls spread over at least part of the caldera floor. The core of the caldera was domed (fig. 8.1F), probably by mag- matic intrusion, and a complex graben formed along the crest of the arch. Viscous quartz latitic lava was erupted along the broken margin of the caldera to form local flows and domes of Fisher quartz latite, and stream and lake sedi— ments and travertine accumulated elsewhere around the domed core to form the Creede formation. Following Fisher volcanism and Creede alluviation, the graben extending northward from the caldera (fig. 8.2 ) was again broken. This was the last major struc— tural event in the area, and it is of particular impor— tance as the faults active at this time were extensively mineralized to form the major lead-zinc-silver deposits in the Creede district. , The main displacement on the Creede graben has, been on two pairs of faults with opposing dips. The core of the graben is bounded on the east by the Ame- thyst fault, which originated during early caldera sub- METALLIFEROUS 107° 106°45’ I 380 SAN CRISTOBAL 1 CREEDE 2 OUADRANGLE UADRANGLE Rhyolite Rhyolite}. Quartz latite f...61"”:__Bachelor "$199 659.3,. Mtn . {G :3...“ ‘. :- ’° “a, 37°45' p“; ----- _ G'a/;"‘-a Sen?” 0'6 SPAR CITY QUADRANGLE A. Precaldera stage [ 51/ W x #3 E. Late caldera stage 0 1 10 l DEPOSITS B15 / Engsed margin of early caldera '- 3. Early caldera stage D. Quartz latitic intracaldera stage Creede graben Fisher quartz ; l 3 latite Creede formation . " Fisher quartz latite F. Postcaldera stage 20 30 MILES J J FIGURE 8.1.—Stages in the geologic history of the Creede district, Colorado. B16 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES X Nelson Mtn TRUE NORTH EXPLANATION 70 . _{ A — — — Creede formatlon :0 Fault, showmg dlp g Dashed where approximately located :0 -< _ __ __ Undivided volcanic rocks Contact Dashed where approaéimately located 0 4000 FEET FIGURE 8.2.—Fault pattern in the Creede district, Colorado. METALLIFEROUS DEPOSITS sidence and was recurrently active until after the Creede formation was deposited. The Bulldog Mountain fault zone on the West side of the core apparently originated during early caldera subsidence when the west side was downthrown; later movement reversed the direction of displacement along the mapped faults (fig. 8.2). The Alpha-Corsair fault near the west margin of the graben had its main movement after the Creede formation was deposited, but it followed the trend of an older series of echelon fissures marked by dikes. Movement on the Solomon-Holy Moses fault zone on the east side of the graben cannot be dated closely, nor is it known whether faulting took place during more than one period. Mine production in the Creede district has come from three of the four main fault zones in the graben, and from disseminated deposits in the Creede formation. The Amethyst fault and related fractures have pro— duced about $55,000,000 worth of metals, and the Alpha- Corsair and Solomon-Holy Moses fault zones about $600,000 and $2,200,000 worth respectively. The Monon B17 Hill area has produced about $800,000 worth of metals from basal beds in the Creede formation where it rests on a highly faulted segment of the caldera margin. The Bulldog Mountain fault zone appears to be the most favorable structure to prospect in the Creede district. It is a major fault zone with recurrent move- ment that bounds the west side of the core of the graben, and is thus comparable in several respects with the highly productive Amethyst fault zone. Prospecting to date has been confined to near-surface formations which are underlain by soft tufl's that may have inhib- ited passage of mineralizing solutions. Important ore bodies are more likely to be found at depth, where the rocks are the same hard rhyolites that enclose the ore bodies on the Amethyst, Alpha-Corsair, and Solomon- Holy Moses fault zones. REFERENCE Larsen, E. S., Jr., and Cross, Whitman, 1956, Geology and petrol- ogy of the San Juan Region, Southwestern Colorado: U.S. Geol. Survey Prof. Paper 258. ’X‘ 9. ALINEMENT OF MINING DISTRICTS IN NORTH-CENTRAL NEVADA By RALPH J. ROBERTS, Menlo Park, Calif. Work done in cooperation with the Nevada Bureau of Mines The mining districts of north—central Nevada are 10- calized by major structural features. One of these is the Roberts Mountains thrust fault, on which elastic and volcanic rocks of early and middle Paleozoic age (western assemblage) have ridden eastward over cor- relative carbonate rocks (eastern assemblage) (Roberts and others, 1958). The thrusting took place in Missis— sippian time, at the culmination of the Antler orogeny; post-thrust uplift and doming caused the upper plate to be locally removed by erosion, so that carbonate rocks of the lower plate were exposed in windows. As the principal mining districts are in and around these win- dows, study of the origin and history of the windows will shed light on the regional and economic geolOgy of the area. Recent mapping in Eureka County and adjacent areas has shown that the windows are alined in two northwest-trending belts, and that they contain many of the intrusive bodies (Roberts, 1957). The western, or Shoshone-Eureka belt, extends from the Shoshone Range southeastward to the Eureka district, and the other, the Lynn-Pinyon belt, from the Lynn district south-southeastward to the Railroad district (fig. 9.1). SHOSHONE-EUREKA BELT The Shoshone-Eureka belt includes the Goat Ridge, Red Rock, and Gold Acres windows in the Shoshone Range (J. Gilluly, written communication, 1958), the Cortez window in the Cortez Mountains, the Keystone, Tonkin, J-D, and Windmill windows in the Simpson Park Mountains, and the Roberts Mountains window in the Roberts Mountains. Lone Mountain also appears to be a window (C. IV. Merriam, oral communication) ; and the rocks of the Eureka district may have been partly covered by the Roberts Mountains thrust plate. lVindows in which the ore deposits were mainly in the carbonate rocks of the lower plate are the Cortez and Lone Mountain windows; the ore bodies in the Eureka district also are in carbonate rocks. The Cortez window contains the Cortez district, a major silver- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 41° 117° 60L CONDA BOOTS TRAP MINE ' B18 -3'4 Elko Maggie Creek district Carlin window Valmy 'CARU/v D/X/E FLA rs / 7pm 0 Z < m (4 z 25 \ O 9 \ >. :v I <0 . z ( i’ \ )3? $3 Slaven Canyon' I I ‘ 7‘ ‘ Pinyon window 3; 5 P/NE VALLE Railroad J/GGS 5’3: .istrict 2 E II) . . , . ‘ g g in o \ o *5 .2 z t *5 < E 3 II c 2 3 Q. m e o 8 5% Z 1:}3 - 8 Gold Acre' ' M/NERAL H/LL _ D: g window ’3- 5/ (I) , . Union Mineral Hill ‘district district ‘ r’—‘ _—__ D H; I k héfwmdmiii window . Window 40“ 4/ | I I I) ‘ X ROBERTS CREEK GARDEN MTN l/ALL Y 4 £7 4/ Mc/Clusky Pass a A e0 Roberts distric w ' 2 A0 Y K t ‘ d E. 4 Q. eys one wm ow F: Z 5 luiEXP o LANATI N / 6 ' g H g. _ G 7 Granitic rocks ap < I i— CL. [:I OQ7LN 2 U M , - - EUREKA 3 SOURCES OF GEOLOGY ppe;ou':;;is;gifs” and M4“ 9 o 1. Roberts,R.J..1951 Z 2. Roberts, R J,, Lehner, R. E., and [EU] I E U R E K a .Bell, M. M Cambrian to Devonian D 3. Gilluly, Gates, Olcott, and other; Wesfern assemb/age rocks above 5 2 E 4 Staff of Dept. of Geology‘Univof RoberIsMounra/hsrhwsr | g g Calif. at Los Angeles, modified m Lone Mam by Roberts. RJ. E , a? E I S H 5. Merriam, C. W, and Anderson, Cambrian t0 Devonian \ D C. A», 1942‘ Eastern assemblage rocks below Eureka 6 Nolan,T B ,and Merriam. c w. Faber“ Mountains f/Wsr district {I} 7. Merriam,C.W. A Contact g MINING DISTRICTS Lead-zinc-silver and silver-gold Gold and gold-silver Copper-gold and copper Barite FIGURE 9.1.—Map showing distribution of Paleozoic facies, granitic rocks, and principal mining districts in Eureka County, Nev., and adjacent areas. . i 10 MILES Antelope district Barbs on upper p/are Roberts Mountains thrust fault i i . 116° >OI. METALLIFEROUS DEPOSITS lead producer between 1870 and 1920. Most of the ore bodies mined were in or near fault zones that cut car- bonate rocks. Lone Mountain, a block of carbonate rocks bordered on the northeast, east, and southeast. by rocks of the upper plate, has yielded a small tonnage of zinc carbonate ore from bodies in Devonian lime— stone. The rocks in the Eureka district may not have been completely covered by the upper plate, but they appear to have been domed like those in the windows along the belt to the northwest. More than $52,000,000 in silver, gold, lead, and zinc ore was produced in this district, mostly between 1870 and 1900; it came chiefly from the Eldorado and Hamburg dolomites, of Cam- brian age. Other windows in the Shoshone Range that contain ore deposits are the Gold Acres window in breccia along the thrust, and the Lewis and Hilltop districts in the upper plate rocks. The Gold Acres window con- tains the Goldacres mine, which has yielded a significant production in gold beginning in 1934. The ore is mostly in the brecciated zone along the Roberts Mountains thrust (Keith Ketner, oral communication). The Lewis and Hilltop districts are in clastic and volcanic rocks of the upper plate, presumably not far from the thrust. The Battle Mountain district northwest of the Shoshone Range, is also in this belt. It is mainly underlain by western assemblage rocks of early Paleozoic age, pre- sumably exposed by warping of the kind indicated by windows to the southeast. LYNN-PINYON BELT The Lynn-Pinyon belt (fig. 9.1) includes the Lynn and Carlin windows in the Tuscarora Mountains and the Pinyon window (formerly called the Bullion win- dow) in the Pinyon Range. The Lynn window con- tains the Lynn district, which produced a small quantity of gold ore, mostly from veins that cut siliceous shale and chert in the upper plate of the Roberts Mountains thrust. The Bootstrap mine, at the north end of the district and just north of the Eureka County line, has produced gold ore from silicified zones along the thrust, from the carbonate rocks in the lower plate, and from altered dikes that out these rocks. The Carlin window contains several properties that have yielded small ton— nages of silver and copper ores and barite. The Copper King mine is near the window, but is in the upper plate and about 200 feet above the thrust. The Pinyon win— dow contains the Railroad district, which has yielded a small amount of silver-lead and copper ore from veins and replacement ore bodies in carbonate rocks. B19 The Mineral Hill and Union districts, in carbonate rocks of the lower plate, south of the Pinyon window in the Sulphur Spring Range, have yielded silver-lead— zinc ore. These districts lie between the Shoshone- Eureka and Lynn-Pinyon belts, and possibly are on a separate, less distinct, belt. ORIGIN AND HISTORY OF THE WINDOWS The windows are the result of doming of the Roberts Mountains thrust. Part of the doming may have oc- curred during or shortly after thrusting, but part of it may have occurred much later. Evidence that some doming occurred shortly after the thrusting is found in the north end of the Monitor Range, where coarse clastic rocks of Permian age containing carbonate boulders (eastern assemblage) rest on rocks of the upper plate, and on the south side of Lone Mountain, where similar clastics may rest on rocks of both the upper and the lower plate. The doming was later in- tensified during the emplacement of igneous bodies in late Mesozoic and early Tertiary time and during the uplift of the ranges in the Tertiary. The alinement of the Windows indicates that the doming occurred in zones of structural weakness in which movement has taken place intermittently. We do not yet fully understand the nature of the deforma— tion or know the precise date of its beginning, but clearly the zones of weakness and the windows along them are penetrated by conduits along which igneous rocks and related ore-bearing fluids rose. The zones probably penetrate to great depths within the crust, and they possibly date back to Precambrian time. SUGGESTIONS FOR PROSPECTING In prospecting within the windows and near them, a special effort should be made to explore the lower units in the carbonate sequence, such as the Eldorado and Hamburg dolomites, for lead—zinc-silver ore bodies in promising structural settings such as fault intersections. The rocks of the upper plate close to the thrust may also be locally mineralized, especially near intrusive bodies. REFERENCES Roberts, R. J., 1957, Major mineral belts in Nevada: Am. Inst. Mining Metall. Engineers program for Reno meeting. . Roberts, R. J., Hotz, P. E., Gilluly, James, and Ferguson, H. G., 1958, Paleozoic rocks in north-central Nevada: Am. Assoc. Petroleum Geologists Bu11., v. 42, no. 12, p. 2813—2857. 6% B20 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 10. MINERAL ASSEMBLAGE OF A PYROMETASOMATIC DEPOSIT NEAR TONOPAH, NEVADA By R. A. GULBRANDSEN and D. G. GIELow, Menlo Park, Calif. Pyrometasomatic deposits in a limestone environ- ment commonly contain andradite and pyroxene (Knopf, 1942, p. 63). A deposit in Paymaster Canyon, about 31 miles southwest of Tonopah, Nevada, is typical in this respect, although the pyroxene is an uncommon manganoan hedenbergite, heretofore found principally in a group of pyrometasomatic zinc de- posits that extends from New Mexico to the central part of old Mexico (Allen and Fahey, 1957). The Paymaster deposit also contains an apparently rare zincian nontronite. The deposit was first examined by J. E. Carlson and R. M. Smith of the US. Geological Survey, and a study of one of their specimens led to the identifica- tion of the» manganoan hedenbergite. Additional samples, on which this preliminary report is based, were collected principally for a detailed study of the hedenbergite and for the identification of the associ- ated minerals. Because of limited sampling, the min- eral assemblage described here is probably incomplete. The Paymaster deposit is on the west side of Pay- master Canyon, in sec. 2, T. 1 N., R. 40 E., Esmeralda County, and about a mile south of a contact, shown by Ball (1907, plate 1), between Cambrian sedimentary rocks and the granite of Lone Mountain. The deposit is a dikelike body about 10 to 15 feet wide, and is ex- posed for about two hundred feet at the surface. It extends along a fault separating Cambrian limestone from Cambrian shale, strikes N. 80° E., and is nearly vertical. The mineralized zone, where it is exposed in a pros- pect pit, consists principally of massive dark-green quartz-hedenbergite rock and massive olive quartz— andradite rock. Masses of soft yellow zincian nontro- nite, as much as 1 or 2 feet across, occur along an ir- regular limestone contact. The nontronite also forms envelopes around small hedenbergite veins, and pseudo- morphs after coarsely bladed clusters of hedenbergite. Some small blocks of limestone appear to be completely enclosed by the rock of the mineralized zone and show sharp contacts with it. The contact between the shale and the hedenbergite and andradite rocks appears sharp, and some of the dark—olive shale is bleached white owing to the destruction of chlorite. Both the hedenbergite rock and the andradite rock contain quartz, sphalerite, galena, magnetite, and calcite, but sphalerite and galena are more abundant in the heden- bergite rock. There is a noteworthy absence of pyrite and other iron sulfides. The minerals of the deposit have been identified principally by X—ray diffraction and X-ray spectro- graphic techniques. Table 10.1 shows X-ray diffrac- TABLE 10.1.—X—ray difiraction data of manganoan hedenbergite and johannsenite Wide range difiractometer, Ni-flltered Cu-radiation (x=1.54050 Angstrom units) Manganoan hedenbergite a J ohannsenlte 5 do I do I 6.58 25 6.59 15 4.76 45 4.77 35 4.51 10 4.54 10 4.28 5 4.27 10 3.34 10 3.34 20 3.27 20 3.28 25 3.001 100 3.012 100 2.910 10 2.915 15 2.587 15 2.595 15 2.552 20 2.550 30 d2.381 15 d2.380 10 d2.342 5 d2.343 5 22.238 5 d2.233 5 2.181 10 e2.184 10 2.149 10 2.155 15 2.124 10 2.128 15 Other peaks not measured I Paymaster Canybn, sec. 2, T. 1 N., R. 40 E., Esmeralda County, Nevada. b Venetla, Italy. Collected by D. F. Hewett. Type specimen no. 6 (Schaller, 1938). a Silicon used as a reference internal standard. Measured in angstroms. d Peak poorly defined. E Broad peak. tion data of the manganoan hedenbergite and of johannsenite, the calcium—manganese analogue of hed- enbergite. The johannsenite specimen was kindly lent by D. F. Hewett and is part of one of the type johann- senite specimens (no. 6) described by Schaller (1938). The X-ray data of the two minerals are very similar, but they differ markedly in composition. The johann- senite contains about 23 percent MnO and 5 percent FeO (Schaller, 1938, p. 580), whereas the manganoan hedenbergite contains about 9 percent MnO and 26 percent FeO, as determined by X—ray spectrography. Composition and other properties will be fully re— ported when the work on the manganoan hedenbergite _ is finished. \ The zincian n‘ontronite is a montmorillonite-type clay mineral intermediate in composition between nontronite and sauconite. The basal .X-ray diffraction peak expands from about 14.8 A to 18 A after treat- ment with glycerol, a change typical of the montmoril— lonites. X—ray spectrography shows more iron than zinc, and the mineral is therefore a nontronite rather than the rarer sauco-nite. The mean index of refraction of the zincian nontronite is approximately 1.58. Much of the nontronite was undoubtedly derived from heden— bergite, as shown by its occurrence in pseudomorphs after hedenbergite, but some of it may have been de- rived from andradite, like that occurring in the dry regions of central Kazakhstan (Ginzburg and Vitov— skaya, 1956). The unit cell size of the andradite, carefully meas- ured by X-ray diffraction with silicon as an internal standard, is 12.057 A, with an estimated precision of :005 A. It is very close to the values reported by Skinner (1956, p. 429), which were 12.069, 12.064, and 12.048, and indicates that the andradite here described is very near the end member in composition. The sphalerite of the deposit contains about 7.3 per- cent iron, as determined by X-ray spectrography with the use of chemically analyzed sphalerite standards. The temperature of formation of this sphalerite cannot be determined accurately from the data of Kullerud (1959, p. 315), because the required iron sulfide phase associated with the sphalerite is not present. The iron content of the sphalerite does make it possible, however, to estimate a minimum temperature of formation that is a little less than 400° C. Stone (1959, p. 1019), using Kullerud’s data, found that the sphalerite in a pyrometasomatic deposit in Mexico, which also con- METALLIFEROUS DEPOSITS B21 tains hedenbergite and andradite, formed at a tem- perature between 500° and 550° C. The economic value of the Paymaster deposit is not yet known, but an appraisal of the deposit’s potential may be aided by noting another similarity between the Paymaster and the deposits in New Mexico and Mexico. This is the tendency for sphalerite and pyroxene to be closely associated. It is so marked in the New Mexico- Mexico deposits that pyroxene appears to be a useful guide to ore (Allen and Fahey, 1957, p. 889). REFERENCES Allen, V. T., and Fahey, J. J., 1957, Some pyroxenes associated - with pyrometasomatic zinc deposits in Mexico and New Mexico: Geol. Soc. America Bull., v. 68, p. 881—896. Ball, S. H., 1907, A geologic reconnaissance in southwestern Nevada and eastern California: US. Geol. Survey Bull. 308, p. 218. Ginzburg, I. 1., and Vitovskaya, I. V., 1956. Vyvetrivaniye granatovykh aksinitovyhh i tremolitovykh porod v zasush- livykh raionakh tsentral’nogo Kazakhstana [The weather— ing of garnet, axinite, and tremolite rocks in the dry regions of central Kazakhstan], in Kora vyvetrivaniya [Crust of weathering]: Akad. Nauk SSSR [Acad. Sci., U.S.S.R.], no. 2, p. 299—316. Mineralog. Abstracts, 1959, v. 14, p. 124. Knopf, Adolph, 1942, Ore deposition in the pyrometasomatic deposits, in Ore deposits as related to structural features: edited by W. H. Newhouse, p. 63—72. Kullerud, Gunnar, 1959, Sulfide systems as geological thermom— eters, in Researches in geochemistry: edited by P. H. Abel- son, p. 301—335. Schaller, W. T., 193.8, J ohannsenite, a new manganese pyroxene: Am. Mineralogist, v. 23, p. 575—582. Skinner, Brian J ., 1956, Physical properties of end-members of the garnet group: Am. Mineralogist, v. 41, p. 428—436. Stone, J . G., 1959, Ore genesis in the Naica district, Chihuahua, Mexico: Econ. Geology, v. 54, p. 1002—1034. ’>% 11. SEDIMENTARY IRON-FORMATION IN THE DEVONIAN MARTIN FORMATION, CHRISTMAS QUADRANGLE, ARIZONA By RONALD WILLDEN, Menlo Park, Calif. Sedimentary iron-formation was discovered in July 1959 in the upper part of the Martin formation, of Devonian age, in sec. 19, T. 2 S., R. 16 E., in the north— west part of the Christmas quadrangle, in Gila County, Ariz. (see fig. 11.1). The iron-formation occurs in a bed from 5 to 7 feet thick. This bed is traceable over a strike length of about 2,150 feet on the north side of Limestone ridge, where it .dips 40°-50° southwest. The oolitic bed lies at the base of a widespread shale unit that is at the top of the Martin formation in much of the surrounding area, and is underlain by a buff to yellowish-brown fine- to medium-grained silty lime- stone. Hematite also occurs at approximately the same horizon in much of the northern part of the Christmas quadrangle, forming either crystalline nodules in the buff limestone or a cement in a rather poorly sorted sandstone that intervenes, in some places, between the shale and limestone. The iron-formation consists of ooliths of hematite and chamosite in a matrix of calcite, dolomite, and quartz silt. Point counts on thin sections of rock from three horizons in the oolitic bed (near the top, at the B22 GEOLOGICAL SURVEY RESEARCH l960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S ° Phoenix 0 Globe Egg 33° °Winkelman 0 25 50 MILES |_I——l oTucson 1 11 ° 1 0° INDEX MAP SHOWING LOCATION OF CHRISTMAS QUADRANGLE, ARIZONA \dn \ db“ , \ II 1/ “NM h“ {U1 “*I u \n " N i Ni ii ,4?) (“‘93: 'u“1:1""u:“h \T» . “n “nun". H ‘ e 5 4 i ’f A A/ l\\\\\\€ Pn Me Dm Ct Cd 5000' " I n \ 5 5 S m D QTS ,7: “db pCm P g 5 fibqvixflut‘ 4000, 5 2‘: k u § APPROXIMATE MEAN z DECLINATION, 1960 110°45’ O 1 2 MILES ; l l I I I J EXPLANATION >- . EQE> “ * ‘* ” I ._ ‘ Egg: 311%: l Gila conglomerate E oz Dlabase I .4 i z I >_z (n < MI W 8 Will E | 22 n: m ~ Z< uJ . E Naco limestone E> I: Troy quartZIte 5 z r (hz o 7 gig as m / z A 2% SE A 5 Escabrosa limestone 55 U Mescal limestone g z 2 ‘-‘ W 5 m a I a Martin formation a Dripping Spring quartzite '1‘ D ————— Contact Dashed where approx/matey /ocafed p — — .... , Fault Dashed where approx/'mafe/y located; def/ed where can- cea/ed ——r'4o Strike and dip of beds .5 Sample location and number FIGURE ILL—Northwest corner of Christmas quadrangle and vicinity, Arizona, showing geology and sample locations. METALLIFEROUS DEPOSITS top of the lower third, and in the lowest 6 inches) show 49 to 58 percent ooliths, 33 to 42 percent carbon- ates, and 7 to 10 percent quartz. The ellipsoidal ooliths are 0.2 mm long and tend to lie parallel to bedding. X-ray diffraction pat-terns of the carbonates have char- acteristic calcite lines, but the principal dolomite line is displaced from the position for pure dolomite by about 02" toward a lower 2-theta value, which may be due to some substitution of iron for magnesium. Partial chemical analyses by D. L. Skinner (written communication, February 1960) of 6 samples, give an iron content of 31.1 to 39.3 percent (table 11.1). X-ray spectographic analyses of 11 chip samples collected at about 51/2-foot intervals from across the bed at the same locality as sample 1 (fig. 11.1) indicate iron content ranging from about 31 percent in the lower part of the bed to about 40 percent at the top, with a maximum of 46 to 49 percent in a 2-foot zone in the upper half. As- suming that the bed maintains a uniform length and thickness downdip, and that it has an average specific B23 TABLE ILL—Iron content of 6‘ samples of ooltttc iron-formation from the Devonian M arttn formation [Analyses by D. L. Skinner; reported as FeaOa] Sample 1 Location Width Total Fe Total Fe (feet) as F8203 1 _________ About 210 ft west of alluvial cover ..... 6 56. 2 39. 3 2 ______________ do ................................ 1 44. 4 31.1 3 2 _____________ do ................................ 7 ____________ 38.1 4 ......... 540 ft west of sample 1 ................. 6. 2 56.0 39. 1 5 _________ 360 it west of sample 4 ..... 3 3 0 50. 5 35. 3 6 _________ 1,040 ft west of sample 5... ____ 5.0 50. 9 35. 6 7 ......... 325 ft west of sample 6 _________________ 1. 2 49. 1 34. 3 1 Sample numbers same as on geologic map (fig. 11.1). 2 Weighted average of samples 1 and 2. 3 Only lower 3 feet of bed could be sampled because upper part of section was covered with tightly cemented rubble. Bed is probably about 6 feet thick at this point. gravity of 3.19, there are about 1,250 tons of iron- formation per foot of depth. Owing to its low grade and small size this deposit probably cannot be profit- ably mined at the present time, but its existence justi- fies a hope that other and perhaps larger deposits may be discovered elsewhere in the Martin formation. 6? 12. EARLY TERTIARY VOLCANIC GEOLOGY OF AN AREA NORTH AND WEST OF BU'l'I‘E, MONTANA By HARRY W. SMEDEs, Washington, DC. Remnants of two unconformable Sequences of early Tertiary volcanic rocks rest on the Boulder batholith and older rocks within a belt about 60 miles long and as much as 18 miles wide, which roughly parallels the northeast-trending axis of the batholith. The younger sequence is of rhyolite, and occupies principally the northeastern part of this belt; the older sequence is of quartz latite, and occupies principally the southwestern part. An unconformable contact between the rocks of the two sequences is exposed in the Champion Pass area, about 19 miles north of Butte. Rocks of the older sequence, which are the principal topic of this paper, occupy an area of about 400 square miles and have a composite thickness of more than 6,000 feet. The lith- ology, and structural and stratigraphic relations of these volcanic rocks, and their known or inferred maxi- mum preserved thickness, are shown diagrammatically in figure 12.1. Volcanic rocks of the older sequence comprise six major unconformable or disconformable units (II— VII). During the earliest phase of volcanism a mix— ture of tufi’ and quartz monzonite detritus (unit II) accumulated on the lower parts of an erosion surface having a relief of about 1,000 or 1,500 feet. Rocks of this unit were slightly tilted and eroded before the ex- trusion of a thick sequence of ash flows (unit III), most of which are now sheets of welded tufl'. This eruption was followed by block faulting and tilting toward the west-northwest, and subsequent erosion produced a surface of moderate relief upon which rocks of unit IV accumulated. The basal part of this unit commonly consists of moderately well sorted sandstone and granule conglomerate, which grade up- ward into breccias containing boulders and blocks of quartz monzonite and welded tuff. Higher up, the breccia contains, instead of these, blocks of porphyritic quartz latite up to 20 feet in diameter, which are indis— tinguishable from the rock of the overlying lava flows. Some of the breccia may be vent agglomerate; all of it was produced by explosive reopening of sealed conduits prior to, or contemporaneous with, the formation of plugs, dikes, and lava flows. Block faulting recurred during deposition of these coarse deposits; as a result, B24 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES F faulting T tilting E erosion FIGURE 12.1.—Diagnammatic section of early Tertiary volcanic rocks of an area north and west of Butte, Mont. 5% some breccia deposits abut against fault scarps in breccia or welded tuff. Breccia of unit IV, and older rocks, are overlain by two unconformable successions of quartz latite lava (units V and VII), locally separated by a vitrophyre (unit VI). Lavas of unit V are preserved only in the western part of the area, where they are overlain With angular discordance of as much as 30° by lavas of unit VII. Many small intrusive bodies were emplaced after and perhaps partly during the extrusion of the lavas of unit V. These lavas, and intrusives which cut them, were eroded before the eruption of the vitrophyre and the lavas of unit VII. In the Champion Pass area the quartz latites of unit» VII are unconformably overlain by rhyolite of the younger sequence (unit VIII). Between almost every one of the volcanic episodes and the next one there was faulting or tilting followed by erosion, and some of the faulting was contempora- neous with the deposition of unit IV. Major faulting and collapse took place after the eruption and welding of the succession of ash flows forming unit III. In the area immediately west of Butte this block faulting pro— duced an L-shaped graben 3/; to 11/2 miles wide in quartz monzonite of the Boulder batholith, into which the sheets of welded tuff collapsed. As a result the welded tuff sheets have a chaotic structure, and many of the blocks of tufl' are nearly vertical. This fact, and the presence of minor breccia vents and marginal dikes, apparently caused earlier workers to interpret the welded tutf as an intrusive rock. Gravity surveys in- dicate that the floor of the graben lies at a depth of about 1,200 feet. The volcanic rocks in this graben are probably underlain by segments of truncated metal- liferous quartz veins in the manganiferous zone in the quartz monzonite of the Butte district. Renewed movement along some of the block faults that followed the volcanism produced intermontane basins, which received debris shed from the bounding scarps, and were thus filled with sand, gravel, silt, ash, and tuif (unit IX). These basins may be as old as late Oligocene; basin deposits near Silverbow contain lower Miocene fossils (Konizeski, 1957, p. 145). Later movement along some of the faults displaced Pleistocene glacial deposits. The net effect of repeated tilting of fault blocks in the area north of Butte is indicated by west—northwest dips of 15° to 35° in the basal unit and the sheets of welded tuff (units II and III). REFERENCE Konizeski, R. L., 1957, I’aleoecology of the middle Pliocene Deer Lodge local fauna, western Montana: Geol. Soc. America Bull., v. 68, no. 2, p. 131—150. METALLIFEROUS DEPOSITS B25 13. TECTONIC SETTING OF THE COEUR D’ALENE DISTRICT, IDAHO By ROBERT E. WALLACE, ALLAN B. GRIGGS, ARTHUR B. CAMPBELL, and S. WARREN HOBBS, Menlo Park, Calif, Menlo Park, Calif., Denver, Colo., and Washington, DC. In gross structural pattern the Coeur d’Alene dis— trict lies at the intersection of the Lewis and Clark line (Billingsley and Locke, 1939, p. 36), represented by the Osburn and related faults, and a broad arch that extends north at least to Kimberly, British Columbia. The rocks of the district have been intensely deformed in a complex pattern that shows a marked discordance of structural elements on opposite sides of the Osburn fault and which well might be referred to as a struc- tural knot (fig. 13.1C). Dominating this structural knot is the Osburn fault which strikes about N. 80° \V. across the area. Strike slip is indicated on the Osburn fault by: (a) the offset of large upwarped blocks more or less delineated by areas of outcrop of the Prichard formation, the oldest unit of the Belt series; (b) the offset of major folds and faults, and the dissimilarity of structural features adjacent to one another on opposite sides of the fault; (c) large—scale drag features; ((1) offset of the same sense along parallel or subparallel faults; and (e) the position of major mining areas on opposite sides of the Osburn fault and the pattern of ore and gangue-mineral distribution within the areas. A maximum of about 16 miles of right—lateral strike slip is indicated on the segment of the Osburn fault east of the Dobson Pass fault and about 12 miles displacement in the same sense is indicated west of the Dobson Pass fault. The dif- ference in displacement on these two segments is be- lieved to be principally the result of contemporaneous dip slip on the Dobson Pass fault, which has effectively lengthened the block north of the Osburn fault relative to the block south. A few miles east of the area shown in figure 13.1, in the vicinity of Superior, Mont., the cumulative lateral movement in the Osburn and the related Boyd Mountain fault, as shown by stratigraphic displacement, appears to be approximately 16 miles, which strongly corroborates the suggested displacement on the Osburn fault in the Coeur d’Alene district. The age of the Osburn fault is known only within broad limits. It cuts rocks of the Belt Series of Pre- cambrian age and is capped by flows of Columbia River basalt of middle Miocene age. The probably con- temporaneous Dobson Pass fault cuts the Gem stocks, which have been dated as about 100 million years old (Jaffe and others, 1959, p. 95—96). Other geologic evi- dence indicates that a lineament in the general position 557753 0—60—3 of the Lewis and Clark line may have been in existence since early Precambrian time. Ages obtained from uraninite from the Sunshine mine (L. R. Stieff and T. W. Stern, written communi- cation, 1957; Eckelmann and Kulp, 1957, p. 1130) indicate that uranium mineralization occurred about 1,250 million years ago. Thus tight folds, such as the Big Creek anticline (fig. 13.1), that are cut by the uraninite veins, must have been developed before that time. In contrast, the principal ore-bearing veins are younger than the Gem stocks of about 100-million-year age. The overall history of development of the structural knot must have been complex; the following summary of a possible sequence of events is suggested. During an early stage of deformation (fig. 13.1A) the prin- cipal folds were developed and overturned to the north- east, and reverse faults that strike northwest and dip southwest were formed. A large domelike structure, the Moon Creek—Pine Creek upwarp, was formed west of the reverse faults. Accompanying a major reorientation of the stress system, the axes of the folds began to boils7 (fig. 13.13), the southern part of the region moved relatively west- ward, and incipient strike-slip faults developed. The Mill Creek and Deadman syncline was separated from the Granite Peak syncline and wrapped around the truncated end of the Granite Peak syncline. The northern flank of the Lookout-Boyd Mountain anticline was sliced off by one of the antecedent fractures of the Osburn fault. Monzonite stocks intruded the structural knot thus produced (fig. 13.10), and the principal period of ore deposition followed. Most of the veins are included in spatial groups that define distinct linear belts trend- ing slightly more northwesterly than the Osburn fault system. The concentration in such belts of veins, which are subparallel but differ in size and orientation, sug- gests that linear feeders for the mineralizing solutions existed at depth, although no through-going structural elements reflect these feeders in the upper crust. After the principal period of ore deposition, strike— slip movement along the ancestral Osburn zone of weak- ness became more through-going than previously, and apparently deep-seated stresses were accommodated at this time by displacement on relatively few faults, most B26 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES A EXPLANATION Monzonite stocks Vein zones (:3 Areas of outcrop of Prichard forma- tion, represent- ing positions of large upwarps / Movement patterns U GULCH FAULT \\_ , Elev 2993' c M “ opper tn 0% X. 1341/21/40 lMILE Cr Ll—J_J__L.__—J Insert map of Thompson Creek drainage We" showing geochemical sediment sample sites Venetiu Cr EXPLANATION LODE DEPOSITS tr: Ore/r E ‘ O . , . 3 fl 64°45’ Native gold, scheellte, and gold- and scheellte- ' % bearing lead and antimony deposit Copper deposit «3;. fie}. O Arsenopyrite-bearing deposit I Bismuth deposit "3- %; 5 O Geochemical sediment sample site a 0; Q s” a «K 1 13 “k \ Q, N X \w Army Peak + 64°30’ :3 5 4 3 2 1 O 5 M iLES C i I l I I I i CAPE NOME FIGURE 16.1.—Map showing location of lode deposits and geochemical sediment sample sites near Nome, Alaska. tains and Bering Sea, in which the Nome goldfields lie (Moffit, 1913, p. 140). The bedrock of the goldfields is composed entirely of low grade schists and interbedded marble. Known lodes of the goldfields, of the type from which the gold of the alluvial and beach placers of the goldfields was derived, are for the most part filling-type deposits in shattered quartz masses (fig. 16.1). Scheelite and native gold are the dominant non-gangue constituents in a few deposits but base metal sulfides predominate in most of them. Except B32 for a single deposit in which native bismuth and bis- muthinite occur and several copper sulfide deposits, most of the lodes are composed of lead and antimony sulfides with minor amounts of scheelite and gold. The Nome goldfields are bounded on the north by the Kigluaik Mountains. The bedrock of the moun- tains is composed entirely of very high grade meta- morphic rocks into which have been intruded many relatively small sills and dikes of silicic and mafic igneous rocks and granite pegmatites. Although the igneous rocks are thought to be genetically related to the mineral deposits of the goldfields, the only direct evidence of hydrothermal mineralization in the Kig— luaik Mountains consists of a single lode on North Star Creek in which arsenopyrite was the only metallic mineral which was recognized. The results obtained from geochemical sediment sam- ples collected in the Nome goldfields closely reflect the presence or absence, and the composition and proximity to sample sites, of the known lode deposits in the drain— age basins of the streams from which the sediments were collected (table 16.1). As might have been ex- pected, most of the samples from the goldfields con- tained greater quantities of antimony and arsenic. However, in specific cases, anomalously high amounts of other metals were obtained from samples collected from drainage basins where lodes containing those metals crop out, such as lead in sample 11 from Steep Creek and bismuth in sample 9 from Charley Creek. In marked contrast with the results obtained from sediment samples from the Nome goldfields were those obtained from samples collected from streams in the Kigluaik Mountains. In the absence of known metal- liferous lodes, no anomalous quantities of the metals de- termined could be expected. In general, none were ob- tained; samples 2 through 8, collected from Widely separated localities throughout the part of the Kigluaik Mountains included in the area of this report, had consistently small amounts of all the metals determined and thus provided a basis for estimating the quantities of these metals in sediments derived from the high grade metamorphic rocks. The only exceptions to these general results were some obtained from sediment sam- ples collected from Thompson Creek a western tribu- tary of the Grand Central River. The first sample (1A) was collected by the authors in 1957 ; other sam- ples of the series (1B—1E) were collected at the re- quest of the authors by D. M. Hopkins in 1959 on the basis of the geochemical results obtained from sample 1A. Samples from Thompson Creek contained more copper, zinc, molybdenum, and bismuth than those from any other part of the area. The resulting anomalies of GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 16.1.——Content (in ppm) of several metals in sediment samples from streams near Nome, Alaska [Analystsz W. L. Jones, H. H. Mehnert, H. M. Nakagawa, H. Neiman, L. E. Patten] Locality Sample Pb Cu Zn As W M0 B1 Sb Thompson 1A <20 120 400 <10 <20 10 <5 2 Creek 1B 25 150 600 <10 <20 8 35 1 IC 25 100 400 10 <20 12 45 2 1D 25 75 125 10 <20 4 10 1 1E 25 75 225 <10 <20 4 50 1 1F 25 100 225 <10 <20 12 10 2 Kigluaik 2 <20 30 80 < 10 <20 10 <5 2 Mountains 3 <20 30 100 < 10 <20 4 5 2 4 <20 30 100 10 <20 2 <5 2 5<20 30 100 <10 <20 4 <5 1 6<20 30 100<10 <20 2 <5 2 7 <20 30 100 30 <20 6 10 l 8 <20 30 100 <10 <20 10 <5 2 Nome goldfields- 9 <20 30 80 300 <20 2 20 6 10 <25 20 50 150 <20 <4 <5 10 11 50 3O 75 60 <20 <4 <5 30 12 <25 20 100 150 <20 <4 5 8 13 <25 30 100 150 <20 <4 <5 10 14 <25 30 125 60 <20 <4 <5 8 15 <25 20 75 40 <20 <4 5 4 16 <25 20 75 30 <20 <4 <5 4 17 <25 20 75 80 <20 <4 <5 6 18 <25 20 75 300 <20 <4 5 6 19 <25 20 75 20 <20 <4 <5 4 20 <25 30 75 60 <20 <4 <5 6 21 25 30 100 150 <20 <4 <5 10 22 <25 30 100 150 <20 <4 <5 4 23 <25 30 75 80 <20 <4 <5 10 24 <25 20 75 20 <20 <4 <5 4 25 <20 30 100 10 <20 2 <5 2 these metals were two to six times greater than the back- ground content estimated from samples 2 to 8. Be- cause no lode material has been found in the Thompson Creek drainage, the difl'erence between the results ob- tained from there and those obtained from drainages with known lode deposits is significant. For example, the Thompson Creek samples contained more bismuth than samples 9 from Charley Creek although a lode containing native bismuth and bismuthinite crops out about half a mile above the sample site and both min- erals are present in placer deposits at least as far downstream as the sample site. Similarly, although sphalerite is abundant in a lode cropping out at the head of Steep Creek, a headwater tributary of the Snake River, the quantity of zinc in a sample collected about a mile downstream did not exceed its background coh- tent. Individually, the Cu, Zn, Mo, and Bi geochemical anomalies are strong indicators of undiscovered metal- METALLIFEROUS DEPOSITS liferous lodes in the Thompson Creek drainage. Taken together, they indicate that the Kigluaik Mountains, and perhaps other areas in which high-grade metamor- phic rocks occur on the Seward Peninsula, contain hydrothermal deposits of base metals, even though they lack the gold-bearing lodes and placer deposits that characterize the Nome goldfields. Briefly summarized, the conclusions of this report are: 1. Meaningful geochemical results were obtained from stream sediments in the mineralized metamorphic terrane of the Seward Peninsula. 2. The greatest quantities of copper, zinc, bismuth, and molybdenum in all of the sediment samples oc- B33 curred in those collected from Thompson Creek in the Kigluaik Mountains and strongly indicate the presence of lode deposits containing these metals in the Thompson Creek drainage basin. 3. The indication of metalliferous lodes near Thompson Creek suggests that hydrothermal deposits may occur in the high-grade metamorphic rocks else— where in the Kigluaik Mountains and, perhaps, in those exposed at other places on the Seward Penin- sula. REFERENCE Moflit, F. H., 1913. Geology of the Nome and Grand Cemtral quadrangles, Alaska: US. Geo]. Survey Bull. 533, p. 140. ’5? l7. STRUCTURAL GEOLOGY AND STRUCTURAL CONTROL OF MINERAL DEPOSITS NEAR NOME, ALASKA By C. L. HUMMEL, Menlo Park, Calif. Structures belonging to systems of two ages have been identified and mapped in the bedrock of an area near Nome, Alaska (fig. 17.1). The lode and placer deposits of the Nome goldfields are closely associated with some of the structures of the younger system. Structures of the older system developed during a period of deep—seated deformation, probably in the Mesozoic era, at which time all the bedrock of the area was regionally metamorphosed. The major structures of this system once formed a series of nearly northward trending folds which may have extended northward for 100 miles across the middle of the Seward Peninsula. Other structures include numerous minor folds of vari- ous sizes and several types of axial lineation; all these features are more or less parallel to the major folds. The major folds were greatly modified by later orogenic activity, so that only deformed remnants of two of them are now recognizable in the area—a broad, open syncline about 25 miles wide in the eastern part of the area and a somewhat tighter but still open anticline in the western part. Structures of the younger system are thought to be related to the eastward-trending uplift, probably of Tertiary age, from which the present Kigluaik moun- tain range developed. This uplift transected the older northward-trending folds about at right angles, leaving within the area the truncated ends of the two folds men- tioned above. Structural features of the uplift are clearly expressed by the present topography. Not only does the range have the same trend as the uplift, but the uplift is bounded by steeply dipping normal faults, one of which marks the northern limit of the range and the other almost coincides with the southern limit. The highest mountains of the range lie along the axis of an arch, formed during the elevation of the uplift, that plunges eastward and westward from Mount Osborn, the highest peak in the range. Because of the arcuate pattern of the faults that bound it, the uplift is also widest through Mount Osborn. The southern boundary fault marks the contact between the high-grade meta- morphic rocks which crop out only in the uplift and those of much lower metamorphic grade which form the bedrock throughout the area. to the south. On the basis of this difference of metamorphic grade and on strati- graphic evidence, it is estimated that at least 30,000 feet of vertical movement has taken place in the center of the uplift. Other structures of the younger system, present only in the area south of the Kigluaik Mountains, are thought to be subsidiary effects of the uplift. These include two folds of considerable size and three sets of faults. The folds, both of them just south of the uplift, are an eastward-plunging syncline in the west- central part of the area and a southwestward-plunging syncline in the northeastern part, superposed upon the eastern and western limbs of the older north-trend- ing syncline. The three sets of faults strike to the north, northeast, and east, respectively. Only the east-west (LIOIOZOE‘IVd HO GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES AHVNHELLVDO DIOZOE‘IVd (UNVIBSWVDEHd B34 “.330 :>:< we $.58 vmizm mgfia \o $59339 “E: 36:3 :53 \e mus: 3:325; 952:? 3959* .I.+.liv.\. wufifin \e ifiwcméfi. SE 253R :53. \a 3:: ©5325; @5335“. yam—Sow .l$!lY\x 32.3 3.22:? 3?: ©5335. Sic—Sm EEO I/T\I 35:3 $533? was: “532% 250sz .330 IlTI 3N: $33553 an ,0 $3.; 533:3: ,2 .Eflemoicu 33‘s fimfieQ 3v mama/cg diam ...... o o 33:00 /|\) image 25: o wiaafim :95: EPSSLQ mammomwv ~3me wmizm $32 2:988“qu wumpuiwmm E Sig: Sflzcgécw ,Emm BUS“; \w2_xu§.e§cfi .flm mEEE 9E amEum _ £%P Ema \ J? fin. mflmoawc vwaaEEmzovcb 3an ZO_F a, >13 QM age/A7 458 0 W. 4 m. w Mx (Ii/40 ‘ m. ,\\\\ in: um \ oA 1;, EN} s” I K 6 T‘ . \‘2. x v , . e \__ a \%/®< ”“1 mil: gift: m 7 “K 7 ~ a N r wt was 2:». w . R 1a: \% as "c“ m , x. O s: a w L‘ vs é 0 PF . . o , \Pé vg CW :2 3’25 U $7 QKE/e» i’ as W ° < - r . i. it 1'0 \V L) K < A > r // {k 71,0 1%. i C}5 Q 57°;_I .,,I_ A.__<.4_l;/__.;{5§\_A AL) .AA, AWH._ _— 57" 137° 135° 133” FIGURE 19.1.——Index map of part of southeastern Alaska show- ing three acres of possible mineral resource potential. METALLIFEROUS DEPOSITS The part of the Chilkat Range north of the Endicott River (3, fig. 19.1) was found to be richer in sulfide minerals than the part south of the river. Orange, red, and brown gossan is widely distributed in the igneous, metamorphic, and volcanic rocks, which underlie an area of more than 200 square miles. The largest out— crops of gossan are several thousand square feet in area, but in general the gossan masses are not so common or extensive here as in central Admiralty Island. Sulfide minerals occur in local concentrations consisting chiefly of veinlets and disseminations of pyrite, pyrrhotite, and chalcopyrite. These minerals contain traces to major amounts of cobalt, copper, zinc, and lead. Magnetite and ilmenite commonly occur in disseminated particles, and in films coating shear surfaces in the rocks. In some places the oxides contain trace quantities of chromium. B39 Small deposits of secondary copper salts are not un- common; malachite, azurite, and chrysocolla form stringers and stained patches in the country rocks near some of the sulfide deposits. The areas have been prospected superficially over a period of many years and several groups recently made reconnaissance mineral surveys of the general region with helicopter support. Little trenching, test pitting, or other physical exploration has been undertaken how- ever, and few claims have been staked. No mineral production has been reported. Thick soil, glacial de- posits, and dense vegetation cover much of the areas under consideration; hence geochemical and geophysi- cal techniques, coupled with physical exploration, prob- ably will be necessary to test fully the mineral potential. 6? 20. A STUDY OF RHENIUM AND MOLYBDENUM IN URANIUM ORE FROM THE RUNGE MINE, FALL RIVER COUNTY, SOUTH DAKOTA, BY MEANS OF A SPECTROGRAPHIC AND CONCENTRATION METHOD By A. T. MYERS, J. C. HAMILTON, and V. R. WILMARTH, Denver, Colo. Work done in cooperation with the U.S. Atomic Energy Commission GEOLOGY The Runge mine is in an elongate lenslike northwest- trending uranium deposit extending along the inter- section of an older and a younger Cretaceous stream channel, both filled with sandstone. The ore consists principally of uraninite, coffinite, haggite, and mont- roseite, with minor quantities of one or both of the blue molybdenum minerals ilsemannite and jordisite, in a gangue of pyrite, calcite, and hematite. It forms elon- gate irregular bodies in sandstone and along fractures. Most of the ore is in a calcite-cemented sandstone that contains abundant pyrite; nearly everywhere in the mine this forms the basal unit in the younger chan- nel. The bottom of the younger sandstone is locally marked by a discontinuous rubble bed made up of an- gular to rounded shale fragments in a sandstone matrix, but throughout the central part of the deposit the cal- cite-cemented sandstone is overlain by a red hematite— rich sandstone that grades upward to a gray pyrite— rich sandstone. In the northeastern, southeastern, and southwestern parts of the deposit, the calcite-cemented sandstone is generally overlain by a sandstone, charac- terized by irregular narrow black-brown stripes, that has gradational contacts with the red and gray sand- stones. Heavily mineralized fractures cut all the sand- stone units. The average grade of the ore produced from the mine is 0.2 percent uranium and 0.5 percent vanadium. The average ratio of vanadium to uranium in ore samples from the fractures and black-striped sandstone is about 0.65; in samples from the other sandstones this ratio ranges from 1.3 to 1.7, being highest in the calcite— cemented sandstone. METHOD OF ANALYSIS Following the work of Peterson and others (1959), we have made a geochemical study of an occurrence of rhenium in uranium ore from the Runge mine. The principal new feature of this study is the application of a simple water extraction and concentration tech- nique prior to spectrographic analysis. The amount of rhenium in ore of this kind has com- monly been estimated by a spectrochemical method of semiquantitative analyses. This is a total-energy method, based on the use of synthetic standards and a visual matching technique. Its limit of detection for rhenium is 50 ppm; and so, in an effort to measure smaller amounts, we used extraction with distilled water B40 to concentrate rhenium in the water-soluble fraction. This procedure does not necessarily give the total rhenium in the sample, but it does allow one to estimate the minimum quantity of rhenium present in soluble salts. This technique lowers the limit of detection by 25 to 500 times, making it possible to study the distribution of rhenium—or at least of water-soluble rhenium—in ore bodies of this type. A 50-gram portion of the ground sample was added to 500 ml of distilled water. After heating to about 100° C for 1 hour the leachate was filtered and evap- orated to dryness on a steam bath. A weighed amount of powdered pure quartz, about one-fourth the weight of the dried leachate, was added and the mixture thor- oughly ground. The spectrographic analysis was made on 10 mg of the mixture. GEOCHEMICAL RESULTS Table 20.1 shows the results of analysis for molybde- num, uranium, vanadium, and rhenium. Of the 27 original samples, only 6 contain rhenium in amounts detectable by conventional methods, but when these same 27 samples were leached with distilled water and GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES the dried leached-out material analyzed, 16 of them were found to contain rhenium. In table 20.1 the samples are arranged as nearly as possible in order of decreasing molybdenum content. Our results indicate that the samples higher in molybde— num tend to be higher in rhenium, and this is also true, in general, of the soluble material leached from the samples. The results of our analyses (table 20.1) show that molybdenum and rhenium are most abundant in samples from the black-striped sandstone and the mineralized fractures. The highest values are 0.007 percent rhenium and 0.7 percent molybdenum. The ore minerals most abundant in the calcite-rich and pyrite-rich sandstones, and locally in the hematite- rich sandstones, are crystalline uraninite, coflinite, and montroseite, which are the low-valence oxides and sili- cates of uranium and vanadium. Oxidation of the ore minerals resulted in formation of paramontroseite, haggite and amorphous uraninite, with a little carnotite in the black -striped sandstone and along fractures. Analyses of the material leached from samples of these sandstones (tables 20.1) indicate that rhenium and TABLE 20.1.—Semiquantitative spectrographic determination of 4 elements in 27 samples from the Range mine, Fall River County, S. Dak. [Add 260000 to sample numbers to obtain laboratory serial numbers. group data on a geometric scale. not found; Pb207/ U235 >> Pb207/Pb206) are reversed; and (c) The szm/ Pb206 ages of the uranium ores in Mississippian-Penn- sylvanian rocks from Mount Pisgah are impossibly old. TABLE 23.2.—0alculated “trial” ages, in mtllioas of yearsl Age of enclosing Number Locality rocks (millions szos/Uzas Pb207/Um Plow/Pb?“ of years) 346 ______ Mount Pisgah , Mississippian— 314 325 413 Pennsylvanian 538 ........... do ........... 330.2 300 312 402 403 ______ Penn Haven Devonian 220 245 305 Junction. 410—355 2 586 ........... do ........... 400—350.a 438 428 368 1 “Trial” ages obtained using Nesquehoning galena (584), Pb“! as the common lead index, and age calculation tables (Stiefi and others, 1959). 2 Kulp (1959). 3 Holmes (1960). The discrepancy between the two Penn Haven J unc— tion szm/Pb206 ages may be a result of past alteration, of original contamination at the time of mineral deposi- tion by an older generation of radiogenic Pb”7 and Pb“, or of mass spectrometric errors. As radon loss cannot account for the age sequence of samples 586 or for the Pb207/Pb206 ratio of the associated clausthalite (sample 512), it seems unlikely that this process is re- sponsible for the discordant age sequence of sample 403 in view of the field and mineralogic relations. If mass spectrometric errors are averaged, the slope of the line passing through the measured N207/N208 and Nzoe/Nm ratios of samples 584, 512,586, and 403 (fig. 23.1) is equal to a N207/N206 ratio of 0.0524 and a PbW/Pb206 age of 315 million years (Stiefl and others, 1959). This average lead-lead age is somewhat low for a syngenetic Devonian deposit. If the bulk of the mass spectrometric errors are assigned to the measurement of the PbW/Pb208 ratio of sample 403 (table 23.1), the PbW/Pb206 ages of 403 and 586 are both approximately 370 million years. Acceptance of the mass spectrometric data, on the other hand, leads to one of two conclusions. First, the alteration of the ore occurred at some time in the past history of the ore and the “true” age of the ore is in B46 0.48 I I I I GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 0.47 I I 0.46 I 0.45 N207 0.44 N208 0.43 - I 0.42 o E l I I I J 0.40 I I A . o. 0.8 0.9 IO U IE IS L4 N206 N208 FIGURE 23.1.—Plot of New/N202 versus Nzoe/Nzos lead isotope ratio of the samples from Penn Haven Junction, Walcksville, and Nesquehoning. excess of 370 million years. Alternately, contamination of the ore at the time of deposition, not only by common lead but also by an older generation of radiogenic lead, would require that the Penn Haven Junction deposit be epigenetic and less than 200 million years old. Whether the assumed alteration was recent or old, the reversal of the Penn Haven Junction age sequences implies that within the same small outcrop sample 403 lost lead or gained uranium, while sample 586 gained lead or lost uranium. The extensive alteration implicit in the magnitude of these discordant age sequences is diflicult to reconcile with the absence of secondary minerals at the outcrop and the fresh appearance of the tightly cemented sandstone host rock. However, the single geologic process—contamination of old radio- genic lead at the time of deposition—is compatible with the discordant age sequences, the observed field rela- tionships, and the occurrence of the radiogenically en- riched clausthalite (sample 512). The most perplexing aspect of the Mount Pisgah age data is the presence of radiogenic lead with a maximum corrected szm/Pb206 age of approximately 415 million years—impossibly old for Mississippian and Pennsyl— vanian sedimentary rocks. The common lead contami- nation for the Mount Pisgah samples is so small that any reasonable choice for the isotopic composition of the contaminating common lead will not signifi- cantly affect the corrected PbW/Pba06 age of the ores. Although secondary uranium minerals are abundant at Mount Pisgah, the older Pb207/Pb206 ages of the ores cannot be explained by recent lead loss, and past altera- tion would only make the age anomaly greater. The METALLIFEROUS DEPOSITS B47 .0 m c) \l I Q 03 I Q 01 I O .1; | Q (N I (N207 / N208)X ’ (N207/ N 208 ) Y (”ass/“boeh'(N235/N208)Y (5 3’8 - 346) O R Q N I (403-586 1 N207 N235 O 538 / 403—Rc | l I l | 0827x1377 D586-RC RC 346 \ 0 001 002 003 004 005 006 007 008 009 Oi thos OR(Nzoe/hbosk‘WNzos/Nzoeh' N238 (N238 /Nzoe)x ' (ste/ N208) Y FIGURE 23.2.—Plots of the total ‘Nzov/Nm versus thoe/Nzas and normalized difference ratios. remaining alternatives are additions of old radiogenic lead or radon loss. In the latter instance, the essential identity of the PEN/Pb206 ages of samples 346 and 538, coupled with the threefold difierence in uranium concentration, strongly suggests that radon loss, pre- dominantly a diffusion process, is not the significant factor in the age discrepancies. The graphical analysis of the discordant Carbon County ages in terms of-old radiogenic lead contamina- tion is shown in figure 23.2. The normalized diflerence ratios for the sample pairs from Penn Haven Junction and Mount Pisgah are represented by the points (403— 586) and (538—346) respectively; the index isotope Pb?“ being used to normalize the data. The points whose coordinates are equivalent to discordant trial lead—uranium ages of table 23.2 are plotted using square symbols. A detailed treatment of this new graphical procedure has been described by Stiefl and Stern (in press). To make the graphical analysis shown in figure 23.2, it is necessary to assume that (a) there was only one period of mineralization for each deposit; (b) the min- eralizing solutions for each deposit were contaminated by a single common lead and a single generation of an older radiogenic lead; and (c) they have not been re- cently altered. These assumptions appear to be geo- logically reasonable. Accepting assumptions (a) through (c), it is now possible to obtain one concordant (PbZOS/U238=Pb2°7/ U235) age for both deposits by passing a line through the points (403—586) and 538—346) and noting the in- tersection with the concordant age curve. This inter- t5 B48 section has Nan/N235 and N206/N238 ratios of approxi- mately 0.127 and 0.0190, respectively, and is equiva- lent to the concordant age of 123 million years. As- suming an isotopic composition of the contaminating common lead similar to the N esquehoning galena plus original radiogenic lead, concordant ages of 115 and 135 million years are obtained for Penn Haven J unc- tion and Mount Pisg‘ah, respectively. Maximum ages of source rock providing the old radiogenic lead range from approximately 350 to 475 million years. The limitations imposed both by the number of sam— ples available and the analytical data do not justify any emphasis on an exact age solution. However, the conclusion that both Carbon County uranium occur- rences were formed near the end of the Jurassic or early in the Cretaceous would appear to be mathe- matically and geologically sound. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCES Genth, F. A., 1875, Preliminary report on the mineralogy of Pennsylvania: Pennsylvania Geol. Survey, 2d, B, p. 144. Holmes, Arthur, 1960, A revised geological time-scale: Edin- burgh Geol. Soc. Trans., v. 17, p. 183—216. Klemic, Harry, and Baker, R.‘L‘., 1954, Occurrences of uranium in Carbon County, Pennsylvania: US Geol. Survey Circ. 350, 8p. Kulp, J. L., 1959, Geological time scale (abs): America Bu11., v. 70, p. 1634. Stieff, L. R., and Stern, T. W., Graphic and algebraic solutions of the discordant lead-uranium age problem: Geochim. et Cosmochim. Acta (in press). Stiefi, L. R., Stern, T. W., Oshiro, Seiki, and Senftle, F. E., 1959, Tables for the calculation of lead isotope ages: U.S. Geol. Survey Prof. Paper 334—A, 40 p. Wherry, E. T., 1912, A new occurrence of carnotite: Am. J our. Sci., 4th ser., v. 33, p. 574—580. Willard, B., 1935, Portage group in Pennsylvania: Geol. Soc. America Bull, v. 46, p. 1195—1218. Geol. Soc. 5% 24. URANIUM AT PALANGANA SALT DOME, DUVAL COUNTY, TEXAS By ALICE D. WEEKS and D. HOYLE EARGLE, Washington, DC, and Austin, TeX. Work done in cooperation with the US. Atomic Energy Commission One of the most unusual uranium deposits discovered in recent years is in Pliocene sediments above the cap- rock of Palangana salt dome, in Duval County, Texas. Palangana is in the Coastal Plain, about 70 miles west of the Gulf of Mexico and 100 miles north of the Rio Grande. The salt dome was discovered in 1916; sulfur was produced from the caprock in the 1920’s and early 1930’s, and during the same period a few thousand bar— rels of oil was produced from shallow sands above the caprock (Barton, 1925). At present brine is being pro- duced by the Columbia Southern Chemical Company, and it was this company that discovered the uranium by gamma-ray logging of holes drilled in a search for potassium. The surface expression of Palangana salt dome is a shallow basin in a brush-covered plain that slopes east- ward about 20 feet per mile and is capped with a nearly continuous layer of caliche. The dome is covered by the Goliad sand (Pliocene), which dips 25 to 40 feet per mile east-southeastward and overlaps middle Ter- tiary rocks (Sayre, 1937) (fig. 24.1). The Goliad sand overlaps unconformably on the Lagarto clay (Mio- cene?), which is dominantly an impervious clay with a few sand lenses, 011 the Oakville sandstone (Miocene) a massive sand with some gravel, clay balls and ashy clay, and on the Catahoula tuft (Miocene?), which contains highly tuffaceous sand and clay and volcanic conglom- erate (Sayre, 1937) , and on the Frio clay (Oligocene?) , which is dominantly clay and relatively impermeable. Most of the Tertiary sediments, but especially the Catahoula tuif, contain large quantities of volcanic detritus, pebbles, sand grains of igneous minerals, and shaids of glass. The most abundant rock types are chiefly andesite, trachyandesite, and soda trachyte (Bailey, 1926). The outcropping rocks of the Catar houla are slightly to considerably altered by alkaline ground water, which caused the development of a caliche cover, opal, and chalcedony cements, and for- mation of zeolites. The most likely sources of the Catahoula sediments appear to be the igneous rocks of Mexico, 100 miles or more to the west, or those of the Big Bend country, 300 miles northwest. Recent analy- ses of a suite of the Big Bend rocks indicate they con- tain more than average quantities of uranium (Davild Gottfried, written communication, 1959). l The salt of the Palangana dome 1s 850 to 1,000 fe 1; below the surface (fig. 24.1). It is capped by anh - drite, gypsum, sulfur, and carbonate rock several hun— i B49 DEPOSITS METALLIFE ROUS .58 .3550 EEO .unwwnfiam was high 50.53 am; 05 «9 SE ofiou :sm «danish no 338% 35.8 oEaSEEwEQIAdn "Enema / \ / \ 3 / w 9 m. 8:3 ucm >38 30.6 59.93 D m. w 9 w >2". 2t 0 M x 3 U 9 33350330 ucu ta: .0 :3 £39.25 m m 853 w accumucum 2:330 M w 3 ~36 otsmfl m» g \(Mu‘l; w FEES: .83 3:00 Wm. m a / \ / / / abcmm U20 Anny Q / / / / / I’llLIA‘ 3.9.. ___.n_ 39m .3333 >N~U 0th ASEwEchoo new tat :3 530288 3.53 80333 2.3me _ >30 otmmfl AHVEHHJ. _ 1 , 9.8 3.8 Eu «ca :39". .WEZDOO 11,.‘4 mwjzz m 0 B50 GEOLOGICAL dred feet in total thickness. The uranium ore, chiefly very fine divided sooty pitchblende, occurs at a depth of about 325 feet, more than 100 feet above the caprock. It is in highly calcareous clay-ball conglomerate inter- bedded with friable fine- to medium-grained sand 10— cally impregnated with a little oil. Only a few beds are firmly cemented. The conglomerate contains black chert pebbles, nodular authigenic chalcedony, a little partly silicified fossil wood, and a few vertebrate fos- sils. Several horse teeth and a dog tooth found by company personnel and by us were identified by Prof. J. A. Wilson, of the University of Texas, as belonging to the fauna of the basal member of the Goliad sand. The electric and the lithologic logs of drill holes on the dome have been correlated with those of drill holes a few miles northwest of the dome. The logs were cor- related by means of clay-ball conglomerate at the base of the Goliad. The deepest core which we examined SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES was 460 feet deep and on the dome. The sediments above the conglomerate show minor variations, but they consist mainly of moderately to very fine grained silty sandstone or sandy clay and are all at least slightly calcareous. The differences between the cores are in the rocks below the conglomerate and in the color of the ore zone. Over the salt dome between depths of about 276 and 460 feet the rocks within the ore zone as well as those in the first 50 feet above it and those below it are greenish gray, whereas off the dome cor— relative rocks are pinkish to yellowish gray. This color and the fine-grained disseminated pyrite in the ore zone and under it are due to the reducing environ- ment of the H28 emanating from the caprock. The sand under the ore zone contains reworked foraminif— era and is believed to be Oakville sandstone. The Lagarto clay is not present on or close to the dome. In March 1959 a suite of samples was collected along 93 3 3 2 II) tv to o g g 2 E E S E E E E o S a; a) n) a) 0 ° 3 iii 5 l}; 2 2 c ‘1’ I: c I: c g 30 ‘D ‘U “U '0 an an 3 E g 3 3 B 7' 5 5 5 5 5 5 5 e a Is a a 3 u 0 w (I) U) U) o o c c c c c 5 g 3-0 3 8 37> 8 3 m w 1.5 0.7 Fe 0.3 ____________ _— 0.3 /___ _______ 0.15 // 0.07 // 0.03 // 0.015 // 0.007 0.003 ‘2 0.0015 LIJ U ______ __ O _______ m LIJ D. 0.07 ——L__l————— 1 0.03 0.015 M00007 _______ ____:l ______ __ 0.03 0.015 I 0.007 0.003 v 0.0015 __ _ 10 5 0 18L12 1 I 115 I I 1 I l I I I I l I I I I m_|TOM m" FEET FIGURE 24.2.—Graph of selected data from radiometric, chemical, and semiquantitative spectrographic analyses of suite of samples through the ore zone at Palangana. METALLIFEROUS DEPOSITS a vertical section through the ore zone in the small prospect mine. The rocks contain much water, are at a temperature of about 90° to 100° F, and give ofi con- siderable HZS. Spectrographic and chemical analyses of the samples show that concentrations of the easily oxidizable and reducible elements iron, uranium, molybdenum, and vanadium are directly correlated (fig. 24.2). The ore zone contains several hundred times as much uranium as average sandstone, about 75 times as much molybdenum, and about 5 times as much vana- dium. Molybdenum and vanadium though much less abundant than uranium are present in amounts that are significant when one considers that these elements com- monly accompany uranium in the Colorado Plateau (Garrels and others, 1957). The carbonate content B51 37 percent; the highest is in the firmly cemented sand- stone 12 feet from the bottom in this suite. The equivalent uranium of these samples differs con- siderably from the actual uranium content. Radio- chemical analyses by J. R. Rosholt, J r., show the na- ture of the disequilibrium (fig. 24.3). If the uranium and its daughter products were in perfect equilibrium, all the ratios would be 1 and would be represented by a horizontal line. The graph shows, however, that the three samples of ore grade are all low in radioactivity, and the six samples below ore grade high in radio- activity, as compared with uranium content determined chemically. The amount of radium in these samples is quite variable, and it is uncertain whether radium was added or uranium extracted from any particular (percentage of acid-soluble fraction) ranges from 17 to sample. Migration is obviously taking place in this Log Sample eU Pa 231 Th 230 Ra? l scale number —— _ ‘_ _‘ amp e 8 U U U U number eU U 7 I (31) 0.007 0.002 6 (30) .022 .005 5 30 / 4 \ (26) .010 .005 31 \ 3 \ (20) .013 .006 20 2 26 Samples below ore (23) 010 .008 grade, high eU 23 21 \ 1 \ (21) .013 .011 , EQUILIBRIUM 0‘9 / //\ \ 33 / \ \ 0.7 , 32 (27) .063 .16 Ore-grade samples, 06 / (33) .22 .32 low eU 0.5 (32) .23 .34 27 0.4 Analyses by J. N. Rosholt. Jr. FIGURE 24.3.—Graph of ratios of uranium daughter products to uranium, showing nature of radioactive disequilibrium for suite of samples at Palangana (same suite as in fig. 24.2). B52 deposit, and in spite of moderately reducing conditions the uranium is not very firmly fixed. We believe that uranium was leached by alkaline carbonate water from the volcanic material in the Tertiary sediments, chiefly from the Catahoula tufi' but possibly in part from other rocks that contain a smaller proportion of volcanic debris. This is highly reason— able because (a) of the large volume of volcanic detritus that contains above average uranium, (b) the sediments consisted of highly reactive or unstable material in a terrestrial deposit, (0) the climate was hot, and so dry that leached products would remain in more concen— trated solution than in humid climates. A consistent geochemical environment is indicated by the extensive caliche cap, the presence of highly mineralized ground water, the widespread occurrence of opal and chalced— ony, the presence of many small concentrations of uranium in surface outcrops of the tufl'aceous rocks, and by the zeolitic alteration of those rocks. Some of the uranyl carbonate in solution probably migrated down- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES dip in permeable beds confined between less permeable clay beds until it reached the reducing environment of the salt dome. The precipitated uranium is very fine grained and disseminated; this fact as well as the radio- chemical relationships indicates that the deposit is very young and unstable, and that it probably is still in the process of formation or modification. REFERENCES Bailey, '1‘. L., 1926, The Gueydan, a new middle Tertiary forma- tion from the southwestern coastal plain of Texas: Univ. Texas Bull. 2645, 187 p. Barton, D. C., 1925, Salt domes of South Texas: Am. Assoc. Petroleum Geologists Bull., v. 9, p. 536—589. Garrels, R. M., Hostetler, P. R, Christ, C. L., and Weeks, A. D., 1957, Stability of uranium, vanadium, copper, and molyb- denum minerals in natural waters at low temperatures and pressures [abs] : Geol. Soc. America Bull., v. 70, p. 1127— 1184. Sayre, A. N., 1937, Geology and ground-water resources of Duval County, Texas: U.S. Geol. Survey Water-Supply ‘ Paper 776. 116 p. 6b 25. PARAGENESIS 0F URANIUM ORES IN TODILTO LIMESTONE NEAR GRANTS, NEW MEXICO By ALFRED H. TRUESDELL and ALICE D. WEEKS, Washington, DC. Work done in cooperation with, the U.S. Atomic Energy Commission The Todilto limestone is locally replaced by minerals of uranium and vanadium, and to a lesser extent by minerals of fluorine, iron, lead, manganese, molyb- denum, and selenium. The replacement started along grain boundaries, especially where the grains were dis- similar—for instance, along the borders of detrital quartz or feldspar, between coarse- and fine-grained calcite, or around carbonaceous masses. The uraninite was initially deposited as colloform coatings from which it expanded in rounded shapes into adjoining fine-grained calcite. The colloform bodies tended to coalesce, and in places they replaced the rock almost completely, leaving only relict quartz grains. The ore can be loosely classified into three types: uranium ore, uranium-fluorine ore, and uranium— vanadium ore (fig. 25.1). The simplest type is uranium ore containing no ap— preciable quantity of vanadium or fluorine. This occurs partly in separate deposits and partly within deposits containing irregularly distributed vanadium minerals. Polished sections show that some pyrite was formed before uraninite and coflinite and was strongly corroded by those minerals. Colloform uraninite re- placed the limestone, starting along grain boundaries and finally replacing the grains themselves. Detrital grains commonly served as nucleating centers, as did boundaries between coarsely crystallized light-colored calcite and their finer grained limestone matrix; ore formed on these boundaries commonly extends into and replaces the limestone. Later, coffinite coated the uraninite and filled shrink- age cracks that developed within it. The last—depos» ited uranium was in a fine-grained intergrowth of calcite and uraninite. Euhedral galena crystals were deposited at the same time as the uraninite and coifinitb and have been partially replaced by calcite. In a few specimens the ore has been shattered and the fractures filled with late calcite. Late pyrite is also found iI some polished sections; it replaces detrital grain , starting along their boundaries, and may surround t e uraninite border of a grain. g s i METALLIFEROUS DEPOSITS U—F ore B53 U—V ore Calcite Pyrite Uraninite Coffinite Galena Fluorite Haggite Paramontroseite Vanadium clay Marcasite Hematite FIGURE 25.1—Paragenesis diagram of three types of uranium ore in Todilto limestone. The fluorite—bearing uranium ore is scarcer than the other types. The limestone has been recrystallized and partly replaced by purple fluorite; certain favorable layers were completely replaced, and irregular masses above and below them partly replaced. The fluorite seems to have been introduced after partial recrystal— lization of the rock but before the uranium mineraliza— tion (fig. 25.1). Some ostracod shells were partly filled with fluorite, but most are filled with recrystallized cal- cite even if completely surrounded with fluorite. This indicates that some recrystallization preceded the in— troduction of fluorite. Later, coarse calcite cut the fluorite, and then both of these were replaced dendriti— cally by uraninite and pyrite (fig. 25.2). Most of the «:éicite ‘52 FIGURE 25.2.—Uranium-fluorine ore. Fluorite (dark-gray, fluor) has replaced fine-grained limestone (medium—gray, lst) and has been itself replaced by coarse calcite (medium- gray, calcite). The calcite and fluorite are replaced den- dritically and along grain boundaries by uraninite (light- gray, u) and pyrite (white, 1)). Uraninite, pyrite, and galena (white, 9) have also precipitated at the boundary between limestone and fluorite. Polished section. Manol pit, sec. 30, T.‘ 13 N., R. 9 W., McKinley County, I. Mex. uraninite is in interstitial replacements in the fine— grained calcite adjacent to the fluorite. Some of the pyrite was replaced by uraninite and galena, but most of it is later than these minerals. Cracks in the late pyrite are filled with fine-grained calcite, which also corrodes and partly replaces galena. N o evidence of uraninite—fluorite intergrowth was noted in the polished sections, nor of a genetic connec— tion between these minerals in time and space. Both the uraninite and the fluorite occur alone as commonly (or more commonly) as they do together. Although the average vanadium—uranium ratio of the Todilto ores is in general less than 1: 1, the vanadium is spottily distributed both areally and in detail. The minerals in relatively unoxidized uranium-vanadium ore are uraninite, cofiinite, haggite, paramontroseite, vanadium clay, barite, pyrite, galena, specular hema- tite, and calcite. In polished sections it can be seen that some recrystal- lization of calcite preceded and some accompanied the deposition of the ore minerals. Precipitation cf ore minerals generally began along grain boundaries and then gradually replaced the grains themselves. Some open spaces, probably solution cavities, became lined with ore minerals and were later filled with coarse cal- cite. Early pyrite became severely corroded and re- placed by the ore minerals. Most of the vanadium min- erals were deposited before the uraninite (fig. 25.1). Haggite (color bronze in polished section, With strong blue, yellow, and orange polarization colors) was partly deposited in blades at the margins of solution channels, partly in fine fibers replacing limestone along grain boundaries (fig. 25.3), and partly intergrown with para— montroseite in rosettes between generations of re- crystallized calcite. Some haggite has replaced mon— troseite (?) to form multiple crystals which together form a blade. In some places the haggite was preceded by a vanadium clay that formed nearly spherical aggre— gates enclosing pyrite or organic matter (fig. 25.3). The B54 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES uranium minerals. Galena was deposited during and after the deposition of the uranium minerals, and it re- placed early pyrite and haggite. The galena nearly always forms cubes; where it is irregular, it is usually in a cubic hole that indicates its original cubic form. The pyrite very seldom forms euhedral grains. The last uranium was precipitated as intimate intergrowths of uraninite and calcite, which in the highest grade samples have almost completely replaced calcite grains. Some late haggite was formed in spaces between blades of earlier h'aggite ringed with uraninite. The solution openings were filled with coarse calcite, often enclosing irregular areas of vanadium clay and ghost crystals of pyrite and marcasite. In a few places vanadium clay is ringed with specular hematite. \Vhere solution cavities were absent, late pyrite or FIGURE 25.3.—-Uranium-vanadium ore. A solution opening has marcaSite appears to have replaced uraninite'ringed been filled with vanadium clay (rubbly appearance, cc), quartz without replacing the uraninite (fig. 25.4)- pyrite (white, 1)), galena (white, 9), haggite (very light gray, h), and coarse calcite (medium gray, calcite). The vanadium clay coats organic matter (black, or) and the haggite has been coated and partially replaced by uraninite (light gray, u). Polished section. F 33 mine, sec. 33, T. 12 N., R. 9 W., Valencia County, N. Mex. borders of detrital grains of quartz and feldspar were favorable sites for deposition of this clay, which has slightly to almost completely replaced them. Haggite was followed by colloform uraninite, which coated the haggite blades and rosettes and has charac- teristic shrinkage cracks. The uraninite was partly or wholly replaced by coflinite, which reflects a little less light in polished section. The coffinite spread inward along the shrinkage cracks in the uraninite and grew along boundaries between uraninite and haggite. The deposition of coffinite may indicate that the replacement of detrital grains by earlier ore minerals had released enough silica to saturate the solution with respect to FIGURE 25.4.—Uraninite (light-gray, u) along grain boundaries of quartz (dark gray, q). Late pyrite (white, 1)) seems to , , , .. , replace quartz grains along boundaries without replacing uranlum Slhcate- Some blades 0f hagglte are almOSt uraninite. Polished section. Faith mine, sec. 29, T. 13 N., completely replaced by calcite, leaving a ring of R.9W., McKinley County, N. Mex. 6b 26. PITCHBLENDE IDENTIFIED IN A SANDSTONE-TYPE URANIUM DEPOSIT IN THE CENTRAL PART OF THE AMBROSIA LAKE DISTRICT, NEW MEXICO By HARRY C. GRANGER, Denver, Colo. The Ambrosia. Lake district, in McKinley County, Most of the uranium in the district occurs in the form N. Mex., contains the largest known reserves of uranium of coflinite in deposits in the VVestwater Canyon mem— in the United States. Its ore deposits are being in- ber of the Morrison formation. Recently, however, a tensively studied by the US. Geological Survey. small amount of pitchblende (uraninite) was identified i i METALLIFEROUS DEPOSITS in the Kermac Sec. 22 mine. This is the first pitch- blende reported from the central part of the district. The occurrence was reported by David Smouse, geol- ogist at the Kermac mine, and was later sampled by me. Identification was verified from X-ray powder pattern by Edward Young, US. Geological Survey. The pattern was somewhat diffuse, indicating either extremely small grain size or poor crystallinity. The pitchblende occurred on the 6,450-level, about 100 feet below the premining water table, in a vug ex- tending along a northwest-trending fracture. Most of it formed a hard, black, vitreous, botryoidal crust less than 2 mm thick and having an area not more than 2 feet in diameter, on the walls of the fracture and vug. B55 The remainder of the vug was filled with calcite, and the adjacent rock contained much disseminated pyrite. Although this occurrence was below the ground- water table, hematite and limonite derived from oxi- dized pyrite also occur extensively on the same level of the mine. It appears likely that the pitchblende was deposited from ground-water solutions that acquired uranium by oxidizing nearby cofiinite. Pitchblende has also been identified from other sand- stone-type deposits near the edges of the district, but these were partly oxidized deposits, near the outcrop and well above the ground-water table. To date, no pitchblende has been recognized in any deposit that is not either above the water table or near oxidized rock below the water table. ’>% 27. METAMORPHIC GRADE AND THE ABUNDANCE 0F Th02 IN MONAZITE By WILLIAM C. OVERSTREET, Beltsville, Md. Work done in cooperation with the 0.8. Atomic Energy Commission Monazite, an anhydrous phosphate of the cerium earths, commonly contains a small amount of thorium. Thorium for industry has been obtained from monazite since the 1880’s. Before that period only a few speci— mens of monazite had been analyzed, to satisfy the curiosity of scientists, but after industrial needs arose, hundreds of samples of monazite from many districts were analyzed to determine whether they could serve as commercial sources of thorium. The results of these analyses are scattered in the literature, and until re- cently many obscurely published analyses were Virtu— ally lost. It is now possible, however, with the help of the extensive bibliographic card file of uranium and thorium compiled by Miss Margaret Cooper and her co-workers in the US. Geological Survey and US. Atomic Energy Commission, to review the world litera- ture in a practicable length of time. During the past year I have examined about 800 of some 1,200 references to monazite published before 1959. From this unfin- ished review a pattern emerges that I interpret as evi- dence that monazite goes through a previously unrec— ognized geologic cycle. The chief features of the cycle, in appropriate rocks, are these: Detrital monazite is unstable in early stages of regional metamorphism, but as the metamorphic grade of its host rises, monazite be- comes increasingly abundant and also richer in ThOZ. GEOLOGIC DISTRIBUTION OF MONAZITE Accessory monazite is widely distributed in meta- morphic rocks of intermediate and high rank derived from pelitic sediments. It is especially common in schists, gneisses, and migmatites of the higher rank subfacies of the amphibolite and granulite facies. It may occur in plutonic rocks ranging in composition from diorite to muscovite granite, and in associated pegmatite, greisen, and vein quartz. In this group it is most often observed in biotite-quartz monzonite, two— mica granite, and cassiterite granite. Monazite is very rarely found in syenites, but it does occur locally in syenite pegmatites and carbonatites. It. is not known to occur in lavas, and it has not been observed in plu— tonic mafic rocks or their metamorphic equivalents. Erosion of its host rocks releases monazite for trans— port, during which it-tends to settle and form placers along streams, lakes, and ocean beaches. Fossil placers are preserved in lithified sediments of many ages, and accessory detrital monazite has been found in sedimen— tary rocks of all ages from Precambrian to Recent. B56 RELATION OF MONAZITE ‘TO GRADE OF METAMORPHISM The opinion has long been current that particles of monazite in paraschists and paragneisses are remnants of detrital grains. If this were true, the abundance of monazite in the paraschists and paragneisses would be controlled by its abundance in the sediments from which the metamorphic rocks were derived, and there would be no relation between the abundance of monazite and the metamorphic facies of the host. The many hun- dreds of references in the literature to the sources of monazite show, however, that such a relation is clearly marked in metamorphosed pelitic rocks. Accessory monazite is exceedingly rare in the greenschist facies, rare to sparse in the epidote-amphibolite facies, sparse to common in the amphibolite facies, and common to abundant in the granulite facies. I interpret this distribution of monazite among the facies as follows: Detrital monazite in pelitic sedi— ments is unstable, so that at the onset of regional meta- morphism it breaks down and shares its components with other minerals; detrital monazite as such disap- pears, and for a while not much of it is recrystallized. This accounts for its great rarity in the greenschist facies and sparseness in the epidote-amphibolite facies. As the grade of metamorphism increases, an environ- ment is reached at which monazite is again stable, and metamorphic monazite begins to form at a few centers of crystallization, which multiply with increasing grade of metamorphism. The paragneisses, formed at very high metamorphic grades, contain more monazite, on the average, than their sedimentary counterparts, for more monazite in them has crystallized than was contained in the detrital grains of the original sedi- ment. The components of this added monazite appar- ently come from trace amounts of thorium, the rare earths, and phosphorus in some of the other original detrital constituents of the sediment. One of the results of increasing metamorphism of pelite is thus the previously unrecognized generation of metamorphic monazite. GEOLOGIC RELATIONS 0F Th02 IN MONAZITE The results of 181 analyses of monazite are grouped in table 27.1 according to geologic environment. They show that in metamorphosed pelites the proportion of thorium in monazite, despite a wide range and certain inconsistencies, increases on the average from 0.5 per— cent Th02 in phyllites of the greenschist facies to as much as 10 or 12 percent in rocks of the granulite facies. Monazite in metamorphosed limestones and other calcareous rocks (Rose, Blade, and Ross, 1958, p. 996) is poor in thorium. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S TABLE 27.1.—-—Abundance of Th0; in monazite as related to geo- logic environment in Africa, Asia (exclusive of the U.S.S.R.), Australia, and South, America Th0, (in percent) Source of monazite Least Greatest Average Metamorphosed pelitic sediments: Greenschist facies, 2 samples, Brazil ______________ Amphibolite facies: Middle and upper subfacies, 1 sample, New Zealand Upper subfacies, 1 sample, New Zealand ____________________________ Upper subfacies and granulite facies, 6 samples, Madagascar, Sierra Leone, and Travancore--. Granulite facies, 6 samples, Ceylon and India _____ Metamorphosed calcareous sediments: Amphibolite facies, 2 samples, Madagascar and Brazil .......................................... .05 1.05 . 55 Metamorphosed pelitic sediments associated with granitic rocks: Greenschist facies(?), 1 sample from diorite in slate, Australia ..................................................... 6.6 Amphibolite facies: Lower subfacies intruded by pegmatite, 2 sam- ples from pegmatite, Australia........; ....... 10.7 19. 4 15. 05 Lower and middle subfacies intruded by granite, 7 samples, Taiwan and Australia _____________ 3. 20 6. 79 5. 23 ____________________ 6. 5 M (ildliile subfacies intruded by granite, 1 sample, aria ________________________________________ Middle subfacies intruded by pegmatite, 8 sam- ples from pegmatite, Japan, Australia, and Brazil. ....................................... 4. 0 8. 0 5. 2 Middle and upper subfacies intruded by gran- ite, 18 samples, Brazil ________________________ 5.0 11.5 5. 8 Upper subfacies intruded by granite, 24 sam- ples, Nigeria, Korea, Australia, and Brazil... 2.3 10.0 6.3 Upper subfacies intruded by pegmatite, 17 samples from pegmatite, Madagascar, Union of South Africa, Japan, India, Bolivia, and Brazil ........................................ i. 5 20. 2 7. 9 Granulite facies: Upper amphibolite subfacies to granulite facies intruded by granite, 18 samples, India ........ 6. 57 9. 24 8. 41 Upper amphibolite subfacies to granulite facies intruded by pegmatite, 1 sample from pegma- tite, India ........................................................ 31. 50 Granulite facies intruded by pegmatite, 11 samples from pegmatite, Madagascar, Ceylon, and India ..................................... 6.00 28. 20 10.72 Granites and pegmatites: Unclassified granite, 5 samples, Burma, Korea, and Brazil ...................................... 1.99 9. 49 7.14 Cassiterite-bearing granites, 31 samples, Indo- nesia, Malaya, and Australia ................... .00 9. 41 3. 46 Cassiterite-bearing pegmatites, 7 samples, Australia and Thailand _________________________ 3. 80 5. 93 5.01 Carbonatites 5 samples, Kenya, Northern Rho- desia, and Nyasaland ............................. .00 <1. 0 <1. 0 Veins: Low-temperature, 6 samples, Belgian Congo, Union of South Africa, Australia, and Bolivia.. .00 2.50 .74 High-temperature(?), 1 sample, Union of South Africa .............................................................. 8.01 The abundance of thorium in monazite from igneous and hydrothermal rocks is also evidently subject to geologic controls. Monazite is less abundant and poorer in thorium in granites that crystallized at shallow depths than it is in plutonic granites. Monazite from cassiterite granites intruded into sandstone, shale, phyllite, and limestone is devoid of thorium, but mona. zite from gneissic cassiterite granites intruded into rocks of the amphibolite facies contains as much as 9 percent of T1102. Monazite found in low-temperature veins, in vugs where it forms open growths, and in car- bonatites contains little or no thorium, whereas mona- zite from high-temperature veins is thorium-rich. The abundance of thorium in monazite appears to be partly determined by pressure and temperature of crystallization, but the chemical composition of the enclosing rock is also involved. LIGHT METALS AND INDUSTRIAL MINERALS Estimates of the intrinsic ages of monazite from plutonic rocks should recognize that even such mona— zite may be of metamorphic origin. B57 REFERENCE Rose, H. J ., Jr., Blade, L. V., and Ross, Malcolm, 1958, Earthy monazite at Magnet Cove, Arkansas: Am. Mineralogist, v. 43, nos. 9—10, p. 995—997. 5? GEOLOGY OF LIGHT METALS AND INDUSTRIAL MINERALS 28. CONCENTRATIONS 0F “ILMENITE” IN THE MIOCENE AND POST-MIOCENE FORMATIONS NEAR TRENTON, NEW JERSEY By JAMES P. OWENS, JAMES P. MINARD, DONALD R. WIESNET, Washington, D.C., and FRANK J. MARKEWICz, New Jersey Geological Survey, Trenton, NJ. An intensive search for economic concentrations of “ilmenite” 1, followed the initial discovery of large low- grade deposits in the New Jersey coastal plain. The most difficult problem to solve in this search has been the relation of these deposits to the known “ilmenite”-bear- ing formations which include the Kirkwood formation of middle Miocene age, the Cohansey sand of the late Miocene( ?) or Pliocene( ?) age and the deposits (prin- cipally the Cape May formation) of Quarternary age. It was concluded from detailed mapping in the Browns Mills quadrangle and an analysis of the data supplied by the New Jersey State Bureau of Geology and Topo- graphy, that the highest concentrations occur in the Kirkwood and Cape May formations. KIRKWOOD FORMATION Moderate concentrations of fine-grained (mostly —60 to 200 mesh) heavy minerals were found in the Kirk— wood formation (fig. 28.1 and table 28.1) . This forma- tion is primarily a massive-bedded marine quartz sand consisting of a lower dark-colored clayey sand and an upper light-colored sand (probably an eluviated bed). The heavy mineral concentrations apparently have the same distribution in both units (table 28.1). “Ilmenite,” generally fine to very fine grained and platy, constitutes between 60 and 80 percent of the heavy mineral fraction. Most of the grains have a black metallic appearance although a small percentage have an overall brown cast. CAPE MAY FORMATION The Cape. May formation, a fluvial deposit in this region, is characterized by high concentrations of 1“Itlmenite” in these formations has been shown by X-ray analyses to be a mixture of ilmenite and ferric and titanium oxides. It has fixed chemical composition as shown by the analyses cited by Markewicz, Parrillo, and Johnson (1958, p. 8). 557753 0—60 5 TABLE 28.1.—-Selected heavy-mineral analyses from the New Jersey coastal plain, Ocean and Burlington Counties Heavy Quadrangle Field No. Depth of mineral Formation boring content (percent) Feet In. Cassville- _ _ _ 259 9 14:4 Not recorded. 236 6 3. 9 Do. 235 7 1. 8 Do. 237 15 2. 3 Do. 66 5 6. 2 D0. 7 51/6 8. 9 Do. 18 3 5 2. 4 Do. 33 11 4 1. 6 Do. 38 7 2 2. 4 Do. 220 8 2. 1 Do. 48 15 1. 0 Do. 198 8 3. 5 Do. New Egypt-- Ne 96 ________ 3. 89 Kirkwood (light). Do. ________ 1. 13 Cohansey. Ne 97 5—10 0. 93 Do. Do. 10—15 0. 78 Do. Do. 15—20 1. 63 Do. Ne 103 5 2. 87 Kirkwood (light). Ne 107 ________ l. 54 Cohansey. Ne 108 ________ 1. 06 Do. Ne 113 ........ 3. 22 Kirkwood (light). Ne 115 ________ 2. 43 Do. Do. ________ 1. 49 Cohansey. Browns Bm 6 8—13 3. 91 Kirkwood (light). Mills. Bm 9 22—24 1. 80 Kirkwood (dark). Bm 15 16—18 6. 58 Do. Do. 26—28 2. 15 Do. Bm 16 8—1.2 7. 04 Cape May. D0. 12—18 5. 46 Do. Do. 18—28 . 88 Cohansey. Do. 28—33 . 43 Do. Bm 41 38 l. 00 Cape May. Bm 40 0—18 11. 14 Do. Do 18—38 1 90 Cohansey. B58 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S TABLE 28.1.—Selecled heavy-mineral analyses from the New Jersey coastal plain, Ocean and Burlington Counties—Cont. heavy minerals (table 28.1) in small discontinuous de- posits. Most of the heavy minerals in these deposits are H ' . Quadrangle Field No. thpth of writ-iii meamn probably reconcentratlons from the Cohansey sand. 0mg ($3233 The heavy mineral suites are very similar mineral- Feet In. 0 icall to those of both the Kirkwood and Cohanse g y y formations but the grain-size distribution closely re- Browns Bm 42 0—38 3- 00 Cape May and Co- sembles the deposits in the Cohansey. A study of a Mills—Cont. hansey. - - - small closed basm 1n the Browns Mllls uadran le Bm 48 0-28 4.60 Cape May and Co- . . . . q g ’ hansey. which is underlain only by the KII'kWOOd and Cohansey Bm 29 7—18 1. 35 Cohansey. sediments, showed the high “ilmenite” concentrations LakthFSt—u 15E ———————— :1: in the Cape May formation to be of the Cohansey ‘ 120 :1: 3:0 type. AN 88 ________ 5. 9 OOH SEY SAND g: -------- :- 2 The Cohansey sand is generally coarser grained than ““““ ' the underl incr Kirkwood formation. It has essential- 132a ________ 2. 2 y c _ . _ 168 ________ 4. 0 ly the same heavy mineral sulte as the Kirkwood, al- 172 ________ 2. 9 though the minerals are commonly of medium sand size (~16 to 60 mesh primarily), and the concentra- 74°30' 74°15' 40°15' 40°15' N .Roosevelt Farmingdale. ,——_.___&)ENT_Y / COUNTY ‘_‘ s‘b/ i o 2 4 6 8 MILES $0/Qék \ I___J__L_J—l 0%, 63* , s 0 74°45' \ \ ’ 193 \ z /430 38° 0 0168 k\ /“ ‘ / \ / Cassville. o172 ‘\\/ / 11: \\(/ .Archers Corner LAKEWOOD .Columbus + 7+ 6g .N < 33° 3152 0154 96 v» GW 2200 160 113 f, Egypt 0 * ¢\ 0 018 CA 17 088 °66 1320 23:20 . Lakehurst 40°oo' 237° 257° 0“ 086 74 15, 40°00 EXPLANATION X Auger hole in Cape May formation + Auger hole in Cohansey sand ir Auger hole in Kirkwood formation 0 Auger hole in unidentified formation \\ C A“ Contact Tkw, Kirkwood format/on TCh, Cohansey sand 74°45’ 74 30' FIGURE 28.1.—Location of auger holes listed in table 28.1. LIGHT METALS AND INDUSTRIAL MINERALS tions are leaner. A high incidence of brown (altered?) grains was noted among the “ilmenite” fractions. Local concentrations of heavy minerals occur in this unit but are for the most part too small to be economi- cally important. SUMMARY It seems from the data presented that two potentially economic sources of “ilmenite” occur near Trenton, N.J. These are: 1. The Kirkwood formation, which generally contains only 1 to 2 percent “ilmenite.” The total available tonnage. of “ilmenite” however is large because of the great volume of the deposit. The fine to very fine grained character of the “ilmenite” might be a problem in recovery operations. B59 2. The Cape May formation, which contains small de- posits of relatively high-grade ore. These deposits are difficult to find, however, because of their fluvial origin. From a study of this formation, it appears that the heavy minerals tend to accumulate in nar— row valleys into which the Cohansey sediments are carried. The best concentrations apparently occur where the “ilmenite” in the Cohansey sand was above average (about 1 percent). REFERENCE Markwicz, F. J., Parrillo, D. G., and Johnson, M. E., 1958, The titanium sand of southern New Jersey: New York, Am. Inst. Mining Metall. Engineers meeting (preprint No. 5818A5), Feb. 1958. 29. BLOATING CLAY IN MIOCENE STRATA 0F MARYLAND, NEW JERSEY, AND VIRGINIA By MAXWELL M. KNECIITEL and JOHN W. HOSTERMAN, Washington, DC, and Beltsville, Md. Work done in cooperwtiion with, Maryland Department of Geology, M ines and Water Resources and U.S. Bureau of Mines The problem of locating supplies of expandable raw material for manufacture of lightweight aggregate- has received attention in the course of a reconnaissance study of clay deposits in Maryland that the Geological Survey has been conducting since 1957. This paper includes information from an interim report (Knechtel, Hosterman, and Hamlin, 1959) on promising deposits of bloating clay in southern Maryland, and announces discoveries of such material, heretofore unreported, at two places in Virginia (fig. 29.1). Samples were tested for bloating at the Electrotech- nical Experiment Station, US. Bureau of Mines, Nor- ris, Tenn. The tests, performed by Howard P. Ham- lin, Supervising Ceramic Engineer, assisted by George Templin, involved drying, crushing, screening, and firing for 15 minutes at 1900°, 2000°, 2100°, 2200°, and 2300°F in a small electrically heated kiln, and also determination of unit weight, water absorption, and color of any fired products that showed suflicient ex- pansion to warrant investigation of their suitability for use as lightweight aggregate. The clue that led to the discoveries in Maryland and Virginia was a reported occurrence of expandable clay in strata of Miocene age in Salem County, NJ. (Lod- ding, 1956, p. 115). As this suggested that similar material might be present in sedimentary formations of that age elsewhere on the Atlantic Coastal Plain, we collected representative samples of argillaceous ma- terial in Maryland from the Calvert Cliffs, which ex- tend along the Chesapeake Bay shore between Annap- olis and the mouth of the Patuxent River. Samples from the Choptank formation and the underlying Cal- vert formation failed to bloat, but a sample of olive- gray silty clay obtained near Cove Point from the St. Marys formation, which rests on the Choptank, bloated satisfactorily. Additional samples of expandable clay were taken from outcrops in Calvert and St. Marys Counties, from holes bored with a truck-mounted 5-inch auger in St. Marys County, and from outcrops at two places in Virginia (fig. 29.1). As the surface of southern Maryland is relatively hilly, sites at which open-pit mining would be feasible are here more numerous than in areas of lower relief more typical of the Atlantic Coastal Plain. Raw or finished material could possibly be shipped by low-cost water transport from some sites to markets in Wash- ington, Baltimore, and Norfolk, and perhaps even to ports at greater distances. There are many sites deserving consideration as po- tential sources of raw material for lightweight aggre- B60 GEOLOGICAL SURVEY RESEARCH lQfiO—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 1 M ° PENNSYLVANIAK‘\\\O° z’ \ ‘ ’\§ / ‘5 \BURLINGToy 102 l A V ‘X o \’ no mm “’/ «I i We {x W c. __# \ , k | (o GLOUCESYER\ C E C | L . oYmktown \ é, % \ r Jpcuml Sit-:3! A Y 6‘ 6/ 4 v 0 Ca pe Henlopen ‘ V C) O - {10 RICHMIND ’1 I. EXPLANATION / ' CNARLES C|TV ONE YKIFIELD 7 7 J O Expandable—clay locality 1.09 ‘\ 10 o 10 20 30 4o 50 KILOMETERS 10 20 3p 4p MILES ’ Norfolk Cape Henry / ’ IPmtsFmflh" K Anus: - DINOM 1‘ FIGURE 29.1—Map showing localities in Maryland, New Jersey, and Virginia at which expandable clay is known to occur in strata of Miocene age. 140 120 § POUNDS PER CUBIC FOOT 8 60 40 20 30 20 10 PERCENT INCREASE IN WEIGHT AFTER 48-HOUR SOAKING PERIOD LIGHT METALS AND INDUSTRIAL MINERALS A / /O ‘ // °>fi “d \ >/° \ O CO", / \ I, 1900 2000 2100 TEMPERATURE, IN DEGREES FAHRENHEIT FIGURE 29.2.—Results of 15-minute bloating tests by US. Bureau of Mines of 2 sampled materials from southern Maryland, plotted together with comparable data on 2 commercial lightweight aggregate raw materials: A, unit weight (lb/ft’) of fired products; B, percentages by weight of water absorbed by fired products in 48 hours. 2200 2300 B61 B62 gate where the St. Marys formation crops out in the Calvert Clifi's. The clay exposed here occurs in a layer that is generally more than 20 feet thick. Its thickness and its capacity for expansion vary, however, from place to place, and the clay is overlain by thick deposits of silt, sand, and gravel. Samples of expandable materials have also been ob- tained from an exposure of the St. Marys formation in the Nomini Cliffs, along the south shore of the Potomac River two miles northeast of Stratford Hall, West- moreland County, Va., and from the next younger unit, the Yorktown formation (Miocene), in cliffs 0n the west shore of the James River 1,000 feet south of Fer- gussons Wharf, Isle of Wight County, Va. According to Lodding (oral communication, 1958) the above—noted expandable clay from New Jersey came from an ex- posure of the Kirkwood formation (Miocene) in a brickyard west of the Alloway-Woodstown road, 1.3 miles south-southwest of Fenwick Salem County. Some of the bloated materials formed at tempera- tures between 2000° and 2200° F are comparable in lightness and low water-absorption capacity to many of the best commercial aggregates produced in the United States. Unit-weight and water-absorption data for two clays from the St. Marys formation of Maryland are compared on figure 29.2 with two commercial ma- terials from other parts of the country. Maryland material 1 is olive-gray silty clay from the bottom of an auger hole 100 feet deep near the west side of State Highway 5, southwest of its junction with Villa Road, in St. Marys County. Maryland material 2 represents olive-gray clayey silt approximately 20 feet thick ex— posed in the Calvert Clifl’s, 5 miles northwest of Cove Point; the base of this material is about 23 feet above high tide. Small concrete cubes of bloated material formed in firing one of the Maryland samples at 2100° F were prepared for tests of unit weight and compression strength. The unit weight, 86.3 pounds per cubic foot, proved to be less than that of much concrete made from domestic lightweight aggregates; the compression GEOLOGICAL SURVEY RESEARCH l960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES strength, 3,500 pounds per square inch, surpassed the requirements of most specifications for lightweight concrete. The 48—hour water-absorption capacity, 21.3 percent, is higher than that of most such concrete, but this percentage would probably have been lower if the aggregate had been fired in a rotary kiln. The clay—minerals in the expandable material are montmorillonite, “illite”, and subordinate amounts of kaolinite. These are intermixed with abundant silt- and sand-sized grains of quartz, and with smaller quantities of muscovite and of many kinds of heavy minerals. The clay mineralogy of the expandable material is similar to that of many sampled materials that gave negative results when tested for expansion. It is hoped that further laboratory study will result in satisfactory explanations for the differences in firing behavior among the materials tested. More testing is needed to determine how sampled raw materials that bloated satisfactorily in the small electric kiln will be— have at comparable temperatures in large rotary kilns. If such testing confirms the results at hand, and if removal of the heavy overburden that is nearly every- where present would not be too costly, the resources of expandable clay available for mining in southern Maryland should be adequate, both in quantity and quality, to satisfy much of the demand for lightweight aggregate here and in adjacent populous areas. The proven occurrence of bloating clay of Miocene age at localities as much as 200 miles apart (fig. 29.1), and the known presence of formations of that age in all the States bordering the eastern seacoast from New Jersey southward, suggest the existence of vast poten- tial resources. The increasing market for expanded aggregate in the east coast region warrants compre- hensive studies of their distribution and possible commercial value. REFERENCES Knechtel, M. M., Hosterman, J. W., and Hamlin, H. P., 1959, Bloating clay deposits in southern Maryland: U.S. Geo]. Survey open-file report. Lodding, William, 1956, Raw materials for lightweight aggregate production in New Jersey: Rutgers Univ., Bur. Mineral Research Bull 7. ’5? LIGHT METALS AND INDUSTRIAL MINERALS B63 30. SIGNIFICANCE OF UNUSUAL MINERAL OCCURRENCE AT HICKS DOME, HARDIN COUNTY, ILLINOIS By ROBERT D. TRACE, Bel'tsville, Md. Hicks Dome in the northern part of the Illinois- Kentucky fluorspar-zinc—lead district is a tectonic fea- ture afl'ecting rocks of Devonian, Mississippian, and Pennsylvanian age. It covers about 100 square miles centered in the western half of Hardin County, Ill. The core of the dome, where the rocks dip 10—15 de- grees, includes nearly 2 square miles of limestone, chert, and black shale of Devonian age in which there are a few tabular and possibly oval—shaped pipelike masses of breccia, some radioactive areas, and an altered mafic dike (Bradbury and others, 1955, p. 1—3). Hicks Dome has been described by Brown and others (1954, p. 895—897) as an incipient cryptovol- canic structure. This interpretation is in part based upon data from a 2,944-foot test well in the approxi- mate center of the dome. Most of the sedimentary rocks in the lower half of the hole are brecciated, but the lateral extent and shape of the brecciated mass are not known. According to Brown and others (1954. p. 897—902), the breccia contains thorium, fluorite, barite, calcite, quartz, pyrite, sphalerite, and galena. The thorium and fluorite seem to be closely associated. N0 igneous or metamorphic rocks have been identi- fied in the breccia from the center of the dome, al- though plugs of explosion breccia containing igneous and metamorphosed rocks are known about 7 miles to the northeast and 1.5 and 7 miles to the south (Clegg and Bradbury, 1956, p. 17). The depth to Precambrian rocks at the center of the dome is at least 7,500 feet as shown by data from the M. D. Davis No. 1 test well near Tolu, Ky. (unpublished data, 1956, Shell Oil Company Information Release, mimeographed), about 11 miles to the southeast of the dome. One of the surface radioactive localities (Bradbury and others, 1955, fig. 1, sample 72) was explored in 1955—56 (under a Defense Minerals Exploration Ad- ministration contract) by shallow diamond drilling and trenching in cherty residuum overlying Devonian limestone. The exploration showed two areas of brec- cia, but most of the radioactivity is concentrated in one—a tabular mass about 10 feet wide that extends N. 24° W. for at least 260 feet, is over 100 feet deep, and dips 85° NE. The highest radioactivity (about 0.1 percent eU) occurs in the central 1 to 2 feet of this tabular body. A surface sample of the most radioactive material was found by semiquantitative spectrographic analysis to contain a high concentration of rare earths and thorium (table 30.1). The radioactive mineral in the sample was isolated and identified tentatively as mona- zite. Florencite, a cerium-aluminum phosphate, was found in association with the monazite. The monazite is in small, soft, earthy, round to sub- round, brownish—yellow grains about 0.1 to 0.2 mm in diameter. Preliminary X—ray diffraction study shows that the mineral has monazite structure, but its cell size appears to be slightly smaller than that of monazite from other localities. Spectrographic analysis of the hand-picked material shows it to be a thorium-bearing rare-earth phosphate (table 30.1) that diflers slightly in composition from most other monazite in that it is relatively rich in yttrium and lean in total rare earths. The abundance of yttrium may account for the small cell size. The relatively low content of cerium and lanthanum and abundance of yttrium suggest that the monazite is relatively unfractionated, or primitive, as described by Murata and others (1953, p. 296—297; 1957, p. 148-150). Florencite is in small, soft, earthy, round to sub— round, pale-orange grains about 0.3 to 0.4 mm across. The florencite was identified from X-ray diffraction traces, and confirmed as a cerium-bearing mineral by X-ray fluorescence study (analyst: Richard Larson, 1959). The narrow surface zone of radioactivity that was sampled is about 200 feet west of the deep test well and dips 85° NE. toward the well. Semiquantitative spectrographic analysis of 8 samples (tables 30.1 and 30.2) obtained by J. W. Hill of the US. Geological Survey from the test well and described by Brown and others (1954, p. 899), disclose above-normal quantities of thorium, the rare earths, niobium, zirconium, and beryllium. According to Warner and others (1959, p. 25—28), the BeO content of sedimentary rocks may be as much as 0.004 percent, although generally it is less than 0.001 percent. In the test well, the Be content is as high as 0.06 percent (table. 30.2). In general, the greater the radioactivity, the more the Be, rare earths, Nb, and Zr. The mineralogic and chemical data presented here provide new evidence for the existence of deep-seated B64 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 30.1.——Analyses of samples from Hicks Dome, Hardin County, Illinois Chemical and semiquantitative spectrographic analysis (weight percent) of surface sample EDT—6 l (Wifith) 0089—0099 0.008 N .D. >10 5—10 1-5 0.5—1 0.1—0.5 0.05—0.1 0.01—0.05 0.005—001 0.001—0.005 00005—0001 00001-0005 inc es 16 eU U Can Si Fe Al Ce, La, K, V, Ba, Ti, Sr, Pb, B, V, Er, Cu, Gd, Yb, Eu, Sn, Ga, Be, Mo Ag P , Ca, Pr, Mn Nb, Tb, Sm, Dy, Co, Lu, Mg, Th Na, Zn Ni, Zr Cr, Sc Quantitative spectrographic analysis (weight percent) of monazite hand picked from sample RDT-6 3 09203 L820; Ndzoa I 8111203 011203 131‘an DY203 Y203 T1102 I P205 SlOZ A1203 MgO 08.0 F6103 TiOz Total 16 11 6| 2 1.5‘ 2.5 1.5 i 4.2 4.4' 29‘ 4.4 2.2 0.2 3.8 6.6 2.7 98 Semiquantitative speetrographic analysis (weight percent) of test-well samples 3 Sample Depth XX. X.+ X X.‘ 0.X+ 0.X 0.X- 0.0X+ 0.0X 0.0X- 0.00X+ 0.00X 0.00X- 0.000X+ Tr no. (feet) 1 1725-1750 Ca S1 Mg A1, Fe K, Ba Tl Th, Y, Mn, Sr Pb, La, Dy, Yb Cr, Cu Bi, Ni ........... Ga Na Zn Sc, V 2 1785-1815 Ca Si Mg Al, Fe K Ti Th Y, Mn, Sr Pb La, Dy, Yb Cr, Cu Bl, Ni ........... Ga a Zn Sc, V Ba 3 1975—2000 Ca Mg Si ......... Al, Fe, K Na Mn Ti Sr Pb, V ........... Sc Cr, Cu, Ba Y Ni, Y 4 2150—2175 Ca Si, Mg __________________ Al, Fe Ti Y, Ba Tllilea, Sr Dy, V Yb Pb, Sc Cr, Cu Ni Bi, La n 5 2370—2400 Ca Si Fe, A1, K _________ Ti Mn, Na Ce, Th, La Dy, Nd Sc Cr, Cu 00, Ni ........... Pb Mg Y, Ba, v Yb Sr 6 2425—2450 Ca Si, Mg Al, Fe, _________ Tl Mn, ........... Ce, Ba, La Nd, Se, Cr Ni, Pb, Co, Cu ___________ Dy, Ga, K P, Sr , Y Yb Th Na 7 2450—2475 Ca Si, Mg _________ Fe A1, K Ti Ba, Na, ___________ Sr La, Pb V, Y Cr, Cu, Ni, Yb Co Ce Dy, n Sc Ga, Th 8 2900—2925 Ca Mg __________________ Fe, K A113 ___________ Mn, Na Ti Pb, Sr Y Cu, V Crs, Ni, Yb a c 1 Analysts, Katherine E. Valentine, C. Johnson, and G. Daniels. Sample RDT—6 analyzed for D. M. E. A. contract. 2 Analyst, Harry J. Rose, Jr., 1960. Analysis on 15 mg. Sample diluted in graphite. 5 Analyst, G. W. Beyes, J r., 1953. Be, Nb, and Zr not shown, see later analysis in table 30.2. igneous activity in the region of the Illinois-Kentucky REFERENCES fluorspar-zinc-lead district, but by themselves may neither confirm nor deny the existence of a connection between the igneous activity and the mineralization of the district. TABLE 30.2.—Analysis of samples from Hicks Dome, Hardin County, Illinois [Chemical and semiquantitative spectrographlc analysis (weight percent) of additional constituents in test well samples 1] Sample Depth eU U CaFg Be Nb Zr (feet) 1725—1750 0.029 0.001 6. 4 0. 06 0. 15 0. 03 1785—1815 .024 . 001 9. 6 . 06 . 15 . 03 1975—2000 . 001 .......... 1. 3 . 007 . 03 . 005 2150—2175 .016 . 001 7.9 .06 .08 . 02 2370—2400 . 011 001 10. 8 . 01 . 10 . 01 2425—2450 _ 6. 6 .006 . 10 .02 _ 2450—2475 4. 6 . 003 . 03 . 01 2900—2925 2. 8 005 . 01 . 006 l Analysts, Pauline J. Dunton, Ferman W. Montjoy, and P. Stuch. Bradbury, J. 0., Ostrom, M. E., and McVicker, L. D., 1955, Pre- liminary report on uranium in Hardin County, Illinois: Illi- nois Geol. Survey Circ. 200, 21 p. Brown, J. S., Emery, J. A., and Meyer, P. A., Jr., 1954, Explosion pipe in test well on Hicks Dome, Hardin County, Illinois: Econ. Geology, v. 49, n0. 8, p. 891—902. Clegg, K. E., and Bradbury, J. C., 1956, Igneous intrusive rocks in Illinois and their economic significance: Illinois Geol. Survey Rept. Inv. 197. Murata, K. J., Rose, H. J., Jr., and Carron, M. K., 1953, Sys- tematic variation of rare earths in monazite: Geochim. et Cosmochim, Acta, v. 4, p. 292—300. Murata, K. J., Rose, H. J., Jr., Carron, M. K., and Glass, J. J., 1957, Systematic variation of rare-earth elements in ce- rium-earth minerals: Geochim. et Cosmochim. Acta, v. 11, p. 141—161. Warner, L. A., Holser, W. T., Wilmarth, V. R., and Cameron, E. N ., 1959, Occurrence of nonpegmatite beryllium in the United States: US. Geol. Survey Prof. Paper 318. LIGHT METALS AND INDUSTRIAL MINERALS B65 31. PHOSPHATE AND ASSOCIATED RESOURCES IN PERMIAN ROCKS OF SOUTHWESTERN MONTANA By ROGER W. SWANSON, Spokane, Wash. Work done in cooperation with the US. Bureau of Reclamation and the U.S. Atomic Energy Commission The phosphate rock in southwestern Montana occurs in two phosphatic shale members of the Permian Phos- phoria formation (McKelvey and others, 1959). The lower, or Meade Peak, phosphatic shale member is mostly less than 15 feet thick; it tongues out to the north and east and has not been recognized in the Mel- rose and. Madison Range districts (fig. 31.1). The upper, or Retort, phosphatic shale member ranges up to 75 feet in thickness and is much more extensive, though it tongues out to the northeast. It contains phosphate of minable quality and thickness in all the districts shown in figure 31.1. No reserves are com- puted for the Permian rocks in the vicinity of Three Forks, because all the phosphorite in them is of poor quality or in thin beds.” Several potentially valuable elements occur in the phosphorite, but at present nothing but phosphorus 113° 112. 45° m Melrose Whitehall o OThrEe Forks district M l Bozeman N e r0580 ngn Bridges Dillon district Shaman Enniso Virginia Cityo Dillon° . / Madison Range district ,\ r, 4 ° ‘1 5 I ' i Ruby Valley Syncline district I I \\ I | \ West’Yellowstone ¢ l \, Limao ‘ \| . I ‘ n . l I \\ Lima district l\ / I /\ ,~.,-\‘> \\ . | ) ) [4591130 NA) Centennial Mountains KL, ‘\ district . \ \ FIGURE 31.1.—Districts in southwestern Montana for which phosphate and uranium reserves in Permian rocks are esti- mated. is being recovered from rock mined in Montana. Fluorine maintains a fairly constant ratio of 1 percent F to 10 percent P205. It will soon be recovered from phosphorite mined in Idaho and treated in Utah (Anonymous, 1958). Uranium, vanadium, chromium, nickel, molybdenum, and rare earths are other elements that are notably concentrated in the phosphorite, but they generally make up only a few tenths to a few thousandths of 1 percent of the rock. Vanadium has been recovered from acid-grade phosphorite mined at Conda, Idaho (Caro, 1949). The ferrophosphorus produced in the electric furnace contains 1 to several percent of vanadium, chromium, and nickel (Banning and Rasmussen, 1951). Oil shale is also present in the Retort member over much of southwestern Montana. Most of the phosphorite coming from the western field is mined by surface methods, and most of the rock mined underground is above entry level. Reserve esti- mates of phosphorite are presented in table 31.1 for rock above entry level, rock within 100 feet vertically below that level, and total reserves in the block regard- less of depth. Reserves of rock that can be mined by surface methods have not been computed separately. Estimates are also presented for grade cutoffs of 31 and 24 percent P20l5 (acid and furnace grades respectively) and for 18 percent rock that might be utilized after beneficiation or by blending. The two phosphatic shale members contain more than 10 billion tons of P205, 80 percent of which is in the Retort member. More than 6 billion tons of rock, almost equally divided between the two members, occurs in beds at least 3 feet thick that contain 24 per- cent or more of P205, but only about 370 million tons is above entry level or within 100 feet below it; 450 million tons, mostly in the Retort member, occurs in beds at least 3 feet thick that contain more than 31 percent P 205, and 50 million tons of this is above entry level or not more than 100 feet below it. Uranium is present in all the phosphorite, though in small amounts. Reserve estimates (table 31. 2) indi- cate that there is more than 400,000 tons of uranium in rock containing 24 percent or more P205, and that B66 nearly 25,000 tons of this is in rock that lies above entry level or not more than 100 feet below it. The acid- grade phosphorite is estimated to contain 35,000 tons of uranium, 20 percent of it. above entry level or not more than 100 feet lower. Most of the phosphorite likely to be mined within the next few decades lies within those limits. Most of the rock at lower levels need not be considered at pres- ent in extraction programs and short-term resource ap- praisals, though some of it is likely to be minable in the future. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCES Banning, L. H., and Rasmussen, P. T. C., 1951, Processes for recovering vanadium from western phosphates: U.S. Bur. Mines Rept. Inv. 4822. Caro, R. J., 1949, Anaconda phosphate plant, beneficiation and treatment of low—grade Idaho phosphate rock: Am. Inst. Mining Metall. Engineers Trans, v. 184, p. 282—284. Anonymous, 1958, Cryolite: Chemical Week, v. 82, no. 8, p. 34, Feb. 22, 1958. McKelvey, V. E., and others, 1959, Phosphoria, Park City, and Shedhorn formations in the western phosphate field: U.S. Geol. Survey Prof. Paper 313A, p. 1—44. TABLE 31.1.—Phosphate reserves in Permian rocks of southwestern Montana, in millions of short tons Basic data Reserve of rock containing more Reserve of rock containing more Reserve of rock containing more than 31 percent P205 than 24 percent P205 1 than 18 percent P105 1 Aver- Aver- Ton- Ton- Ton- age age Total Grade Ton- nage in Total Grade Ton- nage in Total Grade Ton- nage in Total mem- grade tons Thick- (per- nage first tons Thick- (per- nage first tons Thick- (per- nage first tons Reserve block her (per- P205 ness cent above 100 feet of rock ness cent above 100 feet of rock ness cent above 100 feet of rock thick- cent in (feet) P205) entry below in (feet) P205) entry below in (feet) P205) entry below in ness P205) block level entry block level entry block level entry block (feet) level level level Retort phosphatic shale member (Phosphoria for- mation): Melrose district ____________ 23. 3 6. 2 900 12. 4 21. 7 250 50 2, 500 Dillon district ......... 52. G 10. 6 2, 000 12. 4 19. 6 150 50 4, 000 Lima district ............... 76. 7 9. 0 900 6.0 21. 0 50 15 650 Ruby Valley Syncline dis- tric ...................... 49. 6 8.4 4, 000 5. 6 19.9 150 30 5, 500 Centennial Mountains dis- trict _________________ _ 6.0 16. 0 60 4. 0 20. 0 55 5 250 Madison Range distric ___. 10. 6 9. 8 650 4.0 20.3 100 30 2, 500 Totals and averages... 47. 1 9. 9 8,510 3. 4 31.0 8 6 300 4.8 26. l 148 37 2. 600 8. 2 20. 2 755 180 15, 400 Meade Peak phosphatic shale member (Phos- phoria formation): Dillon district .............. 4. 3 10.0 15 ____________________________________ 3.0 25.0 1 1 5 3. 5 22.0 1 1 6 Lima district __________ 24. 3 10. 9 400 ____________________________________ 3. 2 27. 4 20 6 250 6. 5 21. 5 50 15 850 Ruby Valley Syncline 1s— trict ...................... 9. 5 16. 4 1, 500 ____________________________________ 4. 7 26. 6 75 20 3, 000 5. 9 19. 6 100 30 6. 000 Centennial Mountains dis- trict ...................... 13. 7 19. 4 100 3. 5 32. 9 35 4 150 5. 5 28.0 55 5 250 8. 5 23. 2 80 8 400 Totals and averages-.. 12. 6 15. 4 2, 015 3. 5 32. 9 35 4 150 4. 6 26. 8 151 32 3, 505 6. 1 20.0 231 49 7, 256 Grand totals ___________ 40. 5 11.0 10, 525 3. 4 31. 6 43 10 450 4. 7 26. 5 299 69 6,105 7. 5 20.1 986 229 22. 656 1 Includes tonnages in columns to left. TABLE 31.2.—Urantum reserves in Permian phosphortte of southwestern Montana, in short tons Uranium reserves in phosphorite Uranium reserves in phosphorite Uranium reserves in phosphorite containing > 31 percent P105 containing > 24 percent P10; 1 containing > 18 percent P205 1 Grade Tonnage Tonnage in Total Grade Tonnage Tonnage in Total Grade Tonnage Tonnage in Total (percent above first 100 tonnage (percent above first 100 tonnage (percent above first 100 tonnage uranium) entry feet below in block uranium) entry feet below in block uranium) entry feet below in block level entry level level entry level level entry level Retort phosphatic shalt; member . 0. 0049 5, 500 1, 000 55, 000 0. 0049 15, 000 2, 500 100, 000 .0051 1, 500 350 25, 000 . 0051 7, 500 2, 500 200, 000 .......................................... . 0043 l, 500 600 30, 000 Ruby Valley Syn 0080 250 40 10, 000 .0066 9, 000 2, 000 ,000 Centennial Mountains district. .......................................... .005 2, 500 250 15, 000 Madison Range district _____________ 0073 1, 500 200 80, 000 .0058 6,000 2, 000 150, 000 Totals and averages ............. 0. 0062 8, 750 l, 590 170, 000 0. 0058 41, 500 9, 850 845, 000 Meade Peak phosphatic shale member (Phosphoria formation): Dillon district_. .007 70 35 350 .006 65 35 350 Lima district.__- .0087 1, 500 600 25, 000 .0086 4, 500 1, 500 70, 000 Ruby Valley Syncllne district“ _. _.- __ ___ .0061 5, 000 1, 000 200, 000 .0060 6, 000 1, 500 300, 000 Centennial Mountains district ______ 012 4, 000 400 20, 000 . 010 5, 500 500 25, 000 . 009 7, 500 700 35, 000 Totals and averages ............. 0.012 4, 000 400 20, 000 0.0068 12, 070 2,135 250, 350 0.0068 18,065 3, 735 402, 350 Grand totals .................... 0.0090 4, 350 650 35, 000 0.0066 20, 820 3, 725 420, 350 0.0061 59, 565 13, 585 1, 247, 350 1 Includes tonnages in columns to left. LIGHT METALS AND INDUSTRIAL MINERALS B67 32. HUGO PEGMATITE, KEYSTONE, SOUTH DAKOTA By J. J. NORTON, Denver, Colo. The Hugo pegmatite, near Keystone, South Dakota, is a well exposed intrusive body, about whose crystal- lization history much can be inferred from detailed petrographic and structural study. This pegmatite con- sists of two segments, in large part separated from each other by a screen of schist. The larger of these, the south segment contains the seven zones and two replace- ment bodies shown in figure 32.1. The north segment ' ...'..\ /./.'.' ' '.\_‘.\\_\'..7.‘ :L‘ H‘s-H £‘.( 7 \ Cieavelandite—quartz-lithia mica pegmatite (replacement unit) CIeavelandite-microcline-lithia mica . . \ pegmatite (replacement unit) \eo \(1’9 \iow \ 1: f “$4 42'; _ 4560’ \\é\® \§‘\e€‘ v \fg \ 3k l\‘ 31"" al) '— \ \l \ Zone 1. Albite-quartz-muscovite pegmatite 90* 5,7 'Eiiv \X‘ |\ U l“ V 4/7 / x. Zone 2. Quartz-albite-muscovite-pegmatite 6?; 30 [V \\\“ A )3; l: A ‘67)) '3’ Zone 3a. Perthite-quartz-albite pegmatite ’c;9\\\ 7' [L R: 1, V f'vl ”é, - '_ ' ' “‘o\'\ ,4 4V”- K49 , Zone 3b. Quartz perthlte alblte pegmatite 6, 4 / 5 —4520 _ . ¢,\ \\ \‘\i\ N/v ~’ - Zone 3c. Quartz—albite pegmatite \4 \\ \ [’77 II ,0? Zone 4. Quartz-cleaveIandite-microcline-amblygonite pegmatite / 4 Ef/AQ 7 / Zone 5. Quartz-microcline-spodumene pegmatite \ L \\ \i ”/ Zone 6. Quartz-microcline pegmatite \év “ / — 4480’ Zone 7. CIeavelandite—microcline-Iithia mica pegmatite \-/ “ O 50 100 FEET L I I I l __—) N. 50" E. FIGURE 32.1.—Ge010gic section, Hugo pegmatite, Keystone, S. Dak. B68 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 32.1.—Estimated composition of the Hugo pegmatite, Keystone, S.D. Albite Mode (percent)1 Calculated chemical composition (percent)2 Estimated (includ- Segment Zone tons of Quartz ing rock cleave- Perthite Other 3 Other landite and mi- Mica minerals S5102 A1203 Nazo K20 H20+F constit- crocline uents 45, 000 45 __________ 15 T, 2.5 78. 3 13.1 4. 3 1. 6 1.1 1. 6 175,000 35 30 5 T, 2 76. 3 13. 5 4. 0 4. 2 .5 1. 5 230,000 55 __________ 7 __________ 83.7 9. 9 4.1 .9 .5 .9 15,000 55 5 3 __________ 85.3 9.0 4.2 1.2 .2 .1 South ...... 1 and 2 .................................... 165, 000 73. 5 15. 3 3. 9 2. 1 1. 5 3. 7 3 . 200,000 69.8 16. 9 3. 5 8. 9 .3 .6 340, 000 73. 8 12. 8 3. 9 4. 1 .7 4. 7 160, 000 83. 3 10.0 4.1 1. 0 . 5 1.1 165,000 81.3 10.3 4.2 1.5 .4 2.3 170, 000 86.6 7. 3 .9 1. 6 .4 3.2 20,000 87.0 6.8 .4 5.2 .1 .5 7 11,000 66.4 19. 5 4. 4 6. 5 1. 7 1. 5 Cleavelandite-microcline—lithia mica re- 19, 000 67. 4 18. 9 4. 9 5. 9 1. 4 1. 5 placement unit. Cleavelandite-quartz-lithia mica replace- 15, 000 15 4 10 __________ \ 69. 9 17. 9 8. 1 1.8 .8 1. 5 ment unit. Composition of north segment ____________________ 465, 000 47 12 7 80. 5 11. 4. 1 2. 2 . 5 l 2 Composition of south segment" 1, 265,000 41 24 6 77.0 12. 5 3. 5 3. 6 .6 2 8 Composition of both segments _____________________ 1, 730, 000 43 21 6 77. 9 12. 2 3. 7 3. 2 .6 2 4 1 Minerals forming less than 2 percent of a unit, based on visual estimates, are omitted from the modes, but they were used in calculating chemical composition. 1 The modes were not converted from volume percent to weight percent in calculating chemical composition because the change would be too small to be S1gn1ficant. 3 T, tourmaline; Po, iron-manganese phosphates; Amb, amblygonite; and S, spodumene. contains only the four outer zones. By structural study of the pegmatite and estimates of the modes in the many available exposures, the approximate size and composi- tion of the units in this pegmatite prior to erosion and mining have been calculated (table 32.1). About 50 percent of the north segment and 60 percent of the south segment lie between the lowest mine level and the surface, and thus are somewhat better known than the rest of the pegmatite, which has largely been extracted by open—pit mining but also includes material that has been removed by erosion or that lies beneath the lowest mine level. About three—fourths of the rock in this pegmatite is in the outer three zones (Zones 1 to 3 of table 32.1 and figs. 32.1 and 32.2), which consist almost entirely of quartz, feldspar, and muscovite. Albite is the pre- dominant feldspar, but perthite is abundant in the upper part of zone 3. Zones 4 to 6 are highly silicic and contain abundant quartz; they also contain cleave— landite, microcline, spodumene, and amblygonite. Zone 7, the core of the pegmatite, is of quite different composition; it contains quartz, but its most abundant constituents are cleavelandite, microcline, and lithia mica. Small replacement units, resembling the core in their relatively high content of alumina and alkalies and low silica content, extend from the center of the pegmatite outward across the zones, and contain unre- placed remnants of the zones. Textural relations, both megascopic and microscopic, indicate so much overlap in paragenesis of the minerals in each zone as to indicate that all the minerals in any one zone crystallized at virtually the same time. It appears reasonable to assume that as this pegmatite was crystallizing from the contact inward, there was at any given stage a fully crystallized outer part and an en— tirely fluid inner part, separated by a moderate thick- ness of material consisting of a crystal meshwork and an interstitial fluid. If this was so, one can regard the composition of the material inside any zonal contact as indicating, roughly, the composition of the fluid at that point in the crystallizing process; we may neglect the presumably small quantity of material that escaped to the wall rock in hydrothermal or pneumatolytic fluids. Since about 94 percent of the material in the Hugo pegmatite consists of components of the system KAlS‘iaOs—NaAlSiaOg—SiO2, the course of crystalliza- tion can be plotted on the triangular diagram in figure 32.2, which has these three compounds at its corners. The remaining 6 percent of the material includes about 3 percent alumina in excess of the amount required to form feldspar, and only very small quantities of other constituents. Whatever the effect of these minor con— stituents was, the diagram represents the natural sys- tem closely enough for use in discussing the course of crystallization in this pegmatite and for comparison with the results obtained by Tuttle and Bowen (1958) in their detailed studies of the pure system. The quartz-feldspar field boundary, as shown on this figure, is at PH20 of 4000 kg per cmz, for this is the highest pres- sure at which the boundary was determined in the lab- oratory (Tuttle and Bowen, 1958, fig. 38) and is also the lowest pressure at which quartz and the two feld- spars formed together in equilibrium. The diagram shows that: (a) the south segment contains more po— tassium and less sodium than the north segment; (b) the residual fluid became progressively richer in silica during most of the time the pegmatite was forming, but became higher in alumina and alkalies and lower LIGHT METALS AND INDUSTRIAL MINERALS B69 sao2 South segment North segment NaAISi308 KAISi3 o8 Numbered points showing compositions are: 1. Entire body 9P9!” Units inside zones 1 and 2 Units inside zones 3a and 3b Units inside zone 3c Units inside zone 4 6. Units inside zone 5 The field boundary is from Tuttle and Bowen, 1958, fig. 38 FIGURE 32.2.—Inferred course of crystallization of the two segments of the Hugo pegmatite. in silica at, a late stage; and (c) the compositions at which quartz and feldspar crystallized together appear to have been much more silicic in the natural system (shown by points 1 t0 5, fig. 32.2) than in the laboratory system (shown by the field boundary in fig. 32.2). The south segment is at a higher altitude than the north segment, and the mechanism by which it obtained its high potassium content may be the same that caused perthite-rich hoods to form in the upper part of many zoned pegmatites. The narrow channel connecting the B70 two segments must have been sealed after the outer zones had crystallized, and thus the concentration of potassium in the south segment and sodium in the north segment must have taken place at a very early stage, probably by a physical mechanism. Potassium may have been carried upward through the liquid in a vola- tile phase before crystallization began. The most marked feature of the course of crystalliza- tion as indicated in figure 32.2 is progressive enrich- ment in silica. The difference between points 1 to 5 (fig. 32.2) and the field boundary determined by Tuttle and Bowen (1958, fig. 38) suggests that excess of alu- mina and the minor constituents (such as lithium) in the natural system, at the high pressures that pre- sumably prevailed when this pegmatite formed, caused the crystallizing fluid to become progressively richer in silica. The excess alumina surely affected the course of crystallization, because it gave rise to a significant amount of muscovite, but an extended discussion of its influence on the position of the field boundary will not be possible until more laboratory work has been done on systems containing mica, feldspar, and quartz. The increase in silica content ended in zone 6, and the small amount of material that crystallized later, GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES forming zone 7 and the replacement bodies, was low in silica and high in alumina, alkalies, water, and fluorine. The contrast in composition between this material and the rest of the pegmatite, coupled with the evidence for replacement of some previously solidi- fied rock, suggests that a hydrothermal or pneumato- lytic fluid separated from the silicate liquid. During the time that the outer zones were crystallizing, the content of water in the remaining liquid must have in- creased progressively until it had become as high as possible. Subsequently, a fluid phase rich in H20 would have to separate, and dissolved materials would then be distributed between this and the remaining silicate liquid. This process could account for the concentra— tion of alumina, alkalies, and volatiles in some places and of silica in others. At a very late stage the pres- sure of the fluid rich in H20 must have increased until it exceeded the confining pressure, and this fluid then escaped outward and replaced previously crystallized rock. REFERENCE Tuttle, 0. F., and Bowen, N. L., 1958, Origin of granite in the light of experimental studies in the system NaAlSiaOr— KAISiaOs—SiOz—HgO: Geol. Soc. America Mem. 74. 5b 33. A NEW BERYLLIUM DEPOSIT AT THE MOUNT WHEELER MINE, WHITE PINE COUNTY, NEVADA By H. K. STAGER, Menlo Park, Calif. The recent discovery by Mt. Wheeler Mines, Inc. of a large beryllium deposit at the Mount \Vheeler tungsten mine in Pole Canyon, on the west side of the Snake Range, White Pine County, Nev., has caused widespread interest among geologists and mining people. Because the principal beryllium minerals in this deposit—phenacite and bertrandite—are easily mistaken in hand specimens for ordinary quartz, this deposit had escaped the notice of the many geologists and engineers that had mapped the geology and ex- plored the tungsten and other mineral deposits in the district. The geology of the deposit is described here to provide information on the mode of occurrence of this unusual ore that may be useful in searching for similar deposits elsewhere. The rocks exposed in the Pole Canyon area are, from oldest to youngest, the Prospect Mountain quartzite, the Pioche shale, and the Pole Canyon limestone, all of Cambrian age (Drewes and Palmer, 1957). The beds strike northwest and dip 5° to 20° south. About 400 feet of the Prospect Mountain quartzite is exposed in the mine area. The Pioche shale, which overlies the quartzite, is about 450 feet thick. It con— sists mainly of micaceous, siliceous, highly indurated shale, but includes several beds and lenses of limestone. The thickest of the limestone beds, known locally as the “Wheeler limestone”, is about 50 feet above the quartz- ite contact and may be equivalent to the CM (Com— bined Metals) limestone at Pioche, Nev. Its average thickness is about 20 feet, but in places it is as much as 50 feet thick. At the outcrop in Pole Canyon it is pure white to gray, but in the mine workings, about 2,500 feet east of the outcrop, it is a. black, carbonaceous lime- stone. In an area beginning about 3,800 feet east of the outcrop it is almost completely silicified, probably because of a nearby concealed granitic body. The lime- LIGHT METALS AND INDUSTRIAL MINERALS stone is the host rock for the tungsten and beryllium deposit. The sedimentary rocks are cut by three sets of faults. One set strikes north and dips steeply east or west, the second strikes east or northeast and dips steeply north, and the third strikes east and dips gently south nearly parallel with the bedding. These faults are commonly occupied by quartz veinlets from a few inches to as much as five feet wide. Granitic rocks, ranging from quartz monzonite to granodiorite, are exposed about three miles north of the mine and crop out over an area of about 20 square miles (Drewes, 1958). The granitic body is believed to underlie the area at a shallow depth, perhaps less than 1,000 feet, and was possibly the source of the beryllium— bearing solutions that formed the deposit. The Mount Wheeler tungsten deposit was discovered in 1950 and was explored by Mount theeler Mines, Inc., in cooperation with the Defense Minerals Exploration Administration, between 1952 and 1954. Beryl was first found to be present in the ore in 1951, but no signifi— cance was attached to the fact until 1959, when Mr. J. D. Williams, president of Mount Wheeler Mines, had the tungsten concentrates analyzed for beryllium. The analyses revealed more beryllium than could be ac- counted for by the small quantities of beryl that had been observed at the mine. Beryllium Resources, Inc., of Salt Lake City, Utah, then explored part of the beryl- lium deposit, and between September 1959 and March 1960 this company drove about 600 feet of new under- ground workings and did 10,000 feet of underground diamond—drilling. The ore shoots are localized in the lower 15 feet of the “Wheeler limestone”, along quartz veinlets in steeply dipping fault fissures that strike east or northeast. Ex— ploration has shown that the beryllium minerals occur in a zone that extends for about 2,500 feet along the dip of the outcrop of the “Wheeler limestone” in Pole Can- B71 yon and extends eastward into the range along the strike for about 4,000 feet. The size and limits of the deposit have not yet been determined. The ore shoots within the explored area range from a few feet to more than 10 feet in width and from 15 to 20 feet in vertical extent, and one shoot has been traced for a strike length of about 1,500 feet. The average BeO content of the ore is about 1.0 percent. Mineralogical studies by R. G. COleman and others, US. Geological Survey, indicate that more than half the beryllium in the ores is contained in the mineral phenacite (BezSiO4). The phenacite occurs in color- less, translucent, euhedral to subhedral crystals re- sembling quartz. It is found throughout the deposit but is most abundant in the western part, where it is associated with scheelite and pyrite. Bertrandite (BeiSi2O7 (OH)2) is also an important ore mineral and in places accounts for nearly half the beryllium in the ore. It occurs in thin, bladed, translucent crystals and rosettes. It is most abundant in the eastern part of the deposit, where it is accompanied by fluorite and phena- cite; it was probably derived from phenacite. The beryllium minerals are intimately associated with scheelite, fluorite, pyrite, sericite, and manganoan side- rite. In places the ore contains a little galena and sphalerite. The beryl, which is pale blue, forms vein- lets and small isolated euhedral crystals. It is most common in and near the thin quartz veinlets cutting the Pioche shale below the ore bodies, where it is associated with phyrite, calcite, sericite, fluorite, and rarely scheelite. REFERENCES Drewes, Harald, 1958, Structural geology of the southern Snake Range, Nevada: Geol. Soc. America Bu11., v. 69, no. 2, p. 221—240. Drewes, Harald, and Palmer, A. R., 1957, Cambrian rocks of the southern Snake Range, Nevada: Am. Assoc. Petroleum Geologists Bull., v. 41, p. 104—120. 6? 34. PRE-MINERALIZATION F‘AULTIN G IN THE LAKE GEORGE AREA, PARK COUNTY, COLORADO By C. C. HAWLEY, W. N. SHARP and W. R. GRIFFI'I'I‘S, Denver, Colo. The Lake George beryllium area in Park County, (3010., is underlain mainly by Precambrian rocks. The area is traversed by large-scale lineaments trending north-northwest, which coincide at least in part with faults that are older than the mineralization. The rocks in the southwestern part of the area are mainly schists and gneisses, cut by many granite pegmatites of simple composition and by small granitic bodies. The B72 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES K TARRYALL [.5 MI. 105"25’ —O IMILE \ \ EXPLANATION Pikes Peak granite E Gneiss and schist with subor- dinate amounts of pegmatite and granite / Contact Dashed where inferred .——-—- Fault _____ _. .— Major lineament visible on aerial photographs 0 Known beryllium occurrence outside the Boomer mine area >—< 3 U. S. Bureau of Mines trench Numbers are referred to in text, PRECAMBRIAN 39°05’ LAKE GEORGE 7 MI.‘ 105°25’ FIGURE 34.1.—Generalized geologic map of the Lake George beryllium area, Park County, Colo. LIGHT METALS AND INDUSTRIAL MINERALS northeastern part of the area is underlain by the Pikes Peak granite, which is younger than all the other Pre- cambrian rocks (fig. 34.1). The beryllium deposits of the area are small replace— ment veins and pipes localized by fractures and rock contacts. The Boomer mine develops the most im- portant deposits, which are in part extensively greisen— ized zones in the Pikes Peak granite and at its contact with the metamorphic rocks, and in part veins that cross that contact. Other deposits are associated with greisenized zones within the Pikes Peak batholith or along its contact. The lineaments are most evident on areial photo- graphs (fig. 34.1). Detailed mapping near the Boomer mine has shown that there at least these lineaments are faults. The faulting is probably older than the mineralization, for the rocks along the faults are locally greisenized and the greisens contain very small yet significant amounts of beryllium. The fault just west of the Boomer mine is exposed only in three trenches excavated by the US. Bureau of Mines on sites chosen in the light of our mapping. In trenches 1 and 2 (fig. 34.1) the fault is indicated by highly sheared rocks, which in trench 2 are partly greisenized. In trench 3, cut at the site of a beryllium geochemical anomaly, the fault zone is about 15 feet wide and is composed of about 12 feet of soft, sheared, fluorite-bearing rock and a 3-foot vein of iron-stained greisen. B73 The age of these faults that appear to have caused the lineaments is not known; most likely they were formed in several periods of movement. The parallelism of some lineaments in the metamorphic rocks with the main granite contact, particularly in the northern part of the area, suggests that they existed prior to the in- trusion of granite and guided its emplacement. On the other hand, the granite batholith is cut by linea- ments of similar trend, which indicate post-granite movement. The relation of the faults to the beryllium minerali- zation is at this time highly speculative. The principal beryllium deposits of the Lake George area are not closely associated with the major lineaments, and fur- ther study may prove that there is no direct relation between them. The major lineaments, however, are not well prospected, and may be significantly mineral- ized in some places where they have not been examined. Furthermore, movement on the major faults may have caused smaller and less obvious subsidiary fractures along which localized mineralization occurred. A pos- sible result of subsidiary fracturing is the vein and dike zone exposed in the J&S mine between the Boomer mine and the known fault. Since there is good correlation of known deposits with beryllium soil anomalies, systematic soil sampling might be the most efficient way of prospecting the large faults. 5b 35. BERTRANDITE-BEARING GREISEN, A NEW BERYLLIUM ORE, IN THE LAKE GEORGE DISTRICT, COLORADO By W. N. SHARP and C. C. HAWLEY, Denver, Colo. The Lake George beryllium district, in Park County, Colo., has produced most of the beryllium ore mined in recent years in the United States. The ore has consisted largely of beryl, but in 1959 bertrandite (Be.1 (OH)2 Si207 [47 percent BeO]) was discovered in mica—quartz greisen associated with beryl ore. Some of the bertran- dite-bearing greisen has proved to be richer in beryllium than the beryl ore, and it is considerably easier to mine. Visual determination of the grade of bertrandite-bear- ing rock is difficult, but selection of ore-grade rock has been made possible by use of a beryllium—detecting de- vice similar in principle to the one described by Vaughn and others (1960). The Lake George district is at the western edge of the Pikes Peak granite batholith. In the district a number 5577513 0—60—v6 of pipelike bodies and irregular masses of greisen and greisenized rock as much as 20 feet across are present within the main granite mass, and also in small outly— ing bodies of granite and along contacts of granite with the older metamorphic rocks. The Boomer mine, from which most of the ore has been produced, is in a zone of irregularly greisenized rock along the contact of a small granite stock. Both granite and metamorphic rock are intensely altered locally to mica-quartz greisen; related high—temperature veins consisting largely of quartz, muscovite, and beryl are enclosed in greisenized rock and cut adjacent granite and metamorphic rock. The greisen in the Lake George district is generally a gray granular rock consisting of muscovite that is pre— dominantly dark gray but locally yellow, dispersed as B74 single crystals or clots of crystals in granular quartz. The relative amounts of quartz and muscovite in the normal greisen vary, but the granular texture and span- gled gray color of the rock make it conspicuous wher- ever it is exposed. Fluorite is present in almost all of the greisen, and topaz is abundant locally. The greisen contains pyrite, sphalerite, molybdenite, wolframite, galena, chalcopyrite, arsenopyrite, sooty pitchblende, and bertrandite, but these are generally scarce and ir- regularly distributed; locally, however, one or more of them constitutes several percent of the rock. The high-temperature veinlike deposits, generally beryl bearing, are not uniform in appearance or com- position. They range in character from poorly de- fined, highly altered complex veins within strongly greisenized zones to small simple quartz-beryl veins in unaltered granite or metamorphic rock. Most of the beryl ore produced from the mine has come from the veinlike deposits in greisen, near contacts between granite and metamorphic. rocks. The beryl ore consists largely of intergrown green and white beryl crystals with interstitial quartz and muscovite. Locally the beryl—bearing rock has been highly altered, and con- tains bertrandite, and possibly some hitherto uniden- tified beryllium minerals, in association with abundant yellow muscovite. Bertrandite—bearing greisen is a local variant of normal greisen in the Lake George district, and in at least one place it is sufficiently abundant to be ore. This is at the Boomer mine, in a small granite stock, and such rock occurs in at least one of several pipes in Redskin Gulch in the main Pikes Peak granite batholith, several miles to the east. Bertrandite in greisen is an inconspicuous mineral, hard to distinguish from feldspar or stained quartz in hand specimens, and much of the bertrandite-bearing greisen closely resembles normal greisen. At the Boomer mine, however, the bertrandite-bearing greisen appears to contain more fine-grained yellow muscovite than normal greisen, and locally at least it can be dis- tinguished by its lighter color. The contact between the darker gray and the paler yellowish greisen is com- monly sharp but irregular. But yellow‘muscovite can- not be used as a general criterion for bertrandite-bear— GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES ing greisen, for it is a minor but widespread constituent of barren greisen as well. The bertrandite in the greisen forms pale flesh-colored crystalline aggregates and rounded grains evenly distributed through the rock; it is about equal in abundance to quartz and to muscovite. Fluorite appears to be more abundant in the bertrandite-bearing greisen at the Boomer mine than in the normal greisen. The bertrandite-bearing greisen in the Redskin Gulch pipe appears, from a brief preliminary study, to be similar to that at the Boomer deposit. Bertrandite appears to be an original component of the greisen in which it occurs. Quartz and bertrandite form subhedral crystals and granular aggregates that show no replacement relations. Greisen is associated with many granitic intrusive masses throughout the world. It is particularly com- mon in Australia and Russia; other well-known occur- rences are in England, France, China, and Egypt. In most of the major localities, greisen and associated high—temperature veins contain significant amounts of tin, tungsten, and molybdenum, which in places are sufficiently abundant to make the rock an ore. Beryl has been reported in many areas of greisenized rocks, and beryllium may be a more common constituent of these rocks than has heretofore been recognized, for beryllium was not given much attention before its recent increase in economic importance, and was rarely in- cluded in analyses. Beryl itself may occur in greisen in areas other than the Lake George district without hav- ing been recognized, and the same thing is even more likely to be true of the rarer mineral bertrandite. Since known occurrences of bertrandite-bearing greisen in the Lake George district are associated with the Pikes Peak granite batholith, either in its periph— eral zone or in an outlying stock, other, undiscovered areas of greisenized rock probably occur along the pe- riphery, and perhaps deeper within the batholith. A general reconnaissance of the Pikes Peak granite and adjacent rocks might therefore reveal other beryllium deposits. REFERENCE Vaughn, W. W., Wilson, E. E., and Ohm, J. M., 1960, Instrument for quantitative determination of beryllium by activation analysis: U.S. Geol. Survey Circ. 427. 6% FUELS B75 GEOLOGY 0F FUELS 36. REGIONAL AEROMAGNETIC SURVEYS 0F POSSIBLE PETROLEUM PROVINCES IN ALASKA By ISIDORE ZIETZ, G. E. ANDREASEN, and ARTHUR GRANTZ, Washington, DC, Washington, DC, and Menlo Park, Calif. The US. Geological Survey has conducted numerous regional aeromagnetic surveys to help evaluate some of the possible petroleum provinces in Alaska. Figure 36.1 shows the areas which have been surveyed for this purpose. Because most of the work was of a. recon— naissance nature the results have been compiled in the form of “nested” profiles except for the Copper River basin, Kvichak Bay lowland, and on the Arctic slope, where close flight spacing permitted contouring of the data. The aeromagnetic data on which the interpreta- tion discussed in this report is based have been placed on open-file or published (Andreasen, Dempsey, and Henderson, 1958a, 1958b; Andreasen, Dempsey, and Vargo, 1958; Andreasen, 1960; Dempsey and others, 1957; Keller and Henderson, 1947; Meuschke and others, 1957; Zietz and others, 1959). Surveys were flown in areas known to be underlain by sedimentary rocks to provide information about the thickness of these rocks and their extent into unmapped or covered areas. Tracts of low, flat terrain covered by surficial deposits or water, where there is little geologic information, were also investigated to determine if they are underlain by significant thicknesses of nonmagnetic (possibly sedimentary) rocks. The geologic structure of most areas in Alaska is complex, with much folding and faulting. In many places magnetic igneous rocks, both intrusive and eX— trusive, occur within the sedimentary rocks. As a consequence, the interpretation of aeromagnetic data is difficult and must be considered in terms of detailed local geologic information. Where the sedimentary rocks rest on nonmagnetic basement rocks, interpreta- tions based upon the aeromagnetic data are ambiguous. In many of the areas of flat terrain, magnetic rocks were found to be near the surface. Such areas include the Yukon and Susitna flats, Galena, Middle and Upper Tanana, and Selawik lowlands, the northern half of the Copper River Basin, and Norton Sound. It is be- lieved that these areas are underlain at shallow depths by rocks similar to the partly magnetic formations that crop out in adjacent areas. Evaluation of geologic and aeromagnetic data in— dicate that significant thicknesses of sedimentary rocks occur in several areas. For example, large areas of Cook Inlet and the Kenai lowland are underlain by sedimentary rocks 3 to 4 miles thick, and a thick sedi- mentary section is indicated in the Kvichak Bay and Kandik areas. Analysis of magnetic data suggests that much of the southern Copper River basin is underlain by a thick staction of nonmagnetic, possibly sedimentary rock. Thick masses of sedimentary rocks underlie the Yukon- Kuskokwim delta; these are overlain in places by lavas of late Cenozoic age. A sedimentary basin has been outlined in the Koyu- kuk area east of the Seward Peninsula and west of Koyukuk Flats (Zietz and others, 1959). The basin is elliptical in shape, extends in a northeasterly direction and is about 80 miles wide. The basin is bounded on the east by the Yukon and Koyukuk Rivers, on the west and north by the edge of the exposed volcanic rocks, and it extends at least as far south as 64°30’ N. Depths to magnetic basement range from 3 to 5 miles. In the Arctic slope area, magnetic basement deepens to the south from Point Barrow about to the Colville River, where depths of more than 5 miles are indicated. However, at several places along the Colville River, depths become much shallower (2.to 3 miles). Mag— netic basement is also relatively shallow (2 t0 3 miles) to the east in the neighborhood of the Anaktuvuk and Kuparuk Rivers between the latitudes of 69° N. and 70° N. REFERENCES Andreasen, G. E., 1960, Total intensity aeromagnetic profiles for pll‘tS of the Kobuk and Minchumina areas. Alaska: US. Geol. Survey open-file reports, 8 sheets. Andreasen, G. E., Dempsey, W. J., Henderson, J. R., and Gil- christ, F. P., 1958a, Aeromagnetic map of the Copper River basin, Alaska: US. Geol. Survey Geophys. Inv. Map GP—156. Andreasen, G. 141., Dempsey, W. J., and Henderson, J. R., 1958b, Aeromagnetic map of part of the Dillinghani quadrangle, Alaska: US. Geol. Survey open-file report. 1 map. Andreasen, G. E., Dempsey. W. J., and Vargo, J. I... 1958, Aero- magnetic map of parts of the [’gashik, Karluk, and Naknek quadrangles. Alaska: US. Geol. Survey open-file report, 2 maps. B76 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Dempsey, W. J., Meuschke, J. L., and Andreasen, G. E., 1957, Meuschke, J. L., Henderson, J. R., and Dempsey, W. J., 1957, Total intensity aeromagnetic profiles of Bethel Basin, Total intensity aeromagnetic profiles of Cook Inlet, Alaska: Hogatza uplifit, West Hogatza, Koyukuk, Alaska: US. US. Geol. Survey open-file report, 2 sheets. Geol. Survey open-file reports, 7 sheets. Zietz, Isidore, Patton, W. W., and Dempsey, W. J., 1959 Pre— Keller, F., and Henderson, J. R., 1947, Aeromagnetic survey of liminary interpretation of total intensity aeromagnetic pro- Naval Petroleum Reserve N0. 4 and adjacent areas, Alaska: files of the Koyukuk area, Alaska: US. Geol. Survey open- U.S. Geol. Survey open-file report, 16 p., 1 map, 11 figs. file report, 6 p., 7 figs. 172° 164° 156° 148" 140° 132° . Bethe] Basin . Cook Inlet . Copper River . Kobuk . Koyukuk . NPR 4 4 58° . Nushagak . Cape Thompson-Shishmaref traverse . Minchumina . Anchorage-Nome traverse . Ugashik . West Hogatza . Yukon Flats and Kandik These descriptions are project names only and are not intended to outline basin areas. 148° Matthew I 58°\ )oo' 0 100 200 300 400 mo'MIJes 100 o 100 200 300 400 500 Kflumeta-s FIGURE 36.1.—Index map of Alaska showing location of aeronlagnetic surveys over some possible petroleum provinces. ’X‘ FUELS B77 37. STUDIES OF HELIUM AND ASSOCIATED NATURAL GASES By ARTHUR P. PIERCE, Denver, Colo. Work done in cooperation with the US. Atomic Energy Commission Few geologic studies have been made of helium in natural gases since that of Rogers (1921). Since then, a large body of analytical data has accumulated regarding the helium content of natural gases in the United States as the result of the helium surveys made by the US. Bureau of Mines (Anderson and Hinson, 1951; Boone, 1958). These data show that some he- lium is present in all gas fields. Also, the helium con- tent of the gas fields tends to increase systematically with the geologic age of the reservoir rock (fig. 37 .1), as would be expected if the helium were derived from slow decay of uranium and thorium inherent in rocks. Calculations, however, show that the reservoir rocks of the average gas field would have to contain about 0.03 percent~uranium in order to generate the helium that is present in them. This is about one hundred times the uranium content of most sedimentary rocks and raises a serious question as to the origin of the helium. As the hydrocarbons in natural gas fields are almost certainly derived from surrounding sedimentary source rocks, it is probable that at least part of the helium was derived from decay of uranium and thorium in the same rocks. In general such source rocks are saturated with water and are at structurally lower elevations than the gas fields they supply. If it is assumed that the radiogenic helium in these rocks can migrate into a gas field at a rate that is rapid enough to maintain an equilibrium concentration, then the partial pressure of helium in the gas reservoirs can be calculated from Henry’s Law : PHe=Kw where PHe is the partial pressure of helium in the gas field, If is an equilibrium constant, and w is the mole fraction of helium in the pore waters of the source rock. in can be computed from radioactivity laws and rock properties. Doing this, the entire expression becomes: PHe=KUf[8(el‘—l) +7R’(el"—l) +6R”(el””——l):|:i—U where U is the uranium content of the source rock in moles per gram of rock; f is the fraction of radiogenic helium escaping into the effective porosity; I, Z’ and Z" are the decay rates of U—238, U—236, and Th—232, re- spectively: R’ is the present ratio of [7—235 to U—238; R” is the present ratio of Th—232 to U—238 in the rock; d is the rock density; 26 is the age of the rock; and w is the water content in moles per cubic centimeter of rock as calculated from the rock porosity (water sat- urated). For water at the temperatures in the usual sedimentary rock K is about 1.9 X 106 psia. From the above expression we can calculate the par- tial pressure of helium as a function of the age of the rock. On the conservative assumptions that the aver- age gas source rock has a uranium content of 3 ppm, a thorium to uranium ratio of 3.6, a density of 2st g/cc, 13 percent porosity, and retains 50 percent of its radiogenic helium as estimated by Hurley (1954), the helium partial pressure in a gas field in typical sedi- mentary rocks will increase at a rate of about 0.9 psi every 100 million years. As actual gas fields do not retain all the helium migrating into them, this esti mate represents an upper limit. Even the most re— tentive gas fields will lose some helium due to diffusion. The available data on diffusion of helium, however, suggest that its diffusivity through impermeable rocks, such as the cap rocks of a gas field, is at least an order of magnitude less than its diffusivity through water. This would allow the helium partial pressures in gas fields with impermeable cap rocks to become quite close to those calculated from Henry’s Law. Thus, gas fields in rocks of Tertiary age (1 to 60 million years) should have up to about 0.5 psi helium, gases in rocks of Meso- zoic age (60 to 200 million years) should contain up to about 2 psi, and gases in rocks of Paleozoic age (200 to 600 million years) should contain up to about 5 psi helium. Comparison of these estimates with observed helium partial pressures in gas fields of diflereiit ages (fig. 37 .1) indicates that the helium present in most gas fields has probably been derived from decay of trace amounts of uranium and thorium in the sur— rounding rocks. Although the explanation just given will account for the helium present in most gas fields, there are some significant exceptions. Cambrian and Ordovician gas fields of the Central Kansas uplift contain from 10 to 60 psi helium. Most of these gas fields occur in folded rocks underlying a major unconformity. Rocks of Devonian and Mississippian age, including the uranif— B78 GEOLOGICAL SURVEY RESEARCH 1960-—~SHORT PAPERS IN THE GEOLOGICAL SCIENCES PERCENT He 10 4 10 3 10—2 10'} 100 101 I l l I 1 I Age. of _ 80 reserv0Ir rocks Tertiary PERCENT OF 178 GAS FIELDS 0 — 80 Mesozoic W PERCENT OF 183 GAS FIELDS 0 — 80 V Paleozoic / PERCENT OF 609 GAS FIELDS 0 120-— (I) 3 lg 80 — u. (I) < o u. 0 a: I'd z 40— 3 z Nz/He VOLUME PERCENT RAT IO Age of reservoir rocks Tertiary Mesozoic Paleozoic POUNDS PER SQUARE INCH He 0 025 0 10 0.40 1 60 6 40 25 80 - 103.20 80 PERCENT OF 104 GAS FIELDS O /Am //////// ________ VIII/I Ill/lllllllllllll 0 PERCENT OF 157 GAS FIELDS PERCENT OF 317 GAS FIELDS FIGURE 37.1.—Helium percentages, partial pressures, and nitrogen to helium ratios in gas fields of the United States. FUELS erous Chattanooga shale, have been removed and truncated by erosion, and cap rocks of Pennsylvanian age were deposited over the top of the uplift. At least two possible sources exist for the helium in this area: (a) the underlying basement rocks, which should have a large helium content because of their great age; and (b) the truncated uraniferous Chattanooga shale from which the helium could have migrated laterally into the gas fields. Other gas fields in which high helium partial pres- sures may be related to source rocks that are enriched in uranium are the Panhandle field, Texas, and the Harley Dome, Utah. In the Panhandle field reservoir rocks containing the highest partial pressures of he— lium (about 9 psi) are faulted against possible helium source rocks that are unusually radioactive and con— tain uraniferous asphaltite over large areas. In the Harley Dome, gases with an abnormal helium partial pressure (11 psi) occur in the Morrison formation, which is a significant host-rock for uranium deposits in nearby areas. The highest helium partial pressure (about 240 psi) among gas fields of the United States occurs in the Rattlesnake field, New Mexico. No satisfactory expla— nation is known for the origin of the helium in this field. The high partial pressure may be related to the occurrence of the gas field in an area of abnormal geothermal gradients. Nitrogen is intimately associated with helium in nat- ural gases and its origin has never been well under— stood. Unusually high concentrations of nitrogen that are present in gases from mineral springs and in some shallow gas fields evidently represent dissolved air from circulating ground waters. In other gases, particularly helium-rich gases, the amount of nitrogen tends to in- B79 crease with the age of the reservoir rock at a rate similar to the increase in helium. Much of this nitrogen may originate from slow decomposition of nitrogenous or- ganic compounds, such as chitin, porphyrins, and amino acids, present in sedimentary rocks. Studies by Abelson (1959) indicate that the decomposition rates of such nitrogenous compounds are extremely slow under natural conditions, and in the case of some amino acids, may be of the same order of magnitude as the decay rates of uranium and thorium. This suggests that the parallel enrichment of nitrogen with helium in natural gases could be related to its derivation from such sub- stances. The mean ratio of nitrogen to helium in nat- ural gases is about 30 (fig. 37.1), and if the two gases are assumed to be derived from a typical source rock (3 ppm U, 11 ppm Th) would require the decomposition of about 3 ppm organic nitrogen from the rock every 100 million years, or about 20 ppm since the beginning of Cambrian time. This is considerably less than the organic nitrogen content of modern marine sediments (about 0.04 percent organic nitrogen)’. Such a source of nitrogen is, therefore, feasible. REFERENCES Abelson, P. H., 1959, Researches in geochemistry: New York, John Wiley and Sons, Inc., 511 p. Anderson, C. C., and Hinson, H. A., 1951, Helium-bearing nat« ural gases of the United States: U.S. Bur. Mines Bull. 486. Boone, W. J., Jr., 1958, Helium—bearing natural gases of the United States: US. Bur. Mines Bull. 576. Hurley, 1’. M., 1954, The helium age method and the distribu- tion and migration of helium in rocks, in Nuclear geology (Henry Faul, editor), New York, John Wiley & Sons, Inc., p. 301—328. Rogers, G. S., 1921, Helium-bearing natural gas: U.S. Geol. Survey Prof. Paper 121, 113 p. 5b 38. THE INTERPRETATION OF TERTIARY SWAMP TYPES IN BROWN COAL By GERHARD O. W. KREMP and ANTON J. KOVAR, Denver, Colo., and Pennsylvania State University, University Park, Pa. Intensive palynological investigations of brown coal of early Miocene age from the Lower Rhine Basin in Germany made it possible for Thomson (1950) to rec- ognize nine different pollen florules, indicating nine different ancient swamp types, within a seam that reaches a thickness of 300 feet (see table below). This helped decisively in solving some of the problems relat- ing to coal seam correlation in the area (Rein, 1952). Plant associations similar to those he recognized were later recognized in many other lignites, and the distinc- tions between various types of fossil swamps were applied to the study of bituminous coals. This line of thinking also led to a better understanding of the petrography of various substances found in coal seams B80 (Teichmiiller, 1950; Teichmiiller and Thomson, 1958) and aided in solving problems of fuel technology (Pflug, 1957). Fossil swamp types of the Rheim'sche Brown Coal, and their dependence on frequency of flooding [According to P. W. Thomson, 1956, p. 67, fig. 1] Frequency of flooding Light-colored sediment Dark-colored sediment Seldom flooded, mostly dry. Coal of stump horizons (cf. Sequoia) with fusinite (forest fires). Coal of ombrogenous swamps. Coal of forest swamps with many pines and palms (cf. Sabal). Coal of forest swamps with many Myrica- ceae—Betula— ceae. Coal of forest swamps with many Taxodi- aceae (Glypto— strobus, etc.) and Coal of :1; oligo— trophic forest swamps. Periodically flooded. Coal of sedge swamps (cf. Cyperaceae), treeless, and at the base with secondary alloch- thony (the “light Nyssa. layers” of Walk, 1935). Always under Gyttja, rich in clay__ Dy—gyttja. water. After an extensive survey of the literature, Thomson concluded that the modern plant associations most closely related to the nine swamp types that he recog— nized were to be found in the southeastern part of the United States, especially in Florida. Our own field studies in the swamps of this region, however, indicate that Thomson’s comparisons should be altered in some respect for the following swamp types: 7 1. “Treeless sedge swamps.’ It would appear that the plant associations characterizing the light layers of the Rheinische Brown Coal, though usually com- pared with those in the Everglades of Florida (Teichmiiller, 1958), are not yet completely under- stood. VVeyland (1958, p. 530) remarks that to judge from the records, remains of Cyperaceae and Gram- ineae are strikingly scarce in the Brown Coal, and Neuy-Stolz (1958) states that Cyperaceae pollen has not been definitely identified, and that pollen which might belong to the Gramineae has very sel- dom been recorded. The lack of recorded occur- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES rences of these pollen has been explained on the assumption that the pollen as well as the leaves of the Glumiflorae are not preserved. But we found pollen of Cyperaceae and Gramineae in appreciable amounts in the sediments of the Everglades. These types of pollen are also reported in abundance from many Pleistocene localities; we are unaware, how— ever, of any record of their being found in abun- dance in lower and middle Tertiary sediments. Since most pollen is generally well preserved in the Brown Coal, it seems unlikely that just the pollen mentioned above should have been destroyed by fossilization processes. It is more probable that extensive sedge and grass swamps did not exist in middle Tertiary time. Furthermore, quercoid pollen, which is very rare in the Everglades, dominates the light layers of the Brown Coal—eg. Querooidites mierohenm'ci (Poto- nié, 1931), Quereuspollem’tes henm'ci (Potonié, 1931). Thomson supposed that these pollen were blown into the Tertiary swamps of Germany from nearby forests. It is possible, however, that many oaklike species able to grow in swamps existed during the Tertiary. Oaks are actually growing today in the southeastern swamps of the United States~e.g. Quercus micharum'z' Nuttall. 2. “Forest swamps with many Myricaceae-Betulaceae.” Although Myriad and also Betulaceae are found in Florida today, they do not form extensive swamp vegetation, whose occurrence in many lower and middle Tertiary coals has been recorded by palynol— ogists. Current observations favor the conclusions of Gladkova (1956), who states that more species of Myriad must have existed throughout early Ter- tiary time than exist at present. This would mean that the Myricaceae-Betulaceae-forest swamp types of the Tertiary cannot be compared with modern equivalents, simply because most of the Tertiary species of Myriad. are now probably extinct. 3. “Ombrogenous swamp types.” The relative abun- dance of Sphagnum. spores and Ericacea pollen in certain coal layers of the Rhine valley does not necessarily indicate a “humid-lusitanic” climate as Thomson (1952) has suggested. Swamp plant as- sociations in which Sphagnum is important also exist in the Okefenokee Swamp and elsewhere in Florida. These swamps, however, do not represent highmoors or other ombrogenous swamp types. 4. The “forest swamp types with much pine or palm pollen” may represent only bordering zones of other swamp types in which a large percentage of the pine or palm pollen they contain is blown in from drier areas. FUELS 5. The “cf. Sequoia-forest swamp type” may to a cer- tain degree be best compared with modern cypress heads and dense, swampy cypress forests. REFERENCES Gladkova, A. N., 1956, The pollen of some contemporary and fossilized species of the genus Myrica L. (in Russian): Akad. Nauk SSSR Doklady, v. 109, no. 1, p. 213—216, 3 figs. Neuy-Stolz, G., 1958, Zur Flora der Niederrheinischen Bucht wahrend der Hauptflozbildung unter besondere Beriick- sichtigung der Pollen und Pilzreste in den hellen Schichten : Fortschr. Geol. Rheinland u. Westfalen, v. 2, p. 503—525, 7 pls., 2 figs. Pflug, Hans, 1957, Die Untersuchung von Flo’zprofilen aus dem Nordrevier der rheinischen Braunkohle auf ihre Briket- tiereigenschaften: Freiberger Forschungshefte, V. A. 64, p. 1—68, 35 figs. Rein, U., 1952, Die palynologische Flozfeinstratigraphie im Braunkohlenbergbau: Internat. Geol. Cong., 19th, Algiers 1952, Comptes rendus, sec. 1.2, p. 143—171. Thomson, P. W., 1950, Grundsiitzliches zur tertiiiren Pollen- und Sporenmikrostratigraphie auf Grund einer Untersuchung des Hauptfltizes der rheinischen Braunkohle in Liblar, Neurath, Fortuna, und Briihl: Geol. Jah1'b., v. 65, p. 113—126. [1951]. B81 Thomson, P. W., 1952, Ombrogene Moorbildungen in der rhei- nischen Braunkohle: Deutsche geol. Gesell. Zeitschr. Jahrg. 1952, v. 104, p. 159. 1956, Die Braunkohlenmoore des jiingeren Tertiars und ihre Ablagerungen: Geol. Rundschau, v. 45, no. 1, p. 62— 70. Teichmiiller, Marlies, 1950, Zuni petrographischen Aufbau und Werdegang der Weichbraunkohle (mit Beriicksichtigung genetischer Fragen der Steinkohlenpetrographie): Geol. Jahrb., v. 64, p. 429—488, 6 p1s., 1 tab., 5 text figs. 1958, Rekonstruktionen verschiedener Moortypen des Hauptfliizes der niederrheinischen Braunkohle: Fortschr. Geol. Rheinland u. \Vestfalen, v. 2, p. 599—612, 3 pls., 5 figs. Teichmiiller, Marlies, and Thomson, P. W., 1958, Vergleichende mikroskopische und chemische Untersuchung der wichtig- sten Fazies-Typen im Hauptfloz der niederrheinischen Braunkohle: Fortschr. Geol. Rheinland u. \Vestfalen, v. 2, p. 573—598, 4 pls., 3 figs., 5 tab. Weyland, H., 1958, Die Monocotylen des “Hauptfliizes” der Ville : Fortschr. Geol. Rheinland u. Westfalen, v. 2, p. 527—538. Wiilk, E., 1935, Machtigkeit, Gliederung und Entstehung des niederrheinischen Hauptbraunkohlenflozes: Ber iiber die Vers. d. Niederrhein. Geol. Vereinigung, v. 28, p. 81—163, Bonn. ’2? 39. COAL RESERVES OF THE UNITED STATES, JANUARY 1, 1960 By PAUL AVERITT, Denver, Colo. The coal reserves of the United States remaining in the ground on January 1, 1960, totaled 1,660,290 mil- lion tons, as shown in the accompanying table. The re- coverable reserves totaled 830,145 million tons, based on the assumption that half of the coal in the ground Will be lost in mining and half will be recovered. The new totals are based on detailed, classified esti- mates in 14 States and provisional estimates in 5 States prepared since 1947 by the US. Geological Survey; on classified estimates in 7 States prepared by State geo— logical surveys; and on older and incompletely docu- mented estimates for the remaining States. The 26 States for which modern estimates have been prepared include about 90 percent of the total coal reserves of the United States as currently estimated. The information in the table was taken from the fol- lowing sources: Averitt, Paul, Berryhill, L. R., and Taylor, D. A., 1953, Coal resources of the United States (A progress report, October 1, 1953) : US. Geol. Survey Circ. 293, 49 p., [1954]. Barnes, F. F., Alaska coal reserves, written communication, 1959. Brant, R. A., and DeLong, R. M., Coal resources of Ohio: Ohio Div. Geol. Survey Bull. 58 (in press). Culbertson, W. 0., Coal resources of Alabama, written commu- nication, 1960. Haley, B. R., 1960, Coal resources of Arkansas: US. Geol. Sur- vey Bull. 1072—P. Huddle, J. W., and others, Coal resources of eastern Kentucky, written communication, 1960. Landis, E. R., 1959, Coal resources of Colorado: US. Geol. Survey Bull. 1072—0, p. 131—232. Luther, E. T., 1959, ‘The coal reserves of Tennessee: Tennessee Div. Geology Bull. 63, 294 p. Mason, R. S., and Erwin, M. I., 1955, Coal resources of Oregon: US. Geol. Survey Circ. 362, 7 p. Perkins, J. M., and Lonsdale, J. T., 1955, Mineral resources of the Texas coastal plain, a report for Bureau of Reclamation, Dept. of the Interior: Texas Univ., Bur. of Econ. Geology, p. 28—36. Trumbull, J. V. A., 1957, Coal resources of Oklahoma: US. Geol. Survey Bull. 1042—J, p. 307—382. B82 GEOLOGICAL SURVEY RESEARCH 19 6 0—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 391—00111 reserves of th 6 United States, Jan. 1, 1960, by States (In millions of short tons) Estimated original reserves Reserves depleted to Recoverable Jan. 1, 1960 reserves, Date of Remaining Jan. 1, 1960, State publica- Total reserves assuming tion of Bitumi- Subliitumi- Anthracite Production Jan. 1, 1960 50 percent estimate nous coal nous coal Lignite and semi- Productionl plus loss in recovery anthracite mining 2 ALABAMA3 ............................. (1) 5 13,754 ____________ 20 ____________ 513,774 6 23 6 46 13,728 6, 864 K_ . (7) 94. 638 13 26 94, 612 47, 306 7 (4) 2, 622 99 198 2, 424 1, 212 . 1959 81, 785 506 1, 012 80, 773 40,387 . 1953 100 12 24 76 38 . 1953 9 137, 329 "3 474 1“ 948 136, 381 68, 190 . 1953 37, 293 1, 148 2, 296 34, 997 17, 499 . 1909 29, 160 357 714 28, 446 14, 223 KANSAS ________________________________ E—1951 9 20, 774 10 13 10 26 20, 748 10,374 —1952 KENTI'C KY ___________________________ (i) 72, 318 2, 646 5, 292 67, 026 33, 513 MARYLAND _ 1953 “1,200 10 6 1° 12 1, 188 594 MICHIGAN _ 1950 297 46 92 205 102 Missouri. __ _ _ _ 1913 79, 362 287 574 78, 788 39, 394 MONTANA ______ _ 1949 222,047 171 342 221. 705 110,853 NE‘V MEXICO. _ . 1950 10, 948 50, 801 ____________ 6 61, 755 125 250 ' 61, 505 30, 753 NORTH CAROL _ 1955 112 112 1 2 110 55 NORTH DAKOTA . . _ 1953 350. 910 96 192 350, 718 175, 359 _______________ . (4) 46, 488 2, 052 4, 104 42, 384 21, 192 OKLAHOMA . 1957 3, 673 180 360 3, 313 1, 656 ORE GON ..... . 1955 200 3 6 194 97 PENNSYLVANIA ...................... 2—1928 97, 898 13, 508 27, 016 70, 882 35, 441 —1945 SOUTH DAKOTA _____________________ 1952 2,033 1 2 2,031 1, 015 TENNESSEE ______ . 1959 13 1,912 ‘3 1, 912 1‘ 0 1‘ 12 1,900 950 Texas 15 .................................. 24909 8, 000 15, 070 95 190 14, 880 7, 440 -1955 UTAH ___________________________________ (7) 28, 222 28, 378 260 520 27, 858 13, 929 VIRGINIA. . 1952 11. 696 12,051 782 1,564 10, 487 5, 244 \Vashington. _ _ . 1929 11, 413 63, 878 149 298 63, 580 31, 790 WEST VIRGIN IA. . 1940 116, 618 116, 618 6, 369 12, 738 103, 880 51, 940 WYOMING" . 1950 13, 235 3 108, 319 (9) ____________ 121, 554 402 804 120, 750 60, 375 Other States __________________________________________ 1“ 620 17 4, 065 15 50 ____________ 4, 735 7 14 4, 721 2, 360 Total ___________________________________________ 808, 420 437, 742 447. 966 25, 836 1, 719, 964 19 29, 837 59, 674 1, 660, 290 830, 145 1 Production, 1800 through 1885, from “The first century and a quarter of American coal industry,” by 11. N. Eavenson, privately printed, Pittsburgh, 1942; production, 1886 through 1923. from U.S. Geol. Survey Mineral Resources, annual volumes; production, 1924 through 1957. from U.S. Bureau of Mines Mineral Resources (1924—31) and Minerals Yearbook (1932—57), annual volumes, augmented for some States by records of State mine inspectors; production, 1958, from U.S. Bureau of Mines, Mineral Market Summary No. 2974, Sept. 9, 1959; production, 1959, from U.S. Bureau of Mines weekly coal reports and partly estimated. 2 Assuming past losses equal past production. 3 Reserve estimates of States in capital letters supersede estimates prepared by or under the direction of M. R. Campbell prior to 1928. 4 New estimate from report in preparation or in press. 5 Remaining reserves, Jan. 1, 1958. 6 Production 1958 and 1959 only. 7 New estimate presented for first time in this report. See text. 5 Small reserves and production of lignite included under subbituminous coal. '3 Remaining reserves, Jan. 1, 1950 '0 Production 1950 through 1959. 11 Reserve estimates of States in lower case letters were prepared by or under the direction of M. R. Campbell prior to 1928. 12 Small reserves of lignite in beds generally less than 30 inches thick. 13 Remaining reserves, Jan. 1, 1959. 1‘ Estimated production 1959 only. 15 New estimate of lignite reserves; Campbell estimate of bituminous coal reserves. 16 ARIZONA, CALIFORNIA, Idaho, Nebraska, and Nevada. 17 ARIZONA, CALIFORNIA, and Idaho. 1! CALIFORNIA, Idaho, Louisiana, and Nevada. 19 Less than total recorded production of about 34.8 billion tons. 5, 6, 9, 10, 13, and 14. See footnotes ’X 40. RELATION OF THE MINOR ELEMENT CONTENT OF COAL TO POSSIBLE SOURCE ROCKS By PETER ZUBOVIC, TAISIA STADNICHENKO, and NOLA B. SHEFFEY, Washington, DC. As denudation of an area proceeds, progressively older and more deep-seated rocks become exposed. It was therefore thought possible, since the coals of the Eastern Interior region represent a long period of sedi- mentation, that the minor-element content of specimens of these coals would reflect differences in the rocks that were being eroded at successive periods while the coal was being formed. It is reasonable to assume that during the weathering of rocks, the material transported to the depositional sites reflects changes in the character of the rocks being weathered, and that during the periods when coal was being formed, the amounts of minor elements accumu- lated by the coal would depend upon the amounts of these elements being brought into the swamp. It is also reasonable to assume that the amounts of the elements in solution that form stable organic complexes would depend upon the amounts of those elements being brought into the swamp, and that the elements would be almost completely extracted by the coal from the FUELS B83 TABLE 40.1.—Distribution of 46’ bed samples of coal [Beds are arranged in their stratigraphic order] (3110111) Beds Illinois Indiana Kentucky Total McLeansboro _____ No. 7 (Ill.)=VI (1nd.) ___________________________________ 2 1 __________ 3 No. 14 (Ky.) ________________________________________________________________ 2 2 Carbondale _______ N0. 6 (Ill.)=VI (Ind.)=No. 11 (Ky.) ______________________ 7 2 1 10 No. 5 (Ill.)=V (Ind.)=No. 9 (Ky.) ________________________ 8 1 9 18 No. 2 (I11.) _____________________________________________ 2 ____________________ 2 Tradewater _______ 111 (1nd.) ________________________________________________________ 1 __________ 1 DeKoven (111.) __________________________________________ 1 _____________________ 1 Davis (Ill.)=No. 6 (Ky.) _________________________________ 1 __________ 1 2 No. 1=(Murphysboro(?)) (Ill.)=Minshall (1nd.) ____________ 4 __________ 1 5 L. Willis (Ill.)=L. Block (1nd.) ___________________________ 1 1 .......... 2 Totals_____- ________________________________________________________ 26 6 14 46 solutions entering the swamp. Most of the 15 elements looked for in these coals do form organic complexes having various degrees of solubility and stability. The stratigraphic divisions in which the coals are grouped, and the correlation of the beds, are those used by VVanless and Siever (1956). The bed samples aver- aged for this comparison comprise 5 from the McLeans- boro group, 30 from the Carbondale group, and 11 from the Tradewater group, a total of 46 bed samples repre- senting 10 different coal beds. The distribution of the sampled coal among the different beds is shown in table 40.1. Detailed analytical and geologic data will be pub- lished in a later report. DISCUSSION OF THE DATA During the differentiation of an igneous magma, certain elements, such as V, Cr, Co, Ni, and Cu, are generally associated with the earlier, more mafic dif- ferentiates. Later and more silicic differentiates are generally enriched in such elements as Be, B, Ga, Ge, Mo, Y, and La. The minerals consisting largely of the mafic elements are less stable and usually weather more rapidly than those consisting mainly of the silicic ele- ments. Recycled sedimentary rocks, therefore, should contain smaller amounts of mafic elements released by weathering than sediments derived directly from the weathering and erosion of igneous materials. This is especially true of sediments of early pre-Paleozoic age. As boron is very high in these samples, only one—tenth of the boron is actually used in the summation in table 40.2, where the group Be+B/10+Ga+Ge+Mo+ La+Y comprises the silicic elements and the group V+Cr+Co+NitCu the mafic elements. TABLE 40.2—Average minor element content of the coals from three groups of the Pennsylvanian series of the Eastern Interior region [Parts per million in coal] Group Be B Ti V Cr Co Ni Cu Zn Ga Ge Mo Sn Y La MCLeansboro _______ 3. 2 112 510 33 23 5. 4 18 10 14 5. 2 12 3. 9 5. 3 9. 4 3. 1 Carbondale _________ 2. 0 107 440 39 20 2. 7 14 12 56 3. 9 13 4 8 1. 1 6. 3 3. 5 Tradewater _________ 3. 2 66 400 22 16 6. 3 15 9. 3 28 3. 7 11 2. 3 . 6 8. 7 10. 5 A summation of the figures in table 40.2 gives: Group Siliclc elements Maflc elements Ratios (mafic (ppm in coal) (ppm in coal) to silicic) McLeansboro _______ 48 89. 4 1. 9 Carbondale _________ 44. 2 87. 7 2. 0 Tradewater _________ 46 68. 6 1. 5 This summation shows that the quantity of silicic elements in the coal is nearly the same in the three groups. There is, however, an appreciable difference in the mafic elements, which are much less abundant in the Tradewater group than in the others. The ratios of mafic to silicic elements in the three groups are also significantly difl’erent. According to the theory of changing source rocks expressed above, the ratio in B84 the Carbondale coals should lie between those in the McLeansboro and the Tradewater coals, but in fact it is the highest of the three. The apparent discrepancy, however, is mainly due to the abnormally high vana- dium content of some of the coals of bed 9 of western Kentucky. Nine samples from this bed average 70 ppm of vanadium, whereas eight samples from the same bed in Illinois average 25 ppm. Most of the vanadium in bed No. 9, in the area where it is so abundant, is in the extreme upper part of the bed. There is evidence, however, that the deposition of this coal was terminated in this area by a marine invasion, and it. therefore seems possible that the anomalous vanadium was accumulated by marine organisms and thus incorporated in the uppermost part of the bed. If that is true, it should not be considered in making comparisons with the other coals. The ratio of the mafic to silicic elements is 1.7 for bed No. 6 in Illinois, and 1.6 for its correlatives in the other two States. For bed No. 5 in Illinois and its correlatives elsewhere, the ratio is 2.3. If, however, vanadium is excluded from the mafic group, the ratios are 1.2 and 1.1 for beds Nos. 6 and 5, respectively. This shows a great deal of similarity between the two beds. A further degree of similarity is expressed by Co, Ni, and Cu, and by Y and La. The ratios of Co :Ni :Cu are 1 :5.4:4.5 for bed No. 5, and 1:54;?) for bed No. 6. The ratio of Y to La is 1.6 for bed No. 5 and its correlatives; 1.7 for bed No. 6 and its correlatives. Not only are these ratios very close together, but the Be and Ge averages for the two beds are identical, and Ti, Cr, Mo, Y, and La differ by less than 25 percent. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES The differences are slightly higher for B, CO, Ni, Cu, and Ga. From the above observations and discussions it may be seen that there is a. similarity between the minor element content of beds Nos. 5 and 6 and that of their correlatives. It is also true that if the anomalous vana- dium of bed No. 5 is discounted, the ratio for that bed (about 1.6) corresponds closely to that for bed N0. 6 (about 1.7). With such a ratio for bed No. 5, the Car- bondale group of beds bear out the assumption that the ratio of mafic to silicic elements should increase up- ward. It is therefore almost certain that the changing minor element content of these coals reflects the progressive exposure and erosion of deeper seated rocks as Pennsyl- vanian sedimentation progressed. This conclusion ac- cords with one expressed by Potter and Glass (1958, p. 52—53). They believe that in the earlier sedimentary history of the Eastern Interior basin, sedimentary rocks formed by repeated reworking of detritus from parental igneous rocks contributed most of the detritus to the basin, but that as Pennsylvanian sedimentation in the basin proceeded, crystalline rocks contributed an in- creasing proportion of detritus. REFERENCES Potter, P. F1, and Glass, H. D., 1958, Petrology and sedimenta- tion of the Pennsylvanian sediments in southern Illinois; a vertical profile: Illinois Geol. Survey Rept. Inv. no. 204, 60 p. Wanless, H. R., and Siever, Raymond, 1956, Classification of the Pennsylvanian rocks of Illinois as of 1956: Illinois Geol. Survey cine. no. 217. 14 p. 6% 41. THE ASSOCIATION OF SOME MINOR ELEMENTS WITH ORGANIC AND INORGANIC PHASES OF COAL By PETER ZUBOVIC, TAISIA STADNICHENKO, and NOLA B. SHEFFEY, Washington, DC. In studying the minor elements contained in coal, it is worth while to estimate the degree to which each of the elements is associated with the organic and inor- ganic substances in the coal. Complete separation of organic and inorganic material is impossible, but a fair degree of separation can be achieved by relatively simple flotation procedures. Although most of the fractions in these separations consist predominantly of organic matter, there is less organic and more inorganic matter (ash) in the fractions of higher specific gravity. In the two-fraction separations, the float fractions con- tain about 2 to 4 percent inorganic matter (ash) and 96 to 98 percent organic matter, while the sink frac— tions contain about 20 to 30 percent ash and 70 to 80 percent organic matter. In multiple-fraction separa- tions, the inorganic matter is more than 50 percent in the sink fractions, and the organic matter less than 50 percent. By comparing the recovery of each of the ele- ments against the recovery of organic and inorganic matter in each of the fractions, it is possible to calculate the degree of association of the elements with either the organic or inorganic matter of the coal. In making FUELS the calculation the organic matter is considered to be ashless and all the ash content of each of the separated fractions is included in the inorganic matter of that fraction. This procedure introduces a small error which can be ignored. A procedure similar to this was used by Horton and Aubrey (1950). Thirteen samples of coal, 12 having a specific gravity of 1.32 and 1 a specific gravity of 1.36, were separated into float and sink fractions. Two samples were separated into 5 fractions and 1 sample into 3 fractions. The coals represent several different beds, and blocks taken from different parts of the beds. The recoveries of coal in the float fractions ranged from 10.6 percent to 92.7 percent. Figure 41.1 illustrates the method by which the degree of association with the organic phase of the coal was plotted for each of the 13 samples. This figure shows that 60 percent of the organic and 23 per— cent of the inorganic matter of the sample was recovered in the float fractions, while 90 percent of the organic and 77 percent of the inorganic matter was recovered 100 100 —Be— 75—_ a _ -—Co— PERCENT OF MATERIAL RECOVERED IN FLOAT FRACTION 0| 0 l PERCENT OF MATERIAL RECOVERED IN SINK FRACTION —Be— 0 o FIGURE 41.1.—Association of minor elements with the organic and inorganic fractions of coal; two-fraction separations. (Specific gravity of float media is 1.32.) B85 in the sink fraction. Over 60 percent of the Be, B, Ge, and V was found in the float fraction, and less than 40 percent in the sink fraction. There is thus a correla- tion between these four elements and the organic mat- ter. A similar correlation was found between Zn and La and the inorganic matter. The other elements have various degrees of correlation with the organic and inorganic matter. The dashed lines indicate divisions of 25, 50, and 75 percent correlation. The data for the 13 samples are summarized in table 41.1. In several of the samples Zn, Sn, and La were below the limit of detection and could not be evaluated. TABLE 41.1.—Frequency of association of elements with the organic fractions [n.d. =not determined] Percent Ranges for Element Horton and Aubrey (1950) 100—75 75—50 50—25 25—0 (3 samples) Be ________ 8 3 1 1 75— 100 B _________ 8 2 2 1 75— 100 Ti ________ 8 3 1 1 > 75~ 100 V _________ 8 3 2 0 100 Cr ________ 3 5 3 2 0— 100 Co ________ 2 5 5 1 > 25—50 Ni ________ 4 6 0 3 0— > 75 Cu ________ 1 3 3 6 25—50 Zn ________ 0 0 O 7 0—< 50 Ga ________ 9 2 0 2 > 75—100 Ge ________ 10 2 0 1 100 Mo _______ 1 5 3 4 50—75 Sn ________ 1 l 1 6 0 Y _________ 5 2 2 4 n .d. La ________ 0 0 0 10 n .d. The order of decreasing association with organic mat- ter as determined from the 13 two-fraction separations is: Ge, Ga, V, Be, Ti, B, Ni, Cr, Co, Y, Mo, Cu, Sn, Zn, and La. The first six of these elements are exactly the group of elements for which Horton and Aubrey (1950) showed the greatest degree of association with the or- ganic matter of vitrains. The elements Cr, Ni, Zn, and Sn also show a correspondence to Horton and Aubrey’s data. In their report, zinc and tin show a decided asso- ciation with inorganic matter, and our results show that these two elements, and also lanthanum, are asso- ciated predominantly with the inorganic matter. Curves were drawn for percentage recovery of or- ganic and inorganic matter in each of the fractions of three multiple-fraction separations (fig. 41.2). Each element is treated as before, and the curves for the ele- ments are compared with those for the organic and the inorganic matter. The degree of similarity between the curves for the elements and those for the organic or RS IN THE GEOLOGICAL SCIENCES A SURVEY RESEARCH 1960—SHORT PAPB GEOLOGICAL B86 68A no Mflw can nom: .wmA .NmH .wmé do 33¢ a: n can .w ”m .N ”H 383$“ ”835$ 95 Mafia $5 5 .NmA :0 Mfim can .NmA .wNA .5 30¢ 95 m 35 N .H wcoflofiw fiJPIWIcQH :5 .wacfinbfiww Sfioiwédzfisfi “Eon no £55.,an omnmwuoi can 25%.8 $5 5?» 3:2:me .555 we :cflflocwwaNlNAw 55th n W/ I I Nlmlzmlxx m:>lw|U:_ NOILOVHJ HOVE NI GEHEAOOEH 'IVIHELVW do iNEOHEd FUELS inorganic fractions shows the degree of association of the element with either fraction. In sample KY—PR—9—2 of figure 41.2, the elements Be, B, V, Ni, Ge, Mo, and Ga follow closely the pat- terns set by the distribution of the organic fraction, Ti, Co, Sn, and La have profiles similar to the inorganic fraction, while Cr, Cu, and Y are intermediate. In Ky— T—9—1, the elements Be, B, Ni, Ge, and Mo are pre- dominantly associated with organic fraction, and Cu, C0, Ga, and Y with the inorganic, and Ti, V, and Cr are intermediate. In Ill—S—5—3, the elements Be, B, Ti, Mo, and La are associated with the organic fraction, Cr, Cu, Zn, and Y with the inorganic, while V, Ni, Co, Ga, and Sn are intermediate. These data indicate that cer- tain elements are usually associated with either the or— ganic or the inorganic matter; there are, however, some deviations from this general rule. The data reveal several interesting relations between elements that are chemically similar, such as Ni and Co, V and Cr, and Y and La. Hirst and Nicholls (1958, p. 478—480) suggest an association of Ni and V with the nondetrital and of Co and Cr with the detrital portions of limestones. A similar association is shown by our data on coal : Ni and V are more closely associated with the organic or nondetrital fraction than (‘0 and Cr, and Y shows a greater association with the organic fraction than La. It is significant that the elements whose ions are small and highly charged are generally associated with the B87 organic fractions. In this group are Be, B, Ti, V, and Ge, and to a lesser extent Ga. Elements, such as Zn, La, and Sn, consisting of large ions, are associated with the inorganic fraction of coal. We believe that Sn is reduced to the Sn+2 valence state in the reducing con- ditions of the coal swamp, thus putting it with the group consisting of large ions. Of the pairs of chem- ically similar elements, such as Co-Ni and Y-La, those with the smaller ions (Ni and Y) generally show a greater association with the organic fraction than those with larger ions (Co and La). It is generally known that large charge and a small ionic radius produce stable organic complexes. Numerous other factors are involved in the. accumu— lation of minor elements in coal ; these include plant ac— cumulation, the resistivity to weathering of certain minerals, post-depositional influences, and many others. One of the most important factors, however, is prob- ably the formation of metallo-organic complexes, par- ticularly at the time of coal deposition. REFERENCES Hirst, D. 31., and Nicholls, G. D., 1958, Techniques in sedi- mentary geochemistry. (1) Separation of detrital and non- detrital fractions of limestones: Jour. Sed. Petrology, v. 28, no. 4, p. 468—482. Horton, L., and Aubrey, K. V., 1950, The distribution of minor elements in vitrain: Three Vitrains from the Barnsley seam: Soc. Chem. Industry Jour., v. 69, Supp. Issue 1, p. 541—548. 42. COMPARATIVE ABUNDANCE OF THE MINOR ELEMENTS IN COALS FROM DIFFERENT PARTS OF THE ° UNITED STATES By PETER ZUBOVIC, TAISIA STADNICHENKO, and NOLA B. SHEFFEY, Washington, DC. This discussion is based on spectrographic analyses of 1,000 samples of ash from coals of the major coal—pro- ducing areas in the United States. The results of these analyses were first computed as averages of columnar samples of beds, and these bed averages were used to compute the averages for three great areas, the Northern Great Plains province, the Eastern Interior region, and the Appalachian region. (See table 42.1.) The coals sampled range in age from Eocene to Penn- sylvanian. The 46 bed samples from the Northern Great Plains province are of Eocene to Jurassic age, 35 being of Paleocene age, 6 of Eocene, 4 of Jurassic, and 1 of Cretaceous age. The 47 bed samples from the Eastern Interior region and the 65 bed samples of the Appalachian region are all of Pennsylvanian age. The rank of the coals ranges from the lignite, sub- bituminous, and high—volatile bituminous coals of the Northern Great Plains province, through high-volatile bituminous coals of the Eastern Interior region, to high—, medium-, and low-volatile bituminous coals of the Appalachian region. The averages shown in table 42.1 indicate that few of these minor elements are much more abundant in any one of the three great areas than in the others. The Northern Great Plains coal is highest in B, Ti, Zn, Ga, and La, and this area and the Appalachian region are B88 highest in Cu. The Eastern Interior region is highest in V, Cr, Ni, Ge, Mo, and shares the highest figure for Be with the Appalachian region. The Appalachian re- gion is highest in Co and Y, one of the two highest in Be and Cu, and close to the highest in Ni, Ga, and La. It is strikingly poor in B and Zn, which have a much wider range of. abundance than any of the other elements. This general similarity of abundance in regions whose coals differ widely in age suggests that the total amount of each inorganic element (except B and Zn) associated with the coal substance was in general fairly constant. TABLE 42.1.—Average content of each minor element in coals from three major coal producing areas of the United States ‘[Parts per‘million in coal] Northern Great Eastern Interior Appalachian region Elements Plains province region (avg. 01' 47 (avg. of 65 bed (avg. of 46 bed bed samples) samples) samples) Be ___________ 1. 5 2. 5 2. 5 B ____________ 116 96 25 Ti ___________ 590 450 340 V ____________ 16 35 21 Cr ___________ 7 20 13 C0 ___________ 2. 7 3 8 5 1 N1 ___________ 7. 2 15 14 Cu __________ 15 11 15 Zn ___________ 59 44 7. 6 Ga __________ 5. 5 4. 1 4. 9 Ge ___________ 1. 6 13 5. 8 M0 __________ 1. 7 4. 3 3. 5 Sn ___________ . 9 1. 5 . 4 Y ___________ 13 7. 7 14 La ___________ 9 5 5. 1 9. 4 The element most uniformly distributed among the three main areas is gallium. Copper and beryllium are next in the uniformity of their distribution. The aver— age for copper in the Eastern Interior region is sur- prisingly low; it is lower than in either of the other two areas, although there is copper mineralization north of the region, in areas from which some of the sediments in the basin were derived. The somewhat higher beryl- lium content of the Eastern Interior and the Appala- chian coals can be related to the sedimentary sources of the two areas. This aspect is discussed in detail in a report by the authors now in preparation. Tin and zinc are not considered because they were found, in only about 25 percent of the analyses. The metals for which the averages difl'er most widely among the three areas are germanium and boron. Nickel is in its expected order, and is highest in the Eastern Interior region. Cobalt averages highest in the Appalachian coals; in the northern part of that region the bed averages are GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES about the same as in the Eastern Interior region, and in the southern part they are higher. Cobalt minerali- zation has occurred at many places in the southern Appalachians, and the high average for cobalt in the coal of that region may be related to this mineraliza- tion. \Ve do not mean to imply that a high proportion of an element in coal is everywhere due to erosion of mineralized rocks; in some areas it may indicate that the coal is in a geochemical province in which the rocks contain that element in more than average abundance. In such areas the metal may have been freed by ero— sion of the common country rocks rather than of rocks or veins in which the metal has been concentrated by secondary processes. The differences in germanium and molybdenum con- tents between the coals of the three areas cannot yet be explained. In all three areas, the content of boron and titanium is about inversely proportional to the rank of the coal, being lowest in the highest grade coals. Boron, which forms organic esters, could easily be lost as a result of the metamorphism of coals; whether the same is true for titanium is uncertain. The relatively high boron content of the coals in the Northern Great Plains province could be due to the character of the sedimentary rocks in that province. It is generally known that the Fort Union sediments are chiefly de- rived from volcanic rocks. Large amounts of bentonitic material are intercalated also with those sediments in— dicating contemporaneous volcanism, which might well have produced considerable quantities of volatile mat- ter containing large amounts of boron, some of which could have become incorporated in the coal. Boron is also relatively abundant, on the average, in the coals of the Eastern Interior region, but its origin in this re— gion is hard to explain. The two chemically similar elements yttrium and lanthanum are twice as abundant in some areas as in others, but the ratio between them is remarkably con- stant; the highest average content being less than 7 percent above the lowest. It is about 1.5 and 1.4 in the coals, as compared with 1.6 in the earth’s crust. These figures suggest that the two elements were weathered out, transported, and incorporated in the coal at nearly the same rate. The distribution of minor elements taken collectively among the three areas is relatively uniform. Boron content and perhaps titanium content may depend on the degree of metamorphism of the coal. In general, however, the quantity of any minor element in a coal appears to have been controlled by the availability of that element to the swamp in which the coal was formed. 61‘ GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES B89 EXPLORATION AND MAPPING TECHNIQUES 43. FIELD APPLICATION OF ION-EXCHANGE RESINS IN HYDROGEOCHEMICAL PROSPECTING By F. C. CANNEY and D. B. HAWKINS, Denver, Colo. The resin-collection technique developed by the Geo— logical Survey for use in hydrogeochemical prospecting was first used successfully in northwestern Maine in 1958 to determine copper, lead, zinc, cobalt, and nickel in the barren surface waters, which usually contain only 25 to 50 parts per million total dissolved solids. Conventional methods of conducting geochemical water surveys require either (a) that heavy and bulky water samples be collected and shipped to a laboratory for analysis, or (b) that the bulk water be analyzed di- rectly in the field with a. chemical kit. Procedure (a) is relatively ineflicient, and may entail a loss of trace metals from solution before analysis. Procedure (b) is free from these disadvantages, but few of the avail- able field methods of analysis are sufficiently sensitive for direct use. It is partly for these reasons that few geochemical water surveys have been made in recent years. Synthetic ion—exchange resins became available shortly after World War II. Because of their ability to collect ions from very dilute aqueous solutions, coupled with the ease by which these ions can be re- leased and concentrated in a small volume of eluant, many investigators have speculated on the possible use- fulness of such resins in hydrogeochemical prospecting surveys. Kunin (1958, p. 262) suggested the feasibility of preparing resins in the form of cartridge columns which could be taken to the field and used to concen- trate the ionic constituents in a water sample, and Rid— dell (in press) mentions the use of ion-exchange resins placed in waterways for fixed time intervals. The work of Nydahl (1950), who described the use of ion- exchange resins to collect elements of biological interest from lake water, was of considerable help to us in work- ing out the technique described in this paper. This technique consists, in brief, of using a plastic tube packed with a resin known commercially as IR— 120 to collect the metals from a water sample, at the sample site, by allowing a known volume of water to percolate through the resin at a controlled rate. No apparatus other than this light and durable tube need be taken to the field or base laboratory, where the sorbed metals are easily eluted. The eluant, in which the metals of interest are much more highly concentrated 557753 0—60—7 than in the bulk water, can there be analyzed by con- ventional field or laboratory methods. The apparatus used for collecting and elution is shown in figure 43.1 Some of the more important factors in successful use of resins in geochemical water surveys are enumerated below. These remarks apply specifically to the collec— tion of copper, lead, zinc, cobalt, and nickel. Any at- tempt to apply this technique to other elements should be preceded by experimental work on solutions of known metal content. 1. Purification of the 113—120 resin—This is ac- complished by alternately soaking the resin in 6N 0 0 0 0 Collection Elution Not to scale FIGURE 43.1.—~Collection and elution apparatus. A, polyethy- lene bottle, l—gallon size, for holding water sample; B, plastic tubing; 0, glass wool plug, pyrex; D, screw-clamp; E, resin cartridge consisting of a 6-inch polyethylene drying tube (25 1111 vol) packed with resin (IR—120, —20 to +50 mesh size) ; F, glass funnel; G, glass U-tube; H, volumetric flask, 100-ml capacity. B90 hydrochloric acid and washing it in metal-free water until satisfactory blanks are obtained for iron and zinc. Zinc is the most difficult element to eliminate. ‘2. Preparation of the cartridge—The resin cartridge is prepared by pouring a slurry of the purified resin onto a plug of glass wool in the bottom of the poly- ethylene tube; a similar plug is then placed over the resin. The resin should not be allowed to drain dry, for doing this will allow air bubbles to enter the cart- ridge and interfere in the collection step. 3. Uolleotion.—The pH of the water sample should be checked, and then adjusted if necessary with hydro- chloric acid or ammonium hydroxide until it is be- tween 6.5 and 7.5. A flow rate through the column of about 100 ml per minute gives a recovery satisfactory for most geochemical prospecting investigations. After the water-sample bottle is attached to the cartridge, the top screw clamp should be opened first, and then the bottom clamp. 4. Elation—The metals are eluted by passing 20 ml of 2N hydrochloric acid, and then 80 ml of demineral- ized water, through the column. An upflow technique should be used, as shown in figure 43.1, and the direction of flow through the resin cartridge should be opposite to that used in the collection step. A flow rate of 1 ml per minute is satisfactory. Precautions should be taken to prevent air bubbles entering the column when the elution process is started. When l-gallon samples are passed through the col- umn an enrichment factor of 38 is obtained. If field colorimetric methods are used to analyze the eluant, their detection limits, expressed in terms of the concen- tration in bulk water, are about as follows: Concentration Metal (micrograms per liter) Cu _____________________________________________ 0. 2 Pb ______________________________________________ 1 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Concentration Metal (micrograms per liter) Zn _____________________________________________ 1 Go _____________________________________________ 0.5 Ni _____________________________________________ 0. 5 These detection limits can be lowered considerably by increasing the volume of the sample. As a measure of the effectiveness of this technique to recover metals under field conditions, zinc was de- termined directly on 6 bulk waters, and the values compared with those obtained with the resin tech- nique. That the agreement was satisfactory is shown by the following comparative data. Zinc content, in micrograms per liter Resin collection Direet analysis MODCDNODHB wawflkcfl Major advantages of this resin-collection technique, which should appeal to investigators in the field of hydrogeochemical prospecting, are these: it is more sensitive than other methods; it eliminates the shipping of bulky water samples; and it prevents the loss of trace constituents from solution that may occur with other methods. REFERENCES Kunin, Robert, 1958, Ion exchange resins: New York, John Wiley and Sons, 466 p. Nydahl, Folke, 1950, Sampling and analysis of lake waters by means of ion exchangers: Internat. Limnological Cong, 11th, Belgium 1950, Proceedings, p. 276—290. Riddell, J. E., in press, A survey of geochemical exploration in eastern Canada: Internat. Geol. Cong., 20th, Mexico City 1956, Geochem. Symp. ’R‘ 44. GEOCHEMICAL PROSPECTING FOR BERYLLIUM By WALLACE R. GRIFFITTS and U. ODA, Denver, Colo. A major problem in prospecting for nonpegmatitic deposits of beryllium is to determine by some inexpen- sive reconnaissance method what districts are most worthy of further work. Random sampling or inspec— tion of outcrops is time-consuming and is likely to be ineffective, for beryllium minerals in tactite, greisen, and granite generally have a spotty distribution, and veins containing beryl and bertrandite are commonly friable and readily broken down into fine rubble or soil. Searching alluvium for traces of valuable minerals has long been an important technique in reconnaissance prospecting because a sample of alluvium from a small stream may roughly indicate the composition of the rocks exposed in the drainage basin. Thisvtechnique EXPLORATION AND MAPPING TECHNIQUES is very useful in seeking heavy minerals, such as gold, wolframite, or cassit'erite, because they are concen— trated in the alluvium. Unfortunately, however, the common beryllium minerals are too light to be concen- trated readily and are difficult to recognize: their pres- ence, therefore, must be inferred from the relatively high beryllium content of alluvium that contains them. The concentration of beryllium in most alluvium is less than 5 ppm (5 parts per million or 0.0005 percent), so that a few fragments of a beryllium mineral will in- crease the tenor of a sample by an amount readily de- tectable by rapid spectrographic or fluorimetric analyses. We have made fairly thorough studies of alluvium in the beryllium districts near Lake George, 0010., at Iron Mountain, N. Mex., and in the Sheeprock Range, Utah; less thorough studies in other places confirm the con- clusions reached in those three districts. V. Venkatesh and Y. G. K. Murty of the Geological Survey of India worked with us in the Lake George and Iron Mountain areas respectively. Most of the beryl- and bertrandite-bearing veins in the Lake George area are in a broad intermontane valley underlain by schist and gneiss that are deeply covered with soils. The mountains at the eastern edge of the valley are underlain by granite of the Pikes Peak batho— lith. The soils and alluvium derived from the meta.- morphic rocks contain 2 to 3 ppm of Be; those derived from the granite may contain as much as 10 ppm. Near the beryllium-rich parts of veins, which weather readily, alluvium may contain as much as 20 ppm of Be. Figure 44.1 shows the increase in beryllium con- tent of alluvial samples from a wash that flows eastward past the veins in and near the Boomer mine. Boomer shaft, about 100 ft north of wash 10 /\ 5 ”v’§/ 1 PARTS PER MILLION 1000 1500 2000 FEET . l 1 E 00 w ‘3 5. BERYLLIUM CONTENT, IN FIGURE 44.1.—Beryllium content of alluvium in wash south of Boomer mine. In the Iron Mountain district, New Mexico, tactite has replaced limestone of the Magdalena group near intrusive masses of fine-grained monzonite, granite, and porphyritic rhyolite. Helvite occurs near the B91 north end of the largest mass of tactite, but most of the known localities are in smaller masses west of the ridge crest. Samples of alluvium taken from washes and near the mountain front contain no more than 2 ppm of Be south of the area of figure 44.2. Nearer the min- eralized rocks the beryllium content of similar alluvium samples is higher, reaching a maximum in the washes that drain the known helvite-bearing rocks in the NW quarter of section 2 (see figure 44.2). The low beryl— lium content of most alluvial samples taken east of the crest reflects the absence of known helvite occurrences in most of the large tactite mass. The two washes east of the ridge crest that yield the richest samples—with 30 and 100 ppm——drain the only known helvite-bearing rocks east of the divide. The two soil samples taken at the north end of the mountain indicate that the layer of tactite exposed there can account for the 30 ppm of Be found in the alluvium to the west. Samples of residual soil taken along several traverses in section 2 show anomalous beryllium content immediately above and downhill from metallized tactite layers. The northwesterly-trending Sheeprock Range, near Eureka, Utah, is flanked by desert basins that contain Quaternary and older alluvium and volcanic rocks. The range consists mainly of Precambrian and Paleo- zoic sedimentary rocks, but a stock of granite extends about six miles along the range. Soils are poorly de— veloped over this granite. Near the center of the stock clusters of blue beryl crystals are embedded in appar- ently unaltered granite. Beryl—free granite between the clusters of beryl crystals in this central area con— tains 10 to 15 ppm of Be, whereas granite from other parts of the stock generally contains less than 10 ppm. The coarser (over 200-mesh) fractions of alluvium contain more beryllium over the beryllium~rich granite than elsewhere, but the finer fraction contains a rather uniform 2 to 5 ppm in most places sampled over the stock. Analysis of alluvium is an effective way to find dis- tricts in which beryllium-rich rocks crop out, and it is relatively economical, because taking and analyzing samples in a district of ordinary size requires about two man-weeks. In general, any district should be considered favorable if it yields samples containing 10 ppm or more of Be, but even values between 5 ppm and 10 ppm may be promising in samples taken from geo— logically favorable places. Analyses of residual soils can be used to find individual bodies of beryllium-rich rock, in the same way that float has long been used in finding veins. B92 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES IQOO EXPLANATION Tertiary and younger sediments D Older sedimentary rocks \ \\/\ Q71“ 1‘ ’l \ / Intrusive rocks Tactite X3 Sampled locality and Be content of alluvium, in parts per million 0 2 0.00 30.00 Geology after R H Jahns AOPO FEET FIGURE 44.2.—Simplified geologic map of the Iron Mountain area, N. Mex., showing beryllium content of alluvium. 6% WWW M. . l. A Al ‘ w EXPLORATION AND MAPPING TECHNIQUES B93 45. VARIATIONS IN BASE-METAL CONTENTS OF MONZONITIC INTRUSIVES By WALLACE R. GRIFFI'ITS and H. M. NAKAGAWA, Denver, Colo. Marked differences in the base-metal content of ap- parently unaltered igneous rocks from many mining districts in the Western United States cannot be ascribed entirely to magmatic, deuteric, or early post- magmatic processes. The metals were largely intro— duced into the rocks and were sorbed by the surfaces of dark minerals, without inducing any alteration that is recognizable either in outcrops or in thin sections. The metals can in large part be removed from the rocks with very dilute acid. In most districts the content of introduced metal increases toward major centers of mineralization, giving rise to broad hypogene geo- chemical anomalies that may extend as much as a mile from the center. Such anomalies are well developed in districts characterized by mesothermal ores containing dark sphalerite, pyrite, galena, copper sulfides, and carbonates, but are poorly developed in districts with epithermal-type gold or silver ores, even though they contain copper, zinc, and lead minerals. Zinc is par- ticularly mobile, and forms anomalies that are larger than those of most other metals. Copper and manga- nese also form notable anomalies, but those of lead are slight and of small extent. In some districts introduced metals are not most abundant near known centers of mineralization. In the Jamestown district of Colorado, for example, a prominent copper anomaly (fig. 45.1) and a nearly congruent zinc anomaly (not shown) have no appar- ent spatial relation to groups of fluorite, gold, or silver veins. The highest concentrations of metal are in mon~ zonite along the western edge of the stock; they are not near any known ore deposits and presumably were due to deposition from solutions that moved along or near the contact. Most of the anomalous metal is aifixed to augite, hornblende, biotite, and sphene; pyrite, which occurs in trace amounts in the monzonite, was altered to sulfides of zinc and copper in the metal-rich rocks. The wide range in metal content within an indi— vidual stock, as shown at Jamestown, indicates that neither the average metal content of the monzonite nor its pre-mineralization metal content can be determined accurately from a small number of samples. Samples must be collected from sufficiently numerous and widely distributed localities to ensure that both metal— rich and metal-poor parts of the stock are adequately represented. In some districts the metal content of unmineralized or only slightly mineralized rocks var- ies widely (table 45.1). This suggests that some miner- alized rocks were probably included in the table; if so, the averages are too high. The high copper and zinc content of igneous rocks around ore deposits of those metals is probably due to leakage from the deposits during mineralization, rather than to an originally high metal content of the parent magma. The total metal contents therefore tell little about the relationship between magmas and ores. Some metallogenic provinces, however, may be related to large bodies of monzonite whose original base-metal content was exceptionally high. TABLE 45.1.—Metal contents of monzonittc rocks from Western United States. [Colorimetric analyses by H. M. Nakagawa, A. P. Marranzino, and H. L. Neiman except where there is an asterisk (*) after the district name. Asterisks indicate spectro- graphic analyses by U. Oda and E. F. Cooley. 7 indicates uncertainty in mean, usually because there were many samples in which the metal was not detected. Feld- spar proportions of all the rocks correspond to those of monzonites or quartz monzonites; rock names in parentheses were applied by other workers.) Metal content, in parts per million Source of sample Copper Lead Zinc Number of samples Minimum Mean Maximum Minimum Me an Maximum Minimum Mean Maximum Colorado: Jamestown district ________________ 13 46 80 11 17 28 20 71 95 27 Ward area ________________________ 5 9 12 24 34 50 65 95 110 15 Albion stock ______________________ 5 28 85 10 16 36 26 70 110 19 Caribou district ___________________ 8 17 48 13 17 24 50 79 120 12 Empire district ____________________ 6 10 15 13 35 70 60 120 190 15 Montezuma stock _________________ 4 16 50 15 17 24 10 37 80 19 Breckenridge district: Swan Mountain _______________ 4 9 24 10 31 65 28 61 130 50 Bald Mountain _______________ 7 14 110 8 22 50 65 110 190 24 B94: GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 45.1.—Metal contents of monzonitic rocks from Western United States—Continued Metal content, in parts per million Source of sample Copper Lead Zinc Number of . . . . . samples Minimum Mean Max1mum Minimum Mean Maximum Minimum Mean Maximum New Mexico: Cook Mountain ___________________ 22 26 30 12 15 20 65 74 85 5 Santa Rita (granodiorite) ___________ 5 8 14 17 28 36 65 109 220 5 Hanover (granodiorite) _____________ 5 26 55 6 9 14 28 58 120 8 Black Range ______________________ 13 20 30 7 11 14 65 83 95 6 Iron Mountain* ___________________ <5 5 10 15 33 100 ______________ <200 9 Arizona: Cochise County: Schieflelin granodiorite _________ 18 25 42 11 13 16 44 53 70 5 Uncle Sam porphyry ___________ 5 10 42 7 16 20 48 54 80 22 Cochise Peak quartz monzonite- 14 15 19 14 17 20 32 37 40 3 Gleason quartz monzonite ______ 5 7 10 7 13 28 10 29 60 8 Bagdad district, stocks _____________ 5 22 40 8 18 60 10 54 130 8 Bagdad district, dikes ______________ 7 18 55 5 22 120 10 77 130 19 Christmas district _________________ 60 70 80 6 10 11 16 30 48 5 Superior district ___________________ 6 15 20 8 9 12 70 ‘80 85 4 Utah: Frisco district, Estelle area __________ 20 36 70 12 16 22 55 68 90 13 Frisco district, Copper Canyon area*. 50 75 100 <10 <10 20 ______________ <200 5 Stockton area* ____________________ 3 26 75 <10 19 50 ______________ <200 7 Deep Creek Range (granite) ________ <1 1? 3 20 27 34 22 42 60 11 Gold Hill district __________________ 6 25 34 14 29 42 38 54 75 7 West Tintic district ________________ 3 9 14 16 19 20 40 55 80 5 Sheeprock Range (granite) __________ <1 3 10 19 29 90 14 32 85 64 Desert Mountain __________________ <1 2? 12 24 26 28 6 33 60 8 Mineral Range ____________________ <1 <1 <1 16 19 22 22 31 50 3 Cedar City district, Stoddard Moun- tain ____________________________ 8 37 70 18 24 38 65 75 130 53 Nevada: Cortez quadrangle, stock ___________ <2 7 22 15 25 34 12 36 60 25 Carlin quadrangle* ________________ 30 80 150 10 10 10 ______________ <200 3 Austin area _______________________ 4 7 20 19 25 40 10 47 70 26 Gabbs area* ______________________ <1 13 50 10 11 75 ______________ <200 5 Unionville quadrangle, Rocky Can— yon area _______________________ 5 8 10 20 26 36 16 41 60 7 Average ______________________________ 24 ________________ 19 ________________ 63 ________________ c EXPLORATION AND MAPPING TECHNIQUES B95 105025, 105°20' EXPLANATION \ Granite g E 8 5 >2 uJ . [— l- Monzonlte Lu 0 D: Z ./d’ D < Dikes / z E [I m . . . E Granlte, schist, and guess 5 » E n. Faults W Fluorspar veins J Gold and silver veins 93 X 40., 5, Sample locality, with copper content in parts per million 2 0 'h-n «m "1““ Line of equal copper concentration Lines drawn at 20, 50, and 100 parts per million. Hachures point toward area with lower values Geology after E. N. Goddard O l 2 3 4 MILES J J P FIGURE 45.1.—Geochemical map of the Jamestown district, Colorado. 6% B96 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 46. GEOCHEMISTRY 0F SANDSTONES AND RELATED VEGETATION IN THE YELLOW CAT AREA OF THE THOMPSON DISTRICT, GRAND COUNTY, UTAH By HELEN L. CANNON, Denver, Colo. Work done in cooperation with US. Atomic Energy Commission Oxidized ore bodies and the surrounding sandstone in the Yellow Cat area of the Thompson district were studied to establish what other elements are concen- trated with uranium and vanadium in the ore deposits, to determine the geochemical behavior of these elements during weathering, and to decide whether selenium, molybdenum, or some other metal could be used as a pathfinder element in prospecting for uranium-va- nadium deposits. GEOCHEMISTRY OF HOST ROCKS The distribution of metals in the Salt Wash sand- stone member of the Morrison formation, in which the ores of the Yellow Cat area occur, is shown in table 46.1. The mean percentages of metals given in columns 2—5 were computed from analyses of channel samples taken for this purpose through 13 ore bodies and the TABLE 46.1.——Distribution of selected elements (parts per mil- lion) in sandstones of the Salt Wash member of the Morrison formation Colorado Yellow Cat area Plateau 1 2 3 4 5 6 Element Unmineralized Unminer- Mlneral- Ores Ratio ore/ rocks I (<40 U) alized ized rocks (>84 U) unmineral- rocks (40—84 U) ized rocks (<40 U) U __________ 2 13 183 3, 800 292 S __________ — 430 1, 400 7, 300 17 V __________ 18 578 1, 280 9, 510 16 Se _________ <0. 5—8 <14 51 190 >13. 5 As _________ < 15 32 100 417 13 Mo ________ < 7 < 8 41 100 > 12. 5 Ni _________ <. 7 <5 23 35 >7 Co _________ 7 <8 45 59 > 6. 5 Pb____----- <2 <12 11 52 >4. 5 Cu _________ 20 7 9 23 3. 3 Ag _________ ~. 5 <1 <. 6 3. 5 >3. 5 Zn _________ <30 <89 <71 228 >2. 6 Fe _________ 3, 000 15, 000 19, 000 28, 000 l. 8 Cr _________ 9 73 76 107 1. 4 Mn ________ 380 496 338 292 . 59 CaCOa _____ 180, 000 71, 000 46, 000 30, 700 . 4 l 1 Arithmetic means compiled from data presented by Newman (1957) and by Shoemaker and others (1959). surrounding sandstones. The samples were divided into unmineralized, mineralized, and ore categories ac— cording to grade cutoffs commonly used for Colorado Plateau ores. The contents of sulfur, selenium, arsenic, and molybdenum were found to be more than 10 times greater in the uranium-vanadium ore bodies than in the enclosing sandstones and these elements were assumed to be an intrinsic part of the ore. The same elements were also distinctly more abundant in the sandstones surrounding the ore bodies (columns 3 and 4) than Newman (1957) and Shoemaker and others (1959) later found them to be in more distant country rock (column 1). In other words, each ore body is enveloped by a geochemical halo of these metals, which enlarges the target for prospecting. Special studies were made of an open pit where ore occurred at a depth of 44 feet. Selenium and molyb- denum were found to be concentrated to a greater de- gree in the partially mineralized sandstone just above the ore than in the ore itself, and anomalous values of uranium, arsenic, and vanadium were also found in the sandstones and mudstones for varying distances above the ore. All these elements, therefore, were considered potentially useful in prospecting by plant analysis. PROSPECTING BY PLANT ANALYSIS Because surface waters and residual soil cover are lacking in the Yellow Cat area, its vegetation was in- vestigated as a prospecting medium. Differences in absorption of uranium, vanadium, and molybdenum by three classes of vegetation are shown in table 46.2. All species of plants rooted in mineralized ground were found to contain concentrations of uranium, vanadium, selenium, and molybdenum sufficiently high to be useful in prospecting. The ratio of uranium, however, in plants growing on mineralized ground (In) to that in plants growing on unmineralized ground (unm) was greater than for any other element. As the uranium content in the leaves and end branches of trees and deep- rooted perennial shrubs was found to be consistent, several hundred samples of juniper and shadscale (Atriplem eonfertl'folia) were collected and analyzed fluorimetrically; the limit of sensitivity of the method is 0.3 ppm uranium in the ash. On unmineralized EXPLORATION AND MAPPING TECHNIQUES TABLE 46.2.w—Urantum, vanadium, and molybdenum content in vegetation of the Yellow Cat area Uranium Vanadium Molybdenum Classes of vegetation Mean ratio mean ratio mean ratio (ppm) m/unm (ppm) m/unm (ppm) m/unm Grasses _________________ 6. 1 ______ 3. 3 ______ 1. 3 On unmineralized ground ________ 5. 7 ______ 40 ______ 25 ______ On mineralized ground ________ 35. 0 ,,,,,, 135 ,,,,,, 32 ,,,,,, Other herbs (includ- ing Se indica- tors) ________________ 11. 0 ,,,,,, 5. 3 ______ 3. 7 ()n unmineralized ground__-,__,, 1. 9 ,,,,,, 36 ______ 42 ______ On mineralized ground___,____ 21.0 ,,,,,, 191 ______ 155 ______ Trees and shrubs,“ ______ 9. 8 ______ 2. 6 ,,,,,, 3. 6 On unmineralized ground________ .9 ,,,,,, 19. 8 ,,,,,, 14. 2 ______ 0n mineralized ground_____,__ 8. 7 ...... 51 ,,,,,, 36. 5 ______ ground the content was generally around 0.5 ppm, whereas on mineralized ground it was commonly greater than 2 ppm. Both juniper and shadscale con— tained anomalous amounts of uranium where the ore was less than 35 feet beneath the surface; Where the ore lay at greater depths the water—loving juniper con— tinued to be an effective guide but the shallow—rooted xerophytic shadscale failed to indicate any mineraliza— tion. Ore has since been mined from areas outlined by analysis of both juniper and shadscale. PROSPECTING BY INDICATOR PLANTS Near the uranium deposits there is an excess of metals, increased radioactivity, and a local change in pH, and the environment is consequently favorable for the growth of certain indicator plants listed in table 46.3. The selenium indicator plants starred in that table were selected as being the best mappable indi- cators of ore deposits. It was found that Astragabus pattersoni, a white—flowered poisonvetch, and Astraga— lug preussi, a purple species, are accumulators not only B97 of selenium as they were long known to be, but of uranium, vanadium, and molybdenum as well, and that their distribution correlates more consistently than that of any of the other plants listed with mineralized ground. i TABLE MIL—Plants favored by mtnerah'zed ground in Yellow Oat area [Asterisk:selenium-indicator plants] *Oryzopsis hymenoides (ricegrass) Stipa comata (needleandthread) Calochortus nutallt (Sego lily) Alltum acuminatum (onion) Ztgadenus gramineus (deathcamas) Eriogonum tnflatum (deserttrumpet) *Astragalus pattersom‘ (Patterson loco) *Astragalus preusst (Preuss loco) *Astragalus thompsonae (Thompson loco) *Astra-galus conferttflorus (blue loco) Cryptantha flava (cryptanthe) Grtndelta squarrosa (gumweed) *Townsendta tncana (townsendia) Aplopappus armertodes (goldenweed) Senecto longtlobus (groundsel) *Aster venustus (woody aster) Grasses : Lily family : Buckwheat family : Legume family: Borage family: Sunflower family : By comparison of the indicator plant data with drill- ing results in the Yellow Cat area, it was found that plant mapping indicated 81 percent of the mineralized ground less than 32 feet below the surface, and 42 per- cent of the mineralized ground lying at depths between 32 and 170 feet. For mineralized ground at depths exceeding 170 feet, the ratio dropped abruptly to 16 percent, or about the same as on barren ground. Sev- eral ore bodies were found by means of plants in areas that had been believed from geologic evidence to be unfavorable for finding ore. REFERENCES Newman, W. L., 1957, Distribution of elements, in Geologic in- vestigations of radioactive deposits—Semi-annual progress report, Dec. 1, 1956 to May 31, 1957: US. Geol. Survey TEI 690, book 2, p. 480, issued by US. Atomic Energy Comm. Tech. Inf. Service, Oak Ridge, Tenn. Shoemaker, E. M., and others, 1959, Elemental composition of the sandstone-type deposits, in Garrels, R. M., and Larsen, E. S. 3d, Geoehemistry and mineralogy of the Colorado Plateau uranium ores: U.S. Geol. Survey Prof. Paper 320, p. 25—31. B98 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 47. GEOCHEMICAL PROSPECTING FOR COPPER IN THE ROCKY RANGE, BEAVER COUNTY, UTAH By R. L. ERICKSON and A. P. MARRANZINO, Denver, Colo. The distribution of copper in transported alluvium on a pediment of the Rocky Range, Beaver County, Utah, was studied to determine whether known copper deposits in bedrock concealed by alluvium could be detected by geochemical methods. The principal prob— lem in these studies is to distinguish between metal anomalies caused by detrital minerals, washed down- slope from mineralized outcrops, and anomalies caused by metals carried upward in solution from underlying rock and precipitated in the alluvium. The part of the Rocky Range pediment investigated in this study is in sec. 22, T. 27 S., R. 11 W., northwest of the Old Hickory copper mine, and separates the southern tip of the range from its main body. The rocks exposed upslope from this pediment include quartzite, marble, hornfels, and skarn that are intruded by medium- to coarse— grained quartz monzonite; they strike about N. 45° W., dip steeply northeastward, and can be projected across the pediment to similar outcrops in the southern tip of the range. Most of the copper deposits in the Rocky Range are tabular replacement pods composed of magnetite, chalcopyrite, garnet, and diopside, that occur in skarn near the contact with quartz monzonite. The con- cealed copper deposit in the mapped area occurs at depths ranging from 20 to 225 feet in a skarn zone that dips steeply northeast. The thickness of the alluvium over the deposit ranges from 6 to 72 feet. The area was mapped on a scale of 1: 1,200 to show the distribution of copper in alluvium in relation to topography, drainage, geology, and location of core holes in mineralized rock. Samples of alluvium were collected on the pediment on approximately 100-f00t centers and at a depth of 8 to 12 inches. At this depth cobbles and pebbles in the alluvium are coated with caliche. The term “caliche” as here used is restricted to calcareous material precipitated in the zone of weathering, probably by evaporation of water. The copper content of the minus-80-mesh fraction of the alluvial soil, determined by adding 2-2’ biquinoline in an isoamyl alcohol extract to the solution obtained by fusing the sample with potassium pyrosulfate, pow- dering the melt, and leaching the melt with dilute HCl (Almond, 1955), is highest in samples from the drain— age systems in the eastern and western parts of the mapped area, and has no apparent spatial relation to the core holes in mineralized rock (fig. 47.1). These copper “highs” are caused by the concentration of detrital copper minerals that have been washed from old prospect pits and mines downslope into the drainage. The small “highs” near the center of the mapped area may come from accumulations of detrital copper min- erals derived from the underlying mineralized skarn. In an attempt to distinguish between the copper con- tributed by detrital minerals and the copper transported in solution, the white to light-gray and the light-gray— ish-brown caliche coatings on pebbles and cobbles in the alluvium were removed and analyzed for copper. If caliche is a chemical precipitate formed by evaporation of water, the composition of caliche must closely reflect the composition of the water from which the caliche was precipitated. Copper was determined by adding 2-2’ biquinoline, in an isoamyl alcohol extract, to the solution obtained by leaching powdered caliche with hot 6N HCl. Figure 47.2 shows that the largest “highs” of copper in caliche, as thus determined, occur near the known concealed copper deposit, whereas the “highs” that can be ascribed to detrital copper are compara- tively small. Within the area having the highest concentration of copper in caliche, the caliche coatings contain more copper than the alluvium, whereas in most of the re— mainder of the mapped area the alluvial soil contains more copper than the caliche (fig. 47.3). The most significant features shown on this map are these: (a) all the core holes in mineralized rock occur within the area in which the ratio of copper in caliche to copper in alluvium is one or greater, and (b) the strong detrital-copper “highs” (fig. 47.1) are eliminated. This suggests that the copper in caliche and ratio “highs” were not derived from detrital copper minerals, but from upward moving water that leached copper from a restricted bedrock source below the pediment. This source is probably the known copper deposit that underlies the caliche that is comparatively rich in copper. REFERENCE Almond, By, 1955, Rapid field and laboratory method for the determination of copper in soil and rocks: U.S. Geol. Sur- vey Bull. 1036—A, p. 1—8. B99 EXPLORATION AND MAPPING TECHNIQUES 5.5 5:30 “Exam ”mafia 38m 2: E anEaa a :o :8 2:25“. we 23:8 “938 wiaofi gala: Masai mocmw .>> .>> ucm 952;: m <58fi§ 4 ,m 3 BE om 25E; ”5928 33.3qu cam _>mo_owm,.§m_Emzoomo Emu. 00m 09 o. 8% 3v Ema omfilmbA % g 0 Sam oomqomHA can oomA 5583 299% x 2o: 28 comm—«.852 0 fig H8985 ,thfi 8§§§s 2wa “.33 83:00 mflmwfiom a €33»an .55? can .BEEEV 6:3385 m3 fl 3E8 oE=3mEu 33:30 a Baggage E V BESEE 5.350 Q. a a ”2 E/ \ SQ . 83%.? EC.» zoFwom .ownwm 530m 93 E 325ch m no 55333 E 3133 cam $538 :0 mmnfiwoo 26:3 mo “:3on .5930 @5255 QmElNEw HERE.— wmcfi, .>> .>> ucm 655.8%: m .< .cowxotm i_ .m E Emmi ON J_<>mm._.z_ KDOFZOO EQSMOQB Ucm »>mo_omm .Eflszogo Emu. 00m 09 o E5 89 s can oomlooHA @ can STOONA 0 Eng oowA 3&8 8532 mEEmm x 2o: 28 @wszgwfifi 0 fig 838$ /.\._/T\ 36$§§§6 ESE $592M womanoo 2353» v. .C wogwfiwufi .mem can .Bfifiwsw 555385 mg a 3628 2533.5 E0230 0 3 BE 5-1 a: :s C? BEONEE 3.350 .. h E U m E 8/ 8% 833:2 EU 5.2.. _mU ZO_F> ucm .oENcmth.1.<.c0mv_otm.u_ .m .5 Hmmm ON 4<>mm._y2_ mDOHZOO Easmoqfl ucm ésoww éEEwcoooo Em: com _ 09 o. .v @ 2AA g mumAA U 822:? E fiasco . NA 23:8 E uwmmoo 65me .8582 magnum 8 2o: 88 wgzfiofiz E 6385 Sagwaesgs 93S: @wxmg 33:00 w .— :3 ._ SE 0 :1: 3385...: .waw {$5.35 28385 y 3.23 w: :35 033.580 :3 B o g o ”E 0* :3 or V... _H 858 E E>==< Eu 0...... ZO_F100—180 ___________________________________ some granitic rocks. Soil C horizon Area Rock type Background (ppm) Anomalous (ppm) Pb Zn Cu Ni As Sb Hg Pb Zn Cu Ni As Sb Hg Mahoney Creek... Slate ___________________ <20—50 <20—50 80—1000) ________________________________ >50— >50— >10()— ................................. >3, 000 2, 000 300 Yakobi Island ______ Amphibole schist _______________________ <20 <20 ____________________________________________________________________________________ Yakobi Island ...... G a b b r o a n d s o m e _________________ 50—70 20—50 ___________________________________________ 100— 100—600 _________________________ diorite. 1, 500 Yakobi Island ...... N orite __________________________________ 20—100 20—70 ___________________________________________ >ioo- 100—600 _________________________ 1, 500 Latouche Island.... Graywacke and slate... 10—80+ 10—50 ________________________________ 80—200 100(?)— 80—800 _________________________________ 4, 000 Red Devil. . Graywacke and shale... __________________________________ 150— >6—900 9—160+ 150(?) 6 5 3, 600 Kantishna ......... Quartz-mica schist. <2o— lO— ________ <1o— 1—100) ........ >1oo— >1oo— >1oo— ________ >20()— >10— ........ 100(?) 100(?) 100(?) 200(?) 4, 000 3, 000 300 2, 400 1, 100 or 4, 000 Maclaren Riven.-. Basaltic rocks ___________________________ 40—200 ___________________________________________________ >200— _________________________________ 1, 200 Livengood. . . _._... Ultramafic and maflc <20—50 25—120 20—80 50—400 ________________ <2. 5— ____________________________________________________________ rocks. 30) Livengood. . Chert and metasedi- <20—20 20—1200) 10—80 <25— ________________ <2. 5— ____________________________________________________ >6(?)- mentary rocks. 100 ('3) (9) 15(?) Fairbanks .......... Quartz-mica schist and <20—4o 20—1500) 10—(?) ________________ <1-4 ________ 50—8, 000 >150(?)— ......................................... some granitic rocks. 7, 000 557753 0—60—8 BIOO GEOLOGICAL SURVEY RESEARCH l960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES high soil values, but at an adjacent site. The direc- tion of root’growth of the plant in response to other soil factors having a physiological effect may cause this displacement. 5. Plant roots do not extend to great depths in Alaska, owing to (a) the general abundance of water in the upper soil horizons, (b) the thin soil mantle that usually overlies bedrock, and (c) the occur- rence of permafrost or late-thawing cold subsoil which limits downward root growth. This growth characteristic restricts the usefulness of plants in indicating deeply buried metal deposits. 6. The ability of plants to indicate anomalous metal occurrence in the substratum on which they are growing varies with the species of plant and kind of metal. A species that accurately indicates anomalous amounts of one metal may be useless for indicating another metal. 7. The average metal content of all species for all areas studied varied with the different metals, and ranked in descending order as follows: zinc, iron, nickel, copper, lead, and molybdenum (table 49.2). High, low, and median values for these elements are also given. TABLE 49.2.-Mean metal content of 38 speates of Alaskan plants, based on 5,126 analyses. Values expressed as percent in ash [Analyses by rapid wet chemical field tests by stafi of U.S. Geological Survey laboratory] Metal content in number of analyses indicated V . amp Lead Copper Zinc Nickel Iron Molyb- (1,439) (1,502) (1,439) (396) (338) deal;)m 0. 500 0.300 4. 00 0. 600 7. 50 0. 003 . 002 .001 . 02 . 002 .04 . 001 .012 .027 . 32 . 034 .28 . 001 Median _____________ .010 . 022 . 15 .015 . 25 .001 8. There is commonly a great variation in amounts of a particular metal absorbed by different species of plants growing at the same site. This may repre- sent the inherent limitations of the species in their range of metal absorption. Some species show a ratio of high to low metal content as great as 200:1, whereas others cover a range of only 5:1 to 10:1. Ratios of high to low percentages of several plants, which are considered to be representative of the total species analyzed, are given in table 49.3. Plants with high ratios have the capacity to indicate anomalous metal concentrations, whereas species with low ratios may be limited in this respect. These ratios may vary within a species, depending on the metal. 9. No definite geobotanical indicator species of flower- ing plants were observed in Alaska, although some of the species found on soil derived in part from serpen- tine may be included in this category. Several species of mosses and liverworts, however, were found which are generally recognized as occurring only on metal—rich substrata. The Alaskan specimens were found only on substrata containing, or presumed to contain, anomalous metal concentrations. TABLE 49.3.—Ratios of hlgh to low content of metals in selected species of Alaskan pwnts [Analyses by rapid wet chemical field tests by staff of U.S. Geological Survey laboratory] Ratio of high to low metal content (number of analyses in parentheses) Lead Copper Zinc Nickel Iron Alder (Alnas crispa (Ait.) Pursh) (122) (122) (122) (17) _________ 200:1 20:1 14:1 5:1 _________ Crowberry (Empetrum niarum L.). (38) (65) (38) (7) (14) 40:1 8:1 3:1 30:1 8:1 Deer cabbage (Fauna Cristaaalli (73) (73) (73) (17) (56) (Menz.) Makino). 15:1 10:1 10:1 10:1 721 Dwarf blueberry (Vaccinium aligi- (166) (195) (166) (40) (14) nomm L.). 20:1 40:1 25:1 150:1 3:1 False hellebore (Veratrum Esch- (44) (44) (44) (21) (23) schollzii A. Gray). 10:1 100:1 10:1 50:1 5:1 Menziesia (Menziesia ferrnyinea (76) (76) (76) (15) (26) Smith). 60:1 20:1 8:1 25:1 16:1 Mountain hemlock (Tsuga Mer- (66) (66) (66) (7) (56) tensiana (Bong.) Sarg.). 200:1 20:1 2:1 20:1 8:1 White birch (Betula resinifera (51) (51) (51) (47) _________ Britton). 200:1 15:1 27:1 32:1 _________ 10. Stream sediments that were collected from 0.5 mile to as much as 2 or 3 miles downstream from de- posits bearing one or more metals other than gdld, generally showed an anomalous content of at least one metal (table 49.4). Lead, zinc, copper, antimony, arsenic, nickel, and chromium all give identifiable anomalies. Tests for tungsten, co- balt, molybdenum, titanium, manganese, and several other metals did not appear to be as use- ful, although these metals were not tested as ex- tensively as the former group of metals. 11. Stream sediment derived chiefly or entirely from loessial mantle generally gives no clue to mineral deposits in the watershed. 12. Stream sediment sampling failed to detect placer de- posits that lie beneath a relatively thick muck and gravel cover, which in most localities in interior Alaska is frozen. Apparently such deposits do not yield detrital or dissolved metal to the surfi- cial stream sediment. 13. Stream water samples do not consistently give re- liable leads to metalliferous deposits in the drain- EXPLORATION AND MAPPING TECHNIQUES B107 TABLE 49.4.—Metal content of stream sediments in several areas of Alaska, based on approm'mately 455 samples [Analyses of —80 mesh material, after grinding it to —200 mesh, by rapid wet chemical field tests, by staff of US. Geological Survey laboratory] Background metal content (in ppm) Area and rock types Anomalous metal content (in ppm) Pb Zn Cu Ni Cr As Sb W Pb Zn Cu Ni Cr As Sb W Southeastern Alaska <20— <20— <10— <20— 20—150 ........ <1—4 ....... 50(?)— 80(?)— >50(?)— >80(?)— >150(?)— __________ 5(?)—15 ______ Many rock types. 40(?) 80(?) 50(?) 80(?) (9) 4, 000+ 4, 000 400 1, 200 1,500 Yakobi Island. Gabbro, norite, diorites and 30— 20— 60(?)— 100(?)- schist ___________________________________ 50(?) 80(?) __________________________________________________ 400 400 ___________________________________ Latouche Island. Gray- (10— 50— 10— 10— 3— wacke and slate. _ _ __._. 40(7) 100(?) 60(?) _________________ 80(?) 10(?) Interior Alaska. Many <20~ <20— <10— <10— <1— rock types ______________ 60(?) 100(?) 50(‘?) _________________ 120(?) Kantishna. Quartz-mica 10— 20— 20— <10— 1— and chlorite schist ______ 80(?) 120(?) 50(?) _________________ 120(?) <20(?)>6{)(?)— 120(?>— 60(?)— >120(?)— 6(?)—45 20—40 _______ 3000) 700 so 300 ‘ >80(?)— >120(?)— >50(?)— >120(?)— >120)— _______ 1,500 2,500 150 3, 200 600 age basins. Some base metal deposits were de- tected by anomalously high amounts of copper, lead, or zinc in water 0.5 mile downstream. Al- though this condition seemed to be detectable for as much as 3 miles downstream, it diminished to indefiniteness at that distance. In contrast, some other streams draining areas having similar deposits showed only normal metal content. 14. Apparently no useful correlation can be made be— tween pH and metal content of stream waters, or between sulfide deposits and the sulfate content of waters draining from such deposits. The analytical values given in tables 49.1 through 49.4 were determined by rapid wet chemical field tests that have a precision of —50 to +100 percent. Due consideration should also be given to the distance of the sample from the source deposit and t0 the rock type from which the sample material is derived. Thus, it is impossible to give an exact figure that divides background from anomalous values. 6% 50. THERMOLUMINESCENCE AND POROSITY OF HOST ROCKS AT THE EAGLE MINE, GILMAN, COLO. By CARL H. ROACH, Denver, Colo. Preliminary results of a study of the base-metal re- placement deposits in the Eagle mine, Gilman, C010., indicate that thermoluminescence and porosity of host rocks adjacent to some ore bodies may be related to dis— tance from ore and to alteration associated with ore. The number 3 Lower Chimney ore body is enclosed by a large mass of dark aphanitic Leadville dolomite (Mississippian) that has been altered to “sanded dolo- mite” near the ore body (Lovering and Tweto, 1944). A few small patches of sanded dolomite occur at greater distances from the ore body. The sanding process changed the dark aphanitic dolomite to a coarse grained incoherent mass of light-gray dolomite sand. Gener- ally, samples of sanded dolomite have less thermo- luminescence than unaltered aphanitic dolomite and the amount of thermoluminescence of aphan‘itic dolomite increases with distance from the ore body (fig. 50.1). Exceptions are samples 49 through 52, which are slightly sanded and represent a rock type similar to the sanded dolomite near the chimney. The porosity of the host rock near the number 3 Lower Chimney ore body is also related to intensity of alteration and to distance from ore (fig. 50.2). The porosity of sanded dolomite near ore ranges from 16 to 25 percent, whereas all dolomite samples more distant from ore than the mass of sanded dolomite have porosi- ties of about 6 percent or less. An exception is sample number 38, which has a porosity between the'two groups of samples. Sample 38 is very close to the mapped con— tact of sanded dolomite, and has probably been affected slightly by the sanding process even though this is not megascopically apparent. It is noteworthy that the porosity of samples 49 through 52 is not high with respect to the porosity of adjacent samples of aphanitic dolomite, even though these samples are slightly sanded. The thermoluminescence of samples 49 through 52 w p—A Q m GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES in” %$ 52 100 31 33 36 37 38 39 41 100 (I’D "I § Lu a .‘ I n — 2 1' I r. ‘ ‘. ' ‘ $2 ,\\ I, \\\ II, “ III “ ’l‘ ,'\‘ I: \ 0d "I ’l I ‘ I I I, ‘ ' 21 0 l—v—IJA fl—r‘fi f—I—I‘IA I—T—I"¢ I 0 g; {100° 400° {100 400° {100° 400° {100° 400° {100° 400° {100° 400° {100° 400° {100° 400° {.— at 23 44 46 48 9 m_ 4 50 52 51 53 8% 100 I: I, , . 1°C EU I I ll I S 2 I‘ I ‘ l “ I, ._ I ’ l I \ " l 3< , I I \ I I \ _J_J ‘ ‘ E \ I ow ’ L/\ ' ' i X I I LiJg {100° 400° {100° 400° {100° 400° {100° 400° {100° 400° {100° 400° {100° 400° {100° 400° {— . TEMPERATURE IN DEGREES CENT‘IGRADE .v .444 A 46v I -48 , I 49 I §2_ WM-fi 3 4"} A“:«W°fi£§i‘f§f”l // ld //-// I/ If I/ 1/ ll-ll // l/ l/ /;5 - ”Hr . / / / / / / / / / / / / / ' I'll, /4 /,/,L/ III Ill, /, I'lll/IJ/l [I'll/7 .50 51 0 10 FEET l__l EXPLANATION 7 ~\ W Massive pyrite Mudstone Contact W E A 1:30 . / . ‘ ‘ *~ 1: 10 Mixed sulfides Dolomite Scale, factor iii.” lam-I 1 "ml Manganosiderite rubble Altered sulfides “Sanded” dolomite Room temperature q .. . 4‘4“ Dolomite breccia Sample location FIGURE 50.1.-—Variations in thermoluminescence of the Leadville dolomite adjacent to the number 3 Lower Chimney ore body, Eagle Mine, Gilnnan, Colo. was found to be similar to that of the sanded dolomite near the ore body (fig. 50.1). These relations suggest that porosity ahd thermoluminescence measurements might be useful in locating ore bodies. Porosity meas- urements might make it, possible to difl'erentiate be- tween masses of intensely altered sanded dolomite near large ore bodies and small, less intensely altered masses of sanded dolomite that are far removed from ore. The porosity of sanded dolomite seems to be related to the intensity of alteration, which in turn seems to be related to nearness to ore bodies. The Dyer dolomite member of the Chafl'ee formation (Upper Devonian) adjacent to the 18~35 chimney does not appear megascopically to have been intensely altered by sanding as is apparent near the ore body in the overlying Leadville dolomite. However, measure- EXPLORATION AND MAPPING TECHNIQUES B109 25 z 20 as O 5 15 D. I— E 10 O O: Lu CL 5 o A o 10 20 30FEET I____;L__l > I'— a O n: O n. t»— Z LLJ E2 w s Q. ' o of chimney B O 10 20 FEET |____l—_J EXPLANATION W/l///A E Ore Dolomite . , . ‘ A A Manganosiderite rubble Dolomite breccia mi ’ ‘ 5—4;! Sample location “Sanded” dolomite FIGURE 50.2.——Variations in porosity of (A) the Leadville dolomite adjacent to the number 3 Lower Chimney ore body, and (B) the Dyer dolomite member of the Chaffee formation adjacent to the 18—35 chimney ore body, Eagle Mine, Gilman, Colo. ments show that the porosity of the Dyer dolomite that alteration may have been more effective than is member is high (15 to 20 percent) near ore and de- apparent megaseopically. Dolomite more distant from creases with distance from ore (fig. 50.23), indicating ore than sample 8 may have lower porosity. B110 EXPLANATION A— 1:30 , — - — - 1:10 Scale factor W Sulfide ore t Barren quartzite Room temperature 0 Sample location ”Sanded" quartzite GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 100 62 , 63 64 65 66 _100 U) I l— ‘ I _ 2 .' D II I‘ - u.| I ' > n ' I“ - E . .' .' : ‘ ~ ' ,~_a' E O - . v 1 'VI . v v 'Iv“ /. . u y u If: . I . u I,“ #‘0 g 1 f f f m E’ m 59 6O 61 68 8 100 . 100 LLJ H E ' ' r 2 ' ‘ I‘ D I ‘. : ‘..‘ .4 I ' \ O I‘\ I ‘\‘ ,' \ E , If- ‘ ' " 1' X‘ 5‘3 0 I' ~---_, 4}“, I'/k ,I/\’\ 0 '- | l I I I l r 1 l l l l l l l l l ‘ I I f 100° 400° f100° 400° “00° 400° f 100° 400° 400° TEMPERATURE IN DEGREES CENTIGRADE 20 E 66 8 15 \y D: O Q. E 10 8 63 65 E 5 6 [L 64 o 62 6360 64 65 6g ...... . n' ' 59 7,, -.. 61 )— ’— g 10 m 0 D. E 5 59 68 m 60 61 _ _ _ 7 _____ 7 _______ _ E o ' _ _ _ - ‘67 Lu 0. 0 10 FEET FIGURE 50.3.—Variations in thermoluminescence and porosity in and adjacent to a sulfide ore body in the Sawatch quartzite, Eagle Mine, Gilman, Colo. EXPLORATION AND MAPPING TECHNIQUES It seems that alteration associated with the ore bodies has greatly increased the porosity of both the Leadville dolomite and the Dyer dolomite member of the Chaf'fee formation adjacent to ore (figs. 50.2A and 50.28 ). The increased porosity associated with alteration in the Leadville dolomite is seemingly restricted to distances no greater than 50 feet from ore and terminates abruptly, whereas alteration in the Dyer dolomite mem- ber seems to have been more pervasive and to decrease gradually with distance from ore. These relations sug- gest that a unique porosity variation with distance from ore may be characteristic of each carbonate unit. These different variations taken together may be useful as a guide to ore. Sulfide ore bodies also occur in the Sawatch quartzite (Upper Cambrian) in the deepest workings of the Eagle mine. One of these ore bodies consists of two layers of sulfide ore separated by a thin layer of B111 quartzite (fig. 50.3) and is bisected by a vertical silver- bearing galena vein. Quartzite at the lateral edges of the two ore layers has been sanded. The thermo- luminescence of the quartzite in the thin bed between the ore layers seems to be related to distance of the samples from the vein (fig. 50.3) ; the sanded quartzite has much less thermoluminescence than adjacent sam- ples of unaltered quartzite. The ore and altered quartzite have higher porosity than the barren unaltered quartzite (fig. 50.3). The sanded host rock has a much higher porosity than un— altered quartzite, but unlike sanded dolomite near ore in the Leadville, the sanded quartzite is limited to a very narrow zone at the edges of the ore body. REFERENCE Lovering, T. S., and Tweto, Ogden, 1944, Preliminary report on geology and ore deposits of the Minturn quadrangle, Colo- rado: U.S. Geol. Survey open-file report. 6% 51. USEFULNESS OF THE EMANATION METHOD IN GEOLOGIC EXPLORATION By ALLEN B. TANNER, Salt Lake City, Utah Work done in cooperation with the US. Atomic Energy Commission Exploration for radioactive materials or geologic features by measurement of one or more of the emana- tion isotopes, radon, thoron, and actinon, contained in soil gas near the surface of the earth, is called the emanation method. The basic concept is that the emanation isotopes, being gaseous, may migrate by dif- fusion and transport for a distance from their source through soil overburden greater than the distance ef— fectively penetrated by gamma rays from the same source. Because the techniques for emanation meas- urement are also more sensitive and more specific than field gamma—ray measurements, emanation surveying— particularly that using radon—222 measurement—has been practiced occasionally for about forty years (Am- bronn, 1928). In the United States it has not won recognition or general acceptance as a practical method because of contradictory results of field testing. The principal matter of dispute has been the depth of pene- tration of the method, estimates of which—based on apparent field success—have ranged from several inches to hundreds of feet. The theoretical approach has been fruitful and has been presented by Grammakov (1936), who showed the extent of emanation migration through permeable material to be a sharply decreasing hyperbolic func- tion of distance. From various theoretical and labora- tory results it may be estimated that the emanation method is accurate and effective to a maximum depth of about 30 feet in dry, coarse, nonradioactive over- burden. Soil moisture content of more than about 6 percent reduces the effective depth many-fold, and moist clay layers practically prevent radon migration. It is becoming apparent that most of the “radon” anomalies described in the literature probably occur not because of the migration of the gaseous but short- lived radon, but because of migration of radium and other intermediate decay products of uranium in solu- tion. Rosholt (1959) has shown that the radioactive disequilibrium that would accompany such migration in solution is the rule, rather than the exception, in uranium ores. In Karnes County, Tex., a radon anomaly over a uranium ore body covered by 1 to 10 feet of overburden was due to migration of radium and other intermediate decay products of uranium; radon migration was virtually nil. Such anomalies tend to be displaced in the direction of ground-water move- B112 ment and therefore to be inaccurate in locating geologic features unless the features are large compared with the thickness of overburden. REFERENCES Ambronn, Richard, 1928, Elements of geophysics, translated by Margaret C. Cobb: New York, McGraw-Hill Book Co. (Chap. IV). GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Grammakov, A. G., 1936, O vliyanii nekotorykh faktorov na rasprostraneniye radioaktivnykh emanatsiy v prirodnykh usloviyakh (0n the influence of certain factors on the spreading of radioactive emanations under natural condi- tions) : Zhurnal Geofiziki, v. 6, no. 2—3, p. 123—148. Rosholt, J. N., Jr., 1959, Natural radioactive disequilibrium of the uranium series: U.S. Geol. Survey Bull. 1084—A, p. 1—30. 52. POLAR CHARTS FOR EVALUATING MAGNETIC ANOMALIES OF THREE-DIMENSIONAL BODIES By ROLAND G. HENDERSON, Washington, DC. CHART DEVELOPMENT In the indirect approach to the interpretation of total-magnetic intensity anomalies, one makes an in- telligent guess concerning the depth, size, shape, and magnetization of the disturbing body, and checks his hypothesis by calculations. For three-dimensional bodies (that is bodies with both horizontal dimensions not large in relation to the depth of burial) the calcu- lations are quite difficult; accordingly, graphical meth- ods are indicated. In this report we present a new and simple polar chart method for the rapid computation of the magnetic effect of any magnetic body. The charts are based on the formula for the mag- netic effect of an elemental solid sector cut, from a buried hollow vertical cylinder of infinite depth extent. FIGURE 52.1.—Geometrical basis for effect at P due to elemen- tal semi-infinite vertical cylinder magnetized by induction in a field, T... In figure 52.1, let P: (0,0,0) be a point in the xy-plane on which the observations are presumed to have been made, and let the upper face of the cylinder terminate in a plane which is one depth unit below the xy-plane. Let r, and rm be the radii of the elemental hollow cylinder and let 0, and 01+] be azimuths of the radial line boundaries of the sector. At P, the total magnetic intensity anomaly per unit magnetization produced by the elemental column is given by AT) _ kTO Lj— I'1+I 01+1 2i f f {005 ( 1_—1)(1—2cos20) r 1/1'2—H I‘ 0] _rcos2Icos20 2r2 sinIcosIcos0 can” curl)” rsin2 I ‘— . . . . 1 +(r,+l),,,}drdo . . . . . . () where k is the magnetic susceptibility, To the magni- tude of the earth’s normal magnetic field and I its in— clination. For a given I, the infinite half-space anom- aly per unit magnetization at P is, (kATF) 1Ag—space: «(2 sin2 I~cos21) By integrating (1) from 01:0 to 91+1=27r, we obtain the anomaly at P due to the i-th ring cylinder of radii r, and rm. We use this formula to divide the half-space into a family of consecutive concentric cylinders each having an arbitrarily pre- scribed percent of the half-space magnetic intensity ’ value. Next we find for each ring cylinder, in turn, the various azimuths 0,, which divide the ring into sectors each having the same effect at P. A facsimile of the polar chart constructed for I=75° is shown in figure 52.2. Each non—numbered sector has the effect of 0.005652 gammas per unit magnetization at the center EXPLORATION AND MAPPING TECHNIQUES UNIT DEPTH \__1 FIGURE 52.2.—P01ar chart for computing the magnetic anomaly of three-dimensional bodies magnetized in a field of inclina- tion I=75°. ' of the chart. The sectors in the lower portion of the chart set off by heavy radial lines are negatives. Num— bers indicate the partial value (in percent) for incom— plete sectors. Similar polar charts have been con- structed for inclinations I=90°, 75°, and 45°. Charts for I=30°, 20°, and 0° will be constructed. The com- putation of the charts is being carried out by Alphonso Wilson of the US. Geological Survey. USE OF CHARTS For desk use, film positives of the charts are repro— duced at a scale one-half inch equals a depth of burial. In a three-dimensional computation the body is subdi- vided into horizontal layers represented by contours. Through each point to be computed on the plane of observations, a line is drawn in the direction of mag- netic north. Because the depth of every level is differ- ent the scale at each level must be adjusted to agree with that of the chart. This scale reduction can be done either photographically or optically on a projec- .tor. The center of the chart is placed at the point to be computed, the axis being alined with magnetic north. The chart elements or portions thereof covering the area inside the contour are counted. At each level counts for the bottom contour of the overlying layer are prefixed with a negative sign, and counts for the top con- tour of the lower layer are prefixed with a positive sign. B113 The counts for all levels are added algebraically to ob- tain the anomaly of the body at a given point on the sur- face. Tests show that the charts yield accurate results. The method, although still developmental, is being used by J. W. Allingham and Montgomery Higgins of the US. Geological Survey to interpret anomalies caused by topography in southeast Missouri. Their computations for Bald Knob are illustrated in figure 52.3, which shows the generalized elevation contours, and in figure 52.4, which shows both a vertical section along A—1)’ and the computed (solid line) together with the observed (broken line) magnetic profiles; The mis- fit on the north limb of figure 52.4 is attributed to the influence of adjacent magnetic material not included in the calculation. The charts have a wide variety of applications. Since at a radius of 20 depth units the charts cover 95 percent of the half-space anomaly, they also can be used on bodies traditionally computed by two-dimensional methods. Vertical contacts, horsts, grabens, dikes, plugs, pipes, etc., are examples of bodies rapidly com- puted in this way. REMANENT MAGNETIZATION CALCULATIONS Remanent magnetization, invariably neglected in calculations, may sometimes be many times greater than the induced magnetization. In View of the in- FIGURE 52.3.—Genera1ized topography of Bald Knob, southeast Missouri, showing location of section A-B. B114 w < 2 2 <2: (5 Computed _ _ _ Observed 1000 FEET FIGURE 52.4.—Vertical section of Bald Knob taken along A—B and magnetic profile computed for threedimensional topo- graphic relief. creasing volume of data on remanent magnetization, methods must be developed for making total magnetic GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES intensity calculations when some knowledge of the remanent moment and shape of the body is available. Polar charts constructed for AZ and AH for various inclinations are required for these calculations. One excursion over the body must be made with each chart. The AZ charts also would be of much value to those conducting vertical component surveys. CHARTS FOR OPTICAL ANALOGUE COMPUTER Use of a chart involves a counting of the covering chart elements. This is an operation which can be performed on a commercially available optical analogue computer designed for gravity calculations. To adapt this equipment for magnetic applications we have de- vised charts equipped with a uniform number of light apertures per sector. The transmitted light is pro- portional to the anomaly and as it falls upon a photo- electric cell is measured in a potentiometer circuit. In a recent test the anomaly of a vertical cylinder was computed with an error of less than two percent. Methods of improving the sensitivity and drift char— acteristics of the equipment are being studied. This adaptation of the computer may be a major break- through in calculations for magnetic interpretation. 6% 53. MAGNETIC EVIDENCE FOR THE ATTITUDE OF A BURIED MAGNETIC MASS By GORDON E. ANDREASEN and ISIDORE ZIETZ, Washington, D.C. It has long been recognized that one of the short- comings in the analysis of magnetic and gravity data is the inability to determine a unique configuration for a rock mass that is assumed to produce an anomaly. The purpose of this paper is to show that despite this am- biguity, the dip of a dikelike mass at known depth can be confidently ascertained within narrow limits, irre— spective of the thickness of the mass. To illustrate the interpretive procedure, a typical linear aeromagnetic anomaly was selected for analysis. A total-intensity aeromagnetic map of east-central Indiana (Henderson and Zietz, 1958, plate 4) shows a two-dimensional anomaly extending from Fayette County across Wayne County and into Randolph County (fig. 53.1). This anomaly trends northeast and has a magnetic relief .ranging from 200 to 400 gammas. Magnetic profiles were flown, approximately 1,000 feet above the ground, along north-south lines one mile apart. Others were flown at the same altitude but crossing the feature at right angles to its trend (fig. 53.1). All these profiles are very similar in shape but differ in amplitude. From these, profile C was selected to represent the essentially two-dimensional feature producing the anomaly (fig. 53.2). GEOLOGY The area is underlain at depth by sedimentary rocks of Precambrian and Paleozoic age up to and including the Pennsylvanian, and the Pennsylvanian rocks are overlain by Quaternary sediments. There are three drill holes in the area. Two of these are on the east and west flanks of the anomaly (fig. 53.1), and reach Precambrian .rocks at depths of 2,478 and 2,617 feet below mean sea level respectively. The third, in Jay County immediately north of Randolph County, reaches Precambrian rocks at a depth of 2,471 feet be- low mean sea level. Hence it is reasonable to assume that the relief of the Precambrian surface in the area EXPLORATION AND MAPPING TECHNIQUES 85° / / I l ANDOLPH R EXPLANATION -2617 0 Drill hole depth to Precambrian Datum is sea level b Additional flight traverses 40° i Ii» / /qao(<—£ZMN @ | I 2 o 2 4 a L I l I l l I flush/FAYETTE | > I 114 MILES CONTOUR INTERVAL 50 GAMMAS FIGURE 53.1.—Tota1 intensity aeromagnetic map of part of Indiana (from Henderson and Zietz, 1958, pl. 4). considered is at most only a few hundred feet. The magnetic anomaly could be due to igneous rock in— truded into the sedimentary rocks, but no intrusive rocks are now known to be exposed in Indiana. ASSUMPTIONS AND PROCEDURE It is assumed that the upper surface of the anomaly- producing rock mass coincides with the surface of the Precambrian and that it is flat-topped, for topographic relief of several hundred feet at this depth would con- tribute little, if at all, to the magnetic anomaly. Ex— perience has shown, also, that the magnetic suscepti- bility of the sedimentary rocks may be considered negli- gible. B115 200 \ Com uted 9 100 < p 2 f \ E < o E / E o m 5 “Observed (profile C) E i l- — 100 '9‘ ‘\\_A/ —200 NW 2 1 0 1 2 SE DISTANCE, IN MILES 1000 0 K Plane of observation h o dendrite? DJ Lu LL 3000 : w=dike width=2000 ft _—_:__: r t=dike thickness: 1414 ft }:—:— FIGURE 53.2.—-Observed and computed magnetic profiles over an assumed dike of infinite depth extent. Because of the linearity of the magnetic feature, it was believed that the anomaly might be produced by the juxtaposition of two rock masses of different magnetic properties within the Precambrian complex. One possible cause of such a juxtaposition would be faulting in the Precambrian basement, but computed magnetic profiles based on this assumption did not closely resemble the observed profile. Excellent agree- ment was obtained, however, by assuming a dikelike mass dipping to the southeast as shown in figure 53.2. It was also assumed that the rock mass was magnetized by induction in the earth’s field, and that remanent magnetization, if present, was also in the same direction or was negligible. Geophysical evidence thus indicated the probable existence of a dikelike mass whose top is at the surface of the Precambrian rocks. It remained to determine the numerous possible combinations of dike width and dip for which the profiles computed from the above- stated assumptions will provide reasonable fits to the observed anomaly. B 1 16 GEOLOGICAL SURVEY RESEARCH 19 6 o GOODNESS OF FIT As a help in making a quantitative estimate of the “goodness of fit,” the symbol “G” was introduced. This represents a quantity that corresponds to the Chi- square of least~square theory and is the sum of the square of the differences between observed and com- puted values at equally spaced intervals (fig. 53.3) and is expressed ]:n ij12(AT1< O 0) Gray slate gx Gray slate 8 l‘ x X 0 2 MILES FIGURE 54.2.—Attitude of the gabbro near Moxie Pond as de termined from aeroniagnetio profiles A and B. Q Inclination of \ earth's field I 6 2 00 80° GAM MAS 2400 Observed / / // / I 04* 0/ Computed ‘1‘: \,\, FIGURE 54.3.——Shape of diorite body in granite, near Mount Katahdin, as determined from aeromagnetic profile. Bed- rock geology by A. Griscom. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES From an examination of several profiles the dips of other linear sheetlike bodies, such as the gabbro near Moxie Pond (fig. 54.2), can be determined Within 15 degrees. Locally the dip of this gabbro sheet changes abruptly from nearly vertical to about 60 degrees north— westward. This change in dip may indicate a signifi- cant structural dislocation in the rocks of this area. Isolated magnetic anomalies Within a felsic intrusive body may indicate mafic differentiates, separate in- trusions, or large inclusions Within the intrusive body, such as 'the diorite body in the granite near Mount Katahdin (fig. 54.3). A simple two-dimensional analysis (Pirson, 1940) of the aeromagnetic informa- tion (Balsley and others, 1957) gives a rapid estimate of the attitude of the contacts, and therefore determines the shape of the body. Irregularities in the profile near its peak indicate inhomogeneities in the diorite but do not materially affect the interpretation. Magnetic slate containing pyrite and pyrrhotite is interbedded near Bingham with calcareous slate. The attitude of the slate, obtained by fitting computed data N (A) 01 0 Observed GAMMAS ET BM 0 oo oo l—i—lm Gray slate FIGURE 54.4.—Attitude of magnetic slate as determined from aeromagnetic profile. 2800 - Observed profile 2600 GAMMAS 2400 1500 y. I \ -I \ I \ \ 7 mlOOO _’,(Quartz monzonite\_‘-_','/ x ‘Q‘ s x x E: , j: of baserliier}t\‘>’£j/x , i. “E": ,. \I / /\/\ \ x» monzonl e //\l_>_l~\/\\/‘S_'.C/‘ " a t ' o-/ x x I i- 1...] .v/ 500 ‘ o 2090 FEET 10100 FIGURE 54.5.-—Aeromagnetic profile over quartz monzonite. Bedrock geology by A. A. Albee. EXPLORATION AND MAPPING TECHNIQUES to observed profiles, possibly indicates a significant fold, which may be either an asymetric syncline or an over- turned anticline (fig. 54.4). Some plutons, such as the intrusive quartz monzonite on Hog Island (fig. 54.5), are outlined by a more mag- netic rim of hornfels, whereas other plutons, such as the granite at Bald Mountain, are not shown by the magnetic data, because they are not rimmed with mag- netic metamorphosed rock. Bodies of gabbro and diorite commonly have a border more magnetic than the interior. Interpretation of magnetic profiles is sometimes complicated by these magnetic borders or by rims of hornfels; in such cases, however, much struc- B119 tural information, particularly the attitude of contacts, can be obtained by analysis of selected aeromagnetic data. REFERENCES Balsley, J. R., Blanchett, Jean, and Kirby, J. R., 1957, Aeromag- netic map of Harrington Lake quadrangle, Piscataquis County, Maine: U.S. Geol. Survey, Geophys. Inv. Map GP 155. Boucot, A. F., Griscom, Andrew, Allingham, J. W., and Dempsey, W. J ., 1960, Geologic and aeromagnetic map of northern Maine: U .S. Geo]. Survey open-file report. Pirson, S. J., 1940, Polar charts for interpreting ‘magnetic anomalies: Am. Inst. Mining Metall. Engineers Trans, v. 138, p. 173—192. 6% 55. CORRELATION 0F AERORADIOACTIVITY DATA AND AREAL GEOLOGY By ROBERT B. GUILLOU and ROBERT G. SCHMIDT, Washington, DC. Work done in cooperation with the U.S. Atomic Energy Commission The correlation of aeroradioactivity data and areal geology in several areas of the United States is being investigated by the US. Geological Survey. Study of aeroradioactivity profiles obtained using equipment and surveying techniques developed in the search for de- posits of radioactive materials indicates that aeroradio- activity surveying can be an important adjunct to a geological mapping program. Aeroradioactivity surveys are flown at 500 feet above the ground on parallel flight lines oriented normal to geologic trends. A flight—line spacing of a quarter of a mile is used for detailed surveying and a. spacing of 1 or 2 miles is used for reconnaissance surveys. The scintillation detection equipment used in the surveys, which utilizes six thallium-activated sodium iodide crystals (4 inches in diameter, 2 inches thick), has been described by Davis and Reinhardt (1957). Gamma radiation emanating from the top six inches or so of surficial material of a strip about 1,000 feet wide is recorded in counts per second (cps) as a continuous profile. The cosmic background component is removed and the data are compensated for deviations from the nominal 500 foot surveying altitude. Correlation of aeroradioactivity data and areal geol- ogy is similar to subsurface correlation using gamma- ray logs of drill holes. Radiation units are delineated by connecting similar radioactivity features on adjacent profiles. The contact between radioactivity units is assumed to be the point where a reading halfway be— tween two levels is recorded (fig. 55.1). Each unit is considered to represent an area on the ground that has a particular content of gamma emitters in the surfi- NV_V Boundary of §E aeroradioactivity unit l i | Line“ i l . . I A ' COU NTS PER SECON D \ 3’ § COUNTS PER SECOND Line 9 800 u I l \ l l I Line 8 I 300 600 l ‘ l Sedimentary i Diabase rock Diabase Sedimentary J " rock DC VA \ 1 0 L4. J I 1I MILE FIGURE 55.1.—Aeroradioactivity profiles in the Bealeton area, Virginia. B120 cial material. Where bedrock and residual soil are the surficial material, the major and minor aeroradioactiv- ity features match the trends, and, in many places, the boundaries of geologic units. In areas of alluvium and eolian deposits, the radioactivity units are not related to bedrock but reflect the distribution of the transported material. Water is an effective radiation shield, a few inches being sufficient to mask the radioactivity of the ground. The areal distribution of Triassic diabase and sedi- mentary rocks in an area near Bealeton, Virginia, can be determined from aeroradioactivity data recorded on flight lines spaced a quarter of a mile apart. The three contacts between aeroradioactivity units shown in fig— ure 55.1 are within a few hundred feet of the lithologic contacts. The width of the diabase unit (about 1,300 feet) approaches the minimum width of a broad source (Sakakura, 1957). Narrower units can be detected easily but their boundaries cannot be picked accurately. A comparison of areal geology and gamma aero- radioactivity has been made in the Savannah River area, South Carolina and Georgia (fig. 55.2, index map). In the Piedmont part of the area most of the granite has a high aeroradioactivity level (generally 1,000 to 1,500 cps), the slate is generally low (usually below 600 cps), and the metamorphic complex includes / 5.7.: // ,: jW W, / u/ we , M‘~.:<’é2:: ate 9 '4,4 // /«‘ . ‘ ‘ ”Q20 . ~ ‘3‘- 4 ‘A‘A *, 4., WINE. v900—1800cps. , 4;; //l/V\- ‘A<;’%\- “*t y. ‘1 a \ \ .\ .‘ .‘50 ” ¢ A a A __ __ I 560-800 c253 Geology and radiometry .‘e‘fib 15 .‘v -'< h\ " 4 ‘1- /_ 1 u . r " "Eb A ‘SAI < x A v. t 4 A ~ Base from County Road Map EXPLANATION lg by R. G. Schmidt. 1959 L :0 ‘ m8 ____ . ' ‘ . tact 3‘ - Tuscaloosa formatlon 00 Con 7 2 6 Dashed where 33_ M E S appraxzmarely located Slate m'j ............... 2“ Boundary of aeroradio- V <0. , 32. 11 an: activity unlt Index map of Granite 0:0 Savannah River area “' 10094200, E 800‘”) Flight line and aero- 1 o 1 2 MILES radioactivity meas- ured in counts per N second (cps) Hachu/“es ind/cafe change in aeroradioactivity and pain! fa ward lower level FIGURE 55.2.—Geology and aeroradioactivity of an area in Lexington County, SC. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES areas of high and low aeroradioactivity. In the Coastal Plain part of the area, the aeroradioactivity of the Upper Cretaceous and Eocene rocks ranges from low to high and the Oligocene and younger formations are generally low in aeroradioactivity. The change in aeroradioactivity level can be used to locate geologic contacts at several places in the Pied- mont part of the area, irrespective of the deep weath— ering of the rocks. The contact between granite and slate in an area in Lexington County, South Carolina (fig. 55.2) is marked by a change in level of about 500 cps. The sinuous contact between the granite and the overlapping Tuscaloosa formation could not be de- lineated with data from flight lines spaced one mile apart but on many profiles a good break in radioac- tivity level appears where the contact is crossed. Approximately parallel aeroradioactivity units in Saluda County, South Carolina (fig. 55.3), indicate a zoning in the slate that could-not be found in the field. The two distinct levels of aeroradioactivity are present for more than 35 miles. Areas of Piedmont rocks ex- posed in valleys in the Coastal Plain are, in many places, clearly indicated by the radioactivity data." The highest aeroradioactivity levels in the surveyed part of the Coastal Plain are in Lexington and north- east Aiken Counties (in part shown on fig. 55.3). Monazite is probably the radioactive mineral in these irregular areas that occur in residual soil derived from Upper Cretaceous and Eocene strata. Monazite and other heavy minerals were mined until recently in Horse Creek near Aiken, South Carolina, from a large placer that probably developed by the reworking of Coastal Plain sedimentary rocks. The Coastal Plain rocks near Horse Creek are much less radioactive than those in Lexington and northeastern Aiken Counties, which suggests that the valleys of streams draining the more radioactive areas may be favorable sites for placer mineral deposits. Alluvium and water shielded the placers themselves from detection in this airborne survey. The radioactivity of the flood plains of the larger streams in the Coastal Plain is related to the geology of their headwater areas. The flood plains of rivers hav- ing headwaters in the Piedmont or older Coastal Plain formations (the Savannah, Edisto, and Ogeechee Rivers) are more radioactive than the adjacent uplands. The flood plains of rivers that drain only the younger Coastal Plain formations (the Salkehatchie and Coosa- whatchee Rivers) are equally or less radioactive than the adjacent formations. The correlations between aeroradioactivity data and areal geology that have been made in several parts of the United States indicate that this technique is a use- EXPLORATION AND MAPPING TECHNIQUES B121 81 °30’ § § EXPLANATION g >_ 9 Q) .,__ n: B 0 Lu 3;; Q 22;: E "g Barnwell and Tuscaloosa formations E < E E 3 I3: '— 9- x x x U D x x Granite z 2 ' .x_ 7 < 8 . ‘ 34°oo' _ /////. s3 ' Slate E _l U < Lu 0... 4 r 7 I~ Q: [E to Metamorphic cemplex Includes slate, schist, amiss, and granite Contact— _ _ Dashed where approximately located Boundary of aeroradioactivity unit Dashed where approximately located AERORADIOACTIVITY LEVELS :l 750—1500 cps 450-600 cps 300-450 cps 33°45' 5 O 5 10 MILES .. _ . ' I I I I I I I 4 Base from Army Map Service Geo|ogy and radiometry by 1:250,000 sheets R. G, Schmidt, 1959 FIGURE 55.3.—Geology and generalized aeroradioactivity of an area near Batesburg, S.C. ful mapping tool. It is of most value in areas of low to REFERENCES moderate topographic relief, residual soil, and poor out- , Davis, F. J., and Reinhardt, I’. W., 1957, Instrumentation in crop, such as the Piedmont. These are the areas, of aircraft for radiation measurements: Nuclear Science and course, in which it is most difficult to determine the dis- Engineering, V. 2, no. 6, p_ 713421 tribution and contlnmty 0f hthOIOglc unlts by ordlnary Sakakura, A. Y., 1957, Scattered gamma-rays from thick uran- field methods. ium sources: U.S. Geol. Survey Bull. 1052—A, p. 1—50. ’2 56. MAPPING CONDUCTIVE STRATA BY ELECTROMAGNETIC METHODS By F. C. FRISCHKNECHT and E. B. EKRE‘N, Denver, Colo. Since 1957 the US. Geological Survey has been study- cousin, and Maine. The objectives are to develop tech— ing the use of electromagnetic methods in tracing con— niques that can be used in mapping bedrock geology ductive strata beneath glacial drift in Minnesota, Wis- in areas of extensive glacial drift or thick residual soil. 557753 0—60—9 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S B122 .EmacowEP swung oEamow .noEsanH :9: .83 350.5 Swhwfigwléém mmbcmrm iNEIOHBd NI 'SiNENOdWOO ESVHd'iO‘an w4 oz< 4.r_>:.m_wmm RN. lllllllllllll \Vxn ./womt:m xoo‘fiom \Ix 00.. Czafimmomzw/ / ucaem E womtaw \ // / @333 «02 com \oo\/ .08. < .553»: \ \Xq II \ p o\.o’o o /XU\ I” lml\ll I I l |X\ II X\\QXI 8| x-.. x 1 Jr 1 \f,\o/ \,J x---x--.x---x/ owl o/ 08 < 8 um; 38 com “.282 @583 68- SN l\oo 8+ m ”952;: CO Ja‘ IN (\ InXII X V \kl I! II I I II I Ii |\ I II I X X X / \MI IIIv’IIXl‘ /\A»/ X IIXII X\\|QA// 0 IX ONI b4 II [XII 0 1x11 I (T XII ovl . Z r _ _ _ _ _ _ tr _ _ _ b _ — _ hum“. SVH OON~ OOO~ 00w 00m 00? CON 0 iNHOHEd NI 'SlNENOdWOO 38VHdN| EXPLORATION AND MAPPING TECHNIQUES DESCRIPTION OF METHOD In most of these studies the slingram method (Frisch- knecht, 1959) was used. The apparatus consists of a battery—powered source of alternating current, a trans- mitting coil, a receiving coil, and a ratiometer. The ratiometer compares the signal picked up by the re- ceiving coil with a. reference signal transmitted by wire from the power source to the ratiometer. The signal picked up by the receiving coil varies in magnitude and phase with the electrical conductivity and magnetic susceptibility of the earth. The coils are moved to- gether at a fixed separation which is usually between 100 and 300 feet. Measurements can be made rapidly, and because of the compactness and portability of the equipment, the method is well suited for reconnaissance work, even in heavy forest and brush. CONDUCTORS Electromagnetic conductors in metamorphic terranes of Minnesota, Wisconsin, and Maine commonly contain such metallic minerals as magnetic, specular hematite, and various sulphides, or graphite and carbon. This study is concerned with lithologic units that contain concentrations of conductive minerals. Conductive beds comprise only a small part of the total volume of metasedimentary rocks in the areas studied but they are sufficiently numerous and continuous to be used in trac- ing bedrock geology. For a rock to have high conductivity, conductive minerals in the rock must be in the form of connected chains or bands. Some magnetic taconites containing abundant magnetite have low conductivity because indi— vidual magnetite grains are insulated from each other. Similarly, pyrite crystals in many black slates are dis- seminated and add little to the overall conductivity of the slate. Most igneous rocks as well as quartzite, graywacke, and light-colored slate have low conductivity and give little electromagnetic response. Glacial drift masks bedrock anomalies only where it is thick or conductive. MINNESOTA AN'D WISCONSIN Studies were made over iron formations containing both oxidized and unoxidized iron ores in Minnesota and Wisconsin. Oxidized iron ores beneath thick de- posits of glacial drift on the Cuyuna range in Minnesota could not be detected by the slingram measurements, but graphitic or other carbonaceous beds associated with the hanging-wall formation were readily located. Elec- tromagnetic methods should prove useful in mapping new areas on the Cuyuna and Mesabi ranges because con— ductive beds commonly occur in the hanging-wall formations. B123 The magnetic taconite rocks of the eastern Mesabi and western Gogebic ranges were found to be suffi- ciently conductive over large areas to be traced easily, even under considerable thicknesses of glacial drift. The contact between the footwall and the iron forma- tion was readily located. However, anomalies from the conductive graphitic strata, which occur in the basal part of the hanging-wall formation, make it diffi— cult to distinguish between the iron formation and the hanging—wall formation (fig. 56.1). The various peaks and troughs on the slingram profiles can be correlated from traverse to traverse. If the stratigraphy is known on one traverse by drill—hole information or by surface exposures, it should be possible to trace a litho- logic unit laterally for considerable distances by means of electromagnetic measurements. MAINE The most common electromagnetic conductors in Maine are 1) graphitic or carbonaceous beds associated with black pyritic slates and schists, and 2) massive CANADA Bridgewater Island Falls Shin Pond Di] Danforth —| Greenville The Forks Binfiam NEW HAMPSHIRE 40 MILES FIGURE 56.2.—Index map of Maine showing areas of study. B124 INPHASE COMPONENTS, IN PERCENT 110 100 90 80 70 110 100 90 80 70 110 100 90 120 110 100 90 80 70 60 50 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES —30 —20 Pl “ ({Inphase component —10 0‘ ' \ 0‘ , ‘ [— 0“ I \0, 0‘ 0‘3 II ‘3‘ I \ 0‘ -0 °\\ D- ’.°\ ’0‘ 0 ‘x o V ‘“"’"“$ \L - ‘0‘,’ ‘ , Out-of-phase component I . \I I ll . +10 ‘ I l‘ I ‘ I \ I I o 2,000 feet between traverses — _3o —20 _. {lnphase component _10 ‘ 0 \ o o I ‘. 1%, " ° ‘ I ' 1’ Out-of—phase component +10 1' l I _ l I I I 4,800 feet between traverses — \ ’ ' '_ 0 - R -10 O~~o_‘ol 0‘ 0’ 0 33“ ° I ‘o .o _ \ I ‘ / +10 Out-of-phase component TOPOEVaPh'C effects —40 1,700 feet between traverses —— 30 '\ — I —20 I o I l ‘ _ , \\ I I \O/ lnphase component _10 I I \ l ‘ p- I I x ’0‘ I 0- 6.4M ‘0 MIA0 I 1 \ 0‘ 0‘; ’ \ 1 o L O I; 11 p/ I :mfvw we 2» ‘° -0 ' I Out-of—phase component _ I I +10 ' I I I " I | I l— \ o‘ - . \ ,é Volcanic VOCkS Green slate and graywacke and conglomerate l. Conductive bed inferred from profiles Graphitic and pyritic black slate and graywacke O 500 1000 FEET FIGURE 56.3.—Slingram profiles from Shin Pond quadrangle, Maine. OUTDF-PHASE COMPONENTS. IN PERCENT EXPLORATION AND MAPPING TECHNIQUES sulfide deposits occurring in mafic intrusive igneous masses. Conductors were found in traversing over belts of steeply dipping black slate and contiguous rocks in the Bridgewater, Shin Pond, Bingham, Greenville, Island Falls, and The Forks quadrangles (fig. 56.2). A black graptolite-bearing chert associated with volcanic rocks in the Danforth quadrangle was found to be conductive. In the Shin Pond quadrangle, from east to west, the traverses crossed green slate and graywacke; black, pyritic slate and graywacke; volcanic rocks; and a coarse conglomerate (fig. 56.3). The black slate belt is about a quarter of a mile wide but the conductive bed is commonly less than 200 feet wide. Similar conditions are found to prevail in nearly every area studied and ' it is concluded that the presence of black slate is no guarantee that a conductor is also present. The Shin Pond conductor was traced for several miles by 15 traverses, four of which are shown in figure B125 56.3. The anomalies over this conductor are very dis— tinct from “background” variations in the profiles; most of the small features in the inphase component are caused by steep topography and can be discounted in the field. Consequently, there is little difficulty in cor- relating traverses spaced half a mile to one mile apart. In other areas such as the Danforth quadrangle, the width and amplitude of the anomalies varies greatly along the strike of the conducting bed and it is then necessary to space the traverses more closely. REFERENCES Frischknecht, F. C., 1959, Scandinavian electromagnetic pros- pecting: Am. Inst. Mining Metall. Engineers Trans, v. 214, p. 932—937. Zablocki, C. J., and Keller, G. V., 1957, Borehole geophysical logging methods in the Lake Superior district, in Drilling Symposium. 7th annual, exploration drilling: Minneapolis, Minnesota Univ. Center for Continuation Study, p. 15—24. 57. ELECTRICAL PROPERTIES OF SULFIDE ORES IN IGNEOUS AND METAMORPHIC ROCKS NEAR EAST UNION, MAINE By L. A. ANDERSON, Denver, Colo. Electrical properties of rocks in and around a large sulfide deposit near East Union, Maine, were measured using in-hole logging methods, which included resis- tivity, self-potential, and induced polarization. In addition, laboratory measurements were made for resistivity, induced polarization, grain density, and porosity on core samples taken at two-foot intervals from a drill hole that penetrated representative rocks in the area. The sulfide minerals occur in a peridotite body that trends S. 20° W. and plunges gently to the south under quartz-biotite schist. The peridotite is intruded by pegmatites that are generally associated with mineral- ized areas. Pyrrhotite is the most abundant sulfide mineral. Pentlandite occurs along the borders of the most massive pyrrhotite-bearing zones, and chalcopy- rite is found as irregular interstitial grains between pyrrhotite crystals and as veinlets along the borders of pyrrhotite crystals and the silicate minerals. Mag- netite has formed as an alteration product between grains of olivine and pyrrhotite. The negative potentials (fig. 57.1) in sections having concentrations of sulfide minerals indicate that the sulfides are being oxidized. Water samples collected below 30 feet revealed an oxygen content of less than one part per million, so the rate of oxidation may be slow. The low oxidation rate is further suggested by the lack of secondary oxidized minerals in the ore zone. The self-potential is more negative in the sulfide con- centrations toward the top of the drill hole, suggesting a greater rate of oxidation owing to oxygen-charged surface waters. The resistivity ranges from nearly zero to about 3,000 ohm-meters; the highest values occur in gabbro and the lowest occur in the zone of major sulfide concentration and in the graphi‘tic schist below the sulfide zone. Where sulfide minerals occur in excess of 5 percent by weight, the individual grains are in physical contact with one another, forming continuous conductors. Therefore, any deviation from the 5 percent sulfide con- tent will result in resistivity measurements that are either extremely low or are near the true resistivity of the host rock. The resistivity log of a drill’hole near that shown in figure 57.1 shows four major zones of extremely low resistivity (fig. 57.2). The low resistivity and high B126 DEPTH, IN FEET 10 20 30 4O 50 60 7O 80 90 100 1 10 120 130 140 150 160 170 DEPTH, IN FEET 10 20 3O 40 50 60 7O 80 90 100 110 120 130 140 150 160 170 FIGURE 57.1.—In-hole and laboratory results of electrical and physical property measurements of a drill 0 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN SELF POTENTIAL 100 .4 mv RESISTIVITY, IN OHM-METERS IN RESISTIVITY, IN E)O 1000 2000 3000 O —HOLE MEASUREMENTS INDUCED OHM-METERS POLARIZATION 1290 2500 ’ SULFIDES, IN 0 PERCENT 50 100 lTr‘uJH—J H rI I \ P\/>f\ D —D I D\\l>> /\\, tv 9 21> \/ \/ / /\\ \ / '— \ \A\ / z \/ -\ / ’\’AI § \ II 9 LABORATORY MEASUREMENTS INDUCED POLARIZATION, IN PERCENT 50 100 150 2.5 GRAIN DENSITY. IN GRAMS PER CUBIC CENTIMETER 4.0 3.0 3.5 4.5 0 THE GEOLOGICAL SCIENCES EXPLANATION 0 0° . o 00 w 9 / \ ’\ I Peridoti F.’ e EP< C'VA §> o a v '0 m 00 3 n: F.‘ :4» m E Graphitic schist i ~\/ schist (D Quartz biotit m Undifferentiated sulfides H Pyrrhotite POROSITY, IN PERCENT 0.5 1.0 SULFIDES, IN PERCENT 1.5 0 50 100 hole and core specimens from East Union, Maine. / o -oou \ Q no \\ "/ ’I/\\/\ x \/\I \/ \\\ ’I Y \’ I\ :1: \/\ / \//I >\/>/ v \<\ y, \/.~ /E \\l: /V EXPLORATION AND MAPPING TECHNIQUES SELF POTENTIAL RESISTIVITY, IN SULFIDES, IN OHM—METERS PERCENT lOO mv‘ei |<—+ O 135 270 405 O 50 100 DEPTH, IN FEET 20 40 6O 80 100 120 140 160 180 200 220 \ \ \ 24o /\ l\\/ _A_4_W 260_ \/\)/ /\\ \'/\/ 280 /\\\ 300 320 340 N\1 EXPLANATION Soil Gneiss Graphitic schist W/A Schist Pegmatite Peridotite FIGURE 57.2.—Se1f-p0tentia1, resistivity, from a drill hole near East Union, Maine. and lithologic logs negative self-potential values at depths of 140 to 185 feet and 195 to 245 feet suggest the presence of sulfide minerals undergoing oxidation. The upper and lower conducting zones at depths of 85 to 105 feet and 285 to 322 feet, respectively, on the resistivity log do not B127 clearly define continuous conductors. In the lower zone, the self-potential has a high negative value sug- gesting the presence of sulfides, whereas the more posi- tive self-potential values of the uppermost zone indicate graphite. The concentration of graphite in the schist (fig. 57.1) at a depth of 105 to 115 feet is thought to be too low or perhaps too localized to generate a significant potential. The induced—polarization measurements on core samples from the graphite zone show very little response, suggesting a low graphite content within the schist. Induced polarization occurs at a metal-solution inter— face when it is exposed to a flow of current. The energy barrier at the interface acts as a resistance in associa- tion with a capacitance. During a flow of current, the capacitance stores a charge, and upon termination of the current flow, the charge Will decay at a rate deter- mined by the time constant of the simulated resistance- capacitance network at the interface. The discharge voltage is therefore a measure of the polarization that can be induced in a particular rock. Rocks containing disseminated sulfides, and therefore numerous energy barriers, are good polarizers, Whereas rocks containing sulfides in the form of continuous conductors are poor polarizers. The in-hole induced—polarization log (fig. 57.1) does not contribute significant data owing to the apparent continuity of the sulfides in the mineralized zones. The instrumentation relies upon a constant applied voltage, but in highly conductive rocks it becomes impossible to generate a potential field because the power supply is virtually shorted. The induced polarization log there- fore closely follows the resistivity, reflecting the in- ability of the system to operate in very conductive rock. Good correlation exists between the in-hole and lab- oratory resistivity measurements. Minor discrepancies between the in-hole and laboratory resistivity measure- ments are due to local variations within the rock. These variations are significant in the core samples but could not be detected in the massive rock. The induced-polarization measurements made on the core samples give an accurate indication of the content and distribution of the sulfides Within the mineralized zones. The dense barren rocks such as the gabbro show negligible polarization effects, and the sulfide- bearing peridotite has a polarization response pro- portional to the sulfide content and to its degree of dis- semination. Porosity and grain density of the core samples were correlated with the electrical-property measurements. The grain density reflects the sulfide content of the peri— B128 EXPLANATION (2) 0 0 Number of Polarization Resistivity samples 10,000 (9) (18) 1000 1000 (I) E (2) E 2. 100 100 E (30) '— 11 Z (I) ( ) ‘5 g a >> O. i: (30) g 2 \ . I— 10 10 z 1) 9 08> (11) E <( _I 0 EL (9) 1,0 \ 1.0 2 0.1 ( ) 0.1 2.5 3:0 3.5 4.0 4.5 GRAIN DENSITY, IN GRAMS PER CUBIC CENTIMETER FIGURE 57.3.—Resistivity and polarization as a function of grain density for mineralized core samples. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES dotite, and as would be expected, the zones of massive sulfides have the highest grain—density values. Low porosity values are indicative of the fine-grained texture of the representative rocks in this area. Polarization and resistivity were plotted with respect to the grain density (fig. 57.3). As the grain density increases, the resistivity falls rapidly (fig. 57.3) indi- cating that a small increase in the sulfide concentration will cause a significant decrease in the resistivity. The polarization response increases with increasing grain density indicating that the sulfide concentration is not truly massive but that sulfide minerals are probably distributed in veins that yield high local polarization values. The in-hole logging measurements show conductive zones that may be attributed to sulfide content or to the presence of gaphite. The resistivity response to sul- fide percentage could not be related quantitatively be- cause of the apparent continuity of sulfide grains where the content is in excess of approximately five percent by weight. The self-potential log can, in some cases, be used to distinguish between sulfides that exist in quantities greater than a few percent by their more negative self-potentials as compared to the self—po- tentials measured in the graphitic zones. The laboratory measurements show that induced polarization is an excellent method for estimating the relative sulfide concentration. The author wishes to express his gratitude to the Roland F. Beers Company for allowing access to the drill holes and providing core samples and lithologic logs. 6% 58. ELECTRICAL PROPERTIES OF ZINC-BEARING ROCKS IN JEFFERSON COUNTY, TENNESSEE By G. V. KELLER, Denver, Colo. An important belt of zinc ore low in iron occurs in the Knox group, of Cambrian and Ordovician age, in the area between the towns of Mascot and Jefferson City, in Knox and Jefferson Counties, Tennessee. The American Zinc Company drilled several dozen explora- tion holes north of the town of Strawberry Plains in 1957 as part of a Defense Minerals Exploration Ad- ministration project. Electric logs were run in 11 of ‘ these drill holes to determine whether anomalous elec— trical properties were associated with sphalerite min— eralization and might serve as a guide for geophysical exploration. The stratigraphy of the Mascot—Jefferson City zinc district has been described by Oder and Miller (1945) and by Bridge (1956). Sphalerite occurs in replace- ment deposits in the Kingsport limestone of the Knox group, which is of Ordovician age. The deposits con- form roughly to the bedding in coarsely crystalline dolomitized limestone, and are accompanied by breccia filling in associated fine—grained primary dolomite. EXPLORATION AND MAPPING TECHNIQUES The Kingsport limestone consists of 350 to 400 feet of limestone and dolomite, and the main ore horizons are in the lower two-thirds of this unit. Sphalerite is the only ore mineral, and the gangue mostly consists of white crystalline dolomite. Drill holes in the Strawberry Plains drilling project ranged in depth from 900 to 2,700 feet. They pene- trated several formations overlying the Kingsport lime- stone of the Knox group, including the Mascot dolo- mite of the Knox group, Lenoir limestone (including the Mosheim member), the Holston marble, and, in the deeper holes, the Ottosee formation. All of these are of Ordovician age. RESISTIVITY (30 IN. NORMAL) DEPTH, 20 15,000 30,000 45,000 — IN FEET —"1 M.V.l‘_‘ 1500 3000 4500--- 50 100 E 150 200 O 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 B129 The resistivity log from a hole in the Lenoir lime- stone including the Mosheim member, the Mascot dolo- mite, and the Kingsport limestone (fig. 58.1), indi- cates that the resistivity of most of the rock ranges from 7,000 to over 30,000 ohm-meters, but that in a mineralized zone between 900 and 1,000 feet, it is only 500 to 6,000 ohm-meters. The assay log for this zone shows only a few percent of iron between 950 and 1,000 feet. This indicates that there is only a little pyrite in the rock, and as sphalerite is not conductive the higher conductivity in the mineralized zone must be due to increased porosity rather than to solid conduc- tion. When the resistivity log in the ore zone is com- INDUCED POLARIZATION (4 IN. NORMAL) STRATIGRAPHIC COLUMN AND ZINC ASSAY 10 PERCENT O 1 2 3 PERCENT O 5 ,3 3; FIGURE 58.1.—E1ectrical and induced polarization logs from a drill hole penetrating sphalerite-bearing dolomite in eastern Tennessee. B130 pared in detail with the assay log it is found that there is no quantitative relation between resistivity and ore grade. Neither the self-potential nor the induced-polariza— tion logs show as striking a change in the ore zone as the resistivity log. The self-potential log opposite the ore deflects approximately 30 millivolts in a positive di- rection; why it does so is not known. Induced- polarization response in the ore zone is about 50 per- cent greater than in adjacent beds, but it is still low. It is therefore unlikely that either the self-potential method or the induced-polarization method would be of any use in exploring for ore such as is penetrated by this drill hole. The large resistivity contrast between ore and bar- ren rock does offer some hope that galvanic or inductive resistivity methods can be used. To determine the limiting conditions, such as depth of burial, for which electrical methods might. work, average resistivities for the ore and overlying rocks were calculated (table 58.1) using Kalenov’s method (1957). The probable results of resistivity depth soundings may be calculated on the basis of the data in table 58.1. The low coefficient of macro-anisotropy for the rocks overlying the ore zone reflects the electrical uniformity of these rocks and provides ideal conditions for re- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 58.1.—Average electrical resistivities from the log shown in figure 58.1 Average Average Coefficient Rock unit Transverse Longitudinal of macro- resistivity resistivity anisotropy (ohm—meters) (ohm-meters) Lenoir limestone (excluding Mosheim member) _____________________________ 7, 550 5, 800 1. l4 Mosheim member of Lenoir limestone. . 15, 500 14, 700 1. 04 Mascot dolomite ________________________ 12, 700 11, 300 ‘1.07 Kingsport limestone (barren) ___________ 13, 800 13,400 1.01 Kingsport limestone (mineralized) ...... 820 260 1.77 sistivity depth soundings. The large coefficient of anisotropy for the ore zone is also a favorable condi— tion. In the case illustrated in figure 58.1, for example, the conducting zone would appear on a depth-sound- ing curve as 177 feet thick, rather than 100. Using charts prepared by Mooney and Wetzel (1956), depth- sounding curves were drawn that would be obtained at the location of the drill hole in figure 58.1 for various depths of burial (fig. 58.2). On these curves the ef- fect of the ore horizon could easily be seen even when the depth of burial was 700 feet. The theoretical curves are based, however, on the assumption that the lateral extent of the conducting zone is infinite, and if it is less than several thousand feet the effect on the sourfiiing curves will be reduced. 20,000 \ \ ‘\\\’_\\ 10.000 \ a \\ \ / / / 7y MEASURED APPARENT RESISTIVITY, IN OHM-METERS \. \ >4 5000 \ / 3000 a—Top of ore zone at 175 ft _ b—Top of ore zone at 350 ft c—Top of ore zone at 525 ft d—Top of ore zone at 700 ft 2000 I 70 100 200 300 500 700 1000 2000 3000 WENNER ELECTRODE SPACING. IN FEET FIGURE 58.2.——-The0retical resistivity sounding curves for a bed 175 feet thick imbedded in beds with resistivity 20 times larger. OUT-OF-PHASE COMPONENT, IN PERCENT INPHASE COMPONENT, IN PERCENT EXPLORATION AND MAPPING TECHNIQUES B131 +15 __ +10— +5—— h 'r_:o.6 h ?=°4 —=03 h —;O.3 r 125 —‘ 120 — 110—— 105 — 100 FREQUENCY, IN CYCLES PER SECOND 41110 8?0 17160 35120 F l T I T l 0.8 1.0 1.2 1.4 d (—W 01/2 p FIGURE 58.3.—Mutua1 impedance ratio between loops above a thin conducting sheet from model data. 1.6 B132 It is also likely that the conducting zone might be detected by using electromagnetic methods (EM) for measuring conductivity. Mutual coupling curves were obtained for the case presented in table 58.1 for several depths of burial of the conducting zone, using an EM model (F. C. F rischknecht, oral communication). In- phase and out—of—phase components of the mutual im- pedance ratio for loops raised in air above a thin con- ducting sheet are shown in figure 58.3. The symbols used are: ,u for magnetic permeability of free space (4 1rx10'7 cgs), u for the angular frequency, p for the thickness of the conducting sheet and r for the separa— tion between loops, and h is the height of the loops above the sheet. At a frequency of 5 kilocycles per second, for exam- ple, the affect of overburden would be small: the re— sponse from a thick overburden having a resistivity of 10,000 ohm—meters would be less than 6 percent in the out-of-phase component and less than 3 percent in the in-phase component. At lower frequencies the response from the overburden would be even less. It is evident that the conducting zone could be readily located with EM methods even if deeply buried. If the conducting GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES zone were buried at a depth of 1,000 feet, and if a coil separation of 2,000 feet were used, the in-phase com- ponent would be 112 percent and the out-of—phase com- ponent would be +13 percent, representing anomalies of 12 and 13 percent respectively (fig. 58.3). ACKNOWLEDGMENTS I am grateful to the American Zinc Company, and particularly to C. R. L. Oder, for providing me with core logs and assay data. REFERENCES Bridge, Josiah, 1956, Stratigraphy of the Mascot-Jefferson City zinc district, Tennessee: U.S. Geol. Survey Prof. Paper 277. Kalenov, E. N., 1957, Interpretatsiya krivykh vertikal‘nogo elektricheskogo zondirovaniya: Gostoptekizdat, Moscow, 468 D. Mooney, H. M., and Wetzel, W. W., 1956, The potentials about a point electrode and apparent resistivity curves for a two-, three, and four-layer earth: Minnesota Univ. Press, Minne- apolis, 146 p. Oder, O. R. L., and Miller, H. W., 1945, Stratigraphy of the Mascot-Jefferson City zinc district: Am. Inst. Mining Metal]. Engineers, Tech. Pub. 110. 1818, 9 p. ’X‘ 59. TERRAIN CORRECTIONS USING AN ELECTRONIC DIGITAL COMPUTER By MARTIN F. KANE, Washington, DC. Computation of terrain corrections for gravity sta- tions in irregular or mountainous terrain is the most time consuming part of the reduction of gravity data. Because of the variable nature of terrain, a correction is usually made by dividing the area around a station into a series of zones and compartments, and computing the terrain effect of each compartment. The effect of any compartment is a function of its elevation, size, and position relative to the gravity station. The sum of the effects of all the compartments is the terrain cor- rection. In conventional methods, the computation is made by first dividing the area into a series of circular zones concentric about the station, and then subdividing each zone into compartments of equal area. The gravity attraction of a circular zone on a point at its center is readily calculated, and the attraction of a compart- ment is a simple fraction of the attraction of the whole zone. The final correction usually includes an area within a 5- to 15—mile radius of the station, so that for surveys with a station-spacing of a few miles or less, considerable overlap occurs between the compartments about adjacent stations. Because of the relationship between the correction formula and the concentric ar- rangement of the compartments, however, the eleva- tion data assembled for one station are not applicable to another. In gravity surveys with a dense station network, it is necessary to consider the same topography many times over. A method that makes use of electronic computers has been developed to expedite the computation of these terrain corrections. In this method the topography of the entire survey area is converted to digital form by dividing the terrain into kilometer squares and tabu— lating the average elevations of the terrain Within the squares. The average elevations are punched on cards and stored in the computer memory. They are not sufficiently precise for the area close to the station where EXPLORATION AND MAPPING TECHNIQUES small changes in topography cause large terrain ef- fects; and they are unnecessarily precise for distant areas where large changes in terrain contribute little, if any, terrain effect. The computer correction there— fore, is limited to an area 40 by 40 kilometers square with the station at the center, and excludes a central area 2 by 2 kilometers square. The terrain beyond 40 kilometers can be safely ignored in most places, and the terrain Within 2 kilometers of the station can be easily calculated by conventional methods. The electronic-computer method was programte and tested on the US. Geological Survey’s Datatron 205 for gravity stations in a moderately mountainous area in southern Nevada. The results were compared B133 with conventional calculations for 10 stations and showed a maximum difference of 0.1 milligal. The electronic computer method is considerably faster and is internally more consistent because it uses identical field data for all corrections. The cost is presently about twice that of conventional methods, but this will be reduced by a factor of four when the program is completed for the newer and faster Datatron 220. The cost depends, to a great extent, on the station spacing, and the greatest savings are realized in surveys with a relatively dense network of stations. In surveys where the stations are widely spaced the method is more expensive, but its increased speed and improved internal consistency may justify the additional cost. 52‘ 60. APPLICATION OF GRAVITY SURVEYS TO CHROMITE EXPLORATION IN CAMAGUEY PROVINCE, CUBA By W. E. DAVIS, W. H. JACKSON, and D. H. RICHTER, Washington, DC, Denver, 0010., and Hawaiian Volcano Observatory, Hawaii Work done in cooperation with the General Services Administration Chromite deposits in the Camagiiey district, Cuba (fig. 60.1), occur in an ultramafic complex that consists principally of a lower serpentinized peridotite and dunite member and an upper feldspathic member. The complex was intruded into a series of metamorphic rocks as a nearly stratiform mass, and is unconform- ably overlain by Upper Cretaceous volcanic rocks inter- bedded with limestone and chert. Folding, probably concurrent with overthrusting from the north during early Tertiary time, has formed a number of long arou— ate structures. Subsequent uplift was followed by ero- sion that has removed most of the overlying volcanic and feldspathic rocks except in deep synclinal areas. The deposits are irregular tabular bodies ranging in size from small pods to masses several hundred feet long that contain 200,000 tons or more, and occur in the upper part of the serpentinized rocks within half a mile of the feldspathic member. Detailed gravity surveys made in this district be- tween August 1954 and April 1956 successfully deline- ated bodies of high-density materials and, combined with evidence revealed by geologic. mapping, helped guide exploration for chromite by drilling. The methods and principal results of this survey have al- ready been published in a geophysical journal (Davis and others, 1957), but some of the results are repeated here to call wider attention to the potential use of gravity methods in the exploration of ultramafic com- plexes. The difference in density between the chromite con- tained in commercial deposits of the district and the serpentinized peridotite and dunite is about 1.5 grams per cubic centimeter. This difference is sufficient for chromite masses lying at commercially exploitable depths to cause positive gravity anomalies of more than 0.5 gravity unit (0.05 milligal). Feldspathic rocks in the serpentinized peridotite and dunite range in density from 2.4 to 3.0 g per cu cm. Some of these rocks are dense enough to cause anomalies of much the same lateral extent and magnitude as the chromite. Similar anomalies are also created by density contrasts between different parts of the serpentinized masses, which vary in density from 2.2 to 2.8 g per cu cm. During a 20-month exploration program in nine areas embracing about 12 square miles (fig. 60.1), a large number of anomalies with a gravity relief of 0.5 gravity unit or more were found and evaluated accord- ing to geology, areal extent, and gravity relief. Those B134 EXPLANATION Z Feldspathic and volcanic rocks Serpentinized peridotite Areas investigated 0 10 KILOMETERS GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES ORI ENTE FIGURE 60.1.—Index map showing location of areas investigated by the U.S. Geological Survey in the Camagiiey chromite district, Cuba. not obviously associated with feldspathic rocks were selected for drilling. To guide the drilling, depths to the top and center of hypothetical bodies that would cause anomalies of similar magnitude were computed in terms of chromite and feldspathic rock. Test holes from 27 to 375 feet in depth were drilled on 106 gravity anomalies, which constituted probably less than a third of the total number found. These holes revealed that 10 anomalies were over deposits of chromite, 47 over feldspathic rock, 40 over dense parts of the serpentinized rocks, 2 over deposits of magnesite- talc-quartz rock, and 7 over serpentinized rocks, cored samples of which did not indicate sufficient density to cause variations in gravity. Drilling on five of the chromite deposits revealed about 236,000 tons of chromite, of which 19,000 tons was disseminated ore. It was estimated that 6,000 tons of shipping-grade chromite and 6,000 tons of disseminated chromite was contained in three other deposits that were not blocked out. No estimate was made of the tonnage in two small chromite deposits. A residual gravity anomaly associated with a deposit containing 115,000 tons of chromite is shown in figure 60.2. The anomaly is prominent and of a regular shape, involves 12 stations, and has a gravity relief of 1.6 gravity units. It delineates the chromite deposit fairly accurately. The chromite body comes within 10 feet of the surface (fig. 60.3), and dips steeply toward the southwest. Most of the ore lies below 75 feet, and the bottom of the deposit is between 224 and 250 feet deep. The investigation revealed that in the Camagiiey chromite district detailed gravity surveys combined EXPLORATION AND MAPPING TECHNIQUES B135 16W 15W 14W 13W 12W 1 1W 10W 9W 8W 7W 0 0 EXPLANATION S Serpentinized peridotite F =\ Troctolite Mme W‘s / / / / Inferred contact + (:2 Mine dumps Gravity station and value Drill hole ,barren Drill hole, chromite 40 0 410 M ET E R S I | I I 100 0 100 200 L I 1 l I 1 1 CONTOUR INTERVAL 0.2 GRAVITY UNIT 300 FEET 41 FIGURE 60.2.—Residua1 gravity anomaly over a chromite deposit containing 115,000 tons. with geological mapping can be used to delineate areas but does not serve to distinguish anomalies caused by in which chromite may be found, and to obtain data for chromite from those caused by unexposed masses of locating and determining depths of drill holes. Evalua— high-density rocks. The accuracy required in measur- tion of the anomalies on the basis of geology, areal ex- ing small gravity differences that are significant in ex- tent, and gravity relief is helpful in limiting drilling, ploration can be attained by using gravimeters having B136 low scale constants, by exercising normal care in han— dling and reading the meters, and by frequently re—ob- serving base stations and a limited number of inter- mediate stations to check the instrumental drift. SECTION 20—2N FEET 0 2M GEOLOGICAL SURVEY RESEARCH l960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCE Davis, W. E., Jackson, W. H., and Richter, D. H., 1957, Gravity prospecting for chromite deposits in Camagiiey Province, Cuba: Geophysics, v. 22, p. 848—869. SECTION 2P-2I 100 SECTION ZD-ZH 0 2D 2C 25 2A 2K 2H 20 2N 2 2L 2] / / /, // / / // / z/ / / / / / / // / / / / / / I / / / / / SECTION 2J-28 ZJ 26 2F 2R 25 2 EXPLANATION Chromite Serpentinized peridotite Troctol ite 100 0 L i . I 100 n 40 M ETERS *g——J 200 l 390- FEET FIGURE 60.3.—Drill-hole sections through the chromite deposit illustrated in figure 60.2. ’X‘ 61. SPECTRAL REFLECTANCE MEASUREMENTS AS A BASIS FOR FILM-FILTER SELECTION FOR PHOTOGRAPHIC DIFFERENTIATION OF ROCK UNITS By WILLIAM A. FISCHER, Washington, DC. Measurements of the reflectance spectra of several specimens of diflerently colored rocks collected near Corona, N. Mex., suggest that certain rocks may be more readily distinguishable on aerial photographs that record only selected wave lengths of light than on con— ventional aerial photographs. Figure 61.1 shows spec- tral reflectance curves, determined in the laboratory for samples of a light-brown sandstone (A), a gray lime— stone (B), a red shaly siltstone (0), and a gray sand- stone (D). The determinations were made with a Bausch and Lomb Spectronic 20 colorimeter with color analyzer reflectance attachment. Reflectance curves for A, B, and D are close together at the short (blue) end of the spectrum; these rocks re- flect more blue light and will photograph lighter in tone than 0, when only the short end of the spectrum is re- EXPLORATION AND MAPPING TECHNIQUES 50 | l REFLECTANCE, IN PERCENT Rock unit A \____ __ __—— —— —— / / / l I l 400 450 500 550 600 650 700 WAVELENGTH, IN MILLIMICRONS FIGURE 61.1.——Spectra1 reflectance curves of fresh samples of light-brown sandstone A, gray limestone B, red shaly siltstone 0, and gray sandstone D. corded (see fig. 61.2). If, on the other hand, only the long end of the spectrum is recorded, B, 0, and D will photograph darker than A (see fig. 61.3). On conventional aerial photographs there is usually but little tonal distinction between the various rocks, because light-reflectance difierences are largely bal— anced out. Figures 61.2 and 61.3 suggest that for rocks in the area tested, film-filter systems could be designed that would make it easier than it is now to distinguish the different rocks on aerial photographs. Figure 61.2 was taken with a combination of N0. 8 and 47B Wrat- ten filters and records only reflected light less than 500 millimicrons in wave length. Figure 61.3 was taken with a N o. 25 Wratten filter and records only reflected light more than 685 millimicrons in wave length. 557753 0—60—10 No aerial photographs taken through selected filters have, as yet, been obtained, but experimental rephoto- graphing of aerial color photographs through selected filters has shown that tonal differences not readily seen on conventional aerial photographs are accentuated on photographs that record only selected wave lengths of light. This is seen by comparing figures 61.4 and 61.5. Figure 61.4 is a conventional aerial photograph; Figure 61.5 depicts approximately the same area on a photo— graph of an ecktachrome transparency rephotographed through a No. 47 Wratten filter on panchromatic film. Increased tonal contrast may be seen at a on figure 61.5, where it marks the contact between two different sur- ficial materials. Filter selection in rephotographing the color transparency was based on spectral transmission measurements made on a densitometer. B138 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES l a " . 9%?” ‘ a? “a, a. FIGURE 61.2.—Photograph of fresh samples of light-brown FIGURE 61.3.—Photograph of fresh samples of light-brown sandstone (a), gray limestone (12), red shaly siltstone (c), sandstone (a), gray limestone (1)), red shaly siltstone (c), i and gray sandstone ((1), taken through a combination of and gray sandstone ((1) taken through a No. 25 Wratten ‘ No. 8 and 47B Wratten filters on panchromatic film. Note filter on panchromatic film. Note that b, c, and d appear that samples a, b, and d appear lighter in tone than c. darker in tone than a. FIGURE 61.4.—Part of a conventional aerial photo- FIGURE 61.5.—Part of an ektachrome transparency q graph showing several rock types and surflcial photographed through a N0. 47 Wratten filter materials of contrasting colors. showing same area as figure 61.4. The strength- ening of tonal contrasts between different rocks is especially well seen at a. EXPLORATION AND MAPPING TECHNIQUES B139 62. TECHNIQUE FOR VIEWING MOON PHOTOGRAPHS STEREOSCOPICALLY By ROBERT J. HACKMAN, Washington, DC. Work done in cooperation with the U.S. Army Corps of Engineers The US. Geological Survey is engaged in a terrain study of the moon. Much of this work is being ac- complished by a stereoscopic study of lunar photo- graphs. To the viewer on the earth, the moon has an appar- ent oscillation, known as libration. Because of this, a zone along the moon’s perimeter is visible in one libration position but not in another. Photographs of the moon taken at different libration positions have an angular difference in View permitting a three- dimensional picture when viewed stereoscopically. The maximum angular difference is about 20°. Were it not for the libration, the maximum angular differ— ence of view—from opposite sides of the earth—would be only %°, much too small for useful stereoscopic vision. Figure 62.1A shows the moon at two different libra- tions with respect to an earth station (A and A’), Photographs of the moon taken from this station would be the same as if photographs of the moon were taken simultaneously from two different stations in o a A’ r) EARTH 50,000 MILES {h {b FIGURE 62.1.——A, Diagram showing moon at 2 different libra- tions; B, diagram showing how photographs of moon at the 2 librations are the same as though they were taken simul- taneously from 2 different points in space. space about 50,000 miles apart (fig. 62.13 ). The angu- lar difference of View would be 12°. For best stereoscopic viewing, two lunar photo— graphs should have the same scale, include the same area, be taken at different librations, and have image shadows that fall in the same direction. Although such photographs can be approximately positioned under the stereoscope by a trial and error method, a systematic method of orientation is best. A procedure for properly alining two moon photographs for stereo- scopic viewing is as follows: 1. Locate on each picture the geometric center of curva- ture. (See fig. 62.2, points A and B.) This can be done by geometric construction or by use of a circular template. 2. Identify the conjugate image point of A on the photograph to the right (at point A’) and con- versely the conjugate image point of B on the photograph to the left (at point B’). 3. Draw a straight line through the center and conju— gate center of each photograph. 4. Position the photographs under the stereoscope so that all four points fall in a straight line (called the x-direction, fig. 62.20D) and are in the follow- ing order: A, B’, A’ and B. Adjust the separa- tion of the two photographs and the stereoscopic model is ready for viewing. If several moon pictures taken at different librations are to be viewed stereoscopically, the following proce- dure for orienting the photographs may be preferable. Locate only the geometric center on each photograph. Flip one photograph up and down over the other so that image points appear to approximately coincide; determine the alinement of the two geometric centers. Note which geometric center is to the right and which is to the left in respect to the alinement. This will determine the right and left members of the stereo— scopic pair. Maintaining approximate coincidence of image points, position the photographs so that aline- ment of the two centers is in the x-direction of the stereoscope. Adjust for proper separation, and the photographs are ready for stereoscopic viewing. B140 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES FIGURE 62.2.—Two moon photographs of different libration oriented for stereoscopic viewing with a lens or pocket stereoscope. Enlarged photographs, approximate scale 1 24,270,000 (moon diameter 32”) , are more suitable for a detailed study of lunar features than the smaller scale contact photographs, approximate scale 1 :17 ,100,000 (moon di— ameter 8”). The enlargements, however, cannot be successfully handled under the desk—type mirror or prism stereoscope and must be cut into smaller sections. \Vhen enlarged sections of lunar photographs are pre- pared for stereoscopic Viewing, allowance must be made for the fact that the image position of the geographic center of the moon (except at zero libration) can be in any direction from the geometric center of the photo— graph. A hexagonal format of enlarged sections was selected since it seemed most useful in accommodating the different orientations. Figure 62.3 is an example of a hexagonal pattern used on a series of enlarged moon photographs. Before the moon photograph is cut into sections, the geometric center, E, is located. A reference point, F, is then selected near the mean libra— tion or geographic center; the crater Blagg in Sinus Media is near this center and will be satisfactory for this purpose. An additional reference point is located, preferably near the center of each hexagon (examples: F’, F”, etc. of fig. 62.3). The distance and bearing of the approximate geographic center, F, to the geometric center, E, is then plotted on each hexagon with respect to the reference point previously selected (examples: E’F’, E”F”, etc.). The hexagons are indexed and cut apart. The proc- ess is repeated on a second moon enlargement of differ- ent libration. The geometric center is located and reference points F, F ’, etc., of the first enlargement are transferred to the second photograph. The image points at the apices of each hexagonal section of the first photograph are used to identify conjugate image points on each new photograph. (The new six-sided GEOLOGY IN ENGINEERING AND PUBLIC HEALTH FIGURE 62.3.—Diagram showing how enlarged moon photo graphs are subdivided for viewing with a desk-type mirror or prism stereoscope. B141 figures will not be true hexagons. Some will be squeezed and others stretched, depending on the amount of in- herent libration. However, each will cover the identi- cal area.) The distance and bearing of the approx- imate geographic center, F, to the geometric center of the second photograph, is then plotted on each new hexagonal section With respect to the reference points F, F’, etc., transferred from the first photograph. The same index is used and the enlargement is cut into sec- tions. Additional moon enlargements are prepared in a similar manner. Any pair of hexagonal sections hav- ing the same index number and not having opposing image shadows can be viewed stereoscopically using the same procedure for alinement described earlier in this paper. Because many features of the moon show up better on one photograph than another, depending on the phase and libration of the moon at the time the photograph was taken, stereoscopic viewing of different pairs of such photographs permit the viewer to see many more features than would be visible on any single photograph. X‘ GEOLOGY APPLIED T0 ENGINEERING AND PUBLIC HEALTH 63. SOME THERMAL EFFECTS OF A ROADWAY 0N PERMAFROST By GORDON W. GREENE, ARTHUR H. LACHENBRUCH, and MAX C. BREWER, Menlo Park, Calif. Work done in cooperation with the Bureau of Public Roads, Office of Naval Research, Air Force Cambridge Research Center. and the Bureau of Yards and Docks The effects of a roadway on the thermal regime of the ground constitute one of the more important problems in permafrost engineering. A sizeable portion of the highway maintenance effort in permafrost terrain is di- rected toward repairing the results of differential set- tling and heaving in the subgrade materials. These thermal problems have been under study for several years by the US. Geological Survey in various places in Alaska. The most conspicuous thermal effect of building a roadway is probably the increase in variability of ground temperature, that is, the increased sensitivity of ground temperature to changes in air temperature and surface radiation from summer to winter and from year to year. The effect is illustrated with data from the Richardson Highway in figure 63.1. It is seen that the total range of temperature from summer to winter at each depth is much greater beneath the roadway than beneath the nearby undisturbed ground. In the sum— mer roadways are generally warmer than surrounding ground because of greater net absorption of radiation by their dark unshaded surfaces, and the absence of the cooling effect of evaporating moisture. In the winter roadways are generally cooler than the surrounding ground because snow, which serves as an insulator, is removed by plows or wind, or the insulating quality is destroyed by compaction under vehicular traffic. A larger seasonal range of temperature at the surface B142 GEOLOGICAL SURVEY RESEARCH .— m m u. E weer :- were q- In no u on E <2 m to I\ no 3 3 3 3 3 w 3 3 3 3 3 ,4 r-I H —c .4 D rd '1 H -u u-c 40 35—- N30—- 3 c“25— 9 |— _ 220 1.25 w 015... 3 “J10— I (5 USP- 0 E0 II LJ (5 E IZO- ‘6? E15l'— 6.25 E10— uJ [I Q. 25" m I ll "0 ll ll__lll 3‘ D Z Z (lO— lP.25 5—— oll lllr—ull r—ir—np—a.—..—. CENTERLINE OF ROAD UNDISTURBED GROUND. EAST FIGURE 63.1.—Comparison of annual temperature ranges at selected depths beneath the surface of the roadway and nearby undisturbed ground, for the period July 1954 to June 1959, mile 130, Richardson Highway, Alaska. generally results in a proportionally larger range at depth. Where coarse fill materials are used beneath the road the eflect is accentuated as thermal changes are propagated downward with less attenuation in such high-diffusivity, low-moisture-content materials. Almost as important as the seasonal range of tem- perature is the change in mean annual temperature be-I neath a roadway. Inasmuch as a roadway causes in— creased summer temperatures and decreases winter temperatures its effect on the mean is not obvious. Mean annual temperatures (for years beginning July 1) beneath the roadway and undisturbed ground are compared in figures 63.2 and 63.3. Shown also is the mean annual air temperature as recorded by the Weather Bureau at Gulkana Airfield, approximately 12 miles away. The changes in air temperature from year to year are followed by similar changes beneath the ground surface. Again the roadway shows a greater sensitivity to changing surface conditions. In both environments the temperature changes are at- tenuated with increasing depth. 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Now consider the depth of thaw as illustrated in figure 63.4. We first notice that the thaw depth is con- sistently greater beneath the centerline of the roadway than at peripheral installations. This is the expected effect of the increased amplitude discussed above. It is interesting to note (figs. 63.2 and 63.3) that during the first three years the more deeply thawing center- line had lower mean temperatures than the undis- turbed ground. This illustrates the independent roles played by amplitude and mean. A striking feature of figure 63.4 is the sudden in- crease in maximum thaw depth beneath the centerline during the summer of 1957, and the persistence of this deep thawing in subsequent years. Inasmuch as the road was surfaced with asphalt late in the summer of 1956 it seems reasonable to suspect that the deep thaw- ing was caused by an increase in the net radiation ab- sorption by the dark surface during subsequent sum- mers. If this were so, however, we should expect the cumulative thawing index beneath the surface to show an increase commensurate with the increased thaw depth. That it does not is shown by the data presented in table 63.1. The thawing index (maximum cumula- tive degree centigrade-days above freezing) at a depth of 5 feet is a rough measure of the quantity of heat available to thaw the material below 5 feet. The un- usually warm summer of 1957 is associated with a large thawing index at 5 feet (487 degree centigrade-days) and an increase in active layer thickness from 6.9 feet to 10.5 feet. It is significant that roughly the same amount of thawing was accomplished in 1958 with only about half as much heat (258 degree centigrade-days) and in 1959 with less than one-fourth as much (104 de- gree centigrade-days). Clearly, the deep thawing in 1957, 1958, and 1959 is not the result of sustained in- crease in summer heat input due to surfacing the road, but the result of a progressive reduction in the amount of heat required to thaw to 10+ feet; that is, a reduc- tion in moisture content. This conclusion is supported by the observation that thawing proceeds rapidly in ground previously thawed, and much more slowly at the degrading permafrost surface. The effects can now be summarized in fairly general terms as follows. The presence of the road increases TABLE 63.1— Thawing index measured at 5 ft below surface of road at the centerline compared with depth of thawing beneath road. Year Thawlng index, Depth of (J uly—J une) degree thaw centigrade-days (feet) 1954—55 ________________________________ 108 6. 1 1955—56 ________________________________ 140 6. 5 1956—57 ________________________________ 172 6. 9 1957—58 ________________________________ 487 10. 5 1958—59 ________________________________ 258 10. 7 1959—60 ________________________________ 104 10. 2 GEOLOGY IN ENGINEERING AND PUBLIC HEALTH B143 o 0 .— LU _ b [A] LI. Lu i; u, .2. 3 “J 3 f z '1 ’— ‘L a: ‘1 _ E g E 9 Lu I— _ I- a Z I Z Lu .— Id 0 — Q. U — w m 20. O (n E o g 15 - 2 a: 10 - (D (D In — — ‘2 — 5 I a 2 B E E U ~ AIR - g — 3:1 i— : I? I: E E E _3 _ _3 .— 5 E I- I- i 2’ D — 3 _ Z Z z Z < < Z Z 5 '4 _ E '4 — 2 2 ‘5 I I I l I ‘5 I I I I I I954-55 1955-56 1956-57 1957-58 1958-59 1954-55 1955-56 1956-57 1957-58 1958-59 FIGURE 63.2.—Mean annual temperatures, centerline, mile 130, FIGURE 63.3.—Mean annual temperatures, undisturbed ground, Richardson Highway, Alaska. east, mile 130, Richardson Highway, Alaska. 33.7339. are??? 3“"??333‘35? I I I Qt m \D '\ (D O} V In 0 '\ w 01 ‘3' l0 ‘0 N m 03 In K) “7 Ln In K) In D In In ln ln LO lo In |n K) In ,_ 2 3 3 2 S 5.”. S 2 2 S 1’ 2 2 32 3 S 2 2 w 0 Li LU LI— <5 2- E 3 E I— 4- .J < 5 3 6L— (I) LL 0 I 3— p— D. N o 210— n. :a — __ E >< < 212 UNDISTURBED GROUND, WEST CENTERLINE 0F ROAD UNDISTURBED GROUND, EAST FIGURE 63.4.—Maximum depths of seasonal thawing at mile 130, Richardson Highway, Alaska. the seasonal range of temperature (fig. 63.1) and hence year (figs. 63.2 and 63.3) and hence the deep thaw is increases the seasonal depth of thaw, causing the active accentuated during an anomalously warm season. If layer to encroach on permafrost. The roadway is more the excess water formed by melting ice in the surficial sensitive to random climatic variation from year to permafrost layers can drain off, the thickened active B144 layer will be drier and more easily thawed in subse- quent years. This, of course, will result in a settling of the road- way at the point where this progressive deep thawing occurs. The water would be expected to migrate in the thawed trough beneath the roadway until it is trapped in a basin, or escapes by exterior drainage. When it is trapped in a basin, as when the road crosses a swale or a large culvert, the water is ultimately re- frozen and some heaving might be expected. In the case illustrated in figure 63.4, these effects were prob- ably accentuated by the presence of a 23-foot sand layer known to occur between the depths of 8 and 11 feet. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S When the thaw depth exceeded 8 feet it is likely that water drained off through this permeable horizon. Transport of heat by the moving water probably aided the thawing process. The continuing study of the thermal budget of the subgrade is expected to lead to a more detailed elabora- tion of the thermal and mechanical processes responsi- ble for highway problems in permafrost. A regular unbroken series of field measurements, such as that now being obtained through the cooperation of the Bureau of Public Roads, will permit a more satisfactory quanti— tative treatment of the problem. 64. TENTATIVE CORRELATION BETWEEN COAL BUMPS AND ORIENTATION OF MINE WORKINGS IN THE SUNNYSIDE N0. 1 MINE, UTAH By FRANK W. OSTERWALD and HAROLD BRODSKY, Denver, Colo. Work done in cooperation with the US. Bureau of Mines Violent, spontaneous destruction of coal faces, in what are commonly called bumps, endangers and at times destroys life and property in mines of the Book Cliffs coal field, Carbon County, Utah. The geometric arrangement of pillars, and redistribution of stress, causes many bumps, but other bumps, at least in the Sunnyside mines, occur at long distances from pillar workings (Peperakis, 1958). Much of the S‘unnyside coal is under marked stress, and while being mined it shatters continuously (Clark, 1928, p. 80) and falls from the face. Mapping in the Sunnyside No. 1 mine to date supports the View that stress is released violently in workings that diverge at large angles from the orien- tation of predominant fractures within the coal. Re- cent mining operations in the Sunnyside mines also show that, in areas subject to violent bumps, some workings nearly parallel to a major fracture direction are less subject to bumps and require less roof support than nearby workings that intersect major fracture directions at large angles. This behavior may vary, and the theory here proposed to explain it may later have to be modified; it needs to be verified by mapping in other parts of this mine and in other mines, by measuring stress distribution in this and other mines, and by further testing of triaxial strength of the coal. Fracture zones trending west and north to north- northwest (fig. 64.1) are common throughout the mine, and they, together with other structures, may directly influence the distribution and violence of bumps. The fracture zones are nearly tabular and consist of steeply dipping fractures; individual fractures within a zone vary slightly in strike and dip, and most of them are not parallel to the trend of the zone. A few of the fracture zones are parallel to mine workings and may have been formed after the workings were opened, but those that strike west and north-northwest are a part of the structural pattern of the district and are clearly older than the workings. In the Sunnyside No. 1 mine, some headings were diverted from the normal N. 30° W., and N. 60° E. directions to take advantage of changes in strike or to make mining easy. Fracture zones at motor road part- ing (fig. 64.1) commonly trend about N. 7 0° W.; other zones trending about north-south are common but are narrower, less extensive, and less well marked than those trending N. 70° W. Where mine workings ex- tend nearly parallel to fracture zones trending N. 70° W., rib failures occur frequently, indicating that stresses do not accumulate long before being relieved. Individual fractures in the zones are rotated inward toward the workings. The rotation is aided in part by failure of the ribs along new breaks that parallel the GEOLOGY IN ENGINEERING AND PUBLIC HEALTH MOTOR ROAD:I RAISE ‘— Numerous small bumps aided driving of entry Violent bumps during driving of entry Numerous small bumps aided driving of entry EXPLANATION 4?‘ Fault, showing dip "'\ Fault in rib Steepens downward // jag/70 Fracture zone showing dip y??? Vertical fracture zone 70 14?“ Overturned fracture zone /(8 Strike and dip of beds Mine working 0 200 400 FEET MAIN MOTOR ROAD J \ 9000 FT TO PORTAL FIGURE 64.1.—-Underground map of parting for motor road raise, Sunnyside No. 1 mine, Utah. B145 bedding near the roof but curve downward into steeply dipping fracture zones in the rib. Ribs that nearly coincide in direction with major fractures are strongly rock-bolted, and covered with heavy steel mesh, to pre- vent falls of coal. Rib failures occur at much longer time intervals along workings that intersect the major fracture direc- tion at large angles than they do in workings that inter- sect them at small angles (fig. 64.1). Miners report, moreover, that severe bumps, some of them powerful enough to Overturn mine cars loaded with sand, have occurred during the driving of those headings in the parting that intersect the major fractures at large angles (fig. 64.1) , whereas the bumps that attended the driving of headings nearly parallel to the major frac- ture zones were frequent, but so small that they helped to make mining easy. The correlation here tentatively proposed of bumps with the angle between mine workings and fracture zones can be explained theoretically. The theory ap- plies to all fractures, and may explain the observed relation between bumps and faults at Sunnyside (Watts, 1918; Peperakis, 1958). Bumps originate when strain energy stored in coal or in rock is released along a fracture; they can be regarded as small earth- quakes of very shallow focus (Richter, 1958, p. 156— 157). The fracture may form during the bump, or it may be older than the bump. Where only small amounts of stored energy are released, bumps are an aid to mining, but when the amounts are large they are a serious hazard. While a heading is being driven, abnormal stresses are concentrated around it. The decrease of these con- centrations away from the face is inversely proportional to the cube of the distance ahead of the face, but in- versely proportional to the square of the distance into the rib (Isaacson, 1958, p. 119). The highest stress con- centrations occur in a mass of coal whose long axis extends into the face at an angle of about 70° with the direction of the heading (fig. 64.2) (Isaacson, 1958, p. 78). Where the heading is near a fault or fracture, the volume of highly stressed coal becomes larger than Where there is no fault nearby (Isaacson, 1958, p. 78). If a heading approaches a fault or fracture that is oriented at a large angle to its trend, stress is distrib- uted uniformly over much of the face, and is not con— centrated in a small volume of coal (fig. 64.2a). A violent bump may then occur over much of the face as soon as the accumulated stress exceeds the strength of the coal. If, on the other hand, the heading approaches a fault or fracture that is oriented at a small angle to its trend, stress is concentrated behind a small area of the face and causes only small bumps (fig. 64.2b). B146 vi §.\ \ \‘ \\‘§ A HYPOTHETICAL SHEAR-STRESS CONTOURS (ARBITRARY UNITS) AROUND HEADING APPROACHING FAULT AT LARGE ANGLE B SHEAR- STRESS CONCENTRATION (ARBITRARY UNITS) AROUND HEADING APPROACHING FAULT AT SMALL ANGLE FIGURE 64.2.—-Stress concentrations around a heading driven toward a fault. Small bumps originating at the upper corner of a head- ing approaching an oblique fault were observed in the Sunnyside No.2 mine in 1958. When forces generated in mining cause renewed mo- tion along a fault or fracture in a pillar, stress should be mainly concentrated in the coal near the ends of the 5% GEOLOGICAL SURVEY RESEARCH lQGO—SHORT PAPERS IN THE GEOLOGICAL SCIENCES fracture and about 70° to the right or left of its trend because the highest stress around a crack (Williams, 1957; 1959, p. 203—204) or a fault (St. Amand, 1956, p. 43—44) is ahead of and 70° to the right or left of its head. If, therefore, a fracture nearly parallel to a mine rib is reactivated, stress will be concentrated in a small volume of coal between the fracture and the rib, and bumping will occur before a large amount of stress can accumulate; but if the fracture makes a large angle with the rib, more strain energy will be stored in more coal, and failure will be more violent, Finally, if the principal lateral stress in a pillar inter- sects a fault or fracture at a large angle, there is little slipping along the break. Laboratory tests have shown that smooth preexisting fractures in test cylinders of rock subjected to stress are most likely to slip when the angle between the fracture and the principal stress di- rection is between 15° and 33° (J aeger, 1959). If, therefore, one of the principal stress directions in a pillar intersects a fault or fracture at a small angle, slippage will occur before much stress can accumulate; but if one of the principal stress directions intersects a fault or fracture at large angle, a large stress con— centration and a violent bump may result. REFERENCES Clark, F. R., 1928, Economic geology of the Castlegate, Well- ington, and Sunnyside quadrangles, Carbon County, Utah: U.S. Geol. Survey Bull. 793, 165 p. Isaacson, E. de St. Q., 1958, Rock pressure in mines: London, Mining Publications Ltd., 212 p. Jaeger, J. 0., 1959, The frictional properties of joints in rocks: Geoflsica pura e applicata, v. 43, p. 148—158. Peperakis, John, 1958, Mountain bumps at the Sunnyside mines: Mining Eng., v. 10, p. 982—986. Richter, C. F., 1958, Elementary seismology: San Francisco, W. H. Freeman & 00., 768 p. St. Amand, Pierre, 1956, Two proposed measures of seismicity: Seismol. Soc. America Bull.., v. 46, p. 41—46. Watts, A. 0., 1918, An unusual “bounce" condition: Coal Age, v. 14, p. 1028—1030. Williams, M. L., 1957, On the stress distribution at the base of a stationary crack: J our. Applied Mechanics, v. 24, p. 109— 114. 1959, The stresses around a fault or crack in dissimilar media: Seismol. Soc. America Bull., v. 49, p. 199—204. GEOLOGY IN ENGINEERING AND PUBLIC HEALTH B147 65. REVIEW OF THE CAUSES OF SUBSIDENCE By ALICE S. ALLEN, Washington, DC. Subsidence is the sagging or collapse of the ground surface. The area may be large or small; the movement may be abrupt or barely perceptible. The need to understand this phenomenon is increasing with the growing number and variety of engineering problems that are related to contemporary subsidence. Because subsidence problems have been encountered in many diverse fields, the Geological Survey has felt it desirable to search the literature of the various disciplines in an effort to inventory knowledge of the occurrences and causes of subsidence. Some of the results of this search are summarized here. Presently recognized causes of subsidence include compaction of soil and subsurface materials, progressive readjustment around cavities, geochemical changes, melting, lateral migration of subsurface material, and contemporary tectonic disturbance. Rarely is it found that subsidence can be attributed without questi n to a. single cause. Though evidence may show that of. cause predominates, the exclusion of other possible c uses is not easy because evidence of subsurface processes is largely circumstantial. Compaction is the most frequently cited contributor to the subsidence cases being studied today. Much new evidence is becoming available in those areas where com— paction is accelerated by the withdrawal of large quan- tities of artesian water, Oil, or gas from subsuface forma- tions. A significant new approach is the measurement of the differential compaction that takes place in dif— ferent segments of the subsurface column. In subsiding areas in the San Joaquin Valley, Calif. (Inter—Agency Committee on Land Subsidence in the San Joaquin Val- ley, 1958, p. 97—106; 155—156), and in Mexico City (Zee- vaert, 1957), subsurface bench marks have been installed at several stratigraphic horizons for measuring rates of differential compaction. Ground-water hydrology and petroleum reservoir engineering techniques are furnish— ing valuable quantitative data on two pertinent factors in compaction—pore space and fluid pressures. A check on compaction theories is provided by periodic measure- ments of fluid pressure changes in the producing zones, coordinated with subsidence measurements as rates of pumping increase or decrease. The most spectacular de— velopment in the control of subsidence is the injection under pressure of large quantities of sea water into the oil-producing zones of the Wilmington oil field, Cali- fornia (Stormont, 1959 a, b, and c), to halt subsidence and increase oil recovery. Subsidence over cavities created by mining has been studied for more than a century, and papers that de‘ scribe cases or analyze the mechanics of mine subsid- ence form the bulk of subsidence literature. Further- more, research on. many other mining problems, such as strength of roof and pillars, mine drainage, and intentional caving, has application to subsidence. Most promising is the modern resurgence of interest in sub- sidence as a part of the total picture of rock mechanics (Colorado School of Mines, 1956, 1957, 1959; European Congress on Ground Movement, 1957—1959; Interna— tional Strata Control Congress, 1958). Several chemical and physico-chemical processes are also causes of subsidence. The karst topography and thick layers of residuum found in humid climates show that subsidence takes place as the result of the solu- tion of carbonate rocks, salines, and under some con- ditions, even igneous rocks. Although a new sinkhole may form suddenly by collapse of unconsolidated ma— terials over a cavern, subsidence caused by solution gen- erally proceeds too slowly to affect engineering works. Volume changes in clays stemming from changes in their state of hydration are being investigated in con- nection with foundation engineering. Oxidation of peat, with its extreme reduction in volume, accounts for large areas of subsidence. The subsidence of peat soils reclaimed by drainage has been studied in the San Joaquin delta, California, (Weir, 1950) and the Florida Everglades (Stephens, 1956). Subsidence due to melting of large ice masses in permafrost often fol— lows changes in the thermal regime at the ground sur— face, and contributes to the destruction of roadways and structural foundations in Alaska and elsewhere. Lateral migration of subsurface material includes squeezing of plastic clay and salt under load, and move- ment of molten lava beneath the surface. Ground-sur- face movements in response to underground movement of lava have been measured at Kilauea Volcano in Hawaii by high-precision survey methods (Wilson, 1935), and are being studied currently by the Geological Survey (K. J. Murata, 1959, written communication). Subsidence occurs at the summit and on the flanks of active volcanoes as the result of stoping, melting, and the withdrawal of lava, forming summit calderas, pit B148 craters, sector grabens, and trenches over lava tubes. Internal landsliding enlarges these features and other volcanic craters (such as the crater of Vesuvius follow- ing the “gas phase” of the 1906 eruption). Much larger scale subsidence takes place in response to par- oxysmal explosions of ash, as occurred at Crater Lake in prehistoric times, at Krakatau in 1888, at Katmai in 1912, and in 1955 at Bezymianny in Kamchatka. Appraisal of the role of tectonic movements in sub- sidence is difficult because most suspect areas are also areas where compaction is known to be a large factor. From the field of seismology, records of tilt, earthquake shocks, and ground—movement observations may pro- vide data that can be correlated with subsidence. Eval- uation of tectonic movements versus other factors caus- ing subsidence has been attempted for the Wilmington area in California (Gilluly and Grant, 1949) ; the Mis- sissippi Delta (Kolb and Van Lopik, 1958); and the coastal Netherlands (Symposium on Quaternary changes in Level, especially in the Netherlands, 1954). Part of the problem in coastal areas is to judge how much of the apparent subsidence of the coast actually represents sea-level rise. This problem has been ap- proached from the analyses of tide—gage records and oceanographic studies of eustatic sea-level changes. Whatever the local cause or causes of a particular case of subsidence may be, all subsidence investigations have two common requirements. First, and continuing through all stages of any subsidence study, is the need for a reliable datum, and for high-precision, repeated surveys of the same points, tied into that datum. In the United States the Coast and Geodetic Survey’s first- order level net, plus special surveys connecting indi- vidual subsiding areas, furnish vertical control (Small, 1959). Secondly, for those reference points that. are installed on some sort of manmade structure, the possi- bility that the individual structure may be settling on its own foundation must be evaluated. Soil mechanics techniques for studying soil consolidation provide a basis for judging whether subsidence rates recorded at individual stations are representative of the surround— ing area. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCES Colorado School of Mines, 1956, Symposium on rock mechanics: Colorado School Mines Quart, v. 51, no. 3. 1957, Second annual symposium on rock mechanics: Colorado School Mines Quart, v. 52, no. 3. 1959, Third symposium on rock mechanics: Colorado School Mines Quart, v. 54, no. 3. European Congress on Ground Movement, 1957—1959, 19 papers published separately in various issues of Colliery Engi- neering, v. 34, 35, and 36 [London]. Gilluly, James, and Grant, U. S., 1949, Subsidence in the Long Beach Harbor area, California: Geoi. Soc. America Bu11., v. 60, no. 3, p. 461—529. Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1958, Progress report on land-subsidence investigations in the San Joaquin Valley, California, through 1957: Sacramento, Calif. International Strata Control Congress, Leipzig, 1958, (Deutsche Akad. der Wiss. zu Berlin, Sektion fiir Bergbau), 319 p. 140 p1. Kolb, C. R., and Van Lopik, J. B., 1958, Geology of the Missis- sippi River deltaic plain, southeastern Louisiana: US. Army Eng. Waterways Expt. Sta., [Vicksburg] Tech. Rept. ' no. 3483. Small, J. B., 1959, Settlement investigations in the vicinity of Galveston-Houston, Texas, and San Joaquin Valley, Cali- fornia: Jour. Geophys. Research, v. 64, no. 8, p. 1124—1125. Stephens, J. (7., 1956, Subsidence of organic soils in the Florida Everglades: Soil Sci. Soc. America, Proc., v. 20, no. 1, p. 77—80. Stormont, I). H., 1959a, Speed is watchword at Wilmington: Oil and Gas Jour. v. 57, no. 31, p. 106—107. 1959b, World’s biggest water flood: Oil and Gas Jour., v. 57, no. 36, p. 55430. 1959c, New plants boost Wilmington‘s water-injection ca- pacity: Oil and Gas Jour., v. 57, no. 52, p. 66—69. Symposium on Quaternary changes in level, especially in the Netherlands, 1954, Geol. en Mijnb., new ser., v. 16, no. 6, p. 148—267. Weir, W. W., 1950, Subsidence of peat lands of the Sacramento- San Joaquin Delta, California: Hilgardia, v. 20, p. 37—56. Wilson, R. M., 1935, Ground surface movements at Kilauea Vol- cano, Hawaii : Hawaii lfniv. Research Pub., no. 10. Zeevaert, L., 1957, Compensated friction-pile foundation to re- duce the settlement of buildings on the highly compressible volcanic clay of Mexico City: Internat. Conf. on Soil Me- chanics and Foundation Eng, 4th [London] Proc., v. 2, p. 81—86. GEOLOGY IN ENGINEERING AND PUBLIC HEALTH B149 66. A SAMPLE OF CALIFORNIA COAST RANGE LANDSLIDES By M. G. BONILLA, Menlo Park, Calif. The landslides in the San Francisco South quad- rangle, California, are probably a fair sample, in regard to character and frequency, of those that are likely to become increasingly troublesome throughout the Cali- fornia Coast Ranges as construction increases. This area is intermediate in climate between the more humid area to the north and the less humid area to the south; it contains exposures of most of the rocks commOn in the Coast Ranges; and it is affected by landslides of many kinds. ' At least 132 landslides have occurred in the quad- rangle—an average of 2.4 per square mile. These exemplify all but 3 of the 16 types in the Highway Research Board’s classification (Varnes, 1958). Debris slides have been by far the most common. Other types of slides that have occurred here, named in approxi- mate order of decreasing number, are earthflow, com- plex landslide, slump, sand run, mudflow, debris avalanche, block glide, sandflow, debris flow, soilfall, rockslide, and rockfall. The only types in the High— way Research Board’s classification that have not been recognized are failure by lateral spreading, rock-frag— ment flow, and loess flow. Complex landslides affect the greatest total area, followed in decreasing order by earthflows, slumps, and debris slides. About 70 percent of the landslides cover less than 2,500 square yards apiece, but a few cover more than 100,000 square yards apiece. Many kinds of material are affected by the landslides. About one-third of the slides involve only slope debris, consisting mostly of stony clay. Landslides in slightly indurated sediments of the Merced formation are al- most as common, but nearly all are in the steep sea cliffs cut in that formation. Other materials, named in decreasing order of susceptibility to slides, are: sand- stone and shale of the Franciscan formation, artificial fill, sheared rocks, serpentine, greenstone and chert of the Franciscan formation, and clayey sand of the ColIITa formation. No slides are known to have occurred in metamorphic rocks of the Franciscan formation. Quaternary alluvium, beach deposits, sand dunes, marine terrace deposits, and bay mud are not involved in sliding in' this quadrangle, probably because they are rarely exposed there in steep slopes. Landslides occur on slopes ranging from 10° to 55°, but most are on moderate slopes; more than one-third are on slopes of 20° to 25°. About one-sixth occur on slopes of about 40°; a large proportion of these, how- ever, are on a long sea cliff having approximately that inclination. Most landslides are on slopes that face west or south- west; this is in contrast to areas east and north of Berkeley, Calif, where Beaty (1956) found that most of the shallow landslides were on slopes that face north or east. REFERENCES Beaty, C. B., 1956, Landslides and slope exposure : J our. Geology, v. 64, no. 1, p. 70—74. Varnes, D. J., 1958, Landslide types and processes, in Eckel, E. B., ed., Landslides and engineering practice: Highway Research Board, Spec. Rept. 29, p. 20—47. 6% 67. ALTERATION OF TUFFS BY RAINIER UNDERGROUND NUCLEAR EXPLOSION, NEVADA TEST SITE, NYE COUNTY, NEVADA By V. R. WILMARTH, THEODORE BOTINELLY, and R. E. WILcox, Denver, Colo. Work done in cooperation with the US. Atomic Energy Commission The Rainier explosion occurred at the Nevada Test Site on September 19, 1957. According to Johnson and others (1959, p. 1467—1468) it released 1.7 kilotons of energy, raised the temperature to 1,000,000°K and the pressure to 7,000,000 atmospheres within a few micro- seconds, and formed a cavity having a radius of 62 feet B150 within 80 milliseconds. Kennedy and Higgins (1958) concluded that before the cavity collapsed it was lined with a shell of radioactive molten glass about 10 cm thick, and that during the interval bet-ween 30 and 120 seconds after detonation the cavity was filled with steam at 40 atmospheres pressure and a temperature of 1,500°C. One year after the explosion, a temperature of 50°C was measured in a drill hole 60 feet below the explosion chamber (Diment and others, 1959, fig. 9—1). The Rainier explosion occurred in bedded, indurated, porphyritic, rhyolitic to quartz-latitic tuifs in the Oak Spring formation, of Tertiary age. As determined from samples taken before the explosion and near its point of release, these tuffs have a high proportion of shards and lapilli, and a high content of water (table 67.1). The water is largely in a fine-grained mixture of zeolite, clay, beta-cristobalite, and amorphous material that has replaced almost anhydrous glass. The zeolite is mainly clinoptilolite, a close relative of heulandite, but containing more potassium and silica. It has been recently recognized as an important constituent of many tufl'aceous sediments (for example Defleyes, 1959; Mumpton, 1960; Mason and Sands, 1960). The clay appears to be mainly montmorillonite, and the beta-cris— tobalite and amorphous material are presumably com- ponents of opaline silica. TABLE 67.1.—Average composition of tufi close to Rainier explosion chamber Chemical composi- tion, 47 samples Mineral composition, 52 samples (percent by weight) (percent by volume) SiOz 66. 9 Phenocrysts _________________ 17. 4 ______ A1203 12. 4 Quartz _______________________ 2. 6 Fe203 2. 3 Alkali feldspar ________________ 6. 1 FeO . 23 Plagioclase ____________________ 6 8 MgO 1.1 Biotite______-__________ _.____ 13 CaO 2. 4 Pyroxene and amphib01e__ ______ 2 Na20 1. 4 Magnetite ____________________ . 4 K20 2. 3 Xenoliths ___________________ 6. 9 6. 9 H20 + 5. 5 Shards and lapilli ____________ 68 ______ H20 5. 3 Zeolite: Clinoptilolite (‘1’) _ _ ______ 23 C03 6 Clay: Montmorillonite__ __ ______ 12 Beta-cristobalite _______________ 11 Amorphous material ___________ 22 Vesicles _____________________ 7 7 7. 7 Total _________________ 100. 0 100. 0 The heat and pressure produced by the Rainier explo- sion formed a breccia around the explosion chamber and fused some of the tuff to radioactive glass (see Bunker, Wilmarth, and Diment, Art. 68). The glass is most abundant in the matrix of the breccia, where it forms irregular to rounded masses as much as 3 inches wide GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES and 1.5 feet long. The glass is black, red, or gray, opaque to clear, compact to frothy, and has a vitreous to dull luster. Its contacts with adjacent tuff are com- monly sharp, and the tufl' is stained brick red for a distance of about 2 inches from the glass. Small tufi' samples from the breccia containing radio- active glass were disintegrated in water and the glassy particles examined under a binocular microscope. A few of the particles are smooth spheres, 0.1 to 0.5 mm in diameter, of clear glass containing bubbles and dark streaks, but most of the particles have grooved and crenulated surfaces to which tuffaceous material is at- tached. Many of the particles are fragments of stemlike and hairlike masses with longitudinal markings and elongate bubbles and dark streaks. Some masses as much as 5 mm in diameter roughly resemble hubs with spokes and blunt protuberances. Indices of refraction in the glass range from 1.495 to 1.530, as in medium to silicic natural glass. They vary not only from one particle to another but also within the same particle: For instance, in one particle they range from 1.507 to 1.530, and in another from 1.510 to 1.528. In thin sections the glass contains minor quantities of red to black opaque fragments, and numerous elon- gate bubbles a few millimeters across; many of the smaller particles are simply hollow spheres. The pheno- crysts in the glass are principally quartz, feldspar, and biotite with diffuse boundaries. Samples from the outer edge of the breccia have minute rounded masses of pale- gray glass in the tufl' matrix but show no alteration of the phenocrysts. Some of this glass is radioactive. These data suggest that fusion began in the tuff matrix, and proceeded in some places until only the phenocrysts remained; most of the glass is therefore presumed to have resulted from the melting of the zeolite and clay of the matrix. Tufl’ samples from the outer edge of the breccia zone show noticeable changes in texture. They contain many dark-gray and brown fine-grained irregular veinlets as much as 6 inches wide, a few of which are more radio- active than the adjacent tuff. The mineral content of the veinlets, however, appears from X-ray diffractome- ter analysis to be similar to that of the enclosing tufi‘s, except for a locally greater proportion of noncrystalline material. The darker color of the veinlets is presumably due to comminution of the tufi' during brecciation. The principal changes outside of the breccia zone are textural. Microscopic study of tuff samples taken 70 to 75 feet from the explosion show a network of irregular anastomosing veinlets, 0.003 to 0.05 mm wide, filled with fine—grained opaque material. In many sections these veinlets have no preferred orientation, but in others GEOLOGY IN ENGINEERING AND PUBLIC HEALTH one direction is dominant. Autoradiographs made a year after the explosion indicate that the veinlets are not appreciably more radioactive than the intervening tufi'. Between 75 and130 feet from the explosion the veinlets decrease in size and abundance. At 130 feet the largest veinlet observed is 0.003 mm wide and 0.01 mm long, with tapered ends. Index of refraction and optic angle determinations on biotite, pyroxene and amphibole phenocrysts indi- cate no systematic variation with distance from the ex- plosion. Undulatory extinction in quartz grains ap- pears to be about equally marked in samples taken be- fore and after the explosion, except that it is especially marked in some of the remelted tufl'. .X—ray diffraction analyses of. phenocrysts and their matrix show no changes of pattern that can be related to the explosion. The change in cation-exchange capacity from the breccia zone out-ward was determined by ammonia dis- tillation (H. C. Starkey, written communication). Samples of tufi‘ taken 40 to 135 feet from the breccia zone have exchange capacities of 72 to 90 milliequiva- lents per 100 grams. Between 40 and 0 feet the capacity decreases sharply, the lowest value (50.2 milliequiva« lents) being obtained on a sample adjacent to the breccia. X-ray analysis of the minerals gave about the same results for samples having low and high exchange capacities. Morey (1958) has shown that the clinoptilo- lite in the tuif changes to plagioclase when heated to 500° C under 5,000 psi of steam for 3 hours, and Mump- ton (1960) has shown that clinoptilolite when heated above 700° C in air decomposes to amorphous material. The decrease in cation-exchange capacity toward the breccia zone may therefore be related to alteration of the zeolite by heat from the explosion. Differential thermal and thermobalance analyses of tufl' samples taken before the explosion show that the B151 main effect of heating in air to 700° C is loss of water; upon cooling, however, the tuft regains the water. Samples taken after the explosion, 5 to 10 feet outside the breccia zone, give similar results, indicating that the temperatures and pressures at these distances were not high enough to cause any drastic change in the mineral constituents. Thermoluminescence curves of tufi' matrix from samples 2 to 70 feet outside the breccia zone show only minor differences, which cannot be related directly to the explosion. We are grateful to Dr. Barrie Bieler and the Dow Chemical Company, Rocky Flats, 0010., for providing facilities and for help in preparing thin sections of the radioactive glass, and to John R. Dooley of the Geologi- cal Survey for making autoradiographs. REFERENCES Deffeyes, K. S., 1959, Zeolites in sedimentary rocks: J our. Sed. Petrology, v. 29, no. 4, p. 602—609. Diment, W. H., Wilmarth, V. R., and others, 1959, Geologic effects of the Rainier underground nuclear explosion: U.S. Geol. Survey TEI—355 (preliminary draft), open-file report. Johnson, G. W., and others, 1959, Underground nuclear detona- tions: Jour. Geophys. Research, v. 64, no. 10, p. 1457—1470. Kennedy,‘ G. 0., and Higgins, G. H., 1958, Temperatures and pressures associated with the cavity produced by the Rainier event: Univ. California, Livermore, Radiation Laboratory, UCRIr-5281. Mason, Brian, and Sands, L. B., 1960, Clinoptilolite from Patagonia; the relationship between clinoptilolite and heulandite: Am. Mineralogist, v. 45, p. 341—350. Morey, G. W., 1958, The action of heat and of superheated steam on the tuif of the Oak Spring formation: U.S. Geol. Survey TEiI—729, open-file report. Mumpton, F. A., 1960, Clinoptilolite redefined: Am Mineralogist, v. 45, p. 351—369. 6% 68. DISTRIBUTION OF GAMMA RADIOAC’I‘IVITY, RADIOACTIVE GLASS, AND TEMPERATURE SURROUNDING THE SITE OF THE RAINIER UNDERGROUND NUCLEAR EXPLOSION, NEVADA I By C. M. BUNKER, W. H. DIMENT, and V. R. WILMARTH, Denver, Colo. Work done in cooperation with the US. Atomic Energy Commission The distribution of anomalous gamma .radioactivity and temperature produced by the Rainier explosion of September 19, 1957, was determined in drill holes and in tunnels driven through the zone disturbed by the explosion. The 1.7 kiloton nuclear explosion was 900 feet vertically below the surface of the ground, in l B152 bedded tufl' of the Oak Spring formation. The pore space of the tufl' (about 30 percent by volume) was saturated with water (Keller and Robertson, 1959). DISTRIBUTION OF RADIOACTIVITY Gamma radioactivity was determined with scintilla- tion and Geiger-Mueller sensing elements from Sep- tember 1958 to February 1960 (Bunker, 1959). Most of the anomalous gamma-radioactivity is con- centrated below the explosion point (fig. 68.1), and most of it is contained in glass formed by the explo- sion. The distribution of radioactivity supports the theory developed by Johnson and others (1959) that the explosion formed a cavity, lined with radioactive glass, the upper part of which collapsed shortly after the explosion. Most of the radioactive glass is there- fore concentrated in the form of a bowl below the explosion point. In this region the outer limit of the anomalous radioactivity corresponds closely with the outer limit of the breccia produced by the explosion. The breccia consists of blocks and smaller fragments of rock that were crushed and disoriented by the explo- Outer limit of breccia zone JQ‘L-fi lsvsl _____ ix ________ i _ __ Exploratory Zone of greatest tunnel anomalous radioactivity EXPLANATION ——i Drill hole logged for radioactivity O 20 4O 60 80 FEET FIGURE 68.1.—Generalized vertical section through the Rainier explosion point showing generalized distribution of gamma radioactivity greater than about 1 mr per hr. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES sion. Fracturing without disorientation of blocks ex- tends outward from the breccia (Wilmarth, 1959). The outer limit of radioactivity as shown in figure 68.1 is the line bounding the region of clearly anoma— lous radioactivity as measured in drill holes. This is about one milliroentgen per hour (mr per hr), as com- pared with a pre-explosion background of about 0.03 mr per hr. Anomalous radioactivity undoubtedly ex- tends beyond this limit, but the distance is difficult to establish because of the contamination that occurred in the drill holes and in the exploratory tunnel while they were being driven. Fission products having gaseous precursors were found to be relatively scarce in the radioactive glass (Johnson and others, 1959), and it is assumed that they moved considerably outside of the zone of obvious radioactivity. Krypton—85, a gaseous fission product, was found in a cavity of 385 feet above the explosion point about 6 weeks after the explosion (Johnson and others, 1958). No anomalous radioactiv- ity was detected in the part of the original tunnel that was accessible after the explosion (radial distances greater than 200 feet from the explosion). Gamma—radioactivity logs in the tunnel and in some drill holes (fig. 68.2) illustrate the uneven distribution of the radioactivity. The log for drill hole D shows that radioactivity was small directly above the ex- plosion point but was concentrated toward the edges of the bowl. This concentration is particularly well shown by the measurements made in the exploratory tunnel. RADIOACTIVE GLASS Radiometric examination of tunnel workings and correlation of sample and gamma-radioactivity logs indicates that most of the radioactivity is contained in explosion-produced glass. Not all of it, however, is in the glass. Fine fractions (less than 0.01 mm) of the breccia contain some radioactive materials, and so do the solids in suspension in water samples from the ex- ploratory tunnel (A. Clebsch, 1959, written communi- cation), but it is not certain whether the radioactivity is in finely divided glass or not. The appearance of the glass varies widely (Wilcox and Wilmarth, 1959). It may be black, gray, or red, opaque or clear, and compact or frothy. Most of the black and clear glass is compact and has a vitreous luster, Whereas the gray glass is frothy and has a dull luster. Some of the frothy gray glass contains discrete schlieren-like masses of black glass. In some places cores consisting of brown clayey material and red com- pact glass are enclosed in shells of black glass. Measurements of the radioactivity of glass speci- mens of approximately the same size, made in the ex- ploratory tunnel, indicate that in general the black, B153 Sufifiowowcg Ho 3533“?» mafiabmflm was: 5.6 was H255 SSH mwofi 3Efiowowcfi$fifiwwldww 592nm GEOLOGY IN ENGINEERING AND PUBLIC HEALTH So; .8 mcmmgconzE E 05% 3330863.. Puma om ow 0v ON 0 ZO._F 90 per- cent) ____________________________________ 3 (1.0) (.04—2.0) (C) _________ (. 1) (OI—.28) (D) ________________________________________ b. Normal quartz sandstone and quartzite (SiOz 75 percent-90 percent) ________________________________ (4.0) (2.0—6. 0) (A) ......... (1.5) (. 3-2. 7) (A) ________________________________________ c. Clayey and arkosic sandstone g and quartzite, arkose, gray- wacke ___________________________________ (7.5) (4. 0—10. 0) (A) ________ (2.0) (1.2—4.0) (A) ________________________________________ IV. Argillaceous sediments and metasedi— ments (chiefly shales and slates)__ 8.05 8. 2 4. 7—12 A a. Normal shale and slate ........... (9.0) (6—14) (A) b. Calcareous shale and slate ....... (8. 5) (4-14) (A) c. Siliceous shale and slate __________ (4.0) (. 9—6) (G) V. Calcareous sediments and metasedi- ments (chiefly limestone, dolomite, . and marble) ________________________ .50 .3 .05—1.3 1) .11 .06 .01—.26 E .19 .10 .02—.5 E VI. Gneiss and granulite. 8. 46 8.3 6. 5—9.5 A 2.54 2.3 1.5—4.0 A .07 .06 .02-.12 B VII. Schist and phyllite. _ . __ .._ 8. 02 8. 3 2. 2—12. 6 A 1. 12 . 9 .2—2. 6 B . 23 . 10 <. 01—. 25 l) VIII. Amphibolite and greenstone._ - 7.75 8.2 44-100 A 1.30 1.3 .7—1.8 A .18 .15 .08-.3 B IX. Serpentinite __________________________ .82 .9 .25—1.2 A .16 .12 .04—.37 B .06 .06 .02—. 14 B 1 The most common range is established, for this presentation. by eliminating the highest 10 percent and the lowest 10 percent of values observed. 2 Under “remarks”, the variability is summarized as follows: A. B. C. D. E. At least 80 percent of the values difier from the median by a factor of 2 or less (that is, fall between )é median and 2 times median). At least 80 percent of the values difler from the median by a factor of 3 or less. At least 60 percent of the values differ from the median by a factor of 2 or less. At least 60 percent of the actual values differ from the median by a factor of 3 or less. At least 70 percent of the actual values differ from the median by a factor of 5 or less, and at least 50 percent differ by a factor of 3 or less. 3 Data in parentheses have been estimated for subcategories by visual inspection of the data and by interpretation of lithologic properties from the chemical analyses; other data are based on actual frequency counts or computation. other statistical data were obtained by frequency counts and construction of cumulative frequency curves. Within certain categories, the content of sodium and aluminum showed a recognizable relationship to that of silicon or calcium, and on this basis it was possible to divide categories III and IV each into three subcate- gories, for which medians and ranges were estimated. These subcategories represent numerically about the following portions of categories III and IV: category III: subcategory a, 20 percent; b, 15 percent; and c, 65 percent; category IV: subcategory a, 85 percent; b, 10 percent; and c, 5 percent. Selected results appear in the accompanying table. Summaries for each of the first seven categories are based on about 40 to 75 analyses. Eleven analyses were used for category VIII, and seven for category IX. W'ithin most categories and subcategories the common range (60 percent to 80 percent of cases observed) is one-half M (median) to 2M for aluminum, 1/3M to 3M for sodium, and 1/5M to 5M for manganese. Medians of different groups generally differ less than the range within a single group. These results are intended to provide a measure of the broad patterns of chemical variation within major groups of rocks. They cannot be directly compared with the numerous more refined computations of aver- age composition made by other workers, because each rock category of the present study contains several di- verse rock types, each weighted according to its abundance. 6% B166 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES GEOLOGY 0F EASTERN UNITED STATES 74. PRE-SILURIAN STRATIGRAPHY IN THE SHIN POND AND STACYVILLE QUADRANGLES, MAINE By ROBERT B. NEUMAN, Washington, DC. Ordovician graptolites were found in slates associated with chert near the mouth of Wassataquoik Stream (A of fig. 74.1) by W. W. Dodge in 1881, and the trace fossil Old/Lamar. was discovered by E. S. (T. Smith along the East Branch of the Penobscot River in 1928, leading him to conclude that beds there are Cambrian in age. These early workers, however, did not establish the geo- logic relations between these occurrences. ‘ The present mapping indicates that both are contained in the same anticlinorium, and that they are separated by a great thickness of Ordovician volcanic rocks. The formation (Cg of fig. 74.1) containing Oldlmmia was named Grand Falls formation by Ruedemann and Smith (1935, p. 354), but this name was preoccupied by the Grand Falls chert of Winslow (1894, p. 417—419). The ()Zdhamia occurs in maroon siltstone and slate both at Bowlin Falls (B of fig. 74.1) and at the type locality of the formation, which is indicated on the topographic map of the Shin Pond quadrangle as the Grand Pitch of the East Branch of the Penobscot River (C of fig. 74.1). Maroon rocks are a minor but conspicuous com- ponent of the formation; its more common constituents are gray to greenish—gray quartzite, and gray, greenish- gray, and dark-gray slate. Steep dips and tight folds characterize exposures of these rocks, and steeply dip- ping faults of unknown displacement can be identified at several places. Although the boundaries of the for- mation are fairly well established in the Shin Pond and Stacyville quadrangles, the tectonic pattern and strati- graphic succession within the formation are not yet understood. Through most of this area the “Grand Falls” forma- tion is overlain by greenstone (Ov of fig. 74.1). Vol— canic conglomerate, graywacke, and fossiliferous tuf- faceous sandstone (Ovt of fig. 74.1) intervene between them in the southwestern part of the synclinal belt that terminates on Sugarloaf Mountain. These sedimentary rocks are a thousand feet thick along Shin Brook; they may continue for a considerable distance to the north- east, but poor exposures hamper tracing them in that direction. Studies of the fossils from these rocks are not yet complete, but the assemblage of orthoid brachio- pods, gastropods, cystid plates, bryozoans, and trilobites suggests an early Middle Ordovician age. The greenstone and associated rocks have been in- tensely deformed. Although they have steep dips and strong cleavage, they are much less complex in structure than the sequence of interbedded quartzite and slate of the “Grand Falls” formation which underlies them. Some of this contrast may be due to differences in their tectonic competency in response to the Taconic and Acadian orogenies. Nevertheless, the abrupt lithic change, the structural contrast, and the presence in the volcanic conglomerate of pebbles of quartzite like that of the rocks below, all make it probable that the contact between these units is an angular unconformity, and that the quartzites and slates were folded before the deposition of the volcanic debris. Greenstones immediately overlie the quartzite and slate units along a contact that follows the East Branch for almost ten miles and then swings northward around the southern flank of the anticlinorium. The chert and slate (Ovc of fig. 74.1), in which the graptolites were found, lie at the southeastern margin of these green- stones, apparently at their top. The present work has failed to uncover additional graptolite localities, al- though similar cherty rocks lie along the eastern border of the smaller body of volcanic rock that is probably a fault slice. Ruedemann (Ruedemann and Smith, 1935, p. 353— 354) identified the graptolites both in Dodge’s collec- tion and in one made by Smith at the same locality, and concluded that they were of Normanskill age. My own more recent collections, which contain conodonts as well as graptolites, do not alter this conclusion. If the vol- canic rocks of the Sugarloaf-Roberts Mountain belt are of the same age as those to the southwest, the fossils at the base of the former and the top of the latter limit the time of their formation to the Middle Ordovician. Intruding both the greenstones and the quartzite and slate is a porphyritic quartz diorite (qu of fig. 74.1) which contains fragments of greenstone and in one place forms the matrix of a greenstone breccia. There are two reasons for believing that this diorite is of Ordovician age: (a) the abundance of calcite in mi- nute fractures pervading the diorite indicates that it is more altered than the Acadian intrusives in the region; and (b) cobbles of the diorite occur in conglomerate that overlies the greenstone on the east, and at one place graywacke associated with this conglomerate GEOLOGY OF EASTERN UNITED STATES B167 68°45' 68°30’ 46“15’ SHIN POND ISLAND FALLS Roberts Mtn Cg X / ; Hay Brook Mtn / 5 x i \ qu ,/ ) ‘ Marble Pond 0v \ t A M t h Jerry Pond Xoun C ase Ov ii cg \\ / \ \ "a Lunksoos Lake ( a CV g?” V ‘ Ovc % 0v 1/ TRAVELLER 0V e' a 4 MTN '39 ) 46°OO’ KATAHDIN Patten%ERMAN \ EXPLANATION Porphyritic quartz diorite Deasey Mtn >< Ovc Ov Greenstone Cherry beds, Ovc, and water-Laid tuffs and related rocks, Ovt, shown separately Quartzite and slate Grand Falls formation of Ruedemamt and Smith (1.935) 6R56VEIAN He__l CAMBRIAN Stacyville 5 O 5 MILES J STACYVILLE FIGURE 74.1.——Geologic map of. the preSilurian rocks in the Shin Pond and Stacyville quadrangles, Maine. Localities referred to in text: A, Dodge’s graptolite locality; B, Bowlin Falls, Smith’s Oldhamia locality; 0, Grand Pitch of the East Branch of the Penobscot River. Geo-logic mapping by R. B. Neuman, assisted by John Duane (1957),, R. H. Raymond (1958), and H. H. Roepke (1959), supplemented by unpublished mapping in the Traveller Mountain quadrangle by D. W. Rankin (Vanderbilt University) and in the Island Falls quadrangle by E. B. Ekren (US. Geological Survey). Planimetry from US Army Map Service Millinocket and Presque Isle 1:250,000 sheets, and place names from the U.S. Geological Survey topographic quadrangles indicated. B168 contains fragmentary fossils that are probably of Silurian age. REFERENCES Dodge, W. W., 1881, Lower Silurian fossils in northern Maine: Am. Jour. Sci., ser. 3, v. 22, p. 434—436. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Ruedemann, Rudolph, and Smith, E. S. 0., 1935, The Ordo- vician in Maine: Am. Jour. Sci., ser. 5, v. 30, p. 353—355. Smith, E. S. 0., 1928, The Cambrian in northern Maine: Am. Jour. Sci., ser. 5, v. 15, p. 484—486. Winslow, Arthur, 1894, Lead and zinc in Missouri: Missouri Geol. Survey, v. 7, sec. 2-, p. 389—542. 62‘ 75. A COMPARISON OF TWO ESTIMATES OF THE THORIUM CONTENT OF THE CONWAY GRANITE, NEW HAMPSHIRE By F. J. FLANAGAN, W. L. SMITH, and A. M. SHERWOOD, Washington, DC, Battelle Memorial Institute, Columbus, Ohio, and Alexandria, Va. Determining the distribution of uranium and tho- rium in the Conway granite of New Hampshire is part of a broader study of these elements in igneous rocks. The radioactivity of the red and green phases of the Conway granite from the quarry at Redstone, Carroll County, N.H., has been discussed by Smith and Flana- gan (1956), who observed the differences in radioac- tivity of samples taken at closely spaced intervals. The differing amounts of the major contributors to the radioactivity in these samples might also prove valuable for future comparison with results obtained from sam- ples taken over wide areas. Analyses of the two phases of the granite by W. H. Herdsman (Billings, 1928) in- dicate that potassium should also be classified as a major contributor to the radioactivity of the samples. Uranium is present in igneous rocks approximately in the range 0.1 to 20 ppm and thorium from 1 to 100 ppm. The determination of these elements in igneous rocks, especially that of thorium, is time-consuming in spite of continuing improvements in analytical methods; potassium, on the other hand, can be deter- mined rapidly by the methods of Shapiro and Brannock (1956), and the determination of radioactivity by beta- counting is a simple physical measurement. Other investigators, for example Hurley (1956) and Adams and others (1958), have described methods for determining thorium in the parts-per-million range by gamma-scintillation spectroscopy and by alpha-count- ing methods. While thorium can be determined di- rectly by gamma-scintillation spectroscopy, the method may require long counting periods, and the uranium content has to be known before the thorium content can be calculated from the alpha-counts. Although the technique described below probably cannot be used in the low (1 to 10 ppm) thorium range and is none too accurate for individual determinations, its less stringent requirements, such as short counting times (each sam- ple in table 75.1 was counted for five minutes), and the use of an average potassium content of the rock under study, recommend its use in reconnaissance work where replicate samples are available. The useful range of the method covers only granites and some granodiorites and rocks abnormally enriched in thorium, but the method may be useful as an assay tool for low grade thorium ores. Indirect estimates of the thorium content of uranium ores have been made for years by subtracting the uranium content of the ore from the radioactivity ex— pressed as equivalent uranium, and then multiplying the remaining radioactivity by the specific counting rate ratio for U/Th. As the potassium contribution to the radioactivity of uranium ores is negligible, the cor- rectness of these estimates depends on whether the uranium and thorium series are in equilibrium. When they are not in equilibrium the estimates are of little value. / If we are justified in assuming that radioactive equilibrium exists in the Conway granite, the indirect thorium values obtained by subtraction can be used in estimating the thorium content, despite the fact that both the radioactivity and the uranium and thorium content of the granite are two or three orders of magni- tude lower than those of uranium ores. The correctness of these estimates, and hence the validity of the under- lying assumption, can be tested by comparing them to values determined chemically. INDIRECT THORIUM ESTIMATES To determine if such indirect thorium estimates are valid, four samples were picked at random from ,each of the four groups (weathered and fresh, red and green) of samples of the Conway granite from the Red- GEOLOGY 0F EASTERN UNITED stone quarry (Smith and Flanagan, 1956). Uranium was then determined fluorimetrically, potassium by pre- cipitation with tetraphenyl boron, and thorium colori- metrically with thoron as a reagent, after separation. Using the equation eTh=R1 [eU— (U+R2K) ], where R1 is the U/Th counting-rate ratio for the counting system used, eU the radioactivity expressed as percent equivalent. uranium, U the percent uranium, K the per- cent potassium, and R2 the K/U counting—rate ratio, estimates of the thorium content can be calculated. These estimates and the determined values of eU, U, K, and Th are shown in table 75.1. The counting-rate ratios used were 4.0 for U/Th and 2,000 for U/K, in accord with the coaxial method of counting (Smith and Flanagan, 1956). For comparing the value of the two methods—~the chemical method and that proposed above—for esti— mating small amounts of thorium, several statistical methods are available, but the most attractive of these is the one that involves the pairing of observations and the use of Student’s “t” test on the differences between pairs (Youden, 1951). For this test the variances of the two sets of data need not be homogeneous. After one has noted the differences between the 16 pairs in column 6, table 75.1, the average difference, J(+ 1.5), and its standard deviation, 8,;(212), can be calculated. The hypothesis to be tested is that the average of the n differences, d: is not significantly dif— ferent from zero, or in other words that the averages of the two methods are virtually equal. Substitu— tion in the equation t =dsx/n yields 25: 0.28. d The 95-percent critical value for t with 15 degrees of freedom is d: 2.13. As the calculated value is much less than the critical value, it can be concluded that there is insufficient evidence for stating that the means of the two methods are significantly different. It is there- fore justifiable to use the calculated thorium mean as an estimate of the mean of the chemical determinations. Inspection of these means (table 75.1) shows that the mean of the calculated values is about three percent greater than the average of the chemical determinations. Although three significant figures for potassium are reported in table 75.1, results obtained by rapid analy- sis (Shapiro and Brannock, 1956) would be adequate, for the second decimal place will not noticeably affect the calculated thorium values. 557753 0—60—12 STATES B169 TABLE 75.1.—D‘etermina,tionis of eU, U, K, and Th in samples of Conway granite 1 2 3 4 5 6 Character Sample eU U K Th Difier- calcu- deter- enoe (ppm) (ppm) (per- lated mined (4-5) Cent) (ppm) (ppm) Weathered green. 137 46 7. 6 4. 64 61 62 —1 142 44 7. 5 4. 85 49 53 —4 143 47 8. 6 4. 64 61 52 9 144 48 13. 5 4. 36 51 52 --1 Fresh green. 113 41 8. 7 4. 46 40 45 —5 117 41 8. 6 4. 69 36 71 —35 118 44 8. 2 4. 75 48 52 —4 121 42 10. 7 4. 72 31 76 —45 Weathered red. 123 48 10. 5 3. 36 85 73 12 128 55 12. l 4. 25 87 65 22 131 58 10. 8 3. 02 128 79 49 134 51 10. 1 3. 29 98 83 15 Fresh red. 101 55 14. 1 3. 44 95 89 6 103 60 16. 6 3. 90 96 98 —2 109 57 17. 8 4. 18 73 74 -l 111 63 16. 5 3. 90 108 99 9 Average ______________ 50.0 11. 4 4.15 71. 7 70. 2 +1.5 Standard deviation... 7. 1 3. 4 .60 28. 7 16. 9 21. 2 When the average potassium contents of the red and green phases are used in place of the individual deter- minations in a phase, the average difference between the two methods is 0.25 ppm. Although this excellent agreement is undoubtedly fortuitous, it demonstrates that one need not use individual determinations if a reliable determination of average potassium content is available. REFERENCES Adams, J. A. S., Richardson, J. E., and Templeton, C. 0., 1958, Determinations of thorium and uranium in sedimentary rocks by two independent methods : Geochim. et Cosmochim. A'cta, v. 13, p. 270—279. Billings, M. P., 1928, The petrology of the North Conway quad- rangle in the White Mountains of New Hampshire: Am. Acad‘. Arts Sci. Proc., v. 63, p. 67—137. Hurley, P. M., 1956, Direct radiometric measurement by gamma- ray scintillation spectrometer: Geol. Soc. America Bull., v. 67, p. 395—411. Shapiro, Leonard, and Brannock, W. W., 1956, Rapid analysis of silicate rocks: U. S. Geol. Survey Bull. 1036—0, p. 19—56. Smith, W. L., and Flanagan, F. J., 1956, Use of statistical methods to detect radioactivity change due to weathering of a granite: Am. Jour. Sci., v. 254, p. 316—324. Youden, W. J., 1951, Statistical methods for chemists: New York, John Wiley and Sons, p. 28. 6% B170 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 76. POSSIBLE USE OF BORON, CHROMIUM, AND NICKEL CONTENT IN CORRELATING TRIASSIC IGNEOUS ROCKS IN CONNECTICUT By P. M. HANSHAW and P. R. BARNETT, Boston, Mass, and Denver, Colo. Work done in cooperation with Connecticut Geological and Natural History Survey The general distribution, lithology, and structure of the Triassic rocks in Connecticut have been known for many years, and three layers of extrusive basalt, some of them consisting of more than one flow, are easily rec— ognized where well exposed. In places, however, glacial deposits cover all bedrock except a few small outcrops of basalt, which are nearly indistinguishable by field and microscopic study, and therefore difficult to place in proper stratigraphic position. The intrusive rocks of different ages differ in character in some places; near Mount Carmel, for example, the porphyritic dikes are younger than both the nonporphyritic dikes and a large intrusive sheet (C. E. Fritts, written communication, November 17, 1959). Quantitative spectrographic analyses of 37 random samples of Triassic basalt and diabase from the Con- necticut Valley Lowland appear to show differences in boron, chromium, and nickel content which may possi- bly aid in correlating outcrops of these rocks, and thereby help in interpreting the geologic structure (fig. 76.1). REGIONAL GEOLOGY The Triassic rocks in Connecticut underlie the Con- necticut Valley Lowland. They comprise a wedge of continental sedimentary rocks (red beds) dipping gently eastward, intercalated with three layers of basalt and cut by at least one intrusive sheet and many dikes of diabase. The three basalt layers from oldest to youngest, are called the Talcott basalt, the Holyoke basalt, and the Hampden basalt. The regional geology of Triassic rocks in Connecticut has been described by Percival (1842), Davis (1898), Longwell (1922), and Krynine (1950). A preliminary geologic map and de- scription of bedrock units is contained in Rodgers and others (1959). The set of northeast-trending faults, generally down— thrown on the west, cuts the Triassic rocks in the low- land and is especially prominent in the area between Meriden and Hartford. Erosion along these faults has formed many subparallel northeast-trending ridges of basalt. As the sedimentary rocks stratigraphic-ally be- low and above the basalt layers are covered by glacial deposits, and the basalts look alike both megascopically and microscopically, little evidence can be found for assigning any basalt outcrop to a particular strati- graphic position. It is necessary, however, to deter- mine the stratigraphic positions of many outcrops of basalt before the structure of the Triassic in this area can be delineated and interpreted in detail. DESCRIPTIONS 0F BASAL’I‘S The basalts are greenish to bluish gray, dense, and generally fine grained, but are coarse grained in places near the center of a flow. They are homogeneous in composition, being composed of augite, pigeonite, and labradorite with interstitial chloritic material and ac- cessory magnetite( ?). In central Connecticut, the Tal- cott basalt commonly has pillow structure and averages about 150 feet in thickness, the Holyoke basalt has well-developed columnar joints at many localities and is about 600 feet thick, and the Hampden basalt shows columnar joints in places and is about 160 feet thick. Locally each of these basalts consists of more than one flow, but where that is true the individual flows cannot be traced for more than a short distance, and their relative stratigraphic position within the basalt cannot be determined. RESULTS OF SPECTROGRAPHIC ANALYSES Samples were collected by C. E. Fritts, P. M. Han- Shaw, R. W. Schnabel, and H. E. Simpson. The sam- ples included (a) grab samples from various levels within each basalt layer, and (b) composite samples taken at regular intervals stratigraphically across one layer. Samples were also taken from intrusive masses. No mineralogic zoning of units was noted in the field. The analyses indicate that the boron content of the Talcott and Hampden basalts is greater than that of the intrusive .rocks. The boron content of the Holyoke basalt varies from place to place but averages higher GEOLOGY 0F EASTERN UNITED STATES Intrusive rocks 6 samples Talcott basalt 11 samples Holyoke basalt 14 samples Hampden basalt 6 samples Parts per million Boron 1 200— 180- 160— 140— 120— 100- 80- 60 — 40 — 20— Average : 86 Average : 13 .410 Average : 2360 —; .800 .860, 3500 .9200 Average : 75 (20 Parts per million Chromium 500— 400 — 300 — 200 — 100— O Average:275 0 Average: 293 Average : 80 O 47......L;_'_.' ._._._ Average: 32 Parts per million Nickel 110— 100-— 90-— 80- 70 — 60 —- 50-— 4o-— 30 - 20 Average:74 Average: 72 Average: 37 lValues assumed to be 10 ppm when cal 20 parts per million (me lower limit of delectlon) arbitrarily culating averages. FIGURE 76.1.—Quantitative spectrographic analyses of boron, chromium, and nickel in 37 samples of Triassic igneous rocks from Connecticut. Analysts, P. R. Barnett and N. M. Conklin, U.S. Geological Survey. B171 B172 than that of the intrusives. If the low boron content of the intrusives is substantiated by further analyses, it may be a useful criterion for determining the in- trusive origin of a diabase body where field evidence of origin is lacking. Analyses of the extrusive .rocks indicate that the aver— age chromium content of the Holyoke basalt is about one-half that of the Hampden basalt and about one- tenth that of the Talcott basalt. Several small outcrops of basalt in central Connecticut are inferred, on the basis of structural interpretations, to be Hampden, and the analyses made thus far have supported these infer- ences. These analyses are not shown in figure 76.1. The nickel content of the Holyoke basalt appears to be about one-half that of other Triassic volcanic rocks in Connecticut. Low nickel content in conjunction with low chromium content might therefore permit correlat- ing a basalt outcrop of unknown stratigraphic position with the Holyoke. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE-S The analytical results summarized here are prelim- inary. Analyses of many additional samples, combined with field and petrographic study, will be needed to establish the trends indicated, their mineralogical re- lationships, and their geologic significance. REFERENCES Davis, W. M., 1898, The Triassic formation of Connecticut: U.S. Geol. Survey 18th Ann. Rept, pt. 2, p. 1—192. Krynine, P. D., 1950, Petrology, stratigraphy, and origin of the Triassic sedimentary rocks of Connecticut: Connecticut Geol. and Nat. History Bull. 73. Longwell, C. R., 1922, Notes on the structure of the Triassic rocks in southern Connecticut: Am. Jour. Sci., 5th sen, v. 4, p. 223—236. Percival, J. G., 1842, Report on the geology of the State of Con- necticut: New Haven. Rodgers, John, Gates, R. M., and Rosenfeld, J. L., 1959, Ex- planatory text. for Preliminary Geological Map of Connecti- cut, 1956: Connecticut Geol. and Nat. History Survey Bull. 84. 77. CORAL FAUNAS IN THE ONONDAGA LIMESTONE OF NEW YORK By WILLIAM A. OLIVER, J R., Washington, DC. Study of extensive collections of rugose corals from the Onondaga limestone in New York State has demon- strated the presence of two distinct coral assemblages, the upper one occupying a much greater stratigraphic thickness than the lower. The lower assemblage has not been described, and its recognition makes possible the correlation of the beds containing it over a large area. The lower assemblage has been found in New York only in discontinuous beds, 2 to 4 feet thick, exposed at the base of the formation in the western part of the State. Characteristic and common rugose corals from these basal beds are Acrophyllum onez'deme, Aemulo- phyllum emiguum, “Oystiphyllum” sulcatum, “0.” squamosum, Kionelasma sp., Scenophyllum com'gemm, and Syringawon sp. Several other, less common, species of corals are apparently limited to the lower assemblage. Associated forms include Am-phz'gem'a sp. cf. A. 0mm, Uentmnella sp., Eodwonam'a sp. (iden— tified by A. J. Boucot, oral communication, 1959) and several other brachiopods, platyceratid gastropods, and trilobites. The strata carrying the lower assemblage were designated by Oliver (1954, p. 626 and 632) as zone B (the Amphigenia zone) of the Edgeclifi' member. The subdivisions of the Onondaga limestone in west- ern New York are shown in figure 77.1 (after Oliver, 1954). The Amphigem’a zone is lithologically as well as paleontologically distinct from the Edgeclifl' men;- ber and should no longer be included in it. The Edge- clifl' member is a distinctive coralline biostromal and biohermal limestone extending all the way across New York State and into Ontario. Paleontologically, it is characterized by a completely different group of rugose corals, here referred to as the upper coral assemblage. Among the common genera in this member are Acinophyllum, Bethanyphyllum, Billingsastmea, Blothrophyllum, Cylindrophyllum, Oystiphylloz'des, Eridophyllum, Heliophyllum, Hemagomm'a, Siphono- phrentz's, and Synaptophyllum (see Oliver, 1954, p. 638—641, for lists of fossils occurring in all members). Although some genera occur in both the lower and upper assemblages, the rugose corals in the two are, as a whole, distinctive on a generic and even a family level. The upper coral assemblage, broadly defined, is found throughout the Onondaga limestone of New York in the light—colored, coarser grained facies (Oliver, 1954, 1956), and similar corals (families, many genera GEOLOGY 0F EASTERN UNITED STATES B173 FALLS OF THE OHIO RIVER, WOODSTOCK AREA, ONTARIO WESTERN NEW YORK AND CORAL INDIANA AND KENTUCKY (THICKNESS FROM STUMM NIAGARA PENINSULA OF FAUNAS AND OTHERS, 1956) ONTARIO _ _? ______ 7 _ _ ____. Beechwood and Silver Creek limestone Hamilton group members of Sellersburg limestone ?— ? — — —< \ \\ Delaware limestone Seneca member (30 + feet) L —. —?— — . 5. Paraspirifer zone (11 ft +) COIUmbus 15. (15 feet) Q) - ‘ ~ 9‘ Moorehouse member 4. Bremsmmfer zone (3 ft) g (Western coral facies) 2 Lucas formation of E (50 feet) 3 Ehlers and Stumn '7'; 3 N 8 be a i: a 43 3’ 3 = 7 7 x: ,3 «a Q) . O E) ._e : . . . = 3 cs '5 Detr01t River formation 0 IE ‘8‘ g (80 feet) Nedrow member g 1.. E (45 feet) g g *0 g :> H 3. Coral-stromatoporoid zone. (7 ft ) _? ———— ? — ‘— Amherstburg dolomite of . 2- Upper coral zone (5 ft) Ehlers and Stumn Edged‘ff member ___________ ______________ (5~30 feet) _____ 1. Lower coral zone (4 ft) Zone B (A mph igem‘a zn) (2 ft) sag JVVVVVWVVV‘ANVV‘ . Bois Blanc formation (100—150 feet) ——JVVVVV‘ :wvvm <13 Lower coral fauna FIGURE 77.1.—Distribution of principal coral faunas in the Onondaga limestone and correlations with sections in Ontario and Indiana-Kentucky. The range of Amphigem‘a in western New York is shown on the right side of the New York column. and some species) are found in the calcareous members of the overlying Hamilton group. Stratigraphic sub— division (zonation) of the strata carrying the upper assemblage is under study, but for present purposes the contrast of this assemblage with the lower one is its most significant feature. The Onondaga formatiOn has the same character in the Niagara Peninsula of Ontario. The Amphigenia zone thickens westward (lower brachiopod beds of Staufl'er, 1915), but in other respects the lower members change only gradually and can be recognized as far as Hagarsville, 60 miles west of Buffalo. Between Hagarsville and the Woodstock, Ontario area, 40 miles to the northwest, almost no outcrops are known. In the Woodstock area the rocks are com— pletely different from what they are at Hagarsville, and Michigan stratigraphic terminology has been applied (section included in figure 77.1). The formations of the Woodstock area differ from the Onondaga limestone in facies and partly in age. At Innerkip, exposures of the lower 10 feet of the Bois Blane formation carry the distinctive lower coral assemblage. The total thickness of the Bois Blanc is over 100 feet (Stumm and others, 1956) ; outcrops are few, but according to Best 1 most or all of this thickness carries the lower assemblage. The pre-Edgeclifl‘ Amphigenia zone, in 'western New York and adjacent Ontario, can be considered as the eastern feather edge of the Bois Blane formation. Lateral discontinuity of the zone in western New York (Oliver, 1954), and possibly in the Niagara Peninsula of Ontario, suggests that the strata containing the upper assemblage may be separated from the Am- phigenia zone by an unconformity. The upper coral assemblage is found in the lower part of the Detroit River formation (Amherstburg dolomite of Ehlers and Stumm, 1951) in the Woodstock area, 1Best, E. W., 1953, Pre-Hamilton Devonian stratigraphy, southwest- ern Ontario, Canada: University of Wisconsin, unpublished Ph.I). thesis. B174 and also at Gorrie, farther north. The upper two- thirds of the Detroit River formation (Lucas forma- tion of Ehlers and Stumm, 1951) contains a different coral assemblage, apparently reflecting environmental differences. The Detroit River formation correlates with most of the New York Onondaga. The overlying Columbus limestone is correlated with the upper part of the Moorehouse or Seneca on the presence of Par- aspz'm'fer. These general relationships are shown in figure 77.1 At the Falls of the Ohio River, near Louisville, Ky., several zones are recognized, partly on the basis of studies by Campbell (1942) and earlier workers (fig. 77.1). The lower coral zone (zone 1) carries the lower coral assemblage and is correlated with the Bois Blane formation of Ontario and the pre-Edgeclifi' Amphi- gem’a zone of western New York. Approximate cor- relations of zones 2 to 5, which carry the upper coral fauna, are shown in figure 77.1. CONCLUSIONS The corals of the upper assemblage of the Onondaga limestone are of distinctly Middle Devonian types. They are associated with nautiloid cephalopods of Mid- dle Devonian age (R. H. Flower, oral communication, 1959), and with rare goniatites that are also of Middle Devonian age (M. R. House, oral communication, 1959). There is little doubt that the nearest faunal affinities of the corals and cephalopods from the Onon— daga limestone of New York (exclusive of zone B) and its correlatives are with the Couvinian (early Middle Devonian) of Europe. The corals of the lower assemblage are associated with brachiopods referred to the Schoharie fauna, of GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE’S Cooper and others (1942, p. 1780). The Schoharie grit underlies the Onondaga limestone in east-central New York and carries some at least of the corals occurring in the lower assemblage. Most of the arguments for regarding the Onondaga limestone as Early Devonian have been based on faunas (principally brachiopods) of units correlative with the Schoharie rather than with the Onondaga proper. The corals of the lower assemblage are more closely related to known Middle Devonian corals than to Early Devonian ones, but the species and many of the genera are not known to occur outside of northeastern North America and may be en- demic to that area. The age of the pre-Edgecliif Amphigem'a zone and its correlatives may be late Early Devonian (Emsian of Europe), but present knowledge of the lower corals neither proves nor disproves this. REFERENCES Campbell, Guy, 1942, Middle Devonian stratigraphy of Indiana: Geol. Soc. America 31111., v. 53, p. 1055—1072. Cooper, G. A., and others, 1942, Correlation of the Devonian sedimentary formations of North America: Geol. Soc. Amer- ica Bull., v. 53, p. 1729—1794. Ehlers, G. M., and Stumm, E. C., 1951, Middle Devonian Colum- bus limestone near Ingersoll, Ontario, Canada: Am. Assoc. Petroleum Geologists Bull., v. 35, p. 1879—1888. Oliver, W. A., Jr., 1954, Stratigraphy of the Onondaga lime- stone (Devonian) in central New York: Geol. Soc. Amer- ica Bull., v. 65, p. 621—651. , 1956, Stratigraphy of the Onondaga limestone in eastern New York: Geol. Soc. America Bull., v. 67, p. 1441—1474. Stauffer, C. R., 1915, The Devonian of southwestern Ontario: Canada Geol. Survey, Mem. 34, 341 p. Stumm, E. C., and others, 1956, The Devonian strata of the London-Sarnia area, southwestern Ontario: Michigan Geol. Soc, Guidebook annual field trip, June 9—10, 1956, 21 p. 78. GEOPHYSICAL AND GEOLOGICAL INTERPRETATION OF A TRIASSIC STRUCTURE IN EASTERN PENNSYLVANIA By ISIDORE ZIETZ and CARLYLE GRAY, Washington, D.C., and Bureau of Topographic and Geologic Survey, Harrisburg, Pa. Work done in cooperation with the Bureau of Topographic and Geologic Survey, Commonwealth of Pennsylvania GEOLOGY The Triassic rocks of the Newark-Gettysburg basin are extensively exposed in Bucks County, eastern Penn— sylvania (McLaughlin, 1959) (fig. 78.1). Here the basin contains three sedimentary formations; these are, in order of increasing age, the Stockton, Lockatong and Brunswick. The sequence is duplicated by faulting, and on Buckingham Mountain near the center of the GEOLOGY 0F EASTERN UNITED STATES B175 :::::.'\‘\'- ~ s ‘ e \\ y“ \ \ \ \\\\\\\. _ / eW“ A. A " M Section lines \ \‘°\\‘° Lefler referred fo [/7 F figures 78.2 and .3 "lg. llii EXPLANATION Diabase Stockton formation l 1:.L Lockatong formation Brunswick formation TRlASSlC \\\\~ \\ \. \\\\\\\‘\\ Sedimentary rocks } CAMBRlAN AND ORDOVICIAN Furlong fault D Buckmanville fault E Chalfont fault F Gravity traverse | IIIIIIII|I iIIIlI "I "'Illiiilfll!‘ ' II 1M|LE 4| CONTOUR INTERVAL 50 GAMMAS FIGURE 78.1.—Aeromagnetic map of the Buckingham Mountain area, Pennsylvania. basin, the two areas of Triassic rocks are separated by a sizeable area of pre-Triassic rocks. The pre-Triassic floor in the vicinity of Buckingham Mountain consists of Cambrian and Ordovician rocks. On the southeast side of the Buckingham Mountain area, the Furlong fault (0, fig. 78.1) brings Lower, Middle, and Upper Cambrian rocks in contact with the Brunswick formation. Northwest of the exposed Pale- ozoic rocks the Stockton formation lies unconformably on the Paleozoic sedimentary rocks. In one small area on Buckingham Mountain the presence of gneiss float blocks indicates that crystalline Precambrian basement rocks are actually exposed. The dip of the bedding in the Paleozoic sedimentary rocks is generally to the northwest. At the southwest end of the inlier, the Furlong fault joins the Chalfont fault (E, fig. 78.1). McLaughlin (1959, p. 131) has estimated a maximum stratigraphic displacement of 10,000 feet on the Furlong fault and 6,500 feet on the Chalfont fault. The Chalfont fault extends east of its junction with the Furlong fault for about four miles and is then overlapped en echelon by B176 the Buckmanville fault (D, fig. 78.1), which extends the displacement to the Delaware River. The strati- graphic throw of these faults was computed from esti— mates of the total thickness of the Triassic sedimentary formations. It has long been recognized, however, that these formations may be in part equivalent to one an- other, and that in places the Brunswick formation lies on the pre-Triassic rocks. Such considerations indi- cate that the estimated stratigraphic throw on the faults may be only an approximation of the true throw. The structure associated with the Furlong fault in the Buckingham area has magnetic expression, because the Precambrian basement rocks, which are much more magnetic than either the Triassic or the Paleozoic sedi- mentary rocks, are close to the surface on the northwest side of the fault. INTERPRETATION The most prominent feature on the areomagnetic map (fig. 78.1) is a large anomaly, striking northeast and having an amplitude of more than 1,000 gammas, that is centered over the Furlong fault. The map re— veals differences between the countour features north- east and southwest of traverse B. The areomagnetic profile and the inferred geologic section along traverse B, which we regard as typical of the southwestern part of the Buckingham anomaly, is presented in figure GAM MAS 10003 500 W L Observed and computed data 0 NW ris Sea level .»,- E EXPLANATION _‘\\\ \\\\ \\\\\\\\\\\ \3.‘ x tlLi 2 ¢/ Stockton formation a mourL . // __ it)? E E 12‘ Brunswick formation " E g 1000' FURLONG FAU \ } 2%: ”c -: Sedimentaryrocks , S E . a tea . g; ° FIGURE 78.2.—Geologic section and aeromagnetic profile along traverse B. 78.2. The geologic section was constructed partly from surface mapping and stratigraphic considera- tions, and partly from calculations based on aeromag- netic data. Magnetic profiles for several hypothetical Precambrian surfaces were computed on the basis of a Pirson polar chart modified for total—intensity cal- culations (Pirson, 1940). The Precambrian surface shown in figure 78.2 is the one that produces the best fit to the observed profile. The circled points are com- puted data, based on the assumption that remanent magnetization is negligible and that the susceptibility of the Precambrian rocks exceeds that of the sediment- ary rocks by 0.005 cgs units. The configuration and GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES structure of the Precambrian surface as deduced from aeromagnetic data differ in two important respects from those based on geology alone: (a) The displace- ment along the Furlong fault is less than 3,000 feet, whereas stratigraphic data indicate that the total thickness of the sedimentary rocks, and therefore dis- placement, on this fault, is about 10,000 feet; (b) The Precambrian surface southeast of the Furlong fault dips southeastward, instead of northwestward as was expected from the surface structure of the Triassic rocks. Northeast of traverse B magnetic gradients are much steeper than they are southwest of it, and there is a broad minimum northwest of the Paleozoic rocks; and although the total Paleozoic sedimentary section is apparently thicker on the northeast side than on the southwest side, the amplitude of the anomalies and the magnetic gradients are higher on the southwest side. EXPLANATION GAM MAS 1000 is 0 Observed Stockton formation $ 800 .. S 55122 E Brunswick formation 2 E 600 \ S 5 . ¢o_ \ \ } mz> Sedimentary rocks 2‘8 400 i S ,1 / Z ES: 0 200 Basement rocks i'é‘g V‘ ‘°~ :0/ Computed of: Sea _ level FIGURE 78.3.——Geologic section and aeromagnetic profile along traverse A. Figure 78.3 shows an aeromagnetic profile, along traverse A, that we regard as typical of the northeast.— ern half of the Buckingham anomaly. Superimposed on the observed profile is a magnetic profile computed from a structure section based on geological data and the computed section of traverse B. It is evident that in this province, if the susceptibility contrast is 0.005 cgs units as assumed in traverse B, the Precambrian structure does not contribute very much to the anomaly amplitude. Subtraction of the magnetic fields of the observed and computed profiles results in a residual magnetic profile shown in figure 78.4. This anomaly could be accounted for by assuming that a tabular GEOLOGY 0F EASTERN UNITED STATES body, of small width but large vertical extent (fig. 78.4), cuts across the Paleozoic rocks, that its top is approximately 1,000 feet below the surface and 1,000 feet northwest of the Furlong fault, that this body is parallel to the Furlong fault and that its southwest end is near traverse B. Assuming that this body is 100 feet wide, its susceptibility is computed to be 0.09 cgs units, which corresponds to a magnetite content of over 25 percent by volume. If the body is only 50 feet wide, the magnetite content is over 50 percent. GAM MAS 100° EXPLANATION i .‘Ejsi ’ 800 Stockton ormation} TRIASSIC :EEKbEI: 600 Brunswick formation E 12‘ Residual \m Egg . ‘ an 400 Sedlmentary rocks i 2‘8 m 512:5 g 200 Basement rocks Egg D. Computed tabular body NW SE m Sea level / /\ FIGURE 78.4.—Aeromagnetic profile across inferred dike. [1000' 1000’ a, body /z/// In any curve-matching procedure involving mag- netic data such as the one presented here, it is im- portant to remember that a given observed profile could be satisfied by any one of many possible configurations; for example, the same anomaly might be produced by a shallow weakly magnetic body or a deep highly mag- netic body. The dike postulated here is assumed to be of small mass and to lie at a depth of about 1,000 feet-— the maximum depth at which a magetic source could yield the anomaly observed. The reason for assuming that the dike is small is that a large dense mass could be detected by gravity measurements if it lay near the surface; no such mass was indicated by a detailed gravity profile made in this vicinity under the direction of Martin Kane using a gravimeter with a sensitivity of 0.01 mgls per dial division. Because of the geological setting, this thin tabular body might have economic importance. Approximately 10 miles south of the intersection of the Furlong fault and traverse A, Precambrian rocks are exposed on the surface. They are described (Arm- strong, 1941) as Baltimore gneiss ranging in composi— tion from mafic to felsic. Magnetic anomalies in the B177 vicinity of this exposure are numerous, and depth cal- culations based on the method described by Vacquier and others (1951) yield depths equal to the flight ele- vation. This partly confirms the belief that these methods are applicable in this area. Depths to the Precambrian surface approximately 3 miles north of this area are computed to be about 3,000 feet. Extra- polating linearly and using this depth and the points at the surface of the Precambrian as controls, we have computed that the depth near the south end of the pro- file in figure 78.2 is approximately 7,000 feet. This figure is in good agreement with the depth obtained by using the curve-matching procedures (see fig. 78.2), and confidence may be placed in figures that agree so closely though obtained by two entirely different methods of approach. A cross section of the southern half of the Triassic basin is shown in figure 78.5. The configuration of the Precambrian surface is based entirely on interpretation FAULT FURLONG FAULT ‘ib 'is N r;\\;§\\\\§\\ «mm \ . \\'Xe\\\\§\\\\ ............. . ,0 5 MILES CHALFONT FAULT _. BUCKMANVILLE ."I » EXPLANATION z '. 3 5 \‘V ED- ”W“ 9 -il ' s. mZ> Diabase a L'ockatong formation Sedimentay rocks . 3(3) < z m _ ’/_ ’ <2 U 0 IE I E .m 71;; ES Stockton formation I Brunswick formation as: | a. FIGURE 78.5.—A geologic section across the southern half of the Triassic basin, Bucks County, Pa. of the magnetic data, and the stratigraphic colunm is based entirely on geologic mapping. Southeast of the Furlong fault, there are prominent magnetic anomalies over outcrops of diabase. These anomalies could be caused by strong magnetization of the rocks, either in- duced or remanent, or by the shape and attitude of the diabase mass. The simplest way to determine the con- figuration of the mass is by means of a gravity traverse at right angles to the strike of the diabase since there is a strong density contrast between it and the surround- ing sedimentary rocks (approximately 0.4 g per cm3). Toward this end, a gravity traverse (F), shown in figure 78.1, was made under the supervision of Martin Kane. The results show that the diabase is a sheet dip- ping to the northeast, nearly concordant with the bed- ding in the Triassic sedimentary rocks. B 178 REFERENCES Armstrong, Elizabeth, 1941, Mylonization of hybrid rocks near Philadelphia, Pennsylvania: Geol. Soc. America Bull., v. 52, no. 5, p. 667—694. McLaughlin, D. B., 1959, Mesozic rocks, in Willard, Bradford, and others, Geology and Mineral Resources of Bucks County, 76. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN 5% THE GEOLOGICAL SCIENCES Pennsylvania : 0—9. Pirson, S. J., 1940, Polar charts for interpreting magnetic anomalies: Am. Inst. Mining Metall. Engineers Trans, v. 138, p. 179—192. Vacquier, V., and others, 1951, Interpretation of aeromagnetic maps: Geol. Soc. America Mem. 47, 151 p. Pennsylvania Geol. Survey, 4th sen, Bull. PRELIMINARY INTERPRETATION OF AEROMAGNETIC DATA IN THE ALLENTOWN QUADRANGLE, PENNSYLVANIA By RANDOLPH W. BROMERY, Washington, DC. Prepared in cooperation with the Bureau of Topographic and Geologic Survey, Commonwealth of Pennsylvania The Allentown quadrangle was surveyed with the air- borne magnetometer in 1956 as part of a detailed survey in southeastern Pennsylvania, to obtain geophysical data useful in area] geologic mapping and in searching for magnetic iron deposits. The flying was done at 500 feet above the ground surface, on traverses a quarter of a mile apart. Precambrian metamorphic and igneous rocks of com— plex geologic structure form a continuous belt that trends northeast across the south-central part of the quadrangle, separating the Paleozoic sedimentary rocks in the northern half of the quadrangle from the Trias- sic sedimentary and igneous rocks in the southeastern part of the quadrangle (fig. 79.1). The exposed Precambrian rocks are delineated in detail by a “bird’s—eye maple” magnetic pattern. Some of this detail has been sacrificed in preparing figure 79.1, but the original magnetic contours (Bromery and others, 1959) have proved useful in mapping the areal extent of the underlying Precambrian rocks. The mag- netic data indicate that some previously mapped faults are longer than was supposed, and that faulting may have occurred in some areas where it had not hitherto been recognized. The Paleozoic sedimentary rocks in Saucon Valley are characterized by a uniform magnetic gradient lead- ing to a magnetic low. This gradient extends north— eastward along the northern edge of the valley beyond the head of the valley. To show the possible configuration and depth of burial of magnetic rocks, three theoretical structure sections, A, B, and 0, were graphically computed from the magnetic profiles across the Reading Prong. This analysis was performed by using a modified Pirson Polar Chart (Pirson, 1940). The calculations indicate that the Precambrian rock surface along the northern edge of Saucon Valley and its apparent northeast ex- tension is nearly vertical. The buried surface of the magnetic rocks underlying Saucon Valley is approxi- mately a mile deep. Low—amplitude magnetic anom- alies observed along the southern edge of Saucon Valley are underlain by Precambrian rocks, and if a uniform magnetic susceptibility is assumed for these rocks the magnetic data along section A show that they are less: than 1,000 feet thick. Magnetic anomalies of higher amplitude are observed along sections B and 0', on strike with the low-amplitude anomalies, and calcula- tions indicate that here the thickness of the underlying Precambrian rocks is far greater—4,000 feet. The Precambrian rock surface at the Triassic Border fault along sections A and B is nearly vertical, and there is no magnetic expression of buried Precambrian rocks over the Triassic Basin. Possibly this is because Pre- cambrian rocks are deeply buried, so that any weak magnetic expression is masked by anomalies associated with Triassic diabase rocks, as for example at the southeast end of section A. Along the northern edge of the Reading Prong, the magnetic profiles indicate that the Precambrian rocks were dropped 1,000 feet on the north side of a nearly vertical fault; and that the Precambrian surface north of the fault slopes northward beneath Paleozoic sedi- mentary rocks. Along section D, magnetic computations indicate that an arching surface of Precambrian rocks four miles wide is buried a mile below the surface. An anticline in the overlying Paleozoic sedimentary rocks, GEOLOGY OF EASTERN UNITED STATES B179 o 75I°30’ 75°25’ 75°20’ 75:18:45! 40 45 EXPLANATION D I /l/ Triassic rocks South of fil'assic Border fault Paleozoic rocks North of Triassic Border fault V /////% Precambrian rocks Boufiia—ry; R—ea-Jnfirong Magnetic contour enclosing area of lower magnetic intensity VA? 40°4o’ ~ \A‘) 40°4o' 6 a (OD M f «0? ?\ C B 0 D . O \ Q A 0 ‘V . ' 0‘?’Vx a“? 40°35’~ . 40°35’ 6 $6“ . . We . . . yd ' $0“ ‘1», V o \ . 0“ 0“ P C EO’D’ RV FTITT ‘ _ 9990 ,5» / : i :/j c:\ 75°30’ 75°25’ 75°20’ 75°15’ 1 O 1 3 4 MILES i_l . i I l l | | CONTOUR lNTERVAL 50 AND 250 GAMMAS 40°3o' i b/ l B‘ <3(\«mwo' 2 FIGURE 79.1.—Aeromagnetic and generalized geologic map of the Allentown quadrangle, Northampton, Lehigh, and Bucks Counties, Pa. Magnetic data from Bromery and others (1959). B180 ShOWn on the new Pennsylvania. State Geologic Map, is centered over this buried arch; the exposure of ap- parently non—magnetic Precambrian rocks on Pine Top and Camels Hump (fig. 79.1) extends along its southern edge. The magnetic anomaly associated with this buried structural feature extends to the northeast and increases in amplitude in the adjacent Easton quad- rangle (Bromery and others, 1960), where it is under- lain by exposed Precambrian rocks at Chestnut Hill. The exposed Precambrian rocks on Pine Top and Camels Hump are probably related to those at Chest- nut Hill and to the buried magnetic mass along section D, but these relationships are not yet clear. Analysis of the magnetic data in the Allentown quadrangle and GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES in the adjoining quadrangles indicates areas where Precambrian rocks may be relatively thin. REFERENCES Bromery, R. W., Bennett, B. L., and others, 1959, Aeromagnetic map of the Allentown quadrangle, Northampton, Lehigh, and Bucks Counties, Pennsylvania: US. Gebl. Survey Geophys. Inv. Map GP—213. Bromery, R. W., Henderson, J. R., Zandle, G. L., and others, 1960, Aeromagnetic map of part of the Easton quadrangle, Northampton County, Pennsylvania, and Warren County, New Jersey: U.S. Geol. Survey Geophys. Inv. Map GP—235. Pirson, S. J., 1940, Polar charts for interpreting magnetic anomalies: Am. Inst. Mining Metall. Engineers Trans., v. 138, p. 179—192. 61‘ 80. TACONIC AND POST-TACONIC FOLDS IN EASTERN PENNSYLVANIA AND WESTERN NEW JERSEY By AVERY A. DRAKE, JR., ROBERT E. DAVIS, and DONALD C. ALVORD, Washington, D.C., Denver, 0010., and Denver, Colo. Papers reviewing Appalachian structural geology and the chronology of Appalachian folding have recently been published by Spieker (1956) and by Woodward (1957a, 1957b, and 1958). Woodward agrees with some previous workers in believing that the folds in the Appalachians were produced in three similar but sepa— rate periods of deformation, rather than in a single period of disturbance at the close of the Paleozoic era. The purpose of this paper is to describe some of the structural relations along the Delaware River in eastern Pennsylvania and western New Jersey, and to state our present views regarding the relative intensity of the TacOnic and post-Taconic orogenies. The area considered here includes segments of the Reading Prong, Great Valley, and Folded Appalach- ians, and is underlain by rocks of Precambrian to Late Devonian age. It has long been recognized that an un— conformity separates the Martinsburg shale, of Middle and Late Ordovician age, from the Shawangunk con- glomerate of Silurian age, and that the pre-Silurian rocks were folded twice (Behre, 1925; Miller,’1926; and Stose, 1930). Stose thought that the pre-Silurian (Taconic) .folding was less intense than the later (Ap— palachian) folding, whereas Behre and Miller thought that in eastern Pennsylvania the Taconic folding was almost if not quite as intense as the Appalachian. It is our thesis that in this area the Taconic folding was by far the stronger. In the part of the Appalachians we have studied it has been difficult to relate the folds to specific periods of deformation, because there the structural trends are all nearly parallel. Detailed mapping and careful cataloguing of minor structural features has shown, however, that the folds in the pre-Silurian rocks are vastly different from those in the younger rocks. The pre-Silurian sedimentary rocks—largely Cam- brian and Ordovician carbonate rocks—and the Mar- tinsburg shale are strongly folded. The folds, which range in amplitude from microscopic dimensions to at least 5 miles, are nearly all overturned to the north- west. Some are recumbent, and the axial planes of a few have been rotated past the horizontal. The traces of axial planes are hard to follow because of faulting and flowage, but major synclines and synclinoria have been mapped in the Musconetcong and Pohatcong Val— leys, and also in the Great Valley north of Easton, Pa. The synclinorium in the Great Valley is the largest fold yet recognized in the area; its northwest limb ex- tends even beyond the north boundary of the Bangor 71/2-minute quadrangle. Its constituent folds are mostly recumbent. Their axes plunge, in places, gently east—northeast or west-southwest, but on the average they are probably almost horizontal. Flow cleavage is present in all of the pre-Silurian rocks, and is by far the most prominent planar struc- ture in the argillaceous Hershey limestone (Gray, GEOLOGY OF EASTERN UNITED STATES 1952) and the Martinsburg shale. This cleavage is warped and folded, showing that subsequent stress was: released along these planes rather than along bedding planes. Folds affecting the flow cleavage are super— posed on preexisting folds in the argillaceous rocks, and slip cleavage has developed that. is about parallel to the axial planes of the folds of the flow cleavage. Many of the thrust faults that can be recognized in out- crop are parallel to the slip cleavage, and these faults commonly extend along the crests of arches in the flow cleavage. These folds are certainly younger than the folds that affected the bedding, and it seems likely that they are post~Taconic. The dips of the Silurian and Devonian beds, from their southernmost exposure at the Delaware Water Gap to the Pocono Plateau, are prevailingly north- westward. The regional dip is interrupted by several folds that are characterized by short southeast limbs. As one goes southeastward across these folds, one finds that the structural height of their successive crests in- creases, as if these folds were satellitic to a major anti~ cline that once flanked them on the southeast. Linear elements in these rocks are nearly horizontal, but out- crop patterns indicate that the large folds in them plunge west-southwest. Folding becomes less intense toward the northwest, where the last mappable folds occur in the limestones of the Onondaga formation. There are asymmetric folds, too small to map, in the overlying Hamilton formation, but on the whole the rocks of this group are only gently flexed. The pre- Upper Devonian rocks have well-developed cleavage, which dip steeply southeastward and is nowhere ro— tated or folded. Folds in the Silurian and Devonian rocks become tighter and even overturned along strike to the south- west, where they presumably pass into the structurally more complex terrane of the Wind Cap and Lehight Gap areas. It can be seen from the above discussion that the rather simply folded Silurian and Devonian rocks overlie very complexly folded Ordovician rocks. Beer- bower (1956), in describing the Ordovician-Silurian contact at the Delaware Water Gap, concluded that the Taconic disturbance was much less intense in this area than it was farther north and east. This conclu- sion, however, was based on the nearly parallel atti- tudes of the Shawangunk and Martinsburg forma- B181 tions in a single poor exposure. The fact is that the Martinsburg in this area was thrown into overturned and recumbent folds during the Taconic orogeny; in exposures both east and west of the contact described by Beerbower, beds have been rotated more than 180°, and Ordovician beds diverge at various angles from Silurian beds exposed nearby. The Ordovician-Silu- rian contact was folded after the deposition of the De- vonian rocks, and the Martinsburg shale reaches the surface in several small anticlines along the southeast- ern slope of Kittatinny Mountain. The structural re- lations here are not yet fully understood, but as the Martinsburg farther south was sheared along its flow cleavage, the arches in this cleavage are probably parallel to anticlines in the beds of the Shawangunk formation. In summary, the Taconic folding was very much stronger in this area than the post-Taconic folding, which was in fact rather gentle. During the later orog- eny, pre-existing Taconic folds were deformed by fold- ing that affected flow cleavage, and also by thrusting. The post-Taconic orogeny cannot be precisely dated, but it can probably be ascribed to the Appalachian disturbance. REFERENCES Beerbower, J. R., 1956, The Ordovician-Silurian contact, Dela- ware Water Gap, New Jersey: Pennsylvania Acad. Sci. Proc., v.30, p. 146.149. Behre, G. H., 1925, Taconic folding in the Martinsburg shales [abs]: Geol. Soc. America Bull., v. 36, p. 157—158. Gray, Carlyle, 1952, The high calcium liniestones of the Ann- ville belt in Lebanon and Berks Counties, Pennsylvania: Pennsylvania Geol. Survey, 4th ser., Progress Rept. 140, p. 4—5. Miller, B. L., 1926, Taconic folding in Pennsylvania: Geol. Soc. America Bull., v. 37, p. 497—511. Spieker, E. M., 1956, Mountain-building chronology and nature of geologic time scale: Am. Assoc. Petroleum Geologists Bull., v. 40, no. 8, p. 1769—1815. Stose, G. W., 1930, Unconformity at the base of the Silurian in southeastern Pennsylvania: Geol. Soc. America Bull., v. 41, p. 629—658. Woodward, H. P., 1957a, Structural elements of northeastern Appalachians: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 7, p. 1429-1440. 1957b, Chronology of Appalachian folding: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 10, p. 2312—2327. 1958, Ordovician and Silurian deformation at the north- east end of the Appalachian Basin [abs] : Geol. Soc. Amer- ica Bull., v. 69, no. 12, pt. 2, p. 1666. B182 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 81. LATE PALEOZOIC OROGENY IN EASTERN PENNSYLVANIA CONSISTS OF FIVE PROGRESSIVE STAGES By HAROLD H. ARNDT and GORDON H. WOOD, J R., Washington, DC. Deformation during the late Paleozoic Appalachian orogeny is recorded by structural features in rocks of Cambrian to Pennsylvanian age in eastern Pennsyl- vania. The orogeny began after rocks of Pennsyl- vanian age were consolidated and prior to deposition of rocks of Late Triassic age. Moderately folded rocks are present in the Allegheny and Pocono plateaus. Strongly folded and faulted rocks occur in the Ridge and Valley province, and rocks in the Great Valley are even more complexly deformed. Although part of this complex deformation in the Great Valley is attributable to the Taconic disturbance Of early Paleozoic age, it has been long recognized that the structural complexity of rocks effected by the Appalachian orogeny increases southeastward across these areas. The increase is most noticeable across the Anthracite region of eastern Penn- sylvania which lies principally in the Ridge and Valley province, but also includes parts of the Allegheny and Pocono plateaus (fig. 81.1). Detailed studies in the Anthracite region and interpretation of data on the Great Valley (Gray, 1959) Show that the structural features formed progressively in a sequence; this se— quence is here classified on the basis Of the increasing complexity of these features into five structural stages as follows : 1. Folding of horizontal strata. into broad anticlines and synclines. 2. Low-angle thrusting and imbricate faulting, fol- lowed by formation of subsidiary folds on the larger folds to develop anticlinoria and syncli- noria. Additional low-angle thrusting followed by high—angle thrusting accompanied the subsid- iary folding. 3. Folding of low-angle and high-angle thrusts, and offsetting of pre-existing structural features by high—angle thrusts. 4. Development Of overturned folds, and offsetting of overturned folds by tear faults and high-angle thrusts. 5. Development of recumbent folds and nappes. In this sequence it is obvious that an area. with struc- tural features of stage 5 had previously undergone deformation attendant with each of the preceding stages. CONCEPT OF PROGRESSIVE DEFORMATION Much speculation persists as to the relative times and the sequence of structural events during the Appala- chian orogeny in eastern Pennsylvania. The authors believe that all structural features were formed during a single orogeny, and that orogenic forces were con- tinuously transmitted through the Anthracite region from southeast to northwest with gradually increasing intensity so that the strata in the southeastern part of the region were deformed before those in the north- western part. The simple folds of stage 1, therefore, probably formed in the southeastern part of the region before they did in the northwestern part. Further, the complicated folds and faults of stage 4 in the south- eastern part of the region’probably formed simultane- ously with the simple folds of stage 1 in the northwest- ern part. Thus, deformation resulting from the Appa- lachian orogeny apparently was progressive both tem- porally and geographically. AREAL DISTRIBUTION OF STRUCTURAL STAGES From north to south the Anthracite region and Great Valley are divisible on the basis of increasing complexity of structural features into five geographic areas corre- sponding with the five stages. The features in the northwestern part of the Anthra— cite region consists Of large symmetrical Open folds of stage 1 (fig. 81.1). In the north-central part of the region the principal features are anticlinoria and syn- clinoria composed of en echelon symmetric and asym- metric subsidiary folds that are commonly broken by folded low-angle and high-angle thrusts. Features of stage 2 are superimposed on folds of stage I in this part of the region. Features indicative of stage 3 occur in the south— central part of the region. Here the folds and faults formed during the preceding two stages were further folded and offset by high—angle thrusts. The overturned folds, tear faults, and high-angle thrusts of stage 4 are present in the southernmost part of the Anthracite region. Folds and faults that formed there during the preceding three stages were intensively deformed. GEOLOGY 0F EASTERN UNITED STATES B183 O 100 MILES FLI_J_J EXPLANATION Pennsylvanian rocks Mississippian, Devonian, and Silurian rocks _1__ Anticlinorium _*__ Synclinorium .q. Overturned beds , 2” ’49 Fault, showing direction of relative movement A A’ Line of section B Area of structural stage 1 Area of structural U: n h) E m m N Area of structural in F. n: W m on Area of structural stage 4 Index map of Pennsylvania showing area of Anthracite region 76°00' 75:30' 0 a ”‘6 eM s‘ee’ ‘\ 09 6‘“ Generalized map of Anthracite region subdivided into five areas of increasing structural complexity MDS 10 o 10 MILES ' scram)“ L_i_i_i_i Pocono Plateau 8 S 75°30’ Cross sections showing structural features indicative of five structural stages 1 0 1 1% l l HORIZONTAL AND VERTICAL SCALE 2MlLES J FIGURE 81.1.——Generalized map and cross sections of the Anthracite region, subdivided into five stages which are defined on the basis of structural complexity. B184 Small to large recumbent folds and nappes of stage 5 occur in the Great Valley, south of the Anthracite re- gion. These structural features were probably super- imposed on less complex features formed during the Taconic disturbance. Some local areas did not undergo the stage of de— formation that would be suggested by their geographic location, and others advanced beyond the stage indi- cated. These apparent discrepancies are explainable, however, because the varying structural competency of stratigraphic units and other stratigraphic and struc- tural complications locally retarded or concentrated the stress, so that the resultant features were either less complicated or more complicated than normal for their geographic location. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES CONCLUSIONS The Appalachian orogeny in eastern Pennsylvania proceeded through a sequence of five structural stages. In the Anthracite region, the areas of most complex structures to the southeast underwent each of the first. four stages of deformation, whereas the least in- tensively deformed area to the northwest was sub- jected only to the last orogenic force and contains fea- tures characteristic of only the first stage of deforma- tion. The process of structural evolution appears to have been continuous and the result of a single orogeny that was not necessarily punctuated by pulsations. REFERENCE Gray, Carlyle, 1959, Nappe structures in Pennsylvania [abs]: Geol. Soc. America Bull, v. 70, no. 12, pt. 2, p. 1611. 6% 82. DIFFERENTIAL SUBSIDENCE OF THE SOUTHERN PART OF THE NEW JERSEY COASTAL PLAIN SINCE EARLY LATE CRETACEOUS TIME By JAMES P. MINARD and JAMES P. OWENS, Washington, DC. Even the small—scale geologic map of the State of New Jersey reveals that there is a progressive easterly shift in strike of the successively younger formations of the coastal plain (fig. 821 and table 82.1). Re— cent detailed mapping in four 71/2-minute quadrangles southeast of Trenton (fig. 82.1) corroborates this fact, and yet surprisingly, most workers have failed to rec- ognize it or have passed it over without comment. Recognition of this shift, however, has a far—reaching effect on interpretation of the geology of this region, TABLE 82.1.—Average attitudes and contact relations of the Late Cretaceous to Pliocene(?) formations southeast of Trenton Average Average dip Age Series or group Formation Symbol strike (SE) in feet Basal contact relations (degrees) per mile Pliocene(?) Cohansey sand __________________ Tch N72E 10 Unconformable. Miocene (7) Kirkwood ,,,,,,,,,,,,,,,,,,,,,, Tkw N70E 18 D0. Tertiary Manasquan _____________________ qu N62E 25 Do. Rancocas Vincentown _____________________ Tvt N56E 30 Do. Hornerstown sand _______________ Tht N53E 45 Do. Red Bank ,,,,,,,,,,,,,,,,,,,,,, Krb N47E 35 Conformable. Monmouth Navesink _______________________ Kns N47E 35 Unconformable. Mount Laurel sand ,,,,,,,,,,,,,, Km] N47E 35 Do. Late Cretaceous Wenonah _______________________ Kw N46E 35 Conformable. Marshalltown ,,,,,,,,,,,,,,,,,,, Kmt NAME 35 Unconformable. Matawan Englishtown ____________________ Ket N45E 38 D0. Woodbury clay __________________ wa N44E 40 Conformable. Merchantville ___________________ Kmv N44E 40 Unconformable. Magothy _______________________ Km N42E 42 Do. Raritan ,,,,,,,,,,,,,,, , __________ Kr N 40E 60+ Do. GEOLOGY OF EASTERN UNITED STATES 2 Trenton EXPLANATION Matawan group Monmouth group Rancocas group Miocene and Pliocene(?) rocks FIGURE 82.2.—Block diagram of several groups of formations in the New Jersey coastal plain. Thickening down dip is a re- sult of subsidence during deposition. Erosion of the uplifted northeast part exposed thicker down dip facies or sections of the Cretaceous and early Tertiary formations in this region. Erosion exposed thicker down dip facies or sections of the two youngest formations in the southwest during Pleistocene Atlantic City EXPLANATION DELA WARE BA Y uplift. TABLE 82.2.—Average thicknesses of formations in difierent parts 1 2 of the New Jersey coastal plain & 4 3 Average ' . ‘ o 15 was 71/z'quadranglw ass; ms; sass. has Dates?” 1. Columbus Formation thickness thickness (feet) at formation compared. with 2 New E t (feet) near (feet) SE or near Ithlckens outcrop thickness 3. Bmwnsgizns 213313313; of Trenton Rgétyan 1n outcrop 4. Pemberbon Cohansey ______ 200 :l; 200 :l: 50 3|: SW Nearly the '. same. Area of outcrop of Cretaceous rocks Kirkwood _____ 120 60 30? SW Thicker. Km“ Manasquan_ _ _ _ 15 40 60 NE Do. . A Vincentown-___ 25 55 100 NE Do. Sitm 21; fioflgtmis Hornerstown 20 30 30 NE Do. . sand. FIGURE 82.1.—Map of the coastal plain in New Jersey. Tinton sand____ 0 0 20 NE Do. Red Bank _____ 0 0—50 140 NE Thinner? _ ' . . ' Navesink ______ 10 20 40 NE (?). belng particularly helpful in assessmg the role of fa01es Mount Laurel (?) 2o 20 (‘2) Thicker. changes both along strike and down dip. Our ex- sand. planation of the shift is based on the following facts: Wenonah ------ C?) 20 20 (1?) D0- Marshalltown, - 35 .35 35? (?) D0. 1. Nearly all the pie-Quaternary coastal plain forma- EnglishtOWD—u 20 45 140 NE D0- tions thicken down dip or basinward, generally WOOdbury Clay- 50 50 50? (‘0 D0?- - . - Merchantville__ 48 60 60? NE D0. in a southeasterly dlrection (figure 82.2 and table Magothy 25 30 120 NE D0 822): 39d the Older formations generally dip Raritan- :::: 300? 300? 300? (‘1) Do. progresswely more steeply than the younger formations (table 82.2). 2. Most formations are thicker and wider in outcrop in the northeastern part of the coastal plain than in the southwestern part (fig. 82.1 and table 82.2). 557763 0—60—13 3. More unconformities are present in the stratigraphic sequence than had been previously (table 82.1). recognized B186 4. Marine planation was the dominant eroding agent throughout the area considered. This is suggested by the reworked sediments and marine fossils in the bases of the formations, and by the absence of subaerial weathering. In the light of these facts, the simplest explanation for the progressive changes in strike is the presence of a large downwarp south of the New Jersey coastal plain, possibly near Delaware Bay, accompanied by differential uplift in the northern part of the coastal plain. Downwarping while deposition was going on ex— plains the sediments’ thickening basinward—to the south and southeast. Subsequent marine planation, especially in the northeastern part of the coastal plain, eroded the nearshore facies of the sediments, exposing the thicker ofl'shore facies or section. Repeated cycles of deposition and marine planation during Late Cretaceous and early Tertiary time are indicated by the fact that most of the contacts between formations are unconformable. Throughout this time the locus of downwarping migrated westward, and therefore each younger formation was laid down on a GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES surface that sloped more nearly southward than the surface underlying the next older formation, and the strike of each younger formation is more easterly than that of the formation beneath it. The direction of downwarping was reversed at some time in the Pleistocene, and in the western and south- western parts of the coastal plain, the Kirkwood and Cohansey formations were much eroded. The thicker ofl’shore facies, particularly of the Kirkwood, were ex— posed, and outcrops of this formation consequently show a thickening toward the southwest. Recognition of the progressively more eastward strike of the younger formations, and of the basin- ward thickening along outcrops, helps to explain the changes in the lithology of the formations along their strike. The glauconite and quartz sand of the Mar- shalltown formation near Camden is probably a near- shore facies, whereas the clay in the formation near Raritan Bay is probably an offshore facies. Similarly the thick clay in the Kirkwood formation near Salem is probably an offshore facies, whereas the sand and small pebbles in the formation east of Trenton suggest a near-shore facies. ’X 83. DROWNED VALLEY TOPOGRAPHY AT BEGINNING OF MIDDLE ORDOVICIAN DEPOSITION IN SOUTHWEST VIRGINIA AND NORTHERN TENNESSEE By LEONARD D. HARRIS, Washington, DC. A disconformity between the Lower Ordovician part of the Knox group and the overlying Middle Ordovi- cian rocks in southwest Virginia and northern Tennes— see is widely recognized. Several authors (Cooper and Prouty, 1943, p. 823; Rogers and Kent, 1948, p. 32; Miller and Fuller, 1954, p. 67; and Bridge, 1955, p. 727) reported as much as 200 feet of relief on this sur- face. Because of the subtle nature of the topography on this disconformable surface a regional paleogeo- morphic pattern has not been generally recognized or described. This paper briefly discusses the regional pre-Middle Ordovician paleogeomorphology in Lee County, Va., and northern Claiborne and Hancock Counties, Tenn. (fig. 83.1). In these counties the Lower and Middle Ordovician rocks dip from 15° to 35°. The outcrops are thus restricted to narrow northeast-trend- ing belts, and, consequently, only profiles parallel to the regional strike can be drawn. Control for construc- tion of these profiles is based on measured sections and detailed field mapping of key beds between sections. GENERAL GEOLOGY AND PALEOGEOMORPHOLOGY Detailed mapping and section measuring of the rocks below and above the disconformity indicate that the Lower Ordovician rocks were relatively flat lying at the time of erosion of the disconformable surface. Key beds that are cut out where valleys were eroded into the Lower Ordovician rocks retain their same stratigraphic position under highs on that surface. In general, the bedding of the Middle Ordovician rocks is parallel to that of the underlying Knox group, but locally the lower beds of the Middle Ordovician are draped nearly parallel to the slopes, and dip away at a small angle. Subaerial erosion of the surface on the Knox group was long enough to have removed a maximum of 170 feet of dolomite, and to have developed a residuum of GEOLOGY OF EASTERN UNITED STATES B187 T\\\\\\\\\\\\\ /_____ _,/ \\\\\\\;/\§A’(\\v \\\\\ ‘l / B, NUO‘S’ \> B/ / x03 49» / // /”st‘ / ,. A I / A // ’/ X Xx/A/ / 3 EWING ’ / / M A _ I, x / / // LL LI. ¥~—~——/ // x / ' :> x // /-% STl/CKLEVILLE a ' / / «\dge/ /// SA/C? \\\\\\\\\\\\\\\\. // p / \gl \\\\\\\\\\\ \\\ \\\\\\\\\\\\\\\\\\ // <9“) 5755 N7 COLEMAN GAP LEE CO wa\\e/V‘// )9) é” ‘\e '_ T'HANCO‘CE co _;»C———-_/___XI_IEGLNE____L__________ 0 <4» // // TENNESSEE 44900 C’ / // 5&5? C // pow°“/ w ‘ EXPLANATION é) / / \\\ \ \\ \ B B, C\OO §’ // EWING x —— O y/ x // unnuuu“ Spot observations Profile section // \ // 7; min. quadrangle / \/ mapped in detail 5 o 5 MILES / /\/\ I . i . . I I / \\\X\\\\\\\\x(\\\\\ FIGURE 83.1.—Map of southwestern Virginia and northern Tennessee showing areas of detailed mapping, single points of observation, and location of profile sections. unknown thickness. The residuum included the in- soluble constituents in the dolomite, namely, clay, sand, and chert. There is some evidence to suggest that a soil profile was developed on the dolomite. This pro- file may have included an upper oxidized zone; at least the oldest deposits, which occur only in the lowest parts of the valleys, are invariably grayish—red dolomitic shale with some coarse elastic material. The very lim- ited distribution of this grayish-red shale suggests that, upon submergence, red clay was the first sediment win- nowed from the residuum. The topography carved on top of the Lower Ordo- vician rocks is one of rolling hills and, in general, broad valleys (fig. 83.2). Relief ranges from about 100 feet to a maximum of 170 feet. Locally, some slopes are relatively steep; as shown in profile section 0—0’ (fig. 83.2), in the southwest part of the area, the west side of one valley was a nearly vertical cliff 110 feet high. The ancient topography resembles a nearly mature coastal plain very near sea level. If this plain bordered on old land of greater relief, the area of investigation must have been far removed from the old land, because the first deposits above the disconformity were locally derived from the residuum developed on top of the Lower Ordovician rocks. These basal deposits, which range from 1 to 40 feet in thickness, include clay, small amounts of sand, and abundant fragments of chert and dolomite. Limestone, about 1,500 feet thick, overlies this reworked residuum. During Middle Ordovician time, as this gently roll- ing plain was inundated by the sea, the coastline must have been quite irregular, and its appearance was that of a submerged coastal plain with many drowned val- leys. The submergence probably was relatively con- stant and rapid, but not rapid enough to keep wave action from winnowing the residuum developed on the erosion surface. Winnowing separated the clay and small amounts of fine chert fragments and sand from the hill tops and partly filled the intervening valleys. The coarser pieces of chert and dolomite were concen- trated as a lag deposit on the hill slopes and tops. Wave action was not intense enough to round the larger pieces (fig. 83.3) or to materially modify the topog- raphy. REFERENCES Bridge, Josiah, 1955, Disconformity between Lower and Middle Ordovician series at Douglas Lake, Tennessee: Geol. Soc. America Bull., v. 66, p. 725—730. Cooper, B. N., and Prouty, C. E., 1943, Stratigraphy of the Lower Middle Ordovician of Tazewell County, Virginia: Geol. Soc. America Bull., v. 54, p. 819—886. Miller, R. L., and Fuller, J. 0., 1954, Geology and oil resources of the Rose Hill district—the fenster area of the C'umber- land overthrust block—Lee County, Virginia : Virginia Geol. Survey Bull. 71, 283 p. Rogers, John, and Kent, D. R, 1948, Stratigraphic section at Lee Valley, Hawkins County, Tennessee: Tennessee Div. Geol. Bull. 55, 47 p. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES B188 1235 no .823 8.5qu .2388 20953 was hog no ~33qu 3:38 .93 2833a 62: .®@mmo::em. 505.8: and 35.3; EEwaBfisom 5 goon .3836qu noBoA Ha Q8 2: no mfifiuomnoomg 05 we wwEouthfim ”553% cozowm 09:5me E :0 %%fl miom JEZONEOI No.2; m._ rv r >VA L4>L v (VA? b 7 v 7 v A 1 L A < < L 0‘ < v > I. 4 *tn/IM¢V\ 4 1 4 < < 7/\“/ v 4v 7 “that: b A §¢‘I > v v x. »A > L v , p 7/L/4)L VP 4 n. n.“ ;m~su, ZOC. >p v> .V >L A4 $33 $20 ( $3.38 was JmEom stag .SEfiasa 9—08 assofioiflcfi c5 Eswfimwomfiofi :ainfiwooum 8mg 3% San: so manna .333 amine { Etwg m§§ 3.35 :3 3.32m $5 Ho 2338: van .umEom daEEE 832 23813 //§§ \ 777M ZO_._.w:m< 425928 0 \\ \wakcsé Emoz7 o ¢_:>:ww..0 1 ‘LI l 5533 =3m£§£nv o ‘ . zzx/ \ Lllll‘t“!lll!l \ \ \ mmwmmZZm—H 528m; . (J \I ewm3\\ 1—, _$_<0 ooom MGOE NDJm — _ A _ 1. Ba: 09 8 0 mm om 68.8 .r VIV: E v v Vt. I V E ry r, f/ I .08.? / All! x09. ucmE bEmEEonPa .0 :85 In» v\( ft E YEP? é 180.8 T 680 $38 baucwEfiwm uzwcmmEcoz coax—52 c022... S no... 4m>m3 (mm - beam MODE OZ< >mn_n_<> D>O|_ mOEmFZ. GEOLOGY 0F EASTERN UNITED STATES area the total thickness of the Paleozoic rocks is not known. The regional structures’may be assigned to three major subdivisions of the area: (a) a central stable region, (b) a foreland, and (c) the Paleozoic basin (King, 1951). The first coincides roughly with the Interior Low Plateaus; it is bordered on the southeast by a series of structurally high areas, including the Nashville dome, the Cincinnati arch, and the Findlay arch, which are alined along the northwest side of a zone of downwarping. In this stable region the Pa- leozoic rocks are relatively thin except in local basins. The foreland lies east of the zone of downwarping; its structure consists of the broad Allegheny syn- clinorium, which underlies the Appalachian Plateau. The third sub-division is in the Valley and Ridge prov- ince or folded Appalachians, and forms part of the main basin of deposition of the Appalachian geosyn- cline. Little is known about the Precambrian rocks be- neath the Paleozoic sedimentary rocks. Precambrian rocks are exposed at the surface in the Blue Ridge to the east, where intrusion and metamorphism have produced a crystalline complex. Some of the later Precambrian sedimentary rocks, such as those of the Ocoee series and the Talladega series, do not differ greatly from the PaleOZOic'rocks except for their lack of fossils. Since magnetic anomalies are generally caused by igneous and metamorphic rocks and not by unmetamorphosed sedimentary rocks, depths to mag- netic rocks calculated from the magnetic anomalies will not distinguish between an all-Paleozoic section and one that includes both Paleozoic and unmeta- morphosed Precambrian rocks. Our preliminary interpretations are mostly based on nine aeromagnetic profiles extending from a part of the Blue Ridge just north of Asheville, N.C‘., to the Ohio River at Louisville, Ky. The profiles intersect the prevailing structural trend at right angles, and cover a strip about 20 miles wide and 250 miles long across the southern Appalachian Mountains and the part of the plateau region that. adjoins it on the west (fig. 88.1). The individual magnetic anomalies have a pro- nounced northeasterly trend, parallel to the regional tectonic trend of the Appalachian Mountains. Their dominant feature is a group of exceptionally large anomalies which delineate a block of strongly magnetic rock, approximately 100 miles wide, under the Ap— palachian Plateau. The few gravity data available along this same strip (G. P. Woollard, written com- munication, 1960), show a marked resemblence to the 557753 0—60—14 B201 over all magnetic pattern; a positive gravity anomaly, having a maximum Bouguer value of +30 milligals, coincides with the group of large magnetic anomalies. These magnetic and gravity anomalies probably in- dicate a large mass of predominently mafic igneous rock. Both the magnetic and gravity anomalies may be augmented by topography, for the crystalline rocks lie much deeper on both sides of this block (fig. 88.1). But topography alone cannot explain the large magnetic anomalies, for if they are projected even two miles upward, by the method of Henderson and Zietz (1949), they are still much larger than those ob- served in adjacent areas. A lithologic contrast is also indicated by the fact that Where positive gravity anomalies of such amplitude occur over continental rocks, they are usually associated with dense, mafic rocks. Depth to magnetic rock has been estimated from many of the individual magnetic anomalies. The re— sults were generally consistent, and they indicate that in this part of the Appalachian Plateau province there are 8,000 to 10,000 feet of sedimentary rocks (fig. 88.1). These thicknesses are less than those predicted from stratigraphic evidence, but are supported by data from recently drilled wells that reach the basement. How far this block of magnetic rock extends to the north and south is not clearly shown by the other magnetic profiles now available. The group of large anomalies is equally prominent on profiles between Knoxville and Nashville, Tennessee, but it is much less distinct and of smaller amplitude farther south, and is not observed on a profile across Alabama west of Birmingham. It is present, but much subdued, on a profile between Charleston, W. Va., and Lexington, Ky., and is not seen on profiles across southern Ohio. In the Valley and Ridge province, depths to magnetic rocks calculated from anomalies on the nine profiles across southern Kentucky indicate that the thickness of the Paleozoic section averages about. 17,000 feet but increases southeastward (fig. 88.1), as if the basement surface plunged in that direction. West of the Appa- lachian Plateau, over the Cincinnati arch, depths of about 15,000 feet were obtained—depths not only much greater than under the Plateau itself, but much greater than had previously been estimated for Paleozoic rocks of the central stable region. One possible explanation is that the arch is underlain by a great thickness of Pre- cambrian sediments or other nonmagnetic rocks. In eastern Indiana, also, near the crest of the Cincinnati arch, the state-wide aeromagnetic survey revealed broad low-amplitude magnetic anomalies in Jay, Blackford, and Delaware Counties that suggest the presence of relatively nonmagnetic rock. This was confirmed in B202 Jay County where a drill hole penetrated Precambrian dolomite (Henderson and Zietz, 1958, p. 22). In the region northeast of Kentucky northeasterly magnetic trends appear to be indicated by sets of pro- files across Ohio, West Virginia, and Pennsylvania. The magnetic data indicate also a much greater thick- ness of sedimentary rocks in the northern part of the Appalachian Plateau province. The Hope well, 15 miles east of Parkersburg, IV. Va., reached basement at 13,310 feet. As a depth of over 10,000 feet was calcu- lated from magnetic. data obtained just west of Parkers- burg, the deepest part of the basin may lie still farther east. The thickness also increases northeast of Parkers- burg, on the Allegheny Plateau in central Pennsyl- vania, where depths of 19,000 to 22,000 feet were calcu- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES lated from an aeromagnetic survey of Clearfield County (J oesting and others, 1949). REFERENCES Henderson, J. R., Jr., and Zeitz, Isidore, 1958, Interpretation of an aeromagnetic survey of Indiana : U.S. Geol. Survey Prof. Paper 316—B, p. 19—37. Henderson, R. G., and Zeitz, Isidore, 1949. The upward con- tinuation of anomalies in total magnetic intensity fields: Geophysics, v. 14, p. 517—534. Joesting, H. R., Keller, Fred, and King, E. R., 1949, Geologic implications of aeromagnetic survey of Clearfleld-Philips- burg area, central Pennsylvania: Am. Assoc. Petroleum Geologists Bull., v. 33, p. 1747—1766. King, P. B., 1951, The tectonics of Middle North America: Princeton, New Jersey, Princeton University Press, 203 p. ’X 89. RESIDUAL ORIGIN OF THE “PLEISTOCENE” SAND MANTLE IN CENTRAL FLORIDA UPLANDS AND ITS BEARING 0N MARINE TERRACES AND CENOZOIC UPLIFT By Z. S. ALTSCHULER and E. J. YOUNG, Washington, DC. The sedimentology of the quartz sands blanketing the Land Pebble phosphate field in west-central Florida was studied in relation to the lateritic weathering that affected the underlying Pliocene p‘hosphorite (Alt- schuler and others, 1956). The sands are generally 3 to 8 feet thick. They are usually mapped as Pleistocene and are regarded as a succession of transgressive marine terraces, extensive, subparallel along the strike, and separated by scarps. The presumed terraces are mapped on the basis of altitude accordance, thus presupposing the absence of post-depositional differential uplift. Three aspects of the prevailing viewpoint will therefore be critically examined: (a) that the sands are trans- gressive deposits of Pleistocene age; (b) that the blank- eted area is structurally stable; (0) that the sands are differentiated in a pattern, and at altitudes consistent with the terrace hypothesis. The area studied begins about 20 miles east of the Tampa Bay region. It is generally very flat except for a low north-south ridge of karst topography that di— vides the Alafia and Peace River drainages and rises to over 250 feet (figs. 89.1 and 89.2). The central Flor- ida region has many such long north-south ridges, which are the locales of the many sinkhole lakes. Off the ridge the prevailing altitude is 100 to 130 feet. According to Cooke (1945) the Sunderland and Coharie shorelines would be present at 170 feet and 215 feet. In MacNeil’s (1950) modification, the Okefenokee shoreline would be present at 150 feet, but higher ter- races would be absent in this area. The contact between the sand mantle and the under- lying clayey sands of the Pliocene Bone Valley forma- tion is irregular and gradational in detail. Patches of clayey sand occur in the sand mantle above the “con- tact” and nests of eluviated loose quartz sand occur in the clayey sand beneath it. Size analyses and heavy mineral analyses of closely spaced samples through sev- eral vertical sections reveal that the sand blanket is essentially identical to the sand fraction of the sub- jacent Pliocene Bone Valley formation (fig. 89.2). Where observed along extensive plains, the sand mantle thins with corresponding thinning in the zone of lateritically altered clayey sand beneath it. These facts indicate that the quartz sand blanket is mainly an in- soluble residue of the lateritic alteration of the Bone Valley formation, and not a transgressive Pleistocene deposit. Sellards (1915) and Ketner and McGreevey (1959) have also interpreted the sands to be residual. A few channel and dune deposits of Pleistocene to Re— cent age, and a thin veneer of wind-reworked material represent the principal nonresidual deposits. The differentiation of the sand blanket (originally a clayey sand) was studied in terms of the size, sorting, and skewness properties of over 100 samples distributed GEOLOGY OF EASTERN UNITED STATES mainly across 9 townships (fig. 89.1a). Samples were taken from a zone 8 inches to 3 feet below the surface after numerous tests of the entire profile revealed essen- tial identity throughout. However, most of the samples came from close to the surface. When the size data are plotted by sample location and contoured a definite re- lation to present-day topography is revealed. As seen in figure 89.1b, the coarser sands mantle the ridge, and the coarsest deposits form barlike accumulations on the ridge flanks. The finer sands are lowland deposits, flooring the valleys and straddling the lower parts of the ridge. Transitions between fine and coarse deposits are gradual eXcept near the “bars.” Despite this general relation of median size to topography (exhibited also by quartile, skewness, and sorting data) the sand dif- ferentiation is discordant to any of the proposed Pleistocene shorelines and to absolute altitudes. Note that the 160 foot contour outlining the ridge cuts di— rectly across both the coarsest and finest deposits. In other words, the grade size distribution of the body of sand is completely independent of the previously pro- posed Coharie (215 feet), Sunderland (170 feet), or Okefenokee (150 feet) terraces. It reflects the size difl'erentiation of Bone Valley time and suggests that the modern ridge existed as a shallow submerged ridge during Bone Valley time. (The phosphate pebble zone comprising the lower two-thirds of the Bone Valley formation is conglomeratic in the ridge and consid- erably finer in the adjoining low areas.) It is known from a great volume of drilling data that the Bone Valley formation is continuous across the Land Pebble field. From this continuity and the struc— tural relation of the formation to the central north- south ridge (fig. 89.3), it is evident that the formation has been considerably bowed up since deposition. This follows from the fact that a maximum altitude differ- ence of the formation exceeds 100 feet, whereas the formation is generally only about 30 to 40 feet thick, although quite widespread over the region. Thus, up- lift initiated in Pliocene or late pre-Pliocene time resulted in the development of shallow water facies in the Bone Valley formation, yielding a conglomeratic lower zone, and winnowed, barlike deposits in the clayey sands. Lateritic weathering has created a residual sand plain over the region, which preserves the original sediment differentiation. The larger ridges of the present landscape in the Land Pebble field result from the renewal or continuation of uplift rather than sand accumulations of presumed Pleistocene shorelines. The thickening of the deposits in some ridge areas is related to the influence of the uplift in localizing coarse detrital accumulation. The derivation of the linear ridges by uplift dating B203 back to pre-Pliocene offers a key to the pronounced con- centration of simple and compound sinkhole lakes within the narrow uplifts. In contrast to the numer- ous shallow lakes and swamps of the surrounding flat- lands, the lake basins of the ridges are deep, steep walled, often lacking in external drainage, and con- nected to a cavernous underground drainage network (Stewart, 1959). Many ridge basins have a present- day record of renewed, sudden deepening indicated by stepped profiles, soil movements and slanting trees, and dramatic historic accounts. Clusters of round sinkhole lakes occur as well where the ridges extend below pre- sumed terrace altitudes, although MacNeil (1950, p. 101) asserted their general absence below 150 feet, and attributed this supposed absence to filling by the Okefenokee sea. (MacNeil’s paper predates much of the topographic mapping in this region). Studies of the bottom configuration and stratigraphy of some of the lake sediments indicate a record of existence and renewal of collapse dating back, like the ridge uplifts, at least to pre-Pliocene. It seems clear, therefore, that the lakes in the ridges represent a renewal and intensifi- cation of karst development, generated by uplift. Such uplift initiates readjustments in the cavernous drainage network of the basement limestones, reactivating solu- tional downcutting and additional collapse in older sinks, and furthers the generation of new sinks. Sink- holes outside of the ridges are less numerous, generally less youthful, and more frequently plugged or filled. Such collapse is also evident in faulting within the Bone Valley formation in the Lakeland ridge. The linearity and alinement of the ridges, the aline- ment of lake chains and sink holes within them, and our knowledge of major fault systems in peninsular Florida (Vernon, 1951) suggest that the uplift is caused by major faulting in deeper rock. REFERENCES Altschuler, Z. S., Jaffe, E. R., and Cuttitta, Frank, 1956, The aluminum phosphate zone of the Bone Valley formation, Florida, and its uranium deposits: U.S. Geol. Survey Prof. Paper 300, p. 495—504. Cooke, G. W., 1945, Geology of Florida: Florida Geol. Survey Bull. 29. Ketner, K. B., and McGreevey, L. J., 1959, Stratigraphy of the area between Herando and Hardee Counties, Florida: US. leol. Survey Bull. 1074~C, p. 49—124. MacNeil, F. S., 1950, Pleistocene shore lines in Florida and Georgia: US. Geol. Survey Prof. Paper 221—F‘, p. 95—107 [1951]. Sellards, E. H., 1915, The pebble phosphates of Florida: Florida Geol. Survey, 7th Ann. Rept., p. 25—117. Stewart, H. G., 1959, Interim report on the geology and ground- Water resources of northwestern Polk County, Florida: Florida Geol. Survey Information Circ. No. 23. Vernon, R. 0., 1951, Geology of Citrus and Levy Counties, Flor- ida: Florida Geol. Survey Bull. 33. B204 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES \ / M 97¢ V)“ /—«~/ Bradley Junction FIGURE 89.1.—T0pographic map of parts of Hillsborough and Polk Counties, Fla. R.23E R. 24 E. O interva1=20 feet. R.25E Black dots are sample locations. Contour GEOLOGY 0F EASTERN UNITED STATES B205 9 W / a 0-1 m . ,\\ \Qljloég" \ y) \ Fort Meade > C/ FIGURE 89.2.——Median size distribution of sand in surface mantle in parts of Polk and Hillsborough Counties, Fla. Data ob- tained from cumulative frequency curves. Isograde contour interval=0.01 mm. Heavy lines are the 160- and ISO-foot topographic contours. L«flinctlon GEOLOGICAL SURVEY RESEARCH lQGO—SHORT PAPERS IN THE GEOLOGICAL SCIENCES B206 .335 25 38¢ 65% 3.555 9: we use 3 on: 628 05 :58 m??? 95 no 45532“ 65$ 95 no aim—wad 3% 05 mm 05:0 882% 95. .959“ 535m mammfiana SE var—En 05 you 33302 295% 95 M53: 8850 695E .AwmmH $850 was heanowfidv 3398.3 8558:? 3 E33 EEOEEBE :03 053 :85» we 53 A53 wage and waflofiwmofim 6035: @0395 we $28563 MQEQE 3”.de .83 can 358%an 33833“ «c 20528 33.5de an £35 33 NH can ME: 33 95% mm nozoem wmonO .S'A .cnfiwfiom 3 93m mwzfio warm—.593 95 2:5: 653 we £8522 oiwédfiw was 3355'.de 553% . . . . .o/ooooooooooCoo I t 0 0,000 i, . is. . s, . Is, . “a . j, . .344 gal 3.2: 4v z_ 35 9.2: fl 2. mum mtz: .v z_ .uum o m v m N H o o . o n w m V om M ow _.J m m m m m m H 1 W. I. I I ow I I 3 N A M. M m m w a m 3 9 H m m 1 .I l I N d .1.— ..J a a O o 3 m N I. i on I ow I on: GEOLOGY 0F EASTERN Bonny Lake 4 Hana/Ia La/re Q) E A B s C 200' Saddle Creek PauwayE A h c an ———\~ in -_“| 0 I00' Vertical Exaggevulion=60 09 5000 FIGURE 89.4.——Relation of Bone Valley formation to topography face topography. Lower profile is basal Bone Valley contact collapsing. 90. A TROPICAL SEA IN CENTRAL G UNITED STATES B207 200' Norulyn Homeland Peace Valley ”‘9 Vu rn ~ I00 Peace River R22 23 24 25 26E. 27 lean 28 addleCreek auway l 29 r he now orulyn 30 Peace Valley F1 Me de- 3| S. in Land Pebble phosphate field, Florida. Upper profile is sur- Lower profile is not drawn in area of pronounced sinkhole EORGIA IN LATE OLIGOCENE TIME By ESTHER R. APPLIN, Jackson, Miss. The discovery of many well preserved specimens of the foraminiferal genus Miogypcina in samples from a well in Coffee County, Ga., leads to the inference that a sea extended into central Georgia in late Oligocene time (figs. 90.1 and 90.2). The nearest previously known occurrence of the genus was in test well 3 at Port St. Joe, Gulf County, Fla. (Cole, 1938, p. 8—19) ; there is no published record of its having been found in any well or in any outcrop of Oligocene rocks between Gulf County, Fla., and Cofl'ee County, Ga., which are about 200 miles apart (fig. 1). The genus Miogypsina, which lived in warm, clear, shallow seas, has been found, how- ever, in sediments of late Oligocene age in the Panama Canal Zone (Cole, 1957) and in Puerto Rico (Sachs, 1959). The geographic distribution of the genus in the central and eastern Gulf Coast was described by Akers and Drooger (1957). Numerous detailed studies of the effects of environ- mental conditions on various groups of living organisms indicate that closely similar fossil genera probably grew in similar environments. It therefore seems likely that sediments containing the miogypsinids found in Georgia were deposited in one of the marginal over- laps of the sea which oscillated back and forth over the inner Continental Shelf in late Oligocene time, when the waters of the Atlantic Ocean were still warm and equable. The temperature of this sea is believed to have been appreciably lowered in Miocene time by an influx of Arctic waters. Although the Oligocene sea in Georgia, like other seas of Oligocene time, was prob- ably an inner neritic, fluctuating sea, it covered the area long enough to deposit about 600 feet of fine—tex- tured, impure calcium-carbonate sediments, and long enough to allow the periodic. introduction of several microfaunas, which appeared in the same sequence here as in the Panamanian region. The miogypsinid zone is the youngest faunal zone represented in this sequence. Miogypsinids are particularly significant because. of their very limited time—range, and because of their wide geographic distribution in the Gulf of Mexico, Carib- bean, and Mediterranean areas. They are therefore use- ful in helping to solve interregional correlation prob- lems, and since little had been published regarding the Oligocene rocks of the Atlantic Coastal Plain, the dis- covery of a moderately thick body of Oligocene sedi- ments, identified by their containing Myogypsina and other characteristic Oligocene micro-fossils, in eastern Georgia, adds greatly to our knowledge of the Teritiary geology of that region. In a report on the geology of the Coastal Plain in the central Atlantic States, Spangler and Peterson (1950, p. 97) wrote, “Uplift followed Eocene deposition and B208 during Oligocene and part of lower Miocene erosion took place.” According to Spangler (1950, p. 131) “No Oligocene has been identified either in outcrop or from well samples in North Carolina.” Swain (1951, p. 6, 7), however, assigned a questionable Oligocene age to a part of the sections in Hatteras Light well No. 1, and the North Carolina Esso well No. 2, both in North Carolina. Very little information has been published regarding sediments of Oligocene age in the eastern part of the Florida peninsula. Cole (1944, p. 23—24) identified five feet of Oligocene beds in a well in Nassau County, F 1a., and the occurrence of 20 feet of Oligocene rocks penetrated in a well in Duval County is described in an unpublished report of my own. No miogypsinids were found, however, in either of these Florida wells, and none were found in the North Carolina wells. REFERENCES Akers, W. H., and Drooger, C. W., 1957, Miogypsinids, plank- tonic Foraminifera. and Gulf Coast Oligocene-Miocene cor- relations: Am. Assoc. Petroleum Geologists Bull., V. 41, p. 656—678. O 150 MILES L__l—I__J EXPLANATION 0 Previously known occurrences 9‘6 1 I New discovery (Carpenter Oil Co. C. T. Thurman No. 2; a Coffee County, Ga.) FIGURE 90.1.—Geographic distribution of Miogypsinadae in cen- tral and eastern Gulf Coast. (Adapted from Akers and Drooger, 1957, fig. 2). GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES o. 100' First sample Diatomaceous clay 200' Undifferentiated Undifferentiated 300' 400’ 7 .2 'c E 2 M. antillea M. yunten' Miogyps’ma Elphidium lemw’nsis 500' Nearo mlm mecatepecmsis 600' Neorotalia sp. Eulepidina zone Lepidocyclim Widow Operculina did. 7 00’ Oligocene TERTIARY 800’ Coskn'mlimz floridana 1000' Many Bryozoa Lepidocyclim pustulosa 1100' Operculim flo'mldensis Helicalepidim paucisp’ira Asterocyclina sp. \ Eponides jacksonensis Lemldocyclim ocalana Ocala limestone 1200' Glauconitic 1300’ B arnwe l 1 sand Small foraminifera 1400' TD 1430’ Middle '4 EXPLANATION Dolomite Sandy claystone Calcareous Limestone sandstone Sandstone FIGURE 90.2.—Log prepared from samples from the upper part of the Carpenter Oil 00., C. T. Thurman No. 2, Coffee County, Ga. (Specific determinations of “larger Foraminifera” made by W. Storrs Cole.) GEOLOGY OF EASTERN UNITED STATES Cole, W. S., 1938, Port St. Joe Test Wells 3 and 4: Florida Geol. Survey Bull. 16, p. 8—19. 1944, St. Mary’s Oil Corp, Hilliard Turpentine Co. No. 1 well: Florida Geol. Survey Bull. 26, p. 18-100. 1957, Late Oligocene larger Foraminifera from Barro Colorado Island, Panama Canal Zone: Am. Paleontology Bull., v. 37, no. 163, p. 313-338. Sachs, K. N., Jr., 1958, Puerto Rican upper Oligocene larger Foraminifera: Am. Paleontology Bu11., v. 39, no. 183, p. 399—413. B209 Spangler, W. B., 1950, Subsurface geology of Atlantic Coastal Plain of North Carolina: Am. Assoc. Petroleum Geologists Bu11., v. 34, p. 100—132. Spangler, W. 13., and Peterson, J. J., 1950, Geology of Atlantic Coastal Plain of New Jersey, Delaware, Maryland, and Vir- ginia: Am. Assoc. Petroleum Geologists Bu11., v. 34, p. 1~ 100. Swain, F. M., 1951, Ostracoda from wells in North Carolina, Part 1, Cenozoic Ostracods: US. Geol. Survey Prof. Paper 234—A, p. 1—53. 5% 91. SIGNIFICANCE OF CHANGES IN THICKNESS AND LITHOFACIES OF THE SUNNILAND LIMESTONE, COLLIER COUNTY, FLA. By PAUL L. APPLIN, Jackson, Miss. The Sunniland limestone, of Trinity (Comanche) age, was penetrated in about 60 deep test wells in central and southern Florida. This Lower Cretaceous lime- stone contains the reservoir rock of the Sunniland oil field (fig. 91.1) , Florida’s only producing field. In the short-lived (1954—55) Forty Mile Bend field (fig. 91.1), in Dade County, two wells produced a small quantity of oil from the Sunniland limestone; and showings of oil have been observed in the limestone in scattered wildcat best wells in southern Florida. The term “Sunniland,” as applied to a rock unit, was first published by Pressler (1947, p. 1859 and fig. 3), who referred to the “Sunniland zone,” the “Sunniland limestone,” and “the formation.” Although neither Pressler nor later writers defined the unit or described a type section in a published article, common usage has established the name “Sunniland limestone” in the geologic nomenclature of Florida. It is here used to designate a subsurface unit (fig. 91.2) of middle Trin— ity (Comanche) age in southern Florida. The Sunni— land is composed chiefly of limestone, dolomite, and shale. It overlies the so-called “thick anhydrite” or “lower anhydrite” unit, and underlies the so-called “upper anhydrite” unit, both of Trinity age. The Sunniland limestone is about 100 feet thick in several wells in central Florida, but appears to thin northeastward and pinch out on the southwest flank of the Peninsular arch (fig. 91.1). It gradually thick- ens southwestward from the wells in central Florida, and is 200 to 275 feet thick in wells in southern Florida between Punta Gorda on the west coast and Key Largo on the east coast. The Sunniland limestone (fig. 91.2) is 250 to 275 feet thick in wells in and near the Sunni- land field; but about 25 miles southwestward, in the Humble Oil & Refining Co’s Collier Corp. well 1 in Collier County, it is only 69 feet thick (fig. 91.2). \ GEORQI} \___ _,__ FLORIDA 50 0 100 MILES ' FIGURE 91.1.—Outline map of the Florida peninsula showing location of Collier County; 1, Sunniland oil field; 2, Collier Corporation well; 3, Forty Mile Bend oil field; 4, axis of Peninsular arch; 5, Punta Gorda; 6, Miami; 7, Tampa; 8, Key Largo; approximate northern limit of Sunniland lime- stone (A—A’) ; line of cross section, figure 91.2 (B—B’). B210 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S I1 , > | 88 miles 4 Collier Sunniland Southwest flank of Peninsular arch Corp. oil field well B Base of beds of Fredericksburg age B ’ % ? iooo' 0 10 20 MILES L—_l__.—l VERTICAL EXAGGERATION x 83.3 "Upper anhydrite" unit Sunniland limestone unit “WWW 1/ 2/”- $0 . , c“ m .g ,v’.”1;n; I; E ,,/’fi,,wiW’”s l: 5 r” chaff“la '- ‘= ,r’i/wvd 3 “ ,,r E a s EXPLANATION / / / /*;\° \35 Carbonate-evaporite lacies 69‘“, «39*: @ “axe / \0 400/ / o°° *5 (\c Shale facies '<\ r)", (of Sunniland limestone) “fie // 3 7/ § / *5 u 0° ,- oé‘c‘ E Anhydrite "\c 3 E + + + + e Bedded salt L FIGURE 91.2.-——Stratigraphic cross section of beds of Trinity (Comanche) nage penetrated in wells from Collier County to High- lands County, Fla. B—B’ of figure 91.1. The Sunniland limestone is composed in general of dark dense argillaceous limestone and light-tan chalky limestone, interbedded with lenses of fine- to very fine- grained brown dolomite and dark-gray shale. Near the base of the unit in some wells, thin lenses of anhy- drite alternate with lenses of limestone, dolomite, and shale that contain fossils characteristic of the Sunni- land. Several wells also penetrated a few thin lenses of anhydrite near the top of the unit. Stylolites are common in the Sunniland limestone, but these, unlike the stylolites in other units of Comanche age, are gen- erally filled with bituminous residue. The unit con- tains irregularly spaced lenses of bioclastic limestone, some of which are composed of broken shell fragments and others of algal debris. In the Sunniland field the uppermost 36 to 40 feet (Pressler, 1947, p. 1859) of the Sunniland limestone forms the reservoir rock, which consists mainly of interbedded hard, dense to porous limestone and hard, dense dolomite. Cross section shows changes in thickness and lithofacies of the Sunniland limestone. Section along In contrast to the prevailing carbonate lithofacies of the Sunniland limestone, the stratigraphically equiva- lent unit in the Collier Corp. well southwest of the Sunniland field consists chiefly of dark-gray to black thinly laminated calcareous shale that has a strong odor of sulfur and contains free sulfur. in the shale partings. Interbedded with the shale are thin lenses of dark argil- laceous limestone, which is fossiliferous and somewhat stained with oil. The variations in thickness of the Sunniland lime- stone, and the marked changes in lithologic facies indi- cated by samples from wells in Collier County, suggest that during Sunniland time the site of the Sunniland oil field was near the margin of a shelf that bordered the northeastern rim of a rapidly subsiding basin. The changes in thickness and lithofacies of this unit from the Sunniland field southwestward to the Collier Corp. well are analogous, in general, to changes in the Penn- sylvanian rocks of west Texas described by Adams and GEOLOGY OF EASTERN UNITED STATES others (1951) as originating in “unfilled basins * * * surrounded by broad sediment-hoarding epicontinental shelves.” These basins, in which the rate of subsidence was materially greater than the rate of deposition, were termed “starved basins.” The available subsurface data indicate that a starved basin existed in southern Florida during Sunniland time. The greatly thickened “upper anhydrite” unit that overlies the thin Sunniland limestone in the Collier Corp. well apparently filled the basin after the deposi- tion of the Sunniland limestone. Since the Collier Corp. well provides the only evidence of a starved basin B211 environment, data from additional deep test wells are needed to confirm the interpretation, to define the areal extent of the basin, and to determine the relation of the basin to relatively thick sections of the Sunniland lime- stone in other parts of southern Florida. REFERENCES Adams, J. E., Frenzel, H. N., Rhodes, M. L., and Johnson, D. P., 1951, Starved Pennsylvanian Midland basin: Am. Assoc. Petroleum Geologists Bu11., v. 35, p. 2600—2607. Pressler, E. D., 1947, Geology and occurrence of oil in Florida: Am. Assoc. Petroleum Geologists Bull., v. 31, p. 1851—1862. 6% 92. SIGNIFICANCE OF LOESS DEPOSITS ALONG THE OHIO RIVER VALLEY By LOUIS L. RAY, Washington, D.C. A stratigraphic succession of four loess deposits of Quaternary age occurs along the valley of the Ohio River between Louisville, Ky., and its mouth. The old- est, of Kansan age, is exposed in only two outcrops, one near Yankeetown, Ind., and the other near Cairo, Ill. At each of these places the Kansan loess overlies mate- rials that were deeply altered by weathering during the pre-Kansan (Aftonian) interglacial age. The loess de- posited on this weathered surface was, in turn, deeply weathered during the succeeding post-Kansan (Yar- mouth) interglacial age. Overlying the weathered Kansan loess at each outcrop is a sequence of three dis- tinct loess deposits that are well exposed at many points along the Ohio River valley. They are: the Loveland loess, of Illinoian age, on which a characteristic profile of weathering was developed during the Sangamon in— terglacial age, and the distinctive Farmdale and Peorian loesses, both of Wisconsin age. The physical properties of these three loesses indicate remarkable regional uni- formity. The well-recognized relationship of loess to valley trains, from which the loessial silts were derived by wind deflation, leads ineScapably to the conclusion that four valley trains, each of the same age as one of the four loess deposits, were developed within the valley of the Ohio River. The older valley trains, developed by the aggrading river during glacial invasion of its drain- age basin, were in part removed by degradation during succeeding interglacial intervals, and their remnants were buried by later valley trains. The surfaces of only the last two valley trains, of Wisconsin age, are now 5% observable as terrace remnants along the river. The surface of the higher terrace, of Tazewell age, marks the maximum Quaternary alluviation of the valley below Louisville; the lower terrace represents the modified surface of the youngest valley train, of Cary age. The exposure near Cairo, 111., in which all four of the loess deposits crop out, is adjacent to the ancient aban- doned valley of the Ohio River, to which the three older loesses are closely related. As the present courses of both the Mississippi and Ohio Rivers in this area are believed to have been established during the Wisconsin age, the youngest loess, the Peorian, may be in large part more closely related to the valley trains of the Mis- sissippi than to those of the more distant Ohio River. Glacial drifts of Kansan, Illinoian, and Wisconsin ages are recognized along and adjacent to the valley of the Ohio above Louisville, but thus far no drift as- signable to the Farmdale substage of the Wisconsin has been reported, although its existence is implied by the presence of the Farmdale loess. In all loess sequences examined, no loess deposit has been observed between the weathered surface of the Loveland and the base of the overlying Farmdale loess. There is thus no evidence to support the idea, suggested by some geologists, that an ice sheet advanced into the drainage basin of the Ohio during the interval between the deposition of the Loveland and that of the overlying Farmdale loess. If such a glaciation had occurred, a valley train con- temporaneous with it should have been developed by the Ohio River, and a correlative loess deposit should occur in the outcrops adjacent to the river valley. B212 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 93. MAGNETIZATION 0F VOLCANIC ROCKS IN THE LAKE SUPERIOR GEOSYNCLINE The magnetization of the huge mass of Keweenawan lava flows in the Lake Superior geosyncline is of funda- mental importance in the interpretation of magnetic surveys in nearby areas. Unexpected magnetic anomalies were found in the area of the Duluth gabbro of northern Minnesota, and it is difficult to distinguish the magnetic effect of the gabbro and associated rocks from the wide-spread lateral effect produced by the large mass of lava flows. One of the constants needed for calculating the magnitude and extent of this lateral effect is the magnetization of the lava. The purpose of this paper is to explain the magneti- zation by an indirect method, which consists of com- paring the aeromagnetic anomalies found over the lava with the computed anomaly for the rock mass. The dominant factor in the calculations is the configuration of the rock mass. Fortunately the general structure of the lavas of the geosyncline is well known from geolog- ical studies that have been made over the past 75 years, and from recent gravity surveys by Thiel (1956). The lava flows on the northwest limb of the geosyn- cline dip about 10° southeastward, and those on the southeast limb dip 35° to nearly 90° northwestward. The axial part of the structure is occupied by upper Keweenawan sedimentary rocks (fig. 93.1). In the area of the aeromagnetic traverses, the lavas are disrupted on the north limb by the Douglas fault, and on the south limb by a similar fault which was indicated only by the gravity data. The lower part of figure 93.2, which shows the vol— canic rock mass as a large block of simple form, is a reasonable representation of the general structure. The general character of Thiel’s gravity profile, section A—A’, suggests a nearly symmetrical distribution of anomalous density in this mass. Thiel computed a maximum lava thickness of 33,000 feet along the pro- file, assuming densities of 2.90 g per cm3 for the lavas and 2.67 g cm3 for the sedimentary rocks. The areomagnetic profiles B—B’ and 0—0’ show a re.- markable similarity for profiles 10 miles apart. The flight elevation was 1,000 feet above the ground surface, and small anomalies were found over places where the volcanic rocks are near the surface. The anomaly for the structure reaches about 700 gammas over the axial part of the geosyncline, which is an area of nonmagnetic sandstone, arkose, and shale. If these sediments were By GORDON D. BATH, Menlo Park, Calif. replaced by an equal volume of volcanic rock, the magnetic field here would be as great as 1,000 gammas. The theoretical anomalies of figure 93.2 were com- puted for several directions of magnetization, following the general procedure of Press and Ewing (1952). The magnetized rock mass was assumed to have a uni- form cross section and uniform magnetization, and an average magnetic susceptibility of 0.003 cgs. Mooney (Mooney and Bleifuss, 1953) found a mean value of 0.004 cgs for 16 small rock samples measured in the 1s,\ I ’ l-l\\l o "I \\ 4' ’ \~ \\ 92° 91° 0 10 20 30 410 50 MILES l l l l l EXPLANATION ' Sandstone, arkose, and shale Lava flows Duluth gabbro FIGURE 93.1.—Geologic map of part of the Lake Superior geo- syncline, showing locations of gravity profile A—A’, and areo- magnetic profiles B—B’ and (7—0”. GEOLOGY OF EASTERN UNITED STATES —100 _ /"\ 2' 60 / \ 9 f / \ g —40 / \ 2 / \ —20_// \ A’ A \_,’ (D < 2 2 < (D 1500 1000 (I) ‘2‘ 2 500 < (D l l l I l I l l | I t ~~ \~ \~ MTV-7‘ ' —'. ’r’t','¢’,’:“‘4“ 30,000FEET ‘ “,|"|~,|.'i~'\.' ’ r a EXPLANATION / "' \ Observed Bouguer anomaly W Observed magnetic anomaly CALCULATED MAGNETIC ANOMALIES ”.11).... ,.z<2>~.\ ’/(3)\\ Induced magnetization Remanent magnetization Combination of induced and remanent magnetization Sandstone, arkose, and shale Lava flows FIGURE 93.2.—0bserved gravity profile and observed and cal- culated magnetic profiles over an idealized section of the Lake Superior geosyncline. B213 laboratory, and 0.003 cgs for 37 large samples measured at the outcrop site. The direction of magnetization is measured in a vertical plane normal to the axis of the syncline shown in figure 93.1. Assuming that there was only induced magnetization and that the general structure is as shown in figure 93.2, a 1,000-gamma high over the axial part of the syncline would require a magnetization of 0.008 gauss and a magnetic susceptibility of 0.013 cgs. These values are about four times the values found by Mooney. A mag- netic susceptibility of 0.003 cgs gives the small anomaly (1) of figure 93.2. A closer correlation between observed and calculated anomaly is obtained by assuming that the rock mass has a remanent magnetization in addition to its in- duced magnetization. Twenty rock samples of basalt collected by the U.S. Geological Survey from the north limb have an average remanent intensity of 0.01 gauss and a remanent direction normal to the axis of about 40° for flows dipping 20° to the southeast. DuBois (1955) found that samples of lava from the south limb have a similar direction after correcting for the angle of dip. The lavas are not metamorphosed, and the remanent magnetization was probably acquired when the rocks solidified and cooled through the Curie tem- perature. Subsequent change in attitude would there- fore give a corresponding change in direction of mag- netization. This would be expected to differ in the two limbs because of the great difference in the average dip of the flows. The calculated anomaly (2) in figure 93.2 shows the effect of a remanent magnetization of 0.01 gauss for nearly horizontal flows on the north limb, and for flows with an average dip of 60° on the south limb. Calculated profile (3) shows the combined effect of a 0.002—gauss induced magnetization and a 0.01—gauss remanent magnetization. Profile (3) is so similar to observed profiles B—B’ and 0—0’ as to establish the order of magnitude of the magnetization of the large rock mass. The aeromagnetic anomalies produced by the bulk magnetic effect of the Keweenawan lava flows can thus be explained by combining the induced mag- netization with a remanent magnetization of about 0.01 gauss. REFERENCES DuBois, P. M., 1955, Paleomagnetic measurements of the Ke- weenawan : Nature, v. 176, p. 506. Leith, C. K., Lund, R. J ., and Leith, Andrew, 1935, Precambrian rocks of the Lake Superior region, a review of newly dis- covered geologic features, with a revised geologic map: U.S. Geol. Survey Prof. Paper 184. Mooney, H. M., and Bleifuss, Rodney, 1953, Magnetic suscep- tibility measurements in Minnesota, Part II: Analysis of field results: Geophysics, v. 28, no. 2, p. 383—392. B214 Press, Frank, and Ewing, Maurice, 1952, Magnetic anomalies over oceanic structures: Am. Geophys. Union Trans. v. 33, no. 3, p. 349—355. 6% GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Thiel, Edward, 1956, Correlation of gravity anomalies with the Keweenawan geology of Wisconsin and Minnesota: Geol. Soc. America Bull., v. 67, no. 8, p. 1079—1100. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES 94. MEASUREMENTS OF ELECTRICAL PROPERTIES OF ROCKS IN SOUTHEAST MISSOURI By C. J. ZABLOCKI, Denver, Colo. Electrical-property measurements were made of the rocks penetrated by 6 drill holes in southeast Missouri using inhole logging methods. The properties studied included self-potential, resistivity, induced polarization, and magnetic susceptibility. The holes ranged from 2,000 to 3,000 feet in depth and penetrated sedimentary rocks of Late Cambrian age underlain by a Precambrian complex of metavolcanic and intrusive rocks. The Pre- cambrian rocks, about 1,500 feet from the surface, con- tain large amounts of magnetite, and in places, traces of sulfides. The Wide range in electrical properties on all the logs (fig. 94.1) are similar to those of many Precam- brian rocks logged in other areas (Zablocki and Keller, 1957). The self-potential log, which for the most part is a “mirror image” of the resistivity log, shows varia- tions as large as one’half volt. The mechanism of self— potentials developed in hard rocks is not fully under— stood; thus an interpretation is of little value at this time. The Lamotte sandstone of Late Cambrian age has a resistivity of 800 to 1,000 ohm-meters, which corre- sponds to a porosity of about 6 percent. The tOp of the Precambrian, a weathered pink-gray quartz por- phyry, has a slightly lower resistivity, probably be- cause of a higher porosity developed by weathering. The reddish—gray quartz porphyry has a fairly high resistivity of 14,000 ohm-meters because of the low porosity. The magnetic susceptibility of this section is low, indicating that most of any original magnetite has been altered to hematite. (See table 94.1.) The rock below 1,500 feet is mainly reddish to gray quartz monzonite that contains introduced magnetite up to about 15 percent by volume, and sulfides. Vari— ations in the magnetic susceptibility log correspond to a striking degree with the color of the quartz mon- zonite as given in the detailed core log—that is, red- TABLE 94.1.—Average values of the properties measured for the major rock types encountered Resistivity Induced Magnetic Geologic unit Lithology (ohm- polariza- suscepti- meters) tion bility (Percent) ( x 10-0 cgs) Upper Cambrian: X103 X10 3 Elvins group _______ Shale, dolomite ....... 0.300—1.3 3 nil Bonneterre dolo— Dolomite ............. 6. 2 3 nil mite. Lamotte sand- Sandstone _____________ .800—1 3 nil stone. Precambrian: Intrusive rocks _____ Weathered pink-gray .400—1 3 nil quartz porphyry. Reddlsh-gray quartz 14 3 nil porphyry. Red quartz monzo- 14 3 nil nite. Reddish-gray monzo- 1-16 5 5—18 nite. Gray quartz monzo- .0001—16 10 15—40 uite. Dark basic dike _______ 14 ____________ 2 Pink granite __________ 32 l nil Volcanic rocks ..... Andesite porphyry“ __ 37 3 25 Welded agglommerate, 28 3 10-20 Reddish rhyolite por- 14 ............ 10-60 phyry. dish zones have low susceptibility, gray zones have high susceptibility. The magnetic susceptibility log also indicates that most of the zones of low resistivity are caused by higher concentrations of magnetite. The zones of pink granite are identified readily by their high resistivity and low magnetic susceptibility. Zones of abundant sulfide minerals indicated on the log as good traces, have low resistivity owing to the combined presence of the magnetite and sulfides. In sections of minor sul- fide concentration, the resistivity is fairly high. An anomalous zone with resistivity of nearly zero exists between 1,580 and 1,610 feet. A resistivity as low as this almost always indicates that the primary GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES SELF POTENTIAL RESISTIVITY, IN INDUCED DEPTH OHM-METERS POLARIZATION, SCRIPTI N ' — 100 + (4|N. NORMAL) IN PERCENT CORE DE 0 IN FEET _, M.v.|* 1 0 10 20 Lamotte sandstone (Top of the Precambrian) 1350 Weathered pink to gray quartz porphyry 1400 Reddish-gray quartz porphyry, fine hematite, epidote alteration 1450 1500 1550 1600 1650 Reddish-gray to gray quartz mon- zonite with magnetite and minor 1700 amounts of sulfides 22222 1750 EXPLANATIO N ::: 22m ' Specks of sulfides 1800 : E E I % Good traces of sulfides «AW/\(‘Nmfloww WWW MWWWW\ 1850 m Pink granite m 1900 21950 // FIGURE 94.1.—Electric logs from a drill hole in southeast Missouri. B215 MAGNETIC SUSCEPTIBILITY (X10‘6Cgs) 10K 20K 30K 40K B216 mode of conduction is through metallic grains rather than pore waters. The magnetic susceptibility, which is also low in this interval, indicates only that the amount of magnetite is small. Three possible expla- nations for the extremely low resistivity are : 1. A small amount of continuously connected grains of magnetite. 2. The presence of specular hematite (metallic), or 3. An abundant amount of sulfide minerals not indicated on the core log. The Lamotte sandstone has an induced polarization response of about 5 percent. The response of the GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES quartz monzonite is moderately high (about 8 percent) because of the presence of magnetite and sulfides. The pink granite has virtually no response, and the sulfide mineralized zones are indistinguishable from the mag— netite-bearing sections. REFERENCE Zablocki, C. J., and Keller, G. V., 1957, Borehole geophysical logging methods in the Lake Superior district, in Drilling Symposium, 7th annual, exploration drilling: Minnea- polis, Minnesota Univ. Center for Continuation Study, p. 15—24. 95. INTERPRETATION OF AEROMAGNETIC ANOMALIES IN SOUTHEAST MISSOURI By JOHN W. ALLINGHAM, Washington, DC. Work done in cooperation with the Missouri Geological Survey a/ml Water Resources The Ozark uplift, the major structural feature in the Paleozoic rocks of southeastern Missouri, is a gentle arch of low structural relief surrounded by shallow basins and terminated on the north end by the St. Gene- vieve fault zone. Exposed in a part of the uplift is the top of a granite batholith, which was intruded into volcanic rock and encloses small bodies of granophyre and roof pendants of resistant extrusive rock. These rocks are part of the basement on which Paleozoic strata were deposited. The major faults and dominant fracture patterns trend northeast, northwest, and west. Faulting and tilting of the basement rocks, prior to sedimentation, provided sufficient local relief for the development of a maturely dissected landscape of ridges and rounded knobs. The fault zones are believed to be channelways or permeable zones in which mineral-bearing fluids mi- grated upward (Brown, 1958). This migration was partly controlled by the pinchout line of sandy beds around the knobs, and by peripheral fractures de- veloped in the Paleozoic rocks. In early Paleozoic time the dissected, hilly, partly faulted, platformlike borders of the basins of sedimentation formed an archipelago environment, characterized by sand ridges, wave-cut benches, reef structures, and slide breccias. These sedi- mentary features and their controlling topography lo- calized later deposits of lead (James, 1952; Ohle and Brown, 1954; Snyder and Odell, 1958). Much of the region surrounding the mountainous or hilly core of Precambrian rock is characterized by a flat landscape, with flat-lying Cambrian sedimentary carbonate forma- tions that lap up against or bury ridges and knobs of Precambrian rock. As most of the magnetic patterns are caused by Pre- cambrian igneous rocks, interpretation of regional aero- magnetic maps of southeast Missouri permits us to sep- arate areas underlain by granite from those underlain by volcanic rocks, to locate and define some basement ridges and hills, to determine the extent and depth of shallow Paleozoic basins, to outline basin areas under— lain by granite, and to trace faults that may partly con— trol basement topography. Figure 95.1 shows an aeromagnetic map covering an area of buried Precambrian igneous rock. This area can be divided into two parts of different magnetic character: (a) a magnetically flat basin underlain by granite of low susceptibility (shown at right), and (b) a magnetically complex area underlain by older volcanic rocks of high susceptibility that form near-surface fea- tures (shown at left). The magnetic pattern asso- ciated with the border of the basin results mainly from the contrasting magnetic character of granite and vol- canic rock. The map shows several types of anomalies: (a) broad high-amplitude anomalies (as much as 2,500 gammas) partly caused by magnetite-bearing volcanic rock and partly by magnetite—rich iron deposits of eco— nomic importance, such as the one causing the Pea Ridge . anomaly (near point shown as 5,175) ; (b) broad ano- GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES 91 “OO' 38°00’ Plane of observation at 1800 feet 0 10 MILES I_gi__i_1_._i CONTOUR INTERVAL 250 GAMMAS FIGURE 95.1.—Total-intensity aeromagnetic map of part of south- east Missouri. 2 F l-twoodl 500 “L SEA LEVEL rn V Granite I; FIGURE 95.2.—Profile showing correlation of aeromagnetic data with geology. malies of relatively low amplitude (less than 600 gammas), such as the one in the Richwoods area (3,169), due to a roof pendant of volcanic rock in granite; (0) small, low amplitude anomalies (less than 300 gammas), such as the one over a buried knob at Potosi, east of 1,795. The low-amplitude anomalies (less than 150 gammas) are commonly caused by topo- graphic relief, and to a lesser degree by lithologic differences, altered zones at intrusive contacts, or local concentration of magnetic minerals in the Precambrain rocks. The magnitude of magnetic anomalies asso- ciated with knobs of volcanic rock is generally twice as large as that of anomalies over comparable surfaces of granite. The distinctive magnetically flat pattern as— sociated with the granite outlines partly rounded structural basins containing Paleozoic carbonate strata, and shows a distinct gradient sloping southwest. This gradient is interpreted as indicating that the faulted granite blocks are tilted southwestward. The presence of small bodies of granophyre and isolated pendants of volcanic rock complicates the magnetic pattern in areas of relatively low magnetic relief. 557753 0—60—15 B217 Computed ° 6/ m 2000 < Observed Z Z < ‘5 1800 A K=1.5Xlo T3 cgs S Flightline N 1500' 51000- V .V “MI,“ W if 500 - X X X x i<7\’/\\'_\:’|7 "WU/>1 \/ "i‘n<‘/\Q~':'\" )( le , —\\ 0 - Granophyre \lV‘? /\\/ “Granite 7 ('2 "‘ X X X X X 4'/\\/\\Tl\/\\I\_\\<\/\"\£\l\/\/ y’H‘A 'jl’ /\’\l\ / X X X X (\l “K \,l< I/I\ \ A 2400‘ /Computed Inclination of 2200 _ earth sofueld 2 7° Observed Z Z < ‘5 2000 - J AK:3.2>(10 ‘3ch 1800 S Flightline N \’ Iv i\~“,\ l\/\ \/ "(7‘11 \>‘\ /\ I" \G_I/\l\//\\ ~\V’/\ Granite ‘/\’\,l\ ,l /|\ \"\ ./\/ _ |\ \ |\ [\7\’,(’ V/\ VVolcanic rocks < /\< >ALAVA \l \ >4V>4400 E .\I>l\/‘\/\/\‘/‘-\’\7\"/\/\I/ G’laiii‘t‘" 7? is, 10 ‘3 " /\ z 7 \ SEA (’h7l~\L\7'c)(\'. AVA ,h' Nf‘cn i7—'.\).(\ \ .x‘i‘.§\7.g,\\\_\/,\l\,m-A LLEVEL 0 4000 FEET 2—:— FIGURE 95.4.—Magnetic expression of a roof pendant of volcanic rock in granite. of volcanic rocks forming roof pendants have an in- creased magnetite content near the granite contacts, and the same is true of masses of intrusive felsite. Some ridges of volcanic rock, such as the one at Indian Creek, can be represented by prisms of infinite depth (fig. 95.5). The contacts there seems to be nearly verti- cal. The magnetic contribution of the topographic relief of the ridge to the total intensity field is compara- __.— Computed prism + topography AK=5.7 x 10‘3cgs GAM MAS 500 O / Observed Topographic Flightline m \i \ \/\l/\/\\ /\/ VAV (\\/\, \\\ \ ' (1’30), ’<}(/\l/‘\ A V; A v A 7 v Vs §< A lflq) ‘(f’RI‘HC ’ V Trachyte VTX< 94” Granite 3" /\//,\ zl/|\ VF _\,I\/\’/\/’7L\ A4< \/ ’- K—17x10 ‘3: ‘ ’I \'/\/l‘/\:'\ ’/\/‘/V’ \"\\ \l l\ —3 >V (Au), \r\/\/\/ vv K=7.4)<10 V /\’C\,/\‘/( n, >[xv /\< AV7\J I _ ‘ _ ‘,< I\‘\\,<< AV ‘1 IN /\I \\ 1 O 1 2 l l l J MILES Trachyte ranges from K=3.5)<10 ‘3 to K215.4x10'3cgs FIGURE 95.5. Aeromagnetic profile over a ridge of trachyte of high susceptibility near Indian Creek. Susceptibility of trachyte ranges from 3.:")><10‘3 to 15.4X10’3 cgs. Subsurface data supplied by St. Joseph Lead (70. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES tively small. The magnitude of the anomaly indicates a rock of high susceptibility containing an abnormally high concentration of magnetite. Recognition of faulting from the magnetic pattern is important in mineral exploration. Generally the anom- alies observed over fault zones are small. Major fault zones, where magnetic minerals have been altered, can be detected from a series of closed lows on contour maps (fig. 95.1) or by inflections or dips in magnetic profiles (fig. 95.6). /lrondale faults Computed —2200 g 2 LQW ( Observed ——2100 (D S Flightline N \/\ |/\\l)l/I/l\ /\—/\/\\I‘\/ \|/> \l_\\_\/\;/ ‘/‘7" _\/ 1\,/\7\ 13,11 A740 , (3/8 \/ l\\\//RLL\/\ X) \l’\ \ (74) C I>\ d) ‘\l\ \ \l\ /| ’|\ /\/| \b '/\—/\ "’4 /_\/ V\/ I; \\ /\/\, z __ /\\ \ [\/, ,\ 1.14216. X31 ‘ \ , W10 T/\\/ \A’ + 032/ —‘.<> (.1 <2 L‘lL/ Granite 92‘ \l>,l\ [\ll :14 \x‘ \SOO-foot fault zone, ,7 _ ~ / _, \l \C‘ Li \/_‘—\\/\ /_\ :p/l ‘ /\,<\/‘\7|\ 7\'/ >'\~\\’7‘>;\>\/ /\\/‘\‘1\ ’ ’ \ , ’ _ ‘ 1.. _ " (fix/35 “\I‘ >/\\ \<\" \ :l\‘ I (I AK=l-7 x10‘3cgs , \\—" /~ |/\‘I '\l /\"/;\/_\, \ /\,\ (\ ,\\ I “K [\I \/\/\I/ 1/ /\/\ I /\ .\ q _..—- O lMlLE 1 FIGURE 95.6.-—Aer0magnetic profile over the Irondale fault zone. Profiles computed from two-dimensional models for the interpretation of flat-lying flows and pyroclastic rocks show the characteristic edge effects exhibited by the magnetic field associated with this type of geometry. A profile computed from a slab model shows that the Criswell anomaly results mainly from the effect of topo- graphic relief (fig. 95.7). /Computed Observed 42600 -2500 GAMMAS Flightline AV/\ Volcanic flowsv l‘/\< > V b V /\ VVQVVAQ>L54 >\/>/\v < \i 1 0 IMILE 1 i 1 FIGURE 95.7.—Aeromagnetic profile over a volcanic flow near Criswell, Mo. Magnetic relief of low—amplitude aeromagnetic anom— alies can be exaggerated by second-vertical derivative or continuation downward of the total intensity mag- netic field (Henderson and Zietz, 1949; Henderson, 1960) . Contour maps of these intensified fields resemble the basement topography. Use of these fields in areas where anomalies are caused by irregularities on the buried Precambrian surface can eliminate the need for GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES some conventional ground magnetic surveys. As buried hills of granite and volcanic rock control the sedimen- tary and structural environment of some lead deposits, the total-intensity aeromagnetic field over one knob of rhyolite was continued downward to a level correspond— ing to the surface of the basement rocks and correlated with second-vertical derivative maps of these fields (fig. 95.8). The zero contour of the second-derivative of the ob— served field corresponds to the outer extremities of mine EXPLANATION [’9‘ -—B—E— Observed field 1900 ft / —— —e— —e— — I Field continued downward to —100 ft .. ...e... ..e..... Secondwertical derivative of data / \ — - —a.— — —A— - — \ Second-vertical derivative I \ of continued field , \ — 2700 l l l l l l l - 2600 U) E _ -2500 2 <1: (5 «1300— E ,_ E o D Z w m — 2400 E Z —' 3 l— ,_ <0 E 2200s 5 n: 3 2 g (I D m — 2300 4 0 <1 ,,/ L3 E 33 '° “- 8 2100- 0’ z < 0 * 2200 (”W/E: 2100 Bonneterre dolomite 0 1000 FEET %—_l ELEVATION Rhyolite ;_ ' y porphyry \‘: _ .“/\< [\ V [\\-' .. "-/>V29,000 to >37,000 years (Ruhe and Scholtes, 1959). It is then probably older than the Farmdale loess of Illinois, dated as between 22,900i900 years to 26,100t600 years (Frye and VVillman, 1960). The younger, or Pinedale glaciation, consists of three advances separated by minor recessions. These are cor- related with the advances of classical Wisconsin glacia- tion of Illinois. The till of the early advance merges with an equivalent continental till about 9 miles north- east of the mountain front. Farther out, it is either overlain by that till or lies on uplands above deposits of it on the valley floors. The outer limit of this continen- tal drift, called “Outer Continental drift” by Horberg (1954) has been traced like the continental drift of Bull Lake age as far south as Choteau, Mont. Northwest of Cutbank it lies immediately back of that older drift border, but to the south is 10 to 15 miles from it. End moraines of the intermediate advance of Pine— dale glaciation lie at the mouths of canyons along the B224 mountain front, and are correlated with the continental drift of the “Lethbridge moraine” and the “Lower till” of Horberg (1952). End moraines of the last advance of Pinedale glaciation lie 3 t0 7 miles upstream from those of the intermediate advance, and are tentatively corre- lated with the Valders advance of the continental ice. Moraines of two small postaltithermal advances of the ice in the cirques are correlated with those of the Temple Lake and historic advances of the ice in the Wind River Mountains of Wyoming. 5? GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCES Frye, J. C., and Willman, H. B., 1960, Classification of the Wis- consinian stage in the Lake Michigan glacial lobe: Illinois State Geol. Survey Circ. 285, 16 p. Horberg, Leland, 1952, Pleistocene drift sheets in the Lethbridge region, Alberta, Canada: Jour. Geology, v. 60, p. 303-330. 1954, Rocky Mountain and continental Pleistocene de- posits in the Waterton region, Alberta, Canada: Geol. Soc. America Bull., v. 65, p. 1093—1150. Ruhe, R. V., and Scholtes, W. H., 1959, Important elements in the classification of the Wisconsin glacial stage: J our. Geology, v. 67, p. 585-593. 99. THE LATE QUATERNARY AGE OF OBSIDIAN-RHYOLITE FLOWS IN THE WESTERN PART OF YELLOWSTONE NATIONAL PARK, WYOMING By GERALD M. RICHMOND and WARREN HAMILTON, Denver, Colo. While participating in a reconnaissance study of the Hebgen Lake earthquake, we found that some of the obsidian-rhyolite flows of the Madison Plateau are of late Quaternary age. Near the headwaters of the ‘ Moraines of'tiie :;. Bull Lake glaciation I:-ObSldlan sand:-. Older flows . . glaCIatIon Obsidian- rhyolite flow N 1 MILE L___l 8000’ 7500' ObSIdIan-rhyolite flow 7000, ’,____ Older flows overlain locally by till and erratics of Bull Lake Older flows wTerminal moraine of Pinedale glaciation Alluvium : Upper limit of ; Pinedale glaciation Obsidian-rhyolite '- a flow .. . - ‘ Lateral /' \ col/”HI,“ l m‘“ H‘ “ \lce- scoured margin of obsidian- moraine of " . m’l‘" .'./’/r, rhyolite flow . / Pinedale glaciation" . . : ”at Lateral moraine of Pinedale glaciation _l Terminal moraine of Pinedale _ glaciation _..—.—_~___<:,_“_ ______ Obsidian Till of Bull Lake glaciation ‘ _ sand 3 Older flows 3’ FIGURE 99.1.——Sketch map and sections showing relations of obsidian-rhyolite flow to moraines of the Bull Lake and Pinedale glaciations. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES South Fork of the Madison River one of these flows, about 500 feet thick, overlaps large lateral moraines of the late Quaternary Bull Lake glaciation (fig. 99.1). A layer of obsidian sand 40 to 100 feet thick, derived from the lava flow, overlies glacial lake beds retained by the moraines. The moraines, the obsidian sand, and a loess capping the flow are all mantled with a similar maturely developed zonal soil. The outermost terminal moraine of the subsequent Pinedale glaciation overlaps the obsidian sand at the mouth of the Madison Canyon east of West Yellow— stone, and the lateral moraines of the Pinedale glacia— 100. 3225 tion overlap the flow west of the Lower Geyser Basin in Yellowstone National Park. The deposits of the Pinedale glaciation bear a submature zonal soil, which commonly contains a layer of volcanic ash and is quite distinct from the mature zonal soil on deposits of the Bull Lake glaciation. The obsidian—rhyolite flow must therefore have been extruded between the Bull Lake and the Pinedale glaciations and before the period in which post- Bull Lake—pre-Pinedale soil formation reached a maximum. 5% DISTRIBUTION OF CORALS IN THE MADISON GROUP AND CORRELATIVE STRATA IN MONTANA, WESTERN WYOMING, AND NORTHEASTERN UTAH By WILLIAM J. SANDO, Washington, DC. Preliminary studies of corals collected from sections of the Madison group and correlative rocks of Missis— sippian age in the northern Cordilleran region (fig. 100.1) suggest the following tentative zonation (figs. 100.2, 100.3). Zone A comprises the lower 10 to 50 feet of the Lodge- pole limestone and equivalent beds in the Harman lime- stone. It is characterized by a few species of small corals, including “Metfiophyllum” cf. “M.” demimati- vum Easton, Oyazthawom'a cf. 0. tantilla (Miller), and species of Pemz‘a?, Zaph’rentites, and “Ampleams.” Zone B includes beds in the lower part of the Lodge- pole limestone, and equivalent beds in the Hannan lime- stone, that are characterized by a few amplexoid corals and Oyathawonia. Zone C includes the middle and upper parts of the Lodgepole limestone, the lower parts of the Mission Canyon, Brazer, and Charles formations, and equiva- lent strata in the middle and upper parts of the Harman limestone. This zone contains a distinctive coral as- semblage characterized by species of Homalopyllites, Vesiculophyllum, and Zaphrentites. Its lower part, designated Cl, also contains species of Rylstonia, Miche- limla, Oleistopom, and Lithostrotiomlla. In its up- per part, designated C2, Lithostrotionella and Bystonia are rare and Michelinia and Oleistopom are absent. The boundary between C1 and C2 cannot be precisely estab- lished on present information, but it is now placed arbitrarily at the top of the Lodgepole limestone. The C1 index corals occur at various levels below this boundary but not above it. More detailed work, par- 112° 110° 108° 106° . .7 6 M o N T A N A , 8 46° .5 .4 —- __— V‘J\\:l_ 44° 1' IDAH0:.2 w Y o M I N G ! 42°—- P UTAH-'1 FIGURE 100.1.—Index map showing location of sections studied. 1. Type section of Brazer dolomite, Brazer Canyon, Rich County, Utah. 2. Southeast of Haystack Peak along north tributary of Straw— berry Creek, Lincoln County, Wyo. Darby Canyon, Teton County, Wyo. Baldy Mountain, Madison County, Mont. Type section of Madison group, north of Logan, Gallatin County, Mont. Gibson Reservoir on Sun River, Teton County, Mont. Type section of Lodgepole limestone, along Lodgepole Creek, Blaine County, Mont. Shell Oil Co. Pine Unit No. 1 well, Wlbaux County, Mont. 9" T‘?’ P‘P?’ B226 GEOLOGICAL AMSDEN rFlEBEOrO FORMATION BIG SNOW WELLS GROUP \ TION —1600 FORMA u, \ SAW'roonrjJ / z \FORMATIO .v 0 ‘ l— ” 3 \. / .5 E —1400 m ' w —' .: \ / E 2 ,., 3 9 -1200 .4 AMSDEN ZONE D ........... m -. FORMATION .w' ....... Lu .3} / Z ......... 2 '— / '2 z o 2 n: E m o > m _, —' > Z < < z < w —1ooo > 2 < o z _ 3 Q o . 3 0?,.- z 5 ._ '-..u.l “1'. ' o :7) 3 g 2 3 _. Z " 80° 2 z ZONE c2 2 g N ................................. 7 5 s z 0 m ._ 0 Z Z 6‘” E a 5 2 2 2 O m _ u) 0 ,,_ — w z m 2 (g u.» :3 < “4 2 E m I z 4 2 -‘ 3 -400 2 \ 1 MJ ..... 3 § _ a ............... £5 8 ZONE cl 8 ............. ‘9 “J Lu “J ......... 8 § m .8 " a _ 200 _. ............... Lu. -. é 3 g 9 g ". ZONE 8 8 {ONE A S ............................. .e 20”“ .......... —o ....... J O 50 100 MlLES L.__L FIGURE 100.2.—S,tratigraphic sections from northeastern Utah to northwestern Montana, showing distribution of coral zones in formations of the Madison group and their equivalents. ticularly on the distribution of species, may provide a more satisfactory basis for subdivision of Zone C. Zone D includes the upper parts Of the Brazer, Mis- sion Canyon, and Charles formations, and equivalent strata in the upper part of the Harman limestone. This zone is characterized by species of Vesiculophyllum, Faberophyllwm, and fasciculate lithostrotionoids, chiefly belonging to Siphonodendron and Diphyphgl- lwm. A distinctive new horn coral genus also occurs in the upper part of the Brazer and upper part of the Harman. Coral genera other than those mentioned occur in all the zones. Many of these are rare, and details of the taxonomy of some are yet to be worked out. Species of Syringopom are abundant throughout the sequence, but these are not considered important at present be— cause of the difficulty of recognizing stratigraphically useful species. Correlations cannot be made with equal confidence between all the sections studied, because several deposi- tional provinces appear to be represented. As corals are rather sensitive to environmental changes, diflerent lithic facies tend to contain different assemblages of corals. The scarcity of fossils in the Brazer may be SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES AMSDEN FEET V 1800 FORMATION —1eoo \ E \ BIG SNOWY 71400 '9 ZONE D \ GROUP fl E \ E A _ E ' > / g —1200 E ........... \ / m 5 IIIIIIIIIII , / ZONE D u. g . 7 ........... ‘11 — _ ........... m -1000 Q \ / E 2 7/ , ,x , 9a ZONE c2 \ ELLIS / H7777 GROUP/ 5 —800 2‘“ < z 22% 0° 900 ZS w25 3% 2 w _ #600 ‘2 Egg £4 8 _l m LIJ LU Z 3 ZONE Cl uZJ E —400 .3 g a O L” g E E J g .............. 4 a ............. m —200 9 """"""""" 5 g """ & ........ 8 ZONE B 8 ......................... O ZONE A 9 ............... T.’ ................. 7 -0 J 7 8 0 5,0 190 MILES |_ __L , FIGURE 100.3.—Stratigraphic sections from southwestern Mon- tana to northeastern Montana, showing distribution Of coral zones in the Madison group. related to the predominance of dolomite in that unit. The lower part of the Brazer contains the critical ele- ments of the C2 fauna, whereas only one, or possibly two, of the corals of Zone D have been found in the upper part, most of which is unfossiliferous, and whose late Mission Canyon age is therefore not well estab- lished. The coral assemblages of sections 2, 3, 4, and 5 are very similar, except that the Zone D assemblage is poorly represented in sections 3 and 5. The five zones can all be identified in the Hannan limestone, but. the positions of most of their boundaries are uncertain. The Hannan may be more similar in faunal content and lithic succession to the Mississippian sequence in the Canadian Rockies than it is to the sections south of it. In each of the western sections (1 through 6), the thicknesses of all the zones are roughly proportional to the total thicknesses of the formations. Thickening and thinning thus appear to depend mainly on varying rates of deposition. Erosion at the top of the Mission Canyon limestone and its equivalents has not appreci- ably altered the general pattern of thickness variation in these sections. In central Montana (section 7), how- ever, beds included in Zone D and part of Zone C have been removed by post-Mission Canyon erosion. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES In central and eastern Montana (sections 7 and 8), the Zone A assemblage was not identified, and rocks containing the Zone B assemblage appear to thin east— ward. This suggests that Zone A may not be present in these sections. Zone A and part of Zone B may be represented in the Little Chief Canyon member of the Lodgepole limestone of central Montana and the Bak— ken formation of the \Villiston basin. Zones Cl, C2, and D are readily identified in cores drilled in the Williston basin (section 8). Cores from the Charles format-ion contain C2 and D assemblages, suggesting correlation with the upper part of the Mission Canyon as exposed at the surface. Coral faunas of the Madison group and its correla- tives do not provide a satisfactory basis for detailed correlation with the type Mississip-pian of the Mid- B227 Continent region, because their sensitivity to deposi- tional conditions appears to have given rise to different assemblages and distribution patterns in rocks be- lieved to be nearly contemporaneous. Preliminary studies by J. T. Dutro, Jr., of brachiopods associated with the coral assemblages suggests the following ten- tative correlations with the type Mississippian: Zone A appears to be entirely of Kinderhook age. Beds equivalent to part of Kinderhook may be present in Zone B, and they possibly extend into Cl. Osage equivalents are found in Cl, CZ, and D, but part of Zone D is probably of Meramec age. These correlations are confirmed, in general, by the distribution patterns of coral genera common to the Madison and the type Mis- sissippian sequences. 6% 101. MIDDLE TERTIARY UNCONFORMITY IN SOUTHWESTERN MONTANA By G. D. ROBINSON, Denver, Colo. Since the earliest paleontologic work by Douglass (1899 and several later papers), geologists have sus- pected that there was a regional middle Tertiary uncon- formity in the Cenozoic basins of southwestern Montana (see fig. 101.1). In several basins, Douglass found many early Oligocene and many late Miocene vertebrates but few of intervening age, and this has been the experience of all later workers. The existence of an unconformity thus became increasingly certain, and the nature and duration of the unconformity are gradually being demonstrated by detailed mapping combined with intensive fossil collecting. In the south- ern part of the Townsend basin, the unconformity has been mapped as an erosional one separating lower Oligocene from upper Miocene or lower Pliocene strata. (For southeastern part, see H. D. Klemme, unpublished Ph. D. thesis, Princeton University, 1949; and for southwestern part, see Freeman, Ruppel, and Klepper, 1958) Recent detailed mapping of the Toston 15-minute quadrangle (see fig. 101.1) has shown that in the south eastern part of the Townsend basin middle as well as lower Oligocene rocks are preserved beneaththe uncon— formity; inconclusive structural evidence suggests that during the hiatus these rocks were probably folded and faulted as well as deeply eroded. The unconformity has been traced southward throughout the Clarkston WYOMING o Cenozoic basins stippled. Townsend, Clarkston, and Three Forks basins FIGURE 101.1.—Index map of southwestern Montana. diagonally ruled. Toston quadrangle heavily outlined. basin, where the youngest rocks beneath it are lower Oligocene; in this basin also, the existence of an angular unconformity is probable but not certain. Reconnais- sance observations make it seem likely that the hiatus B228 can be mapped northward at least throughout the Townsend basin and southward throughout the Three Forks basin; these basins contain an area of more than 1,500 square miles of Tertiary rocks. The present flood plain of the Missouri River and that of its main headwater tributary, the Madison, are remarkably close to the trace of the imconformity. In the three basins studied, most of the Tertiary rocks exposed west of these rivers are Oligocene or older; most of those east of the rivers are Miocene or younger. These basins were being eroded by through-flowing streams during most of late Oligocene to middle Mio- cene time. In some places, however, a little alluvium was deposited and is still partly preserved. The Tertiary rocks above and below the unconform- ity have much in commonwthey are rich in contempo- raneous volcanic ash, and are of complex origin, having been deposited in streams, lakes, and bolsons———yet they show persistent differences, apparent in the field, that make it possible to distinguish the older assemblage from the younger. The most useful of these involves waterlaid glass shards. In the older rocks most of them are so much devitrified as to appear cloudy and dull in hand specimens; in the younger rocks almost all are notably clear and bright. But this criterion applies only to rocks deposited in water, for unaltered glass is abundant in much of the Tertiary tuff deposited on dry land irrespective of age. Tuffaceous rocks that con— tain intimately mixed rounded grains of terrigenous sand must have been deposited in water, and in practice the test is used only on visibly polygenetic sandstone, thin beds of which‘are common both in the rocks above the hiatus and in those below. Why the shards in the older and younger waterlaid beds are so differently altered is unknown. The older glass is not more altered simply because it is older or because it was deeply weathered during the erosion interval, for if either age or weathering were decisive the glass of the older tufl’s deposited on dry land would be as much altered as that in water laid tuffsz Unde- ciphered differences in depositional or diagenetic environment are probably responsible. Certain differences between pre- and post-hiatus conglomerates are also helpful. Conglomerate is a minor component of the Oligocene section, even near basin edges. The few beds are usually thin, the stones are rarely larger than small cobbles, and consolidation is generally only poor to fair. In the Miocene and GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S Pliocene formations, on the other hand, conglomerate is a major constituent. Here, moreover, the beds are very thick, cobble and boulder sizes are abundant, and the conglomerates are firmly cemented with calcite and clay. These differences reflect rather low relief and equable climate in early Oligocene time, as opposed to high relief and semiarid climate in late Miocene and early Pliocene time. It must be emphasized, however, that the conglom- erates are helpful only in distinguishing Oligocene from younger strata. Eocene rocks in the Three Forks basin (Robinson and others, 1957) and Eocene and Paleocene rocks in other basins of southwestern Mon- tana (Peale, 1896; Lowell and Klepper, 1953) also include much coarse conglomerate, in thick beds, with calcite cement. The validity of the contacts mapped with the aid of these crude lithologic guides is confirmed by paleon- tologic evidence. Nearly every sizable body of rocks in southeastern Townsend Valley and in Clarkston Val- ley that was assigned to the early Tertiary 0n lithologic grounds has yielded diagnostic middle Oligocene or older vertebrate fossils; and almost every large mass mapped as late Tertiary has yielded diagnostic Miocene or younger fossils. (I am indebted to Edward Lewis for identifying the collections, some of which were made by others, notably H. Morton Sperry of Townsend.) It remains for future study to delimit the areas within which the unconformity can be confidently mapped on lithologic grounds, even where diagnostic fossils may be lacking. REFERENCES Douglass, Earl, 1899, The Neocene lake beds of western Mon- tana and descriptions of some new vertebrates from the Loup Fork: Master’s thesis, Montana University (pub- lished by the University). Freeman, V. L., Ruppel, E. T., and Klepper, M. R., 1958, Geology of part of the Townsend Valley, Broadwater and Jefierson Counties, Montana: U.S. Geol. Survey Bull. 1042—N, p. 481—556. Lowell, W.R., and Klepper, M.R., 1953, Beaverhead formation, a Laramide deposit in Beaverhead County, Montana: Geol. Soc. America Bull., v. 64, n0. 2, p. 235—243. Peale, A. 0., 1896, Description of the Three Forks sheet, Mon- tana: U.S. Geol. Survey, Geol. Atlas Folio 24. Robinson, G. D., Lewis, Edward, and Taylor, D. W., 1957, Eocene continental deposits in Three Forks Basin, Mont. (abs) : Geol. Soc. America Bull., v. 68, no. 12, pt. 2, p. 1786. ’X GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES 102. B229 CONFIGURATION OF THE 10N PLUTON, THREE FORKS, MONTANA By ISIDORE ZIETZ, Washington, DC. In the summer of 1959, the US. Geological Survey made a detailed aeromagnetic survey in the Three Forks area, Montana, to determine the approximate shape of the ION pluton (named for US. Highway ION, which crosses it.) and its relation to the Lombard thrust, which crops out about a mile to the east. The pluton has been described by G. D. Robinson of the U.S. Geological Survey in a report now in prepara- tion, as an igneous mass made up of a wide variety of rock types but consisting chiefly of light—colored pink- ish quartz monzonite. It intrudes Paleozoic and younger sedimentary rocks and has a surface extent of more than three miles east-west and more than a mile north-south (fig. 102.1). 111°37’ 111°35' ) I I é’ 46'00’ ‘ 45°57’— EXPLANATION Exposed pluton -.-.. Estimated lower contact of pluton 1 0 1MILE L~L___L_J_%._I CONTOUR INTERVAL 100 GAMMAS FLOWN 800 FEET ABOVE GROUND FIGURE 102.1.—-Aer0magnetic map of Three Forks area, Montana. The aeromagnetic survey, which was made at Robin- son’s request, was flown north-south at an elevation of approximately 800 feet above the ground and with a flight separation of a quarter of a mile. The upper surface of the pluton is well defined by the magnetic contours, and is interpreted to have the boundary indi- cated by the dashed line in figure 102.1. The contours also suggest the presence of two spurs at the north edge of the pluton. To the north, west, and southwest of the pluton, the gradients are sharp and the amplitude large, indicating that. the pluton extends downward for sev- eral thousand feet. To the southeast, the gradient is flatter and the amplitude smaller, indicating that the pluton is buried beneath a sedimentary cover and thins to the southeast. In other parts of the area, especially to the north, the aeromagnetic data imply local thin- ning, as is indicated on the map. 1900- /"\ %\ / g; I a I m\ 1700— I 0 <3, I 7~\ m (I) \\\ 6‘ < I 0 an E I ' \ f“ E: I u>\ 0 0 I \ l \ 1500- I \ l \ ll \\\ 1300 (I) / I I I J A25“ 5 10 15 20 fiflz— PLUTON THOUSANDS OF FEET 833— E 4 1900* 1700- (I) < E 2 < w 1500- 1300 J A 5 10 15 \\\ 20 THOUSANDS OF FEET TO INFINITY t THOUSANDS OF FEET \ a w M ... FIGURE 102.2.——Magnetic profiles across the ION pluton, Three Forks area, Montana. B230 To determine the approximate shape of the pluton, and especially its vertical extent, a magnetic profile, A—B, at right angles to the main magnetic trend, was analyzed (figs. 102.1 and 102.2). The magnetic anoma- lies of two possible geologic cross sections were then computed (fig. 102.2) and compared with the observed profile A—B. On both cross sections the upper surface dips to the southeast at an angle of 30°, corresponding to the dip of the overlying sedimentary rocks. In the upper figure the pluton is assumed to have a bottom 3,800 feet below the surface, and in the lower figure it is assumed to extend indefinitely downward. At the northwest edge there is good agreement for both config- urations. At the southeast, however, the fit for the GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES bottomed pluton is much better than for the other. The magnetic susceptibilities calculated for both masses, K=0.003 cgs and K=0.002 cgs, are reasonable for quartz monzonite. Because of the ambiguity inherent in magnetic cal- culations, there are a large number of masses with dif- ferent shapes that could produce reasonable fits to the observed magnetic profile, and for this reason the avail- able evidence for the configuration of the pluton is not conclusive. The calculations strongly suggest, how- ever, that the pluton is bottomed at a depth of several thousand feet. This would imply that the thrusting may be younger than the intrusive and that the 10N pluton may be cut off by the Lombard thrust. 6% 103. METAMORPHISM AND THRUST FAULTING IN THE RIGGINS QUADRANGLE, IDAHO By WARREN HAMILTON, Denver, Colo. In the Riggins quadrangle, Idaho, metamorphosed volcanic rocks of the andesite-keratophyre kindred, and associated metasedimentary rocks dominantly of volcanic origin, increase in metamorphic grade east— ward toward a broad complex of intrusive and meta- morphic gneisses marginal to the Idaho batholith of Cretaceous age. The rocks to be considered here (which have not yet been given a geologic name) pass eastward from, for example, greenstone through green phyllite, greenschist, and hornblende schist to amphi- bolite. Isograds have been drawn through the western- most points at which each of the following minerals appears: aluminian prochlorite, biotite, clinozoisite, garnet, oligoclase, andesine, and, in calc-silicate rocks only, clinopyroxene (fig. 103.1). Black hornblende ap- pears first near the garnet isograd. Neither staurolite, kyanite, nor sillimanite is anywhere present. Although the upper grade limit of ferroan prochlor— ite is at about the garnet. isograd, that of aluminian prochlorite is near the andesine isograd. Aluminian prochlorite, muscovite, garnet, and oligoclase occur in apparently equilibrium assemblages in some specimens. In the western part of the quadrangle, a postmeta— morphic, west-directed overthrust fault trending north- northeast has pushed the rocks here considered over the low-grade rocks of the Seven Devils volcanics and associated formations (Permian and Triassic) on the west. Within the quadrangle, all the isograds in the upper plate from aluminian prochlorite to andesine are truncated by the fault and brought against rocks of the ferroan-prochlorite zone in the lower plate (fig. 103.1). In the northern part of the quadrangle, the fault is hidden by Miocene basalt. Where it emerges from the basalt cover the fault is folded, and a few miles farther north the upper plate is cut, off by a sheet of intrusive quartz diorite gneiss. Above this overt-hrust is another, subparallel to it but converging with it southward; the average distance between the two is about a mile (fig. 103.1). Amphi— bolite and trondhjemite were shoved westward over middle-grade schists on this upper fault, which is marked by a thick zone of phyllonites and flaser gneisses. The total displacement on the two thrust faults is about 10 miles. Toward the north the upper fault dies out and a greater proportion of the total dis— placement is taken up by the lower one. Thrusting east of the Idaho batholith is mostly di- rected eastward. If the west-directed thrust faulting west of the batholith is of regional extent, tectonic sym- metry on a grand scale exists that may be genetically related to the batholith. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B231 116°30' 116.10, . , 116°20’ 45 30 g I § 0 ¢ 0 I e O 0 g C O 9 Columbia 0 ‘ 45°20'— Rocks of ferroan prochlorite zone EXPLANATION Lines show western limits of minerals in the metamorphic rocks -— L — Aluminian prochlorite — B — Biotite — C — Clinozoisite — G — Garnet -— O — Oligoclase ——- A — Andesine — P— Clinopyroxene In cats—silicate rocks only A—k.‘ Thrust fault Teeth an upper plate 1") MILES FIGURE 103.1.—Thrust faults and isograds in metamorphic rocks of northwest part of Riggins quadrangle, Idaho. 5% B232 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 104. DIVERSE INTERFINGERING CARBONIFEROUS STRATA IN THE MACKAY QUADRANGLE, IDAHO By CLYDE P. Ross, Denver, Colo. Throughout the limited area in central Idaho, north of the Snake River Plain, in which Paleozoic sedi- mentary rocks occur, those rocks vary in composition and stratigraphic relations within short distances. This is particularly true of the post-Devonian part of the sequence. Exposures of late Paleozoic strata in the Mackay quadrangle furnish essential clues to the rea— sons for the stratigraphic variation in the surrounding region. The region contains the Milligen formation (Missis- sippian and Devonian?), the Brazer limestone (mainly Mississippian), and the Wood River forma- tion (Pennsylvanian and Permian). The Milligen for— mation in its type locality (Umpleby and others, 1930, p. 25—29), which is west of the Mackay quadrangle, is very heterogeneous, but its distinguishing feature is the presence of abundant black, carbonaceous argillite. The formation contains some graphitic coal. The Mil- ligen formation may be over 7,000 feet thick (Kiils- gaard, 1950). In this locality the formation was deposited close to the western shore of the Paleozoic sea, perhaps mainly in estuaries and other relatively stagnant bodies of water. It contains hardly any diag— nostic fossils, but its relations to other formations indi- cate that the formation may represent all of Missis- sippian time and may possibly range downward into the Devonian. Rocks assigned to the Milligen, largely because of their carbon content, have been mapped over a Wide region in the southeastern part of central Idaho. In the mountain range east and northeast of the princi- pal exposures of the Carboniferous rocks of the Mackay quadrangle the Milligen formation attains a maximum thickness of at least 1,000 feet and is clearly of Early Mississippian age, for it is underlain by fossiliferous rocks of very late Devonian age and overlain by fossil- iferous limestone of Late Mississippian age that be- longs to the Brazer limestone as that term is applied locally. The Wood River formation where exposed west of the Mackay quadrangle (Umpleby, Westgate, and Ross, 1930, p. 24—34) is lithologically diverse, but is character- ized by abundant sandy beds and, especially near the base, by abundant conglomerate, part of it coarse and in thick layers. The formation must have been de— posited close to the shore; the conglomerate in it may be at least in part of fluviatile origin. The Wood River formation has been regarded as of Pennsylvanian age (Umpleby, Westgate, and Ross, 1930, p. 32—34), but microfossils (Bostwick, 1955), discovered since the for- mation was defined, have shown that large thicknesses of beds assigned to it by Bostwick are of Permian age. These beds have nowhere been separately mapped. The Wood River formation west of the Mackay quadrangle is probably at least 8,000 feet thick, and may be much thicker if the beds containing Permian fossils are in- cluded in it. Beds definitely assignable to the Wood River formation are not known to occur east of the western part of the Mackay quadrangle, but the name has been used tentatively as far east as the Montana boundary (Scholten, 1957a, p. 165; Scholten, 1957b). Rocks commonly called Brazer limestone are wide— spread from an interrupted zone trending nearly north through the middle of the Mackay quadrangle well to the north and eastward into Montana, and of large but variable thickness. In the Mackay quadrangle itself their thickness exceeds 8,000 feet. They consist mainly of limestone but include some quartzite and conglom- erate of Mississippian age. As originally used in cen- tral Idaho (Ross, 1934, fig. 2, p. 977—985) the Brazer limestone is of Late Mississippian age, but in localities far to the northeast of the Mackay quadrangle, limestone that has not yet been mapped separately from the Brazer limestone has yielded fossils of Pennsylvanian and Permian age. In that part of Idaho the Brazer lime- stone together with these younger, associated beds may have an aggregate thickness of more than 10,000 feet. In the Mackay quadrangle, rocks that were mapped in the field as Brazer limestone are now knownon paleon— tologic evidence to be largely of late Early to Late Mis- sissippian age, and in several outcrops they even include rocks of Pennsylvanian age (Dutro, J. T., J r., oral com- munication, 1959; Douglass, R. 0., and Yochelson, E. L., 1958, written communication), but the Pennsylvanian limestone cannot be distinguished in mapping from the limestone of Mississippian age without far more refined work than it has been practicable to do in making the present map of that quadrangle. In the northern part of the Mackay quadrangle the Pennsylvanian limestone is intercalated with clastic beds of nearshore origin (Skipp, 1958). The Mackay quadrangle contains a stratigraphic unit, not previously recognized anywhere else in Idaho, that includes lithologic equivalents of nearly all the components of the three formations briefly described GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES above, but these rocks are so intermingled that they can- not be mapped separately. They include much quart- zite, siltstone, argillite, and conglomerate, but in most places little or no limestone. This unit, at least 5,000 feet thick where mapped, constitutes a formation that interfingers with the local representatives of the Milli- gen and Wood River formations and the Brazer lime- stone. Relations to these three formations demonstrate that this unit ranges in age from Early Mississip‘pian well into the Pennsylvanian. No fossils of Permian age are known in the Mackay quadrangle, and struc- tural relations make it improbable that any beds of that age are exposed there. It is reasonable to surmise, how- ever, that somewhere, presumably south or southwest of the Mackay quadrangle, the newly recognized unit includes beds of Permian age. This unit is known only in the western part of a geo— synclinal lobe that extends into central Idaho from the south. It constitutes a mingling of beds of diverse but largely elastic character that were laid down near shore in late Paleozoic time. Farther east, in the middle part of that lobe, carbonate rocks predominate. Northeast of the boundary between Idaho and Montana beds of late Paleozoic age were deposited on a broad shelf. In that region the stratigraphy is drastically different from 105. B233 that outlined here. The lobe in central Idaho is the northern part of the large geosynclinal mass that is widespread in southeastern Idaho and regions farther south. REFERENCES Bostwick, D. A., 1955, Stratigraphy of the Wood River formation, south-central Idaho: Jour. Paleontology, v. 29, p. 941—951. Kiilsgaard, T. H., 1950, The Geology and ore deposits of the Triumph-Parker mine mineral belt: Part II in Anderson, A. L., Kiilsgaard, T. H., and Fryklund, V. 0., Jr., Detailed geology of certain areas in the Mineral Hill and Warm Springs mining districts: Idaho Bur. Mines and Geology Pamph. 90, p. 39—62. Ross, C. P., 1934, Correlation and interpretation of Paleozoic stratigraphy in south-central Idaho: Geol. Soc. America Bu11., v. 45, p. 937—1000. Scholten, Robert, 1957a, Paleozoic evolution of the geosynclinal margin nonth of the Snake River Plain, Idaho—Montana: Geol. Soc. America Bu11., v. 68, no. 2, p. 151-170. 1957b, Preliminary interpretation of Perdearbonif- erous stratigraphy in east-central Idaho [abs.] : Geol. Soc. America Bull, v. 68, no. 12, pt. 2, p. 1794. Skipp, B. A. L., 1958, Significant sedimentary features in Mis- sissippian rocks in Custer County, Idaho [abs]: Geol. Soc. America Bu11., v. 69, no. 12, pt. 2, p. 1744. Umpleby, J. B., Westgate, L. C., and Ross, C. P., 1930, Geology and ore deposits of the Wood River regions: U.S. Geol. Survey Bull. 814. 'X PROGRESSIVE GROWTH OF ANTICLINES DURING LATE CRETACEOUS AND PALEOCENE TIME IN CENTRAL WYOMING By WILLIAM R. KEEFER, Laramie, Wyo. The progressive growth of some anticlines during Late Cretaceous and early Tertiary time can be demon- strated in the Wind River Basin, central Wyoming. This information helps in local and regional correlation of stratigraphic units and in the interpretation of geo- physical data and well records. The stratigraphic and structural relations have especial importance in the Wind River Basin, because the rocks involved contain oil and gas in some parts of the basin, and an under- standing of the history of folding and sedimentation may lead to the discovery of traps in other parts. The geology of two areas, Shotgun Butte and Alkali Butte, illustrate progressive growth of anticlines. Basic data were obtained by measuring sections in de- tail and mapping individual beds or groups of beds in the field. A multiplex stereo—plotter was used to com- plete the mapping, and compilation was made on topo- 55 7753 0—60—1 6 graphic base maps. Ages of the rocks were determined by fossil vertebrates, leaves,-and pollen. SHOTGUN BUTTE Figure 105.1 shows changes in thickness of the Meeteetse, Lance, and Fort Union formations in out- crops extending southward from the vicinity of Shot— gun Butte (Troyer and Keefer, 1955; Keefer and Troyer, 1956). The line of section crosses a series of southeast-plunging anticlines and synclines, the Shot— gun Butte syncline, an extension of one of the major structural troughs of the “rind River Basin, being at its north end and the Little Dome anticline at its south end (inset, fig. 105.1). The relations shown in figure 105.1 indicate that sev- eral folds began to form during deposition of the Meeteetse formation, and that moderate deformation B234 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Shotgun Butte Blacktail Eagle Point and Shotgun Merriam anticline and Little Dome syncllne anticline Bench synclmes assocnated syncline anticline 1 2 Eocene rocks 3 4 5 6 Datum Lu Upper part of Fort Union 5 formation 0 O / L|J <73 / 0- Lower part of Fort Union formation \ m / Lance formation \ \ 3 8 / Meeteetse formation \ 2 ,— LIJ n: FEET R. l W. \° 1000 44 C 6;, 4,7341 o G} , T_ o 1/2 1 MILE. $90 "1—"_“—"—'"—"—“ / > ”r a: l Amp _._l ' Sic/Pane i 44’ [Cl/‘1, 4- ‘1’ xShotgun Butte : (W w ”VD R I vs I L SYNC BASIN ’9 u ’TTLE Alkali Butte x u o N ! I W Y o M 1 N G l I I |______________________J 5 MILES o 20 40 MILES Li-l—A—J FIGURE Nil—Stratigraphic relations of uppermost Cretaceous and Palemene rocks in vicinity of Shotgun Butte and Little Dome anticline. was generally continuous through latest Cretaceous and Paleocene time. During this time sediments ac- cumulated in thick conformable sequences in certain rough areas, whereas the sediments on the crest and along the north flank of Little Dome anticline are much thinner and are broken by unconformities. As a re- sult of continuous downwarping, the trough areas in this region contain some of the thickest and most com- plete sections of Upper Cretaceous and Paleocene rocks exposed in central Wyoming. Paleontologic studies of numerous plant and vertebrate fossils also indicate that sedimentation in these troughs was continuous. At some places the upwarps and downwarps which began to form in Late Cretaceous time continued to develop along the same structural trends throughout the later and major phases of the Laramide orogeny, in latest Paleocene and early Eocene times. The present sites of the Little Dome anticline and the Shotgun Butte syncline, for example, coincide closely with the Inset map shows location of Alkali Butte and Shotgun Butte with reference to Wind River basin. features ancestral to them. The Merriam anticline and the Shotgun Bench syncline, on the other hand, were probably the sites of a trough and an upfold, respec- tively, during Late Cretaceous and Paleocene time. Murphy and others (1956) and Troyer and Keefer (1955), basing their conclusions largely on structural data, have pointed out that neither the Merriam anti- cline nor the Shotgun Bench syncline was formed until late early Eocene time, and that they trend east—west whereas the older folds trend northwest (inset, fig. 105.1). The stratigraphic relations tend to confirm these Views as to the time of folding of the older struc- tural features. Thinning of Upper Cretaceous and Paleocene sediments toward the present site of the Shot- gun Bench syncline was probably caused by the initial folding of the Maverick Spring anticline, which lies directly northwest of the Little Dome anticline in the southwestern part of T. 6 N., and the northwestern part of T. 5 N., R. 1 W. (fig. 105.1). The‘ thickening of GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES EXPLANATION g '- ”3 e { s g r3 Wind River formation E § Lance formation 0 § 5 § Kmv 3 g E E Mesaverde formation E . Lu _ _ Lu 3 Fort Union formatlon |-- S. a: f Tfu, upper part é‘ Cod h 1 U Tfl, lower part y S a e Contact Fault Locally mappable bed 0 1 12 MlLES FIGURE 105.2.—Geologic map and structure sections of Alkali Butte anticline (mapping partly adapted: from Thompson and White, 1954). B235 strata toward the present site of the Merriam anticline may be a reflection of the ancestral syncline between Maverick Spring and Little Dome anticlines. ALKALI BUTTE The Alkali Butte anticline (fig. 105.2) is an elongate north-plunging fold in Late Cretaceous and early Ter- tiary rocks. As shown by the areal distribution of the geologic units on figure 105.2, unconformities are pres- ent on the flanks of the anticline at the base of the Lance formation, at the base of arkosic conglomerate beds be- lieved to form the upper part of the Fort Union forma- tion, and at the base of the Wind River formation. The same unconformable relationships exist along the axis of the anticline, but are less apparent than on the flanks (compare sections A—A’ and B—B’, figure 105.2). These unconformities were produced by intermittent arching of the anticline during late Cretaceous and Paleocene time. Of particular significance is the con- spicuous overlap of the upper beds in the Fort Union formation. These rocks form the upper few feet of Alkali Butte, where they rest with an angular discord- ance of about 200 on strata in the lower part of the Mesaverde formation (fig. 105.2). The Wind River formation has been tilted about 5° along both flanks of the fold, indicating that the final minor movements occurred later than early Eocene time. The main outcrop belt of Upper Cretaceous and Paleocene rocks along the southern margin of the Wind River Basin extends nearly eastward from Alkali Butte for about 25 miles (Love and others, 1955). In this belt the surfaces of unconformity maintain relatively constant stratigraphic positions, indicating a regional northward tilting of the south margin of the basin, pre- sumably caused by orogenic pulsations in the Granite Mountains to the south. The only appreciable devia- tions in this pattern of unconformity occur on such fea- tures as the Alkali Butte anticline, in outcrops that ex- tend farther north or south than the main belt of ex- posures. These facts imply that the degree of dis- cordance between any two formations in the Upper Cretaceous and Paleocene sequence decreases progres- sively toward the center of the Wind River Basin, in much the same manner as may now be observed from south to north along the crest of Alkali Butte anti- cline. REFERENCES Keefer, W. R., and Troyer, M. L., 1956, Stratigraphy of the Upper Cretaceous and Lower Tertiary rocks of the Shotgun Butte area, Fremont County, Wyoming: US. Geol. Survey Oil and Gas Inv. Chart 00—56. Love, J. 1)., Weitz, J. L., and Hose, R. K., 1955, Geologic map of Wyoming: U.S. Geol. Survey. B236 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S Murphy, J. F., Privrasky, N. C., and Moerlein, G. A., 1956, Geol- ton area, Central Wyoming: US. Geol. Survey Oil and ogy of the Sheldon-Little Dome area, Fremont County, Gas Inv. Map 0M—127. Wyoming: U.S. Geo]. Survey Oil and Gas Inv. Map OM— Troyer, M. L., and Keefer, W. R., 1955, Geology of the Shotgun 181. Butte area, Fremont County, Wyoming: U.S. Geol. Survey Thompson, R. M., and White, V. L., 1954, Geology of the River- on and Gas Inv. Map OM—172. 6b 106. THE “BREAK-AWAY” POINT OF THE HEART MOUNTAIN DETACHMENT FAULT IN NORTHWESTERN WYOMING By WILLIAM G. PIERCE, Menlo Park, Calif. The Heart Mountain detachment fault, or “over— ward from the northeast corner of Yellowstone Park. thrust” as it was originally called, extends southeast- I had previously described this fault as the result of NW A SE k—x 35 muss * 30 MILES M Horizon of Heart Mountain detachment fault B , \ Magma source for volcanic rocks \._. , --\ _ I / FIGURE 106.1.—Diagrammaitic cross sections illustrating formation of Heart Mountain detachment fault. Diagram A, before faulting: B, after last movement showing “break-away”. a, Precambrian; b, Cambrian; c, Ordovician, Devonian, and Mississippian; d, Pennsylvanian, Permian, Triassic, and Jurassic; 6, Cretaceous; f, Tertiary. GEOLOGY OF WESTERN CO NTERMINOUS UNITED STATES B237 YELLOWSTONE ilPARK COUNTY PARK | WYOMING FEET O 9 E -1o,ooo E . o . ’3? Republic 5 Q a: 9 ’9 Early basrc breccra G 4} Mountain 2 VI ‘3 13 a 13 4 D 0 o G J‘— E ‘B 0 1;: - _ 4‘ ‘7 9 Heart Mountain detachment fault & Early acrd volcanics Eav __ __ J ________________________ y 9000 _ . l' M g 2 Madison imestone ( m) WBreak-away fault 9 Q7 .9 $ 2 ‘2‘ [Three Forks shale (th) Q E s 9{ Jefferson limestone (Di) Surface of tectonic . ‘3 4 9 B . . denudation qu Bedding D' 3 Ob 5—{ Bighorn dolomite (Ob) W fault \r‘x] /—,é—\ '_ 8000 I I T I 1’ l l I I I I I I I I I I I I I I I E g Snowy Range formation Grove Creek formation 0 Di 7 l l | I | l l l l | T l l l l | l l l l l | l l l | g \ Pilgrim limestone S Gros Ventre formation 7000 o 1 2 MILES J FIGURE 106.2.—Diiagrammatic section showing relation of Heart Mountain detachment fault to break-away fault. The early basic breccia postdates the faulting. faulting of three types: (a) a bedding fault, (b) trans- gressive faulting (called shear faulting in a previous paper) where the fault passes upward from a bedding- plane fault across younger beds until it reaches the sur- face, and (c) a fault in which the displaced blocks move over the land surface (Pierce, 1957, p. 597). To these there can now be added a fourth type of fault, which occurred at the place where the detached mass broke away from unfaulted beds (see fig. 106.1B). This will be referred to by the simple descriptive term of “break—away fault”. Although these four types of faults are only phases of one large detachment fault, it is important to distinguish them because their strongly contrasting field characteristics may erroneously sug- gest unrelated faults. The “break-away” of the Heart Mountain fault was observed at the northeastern corner of Yellowstone Park, only a few hundred feet west of the Park bound- ary, this being possibly the first time that such a fea- ture has been recognized. The stratigraphic and struc- tural relations at this place are shown in figure 106.2. The rocks at the left side of the figure are unfaulted and are in the normal sequence of Paleozoic rocks in this area. Beginning at the break—away fault, the rocks from the Bighorn dolomite up to and including the early acid volcanics have moved to the right, or eastward, along the Heart. Mountain detachment plane, which is at the base of the massive Bighorn dolomite. A large open space was created immediately to the east of the break-away fault, and the top of the Grove Creek limestone became exposed on what could be called a surface of tectonic denudation. Some smaller blocks toppled off the larger ones as they moved laterally, and came to rest on the bedding-fault surface. The break-away fault is nearly vertical and trends almost due north. Reconnaissance mapping indicates that it has an observable length of 6 miles; it is con- cealed beneath volcanic rocks on the south, and its trace has been removed by erosion to the north. Some indi- cation of brecciation along the break-away fault sug- gests the possibility that there may have been some slight lateral movement parallel to this fault before the main lateral movement to the east took place. The fault blocks were immediately engulfed by the great mass of early basic breccia, and a record of the sequence in which the events took place was thus preserved intact until exposed by Recent erosion. REFERENCE Pierce, W. G., 1957, Heart Mountain and South Fork detach- ment thrusts of Wyoming: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 4, p. 591—626. ’2 B238 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 107. REGIONAL GEOLOGICAL INTERPRETATION OF AEROMAGNETIC AND GRAVITY DATA FOR THE ROWE- MORA AREA, NEW MEXICO By GORDON E. ANDREASEN, MARTIN F. KANE, and ISIDORE ZIETZ, Washington, DC. The Rowe-Mora area of northeastern New Mexico is characterized by high plateaus in the north, lower plains in the south, and by the lower ranges of the eastern Sangre de Cristo Mountains on the west. The plateaus and plains consist of flat—lying Triassic and Cretaceous strata with numerous volcanic features surmounting the northern Plateaus (Harley, 1940). Pennsylvanian elastic sedimentary rocks and an undivided complex of Precambrian gneisses, schists, and intrusive rocks crop out in the core of the Sangre de Cristo Mountains. Deep ° 104 ° I COLORADO __ | ____37 _'_—" 7'—_"}5:—x160_— 7 EXPLANATION / tNEW M Ram a 0 l Depths calculated from / 30° magnetic data ' Hoxie Jct Depths from drill 90° holes 00 ? indicates uncertainty . that drill reached basement 7'0 V‘\ CRIS E \0 36° — a 2000 I G all???” no ~ ° Conc .osDam Igloo ‘l \\___l{, i | / '\ . $1} j/oucumcari or . / Newkirk _ 35° ‘p . I ' o __ _| ”K _____ , D E \ B A c A ' 10 0 10 20 30 MILES |_1_J¥JHV_,’J___J CONTOUR INTERVAL 1000 FEET DATUM IS SEA LEVEL FIGURE 107.1.—C‘ontour map of the Precambrian surface, Rowe- Mora area, New Mexico. drill holes in the plains-plateau area east of the foot- hills penetrate essentially flat-lying Mesozoic and Pale— ozoic sedimentary rocks up to several thousand feet thick, and bottom in Precambrian crystalline rocks sim- ilar to those exposed in the mountains to the west. Igneous rocks intrude the Paleozoic and Mesozoic strata in western Mora County, in an area south of Eaton, and possibly in central Mora County. A contour map of the Precambrian surface (fig. 107.1) was prepared using 40 depths computed from aeromagnetic anomalies, 45 depths from drill holes, and exposures of Precambrian rocks along the east edge of the Sangre de Cristo Mountains. Only a few depths were computed in the northern part of the area be- cause the magnetic anomalies caused by the Precam- brian rocks are partly obscured by the magnetic expres- sion due to the widespread instrusive and extrusive rocks of younger age. In the southern part of the area, where good depth control is available, a close correla- tion was found between gravity anomalies and basement relief. The regional gravity data, therefore, provide a basis for contouring the Precambrian surface in areas of meager depth control, especially in the north, where the younger igneous rocks are present. The major feature of the contour map is the Sierra Grande arch, a basement highland trending northeast across the area. The highland stands 3,000 to 7,000 feet above the nearby basins and is separated into two parts by a saddle northeast of Wagon Mound. Major depressions are outlined west of Vegas Junction, north- east of Santa Rosa, and west of Wagon Mound. The largest of these, Las Vegas basin, is more than 7,000 feet in depth and more than 1,000 square miles in area. Its thick section of sedimentary rocks marks it as a favor- able prospect for petroleum exploration. The gravity data indicate that the east edge of the basin may be formed by a fault in the Precambrian basement. A gravity low trending northward from the vicinity of Las Vegas to (limarron indicates that Las Vegas basin extends to Cimarron and probably connects with the Raton basin of northeastern New Mexico and south- eastern Colorado (Johnson and Wood, 1956) through a low saddle. In the southern part of the Rowe-Mora area, steep, basement surfaces suggest the presence of faults near Newkirk and Vegas Junction. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B239 REFERENCES Harley, G. T., 1940, The geology and ore deposits of northeast— ern New Mexico (exclusive of Colfax County) : New Mex- ico School of Mines, State Bur. Mines and Mineral Resources Bull. 15. Johnson, R. B., and Wood, G. H., 1956, Stratography of Upper Cretaceous and Tertiary rocks of Baton basin, Colorado and New Mexico: Am. Assoc. Petroleum Geologists Bull, v. 40, no. 4, p. 707. ’5? 108. SOUTHWESTERN EDGE OF LATE PALEOZOIC LANDMASS IN NEW MEXICO By GEORGE O. BACHMAN, Denver, Colo. At many localities in central New Mexico, Permian strata lie directly on Precambrian rocks. The surface on the Precambrian rocks is highly irregular, being locally diversified with hills, ridges, and even moun- tains. Thompson (1942) said that “these pre—Cam- brian rocks probably represent the buried remnants of a large land area of the Ancestral Rocky Mountains,” and he named this positive element the Pedernal land- mass. It is difficult, if not impossible, to determine the exact extent of the Pedernal landmass; in many parts of New Mexico evidence on this point can be obtained only from widely spaced outcrops and drill holes. It has been shown, however, that during parts of Pennsylvanian and Permian time this landmass extended north-south at least 150 miles in central New Mexico. The remarkable influence of the Pedernal landmass on Pennsylvanian and Permian sedimentation has been discussed by other workers (Read and Wood, 1947 ; Cline, 1959; Otte, 1959). During reconnaissance geologic mapping in 1954, R. L. Sutton and I discovered exposures in northern Otero County, N. Mex., where the Abo formation of Permian age lies on rocks of Precambrian age (Bach- man, 1954; Dane and Bachman, 1958). These expo— sures are near Bent, which is about 12 miles northeast of Tularosa, in secs. 25 and 26, T. 13 S., R. 11 E., and sec. 30, T. 13 S., R. 12 E. The outcrops are on the east flank of a small dome, here called Bent dome. I have since mapped these exposures in more detail (fig. 108.1). They are the southernmost exposures in New Mexico, so far as I know, in which this relation may be observed at the surface, and they are of particular interest be- cause in the Sacramento Mountains, about 20 miles to the south of Bent dome, pre-Permian Paleozoic rocks attain a thickness of about 5,500 feet (Pray, 1959, p. 88). The Precambrian rocks on Bent dome consist chiefly of light-gray quartzite. At one small exposure (sec. 25, T. 13 S., R. 11 E.) the quartzite appears to be intruded by coarsely crystalline granite, which closely resembles that forming cobbles and pebbles in the Abo formation on Bent dome and in areas to the west. The Abo forma- tion contains cobbles and pebbles of quartzite that re- sembles Precambrian quartzite in texture but not in color, being generally dark gray, maroon, or purple whereas the quartzite of the Precambrian exposures is light gray. Diorite exposed on the west side of Bent dome (sec. 26, T. 13 S., R. 11 E.) may also be of Precambrian age (Foster, 1959, p. 143), but its age is uncertain. This diorite is very similar to Tertiary diorite found else- where in the region; and, moreover, it is not intricately jointed as are the rocks known to be Precambrian, and no pebbles of diorite like that on Bent dome have been identified in the Abo formation. On the west side of Bent dome, and also in the vicinity of the Virginia Mine and at a locality on US. Highway 70 one mile east of Bent, there are exposures of light- gray, medium-grained, well-sorted sandstone beds thought to be of Pennsylvanian age. The Abo formation overlies these beds unconformably. The supposedly Pennsylvanian beds are estimated to be about 200 feet thick near the Virginia Mine, but they are absent on the east side of the dome and are presumed to wedge out eastward from the mine. The high degree of sorting indicates that these beds may have been deposited before major uplift of the Pedernal landmass. The Abo formation on Bent dome consists of poorly consolidated dark-red shale, arkose, and conglomerate. Cobbles of granite and quartzite as much as 10 inches in diameter have been observed at the base of the forma- tion, and also some pebbles of a distinctive brownish-red rhyolite porphyry. The formation is 220 feet thick on B240 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES R. 11 E. R. 12 E. P m EXPLANATION y P SEDIMENTARY ROCKS E Py g 0: Lu l; , g +* Pa 3 ., 26 o 4» 30 O . . 0 >— U ‘ ‘ n: - : P *lo 'n on -- ++C 5»- ,Q3* . '* » ~ m . *2 ‘1 Py :5 . " ‘ o° c°o 9 1°09 on o: T. E o°°°° 9:8 13 a. ‘ 5. z 9 on < oo°°°°° ° E . °°.,°°° th ‘ 0: Pa_ [‘33: E 33" a ~ . .. Ca > 3' p, 95 ~ ‘ 5' P Pennsylvanian(?) rocks undivided 5 E /7 , y 0- g l i"\»\‘ ~ng-( 2 35 36 31 “iv ‘ 5 Granite g E + T4, < w 953‘:+ 8 Q ‘ rt ‘te E ua z1 0 1/2 1 MILE 1 i I f—‘\\ Contact , Dashed where approximately located U D ..... Fault Dotted where concealed. U, upthrown side D, downthrown side /7 2’ Strike and dip of beds 5% Virginia Mine Abandoned \l x! ‘1: Line of measured section FIGURE 108.1.—-Geologic map of Bent dome, Otero County, N. Mex. the southeastern part of the dome (fig. 108.2). On the eastern flank of the dome the Abo is apparently thinner and it may be no more than 100 feet thick Where it overlies the highest points on the surface of Precam- brian rocks (NW%8W% sec. 30, T. 13 S., R. 12 E.). About 6 miles west of Bent dome the Abo formation is about 1,400 feet thick (Pray, 1959, p. 118) and rests on rocks of Late Pennsylvanian and early Permian age. The unconformity at the base of the Abo sandstone and the onlap of the Abo on pre-Permian rocks of vari- ous ages in the Sacramento Mountains have long been known (Pray, 1949, p. 1914—1915). Early Permian folding and faulting are indicated throughout the length of the Sacramento Mountains and are directly related to uplift of the Pedernal landmass. The ex- posures at Bent dome provide a point of geographic control for the southwestern part of the landmass and probably represent a part of the early Permian tectonic system of the Sacramento Mountains. REFERENCES Bachman, G. 0., 1954, Reconnaissance map of an area southeast of Sierra Blanca in Lincoln, Otero, and Chaves Counties, New Mexico, in. New Mexico Geo]. Soc. Guidebook, 5th, Field Conf., 1954: p. 94b. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES EXPLANATION Yeso formation Abo formation :3 Covered 50 FEET 25 ' '- Precambrian quartzite FIGURE 108.2.—Graphic section of Abo formation and adjacent rocks at Bent dome (NWJA sec. 36, T. 13 S., R. 11 E). B241 Cline, L. M., 1959, Preliminary studies of the cyclical sedimen- tation and paleontology of upper Virgil strata of the La Luz area, in Permian Basin Sec. Soc. Econ. Paleontologists and Mineralogists and Roswell Geol. Soc. Guidebook, Sac- ramento Mtns., 1959: p. 172—185. Dane, C. H., and Bachman, G. 0., 1958, Preliminary geologic map of the southeastern part of New Mexico: U.S. Geol. Survey Misc. Geol. Inv. Map I—256. Foster, R. “7., 1959, Precambrian rocks of the Sacramento Mountains and vicinity, in Permian Basin Sec. Soc. Econ. Paleontologists and Mineralogists and Roswell Geol. Soc. Guidebook, Sacramento Mtns., 1959: p. 137-153. Otte, Carel, Jr., 1959, Late Pennsylvanian and early Permian stratigraphy of the northern Sacramento Mountains, Otero County, New Mexico : New Mexico Inst. Mining Technology, State Bur. Mines and Mineral Resources Bull. 50, p. 21—58. Pray, L. C., 1949, Pre-Abo deformation in the Sacramento Moun- tains, New Mexico [abs]: Geol. Soc. America Bull., V. 60, no. 12, p. 1914—1915. ,1959, Stratigraphy and structure of the Sacramento Mountains, in Permian Basin Sec. Soc. Econ. Paleontolo- gists and Mineralogists and Roswell Geol. Soc. Guidebook, Sacramento Mtns., 1959: p. 86—130. Read, 0. B., and Wood, G. H., Jr., 1947, Distribution and cor- relation of Pennsylvanian rocks in late Paleozoic sedimen- tary basins in northern New Mexico: J our. Geology, v. 55, no. 3, p. 220—236. Thompson, M. L., 1942, Pennsylvania System in New Mexico: New Mexico School Mines, State Bur. Mines and Mineral Resources Bull. 17, p. 12—13. 5% 109. NEW INFORMATION ON THE AREAL EXTENT OF SOME UPPER CRETACEOUS UNITS IN NORTHWESTERN NEW MEXICO By CABLE H. DANE, Washington, D.C. Stratigraphic studies of Upper Cretaceous rocks in parts of northwestern New Mexico, made in connection with the compilation of a new geologic map of New Mexico by Carle H. Dane and George 0. Bachman, have recently been supplemented by paleontologic studies by W. A. Cobban. Although incomplete, these combined studies give a. new picture of the distribution of sev- eral of the rock units of Late Cretaceous age (fig. 109.1). The Tres Hermanos sandstone member of the Mancos shale of early Greenhorn age (fig. 109.1, A), including the sandstones probably equivalent to it, is believed to have a much greater extent than previously recognized. This interpretation is based in part on indications that equivalents of the somewhat older Dakota sandstone are missing in southwestern New Mexico. The Dakota is locally absent south and southwest of Santa Fe (Stearns, 1953, p. 964—966) ; it is inferred to be absent east of Socorro, where shales lie at the base of the Upper Cretaceous (Wilpolt and Wanek, 1951, sections on sheet No. 2) ; and it is locally absent northwest of Socorro (Gadway, 1959, p. 18). In all of these areas, the Tres Hermanos sandstone is thick and extensive. Further- more, fossils of the oldest Late Cretaceous faunal zones are not known in soiithwestern New Mexico. There- fore, some of the upper parts of the Beartooth quartzite and the Sarten sandstone of southwestern New Mexico, and the so-called Dakota sandstone of south-central New Mexico may be equivalent to the Tres Hermanos sandstone member. This interpretation is consistent with paleontologic data now available. The Tres Her- GEOLOGICAL SURVEY RESEARCH l960—SHORT PAPERS IN THE GEOLOGICAL‘SCIENCES B242 .www 53.537: 263:: 6:95:53 “53:95 SEA 0:: we 2%:8 Smom mm ”own «3.537: 263:: 3.53 .:o5w::.:om :om:w0 wwmgwao 25 me 33:85 «Ecumwfiwm :SEQ um ”:oEmESw ENSEZ 2: mo .5289: 0:3mw82 mmwm ”Earn u:¢:¢>:::dw 393: 05 “Ed find: 93:: .27: 5.3:: mo 26: 98:3:3 “5335:! bouagwoaam mid Swag flatmaom 6:“ :55 ”Exam «c “9:835; £385: 2:: .Q ”as 39337: 302.3: :9: 3::th $83 no mg 28%:3 ”25:55::3 9:: .5989: 0:95:53 0335 9:: wEwEoE, .o:o:mc:wm 35:8 0:: mo ”Ed: :23: 6 ”8:52 32/: 58mg 6:“ 95:95: 5 6w“ 98:33.:6 93:3 «o cm? .39? 30:52 2: no .8252: 0:838: 95:52»: 2:: 9:» .8:on 3oz ESwoBfidg 5 own: :.:,o::¢w:¢ amend: mo 0:3mc:dm .M ”03:82 39/: Ema—33:38 :: mud Ecnfixiw 5:8 0:36 0:: 39% 3839:: we 3:0? 65% 6:: 5:2? 30:52 0:: m6 5:89: w:8mw::m wogfiuom moan. 2:: J: 63:32 >37: 985.5: 6:5 533% :: 52:: 8 335553 3:09: Him 0%: 38050.5 3de yo BE: w:8mc:mm void: Samara 9:: mo 08% mo ”BREE :«Emio 3.28:: 9:: m: «as: w:§>o:w mag: :oumxmlédofi auburn wcofiwEfi 22m 9.:ng wcoumucaw 3.3an octhcoz I _.||:|_ l I omO: ZO_._.anom - _ _ .mm Lfl _ VNOZIHV VNOZIHV H. “ fii . _ WIL _ T j :5: <1—MO: _. _ : a : VNOZIHV SVXEL <<)))))\ o|:.®t—22 MlLES—e©‘—15 MILES—4 (9 Axial Basin- Vicinity of Vicinity ‘of Craig Pagoda 1925) (Bass, et al, 1955) .— 35 MlLES fi—l2 MlLES—0® Coal Creek Southwest flank Rangely anticline, Colorado l Lewrs shale (Kle) / ® Williams Fork Cow Wash, Utah (Walton, 1944) (KM) lles Mesaverde group (KI) L Mancos . Fm. ,, ., . shale Rimrock --- ,. $0 ~ ,3.” ..... ..... - (ch) sandstone Mancos @ shale M B—Bucli tongue of Manch shale of Hale (1959) C—Ca fl ‘ d t f“ I 1959 TM—Twentymile sandstone member of Sandstone members of Mancos shale s ega e san 5 one D a e ( ) Williams Fork formation L—Loyd sandstone member of Konishl (1959) TC—Trout Creek $3"d3‘°"° member 0’ F—“First Mancos sandstone" of Konishl (1959) '51“ '°"“3"°" S—"Second Mancos sandstone” of Konishi (1959) EXPLANATION ROCKS OF NONMARINE ORlGlN I§I Undifferentiated lenticular deposits of sandstone, shale, and coal M—Morapos sandstone member NORTH SOUTH 28 MlLES ‘—> IQI ®Axial Basin- *— 23 WES —'@ L‘s Craig ®‘—— 40 MILES —. North Thompson Persistent units of irregularly = a“? (Insignia: Creek bedded sandstone E 2 Newcastle (Donnell, 1959) E _> Eby. 1930) (Gale, 1910) ROCKS OF MARINE ORIGIN FEET E .3 Wasatch formatia" o E 5'; Ifil fie . Lion Canyon Sandstone,br;i:::ge to evenly 1000 _= sandstone member § 5, ——— S g \ E a IEI “ Williams Fork \ E g 2000 formation \ § § Shale and siltstone, evenly bedded x \ g =‘ FOSSIL ZONES E 5 Mt!" 6°" §\ E E Spherwdiscus cf. 3. lentioularis 3000 E E Q i ” chuli'tes clrmlobam =3 g 1»; at {E} Baculiws grandee 3 Wheeler coal 4\\‘ Becomes baculus 4000 " Baculites eliast' a: Biwulitex reesilder' g ,,. .1 ' ’ ' ' Batulites aff. B. comm—estrus Z 5 Thin coaly uni 3 v Bmlites camp'ressus 8 5000 E E Bmlitescmwatus > L . ....... ..... m 2“ 33mm” jennem' _ Mancos shale Thin coaly unit ymoceras sleoemm m Didymocems mbmscense TMvaentymrle sandstone member of m Bmh’tes scotti ix Williams Fork formation Buculiles meow-yew ‘5' TC.—Trout Creek member of lsles Bmlrtes n, 513- “F" 5‘ formation a Boculrtes n. so. "E" Boculr’tes n. sp. “D” Baculites asperfirrmis m Bmlites miwlearni Approximate continuity of certain EAST sandstone units in Mancos shale <—2O MILES—.® along lines of sections indicated ‘— 25 MILES ——'® Bowie, by dotted lines between columns 40 M‘LES Northwest of Colorado See fig.112.3 for explanation of Palisade Cedaredge (Lee, 192) WEST letter symbols in Circles (Erdmann, 1934? 52 MlLES ———> GM" Rm" West Salt Creek Tuscher Canyon, Utah (Erdmann, 1934) (Fisher, 1936) Wasatch formation Mesaverde formation Mancos shale Anchor tongue of Mancos shale Lower member of Sego sandstone Price River formation PiPaonia shale member Marine Castlegate B—Bome shale member sandstone Rikollins sandstone member S—Sego sandstone member RL—Rollins sandstone memberof Mount Garfield formation (EM—Cameo member of Neslen facies of Young (1955) B—Buck tongue of Mancos shale PS—Palisade coal zone of Mount Garfield formation CZ~Cozzette member of Neslen facies of Young (1955) C7Castlegate sandstone S—Sego sandstone CC—Corcoran member of Neslen facies of Young (1955) FIGURE 112.2.—Generalized columnar sections of uppermost Cretaceous rocks in northwestern Colo- rado and northeastern Utah, showing distribution of facies and correlation of named strati- graphic units. For location of sections see figure 112.3. Sections are modified after the authors cited. B247 B248 REGRESSIVE-TRANSGRESSIVE CYCLES Regressive movements of the sea are recorded by superposition of nonmarine upon marine strata; trans- gressive movements are recorded by reversal of that succession. The wedge-edge of a tongue of marine rocks penetrating nonmarine rocks, or of nonmarine rocks penetrating marine rocks, marks the position of an ancient strand line. A large number of regressive- transgressive cycles are recorded by interfingered ma- rine and nonmarine Upper Cretaceous rocks in this area, but only cycles that involve at least 300 feet of strata are enumerated here. In the northeastern part of the area, the transgressive marine tongues include considerable shale and siltstone. Regressive marine sandstone is invariably at the top of the shaly tongues, and transgressive marine sandstone commonly occurs at the base. Sandstone may be the only marine facies present toward the landward tips of the tongues. In the thinner sections along the Book Cliffs to the south, marine shale and siltstone are subordinate in the tongues, and transgressive sandstones have not been observed. Regressive pulses may be reflected for variable dis- tances seaward from the strand line by tongues of ma- rine sandstone penetrating the shale-siltstone facies. The Morapos sandstone member of the Mancos shale (columns 4 and 5, fig. 112.2) may thus reflect a regressive movement older than those here enumerated, for fossil evidence (fig. 112.2) shows the Morapos to be older than the marine Castlegate sandstone. The several nonmarine and marine tongues that have been recognized are identified on figure 112.2 and the general positions of corresponding strand lines, as in— ferred from the results of lateral tracing of those tongues and from paleontologic evidence, are shown in figure 112.3. Hale (1959, p. 64—65) has previously de- picted the TA strand line, and Weimer (1960, p. 16) has shown the TF strand line. The following relates to data not evident in figure 112.2. 1. The lower Iles cycle (RB and TB, figs. 112.2 and 112.3) has not been identified along the Book Clifl's. Possibly it is reflected in the lower Sego sandstone-Anchor tongue marine sequence near the Colorado-Utah line (column 11, fig. 112.2), in which case the corresponding nonmarine-marine cycle may be present somewhere farther west. If so, the southwestward extension of lines RB and TB (fig. 112.3) must swing to a west-southwest- erly direction. That the sea lingered relatively longer in eastern Utah is also suggested by ma- rine fossils as young as the basal part of the Ba- culz'tes 800m zone in the Sego sandstone of that area (fig. 112.2). GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES EXPLANATION {,___' Principal outcrop area of Mesaverde formation or group and younger Cretaceous rocks R—1—R Approxumate seaward limit of deposition of tongues of nonmarine rocks, Hachures point in landward direction T—I—T Approximate landward limit ot depOSItion ot tongues of marine rocks. Hachures point in seaward direction lF—Upper Williams Fork—Lewis transgression RF-Upper Williams Fork regression lE—Middle Williams Fork transgression TD-Upper Bowie transgression RD—Lower Williams Fork—lower Bowie regression ‘ TC—Upper Iles—lower Mount Garfield transgressnon RC—Middle Iles-Palisade regression TB—Lower lles transgressuon RB—Lower Iles regressmn TA-Buck transgression RA—Castlegate—Rimrock regression YOUNGER —> < OLDER 1 Locations of columnar sections of figure 1122 Y Z Localities mentioned in text 50 O 50 M l LES ..4_J__#.. 7 7,, ‘1 L -. 114A. FIGURE 112.3.—Map showing location of sections in figure 112.2 and general location and trend of certain regressive and transgressive strand lines during Late Cretaceous time, as inferred from outcrop studies. 2. A marine intercalation correlated with the TC tongue 0n the basis of stratigraphic position oc- curs southeast of Baggs, Wyo. at locality Z (fig. 112.3) but was not found at locality Y (fig. 112.3), Another marine intercalation similarly correlated with the TE tongue occurs at locality Y (fig. 112.3) but is absent about ten miles northwest. 3. The RC and RD nonmarine tongues, though thin- ning rapidly, are still present in the easternmost GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES exposures near Oak Creek (column 6, fig. 112.2) but equivalent rocks are entirely marine in the next exposed section about 25 miles to the east. 4. The exact correlation of the transgressive tongues above the RD tongue in columns 14, 8, and 5 (fig. 112.2), is not known. The upper tongue of the Bowie shale member of column 14 undoubtedly correlates with one of the two prominent tongues below the Allen coal of column 8; in either case, there must have been a strand line in the general position of TD (fig. 112.3). The TE strand line (fig. 112.3) represents the known extent of the Twentymile sandstone member and associated ma- rine rocks. It may be represented by the upper— most marine tongue of column 8. 5. The position of the upper Williams Fork regressive strand line (RF, fig. 112.3) is poorly known. The basal part of the Lewis shale overlying the greatly thinned RF tongue near Oak Creek (column 6, fig. 112.3) has yielded fossils indicative of the zone of Baculites grandis. The basal Lewis at locality Z (fig. 112.3) has yielded the older Baculz'tes eliasz', indicating that the RF tongue is replaced by ma— rine rocks in the intervening area. REFERENCES Bass, N. W., Eby, J. B., and Campbell, M. R., 1955, Geology and mineral fuels of parts of Rouvtit and Moffat Counties, Colo- rado: U.S. Geol. Survey Bull. 1027—D, p. 143—250. Donnell, J. R., 1959, Mesaverde stratigraphy in the Carbondale area, northwestern Colorado, in Rocky Mtn. Assoc. Geo- logists, Guidebook 11th Ann. Field Conf., Washakie, Sand Wash, and Piceance Basins, 1959: p. 76—77. Dorf, Erling, 1938, Upper Cretaceous floras of the Rocky Moun- tain region; 1, Stratigraphy and paleontology of the Fox I B249 Hills and lower Medicine Bow formations of southern Wy- oming and northwestern Colorado: Carnegie Inst. Wash- ington Pub. 508, p. 1—78 [1942]. Erdmann, C. E.. 1934, The Book Cliffs coal field in Garfield and Mesa Counties, Colorado: US. Geol. Survey Bull. 851, and Mesa Counties, Colorado: US. Geol. Survey Bull. 851, Fisher, D. J., 1936, The Book Cliffs coal field in Emery and Grand Counties, Utah: US. Geol. Survey Bull. 852, 104 p. Gale, H. S., 1910, Coal fields of northwestern Colorado and north- eastern Utah: U.S Geol.. Survey Bull. 415, 265 p. Hale, L. A., 1959, Intertonguing Upper Cretaceous sediments of northeastern Utah—northwestern Colorado, in Rocky Mtn. Assoc. Geologists, Guidebook 11th Ann. Field Conf., Wash- akie, Sand Wash. and Piceance Basins, 1959: p. 55—56. Hancock, E. T., 1925, Geology and coal resources of the Axial and Monument Butte quadrangles, Moffat County, Colo- rado: U.S. Geol. Survey Bull. 757, 134 p. Hancock, E. T., and Eb_v, J. B., 1930, Geology and coal resources of the Meeker quadrangle, Moffat and Rio Blanco Counties, Colorado: US. Geol. Survey Bull. 812—0, p. 191—242. Konishi, Kenji, 1959, I'pper Cretaceous surface stratigraphy, Axial Basin and Williams Fork area, Moffat and Routt Counties, Colorado, in Rocky Mtn. Assoc. Geologists, Guide- book 11th Ann. Field Conf., Washakie, Sand Wash, and Piceance Basins, 1959: p. 67—73. Lee, W. T., 1912, Coal fields of Grand Mesa and the west Elk Mountains, Colorado: US. Geol. Survey Bull. 510, 237 p. Spieker, E. M., 1949, Sedimentary facies and associated diastro- phism in the Upper Cretaceous of central and eastern Utah, in Sedimentary facies in geologic history: Geol. Soc. Amer- ica Mem. 39, p. 55—82. Walton, P. T., 1944, Geology of the Cretaceous of the Uinta Basin, Utah: Geol. Soc. America Bull., v. 55, no. 1, p. 91—130. Weimer, R. J ., 1960, Upper Cretaceous stratigraphy, Rocky Mountain area: Am. Assoc. Petroleum Geologists Bull., v. 44, no. 1, p. 1—20. Young, R. G., 1955, Sedimentary facies and intertonguing in the Upper Cretaceous of the Book Cliffs, Utah-Colorado: Geol. Soc. America Bull., v. 66, no. 2, p. 177—202. 113. STRATIGRAPHY AND STRUCTURE OF THE PRECAMBRIAN METAMORPHIC ROCKS IN THE TENMILE RANGE, COLORADO By A. H. KOSCHMANN and M. H. BERGENDAHL, Denver, Colo. Work done in cooperation with the Colorado State M etdl Mining Fund Board The Tenmile Range lies in north—central Colorado, in the southern part of Summit County, about 80 miles west-southwest of Denver (fig. 113.1). Exposed along the crest and upper slopes of the range is a complex of Precambrian contorted metasedimentary granulite, gneiss, and migmatite, which have been intruded by 557753 0—60—17 Precambrian granite and Tertiary granodiorite. On the geologic map of Colorado (Burbank and others, 1935) this complex is included in a much larger mass of Precambrian rocks that extends northwestward into the Gore Range and southward into the Mosquito Range. These rocks can be subdivided into four dis— B250 106°30’ 106.00, 39°30 39.30. Location of geologic map ‘1 0: Lu //!:"’~ (5 I z 0 < \l— 1 39°15 I": 39'15' 3 O _ O < I~ Falrplay D O (I) O E 106°00' 10 MILES g FIGURE 113.1.—Index map showing location of the Tenmile Range, Colo. crete and persistent stratigraphic units, whose relative age can be determined by their order of superposition in areas where their layering and foliation have relatively flat dips. These units consist, in ascending order, of granulite, banded gneiss, migmatite, and pink quartz- biotite-plagioclase gneiss. The high metamorphic grade of these rocks is indicated by the presence of hornblende, pyroxene, garnet, and sillimanite, chiefly in the banded gneiss and migmatite (see fig. 113.2). The major structure in the area is a syncline that trends eastward and southeastward and is flanked by anti- clines. LITHOLOGY GRANULITE The granulite of the Tenmile Range is a high-grade metamorphic rock of granoblastic texture, consisting essentially of quartz, white oligoclase—andesine, and white microcline; its chief accessories are biotite and muscovite. The proportions of these components vary locally, producing dominantly quartzose facies at some localities and a feldspathic facies at others. Much of GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES the rock displays gneissic foliation, imparted by ori- ented flakes of mica and lenticles of quartz and feld— spar, but in some places foliation is very faint or absent. The use of the term granulite accords with that of Harker (1939, p. 246—248). The granulite is exposed only along the axes of the anticlines, and no exposure shows its base; hence its true thickness cannot be determined. An approximate minimum thickness is about 6,500 feet. BANDED GNEISS Overlying the granulite is a banded rock made up of alternate layers of amphibolite and granulite that range in thickness from about a sixteenth of an inch to several feet. The total thickness of the banded gneiss ranges from 20 feet to 1,600 feet. Locally, probably through tectonic processes, this unit is absent. The amphibolite layers in the gneiss are traceable in places for more than 100 feet, but more commonly they are fractured at short intervals, or broken into strings of boudins. The granulite layers were the more plastic, having flowed locally; the amphibolite layers were more competent and yielded by fracture. Near the contact of the banded gneiss with the underlying granulite, the rock layers of the banded gneiss are usually thicker than elsewhere. The upper third of the gneiss is com- posed of thinner layers, and the mafic layers there con— tain variable amounts of biotite in addition to horn- blende. The contact of the banded gneiss with the overlying migmatite is gradational through as much as 200 feet. MIGMATITE The most widespread rock unit in the area is a mig- matite, composed mainly of quartz-biotite-plagioclase gneiss and schist interlayered with subparallel lenses and stringers of a quartz-feldspar rock of granitoid to pegmatitic texture. In some places the unit contains lenses and layers rich in sillimanite, garnet, calcite, and lime silicates. The layering is usually wavy and con- torted, and much less regular than that of the banded gneiss. As this unit is exposed only along axes of synclines, its true thickness cannot be ascertained; it is estimated, however, to be at least 15,000 feet. PINK GNEISS Exposed along the western margin of the area, imme- diately west of a large north-south fault, is a gneiss that consists mainly of quartz, biotite, and a characteristic pink plagioclase but that locally contains lenses of lime- silicate gneiss. This rock apparently overlies the migmatite (fig. 113.2), but the exact. relations are not clear. No complete section of this rock unit is exposed in the mapped area and its thickness is not known. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B251 ° ' 106° 5’ a , 39°35, 106' 10 O 39 35 ‘ ~ ~ ~ 8 8 8 8 b ‘0 O O O O O O ('1) N u—c o O O ‘ .—4 r—4 r4 '—< 0‘! w ”573%; 2503 QC . fl \fi';<:/ . ’E ‘ ”/3 [h 1) (>32! 7 fr [CL L\ l U“ /// :0) ¢7 1v \ I/‘ ’11 \ ,4 W .1' / ‘.‘\ /’/ I \ x o :_ --‘- l o I < 39 30 , 39 30 | m ‘I] D. < x Breekenri ge . _ 5+3 é a: 4% BEND IN \\\ < g SECTION \ , Z m 9 :5 l— r— , Q E :UD—fi' Covered '6')" i V _ / g Paleozoic :1: \x‘ ‘ \ \ sedimentary 1313133“? g’ \, \ g §\;\\ rocks ’ > \ \ \ {l \ ‘ \ ‘ 390257_ \7 5 39°25’ EXPLANATION >_ z E \ ‘ r, ’ ‘ \ - .4 E] E . E3 ‘ 'j/JIQQLCS/j Glacial drift m Sllver Plume :01 ' \‘Q ’ and alluvium 20>: granite 2 m 35 <_t <2 Intrusive rocks 0E Pink gneiss II . Dominantly gramd'io’r'lte "Lu >§ Compiled by A. H, Koschmann 0}— and M. H. Bergendahl o l N . . < 106 10 M lllllllll ks }OU Mlg'matlte B 0 1 2 3 MILES esozo‘c m [35 W n: E }58 Banded g'neiss “- Permian and Lu Pennsylvanian rocks .1 < Granuhte n. Comte—let—m Dashed where approximately located; dotted where concealed i_... l D Fault Dashed where approximately located; dotted where concealed; U, upthrown side; 0, downthrown side. Only major faults are shown \\47 Generalized strike and dip of foliation FIGURE 113.2—Gene1'a1ized geologic map and cross section of the Tenmile Range, 0010. B252 STRATIGRAPHIC SUCCESSION The stratigraphic sequence of the metamorphic rocks had to be determined by means of structural evidence, for they contain few relict sedimentary structures and those that were found were too poorly preserved to be useful. In the northern and southern parts of the area, where the dips of the layers and foliation range from 35° to 60°, the stratigraphic relations are everywhere the same; the granulite is overlain by banded gneiss, ‘ which is overlain by migmatite. In some areas where the dips are steeper (fig. 113.2), an overturned limb of a fold may suggest that the migmatite is oldest, but this relation is always very local and was never ob— served where the dips of f‘oliation are relatively flat. The persistent stratigraphic sequence in areas of low dips also makes it unlikely that there has been any re— cumbent folding, for if such folding had occurred for , considerable distances along an inverted limb—and it has never been seen to do so—the migmatite would ‘ somewhere underlie the granulite. Furthermore, no Alpine—type folding is known to exist elsewhere in the central Rocky Mountains. The relation of the pink gneiss to the other gneisses is not clearly revealed. The pink gneiss is exposed only in the northwestern part of the area, and there it seems to overlie the migmatite. For this reason it is considered younger than the migmatite. STRUCTURE The metamorphic rocks have been thrown into a series of isoclinal folds and cut by faults. a GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES FOLDS The principal fold in the area is a syncline trending . eastward or southeastward, flanked on the south by a southeastward-plunging anticlinal nose and on the north by an anticline trending east-west (fig. 113.2). On the limbs of the northern anticline there are minor 1 folds, some due to drag and others due to local flowage of the felsic rock layers. In the extreme northern part of the area, west of Frisco, only the west limb of a northward-trending anticline or the truncated nose of an anticline is exposed. It is separated from the struc- tures to the south by a fault and their mutual rela- tions are not revealed. FAULTS The Precambrian rocks in the Tenmile Range are cut by several large high-angle faults, marked by shatter zones that range in width from a few tens of feet to several hundred feet (fig. 113.2). Most of the shattered rock in these zones has been cemented by silica, and they are interlaced with quartz veins carry- ing variable amounts of sulfides. The north—south fault fissure southeast of Frisco contains potassium feldspar. Numerous slickensides in the sheared rocks indicate recurrent movements in various directions. REFERENCES Burbank, W. S., Lovering, T. S., Goddard, E. N., and Eckel, E. B., 1935, Geologic map of Colorado: US. Ge01., Survey. Harker, Alfred, 1939, Metamorphism, 2d ed. rev.: Methuen and Co., Ltd. London. 114. SALT ANTICLINES AND DEEP-SEATED STRUCTURES IN THE PARADOX BASIN, COLORADO AND UTAH By H. R. JOESTING and J. E. CASE, Washington, D.C., and Berkeley, Calif. Work done partly in cooperation. with the US. Atomic Energy Commission The salt anticlines of the Paradox basin (fig. 114.1) were formed by plastic flow of evaporites of Pennsyl- vanian age, which were originally more than 6,000 feet- thick in the deepest parts of the basin. Some of the anticlines are as much as 75 miles long, and their salt cores are something like 2 miles high and 2 to 4 miles long. The cores of the larger anticlines were exposed during much of their growth, so that sediments de- posited during that period pinch out against their flanks. Thick deposits of limestone and elastic rocks of late Paleozoic and Mesozoic age now cover the evapo- rites, except over the axes of the anticlines. All of the larger salt antinclines are in the deeper, northeastern part of the Paradox basin, Where the Pre— cambrian basement may in some places be as much as 17,000 feet beneath the surface. The anticlines all strike northwestward, parallel to the axis of the basin and to the structural front of the uplifted Uncom- 40° 37° 36° GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES 111° 110° 109° 108° 107° o Rangely \ 132.21g 7‘ —— UTAH cofoTzADO Glenwood Springs _ T _ — XRIZONK o Escalante O Cortez 4" U T E M TS NEW MEXICO "OK.\B°6_SIN .u'. Shim}; ' EXPLANATION Lees Ferry CARRIZO MTS J i i Faulted salt anticiine / Fault. hachures on downthrown side x Salt dome 50 O 50 IOOMILES L: . l 1 1 1 | )4 Anticline CONTOUR INTERVAL 100 GAMMAS ,4 Monocline FIGURE 114.1.——Sketch map of northern Colorado Plateau, showing Paradox basin and area discussed. B253 B254 pahgre Plateau (fig. 114.1). This fact suggests a re- lation between the anticlines and deep-seated regional structures, but if such a relation exists direct geologic evidence for it is buried beneath thick deposits of Per- mian and Mesozoic rocks. The tectonics of the Paradox basin, the nature and history of the salt structures, and the causes of salt flow, have been studied by many investigators. Se- lected bibliographies accompany publications by Shoe- maker, Case, and Elston (1958) ; Joesting and Byerly (1958); and Jones ( 1959). Jones thinks it probable that the salt anticlines were formed solely as a result of differential loading of the evaporites, rather than by compressional folding or deep-seated faulting as be- lieved by some of the earlier investigators. In this paper we are concerned only with the magnetic and gravity evidence bearing on the configuration and struc- ture of the Precambrian basement in the salt anticline area. of the Paradox basin, and on the association of deep-seated structures with the salt anticlines. ACKNOWLEDGMENTS Associated with us during most of the investigations were P. Edward Byerly and Donald Ploufi" of the Geo- logical Survey, who conducted much of the gravity work and made many of the interpretations based upon it. The aeromagnetic surveys were made under the direction of J. L. Meuschke and R. W. Bromery of the Geological Survey. SIGNIFICANCE OF THE MAGNETIC AND GRAVITY MAPS Preliminary aeromagnetic and gravity maps of the area are shown in figures 114.2 and 114.3. They are based on procedures described by J oesting and Byerly (1958) and Byerly and J oesting (1959). Because of the small scale and large contour intervals of the maps, they show only the more prominent anomalies. Magnetic and gravity highs are associated with the uplifted Uncompahgre Plateau and its buried north- western extension, where the generally magnetic and dense rocks of the Precambrian complex are closer to the surface than in the adjoining basin. Others are asso- ciated with the diorite porphyry laccoliths of the La Sal Mountains, which are denser and more magnetic than the enclosing sedimentary rocks. Large gravity lows, on the other hand, are associated with the larger salt anticlines, because the density of the thickened salt masses is only about 2.2 g per cm3, compared with about 2.55 g per cm3 for the adjoining rocks (Joesting and Byerly, 1958, p. 14—15). The evaporites and other sedi- mentary rocks are Virtually nonmagnetic. GEOLOGICAL SURVEY RESEARCH 1960-—-SHORT PAPERS IN THE GEOLOGICAL SCIENCES Ridges or upwarps of Precambrian basement rocks, some of them having a vertical relief of several thousand feet, are indicated by the magnetic highs bordering Gypsum Valley on the southwest and Moab Valley on the south and southwest (Joesting and Byerly, 1958, p. 10; Joesting and Ploufl, 1958, p. 89). These base— ment highs apparently form the southwestern bound- aries of the deeper parts of the Paradox salt basin. Estimates of depths to these sources of the magnetic highs were based on the methods of Vacquier and others (1951), and on methods described by Heiland (1940). The magnetic evidence for basement highs is sup- ported by regional gravity gradients along parts of Gypsum and Moab Valleys. These gradients indicate that the basement is denser or nearer the surface to the southwest and south, but the gradients are also partly due to the thinning of salt. The evidence for basement highs is partly confirmed by recently drilled holes that penetrated rocks of Mississippian age; the locations of some of these holes are shown in figure 114.2. Esti- mates of the thickness of the underlying sedimentary rocks were made from the isopach maps of Cooper (1955), Baars (1958), and Neff and Brown (1958). In some localities these estimates may be in error because of irregularities on the Precambrian surface, and be- cause we know little about the stratigraphy and struc— ture of the older Paleozoic rocks. Estimates of depths from magnetic data may, of course, also be in error. The magnetic and gravity evidence also suggests com- paratively shallow depths to the basement just north and also southwest of Lisbon Valley salt anticline (Byerly and J oesting, 1959, p. 44—45). This evidence is partly confirmed by recent drilling, which penetrated rocks of Mississippian age. Southwest of Lisbon Val— ley, however, the depth indicated by drilling is much greater than that estimated from the magnetic data. Gravity evidence (Byerly and Joesting, 1959, p. 46) also indicates that the basement lies deeper northeast of Lisbon Valley anticline, but the effects of changes in density and depth cannot be separated. The gravity and magnetic data further indicate that the La Sal Mountains and a large area to the southeast rest on a broad basement platform. The northeastern boundary of this platform is apparently defined by a continuation of the Paradox Valley regional gravity and magnetic gradients past the La Sal Mountains, the southeastern boundary by a southwest-trending gravity gradient extending from Paradox Valley to the northwest end of Gypsum Valley, and the northwestern boundary by a gravity gradient that bounds the La Sal Mountains on the northwest. These inferred bound— aries are shown on figures 114.2 and 114.3. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES 110°00’ 39°00, 109°30’ B255 i09°oo' 108°30’ Thompson 0 Cisco \9 —ll,000 / l J Crescent Junction 39°OO’ EXPLANATION 6:155? Magnetic contour enclosing area of lower intensity Thickened salt core of anticline (after Shoemaker and others, 1958) 3700 Drill hole showing estimated sea— level elevation of Precambrian basement / 38°30’ 38"OO’ HHHHHHHHHHHl Inferred structural boundary C A: Flown 8500 feet above sea level 8: Flown 12,500 lee! above sea level c: Flown 500 feet above surface 38°30’ & \ k <1) 15/ 6:7‘15/ 0 As/ / I8 OUravan as» E-i DIS 0 IO I0 110°00' 109°3o' 10 O L 109°OO’ 210 MILES FIGURE 114.2.—Preliminary aeromagnetic map of salt anticline area of Paradox basin, Colorado and Utah. The gravity anomalies along the inferred boundaries of the platform are probably caused in part by thin- ning of salt; for example, from Moab and Castle Val- leys southeastward toward the La Sal Mountains, and from Gypsum and Paradox Valleys northwestward. Their main causes, however, are differences in the den— sity or depth of the basement rocks. Magnetic evidence indicates comparatively shallow depth to basement at the northwestern end of Paradox Valley, and it there- fore seems likely that the regional anomalies may be due in part to relief on the surface of the Precambrian basement. REFERENCES Baars, D. L., 1958, Cambrian stratigraphy of the Paradox basin region, in Intermountain Assoc. Petroleum Geologists Guide- book 9th Ann. Field Conf., Guidebook to the geology of the Paradox basin, 1958': p. 93—101. Byerly, P. E., and Joesting, H. R., 1959, Regional geophysical investigations of the Lisbon Valley area, Utah and Colo- rado: U.S. Geol. Survey Prof. Paper 316—0. Cooper, J. 0., 1955, Cambrian, Devonian, and Mississippian rocks of the Four Corners area: Four Corners Geol. Soc. Field Conf. Guidebook, p. 59-65. Heiland, C. A., 1940, Geophysical exploration: New York, Pren- tice-Hall, Inc. Joesting, H. R., and Byerly, P. E., 1958, Regional geophysical investigations of the Uravan area, Colorado: US. Geol. Survey Prof. Paper 316—A. Joesting, H. R., and Plouff, Donald, 1958, Geophysical studies of the Upheaval Dome area, San Juan County, Utah, in Intermountain Assoc. Petroleum Geologists Guidebook 9th Ann. Field Conf., Guidebook to the geology of the Paradox basin, 1958: p. 86—92. B256 110°OO' 39°00, 109°30' GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 109°00’ 108°30’ @ Thompson Crescent J unctnon 38°30’ _____M_ESé£0_QI‘LTX_ MOIjTROSE COUNTY // / \ / \ / \ m,” ////fl 0 sq ‘ SAN IGUEL _COUNT_Y_ 38°OO' EXPLANATION Gravity contour enclosmg area of lower intensity C ’ _./ Thickened salt core of anticline (after Shoemaker and others, 1958) Laccoliths and related igneous intrusions ‘IHIIHIIIHIIIH Inferred structural boundary @o 00 0 Gateway 1‘0 29 MILES CONTOUR lNTERVAL 10 MILLIGALS FIGURE 114.3.—Preliminary gravity map of salt antieline area of Paradox basin, Colorado and Utah. Jones, R. W., 1959, Origin of salt aniticlines of Paradox basin: Am. Assoc. Petroleum Geologists Bu11., v. 43, no. 8, p. 1869~ 1895. Neft, A. W., and Brown, S. C., 1958, Ordovician-Mississippian rocks of the Paradox basin, in Intermountain Assoc. Pe- troleum Geologists Guidebook 9th Ann. Field Conf., Guide- book to the geology of the Paradox basin, 1958: p. 102—108. 5% Shoemaker, E. M., Case, J. E., and Elston, D. P., 1958, Salt anticlines of the Paradox basin, in Intermountain Assoc. Petroleum Geologists Guidebook 9th Ann. Field Cont, Guidebook to the geology of the Paradox basin, 1958: p. 86—92. Vacquier, Victor, and others, 1951, Interpretation of aeromag- netic maps: Geol. Soc. America Mem. 47, 151 p. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B257 115. DISTRIBUTION AND PHYSIOGRAPHIC SIGNIFICANCE OF THE BROWNS PARK FORMATION, FLAMING ' GORGE AND RED CANYON AREAS, UTAH-COLORADO By WALLACE R. HANSEN, DOUGLAS M. KINNEY, AND JOHN M. Goon, Denver, Colo., Washington, DC, and U .S. National Park Service, Washington, DC. The Browns Park formation (Miocene?), named by Powell (1876, p. 44 and 168), is typically exposed in the valley of Browns Park, in the Uinta Mountains, . which lies astride the Utah—Colorado State line. From its type area the formation extends eastward as an un- broken blanket almost to Craig, Colorado (Sears, 1924a, pl. 35; 1924b, fig. 1), a distance of about 85 miles; from Craig it extends discontinuously northward to and beyond Saratoga, ‘Vyoming (Love, IVeitz, and Hose, 1955). Its outcrop belt marks the course of an ancestral stream that probably flowed eastward toward the Mississippi drainage system (Bradley, 1936, p. 188). Recently discovered remnants of the Browns Park formation extend discontinuously westward from the type area for another 25 miles or so, in and along- side Red Canyon of the Green River. On the south slope of the Uinta Mountains, the formation is repre- sented by blanketlike deposits that cover broad areas north of Vernal, Utah (fig. 115.1). In its type area the Browns Park formation is widely and well exposed. Along the north side of the valley, its boundary is rather well defined by faulting, flexing, and erosion that occurred after its deposition. Along the south side of the valley, however, the formation has an irregular depositional boundary, because it extends partway up tributary valleys that had previously been cut into the Uinta Mountain group (Precambrian). Long tongue-shaped remnants of the Browns Park formation that have a different history occur in the headward parts of most of these tributary valleys, in- cluding the valleys of Crouse Creek, Sears Creek, War— ren Draw, Jackson Creek, Gorge Creek, and Cart Creek. These remnants, never previously mapped, are scattered over a maturely dissected terrain along the main divide of the Uinta range, and fill valleys cut by streams that originally flowed southward. They have been separated from the main body of the formation by subsequent erosion, and near their mouths the streams mentioned above have stripped off the Browns Park deposits or cut through them into the underlying Uinta Mountain group. Each tributary valley now has a pre— cipitous inner canyon near its mouth, cut into the Uinta Mountain group. Farther south the tonguelike rem— nants merge into a blanket that fills Summit Valley and tops Diamond Mountain, north of Vernal (Kinney, Hansen, and Good, 1959, p. 1630). The formation must once have extended across the eastern end of the Uinta range as a continuous blanket, above which only the higher peaks and ridges protruded. The configuration of the hard-rock floor of the axial portion of Browns Park Valley is unknown. Along the margins of the valley, however—particularly the south margin~the floor is highly irregular. In many places windows, spurs, and salients of Precambrian rock protrude through the Browns Park formation; the most notable of these is Kings Point, through which Swallow Canyon has been out by the Green River in a classic example of superposition. Westward from the type area, discontinuous remnants of the Browns Park formation become progressively smaller, thinner, and more widely separated. They consist of interbedded fanglomerates, sandstones, tufl's, and tufl’aceous sandstones, lithologically similar to equivalent deposits in the type area. Thick and rather extensive remnants at Little Hole reach from the river, which here is about 5,500 feet above sea level, to an altitude of more than 7,000 feet. The formation was deposited here on the walls and floor of a deep, irreg- ular canyon. Smaller remnants along Red Canyon west of Little Hole (fig. 115.1) have similar physio- graphic relations but do not reach river level; the sur- face on which they rest slopes upward toward the west. As remnants of the Browns Park formation in the Red Canyon area lie well below the Bear Mountain erosion surface, they must be a good deal younger than that surface. Eastward the Bear Mountain erosion surface appears to project into the air above Browns Park, rather than beneath it as Bradley supposed (1936, p. 163 and 180), and to merge into the remnants of the Gilbert Peak erosion surface that are preserved north of Browns Park on Goslin, Mountain Home, Head of Cottonwood, Bender, O-Wi-Yu-Kuts, and Cold Spring Mountains. Discordances in altitude between remnants of the Bear Mountain surface in the Red Canyon area and remnants of the Gilbert Peak sur— face on adjacent Goslin Mountain are attributed to faulting and warping that occurred before, during, and after the deposition of the Browns Park forma- tion. A cycle of valley cutting intervened between develop— ment of the Bear Mountain erosion surface and the deposition of the Browns Park formation. The shift GEOLOGICAL SURVEY RESEARCH lQGO—SHORT PAPERS IN THE GEOLOGICAL SCIENCES B258 .299 .3; $398 Mao? 3395893 c5“ wondmmfinnogh .8 van SSEUH .3 32m RES no EH» :95me an 32m 53¢ no wnfimdfi 50:38 no woman .owfifloOéfiD £53552 35D 5333 no “Ban 5 Avaaaswv nosaauom “ism makeum «o mesa—5.536 33qu MEBEE Qua :Rxfiwlfifii "293% mmgz m; o; m o .3 «9 .m ‘3 m9 .a ~8&9 .3 v9 .x m 3 ‘m m «N .m \mrmofl m 8 .m .m mm .z Somomofi .m .N ,m .m cm .m .sz Smwoov . .z : p awn 0 .52. 53:9 E3552 E600 ‘ . .z N— F Z m H w oofivlfill|onla~mg.fil|WI|rl..r|TI1|,II-IIJJI Irrll.ll,l||m<.m.blwll1ll IJ . IIIHKWJ .IlJooLv K a .3 N92 07:20.55 ‘>>mo_ m booms iv? v... m mm x m VN m \meoH m MN m 07:20.55 m MN m 699: m _N m m ON m GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES from degradation to aggradation may have been caused by heavy falls of volcanic ash, that mantled hillsides and clogged valleys and that were preceded and ac- companied by tectonic adjustments, rather than a cli- matic change. °The Browns Park formation thus has a haphazard relation to earlier topography; it caps a pediment remnant here, fills a valley there, or overtops a hillock somewhere else. In the Red Canyon area it filled an old canyon, overtopped the rims, and spread out onto the Bear Mountain surface. Subsequent re- juvenation entrenched the present Green River, which then carved Red Canyon by cutting through the Browns Park formation and into the Uinta Mountain group. REFERENCES Bradley, W. H., 1936, Geomorphology 0f the north flank of the B259 Uinta Mountains: U.S. Geol. Survey Prof. Paper 185—1, p. 163—199. Kinney, D. M., Hansen, W. R., and Good, J. M., 1959, Distribu- tion of Browns Park formation in eastern Uinta Mountains, northeastern Utah and northwestern Colorado [abs] : Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1630. Love, J. D., Weitz, J. L., and Hose, R. K., 1955, Geologic map of Wyoming: U.S. Geol. Survey. Powell, J. W., 1876, Report on the geology of the eastern por— tion of the Uinta Mountains: U.S. Geol. and Geog. Survey Tern, 218 p. Sears, J. D., 1924a, Geology and oil and gas prospects of part of Moffat County, Colorado, and southern Sweetwater County, Wyoming: U.S. Geol. Survey Bull. 751, p. 269— 319. 1924b, Relations of the Browns Park formation and the Bishop conglomerate and their role in the origin of Green and Yampa Rivers: Geol. Soc. America Bull., v. 35, p. 279—304. 116. PROBABLE LATE MIOCENE AGE OF THE NORTH PARK FORMATION IN THE NORTH PARK AREA, COLORADO By IV. J. HAIL, Jr., and G. EDWARD LEWIS, Denver, Colo. The discovery of fragments of fossil vertebrates of probable late Miocene age in the North Park formation in its type area in North Park, Colo., permits tentative dating of the formation, and supports correlation with rocks of late Miocene age (Montagne and Barnes, 1957, p. 59) mapped as the North Park formation in the Sara- toga basin of northern Colorado and southern Wyo- ming, and in other nearby areas. Beekly’s (1915, p. 66) redefinition of the North Park formation has generally been followed by subsequent workers. In the type area south of Walden in central Jackson County, Colo., the formation is at least 2,000 feet thick, and at different places lies on the White River formation of Oligocene age and on the Coalmont formation of Paleocene and Eocene age. Oligocene rocks underlying part of the North Park formation were recognized by Montagne (Montagne and Barnes, 1957, p. 56). The North Park formation of the type area is not continuous with rocks mapped as the North Park formation 20 to 30 miles farther north in the Saratoga basin of northern Colorado and southern Wyoming (McGrew, 1951, p. 54—57; 1953, p. 63—64; and Montagne and Barnes, 1957, p. 55—60). In the Sara- toga basin area, the North Park formation lies on rocks as old as Precambrian. The North Park formation both in its type area and to the north in Colorado and adjacent parts of southern Wyoming consists mostly of calcareous sandstone, with abundant conglomerate, conglomeratic sandstone, and limestone, and lesser amounts of shale, bentonitic clay, volcanic ash, and tufi'. Volcanic detritus composes much of the formation. Vertebrate fossils were collected at three localities. Locality D437 is in the type area southwest of Walden, Colo., and localities D146 and D272 are in the southern Saratoga basin, Colorado and Wyoming. At locality D437 two Weathered fragments of a fossil horse tooth were found in a bed of light-gray fine—grained calcare- ous sandstone about 900 feet above the base of the for- mation. In this area, the North Park formation lies unconformably on the Coalmont formation of Paleo- cene and Eocene age, and is about 1,100 feet thick; younger beds of the North Park have been eroded away. At locality D146 fragments of fossil horse teeth were found in beds of light-brown fine-grained calcareous sandstone that are estimated to be several hundred feet above the base of the formation. The formation in this area lies on Precambrian metamorphic rocks. At local- ity D272, fragments of an oreodont jaw were found in a bed of light-gray fine-grained calcareous sandstone 200 to 300 feet above the base of the formation. At this 10— cality the North Park also lies on Precambrian metamor- phic rocks. Tentative identification of the specimens and the localities from which they came are as follows: B260 Merychippus sp. ; USGS fossil vertebrate 10c. D437, NW% SW14 sec. 17, T. 8 N., R. 80 W., Jackson County, 0010.; two fragments of an upper cheek tooth. Merychippus sp.; USGS fossil vertebrate loc. D146, SWI/J, sec. 7, T. 12 N., R. 80 W., Carbon County, Wyo.; four fragments of upper cheek teeth. ?Brachycrus sp.; USGS fossil vertebrate loc. D272, NE1/4 NE1/4 sec. 7, T. 11 N., R. 80 W., Jackson County, 0010.; frag- ment of right ramus with one incomplete lower molar, and fragment of left ramus with lower molar and incomplete lower molars 1 and 3. These identified forms are elements of a fauna, prob- ably of late Miocene age, comparable to the fauna in the upper part of the Hemingford group of Nebraska which Lugn (1939, p. 1253—1258, 1264, table 2) be— lieves to be of latest Miocene age. Many authorities believe that this fauna may be as old as early late Mio- cene, somewhat older than Lugn believed it. to be (Wood and others, 1941, pl. 1). 117. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCES Beekly, A. L., 1915, Geology and coal resources of North Park, Colorado: U.S. Geol. Survey Bull. 596, 121 p. Lugn, A. L., 1939, Classification of the Tertiary system in Ne- braska: Geol. Soc. America Bull., v. 50, p. 1245—1276. McGrew, P. 0., 1951, Tertiary stratigraphy and paleontology of south-central Wyoming, in Wyoming Geol. Assoc. Guidebook 6th Ann. Field Conf., south—central Wyoming, 1951: p 54—57. 1953, Tertiary deposits of southeastern Wyoming, in Wyoming Geol. Assoc. Guidebook 8th Ann. Field Conf., Lar- amie Basin, ‘Vyoming, and North Park, Colorado, 1953;‘p. 61—64. Montagne, John De la, and Barnes, W. C., 1957, Stratigraphy of the North Park formation in the North Park area, Colorado, in Rocky Mountain Assoc. of Geologists, Guide book to the geology of North and Middle Park Basins, Colorado: p. 55—60. Wood, H. 13)., 2d, and others, 1941, Nomenclature and correla- lation of the North American continental Tertiary: Geol. Soc. America Bu11., v. 52, p. 1—48. PALEOCENE AND EOCENE AGE OF THE COALMONT FORMATION, NORTH PARK, COLORADO By W. J. HAIL, J 12., and ESTELLA B. LEOPOLD, Denver, Colo. Study of pollen and spore assemblages from the Coalmont formation of the North Park basin, Jackson County, Colo., indicates an Eocene age for the upper part of the formation instead of a Paleocene age as was previously thought. The Coalmont formation has an aggregate thickness of as much as 9,000 feet in parts of North Park. It unconformably overlies rocks mostly of Cretaceous age, and is unconformably overlain locally by the White River formation of Oligocene age and by the North Park formation of late Miocene age. The Coalmont formation forms the surface rock for much of the North Park basin. The Coalmont formation has been correlated in earlier studies entirely or in part with the Fort Union formation of Paleocene age in the western interior basin (Beekly, 1915, p. 62—63; Brown, 1949). This cor- relation was based on fossil leaves collected by A. L. Beekly and studied by F. H. Knowlton (Beekly, 1915, p. 61—66), and on fossil leaves collected and studied by R. W. Brown. More recently, however, R. W. Brown (written communication, 1958) suggest-ed that a collec- tion of fragmentary leaves from a bed of shaly sand- stone in the upper part of the formation might be younger than Paleocene. A sample of carbonaceous shale for pollen and spore study was collected at USGS paleobotanical loc. D1369, about 5 miles southwest of Walden (NWlfll sec. 8, T. 8 N., R. 80 “7.), from a bed at least 900 feet strati- graphically below the horizon of the fragmentary leaf collection examined by Brown (written communication, 1958) but at least 2,000 feet stratigraphically above any of B‘eekly’s leaf collections in western North Park (Beekly, 1915, p. 64-66). This sample contains five pollen and spore species common to Paleocene and E0- cene rocks of Wyoming; but, significantly, the sample also contains pollen of Platyca'rya. The genus Platy- camya, a member of the walnut family, has only one liv- ing species, which is now restricted to forests of north- ern China and Japan. To date, Platycarya pollen is known in the New World only from rocks of Eocene age; it is present in the Knight, Wasatch, and Green River formations in Wyoming, and the Clarno forma— tion in Oregon (E. B. Leopold and R. A. Scott, unpub- lished data). Many additional samples for pollen and spore studies were collected in the Pole Mountain-Coalmont area, the type area of the Coalmont formation in southwest- ern Jackson County. This area is about 14 miles south- west of \Valden. The stratigraphically highest sample (USGS paleobotanical loc. D1359, NE 14 sec. 21, T. 7 N., R. 80 W.) collected in the Pole Mountain- Coalmont area was from a bed of carbonaceous shale GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES about 3,500 feet below the top of the formation. This sample contains eight pollen and spore forms regionally common to Paleocene and Eocene rocks, as well as abun- dant pollen of Plug/cargo and Gramineae. Pollen similar to modern Gramineae (grass) pollen is not yet known from rocks older than Eocene. Gramineae pol- len has been found in Wyoming in the Green River formation of early and middle Eocene age, and in rocks younger than Green River. A suite of abundantly fossiliferous samples was col- lected at USGS paleobotanical loc. D1408 (SW 14 sec. 4, T. 6 N., R. 81 W.) and D1409 (NW 14 sec. 4, T. 6 N., R. 81 W.) from an 800-foot-thick carbonaceous shale sequence which lies about 2,800 feet stratigraphically below loc. D1359. Ten samples yielded 38 species of pollen and spores, of which the dominant form in most of the samples is pollen of Platycarya. Also present is pollen of Tiliaceae (linden family), here assigned to Tilda crassz'pites Wodehouse; Tilia, crassipz'tes pollen is known in Wyoming and Colorado from rocks of early Eocene through Oligocene age, but is lacking in rocks of Paleocene age. All but 2 of the 38 species occur in the Wasatch formation of early Eocene age, near Sheridan, Wyo. The other two species are found B261 in the Green River formation of early and middle Eocene age in southwestern Wyoming. A local unconformity in the Coalmont formation in the Pole Mountain-Coalmont area separates the 800- foot-thick carbonaceous shale sequence from the lower part of the formation; in this area the part below the unconformity has a minimum thickness of about 1,500 feet. Carbonaceous shale samples from several locali— ties in this lower part of the formation yielded only six pollen species, none of which is an exclusively Eocene form, but all of which are common in early Tertiary rocks of the Western United States. The authors conclude that the lower part of the Coalmont formation is of Paleocene age, based on the presence of Paleocene leaves; and that the upper part of the Coalmont is of Eocene age, perhaps early Eocene, based on the presence of pollen of Platycarya, Gramineae, and Tilia crassipites. REFERENCES Beekly, A. L., 1915, Geology and coal resources of North Park, Colorado: US. Geol. Survey Bull. 596‘, 121 p. Brown, R. W., 1949, Paleocene deposits of the Rocky Mountains and Plains: U.S. Geol. Survey map. ’5? 118. PRE-CUTLER UNCONFORMITIES AND EARLY GROWTH OF THE PARADOX VALLEY AND GYPSUM VALLEY SALT ANTICLIN ES, COLORADO D. P. ELSTON and E. R. LANDIS, Denver, Colo. Work done in cooperation with the U.S. Atomic Energy Commission The salt anticline region of the Colorado Plateau 0c- cupies the deep, axial part of the Paradox basin in west- ern Colorado and eastern Utah. The five major north- west-trending salt anticlines (inset, fig. 118.1), which are 30 to 70 miles long, have structurally complex cen- tral parts 2 to 6 miles wide, and salt cores 4,100 to 13,- 700 feet thick. Southwest of these, the salt-bearing unit of the Paradox member of the Hermosa formation (Middle Pennsylvanian) ranges from 0 to about 3,000 feet in thickness, whereas its original thickness in the deep part of the basin may have been about. 7,000 feet. Rocks of the Paradox member, consisting of gypsum, generally fine-grained clastics, and carbonates, crop out locally in several valleys eroded along the axes of the salt anticlines, together with some broken beds of clayey gypsum, that appear to be residual from leached salt beds. These rocks are about 400 to 1,300 feet thick. They overlie the salt and are unconformably overlap- ped by Paleozoic beds that consist of marine limestone and shale and of marine and continental siltstone, arko- sic sandstone, and conglomerate. The aggregate thick- ness of the younger Paleozoic ‘beds is only a few hun— dred feet over parts of the salt structures, but is more than 5,000 feet in areas between the salt structures. PARADOX VALLEY Unconformities have been found at several places in Paradox Valley beneath thinned sequences of the up- per member of the Hermosa formation (Middle Penn- sylvanian), the Rico formation (Middle and Late Pennsylvanian in the Gypsum Valley and Paradox Valley areas), and the Cutler formation (Permian). B262 The upper member of the Hermosa formation is com- monly less than 50 feet thick in scattered outcrops, and in the northwest part of Paradox Valley it is separated from the Cutler formation by about 150 feet of inter- bedded limestone and arkosic sandstone of the Rico for— mation, both of whose contacts are unconformable. Both the upper member of the Hermosa formation and the Rico formation are about 3,000 feet thick on the south flank of the Paradox Valley salt anticline. There is a marked unconformity beneath the Cutler formation (fig. 118.1). The basal beds (units Pea, Feb and P00) consist of about 100 feet of gray, platy— bedded to indistinctly bedded, marine (?) sandstone and conglomerate, which grade. upward into fluviatile red beds typical of the Cutler (unit Fed). The lowest unit of the Cutler (Pca), which is about 50 feet thick in the eastern part of the map area and contains scattered pebbles derived from underlying rocks, was deposited in fold troughs on an irregular erosion surface. Although this unit (Pca) pinches out locally to the west, an out- lier rests unconformably on the Paradox member of the Hermosa formation about 900 feet to the south of the pinch-out. In the western part of the map area, the next younger unit (Pcb) unconformably overlies the upper member of the Hermosa formation, which appar- ently truncates a part of the Paradox member. GYPSUM VALLEY Unconformities are seen in Gypsum Valley beneath the Cutler and Rico formations and beneath the upper member of the Hermosa formation in the map area of figure 118.2, and also two unconformities within that member. The upper member of the Hermosa forma- tion and the Rico formation rest unconformably on sev~ eral different units of the Paradox member. The upper member of the Hermosa formation, which pinches out over the anticline in the central part of the map area but which is about 100 feet thick 011 its flanks, consists chiefly of gray dolomite and limestone. Its lowermost persistent unit is a bed of resistant dolo- mite, about 5 feet thick. \Vest of the topographic saddle near the crest of the anticline, this dolomite over- lies black shale of the Paradox member with sharp angular discordance, and also truncates an isolated dolo- mite bed of the upper member of the Hermosa that is sharply folded into the black shale. About 300 feet south of the anticline, the persistent dolomite over- lies a gypsum unit of the Paradox member. On the southwest side of the saddle, about 50 feet of thin- bedded dolomite in the upper member of the Hermosa is truncated in a distance of about 150 feet beneath a breccia—rubble that contains pebbles, cobbles, and boul- GEOLOGICAL SURVEY RESEARCH 1960—SHOR’I‘ PAPERS IN THE GEOLOGICAL SCIENCES ders of limestone and sandstone. An overlying dolo- mite is truncated in turn by the Rico formation. The Rico formation, which is about 100 feet in maxi- mum thickness but pinches out over the salt structure, consists of irregularly bedded grayish-red siltstone, sandstone, limestone, and dolomite. Some of the car- bonate beds in the upper half of the formation are elastic and consist of angular carbonate fragments in carbonate cement, indicating unsettled conditions of deposition. In the northeast part of the map area the Rico formation is unconformably overlain by a thin wedge of purplish arkosic to conglomeratic sandstone, typical of the Cutler formation. CONCLUSIONS The facts outlined above show that the cores of the Paradox Valley and Gypsum Valley salt anticlines are overlain by thin post-Paradox formations of Pennsyl- vanian and Permian age, pinching out over the anti- clines and separated by unconformities. These facts in— dicate that the growth of the salt cores in both anti- clines began in Middle Pennsylvanian time, not later than sometime during the deposition of the upper mem- ber of the Hermosa formation, that the tops of the salt structures generally stayed near local base level, and that the unconformities within, and separating, the thinned late Paleozoic formations record pulses of ver— tical movement in the salt cores. Because of the relatively thin cover of rocks above the salt prior to growth of the cores, it is thought that growth of the salt core was initiated by tectonic activ- ity. Such activity is recorded at some places by the arkosic debris, shed from the ancestral Uncompahgre Range, that is interbedded with evaporite and carbon- ate rocks in the Hermosa and Rico formations. Re- peated tectonic pulses may have caused continual growth, or at least intermittent growth, in Pennsyl- vanian time, during which more sedimentation took place alongside the growing salt structures than on their tops. After the uplift of the Uncompahgre Range, however, the continued growth of the salt cores during much of Permian time probably resulted from differential loading. The widely held concept that a great thickness of late Paleozoic beds was pierced by intrusive salt masses during inception of the salt anticlines is not compatible with the field evidence. This, however, does not pre— clude later intrusion into beds of the Cutler formation that may have covered the salt structures in Permian time. REFERENCES Cater, F. W., Jr., 1955a, The salt anticlines of southwestern Colorado and southeastern Utah, in Four Corners Geol. Soc. B263 STATE S GEOLOGY OF WESTERN CONTERMINOUS UNITED .860 56:?» xowgam mo 9:3 He 92: ommgcownlawz $5lo NVlNYA'IASNNBd NVIWHEd AHVNHBLVHO 63 we efla. 2.5m a. Q3395 833 10.9.35 “1333.3 93:3 “.831 €333 hfiwaEfi—Eaas :23 ‘3an .22.: 3.13 5. 393 3:33;. 28 3:25 ....III~|+|\ 33.9.8 :33 @826 i833 Suoefimuesaau 93:3 ‘2‘an .333 3.3:. 5. 33.3 35335. 28 :53: :..|||T'\ £8 #3252393 6 $3.: 8325:: .3 2:3 2:35 \. fl imi \ 3333 finds 3.235 £3338 E33 33% Sign». 3%.;5. 31.33.33 3E§§ ~33 392:8 wutoxgm 33:3: 33:8 3:5qu ..+.I:--T:--T. ugg 2.33 @333 .6833 finggc 233 swig no :90 \ 3S: .8:: :32 v.3 6:833; .33? $39 3:3.u33e 8 :Uxhéiafiiazm 8322.: NE... u§~§£uaas§w~e“55:33.32“— Qseoqu: Sagas. .SIK £33395 3283:: u§=§8 int—Eu “2% 8 aE§.§3.fi§= .8 ga— .§3§§Q $35: .3»: .63 2.832»: 93.2:38» SE3. £2533; 5.3. 33:: 339:.»03 33233“ tesaéssn .8wa figs .ERuQE: 3333233 {$333.3 $633 :35 EXEQE Lugs .25 .5855 novuham >LL . ‘ a 023 $352: “RED r E >LLva=< E 225:8 r E 20 _F> S .m :2 31h .Nm .uow S25 «\D E a. no; n32 ucu cofim ,a o E xusouo kmwu 0mg OOH Om o “.2553. 2 £33 6.8m 32:2, 2250 23m .3550: .«muo moo! :65 .. 3 2:6 3 =uz «mac Eat c303 .03 28:22 23.03 .6 EEuNE “ NV ., an» AP \ ~ 8.; \ OS \.. m2: .228 ca .29:me E9: 2333 unE .39: .I I I I I J :2 N o" o _ .t u.— E :32? 3.3 an: _o¢veo It ._ I weeping: 2:33:- mc 28 «Em I: I cos-2:2 umoELoI .o .3506 Loan: *0 ocofioE= uEEoB 2 2:: uofiazm .50; :55: 303 265.35 use: 8 can 03% “En 33380... 32200 95 :33 6032 056:5 :3 we 3E xovs 4—..L. < . v .. 5552:. 9/1.... 29920 THE GEOLOGICAL SCIENCES SURVEY RESEARCH 1960—SHORT PAPERS IN GEOLOGICAL B264 .300 $31.. > Eswahw @5an we flan we 92: Bwofiowwlnfiwfifi amwah .: .3 £33358 $353 ESSQ oEBEnm 133%:8 E33 E83 2:222 wfiura 339:: 339 .0 3%.; £3933: £23389 SSS: 3er :swm .LI @333 Ssgwaga s fiégw 23:; Esq NVINVAWASNNEd NVIWHEd AaVNHBiVflO DISSVIHJ. 5380 €393.33 $553 1:: 33E: EESENS 33:. $39 .5232: Rcfiasuk 5 sn— timekzoozx. 53§§ L233 55n— aoSwEgom «moEwm __ : =_= In .I >2 «£2002: 55558 8E E t:<&0k2 Q 023 55558 .5350 tIiQDkZOUZD :ofiuEuom 2220 E ocoumcnam 8a???» E \C. \EQDkZOUZD 329% wagon. nywv h mmmfl 53mm m ‘0 tea £98.. .1 .m. 3 E280 anon 8.5.th «o .5 28 gram 3%.. mum: mo Ev can Siam 0M1 \mm_._.z_ «Dokzoo . _ ”3.2 g.» , w» o .3 m: .m :z B: D 8m _ E Sm 02 .558 mmomezofl 4 ‘ xxxxxxxx. 000m 00mm ~ GEOLOGY OF WESTERN CpNTERMINOUS UNITED STATES Guidebook Field Conf. No. 1, Geology of parts of Paradox, Black Mesa, and San Juan Basins, 1955: p. 125—131. . 1955b, Geology of the Davis Mesa quadrangle, Colorado: US Geol. Survey Geol. Quad. Map GQ—71. 1955c, Geology of the Anderson Mesa quadrangle, Colo- rado: U.S. Geol. Survey Geol. Quad. Map GQ—77. Herman, George, and Barkell. C. A., 1957, Paradox salt basin: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 5, p. 861— 881. Jones, R. W., 1959, Origin of salt anticlines of Paradox Basin: Am. Assoc. Petroleum Geologists Bull., v. 43, no. 8, p. 1869— 1895. Prommel, H. W. C., and Crum, H. E., 1927, Salt domes of Permian and Pennsylvanian age in southeastern Utah and their influence on oil accumulation: Am. Assoc. Petroleum Geologists Bull., v. 11, no. 4, p. 373—393. Shoemaker, E. M., 1954, Structural features of southeastern Utah and adjacent parts of Colorado, New Mexico, and Arizona, in Utah Geol. Soc, Guidebook to the geology of Utah, No. 9, 1954 : p. 48—69. Shoemaker, E. M., Case, J. E., and Elston, D. P., 1958, Salt anticlines of the Paradox basin, in Intermountain Assoc. [19. B265 Petroleum Geologists Guidebook 9th Ann. Field Cont, Guidebook to the geology of the Paradox basin, 1958: p. 39—59. Stokes, W. L., 1948, Geology of the Utah-Colorado salt dome region with emphasis on Gypsum Valley, Colorado: Utah Geol. Soc, Guidebook to the geology of Utah, No. 3, 50 p. 1956, Nature and origin of Paradox basin salt struc- tures, in Intermountain Assoc. Petroleum Geologists Guide- book 7th Ann. Field Conf., Geology and economic deposits of east central Utah, 1956 : 1). 42—47. Stokes, W. L., and Phoenix, D. A., 1948, Geology of the Egnar- Gypsum Valley area, San Miguel and Montrose Counties, Colorado: US Geol. Survey Oil and Gas Inv. Prelim. Map 93. Wengerd, S. A., and Matheny, M. L., 1958, Pennsylvanian system of Four Corners region: Am. Assoc. Petroleum Geologists Bull., v. 42, no. 9, p. 2048—2106. Wengerd, S. A., and Strickland, J. W., 1954, Pennsylvanian stratigraphy of Paradox salt basin, Four Corners region, Colorado and Utah: Am. Assoc. Petroleum Geologists Bull., v. 38, no. 10, p. 2157—2199. 6% STRUCTURE OF PALEOZOIC AND EARLY MESOZOIC ROCKS IN THE NORTHERN PART OF THE SHOSHONE RANGE, NEVADA By JAMES GILLULY, Denver, Colo. Work done in cooperation with the Nevada Bureau of Mines Structural analysis of the area has revealed struc- tures that rival those of the Alps in complexity. The Roberts thrust has moved sheets many thousands of feet thick, composed of siliceous Ordovician, Silurian, and Devonian rocks, over carbonate rocks of Cambrian, Ordovician, Silurian, and Devonian age. Not only is the Roberts thrust itself folded into a tight overturned anticline, but the numerous thrust slices composing its upper plate have been folded into isoclinal folds, some of them several thousand feet across. Some of these folds are recumbent, others upright, but all ride on the Roberts thrust. They are cut by a vertical fault about 10 miles long, almost normal to their trend, on 5577.53 0—60—18 either side of which very diverse structures have been developed simultaneously. All these structures are probably of Early Mississippian age. Superimposed on, and doubtless to some extent modi- fying, the Paleozoic structures are thrust sheets involv- ing rocks of Ordovician, Pennsylvanian, Permian, and probable Triassic age. These sheets, though warped, are much less complexly folded than those below. Their transection of the underlying thrust sheets, as well as their simpler structure and differing facies, prove them to be younger, but the absence of any dated rocks be- tween Triassic and Miocene in the area. makes it impos— sible to assign a precise date to this orogeny. B266 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S 120. STRUCTURAL FEATURES OF PYROCLASTIC ROCKS OF THE OAK SPRING FORMATION AT THE NEVADA TEST SITE, NYE COUNTY, NEVADA, AS RELATED TO THE TOPOGRAPHY OF THE UNDERLYING SURFACE By F. N. HOUSER and F. G. POOLE, Denver, Colo. Based on work done in cooperation with the US. Atomic Energy Commission All the contained underground nuclear explosions of the past few years at the Nevada Test Site have been in tuff of the Oak Spring formation, of Tertiary age. For a complete understanding of the regional Tertiary geologic history and the local geology of the under- ground test sites, it is necessary to decipher the local structure—part-icularly the anticlines and synclines that were mainly formed by deposition on the hilly erosion surface underlying the Oak Spring formation—— and to distinguish them from similar structures of tectonic origin. These anticlines and synclines (termed primary for purposes of this report) are moulded on pre-existing ridges and valleys, to which they roughly conform, and delimit the areas of relatively thin and thick tuff. The initial dips assumed by the beds have been modified to an unknown extent by differential compaction. Ray E. Wilcox (1958) and W. R. Hansen and R. W. Lemke (written communication, 1958) were among the first to attribute these anticlines and syn- clines to the causes above outlined. The primary anticlines and synclines in the pyro~ clastic rocks at the Nevada Test Site have been modi- fied by tectonic tilting, folding, and normal faulting. In the mapped area (fig. 120.1), known faulting has been taken into account in analyzing the structure. This area may have been tilted or folded as a whole, though evidence for this is lacking. In the northern part of the Test Site the Oak Spring formation is as much as 2,300 feet thick and consists of very thick to thin layers of welded and nonwelded tuff and thick-bedded to laminated fluvial, lacustrine, and possibly eolian tuffaceous deposits. The tufls were initially deposited, as ash falls or ash flows, on an ir- regular surface of considerable relief, and were subse- quently reworked in large part by water and wind to form tuifaceous sedimentary rocks. The width, length, amplitude, and location of the primary folds in the Oak Spring formation depend directly on the local relief of the underlying surface and the thickness and character of the deposit—ash- fall tufl's, ash-flow tuffs, or tuifaceous sediments. Detailed study has shown that the local relief on the erosion surface under the Oak Spring formation is of the same order of magnitude as the relief on the present topography of nearby surfaces carved from Paleozoic rocks and not covered by pyroclastics (fig. 120.1). The maximum local relief on the old surface ranges from 400 to 1,600 feet in horizontal distances of 1,200 to 19,000 feet. The rocks on which this surface is cut are structurally complex Paleozoic argillites, quart- zites, and carbonates, and an igneous stock of Mesozoic or early Tertiary age. In some localities the present stream valleys and ridges developed in these rocks are in part alined with those in the surface underlying the Oak Spring formation. The variations in the thickness and structure of the Oak Spring formation in the mapped area reflect the underlying topography. Because it was deposited on a highly irregular surface, the Oak Spring formation has a range in thickness of at. least 1,200 feet. But although the thicker parts overlie the old hollows they never completely filled them; and volcanic rocks only partly filled the valleys and draped themselves, in smaller thickness, over buried ridges. The bedding in the basal part of the formation is generally subparallel to the underlying surface. Dips of about 30° are most common, but locally, adjacent to steep slopes or cliffs on the old surface, dips of as much as 40° were ob— served. Farther from this surface the dips have be- come progressively lower, because the topographic re— lief was gradually subdued by continued deposition, erosion and redistribution of volcanic material. Figure 120.1 shows the close relationship of primary anticlines and synclines to the configuration of the un- derlying surface. The mapping of the major drainage and contours on that surface is based on study of out- crops. The primary structural axes are taken from structure contours drawn on the base of a persistent welded tuff. The clOseness with which the old topography is ex- pressed by the primary structures differs for the three different types of deposits—lacustrine and fluvial tuf- faceous sediments, ash flows, and ash falls. The tuifaceous sediments were deposited in valleys and are generally in horizontal or gently dipping beds, depending on the slope of the underlying surface, and they generally form lenticular bodies. B267 STATES GEOLOGY OF WESTERN CONTERMINOUS UNITED 05 5 3:: .53in £5 60395 d we wusuosbw Egg—ow 93 5853 mscfifioa 9: warscam 362 93530 wzz £95 33m wsiaw wa 25 mo anzlédmfi ”55th 3.3 mac. 2: E 550:: 9:». mEom 2:393 0: £255 5:59: 2: 5:3 wwauEOmma A559,? .35 mEonv MFG E02 how unwoxm— .coEuwaEOo .qmazuhwmtc cum :Sfimonwv an twee—Law $05 93 mas—=25» uca moi—05.5 hum—5.5. $8 EEEom 6 was mo a6 a; 3:8 Q/ szagew. 3&5; Egg .Sokao Sefifiuéfi 33.2% @9256 now—«SSH MEEm “30.95 5.32 dwh 833?. 333(st $5er is :9833 .Eimkf 32%: EiéQ $3.:an Kc Sinai». Etc 2§3 3:23? 33.: u§§§m oE—uczm KNEE . //l v \1 ¢ :33? axsuxsek. ESQR is 39:33 .uwthg 32%: ESEGQ .wuxfa \e ficfiuwtv ~32. 363 33.3% was: 9:323. cam—owns Edema //I+\< :33? we: 38; gtam 930.st :w @2313 33:: $3» :Sogffificv d £5. SSESA‘: ‘3 $333 Euuegwaesaas :23. EfiaQ “wow 5 “55033va .35.?» MERE? .fisfim — £833 Smugfigd 2339 ~5de 8350 ///I‘||\ ZOC._ H N» o «A. :oEmEufi MEEm Two 9/ f/ “ uennmEcD 9.8. mctaw xmoAta B268 In the ash flows, at least in the welded flows, most of the layering is horizontal or gently dipping. The initial dips measured in the welded-tut]? marker unit (fig. 120.1) are mostly between 3° and 6° and average about 4°; the highest dip measured in them was 7°. Some tufl units in the lower part of the Oak Spring formation that exhibit characteristics of ash flows are restricted to the old valleys. These units thicken in the lower parts of the valleys and generally have a flat or slightly concave upper surface and an uneven or con- vex base. They are structureless, very thick bedded, and poorly sorted, and in places they show a poorly developed columnar structure. The ash falls are blanketlike and conform most closely to the old topography. It is in these deposits that high primary dips are found. At one locality in the southwestern part of the mapped area, where both ash—fall and ash-flow tuifs were deposited against a buried hill, the primary dips about 150 feet from the old erosion surface are 25° in the ash fall but only 7° in the ash flow. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Many other primary structures, including contorted strata, cross-bedding, ripple marks, erosional uncon- formities, graded bedding, and faults of small offset as- sociated with slump structures, characterize parts of the tuffaceous sediments and the nonwelded tuffs. These features appear to be commonest in the deposits that lie in the medial parts of the old valleys or extend along steep slopes. Although their total effect is small as compared with the volume of the rocks affected by them within the map area, they indicate that deposi- tion of tuff was locally interrupted for long enough pe- riods to permit redistribution of some material by slumping and by fluvial and possibly eolian transport. REFERENCE Wilcox, R. E., 1958, Petrography and chemistry of the Oak Spring formation, Chapter 2, in Diment, W. H., and others, Properties of the Oak Spring formation in Area 12 at the Nevada Test Site: U.S. Geo]. Survey TEI-672 (preliminary draft), open-file report. 121. ORIGIN OF THE AMARGOSA THRUST FAULT, DEATH VALLEY AREA, CALIFORNIA: A RESULT OF STRIKE-SLIP FAULTING IN TERTIARY TIME By HARALI) DREWEs, Denver, Colo. BLACK MOUNTAINS FAULT BLOCK The Black Mountains block is a lozenge-shaped struc- tural block 70 miles long and 25 miles wide just east of Death Valley. It is bounded on the northeast and southwest by faults that appear to be strike-slip faults, and is probably bounded on the east and west by simi- lar faults buried beneath Death Valley and Amargosa Valley. The strike-slip fault on the southwest (Noble and Wright, 1954, pl. 7) branches from the Garlock strike—slip fault where it swings southward to join the Soda-Avawatz strike-slip fault. Precambrian metamorphic and sedimentary rocks are unconformably overlain in this region by Paleozoic carbonate and clastic rocks about 4 miles thick, and are intruded by monzonitic stocks of Mesozoic or Ter— tiary age. These rocks are unconformably overlain in most places by thin continental sedimentary deposits and by volcanic rocks, collectively of middle and late Tertiary age. The rocks are broken into large, tilted structural blocks bounded, at least in part, by faults presumably typical of the Basin and Range province. Thick Quaternary deposits fill parts of the fault— controlled valleys. In the Black Mountains block the only Paleozoic rocks remaining are in small masses chaotically scat- tered between the underlying Amargosa thrust fault and the overlying volcanic rocks. The block also con- tains monzonitic rocks of early or middle Tertiary age (Drewes, 1959, p. 1500). Fanglomerate of middle Tertiary age, consisting of fragments eroded from the Black Mountains block before the extrusion of the vol- canics, lies high on the mountains northeast of the block. At least two small basins on the block are filled with sediments about 2 miles thick, deposited during late Tertiary time. The block was unusually mobile during Tertiary time. During middle Tertiary time and before extru- sion of rhyolitic lavas, it was raised several miles and most of the Paleozoic rocks were removed, some to be deposited as the fanglomerate to the northeast. Before late Tertiary time the lavas were much faulted and tilted, and at least two parts of the block subsided to GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES form basins in which sediments several miles thick were deposited. One of these basins lies adjacent to the fanglomerate to the northeast; hence displacement of the block washreversed. The rate of uplift of the Black Mountains with respect to Death Valley has increased from middle Tertiary to Recent time, judging from the disproportionately large displacement of the younger rocks, as compared with the older rocks, along the front fault. Such large recurrent. and reversible movements support the' inference that the faults do bound the block and do extend beneath the adjacent valleys to enclose the Black Mountains block as a large horse in a strike-slip fault zone. AMARGOSA THRUST FAULT The Amargosa thrust fault is restricted to the Black Mountains block; it is extensively exposed in the south- ern part of the block, largely eroded from the central part, and either eroded away or buried in the northern part. Sedimentary rocks of younger Precambrian and older Paleozoic ages are chaotically broken into blocks hundreds to thousands of feet long, which are sepa- rated from each other and from the underlying rocks by gouge sheets a few inches to a few feet thick. This assemblage is the Amargosa Chaos of Noble (1941). The blocks comprise small parts of many formations that are locally imbricated in a normal, but foreshort- ened, stratigraphic sequence (Noble, 1941, p. 966). The chaotic blocks are surrounded by gouge, and are less shattered and more heterogeneous than those in the megabreccias common in many younger formations of the region, and they are not interbedded in fanglom- erates as the megabreccias are. The net displacement on the Amargosa thrust fault is small, for most of the adjacent ranges contain undisturbed Paleozoic rocks or rocks with less-broken plates between bedding-plane thrust faults; yet the total movement was considerable, judging from the many thousands of feet of missing strata. The Amargosa thrust fault is younger than the stocks, for unaltered Paleozoic rocks are thrust over coarse-grained monzonitic rocks, and monzonitic rock is included with the chaotic blocks; but it is older than the volcanics, for lavas lie unconformably on chaotic blocks, and feeders to the lavas cut the blocks. Three hypotheses of the origin of the Amargosa thrust fault, as illustrated in figure 121.1, involve (a) a rooted thrust fault branching near the surface, (b) landsliding, and (c) jostling within a large block in a strike-slip fault. A rooted structure does not explain the areal restriction of the Amargosa fault, and the short distance of movement available to such a. fault does not explain the absence of so much of the Paleozoic sequence. A landslide origin fails to explain either B269 EXPLANATION Rocks of the upper plate \ \ / \ Rocks of the lower plate / Fault or glide plane under landslide, showing di- rection of movement Recurrent fault, direction of movement alternates 9w Section represented by the chaotic blocks in the Black Mountains fault block FIGURE 121.1.—Block diagrams illustrating three basic hy- potheses of the origin of the Amargosa thrust fault. A, local thrust fault branching near the surface. B, shingled land- slides from raised area. 0, j0stling within a large block in a recurrently shifting strike-slip fault. the normal stratigraphic sequence or the missing strata. It also fails to explain the relatively unshattered blocks surrounded by gouge, which differ markedly from those in the magabreccia deposits demonstrably of landslide origin. The hypothesis that I favor ascribes the Amar- gosa thrust fault to jostling within a large fault block as a result of recurrent movement on the bounding strike-slip faults. It explains the localization of the fault and the fact that the rocks in parts of the block are in the normal stratigraphic sequence. It also pro- Vides much movement with little displacement, which could have ground up the missing rocks. How the ground-up rock was removed is not clear, but that process is not fully explained by the other hypotheses either. . Noble and Wright (1954, p. 152) explain the origin of the fault by a squeezing and arching of the Black Mountains block that produced landsliding off the crests of the arches or possibly caused bedding-plane rupture along their limbs. The age of the folds, how- B270 ever, is probably Precambrian, for some of the younger Precambrian rocks in the region are not folded. Some of the difficulties of the first hypothesis (a) are also inherent in their explanation. The explanations of- fered by Sears (1953, p. 182—186) and Bucher (1956, p. 1311) also involve gravity sliding plus other modi- fications. IMPLICATION TO REGIONAL STRUCTURE The Riggs Chaos in the Silurian Hills, 40 miles southeast of the Amargosa Chaos, is thrust along near- ly the same horizons as the Amargosa Chaos (Kupfer, 1960) ; it also lies adjacent to a large strike-slip fault, and according to Kupfer (1960, p. 205) it did not orig- inate by landsliding. I suspect that this is another structure formed by thrust faults resulting from re- current movement along a strike-slip fault. Bedding-plane thrust faults along which younger rocks are moved over older ones are common in east- ern Nevada and western Utah. Perhaps some of them are neither rooted thrust faults nor gravity-slid plates, but are formed, like the Amargosa thrust fault, as a rupture within blocks adjacent to recurrent-1y and com- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES plexly moving faults. Thrust faults along the same stratigraphic horizons on opposite sides of a strike-slip fault need not have been continuous. The amount of movement along thrust faults should diminish away from widely spaced strike-slip faults. REFERENCES Bucher, W. H., 1956, Role of gravity in orogenesis: Geol. Soc. America Bu11., v. 67, no. 10, p. 1295—1318. Drewes, Harald, 1959, Turtleback faults of Death Valley, Cali- fornia; a reinterpretation: Geol. Soc. America Bull., v. 70, no. 12, pt. 1, p. 1497—1508. Kupfer, D. H., 1960, Thrust faulting and chaos structure, Silu- rian Hills, San Bernardino County, California: Geol Soc. America Bull., v. 71, no. 2, p. 181—214. Noble, Levi, 1941, Structural features of the Virgin Spring area, Death Valley, California: Geol. Soc. America Bu11., v. 52, no. 7, p. 941—1000. Noble, Levi, and Wright, L. A., 1954, Geology of the central and southern Death Valley region, California, pt. 10 in chap. 2 of Jahns, R. H. ed., Geology of southern Califor- nia: California Div. Mines Bull. 170, p. 143—160. Sears, D. H., 1953, Origin of Amargosa chaos, Virgin Spring Area, Death Valley, California: J our. Geology, v. 61, no. 2, p. 182—186. 122. BEDDING-PLANE THRUST FAULTS EAST OF CONN ORS PASS, SCHELL CREEK RANGE, EASTERN ‘NEVADA By HARALD DREWEs, Denver, Colo. Connors Pass, in which US. Highways 6 and 93 cross the Schell Creek Range, lies about 20 miles south- east of Ely, Nev. Geologic mapping east of the pass (fig. 122.1) confirms Misch and Easton’s (1954) rec- ognition of thrust faults in a Paleozoic section, but it has led to a different interpretation of the stratigraphy and structure. Whereas Misch and Easton believed that an inverted Devonian and Mississippian sequence had overridden the Prospect Mountain quartzite and remnants of Cambrian limestone, I regard the overrid- ing rocks as a sequence of Cambrian to Permian for- mations in normal order but tectonically thinned along thrust faults that are near bedding planes. The larg- est thrust fault has cut out all the many thousands of feet of rocks of Middle Ordovician to Pennsylvanian age, with the exception of two small blocks of Middle Devonian age. The rocks of the lower major plate are similar to those in the southern part of the Snake Range, across Spring Valley (Drewes and Palmer, 1957). They in- clude parts of the Prospect Mountain quartzite, Pioche shale, Pole Canyon limestone, Lincoln Peak formation, and Windfall formation-Pogonip group undifferenti- ated (essentially the Pogonip limestone of Hague). The Pole Canyon limestone is recrystallized, and near its top it is much sheared. It is alternately thickened and thinned northward by an overlying minor thrust fault that cuts its beds at varying angles. The Lin- coln Peak formation, which provisionally includes beds a. little younger than the youngest in the type section, generally consists of shale and shaly limestone with a few thin limestone beds, but here the shale is meta- morphosed to phyllite and slate, though the interbed- ded limestone is little changed. This formation has commonly been correlated with the Pilot shale, of Dev- onian and Mississippian age, but it is continuous With less metamorphosed and abundantly fossiliferous Cam- brian shale eight miles farther north. The overlying thin, strongly sheared limestone is a klippe of the Po- gonip group, three units of which have been traced GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B’ Cpc Qngm Qg k/Wpflf-v B271 EXPLANATION FIGURE 122.1.—Mvap and structure sections of an area east of Connors Pass, Schell Creek Range, Nev. northward to fossiliferous rocks. The basal few hun- dred feet of the group, though present to the north, are missing here, and at the top of the group several thousand feet of beds are progressively sheared out southward, so that south of the junction of High- ways 6 and 93 scarcely 100 feet of the group remains beneath the rocks of the upper major plate. The rocks of the upper major plate include much limy siltstone, sandstone, and limestone of the Arcturus formation, together with a large wedge of Ely limestone and two small blocks of limestone and dolomite of the Guilmette formation. The Arcturus formation is unconformably overlain by red conglomerate inter- bedded with a little limestone and associated with black shale and tufl'. The conglomerate contains pebbles of g E m . ’ > Gravel E Gu1lmette formatlon g 2 ‘ ' ~ 0 — z E . - s: ' > . . ET: 8 Conglomerate E Pogonlp group and Wmdfall 3 g E formation,undifferentlated U a Cl Rhyollte dlkes . \ Lincoln Peak formation \ \‘ § Cpc Red conglomerate, sandstone, g z _ ' < limestone, and shale 3 Pole Canyon formation >5 E . 2 Pa - ‘ I 5 Arcturus formation 2 Pioche shale < ‘ Z \er } E >. Ely limestone E Prospect Mountaln quartzite / —_.____ ...... 410 Contact Strike and dip of beds Dashed where inferred, dotted where concealed 62L./0 Strike and dip of axial plane of ———' """ small fold and plunge of axis Fault Dashed where inferred , dotted -‘—‘--L* ------ where concealed; 0, down- Thrust fault ”WWW SM“ Dashed where inferred, dotted where concealed; saw teeth —————— on upper plate Marker beds Number of dots distinguish different marker beds in formations 9 1 , MILES l I I 5000 10,000 FEET CONTOUR INTERVAL 400 FEET chert and quartzite foreign to the area. The Arcturus formation beneath the red conglomerate contains fusu- linids of Wolfcamp age or slightly older; the lime- stone in the conglomerate, according to J. T. Dutro, J r., contains the brachiopods Heteralosia sp., Phrico- dothyris? sp., and an aulostegid brachiopod of a new genus, probably of Wolfcamp or Leonard age. These rocks closely bracket an orogenic episode that probably occurred in Wolfcamp time. The Guilmette formation (Devonian) and the Ely limestone (Pennsylvanian) are also fossiliferous and their ages were verified locally. The relations between the red conglomerate and small patch of black shale and tuffaceous sandstone exposed only along the highway is uncertain; the shale may be surrounded by faults. Plant remains collected B272 from the shale by F. E. Digert and Neal Smith were identified by D. I. Axelrod as possibly of Late Creta- ceous or early Paleocene age (Van Houten, 1956, p. 2808, and F. E. Digert, written communication). For the present, however, the shale is mapped with the Per- mian conglomerate until more plant remains are col- lected and the local structure is clarified. Poorly consolidated conglomerate with locally de- rived cobbles, and tutfaceous sandstone, similar to rocks beneath the volcanics to the north, are probably of Ter- tiary age. The other rocks in this area include two rhyolitic dikes and some younger gravels. Structurally, the area is chiefly characterized by thrust faults that nearly follow bedding planes and it contains a few normal faults. Most of the thrust faults have cut out only a few tens or a few hundreds of feet of beds, but one fault has cut out many thousands of feet. The thrust faults of large stratigraphic throw are generally traceable for longer distances than those of smaller throw. Rocks along the thrust faults, espe- cially the larger ones, are sheared, and locally the beds on both sides of the fault dip into the fault. Folds, commonly less than 20 feet. in amplitude, are abundant in phyllitic rocks of the Lincoln Peak formation just northeast of the highway. Their axes trend northwest— ward, and most of their axial planes dip steeply northeast-ward, or about normal to the thrust plane. Some of the normal faults adjacent to the red con- glomerate end at the thrust fault and are therefore contemporaneous with it, or older; others bend north— ward and follow a large thrust fault a few miles and therefore must be younger than it is. The Tertiary conglomerate may thus be downfaulted on a normal 6? GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES fault localized by the thrust fault. Further mapping of the Tertiary rocks to the northwest, which appear to be in similar relations to the thrust fault, may clarify this point. Since the present interpretation of the structure east of Connors Pass does not assume that an overturned stratigraphic section was thrust over the Prospect Mountain quartzite, it. requires fewer major thrust faults than the concept of Misch and Easton (1954). It is consistent, moreover, with the structures mapped along 15 miles of the east flank of the Schell Creek Range, and also with those in the southern part of the Snake Range (Drewes, 1958). Some thrust faults fol— low the same weak formations in both ranges, but this does not make it possible to correlate individual faults from range to range. Neither the amount of move- ment nor the amount of displacement on any of the thrust faults is known; but both of these probably exceed the stratigraphic throw. REFERENCES Drewes, Harald, 1958, Structural geology of the southern Snake Range, Nevada: Geol. Soc. America Bull., v. 69, no. 2, p. 221—240. Drewes, Harald, and Palmer, A. R., 1957, Cambrian rocks of the southern Snake Range, Nevada: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 1, p. 104—120. )Iisch, Peter, and Easton, W. H., 1954, Large overthrusts near Connors Pass in the southern Schell Creek Range, White Pine County, Eastern Nevada [abs]: Geol. Soc. America Bull., v. 65, no. 12, pt. 2, p. 1347. Van Houten, F. B., 1956, Reconnaissance of Cenozoic sedimen- tary rocks of Nevada: Am. Assoc. Petroleum Geologists Bull., v. 40, no. 12, p. 2801—2825. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES , B273 123. POSSIBLE INTERBASIN CIRCULATION OF GROUND WATER IN THE SOUTHERN PART OF THE GREAT BASIN By CHARLES B. HUNT and T. W. ROBINSON, Denver, 0010., and Water Resources Division, Menlo Park, Calif. Large springs on both sides of the north end of the Death Valley salt pan, California, have catchment areas that seem too small to supply the quantity of water that is being discharged from them. As these springs are on fault zones, the water may have flowed to them un- derground along fault fissures that reached higher ba- sins nearby. This hypothesis is supported by geochem- ical studies of the water. Water from springs on the northwest side of the salt pan is chemically similar to that from springs on Mesquite Flat, in the next basin to the northwest; water from springs on the east side of the salt pan is like that from springs at Ash Mead— ows, in the Amargo‘sa Desert, Nevada, in the next basin to the east. This evidence is forceful because the water on the two sides of the salt pan is very different (fig. 123.1). The water on the east side is a bicarbonate-sulfate water high in calcium and fluoride, whereas water on the west side is chloride- sulfate water low in calcium and fluoride but con— taining some arsenic (fig. 123.2); and there are cor- responding differences between the waters from the adjacent higher basins. The hypothesis here advanced, if it could be verified by tracers, would have considerable importance. If the water is moving for long distances along faults, it may be moving in open conduits through the thick Paleozoic carbonate formations, and therefore at much faster rates than ground water ordinarily does. This would affect estimates of water resources in the Great Basin and opinions about the suitability of certain areas for underground storage of radioactive wastes. O 50 MILES l l l l l I FIGURE 123.1.—Index map of the area in the vicinity of the Death Valley salt pan, showing location of major faults and springs from which samples were taken. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES B274 00 6685a: 3.85m we owns?» 05 393632 .33 JUNE 63¢de o: wfigaco and our—35 “EN 83013 E AME “3&3 Ewugsméamaon «~on 3 game one 89d ”:25 ”flamed 088 Mfififinco a5: 03.83“ was 8538 E 33 .833 oumfismAacioEo 3 pm?» 95 Sony 3:8 545.5%“. 98> 3 E85856 9,5 95 89G .553 .3 @36me made; ”3.»an mo umww fimmwQ «mowpwazw an“ E @506on am< ad HESS am: 3 Am aEEmmv 325w 58D mo wgw 22$ 93 maimed». .5353 an :8 ofi we 5035.5: AH 298me ugh 836on as .8ng 95 ex: mzaofifiono ww AN QESamv 53:5? 56an we 03m um?» 05 @53on “85>? .mwfi‘aw mo mags 30.5%an .53 SOC mafia? mo flaw—@888 9:32? $ng pawlfidfi ”:5lo AOOHXV e m mm 2 m L Lm 2 _o 8 8: x m2 m2 «M NH A VM NM . vm NH «m NH «M NH ¢m m“ ‘ NH «m NH m H «m IHO fiéo V, A18 0 mmoo jog 70a fio 7/ , X k CKXYXXXXXXXXXXXXXX>7§OQ§OOO LD 0 O lmN va uNO A k -o.m -o m no _\011 _\m1 HZmommm mo pzmommm GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B275 124. OBSERVATIONS OF CURRENT TILTING OF THE EARTH’S SURFACE IN THE DEATH VALLEY, CALIFORNIA, AREA By GORDON W. GREENE and CHARLES B. HUNT, Menlo Park, Calif, and Denver, Colo. Archeological and geological studies in Death Val- ley, Calif, indicate that the valley floor has been tilted 20 feet over a distance of about 3 miles during the last 2,000 years. The eastern shoreline of a. shallow lake, which flooded the floor just prior to introduction of the bow and arrow, is now 20 feet lower than the western shoreline. Part. of the tilt can be explained by the presence of a recent fault scarp with 10 feet of vertical displacement at. the foot of the Black Mountains; the balance appears to be the result of slow surface defor- mation. Whether earth movements occur in episodes, fol- lowed by relatively long periods of stability, or wheth- er the earth’s surface is subject to slow continuous movement, is a fundamental problem in the study of earth mechanics and seismology. To explore this prob— lem in the Death Valley area, seven tiltmeter stations were established across the valley (fig. 124.1) during 1958 and 1959. INSTRUMENTATION Each tiltmeter station consists of three machined brass hubs placed in concrete upon rock outcrops. The hubs are positioned to form a nearly equilateral tri- angle with sides 30 to 50 m long. Hub tops are estab- lished within :05 cm of a level plane. The portable tiltmeter used in the Death Valley study was developed by U. S. Geological Survey personnel at the Hawaii Volcano Observatory under the direction of Jerry P. Eaton, and used successfully to observe tilting of the ground associated with subsurface magma movement at Kilauea. The tiltmeter consists of two closed cylindrical water pots connected by two tubes. When the pots are partly filled with water, one tube provides a continuous water connection, while the second tube connects the vapor phase of each pot. A sharp point on a. micrometer screw extends through the bottom of each pot. The micrometer point is viewed through a lens and adjusted to just touch the water surface. This serves to measure the relative height of water in each pot. By reversing the water pots and repeating the procedure, the eleva- tion difference between the two hubs may be measured with an error of less than three microns. If the hubs are spaced 30 m apart a sensitivity of one part in 10 million is realized. \ I ll .Furnace Creek Ranch \ / \, i \ N“ \ 5 10 MILES \ \ \ CONTOUR INTERVAL 2500 FEET \J ITILTMETER STATION 05. 117° 36° _ 36. FIGURE 124.1.——Map of Death Valley showing extent of old lake bed (broken line) that has been tilted eastward and the locations of tiltmeter stations (numbered). ‘ Because the system is sensitive to temperature changes, it cannot be used where solar radiation, or rapid changes in air temperature, are present. There- fore, it. is necessary to use the tiltmeter at night. Best results are obtained with an overcast sky to reduce radiation losses and with a. slight wind blowing to assist in maintaining a constant temperature in the system. A detailed description of the tiltmeter and how it is used is given by Eaton (1959). The precision of the measurements may be checked by adding the measured elevation difl'erences for the three sides of the triangle. The closure error, which should be less than 10 microns for valid readings, is then distributed around the circuit. RESULTS There appears to be good evidence of tilting occurr- ing at the present time in the Death Valley area. The B276 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 124.1.~Summary of tilting observed at selected locations in Death Valley, California Observed Component of tilting in Number of micro-radians toward—— N 0. Station observations __ From— To~ North East 1 Aguereberry Point _______________ May 1958 ____________ April 1960 ____________ 5 1 36 12 2 Trail Canyon ____________________ April 1959 ____________ April 1960 ____________ 2 1 2 3 Trail Canyon Fan ________________ Oct. 1959 _____________ April 1960 ____________ 2 2 —1 l 4 East Coleman Hills _______________ Oct. 1959 _____________ April 1960 ____________ 2 3 2 __________ 5 Gower Gulch ____________________ Oct. 1959 _____________ April 1960 ____________ 2 4 1 __________ 6 Artists Drive ____________________ Jan. 1959 _____________ April 1960 ____________ 4 —4 —3 7 Dantes View ____________________ Jan. 1959 _____________ Oct. 1959 _____________ 2 —2 1 1 Maximum tilting, observed in October 1959, was 35)(10—6 radians northward and 25x10-3 radians eastward. 2 A negative value indicates tilting toward the south or west. 3 Tilting measured in an adit lying N 2° W. 4 Tilting measured in an adit lying N 19° E. amount and direction of observed tilting is different from one station to another, and the rate of tilting at a given station varies from time to time. Table 124.1 summarizes the data from each of the seven stations. Usually the amount of tilting occurring between successive observations is so small as to be of the same order of magnitude as probable instrument error. However, as readings are accumulated over a longer period of time, the total observed tilting becomes sev- eral times larger than probable instrument errors. In general, geologic studies have shown that the area is broken into a number of distinct blocks, most of Which have been tilted toward the east since the time they were formed. It is significant that the direction and amount of tilting measured thus far agree with 125. the known geologic structure and movements in the recent geologic past. The structural relationships in Death Valley are very similar to those at Hebgen Lake, near West Yellow— stone, scene of the August 1959 earthquake. This earthquake resulted from faulting along one side of the valley and tilting of the valley floor toward the faulted side. The amount of displacement and tilting are about the same as at Death Valley. It is planned to apply the methods now being used in Death Valley to the area of Hebgen Lake. REFERENCE Eaton, J. P., 1959, A portable water-tube tiltmeter: Seismol. Soc. America Bull., v. 49, no. 4, p. 301—316. 5% PLIOCENE(?) SEDIMENTS OF SALT WATER ORIGIN NEAR BLYTHE, SOUTHEASTERN CALIFORNIA By WARREN HAMILTON, Denver, Colo. Sediments of late Cenozoic age carrying abundant fossils, dominantly of marine types, occur in the south- eastern part of the Big Maria Mountains, west of the Colorado River and about 75 miles north of the Mexican border. The oldest and most widely distributed of these sediments are “lime caps,” similar in part to the beachrock of tropical shores. “Lime caps” are found at altitudes of at least 800 feet. (The present altitude of the Colorado River here is about 290 feet.) They form the tops of many hills of pre-Tertiary rocks and encircle others. The caps consist of pure, hard travertine, and of talus, crossbedded gravel, and coquina, all firmly cemented by dense calcite. They contain abundant algae, barnacles, and pelecypods. Some of the caps are richly manganiferous, and contain large and possibly commercial quantities of soft manganese oxide inter- layered in their lower portions, particularly in valley bottoms and low on the hillsides. Unconsolidated beds of clay, silt, sand, and gravel overlie the “lime caps.” These sediments are generally thin but are locally several hundred feet thick. Rem- nants of them occur as much as 650 feet above sea level. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES They contain abundant Foraminifera and ostracods and sparse pelecypods. The fossils were identified by W. P. VVoodring, Patsy B. Smith, I. G. Sohn, and Richard Rezak, who believe that they grew either in sea water or marinelike brackish water. (The present Colorado River carries more sulfate than chloride.) B277 Either the Gulf of California previously extended into this area, or else a huge saline lake existed here. Such a lake might have been dammed by the rising of the Chocolate Mountains, 50 miles to the south, across the Colorado River, but if so, the mountains have since been lowered by subsidence as well as by erosion. The salt water sediments were largely buried during early Pleistocene time by fan gravels and river alluvium. 126. STRUCTURE IN THE BIG MARIA MOUNTAINS 0F SOUTHEASTERN CALIFORNIA By WARREN HAMILTON, Denver, Colo. In the arid Big Maria Mountains, north of Blythe in southeastern California, there are almost continuous exposures of a sequence of thin distinctive sedimentary format-ions probably of Paleozoic age. These have been metamorphosed and extremely deformed, probably dur- ing late Mesozoic time. The metasedimentary rocks are underlain by a complex of granitic and gneissic rocks, over which they slid along a surface at or near their base. Both the metasedimentary and the base- ment rocks were invaded, after being metamorphosed, by hornblende gabbro and by leucocratic quartz mon- zonite. The most pervasive structures in the metasedimen- tary rocks are shears and isoclinal folds subparallel to the bedding (fig. 126.1A). The limbs of the isoclinal folds are mostly between 5 and 200 feet in length, and the same is true of the lenses bounded by shear planes. The structure is particularly well displayed in a thin formation consisting of marble interlayered with chert. The total thickness of this unit commonly ranges be- tween 50 and 100 feet, but reaches a» maximum of 500 feet; the variations are due primarily to thinning and thickening by shear. The formation now consists of a parallel bundle of isoclines and limbs of isoclines sheared apart along planes nearly parallel to the bed— ding; but the shears have nowhere displaced the for- mation as a whole, and it crops out as a continuous band for many miles. The rocks of each formation are isoclinally interfolded along both upper and lower contacts with those of the adjacent formations but the zones of interfolding are generally less than 20 feet thick. The isoclinal folds must have been formed by a rolling progression of drag folds due to shear along the bedding, so that they were isoclinal at all times. Superimposed upon these small-scale structures are some on a larger scale. Figure 126.13 illustrates com- paratively large isoclines, and 126.10 a thrust fault; the rocks of each formation in these structures are com- plexly deformed by bedding-plane isoclines too small to be shown in the drawings. Many of the thrust faults have themselves been folded almost isoclinally (fig. 126.10). Most of the structures are directed northeastward; the dips are low and in all directions. The plutonic rocks were variably sheared and retro- gressively reconstituted near the decollement surface, and were broken by thrust faults subparallel to it at lower levels, but they are surprisingly little deformed and metamorphosed in View of the complexity of structure in the metasedimentary rocks above. The latest deformation consisted of normal faulting, which affected all the rocks, including the intrusives. B278 K /__/_,_/—’—\ w 10 FEET A. Laminated marble sheared and folded isoclinally parallel to bedding l 500 FEET Metachert Green and marble schist C. Thrust fault and drag fold GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 50 FEET I White calcite marble Metachert Buff dolomite marble B. Recumbent isoclines. Stratigraphic succession is metachert (oldest)—limestone—dolomite _ Buff dolomite marble 100 FEET D. Folded thrust faults (heavy lines) FIGURE 126.1.—Field sketches of structures exposed in cliffs in the Big Maria Mountains. ’X‘ 127. FOSSIL FORAMINIFERA FROM THE SOUTHEASTERN CALIFORNIA DESERTS By PATSY BECKSTEAD SMITH, Menlo Park, Calif. Fossil Foraminifera have been found in flat—lying upper Cenozoic sediments over an extensive area of desert in southeastern California. At all localities except Panamint dry lake, the F oraminifera are asso- ciated with gastropods, barnacles, and ostracodes that indicate brackish water or lagoonal conditions (W. P. Woodring, written communication, 1953). The fossils have been found along the Colorado River between Earp, Calif, and the Palo Verde Mountains, 25 miles south of Blythe, at elevations of 300 to 650 feet above sea level. They are also found in cores from Danby and Cadiz dry lakes (Bassett and others, 1959), located 50 and 60 miles west of Earp, in southeast- trending depressions now separated from the Colorado River by low passes. Foraminifera occur also in cores from Panamint dry lake (Smith and Pratt, 1957), which is about 200 miles northwest of Earp and is sepa- rated from the other localities by numerous high ranges. The foraminiferal faunas from all these locali- ties except Panamint dry lake are very similar to one GEOLOGY OF WESTERN CONTERMINOUS UNITED another, and also to the lagoonal faunas of the Gulf of California (Bandy, 1960). The Foraminifera are Streblus becoarii (Linné), E lphidz'um cf. E. poeyamum (d’Orbigny) , and a few other rare species. In the cores from Danby dry lake, whose surface is 541 feet above sea level, Foraminifera are found within two stratigraphic intervals, 396 to 439 feet, and 648 to 845 feet. The fossil-bearing sediments are green clay. The specimens are large and regular except at 648 feet, where they are small and stunted; their relative abundance is as follows: [A=abundant, C=common, R:rare] Depth (feet) 396—439 648—680 688—732 738—845 Streblus beccam'i _________ A ______ A ______ A ______ A Elphidium cf. E. poeyanum ____________ C ______ C ______ C ______ C Bolivina cf. B. brevior ____________________ R _____ In the cores from Cadiz dry lake, whose surface is 612 feet in elevation, F oraminifera are found in green clay at depths of 267 to 271 feet. Only Streblus bec- cam’i is present here. Core Panamint 1, from Panamint dry lake, contains Foraminifera at depths of 134 to 137 feet. They are all of one species, Elphidium cf. E. poeyanum, which is abundant. Specimens are large and regular. As in the other cores, the fossil-bearing sediments are green clay. Fossiliferous sediments are exposed in a road-cut along the west side of the highway between Earp, California, and Parker, Arizona; they consist of 10 to 20 feet of cross-bedded gravels and coarse to fine sands. The section appears to be interbedded with river grav- els, but their relations are obscure. Foraminifera (S. beccarii) are abundant in the finer grained beds, but they are dwarfed. Several hundred feet of well-bedded fossiliferous clay and fine sand crop out in the Big Maria Mountains at elevations from a few feet to 350 feet above the pres— ent level of the Colorado River (Hamilton, see Art. 125). These sediments contain Foraminifera belong- ing to the following species: STATES B279 Stweblus beccam'i—Abundant Elphidium cf. E. poeg/cmum—Common E lphidiella sp.—Rare The specimens throughout the part of the section ex- amined are consistently large and well formed, which probably indicates a uniform and favorable environ- ment. A statistical study is now being made of the morpho- logical variation in Streblus beccam'i from these thick fossiliferous sect-ions to determine whether or not they indicate environmental changes. Laboratory studies on living S. beccam'z' (Bradshaw, 1957) indicate that the species will grow and reproduce normally in a sa- linity range of 2 to 4 percent. Lower salinities result in a larger number of chambers before reproduction (and death); growth and reproduction cease below a salinity of 0.7 percent. The significance and relative ages of these widely scattered fossiliferous sections are problematical. The thick fossiliferous sections of the Cadiz and Danby dry lakes and along the Colorado River are charac- terized by quite uniform and similar faunas; they all might represent either a shallow marine invasion, one large saline lake, or several isolated saline lakes. Al- though the method of introducing these faunas into lakes is a serious problem, Panamint Lake could not have been connected with the sea at the time the fos- siliferous sediments were deposited, and the existence of even a limited foraminiferal fauna in this distant body of water forces consideration of the saline lakes environments. REFERENCES Bandy, O. L., 1960, Foraminiferal ecology of the Gulf of Cal- ifornia (abs): Geol. Soc. America, Cordilleran Section meeting, Vancouver, B.C., program, p. 13-14. Bradshaw, J. S., 1957, Laboratory studies on the rate of growth of the Foraminifer, “Streblus beccam'i (Linné) var. tepida (Cushman)”: Jour. Paleontology, v. 31, p. 1138—1147. Bassett, A. M., Kupfer, D. H., and Barstow, F. (1., 1959, Core logs from Bristol, Cadiz, and Danby dry lakes, San Ber- nardino County, California: U.S. Geol. Survey Bull. 1045—D. Smith, G. I., and Pratt, W. P., 1957, Core logs from Owens, China, Searles, and Panamint Basins, California: US. Geol. Survey Bull. 1045—A. 5b B280 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 128. TIME OF THE LAST DISPLACEMENT ON THE MIDDLE PART OF THE GARLOCK FAULT, CALIFORNIA By GEORGE I. SMITH, Menlo Park, Calif. Work done in cooperation with the California Division of Mines Throughout the southern half of the Searles Lake basin, in California, there are numerous deposits of tufa. From their position within the basin, and from their internal structures, it is evident that these de- posits were formed at or below the surface of the water in Searles Lake, which stood at levels as high as its spillway (at an elevation of 2,250 feet) in Pleistocene time. One of them, at an elevation of about 2,200 feet, in SW1/4NW14 sec. 12, T. 28 S., R. 43 E., rests on a well-preserved north-sloping scarp, 40 feet high, of the strike-slip Garlock fault. The tufa was clearly formed later than this scarp, and it is almost certain that the scarp was formed during the most recent displacement along this segment of the fault that resulted in appre- ciable uplift; in this area, the Garlock fault is expressed physiographically by a single line of scarps and linea— ments, and it is highly improbable that the traces of successive displacements on strike-slip faults would precisely coincide. Where the highest shoreline crosses the fault scarp, it does not appear to have been offset. This does not prove conclusively that there has been no later movement whatever on the fault here inas- much as the angle between the fault and the shoreline is too small to allow the detection of minor horizontal displacements; it does support the conclusion, how- ever, that there has not been considerable movement since the shoreline and the tufa were formed. Surface and subsurface evidence obtained from Searles Lake and related basins indicates that the lake has not stood as high as 2,200 feet since the time that immediately followed its last period of overflow; this overflow occurred during the latter part of the Pleisto— cene pluvial stage that is correlated with the Tahoe glacial stage of Blackwelder (1931) in the Sierra Nevada. In Searles Lake core L—W—D (Smith and Pratt, 1957), the sediments regarded as contemporane- ous with this last period of overflow lie at a depth of about 140 feet, about 20 feet below the top of the muds correlated with the Tahoe glacial deposits. A carbon- 14 date of 46,350 : 1,500 years B. P. has been obtained on a sample collected from about 10 feet below the top of these muds (Flint and Gale, 1958, p. 704). As sedimentation rates of 1,000 years or more per foot are indicated for muds of this type (Flint and Gale, 1958, p. 706), the sediments deposited during the last period of overflow are probably at least 10,000 years older than this carbon—14 date, and may therefore be between 55,000 and 60,000 years old. It appears quite safe to say that they are at least 50,000 years old, and that the tufa described above is about the same age. The above evidence contradicts the widely held be- lief, based on the existence of well—perserved scarps such as the one here described, that the Garlock fault was active in Recent time. REFERENCES Blackwelder, Eliot, 1931, Pleistocene glaciation in the Sierra Nevada and Basin Ranges: Geol. Soc. America Bull., v. 42, no. 4, p. 865-922. Flint, R. F., and Gale, W. A., 1958, Stratigraphy and radiocarbon dates at Searles Lake, California: Am. Jour. Sci., v. 256, p. 689—714. Smith, G. I., and Pratt, W. P., 1957, Core logs from Owens, China, Searles, and Panamint basins, California: U.S. Geol. Survey Bull. 1045—A, p. 1—62. 5% GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B281 129. WELDED TUFFS IN THE NORTHERN TOIYABE RANGE, NEVADA By HAROLD MASURSKY, Denver, Colo. Work done in cooperation with the Nevada Bureau of Mines m In central Nevada, near the place where the north end of the Toiyabe Range abuts against the Cortez and Shoshone Ranges (fig. 129.1), a thick sequence of welded tutfs occupies a trough about 50 miles long and 10 miles wide. Described here is an area about 6 miles on a side at the east end of this trough, mapped by James Gilluly and me in 1957—59. In this area the tufl’s, deeply dissected and well exposed, are bounded by high-angle faults on the north and south and by alluvium on the east and west. STRATIGRAPHY The volcanic sequence, about 8,000 feet thick, consists of pinkish-gray to light-gray vitric crystal tufl inter- bedded with water-laid tuff with pebble conglomerates eroded from Paleozoic rocks. The sequence contains many lenticular layered ash-flow units (a term proposed by R. L. Smith, written communication) as much as 1,200 feet thick and 2 miles long (table 129.1). The beautifully developed vitroclastic texture, char- acterized by deformed and agglutinated glass frag- ments, demonstrates that the tuifs are welded, that they are ash flows emplaced when they were so hot that the glass fragments stuck together (F enner, 1923; Mar- shall, 1935). The xenoliths 0f chert, mostly scattered through the ash rather than in discrete layers, indicate that the ash flows moved in a very turbulent fashion. The few interbedded layers of gravel are mainly peb- ble conglomerates with red silt matrix. The pebbles are of chert, quartzite, argillite, and limestone from nearby Paleozoic rocks. Near the northern boundary there are giant boulder conglomerates containing blocks of chert and quartzite more than 100 feet long; toward the center of the volcanic area the gravel beds are thinner and finer grained. The phenocryst composition together with the bulk chemical composition shown by eight analyses, to be published elsewhere, match very closely Nockolds’ (1954) rhyolite plus rhyolite obsidian. GEOLOGIC RELATIONS AND AGE The welded tufi's lie unconformably on lower and middle Paleozoic rocks that were complexly faulted in late Paleozoic time (Roberts and others, 1958), and 557753 0—60—19 TABLE 129.1.—Sequence of rock types in an ash-flow unit Lithology 1 Consolidation Thickness (feet) Top . Pale red-purple to medium-gray Partially 150 to 500. vitric crystal tufl" contain- welded. ing numerous fragments of white devitrified pumice. Pale red—purple vitric crystal Thoroughly 200 to 800. tuff; crude layering due to welded. schlieren and blebs of de- formed glass, mostly devit- rifled. Black vitrophyre interbedded Thoroughly Vitrophyre with medium light-gray vi- welded. layers 10 tric crystal tufl"; commonly to 50 each; two vitrophyre layers. total of unit 50 to 200. Pinkish—gray vitric crystal Not welded _____ 0 to 20. mil. Base X In the unit as a whole, phenocrysts average about 25 percent; they are mainly sanidine and quartz, with subordinate oligoclase and a little biotite and magnetite. Pumice, in places devitrified, is scattered throughout, increasing in abundance up- ward. Pebbles of black chert and, rarely, of quartzite are scattered throughout but are most abundant at the base. into which a quartz monzonite stock was intruded in Tertiary time. (See fig. 129.1.) On the west, the welded tufl's are partly overlapped by, and partly in fault contact with, a thick sequence of gravel, sand, fresh-water limestone, and vitric tuif that has yielded remains of early and late Pliocene horses (Edward Lewis, written communication) and middle Pliocene snails (D. W. Taylor, written communication). Scanty fossil evidence indicates that the welded tufl's are of early Tertiary age. Interbedded water-laid tufl's have yielded scraps of vertebrates that, though of un- identifiable species, are surely Tertiary, and also Ter- tiary pollens that are Miocene or older (Estella B. Leopold, written communication). Regional evidence indicates that the tufi's are pre-Miocene, possibly Oligo- cene. As they seem to be older than the basalt 30 miles to the northeast in the Cortez Range, whose age GEOLOGICAL SURVEY RESEAECH B282 116°45' 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 116°35’ ‘ EXPLANATION # éUATERNARY Alluvium, colluvium, and lacustrine sediments \ Wt" Water-laid tuff, sand and gravel :. , _- / \ l“:\ / Tot-II?“ \ZTéLnI’D Welded tuff Quartz with monzonite interbedded stock gravel 1e 1 Shale, chert, quartzite, and and dolomite with greenstone minor clastics Pliocene Pleistocene TERTIARY CAMBR‘IAN TO DEVONIAN ’C’ I’ \/ \I) l/I .// Normal fault Rods on downthrown block; dotted where concealed Amman-O Thrust fault Teeth on overriding block; dotted where concealed 30 Strike and dip of beds INDEX MAP 2 1711 O 1 MILE |_;L_L_I R. 48 E. Geology by J, Gilluly and H. Masursky. 1957—59 FIGURE 129.1.——Sketch map showing geology in the northern Toiyabe Range, Nev. is regarded on vertebrate fossil evidence as pre-late Miocene (Jerome Regnier, written communication), they are very likely of about the same age as similar rocks in eastern Nevada that E. F. Cook (oral com- munication), on the basis of a biotite age of 37 million years, has dated as Oligocene. STRUCTURE The east-trending high-angle Wenban fault, which forms the south boundary of the volcanic area, crosses the Toiyabe Range and continues west across the Sho- shone Range. The Copper fault, which bounds the area on the north, separates the volcanic rocks from GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES the Paleozoic rocks, continues westward across the range, and is ofl'set by the Crescent fault; still farther west, it crosses the Shoshone Range at Wilson Pass. The outcrops of Paleozoic rocks at the head of Grass Valley, on the projected trace of the Copper fault, show that a fault must be concealed there beneath the allu- vium, for the thick body of volcanics all disappears within a mile and a half. Gravity surveys by the Geo- logical Survey in this place also indicate a major break. Since the volcanics are missing on the upthrown sides of both the Wenban fault and the Copper fault, the throw of each of these faults must have been more than 8,000 feet. The Crescent fault cuts and repeats the entire vol- canic sequence, crosses Grass Valley, and marks the northwest boundary of the Cortez Range. Gravity measurements and displacement of basalt sheets in the Shoshone and Cortez Ranges indicate that it has a throw of more than 10,000 feet along a 60 degree dipping surface. The accordance of the range front with the Crescent fault and the many scarplets in the alluvium show that this fault and a branch of it, the Cortez fault, are still active. The interbedded gravels that pinch out and become finer grained away from the faults are probably fans deposited at the feet of active scarps. The east-trend- ing Wenban and Copper faults thus appear to have bounded a linear trough, or volcano-tectonic depres- sion (Williams, 1941, p. 246), that was actively sinking during the deposition of the volcanics, probably in Oli— gocene time. B283 The extreme lenticularity of the individual units in the welded tufl' here described, and their extraordinary total thickness and absence from the surrounding area, are evidence of their having been deposited originally in a local basin. That is, they are not remnants of a formerly extensive cover preserved in a graben. Other deposits of welded tuff in eastern Nevada and western Utah (Cook, 1957; Mackin, 1960) are very thin and very widespread, and they must have been deposited in a manner analogous to flood or plateau basalts in contrast to the local tectonic basin fills described here. Much later, probably during Pliocene and Pleistocene time, the Crescent and Cortez faults blocked out the present basin ranges almost at right angles to the earlier fault system. REFERENCES Cook, E. F., 1957, Geology of the Pine Valley Mountains, Utah: Utah Geol. Mineralog. Survey Bull. 58, 111 p. Fenner, C. N ., 1923, The origin and mode of emplacement of the great tuft deposit in the Valley of Ten Thousand Smokes: Natl. Geog. Soc. Contr. Techn. Papers, Katmai ser., no. 1, 74 p. Mackin, J. H., 1960, Structural significance of Tertiary volcanic rocks in southwestern Utah: Am. Jour. Sci, v. 258, no. 2, p. 81—131. Marshall, P., 1935, Acid rocks of the Taupe-Rotorua volcanic district: Royal Soc. New Zealand Trans, v. 64, p. 323—366. Nockolds, S. R., 1954, Average chemical compositions of some igneous rocks: Geol. Soc. America Bull., v. 65, no. 10, p. 1007—1032. Roberts, R. J., Hotz, P. E., Gilluly, James, and Ferguson, H. G., 1958, Paleozoic rocks of north-central Nevada: Am. Assoc. Petroleum Geologists Bull., v. 42, no. 12, p. 2813—2857. Williams, Howel, 1941, Calderas and their origin: California Univ. Dept. Geol. Sci. Bull., v. 25, no. 6, p. 239—346. 61‘ 130. REGIONAL GRAVITY SURVEY OF PART OF THE BASIN AND RANGE PROVINCE By DON R. MABEY, Menlo Park, Calif. For several years the U.S. Geological Survey has been conducting gravity studies in the Basin and Range province in Utah, Nevada, and California. Gravity measurements have been made to determine local structure in several areas where geologic mapping was going on; these surveys, however, cover only a small part of the total area. In the areas not covered by the local surveys, gravity observations have been made at bench marks, at triangulation stations, and along major highways. All the gravity data collected by the Survey have been tied to a common datum through a network of base stations. This network is referred to four airport base stations established by VVoollard (1958). The data thus collected have been useful in studying the structural geology in the basins and in parts of some of the mountain ranges. Over most of the region the dominant local Bouguer gravity anomalies are produced by the density contrast between the pre-Ter- tiary rocks and the generally less dense younger vol- canic and sedimentary rocks. These local anomalies, which have amplitudes up to 60 milligals, are usually B284 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 120°00’ 118°00’ 116°00’ 114°00’ 112°00’ I I I I I ' OREGON —— __ __ __%__l __ 50 / I /‘ o \b . / ((1-733‘ Winnemucca ll / / \ p— / O / l Beaver/ é’ r\ / O Bakersfield EXPLANATION / ‘I60// G“; \ O\o\ \\ \ [00 Bouguer anomaly contours Dashed where approximately located OLOS Angeles CONTOUR INTERVAL 20 MILLIGALS ————— 2000— _ — —— ’ ’ Regionalized topographic contours CONTOUR INTERVAL 1000 FEET 42°00’ 40°00’ ~38°OO’ — 36°OO’ — 34°OO’ FIGURE 130.1.—Regiona1ized Bouguer anomaly and topographic map of part of the Basin and Range province. The gravity contours are based on representative stations in the ranges. The topography is averaged over circles 128 km in diameter. The gravity data are from surveys made under the supervision of K. L. Cook, R. W. Decker, D. L. Healey, D. R. Mabey, L. C. Pakiser, S. W. Stewart, and G. A. Thompson. M. F. Kane, GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES located in basin areas underlain by thick accumulations of Tertiary rocks and valley fill. They can be inter- preted in terms of the thickness of the low—density rocks and the configuration of the basins in which they occur. The local anomalies associated with den- sity contrasts within the pre-Tertiary rocks are gen- erally of smaller amplitude, but significant local anomalies associated with bedrock features have been observed. A knowledge of the broad regional variations in Bouguer anomaly values is of great use in the study of the large-scale variations in the thickness and com- position of the crust. It is also helpful in isolating the local gravity anomalies superimposed on the re- gional variations. In the Basin and Range province the preparation of a contour map to illustrate the re- gional gravity anomalies is complicated by numerous local anomalies of large amplitude. The anomaly value for an individual gravity station may not be even approximately representative of the anomaly values over an area of even a few square miles, particu- larly if the station is near the margin of a basin under- lain by several thousand feet of low density Cenozoic rocks. To prepare an anomaly map that will show the regional gravity anomalies some method of averaging values or selecting stations must be used. The map in figure 130.1 was prepared by contouring the anomaly values for representative stations located in the ranges. The regional Bouguer anomaly values range from about —60 milligals to ~240 milligals, and show an inverse correlation with the regional topography. The highest anomaly values are at the southwest edge of the map. Here the anomaly values rise abruptly where the regional elevation decreases toward the Pa- cific Ocean. Over the western Mojave Desert, where the surface relief is small, the regional gravity relief is small. North of the western Mojave Desert the B285 anomaly values decrease as the surface rises to a high over the Sierra Nevada and White‘Mountains. Rel- atively high anomaly values occur in topographically low areas around Death Valley and the Colorado River. Northward from these areas the general level of the surface rises and the anomaly values decrease. In east—central Nevada the surface is higher, and the Bouguer anomaly values are lower than in any other part of the State. Along the west-central border of Nevada the anom- aly values decrease as the surface rises toward the Sierra Nevada. In northwestern Nevada the main gravity feature is a high, which is in the topographic low containing the Smoke Creek and Black Rock Deserts, Desert Valley, the lower Humboldt River valley, and the Carson Sink. Northwest of this area the anomaly values decrease over a topographic high- land. A strip in which gravity is low and the surface is high extends northward from the Ely area to the Idaho-Nevada State line. East of this low trend there is a gravity high in the Lake Bonneville basin. East of the Lake Bonneville basin the anomaly values are lower over the Wasatch Range. The correlation between low Bouguer anomaly values and high regional topography clearly shows that there is a relative mass deficiency under the regional high- lands. Although the gravity data do not. indicate the nature of the mass deficiency, which can occur any- where Within the crust or in the upper mantle, the cor- relation with topography suggests that some form of .regional isostatic compensation exists. REFERENCE Woollard, G. P., 1958, Results for a gravity control network at airports in the United States: Geophysics, v. 23, no. 3, p. 520—536. 6% 131. MESOZOIC AGE OF ROOF PENDANTS IN WEST-CENTRAL NEVADA By JAMES G. MOORE, Menlo Park, Calif. Work done in cooperation with the Nevada Bureau of Mines In an area of roughly 3,000 square miles in the western Great Basin, lying mainly in Lyon, Douglas, and Ormsby Counties, Nev. (fig. 131.1), about 430 square miles are underlain by Cretaceous( '9) intrusive rocks, largely granitic, related to the Sierra Nevada batholith, and about 180 square miles by partly metamorphosed rocks older than the bat-holith. The metamorphic rocks occur in irregular roof pendants and septa, which have B286 120° 0 50 NEVADA Lyon, Douglas, and Ormsby Counties 100 MILES Ii 2Y6 . 20 MILES I /'7 l/I ll / / / I' / l / ''''' J, I/ /' ° ’ I Fernley /' I I l/ ,/ / / I / / / / I I / .\\ \\ \ rington «as? 119° GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES EXPLANATION 2 o N o E Volcanic and sedimentary u rock U) D - 0 LL! 0 <—— ——~> DISTRICT, ES CREEK, 55 "MS RANGE, NEVADA NEVADA UTAH Windfall formation W" _______________ l . Chokecherry dolomite Corseth shale i Dunderberg shale Dunderbergia zone Dunderbergia zone ° --------------------------- Hicks formation ? Aphelaspt's zone Aphelasm's zone 7 _____________________ Lamb dolomite Hamburg dolomite . a ',.- - Trippe limestone Exap’fofam ' ' ' O ——* 31.49794??? .......... 100 Secret Canyon . ............ Shale 200 FEET 0 Fossil collection FIGURE 132.1.—Correlation of lower parts of Upper Cambrian sections at Eureka and Cherry Creek, Nev., and in the Deep Creek Range, Utah. REFERENCES Palmer, A. R., 1956, The Cambrian system of the Great Basin in western United States: in El Sistema Cambrico, su paleo- Bentle , C. B., 1958, U r Cambrian strati ra h Of western y ppe g p y geografia y el problema de su base, XX Internat. Geol. Con- Utah: Brigham Young Univ. Research Studies, Geol. Sen, _ v. 5’ no. 6, 70 p., 5 p1., 7 fig. gress symposrum, v. 2, part 2, p. 663—681. Nolan, T. B., Merriam, C. W., and Williams, J. S., 1956, The 1960, Trilobites of the Upper Cambrian Dunderberg shale, stratigraphic section in the Vicinity of Eureka, Nevada: Eureka district, Nevada: US. Geol. Survey Prof. Paper U.S. Geol. Survey Prof. Paper 276, 77 p. 334—0, p. 53—109. 6% GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B291 133. INTRUSIVE ROCKS OF PERMIAN AND TRIASSIC AGE IN THE HUMBOLDT RANGE, NEVADA By ROBERT E. WALLACE, DONALD B. TATLOCK, and NORMAN J. SILBERLING, Menlo Park, Calif. Work done in cooperation with the N evade Bureau of Mines Numerous bodies of rhyolite porphyry and leuco- granite in the Humboldt Range, Nev. (fig. 133.1) have been found to represent feeders for, or intrusive rela- tives of, the volcanic rocks of the Koipato group, which are of Permian( ?) and Triassic age. This relation— ship had not previously been recognized, although the volcanic rocks of the Koipato group had long been known (King, 1878, p. 270; Knopf, 1924, p. 13). Volcanic rocks of the Koipato group having a total thickness of more than 12,000 feet are exposed in the Humboldt Range. They are divisible into three units. The oldest unit of Permian( ?) and Early Triassic( ?) age is the Limerick greenstone (Limerick keratophyre of J enney, 1935, p. 19), the exposed part of which con- sists of about 4,000 feet of greenstone; this grades up- ward into a heterogeneous assortment of tufl's, brec- cias, and flows of the Rochester rhyolite (Rochester trachyte of Knopf, 1924, p. 14) of Permian(?) and Early Triassic( ?) age. The uppermost unit of Per— mian( ?) and Early Triassic age, the Weaver rhyolite (Knopf, 1924, p. 26), is characterized by flows of por- phyritic rhyolite and of felsite, and by rhyolitic tufl's. Numerous dikes, sills, and stocks of leucogranite, rhyolite porphyry, and quartz monzonite were intruded into this thick pile of extrusive rocks. The quartz monzonite, which cuts Triassic rocks and is probably of late Mesozoic or Tertiary age, is not included in the following discussion. The leucogranite is a fine- to medium-grained, light- colored granite containing quartz and both potassic and sodic feldspars; it contains very little mafic minerals and much tourmaline. Much of this rock could appro- priately be termed aplite. Stocks of leucogranite, one of which underlies an area of more than four square miles, are exposed near the axes of major anticlines. Some of these cut the lower part of the Koipato group, but none is known to have penetrated as high as the Weaver rhyolite. The rhyolite porphyry contains small (< 2 mm) phenocrysts of quartz and larger (1 to 5 mm) pheno- crysts of K-feldspar, embedded in a vitreous-appearing groundmass so fine grained that much of it can hardly be resolved under the microscope. Rhyolite porphyry dikes intrude the leucogranite as well as all units of the Koipato group below the Weaver rhyolite. Some irregular swarms of dikes and sills of porphyry are clustered near the stocks of leucogranite, and a group of large elongate stocks of rhyolite porphyry, one of them over a mile long and nearly half a. mile wide, are distributed in a belt along the east side of the Hum- boldt Range. The Weaver rhyolite appears to be genetically re- lated to both the rhyolite porphyry and the leucogran- ite; the rhyolite porphyry bodies probably represent, in part, direct feeders for the Weaver rhyolite, but the leucogranite is less closely related to the rhyolite. Chemical, microscopic, and X-ray analyses of the Wea- ver rhyolite and the intrusive rhyolite porphyry are so similar as to be almost indistinguishable. In many places only field relations, such as cross-cutting con- tacts or the presence of tuffs interbedded with the rhyo- lite, enable one to distinguish between intrusive and volcanic rocks. Although the rhyolite porphyry cuts the Koipato group, it has nowhere been found to cut the rocks of the Star Peak group, which is of Middle and Late Triassic age and overlies the Koipato group with slight angular unconformity. At a few places, in- deed, field relations suggest that rocks of the Star Peak group overlie the rhyolite porphyry in sedimentary con- tact. The largest rhyolite porphyry stock, about a mile and a half southwest of Unionville, is in contact with rocks of the Star Peak group, but all the contacts be- tween the two units are believed to be faults. Two samples of rhyolite porphyry from the stock southwest of Unionville gave lead-alpha ages of 230 $40 and 290:45 million years (Thomas W. Stern, 1960, written communication). This, according to Kulp, would indicate that the porphyry is of late Paleo- zoic age, for he has estimated on the basis of isotopic age measurements, that the Mesozoic era began 220 million years ago (Kulp, 1959, p. 1634). Early Early Triassic ammonoids are found in tuffs immediately overlying, or perhaps in part interbedded with, the Weaver rhyolite, and one specimen of “Helicopm'o’n” reported from the Rochester by Wheeler (1939, p. 109) is probably pre-Mesozoic (David H. Dunkle, 1957, writ— ten communication). The lead-alpha ages obtained for B292 118°15 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCE‘S 40°30 .. ‘ ._ ¢++++t+++ + + +\\ + +l’t‘ +++++++7 EXPLANATION 40°15". ', ' >_ > E m z . . 500: ' ' 2 Upper Tertiary and Quaternary AA E- F :1 30.1 + + + + o< 0 +++++++ - + + + 1510—: Quartz (LIJ monzonite stocks Ell— s [rm § / W 000 pg — ms 3 m g: > U) V : Star Peak group < $5 Limestone, dolomite, siltswne, and 0—: E andesitic volcanic rock [— F f 4;. + 45+ A 4;. 1" 4k 1 ‘ t ++++ 4r” “ U .3 Weaver rhyolite Rhyol‘ite porphyry E g stocks, sills, and dikes U) . < § E / \ e e ' 7‘<\\/L\ I— § 5 Rochester rhyolite “\(/ \ / Q d{ 8* Leucogranite stocks r2 g g and dikes < .3 Limerick greenstone E . § 1‘ m E 05 LIJ D. K. J Contact F31 f ... . . . .. Dashed where questiomble; dotted where concealed _t_ Strike and dip, generalized 182 I I E ’— o g z z o \g E E 5 < E 0 1 g 13‘ 4 MILES 118°15’ the rhyolite porphyry thus appear to be consistent with the paleontologic evidence for the ages of the Weaver and Rochester rhyolites. FIGURE 133.1.—Geologic map of a part of the Humboldt Range, Nev. Although the rhyolite porphyry cuts the leucogran— ite, contacts between the two are in places clearly grada- tional, as though the leucogranite had not been GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES completely solidified when the rhyolite porphyry dikes were intruded. The leucogranite cuts the Rochester rhyolite, but does not. extend high enough into the pile of volcanic rocks to reach the lVeaver rhyolite. The time of mobilization of the leucogranite must there- fore have been only slightly earlier than, or even partly contemporaneous with, the mobilization of the rhyolite porphyry and its extrusive eqiuvalent, the Weaver rhyolite. Since the rhyolite, the rhyolite porphyry, and the leucogranite are so nearly of the same age and so much alike in chemical and mineralogic composition, they are probably differentiates of the same magma. This evidence, taken as a whole, shows that both the B293 leucogranite and rhyolite porphyry bodies must have been emplaced very near the beginning of the Mesozoic era. REFERENCES Jenney, (‘. l’., 1935, Geology of the central Humboldt Range, Nevada 2 Univ. Nevada Bull., v. 29, no. 6, p. 1—73. King, Clarence, 1878, Systematic geology: U.S. Geol. Explor. of the Fortieth Parallel, v. 1, p. 270. Knopf, Adolph, 1924, Geology and ore deposits of the Rochester district, Nev. : U.S. Geol. Survey Bull. 762, 78 p. Kulp, J. L., 1959, Geologic time scale: Geol. Soc. America Bull., v. 70, no. 12, pt. 2, p. 1634. Wheeler, H. E., 1939, Helicoprion in the Anthracolithic (Late Paleozoic) of Nevada and California, and its stratigraphic significance: Jour. Paleontology, v. 13, no. 1, p. 103—114. ’X 134. REGIONAL SIGNIFICANCE OF SOME LACUSTRINE LIMESTONES IN LINCOLN COUNTY, NEVADA, RECENTLY DATED AS MIOCENE By CHARLES M. TsanNz, Menlo Park, Calif. Recent independent fossil and radioactive dating of lacustrine limestones from many widely separated lo- calities in Lincoln and Clark Counties, Nev., has clari- fied certain stratigraphic relationships, and has conse- quently advanced the understanding of the structural history of southeastern Nevada and southwestern Utah. These limestones have all been assigned a Miocene age, chiefly on the basis of pollen studies, but a lacus— trine limestone unit in the Horse Spring formation, which was previously thought to be Cretaceous or early Tertiary, has now been assigned to the Miocene 011 the basis of a potassium-argon (K—Ar) date of biotite from an interbedded tuff. Similar limestones of Miocene( ?) age occur in the Oak Spring formation, which crops out in Nye County, Nev., and in southwestern Utah. Lacustrine limestone from nine localities (fig. 134.1) was studied by G. O. W. Kremp, who identified 31 pol- len species in six samples that also contain abundant algal fragments and some fungispores. A complete list of these fossils will be published in a subsequent report. Five samples from Lincoln County (1—5) were dated as Miocene or possibly younger by Comparsime pollen. Samples 6, 8, and 9 did not contain pollen, and sample 7 contained only 2 grains of pollen of possible Miocene( ’3) age. Cr. 0. W. Kremp (1960, written com- munications) says: The pollen association found in the [first] four samples is prac- tically the same. The flora shows a dominance of pinelike pollen * * * associated with other coniferous pollen * * * The relative high frequency of Compositac pollen is remark- able. * * * pollen of the Compositae appear first in sediments of late Oligocene age; these pollen become common. in the Rocky Mountain area beginning with Miocene. This would date your samples as Miocene or possibly younger. * * * only very few of the 31 species * * * are identical with the upper Oligocene pollen and spore from the Florissant lake beds, Colorado. This * * * makes me somewhat more confident about my Miocene age determination * * *. . The pollen-bearing limestone in Lincoln County is correlated with limestone of the Horse Spring forma- tion in Clark County, which is interbedded with tufl' containing biotite that was determined to have a. K-Ar age of less than 24 million years (middle Miocene) (G. H. Curtis and J. F. Ever-den, K-Ar laboratory, University of California, as orally reported to Dr. C. R. Longwell). Pollen was not found in the lime- stone near the tufi’ (sample 9). The Horse Spring formation was previously assigned to the Cretaceous or early Tertiary on the basis of plants, ostracods, and snails, which, however, were too poorly preserved to be identified generically. The upper part of the basal limestone of the Oak Spring formation in Nye County (locality A, fig. 134.1) contains a fossil fish, F undulm, that according to Miller (1955) is restricted to the Pliocene and Quaternary (David Dunkle, 1956, written communication). The fish occurs 150 feet. above the base of the exposed sequence (A. B. Gibbons, 1958, written communication). The lower part of this limestone, however, is similar B294 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 7// CRETACEOUS(?) AND Horse Spring forma- tion and Overton fanglomerate, un- differentiated 116° 115° 114° \‘ I Curranto \\\‘ / ____: / 9X 5 | N I 3 l | 33 0 Sunnyside I ' I? ‘1. I l i ' | N ! . r'—‘—'—'Y—'£'—“‘ : I oPioche I I i 6’ oPanaca I I I :2 I I- I Hike ' ’ 7 oCaliente I 1;: ‘0. o I 0 l u g1 ' Z I (9 Z > I L 1 g) N c 0 L N I % v > I o “$13.2 (Alamo Elgino 4 l g I n29“? gs“ ‘3 \l D. | 59‘ ~ <= i ‘33:» :8_ El UTAH 7° A. l :\Nfl9°' ET" ARIZONA . _F_ _______ __,_ _________ _I l— 9 <9 97 ' D 5% Q g Glendaleo I Mercury 9 l ' l I C L A R K | I w g | | , l i § ° = \ . ‘~ LAS VEGASO p ,../\-A\ [J \ . K ' ' ‘J ‘. K‘ / 36° \ [3 EXPLANATION @942"; l g ’I O» “70 ~§ { 0\v?‘:y \I E Lacustrine 4/}4\ ( limestone \ § %/ v :22, \\ “ :3 l ///% O 10 2O 3O 40 MILES 4‘ \ Sheep. Pas: vsor- Conglomerate l t n- \ I 333532) 1 \‘ \ \ x x \3 Oil field TERTIARY FIGURE 134.1.—Map showing sample locations and outcrops of Tertiary and Crebaowusfl) rocks in southeastern Nevada. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES to Miocene limestone in Lincoln County and contains poorly preserved gastropods which Teng Chien Yen has dated as late Tertiary, possibly Miocene, (Johnson and Hibbard, 1957, p. 369). This suggests that the limestone of the Oak Spring may be partly Miocene and partly Pliocene, and that the lower part is correlative with the widespread Miocene limestone in Lincoln and Clark Counties. The Miocene limestones in Nevada are equivalent to lacustrine limestone and conglomerate near the base of the Rencher and the overlying Grass Valley formation of Cook (1957, p. 16) in the Pine Valley Mountains, Utah. These formations overlie the Quichapa forma- tion of Mackin (1960), whose lowest member has a lead—alpha age of 28 million years (early Miocene) (Mackin, 1960, p. 98). This member in turn lies on lacustrine limestone of the Claron formation. Cook correlates a biotite ignimbrite unit, part of the Needles Range formation of Mackin (1960, p. 100-102), inter- bedded with limestone in the upper part of the Claron, with one in the Grant Range, Nev., which has a K-A age of 34 million years (middle Oligocene) (Winfrey, 1958, p. 77—82). These facts indicate that the lacu— strine limestone near the top of the Claron is Oligo- cene or earliest Miocene, instead of Eocene as formerly believed. All the lacustrine limestones discussed here were de- posited in local basins on an extensive land surface of low relief that formed during a long period of erosion following Laramide orogeny. These limestones lie un- conformably on truncated folds or thrust faults in pre- Jurassic rocks, or on thick orogenic clastic rocks com- B295 posed chiefly of well—rounded pebbles of Paleozoic rocks. These clastic rocks include the conglomerate in the lower Claron and Wasatch formations, the Over- ton fanglomerate, and an unnamed conglomerate in southwest Lincoln County (fig. 134.1). They may range in age from Late Cretaceous to Oligocene. In a few places the limestone rests on volcanic rocks. The limestones are generally overlain by thick v01- canic rocks of Miocene and Pliocene age. After the volcanic activity had almost ceased, basin-and-range faulting occurred, most of it in late Miocene and Early Pliocene time. It is economically important to distinguish the Mio- cene lacustrine rocks discussed in the paper from the similar rocks of Eocene age. The borate deposits for- merly mined from the Horse Spring formation, in Clark County, occur, like the other major borate deposits in California and Nevada, in Miocene or younger rocks, whereas the similar Eocene rocks, such as the Sheep Pass formation of Winfrey (fig. 134.1), contain petroleum. REFERENCES (look, E. F., 1957, Geology of the Pine Valley Mountains, Utah: Utah Geol. and Mineralog. Survey Bull. 58, 111 p. Johnson, M. S., and Hibbard, D. E., 1957, Geology of the Atomic Energy Commission Nevada Proving Grounds Area, Ne- vada: U.S. Geol. Survey Bull. 1021—K, p. 333—384. Mackin, J. H., 1960,. Structural significance of Tertiary volcanic rocks in southwestern Utah: Am. Jour. Sci., v. 258, p. 81—131. Winfrey, W. M., Jr., 1958, Stratigraphy, correlation, and oil potential of the Sheep Pass formation, east-central Nevada : Am. Assoc. Petroleum Geologists, 1958 Geol. Record, Rocky Mountain Section, p. 77—82. 135. EVIDENCE IN THE SNAKE RIVER PLAIN, IDAHO, OF A CATASTROPHIC FLOOD FROM PLEISTOCENE LAKE BONNEVILLE By HAROLD E. MALDE, Denver, Colo. When G. K. Gilbert discovered that Lake Bonneville had overflowed at Red Rock Pass, near Preston, Idaho, and had rapidly discharged a vast amount of water northward into the Snake River, he looked downstream for effects of the sudden outflow. Near McCammon, 22 miles downstream from Red Rock Pass, he found (1890, p. 177) a lava flow Whose upper surface “is fluted and polished, and pitted with pot-holes after the manner of a riverbed.” The present paper is a summary of the effects of the Lake Bonneville outflow found farther downstream along the Snake River. The Lake BOnneville outflow from Red Rock Pass joined the Portneuf River valley near McCammon and flowed northwestward to the Snake River Plain at Pocatello. At the mouth of the Portneuf River, in the area known as Michaud Flats, the overflow deposited a fan-shaped body of gravel about 50 feet thick whose upper surface is diversified by ridges as much as 20 B296 feet high and a mile long and by irregular closed depressions of similar dimensions. Dissected remnants of the gravel extend 20 miles southwestward, almost to American Falls. Current studies by I). E. Trimble and W. J. Carr, US. Geological Survey, show that the gravel was deposited in a shallow lake that was impounded by a lava dam a few miles downstream from American Falls (see also Stearns and Isotoff, 1956, p. 27—28). A rapid downstream decrease in the coarseness of the gravel supports this interpretation. Boulders as much as 8 feet in diameter are abundant at Pocatello, but the gravel 10 miles southwest contains nothing larger than small pebbles, and at Aberdeen, 20 miles west of Pocatello, equivalent deposits near the opposite shore of the former lake consist only of sand and silt. Spectacular erosion across the lava dam downstream from American Falls is attributed by Trimble and Carr to the Lake Bonneville outflow. Southwest of Ameri- can Falls, on the upland northwest of the Snake River canyon, there is a strip of scabland 10 miles long and 1 to 4 miles broad, which was a spillway from the former lake. It is bounded downstream by abandoned cataracts, one of which is at the head of Lake Channel, a vertical-walled coulee 6 miles long, half a mile broad, and 100 feet deep (see map in Stearns and others, 1938, pl. 6). Other abandoned cataracts at the heads of al- coves and channels demonstrate that 8 miles of the Snake River canyon in this reach was formed by cata- ract recession. At the mouths of the alcoves and chan- nels are gravel bars that contain basalt boulders as much as 20 feet in diameter. Erosion by Lake Bonneville outflow took place on a grand scale near Twin Falls, where the Snake River canyon is half a mile wide, 40 miles long, and as much as 500 feet deep. H. A. Powers, of the US. Geological Survey, has shown that at least 24 miles of this canyon was cut by cataract recession contemporaneous with deposition of boulder gravel, most of which accumu- lated farther downstream. The northern canyon wall near Twin Falls is indented by a series of large cataract alcoves that probably represent successive stages of canyon recession; the three most conspicuous are known as Blue Lake alcove, Devils Corral, and Devils Wash— bowl. (See map in Stearns and others, 1938, pl. 5.) These cataracts were thought by Russell (1902, p. 127— 130) and Stearns (1936) to have been formed by springs, but they, like the alcoves and side channels near American Falls, resemble the abandoned cataracts in the channeled scabland of eastern “lashington (Bretz and others, 1956). Deposits of boulder gravel dating from the period when canyon cutting was in progress near Twin Falls form bars more than 100 feet high GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES on the canyon floor. Deposits containing boulders as much as 5 feet in diameter can be seen on the upland north of the canyon along State Highway 25 about 11 miles east-northeast of Twin Falls, and along US. Highway 93 about 5 miles north of Twin Falls. Boulder gravel is especially abundant within the Snake River canyon along a stretch beginning 20 miles downstream from Twin Falls and extending nearly to the Oregon State line. The gravel displays various features that indicate deposition in rapidly moving deep water. The boulders average 3 feet in diameter, and some are as much as 10 feet in diameter. The gravel occurs mainly in wide segments of the canyon, where it forms huge bars and boulder terraces that partly fill the canyon to a depth as great as 300 feet. The gravel bars block the mouths of tributary valleys, and at most places they are separated from the can— yon walls by marginal troughs as much as 150 feet deep. Because the boulder gravel commonly occurs downstream from basalt outcrops, Stearns (1936, p. 441—442) mistakenly attributed the boulders to erosion at the toes of successive intracanyon lava flows, not realizing that all the boulder deposits are contempo- raneous and that their source rocks are mostly older than the present canyon. Backwater deposits in tributary valleys, together with internal features of the boulder gravel, indicate that the gravel was depdsited in temporary lakes up- stream from canyon constrictions. The gravel varies in texture but consists mainly of boulders and sand, both derived almost entirely from the local basalt. Al- though the boulders are ordinarily distributed at ran- dom, some lie in inclined layers, alternating with lay- ers of sand. The inclined layers resemble deltaic fore- set beds arranged in courses as much as 50 feet thick between horizontal crossbeds. Such bedding indicates deposition in ponded water. The surfaces of the gravel bars and terraces are conspicuously strewn with lag boulders that seem to indicate reworking during sub- sidence of the ponded water. In all these respects, the boulder gravel of the Snake River canyon is similar to the gravel bars in the channeled scabland of east- ern W'ashington (Bretz and others, 1956), and like the scabland bars it can be accounted for by the passage of a catastrophic flood. REFERENCES Bretz, J H., Smith, H. T. I'.. and Nefi', Gr. It. 1956, Channeled scabland of Washington;»new data and interpretations: Geol. Soc. America Bull., V. 67, no. 8, 1). 957—1050. Gilbert, G. K., 1890, Lake Bonneville: U.S. Geol. Survey Mon. 1, 438 1). Russell, 1. C., 1902, Geology and water resources of the Snake River Plains of Idaho: U. S. Geol. Survey Bull. 199, 192 p. GEOLOGY OF WESTERN OONTERMINOUS UNITED STATES Stearns, H. T., 1936, Origin of the large springs and their alcoves along the Snake River in southern Idaho: Jour. Geology, v. 44, no. 4, p. 429—450. Stearns, H. T., Crandall, Lynn, and Steward, W. G., 1938, Geology and ground-water resources of the Snake River B297 Plain in southeastern Idaho: U. S. Geol. Survey Water- Supply Paper 774, 268 p. Stearns, H. T., and Isotoff, Andrei, 1956, Stratigraphic sequence in the Eagle Rock Volcanic area near American Falls, Idaho: Geol. Soc. America Bu11., v. 67, no. 1, p. 19—34. 5% 136. ALKALIC LAVA FLOW, WITH FLUIDITY OF BASALT, IN THE SNAKE RIVER PLAIN, IDAHO By HOWARD A. POWERS, Denver, Colo. F inc-grained alkalic lava of middle Pleistocene age occupies an area about 10 miles long and 1 mile Wide near King Hill, Idaho. Three separate sheets of the molten rock, each less than 30 feet thick, flowed down a gentle slope, the gradient of which decreases from 80 feet per mile to 25 feet per mile. The distribution and thickness of the flow units indicate that the fluid lava had as great mobility as that of the common basalt in the area, which contains labradorite plagioclase. ' The upper parts of the flow units are black and are aphanitic to glassy; their vesicular texture resembles that of Swiss cheese. The internal and basal parts are holocrystalline but very fine grained. Olivine and plagioclase are the only minerals Visible in the hand sample, mostly as microphenocrysts less than 1 mm in greatest dimension. Rare tablets of plagioclase, only a millimeter thick but as much as 2 cm long by 2 cm wide, are characteristic of one flow unit. The microscopic texture is dominated by stubby tab- lets of plagioclase, commonly in jackstraw pattern, but locally oriented in flow pattern. Interstitial spaces are occupied by euhedral to subhedral crystals of clino- pyroxene, olivine, magnetite, ilmenite, and apatite, and by patches of anhedral alkali feldspar. The plagio- clase is sodic andesine, about An35. The olivine ranges from F040 to Fo25 as determined by powder X-ray dif- fraction pattern (Yoder and Sahama, 1957, p. 484). The clinopyroxene is iron rich and probably also tita- nium rich because there is not enough visible ilmenite to account for all of the TiO2 found by chemical analysis. The rock is too fine grained for modal analysis, but the computed norm has been adjusted to approximate the mineral content, as shown in the table below. Some ab was combined with the or in orthoclase, and most of the TiO2 was allotted to pyroxene. The olivine was computed to agree with the composition indicated by X-ray analysis. Lava of the composition shown by these analyses does not fall within the range of basalt adopted by 557753 0—60—20 TABLE 136.1.—0hemlcal and approa‘lmate mineral composition of lava near King Hill, Idaho, as deternm'ncd from five analyses [D. F. Powers, U.S. Geological Survey, analyst] Results of 5 analyses Approximate mineral composition Aver- Range Norm ago 8102 ................. 49. 45 47.17—51.23 Q .15 A1203 ________________ 13. 71 13. 34—14. 45 or 14. 7 Alkali feldspar 16 T102 _________________ 3. 32 4.15— 2. 90 ab 28. 8 Plagioclase Anss 42 Fean ................ 3. 07 an 14. 6 15. 45—13. 27 Clinopyroxene 31 F90 11. 28 wo 4 1 Olivine 2 MnO ................ .22 .24— .20 fs 13.2 MgO ________________ 3.68 4.42— 3.33 en 9.2 CaO _________________ 6.77 7. 68— 6. 36 i] 6.2 Ilmenite .5 N320 ................ 3. 39 3.18— 3.54 mt 4.4 Magnetite 4.4 K20 ................. 2.43 2. 00- 2.60 ap 3.4 Apatite 3.4 P205 ................. 1.40 2. 05— .90 H20 _________________ .80 .41— 1.09 Green and Poldervaart (1955), because it is too low in lime and magnesia, and too high in potassia and phos- phate. Nor does the composition match that of any igneous rock average in the compilation of Nockolds (1954). The ratio of lime to alkalies in the King Hill Rock approximates that of Nockolds’ average alkali doreite, but the King Hill rock is lower in total feld- spar, and higher in iron, titania, and phosphate. In content of silica and alumina, the King Hill rock com- pares reasonably with the average alkali andesite. It is significantly higher than average alkali andesite, however, in titania, total iron, potassia and phosphate and it is much lower in magnesia and lime. REFERENCES Green, Jack, and Poldervaart, Arie, 1955, Some basaltic prov— inces: Geochim. et Cosmochim. Acta, v. 7, p. 177—188. Nockolds, S. R., 1954, Chemical compositions of igneous rocks: Geol. Soc. America Bull., v. 65, no. 10, p. 1007—1032. Yoder, H. 8., Jr., and Sahama, Th. G., 1957, Olivine X-ray deter- minative curve: Am. Mineralogist, v. 42, p. 475—491. ’X B298 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 137. A DISTINCTIVE CHEMICAL CHARACTERISTIC 0F SNAKE RIVER BASALTS OF IDAHO By HOWARD A. POWERS, Denver, Colo. The basaltic rocks, of Pliocene to Recent age, from the Snake River valley in southern Idaho are shown by chemical analyses to have a high degree of consan- guinity. These basalts may constitute a clan in the sense proposed by Tyrrell (1926, p. 136)——that is a group of rocks with the highest degree of consanguin- ity within a kindred. Preliminary comparisons have shown, also, that the Snake River basalts differ significantly from other basalts of the northwestern United States. One promi— nent difference is portrayed in figure 137.1, a three- component plot of the ratios between silica, magnesia, and total iron plus manganese in chemical analyses. The diagram shows these ratios for all available analy- ses of Snake River basalts (except one of a nepheline basalt and a few that contain less than four percent by weight of magnesia) together with all the available analyses of Columbia River basalts, as compiled by A. C. Waters (1960). To represent the basalts of the Cascades, two sample groups of analyses containing more than three percent magnesia were arbitrarily chosen; one sample group was from near Mount Lassen and the other from near Mount Hood. The rocks from the Snake River valley are all lower in silica than those from other areas. In the Snake River clan, moreover, the silica generally decreases as the ratio of iron to magnesia increases, whereas the Opposite is true of the other rocks. The reasons for these and other differences may become apparent as more data are accumulated. 100 Si02 EXPLANATION 0 Snake River basalt O 0“ Columbia River basalt N 90 " Basalt of Cascade Range «0 9 “b Sl02 75 7O SiOz \ /\ /\ /\ /\ /\ Ad‘ ‘0/ ”3» S ‘3‘; on? ‘6“ n? 9 0": $3 «a? gtb «0 Q) 03? “by? FIGURE 137.1.—Ratios between SI02, MgO, and total iron plus manganese in some basalts of the northwestern United States. Data plotted are weight percent of SiOg, MgO, and sum of Fe0+0.9Fe203+MnO computed to 100 percent. REFERENCES Tyrrell, F. W., 1926, The principles of petrology: London, Methuen & 00., Ltd. Waters, A. 0., 1960, Stratigraphic and lithologic variations in the Columbia River basalt: Am. J our. Sci. (in press) 138. AGE AND CORRELATION OF SOME UNNAMED VOLCANIC ROCKS IN SOUTH-CENTRAL OREGON By GEORGE W. WALKER, Menlo Park, Calif. Fragmentary collections of vertebrate fossils from several newly discovered localities in southeastern Lake 'lounty, Oreg., (fig. 138.1) indicate that the enclosing rocks are of approximately the same age as certain Miocene volcanic rocks of central Oregon and adjacent parts of Nevada and California. The fossils, consisting principally of bone fragments and teeth that have weathered out of tufiaceous beds, apparently represent a single fauna including Mery- chiplms, Camelidae, Dromomeryx sp. (tentative identi- fications by G. E. Lewis, 1959), and other mammalian genera. According to Lewis, this fauna is comparable GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES to that of the Mascall formation of Grant, Crook, and Jefferson Counties, Oreg., (Downs, 1956); it also re- sembles the mammalian faunas from Beat-ty and Corral Buttes, Oregon (Wallace, 1946), and Virgin Valley, Nevada (Merriam, 1910) , all of which are considered to be of late middle to early late Miocene age. Andesitic and rhyodacitic volcanic rocks of compara- ble age, mapped by Russell (1928) as the upper part of the Cedarville series, are exposed in northeastern Cali- fornia and northwestern Nevada. The age assignment of these rocks and their correlation with the Mascall formation is based on studies of fossil floras by Chaney (in Russell, 1928) and LaMotte (1936). The vertebrate-bearing strata of southeastern Lake County are in a section several hundred feet thick B299 largely composed of fine-grained poorly bedded silicic tufl' and tufl'aceous sedimentary rocks that range in color from pale yellowish-orange to tan, yellow, and light gray. These strata were probably deposited for the most part on dry land, but to a minor extent in shallow lakes. Near major volcanic centers of south- central Oregon some of the fine-grained tufl'aceous rocks grade laterally into coarse pumice lapilli tufl's, and interstratified layers of sintered or welded tuff become more abundant. These pyroclastic rocks rest with an— gular discordance on an extensive series of basalt flows locally more than 1,000 feet thick. Flows near the top of the series consist of ophitic to subophitic dikty- taxitic, locally olivine-bearing, basalt that contains little mafic glass; in some of these flows plagioclase pheno- m l s O R E . G O N i | E; . |_ HARNEY_ COUN_TY _ LAKE COUNTY I 0 Paisley , I l EX F’LA N ATlON / ® | ® Recently discovered Miocene vertebrate ' Valley ® £085“ localities Falls 36 S I Beatty Butte locality Previously known Miocene vertebrate ® fossil localities OPlus'h $39? 22E 23E 24E l 25E 26E 27E I 29E W" 37 s i I 38 S I I nGuann I XV/ ' Lakeview kNAdel ASH,“ I ® ® 40 S I Goose ® I Lake W l 42°00, "" —'— —— ~T —-— —-—l -— I —— —— —. CALIFORNIA 120°00' NEVADA 119°00’ l l Virgin Valley locality® O 10 20 MlLES L—__l—| FIGURE 138.1.—Index map showing distribution of Miocene vertebrate fossil localities. B300 crysts are abundant. These flows are fresh; the con- stituent minerals reveal only slight evidence of altera- tion. Other flows, chiefly in the lower part of the basalt series, contain altered phenocrystic and ground- mass olivine, altered mafic glass, and zeolites. Dustlike grains of hematite appear on plagioclase cleavage sur- faces and surfaces of discontinuity between crystals. Beneath the basalts are silicic pyroclastic rocks litho- logically similar to, and probably correlative with, py- roclastic rocks exposed several tens of miles to the west; the latter have been dated as of lower Miocene or John Day age on the basis of a D’icemtherium tooth, or pos- sibly of middle Miocene (Hemingfordian) age on the basis of fossil plants collected from the same beds that contained the tooth (Peterson, 1959). These rocks in turn are underlain discordantly, south and southeast of Paisley, by andesitic volcanic rocks presumably of pre- Miocene age. The general sequence of Miocene and older volcanic rocks in southern Lake County is similar to that which comprises the Clarno, John Day, Columbia River, and Mascall formations of central Oregon, but differs from it in some details, particularly in the mineralogy and physical characteristics of the mafic flow units. The late middle to early late Miocene silicic tuff and tuf- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES faceous sedimentary rocks of southeastern Lake County are roughly similar in bulk lithology to rocks of com- parable age in Virgin Valley, Nev. Although both these units are apparently of the same age as the upper part of the Cedarville series, exposed in northeastern California and northwestern Nevada, similarities in bulk lithology between the two sections are not obvious. REFERENCES Downs, Theodore, 1956, The Mascall fauna from the Miocene of Oregon: California Univ. Dept. Geol. Sci. Bull., v. 31, p. 199—354. LaMotte, R. S., 1936, The Upper Cedarville flora of north- western Nevada and adjacent California: Carnegie Inst. Washington Pub. 455, p. 57—142. Merriam, J. 0., 1910, Tertiary mammal beds of Virgin Valley and Thousand Creek in northwestern Nevada: California Univ. Dept. Geol. Sci. Bull., v. 6, p. 21—53. Peterson, N. V., 1959, Preliminary geology of the Lakeview uranium area, Oregon: Oregon State Dept. of Geology and Mineral Industries, The Ore-Bin, V. 21, p. 11—16. Russell, R. J., 1928, Basin Range structure and stratigraphy of the Warner Range, northeastern California: California Univ. Dept. Geol. Sci. Bull.. v. 17, p. 387—496. Wallace, R. E., 1946, A Miocene mammalian fauna from Beatty Buttes, Oregon: Carnegie Inst. Washington Pub. 551, p. 113—134. ‘ 5% 139. UPPER TRIASSIC GRAYWACKES AND ASSOCIATED ROCKS IN THE ALDRICH MOUNTAINS, OREGON By T. P. THAYER and C. E. BROWN, Washington, DC. Upper Triassic rocks aggregating 40,000 to 50,000 feet in maximum thickness occupy a triangular area about 35 miles from east to west and 16 to 18 miles from north to south in the Aldrich Mountains, Oregon. These rocks are mainly volcanic graywackes and shales, andesitic tufl's, basaltic lavas, and conglomerates that include boulders and fragments of Upper Triassic sedimentary rocks. Slide breccias consisting largely or entirely of basement rocks characterize parts of the section, and the graywackes are in large part turbidites. Although most. individual beds or corresponding volca— nic units are lenticular and of relatively small extent, angular unconformities and differences in lithology make it possible to recognize three major stratigraphic divisions. The oldest of these comprises three members (fig. 139.1). The lowest member, exposed near the western edge of the area, west. of the fault which crosses Murderers and Deer Creeks, is at least 8,000 feet thick; it is dominantly conglomeratic but includes some basalt flows near the base. The middle member, which oc— cupies the northwestern part of the map area between Fields and Riley Creeks, is 17,000 to 18,000 feet thick. The lowest 5,000 feet of this member is characterized by slide breccias and volcanic flows and breccias inter- layered with mudstone and shale, the middle part by mudstones, shale, and graywackes, and the upper 3,000 to 8,500 feet by massive tufl'. The upper member is a wedge of interbedded tuft, graywacke, and shale which lies with its thin edge at Riley Creek Butte, near the center of the map, and thickens to 10,000 or 11,000 feet near Fall Mountain, 8 miles to the east. The middle division is a relatively uniform sheet, 1,000 to 2,000 feet thick, which forms the only strati— graphic unit that can confidently be traced across the map area. It contains no volcanic rocks, and consists B301 GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES ha a: .uoao £53552 :LEEAw 2: 5 $35 UmmxxEB $.53 22 we 3:: 93:1.oavlfia2 ESE; EXCESS EESZ “Ia. x0388 unofiomwm Mug W mmmfi 63:33; 36 co>cmo w_>_< E0: mmmm— quzoczm @5935 W M g m. cm W 933 Ewazmfimuwm $3.. mmfiz_ ”59200 “555295 EanZ 3 >5. .m:Oum:®w.~m H E .33 M :w 9 m m _ _ _ _ _ _ _ _ _ ‘ 4 mwczoflmm MEMQSE ywxowkszgw can “2.2m .wsgmwsz m NCNEEOQ BEES 8.22 0H m o ZO_m_>_n_ , (TI Ll; E a + 1 $264 m M g a fi \ 3 . 39$. #333533. .9 SEW. m 2.2m was 668.5 $5388: a 3 WVQ/WW .. n , SSESR: ,3 .fiws‘ewbfi 95:3 32‘st W .wxooh Earfiwfi mflowhdo—NO M O m mudhmgoflmaso W1: .. . xufim m zoasa mew! m 5 l& c Q o , 1: mines. ‘ I. .w 1 n K V Saggcsaas :33" fifixmsQ mwdu 6:6 hwxufizfnmhw Kiss—w m. M W ulG. meOM MOMQSOV Z 8350 205:5! vow g \l/{\ 5%: w w L a K. Z O _._.< Z w__m _ y H :e ‘. M>o=a> (3am . . .. 1 gmwm we. . HO ../\ .. W o . ‘ , H . . 1 x. o a . ..._.O\ ., , %o0m 6.. a WW » . . a a a . \ mm o m QW b a ...m . s .5; a W . w / .. M o .. u . . / oz H A D 00 .. o a . O a g, . 0 x . . .. , H c a so fl JD , o o a: 7 . . 0 km . m @ .. a d o ba 0 Ik 3 ° N w v a 0 cw o . / Q 00 n . § 0 Q 0 o O V . 0 . o H o 7 . o . .‘ n.<2..xmoz_ n / T. g V . . ‘ a . y .7 ? , __ Q a .u ..v\,\ _ / m a / o ZOUMMO \. MW . g up a . o n a / . W1 . W. a .o o . oo: . ‘ o S \5Q {13. . ‘ . u nQ ,. A . .m : _ V. .. ., o . Q @ . 3 . . ‘ . . . ., ‘ . .. . Kam/ Sfirvai \MU P733 1:5 N . . k r boom: bro: ‘Omom: B302 mainly of well-bedded coarse- to fine—grained gray- wacke and shale in which the matrix is mostly carbonate. Its basal part contains lenticular masses of limestone breccia and conglomerate as much as 75 feet thick and 1,200 feet long associated with beds of detrital lime- stone. The upper division consists mainly of graywacke and shale whose total thickness is between 5,000 and 7,000 feet. It contains only a few thin layers of tufl'. In the valley of the South Fork of Deer Creek the lower part of this unit contains at least a thousand feet of cobbly mudstone in which many of the cobbles are of Paleozoic limestone. This division is overlain unconformably by Lower Jurassic beds. The area mapped is believed to cover the northwest- ern corner of a large basin of deposition. Along the western margin of the basin the Triassic rocks lie on a basement of Paleozoic metavolcanic rocks and ser- pentine. The present northern border of the basin, where not concealed under younger rocks, is a steep north—dipping reverse fault, along which Paleozoic rocks, serpentine, and Triassic rocks believed to be part of the lower member of the lower division lie against overturned Upper Triassic beds. The successive divi- sions and members overlap eastward and southward on angular unconformities. The middle member of the lower division lies across tight folds of northeast- erly trend that involve the lower member. The upper member in turn lies across folds of northwesterly trend in the middle member, and changes abruptly in thick- ness across faults related to the folds. The middle and upper divisions together lie partly conformably, partly unconformably, across the lower unit, and in places they are themselves separated by erosional unconformities. Strong and almost continuous deformation while the rocks were accumulating is recorded by the nature of the sediments and by numerous unconformities. The abrupt thickening in the beds of the upper member of the lower division where they cross folds and faults in GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES the middle member can be explained only by contem- poraneous fault movements of 3,000 to 4,000 feet. Several lines of evidence indicate recurrent movement totaling many thousands of feet along the northern border fault; this movement began at least as early as the deposition of the middle member of the lower division, and it involved beds of the upper division. The northeast-trending folds in the middle and upper division differ in strike by 60 to 70 degrees from the older northwest—trending major folds in the middle member of the lower division, and tight cross-folding has been found only in the lower member of the lower division. The prevalence of materials deposited by mass transport, such as slide breccias, cobbly mud- stones, massive graywackes, and graded graywackes, shows that conditions around the margins of the basin were unstable, and the abundance of reworked Upper Triassic debris in the conglomerates and breccias shows extensive “cannibalism” of the rocks soon after their deposition. Diagnostic fossils and unconformable re- lations with overlying Jurassic formations indicate that all the rocks here described were probably depos- ited during the later half of Late Triassic (Norian) time, and were deformed as shown in figure 139.1 before Early Jurassic (Sinemurian) time. Although even the upper division has been tightly folded and overturned in places, none of the rocks are foliated. Much of the coarser tuff and graywacke is extensively altered to laumontite, prehnite, albite, and chlorite, and pumpellyite is common in the lavas. Ex- cept for local development of actinolite, mica, and py- roxene near contacts with later intrusives, the rocks are in the zeolite metamorphic facies described by Coombs and others (1959). REFERENCE Coombs, D. 0., Ellis, A. J., Fyfe, W. S., and Taylor, A. M., 1959, The zeolite facies, with comments on the interpretation of hydrothermal syntheses: Geochm. et Cosmochim. Acta, v. 17, p. 53—107. 140. THE JOHN DAY FORMATION IN THE MONUMENT QUADRANGLE, OREGON By RICHARD V. FISHER and RAY E. WILCOX, Denver, Colo. The Monument quadrangle, located in Grant County, Oreg., 30 miles northwest of the town of John Day, includes the Clarno formation of Eocene age, the John Day formation of late Oligocene and early Miocene age, the Columbia River basalt of Miocene age, and the Rattlesnake formation of Pliocene and Pleistocene age. The John Day formation is exposed mainly in the southern part of the quadrangle. It has an aggregate GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES thickness of about 950 feet, and consists of primary and reworked pyroclastic material that fell on dry land. The lower part, which is dominantly deep red, grades upward through lighter red, green, and buff beds into the light—gray and buff material that forms the upper part. We have tentatively divided the formation into three members, which do not strictly conform to those proposed by Merriam (1901) for the section at Picture Gorge: Local Monument quadrangle measured Merriam (1901) thickness (feet) :1 .2 Upper member ___________ 346 d3 . . . E Upper d1v1s1on. 5 Middle member (welded ‘2; tuff locally present in 530 ————— 5 upper part). Middle division. c: g Lower member ___________ 67 Lower division. in LOWER MEMBER The lower member consists of deep—red friable mud- stones and siltstones, rich in montmorillonitic clays and locally containing black manganese- and barium-bear- ing nodules. It weathers to a clayey, silty red soil. A thickness of 67 feet of this member was measured in NE14 sec. 30, T. 9 S., R. 28 E, but there its base is not exposed. Four miles away, near the town of Ham— ilton (sec. 3, T. 10 S., R. 28 E., Courtrock quadrangle), the) member is 241 feet thick and lies upon weathered andesite of the Clarno formation. Its top is taken as the contact with a thin but distinctive layer of tufi' con- taining fragments of green phyllite. No mammal or plant remains were found in this member in the Monument quadrangle. MIDDLE MEMBER The middle member may be divided into two parts, the lower dominantly reddish and the upper colored in light shades of red, yellow, gray, and green. Its composite thickness is 530 feet. Its rocks weather to a hard, cloddy soil that. is distinct from the soils on the upper and lower members, and it erodes into a char- acteristic pinnacled badlands topography. It is found under the microscope to consist mainly of glass frag- ments, largely altered to a zeolite (clinoptilolite?), mixed with montmorillonite and opaline material. Al— though this member appears distinctly bedded when viewed from a distance, it has few sharply defined bed- ding planes. Some layers contain rounded and sub- angular aggregates up to an inch in diameter that have the same general constitution as the surrounding B303 material. Vertebrate remains occur in this member, being most common in its upper part, but here as else- where in the formation they are usually disarticulated. A layer of welded tufl', about 50 feet in maximum thickness, is locally present in the upper part of this member. In El/z sec. 13, T. 9 S., R. 27 E., where this tuff lies 140 feet below the top, a layer of tqu' 13 feet below it contains a few fossil leaves, and apparently equivalent layers occur below the welded tuff in SW14 sec. 6, T. 9 S., R. 28 E., and in SW14 sec. 9, T. 9 S., R. 27 E. This welded tufl' layer may be equivalent to a similar layer near Picture Gorge that Merriam (1901) regarded as the top of his “Middle division” of the John Day formation. At its contact with the upper member there is a marked change in color and soil type. UPPER MEMBER The upper member, which is 346 feet thick in 813% sec. 28, T. 9 S., R. 28 E., is characterized by light-gray or buff colors and weathers to silty powdery soil. It is found under the microscope to consist mainly of glass fragments partly altered to clay (montmorillonite?) ; both siliceous and basaltic glass shards are present, and the rock contains iddingsite pseudomorphs after olivine. Bedding is inconspicuous in the upper member, except where it is marked by local conglomeratic and sandy beds consisting of reworked John Day material. In many places at the base of the overlying Columbia River basalt, beds of reworked basaltic pyroclastics occur, and these perhaps are more appropriately regarded as part of the Columbia River basalt. Structures within the John Day formation are rela- tively simple, with dips generally less than 25°. The apparent folds (regarding which more will be said presently) form a branching rather than a parallel pattern, and they plunge in various directions. Dips are usually gentler in the upper member than in the middle member. The formation is out by fractures and by feeder dikes of the Columbia River basalt, both trending north-northwest, and the beds are locally disturbed by boss—like intrusions of basalt. A major normal fault near the southern edge of the quadrangle drops John Day beds on the north side against. vol- canics in the Clarno formation, and also cuts the Columbia River basalt. ORIGIN The preponderance of pyroclastic material in the John Day formation and the evidence that it could not have been deposited in lakes, as formerly presumed, was pointed out by Calkins (1902). In the Monument quadrangle the John Day formation was apparently deposited during a prolonged period of pyroclastic B304 volcanic activity in a nearby region. The pyroclastic debris in the lower member is mixed, however, with much red clay and silt, probably derived from sapro- lite developed on the Clarno formation. The smaller proportion of red material in the middle and upper members is presumably due to progressive mantling of the Clarno rocks by volcanic ash. Some beds consisting almost exclusively of pyroclastic material may have been formed by thicker falls of ash that remained where it fell. The bulk of the material, however, appears to have been deposited in such small increments that it did not greatly interfere with the growth of animals and plants. This indicates that most of the material in the formation was carried in by the winds from weathered surfaces and loose primary pyroclastic deposits. The rounded and subangular aggregates found locally in some beds are ascribed to colluvial action. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES The structures that simulate folds may be regarded as mainly due to initial dips in material mantling a ridge-and-valley topography which became progres- sively more subdued as deposition continued. The welded tuff at the top of the middle member represents an ash flow that followed the valleys. During diagene- sis of the buried sediments, differential compaction locally increased the dips, especially in material that contained much clay, and intrusion by the feeders of the Columbia River basalt resulted in further local disturbances. REFERENCES Calkins, F. C., 1902, A contribution to the petrography of the John Day Basin: California Univ., Dept. Geol. Sci. Bull, v. 3, p. 109—172. Merriam, J. C., 1901, A contribution to the geology of the John Day Basin, Oregon: California Univ., Dept. Geol. Sci. Bull., v. 2, p. 269—314. 5% 141. THE REPUBLIC GRABEN, A MAJOR STRUCTURE IN NORTHEASTERN WASHINGTON By MORTIMER H. STAATZ, Denver, Colo. A large graben, named for the old gold-mining town of Republic, has been outlined in the central part of the Okanogan Highlands, and mapped in detail by R. L. Parker, J. A. Calkins, S. J. Muessig, and M. H. Staatz (fig. 141.1). The graben is about 4 to 10 miles wide and at least 52 miles long. It is'bounded on the northwest by the branching faults that make up the Scatter Creek fault zone, and on the southeast by the Sherman fault. The bounding faults are either nearly vertical or dip toward the middle of the graben. The total vertical displacement on them is not known, but in the northern part of the Bald Knob quadrangle the middle of the graben is at least 7,000 feet lower struc- turally than the adjacent blocks. Rocks formed before the graben faulting include metamorphosed sedimentary and igneous rocks, unmet— amorphosed intrusive rocks in stocks and batholiths of Mesozoic and early Tertiary age, and intrusive porphyry and volcanic rocks that are probably Eocene. Rocks formed during and after the graben faulting are intrusive porphyry and volcanic extrusives. The vol- canics are mainly rhyodacite flows but include some beds of tufl' and breccia. Over 90 percent of them were formed after the graben started to subside. The flows are the extrusive equivalents of the por- phyry, and are closely similar to them in mineral and chemical composition. In the central part of the Bald Knob quadrangle a rhyodacite body showing intrusive relations along its west side has been traced eastward into extrusive rhyodacite with well-developed flow structure. Dikes and other small intrusions of por- phyry are found both inside and outside the graben; the volcanic rocks, however, are now found only Within the graben, having elsewhere been eroded away. Por- phyry masses that probably solidified in volcanic vents occur at a number of places within the graben, but are most common along the marginal faults. The flows were likewise extruded mainly along the marginal faults although some rose along smaller breaks within the graben. The Republic graben was formed in early or middle Tertiary time. It started to sink soon after the earliest volcanic rocks were erupted, and continued to sink while the succeeding thick flows and pyroclastic rocks were erupted. The sinking of this block was caused by the weight of the thick sequence of volcanic rocks deposited on its top, coupled with removal of the support that was given by the volcanic material before it was ex- GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B305 118°45’ CANADA 118°30’ 49°00“??? - ;.-49°OO’ I Spokane I ........... AFN § [RE x x x ': x x x , INDEX MAP OF WASHlNGTON x "’x x x x _ x x x x x x .'. >LLI x x x x x x x x g >‘ x x X X X x EXPLANATION 119°OQ’ AN x x ?%x x x x x x :2 o , 48 45 7 x x ._ 7-)“ at): .. 4 48 45 x x x x Curlew (S \/ l‘ x {Jake . (€113 , /\ x x x I < \l A} '3" \l Volcanic rocks with minor porphyry intruswes 1 x x x x / Volcanic rocks are mainly rhyodacite flows but a " " “ x x " include some tufi’aud breccia 4 V e X X X X X 3 x x x x x ’\ l\ /\ 7 V O -I x x Republic . _ A 13/." x x >0 x x x x x , Bathohthxc rocks p? x ‘43» l’ Quartz momonite, granodiorite, WAUCON DA 4 ‘ " ‘Rfifi‘u’éué ‘2’? Sgnpoik and quartz diorite QUADRANGLE x QUADRANGLE p... L'. \l l‘ X X X X X X X X X X X X " X " Diorite X X X X x x x x . . Metamo hosed sedlmentary and 1gneous rocks x x x x I'p x x x x ,,_——- ————— x x x x Contact __48°30’ Dashed where approximately located U fl’?“ / Fault / Dashed where approximately located I <5 U,upthrowri side; 0, dowuthrowrl side 5 I, ‘r Id 3: I to / / SEVENTEENMILE / MOUNTAIN O" O —U'l 10 MILES J XXXXXXXXXXXXXXXXXXXXX BALD KNOB QUADRANGLE QUADRANGLE x x x x x x x r x x x x x x x :I X X X X X X X ’ x x x x x x x ) xo‘ux x x x x x x 1 + . x § x x x x x x x 48°15' x )‘ x x x x x x x/ + 48°15’ 119°00’ 118°45’ 118°30’ Geology in the Curlew quadrangle by R. L Parker and J, A. Calkins, in the Republic and Wauconda Quadrangles by S J. MueSSlg‘ and in the Bald Knob and Seventeenmile quadrangles by M H Staatz FIGURE ELL—Generalized geologic map of the Republic graben. B306 truded. Five angular unconformities that separate tuff beds in different parts of the graben indicate that the graben sank unevenly. The sinking was probably almost continuous but varied in direction and amount. During and since the formation of the graben the rocks of this region were eroded, and any volcanic rocks that may have accumulated on the blocks adja- cent to the graben were thus removed. Several small bodies of porphyry are found in the adjacent blocks, GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES and some of these presumably fill vents from which flows were extruded. The volcanic rocks in the graben itself were protected from erosion because of their lower elevations. The Republic graben has remarkably little topo- graphic expression for so large a structural feature. The surrounding mountains have gently rounded tops, and in many places one observes little difference of relief in passing across the graben. 6% 142. SUGGESTED SOURCE OF MIOCENE VOLCANIC DETRITUS FLANKING THE CENTRAL CASCADE RANGE, WASHINGTON .By LEONARD jM. GARD, J 12., Denver, Colo. Poorly consolidated pumiceous fluvial and lacustrine sediments of late Miocene age, interbedded with ash layers and volcanic mudflows, have been recognized on the west flank of the Cascade Range in Washington (Mullineaux, Gard, and Crandell, 1959) (fig. 142.1). As these deposits contain fragments of hornblende, and of hornblende andesite that is markedly different from the earlier Tertiary pyroxene-rich volcanic rocks that predominate in the central Cascade Range, they may be products of an eruptive phase of the Snoqualmie gra- nodiorite batholith. These sediments are correlated in part, on the basis of lithologic similarity and age (Mullineaux, Gard, and Crandell, 1959, p. 695), with the Ellensburg formation (Miocene-Pliocene) which overlaps the east flank of the Cascades (fig. 142.1). The Ellensburg also is char— acterized by pumiceous volcanic mudflows and alluvial deposits rich in hornblende andesite debris, which ac- cording to Waters (1955, p. 673) was derived from a growing chain of explosive andesitic volcanoes to the west of the Yakima area. But although the volcanic materials in the Ellensburg must have been derived from vents in the Cascades, none of these vents have been recognized. Waters (1955, p. 664) states that ex- tensive remnants of volcanoes of the requisite age are exposed in the present Cascade Mountains, but he does not specifically identify or locate any one of these rem- nants, and a. search of the published literature has not revealed any reference to them. The Snoqualmie granodiorite was intruded into earlier Tertiary rocks that now form much of the Cas- cade Range. The time of intrusion is inexactly known. Warren (1941, p. 797) indicated that it was intruded in Oligocene( ?) time, whereas Smith and Calkins (1906) suggested a late Miocene age of intrusion. Coombs (1936, p. 167), as well as Smith and Calkins, pointed out that green hornblende and biotite are the predominant ferromagnesian minerals in the granodi- orite. Fuller1 suggested that the lack, in the Sno— qualmie granodiorite, of both ore deposits and late dif- ferentiates was due to its having solidified prematurely because it lost a vast quantity of volatile constituents that broke through to the surface. It is here suggested that the magma reached the sur- face and the volatile constituents were given off during explosive volcanism. This eruptive phase of the Sno- qualmie produced the hornblende-bearing pumice, ash, and mudflow deposits of late Miocene age now preserved only on the flanks of the Cascades. If, as suggested here, the Snoqualmie is the source of this volcanic detritus, then at least some granodiorite must have been intruded in late Miocene time. Recently published in- formation by Waters (1955, p. 664) and Cheney (1959, p. 122) indicates that the upper part of the Ellensburg formation is of early Pliocene age. The abundance of newly erupted volcanic material in the Ellensburg sug— gests that the extrusive phase of the Snoqualmie might have lasted into early Pliocene time. Snoqual- mie volcanoes probably have been removed completely by erosion that has exposed the top of the batholith in many places (fig. 142.1). This idea, although partly anticipated some 35 years ago, has recently been reached independently and by way of different lines of evidence 1Fuller, R. E., 1925, The geology of the northeastern part of the Cedar Lake quadrangle, with special reference to the deroofed Snoqual- mie batholith : Washington Univ. [Seattle], unpublished Master’s thesis. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES 123 ° 122 ° 121 " ° 12919" X Mt Baker x . 48° GIaCIer Pea 48° Q Seattle / s O acoma ® 47° 0 47° Ellensburg ® Yakima 46°\ 123° 50 100 MILES EXPLANATION General distribution of Snoqualmie granodiorite and similar granitic intrusive rocks in the central Cascades. Other probably equivalent rocks not shown General distribution of upper Miocene homblende- rich detrital rocks of volcanic origin X Quaternary volcanoes 123° 120° ‘ V INDEX MAP OF WASHINGTON FIGURE 142.1.—Sketch map of Miocene intrusive rocks and re- lated volcanic debris in and near the central Cascade Range, Wash. B307 by others working in the central Cascade Range. Therefore, more evidence on the problem will be forthcoming. REFERENCES Cheney, R. W., 1959, Miocene floras of the Columbia River Plateau: Carnegie Inst. of Washington Publ. 617, Part 1, 134p. Coombs, H. A., 1936, The geology of Mount Rainer National Park: Washington Univ. [Seattle] Pub. in Geology, v. 3, n0. 2, p. 121—212. Mullineaux, D. R, Gard, L. M., and Crandell, D. R., 1959, Con- tinental sediments of Miocene age in the Puget Sound lowland, Washington: A111. Assoc. Petroleum Geologists Bull., v. 43, p. 688—696. Roberts, A. E., 1958, Geology and coal resources of the Toledo— Castle Rock district, Cowlitz and Lewis Counties, Washing- ton: U.S. Geol. Survey Bull. 1062, 71 1). Smith, G. 0., and Calkins, F. C., 1906, Description of the Snoqualmie quadrangle, Washington: US. Geol. Survey Geol. Atlas, Folio 139. Snavely, P. D., Jr., Brown, R. D., Roberts, A. E., and Rau, W. W., 1958, Geology and coal resources of the Centralia- Chehalis district, Washington: U.S. Geol. Survey Bull. 1053, 159 p. Washington Division of Geology, 1936, Preliminary geologic map, State of Washington; Washington State Dept. Con- serv. and Devel., scale 1 : 500,000. Warren, W. C., 1941, Relation of the Yakima basalt to the Keechelus andesitic series: J our. Geology, v. 49, no. 8, p. 795—814. Waters, A. (3., 1955, Geomorphology of south-central Washing- ton, illustrated by the Yakima East quadrangle: Geol. Soc. America Bu11., v. 66, p. 663—684. 6? LATE RECENT AGE OF MOUNT ST. HELENS VOLCANO, WASHINGTON 143. By D. R. MULLINEAUX and D. R. CRANDELL, Denver, Colo. Mount St. Helens is a high symmetrical stratovolcano on the western flank of the Cascade Range in southern Washington. The modern cone, composed of pyroxene andesite and olivine basalt, is built on an older cone of hornblende dacite and hornblende-hypersthene andesite (Verhoogen, 1937). From the time of the early geolog— ical exploration of the Pacific Northwest in the 19th century, the smooth slopes and lack of pronounced glacial features on Mount St. Helens have been inter- preted as evidence that the volcano is young. Ver- hoogen believed that many flows from the mountain were no more than a few hundred years old, and he noted that actual eruptions were reported in 1842 and B308 1854. Because of the topographic evidence and the absence of olivine basalt stones in terrace deposits in the Toutle River valley northwest of the volcano, Verhoogen dated the modern volcano as Recent. He regarded the terrace deposits as glaciofluvial gravel derived from the older Mount St. Helens during Pleis- tocene time. Our studies indicate that the terrace deposits in the Toutle River valley consist of interbedded debris flows and alluvium composed almost entirely of the older rocks from Mount St. Helens. These deposits are traceable downvalley for a distance of 55 miles. A fragment of a conifer stem and branch from within a debris flow in the terrace deposits at Silver Lake, 25 miles west of the volcano, has a radiocarbon age of 2,030i240 years (U.S. Geological Survey sample W—811, Meyer Rubin, written communication). In the upper part of the debris flow that contained the wood is a soil about 12 inches thick, consisting of a humified zone and an oxidized zone, separated by a thin lighter colored layer that is interpreted as the bleached horizon of a podzolic soil. This soil is over— lain by alluvial gravel, which is overlain in turn by two younger debris flows. None of these deposits con- tain stones of either the pyroxene andesite or the olivine GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES basalt typical of the modern Mount St. Helens. The uppermost debris flow, which forms the top of the terrace here, is oxidized to an average depth of about 18 inches, but no bleached horizon has been seen under the 1- t0 2-inch layer of organic material at the top. As environmental conditions during the formation of the two soil profiles were probably similar, the lower profile probably required at least as long a time to form as the upper profile. If so, the volcano must have continued to erupt only the hornblende dacite and hornblende-hypersthene andesite of the older Mount St. Helens for another thousand years after the dated wood was incorporated. From the composition of the debris flows, the radio— carbon age of the wood sample, and the soil profiles within the flows, it is inferred that Mount St. Helens did not begin to erupt the olivine basalt and pyroxene andesite of the present cone until very late in Recent time, and that the modern cone may well be a product of the last thousand years. REFERENCE Verhoogen, Jean, 1937, Mount St. Helens, a recent Cascade volcano: California Univ. Dept. Geo]. Sci. 131111., v. 24, p.263—302. 5% 144. CENOZOIC VOLCANISM IN THE OREGON CASCADES By DALLAS L. PECK, Menlo Park, Calif. Work done in cooperation with the Oregon Department of Geology aml M moral Industries The Cascade Range in Oregon comprises two major sequences of volcanic rocks of Cenozoic age (Callaghan, 1933). The older sequence, the volcanic rocks of the Western Cascades, makes up the western slope of the range, and consists of warped, faulted, and partially altered upper Eocene to upper Miocene flows and pyro- clastic rocks, 12,000 feet thick on the average. The younger sequence, the volcanic rocks of the High Cas- cades, forms the crest and most of the eastern slope of the range, and consists predominantly of unaltered and undeformed Pliocene to Recent andesite1 and basalt flows from relatively undissected shield and strato- volcanoes (\Villiams, 1942). 1The rock classification of Williams and others (1954) is followed in this report. The age, lithology, and thickness of the major vol- canic units of the Cascade Range are summarized in table 144.1. The formations are dated on the basis of fossil plants from more than 50 localities. Marine strata that un— derlie and interfinger with the volcanic rocks along the western foothills have yielded fossil mollusks and Foraminifera of Eocene, Oligocene, and early Miocene age. Fossiliferous lacustrine and fiuviatile tuffaceous strata of late Miocene and Pliocene age interfinger with the volcanic rocks along the eastern and western flanks of the range. The rocks of the Cascades are calc-alkaline, similar chemically to Nockolds’ (1954) average “central” basalt, andesite, dacite, rhyodacite, and dellinite. They have GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES TABLE l44.1.——Summury of'the major Cenozoic units in the Cascade Range in Oregon B309 Age Name Lithology Thickness (feet) Pliocene and Quater- nary. Volcanic rocks of the High Cascades. Flows and minor pyroclastic rocks of olivine andesite and olivine basalt, subordinate pyroxene andesite, and minor dacite. Flows are typically porous textured and sparsely porphyritic, and contain phenocrysts of olivine that are partially altered to iddingsite. Vents represented by line 5 in fig. 144.]. Middle and late Miocene. Unnamed volcanic formation. Unconformity 0—73,000 Flows, tuff breccia, and tufi of hypersthene andesite and mafic hypersthene dacite, subordinate labradorite andesite, olivine andesite, augite andesite, and mafic dacite, and sparse felsic dacite and olivine basalt. Flows are typically platy and porphyritic, and contain phenocrysts of calcic plagioclase and prismatic black hypersthene. Massive beds of mudflow breccia are locally abundant. Vents represented by line 4 in fig. 144.1. 0—10,000, avg about 3,000. Middle Miocene _____ Columbia River ba- salt. Flows of tholeiitic basalt and basaltic andesite. ically columnar-jointed, and are composed of very fine-grained black basalt that contains abundant glass, intermediate pla- gioclase, augitic pyroxene, and chlorophaeite, but little or no olivine. Extruded from fissures that are outside the Cascade Range and not shown on fig. 144.1; present only locally within the range. Oligocene and early Miocene. Unnamed volcanic series. Unconformity Dacitic and andesitic tuff and less abundant flows and breccia of olivine basalt, olivine andesite, and pyroxene andesite, dacitic and rhyodacitic flows and domes, and rhyodacitic tufi‘. Pum- ice lapilli vitric tui’f in massive beds that were presumably deposited as glowing avalanches is the most abundant rock type. Basaltic flows typically contain sparse phenocrysts of pyroxene (salite) and altered olivine, as well as micropheno- crysts of calcic plagioclase and pyroxene. tains internal disconformity east of Eugene. sented by lines 1, 2, and 3 in fig. 144.1. Late Eocene ________ Colestin formations _ - Local unconformity Andesitic tufl, conglomerate tufiaceous siltstone and sandstone, and less abundant flows and breccia of olivine andesite and pyroxene andesite. Location of vents uncertain. questinnablv represented by line 1 on fig. 144.1. Flows are typ- 0-2, 500 3, 000—15, 000 The series con- Vents repre- 0—3, 000 Andesite a total volume of about 30,000 cubic miles. that has a silica content of about 56 percent is the most abundant rock type; rocks containing 63 to 68 percent silica are sparse, and rocks that have about 70 percent silica are moderately abundant. The nature and rela- tive abundance of phenocrysts in the volcanic rocks of different composition are shown in figure 144.1. The Miocene and older volcanic rocks are partly altered. Throughout most of the Western Cascades volcanic glass in pyroclastic rocks and flows is replaced by fine-grained aggregates consisting chiefly of zeolite (mordenite or clinoptilolite) or alkalic feldspar, to— gether with cristobalite or chalcedonic quartz and mont- morillonitic clay. In restricted areas around former volcanic centers the rocks are propylitically altered and are intruded by small dioritic and granitic stocks, pipes, and dikes. The regional alinement of successive series of vents of the volcanic rocks of the Cascade Range in Oregon is indicated in figure 144.2. Vents for the different volcanic units are apparently alined in northward trending belts that generally shifted progressively east- ward during the Cenozoic. During the latter part of the Oligocene and the early Miocene groups of vents were alined in two separate belts; vents in the western belt yielded mostly flows of olivine basalt and olivine andesite whereas contemporaneous vents farther east yielded mostly dacitic and rhyodacitic pyroclastic rocks. B310 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES N REFERENCES Callaghan, Eugene, 1933, Some features of the volcanic sequence 46 1 in the Cascade Range in Oregon: Am. Geophys. Union, K Trans. 14th Ann. Mtg, p. 243—249. ( w A s H I N G T O N OREGON \, / Nockolds, S. R., 1954, Average chemical compositions of some (\ /"~" igneous rocks: Geol. Soc. America Bull., v. 65, p. 1007—1032. \\~_, ,/” Portland T‘--\_—( I Williams, Howel, 1942, The geology of Crater Lake National ° Park, Oregon, with a reconnaissance of the Cascade Range K southward to Mount Shasta: Carnegie Inst. Washington 3 Pub. 540, 162 p. (j — 1954, in Williams, Howel, Turner, F. J., and Gilbert, C. TVV M., Petrography—an introduction to the study of rocks in A / . . ‘ _ . 45° thIn sections. San Franc1sco, W. H. Freeman and Co., Salemo © 406 p. ‘ m I~ BASALT l ANDESITE I DACITE IRHYODACITE I~ . . . , Lu : 3 ' z Chrysolite » —E — , < @ / z I Z ~I E E E 4 \A 3 I I ‘ [Ll Hypersthene 3— .— — x 3 U i 5 z 3 E E <2: Ferrohypersthene ; —— 2—.— k ; 2 I Eugeneo ; a 5 44° Salite ._ é 2 § @ Lu A .t r i E o —— —. : ugl e 3 2 : q. 3 s 2 J» 0 . E : : V w - — :— ‘— Ferroauglte _ : v: E o Hornblende ————— -_.— (Roseburg (D Biotite E 43° : x : I- 3 > . - ' z Magnetlte E E > : : -4 . I Bytownite .—i E : E E 3 : g g o I ‘ I C o Labradorite * : 2 Medford : ; f A 3 s 2 Z . g ‘ ‘ z Andesune : —-.— U, _ ——--—l— : 3 g 4221— _____ ____ —— - E 3 123° CALIFORNIA 122° Oligoclase f E C o 25 50 MILES . . g._____.l_____l A h FIGURE 144.2.—Center lines of belts of vents of Cenozoic vol- "0" “'3“ _< canic rocks in the Cascade Range in Oregon. 1, Vents 0f upper Eocene( ?) and lower Oligocene andesitic volcanic Quartz §_____ 5 rocks; 2, middle Oligocene to lower Miocene flows of basalt 5 l and basaltic andesite; 3, Oligocene and lower Miocene daciltic, andesitic, and rhyodacitic pyroclastic rocks; 4, middle and upper Miocene andesitic volcanic rocks; 5, Pliocene and Quaternary andesitic and basaltic volcanic rocks. FIGURE 144.1.—I’henocrysts in volcanic rocks of the Cascade Range in Oregon. ’X‘ GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES 145. B311 RODINGITE FROM ANGEL ISLAND, SAN FRANCISCO BAY, CALIFORNIA By JULIUS SCHLOCKER, Menlo Park, Calif. The calcium silicate-rich rock rodingite, found in serpentine thorughout the world, is also found in the serpentine of Angel Island, in San Francisco Bay, Calif. Rodingite at other localities is described as forming altered dikes of calcium-rich gabbro or diorite, though a rodingite in the Ural Mountains is said to form pyroxenite schlieren in serpentine (Baker, 1959, p. 33; Suzuki, 1953, p. 425; Miles, 1950, p. 126; Cater and Wells, 1953, p. 103, Wells, Hotz, and Cater, 1949, p. 12). The serpentine that encloses the rodingite on Angel Island is a steep, tabular body, about 600 feet thick, squeezed into rocks of the Franciscan formation. The rodingite occurs, together with various clearly meta— morphic rocks, in scattered, isolated fragments oriented at random in the serpentine. These are all “tectonic inclusions” as defined by Brothers (1954, p. 616). The inclusions of rodingite are round masses 1 to 4 feet in diameter. They are fine- to medium-grained, are very tough, and generally have a specific gravity well above 3.0. Their color ranges from light yellowish gray to dark greenish gray. The most conspicuous and abun- dant ones have light-colored cores and medium- to dark-gray rims 1 to 3 inches thick (fig. 145.1). MINERALOGY The Angel Island rodingite consists mainly of calc- silicates and several species of chlorite. Several min» eralogical types have been recognized: garnet-vesuvian— ite, garnet-chlorite—vesuvianite, clinozoisite-diopside— garnet-vesuvianite, chlorite-sphene-vesuvianite, and diopside-chlorite. Accessories are calcite, magnetite, ilmenite, pyrite, stilpnomelane, garnet, vesuvianite, sphene, and chlorite. The composition of the garnets and garnet-like min- erals, which are abundant in most of the Angel Island rodingite, was determined by measuring refractive in- dices and unit-cell edges. Graphs of Sriramadas (1957, p. 295—296) show that one specimen of garnet is ap- proximately 45 percent grossularite and 45 percent an- dradite. More common are garnet-like minerals whose refractive index is too low and whose unit-cell edge is too large for garnet. These fall on Winchell and Win— chell’s (1951, p. 493) graph for minerals of the garnet- hydrogarnet (hibschite) series, which consist of the following four components: grossularite (Ca3A12- rVUAN'I'VJ )r K”: N/xrixlw («I A s.~ w «1% V?» ‘H ) , SJll > (H r((',‘§ ){l(/~ ( l ( ‘S / if \ )K \ / S ( I; ., ~{N‘l ( ‘\ 3 //r \x- \ Dark-gray chlo— / C] ( C), rite, magnetite )/ f k \ (stilpnomelane) ”f1; \ 3/ ' /C C] Light yellowish gray \\ 0) / garnet-hydrogarnet, (J I; clinozoisite, diopside, >\ \\ . vesuvianite, chlorite. H“ i/ tC sphene //\ *-\. . r’ r - ”’\ f: ” ( I) «- /( / xv~ ‘9, U” , /\ 59‘ . A2 ((\ f . ‘ 5‘13 (\Sfl 2< '\ J “x \\ I (/ I ~~ / .. \‘V‘ R , "‘l W”, ;: «sewn! u~ «\fxx :xwrsx—f/ A > , L1,}! 0 1 FOOT |______J FIGURE 145.1.—Diagrammatic sketch of typical rodingite inclu- sion, Angel Island, San Francisco Bay, Calif. (Sio4)3), andradite (CagFe2(Si04)3), Ca3A12Os-6HZO, and CagFegOe-GHZO. The Angel Island garnet-hydro- garnets contain 40 to 70 percent grossularite, 30 to 60 percent andradite,.and 1 to 1.2 moles H20. Hydro- grossular, a hydrogarnet high in grossularite contain- ing 0.72 moles H20, was first identified in rodingite from New Zealand (Hutton, 1943, p. 17 4—180) and has been found in other rodingites (Miles, 1950, p. 128). The dark rims found on most rodingite inclusions con- sist. predominantly of chlorite and disseminated mag- netite. Cale-silicates, similar to those in the rodingite cores, are generally present in small amount near the inner borders of the rims. Stilpnomelane Vein-lets oc- cur in these rims, and also veinlets and masses of anti- gorite. A pyrite-rich zone is found on or near the borders‘of some rodingite inclusions. B312 ORIGIN OF ANGEL ISLAND RODINGITE The origin of some of the rodingite is indicated by relict textures and minerals. Euhedral to subhedral crystals of diopsidic augite occur in what appear to be relicts of a porphyritic rock or a crystal tufli. Some of the rodingite, however, shows well-preserved textures of porphyritic basaltic glass or tachylite identical with those found in surficial volcanic rocks (greenstones) of the Franciscan formation of Angel Island (Schlocker and others, 1958). What appear to be relict vesicles and euhedral laths, probably once plagio- clase, are now mostly represented by masses of color- less chlorite sharply outlined against a groundmass of cloudy garnet aggregates. The groundmass shows ir- regular, flat-sided and rounded masses identical in structure with those seen in tachylitic pyroclastic rocks and pillow greenstones of the Franciscan formation. Greenstone structures and textures are also represented in the dark rims of the rodingite fragments by layers consisting of tiny aggregates of magnetite, sphene, and garnet embedded in chlorite. Rodingite of tachylite origin may be 01er than, or contemporaneous with, serpentine; other rodingite may be younger than serpentine. Veins of serpentine in rodingite merely show that the veining is younger than the rodingite. The high mobility of serpentine com- plicates the problem of deciding relative age on the basis of cross cutting, for crustal pressures may have mobilized the serpentine many times after it was first formed. Some of the Angel Island rodingite may have formed igneous dikes which cut an ultramafic rock but which were broken up and moved about during and after the serpentinization of that. rock. Fragments of tachylitic greenstone may have become altered to rodingite either before or after they were caught up in the serpentine. Other masses of rodingite throughout the world are generally regarded as dikes cutting older serpentine; Baker (1959, p. 33), however, concluded that the Tasmanian rodingite formed before the ser- pentine intruded it. A Although no chemical analyses of the Angel Island rodingites are yet available, the mineral content of the rocks indicates that the conversion of greenstone to rodingite was accompanied by a considerable increase in calcium and loss of silica. A calculation was made on the assumption that the dark rims were originally GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES greenstone and that the additional calcium in the cores was derived from them, but this calculation showed that the cores contained considerably more calcium than could have been obtained from the rims. Serpentiniza- tion of diallage, which was probably common in the original ultramafic rock, may have freed calcium that migrated to tectonic inclusions of rocks such as green- stone, which were probably the only other calcium- bearing materials in the ultramafic rock, and the cal- cium may have become bonded to other atoms in the inclusions to form calc-silicates. Such a concentration of calcium could have been accompanied by migration of silica from the inclusion to the surrounding silica- undersaturated ultramafic rock. If tectonic inclusions of greenstone of the Franciscan formation were converted to rodingite, the same change may have operated on other rocks of the forma- tion, similar in chemical composition, such as volcanic graywackes. REFERENCES Baker, George, 1959, Rodingite in nickeliferous serpentinite, near Beaconsfield, Northern Tasmania: Geol. Soc. Aus- tralia Jour., v. 6, pt. 1, p. 21—35. Brothers, R. N., 1954, Glaucophane schist from the north Berk- eley Hills, California: Am. Jour. Sci., v. 252, p. 614—626. Cater, F. W., Jr., and Wells, F. G., 1953, Geology and mineral resources of the Gasquet quadrangle, California-Oregon: 1'. S. Geol. Survey Bull. 995—0, p. 79—133. Hutton, C. 0., 1943, Hydrogrossular, a new mineral of the gar- net—hydrogarnet series: Royal Soc. New Zealand Trans, v. 73, p. 174—180. Miles, K. R., 1950, Garnetized gabbros from the Eulaminna dis- trict, Mount Margaret Goldfield: Western Australia Geol. Survey Bull. 103, pt. 2, p. 108—130. Schlocker, Julius, Bonilla, M. G., and Radbruch, D. H., 1958, Geology of the San Francisco North quadrangle, Califor- nia: U.S. Geol. Survey Misc. Geol. Inv. Map 1—272. Sriramadas, A., 1957, Diagrams for the correlation of unit cell edges and refractive indices with the chemical composition of gums: Am. Mineralogist, v. 42, nos. 3—4, p. 294—298. Suzuki, Jun, 1953, On the rodingitic rocks within the serpen- tinite masses of Hokkaido: Jour. Fae. Sci. Hokkaido Univ., ser. 4, v. 8, no. 4, p. 419430. Turner, F. J ., and Verhoogen, Jean, 1951, Igneous and metamor- phic petrology: New York, McGraw-Hill Book 00., Inc., 602 1). Wells, F. G., Hotz, 1’. 14]., and Cater, F. W., Jr., 1949, Prelimi- nary description of the Kerby quadrangle, Oregon: Oregon Dept. Geology and Mineral Industries Bull. 40, p. 1—23. Winchell, A. N., and Winchell, Horace, 1951, Elements of opti- cal mineralogy, 4th ed: New York, John Wiley and Sons, 551 p. ’X‘ GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B313 146. GRAVITY ANOMALIES AT MOUNT WHITNEY, CALIFORNIA By H. W. OLIVER, Washington, DC. A gravity station on the top of Mount \Vhitney, California, was occupied with a Worden gravimeter on August 18, 1957, in connection with a regional gravity study of the southern half of the Sierra Nevada. The station was established by L. C. Pakiser and G. Turner relative to a gravity station at Whitney Pass, which had previously been tied to US. Coast and Geodetic Survey pendulum stations at Independence and \Vaukena (Duerksen, 1949, p. 36) and to airport gravity bases at Merced and Fresno (Woollard, 1958, p. 532). The Mount Whitney station is now the highest gravity station in North America (14,496 feet above sea level) and provides important data for testing the principle of isostasy. GRAVITY DATA Gravity reductions were carried out for the station on Mount Whitney according to the methods described by Swick (1942) and Heiskanen (1938). A Bouguer reduction density of 2.67 g per cm3 was used, and the corrections for topography and compensation for zones 10 to 1 were taken from the world reduction charts pre- pared by Niskanen and Kivioja (1951). Table 146.1 lists the principal gravity data at Mount Whitney, and for comparison it includes similar data for Pikes Peak, in the Colorado Front Range. Figure 146.1 is a plot of the Mount Whitney data, showing the effect of different assumptions on the value of the gravity anomalies. The free-air anomaly is treated in the figure as a Hayford anomaly (Hayford and Bowie, 1912) for which the depth of compensation, D, is zero. The free-air anomaly is also treated as a Heiskanen anomaly (Heiskanen, 1938) for which the thickness of the normal crust, T, is zero relative to the earth’s sur— face, which becomes a negative thickness relative to sea level. The Bouguer anomaly, likewise, may be con- sidered as either a Hayford or a Heiskanen anomaly for which the depth of compensation or the normal crustal thickness, respectively, is infinite. DISCUSSION OF RESULTS It is seen from figure 146.1 that the gravity anomalies at Mount Whitney can be reduced to zero by assuming a Hayford isostatic system with I)=71 km or a Heis— kanen system with T = 17 km. These values for I) and T are somewhat smaller than the “best” values of I)=96 km derived by Bowie from gravity data at stations in 557753 0—60—21 TABLE 1.—Gram'ty data at Mount Whitney, California, and Pikes Peak, Colorado. All gravity values and anomalies are in mllligals Mount Pikes Peak Whitney Elevation (feet) ______________________ 14, 496 1 14, 086 Observed gravity ____________________ 978735 1 978959 Free-air anomaly ____________________ + 217 1 +203 Simple Bouguer anomaly ______________ —278 —277 Terrain correction ____________________ 76 2 57 Bouguer anomaly ____________________ — 202 1 — 220 Isostatic anomalies Hayford, D=56.9 km ,,,,,,,,,,,,,, +18 1 +45 D = 96 km ________________ — 22 1 + 24 D=113.7 km ,,,,,,,,,,,,, ——34 1 +18 D=127.9 km _____________ —42 3 +13 Heiskanen, T=20 km ______________ — 11 ? T: 30 km ______________ — 31 4 + 17 T: 40 km ______________ — 47 5 + 3 T: 60 km ______________ —- 72 5 ~ 7 1 Duerksen (1949, p. 8). 2 Rice, Donald (1960, oral communication). 3 Bowie (1917, p. 103). Eleven mgals have been subtracted from Bowie’s value of the Hayford anomaly corresponding to D=127.9 km, in order to bring it in line with Duerksen’s more recent determination of Hayford anomalies corresponding to D= 56.9, 96, and 113.7 km. This difierence is due largely to a change in reference gravity from the Helmert formula of 1901 to the International Gravity Formula 01‘ 1930. 4 Quresky, M. N., 1958, Gravity anomalies and computed variations in the thick- ness of the earth’s crust in Colorado: Colorado School of Mines, Ph.D. thesis, pl. 3. 5 Heiskanen (1939, p. 31). Five mgals have been subtracted from the cited values of Heiskanen anomalies corresponding to T=40 km and 60 km, in order to bring these data in line with Duerksen’s more recent determination of the Bouguer anomaly. mountainous regions (1917, p. 133), and of T=30 km determined seismically as the normal sea-level thick- ness of the earth’s crust in California (Press, 1957). Isostatic anomalies correspOnding to these values are negative by about 30 mgals. There are two possible interpretations of these data: (a) the Mount Whitney region is slightly overcompen- sated and will tend to approach isostatic equilibrium by further uplift of the mountain block, or (b) both the Heiskanen and Hayford systems are incorrect and do not adequately represent the true nature of isostatic compensation for the southern Sierra Nevada. The first interpretation is supported by geologic evi- dence that the Sierra is still rising relative to the sur— rounding valleys, but there is some question regarding the absolute sense of the vertical displacements (Paul Bateman, 1960, written communication). B314 HAYFORD DEPTH OF COMPENSATION (D), IN KILOMETERS 50 100 150 I I I I +200 +150 + 100 \ +50 \ 7:17 km A / /D=71 km \ \ A o <— Best values/ \ \A‘ O I U! 0 I —100 — GRAVITY ANOMALIES AT MT WHITNEY, IN MILLIGALS —150 — Bouguer anomaly: _ goianais _200 =,,,, , ,, l I 1 I J O 50 100 150 200 HEISKANEN NORMAL CRUSTAL THICKNESS (T), IN KILOMETERS FIGURE 146.1.—Isostatic anomalies at Mount Whitney, Calif. The Hayford and Heiskanen anomaly curves approach the Bouguer anomaly value of —202 milligals as D and T, re- spectively, approach infinity. The Airy—Heiskanen model of isostatic compensation is favored over the Pratt-Hayford model by seismic evidence of thickening of the earth’s crust beneath the Sierra Nevada (Byerly, 1938; Gutenberg, 1943; Press, 1956). It has become increasingly apparent, however, that the Airy—Heiskanen model is only a first-order ap- proximation to a very complex phenomenon. Press (1960) has recently shown that the earth’s crust in the desert areas south of the Sierra Nevada is made up of at least two discrete layers, and that there are sig- nificant lateral Variations in the velocity and presum- ably the density of the lower layer- Gravity gradients at the west edge of the Sierra Nevada indicate that part of the mass deficiency under the range is produced by a lateral variation in the density of rocks of the upper crustal layer. This conclusion is further sup- ported by density measurements of surface samples, which show a systematic decrease from a value of about 2.8 g per cm3 in the western foothills to about 2.6 g per GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES cm3 near the eastern crest of the Sierra Navada. A modification of Heiskanen’s model by the introduction of mass deficiencies within the earth’s crust tends to re- duce the magnitude of the negative Heiskanen anom- alies at Mount Whitney by bringing part of the com- pensating mass closer to the earth’s surface. COMPARISON OF CALIFORNIA AND COLORADO ANOMALIES Table 146.1 shows that the isostatic anomalies at Pikes Peak are generally positive, in contrast to the negative anomalies observed at Mount Whitney. The algebraic differences average about 50 mgals. The contrast in the geologic history of these two re— gions is also striking. The Nevadan orogeny in the Sierra Nevada is characterized by tight isoclinal fold- ing, a high degree of metamorphism, and perhaps the complete transformation of older rocks to form the Sierra Nevada batholith. The Laramide orogeny, on the other hand, did not extensively alter the lithologic character of the Rocky Mountains in Colorado; upper Paleozoic and Mesozoic rocks were broadly folded, thrusted and uplifted without much lithologic trans- formation. This comparison suggests that there may possibly be a relation between isostatic anomalies and the extent of deformation and lithologic change. CONCLUSION Bouguer and isostatic anomalies at Mount Whitney show that there is a large mass deficiency below the Sierra Nevada, which is in general accOrdance with the principle of isostasy, and that the gravitational efl'ect of this “defective” mass on Mount Whitney is approxi- mated within 85 percent by Heiskanen and Hayford models that correspond to T =30 km and D=96 km, re— spectively. A better isostatic model for the Sierra Nevada would probably be a combination of the Hieskanen and Hayford models, the parameters for which cannot be determined uniquely except by the application of several geophysical methods. Isostatic anomalies based on present models are probably indica- tive in many cases of density changes within the earth’s crust resulting from orogenic activity. REFERENCES Bowie, William, 1917, Investigations of gravity and isostasy: US. Coast and Geod. Survey, Spec. Pub. No. 40, 196 p. Byerly, Perry, 1938, The Sierra Nevada in the light of isostasy: Geol. Soc. America Bu11., v. 48, p. 2025-2031. Duerksen, J. A., 1949, Pendulum gravity data in the United States: US. Coast and Geod. Survey, Spec. Pub. No. 244, 218 p. Gutenberg, Beno, 1943, Seismological evidence for roots of mountains: Geol. Soc. America Bu11., v. 54, p. 473—498. GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES Hayford, J. R, and Bowie, William, 1912, The effect of topog- raphy and isostatic compensation upon the intensity of gravity: U.S. Coast and Geod. Survey, Spec. Pub. No. 10, 132 p. Heiskanen, W., 1938, New isostatic tables for the reduction of gravity values calculated on the basis of Airy’s hypothesis: Internat. Assoc. of Geodesy, Isostatic Inst. Pub. No. 2, 42 p. 1939, Catalogue of the isostatically reduced gravity sta- tions: Internat. Assoc. of Geodesy, Isostatic Inst. Pub. No. 5, 139 p. Niskanen, E., and Kivioja, L., 1951, Topographic-isostatic world maps of the effect of the Hayford zones 10 to 1 for the Airy-Heiskanen and Pratt-Hayford systems: Internat. Assoc. of Geodesy, Isostatic Inst. Pub. No. 27, 6 p. B315 Press, Frank, 1956, Determination of crustal structure from phase velocity of Rayleigh waves, Part 1: Southern Cali- fornia: Geol. Soc. America Bu11., v. 67, p. 1647—1658. 1957, Determination of crustal structure from phase velocity of Rayleigh waves, Part II: San Francisco Bay region: Seismol. Soc. America Bu11., v. 47, no. 2, p. 87—88. ———- 1960, Crustal structures in the California-Nevada region: J our. Geophys. Research, v. 65, no. 3, p. 1039—1051. Swick, C. H., 1942, Pendulum gravity measurements and isostatic reductions: US. Coast and Geod. Survey, Spec. Pub. No. 232, 82 p. Woollard, G. P., 1958, Results for a gravity control network at airports in the United States: Geophysics, v. 23, no. 3, p. 520—535. ’X‘ 147. RELATIONS BETWEEN ABRAMS MICA SCHIST AND SALMON HORNBLENDE SCHIST IN WEAVERVILLE QUADRANGLE, CALIFORNIA By WILLIAM P. IRWIN, Menlo Park, Calif. Work done in cooperation with the California Division of M ines Metamorphic rocks form an arcuate belt, 10 miles wide and trending nearly north-south for 90 miles, in the central part of the Klamath Mountains of California (fig. 147.1). A smaller area of similar rocks lies farther north, extending beyond the Oregon boundary. The metamorphic rocks midway along the belt were divided by Hershey (1901, p. 226—230) into the Abrams mica schist and the Salmon hornblende schist. These units can be recognized in at least the southern half of the belt, where detailed reconnaissance was done later by J. S. Diller and H. G. Ferguson (unpublished data, 1922) and by Hinds (1933). These early workers noted that the Abrams formation contained lenses of marble, but they attached no particular stratigraphic signifi- cance to them. Hershey and Hinds regarded the amphibolitic Sal- mon formation as a thick layer of metamorphosed mafic volcanic rock that overlay the Abrams formation. Diller and Ferguson, on the other hand, believe that the Sal- mon formation probably consisted originally of diorite or gabbro that had been intruded into the Abrams for- mation; they noted, however, that there were irregulari- ties in the contact between the two formations, and ad- mitted that these might have resulted from interfinger- ing of volcanic rock with sedimentary rock rather than from intrusion. It now appears certain that the Salmon is of volcanic origin. The age of all these rocks is gen— erally regarded as pre-Silurian or Precambrian. Geologic mapping in the Weaverville 15-minute quad- rangle (fig. 147.1) indicates that (a) the structure of the metamorphic rocks included in that quadrangle is synclinorial, with the Abrams mica schist overlying the Salmon hornblende schist, (b) the Abrams is probably younger rather than older than the Salmon, and (c) the marble lenses are of stratigraphic significance in that they are chiefly in the lower part of the Abrams. In the Weaverville 15-minute quadrangle the Abrams mica schist predominates in the central part of the belt. The Salmon hornblende schist crops out chiefly along the margins of the belt, but it is also exposed at a few places in the central part of the belt on the crests of minor anticlines. The marble lenses and the folia- tion and compositional banding in the Abrams are gen- erally parallel to the contact between the two schists, and generally dip away from areas of the Salmon. The dominant structure appears to be an open synclinorium, although some of the minor folds are isoclinal. The Abrams occupies the trough of the synclinorium, and thus structurally overlies the Salmon. The marble is chiefly in the lower part of the Abrams, near the contact with the Salmon. At a few places, however, the Salmon contains thin layers of marble B316 OREGON —-—-1 -- —r-—-r CALIFORNIA Weaverville ureka quadrangle 40° O 10 20 30 MILES FIGURE 147.1.—Map of part of northwestern California showing the Klamath Mountains province (diagonal pattern) and Weaverville lfrminute quadrangle. The central belt of meta- morphic rocks and area of related rocks are indicated by schist pattern. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES near this contact. The marble occurs mostly in short lenses that are widely and unevenly spaced. Some of the discontinuity of the marble lenses has probably re— sulted from pinching off of limestone beds during de- formation, but some of it may be a feature of original deposition. Along the east margin of the belt of met~ amorphic rocks, however, the marble is essentially con— tinuous for more than 5 miles, and closely follows the contact between the Abrams and Salmon schists. At some places in the quadrangle several closely spaced layers of marble alternate with mica schist 0f the Abrams, and at these places it is uncertain whether the marble layers represent several original beds or a single bed repeated by isoclinal folding. The early workers believed that the Salmon horn- blende schist overlay the Abrams mica schist, but this view, based chiefly on reconnaissance, now seems to be erroneous, and so does the view, tentatively advanced by Diller and Ferguson, that the Salmon represents an intrusive body. The Abrams appears to overlie the Salmon in a large part of the Weaverville 15-minute quadrangle, and unless the normal stratigraphic se- quence has been complicated by thrust. faulting or over— turning on a grand scale, no evidence of which has been recognized, the Abrams mica schist is the younger. REFERENCES Hershey, O. H., 1901, Metamorphic formations of northwestern California: Am. Geologist, v. 27, p. 225—245. Hinds, N. E. A., 1933, Geologic formations of the Bedding- Weaverville districts, northern California, in 29th report of the State Mineralogist: California Div. Mines, v. 29, nos. 1, 2, p. 77—122. 148. EVIDENCE FOR TWO STAGES OF DEFORMATION IN THE WESTERN SIERRA NEVADA METAMORPHIC BELT, CALIFORNIA By LORIN D. CLARK, Menlo Park, Calif. Work done in cooperation with the California Division of Mines Structures in the metamorphosed sedimentary and volcanic rocks exposed in the western Sierra. Nevada are related to two distinct stages of deformation. Dur- ing the first stage, major folds having nearly horizontal axes and steeply dipping axial planes were formed. During the second, thesefolds were truncated by large faults (Clark, 1960) in the western part of the belt, and were modified by pervasive shearing and attendant development of steeply plunging b-lineations and minor folds in the eastern part of the region. Attitudes of sheer surfaces related to the second deformation make an angle of less than 30° in most places with the atti- tudes of axial planes of folds resulting from the first deformation, suggesting significant changes in the di- rections of the deforming pressures between the two stages. Had there been little change in pressure direc— GEOLOGY OF WESTERN CONTERMINOUS UNITED STATES B317 121° , .. 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N | . u 8 H. _I I A” I M = w: __ _ ~ _ _ fl _ 4. w w w m. we M W ._ m o u w ma MW m m M w w m g ., WW a. m ) 9 m u 01‘? ,c w erw ma w MI 362$ acaEszh .0 «:0: .535 hr/ \ .V I \ / \04 W S M y w m m w m W / |.\~4 I l m I a c, _ P \+L,L :g H 4. W 3 a x/ W \ /\ m n m km. W ( / I \ / I| \_/ |\ _ mNL .. s .0436 Z>OHn_> “ 3.131% n Z<>>O_ " ZOE>O.E coon xv m._Ow u4 LIJ _l < (D LLJ [I (D L|J *— LIJ E 0 L4 1000 METERS 500 FIGURE 155.1.—Profile through beach ridges at Point Hope, Alaska, with estimated absolute time scale. GEOLOGY OF ALASKA ceivably have been due to downwarping, but it appears far more likely, in View of the evidence for the general stability of the coast, that the submergence resulted from eustatic rise of sea level. At Point Hope the youngest beach ridges have been related to an absolute time scale (fig. 155.1) by the Tigara culture (A. D. 1300—17 00) and the Ipiutak cul- ture (A.D. 100—500), which have both been dated by the radiocarbon method (Rainey and Ralph, 1959). The oldest beach ridges now preserved at Point Hope were formed about 200 B. C. Older ridges have been removed by wave erosion cutting inward from the op- posite side of the point. The shoreline south of Point Hope is prograding at about 80 m a century, and new ridges have formed at average intervals of about 60 years. Two especially high beach ridges indicate that sea level may have been relatively high from A. D. 1000 to 1100 and from 1700 to 1850, and two especially lOW 156. B337 swales indicate that it may have been relatively low from 900 to 1000 and from 1400 to 1500. Whether these fluctuations are general and accurately dated must remain uncertain until similar studies have been made in other stable parts of the world. As it stands, however, this evidence from Arctic beach ridges indicates that sea level rose about 3 m during the last 5,000 years, and that the rise was characterized by minor fluctuations with an amplitude of 1 to '2 m. The highest stand of sea level since the Wisconsin stage was attained in the 19th century. REFERENCES Giddings, J. L., 1960, The archeology of Bering Strait: Current Anthropology, v. 1, p. 121—138. Hopkins, D. M., 1959, Cenozoic history of the Bering land bridge: Science, v. 129, p. 1519—1528. Rainey, F., and Ralph, E., 1959, Radiocarbon dating in the Arctic: Am. Antiquity, v. 24, p. 365—374. 5? GENERALIZED STRATIGRAPHIC SECTION OF THE LISBURNE GROUP IN THE POINT HOPE A—Z QUADRANGLE, NORTHWESTERN ALASKA By RUSSELL H. CAMPBELL, Menlo Park, Calif. Work done in cooperation with the U.S. Atomic Energy Commission During the summer of 1959 a stratigraphic section of rocks of the Lisburne group, of Early and Late Missis- sippian age, was measured along continuous sea-clifl’ ex- posures southeast of Point Hope, Alaska. Five distinc- tive lithologic units were recognized in the Lisburne group, which has a total thickness of more than 5,700 feet. The units have been tentatively designated, from oldest to youngest, M11, M12, M13, M14, and M15. UNIT M11 Unit M11 is about 165 feet thick where measured and is composed of interbedded dark-gray to grayish—black silt-clay shale, medium-gray to dark-gray bioclastic limestone, and grayish-black to black chert. The upper 45 feet consists predominantly of grayish-black shale in beds 0.1 foot to 5 feet thick, composed of fine quartz silt and clay (illite ?) with generally minor amounts of dis- seminated very fine-grained calcite, but it includes a few interbeds of dark-gray limestone. The middle 35 feet consists of grayish-black chert and minor amounts of interbedded dark-gray bioclastic limestone in beds com- monly about 0.5 foot thick. The lower part of the unit consists chiefly of medium—dark-gray mudstone, in beds 0.1 foot to 8 feet thick, composed of fine quartz silt, clay, and some disseminated fine calcite; but this is inter- bedded with minor amounts of partly dolomitized bio- clastic limestone in beds commonly about 0.5 foot thick. The bioclasts are chiefly crinoid columnals and Bryozoa, but brachiopods and horn corals are locally abundant, and the unit. contains a few colonial corals and gastro— pods. The upper shaly zone locally intertongues with the overlying unit, M12. The contact of M11 with the sand- stone—shale formation that underlies the Lisburne group is gradational. UNIT M12 Unit M12 is about 225 feet thick. It consists wholly of light-gray to light olive-gray bioclastic limestone composed predominantly of sparry calcite fossil frag- ments ranging from fine sand to very fine pebbles in size, with generally minor amounts of very fine quartz B338 silt, cemented with sparry calcite and microcrystalline quartz in varying proportions. Microcrystalline quartz also commonly forms rims around fossil frag- ments and spongy intergrowths with calcite that pre- serve organic structures within the fragments. In some places fossil fragments have been partly dolom- itized. The chief recognizable fossils are crinoid col- umnals and Bryozoa, but brachiopods and horn corals are also present. The unit is very thick bedded, locally cropping out as a single thick bed with a few short, discontinuous, un- even bedding planes. Bedding is expressed internally by crinkly uneven laminae at generally regular inter- vals of 0.5 inch to 1 foot. The contact with the over- lying unit M13 is conformable. UNIT M13 Unit M13 is about 1,650 feet thick and consists pre- dominantly of interbedded dark-gray bioclastic lime- stone and grayish-black quartz-calcite siltstone. It contains relatively abundant well—preserved fossils. The limestone is composed chiefly of sparry calcite bio- clasts of fine—sand to fine pebble size with variable amounts of fine quartz silt, sparry calcite cement, mi- crocrystalline quartz cement, very finely crystalline dolomite cement, and, in a few beds, a small amount of clay (illite? ). Replacement of fossils by microcrystal- line quartz has occurred, and may be found in all stages from thin rims around bioclasts, through spongy inter- growths preserving organic structure, to complete re— placement. The most abundant fossils are crinoid col- umnals and Bryozoa, but brachiopods, horn corals, and colonial corals are also locally common. Nodular lime- stone beds containing variable amounts of dark-gray to black chert are common at some horizons. Dark chert is locally abundant in several zones, chiefly as lenticular nodules and irregular angular masses in limestone. The basal 50 feet of unit Ml3 contains several very thick beds of grayish-black quartz-clay-calcite siltstone con- taining sparsely scattered small pyrite concretions and a few pyritized fossils. Rhythmic interbedding of limestone beds 0.2 to 1 foot thick with silt shale laminae 0.01 to 0.1 foot thick is characteristic of the unit. The bedding is generally regular and continuous, although the bedding surfaces are very slightly undulating to very uneven, the uneven surfaces being on nodular beds. The thickness of the silt shale interbeds and the abundance of shaly zones generally decrease upward. The contact between units M13 and M14 was arbitrarily placed at the base of the lowermost thick-bedded dolomitic limestone, but the units grade into each other. GEOLOGICAL SURVEY RESEARCH 1960—SI-IORT PAPERS IN THE GEOLOGICAL SCIENCES UNIT M14 Unit Ml4 consists predominantly of light-gray to dark-gray very finely crystalline dolomitic limestone, interbedded with generally minor amounts of dark- gray partly dolomitized bioclastic limestone and a few interbeds and partings apparently consisting largely of calcareous quartz clay siltstone. The bioclastic lime- stone consists chiefly of sparry calcite fossil fragments ranging in size from fine sand grains to fine pebbles. In some beds the fragments are cemented and in places partly replaced by very finely crystalline dolomite; in other beds they are in a matrix of microcrystalline cal- cite or dolomite or both. Light-gray and dark-gray chert commonly forms nodules and continuous and dis— continuous layers in some limestone beds. The chert content varies greatly from bed to bed, and also along the strike of individual beds. About 140 feet below the top of the unit is a zone of breccia about 400 feet thick, composed of very small to very large fragments of chert and dolomitic limestone in a microcrystalline matrix that is predominantly dolomite. Crinoid col— umnals and bryozoa predominate in the bioclastic limestone, but horn corals, colonial corals, brachiopods, and a blastoid (Pentremites?) were also found. A total of about 3,330 feet of strata was assigned to unit Ml.1 where the section was measured. An unknown thickness has been faulted out of the upper part by three high-angle faults, one of which forms the contact with the unit M15. Irregular interbedding of thin, medium, thick, and very thick beds is characteristic of the unit. Very thick beds, one as much as 140 feet thick, of crystalline dolomitic limestone are relatively abundant and com- monly show internal horizontal and gently cross- stratified current lamination, brought out by low-con- trast color banding. The bedding planes are commonly even but many are discontinuous. The contact between units M14 and M15 is a high- angle fault where well exposed on the sea clifl', but probably only a few hundred feet. of strata are missing. UNIT M15 Unit M15, the youngest unit of the Lisburne group, is about 330 feet thick in the incomplete section meas- ured. It consists of interbedded grayish—black chert, dark—gray to medium—dark-gray calcareous and non— calcareous siltstone and mudstone, dark-gray to light medium-gray very finely crystalline to microcrystal— line calcitic limestone, and a smaller amount of green- ish-black to dark-greenish-gray chert and noncalcare- ous argillite. Most of the chert is in beds 0.1 foot to GEOLOGY OF ALASKA 2 feet thick, with slightly uneven but generally con- tinuous bedding surfaces. The limestone beds contain variable but generally small amounts of nodular chert. The siltstone and mudstone beds range from less than 0.1 foot to 3 feet in thickness. The limestone is com- monly in beds 0.6 to 1 foot thick. The bedding is generally continuous, regular, and even. Fossils are very rare, but a few gastropods were collected from one siltstone bed. 157. B339 The contact with the overlying Siksikpuk formation, of Permian( ?) age, is a high-angle fault where the rocks are well exposed. Further inland, however, the configuration of the contact, together with the presence in unit Ml5 of interbedded greenish-gray chert and argillite resembling rocks in the Siksikpuk formation, suggests that the Siksikpuk grades into the Lisburne group, and that the missing part of the measured sec- tion is not more than a few hundred feet thick. A MARINE FAUNA PROBABLY OF LATE PLIOCENE AGE NEAR KIVALINA, ALASKA By D. M. HOPKINS and F. S. MACNEIL, Menlo Park, Calif. In 1957, the Rev. Milton Swan of Kivalina, Alaska, found a beautifully preserved shell of Patinopecten (Fortipecten) hallae (Dall) near Kivalina, Alaska, on the coast of Chukchi Sea about 200 miles north of Ber- ing Strait (fig. 157.1). Because of the importance of the find (Hopkins, 1959, p. 1521) Hopkins visited the Kivalina locality briefly in 1959 to examine the strati- graphy and to collect additional fossils. This report summarizes the results of field observations by Hopkins, and studies of the mollusks by MacNeil, of the Foramin- ifera by Ruth Todd, and of the ostracodes by I. G. Sohn. GEOLO GIC SETTING The fossiliferous sediments lie at the inner edge of a coastal plain that fringes the Chukchi Sea coast from 30 miles to the northwest to 150 miles to the southeast of Kivalina. Northwest of Kivalina Lagoon, the coastal plain consists of a nearly horizontal surface less than 25 feet above sea level, terminated at its inner edge by a scarp (fig. 157.1), apparently carved in uncon- solidated material, that is similar in appearance and altitude to the ancient wave-cut scarp of Second Beach, of Sangamon age, at Nome (MacNeil, Mertie, and Pilsbry, 1943; Hopkins, MacNeil, and Leopold, in press). Inland from this scarp a smooth surface slopes gently upward, but just north of Kivalina Lagoon and about 50 feet above sea level it is interrupted by a sec- ond row of scarps carved in bedrock. The marine fossils were obtained near the projected trend of the second row of scarps, in a small valley that enters the Kivalina River about 1.3 miles above Kivalina Lagoon. The second row of scarps probably represents a wave- cut clifl' carved during the maximum landward trans- gression of Chukchi Sea during late Cenozoic time; it may represent the shoreline at the time that the fossili- ferous sediments were deposited. The marine fauna was obtained from black organic clay, pebbly clay, and silty sand, having a total thick- ness of 10—15 feet. The sediments rest upon limestone bedrock containing abundant corals of Mississippian age (Helen Duncan, written communication, 1960), and are overlain by 10 to 15 feet of light olive gray sand- free pebble gravel and sandy pebble gravel and 5 to 10 feet of windblown silt (fig. 157.2). The base of the marine clay lies 17.5 feet above the surface of the Kiva- lina River and probably about 20 feet above sea level; the top lies about 30 feet above the river. Scattered through the basal layers are poorly rounded cobbles and boulders as much as 3 feet across, some consisting of limestone perforated with pholad borings, and others of pebble conglomerate and basalt. The fauna obtained 'from the marine clay is listed in table 157.1. The pebble gravel overlying the fossiliferous marine clay is considerably more extensive than the clay itself; it rests directly on the limestone bedrock along the north bank of the Kivalina River downstream from the creek in which the marine clay is exposed, and it may extend throughout the gently sloping area at the inner edge of the coastal plain north of Kivalina La- goon. Although the gravel is only 10 to 15 feet thick where it overlies the marine clay, it is at least 30 feet thick nearer Kivalina Lagoon. The gravel consists chiefly of pebbles of chert and limestone a quarter of an inch to an inch in diameter; the small pebbles are well rounded, but the large ones are subrounded to subangular. Limestone pebbles in B340 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 164°50’ 164°40’ 164°30’ I V/ W 67°51, O" LOWLAND MANY LAKES LOWLAND M A N Y L A K E S (P Kivalina @ 67°45' I E O z 415 " Kivalina APPROXIMATE MEAN Village C DECLINATION, 1960 N I 67°43’ 1 o 1 2 3‘: MILES lllllllllll l I CONTOUR INTERVAL 50 FEET FIGURE 157.1.—Location of fauna probably of Pliocene age near Kivalina, Alaska. Hachures represent scarps believed to be ancient wave-cut cliffs. The lower scarp was probably formed during the last Pleistocene interglac'ial interval; the upper scarp (between the 50- and 100—foot contours) may have been formed during Pliocene time. Base map adapted from Coast and Geodetic Survey preliminary topographic sheets the gravel are strongly leached. Where the gravel rests Cenozoic fossils have been found in the gravel. The directly on bedrock, the basal layers contain boulders fineness of the gravel, the lack of a sandy matrix in of basalt and limestone one or two feet in diameter, some layers, and the pholad—bored boulders in the basal some of which are riddled with pholad borings. No layers suggest that the gravel is a marine sediment, but GEOLOGY OF ALASKA TABLE 157.1.—-L1,'st of fossils from marine clay near Kivalina, Alaska, and their occurrence at Nome, Alaska, and in Bering and Chukchi Seas 1 ' Third Recent Subma- Beach- Second in Ber- rine Int. Beach mg and Beach Beach Chukchi Seas Pelecypoda: Patinopecten (Fortipecten) hal- lae (Dall) __________________ ? Astarte hemicymata Dall ________ X X Astarte nortonensis MacNeil- _ - _ X X Cardita (Cyclocardia) subcras- sidens MacNeil _____________ X X X X Cardita (Cyclocardia) crebico— stata (Krause) ______________ X X X X Serripes groenlandicus (Brugi- ere) _______________________ ? ______ X X M ya sp. (truncata or japam'ca)- _ X X X Saan'cava arctica (Linné) ________ X X X X Gastropoda: Admete or Buccinum ___________ X X ______ X N eptunea afi'. N. ventricosa (Gmelin) ____________________________________ X Colus aff. C. halibrectus Dall--_ __________________ ? Boreotrophon sp. cf. B. rotun- datus (Dall) __________________________________ ? Polinices pallida Broderip and ’ Sowerby _____________________________________ X Foraminifera: Buccella inusitata Andersen- _ _ _ X ____________ X Elphidiella hannai (Cushman and Grant) _________________ X Elphid’iella nitida Cushman _ _ - - X X Elphidt'um clavatum Cushman_ - _ X X X X Elphidium orbiculare (Brady)__ _ X X Elphidium subarcticum Cushman- X X ...... X Quinqueloculina seminulum (Linne) ______________________________________ X Ostracoda: Clithrocyther'idea sp ___________ ? ____________ ? Haplocytheridea sp ______________________________ ? Cythen'dea? s.l. sp ________________________________ ? Hemicytherura? sp ______________________________ ‘? “Cythereis” s.l. sp ________________________________ ? Gen. afl. Trachyleberis sp _________________________ ? Gen. afl‘. Lozoconcha sp __________________________ ? 1 Fossil occurrences at Nome from MacNeil, Mertie, and Pilsbry (1943) and Hop- kins, MacNeil, and Leopold (in press). Recent occurrences in Bering and Chukchi Seas from those sources and from MacO'mitie (1959), Loeblich and Tappan (1953), and Patsy Smith, table 3 in Scholl and Sainsbury (1960). the relatively poor rounding of the larger pebbles sug- gests a fluvial origin. AGE AND AFFINITIES OF THE FAUNA FROM THE MARINE CLAY The fauna in the marine clay near Kivalina is prob- ably of late Pliocene age but possibly of early Pleisto- cene age. It is closely similar to both the fauna of B341 Submarine Beach (probably late Pliocene) and that of Third Beach-Intermediate Beach (middle Pleistocene) at Nome (table 157.1). The stratigraphic relations, however, suggest a. correlation with Submarine Beach rather than with Third Beach-Intermediate Beach. The fauna is generally similar to Pliocene and Pleisto- cene molluscan faunas from the Gubik formation in northern Alaska described by MacNeil (1957), and quite different from Miocene and Pliocene molluscan and foraminiferal faunas from the N uwok formation of Dall (1919) of northeastern Alaska described by MacNeil (1957) and Todd (1957). One of the (ostra- code species, Clithrocytheridea sp., is present in the Gubik formation, and the others are similar to un- described species in the Gubik formation (I. G. Sohn, written communication, 1960). Representatives of all of the mollusks except Patinopecten (F ortipecten) hallae and Astarte hemicy- mata, and of all of the Foraminifera except Elphz'dz'ella hannai and Elphidiella m'tida, are found in Bering and Chukchi Seas today. Patimpecten (Fortipecten) hallae and Astarte hemicymata are extinct; Elphz’dz’ella hannai and Elphz'dz'ella nitz'da have been reported as living forms only from the North Pacific Ocean. The presence of Fortipecten in the Kivalina fauna con- stitutes strong evidence for regarding that fauna as Pliocene, because in Japan and Sakhalin that subgenus is confined to beds of Pliocene age (Yabe and Hatai, 1940; K. Kobayashi, written communication, 1959). However, Fortipecten could not have reached Kivalina until Bering Strait came into existence, and Hopkins (1959) presents evidence indicating that the first sea- way through Bering Strait opened no earlier than late Pliocene time. A minimum age for the marine clay is established by the stratigraphic relations between the overlying gravel and the windblown silt by which the grave] is itself overlain. Study of air photos suggests that the low- land southeast of the Kivalina River represents an out- wash plain mantled within the area of figure 157.1 by marine sediments of Second Beach (Sangamon) age. This plain terminates to the east against moraines re- sembling those of the Nome River glaciation, of Illi- noian age, at Nome. The gravel overlying the fos- siliferous marine clay lies above the level of the pre- sumed outwash plain and therefore is probably older. The windblown silt overlying the gravel is probably of the same age as the nearby outwash and therefore ‘ largely of Illinoian age. If this reasoning is correct, the marine clay can be no younger than middle Pleistocene. The physical stratigraphy indicates that the marine clay is the correlative of either Submarine Beach or B342 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES SOUTH NORTH 100' EXPLANATION - E i l ‘ l S < S g c 1°31 s_ z 3 g Windblown silt 0: in a w l— ; - 50, a a . . I; .g 2 «95° 3 .9 , x . . » _ v ., , _ _____ f - o E ’vvvmyzz’ Q Gravel F >- ,, A A “ “Melting!" ; .32.“ a: CI Marine pebbly clay '7 Z (.0 5.0 . . . . 9 5.0 19° FEET r,“ as A A‘A 1!). & Limestone I a Cofit Dashed where approxfl mafe/y located FIGURE 157.2.—Sediments exposed in valley of small tributary entering Kivalina River 1.3 miles above Kivalina Lagoon. Sur- face of Kivalina River at left is probably less than 5 feet above sea level. Third Beach-Intermediate Beach at Nome (Hopkins, MacNeil, and Leopold, in press). The fauna is more closely similar to the fauna of Submarine Beach than to that of Third Beach-Intermediate Beach at Nome; and the presence of Fortipecten provides strong evi- dence for a late Pliocene age and for correlation With . Submarine Beach at Nome. REFERENCES Dall, W. H., 1919, Mollusks, Recent and Pleistocene: Report of the Canadian Arctic Expedition, 1913—1918, v. 8, pt. A, Ottawa. Hopkins, D- M., 1959, The Cenozoic history of the Bering land bridge: Science, v. 129, p. 1519—1528. Hopkins, D. M., MacNeil, F. S., and Leopold, E. B., in press, The coastal plain at Nome, Alaska: a late Cenozoic type section for the Bering Strait region: Internat. Geol. Cong, 21st, Copenhagen, 1960. Loeblich, A. R., Jr., and Tappan, Helen, 1953, Studies of Arctic Foraminifera: Smithsonian Pub. 4105, 150 p. 158. MacGinitie, Nettie, 1959, Marine mollusca of Point Barrow, Alaska: US. Natl. Museum Proc., v. 109, p. 59—208. MacNeil, F. S., 1957, Cenozoic megafossils of northern Alaska: US Geol. Survey Prof. Paper 294—0, p. 99—126. MacNeil, F. S., Mertie, J. B., and Pilsbry, H. A., 1943, Marine invertebrate faunas of the buried beaches near Nome, Alaska: Jour. Paleontology, v. 17, p. 69—96. Scholl, D. W., and Sainsbury, C. L., 1960, Marine geology and bathymetry of the nearshore shelf of the Chukchi Sea- Ogotoruk Creek area, northwest Alaska: U.S. Geo]. Survey TIM—606, issued by US. Atomic Energy Comm. Tech. Inf. Service, Oak Ridge, Tenn; also U.S. Geol. Survey open-file report. Todd, Ruth, 1957, Foraminifera from Carter Creek, northeast— ern Alaska: US. Geol. Survey Prof. Paper 294—F, p. 223— 234. Yabe, Hisakatsu, and Hatai, K. M., 1940, A note on Pecten (Fortipecten subg. nov.) takahashii Yokoyama and its bearing on the Neogene deposits of Japan: Tohoku Imp. Univ. Sci. Rept., ser. 2 (Geology), v. 21, p. 147—160. POSSIBLE SIGNIFICANCE OF BROAD MAGNETIC HIGHS OVER BELTS 0F MODERATELY DEFORMED SEDIMENTARY ROCKS IN ALASKA AND CALIFORNIA By ARTHUR GRANTZ and ISIDORE ZIETz, Menlo Park, Calif., and Washington, DC. Regional aeromagnetic surveys over the Cook Inlet and Copper River Lowlands, Alaska, and the northern and central Great Valley, Calif., record broad total in- tensity magnetic highs over the belts of Jurassic and Cretaceous marine sedimentary rocks that underlie these areas. These highs are parallel to the major geo- logic features in each area, and are absent over parallel belts of more severely deformed sedimentary rocks of similar age, which occur in the bordering Chugach Mountains and Alaska Range in Alaska and the Coast Ranges in California. Available magnetic data over the Jurassic slate and greenstone belt in the foothills GEOLOGY OF ALASKA B343 Chugach / ‘ . Mountains Copper River Lowland Foothills of Alaska Range + 4 A ‘ a fi u h 6 Q, . 6‘ i ( ‘4 o‘p‘k ‘0°®:X\§*w 0&4 ”(36" t 93 a“ a“ o .3V 6‘ 6’ Flight elevation 4000 feet «'6 92) (59° 0* $ ‘Kb above sea level i 1 (Approximately 500 to 2000 feet above terrain) COPPER RIVER LOWLAND ANOMALY NORTH SOUTH Seldovia Matanuska Talkeetna (Tectonic elements geanticline geosyncline geanticline after Payne,1955) Southerly regional gradient not removed from the 9mm“ Datum arbitrary, scale applies to all three profiles Pacific Ocean 3000 GAMMAS~ ( Coast Ranges. Sacramento Valley N A r A . o \0'5 93‘ 6 \0 e9 be” ‘ WEST rec EAST Fort l Bragg Eel River 2000-‘ 1 GREAT VALLEY ANOMALY Flight elevation approximately 2000 feet above terrain Structurally complex sedimentary rocks of graywacke Laée Mesozoic and 1000—4 type, slightly metamorphosed in eastern part. enozoic sedimentary_ . Chiefly Franciscan formation roclts of the Great Valley, (Data on outcropplng rocks gen- Ultramafic rocks California eralized from Irwin, 1960) Sacramento Valley A 0. Flight elevation 10,000 feet (4“ above sea level “KOQ 606* Q‘S‘e‘ 5‘0“ {go «‘0‘ 90‘ l 9" i go” 1 10 V 0 10 20 30 MILES l I I i I l l l 9 WEST EAST GREAT VALLEY ANOMALY . n! l Sadie .snetic on" m Res" FIGURE 158.1.—Aeromagnetic profiles across Copper River Lowland, Alaska, and Great Valley and Coast Ranges, Calif. B344 GEOLOGICAL SURVEY RESEARCH l960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Kuskokwim- Susutna Alaska Tanana Lowland Range Lowland L L A Y Y Flight elevation 3000 feet above sea . level at southeast end of profile, NORTHWEST :f‘s'ma Skwentna River increasing to 9000 feet over the Iver Alaska Range and the northwest end of the profile Farewell fault SOUTHEAST Estim . ated regional magnetic gradient Talkeetna Alaska Range Tanana geanticline geosyncline geanticline Datum arbitrary, scale applies to all three profiles —2ooo GAMMAS Chugach Cook Inlet Southern Alaska Mountains Lowland Range JS 4 P fl Y , . Kachemak Kenai lniskin “magmas: :32? fee‘ Bay ‘Lowland Cook Inlet Peninsula (A L r ‘ (Approximately 500 to 2500 feet above terrain) EAST COOK lNLET ANOMALY — 1000 10 0 10 20 30 MILES l l 1 l l I l 1 J Westerly regional gradient not removed from the profile §eldovia i Matanuska geanticline geosynclihe Talkeetna _ 0 geanticline Hinchinbrook Cook Inlet Island Prince William Sound Chugach Mountains Lowland Y A V J j A WEST Anchorage Flight elevation 2200 feet above sea Johnstone Point Eleanor I land - ‘ level at Anchorage, increasing to s Whittler 9500 feet over Whittier and the east end of the profile EAST Knik Arm . anomaly Estimated regional magnetic gradient Slate, graywacke.and greenstone of Cretaceous 4‘ Chugach Mountains , g Seldovia and possibly of Jurassic age ' geosyncline T geanticline FIGURE 158.2.—Aer0maguetic profiles across Cook Inlet Lowland, Chugach Mountains, and Alaska Range, Alaska. 122°30’ 40°00’ 30' 39°00' 30’ 122"OO' GEOLOGY OF ALASKA ) x4 \\ / I \ / \ ‘ I \ \ \ I —WEST \f" > °°\/> LMMT OF‘ GREAT VALLEY \L z’ I . \ 122°30' 38°00’ 37°30' ’ \ \éfifia flgggw\ m I \ \ \ \ \M "L/qt' t22> 40°00’ 30' 121°OO' | I EAST LIMIT OF \ GREAT VALLEY 39°OO' 120° 30’ B345 38°00' 37°30' 10 O 10 CONTOUR INTERVAL 100 GAMMAS 20 MILES Henderson and R W. Bromery, U. 8. Geological Survey FLOWN 10.000 FEET ABOVE SEA LEVEL FLIGHT INTERVAL 3 TO 12 MILES FIGURE 158.3.—Total intensity aeromagnetic map of part of the Great Valley, Calif., relative to arbitrary datum. 557 753 0—60—23 I 120°30’ Aeromagnetic survey 1951—54 by J. R. B346 of the Sierra Nevada, which borders the Great Valley on the east, record so many magnetic features of shal- low origin t'hat it is difficult to determine whether or not broad magnetic highs occur there. Aeromagnetic profiles across the moderately de— 1 formed rocks of the lowland areas and the parallel g belts of more severely deformed sedimentary rocks are ‘1 were deposited. seen more clearly if viewed with respect to the sloping ‘ shown in figures 158.1 and 158.2. The anomalies are regional magnetic gradient. An aeromagnetic map of the northern and central Great Valley is shown in fig— ure 158.3. The magnetic high over the Cook Inlet Lowland trends northeastward for at least 150 miles, is 50 to 75 miles wide, and has a maximum observed amplitude of about 500 gammas. The magnetic high over the south— ern Copper River Lowland trends eastward for at least 60 miles, is 35 to 40 miles wide, and has an amplitude of about 400 gammas. The anomaly over the northern and central Great Valley trends northwest along the valley for at least 180 miles, is about 30 miles wide, and ranges in amplitude from a few hundred to more than 1,000 gammas. A broad positive Bouguer gravity anomaly with about the position and width of the mag- netic anomaly was found in the Great Valley between the latitudes of Sacramento and Sutter Buttes by George A. Thompson and Manik Talwani (oral com- munication, March 1960). The size and gradients of the broad magnetic anoma- lies suggest that they are produced by areally extensive and thick rock masses that are more magnetic than the surrounding rocks. Depth estimates based on these gradients, patterned after the methods described by Vacquier and others (1951), indicate that a magnetic rock mass may lie 5 to 10 miles beneath Cook Inlet and perhaps as much as 10 miles beneath the southern Copper River Lowland. Depth estimates also indicate that the rocks producing the Great Valley anomaly are buried about 5 to 10 miles, but sharper, superim- posed anomalies yield depths that approximate the base of the Mesozoic and Tertiary sedimentary rocks. Be- cause they are magnetic and very large, the rock masses which produce the broad magnetic highs are thought to be igneous. The Cook Inlet and Copper River Lowland anomalies occur over marine sedimentary rocks deposited in the Matanuska geosyncline (Payne, 1955), which at least in places was a narrow depositional trough. This geo— syncline received a thick section of sedimentary rocks of Middle Jurassic to Late Cretaceous age and extended for at least 800 miles from the upper Chitina Valley near the Alaska-Yukon border to a point beyond He- rendeen Bay near the tip of the Alaska Peninsula. The GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Great Valley anomaly occurs over a belt of marine sedi- mentary rocks of Late Jurassic to Late Cretaceous age. The crests of the magnetic highs lie several miles north and a few miles east, respectively, of the thickest part of the Mesozoic sedimentary prisms in the Copper River Lowland and the Great Valley, and are probably on the more stable side of the troughs in which the sediments The late Mesozoic sedimentary rocks in, the Mata- nuska geosyncline'and the Great Valley are character- ized by sandstones that are gradational in lithology be- tween wacke and arenite. They are generally somewhat better sorted than the sandstones in the parallel belts of slate or shale and graywacke in the Chugach Moun- tains and the Alaska Range in Alaska, and in the Fran- ciscan formation in the Coast Ranges of California. The sequences of slate or shale and graywacke are apparently very thick, for, although they are intensely folded and faulted, they are the only rocks that crop out over large tracts of mountainous terrain. Their apparent great thickness, poor sorting, and lenticu- larity, and the presence of interstratified volcanic rocks in some areas, suggest that they were deposited in un- stable or tectonically active deep geosynclinal troughs with steep slopes. The sedimentary rocks of the Mata— nuska geosyncline and the Great Valley are better sorted, probably thinner, and lack interstratified vol— canic rocks except thin beds of volcanic ash. They seem to have been deposited in more stable and shallower geo- synclinal troughs than the sequences with g aywacke. Structural deformation of the sedimentar rocks of the Matanuska geosyncline and the Great Valley is char- acteristically gentle to moderate. In contrast. the par- allel belts with graywacke are severely deformed. The marked difference in structural deformation between the belts of contrasting lithologic aspect indicates that the area of the Matanuska geosyncline and of the Great Valley continued to be tectonically more stable in latest Mesozoic and Cenozoic time than the belts containing slate or shale and graywacke. There may be a casual relationship between the ex— istence of the rocks that produce the broad magnetic highs and the structure and lithology of the sedimen- tary prisms that overlie them. This could be true if the magnetic rock masses are structurally more compe- tent than the rocks under the severely deformed belts, where such broad magnetic highs were not observed. ( Large competent igneous masses beneath the Matanuska geosyncline and the Great Valley could explain the more stable late Mesozoic depositional environment of these areas and their subsequent greater structural stability. The suggested contrasts in structural competence be— 1 GEOLOGY OF ALASKA tween the rocks underlying the moderately and the se- verely deformed belts of sedimentary rocks cannot be considered as established by the data at hand, and must be tested by other geophysical methods. For example, it is possible that large, nonmagnetic, structurally com- petent rock masses underlie the severely deformed belts. Magnetic studies of other areas with analogous struc- tural and stratigraphic conditions are desirable to de- termine whether the association of the magnetic highs with the tectonically more stable sedimentary belts is more than a local coincidence. B347 REFERENCES Irwin, W. P., 1960, Geologic reconnaissance of the northern Coast Ranges and Klamath Mountains, California: Calif. Div. Mines Bull. 179 (in press). Payne, '1‘. G., 1955, Mesozoic and Cenozoic tectonic elements of Alaska: U. S. Geol. Survey Misc. Geol. Inv. Map I—84. Vacquier, Victor, Steenland, N.C., Henderson, R. G., and Zietz, Isidore, 1951, Interpretation of aeromagnetic maps: Geol. Soc. America Mem. 47. Vestine, E. H., and others, 1947, Description of the earth’s main magnetic field and its secular change, 1905—1945: Carnegie Inst. Washington Pub. 578. 159. STRATIGRAPHY AND AGE OF THE MATANUSKA FORMATION, SOUTH-CENTRAL ALASKA By ARTHUR GRANTZ and DAVID L. JONES, Menlo Park, Calif. A thick sequence of dark-gray siltstones and shales and light-colored sandstones and conglomerates, all of marine origin, is well exposed in the narrow Matanuska Valley, which extends westward from the southwest Copper River lowland to the town of Palmer (see inset map, fig. 159.1). Martin and Katz (1912, p. 34—39) measured a section of these rocks and were the first to show that they were of Cretaceous age. Martin (1926, p. 317) stated that these rocks “* * * have a broad ex- tent and attain a great thickness in the Matanuska Valley, but they apparently constitute only a single formation * * *”, and he proposed that they be named the Matanuska formation. Mapping by Grantz in the Nelchina area in 1952—57, followed by a stratigraphic reconnaissance by Grantz and Jones farther west in the Matanuska Valley in 1959, demonstrated that several lithologic units within the formation can be mapped in the Nelchina area, and that at least two units can be distinguished by recon- naissance methods in the structurally 'and stratigraph- ically complex Matanuska Valley. The difference in the number of units that can be distinguished in the two areas arises from the fact that the structure is simpler, and the exposures more complete, in the Nel- china area than in the Matanuska Valley. The units recognized in the Nelchina area are designated in the schematic columnar sections of figure 159.2. Many of these units are limited at the top by unconformities that record deep erosion. The number indicates that the Matanuska formation was deposited in an unstable seaway. 0 In the Nelchina area the Matanuska formation un- conformably overlies beds of Sinemurian to Neocomian age and is succeeded by coal-bearing rocks of Paleocene or early Eocene age, but the contact at the top of the Matanuska has not been observed. In the Matanuska Valley the Matanuska formation probably rests direct- ly on Lower Jurassic rocks in most places, and regional relations indicate that it is unconformably overlain by the Chickaloon formation, of Paleocene or early Eocene age. As it is here more indurated and more deformed than the Chickaloon formation, it was probably in— volved in tectonic events that occurred before the Chick- aloon formation was deposited. Study of the numerous collections of mollusks ob- tained from the formation, and determination of their ages, was begun by Ralph W. Imlay and completed by David L. Jones. These mollusks can be grouped into assemblages of Albian, Cenomanian, Turonian, Cam- panian, and Upper Campanian and Maestrichtian( ?) ages. The critical fossils of these assemblages are listed in table 159.1. Their position in the lithogenetic units is shown in figure 159.2, and the locations of those col- lected in the Matanuska Valley are shown in figure 159.1. Albian fossils occur in hard siltstones with sandstone interbeds along the north front of the Chugach Moun- tains from Palmer to Tazlina Lake, and in distinctly different soft coaly sandstone and abundantly fossil- iferous claystone that crop out in the northern part of the Nelchina area. The difference between these rocks is due in part to structural deformation, which was ac- GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOIflGICAL SCIENCEIS B348 .32 2:3 5 Raw: mowasaamwa :won 5:» 25% -330 “BE? 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GEOLOGY OF ALASKA NORTHERN FRONT OF CHUGACH MOUNTAINS South of Matanuska River near Caribou Creek B349 SOUTHEAST TALKEETNA MOUNTAINS Squaw Creek and Syncline Mountain Between upper Billy \ \Middle Creek \ ”gr—”(ID Creek and the head- waters of Flume Creek Between Sheep Creek and Billy Creek ® near Caribou Creek 1,500 1.000 EXPLANATION - Sedimentary rocks Slltstoneand shale younger or older than the Matanuska formation 500 FIGURE 159.2.—Schematic columnar sections of the Matanuska formation, Nelchina area, Alaska. Sandstone and conglomerate VV vVv Volcanic rocks of Early Jurassic age Structurally hardened or crumpled silt- stone. shale, and sandstone Letters correspond with fossil assemblages listed in table 159.1. Circled letters indicate lithogenetic units from which critical fossils were col- lected. Uncircled letters indicate lithogenetic units correlated on the basis of lithology. tive along the Chugach Mountains but not in the north- ern Nelchina area. This deformation occurred before the overlying Cenomanian to Maestrichtian rocks were deposited. I The structural contrasts in the Albian sedimentary rocks, the rapid coarsening and other changes in the lithology of Cenomanian and Turonian sedimentary rocks in approaching the north front of the Chugach Mountains, and the absence of Bajocian to Valanginian beds in the south part of the Nelchina area suggest that during post-Valanginian Cretaceous time and much of Matanuska time the area of the northern Chugach Mountains was positive and contributed sediment to the Matanuska formation. A more important source of sediment, however, and probably a larger landmass, lay to the north of the Nelchina area. TABLE 159.1.——F088il assemblages and critical fossils found in the Matanuska formation Lithologic um‘t E Upper Campanian and Maestrichtian( '9) Pachydiscus (Neodesmoceras) n. sp. Pachydiscus ootacodensis (Stoliczka) Pachydi‘scus n. Sp. Pseudophyllites indm (Forbes) Baculttes occidentalis Meek Baculites n. sp. Didymoceras hornbycnsc (Whiteaves) Diplomoceras notabtlc Whiteaves Inoceramus subundatus Meek Age and‘ fossils D Campanian Inoccramus schmidti Michael Anapachydtscus sp. Helcirm cf. H. giganteus Schmidt B350 TABLE 159.7.—Fossil assemblages and critical fossils found in the M atwnuska formation—Continued Lithologic um't C Turonian Inocemmus aff. I. corpulentus McLearn Scipcmoceras aff. S. bohemicus (Fritsch) I noceramus woodsi Boehm (=Inoceramus costellatus Woods) Mesopuzosia indopalcifioa (Kossmat) Tetragomtes aff. T. ylabrus (J imbo) Inocemmus alf. I. oum'erii Sowerby Otoscaphites puerculus (Yabe) B Cenomanian Calycocems sp. indeter. Desmoceras (Pseudouhligella) japom'cum Yabe Inocemmus n. sp. alf. I. yabei Nagao and Matsumoto A Albian Brewericeras hulenense (Anderson) Freboldiceras singulare Imlay Beudanticems glabrum (Whiteaves) Lemurocems sp. Age and fossils Because of the northward coarsening in some units, the northward thinning and overlapping of others, and the beach deposits and coal in the basal Albian deposits of the northern Nelchina area, it seems likely that the GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES north edge of the Matanuska seaway was not far be- yond the present northern limit of the Matanuska formation in the Nelchina area. The Matanuska formation underlies a part of the Cook Inlet lowland and much of the southern Copper River lowland. Since the formation is very thick (see fig. 159.2), consists predominantly of dark—gray marine siltstone and shale, and contains abundant mollusks, foraminifers, and radiolaria in many beds, it may be a source of petroleum in the Cook Inlet and Copper River lowlands. In the Nelchina area, however, pre- liminary tests of porosity and permeability based on a few samples collected at the surface suggest that reservoir rocks may not beE abundant even among the beds of sandstone and conglomerate which occur in the formation there at many levels. REFERENCES Capps, S. R., 1940, Geology of the Alaska Railroad region: U.S. Geol. Survey Bull. 907, 201 D Martin, G. 0., 1926, The Mesozoiic stratigraphy of Alaska: US Geol. Survey Bull. 776, 493 pi. Martin, G. 0., and Katz, F. J ., i912, Geology and coal fields of the lower Matanuska Valley, Alaska: U.S. Geol. Survey Bull. 500, 98 p. 5% 160. RADIOCARBON DATES RELATING TO THE GUBIK FORMATION, NORTHERN ALASKA By HENRY W. COULTER, KEITH M. HUSSEY, and JOHN B O’SULLIVAN, Washington, 11C, Iowa State University, Ames, Iowa, and Iowa State University, Ames, Iowa Radiocarbon dates indicate that deposition of the upper member of the Gubik formation near Barrow was initiated prior to 38,000 years BF. and was termi- nated prior to 9,100 years B.P. In the eastern part of the Arctic coastal plain province the Quaternary Gubik formation, consisting of as much as 150 feet of unconsolidated marine and nonmarine gravel, sand, silt, and clay, unconforma’bly overlies the Upper Cre- taceous Colville group (Miller, Payne and Gryc, 1959, p. 106). Near Barrow the upper member of the for— mation comprises 15 to 25 feet of tan, fine—grained sand with cross-bedded gravel lenses and contains an extensive marine fauna. A log (sample W—380) from the base of the upper member of the Gubik formation has been dated at greater than 38,000 years. Although not found in growth position the log showed no evidence of the de- gree of abrasion which would be expected if it had been successively buried, uncovered, and redeposited. Fur- thermore, the unweathered bondition of the wood sug- gests that it did not remain long at the surface prior to burial. Consequently, the log cannot predate the enclosing deposits by more than a relatively short period and deposition of the basal sediments must have begun more than 38,000 years ago. Bedded lacustrine silt, deposited in thaw-lake basins, overlies the upper member of the Gubik formation in many localities near Barrow. Pits dug in the bottom of an artificially drained lake basin 4 miles south of Barrow show two peat-bearing beds in lacustrine silt, one 12 inches and the other one 44 inches below the top of the lake deposits. Radiocarbon age determinations GEOLOGY OF ALASKA on samples from these two beds give dates of 3,540:300 years (W432) and 9,100i260 years (W—847) respec- tively. Therefore, the uppermost beds of the Gubik formation were deposited more than 9,100 years ago. B351 REFERENCE Miller, D. J., Payne, '1‘. G., and Gryc, George, 1959, Geology of possible petroleum provinces in Alaska: U.S. Geol. Sur— vey Bull. 1094, 131 p. 161. METASEDIMENTARY ROCKS IN THE SOUTH-CENTRAL BROOKS RANGE, ALASKA By WILLIAM P. BROSGE, Menlo Park, Calif. Devonian and older metasedimentary rocks and post— Devonian mafic intrusive rocks form most of the south- ern Brooks Range in the John River-Wiseman area (fig. 161.1). The Lisburne group and Kayak shale of Mississippian age and the Kanayut conglomerate, in contact with the underlying sandstone of Late Devonian age, occur only near the crest of the range. The Kan— ayut conglomerate wedges out southward beneath Mis- sissippian rocks. South of the crest a thick unit of black slate and phyllite lies beneath the Upper Dev- onian sandstone and rests with apparent conformity on the Skajit limestone and with apparent unconform- ity on Middle( ?) Devonian and older chloritic to cal- careous schists, chloritic phyllites, black siltstones and limestones. Although the Skajit limestone has been referred to the Silurian (Schrader; Smith and Mertie) , in the type area on the John River it seems related to limestone that is locally interbedded in the basal part of the black slate and phyllite unit and that contains fossils of Middle( ?) Devonian age. Furthermore, fossils of Middle or Late Devonian age were collected by I. L. Tailleur (personal communication, 1955) in the West- ern Brooks Range from limestone which had been mapped as Skajit by Smith and Mertie (1930). The black slate—phyllite unit that overlies the Skajit lime- stone is correlated tentatively with black mica schist that overlies interbedded marble and calcareous schist in a belt south of the outcrop belt of typical Skajit limestone. A previously unmapped thick silty limestone may be the youngest unit beneath the unconformity. The metamorphic grade of the rocks near the crest of the range increases southward, from slate to schist of the greenschist facies. Farther south the metamorphic grade decreases sharply to slate and phyllite in the south front of the range. A belt of Jurassic( ?) and Cretaceous graywacke, conglomerate, shale, chert, and mafic igneous rocks lies south of the range and pinches out eastward. Schist pebbles in the graywackes show pre-middle Cretaceous metamorphism. Granite, granodiorite, and granite gneiss intrude the northern part of the schist belt in the Chandalar Lake area (fig. 161.1). Most of the known metal prospects and zones of silicification lie in the schist belt near the granite and along a line between the granite near Chandalar Lake and an uninvestigated granite on the Alatna River to the west. Lode gold occurs near Chandalar Lake, stibnite and some copper sulfides oc- cur near Wiseman, and small amounts of copper sul- fides are common in breccia beneath the Skajit lime- stone from Wild Lake to the John River. In addition, copper sulfides occur on the West Fork of Chandalar River in mafic igneous bodies in the Mesozoic rocks. Analyses of stream sediments show a slight concentration of copper around the mafic intru- sive rocks at Mount Doonerak and Boreal Mountain, and a marked concentration of zinc at Cladonia Creek. Cymrite was identified by X-ray diffraction analysis in samples collected from a pyritized zone near the head of Bonanza Creek in the Wiseman quadrangle. This is the first known United States occurrence of that rare barium silicate mineral. REFERENCES Schrader, F. 0., 1902, A reconnaissance in Northern Alaska: U.S. Geol. Survey Prof. Paper 20, 139 p. Smith, P. 8., and Mertie, J. B., Jr., 1930, Geology and mineral resources of northwestern Alaska: U.S. Geol. Survey Bull. 815, 351 p. B352 154 '00! 152°‘oo' 150°00' 148°00’ —70°oo' ll l —.’ 7—; - ~ " ll ;’/’\\ ‘- (‘7 = ”’5’" ‘ W; W” ‘*‘ .‘t; l , I / ’71.)?” I § \\ A \ A J'n 1174‘.» x '4 Q \\\ EXPLANATION SEDIMENTARY AND METASEDIMENTARY ROCKS INTRUSIVE ROCKS .- (I) t, D ‘. mzu __ << 2 Graywacke, conglomerate. g l- - - 0 shale, and chert a E Maflc Igneous rocks 5 U D I'_ UNCONFORM/TY \I/./_\ - 8 752: NE 30 was 5.835 >3 6:83 ESEEflE firs £on 3522, .895 838 2.323 5th ZOC. 100 SEA LEVEL A A‘ 300 METERS SEA LEVEL< SEA LEVEL 0 V2 lKlLOMETER # FIGURE 166.1.—Geologic map and sections of part of the Rio Descalabrado quadrangle, and 66°27’30”, and lat. 18°01’14” and 18°04’18”. EXPLANATION‘ Position of boxes only generally indicative of stratigraphic position Conglomerate, tuffaceous, thickAbedded ‘ n. Tuff breocia and tuft, mmive m l Sandstone and siltstone, tuffaceous, thin-bedded E Limmtone, Tl, at several levels Contains fmqments ofcalcareous algae TERTIARY Sandstone and siltswne, tuffaceous, thin-bedded Includes several thin beds oflimestoner which generally contain fragments of ralcarem algae l _ l mu l Limawne, at several levels Ymmgesl szust below Eocene or Cretacwu sandstone and tantalns oysters and rudistx, others are poorly fossiliferm [77 Tuff breccia and tuff, mmive WW —_l Sandstone and siltstone, tuffaweousv CRETACEOUS L thin-bedded /\ Contact W H D Fault u, upthrown side; D, downthrown side; arrows Show direction of horizontal movement (v5 Thrust fault l Saw teeth In: upper plate T A A l l Fault 0n yeologic sections only. T, xide mmmi toward observer; A. side moved away from observer; arrnw indtcates relative direction of dtpaslip movement Fault breocia (—$-\ Anticline Showing dim-mm nfplmloe —*— Syncline I Strike and dip of beds ,5 Strike and dip of beds Strike uncertain X Strike of vertical bedding $ Horizontal beds 41 75 Overturned beds Puerto Rico, between long. 66°25’04" GEOLOGY OF HAWAII, PUERTO RICO, PACIFIC ISLANDS, AND ANTARCTICA by gravity sliding in that direction. The transcurrent faults indicate compression in a N. 80° E. direction later than the thrusting. Both events occurred after the middle Eocene and before the middle Oligocene. ’X B365 REFERENCE Pessagno, E. A., Jr., 1959, Preliminary note on the geology of the Ponce-Coamo area, Puerto Rico [abs] : Caribbean Geol. Conf, 2d Mayaguez, P. R. Program, p. 25. 167. COMPRESSIONAL GRABEN AND HORST STRUCTURES IN EAST-CENTRAL PUERTO RICO By R. P. BRIGGS and M. H. PEASE, J R., San Juan, PR. Work done in cooperation with the Department of Industrial Research, Puerto Rico Economic Development Administration Grabens and horsts showing apparent stratigraphic displacements of as much as 2,000 meters are common features of the structural pattern in east-central Puerto Rico (fig. 167.1). Of these structures, only those in which stratigraphic displacement is large and in which the ratio of the width of the block to the apparent stratigraphic offset on either side approaches unity are discussed. In the area studied two types of such grabens occur. The first is shown by graben G—1 and graben G—Q and its faulted extension G—QA (fig. 167.1). Southern boundary faults in this type of graben have greater apparent stratigraphic displacement than their north- ern boundary faults, and the boundary faults are verti- cal or dip away from the graben. The second type is shown by grabens G—3 and G—4 which are considered as highly deformed slivers or slices in the large fault zone that is east-central Puerto Rico. Three types of horsts are present in this area. Horst H—l is bounded on the north and south by faults that decrease in displacement eastward; the apparent strati- graphic displacement is greatest on its southern bound- ary fault. Horst H—2 is a block that seems to have been squeezed upward between two major faults, and the apparent displacement on its northern boundary fault is greater than on its southern boundary fault. Horst H—3 is a block tilted up to the northwest be- tween a transcurrent fault that strikes northwest. and a dip-slip fault striking generally north. The fault system in which these features occur is dominated by transcurrent faults trending west to west-northwest, some of which have important dip-slip components, and by faults that trend northwest in which the dip—slip component of movement was local- ly greater than the strike-slip component. Left-lateral drag is evident at a number of places, but is best shown south of horst H—1 and north of graben G—l (fig. 167.1), where the beds have been warped by movement along the fault zone in which H—1 and G—l occur. Left-lateral displacement along this fault zone is at least 4 kilometers and may be as much as 15 kilometers in aggregate. \Varping of beds northeast of horst H—3 also indicates possible left-lateral drag, despite the ap— parent right-lateral displacement of the rocks. This inconsistency is best explained by assuming a dip-slip component of movement considerably exceeding the strike-slip component along the northwest trending fault on the northeast side of H—3. Strong support for this assumption in relation to this fault is found along another fault that has a similar trend but along which the exposures are considerably better; this is the high-angle reverse fault that strikes northwest from Barranquitas and then curves westward parallel to the southern boundary fault of graben G—l. On the north— west-trending part of this fault, dip-slip displacement is dominant; no evidence of important strike-slip dis- placement was seen. However, along the west-trending section of the same fault, left-lateral transcurrent movement is apparently. dominant over dip-slip movement. Apparent right-lateral stratigraphic displacement is shown along a number of faults in figure 167.1, but evidences of right-lateral drag are lacking. Whether these occurrences represent real right-lateral movement or whether these relationships are principally due to dip—slip displacement is as yet not clear. Nevertheless, it is certain that regional compression, most likely re— sulting from opposing forces from the southwest and northeast, was the prime mover in forming the struc- tural pattern in east—central Puerto Rico, and that the grabens and horsts were results of this compression. 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X m .Om,u mm 60.000 \omooo ‘Ooonm , ,fl fl \ 24 V N m m N m «a D , 7 .v 7 , . a i 00 ma 11.“l|.|s \\\\ {R A, \\ , ‘ «v a,» / NA.‘\.{ ‘\ A 00 wH A o z 7 a .H Oh i a Q A _ a f .3535 0% m m l— 1:_ _ D m 0 04/ .\l 39.35550 2% , Mfr , ‘ a , KC}; < m P z m ofl , :3sz “.31? a 4, % .fl _o?w72!\1|1]|TIJ ! 1\\\‘\\\1 ‘ 1 \1J ,,,,,,,, x 5. NE...» E. 5: \o Rio 6 > 5. <4EDSS< 11‘ \\ ‘ bmom: .om.mw .Ooonm ZVHDO DNEZV‘NRV THE GEOLOGICAL SCIENCES GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN B370 .m 3958 ac 5:3 38 cow was $8 $3 oobhm “5383 a Son.“— mw «Baum 529 ofliswn gafimnfig Egon/w .m mas—mm «a 5.5: ”33 con can Him? 33 oowdw Swnficasw 3:25p 23 Bob 3 m 295% Euhwad .w 392nm we 55% Hoom CONN 65w an? 33 @841: x“ 3.53m Ego 3:55: cesfimsnna umoEFSuwnw 35 we E532 25.. .5523 “on can :3 3w? US$559 2: 59¢ onSwm 53o Banana .550 canard 3.: 63.85 we 55% so; 95 E @3953 230 Sufism: wosfisadas and 353$; Ho $8553 “3335 ANS :wawlddwfi ”553% _ONowH :Om‘NNowH :oPNmawo .mm.®® mi: 11111] H «x. 0 mm mm. 2 012x \ _ _ C i 1 T14 4 . 4 4 F N H m. o \ r \ x x ‘ ufififiom mcwcrfimoo‘ mw_@Emm‘uw‘N>_a=a:oZ / _ o 1 ‘ ‘ ‘ 1 w ‘ $33 § MSQSS. fig Egmwgo quESZ V\ 335% wank—«5‘ l /\\ V 4 \ Z O _._.< 2 <1. n. Xm A \\ § § // / / u/ £2882 :OmuNm owe GEOLOGY OF HAWAII, PUERTO RICO, PACIFIC ISLANDS, AND ANTARCTICA TABLE 169.1.—0hemical analyses of bauwitic clays1 from the Florida and Utuado quadrangles, Puerto Rico [Analysts, Paul L. D. Elmore, Samuel D. Botts, and Marvin D. Mack. Samples were analyzed by rapid rock analysis methods similar to those described by Sha- piro and Brannock (1956)] Locality and PR—FAH sample number 7 1 2 3 4 5 6 7 8 1304 1318—0 1305 1361 1336 1353 1357 1339 8101 ___________________ 18.7 22. 5 23.0 29. 7 29. 0 26. 3 30. 2 36. 9 A1203 __________________ 40. 7 38. 2 36.0 32. 6 32. 5 31. 6 27. 2 23. 2 Total iron 3 as F6103... 18. 3 17. 4 16. 4 14. 4 18. 2 16.0 15.0 10. 8 1.6 1.6 1.3 1.4 1.8 1.4 1.0 .22 .62 .64 .24 .72 1.0 2.1 .43 .45 .60 .48 .70 1.4 1.8 .22 .24 .27 .20 .40 .42 .37 .06 .06 .08 .07 .07 .09 .32 .66 2.5 .81 1.0 2.4 2.3 .68 .18 <.05 .30 .06 .12 .14 .18 .06 .12 .04 .32 .46 .31 .37 15. 8 15.5 14.4 14. 7 13. 8 14. 2 13. 4 2.0 1.7 2.7 1.5 2.7 3.0 3.9 99 98 98 100 97 97 95 1 Bauxitic clay, as used in this paper is not meant to imply that a major contribution of SiOz and A120; to the analyses is attributable to kaolinite, halloysite, and feldspar. The mineralogical examinations show that most of the $102 content is contributed by megaseopically visible quartz grains and that nearly all of the A1203 content is contributed by boehmite. X-ray powder diffraction patterns of bulk samples from which the quartz grains have been removed by hand picking show that only traces of quartz occur in the fine-grained boehmitic matrix. 9 At edge of karst area. 3 Samples contained organic matter which precluded accurate determinations of FeO. The locations of these samples are shown in figure 169.2. 1. Florida quadrangle. Tan clay overlying weathered volcanic rocks in roadcut. 2. Florida quadrangle. cut in sinkhole. 3. Florida quadrangle. Tan surface soil sample from plowed field in bottom of large, deep sinkhole. 4. Florida quadrangle. Tan surface soil sample from creek bank in large, circular sinkhole. 5. Florida quadrangle. Tan clay from base of shallow roadcut in sad- dle between sinkholes. 6. Florida quadrangle. Tan surface soil sample from bottom of deep. oval-shaped sinkhole. 7. Florida quadrangle. Tan surface soil sample from bottom of large, deep sinkhole. 8. Utuado quadrangle. Tan clay from 3 feet beneath surface in road- Tan clay from base of roadcut. from the Pedernales—El Fondo de Milla trail area of the Dominican Republic (Goldich and Bergquist, 1947, p. 72). Quartz, anatase, and kaolinite were found in nearly all of the 42 samples. Kaolinite and halloysite were found in 37 samples. Seven samples collected from the Quaternary deposits north of the Florida area contain kaolinite as the dominant constituent. Six samples B371 containing halloysite and 24 containing moderate amounts of kaolinite came from within the bauxitic clay belt. Four samples consisting almost wholly of oligoclase or sanidine came from the south edge of the karst area near the contact of the Tertiary and Cretace- ous rocks. Small quantities of feldspars were found in about 13 samples from the belt, but no significant cor- relation could be made between their abundance and distribution in relation to the contact of the Cretaceous and Tertiary rocks. The age and origin of the bauxitic clay deposits are uncertain. This investigation indicates that the baux- itic clay is a clastic fine-grained rock in which feld- spars are widely distributed. It also shows that the clay is widely distributed in the southern part of the karst area as far north as the town of Florida. Water- well data in the Florida area (McGuinness, 1946) show that the clays overlie at least 350 feet of limestone. These observations suggest that the parent rock was not a limestone but a volcanic rock. According to Zans (in press) bauxite deposits in Jamaica developed (and may still be forming) in a mature karst area by baux- itization of an andesitic volcanic detritus carried into cavernous limestones when the basement rocks of the karst area are laid bare in upland areas. Zans believes that bauxitization of the volcanic detritus was aided by alkaline solutions from the limestone environment. The Puerto Rico deposits may have developed similarly or the bauxitic clay may have been transported into the karst from bauxitized andesitic rocks on highland surfaces to the south. The writer does not have suffi- cient evidence to determine if bauxitization processes are currently taking place in Puerto Rico. REFERENCES Goldich, 'S. S., and Bergquist, H. R., 1947, Aluminous lateritic soil of the Sierra de Bahoruco area, Dominican Republic, W. 1.: US. Geol. Survey Bull. 953—0, p. 53—84. McGuinness, C. L., 1946, Records of wells in Puerto Rico: San Juan, Puerto Rico Aqueduct and Sewer Service, 267 p. Shapiro, Leonard, and Brannock, W. W., 1956, Rapid analysis of silicate rocks: U.'S. Geol. Survey Bull. 1036—0, p. 19—56. Zans, V. A., in press The origin of the bauxite deposits of Jamaica: Internat. Geol. Cong, 20th, Mexico City 1956 (in press). Zapp, A. D., Bergquist, H. R., and Thomas, G. R., 1948, Tertiary geology of the coastal plains of Puerto Rico: U.S. Geol. Survey Oil and Gas Inv. Prelim. Map 85. '2 B372 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 170. THE STRATIGRAPHY OF ISHIGAKI-SHIMA, RYEKYB-RETTO By HELEN L. FOSTER, Washington, DC. (Work done in coopcration, with Ofiicc, Chief of Engineers) Ishigaki-shima is one of the southernmost islands of the Ryfikyi‘i-retto, an arcuate chain of islands which ex— tends from southern Japan southwestward nearly to Taiwan. It lies about 275 miles southwest of Okinawa- jima and 150 miles east of Taiwan. It has an area of 86 square miles, and the highest summit on it is a little more than 1,700 feet above sea level. Most of the northern part of the island is mountainous and bordered by narrow marine terraces. The southern part consists largely of gently sloping marine terraces in various stages of dissection, but. also is partly moun- tainous and hilly. The foundation of Ishigaki-shima consists of low- grade metamorphic rocks, probably of Paleozoic age, which include green schist, glaucophane schist, phyllite, quartz-mica schist, chert, sandstone, and a little marble. These rocks have been folded, faulted, uplifted, and eroded. They have also been intruded by granitic, granodioritic, and dioritic rocks, probably of late Mesozoic or Tertiary age, which occupy an area of about 10 square miles. Granular intrusive rocks such as these are not known to occur elsewhere in the south— ern part of the Ryukyfi-retto, though intrusive rhyo— lite porphyry, andesite porphyry, and hypersthene andesite occur on Okinawa-jima. Upper Eocene (Tertiary b) limestone, sandstone, and conglomerate unconformably overlie the meta- morphic rocks in scattered small patches totaling 1.5 square miles in area at elevations ranging from sea level to about 300 feet. These rocks are tilted and faulted, but not folded. Their age was determined from larger F oraminifera, and from calcareous algae which are exceptionally well preserved. A major period of Tertiary submarine volcanic activity followed the deposition of the Eocene sedi- ments, or possibly began before its close. The volcanic rocks——interbedded tuff, breccia, and lava—are chiefly andesitic, but partly dacitic and rhyolitic. They are at least 600 feet and probably more than 1,000 feet thick, and underlie an area of about 9 square miles. Later Tertiary deposits have not been identified; most of the island’s area was probably land throughout late Tertiary time. The earliest Pleistocene deposit is a fossiliferous gray marine clay containing abundant larger and smaller Foraminifera, ostracodes, and mollusks, some corals, bryozoans, and pollen, and deer bones in one area. The clay is overlain in places by gravel deposits from a few feet to more than 70 feet thick. The youngest Pleistocene deposit is the Ryfikyfi limestone, a raised reef limestone, which constitutes much of the southern part of the island and forms a discontinuous fringe along the coast on other parts of the island. Recent deposits include sand and gravel on raised beaches, sand dunes, stream alluvium, and sand and gravel on the present beaches. Bones of pigs were found in a Recent terrace deposit. 171. FOSSIL MAMMALS FROM ISHIGAKI-SHIMA, RYUKYU-RETTO By FRANK C. WHITMORE, J R., Washington, DC. A field party under the direction of Helen L. Foster has collected two suites of fossil mammal remains in the course of mapping the island of Ishigaki in the Ryukyu-retto, about 150 miles east of Taiwan. The Ryfikyfis comprise an island arc extending from Taiwan on the south to Kyushu, the southernmost of the Japa- nese islands, on the north. The rocks exposed on the islands record a complex history of tectonic changes in GEOLOGY OF HAWAII, PUERTO RICO, PACIFIC ISLANDS, AND ANTARCTICA land levels during Tertiary and Quaternary time, ac- companied in the Quaternary by eustatic changes in sea level. It is certain that the islands have been connected at one time or another and that land bridges at times connected the arc with the Asiatic mainland by way of Japan and Taiwan. The exact times when these con- nections existed are still, however, a matter of specula- tion. Study of fossil mammals from the island may help solve this paleogeographic problem. The older suite of fossil mammals consists mainly of Metacervulus astylodon (Matsumoto), a small extinct deer related to the Muntjac now living in Southeast Asia; there is also a box turtle (cf. Geoemyda) similar to but larger than those now living in the Ryukyfis, and a few small bones, as yet undetermined, which probably represent rodents. These bones are found in a gray marine clay below gravel. The age of both the clay and gravel is in doubt; the clay also contains inverte- brates which seem to indicate a Pleistocene age. Metacervulus has also been found on Okinawa and neighboring islets, where it. is abundant, and on Miya- ko-jima, an island about 60 miles east of Ishigaki- shima. These finds differ from those of Ishigaki-shima in that the bones are found in fissure deposits rather than in clay beds. The Ishigaki bones therefore seem to be stratigraphically more significant than those found on the other islands. Metaoem‘ulus wstylodon occurs in the middle Pliocene of North China. In the Ryukyfis it is younger: probably Pleistocene, although possibly late Pliocene. The presence of these deer in- dicates a probable emergence of this area during the Pliocene so that mammals could have migrated through the southern Ryfikyfis. The three islands where Met- acervulus is found are all south of the lVatase Line or Tokara Strait, a deep channel between Yaku-shima and Amami-o-shima which divides the Ryfikyfi-retto into north and south halves. The absence of this deer in fossil fauna of islands north of Tokara Strait and of the Japanese islands implies that this strait existed during the Pleistocene and possibly in the late Pliocene, and that mammalian migration was from South China via Taiwan. The younger of the two fossil suites consists entirely of bones of a pig, probably related to the Recent variety Sus Zeucomystaac Mulciuanus Kuroda. The bones, which are unmineralized, have been C 14 dated by Meyer Rubin of the US. Geological Survey at 8,500i500 years. Because of the presence of inorganic carbonates in fossil bone, dates based on such material are prob- ably inaccurate, and the actual age is almost certainly greater than the result of the C 1“ determination. The pig bones occur as a densely packed bone breccia, ce- B373 mented by travertine, in terrace deposits laid down in a nip, 0r undercut shelter, which resulted from erosion of a limestone cliff at sea level. A peculiar feature of this collection is that almost all of the bones are of young individuals. Several explanations of this high proportion of young individuals are possible. One is that they were domestic stock, selectively killed by man. No artifacts have been found associated with the bones, however, although some chert flakes which occur in the deposit may have resulted from the sharpening of stone implements. No tool marks are found on the bones, and they have been so broken during burial that it is impossible to tell whether long bones were split as they would be to obtain marrow. Some of the bones are blackened by a carbonaceous residue, which may have resulted from cooking or from slow oxidation through time. Further study of Recent and extinct pig species may indicate whether these pigs were introduced by man or migrated in the wild state. If they are shown to have been domesticated, it would be one of the earliest examples of pig domestication known. The subfossil pig is intermediate in size between species of Sue found on the Asiatic mainland and that living on Ishigaki today. This is in keeping with the general rule that island species of mammals tend to be smaller than their mainland ancestors. Detailed morphological studies, such as consideration of the accessory conules of the molar teeth, may aid in estab- lishing the mainland relatives of the Ishigaki pigs and also, perhaps, in establishing the length of time during which the island form was isolated. It is perhaps significant that the modern wild pigs of the Ryfikyus are only found south of the Tokara Strait. This may mean that their ancestors either migrated or were in- troduced from the south. Hanzawa (1935) has discussed the distribution in the Ryflkyfis of Trimeresums, a viper locally known as the habu. This snake is not present on all islands of the group; it is Hanzawa’s opinion (1935, p. 56—59) that the snakes migrated from Taiwan in post-Shima- jiri (probably Pliocene) time over a‘land bridge. Sub- sequent. rise in sea level, according to Hanzawa, divid— ed the area into several large islands on each one of which a. distinct species of Tm'meresmms developed. Islands which do not have the habu were submerged at that, time. This stage was succeeded by a period of submergence with limestone deposition. Then, in post- N aha (Pleistocene) time, an extensive deposition of elastic materials took place which again probably indi- cates an extensive land surface in the area of the archi- pelago. It is possible that the pigs could have reached B3174 the area at this time; migration at an earlier date does not seem reasonable because the Ishigaki subfossil pigs seem to differ only in minor characteristics from those of the Asiatic mainland. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCE Hanzawa, S., 1935, Topography and geology of the Riukiu Islands: Tokoku Imp. Univ., Sci. Repts, 2nd ser. (Geol- ogy), v. 18, p. 56—59. 172. DISTRIBUTION OF MOLLUSCAN FAUNAS IN THE PACIFIC ISLANDS DURING THE CENOZOIC By HARRY S. LADD, Washington, D.C. Studies of large collections of fossil mollusks from outcrops and drill holes in six island groups in the western Pacific suggest that the faunas were more abundant and diversified during parts of Tertiary time than they are in the same areas today. As shown in figure 172.1, the islands form a broad belt spreading nearly 4,000 miles across the tropical latitudes of the western Pacific from Palau and the Marianas on the northwest to Fiji and the New Hebrides 0n the southeast. Most of the collections on which the study is based were obtained in the field by Geological Survey personnel; others have been loaned for study by museums. Four of the island groups—Palau, the Marianas, Fiji, and the New Hebrides—lie southwest of the andesite line in an area characterized by eleva- tion in late Cenozoic time. The other two groups—the Marshall and Ellice Islands—lie to the northeast of the line in the Pacific Basin proper, an area characterized by deep subsidence. Collections from the elevated island groups are from outcrops; those from the sub- merged areas are from drill holes. Fossil mollusks and other organisms that are found above the sea to the west occur below the sea to the east. Detailed studies of the molluscan faunas will not be completed for some time, but. the work done thus far supports the hypothesis that many elements of the “Indo-Pacific fauna,” generally believed to have spread from Indonesia, may have originated among the islands in the Pacific Basin in Cretaceous and Tertiary times. During these times there were more island “stepping stones” than now, many of them being located in the broad island-free area that now separates the Mar- shalls from Hawaii (Hamilton, 1956). Mollusks and other shallow water forms could have migrated from the islands toward Indonesia with the aid of favorable waves and currents such as those prevailing today (Ladd, 1960). Most of the sediments from which fossil mollusks have been obtained represent deposits in shallow waters. Many of the limestones are reef ‘limestones or clearly represent sediments that accumulated in lagoons not far removed from reefs (Emery and others, 1954; Ladd and Schlanger, 1960). A few mollusk-bearing limestones and some of the marls appear to represent off-reef de- posits in somewhat deeper waters, but no deposits sug- gesting abyssal depths have been recognized. The oldest mollusks found to date are Eocene but they are few in number and poorly preserved. Miocene mollusks are abundant and varied. Lagoonal sedi- ments obtained from drill holes appear to be far richer in mollusks than any sediments dredged from existing lagoons in the same area. Younger mollusk faunas, presumably Pleistocene, contain mostly still-living species but they include a number that now have a more restricted distribution. REFERENCES Emery, K. 0., Tracey, J. 1., Jr., and Ladd, H. S., 1954, Geology of Bikini and nearby atolls: U.S. Geol. Survey Prof. Paper 260, pt. 1, chap. A, 265 p. Hamilton, E. L., 1956, Sunken islands of the Mid-Pacific Moun- tains: Geol. Soc. America Mem. 64, 97 p. Ladd, H. S., 1960, Origin of the Pacific island molluscan fauna: Am. Jour. Sci, v. 258—A, p. 137—150. Ladd, H. S., and Schlanger, S. 0., 1960, Drilling operations on Eniwetok Atoll: U.S. Geol. Survey Prof. Paper 260—Y. (In press.) GEOLOGY OF HAWAII, PUERTO RICO, PACIFIC ISLANDS, AND ANTARCTICA B375 “‘51an GREENMCH FIGURE 172.1.—Location of island area from which fossil mollusks have been Obtained. Dashed line marks structural boundary of Pacific Basin (andesite line). 6% B376 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 173. GEOLOGY 0F TAYLOR GLACIER-TAYLOR DRY VALLEY REGION, SOUTH VICTORIA LAND, ANTARCTICA By WAEREN HAMILTON and PHILIP T. HAYES, Denver, Colo. Work: done in cooperation with National Science Foundation During the southern summer 1958—9, the U.S. Geo- logical Survey began field work west of McMurdo Sound, Antarctica, as part of the U.S. Antractic Re- search Program administered by the National Science Foundation. Field camps were established by U.S. Navy aircraft on the upper Taylor Glacier, at Bonney Lake and at Suess Glacier in Taylor Dry Valley, and in a previously unvisited dry valley north of lower Taylor Glacier. Geology was studied in a. strip 50 miles long, extending most of the way through the mountains from McMurdo Sound to the interior ice plateau. The coastal metamorphic belt, here 15 miles wide, consists of metasedimentary rocks, among which meta— pelitic rocks and calc-silicate schists and gneisses of probable late Precambrian and Early Cambrian age are dominant. The metasediments strike subparallel t0 the coast; they vary in dip but are nearly vertical near the batholith which intruded them from the west (fig. 173.1). The batholith is a composite mass of plutons of quartz diorite, granodiorite, quartz monzonite, and granite, varying to diorite, monzonite, and quartz syenite. Accessory minerals are hornblende or biotite or both and, in one mass of quartz diorite and diorite, minor augite is present. There is no orthopyro- xene, such as is widespread in some parts of East Antarctica. Some of the plutons are separated by septa of para-amphibolite and calc-silicate gneisses. Dikes of mafic, lamprophyric hornblende diorites and quartz latites out these basement rocks, and are particu- larly abundant near the contact between the metasedi- ments and the batholith. Prior to the deposition of the overlying Beacon sandstone (named by Ferrar, 1907, p. 39), the diked basement complex was intri— cately broken by minor faults (fig. 173.1). The Beacon sandstone, known from other areas to have a stratigraphic range from Devonian to Permian, was deposited upon an essentially horizontal erosion surface on the basement rocks. The Beacon consists of coarse-grained, crossbedded sandstone, mostly quartz- rich but partly arkosic, and lesser amounts of siltstone peble conglomerate, and, high in the section, thin beds of coal (fig. 173.2). Its thickness is only about 3,000 feet, exclusive of diabase sills. At. least four great sills of quartz diabase, each 500 to 1,300 feet thick, were intruded within the Beacon sand- stone (fig. 173.2). Another such sill lies at or near the contact between Beacon and basement, and another, probably continuous for scores of miles, follows exfolia- tion joints in the basement related to and 500 to 1,500 feet below the pre-Beacon erosion surface. The dia- bases are strongly differentiated, and contain abundant mafic and silicic granophyre and gabbro-pegmatite in their upper portions. Differentiation has been docu- mented by 19 chemical analyses, which show the normal diabase to have 55 percent SiOz. The quartz of most of the Beacon sandstone was recrystallized, and the coal was baked, by heat released from the sills. Several normal faults trend parallel to the coast and offset the Beacon sandstone and the diabases about 1,000 feet, but the gross structure of the mountain sys- tem is anticlinal. There is no “Great. Antarctic horst” here, although such a structure has long been assumed to be present. Past glaciers filled the valleys 1,000 to 1,500 feet above present ice surfaces, but. there has been very little change—possibly slight local advances of the ice—since the region was first Visited in the early 1900’s by British expeditions. Numerous small cinder cones and lava flows of mafic, alkaline basalts (SiO2 42 to 48 percent by weight, NaZO 3.7 to 4.7 percent, K20 1.5 to 1.8 percent, in four analyses) were erupted within Taylor Valley before, between, and since past episodes of glaciation. REFERENCE Ferrar, H. T., 1907, Report on the field-geology of the region explored during the “Discovery" Antarctic Expedition, 1901—4: Natl. Antarctic Exped. Natural History, v. 1, pt. 1, p. 1—100. GEOLOGY OF HAWAII, PUERTO RICO, PACIFIC ISLANDS, AND ANTARCTICA B377 FIGURE 173.1.—~Contact between metamorphic and granitic rocks. Cale-silicate hornfels, gneiss, and schist (left) are mostly light colored. Darker, gneissie border zone of batholith. (right) consists of quartz monzonibe—quartz diorite mig‘matite. Crosscutting dikes, mostly hornblende dioribe, are oflset along minor faults. Looking south across Taylor Dry Valley to north side of Kukri Hills. US. Navy photograph. 557‘7‘53 0—60—25 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES B378 no dag 95 3 mean cm 3 63:5 06.3252 and .aniv 59$ 05 3 0.583 05 no go “in“ m_ "53.29 on; SE85 25. #3926 ~2th .893 «o and: 05 and. 45.8: 25 Sam 69.5? ma 55582 uewfih 9.25m 83 amigos—Q 25.. .33 coofi EH3: mm fine as no .590: 95.. .309? 8‘3qu one 5953 wusmwndm 25 gig 38 no @853 £885 Q5 3 $3 emu“ Em “3.538 a 8883 32% 35—95 25. .9556de gm 5 335:. 5.:25 mo flgnmifiafi mania GEOLOGY OF HAWAII, PUERTO RICO, PACIFIC ISLANDS, AND ANTARCTICA B379 174. NEW INTERPRETATION OF ANTARCFIC TECTONICS By WARREN HAMILTON, Denver, Colo. Work done in cooperation. with National Science Foundation A continuous chain of high mountains, 2,500 miles long, crosses Antarctica near the South Pole and borders the Ross and Weddell Seas. It extends from south of New Zealand to south of West Africa. These mountains have long been assumed to be a great horst of rocks of an ancient Precambrian shield, but incom— plete data suggest that they lie instead along a belt of crystalline rocks metamorphosed and intruded by bath- oliths during Cambrian time.1 The mountain chain is composed of varied crystalline rocks overlain unconformably by thin, slightly de- formed sandstones, the stratigraphic range of which is Devonian to Permian, and by huge sills of diabase. The concept that the mountains form a “Great Ant- arctic horst” was based upon extrapolation from the inferred horst structure of the imposing Royal Society Range, which accounts for one-quarter of the width of the mountain system in the McMurdo Sound region. West of that range, the sandstones dip gently west- ward, beneath the interior ice plateau, broken only by relatively minor faults. At least at Granite Harbour, on the east side of the mountains north of the Royal Society Range, structures dip gently eastward toward the Ross Sea. The broad structure of the mountain system in the McMurdo Sound region is domical and similar structure probably characterizes the mountain system at least from Granite Harbour to the Beardmore Glacier. Analogy with other continents indicates that a vast mountain system such as this is far morexlikely to lie along an orogen than to be a crosscutting uplift. That this is indeed the case for the Antarctic ranges is strongly‘ suggested by the petrologic and structural continuity of the province at least from the Horlick Mountains to Terra Nova Bay, a distance of 1,100 miles. The dominant rocks of this part of the chain belong to a composite batholith of plutons of various types of granitic rocks, the characteristic type being coarse- grained pink quartz monzonite ranging to granite. The batholith is intrusive into nonvolcanic metasedimen- tary rocks of various types, among which metashales and Gale-silicate rocks are particularly widespread. In 1The following discussion is based upon published references too numerous to acknowledge in this note, upon unpublished information given by Jon Stephenson, W. E. Long, and others. and upon my field studies in the McMurdo Sound region and my petrographic studies of Antarctic and Australian granites, the McMurdo Sound region, the metasedimentary rocks occur chiefly in a belt along the coast—that is, gross structures are subparallel to the mountain system. Many granodiorites, quartz monzonites, and granites known from this Antarctic batholith are characterized by lightly colored potassic feldspar which is in well- shaped crystals but is not generally phenoerystic. Plagioclase is only obscurely zoned. As most other batholiths contain potassic feldspar that is more com- monly white than colored and more commonly anhedral than not, and as plagioclase in most other batholiths is commonly zoned, these granitic rocks are distinctive. A striking feature of composite batholiths is that rock types within them repeat over distances of hundreds or even thousands of miles; the petrologic continuity in the Antarctic mountains suggests tectonic continuity also. Cobbles and erratics containing Early Cambrian pleosponges, both metamorphosed and nonmetamor- phosed, have been found in four places in or near the trans-Antarctic mountains, in positions consistent with derivation from ice-buried geosynclinal materials along the inland side of the mountains. Similar fossils char- acterize the Adelaide geosyncline of South Australia. The Antarctic coast from 50° to 145° east longitude is characterized by charnockitic (orthopyroxene-bear— ing) granitic and gneissic rocks. The various age de- terminations made on these rocks indicate Precambrian ages (Starik, Ravich, Krylov, and Silin, 1959; 1960). No similar rocks have been found in the trans- Antarctic mountains. A K/Ar analysis of biotite in gneiss indicates an age of 500 million years (Cameron, Goldich, and Hoffman, 1960) at Marble Point, and seven Whole-rock K/Ar determinations in the same tectonic belt in Oates Land indicate an age of metamor- phism and formation of granitic rocks of about 500 mil— lion years (Starik, Ravich, Krylov, and Silin, 1959 2). This appears to confirm the Cambrian orogeny inferred on geologic grounds. East Antarctica can thus be interpreted to be largely formed of a Precambrian shield, along whose Ross Sea- ‘The actual measurements yielded calculated ages of 425—460 mil- lion years; but these must be increased by 20 or 30 percent to indicate true ages, because of the loss of argon from feldspars in the rocks, according to J. L. Kulp (oral communication). B380 Weddell Sea side a geosyncline was filled by early Cambrian and, presumably, late Precambrian sedi- ments. The contents of this geosyncline were meta- morphosed and intruded by batholiths during Cambrian time. This inferred pattern is strikingly similar to that of Australia, where the Precambrian shield of western Australia gives way in South Australia to the Adelaide geosyncline of Lower Cambrian and upper Precam- brian sediments, and that to a Cambrian batholith characterized by granitic rocks (for example, the Mur- ray Bridge granite) which are remarkably similar to those of the trans—Antarctic mountains. (The younger Paleozoic granites of Australia are very different.) Analogy with structures in Australia and New Zea- land suggests that orogenic belts of middle and late Paleozoic age may be present in Antarctica. One may be in eastern Marie Byrd Land, between the trans- Antarctic mountains and the Andean-type ranges of the Palmer Peninsula and in the Cape Adare region of eastern Antarctica. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES It may be significant that the position of the Cam— brian( ?) orogen of Antarctica accords with Du Toit’s (1937) theoretical reassembly of the southern-hemis- phere continents, and forms a bridge between the Cam- brian batholiths of Australia and South Africa; Du Toit was not aware of the correlations between these granites, nor of their petrologic kinship. Many other features of Antarctic geology also fit well with Du Toit’s reconstruction. REFERENCES Cameron, R. L., Goldich, S. S., and Hoffman, J. H., 1960, Radio- activity age of rocks from the Windmill Islands, Budd Coast, Antarctica: Stockholm Univ. C‘ontribs. Geol., v. 6, p. 1—6. Du Toit, A. L., 1937, Our wandering continents: Edinburgh, Oliver and Boyd, 366 p. Starik, I. Ye, Ravich, M. G., Krylov, A. Ya, and Silin, Yu. 1., 1959, Oh absolyutnom vozraste porod vostochna- Antarkticheskoi platformy: Akad. Nauk SSSR. Doklady, V. 126, no. 1, p. 144—146. PALEONTOLOGY, GEOMORPHOLOGY, AND PLANT ECOLOGY 175. GIGANTOPTERIDACEAE IN PERMIAN FLORAS OF THE SOUTHWESTERN UNITED STATES By SERGIUS H. MAMAY, Washington, DC. The plant genus Gigantoptem’s is important as the Northern Hemisphere contemporary of Glossopteris, which dominated the Permian floras of Gondwanaland. In eastern Asia the gigantopterids had a broad geo- graphic distribution, but in North America they are known in only a small province east of the Ancestral Rocky Mountains; there they occur in Leonard—equiv- alent rocks. Their most significant occurrences are in north-central Texas, where they show the longest strati- graphic range and greatest floristic differentiation. Gigantopteris amem'cana White is the oldest and only previously described American gigantopterid species. It apparently is limited to the Belle Plains and basal Clyde formations of the Wichita group, with question- able occurrences beneath the Talpa limestone member of the Clyde formation marking the upper limit of its stratigraphic range. Associated with it is the most di- verse North American Permian flora known. This in- cludes many coal—swamp types, some representing new taxa. Above the Talpa limestone member, G. america'na, is succeeded by two new gigantopterid species. They both have approximately the same stratigraphic range, extending upward into the Vale formation of the Clear Fork group. Associated floras contain fewer coal- swamp types than the Belle Plains and Clyde floras, and in their highest known occurrence near the top of the Vale, the new gigantopterid species are associated with dominant conifers and other elements suggestive of increased aridity. The Texas gigantopterids and some associated spe- cies strikingly resemble plants of the Permian Shih- hotse series of central China and correlative strata of adjacent areas; still others resemble Permian plants from the Ural region of Russia. Plant migration be- tween North America and Asia is thus suggested, with the southwestern United States a likely point of origin. PALEONTOLOGY, GEOMORPHOLOGY, AND PLANT ECOLOGY 176. B381 UPPER PALEOZOIC FLORAL ZONES OF THE UNITED STATES By CHARLES B. READ and SERGIUS H. MAMAY, Albuquerque, N. Mex, Washington, DC. Much information has now accumulated regarding the stratigraphic and lateral distribution of upper Paleozoic megafossil floras in the United States. The ensuing account is to be regarded as a report of prog- ress based on data that are admittedly incomplete and that very likely will continue to be incomplete for some decades. Investigations of upper Paleozoic floras have been chiefly of the plants in or associated with coal, although a number of floras have been reported that do not seem to have grown in coal—forming swamps. Facies prob- lems, therefore, exist in interpreting the sequences sand distributions of fioras. At present, 15 floral zones are recognized in the Mississippian (Read, 1955), Pennsylvanian (Read, 1947), and Permian systems (Mamay and Read, 1954) in the United States (tables 176.1 and 176.2). Three of these are in the Mississippian, nine in the Pennsyl- TABLE 176.1.—Mississippian and Pennsylvanian floral zones Zone Name Appalachian region except for Southern Southern anthracite field Midcontinent region anthracite field Upper Pennsylvanian 12 Danaeites spp---- _ _ _ , _ _ r _ , Upper part Monogahela for- Not known ,,,,,,,,,,,,,,,,,,, Missouri and Virgil series. mation. ll Lescuropteris spp __________ Lower part Monogahela for- _____ do ,,,,,,,,,,, , ___________ In Midcontinent region mation and upper part zones 11 and 12 are not Conemaugh formation. separable and are to- gether designated the zone of Odonopterfs spp. 10 Neuroptem's flexuosa and Lower part Conemaugh forma- Post-Pottsville rocks undifferen— Upper part of the Des tion and. upper part Alle- gheny formation. Pecopteris spp. tiated. Moines series. Middle Pennsylvanian Lower part Allegheny for- mation. 9 N. rarinervis ______________ 8 N. tenuifolia ______________ Major part Kanawha forma- tion. 7 M egaloptem's spp __________ Base of Kanawha formation” Upper part Sharp Mountain Lower part of Des Moines conglomerate member, Potts- series. ville formation. Not known ____________________ Major portion of Atoka series. _____ do_-,,-,___________,-,-__ Base of Atoka series. Lower Pennsylvanian 6 Mariopteris pygmaea and N. Upper part New River forma- tennesseeana ____________ tion and upper part Lee formation. 5 Mariopteris pottsvillea an.d Lower part New River for- Aneimites spp. mation. 4 N. pocahontas and Mario];- teris eremopteroides. Pocahontas formation ________ Schuylkill conglomerate mem- Bloyd shale, Morrow series. ber, Pottsville formation. Lykens Valley No. 4 coal bed and adjacent strata of Tum- bling Run conglomerate mem- ber, Pottsville formation. Lykens Valley No. 5 and No. 6 coal beds and adjacent strata of Tumbling Run conglom- erate member, Pottsville for- mation. Locally basal strata of Penn- sylvanian system in Mid- continent region. B382 GEOLOGICAL SURVEY RESEARCH l 96 0—SHOR’I‘ PAPERS IN THE GEOLOGICAL SCIENCES TABLE 176.1.—Mississippian and Pennsylvanian floral zones——Continued Zone Name Appalachian region except for Southern Southern anthracite field Midcontinent region anthracite field 3 Cardiopteris spp. and Spen- opteridium spp. Upper part of Pocono and Price formations. Lower part of Pocono and Price formations. 2 Triphyllopteris spp ________ 1 Adiantites spp, ___________ Mississippian Mauch Chunk formation _____ (No floras known) ___________ Chester series (similar flora occur in Stanley shale). Mauch Chunk formation _______ (No floras known) _____________ Meramec series (no floras known). Upper part of Pocono formation_ Osage series (no floras known). Lower part of Pocono formation- Kinderhook series (only spores and fossil wood known). TABLE 176.2.——Permian floral zones Zone Name Kansas Oklahoma North Texas Arizona and New Mexico 15 Younger Gigantopteris ____________________ flora. 14 Zone of older Gigantop- teris flora. Glenop- teris flora; Supaia flora. 13 Callipteris spp __________ Summer group (Glcnopteris). flora). Wolfcamp equiva- lents; highest occurrences in Chase group. Garber sandstone (older Gigantopteris Wolfcamp equiva- lents; highest occurrences in Stratford formation. Clear Fork group ______ Upper part Abo for— mation; Hermit shale (Supaia Belle Plains forma- (older Gigantopteris flora). _ flora). Wolfcamp equiva- Lower part of Abo lents; highest formation. occurrences in Moran formation. vanian, and three in the Permian. Although each of the Mississippian and Pennsylvanian zones is reason- ably consistent in its botanical makeup, the floristic zonation in the Permian is more complex. The floras of lowermost Permian maintain much similarity wher. ever found, but the succeeding floras display a striking provinciality that invites speculation as to the reasons therefor, in terms of evolving paleogeography, paleoe- daphology, and other ecologic factors. The upper Paleozoic floral zones (tables 176.1 and 176.2) are named for one or more especially character- istic plants. The following notes are intended to sup- plement briefly the tables and to report other common plant forms in the floral zones. Zone 1. Rhodca, Rhucoptcm’s, Alcicornoptcris, Lagcnospcrmum, Calathiops, Girtya, Lepidodendropsis. Zone 2. Rhodea, early forms of Cardioptc‘ris. Zone 3. Appearance of Sphenopteridium, Aneimites-like Adian- tites. Zone 4. Diminutive, round-lobed Sphenopteris; early Eremop- teris. Zone 5. N europteris smithsii, Alethoptem‘s. Sphenophyllum tenue, early Zone 6. Neuropteris smithsii, Diplothmema cheathami; in Rocky Mountains, Trichopitys. Zone 7. Ncrioptcris lanccolata, Cartiiocarpon phillipsi group. Zone 8. Appearance of Neuroptcris rarinervis, N. flea-now, Pecopteris vestita. Zone 9. Pccoptcris rcstita, Marioptcris occidcn-talis, Neurop- tem‘s ovata, Linoptcfis rubella, cyatheoid pecopterids. Zone 10. N europtem‘s ova ta, cyatheoid pecopterids. Zone 11. Neuroptem’s ovata, Odontoptcris spp, cyatheoid pecop- terids; the Midcontinent and the ancestral Rocky Moun- tains Lebachia piniformis sporadic. Zone 12. Pecopterids of zones 10 and 11 abundant, chidoden- (iron spp., Nigillaria spp. abundant. Zones 11 and 12 (locally combined). These zones differentiated in Appalachians, not recognized farther west. Interval, characterized by Odontopteris spp., Neuroptem‘s lindahh‘, cyatheoid pecopterids. Zone 13. Many species common in zones 11 and 12. Conifers locally abundant. ' Zone 14. Flor-as provincial, the distribution dependent on pale- ogeographic and paleoedaphic factors. The Gigantopteris spp. and Glcnoptcris spp. floras contain elements present in zones 11, 12, 13. The Snpaia spp. flora has some elements that suggest relationships with contemporary austral plant associations. Zone 15. Floras of this zone less diversified than in zone 14; contain elements of Permian Angara floras of Siberia. PALEONTOLOGY, GEOMORPHOLOGY, AND PLANT ECOLOGY REFERENCES Mamay, S. H., and Read, 0. B., 1954, Differentiation of Permian floras in the southwestern United States: Internat. Bot. Cong, 8th, Paris, 1954, Rept. and Commun, sec. 5, p. 157—158. 51‘ 177. B383 Read, 0. B., 1947, Pennsylvanian floral zones and floral provinces: Jour. Geology, v. 55, no. 3, p. 271—279. 1955, Floras of the Pocono formation and Price sand- stone in parts of Pennsylcania, Maryland, West Virginia, and Virginia: US. Geol. Survey Prof. Paper 263, 32 p. FOSSIL SPOOR AND THEIR ENVIRONMENTAL SIGNIFICANCE IN MORROW AND ATOKA SERIES, PENNSYLVANIAN, WASHINGTON COUNTY, ARKANSAS By LLOYD G. HENBEST, Washington, DC. The Morrow flora and fauna of northwestern Arkan— sas are widely recognized as a standard of reference for early Pennsylvanian stratigraphy (Mather, 1915; Pur- due and Miser, 1916; Henbest, 1953). Though the over- lying Atoka series is a standard of reference in the Mid-Continent for rocks of early Middle Pennsylvanian age, its fossils are less well known (Miller, Downs, and Henbest, 1948). Among the most abundant but least studied of the fossils of both series, however, are the spoor (that is, tracks, burrow marks, or other artifacts) of unknown animals. The spoor are commonly pre- served in sandstone, siltstone, or claystone beds that are virtually barren of other fossils. The nature of such animals can be inferred only by the shape, position, and sedimentary environment of their artifacts compared with similar spoor of living forms. Such spoor have commonly been treated as oddities and, because of prob-- lematic origin, as unworthy of taxonomic nomencla- ture. Many kinds of spoor, including several new and pre- viously undescribed' forms, compose the Morrow and Atoka assemblages. Six of the most typical are illus- trated on figure 177.1. Arthrophycid and paleophycid burrows are particularly characteristic of sediments composed of thin, alternating, ripplemarked beds of sandstone and of clay or siltstone shale. Uonostz'chus Lesquereux, 1876, and Laevicyclus Quenstedt also be— long in this association. The bottom side of the sand- stone sheets are commonly crowded with the paleo- phycid and arthrophycid burrows (fig. 177.1F). This is especially true of the Cane Hill member of the Hale formation (Henbest, 1953, p. 1938—9) and a phase of the cyclothems in the Atoka (unit 4 and 9—same bed but offset by fault) of Miller, Downs, and Henbest (1948, p. 674—5). Taonums collettz' (Lesquereux), 1890, and Sealant- tuba Weller, 1899 (see unit 6 and 11 (same bed), idem) are commonly associated and overlap with a marine in- vertebrate zone. These marine invertebrate faunas in- clude forms that are common in the marine phases of Illinois cyclothems and in cyclical sequences of the Pennsylvanian of Kansas. No evidence of abyssal ori— gin for the cyclothems in Illinois, Kansas, or in the Atoka series in the Ozark region has been seen by this writer. On the contrary, evidence of shallow, near strand, and near sea level conditions is abundant. The Tammi-us and Scalam’tuba assemblages are characteris- tic of the Atoka and higher Pennsylvanian rocks of the Ozark and Arkansas Valley provinces. CONCLUSIONS The assemblages characterized by Taonums and those characterized by arthrophycids and paleophycids are regarded by some specialists as exclusively charac— teristic of flysch deposits and as indicators of abyssal environment. Without questioning the occurrence of similar spoor in abyssal environment or in flysch, it is evident that (a) these spoor in the Morrow and in the Atoka series are preserved in sediments that were laid down in shallow, well-circulated, or well—aerated marine and possibly estuarine waters, (b) the organisms were burrowing forms, (0) the environment supported a rela- tively meager fauna of shell-bearing invertebrates, and (d) of the few invertebrate shells preserved, some were probably detrital and exotic. So far as identifiable, most of the Morrow and Atoka genera of spoor have a long stratigraphic range and are unreliable as indicators of age. Preliminary studies indicate that the fossil spoor in the Morrow and Atoka series are significant as indicators of environment and conditions of deposition and that they comprise val- uable local aids in differentiating and tracing sedimen- tary facies or rock units in mapping. The use of such spoor as the arthrophycids for determining the original attitude of sedimentary rocks in complex structures in B384 the Ouachita Mountains is supported by these occur- rences in the related but undisturbed rocks of the Ozark Highlands. REFERENCES Branson, C. 0., 1959, Some problematical fossils: Oklahoma Geol. Notes, Oklahoma Geol. Survey, v. 19, p. 82—87. Croneis, C. G., 1930, Geology of the Arkansas Paleozoic area with special reference to oil and gas possibilities: Arkansas Geol. Survey Bull., v. 3, 457 p., 30 figs., 45 pls., maps. Henbest, L. G., 1953, Morrow group and lower Atoka formation of Arkansas: Am. Assoc. Petroleum Geologists Bull., v. 37, p. 1935—1953, 2 figs. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Mather, K. F., 1915, The fauna of the Morrow group of Arkan- sas and Oklahoma: Denison Univ. Sci. Lab. Bull., v. 18, p. 59—284, pls. 1—16. Miller, A. K., Downs, R. H., and Henbest, L. G., 1948, A cephalopod fauna from the type section of the Pennsyl- vanian “Winslow formation” of Arkansas: Jour. Paleon- tology, v. 22, p. 672—680, pls. 101—103. Purdue, A. H., and Miser, H. D., 1916, Geology of the Eureka SpringsHarI-ison quadrangles, Arkansas and Missouri, US. Geol. Survey, Geol. Atlas, Folio 202, 22 p., maps, illus. Seilacher, A., 1953, Studien zur Palichnologie; 1. fiber die Methoden der Palichnologie: Neues Jahrb., Geologic u. Paliiontologie, Stuttgart, v. 96, p. 421—452. Explanation of figure 177.1 A—C, Comstichus sp. Specimen cut in half. A, top; B, sectional view; 0, side. USNM 120231. Marine or estuarine shale above the Baldwin coal, Bloyd shale; Round Mountain, NW1/4, sec. 14, T. 16 N.,R. 29 W. Conostichus Lesquereux, 1876 (see also Branson, 1959), originally thought to be a plant fossil, is here tentatively interpreted as the sand-filled spoor of a sedentary burrowing animal. Natural attitude, apex down. Some speci- mens show cone-in-cone vertical column, each cone flush with successive layers of sand and representing ascent with increment of sediment. Locally abundant in Cane Hill member, Hale formation, and in Atoka series. H H Spoor of unknown animal. Casts on bottom side, slab 5—8 cm thick, fine-grained sandstone. Specimen collected and deposited in University of Arkansas Museum, by L. G. Henbest, 1923. Loose block probably from Cane Hill member, Hale formation: near center El/g, sec. 24, T. 14 N, R. 32 W. Although appearing to be vertebrate tracks, presence of six digits, irregular retnacking, and absence of series of tracks for left legs suggest (but not conclusively) invertebrate origin, possibly the spoor of a side—walking crustacean. Sparsely scattered impressions of small crinoid columnals and brachiopod shells. Opposite side of sandstone slab bears oscilla- tion ripple marks and trail of a gastropod. Laevicyclus sp. Concentric marks on sandstone slab, Cane Hill member, Hale formation; cut, state highway 59, near center, south side, sec. 35, T- 13 N, R. 33 “V USNM 120232. These concentric marks were probably made by the waving tentacles of a polychaete worm (see also Seilacher, 1953, p. 430). A peculiar feature of several is the diametral ridge through the center which has no apparent correlation with polychaetid morphology. Spoor related to Arthrophycus Hall, 1852, and Paleophycus Hall, 1847. USNM 120233; abundant in Cane Hill member, Hale formation. at same source as E. Genera originally classed as algae. Now regarded by some as spoor of burrow- ing animal, an interpretation here adopted. Sand-filled, attached to bottom side of sandstone slab, and extending into underlying, somewhat organic, dark shale. “Claw” or digging marks present. Weathered vertical joint face on cliff of typical “honeycombed”, calcareous sandstone, Prairie Grove member, Hale for- mation. Source same as of specimens in E and F, but half a mile north. Not collected. Origin of this prominent and characteristic feature of the Prairie Grove member demonstrated at locality of E and F where cavities are directly traceable into arthrophycid spoor. (left side) Taon'urus rolletti Lesquereux. 1870. Roughly 150 feet above base, Atoka series, near center, sec. 23, T. 13 N., R. 31 W. IISNM 120234. Originally thought to be plant impressions, now regarded by most paleontologists as marks of a burrow— ing sedentary animal. Scailam'tuba. sp. These tubes with cone-in-cone septa are more or less horizontal, commonly hook- or U-shaped. Abundant in many sandstone beds of Atoka and later Pennsylvanian rocks of Boston Mountain and Arkan- sas Valley provinces. Also found in thin-bedded limestone, Early Mississippian age, New Mexico and Missis- sippi Valley. Here interpreted as spoor of sediment-eating, burrowing, worm-like animal in shallow marine and estuarine waters. south side, (right side) PALEONTOLOGY, GEOMORPHOLOGY, AND PLANT ECOLOGY B385 FIGURE 177.1.—Fossil spoor from Pennsylvanian roéks of Washington County, Ark. 'X‘ B386 GEOLOGICAL SURVEY RESEARCH 1960—SHOR’1‘ PAPERS IN THE GEOLOGICAL SCIENCES 178. PALEONTOLOGIC SIGNIFICANCE OF SHELL COMPOSITION AND DIAGENESIS OF CERTAIN LATE PALEOZOIC SEDENTARY FORAMINIFERA By LLOYD G. HENBEST, Washington, DC. Foraminfera that had tube-shaped tests and lived permanently attached to invertebrate shells and sea- weed have been abundant in shelf seas since middle Paleozoic time. Their shells are widely distributed in most marine limestones, but their protean growth form together with striking similarities in external appear- ance between common but unrelated genera has con- fused efforts to classify them and has led to neglect. The neglect is disproportionate, however, to the poten— tial value of these foraminifers in paleoecology, partic- ularly for subsurface exploration for oil. The sedentary, tubiform foraminifers are divided in- to two unrelated families primarily on shell composi- tion. Those whose shells are composed of cemented aggregates of bottom detritus are classed with the Tolypamminidae and those with secreted carbonate shells are classed witih Cornuspirinae, family Opth- almidiidae. These differences in shell composition provide a simple means of recognizing the family rela— tions of living species, but diagenetic changes in shells as old as the late Paleozoic have-introduced confusing alterations in both the tolypamminid and cornuspirid fossils. Petrologic study of the shell material of SerpuZOpsz's Girty, 1911, and of Apterm'nella Cushman and Waters, 1928, respectively among the most typical and abun- dant genera of Tolypamminidae and Cornuspirinae in the late Paleozoic, together with a study of Osagia Twenhofel, 1919, an algal-foraminiferal commensal, has revealed information applicable for classifying re- lated genera. SHELL COMPOSITION AND CLASSIFICATION OF SERPULOPSIS GIRTY, 1911 Girty (1911, p. 124; 1915, p. 41) originally classed Serpulopsis as the shell of a sedentary, marine worm. In 1934, however, he suspected that Serpulopsis was a foraminifer and asked me to correct the error. The shell consists of a proloculus followed by a tight coil of one to two volutions. The coil is followed by linear or wandering growth conforming to the surface of the support. Beginning with the proloculus, the shell has a low profile in cross-section and its attachment to the support is broadly festooned—a characteristic of tubi- form, sedentary foraminifers that live in shallow waters and therefore are subject to wave or current- action and attrition or to capture by grazing animals. Externally, the shells of Girty’s types have an agglu- tinate appearance, being composed of quartz grains of clay and silt sizes up to 15 microns in diameter. Some of the grains have glittering faces, indicative of second- ary enlargement. In collections from other localities, many serpulosid and related shells are covered with a distinct, euhedral quartz druse. These facts have been interpreted by some as positive evidence that the shell is a replacement, by quartz, of an original carbonate shell, and that such fossils belong to the cornuspirids instead of the tolypamminids. Others have claimed that the shells were actually agglutinate as they appear. To test these counter claims, very thin sections of Serpulopsis shells were made from Girty’s type mate- rial and were mounted in Hyrax——a cement of 1.71 re- fractive index. The sections reveal that: (a) the grains are poorly sorted, the largest being 15 microns in diameter, and are composed mostly of quartz; (b) the boundaries of adjacent grains are dissimilar and do not mesh; (0) the grains of the innermost zone are fitted and laid like masonry with the largest or flat faces toward the sarcode, forming a smooth inner surface; (d) the grains have random optical orientation; (e) the larger grains can be resolved in sufficient detail to reveal that some have simultaneous and some have wavy extinction. These conditions show that the grains were of different origins and that the shell was originally a cemented aggregate of detrital grains, at least a part of which were quartz. For these reasons Serpulopsis Girty, 1911, should be classed as a tolypamminid. The same criteria may be applied to determine the origin for other supposedly agglutinate shells. COMPOSITION AND DIAGENESIS OF CORNUSPIRID SHELLS A perplexing feature of virtually all late Paleozoic foraminifer shells that appear externally to be cornu- spirids is that in thin sections they prove to be com- posed of a dark, finely granular material which is unlike the shell material of most other foraminifers and invertebrates. Irregular parts of such shells resist digestion in very weak acid but no recognizable parts of the shells remain after digestion in 10 percent HCl. Preliminary X—ray analysis does not indicate the pres- PALEONTOLOGY, GEOMORPHOLOGY, AND PLANT ECOLOGY ence of dolomite in the dark shell material. Question arose whether such shell material was originally (a) a chitinoid or other organic secretion, (b) an extremely fine aggregate of detritus masked by metamorphosed cement, or (c) a diagenetic end product of a peculiar carbonate material. A study of type material of Apterm'nella Cushman and Waters, 1928, from a well core from the “Dothan limestone” of Permian age in Archer County, Texas, revealed preservations of very rare quality in which the shells have a “porcellaneous” or ivory luster externally and a slightly brownish hue and amorphous structure in section. At magnifications of X 1200, the shell material shows a vaguely granular appearance. These features characterize the shells of living species of Ophthalmidiidae (Wood, 1949, p. 235). A further in- dication of the quality of preservation is seen with polarized light. The submicroscopic crystals in the shells of living ophthalmids show little or no preferred orientation. In these rare preservations of Aptem- nella, the crystal orientation remains partly random and such orientation as exists is related to the matrix rather than to the shell structure. Though apterri- nellid and similar shells of the Paleozoic have long been accepted as originally “porcellaneous,” these preserva- tions comprise the first mineralogic proof known to me. The significance of the Archer County preservations is extended by recent collections from the Ibex lime— stone of Cheney at Ibex, Shackelford County, Texas, in which numerous specimens of the same species of Aptem-z'nella show, within single shells, the diagenetic stages from “porcellaneous” carbonate material to the dark, finely granular end product that heretofore has been so perplexing and confusing. The diagenetic re- construction also resulted in a volume change and loss of all but the gross shell structures. The fact that a surface ornamentation consisting of deep, honeycomb- like pits, heretofore unrecognized, is preserved in the unaltered parts of these shells suggests that a more careful study of the Paleozoic sessile cornuspirids may 5% 179. B387 reveal structures of unsuspected taxonomic value. A study of Osagz'a TWenhofel, 1919, and Ottonosia Twen- hofel, 1919, of Pennsylvanian and Permian age (form genera composed of more or less concentric colonies of stony algae and sessile cornuspirid Foraminifera) in- dicates a similar diagenesis in both the algal and the foraminiferal shell material. In a recent import-ant paper on shell composition, Blackmon and Todd (1959, p. 4) determined that the shells of seven living species of Ophthalmidii-dae from shallow water were composed of calcite that has the very high magnesian content of 14 to 18 mol percent. It is here proposed that the shells of the late Paleozoic Cornuspirinae and of Osagia and Ottonosz'a colonies were likewise composed of magnesian calcite and that their instability was a result of a high magnesian con- tent. It is also suggested that the magnesian content of the ophthalmid shells is determined by the role of sym- biotic, chlorophyll-bearing Algae in the internal econ- omy of the animal. Pseudovemm'porella Elliott, 1958, late Permian of Asia Minor, was classed with some uncertainty by its author as Algae. Its peculiar, alveolar surface orna- mentation is related to that possessed by the early Permian apterrinellids from Ibex, Texas. The orna- mentation is usually obscured by diagenesis and here- tofore has been unrecognized. Pseudovermiporella is here transferred from the Algae to the protozoan family Ophthalmidiidae. REFERENCES Blackmon, P. D., and Todd, Ruth, 1959, Mineralogy of some Foraminifera as related to their classification and ecology: Jour. Paleontology, v. 33, p. 1—15, 1 fig., 4 tables. Girty, G. H., 1911, On some new genera and species of Penn- sylvanian fossils from the Wewoka formation of Okla- homa: New York Acad. Sci., Annals v. '21, p. 119—156. 1915, Fauna of the Wewoka formation of Oklahoma: US. Geo]. Survey Bull. 544, 353 p., 35 pls. Wood, A., 1949, The structure of the wall of the test in Foraminifera: its value in classification: Geol. Soc. London Quart. Jour., v. 104, p. 229—255. RELATION OF SOLUTION FEATURES T0 CHEMICAL CHARACTER OF WATER IN THE SHENANDOAH VALLEY, VIRGINIA By JOHN T. HACK, Washington, DC. The Shenandoah Valley, Virginia (fig. 179.1), is an area about 130 miles long and 40 miles wide in the Appalachian Mountains. The valley floor is underlain by intensely deformed Cambrian and Ordovician lime- stone and dolomite. The valley is flanked on the south- east by the Blue Ridge, a highland area of resistant B388 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Z z < ‘ S E o _ h ESE Mostly sandstone, arkosic g 3 sandstone, and shale o E I 2 °5 2 2 Mostly shale O > Z Z < E E D 2 m z > 2 < 8 Mostly limestone and dolomite 3 g V E" Q g Mostly quartzite and arg'illite z 5 + o 2' 1-: 4 ‘ ¢ ‘ < \Z/ . . . < Gran1t1c and metavolcanic rocks E E 9. [D Outline of drainage basin Lar esinks and ou s g gr p of Shenandoah River of sinks and Opequon Creek 2A Water sample and c type number Commercial cavern O 10 20 310 MILES FIGURE 179.1.—Map of Shenandoah Valley, Virginia and west Virginia, showing the distribution of the principal kinds of rock and the location of sinks. Geology simplified from several sources, principally Butts (1933) and Edmundson (1945). Faults are not shown except for the North Mountain fault, on the northwest side of the valley. PALEONTOLOGY, GEOMORPI—IOLOGY, AND PLANT ECOLOGY Precambrian( ?) igneous rocks and Cambrian( ?) quartzite, graywacke, and argillite. On the northwest side of the valley, separated from the carbonate area by the North Mountain thrust fault, is another moun- tainous area, underlain by shale and sandstone of Ordovician to Mississippian age. The Massanutten syncline, a major structural feature in the center of the valley, brings Ordovician, Silurian, and Devonian rocks down to the present topographic surface. The chemical quality of the water of each stream in this region, at periods of low or normal flow, depends on the kinds of rock in the drainage basin. The range in composition of the waters is illustrated by the ex- amples shown in table 179.1, chosen from analyses of water at about 30 localities (Connor and Schroeder, 1957, Schroeder and Kapustka, 1957, and data collected by the writer). Water from quartzite basins in the Blue Ridge has an extremely low content of dissolved solids, low bicarbonate content, and a pH that is con- sistently below 7 and may go as low as 5.0 (type 1, table 179.1). The water of the few streams that drain areas of granitic and met-avolcanic rock in the Blue Ridge is higher in sodium and potassium and higher in silica than that of other streams, but like type 1 it is rela- tively low in bicarbonate and its pH averages about 7.0 TABLE 179.1.—Analyses (in parts per million) of water of four streams typical of the Shenandoah Valley, Va. Type 1 Type 2 (ig- Type 3 Type 4 (quartzite neous rock (sandstone- (carbonate area) area) shale area) rock area) Silica __________________ 7. 2 14. 0 5. 9 4. 4 Iron ___________________ .00 . 00 .01 . 01 Calcium _______________ . 8 4. 8 13. 0 50. 0 Magnesium ____________ 1. 4 2. 2 3. 5 19. 0 Sodium and potassium--- 1. 1 5. 4 4. 5 4. 2 Bicarbonate ____________ 5. 8 25. 0 49. 0 236. 0 Sulfate ________________ . 6 9. 2 8. 2 7. 7 Chloride _______________ . 4 1. 0 2. 5 3. 0 Fluoride _______________ . 0 . 2 . 0 . 1 Nitrate ________________ . 1 1. 0 2. 0 2. 7 Total dissolved solids--- _ 14. 0 50. 0 63 204 Alkalinity (as CaC03) _ _ _ 4. 8 21. 0 47 203 pH (laboratory measure- ment) _______________ 6. 4 6. 8 7. 6 8. 1 pH (measured in field)__- 6. 0 7. 5 ________________ Type 1. Canada Run, Augusta Co., Va. Drainage area $4 square mile, whole in quartzite. Collected by J. T. Hack, April 8, 1959. pH measured in field. J. W. Barnhart and W. B. Hurlburt, analysts. Type 2. East Fork, Stony Run, Page 00., Va. Drainage area 1 square mile, mostly in granodiorite. Collected by J. T. Hack, April 8. 1959. pH measured in field. J. W. Barnhart and W. B. Hurlburt, analysts. Type 3. North Fork, Shenandoah River, at Cootes Store. Drainage area 215 square miles in sandstone, arkosic sandstone and shale (Data from Schroeder and Kapustka, 1957, p. 28). Type 4. Middle River near Grottoes. Drainage area 360 square miles. Mostly in limestone but includes shale and some sandstone (Data from Schroeder and Kapustka, 1957, p. 27). B389 (type 2, table 179.1). A third class of streams drains areas of Mississippian to Ordovician sandstone and shale along the northwest side of the valley and on Massanutten Mountain. The water of these streams is intermediate in calcium and bicarbonate content be— tween the waters from basins in quartzite and carbonate rocks. Its pH ranges from 6.8 to 7.8 (type 3, table 17 9.1.). Water that drains areas of limestone and dol- omite is high in calcium, magnesium, and bicarbonate. Its total content of dissolved solids is high, averaging about 200, and its pH ranges from about 7.6 to 8.2 (type 4, table 17 9.1). Many streams in the limestone area may be saturated in calcium carbonate at periods of low flow, during which travertine is deposited on the beds at many riflles. Though the sample of this kind of water shown in table 179.1 (type 4) is from a large stream, the quality of these waters is independent of the size of the drainage basin. Water from a certain small stream in carbonate rocks was found to have a similar composition, its bicarbonate content being 171 ppm. and its pH 8.1 (Bell Creek, drainage area 9 sq mi, Schroeder and Kapustka, 1957, p. 28). The solution cavities in the carbonate rocks of the Shenandoah Valley are distributed with relation to the streams in a way that suggests a relation to the source of the water. In figure 17 9.1 the distribution of all the sinks large enough to be enclosed by 20-foot contours and shown on the Geological Survey’s topographic maps of the area are indicated. Sinks are abundant in carbonate rock areas flanked by highlands of elastic rocks from which waters of low alkalinity issue. The map shows that at either end of the valley, where there are large areas of carbonate rocks in which most of the drainage is local, sinks are rare and occur only near the large rivers. Sinks tend to be further localized along streams, such as Cedar Creek and the North River, that drain areas of elastic rock. The solution of carbonate rocks may be favored, therefore, by a large source of water of low alkalinity, in which the pH is less than 7 .8 (Krumbein and Garrels, 1952, p. 8 and 24). Other factors, of course, contribute to the localization of sinks and must be at least. as important as the original character of the water entering the car- bonate rocks. These include various qualities of the rocks themselves, such as composition, permeability, and structural features like fractures and joints. Data on aerial photographs of the southern part of the valley show, for example, that the Ordovician carbonate rocks have, on the average, 4.25 sinks per square mile, where- as the Cambrian carbonate rocks have only 1.5 sinks per square mile. Solution features also appear to be especially numerous in areas where the rocks have low dips. B390 FIGURE 179.2.—~-Diagra1nmatic cross section showing inferred geologic conditions along the northwest foot of the Blue Ridge. 1, Quartzite in foothills of Blue Ridge; 2, dolomite and impure limestone of Cambrian age; 3, residuum of clay, silt, and sand; 4, quartzite gravel derived from (1) on ter- races and flood plains. Sinks filled with gravel are common along the north— west foot of the Blue Ridge, where impure Cambrian limestone and dolomite are overlain and almost com- pletely blanketed by gravel derived from the quartzite areas in the mountains, as shown diagrammatically in figure 179.2. The waters issuing from the mountains at temperatures between 11° and 25° C have pH values ranging from 5 to 6.8 and Eh values ranging from +0.3 to +0.5 volts, as measured by the writer in the field. These waters infiltrate the gravelly and cobbly alluvium on entering the limestone area, then react with the carbonate bedrock and emerge with a high alkalinity and pH, which clearly shows that solution is taking place beneath the alluvial cover. As the in- soluble residue of the carbonate rocks cannot escape be- cause of the gravel cover, the fresh bedrock is overlain by silty and clayey residuum that is in many places GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES over 100 feet thick. This process contributes to the formation of iron and manganese deposits, which oc- cur in considerable numbers in the residuum. What- ever iron and manganese are present in the carbonate rocks is nearly insoluble in water having the pH and oxidation potential of the water of the Blue Ridge streams (Krauskopf, 1957). These elements, therefore, like the siliceous residues, accumulate beneath the al— luvium as oxides and hydroxides, and in some places they are concentrated in deposits of minable grade. REFERENCES Butts, Charles, 1933, Geologic map of the Appalachian Valley of Virginia; scale 1:250,000: Virginia Geol. Survey. Connor, J. G., and Schroeder, M. E., 1957, Chemical and physi- cal character of surface waters of Virginia: Virginia, Dept. Conserv. and Devel., Div. Water Resources, Bull. 20, 107 p. Edmundson, R. S., 1945, Industrial limestones and dolomites in Virginia; northern and. central parts of the Shenandoah Valley: Virginia Geol. Survey Bull. 65, 195 p. Krauskopf, K. B., 1957, Separation of manganese from iron in sedimentary proceSSes: Geochim. et Cosmochim. Acta, v. 12, p. 61—84. Krumbein, W. 0., and Garrels, R. M., 1952, Origin and classi- fication of chemical sediments in terms of pH and oxida- tion-reduction potentials: Jour. Geology, v. 60, p. 1—33. Schroeder, M. E., and Kapustka, S. F., 1957, Chemical and physical character of surface waters of Virginia: Virginia, Dept. Conserv. and Devel., Div. Water Resources, Bull. 21, 199 p. . I80. SOME EXAMPLES OF GEOLOGIC FACTORS IN PLANT DISTRIBUTION By CHARLES B. HUNT, Denver, Colo. In Death Valley, Calif, the area below about 1,000 feet above sea level supports three quite different floral assemblages, reflecting three equally different kinds of ground. The area lies entirely within the Lower Sonoran Zone, and its climate is essentially uniform. Annual rainfall is about 1.5 inches; evaporation is about 150 inches a year; average temperatures in July exceed 100°F ; minimum temperatures in winter rarely reach freezing; ground temperatures in summer go as high as 190°F. The gravel fans surrounding the salt pan consist mainly of permeable ground, in which the water table is scores to hundreds of feet below the surface. They support stands of xerophytes (fig. 180.1), plants that root in the zone of vadose water above the water table and that are capable of surviving protracted drought. At the foot of the fans and at the edge of the salt pan, ground water comes near the surface, and the plants Panamint Range Black Mountains Phreatophytes Phreawphytes No flowering plants o., n, “on . Gravel fan Salt pan FIGURE 180.1.—Generalized section across Death Valley, Calif., showing distribution of plants. Xerophybes grow on gravel fans, phreatophytes grow at the foot of the fans where ground water is shallow. There are no flowering plants on the salt pans. PALEONTOLOGY, GEOMORPHOLOGY, AND PLANT ECOLOGY there are phreatophytes—plants that cannot live unless their roots reach the water table or the capillary fringe above it. The salt pan, covering the lowest part of the valley, is without flowering plants, because the water in it is too saline to support them. FIGURE 180.2.—Detai1s of distribution of xerophytes on gravel fans in Death Valley. The main washes, which benefit by runoff from the mountains, support stands of burroweed (b). Tributary washes that collect runoff from benchlands on the fans have stands of creosote bush (0) flanked by stands of desert holly (h). Benchlands between the washes commonly have an impermeable surface of desert pavement and are bare. The xerophytes are distributed in three principal zones (fig. 180.2). At the foot of the fans the com- monest shrub is desert holly (Atriplem hymenelytm). Above this is a belt of creosote bush (Larrea tridentata). The highest parts of the fans have stands of burroweed (F ransem‘a dumosa). The distribution of these shrubs, however, when looked at in detail, is con- trolled chiefly by differences in ground conditions; the climatic differences due to the differences in altitude are slight. For example, the most barren ground on the fans is gravel having an impermeable pavement of caliche at the surface, which favors very rapid runoff. This kind of ground is without flowering plants whether it is on the high or low parts of the fans. Ground around the foot of the fans, also, that contains more than 5 percent (by volume) of salts is bare. ’5? B391 Burroweed occupies those high parts of the fans that benefit by runoff from the mountains, where rainfall is much greater than it is on the fans. But because the runoff rapidly collects in washes floored with highly permeable gravel, it rarely extends far down on the fans. Vadose water on the middle and lower parts of the fans is replenished chiefly by the rainwater that falls there, and by the runoff from neighboring im- permeable surfaces. Creosote bush grows Where the catchment areas are moderately large; desert holly grows where the catchment areas are small. The dis- tribution of each of the species is clearly a function of the availability of vadose water. >..§ 5% E 5 Pickleweed Bare salt pan SALTS IN GROUND WATER, 0.5 3.0 6.0 >6 IN PERCENT FIGURE 180.3.—Zoning of phreatophytes with respect to salinity of the ground water in Death Valley. The phreatophytes in the belt of near-surface ground water at the foot of the fans are zoned in an orderly way with respect to the salinity of the ground water around their roots (fig. 180.3) Honey mesquite (Prosopsis julz'flom) grows where the water contains less than 0-5 percent of salts. Arrowweed (Pluchea sericea) grows farther panward, to where the ground water contains 3 percent of salts. Pickleweed (Allen- rolfea occidentalis), the most salt-tolerant plant, ex- tends panward to where the ground water contains 6 percent of salts. The salinity of the ground water varies seasonally; the limits represent the maxima reached during dry seasons. In the salt pan proper, where the brines contain more than 6 percent of salts, there are no flowering plants, and even thallophytes (algae, fungi, and bac- teria) are few. B392 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES GEOPH Y SI CS 181. RATE OF MELTING AT THE BOTTOM OF FLOATING ICE By DAVID F. BARNES and JOHN E. HOBBIE, Menlo Park, Calif., and Arctic Institute of North America, Bloomington, Ind. Work done in cooperation with the Arctic Institute of North America, the Air Force Cambridge Research Center, and the Office of Naval Research The ice sheets covering Arctic lakes and seas have an important influence on both the surficial geology and the climate of their environment. Yet the influence of the underlying water on the thickness and duration of these ice sheets has received little attention, although important effects are sometimes attributed to small changes in water temperature. Research on the thermal regimen and physical properties of a melting ice sheet at Lake Peters, Alaska, provided an opportunity to study the effect of a deep, current-free body of fresh water on an overlying sheet of ice. At Lake Peters a nearly continuous record was main- tained of the micrometeorological and limnological fac- tors influencing ice melt. The study began early in May, when the temperature of the 6-foot-thick ice cover was still below freezing, and ended in the last week of July, when the last ice melted off the lake. The rate of melting at the bottom of the ice sheet was obtained by freezing translucent plastic horizon markers into the ice early in the season and measuring their dis— tances from the top and bottom of the ice sheet at 4—day intervals during the melting season. Many of these markers were originally attached to white wooden poles, but these poles absorbed so much solar radiation that they became loose midway in the season. Another marker, however, attached to a white wire, persisted nearly throughout the melting season. Because of the loosening of the markers and the unevenness of the top and bottom ice surfaces, there is considerable scat— ter in the measurements. Nevertheless the data indi- cate that not more than a few centimeters melted from the bottom of the ice sheet during the entire melting season. This small amount of melting is consistent with the thermal gradients measured in the water beneath the ice. Water temperatures at various depths in the lake were determined at frequent intervals with a small ther- mistor probe lowered into the lake. Four curves ob- tained at the middle of Lake Peters during the melting season are shown in figure 181.1. The three early-sea- TEMPERATURE, IN DEGREES CENTIGRADE ,_. N 0) h UI l Z0“- 0 J .1 ”x“? 45> \7’ X "xx 0 0/ 20 \ | I — m0 m0 2 V :6 2’ a 2 5v 37 h z 3i “T /. we )2 u o /o ,_ - X n O 0 Lu \ | U L z 60- XI] 0 O _: \ | Lu 5 ‘ O o _l 5 \ l E 80— D o , 3 \l | g _ flO . .1 a \/ \ I 100— 9 o p— 0. w \ a _ % . c1 8 o | :j/ 0 Q 120 — 140'— 150 FIGURE 181.1.—Water temperature versus depth curves from Lake Peters, 1959. son curves show a well-mixed constant-temperature layer which grows warmer and thicker as the season progresses. The temperature gradient beneath the ice may be computed for the early part of the melting sea- son, during which this constant-temperature layer is GEOPHYSICS developing, but the proposed theory does not give the gradient in the later part of the melting season. The water temperature is below the maximum-density point, and the well-mixed layer can be created by warm- ing the water just beneath the ice so that it sinks and creates convection. Solar radiation penetrating the ice is the major source of heat for the lake water before mid-June, when rivers begin to flow and a shoreline moat develops. The heat radiated into the well-mixed layer is transferred downward by convection. Above the well-mixed layer is a thin, stably stratified boundary layer where the absorbed radiant heat is transferred upward by conduction. This is the heat that causes melting at the bottom of the ice, and its source is solar radiation. Because the convective processes in the well-mixed layer are very slow, we may assume that almost no heat is transferred from this layer to the boundary layer. The thermal processes in the stable boundary layer may then be expressed mathematically for steady-state conditions by the equation : (1) Lm=K9 =I°(1_e_"h) 533 120 where L is the latent heat of ice, m the mass of ice melted per unit time and area, If the thermal-con- ductivity of water, 4; the temperature at depth ac below the bottom of the ice, L, the solar radiation that enters the water, 7; the extinction coefficient of water, and Z the thickness of the stable boundary layer. This equa- tion does not take into account the heat transferred up- ward by a thermal gradient within the ice. Measure- ments reveal, however, that during the melting season such gradients are negligible. During the winter and before the melting condition is established the right- hand side of equation (1) gives the heat which is sup- plied to the ice by the water and which tends to reduce the amount of new ice formed by a thermal gradient in the ice. It thus furnishes a correction for Stefan’s (1889) formula for ice growth. Equation (1) shows that in the absence of currents the heat available for melting ice cannot exceed the radiation reaching the lake water. At Lake Peters the solar radiation at the top of the ice was about 700 cal per cm2 per day, but less than 1/10 of this passed through the ice. In the following paragraphs we show that only about 1/5 of the radiation reaching the water was ab— sorbed in the stable boundary layer and caused melting of the ice. The thickness of the boundary layer, Z, may be ob- tained by integrating 022; I (2) b—xg=—%e_"’ 5.57753 O——60——-26 B393 Using the boundary conditions x=l, 3—: =0 and 25:0, 71:0 we get: _A__IL - z_1ix — l (3) ”—11K "K6 'I K e n which gives the water temperature at any depth in the boundary layer. Since the temperature at the base of the boundary layer (w=h) is e=T, the temperature of the mixed layer, we get: (4) (1+nh)e""=1—nII{T 0 17K T_ which defines nl as a function of Figure 181.2 0 ”KT and both 17h and shows the relation between I 0 (l—e‘flt). The latter gives from equation (1) the proportion of radiation that goes into melting ice. The dashed line in figure 181.2 shows an approximation that leads to: (5) Lmzle/nKTIo which shows that T, and I 0 all have an equal effect on the rate of melting. However, solar radiation and water transparency are more variable and cause greater variations in melting rate. ‘01 and (I-e'nl) 10 0.01 0.02 0.04 0.07 0.1 0.2 0.4 0.7 1.0 ' | I | I 0] I I I I (I— — l) / e 7] / 0 I, 77% / / 7;KT / I.4./ lo / 0.2 — 0.1 — 007 '— o.o4 — / 0.02 ~— m / Io 0.01 I— / 0.007 I— / 0.004 r— / 0.002 — 0.001 — 0.0007 — 0.0004 '- 0.0002 I 0.0001 FIGURE 181. 2.—Relationship between "KT and both 11h and (l—e‘”). 0 B394 GEOLOGICAL Sufficient data were obtained at Lake Peters to check the reliability of these formulas. The values of L and K are well known; they are about 80 cal/gm and 0.0013 cal °C‘1 cm“1 sec“1 respectively. The values of T and k may be obtained by plotting water temperature against depth. The extinction coefficient 1] and solar radiation [0 were measured with a submarine photom- eter. Some uncertainty is involved in the photocell calibration, which depends on both the spectral dis- tribution and the angular incidence of radiation at the point of measurement. However, an analysis of data obtained from Moon (1940), Lyons and Stoiber (1959), and the photocell manufacturer has provided a calibra- tion factor which is also supported by computations of water—heat increments from the temperature-depth curves. The extinction coefficient varied from 0.002 cm—1 to 0.005 cm“, and we used an average value of 0.003 cm“ 1. In the early part of June the radiation penetrating the ice was about 63 cal/cmz/ day, or 0.0007 cal/cmZ/sec, and the temperature of the mixed layer was about 3° C. From figure 181.2 these values give a boundary-layer thickness of about 67 cm, which is very close to the measured value of a little more than 60 cm. The calcu- lated heat flow to the overlying ice is about 10 cal per day, which implies an ablation rate of about one centi— meter per week. This agrees well with the measured ablation data. The variation of temperature with depth in the boundary layer may best be measured early in the sea- son, when the boundary layer is thicker then it is later on when there is no snow cover to absorb radiation. The May 16 temperature curve in figure 181.1 was ob— tained under snow-covered ice, and figure 181.3 shows how well the data from the upper part of this curve agree with a theoretical curve obtained by using an L, of 0.00004 in equation (3). N 0 radiation measurements were made on May 16, but a value of 0.00004 is con- sistent with a value measured a few days later. These formulas seem to provide a reliable method for estimating the steady-state, under-ice thermal gradient during the freeze-up, winter, and early melting season. They do not take account of turbulent heat transfers re- sulting from water currents or ice drift. Later in the melting season (after mid-June at Lake Peters in 1959 when the ice was about four feet thick) such turbulent transfers may become important. Furthermore, when 6% SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TEMPERATURE. IN DEGREES CENTIGRADE o 0.5 1.0 1.5 2.0 2.5 0 I I I I- 2 .— ” o 4 _ a _ u u. E 6 ' u‘ 9 _ E s — .1 U m - o E 3, 10 — o OBSERVED VALUES 0 1520 h., May 16, 1959 ‘ THEORETICAL CURVE _ lo: 0.00004 cal/cmz/sec 12 n: 0.003 (:m'1 T=2.1 DEGREES CENTIGRADE 14 — o FIGURE 181.3.—Comparison of observed. and theoretical water temperatures beneath Lake Peters ice on May 16, 1959. the water temperature approaches the maximum density value of 4°C small variations in salinity become im- portant, and layers of warmer, fresher water (Birge, 1910) may develop beneath the ice, as shown in the July 8 curve of figure 181.1. Analyses of the Lake Peters thermal data for this portion of the melting season are not complete, but the ablation-marker data show that the rate of melting at the bottom of the ice did not ex- ceed 1 cm per week before the last week of the melting season. REFERENCES Birge, E. A., 1910, The apparent sinking of ice in lakes: Science, v. 32, p. 81—82. Lyons, J. B., and Stoiber, R. E., 1959, The absorptivity of ice: A critical review: Scientific Report No. 3, Dartmouth College, Contract AF 19(604)—2159, Oct. 31, 1959, AFCRC— TN—59—656. Moon, Parry, 1940, Proposed standard solar-radiation curves for engineering use: Jour. Franklin Inst., v. 230, no. 5, p. 583—618. Stefan, Julius, 1889, Uber die Theorien des insbesondere fiber die Eisbildung in Polarmeere: Sitzungsber. Akad. Wiss., A, v. 42, pt. 2, p. 965—83. Eisbildung Wien GEOPHYSICS 182. B395 INTERNAL FRICTION AND RIGIDITY MODULUS OF SOLENHOFEN LIMESTONE OVER A WIDE FREQUENCY RANGE By L. PESELNICK and W.F. OUTERBRIDGE, Washington, DC. Previous work on internal friction of fine—grained limestone (Peselnick and Zietz, 1959) has shown a linear dependence of the absorption coefficient with fre- quency in the range 3 to 10 megacycles per second, and no variation in the modulus of rigidity with frequency within 4 percent experimental precision. A measurement of internal friction and rigidity was made for one of these samples, Solenhofen limestone, at 3.59 cycles per second using the torsion pendulum. The internal friction, expressed in terms of the logarithmic decrement and amplitude absorption coefficient, was ob- tained for maximum surface shear strains of the order of 10'5 cm per cm, and at a temperature of 25° C. The absolute error in this low frequency measurement of in- ternal friction was estimated to be less than 7 percent. The rigidity or shear modulus ,u. was obtained to Within an error of :1 percent and with a precision of one—half percent. The rigidity modulus p for the limestone at 3.59 cycles per second was found to be 2.29 x 1011 dynes per sq cm and was independent of the applied strains. This low frequency determination of M agrees with the high frequency value of 2.2 x 1011 to 4 percent, which is within the experimental precision of the high frequency method. Therefore, the rigidity modulus for Solen- hofen limestone is the same for either low or high fre- quencies within 4 percent. Figure 182.1 shows the shear absorption coefficient for Solenhofen limestone plotted against frequency for the high frequency data of Peselnick and Zietz l l I l l l I I | 7— /q a. 5:13.125x 10—8f1'°35?// 5' / / / / _ / / as=5.0x10_7f GS. IN DECIBLES PER CENTIMETER 3 — / _ 0 /°’ _ 2 _ / / / / _. l— / / / | 1 1 I 1 1 x l 1 l 1 J O 2 4 6 8 IO 12 FREQUENCY. IN MEGACYCLES PER SECOND FIGURE 182.1—Shear absorption coefficient as versus frequency for Solenhofen limestone. l l 1 r I l l w I N L] —7 2 20x10 — '0‘ — r: {9 Z ‘6‘ 06,80 —7 15x10 — o q 5 e” a. ,fi 3 e“ 5 -7 09 ‘13, 10x10 — AK 0‘). 0,36. /GRE“E“1 'i / iii ‘0 6‘ ‘2?)ng i M95 0 + (90 $13 , ’uL" z —7 6,9 l‘ 0'} / _ 5x 10 — ,/ J / t ORS‘O - a a 41° / / ’ ‘ 3 °' «‘3‘ / / / / /1 L 1 j l l 1 41 o 1 2 a 4 5 5 7 s FREQUENCY.IN CYCLES PER SECOND FIGURE 182.2-—Expanded section near origin of figure 182.1 for as versus frequency. (1959). The graph is a straight line drawn through the origin, 015:5.0 x 10‘1 (f) db per cm, where f is in cycles per second. Figure 182.2 is an enlarged drawing of the section near the origin of the graph of figure 182.1. The loga- rithmic decrement at 3.59 cycles per second was found to be 5.0 x 10—3.} The relation between the logarithmic decrement 8 and the absorption coefficient as for shear vibration is (Peselnick and Zietz, 1959; Born, VV.T., 1941) a.= 8f 2.686 (1) where f is the frequency of vibration in cycles per sec- ond and 0 is the shear velocity in cycles per second. The shear velocity, calculated from the measurements of density (2.59 grams per cc) and rigidity (”=2.29 x 1011 dynes per sq cm) is 0=\//L per p=2.97 x 105 cycles per second. By substitution of the appropriate quanti- ties into equation one, the shear absorption coefficient at 3.59 cycles per second is 5.25 x 10‘7 db per cm: the extrapolated value of as at 3.59 cycles per second from the high frequency data is 18 x 10'7 (see fig. 182.2). Thus, the internal friction is a factor of 3.5 times lower than that obtained by linearly extrapolating the high frequency data to 3.59 cycles per second. The factor of 3.5, representing the ratio of internal friction at the specified high and low frequencies, can- not be accounted for solely by experimental error. An immediate consequence of this is that the absorption coefficient is not a linear function of the frequency over db per cm B396 the extended frequency range of 3.59 cycles per second to 10 megacycles per second. Thus, the previously re- ported linear function for the shear absorption coeffi- cient in Solenhofen limestone (Peselnick and Zietz, 1959), (15:5.0X10'7 (f) db per cm, must be modified to express the dependence of internal friction for the extended frequency range. The exponential function, «5:13.125 X 10F8 (f) “’85 db per cm, was chosen, and the agreement is within experimental error (see figs. 182.1 and 182.2). It should be noted that the newer exponen- tial function is very close to a linear function in the frequency range from 3 to 10 megacycles per second, the exponent being nearly equal to one. More data are required to complete the spectrum; frequencies higher than 107 are required to show Where scattering losses become predominant while lower fre- quencies are of interest to define carefully the loss function. The shear velocity as calculated from the rigidity at 3.59 cycles per second is the same as the velocity de- termined in the megacycle frequency range within the experimental uncertainty of 4 percent, at 25° C and at atmospheric pressure. A relaxation process might have GEOLOGICAL SURVEY RESEARCH 1960—SI—IORT PAPERS IN THE GEOLOGICAL SCIENCES been suspected as a result of viscous behavior of the grain boundaries (Ké, 1947), since grain boundary losses were found to be prevalent in Solenhofen lime- stone (Peselnick and Zietz, 1959). Any difference be- tween the relaxed and unrelaxed velocities would nec- essarily be less than 4 percent had such a process taken place between 3.59 cycles per second and 10 megacycles per second. If it is assumed that no relaxation mech- anisms exist in this frequency range, it is reasonable that the elastic moduli at high and low frequencies should agree closely, because their magnitudes are re- lated through intergranular and interatomic forces, both of which presumably do not change for small amplitude measurements. REFERENCES Born, W. T., 1941, The attenuation constant of earth materials: Geophysics, v. 6, p. 140. Ké, T. 8., 1947, Experimental evidence of the viscous behavior of grain boundaries in metals: Phys. Rev., v. 54, p. 293. Peselnick, L., and Zietz, I., 1959, Internal friction of fine- grained limestones at ultrasonic frequencies: Geophysics, v. 24, p. 285-296. 183. PHYSICAL PROPERTIES OF TUFFS OF THE OAK SPRING FORMATION, NEVADA By GEORGE V. KELLER, Denver, 0010. Work done in cooperation with the US. Atomic Energy Commission The US. Geological Survey has made intensive physical properties studies in support of the Atomic Energy Commission’s underground weapons test pro- gram at the Nevada Test Site. Most of the under- ground nuclear explosions in the 1 to 20 kiloton range have been detonated in the tufl's of the Oak Spring for- mation of Tertiary age. The underground test area is located in a mesa at the northwest corner of the Nevada Test Site, approximately 55 miles north of Mercury, Nev. Near the test chambers, the tuffs are about 2,000 feet thick. All are rhyolitic to quartz latitic in composi- tion (Wilcox, 1959). The tuffs may be subdivided into three groups on the basis of texture: bedded tufl‘, friable tufi', and welded tufi'. The bedded tuffs are dis- tinguishable from the friable tufl’s by their greater coherency. The chemical difference between bedded and friable tuffs is small, except for a greater content of water in the bedded tuffs. In the friable tuifs, the conversion of glass fragments to zeolite is not so exten- sive as in the bedded tufts, and only a thin rind of zeo- lite surrounds the glass fragments, so the rock is only weakly cemented and crumbles readily. The welded tuifs do not differ from the other units significantly in bulk chemical composition, and generally the lower parts of welded units grade into bedded and friable tuff. Samples for testing were obtained from several core holes drilled near the test chambers and from under— ground workings. Properties studied included textural properties, such as porosity, density, permeability and water content; strength and elastic properties, includ- ing acoustic velocities; thermal properties, including conductivity, enthalpy and entropy; and electrical properties. GEOPHYSICS TABLE 183.1.—Summary of physical properties of volcanic tufi‘s from the Oak Spring formation B397 Permeability water 2 Permeability air 2 Bulk density dry 1 Grain or powder (millidareys) (millidarcys) Textural subdivision Porosity 1 (g per em3) (g per cm3) density (g per cma) Average Range Average Range Bedded tuffs _________________ 0. 388:1;0 070 1. 5010. 16 2. 44i0. 11 0. 040 0. 00076—17 0. 90 0. 07 —39 Bedded tufis (pumiceous) ______ . 402:1: . 126 1. 37i0. 30 2. 28:1:0. 12 11. 5 3. 7 —61 21 4. 1 —75 Friable tufls ________ ' _________ . 355i . 138 1. 50i0. 35 2. 33:1:0. 24 1. 4 0. 084 —27 6. 0 0. 95 —41 Welded tuffs _________________ . 141 j; . 089 2. 1810. 23 2. 55:|:0. 09 . 33 0. 00092—58 0. 66 0. 022—58 1 Ranges expressed are one standard deviation. 2 Ranges expressed are the complete range of observed values. TEXTURAL PROPERTIES The porosities, densities and permeabilities measured on drill cores from the tuffs in the Oak Spring are sum- marized in table 183.1. Porosities were determined by measuring the volume of water required to saturate samples, so the values presented in table 183.1 represent interconnected pore volumes. Grain density measure- ments indicate that there is almost no “blind” or un- saturable porosity in the wit. The porosities are very high. Many hundreds of water—content determinations have been made on sam- ples obtained in their natural state from the mine workings, and in almost every determination the rocks have been found to be almost completely saturated with water. Almost complete saturation with water is found in rocks several hundred feet above the permanent water table. The water is held by impermeable beds in perched water tables and by capillarity in fine pores in rock. STRENGTH AND ELASTIC PROPERTIES Tensile and compressive strengths were determined for several samples of bedded and welded tufl's at the Geological Survey laboratory, and by the Applied Physics Laboratory of the US. Bureau of Mines (Robertson, 1959). No samples of friable tuff were ob- tained for strength tests, because the strength was too low to permit coring of a long enough specimen. Av— erage uniaxial tensile and compressiVe strengths under atmospheric confining pressure, are listed in table 183.2. Values of compressive strength are about 25,000 pounds per square inch (psi) for the welded tuff and about 5,000 psi for the bedded tufl'. As might be ex- pected, the compressive strengths of both types of tuif are much higher than the tensile strengths. The tensile strength, under atmospheric confining pressure, is about 500 psi for welded tuif and about 200 psi for bedded tufl'. Elastic moduli given in table 183.2 were determined by the Bureau of Mines by measuring the resonant fre- quencies of 2-inch samples excited in longitudinal and torsional modes, and also from the slope of the stress- strain curves obtained during static load tests. Shear and dilatational velocities given in table 183.2 were measured in small samples of tuff using an ultra- sonic pulse technique at a frequency of 400 kilocycles per second (Peselnick, 1959). Dilatational velocities were also measured at confining pressures up to 450 psi and it was found that velocity of acoustic waves was in- creased 50 to 100 percent over the value at atmospheric confining pressure for friable tufl's, 10 to 20 percent for bedded tufi's, and not appreciably in welded samples. A great amount of information was obtained con- cerning acoustic velocities in place by refraction seismic surveys in drill holes and in tunnels and by acoustic logging of drill holes. It is likely that the acoustic velocity of rock in place is determined to a large extent by fracturing in the rock and by the confining pressure. This is particularly well shown by the acoustic log in the right column of figure 183.1. A linear increase in velocity with depth is apparent, probably representing the effect of increasing overburden pressure. The rock between depths of 1.050 and 1,120 feet through which an exceptionally low velocity is recorded is welded tufi', which the laboratory measurements showed to haye a high inherent velocity. The low recorded velocity is apparently caused by dry fractures. THERMAL PROPERTIES The enthalpy, or heat required to melt the tufl’ of the Oak Spring formation and to raise the liquid to a tem- perature of 1,500°C, given in table 183.3, was calculated from modal analyses by F. C. Kracek (1959) of the Geological Survey. Variations in total enthalpy de- pend on the mineral composition, particularly the amount of water in the rock, because water absorbs the highest amount of energy per unit mass. Thermal conductivities were measured at room tem- peratures on several hundred drill cores of wit. The conventional divided-bar technique was used. Meas- urements were made both with the samples dry and sat— urated with water. The data (fig. 183.2) may be B398 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 183.2.—Summary of strengths and elastic properties for tufi of the Oak Spring formation [All measurements were made on dry samples. Velocity data for tufi in its natural state are best obtained from velocity logs (flg. 183.1).] Bedded tufi (psi) Welded tufl (psi) Test Avg. Range Avg. Range Uniaxial strength tests Tensile ____________________________________________________ 120 85—165 330 165—480 Compressive _______________________________________________ 4.9)(103 3.4—8.7 21.1>< 103 6.8—29.1 Dynamic tests Young’s modulus ___________________________________________ 0.61 X 10" 0.40—1.07 1.48X 10° 1.22—2.01 Rigidity modulus ___________________________________________ 0.30 ><106 0.20—0.49 0.59 X 106 0.40—0.77 Poisson’s ratio ___________________________________________________________ 0.06—0.09 ______________ 0.02—0.53 Static tension tests Young’s moclulus_._________________v._.._v_l_l_,T ___________ 0.71X10" 0.40-1.60 1.69X106 0.86—1.75 Rigidity modulus ___________________________________________ 0.25 X10“ 0.19—0.32 0.78 ><10'3 0.40—0.82 Poisson’s ratio _____________________________________________ 0.03 0.02—0.04 0.08 005—0. 15 Acoustic velocities Bedded tuff (fps) Friable tufi (fps) Welded tufi (fps) Test Avg. Range Avg. Range _ Avg. Range Dilatational _______________________________ 5700 2750—10,500 5690 3250—8750 9750 9100—11,000 Shear ___________________________________ 3300 2000—6200 2900 1700—5500 6360 5600—7150 TABLE 183.3.——Modes and calculated enthalpy for ta)?r of the Oak Spring formation Welded tufi Bedded tufi Constituent Enthalpy Enthalpy Percent- contribution Percent- contribution age by (cal per g age by (cal per g weight of rock) weight of rock) Quartz _______________________________ 35 141.9 19 77.0 Orthoclase ........................... 23 111. 9 10 48. 6 Alblte ............................... 25 119. 3 10 47. 6 Anorthlte ____________________________ 3 15. 0 2 10.0 Zeolite ..................................................... 25 146. 0 Montmorillonite _____________________ 5 38. 0 9 68. 4 N ontronite _________________________________________________ 1 6. 5 Micas ______________________________________________________ l 5.8 Magnetite ___________________________ 1 2. 5 1 2. 5 Water ............................... 8 115. 0 20 288. 0 Total ____________________________________ 543. 6 .......... 705. 4 extrapolated to zero porosity to obtain an estimate of the conductivity of the mineral grains. Extrapolating the curve for measurements on dry samples gives a thermal conductivity of 2.67 cgs units, and for wet samples, 3.09 cgs units. The extrapolated value for dry samples is probably low because of the effects of boundaries between grains. Such boundary resistances should be less in wet samples. The thermal conductiv- ity may be expressed in terms of porosity by an em— pirical equation: ¢r,1=2.67(1—¢)1-34 a,,,=3.09(1—¢)1-84+ (1) 0.088 (2) (1—¢)4.8 where an and aw are the dry and wet conductivities, re- spectively, in millicalories per centimeter second degree, and 4> is the pore fraction. ELECTRICAL PROPERTIES The electrical properties of the mil in the Oak Spring formation were studied to determine water content of the rock in place. Direct determinations of water con- tent are difficult because drilling water may contami- nate drill—core samples, and tunnel-wall samples may be dried by circulating air. Water content may be esti- mated from electrical resistivity measurements, if the ground water resistivity is known. Measurements of electrical properties consisted of two types; in-place measurement of resistivities in drill holes and tunnels, GEOPHYSICS SELF POTENTIAL RESISTIVITY, IN OHM—METERS (16 IN. NORMAL) DEPTH, — + IN FEET 50mv "I I'- 0 NEUTRON 50 100 150 200 250 300 350 4OOCPH 5000 B399 ACOUSTIC VELOCITY, IN FEET PER SECOND 7000 10,000 15,000 400 ( its 500 \ 2 600 700 800 Friable tuff 900 1000 Mmmm A 1100 Welded tuff A A 1200 — 1 300 1400 — 1500 WWMM 1600 Bedded tuff 1r A ”www‘” 1700 E 1800 1900 g :— a «i 2000 \- Limestone FIGURE 183.1.—Eleetric, neutron, and acoustic velocity logs of the Oak Spring formation in a drill hole near the underground test chamber. and laboratory studies of the correlation between water content and electrical properties. Resistivity measurements were made by routine methods on core samples resaturated in the laboratory with salt solutions of known concentrations (fig. 183.3). The relationship may be represented by an empirical equation: p=1.5pr_2'2 (3) where p is the resistivity of the rock, in ohm-meters, pm is the resistivity of the water saturating the rock and W is the volume fraction of water in the rock. Rock resistivities were measured for about 100 samples of tuff obtained in the natural state by under— ground air drilling. These data were used with equa- tion 3 to determine the resistivity of the pore water in the rock. The average value so determined was 1.6 B400 1.0 (22) 0'9 (22> ‘\ 08 \(21) - . o 5 (22K \ (8) as. o. W) \ E i (18) N a 0.6 "5 wiet Dry samples samples 0.5 -3 -3 -3 —3 73 2.5x10 2.0x10 1.5x10 1.2x10 1.0x10 THERMAL CONDUCTIVITY, IN CALORIES PER SECOND PER CENTIMETER-DEGREE-CENTIGRADE FIGURE 183.2.——Empirical correlation between average values of thermal conductivity and porosity for groups of tufit‘ samples. The number of samples in each group is shown in parentheses. ohm-meters, with a total range in measurements from 1.04 to 2.13 ohm-meters. Interpretation of the in-place resistivity measure- ments on the basis of equation 3 shows that the tufl' in the Oak Spring formation in the area of the under- ground tests is water-saturated at depths of more than 200 feet, but that fractures are not saturated, even at a depth of 900 feet. SUMMARY The amount of water in the rock was found to be the most important single factor in determining the physical properties of the tufl' in Oak Spring forma- tion. Variations in thermal conductivity, bulk density, enthalpy, and electrical properties of the tuff are all determined by the water content, directly or indirectly. Variations in strength and acoustic velocity are prob- ably controlled by the fractures as well as by water con- tent. The ability of the tufl' to transmit fluids is prob— ably more dependent upon fractures than upon permeability, because the permeability of unfractured samples is lOW. ACKNOWLEDGMENTS Much of the information in this report has been abstracted from unpublished reports by other Survey investigators. In particular, information about strengths was obtained from work by E. C. Robertson; about enthalpy, from F. C. Kracek; about acoustic velocities, from Louis Peselnick, and about mineralogy, from R. E. Wilcox. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES \ \\ \ \ \Q, \N\ 0.60 ‘E \ (15) 0.50 \ l (4) 040 W13) ' 17 E 0.35 fi\( ) E 030 W22) z - (32) — 0 YO—‘\ 0 0.25 \\ ‘\ a \ <3: 0.20 IL Jl\ _, _1.27(:0.o7)\ g r=45(:o.2)w \ 9 I— O < E 0.10 . . EXPLANATION (4) Number of samples per point 0—0—1 Average valueistandard deviation 0044 5 6 7 8 10 15 20 25 3o 50 ROCK RESISTIVITY PER WATER RESISTIVITY FIGURE 183.3—Correlation between average values of resistivity and porosity for samples of tuft'. REFERENCES Keller, G. V., 1959, Chap. 6, Thermal conductivity of the Oak Spring tuff, in Diment, W. H., and others, Properties of Oak Spring formation in area 12 at the Nevada Test Site: U.S. Geol. Survey TIM-672, open-file report. Kracek, F. 0., 1959, Chap. 7, Heat required to melt Oak Spring tuft from Nevada Test Site, and to raise the liquid to 1500°C and 2000°O, m Diment, W. H., and others, Prop- erties of Oak Spring formation in area 12 at the Nevada Test Site: U.S. Geol. Survey TIM—672, open-file report. Peselnick, Louis, 1959, Chap. 9, Velocity measurements on samples of Oak Spring tuft, m Diment, W. H., and others, Properties of Oak Spring formation in area 12 at the Nevada Test Site: U.S. Geol. Survey TEI-672, open-file report. Robertson, E. 0., 1959, Chap. 10, Strength and elastic properties of Oak Spring tuft, in Diment, W. H., and others, Prop- erties of Oak Spring formation in area 12 at the Nevada Test Site: U.S. Geol. Survey TEI—672, open-file report. Wilcox, R. E., 1959, Chap. 2, Petrography and chemistry of the Oak Spring formation, in Diment, W. H., and others, Prop- erties of Oak Spring formation in area 12 at the Nevada Test Site: U.S. Geol. Survey TIM—672, open-file report. GEOPHYSICS B401 184. MAGNETIC SUSCEPTIBILITY AND THERMOLUMINESCENCE OF CALCITE By FRANK E. SENFTLE, ARTHUR THORPE, and FRANCIS J. FLANAGAN, Washington, DC. Work done in cooperation with the US. Atomic Energy Commission It is well known that both magnetic susceptibility and thermoluminescence are related to trapped electrons in a crystal lattice. It is therefore of interest to ex- amine the magnetic effects in crystals known to be thermoluminescent. Thermo'luminescent light is produced when a crystal is heated, thereby causing a release of trapped electrons from one excited state to some other lower energy state. Electrons displaced by ionizing radiation can be trapped by impurity centers or at so-called F—centers in the crystal. If an ionic crystal has impurity ions held in— terstitially, it is possible for such an ion to trap an elec- tron in its field. On heating, the electron is released and moves to a region in which de-excitation can occur. The result is a drop in energy and the emission of light. Alternately, if an ionic crystal is irradiated, electrons are also released from the anions and diffuse through the crystal until they are trapped by an anion vacancy site. The trapped electron is known as an F-center and is capable of absorbing visible light of a given fre- quency, thus producing a characteristic color. When the crystal is subsequently heated, the electron will be released from the F-center and will certainly re- combine with a neutral atom or a positive hole. As be- fore, the recombination results in the emission of thermoluminescent light (Friedman and Glover, 1952). Both of the above mechanisms of thermoluminescence involve electrons which may be unpaired with neighbor— ing electrons, that is, these electrons will have a result— ant spin and will thus contribute to the magnetic sus- ceptibility of the crystal (Jensen, 1939; Heer and Ranch, 1953). Therefore if the number of electrons involved is large enough, there should be a noticeable change in the magnetic susceptibility of an irradiated crystal after heating. To determine whether the an- nealing of electron traps as observed in thermolumines- cence phenomena would also cause perceptible changes in the magnetic susceptibilty, some exploratory experi- ments were made. THEORY AND EXPERIMENTAL RESULTS Let us consider the contribution of these crystal de- fects to the magnetic susceptibility. If an electron is trapped at such an impurity site or an F-center, the spin only will contribute to the magnetic susceptibility as the orbital angular momentum will be quenched by the interatomic forces in the lattice. The magnetic sus— ceptibility per gram will be given by Effigaswfln (1) where n is the number of defect centers, B is the unit Bohr magneton, K is Boltzmann’s constant, T is abso- lute temperature, M is the molecular weight, and S is the spin quantum number. As pointed out by McClel— land (1953), depending on whether the impurity is a doubly or singly charged ion or a neutral atom, the value of 8 may be 0, 7:7, or 1. An F—center, of course, will have a spin of 717. For the preliminary experiments, a specimen of nat- ural pink calcite was chosen. The pink color is due to manganese impurity and hence, if it is interstital, it will be a bivalent ion or a neutral atom. If it is a biva- lent ion, the spin will be zero, and it will not contribute to the susceptibility; if it is a neutral atom, the spin will be 1. Thus the susceptibility of n such manganese atoms per gram can be shown from equation (1) to be x=0.556><10-28n (2) Assuming a manganese content of 8 percent, which is about the amount necessary to produce a light pink calcite, there would be some 8.7 x 10 2° impurity centers per gram if they were all interstital. The susceptibility due to these would be 0.048 x 10‘6 emu per gram from equation (2). Medlin (1959) has 'shown that manganese produces thermoluminescent peaks at 77° C. and 197° C. in cal- cite. The low temperature peak Will have been an- nealed out by normal earth temperatures, but the higher peak will remain. The specimen was therefore heated to several temperatures on either side of the 197° C. and the magnetic susceptibility measured after each heating cycle, using the quartz helical spring balance (Senftle and others, 1958). The results in table 184.1 indicate a substantial change in susceptibility and of the same order as predicted from the rough calcula- tion, that is, 0.055 X 10'6 emu/gram. In a second experiment, the blue and green portions of calcite from Las Cruces, New Mexico were separated B402 TABLE 184.1.——Magnetic susceptibility of pink calcite Time and temperature Magnetic susceptibility (emu/gram) Unheated ________________ 0.19>< 10—6 60°C fox 30 min __________ .19><10‘6 145°C fot 60 min ......... .178><10‘6 AX=0.055><10‘6 244°C for 60 min _________ .135><10‘6 by hand-picking. The crystals were first heated to about 500° C. in an inert atmosphere to anneal out any naturally trapped electrons. They were then X-rayed for '10 minutes at 50 kv to refill the electron traps. The subsequent magnetic susceptibility data are shown in table 184.2. Why the susceptibility dropped in one case and not in the other is not obvious, but the reason may be related to the type of impurity content. Upon reheating to 500° C., the electron traps were again an— nealed out, and there was an accompanying drop in the magnetic susceptibility. Similar measurement on other calcite specimens generally showed analogous decreases after the thermoluminescent peaks were annealed out. TABLE 184.2«Magnetic susceptibility of calcite from Las Cruces, N. M ex. Magnetic susceptibility (emu/gram) Treatment Blue Green Unheated calcite ___________ —0. 41X 10—6 —0. 31 X 10—6 Heated to 500° C and X-rayed ________________ —0. 29 ><10—6 —0. 91 X 10“6 Same sample, reheated to 500° C _________________ —0. 07><10—6 Sample lost To investigate the effect of F -centersvon the mag- netic susceptibility, a clear crystal of a natural sample of calcite was chosen. This specimen contained less impurities than the previous specimens and hence would have few trapped electrons associated with im- purities. It was irradiated with X-rays until it was colored a deep purple due to F—center formation. The magnetic susceptibility before and after irradiation was almost'identical. It is not clear why a change in the susceptibility did not occur. Although the crystal was purple due to X-radiation, it may not have had a suflicient number of F -centers formed to produce a measureable change. A barely perceptible coloration by the unaided eye is equivalent to about 1015 F -centers and from the density of coloration in the above crystals one would estimate a minimum of 1018 or 1019 centers. For a spin of 1A;, the magnetic susceptibility per gram due to F-oenter formation can be shown to be x=0.209 x 10-2811 (3) GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES Thus 1019 F—centers per gram would yield a magnetic susceptibility of 0.0002X10'6 emu/gram, a value too low to be detected. To obtain additional data on the effect, the suscepti- bility of a relatively fresh nonmetamict zircon, dis- tinctly purple in color, was measured. It was then heated to 600° C. in a helium atmosphere for one hour, after which the F—centers were completely bleached, leaving clear granular sugarlike crystals of zircon. There was, however, no difference between the mag- netic susceptibility before and after heating. CONCLUSIONS These experiments indicate that natural crystals, such as calcite, which are thermoluminescent owing to im- purity content, have enough electron traps to signifi- cantly affect the magnetic susceptibility. On the other hand, crystals colored by F-center formation will prob— ably not have enough traps, unless they have received a large radiation dose to perceptibly alter the magnetic properties. While thermoluminescence “glow curves” are only qualitative, thermomagnetic curves can prob- ably be determined for natural minerals from which the actual number of interstitial impurity atoms can be calculated. Comparison of the experimental curve with that calculated from a knowledge of the chemical impurity data might shed some light on the past thermal history of the mineral. Also as thermolumi- nescence is used for radiation dosimetry, it may also be useful to use magnetic susceptibility to measure radia- tion doses. REFERENCES Friedman, H., and Glover, C. P., 1952, Radiosensitivity of alkali halide crystals: N ucleonics, v. 10, p. 24—29. Heer, C. V., and Rauch, J., 1953, Magnetic susceptibility of colored potassium chloride from 1°K to 300°K: Phys. Rev., v. 90, p. 530. Jensen, P., 1939, Die magnetisch Suszeptibilitiit von Kalum Bromidkristallen mit Farbzentven: Ann. Physik, v. 34, p. 161. McClelland, J. D., 1953, Effect of neutron bombardment upon the magnetic susceptibility of various oxides: US. Atomic Energy Commission, NAA—SR—263. Medlin, W. L., 1959, Thermoluminescent properties of calcite: J our. Chem. PhySics, v.30, p. 451—458. Senftle, F. E., Lee, M. D., Monkewiez, A. A., Mayo, J. U., and Pankey, T., 1958, Quartz helix magnetic susceptibility bal- ance using the Curie-Gheneveau principle: Rev. Sci. Instru- ' ments, v. 29, p. 429—432. GEOPHYSICS 185. B403 SALT FEATURES THAT SIMULATE GROUND PATTERNS FORMED IN COLD CLIMATES By CHARLES B. HUNT and A. L. WASHBURN, Denver, Colo., and University of Canterbury, Christchurch, New Zealand Polar, subpolar, and alpine regions are characterized by ground patterns consisting of circles, nets, polygons, steps, and stripes. The mechanisms that produce these ground patterns are not fully understood, but frost action is clearly a major factor. Very similar ground patterns have recently been studied in Death Valley, Calif, where freezing temperatures are seldom reached and the patterns must be attributed to deposi- tion, solution, and cracking of salts. Sorted polygons resembling those associated with frost action have developed where there is a layer of rock salt a few inches below the surface (fig. 185.1A). The salt, commonly about 6 inches thick, is cracked polygonally, and the positions of the cracks at the sur- face are marked by shallow troughs in which stones have collected. . N onsorted polygonal patterns have formed also above some gypsum deposits, where a surface layer of loose grains of gypsum 1 to 6 inches thick is underlain by a firm layer of anhydrite 3 to 6 inches thick (fig. 185.13 ) . The anhydrite is broken by polygonal cracks, which widen into troughs at the surface. Other nonsorted polygons in Death Valley, ap- parently due to desiccation or thermal cracking, are out- lined by wedges of salt and resemble the ice-wedge polygons found in cold climates. The gravel fans around the sides of Death Valley are terraced with sorted steps, each consisting of a lo- bate riser of stones and a tread of finer material (fig. 185.10). These are very similar to the terracettes ob- served in cold climates. In Death Valley the fine- grained material of the treads contains up to 10 times more water-soluble salt (up to 5 percent by volume) than the stable ground around the steps, but we cannot be sure whether the steps developed because of the salt or the salt accumulated because of the steps. Rows of pegs across two steps show that no significant move- ment has occurred in three years, despite several soak- ing rains. These Death Valley terracettes appear to be fossil features that date from a past climatic condition, and that are developing very slowly if at all under the present climate. Other kinds of ground patterns noted in Death Val- ley that resemble those in cold climates include sorted circles, sorted and nonsorted nets, and sorted stripes. A Tr ' ‘ Stones in interior of oughs containing stones polygons rest on pedestals; some ., e}: I ’— ’ ‘1 1’0”- :4» \ . _ , - a - stand on edg 5r ’ (1/719 / , / ’35/ , >5}; .-.. v [[5 ii’zb—oxs , ”2377. ;7\~ 5A _1, .5 4-7 a / . z ' x . 'r ’ \- . , \ i, 49/ / n / ) / v ’91” ’o ’ (:7 a v' a O \ 0 O \ I, o / gfl / ock salt / Gypsiferous / and stoney silt Wedgeshaped o 6 FEET mass of hardened gypsum above open crack in rock salt Surface layer of loose granular B gypsum with secondary desiccation cracks ending downward at caprock Primary cracks 3cm..- segment; z : ~ ‘ '- " K9? batsenite) -. r ~‘ ‘/ \u...~ v ' , Crumbly, porous gypsum . 0 12 INCHES Pavement of small pebbles C on sche °f tread ‘ Spots of salt efflorescence ‘OQB \ .. -. : \ ~92: fporoas. ‘véh ‘~-‘-,’:~$\t ‘ Damp layer ‘ ~- Cement°ed layer» -,—.: “ \ a. Riser, with embankment - of stones FIGURE 185.1.—Sketch and cross sections of ground patterns in Death Valley. .4, Diagram ofsorted polygons above layer of rock salrt; B, cross section of nonsorted polygons in anhy— drite caprock on gypsum; 0, cross section of sorted step (terracette). 6% B404 186. GEOLOGICAL SURVEY RESEARCH l960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES THERMAL CONTRACTION CRACKS AND ICE WEDGES IN PERMAFROST By ARTHUR H. LACHENBRUCH, Menlo Park, Calif. Ice wedges are relatively clear, vertical wedge-shaped masses of ice which taper downward into permafrost to depths of several meters (fig. 186.1). They intersect every 20 meters or so to produce a honeycomb of ice, the trace of which produces a polygonal pattern on the tundra surface. Although ice wedges have been discussed widely by geologists for more than a century, and their difl’erential thawing has long plagued engineers, their origin and significance are still imperfectly understood. It is now generally accepted that ice wedges form in response to thermal tension set up in the frozen ground by its tendency to contract during the cold Artic winter (see, for example, Popov, 1955). Thermal contraction cracks, formed in winter, penetrate permafrost to depths as great as 5 to 10 meters (fig. 186.2A). They are sealed by the freezing of surface water which enters when the surface thaws in early summer. The result- ing vertical ice vein (fig. 186.2B) is a zone of weakness subject to recurrent fracture and growth by repetition of the cycle in succeeding winters (fig. 186.20). The thickened veins or “ice wedges,” (fig. 186.2D) underlie the boundaries of the surface polygons and their dif- ferential thawing produces the shallow troughs by which ice-wedge polygons are usually delineated on the tundra surface. The size and configuration of the polygons are con— trolled to a large measure by the depth and mode of propagation of the thermal contraction cracks, and these in turn depend upon the nature of the thermally induced volume change and the rheological properties of the permafrost. In an attempt to gain a better understanding of how these factors interrelate to con— trol ice-wedge polygons, and the related phenomena of mud-crack polygons and basalt-joint polygons, a theoretical study was carried out. A qualitative sum- mary of those findings pertinent to the evolution of a single crack is outlined below. In the companion ar- ticle (187), multiple cracking and the evolution of polygonal form will be discussed. Numerical and analytical details of the study will be elaborated else- where. RELATION BETWEEN TEMPERATURE AND STRESS IN THE UNFRACTURED MEDIUM The stresses that lead to fracture of the frozen ground must be accounted for by a visco-elastic response to FIGURE 186.1—Ice wedge in permafrost (photo by Troy L. Péwé) thermal contraction, not an elastic one; for a formal calculation shows that thermal stresses developed in an elastic medium under the thermal regime of permafrost would be too large by an order of magnitude to satisfy requirements of the frost-crack theory. A simple linear relation between rate of cooling and stress is also un- satisfactory for it predicts that the stress falls off too rapidly with depth to account for observed details of the fracture process. MW. 4. r ‘: 5 FROZEN i GEOPHYSICS ACTIVE LAYER THAWED PERMA- FROST ‘ n . ‘T . ~_._ '.._-. - . J-J; ..'_'_"-_'._ .. '_'.-.r.‘_-_. w ~ [\— ~ F‘— _\ /‘—— A, N A /\ ICE A A w W m ~/\, .....__ _ .. _ .. — __._______________4 .________ _________‘ ______.___________4 ._________ _._______{ _._______._._..—_._____‘ .________. ________ _____________________________ __ _. .__..— _-.._ _- ___.——4 ._ _ _-_._. _..._ ___._. _. _ ._ -._._ _.._. _.__. ACTIVE LAYER —__W__ PERMA- FROST __J 100TH WINTER C 100TH FALL D FIGURE 186.2—The evolution of an ice wedge in permafrost. B406 GEOLOGICAL A nonlinear relation between the principal com— ponents of distortional stress (P4) and distortional strain (E,) of the form 1 E. Q a " dt _" dt yields stress distributions compatible with field in- , i=1,2,3 (1) ferences regarding the fracture process. Numerical values required for the exponent n, the elastic shear modulus ,u, and the viscoelastic parameter 7; are consist— ent with pertinent laboratory results. Assuming the nondistortional component of deforma- tion to be elastic, horizontal stress 1' (m, t) and ground temperature 9 (w, t) are given at any depth, m, and any time, t, by the nonlinear differential equation dr Y 1 n_—Yde a? —1—v3n_2;,T——1—ud—t (2) Where Y and v are Young’s modulus and Poisson’s ra- tio respectively. Application of (2) indicates that rapid cooling is as important as low temperature in producing the large stresses that crack frozen ground. MECHANICS OF THE FRACTURE PROCESS AND PREDICTION OF CRACK DEPTH When the tension near the surface is approaching the tensile strength, stresses at depths on the order of 10 feet and more are generally compressive owing to the combined effects of the time lag in the penetration of the seasonal thermal wave, and compression caused by the weight of overburden. When the tensile strength is exceeded near the surface, a tension crack forms and propagates downward. The depth at which it stops depends primarily upon the opposing effect of com- SURVEY RESEARCH lQfiO—SHORT PAPERS IN THE GEOLOGICAL SCIENCES pression at depth, and the dissipation of strain energy by plastic deformation near the leading edge of the crack. Theoretical calculations show that if the me- dium is relatively nonplastic, the tension crack will penetrate deep into the compressional zone; if not, it will stop near the neutral horizon at the base of the sur- ficial tensile zone. Judging from experimental results reported by_Irwin (1958) for other materials, it is likely that initial crack depths in most solidly frozen earth materials can be approximated satisfactorily by neglecting the plastic dissipation. Thus it is probable that most contraction cracks in permafrost penetrate initially much deeper than the tension that produced them, with more than half of the crack lying in strata that were in compression at the time of cracking. Subsequent viscOelastic effects might be expected to produce a slow closing of part of the crack from the bottom. The crack depth is dependent on the actual stress distribution at the time of cracking. Other things be— ing equal, deeper cooling generally produces deeper tension and deeper cracks. The depth of a crack can, of course, change as the stress regime changes with the progressing season. Numerical calculations based upon temperatures measured in Alaskan permafrost, equa- tion (2), and a mathematical formulation of the pres- ent considerations of fracture mechanics yield results consistent with the observed depth, frequency, and mode of cracking. REFERENCES Irwin, G. R., 1958, Fracture, in Handbuch der Physik; v. 6, Springer-Verlag, p. 551—590. Popov, A. I., 1955, The origin and evolution of fossil ice: Inst. Merzlotovedeniya, Akad. Nauk SSSR, no. 2, p. 5—25. 187. CONTRACTION-CRACK POLYGONS By ARTHUR H. LACHE‘NBRUCH, Menlo Park, Calif. “Contraction-crack polygons” is the name applied to a reticulate system of intersecting contraction cracks on the surface of a body. They form in response to tension resulting from decrease in volume, usually caused by cooling or dessication. They occur in di- verse media on a variety of scales ranging from a few millimeters in cooling ceramic ware to 50 meters in permafrost. They include mud cracks, columnar- basalt joints and shrinkage cracks in concrete. Some mechanical considerations arising from a theoretical study of ice-wedge polygons are applied briefly to the general problem of contraction-crack polygons in the qualitative summary that follows. THE “ZONE OF STRESS RELIEF” AND POLYGON DIAMETERS When tension (To), caused by dessication or thermal contraction exceeds the tensile strength at the surface GEOPHYSICS HORIZONTAL STRESS HORlZONTAL s RESS o FFERENCE , -Ty) _ V x FIGURE 187.1.—Stress at ground surface near an isolated con- traction crack. ro=uniform horizontal tension before fracture. n=component of tension parallel to crack after fracture. ry=component of tension perpendicular to crack after fracture. (x=0), a crack forms and penetrates the medium to some finite depth (x=b), determined by factors dis- cussed in the previous article. The horizontal com- ponent of stress, Ty, in the direction normal to the crack vanishes at the crack walls (y=0), but it in- creases asymptotically to the precracking value (r0) at large horizontal distance from the crack (y> >b) (see fig. 187.1). Each crack is therefore surrounded by a band in which the cracking has caused appreciable re- duction of horizontal tension: the “zone of stress-re- lief.” The stress configuration in the zone of stress- relief depends primarily upon the stress distribution that would exist in the medium if it were not fractured, i.e. upon the thermal stress. It has been calculated approximately by applying Muskhelishvili’s method of complex stress functions to the problem of a crack in a semi-infinite elastic medium with a nonuniform stress field. The thermal stress upon which this solution is superimposed is calculated from a visco-elastic relation (like equation 2, p. B406) and hence most inelastic effects are accounted for. (The problem of nonlinearity is handled separately.) In general, increased depth of thermal tension and (or) increased crack-depth re- sults in wider zones of stress-relief, and hence more widely spaced cracks and larger polygons. Applica- tion of the theory to ice—wedge polygons yield numerical results compatible with observed polygon diameters. B407 MULTIPLE CRACKING AND EVOLUTION OF POLYGONAL FORM The component of thermal tension (r,) at the ground surface in the direction parallel to the crack is relieved only slightly by the cracking, and hence large hori— zontal stress difl'erences (rz—ry) occur within the zone of stress relief (fig. 187.1). A second crack entering this zone of stress relief tends to aline itself perpen- dicular to the greatest tension, rz, and hence tends to intersect the first crack at right angles. Conversely the occurrence of an orthogonal intersection generally im- plies that one of the. cracks predated the other. This suggests a useful scheme for classifying contraction- crack polygons as follows: ORTHOGONAL SYSTEMS Orthogonal systems of polygons are those that have a preponderance of orthogonal intersections. They are evidently characteristic of somewhat inhomogene- ous or plastic media in which the stress builds up grad- ually, with cracks forming first at loci of low strength or high stress concentration. With increasing thermal (or dessication) stress, polygons are subdivided by cracks initiating near polygon centers. The polygons attain such a size that zones of stress-relief of neigh- boring cracks are superimposed at the polygon centers in such a way as to keep the stress there below the ten- sile strength. The polygon size at any time depends upon the nature of the applied stress and configuration of the zones of stress relief of individual cracks. The cracks do not all form simultaneously and hence each AW”? FIGURE 187.2.—Randon1 orthogonal ice-wedge polygons in perma- frost, 1 inch~100 yards in foreground. W. Greene.) (Photo by Gordon B408 new crack tends to join existing ones at orthogonal intersections. Orthogonal systems can be conveniently divided. into two subgroups: a. Random orthogonal systems in which the cracks have no preferred directional orientation (fig. 187.2). b. Oriented orthogonal systems in which the cracks have preferred directional orientation. Most oriented orthogonal systems in permafrost are probably caused by horizontal stress differences which are generated by horizontal thermal gradients near the edges of grad- ually receding bodies of water (for example, slowly draining lakes and shifting river channels). Under such conditions the induced polygonal system forms with one set of cracks parallel to the position of the water’s edge and the second set normal to it (fig. 187.3). Oriented orthogonal systems can also result from top- ographic effects or from anisotropy of horizontal ten- sile strength as in steeply dipping shales. v NONORTHOGONAL SYSTEMS Nonorthogonal systems of polygons are those that have a preponderance of tri—radial intersections, us- ually forming three obtuse angles of about 120°. It is suggested that they result from the uniform cooling of very homogeneous, relatively nonplastic media. J udg- FIGURE 187.3.—Oriented orthogonal ice-wedge polygons in per- mafrost, Alaskan Arctic Coastal Plain. Pattern generated on slip-off slopes by thermomechanical effect of migrating meanders. 1 inch~1,500 feet. GEOLOGICAL SURVEY RESEARCH 1960—- SHORT PAPERS IN THE GEOLOGICAL SCIENCES ing from experimental and theoretical results from the field of fracture mechanics, it is likely that under these conditions cracks propagate laterally until they reach a critical velocity (on the order of half that of elastic shear waves) and then branch at obtuse angles. The branches then accelerate to critical velocity and branch, and so on. Unlike in the orthogonal system, all ele- ments of a nonorthogonal intersection are generated Vir- tually simultaneously. SIMULTANEOUS BRANCHES SECONDARY CRACK CRACK a b FIGURE 187.4.—Comparison of nonorthogonal intersection (a) and an orthogonal intersection (b) at a convex bend in a primary fracture. Arrows indicate direction of propagation. When crack 'trace Widens (dotted lines), the two forms may be indistinguishable. Although many ice-wedge intersections appear to be of the nonorthogonal type, the surface expression of a wedge is so wide that it is generally difficult to distin- guish between a nonorthogonal intersection (fig. 187.4a) and an orthogonal intersection at a convexity in the primary fracture (fig. 187 .4b). From mechanical con- siderations it can be shown that if a curve exists in a primary fracture, its convex side is favored as a site of (orthogonal) intersection by a secondary fracture. It is therefore difl‘icult to determine with certainty whether any fracture systems in permafrost are nonorthogonal. It is worth noting, however, that ice-wedge polygons, which superficially at least seem to be nonorthogonal, occur commonly in the homogeneous sediments of rapidly drained lake basins. On the basis of the pres ent point of View such an environment, thermally and mechanically uniform, would favor nonorthogonal systems. THE CLASSIFICATION APPLIED TO OTHER TYPES OF CONTRACTION-CRACK POLYGONS Inasmuch as this geometric classification seems to have genetic significance, at least for ice-wedge poly- gons, it might be useful when applied to contraction- crack polygons in general. Crackle-finish ceramic ware generally displays a random orthogonal pattern, except locally where topography of the object (ash tray, vase, ' PRIMARY ' GEOPHYSICS FIGURE 187.5.—Nonorthogonal contraction-crack polygons in basal't, Devils Post Pile National Monument, Calif. by Gordon W. Greene.) ( Photo 6% B409 etc.) may produce an oriented orthogonal system. This is consistent with the observed fact that ceramic poly- gons evolve gradually. The classic occurrences of col- umnar basalt joints described in the literature seem to be of the nonorthogonal type; consistent with the re- quirements of thermal and mechanical homogeneity and low plasticity (fig. 187.5). Dessication polygons in mud and shrinkage polygons in concrete seem generally to be of the orthogonal type, although certain complications beyond the scope of this paper are introduced by their plastic behavior. Inas- much as cracks in these media are often irregular, they have many “convexities” at which orthogonal intersec- tions (fig. 187.4a) could be confused with nonorthogonal ones (fig. 187 Aeb) as the cracks widened. Laboratory ex- periments by the writer confirm that in general mud- cracks propagate slowly, do not branch, and form orthogonal intersections. This is consistent with the present point of view which calls for high propagation velocities and branching to produce nonorthogonal intersections. 188. CURVATURE OF N0.RMAL FAULTS IN THE BASIN AND RANGE PROVINCE OF THE WESTERN UNITED STATES By JAMES G. MOORE, Menlo Park, Calif. Work done in cooperation with the Nevada Bureau, of Mines Recently many new data have become available on details of the topography of the Basin and Range prov- ince. The new series of Army Map Service topographic maps provides almost complete coverage of the province at a scale of 1: 250,000 with a 200—foot contour interval. One of the most striking features that the maps show is the nonlinearity of the ranges. Many of the ranges are arcuate, the longer ranges being linked segments of arcs. The arcuate pattern of a range as a whole is be- lieved to reflect the arcuate pattern of the main bound— ing fault. ’ Many of the individual ranges of the Basin and Range province are tilted Cenozoic fault blocks (Davis, 1925; Mackin, 1960; Osmond, 1960). The geology of many ranges is still little understood, but geologic map- ping in recent years has yielded information on the direction of tilt of some of the ranges. The criteria by which the direction of Cenozoic tilt of ranges is deter- ‘mined are listed in order of decreasing reliability: (3.) 557753 0—60—27 general direction of dip of Cenozoic sedimentary and volcanic rocks, (b) distribution of rocks of different ages within'a range, (0) topographic asymmetry of a range, (d) dip of major Cenozoic normal faults, and (e) general dip and structure of pre-Tertiary strata. In addition, criteria which point to the asymmetry / (and hence direction of tilt) of the intermontane basins also provide data on the Cenozoic tilt of adjacent ranges. These criteria include topographic shape of basin surface as well as the topography of the buried bedrock surface determined by geophysical measure- ments, chiefly gravity surveys. An interesting relation appears to exist between the tilt of each range and its map plan. Many of the ranges exhibit an arcuate map pattern. Fairly simple tilted block mountains are made up of a single are which is generally from 10 to 30 miles long With a radius of curvature of 20 to 40 miles, and the ranges are generally tilted toward the convex side of the arc. B410 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES TABLE 188.1.—Fault block ranges in the Basin and Range province showing direction of curvature and probable Cenozoic tilt. of better known ranges have been selected Fifty-five Range Army Map Service sheet East tilt West tilt Convex east Convex west Straight, irregular Convex east Straight, irregular Abeit Din; __________________________________ Amargosa Range ______________________________ Argus Range _________________________________ Bare Mountain ______________________________ Belted Range _________________________________ Black Rock Range, south end __________________ Bristol Range ________________________________ Buckskin Range ______________________________ Cedar Mountains _____________________________ GortezMountains _____________________________ Coso Range _________________________________ Deep Creek Range ____________________________ Dove Creek Mountains__-_____-______________: East Humboldt Range _________________________ Egan Range, northern part _____________________ Egan Range, southern part _____________________ Eugne Mountains ____________________________ Fish Springs Range ___________________________ Fortification Range ___________________________ Grant Range ________________________________ House Range _______________________________ Inyo Range, south end ________________________ Kawich Range ________________________________ Kingsley Range__.__-_-_-_-___--_--___-_-___;_ Kings River Range, southern part ______________ Klamath Lake, rim east ef- ____________________ Last Chance Range_-_-___---__._ ______________ Mineral Mountains _________________ i _ _ ‘_ ______ Monitor Range ______________________________ Newfoundland rMountains ______________________ North f‘romontory Mountains ________________ Oquirrh Mountains ___________________________ Osgood Mountains, southern part _______________ Pahrock Range (southern) _____________________ Panamint Range _____________________________ Poker Jim Ridge _____________________________ Reveille Range _______________________________ Ruby Mountains _____________________________ Seven Troughs Range _________________________ Sheep Range _________________________________ Shoshone Range, south part ~Simpson Park Mountains ______________________ Singatse Range ______________________________ Spruce Mountain Ridge _______________________ Stansbury Mountains _________________________ Steens Mountain ______________________________ Sulphur Springs Range ________________________ Terrill Mountains ___________________________ Toiyabe Range _______________________________ Virginia Range ______________________________ Wah Wah Mountains _________________________ Warner Mountains __________________________ West Humboldt Range ________________________ West Tintic Mountains ________________________ Winter Rim __________________________________ Total _________________________________ Klamath Falls _______ Death Valley ________ Death Valley ________ Death Valley ________ Goldfield ___________ Tooele _____________ Winnemucca ....... Death Valley ________ Delta ______________ Brigham City _______ Winnemucca _______ Ely ________________ Lund _______________ Lovelock ___________ Delta ______________ Lund ______________ Lund _______________ Delta ______________ Death Valleyi _______ Goldfield ___________ Elko _______________ Vya ________________ Klamath Falls _______ Goldfield ___________ Richfield ___________ Millett ____________ Brigham City _______ Brigham City _______ Tooele _____________ McDermitt _________ Caliente ___________ Death Valley ________ Adel _______________ Goldfield ___________ Elko _______________ Lovelock ___________ Caliente ___________ Winnemucca _______ Millett ____________ Reno ______________ Elko _______________ Tooele _____________ Adel _______________ Millett _____________ Reno ______________ Millett _____________ Richfield ___________ Alturas Lovelock-_ __________ Delta ______________ Klamath Falls _______ 1 Refers to ranges composed of more than one linked arcuate segment. GEOPHYSICS For example, the north-trending House Range in west- ern Utah is convex to the east in plan and is tilted to the east. The central Ruby Mountains of northeastern Nevada is convex to the west in plan and is tilted to the west. More complex ranges are made of several of these arcuate segments, as, for example, the Egan Range and the Toiyabe Range of central Nevada. Each segment must be considered rather than the range as a whole, and clearly defined arcs of the scale indicated above generally are convex toward the direction the ' range is tilted. Ranges that are nearly straight in plan are generally those which are more horstlike, that , is, flanked on both sides by major faults. Table 188.1 lists 55 ranges about which there is some data on the direction of tilting. Of 34 ranges tilted east, 25 are convex east, 1 is convex west, and 8 are rather straight or irregular in shape. Of 21 ranges tilted west, 16 are convex west, 1 is convex east, and 4 are straight or irregular in shape. This relation be- tween the arcuate plan and sense of tilt of mountain blocks is not entirely consistent, but the pattern is re- peated so frequently that it is considered to be an important feature of basin-range structure. The curva- ture of the fault block ranges reflects the curvature of the main bounding fault in plan; hence, the fault itself FIGURE 188.1.—Block diagram showing typical curvature and tilt of ranges in the Basin and Range province. The fault surface is believed to be doubly concave (spoon-shaped) toward the dowmthrown side. ’5? 189. B411 is believed to be convex toward the direction of tilt of the range, or concave toward the downthrown side of the fault (fig. 188.1). There is evidence that the master normal faults which bound the ranges are also curved in section so that they ,dip less steeply with depth. Tilting and rotation of blocks is facilitated by a downward flattening of the fault surface (De Sitter, 1956, p. 155), and perhaps for this reason the main normal faults are shown in recent papers (Mackin, 1960, p. 112; and Osmond, 1960) to flatten with depth. Davis (1925) calls on a mathemati- cal analysis and experiments to show that normal faults should flatten with depth. Longwell (1945) finds that many normal faults in southern Nevada flatten down- wards. The fact that many normal faults in the Basin and Range province are concave in plan toward the down- thrown side, together with the evidence that many are concave in section upwards, indicates that many of the fault surfaces are probably doubly concave toward the downthrown side. This double concavity suggests that the fault surfaces are spoon-shaped in much the same way that the faults that bound many landslides are spoon-shaped surfaces (Eckel, 1958, p. 24). REFERENCES Davis, W. M., 1925, The Basin Range problem: Natl. Acad. Sci. Proc., v. 11, p. 387—392. Eckel, E. B. (ed.), 1958, Landslides and engineering practice: Highway Research Board, Special Report 29, Washington, D.O., 232 p. Longwell, C. R., 1945, Low-angle normal faults in the Basin and Range Province: Am. Geophys. Union Trans, v. 26, pt. 1, p. 107—118. Mackin, J. H., 1960, Structural significance of Tertiary volcanic rocks in southwestern Utah: Am. J our. Sci., v. 258, p. 81—131. Osmond, J. 0., 1960, Tectonic history of the Basin and Range province in Utah and Nevada: Mining Engineering, v. 12, no. 3, p. 251465. Sitter, L. U. de, 1956, Structural geology: New York, McGraw- Hill Book Company, Inc., 552. p. VOLCANISM IN EASTERN CALIFORNIA—A PROPOSED ERUPTION MECHANISM By L. C. PAKISER, Denver, Colo. Geologic and geophysical evidence suggests that the volcanic rocks along the eastern front of the Sierra Nevada were erupted from regions of relative tension or stress relief in offsets of a major left-lateral en— echelon shear zone (fig. 189.1). This hypothesis was recently put forward for the volcanic activity in Owens B412 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES / r I / “M Exp—O” I '9 1 ’yl" /, Volcanic rocks of Cenozoic age I A / 44’th "y‘fi oney Lake I ,7, «x m 44 Pk / ”/ 9/3 sfiv ” / . - ‘fia‘g‘gj \o‘ ' fl) 4:28 ——:__ - - Known or inferred major fault, showing direction of strike slip if known 31/2 miles of left-lateral ’39» strike-slip displacement (Durrell. 1950 and writ- ten communication) Walker Lane showing assumed direction of strike slip 1 S 32° E Assumed direction of motion of Sierra Nevada 25 O LJ_L_L.J__L__—l____l 25 .. _ \1‘21° 1go° 1i9° lie \ 1,17 1116 FIGURE 189.1—Tectonic pattern of eastern California and western Nevada. GE OPHYSICS Valley, which seems to have taken place near the ends of left-lateral faults where tension would be expected (Pakiser, 1960). It seems a reasonable explanation also for the Mono Basin and Long Valley subsidence structures. These have been identified as volcano- tectonic depressions (Pakiser, Press, and Kane, 1960) and they lie in a large offset in the eastern front of the Sierra Nevada. If the Sierra Nevada moved south with respect to the Great Basin, the crust in this offset would have been under tension; as a zone of weakness, the area might therefore have been susceptible to vol- canic eruption. Similar offsets of the eastern front of the Sierra Nevada are found farther north (fig. 189.1). One of these ofl'sets, east of Blairsden, contains Sierra Valley. Gravity data and outcropping volcanic rocks suggest that this valley may be a volcano-tectonic depression similar to Mono Basin and Long Valley. Cordell Dur- rell (1950 and written communication) mapped a fault west of Blairsden (fig. 189.1) with 31/2 miles of left— lateral strike-slip displacement. This fault is nearly parallel to Owens Valley and the strike-slip displace- ment is several times the dip-slip displacement. In the Sierra Valley area, the Sierra Nevada block moved south with respect to the area to the east. The concept that the Sierra Nevada block moved southward along left-lateral strike—slip faults is also supported by the thrusting on the White Wolf fault and by Scheidegger’s (1959) determination that the direction ' #400\ 122 \\ 120° 118° Lassen Pk\ \:\ \ n \\ l \ SIERRA VALLEY \\ B413 of tectonic motion for the aftershocks of the Arvin- Tehachapi earthquake of 1952 was N. 32° W. (fig. 189.1). Southward movement of the Sierra block is compatible with the right—lateral strike slip along the San Andreas fault and the Walker Lane (Longwell, 1950). These facts and inferences suggest that the eastern front of the Sierra Nevada is an en—echelon shear zone along which left-lateral strike—slip movements (and in most places larger vertical movements) took place (fig. 189.2). Discontinuities or overlapping ofl'sets in this shear zone would be regions of relative tension or stress relief in which volcanic eruptions would be facilitated by reduction of the confining pressure on magma cham- bers (fig. 189.3). Gravity lows with residual relief of about — 50 mgals were found in Mono Basin and Long Valley (Pakiser, Press, and Kane, 1960). These gravity lows represent low-density volcanic debris and sediments that fill the subsidence structures. In more general terms, the gravity lows express the mass deficiency that results when intermediate to silicic magma is erupted from a bounded magma chamber within the earth’s sialic crust and is spread as lower density volcanic debris over an area large compared to that of the magma chamber. FIGURE 189.3.—Interpreta‘tion of strike—slip fault system of eastern California and western Nevada. FIGURE 189.2.—Reg-ion of stress relief in an en-echelon shear zone. B414 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES ~40°45 . l l I 122°00’ 121°45’ 121°30' 121°15' 121l°00' \\ 40°45'- o° m ,\ A W Prospect Pk (8172) TV) LASSEN VOLCANIC O 7s o r \60 ULassen Pk (10,457) 40°30’- —224 V NATIONAL PARK x175 —72 7E :fi l-\____. (1885) \ . - s. ‘ w \ , °é EXPLANATION . . . Gravuty In mgals and elevation N 4'00 \_ above sea level in feet given . - at Lassen Peak, W. Prospect S'Tgfigfxgcuofltgfrvm Peak, and station 175 terval 20 mgals 5 o 5 10 MILES Ll_.l_l_l_L____L—l 40°15" 122l°00’ 121:45’ 121:30’ 121:15’ 121:00’ FIGURE 189.4.—Gnavity in and around Lassen Volcanic National Park, Calif. Field work in and around Lassen Volcanic National Park in 1958 and 1959 revealed a large gravity low (fig. 189.4) associated with the volcanic rocks there. The zone of steep gravity gradients directly west of Lassen Peak may express a northward continuation under volcanic cover into the southern Cascades of the en-echelon shear zone along the eastern front of the Sierra Nevada (fig. 189.2). If this interpretation is correct, the Lassen volcanic field lies in an offset of this shear zone similar to the one containing Mono Basin and Long Valley. REFERENCES American Association of Petroleum Geologists, 1944, Tectonic map of the United States: Tulsa, Oklahoma. Durrell, Cordell, 1950, Strike-slip faulting in the eastern Sierra Nevada near Blairsden, California (abs) : Geol. Soc. America Bull., v. 61, p. 1522. Longwell, C. R., 1950, Tectonic theory viewed from the Basin Ranges: Geol. Soc. America Bull., v. 61, p. 413—434. Pakiser, L. 0., 1960, Transcurrent faulting and volcanism in Owens Valley, California: Geol. Soc. America Bull., v. 71, p. 153—160. Pakiser, L. 0., Press, Frank, and Kane, M. F., 1960, Geophysical investigation of Mono Basin, California: Geol. Soc. America Bull., v. 71, p. 415—448. Scheidegger, A. E., 1959, Note on the tectonics of Kern County, California, as evidenced by the 1952 earthquakes: Jour. Geophys. Res, v. 64, p. 1499—1501. Stose, G. W., and Ljungstedt, O. A., 1932, Geologic map of the United States: U.S. Geological Survey. GEOPHYSICS 190. B415 SOME RELATIONS BETWEEN GEOLOGY AND EFFECTS OF UNDERGROUND NUCLEAR EXPLOSIONS AT NEVADA TEST SITE, NYE COUNTY, NEVADA By F. A. MCKEOWN and D. D. DICKEY, Denver, Colo. Work done in cooperation with the us. Atomic Energy Commission The underground nuclear explosions, code named Logan and Blanca, with yields of 5 and 19 kilotons, re— spectively (Johnson and others, 1959, p. 1461), pro- vide data for evaluating geologic control of fracturing within tunnels and at the surface. The Logan explosion was detonated October 15, 1958, and Blanca was detonated October 30, 1958. Both ex- plosions were detonated in tufl' of the Oak Spring formation, of Tertiary age, in straight tunnels having a minimum depth over the explosion chambers of 830 and 835 feet, respectively. One of the phenomena resulting from an under- ground explosion that must be considered when eval- uating the effects on rock in tunnels or at the surface is the passage of high-velocity stress waves generated during the momentary confinement by the rock of an Blanca shot point . o 100 200 300 400 Logan shot pomt —.' 50.0 FEET EX P LA N ATI O N TosZ—TosgA-D Units in the Oak Spring formation Fault 5/\/ Collapsed tunnel Strike and dip of beds W Moderately to badly damaged tunnel / >4 5K /6°°\ Strike of dominant steeply dipping joint sets Line of equal distance from Logan shot point. in feet FIGURE 190.1.—Generalized geologic map showing U12e.02, U12e.05, and part of U12e tunnels and extent of collapse due to the Logan explosion. extremely high pressure system of gases and other ex- plosion products. Part of the energy of a contained explosion is transmitted in a stress wave as kinetic energy. This energy is a function of the particle veloc- ity of the wave. Particle velocity, however, is a func- tion of the amplitude, shape, and propagation velocity of the wave. Changes in these variables per unit dis— tance in rocks are determined primarily by fractures and beds or layers of rocks that differ in composition and physical properties. Since the number of fractures and the average compositions of beds differ in different directions, the attenuation of the energy of a stress wave during propagation away from an explosion like— wise depends on the direction of the wave. For the \ \ °<:>, ‘3 Blanca shot point _ .o 100 200 300 400 500 FEET Logan shot pomt ~ |—_l—l‘_l__l__l E X P LA N ATI O N Tosz—Tos3A—D Units in the Oak Spring formation / Fault Collapsed tunnel due to 25/ Logan explosion Strike and dip of beds Strike of dominant steeply dipping joint sets minimum Collapsed tunnel due to Blanca explosion /600\ Line of equal distance from Blanca shot point.in feet FIGURE 190.2.—Generalized geologic map showing U12e.02, U12e.05, and part of U12e tunnels and extent of collapse due to the Blanca explosion. B416 GEOLOGICAL 0 Pole of fault Contoured in percent of poles of joints FIGURE 190.3.—Contour diagram of 287 poles of joints and plot of 2 faults mapped in U12e.02 and U12e tunnels from the explosion chamber to end of collapsed part of tunnel. Upper- hemisphere plot. N 0 Pole of fault Contoured in percent of poles of joints FIGURE 190.4.—Contour diagram of 324 poles of joints and plot of the poles of 17 faults mapped in U129.05 and U12e tunnels from the explosion chamber to end of collapsed part of tun- nel. Upper-hemisphere plot. SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES N Logan and Blanca explosions these differences can be estimated only roughly. Since the effectiveness of an explosion in breaking rock is approximately proportional to the cube root of the yield, the Blanca explosion should, if the two tun- nels had had the same geologic environment, have col- lapsed its tunnel approximately 1.6 times as far from the explosion point as the much weaker Logan ex- plosion. 151: g 1.6 In fact, however, the tunnel collapse due to the Logan explosion extended for a radial distance of 820 feet from the shot point, and that due to the Blanca ex- plosion for only 860 feet—a ratio of 1.05 (figs. 190.1 and 190.2). This disproportionate extent of damage could be due in part to the difference in the proper- ties of the rocks traversed by the stress waves from the Logan explosion. This conjecture can be checked by comparing the properties of the rocks affected by the two explosions. The parts of U12e and U12e.05 tunnels (fig. 190.1) most heavily damaged by the Logan explosion are in or near subunit A of T033. (See fig. 190.2). The tufl in this subunit is harder than the other beds of tuff ex- posed in the tunnels. It contains three to five times as many phenocrysts, fewer vesicles, and less zeolite and clay minerals than the overlying tufi'; and it has a density of 2.11:0.06 g per cc, a grain density of 2.6:0016 g per cc, and a porosity of 30.6:32 percent, as compared to averages of 1.95 g per cc, 2.38 g per cc, and 32.9 percent, respectively, for adjacent units (F.M. Byers, Jr., written communication). It may be in-_ ferred from these data that stress waves have a higher acoustic velocity, and a lower rate of attenuation, in subunit A than in adjacent rocks. The kinetic energy of stress waves, at points equally distant from their source, would therefore be greater in subunit A than in adjacent rocks. The very close relation between amount of tunnel damage and character of rock in U12e.05 tunnel (fig. 190.1) seems to support this inference. The attitudes and relative abundance of fractures in the tutfs may cause directional variations in attenua- tion of stress waves. Fractures produced by the Logan explosion, which was detonated before the Blanca ex- plosion, are known to be relatively few in the rock sev— eral hundred feet from the explosion chambers and exposed by postexplosion tunneling. Attenuation due to these fractures is therefore probably local and rela- tively insignificant compared with natural fractures. Figures 190.3 shows that the direction of propagation of waves from the Logan explosion point to the col- lapsed tunnel is nearly parallel to one set of joints and B417 GEOPHYSICS E634000 =;_ E63 5000 /,—»——~\ E63 7000 E638000 EX P L A N AT] 0 N =2 \\ :53 Line enclosmg surface fractures O ‘ resulting from the Logan explosion 8 :5 ‘ 1800— e” / \ f 810\ z / .5: \ // lsodistan lines £2: 13300 e / Lines on f/ve ground surface connecf/ng BE . 0‘1 / ,oo/m‘s ofequa/ o’isfances from file s/Jof 8 ‘2: mm of tunne ‘ chamber, [n feef o 2, \ closure // 0'3 \ uT2e.os7’ / . .+-.—- —--- — —-> . . 02° ,' a} / Direction lines of maxima and minlma a \ cf, // extent of fracturing Shot 4‘" / O gchamber¥{8lovt7/ IllllllllllllllltlIlllllllllll o 5; / / Cliff ~ \4 - 00 / \\ \4 \ Z 5 /: 8 / / / / g , \ / / 00 i2 \ \ / / _= / Q g \~_._./)\ // es / O 400 800 1200 1600 FEET FIGURE 190.5.—Map showing extent of fracturing due to Logan explosion. two faults, and perpendicular to another set of joints. The direction of propagation of waves from the Blanca explosion point to tunnel collapse, on the other hand, intersects two sets of fractures and 17 faults at about 45° (fig. 190.4). The limits of fractured rock at the surface above the explosion sites are lobate (figs. 190.5 and 190.6), and the alinements of lobes about 180° apart coincide ap- proximately with directions of sets of fractures. Both the underground and the surface data show that explosion-produced fracturing extends farthest in the directions of sets of fractures. A corollary is that at equal distances from an explosion, the greatest frac- turing may be expected to occur along radii parallel to a set of fractures. In summary, the extent and intensity of fracturing in different directions, and consequently tunnel damage, may to a significant degree depend upon (a) the rela- tions of beds of different chemical and physical prop- erties to the direction of propagation of stress waves and (b) the angles between the direction of propaga- tion and sets of fractures in the rock. REFERENCES Johnson, G. W., and others, 1959, Underground nuclear detona- tions: Jour. Geophys. Research, v. 64, no. 10, p. 1457—1470. B418 GEOLOGICAL SURVEY RESEARCH 1960—SI-IORT PAPERS IN THE GEOLOGICAL SCIENCES 8 E634000 E635000 3400 E636000 E63 7000 EX P LA N ATI O N 0 g \‘éf ———/ 2 Line enclosing surface fractures resulting from the Blanca explosion g \ 88 a —\ g / /2400 / lsodistan lines / Lines on the ground surface con- 8 nect/ng ,oo/nts ofequa/ distances 8 / from the shot chamber, m feet a? I z // k,_,,,. ’1 Direction lines of maxima and r,_—/-""'/ minima extent of fracturing ‘73” 0,/ I . ,\ *Pomt of ml'llllllmlln 3E tunnel closure Cliff o \ N ’ O 8 . \ / oo \‘ : X I N 00 2 Z 52 \ \ L0 00 E V w ‘ v z s O 400. 800 1200 FEET FIGURE 190.6.——Map showing extent of fracturing due to Blanca explosion. Q 191. STRUCTURAL EFFECTS OF RAINIER, LOGAN, AND BLANCA UNDERGROUND NUCLEAR EXPLOSIONS, NEVADA TEST SITE, NYE COUNTY, NEVADA By V. R. WILMARTH and F. A. MCKEOWN, Denver, Colo. Work done in cooperation with the U.S. Atomic Energy Commission The Rainier, Logan, and Blanca contained nuclear explosions, with energy yields of 1.7, 5, and 19 kilotons (Johnson and others, 1959, p. 1461), were detonated at minimum distances below the nearest ground surface of 820, 830, and 835 feet respectively. The explosion chambers were at the ends of tunnels 2,000 to 3,000 feet long, driven from the steep east slope of Rainier Mesa in massive to well—bedded friable to compact tufl's of the Oak Spring formation (Tertiary). Rainier Mesa is capped with about 270 feet of cliff-forming welded tufl' N89000O Welded tuff ) >£5°° \ 55‘ Friable (,0 \ tufl 1‘ FIGURE 191.1.—Geologic map Geology by W. R. Hansen and R. W. Lernke. Posiexplosion effects by A, B Gibbons, J S. Pomeroy, and A. Mason, 1957 0 200 GEOPHYSICS EXPLANATION Dashed where approx/matey /ocalea’ _.'.—___. 65 D Pretest fault Pretest lineaments \ ‘K \ Posttest fractures .———950\ Line of equal distance in feet, from explosion chamber 400 FEET L_L~__‘L.._—J CONTOUR INTERVAL 100 FEET showing fractures caused by Rainier explosion, Nevada Test Site, Nye County, Nev. B419 of this formation, broken by many northeast- to north- west-trending fractures On the surface, the most obvious result of the explo— sions was to produce rockslides and rockfalls from the welded tufl'. These extend discontinuously for 3,200 to 3,500 feet north and south of the ground zeros (Glass- tone, 1957, p. 549), though the slides are notably more abundant and larger within 1,500 feet than at greater distances. Nearly all the fractures produced by the Rainier, Logan, and Blanca explosions that have been mapped on the surface (figs. 191.1—191.3) are within the 1,000—, 2,600-, and 3,300-foot isodistan lines 1 respectively. These fractures are most numerous in the welded tulf and in the bedded compact tufi's east of the epicenters— the points on the surface nearest the shot chambers. The mesa area around the epicenters is immediately underlain by friable tuffs in which fractures are less nu— 1Lines on surface connecting points equidistant from the explosion chamber. EXPLANATION Tos i Oak Spring formation h‘ DEVONIAN TERTIARY Devils Gate(?) limestone and Nevada formation /— Contact U 23 D Fault resulting from explosion, showing dip U, upfhrown side, D, downfhrown side 18 Fractures resulting from explosion. showing clip //’-— Preshot lineaments /3 .1— Strike and dip of beds I500 "" Lines of equal distance, in feet, from shot chamber «“‘l‘W’l/flm C l iff O 400 800 FEET Geology by W. R. Hansen and R. W. Lemke, 1957. Postexplosion effects by D, D, Dickey, F. N. Houser, F. A. McKeown, F. G. Poole, and V. R. Wilmarth, October 1958 CONTOUR INTERVAL 300 FEET FIGURE 191.2.—Geologic map of the U12e tunnel area, showing fractures and faults caused by the Logan explosion, Nevada Test Site, Nye County, Nev. IN THE GEOLOGICAL SCIENCES GEOLOGICAL SURVEY RESEARCH 1 9 6 0—- SHORT PAPERS B420 .52 .5580 ohz 63w award 33.52 .nfiwoaxo monfimm 3: he gmswo $35“ was 35% mEBonm «93 35:: $33 93 no _ _ Hmmu 000m OOON womtsm Loan: .o 306 F0 cozuotu ucm x83 95% B 3:: E5“. 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NVINOAEIC] ZO_._.oz 555:; .m > ncm éoom .0 m 538%: .< ..._ 530: .z ..._ $965 a ,o E 3083 xmmfi .283 .31 was :3ch ,m .>> 3 $280 3523381 com 3:: owwgoomvllfiémfi ambabm TN ‘ fa ’ \ ‘ ‘m m.mtm\“/?’ ‘1 O mum q» V ”W A muum A.“ ll/Il/l . a‘ 4/ ’% 1/ mop GE OPHYSICS 105 f of line with of D upon W: 0:50 W‘14 10‘ Rainier 103 (nuclear) YIELD OF EXPLOSION, IN TONS (W) 102 uncertain l 10 10 102 103 10‘ MAXIMUM DISTANCE OF FRACTURE FROM EXPLOSION, IN FEET (0) FIGURE 191.4.—Graph showing relation of yield of explosion. to distance of fractures from explosion in tufl’ of Oak Spring formation. ' merous than in the welded tufi' and are poorly devel- oped. Many of the postexplosion fractures coincide with or parallel the tectonic fractures, which are par— ticularly numerous in the welded tufi'. Most of the ex- plosion-produced fractures (figs. 191.2 and 191.3) dip steeply; they range from 15 to 600 feet in length, and some are open as much as 3 feet in width. Some of the Blanca-produced fractures are open to depths of at least 40 feet below the surface, which is about as far down as one can see. The nuclear explosions produced both overthrusts and normal faults. Gently dipping thrust faults are along or near bedding planes and are traceable along strike for a maximum of 2,200 feet (figs. 1912 and 191.3). The hanging walls of the thrust faults have moved up- ward and away from the explosion chamber, in some places as much as 5 feet. Most of the thrust faults crop out more than 1,800 feet from the chamber (figs. 191.2 and 191.3), in areas Where the bedding planes are nearly parallel to radii from the shot chamber. In contrast the steeply dipping normal faults trend predomi- nantly northwest to northeast, parallel to tectonic frac- B421 Note: Lithologic units V to Z are part of Oak Spring formation, Tertiary age. Original position of the units are shown within the explosion breccia Syncline axis Explosion chamber , . Original tunnel—1.7277“, / \‘\“e 39 /fi7 0 . , 9075,72» 902 /_\\ ‘\8’ :2‘30 5x ~ / Y X 0 saw Tunnel collapsed / /w by explosion _ a this pom! Center line of lOO-ft level 0 40 80 120 FEET l—A_L_L_l Preexplosion geology by A. B. Gibbons and E. B. Eckel, 1957. Postexplosion A’ geology by V. R. Wilmarth, F. A. McKeown, and H. Barnes, 1958—60 EXPLANATION // / // // Approximate contact 90 ,’——" / Strike of vertical fault Dashed where approximate/y /ocafeo’ \ M Strike and dip of fault U, upr/zrown side; D, downfhrown side % Strike and dip of shear zone \6 Strike and dip of beds \90 Vertical joint 75 r Strike and dip of joint as Strike and plunge of slickensides FIGURE 191.5.—Geologic map of Rainier tunnel showing effects of Rainier explosion. tures, and generally have strike lengths of less than 500 feet; the displacements on most of them range from 6 inches to 5 feet. The maximum radial distance from the explosion chambers of fractures in tufl's of the Oak Spring forma- tion scales empirically as the 0.4 power of the yield in tons of the explosion. This figure applies to both nu- clear and high-explosive tests (fig. 191.4). The largest structure formed at the surface by the Blanca test is a northwest-trending graben southwest of the epicenter (fig. 191.3). Vertical displacements B422 . +_——i-—'L Explosion brecaa Workin point D8 ———————————— Q— 88 ”C Unit v u ‘ ‘\“ \ / nit V ‘—§\s‘__‘\_‘:2\8 f lxploratory tupggl,- Units u to Q B ""Jnits u to Q/ l Fria le tug i— Welded tuff+————— Friable tuff //E/LXPLANATIO Radioactive glass o 20 40 60 FEET‘ \\\\\\\ /// ______ Geology by V. R. Wilmarth, F. A. McKeown, and D. D. Dickey, 1959 FIGURE 191.6.—Section A—A’ through zone affected by Rainier explosion. on the bounding faults are as much as 65 feet, but the movement here was not of the same sort as that on the small normal faults. The graben resulted primarily from collapse of a cavity, produced by explosion, though its large size is due in part to the extensive fracturing of the tufl's by the earlier Logan explosion. In the tunnels, the amount of rock spalled from the walls increased from the portal inward to points where the tunnels were completely collapsed. This point is at a radial distance of 205 feet from the chamber, for the Rainier test, and at 820 and 870 feet, for the Logan and Blanca tests, respectively. Portalward from the collapsed areas, the explosions formed new faults and joints, deformed the tunnels by movement of the tuffs along shear planes parallel to and dipping steeply away from the tunnel, and opened and extended pre-existing fractures. The newly formed joints are most numerous in the competent tuff and are coincident with or parallel to preexplosion fractures. The most prominent new faults are bedding—plane thrust faults that dip 3° to 10° to- ward the chambers and have displaced the beds hori— zontally as much as 4 feet. Thrusting occurred most commonly where a layer of wet soft clay separates competent tuff beds. The amount of radial displacement of the tuffs by the Rainier test increases abruptly within 400 feet of the chamber. The tufl' beds 60 feet radially from the explosion were moved horizontally as much as 38 feet (fig. 191.5). Radial displacement of surveyed stations GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES B’ I l :‘T R.R—2 l Holes ,l Fracture zone _ 4 E ________ Explosion ‘ __,,~-_————”"'t 2 ----- breccia ' __ _ g ___________ s__-_-— ————-v" E Working l _ pount _i/She ________ —_ *""fi ‘ 660° — Unit V III" ,LL/r ”" _________ \\ ,_”""’” Fault zofie ~—\\ Units U to Q Units U to Q ___________ E 8 EXPLANATION E —_—O-0-¢- a, Radioactive glass 0 20 40 so FEET 3 __.__._. Disseminated radioactive glass Geology by V. R. Wilmarth. F. A. McKeown, and D. D. Dickey. 1959 FIGURE 191.7.——Section B—B’ through zone affected by Rainier explosion. in the Rainier tunnel was 2.5 feet at 200 feet from the chamber, 1.0 foot at 400 feet, and less than 6 inches at 1,100 feet. In the Blanca test, the radial displacement of surveyed stations in the tunnel 1,100 feet from the chamber following was about ten times as great as in the Rainier test. The tuff adjacent to the explosion chambers was brec- ciated and extensively fractured. The breccia zone around the Rainier chamber is, at the level of the ex- plosion, roughly circular in plan and 190 feet in maxi- mum diameter (fig. 191.5). In vertical sections through the chamber, the breccia zone is elliptical, (figs. 191.6 and 191.7). This zone extends for about 80 feet below the chamber. According to Johnson and others (1959, p. 1465) it extends about 386 feet above the chamber. The estimated volume of the breccia zone is about 245,000 cubic yards. Where exposed in the Rainier tun- nel, the breccia zone is separated by shear and fracture zones 2 to 6 feet Wide from highly fractured tufl', which below the chamber extends as much as 70 feet outward from the breccia zone. The breccia zone produced by the Logan explosion (fig. 191.8) is a nearly vertical prolate spheroid having an estimated volume of 190,000 cubic yards. The brec— cia zone produced by the Blanca explosion has not been so fully studied, but it appears to be similar in shape, size, and orientation to that produced by the Logan explosion. The volume of a breccia zone produced by a nuclear explosion in tufi' depends partly on the properties of B423 GEOPHYSICS D D’ 6200 ‘ I T ’ 6400 'l «7'. 6400 l 6000 o 100 200 300 400 FEET “i 4/ SCALE FOR SECTIONS J / 6200 l / T054 6200 Shot chamber 3. ‘ a’ / Tos3 ‘ 6000 Blanca chamber—V T05 )( 2 )6 I Tos1 * U12e 1.0.+99~3 w.3 001524 \ A A A, \ / s s\s 3; (U! “-1 6400 T084 ; 6400 / L h b o 200 400 600 800 FEET g ’ oganc am er SCALE FOR TUNNEL —__ E B’ /" F 6200 T \ 620 6200 \ °53 Ch b \ \ \\...:a~r.n er 1e 2H Chamber Tos3 - 6200 _____ \ . ‘ _\ 7 /‘ l a = ...., L . / 6000 6000 \-—’ T°52 6000 6000 Geology by F. A. McKeown. D. D. Dickey, and V. R. Wilmarth, 1959—60 EXPLANATION —H~—m\-\— T051, T052, T053, and Tos4 Fracture zone L/‘Iho/og/c um'ls in Oak Spr/ng formal/on of Tertiary age 5 Permanent displacement vector Number ind/cafes feef Strike of dominant joint sets FIGURE 191.8.—-Geologic map and sections of part of U12e tunnel complex, showing exploratory drill holes and some eifects of the Logan and the rock. The tufi's surrounding the Rainier explosion are friable, Whereas those around the Logan are tough and compact, and as a result the volume of breccia formed per kiloton of yield is 3.4 times as large for the Rainier as for the Logan explosion. Blanca explosions. REFERENCES Glasstone, Samuel, ed., 1957, The efiects of nuclear weapons: U.S. Atomic Energy Comm., Washington, U.S. Govt. Print- ing Oflice, 579 p. Johnson, G. W., and others, 1959, Underground nuclear detona- tions: J our. Geophys. Research, v. 64, no. 10, p. 1457—1470. 5% 192. BRECCIATION AND MIXING OF ROCK BY STRONG SHOCK By EUGENE M. SHOEMAKER, Menlo Park, Calif. Work done in cooperation with the U.S. Atomic Energy Commission Investigation of the fragmentation and displacement of earth materials engulfed by strong shock reveals that complex movement of these materials behind the shock front extends out to a fairly sharply defined limit. Within this limit is a domain in which fragments that were originally at Widely different distances from the origin of the shock are mixed; beyond this limit the rocks are fractured, but the fragments, though dis- B424 placed outward, are not mixed. The mixed debris formed in small-scale explosions is commonly unconsoli- dated, and in some cases it is expelled from the region of strong shock. The mixed debris, where preserved, and its contact with unmixed material are most easily observed in craters. NUCLEAR EXPLOSIONS IN ALLUVIUM At the Nevada Test Site, two nuclear explosions (J angle U and Teapot ESS experiments), of 12:05 kiloton (TNT equivalent) yield (Johnson, 1959, p. 10) have been detonated by the US. Atomic Energy Com- mission at shallow depth in alluvium. The particles of which the alluvium is composed are about 50 percent felsic tuflz' and about 50 percent quartzite. The floors and lower walls of the two craters formed by these ex— plosions are underlain by a compact breccia consisting of slightly to strongly compressed and sheared blocks of alluvium, set in a matrix of smaller blocks and alluvial detritus. The original bedding of the alluvium is partially preserved in the breccia, but in some places individual blocks derived from one stratigraphic hori- zon have been introduced into parts of the breccia com- posed mainly of blocks from another horizon. Glass, formed by fusion of alluvium resulting from shock, is dispersed through the matrix of the breccia in the form of droplike, spindle-shaped, and irregular lapilli. Bed- ding in the breccia is overturned and is locally in fault contact with less disturbed beds along the walls. The base of the breccia in the Teapot ESS crater is 61 feet below the center of the detonated nuclear device, but its depth in the J angle U crater is not known. A thin patchy layer of material formed by falling back of ejected debris overlies the breccia in both craters. METEOR CRATER, ARIZONA The structure of the Teapot ESS crater (Shoemaker, 1960) is closely similar to that of Meteor Crater, in Arizona. Rocks intersected by Meteor Crater include, in descending order, about 50 feet of sandstone and shale, 265 to 270 feet of sandy dolomite, and several hundred feet of quartzose sandstone. The lower walls and floor of the crater are underlain by a lens of breccia composed chiefly of shattered, twisted, and compressed blocks of sandstone. Glass, composed of sandstone and dolomite fused by shock, is dispersed in the breccia; the glass derived from dolomite contains minute par- ticles of meteoritic nickel-iron. The base of the breccia lies at an average depth of about 1,100 feet from the original ground surface. The breccia is overlain by about 30 feet of debris formed by falling back of ejected fragments. The total energy released by meteorite impact, estimated by scaling of horizontal crater GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES dimensions from the Teapot ESS crater, was about 1.4 to 1.7 megatons, and the center of gravity of the energy released is estimated to have been between 320 and 400 feet from the surface along the path of meteorite pene- tration (Shoemaker, 1960). UNDERGROUND EXPLOSIONS IN BEDDED TUFF The effects of three underground explosions in pumiceous bedded tufl' at the Nevada Test Site have been described in detail by various workers, and I have studied them independently. These explosions were: (a) the Rainier experiment, in which a nuclear device of 1.7 :05 kiloton yield was detonated (Johnson, 1959, p. 10) ; (b) explosion of 50 tons of dynamite (60 per- cent nitroglycerin gelatin); and (c) explosion of 10 tons of dynamite (60 percent nitroglycerin gelatin). The Rainier experiment produced a breccia of mixed fragments containing dispersed glass in various forms, that closely resembles the mixed breccia in the J angle U and Teapot ESS craters. Where the breccia was intersected in an exploratory drift, the distance from the nearest wall of the original explosion chamber to the limit of the domain of mixing ranges from 62 to 72 feet (measured from Diment and others, 1959, fig. 4.4). In the 50-ton dynamite shot a mixed breccia was formed, whose edge is about 23 feet from the nearest wall of the explosion chamber where intersected by an exploratory drift (measured from map transmitted by J. M. Cattermole, 1958). In the 10-ton dynamite shot, rock compressed and disaggregated by shock was expelled from the vicinity of the shot chamber by venting the explosion gases. Rocks in the walls of the cavity thus formed are not mixed. The fragments in the expelled debris are very similar in size, frequency distribution, and degree of shearing to those in the mixed breccia of the nuclear explosion craters. Except on the side of the original entryway, the horizontal distance from the walls of the original explosion chamber to the walls of the multant cavity ranges from 10 to 15 feet and averages about 12 feet (measured from map transmitted by J. M. Catter- mole, 1958). EXPLOSIONS IN SANDSTONE Vertical drill holes 1.8 inches in diameter in sand- stone in Unaweep Canyon, Colorado, sprung with charges of dynamite, have been transformed into elongate cavities 8 to 9 inches in diameter surrounded by an aureole of fractured rock. The horizontal dis- tance from the walls of the original drill holes to the walls of the cavities produced by the dynamite explo- sions ranges from about 0.2 to 0.3 feet. Most of the Gnopmsms B425 TOTAL ENERGY RELEASED IN CALORIES 10 10 io io7 10 10 13 H 15 16 10” 1012 to 10 10 10 10 10‘ USGS tunnel 10 ' IN FEET (I?) in tuft 1 _ Unaweep Canyon, DISTANCE FROM EXPLOSION CHAMBER OR ORIGIN OF SHOCK T0 LIMIT OF DOMAIN OF MIXING 110 grams at dynamite (estimated) detonated In sandstone 1 NW“ USGS tunnel 10 tons of dyna- mite detonated 'Meteor Crater' Ariz, 1.4—1.8 megatons (estimated) en- ergy released in dolomite and “e 195‘5 sandstone Rainier Teapot E58 .4 .7~ki|oton nucle- av device det- 1.2-kiloton nucIe- “and '" m" ar device det- onated In allu- vuum 50 tons of dyna- mite detonated in tuft Rectangles show uncertainties of data indicated in text l A I to" to" 10" 1 10 102 10’ 10‘ to“ TOTAL ENERGY RELEASED IN TONS TNT EQUIVALENT(W) FIGURE 192.1.—Distance from origin of shock to limit of domain of mixing as a function of total energy released. rock crushed and disaggregated by shock has been ex- pelled from the holes. A right circular cylinder of dynamite having the diameter of the drill holes and a height equal to its diameter would weigh about 110 grams. SCALING LAW FOR DOMAIN 0]? MIXING The mixed breccia underlying the nuclear explosion craters and Meteor Crater, Arizona, is here interpreted as strictly homologous with the mixed breccia produced by the contained nuclear and dynamite explosions, with the debris expelled from the sprung drill holes and the cavity produced by the 10-ton dynamite shot. The mixing appears to have occurred in the shock wave (compare with Johnson and others, 1958, and Kennedy and Higgins, 1958). The limit of the domain of mix- ing initially extends in all directions to roughly equal distances from the origin of the shock or from the walls of the shot chamber. This distance obeys a simple scaling law with respect to the total energy released (fig. 192.1), which appears to be virtually independent of the character of the material affected and of the mechanism by which the shock is genera-ted. In the explosions that form craters, the mixed breccia is probably at first in the form of a roughly spherical shell, but the upper part of the shell is ejected and the lower part is sheared out laterally into the form of a deep concave-convex lens. Only the vertical distance from the origin of the shock to the base of the lens, therefore, is directly comparable with the dimensions of shells formed in contained explosions. In figure 192.1 an uncertainty of 5 feet has been arbitrarily as- signed to this distance for the Teapot ESS crater and to '5? 557753 0—60—28 the lateral dimensions of the shell for the 50-ton dyna- mite shot. Twenty percent uncertainty has been arbi- trarily assigned to the total energy released in the dynamite shots. For the sprung drill holes the efl'ect on scaling of differences between conical and spherical divergence of the shock has been neglected. The following equation gives the relation between the limit of the domain of mixing and the energy released: R feet W=K=5I7 m, where R is the distance in feet from the explosion chamber or origin of shock to the limit of the domain of mixing, and W is the total energy released in tons TNT equivalent. REFERENCES Diment, W. H., and others, 1959, Effects of the Rainier under- ground explosion: U.S. Geol. Survey open-file report, TEI— 355, 134 p., May 12, 1959. Johnson, G. W., 1959, Mineral resource development by the use of nuclear explosives: California Univ., Lawrence Radia- tion Lab. Rept. UCRL—5458, 18 p. Johnson, G. W., Pelsor, G. T., Preston, R. G., and Violet, C. E., 1958, The underground nuclear detonation of September 19, 1957, Rainier Operation Plumbbob: California Univ., Lawrence Radiation Lab. Rept. UORL—5124, 27 p. Kennedy, G. 0., and Higgins, G. H., 1958, Temperatures and pressures associated with the cavity produced by the Rainier event: California Univ., Lawrence Radiation Lab. Rept. UCRL—5281, 9 p. Shoemaker, E. M., 1960, Impact mechanics at Meteor Crater, Arizona, in Kuiper, G. P. (ed.), The solar system, v. 4, Planets and comets, part 2: Chicago, Illinois, Chicago Univ. Press (in press); also U.S. Geol. Survey open-file report, 55 p., Dec. 28, 1959. B426 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES 193. PALEOMAGNETISM, POLAR WANDERING, AND CONTINENTAL DRIFT By RICHARD R. DOELL and ALLAN V. Cox, Menlo Park, Calif. Most recently workers in the field of paleomagnetism have concluded that paleomagnetic evidence indicates movements of the earth’s axis of rotation as well as large-scale relative displacements of continents. India and Australia, for example, are thought to have been displaced 5,000 and 1,000 kilometers, respectively, with respect to Europe and North America since Eocene time. In an attempt to evaluate these interpretations criti- cally, the available paleomagnetic data have been re- viewed with special attention to evidence for stability and paleomagnetic applicability of the observed rem— anent magnetizations; moreover, because of the impor- tance of statistics in these interpretations, statistical _ analyses have been made of original data when these were available and when the original workers did not use the standard methods. We have concluded, from the paleomagnetic data now available, that the earth’s magnetic field had vastly dif- ferent characteristics during the following periods: post-early Pleistocene, Oligocene to early Pleistocene, Mesozoic to early Tertiary, late Paleozoic, early Paleo- zoic, and Precambrian. If paleomagnetic results are to be used as evidence supporting or refuting conti- nental drift, it is first essential to determine the con- figuration of the earth’s magnetic field during the time when contemporaneous rocks from different continents were magnetized. For only a few of the above tem- poral subdivisions has the configuration of the geomag— netic field been established with sufficient certainty to justify application to the problem of continental drift. Rocks of late Pleistocene to Recent age have yielded, in scores of studies, directions of magnetization consist- ent with positions of the geomagnetic pole that fre- quently differ significantly from that of the present geomagnetic pole, but rarely differ from that of the present geographic pole. These data offer strong evi— dence in favor of the dynamo theory which relates the earth’s main magnetic field to the axis of rotation and they indicate that the present inclined dipole field must be regarded as only a transient feature. Moreover, the directions of magnetization in these rocks are all of the same polarity as the present field, indicating a total absence of processes causing self-reversal of the rema- nent magnetization. Measurements on rocks of Oligocene to early Pleisto- cene age differ from those on late Pleistocene rocks in that about half of the measured directions are nearly 180 degrees from the present field directions. The earth’s magnetic field may have undergone at least a dozen complete reversals during this interval, the last occurring in the early Pleistocene. The geomagnetic poles calculated from measurements on Oligocene to early Pleistocene rocks on all continents are grouped around the present geographic poles, with somewhat more scatter than those calculated for late Pleistocene rocks. On the basis of the dynamo theory, polar wan- dering since the beginning of the Oligocene greater than about 10 degrees (the average confidence interval of most of these measurements) is excluded. These re— sults similarly exclude continental displacements greater than about 10 degrees since the beginning of the Oligocene. Measurements made on rocks of Precambrian age are in striking contrast with those on rocks of Oli- gocene age and younger. Of the more than 40 studies reported, not one of the virtual geomagnetic poles (the pole for a dipole field that would give the measured directions of magnetization) lies near the present geo— graphic pole, and an impressive grouping of poles lies near the equator and slightly east of the 180th meridi- an. Measurements from different continents do not ap- pear to differ significantly, which limits the amount of continental drift since Precambrian time. The North American measurements, however, which far outnum- ber all the others, do include some widely scattered average pole positions. Virtual geomagnetic poles calculated from measure- ments on rocks of early Paleozoic age are much more scattered than the Precambian poles, altogether the latter span a much greater time interval. Continental drift interpretations based on these early Paleozoic data are extremely hazardous. Of the pre-Tertiary rocks, those of Permian and Carboniferous age yield the most interesting and con— sistent virtual geomagnetic poles. All but a few of the poles lie between 30 and 40 degrees of latitude; all of the more than 40 poles calculated from measure- ments made on North American and European rocks lie between 90 and 180 degrees east longitude, whereas the 4 from Australia lie just west of Greenwich. Most of the North American Permian poles are west of the European Permian poles; the Carboniferous poles, however, from both continents are grouped to- GEOPHYSICS gether. On the assumption that the earth’s field was dipolar, these measurements on late Paleozoic rocks have been interpreted in terms of large drift of Aus- tralia relative to the northern hemisphere continents since the Paleozoic, and a smaller westward drift of North America relative to Europe. Although this lat- ter interpretation is suggested by the Permian poles, a simple westward drift of North America does not ex- plain both the Permian and Carboniferous data. An interpretation based on continental drift would require rather improbable relative movements between North America and Europe, and more data from Permian and Carboniferous rocks are highly desirable. Another interesting feature of the Permian data is that, with one poorly documented exception, all of the Virtual geomagnetic poles have the same polarity; re- versals are entirely absent. Since reversals are abun- dant in rocks of younger and older ages, the Permian field appears to be unique in having had a constant polarity over millions of years. To explain this fact on the self-reversal hypothesis requires that the special B427 mechanisms and compositions necessary for self—re— versal were entirely absent from Permian rocks but abundant in rocks of all other ages, which is rather un— likely. Although over 50 measurements on rocks of Mesozoic and early Tertiary age have now been reported, no magnetic field configuration has emerged that is com— parable in consistency and simplicity with that found in the late Paleozoic and late Tertiary rocks. Some of the virtual geomagnetic poles calculated from these measurements lie near the present geographic poles, but a significantly large number lie in very low lati- tudes. Although these rather divergent poles have recently been cited in support of large relative displace- ments of most of the continents, the character of the earth’s magnetic field during this time has not, in our opinion, been sufficiently well delineated to justify in- terpretation of the pa‘leomagnetic data as evidence either for or against continental displacement during this time. 6% 194. PREPARATION OF AN ACCURATE EQUAL-AREA PROJECTION By RICHARD R. DOELL and ROBERT E. ALTENHOFEN, Topographic Division, Menlo Park, Calif. Many of the problems that arise in measuring rema- nent magnetism and in interpreting paleomagnetic data are essentially problems in spherical trigonometry or three—dimensional geometry. Nor is paleomagnetism unique in posing such problems; others arise in struc— tural geology (Phillips, 1954) and structural petrology (F airbairn, 1949), and even in the prediction of satel- lite orbits (Wallace, 1959). When many such problems arise in a given study, especially if not great accuracy is required, it is desirable to replace the tedious analvt- ical methods of solution by graphical aids. By far the most useful of these aids are those which, by one means or another, project an orderly array of points from a. hemisphere to a plane. The most common are the stereographic projection (often called a “Wulif net”) and the Lambert equal-area projection (also known as a “Schmidt net”). The principal advantage of the stereographic projec— tion is that it is direction-true—circles on the sphere project as circles on the projection, and angles between lines on the sphere are preserved on the projection. Its main disadvantage is that it is not area-true. The equal-area projection distorts directions and shapes, but, as its name implies, it gives the same areal rela- tions on the projection that were on the sphere. A further slight advantage of the equal-area projection is that the accuracy with which points may be plotted on it is nearly uniform over the entire projection, whereas on the stereographic projection the accuracy of plotting varies by a factor of two. There is little choice between the two projections when used for solving problems in spherical trigo- nometry or three-dimensional geometry; any problem that can be solved on one projection can also be solved on the other by exactly the same procedures. Which one is the more desirable depends on the particular problem at hand and the type of presentation desired. Phillips (1954) and Fairbairn (1949, p. 275-296) de- scribe various methods of employing these projections in structural geology and structural petrology and give other references on the use of these projections for general and specialized studies. The equal-area projection is generally preferable in studies of remanent magnetism and in paleomagnetic B428 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES O '; G !/\P( I l FIGURE 194.1.—Relations in the construction of a Lambert equal-area projection. research, when it is usually necessary to present and compare groupings of directions. The significance of a separation between groups of directions is more easily determined on the equal-area projection than on the stereographic projection. Graphical methods of solv— ing 'many of the problems that arise in research on remanent magnetism have been given by Graham (1949). A Lambert equal-area projection may be constructed by rotating each point of intersection of the parallels and meridians on the hemisphere into a projection plane (a plane tangent to the hemisphere), about the point of tangency, in a plane normal to the projection plane. If the projection plane is tangent to the hemi- sphere at its pole, the projection is a polar equal-area projection, useful only for presentation of data and not for the solution of problems; and if the point of tangency lies on the equator the projection is called a meridional equal-area projection. The construction of a meridional projection is de— picted in figure 194.1, where any is the projection plane, T the point of tangency, and Q the intersection of the parallel d) and the meridian )x. Q is to be rotated to Q’ in the plane my; TQ— is used as a radius, and the rotation takes place in the plane TOQ. T—Q is also the distance from the center of the projection (T) to the projected point Q’, and we wish to find the coordinates x, 3/. From the law of cosines of spherical trigonometry in APTQ, (1) cos m=c0s13b cosP/i’+sin Pfisin P?cos AQPT, where A is used to designate a side of the triangle and A is used to designate an angle. Since PT: 1r/2, sin PQ= cos 4), and AQPT: A, equation (1) becomes (2) cos T’a=cos 45 cos x. Letting fQ=a, we find the length of the line T_Q to be (3) m=2a sin a/2, Where a is the radius of the sphere. From the law of sines of spherical trigonometry in ATQR, (4) sin ARTQ/sin ¢=sin ATRQ/sin :1. Since ARTQ=0 and ZTRer/2, equation (4) be- comes (5) sin 0=sin ¢>/sin a. We may then get the desired coordinates from (6) ac: TQ‘ sin a y: 7? cos 0. MINERALOGY, GEOCHEMISTRY, AND PETROLOGY Since each quadrant of the projection is a. mirror image of the adjacent quadrants, only the points in one quadrant of the hemisphere need be computed, but even so there are 8011 intersections of the integral-degree parallels and meridians in a single quadrant. For this reason the computations for the projection described here were made by Walter Anderson With the Geologi— cal Survey’s Datatron, which computed the 8011 coordi- nate pairs in 31/2 hours. The points for one quadrant were then plotted on a stable transparent mylar sheet by a rectilinear coordi- nate p'l'otte'r. Finally, four quadrants were fitted to- gether by precise photographic methods to furnish a master negative for the entire projection. Positive copies on stable film may now be obtained by standard photographic means. For ease of use, a short segment of the meridian is drawn through every other point on the 10° longitude lines, and every fifth longitude and latitude intersection (except those north and south of 75°) is marked by a small cross. B429 Near the center of the 15—inch standard-size projec- tion the integral degree points are 0.093 inch apart, and near the edges, 0.068 inch—averaging about 0.08 inch. Because positions on the projection may be estimated to about one-tenth degree, or 0.008 inch on the average, the points were plotted to an accuracy of 0.001 inch. No distortions, misalignments, or comp ing errors greater than a few thousandths of an i ch have been detected, so that calculations to an accuracy of one-tenth degree may be made with confidence. REFERENCES Fairbairn, H. W., 1949, Structural petrology of deformed rocks, 2nd ed.: Cambridge, Mass, Addison-Wesley Press, 344 p. Graham, J. W., 1949, The stability and significance of mag— netism in sedimentary rocks: Jour. Geophys. Research, v. 54, p. 126—136. Phillips, F. 0., 1954, The use of stereographic projection in structural geology: London (publishers, Edward Arnold), 86 p. Wallace, R. E., 1959, Graphic solution of some earth satellite problems by use of the stereographic net: Jour. British Interplanetary Soc, v. 17, p. 120—123. MINERALOGY, GEOC’HEMISTRY, AND PETROLOGY 195. CRYSTAL HABIT 0F FRONDELITE, SAPUCAIA PEGMATITE MINE, MINAS GERAIS, BRAZIL By MARIE LOUISE LINDBERG, Washington, DC. F rondelite, Mn”Fe4”’(PO4)3(OH)5, was described some years ago as a new mineral from the Sapucaia peg- matite mine, Minas Gerais, Brazil (Lindberg, 1949). The specimens on which the description was based con- sisted of brown botryoidal masses with a radiating fi— brous structure. Frondelite forms an isomorphous series with rockbridgeite, F e"F e4’” (P04) 3 (OH)5. Bot— ryoidal masses of minerals in this series are of wide- spread occurrence, but no single crystals of any of them have yet been described. Minute, doubly terminated, stubby crystals of fronde- lite (fig. 195.1) with high luster have been found, to- gether with crystals of avelinoite, ( =cyrilovite) (Lind- berg, 1957a), metastrengite, and leucophosphite (Lind- berg, 1957b). These form loose aggregates of sugary grains in a vuggy zone in the larger botryoidal masses of frondelite. The crystals are up to 0.2 mm in length. The crystal forms include {100}, {010}, {110}, and {101} (table 195.1). TABLE 195.1.—Morphological data for frondelite Crystal class: 222 Space group B2212 Calculated data po:q0:ro=0.3751:0.3063: 1 r2zp2:q2=3.265: 1.225: 1 a:b:c=0.8166:1:0.3063 q1:r1:p1=0.8166:2.666.l Forms 40 p=C (pl p1=A (p2 p2=B 010 0°00' 90°00’ 90°00’ 90°00' _ 1 ...... 0°00, 100 90°00' 90°00’ ________ 0°00, 0°00' 90°00’ 110 50°46' 90°00, 90°00’ 39°14, 0°00’ 50°46’ 101 90°00’ 20°34’ 0°00’ 69°26, 69°26' 90°00, Frondelite is orthorhombic; its space group is B2212; a: 13.89, b = 17.01, c= 5.21 A (Lindberg, 1949). Similarities in the powder pattern to that of mangano‘an lipscombite, (Mn”,Fe”)Fe”’2 (P04) 2 (OH) 2, (Lind- B430 (“P ~ ‘ \‘ ' ‘‘‘‘‘‘ ~r------- —""——-?= I I IOI : ' I I I l I I I I I I ' I I I I l I | ' I I : = ' I I : I I I I 'I 0 ID I : 100 I l I 0 (-5 l I I ' l I I I : I I I . : . I , l | . : I ' ' I . , , a ’ ——————— -.!\ l I / r \ \ I / / ’ \ I ’ , / \ \ FIGURE 195.1.—Crystal habit of frondelite. 196. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES berg and Pecora, 1958) suggest that the crystal struc- ture may be derived from that of lipscombite (Katz and Lipscomb, 1951) by systematic omission in the filling of octahedral and tetrahedral spaces, in a manner similar to that by which the crystal structure of the lazulite- scorzalite-barbosalite series can be derived from that of lipscombite (Lindberg and Christ, 1959). Intensity data for the determination of the crystal structure are being collected from the frondelite crystals. REFERENCES Katz, Lewis, and Lipscomb, W. N., 1951, Crystal structure of iron lazulite, a synthetic mineral related to lazulite: Acta Cryst, v.4, p. 345—348. Lindberg, M. L., 1949, Frondelite and the frondelite—rock- bridgeite series: Am. Mineralogist, v. 34, p. 541-549. 1957a, Relationship of the minerals avelinoite, cyrilovite, and wardite: Am. Mineralogist, v. 42, p. 204—213. 1957b, Leucophosphite from the Sapucaia pegmatite mine, Minas Gerais, Brazil: Am. Mineralogist, v. 42, p. 214—221. Lindberg, M. L., and Christ, 0. L., 1959, Crystal structures of the isostructural minerals lazulite, scorzalite, and barbosa- lite: Acta Cryst, v. 12, p. 695—697. Lindberg, M. L., and Pecora, W. T., 1958, Phosphate minerals from the Sapucaia pegmatite mine, Minas Gerais: Soc. Brasileira Geologia Bol., v. 7, no. 2, p. 5—14. SOME CHARACTERISTICS OF GLAUCONITE FROM THE COASTAL PLAIN FORMATIONS OF NEW JERSEY By JAMES P. OWENS and JAMES P. MINARD, Washington, DC. Glauconite concentrates were collected from most of the formations of the New Jersey coastal plain near Trenton, NJ. A sample was collected from each of 9 formations of Late Cretaceous to early Tertiary age, and 2 samples were taken from the Cape May forma- tion of Quaternary age. The 11 samples were sub- j ected to a variety of tests to determine whether chemi- cal or physical properties provide criteria for distin- guishing between primary and reworked glauconite. A method for differentiating the two types is proposed, based chiefly on grain morphology and chemical char- acteristics. In addition, it is proposed that the re— worked glauconite can be further subdivided into two types: the marine detrital and the fluvial detrital. All the samples were concentrated by magnetic sep— aration, and final purification was made by a heavy liquid separation. BINOCULAR EXAMINATION The dominant grain morphology for each concen- trate was determined microscopically. The major types were found to be (a) rounded or subrounded grains with smooth to grooved surfaces (botryoidal) and (b) elongate grains which appear to be stacks of green micaceous plates—“accordion” forms of Galliher (1935) or “tabular” forms of Light (1952). All the concentrates consist chiefly of the rounded grains, but the presence of the accordion forms in quan- tity in some of the suites suggests that much of the glauconite is primary. High concentrations of ac- cordion forms occur in the Merchantville and Marshalltown formations and in the Red Bank sand. The rounded types are decidely larger than the other types, commonly occurring as coarse sands, whereas the accordion forms rarely exceed medium sand size. MINERALOGY, GEOCHEMISTRY, AND PETROLOGY CHEMICAL ANALYSES The concentrates were chemically analyzed and the structural formulas computed for each (table 196.1). The samples containing abundant accordion forms show a significant deficiency in the total interlayer ions as compared with the reworked sands. The glauconite samples from the reworked fluvial sands of Quaternary age also show a much higher fer- ric to ferrous ratio than the older primary and re- worked sands of marine origin. X-RAY STUDIES X-ray diifractometer studies were undertaken to de- termine the homogeneity of the glauconite concen- trates and the degree of ordering in the structure (fol- lowing Burst’s (1958) classification). Contamination by other minerals such as clay and quartz was notably low. Small amounts of apatite were detected in some samples, however, particularly those from the Manasquan and Mount Laurel form-a.- TABLE 196.1.—Structural formulas computed from chemical analyses of glauconite concentrates from formations of the coastal plain Cape May formation: [K.mNamHMg.aasFefésaFeI 73’27A1.249Ti.o75118ia.501A1.4930101(0H)2 E: 2:.680 2:2.07 2:4.00 E Cape May formation: [K.70Na,m][Mg_35Fe'_é7Fe1";;Al _33Ti][Si3,62A1_380m](OH)2 2:.709 2:202 2:4.0 a Kirkwood fox mation: c: g f [K.747Na.oosl[Mg.47Feis’saFeiiol A] .34TillSia.76A1.24010l(OH)2 2 .2=.755 2:2.046 2=4.0 v Manasquan formation: g IIK,mNa.0130a_m]_[Mg_45Fe'_{5Fe 3;;A1 _42Ti.003][Si3.mA1 310.0](OH); a Z=.84 2:1.968 2:4.0 Vincentown formation (basal member) : [K.95Na.mCa.08][Mg.33Fe'.2’3Fe,"3§A1,31Ti,05][Si3.a7Al.330101(OH)2 :5; 2:.74 2:2.00 2:4.00 :3: Hornerstown sand: [K ,mNamCa WuMg mFe f 2'04Fe1'fogAl‘35Ti 1,03] [Sis “A1 Mow] (OH); 2:.780 2:2.031 2:4.00 B431 TABLE 196.1.——Structwral formulas computed from chemical analyses of glauconite concentrates from formations of the coastal plain—Continued Red Bank sand: III [K .oseNa.oosca.01llMg.asFel.isF€1 .o A1.43Ti .oo4l[Sia.asA1.320wl (OH): 2:.655 2:2.014 2:4.00 Navesink formation: /II [K.mNa.oooCansllMgesFeiz/sFei .1 A1.34Ti.ooallSia.69A1.3101ol(0H)2 w 2:.737 2=2fl4 i=4-0 i Mount Laurel sand: E [K.727Na.004ca.03l[Mg.31Fei2’1FefilIAAlJGTi.006][Si3.59A1.410101(OH)2 :2; 2:761 2:2.026 2=40 D , Marshalltown formation: IH [K.634Na.oosCamsllMgssFeh/sFe.91 A1.5aTi.004llSi3.'/3A1.270101(0H)2 2:.657 2:2.004 2:4.0 Merchantville formation: III [K.621Na.oooca.025][Mg.293FeiisFe .99 Al.58Ti .005][Si3.61A-l.39010l(OH)2 2:.655 2:2.028 2:4-0 Idealized formula (Hendricks and Ross) :. (K, Can, Na).84(A1.47Feii7’Fe’.i9Mg.4)(Si3.osA].35010)(0H)2 2:.84 2:2.03 2:4.00 tions. Because of this, the P205 determined by chem- ical analysis in all the concentrates was combined with an equal amount of 09.0 before computing the formulas. Four X-ray classes of glauconite were defined by Burst (1958), two of these, the “well-ordered” (1 M mica structure) and “disordered” (1 Md mica struc- ture), reflected a high degree of homogeneity for this mineral. X-ray analyses of all the concentrates showed them to be either the “well-ordered” or “disordered” types. No consistent relationship could be established by this method to differentiate between the primary and re- worked types. INFRARED ANALYSES An attempt was made to characterize the glauconites by means of infrared analyses. The results obtained from all the specimens are fairly similar, as was true with the X—ray analyses. A typical pattern has well- developed troughs at the wave lengths 9.4 and 10.2 microns, and a weak reflection at 12.5 microns. Small differences in the magnitude of the troughs are espe- B432 cially noted from the glauconite in the Kirkwood. The reason for this difference is still not known, but a possi— ble explanation may be in the Fe’” to Fe” ratio. Of all the samples, this ratio is lowest in the Kirkwood, about 3:1. The ratio in most specimens ranges from 6: or 8:1, but in the fluvially reworked glauconites it is as much as 20 :1. . EXCHANGE CAPACITY STUDIES The exchange capacity for glauconite from two of the Coastal Plain formations (table 196.2) shows the stability of the major interlayer ion, potassium, in the glauconite structure. TABLE 196.2.——Ewchange capacity and exchangeable cations of glauctmtte concentrates from Sewcll, N .J. [Analyst, Dorothy Carroll] Meq per 100 g {{I‘tbtal 2 1n Formation Sieve sample size (per- Na K Ca Mg Total A B cent) (sum) Hornerstown ....... +35 0. 06 0. 03 15. 4 9. 8 25. 3 21 22. 3 7. 4 Hornerstown ....... +60 . 12 . 02 15. 4 7. 0 22. 4 22.0 24. 0 ________ Navesink ___________ +35 .05 .02 15.8 4. 9 20. 8 23. 0 26. 4 7.2 Navesink ........... +60 .03 .02 15. 4 5. 6 21. 0 ...... 22. 8 ______ Navesink ........... +120 .07 .02 18. 5 7. 7 26. 3 25 26. 4 ........ A=Determined after leaching with NILCI. B = Colorimetric manganese method. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES These data suggest that if a primary grain (low but stable interlayer ion total) is reworked in an environ- ment where the necessary interlayer ions are readily available, an increase in the interlayer summation should be expected. This is clearly shown in table 196.1. SUMMARY In summary, those glauconites with low interlayer ion summation, medium to fine grain size, and large concentrations of accordion forms are thought to repre- sent primary types. The glauconites of the Merchant— ville, Marshalltown, and Red Bank are chiefly this type. Those glauconites with high interlayer ion summations, rounded shapes, and coarse grain sizes, are considered to be reworked marine types. The glauconites of the Mount Laurel, Navesink, Hornerstown, Vincentown, and Manasquan are mostly this type. Those glau- conites with a high Fe’" to Fe” ratio are considered to be subaerially altered and are of fluvial origin. The glauconite of the Cape May is this type. REFERENCES Burst. J. F., 1958, Mineral heterogeneity in glauconite pellets: Am. Mineralogist, v. 43, p. 481—497. Galliher, E. W., 1935, Geology of glauconite: Am. Assoc. Petro- leum Geologists Bull, v. 19, no. 11, p. 1569—1601. Light, Mitchell, 1952, Evidence of authigenic and detrital glauconite: Science, v. 115. no. 2977, p. 73-75. 6% 197. X-RAY DETERMINATIVE CURVE FOR NATURAL OLIVINE OF COMPOSITION Foaom By EVERETT D. JACKSON, Menlo Park, Calif. X-ray diffraction determinative curves for the entire range of olivine composition between forsterite and fayalite have recently been published by Yoder and Sahama (1957, p. 475—491), Eliseev (1957, p. 657—670), and Heckroodt (1958, p. 377—386). Yoder and Sa- hama state that the error attached to an individual estimate of composition on their determinative curve is :3 or 4 mol percent F0. Although Eliseev and Heck— roodt have not carried out statistical analysis of their data, the errors in their curves appear to be of the same order of magnitude. A more precise curve has been constructed to determine the F0 content of a large num- ber of olivines from the Peridotite member of the Still— water complex, where the entire range of olivine com— position is only 10 mol percent. Olivine concentrates from five specimens of olivine- bearing rocks of the Peridotite member were crushed to —325 mesh and cleaned by centrifuging in Clerici solution. Optical grain counts indicate that the sam- ples thus obtained are more than 99 percent pure oli— vine. Two of the samples were split to make hidden duplicates, which were then treated as separate samples. All seven samples were analyzed by a spectrogravi- metric method devised by Stevens and others (Art. 228), and the F0 Content was calculated as the atomic ratio of Mg to total octahedral cations. Splits of each of the 7 samples were further divided into 3 subsamples for X—ray examination. These subsamples were as— signed random numbers to determine run order, mixed with about 10 percent lithium fluoride (reagent), and MINERALOGY, GEOCHEMTSTRY, AND PETROLOGY prepared as slurrys on cover glasses 7/8 inch in diameter. The cover glasses containing the slurrys were placed in a rotating sample holder, and sample heights were ad- justed by placing prepared disks of the proper thick- ness under the sample. Each of the 21 subsamples was allowed to oscillate twice up and down between 62° and 67°20 on a Norelco diffractometer using copper radia- tion and a nickel, filter. One degree divergent and scatter slits were used; the receiving slit was 0.006 inch wide, the scan speed 14° per minute, and the chart speed 1 inch per degree 20. The distance between the olivine (062) peak and the lithium fluoride (220) peak was measured directly in degrees from the charts and com- piled, and means and standard deviations of A 20 were calculated from them. F0 content, calculated from the analyses, and X-ray data are summarized in table 197.1. TABLE 197.1.———X—ray measurements and F0 content of seven olivine samples from the Stillwater complex Mean of 12 read- Standard ings A20 (062) deviation Field No. Lab. N0. F0 1 olivine-(220) of 12 lithium fluoride readings (degrees) 2 (degrees) 3 55MV—49 ______________ 9 89. 7 2. 857 0. 0014 55MV—40 ______________ 8 85. 8 2. 926 . 0010 55BE—44 4 ______________ 11 85. 8 2. 928 . 0013 55MV—26 ______________ 6 84. 9 2. 947 . 0025 55BE-37 5 ______________ 10 84. 7 2. 945 . 0019 55MV—29 ______________ 7 84. 0 2. 958 . 0015 52MV—9 _______________ 5 80. 5 3. 019 . 0015 I Atomic ratio of Mg to total octahedral cations. 1 For Cu radiation. 3 There appear to be no significant run and smear differences. 4 Hidden duplicate of 55MV—40. ‘ Hidden duplicate of 55MV—26. The information in table 197.1 forms the basis for the determinative curve in figure 197.1. It was most con- venient to plot X-ray measurements directly as A26 (Cu) 0n the ordinate. A regression analysis of the data in table 197 .1 was made, considering each of the seven measurement sets to be individual determinations and taking the chemically derived F0 value as the in- dependent variable. The equation for the straight line curve is: A20 (062) olivine—(220) lithium fluoride= 4.4587—0017 855 F0 The 95 percent confidence intervals (based on assumed normal distribution) for the regression equation are :0.006°20 at 85 mol percent F0 and i0.0075°26 at 80 and 90 mol percent F0. These limits correspond to an uncertainty of about :035 mol percent F0 at the center 3.02 2.98 2.94 2.90 AT F035 THE 95 PERCENT CONFIDENCE INTERVAL IS i0.006° DEGREES A 29 (062) OLIVINE —(220) LITHIUM FLUORIDE (Cu RADIATION) 90 88 86 84 82 80 F°(AT°M'C RAT'O Mg/TOTAL OCTAHEDRAL CATIONS) FIGURE 197.1.—X-ray determinative curve for natural olivine of composition F030.” of the curve and $0.43 mol percent F0 at the limits of the curve. The absolute values of d130 were also determined by means of a silicon internal standard, after the method of Yoder and Sahama (1957, p. 475—491), but the standard deviations and the standard error obtained by this method were considerably greater. Measure— ments of the (062) peak are inherently more precise than measurements of (130), because (062) appears at a larger 26 angle and because the (062) spacing changes more over the range forsterite-fayalite (Eli- seev, 1957, p. 660—661). Disadvantages of (062) as compared with (130) are that it is less intense and more subject to interference from reflections of some com- monly associated minerals. The determinative curve shown in figure 197.1 is based on olivine from a single petrographic province. Yoder and Sahama (1957, p. 487) have shown that X-ray parameters of olivines are sensitive to variation in minor element content and possibly to temperature of formation. The curve therefore should be used with caution in estimating or comparing compositions of olivine from diverse environments. B434 GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES REFERENCES Eliseev, E. N., 1957, Rentgenometricheskoye izucheniye miner- alov isomorfnogo ryada forsterit-fayalit [X-ray investiga— tion of the minerals of the isomorphous series forsterite fayalite]: Zapiski Vsesoyuznogo Mineralogicheskogo Ob- shchestva, v. 86, no. 6, p. 657—670. Heckroodt, R. 0., 1958, An X-ray method for the determination of olivine: Geol. Soc. South Africa Trans. and Proc., v. 61, p. 377—386. Yoder, H. 8., Jr., and Sahama, Th. G., 1957, Olivine X-ray determinative curve: Am. Mineralogist, v. 42, p. 475—491. ’X‘ 198. ACIDIC PROPERTIES OF FITHIAN “ILLITE” By DOROTHY CARROLL and ALFRED M. POMMER, Washington, DC. Work done partly in cooperation with the U.S. Atomic Energy Commission If the pH values obtained by discontinuous potentio- metric titration of the H-form of Fithian “illite” (A.P.I. reference clay mineral No. 35) are plotted against log NaOH concentration, curves are obtained that are unlike those found for H—montmorillonite (Pommer and Carroll, 1960). The principal differences are in slope and in the positions of equivalence points for the two clay acids which, theoretically, should be present. The pH values obtained change with time, ap- parently because the “illite” reacts slowly with the base. These difl'erences are shown in figure 198.1. Garrels and Christ (1956) showed that “illite” be- haves as a mixture of two clay acids, and suggested that both interlayer and edge sites of the mineral may contribute to its acidity. Hendricks (1945) believes that cation exchange in micaceous minerals is due primarily to neutralization of charges at the surfaces and edges of mineral platelets, and secondarily to re- placement of cations in between the sheets. These sheets are firmly held together by K+ ions as in mus- covite, but as the K+ ions are leached out by weathering other cations enter to make up the total positive charge required to keep the mineral electrically neutral. The total exchange capacity of these micaceous minerals and the ease with which their exchangeable cations can be replaced is very much less than for montmorillonite. The structural formula of the “illite” sample used for the titration was calculated from a chemical analy- sis by W. W. Brannock. The charge deficiency of the cations is almost equally divided between the octahedral and tetrahedral layers: —.34 —.33 3+ 2+ . (A11.44Fe.32Mg.19) (813.67A1.33) 010 (OH) K2-46 (Ca,Na) .13 The exchange capacity determined experimentally, 26 milliequivalents per 100 grams, agrees satisfactorily with the calculated figure of 20 milliequivalents per 100 grams. In recording successive pH values for the 32 samples in the discontinuous titration (table 198.1) it became apparent that the values were steadily decreasing. Part of this decrease was undoubtedly due to reaction of atmospheric CO2 with the NaOH, as explained else- where (see Art. 199). The pH figures for the “illite” sample suspended in distilled water decreased steadily from 5.0 to 2.90 over a period of 75 days, and this lowering of pH values cannot have resulted from COZ absorption by the water, because the pH values are much too low. Apparently the “illite” releases H ions very slowly. The data plotted in figure 198.1, curve (A), obtained after 1 day, showed that the “illite” reacted to the NaOH as a monobasic acid. The pK value was calcu— lated to be 6.9 and this value is not consistent with the low pH of the distilled water in contact with “illite”. The material even initially appeared to have a higher acidity than an acid with a pK of 6.9. Curve (B) has no definite inflection point; in fact it is almost a straight line. The “illite” here reacts as a substrate with an infinite number of exchange sites, and the ex- change can be considered a surface reaction. Curve (0), obtained as a result of 75 days reaction of the “illite” samples with NaOH solutions, shows three dis- tinct breaks. This curve resembles somewhat vaguely that obtained for H—montmorillonite (Pommer and Carroll, 1960). Its principal intersection point is at pH 3.8; an inflection point appears at pH 5.6. The first part of each of the three titration curves is similar in slope, although at different pH values. The pH values suggest that some of the H+ ions are very loosely MINERALOGY, GEOCHEMISTRY, AND PETROLOGY B435 I I I I I I I I I I 2.00 — 1.50 1.00 0.90 0.80 0.70 0.60 .O 01 O .0 4; O 0.30‘ MILLILITER 0.01 N NaOH 0.20 “ILLITE” 0.10 - 0.09 _ 0.08 — m 0.07 - ._ 0.06 O O O "I 0.05 I I I I I I I I l I I I L 4.0 5.0 6.0 7.0 8.0 9.0 10.0 pH FIGURE 198.1.——Discontinuous potentiometric titration of 1-percent suspensions of H-“illite” with 0.01N NaOH (each sample has a volume of 6.8 ml). A, Curve obtained 1 day after NaOH increments were added; B, average curve for the suc- ceeding 5 days; 0, curve obtained after NaOH had been in contact with the “illite” samples for 75 days. B436 TABLE 198.1.—pH values for the titration of 70 my samples of H—“illite” with 0.01 N NaOH [Total volume per sample is 6.8 m1. n.d.=not determined.) NaOH pH after number of days indicated Na Sam- added ppm ple (ml) per 100 1 l 3 4 6 7 3—7 2 75 3 ml 4 1 ...... nil 5. 0 4. 70 4. 55 4. 31 4. 08 4. 40 2. 90 5 0. 71 2 ______ 0.06 5. 45 5. 00 4. 80 4. 60 4. 45 4. 71 3. 00 . 68 3 ...... . 12 6. 20 4. 75 5. 25 5. 01 4. 70 4. 92 3. 10 . 81 4 ...... .18 6. 40 5. 90 5. 20 5. 31 5.05 5. 36 3.15 . 86 5 ...... . 24 6. 52 6.02 5. 85 5. 65 5. 30 5. 70 3. 20 . 67 6. _ . .-. .30 6. 75 6. 32 6. 02 5. 90 5. 40 5. 91 3. 25 . 77 7 ______ . 36 6. 85 6. 45 6. 10 6. 05 5. 62 6. 05 3. 35 . 25 8 ...... . 42 6. 90 6. 60 6. 21 6. 28 6. 00 6. 27 3. 51 . 77 9 ...... . 48 7. 10 6. 60 6. 45 6. 45 6. 05 6. 38 3. 50 . 84 10 ..... . 54 7.05 6. 63 6. 55 6. 58 6. 33 6. 52 3. 71 .91 11 _____ . 60 7.05 6. 75 6. 55 6. 65 6. 25 6. 55 3. 81 . 94 12.. ._ .66 7.25 6. 70 6.65 6.83 6.50 6.67 4.15 1.16 13 ..... . 72 7. 30 6. 95 6. 69 6. 90 6. 60 6. 78 4. 13 1. 20 14 ..... . 78 7. 42 6. 97 6. 75 7. 03 6. 72 6. 86 4. 35 4. 19 15 ..... . 84 7. 51 7. 10 6. 98 7. 12 6. 83 7. 01 4. 85 4. 27 16 _____ . 90 7. 65 7. 10 6. 97 7. 15 6. 82 7. 01 5. 00 4. 09 17 ..... . 96 7. 50 7. 20 6. 95 7. 23 6. 88 7. 06 5. 10 4. 13 18 ..... 1. 02 7. 70 7. 25 7. 05 7. 37 7. O5 7. 18 6. 20 4. 13 19 ..... 1. 08 7. 80 7. 31 7. 25 7. 45 7. 10 7. 27 6. 60 n.d. 20 ..... 1. 14 8. 12 7. 35 7. 30 7. 40 7. 13 7. 30 6. 75 4. 21 21 ..... 1. 20 8. 30 7. 43 7. 35 7. 51 7. 20 7. 37 7. 00 1. 16 22 _____ 1. 26 8. 70 7. 62 7. 45 7. 55 7. 25 7. 46 7. 05 2. 24 23 ..... 1.32 8. 58 7. 50 7. 40 7. 60 7. 38 7. 47 7. 20 1. 96 24 ..... 1. 38 8. 80 7. 08 7. 51 7. 65 7. 41 7. 56 7. 30 1. 92 25 ..... 1. 44 8. 89 7. 80 7. 55 7. 69 7. 42 7. 61 7. 35 3. 20 26 ..... 1. 50 9. 10 7. 75 7. 55 7. 77 7. 45 7. 63 7. 05 4. 30 27 ..... 1. 56 9, 25 7. 83 7. 67 7. 71 7. 52 7. 68 7. 45 4. 42 28 ..... 1.62 9. 30 7. 98 7. 70 7. 82 7. 55 7. 76 7. l5 4. 44 29 _____ l. 68 9. 25 7. 80 7. 77 7. 80 7. 61 7. 74 7. 52 4. 53 30 ..... 1. 74 9. 30 8. 00 7. 81 7. 90 7. 65 7. 74 7. 6O 4. 33 31 ..... 1. 80 9. 55 8. 20 7. 98 8. 00 7. 75 7. 98 7. 65 4. 45 32 0- .._ 1. 80 10. 61 9. 68 9.18 8. 50 8. 20 8. 89 8. 12 4. 89 I Readings for curve A, figure 198.1. 1 Average of 3—7 days. Readings for curve B, figure 198.1. 3 Readings for curve 0, figure 198.1. ‘ Determined in 100 ml filtrate removed from “illite” after 75 days. 5 Sample 1, blank; contains 70 mg illite in water. 6 Sample 32, blank; contains 1.8 mg. 0.01 N NaOH in water but no “illite.” 199. GEOLOGICAL SURVEY RESEARCH 1960—SHORT PAPERS IN THE GEOLOGICAL SCIENCES held by the “illite”. The lowering of the inflection point from curve (a) to curve (c) appears to show a decrease in the exchange capacity, perhaps caused by flocculation and consequent loss of exchange sites by the clays. The solutions were removed from the “illite” samples and sodium was determined in the filtrates (table 198.1, column 7). The results indicate that during addition of the first 12 increments of sodium hydroxide the “il— lite” removed sodium from the solutions. The solu- tions from samples 14 to 31 contained considerably higher amounts of sodium than those from the other samples. The results of the potentiometric titration emphasize the difficulty and slowness with which micaceous min- erals react, probably because of the presence of K+ ions that hold the octahedral sheets firmly together. Fithian “illite” is much more compact than montmorillonite and has a high inherent charge (Marshall, 1949, p. 22). Chemical analyses of micaceous minerals show that they form a series in which the exchange reaction will increase as K* ions are removed and are replaced by other cations such as Ca2+ and Mg“. REFERENCES Garrels, R. M., and Christ, 0. L., 1956, Application of cation exchange reactions to the beidellite of the Putnam silt loam soil: Am. J our. Sci., v. 254, p. 372—379. Hendricks, S. B., 1945, Base exchange of crystalline silicates: Indus. and Eng. Chemistry, v. 37, p. 625—630. Marshall, 0. E., 1949, The colloid chemistry of the silicate min- erals: New York, Academic Press, 195 p. Pommer, A. M., and Carroll, Dorothy, 1960, Interpretation of potentiometric titration of H-montmorillonite: Nature, v. 185, p. 595—596. CARBON DIOXIDE AND ALUMINA IN THE POTENTIOMETRIC TITRATION OF H-MONTMORILLONITE By Donomr CARROLL, Washington, D.C. Work done in cooperation with the U.S. Atomic Energy Commission Interpretation of the results of potentiometric titra- tions of hydrogen-clays with a base may be somewhat uncertain for two reasons: (a) pH values are influenced by the chemical reaction of atmospheric 002 with the base; and (b) alumina in the exchange positions of the mineral may interfere with the replacement of H“ ions by other cations in the neutralization of the clay acid. Discontinuous potentiometric titrations of H-mont- morillonite (Pommer and Carroll, 1960) with NaOH yield values in the range of pH 4 to 12. A number of blanks containing NaOH solutions without clay sam- ples were inserted among the samples to show the effect of their reaction with 002. The samples were all in glass weighing bottles with tightly closed but not air- MINERALOGY, GEOCI-IEMISTRY, AND PETROLOGY tight covers. The bottles were opened to make pH reading. In accordance with the experimental design the pH was determined after the solutions had been mixed and allowed to stand for 1 day and for 12 days (table 199.1). TABLE 199.1.—pH values of solutions to which increments of 0.1N NaOH were added [Total volume of each is 6.2 m1] N aOH N 80H, pH values after number of days indicated Differ- Sample added micro- ence in (m1) moles in pH in solution 1 2 5 7 12 11 days la _______ 0.02 0. 32 7. 60 6. 40 6. 10 6. 10 6.05 1. 55 Ga _______ . 10 1. 61 9. 85 9. 50 7. 80 7.45 7. 20 2. 65 12a ______ . 22 3. 54 10. 50 10. 30 9. 75 9. 15 8. 00 2. 50 183 ...... .44 7. 10 11.00 10. 95 10. 90 10. 60 9. 70 1. 30 24a ______ .68 10. 96 11.50 11.35 11. 40 11.35 11. 35 . 15 303 ...... .92 14.83 11.75 11.58 11.52 11.65 11.65 .10 38 _______ 1. 20 19, 35 11.85 11.65 11. 75 11.75 11.85 nil A semilog plot of pH values against concentration of NaOH shows the efi'ect of COzin this particular titra- tion by the divergence of the lines for the first and second series of pH readings (fig. 199.1). A plot such as figure 199.1 can be used to estimate the maximum deviations due to COZ absorption. These values are helpful in deciding whether CO2 absorption affects the results of such titration experiments to a significant degree. 30-0 I I I l I I ‘I 1 l I ‘f l I 20.0r |0.0 .U' o 'o lllllll 'o- MICROMOLES NaOH IN SOLUTlON B437 The figures in table 199.1 show that under experi- mental conditions, even with carefully closed con- tainers, there may be appreciable lowering of pH values in potentiometric titrations of H—clays. It has been found, however, that this does not necessarily interfere with the interpretation of curves for clay acids. The second difficulty that may occur in titration of an H-clay with a base is caused by movement of alumina from the octahedral layer of the mineral to the ex— change positions during the preparation of the H—clay. The clay has then become an H—Al-clay and behaves differently from an H-clay on titration with a base. Paver and Marshall (1934) first drew attention to the release of A1203 from clay minerals by electrodialysis. Subsequently various investigators (Low, 1955; Mo- Aulifl'e and Coleman, 1955; Aldrich and Buchanan, 1958; Higdon and Marshall, 1958) have described the effect of titration of H-Al—clays with bases. Thompson and Culbertson (1959) have said that autodigestion takes place if H-montmorillonite is stored after pre- paration. No additional alumina is released, however, if all traces of HCl are removed by careful washing, and Taylor (1959) has shown that the decay of acid- washed clays from H- to Al—systems cannot be inhibited by washing out the excess acid with water. Higdon and Marshall (1958) conclude from a series of experi- ments that true H-clays can be prepared by treatment with H—exchange resins but not by electrodialysis. Samples of H-montmorillonite from Chambers, Ariz., prepared by treatment with 1 N HCl at room temperature, were used for a discontinuous potentio- TABLE 1992—14120; found in filtrates from the titration of H—montmorillonitc with 0.1 N NaOH [65 mg samples in a total volume of 6.2 m1] pH FIGURE 199.1—Effect of reaction of 002 with very dilute NaOH solutions in closed glass containers. A, pH readings 1 day after mixing; B, pH readings 12 days after mixing. The lowest point on curve A indicates a lower pH than was theo- retically expected, because reaction with 002 is more strongly shown in such dilute- solutions than in more concentrated solutions. Sample NaOH added A1203 (mg) Sample NaOH added A1203 (mg) (HID (1111) 1 _______ nil 0. 06 19 ______ 0. 48 2. 32 2 _______ 0.02 nil 20_-____ . 52 2. 87 3 _______ .04 .06 21 ------ . 56 3. 53 4 _______ .06 nil 22 ------ . 60 3. 95 5 ------- .08 nil 23-_____ .64 3.11 6 ------- . 10 nil 24 ------ . 68 3. 95 7 ------- . 12 . 25 25 ------ . 72 3. 95 8 _______ .14 .37 26_----- .76 3.11 9 ------- .16 .50 27__---_ .82 2.99 10_--__- .18 .82 28 ______ .86 2.39 11 ------ .20 .99 29 ______ .90 4. 31 12--._-- .22 .99 30__-_-. .94 3.53 13 ------ .24 1.75 3] ______ .98 3.05 14_-__ .28 2. 75 32 ______ 1.06 4.19 15 ------ .32 4. 13 34 ------ 1. 10 4. 31 16 ------ .36 3. 92 35 ______ 1. 14 5. 38 17 ------ .40 3. 69 36----- 1.16 4. 84 18-___. .44 .87 37 ------ 1. 20 5.26 B438 metric titration with 0.1 N NaOH (Pommer and Car- roll, 1960). The filtrates of 36 samples from this titra- tion were analyzed for A1203. If A1203 had been moved from the octahedral layers of the clay to the ex- change positions during the preparation of the H—form, it should either prevent the replacement of H* ions during titration or be present in the solutions that had been in contact with the clay samples. The titration curve obtained indicates that the clay titrated was an H—clay and not an H-Al-clay. A negligible amount of A1203 was removed during the titration of the first clay acid, and amounts up to the second equivalence point remained small. The A1203 found in the filtrates to- wards the end of the titration is due to decomposition of the montmorillonite by NaOH. The amounts of A1203 found in the filtrates are given in table 199.2. It is concluded that this method of preparation with 1 N HCl formed H-montmorillonite and not H—Al- montmorillonite. GEOLOGICAL SURVEY RESEARCH 1960—SHORT‘ PAPERS IN THE GEOLOGICAL SCIENCES REFERENCES Aldrich, D. G., and Buchanan, J. R., 1958, Anomalies in tech- niques for preparing H