The Boulder Creek Batholith, Front Range, Colorado By DOLORES J. GABLE GEOLOGICAL SURVEY PROFESSIONAL PAPER 1101 A study of difirerentiation, assimilation, and origin of a granodiorite bat/zolith showing interrelated differences in chemistry and mineralogy in the bat/zolit/z and eogenetie rock types UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1980 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Gable, Dolores J. l922— The Boulder Creek batholith, Front Range, Colorado (Geological Survey Professional Paper 1101) Bibliography: p. 85 Supt. of Docs. No.2 I 19.16:]101 1. Batholiths—Colorado—Boulder region. I. Title. II. Series: United States Geological Survey Professional Paper 1101. QE611.5.U6G3 551.8'8 78—24482 For sale by the Superintendent of Documents, US. Government Printing Office Washington, DC. 20402 CONTENTS Page Page Abstract ................................................ 1 Origin of the Boulder Creek Granodiorite and the Twin Introduction ............................................ 1 Spruce Quartz Monzonite .......................... 62 Previous work ........................................... 2 Mineralogy, petrology, and chemistry of minerals in the Techniques used in this Study --------------------------- 2 batholith .......................................... 64 Ge°1°gic setting ---------------------------------------- 3 Biotite ...- ........................................... 64 The batholith .............. : ............................ 3 Boulder Creek Granodiorite ....................... 64 Constitution of the batholith .......................... 4 Twin Spruce Quartz M onz onit e ................... 69 Contact relations and mode of emplacement ............ 6 M afi c inclusions and lampr ophyr e dikes in the Constituent rocks of the batholith ..................... 7 Boulder Creek Gran 0 di orite ..................... 69 Boulder Creek Granodiorite """""""""""" 7 Petrogenesis .................................... 69 Inclusions in Boulder Creek Granodiorite """"" 17 Hornblende ......................................... 71 Mafic plutonic rocks ' ' ' z """"""""""""" 20 Boulder Creek Granodiorite ....................... 71 Gabbro and pyroxenite . . . . . .. ................. 23 Mafic inclusions and lamprophyre dikes in the Hornblendite, hornblende diorite, quartz Boulder Creek Granodiorite ..................... 73 dlorite """""""" : """"""""""" 25 Hornblende diorite and hornblendite ............... 73 Twin Spruce Quartz Monzonite """""""""" 26 Petrogenesis .................................... 73 Granite gneiss, gneissic aplite, and pegrnatite """ 34 Plagioclase .......................................... 73 Ages 0f batholithic rocks """"""""""""" 35 Boulder Creek Granodiorite ....................... 73 Structure ............................................... 35 Twin Spruce Quartz M onz onit e ................... 77 Geochemistry ........... I . .. ............................. 38 Mafic inclusions in the Boulder Creek Granodiorite. 77 Boulder Creek Granodiorite .......... . ................. 38 Potassium feldspar .................................. 77 Chemical trends Within the batholith """"""" 38 Boulder Creek Granodiorite ....................... 77 Mineralogy in relation to chemical trends .......... 45 M afi c inclusions and lamprophyre dikes in the Chemical trends In mafic 1nclusions ................ 48 Boulder Creek Gran 0 di orit e .................... 79 Chemical trends in gabbro, pyroxenite, and horn- Twin Spruce Quartz Monzonite ................... 79 blende diorite """"""""""""""""" 50 Quartz .............................................. 79 Chemical and mineralogical trends in the Twin Accessory minerals .................................. 80 Spruce Quartz Monzonite """""""""""" 50 Alteration minerals .................................. 83 Chemical equilibrium in the Boulder Creek Granodiorite . . . . 51 _ Assimilation and differentiation in the Boulder Creek Grano- References c1ted ......................................... 85 diorite ............................................ 52 Index ................................................... 87 ILLUSTRATIONS Page PLATE 1. Generalized geologic map of the Boulder Creek batholith with emphasis on cogenetic mafic rocks in the vicinity of the Boulder Creek batholith, central Colorado ................................................................ In pocket 2. Geologic map of the Boulder Creek batholith .................................................................. In pocket FIGURE 1. Index map of the Boulder Creek batholith ....................................................................... 2 2. Photographs of typical weathered bouldery outcrops of Boulder Creek Granodiorite ................................. 4 3. Map of Boulder Creek batholith showing rock types .............................................................. 5 4. Photographs of typical Boulder Creek Granodiorite in hand specimen .............................................. 8 5. Photomicrographs of Boulder Creek Granodiorite ................................................................ 9 6. Maps showing modal distribution of quartz, ores, sphene, allanite, hornblende, and potassium feldspar: plagioclase ratios and An content of plagioclase in Boulder Creek Granodiorite ............................................. 10 7. Map and diagrams showing modal variation of quartz, plagioclase, and potassium feldspar for Boulder Creek Granodiorite .............................................................................................. 21 8. Photographs of exposures of mafic inclusions in Boulder Creek Granodiorite ........................................ 22 9. Photographs of hand specimens of mafic inclusions in Boulder Creek Granodiorite .................................. 23 10. Photograph of oval-shaped lenses of Boulder Creek Granodiorite in mafic inclusion .................................. 25 11. Photomicrographs of mafic inclusions in Boulder Creek Granodiorite ............................................... 26 III IV FIGURE 12. 13. 14. 15. TABLE 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. HH 13. 14. 15. .16. 17. 18. 19. 20. 21. 22. 23. 24. t".°$°.°°>‘95.°':“‘9°!°!“ CONTENTS Photographs of outcrops of layered and foliated biotitic hornblende diorite and massive pyroxenite ................... Photomicrographs of Twin Spruce Quartz Monzonite ............................................................. Ternary diagrams of modal variation of quartz-plagioclase-potassium feldspar for Twin Spruce Quartz Monzonite ..... Ternary diagram of modal variation in quartz-plagioclase-potassium feldspar for granite gneiss from the granite gneiss and pegmatite unit ......................................................................................... Diagram of more prominent joint sets, Tungsten and Gold Hill quadrangles ........................................ Sample locality map for rock and mineral analyses shown in tables in this report .................................... Graphs of minor elements for rock units included in text .......................................................... Variation diagrams of common oxides in Boulder Creek Granodiorite plotted against SiO2 ........................... Variation diagrams of CaO plotted against other oxides and fluorine for Boulder Creek Granodiorite .................. Ternary diagrams of KZO-NaZO-CaO chemical variation of Boulder Creek Granodiorite ............................... Ternary diagram of chemical variation of Boulder Creek Granodiorite expressed in terms of normative Q-Ab+An-Or . . . Mole percent variation in an AFM diagram for Boulder Creek Granodiorite and mafic rocks .......................... Diagrams of CaO content plotted against weight percent of rock-forming minerals in the Boulder Creek Granodiorite . . Ternary plot of KZO-NazO-CaO showing chemical variation of Twin Spruce Quartz Monzonite ........................ Ternary plot of normative Q-Ab+An-Or showing chemical variation of Twin Spruce Quartz Monzonite ............... AFM diagram showing molar variation of Twin Spruce Quartz Monzonite .......................................... Diagram of sample variation of plagioclase in relation to CaO in Twin Spruce Quartz Monzonite ...................... Diagram of distribution of manganese in biotite and hornblende in Boulder Creek Granodiorite and hornblende diorite . Diagram of phase relations for Boulder Creek Granodiorite in system SiOz-NaAlSi305-KAlSi303-CaAIZSiZOa-HZO ....... Graph of strontium, rubidium, and potassium feldspar plotted against Or/Ab in Boulder Creek Granodiorite .......... Modal biotite plotted against potassium feldspar for the batholith .......... , ....................................... Graph of percent biotite in Boulder Creek Granodiorite and Twin Spruce Quartz Monzonite in relation to percent SiO2 in rock .................................................................................................... Plot of compositional variations of K20, MgO, FeO, A1203, and SiO2 in biotites ...................................... Graph of fluorine in biotite plotted against duos) spacing of biotite .................................................. Ternary diagram of relation of Fe‘a-Fe”-Mg between biotites ...................................................... Photomicrograph of allanite and monazite crystals ............................................................... TABLE S Modes for Boulder Creek Granodiorite from the batholith ......................................................... Modes for Boulder Creek Granodiorite from small plutons and small lenses in biotite gneiss and schist ................ Modes for Boulder Creek Granodiorite from contact area of batholith .............................................. Modes for Boulder Creek Granodiorite adjacent to known faults ................................................... Summary of modal data for the Boulder Creek Granodiorite ....................................................... Modes for mafic inclusions and metamorphosed lamprophyre dikes in Boulder Creek Granodiorite .................... Modes for gabbro, hornblendite. hornblende diorite, quartz diorite, and hornblende pyroxenite ....................... Modes for Twin Spruce Quartz Monzonite ....................................................................... Modes for aplite. aplitic pegmatite, and granitic gneiss ............................................................ Chemical and spectrographic analyses and modes for Boulder Creek Granodiorite ................................... Chemical and spectrographic analyses and modes for mafic inclusions and lamprophyre dikes in Boulder Creek Granodiorite .............................................................................................. Chemical and spectrographic analyses for mafic rocks ............................................................ Chemical and spectrographic analyses and modes for Twin Spruce Quartz Monzonite ................................ Total iron expressed as FeO in biotite and hornblende ............................................................. Comparison of sillimanite-biotite gneiss and schist country rocks with averaged compositions of Boulder Creek Granodiorite .............................................................................................. Rubidium, strontium, and potassium analyses of Boulder Creek Granodiorite samples ............................... Mode summary of major minerals in the Boulder Creek batholith .................................................. Chemical and spectrographic analyses and mineral formula for biotite from Boulder Creek Granodiorite, hornblende diorite, mafic inclusions, and a lamprophyre dike ............................................................. Chemical and spectrographic analyses and mineral formula for biotite from Twin Spruce Quartz Monzonite ........... Chemical and spectrographic analyses and mineral formula for hornblende from Boulder Creek Granodiorite, mafic inclusions, a lamprophyre dike, hornblende diorite, and hornblendite ........................................... Comparison of partial hornblende lattice structures .............................................................. Chemical and semiquantitative spectrographic analyses of potassium feldspar from Boulder Creek Granodiorite ....... Chemical and semiquantitative spectrographic analyses of potassium feldspar from mafic inclusions and a lamprophyre dike in Boulder Creek Granodiorite .......................................................................... Chemical and semiquantitative spectrographic analyses of potassium feldspar in Twin Spruce Quartz Monzonite ..... Page 27 29 35 37 37 49 50 52 54 56 56 57 58 59 59 59 59 60 62 63 65 65 72 72 72 82 Page 12 18 19 19 20 24 28 30 36 40 44 46 47 60 61 63 65 66 70 74 77 78 79 80 CONTENTS V Page TABLE 25. Chemical and semiquantitative spectrographic analyses of sphene in Boulder Creek Granodiorite, inclusions, in granodiorite and Twin Spruce Quartz Monzonite ............................................................. 81 26. Chemical and spectrographic analyses of allanite in Boulder Creek Granodiorite, inclusions, and biotitic hornblende diorite .................................................................................................... 84 THE BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO By DOLORESJ. GABLE ABSTRACT The Boulder Creek batholith is the best known of several large Precambrian batholiths of similar rock composition that crop out across central Colorado. The rocks in the batholith belong to the calc-alkaline series and range in composition from granodiorite through quartz diorite (tonalite) to gneissic aplite. Two rock types dominate: the Boulder Creek Granodiorite, the major rock unit, and a more leucocratic and slightly younger unit herein named Twin Spruce Quartz Monzonite. Besides mafic inclusions, which occur mainly in hornblende-bearing phases of the Boulder Creek Granodiorite, there are cogenetic older and younger lenses, dikes, and small plutons of hornblende diorite, hornblendite, gabbro, and pyroxenite. Pyroxenite is not found in the batholith. The Boulder Creek Granodiorite in the batholith represents essentially two con- temporaneous magmas, a northern body occurring in the Gold Hill and Boulder quadrangles and a larger southern body exposed in the Blackhawk and the greater parts of the Tungsten and Eldorado Springs quadrangles. The two bodies are chemically and mineralogically distinct. The northern body is richer in CaO and poorer in K20, is more mafic, and has a larger percentage of plagioclase than the southern body. A crude sequence of rock types occurs from west to east in the batholith accompanied by a change in plagioclase composition from calcic plagioclase on the west to sodic on the east. Ore minerals tend to decrease, and the ratio potassium feldsparzplagioclase increases inward from the western contact of the batholith, indicating that the Boulder Creek batholith is similar to granodiorite batholiths the world over. Emplacement of the Boulder Creek batholith was con- temporaneous with plastic deformation and high-grade regional metamorphism that folded the country rock and the batholith con- tact along west-northwest and north-northwest axes. Also, smaller satellitic granodiorite bodies tend to conform to the trends of folia- tion and fold axes in the country rock, suggesting that emplacement was controlled by preexisting structures in the country rock. On a gross scale, chemical equilibrium in the Boulder Creek Granodiorite is expressed by a near 1:1 ratio, or straight-line rela- tionship in the distribution of iron, magnesium, and manganese in biotite and hornblende. General mineralogical trends in the Boulder Creek Granodiorite indicate that modal biotite, hornblende, and plagioclase tend to increase and quartz and microcline tend to decrease as CaO increases. These trends were not found in the Twin Spruce Quartz Monzonite. Differentiation is believed to have played a major role and assimilation a minor role in the development of the Boulder Creek batholith. The Boulder Creek Granodiorite is of probable mantle or lower crust origin, and, based on the scant data available, the Twin Spruce Quartz Monzonite may be of crustal origin, but the magma was extensively altered by contaminants of ambiguous origin. Mafic inclusions, possibly derived from a dioritic magma which was an early differentiate associated temporally with the Boulder Creek Granodiorite and (or) the Twin Spruce Quartz Monzonite, were in- jected into the Boulder Creek Granodiorite during the mush stage and before the batholith was completely crystallized. Biotite, hornblende, and potassium feldspar were studied exten- sively. Their chemistry and petrology indicate a homogeneity throughout the batholith not believed possible by a casual observ- ance of the batholithic rocks in the field. The accessory minerals, where investigated, also tend to indicate this same pervasive homogeneity. INTRODUCTION Geologic investigations, of which this report is a product, have been carried out in the Front Range of Colorado since the early 1950’s when detailed geologic studies of the crystalline rocks west of Denver were begun. The Boulder Creek batholith, just west of Boulder, Colo., occupies an area 14 km by 27 km (fig. 1). The batholith is the type area of similar masses of granodiorite that constitute a major part of the Precambrian intrusive rocks of Colorado. This report is a composite of some old and much new work, both published and unpublished. The Boulder Creek batholith was first briefly described by Boos and Boos (1934); in 1950, Lovering and Goddard mapped and presented a short description of the batholith; in 1953, Lovering and Tweto presented a more detailed description. More recently, mineralogic and geochemical aspects of the batholith have been described by George Phair and colleagues of the US. Geological Survey; these are discussed later in this report. This paper summarizes the field data concern- ing the batholith, gained by the quadrangle mapping of others as well as myself, and presents much new data on the overall mineralogy, geochemistry, and origin of the batholithic rocks. Chemical, mineralogical, and structural data in- dicate that the Boulder Creek batholith is represented by two similar but chemically different granodiorite magmas and by a distinctly different quartz mon- zonite unit, the Twin Spruce Quartz Monzonite, that is in part the same age and in part younger than the Boulder Creek Granodiorite. Like the Boulder batholith in Montana (Tilling, 1973), the two similar but chemically different granodiorite magmas were 1 1720-8 2 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO 105°30’ O Jamestown (is t‘\\\\° um} \"\\\ \ o .. O F. D. m . 40° _ 00’ Nederland o BOULDER CREEK BATHOLITH \\ uoH \\\\\\ \\ Area of reportfl CO LO RADO 0 5 10 KILOMETEHS gJ—J FIGURE 1,—Index map of the Boulder Creek batholith, Front Range, Colorado. emplaced nearly contemporaneously. The Boulder Creek batholith was emplaced during the major regional metamorphism and sufficiently early for parts of the batholith to reflect this regional deformation. PREVIOUS WORK The early work of Boos and Boos (1934), Lovering and Goddard (1950), and Lovering and Tweto (1953) on the batholith was followed by detailed quadrangle mapping and by reports on various parts of the batholith. These reports are: Boulder quadrangle (Wrucke and Wilson, 1967); N ederland and Tungsten quadrangles (Gable, 1969, 1972); Ward quadrangle (Gable and Madole, 1976); Gold Hill quadrangle (Gable, 1977); Blackhawk quadrangle (Taylor, 1976); Eldorado Springs quadrangle (Wells, 1967); and Ralston Buttes quadrangle (Sheridan and others, 1967). In addition, Sims and Gable (1964, 1967) described a few of the satellitic plutons in the metasedimentary rocks west and southwest of the batholith, and Pearson and Speltz (1975) mapped Boulder Creek Granodiorite in the Indian Peaks Wilderness area west of the Ward quadrangle. Recent topical studies of minerals from the batholith include those by Wrucke (1965) on prehnite and hydrogarnet; Hickling, Phair, Moore, and Rose (1970) on allanite; Stern, Phair, and N ewell (1971) on isotopic ages and morphology of zircon; and Phair, Stern, and Gottfried (1971) on fingerprinting discordant zircon ages. TECHNIQUES USED IN THIS STUDY The compositional classification and patterns of mineral distribution described in this report are based on modal analyses in which point counts of sufficient number (800—1,000 counts per thin section) were made to accurately represent the rock composition. Modes rounded to the nearest percent reflect less accuracy than those carried to the nearest tenth. Modal analyses of very coarse-grained rocks, such as were found in the central part of the batholith, were made using stained rock slabs, but a relatively small number of modes were made by this method. Only quartz, plagioclase, potassium feldspar, and total mafic minerals were counted on these slabs; the total mafic minerals were broken down by using a proportion determined by thin-section counts of the mafic minerals. Boundaries between composition fields in a triangular diagram (quartz, plagioclase, potassium feldspar) were deter- mined as follows: granodiorite—5 to 20 percent dark minerals, more than 5 percent quartz, soda-lime feldspar at least equal to double the amount of the potassium feldspar; potassium feldspar may vary by 8 to 20 percent in rock of 60 percent feldspar. Below the granodiorite field the rock is a quartz diorite (tonalite); above it, the rock is a quartz monzonite. In quartz monzonite, alkali feldspar (microcline plus microper— thite) ranges from 20 to 40 percent of a total of 60 per- cent feldspar. Rock units were named by using an average composition for the unit. Due to the large amount of quartz in these rocks the quartz monzonites generally fall in the granite or granitoid group of rocks according to Streckeisen’s (1976) classification. Almost none of the rocks described in this report would be classified as quartz monzonite according to the classification of Streckeisen. Therefore only the more mafic rocks within this report generally are classified by the system of Streckeisen. THE BATHOLITH 3 A total of 78 samples representative of all the rock types discussed here, excluding aplite and pegmatite, were chemically analyzed for both major and minor elements; 44 of the analyses have never been published before. Whole-rock samples were analyzed by standard (Peck, 1964) and rapid rock (Shapiro and Brannock, 1962) techniques. Minor elements were determined by semiquantitative spectrographic methods, and each result reported is the standard deviation of any single determination and should be taken as plus 50 percent and minus 33 percent. Analyzed mineral concentrates were purified by first subjecting them to ultrasonic vibrations, then cen- trifuging in adjusted mixtures of methylene iodide and bromoform, and finally passed through an isodynamic separator. Samples were then examined under a binocular microscope. This process was repeated until only 1—2 percent impurities remained. Feldspar- concentrate powders were X-rayed for purity. Analytical procedures used for each mineral are given in the chemical tables (tables 10—13, 16, 18—20 and 22—26). Other procedures not applicable to all samples have been included at appropriate places in the text. Composition of plagioclase was determined by measuring the refractive indices in index oils. Ac- curacy using this method is in the range of i003. Another method that is less time consuming but not quite as accurate used extinction angles in conjunction with albite twinning (Deer and others, 1963, p. 135—139). Figure 60 was mostly compiled by this last method. GEOLOGIC SETTING Precambrian igneous and metamorphic rocks ac- count for the greater part of the Colorado Front Range basement and are representative of the crystalline basement underlying the entire southern Rocky Moun- tain region. The Boulder Creek batholith is the oldest (1,700 my) of three extensive intrusive episodes of plutonic- rock emplacement in the Front Range. Its emplace- ment was syntectonic with the earlier major regional metamorphism. The Silver Plume Quartz Monzonite, a 1,450-m.y.-old intrusive suite, is exposed extensively north and west of the batholith but only occurs as small dikes and lenses within the batholith. Cataclasis affecting the batholith along the southeast contact (pl. 1), however, is related to the Silver Plume period of magmatism. The Pikes Peak Granite, representing the youngest Precambrian intrusive episode (1,040 my), lies well outside the area of main concern and except for a few lamprophyre dikes in the batholith that are perhaps of Pikes Peak Granite age, the batholith was not involved in that period of metamorphism. Paleozoic and younger rocks upturned during the Laramide orogeny (Tweto and Sims, 1963) overlap the Boulder Creek batholith on the east. Elsewhere, Precambrian rocks representing a high-grade metamorphic gneiss terrane constitute the country rocks into which the batholith was emplaced. The country rock consists of biotite-sillimanite gneiss and schist for the most part, but layers of microcline gneiss and quartzite occur along the southeast contact. In- terlayered with the schist and gneiss, but, at some distance from the batholith, are several layers of horn- blende gneiss that include some calc-silicate rocks and impure quartzite. Other than the mafic rocks shown on plate 1, only sparse, small dikes or sills of quartz diorite and hornblendite cut the schist and gneiss country rock. Intrusive dikes and stocks of Cretaceous to Eocene age that are coextensive with the Colorado mineral belt occur mostly to the west of the batholith; a few smaller stocks and dikes occur along the contact, but only dikes are found within the batholith. THE BATHOLITH The Boulder Creek batholith crops out typically as pictured in figure 2, as a north-south-trending body along the eastern side of the Front Range just west of Boulder, Colo., and within the Colorado mineral belt. Extending from this centrally located batholith, both to the northwest and southwest across central Col- orado, are lenses, plutons, and even other batholiths of similar composition. The batholith was emplaced in the catazone, roughly at a depth of 12—20 km. As defined by Buddington (1959), the catazone is represented by an environment of intense pressure-temperature conditions. The batholith was emplaced partly by pushing aside the surrounding country rocks, as seen in outcrops on the west side of the batholith, partly by assimilation, and partly by passive magma emplacement into fold structures. To the west of the batholith is a series of granodioritic and comagmatic mafic rocks that are crudely alined forming a continuous pattern of outcrop from the Strawberry Lake batholith to the northwest of the Boulder Creek batholith to the Mt. Evans batholith southeast of the Boulder Creek batholith (pl. 1). This pattern reflects a common tendency for associated mafic rocks to be satellitic to a major mass of granodiorite. Emplacement of the batholithic rocks apparently followed definite compositional trends as delineated in figure 3. The presumed concentric order 4 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO 4-.' FIGURE 2.—Typical weathered bouldery outcrops of Boulder Creek Granodiorite, Pinecliffe area, Coal Creek Canyon, Colorado. A, view looking north across South Boulder Creek from turnout on Colorado Highway 72. B, an outcrop along dirt road leading to Gross Reservoir from Colorado Highway 72. of emplacement was (1) quartz diorite, predominantly on the west; (2) quartz monzonite, to the east and adja- cent to the batholith contact, followed in the batholith proper at the contact by mafic quartz diorite; inward in the batholith the quartz diorite grades into granodiorite, quartz monzonite, and some granite. The eastern part of the batholith is buried, so it is not possible to comment on that part of the batholith. From figure 3 it appears that the three major rock types are nearly equally represented in the exposed part of the batholith. This crude zonal arrangement resembles that in plutons of similar composition the world over (Whitten, 1962; Nilssen and Smithson, 1965; Bateman and others, 1963). CONSTITUTION OF THE BATHOLITH The Boulder Creek batholith consists mainly of two rock types (pl. 2): (1) the Boulder Creek Granodiorite, generally the coarser grained, more mafic rock most often referred to in the literature and formally named by Sims and Gable (1964), and (2) quartz monzonite, a finer grained, often thinly slabbed, leucocratic rock that first was recognized as a distinct rock unit by Wells (1967, p. D24—D27) but not formally defined. In order to identify this rock type specifically and distinguish it from another variety of quartz mon- zonite in the Boulder Creek Granodiorite from the same area, the name Twin Spruce Quartz Monzonite is formally proposed for the unit later in this report. Also included in the batholith are scattered smaller masses of darker plutonic rock that are both older and younger than the granodiorite, profuse large and small pegmatites, numerous aplites, and remnants of metamorphic rocks. Approximately three-fourths of the Boulder Creek batholith consists of Boulder Creek Granodiorite, which is the name given a series of rocks that have the same macroscopic and microscopic characteristics and vary in composition from quartz diorite to quartz mon- zonite but average granodiorite. The granodiorite in the batholith appears to be related to two magma in- trusions. A smaller northern intrusion is separated from a larger southern intrusion by quartz diorite similar in composition to that in the contact zones of the batholith. This area of quartz diorite is north of Magnolia (Magnolia is in the northeast quarter of sec- tion 6 in the Eldorado Springs quadrangle) and trends diagonally across the batholith in an east-southeast direction along the 40° latitude (fig. 3). Twin Spruce Quartz Monzonite occurs predominant- ly in the central part of the batholith and along the southeast contact. Its composition is much less variable than that of the Boulder Creek Granodiorite. The extent to which the Twin Spruce Quartz Mon- zonite accompanies the Boulder Creek Granodiorite in plutons and batholiths other than the Boulder Creek batholith is unknown. It is found in the Mt. Evans batholith; the Rosalie lobe, studied by Bryant and Hedge, (1978), appears to be Twin Spruce Quartz Mon- THE BATHOLITH 105°37’30” 30' 22/30“ 105°14’30” 40° I | I 07' 30’ EXPLANATION Quartz diorite (tonalite) Granodiorite __ T. 2 N. Quartz monzonite T. 1 N. 00’ 39° 52’ 30” Twin Spruce Quartz Monzonite L | l R.72 W. R.71 W. i) 1J0 KILDMETERS l I 1 | APPROXIMATE SCALE 7:: T1 5‘ TiZS. FIGURE 3.—Boulder Creek batholith showing rock types as indicated from modes. Dots are mode localities; dashes represent areas of insufficient data to place boundaries accurately. 6 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO zonite (pl. 1). The Boulder Creek Granodiorite on Rollins Pass (an area between the Boulder Creek batholith and the Strawberry Lake batholith) is also accompanied by large lenses of Twin Spruce Quartz Monzonite. Further detailed mapping, however, is needed to determine the extent of the Twin Spruce in all areas of Boulder Creek Granodiorite. Gabbro, pyroxenite, hornblendite, and hornblende diorite (pl. 1) are believed to be associated in time and space with the Boulder Creek Granodiorite. Some of these mafic rocks appear to be older than the Boulder Creek Granodiorite because of their intense alteration; probably they belong to the same igneous event but were emplaced earlier than the granodiorite, as also suggested by Braddock in the Empire area (1969, p. 18). Other mafic bodies are probably the same age as the granodiorite, and still others probably are younger (Sims and Gable, 1967, p. E41). CONTACT RELATIONS AND MODE OF EMPLACEMENT Contacts of the Boulder Creek Granodiorite in the batholith with the country rocks are grossly sharp, and dips are steep to nearly vertical, although there are local variations. Foliations in the contact zone of the granodiorite are defined principally by the segregation of minerals into darker biotite-rich and lighter quartz- plagioclase-rich layers, and foliations in country rock and batholith are conformable, especially on the west side of the batholith. Forceful emplacement of the batholithic rocks is evident both along the west and south sides of the batholith; on the west, whereas folia- tions in the schist parallel the batholithic contact on a large scale, the schists are tightly folded on the scale of a hand specimen. Often chevron-type folding occurs at the contact with more open folds replacing the chevron folding out from the contact. Along the southern border of the batholith, as described by Taylor (1976), forceful emplacement of the Boulder Creek Granodiorite is suggested by the warping of adjacent gneiss into folds having overturned limbs and by the bending of the axial surfaces of older folds. To the north the schist-granodiorite contact from the Peak to Peak highway to just south of Gold Hill is folded along northwest-trending axes, and the granodiorite has been conformably emplaced along these fold axes giv- ing the batholith contact an irregular or scalloped ap- pearance (pl. 2). North of Gold Hill the trend of folia- tion in the batholith and in the gneiss and schist at the contact are parallel; however, the batholith and the ad- joining metasedimentary rocks are folded along an east-northeast synclinal axis. Interlensing of metasedimentary and batholithic rocks is common locally; at Nederland, for example, it is difficult to recognize and map a distinct, definite contact for the batholith. Along most of the western margin, however, the contact is relatively sharp, although bodies of pegmatite and aplite occur in the contact zone. The south and southeast contacts lie in the Idaho Springs—Ralston cataclastic zone (pl. 1); shearing in this zone produced a shear foliation in the rocks that extends into the batholith and masks original irregularities of the contact zone. On the north margin between the Peak to Peak highway and Sugarloaf Mountain (pl. 2), the contact zone is not nearly so foliated as on the west flank. Dips also vary only from 50° to 80° to the north, away from the batholith, whereas elsewhere dips are very steep. As the predominant country rock adjacent to the batholith is biotite schist and gneiss, it stands to reason most inclusions in the contact zone of the batholith are predominantly schist and gneiss; however, along the southeast batholith contact, there are inclusions of quartzite and microcline gneiss. Contacts between Boulder Creek Granodiorite and the finer grained Twin Spruce Quartz Monzonite within the batholith are both gradational and sharp or they are locally separated by thin pegmatite lenses or mafic (biotitic) layers; also, occasional shearing may occur along the contact. Granodiorite in contact with quartz monzonite is commonly foliated, but elsewhere the contact may be blurred due to structural similarities between granodiorite and quartz mon- zonite. In the southern part of the batholith, north of Tremont Mountain and along South Boulder Creek, irregular-shaped inclusions of granodiorite are found in the finer grained quartz monzonite. Dips of the granodiorite-quartz monzonite contacts vary from near horizontal, as in the central part of the batholith, to vertical in the southern part. The mineralogy of biotite gneiss and schist country rock is normally quite variable but from observations made while walking over contacts of metasedimentary rock and granodiorite it appears all gneiss and schist adjacent to the batholith are sillimanite bearing and abnormally rich in biotite. Along the west contact, the metasedimentary rocks in thin section are very rich in biotite, sillimanite, and quartz; plagioclase is very cor- roded, poorly twinned (the twins are indistinct and poorly developed), and very sparse as much as several tens of meters from the contact. Also, these rocks are ptygmatically folded. At Nederland, both plagioclase and potassium feldspar are noticeably absent, but as much as 10 or 15 percent kaolinite is present in the con- tact rocks. This alteration does not appear to be related to emplacement of the batholith but instead to processes associated with the Laramide mineralization in the Nederland-Tungsten district. Northward from Nederland, plagioclase in gneiss adjacent to the con- tact is very corroded, poorly twinned, and commonly THE BATHOLITH / 7 zoned (normal zoning), but is not diminished in quan- tity; potassium feldspar in the same rocks as indicated by modes varies no more than between samples from outcrops at a distance from the batholith. In the Caribou pluton, a satellitic body between Boulder County Hill, Nederland quadrangle, and Mount Albion in the Ward quadrangle (pl. 1), granodiorite on the southeast side bears profuse biotite gneiss and schist inclusions. West of Overland Mountain in the Gold Hill quadrangle the Overland pluton is very coarse grained similar to coarse-grained, nonfoliated granodiorite from the central part of the batholith prOper; it is less foliated than any of the other satellitic plutons. It also has a pronounced linea- tion due to the alinement and increase in length of the feldspar crystals in the granodiorite. In the Overland pluton biotite gneiss and schist inclusions occur throughout but are more profuse along the contact. In both these satellitic plutons, some gneiss and schist in- clusions show alteration several millimeters in from the contact, especially where contacts are indistinct due to assimilation at the boundary of inclusion and granodiorite. South of the Ward and Gold Hill quadrangles and west of the batholith proper the metasedimentary rocks are pierced by many bodies of Boulder Creek Granodiorite. At Mt. Pisgah (Central City quadrangle), the Pisgah pluton has sharp contacts with the adjacent metasedimentary rocks except along the northeast margin where again assimilation of the gneiss by granodiorite is evident. At this locality biotite stringers derived from the gneiss occur abun- dantly in the granodiorite across a distance of sev- eral meters. Emplacement of batholithic rocks, in general, ap- pears to have been from west to east although nothing is known about the easternmost edge of the batholith. Most satellitic plutons and batholithic contact rocks were probably emplaced a1m0st simultaneously. The contact magma was followed by core magma that is represented predominantly by hornblende-bearing rocks (fig. 6A). This core magma broke through the contact rocks at Gold Hill and just north and east of N ederland. The tongue of magma to the north of Nederland moved west and cut into the southern part of the Caribou pluton. The larger structural features represented by folia- tion trends throughout the batholith (pl. 2) have been deflected to varying degrees by high-grade regional metamorphism. Lineations for the greater part of the batholith have conformed to foliation trends; however, lineation trends do not always agree with foliation trends especially in the area including Pinecliffe, Tre- mont Mountain, and Gross Reservoir. That lineations are askew of foliations may be because of late magma adjustments or there may be some other reason not understood. These structural trends in the batholith led Lovering (Lovering and Tweto, 1953) to believe the magma for the entire batholith welled up from a con- duit just east of Gold Hill and spread southward, ris- ing at an angle of about 50° with the horizontal. It is possible that Lovering’s conduit represents the final emplacement of magma for the smaller northern mass whose east-to-west compositional trend is not nearly as consistent as the trend in the southern part of the batholith (fig. 3). Chemical and structural relationships tend to in- dicate that two magma intrusions may have been emplaced almost simultaneously in the batholith: a smaller northern mass that has not differentiated to the extent of a larger southern mass. CONSTITUENT ROCKS OF THE BATHOLITH BOULDER CREEK GRANODIORITE The Boulder Creek Granodiorite in the batholith is a medium- to very coarse-grained (0.6—2.0+ mm), locally porphyritic rock that has both massive and foliated facies (fig. 4). Porphyritic granodiorite generally is found in the more mafic parts of the batholith or in those parts of the batholith and adjoining plutons that have been extensively sheared and perhaps locally metasomatized. The massive and coarser grained rocks are generally found near the center of the batholith (fig. 5D). Such an area lies north and east of Pinecliffe, where the rock is very coarse and generally non- foliated, but the feldspars show a good lineation that appears to be a primary structure. The feldspars in the batholithic rocks also may be alined because of recrystallization accompanying shearing, but these textures are distinctly different because alined feldspars are accompanied by a foliation not found in the primary structure. Foliated, medium-grained, and nearly equigranular granodiorite, having perhaps both primary and secondary structures but chiefly second- ary ones, generally occurs in marginal zones of the batholith, in lenses and plutons in adjacent metasedimentary rocks, or along the many faults within the batholith proper. This foliation results from oriented alined feldspar phenocrysts, stringers of biotite and less commonly hornblende, and a weak compositional layering due to segregatiOn of biotite, quartz, and the feldspars. While the granodiorite ap- pears to vary in texture and composition within a single outcrop, it has a surprising characteristic uni- formity in texture and in mineral composition across the entire batholith. The granodiorite is typically a mottled grayish-white and black rock on weathered surfaces but appears dark bluish gray on freshly broken surfaces. Weathered sur- 8 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO FIGURE 4.—Typical Boulder Creek Granodiorite. A, foliated granodiorite from west contact (29). B, biotitic, slightly porphyritic granodiorite from north contact (50). C, slightly foliated, medium- grained granodiorite with good lineation (129). D, medium-coarse- faces are commonly pitted by bowl-shaped depressions from 1 cm to 1 m in diameter and from several cen- timeters to several tens of centimeters in depth. Weathering also produces bouldery outcrops and a knobby topography, especially in areas where the finer grained, more easily weathered quartz monzonite has been weathered out of granodiorite. Jointing also causes differential weathering and is partly responsi- ble for the development of the bouldery topography from which Boulder Creek derives its name. The dominant minerals in the Boulder Creek Granodiorite include plagioclase, potassium feldspar (microcline and microperthite), quartz, and biotite. Hornblende is either disseminated throughout the rock, as is common in the central and northern part of the batholith (fig. 6), or occurs in spotty distribution as grained, slightly porphyritic granodiorite (41). Photographs by Louise Hedricks, US. Geological Survey. Numbers in parentheses are sample localities (tables 1 and 10). Scale in centimeters. in the granodiorite in the southern part of the batholith. In figure 6 it can be seen that the ores, main- ly magnetite, are more profuse to the west of the batholith as is to be expected because the mafic rocks related to the Boulder Creek batholith occur domi- nantly in this area. Probably both the ores and the mafic rocks represent an early phase of a differen- tiating magma. This trend also coincides with the trend in plagioclase composition and with the ratio potassium-feldspar:plagioclase. Alternatively, the north to northwest modal trend of the ores, quartz, feldspar proportions, and sphene also may have developed during emplacement of the batholith and represent a regional dynamic imprint for the batholith. Modes representative of the Boulder Creek Granodiorite in the area of this report are given in THE BATHOLITH 9 FIGURE 5.—Photomicrographs of Boulder Creek Granodiorite. A, near west contact with metasedimentary rocks (389), x-polarizers, X10, B, shearing along crystal boundaries in granodiorite (4’7), x-polarizers X12. C, granodiorite, medium grained from interior of batholith (50), x-polarizers, X12. D, same section as in C; note tables 1—5. In the tables, the modes are grouped in order to show variations in mineralogy to best advan- tage. A summary of the modal data is here, in two categories: (1) lenses and small plutons within metasedimentary rocks that are adjacent (contact zone) to the batholith; and (2) the batholith proper, with three groups; granodiorite from the contact zone, clustering of mafic minerals, plain light, X12. Photographs by Louise Hedricks, US. Geological Survey. Ap, apatite; E, epidote; B, biotite; H, hornblende; MC, microcline; Mu, muscovite;0, ores; P, plagioclase; Q, quartz; S, sphene. ,) ._ w, sheared and faulted segments, and the main bulk of the batholith. From the summation above, the following conclu- sions appear valid: (1) the granodiorite in lenses and plutons in the metasedimentary rocks and in the batholith proper is similar in composition, except that ores are more common in the satellitic bodies and 10 BOULDER CREEK BATHOLITH. FRONT RANGE, COLORADO 105°30' 105°30' EXPLANATION EXPLANATION §§§ 540 III >1o 0.5—1.0 - >1.0 2‘s ZNfl $‘fl Z‘fl w~a wee R.72 W. R.71 W. R.72 W. R.71 W. U 5 II] KILOMETERS 0 5 10 KlOMEIERS APPROXIMATE SCALE APPROXIMATE SCALE mew “5.30. EXPLANA trace—0.2 §§§ 0204 III >04 ..\ EXHANAHON 0.1-0.5 m 0.5-1.0 IIILOJfl F‘fi ZNfi wee z‘fi 9""." 50"." R72 W- R.71 W. R.72 W. R.71 W. 0 5 10 KILOMEI'BRS 0 5 10 KlOMEI'BZS l__—L—l |—__|—l APPROXIMATE SCALE APPROXIMATE SCALE FIGURE 6.—Modal distribution of quartz, ores, sphene, allanite, hornblende, and potassium feldsparzplagioclase ratios and An content of plagioclase in Boulder Creek Granodiorite. Modal distribution, in percent, of A, hornblende; B, ores (mainly magnetite); C, sphene; D, allanite; E, quartz; F, apatite; G, composi- F‘fl ZNH wee z‘fi @Nfi W‘H zafi ZNfl via zrfi SI’NT‘ pd.“ Z‘H 2"." W‘fi Z‘fi V’NT' 5"‘T' 11 z-fi ZNfi W‘T' Z‘T‘ “NT' 50-2-1 THE BATHOLITH 109w 1w”, I l EXPLANATION T1 EXPLANATION \ '_ 1—25 ’ fl Oligoclase __ W 25-30 A 1 , 1- m Andesine [J 4 . N. . . - >30 fi - Labradorite "4 “5\ 1 . —— 4o" ‘ N, 40° a 00' oo' 1‘ <7 '1‘ s. n 1 I ,\ l g x a _ re; \ T. j} 4 c 1 I: E ~ ,‘ S- G 7 r T. l g, 3 \ " Q g "1/ Q ( .: h I. 1/ r. ’ ”I .4 f I I I r . ' A A I 9‘ I | l I l 3.72 W. R71 W. R.72 W. R.71 W. o 5 1o KILDMEl'ElS a 5 w KLOMErms APPROXWIATE SCALE APPROXIMATE SCALE mew may EXPLANATION T. EXPLANATION 2 QZO£ N. 0205 a ‘ . . 1' a ‘ - . \\\\ o 6-0 9 T \\\\\ o H 9 N. - >0.9 - >0-9 T. 1 40' N. 00' T. 1 s. T. 1 s. T. 2 s. R.72 W. 11.71 W. K72 W. 3.71 W. o 5 w mamas a 5 w KlOMETEiS APPROXIMATE SCALE APPROXIMATE SCALE tions of plagioclase in percent An; H, ratio of potassium feldspar to plagioclase. Homblende in southeast part of batholith approximate, plotted from modes and text in Wells (1967). Areas shaded gray represent Twin Spruce Quartz Monzonite; dots indicate sample localities. 12 BOULDER CREEK BATHOLITH, FRONT RAN GE. COLORADO TABLE 1.—Modes (volume percent) for Boulder Creek Granodiorite, from the batholith, Front Range, Colo. [(4, not found; Tn, trace; ’I‘r.?. may be present; ores include all opaque minerals. Samples 1—76 and 192-217. Tungsten quadrangle; 99—131, Gold Hill quadrangle; 132—169. Boulder quadrangle; 170— 191. Neda-land quadrangle; 403—407. Ward quadrangle] Sample No.——-----—-- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Potassium feldspar-— 26.1 10.8 8.2 8.2 5.2 12.0 11.1 15.3 22.3 20.0 5.5 40.2 13.2 16.7 Plagioclase-—-—--——— 33.4 41.1 53.0 43.4 47.0 46.3 41.5 45.1 36.6 41.4 46.0 32.0 39.0 47.0 Quartz -------------- 30.7 33.1 17.7 30.4 31.3 25.2 30.1 17.5 29.1 22.6 19.0 6.0 33.7 20.8 Biotite ------------- 8.1 12.9 17.3 15.5 15.0 15.3 15.2 19.8 9.1 13.3 18.7 4.5 13.5 10.6 Muscovlte —————————— 0.1 0.1 —- 0.1 >-- 0.1 0.2 0.1 -- -— —— -— —— —- Ores -------------- 0.5 1.2 0.8 0.8 0.6 0.5 0.8 1.0 0.4 0.5 1.0 0.3 0.1 1.0 Hornblende —————————— -— —— 1.8 -— -- -~ -- —- —- 0.5 8.5 14.6 —— Tr. Allanite --------- - Tr. -- -- 0.6 -- 0.1 -- Tr. Tr. 0.2 0.1 0.2 0.3 0.1 Apatite ----------- 0.2 0.2 0.3 0.7 0.6 0.3 0.4 0.5 0.3 0.3 0.5 0.6 —— 0.5 Zircon ———————————— Tr. Tr. Tr. 0.1 Tr. 0.1 Tr. Tr. 0.1 Tr. 0.2 0.1 0.1 Tr. Monazite-xenotime—-- -— -— —— —— —- —- -- -- —- —— -- -- -- -— Calcite ----------- —- 0.4 —- -— Tr. —— —— —— -— -- -- -- -— -- -- Chlorite --------- —~ 0.2 -— —— 0.1 -— -- -— 0.1 -- -— —— -- -— 0.4 Epidote-clinozoisite 0.3 0.1 0.1 0.1 Tr. -- -- Tr. 1.5 0.8 -- 0.4 0.1 2.0 Rutile—————--——-—-~- -— -— —— Tr. -- -- -— -— -- -- -- -- -- -- Sillimanite-—---—--- -— —— ~- ~— —- —- -— -- —- -— -- -— -- -- Garnet---———————---— -- —— —- -- —- -- -- —— -— -- -- -- -- —- Sphene———----——--—— -— 0.5 0.8 Tr. 0.3 0.1 0.7 0.6 0.6 0.4 0.5 1.1 Tr. 0.9 Kaolinite----------- -— -- -- -- -- -- -- -- -- -- -- -- -- '- Prehnite-———-----——- -- -- -- -- -— —- —— —- —- -- —- -- -- -- Total ---------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. ---------- 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Potassium feldspar-— 15.3 15.0 13.1 22.5 .26.8 27.4 17.5 13.8 11.3 10.6 24.4 20.7 14.5 27.1 Plagioclase --------- 49.3 41.8 46.7 35.1 33.6 28.0 40.3 37.7 46.5 46.6 36.3 41.9 44.4 36.3 Quartz-----—---—--—- 17.9 29.8 23.3 30.7 30.4 25.7 26.8 30.7 24.4 28.2 30.2 24.8 21.3 24.4 Biotite ———————————— 13.4 11.8 11.5 9.1 5.5 14.1 10.4 13.2 13.2 12.8 6.7 9.9 16.0 10.6 Muscovite --------- —- 0.1 -- 0.1 1.8 0.1 -- -— -- 0.3 0.2 —— —- —— Ores ———————————————— 2.0 0.1 2.4 1.2 1.1 0.7 0.5 0.6 0.3 0.1 1.1 0.4 0.4 0.8 Hornblende —————————— -- -- 0.3 —— -- 2.8 1.9 1.3 1.9 -— -— 0.2 0.5 -— Allenite ----------- -— 0.6 -- 0.3 -- 0.1 0.1 0.1 0.3 Tr. -- -- Tr. 0.2 Apatite ------------- 0.5 0.4 0.6 0.6 0.8 0.7 0.5 0.1 0.3 0.2 0.7 0.6 0.7 0.2 Zircon---———---—---- 0.1 Tr. 0.1 Tr. Tr. 0.1 Tr. Tr. 0.1 Tr. Tr. 0.1 Tr. Tr. Monazite—xenotime-—- —- -— -- —- —- —— —- —— —- -— -- -- -- —— Ca1cite-—--—-~--——-— -- -— 0.4 0.1 -— —- —- —— -- 0.3 -— —- 0.1 -— Chlorite ------------ 0.6 0.2 0.1 0.1 Tr. -- —- -— 0.2 0.2 0.1 0.1 —— -4 Epidote-clinozoisite 0.6 -— 1.0 Tr. Tr. 0.2 0.9 1.1 0.2 0.6 —- 0.7 1.4 —- Rutile -------------- —— -— -- Tr . —— -— -- -- —- —— -— -- -- —- Sillimanite-——----—- -- -- -- —- -— -- -- —- —- -— -— -— —— -- Garnet ------------ —— —- —- -- -- -— —— —- -- -- -— -- —- —- Sphene -------------- 0.3 0.2 0.5 0.2 -- 0.1 1.1 1.4 1.3 0.1 0.3 0.6 0.7 0.4 Kaolinite —————————— —- -- -— -- —— -- -— —- —- —- -- -— —- -- Prehnite ———————————— -— -- —— -- —- -— —- —— —— -- -— -- —- —— Total ----------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 TABLE 1.—Modes (volume percent) for Boulder Creek Granodion'te, from the batholith, Front Range, Com—Continued THE BATHOLITH 13 Sample No. —————————— 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Potassium feldspar—— 18.4 8.1 36.4 8.3 16.7 17.8 13.6 17.4 0.3 18.2 10.8 16.9 16.0 1.7 Plagioclase ————————— 37.8 48.2 27.4 47.4 36.1 46.6 47.5 42.1 47.2 38.3 48.3 37.5 43.0 62.1 Quartz -------------- 29.0 26.9 25.9 23.2 23.3 22.7 25.1 21.8 32.3 31.6 27.8 26.6 22.0 11.1 Biotite ————————————— 14.0 15.7 8.1 14.5 15.8 10.5 11.8 15.9 18.2 9.8 11.2 17.3 14.7 15.9 Muscovite ----------- 0.1 0.2 0.3 -- -- —— -— 0.1 0.1 0.5 —— 0.1 -— -- Ores ———————————————— 0.5 0.3 1.0 0.2 0.8 0.2 0.7 0.9 0.8 0.4 0.9 0.5 0.9 0.5 Hornblende —————————— —— —— —— 5.3 4.7 0.9 —— —— —— —- -— —- 1.4 7.4 Allanite——— —— 0.1 —— Tr. 0.1 Tr. 0.2 0.3 0.1 0.4 0.1 —— 0.4 Tr. Apatite—--— 0.2 Tr. 0.3 0.2 0.5 0.1 0.4 0.8 0.7 0.3 0.7 0.6 0.5 0.6 Zircon -------------- Tr. Tr. 0.1 0.1 0.1 0.1 Tr. 0.1 —- Tr. Tr. Tr Tr. Tr. Monazite-xenotime—-— —- —— —— —— —— —- -- —— -— -— -— -— -- —- Calcite ————————————— —— -- -- -— —- —— —— —- —- 0.4 —— -— 0.2 —- Chlorite ------------ —- 0.1 0.3 —- 0.1 —— —— —— -— Tr. —— Tr. —- -— Epidote-clinozoisite -- 0.2 0.2 0.4 1.5 0.9 0.3 —— —— 0.1 -— Tr. 0.5 0.3 Rutile —————————————— —— —— -- -— —— —— —— —— -— —— —— —— -— -— Sillimanite --------- -— —— —— —— -- —— —— —— —— —— —— —— —— —— Garnet —————————————— -- —— -- -- —- -- -- —- -- -- —— -- -- —— Sphene —————————————— Tr. 0.2 Tr. 0.6 0.3 0.2 0.4 0.6 0.3 -- 0.2 0.4 0.4 0.4 Kaolinite —————————— -- -- -— -- -- -- -- -- -- -- -- -- -- -- Prehnite-—-—-———---— -— —— —— —— —- -— -— -- -- —— -- —- -- -- Total----------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. ---------- 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Potassium feldspar—— 37.6 23.4 34.5 21.1 10.6 16.6 19.0 2.5 19.4 17.1 11.8 14.0 9.2 25.3 Plagioclase ————————— 36.8 25.7 32.4 33.7 48.5 40.7 34.3 46.7 40.8 30.9 41.1 34.3 44.7 41.2 Quartz—---—----—---- 7.1 9.1 24.4 38.4 24.9 18.7 27.6 14.1 26.5 27.8 25.0 34.4 30.3 23.0 Biotite ————————————— 13.6 13.3 7.0 5.5 12.9 14.6 14.4 17.9 10.4 8.2 17.3 12.3 12.5 8.4 Muscovite ----------- -— ~- —— 0.2 —- —— -- -- 0.5 -- 0.1 -— 0.4 -- Ores ---------------- 0.4 0.9 0.5 0.1 0.6 0.6 0.7 0.4 0.4 1.0 0.5 0.7 1.0 0.5 Hornblende —————————— 3.7 23.3 —- —— 0.7 7.8 0.2 14.1 -- 12.4 1.3 2.3 —— -- Allanite ------------ Tr. 0.2 Tr. -- Tr. -— 0.3 -- 0.5 -- —— 0.4 0.3 0.4 Apatite ————————————— 0.4 0.9 0.5 Tr. 0.4 0.5 0.7 1.1 0.2 0.3 0.6 0.2 0.5 0.4 Zircon ------------- 0.1 0.1 0.1 0.1 0.1 Tr. Tr. Tr. Tr. 0.1 0.1 Tr. Tr. Tr. Monazite—xenotime——- —— —— —— —— —— —— —— -— —— -— -- -- -— ~— Calcite——— —— —- 0.2 -- 0.2 0.2 -- 0.5 0.4 —— Tr. —- -- -- Tr. Chlorite ———————————— —— —— 0.1 0.1 —— —— —— 0.1 0.2 —— —— Tr 0.2 0.2 Epidote—clinozoisite —— 2.3 0.3 0.5 0.2 0.4 1.7 1.6 0.2 1.8 1.6 0.6 0.3 0.3 Rutile —————————————— —- —— —— -— —— -— —— —— —— —— -- —— -— -- Sillimanite———————-— —— —— —- —- —- —— -— —- —— -— —— —— —— —- Garnet -------------- —— —— -— -— —— —— —— —— -- —- -— -- -— -— Sphene —————————————— 0.3 0.6 0.2 0.1 0.9 0.1 0.6 1.1 0.9 0.4 0.6 0.3 0.6 0.3 Kaolinite ----------- —— -- -- —- -- -— -- -- —— —- —— —— -- —— Prehnite ———————————— —— —- —— -- —— —— —— —— —— —— —— —— —— —— Total ----------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE 1.—Modes (volume percent) for Boulder Creek Granodiorite, from the batholith, Front Range, Cow—Continued Sample No. —————————— 57 58 59 60 61 62 63 64 65 66 67 68 69 70 Potassium feldspar—— 6.2 0.7 27.6 27.8 18.6 14.0 5.6 15.2 30.5 25.6 31.9 12.1 29.7 26.7 Plagioclase ————————— 53.0 56.7 37.2 35.5 39.9 42.5 48.9 42.8 34.4 42.8 35.1 50.0 34.7 27.6 Quartz -------------- 3.0 17.3 28.7 31.5 33.0 31.6 17.5 24.9 24.8 20.4 26.8 19.3 25.0 31.3 Biotite ————————————— 12.8 22.9 5.1 3.6 4.8 10.9 20.4 14.7 8.2 9.6 4.6 13.6 7.9 12.0 Muscovite—-------——- —— 0.6 1.3 1.2 2.6 —— —- 0.1 0.3 0.4 0.7 -— 1.1 —— Ores ———————————————— 0.2 0.5 0.1 0.4 1.1 0.1 0.5 0.8 1.5 0.5 0.8 0.6 0.4 0.9 Hornblende ---------- 22.6 —— —- —- —— —— 4.4 -— —- -- -— 2.7 -— -- Allanite ———————————— -- Tr. -- -- —— Tr. 0.2 0.2 Tr. -- Tr. 0.3 0.3 0.3 Apatite-———————————— Tr. 0.2 Tr. Tr. Tr. 0.1 0.9 0.2 0.2 0.5 0.1 0.6 0.5 0.6 Zircon ———————————— Tr. 0.1 Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. 0.1 Tr. Tr. Monazite-xenotime——— —- -— —— —— —- -- -- —- —— —— —— —— -- -— Calcite ————————————— -— -- -— —— —— Tr. Tr. -- 0.1 —- —— —— —— —- Chlorite ———————————— 0.1 —— —— Tr. —— 0.2 —— 0.2 Tr. 0.1 -- -- 0.3 —— Epidote—clinozoisite 1.4 —— Tr. —- Tr. 0.4 0.7 Tr. —— 0.1 —- 0.3 -— —- Rutile —————————————— —— -— —— —— —— —— -— —— Tr. Tr. —— —— -— -— Garnet ————————————— —— —— —— —- -— -- -— —— —— —— —— —- -- -— Sphene —————————————— 0.7 1.0 Tr. —— —- 0.2 0.9 0.9 Tr. Tr. —— 0.4 0.1 0.3 Kaolinite ————————— -— —— —- —— —— —— —— -- -- -- -- -- —— —— —— Prehnire ———————————— —- —— —— —- -— -— —- -- —— —— —— —— —- —— Total ——————————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. —————————— 71 72 73 74 75 76 99 100 101 102 103 104 105 106 Potassium feldspar—- 18.8 20.3 10.7 13.0 9.3 27.4 0.5 0.3 —— 23.6 0.5 0.7 3.7 2.0 Plagioclase-------—— 43.5 36.3 52.9 42.2 51.6 31.1 59.6 47.3 41.6 38.2 44.5 50.1 52.6 54.7 Quartz -------------- 27.2 29.0 11.1 24.3 27.3 32.4 16.9 18.2 34.4 24.4 25.9 20.1 21.0 21.3 Biotite ------------- 10.0 12.7 14.0 17.3 9.5 6.9 19.4 21.7 21.5 10.4 27.5 19.3 13.3 15.3 Muscovite ——————————— —— 0.1 0.1 0.6 —- 0.3 -- —— —- —— —— -- -- —- Ores ——————————————— 0.3 0.5 1.0 0.8 0.5 0.5 0.6 Tr. 0.7 1.7 0.3 0.5 0.6 0.5 Hornblende —————————— -— —— 9.6 —— -- -- —— 7.6 0.2 -— -- 7.8 5.0 5.1 Allanite ------------ 0.1 —- -- 0.1 0.3 Tr. Tr. 0.1 Tr. 0.1 -- 0.1 Tr. Tr. Apatite ------------- 0.1 0.4 0.1 0.7 1.1 1.0 1.3 0.8 0.4 0.1 0.6 1.0 0.7 0.3 Zircon------------—- Tr. Tr. Tr. Tr. Tr. Tr. —— Tr. 0.2 Tr. " -— 0.3 Tr. Monazite—xenotime—- —— —— —- —- 0.1 -- —- -- -— -- -- -- -- -- Ca1cite———————————— -- 0.1 —— —— —— -- 0.1 -- -- -- -- -- -- -- Chlorite ——————————— —- Tr. —— —— —— Tr. 0.3 -- Tr. -— -- -- -- —— Epidote—clinozoisite -— -- 0.1 Tr. -- 0.3 0.5 3.7 0.7 0.6 0.1 0.1 1.2 0.3 Rutile -------------- -- —— -- —— -- -- -— -- —- -- -- -- —- —— Sillimanite ———————— —- —— -- -- -- —— —— —— —— -- —- -- -- -- Garnet ———————————— -— —— —— —— —— -— —— —— -— —— —— -- -- -- Tr. 0.6 0 4 1 0 0.3 0.1 0.8 0.3 O 3 0.9 0 6 0.3 1.2 0.5 Kaolinite —————————— —— -— —- -- -- —- -- -- —- -- -- -- 0-4 -- Prehnite ——————————— —— -- —— -— —— -— —— —— —— —- —- -- -- -- Total ---------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 THE BATHOLITH TABLE 1,—Modes (volume percent) for Boulder Creek Granodion'te, from the batholith, Front Range, Cola—Continued 15 Sample No. ---------- 107 108 109 110 111 112 113 114 115 116 117 118 119 120 Potassium feldspar-- 23.5 0.3 1.4 0.4 0.2 25.3 17.5 7.8 7.1 -— 28.0 37.4 -- -— Plagioclase --------- 39.0 51.6 46.1 52.9 51.5 32.6 38.0 46.0 50.9 57.0 25.6 24.0 53.9 17.8 Quartz ————————————— 24.6 16.6 27.0 19.5 12.2 30.6 13.6 20.0 20.5 4.4 34.5 32.0 22.6 47.3 Biotite ------------- 0.5 23.5 18.7 19.9 36.5 9.5 18.9 18.7 14.6 17.2 5.0 1.0 21.0 16.4 Muscovite ----------- 1.6 -- -- -- —- -- 0.1 -- -- -- 4.6 1.9 —- -- Ores ---------------- 0.8 0.8 1.8 1.6 0.9 0.5 0.1 0.6 0.4 1.1 2.2 1.0 1.2 0.4 Hornblende ------ -— 3.8 4.4 5.0 -- 0.5 8.5 4.8 4.2 17.6 —- —— —— 17.0 Allanite ———————————— -- -— 0.1 Tr. 0.2 0.1 -— —- 0.1 0.1 Tr. -— Tr. Tr. Apatite ------------- 0.3 0.8 0.5 0.4 1.5 0.1 1.4 0.7 0.4 0.6 0.1 0.3 0.7 0.1 Zircon -------------- Tr. 0.2 Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Monazite-xenotime--- -— —- —- -- —- —— —— —— -- -- —- -- -— -— Calcite ------------- Tr. 0.2 —— Tr. —— -- 0.1 —— 0.1 0.3 —— -- -- —— Chlorite ------------ Tr. -- -- Tr. -— -- Tr -- 0.3 0.6 —- 2.2 0.1 -- Epidote—clinozoisite 0.3 1.7 Tr. 0.3 Tr. 0.7 0.9 0.8 Tr. 0.8 Tr. 0.1 0.5 0.6 Rutile —————————————— -— -— —— —- -— —— —— -- -- -- -— -— —— -— Sillimanite --------- -— -- -- -- —- -- —— —- —— —— -— Tr. -— -- Garnet ------------- -- -- -- -— -- -- -— —— —- —- —- 0.1 —- —- Sphene ————————————— 0.6 0.5 —— Tr. -- 0.1 0.9 0.6 1.4 0.3 -- —— —— 0.4 Kaolinite ----------- a8.8 -— —— —- —— -- -- -- —— —— —— —— —— -- Prehnite ——————————— -— —— -- -— -— -- -- -— —- —- —— —- —— -- Total ----------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. ---------- 121 122 123 124 125 126 127 128 129 130 131 132 133 134 Potassium feldspar—- -- —— -— 37.5 Tr. 11.0 —— 22.9 25.9 17.6 11.8 4.9 10.0 2.3 Plagioclase———-—---- 44.4 55.2 47.5 25.8 48.6 37.0 53.6 33.3 36.8 34.6 40.6 46.0 44.3 55.7 Quartz —————————————— 18.5 24.6 19.6 24.3 24.7 29.0 15.0 26.8 23.2 35.4 23.0 21.3 25.8 21.1 Biotite——-—--—-—-—-— 24.5 19.5 30.4 10.7 23.6 18.8 22.8 13.3 11.0 9.7 13.3 20.3 16.4 3.1 Muscovite ----------- -— -— -— -— 0.4 -- -- 0.6 0.6 0.7 -- —- 0.1 —- Ores ---------------- 0.7 0.3 1.3 0.2 1.8 0.4 0.3 2.3 1.8 1.4 0.4 0.5 0.3 2.4 Hornblende---—-——--- 8.9 -- -- —— -- 2.9 7.0 —— -- -- 6.2 5.0 1.0 1.9 0.2 Tr. 0.1 Tr. —- 0.1 0.3 —— Tr. —- Tr. 0.1 0.1 0.1 Apatite ------------- 1.2 0.3 Tr. 0.1 0.8 0.1 0.4 0.8 0.3 0.6 0.6 0.4 0.1 0.5 Zircon —————————————— Tr. Tr. Tr. 0.1 Tr. Tr. Tr. Tr. Tr. Tr. -- Tr. —— —— Monazite-xenotime—-- -— —— —— —- —— -- —— Tr. 0.4 Tr. —- -- —— -— Calcite ------------ -- -— —— -- —— —— Tr. -- -— —— 0.2 —- —— Tr Chlorite ———————————— —- Tr. 0.2 0.4 __ 0.3 0.3 Tr. -— Tr. 0.6 Tr. —- 9.3 Epidote—clinozoisite 0.8 0.1 0.1 0.6 0.1 0.4 Tr. —— -— Tr. 2.2 1.1 1.5 3.1 Rutile —————————————— -- -- -— -— -— —- -— —— —— —— -- -— -- -- Sillimanite --------- —- -— -- -— -— -- —— —- -- -— —— —— -— —— Garnet -------------- -— -- 0.8 -- -— -- -- —— -— —— —— -— -- —— Sphene —————————————— 0.8 -- -- 0.3 -- —— 0.3 -— —— -— 111 0.4 0.4 0.5 Kaolinite ----------- —— -- —— —— —- —— -— —- —— -- -- -- -— -— Prehnite ------------ Tr.? -— -— —- -— -- Tr.? -- -— —— -— —— —— -- Total ----------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE 1.—Modes (volume percent) for Boulder Creek Granodiorite, from the batholith, Front Range, Cola—Continued Sample No. ---------- 135 136 137 138 139 140 141 142 143 144 145 146 147 148 Potassium feldspar—- 24.0 0.1 4.3 6.4 0.3 0.1 7.7 2.1 15.4 24.6 15.3 22.8 13.3 14.0 P1agioclase-———-——-- 29.4 53.3 43.8 46.9 39.5 61.6 35.4 40.4 40.3 36.2 37.5 38.8 35.5 40.5 Quartz ------------- 29.6 20.3 19.7 25.4 25.3 31.0 32.1 32.5 24.1 26.1 27.1 20.3 26.8 33.4 Biotite ——————————— —— 7.9 22.5 20.6 12.2 24.3 5.8 18.5 22.8 8.6 0.7 9.9 13.3 21.1 10.5 Muscovite ----------- -- -- —- —— -— —— b5.8 2.1 —— 0.1 —— —- —- 0.3 Ores————-——-—--———-— 1.1 0.9 1.1 0.8 0.9 0.5 Tr. 0.1 0.3 0.3 1.6 Tr. 0.2 0.1 Hornblende-—---——--— 4.2 —— 6.8 5.4 6.5 -- —— —— 8.4 0.9 2.8 2.3 —— —- Allanite ———————————— -— Tr. Tr. 0.1 Tr. Tr. —— —— -- Tr. 0.1 0.1 0.2 0.1 Apatite ------------ 0.3 1.0 0.6 0.9 0.8 0.1 0.1 Tr. 0.7 Tr. 0.7 0.1 0.2 0.1 Zircon——-------——--— —— —— Tr. —- Tr. Tr. 0.3 Tr Tr. 0.1 Tr. Tr. 0.1 0.3 Monazite—xenotime—-— —— —— -— —- -- Tr. Tr. Tr. -- -- —— -— -- —- Calcite ————————————— 0.1 —— —— 0.1 -- 0.6 —— —— -— -— 1.2 0.3 Tr -— Chlorite ———————————— 0.7 -— -- 0.3 -- 0.3 0.1 -- 0.4 6.6 0.4 -- 0.2 —— Epidote-clinozoisite 1.1 1.0 1.4 0.9 1.5 —- -- Tr. -- 1.2 3.2 1.6 0.9 0.3 Rutile ————————————— -— -— -- -- -— -— -- -- —— -— -— —— —— -- Sillimanite -------- —- —— -— —— -- —— —— —- -- -— —- -- -— -— Garnet -------------- -— -— —— —— -- —— —— -- 1.8 0.3 Tr. —- 0.3 —— Sphene-—————--—----— 1.2 0.9 0.7 0.5 0.9 Tr. -- —— Tr. 0.3 0.1 0.4 1.2 0.4 Kaolinite—-—-—-—-——— —— -- -- -- —— —— —- -— —- —— -- —— —— —— Prehnite ------------ 0.4 -— -- 0.1 —— Tr. -— —— Tr 2.6 0.1 —— -- ~- Total—---—-—---- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. ---------- 149 150 151 152 153 154 155 156 157 158 159 160 161 162 Potassium feldspar—— 0.3 27.0 8.3 18.1 12.8 8.8 17.3 16.2 9.4 5.6 15.2 12.9 14.6 7.6 Plagioclase ————————— 46.0 30.3 48.5 35.5 43.8 40.6 35.0 37.0 46.5 43.0 38.5 37.4 42.3 49.7 Quartz —————————————— 31.8 31.7 24.2 34.6 23.8 26.9 32.0 23.8 23.0 31.0 33.0 32.3 30.2 20.5 Biotite ————————————— 19.8 8.8 17.2 9.2 14.8 16.8 12.5 18.3 16.0 16.2 10.1 15.3 11.2 18.6 Muscovite ————————— - -- -- -- —— —- —— 1.0 Tr. -- —— 0.7 -- 0.6 Tr. Ores ---------------- Tr. 1.3 0.7 0.2 0.4 0.9 0.4 0.2 0.1 0.4 1.3 0.1 0.4 0.2 Horhblende ---------- 0.5 -F -- 1.1 1.7 4.4 Tr. 1.7 1.6 1.2 -- —- —— 1.3 Allenite ———————————— —— Tr. 0.7 0.1 0.1 Tr. Tr. Tr. 0.1 0.4 —- Tr. -- 0.3 Apatite ————————————— 0.5 0.7 0.1 0.2 0.7 0.4 Tr. 0.6 1.3 0.1 0.1 0.3 0.3 0.3 Zircon -------------- 0.3 —— 0.3 Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr Tr. Tr. Monazite-xenotime——— —— -- -— -— -- —— —- -- —— —- -- —— -- -- Calcite ------------- —— -— -- -- -- 0.4 0.7 0.1 —— -- 0.1 —- -- —— Chlorite—------—--—- —— 0.1 —— -— 0.3 -— 0.3 0.4 —— 0.1 Tr. -— 0.3 -- Epidote-clinozoisite 0.3 —— Tr. 0.5 0.9 0.1 0.6 1.1 1.4 1.6 Tr. 0.4 0.1 0.8 Rutile —————————————— -- -- —- —— -- -- —— -- -- —- -- -- -- -- Sillimanite———-————- -— —— —— —- -- —— -- -— —— —— —- -- —— -— Garnet--—----- —— -- —- —— -- -— —- -- -— -- —- —- -- -— Sphene—————--——————— 0.5 0.1 Tr. 0.5 0.7 0.7 0.2 0.6 0.6 0.4 0.6 1.3 —— 0.7 Kaolinite ————————— — -- -- —- —— -- -— —- -- —— -- —— -- —— —- Prehnite ----------- -- -- —— Tr.? -— —- -— —— -- —- -- —— -- -- Total ----------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 THE BATHOLITH 1 7 TABLE 1.—-Modes (volume percent) for Boulder Creek Gmnodiorite, from the batholith, Front Range, Colo—Continued Sample No. ---------- 163 164 165 166 167 168 169 403 404 405 406 407 Potassium feldspar-- 20.3 11.2 5.1 11.0 21.2 19.3 -— Tr. 30.0 42.1 24.4 10.3 Plagioclase --------- 40.8 42.3 43.2 43.5 39.5 43.1 49.7 34.4 35.0 9.9 22.1 42.8 Quartz -------------- 24.8 26.3 20.8 23.2 21.0 23.3 23.8 49.2 27.0 21.0 32.9 28.3 Biotite ------------ 11.1 14.9 21.9 18.1 15.4 10.4 21.4 14.9 6.0 26.5 18.3 6.8 Muscovite ————————— 1.5 -- Tr. Tr. -— Tr. -— Tr. -— 0.2 —- -- Ores -------------- 0.4 0.4 0.3 0.2 Tr. Tr. 0.4 1.5 1.0 0.3 1.3 1.8 Hornblende -------- -— -- 3.7 5.7 1.3 1.0 2.6 1.7 -— —- —- -- -- Allanite—-—~—-——--—- Tr. Tr. 0.5 Tr. Tr. —- 0.1 -— 0.5 -- 0.1 —- Apatite ------------- 0.4 Tr. 0.6 0.6 0.5 0.6 0.6 Tr. 0.5 -— 0.6 0.5 Zircon---——--------- Tr. Tr. -— Tr. Tr. Tr. Tr Tr. -— Tr. -- Tr. Monazite-xenotime-—- —- —- —- —— —— —- -— -- -- —- —— —— Calcite ------------ -- —— 0.4 -- Tr. —- Tr. —— —— -— -— —- Chlorite --------- - —- -— 0.1 0.1 0.2 -- 0.3 -— -- -- -- —— Epidote—clinozoisite 0.4 0.7 0.8 1.7 0.5 0.7 1.6 -- -- -- —- 8.3 Rutile -------------- -- -— —— -— -- -— -- -- -- —- -- -- Sillimanite --------- —- —— —— —— —— —— —— —— —— —— —— —— Garnet--~-—-—-—--—-- -- -- -- —- —— -- -— —- -- -- —— -~ Sphene-----—-—---—-- 0.3 0.5 0.5 0.3 0.7 Tr. 0.4 Tr. Tr. —— 0.3 1.2 Kaolinite-—-—--—--- -— -— -- —- -— —- —- -— —- -— —- —— Prehnite ----------- —— —- Tr. Tr2 —— —- -- —- -- -— —— -— Total --------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 aIncludes some chlorite. b potassium feldspar and hornblende are more abundant within the batholith; (2) the contact zone and segments adjacent to faults are similar compositionally, sug- gesting that rocks in both environments have been recrystallized; the potassium went into biotite and the rest of the constituents into plagioclase. The distribution of the major minerals of the Boulder Creek Granodiorite within the batholith and adjacent satellitic bodies may also be shown by the use of quartz-plagioclase-potassium feldspar triangular diagrams in figure 7. These diagrams show that the southeast part of the batholith is the most siliceous and the central part of the batholith the least siliceous. The abundance of quartz diorite in the triangular diagrams (fig. 7) for the Blackhawk, Tungsten, and Gold Hill quadrangles reflects border areas of the batholith. Most modes fall in the granodioritequartz monzonite fields; however, those for the Ward quadrangle plot on the granitic side of the quartz mon- zonite field. Boulder Creek Granodiorite has a predominant hypidiomorphic granular texture in which the mafic minerals tend to cluster. The mafic clusters consist of biotite, hornblende, apatite, sphene, allanite, zircon, and the alteration mineral epidote. Plagioclase, quartz, Sillimanite altered to muscovite. and some potassium feldspar form the largest crystals. Biotite and hornblende are the most prominent mafic minerals but only biotite is ubiquitous in granodiorite. Potassium feldspar, represented chiefly by microcline, forms both large crystals similar in size to plagioclase and smaller interstitial crystals. Rocks of the batholith have been sheared and recrystallized and tend to have a preferred mineral alteration adjacent to faults and along much of the contact zone. Serrate quartz and anhedral feldspar (mostly microcline) occur interstitial to larger mineral grains in these rocks. INCLUSIONS IN BOULDER CREEK GRANODIORITE Inclusions in the Boulder Creek Granodiorite are mainly of three types: (1) lenses, some quite large, of biotite and sillimanite-biotite gneiss and schist; (2) massive to foliated mafic inclusions in discrete clots, spindles, and lenses consisting essentially of biotite, hornblende, and plagioclase and containing generally less than 10 percent quartz and 2 percent or less of potassium feldspar; (3) very old foliated and altered lamprophyres in eroded sills that are now rounded elongate bodies so altered that they often resemble mafic inclusions of type 2. 18 BOULDER CREEK BATHOLITH. FRONT RANGE, COLORADO TABLE 2.—Modes (volume percent) for Boulder Creek Granodiorite from small plutons and small lenses in biotite gneiss and schist, Front Range, Colo. [(—). not found: Tn, trace; ores include all opaque minerals. Samples 170—185 from Nederlnnd quadrangle; 186—191 from Tungsten quadrangle] Sample No. ---------- 170 171 172 173 174 175 176 177 178 179 180 Potassium feldspar-— 3.7 11.0 7.0 0.1 12.5 23.3 17.0 —— 0.3 0.1 6.2 Plagioclase ————————— 43.9 46.5 40.8 34.6 44.9 36.4 44.0 49.2 54.8 48.8 49.6 Quartz -------------- 29.8 29.1 20.7 25.6 33.1 23.0 23.2 32.7 22.1 17.4 23.8 Biotite—--—-——————-- 6119.3 a11. 3 22.3 30.0 as. 7 6111.4 11. 0 17.9 a18.3 17.1 13 .6 Muscovite----------— 0.3 0.4 -- 0.4 1.1 1.1 O 1 0.1 -— -— b1.0 Ores --------------- 2.0 1.6 4.2 4.8 1.3 1.9 2.0 0.1 2.7 5.6 3.1 Hornblende ————————— -- —— -- -- —— -— —- -— —— 6 .4 —— Actinolite ————————— —— —— -— -— -- -- —— —— -— -— —- Allanite————————-—-— -— -- -- -— 0. 1 0. 1 0. 1 -—- 0. 4 0. 7 -- Apatite—-—---———-——— 0.3 0.1 1.8 1.7 —— 0.7 0.8 Tr. 0.3 2.2 1.3 Zircon —————————————— Tr. Tr. 0. 1 —— Tr . Tr. 0. 1 Tr. Tr . —— Tr. Ca1cite—--——————-—-— —— -— —- —— Tr . —- Tr . —- —— O . 4 —- Chlorite-——————-———— -— —- —— —— -- -- -- —— —— 0. 3 -- Epidote ————————————— 0.7 -- Tr. -— 1.3 —— 0.1 —— 0.7 —— 1.4 Rutile ------------ —- -- -~ —— Tr . —— -- —— —— —- Tr . Sphene ------------- —— -- 3.1 2.8 —- 2.1 1.6 —~ 0.4 1.0 -- Total————------ 100. 0 100 . 0 100. 0 100 . 0 100. 0 100 . 0 100 . 0 100 . 0 100 . 0 100 . 0 100 . 0 Sample No. ---------- 181 182 183 184 185 186 187 188 189 190 191 Potassium feldspar—— Tr. 1.7 Tr. 0.1 24.3 28.8 22.1 22.9 21.4 26.9 17.5 Plagioclase --------- 46.8 53.5 40.3 46.2 34.8 24.9 30.3 30.6 36.2 28.5 38.1 Quartz—--—--—-——-——- 23.5 19.1 16.3 20.8 31.3 28.0 30.2 30.0 25.9 30.2 27.2 Biotite---—-———--——- 19.0 17.7 21.8 25.7 5.1 12.6 10.4 11.0 9.8 11.0 13.2 Muscovite —————————— b1.0 b1.9 b4.4 -— 1.7 2.9 4.2 3.2 3.7 0.9 1.5 Ores ———————————————— 2.2 1.0 5.2 3.5 2.7 2.0 2.3 1.6 1.8 1.2 1.6 Hornblende —————————— 1. 4 3 . O 8 . 2 1 . 4 —- —— -— —- —- —— -- Actinolite ---------- -- Tr. —— —- —- —— -- -- —- —— -— Allanite ——————————— 0.1 Tr. 0.1 0.3 —- -— -- 0.1 0.1 0.5 —- Apatite~--—--——--—-- 1.8 0.1 2.0 1.3 —— 0.5 0.3 0.4 0.9 0.6 0.6 Zircon———-—---—————- Tr . -— O . 1 —- 0 . 1 0 . 2 0 . 2 0 . 1 0 . 1 Tr . 0 . 3 Calcite ———————————— —- 0.3 -— -- —- -- —- -~ -- -- -- Chloirite—-—----—--— 0 . 1 0. 4 O . 1 -~ —— Tr . —— -— O . 1 0 . 1 -- Epidote--——-—---—-—— 2 . 0 1 . O 0. 8 0 . 3 —- 0 . 1 ——. 0 . 1 -— 0 . 1 -— Rutile —————————————— —— -— —— -- Tr . -- -- -- -- -- —- Sphene —————————————— 2 . 1 0 . 3 O . 7 0 . 4 -- -- —— —- -— —- -— Total—————-—--- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 aIncludes some chlorite. bIneludes sericite. THEBATHOLHEI TABLE 3.—Modes (volume percent) for Boulder Creek Granodion'te from contact area of batholith, Front Range, Colo. [(—L not found; ’1‘r.. trace; ores include all opaque minerals. Samples 192—199 from Tungsten quadrangle; 200—204 from Gold Hill quadrangle] 19 Sample No. —————————— 193 194 195 196 197 198 199 200 201 202 203 204 Potassium feldspar—— 4.0 0.2 —— —- 7.7 0.2 —— 0.5 -- —— —— 1.3 Plagioclase ————————— 44.7 57.5 35.7 46.0 37.8 48.8 55.1 50.8 58.1 50.2 44.4 49.8 Quartz—-—--—-——————- 28.1 5-0 23.3 25.0 38.6 31.8 11.8 18.8 22.1 23.4 24.7 25.8 Biotite ———————————— 17.5 23.6 28.6 17.0 15.0 18.5 23.1 22.8 18.8 23.0 23.4 16.5 Muscovite ——————————— 1.5 0.2 0.4 1.0 0.2 0.1 -— a0.7 -— 0.1 Tr. -— Ores ———————————————— 2.7 0.5 7.0 3.0 0.6 0.3 0.2 1.8 0.4 1.8 3.1 0.6 Hornblende —————————— -— 11-2 0.5 —— —— —— 8.4 1.7 —— —— -— 3.4 Allanite ———————————— 0.1 0.1 0.1 Tr. -- —— 0.3 -— Tr. 0.1 Tr. 0.2 Apatite ————————————— 1.1 0.8 1.4 Tr. 0.1 0.3 0.2 1.2 0.4 0.1 0.5 0.7 Zircon———f-————————- 0.3 Tr. 0.1 Tr. Tr. Tr. Tr. 0.2 —— 0.1 -- Tr. Calcite ———————————— —— -— —- —— -- —— -- 0.5 Tr. —— 0.1 -- Chlorite ———————————— -- 0.3 0.2 5.0 -— —— 0.1 —— 0.1 0.3 1.8 -- Epidote ————————————— —— 0.6 0.6 3.0 —— -— 0.1 0.5 0.1 0.9 2.0 0.5 Clinozoisite ———————— —— -— —— —— —— —- —— Tr. Tr. Tr. Tr. —— Sphene—--——--——----- —— —— 2.1 —— —- —— 0 . 7 o . 5 —— Tr . —- 1 . 2 Total —————————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 aKaolin 0.2 percent of total muscovite. TABLE 4,—Modes (volume percent) for Boulder Creek Granodiorite adjacent to known faults, Front Range, Colo. [1»). not found; Tn, trace; ores include all opaque minerals. All samples are from Tungsten quadrangle] Sample No. —————————— 205 206 207 208 209 210 211 212 213 214 215 216 217 Potassium feldspar-— 0.3 —- 0.3 0.2 1.3 3.5 0.8 2.2 5.3 —- 9.6 8.1 0.4 Plagioclase -------- 59.3 55.2 52.0 54.4 38.3 51.9 57.8 49.0 42.8 63.3 47.7 45.6 48.2 Quartz ————————————— 21.6 16.0 24.0 26.3 24.4 23.3 22.6 20.1 25.4 9.3 28.5 31.8 26.8 Biotite ————————————— 13.1 27.8 21.1 16.9 18.7 14.9 13.1 23.9 16.8 25.4 12.6 12.7 23.2 Muscovite ——————————— -— -— -- -— -- —— -- 0.2 —- —— -— 1.2 -- Ores ———————————————— 1.4 0.2 1.1 0.2 .6 0.1 1.1 1.2 0.4 0.8 0.5 0.2 0.2 Hornblende ---------- -- -- -- 1.5 7. 5.1 3.0 —— 5.9 ~— -- —— —- Allanite ———————————— 0.6 0.1 -— Tr. —— 0.2 0.2 —— 0.3 Tr. 0.2 0.1 0.1 Apatite ------------- 0.7 0.5 0.6 0.2 1.5 0.5 0.4 0.7 0.7 0.6 0.1 0.2 1.1 Zircon -------------- -- 0.1 Tr. 0.1 0.1 Tr. 0.5 Tr. Tr. Tr. —- Tr Tr Calcite ------------ -- —— -- —— -- —— 0.2 0.2 —- —— —— -- -— Chlorite ------------ Tr. —— —— Tr. —— 0.1 0.1 —— 0.1 -- 0.6 —- -- Epidote-clinozoisite 1.7 0.1 0.3 0.2 —- 0.2 0.2 2.3 1.5 0.3 0.1 0.1 Tr Sphene —————————————— 1.3 -— 0.6 -— 3.0 0.2 -- 0.2 0.8 0.3 0.1 -- -- Total———--—-——— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 20 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE 5.——Summary of modal data (volume percent) for the Boulder Creek Granodiorite, Front Range, Colo. [Ores include all opaque minerals] Granodior its in bathe 11th Granodiorite Contact in metasedimentary zone rocks Known Remainder fault of areas batholith Potassium feldspar —————————— 10.0 1.0 2.0 16.1 Plagioclase ———————————————— 42.0 147.0 51.0 40.5 Quartz -------------------- — 25.0 23.0 23.0 25.0 Biotite ————————————————————— 16.0 21.0 19.0 13.6 Hornblende ------------------- 1.0 2.0 1.7 2.1 Gras--—----------—----—-----— 2. 5 1. 7 1 . 1 o. 7 Allanite ————————————————————— 0.1 0.1 0.1 0.2 Apatite ---------------------- 0.8 0.6 0.7 0.5 Epidote ---------------------- 0.4 0.6 0.5 0.5 Sphene —————————————————————— 0.7 0.3 0.5 0.4 Muscovite—sericite--—---————— 1 . 3 0. 3 0 . 1 0. 4 The mafic inclusions of type 2 (figs. 8 and 9 and samples 318—327, table 6) are believed to be plutonic in origin because of their physical characteristics and composition, especially trace-element composition, that is more nearly related to diorite-quartz diorite. These inclusions are found in the hornblende-bearing part of the batholith and are common in the roadcuts of Boulder Creek Granodiorite along Middle Boulder Creek, along the slopes north and south of Pinecliffe, and in roadcuts of the Salina—Gold Hill (County 89) and Gold Hill—Bighorn (County 52) mountain roads. While these mafic inclusions are widely scattered throughout the granodiorite, they are, or appear to be, more profuse in the central part of the batholith, ex- tending from Thorodin Mountain to Bighorn Moun- tain. The inclusions of type 2 occur in discrete clots, spindles, and lenses oriented either along the regional foliation or at an angle to it; their plunge is moderate to steep. Small inclusions as much as 0.5 min size have blunt ends or rounded terminations and in cross sec- tion most are ellipsoidal; the larger inclusions range from a few meters to more than several hundred meters in length and have widths of as much as several tens of meters. Smaller inclusions can often be picked out with a hammer, leaving a somewhat smooth depression, especially in intensely weathered granodiorite. The larger inclusions are nearly always foliated and occur in irregular masses or lenticular bodies along foliation planes; some enclose small areas of granodiorite, forming augenlike segregations of the granodiorite (fig. 10). The larger inclusions are com- posite rocks that have a composition of diorite, quartz diorite, and may include some granodiorite; they are coarse to fine grained, dark gray to almost black. The smaller inclusions are finer grained and have a mottled texture due to a finer grained salt-and-pepper ground- mass having large hornblende or feldspar crystals and clots of mafic minerals either alined or in random orien- tation throughout the groundmass. Whereas some in- clusions have a mafic rim or a border of pegmatite, others grade into granodiorite with no distinct border. The larger inclusions are generally gradational with the Boulder Creek Granodiorite and often appear to in- terlens with the granodiorite for some distance along the contact. Biotite and hornblende make up 26—65 percent by volume of the mafic inclusions (table 6). Quartz rarely exceeds 10 percent and generally is in the range of 2-8 percent. Apatite and ores each are in the range of 1—2 percent. In thin section the mafic inclusions have a xenomorphic granular texture (fig. 11). The third type of inclusion is lamprophyre (samples 328, 329, 331, 332, table 6); it is not an inclusion like types 1 and 2 but occurs as eroded sills and dikes and is referred to as sills and dikes in the remainder of this report. The sills and dikes are of two ages. The older ones are generally found only in the central part of the batholith as altered and well-foliated stubby lenses from several meters to 300—400 In in length and are probably comagmatic with the Boulder Creek Granodiorite. The younger lamprophyre occurs as dikes and sills, is fresh looking, and may belong to the Pikes Peak Granite plutonism. The younger lam- prophyre is of no further concern to this paper and is thus discussed no further. The metamorphosed lamprophyre of concern to this report varies in composition from syenodiorite to mela- syenodiorite, according to modes in samples 328, 329, 331, and 332 (table 6), and samples 387 and 388 (table 11). Biotite, hornblende, and pyroxene make up 48—86 percent by volume of the lamprophyre; a few bodies are pyroxene rich, and quartz is nearly absent. Allanite, apatite, and sphene average 6 percent. These altered and well-foliated lamprophyric dikes often take on the appearance of porphyritic microgranular inclusions of type 2, and the distinction between types 2 and 3 is made on texture and the presence or absence of potassium feldspar. In thin section, the lamprophyre has a diabasic to xenomorphic texture depending on degree of metamor- phism. Figure 11C shows a lamprophyre with xenomorphic texture. MAFIC PLUTONIC ROCKS The mafic intrusive rocks, pyroxenite, gabbro, horn- blendite, hornblende diorite, and quartz diorite, and related aplites and pegmatites, occur mainly in metasedimentary rocks as satellitic bodies, although a few scattered lenses of all rock types except pyroxenite occur within the batholith itself. Radiometric age determinations have not been made on any of the mafic intrusives, but field relations suggest that they are ap- proximately the same age as the Boulder Creek 105°30’ THE BATHOLITH 21 105°22 ' 30" u: 3: C 3 C o E N l: (U 3. Q 40° Q“ \ \ \ covered \ A Ward AGOld Hill \\\\ l BOULDER 00’ 39° 52’ 30” NEDERLAND ELDORADO SPRINGS CENTRAL CITY / 7 _ BLACK HAWK RALSTON BUTTES P O 6 O 0 O K P FIGURE 7.—Modal variation (in volume percent) of quartz, plagia- clase, and potassium feldspar for Boulder Creek Granodiorite in the batholith and adjacent lenses. Q, quartz; P, plagioclase; K, potassium feldspar. Distribution of modes across the batholith and in lenses indicated in figure 3. Each diagram occurs with its corresponding 71/2-minute quadrangle or quadrangles. 22 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO FIGURE 8.—Photographs of exposures of mafic inclusions in Boulder Creek Granodiorite, mainly from Boulder Canyon. A, mafic str- ingers in a biotitic phase of Boulder Creek. B, mafic clots in a more leucocratic Boulder Creek Granodiorite; note the leucocratic halo between granodiorite and inclusion. C, a foliated lens of Granodiorite although some appear both older and younger (Sims and Gable, 1967, p. E29—E39; Brad- dock, 1969, p. 18). Most were emplaced in a period of deformation and metamorphism that attained sillimanite grade, and, accordingly, they were to some dense biotite-quartz diorite and small pegmatite veins in granodiorite. D, a remanent, dense mafic lens; note the ghostlike leucocratic areas segregating darker granodiorite into patchy areas. extent deformed and metamorphosed. Most plutonic bodies are massive to strongly foliated (fig. 12) and oc- cur as stocks or blunt, narrow dikes and sills or lenses along Precambrian structures, especially in fold axes. Although they locally transect structures in the gneiss THE BATHOLITH 23 FIGURE 9.—Photographs of hand specimens of mafic inclusions in Boulder Creek Granodiorite. A, small bleb, regular outline with in- dentations of leucocratic minerals, biotite clusters at contact. B, inclusion, part of a larger mass of hornblende-bearing quartz diorite; assimilation is quite advanced. Photographs by Louise Hedricks, US. Geological Survey. and schist country rock, they are subconformable to the regional foliation. Lineations within the rock are due to alined hornblende and biotite and are generally parallel to that in the enclosing gneiss. These mafic rocks compose a distinct belt west of the Boulder Creek batholith that is semicircular, as can be seen in plates 1 and 2. The bodies are small; the largest is less than 2 km in length. Most of the mafic bodies that were plotted on 71/2-minute quadrangle maps are shown on plate 1, but hundreds of bodies observed in the field are too small to plot at the scale of a quadrangle map. The distribution of these rocks as shown on plate 1, however, is representative of their outcrop pattern. GABBRO AND PYROXENITE Gabbro is best known from its outcrop in the Elk Creek pluton in the northwest part of the Central City quadrangle (Taylor and Sims, 1962, p. D1 18; Sims and Gable, 1967, p. E35), but it also occurs in the southwest corner of the N ederland quadrangle—an ex- tension of a lens from the Elk Creek pluton—and in two small bodies west of Gold Hill, both of which are strongly altered by a Tertiary diabase dike. Also, metagabbro was mapped by Wrucke and Wilson (1967) in the northern part of the Boulder Creek batholith. The gabbro is a dark-gray, medium— to coarse- grained, massive, nearly equigranular rock that has a mottled texture due to large poikiloblastic mafic clusters. The matrix consists of interlocking plagio- clase and pyroxene crystals. Typically the rock con- tains roughly 50 percent plagioclase. Where in contact with schist and gneiss, the smaller lenses are biotite rich and commonly weakly foliated. Samples 335—337 in table 7 are from a lens in the southwest corner of the Nederland quadrangle and vary little mineralogically from the Elk Creek pluton itself. Gabbro is character- ized by calcic plagioclase (An“_54), orthopyroxene, clinopyroxene, hornblende, biotite, ores, and about 5 percent quartz. The pyroxenites are best developed in the Los Lagos lens, north of Rollinsville (pl. 2), in the southeast half of the Nederland quadrangle. Here contacts between pyroxenite and hornblende diorite with country rock or hornblende gneiss, where exposed, are indistinct, probably in part because of contact heating and in part because of retrograde metamorphism that occurred during or shortly after their emplacement. Another pyroxenite occurs west of Lakewood Reservoir and north of Nederland. It shows extensive alteration in thin section, in part due to thermal metamorphism caused by emplacement of younger hornblendite. The rock originally consisted almost wholly of pyroxene but now is composed of 50 percent pyroxene, about 40 percent hornblende, and 10 percent ores. Skeletal crystals in the rock consisting of serpentine and calcite probably were originally olivine. Olivine, however, never accounts for more than 2 percent of the total rock. Hornblende pyroxenite is a grayish-black, medium- grained, massive rock that breaks with a glistening hackly surface. It occurs as clots in diorite or is grada- tional into hornblende diorite. The Los Lagos lens is representative of these gradational features. 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Pegmatite occurs around periphery of granodiorite, especially at each end; roadcut, middle of Boulder Canyon, Tungsten quadrangle. Severance lens (fig. 12; pl. 2), in the west half of the Tungsten quadrangle, was perhaps originally in part a pyroxenite; in a roadcut adjacent to the Bureau of Standards building on Colorado Highway 119, the more mafic part of the Severance lens is too crumbly and weathered to sample, but from outward ap- pearances it is very probably an altered pyroxenite. If so, it too is gradational into hornblende-bearing quartz diorite and its outer border of biotitic hornblende- bearing quartz diorite is gradational into mafic Boulder Creek Granodiorite. These altered pyroxenites have a hornblende to pyroxene ratio that is quite variable, ranging from 1:1 to 1:4, and a few are pyroxene-bearing hornblendites (table 7, samples 347-355). The pyroxene minerals in pyroxenite are augite and bronzite. Biotite forms small slender laths and is reddish brown. Plagioclase is interstitial, and crystals are normally zoned and poorly twinned. In thin section, pyroxenites have a texture similar to the gabbro described earlier but are somewhat finer grained. HORNBLENDITE, HORNBLENDE DIORITE, AND QUARTZ DIORITE Black to mottled black and white, medium-grained, rarely slightly porphyritic rocks consisting principally of hornblende or of hornblende and plagioclase were mapped as hornblendite and diorite (pl. 2). The rocks are massive to foliated but lack the strong foliation characteristic of amphibolite of the area. Foliated diorite generally occurs at the margins of the larger dioritic bodies. Lighter colored, finer grained, foliated hornblende diorite has a salt-and-pepper appearance due predominantly to plagioclase in the rock. Quartz diorite, similar in appearance to hornblende diorite, consists of hornblende and plagioclase and at least 10 percent quartz. The hornblendite in samples 338—340 (table 7) con- tains more than 70 percent hornblende; pyroxene and plagioclase account for most of the remaining 30 per- cent. Sample 339 contains 27 percent pyroxene and may be altered pyroxenite because its composition ap- proaches that in the Severance lens, samples 352—354, table 7. In hornblendite, plagioclase is interstitial and is invariably altered to an aggregate of muscovite- sericite. The hornblende in thin section is generally brown, but some hornblendes are green; there is also some alteration of hornblende to actinolite or tremolite along cleavage. From optical data the pyroxene is probably diopside. Most pyroxene crystals are subrounded and are mantled somewhat by hornblende. The accessories are much the same as for the diorites and include ores, apatite, sphene, allanite, and zircon. The diorites are principally hornblende and plagioclase bearing and contain less than 15 percent of other minerals including quartz, biotite, pyroxene, ores, and accessory minerals. Samples 341—344 (table 7) are representative of the diorites. Most diorites con- tain some chlorite, calcite, and secondary epidote. The diorites have a hypautomorphic to allotriomor- phic texture, depending upon degree of schistosity. The mafic minerals generally display the better developed crystal faces. The potassium feldspar in hornblende diorite is orthoclase. It forms small, subrounded, nontwinned, clear to partly cloudy grains that are easily misidentified as quartz. Plagioclase ranges in composition from andesine to labradorite and is normally zoned. Plagioclase from quartz diorite tends to be less calcic than from diorite and poikilitic with subrounded quartz inclusions. Plagioclase twin- ning includes Carlsbad, albite, pericline, and complex twins, with albite and pericline dominant. Alteration of plagioclase varies between diorites; in some the plagioclase is fresh, whereas in others it is completely altered to sericite and muscovite. Mafic minerals tend to cluster, similar to the texture in other Precambrian intrusive rocks in the area. Hornblende appears black in hand specimen and varies from grayish green to olive brown in thin section. It is often anhedral, and in a few sections traces of actinolite occur along grain boundaries and cleavage. In others, a twinning characteristic of cummingtonite indicates cum- 26 BOULDER CREEK BATHOLITH. FRONT RANGE, COLORADO FIGURE 11.—-Mafic inclusions in Boulder Creek Granodiorite. A, type 2 inclusion, biotitic quartz diorite inclusion (322); typical elongated clot but a little more leucocratic than in figure 8, x-polarizers, X16. B, same section, plain light, X12. C, type 3 in- clusion, lamprophyre 1331), plain light X16. A, allanite; Ap, apatite; B, biotite; E, epidote; H, hornblende; O, ores; Or, 0r- thoclase; P, plagioclase; Q, quartz; S, sphene. Photographs by Louise Hedricks, US. Geological Survey; sample numbers in parentheses. mingtonite may be replacing hornblende on a small scale. Biotite varies in amount by as much as 20 per- cent in the more schistose diorites and is more promi- nent in the outer zones of the larger mafic bodies. It is reddish brown and is commonly of two generations: one generation forms stubby crystals that are in mutual contact with the other mafic minerals, whereas the other is more acicular and rarely forms radiating crystals that penetrate or sever hornblende and plagioclase crystals. Pyroxene in diorites occurs as relict grains that have been extensively replaced by hornblende. Where relict pyroxene exists, ores are in greater abundance and biotite is less common than in nonpyroxene-bearing diorites. TWIN SPRUCE QUARTZ MONZONITE The Twin Spruce Quartz Monzonite is herein named for the small settlement of Twin Spruce in the Eldorado Springs quadrangle. The type locality is just THE BATHOLITH 27 FIGURE 12.—Outcrops of layered and foliated biotitic hornblende diorite and massive pyroxenite(?): A, layered biotite-hornblende diorite in roadcut, Colorado 72 south of Rollinsville. B, same loca- tion as A, weathered rubble roadcut with resistant pyroxenite(?) cut by feldspar-rich pegmatites. northeast of Twin Spruce where typical quartz mon- zonite crops out in Coal Creek Canyon. Twin Spruce Quartz Monzonite is a finer grained and more leucocratic rock than the Boulder Creek Granodiorite with which it is commonly associated, and although its composition ranges from granite to quartz monzonite, it is chiefly quartz monzonite. The unit occupies nearly a quarter of the batholith and is more extensive and definitely more massive in the southern part of the batholith (pl. 2) adjacent to the schist and gneiss con- tact than farther north in the central part of the Tungsten quadrangle. Aplite, pegmatite, and rarely trondhjemite accompany the quartz monzonite. Although most bodies of quartz monzonite in the Boulder Creek Granodiorite are generally mappable, local thin lenses commonly are intermixed with the granodiorite or are gradational into it and cannot be mapped separately at a scale of 1:24,000. Twin Spruce Quartz Monzonite was mapped by Lovering and Goddard (1950) as granite gneiss and gneissic aplite; however, recent mapping in the Front Range has shown that the granite gneiss and gneissic aplite unit of Lovering and Goddard includes more than one rock unit. In addition to the quartz monzonite delineated by Wells (1967), thick layers of older Precambrian microcline gneiss (microcline-quartz- plagioclase-biotite gneiss) conformably interlayered with biotite gneiss can also be distinguished locally (Moench and others, 1962; Sims and Gable, 1964; Hawley and Moore, 1967). Geologic mapping indicates the Twin Spruce Quartz Monzonite is certainly younger than the Boulder Creek Granodiorite in some places; elsewhere the field evidence is not as con- clusive. Rb/Sr determinations on samples of this rock from the Eldorado Springs quadrangle indicate the ages isotopically fit the 1,710: 40 my. isochron of the Boulder Creek Granodiorite (Hedge 1969). Weighing all evidence, it appears safe to say that the Twin Spruce Quartz Monzonite is in part late Boulder Creek in age and in part younger than Boulder Creek. Quartz monzonite is generally gray where fresh but has a characteristic zonal weathering pattern adjacent to joints that broke the rock into rough blocks that now weather into orange-brown and light-brown con- centric zones. This form of weathering is typical of the quartz monzonite found in roadcuts in Middle Boulder Creek canyon. Joints or weathering also produce slab- by rocks that break into thin layers much like shale, and these thin slabs tend to spread over weathered sur- faces, obscuring contacts. One such area occurs in the extreme southeast corner of the Tungsten quadrangle; another is in the central part of the Tungsten mining district. Both areas are covered with pieces of quartz monzonite that give the ground a littered appearance. The monzonite in the batholith proper typically has a weak foliation and lineation produced by laths of biotite and tabular feldspar. In adjacent metasedimen- tary rocks, bodies of quartz monzonite have a pro- nounced gneissic structure; this structure is especially noticeable in the lens north and west of N ederland. BOULDERCREEKBATHOLHELFRONTRANGEJXHDRADO .EflmuHMUHHDm o.OOH o.OOH o.OOH c.00H c.00H o.o0H o.OOH c.00H o.OOH c.00H o.OOH c.00H c.00H c.00H 0.00H c.00H 0.00H 0.00H 0.00H 0.00H 0.00H IIIIII HauoH .»H II H.N H.o II II II II II II II II II II II II II .uH II II II IIIIIIIImdmnmm II II II II II II II II II II II II .ua II H.o II II II II II II IIIIIIImuHUHmo II 9N m.H OH H .HH « II N II m m w.o .HH 0 .0 .HH II m II II II IIIIIIIwuovam II II II II II II II II II II H II II II II II II II II II II IIIII mwuficfimum II II II II II II II II II II II II II II II II II II II II .MH II IIIIII mHHusm H o.N m.m m.H .nH .ua II II II II II II H.o .aH H.o .ue .Hs .uH II II .HH IIIIIIIwuHumm< .uH II N.o m.o H II N H m m .MH .ua II H w.o .HH .uH .HH N H m IIIIIIIIII mmuo II . Hm. II . RH II II II II II . .HH II II II II .II . Hm. II II II II II IIIIII muHfimij . .HH . NH m . 0 II II II II II II II II II II II . .HH II . .HH II II II II I IIIIIII GOUMHN H II m.« II m « II 0 II II w mN N.w II II « II m H II II IIIImuHoHHmm Iwufi>oum32 .HH II II II m H II II II .HH m m II II II H II II H II « IIIIIImuHNOHsu N «.HN II w.0N .ue m .9H II N w NH N II 0H m.« H .up II «H a m IIIIIII muHuOHm II II II II II H II 0H II II II II II II II II II II II II II IImuHmHououHHo II II II II II NM mm NH II II II. II II II II II « «H II Imamxouzaocuuo o« m.o m.m II H .ua m mm m« II .MH II II II H.N H NN m m mH o ImamxouzmoaHHo II II II II II II II II II II .HH II II II II .HH II II II .HH N IIImuHHoEmHu IwuHHodHuu< N« N.Nm o.wn m.N« mm o« Nm nH mm mm NN «m m.om o« o.om Hm Hm mm «H N NN IIIIwuamHnauom N m.o H.H w.m N .HH II II II NH NH N m.m m II N H .NH m .uH m IIIII IIInuumzo m N.om w.o N.¢N mm a« H .HH m mm aN .HH m.wN o« «.mm OH H H mm mm m« IIIwmmHUOmeHm II II o.« II II II II II II II II II . MH . .HH II II II II II II II IIIIHmmmmHmw Esamwmuom mmm «mm mmm Nmm Hmm omm m«m w«m m«m o«m m«m ««m m«m N«m H«m o«m mmm mmm Nmm omm mmm IIII.oz mHmEMm mumH moamuw>wm mumH .06me moH mafiuoww wuHuOHw muumHnnpom wuHucanduom own—paw ouHHOHw wuawHQcHozlmuHuOHn ou wufiawxonma mvameauom uukmso 28 _w_w:m.€m=w “Ea—nave Z 59a mmm .omm NE .3». .mvm .34.. .mwm .Nvm .on .mmm Nam .25 6356.25 54335. :5: «3&3 .Em .mvm .wvm .mvm ,va .mmm .mmm manam .2225 25% EN 332: $3 58: £9 €58 8: .T: 200 ”mwnumw «:93 693 «£053 ~3ng SENSE .SESREAR @5323.‘ 33 3.20.8 3.335 62.8% QESSESH ~mfi€§3§§ “233% Bx nguxma 2:333 mmfioSHIH. mqmfih THE BATHOLITH Twin Spruce Quartz Monzonite is chiefly a fine- grained rock having an average grain size of 4—5 mm (fig. 13A), but a medium-grained (0.6—0.8 mm) phase (fig. 133) and a speckled phase occur locally. The speckled phase, not shown in figure 13, is due to clots of minerals surrounded by lighter haloes that are scat- tered randomly throughout the rock. These phases have not been mapped separately, especially as con- tacts are in general gradational. Twin Spruce Quartz Monzonite is predominantly a microcline-, plagioclase-, and quartz-bearing rock with biotite, muscovite, and ores making up approximately 15 percent of the total rock (table 8). Accessory minerals are the same but are scarcer than in the Boulder Creek Granodiorite. Modally, quartz mon- zonite is restricted within the quartz monzonite field of a ternary quartz-potassium feldspar-plagioclase diagram; only a few modes plot in the granodiorite and granite fields (fig. 14). Quartz monzonite in the Eldorado Springs (Wells, 1967) and Ralston Buttes FIGURE 13.—Photomicrographs of Twin Spruce Quartz Monzonite. A, fine-grained quartz monzonite (sample 87, table 8), x-polarizers, X12. B, coarse-grained quartz monzonite, slightly sheared (sample 380, table 13), x-polarizers, X12. C, same section as B, except plain light. Ap, apatite; B, biotite; MC, microcline; Mu, muscovite; O, ores; P, plagioclase; Q, quartz; Z, zircon. Photographs by Louise Hedricks, US. Geological Survey. 29 30 BOULDER CREEK BATHOLITH. FRONT RANGE, COLORADO TABLE 8.—Modes (volume percent) for Twin Spruce Quartz Monzonite, Front Range, Colo. [(--), not found; TL, trace; ores include all opaque minerals. Samples 77—98 and 218-289 from Tungsten quadrangle; 290-303 from Nederland quadrangle; 304-311 from Ward quadrangle; 312—317 from Gold Hill quadrangle] Sample No. —————————— 77 78 79 80 81 82 83 84 86 87 88 89 90 91 Potassium feldspar-— 47.8 35.5 37.7 36.8 44.8 36.5 38.5 35.8 42.6 40.4 34.5 33.6 28.6 21.8 Plagioclase ————————— 21.6 26.6 28.8 29.2 18.4 28.2 25.5 31.4 23.4 23.8 32.3 30.0 37.4 40.3 Quartz —————————————— 28.8 27.5 26.6 28.1 35.8 29.5 32.4 31.2 24.1 29.5 27.3 30.6 29.1 27.4 Biotite ————————————— 1.3 7.0 1.8 3.2 0.1 1.0 0.1 0.7 4.9 2.6 4.5 4.2 3.4 6.1 Muscovite ----------- 0.1 1.0 3.4 1.3 0.2 2.2 1.8 0.5 1.4 2.9 -- 0.9 1.1 3.0 Ores ---------------- 0.4 1.1 1.3 0.9 0.5 2.5 1.6 0.2 2.2 0.4 0.9 0.7 0.4 0.6 Apatite ------------- Tr. 0.3 0.1 0.2 Tr. Tr. Tr. 0.1 0.4 0.4 0.4 —- Tr. 0.1 Allanite ------------ Tr. 0.6 -- Tr. -- -- —— —- 0.6 Tr. Tr. —~ -- 0.4 Zircon -------------- Tr. 0.1 —— 0.1 -— Tr. -- -- —— -— -— Tr. Tr. -- Calcite—---——-——-——— —— —— —- -— -— —— —- -— —— -— —— -— ~— —- Epidote—-—————----—- -- Tr. -— 0.1 —~ —— -- —- 0.1 —— -— Tr. Tr. 0.1 Rutile —————————————— —- —— —— -- -- -— —— Tr. -- -- -- -— -— -- Chlorite ———————————— —— 0.3 0.3 0.1 0.2 0.1 0.1 0.1 0.3 —— -— —— —— 0.1 Sillimanite ————————— -- -- -— -— —— -- -— —— ~— —- —- -- —- —— Sphene ------------- -— -- -- —— —— —- —— -- Tr. Tr. 0.1 —- -— 0.1 Monazite-xenotime--- -— —- -- —— —— -— -- Tr. -- —— —— Tr. Tr. —- Total —————————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. ---------- 92 93 94 95 96 97 98 218 219 220 221 222 223 224 Potassium feldspar—— 17.8 33.6 42.7 31.3 37.8 5.9 37.3 32.7 48.0 32.1 37.8 33.7 7.8 26.5 Plagioclase ————————— 41.1 29.0 23.9 31.8 30.2 45.7 27.0 35.1 21.6 30.6 21.5 22.0 13.9 37.2 Quartz —————————————— 24.9 20.2 29.4 32.6 30.0 40.9 26.5 27.7 26.7 25.7 35.3 38.4 67.6 26.9 Biotite ————————————— 10.7 10.6 1.0 2.8 1.5 5.1 6.2 3.4 1.1 5.1 4.9 4.8 8.9 7.2 Muscovite ——————————— 2.4 3.0 0.4 0.7 0.3 0.8 0.7 0.1 1.9 2.5 Tr. 0.6 0.3 1.0 Ores ———————————————— 1.9 2.9 1.2 0.8 0.1 1.0 2.3 0.9 0.7 2.1 0.4 0.5 1.5 1.1 Apatite ------------- 0.2 0.4 0.2 Tr. 0.1 0.4 Tr. 0.1 Tr. 0.7 0.1 —— -— 0.1 Allanite ——————————— 0.2 0.3 0.2 —— -- Tr. -- -— Tr. -- -- -- —v Tr. Zircon——--—--—---——- Tr. Tr. -- Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Tr. Calcite---—-————--—— —- -- -- —- —— —- -- -- —- Tr. -- -— —— Tr. Epidote ------------- —— -- -- -— —— —- -- Tr. Tr. —— -- -— —— Tr. Rutile——------—--—-- Tr. —— Tr. —- -- -— -— —— Tr. 0.1 Tr. -- -- Tr. Chlorite ------------ —— Tr. 1.0 Tr. -— —— Tr. -- Tr. 1.1 Tr. —- —— Tr. Sillimanite --------- —— -- -- —— —~ —- -— -- —— -— -— —- —- -— Sphene —————————————— 0-8 -- —- -- —- 0.2 —— -— —— —- —- -- -- Tr. Monazite-xenotime--- —— —— -- Tr. Tr. —— —— —— Tr. Tr. —- Tr. Tr. -- Total ---------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 THE BATHOLITH TABLE 8.—Modes (volume percent} for Twin Spruce Quartz Monzonite, Front Range, Cola—Continued 31 Sample No. —————————— 225 226 227 228 229 230 231 232 233 234 235 236 237 238 Potassium feldspar—- 29.2 34.1 39.4 36.4 35.8 4.1 32.0 23.5 29.7 14.1 30.6 34.6 31.5 31.3 Plagioclase ————————— 28.2 24.8 24.0 24.7 12.9 14.3 30.3 18.5 32.4 27.7 31.0 27.5 16.2 28.4 Quartz -------------- 27.7 29.2 24.8 28.4 40.3 69.0 27.0 51.6 26.4 51.9 27.1 27.7 46.6 26.7 Biotite ------------- 6.8 7.5 7.2 6.9 6.2 7.5 6.4 3.3 5.9 2.8 1.1 6.0 3.1 9.5 Muscovite ----------- 6.2 3.0 2.9 2.2 3.5 3.8 2.1 2.2 2.2 2.5 1.8 1.9 1.6 1.9 Ores ---------------- 1.1 1.0 1.3 1.2 1.1 Tr. 1.8 0.8 1.9 1.0 1.5 1.2 1.0 1.9 Apatite ------------- 0.1 0.3 0.3 0.1 —— -- Tr. Tr. 0.2' —~ 0.7 0.4 —- 0.3 Allanite ———————————— 0.5 0.1 —— —— —- —— —— —— -- —- 0.3 0.1 —— —— Zircon -------------- 0.1 Tr. 0.1 0.1 0.2 Tr. 0.2 Tr. Tr. Tr Tr. 0.2 Tr. Tr. Calcite ————————————— -— —— —- ~— —— -- Tr. -- -— -— —- —- -— -- Epidote ————————————— Tr. —- -- —— -- —- -— —— -- —- —— —— -- —— Rutile -------------- —— Tr. Tr. —- —- —— —- —— Tr. -- 0.2 Tr. —— Tr. Chlorite ----------- 0.1 Tr. Tr. -~ Tr. —— 0.2 —- 1.3 —— 5.7 0.4 —— -— Sillimanite --------- -— —— -— —— —- Tr. Tr. 0.1 —- -— —- —- -- —— Sphene——-—----——--- -- -— -- -— —- -— -— —— —- —- —— -- —— -- Monazite-xenotime—-- Tr. Tr. Tr. Tr. Tr. -— Tr. Tr. Tr. -- —- Tr. Tr. Tr. Total ---------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. —————————— 239 240 241 242 243 244 245 246 247 248 249 250 251 252 Potassium feldspar—— 45.5 42.1 44.5 33.2 36.9 26.0 45.5 33.2 31.3 36.5 52.3 35.6 37.8 43.3 Plagioclase ————————— 21.4 25.2 22.8 25.3 27.6 39.4 23.4 29.7 31.1 24.8 16.2 25.5 21.1 22.4 Quartz —————————————— 26.3 25.1 28.0 30.3 23.4 27.1 26.8 26.2 26.9 31.7 20.8 29.4 29.2 30.4 Biotite ————————————— 3.5 2.0 2.0 7.7 8.5 4.9 2.2 7.2 6.4 4.1 4.0 7.4 3.1 1.5 Muscovite—-—-———--—- 1.4 1.4 1.2 0.4 2.1 0.6 1.0 1.2 2.5 0.3 1.9 1.8 7.7 2.0 Ores ———————————————— 1.3 1.3 1.0 2.1 0.9 1.2 0.8 1.6 1.6 1.0 3.3 0.2 0.7 0.1 Apatite ------------- Tr. 0.1 Tr. 0.3 0.4 0.1 Tr. 0.7 0.2 0.2 Tr. 0.1 0.3 —— Allanite ———————————— —— 0.1 0.3 0.6 Tr. —— —— Tr. -— -— 0.3 —— -- -- Zircon —————————————— 0.6 0.1 Tr. Tr. Tr. Tr. —— 0.2 Tr. 0.1 Tr. Tr. 0.1 -- Calcite ------------- -— —— —- —- -- —- —- —- -- -— —— -- -- -- Epidote ————————————— —— —— -- —- —— —— —— —— -— 0.7 -— —- -- -- Rutile —————————————— Tr. —~ —— —— -— -- Tr. —- —— —— —— —— -— Tr. Chlorite ———————————— Tr. 2.6 0.2 0.1 0.2 0.7 0.3 Tr. -- 0.6 1.2 —- —— 0.3 Sillimanite ————————— —— -- -— —— -— -- -- —- —- -— —— -— -— —— Sphene —————————————— -— —— —— —— —- —- —- —— Tr. —— -— —— —— —- Monazite—xenotime——— Tr. -— —— —— Tr. —— —— Tr. -- —- —— —— —— Tr. Total ---------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 32 BOULDERCREEKBATHOLHELFRONTRANGEJXHDRADO TABLE 8.—Modes (volume percent) for Twin Spruce Quartz Monzonite, Front Range, Cola—Continued Sample No. —————————— 253 254 255 256 257 258 259 260 261 262 263 264 265 266 Potassium feldspar—— 28.8 35.3 38.9 23.9 32.4 38.9 48.2 30.2 41.4 41.7 33.3 34.8 34.7 34.5 Plagioclase ————————— 36.1 26.8 22.4 39.3 33.4 25.8 17.9 33.4 19.6 32.5 30.6 32.2 25.8 29.2 Quartz —————————————— 30.3 34.9 28.9 25.3 28.4 30.2 32.8 30.2 30.0 21.7 31.2 28.0 25.7 30.6 Biotite ————————————— 2.5 2.5 6.2 6.7 2.0 0.9 -- 5.4 5.0 1.6 2.4 0.4 7.5 2.5 Muscovite ——————————— 1.9 0.1 1.8 1.9 3.0 1.8 0.6 0.1 2.7 1.9 1.2 1.6 3.7 1.8 Ores ———————————————— 0.3 0.4 1.6 2.4 0.8 0.6 0.1 0.6 0.6 0.4 0.8 1.3 2.1 0.8 Apatite ————————————— Tr. Tr. Tr. 0.5 Tr. Tr. 0.1 0.1 0.3 Tr. Tr. Tr. 0.4 0.1 Allanite ———————————— -— —— 0.1 —— —— 0.1 Tr. -— Tr. Tr. Tr. 0.1 —— Tr. Zircon —————————————— 0.1 Tr Tr. Tr. Tr. Tr. —— Tr. Tr. 0.1 0.2 Tr. 0.1 Tr. Calcite ————————————— —— —- —— —— —— —— —— —— —— -— -- -- -- -- Epidote ————————————— —— —— —- —— —— —— —— —— -— -— -— 0-1 —- 0.4 Rutile —————————————— Tr. -- —— —- —— 0.2 —- —— —— Tr. Tr. Tr. -— -— Chlorite ------------ -— -— 0.1 Tr. -— 1.5 0.3 —- 0.4 0.1 0.3 1.5 -— 0.1 Sillimanite ————————— —— —— -— —— —— -— -— -— -— -— —— -— -— -— Sphene —————————————— —— —— —— -- —- —- —— —— —— —— —- —— —— Tr. Monazite—xenotime——— Tr. Tr. —— —— —— -— -— -— Tr. -— Tr. Tr. Tr. —— Total —————————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. —————————— 267 268 269 270 271 272 273 274 275 276 277 278 279 280. Potassium feldspar-— 47.8 35.5 37.7 36.8 44.8 36.5 38.5 35.8 42.6 40.4 34.5 33.6 28.6 21.8 Plagioclase ————————— 21.6 26.6 28.8 29.2 18.4 28.2 25.5 31.4 23.4 23.8 32.3 30.0 37.4 40.3 Quartz —————————————— 28.8 27.5 26.6 28.1 35.8 29.5 32.4 31.2 24.1 29.5 27.3 30.6 29.1 27.4 Biotite ————————————— 1.3 7.0 1.8 3.2 0.1 1.0 0.1 0.7 4.9 2.6 4.5 4.2 3.4 6.1 Muscovite ——————————— 0.1 1.0 3.4 1.3 0.2 2.2 1.8 0.5 1.4 2.9 —— 0.9 1.1 3.0 Ores ———————————————— 0.4 1.1 '1.3 0.9 0.5 2.5 1.6 0.2 2.2 0.4 0.9 0.7 0.4 0.6 Apatite ————————————— Tr. 0.3 0.1 0.2 Tr. Tr. Tr. 0.1 0.4 0.4 0.4 —— Tr. 0.1 Allanite ———————————— Tr. 0.6 -- Tr. —— —— ~— —— 0.6 ‘Tr, Tr, __ __ 0,4 Zircon —————————————— .Tr . 0 . l —- O . l —— Tr . -~ -- -- -- -- Tr . Tr -- Calcite ————————————— —— —— -- —— —— __ __ __ __ -_ __ __ __ -_ 'Epidote ————————————— —— Tr. —— 0.1 -— -- -- -" 0.1 —- " 0-1 Rutile—————-—-—————— —— —— —— -- -— —— —- Tr. —— -- -- -- -- -- Chlorite ———————————— -—— 0.3 0.3 0.1 0.2 0.1 0.1 0.1 0.3 —— —' '— —‘ 0-1 Sillimanite —————————— -— —— —— —— —- —— —— —- -- -— —— -— -- -- Sphene -------------- -— -— —— —— —- -— —— —- Tr. -— 0.1 —— —— 0.1 Monazite—xenotime—-- -— -- -— —- -- -- -- Tr. -- -— —‘ " '— -‘ Total —————————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 THE BATHOLITH TABLE 8.—Modes (volume percent) for Twin Spruce Quartz Monzonite, Front Range, Cola—Continued 33 Sample No. ---------- 281 282 283 284 285 286 287 .288 289 290 291 292 293 294 Potassium feldspar—— 28.1 17.8 33.6 42.7 31.3 37.8 3.0 5.9 37.3 43.3 49.0 26.9 27.4 31.2 Plagioclase ————————— 33.2 41.1 29.0 23.9 31.8 30.2 48.6 45.7 27.0 23.9 21.0 35.6 32.8 29.3 Quartz -------------- 23.9 24.9 20.2 29.4 32.6 30.0 42.8 40.9 26.5 29.3 29.0 32.4 29.2 38.6 Biotite ------------- 9.7 10.7 10.6 1.0 2.8 1.5 Tr. 5.1 6.2 a2.0 a1.0 3.4 8.6 0.9 Muscovite-——-—------ 2.0 2.4 3.0 0.4 0.7 0.3 —- 0.8 0.7 0.7 Tr. 0.9 0.8 Tr. Ores ———————————————— 1.7 1.9 2.9 1.2 0.8 0.1 3.0 1.0 2.3 0.8 —— 0.5 0.9 Tr. Apatite ———————————— 0.7 0.2 0.4 0.2 Tr. 0.1 0.4 0.4 Tr. Tr. —— -— 0.3 —— Allanite ------------ 0.4 0.2 0.3 0.2 -— -- 1.1 —— Tr. -— —— -- -- —- Zircon-—---------—-— 0.2 Tr. Tr. —— Tr. Tr. 1.1 0.2 Tr. 0.1 Tr. Tr. Tr. Tr. Ca1cite———-——-—————— —— -— -- -— —— —- —- —- —- -- -— -— -- —— Epidote ———————————— Tr. -— -— —— —— —— -— -— —— —— —- —— —— —— Rutile -------------- —— Tr. —— Tr. -- —- -— -— —- Tr. —- —— —— —— Chlorite ———————————— 0.1 -— Tr. 1.0 Tr. -— —— —— Tr. —— —- -— —— -— Sillimanite—----——-- —— —— -— -— —- —— -— -- —— —— —— 0.3 —- —— Sphene ————————————— —- 0.8 —— —— —- —— -— —- -— -- —— -— —— -— Monazite—xenotime——- —— —- —- —— —— —— —— —- —— -— —— —- —— Tr. Total ---------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. —————————— 295 296 297 298 299 300 301 302 303 304 305 306 307 308 Potassium feldspar-— 31.5 43.0 22.7 24.7 35.3 24.9 44.4 43.6 31.9 41.9 47.9 41.1 34.6 43.7 Plagioclase ————————— 19.7 17.4 19.2 22.2 32.7 36.0 26.0 26.3 24.8 25.4 22.2 21.8 28.6 22.3 Quartz —————————————— 39.4 36.5 54.0 47.7 27.7 27.9 24.6 26.8 38.6 23.5 26.2 26.3 26.6 26.5 Biotite ------------ 7.4 Tr. 3.1 3.8 1.3 a5.4 4.1 1.5 3.5 6.4 0.6 3.2 0.4 5.9 Muscovite ——————————— 1.0 2.4 0.1 0.6 1.0 1.8 0.6 0.2 0.6 0.1 0.6 6.4 0.4 —— Ores ———————————————— 1.0 0.6 b0.9 0.7 1.0 3.6 0.3 -— 0.6 2.0 0.8 0.2 1.4 1.3 Apatite ------------- -- -— -- —— —— 0.3 Tr. Tr. -- —— 0.4 —— 0.6 Tr. Allanite ———————————— -— —- —— —— —— —— —- Tr. -- 0.3 —— -— -— —— Zircon -------------- Tr. 0.1 Tr. Tr. Tr. 0.1 Tr. Tr. Tr. Tr. 0.1 —- 0.1 Tr. Calcite ————————————— —- —— —— —— —- —— -— —— -- —— —— —— —- —- Epidote ————————————— -- -— -— —- -- —— -- Tr. -- 0.3 —— —— 0.1 Tr. Rutile—--—-----———-- —- —— -— -— -— -- —- —- Tr. -- -- Tr. —— —- Chlorite ----------- —- —— —— —- 1.0 -- -- —- -- 0.1 1.2 1.0 7.2 0.3 Sillimanite ————————— —— -— —— Tr . —— —— —-— —- -— -— —— Tr . Tr . —- Sphene ————————————— -- - -- -— —- —- —— -- —- —- -- —— Tr. -— Monazite—xenotime-—— Tr. Tr. -- —- Tr. Tr. Tr. -— Tr. —— —— Tr. Tr. Tr. Total ————————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 34 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE 8.—Modes (volume percent) for Twin Spruce Quartz Monzonite, Front Range, Cola—Continued Sample No. —————————— 309 310 311 312 313 314 315 316 317 Potassium feldspar-— 42.2 42.2 35.5 27.3 34.0 42.6 26.9 35.3 14.6 PlagLoclase ————————— 22.0 29.1 31.4 34.7 34.0 27.8 30.2 34.3 44.8 Quartz —————————————— 27.5 21.5 26.4 26.2 25.9 24.8 32.4 28.3 31.7 Biotite ————————————— .8 3.9 4.6 6.9 1.9 .2 7.5 1.3 7.0 Muscovite ——————————— .3 0.4 0.1 1.8 3.3 .0 0.7 -— 0.5 Ores ———————————————— 1.3 1.6 1.5 1.4 0.7 1 5 0.7 0.3 Apatite ————————————— 0.2 9 l Tr. 0.1 0.3 0.1 O Allanite ———————————— 0.2 Tr. -— Tr. -— 0.1 —- Tr. Zircon —————————————— Tr. 0.1 Tr. —- —— -- Tr -- —— Calcite ————————————— -— -— —— -- —— —— —— -- —— Epidote ------------- Tr. Tr. —— Tr 0.1 O 3 Tr. Tr 0.3 Rutile -------------- -- Tr. -- —— —— —- -— —- -- Chlorite ———————————— 0.5 0.3 0.3 Tr. O 1 0.1 Tr. Tr. 0.5 Sillimanite ————————— —— —- —— -— —- —— 0.1 -— —— Sphene —————————————— —— Tr. -— 1.3 -— -- 0.3 -- —- Monazite-xenotime-—- Tr. Tr. Tr. —- Tr. -- —— -- Tr. Total ---------- 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 aBiotite and chlorite undifferentiated. areas (Sheridan and others, 1967), in the southeastern part of the batholith, contains not only more quartz but also more plagioclase than similar rocks within the batholith. To the west of the batholith, Within metasedimentary units, the quartz monzonite lenses also have a greater proportion of quartz, probably as a result of local contamination from the biotite gneiss and schist. In general, the speckled and fine-grained quartz monzonite phases have a greater spread in modal composition than does medium-grained quartz monzonite. Medium-grained quartz monzonite clusters imperfectly between 24 and 40 percent quartz, 35 and 45 percent microcline, and 20 and 35 percent plagioclase. GRANITE GNEISS, GNEISSIC APLITE, AND PEGMATITE Granite gneiss, gneissic aplite, and pegmatite occur as dikes and lenses in the batholith and in the adjacent metasedimentary rocks. Whereas these dikes and lenses are nearly all of Boulder Creek age (1,700 my), it is possible some are of Silver Plume age (1,450 my). Generally, but not always, they can be identified with one intrusive or the other. Granite gneiss and pegmatite form topographically high ridges that can be easily mapped on the north and south sides of Lefthand Canyon, northeast of Gold Hill (pl. 2). At Gold Hill granite gneiss, gneissic aplite, and bTraces of green spinal. pegmatite form profuse lenticular masses, dikes, and thin lenses that are generally associated with Boulder Creek Granodiorite adjacent to the batholith as well as in the batholith. An area of extensive pegmatite occur- rence is north of Golden Gate Canyon for perhaps 2 or 3 m adjacent to the batholith in an area of large satellitic plutons. Granite gneiss and pegmatite are also present in the Central City quadrangle, especially the southern half. Granite gneiss is a leucocratic, generally medium- to coarse—grained rock that is locally gradational into pegmatite and aplite. It is predominantly a feldspar rock containing 20—35 percent quartz and having less than 5 percent accessory minerals, including biotite, muscovite, and the ores (table 9). Locally, granite gneiss and pegmatite bear stringers of biotite gneiss or of biotite, muscovite, and sillimanite. In thin section granite gneiss and pegmatite are leucocratic rocks having an allotriomorphic granular texture. The predominant minerals, microcline, plagioclase, and quartz, are equigranular in some of the finer grained granite gneisses, but more commonly microcline occurs as distinctly larger crystals. The microcline generally appears fresh, but the plagioclase is characteristically altered, and twinning is commonly indistinct and discontinuous. In a ternary quartz- plagioclase—potassium feldspar diagram (fig. 15) modal STRUCTURE 35 distribution of granite gneiss extends form the quartz monzonite field into the granite field with a quartz range between 20 and 40 percent. EXPLANATION 0 Tungsten ' Eldorado Springs A Gold Hill A Black Hawk x Ralston Buttes K . ' P A. ' \ EXPLANATION A Ward 0 Nederland ' Tungsten K P s 0 4° (9 o EXPLANATION 0 Fine»grained 0 Medium-coarse x Speckled Quartz ”U! monzonite C FIGURE 14.—Modal variation in quartz, plagioclase, and potassium feldspar (volume percent) for Twin Spruce Quartz Monzonite. A, composite of all Twin Spruce Quartz Monzonite modes for the batholith. B, variation in lens west of the Boulder Creek batholith. C, modes for the Tungsten quadrangle showing distribution of medium-grained quartz monzonite. Dashed area encloses medium-coarse-grained quartz monzonite. P, plagioclase; K, potassium feldspar; Q, quartz. AGES OF BATHOLITHIC ROCKS Both the Boulder Creek Granodiorite and the Twin Spruce Quartz Monzonite have been dated by deter- mining Pbm/Pb”6 in zircons from the rock samples and by rubidium-strontium whole-rock methods. Perhaps the earliest reliable dates for the batholithic rocks were made by the US Geological Survey (1964) on zircons and indicated an average age for the batholith of 1,730 my. Later, Stern, Phair, and Newell (1971) indicated an average age of the batholith based on six zircon samples to be 1,714 my and emplacement age of the batholith, 1,725 my. Peterman, Hedge, and Braddock (1968) dated 13 samples from the batholith and smaller plutons of granodiorite to the north of the batholith. The results of their rubidium-strontium age determina- tions indicated the batholith was 1,700 my. years old. This age is in agreement with the zircon age of 1,714 my. obtained by Stern, Phair, and Newell (1971). Also, Peterman, Hedge, and Braddock (1968) indicated that a postcrystallization event was superimposed on the batholith as suggested by a Sr*’"/Sr86 age of 1,340 my. Sr87 is suggested to have partly or completely re— equilibrated at that time. Several samples of Twin Spruce Quartz Monzonite from near the type area in the Eldorado Springs quadrangle were dated by Hedge (1969). He obtained rubidium-strontium whole-rock ages that isotopically fit the 1,700-m.y. isochron of the Boulder Creek Granodiorite. Geologic mapping, principally by Wells (1967) and Gable (1972), indicated that Twin Spruce Quartz Mon- zonite is in part younger than the Boulder Creek Granodiorite. The field evidence indicates that the Twin Spruce Quartz Monzonite is in part the same age as the Boulder Creek Granodiorite, but the greater part of it is younger; the younger age is still within the limits of the isochron date (Hedge, 1969) determined for the quartz monzonite. STRUCTURE The Boulder Creek batholith was emplaced into a generally conformable sequence of \ high-grade metamorphic rocks that were folded into a series of complex antiforms and synforms and, locally, cataclastically deformed and faulted. Intrusion of the batholithic rock, metamorphism, folding, cataclasis, and major faulting in the area all took place during Precambrian time. Whereas Cretaceous to Tertiary in- trusive stocks pierced the metasedimentary rocks to the north and northwest of the batholith, only dikes, sills, and small lenses occur within the batholith. The Boulder Creek batholith and its satellitic plutons of similar composition and age shown on plate 1 compose a semicircular structural feature that is 36 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE 9.—Modes (volume percent) for aplite, aplitic pegmatite, and granite gneiss from the map unit Granite Gneiss and Pegmatite (pl. 1), Boulder Creek batholith, Front Range, Colo [(--). not found; Tn, trace; ores include all opaque minerals. Sample 356 from Nederland quadrangle; 357-360 from Tungsten quadrangle; 361 from Ward quadrangle; 362—374 from Gold Hill quadrangle] Sample No. ---------- 356 357 358 359 360 361 362 363 364 355 366 Potassium feldspar—— 33.4 52.9 34.6 56.4 38.7 52.0 46.0 38.6 45.3 39.0 35.4 Plagioclase ————————— 30.2 16.6 31.4 14.8 24.8 32.0 22.0 38.6 22.1 17.0 24.7 Quartz -------------- 32.7 29.3 30.9 26.9 33.7 12.0 30.0 22.8 31.9 34.0 33.9 Biotite ————————————— —— —- 0.7 0.6 -— 3.0 —— Tr. -— 2.0 4.4 Muscovite—---—-———-— 2. 2 30.3 1. 4 0.5 -— 1. o 2.0 —— 0.4 8.0 1.3 Ores ———————————————— 1.5 —— 0.4 —— 0.1 —— Tr. Tr. -— Tr. 0.3 Apatite ————————————— —— Tr. Tr. Tr. 0.4 Tr. Tr. —— —— -— —— Zircon————----—————— —— —— Tr . —- —— Tr . —— Tr . —'— —— —— Chlorite ——————————— —— —— 0.6 0.8 1.1 —— —— —— —— -— —— Epidote ————————————— —— —— —— —— 1.0 —— —— —— —- —— —— Rutile —————————————— —— —— —— —— —- -- —— —— —- —- —— Allanite ———————————— -— —— —— —— 0.1 —— —- —— —— -— -- Monazite—xenotime——— —— —— —— —— —- —— —— -— —— —— —- Calcite ————————————— —- -— —— —— 0.1 —— —— —— -— —— —— Sillimanite ————————— -— -~ —— —— —— —— —- —— 0.3 —— —— Tota1———- —————— 100.0 100.0 100.0 100.0 99.3 100.0 100.0 100.0 100.0 100.0 100.0 Sample No. —————————— 367 368 369 370 371 372 373 374 Potassium feldspar—— 55.5 40.8 44.6 38.7 40.1 28.0 27.1 50.9 Plagioclase ————————— 17.8 25.5 30.1 25.7 20.4 34.4 33.9 20.5 Quartz —————————————— 26.0 29.0 25.2 34.0 36.4 32.7 33.8 26.5 Biotite ————————————— —— 0.9 —— —— Tr. 4.0 -— —— Muscovite ——————————— 0.3 2.4 —— 0.8 2.3 0.1 4.4 1.5 Ores ———————————————— 0.3 1.2 0.1 0.8 0.1 Tr. Tr. 0.1 Apatite ————————————— Tr. —— —— Tr. Tr. 0.1 —- —— Zircon—————--—-————— —— —— —— Tr. —- —— —— —— Chlorite ———————————— —— 0.2 —— —— 0.7 0.7 Tr. —— Epidote ————————————— —— —- -— —— Tr. Tr. —- -— Rutile——--—-———————— —— Tr. —— —— —— —— -— —— Allanite ———————————— —— —- —— Tr. —— Tr. Tr. —— Monazite—xenotime——— 0.1 Tr. —— —— —— —- —- —- Calcite ————————————— —— —— —- —— -— —— -— —— Sillimanite ————————— Tr. —4 —— —— —- —— 0.8 0.5 Total ——————————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 a . . Includes ser1c1te. STRUCTURE ' 37 EXPLANATION 0 Central City AGold Hill - Nederland K P FIGURE 15.—Modal variation in quartz, plagioclase, and potassium feldspar (volume percent) for granite gneiss from the granite gneiss and pegmatite unit. P, plagioclase; K, potassium feldspar; Q, quartz. midway between the Strawberry and Mt. Evans batholiths. In addition to Boulder Creek Granodiorite, ultramafic, mafic, and distinctly leucocratic rocks were emplaced as plugs, dikes, sills, lenses, and plutons along this semicircular feature. The smaller bodies of intrusive rocks roughly conform to the trends of folia- tion and fold axes in the older country rocks, sug- gesting that their emplacement was controlled, to a large degree at least, by preexisting structures in the country rocks. Regional mapping has shown that the Precambrian country rocks of the batholith were deformed and metamorphosed during at least two episodes of regional metamorphism and deformation and a later episode of cataclastic deformation. Emplacement of the granodiorite apparently began late in the first period of synmetamorphic deformation and culminated during the second period. The first defor- mation formed tight to isoclinal folds that apparently have dominantly west— and northwest-trending axial surfaces. This fold set is represented by the overturned Buckeye Mountain anticline and the overturned Jenny Lind and Nederland synclines in the vicinity of Eldora and south of Gold Hill (pl. 2), where the granodiorite is subconformable to deformed country rocks that were folded on northwest-trending axes. Subsequently, the folds were refolded during a deformation that pro- duced north- to northeast-trending folds, which are the dominant structures in the region (Sims and Gable, 1967; Gable, 1969; Gable and Madole 1976; Taylor, 1976). Both the northern and southern parts of the batholith have foliations that have been folded on east- northeast-trending axes that extend from the country rock into the batholith (pl. 2). Foliations along the west contact parallel the contact and vary sharply from those in the interior of the batholith where foliations undulate from northeast to northwest. Both trends in foliation are probably primary, that is, they were formed through flowage of magma that was still plastic during the time of metamorphic deformation and presumably were caused by protoclastic deforma- tion or by the differential flow of magma before com- plete consolidation. Continued shearing produced secondary foliations and recrystallization in the granodiorite along fault zones, particularly along the southern margin of the batholith. Both deformations took place under temperature-pressure conditions represented by 300—500 MPa [3—5 kb] at 620—710°C (Gable and Sims, 1969) and are characteristic of a sillimanite-potassium feldspar grade metamorphism. The later and more restricted cataclastic deformation was confined mainly to a relatively narrow zone pass- ing through the southeast part of the map area (pl. 1) and the southernmost part of the batholith and was ac- companied by retrograde metamorphism. The cataclastic deformation has been dated at about 1,440 my. by Hedge (1969), which is approximately the time of emplacement of the Silver Plume Quartz Monzonite. J ointing is well developed throughout the batholith but data are available for only the western half of the batholith. Joints mapped in the Tungsten and Gold Hill quadrangles are fairly uniform; figure 16 syn- thesizes the similarities. Flat-lying joints (not shown in fig. 16) in the northern part of the batholith trend N. 72 ° E. and dip approximately 10° NW; this same joint set to the south has about the same trend, N. 80° E., and dips 15 ° SE. If these primary flat-lying joints formed when magmatic pressure decreased, they probably indicate a 0\ ‘3“ o\ “(a “fig?“ IV IV eh, 9' 6% O\N 69 by . 16%?» Sm ' . ’1 N. 65 WW 57~ge4ig€ $\~\ ’1. N5. 9°’ ’1’ q 6‘ ‘S‘ RS6; 7) 06: ))‘96‘ (PG/1f," FIGURE 16,—Synthesis of the more prominent joint sets in the Tungsten and Gold Hill quadrangles, showing similarities in orientation; 963 poles represented. No, north half of batholith; So, south half of batholith. 38 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO doming of the batholith; another possibility is that the joints were related to contractions of the batholithic mass on cooling, or alternatively, represent fractures formed by release of pressure as the batholith was un- covered. Of the three possibilities, the last seems preferable, especially if the batholith does consist of two magma series. A joint set that dips to the west on the west slope of the southern part of the batholith (Gable, 1973) and a complementary set that dips east may also be related to the release of pressure. GEOCHEMISTRY Geochemical data indicate that the Boulder Creek Granodiorite consists of two magma sequences both regulated in part at least by CaO and SiO,: (1) a northern sequence that has more SiOz, CaO, and Na20 than (2), a southern sequence that is richer in A1203, FeO, MgO, and K20. In the Twin Spruce Quartz Mon- zonite, however, CaO and SiO2 do not appear to have influenced distribution of the oxides. Chemical data were obtained for Boulder Creek Granodiorite and each of the significant rock types associated with the granodiorite. Major- and minor- element analyses of these rocks are given in tables 10, 11, 12, and 13. Data from analyses published since 1950, when usable, have also been used in many of the figures (for example, figs. 18—27), especially those from the Eldorado Springs quadrangle, in order to have more complete coverage of the batholith. Localities of chemically analyzed samples in this report are plotted in figure 17. BOULDER CREEK GRANODIORITE The Boulder Creek Granodiorite has two distinct chemical compositions based on the presence or absence of hornblende. Biotitic Boulder Creek Granodiorite generally has higher SiO2 and CaO and lower TiOz, FeO, and MgO than biotite-hornblende granodiorite. Chemically, Boulder Creek Granodiorite, on the average, shows the same variability in composi- tion, based on the minerals biotite and hornblende, as do equivalent analyses of biotitic granodiorite and biotite-hornblende granodiorite published by Nockolds (1954, p. 1014); the Boulder Creek Granodiorite on the average, however, contains less SiOz, Fe203, and N aZO and more A1203, total iron as FeO, and MgO. Chemical data on the mafic inclusions in the Boulder Creek Granodiorite are given in table 11. The small spindle type of mafic inclusion associated with the granodiorite, shown in figures 8A and 9 was not chemically analyzed; it is too greatly altered. All analyses are of larger dioritic inclusions (samples 334, 385, and 386, table 11). Trace-element data for the mafic inclusions are quite similar to data for Twin Spruce Quartz Monzonite (fig. 18). Trace elements for hornblende gneiss and amphibolite (fig. 18, col. 1), a rock type suggested as a source for the mafic inclu- sions and trace elements in the inclusions, vary widely. Gabbro, hornblende pyroxenite, pyroxene-bearing hornblendite, hornblende diorite, and biotitic horn- blende diorite, which are all spatially associated with the Boulder Creek Granodiorite, were also analyzed (table 12). Modes for these rocks are a part of table 7. Chemical analyses and modes indicate that these mafic rocks are composite and partly gradational into one another and even into granodiorite. Twin Spruce Quartz Monzonite is a high-SiOz, low- MgO rock, as indicated by 13 analyses from localities in the N ederland and Tungsten quadrangles (table 13). Average Twin Spruce Quartz Monzonite does not vary much from N ockolds’ (1954) biotite adamellite or from his muscovite—biotite quartz monzonite. The Twin Spruce Quartz Monzonite has higher Fe203, due to ox- idation, than N ockolds’ average quartz monzonite. Amounts of K20 in the Twin Spruce Quartz Monzonite are extremely variable between samples. CHEMICAL TRENDS WITHIN THE BATHOLITH Chemical trends occur from east to west across the southern part of the batholith as represented by samples from the Tungsten and Eldorado Springs quadrangles. However, in the northern part of the batholith, no east-west trend is indicated by the samples from the Gold Hill and Boulder quadrangles. Trends across the southern part of the batholith are defined by the percent of SiO2 and (or) CaO in the rock in relation to most major oxides. In the northern part of the batholith the single east-to-west trend'is re- placed by two separate trends in which SiO2 for both the border and interior of the batholith lie in exactly the same range. In general, the southern part of the batholith has more FeO, MgO, and K20 and less CaO, P205, and possibly less N a20 than the smaller northern part. Modal and chemical trends seem to indicate that there were two magmas involved in the batholith, the northern magma showing less differentiation from con- tact to central part of the batholith. Chemical trends of CaO and SiO2 to the major oxides in granodiorite from the Boulder Creek batholith are indicated in figures 19 and 20, and in general, as TiOz, MgO, and FeO representing total iron increase, CaO in- creases, whereas K20 and SiO2 decrease as CaO in- creases. P205 and Na20 show no direct relationship to CaO; no trend as such is indicated. Chemical trends of calcic, sodic, and femic oxides relative to SiO2 in the batholith (fig. 19) show con- GEOCHEMISTRY 39 siderable scatter except for total iron, which has a nearly straight-line relationship to $0,, even within the satellitic plutons of granodiorite. Silica ranges from about 60—70 percent, and, as can be seen in figure 19, there is a distinct break in distribution of the ox- ides in the southern part of the batholith at about 64 weight-percent SiOZ, the greater part of the Eldorado Springs quadrangle samples (interior of the batholith) plotting between 60 and 65 percent SiOz, and Tungsten samples (batholith border) plotting above 64 percent $0,. In the northern part of the batholith, Gold Hill and Boulder quadrangle samples each cover the entire range from 60 to 72 percent $0,. In the batholith, K20 in relation to SiO2 is steplike. Gold Hill quadrangle samples occupy mostly the 1—2.5 percent range of K20, Tungsten quadrangle samples occupy the 2.5—4.0 per- cent range, and Eldorado Springs quadrangle samples occupy the 3—4.5 percent range, but Boulder quadrangle samples cover nearly the entire range from 1.5 to nearly 5 percent. CaO and NaZO in the northern part of the batholith represented by Boulder and Gold Hill quadrangle samples plot mostly above the Tungsten-Eldorado Springs samples from the southern part of the batholith, indicating greater CaO and N ago in the northern part of the batholith. CaO is the only oxide in which trends are readily defined in the two parts of the batholith and whereas the southern batholithic samples divide readily along the CaO—SiO2 trend, those in the northern part of the batholith are separated by differences in amounts of SiO2 rather than CaO. Oxide distribution in relation to the percent of calcium present, especially between the northern and southern parts of the batholith, is expressed in figure 20. In the southern part of the batholith, analyses having greater than 4 percent CaO are represented pre- dominantly by Tungsten quadrangle plots, and less than 4 percent CaO by Eldorado Springs quadrangle plots. In the northern part of the batholith no such zoning occurs; as the contact is approached, there is an increase in both sodium and calcium. Calcium ap- parently regulates a number of oxides, especially TiO2 and MgO, and perhaps FeO, A120,, and fluorine, but virtually not N a2O and P205 at all. Na20 is relatively stable throughout the batholith and varies mostly be- tween 3 and 4 percent of the total oxides. MgO in the southern part of the batholith follows a single trend, whereas in the northern part, represented by Boulder-Gold Hill quadrangle samples, it occurs in two separate trends, one representing the border area and the other the interior of the batholith. MgO trends are very distinct in comparison with trends for the other oxides in relation to CaO. Fluorine in the batholith is abnormally high for a granitic rock, but a relatively high fluorine content is characteristic of almost all granitic Precambrian Front Range rocks (Shawe, 1976, p. 25). Fluorine in at least the northern part of the batholith shows a regular distribution trend with calcium that indicates that calcium increases as fluorine increases. Lee and Van Loenen (1971, p. 21) noted also that with an increase in calcium, fluorine also increased in gneissic granitoid rocks in the southern Snake Range of Nevada. Unfortunately, in the southern part of the Boulder Creek batholith there are insufficient analyses to come to any conclusion. In a ternary KZO-NaZO-CaO diagram (fig. 21), the trend (A) for the northern. part of the batholith represented by the Boulder—Gold Hill quadrangle plots (non-shaded area) tends to increase in NaZO as CaO increases, whereas in the Tungsten and Eldorado Springs quadrangles, the trend (B) shows a decrease in NaZO as CaO increases. The Tungsten and Eldorado Springs plots from the southern part of the batholith are not only widely scattered but split at about 38 per- cent (on the basis of 100 percent) CaO and 32 percent for both K20 and Na20. Tungsten quadrangle samples plot on the sodic side and those from the Eldorado Springs quadrangle on the potassic side of the diagram. The northern part of the batholith tends to be more calcic, the trend is well defined, and the scatter of points is small. The tendency of N aZO to vary only be- tween 25 and 35 percent on a KZO-Nazo-CaO ternary diagram is consistent with observations of many others. Bowen (1928, p. 100) was the first to note this close approach to a constant value for sodium in calc- alkaline rocks containing 55 to 75 percent SiOZ. On a Q-Ab+An—Or (quartz-albite plus anorthite- orthoclase) diagram (fig. 22), samples from the Gold Hill quadrangle in the northern part of the batholith plot dominantly on the Ab +An side and to the left of the Tungsten and Eldorado Springs quadrangle samples from the southern part of the batholith. Samples from the Boulder quadrangle plot dominantly in the same field as those from the Tungsten and Eldorado Springs quadrangles. The trend of the granodiorite field is extended to the Ab +An corner by plotting the more mafic rocks associated with the granodiorite. 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N.d.. not determined; H, not found; TL, trace: <, less than; ores include all opaque minerals] Mafic inclusions Lamprophyre dikes Sample No. ----------- 334 385 386 387 388 Lab. No.-—--——--——-— w171193 w185231 w171834 W171832 W171833 5102 ———————————————— 52.6 53.6 52.2 48.8 50-7 A1203 ———————————————— 16.6 15.6 19.0 12.5 13-3 Fe203--_--__-_---___- 4.7 2.9 2.6 2.7 3.0 FeO ——————————————— —— 5.0 5.5 4.9 5.2 5-7 MgO----------—-—--—-- 3.0 4.4 5.0 8.4 7.9 Ca0-————-----—------- 5.4 7.9 7.4 9.6 7-8 Na20-_-_---_-___-_;__ 3.3 3.1 3.9 1.5 1.7 K20 _________________ 3.7 2.6 2.4 5.9 6-6 H 0-__--_____________ 0.11 1.3 1.2 0.14 0-15 020+ ................ 1.1 0.09 0.14 1.3 0.40 T102 ——————————————— 2.7 0.64 0.82 1.7 1-3 9205 ————————————————— 1.1 0.71 0.23 1.2 1-2 MnO .................. 0.12 0.18 0.15 0.09 0.16 co2 —————————————————— <0.05 0.02 <0.05 <0.05 <0-05 F ___________________ 0.20 n.d. 0.19 0.62 0.59 CI ___________________ 0.03 n.d. 0.04 0.04 0.04 Total----—--——— 99.00 99.00 100.00 99.00 100.00 Powder density ------ n.d. n.d. 3.00 3.00 3.00 Semiquantitative spectrographic analyses, in parts per million 33 ___________________ 2,000 1,120 500 1,000 1,000 Be ——————————————————— 1 4 1 5 5 Ce_-_-__-_-_-_--_-___ 2,000 191 500 1,500 3,000 Co ——————————————————— 20 31 3O 30 30 Cr__ _________________ 70 153 150 200 200 Cu--—-------—-------- 20 123 200 20 30 Ga ________________ __ 20 36 15 10 10 La ___________________ 500 80 70 500 1,000 Mo ————————————————— —— 5 -- 10 5 5 Nb ________________ 20 —- 100 15 15 Nd __________________ 500 —— —— 1,000 1,500 Ni ___________________ 30 102 100 300 200 Pb ------------------- -— -- 7 —- -— Sc ——————————————————— 10 46 20 15 15 Sm ___________________ _— 14 -- 100 100 5r ___________________ 1 000 660 1,000 2,000 2,000 v ................... 150 136 150 150 150 Y ____________________ 50 67 50 100 100 GEOCHEMISTRY 45 TABLE 1 1.—Chemical and spectrographic analyses and modes for mafic inclusions and kimpnophyre dikes in Boulder Creek Granodiorite, Front Range, Cold—Continued Mafia inclusions Lamprophyre dikes Sample No. ----------- 334 385 386 387 388 Lab. No.—-—------——-— w171193 W185231 W171834 W171832 W171833 Yb-—---——------——--—— 5 9 5 10 10 Zr ————————————————— 1, 000 734 150 700 500 Modes, in volume percent Potassium feldspar--— 15.6 1.9 6.2 31.5 39.2 Plagioclase --------- 42.7 46.7 53.0 0.2 0.6 Quartz--------———--- 15.5 7.7 3.0 -- 0.2 Biotite—-—--——-——-—-- 19.0 14.8 12.8 19.6 14.5 Hornblende- ------ -— -- 23.5 22.6 41.9 37.0 Pyroxene——---—-———-- -- Tr. -- 0.2 -— Ores—---—-—---——--—-— 3.0 -— 0.2 -— 0.9 Allanite ————————— -— 0.3 —— Tr. 0.6 1.1 Apatite -------- 0.9 1.2 Tr. 2.8 2.4 Sphene ---------- —- 2.6 0.5 0.7 3.2 3.9 Zircon ------------ ——- -— —- Tr. -- —— Calcite ------------ -- 0.3 -- -— —- Chlorite ------------ 0.2 1.3 0.1 -- -- Prehnite——-———------— -- Tr. -— —- -— Muscovite ------------ 0.2 -- -- -- —— Epidote- clinozoisite —————— —- 2.1 1.4 Tr. 0.2 Total---—------ 100.0 100.0 100.0 100.0 100.0 Composition of plagioclase ——————— AnZ6 An30 An31 n.d. An43 Whereas the major elements vary rather sys- tematically with SiO2 or CaO, this is not particularly true for the trace elements. Of 20 minor elements only chromium, nickel, and vanadium appear to vary directly with CaO or SiO2 content. Chromium, nickel, and vanadium increase as CaO increases and all three decrease as SiO2 increases. RAHQERAJXDGY'IN REIJNTKDN'TC)CHiEhAHZAL’TREDUDS Chemical trends in the granodiorite (fig. 20) are more definitely related to calcium than they are to silicon and are better defined than those related to silicon (fig. 19); therefore, weight percents of essential minerals were plotted against calcium (fig. 24) to determine related mineralogical trends. Modes are not available for chemically analyzed samples from the Eldorado Springs quadrangle, and accordingly these samples do not appear on any of the plots. All trends have widely scattered points except biotite in biotitic granodiorite and hornblende in biotite-homblende granodiorite. Trends for modal potassium feldspar and quartz are inversely related to CaO in the rock, and from figure 24, those trends for potassium feldspar are more con- sistent. Microcline accounts for the greater part of the potassium feldspar in the granodiorite, and, according- ly, trends approximate those of quartz; however, with an increase in the amount of biotite, the K20 is used first to form biotite and less K20 is left to form potassium feldspar, causing some scattering of plots. Modal biotite, hornblende, and plagioclase increase as CaO increases (although biotite uses no CaO), and their trends are opposite to those of quartz and microcline. 46 BOULDER CREEK BATHOLITH. FRONT RANGE, COLORADO TABLE 12.—Chemical and spectrographic analyses for gabbro, hornblende, pyroxenite, pyroxene-bearing hornblendite, hornblende diorite, biotitic hornblende diorite, Boulder Creek batholith area, Front Range, Colo. [Rapid-rock analyses by Joseph Budinsky. P. L. D. Elmore. Lowell Artis. J. L. Glenn, Gillison Chloe, Hezekiah Smith, and James Kelsey for sample 343, all other samples by Leung Mei. Spectrographic analysis for sample 343 by J. L. Harris; all other samples by H. W. Worthing. (u), not found] Pyroxene-bearing Biotitic hornblende Gabbro Hornblende pyroxenite hornblendite Hornhlende diorite diorite Sample No. ------- 336 348 349 353 338 3351 343 352 Lab. No. ————————— w179527 w179530 w179528 w179533 W179529 wl7953l w173309 W179532 Chemical composition, in weight percent 53.3 52.9 50.1 50.5 50.2 50.0 55.1 47.8 17.8 5.8 5.4 8.8 9.9 17.1 13.4 14.3 1.4 2.0 4.8 2.9 2.9 2.8 3.8 3.6 6.4 6.3 5.6 5.8 5.9 6.7 6.1 7.0 7.8 17.0 17.3 13.4 13.1 7.5 7.7 9.7 7.6 13.2 12.1 12.4 13.2 10.0 8.6 9.8 3.4 0.43 0.53 0.73 1.2 2.7 1.9 2.0 0.68 0.16 0.20 1.6 0.79 0.56 1.1 2.5 0.77 0.40 1.1 0.61 0.59 1.3 0.51 1.1 0.07 0.02 0.02 0.09 0.01 0.08 0.10 0.16 0.49 0.31 0.35 0.84 0.82 0.95 0.55 1.1 0.24 0.10 0.24 1.10 0.16 0.11 0.09 0.86 0.11 0.17 0.21 0.21 0.16 0.15 0.24 0.18 0.01 0.08 0.08 0.03 0.01 0.05 0.05 0.05 0.04 0.02 0.02 0.03 0.01 0.04 0.03 0.09 0.05 -- 0.01 0.24 0.17 0.53 0.13 0.32 100.00 99.00 99.00 99.00 99.00 100.00 99.00 100.00 Semiquantitative spectrographic analyses, in parts per million Ba-—-----———-—--- 700 1,500 70 1,500 200 150 150 500 Be——-————-—--—-—— 1 1 1 1 1 —— —— 1 Ce --------------- 70 —— 70 200 100 —— —— 325 Co --------------- 30 7o 70 30 50 60 50 40 m —————————————— 3m Lsm Low Lsm 5m 1w mo mo Cu ——————————————— 70 200 200 20 50 100 10 7 Ga ——————————————— 20 7 7 10 1o 12 10 17 La ——————————————— —— —— -— 200 50 -- 30 125 Ni ——————————————— 150 500 700 200 500 135 150 200 Pb ——————————————— 5 5 5 5 5 5 5 5 Sc ———————————————— 15 70 7o 70 50 3o 70 60 Sn——————-----—--— -- 7 10 7 —— —— —- —— Sr ——————————————— 1,000 200 100 1,500 1,000 300 300 700 v-—-—--———-—-—--— 100 150 150 100 150 200 150 150 15 15 20 50 30 25 30 60 1.5 1.5 2 5 3 2 3 6 50 50 so 200 100 40 150 125 aAverage of two analyses. GEOCHEMISTRY 47 TABLE 13.—Chemical and spectrographic analyses and modes for Twin Spruce Quartz Monzonite, Front Range, Colo. [Wet chemical analyses for samples 1 and 2 by C. L. Parker; rapid-rock analyses for samples 3. 4. and 5 by P. L. D. Elmore, Lowell Artis, Gillison Chloe. J. L. Glenn. S. D. Botts, Hezekiah Smith, James Kelsey; spectrographic analyses for samples 1 and 2 by G. W. Sears. J12. for samples 3—5. J. L. Harris. for samples 9—13, H. W. Worthing. N.d., not. determined; <. less than; (u). not found; Tr.. trace; L, present but below limit of determination; ores include all opaque minerals unless stated otherwise] Sample No. ------ a232 a235 37s 85 376 377 378 379 380 ass: a382 a383 a' b384 Lab. No. ———————— D101719 D10172D w170101 w171192 w171191 W173306 w1733o7 w173308 W177080 w177081 W177083 w177084 w177082 75.06 68.91 69.4 71.9 62.0 72.4 71.5 72.4 69.4 68.7 78.9 70.9 69.7 12.27 14.72 15.7 14.9 16.9 14.0 14.5 14.8 14.9 16.1 9 7 13.3 14.2 1.34 1.62 0.89 0.42 3.2 0.34 0.62 0.93 2.0 2.6 1.8 1.8 2.4 1.71 1.96 0.92 1.2 2.7 1.9 1.8 0.88 3 1.1 2 5 3.3 2.1 0.67 0.84 0.38 0.38 1.6 0.45 0.53 0.38 0.54 0.24 1 1 1.0 0.5 0.93 1.6 1.5 1. 3.2 0.92 1.9 1.7 1.7 2.4 1.3 1.1 1.5 2.85 2.57 3.4 2. 3. 3. 3.8 3.7 2.7 4.4 1. 2.3 2.5 3.9 5.89 6.2 6. 5. 5. 4.2 4.5 5.5 2.4 1.3 3.6 5.3 0.34 0.51 0.48 0.39 0.51 0.69 0.41 —- 0.8 0.66 0.84 1.1 0.78 0.03 0.02 0.04 0.07 0.1 0.17 0.03 0.1 0.07 0.08 0.05 0.11 0.08 0.35 0.6 0.18 0.19 0.96 0.36 0.31 0.24 0.53 0.21 0.57 0.75 0.56 0.04 0.26 0.09 0.06 0.34 0.07 0.09 0.05 0.33 0.03 0.09 0.04 0.12 0.05 0.04 0.04 0.04 0.09 0.07 0.06 0.05 0.05 0.09 0.03 0.12 0.09 0.05 0.02 0.09 0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 0.01 0.02 n. 0.001 0.02 0.011 0.006 0.004 <0.001 <0.001 0.012 0.010 0.010 0.06 0.12 n.d. 0.02 0.12 0.06 0.05 0.04 0.05 0.01 0.01 0.03 0.02 n.d. n.d. n. n.d. n.d. n.d. n.d. n.d. 0.02 —— >~- -- 0.02 Subtota1-—- 99.66 99.70 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.0 100.0 99.0 100-0 Less 0 ----- 0.03 0.05 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d n d n d Total———-—— 99.63 99.65 100.0 100.0 100.0 100.0 100.0 100.0 100.0 99.0 100.0 99.0 100.0 Powder density—— 2.69 2.70 c2.6.3 n.d. n.d. C2.56 c2.56 C2.56. n.d. n.d. n.d. n.d. n.d. Spectrographic analyses, in parts per million Ba —————————————— 1,500 1,500 2,000 2,000 2,000 700 700 700 1,500 1,000 300 1,500 2,000 Be -------------- -— -- 2 1 1 —— —— —— <1 1 <1 <1 <1 Ce -------------- <150 700 500 500 1,000 500 200 500 500 100 100 150 200 5 5 —— —— 10 —— -- -- 5 3 10 10 5 30 10 3 3 20 7 10 10 15 1 310 50 5 1 30 10 7 500 50 2 3 50 3 3 3 5 30 30 10 15 20 15 15 15 20 30 20 20 20 La —————————————— 70 300 150 150 500 150 70 100 500 100 70 100 200 Mo -------------- -— —— -- -— -- 3 3 3 -— 5 —— 3 L Nb —————————————— 10 10 3 —— 5 20 7 10 20 —— -- 7 7 Nd —————————————— 70 300 —— -- 300 —— -- —— 500 -- —- -- 200 N1 —————————————— 10 5 -- -- L -- —— L 5 -- 30 10 7 Pb -------------- 50 7O 30 30 20 50 30 50 50 15 10 20 20 Pr -------------- -- <1oo -— —— -- -— -- —- 50 —- —- —— -- 10 5 3 3 10 10 7 5 10 5 10 15 7 5r ______________ 300 500 300 3 000 1,000 200 200 200 300 300 100 200 500 30 70 10 20 70 30 30 20 70 10 100 70 30 Y --------------- 70 50 10 20 30 20 20 20 50 100 50 100 70 Yb —————————————— 10 3 1 2 3 2 2 2 3 15 5 10 5 z: —————————————— soo 500 15 200 700 700 300 150 1,000 200 200 700 1.000 48 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE l3.—Chemical and spectrographic analyses and modes for Twin Spruce Quartz Monzonite, Front Range, Cola—Continued Sample No. —————— a232 a235 375 85 376 377 378 329 380 a381 a382 aasa a’basa Lab. No. -------- 0101719 D10172D w170101 w171192 w171191 w173306 w173307 w173308 wl77080 w177081 w177083 W177084 w177082 Modes, in volume percent Potassium feldspar ------ 23.5 34.6 34.3 45.5 31.6 31.2 28.4 34.3 35.1 15.1 0.9 18.0 36.2 Plagioclase ————— 18.5 27.5 31.5 21.2 39.3 29.1 33.4 33.9 31.4 51.8 23.4 28.3 27.4 Quartz ---------- 51.6 27.7 31.3 27.0 13.6 32.6 30.0 25.2 22.6 27.9 62.5 39.3 28.1 Biotite ————————— 3.3 6.0 0.5 3.6 10.3 4.4 6.4 2.9 8.4 3.2 12.0 11.1 5.3 Muscovite-----—— 2.2 1.9 0.1 1.5 0.6 2.0 0.8 2.9 0.8 —- —— 0.3 1.2 Ores ———————————— 0.8 1.2 0.5 0.4 2.4 0.7 0.8 0.4 1.2 1.5 1.0 0.8 1.7 Sillimanite ----- 0.1 —- —— —— " -- —— -— -- —— -- Tr. -- Apatite ————————— Tr. 0.4 0.1 Tr. 0.4 -- 0.1 Tr. 0.1 Tr 0.1 -— Tr. Xenotime —————— —- Tr. Tr. —— —— -— —— —- —— Tr. —— -— -- -- Monazite ———————— —— —— —- -- Tr. —- —— Tr. —- —— Tr. -- Tr. Zircon —————————— Tr. 0.2 Tr. —— -— Tr. 0.1 Tr. Tr Tr. 0.1 0.1 0.1 Chlorite-—-————- —— 0.4 1.6 —- Tr -- —— 0.4 0.3 —- -— —— (d) Calcite ————————— -— -- 0.1 —- —- —— —- —- —— -- -- -- -- Allanite ———————— —— 0.1 Tr. 0.3 0.1 —— —— -— 0.1 —— —- —— Tr. Rutile —————————— —— Tr. -- -- —— —— —— —- —- —- -- -- -- Sphene-——————--- —— —— —— 0.1 1.6 —— —— -— -- —— —— -- -- Epidote ————————— —— —- -- 0.4 0.1 -- —— —— —- -- -- —— —— Garnet —————————— —— —— —— —- —- -— -— —— —— 0.5 —- 2.1 —— Total —————— 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Composition of 1 1 --- p ag oclase An14 Anz4 Anl8 An22 An19 An23 n.d. n.d. An28 An19 An28 Anz4 An22 a b Samples 232, 235, 381, 382, 383, 384 are from quartz monzonite in metasedimentary rocks. Ores in separate include molybdenum, pyrite, chalcopyrite, and magnetite. cBulk density. dBiotite and chlorite undifferentiated. The spread in points, however, is so great that systematic relationships are nearly impossible to define except for hornblende in biotite-hornblende granodiorite and biotite in biotite granodiorite (fig. 24). Chemical differences between the granodioritic rocks in the northern and southern parts of the batholith, especially in calcium, potassium, and to a lesser degree sodium, are indicated by larger percentages of plagioclase, biotite, hornblende, and apatite in the northern part. In the chemical variation diagram (fig. 23) the ratio of iron to magnesium in the northern part of the batholith is expressed in a differentiation trend ' that distinctly differs from the differentiation trend for the southern part of the batholith. The presence of more biotite and. hornblende and less potassium feldspar in the northern part of the batholith reflects this chemical difference as indicated by the following modes (in percent): for the southern part of the batholith, potassium feldspar, 20; plagioclase, 39; quartz, 26; biotite, 11; hornblende, 1.4; for the northern part of the batholith, potassium feldspar, 10; plagioclase, 44; quartz, 24; biotite, 15; hornblende, 2.9. CHEMICAL TRENDS IN MAFIC INCLUSIONS The mafic inclusions (table 11, nos. 334, 385, 386) are, according to their major oxides, allied to the horn- blende diorite, but the inclusions have larger amounts of sodium and potassium and less calcium and magnesium than the hornblende diorite. The lam- prophyre represented by samples 387 and 388 in table 11 is chemically distinct from the mafic inclusions in that it has low aluminum and high magnesium, calcium, and potassium. The major chemical characteristics of inclusions are compared with the Boulder Creek Granodiorite and associated rocks in a Q-Ab+An-Or variation diagram (fig. 22). The analyzed inclusions plot with diorite in the Ab+An part of the diagram. On an AFM diagram (fig. 23) of the same rocks the inclusions plot farther GEOCHEMISTRY 105°37’30" 30, 1050 2230, 40° I 07' i— -/V 30" 7 , AAAAAAA 7 EXPLANATION ? I Twin Spruce Quartz Monzonite "a- ‘‘‘‘‘ W 476% . \J F’ Q */”s '140 T_ W ' . 2 n flgé fl 0 139 N. Vw Q" .1 ) T- M’ Q / p 5 1 Q N 027 Q~ o N. 399 1 . O '1! 4 “if ‘0 I 0 l . i . _,_‘,, ,~,,,*,__.__7{<,4.A.,. A o . \ 40° 5201.10106 .133 ; ' 00' i; 3 7-8 1 ‘i . 1 i 83W) , , n_.,,,‘, m! 0 s 5’ z «’0’ K, T. 1 S. T. 2 S. 39° 52' 30” R. 72 W. R. 71 W. 0 5 1o KILOMETEHS I 1 | APPROXIMATE SCALE FIGURE 17 .—Sample localities for rock and mineral analyses shown in tables in this report. Batholith covered by grid showmg section, township, and range. Dots without numbers indicate samples for which modes have been made but which have no chemical data. I I I 1 50 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO ,DL kwwmam :2: 7 9 m SS Nd 08 I W l 3 Y U" 00 m m m 100 E ’7 6 so —aso 200 l (3 100 V a D 50_ Q, 0 V7 0 m I] 50— ,— 200_ z o a ._ o z 2 +875 5 400» ) zoor Q. U) Q) 200— 'E o E o 5— g .0 0 Fl Z a .. :LLE V- “2% 1500 — L IL 1000— £ H 500— , a (a 4 0 1 2 3 mm mm La N 08% m E 1 200 07 31 w m \\\\\w i am 3 4 ROCK TYPES FIGURE 18.—Abundances of minor elements for 1, hornblende gneiss and amphibolite, average of 20 analyses; 2, Boulder Creek Granodiorite (white bar, northern part of batholith, average of 15 analyses; black bar, rest of batholith, average of 16 analyses); 3, inclusions in Boulder Creek Granodiorite, average of three from the M corner and closer to the F corner of the diagram than do other major rock types, indicating less MgO and more FeO than in the Boulder Creek Granodiorite or Twin Spruce Quartz Monzonite. Inclu- sions, however, plot closer to the quartz monzonite trend with one inclusion plotting on the quartz mon- zonite trend (see fig. 27). The trace elements in the inclusions are more nearly allied to hornblende diorite and the Twin Spruce Quartz Monzonite (fig. 18) than to the Boulder Creek Granodiorite. The mafic inclusions are richer in cerium, copper, lanthanum, nickel, niobium, neodymium, and zirconium than are granodiorite rocks. CHEMICAL TRENDS IN GABBRO, PYROXENITE, AND HORNBLENDE DIORITE The composition of gabbro (sample 336, table 12) is similar to that of hornblende diorite (samples 351, 343) and probably reflects a common origin for the two. analyses excluding the lamprophyres; 4, mafic rocks, average of eight analyses; 5, Twin Spruce Quartz Monzonite, average of 13 analyses; 6, biotite gneiss, average of 27 analyses. Number beside bar indicates length bar should have been. Biotitic hornblende diorite (sample 352) is an altered hornblende diorite; potassium apparently was in- troduced at the time of alteration. Hornblende pyrox- enite and the pyroxene-bearing hornblendite (sample 338, table 7; and samples 348, 349, and 353, table 12) are chemically similar and reflect degrees of alteration indicated by the amount of hornblende present. Except for copper, cobalt, chromium, nickel, and scandium, the trace elements in gabbro, pyroxenite, and diorite are very similar to those in the Boulder Creek Granodiorite and differ greatly from the mafic inclusions in the granodiorite (fig. 18). Chromium and nickel are especially abundant in these mafic rocks while all are devoid of niobium and neodymium. CHEMICAL AND MINERALOGICAL TRENDS IN THE TWIN SPRUCE QUARTZ MONZONITE In the Twin Spruce Quartz Monzonite, MgO, FeO, SiOz, and Na20 generally increase as K20 and A1203 decrease. Most oxide relationships are graphically CHEMICAL EQUILIBRIUM IN THE BOULDER CREEK GRANODIORITE 51 shown in: (1) a K20-NaZO-Ca0 diagram where most quartz monzonite samples plot on the K20 side of the Boulder Creek Granodiorite samples and NaZO in quartz monzonite samples is more variable than in granodiorite samples (fig. 25); (2) a Q-Ab+An-Or diagram where quartz monzonite samples plot in the same quartz range as Boulder Creek Granodiorite samples (figs. 22, 26); and (3) an AFM diagram where as iron decreases MgO also decreases forming an order- ly trend toward the N a20+K20 corner of the diagram (fig. 27). Chemical trends are difficult to define in the quartz monzonite because neither SiO2 nor CaO appear to have controlled oxide distribution. In a ternary plot of KzO-NazO-CaO (fig. 25), NazO was more important in the distribution of other oxides than it was in the Boulder Creek Granodiorite. The general trend in- dicates that as NaZO increases, CaO also increases, and points are widely scattered on the K20 side of the diagram and to the left of those for Boulder Creek Granodiorite. In the Q-Ab+An—Or ternary diagram (fig. 26), Twin Spruce Quartz Monzonite points are scattered but do tend top cluster around 25-40 percent for normative quartz and are centered between the normative or- thoclase and plagioclase fields. Normative values agree quite well with modal values (fig. 14) for the same areas. On the AFM diagram (fig. 27), all quartz monzonite samples plot close to a curved trend line that is parallel to that of the Boulder Creek Granodiorite in figure 23, especially the trend line of samples from the Boulder and Gold Hill quadrangles in the northern part of the batholith. The quartz mon- zonite samples, however, plot closer to the FeO+Fe203+MnO side, reflecting the low MgO con- tent of quartz monzonite. Plagioclase having an anorthite content averaging 21—22 percent is the only major mineral in quartz mon- zonite that plots in a trend that is characteristic of a differentiated intrusion. Plagioclase generally in- creases as CaO increases (fig. 28). In Twin Spruce Quartz Monzonite, minor elements, especially barium, cerium, lanthanum, strontium, and zirconium, are surprisingly abundant. In addition, quartz monzonite lenses in schist and gneiss also ap- pear to have high amounts of chromium, yttrium, and nickel (table 13). Analyses indicate that quartz mon- zonite is poorer in the trace elements beryllium, cobalt, chromium, and strontium than the Boulder Creek Granodiorite, but quartz monzonite is richer in barium, lanthanum, lead, and zirconium. Quartz monzonite and the mafic inclusions in granodiorite have similar amounts of trace elements (fig. 18), but quartz mon- zonite contains more copper, vanadium, and stron- tium, and, to a lesser extent, more chromium. Lead does not occur in the mafic inclusions but does in quartz monzonite. CHEMICAL EQUILIBRIUM IN THE BOULDER CREEK GRANODIORITE On a gross scale the major minerals hornblende, biotite, potassium feldspar, and perhaps plagioclase are in imperfect chemical equilibrium with one another, as indicated by similar mineral compositions in samples throughout the batholith (see mineral descriptions in the section on “Mineralogy, petrology, and chemistry of minerals in the batholith”). On a microscale, however, inequilibrium apparently exists locally between most major minerals, because some plagioclase is normally zoned, myrmekite appears be- tween plagioclase and potassium feldspar crystals, and hornblende has bleached contacts and is corroded and replaced by biotite and iron oxides. Where altered, biotite contains irregular crystals of allanite that com- monly are rimmed by epidote; also, chlorite, sphene, and tiny red-brown blebs (probably hematite) occur along cleavage and grain boundaries. Hornblende, biotite, allanite, and plagioclase have been locally replaced by some epidote. Muscovite forms rims on magnetite, occurs in veins, or is associated with sericite in replacing plagioclase. Sparse muscovite oc- curs in hornblende-bearing granodiorite, even where sheared or foliated and considerably altered; under the same circumstances, biotite-bearing granodiorite may contain substantial muscovite. As suggested by Kretz (1959, p. 374), primary muscovite does not occur with hornblende; the only muscovite present occurs as an alteration mineral in biotite or plagioclase, and in quartz. In the recrystallized border zones of the batholith muscovite in non—hornblende-bearing granodiorite has cross-cutting characteristics of a primary mineral. Most indications of inequilibrium found between minerals, however, are believed to be related to retrograde and, locally, later hydrothermal metamorphism. Gable and Smith (1975) determined manganese, iron, and magnesium contents of hornblende and biotite while making a study of hornblende coexisting with biotite in a part of the Boulder Creek batholith. The amount of iron in both biotite and hornblende was nearly identical in the batholith and mafic inclusion samples, as shown in table 14. Manganese in both minerals, expressed as Mn/Fe”+Mg+Mn+Ti, is in equilibrium as shown in figure 29. Magnesium in biotite and hornblende has a straight-line relationship to ferric iron; as magnesium increases, ferric iron decreases. Alkali feldspar from the same samples also 52 | | 4 _ ‘ — ‘ m o ‘ 3‘ m <( 92 e O ‘D O u' 2 ~ 0 . o m .0 .90. 0038‘:08°80 o O ' O 0 o 0 I I I O I | T ; North part of batholith 6 H A Boulder trend 9 0 Gold HI|| trend A O (U 0 U 4 Tungsten-Eldorado — Springs trend 0 South part of batholith 2 I I I . O 0) LL 7 I~ I I _ 6 a b O _ 5 _ 8 _ O 4 m . o ‘ O L N 8 C é“ 3_ 9.0.».010” 0°8zg‘g). o T 2 g a 1 g L o I I 2 T I A O 07 ON 2 ._ 1 — A I— ‘o .5 0‘. o p 7 oo .0... 0°? 0 o o , o . o. o . o 8 300 . | I I 55 60 65 7O 75 Si02 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO 20 I ‘I 18— — A ‘ 0 $0 of". 09° 7 _ 0 A — 16— :3 ‘ 0.8 00.8%.00 _ 14 I A I 0 0| 0 5 I I I 00 ° 8on o 4— 0 o 0 ° — o ’ 0 o 0 ‘ 0 . 3- 0 at 0 — ‘o u . o ‘ o 2— 0 0A _ O 1 I I P I E I I I I o o O 4—‘ o _ ‘ 2 9...'0 A A0 Q _ ‘0 8° °o° 28° _ 2 00 000. 0 0 o O 0 I I | I I | | | 4— I O A '9 . o o” o 2 o ‘0 30 _ . _ .flggo o . 8 o. A ‘ O 0.0 O O 0 I I I I 50 55 60 65 70 75 Sio2 FIGURE 19 (above and right).—Variation diagrams of common oxides plotted against SiO2 for Boulder Creek Granodiorite (in weight percent). has a range in composition of Ab, An, and Or that is very similar (see table 22). Ab, An, and Or contents for alkali feldspar from the Twin Spruce Quartz Mon- zonite, on the other hand, are quite variable (see table 24). Judged by the limited data available (see tables 25 and 26), sphene and allanite do not vary noticeably in composition in the Boulder Creek Granodiorite but do vary between it and associated rock types. Plagioclase is the single mineral, according to our data, that changes in composition zonally across the batholith (fig. 60) from oligoclase in the central part of the batholith to andesine along its contacts with metasedimentary rocks to labradorite in plutons of granodiorite in the metasedimentary rocks west of the batholith. ASSIMILATION AND DIFFERENTIATION IN THE BOULDER CREEK GRANODIORITE Geochemical data, as presented, indicates that dif- ferentiation and not large-scale assimilation of country rock was responsible for producing the Boulder Creek ASSIMILATION AND DIFFERENTIATION 53 10 1 90 0 fl) LL ‘ A 2 x z o o E _‘ A E o I— 5 _ _ . O A o °x o o O o 4 — o O — n O 0 o o o o o o 0 o 0 Q. 3 — o o — 0 o O o EXPLANATION 2 — AWard _ OGold Hill 0 Boulder O o 0 Tungsten <> Eldorado Springs >< Satellitic plutons 1 l i 50 60 70 80 SiOZ Granodiorite. Despite variations within the granodiorite, apparent even within a single outcrop, definite chemical trends occur, indicating considerable orderliness in the distribution of the major oxides within the batholithic rocks. In an attempt to determine whether assimilation or contamination by country rock played a major role in the makeup of the batholith, samples of metasedimen- tary rock west of the batholith, and granodiorite at the contact, within the batholith, and across the batholith were collected and chemically analyzed. A summation of these data is given in table 15. The biotite- sillimanite gneiss and schist samples (col. 1, table 15), typical of the gneiss and schist west of the batholith, were taken at some distance from the batholith. The granodiorite samples listed in column 2 were taken from 100 to 1,000 m from the contact. Columns 3 and 4 are averaged analyses for granodiorite samples grouped into biotite—bearing and biotite—hornblende— bearing granodiorite from the central part of the batholith. Columns 5 through 7 are averaged granodiorite samples that are grouped to facilitate comparison of compositional variations within the batholith. From the data in table 15 it would seem that the role assimilation played in the generation of Boulder Creek Granodiorite in the batholith is mainly confined to local border phases. Sillimanite-biotite gneiss, the country rock to the west of the batholith, is typically impoverished in both CaO and Na20 with respect to rocks of the batholith. Both oxides occur in amounts of less than 1 percent in the gneiss and schist country rock and contrast sharply with amounts of these ox- ides in granodiorite from the contact and the batholith proper (table 15). Also, the contact zone of the batholith has less K20 than the main part of the batholith or the average sillimanite-biotite gneiss country rock. Whereas both FeO and MgO are higher, in the contact zone than in the rest of the batholith, only FeO is considerably higher in comparison with the rest of the batholith. In the satellitic plutons on the west (col. 7, table 15) FeO is high as in the contact zone, but MgO is low. A transfer of iron to the batholith from the contact rocks cannot be ruled out, but the data in figure 6 suggest that the high amounts of iron may be due in large part to an early, more mafic magma. Granodiorite from the contact zone along the west side of the batholith in the Tungsten quadrangle (col. 2, table 15) is quite different from averaged granodiorite samples from the Tungsten and Eldorado Springs quadrangles in the south-central part of the batholith (col. 5) and the Boulder quadrangle samples from the north-central part of the batholith (col. 6b). This lack of large-scale assimilation may be ex- plained if, as suggested by Vance (1961), crystalliza- tion of a granite pluton begins from the border against 54 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO 4 I 0’ O 0 ° 0 part of batholith . o O O Zé“ 3 L— TUNGSTEN _ ‘ o o ELDORADO SPRINGS ’ South pan of batholith 2 I I 2 3 4 5 6 C30 1.0 I 1.0 o O O O o . 0.8 _ o . / ~ 0.8 _ North part of batholuth / 0 /V o / ° ° / O O o. . V0 0 . '/ ° 0.6 — /. O — 0.6 — o/ATungsten-Eldorado Springs trend 0 . N 0 0 9 o / 0 Cl? 0 . I— o/ o i“ 0 ° 0 o o o o 0 . 0 o 0.4 — o o — 0.4 / o / . o 0 o o 3 o EXPLANATION ’ o A Ward 0 0.2 — 0 Gold Hill — 0.2 — 0 ° South part of batholith 0 Boulder . . Tungsten 1 88 0 Eldorado Springs 0 o o | 1 0 1 2 4 6 8 2 4 5 CaO FIGURE 20,—Variation diagrams of CaO plotted against other oxides CaO ASSIMILATION AND DIFFERENTIATION 4 l l | O // ' 0 South part of bathollth //. o . , 0 . 2' o /. Tungsten-Eldorado Springs trend y/ ‘0 ./ ’ o O /o ,< o c» 2 - o //{ Boulder _ 2 ”V o/ trend 0 o / o ’ / // Gold Hill trend>/°°/ / // 0 }/ o / //( o /// / /4’ //// //// ° North part of batholith / o l l 0 2 4 6 CaO 0.40 — A — A 0.30 — *— A 0.20 — ~ 0 o o 0 0 o o. / o o ’6 / o 0.10 — // — - ' oo Boulder Gold Hill trenfiy o o/ . / / o / o / o to . : I l 2 4 G ‘ 8 C30 and fluorine for Boulder Creek Granodiorite (in weight percent). 55 6 South part of batholith Tungsten-Eldorado Springs trendy O a.) U. 2 _ oo 0 ° Nonh pan of batholith o l | 2 4 6 8 CaO 20 South part of batholith 18 —- — Tungsten-Eldorado K Springs trend 7 ‘ m / 0 EL . 0/ /t>/ < o /. A / / Boulder-Gold Hill trend / o / . o o 3’ _ 16 — / ° / 0 /‘ O Q”, 0 o / o /3 /o ‘ 0 North part of batholith 0 O. ’0’ / ° / A o / ' ‘ 14 1 I 2 4 6 C30 56 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO NaZO / EXPLANATION Gold Hill Tungsten Eldorado Springs Boulder 0000 K20 C80 FIGURE 21.—Ternary diagrams of KZO—NaZO—Ca'O chemical variation of Boulder Creek Granodiorite (recalculated to 100 percent). Dashed outline enclosed total area covered by Boulder- Gold Hill area; shaded area represents total area analyses cover for Tungsten and Eldorado Springs; A, trend for Boulder—Gold Hill analyses. B, trend for Tungsten and Eldorado Springs analyses. EXPLANATION Ward Gold Hill Tungsten Eldorado Springs Boulder Inclusion Diorite OXOOOO) Ab+An 3e 0, A FIGURE 22.—Ternary diagrams of chemical variation of Boulder Creek Granodiorite expressed in terms of normative Q—Ab+An—-Or (recalculated to 100 percent). cooler country rock that tends to seal in released tween country rock and the batholith magma. In the volatiles. Accordingly, other elements will be sealed in Boulder Creek batholith, there may have been some and out preventing an interchange of elements be- movement of oxides into the country rock from the ASSIMILATION AN D, DIFFERENTIATION 57 batholith because migmatite and pegmatite are more prevalent near the batholith contact and appear to be related to the Boulder Creek Granodiorite, indicating that the magma, at least in its later stages, was prob- ably saturated in H20 that partly escaped into the country rock. Except for water, mobilization and recrystallization in the Boulder Creek Granodiorite along the contact may be only slightly related to chemical exchanges such as iron between the batholith and country rock. Assimilation of quartz from the quartzite unit (pl. 2) in the southeastern part of the batholith is possible and was likely caused by cataclasis and recrystallization due to proximity to the large Idaho Springs—Ralston shear zone. This assimila- tion of quartz by the granodiorite is related to retrograde metamorphism rather than to processes in the batholith itself. Differentiation trends in figures 19, 20, 21, and 23 for the Boulder Creek Granodiorite, based on major- oxide chemistry, are typical for a calc-alkaline series and suggest that the analyzed rocks are comagmatic. Mineralogical data, especially for biotite and horn- blende, in the section on “Mineralogy, petrology, and chemistry of minerals in the batholith,” support this FeO+Fe203+ MnO (F) assumption. Fractionation trends in the Boulder Creek Granodiorite, expressed by fractionation curves (Tut- tle and Bowen, 1958) and phase relationships (Winkler and others, 1975) of crystallizing granitic and granodioritic melts in the system SiOz-NaAlSiaos- KAlSiaos-CaAIZSiZOB-HZO are analyzed below. Both fractionation trends and phase relationships are impor- tant in the interpretation of the origin of the Boulder Creek Granodiorite. Comparisons of Boulder Creek Granodiorite with Tuttle and Bowen’s (1958) fractionation curves that are based on a rock containing 80 percent or more Ab- Or-Q (albite-orthoclase-quartz) are risky, especially because Boulder Creek samples have a fairly large An content and Ab—Or—Q totals less than 80 percent. However, representative Boulder Creek samples from the interior of the batholith concentrate in Bowen’s (1937) thermal valley in the area represented by the lower phase boundary (fig. 30A). Here the two feldspars, plagioclase and potassium feldspar, are dominant. but because of the high- An content in plagioclase, plots occur predominantly in the plagioclase field rather than in the orthoclase field of granite. Analyzed samples from the Ward quadrangle and from the contact areas of the Tungsten, Boulder, A / Boulder-Gold Hill envelope 0 Boulder-Gold Hill trend, north part of batholith Tungsten-Eldorado Springs trend, south part of batholith (A) EXPLANATION Eldorado Springs Tungsten Boulder Inclusions 0 Gold Hill A Ward 0 Hornblende diorite O Hornblendite A Pyroxenite * Gabbro X090 (M) Nazo+KzO MgO FIGURE 23.—Mole precent variation in an AFM diagram for Boulder Creek Granodiorite and the more mafic rocks associated with the granodiorite. 58 PLAGIOCLASE POTASSIUM FELDSPAR BIOTITE FIGURE 24.—CaO content (in weight percent) plotted against weight percent of rock-forming minerals (weight percent calculated from 30 20 60 50 30 20 3O 20 10 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO CaO modal percent) in the Boulder Creek Granodiorite. l I I 3° ' I' I I o o o o o o 20 — o —l . o o l'i . z o ,: . o 9 o In 0 _ 1o _ . o . o O o 0 Biotite—hornblende granodiorite . o I ¢ ¢ l - 0 0 I I | . T _ 40_ o 9 o o . o o o o o _ 30 _ o . . O O Q o o . O o O l o 0 IE 0 . o O E ’ — <(20 — ° ° 0 o O I) o O o o o _ 10 n o o l | 0 l I 30 I I o o . EXPLANATION 0 Gold Hill 0 Boulder o Tungsten _ 820 _ o Eldorado Springs 2 Lu _l 0 E 0 .0 (I O A I 10 — o . o Coo Biotite granodiorite Biotite—hornblende granodiorite 9 . o I I L I 0 l o ' lo ’. ' I 3 4 5 6 2 3 4 6 ASSIMILATION AND DIFFERENTIATION 59 O 0 o o o o r _ g _ \ / / , .1 o 0 QB /Bou|der Creek _ _ / o \ Granodiorite o O o\ , g / J O CaO K20 FIGURE 25.—Ternary plot of the oxides KZO-Nazo-CaO showing chemical variation for Twin Spruce Quartz Monzonite (open circle). Dashed outline encloses field occupied by Boulder Creek Granodiorite samples. and Gold Hill quadrangles, from within the batholith. do not fall in the thermal valley, but most do define dif- ferentiation trends (figs. 19 and 20). That the older con- tact samples fall on the Ab side, or plagioclase side, of figure 30A, and outside the thermal valley, is to be ex- pected in samples that contain less K20 than CaO. Contact rocks (table 14) are in this category, and, as in- dicated by Chayes (1952, p. 243), “crystallization of a liquid whose initial composition lies in the diagram [Tuttle and Bowen’s equilibrium diagram] generates a liquid residue which approaches and finally enters the thermal valley; and unless heat is added, the liquid cannot escape the valley, once it has entered. The com- position of adequate samples of such a crystallizing mass would necessarily fall either in the valley or out- side it on the side nearest the initial composition.” EX PLANATION O Nederland O Tungsten 0 Eldorado Springs Or Ab+An 50 FIGURE 26.—Ternary plot of normative Q-Ab+An—Or showing chemical variation for Twin Spruce Quartz Monzonite (recalculated to 100 percent). (F) ’FeO, Fe203+ MnO EXPLANATION 0 Eldorado Springs 9 Tungsten I Nederland 0 Inclusion (A) / (M) NazO+K20 MgO FIGURE 27.—AFM diagram showing molar variation for Twin Spruce Quartz Monzonite (in weight percent). Dashed lines are trends for Boulder Creek Granodiorite from figure 23; trend A represents the southern part of the batholith, trend B represents the north- ern part of the batholith. New research on low-temperature granitic melts has been carried out in the system SiOz-NaAISiSOS- KAlSiaOa-CaAlzsiZOB-HzO (Winkler and others, 1975; Winkler, 1976). Winkler, Boese, and Marcopoulos PLAGIOCLASE ) I o 2.0 3.0 4.0 CaO FIGURE 28.—Sample variation of plagioclase (calculated in weight percent from the mode) in relation to CaO (weight percent) in Twin Spruce Quartz Monzonite. Straight line is statistical trend of data. 60 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE 14.—Total iron expressed as FeO (in percent) in biotite and hornblende, Boulder Creek batholith area, Front Range, Colo. Boulder Creek Granodiorite Mafia inclusions Hornblende diorite Sample No. ————— 41 48 50 385 386 352 Hornblende ----- 17.3 17.0 17.1 17.0 16.8 14.6 Biotite—--—-—-- 17.0 17.1 17.2 17.6 16.8 15.7 (1975) have done considerable research on phase rela- tions in the system Q-Ab-Or-An-HZO, especially on low-temperature granitic melts, and they believe from their data that two fundamentally different processes of granitic magma generation—magmatic or anatec— tic—can be recognized, although Winkler (1976) now believes all granitic-granodiorite rocks were derived by anatexis. Tuttle and Bowen’s research (1958) ignored the An content of feldspar. Winkler, Boese, and Mar- copoulos (1975), took into consideration the An con- 0.18 I r I , 0.16 —— 0.14 — 0.12 — Mn/Fe+2+Mg+Mn+Ti IN HORNBLENDE (ATOMS) 0.08 — 0.06 I I i l i 0.02 0.04 0.06 0.08 Mn/Fe+2+Mg+Mn+Ti IN BIOTITE (ATOMS) 0.10 FIGURE 29.—Distribution of manganese in biotite and hornblende in Boulder Creek Granodiorite and hornblende diorite. Square, Boulder Creek Granodiorite; solid triangle, hornblende diorite from Gable and Smith (1975, table 9); square with dot, mafic inclu- sion (this report); straight line is statistical trend of data (table 14). tent of the feldspar, and, by making certain assump- tions, presented a Q-Ab-Or diagram (fig. BOB) in which the An content in weight percent is shown as a radial projection onto the Q-Ab-Or surface. Nine samples of Boulder Creek Granodiorite, Where data are complete, have been plotted on the 500 MPa (mega pascals) phase diagram presented by Winkler, (1976) (fig. 303). In application of the system to natural rocks, Winkler, Boese, and Marcopoulos (1975), and Winkler (1976) ignored the potassium in biotite and the calcium in hornblende because, ac- cording to their experiments, it did not affect the overall conclusions concerning the crystallization or melting history of plagioclase, alkali feldspar, or quartz. The data, as plotted in figure SOB, are from modes, An was determined on plagioclase in thin sec- tion, and the alkali-feldspar minerals were chemically analyzed. Normative data derived from whole-rock chemical analyses indicate that plagioclase seldom contains more than a small amount of potassium so that points as plotted would only shift slightly to the Or side of the diagram, and the An content would decrease only slightly. In applying the 500 MPa water pressure Q-Ab-Or diagram to Boulder Creek rocks it must be remembered that Winkler (1976) found that the compositions determined at 500 MPa water pressure were also a good approximation of conditions at somewhat lower (300—400 MPa) and higher (700 MPa) pressures. Temperatures at 300—400 MPa pressure were about 5 °—10°C higher and the An com- position was 1 or 2 percent lower; the opposite was true at 700 MPa pressure. Boulder Creek Granodiorite plots in the plagioclase-quartz field of the Q-Ab-Or diagram (fig. 303) and pierces the cotectic surface quartz+plagioclase+liquid+vapor with a somewhat higher An content than that shown on the isotherms. For larger departures from the cotectic plane, as in Boulder Creek rocks, there is a marked increase in temperature. Most Boulder Creek plots lie between 660° and 685°C (as projected onto the isotherms) where the An on the isotherms is between 4 and 6 per- cent. However, as all but one Boulder Creek sample has more than 10 percent An above the An indicated on the nearest isotherm, nearly all crystallized at higher temperatures than the 660 °—685 °C indicated. From the experiments of Winkler, Boese, and Mar- copoulos (1975, fig. 11, p. 264) the temperature for crystallization of Boulder Creek plagioclase appears to be in the range of or above 750°C at 500 MPa water pressure. This temperature suggests that plagioclase in the Boulder Creek batholith is of magmatic origin and it tends to support the data in figure 30A wherein most samples lie in Bowen’s thermal valley. From figure 303, the stages of crystallization for plagioclase, alkali feldspar, and quartz appear to be: 61 ASSIMILATION AND DIFFERENTIATION N w R 3 S S S q 3 83328 vmmmumzw 5M3 odoa m.oo._H o.oo.n 5mm 0.03” m.mm m.mm m.ma IIIHmuom. wd m6 0.0 Nd m6 m5 m6 «.0 ad ....... momm m4 0.0 To m5 o.o To c6 04 04 IIIIIII No: fio ma To 90 To ma To HA HA ....... +o~m fie fie do H6 H6 fio 59 H5 fie ........ on: fin .2 m.~ H3 .2 a.~ 06 fig H... ........ cum o.m «6 m.m N6 N6 «6 o.m o.m w.o I llllll onz N.m Né wé H...” Né mé m.m o.m To llllllll omo 9N m4 «4 o.~ Wm fim 9H 9N 9N IIIIIIII ow: m6 fm od Wm w.~ mg m.N H3 90 uuuuuuuu omm o.m m4 mA 04 “4 m4 #4 N.N ad .. lllll monm #2 «.3 93 0.2 $3 N4: 92 5.3 $3 IIIIII MONE ode w.mo 0.8 «.3 9mm Héo N.$ 93 o.$ 1111111 Noam 3:030:me 3303955 3303053 3303985 mufluofiwoamyw 33038me 3303285 mfiuoawoamum umEom new mucusaa mawnmuvmsw mawnmuwmav mawamuvmsv mamamfiumsv mwaancnon wufiuofiy 3.30.3 mmflmaw wngo owuHHkuMm chaaom HE”: vaou mwcflumm owmuovam amumwusH ImufluOHn mwmuwfiw nomufioo muHuOHQ 3v 3 2V 3 wwfioé -mfiamfiaim fiuoz finom fiflofimm n m n q m N H IIIII 95:00 .300 .umsum «28E £10.69:ch $20 swgaom kc m=oEmc§=oo fimmswau 5.2: $32 BESS “Mien ~23 mmmgm SBQSSEQSEQ kc tentaafioolfifi EEC. 62 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO first, plagioclase, then plagioclase+quartz, and then plagioclase+quartz +a1kali feldspar; this is essentially the paragenetic sequence observed in thin section. Fractionation trends based on strontium and rubidium in granodiorite rocks are inconclusive. Frac- tionation as indicated by a decrease in strontium values as normative Or/Ab increases does not exist in the Boulder Creek Granodiorite (table 16, fig. 31), but because strontium is much more mobile than the major mineral-forming elements, this reversal of trend could be expected. Rubidium trends are normal; as nor- mative Or/Ab increases so does rubidium, but this in- crease could also have occurred during alkali exchange in which rubidium accompanied potassium in the feldspar. 7; ’0 4 ° \Bowen' 5 thermal ' valley Ab Qtz+plag+L+V An content in wt pct Ab ORIGIN OF THE BOULDER CREEK GRANODIORITE AND THE TWIN SPRUCE QUARTZ MONZONITE Data from the Boulder Creek Granodiorite are con- sistent with the theory of a calc-alkaline magma derivation from the mantle or lower crust, as sug- gested by modeling and experimental studies of Cawthorn and Brown (1976) and Green and Ringwood (1968) for the genesis of calc-alkaline magmas. The Twin Spruce Quartz Monzonite probably is of crustal origin, but the magma was greatly contaminated either by a deep-seated source or by country rock, as suggested by the lack of differentiation trends. The mafic inclusions in the Boulder Creek Granodiorite could perhaps have been refractory material that re— mained after partial fusion of mantle or lower crust and that was reconstituted as it was carried upward as part of the magma, as suggested by Presnall and Bateman (1973, p. 3197) in the Sierra Nevada batholith. Trace elements in the Twin Spruce Quartz Monzonite and in the inclusion are similar. Data sug- gest that the refractory material was injected into the Boulder Creek Granodiorite during the mush stage and before the batholith was completely crystallized. Evidence supporting the above conclusions, especial- ly for the Boulder Creek Granodiorite, is as follows: 1. Analyses from the major part of the batholith (in the Boulder, Eldorado Springs, and Tungsten quadrangles) plot in Bowen’s (1937) low- temperature thermal valley for granites, sug- gesting fractional crystallization in a system FIGURE 30.—Phase relations for Boulder Creek Granodiorite in the system SiO2-NaAlSi,Og-KAlSiSOS-CaAIZSiZOB-H20, where modes and chemical and optical data are available. A, Ternary diagram of normative Q, Ab, and Or in Boulder Creek Granodiorite from the Boulder Creek bathohth and adjacent plutons. Dotted area, position of thermal valley (Bowen. 1937, Chayes, 1952); dashed hnes represent isotherms, in °C, on liquidus in the system albite— orthoclase-quartz at PH O=2, 000 kg/cm2 (Tuttle and Bowen, 1958, p. 55). Open circle, analyzed samples from main part of the bathohth; solid dot, analyzed samples from the bathohth contact, solid square, analyzed samples from plutons in metasedimentary rocks B, lsobaric system, Q- Ab- Or- An-H 20 with excess H2 O-rich vapor at PH 0=5 Kb (500 MPa or megapascals) for low- temperature granitic melts from Winkler (1976). Projection of cotectic line P- -P2 and isotherms, in °C, (showing weight percent A11 where it pierces isotherms), on cotectic surfaces: quartz +plagioclase+liquid+vap0r, plagioclase+alkali feld- spar+liquid+vapor. Figures in parentheses adjacent to sohd dot, calculated weight percent An (this report). Open circle, location of experimentally determined temperature. ORIGIN, BOULDER CREEK GRANODIORITE, TWIN SPRUCE QUARTZ MONZONITE 63 TABLE 16.—Rubidium, strontium, and potassium analyses (in ppm) of Boulder Creek Granodiorite samples, Front Range, Colo. [Rb analyses by flame emission spectrography: Sr analyses by atomicvabsorption spectrography. Analysts: L. P. Greenland, Roosevelt Moore, and M. M. Schnepfe; K values from table 10] Sample No. ------------- a129 132 138 140 148 150 156 162 167 Lab. No. --------------- D173346W D173347W D173348W D173349W D173350W D173351W \D173352w D173353W D173354W Rb --------------------- 170 120 74 95 120 150 120 92 98 Sr --------------------- 300 580 710 670 690 630 620 510 550 K ---------------------- 31,000 22,000 18,000 13, 000 32,000 33,000 27,000 21,000 24,000 K/Rb ——————————————————— 182 183 243 137 267 220 225 228 245 Rb/Sr ------------------ 0.57 0.20 0.10 0.14 0.17 0.24 0.19 0.18 0.18 aFrom pluton in metasedimentary rocks northwest of batholith. Sr IN PPM similar to that used by Tuttle and Bowen (1958), Na,AlSi,O,-KAlSi,O,-Si02-H,O (fig. 30A). In the experimental ternary phase diagram of Winkler (1976) and Winkler, Boese, and Marcopoulos (1975) (fig. 303) CaAIZSiZO8 is also considered in the system, and the sequence in the crystallization history of plagioclase in the Boulder Creek Granodiorite appears to have begun with high temperatures, thus further substantiating frac- tional crystallization. .In their model for the formation of corundum- normative calc-alkaline magmas, Cawthorn and 800 7 l l i l i I o 700 m 4 o o 600 — _ o 500 m — — fi 300 E u. o o 0. fl 0 . — 200 g .n u: I | l l l | | J l 100 0.2 0.4 0.6 0.8 1.0 NORMATIVE Or/Ab FIGURE 31.—Strontium (circle), rubidium (solid dot), and potas- sium feldspar analyses (in ppm) of Boulder Creek Granodiorite samples from the northern part of the batholith; data from table 16. Lines represent median of values as plotted. Brown (1976) showed a trend in the calc-alkaline suite from diopside normative to corundum nor- mative as SiO, increases. Whereas the magmas they used in their model frequently contained almandine-spessartine garnet, garnet of almandine-spessartine composition is known from only one locality in the Boulder Creek Granodiorite, and that is a pegmatite, an associa- tion not unlike that described by them (1976, p. 474). A most interesting relationship described by them can be related to the Boulder Creek Granodiorite as well and that is the indication that the formation and crystallization of corundum- normative calc-alkaline magmas through am- phibole fractionation may be explained by the crystallization of hornblende in a hydrous magma. They interpret the crystallization trend from diopside-normative to corundum-normative rocks as the result of fractionation (crystallization or melting) of hornblende from a diopside-normative basic magma; normative-corundum trends depend in part on the Na/(Na+K) ratio of the magma. Both the Boulder Creek Granodiorite rocks and the Sierra Nevada batholithic rocks (Bateman and others, 1963) became corundum-normative at about 60 percent Si02. . Experimentally determined fractionation trends in an AFM plot for a calc-alkaline province at 2,700—3,600 MPa under dry conditions deter- mined by Green and Ringwood (1968, p. 153) are similar to the one determined in this report for Boulder Creek Granodiorite (fig. 23). In both plots there is no marked iron enrichment relative to magnesium in the more basic compositions. Alter- natively, according to Green and Ringwood, the same fractionation trend may be obtained ex- perimentally at 900-1,000 MPa under wet condi- tions (PHZO NE mwmbgw :2: 0.30:an 02.0530 3: :0. Z EofinfiESuflu «c FEE 9... 323 :5 03330 .4 ”03983. 3: .Z :8 0333 3: ,3 .5 PS»: :0 0332 mafia 0wEEam_ .200 Gage“ “EEK .333 503530 flmmkb kwgaom .wfifi SAfiQOLQES a 0:: 6:23:05 .9.» .935 $0.280 00:03:30 3.2200236 ”RED $030M EEK 8.30.3 Lox Sagox 3:303 0.3 3333.5 uEQEMEBQO 0:3 ~uomEm£D|0H mam—<9 67 MINERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS o.¢m m.o¢ o.m¢ n.wq ¢.wm H.mq n.N¢ N.Nq m.~q N.mm m.~q H.mq mq.m Nm.m mH.¢ om.m mo.m em.m 0H.m mo.m om.m No.m Hq.m mq.m Nm¢.~ N¢m.m wmm.m NMN.M omm.m o~a.~ qmu.~ wNm.m wqo.m qm.m mqo.m mqm.N omo.o muo.o mmo.o qmo.o wmo.o mmo.o mmo.o omo.o Hmo.o II omo.o mHo.o o~m.o mmm.o NHN.o mom.o mam.o NaN.o mwm.o woN.o wnN.o wN.o mmm.o qu.o No.N ww.H mn.H om.H Hw.H qm.H mm.H Hm.H H H< ..... lam Nnmz+ao Hapwm£muuwfi w Hmuuosmuoo wm «NAHU .m .mo .ovwwowmx manage“ Hmumamm ecu ca AHo .m “mo .ov «N «o mamas ma“ so maoum we “anasz BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO 68 .8303 6% £382 .mmm $38338 . w Mum m+m++m+m N A mSHNOHQ .3 mquNOHQ 1» mamfimw "hamdogmnm umamflndm uon amass: .nmqm o3 cm on com 2 on ooa om om own om 03 uuuuuuuuuuuuuuu HN 00m Z com com com Z Z Z Z Z Z Z lllllllllllllll EN 2 z z z z z N N H z N m IIIIIIIIIIIIIII A; 3 z z z A z ON 2 2 cm 2 z uuuuuuuuuuuuuuuu w 0% 8m 8m com com com com com 8m 03 com com uuuuuuuuuuuuuuuu > OS” on Om Om On ON ON 2” ON ON mH ON IIIIIIIIIIIIIII Hm N 3 ma om N cm on 3 om 00 ON on lllllllllllllll um ea 3 z 3 z z z z z z z om uuuuuuuuuuuuuuu pm ooh 8m 03 02 8m 2: SH 03 03 om E E uuuuuuuuuuuuuuu E z z z A ON 3 z z z om 2 cm I IIIIIIIIIIIIII 92 n N z n m m m om m 2 ON m IIIIIIIIIIIIIII o: z 2 0m Z Z Z Z Z Z z Z OM IIIIIIIIIIIIIII NA 2 on em 03 on om om om om om om om IIIIIIIIIIIIIII ma 3 com 03 om com 2: 3 03 oN 3 om S l. uuuuuuuuuuuuu 5 z SN 08 z 8 03 02 SN o3 03 SH 2: ............... 5 03 2: om E E 03 03 03 03 cm 2 on -I- ........... 8 ooo.m oooJ OE ooo.m ooofi. 084 08; 08; 08; com; 2K 804 uuuuuuuuuuuuuuu mm SOHHHHE Hmm muumm dun .mwmbumam owammumohflommm w>fiumufiuam=35mm wmm own 2% qmm Nmm M3 3 cm 3 gm 3 q lllllll m.oz wanfiwm 95v m:0Hm=Hod.m ounwmz muHuofi‘. wuHHOHwofimno xmmuo waHsom wuhnmouafimq mwdmanhuom wwsmfiqooldgo smiufl €ch 633 iaoig ”RED SESQN .323 qu£QEQES 6 ~33 $8.532)» first .mutomfi 3.5353 .Stcwfiouugw ~3ka QEVBN 52.x 8.60.3 .Sk SSEQ 3855 N33 $335. oEp‘Emofiuwmm ~23 NaqumSQIwH mqmfib MINERALOGY, PETROLOGY. AND CHEMISTRY OF MINERALS 69 Minor elements in biotite were determined by semi- quantitative spectrographic analysis and it was found that the trace elements in biotites were fairly consis- tent from one sample to another. Trace amounts of zir- conium are probably due to tiny zircons not completely removed from the samples during separation and purification. TWIN SPRUCE QUARTZ MONZONITE General description. Biotite in the Twin Spruce Quartz Monzonite occurs mostly as an interstitial mineral to plagioclase. microcline, and quartz, and, unlike biotite laths in granodiorite, the laths are generally smaller and quite ragged. Their color is similar to that of biotite in Boulder Creek Granodiorite. Accessory minerals in the Boulder Creek Granodiorite tend to cluster with the biotite and other mafic minerals whereas in the quartz monzonite ac- cessories occur both with biotite or completely separated but in foliation trends with biotite. Ac- cessories associated with biotite in quartz monzonite include apatite, ores, zircon, monazite or xenotime and allanite. Biotite alters somewhat to chlorite, contains many opaque blebs, and enters into a reaction forming allanite. Biotite in quartz monzonite varies in abun- dance between outcrops but is rarely more than 10 per- cent of the rock and averages close to 6 percent. Chemistry. Nine biotite samples separated from quartz monzonite were chemically analyzed (table 19) by the same methods used for the biotite from granodiorite. Quartz monzonite biotites are richer in A1203, TiOz, and FeO but contain less MgO and SiO2 than Boulder Creek Granodiorite biotites (fig. 34; TiO2 not shown). CaO, K20, and N a20 are nearly constant in biotites from both rock types. Biotites from Twin Spruce Quartz Monzonite also appear to be much more uniform in major-element composition than the host- rock composition would indicate; this uniformity was also true for biotites in the Boulder Creek Granodiorite. The minor elements cerium, neodymium, and zinc, though occurring in quartz monzonite biotites, are not found in the granodiorite biotites. Lead and tin are reported in most quartz monzonite biotites and rarely in granodiorite biotites; chromium, however, is con- sistently higher in Boulder Creek Granodiorite biotite than in biotite in quartz monzonite. X-ray of the basal (005) interplanar spacing of biotite from quartz monzonite indicates an increase in fluorine as do“ spacings decrease that is similar to the findings of Dodge, Smith, and Mays (1969), and Lee and Van Loenen (1971). In figure 35 biotite in quartz monzonite occurs in two trends that are subparallel. Both trends definitely show an increase in fluorine as d005 spacings increase. Why the quartz monzonite biotites plot in two distinct trends is not obvious. The only consistent variation is in the number of potassium atoms in biotite (table 19); those biotite samples having the higher potassium values plot in a lower range of do“ spacings, but this may not be a complete explanation. Biotite from the younger Silver Plume Quartz Mon- zonite was plotted and the d006 spacings also formed a single straight line indicating again that the do“ spacings increase as fluorine increases. Biotite in the Boulder Creek Granodiorite is plotted on the same figure but it shows no such relationship; points cluster between 0.20140 and 0.20180 nm (nanometers) for 0.5 to 1.0 weight percent fluorine. MAFIC INCLUSIONS AND LAMPROPHYRE DIKES IN THE BOULDER CREEK GRANODIORITE General description Thin sections show that biotite and hornblende do not tend to cluster in most inclu- sions as they do in the Boulder Creek Granodiorite. Biotite replaces both hornblende and pyroxene and it can be generally assumed that even though some biotite may be primary, the greater the percentage of biotite the greater the alteration of the inclusion. Some biotite is reddish and some is greenish brown in color, is frayed and eroded, and, in general, its habit and form of alteration is similar to that of biotite in the Boulder Creek Granodiorite. Chemistry. The distribution of the major oxides in biotite from the syenodiorite or lamprophyre (sample 388, table 18) is not much different from that in biotite from mafic inclusions; however, Ti02, P205, and fluo- rine do not follow this distribution. Both P205 and fluorine amounts are higher in the lamprophyre; TiO2 is lower. Other oxides vary as much between the various mafic inclusions as between rock types. Biotite from inclusions tends to contain more nickel, zinc, and lithium than granodiorite biotite. X-ray determination of the d005 spacing (fig. 35) in- dicates that biotites from inclusions plot near biotites from the Boulder Creek Granodiorite and Twin Spruce Quartz Monzonite whereas the biotite from a lam- prophyre is isolated owing to its high fluorine content. PETROGENESIS Figure 36 shows that biotites from the Boulder Creek Granodiorite, the Twin Spruce Quartz Mon- zonite, and the inclusions all belong to the assemblage magnetite-potassium feldspar-biotite and plot along a 70 BOULDERCREEKBATHOLHELFRONTRANGECOLORADO TABLE 19.—Chemical and spectrographic analyses and mineral formula for biotite from Twin Spruce Quartz Monzonite, Front Range, Colo. [Standard rock wet chemical analyses by V. C. Smith; spectrographic analyses by L. A. Bradley: (--). not found; N .d.. not determined] Sample No. ------------------- 232 235 85 316 380 381 382 383 384 Lab No. ---------------------- D102154 D102153 D102513 D102514 D102155 D102157 D102156 D102152 D102158 Chemical analyses, in weight percent SiO2 ------------------------- 35.79 35.74 36.90 36.99 36.62 35.56 35.50 35.86 36.69 A1203 ------------------------ 18.47 16.52 16.52 16.31 16.63 16.19 17.16 18.35 17.19 Fe203 ———————————————————————— 2.63 2.70 2.81 2.57 4.32 2.85 2.58 2.36 2.38 FeO —————————————————————————— 17.44 18.10 17.10 15.82 15.51 18.94 17.89 17.91 17.26 M30 -------------------------- 8.36 10.06 10.17 11.42 9.99 9.03 9.27 8.30 9.63 CaO -------------------------- 0.00 0.61 0.73 0.38 0.00 0.00 0.00 0.00 0.19 N320 ------------------------- 0.15 0.24 0.32 0.24 0.28 0.22 0.19 0.19 0.27 K20 -------------------------- 9.41 8.52 8.51 9.36 9.28 8.85 9.44 9.10 9.23 H20+ ------------------------- 2.84 3.08 3.75 3.13 3.21 3.09 2.89 2.86 2.89 H20_ ------------------------- 0.02 0.20 0.09 0.07 0.13 0.15 0.05 0.08 0.11 T102 ------------------------- 3.22 2.50 2.10 2.41 2.76 3.50 4.15 3.78 2.88 P205 ------------------------- 0.01 0.04 0.02 0.04 0.04 0.03 0.03 (a) (a) Mno -------------------------- 0.32 0.16 0.33 0.38 0.16 0.39 0.22 0.08 0.38 C1 --------------------------- 0.07 0.19 0.05 0.08 0.18 0.14 0.10 0.11 n.d. F 0.73 1.41 0.47 0.83 1.11 1.23 0.47 0.88 1.12 Subtotal -------------- 99.96 100.07 99.87 100.03 100.22 100.17 99.93 99.36 100.22 Less 0 ---------------------- — .33 .63 .21 .37 .51 .55 .22 .39 .47 Total ----------------- 99.63 99.44 99.66 99.66 99.71 99.62 99.71 99.47 99.75 Powder density ---------------- n.d. n.d. 3.05 3.04 n.d. n.d. n.d. n.d. n.d. Number of atoms on the basis of 24 (O, OH, F, C1) in the general formula X2Y628(0’0H’F’C1)24 2 Si ------------- 5.476 5.496 5.574 5.607 5.561 5.486 5.463 5.493 5.612 Octahedral Al ------------- 2.524 2.504 2.426 2.393 2.439 2.514 2.537 2.507 2.388 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 X Al ------------- 0.806 0.490 0.515 0.520 0.538 0.429 0.576 0.806 0.693 Tetrahedral Ti ------------- 0.371 0.289 0.239 0.275 0.275 0.406 0.479 0.435 0.330 Fe+3 ----------- 0.303 0.312 0.319 0.293 0.494 0.331 0.299 0.272 0.275 Fe+2 ----------- 2.231 2.328 2.160 2.005 1.970 2.443 2.302 2.294 2.200 Mn ------------- 0.042 0.021 0.042 0.049 0.021 0.051 0.029 0.010 0.046 Mg ------------- 2.020 2.306 2.290 2.580 2.261 2.076 2.127 1.895 2.200 5.77 5.75 5.57 5.72 5.60 5.74 5.81 5.71 5.75 g Ca ------------- —- 0.101 0.118 0.062 —— -- -- —— 0.028 Na ------------- 0.044 0.072 0.094 0.071 0.082 0.066 0.057 0.056 0.073 K —————————————— 1.836 1.671 1.640 1.810 1.798 1.741 1.853 1.778 1.797 1.88 1.84 1.85 1.94 1.88 1.81 1.91 1.83 1.89 F —————————————— 0.353 0.686 0.225 0.398 0.533 0.600 0.229 0.426 0.541 C1 ————————————— 0.018 0.049 0.013 0.021 0.046 0.037 0.026 0.029 -- 0H ------------- 2.878 2.954 3.778 3.165 3.120 3.025 2.916 2.841 2.824 3.25 3.69 4.02 3.58 3.70 3.66 3.17 3.30 3.36 100(Fe+/Fe++Mg) -------------- 55.60 53.40 52.00 47.00 52.10 57.20 55.00 57.50 52.90 MINERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS 71 TABLE 19.——Chemical and spectrographic analyses and mineral formula for biotite from Twin Spruce Quartz Monzonite, Front Range, Colo.— Continued Sample No. ——————————————————— 232 235 85 376 380 381 382 383 384 Lab No. —————————————————————— D102154 D102153 D102513 D102514 D102155 D102157 D102156 D102152 D102158 Spectrographic analyses, in parts per million 33 ___________________________ 700 700 700 1,000 700 2,000 1,000 1.000 700 cc —- 300 1 —- -- -- -- -- 200 Co ___________________________ so so 100 100 50 50 70 70 50 Cr ___________________________ 150 50 10 30 50 50 500 100 10 Cu ___________________________ 10 150 50 700 200 20 10 10 30 Ga ___________________________ 100 100 70 100 100 50 50 100 100 La --------------------------- 30 200 70 —- 70 ~— —- 30 200 Li --------------------------- —— —— 700 300 —- —— —— —- —— Mo ——————————————————————————— 20 10 10 7 5 5 5 7 5 Nb ___________________________ 20 20 20 -- 20 10 10 20 10 Nd ___________________________ 70 200 70 —- 150 —- —— 100 150 Ni ___________________________ 50 50 50 100 30 10 100 50 20 Pb ___________________________ 20 50 3o -- 20 10 10 -- 20 5c ___________________________ 7o 50 15 30 50 30 50 50 50 Sn ___________________________ 20 50 -- —— 50 20 20 20 20 Sr ___________________________ 15 7o 70 30 15 20 10 20 15 100 300 300 300 300 300 300 200 100 200 20 15 —— —— —— 2o 20 30 Yb ——————————————————————————— 7 2 —— —- 2 5 5 5 5 m ___________________________ 13m quo 5m 7w Low 5% mo 5% 5M Zr ___________________________ 200 50 300 500 50 50 70 100 200 312205 included in A1203. trend paralleling the compositions of “buffered” biotites in the ternary system KFeflAlSi3 O12 (H4)- KFe:,-*2AISi3Ol.,(OH)2 (Wones and Eugster, 1965, p. 1232). This trend suggests that oxygen fugacities in biotite of the Boulder Creek Granodiorite are slightly greater than those of the N i-NiO buffer. One granodiorite sam- ple was not plotted on the ternary diagram; it, too, would have plotted in the concentration of points for granodiorite. In the presence of magnetite acting as a buffer, oxygen fugacities in a crystallizing magma decrease as temperatures decrease and generally as FeTzFeT+Mg ratios increase. Boulder Creek Granodiorite biotites have FeTzFeT+Mg values of 42.5—45.1 (the Mt. Pisgah pluton sample having a ratio of 53.2 is excluded because the granodiorite lies outside the batholith), in- clusions have values of 38.4—46.7, and Twin Spruce Quartz Monzonite from the batholith only, 47 .0—52.1; these values appear consistent for the Boulder Creek Granodiorite and the Twin Spruce Quartz Monzonite because the quartz monzonite was emplaced later in the sequence, after the Boulder Creek Granodiorite, when temperatures would be expected to be somewhat lower. Biotites in the inclusions have FezFe+Mg values that indicate some inclusions are younger and some older than Boulder Creek Granodiorite. These data substantiate the belief stated earlier that some of the inclusions are younger and some older than the granodiorite. HORNBLENDE \ BOULDER CREEK GRANODIORITE General description. The approximate extent of hornblende-bearing granodiorite is outlined in figure 6A. Hornblende is not common in Boulder Creek Granodiorite lenses and plutons that are satellitic to 72 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO 9 8|!11111IF1111111 1°LLLII1VFL11IILTF«I 14I1L1116111111|11”” 1:. c (A) (D 4. _‘ £937 0 O _ w 35 o _ 1||11l 111111111 34 4 47 49 50 4148 386 232 235 85 376380381382 383 384 SAMPLE NUMBERS BIOTITE FROM BOULDER BIOTITE FROM TWIN SPRUCE CREEK GRANODIORITE QUARTZ MONZONITE FIGURE 34.—Compositional variations of K20, MgO, FeO, A1203, and SiO2 in biotites from Boulder Creek Granodiorite and Twin Spruce Quartz Monzonite. Horizontal lines show median separa- tion of each element, except K20, between Boulder Creek Granodiorite and Twin Spruce Quartz Monzonite. Oxides in weight percent. the batholith proper; one exception lies in the southernmost part of the map area (pl. 1). Here the northeast-trending Bald Mountain pluton, if extended northeastward from its outcrop, lies along a trend of hornblende—rich granodiorite which extends into the batholith proper (fig. 6A). Another exception lies north of N ederland in the easternmost part of the Caribou pluton. Hornblende in the batholith proper occurs as disseminated crystals in granodiorite and in clusters containing, besides hornblende, apatite, allanite, biotite, and ores; the occurrence in clusters is more common. About half of the granodiorite samples col- lected were hornblende bearing and contained as much as 23.3 percent hornblende (table 1). In thin section, the hornblende is green or bluish 2°” I 1 l 1 l 1 ‘2018 F Area represented by Boulder _ g ._. _2017 — Creek Granodiorite biotites _ E E .2016 ~— — m v 2015 ~ a 5 2 I M f. ' Twin Spruce Lamprophyrex E .2014 * inclisllbn Quartz Monzonite ‘— g E .2013 k \x Silgflailtgme __ 2 g .2012 —* Monzoniie _ o. 4. U) 2 .2011 -— .E LO 8 —Z- .2010 — _ 1: Twin Spruce Quartz Monzonite .2009 ~ — .2008 1 i 1 I I I ( ( 0.2 0.4 0.6 0.3 1.0 1.2 1.4 1.6 1.8 2.0 FLUORINE IN BIOTITE, 1N WEIGHT PERCENT FIGURE 35.—Fluorine in biotite plotted against d006 spacing of biotite. green and crystals are as much as 1.5 cm in length, but most hornblende is in smaller crystals, some of which are slightly zoned (zoning is principally by color and in- dex difference) and often eroded by other minerals. Magnetite, sphene, calcite, and allanite have replaced hornblende, in some areas extensively. Physical and chemical properties for most of these hornblendes have already been published (Gable and Smith, 1975) and will not be included here except for pertinent chemical data. Chemistry. The hornblendes analyzed are calcic, and Fe+3 \\\\\ <1323047Fe203 Fe+2 M9 FezSiO4- 5102 ~ F9304 FIGURE 36.—Relation of Fe‘a-Fe”-Mg (atomic ratios) between biotites of Boulder Creek Granodiorite and Twin Spruce Quartz Monzonite. Dashed lines represent compositions of buffered bio- tites in ternary system KFeS” AlSi3012H_,KFes‘ZAlSiOHAOHL- KMgaAISiSOMOH)2 depicted byWones and Eugster (1965, fig. 1). Solid circle, Boulder CreekGranodiorite; solid circle with tail, inclusion; x, Twin Spruce Quartz Monzonite. Line through plotted biotites represents composition of buffered biotites. Buffers are: Fe30.-Fe203.Ni-NiO,FeZSi04-Fe30,-SiO,. MINERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS 73 chemical variations among hornblendes in the granodiorite are small, except for Si02, FeO, A120,, and MgO. FeO and A1203, in general, increase as MgO and SiO2 decrease. Table 20 has been reproduced in part from Gable and Smith (1975).1 The same trace elements, except for beryllium occur in both biotite and hornblende in granodiorite rocks. Beryllium, however, occurs only in hornblende. MAFIC INCLUSIONS AND LAMPROPHYRE DIKES IN THE BOULDER CREEK GRANODIORITE General description. Hornblende-rich mafic inclu- sions are particularly abundant in the south-central part of the batholith but are present nearly everywhere in the northern half. The west contact and the Caribou pluton in the Nederland and Ward quadrangles are nearly free of hornblende. Mafic inclusions in the Caribou pluton are biotitic due to alteration and rarely contain hornblende. Hornblende in the lamprophyric rocks is generally poikilitic and has inclusions of potassium feldspar (or- thoclase), apatite, ores, biotite, and allanite. Pyroxene in the lamprophyre is in small subrounded crystals that accompany hornblende or occur as inclusions in hornblende. In the foliated and porphyritic microgranular mafic inclusions, the occurrence of hom- blende is not much different from that in hornblende diorite. In pyroxene-bearing hornblende diorite, however, hornblendes are generally very large and typically poikilitic, containing subrounded pyroxene crystals. Chemistry. The hornblende from the mafic inclusion has a composition similar to hornblendes from the Boulder Creek Granodiorite and hornblende diorite (table 20) except for fluorine, which is a little higher in inclusion hornblendes. Cerium and zirconium found in the hornblende inclusion may be due to small inclu- sions of allanite and zircon crystals within the horn- blende. Hornblendes in the inclusions also contain more chromium, nickel, and strontium than horn- blendes from the granodiorite. HORNBLENDE DIORITE AND HORNBLENDITE Hornblendes from hornblende diorite and hornblend- ite are also calcic. These hornblendes are generally higher in SiO2 than Boulder Creek Granodiorite horn- blendes or inclusion hornblendes. This higher SiO2 con- tent may be due to a small excess amount of SiO2 oc- curring in the hornblende initially and then not being available to form quartz or enter into reactions form- ing other minerals. In hornblendite, high SiO2 is ac- ‘Hornblende from sample 386 (Gable and Smith. 1975. sample T 170-68) was originally included with hornblende of granodiorite but is now believed to be part of a very mafic in- clusion that is gradational into normal Boulder Creek Granodiorite. companied by low A120,, a combination discussed below. Of the minor elements, chromium and nickel are both higher in hornblende from hornblende diorite and hornblendite rocks whereas yttrium is lower. PETROGENESIS Hornblende from granodiorite, inclusions, and horn- blende diorite is chemically similar. Hornblende from lamprophyre and hornblendite contains less A1203 than the more leucocratic rocks; hornblende from horn- blendite carries greater SiO2 and MgO but less FeO+Fe203. In an investigation of aluminum replacement of silicon in the amphibole lattice, Harry (1950) indicated that the higher the temperature of formation, the higher the solid solubility, and at high temperatures aluminum substitutes for silicon and the substitution is controlled by magmatic temperatures at time of crystallization. On the basis of tetrahedrally and oc- tahedrally coordinated aluminum, early formed horn- blendes from rocks of appinitic type belong to Harry’s (1950) type I, hornblendes in diorites and trondh- jemites to type II and hornblendes of late crystalliza- tion to type III (table 21). Silicon-aluminum relationships in hornblendes from the Boulder Creek Granodiorite, mafic inclusions, and hornblende diorite place the hornblende composition of the rock in this report between Harry’s types I and II, which are primary hornblendes; hornblendes from hornblendites of this report belong to type III, which are hornblendes of late crystallization. In a study of Caledonian amphiboles, Nockolds and Mitchell (1946) found that rocks rich in amphibole, that is, hornblendite, have different trace elements in hornblendes in comparison to hornblendes from horn- blende diorites, quartz diorites, and granodiorites. Trace-element abundances vary between hornblendes in this report but not significantly; perhaps more analyses are needed to identify real differences. Lead occurs only in hornblendite; and lanthanum, niobium, and neodymium, although not found in hornblendites, do occur in the hornblendes of other rocks (table 20). PLAGIOCLASE BOULDER CREEK GRANODIORITE Plagioclase is neither as fresh nor as free of inclu- sions as accompanying potassium feldspars, and erod- ed hemihedral to anhedral crystals of plagioclase are about the same size as the potassium feldspars. Plagioclase may be antiperthitic and normally zoned; the zoned crystals have rims ranging in composition from oligoclase to albite. Reaction rims are broader BOULDERCREEKBATHOLFH£FRONTRANGEJXHDRADO 74 00.00H «5.00 00.00 NN.00H «0.00 00.00 H0.00H «0.00 mw.mm mm.mm .0.: IIIIII HmuOH 00.0 0N.0 mH.0 00.0 0m.0 mH.0 NH.0 «H.0 0H.0 «H.0 .0.a IIIII 0 wqu HH.00H qm.mm 00.00H 0m.00H «H.00H m0.00H mH.00H 00.00 m0.00H 00.00H .u.d IIIHMuounam 00.0 «v.0 0m.0 ma.0 00.0 mm.0 NN.0 nm.0 mm.0 m~.0 .w.a IIIIIIIIIIIIIII m .w.u «0.0 nH.0 00.0 no.0 0H.0 NH.0 qa.0 MH.0 «H.0 .0.: IIIIIIIIIIIIII Ho 0H.0 HN.0 0m.0 0m.0 0m.0 Hm.0 mq.0 0q.0 eq.0 nm.0 .0.a III IIIIIIIIII 0nz 00.0 «0.0 HH.0 H0.0 ma.0 00.0 NH.0 00.0 Hm.0 No.0 .w.¢ III IIIIIIIII moum am.0 «5.0 00.H mw.0 mn.0 00.0 0H.H «N.H 0N.H MH.H .0.a IIIIIIIIIIII NOHH 00.0 H0.0 «0.0 00.0 H0.0 no.0 00.0 00.0 m0.0 No.0 .0.: IIIIIIIIIIII low: 0H.N qm.a N0.H @0.H om.H 00.H mn.H mm.H «0.H 05.H .0.: II IIIIIIIIII +0Nm N~.0 Hq.0 ~0.H mm.0 mm.0 «H.H 50.H Hm.H ¢m.a NH.H qm.a IIIIIIIIIIIII 0NM «q.0 no.0 nH.H 0H.H mm.H 0H.H N0.H 00.H mH.H 0N.H 0H.H II IIIIIIIIII 0Nmz 00.NH mq.NH 0H.NH 0N.HH H0.NH mm.HH N0.HH mw.HH mm.HH mw.HH 0.HH IIIIIIIIIIIII omo no.0a um.mH qm.NH 0¢.mH mo.NH N0.0H Hm.0H 00.0H 50.0H mn.0H 0.0M IIIIIIIIIIIII 0w: 0q.m 0H.w NN.0H 00.0H mm.0H H0.HH ww.HH N0.HH HN.AH 00.Ha 0.0Hp II IIIIIIIIIII 00m He.N qm.~ mw.q mo.q Nw.q ow.m 0n.m 0m.m ma.0 mm.m IIIIIIIIIII mommm m0.m mm.n 5N.0H «H.0H mm.0 NH.0H «0.0a nm.0H qq.0a 0N.0H q.HH IIIIIIIIIII m0NH< mm.~m mm.m< mq.qq Nq.0q 00.0¢ mw.mq m0.<¢ ma.mq qw.~q mq.mq «.mq IIIIIIIIIIII Noam unwuumn uswfiwz :H .mwmhamam HNUHEmso NHq Haw «mm mqm 00mm 00m nwm we Hq 0m me llllll .oz wHQEMm muwwamanuuom oufiHOHu wxfiw maofimsaoaH muflu0fivoamu0 xmmuo umvadom mudwanahom muhnmoumamq owwmz 95$ 8.. :5 § 8.62 .1 nEEEES 3: 6.2 $5: fiim 9; 23.6 5 “.3629 22% =.w 55:: b“: .03 “En wwm moi—nun .8 nabs—E oEnoLohoaw .35: :fiEm «Ea $356 5 03:55 225° :5 £35m .0 .> .000 suaflm .4 .m .000 29:: E SHEEP—o: no mama—5E A8.— Euvanum he ambia— 630 $95“ “SEE duke £33530 “RED SESON 3%:3050.‘ ~33 Stem» SSSSESK .323 whEQERSS a .mflommEuE 3&2: 6~Ea§2~2© NEED SESQN EEK 353050: 3x 535.5“ 222:5 E5» «.3335. oSQEMOhome «Ea Eowgmfioldm mqmfir 75 MINERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS w.Hw H< va oo.w oo.w oo.w oc.w oo.w oo.w oo.w oo.m oo.w oo.w oo.w «mm.o owm.o an.H mmN.H N¢H.H qu.H mmq.H «an.a m¢m.a mom.H mmm.a III>H H< Hmuumsmuuwe ooq.n oua.n mwm.o H¢m.o wow.o aqm.o nom.o mw¢.o mmq.o nmq.o mqe.o IIIIIIHm Awu NNowNmMNNHIo< MASEHOM Hmumnww man GM AHU .m .mo .ov «N we mfimmn mnu so macaw mo Honasz BOULDE R CREEK BATHOLITH, FRONT RANGE, COLORADO 76 .omm wwuuommu Hmuou Eouw monm 98 our...r we govxmmun How :OHuHmomEoo mvaancuofi on MHmem Ommpo .0mer mm umuuommu no.5 Hmuoe o. .OHHmNOHo .wwm wHaEmm Mom mmemOHQ mH mwm mHaEmm How “meg: .anm om II Om Om OmH On On OOH cm on II lllllllllllllll MN II II I: II II ..I OON .i |.. .... 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IIIIIIIIIII mm Om OON OmH om OOH On cm On On Om II IIIIIIIIIIIIIII mm GOHHHHE Mom magma SH .393me UHsmwumouuommm 0>HumUHusm=vHEmm NH.» HHq Nmm mqm wwmw 0mm mmmm we He cm 3 111111 .oz meEwm mquumHnFHom muHMOHH. mxHO waonaHuaH wuHuoHOocmuO xmwgo umvHsom wHEoHAFHom wyhaaoumEmH aunwmz Omsfiunoolgob cmium “ESE €33 Saginaw ~3me $339M .wtuthESH «:3 3.20% wwszESH gnu EANQEQES a .m:o..m5u:.~ 3x3: .Stcwwefitw mEEO Sgaom EEK 3.53:8: 3x SEEQ 3355 OS. @9333 uEREMuhqum ~23 NaquuODION mamfib MINERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS 77 TABLE 21.—Comparison of partial hornblende lattice structures [Columns 1. 5, and 6 from Harry (1950)] Type Grano- Hornblende Type Type I diorite Inclusions diotite II III Hornblendica 1 2 3 4 5 6 7 Z group Si---- 6.31 6.52 6.55 6.64 6.79 7.12 7.23 Al——-- 1.69 1.48 1.51 1.34 1.21 0.88 0.74 Y group A1--—- 0.22 0.40 0.33 0.43 0.11 0.15 0.30 and mild cataclasis prevails in plagioclase from rocks in which muscovite occurs. Albite twinning is predomi- nant, but Carlsbad, pericline, and minor complex twins were also observed in thin section. Composition varies from labradorite to oligoclase, but labradorite occurs only in a few lenses satellitic to the batholith, east of the zone of more mafic rocks. Plagioclase in the batholith is of oligoclase-andesine composition (fig. GG). Figure 6G indicates widespread erratic zoning of plagioclase in the granodiorite from west to east. Plagioclase at the batholith contact is andesine and plagioclase in the main part of the batholith is oligoclase. Plagioclase in a northwest-trending wide band in the central northern half of the batholith, like the border rocks, is andesine. It appears that plagioclase in the batholith has had a long crystalliza- tion history because subrounded crystals of plagioclase appear in both biotite and hornblende, sug- gesting that plagioclase may have been the earliest mineral to crystallize or that it formed nearly simultaneously with hornblende and biotite. Locally, smaller and more altered plagioclase crystals occur in younger, larger, and clearer plagioclase crystals. Twin- ning in smaller altered crystals and newer crystals is different; twinning by the same law is disoriented be- tween the older and younger crystals, and twinning by two different laws occurs in the older and host crystals. The younger crystals contain biotite, quartz, and other inclusions, and crystal shape is well defined to subrounded. TWIN SPRUCE QUARTZ MONZONITE Plagioclase in the quartz monzonite is more altered than plagioclase in the granodiorite and composition is much more limited, ranging from sodic to calcic oligoclase. Zoning is normal, and the thin outer zone ranges from calcic albite to sodic oligoclase. Generally plagioclase is the host mineral for myrmekite that is well developed adjacent to potassium feldspar crystals, but myrmekite forms adjacent to potassium feldspars in the absence of plagioclase. MAFIC INCLUSIONS IN THE BOULDER CREEK GRANODIORITE Plagioclase is both fresh looking and sericitized, and crystals are generally subordinate in size to those of the mafic minerals, but the rocks generally contain a few scattered porphyritic plagioclase crystals. Twin- ning is predominantly albite and complex albite- pericline types. Plagioclase unzoned to normally zoned has a composition that varies from calcic oligoclase to calcic andesine. POTASSIUM F ELDSPAR BOULDER CREEK GRANODIORITE General description The alkali feldspars in the granodiorite consist of microcline and microperthite crystals that are slightly smaller to equal in size to the larger plagioclase crystals. Microcline crystals are generally subhedral to anhedral and show good microcline grid twinning. Large crystals are often poikilitic, having inclusions of zoned plagioclase, subhedral quartz, anhedral ores, and frayed, somewhat altered biotite. Myrmekitic intergrowths are par- ticularly common near fault zones or wherever rocks have been sheared and recrystallized; muscovite may also occur in these rocks. Microperthite is more local and seems to be more prevalent near the more mafic lenses that are gradational with granodiorite. Some perthites, as in the southeast part of the batholith, have clear polysynthetic twinned albite rims that formed where two or more potassium feldspars have common grain boundaries. Chemistry. Six potassium feldspars were chemically analyzed (table 22). Feldspar composition ranges from Oras_5_g7.gAb.o,,_,,,oAn1_,_2_,. Six of the seven analyses have a compositional range of only 1 percent for any one component, indicating a quite uniform composi- tion of potassium feldspar throughout the batholith. The minor elements are also fairly consistent in amounts between potassium feldspars with only barium and strontium in more than trace amounts. Determination of triclinicity from X-ray diffraction powder patterns using the 131-131 peaks (Goldsmith and Lavas, 1954) indicates that all chemically analyzed potassium feldspars from the Boulder Creek Granodiorite have a triclinicity (obliquity) of 0.60—0.82:0.05. Nilssen and Smithson (1965) found that low triclinicity values are generally from more mafic rocks. This relationship is true for the Boulder Creek Granodiorite as well; potassium feldspar in the more mafic granodiorite adjacent to the larger mafic inclusions is often a microcline-microperthite having a triclinicity of 0.60—0.65. Elsewhere in the granodiorite 78 BOULDERCREEKBATHOLHHLFRONTRANGEJXHDRADO TABLE 22.—Chemical and semiquantitatiue spectrographic analyses of potassium feldspar from Boulder Creek Granodiorite, Front Range, Colo. [Total Fe and C110 determined by atomic absorption methods, Na,0 and K0 by flame photometric methods; Wayne Mountjoy, analyst. SiOl and ALO, determined by rapid-rock techniques, Sam Botts, analyst; semiquantitative spectrographic analyses by L. A. Bradley. N , not found; L, detected but below limit of determination; N.d., not done] Sample No. —————————————————————— 4 Lab. No.a 41 47 48 49 50 D138923 D138924 D138925 D138926 D138927 D138928 W173436 w173441 W173437 W173431 W173442 W173439 Chemical analyses, in weight percent 64.40 64.40 64.40 64.40 64.40 18.60 18.40 18.60 18.60 18.60 0.09 0.05 0.05 0.05 0.05 0.17 0.24 0.17 0.13 0.18 1.26 1.34 1.26 1.25 1.34 14.10 14.40 14.50 14.40 14.10 SiO2 64.40 Alzg3-—— 18.60 FeO 0.05 CaO 0.11 Na20 1.31 K20 14.80 Total ———————————————— 99.27 98.62 98.83 98.98 98.83 98.67 Semiquantitative spectrographic analyses, in parts per million Ba 5,000 5,000 3,000 5,000 5,000 5,000 Cr N N N N N N Cu 7 7 15 100 5 10 Ga 20 20 20 20 20 20 Ni N L 5 5 N N Pb 70 70 7O 70 50 100 Sr 1,000 1,500 1,000 1,000 1,000 1,000 Composition ratios Ab——— 10.96 10.97 11.40 10.71 10.74 11.59 An 1.17 1.91 2.10 1.60 1.33 1.70 0r 87.87 87.12 86.50 87.69 87.93 86.71 a"w" numbers for A1203 and 8102; ”D" numbers for all other oxides. bTotal Fe as FeO. the triclinicity averages 0.80—0.85, maximum microcline (microcline having maximum obliquity). In- vestigators (Kuroda, 1958; Marmo and others, 1963; Nilssen and Smithson, 1965) have concluded that low triclinicity or low-delta potassium feldspars may be related to porphyroblastesis and metasomatism. They suggest that rocks containing feldspars having low triclinicity may have undergone a change in bulk com- position due to introduced potassium, and the process was arrested before the potassium feldspars were com- pletely inverted to the higher delta values. This ex- planation may be valid for the Boulder Creek Granodiorite as well; it explains the large potassium feldspar crystals often found in the vicinity of mafic areas. It is possible that remobilized potassium, due to shearing, caused this local metasomatism. Variation in distribution of potassium feldspars for the batholith is summarized in figure 6H. The ratio of potassium feldspar to plagioclase in granodiorite has been plotted and contoured for the batholith and a zonal arrangement of areas lacking alkali feldspars and areas rich in potassium feldspars became apparent. The absence of potassium feldspar along the western contact of the batholith and metasedimentary rocks and along a west-northwest trending area between the northern and southern parts of the batholith is evident MINERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS 79 in figure 6H. From areas devoid of potassium feldspar there is an increase in potassium feldspar toward the centers of the north and south halves of the batholith. An Ab content of potassium feldspars of less than 15 percent is generally believed. to indicate that the rocks completed crystallization or were recrystallized at low temperatures (Tuttle and Bowen, 1958, p. 129). Grano- diorite having an 0.80—0.85 triclinicity is believed by some to have crystallized in the presence of excess water vapor. The presence of excess water vapor dur- ing the latter stages of crystallization is possible for the Boulder Creek Granodiorite, especially because large pegmatites accompany the batholithic rocks. MAFIC INCLUSIONS AND LAMPROPHYRE DIKES IN THE BOULDER CREEK GRANODIORITE Potassium feldspars in the mafic inclusions are either orthoclase or microcline, and in the lamprophyre are orthoclase. These feldspars are generally anhedral, poorly twinned to nontwinned, cloudy in appearance, and contain profuse small apatite crystals. Potassium feldspars also occur in rounded blebs as inclusions in other minerals, including hornblende. Analyses of the feldspars (table 23) indicate a composition range of Or.,,.,a_,,,.5Ab,,.7_,,,7An,,5.,.a in the mafic inclusions. A potassium feldspar from lamprophyre has a composi- tion of Or77Ab18An5. The composition of potassium feldspar from the mafic inclusions is more nearly that of the feldspars from more mafic Boulder Creek Granodiorite. TWIN SPRUCE QUARTZ MONZONITE General description. Microcline occurs throughout the Twin Spruce Quartz Monzonite in subhedral to anhedral grid-twinned crystals. Medium-grained quartz monzonite has a variable grain size and chiefly bears large Carlsbad-twinned poikilitic crystals that show good grid twinning or are perthitic. The poikilitic crystals contain inclusions of predominantly zoned plagioclase, biotite, subrounded quartz, and eroded perthitic microcline crystals. Alkali feldspar in fine- grained and speckled quartz monzonite is more nearly equigranular, and plagioclase in the rock appears more altered. Chemistry. The composition of the potassium feldspars in quartz monzonite is more variable than in the Boulder Creek Granodiorite (tables 22 and 24). The potassium feldspar in sample 384 (table 24) is or- thoclase and in sample 381 microcline microperthite; all other analyzed alkali feldspars from quartz mon- zonite are microcline. The range in composition is from Or...7-3...Ab9_5_,.,oAn°,._z,,. Triclinicity of the analyzed TABLE 23.—Chemical and semiquantitative spectrographic anal- yses of potassium feldspar from mafic inclusions and a lam- prophyre dike in Boulder Creek Granodiorite, Front Range, Colo. [Total Fe and CaO determined by atomic absorption methods, NaZO and K20 determined by flame photometric methods, Wayne Mountjoy, analyst; SiO2 and A110, determined by rapid-rock techniques, Sam Butts, analyst; semiquantitative spectrographic analyses by L. A. Bradley. L, detected but below limit of determination; N, not found; N.d., not done] W main/g. orthoclase Microcline Microperthite Sample No. ————————— 334 386 388 Lab. No.5 ---------- 13138909 0138929 D139810 141731440 1.1173444 Chemical analyses, in weight percent 5102 _______________ 63.80 n.d. 62-50 A1233 ______________ 18.60 n.d. 19.20 Feo ______________ 0.05 0.05 0.09 Geo ———————————————— 0.12 0.15 0.28 N320 _______________ 1.12 1.38 2.09 K20 _______________ 14.10 14.10 12.40 Total ------ 97.79 (c) 96.56 Semiquantitative spectrographic analyses, in parts per million Ba _________________ 10,000 10,000 15,000 Cr ----------------- N 1 N Cu ————————————————— 15 15 10 Ga ________________ 30 20 30 Ni ----------------- 5 N L Pb _________________ 70 70 100 Sr ————————————————— 2,000 1,000 7.000 Zr ————————————————— 100 N 50 Composition ratios Ab _________________ 9.71 11.74 17-59 An _________________ 1.78 1.46 5-03 0r _________________ 88.51 86.80 77.38 a"W" numbers for A1203 and 3102; "D" numbers for all other oxides and for A1203 and Sio2 where there are no "w" numbers. bTotal Fe as Feo. CAnalysis incomplete. feldspars varies from 0.65 to 0.82:0.05. Minor elements, especially lead and strontium, are more variable in potassium feldspars from quartz monzonite than in those from granodiorite. QUARTZ Most quartz and feldspars in the Boulder Creek Granodiorite are nearly equigranular; however, larger feldspar crystals are common throughout the granodiorite. In areas of cataclasis smaller quartz crystals cluster in rounded or serrate contact with larger quartz crystals or with other minerals. In general, quartz is conspicuously strained and generally free of inclusions. Inclusions of quartz, especially in the feldspars, are subrounded, clear, and locally abun- dant. As in many of the isopleth maps of other minerals in figure 6 (B, C, E, H), quartz amounts show 80 BOULDERCREEKBATHOLUELFRONTRANGEIXHDRADO TABLE 24.—Chemical and semiquantitatiue analyses of potassium feldspar in Twin Spruce Quartz Monzonite, Front Range, Colo. [Total Fe and 0:10 determined by atomic absorption methods, Map and K10 by flame photometric methods, Wayne Mountjoy, analyst; SiOz and ALO, determined by rapid-rock tech- niques, H. H. Lipp, analyst for sample 384, Sam Botts for all others; semiquantitative spectrographic analyses, L. A. Bradley, analyst. N, not detected] Sample No. ————————————— b381 383 384 380 232 235 85 376 Lab. No.a —————————————— D138912 D138913 D138717 D138915 D138916 D138918 D138921 W173448 W173443 D138914 w173435 W173434 W173438 W173445 W173446 Chemical analyses, in weight percent SiO2 -------------------- 63.80 64.40 67.90 65.70 64.40 65.10 64.40 64.40 A1203 ------------------- 18.60 18.80 17.20 18.40 18.60 18.20 18.80 18.60 FeOCL ——————————————————— 0.07 0.05 0.05 0.11 0.04 0.07 0.05 0.05 CaO --------------------- 0.13 0.13 0.15 0.18 0.16 0.11 0.10 0.10 Na20 ———————————————————— 1.13 1.51 1.54 1.14 1.64 1.24 1.18 1.11 K20 --------------------- 14.20 14.10 13.60 13.80 14.10 14.50 14.70 14.80 Total ——————————— 97.93 98.99 100.44 99.33 99.24 99.22 99.23 99.06 Semiquantitative spectrographic analyses, in parts per million Ba ______________________ 7,000 3,000 3,000 10,000 2,000 3,000 5,000 3,000 Cu ______________________ 15 30 5 15 15 15 2 10 Ga ______________________ 50 20 30 20 30 30 20 20 Ni —————————————————————— N N 5 N N N N N Pb ______________________ 200 100 50 70 100 100 70 70 3r ______________________ 1,000 500 500 2,000 500 500 1,000 500 Zr —————————————————————— 150 100 70 20 50 N 70 50 Composition ratios Ab ---------------------- 9.84 13.02 13.63 10.01 14.00 10.69 10.03 9.52 An ---------------------- 1.35 1.14 1.32 2.21 1.34 0.99 1.10 0.92 0r ---------------------- 88.81 85.84 85.05 87.78 84.66 88.32 88.87 89.56 allwll numbers for A1203 and Si02; "D" numbers for all other oxides and for A1203 and SiO2 where there are no "w" numbers. bSample has low total oxides; SiO2 may be low. cTotal Fe reported as FeO. a strong west to northwest regional percent distribu- lens in schist and gneiss adjacent to the west contact tion pattern in the central and southwestern part of of the Boulder Creek Granodiorite (pl. 2) where it the batholith (fig. 6E). averages 35 percent. In the Twin Spruce Quartz Monzonite, quartz and the feldspars are equigranular. Quartz contacts are ACCESSORY MINERALS mutual, serrate, or embayed; it is always strained, and small blebs of quartz along mineral boundaries are par- Accessory minerals including the ores, allanite, ticularly noticeable in strained and altered rocks. apatite, and sphene, are common and characteristic of Quartz averages about 29 percent of the quartz mon— the Boulder Creek Granodiorite and associated mafic zonite, except in the N ederland quadrangle and in the inclusions but are relatively sparse in the Twin Spruce MINERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS 81 Quartz Monzonite and the more mafic rocks. Apatite, sphene, allanite, zircon, and monazite and (or) xenotime are abundant in that order. Ores. Ores include iron oxides (magnetite, hematite, ilmenite) and the sulfides (pyrite, chalcopyrite, molybdenite). In the Boulder Creek Granodiorite the ores are predominantly magnetite and some hematite and pyrite; other ore minerals are extremely rare. Hematite is generally in the range of 15—20 percent of the ores in Twin Spruce Quartz Monzonite; it occurs as individual grains, as an intergrowth in magnetite, or as an overgrowth on the magnetite. Iron oxides in the Twin Spruce Quartz Monzonite are more complex because ilmenite is also present. Ilmenite is less abun- dant than magnetite or hematite, but, where present, it is associated with magnetite or hematite as single grains or intergrown with hematite.The speckled ap- pearance of quartz monzonite is caused by the cluster- ing of ores and adjacent leucocratic haloes. The domi- nant iron oxide in the clusters is hematite. Sphene. Sphene in the Boulder Creek Granodiorite occurs predominantly along the trend of hornblende- bearing Boulder Creek Granodiorite (fig. 6A and C). Sphene in the batholith proper averages 1.5 percent but along the western contact it is nearly absent. Granodiorite lenses within the metasedimentary rocks, along the western contact, bear almost no sphene but further to the west in lenses of granodiorite associated with the more mafic rocks, sphene averages 3 percent; these lenses are also rich in ores. The occurrence of sphene is twofold: (1) as primary sphene in hemihedral to anhedral crystals clustered with the mafic minerals and the accessory minerals apatite, allanite, and zir- con; or (2) as secondary sphene, which rims magnetite, forms small exsolved blebs in biotite and replaces biotite along cleavage and grain boundaries. Sphene is often bleached along magnetite-sphene contacts. Sphene in the Twin Spruce Quartz Monzonite is generally anhedral and is dominantly a product of the alteration of some plagioclase, magnetite, and biotite; it corrodes magnetite grains and is often in bleached contact with magnetite. Both a light greenish-yellow and a grayish-yellow sphene can be found in a single hand specimen. No ef- fort was made to separate the two for chemical analysis but the greenish-yellow variety is more com- mon and is represented in the chemical analysis. Ac- cording to partial chemical analysis of CaO and TiO2 (table 25), all sphene samples are very similar in regard to CaO and TiOz. Spectrographic analyses, however, indicate that the sphene from Twin Spruce Quartz Monzonite is richer in the trace elements cerium, cop- per, lead, yttrium, zirconium, and neodymium than sphene in Boulder Creek Granodiorite (table 25). Spec- TABLE 25.—Chemical and semiquantitative spectrographic analyses of sphene in Boulder Creek Granodiorite, inclusions in granodiorite, and Twin Spruce Quartz Monzonite, Front Range, Colo. [CaO determined by atomic absorption methods, TiO, colorimetrically determined, John Gardner, analyst; spectrographic analyses by L. A. Bradley. N, not determined] Boulder Creek Win Spruce Granodiorite Inclusions Quartz Monzonite Sample No. ------ 47 49 386 334 376 Lab. No. ———————— D138953 D138956 D138954 D138955 D138957 Chemical analyses, in weight percent CaO ————————————— 29.3 28.8 29.8 27.9 28.3 TioZ--—----——— 35.8 35.4 35.4 36.0 35.4 S-iquantitative spectrographic analyses, in parts per million Ba ______________ 10 30 3o 10 150 Ce ______________ 2,000 2,000 3,000 7,000 5.000 at ____________ 150 100 150 50 50 c“ ______________ 30 20 150 20 1, 000 Dy ______________ 200 200 200 300 150 Ga —————————————— N N N 10 7 La ______________ 300 200 7 00 2 , 000 1 , 500 Mo ______________ 15 30 15 20 15 Nb ____________ .. 300 200 100 300 300 Nd ______________ 3,000 3,000 3,000 7,000 5,000 N1 —————————————— N N S N N Pb ______________ 20 70 50 50 150 p, ______________ 500 200 500 1, 500 1,000 sg---------_____ 20 15 20 20 50 gm ___________ __ 700 700 500 1,500 1,000 5,. ______________ 200 150 100 200 150 s: ______________ 70 100 70 150 150 v ____________ _. 700 700 700 300 500 y ____________ _. 1,500 1,500 1,500 2,000 3.000 Yb _____________ 7o 70 70 50 70 Zr .............. 300 500 200 500 1 , ooo trographic analyses of trace elements in sphene from inclusions indicate that some sphene has trace elements similar to sphene in Twin Spruce Quartz Monzonite and other sphene is more closely allied to Boulder Creek Granodiorite. Apatite. Apatite occurs as small euhedral to anhe- dral crystals that, according to X-ray powder patterns, are fluorapatite. It is very pale greenish in hand specimen, colorless in thin section, and is predominant- ly associated with the mafic clusters in the grano- diorite. Its modal distribution indicates that apatite is partly controlled by rock type. (Compare figs. 3 and 6E). In the Boulder Creek Granodiorite apatite tends to concentrate in the rocks of quartz diorite (tonalite) or granodiorite composition and is nearly absent in those of quartz monzonite composition. Allanite. Allanite is rare in the mafic rocks to the west of the batholith proper, including the Los Lagos and Severance lenses (table 7) but is a common ac- cessory mineral in mafic inclusions in the batholith (table 6, samples 318—327, 333) and also in the lam- 82 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO prophyre (table 6, samples 328, 329, 331, 332). Allanite in the Twin Spruce Quartz Monzonite, however, rarely exceeds 0.2 modal percent and normally if present is in trace amounts only. The distribution of allanite in the Boulder Creek Granodiorite is outlined in figure 6D. The distribution pattern in figure 6D does not agree with the one presented by Hickling, Phair, Moore, and Rose (1970, p. 197 6). Their pattern was based on fewer than one-third of the observation points used here. Areas where allanite is more abundant, greater than 0.2 percent, correspond to areas that are in the trend of hornblende-bearing Boulder Creek Granodiorite. Allanite, however, is not confined to hornblende- bearing rocks, but where it does occur without horn- blende it is found always in less than 0.2 percent amounts. This relationship is also true of the scattered plutons to the west of the batholith. The Pisgah pluton is a good example; large allanite crystals occur in it but no hornblende thus far has been found in the pluton. Physical properties of allanite in the Boulder Creek batholith have been studied extensively by Hickling, Phair, Moore, and Rose (1970) and will only be men- tioned briefly here for consistency in mineral descrip- tion. Allanite in thin section is yellowish brown to red- dish brown and commonly is zoned and rimmed by epidote. The centers of crystals are commonly isotopic, and epidote usually occurs between biotite-allanite contacts. Hickling, Phair, Moore, and Rose (1970) reported high-birefringent allanite in the northwest part of the batholith but high-birefringent allanite is also found sparsely scattered throughout the central part of the batholith extending to the southern border. In separating allanite from rock samples, it was found that allanite is also locally associated with pyrite. Pyrite attached to or as an inclusion in allanite is euhedral to anhedral. This association is rarely seen in thin section. An explanation may be that the small allanite and still smaller pyrite crystals are plucked out in grinding of the section. It is here proposed that both primary and secondary allanite exists in these rocks. This interpretation dif- fers from that of Hickling, Phair, Moore, and Rose (1970), who proposed that allanite was all of secondary origin, principally an alteration product of biotite. True primary allanite is not readily distinguishable because of the large amount of allanite replacing biotite, but small euhedral crystals of allanite in plagioclase and hornblende, hemihedral allanite crystals cutting biotite at an angle, and large allanite crystals in granodiorite plutons well out from the batholith all suggest that some of the allanite is primary. It is suspected that a considerable amount of the larger allanite crystals in the batholith is also primary. The modal distribution pattern of allanite, which follows that of hornblende in a general way, sug- gests that primary allanite is characteristic of the batholith. Allanites in Twin Spruce Quartz Monzonite are often zoned (sometimes as many as five or more distinct zones can be counted) but have sharp contacts against adjacent minerals (fig. 37). Almost no epidote occurs at the contact of allanite and biotite as is commonly FIGURE 37.—Allanite and monazite in Twin Spruce Quartz Mon- zonite. A, Allanite crystal slightly altered to epidote with growth pressure cracks radiating away from it. Allanite may be late primary crystal in Twin Spruce Quartz Monzonite (sample 85, table 13). Plain light, X100. B, Monazite crystal with brown, almost isotropic alteration zone that may be allanite. Epidote oc— curs in radiating growths on allanite (sample 89, table 8). Plain light, X100. A, allanite; B, biotite; E, epidote; M, monzonite; Mu, muscovite; My, myrmekite; P, zoned plagioclase; MC, microcline; Q, quartz. Photographs by Louise Hedricks, US. Geological Survey. MIN ERALOGY, PETROLOGY, AND CHEMISTRY OF MINERALS 83 observed in the Boulder Creek Granodiorite. In quartz monzonite, monazite locally alters to what appears to be allanite (fig. 373). It appears that allanite from hornblende diorite may be richer in copper, yttrium, neodymium, samarium, gadolinium, and dysprosium than allanite from either granodiorite or its inclusions (table 26). Allanite in a quartz monzonite lens along the crest of the ridge north of Boulder County Hill in the Caribou pluton (pl. 1) appears to have formed from the reaction of monazite and biotite. Within the batholith proper, quartz monzonite lenses locally bear monazite that has coronas of what may be secondary allanite (fig. 373). This secondary allanite is mantled by epidote crystals formed by the reaction biotite+plagioclase?+mona- zite->allanite+epidote+iron oxides. Dietrich (1961) noted similar coronas of monazite altering to epidote in the Mount Airy Granite. Monazite and (or) xenotime. Both monazite and xenotime are rare accessory minerals in the Boulder Creek Granodiorite and Twin Spruce Quartz Mon- zonite. Both minerals are difficult to identify in thin section because they usually occur as very small subhedral to subrounded crystals that are associated with apatite, biotite, allanite, and ores. Xenotime has a faint yellow pleochroism and monazite a faint brown pleochroism, but this pleochroism is difficult to observe unless the minerals are isolated in leucocratic areas of the thin section. ALTERATION MINERALS Muscovite-sericite. Muscovite never occurs with hornblende except as small flakes totally within plagioclase crystals. Wells (1967, p. D22) also noted this characteristic from his work in the Eldorado Springs quadrangle. Muscovite laths in Boulder Creek Granodiorite lenses adjacent to the batholith are at large angles to biotite with no evident reaction between them. This muscovite is older than most microcline and quartz and is perhaps a primary muscovite as both microcline and quartz embay it. In addition to this early muscovite, a later muscovite occurs in large lathlike patches that extend across microcline crystals. Within the batholith, all muscovite is clearly secondary; it forms thin rims on the ores, and occurs as overgrowths on biotite, as growths along biotite cleavage, or forms in plagioclase where plagioclase is intensely altered. Epidote and (or) calcite may accompany the muscovite in recrystallized parts of the batholith. Muscovite appears to be both primary and second- ary in the Twin Spruce Quartz Monzonite. Primary muscovite appears to be the same age as biotite and the ores, or younger, and has had a long and complex history. In the southeast part of the batholith, along the granodiorite-quartz monzonite contact, rocks that have been recrystallized contain secondary musocovite laths that are larger than anywhere else in the batholith. In the field muscovite is plainly visible and often profuse. In thin section the large laths appear eroded again by potassium feldspar and quartz. The laths are characteristically bent and strained and dendritic—like. Muscovite having a single orientation has grown in the host mineral, feldspar. Prehnite and hydrogarnet. Both minerals were first described by Wrucke (1965) as occurring in the north- east part of the exposed batholith. This study confirms that this is also the only area of the batholith in which they occur. Prehnite alone has been found only along the northwest contact of the batholith and along its most northern contact in Left Hand Canyon. Growth of prehnite is due to the release of calcium in the altera- tion of plagioclase and hornblende. Prehnite in lens- shaped aggregates parallel to the (001) cleavage in biotite is perhaps epitaxial; the 001 surface provides suitable nucleation sites (Moore, 1976, p. 527). Prehnite was associated with quartz in only one thin section and this was in a small vein cutting other minerals, indicating mobility of Ca2+ ions. Hydrogarnet replaces prehnite but is more likely part of the reaction involving hornblende and (or) biotite+plagioclase. The experiments of Coombs, Ellis, Fyfe, and Taylor (1959) showed that prehnite is not stable above 450°C at water pressure of as much as 500 MPa; thus a magmatic origin is not likely. A calcium or potassium metasomatism accompanying faulting, shearing, and recrystallization may be possible. Epidote, clinozoisite, and piedmontite. Very little clinozoisite has been identified in the southern two- thirds of the batholith because of its similar occurrence to epidote and the difficulty in distinguishing it from epidote; therefore the two are reported together in modes. Piedmontite was only recognized at one local- ity, north of Wallstreet, Gold Hill quadrangle, in a pegmatite outcrop. The piedmontite gives the rock a very pink color. Crystallization was probably from hydrothermal solutions. Like sphene, epidote is nearly absent from grano- diorite lenses in metasedimentary rocks adjacent to the Boulder Creek batholith and from the batholith near its contact, except in areas where hornblende- bearing rocks occur along the contact (fig. 6A). Epidote chiefly replaces biotite or hornblende associated with biotite; hornblende only weakly alters to epidote. Replacement is along crystal boundaries or in aggregates along biotite cleavage. Also, epidote BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO TABLE 26.—Chemical and spectmgmphic analyses of allanite in Boulder Creek Granodion'te, inclusions, and biotific hornblende dion'te, Boulder Creek batholith area, Front Range, Colo: [Oxides determined by lithium borabe fusion. X-ray methods by J. S. Wahlberg; spectrographic analysis by J. C. Hamilton. >. greater than. H. not found; ND. not done] Boulder Creek Hornblende Granod iorite Inclusion diorite Sample No. ————————— E‘49 47 385 334 352 Lab. No. ——————————— Dl38960 D13896l D172033 D138962 Dl38963 Chemical analyses , in weight percent Cao ________________ 13.5 12.1 17.0 12.1 10.6 Ce203 —————————————— 9.0 9.0 12.0 10-5 8-9 FeOb _______________ 12.0 12.2 16.2 12.0 11.5 1,3203 —————————————— 5.5 5.5 3.4 7-2 4-3 MnO ———————————————— 0.2 1.3 0.2 0-3 0-3 Spectrographic analyses , in parts per million B —————————————————— n. d. —— 50 -— 30 Ba _________________ n.d. 70 500 150 300 Co ————————————————— n.d . 20 20 15 30 Cr ————————————————— n.d . 150 700 70 70 cu ————————————————— n.d . 100 100 70 1, 500 Dy ————————————————— n.d . 70 —— 70 500 Er ————————————————— n.d . 7O -- 70 100 Eu _________________ n.d. 150 100 150 150 Ga _________________ n. d. 50 50 30 30 Gd _________________ n.d. 150 300 200 1,500 Ho ————————————————— n.d . 100 70 70 100 Mo ————————————————— n.d . 15 " " _- Nd ————————————————— n.d. >20,000 30,000 30,000 70,000 Ni ————————————————— n. d. 20 50 7 "' Pb ————————————————— n.d. 300 900 150 500 yr _________________ n. d. >10, 000 10, 000 10, 000 15 , 000 Sc _________________ n.d . 500 1,000 700 l, 000 Sm ————————————————— n.d. 3,000 2,000 3,000 7,000 Sr _________________ n.d. 700 1,500 1,000 1,500 Th _________________ n.d. 5,000 10,000 2,000 5.000 V __________________ n.d. 700 500 700 500 Y __________________ n.d. 500 700 700 2,000 Yb ————————————————— n.d . 50 50 15 70 Zr _________________ n. d. 300 150 300 500 aUsual limits of detection do not apply due to dilution technique. bTotal Fe as FeO. REFERENCES CITED 85 replaces allanite, sometimes leaving only an allanite core. Allanite-biotite contacts are generally separated by a zone or layer of epidote, and incomplete reactions involving epidote are: biotite-repidote+sphene; horn- blende+biotite->sphene+epidote+magnetite; horn- blende->epidotei magnetite; allanite+biotite->epidote. Epidote in the batholith modally occurs in numerous small epidote islands that are difficult to correlate with any of the other mineral trends, but if allanite and epidote modes are combined, there is a distinct pattern that again mimics the distribution of hornblende- bearing rocks in the batholith. The higher values of allanite are not in epidote-rich areas but appear to be coincident with the more mafic inclusions in the Boulder Creek batholith. REFERENCES CITED Bateman, P. C., Clark, L. D., Huber, N. K., Moore, J. G., and Rim- hart, C. D., 1963, The Sierra Nevada batholith—a synthesis of recent work across the central part: U.S. Geological Survey Pro- fessional Paper 414-D, p. D1—D46. Boos, M. F., and Boos, C. M., 1934, Granites of the Front Range— the Longs Peak—St. Vrain batholith: Geological Society of America Bulletin, v. 45, no. 2, p. 302—322. Bowen, N. L., 1928, The evolution of the igneous rocks: Princeton, Princeton University Press, 332 p. __1937, Recent high-temperature research on silicates and its significance in igneous geology: American Journal of Science, 5th ser., v. 33, no. 193, p. 1—21. Braddock, W. A., 1969, Geology of the Empire quadrangle, Grand, Gilpin, and Clear Creek Counties, Colorado: U.S. Geological Survey Professional Paper 616, 56 p. Bryant, Bruce, and Hedge, C. E., 1978, Granite of Rosalie Peak, a phase of the 1,700 m.y. 01d Mount Evans pluton, Front Range, 0010.: U.S. Geological Survey Journal of Research, v. 6, no. 4, p. 447—452. Buddington, A. F., 1959, Granite emplacement with special refer- ence to North America: Geological Society of America Bulletin, v. 70, no. 6, p. 671—747. Cawthorn, R. G., and Brown, P. A., 1976, A model for the formation and crystallization of corundum-normative calc-alkaline magmas through amphibole fractionation: Journal of Geology, v. 84, no. 4, p. 467-476. Chayes, Felix, 1952, The finer-grained calc-alkaline granites of New England: Journal of Geology, v. 60, no. 3, p. 207—254. Coombs, D. 8., Ellis, A. J., Fyfe, W. S., and Taylor, A. M., 1959, The zeolite facies, with comments on the interpretation of hydrothermal syntheses: Geochimica et Cosmochimica Acta, v. 17, no. 1—2, p. 53—107. Deer, W. A., Howie, R. A., and Zussman, J ., 1963, Framework sili- cates, v. 4 of Rock forming minerals: New York, John Wiley and Sons, 435 p. Dietrich, R. V., 1961, Petrology of the Mount Airy “granite": Vir- ginia Polytechnic Institute Bulletin, Engineering Experiment Station Series 144, v. 54, no. 6, 63 p. Dodge, F. C. W., Smith, V. C., and Mays, R. E., 1969, Biotites from granitic rocks of the central Sierra Nevada batholith, California: Journal of Petrology, v. 10, no. 2, p. 250—27 1. Gable, D. J ., 1969, Geologic map of the Nederland quadrangle, Boul- der and Gilpin Counties, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ-833, scale 1:24.000. ___1972, Geologic map of the Tungsten quadrangle, Boulder, Gilpin, and Jefferson Counties, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ—978, scale 1:24.000. 1973, Map showing rock fractures and veins in the Tung- sten quadrangle, Boulder, Gilpin, and Jefferson Counties, Colo- rado: U.S. Geological Survey Miscellaneous Geologic Investiga- tions Map I—792—A, scale 124,000. 1977, Preliminary geologic map of the Gold Hill quadrangle, Boulder County, Colorado: U.S. Geological Survey Open-file Report 77 —849. Gable, D. J ., and Madole, R. F., 1976. Geologic map of the Ward quadrangle, Boulder County, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ—127 7, scale 1:24.000. Gable, D. J ., and Sims, P. K., 1969, Geology and regional metamor- phism of some high-grade cordierite gneisses, Front Range, Colorado: Geological Society of America Special Paper 128, 87 p. Gable, D. J ., and Smith, V. C., 1975, Hornblendes from a region of high-grade metamorphism, Front Range, Colorado: U.S. Geological Survey Bulletin 1392, 35 p. Goldsmith, J. R., and Laves, Fritz, 1954, The microcline—sanidine stability relations: Geochimica et Cosmochimica Acta, v. 5, no. 1, p. 1—19. Green, T. H., and Ringwood, A. E., 1968, Genesis of the calc-alkaline igneous rock suite: Contributions to Mineralogy and Petrology. v. 18, no. 1, p. 105—162. Harry, W. T., 1950, Aluminum replacing silicon in some silicate lattices: Mineralogical Magazine, v. 29, p. 142—149. Hawley, C. C., and Moore, F. E., 1967, Geology and ore deposits of the Lawson-Dumont-Fall River district, Clear Creek County, Colorado: U.S. Geological Survey Bulletin 1231, 92 p. Hedge, C. E., 1969, Petrogenetic and geochronologic study of mig- matites and pegmatites in the central Front Range [0010.]: Colo- rado School of Mines unpublished Ph. D. thesis, 158 p. Hickling, N. L., Phair, George, Moore, Roosevelt, and Rose, H. R., Jr., 1970, Boulder Creek batholith, Colorado, Part I—Allanite and its bearing upon age patterns: Geological Society of America Bulletin, v. 81, no. 7, p. 1973—1994. Jackson, E. D., Stevens, R. E., and Bowen, R. W., 1967, A computer- based procedure for deriving mineral formulas from mineral analyses in Geological Survey Research 1967: U.S. Geological Survey Professional Paper 575~C, p. C23—C31. Kretz, R. A., 1959, Chemical study of garnet, biotite, and hornblende from gneisses of southwestern Quebec, with emphasis on distribution of elements in coexisting minerals: Journal of Geology, v. 67, no. 4, p. 371—402. Kuroda, Yashimasu, 1958, Notes on some soda-potash feldspars in metamorphic rocks, Japan: Tokyo Kyoiku Daigaku, Science Report, sec. C, v. 6, no. 52—54, p. 117—125. Lee, D. E., and Van Loenen, R. E., 1971, Hybrid granitoid rocks of the southern Snake Range, Nevada: U.S. Geological Survey Professional Paper 668, 48 p. Lovering, T. S., and Goddard, E. N ., 1950, Geology and ore deposits of the Front Range, Colorado: U.S. Geological Survey Profes- sional Paper 223, 319 p. Lovering, T. S., and Tweto, O. L., 1953, Geology and ore deposits of the Boulder County tungsten district, Colorado: U.S. Geological Survey Professional Paper 245, 199 p. Marmo, Vladi, Hytfinen, K., and Vorma, A., 1963, On the occur- rence of potash feldspars of inferior triclinicity within the Precambrian rocks in Finland: Finland, Commission Géologique (Geologinen Tutkimuslaitos), Bulletin 212, p. 51—78. 86 BOULDER CREEK BATHOLITH, FRONT RANGE, COLORADO Moench, R. H., Harrison, J. E., and Sims, P. K., 1962, Precambrian folding in the Idaho Springs-Central City area, Front Range, Colorado: Geological Society of America Bulletin, v. 73, no. 1, p. 35—58. Moore, A. C., 1976, Intergrowth of prehnite and biotite: Mineral- ogy Magazine, v. 40, no. 313, p. 526-529. Nilssen, Borghild, and Smithson, S. B., 1965, Studies of the Pre- cambrian Herefoss granite, [Part] I. K-feldspar obliquity: N orsk Geologisk Tidsskrift, v. 45, p. 367—396. Nockolds, S. R., 1954, Average chemical composition of some ig- neous rocks: Geological Society of America Bulletin, v. 65, no. 10, p. 1007—1032. Nockolds, S. R., and Mitchell, R. L., 1946, The geochemistry of some Caledonian plutonic rocks—a study in the relationship between major and trace elements of igneous rocks and their minerals: Royal Society of Edinburgh Transactions, v. 61, pt. 2, p. 533—575 [1948]. Pearson, R. C., and Speltz, C. N., 1975, Mineral resources of the Indian Peaks study area, Boulder and Grand Counties, 0010., with a section on Interpretation of aeromagnetic data, by Gor- don Johnson: US Geological Survey Open-file Report 75—500, 179 p. Peck, L. C., 1964, Systematic analysis of silicates: US. Geological Survey Bulletin 1 170, 89 p. Peterman, Z. E., Hedge, C. E., and Braddock, W. A., 1968, Age of Precambrian events in the northeastern Front Range, Colorado: Journal of Geophysical Research, v. 73, no. 6, p. 227 7-2296. Phair, George, Stern, T. W., and Gottfried, David, 1971, Boulder Creek batholith, Colorado, Part III—Fingerprinting discordant zircon ages in a complex intrusion: Geological Society of America Bulletin, v.82, no. 6, p. 1635—1656. Presnall, D. C., and Bateman, P. C., 1973, Fusion relations in the system NaAlSi,O,,-CaAl,Si,O,-KAlSi,,O,-Si0,-H20 and genera- tion of granitic magmas in the Sierra Nevada batholith: Geological Society of America Bulletin, v. 84, no. 10, p. 3181—3202. Shapiro, Leonard, and Brannock, W. W., 1962, Rapid analysis of silicate, carbonate, and phosphate rocks: US. Geological Survey Bulletin 1144-A, p. A1—A56. Shawe, D. R., ed., 1976, Geology and resources of fluorine in the United States, with sections by Shawe, D. R., Van Alstine, R. E., Worl, R. G., Heyl, A. V., Trace, R. D., Parker, R. L., Grif- fits, W. R., Sainsbury, C. L., and Cathcart, J. B.: US Geological Survey Professional Paper 933, 99 p. Sheridan, D. M., Maxwell, C. H., Albee, A. L., and Van Horn, Rich- ard, 1967, Geology and uranium deposits of the Ralston Buttes district, Jefferson County, Colorado: US. Geological Survey Professional Paper 520, 121 p. Sims, P. K., and Gable, D. J ., 1964, Geology of Precambrian rocks, Central City district, Colorado: US. Geological Survey Profes- sional Paper 474-C, p. 01—052 [1965]. _1967, Petrology and structure of Precambrian rocks, Central City quadrangle, Colorado: US. Geological Survey Professional Paper 554—E, p. E1—E56. Stern, T. W., Phair, George, and Newell, M. F., 1971, Boulder Creek batholith, Colorado, Part II—Isotopic age of emplacement and morphology of zircon: Geological Society of America Bulletin, v. 82, no. 6, p. 1615—1634. Streckeisen, A. L., 1976, To each plutonic rock its proper name: Earth-Science Reviews, v. 12, no. 1, p. 1-33. Taylor, R. B., 1976, Geologic map of the Black Hawk quadrangle, Gilpin, Jefferson, and Clear Creek Counties, Colorado: US. Geological Survey Geologic Quadrangle Map GQ—1248, scale 1:24.000. Taylor, R. B., and Sims, P. K., 1962, Precambrian gabbro in the central Front Range, Colorado, in. Geological Survey Research 1962: US. Geological Survey Professional Paper 450—D, p. D118-D122. Tilling, R. I., 1973, Boulder batholith, Montana; a product of two contemporaneous but chemically distinct magma series: Geological Society of America Bulletin, v. 84, no. 12, p. 3879—3900. Tuttle, 0. F., and Bowen, N. L., 1958, Origin of granite in the light of experimental studies in the system N aAlSiaOs-KAlSiaOS-Sioz- H20: Geological Society of America Memoir 74, 153 p. Tweto, Ogden, and Sims, P. K., 1963, Precambrian ancestry of the Colorado mineral belt: Geological Society of America Bulletin, v. 74, no. 8, p. 991—1014. US. Geological Survey, 1964, Boulder Creek zircon yields highest isotopic ages reported in Front Range [0010.] in US. Geological Survey research 1964: US. Geological Survey Professional Paper 501—A, p. A95. Vance, J. A., 1961, Zoned granitic intrusions—an alternative hypo- thesis of origin: Geological Society of America Bulletin, v. 72, no. 11, p. 1723—1727. Wells, J. D., 1967, Geology of the Eldorado Springs quadrangle, Boulder and Jefferson Counties, Colorado: US. Geological Survey Bulletin 1221—D, p. D1—D85. Whitten, E. H. T., 1962, A new method for determination of the average composition of a granite massif: Geochimica et Cosmochimica Acta, v. 26, p. 545—560. Winkler, H. G. F., 197 6, Petrogenesis of metamorphic rocks [4th ed.]: New York, Springer-Verlag, 334 p. Winkler, H. G. F., Boese, Manfred, and Marcopoulos, Theodor, 1975, Low temperature granitic melts: Neues Jahrbuch fiir Mineralogie, no. 6, p. 245—290. Wones, D. R., and Eugster, H. P., 1965, Stability of biotite—exper- iment, theory and application: American Mineralogist, v. 50, no. 9, p. 1228—1272. Wrucke, C. T., 1965, Prehnite and hydrogarnet(?) in Precambrian rocks near Boulder, Colorado in Geological Survey Research 1965: US. Geological Survey Professional Paper 525-D, p. D55—D58. Wrucke, C. T., and Wilson, R. F., 1967, Geologic map of the Boulder quadrangle, Boulder County, Colorado: US. Geological Survey Open-file report, scale 1224,000. Page Abstract . . . . 1 Actinolite . . . . 25 Age .................................... 3, 20, 27, 35 Alkali feldspar, Boulder Creek Granodiorite . . . 51 Twin Spruce Quartz Monzonite .......... 51 Allanite ............................ 25, 78,81, 83, 85 Boulder Creek Granodiorite ...... 17, 51, 64, 72, 73 in lamprophyre ......................... 20 Twin Spruce Quartz Monzonite . 69 Aluminum ..................... . . 73 in lamprophyre . . . . . 48 Analyses, techniques ....................... 2 Andesine, Boulder Creek Granodiorite ........ 52 Apatite ................................ 25, 48, 81, 83 Boulder Creek Granodiorite ............. 17, 72, 73 in Iamprophyre ............ 20 in mafic inclusions ............. 20, 79 Twin Spruce Quartz Monzonite . . i 69 Aplite ..................................... 6, 20 gneissic ................................ 34 Twin Spruce Quartz Monzonite .......... 27 Assimilation, in Boulder Creek Granodiorite . . 52 Augite ..................................... 25 B Bald Mountain pluton ....................... 72 Barium. Boulder Creek Granodiorite ........ 77 Twin Spruce Quartz Monzonite .......... 51 Beryllium, Boulder Creek Granodiorite ....... 73 in quartz monzonite ..................... 51 Bibliography ...................... 85 Bighorn Mountain, mafic inclusions .......... 20 Biotite ........................ 6, 23, 24, 34, 45, 48, 83 Boulder Creek Granodiorite ............. 7, 17, 38, 51, 64, 72, 73 inlamprophyres.....................:.. 20 in mafic inclusions ...................... 20 Twin Spruce Quartz Monzonite ......... 28, 69, 79 Biotite gneiss .............................. 17 Biotite schist ............. . . 6 Biotitesillimanite gneiss ............. . 3, 17, 53 Blackhawk quadrangle, quartz diorite . . . 17 Boulder batholith, Montana ................. 1 Boulder Creek, Middle, mafic inclusions ...... 2O Boulder Creek Granodiorite, constituent rocks 7 defined ................................ 4 geochemistry ........................... 38 Bronzite ................................... 25 Buckeye Mountain anticline, folds ........... 37 C Calcite .................................... 23, 25, 83 Boulder Creek Granodiorite .............. 72 Calcium ................................... 48, 83 in lamprophyre . . . 48 relation to oxides . . . . . . 39 Caribou pluton ................. 7, 72, 73, 83 Central City quadrangle, gabbro ............. 23 granite gneiss .......................... 34 pegmatite .............................. 34 Pisgah pluton .......................... 7 Cerium ..................... 81 Boulder Creek Granodiorite . . . 72 in mafic inclusions ............ 50 Twin Spruce Quartz Monzonite . . 51, 69 INDEX [Italic page numbers indicate major references] Page Chalcopyrite .......... . . . . 81 Chemical equilibrium . . . 51 Chemical trends ............................ 38 Chlorite .................................... 25 Boulder Creek Granodiorite ...... 51, 64 Twin Spruce Quartz Monzonite . . . . . . 69 Chromium ........................ . 45, 50, 73 Boulder Creek Granodiorite . . 73 in quartz monzonite ............. 51 Twin Spruce Quartz Monzonite .......... 69 Classification. rock ......................... 2 Clinopyroxene .............................. 23 Clinozoisite ................................ 83 Coal Creek Canyon, quartz monzonite ........ 27 Cobalt ...................................... 50 in quartz monzonite . . 51 Colorado mineral belt . . 3 Constitution .......... . 4 Contact relations ........................... 6 Copper ................................... 50, 81, 83 in mafic inclusion ....................... 50 Country rock .............................. 23, 37, 53 Cummingtonite ............................ 25 D Deformation ............................... 37 Differentiation, in Boulder Creek Granodiorite 52 Dikes ...................................... 20, 34 Diopside ................................... 25 Diorite .................................... 20, 23 Dysprosium ................................ 83 E Eldora, folds ............................... 37 Eldorado Springs, quartz monzonite .......... 29 Elk Creek pluton, gabbro .................... 23 Eldorado Springs quadrangle ................ 4, 39, 83 Emplacement, mode ........................ 6 Epidote ....................... . . 25, 82, 83 Boulder Creek Granodiorite ............. 17, 51, 64 F Feldspar ................................... 8 lineation ............................... 7 Fluorine . . . Folia tion . . . Formation ................................. G Gabbro .................................... 6, 20, 2.? chemical trends . . 50 Gadolinium ........................ 83 Garnet, Boulder Creek Granodiorite . . 63 Geochemistry ...................... 38 Gold Hill, contact relations . . . . 6 folds ................................... 37 gabbro ................................. 23 gneissic aplite .......................... 34 granite gneiss .......................... 34 pegmatite ........................ 34 Gold Hill—Bighorn road, mafic inclusions 20 Gold Hill quadrangle .................. . . . 7 quartz diorite ........................... 17 Page Golden Gate Canyon, pegmatite ............. 34 Granite .................................... 4 Granite gneiss .............................. 34 Granodiorite ............................... 4, 20 Gross Reservoir, lineation trends ............. 7 H Hematite .................................. 81 Boulder Creek Granodiorite .............. 51 Hornblende ............................. 6, 23, 48, 64 Boulder Creek Granodiorite ........ 8, 17, 38, 51, 71 in lamprophyres ........................ 20 in mafic inclusions ....... 20 Hornblende diorite ........... 20, 23, 25 chemical trends . . . . 50 Hornblende gneiss . ........ 3, 23 Hornblendite ............. 6, 20, 25 Hydrogarnet ............................... 83 I Idaho Springs—Balaton cataclastic zone, con- tact relations ................... 6 Idaho Springs- Ralston shear zone ........... 57 Ilmenite ............................. 81 Inclusions, Boulder Creek Granodiorite . . . 17 mafic ............................ 17, 38 allanite .............. . 81 Boulder Creek Granodiorite . . i. 69, 73, 77, 79 chemical trends ..................... 48 Iron oxides ................................. 81 Boulder Creek Granodiorite .............. 51, 64 J, K Jenny Lind syncline, folds ................... 37 J ointing ................................... 37 Kaolinite .................................. 6 L Labradorite ................................ 52, 77 Lakewood Reservoir, pyroxenite . . 23 Lamprophyre .............................. 17, 20 allanite ................................ 82 Lamprophyre dike, Boulder Creek Granodiorite . 69, 73, 79 Lanthanum, in mafic inclusion ............... 50 Twin Spruce Quartz Monzonite . . 51 Lead ................... 81 in quartz monzonite ............ . . 51 Twin Spruce Quartz Monzonite .......... 69, 79 Lefthand Canyon, granite gneiss ............. 34 pegmatite .............................. 34 prehnite ................................ 83 Lenses .............. 34 Lineations, mafic rocks . . . 22 Los Lagos lens ...... . 81 pyroxenite ............................. 23 M Magma, emplacement ....................... 7 Boulder Creek Granodiorite . . 51 Magnesium, in lamprophyre ................. 48 87 88 Page Magnetite ................................. 81 Boulder Creek Granodiorite . 51. 72 Magnetite ore ................. 8 Magnolia ........................... . 4 Manganese. Boulder Creek Granodiorite ...... 51 Metagabbro ................................ 23 Metamorphism ............................. 37 hydrothermal ........................... 51 Microcline ............... . 34. 45 Boulder Creek Granodiorite ..... . 8, 17. 77 Twin Spruce Quartz Monzonite . 69, 79 Microcline gneiss ........................... 3. 6 Microperthite. Boulder Creek Granodiorite . . . . 8, 77 Molybdenite ............................... 81 Monazite .................................. 81. 83 Boulder Creek Granodiorite .............. 64, 69 Twin Spruce Quartz Monzonite .......... 69 Mt. Evans batholith ............... 3, 37 Mt. Pisgah, contact relations . . . 7 Muscovite ..................... 25, 34. 8.? Boulder Creek Granodiorite .............. 51, 77 Twin Spruce Quartz Monzonite .......... 29 Myrmekite. Boulder Creek Granodiorite ...... 51, 77 Twin Spruce Quartz Monzonite .......... 77 N Nederland, contact relations ................. 6 quartz monzonite .......... 27 Nederland quadrangle. gabbro . . 23 pyroxenite ................ 23 quartz . . .. . . 80 Nederland syncline, folds .................... 37 Nederland-Tungsten district. Laramide min~ eralization ...................... 6 Neodymium ................................ 81, 83 in mafic inclusions .............. ' ........ 50 Twin Spruce Quartz Monzonite .......... 69 Nickel .................................... 45, 50. 73 in mafic inclusions . . 50. 73 in quartz monzonite . . . 51 O Oligoclase, Boulder Creek Granodiorite ....... 52 Olivine .................................... 23 Ores .......................... . 23, 25, 34. 80, 83 Boulder Creek Granodiorite. . . ........ 64. 72. 73 Twin Spruce Quartz Monzonite .......... 29, 69 Origin ..................................... 62 Orthopyroxene ............................. 23 Overland Mountain ......................... 7 Overland pluton. described . . . 7 Oxides .................................... 38. 64. 69 INDEX Page P Peak to Peak highway. contact relations ...... 6 Peg'matite ............................ . . . 6, 20. 34 Twin Spruce Quartz Monzonite . . 27 Piedmontite ........................ . . . 83 Pikes Peak Granite ......................... 3 Pinecliffe, lineation trends ................... 7 mafic inclusions ........................ 20 Pisgah pluton .............................. 7. 65. 82 Plagioclase ................ 6. 23. 25. 34. 48. 57. 64. 81 Boulder Creek Granodiorite ........... 8, 17, 51. 73 in quartz monzonite ............. . . . 51 Twin Spruce Quartz Monzonite . . . 69, 77, 79 Potassium ......................... . . . 48 in lamprophyre ......................... 48 Potassium feldspar ......................... 7, 45, 57 Boulder Creek Granodiorite . . . . 8, 17, 51, 64, 73, 77 Twin Spruce Quartz Monzonite .......... 79 Prehnite ........................... 83 Pyrite ... . 81. 82 Pyroxene .......... . 23, 25, 69 in lamprophyre ......................... 20. 73 Pyroxenite .............................. 6. 20. 23, 25 chemical trends ......................... 50 Q. R Quartz ........................... 6, 23, 34, 64. 79, 83 Boulder Creek Granodiorite ........ . . 8, 17 in lamprophyre ............. 20 in mafic inclusions ...................... 20 Twin Spruce Quartz Monzonite .......... 69, 79 Quartz diorite .............................. 4, 20, 25 Quartz monzonite .......................... 4. 26 Quartzite .................................. 3, 6 Ralston Buttes. quartz monzonite ............ 29 Rollins Pass ................................ 6 Rosalie lobe ................................ 4 S Salina—Gold Hill road, mafic inclusions ....... 20 Samarium ................................. 83 Scandium . . 50 Sericite ........................ 25, 83 Boulder Creek Granodiorite . . . . . 51 Serpentine ................................. 23 Severance lens ............................. 81 pyroxenite ............................. 25 Sillimanite ................................. 6, 34 Sillimanite-biotite gneiss . . . . 3. 17 Sills ....................................... 20 Page Silver Plume Quartz Monzonite .............. 3 biotite ................................. 69 Sodium .................................... 48 South Boulder Creek. contact relations . . . 6 Sphene ...................... . . . . 8, 25. 81 Boulder Creek Granodiorite . 17. 51, 64, 72 in lamprophyre ......................... 20 Strawberry batholith ....................... 37 Strawberry Lake batholith .................. 3 Strontium, Boulder Creek Granodiorite ....... 73, 77 Twin Spruce Quartz Monzonite .......... 51. 79 Structure .................................. 35 Studies. previous ..................... 1, 2 Sugarloaf Mountain, contact relations . . 6 Summary .................................. I T Thorodin Mountain. mafic inclusions ......... 20 Tremolite ............................ 25 Tremont Mountain. contact relations . . . 6 lineation trends ................. . . 7 ’I‘rondhjemite .............................. 73 Twin Spruce Quartz Monzonite .......... 27 Tungsten mining district, quartz monzonite . . . 27 Tungsten quadrangle ....................... 39 quartz diorite ...... 17 quartz monzonite . . 27 Severance lens .......................... 25 Twin Spruce Quartz Monzonite. chemical trends .......................... 50 defined ................................ 4 mineralogical trends .................... 50 V. W, X Vanadium .............. . . 45 in quartz monzonite ..................... 51 Ward quadrangle ........................... 7, 17 Xenotime .............................. 64. 69. 81. 83 Y, Z Yttrium .................................. 73. 81, 83 in quartz monzonite ..................... 51 Zinc, Twin Spruce Quartz Monzonite ......... 69 Zircon ............................. 25, 81 Boulder Creek Granodiorite ...... 17 Twin Spruce Quartz Monzonite . . 69 Zirconium .................................. 81 in mafic inclusions ...................... 50. 73 Twin Spruce Quartz Monzonite .......... 51 or Us. GOVERNMENT PRINTING OFFICE: 193m577.129/57 ) 'J UNITED STATES DEPARTMENT OF THE INTERIOR . PROFESSIONAL PAPER 1101 PLATE 1 GEOLOGICAL SURVEY 105°15' 40o15' 105°52'30" 45' 30 40°15, U.s_. DEPOSiToRY //~ \ /\ /\//I \\ / \ \ \ ( \ \_ \ \ \ \ \ \ \ I \ m \ \ / 7 LTD \V/ \\\ / / w) \7 / //\I / / / / r I I / / I \M ,/ // I /—*\ \ / // \\\ C\ / /OVERLANOI \ \ 94/ I MTN \ \ //TV\] \ PLUTONJJ \ \T / / \ / ) \ / \ / \ / \ / STRAWBERRY LAKE \\ // BATHOLITH <9 ) 3* z / (g / /7 $3 / $3 ( / / <9 R“ / /\ ($9 / / $6 99 Q / / / Co Q \ \ r <3 BOULDER CREEK (9 b _ BATHOLITH 40°OO’ M 40000, O \ uCARIBOU \ PLUTON ' r e \@ j , .6 /‘ QQQ‘ <83 \ ‘5 , Reservoir \ / \\ é; Area shown 0 $8 \ V _-" - H \/ \Q on plate 2 \\ LOS LAGOS \‘\. -- . i \ / LENS _ ; a » S5 . % - __ _ SEVERANCEN ~ \B Q I E y 0 J0 II 0 fl% V n / I) ,. ' V / I 4., I e of I 5 § 5' ()6 Ia \ éfi‘y \QSQ 0 OI 69/ $8 \ '4 (<1 ['1 MT PISGAH I \ Q & PLUTON / BALD MTN PLUTON M if D , i I ’ ' ”A; . j/F/ / i 45' «A‘fl '1 f 45 U‘. 0 l \\‘ I //\.. a ) / / I / y// /,, / /~/ I x, S/ {$9 /§ ,QLL QT \\\ \\ \_/ I J\/W MOUNT EVANS \ BATHOLITH \ \ \ \\ ‘7 m/ EXPLANATION / m / - Mafic bodies (gabbro, pyroxenite, diorite, ) 1L / / homblendite) I A A\“ / VF W / I I { (// \ fMC\ Idaho Springs—Ralston cataclastic zone, from A \fit/ W I Tweto and Sims (1963) r / \\ - ROSAUE ,AV,\ \ \7 ) \\‘ LOBE T L“\ I¥ /L\ J Area from Levering and Goddard (1950) \"/ ‘\ J \ PM”) \/ ”\—/ CD Area from Wrucke and Wilson (1967), Gable (1969, 1972, 1977), Gable and Madole (1976), Taylor (1976), Sims and Gable (1967), Braddock (1969), Pearson and Speltz (1975) 39030' I 105°52’30" 45’ 30' 1053195730, .!?‘/g 7—4 H o 2 4 6 8 10 KILOMETERS I——i I—i l—I E E COLORADO APPROXIMATE MEAN DECLINATION,1950 Location of study area GENERALIZED GEOLOGIC MAP OF BOULDER CREEK GRANODIORITE WITH EMPHASIS ON COGENETIC MAFIC ROCKS, IN THE VICINITY OF THE BOULDER CREEK BATHOLITH, CENTRAL COLORADO c: U 5 GOVERNMENT PRINTING OFFICE: 1980” 677.!29/57 ‘ ‘ 11.8 ) .\ . DEPOSIT-CRY AUG 6 13;; of UNITED STATES DEPARTMENT OF THE INTERIOR PROFESSIONAL. PAPER 1101 GEOLOGICAL SURVEY W”, PLATE 2° , 1048,30. “Mam.“ “Home, ‘ an ”“13"?” 2230” ”Twill" nmw 1024130730,, 2'30” a 2 1. \ M I y 1 A, 7, _ , ‘ , , ‘ i ,, , _ __ 1 , _ 7‘ , I” _ A , / ‘ 2,30,. Jo m Axutuxo GLACIER z m 40°00' 40°00 umsmu 2 a 57,30" , ’ 1‘ \ ,7 \ 7,, [j ./ :77 - ’ ,, 1, x .7 _ ' , ’ - r '. " N: ,‘ _‘ I / x I, 3730 u-nsnu , [are ._ Moumin‘r‘f'," - com 9: mum rcrvv mm a m 05 CORRELATION OF MAP UNITS v A .t” i, * «TKI - 4 \x , ‘ V Rf} Tertiary t0 Cretaceous conformity st kYJ PALEOZOIC Unconformity - } Intruded about 1,440 my ago WJ Precambrian Y Intruded about ' , 50’ 1,700 my. ago \F PRECAMBRIAN Precambrian X Layered rocks; no stratigraphic order implied CONTACT—Dotted where concealed DESCRIPTION OF MAP UNITS FOLDS—Showing approximate trace of axial surface. Arrows show direction of plunge of axis INTRUSIVE ROCKS ‘ INTRUSIVE ROCKS UNDIFFEREN’I‘IATED (TERTIARY To Swim..." ‘ . , ' ~ Mk , I -‘ V , j 1' i“ I _ ‘- g l ” ; a. " n , - W ' , 3 Overturned antiform CRETACEOUS) , -- r ‘ : _ _“fi ‘ 7 ‘ _ y ' pfl TV§_*~‘E, ,7 r ff; ‘ “ 3 _ ‘ SILVERPLUME QUARTZMONZONITE(PRECAMBRIANY) ' ’ i ' ' ‘ ‘ ‘ " ’ I W ' H ’ ” ’ " ‘0 ' 0‘ ‘0 ‘ GRANITE GNEISS AND PEGMATITE (PRECAMBRIAN Y AND X) TWIN SPRUCE QUARTZ MONZONITE (PRECAMBRIAN X) GABBRO, DIORITE, HORNBLENDITE (PRECAMBRIAN X) n BOULDER CREEK GRANODIORITE (PRECAMBRIAN X) METASEDIMENTARY ROCKS QUARTZITE (PRECAMBRIAN X) BIOTITE GNEISS UNDIFFERENTIATED (PRECAMBRIAN X) Antiform 4730" 4730" Overturned synform BEARING AND PLUNGE OF MINOR FOLDS—Symbol shows plan view of fold STRIKE AND DIP OF FOLIATION Inclined Vertical BEARING AND PLUNGE OF LINEATION—Lineations are de— _ fined by alined minerals, mineral streaks, and axes of small 59’ Silver Plume lenses folds. Symbol may be combined with foliation symbol at MICROCLINE GNEISS (PRECAMBRIAN X) T30int 0‘ Observation SEDIMENTARY ROCKS W FAULT—Dashed where approximately located; dotted where SEDIMENTARY ROCKS, UNDIFFERENTIATED concealed. Sheared pattern indicates broad zone of shear— (PALEOZOIC) ed rock commonly iron stained yellowish brown,or reddish brown omvzmmu-nsurs :5) u m cm (,,_ \ 39°45 ' I " WWW“:- ‘ I .. I ' I V I ‘ I H ‘ ' A ‘L A I L I I 39mg 105037.30” 53413331: on 30 2730' 2230" 10915, - 1 o SCALE 1:48 000 Base from US. Geological Survey 33/5 v M m I 1 Ward, Go'd Hi”, 1957, Bou'der' 1971’ 1 1b 0 1|. 2 3 MILES I Q U.5. GO ERN E PR NTING OFFICE: 950—677-129/57 Nederland,'Tungsten. Central City, ':‘ H H H H ' ' 1 COLORADO Blackhawk, 1972, Eldorado Springs, 1975, 1 .5 o 1 2 Ralston Buttes, 1976 3 KlLOMEl'ERS H H H H H ,____.____i L Location of study area TRUE NORTH CONTOUR INTERVAL40 FEET ‘§§§Eflfliéi.'l:3 NATIONAL GEODETIC VERTICAL DATUM or 1929 GENERALIZED GEOLOGIC MAP OF THE BOULDER CREEK BATHOLITH AND SATELLITIC PLUTONS, CENTRAL COLORADO 96 ‘°°‘Integrated Tarrain Mapping With Digital Landsat Image ‘ Prepared in cooperation with the Queensland Department of Primary Industries, Australia Integrated Terrain Mapping With Digital Landsat Images in Queensland, Australia By CHARLES J. ROBINOVE GEOLOGICAL SURVEY PROFESSIONAL PAPER 1102 Prepared in cooperation with the Queensland Department of Primary Industries, Australia UNITED STATES GOVERNMENT PRINTING OFFICE, \VASHINGTON : 1979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataoging in Pubication Data Robinove, Charles Joseph, 1931— Integrated terrain mapping with digital Landsat images in Queensland, Australia. (Geological Survey professional paper ; 1102) Bibliography: p. 1. Land use—Australia—Queensland—Classification. 2. Cartography—Data processing. 3. Landsat satellites. 1. Queensland. Dept. of Primary Industries. II. Title. III. Series: United States. Geological Survey. Pro- fessional paper ; 1102. HD1039.Q83R6 333.7'09943 78—11682 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20102 (Paper cover) Stock No. 024—001—03157-4 FIGURE 5"!“ 99“???" 9° 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. CONTENTS Page Abstract _________________________________________________________________ 1 Introduction ______________________________________________________________ 1 Acknowledgments _________________________________________________________ 2 Methods of terrain classification ___________________________________________ 2 Hypotheses being tested __________________________________________________ 3 Characteristics of Landsat data ___________________________________________ 4 The Queensland experiment _______________________________________________ 5 Wet season image analysis ____________________________________________ 6 Subscene 1 _______________________________________________________ 6 Subscene 2 _______________________________________________________ 12 Subscene 3 _______________________________________________________ 13 Contrast stretching ___________________________________________ 16 Multispectral classification ____________________________________ 17 Correspondence of multispectrally classified themes with terrain features ___________________________________________________ 19 Extrapolation of partial scene classifications to a full Landsat scene __ 28 Dry season image analysis _____________________________________________ 29 Unsupervised classification of a full Landsat scene _____________________ 29 Conclusions ______________________________________________________________ 31 Selected bibliography _____________________________________________________ 33 ILLUSTRATIONS Methods of mapping used with Landsat data ______________________________________________________ Land system map information was available for alm0st all of the area covered by the Landsat image used ______________________________________________________________________________________ Landsat Image 1365—23570 (dry season) showing the four bands __________________________________ Color composite of Landsat Image 1365—23570 showing dry season conditions (July 1973) ___________ Landsat Image 1563—23530 (wet season) showing the four bands __________________________________ Color compOSite of Landsat Image 1563-23530 showing wet season (February 1974) conditions ______ Subscene 1 is displayed as a composite of bands 4, 5, and 7. All pixels in the 512 by 369 area are dis- played. The land systems map is overlaid on the image ________________________________________ The Arrabury and Santos land systems are multispectrally classified ______________________________ Arrabury and Santos land systems. Aerial oblique photos from 300 meters altitude __________________ Subscene 2, a 1022 by 738 pixel array with 25 percent of the pixels displayed, is overlaid with the land systems map and is used for multispec‘tral classification ______________________________________ Six category classified map of subscene 2 With land systems map overlay __________________________ Histograms of the six classes in subscene 2 which are mapped in figure 11 ________________________ Standard color composite of subscene 3 and contrast-stretched composite ____________________________ Histograms of the unstretched and contrast-stretched subscene 3 _________________________________ Land system map of subscene 3 _________________________________________________________________ Seven multispectrally classified themes in subscene 3 _______________________________________________ Parallelepiped classification and separability of seven themes in the northwest subscene 1365—23570 -__ Seven themes classified in subscene 3 with examples of interpretive boundaries around homogeneous classes and heterogeneous classes ____________________________________________________________ Classification of the upland areas of Landsat scene 1563—23530, February 6, 1974 ___________________ Classification of the alluvial valley of Cooper Creek, Landsat scene 1365—23570, July 25, 1973 ________ Unsupervised classification of sampled Landsat image 1563—23530 _________________________________ III Page 5 16 18 2O 22 23 24 25 27 28 30 32 IV TABLE 9° CONTENTS TABLES Lower radiance boundaries (LB) and upper radiance boundaries (UB) of training sets in the Arra- bury land system in subscene 1 and number of pixels classified with large, medium, and small training sets _______________________________________________________________________________ Statistical summary of seven themes classified for subscene 3 _____________________________________ Bands in Which separability is produced between pairs of themes in the northwest subscene 1365—23530 Correspondence of multispectral themes with mapped land systems _________________________________ Page 12 19 19 26 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES IN QUEENSLAND, AUSTRALIA By CHARLES J. ROBINOVE ABSTRACT Mapping with Landsat images usually is done by selecting single types of features, such as soils, vegetation, or rocks, and creating visually interpreted or digitally classified maps of each feature. Individual maps can then be overlaid on or combined with other maps to characterize the terrain. In- tegrated terrain mapping combines several terrain features into each map unit which, in many cases, is more directly related to uses of the land and to methods of land manage- ment than the single features alone. Terrain brightness, as measured by the multispectral scanners in Landsat 1 and 2, represents an integration of reflectance from the terrain features within the scanner’s instantaneous field of view and is therefore more correlatable with integrated terrain units than With differentiated ones, such as rocks, soils, and vegetation. A test of the feasibilty of the technique of mapping in- tegrated terrain units Was conducted in a part of south- western Queensland, Australia, in cooperation with scientists of the Queensland Department of Primary Industries. The primary purpose was to test the use of digital classification techniques to create a “land systems map” usable for graz- ing land management. A recently published map of “land systems” in the area (made by aerial photograph interpreta- tion and ground surveys), which are integrated terrain units composed of vegetation, soil, topography, and geomorphic features, was used as a basis for comparison with digitally classified Landsat multispectral images. The land systems, in turn, each have a specific grazing capacity for cattle (ex- pressed in beasts per km”) which is estimated following analysis of both research results and property carrying capacities. Landsat images, in computer—compatible tape form, were first contrast-stretched to increase their visual interpretabil- ity, and digitally classified by the parallelepiped method into distinct spectral classes to determine their correspondence to the land systems classes and to areally smaller, but readily recognizable, “land units.” Many land systems appeared as distinct spectral classes or as acceptably homogeneous combinations of several spec- tral classes. The digitally classified map corresponded to the general geographic patterns of many of the land systems. Statistical correlation of the digitally classified map and the published map was not possible because the published map showed only land systems whereas the digitally classified map showed some land units as well as systems. The general correspondence of spectral classes to the in- tegrated terrain units means that the digital mapping of the units may precede fieldwork and act as a guide to field sam— pling and detailed terrain unit description as well as meas- uring of the location, area, and extent of each unit. Extension of the Landsat mapping and classification tech- nique to other arid and semi-arid regions of the world may be feasible. INTRODUCTION Maps and descriptions of “land” as a resource in order to provide basic information on its capabilities and limitations are presented in numerous ways. These include geologic maps, soil maps, vegetation maps, topographic maps, water resource maps, and a multitude of other thematic maps. Each one is usually specific to a single scientific discipline or to a single factor that characterizes the land. A method of describing and characterizing land which is Wide- ly used throughout the world, but is only minimally used in the United States, is the Australian land systems approach. The Australian approach characterizes land as “* * * the land surface and all of its characteristics of importance to man’s existence and success. It is the integration of all these factors rather than mere likeness or unlikeness in some of the more observ- able characteristics which determine the similarity or dissimilarity of areal subdivisions in respect to land use potential” (Christian and Stewart, 1968, p. 238). Christian (1958) and Christian and Stewart (1968) provide a complete description of the phi- losophy, methods, and results of surveys using the Australian land systems approach. Since 1972, Landsat satellite imagery has been available and has been used for many types of land surveys. The imagery is uniform, repetitive, avail- able worldwide, and is eminently suitable for recon- naissance investigations of large areas. It has the 2 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES further advantage of being ideally suited for pro- viding basic map data for surveys conducted by the Australian land systems approach. The purpose of this report is to: 1. Describe a land mapping basis by which land can be classified, described, and mapped by the use of Landsat imagery. 2. Relate the description of land mapping by Land- sat imagery to land system mapping by the well established Australian methods. 3. Describe a land system mapping experiment us- ing Landsat images in southwestern Queens- land, Australia, where conventional land sys- tem mapping was being done in 1975 and 1976. 4. Compare conventional and experimental methods of land mapping. 5. Recommend operational methods for use of Landsat imagery for land system mapping. ACKNOWLEDGMENTS The author is grateful for the advice and assist- ance given by many colleagues during this study. Special thanks go to William A. Fischer for many stimulating discussions of integrated terrain map— ping principles. The cooperation of Noel Dawson, Desmond Boyland, Keith Hughes, and John Mills of the Queensland Department of Primary Industries was invaluable in the field and the office, and by correspondence. Since this study is based on their original mapping and descriptions of the terrain of southwestern Queensland, their help and advice made the study possible. The staff of the Data Analysis Laboratory at the EROS Data Center, in- cluding Fred Waltz, Dave Greenlee, Charlotte Muchow, and Charles Nelson made possible the analyses reported here. David Carneggie of the EROS Data Center provided an especially critical and helpful review of the manuscript. METHODS OF TERRAIN CLASSIFICATION Terrain classification, whether for general or spe- cific purposes, may be based on genetic, parametric, or landscape criteria. Each of these has advantages and disadvantages related to mapping methods, for- mat for display of map information, and usability by the reader of maps. Mabbutt (1968) has defined and explained the three approaches and has wisely predicted “Ultimately, there comes a level of investi- gation at which the greater precision and reliability of the parametric approach are needed and to the extent that improvements in (remote sensor) scan- ning render the method more comprehensive, its in- herent advantages of reliability will be exploited even at the reconnaissance (landscape) level of in— vestigation.” (Mabbutt, 1968, p. 26). Genetic methods of terrain classification are de- scribed by Mabbutt (1968, p. 12) who states, “At- tempts to arrive at distinctive land units by repeated subdivision on the basis of causal environmental fac- tors may be grouped as the genetic approach.” Normal geologic mapping and geomorphological mapping are examples of the genetic approach. Maps made on the basis of genetic classification do not generally indicate land potential or land capability and, although such information can be derived in part from them, such derivation generally requires large amounts of corollary information from other sources and a reasonable means of correlating such information. Parametric classifications are defined by Mabbutt (1968, p. 21) as “* * * the division and classification of land on the basis of selected attribute values.” A slope map, depth-to-water-table map or lithologic map are examples of parametric maps. The reflection of light from the land surface can be considered as an attribute of the land, and thus the reflectance in several wavelength bands as measured by the multi- spectral scanner in Landsat can be mapped as “at- tributes” or “parameters.” Individual parametric maps are generally prepared for a specific purpose of land development and management and may be difficult to correlate quantitatively or even qualita— tively with other parametric maps. Correlation is generally done by means of map overlays. Maps of a given area may be made at different times by specialists in different disciplines, and at different scales. Such maps are often difficult to correlate to obtain information bearing on a specific develop- ment problem, although they may individually con- tain important and useful information. The parametric approach provides, in its most rigorous application, a numerical terrain measure— ment which is calibratable and generally repeatable. This approach is more objective than landscape map- ping but is of necessity more expensive and time consuming and, therefore, limited in application to large areas. The landscape approach classifies land, particular- ly at the reconnaissance level, on the basis of a com- plex of factors and attributes. Mabbutt (1968, p. 16) states, “The land complex as a whole is the object of study, even where a particular attribute may be of prime interest to a land classifier.” HYPOTHESES BEING TESTED 3 Two major factors account for the success of the landscape approach; the use of integrated mapping units which combine geomorphic features, soils, and vegetation as the basis for mapping and the forma- tion of an integrated mapping team consisting of specialists in several disciplines working in concert to produce the landscape maps and land descriptions. The approach is well described in two books, “Aerial surveys and integrated studies,” (UNESCO, 1968) and “Land evaluation” papers of a Commonwealth Scientific and Industrial Research Organization of Australia (CSIRO) symposium organized in coop- eration with UNESCO, (Stewart, 1968). Both books are listed in the references in this report and the reader is referred to them for details of the map- ping, philosophy, methods, and results. The landscape approach, developed by the CSIRO is now readily utilized by the Australian States and by workers in the United Kingdom and other coun- tries. Similar parallel approaches are used in the Soviet Union (Mitchell, 1973). Terrain classification in the landscape approach is based on four hierarchical categories as proposed by Christian and Stewart (1968). A site is part of the land surface which is for all practical purposes, uniform throughout its extent in landform, soil, and vegetation. A land unit is usually a group of related sites which have a particular landform within the land system and wherever the land unit occurs again it would have the same association of sites. A land system is an area or group of areas, throughout which there is a recurring pattern of topography, soils, and vegetation. A land zone is a grouping of genetically related land systems. The landscape approach always involves some sub- jectivity in the assignment of each area of land to a specific unit, system, or zone—but particularly where an area is described as being a mixture of two or more systems or where two areas belonging to the same system contain identical land units but in different proportions. In the approach used by the Queensland Depart- ment of Primary Industries in the arid lands, the attribute of prime interest is the grazing capacity of the land (beasts per km 2) in wet and dry years and the reaction of the land to grazing pressure, and yet the landscape approach is particularly suitable because the ultimate numerical parameter of interest can only be arrived at by integration of a number of other attributes, some of which are difficult or impossible to measure quantitatively. The main in- terest is how the land will react or how it has re- acted to different land uses, particularly grazing, and how productivity might be increased or de- creased to ensure long term stability. This is the basis for property planning. Remote sensing has the capabiilty to provide some numerical measurements economically and efficiently for very large areas and thus is capable of forming a bridge between the objective (parametric) and subjective (landscape) approaches. The hypotheses and experiment described in this report are an application of the parametric (quan- titative) methods to the landscape approach. HYPOTHESES BEING TESTED One major and several minor hypotheses have been formulated and tested in this research on ap- plication of Landsat images to integrated terrain mapping. The major, and fundamental, hypothesis governing this study is that the radiance measured in a single Landsat picture element is an integration of the radiance of all features within the 0.45 ha area measured on the ground, such as vegetation, soil, rock, water, and artifacts, and a group of pixels therefore is statistically indicative of an integrated mapping unit that can characterize the similarities and differences of natural terrain units. Since the Australian land systems approach is based on in- tegrated terrain units, the correspondence between maps made by the two systems should be high. Minor hypotheses are that the upland terrain units in the study area should be more readily differentiable in the wet season than in the dry and that repetitive monitoring can characterize changes in land systems that are of importance in land management deci- sions. Indeed, it is quite important to analyze data in the right year, usually one in which vegetation production is at a maximum. It is further hypothesized that spectrally homo- geneous units seen in Landsat images may actually be coherent terrain units (and consequently usable land management units) and can be properly named and described. This is the antithesis of the normal mapping method of deciding on a terrain inventory classification which will be used in a given area and then mapping and describing the features in accord- ance with the selected classification. The combination of the integrated radiance meas- urement-integrated mapping unit may logically be extended to land inventory units, and from that to land capability units. One would not expect that the integrated units would correspond exactly in bound- aries or descriptions with those mapped by the Australian land system approach or by other similar 4 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES methods, but they may well be reasonable and usable units. The Australian land system approach utilizes mapping units which include geomorphic features, soils, and vegetation in the description of each unit, rather than separate mapping of each category of information. Each Landsat pixel, which has the di- mensions of approximately 59x79 meters on the ground (0.45 ha), measures the radiance of the terrain in four bands (green, red, and two bands in the near or reflected infrared). Because the meas- ured radiance is that of all features of the ground, it is an areally integrated radiance unit. The major question is then: what is the relationship of an in- tegrated radiance mapping unit (pixel) to the in- tegrated attributes of the terrain mapping unit? Be- cause the Australian land systems approach is a widely used one which utilizes integrated terrain units, this experiment is designed to see how close- ly Australian land systems maps can be made on the basis of integrated radiance measurements. CHARACTERISTICS OF LANDSAT DATA Landsat satellites provide worldwide multispectral images on a repeated basis. Landsat 1 operated be- tween July 1972 and January 1978. Landsat 2 began operation in January 1975. The major sensor on both Landsats is a multispectral scanner which pro- vides images of 185><185 km areas on an 18 day cycle. Each scene consists of four separate images: Image Spectral Interval Spectral Range Band 4 ____________ Green ______________ 500nm—600am Band 5 ____________ Red _________________ 600um—700am Band 6 ____________ Infrared ____________ 700ym—800am Band 7 ____________ Infrared ____________ 800am—1,100am Each band of each image set consists of 2,340 scan lines (perpendicular to the orbital track) and 3,240 picture elements (pixels) along each scan line, a total of 7.58><10 0 pixels per band per frame. Each pixel represents an area of approximately 0.45 ha on the ground. One hundred twenty-eight radiance levels (7 bits) are recorded in bands 4, 5, and 6, and 64 radiance levels (6 bits) are recorded in band 7. The images may be produced in photographic form and analyzed either by photointerpretive techniques (including photo-optical image enhancement) or may be pro- duced as computer-compatible magnetic tapes (CCT) and be analyzed by digital techniques. Fur- ther details of the Landsat image characteristics may be found in the “ERTS Data Users Handbook” (General Electric, 1972). Landsat images in photographic form can be en- larged for practical purposes to scales as large as 1:100,000. Larger scales have been used by some investigators, but they require highly accurate photographic equipment and quality control. Digital images can be displayed at any reasonable scale, but the smallest area for which data is available is 0.45 ha. Once an image has been digitally enlarged and displayed so that each pixel can be seen by the eye, no further information is gained by further enlarge— ment, but the images can be matched to larger scale maps. Landsat images are ideally suited to medium and small-scale mapping because of their uniformity over large areas. Three methods of mapping with Landsat images are commonly employed. Each has its advantages and disadvantages which depend upon the purpose of the mapping, the skill and experience of the mapper, the interpretive and computer facilities available, and the cost. Figure 1 shows schematically the three methods. The basic method (A) involves visual interpretation of the photographic images in color composite form at the desired scale. Interpretation for some pur- poses from the black and white prints is preferred by some interpreters but in general the color images are much more useful. Normal photointerpretive methods using photographic tone, texture, pattern, and spatial association are used, keeping in mind the small scale and large area portrayed. The second method (B) involves enhancement of Landsat images to increase their contrast for greater discriminability and recognizability of features, ratioing of spectral bands of images to locate new interpretable combinations of radiance values, and scaling of brightness values of individual bands, which is a form of contrast enhancement. Contrast stretching can be done either photographically or digitally, but the digital processes can be calibrated and repeated more precisely and accurately than the photographic processes. The third method (C) uses the radiance values measured by the multispectral scanner to classify the terrain and produces graphic maps (rather than solely enhanced images). Landsat computer-com- patible tapes are utilized in a digital computer usually with an interactive image display. Succes- sive iterations of radiance classifications are made and checked with ground information until the analyst is satisfied that a satisfactorily accurate map has been made and it is ready for field checking. A number of algorithms have been developed for mul- tispectral classification ranging from the simple - THE QUEENSLAND EXPERIMENT 5 LANDSAT IMAGE BASE MAP FILM POSITIVE PHOTOGRAPHIC PRODUCT FOR VISUAL INTERPRETATION COLOR + OVERLAY COMPOSITE —__J BASE MAP FILM POSITIVE LANDSAT —_» INPUT SCANNER CCT CONTRAST STRETCH PHOTOGRAPHIC PRODUCTS FOR MULT'SPECTRAL RATIOING INCREASED INTERPRETABILITY OF IMAGE ANALYZER B SCALING TERRAIN FEATURES BASE MAP FILM POSITIVE ——>— INPUT SCANNER CONTRAST — PHOTOGRAPHICALLY PRODUCED MAPS MULTISPECTRAL STRETCH MULTISPECTRAL _ALPHANUMERIC THEMATIC MAFPSS IMAGE ANALYZER RATIOING CLASSWCATION —DOT PRINTOUT THEMATIC MA C TRANSFOR- — HISTOGRAMS MATION —THEME AREA SUMMARIES A. INVOLVES SIMPLE VISUAL INTERPRETATION OF LANDSAT PHOTOGRAPHIC PRODUCTS WITH A FILM POSITIVE BASE MAP OVERLAY FOR LOCATION B. INVOLVES DIGITAL LANDSAT IMAGE PROCESSING TO CREATE PHOTOGRAPHIC PRODUCTS WITH INCREASED COLOR CONTRAST TO IMPROVE VISUAL INTERPRETABILITY C. INVOLVES DIGITAL LANDSAT IMAGE PROCESSING FOLLOWED BY MULTISPECTRAL CLASSIFICATION TO PRODUCE THEMATIC MAPS OF LAND FEATURES FIGURE 1.—Methods of mapping used with Landsat data. parallelepiped method to the more complex maxi- mum likelihood classification method. Images and maps shown in this report were pro- duced by the General Electric Image 1001 multi— spectral analysis system at the EROS Data Center, Sioux Falls, S.D., and by the computers and pro- grams of the Laboratory for Applications of Remote Sensing at Purdue University. THE QUEENSLAND EXPERIMENT Recent land systems maps in western Queensland (Division of Land Utilization, 1974) made by aerial photointerpretation and field checking were used as the basis for an experiment in application of Land- sat images to land systems mapping. An area of about 148,000 km 2 was mapped at a scale of 1:500,000 and described by the Queensland Depart- 1Trade names used in this report are solely for purposes of identifica- tion and do not constitute endorsements by the U.S. Geological Survey. ment of Primary Industries. At the time of this project, the map of Part 1 was published, but the map of Part 2 was in manuscript form and was used with permission of the authors. Landsat images were available for the area, and a set of Landsat images that covered portions of both Part 1 and Part 2 areas was selected for detailed analysis. Figure 2 shows the area covered by Landsat images and the available published and manuscript land system maps. Cloud free Landsat images of the western part of the mapped area were taken on March 1, 1973, July 23, 1973, and February 6, 1974. The July 1973 image was taken during the dry season; the Febru- ary 1974 image was taken during a major flood which inundated almost all of the Cooper Creek Valley. These tw0 scenes (1365—23570 and 1563— 23530) were analyzed as being representative of the dry and wet seasons. Unfortunately, the previous 6 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES AREA ANALYZED :5 WITH LANDSAT IMAGES NORTHERN TERRITORY :i__ QUEENSLAND 600 800 KILOMETERS 2 SOUTH AUSTRALIA 400 MILES FIGURE 2.—Land system map information was available for almost all of the area covered by the Landsat image used. Part 1 was published (Division of Land Utilization, 1974) and Part 2 was in manuscript form when the study was done. years were dry years, and it was not until 1975 and 1976 that full development of vegetation occurred. The greater growth of vegetation would have made it easier to separate land units in the silcrete—cov- ered uplands. In the Part I mapped area, 93 land units are grouped into 53 land systems, which in turn are grouped into 10 land zones. For example, the “dune fields” land zone includes eight types of sand-dune fields with varying geomorphic characteristics, vege- tation, and soils. Each of the eight dune-field land systems is a fairly distinctive type, such as longi- tudinal dunes or reticulate dunes, but they may grade into each other without sharp boundaries. Within each of the dune-field systems various land units occur, such as the mobile dune crest, vegetated dune flank, and scalded dune margin. The available land systems maps are at a scale of 1:500,000 and show only the distribution of the land systems. A one-to-one correspondence was not expected between the map and multispectral classification of the Land- sat images. The smallest area classified on the Land- sat images is 0.45 ha (one pixel), too small to be shown on a 1 :500,000-sca1e map. The two Landsat images used in the experiment are shown in figures 3-6 and indicate the locations of the subscenes analysed in the following sections. The image analysis method used is outlined as follows: 1. A selected sample of a Landsat scene was ex- tracted from the digital tape, placed in the analysis system, and displayed on the cathode- ray color-display tube. 2. A film positive of the land systems map of the subscene area was scanned by a television camera, digitized, stored, and registered to the Landsat subscene by visual correlation of ground features. 3. Multispectral supervised parallelepiped classi- fication of the subscene into a number of units was done and the resulting classified image was checked with the land systems map. The process was repeated until a map was obtained that corresponded closely to the land systems map or showed consistently mappable units whose specific identification required field checking. WET SEASON IMAGE ANALYSIS Landsat image 1563—23530 was taken during the wet season and during a major flood of Cooper Creek. It was selected for analysis of the upland areas because the vegetation is more vigorous and therefore more recognizable than during the dry season. Several subscenes of various sizes and the entire scene were analyzed to determine the recog- nizability and separability of various terrain types with various levels of sampling of the image data. SUBSCENE l The initial subscene, an area in the uplands be- tween Cooper Creek and Lake Yamma Yamma was selected for analysis and displayed on the screen. This subscene is a 512 by 369 pixel area, covers 85,000 ha, and was analyzed using every pixel. Fig- ure 7 shows the subscene as it is displayed on the cathode ray tube. It is part of scene 1563—23530 that was taken during a major flood in the valley of Cooper Creek. The northwest and northeast corners of the subscene show the flood water. THE QUEENSLAND EXPERIMENT 7 a. .39 gust» ‘ W» N!“ mww 1 law. my. low . amunw ‘ a! L a 2x923 : $25321!" N 525 “M m ,5‘ R sun my mm assess-"3 v2L fii iii is BAND 4 Ewan! mace: ”W38 BAND 6 EH -I {"10- seam-3e marmwl lulu.” v m~ a gamma 5 525-33? 47 N szswa/cmlsv "is s39 l 504 Eng 52944 uses BAND 5 ”(Wm .w.m~am BAND 7 FIGURE 3.—Landsat Image 1365—23570 (dry season) showing the four bands. The major land systems Within the dune field zone were readily differentiated in this subscene. Figure 8 shows maps of 2 of the land systems as classified from small training sets of 4 to 12 picture elements that were located within each land system. The descriptions of the two land systems as given in the legend of the published map are: Arrabury-Plains with longitudinal dunes 5—19 meters high, some converging and diverging with mobile crests; spinifex shrubby hummock grassland; sandy red earths and red INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES - rnmwusu ¢ MN 4 runny”; IN“) 5 Z é 3 3828—36! El“! 391 £142 62” , 23JUL73 C SZS~4S/EM)-47 N SZS-QB/Elal-Sl nss ? FIGURE 4.—Color composite of Landsat Image 1365—23570 showing dry season conditions (July, 1973) using bands, 4, 5, and 7. THE QUEENSLAND EXPERIMENT 9 WKUNW! so-wa—nl nun—m ,_._m I-uxu'wn —.—.-.. vthlwow 00 Wow)...” vm- ow” Imo .owmm m I “5197?? 35-592mm u méié’fif-‘nn ms was.» _ rmu'lm 3'3““. isms”: m x a v 39157 :1 g~$€f€l¢h57 u szs~ “duh—mu ”run—m! mo‘ml 9m «meow mu » M0; M'E'Q-Mlal-s n asAé'pi’IUqf-ba «as s a an ans 3‘ -a m E ”Hwy-gammy I 55- “(4%), ms 7 2 sm cue u§fi§§~$mm>i~n~n~m msa iii i F1523 ‘7 m .._ Lg _ i .- BAND 6 BAND 7 FIGURE 5.—Landsat Image 1563—23530 (wet season) showing the four bands. earthy sands occur on the interdune area with red siliceous siliceous sands with grey clays and texture contrast soils sands on the dunes. on the interdune clay pan. Santos-Plains with converging and diverging dunes 4—8 _ _ . meters high, sporadic mobile crests, spinifex shrubby hum- From the above descriptions, one mlg’ht n0t 9X- mock grassland; red earthy sands, sandy red earths and red pect to see Significant spectral differences between INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES £2141 ~38! 7 , - , 5:42-39: FIGURE 6.—Co-lor composite of Landsat Image 1563—23530 showing wet season (February, 1974) conditions using bands 4, 5, and Subscenes analyzed are outlined in black. THE QUEENSLAND EXPERIMENT 11 FIGURE 7.—Subscene 1 is displayed as a composite of bands, 4, 5, and 7. All pixels in the 512 by 369 area are displayed. The land systems map is overlaid on the image. the two land systems except those caused by the soils in the clay pans, and yet they are readily dif- ferentiated by classifying the digital Landsat data. Figure 9 shows photographs of the two land sys— tems taken by the author from an aircraft at an al- titude of about 300 meters. The differences in the multispectral data for the two systems are probably due to the shape of the dunes and interdune areas, to differing density of the vegetation, and to the clay pan soils. The conclusion from the analysis of subscene 1 is that two land systems within the same land zone, which are basically similar, can be differentiated on the basis of a multispectral classification. In the initial processes of classification, large training sets were used as the basis for classification. It was found, however, that a closer correspondence betwen the ground information and the classified Landsat data was achieved when smaller trainig sets were used. Table 1 compares the training set sizes and the multispectral data for classification of the Arrabury land systems with three sizes of train— ing sets. Fewer errors of commission were present when smaller training sets were used, and although errors of omission increased slightly with the small training sets, the boundaries of the land system were more rigorously mapped with small training sets than with large ones. 12 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES FIGURE 8.——The Arrabury (left, yellow) and Santos (right, light blue) land systems are multispectrally classified. Although the two land systems are quite similar except for the shape of the sand dunes and the density of vegetation, the multispectral separation is quite distinct. TABLE 1.—Lower radiance boundaries (LB) and upper radi- ance boundaries (UB) of training sets in the Arrabury Land system in subscene 1 and num- ber of pixels classified with large, medium, and small training sets 6372 pixel 364 pixel 40 pixel training set training set training set LB UB A LB UB A LB UB A Band 4 __________ 27—37 11 31 —-36 6 30—34 5 Band 5 _________ 26—53 28 36—49 14 31 —47 17 Band 6 __________ 39 — 62 24 42 — 5-7 16 42 — 52 11 Band 7 __________ 30—46 17 36—48 13 32—44 13 Pixels classified __ 90,132 89,350 57,480 SUBSCENE 2 A 1,022 by 738 pixel area (340,000 ha), including subscene 1 described in the previous section, was selected and displayed with the land systems map as ground control. Owing to the limited memory and display capacity of the multispectral analysis sys- tem, every other pixel in each row and column, or 25 percent of the total pixels in the subscene, could be analyzed and displayed. This provided an op- portunity to test whether or not the classification ac— curacy would be as satisfactory as that achieved in subscene 1 where 100 percent of the pixels were used. Figure 10 shows this subscene in a composite of bands 4, 5, and 7 with an overlay of the land sys— tems map. Training sets ranging in size from 8 to 16 pixels were used to develop 6 non-overlapping cate— gories that covered a high percentage of the land area in the scene. The classified map is shown in fig- ure 11. Note that almost all of the land area is THE QUEENSLAND EXPERIMENT 13 FIGURE 8.—Continued. classified and that there is a reasonably good corre- spondence with the land systems map. Histograms showing the number of pixels of each brightness value for the six classes are shown in figure 12. Many of the histograms have small intervals indicat- ing classes that may be practically unique. Supervised classification produced a map that re- sembles the land systems (ground control map) in its gross characteristics, such as the boundaries of land systems, and correct classification of a large part of each land system. In addition, the use of only 25 percent of the available pixels provided an adequate sampling for analysis. The thematic map should, however, not be considered as a final product because additional interpretive judgment is needed. SUBSCENE 3 The third subscene analyzed was a 1,536 by 1,107 pixel area (about 765,000 ha) covering the north- western quarter of scene 1563—23530 that was analyzed on the multispectral system using as a sample every third pixel in every third line, or one- ninth of the pixels. Image enhancement by contract stretching and multispectral classification were both used. Figure 13 shows the standard color composite of bands 4, 5, and 7, and the contrast-stretched com- posite of the same bands. Figure 14 shows the histo- grams of the two data sets. The contrast-stretched image is displayed on the screen, the image data is classified, and each class is displayed as an overlay on the image. Decisions on the “correctness” of the 14 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES .cofifiowe> mo 365% was wcmodnw was madam 9:6 E555 as mwoCmgwtmw 03853? 95. $3551.. 232: com Scam moaosn @5330 323‘ .wEBmhm 932.830: men—Em vchangnvhgsnduh<$d mabcrm T N E M I R E P X E D N A L S N E E U Q E H T 16 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES FIGURE 10.—Subscene 2, a 1022 by 738 pixel array with 25 percent of the pixels displayed, is overlaid with the land systems map and is used for multispectral classification. classification are made on the basis of both ground information and photointerpretation of the image. The contrast—stretched image is more suitable for this purpose than the image displayed from the raw data. Figure 15 ShOWS the land systems map covering the area of subscene 3. The legend for the manu- script land systems map is not shown because of its detail. The important comparison to be made is be— tween the features that are readily discriminated in the image and the general pattern shown on the land systems map. The purpose of the analysis of subscene 3 was to determine if a satisfactory classi— fication could be achieved using only one-ninth of the pixels. This would be desirable for efficiency in computer mapping and in cartographic display of the classified map units. At a scale of 1:500,000, the normal publication scale of the Australian land sys- tems maps, the area covered by a 3 by 3 pixel array is 0.36 mm by 0.48 mm (approximately 4 ha), which is about the size limit that can be shown carto- graphically and is also at about the limit that can readily be seen on a map with the naked eye. CONTRAST STRETCHING Subscene 3 was displayed on the screen and con- trast stretched to increase the color contrast of the terrain features and to increase their Visual inter— pretability. The contrast—stretch program used was THE QUEENSLAND EXPERIMENT 17 FIGURE 11.—Six category classified map of subscene 2 with land systems map overlay. the proportional frequency distribution program,2 which assigns an equal number of pixels to each un- equal interval of digital counts. The contrast stretch utilizes the entire digital dynamic range and thus increases contrast in each band and subsequently in a multiband color composite. It does not affect the accuracy or precision of subsequent classification. Comparison of the contrast stretched image with the standard digital display (fig. 12) and the land systems map (fig. 15) show that many terrain fea- tures are more highly contrasted with their sur- roundings. The dune fields and sand plains, particu— larly, show in green tones in contrast to the sur- rounding reddish and brownish tones. Distinctions 2Also termed “equal area stretch" or “histogram equalization stretch.” A standard name has not yet been adopted. between alluvial valleys and upland areas are more Visible on the stretched image. Visual interpretation of the stretched image should be done along with mapping of the land sys- tems on the basis of enhanced spectral reflectance, texture, and shape. Because the color contrast is much greater than that of the standard color com- posite, the recognition of some, if not most, land systems should be easier and more reliable. BIULTISPECTRAL CLASSIFICATION Classification of subscene 3 was done by super- vised training methods. A training set was selected that represented a single homogeneous terrain fea- ture and the multispectral analysis system searched 18 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES Jlllllllll I lllILLII ' I ' v 388 OUEPUIEU 388 4 3 LB UB DEL PERK HEM UAR 9 1 32 3’7 6 3 33 4 E 5 t a 34 44 11 a 38 a 12 2 + 3 36 54 19 E. 46 1 30 4 + 4 K 48 23 2 37 7 42 4 + TRAINIm "(ER- 3 PIXELS 4 RMD *ER- 39921 PIXELSI 15 2X)0 TVF’E‘ CHANEL 3 0R EIXHT llllllll|l \l Illllllll] SUBS? Ta DUNEFIELDS llllllllll llllilllll + 3 LB UB DEL PEAK FERN UN? 4 1 38 44 7 5 40 7 3 3 9 a 39 53 1S 5 44 5 15 5 4‘ 3 S4 63 9 G 59 8 6 6 4 4B 56 9 5 51 5 4 7 +- TRAINIM MER- 16 PIXELS 4- RMD MER- 8006 PIXELS( 3 1309 TYPE ML 1 OR EIXHT SUBS" T5 PENINSULA HIGHLANDS . . — 4 5 .Illllll'llT vvvvv Ilvvlvvv » u _ 6 7 E . 1. 8“ OUERUIEU 383 o 8 LB UB DEL PEAK FERN UAR 9 1 33 36 4 3 34 4 1 7 + 2 45 SI 7 2 48 6 2 7 + 3 se 57 6 a 54 8 3 5 + 4 44 46 3 4 4S 0 1 6 + TQQINING NEA- 3 PIXELS ¢ 5288 PIXELS( 2 9’04 ALMD NEA- TVPE‘ ML 8 a? E(X)IT SUBS? T7 DUNE CRESTS . 828 OUERU [EU 88! ! LB UB DEL F'EfiW~ FERN 1 34 37 4 4 3S 4 E 34 45 18 a 38 7 3 SS 65 H 3 SO 4 56 62 13 3 S4 7 TRQINXNG AREfi- 8 PIXELS RLQRPED MER- 12148 PIXELSK TVPE CML 3 ow E()<)IT IllllllllJ JlLlllllll 1 15 15 26 4 SUBS? T4 CENTRAL NUMBER OF PlXELS—-> W 888 OUERUIEU C” 8 LB U3 DEL PEI-WK MEAN UN? 1 42 S4 23 2 S3 5 58 7 E 51 78 28 P. 64 2 74 0 9 3 59 80 22 2 7G 5 34 2 9 4 52 64 13 3 57 5 20 7 0 TRAINIM NiEfl- 12 PIXELS FILARV'ED ARE?" 10641 PIXELSK TVPE‘ OWL 3 OR E(X)IT 388 OUERU IEU 883 3 LB UB L FEM FERN 1 27 32 6 4 29 l a 23 31 9 a 26 6 3 41 52 la 3 44 7 4 4O 50 U 3 43 5 TRAINIM WES" 8 PIXELS ALMV'ED ARER- 1316 PIXELS( TVPE (El-ML 8 OP E(X)IT 4 1X)? BRIGHTN E.SS‘ VALUES 9 DWEFIELDS . n n I u n n n n BRIGHTNE'SS VALUES—> SUBS? 1‘6 PENINSULA EDGE U) _l LIJ 5 0. U. 0 cc LLI CD 2 D Z : BRIGHTNE'ss VALUES—> ).SUBS7 1'8 INTERDUVE AREAS FIGURE 12.-—Histograms of the six classes in subscene 2 Which are mapped in figure 11. THE QUEENSLAND EXPERIMENT 19 TABLE 2.—Statistical summary of seven themes classified for subscene 3 Radiance . . Pixels Percent Theme Band £13135; Ibioplpledr Difference Mean Variance classified clgsiiefliid Hectares 1 Dunefields _________ 4 62 72 11 68.0 7.2 23,256 12.3 94670 5 84 100 17 89.3 17.8 6 90 110 21 99.9 22.4 7 76 88 13 83.6 14.9 2 Bare ground_ ________ 4 68 84 17 76.2 24.5 9,362 5.0 38150 5 101 154 54 108.5 42.3 6 92 168 77 120.6 74.3 7 76 136 61 102.9 76.9 3 Lowlands __________ 4 60 68 9 67.0 4.2 4,442 2.3 18080 5 74 90 17 81.0 28.1 6 106 110 5 108.2 2.8 _ 7 96 100 5 97.5 3.7 4 Bright vegetation __- 4 60 73 14 67.4 12.6 8,897 4.7 36210 5 46 67 22 61.6 25.2 6 100 118 19 107.8 20.4 . 7 99 124 26 104.9 26.4 5 Brlght valleys ______ 4 88 108 21 93.7 31.0 4,025 2.1 16410 5 92 148 57 117.5 133.6 6 118 150 33 132.5 64.0 7 104 136 33 114.8 51.5 6 Medium vegetation __ 4 64 73 10 68.5 7.2 28,975 15.3 117900 5 58 76 19 68.7 25.0 6 70 105 16 97.2 19.3 7 64 96 33 87.8 36.9 7 Divides ____________ 4 72 80 9 73.6 5.7 6,398 2.4 26050 5 74 86 13 79.9 17.1 6 106 112 7 108.5 4.2 7 91 100 10 96.9 8.5 Total ____________ __ _-_ __- _- ____ ____ 85,355 45.1 the subscene for pixels whose combination of radi- ance values were within those of the training set pixels. It then classified each pixel according to those values and displayed them on the scene as a single theme. Table 2 shows a statistical summary of seven themes that were claSSified in the subscene. Figure 16 shows the combination of the seven themes. The number of pixels, acres, and hectares for each theme are calculated by counting the number of pixels classified in each theme and are shown in the following table: Number of Acres Hectares pixels Theme 1 _______ 209,241 234,000 94,700 Theme 2 _______ 84,312 94,300 38,100 Theme 3 _______ 39,951 44,700 18,100 Theme 4 ________ 80,037 89,500 36,200 Theme 5 _______ 36,261 40,500 16,400 Theme 6 _______ 260,613 291,000 118,000 Theme 7 _______ 57,573 64,000 26,000 Total ____ 767,988 Separability of the seven themes is established by a lack of overlap of the upper and lower radiance limits of pairs of themes in any single band al- though they may overlap in other bands. For ex- ample, themes 1 and 2 are separable in band 5, al- though they overlap in bands 4, 6, and 7. Table 3 shows the separability of the seven themes. TABLE 3.—Band.s in which separability is produced between pans of themes in the northwest subscene, 1365—23530 Themes 1 2 3 4 5 6 7 1 2 5 3 7 5 4 5, 7 5 5 5 4,6,7 4 4,5,6,7 4,5 6 5 5 6 7 4, 5, 6, 7 7 7 5 4 5 4, 5, 6, 7 6 Figure 17 shows the range, size, and relation of the brightness values of the seven themes based on their parallelepiped classification in bands 4, 5, and 7. The four-dimensional boundaries of the classes cannot be shown because of the three-dimensional nature of the diagram, but it does illustrate the closeness of the themes. Because only bands 4, 5, and 7 were used in construction of the diagram, it does not show well the separability of themes 3 and 6 and themes 6 and 7, and because they are sepa— rated only on the basis of band 6. CORRESPONDENCE OF MULTISPECTRALLY CLASSIFIED THEBIES WITH TERRAIN FEATURES The themes that have been classified and mapped With the Landsat data are groupings of pixels with similar brightness values. In order to describe them INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES FIGURE 13.—Standard color composite of subscene 3, using every third pixel in every third row, of bands 4, 5, and 7 (left) and contrast-stretched composite of bands 4, 5, and 7 (right). adequately in terms of terrain features, it is neces- sary to relate them to the previously mapped land systems. This was done by overlaying a film positive of the land systems map over a photographic print of the thematic map to see which themes occurred within each of the various land systems. Table 4 shows a descriptive comparison of the themes with the land systems. No statistical correlation was attempted for sev- eral reasons. First, the original mapping was some- what subjective and arbitrary. The aerial photo in- terpreter or field mapper may assign a given terrain THE QUEENSLAND EXPERIMENT FIGURE 13.—Continued. area to a given land system rather than to another based upon a subjective similarity or may group some units because of the small map scale. Second, some land units, rather than the larger land sys- tems, are recognizable multispectrally and the same unit may occur in several land systems. An example is the mobile, unvegetated crests of dunes which occur in each of the eight dune field land systems. Third, a single feature may control the spectral re- flectance and yet it may be only a single factor used in assigning a given area to a specific land system. As an example, dense vegetation or silcrete that com- 22 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES llllllllLl llllllllll .- -.----.------.-----.-- _: : Al. _: i ‘3— : : m _. . x— _: : :fl : : u_ '—‘I I — _= l O_ __5 E 5.. _1 i m- I I _: : §_ _3 i z_ I I I I E E . ALARM RESOLUTION 128 128 128 123 + BRKSHTNESS VALUES-€> 8 LB UB DEL PEAK MEAN UAR + 1 12 89 78 58706. 36.0 37.5 + 2 1 118 118 15359. 41.2 101.9 + 3 6 106 101 13133. 51.1 62.1 + 4 0 90 91 23612. 44.2 92.4 + TRAINING AREA-185196. PIXELS + ALARMED AREA-188928.PIXELS( 72.1%)+ TVPE CHANNEL (1-4), 0R EIX)IT NU SUBSCENE ._ : __ __ :._ : 5 _ ._ I — '— I I __ ._ I —— '— I I I _ ._ I _ I I ._ z I ——1 '— I I I I _ 215 ' ._ :mj: 7 0—! I — 2:24 —: :E~: . ._: ‘L‘L—w‘ : I I I I —: :0—4: : —s 25% —: :m_1; —s 2%: 2 .Z-fi'l it IIIIII'IIII I “I! I'II'TIIIIIII ALARM RESOLUTION 128 128 128 128 + BRNSHTNESS VALUES'€> 8 LB UB DEL PEAK MEAN UAR + 1 1 127 127 58716. 64.0127S.2 + 2 1 127 12? 15355. 64.01326.2 + 3 1 127 127 13138. 64.01329.4 + 4 1 127 127 23603. 64.11326.9 + TRAINING AREA-185196. PIXELS + ALARMED AREA-188928.PIXELS( 72.1%)+ TYPE CHANNEL (1-4), 0R E(K)IT NU SUBSCENE EO. AREA STRETCH FIGURE 14.—Histograms of the unstretched and contrast-stretched subscene 3. THE QUEENSLAND EXPERIMENT 23 VF! FIGURE 15.—Land system map of subscene 3. (Unpublished map from Queensland Department of Primary Industries.) pletely covers the ground will control the spectral reflectance although the soil type may be highly sig- nificant in a land system assignment. The relation shown in Table 4 is valid in many cases, but it is not always highly correlated because of the reasons noted above. The correspondence indicates that the map pro- duced by digital classification may not represent a classical “land systems” map. However, it may be used for land management decisions. If, for some areas, the bedrock-soils-vegetation complex controls the spectral reflectance, the map is similar to a land systems map but if only 'a single terrain factor con- trols the reflectance at a particular point in time, that factor may not only be dominant in the analysis but may be a dominant control on land management and use. A second method of correlating the multisp‘ectral analysis results With the published map involves a visual interpretation and mapping of data on the thematic map. Figure 18 shows subscene 3 (the northwest subscene) with boundaries drawn around single or multiple themes to create a generalized map. Varnes (1974, p. 4) states “The essence of map- ping is to delineate areas that are homogeneous or acceptably heterogeneous for the intended purpose of the map” [italics are the author’s]. Each theme (individual color) is homogeneous with respect to 24 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES FIGURE 16.—Seven multispectrally classified themes in subscene 3. a single terrain attribute, the brightness value in each band. Where a reasonably sized geographic area consists of a single theme, it may be considered to be a terrain mapping unit. Where a reasonably sized geographic area consists of a random appearing set of two or more themes, it may also be considered as a terrain mapping unit with “acceptable hetero- geneity.” Each of the lettered regions on the map is either “homogeneous” (A) or “acceptably hetero— geneous.” (B and C) It should be recognized that mapping by the digi- tal analysis of multispectral imagery is an a priori method of creating homogeneous map units (with respect to brightness values). Normal mapping methods involve drawing boundaries around areas which are determined to be internally homogeneous THE QUEENSLAND EXPERIMENT 128'— 110 __ 100 —— 90 -— 80 - 70 ‘— 25 ~128 120 110 BAND 5 60 —- 50 ‘— 7O 60 40 ‘— 50 $0 40 30 20 I I | l | I 20 30 40 so 60 I I I I I I J 70 80 90 100 110 120 128 BAND 7 (BRIGHTNESS VALUES) FIGURE 17.—Parallelepiped classification and separability of seven themes in the northwest subscene 1365—23570. Band 6 is not shown in the diagram but it provides the separability between themes 3 and 6 and between themes 6 and 7. or acceptably heterogeneous by some limited sam- pling and testing method. However, multispectral analysis identifies areas Which conform to rigorous numerical limits of radiance, which is an attribute of the terrain unit. Only after the area of a unit of similar (homogeneous) radiance is mapped is a boundary drawn around it. The choice of the bound- ary location can then be based on (1) drawing a boundary around a homogeneous radiance unit which can be considered representative of a terrain unit for the purposes of the map, or (2) drawing a boundary around a group of several individually 26 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES TABLE 4.—Cor’respondence of multispectral themes with mapped land systems Dominant features Land systems .- - 01325212211 mapped and described Defcélffe’gon of theme Remarks on published map 0 e reflectance 1. Dunefields _____ D1 Arrabury and Sand dunes, both longi- Moderate reflectance Kidd, D2 Poonga- mulla, S6 Galway with some mixed. 2. Bare ground Occurs within almost (mainly red every land system. soils). Bare ground is not a land system in itself, but is diagnostic of lands that do not or cannot support vege— tation and which have a light color. 3. Lowlands ______ Primarily Durham with some areas of alluvium of small streams and hard mulgas. 4. Bright F1—4 Downs with some vegetation. in A5 Dingera, H5 Noccunda, and $6 Galway. 5. Bright valleys __ A2 Eromanga and A5 Dingera—alluvial valleys and in addi- tion scalded areas in dunefields and in downs. 6. Medium Primarily associated vegetation. with Downs (F) and gidgee lands (G). 7. Divides ________ Occurs in conjunction with almost all land systems, generally along divides. homogeneous radiance units and defining their heter- ogeneity of radiance as representative of a terrain unit for the purposes of the map. The method that follows from this description is that the digital mapping of areas should be done as a first step, boundaries should be drawn in a rea- tudinal and retic~ ulate with spinifex hummock grassland, predominantly red earthy sands with some siliceous sands. Includes numerous areas of bare ground which are dune flanks, scalds, or clay pans. Bare ground with little or no vegetation. They are quite scattered and inter- spersed with other themes. It may rep- resent bare rock with a dark color. May be areas of dense vigorous vegetation whether grasses or shrubs. Its occur- rence in the downs indicates that it may be Mitchell grass or salt bush. It also occurs where mulga is abundant. In the stretched color composite it ShOWS as the brightest red areas. Alluvial plains of minor streams and scalded areas with little or no vegeta- tion. Similar to clay pans and scalded areas. Areas of, trees on plains with a low density of vegeta- tion. Difficult to describe because of its wide— spread occurrence in small areas and as— sociation with nu- merous land systems. in all four bands. The reflectance of the red sands is modified by the re- flectance of the vege- tation. This in turn is controlled, not by the type of vegeta- tion, but basically by its density and cover. Low to moderate re- flectance in the in- frared bands indicat- ing lack of vegeta- tion. Moderate reflectance with narrow bound- aries in all four bands. High reflectance in the infrared bands. High reflectance in all bands. Usually white on standard color composite image. Somewhat narrow re- flectance intervals in all four bands. Very narrow radiance Intervals With moderate reflectance. May be a highly sig- nificant theme for monitoring purposes to detect changes in size of bare areas or detection of newly bare areas which in— dicate degradation of the vegetation by seasons or over graz- ing. May be related to increased erosion. Because it occurs in both grassland and shrub areas it is diagnostic only of dense vigorous vege- tation rather than any specific types. May be useful for monitoring changes and increase in erosion. Much lower radiance in band 7 than for theme 4, bright vegetation. Silcrete cover could be masking soil and vegetation difi‘er- ences. sonable manner around various areas as a second step, and only then should the sampling and testing strategy (that is, field mapping) be applied. At this point, the mapper is aware of the relative propor— tions of the whole area that are described by each class and can plan the number and site of his field THE QUEENSLAND EXPERIMENT FIGURE 18.—Seven themes classified in subscene 3 with examples of interpretive boundaries around homogeneous classes and heterogeneous classes. observations in accordance with a statistically valid sampling scheme and with due regard for field ac— cessibility, logistics, and efiiciency. Figure 18 is presented as a first step in grouping themes into terrain categories. Figure 18 is the same as figure 16 with the addition of boundaries drawn around three areas, each presenting an ex- ample of a different decision for grouping themes. Area A is composed of one theme which occupies a reasonably sized mappable area and may be con- sidered as a homogeneous theme. Area B consists of three themes (plus water) with the theme shown in red occupying over 70 percent of the area. It may be considered to be an “acceptably heterogeneous” 98 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES FIGURE 19.—Classification of the upland areas of Landsat scene 1563—23530, February 6, 1974. Band 5 is shown in black and White. Eight themes developed by multispectral classification are shown in color for upland areas. The alluvial valley of Cooper Creek is not classified because it is flooded. Areas are automatically computed from theme pixel counts. Unmapped areas are shown by the background image. theme for the purpose of the map. Area C is oc- EXTRAPOLATION OF PARTIAL SCENE cupied by a heterogeneous, but well distributed, CLASSIFICATIONS To A FULL LANDSAT SCENE mixture of five themes. It also may be considered to Multisp‘ectral classification of the total Landsat be “acceptably heterogeneous” for the purpose of scene can be done on a large general-purpose com- the map. puter but it requires much time and is quite expen- THE QUEENSLAND EXPERIMENT 29 LEGEND AREA Hectares - Dunefields 178.000 ho - Bore ground I l l. UUU ho - Lowlands 38. 800 ha - Bright vegetation 79. 200 ha - Bright volleys 82. BUD ho - Medium vegetation 375. 000 ha - Divides BB. BUD ho Unknown 84. SUE] ho sive since either 7.58 by 10 0 pixels must be analyzed or the scene must be sampled. The analytical device used for the analysis in this report can only display and store an entire scene if a sampled array of 512 by 369 pixels issued. This is only 2.49 percent of the available data. When the sampled image of an entire scene was used for supervised classification by selecting train- ing sets, the resulting classification was very poor, with large errors of omission and commission. In order to overcome these errors, the brightness values in each band for each of the seven themes (which are listed in table 2) were read into the computer and the sampled full scene was then classified and mapped. Interpretive inspection showed few errors of commission but a moderate part of the full scene was not classified. A. training set was then selected in the unclassified region, and this region was, for the most part, classified as an eighth theme. Figure 19 shows the eight themes overlaid on the band 5 image. The same procedures can be used to evaluate the full scene image as those used for the northwest subscene 3 previously. DRY SEASON IMAGE ANALYSIS Landsat scene 1365—23570 was imaged on July 23, 1973, during the dry season, and consequently is suitable for mapping land systems in the alluvial valley of Copper Creek, because the only water present is in water holes along deep reaches of the stream channels. Because of the simplicity of the alluvial land systems, it was not believed necessary to analyze a small subscene and extrapolate to the entire Landsat scene, but to analyze directly the whole scene. This was done by sampling and dis- playing 2.49 percent of the pixels and classifying the alluvial valley into four themes. Figure 20 shows the classification, which corresponds rather closely with the published map. Mr. Brian Senior of the Geological Branch, Bureau of Mineral Resources, Geology, and Geophysics, Australia, has commented on this classification (per- sonal communication, 1976) The vegetation classification of the alluviated lowlands is most convincing. Dark vegetation * corresponds to belts of large river gums which line trunk sectors of the major channels. Bright vegetation * corresponds with levees and flood plains which in favorable seasons support a thick cover of grass and flowering annuals. Both former categories correspond with land form unit Qa2 (reticulate channel, pointbar, and flood plains) on the 1:250,000—scale geologic and geomorphic map. The swamp areas correspond with land form unit Qa3 (distributaries, floodouts, and marginal flood plains). Dry vegetation “" coincides with ‘islands’ of aeolian sand which remain largely above the in- fluence of flooding and support a thin cover of herbaceous perennials and a variable seasonal ground cover. For studies of land cover, the presentation is judged to be potentially useful as a planning document to guide more detailed work including ground checking. The classification of the alluvial valley is not a difficult one and could be done by visual interpre- tation of the Landsat color-composite image. The digital classification, however, has a major advant- age of consistency throughout the image which, when combined with the judgment of the inter- preter, provides a more complete analysis than vis- ual interpretation alone. UNSUPERVISED CLASSIFICATION OF A FULL LANDSAT SCENE An empirical experiment was conducted by per- forming an unsupervised classification of image 1563—23530 using the maximum-likelihood classifica— tion algorithm developed by the Purdue University Laboratory for Applications of Remote Sensing. Un- supervised classification simply separates the pixels into statistically distinct classes without selection by the interpreter. Figure 21 shows the results of 30 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES '11t3‘ww en - FIGURE 20.—Classification of the alluvial valley of Cooper Creek, Landsat scene 1365—23570, July 25, 1973. Band 5 is shown in black and white. Four themes developed by multispectra] classification are shown in color for the alluvial valley of Cooper Creek and adjacent uplands. Areas are automatically computed from theme pixel counts. Unmapped areas are shown by the background image. CONCLUSIONS 31 LEGEND AREA Hectares - Bright vegetation 18. 200 ha - Swamps 111.000 ha - Dark vegetation 5|. 500 ha - Dry vegetation B5. 200 ha that classification. To minimize computing time and cost, the image was sampled by using every 23rd line and every 32nd column, thereby selecting 10,000 evenly spaced pixels in the 2340 line by 3240 column scene. Only 0.136 percent of the scene was used and therefore each pixel represented approximately 330 hectares. The sole classification instruction given was to classify the sampled scene into 20 clusters on the basis of statistical similarities. The resulting 20 clusters were combined into 12 groups. Thus, fig- ure 21 shows 20 symbols but only 12 colors. The unsupervised classified image was not geo- metrically corrected, but it does represent the major land systems present in the area in its patterns. Such a classification method might be applicable as a first step in analysis of an area. Modified clustering techniques might also provide equally good and pos- sibly more accurate results, but were not explored in this study. CONCLUSIONS The major conclusion of the research reported here is that the integrated mapping of land by com- puter processing of Landsat images is feasible in situations Where the dominant reflectance of the land is characteristic of terrain attributes of im- portance for the purpose of the map at the time the image is taken. Mapping of discrete classes with single attributes is more difficult and more prone to error than is the mapping of integrated classes. Digital classification of the Queensland Landsat images into integrated units produced a map that is not identical to the published land systems map, but which resembles it in large part and is as useful. The classification of the land into homogeneous units based on the statistical distribution of brightness values provides a first map product by delineating areas of known attributes and radiance. The second map product, which includes the interpretive bound- aries and the names and descriptions of the unit, provides an integrated map which can be used as a guide for field checking and sampling. Interactive digital processing has proven to be highly useful because the terrain classifications dis- played can be readily checked to see if they are “photointerpretively reasonable;” as well as sta- tistically precise. The analyses reported here were done by sampling pixels for large areas. In the future, it would be most practical to use an interactive system to ana- lyze sample areas using every pixel in the area, de- veloping the means and covariance matrices for each theme, and then using a statistically powerful but less interactive system for maximum likelihood classification of an entire Landsat scene using every pixel. Such a process would use the advantages of human interaction plus the statistical and comput- ing advantages of a larger computer system and would maximize the advantages of each system for the analysis. 32 i” {A H fi fi n P 8 i ‘ efirwwunncéd ‘x INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES :x {Sm ' 1w»: ' _' , mm W. ”M'mmnr ' . ‘ W. «a “Hymn imam" “new annv'ans: _ , _ _ -' flflflflnflnfifinfl31‘!{ ippva A & Am177nnrannnnna Hanna?fifinnlnnib?fia7h”nnifia’11‘4 7a!107Gsa'101167413‘7“1%‘1“31%7‘ in: 3.33“ ugsau a ban 1 WV wwgdgfinnapaesq;a ridawmflnvw~wu 0» w» as firm-rm ’ _ , ' WNW V ‘ mmauq‘m- mum/u- ?§i»-v€ 1": FIGURE 21.-Unsupervised classification of sampled Landsat image 1563—23530. SELECTED BIBLIOGRAPHY 33 SELECTED BIBLIOGRAPHY Addor, E. E., 1963, Vegetation description for military pur— poses: U.S. Army Engineer Waterways Experiment Sta- tion (USAWES), Military Evaluation of Geographic Areas, Report on activities to April 1963, Misc. Paper no. 3—610. Aitchison, G. D., and Grant, K., 1967, the P.U.C.E. pro- gramme of terrain description, evaluation, and inter- pretation for engineering purposes: 4th Regional Con- ference for Africa on Soil Mechanics and Foundation Engineering, Cape Town, v. 1, p. 1—8. Anderson, J. E., Hardy, E. E., Roach, J. T., and Witmer, R. E., 1976, A land use and land cover classification system for use With remote sensor data: U.S. Geological Survey Professional Paper 964, 28 p. Anuta, P. E., 1976, Digital registration of topographic data and satellite MSS data for augmented spectral analysis: Proceedings of the American Society of Photogrammetry, 42d Annual Meeting, p. 180—187. Arjanov, E. P., and Kienko, Yu. P., 1974, Some questions of exploring natural resources: Proceedings of Symposium on Remote Sensing and Photointerpretation, Ottawa, v. 2, p. 527—533. Armand, D. L., 1965, The logic of geographic classification and regionalization schemes: Soviet Geography—Review and Translation, v. 6, no. 9, p. 20—38. Armand, D. L., Gerasimov, I. P., Salishehev, K. A., and Saushkin, Yu. G., 1960, The role of geographers in the study, mapping, economic appraisal, utilization, con- servation, and renewal of the natural resources of the USSR: Soviet Geography—Review and Translation, v. 1, no. 6, p. 3—10. Ball, G. H., and Hall, D. J., 1965, ISODATA, A novel method of data analysis and pattern classification: Technical Report, Stanford Research Institute, Menlo Park. Batisse, M., 1966, Etudes integrees du milieu naturel: Pub- lications of the ITO-UNESCO Centre for Integrated Surveys, Delft, Netherlands, S1—3—32. Baulkwill, W. J., 1972, The land resources division of the overseas development administration, Tropical Science, v. 14, no. 4, p. 305—322. Bawden, M. G., 1965, A reconnaissance of the land resources of eastern Bechuanaland: Journal of Applied Ecology, v.2, p. 357—365. 1967, Applications of aerial photography in land sys- tems mapping: Photogrammetric Record, v. 5, p. 461—— 464. Beckett, P. H. T., 1973, The cost effectiveness of terrain evaluation, v. 1: Oxford University, Department of Agricultural Science, Final Technical Report, 131 p. Beckett, P. H. T., and Webster, R., 1962, The storage and collation of information on terrain: Military Engineer- ing Experimental Establishment (MEXE) Rept. no. 871, Christchurch. 1965a, A classification system for terrain: MEXE Rept., no. 872, Christchurch, 247 p. 1965b, Minor statistical studies on terrain evaluation: MEXE Rept. no. 877. 1969, A review of studies on terrain evaluation by the Oxford-MEXE-Cambridge Group, 1960—1969: MEXI Rept. no. 1123. 1971, The development of a system for terrain eval- uation over large areas: Royal Engineers Journal, v. 85, p. 243—258. Beckett, P. H. T., Webster, R., McNeil, G. M., Mitchell, C. W., 1972, Terrain evaluation by means of a data bank: The Geologic-a1 Journal, V. 138, no. 4, p. 430—456. Bentley, R. G., Jr., Salmon-Drexler, B. C., Bonner, W. J., and Vincent, R. K., 1976, A Landsat study of ephemeral and perennial rangeland vegetation and soils: U.S. Bureau of Land Management, Denver. Bibby, J. S., and Mackney, D., 1969, Land use capability clas— sification (Soil Survey of England and Wales, Har- penden, United Kingdom): Technical Monograph 1. Bie, S. W., and Beckett, P. H. T., 1973, Comparison of four independent soil surveys by airphoto interpretation, Paphos area (Cyprus): Photogrammetria, v. 29, p. 189— 202. Bobek, H., 1957, Gedanken uber das logische system der geographie: Mittelungen der Geographische Seselschaft in Wien, p. 122—145. Bobek, H. and Schmithusen, J., 1949, Die landschaft im logischen system der geographie: Erdkunde, Band III, Heft 2/3, p. 112—120. Bourne, R., 1931, Regional survey and its relation to stock- taking of the agricultural resources of the British Em- pire: Oxford Forestry Memoirs v. 13. Boydell, A. N., 1975, Evaluation of the potential uses of Earth Resources Technology Satellite (ERTS—l), data for small-scale terrain mapping in Canada’s north: Canadian Geological Survey Paper no. 75—1, Part A, p. 389—392. Brink, A. B. A., Mabbutt, J. A., Webster, R., and Beckett, P. H. T., 1966, Report of the working group on land classification and data storage: MEXE Rept. no. 940, Christchurch, 97 p. Brink, A. B. A., and Partridge, T. C., 1967, Kyalami land system, an example of physiographic classification for the storage of terrain data: 4th Regional Conference for Africa on Soil Mechanics and Foundation Engineering, Cape Town, v. 1, p. 9—14. Brink, A. B. A., Partridge, T. C., Webster, R., and Williams, A. A. B., 1968, Land classification and data storage for the engineering usage of natural materials: Proceedings 4th Conference Australian Road Research Board, p. 1624~ 1647. Brink, A. B. A., Partridge, T. C., and Matthews, G. B., 1970, Airphoto interpretation in terrain evaluation: Photo In~ terpretation, v. 5, p. 15—30. Brunt, M., 1967, The methods employed by the Directorate of Overseas Surveys in the assessment of land resources: 'Etudes de Synthese, v. 6, p. 3—10. Canada Committee on Ecological (Biophysical) Land Classi- fication, 1977, Newsletter, no. 2, 4 p. Cary, T. K., and Lindenlaub, J. C., 1975, A case study using LARSYS for analysis of Landsat data: LARS informa- tion Note 050575. Laboratory for Applications of Remote Sensing (LARS), Purdue university, West Lafayette, 134 p. Casson, J., Harthrup, R., and Jarvis, R., 1973, Soil surveys for integrated land use planning: The Planner, v. 59, no. 9, p. 400—406. Christian, C. S., 1952, Regional land surveys: Journal of the Australian Institute of Agricultural Sciences, v. 18, p. 140—146. 34 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES 1958, The concept of land units and land systems: Proceedings 9th Pacific Science Congress, 1957, v. 20, p. 74—81. Christian, C. S., and Stewart, G. A., 1953, Summary of gen- eral report on survey of Katherine-Darwin Region, 1946: Land Research Series 1, 24 p. 1968, Methodology of integrated survey: Aerial Sur- veys and Integrated Studies, UNESCO, Paris, p. 233— 280. Christian, C. S., Stewart, G. A., and Perry, R. A., 1960, Land Research in northern Australia: Australian Geographer, v. 7, p. 217—231. Cipra, J. E., 1973, Mapping soil associations using ERTS MSS data: Machine processing of remotely sensed data: Laboratory for Applications of Remote Sensing. Purdue University, West Lafayette, p. 3A1—3A10. Cline, M. G., 1949, Basic principles of soil classification: Soil Science, V. 67, p. 81—91. Coaldrake, J. E., 1961, The ecosystem of the coastal lowlands of southern Queensland. Commonwealth Scientific and In— dustrial Research Organization (CSIRO). Melbourne, 138 p. Colwell, J. E., 1974, Vegetation canopy reflectance: Remote Sensing of Environment, v. 3, p. 175—183. Colwell, R. N., 1968, Remote sensing of natural resources: Scientific American, v. 218, p. 54—69. Commonwealth Scientific and Industrial Research Organiza— tion, 1960, The Australian Environment: Melbourne, 151 p. Cooke, R. U., and Doornkamp, J. C., 1974, Geomorphology in environmental management: Clarendon Press, Oxford, 413 p. Cooke, R. U., and Harris, D. R., 1970, Remote sensing of the terrestrial environment—principles and progress: Trans- actions and Papers, Institute of British Geography, v. 50, p. 1—23. Cornell Aeronautical Laboratory, Inc., 1963, Matrix methods for terrain profile simulation: Project CATVAR. Craib, K. B., 1973, Regional resource surveys in Latin America: Remote Sensing of Earth Resources, v. 11, p. ‘= 289—298. Dansereau, P., 1958. A universal system for recording vege- tation: Institute Botanique de l’Universite de Montreal, Canada. Division of Land Utilization, 1974, Western arid region land I use study: Information and Extension Training Branch of the Queensland Department of Primary Indsutries, 131 p. Dregne, H. E., 1967, Inventory of research on surface ma- terials of desert environments: Office of Arid Lands Study, University of Arizona, Tucson. Electromagnetic Systems Laboratories, 1976, IDIMS User’s Guide: ESL Technical Memorandum ESL—TM705. 1977, IDIMS User’s Guide: Earth Processing Func- tion: ESL Technical Memorandum ESL—TM705, Supple- ment 1. Fitzpatrick-Lins, K., 1978, Accuracy and consistency of land use and land cover maps made from high-altitude photographs and Landsat multispectral imagery: Journal of Research, U.S. Geological Survey, v. 6, p. 23—40. Fleming, M. D., Berkebile, J. S., and Hoffer, R. M., 1975, Computer-aided analysis of Landsat-1 MSS data—A com- parison of three approaches, including a “modified clus- tering” approach: Laboratory for Applications of Remote Sensing (LARS), Information Note 72875, Purdue Uni- versity, 8 p. Fosberg, M. A., and Chugg, J. C., 1967, Landform definitions for soil surveys and IBM data code processing: Univer- sity of Idaho, College of Agriculture, Department of Agricultural Biochemistry and Soils. Fukunaga, K., 1972, Introduction to statistical pattern recog- nition: Academic Press, New York. Gaussen, Henri, 1958, Integration of data by means of vege- tation maps: Proceedings, 9th Pacific Science Congress, Bangkok, p. 57. Genderen, J. L., van, 1972, An integrated resource study using orbital imagery: an example in southeast Spain: Proceedings of the 8th International Symposium on Re- mote Sensing of Environment. Environmental Research Institute of Michigan, Ann Arbor, p. 117—136. 1973, The use of Skylab and ERTS data in an inte- grated natural resource development program: Journal of the British Interplanetary Society, v. 26, p. 577—588. Genderen, J. L. van, and Lock, B. F., 1977. A methodology for producing small scale rural land use maps in semi- arid developing countries using orbital imagery: Final Report to NASA under investigation SR9686. Depart- ment of Industry, London, 270 p. General Electric Company, 1972, ERTS data users hand- bank: National Aeronautics and Space Administration (NASA), Goddard Space Flight Center. 1974, Imiga—lOO Users Manual: General Electric, Daytona Beach, Florida. Gerenchuk, K. I., Gorash, I. K., and Topchiyev, A. G., 1970, A method for establishing some parameters of the mor- phologic structure of landscapes: Soviet Geography—Re- view and Translation, v. 11, no. 4, p. 262-271. Gimbarzevsky, P., 1966, Land inventory interpretation: Pho- togrammetric Engineering, v. 32, no. 6, p. 967—976. Goetz, A. F. H., Billingsley, F. C., Gillespie, A. R., Abrams, M. J., Squires, R. L., Shoemaker, E. M., Lucchitta, I., and Elston, D. P., 1975, Application of ERTS images and image processing to regional geologic problems and geologic mapping in northern Arizona: Jet Propulsion Laboratory, California Institute of Technology, Technical Report 32—1597, 188 p. Grabau, W. E., and Rushing, W. N., 1968, A computer- compatible system for quantitatively describing the phys— iognomy of vegetation assemblages, in Stewart, G. A., ed., Land Evaluation: MacMillan, Melbourne, p. 263—275. Grant, K., 1971, Terrain evaluation as a basis for engineer- ing geology: Australia-New Zealand Conference on Geo— mechanics, Proceedings, no. 1, v. 1, p. 401—408. 1972, Terrain classification for engineering purposes of the Melbourne area, Victoria: Australian CSIRO Divi- sion of Applied Geomechanics Technical Paper no. 11, 209 p. Grigg, D., 1965, The logic of regional systems: Annals of the Association of American Geographers, v. 55, no. 3, p. 465—491. 1967, Regions, models, and classes, in Chorley, R. J., and Haggett, P., eds., Models in Geography: Methuen, London, p. 461—509. Grishankov, G. Ye., 1973, The landscape levels of continents and geographic zonality: Soviet Geography—Review and Translation, v. 14, no. 2, p. 76—78. Gvozdetskiy N. A., Gerenchuk, K. I., Isachenko, A. G., and Preobrazhenskiy, V. S., 1971, The present state and fu- SELECTED BIBLIOGRAPHY 35 ture tasks of physical geography: Soviet Geography— Review and Translation, v. 12, no. 5, p. 257—266. Haantjens, H. A., 1965, Practical aspects of land system sur- veys in New Guinea: Journal of Tropical Geography, v. 21, p. 12—20. 1968, The relevance for engineering of principles, lim- itations, and developments in land system surveys in New Guinea: Proceedings 4th Conference Australian Road Research Board, v. 4, p. 1593—1612. — (compiler), 1972, Lands of the Aitpe-Ambunti area, Papua, New Guinea: CSIRO Australia, Land Research series 30, 243 p. Haas, R. H., Deering, D. W., Rouse, J. W., Jr., and Schell, J. A., 1975, Monitoring vegetation conditions from Land- sat for use in range management: Proceedings of NASA Earth Resources Survey Symposium Houston, Texas, June 1975, NASA TMX—58168 JSC 09930, v. 1A, p. 43—52. Haefner, H., and Itten, K., 1974, National report of Switzer- land on Earth resources observation from satellite imag- ery: Approaches to Earth survey problems through use of space techniques, p. 413—419. Haralick, R. M., 1976, Automatic remote sensor image proc- essing, in Rosenfield, A., ed., Digital picture analysis: Springer-Verlag, New York, p. 5—63. Hartshorne, R., 1939, The nature of geography: a critical survey of current thought in light of the past: Associa— tion of American Geographers, Lancaster. 1959, Perspective on the nature of geography: Rand- McNally, Chicago. Harvey, David, 1969, Explanation in geography: Arnold, London, 521 p. Heath, G. R., 1956, A comparison of two basic theories of land classification and their adaptability to regional photo-interpretation key techniques: Photogrammetic Engineering, v. 22, p. 144—168. Herbertson, A. J., 1905, The major natural regions: an essay in systematic geography: Geographical Journal, v. 20, p. 300—312. Heyligers, P. C., 1968, Quantification of vegetation structure on vertical aerial photography in Stewart, G. A., ed., Land evaluation: Macmillan, Melbourne, p. 251—262. Hill, D. E., and Thomas, H. F., 1972, Use of natural resource data in land and water planning: Bulletin of the Con- necticut Agricultural Experiment. Hilwig, F. W., 1976, Visual interpretation of Landsat imagery for a reconnaissance soil survey of the Ganges River fan, southwest of Hardwar, India: ITC Journal, 1976—1, p. 26—41. Hofi‘er, R. M., Fleming, M. D., and Krebs, P. V., 1974, Use of computer-aided analysis techniques for cover type map- ping in areas of mountainous terrain: LARS Informa- tion Note 091274, Laboratory for Applications of Remote Sensing, Purdue University, West Lafayette, 13 p. Howard, J. A., 1970a, Multiband concepts of forested land units: Symposium on Photo-interpretation, International Society of Photogrammetry, Commission 7, Dresden. 1970b, Stereoscopic profiling of land units from aerial photographs: The Australian Geographer, p. 259— 268. 1974, Concepts of integrated satellite surveys, Third ERTS—1 Symposium, v. 1: Technical presentation; Sec- tion A, Greenbelt, Md. Goddard Space Flight Center, 523— 537 (NASA—SP—351—v. 1—Section A). Edward Hudson, G. D., 1936, The unit area method of land classifica- tion: Annals of the Association of American Geographers, v. 26, no. 2, p. 99—112. Hunt, C. B., 1950, Military geology—Application of geology to engineering practice: Geological Society of America, Berkeley v., p. 295—327. Hunting Technical Services LTD, 1956,'Report on the range classification survey of the Has‘hemite Kingdom of Jor- dan: United States Joint Fund for Special Economic Assistance. Ignat’yev, G. M., 1968a, Classification of cultural and na- tural vegetation sites as a basis for land evaluation: in Stewart, G. A., ed., Land evaluation: Macmillan, Mel- bourne, p. 104—111. 1968b, Landscape methods abroad: Soviet Geography— Review and Translation, v. 9, no. 10, p. 857—863. Isachenko, A. G., 1961, Landscape mapping—its significance, its present state, and its tasks: Soviet Geography—Re- view and Translation, v. 2, no. 2, p. 34—47. 1973, On the method of applied landscape research: Soviet Geography—Review and Translation, v. 14, no. 4, p. 229—243. James, P. E., 1954, The field of geography, in American Geography Inventory and Prospect: Association of American Geographers. 1972, All possible worlds: A history of geographical ideas: Odyssey Press, New York, 622 p. Japan, National Survey, 1973, Fundamental land classifica- tion survey; geomorphology, subsurface geology and soil: Japan Economic Planning Agency, v. 1. Johnson, C. W., and Coleman, V. B., 1973, Semi-automated crop inventory from sequential ERTS—1 imagery: Sym- posium on Significant Results Obtained from ERTS—1, NASA/Goddard Space Flight Center, Greenbelt, p. 19—25. Kalesnik, S. V., 1961, The present state of landscape studies: Soviet Geography—Review and Translation, v. 2, no. 2, p. 24—34. Kellogg, C. E., 1951, Soil and land classification: Journal Farm. Econ., v. 33, p. 449—513. Kiefer, R. W., 1967, Terrain analysis for metropolitan fringe area planning: Journal of the Urban Planning and De- velopment Division, Proceedings of the American Society of Civil Engineers, UP 4, v. 93, 119—39. King, R. B., 1970, A parametric approach to land system classification: Geoderma, v. 4, p. 37—47. King, R. B., and Rains, A. Blair, 1974, A comparison of ERTS imagery with conventional aerial photography for land resource surveys in less developed countries—examples from the Rift Valley Lakes Basin, Ethiopia: European Earth-Resources Satellite Experiments, European Space Research Organization, Neuilly, p. 371—379. Klingebiel, A. A., and Montgomery, P. H., 1961, Land capa- bility classification: Soil Conservation Service, U. S. Department of Agriculture, Agricultural Handbook 210, 210 p. Kuchler, A. W., 1949, A physiognomic classification of vegeta- tion: Annals of the Association of American Geographers, v. 39, p. 201—210. Lacate, D. S., compiler, 1969, Guidelines for bio-physical land classification: Department of Fisheries and Forestry, Canada Forestry Service, publication no. 1264. Landgreb‘e, D. A., 1973, Machine processing for remotely ac- quired data. LARS Information Note 031573, Laboratory 36 INTEGRATED TERRAIN MAPPING for Applications of Remote Sensing, Purdue University, West Lafayette, 48 p. Leggie, A. H., Jacques, D. R., Poulton, C. E., Kirby, C. L., and VanEck, P., 1974, Development and application of an ecologically based remote sensing legend system for the Kananaskis, Alberta remote sensing test corridor: International Society of Photogrammetry, Banfi’, Alberta. Lewis, J. K., 1969, Range management viewed in the ecosys- tem framework, in Van Dyne, G. M., ed., The ecosystem concept in natural resource management: Academic Press, New York, p. 97—187. Lins, H. F., 1976, Land use mapping from Skylab S—190B photography: Photogrammetric Engineering and Remote Sensing, v. 42, p. 301—307. Linton, D. L., 1951, The delimitation of morphological re gions: London Essays in Geography, Longman, London, p. 199—217. Leuder, D. R., 1959, Aerial photographic interpretation—— Principles and application: McGraw—Hill, New York, 462 p. Mabbutt, J. A., 1968, Review of concepts of land classifica- tion, in Stewart, G. A., ed., Land evaluation: Macmillan, Melbourne, p. 11—28. Mabbutt, J. A., and Stewart, G. A., 1963, The application of geomorphology in resource surveys on Australia and New Guinea: Revue Geomorphology Dynamique, v. 14, p. 97— 107. Mackay, J. R., 1958, Chi-square as a tool for regional studies. Annals of the Association of American Geographers, 48:164—166. . MacPhail, D. D., 1971, Photomorphic mapping in Chile: Pho- togrammetric Engineering, v. 37, no. 1, p. 1149—1153. MacPhail, D. D., and Yuk, Lee, 1972, A model for photo— morphic analysis—Tennessee Valley test site: Technical Report 71—3, Commission on Geographic Applications of Remote Sensing, East Tennessee State University. Melton, M. A., 1958, List of sample parameters of quantita- tive properties of landforms—Their use in determining the size of geomorphic experiments: Technical Report no. 16, Office of Naval Research, Department of Geology, Columbia University. Mill, J. S., 1879, A system of logic, 10th Edition: Longmans, Queen and Company, London. Milne, G., 1935, Some suggested units of classification and mapping, particularly for East African soils: Soil Re- search, v. 4, no. 3, p. 183—198. Milovidova, N. V., 1970, The use of the tree of logical possi— bilities in the construction and control of physical geo— graphic classifications: Soviet Geography—Review and Translation, v. 11, no. 4, p. 256—262. Ministry of Works, New Zealand, 1971, Land use capability survey handbook: Government Printer, Wellington, N. Z., 139 p. Mitchell, C. W., 1971, An appraisal of a hierarchy of desert land units: Geoforum, p. 69—79. 1973, Terrain evaluation: Longrnan, London, 221 p. Mollard, J. D., 1972, Airphoto terrain classification and map- ping for northern feasibility studies with discussion: Canadian Northern Pipeline Research Conference, 2—4 February 1972, Proceedings, National Research Council of Canada, Technical Memorandum no. 104, p. 105—119. Moss, R. P., 1968, Land use, vegetation, and soil factors in southwest Nigeria—A new approach: Pacific Viewpoint, v. 9, p. 107—127. WITH DIGITAL LANDSAT IMAGES 1969, The appraisal of land resources in tropical Africa: Pacific Viewpoint, v. 10, p. 18—27. Motts, W. S., ed, 1970, Geology and Hydrology of related playas in western United States: University of Massa- chusetts, Amherst, Final scientific report for Air Force Cambridge Research Laboratories. Nakano, T., 1963, Land form type analysis on aerial photo- graphs—its principles and its technique: Transactions of the Symposium of Photo Interpretation, Delft, Ar- chives Internationales de Photogrammetric, v. 14, p. 149—152. National Aeronautics and Space Administration (NASA), 1976, Landsat data user’s handbook: Document no. 76SD5425B, Goddard Space Flight Center, Greenbelt. National Institute for Road Research, 1971, The production of soil engineering maps for roads and the storage ma- terials data: Pretoria, South Africa, Technical Recom- mendation for Highways, 2. Nichol, J. E., 1974, Land type analysis for regional land use planning from photomorphic mapping—An example from Boulder County, Colorado: Proceedings, 9th Inter— national Symposium on Remote Sensing of Environment, Ann Arbor, Environmental Research Institute of Michi- gan, v. 1, p. 589—596. Nossin, I. P., 1970, Applied geomorphology in integrated sur- veys: Scientia, v. 104, p. 1—18. Ollier, C. D., Webster, R., Lawrence, C. J., and Beckett, P. H. T., 1967, The preparation of a land classification map of 1:1,000,000 of Uganda: Actes du IIe Symposium In- ternational de Photo-Interpretation, Paris, Sect. IV, v. 1, p. 115—122. Parry, J. T., Heginbottom, J. A., and Cowan, W. R., 1968, Terrain analysis in mobility studies for military vehicles, in Stewart, G. A., ed., Land evaluation: Macmillan, Melbourne, p. 160—170. Peltier, L. C., 1973, Area sampling for terrain analysis, in Derbyshire, E., ed., Climatic Geomorphology: Barnes and Noble, New York, p. 193—201. Perel’man, A. I., 1961, Geochemical principles of landscape classification: Soviet Geography—Review and Transla- tion, v. 2, no. 3, p. 63—73. Perrin, R. M. S., and Mitchell, C. W., 1970, An appraisal of physiographic units for predicting site conditions in arid areas: MEXE Report no. 1111. Perry, R. A., 1962, General report on lands of the Alice Springs area, 1956—57: CSIRO, Australia, Land Resource Series, no. 6, 280 p. Pettinger, L. R., with contribution by Poulton, C. E., 1970, The application of high altitude photography for vegeta- tion resource inventories in southeastern Arizona: A re— port of research performed under NASA Contract no. NAS9—9577, 147 p. Phillips, E., 1965, Field ecology—a laboratory block: Ameri— can Institute of Biological Sciences, Health, Boston. . Piech, K. R., Gaucher, D. W., Schott, J. R., and Smith, P. G., 1977, Terrain classification using color imagery: Pho- togrammetric Engineering and Remote Sensing, v. 43, no. 4, p. 507—513. Poulton, C. E., 1972, A comprehensive remote sensing legend system for the ecological characterization and annotation of natural and altered landscapes: Proceedings 8th In— ternational Symposium on Remote Sensing of Environ- ment, Environmental Research Institute of Michigan, p. 353—408. SELECTED BIBLIOGRAPHY 37 1975, A comparative interegional analysis of selected data from Landsat—1 and EREP for the inventory and monitoring of natural ecosystems: Proceedings NASA Earth Resources Survey Symposium, Houston, Texas, June 1975, NASATMX—58168, JSC09930, p. 507—568. Poulton, C. E., Faulkner, D. P., and Martin, N. L., 1971, A procedural manual for resource analysis with supporting appendices—Application of ecology and remote sensing in the analysis of range watersheds: Range Management Program, Agricultural Experiment Station, Oregon State University, Corvalis, 97 p., 6 appen. Prokayev, V. I., 1962, The facies as the basic and smallest unit in landscape science: Soviet Geography—Review and Translation, v. 3, no. 6, p. 21—29. Richlen, E. M., compiler, 1976, Land system inventory: U.S. Forest Service, Missoula, 69 p. Rikhter, G. D., 1965, Physical-Geographic regionalization: Soviet Geography—Review and Translation, v. 6, nos. 5—6, p. 101—397. Robinove, C. J., 1972, Earth resources satellite and integrated resource surveys: Procedings of Symposium S.62 Remote Sensing, Pretoria CSIR, May 1972, p. 47—56. Robinove, C. J., and Hutchinson, C. F., 1978, Use of a re- mote computer terminal during field checking of Landsat digital maps. Jour. Research, U.S. Geol. Survey, v. 6, no. 4, P511—514. Root, R. R., 1975, Computerized terrain mapping of Yellow- stone National Park: Doctoral Colorado State, Interna- tional Dissertation Abstract, v. 35, no. 8, p. 3967B. Root, R .R., Smedes, H. W., and Roller, N. E. G., and Despain, D. 1974, Color terrain map of Yellowstone Na- tional Park, computer-derived from ERTS MSS data: Proceedings Ninth International Symposium on Remote Sensing of Environment, Environmental Research Insti- tute of Michigan, v. 11, p. 1369—1398. Rowan, L. C., Wetlaufer, P. H., Goetz, A. F. H., Billingsley, F. C., and Stewart, J. H., 1974, Discrimination of rock types and detection of hydrothermally altered areas in south-central Nevada by the use of computer-enhanced ERTS images: U. S. Geological Survey Professional Pa- per 883, 35 p. Rowe, J. S., 1961, The level-of—integration concept and ecology: Ecology, v. 42, no. 2, p. 420—427. 1969, Vegetation description and classification, in D. S. Lacate, compiler, Guidelines for bio-physical land classification, Ministry of Fisheries and Forestry, Queen’s Printer, Ottawa, p. 17—23. Sauer, C. 0., 1921, The problem of land classification: Annals of the Association of American Geographers, V. 11, p. 3—16. Schneider, S. J., 1966, The contribution of geographical air- photo interpretation to problems of land divisions ac- cording to natural units: Actes du IIe Symposium In— ternational de Photo Interpretation, Paris, II—23 to VI—28. Scott, R, 1964, Areal variations in the class structure of the central place hierarchy: Australian Geographic Studies, 2:76—86. Scott, R. M., and Austin, M. P., 1971, Numerical classifica- tion of land systems using geomorphological attributes: Australian Geographic Studies, v. 9, no. 1, p. 33—40. Shilts, W. W., and Boydell, A. N., 1974, Terrain mapping in the Churchill—Chesterfield inlet corridor, District of Keewatin: Report of activities, Part A, April to October 1973, Canadian Geological Survey Paper no. 74—1, p. 253—256. Shlien, S., and Goodenough, D., 1974, Quantitative methods of processing the information content of ERTS imagery for terrain classification: Second Canadian Symposium on Remote Snsing, v. 1, p. 237—265. Siegal, B. S., and Goetz, A. F. H., 1977, Effect of vegetation on rock and soil type discrimination: Photogrammetric Engineering and Remote Sensing, V. 43, no. 2, p. 191—196. Soil Survey Staff, 1951, Soil Survey Manual: Agricultural Handbook no. 18, U.S. Soil Conservation Service, 503 p. 1975, Soil Taxonomy: Agricultural Handbook 436, U.S. Soil Conservation Service, 754 p. Sokal, R, R., and Sneath, P. H. A., 1963, Principles of nu— merical taxonomy: W. H. Freeman, San Francisco, 359 p. Solntsev, N. A., 1962, Basic problems in Soviet landscape sci— ence: Soviet Geography—Review and Translation, v. 3, no. 6, p. 3—15. Speight, J. G., 1977, Land form pattern description from aerial photographs: Photogrammetria, v. 32, p. 161—182. Steiner, D., and Salerno, A. E., eds., 1976, Remote sensor data systems, processing and management, in R. G. Reeves, ed., Manual of Remote Sensing: American Society of Photogrammetry, Falls Church, p. 611—803. Stewart, G. A., (ed), 1968, Land evaluation: Melbourne, 392 p. Stewart, G .A., and Perry, R. A., 1953, Survey of Townesville- Bowen Region (1950) : CSIRO, Australia, Land Research Series 2, 87 p. Stoddart, D. R., 1965, Geography and the ecological ap— proach: The ecosystem as a geographic principle and method: Geography, v. 50, p. 242—251. Story, R., Yapp, G. A., and Dunn, A. T., 1976, Landsat pat- terns considered in relation to Australian resources sur- veys: Remote Sensing of Environment, v. 4, no. 4, p. 281—303. Swain, P. H., 1973, Pattern recognition: A basis for remote sensing data analysis: LARS Information Note 111572, Laboratory for Applications of Remote Sensing, Purdue University, West Lafayette, 41 p. Szava-Kovats, E., 1966, The present state of landscape theory and its main philosophical problems: Soviet Geography— Review and Translation, V. 7, n0. 7, p. 229—243. Taranik, J. V., and Trautwein, C. M., 1976, Integration of geological remote sensing techniques in subsurface analy- sis: U.S. Geological Survey Open File Report 76—402, Sioux Falls, 60 p. Taylor, P. J., 1977, Quantitative methods in geography: An introduction to spatial analysis: Houghton Mifi‘lin 00., Boston, 386 p. Thie, J., 1976, Evaluation of remote sensing techniques for bio-physical land classification in the Churchill area, Manitoba: M. S. Thesis Department of Soil Sciences, University of Manitoba, 89 p. Thomas, M. F., 1969, Geomorphology and land classification in tropical Africa, in Thomas, M. F., and Whittington, G. T., eds., Environment and land use in Africa: Meth— uen, London, p. 103—145. Troll, C., 1966, Landscape ecology: Paper 54, Proceedings, lst International Seminar on Integrated Survey of the Natural Environment ITO/UNESCO, Delft. United Nations Educational, Scientific, and Cultural Organi- zation, (UNESCO), 1968 Aerial surveys and integrated Macmillan, 38 INTEGRATED TERRAIN MAPPING WITH DIGITAL LANDSAT IMAGES studies: Proceedings of the 1964 Toulouse Conference, UNESCO, Paris, 575 p. United States Army Engineer Waterways Experiment Sta- tion (USAEWES), 1959, Handbook, a technique for preparing desert terrain analogs: Technical Report no. 3—506. 1961, Traflicability of soils—soils classification: Tech- nical Memorandum no. 3—240. 1963a, Forecasting traflicability of soils: Technical Memorandum no. 3—331, v. 2. 1963b, Military evaluation of geographic areas—Re- ports on activities to 1963; Miscellaneous paper no. 3—610. 1963c, Environmental factors affecting ground mobil— ity in Thailand: Technical Report no. 5—625, Appendix C. 1965—67, Terrain evaluation by electromagnetic means: Technical Report no. 3—693, reports 1—4. 1968, Mobility environmental research study, quanti- tative method for describing terrain for ground mobility: Technical Report no. 3—726. U. S. Department of Agriculture, 1958, Land capability clas- sification: Soils Memorandum SOS—22. U. S. Department of the Interior, 1951, Manual, v. 5, Irri— gated Land Use: Bureau of Reclamation, Denver. Unstead, J. F., 1933, A system of regional geography: Geog- raphy, v. 18, p. 175—187. Van Roessel, J., 1971, Automated mapping of forest resources from digitized aerial photographs: International Union of Forest Research Organizations, Section 25, Joint Re- port by working group application of remote sensors in forestry, p. 177—188. Varnes, D. J., 1974, The logic of geological maps with refer- ence to their interpretation and use for engineering purposes: U. S. Geological Survey Professional Paper 837, 48 p. Verstappen, H. Th., 1966, The role of landform classification in integrated surveys: Actes du IIe Symposium Interna- tional de Photo-Interpretation, Paris, VI 35—VI 39. Vink, A. P. A., 1960, Quantitative aspects of land classifica- tion: 7th International Congress of Soil Science, Madi- son. 1966, Integrated surveys and land classification: Pa- per S—12, Proceedings, 1st International Seminar on Inte- grated Survey of the Natural Environment, April 1966, Delft. 1975, Land use in advancing agriculture: Springer- Verlag, New York, 394 p. Vinogradov, B. V., Gerenchuk, K. I., Isachenko, A. G., Raman, K. G., and Tseselchuk, Yu N., 1962, Basic principles of landscape mapping: Soviet Geography—Review and Translation, v. 3, no. 6, p. 15—29. Vinogradov, B. V., and Kondratyev, K. Ya., 1971, Geographic applications of remote sensing: Soviet Geography—Re- view and Translation, v. 12, no. 6, p. 383—392. Wacker, A. G., and Landgrebe, D. A., 1972, Minimum distance classification in remote sensing; Proceedings of the lst Canadian Symposium on Remote Sensing, Ottawa, De- partment of Energy, Mines, and Resources, v. 2, p. 577— 599. Watanabe, A., 1960, Land use survey and land classification survey in Japan: Proceedings of the Ninth Pacific Sci- ence Congress, v. 18, Bangkok (1957), p. 41. Webster, R., 1963, The use of basic physiographic units in airphoto interpretation: Archives Internationales de Pho- togrammetria, v. 14, p. 143—148. Webster, R., and Beckett, P. H. T., 1970, Terrain classifica— tion and evaluation using air photography: Photogram- metria, v. 26, p. 51—57. Welch, D. M., 1977, Ecological land classification in Canada: Department of Fisheries and Environment. Mimeo— graphed, 4 p. Wertz, W. A., and Arnold, J. F., 1972, Land systems inven— tory: US. Forest Service, Intermountain Region, Ogden, 12 p. Westin, F. C., Stout, M., Jr., Bannister, D. L., Frazee, C. J., 1972, Soil surveys for land evaluation in South Dakota: Agronomy Abstracts, p. 122. White, L. P., 1974, Natural resources mapping of Ethiopia from ERTS—l imagery: European Earth Resources Sat- ellite experiments, European Space Research Organiza- tion, Neuilly, p. 179—184. Whittaker, R. H., 1975, Communities and ecosystems: Mac- Millan, New York, 385 p. Whittlesey, D., 1954, The regional concept and the regional method, in P. James and C. F. Jones, eds., American Geography: Inventory and Prospect. Syracuse Univer- sity Press, Syracuse. Williams, D. L., and Coiner, J. C., 1975, Utilization of Land- sat imagery for mapping vegetation on the millionth scale: Proceedings of NASA Earth Resources Survey Symposium, Houston, Texas, June 1975, NASA TMX— 58168, JSC 09930, v. 1A, p. 53—65. Wong, K. W., Thornburn, T. H., and Khourm, M. A., 1976, Automatic soil identification from remote sensing data: Photogrammetric Engineering, v. 43, p. 73—80. Wood, W. F., and Snell, J. B., 1959, Predictive methods in topographic analysis, I—Relief, slope, and dissection on inch-to-the-mile maps in the U.S.A.: H.Q. Quartermaster Research and Engineering Command, Technical Report EP—112, Natick, Mass. 1960, A quantitative system for classifying land- forms: H.Q. Quartermaster Research and Engineering Command, Technical Report EP—124, Natick, Mass. Wooldridge, S. W., 1932, The cycle of erosion, and the repre- sentation of relief: Scottish Geographical Magazine, v. 48, p. 30-36. Wright, A. C. S., 1960, Land classification on the islands of the southwest Pacific: Proceedings of the Ninth Pacific Science Congress, v. 10, p. 44—49. Wright, R. L., 1967, A geomorphological approach to land classification: Ph.D. thesis, University of Sheffield. 1972a, Principles in a geomorphological approach to land classification: Zeitschrift fur Geomorphologie, v. 16, p. 351—373. 1972b, Some perspectives on environmental research for agricultural land use planning in developing coun- tries: Geoforum, v. 10, p. 15—33. Yefremov, Yu. K., 1961a, An approach to integrated physical— geographic description of an area: Soviet Geography— Review and Translation, v. 2, no. 7, p. 42—47. 1961b, The concept of landscape and landscapes of different orders: Soviet Geography#Review and Trans- lation, v. 2, no. 10, p. 32—43. SELECTED BIBLIOGRAPHY 39 Young, A., 1973, Rural land evaluation, in J. A. Dawson and J. C. Doornkamp, eds., Evaluating the human environ- ment: Arnold, London, p. 5—33. Young, H. E., and Stoeckler, E. G., 1956, Quantitative evalua- tion of photo interpretation mapping: Photogrammetric Engineering v. 22, p. 137—143. Zonneveld, I. S., 1972, Land evaluation and land(scape) sci- ence: ITC textbook of photo-interpretation, v. VII, Chap- ter VII, Enschede, The Netherlands. Zube, E. H., Brush, R. 0., Fabos, J. Gy., 1975, Landscape assessment—values, perceptions, and resources: Dowden, Hutchinson, Ross, Stroudsburg, Pa., 367 p. {I US. GOVERNMENT PRINTING OFFICE : 1979 0—287-124 Sculptural Variation of the Pliocene Pelecypod Patinopectert healeyi (Arnold) By ELLEN JAMES MOORE GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 Primary sculpture and microsculpture described and illustrated; includes stratigraphic occurrence and ecology UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Moore, Ellen James. Sculptural variation of the Pliocene pelecypod Patinopecten healeyi (Arnold) (Geological Survey professional paper ; 1103) Bibliography: p. 12-13. Includes index. 1 Supt. of Docs. no.: I 19.16:1103 1. Patinopecten healeyi. 2. Paleontology~Pliocene. 3. Paleontology— California. I. Title. II. Series: United States. Geological Survey. Professional paper ; 1103. QE812.P4M66 564’.11 79-607097 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock Number 024-001-03225-2 CONTENTS Page page Abstract ________________________________________________ 1 Patinopecten healeyi (Arnold)—-continued Introduction ____________________________________________ 1 Microsculpture ______________________________________ 5 Purpose and scope ____________________________________ 1 Comparison with other species ________________________ 6 Abbreviations ________________________________________ 1 Geographic and stratigraphic distribution of Acknowledgments _____________________________________ 2 Patinopecten healeyi (Arnold) and P. lohri Patinopecten healeyi (Arnold) ______________________________ 2 (Hertlein) __________________________________________ 7 Synonymy __________________________________________ 2 Ecology ______________________________________________ 10 Primary sculpture ____________________________________ 2 Conclusion __________________________________________ 11 Right valve ______________________________________ 2 Fossil localities (Pliocene, California) ______________________ 11 Left valve ______________________________________ 3 References cited __________________________________________ 12 Auricles, byssus, and ctenolium __________________ 4 Index ____________________________________________________ 15 Hinge area ______________________________________ 5 ILLUSTRATIONS [Plates follow index] PLATES 1—12. Patinopecten healeyi (Arnold). 13. Patinopecten lohri (Hertlein) and Patinopecten healeyi (Arnold). 14, 15. Patinopecten yessoensis (Jay) and Patinopecten healeyi (Arnold). Page FIGURE 1. Index map showing geographic distribution of Patinopecten healeyi (Arnold) and Patinopecten lohri (Hertlein) _______ 8 III SCULPTURAL VARIATION OF THE PLIOCENE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD) By ELLEN JAMES MOORE ABSTRACT The sculptural variation of both right and left valves of Patinopecten healeyi (Arnold) is more extreme than has been gener- ally known and has led to difficulty in distinguishing P. healeyi from other species, especially Patinopecten lohri (Hertlein) and even in the identification of the species itself. Variants of this common Pliocene species, which occurs in California and Baja California, in- clude a smooth form with subdued dichotomous ribs on the right valve and closely spaced, fine ribs on the left valve with some inter- calaries that are as wide as the primary ribs; right valves with flat, widely spaced, dichotomous ribs and right valves with high, rounded, closely spaced, dichotomous ribs; and left valves with high square ribs and rounded intercalaries and left valves with smooth interspaces and no intercalaries. Scanning electron micrographs of the imbricated microsculpture that is found only on left valves ofP. healeyi show the development of this sculpture. The same microsculpture is present on both the left and the right valves of the living species Patinopecten yessoensis (Jay) of Japan. When more data are available, this microsculpture may prove to be taxonomically significant. P. healeyi is generally more common in southern California than P. lohri and occurs as far south as Vizcaino Peninsula, Baja Cali- fornia. Ecological data concerning the closely related living species Patinopecten caurinus (Gould) include the observations that it lives at depths of 15 to 275 In, is not an active swimmer, is byssally at- tached until it has grown to about 4 cm in shell diameter, and that its predators are Octopus, the large sun-star Pycnopodia, and crabs. INTRODUCTION PURPOSE AND SCOPE The problem of identifying sculptural variants of Patinopecten healeyi (Arnold) became apparent when specimens of right valves of this species that on cur- sory inspection looked like Amusium were found in unnamed Pliocene strata on San Clemente Island, Calif. (Vedder and Moore, 1976). This form has now been named Patinopecten healeyi sanclementensis by Suzuki and Stadum (1978). Patinopecten healeyi (Arnold) was originally de- scribed from the San Diego Formation (Pliocene), Pacific Beach, Calif, as Pecten expansus Dall (1878, p. 14) but later renamed Pecten (Patinopecten) healeyi Arnold (1906, p. 103—105, pl. 36, figs. 1, 1a; pl. 37, figs. 1, 1a, 2) because the older name was preoccupied. Although variation in the sculpture of P. healeyi has been noted (Arnold, 1906, p. 103— 105; Woodring and Bramlette, 1950, p. 84; Hertlein and Grant, 1972, p. 185), the variation is more diversified than has been generally understood. Right valves that are smooth to a height of 30 mm have been figured (Hertlein and Grant, 1972, pl. 33, fig. 9; pl. 36, fig. 9), but none so large as those collected from San Clemente Island (pl. 2, figs. 3—7), from unnamed Pliocene strata, had been previously illustrated (Suzuki and Stadum, 1978). In addition to the smooth form, the right-valve sculpture varies from flat, widely spaced, dichotomous ribs that become obsolete near the ventral margin to high, rounded, closely spaced, dichotomous ribs. The left- valve sculpture ranges from closely spaced, fine ribs of nearly equal size to high, Wide, flat square ribs alter- nating with one or two rounded secondary ribs. These extremes in sculptural variation have not been clearly illustrated or described, and this range of variation has led to confusion between named species. Comparisons made with the similar species Patinopecten lohri (Hertlein), with which P. healeyi has been confused, include geographic and strati- graphic distribution. Observations on the habitat of the closely related Holocene species Patinopecten caurinus (Gould) concern depth of occurrence, swim- ming, attachment, and predators. Scanning electron micrographs of the imbricated microsculpture of P. healeyi show its development, which may prove to be useful taxonomically. Approximately 400 specimens of Patinopecten healeyi from the San Diego Formation and about 100 each from the Fernando Formation in the Newport Beach area and the Niguel Formation in the San Juan Capistrano area were examined in the course of this study. ABBREVIATIONS OAS—California Academy of Sciences, San Francisco, Calif. LAM—Natural History Museum of Los Angeles County, Los Angeles, Calif. SU—Stanford University, Stanford, Calif. [These 1 2 SCULPTURAL VARIATION OF THE PELECYPOD PAT INOPECTEN HEALEYI (ARNOLD) types are now deposited in the California Academy of Sciences.] . UCMP—University of California Museum of Paleon- tology, Berkeley, Calif. USGS—M—U.S. Geological Survey, Menlo Park, Calif, Cenozoic locality register. USNM—National Museum of Natural History,‘ Washington, DC. ACKNOWLEDGMENTS John G. Vedder, US. Geological Survey, provided specimens of Patinopecten healeyi (Arnold) that he had collected from Pliocene strata in southern California and furnished stratigraphic information. F. R. Ber- nard, Pacific Biological Station, Nanaimo, British Columbia, kindly provided information on the living habits of Patinopecten caurinus (Gould). Barry Roth, California Academy of Sciences, searched the Academy collections and loaned specimens of P. healeyi. Judith T. Smith, Palo Alto, California, Louie Marincovich, Jr., US. Geological Survey, and J. W. Durham, University of California, assisted with dis- cussions and the loan of specimens. W. O. Addicott, US. Geological Survey, and T. R. Waller, Smithso— nian Institution, read the manuscript and improved its technical quality. The scanning electron micrographs were taken by Robert Oscarson, the photographs by Kenji Sakamoto, both of the US. Geological Survey, and I thank them for their patience and attention to detail. To E. C. Wilson, Curator, Natural History Museum of Los Angeles County, Los Angeles, Calif, I express my special gratitude for the loan of about 400 speci- mens of P. healeyi from the San Diego Formation and for other courtesies he graciously extended to me. PATINOPECTEN HEALEYI (ARNOLD) Pecten expansus Dall, 1878, US. Natl. Mus. Proc., v. 1, p. 14 [1879]. Not Pecten expansus Smith, 1847, Geol. Soc. London Quart. Jour., v. 3, p. 413, 419, pl. 18, fig. 21. Pecten (Patinopecten) expansus Dall, 1898, Wagner Free Inst. Sci. Trans, v. 3, pt. 4, p. 706, pl. 26, fig. 1. Arnold, 1903, California Acad. Sci. Mem., v. 3, p. 108. Pecten (Patinopecten) healeyi Arnold, 1906, US. Geol. Survey Prof. Paper 47, p. 103, pl. 36, figs. 1, 1a; pl. 37, figs. 1, 1a, 2. Arnold and Anderson, 1907, US. Geol. Survey Bull. 322, p. 154, pl. 26, figs. 1, 2. Grant and Gale, 1931, San Diego Soc. Nat. History Mem., v. 1, p. 196, pl. 6, figs. 2a, 2b. Hertlein and Grant, 1972, San Diego Soc. Nat. History Mem. 2 (pt. 2b), p. 183~185, pl. 31, figs. 1, 4, 6, 7; pl. 33, fig. 9; pl. 36, figs. 8, 9; text fig. 9. Patinopecten healeyi (Dall), Vedder and Moore, 1976, p. 122, pl. 3, figs. 2—6, 8. Pecten (Patinopecten) healeyi Arnold sanclementensis Suzuki and Stadum, 1978, Nat. Hist. Mus, Los Angeles Co., Contrib. Sci. 299, p. 10—11, figs. 18, 19. Holotype.—USNM 148012. Type locality.—San Diego Formation (Pliocene), San Diego County, Calif. A complete synonymy is given in Hertlein and Grant (1972, p. 183—184). The elevation of Patinopec- ten to generic rank does not make it possible to use the specific name expansus for this species, because Pecten expansus Dall is a junior primary homonym. PRIMARY SCULPTURE RIGHT VALVE Plate 1, figures 1—4, 6~8; plate 2, figures 1—3, 5—7; plate 3, figures 1—6; plate 4, figures 1—4, 8; plate 14, figure 3 The typical sculpture of the right valve (Arnold, 1906, p. 103—105; Hertlein and Grant, 1972, p. 185) consists of 18 to 21 prominent squarish, subequal ribs that branch to become dichotomous and on a few indi- viduals trichotomous, after 30 to 40 mm in height (pl. 1, fig. 1). The medial sulcus of the rib may be as deep as the interspace, completely dividing the primary rib. The interspaces are subequal, much narrower than the ribs, deeply channeled, and on some specimens or- namented by a small rounded intercalary riblet. Patinopecten healeyi is easily recognized by the flat-topped sulcated radial ribs on the right valve. Juvenile specimens are smooth in the early stage; ra- dial undulations of the anterior margin typically begin to form after the shell has attained a height of 3 to 5 mm (pl. 1, figs. 4, 6). Some specimens remain smooth to a height of 23 mm. The ribs on the right valve, especially those toward the anterior and poste- rior margins, begin to develop a slight medial sulcus after the shell has attained a height of 10 mm, but such sulcations on the medial ribs are well developed only after a height of 30 to 40 mm has been attained. The ribs on some large specimens bear two sulcations that divide the major ribs into three small riblets, but such forms, so far as known, have no taxonomic sig- nificance (Hertlein and Grant, 1972, p. 185). A narrow unsculptured band may be present at the anterior and posterior margins, usually wider at the posterior side (pl. 1, fig. 8). A smooth form of P. healeyi (pl. 2, figs. 3—7) that tends to be relatively thin shelled occurs only in un- named Pliocene strata on San Clemente Island, southern California (Vedder and Moore, 197 6, p. 122, pl. 3, figs. 2—6, 8; Suzuki and Stadium, 1978, figs. 18, 19). A fragment of a large right valve shows the disk PRIMARY SCULPTURE 3 to be smooth to about 30 mm, at which point strong dichotomous ribs with very narrow interspaces appear (pl. 2, fig. 3). An incomplete right valve that is nearly 100 mm high has the disk smooth in the midportion of the shell to a height of about 40 mm, the rest of the shell being sculptured by very low, closely spaced, dichotomous and trichotomous ribs (pl. 2, fig. 7). A large incomplete worn right valve, originally more than 145 mm long, has a smooth disk to a height of 55 mm and shows subdued dichotomous ribs near the posterior margin; the largest specimen obtained was about 160 mm high with the hinge about 75 mm long. A small complete right valve that is 50 mm high is essentially smooth; traces of the same rib pattern seen on the other right valves from San Clemente Island are visible in low-angle reflected light (pl. 2, fig. 6). These smooth right valves have a wide unsculptured band at both the anterior and posterior margins (pl. 2, figs. 3, 7). Three right valves from the San Diego Formation at Pacific Beach, Calif. (CAS 105, 547), have a smooth disk to a height of 20 mm and ribs somewhat subdued for an additional interval of about 10 mm (pl. 2, fig. 1); one right valve (CAS 105) has closely spaced low ribs that are not dichotomous on the midportion of the shell (pl. 2, fig. 2). Woodring (in Woodring and Bramlette, 1950, p. 84) noted that the interspaces on many right valves of P. healeyi from the Santa Maria basin are much nar- rower than the interspaces on right valves of P. healeyi from the San Diego Formation and that the right valves are more inflated. A few specimens from collections now available from the San Diego Forma- tion show this same sculpture and valve inflation (pl. 3, figs. 1, 5), as do some individuals from the Niguel Formation (pl. 3, fig. 4) of Pliocene age in the San Juan Capistrano quadrangle (USGS M2096, M2098). In one collection from the Fernando Formation (Pliocene), in the Newport Beach quadrangle (USGS M2753), right valves with dichotomous and trichotomous ribs (pl. 4, fig. 2), right valves with nar- row rather subdued ribs (pl. 4, fig. 1), and right valves with smooth disks to a height of about 50 mm followed by low subdued ribs (pl. 4, fig. 4), occur together. In another collection from the same area (USGS M5040), fragments of right valves include the smooth form (pl. 3, fig. 2), some with narrow, widely spaced, dichoto- mous ribs (pl. 3, fig. 6), and others with very closely spaced, dichotomous and trichotomous ribs (pl. 3, fig. 3). On some specimens of right valves from this local- ity, there is no unsculptured band at the posterior shell margin. The right valve of P. healeyi may extend as much as 10 mm beyond the left valve along the entire distal margin of the disk (pl. 6, fig. 7). A similar difference between valves has been noted on Patinopecten caurinus (Gould), the Holocene genotype of Patinopec- ten, which has been collected from sedimentary rocks as old as Pliocene (Grau, 1959, p. 147; Moore, 1963, p. 63). LEFT VALVE Plate 2, figure 4; plate 4, figure 5; plate 5, figures 1—3, 6; plate 6, figures 3, 7; plate 7, figures 1, 2, 4, 5; plate 8, figures 1, 3, 4, 6; plate 9, figures 4, 7; plate 10, figures 1, 3, 4; plate 15, figure 3 Arnold (1906, p. 103—105) described the left valve of P. healeyi as much compressed and the ribs as narrow and rounded on some individuals with a narrow peak along which there may be a narrow, slightly raised line. The interspaces are wide and each is ornamented by a more or less prominent, rounded intercalary rib— let. Although the typical left valve sculpture has been described as primary ribs with interspaces invariably bearing a secondary rib (Arnold, 1906, p. 104; Hert- lein and Grant, 1972, p. 185), it is common to find specimens that have a few smooth interspaces without a secondary rib, and even specimens with no secon- ' dary ribs are occasionally found (pl. 5, fig. 2). The left valve may bear 17 to 21 primary ribs; 18 is the most common number. The umbonal angle, measured on the disk between ears, is between 110° and 120°; 115° is the most common, and on inequilateral specimens with a very enlarged anterior ear, 120°. The left-valve sculpture of specimens of P. healeyi from the San Diego Formation ranges from narrow rounded ribs with wide interspaces that each bear a fine intercalary riblet (pl. 5, fig. 1) to wide square ribs that may bear a fine rib along the top (pl. 8, fig. 1) and that may have some interspaces that do not bear an intercalary. The square—ribbed forms typically begin with a sculpture of narrow rounded ribs that be- come flat when the shell reaches a height of about 60 mm (pl. 6, fig. 4). On some square—ribbed forms, the intercalaries are fine and rounded (pl. 7, fig. 5); on others, the intercalaries, though rounded, are much wider (pl. 8, fig. 4). On some left valves, the ribs tend to become obsolete near the ventral margin (pl. 9, fig. 7), a feature seen on P. caurinus (Moore, 1963, p. 65). Some left valves are markedly thinner than others that bear the same primary rib pattern. Left valves from the N iguel Formation (Pliocene) in the San Juan Capistrano quadrangle (USGS M2096, M2098) show the same marked variation of narrow rounded ribs to square flat ribs as seen on specimens from the San Diego Formation. One fragment of a large left valve has two secondary ribs (or a split sec- ondary) between the primary ribs near the anterior margin (pl. 9, fig. 4). 4 SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD) Left valves in a collection (USGS M2753) from the Fernando Formation (Pliocene) in the Newport Beach quadrangle include one fragment with multiple sec- ondary ribs at the anterior margin (pl. 7, fig. 2). Four left valves were collected from unnamed Pliocene strata on San Clemente Island (USGS M6503) with right valves of the smooth form. Al- though no articulated specimens were found, it is as- sumed that these left valves represent the smooth form. The ribs are unusually fine, narrow, and a bit more closely spaced than is common; some of the in- tercalaries are as wide as the primary ribs (pl. 5, fig. 3). One of these left valves is about 160 mm high. On some left valves, the shell curves upward along the ventral margin away from the soft parts, perhaps in response to pressure from the larger right valve. On most specimens, this extension of the left valve is exceptionally thin and ribs are obsolete; the extension is rarely preserved and may be more common than its preservation indicates. In his discussion of the Argopecten gibbus stock, Waller (1969, p. 31) stated that In the description of plicae, only features of the right valve are discussed because the interlocking of plicae along the distal margin produces a complimentarity***. Thus plicae that are distinctly broader than the interspaces on the right valve will likely be dis- tinctly narrower than the interspaces on the left valve. Grant and Gale (1931, p. 192), in their description of Patinopecten, stated that the left valve will have intercalaries if the right valve primary ribs are dichotomous. In the course of this study, I have found that if the right-valve primary ribs are strongly dichotomous, in essence producing another interspace, the usual left- valve response is to produce a strong secondary rib about equal in size to that of the space produced by the dichotomy. On these left valves, the primary ribs will be larger than average and square rather than rounded. If the right-valve disk is smooth and fol- lowed by low primary ribs that are only shallowly dichotomous, the left valve will usually respond with small rounded primaries and with secondaries of nearly equal size. On articulated specimens, one can usually predict the sculpture of either valve by simply examining the opposing valve. Variation in the sculpture of Holocene specimens of Patinopecten caurinus (Moore, 1963, p. 63—65) is not as extreme as seen on P. healeyi. The ribs on the right valves of large specimens of P. caurinus may become obsolete near the margins, as may the ribs on large left valves. Fine intercalaries are irregularly spaced on parts of the left valve. On some individuals, inter- calaries are occasionally present on the right valve but without a regular pattern or spacing. AURICLES, BYSSUS, AND CTENOLIUM Plate 1, figures 5, 6; plate 4, figures 6, 7; plate 5, figure 5; plate 6, figures 1, 2; plate 7, figure 3; plate 13, figures 1, 2; plate 15, figure 2 The right anterior auricle (ear) is slightly longer than the left anterior auricle, arcuate in front, and ornamented by several faint radial ridges; the byssal notch is prominent. The posterior auricle is slightly obliquely truncated and ornamented by sharp incre- mental lines and, on some specimens, by obsolete radiating ridges. The left-valve auricles are obliquely truncated and similarly sculptured (Arnold, 1906, p. 104). On large specimens (pl. 14, fig. 3), the left anterior auricle is larger than the right anterior auricle. The byssal notch is convexly folded and elevated above the rest of the auricle (pl. 7, fig. 3; pl. 13, fig. 1), a feature noted on P. caurinus, and the left anterior auricle is concavely folded toward the right, opposite the byssal notch, bringing the auricles closer together (pl. 6, figs. 1, 2; pl. 13, fig. 2). The fold on the left anterior auricle typically becomes more pronounced as the shell grows larger such that on very large specimens the byssal opening is nearly closed. Strong evidence suggests that the byssus on P. healeyi was functional at least during the early stages of growth. Several specimens, generally of small size, have been found that show a well-developed ctenolium (comblike row of teeth) below the anterior auricle (pl. 1, figs. 5, 6; pl. 4, figs. 6, 7); others have been seen that are large in size with the shell corroded in such a way as to show the ctenolium along the entire at- tachment margin of the auricle. The presumed func- tion of the ctenolium is to separate the byssal threads and keep them from twisting (Dall, 1898, p. 691). Wal- ler (1969, p. 20), noting that the presence of a ctenolium is correlated with the presence of a deep byssal notch, assumed that a deep byssal notch indi- cates the presence of a byssus or, for earlier growth stages, an active extrudible foot. Dall (1898, p. 691) said that the growth of the margin of the valve and auricle does not always coincide with the development of the ctenolium and that a species that normally shows this feature may have stages when the valve margin has grown over the old ctenolial set and the new set has not yet formed. Waller (1972a, p. 245) later stated ***the absence of a ctenolium and byssal gape on mature shells indicates that the species may lie free at this stage rather than at- tach bysally. Young individuals, which have a distinct ctenolium and byssal gape, are probably bysally attached. The ctenolium is present on small specimens of P. healeyi and is well developed, which probably indi- cates that it was not an obsolete character during the early stages of growth when the byssal opening was of MICROSCULPTURE 5 good size and not yet almost completely closed by the enlarged, strongly folded left anterior ear. The Holocene species Patinopecten caurinus is byssally at— tached in early life to a size of about 3 to 4 cm in shell diameter; above this size the byssus is no longer pres— ent (F. R. Bernard, written commun., 1976). The left-valve anterior auricle of P. healeyi may be higher as well as longer than the posterior auricle (pl. 5, fig. 5; pl. 6, fig. 1; pl 7, fig. 5; pl. 8, fig. 6). Marked enlargement of the left anterior auricle, typically characteristic of large specimens, is seen on some juvenile shells (pl. 10, fig. 3). The enlargement is gen- erally coincident with the increased flexure of the au- ricle and the resultant closing of the byssal gap. Some examples of the difference in size between left-valve auricles are: Posterior auricle 20 mm long and 13 mm high 27 mm long and 9 mm high 30 mm long and 19 mm high 32 mm long and 18 mm high 37 mm long and 19 mm high Anterior auricle 23 mm long and 20 mm high 34 mm long and 22 mm high 35 mm long and 27 mm high 38 mm long and 27 mm high 44 mm long and 27 mm high On complete specimens, the difference in length of right-valve auricles is found to be about the same as the left-valve auricles, but the height of the right- valve auricles remains equal. HINGE AREA Plate 1, figure 5; plate 6, figures 4—6; plate 8, figures 2, 5; plate 9, figures 1—3, 5, 6; plate 10, figure 2 The resilial pit on the right valve is bordered on each side by a narrow, sharp, projecting ridge (pl. 9, figs. 5, 6). The resilial pit on the left valve may be bordered by a ridge that is followed by a groove and a second shorter ridge (pl. 8, fig. 5) or may be bordered by only one ridge (pl. 9, fig. 1). On one articulated specimen, the right-valve resilial ridges rested in grooves between the left-valve resilial ridges. On all specimens, the inner shell is thickened parallel to the line of attachment of the ears. On the anterior portion of the right valve, although the shell is thickened, producing a strong smoothly rounded ridge (pl. 9, fig. 6), the ridge does not end in a denticle. On some specimens, however, the ridge ends in a slightly prominent node which on a few speci- mens could perhaps be considered an auricular denti- cle. At the posterior side of the right valve, the distal portion of the thickened shell ends in a rounded to somewhat pointed denticle (pl. 9, figs. 5, 6). On the anterior portion of the left valve, the thick- ened ridge usually terminates in a rounded denticle or a somewhat triangular ridge (pl. 8, fig. 2); on some specimens, however, no auricular denticle can be dis— tinguished. The thickened ridge on the left-valve posterior side is somewhat larger than the anterior ridge at the distal end and may terminate in a sub- dued denticle (pl. 6, fig. 4). MICROSCULPTURE Plate 5, figure 4; plate 6, figure 2; plate 10, figures 1, 3—5; plate 11, figures 1—3; plate 12, figures 1—3; plate 13, figure 5; plate 14, figures 1, 2; plate 15, figure 1 Small patches of an imbricated microsculpture simi— lar to that found on many different pectinids such as Vertipecten (Moore, 1963, p. 63), Chlamys ( Verrill, 1899, p. 73), and on some, if not all, species referred to Yabepecten by Masuda (1963, pl. 22, fig. 4) are pre- served on some left valves of P. healeyi (pl. 10, figs. 1, 3. 4); one juvenile specimen shows the entire surface to be so sculptured (pl. 10, fig. 4). Meek (1864, p. 26—27), in describing Patinopecten propatulus (Conrad) from the Miocene of Oregon, said ***it shows, under a magnifier, a very peculiar and beautiful style of sculpture resembling somewhat the regularly disposed asperities on the surface of a raSp***. In 1899 Verrill (p. 73—74, pl. 16, figs. 4, 5, 5a, 5b) named a new variety of Chlamys and illustrated a microsculpture similar to that on P. healeyi, which he described as follows: The concentric and divergent laminae and smaller riblets cross each other in such a way that a peculiar decussated sculpture is formed between the primary ribs on the early part of the shell, while on the older parts the interspaces are covered with elevated scales. Dall (1878, p. 14) said, in describing the upper (left) valve of Pecten expansus (= Patinopecten healeyi): The entire surface is covered with fine, slightly raised, sharp lamellae, which are waved in some places so regularly as to produce the appearance of a delicate reticulation, which, however, does not really exist***. Waller (1972a, p. 229) used the term shagreen for a similar microsculpture that he defined as a screenlike pattern of openings between projecting lamellae on the shell exterior. On the caption for his figure 12 (p. 229), he described the specimen illustrated as showing uneroded areas with strongly projecting, cell-forming flanges and eroded areas forming the typical shagreen pattern. MacNeil (1961, p. 227) noted that No specimens of Lituyapecten yet observed show any suggestion of the imbricating microsculpture, resembling the surface of metal lath, that characterizes left valves of Chlamys, Vertipecten, For- tipecten, and some species of Patinopecten such as P. yessoensis, P. propatulus (Conrad), and P. ibaragiensis Masuda ***, imbricating microsculpture occurs rarely in small patches on specimens of P. caurinus. A right valve from the Pliocene Koshiba Formation of Japan referred to Yabepecten tokunagai (Yoko- yama) by Masuda (1963, pl. 22, fig. 4) shows an imbri- cated microsculpture. The right valve of the Holocene west Pacific species Patinopecten yessoensis (Jay) also shows an imbricated microsculpture (pl. 14, fig. 1). Al- 6 SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD) though this microsculpture is fairly common on the left valve of east Pacific Patinopecten, it has not been found on the right valve. One well-preserved juvenile left valve of P. healeyi (pl. 10, figs. 4, 5) was found that had the imbricated microsculpture well preserved and was small enough to be mounted for the scanning electron microscope without destruction. The specimen was scanned from the dorsal to the ventral margin in the center of the disk between the same two ribs, and the progressive development of the microsculpture can be seen (pl. 11, figs. 1—3; pl. 12, figs. 1—3). This imbricated micro— sculpture has been found on young portions of the left valve of P. healeyi but has not been seen on the ma- ture parts of the shell. The fact that it develops on only a small portion of the shell and is fragile and easily abraded makes its preservation fortuitous. Wal- ler (written commun., 1977) said that on some Chlamys this microsculpture can appear, disappear, and reappear more than once during ontogeny and that this uneven occurrence is primary and not the result of erosion. On an especially well-preserved left valve from un- named Pliocene strata on San Clemente Island, closely spaced concentric lamellae are preserved (pl. 5, fig. 3); these lamellae are seen to be parallel and not imbricated on the electron micrograph of a shell fragment broken off the ventral edge (pl. 5, fig. 4). During examination of specimens of the Holocene species Patinopecten yessoensis (Jay), it was noted that imbricated lamellae merge to form a pseudosurface, apparently leaving a honeycomblike structure be— neath. This outer layer is loosely cemented to the un- derlying shell, rarely preserved, and when removed by abrasion leaves a barely traceable pattern on the shell (Moore, 1963, p. 63). Imbricated microsculpture may prove useful in de- termining the evolutionary trend of the Patinopecten bearing it, as it is seen only on left valves in the east Pacific but is also found on right valves of Patinopec- ten yessoensis and Yabepecten tokunagai (Yokoyama) in the west Pacific. Because this paper is intended to call attention to specific variation, and I have not dealt extensively with genera other than Patinopecten, I have chosen a conservative approach and used the genus Patinopec- ten for species that have been assigned by others to Mizuhopecten (Masuda, 1963) but have considered Yabepecten (Masuda and Addicott, 1970) to be a valid genus. I do wish to emphasize, however, that the mi- crosculpture on the west Pacific species of Patinopecten is different from the sculpture on the east Pacific species. It seems plausible to me that as more data are accumulated, using the scanning electron microscope, microsculpture may prove to be useful in the taxonomy of the pectinids. In the course of this study, I have found that large specimens unsuitable for mounting for the scanning electron microscope can be coated with a plastic spray, covered with a thick coat of liquid latex, the coating then removed and filled with colorless fingernail polish and the hardened polish mounted for the scanning electron microscope. This technique proved quite successful and should make it possible to study the microsculpture on specimens of any size. COMPARISON WITH OTHER SPECIES Patinopecten healeyi is closely similar to P. lohri (Hertlein) and sometimes confused with that species. Patinopecten lohri (Hertlein) (1928, p. 93) was origi- nally described as Pecten (Patinopecten) oweni Arnold (1906, p. 63, pl. 8, figs. 1, 1a, 1b), a name that was preoccupied. The holotype of P. lohri (pl. 13, figs. 3, 4, 6), according to Woodring (in Woodring and Bram- lette, 1950, p. 83—84), was presumably collected from the Tinaquaic Sandstone Member (early and middle Pliocene) of the Sisquoc Formation somewhere near Foxen Canyon, Calif. In his discussion of Patinopecten lohri from the Santa Maria basin of California, Woodring (in Woodring and Bramlette, 1950, p. 83) said that The ribs on large left valves of P. lohri are wide and divided, whereas on P. healeyi they are narrow and not divided, or on some very large left valves are moderately wide and faintly divided by one or more shallow grooves. Right valves of P. lohri generally have a strong secondary rib in the space between the primary ribs, whereas on right valves of P. healeyi secondary ribs are absent or, if present, generally are weak. Some right valves of P. lohri, however, lack secondary ribs or have weak secondaries. Left valves of both species have secondaries. Owing to the presence of divided ribs on both valves of P. lohri, right and left valves are difficult to distin- guish unless the ears are preserved, whereas right and left valves of P. healeyi are readily differentiated. The right valve of the holotype (UCMP 12081) of P. lohri (pl. 13, figs. 3, 4) is more inflated than is typi- cal for P. healeyi; the primary ribs are higher, dichotomous at an earlier stage, fewer in number (14), and therefore more widely spaced. Each interspace bears a wide secondary rib that first appears when the shell has reached a height of about 30 mm. The pri- mary ribs are deeply dichotomous, the first division of a rib taking place when the shell is about 15 mm in height, the last at about 55 mm. At the ventral mar- gin of the holotype, which is about 90 mm in height, the primary ribs, except two at each of the margins of the shell, are dichotomous, and two near the posterior margin are completely divided. Both sides of the split ribs are more rounded than on P. healeyi. A narrow unsculptured band is present along the posterior mar- gin of the shell. The right anterior auricle is poorly GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION 7 preserved but seems to be sculptured by subdued rib- lets and to have a byssal notch similar to P. healeyi. The posterior auricle bears a shallow groove bordered by low ridges; this feature is discernible on about two-thirds of the auricle but seems to disappear before reaching the posterior edge. The right anterior auricle is broken at the margin but was possibly not as high as the left anterior auricle. The right valve is notice- ably inequilateral, and the anterior margin, excluding the auricle, forms an angle of about 40° with the hinge; the posterior margin an angle of about 25°. The left valve of the holotype of P. lohri (pl. 13, fig. 6) bears fewer (12) primary ribs than P. healeyi, and these ribs are therefore more widely spaced. The ribs are also higher, especially on the younger portion of the shell, than is typical for P. healeyi. Each in- terspace has a strong secondary rib, and three of the interspaces closest to the posterior margin bear two secondary ribs. The shell is worn, but traces of concen- tric lamellar sculpture similar to that seen on some specimens of P. healeyi are visible under magnifica- tion. A few of the primary ribs near the central por- tion of the shell have subdued shell protuberances that seem not to be primary structures but rather to be related to a time of breakage and subsequent re- pair of the shell. The left valve is strongly inequilat- eral, and the posterior shell margin, excluding the ear, forms an angle of 25° with the hinge and with the anterior margin, 40°. The ears are markedly in— equilateral, the posterior being about 26 mm long and 13 mm high and the anterior about 30 mm long and 22 mm high. As discussed, a similar inequilateralty is seen on large specimens of P. healeyi. Arnold, in describing P. lohri (1906, p. 63) as Pecten (Patinopecten) oweni Arnold, said that it may be dis- tinguished from P. healeyi by its smaller size, greater convexity, fewer and stronger ribs, more prominent intercalary riblets on the right valve, and relatively much longer hinge line. The smooth form of P. healeyi is surprisingly simi- lar in external sculpture to Yabepecten condoni (Hert- lein, 1925, p. 41, pl. 4, figs. 8, 9) from the Montesano Formation (Miocene) of Washington, as figured by Masuda and Addicott (1970, figs. 1, 3—9). The right- valve primary ribs on P. healeyi are typically di- chotomous, whereas they are rarely so on Y. con- doni. The left-valve sculpture of Y. condoni seems to consist of small fine primaries with only occasional secondaries, whereas secondaries are commonly pres— ent in the left-valve interspaces on P. healeyi. Accord- ing to Masuda and Addicott (1970, p. 154), the hinge of Y. condoni has simple cardinal crura and a wide and shallow resilial pit, both characters that would separate it from P. healeyi. Hertlein (1925, p. 41), in describing Y. condoni, said that it has about 16 smooth faint ribs that broaden rapidly as the shell grows and are about two or three times as wide as the very slight interspaces at the ventral margin. He also noted that the right valve bears concentric lines of growth that are very promi- nent on some specimens and almost lacking in others, that the right-valve auricles are small, and that the anterior auricle bears a very slight byssal notch. The left-valve sculpture is similar to that of the right. The slight byssal notch on the right-valve auricle and the similarity of sculpture of the right and left valves are other characters that separate Y. condoni from P. healeyi. Lituyapecten turneri (Arnold) differs from P. healeyi by having very narrow, high, medially sulcated ribs and wide interspaces on the right valve and high nar- row ribs on the left valve with no intercalaries (Ar- nold, 1906, p. 106, pl. 34, fig. 4; pl. 35, figs. 2, 3; Peck, 1960, pl. 21, figs. 15, 16). Yabepecten tokunagai (Yokoyama) differs from P. healeyi in right-valve sculpture, having low, rounded, closely spaced ribs. In addition, an imbricated micro- sculpture is present on the right valve (Masuda, 1963, pl. 12, fig. 4), and this sculpture has been found only on left valves of P. healeyi. The marked consistent dichotomy of the right-valve ribs separates P. healeyi from other Patinopecten with the exception of P. lohri, already discussed. Although several species such as Patinopecten oregonensis (Howe), Patinopecten coosensis (Dall), and Patinopec- ten oregonensis cancellosus Moore may have a few dichotomous ribs at the anterior and posterior mar- gins of the right valve, none bear low, flat, dichoto- mous ribs over the entire shell surface. GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION OF PATINOPECTEN HEALEYI (ARNOLD) AND P. LOHRI (HERTLEIN) Patinopecten lohri is restricted to the Pliocene of California, and Patinopecten healeyi to the Pliocene of California and Baja California. Both species first ap- pear in the early Pliocene and, as unique split-ribbed giant pectinids, are of significance in the interpreta- tion of Neogene zoogeography and age determination (Addicott, 1974, p. 191). The base of the Jacalitos Stage1 is defined by the lowest occurrence of the split-ribbed species of Patinopecten, P. healeyi and P. lohri (Addicott, 1972, p. 15—16). Although most Patinopecten have one or two split ribs on the right valve, none show the unique sculpture of P. healeyi and P. lohri, which typically have all of the right- valve primary ribs split. 1Epoch assignments used herein follow the West Coast provincial usage outlined by Weaver and others (1944). 40 28° 0 SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD) 124° 122° 120° 118° 116° 114° 112° I | I I I 0 I ____ _______________ 0 R E G 0 N 1 13___I§_T_1_1______--——— __________ I '_"_"—"—‘_'—_'_'_-—_———--_- | I 1 I 1 ‘. O 1 1 ' I | 1 Cape I '. Mendo- y I I‘ — _Can l | 1 . i I r g N E V A D A ‘- U T A 11 I I . I " Point I Arena " \\ ||| 0 Sacramento \\\ I“ bu Point Reyes A \\\ '1 “\ l'. O ‘\ II ‘> \\ 1‘ ___________ “P ‘\\ : 0 0 Fresno \\ II Monterey \\ ' ”V \ .~~J — Kettleman / ‘\ .\| 1’ Hills ‘\ -‘ \\ k '6‘ ”1 “\J: I ¢ \‘A R I Z O N A ‘\ 4 " — 0 Santa Cruz Island U L f ;’ San Miguel lslando Q. _\ 1, Santa Rosa lslan? ) Santa Catalina Island“ \ Q: San Nicolas Islando \\I I San Clementefi San Diego’,./-"—_)" ls|and ’rf’” Meficanf"21y{TED 0 .Northeast Bank I M EXPLANATION O A Patinopecten Iohri (Hertlein) 6‘ O Pan‘nopecten healeyi (Arnold) .7 XS southernmost reported modem occurrence of Patinopecten caurinus (Gould) N Northernmost reported occurrence of species ‘4’ S Southernmost reported occurrence of species 0 100 200 MILES EE: 0 100 200 300 KILOMETE RS Bani-a a Sebulu'a'n Isla Cad rosgVizcac'no I FIGURE 1.—Geographic distribution of Patinopecten healeyi (Arnold) and Patinopecten lohri (Hertlein) and southern mod- ern occurrence of Patinopecten caurinus (Gould). (Compiled from Cummings and others, 1962; Dibblee, 1950; Durham and Addicott, 1965; Durham and Yerkes, 1964; Faustman, 1964; Glen, 1959; Hawkins and others, 1971; Hertlein and Grant, 1972; Jordan and Hertlein, 1926; Kern, 1973; Martin, 1916; Minch and others, 1976; Ogle, 1953; Stanton and Dodd, 1976; Vedder and Moore, 1976; Weaver and Meyer, 1969; Winterer and Durham, 1962; Woodring, 1930; Woodring and others, 1940; Woodn'ng and Bramlette, 1950.) GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION 9 The northernmost occurrences of P. healeyi are in the Eureka and Cape Mendocino areas of northern California (Ogle, 1953, pl. 5), the northernmost of P. lohri in the Point Reyes area (fig. 1). Specimens from the Falor Formation (Pliocene) on the bank of Boulder Creek, Blue Lake quadrangle, were loaned to me through the kindness of J. W. Durham, University of California; these specimens are typical P. healeyi. A concretion containing P. healeyi, also loaned me by Durham, was collected from beach drift at the base of the Cliff House in San Francisco. Presumably it came from the Merced Formation (Pliocene) offshore; this formation is known on land to the south. P. lohri has been found no farther south than the Santa Maria basin northwest of Los Angeles (Woodring and Bram- lette, 1950, p. 65), whereas P. healeyi occurs as far south as the Vizcaino Peninsula of Baja California Sur (Jordan and Hertlein, 1926, p. 417; Minch and others, 1976, p. 176). The two species are reported to occur geographically together at only three areas in California: the north- ern Santa Cruz Mountains (Cummings and others, 1962, pl. 24), the Kettleman Hills area (Stanton and Dodd, 1976, p. 91, fig. 4), and the Santa Maria basin (Woodring and Bramlette, 1950, p. 65). As will be shown, nowhere do the two species cooccur in one 10- cality, and, in general, P. lohri occurs stratigraphi- cally lower than P. healeyi. Patinopecten healeyi and P. lohri are reported near each other from the same stratigraphic interval in only one area, the Jacalitos Canyon area near Ket- tleman Hills (Stanton and Dodd, 1976, p. 91, fig. 4). In the Santa Maria basin, P. lohri is found stratigraphi- cally below P. healeyi, but in the Santa Cruz Moun- tains, it is reported to be stratigraphically above. The Santa Cruz Mountains occurrence may be in error, as the forms collected could well be a new species of Patinopecten (Clark, 1966) that closely resembles P. healeyi and is known to occur in the Santa Cruz Mountains. Unfortunately, the material collected by Cummings, Touring, and Brabb (1962) is missing and presumed to be lost. Arnold (1906, p. 63) found P. lohri in the lower part of the Purisima Formation, where, he stated, P. lohri seems to grade into P. healeyi, the form occurring at Lobitas and Purisima identified as P. healeyi serving as the link between the two species. Arnold (1906, p. 104, pl. 37, fig. 2) illustrated a specimen of P. healeyi from San Gregorio in San Mateo County and said that the right-valve specimens of P. healeyi from this area generally have flatter, more deeply dichotomous ribs than are typical of this species and left valves with secondary ribs nearly equal in size to the primary ribs. But he noted also that similar variation occurs in specimens from San Diego County and therefore con- cluded that these differences are not of taxonomic sig- nificance. Specimens that I have collected from San Gregorio certainly all fall within the range of sculptural variation of P. healeyi. The Patinopecten identified as P. (P.) cf. P. (P) healeyi in the Santa Margarita Formation in the Fel- ton quadrangle of the Big Basin area in San Mateo County by Clark (1966) is here assigned to Lituyapec- ten purisimaensis (Arnold). In the northern Santa Cruz Mountains, Patinopec- ten lohri is found in the Pomponio and San Gregorio Members of the Purisima Formation, as used by Cummings, Touring, and Brabb (1962), pl. 24), stratigraphically above the occurrence of Patinopecten healeyi in their Tahana Member of the Purisima For— mation in the same area. As stated, P. healeyi may have been confused with P. n. sp. Clark in this area. Grant and Gale (1931, p. 198) said that P. lohri and P. healeyi commonly occur together but that at some places P. lohri is more common in older horizons. Stewart (in Woodring, Stewart, and Richards, 1940, p. 91—92) noted that the specimen from Elsmere Canyon in Ventura County figured by Grant and Gale (1931, pl. 6, figs. 1a, 1b) as P. lohri probably is P. healeyi, and I concur. Stewart identified P. lohri in the Etche- goin Formation of the Kettleman Hills, where he found it to be especially common in the Patinopecten Zone. Kern (1973, p. 13, 74) recorded P. lohri in the Towsley Formation in the San Fernando quadrangle. Woodring (in Woodring and Bramlette, 1950, p. 83), in discussing the occurrence of Patinopecten in the Santa Maria district, said that P. lohri is found in the oldest formation containing marine Pliocene fossils, P. healeyi in the youngest, and Lituyapecten dilleri in in- tervening strata, and that although their ranges over- lap, the three species are stratigraphically useful. He added that P. lohri is present in the Tinaquaic Sandstone Member of the Sisquoc Formation and a comparable form in diatomaceous strata of the Sis- quoc; a variety of L. dilleri in diatomaceous strata of the Sisquoc and L. dilleri proper in the Foxen Mudstone and the Cebada Member of the Careaga Sandstone; and P. healeyi in the Foxen Mudstone and the Careaga. P. healeyi and P. lohri do not occur within the same stratigraphic interval in the Santa Maria district, although both are associated with L. dilleri. Stanton and Dodd (1976, p. 90—91) noted that P. lohri is more common in the upper part of the Jacalitos Formation of former usage, as it was origi- nally mapped in the Zapato Chino section of the Jacalitos Canyon area, and that the fauna contained in this section is strongly suggestive of zones low in the Etchegoin Formation as exposed in North Dome in the Kettleman Hills. They collected P. lohri from the 10 middle upper part of the so-called Jacalitos and the upper middle part of the San Joaquin Formations and P. healeyi from the middle part of the San Joaquin Formation. In the Jacalitos Canyon sections then P. healeyi and P. lohri occur within the same strati- graphic interval; even there, they were not collected together at the same locality (Stanton and Dodd, 1976, p. 91, fig. 4). Patinopecten lohri has not been found in the Niguel, Fernando, or San Diego Formations in southern Cali— fornia, where P. healeyi is commonly collected, pre— sumably because these areas are beyond the south- ernmost range of P. lohri. It is apparent that part of the stratigraphic range of P. healeyi and P. lohri, as well as part of the geo- graphic range, is the same. Yet the two species seem never to have been collected together from one locality despite reports to the contrary. P. lohri is more com- mon in middle California, P. healeyi more common in southern California; P. lohri is less common generally and much more restricted in its geographic occur- rence. Of a total of approximately 135 species of mol- lusks that occur with P. lohri (Durham and Addicott, 1965, table 1, p. A12—A14), about 40 species are not found with P. healeyi, although the same genera occur with both species. The reported stratigraphic occur- rence of the two species, assuming all identifications to be correct, precludes the possibility sometimes suggested that P. healeyi was the descendant of P. lohri (Arnold, 1906, p. 63; Hertlein, in Hertlein and Grant, 1972, p. 185). Perhaps the explanation for the distribution of P. healeyi and P. lohri lies in ecologic parameters not yet apparent from the fossil record. ECOLOGY On the basis of what we know about the living habits of modern pectinids, especially Patinopecten, some speculations can be made on the ecology of P. healeyi. Fitch (1953, p. 44) stated that the geographic range of the modern Patinopecten caurinus (Gould) is from Wrangell, Alaska, to Eureka, Calif, and that the species is frequently taken in considerable numbers by flatfish trawlers at depths of 58 to 88 m. Grau (1959 p. 147—148) gave the geographic range of P. caurinus as Channel Inlet, Orca Inlet, Cordoba, Alaska, to Point Reyes, Calif, the bathymetric range as 37 to 183 In, or possibly deeper. F. R. Bernard (written com— mun., 1976) says that P. caurinus lives at depths of 15 to 275 m and that in British Columbia its maximum population density occurs at about 35 m on a mixed sand and mud bottom. In the natural habitat, the species has been observed lying in small depressions that are presumed to be a result of current scour SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD) around the shell. P. caurinus, off British Columbia, is not an active swimmer (F. R. Bernard, written commun., 1976). It remains in the same place and moves only when di- rectly threatened by contact with a starfish. The typi— cal pattern of movement consists of vigorous valve- pumping, moving the animal upward at an angle of about 45° for 2 meters or so, then a cessation of activ- ity and fall through the water. At all times, the right valve is downmost. Although all individuals move, the smaller of the nonsessile animals are more active. P. caurinus is bysally attached to a size of about 3 to 4 cm in shell diameter (F. R. Bernard, written com- mun., 1976) and has a ctenolium during its young stage. The predators of P. caurinus are Octopus and the large sun-star Pycnopodia; juveniles are attacked by crabs (F. R. Bernard, written commun., 1976). Flem- ing (1957, p. 14) noted that fossil pectinids under 30 mm long are much rarer than large individuals and believes that predatory benthic fish probably eat more young pectinids than adults. Waller (1972b, p. 55) suggested that radial ribs of pectinid shells serve to buttress the thin growing edges of the shells against crushing forces exerted by predators and to stabilize the living position in shift- ing sediment. As noted earlier, the right valve of P. healeyi, presumed to be the lower, may extend beyond the left valve by as much as 10 mm. This extension may help keep silt from being washed up onto the soft parts of the animal when it is at rest with the valves open. It may also produce a closure less accessible to the possible predators of P. healeyi, such as Octopus and Pycnopodia, for rather than being able to ap- proach the interlocked margin of both valves, it would be necessary for them to pry up the left valve or break off the extension of the right valve. Specimens of P. healeyi in the collections show repeated breakage and subsequent repair to the shell (pl. 1, fig. 8; pl. 7, fig. 1; pl. 8, figs. 3, 6), and this breakage is more common on the left valve. Many shells also show nonrepaired breakage and chipping at the margins, but this dam- age could have occurred after the animal died. Cahn (1951, p. 56) noted that Patinopecten yessoen- sis (Jay) has the following growth rate: 1 year: 3.0 cm. 2 years: 7.0 cm 3 years: 10.3 cm 4 years: 13.0 cm 5 years: 14.8 cm Masuda (1962, p. 213) reported that the shells of Patinopecten yessoensis (Jay) of Japan are rather large in size in calm seas and that the convexity of the right FOSSIL LOCALITIES 1 1 valve is low and the left valve rather inflated, whereas those living in less calm water have thick shells with a more convex right valve and a nearly flat left valve. Waller (1973, p. 46) collected thin specimens of Ar- gopecten gibbus (Linné) in Harrington Sound, Ber- muda, that he felt were within the range of variation of that form. He thought that these specimens might be the offspring of shallow-water populations that had entered the Subthermocline Zone as larvae, where there was little mixing of water, resulting in cooler, oxygen-poor water (Waller, 1973, p. 35). Subsequent growth might then have been modified by the condi- tions present in the subthermocline environment. Clark (1976, p. 607, 610) found that the convexity of the shell of Argopecten gibbus, in Harrington Sound, Bermuda, changed with depth from markedly convex in shallow water (7 m) to only slightly convex in deeper water (21 m) and concluded that turbulence was most likely to be the environmental variable affect— ing shell convexity. It is possible that the smooth form of P. healeyi is a response to some such unusual eco- logic condition. Rowland (1972, p. 27) noted that the fauna in the San Diego Formation exposed at Pacific Beach indi- cates a sand-cobble open coast environment, whereas the fauna in the San Diego Formation exposed on the San Diego Mesa, about 10 km to the northwest, repre- sents quiet water. It has been suggested that the San Diego Formation exposed at Pacific Beach and the San Diego Formation exposed in the San Diego Mesa may represent different times of deposition (Woodring and Bramlette, 1950, p. 104—107; Rowland, 1972, p. 27). Recent geologic mapping in San Diego County (M. P. Kennedy in Kennedy and Peterson, 1975, p. 29, 49—50) has shown, however, that these two areas are not significantly different in age. The fauna that oc- curs in the San Diego Formation in northwestern Baja California, near Tijuana, Mexico, is believed to repre- sent three environments: littoral-sublittoral rocky coast, sublittoral open coast with sand substrate, and sublittoral open coast with fine mud or mud-sand sub- strate (Rowland, 1972, p. 27—28). P. healeyi is found at all these localities in all of these proposed environ- ments but may have been transported into certain en- vironments, such as the rocky coast, rather than have lived in them. Patinopecten healeyi most likely lived at a depth of 15 to 275 m, perhaps with its greatest concentration around 35 to 85 m, depending on the water tempera- ture, as the greatest density of P. caurinus is around 35 m in British Columbia (F. R. Bernard, written commun, 1976) and between 55 and 85 m in more southern waters (Fitch, 1953, p. 44). During the Pleis- tocene, P. caurinus lived as far south as San Pedro in the Los Angeles area (Arnold, 1903, p. 37, 107); the southernmost modern occurrence of P. caurinus is Point Reyes, Calif, north of the known Pliocene dis- tribution of P. lohri and P. healeyi; this suggests that P. caurinus may prefer cooler water than did its pos- sible predecessors. The Pliocene mollusks and other invertebrates that occur with P. healeyi indicate shal- low water, intertidal to 50 m. Patinopecten healeyi was presumably attached by a byssus when young. Mature individuals probably could swim in the sense that they could make a dart up off the bottom and then resettle when directly threatened by their predators, which may have been Octopus and starfish. CONCLUSION It is my opinion that the different sculptural forms of P. healeyi may represent responses to the environ- ment. The sculptural variation within single lots of specimens from the same locality shows that the vari- ation is not of stratigraphic significance. Imbricated microsculpture found on the left valve of P. healeyi occurs only on the left valves of other Patinopecten in the east Pacific. In the west Pacific, this microsculpture is found on both the right and left valves of pectinids assigned to the genera Mizuhopec- ten and Yabepecten by other workers. Use of the scan- ning electron microscope in the study of micro- sculpture may prove useful in the separation of gen- era or subgenera of pectinids and in the study of the evolution of the group. FOSSIL LOCALITIES (PLIOCENE, CALIFORNIA) U.S. Geological Survey: M2096: San Juan Capistrano 75-minute quadrangle (1949 ed.). Between Aliso Creek and U.S. Highway 101 in gully wall about 4.8 km south of El Toro town; 235 m south and 45 m east of NW cor. sec. 11, T. 7 S., R. 8 W., altitude about 120 m. Niguel Formation. J. G. Vedder, 1953 and 1962. M2098: San Juan Capistrano 75-minute quadrangle (1949 ed.). About 4.8 km south of San Juan Capistrano; 505 m south and 775 m west of NW cor. sec. 24, T. 7 S., R. 8 W., altitude about 105 In. Niguel Formation. J. G. Vedder, 1954. M2753: Newport Beach 75-minute quadrangle. Approximately 785 in southeast and 775 m southwest of north corner Irvine Block 52. Altitude about 30 m. In artificial out near top of bluff overlooking upper Newport Bay. Fernando Formation. J. G. Vedder, 1966. M3627: La Jolla 75-minute quadrangle. North end of Pacific Beach, collected from north end of pumping station off Wil- bur Street to a point about 60 m north. San Diego Formation. J. G. Vedder, 1961. M3628: La Jolla 75-minute quadrangle. South end of Pacific Beach, off Law Street, slightly south of dead end. San Diego Formation. J. G. Vedder, 1961. .12 M5040: Newport Beach 75-minute quadrangle, Orange County. Approximately 900 in northeast and 775 m north- west of south corner Irvine Block 52 in new cut trending N. 84° E. Altitude about 10 m. Fernando Formation. J. G. Ved- der, 1972. M6502: San Clemente Island. 610 in east and 135 m north of BM 554, San Clemente Island North 75-minute quadrangle (1950 ed.). Altitude approximately 50 m in resistant limy outcrop high on east side of steep gully draining northeast side of island. Unnamed Pliocene rocks. J. G. Vedder, 1975. M6503: San Clemente Island. 615 in east and 25 m north of BM 553, San Clemente North 75-minute quadrangle (1950 ed.). Altitude approximately 70 In in new road cut not shown on map, about 160 m southwest of lighthouse on seacliff 4,020 m southeast of Wilson Cove. Unnamed Pliocene rocks. J. G. Vedder, 1975. California Academy of Sciences: CAS 105: Sea cliffs at Pacific Beach, La Jolla 75-minute quad- rangle. San Diego Formation. Natural History Museum Los Angeles: LAM 107: Quarry at end of Arroyo Drive, known locally as ‘ Clay Canyon or Clay Quarry. San Diego Formation. G. P. Kanakoff. LAM 122: Pacific Beach, La Jolla 75-minute quadrangle. Ex- posure at shore bluff at bend at end of Loring Street. San Diego Formation. G. P. Kanakoff. LAM 305: North of Mexican border, San Ysidro 75-minute quadrangle. From 30 m of exposure, 1.5 to 4 In thick, exactly 530 m from Mexican border fence. "K” Ranch, Palm City. San Diego Formation. G. P. Kanakoff. LAM 305A: West side of next gully east of LAM 305, same ele- vation. G. P. Kanakoff. LAM 485: National City 7.5-minute quadrangle (1953 ed.). From 6 m thick, mostly unconsolidated, yellow, medium- to coarse-grained sandstone on 30° bulldozed slope at locality north of Market Street and east of Euclid Avenue. Projected intersection of arrows on edges of NW 1/4 of map marked "2.6 mi. to US. 101” and “0.6 mi. to U.S. 80” mark this locality. San Diego Formation. E. C. Wilson, 1967. LAM 4902: Pacific Beach, La Jolla 75-minute quadrangle. South-facing exposure on north side of lot on northeast corner of Edgeworth Road and Belloc Court. Collected from a yellow-tan fine— to medium-grained sandstone, unindurated, 1 to 3 m up bank. San Diego Formation. G. L. Kennedy, 1965, 1966. LAM 5108: A general locality number for LAM localities 20, 107, 108, 122, and 180, which were mixed, but all from San Diego Formation. S anford University: U 1605. Rikuoku (Japan). REFERENCES CITED Addicott, W. 0., 1972, Provincial middle and late Tertiary mollus- can stages, Temblor Range, California, in Symposium on Miocene biostratigraphy of California: Soc. Econ. Paleon- tologists and Mineralogists, Pacific Sec., Bakersfield, Calif, March 1972, p. 1—26, pls. 1—4. —1974, Giant pectinids of the eastern north Pacific margin— Significance in Neogene zoogeography and chronostratigraphy: Jour. Paleontology, v. 48, no. 1, p. 180—194. Arnold, Ralph, 1903, The paleontology and stratigraphy of the marine Pliocene and Pleistocene of San Pedro, California: Cali- fornia Acad. Sci. Mem., v. 3, 419 p., 37 pls. 1906, The Tertiary and Quarternary pectens of California: SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD) U.S. Geol. Survey Prof. Paper 47, 264 p., 53 pls., 2 figs. Cahn, A. R., 1951, Clam culture in Japan: Supreme Commander for the Allied Powers, General Headquarters, Tokyo, Nat. Re- sources Sec. Rept. 146, 103 p., 38 figs, 13 tables. Clark, G. R., 2d, 1976, Shell convexity in Argopecten gibbus— variation with depth in Harrington Sound, Bermuda: Bull. Marine Sci., v. 26, no. 4, p. 605—610, 3 figs. Clark, J. C., 1966, Tertiary stratigraphy of the Felton-Santa Cruz area, Santa Cruz Mountains, California: Stanford Univ., Stan- ford, Calif, Ph.D. thesis, 184 p. Cummings, J. C., Touring, R. M., and Brabb, E. E., 1962, Geology of the northern Santa Cruz Mountains, California, in Bowen, 0. E., ed., Geologic guide to the gas and oil fields of northern Cali- fornia: California Div. Mines and Geology Bull. 181, p. 179— 222, 21 photos, pls. 20—24, 4 figs, 1 table. Dall, W. H., 1878, Fossil mollusks from later Tertiaries of Califor— nia: U.S. Natl. Mus. Proc., v. 1, p. 10—16 [1879]. 1898, Contributions to the Tertiary fauna of Florida, with especial reference to the Miocene silex beds of Tampa and the Pliocene beds of the Caloosahatchie River: Wagner Free Inst. Sci. Trans, v. 3, pt. 4, p. 571—947, pls. 23—35. Dibblee, T. W., Jr., 1950, Geology of southwestern Santa Barbara County, California, Point Arguello, Lompoc, Point Conception, Los Olivos, and Gaviota Quadrangles: California Div. Mines Bull. 150, 95 p., 17 pls., 6 figs. Durham, D. L., and Addicott, W. 0., 1965, Pancho Rico Formation, Salinas Valley, California: U.S. Geol. Survey Prof. Paper 524-A, 22 p., 5 pls. Durham, D. L., and Yerkes, R. F., 1964, Geology and oil resources of the eastern Puente Hills area, southern California: U.S. Geol. Survey Prof. Paper 420-B, p. B1-862. Faustman, W. F., 1964, Paleontology of the Wildcat Group at Scotia and Centerville Beach, California: California Univ. Pubs. Geol. Sci., v. 41, no. 2, p. 97—160, 3 pls., 7 figs. Fitch, J. E., 1953, Common marine bivalves of California: Califor- nia Dept. Fish and Game Fish Bull. 90, 102 p., 63 figs. Fleming, C. A., 1957, The genus Pecten in New Zealand: New Zea- land Geol. Survey Paleontology Bull. 26, 69 p., 15 pls. Glen, William, 1959, Pliocene and lower Pleistocene of the western part of the San Francisco Peninsula: California Univ. Pubs. Geol. Sci., v. 36, no. 2, p. 147—198, pls. 15—17, 5 text figs. Grant, U. S., 4th, and Gale, H. R., 1931, Catalogue of the marine Pliocene and Pleistocene Mollusca of California and adjacent regions: San Diego Soc. Nat. History Mem., v. 1, 1036 p., 32 pls., 15 figs., 3 tables. Grau, Gilbert, 1959, Pectinidae of the eastern Pacific: Los Angeles, Univ. Southern California, Allan Hancock Pacific Exped., v. 23, 308 p., 57 pls. Hawkins, J. W., Allison, E. C., and MacDougall, Doug, 1971, Vol- canic petrology and geologic history of Northeast Bank, south— ern California borderland: Geol. Soc. America Bull., v. 82, no. 1, p. 219—228, 4 figs. Hertlein, L. G., 1925, New species of marine fossil mollusca from western North America: Southern California Acad. Sci. Bull, v. 24, pt. 2, p. 39—46, pls. 3, 4. 1928, Pecten (Patinopecten) lohri, new name for Pecten oweni Arnold, a Pliocene species from California: The Nautilus, v. 41, no. 3, p. 93—94. Hertlein, L. G., and Grant, U.S., IV, 1972, The geology and paleon- tology of the marine Pliocene of San Diego, California (Paleon- tology: Pelecypoda): San Diego Soc. Nat. History Mem. 2, pt. 2b, p. 143—409, 57 pls. Jordan, E. K., and Hertlein, L. G., 1926, Contributions to the geol- ogy and paleontology of the Tertiary of Cedros Island and adja- REFERENCES CITED cent parts of Lower California, in Expedition to the Revil- lagigedo Islands, Mexico, 1925: California Acad. Sci. Proc., ser. 4, v. 15, no. 14, p. 409—464. Kennedy, M. P., and Peterson, G. L., 1975, Geology of the San Diego metropolitan area, California: California Div. Mines and Geol- ogy Bull. 200, 56 p., 6 pls., 8 photos, 12 figs, 3 tables. Kern, J. P., 1973, Early Pliocene marine climate and environment of the eastern Ventura Basin, southern California: California Univ. Pubs. Geol. Sci., v. 96, 117 p., 27 figs, 10 tables. MacNeil, F. S., 1961, Lituyapecten (new subgenus of Patinopecten) from Alaska and California: U.S. Geol. Survey Prof. Paper 354—J, p. 225—239, pls. 35—46 [1962]. Martin, Bruce, 1916, Pliocene of middle and northern California: California Univ. Pub. Geol. Sci. Bull., v. 9, no. 15, p. 215—259. Masuda, Koichiro, 1962, Tertiary Pectinidae of Japan: Tohoku Univ. Sci. Repts., ser. Geology, v. 33, no. 2, p. 117—238, pls. 18—27. 1963, The so-called Patinopecten of Japan: Palaeont. Soc. Japan Trans. and Proc., n.s., no. 52, p. 145—153, pls. 22, 23. Masuda, Koichiro, and Addicott, W. 0., 1970, On Pecten (Amusium) condoni Hertlein from the west coast of North America: The Veliger, V. 13, no. 2, p. 153—156, figs. 1—9. Meek, F. B., 1864, Check list of the invertebrate fossils of North America: Smithsonian Misc. Colln. 183, 32 p. Minch, J. C., Gastil, Gordon, Fink, William, Robinson, John, and James, A. H., 1976, Geology of the Vizcaino Peninsula, in How- ell, D. G., Aspects of the geologic history of the California con- tinental borderland: Am. Assoc. Petroleum Geologists, Pacific Sec., Misc. Pub. 24, p. 136—195, 5 figs, 17 tables. Moore, E. J., 1963, Miocene marine mollusks from the Astoria For- mation in Oregon: U.S. Geol. Survey Prof. Paper 419, 109 p., 33 pls., 9 figs, 3 tables [1964]. Ogle, B. A., 1953, Geology of Eel River Valley area, Humboldt County, California: California Div. Mines Bull. 164, 128 p. Peck, J. H., Jr., 1960, Paleontology and correlation of the Ohlson Ranch Formation: California Univ. Pubs. Geol. Sci., v. 36, no. 4, p. 233—242, pl. 21. Rowland, R. W., 1972, Paleontology and paleoecology of the San Diego Formation in northwestern Baja California: San Diego Soc. Nat. History Trans, v. 17, no. 3, p. 25—32, 2 figs, 2 tables. Stanton, R. J., Jr., and Dodd, J. R., 1976, Pliocene biostratigraphy and depositional environment of the Jacalitos Canyon area, California, in Fritsche, A. E., Best, H. T., Jr., and Wornardt, W. W., The Neogene Symposium: Soc. Econ. Paleontologists and Mineralogists Pacific Sec., Ann. Mtg., p. 85-94, 5 figs, 2 tables. 13 Suzuki, Takeo, and Stadum, C. J ., 1978, A Neogene section, north- eastern San Clemente Island, California: Los Angeles County Mus. Nat. History Contr. Sci. 299, 24 p., 29 figs. Vedder, J. G., and Moore, E. J ., 1976, Paleoenvironmental implica- tions of fossiliferous Miocene and Pliocene strata on San Clemente Island, California, in Howell, D. G., Aspects of the geologic history of the California continental borderland: Am. Assoc. Petroleum Geologists, Pacific Sec., Misc. Pub. 24, p. 107—127, 4 pls., 1 table, 9 figs. Verrill, A. E., 1899, A study of the family Pectinidae with a revision of the genera and subgenera: Connecticut Acad. Arts and Sci. Trans, v. 10, pt. 1, p. 41—95, pls. 16—21. Waller, R. R., 1969, The evolution of the Argopecten gibbus Stock (Mollusca: Bivalvia), with emphasis on the Tertiary and Quaternary species of eastern North America: Jour. Paleontol- ogy, v. 43, suppl. to no. 5, 125 p., 8 pls. 1972a, the Pectinidae (Mollusca: Bivalvia) of Eniwetok Atoll, Marshall Islands: The Veliger, v. 14, no. 3, p. 221—264, 8 pls., 22 text figs. 1972b, Functional significance of some shell microsculptures in the Pectinacea (Mollusca: Bivalvia): Internat. Geol. Cong., 24th, Montreal, Canada, 1972, sec. 7, Paleontology, p. 48—56, 3 figs, 1 table. —1973, The habits and habitats of some Bermudian marine mollusks: The Nautilus, v. 87, no. 2, p. 31—52, 2 pls., 2 text figs. Weaver, C. E., chm., and others, 1944, Correlation of the marine Cenozoic formations of western North America: Geol. Soc. America Bull., v. 55, no. 5, p. 569—598. Weaver, D. W., and Meyer, G. L., 1969, Stratigraphy of northeast- ern Santa Cruz Island, in Weaver, D. W., and others, Geology of the northern Channel Islands: [Calif] Am. Assoc. Petroleum Geologists and Soc. Econ. Paleontologists and Mineralogists, Pacific Secs, Spec. Pub., p. 95—104. Winterer, E. L., and Durham, D. L., 1962, Geology of southeastern Ventura Basin, Los Angeles County, California: U.S. Geol. Survey Prof. Paper 334-H, p. 275—366, pls. 44—49, figs. 49—68, 11 tables. Woodring, W. P., 1930, Pliocene deposits north of Simi Valley, Cali- fornia: California Acad. Sci. Proc., ser. 4, v. 19, no. 6, p. 57—64. Woodring, W. P., and Bramlette, M. N., 1950, Geology and paleon- tology of the Santa Maria district, California: U.S. Geol. Survey Prof. Paper 222, 185 p., 23 pls., 9 figs. [1951]. Woodring, W. P., Stewart, R. E., and Richards, R. W., 1940, Geology of the Kettleman Hills oil field, California: U. S. Geol. Survey Prof. Paper 195, 170 p., 57 pls., 15 figs. INDEX [Italic page numbers indicate major references] Page Acknowledgments ________________________________________________________________ 2 Amusium l Argopecten gibbus ,,,,,, 4, 10, 11 Auricles ________________________________________________________________________ 4 Baja California ______________________________________________________ n" 11 Big Basin, California ________________________ 9 9 Byssus ________________________________________________________________________ 4 cancellosus, Patinopecten omgonensis __________________________________________ 7 Cape Mendocino, California ___________________________________________________ 7 Careaga Sandstone ______________________________________________________________ 9 caurinus, Patinopecten _ _ 1, 2, 3, 4, 5, 10, 11 Cebada Member ___________ ___. 9 Channel Inlet, Alaska ______ Chlamys Conclusion condom, Yabepecten coosensis, Patirwpecten _ , , Cordoba, Alaska Ctenolium ______________________________________________________________________ 4 Dall, WI H., quoted ______________________________________________________________ 5 dilleri, Lituyapecten 9 Ecology ___________________________________________________________________ 10 Etchegoin Formation _______________________________________________________ 9 Eureka, California 7, 10 expansus, Pecten __________________________________________________________ 1, 5 Pecten (Putinopecten) ________________________________________________________ 2 Falor Formation __________________________________________________________ 9 Fernando Formation 1, 3, 10, 11 Fossil localities 11 Foxen Canyon, California ____________________________________________________ 6 Foxen Mudstone ____________________________________________________________ 9 Geographic distribution _________________________________________________________ 7 gibbus, Argopecten _____________________________________________________________ 4 Harrington Sound, Bermuda ____________________________________________________ 11 healeyi, Pecten (Patinopecten) __________________________________________________ 1, 9 sanclementensis, Patinopecten ________________________________________________ 1 Pecten (Patinopecten) ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1 Hinge area ________________________________________________________________ 5 Introduction ____________________________________________________________________ 1 Jacalitos Canyon, California ________________________________________________ 9 J acalitos Formation ________________________________________________________ 9 J acalitos Stage __________________________________________________________________ 7 Kettleman Hills, California __________________________________________________ 9 Koshiba Formation __________________________________________________________ 5 La Jolla area, California ____________________________________________________ 11, 12 Left valve ,___ 3 Lituyapecten dilleri 9 purisimaensis _________________________________________________________ 9 turneri ____________________________________________________________________ 7 lohri, Patinopecten ____________________________________________________ 1, 6, 7, 9, 11 MacNeil, F. S,, quoted __________________________________________________________ 5 Meek, F. B., quoted _________________________________________________________ 5 Merced Formation , _ 9 Microsculpture _____________________ _ _ . _ 5 Mizuhopecten _______________________ 6, 11 Montesano Formation ___________________________________________________________ 7 National City, California _______________________________________________________ 12 Newport Beach, California ________________________________________________ 1, 3, 11 Niguel Formation ______________________________________________________ 1, 3, 10, 11 North Dome, California __________________________________________________________ 9 Octopus ____________________________________________________________________ 10, 11 Page Orca Inlet, Alaska ____________________________________________________________ 10 aregonensis, Patinopecten _____________________________________________________ 7 cancellosus, Patinopecten oweni, Pecten (Patinopecten) Pacific Beach, California ________________________________________________________ 3 Patinopecten caurinus coosensis ,,,,,,,,,,,,,,,,,,, 7 healeyi sanclementensis ______________ lohri ________________________________ aregonensis ___________________________________________________________ cancellosus ___________________________________________________ 7 propatulus ___________________________________________________________ _ 5 yessoensis 5, 6, 10, 12; plsi 14, 15 (Patinopecten) expansus, Pecten ________________________________________________ 2 healeyi, Pecten sanclementensis, Pecten ________ oweni, Pecten ____________________________________________________________ Pecten expansus ____________________________________________________________ 1, 2, 5 (Patinopecten) expansus ____________________________________________________ 2 healeyi _____________ sanclementensis oweni ___________ Point Reyes, California __________________________________________________ Pomponio member ___________ 9 Primary sculpture ___________ 2 Prapatulus, Patinopecten ___________________________________________________ 5 Purisima Formation 9 purisimaensis, Lituyapecten .................................................. 9 Purpose __________________ Pycnopodia ________________________________________________________________ References cited ________________________________________________________________ 12 Right valve 2 Rikuoka, Japan w- 12 San Clemente Island, California sanclementensis, Patinopecten healeyi 1 Pecten (Patinopecten) healeyi ______________________________________________ 2 San Diego Formation __________________________________________ San Diego Mesa __________________ San Gregorio, California San Gregorio Member _ San Joaquin Formation _______ San Juan Capistrano, California _______________________ 1, 3, 11 San Ysidro, California ______________________ _ 12 Santa Cruz Mountains 9 Santa Margarita Formation ______________________________________________________ 9 Santa Maria basin __________________________________________________________ 3, 6, 9 Scope ______________________________________________________________________ 1 Sisquoc Formation Species comparison .,,, starfish _________________ 11 Stratigraphic distribution _________ 7 Tahana Member ________________________________________________________________ Tinaquaic Sandstone Member _____________________________ tokunagai, Yabepecten _______________________________________ Towsley Formation ______________________________________________________________ 9 turneri, Lituyapecten _________________________________________________________ 7 Patinopecten _____________________________________________________________ 7 Verrill, A. E., quoted ________________________________________________________ 5 Vertipecten ____________ 5 Vizcaino Peninsula, Baja California ______________________________________________ 9 Waller, R. R., quoted __________________________ 4 Woodring, W. P., quoted ______________________ 6 Wrangell, Alaska ______________________________________________________________ 10 Yabepecten ________________________________________________________________ 5, 6, 11 condoni ____________________________________________________________________ 7 tokunagai ______________________________________________________________ 5, 6, 7 yessoensis, Patinopecten ________________________________________________ 5, 6, 12, 10 Zapata Chino section _______________________________________________________ 9 15 PLATES 1— l 5 Contact photographs of the plates in this report are available, at cost, from U. S. Geological Survey Library, Federal Center, Denver, Colorado 80225 PLATE 1 FIGURES 1—8. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. 1. Exterior or right valve showing typical dichotomy of primary ribs. 95 mm high; 98 mm wide; hinge 45.5 mm long. LAM Ice. 5108. LAM 5219. 2. Exterior of right valve showing complete dichotomy of rib on anterior por~ tion of shell. 31 mm high; 30 mm wide; hinge 16 mm long. LAM loc. 485. LAM 5220, X2. 3. Exterior of incomplete right valve showing complete dichotomy of ribs on anterior portion of shell and riblets on posterior ear. 39 mm wide; hinge 17.5 mm long. LAM loc. 107. LAM 5221, X150. 4. Exterior of juvenile right valve showing smooth disk and low rounded ribs. 13.2 mm high; 13.0 mm wide; hinge 7.8 mm long, LAM 100. 4902. LAM 5222, X3. 5. Interior of juvenile right valve showing hinge area and ctenolium. (Same specimen illustrated as fig. 4.) , 6. Exterior of right-valve fragment showing smooth disk, low rounded ribs, and ctenolium. Hinge 10.5 mm long. LAM 10c. 107. LAM 5223, X3. 7. Exterior of right valve showing smooth disk, complete dichotomy of ribs at both anterior and posterior margins, and fine striations on posterior ear. 25 mm high; 24 mm wide; hinge 12.5 mm long. LAM loc. 107. LAM 5224, X3. 8. Exterior of right valve showing wide unsculptured band at both anterior and posterior margins and dichotomy of all primary ribs. 153 mm high; 165 mm wide; hinge 85 mm long. LAM 10c. 107. LAM 5225, X0.60. PROFESSIONAL PAPER 1103 PLATE 1 GEOLOGICAL SURVEY PA TINOPECTEN HEALEYI (ARNOLD) PLATE 2 FIGURES 1—7. Patinopecten healeyi (Arnold). 1. Exterior of right valve of intermediate form showing smooth umbo and low subdued ribs. San Diego Formation, San Diego, Calif. 75 mm high; 80 mm wide; hinge 36.5 mm long. CAS 10c. 105. CAS 58250.- 2. Exterior of right valve of intermediate form showing smooth rounded ribs over midportion of shell and dichotomous ribs at posterior margin and one near anterior margin. San Diego Formation, San Diego, Calif. 78 mm high; 81 mm wide; hinge 35.5 mm long. CAS loc. 105. CAS 58251. 3. Fragment of right valve of smooth form showing large smooth disk suc- ceeded by dichotomous but very closely spaced primary ribs. Unnamed Pliocene strata, San Clemente Island, Calif. USGS M6502. USNM 235594. (Illustrated by Vedder and Moore, 1976, pl. 3, fig. 6.) 4. Exterior of juvenile left valve, presumed to be of smooth form. Unnamed Pliocene strata, San Clemente Island, Calif. 15 mm long; 16 mm high; hinge 8.7 mm long. USGS M6503. USNM 235590, X2. (Illustrated by Vedder and Moore, 1976, pl. 3, fig. 2.) 5. Fragment of right valve of smooth form showing dichotomous but very closely spaced ribs. Unnamed Pliocene strata, San Clemente Island, Calif. USGS M6503. USNM 235595. (Illustrated by Vedder and Moore, 1976, pl. 3, fig. 8.) 6. Exterior of small right valve of smooth form showing faint trace of sub- dued rib sculpture. Unnamed Pliocene strata, San Clemente Island, Calif. 50 mm high; 50 mm wide; hinge 23 mm long. USGS M6503. USNM 235592. (Illustrated by Vedder and Moore, 1976, pl. 3, fig. 4.) 7. Exterior of right valve of smooth form showing large smooth area of disk succeeded by very closely spaced dichotomous ribs. Unnamed Pliocene strata, San Clemente Island, Calif. 100 mm high; 101 mm wide; hinge 48 mm long. USGS M6503. USNM 235591. (Illustrated by Vedder and Moore, 1976, pl. 3, fig. 3). GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 2 PA TINOPECTEN HEALEYI (ARNOLD) PLATE 3 FIGURES 1—6. Patinopecten healeyi (Arnold). 1. Exterior of right valve of many-ribbed form showing 22 closely spaced dichotomous ribs and unsculptured bands at anterior and posterior mar- gins. San Diego Formation, San Diego, Calif. 132 mm high; 138 mm wide. LAM loc. 305A. LAM 5226, ><0.66. 2. Fragment of exterior of right valve showing closely spaced ribs, smooth disk, and wide posterior unsculptured band. Fernando Formation, New- port Beach quadrangle, California. Posterior ear 27 mm long. USGS M5040. USNM 249742. 3. Fragment of exterior of right valve showing wide Very closely spaced ribs. Fernando Formation, Newport Beach quadrangle, California. USGS M5040. USNM 249743. 4. Exterior of incomplete right valve showing narrow dichotomous and trichotomous ribs. Niguel Formation (Pliocene), San Juan Capistrano quadrangle, California. 107 mm wide. USGS M2096. USNM 249744. 5. Exterior of right valve of many-ribbed form showing 22 closely spaced dichotomous and trichotomous ribs and unsculptured bands at anterior and posterior margins. San Diego Formation, San Diego, Calif. 150 mm high; 158 mm wide; hinge 71 mm long. LAM 10c. 107. LAM 5227, X060. 6. Fragment of exterior of right valve showing narrow widely spaced ribs. Fernando Formation, Newport Beach quadrangle, California. USGS M5040. USNM 249745. PROFESSIONAL PAPER 1 103 PLATE 3 GEOLOGICAL SURVEY 6211:: ll 1.» \t“ ‘ ‘|. {$15 2:. a PA TINOPECTEN HEALEYI (ARNOLD) PLATE 4 FIGURES 1—8. Patinopecten healeyi (Arnold). 1. Exterior of incomplete right valve showing subdued deeply dichotomous ribs and wide unsculptured bands at anterior and posterior margins. Fernando Formation, Newport Beach quadrangle, California. 165 mm wide; hinge 70 mm long (incomplete). USGS M2753. USNM 249746,. x066. 2. Exterior of fragment of right valve showing wide closely spaced dichoto- mous and trichotomous ribs. Fernando Formation, Newport Beach quad; rangle, California. USGS M2753. USNM 249747. 3. Exterior of right valve of double-valved specimen showing smooth ribs near anterior and posterior margins. San Diego Formation, San Diego, Calif. 50 mm high; 48 mm wide; hinge 21.5 mm long. LAM loc. 107. LAM 5228. 4. Exterior of right-valve fragment showing large smooth disk and subdued ribs. Fernando Formation, Newport Beach quadrangle, California. USGS M2753. USNM 249748. 5. Exterior of left valve of double—valved specimen, showing rounded primary ribs. (Same specimen illustrated as fig. 3.) 6. Enlargement (x3) of anterior auricle of right valve, illustrated in figure 3, showing ctenolium. 7. Enlargement (x3) of right anterior auricle showing ctenolium and auricle sculpture. San Diego Formation, San Diego, Calif. Entire specimen: 65 mm high; 70 mm wide; hinge 32 mm long (incomplete); right anterior auricle 17 mm long. LAM 10c. 305. LAM 5229. 8. Exterior of right valve of double-valved specimen showing dichotomous and trichotomous ribs and addition of secondary ribs near ventral mar- gin. (Left valve illustrated, pl. 6, fig. 3.) San Diego Formation, San Di- ego, Calif. 112 mm high (incomplete); 123 mm wide (incomplete); hinge 62 mm (incomplete). LAM 10c. 122, LAM 5230, X0.75. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 4 PA 771V OPE C TEN HEALE Y1 (ARNOLD) PLATE 5 FIGURES 1—6. Patinopecten healeyi (Arnold). 1. Exterior of left valve showing typical sculpture of alternating primary and secondary ribs. San Diego Formation, San Diego, Calif. 105 mm high; 106 mm wide; hinge 51.5 mm long. LAM loc. 5108. LAM 5231, x075. 2. Exterior of left valve of specimen that has rounded primary ribs but no secondary ribs. San Diego Formation, San Diego, Calif. 87 mm high; 85 mm wide; hinge 35.5 mm long. LAM loc. 5108. LAM 5232. 3. Exterior of left valve of probable smooth form showing closely spaced fine primary and secondary ribs and concentric lamellae. Unnamed Pliocene strata, San Clemente Island, Calif. 100 mm long; 98 mm high; hinge 47.4 mm long. USGS M6503. USNM 235593. (Illustrated by Vedder and Moore, 1976, pl. 3, fig. 5.) 4. Electron micrograph of concentric lamellae of left valve showing parallel rather than imbricated pattern. LAM 10c. 305. LAM 5233, X100. 5. Exterior of left-valve auricles of double-valved specimen. (Right-valve au- ricles illustrated, pl.7, fig. 3). San Diego Formation, San Diego, Calif. Hinge 63 mm long. LAM 106. 5108. LAM 5234. 6. Exterior of left valve showing squaring of ribs toward ventral margin and fine concentric lamellae. San Diego Formation, San Diego, Calif. 94 mm high; 95 mm wide; hinge 42 mm long (incomplete). LAM loc. 5108. LAM 5235. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATES PA TINOPECTEN HEALEYI (ARNOLD) PLATE 6 FIGURES 1—7. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. 1. Exterior of left-valve auricles showing anterior fold and subdued riblets. (Same specimen illustrated pl. 9, fig. 1). Hinge 94 mm long; anterior auricle 49 mm long; posterior auricle 45 mm long..LAM loc. 122. LAM 5236. . Exterior of left-valve anterior auricle showing fold, riblets, and concentric sculpture, and of anterior disk showing imbricated microsculpture. Hinge 44 mm long; anterior auricle 23.5 mm (maximum length). LAM 100. 122. LAM 5237, x3. . Exterior of left valve of double-valved specimen showing a small rib run- ning down the center of some of the primary ribs and two secondary ribs in the interspaces near the anterior margin. 110 mm high; 118 mm wide; 60 mm high. LAM 100. 122. LAM 5230, X0.75. (Right valve illus- trated, pl. 4, fig. 8.) . Interior of left-valve hinge area showing ridges bordering resilial pit and auricular denticles. Hinge 42 mm long. LAM loc. 5108. LAM 5238. . Interior of left-valve hinge area showing ridges and grooves bordering re- silial pit. Hinge 52.5 mm long. LAM Ice. 5108. LAM 5239. . Interior of left-valve hinge area showing ridges and grooves bordering re- silial pit. Hinge 68.3 mm long. LAM Ice. 5108. LAM 5240. . Exterior of left valve of double-valved specimen showing anterior un- sculptured band and overlap of larger right valve along ventral margin. (Right-valve auricles illustrated, pl. 13, fig. 1). 140 mm high; 150 mm wide; hinge 75 mm long (incomplete). LAM Ice. 5108. LAM 5241, X066. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE6 PA TINOI’ECTEN HEALEYI (ARNOLD) PLATE 7 FIGURES L5. Patinopecten healeyi (Arnold). 1. Exterior of left valve showing square, ribbed primaries and two times of breakage and subsequent repair of shell. Niguel Formation, San Juan Capistrano quadrangle, California. 97 mm high; 103 mm wide; hinge 52 mm long (incomplete). USGS M2098. USNM 249749. 2. Exterior of fragment of left valve showing multiple secondary ribs at an- terior margin. Fernando Formation, Newport Beach quadrangle, Cali- fornia. USGS M2753. USNM 249750. 3. Exterior of right valve auricles of double-valved specimen showing sculpture and the enlargement of left anterior auricle opposing the right anterior auricle. (Left-valve auricles illustrated, pl. 5, fig. 5.) San Diego Formation, San Diego, Calif. Hinge 63 mm long. LAM Ice. 5108. LAM 5234. 4. Exterior of fragment of left valve showing wide square primaries and dou- bled secondaries. Niguel Formation, San Juan Capistrano quadrangle, California. USGS M2096. USNM 249751. 5. Exterior of left valve showing narrow ribs on disk that are flat and broad at the ventral margin and showing marked enlargement of anterior au- ricle. San Diego Formation, San Diego, Calif. 127 mm high (incomplete); 130 mm wide (incomplete); hinge 60.4 mm long. USGS M3627. USNM 249752, X0.75. PROFESSIONAL PAPER 1103 PLATE 7 GEOLOGICAL SURVEY PA TINOI’ECTEN HEALEYI (ARNOLD) PLATE 8 FIGURES 1e6. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. 1. Exterior of left valve showing square primaries, some ribbed, and en- largement of anterior auricle. 128 mm high; hinge 66 mm long. LAM loc. 5108. LAM 5242, X0.75. 2. Interior of left valve showing hinge area and auricular denticles. Entire specimen 116 mm high; 120 mm wide; hinge 55 mm long. LAM Ice. 5108. LAM 5243. 3. Exterior of left Valve showing multiple times of breakage and subsequent repair of shell. (Same specimen illustrated as fig. 5.) 140 mm high; 150 mm wide; hinge 68 mm long. LAM Ice. 5108. LAM 5244, X066. 4. Exterior of left valve showing ribbed primaries, some narrow and some round secondaries, one double secondary near anterior margin, and en- larged anterior auricle. 140 mm high; 147 mm wide; hinge 70 mm long. LAM loc. 5108. LAM 5245, x066. 5. Interior of left—valve hinge area. Note grooves and double ridges bordering resilial pit. (Same specimen illustrated as fig. 3.) Hinge 68 mm long (incomplete). 6. Exterior of left valve showing wide, ribbed primaries, narrow to widely rounded secondaries, fine ribs at anterior margin, breakage and repair of shell, and enlarged anterior auricle. 147 mm high; 159 mm wide; hinge 80 mm long. LAM 100. 5108. LAM 5246, X060. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 8 PA TINOPECTEN HEALEYI (ARNOLD) PLATE 9 FIGURES 1—7. Patinopecten healeyi (Arnold). 1. Interior of left valve showing hinge area and anterior auricular denticle. (Same specimen illustrated, pl. 6, fig. 1) San Diego Formation, San Di- ego, Calif. Hinge 92 mm long. LAM loc. 122. LAM 5236. 2. Interior of right—valve hinge area. San Diego Formation, San Diego, Calif. Hinge 77 mm long (incomplete). USGS 10c. M3628. USNM 249753. 3. Interior of left-valve hinge area. San Diego Formation, San Diego, Calif. Hinge 78 mm long. USGS 10c. M3628. USNM 249754. 4. Fragment of exterior of left valve showing wide flat primaries and some narrow and some wide flat secondaries. Niguel Formation, San Juan Capistrano quadrangle, California. USGS loc. M2096. USNM 249755. 5. Interior of right-valve hinge area showing thickened posterior ridge. San Diego Formation, San Diego, Calif. Hinge 55 mm long. LAM loc. 122. LAM 5247. 6. Interior of right-valve hinge area showing thickened posterior ridge. San Diego Formation, San Diego, Calif. Hinge 53 mm long. LAM loc. 122. LAM 5248. 7. Exterior of left valve showing subdued ribs near Ventral margin and en- larged anterior auricle. San Diego Formation, San Diego, Calif. 120 mm high; 130 mm wide; hinge 59 mm long. LAM loc. 122. LAM 5249, X0.75. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 9 PA TINOPEC TEN HEALE YI (ARNOLD) PLATE 10 FIGURES 1«5. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. 1. Exterior of small left valve enlarged to show imbricated microsculpture. Note also fine primary ribs and few secondary ribs. 37 mm high; 36 mm wide (incomplete). LAM loc. 107. LAM 5250, X250. 2. Interior of right-valve hinge area. Hinge 92 mm long. LAM loc. 122. LAM 5251. 3. Exterior of small left valve enlarged to show imbricated and lamellar mi- crosculpture and enlarged anterior auricle. Note also rounded primary ribs and few secondary ribs. 37 mm high; 38 mm wide; hinge 18.8 mm long. LAM loc. 107. LAM 5252, X250. 4. Exterior of juvenile left valve enlarged to show imbricated microsculpture (see also pls. 11—13 for electron micrographs of same specimen). 21.4 mm high; 20.5 mm wide; hinge 10.1 mm high. LAM loc. 107. LAM 5253, x3. 5. Electron micrograph of imbricated microsculpture on specimen illustrated in figure 4. Note that lamellae are not imbricated where they cross ribs. PROFESSIONAL PAPER 1103 PLATE 10 GEOLOGICAL SURVEY .4. all: 3.3.3; ‘1...) i:- l‘lx‘l‘r‘n» , :15} a. lixiii'll 3.1.5:}; 31111113 w 14 v PA TINOPECTEN HEALEYI (ARNOLD) PLATE 11 FIGURES 1—3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. Electron micrographs of left valve illustrated, pl. 10, fig. 4. The specimen was scanned from the dorsal to the ventral margin with fig. 1 showing the dorsal margin and fig. 3 the area about one-third the distance from the dorsal to the ventral margin (pl. 12 continues the scan). 1. The microsculpture consists of longitudinal ridges that are not parallel with the primary ribs. 2. The microsculpture now consists of longitudinal ridges that are nearly parallel with the primary ribs and of concentric ridges that cross the primary ribs. 3. Concentric ridges are prominent between ribs and are starting to become imbricated. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 11 I 1 E: F11 ".-' 1 U U P H 3 PA TIN OPE C TEN HEALE Y1 (ARNOLD) PLATE 12 FIGURES 1-3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. Electron micrographs of left valve illustrated, pl. 10, fig. 4. The specimen was scanned from the dorsal to the ventral margin with fig. 1 representing the midportion of the shell and fig. 3 the shell near the ventral margin (pl. 11 shows dorsal scan). 1. The concentric ridges are now loosely imbricated between the ribs. 2. The concentric ridges are loosely imbricated at the top of the picture but barely scalloped near the bottom of the picture. 3. The concentric ridges are tightly imbricated between the primary ribs. PROFESSIONAL PAPER 1103 PLATE 12 GEOLOGICAL SURVEY ' , 56.|:|1_ PA TINOPECTEN HEALEYI (ARNOLD) PLATE 13 FIGURES 1, 2, 5. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. l. Right-valve auricles of double-valve specimen showing strong flexure of byssus. Note also the unsculptured band at both the anterior and pos- terior margins. (Left valve of same specimen illustrated, pl. 6, fig. 7.) Hinge 62.4 mm long. LAM loc. 5108, LAM 5241. 2. Dorsal View of hinge of double-valved specimen showing relative inflation of valves and strong flexure of left anterior auricle toward right anterior auricle byssus. (Same specimen illustrated, pl. 14, fig. 3; pl. 15, figs. 2. 3.) Hinge 95 mm long. LAM loc. 107. LAM 5254, X0.66. 5. Electron micrograph of portion of anterior auricle of left valve, illustrated pl. 10, fig. 4, and pls. 11 and 12, showing closely spaced lamellae. 3, 4, 6. Patinopecten lohri (Hertlein), holotype (UCMP 12081). Tinaquaic Sandstone Member, Sisquoc Formation, near Foxen Canyon, Calif. 3. Right valve of holotype showing wide, high, dichotomous primary ribs with a wide rounded secondary rib in every interspace. 87 mm high; 88 mm wide, hinge 47 mm long. 4. Dorsal view of holotype showing relative inflation of valves. 6. Left valve of holotype showing strong, rounded primary ribs that are dichotomous near ventral margin, wide rounded secondary ribs, and greatly enlarged anterior auricle. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE l3 PA TINOPECTEN HEALEYI (ARNOLD) AND PA TINOPECTEN LOHRI (H ERTLEIN) PLATE 14 FIGURE 1. Patinopecten yessoensis (Jay), Rikuoku, Japan. Exterior of right valve en- larged to show imbricated microsculpture. 140 mm high; 148 mm wide; hinge 77 mm long. SU loc. 1605. CAS 58773, ><1.50. 2, 3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. 2. Exterior of left valve enlarged to show imbricated microsculpture. 51.7 mm high; 521 mm wide; hinge 22.9 mm long. LAM 10c. 107. LAM 5255, x3. 3. Exterior of right valve of largest double-valve specimen seen in any collec— tion showing folded byssus of right auricle and large overlap of left an- terior auricle. (Left valve of same specimen figured, pl. 15, fig. 3; hinge figured, pl. 13, fig. 2; pl. 15, fig. 2.) 190 mm high; 210 mm wide (broken at margins); hinge 95 mm long. LAM 10c. 107. LAM 5254, ><0.75 PROFESSIONAL PAPER 1103 PLATE l4 GEOLOGICAL SURVEY villain! )4! . ., 1.51.!!rivxe PA TINOPECTEN YESSOENSIS (JAY) AND PA TINOPECTEN HEALE YI (ARNOLD) PLATE 15 FIGURE 1. Patinopecten yessoensis (Jay), Holocene, Rijuoku, Japan. Exterior of left valve enlarged to show imbricated microsculpture. 140 mm high; 148 mm wide; hinge 77 mm long. SU 100. 1605. CAS 58774, ><1.5 2, 3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. 2. Exterior of hinge of left valve showing fold of anterior auricle. (Same specimen illustrated as fig. 3; right valve illustrated, pl. 14, fig. 3.) Hinge 95 mm long. LAM loc. 107. LAM 5254, ><0.75 3. Exterior of left valve of the largest double-valve specimen seen in any collection showing overlap of larger valve along the margins. (Right valve of same specimen illustrated, pl. 14, fig. 3.) LAM loc. 107. LAM 5254. 185 mm high; 205 mm wide; hinge 95 mm long, ><0.75. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 15 .‘C L! .\ 3 PA TINOPECTEN YE SSOENSIS (JAY) AND PA TINOPE C TEN HEALE Y1 (ARNOLD) G PO 689-03 5 ms; Ash—flow Tuffs of the Galiuro Volcanics in the Northern Galiuro Mountains, Pinal County, Arizona By MEDORA H. KRIEGER GEOLOGICAL SURVEY PROFESSIONAL PAPER 1104 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Krieger, Medora Louise Hooper, 1905- Ash-flow tuffs of the Galiuro Volcanics in the northern Galiuro Mountains, Pinal County, Arizona. (Geological Survey Professional paper ; 1104) Bibliography: p. 32. 1. Volcanic ash, tuff, etc.—Arizona—Galiuro Mountains. I. Title. II. Series: United States. Geological Survey. Professional paper; 1104. QE461.K757 552’.2 79-19484 For sale by the Superintendent of Documents, US. Government Printing Office Washington, DC. 20402 Stock number 024-001-03239-2 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. . Photomicrographs of specimens from interior of Aravaipa Member . Photographs of: CONTENTS Page Abstract 1 Introduction 1 Galiuro Volcanics 4 Holy Joe Member 4 Aravaipa Member 11 Changes in chemical composition due to zeolitization ------------------------------------------- 21 Conclusions 23 Tuf‘f of Bear Springs Canyon 26 Rhyolite-obsidian member 27 Hells Half Acre Tuff Member 28 Suggestions for future work 31 References cited 32 ILLUSTRATIONS Page Index map showing distribution of Galiuro Volcanics Geologic map of parts of Brandenburg Mountain, Holy Joe Peak, and Klondyke quadrangles ---------------------------------------- Correlation chart showing relations of stratigraphic units in Galiuro Volcanics Photograph of typical exposure of Holy Joe Member Chart showing some physical characteristics of Holy Joe Member Photomicrographs of Holy Joe Member X-ray diffractographs of selected specimens of Holy Joe and Aravaipa Members Sketch showing effect of buried topography on zonation in Holy Joe Member Photograph of typical exposure of Aravaipa Member Chart showing some physical characteristics of Aravaipa Member 12. Aravaipa Member filling channel in Precambrian rocks 13. Vuggy zone, Aravaipa Member 14. Thunder eggs, Aravaipa Member 15. Platy-jointed zone, Aravaipa Member 16. Distal margin of Aravaipa Member 17. Change in zonation of Aravaipa Member Map showing location of specimens, Aravaipa Member Diagrammatic sketches of zones in Aravaipa Member Chart showing lithologic zones and color, Aravaipa Member Chart showing specific gravity, Aravaipa Member Chart showing approximate composition, Aravaipa Member Photomicrographs of distal margin, Aravaipa Member Ternary diagram showing relative amounts of 0210, NaZO, and K20 in zeolitized and nonzeolitized rocks ------------------------ Photograph of units of Hells Half Acre Tuff Member Diagrammatic sketch showing relations of Hells Half Acre Tuff Member, rhyolite—obsidian member, and upper andesite of Virgus Canyon Photograph of Hells Half Acre Tuff Member and rhyolite-obsidian member Diagrammatic sketch showing relations of middle unit of Hells Half Acre Tuff Member and rhyolite-obsidian member ----- Chart showing approximate composition of Hells Half Acre Tuf‘f Member III 18 18 19 20 20 22 24 24 26 27 28 28 30 30 31 31 32 IV TABLEI. 2. 3. 4. £3" CONTENTS TABLES Page Potassium-argon ages of ash-flow tuffs in Galiuro Volcanics in the northern Galiuro Mountains -------------------------------------- 3 Modes of Holy Joe Member 7 Chemical composition and comparison of glassy and crystallized parts, Holy Joe Member 11 Semiquantitative spectrographic analyses of minor elements in ash-flow tuffs and rhyolite-obsidian member, northern Galiuro Mountains 12 Modes of Aravaipa Member 15 Chemical composition and comparison of glassy and crystallized parts, Aravaipa Member --------------------------------------------- 22 Chemical composition and comparison of zeolitized and nonzeolitized rocks 25 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS IN THE NORTHERN GALIURO MOUNTAINS, PINAL COUNTY, ARIZONA By MEDORA H. KRIEGER ABSTRACT The upper Oligocene and lower Miocene Galiuro Volcanics in the northern part of the Galiuro Mountains contains two distinctive major ash-flow tuffsheets, the Holyjoe and Aravaipa Members. These major ash-flows illustrate many features ofash-f'low geology not generally ex- posed so completely. The Holy joe Member, composed of a series of densely welded flows ofquartz latite composition that make up a simple cooling unit, is a rare example of a cooling unit that has a vitrophyre at the top as well as at the base. The upper vitrophyre does not rep— resent a cooling break. The Arayaipa Member, a rhyolite, is com— pletely exposed in Arayaipa and other canyons and on Table Moun— tain. Remarkable exposures along Whitewash (Ianyon exhibit the complete change from a typical stacked-up interior zonation of an ash How to a nonwelded distal margin. Vertical and horizontal changes in welding, crystallization. specific gravity, and lithology are exposed. The ash flow can be divided into six lithologic zones. The Holy Joe and Arayaipa Members of the Galiuro Volcanics are so well exposed and so clearly show characteristic features of ash-flow tuffs that they could be a valuable teaching aid and a source of theses for geology students. INTRODUCTION The upper Oligocene and lower Miocene Galiuro Vol- canics consists of andesitic to rhyolitic flows, tufts, and ash-flow tuffs. Included in the sequence in the northern part of the Galiuro Mountains are two distinctive ma- jor ash-flow tuff sheets and two minor ash flows. The ma- jor ash-flow tuff sheets provide an excellent example of contrast in types of emplacement, cooling and crystal- lization history, and later alteration, and they illus- trate some features in ash-flow tuffs not normally seen or exposed so completely. The older one has a vitro- phyre at the top as well as at the bottom of a sequence of ash flows that cooled as a unit. The younger one, also a simple cooling unit, has a well-developed horizontal and vertical zonation that suggests a single ash flow, but that may represent at least two additional pulses. The nonwelded distal margin has been zeolitized. The Galiuro Volcanics extends from the southern part of the Christmas quadrangle to the northern part of the Dragoon quadrangle (fig. 1). The first detailed descriptions of the Galiuro Volcanics were by Cooper and Silver (1964) in the Dragoon quadrangle and by Simons (1964) in the Klondyke quadrangle. Blake (1902) had previously used the term Galiuro Rhyolite for tufis and lavas in the central part of the Galiuro Mountains. Willden (1964) published a generalized geologic map of the Christmas quadrangle but he did not correlate the volcanic rocks with the Galiuro Vol- canics. Detailed subdivisions of the volcanic rocks in the northern Galiuro Mountains—the Holy Joe Peak 110°45' 110°30’ C 33°OO' H K _ Area of HJ . figure 2 110°15’ 07W 110°00’ ' O ARIZONA O 5 1O 15 20 K|LOMETERS i—|_F‘J—ll’—l 0 5 10 MILES FIGURE 1.—Distribution of Galiuro Volcanics (shaded), 15- minute quadrangles: Christmas (C), Dragoon (D), Galiuro Mountains (G), Holy Joe Peak (H), Klondyke (K), Mam- moth (M), Reddington (R), Sien'a Bonita Ranch (S), Win- chester Mountains (W), and 71/2-minute quadrangles; Brandenburg Mountain (B) and Holy Joe Peak (HJ). ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA BRANDENBURG 110°32’30" MOUNTAIN 7‘/2‘ 110°30' ’"a. a.- l a o h u ‘VGV )/::\/_\/_\ \v 32°55 52'30" » Little Table Mountain'»‘. 2 KILOMETERS 1 MILE ‘- ' ~ _ . HOLYJ E PEAK 7V2‘ z =:. ' ' YKE1 FIGURE 2.—Geologic map of parts of Brandenburg Mountain, Holy Joe Peak, and Klondyke quadrangles (modified from Krieger, 1968a, b; and Simons, 1964). INTRODUCTION 3 EXPLANATION Younger rocks Andesite of Table Mountain ‘ Apsey Conglomerate Member 1 Hells Half Acre Tuff Member ‘ Rhyolite-obsidian Member — v, vent 36%}ng Upper andesite of Virgus Canyon 7 '/’ ' Includes associated conglomerate ffiav/ Lower andesite of Virgus Canyon — u Includes associated conglomerate ”WWW Aravaipa Member — Includes upper white tuff (upper nonwelded tuff of Lower g , earlier reports) Miocene _ Lower tuff unit—Includes (oldest to young- > to est) tuff of Oak Springs Canyon, andesite Upper of Depression Canyon (shown separately Oligocene only in northwestern part of map area) , and tuff of Bear Springs Canyon (upper part of lower tuff unit; mostly in western part of map area) Galiuro Volcanics A Andesite of Depression Canyon — Includes associated conglomerate Biotite dacite unit. Holy Joe Member , Andesite of Little Table Mountain — Includes coarsely porphyritic ande- site Whitetail(?) Conglomerate (Oligocene) — ,7 Beds less than 15 m thick between prevolcanic rocks and the next overlying unit of the Galiuro Vol— canics (porphyritic andesite, Holy Joe Member, andesite of Depression \ unit n Older rocks Contact —'7— — —Fault — Dashed where approximately located. Ball and bar on downthrown side 4—‘—‘—‘— Thrust fault — Sawteeth on upper plate -A Location of sections and analyzed specimens of Holy Joe Member '6 Location of sections and analyzed specimens of Aravaipa Member 0® Location of other analyzed specimens FIGURE 2.—Continued. quadranglel—were mapped by Krieger (1968a, b); S. C. Creasey (unpub. data) mapped in reconnaissance the central Galiuro Mountains, which contains the thickest section of the formation. The stratigraphy, lithology, chemical composition, and age of the Galiuro Volcanics are summarized by Creasey and Krieger (1978). The formation can be separated into two parts by an erosional unconformity. The lower part is pre- lHoly Joe Peak in this report refers to the 15-minute quadrangle; four geologic maps cover this area (Krieger, 19688—41). The ash-flow tuffs discussed in this report are in the Brandenburg Mountain and Holy Joe Peak 71/2-minute quadrangles and the Klondyke quadrangle; discussion is largely limited to the two 71/2-minute quadrangles, dominantly andesite to rhyodacite flows but it contains three ash-flow tuffs. The upper part is chiefly ash-flow tuffs, but it includes andesite flows and two areas of rhyolite-obsidian flows and domes, one of which is in the northern Galiuro Mountains. The distribution of the Galiuro Volcanics in parts of the Holy Joe Peak and Klondyke quadrangles, which is shown in figure 2, is modified from the published geologic maps. The ter- minology used in each area and my interpretation of the relations of members or units in the Klondyke and Holy Joe Peak quadrangles and in the Christmas quadrangle to the north are given in figure 3. The two major ash-flow tuff sheets—Holy Joe and Ar- avaipa Members—and the two minor ones—tuff of Bear Springs Canyon and Hells Half Acre Tuff Mem- ber—illustrate many features of ash-flow geology. The Holy Joe Member rests on the unconformity that sep- arates the volcanics into two parts, the tuff of Bear Springs Canyon underlies the Aravaipa Member, and the Hells Half Acre Tuff Member is in the upper part of the formation. The ages of the ash-flow tuffs are given in table 1. The Holy Joe Member is composed of a series of densely welded flows of quartz latite composition that make up a simple cooling unit (Smith, 1960a). It is a rare example of a cooling unit that has a vitrophyre at the top as well‘ as at the base. The major zones recog- nized are, in ascending order: the lower vitrophyre, lower devitrified zone, central vapor-phase zone, upper devitrified zone, and upper vitrophyre. The absence of breaks in crystallization across flow boundaries and the gradation between zones and from crystallized to vitric material at the top indicate a single cooling unit. Dense welding and fairly uniform high specific gravity throughout the member indicate that the individual flows were hot. The Aravaipa Member, of rhyolite composition, has a well-developed zonation that indicates a simple cool- ing unit and possibly a single ash flow. It presents a classic example of ash-flow geology, in that the complete change from the stacked-up zonation typical of the in- terior of the ash flow to the nonwelded distal margin, now zeolitized, is completely exposed in some canyon walls. Horizontal and vertical zonation in ash-flow tuffs was first recognized by Smith (1960b). TABLE 1.—Potassium-argon ages ofash-How tufi‘s in the Galiuro Volcanics in the northern Galiuro Mountains (in millions of years) [From Creasey and Krieger, 1978] Member Biotite Ssnidine Hells Half Acre Tuff Member ----- 24.6+0 7 22.5:0.7 Aravaipa Member ------------------- 25.7 t 0 7 22.9 i 0.8 Tufl' of Bear Springs Canyon1 23.8 t 0.7 Holy Joe Member ---------------------- 26.5:0 8 25.6:08 1This analysis may be from one of the underlying tuffs in the lower tuff unit of Simone (1964, p. 81). Brandenburg Mountain and Holy Joe Peak 7V2—minute quadrangles (Krieger, 1968a, b) Andesite of Table Mountain ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA Klondyke 15-minute quadrangle / . // Apsey Conglomerate Member \ \\ (Simons, 1964) / // _\V — “K _ _ _ ’ // / \ \ Upper tuff unit / // Hells Half Acre Tuff Member ‘\ ‘3 g / / , , — ’(\ \ Quartz latite unit of Hawk Canyon / / \ \ Rh oliterobsidian unit Christmas 15»minute //// \ \\ v ‘ quadrangle (Willden, 1964) / / _ . ‘ \\ \ Tuff unit of Hawk Canyon / RhyoliterobSIdian member Basalt of Gila Conglomerate / / , ’ / Upper andesite unit1 Tuff and rhyolite, undivided / / ’ / , / Rhyolite / Upper andesite of Virgus Canyon / ’ I ,;I’ Intermediate andesite Uhit Along southern border of quadrangle , Conglomerate ,:: / _, g . includes Apsey Conglomerate and / , : , , ‘ Lower andesite of Virgus Canyon I — — ‘ ' ' ‘:: Whlte thf ”mt R ‘ fBl k x — 2 - , We} —————— “X _ I, _ , .— <: , Member Partly welded, welded, and lower nonwelded _ ,7 — — Olivine andesite Lower tuft unit2 Hornblende andesite of Parsons Canyon Biotite dacite unit / ConglomeratiZ; / ’ I / I , Lower welded tuff unit Latitic lavas (”A _______ Ratite subunit Heterogeneous siliceous . _ volcanics of Four Mile Lower andeSIte unit - \ \ Tuff of Bear Springs / Basalt and andesite ‘ \ \ \ gnglomerate Canyon Conglomerate / Gravel, possibly Whitetail Conglomerate \: :: \ \ ‘ ‘ \ ‘ Andesite of Depression Canyon METERS \ \\ \\ Conglomerate 400 \\ \ Tuff of Oak Springs Canyon \ \\ \ Holy Joe Member 300 \ \\ Porphyritic andesite of Little Table Mountain \ \ 200 \ \ \ \ ' ' ' \ \ Ande5ite of Little Table Mountain Zapata Wash \ 100 \ 0 \\ Whitetail(?) Conglomerate Canyon 1Simon’s (1964) upper andesite unit consists of two andesites: one resting on rhyolite-obsidian in an area where his upper tuft unit was not deposited; the other along Aravaipa Canyon beneath his upper tuff unit, which he interpreted as also overlying rhyolite-obsmian. 2 Lower tuff unit m the Klondyke quadrangle includes tuft of Bear Springs Canvon,andesiteof Depression Canyon, and a series of tuffs equivalent to or underlying tuff of Oak Springs Canyon. FIGURE 3,—Correlation chart showing relations of stratigraphic units in Galiuro Volcanics, Christmas, Brandenburg Mountain, Holy Joe Peak, and Klondyke quadrangles. Shows maximum thickness of members or units in each area. Suites of specimens were collected from a section vertically across the Holy Joe Member and from six vertical sections across the Aravaipa Member from the interior to near the distal margin. Changes in lithol- ogy, welding, crystallization, specific gravity, and com- position are shown in tables and diagrammatic sketches. Data obtained from chemical analyses of se- lected specimens and from X—ray diffractographs of all specimens are presented. AcknowIedgments—I thank my colleagues of the US. Geological Survey for their important contributions and stimulating discussions of ash-flow problems. Spe- cial thanks are due R. L. Smith and D. W. Peterson for interpreting and first pointing out many of the dis- tinctive features of the ash flows in the northern Gali— uro Mountains and to S. C. Creasey and F. S. Simons for data on the volcanic rocks in adjacent areas. D. W. Peterson, E. D. McKee, E. W. Heldreth, and M. G. Johnson made many helpful comments and sugges- tions during preparation of the manuscript. GALIURO VOLCANICS HOLY JOE MEMBER The Holy Joe Member of the Galiuro Volcanics crops out intermittently from 13 km west of to 8 km east of the boundary between the Holy Joe Peak and Klon— dyke quadrangles (Krieger, 1968a, b; Simone, 1964) and from the northernmost latitude of Aravaipa Can- yon to south of the latitude of Little Table Mountain (fig. 2); it also crops out on a butte about 10 km south of Little Table Mountain. It may extend for many kil- ometers to the south. Its source is unknown. The mem- ber is about 100 m thick in the Klondyke quadrangle (Simone, 1964). Its maximum thickness around Table Mountain (fig. 2) in the Holy Joe Peak quadrangle (Krieger, 1968b) is about 80 m; to the north, the lower part, and locally all of it, laps out against prevolcanic topographic highs. The Holy Joe Member is a cliff-forming unit that has strong horizontal partings (fig. 4), has a rather uniform appearance, and is pale brown to pale red throughout most of its thickness, except for a thin nearly white nonwelded tuff and a dark vitrophyre at the base and another dark vitrophyre at the top. The ash-flow tuff between the lower and upper vitrophyres can be di- vided into three lithologic zones: lower devitrified zone, central vapor-phase zone, and upper devitrified zone. The lower vitrophyre is dark gray, except for the basal part, which is brown due to oxidation. The lower HOLY JOE MEMBER 5 Tat Ta : Tar Th] 80 meters FIGURE 4.—Typical exposure of Holy Joe Member, northwest end of Table Mountain, as viewed from northeast. Horizontal partings probably represent individual flows and possibly zones of denser welding. Andesite of Table Mountain (Tat); Apsey Conglomerate Member (Ta); Aravaipa Member (Tar); Holy Joe Member (Thj). devitrified zone is reddish brown, and the upper one is slightly redder. The vapor-phase zone is brown to pale red except for the middle part, which is light brownish gray. The lower part of the upper vitrophyre is dark gray, and the upper part is red. Black glassy flattened pumice lapilli contrast with the red of the upper vitro- phyre and the brown of the lower vitrophyre. The tran- sition from the lower vitrophyre to the lower devitri- fied zone is abrupt, but that between all the other zones is gradational. Dense welding is characteristic of all the zones except the basal nonwelded zone. A suite of specimens (H201A—Q) was collected ver- tically across the ash-flow sheet in Oak Springs Canyon (fig. 2, 10c. A). The elevation above base, field units, color, zones of welding and crystallization, mineralogic composition (based on X-ray diffractographs), and spe- cific gravities of these specimens are summarized in figure 5. The Holy Joe Member is composed of shards and pumice lapilli, very tiny crystal fragments of feld— spar, quartz, and biotite, and some foreign rock and mineral fragments (table 2). Phenocrysts make up about. 7 percent of the rock, and feldspar, mostly pla- gioclase, makes up about 71 percent of the pheno- crysts. Chemical analyses (see table 3) indicate a quartz latite composition. Photomicrographs (figs. 6A—J) of selected thin sec- tions of the suite of specimens illustrate typical micro- scopic features of the ash-flow sheet. The basal non- welded tuff contains undeformed shards and glass bubbles (not illustrated). All the rocks above the non- welded tuff show evidence of dense welding, eutaxitic texture due to flattening and alinement of pumice lapilli and shards (figs. GB, C, E), collapse of pumice with elimination of most pore space but retention of pumice structure in frayed-out ends (fig. 6A), and molding of pumice and shards against phenocrysts or crystal and lithic fragments (figs. 6A, I, J). Shard structure (figs. 63, C, E, G, I) is preserved in vitrophyres and in most of the crystallized tuff owing to fine-grained axiolitic intergrowths (too small to show at scale of photomi- crographs) of cristobalite and sanidine, the products of devitrification. Outlines of pumice lapilli are generally preserved, but their structure may be destroyed by spherulitic intergrowths around trapped gas in cavi- ties (figs. 6D, F, H). All the tuff between the lower and upper vitrophyre is devitrified, as shown by its nonvitric (stony or lith- oidal) character, by a finely crystalline groundmass (composed of cristobalite and sanidine; see below), and by the alteration of biotite. The vapor-phase zone, in which cristobalite and sanidine are also characteristic, is recognized by its lighter color, the slightly cavernous appearance of pumice lapilli in both hand specimen and thin section (figs. 6D, F), and the presence of dis- crete microscopic crystals of tridymite in cavities. Crystallization in this zone is not as coarse grained as in less densely welded ash flows and is confined largely to pumice lapilli. In addition to the study of hand specimens and thin sections, each specimen was X-rayed; the results are shown in the composition column in figure 5. X-ray diffractographs of the ash flows show not only the phen- ocrysts (feldspar, quartz, and biotite) but also the de- vitrification products (cristobalite and feldspar) and the alteration products (clay and zeolite). Becausev‘of preferred orientations, degrees of crystallinity, mask- ing by noncrystallized material, mass absorption, and other problems, quantitative results are impossible to obtain. The X-ray diffractographs show the apparent abundance of the constituents and are useful in iden- tifying them, especially where thin sections were not available, as in parts of the Aravaipa Member. A few diffractographs of selected specimens of the Holy Joe and Aravaipa Members (fig. 7) are included to illus- trate the type of peak heights involved. Noncrystalline material, such as glass in the vitric parts of the ash flow, is recognized as a “glass hump” (fig. 7A). Cristo- balite is readily recognized by its characterlstic peak (figs. 7B, C). Sanidine and plagioclase can be distin- guished by careful comparisons of the patterns with patterns prepared from pure mineral separates; they are identified only as feldspar in figure 7. Tridymite was not definitely recognized in the X-ray diffracto- ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA Composition 3 Sample Field Zones of Zones of 2’. = . . . H201 units Color welding crystallization % L g Specuflc gravutv 1’ (u N a: a o a- H 0-: O m w ‘- " u. ‘0 m H c >- g -; 3 :1 .9 : 1‘2 -— o u. 0 m U U (D 1.5 2.0 2.5 — 0 Red A O A A — A O O. _ P Vitrophyre Dark gr Vitric A O A A _ _ 0 P7 60 A _~ . . . Pale br to o O O A A — A — O DeVItnfied pale red m 50 a: _ Pale br to _ _ _ {-U N pale red O o O A Lu 2 Z i _ Pale br to .5 _ _ _ L” M pale red .‘2 . . A A 2 40 — .t a, i. m — L Ltbrgr 3:18 OOAA—O— u: 5 5 3 Vapor phase ? D E‘ '- o m g s E Lt br gr 3 > o o A A I K g 9 30 - 0 “J _ J Palered 0 AooA—Aa I — J~1 Paleredto ooAA—A— pale br govw | Palebr OoAA——— | Devitrified “ H Palebr OOAA——— H — G . _ A A A — — a G 10 _ Olive gr _ F V't'ophyre Olive gr 39. A A A A A — o F —— E Dark gr g — A A A — o E M D Mod br , _ - A A A - ‘ ° D _ C Lt br Partial welding _ A A A _ . c _ A White tuff Pk gr No welding — A A A o — A EXPLANATION 0 O A _ Abundant (more than 50 percent) Present but not abundant Recognized Not recognized FIGURE 5.—Some physical characteristics of the Holy Joe Member, based on specimens H201A—Q, collected at location A (fig. 2). Model data in table 2; chemical analyses of specimens F, H, and K in table 3. Color terms: br, brown or brownish; gr, gray; 1t, light; mod, moderate; pk, pinkish. Mineral abundance estimated from X-ray diffractographs of bulk samples. In addition to listed minerals, samples J—1 through N contained tridymite. graphs because it is a very minor constituent and its peaks (figs. 7B, C) are close to some of the peaks of cristobalite, quartz, and feldspar. X-rays are the basis for most modern identification of zeolites in tuffs and sedimentary rocks. The zeolite, clinoptilolite, was rec- ognized only in the X-ray of the basal nonwelded tuff (see composition column, fig. 5); clinoptilolite exten- sively replaced the nonwelded distal parts of the Ar- avaipa Member (fig. 7E). Chemical analyses were made for samples from three different zones in the Holy Joe Member; the lower vitrophyre, lower devitrified zone, and the gray HOLY JOE MEMBER 7 TABLE 2.—Modes of Holy Joe Member [Modes in volume percent. Based on thin-section studies of specimens collected vertically across the member in Oak Springs Canyon (loc. A, fig}. Field units: uv, upper vitrophyre; ud, upper devitrified; vp, vapor phase; ld, lower devitrified; lv, lower vitrop yrel 2); see fig. 5 for other characteristics. Percentage of rock exclusive of foreign fragments Percentage of total rock Foreign rock Field Field Total Feldsparé Quartz mee and mineral Points No, unit Matrixl phenocrysts2 (percentage of phenocrysts) fragments“ counted H201Q 90 10 8 (80) 1 (10) 1 (10) 27 1,062 P uv 87 13 9 (69) 3 (23) 1 (8) 12 1,006 0 ud 87 13 9 (69) 3 (23) 1 (8) 11 1,003 N 90 10 6 (60) 2 (20) 2 (20) 1 1,007 M vp 90 10 6 (60) 3 (30) 1 (10) 4 1,044 L 92 8 4 (50) 3 (38) 1 (12) 5 1,052 J 85 15 11 (73) 3 (20) 1 (7) 4 1,046 J-1 92 8 6 (75) 1 (13) 1 (11) 4 987 I 1d 91 9 7 (78) 1 (11) 1 (11) 7 956 H 89 11 9 (82) 1 (9) 1 (9) 6 1,064 G 91 9 6 (67) 2 (22) 1 (11) 7 970 F lv 88 12 9 (75) 2 (18) 1 (9) 4 971 E 87 13 10 (77) 2 (15) 1 (8) 9 1,000 D 92 8 6 (75) 1 (13) 1 (12) 4 1,062 C 93 7 5 (72) 1 (14) 1 (14) 9 995 Average -------------- 90 10 7 (71) 2 (20) 1 (10) 8 1,015 Range ---------------- 85—93 7—15 4—1 1 1—3 1—2 1—27 1Includes pumice lapilli, average 8 percent. 2Not counted are traces of magnetite and very tiny crystal fragments of quartz, feldspar, and biotite. Includes phenocrysts in pumice lapilli and crystal fragments in matrix. 3Largely plagioclase, includes sanidine (trace to 1 percent of total rock), may include some foreign plagioclase. 4Mostly andesite of Little Table Mountain. part of the vapor-phase zone (table 3). Minor-element contents of these samples are given in table 4. The whole-rock analyses show that chemical differ- ences between zones in the Holy Joe Member are very small. The most significant differences noted are that the vitrophyre has more water than the crystallized tuffs and that the oxidation state of iron in the crys- tallized tuffs is higher than in the vitrophyre. Both of these characteristics are common in ash—flow tuffs throughout the western United States and elsewhere. The high water content of the vitrophyre, most likely the result of secondary hydration, causes prob— lems in comparing the abundances of the nonvolatile constituents (Ross and Smith, 1955, p. 1086—1088). To more readily compare the nonvolatile elements, table 3 lists the analyses recalculated on a water-free basis; Barth cation amounts and C.I.P.W. norms are also listed. A comparison of the recalculated analyses shows a progressive but slight decline in silica and po- tassium upward in the section and increases in sodium and calcium. Without more data, however, it cannot be decided whether these differences are the result of pro- gressive magmatic changes, transfer of elements dur- ing cooling or crystallization, solution during hydra- tion, or simple coincidence. The Holy Joe Member was made up of a series of very hot ash flows that erupted rapidly enough to cool as a unit. Dense welding, characteristic of hot ash flows, results in higher specific gravity than less welded flows. The rather uniform high specific gravity of this ash-flow sheet supports the evidence for dense welding in hand specimens and thin sections.2 The specific gravity of the Holy Joe Member (fig. 5) contrasts mark- edly with the specific gravity of the Aravaipa Member (see fig. 10). The concentration of vapor-phase crystal- lization in the central part of the cooling unit, instead of increasing upward as in most ash flows, probably means that overlying possibly hotter flows trapped gases in this part of the ash flow, which may have been slightly cooler and less welded than overlying and un- derlying flows. Horizontal partings in ash-flow tuffs may define in- dividual flow boundaries, partial cooling breaks, or zones of dense welding. To determine the presence of flow boundaries, studies should be made of density, po- rosity, chemical and modal composition, and size dis- tribution of phenocrysts and lithic fragments, similar to studies made by Ratté and Steven (1967) and Lip- man, Christiansen, and O’Connor (1966). Although a careful search for flow boundaries was not made, an ex- tinct fumarole, formed by escaping gas before the next 2Microprobe analyses of titanomag‘netite and ilmenite from two specimens of the Holy Joe Member (E. W, Hildreth, oral commun, 1979) are consistent with the interpretation, based on dense welding and specific gravity, of high emplacement temperature. Magmatic equilibration temperatures and log [02 values for the lower vitrophyre (HZOIC and 1120113) are 1035D and 1065°C and 7 8.2 and — 7.7 respectively. Temperatures of the upper vitrophyre could not be determined because of oxidation. The TC and log [‘02 values were read graphically from the Buddington-Lindsley (1964) curves, using Hildreth's analyses as recalculated by the method of Carmichael (1967). These are exceptionally high magmatic temperatures for biotite quartz latites. Since both oxide phases are abundant, homogene- ous, and unaltered, however, there is no obvious reason to doubt the data. Buddington and Lindsley (1964) suggested an accuracy of :30°C, and :1 log unit {02; reproducibility for these specimens is far better. 8 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA FIGURE 6,—Photomicrographs of Holy Joe Member. Biotite (B), holes (H), magnetite (M), plagioclase (P), pyroxene (py), pumice (pu), quartz (Q), xenolith or xenocryst (X). Plane polarized light, except as noted. A, Specimen H201G, lower densely welded vitrophyre. Pumice collapsed, but structure retained in frayed-out end at left. Shards have dark-orange center and lighter yellow margins; some larger ones have dull-brown centers, representing original character of glass. Perlitic cracks common. B, Densely welded devitrified rock (H2011). Shard structure well preserved as dark-brown streaks, with lighter margins that are finely devitrified. Pumice and some shard structure destroyed (light areas) by intergrowths of cristobalite and feldspar, some spherulitic intergrowths observed with crossed nicols. C, Dense welding in lower brown vapor-phase zone (H201J—1) evident in alinement of shards (dark streaks) and flattened pumice (hor- izontal light and dark area across middle of photograph). D, Same view as C, crossed nicols. Shows spherulitic intergrowths within pumice and its cavernous character (black areas labeled H in C). E, Dense welding in upper brown vapor-phase zone (H201M) and large flattened pumice lapilli. F, Same view as E, crossed nicols. Shows crystallization within pumice and its cavernous character. Shard matrix devitrified but mostly too fine grained to show in photograph. G, Dense welding in upper brown vapor-phase zone (H201N). Shard structure retained (dark streaks in dark areas). It and pumice structure destroyed by aggregates of feldspar and cristobalite (light areas). H, Same view as G, crossed nicols. Fine-grained devitrification barely visible in dark areas contrasts with coarser grained devitrification and vapor-phase crystallization of shards and pumice in light area. Note alteration of biotite. I, Dense welding in upper devitrified part of ash flow (H2010). Shards (dark streaks) molded against large phenocrysts and crystal fragments; pumice flattened. Spherulitic intergrowths of cristobalite and feldspar developed in pumice; apparent with crossed nicols. J, Densely welded upper vit- rophyre (H201P), containing numerous small and large crystal and lithic fragments. Shard structure and flattened pumice structure preserved, overlying flow was erupted, occurs in Oak Springs Can- underlying flow. This boundary is interpreted as rep- yon (fig. 2, 100. A). A short distance below the upper resenting the base of the last flow. Elsewhere, contrasts vitrophyre (between specimens H2010 and P, see fig. in abundance of crystal and lithic fragments and in the 5) the boundary between two flows is marked by a con- character of pumice fragments suggest different flows. centration of lump pumice that was rafted on top of the Because there is no change in crystallization of the HOLY JOE MEMBER 9 1cm lcm E H FIGURE 6.—Continued. groundmass across the two recognized flow boundaries The vitrophyre at the top of the Holy Joe Member and the gradation from one zone of crystallization to deserves special comment. Vitrophyres commonly oc- another, the partings are not believed to define partial cur near the base of cooling units; a second vitrophyre cooling breaks. in a sequence of ash flows is generally interpreted as 10 INTENSITY ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA 29, IN DEGREES 10 20 30 | B-Biotite C-Cristobalite 8.8 4.4 3.0 !NTERPLANAR SPACINGS, IN ANGSTROMS EXPLANATION CI-Clinoptilolite F-Feldspar O-Quartz T-Tridymite vitrophyre Older rocks I(———APPROXIMATE SCALE 0.4 KlLOMETER——)I FIGURE 8,—Sketch showing effect of buried to- pography on zonation in Holy Joe Member. Lower and upper vitrophyres merge as ash- flow sheet thins against prevolcanic topographic highs. Basal part of ash flow remains vitric and replaces devitrified and vapor-phase zones (dv). Dashed lines below and parallel to upper vitrophyre diagrammatically represent a few boundaries between individual flows. Aravaipa Member (Tar) and a thin basal tuf‘f (not shown) overlie Holy Joe Member. Looking northwest across Oak Springs Canyon, from south of loc. 6A, fig. 2. indicating the base of an overlying cooling unit and a break in cooling history. The following evidence sug- gests that the upper vitrophyre does not represent a cooling break: the boundary marked by the lump pum- ice horizon, described above, is within the upper de- vitrified zone. No break in groundmass crystallization was recognized across this boundary. The devitrified material above the flow boundary grades upward into the upper vitrophyre. This last flow was hot enough to weld, but it cooled too rapidly, in contact with the air, to devitrify. Although a vitrophyre at the top of a cool- ing unit is rare, Lipman, Christiansen, and O’Connor (1966) have described a similar occurrence. I am in- debted to R. L. Smith (oral commun., 1963) for first pointing out many of the features that led to the in- terpretation of this ash-flow sheet. Further evidence of a single cooling unit can be seen Where the ash-flow sheet laps against prevolcanic topographic highs and the lower vitrophyre crosses flow lines until it merges with the upper vitrophyre (fig. 8). { FIGURE 7.—X-ray diffractographs of selected specimens of Holy Joe and Aravaipa Members, showing type of peak heights involved in estimation of composition. Calculated positions of major tri- dymite peaks also shown. Peak intensity (maximum) = 100. Cu/Ni radiation, A CuKa = 1.5418 A. Scan from 4° to 36° at 1° 20/minute. A, Vitrophyre, H201E, Holy Joe Member. B, De- vitrified zone, H201H, Holy Joe Member. C, Vapor-phase zone, H201M, Holy Joe Member. D, Vapor-phase zone, H202Q, Ara- vaipa Member. E, Zeolitized tuff, A3, Aravaipa Member. ARAVAIPA MEMBER 11 TABLE 3.—Chemical composition and comparison of glassy and crystallized parts, Holy Joe Member [Major oxide analyses (weight percent) by P. Elmore, S. Botts, and C. Chloe by rapid methods described by Shapiro and Brannock (1962). See table 4 for minor-element analyses] Original analyses CIPW norms 1 2 3 1 2 3 67.2 68.5 67.1 Quartz ------------------- 23.5 21.3 19.9 14.4 15.2 15.4 Orthoclase — -------- 33.5 34.1 31.3 1.5 2.5 2.6 Albite ----------------- 32.0 32.5 34.5 .63 .30 .33 Anorthite ---- -------- 4.9 5.5 7.8 .77 .80 .77 Corundum -------- 1.0 .8 .4 1.1 1.3 1.8 Enstatite ------------- 2.0 2.0 2.0 3.6 3.8 4.0 Magnetite -------- .9 -- -- 5.4 5.7 5.2 Hematite ------------- 1.0 2.5 2.7 3.5 .53 .58 Ilmenite — 1.0 .8 .8 .40 .32 .56 Rutile ---- -— .1 .2 .48 .56 .60 Apatite ------------ .3 .4 .5 :53 :53 :52 Total ------------ 100.1 100.0 100.1 <05 <05 <05 99 100 99 Barth cations 1 2 3 Recalculated without H20 and C02 655 64.4 63.5 1 2 3 16.6 16.8 17.2 SiO2 ----------------------- 70.5 69.3 68.4 1&1 1:34 1:36 15.1 15.4 15.7 11 1.1 1.1 1.6 2.5 2.7 1.2 1.3 1.8 .66 .30 .34 6.8 6 9 7 3 1.1 1.3 1.8 _35 .40 ’43 3-8 3-8 4-1 .10 :13 :15 5.7 5.8 5.3 .06 06 04 .50 .57 .61 ' 13 .16 19 Total ------------ 99.22 99.93 99.98 07 08 05 Fe total ------------------ 1.61 2.04 2.16 99.97 100.02 99.98 Fe‘Z/Fe total ----------- .32 .12 .12 NOTE: Samples 1—3 from Oak Springs Canyon, NE corner sec. 6, T. 7 S., R. 18 E. (10c. A, fig. 2). 1, Lower vitrophyre, H201F, lab no. 159526. 2, Lower devitrified zone, H201H, lab. no. 159527. 3, Vapor-phase zone, H201K, lab no. 159528. ARAVAIPA MEMBER The Aravaipa Member of the Galiuro Volcanics cov- ers or underlies an area of more than 144 km2, from the northernmost latitude of Aravaipa Canyon (fig. 2) for about 11 km to the south side of Table Mountain (fig. 2), and from about 6 km west of to 6 km east of the boundary between the Holy Joe Peak and Klon- dyke quadrangles. The southernmost exposures on Ta- ble Mountain are about 75 m thick—and they show zoning typical of the central part of the ash-flow sheet. The absence of the member farther south, therefore, suggests its removal by erosion rather than thinning at a distal margin; this interpretation is further sup- ported by the gentle north to northeast dip of the mem- ber and by its southward projection upward above the present land surface. The Aravaipa Member may, how- ever, be present in some of the thick accumulations of ash flows to the southeast that have not yet been divided into separate units (Creasey and Krieger, 1978). To the east and probably to the southwest, the member Has been downfaulted and buried by younger deposits. Its distal edge is exposed to the northwest. North of Ar- avaipa Canyon it is buried by younger members of the Galiuro Volcanics. Except at its distal margin, Where it has been eroded, or where it thins, or is absent over topographic highs of older rocks, the member has a fairly uniform thickness of about 75 m. The Aravaipa Member is an ash-flow tuff of rhyolitic composition that has a well-developed interior zona- tion; this zonation indicates that it has an uninter- rupted cooling history but it may be composed of two or more ash flows. Excellent exposures of the interior vertical zonation occur in near-vertical cliffs along Ar- avaipa Canyon (fig. 9) and along Oak Springs and up- 12 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA TABLE 4.—Semiquantita ti ve spectrographic analyses of minor eIemen ts in ash-flow tufTs and rhyolite-obsidian member, northern Galiuro Mountains, Ariz. [Minor-element analyses by semiquantitative spectrographic methods by l, H. Barlow (nos. 1‘8) and C. H. Heropoulos (nos. 9—13); values reported as the nearest in the series 1.5, 2, 3, 5, 7, 10, Comparison with quantitative analyses indicates that the same class interval is assigned in about 30 percent of the samples. N, not detected; leaders (--), not looked for; <, less than. Looked for but not found: As, Au, Bi, Cd, Eu, Ge, He, In, Li, Pd, Pt, Re, Sb, Sm, Ta, Te, Th, Tl, U W] Quadrangle Holy Joe Peak Brandenburg Mtn. Klondyke Brandenburg Mtn. Tuffof Bear Hells Hf. Rhyolite- Member Holy Joe Member Aravaipa Member Springs Can. Acre Tuff obsidian Unit Vitro- Devitri- Vapor- Brown Black Devitri- Platy- Columnar- Pink Pink Pink Middle Rhyolite phyre fied phase vitro- vitro— fied jointed jointed tuff tuff tuff unit phyre phyre Number 1 2 3 4 5 6 7 8 9 10 11 12 13 Labobfatory 159526 159527 159528 159529 159530 159531 159532 159533 M126691W M126692W M101324W M101323W M101317W Fielblio No H201F H201H H201K H202E H202F H202L H202M H2020 A-4 H343M H414 H410 H409 <0.00007 <0.00007 <0.00007 <0.00007 <0.00007 <0.00007 <0.00007 <0.00007 N N <0.00007 <0.00007 <0.00007 <.003 N N <.003 <.003 <.003 <.003 <.003 .007 .001 N .0015 .001 .1 .2 .2 .03 .03 .05 .07 .07 .02 .02 .05 .02 .005 .0003 .0003 .0003 .0003 .0003 .0005 .0005 .0005 .0007 .0007 .0003 .0003 .0005 .03 .03 .03 .015 .01 .01 .02 .02 _. -- .01 .007 .01 .0003 .0005 .0005 N N N N N N N N N .0005 .002 .0015 .0015 .0005 .0003 <.0003 .0003 .00015 .003 .0001 .00015 N .005 .002 .0015 .0003 .0002 .0003 .0003 .001 .0005 .0007 .0003 .0005 .0003 .0015 .002 .002 .0015 .0015 .002 .002 .002 -- »- .0015 .0015 .002 N .003 N N N N N »- -- N -- -- .01 .015 .01 .007 .005 .005 .007 .007 .005 .01 .005 .005 .007 .0003 .0003 < 0003 .0005 .0005 <.0003 <.0003 .0003 N N N N .0002 .0015 .002 .002 .002 .002 .002 .002 .002 .003 .005 .002 .002 .003 .01 .015 .01 N N N -~ -< N N N .002 .003 .005 .0015 .001 .001 .0015 .001 .00007 ,00007 N .00015 N .003 .003 .003 .007 007 .003 .002 .003 003 003 .003 0.03.005 .0005 .001 .0007 .0005 .0002 .0003 .0005 .0005 .0005 .0007 .0005 0003 .0005 N N N .0005 .0007 N .0003 N N N N .03 .05 .05 .005 .003 .007 .01 .007 0.1 .02 .03 .05 .0007 .002 .005 .007 .0005 .0005 .001 .0007 .001 0007 002 .0015 .0015 .005 .007 .005 .003 .003 .003 .005 0.03 003 .003 .003 I$1.03 .0005 .0007 .0005 .0005 .0003 .0003 .0003 .0005 -- .0003 .0003 .0003 N N N N N N N N .003 .003 N N 1 .1 .07 015 .02 .02 .02 .02 .03 .03 .015 .01 .02 1—3. Oak Sprin sCanyon, NE comer sec. 6, T. 7 S. R 18 E, loc. A, fig. 4—5. East oan Springs Canyon, near center sec. 5, T 7 S. R. 18 E. locz. 6A2, fig. 2 6—8. Upper Bear Springs Canyon, center sec 4, T. 7 S, R. 18E. ,l.oc 6B, fig.2 9. Between Whitewash and Bear Sprin s Canyons, NWV4 sec. 30, T. 6 S. R. 18 E. loc. 2A, fig. 2. 10.C ave Canyon, Wedge, N l/Zsec 18, T68 .18 E, loo. 3, fig2 11. West of Virgus Canyon, loc. 7, fig. 2. 12. Aravaipa Canyon, east ofCave Canyon, loo. 8, fig 2 13. Aravaipa Canyon, east ofJavalina Canyon, SWI/g4 sec. 8, T. 6S., R. 18 E. loo. 9, fig. 2. per Bear Springs Canyons. The ash flow can be sepa- The ash flow IS composed of shards and pumlce lapilh, rated into six lithologic zones, in ascending order, the lower nonwelded to partially welded tuff, densely welded vitrophyre, vuggy, platy-jointed, and colum- nar-jointed zones, and the upper partially welded white tuff. The lower tuff is pale orange, becoming very light brown at the top. The lower part of the vit- rophyre is pale brown from oxidation; the rest of it is dark gray, except for brown spots at the top from in- cipient devitrification. The vuggy zone is light brown— ish gray except at the base, where it is pale brown. The platy-jointed zone is also light brownish gray. The col- umnar—jointed zone is slightly lighter in color. The up- per white tuff grades from pinkish gray at the base to white at the top. A suite of specimens, representing a vertical section across the ash flow, was collected in Oak Springs Can- yon (specimens H202A—H) and upper Bear Springs Canyon (specimens H2021—R) (locations 6A and 6B, fig. 2). The approximate elevation of each specimen above the base of the ash flow, the field units or litho— logic zones, color, zones of welding and crystallization, approximate mineralogic composition (based on X-ray diffractographs), and specific gravity of these speci- mens are summarized in figure 10. phenocrysts of feldspar, quartz, and biotite, and for- eign rock and crystal fragments. Phenocrysts average about 6 percent of the rock, and feldspars (plagioclase and sanidine) make up about 62 percent of the phen- ocrysts (table 5). Most of the lithic fragments are from older andesites, but in the upper part of the ash flow many of them are rhyolite, probably derived from ear- lier crystallization of the ash-flow magma. Photomicrographs (fig. 11) of selected thin sections of the suite of specimens show the microscopic features of the ash-flow sheet. The lower tuff is completely non- welded (fig. 11A) and vitric, except for the basal few meters, which has been altered to clinoptilolite (see composition column, fig. 10). The vitrophyre (fig. 11B) is densely welded and completely glassy, except for phenocrysts and xenoliths. Oxidation was considered the cause of the brown spots in specimens from the top of the vitrophyre (fig. 11C). However, they probably are due largely to incipient devitrification, as seen through crossed nicols (fig. 11D). The lighter areas, in contrast, are largely vitric. Where the ash flow filled a channel in older rocks, rapid chilling of the tuff against the channel walls caused the vitrophyre to reflect the underlying topographic irregularities (fig. 12). ARAVAIPA MEMBER 13 The vuggy zone (fig. 9) consists of densely welded and devitrified rock that is composed largely of cris— tobalite and feldspar, some of it in spherulitic inter- growths (fig. 11E). Biotite is altered, as it is in all crys- tallized parts of the ash flow; it is fresh only in vitric and zeolitized parts. The vuggy zone contains abun- dant large (as much as 10 cm in diameter), somewhat flattened vugs or lithophysae. The cavities are lined with inward-projecting acicular quartz crystals; locally centers contain calcite crystals. The abundance and size of the lithophysae (fig. 13) suggest that this ash flow had retained an uncommonly large proportion of volatiles in solution in the glass (Ross and Smith, 1961, p. 38). The volatiles were released after dense welding and during devitrification. Quartz and calcite were deposited in the vugs after the ash flow had partly crystallized and cooled. Thunder eggs (fig. 14), a dis- tinctive type of lithophysae, formed along the contact between the vitrophyre and devitrified zone near Oak Springs Canyon (10c. 6A, fig. 2). They have a maximum diameter of 15 cm. Gases released during devitrifica— tion accumulated within the spheres and produced suf- ficient pressure to fracture them. Small brown crystals of andradite garnet (identified by X-ray diffraction) occur within some of the voids (fig. 14G) and locally formed larger masses. To my knowledge, andradite has not been reported from rhyolite ash-flow tuffs; possibly it represents metamorphosed calcareous xenoliths. The platy-jointed zone is similar to the vuggy zone, except for closely spaced subhorizontal joints (fig. 15), a slightly lighter color, and fewer or no vugs. It is densely welded and completely devitrified (figs. 11F, G), with some coarse-grained devitrification products not only in pumice, but in some of the finer grained shard areas. Platy joints commonly develop near the zone of maximum compaction. A second thin slightly vuggy zone overlain by a thin platy-jointed zone was observed in many places, especially along Aravaipa Canyon. It was not studied in detail or traced so its significance is not understood. Its presence suggests the possibility of a second pulse of the ash flow. The columnar-jointed zone (figs. 9, 15, see also fig. 25) is a cliff-forming light-brownish-gray devitrified rock, much of which is also quite densely welded. Coarse-grained vapor-phase crystallization is mainly confined to pumice lapilli (fig. 11H). The columnar joints are contraction joints that develop during cool- ing; they are common in densely welded parts of ash flows and are also common in some vapor-phase zones. Welding, crystallization, composition based on X-ray diffractographs, and specific gravity of the lithologic units of the central part of the ash flow will be included with the discussion of the distal margin of the ash flow. The upper white tuff (fig. 9; see also fig. 27) is asoft, JIM/// 9Vfi§>jt «rim 5/)ch 0.1 . 0.3 KILOMETER l l l J Approximate scale FIGURE 9.—Typical exposure of Aravaipa Member (Tar) on north side of Aravaipa Canyon showing normal vertical zonation (see sketch): vuggy (V), platy-jointed (Pj), and columnar-jointed (Cj) zones, overlain, across Horse Camp Canyon, by upper white tuff (Taru). Vitro- phyre below level of creek. Lower andesite (Tlav) and conglomerate (ch) of Virgus Canyon overlie upper white tufi" at top center. 14 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA Composition Specimen 0; location 20 e f 20 e of u’ t above . . n so n s t — . . . base Field units Color welding crystallization :3 E 7: Specific graVIty .9 3 E .313 3 m V3 -E” E § § E E g U u. m U 0 H202 1.5 2.0 2.5 ~R White IoooA——§ Slight 3,253; welding 80 —_ Q tuff White (decreasing 9n; _ . . A A A _ Q (I) upward) I II 0. LLI . E —P Pkgr ngoAvr— P N 2 > E u! C I E (I) _ o umnare -- _ A O < 60- O jointed V It br gr T: O O O A A ”3 .: LLI > > 8 8 AN Ltbrgr oooA7—— N < Platy- l— jointed 5 —M Ltbrgr OOOA——4 M E 3’ I40—ml— Ltbrgr :5 COCA—A— 3 AK Ltbrgr E oooA——7 a; Vuggy zone g co —J Ltbrgr D COCA—7, —| Ltbrgr oooA——— — H Pale br 0 o A A 7 — 20—¥G Grandbr AAAA——o — F Vitrophyre Gr black — A A A — — 0 ~E Palebr oAmA——. *0 Vltbr Slight g AAiA—oo D — C Lower Pale orange welding E A A A — A o C white No welding > B tuff Pale orange A A A _ A . {B T A Pale orange — A A — o — 5A EXPLANATION o o A _ Abundant (more than 50 percent) Present but not abundant Recognized Not recognized FIGURE 10.——Some physical characteristics of interior parts of Aravaipa Member based on specimens collected at locality 6A(H202A— H) and 6B (H2021—R), figure 2‘ Modal data in table 5, chemical analyses of some specimens in table 6. Color terms: br, brown or brownish; gr, gray or grayish; lt, light; pk, pinkish; v, very. Abundance of minerals estimated from X-ray diffractographs of bulk samples. In addition to listed minerals, sample H2020 contained tridymite. slope—forming, slightly welded unit that was referred to in the quadrangle reports as the upper nonwelded zone (Krieger, 1968a, b) and the white tuff unit (Si- mons, 1964). It is shown separately on the quadrangle maps, but not in figure 2 of this report. It is welded (figs. 11I, J), but welding decreases rapidly upward as shown by hand specimens and thin sections. Little welding has occurred at the very top (figs. 11K, L). The rock is devitrified, with some coarse-grained crystal- lization in pumice lapilli. The nonwelded vitric top was largely eroded before deposition of younger rocks. The tuff, in places, is pockmarked by wind erosion, a char- acteristic feature of vapor-phase zones in ash-flow sheets, according to Ross and Smith (1961, p. 30). A low cliff occurs at the top of the white tuff in many of the southern exposures. The induration is due to sili- cification and represents exposure for a long period of time before deposition of younger rocks. The cliff was not observed along Aravaipa Canyon, where the tuff probably was exposed to erosion and weathering for a ARAVAIPA MEMBER 15 TABLE 5.—Modes ofAravaipa Member [Modes in volume percent. Based on thin-section studies of specimens H202A—H, loc. 6A, and H2021—R, loc. 6B (fig. 2). See figure 10 for lithologic zones and other characteristics. Field units: ut, upper tuff; cj, columnar jointed; pj, platyjointed; vug, vuggy; vit, vitrophyre; lt, lower tuff. T = trace] Percentage of rock exclusive of foreign fragments Percentage of total rock , . Foreignrock Field Field Total Feldspara Quartz 8“)th and mineral Points No. unit Matrixl phenocrysts2 (percentage of phenocrysts) fragments“ counted H202R 95 5 3 (60) 1 (20) 1 (20) 1 1,011 H202Q ut 96 4 2 (50) 2 (50) T -- 2 1,025 H202F 95 5 2 (40) 3 (60) T T 1,005 H2020 cj 94 6 5 (83) 1 (17) T -- T 1,001 H202N 91 9 7 (78) 1 (11) 1 (11) T 1,004 H202M pj 86 14 9 (64) 4 (28) 1 (8) T 1,007 H202K 94 6 4 (67) 2 (33) T -- T 1,002 H2021 vug 93 7 5 (71) 1 (15 1 (14) T 1,003 H202H 96 4 2 (50) 1 (25) 1 (25) T 1,003 H202F vit 96 4 3 (75) 1 (25) T -- T 1,019 H202E 97 3 2 (67) 1 (33) T —— T 1,005 H202D 1t 99 1 T (40) T (30) T (30) T 1,010 Average 94 6 4 (62) 2 (29) T (9) T 1,008 Range 86—99 1—14 T—9 -- T—4 -- T—1 -- T—2 --- lIncludes pumice lapilli; H202D has more pore space than overlying specimens, 2Not counted are traces of magnetite and very tiny crystal fragments Includes phenocrysts in pumice lapilli and crystal fragments in matrix, 3Largely plagioclase, includes sanidine (trace to 2 percent of total rock); may include some foreign plagioclase. 4Older vo canic rock, mostly andesite, except for rhyolite in H202P4R. shorter time. Because a zone of “solidly welded” tufT (Simons, 1964, p. 84—85) occurs at the top of the unit west of Parsons Canyon (east-central part of fig. 2, north of latitude 32°52’30”), Simons concluded that the white tuff was not part of his upper welded unit. However, I found no evidence of a break in crystalli- zation across the contact in this area. I interpret this densely welded zone as representing an additional pulse that was hot enough so that it became more densely welded than the underlying part. Crystalli- zation appears gradational, and there is no evidence of any Vitric material at the base of this last flow. The contact between the columnar-jointed and white tuff zones wherever observed is completely gradational. Lithology, specific gravity, and degree of welding and crystallization support the conclusion that the upper white tuff is part of the same cooling unit as the un— derlying ash flow. The vertical zonation described above is character- istic of the Aravaipa Member throughout most of the Holy Joe Peak and Klondyke quadrangles. In the northwestern part of the outcrop area, however, near the distal margin of the ash flow, a marked change in zonation occurs. A remarkable exposure (fig. 16) of the distal margin of the welded part of the ash flow occurs on the north side of lower Whitewash Canyon. The slightly welded, columnar-jointed vapor-phase zone thins rapidly and pinches out. Pink nonwelded tuff underlies, locally overlies, and extends beyond the welded part of the ash flow. This same change can be seen on the northwest side of Bear Springs Canyon, near a small canyon between Hells Half Acre and Whitewash Canyons, and in Cave Canyon north of Aravaipa Canyon. Another view (fig. 17) shows the complete change from the stacked-up zonation typical of the interior of the ash flow at the right to the non- welded distal margin, the view shown in figure 16, at the extreme left. The nonwelded basal tuff becomes progressively thicker away from the interior and suc- cessively replaces the vitrophyre, the vuggy, and the platy-jointed zones. Similarly, the columnar-jointed zone increases in thickness but farther outward is en— tirely replaced by nonwelded tuff. Detailed studies of the ash flow were made at selected localities from the interior toward the northwestern distal margin, and a suite of specimens was collected at each locality (fig. 18; also fig. 2). Figure 19 is 3 dia- grammatic summary of the studies made; it illustrates the general distribution, both horizontally and verti- cally, of lithology, welding, crystallization, mineral- ogy, and specific gravity from the southeast (100. 6A and 6B) to the northwest (10c. 1B). Because no speci- mens were collected from Whitewash Canyon north (loc. 1B), data from Bear Springs Canyon north (100. 1A, 2A, 2B) have been used. Details from the east side of Cave Canyon (Ice. 3) are also inserted between Whitewash Canyon north and south (10c. 1B and 4). This section is of interest because it is one of the few places where the nonwelded zeolitized top has been preserved and because the nonwelded basal tuff has been replaced by mordenite, instead of clinoptilolite, the zeolite that largely replaces nonwelded parts of the ash flow elsewhere. Details of the lithology and color, specific gravity, and mineralogy are shown in figures .tmu. 16 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA 1cm 1cm A I D 1 1cm L211 F |—_l FIGURE 11.——Photomicrographs of specimens from interior of Aravaipa Member. Biotite (B), magnetite (M), plagioclase (P), pumice (pu), quartz (Q), vug (V), xenolith or xenocryst (X). Plane polarized light, except as noted. A, Lower white tufi‘ (H202B); completely nonwelded with undeformed shards and unbroken glass bubbles. B, Strongly welded vitrophyre (H202F). Shards molded against crystal fragments. Large shards have dull-brown centers, representing original character of glass, and colorless margins. Groundmass contains much fine dust. Other parts of thin section show flattened pumice lapilli. C, Densely welded vitrophyre (H202G) with well-preserved shard structure. Shows part of one brown spot (darker area) in lighter colored vitrophyre. D, Same view as C, crossed nicols. Shows that areas that were darker in plane polarized light are clearly devitrified. E, Welded tuff from vuggy zone (H202J), crossed nicols. Show spherulitic inter— growths of cristobalite and feldspar in pumice. Shard structure Visible in plane light. Black areas (except in plagioclase) are vugs and are lined with quartz. F, Strongly welded, platy jointed tuff (H202N). Excellent preservation of shard structure, with dark streak down 1 L511 I 1cm L centers of shards, tube structure visible in large flattened pumice lapillus. G, Same View as E, crossed nicols. Intergrowths ofcristobalite and feldspar transect pumice and shard structure; intergrowths meet to form dark line through center of pumice lapillus. H, Columnar- jointed vapor-phase zone (H2020), crossed nicols. Shows contrast in texture between shard (finer grained) and pumice (coarser grained) areas. Fine-grained devitrification products are cristobalite and feldspar, but coarse-grained vapor-phase products in pumice include small tridymite crystals (too small to recognize in picture). In plane light, shard structure can be recognized. I, Slightly welded upper white tuf‘f(_H202P), showing shard structure and part oflarge pumice lapillus. J, Same view as I, crossed nicols. Vapor-phase minerals, tridymite and cristobalite, converted to quartz (see fig. 10, composition column), K, Nearly nonwelded tuff (H202R) from near top of upper white tuft. Shard structure defined by very fine grained axiolitic intergrowths of cristobalite and feldspar; pumice structure partly destroyed by coarse-grained spherulitic intergrowths. L, Same View as K, crossed nicolsi 18 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA ,4}; :7 4. , . "”4 ’2 I’M» .31! ,1"- , O 0.03KILOMETER l I Approximate scale FIGURE 12.—Aravaipa Member filling channel in Precambrian rocks (or). Sketch shows stratigraphic relations. Basal white tufl' (wt) and vitrophyre (vit) reflect underlying topographic irregularities. Vuggy zone (v) occupies central part of channel and is overlain by columnar-jointed zone (c). Also shown are undifferentiated Ara- vaipa Member (Tar) and upper tuff unit (Taru), rhyolite-obsidian member (Tro) and middle unit of Hells Half Acre Tuff Member (Thh-2). View north across Aravaipa Canyon from west of mouth of Virgus Canyon. Contact dashed where inferred. FIGURE 13.—Vuggy zone, Aravaipa Member showing quartz lining cavities. See pocket knife for scale. East of Oak Springs Canyon (loc. 6A, fig. 2): 20—22. Photomicrographs of selected thin sections (fig. 23) show the microscopic features. The trends shown in figures 19—22 were caused by the decrease in temperature of the ash flow with dis- tance from its source and by the rapid thinning of the ash flow against preexisting topographic highs (see fig. 2 Where, west of Cave Canyon, Hells Half Acre Tuff Member overlaps Aravaipa Member onto the under- lying andesite of Depression Canyon.) At Bear Springs Canyon south (10c. 5) and White- wash Canyon south (loc. 4), the lithologic zones (figs. 19A, 20) are essentially the same as in the interior of the ash flow (loc. 6A, B), except that at Bear Springs Canyon south the vitrophyre extends to, or nearly to, the base of the ash flow, probably because of a topo- graphic high, and at Whitewash Canyon south, pink tuff underlies the vitrophyre. The upper white tuff has been removed by erosion from location 4. The specific gravities (figs. 19E and 21) of the lithologic zones at locations 4 and 5 are similar to those at location 6, ex- cept that in the upper part of the columnar-jointed zone at location 4, specific gravity is as low as it is in the upper part of the white tuff at locations 5 and 6. Northwest of Whitewash Canyon south (loo. 4), only columnar-jointed tuff and pink tufl‘ remain, and spe- cific gravity (figs. 19E and 21) decreases in both zones, reflecting in part a decrease in welding towards the dis- ARAVAIPA MEMBER 19 FIGURE 14.—Thunder eggs from near contact between vitrophyre and vuggy zone, Aravaipa Member. Cauliflowerlike surface (A) caused by spotty incipient devitrification. Upper surface of thunder egg, as originally oriented, is cut by fractures filled with chal- cedony that form low ridges. Upper and lower halves are separated by a fracture, also filled with chalcedony. Fractures, typically three in number, in upper half generally do not extend into lower half. Incipient devitrification extends inward for about 0.5 cm, inside of which ash-flow tuff is completely devitrified into spherulitic intergrowths of cristobalite and feldspar (B—G). Vertical sections (B—E) through typical thunder eggs show irregular, angular character of partly filled voids in which chalcedony was deposited, and concentration of chalcedony in upper part of voids (especially D and E). Angular fragments of detrified tuff occur within voids (B and C). Finer grained material in lower part of some voids (C, D, E) consists of quartz, cristobalite, clay, and locally clinoptilolite. Variations in openings and fillings occur in some thunder eggs (F and G). Small crystals of andradite garnet locally occur in or partly fill voids (G). tal margin. The tip of the columnar-jointed zone at 10- ing in the pink tuff. Shards and glass bubbles are gen- cation 1A is nearly nonwelded (fig. 23H). Thin sections erally well preserved because of axiolitic replacement, (figs. 23A—G) also show the complete absence of weld- regardless of whether the zeolite is clinoptilolite (figs. 20 FIGURE 15.—Platy-jointed zone (P), between vuggy (V) and colum- nar-jointed (C) zones, Aravaipa Member, showing closely spaced subhorizontal joints. Exposed thickness of member, approximately 30 In. North side of Bear Springs Canyon, location 5 (fig. 2). 23A—D) or mordenite (figs. 23E, F). The specific gravity of the pink tuff may have been less than 1.5 before it was zeolitized; Hoover (1966) found that bulk densities of tuffs increase during zeolitization. The specific grav- ity of the pink tuff is low but somewhat variable, in part owing to variations in the number of lithophysae and pumice lapilli, which tend to decrease specific gravity. Each of the specimens collected was X-rayed; the re- sults are shown in figure 22 and summarized diagram- matically in figure 19D. X-ray diffractographs of the ash flow show not only the phenocrysts (feldspar, quartz, ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA and biotite) but also devitrification products (cristo- balite and feldspar), secondary quartz, and alteration products (clay and zeolite). The problems related to determination of mineral composition by X-ray dif- fractographs have been discussed in the section on the Holy Joe Member (p. 5). X-ray diffractographs were very useful in studying the Aravaipa Member, espe- cially the many specimens for which no thin sections were available and those that had been zeolitized. The X-ray patterns indicate that quartz, rather than cris- tobalite, is the principal silica mineral in the colum- nar-jointed zone at locations 2B, 3, 4, and 5, and in most of the upper white tuff at locations 5 and 6 (see fig. 7 for diffractograph of H202Q; this also shows that the principal tridymite peaks may have been masked by peaks of other minerals). At the distal margin of the columnar-jointed zone (locs. 1A, 2A) and in the top of the upper White tuff (locs. 5 and 6), cristobalite is the dominant silica mineral. The common devitrification products developed dur- ing crystallization of a cooling ash flow are cristobalite and feldspar. They start growing at grain boundaries and meet at a central zone of discontinuity that forms a dark line (figs. 11F, CD, producing the typical axiol- itic texture that preserves the shard structure. Vapor-phase crystallization is superimposed on de- vitrification and may obscure shard structure. Vapor- phase crystals develop first in pumice lapilli, where they are coarser than devitrification products. Tridym- ite, together with cristobalite and feldspar, is a com- mon vapor-phase mineral in all younger Tertiary and Quaternary ash-flow tuffs. Tridymite was recognized in thin sections of specimens from the vapor-phase zone (columnar-jointed zone and lower part of upper white tuff at 10c. 6) but not from the columnar-jointed zone FIGURE 16.—Distal margin of welded zone of Aravaipa Member, showing change from section composed mostly of columnar-jointed zone to completely nonwelded zone at left (see accompanying sketch). Lower part of cliff (right) is slightly darker, indicating denser welding and development of vuggy zone (vug), which to left has been replaced by columnar-jointed zone (c). Nonwelded pink tuff (p) farther left replaces lower part of columnar-jointed zone and still farther left overlies and extends beyond columnar-jointed tuff. Aravaipa Member ARAVAIPA MEMBER 21 at locs. 1A, 2A, and 3. It was not definitely recognized in the X-ray diffractographs because it is a minor con- stituent where present, and its peaks are close to some of the peaks of cristobalite, quartz, and feldspar (see figs. 70, D). Quartz rather than cristobalite (and tridymite?) oc- curs in most of the vapor-phase zone (see figs. 190, D). The cristobalite and tridymite probably inverted to high-temperature quartz during a prolonged spell at temperatures just below the inversion temperature. The quartz represents neither the granophyric crys- tallization that occurs in some very thick ash flows nor the conversion of cristobalite and tridymite that occurs in older ash flows. Most of the cristobalite detected by X-ray in the nonwelded pink tuff (fig. 22) probably rep- resents devitrification that formed around lithophysae. Chemical analyses (table 6) were made for two sam- ples of the 'vitrophyre (one brown and one black) and one each of the devitrified, platy—jointed, and vapor- phase zones. Minor-element contents of these samples are given in table 4. The whole-rock analyses show that chemical differ- ences between zones in the Aravaipa Member are very small. The most significant differences are the higher water content in vitrophyre than in the crystallized tuff and a high oxidation state of iron in the crystal- lized tuff than in the black vitrophyre. Both these characteristics are observed in ash-flow tuffs through— out the western United States and elsewhere. The high water content of the vitrophyre causes problems in comparing relative abundance of the non- volatile constituents, and probably is the result of sec- ondary hydration rather than of magmatic, deposi- tional, or cooling processes (Ross and Smith, 1955, p. 1086—1088). To more readily compare the nonvolatile elements, the analyses have been recalculated on a water-free basis; CIPW norms and Barth cation amounts are also listed. The recalculated analyses show a decrease in sodium in the vitrophyre compared to the crystallized rocks. Solution of sodium, some of it in greater amounts than reported here, has been re- ported from vitric parts of many rhyolitic rocks (Lip- man and Christiansen, 1964; Lipman, 1965). The other changes are minor and may reflect random variations among the samples or crystal and lithic fragments. Silica shows an increase; aluminum, magnesium, and calcium show very slight decreases in the vitrophyre compared with the crystallized parts of the ash flow. These changes are the reverse of those found by Lip- man and Christiansen (1964), who explain the higher aluminum, magnesium, and calcium content of the glassy nonwelded tuff by the presence of 5—10 percent of calcic montmorillonitic clay coating glass shards. The vitrophyres in the Aravaipa Member were too densely welded for clay to have developed. The relative amounts of CaO, NaZO, and K20 in the five analyzed samples have been plotted on figure 24 (Nos. 1a—5a) and show a slight but progressive upward increase in N320 and decrease in K20. CHANGES IN CHEMICAL COMPOSITION DUE TO ZEOLITIZATION The Aravaipa Member presents an excellent oppor- tunity to compare the chemical composition of a non- zeolitized tuff with that of its zeolitized parts. Zeoliti- zation took place only in the nonwelded parts of the ///,//// ‘/// WW . ( - r r 1.. _ ~ c- . . -- ‘ , .m <2: I1 " . . «u, \Lluf’ ' Van‘s... 4 O. I6 KlLOMETER Approximate scale is separated locally from overlying Hells Half Acre Tuff Member (upper unit, Thh—3) by thin lenses of conglomerate (ch) derived from lower andesite of Virgus Canyon and is underlain by tuff of Bear Springs Canyon (Ttb), which consists of pink tuff, except for columnar- jointed tuff (Cj) at right. Beneath tuff of Bear Springs Canyon are andesite of Depression Canyon (Tad), Holy Joe Member (Thj), and Whitetail(?) Conglomerate (Tw). Photograph taken from near loc. 1A; end of welded part at 10c. 1B (fig. 18). 22 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA FIGURE 17.—-Change from interior zonation in Aravaipa Member (right) to distal margin of ash flow (left). Most of photograph showsinterior vertical zonation from vitrophyre (V) at base through vuggy zone (vug) to columnar-jointed zone (C) at top (see accompanying sketch). Platy-jointed zone not recognized in photograph; upper tuf‘f has been removed by erosion. To the left, first vitrophyre and then vuggy zone are replaced by pink tufi' (P). Part of exposure to left of vitrophyre and vuggy zones also shown in figure 16. Apsey Conglomerate TABLE 6.—Chemical composition and comparison of glassy and crystallized parts, Aravaipa Member [Major oxide analyses (weight percent) by P. Elmore, S. Botts, and G. Chloe by rapid methods described by Shapiro and Brannock (1962). See table 4 for minor-element analyses] Original analyses Recalculated without H20 and C02 1 2 3 4 5 1a 2a 3a 4a 53 76.0 75.8 74.6 74.9 75.1 13.1 13.3 13.8 13.8 13.7 73.4 73.2 73.4 74.0 74.1 12.7 12.8 13.6 13.6 13.5 1.1 .83 1.2 1.2 1.2 1.1 .86 1.2 1.2 1.2 .13 .34 .08 .05 .04 .13 .35 .08 .05 .04 .25 .24 .47 .39 .35 26 25 .48 39 35 .38 .39 .44 .38 .46 39 40 .45 38 47 3.2 3.3 3.6 3.8 3.8 3 3 3 4 3.7 3 8 3 9 5.4 5.0 5.2 5.0 4.9 5 6 5 2 5.3 5 1 5 0 3.0 3.1 .93 .80 .77 22 23 .24 24 24 .40 .38 .93 .44 .61 .03 .04 .06 .04 .04 .21 .22 .24 .24 .24 .07 .11 .08 .08 .07 .03 .04 .06 .04 .04 .07 .11 .08 .08 .07 Total ----- 100.20 99.94 99.98 99.98 100.11 <05 <.05 <.05 <05 <05 100 100 100 100 100 CIPW norms Barth cations 1 2 3 4 5 1 2 3 4 5 Quartz ------------ 34.1 35.0 31.6 31.9 32.3 71.0 71.0 69.6 69.8 70.0 Orthoclase ------ 32.9 30.6 31.2 29.9 29.3 14 5 14 6 15.2 15 1 15 0 Albite ------------- 28.0 28.9 31.0 32.6 32.6 80 61 .86 85 85 Anorthite ------ 1.7 1.7 1.8 1.6 2.1 11 28 .06 04 03 Corundum ------- 1.0 1.4 1.4 1.4 1.2 36 35 .66 55 49 Enstatite -------- .64 .62 1.0 .98 .88 39 41 .45 38 47 Magnetite ----- .04 .85 -- -- -- 6 0 6 2 6.6 7 0 7 0 Hematite ------ 1.1 .28 1.2 1.2 1.2 6 7 6 2 6.3 6 0 5 9 Ilmenite ---------- .41 .43 .35 .28 .24 15 16 .17 17 17 Rutile ------------- -— -- .06 .10 .12 02 03 .05 03 03 Apatite ----------- .07 .10 .14 .10 .10 06 09 .06 06 06 Total ----- 99.96 99.88 99.75 100.06 100.04 100.09 99 93 100.01 99 98 100 00 Fe total ---------- .91 .89 .92 .89 .88 Fe '2/Fe total —--- .12 .31 .06 .04 .03 NOTE: Samples 1, 2 from east of Oak Springs Canyon, near center sec. 5, T. 7 S., R. 18 13., 10c. 6A, fig. 18. Samples 3—5 from upper Bear Springs Canyon, center sec. 4, T. 7 S., R. 18 E., loc. 6B, fig. 18. 1, Brown vitrophyre, H202E, Lab no. 159529. 2, Black vitrophyre, H202F, Lab no. 159530. 3, Devitrified zone, H202L, Lab no. 159531. 4, Platy-jointed zone, H202M, Lab no. 159532. 5, Vapor-phase zone, H2020, Lab no. 159533. ARAVAIPA MEMBER 23 Member (Ta) forms hills in right distance. Hells Half Acre Tuff Member (upper unit, Thh—3) is separated locally from Aravaipa Member by thin lenses of conglomerate (ch) derived from lower andesite of Virgus Canyon. Tuff of Bear Springs Canyon (Ttb) underlies Ar- avaipa Member and is underlain by andesite of Depression Canyon (Tad). Photograph taken from south of loo. 4 (fig. 18). Distance from left to right side of photograph approximately 2 km. ash flow that had remained vitric during cooling. None of the devitrified or vapor-phase zones were altered (see figs. 22, 190, D; and the X-ray diffractographs, figs. 7 D, E) South of Aravaipa Canyon (fig. 22, locs. 1A, 2A, 2B, and 4), and in the west side of Cave Can- yon, north of Aravaipa Canyon (Krieger, Johnson, and Bigsby, 1979), the nonwelded tuff was altered to cli- noptilolite. On the east side of Cave Canyon, however (fig. 22, Ice. 3), it was altered to mordenite below and to clinoptilolite above the columnar—jointed zone. Hoo- ver and Shepard (1965) found that clinoptilolite, mor- denite, and analcime formed in progressively deeper but overlapping zones. Mordenite, rather than clinop- tilolite, may have formed below the columnar-jointed zone on the east side of Cave Canyon because this part of the ash flow was buried more deeply than it was to the west and south, owing to the gentle north-north- eastward dip of the ash flow and to a thicker section of overlying Hells Half Acre Tuff Member. Zeolitization is believed to have occurred in an unsaturated zone above the water table and above impermeable rocks, conditions similar to those found by Hoover (1968) at the Nevada Test Site. Sheppard and Gude (1965), who compared vitric and zeolitized tuff by assuming con- stant A1203, concluded that formation of pure clinop- tilolite from pure rhyolite glass should involve mainly gains in H20 and CaO and losses in SiO2 and K20. The chemical analysis of the devitrified tuff (no. 3 from table 6) is compared to the analyses of the tuff that has been altered to clinoptilolite and to mordenite (table 7, nos. 1—3; also shown on table 7 are the anal- yses of tuff of Bear Springs Canyon, no. 4; the middle unit of Hells Half Acre Tuff Member, no. 5, both a]- tered to clinoptilolite; and the unaltered rhyolite-ob- sidian member, no. 6). The assumption is made that the devitrified tuff is the closest available approxi- mation to the original composition of the magma. The major change is a large increase in H20. To more read- ily compare the nonvolatile constituents, the analyses have been recalculated on a water-free basis. In addi- tion to H20, the major changes during alteration to both clinoptilolite and mordenite have been an in- crease in C30 (greater when altered to mordenite) and losses in Na20 (greater when altered to clinoptilolite) and K20 (greater when altered to mordenite). Clinop- tilolite shows a small increase in MgO and SiOZ, whereas mordenite shows little change; some of these differences may be due to minute xenoliths or xeno- crysts. The relative amounts of CaO, NaZO, and K20 in all the zeolitized and nonzeolitized rocks (from table 7) are plotted in figure 24. The relative amounts of these constituents in the five samples of the Aravaipa Member (from recalculated analyses, table 6, columns 1—5) are also plotted as nos. 1a—5a. CONCLUSIONS The Aravaipa Member is an outstanding example of vertical and horizontal zonation in an ash-flow tuff that cooled as a unit. The remarkable exposures, especially along Whitewash Canyon, make it posssble to trace the complete change from the typical stacked-up in- terior zonation to the nonwelded distal margin. The Aravaipa Member is a classic area for study of ash—flow tuffs. Vertical and horizontal changes in welding, crys— tallization, specific gravity, and lithology of the ash 24 ASH—FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA 110°32'30" 110°30‘ 1B 2 3 4 5 6 I | I l | | | A Present erosion surface ........ UWt W H CI pj v EXPLANATION ‘3: III Upper white tuff m Vuggy zone I. Columnar-jointed zone Vitrophyre E Platy—jointed zone B White tuff, pink tuff BI l | | I | Present erosion surface ..................... .Ilwt ‘CI' pt 3’1 ’~ v EXPLANATION 4;: m Partial welding _ 32° '1‘ Danse welding 52' - N0 welding 30" | T | I | C Present erosion surface Approximate top of ash flow\ _________________________ pt EXPLANATION ‘wt fl Vapor-phase zone — m Devitrified zone - Vitric zone DI I l I I I _ Present erosion surface 0 1 2 K'LOMETE RS ApprOXImate top of ash flow\ .. o I MlLE ---- uwt EXPLANATION LE]. Locality Location Specimen number ”p; 1A Bear Springs Canyon north A-7, H341K, N, 0, P . ' ' ' . 3 3 I I I I : _ ‘V 18 Whitewash Canyon north . . . _m 2A Bear Springs Canyon north H341A-H, J :wt 28 Bear Springs Canyon north Av1—6 EXPLANATION 3 CaVC Canyon H343A-H, .I-M Q Quartz and feldspar n Zeolite 4 Whitewash Canyon south A-8-16 Cristobalite and feldspar - Glass 5 Bear Springs Canyon south A-l7-25 I 6A Near Oak Springs Canyon H202A—H E GB Upper Bear Springs Canyon H2021-R l l | I 1 FIGURE 18,—Map showing outcrop of Aravaipa Member (shaded), location of specimens, and approximate position of distal margin of columnar-jointed zone (heavy dashed line). EXPLANATION flow are due to decrease in temperature as distance from 1 0.1 5 its source increased and as thinning of the ash flow 1 2K|LOMETERS @1310 against topographic highs caused more rapid cooling. 2'0'2'5 The Aravaipa Member maintains its typical interior FIGURE 19.—Diagrammatic sketches of zones in Aravaipa Member. zonation for a minimum of 9 km in a east-west direc- A, LitholOEY- 3, Welding C, Crystallization. D, Mineralogy E, tion. The rapid thinning of the ash flow and the short Specific gravity. C and D show probable features prior to zeoliti- . . . zation. Numbers and ticks at top show specimen localities (see fig. dIStance (less than 0'7 km) In Wthh the Change takes 18). Ticks (at right) represent boundaries of lithologic zones: uwt, place (IOC. 4 t0 100- 1A, fig. 18) suggest that (3001ng was upper white tuff; cj, columnar-jointed; pj, platy-jointed; v, vuggy; due more to the thinning against older rocks than to vit, vitrophyre; wt, white tuff; and (at left) pk, pink tuf‘f. EXPLANATION Upper tuff Columnar-jointed PIaty-jointed ARAVAIPA MEMBER II | l l l I Tuff 0f lilltl lLIrl lglrl :3} ' Bear Springs " “‘RCOIumnar-iointed \\ canv°n :33 Pink tuff \\\ \I u H202 Vuggy 25 Vitrophyre / Lower tuff-White / 0 Pink tuff 4 24 23A ' P H a 23— lllll 22 or pk ‘ 21 0 2b\ N ..«..°‘un=. \ ogr or pk°n M °_r. 19 L a v 1 u°9°P.n-u.° K s‘rs. “*5 8 ‘ It br gr‘o ybr gr»: .. 1y u u D a >WOUW‘NOI— ‘— 25 FIGURE 20.—Lithologic zones and color, Aravaipa Member, showing change from interior sequence (loo. 6) to distal margin of ash flow (10c. 1A) (see fig. 18 for locations). Color terms: bl, black; br, brown or brownish; d, dark; gr, gray orgrayish; 1t, light; or, orange; pa, pale; pk, pink or pinkish; v, very; w, white. Underlying tuf‘f of Bear Springs Canyon (bottom of Ice. 2A) also shown. TABLE 7.—Chem1'cal analyses and comparisons ofnonzeolitized and zeolitized Ara vaipa Member, zeolitized tut)" of Bear Springs Canyon and Hells Half Acre Tull" Member, and nonzeolitized rhyolite-obsidian member [Major oxide analyses (weight percent), No. l by P. Elmore, S. Butts, and G. Chloe: Nos. [L6 by P. Elmore, L. Artis, G. Chloe, J. Glenn, S. Botts, H. Smith, and D. Taylor by rapid methods described by Shapiro and Brannock (1962i; Nos. 4—6 supplemented by atomic absorption; Nos. 2, 3 by H. Smith by methods described by Shapiro (1967). See table 4 for minor-element analyses] Mineral Original analyses Recalculated without H20 and C02 1 2 3 4 5 6 1 2 3 4 5 6 73.4 67.0 63.6 65.5 69.3 74.6 74.6 75.2 74.4 76.1 76.6 75.3 13.6 12.5 12.1 12.4 11.5 13.5 13.8 14.0 14.1 14.4 12.8 13.6 1.2 12 1.0 1.2 .92 1.3 1.2 1.4 1.2 1.4 1.0 1.3 .08 12 .08 16 .16 .12 .08 13 .09 19 .18 .12 .47 10 .40 1.5 .72 .11 .48 1 l .47 1 7 .8 .11 .44 2 6 3 0 2.9 2.3 .38 .45 2 9 3.5 3 4 2.5 .38 3.6 78 1.9 .80 1.4 4.2 3.7 88 2.2 93 1.5 4.2 5.2 3 5 3.0 1 3 3.6 4.5 5.3 3 9 3.5 1 5 4.0 4.5 .93 7.6 7.9 3.3 2.2 .42 -- - -- -- -- -- .93 4.0 5.6 10.3 7.5 .10 -- -- -- -- -- .24 16 .12 21 .15 .21 .24 .18 .14 .24 .17 .21 .06 .15 .04 .03 .04 .03 .06 .06 .05 .03 .04 .03 .08 .07 06 .06 .07 .10 .08 .08 .07 .07 08 .01 <05 22 06 <05 .11 <.05 -- -- -- -- -- -- 100 100.90 99 100 99.97 100 99.99 99.83 99.72 99.96 99.87 99.76 1. Aravaipa Member, devitrified, H202L, Lab 159531, upper Bear Springs Canyon, center sec. 4, T. 7 S., R. 18E., loc. 6B, fig. 18. 2. Aravaipa Member altered to clinoptilolite, A—4, Lab M126691W, NW1/4 sec. 30, T. 6 S., R. 19 E., between Whitewash and Bear Springs Canyons, loc. 2B, fig. 18. 3. Aravaipa Member, altered to mordenite, H343M, Lab M126692W, west edge Nl/z sec. 18, T. 6 S., R. 18 E., Cave Canyon, Ice. 3, fig. 18. 4. Tuff of Bear Springs Canyon(?), altered to clinoptilolite, H414, Lab M101324W, east edge, N1/2 sec. 4, T. 78., R. 18 E., Ice. 7, fig. 2. 5. Hells Half Acre Tuff Member, middle unit, altered to clinoptilolite, H410, Lab M101323W, north of Aravaipa Canyon, east of Cave Canyon, NW1/4 sec. 18, T. 6 S., R. 18 E., 10c. 8, fig. 2. 6. Rhyolite-obsidian member, unaltered, H409, Lab M101317W, north of Aravaipa Canyon, east of Javalina Canyon, SE cor. sec. 7, T. 6 S., R. 18 E., loo. 9, fig. 2. 26 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA 1A 2A 23 3 4 5 6 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 2.5 1.5 2.0 2.5—1.5 2.0 2.5 H202 A-25 \ H343 // Upper white tuff Q //B /_.A \ / 24 Upper plnk tuff \ / \ 23A / / AA16 '\ \ 23 _ / D \ /H341 / . . 22 H341 / Columnar~ E Jomted 15 zone 21 O / , P J A 6 GF \ o< N H / 20 N ~ \ G — /Platy-jointed zone K F \\ 5 // J \ \ 14} / \ M A-7 E D \\ 19 L 4 x \ Vuggy zone K Lower C pink tuff M K\ \ 13 \ B 3 r \ 12 / 18) L \ /- 17 \ J \ A 2 / \ Vitrophyre I 34 \ Tuffof f \1' / \ \ j“ / METERS \ \ H . \ | \ 10 / \ Bear Springs pink B3 C‘o'urnnar —20 \ G F Canyon tuff —- B2 )ovnted \ //9 / \\ 8 B1 D _ \ C Lower 8 white \A tuff L0 FIGURE 21.—-Specific gravity, Aravaipa Member, superimposed on lithologic zones, showing change from interior sequence (loc. 6) to distal margin (loc. 1A) (see fig. 18 for locations). Also shows underlying tuff of Bear Springs Canyon (bottom of loc. 2A). distance from the source. The distal margin of the ash flow cooled so rapidly that it remained Vitric, and this nonwelded vitric part was later completely zeolitized by ground water. TUFF OF BEAR SPRINGS CANYON The tuff of Bear Springs Canyon (25 In) between Bear Springs and Whitewash Canyons is a rhyolite ash-flow tuff that is nearly coextensive with the over- lying Aravaipa Member (figs. 16 and 17). It is com- posed of shards, pumice lapilli, crystal and accidental fragments, and small lithophysae. The lower part (0— 15 m) is pink tuff, largely altered to clinoptilolite; the upper part (0—10 m) is very light olive-gray to light- brownish-gray columnar-jointed tuff whose ground- mass is composed largely of quartz and feldspar. The lithologic zones, specific gravities, and mineral com- positions of four specimens collected vertically across the tuff are shown in figures 20—22, loc. 2A, below the Aravaipa Member. The pink tuff represents the non- welded part, and the gray columnar-jointed tuff rep- resents the zone of vapor-phase crystallization of an ash flow that was erupted at temperatures not far above the minimum necessary for welding, as indicated by the very minor welding and the absence of a vitro- phyre. The higher specific gravity in the columnar- jointed zone may be due to slight welding. The lower specific gravity in the middle part of the pink tuff may be caused by large pumice lapilli, common in this part of the tuff. Both parts of the ash flow closely resemble the overlying pink tuff and columnar-jointed parts of the distal margin of the Aravaipa Member, but the lower columnar-jointed zone is not so extensive as the upper one. The two ash flows probably are similar in composition and closely related, but they are separated by a period of erosion, as evidenced by channels cut into or through the tuff of Bear Springs Canyon. No chemical analyses of the zeolitized tuff in this area are available. A chemical analysis of a pink tuff collected near the west edge of the Klondyke quadrangle (loo. 7, fig. 2) is included in table 7 (column 4). It may be tuff of Bear Springs Canyon, but it probably is one of the tufTs in the lower part of Simon’s (1964, p. 81) lower tuff unit. This specimen is composed of clinoptilolite with traces of quartz, feldspar, and biotite, similar to the pink tuff of Bear Springs Canyon (fig. 22, 10c. 2A). Its recalculated analysis, however, suggests that it originally may not have had the same composition as the tuff of Bear Springs Canyon or Aravaipa Member; RHYOLITE-OBSIDIAN MEMBER 27 1A 2A 28 3 4 5 6 ID a) a) a) g 1» g cu g a: g a: .t’ a: 3: g E 3: T: 3: B E 6 E T: E § E § : 3 as E E; 7: g; E g; 7: 35 1: 2; '5 saw: flauea oQBSQ onuea oauEa oases w ogusg w casts, w :35'52>$ wax—flaw fiagbg- uhg‘ég‘g WEE?“ .EEE'5::$ 325?“ __32'222 __SBZEE ‘--3._:.‘3— ‘:?.)3.-:_— :33-—:—— h0=.-:_— no) .—:_— diamooo 630110000 5$0mooo ouOmUUO cudmooo omOmooo Uudmooo H202 voA——-— A 000A--- R 25 . Upperwhlte tuff H343 —A—A ——A AooA—A— 24 -ooA———Q Up erpmk uf AEAA.—— B —ooA———23AA.OA___ P °.A___ C A —ooA——— 23 oooA——— 16 AooA——— D AOoA—A— 22 __ —A— 1 H341 AooA —E AooA———15 AO'A 2 oooA—A—o H341 AO.A___ F GA A 20 ___ -__ ___ oo — — OAAAA-- .OOA J AO.A 6 AO.A G Columnar- Pl .. .. d aty-Jomted oooA-—— N ooAA——— ooAA——— H Columnar AooA——— H jOlnte ooAA——— JOinted Lowterffpink QoAAA__ G —o—AOA— J AooA——— 14 A 19 oooA——— M u 000 ——— ooAAo—— AAAA"‘ F oooA——— Lowerpink oooA—A— L AAA—o—— E tuff Vuggyzone oooA-—— K AAAAO—-— AAA—O—- D AAAAO——- 4 ~AAAO—— Lower ink 0AAA--9 18 AAA_°__C tffp _AAA'_‘M 'OOA“‘1 AAAA——o17 000A J u _ ___ AAAAo—— B AoAAo—— 3 AAAAo—-L ooAA-——1 Vitrophyge oooA ‘ -AA—O-— - - ' METER ——— A A:Z:°" 2 02:32:32?“ oAAA——o 1/1 20 ooAA——- H TUffOf CB'S’RnaAV‘fl’ifi‘gd B4 — ._— 1 tuff;rnordenite AAAA__.1? 9233::29 gearSprings AAA—o—— 33 inflpwerpink AAA—oo— 9 —A—A——o E anyon —AA—o—- 32 m AA—A—oo b ‘ ff -A—Aoo— _AAPIDkgtKL- Bl 8 10 AAA——AO C Lowertuff oAAA-Ao B —AA—.—0 A EXPLANATION O o o A _ Abundant ( 50—100 percent) Present but not abundant Recognized Not recognized FIGURE 22.-—Approximate composition of Aravaipa Member, superimposed on lithologic zones, showing change from interior sequence (loo. 6) to distal margin (10c. 1A) of ash fiow. Apparent abundance estimated from X-ray diffractographs of bulk samples. In addition to minerals listed, specimens H2020 and P contain tridymite, and specimens H341L and M (between locations 1A, 2A) appear to contain about equal parts of cristobalite and feldspar, with traces of biotite and quartz. Also shows underlying tuff of Bear Springs Canyon (loc. 2A). it has a higher MgO and CaO and lower K20 content than the tuff of Bear Springs Canyon, and the relative amounts of CaO, NaZO, and K20 are different (see fig. 24). Additional data on tufT of Bear Springs Canyon are given in Krieger, Johnson, and Bigsby (1979). RHYOLITE-OBSIDIAN MEMBER Although the rhyolite-obsidian member is not an ash-flow tuff, it is described here briefly because of its probable close relationship to the Hells Half Acre Tuff Member. The rhyolite-obsidian member underlies an area of about 100 km2, about half of it in the northwest part of the Klondyke quadrangle. It extends from the north side of Aravaipa Canyon (fig. 2) to the south- eastern part of the Christmas quadrangle (fig. 1). The member consists of gray and black flow-banded to mas— sive perlitic to lithophysal obsidian and obsidian brec- cia, and finely laminated to contorted gray stony (de- vitrified) locally lithophysal rhyolite flow and flow breccia. A chemical analysis is given in table 7; see table 4 for minor-element content. The member was extruded as stubby flows and domes (see figs. 26, 27, and 28); only a few of the lowest ones reached the Vicinity of Aravaipa Canyon. The member has an estimated maximum thickness of about 300 m. It probably was erupted from at least two sources: one just north of the canyon on the boundary between the Klondyke and Holy Joe Peak quadrangles (fig. 2) and the other in the northeast part of the Holy Joe Peak quadrangle (Krie- ger, 1968a). Any other earlier sources have been bur- ied by younger flows. The stratigraphic relations of the rhyolite-obsidian member to other members of the Gal- iuro Volcanics and their correlation with units in the Christmas quadrangle are given in figure 3 (see es- pecially footnote 1, in Klondyke quadrangle) and dis- cussed briefly by Creasey and Krieger (1978). 28 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA 1cm A lcm lcm I._l D FIGURE 23.—Photomicrographs of specimens from near distal margin of Aravaipa Member. Biotite (B), hole (H), lithophysa (L), magnetite (M). plagioclase (P), pumice (pu), quartz (Q), xenolith or xenocryst (X). Plane polarized light, except as noted. A, Nonwelded pink tuff (H341A) from base of location 2A. Altered to clinoptilolite. Shard, glass bubble, and pumice structure well preserved. Some dark spots are grinding material. B, Same view as A, crossed nicols. Structure preserved because of axiolitic replacement by clinoptilolite. C, Nonwelded pink tuff (H341D). Excellent preservation of shard structure in tuff that has been altered to clinoptilolite. D, Same View as C, crossed nicols. Crystallization coarser grained in large shard fragment. Tube structure (not shown) preserved, even though finely HELLS HALF ACRE TUFF MEMBER The Hells Half Acre Tuff Member (0—150 m), of rhyolite composition, extends from the northeastern part of the Holy Joe Peak quadrangle (fig. 2) to about 1.6 km north of Aravaipa Canyon and eastward into the Klondyke quadrangle for about 3.5 km (fig. 2). It crops out intermittently beneath the Apsey Conglom- erate Member north of Aravaipa Canyon to the north- west corner of the Brandenburg Mountain quadrangle (Krieger, 1968a). North and south of the canyon, the member is thinner because the lower part laps against topographic highs of older members of the volcanic se- quence and of prevolcanic rocks. Along Aravaipa Can- yon the member can be readily separated into three CaO EXPLANATION o NONZEOLITIZED ROCKS 1a-5a Aravaipa Member from table 6, 3a : 1 in table 7 6 Rhyolite-obsidian Member X ZEOLITIZED TUFFS 2-3 Aravaipa Member 4 Tuff of Bear Springs Canyon 5 Hells Half Acre Tuff Member 23 38 4a 1a all-56.6 N320 1cm l___| F 1cm g4 H crystalline. E, Nonwelded pink tuff (H343J) altered to mordenite, showing shard structure. Abundant dust (dark). F, Same View as E, crossed nicols. Axiolitic intergrowths permit recognition of shard structure. G, Pink tuff (H343K), altered to mordenite; shard and pumice tube structure clearly defined. H, Specimen (H341P) from distal margin of columnar-jointed tuff (loc. 1A). Tuff only slightly welded, even though it still shows columnar jointing. With crossed nicols rock is finely devitrified; but X-ray diffractograph indicates that some birefringence is due to replacement by clinoptilolite. units that are completely exposed in nearly inacces- sible cliffs (fig. 25). The lowest unit (0 to at least 15 m) is a well-bedded cliff-forming porous yellowish-brown to brown rhyolite tuff with pumice lapilli and grains of quartz, feldspar, and biotite in a matrix of shards. Most of the vitric material has been altered to clinoptilolite. The unit, which was deposited in water impounded behind a tongue of rhyolite-obsidian (see figs. 2 and 26), is pres- ent along Aravaipa Canyon from about 0.7 km west of the mouth of J avalina3 Canyon to or nearly to the east aSpelling is that used on Brandenburg Mountain topographic map. { FIGURE 24.—Relative amounts of CaO, NaZO, and K20 in zeolitized and nonzeolitized samples of Aravaipa Member, tuff of Bear Springs Canyon, Hells Half Acre Tuff Member, and rhyolite-ob- sidian member. edge of the quadrangle and up Virgus Canyon for about 1.6 km. Simons (1964, p. 91) describes a similar water-laid tuff at the base of his lowest subunit, just south of Aravaipa Canyon, about 2.4 km east of the quadrangle boundary. The middle unit (up to 120 111 maximum thickness between Javalina and Cave Canyons) is a massive cliff-forming white to very pale pink tuff. It is sepa- rated into two parts by a narrow bench or slope; the upper part thickens to the east and the lower part thickens to the west of Virgus Canyon. The unit is composed of pumice lapilli, some obsidian and rhyolite lapilli, and grains of quartz, feldspar, and minor biotite in a matrix of shards; some of the vitric material has been altered to clinoptilolite. The unit, at least the lower part, is considered a nonwelded or slightly 30 i _ 0.2 KILOMETERS Approximate scale FIGURE 25.—Outcrop of units of Hells Half Acre Tuff Member (upper air-fall and reworked tuff, Thh—3; middle ash-flow(?) tuff, Thh—2; and lower water-laid tuff, Thh—l). Vague columnar jointing in lower part of middle unit suggests ash-flow tuff origin. Hells Half Acre Tuff Member overlain by Apsey Conglomerate Member (Ta) and underlain by a slope that largely conceals upper andesite (Tuav) and conglomerate (ch) of Virgus Canyon; lower andesite (Tlav) only at right side of picture. Lower cliff is Aravaipa Member (Tar, columnar-jointed (cj) and vuggy (v) zones; and Taru, upper slightly welded zone). View northeast across Aravaipa Canyon from just west of mouth of Virgus Canyon; Horse Camp Canyon in lower left. welded ash-flow tuff because it shows vague columnar jointing (fig. 25), a feature common in ash-flow tuffs but not in air-fall tuffs, and because it is massive (fig. 27) and unsorted. Furthermore, the subunit thins against older rocks (rhyolite-obsidian, figs. 27 and 28, and an- desite of Depression Canyon west of Cave Canyon, fig. 2) instead of maintaining a more uniform thickness as would an air-fall tuff. The upper unit (up to 10 m or more), the most ex- tensive unit, is a cliff— and slope-forming white to tan air-fall and partly reworked lithic tuff containing large angular lapilli of lump pumice and rhyolite-obsidian. It is characterized by northeast- and northwest—trend- ing joints along which narrow, deep crevices have de- veloped, especially on Hells Half Acre, between White- wash and Hells Half Acre Canyons (fig. 2). The Hells Half Acre Tuff Member was not studied in detail, so the extent and amount of zeolitization are ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA METERS 180 Horse Camp Canyon | I of KiLOMETER 0 l ' I O 600 METERS APPROXIMATE SCALE FIGURE 26.—Diagrammatic sketch of northwest wall of Horse Camp Canyon, above Aravaipa Canyon, showing units of Hells Half Acre Tuff Member (air-fall and reworked tuff, Thh—3; ash-flow(?) tuff, Thh—2; water-laid tuff, Thh—l) and relations of rhyolite-obsidian member (Tro) to Hells Half Acre Tuff Member and to upper an- desite of Virgus Canyon (Tuav). Exposed contacts (only locally cov- ered with talus) are solid lines; inferred contacts are dashed. Up- per andesite of Virgus Canyon locally separated from rhyolite- obsidian by conglomerate (cg) and from lower unit of Hells Half Acre Tuff Member by a wedge of crossbedded sandstone, washed out from the brecciated nose of rhyolite-obsidian flow. Conglomerate of Virgus Canyon (ch); lower andesite of Virgus Canyon (Tlav), and Aravaipa Member (Tar, showing vuggy and columnar-jointed zones and overlying slightly welded zone, Taru). not known. The compositions of six random specimens of the tuff, estimated from X-ray diffractographs, are shown in figure 29. Four of the specimens (all from the middle unit) have been largely altered to clinoptilolite; the others are vitric. The altered tuff is pink or white; the pumice lapilli are pink, white, or pale brown. A chemical analysis of a specimen of altered tuff and an analysis of a specimen of unaltered rhyolite-obsidian are listed in table 7 together with the analyses recal- culated without H20. The zeolitic alteration of the tuff accounts for the higher CaO and lower NaZO content. Relative amounts of CaO, Na20, and K20 are plotted in figure 24. The minor-element analysis is given in table 4. Zeolitic alteration makes it impossible to tell if the two were originally chemically similar. Addi- tional data on Hells Half Acre Tuff Member is given in Krieger, Johnson and Bigsby (1979). The Hells Half Acre Tuff Member may be part of the same volcanic episode as the rhyolite-obsidian mem- ber, although eruption of flows and tuffs may have al- ternated. The relations on the north side of Aravaipa Canyon east of Javalina Canyon (fig. 27) suggest that an obsidian flow and the overlying middle unit of Hells Half Acre Tuff are contemporaneous. Obsidian breccia underlies, overlies, and wraps around the nose of the flow. Immediate burial by the tuff probably preserved the breccia from erosion. The relations between rhyo- lite-obsidian and the lowest unit of the tuff, as exposed in Horse Camp Canyon (fig. 25), however, suggest suf- ficient time for erosion to form the wedge of crossbed- SUGGESTIONS FOR FUTURE WORK 31 0.15 KILOMETER Approximate scale FIGURE 27,—Massive lower part of middle unit (Thh—Za) of Hells Half Acre Tuff Member and its relation to rhyolite-obsidian mem- ber (Tro) (see sketch). Unit thins over irregular surface of flow, but maintains a horizontal top. This flow impounded water in which lower unit (Thh—l) of tuff was deposited. Flow consists of brec- ciated (hr) and nonbrecciated (Tro) material. Upper part of middle unit (Thh—Zb) is overlain by upper unit (Thh—3). Aravaipa Mem- ber (upper slightly welded tuff, Taru, and cliff-forming, columnar- jointed and vuggy zones, Tar) underlies talus-covered slope con- cealing conglomerate and possibly andesite of Virgus Canyon. View northeast from west of mouth of Virgus Canyon. ded sandstone that is composed of material derived from the brecciated rhyolite-obsidian flow. Finally, some of the large angular airborne(?) lapilli of rhyo- lite-obsidian and lump pumice that are abundant in the upper unit of the tuff may have come from the vent 0 0.05 K' LOMETER f—1_|_'_;l___.‘ 0 50 METERS APPROXIMATE SCALE FIGURE 28.—Diagrammatic sketch showing relations of middle unit (Thh—Z) of Hells Half Acre Tuff Member and rhyolite-obsidian member (Tro). Massive lower part of middle unit has horizontal top and very irregular base, suggesting ash-flow rather than air-fall origin. Interior of obsidian flow (Tro) is flow banded; its margins are brecciated. Preservation of fragmented nose and top of obsidian flow suggests that it was almost immediately covered by Hells Half Acre Tuff Member. Aravaipa Member (Tar) underlies rhyolite-ob- sidian member. Composite of exposures on north side of Aravaipa Canyon east of Javalina Canyon. in the rhyolite—obsidian near the boundary between the Klondyke and Holy Joe Peak quadrangles north of Aravaipa Canyon. These may represent the last major eruption of this sequence. To date no conclusive proof of intermittent eruption of rhyolite-obsidian flows has been found. The relations shown in figure 27, however, suggest that the rhyolite-obsidian flow here may be Slightly older than both the lower and middle units of the tuff. SUGGESTIONS FOR FUTURE WORK The Holy Joe and Aravaipa Members of the Galiuro Volcanics are so well exposed and so clearly show char- acteristic features of ash-flow tuffs that they could be a valuable teaching aid, and a source of theses for ge- ology students. Many detailed studies could be under— taken, for instance: (1) searching for flow boundaries and lithologic and chemical changes across flows in the 32 EXPLANATION o a, E o Abundant (more than Sample g L 3 50 percent) number ‘8 g 5 3 a 0 Present but not abundant :;,' 3 ‘5 ‘5 2 >. fi A Recognized 5 a: G g '6 8 a — Not recognized H180A — A A — A — 0 Upper unit (air-fall tuft) H276 — A o O — — Middle(?) unit H342A — O O A O — — Middle unit (ashaflow tuff) H344 — A O A O — — Middle unit (ash-flow tuff) H410 — A A A O — — Middle unit (ash»flow tuff) H410A -’ A A - — — 0 Upper(?) unit (air~fa|l tuff) FIGURE 29.—Appr0ximate composition of Hells Half Acre Tuff Member, estimated from X-ray diffractographs of bulk samples. H180A, middle branch, Hells Half Acre Canyon, center sec. 20, T. 6 S., R. 18 E. (fig. 2). Contains trace of calcite. H276, Ash Creek, east of Lyon Camp, sec. 21, T. 5 S., R. 18 E., NW1/4 Brandenburg Mountain quad- rangle; H342A, Cave Canyon, NW1/4 sec. 18, T. 6 S., R. 19 E. (fig. 2); H344, Aravaipa Canyon, east of Cave Canyon, NWIA sec. 18, T. 6 S., R. 18 E. (fig. 2); H410, Aravaipa Canyon, near mouth of Cave Canyon, NW1/4 sec. 18, T. 6 S., R. 18 E. (no. 12, fig. 2). (Chemical analysis, see table 7); H410A, Horse Camp Canyon, SW cor. sec. 9, T. 6 S., R. 18 E. (fig, 2). Holy Joe Member, as well as more detailed study of the upper vitrophyre and its distribution than has been made; (2) studying the ash-flow tuff sheet of the Aravaipa Member to determine if it is made up of more than one flow; making a careful selection of samples so as to obtain more meaningful results of changes in chemical composition of glassy and crystalline parts of both ash-flow tuffs and of changes due to zeolitization in the Aravaipa Member; (3) examining the relation of the tuff of Bear Springs Canyon to the tuff of Ara- vaipa Member to determine if they make up a com- posite sheet (Smith, 1960a); (4) determining the age relations of rhyolite—obsidian member and Hells Half Acre Tuff Member and the distribution of zeolitization in the tuff. REFERENCES CITED Blake, W. P., 1902, The geology of the Galiuro Mountains, Ariz., and of the gold-bearing ledge known as Gold Mountain: Engineering Mining Journal, v. 73, p. 546—547. Buddington, A. F., and Lindsley, D. H., 1964, Iron-titanium oxide minerals and synthetic equivalents: Journal of Petrology, v. 5, p. 310—357. Carmichael, I. S. E., 1967, The iron-titanium oxides of salic volcanic rocks and their associated ferromagnesian silicates: Contribu- tions to Mineralogy and Petrology, v. 14, p. 36—64. Cooper, J. R., and Silver, L. T., 1964, Geology and ore deposits of the Dragoon quadrangle, Cochise County, Arizona: US. Geological Survey Professional Paper 416, 196 p. Creasey, S. C., and Krieger, M. H., 1978, The Galiuro Volcanics, Pinal, Graham, and Cochise Counties, Arizona: US. Geological Survey Journal of Research. v. 6, no. 1, p. 115—131. GPO 689-14 3 ASH-FLOW TUFFS OF THE GALIURO VOLCANICS, PINAL COUNTY, ARIZONA Hoover, D. L., 1966, Physical and chemical changes during zeoliti- zation of vitric tuffs and lava flows, Nevada Test Site [abs]: Geo- logical Society of America Special Paper 87, p. 286—287. 1968, Genesis of zeolites, Nevada Test Site, in Eckel, E. B., ed., Nevada Test Site: Geological Society of America Memoir 110, p. 275—284. Hoover, D. L., and Shepard, A. 0., 1965, Zeolite zoning in volcanic rocks at the Nevada Test Site, Nye County, Nevada [abs]: American Mineralogist, v. 50, nos. 1—2, p. 287. Krieger, M. H., 1968a, Geologic map of the Brandenburg Mountain quadrangle, Pinal County, Arizona: US. Geological Survey Geo- logic Quadrangle Map GQ—668, scale 1224,000. 1968b, Geologic map of the Holy Joe Peak quadrangle, Pinal County, Arizona: US. Geological Survey Geologic Quadrangle Map GQ—669, scale 1224,000. 1968c, Geologic map of the Lookout Mountain quadrangle, Pinal County, Arizona: US. Geological Survey Geologic Quad- rangle Map GQ—670, scale 1:24,000. 1968d, Geologic map of the Saddle Mountain quadrangle, Pinal County, Arizona: US. Geological Survey Geologic Quad- rangle Map GQ—671, scale 1224,000. Krieger, M. H., Johnson, M. G., and Bigsby, P. R., 1979, Mineral resources of the Aravaipa Canyon Designated Wilderness area. Pinal and Graham Counties, Arizona: US. Geological Survey Open-File Report 79—291, 183 p. Lipman, P. W., 1965, Chemical comparison of glassy and crystalline volcanic rocks: US. Geological Survey Bulletin 1201—D, 24 p. Lipman, P. W., and Christiansen, R. L., 1964, Zonal features of an ash-flow sheet in the Piapi Canyon Formation, southern Nevada, in Geological Survey Research, 1964: US. Geological Survey Professional Paper 501—B, p. B74—B78. Lipman, P. W., Christiansen, R. L., and O’Connor, J. T., 1966, A compositionally zoned ash-flow sheet in southern Nevada: US. Geological Survey Professional Paper 524—F, 47 p. Ratté, J. C., and Steven, T. A., 1967, Ash flows and related volcanic rocks associated with the Creede caldera, San Juan Mountains, Colorado: US. Geological Survey Prbfessional Paper 524—H, 58 p. Ross, C. S., and Smith, R. L., 1955, Water and other volatiles in vol- canic glasses: American Mineralogist, v. 40, nos. 11—12, p. 1071— 1089. 1961, Ash-flow tuffs—Their origin, geologic relations, and iden- tification: US. Geological Survey Professional Paper 366, 81 p. Shapiro, Leonard, 1967, Rapid analyses of rocks and minerals by a single solution method, in Geological Survey Research 1967: US. Geological Survey Professional Paper 575—B, p. B187— B191. Shapiro, Leonard, and Brannock, W. W., 1962, Rapid analysis of sil- icate, carbonate, and phosphate rocks: US. Geological Survey Bulletin 1144—A, 56 p. Sheppard, R. A., and Gude, A. J., 3d, 1965, Zeolitic authigenesis of tuffs in the Ricardo Formation, Kern County, California, in Geo- logical Survey Research, 1965: US Geological Survey Profes- sional Paper 525—D, p. D44—D47. Simons, F. 8., 1964, Geology of the Klondyke quadrangle, Graham and Pinal Counties, Arizona: US. Geological Survey Profes- sional Paper 461, 173 p. Smith, R. L., 19603, Ash flows: Geological Society of America Bulletin, v. 71, no. 6, p. 795—841. 1960b, Zones and zonal variations in welded ash flows: US. Geological Survey Professional Paper 354—F, p. F149—F159. Willden, Ronald, 1964, Geology of the Christmas quadrangle, Gila and Pinal Counties, Arizona: US. Geological Survey Bulletin 1161—E, 64 p. The Mioccane Seldovia Point Flora from the Kenai Group, Alaska By JACK A. WOLFE and TOSHIMASA TANAI GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: I980 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Wolfe, Jack A. 1936- The Miocene Seldovia Point flora from the Kenai group, Alaska. (Geological Survey professional paper ; 1105) Bibliography: p. 45-47. Includes index. 1. Paleobotany—Miocene. 2. Paleobotany—Alaska—Cook Inlet region. I. Tanai, Toshimassa,joint author. 11. Title. III. Series: United States. Geological Survey. Professional paper ; 1105. QE929.W64 561’.2’097983 79—20550 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock number 024-00 1-03 28 2-1 CONTENTS ,, Page Page Abstract _______________________________________________ 1 Vegetation—Continued Introduction ____________________________________________ 1 Distribution __________________________________________ 15 Geologic occurrence ____________________________________ 3 Communities ________________________________________ 16 Age "-,,_____,_,,___' __________________________________ 7 Floristics ________________________________________________ 16 Floristic composition ____________________________________ 9 Paleoclimatology ________________________________________ 19 Vegetation ______________________________________________ l 1 Systematics ______________________________________________ 24 Megafossils __________________________________________ 11 References cited __________________________________________ 45 Pollen ______________________________________________ 14 Index ____________________________________________________ 49 ILLUSTRATIONS [Plates follow index] PLATE . Filicales, Coniferales, Magnoliidae. FIGURE Hamamelididae, Ranunculidae. Hamamelididae. Hamamelididae. Hamamelididae. . Hamamelididae. . Hamamelididae. . Hamamelididae. _ Hamamelididae. . Hamamelididae. . Hamamelididae, Dilleniidae. . Dilleniidae. . Dilleniidae. . Dilleniidae, Rosidae. . Dilleniidae, Rosidae. . Rosidae. . Rosidae. . Rosidae. . Rosidae. . Rosidae. . Rosidae. . Rosidae, Monocotyledonesi . Rosidae, Monocotyledones. . Rosidae. . Asteridae, Monocotyledones. Page . Map of Alaska ___________________________________________________________________________________________________ 2 . Map of Cook Inlet region _________________________________________________________________________________________ 3 Chart showing changes in usages of stages and ages in the Oligocene through Pliocene series of Alaska _____________ 4 . Map of the Seldovia area _________________________________________________________________________________________ 5 Diagram showing section of Kenai Group exposed between Seldovia and Barbara Points ______________________________ 6 . Suggested correlations of the Kenai Group and the coal-bearing group of the Nenana coalfield _______________________ 9 . Suggested distribution of vegetational types in Alaska during middle Miocene time _________________________________ 15 . Graph showing temperature parameters of modern vegetational types in eastern Asia and in the probable temperature parameters of certain middle Miocene assemblages _________________________________________________ 19 A Map of northeastern Asia showing location of some middle Miocene assemblages ____________________________________ 21 . Map of northwestern North America showing location of some middle Miocene assemblages __________________________ 23 III 1v TABLE 1. 2 3 4 5 6 7 CONTENTS T AB LES Page Average percentages of samples containing pollen of certain broad-leaved genera in Seldovian rocks of the Nenana coalfield, Alaska Range ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 7 . Known stratigraphic ranges of Seldovia Point dicotyledonous species in Japan and conterminous United States ,,,,,,,, 9 i Assumed growth habits of Seldovia Point species __________________________________________________________________ 12 . Distribution of most closely related extant species in vegetational types in eastern Asia ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 12 . Seldovian dicotyledonous Species also occurring in Mixed Mesophytic forest in the early and middle Miocene of the Pacific Northwest ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 13 . Percentages of pollen types in samples from the Seldovia Point beds ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14 . Analysis of the Seldovia Point assemblage in terms of floristic elements ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 17 THE MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA By JACK A. WOLFE and TOSHIMASA TANAI ABSTRACT Approximately 60 species of megafossil plants are illustrated and are assigned to 45 genera. Most of the species are dicotyledonous, although monocotyledons, ginkgo, conifers, and ferns are also rep- resented. Nine species of dicotyledons and one species of monocotyledon are described as new. The flora includes the first de- scribed representatives of Cyclocarya, N ymphar, Sorbaria, Pueraria, Decodon, Kalopanax, Lonicera, and Alisma in the North American Tertiary. The plant-bearing beds are considered to be part of the Kenai Group. The West Foreland Formation (late Paleocene) is excluded from the Kenai Group, but the following formational units are ac- cepted within the group, in ascending order: Hemlock Conglomerate (early Oligocene), Tyonek Formation (early Oligocene through mid- dle Miocene), Beluga Formation (middle and late Miocene), and Sterling Formation (late Miocene and Pliocene). Paleobotanical evi- dence indicates that the Seldovia Point beds are equivalent to part of the Tyonek Formation; the geology of these beds indicates that they represent deposits that filled a valley to the south of the main part of the Kenai basin. Paleobotanical correlations also indicate that the Seldovia Point flora is, in provincial terminology, of late Seldovian age and further that the upper part of the Seldovian Stage is of late early and early middle Miocene age. Analysis of the Seldovia Point assemblage from both floristic and physiognomic standpoints indicates that the assemblage represents Mixed Northern Hardwood forest, although palynological data indi- cate that coniferous forest was close by. The Seldovia Point as- semblage has several genera that no longer participate in Mixed Northern Hardwood forest and that today are restricted to broad- leaved evergreen or Mixed Mesophytic forests. These differences are interpreted in light of the history of Mixed Northern Hardwood and related forest types during the Neogene. Analysis of the Seldovia Point assemblage in terms of the deriva- tion of component lineages indicates that of those species whose lineages are reasonably well known, about one—third of the species are of east Asian origin, one-third of west American (middle latitude) origin, and one-third of high-latitude origin. The lack of penetration of west American species southward into eastern Asia and the lack of penetration of east Asian species southward into middle latitudes of western North America are suggested to be the result of the loss of genetic plasticity in regard to adaptation to dif- ferent photoperiodic conditions. Paleoclimatic conditions inferred from the Seldovia Point as- semblage strongly indicate that since the middle Miocene there has been a moderate decline in mean annual temperature and a major decrease in mean annual range of temperature. Analysis of other middle Miocene plant assemblages at middle latitudes in both east- ern Asia and western North America indicates that the same basic pattern of temperature shifts occurred, although the changes in mean annual range of temperature were most pronounced in west- ern North America and particularly Alaska. The primary tempera— ture parameter that was alterel was warm-month temperatures, which underwent a severe decline; this decline in summer tempera- tures is probably one of the causes of the initiation of glaciation at high latitudes during the late Cenozoic. The Seldovia Point as- semblage, when compared to Alaskan assemblages of early and late Miocene age, is consistent with the concept of a middle Miocene warming, which has been previously documented at middle latitudes. INTRODUCTION The floras of the Kenai Group of the Cook Inlet re- gion in Alaska have attracted the interest of paleo- botanists for over 100 years. Plants collected by or for Furuhjelm, at one time governor of what was then Russian America, were submitted to the Swiss paleo- botanist Oswald Heer; these plants came from two localities—one near the village of Ninilchik on the east shore of Cook Inlet and the second supposedly near English Bay on the southwestern part of the Kenai Peninsula (fig. 1). These plants, along with those from Kuiu Island in southeastern Alaska, were described and illustrated by Heer (1869a) as a part of his monumental Flora Fossilis Arctica. The acquisition of Alaska by the United States in 1867 led ultimately to investigations of the Cook Inlet region by members of the US. Geological Survey. These investigations included collection and analysis of the fossil floras of the Kenai Group (for example, Martin and others, 1915), but the only comprehensive taxonomic analysis of these floras prior to the 1960’s was by Hollick (1936). It is notable that these earlier collections were small and that none were made by paleobotanists. Hollick’s fieldwork in Alaska involved collecting plants from Cretaceous rocks along the Yukon River (Hollick, 1930). Although the late R. W. Chaney discussed the floristic significance of the Kenai floras in numerous papers (for example, Chaney, 1936, 1952, 1967), he never carried out paleobotanical field investigations on the Kenai floras, which occupied a central position in his concept of an “Arcto-Tertiary Geoflora.” The first paleobotanist to undertake collection of the Kenai floras was the late R. W. Brown, who made small collections from five localities in 1955. Brown, however, was nearing retirement and made only ten- tative, unpublished generic determinations of some of the Kenai material. The need for comprehensive field 1 2 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA ARCTIC Barrow 8° 154° ,- Kodiak | 3%? / fl . 100 50 0 100 ZOOMILES 10050 0 100 200 KILOMETERS S" Seldo ' 9 l V13. 00 Ohm/”Kenai Peninsula mt???“ PACIFIC FIGURE 1.—Map of Alaska showing location of Cook Inlet region. investigations and laboratory studies of not only the Kenai floras but also other Alaskan Tertiary floras was emphasized by many geologists working in Alaska and particularly by D. M. Hopkins. Fieldwork was initiated by Wolfe in southeastern Alaska in 1961 and was extended into the Cook Inlet region in 1962. The decision to concentrate on collection and study of the floras of the Kenai Group was made because of the historical significance of these floras, the discovery of petroleum and natural gas in Kenai rocks, and the considerable thickness of this unit, which indicated the possibility of obtaining numerous assemblages in demonstrable stratigraphic succession. Stratigraphi- cally significant species from the Kenai Formation of former usage were discussed and illustrated by Wolfe (.1966), and also incorporating palynological studies by Wolfe and E. B. Leopold, these species formed the basis for a biostratigraphic framework for the Alas- kan Neogene (Wolfe and others, 1966). Wolfe (1966) also gave a tentative list of the Seldovia Point flora. Collections made in 1962 from localities near Sel- dovia and extending southwestward to Port Graham (Heer’s “English Bay” material was, in fact, obtained from Coal Cove on Port Graham; see also Martin and others, 1915) were the largest obtained from the Kenai, in terms of both specimens and species. Collec- tively, the material from USGS palebotanical lo- calities 9856 (Coal Cove), 9857, and 9858 (Seldovia Point) is the basis for the Seldovia Point flora. Addi- tional material was collected by Wolfe in 1967 from Seldovia Point and from new localities along the north shore of Kachemak Bay and elsewhere in the Cook Inlet region. Although the Seldovia Point locality was not visited, we obtained additional material from the GEOLOGIC OCCURRENCE upper part of the Kenai Group in 1973. Added to this material is a modest but nevertheless significant col- lection made by C. E. Allison in 1971 at Seldovia Point. The material now in hand from the Kenai Group allows a far better understanding of the floristic, climatic, and stratigraphic significance of the various Kenai floras. Preliminary statements on the sig- nificance of these fioras have been published elsewhere (Wolfe, 1969a, 1969b, 1972), but this report presents the first thorough study of any of the Kenai floras, a study requisite for the documentation or mod- ification of previous statements. The Seldovia Point flora is particularly significant because it allows an understanding of fioristic and climatic relationships around the North Pacific Basin during the middle Miocene; many fioras of this time have received de- tailed attention both in Japan (Tanai, 1972) and in the conterminous United States (Wolfe, 1969a). We gratefully acknowledge the continuing encour- agement of D. M. Hopkins in our studies; the geologic section of the beds at Seldovia Point is based largely on Hopkins’ field observations made in 1962. Estella B. Leopold has provided us with valuable data based on her largely unpublished but extensive studies of samples from the Nenana coalfield. For assistance in particular taxonomic problems we are grateful to Pro- fessor Huzioka (Akita University) and Dr. H. D. Mac- Ginite (University of California, Berkeley). Dr. Carol Allison (University of Alaska) allowed us to include her university’s collections from Seldovia Point in this study. GEOLOGIC OCCURRENCE The bulk of the Tertiary beds of the Cook Inlet re— gion (fig. 2) have been variously referred to as the Kenai Series, Kenai Group, or Kenai Formation. As well, various informal lithologic subdivisions of the Kenai rocks have been proposed (for example, Kelly, 1963), but only recently have formal lithologic sub- divisions been proposed (Calderwood and Fackler, 1972). Three stages have been previously erected for the time interval during which the Kenai Group was de- posited (Wolfe and others, 1966); in ascending order, these are the Seldovian, Homerian, and Clamgulchian. The Seldovian Stage was considered to be of Oligocene(?) through approximately middle Miocene age, the Homerian to be probably of later Miocene age, and the Clamgulchian to be largely of Pliocene age. The Seldovian stage was, moreover, informally subdivided into a lower(?) and upper(?) part based on the analysis of certain plant assemblages, some of which appeared to be older than those in the type sec- tion of the Seldovian Stage at Capps Glacier and 152° 150“ 143° 0 I so 100 KILOMETEH’S I—I_.| , e 7 / $ 0 ¢//’ ( p. / I Approximate area of QR I outcrops of Kenai V I \ Group ‘1- ' I 9 ., v- I . | 62 v ( -§ ‘ _ v \ 7 | \. a? ’- \ g? \~/’ -’ 3\ \ g: I, in / \ \ I 3 to, l” / tr!- 9 . 7 1:: //°"‘“C'Zuu RM 0 Anihorage 13,}! 7’4 l 2 Tyone ' a) I: ‘ o / 01~ I 5 Jo / o l 1' A; omer ea 3° of fisMurelf‘QL‘lle mk Pbrt4 Graham .51»; Iowa {3’9‘ 0 X)? /./ l 1 FIGURE 2.—Cook Inlet region, showing approximate extent of out— crops of the Kenai Group. along Chuitna River and in its reference section of the Seldovian Stage at Seldovia Point. Continued work (Wahrhaftig and others, 1969) indicated that in the Nenana coalfield of the central part of the Alaska Range plant assemblages approximately correlative with the lower(?) Seldovian assemblages in the Cook Inlet region were demonstrably lower stratigraphi- cally than assemblages correlative with those in the type and reference sections of the Seldovian Stage; the rocks containing these lower(?) Seldovian assemblages were consequently excluded from the Seldovian Stage. Wolfe (1969b, 1972, 1977) has applied the term An- goonian Stage to these Oligocene assemblages for- merly termed lower(?) Seldovian (fig. 3). We are here accepting the elevation of the Kenai Formation to the status of Kenai Group as proposed by Calderwood and Fackler (1972), with the exception that we exclude their West Foreland Formation from the Kenai Group, defined as ”a tuffaceous siltstone— 4 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Wolfe and others Wahrhaftig and Wolfe (1969b, _ (1966) others (1959) 1972) ““5 report 5 s g 9 '5 ‘5’ % s ‘3 '5, a 8 H E $3 9 53 9 E 313 U) U) a (I) ‘0 U) (3 5 w u. u. OJ ‘1’ Clamgulch- g is; ian Stage Clamgulchlan Clamgulchlan Clamgulchlan Sterling E .9 Stage Stage Stage Formation E E.‘ / / c 9?’ 0’ H ‘ n c g / 032$: / .9 Homerian Stage Homerian Stage Beluga 3 / ‘5 Q Formation / E Homerian Stage 3 - / u S B / Upped?) LE 0 3 part of ,_ 5 ._ — a) Seldovian g a . g 2 g a: Stage q.) 9- 8 cu u g 34 3 a >4 .9 .E Se|(d=ol\‘/La:er8(t7a)ge Seldovian Seldovian D 2 § Seldovlan‘) Stage Stage 5 E g 5;? Tyonek .01 Lowerl?) o 0 Formation part of -’ -| Seldovian/ Stage/ I.” Q) g / / Pre—Seldovian 5 8 .———? (= lower(?) Angoonian Stage Angoonian Stage 8 .87 Seldovian) g 0 Hemlock Conglomerate FIGURE 3.—Changes in usages of stages and ages in the Oligocene through Pliocene series of Alaska. claystone unit containing a few conglomeratic type section of the West Foreland, they are also at the sandstone and thin coal beds***” (Calderwood and Fackler, 1972, p. 741). Such lithology differs markedly from the overlying Kenai Group, which typically lacks tuffaceous material; indeed, we have observed only one bed of volcanic ash (primarily glass) in the Kenai; this ash bed occurs in the upper part of the Kenai Group south of Clam Gulch. Some coalbeds of the upper part of the Kenai Group also contain ash part- ings (Triplehorn and others, 1977). The West Foreland Formation, as noted by Calder— wood and Fackler (1972), is probably exposed at the surface along the west side of Cook Inlet. One of the most extensive surface exposures of this unit is south of Capps Glacier and includes rocks mapped as "lower Kenai” by Barnes (1966). These rocks are highly tuf- faceous and are angularly unconformable beneath the type section of the Seldovian Stage; elsewhere the West Foreland Formation has a consistent angularly unconformable relationship to overlying units (Cal- derwood and Fackler, 1972). Although these rocks at Capps Glacier are more conglomeratic than at the margin of the depositional basin and might be ex- pected to be conglomeratic in part. The age of the West Foreland Formation is not certainly known. If, however, the beds south of Capps Glacier are part of this unit, leaf samples from these beds indicate a latest Paleocene age for the West Foreland (Wolfe, unpub. data). This would indicate that an interval of at least 20 million years is represented by the uncon- formity between the West Foreland Formation and the Kenai Group, which is probably no older than early Oligocene. As here recognized, the Hemlock Conglomerate (Calderwood and Fackler, 1972) is the basal formation of the Kenai Group. Surface exposures of the Hemlock Conglomerate are not certainly known, although some of the nonvolcanic conglomerate mapped as "lower Kenai” by Barnes (1966) may represent this unit. Inasmuch as the Hemlock Conglomerate is not sep- arated from the overlying Tyonek Formation by an unconformity and is only about 200 to 250 m thick (Calderwood and Fackler, 1972), the Hemlock is prob- GEOLOGIC OCCURRENCE 5 ably not much older than the Tyonek Formation; the Hemlock Conglomerate is considered to be of early Oligocene age. Indeed, it is possible that the Hemlock is a discontinuous basal conglomerate of the Tyonek Formation and that some typical Tyonek beds may be isochronous with the Hemlock (for example along Harriet Creek). Calderwood and Fackler (1972) considered that they had only redefined Spurr’s (1900) “Tyonek beds.” Be- cause they designated the type section in a well, how- ever, it is clear that their Tyonek Formation is a new concept. Additionally, it was previously noted (Wolfe and others, 1966) that fossils from the outcrops of the "Tyonek beds” near Tyonek represent the Homerian Stage, the type section of which (Wolfe and others, 1966), as Calderwood and Fackler pointed out, is part of the next younger Beluga Formation. Calderwood and Fackler (1972) correlated the Kenai Group along the upper part of the Chuitna River with the type sec- tion of the Tyonek Formation; this correlation places the type section of the Seldovian Stage within the Tyonek Formation. The Tyonek Formation therefore includes rocks of early and middle Miocene age. That the Tyonek Formation also includes rocks of early and late Oligocene Age (Angoonian) is indicated by Cal- derwood and Fackler’s statement (1972, p. 745) that the Chuitna River section is incomplete and evidenced by basal coalbearing rocks of the Tyonek Formation exposed on Harriet Creek that are of pre-Seldovian age. Elsewhere in Alaska (Wahrhaftig and others, 1969), rocks correlated with the Kenai Group, consid- ered by Wolfe, Hopkins, and Leopold (1966) to be “lower(?) Seldovian,” have been excluded from the Seldovian Stage and are now considered to be of early and late Oligocene age. As well, the Tyonek Forma- tion presumably extends into the middle Miocene. This is indicated by the fact that the highest expo- sures of the Tyonek Formation along Chuitna River are of Homerian age, and no unconformity between the Seldovian and Homerian stages was noted in this section. Thus, the Tyonek Formation is here consid- ered to range in age from early Oligocene through middle Miocene. Considering that the Tyonek Forma- tion has such a great age range and considering the thickness of the unit (over 2,300 In), this unit may be capable of further subdivision. The beds at Seldovia Point are thus probably equivalent in age to the Tyonek Formation. The Beluga Formation (Calderwood and Fackler, 1972) is the next youngest unit of the Kenai Group. Calderwood and Fackler correlated the Kenai Group exposed near Homer, representing the Homerian Stage, with the Beluga Formation, and hence this part of the Beluga is of middle and late Miocene age. However, the lower part of the reference section of the Clamgulchian Stage along Kachemak Bay includes calcareous beds, and Calderwood and Fackler (p. 751) indicate that the highest occurrence of calcareous beds in the Kenai Group is in the upper half of the Beluga Formation. Thus, all the Beluga Formation is here considered to be of late middle and late Miocene age. We emphasize, however, that we are accepting the placement of the Miocene-Pliocene boundary gener- ally accepted by European geologists at about 5—6 million years. The youngest unit of the Kenai Group is the Ster- ling Formation (Calderwood and Fackler, 1972). The correlation of this unit with surface outcrops from Clam Gulch south beyond Ninilchik (type exposures of the Clamgulchian Stage) appears convincing (Calder- wood and Fackler, 1972), and thus the Sterling For- mation is considered to be of late Miocene and Pliocene age. The Seldovia Point flora was collected from beds of the Kenai Group exposed in a discontinuous series of outcrops in the sea cliffs from Barabara Point west and south to Coal Cove on Port Graham (fig. 4). These beds are typically weakly lithified, although the leaf impressions were obtained from limy, indurated lenses. These remnants of the Kenai Group rest un- B A Y K E M A Barabara C Point $ b Seldovia ”53 p . Point om" ‘ Q Nashkowhak >2. ‘22 . -‘ V 6 \ Point 0* Pogibsni 0 9357 . 0 Dangerous . Cape RussianO Point 10 15KILOMETERS l 152° FIGURE 4.—Map of Seldovia area. Outcrops of Kenai Group shown by stippling; numbers refer to US. Geological Survey paleobotan- ical localities. 6 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA conformably on altered Mesozoic rocks, which also form the headlands that have protected these rem- nants from total erosion. The outcrop of the Kenai Group at Coal Cove prob- ably yielded the collection of plants described by Heer (1869a), and attributed to a locality on English Bay. No Tertiary rocks are exposed on English Bay, and the Coal Cove outcrops were mined for coal for Rus- sian vessels. At the east end of this outcrop, the Kenai dips gently off the Mesozoic basement and contains coarse clasts probably derived from the subjacent Mesozoic rocks; that is, the Kenai rocks resemble a fossilized talus. Indeed, all outcrops of the Kenai Group from the Coal Cove to Barabara Point have taluslike appearances near the contacts with the Mesozoic rocks. In places, coalified logs or casts of logs are abundant in the Kenai. Where observable in fiords, the outcrops of the Kenai Group do not extend far inland but are apparently continuous along a nar- row belt that parallels the present coast (fig. 4). A reasonable interpretation of the lithology and pattern of outcrops of the Kenai Group in this area is that the Kenai here represents the remnants of an an- cient drainage system. This system drained from the southwest into the main part of the Kenai basin, as indicated by the greater thickness and areal extent of the Kenai Group at Seldovia Point (fig. 5) in compari- son to the outcrops near Point Pogibshi and on Coal Cove. Although most of the rocks represent fluviatile deposits, some of the sediments were deposited in slowly moving water; this is indicated not only by the presence of some coals but also by the abundance at locality 9858 of Potamogeton and N ymphar. The exact altitude at which the Seldovia Point beds accumulated is not known, but it was probably less than about 100 In. Although no marine beds are known in any part of the Kenai Group, the great thickness of this unit (over 8,000 m), the great areal extent of the basin (about 110 km wide and 330 km long), and the duration of apparently continuous dep- osition (about 25 my.) all indicate deposition near sea level for the main part of the basin. The fact that the Seldovia Point beds (particularly the plant- bearing beds) include fine-grained beds associated with coal also indicates that the drainage had a low gradient. We thus think that the Seldovia Point beds were not deposited at an altitude appreciably higher than the remainder of the Kenai Group. The nearest marine beds of middle Miocene age to the Seldovia Point localities are on the northeastern part of Kodiak Island, about 170 km to the south (fig. 1). The marine megafossils from the Kodiak beds indi— cate shallow water (W. O. Addicott, oral commun, Dec. 1973), and this indicates that during the middle Miocene the sea did not extend to the north much be- cévsaéé } 9858 METERS '_:'_____- 35 COVERED (thickness unknown) FEET 100 ooooco 15 5O FIGURE 5.—Section of Kenai Group exposed between Seldovia and Barabara Points. Number refers to US. Geological Survey paleobo- tanical locality. yond northeastern Kodiak Island. To the east of Sel- dovia, the nearest occurrence of middle Miocene marine beds is in the Yakataga District, about 500 km east and slightly north of Seldovia. Some clastic rocks of the Kenai Group indicate derivation from the area now occupied by the Chugach Mountains, but such rocks are younger than the Beluga Formation, which is probably of Homerian and early Clamgulch— ian age. There is thus no evidence that the western part of the Chugach Mountains were elevated during the middle Miocene. Most sediments of the Kenai basin deposited during the early and middle Miocene were apparently de— rived from the southern part of the Alaska Range (Calderwood and Fackler, 1972, p. 751, 754). Presum- ably that source area had considerable relief, and these mountains—about 150 km from Seldovia—were the mountains nearest to Seldovia. The central part of the Alaska Range to the north of the Kenai basin was AGE 7 apparently a low region during the early and middle Miocene, as attested to by the considerable thickness of coals in the Suntrana Formation and the extensive lacustrine deposits of the Sanctuary Formation (Wahrhaftig and others, 1969). AGE The Seldovia Point flora has had varied age assign- ments. Originally dated simply as Miocene by Heer (1869a), the flora from the Port Graham locality (Heer’s English Bay locality) was then—without any substantial factual data—assigned to the Eocene Epoch (Knowlton, 1894). The Eocene age was accepted without question by a number of paleobotanists (for example, Hollick, 1936; Chaney, 1936). Reanalysis of illustrations of the material from Port Graham led Wolfe (in MacNeil and others, 1961) to conclude that this flora was no older than late Oligocene; Mac- Ginitie (1962) concurred in this opinion and suggested that the flora might be as young as early Miocene. Basing their conclusions on new material from both Port Graham and Seldovia Point, Wolfe, Hopkins, and Leopold (1966) assigned the Seldovia Point flora (in- cluding the Port Graham locality) to the Seldovian Stage, which was thought to be of late Oligocene(?) and earlier Miocene age. Although an attempt was made to reassign this flora to the early Oligocene (Chaney, 1967), the factual basis for this reassign- ment proved illusory (Wolfe, 1969b). In the most re- cent summary of Alaskan Tertiary floras, the Seldovia Point assemblage was again assigned to the early Miocene (Wolfe, 1972), but it has also been suggested that the flora is of middle Miocene age (Tanai, 1973). The question of whether the flora is of early Seldovian (earliest Miocene) or late Seldovian (late early and early middle Miocene) age is particularly significant in constructing paleoclimatic models. The rocks containing the Seldovia Point assemblage were designated as a reference section for the Seldo- vian Stage (Wolfe and others, 1966). This designation was made primarily because the flora from this refer- ence section was then (and remains) considerably richer than the flora from the type section of the Sel- dovian Stage at Capps Glacier and along the Chuitna River. Considerable documentation for the early and middle Miocene age of the Seldovian Stage has been presented (Wolfe, 1969b). The occurrence of the Seldovia Point assemblage in an isolated outcrop of the Kenai Group requires that the placement of these rocks within subdivisions of the Seldovian Stage, however, be based solely on paleobotanical evidence. Only two informal sub- divisions—lower and upper—of the Seldovian Stage are recognized at Capps Glacier and along the Chuitna River; plant megafossils have been found primarily in the lower part of the section (Wolfe and others, 1966), but one small flora (loc. 9848 of Wolfe and others, 1966) is probably in the upper part of the Seldovian Stage, judging from Barnes’ (1966) geologic map. Several pollen assemblages, have, however, been studied from both the upper and lower parts of the type section of the Seldovian Stage (Wolfe and others, 1966). The upper Seldovian has been equated to the middle Miocene, the Homerian to the upper Miocene, and the Clamgulchian to the Pliocene (Wolfe, 1969b, 1972). In , terms of the now widely accepted planktonic foram- iniferal chronology, however, the upper Seldovian is of late early and early middle Miocene age and the Homerian is of late middle and early late Miocene age (Wolfe, 1980 ). The Clamgulchian has radiometric ages in its lower part that indicate a latest Miocene age (Triplehorn and others, 1977); the upper Clam- gulchian is assumed to be of Pliocene age. The rocks of the Nenana coalfield of the central Alaska Range (fig. 1) span the entire Seldovian Stage. The lowest megafossil and microfossil assemblages in this conformable sequence are pre-Seldovian, and the highest rocks are of Homerian and Clamgulchian age (Wahrhaftig and others, 1969). This sequence has also been extensively sampled for pollen. Palynologically, some differences are apparent between the pollen as- semblages of the lowest part of the Seldovian (the upper part of the Healy Creek Formation) and the remainder of the stage (Sanctuary Formation and the overlying Suntrana Formation). Upper Seldovian pollen assemblages from the Alaska Range appear to have a greater diversity of broad-leaved trees than do lower Seldovian as- semblages. Ulmus and Liquidambar occur more fre— quently in upper (table 1) than lower Seldovian as- semblages, and F agus and Tilia, which are present in TABpE l.—Average percentages of samples containing pollen of cer- tain broad-leaued genera in the Seldovian rocks of the Nenana coalfield, Alaska Range [Based on unpublished data supplied by E. B. Leopold] Upper part Sanctuary of and Healy Creek Suntrana Formation Formations (12 samples) (28 sam» ples) Fagus ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, O 29 Quercus ______________________________________ 25 29 Liquidambar ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 17 29 U lm us ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 33 89 Tilia ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, O 21 Carya ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 42 54 J uglans ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 8 18 Pterocarya ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 83 71 Ilex ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 58 61 8 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA about one-fourth the upper Seldovian samples, are ab- sent in lower Seldovian samples. The sample from Seldovia Point has Ulmus, Liquidambar, Tilia, and Fagus; the megafossil flora from Seldovia Point also contains representatives of all four genera. Of the four genera, only Ulmus is yet known from any lower Sel- dovian megafossil assemblage. These data indicate that the Seldovia Point flora is of late Seldovian (probably late early and early middle Miocene) age. Although the megafossil assemblages from the Sel- dovian rocks of the Nenana coalfield are admittedly small, these can also be interpreted to indicate that the Seldovia Point flora is of late Seldovian age. The flora of the upper part of the Healy Creek Formation (lower Seldovian) is known from moderate-size collec- tions that include: Metasequoia sp. Populus kenaiana Wolfe Populus aff. P. eotremuloides Knowlt. Salix sp. Carya sp. Pterocarya nigella (Heer) Wolfe Alnus cappsi (Holl.) Wolfe Betula aff. B. thor Knowlt. Quercus furuhjelmi Heer Ulmus sp. Cladrastis aff. C. lutea Michx. Acer chaneyi Knowlt. The flora of the overlying Sanctuary Formation was thought to be very small (Wahrhaftig and others, 1969), but this was due to considering locality 7476 to be in the Healy Creek Formation. Further discussion with Wahrhaftig and reanalysis of Prindle’s original field notes indicate that this locality is probably in the Sanctuary Formation. The flora from this locality in- cludes: Metasequoia sp. Pterocarya nigella (Heer) Wolfe Alnus healyensis Wolfe F agus antipofi Heer Quercus furuhjelmi Heer Cocculus auriculata (Heer) Wolfe To the above list can be added certain elements of the overlying Suntrana flora: Populus kenaiana Wolfe Cyclocarya ezoana (Tanai et Suz.) Wolfe et Tanai Alangium milii Wolfe et Tanai Ulmus sp. Probably significant is that the known Upper Healy Creek flora does not contain certain species that are present in both the Seldovia Point flora and in the flora of the Sanctuary and Suntrana Formations: Cy- clocarya ezoana, Fagus antipofi, Cocculus auriculata, and Alangium mikii. The differences between the microfossil assemblages of the upper and those of the lower part of the type section of the Seldovian Stage are not as apparent as in the Alaska Range section, primarily because fewer samples from the type section have been analyzed. In the three lowest samples (locs. D1946, D1953, D1952 of Wolfe and others, 1966), however, Tilia is absent, and only one sample contains Liquidambar (and the genus is so rare that it did not appear in the pollen counts). In contrast, in the four upper Seldovian pollen sam- ples (locs. D1720, D1718, D1719, D1949) one sample contained rare Tilia, and two samples contained sig- nificant amounts of Liquidambar pollen. The megafossil assemblages from the lower part of the type section of the Seldovian Stage are based on collections almost as extensive as those from Seldovia Point and were obtained from four horizons. The flora, however, is depauperate in comparison to that at Sel- dovia Point. Although some species are common to both floras, and in particular Alangium mikii also oc- curs at Capps Glacier, the Capps Glacier assemblage lacks the other three species considered to be sig- nificant in correlating the Seldovia Point with the Sanctuary-Suntrana flora. The small collection from the upper part of the Seldovian section along Beluga River (loc. 9848) contains only a few species, but it is perhaps significant that this flora has the only other known occurrence of Acer ezoanum in Alaska. Certainly further collecting in both the type section of the Seldovian Stage and in the Seldovian rocks of the Alaska Range is desirable, but the available data—from both megafossils and microfossils— indicate that the Seldovia Point flora is probably of late Seldovian age. Tentative correlations between the Cook Inlet region and Nenana coalfield are given in figure 6. The basis for the early and middle Miocene age of the Seldovian Stage has been discussed at some length previously (Wolfe, 1969b). The current sys- tematic treatment of the Seldovia Point flora, how- ever, allows a more definitive basis for correlating this flora with other plant assemblages at lower latitudes on either side of the Pacific Ocean. Most of the gym- nospermous species—at least those based on mega- scopic characters—have such long ranges during the Tertiary as to be of little value in biostratigraphy. It is only certain dicotyledonous species that are of most value in establishing correlations. Even some of the dicotyledonous species that occur outside of Alaska are of less value than others in bio- stratigraphy. Nymphar ebae, for example, is known both at Seldovia Point and in the early Miocene Aniai flora of Honshu (Huzioka, 1964), but because so little is known of the evolution of Nymphaeaceae during the Tertiary, the stratigraphic value of this species is FLORISTIC COMPOSITION 9 Series Cook Inlet Nonmarine Stage Nenana coalfield Plio- WW— I: , . W ene Sterling Formation Clamguichian W Nenana Gravel Grubstake Formation H . o omerlan Lignite Creek f, U Beluga Formation Formation u _ a. ,9 3 o 2 (5 Suntrana Formation M ,_ Upper m _ Sanctuary Formation E Seldowan _ 1 L Tyonek Lower Healy Creek Formation Formation m U Upper : 8 _ Angoonian ,E» 5 L Hemloc Lower Conglomerate FIGURE 6.—Suggested correlations of the Kenai Group and the coal-bearing group of the Nenana coalfield. Stage nomenclature follows Wolfe, Hopkins, and Leopold (1966) and Wolfe (1968, 1969b). uncertain. In contrast, the occurrence ofAcer ezoanum is much more significant in that this species is con- sidered to be a descendant of the Oligocene S. kushiroanum (Tanai, 1970, 1972). Similarly, the oc- currence in the Seldovia Point flora of species such as Platanus bendirei (see p. 29) is also of considerable significance. In table 2 are listed the Seldovia Point species that occur outside Alaska and the known ranges of these species. Data presented in table 2 indicate that the Seldovia Point flora is probably of late early or early middle Miocene age. This age is consistent with the occur- rence of some Seldovian species elsewhere in Alaska in beds independently dated from marine inverte- brates (Wolfe, 1969a). We emphasize that, as discussed in the section on vegetation, the Seldovia Point as- semblage represents a vegetational type cooler than that found in the late early to early middle Miocene of Japan and the conterminous United States. The oc- currence of some species both at Seldovia Point and farther to the south is analogous to the present dis- tribution of certain woody species that (1) occur from Japan to Alaska and at low altitudes to the conter— minous United States (for example 0plopanax hor— ridum (J.E. Sm.) Miq. and Myrica gale L.), (2) occur from Alaska to the conterminous United States at low altitudes (for example Malus fusca (Raf) Sarg. and Populus trichocarpa Torr. et Gray), and (3) occur from Alaska to Japan (for example, Rhododendron camtschaticum Pall. and Phyllodoce aleutica (Spreng.) Heller). We suggest that the geologic ranges of many dicotyledonous species during the Tertiary are sufficiently restricted to allow correlations to be made TABLE 2,—Known stratigraphic ranges of Seldovia Point di- cotyledonous species in Japan and conterminous United States [ ,,,,, Japan: —~ U.S.] Oligo— Miocene PlioA Species cene L M U cene Nymphar ebae ________________________________________ _ Cocculus auriculata _______________________________ “as: Liquidambar pachyphylla ,,,,,,,,,,,,,,,,,,,,,,,, Platanus bendirei __________________________________ Eucommia montana (cf) ___________ _ Ulmus knowltoni _________________________________________ Ulmus owyheensis _______________________________________ Ulmus speciosa ______________________ Zelkova browni ______________________ —— Zelkova ungeri __________________________________________________ - Alnus cappsi ______________________________________________ _ Alnus fairi _________________________________________________ _ Alnus healyensis ___________________________________ Betula sublutea (cf.) ,,,,,,,, Ostrya Oregoniana (cf.) _____ Fagus antipofi ___________________________________________ Carya bendirei ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Cyclocarya ezoana _,_________________.._,,,,__________,_ _____ _ Pterocarya nigella __________________________________ Populus kenaiana __________________________________ Tilia subnobilis __________________________________________ _. Cladrastis aniensis (cf.) ___________________________________ .. Pueraria miothunbergiana Hemitrapa borealis ______________________________________ _. Acer glabroides ______________________ Acer heterodentatum ,,,,,,,,,,,,,,,, Acer ezoanum ____________________________________________ _ Nyssa knowltoni (cf) ______________________________ Alangium mikii __________________________________________ _ Kalopanax n—suzuki _______________________________________________ _ Total ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 6 21 29 13 3 irrespective of the latitudes at which the species are found. FLORISTIC COMPOSITION In the following list, the classification of the di- cotyledons is that of Takhtajan (1969): Pterophyta Filicinae Filicidae Aspidiales Aspidiaceae Dryopteris sp. Onoclea sensibilis Linnaeus Coniferophyta Coniferae Coniferidae Coniferales Taxodiaceae Glyptostrobus europaeus (Brongniart) Heer Metasequoia cf. M. glyptostroboides Hu et Cheng Ginkgoidae Ginkgoales Ginkgoaceae Ginkgo biloba Linnaeus 10 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Magnoliophyta (Angiospermae) Magnoliatae (Dicotyledones) Magnoliidae Magnolianae Nymphaeales Nymphaeaceae Nymphar ebae (Huzioka) Ozaki Ranunculidae Ranunculanae Ranunculales Menispermaceae Cocculus auriculata (Heer) Wolfe Hamamelididae Hamamelidanae Cercidiphyllales Cercidiphyllaceae Cercidiphyllum alaskanum Wolfe et Tanai Hamamelidales Hamamelidaceae Liquidambar pachyphylla Knowlton Platanaceae Platanus bendirei (Lesquereux) Wolfe Eucommiales Eucommiaceae Eucommia cf. E. montana R. W. Brown Urticales Ulmaceae Celtis Sp. Ulmus knowltoni Tanai et Wolfe Ulmus owyheensis H. V. Smith Ulmus speciosa Newberry Ulmus sp. Zelkova browni Tanai et Wolfe Zelkova ungeri Kovats Fagales Fagaceae Fagus antipofi Heer Fagus aff. F. crenata Blume Quercus furuhjelmi Heer Betulales Betulaceae Alnus cappsi (Hollick) Wolfe Alnus fairi (Knowlton) Wolfe Alnus healyensis Wolfe Betula cf. B. sublutea Tanai et Suzuki Carpinus seldoviana Wolfe Corylus sp. Ostrya cf. 0. oregoniana Chaney Juglandales Juglandaceae Carya bendirei (Lesquereux) Chaney et Axelrod Cyclocarya ezoana (Tanai et Suzuki) Wolfe et Tanai Pterocarya nigella (Heer) Wolfe Dilleniidae Dillenianae Salicales Salicaceae Populus kenaiana Wolfe Populus Sp. Salix cappsensis Wolfe Salix hopkinsi Wolfe et Tanai Salix picroides (Heer) Wolfe Salix seldoviana Wolfe et Tanai Malvanae Malvales Tiliaceae Tilia subnobilis Huzioka Rosidae Rosanae Saxifragales Hydrangeaceae Hydrangea sp. Rosales Rosaceae Crataegus chamisonii (Heer) Wolfe et Tanai Prunus kenaica Wolfe et Tanai Prunus aff. P. padus Linnaeus Sorbaria hopkinsi (Wolfe) Wolfe et Tanai Fabales Leguminosae Cladrastis cf. C. aniensis Huzioka Pueraria miothunbergiana Hu et Chaney Myrtanae Myrtales Lythraceae Decodon alaskana Wolfe et Tanai Trapaceae Hemitrapa borealiis (Heer) Miki Rutanae Sapindales Aceraceae Acer ezoanum Oishi et Huzioka Acer glabroides R. W. Brown Acer grahamensis Knowlton et Cockerell Acer heterodentatum (Chaney) MacGinitie Aralianae Cornales Nyssaceae Nyssa cf. N. knowltoni Berry Alangiaceae Alangium mikii Wolfe et Tanai VEGETATION l 1 Araliaceae Kalopanax n-suzuki Wolfe et Tanai Celastranae Rhamnales Vitidaceae Vitis seldoviana Wolfe et Tanai Oleales Oleaceae Fraxinus kenaica Wolfe et Tanai Asteridae Lamianae Dipsacales Caprifoliaceae Lonicera sp. Liliatae (Monocotyledones) Alismidae Alismanae Alismatales Alismataceae Alisma seldoviana Tanai Najadales Potamogetonaceae Potamogeton alaskanus Wolfe et Tanai Incertae Sedis Monocotylophyllum alaskanum (Heer) Wolfe et Tanai Monocotylophyllum spp. Wolfe et The Seldovia Point flora is composed primarily of members of subclass Hamamelididae (23 species), and particularly the evolutionarily more advanced fam- ilies such as Ulmaceae and Betulaceae. Except for the specialized aquatic Nymphar, Magnoliidae are ab- sent. Also absent or poorly represented are orders con-_ sidered to be primitive in the Dilleniidae (for example, Theales and Dilleniales) and the Rosidae (Saxi- fragales). Within the orders of Dilleniidae and Rosidae, the Seldovia Point species typically belong to the more advanced families in the respective orders, for exam- ple Tiliaceae, Trapaceae, Aceraceae, Alangiaceae, Araliaceae. Evolutionarily, therefore, the Seldovia Point flora is highly advanced. A comparison with the Eocene Copper Basin flora of northern Nevada (Axelrod, 1966) is informative. Al- though the Copper Basin assemblage grew under more equable conditions than did the Seldovia Point assemblage (see section on “Paleoclimatology”), both assemblages represent cool temperate (microthermal) vegetation. In regard to the dicotyledonous flora at the specific level, the representation of most subclasses is distinctly different in the two assemblages: Subclass Copper Basin Seldovia Point (percent) (percent! Magnoliidae _____________________________ 4 2 Ranunculidae ___________________________ 1 1 2 Hamamelididae _________________________ 14 43 Dilleniidae _______________________________ 14 15 Rosidae _________________________________ 57 36 Asteridae _______________________________ 0 2 Despite having a number of families in common, the Copper Basin flora is less advanced than the Seldovia Point flora. One of the most notable differences is in the low diversity of Hamamelididae in the Copper Basin flora, a diversity that is just as low at the generic level as at the specific. Although generic di- versification in the Hamamelididae had been largely completed during the Eocene Epoch (Wolfe, 1973), it is apparent that (1) many of the genera that now include microthermal members had not yet invaded mi- crothermal climates in the Eocene and (2) specific di- versity within the genera that had entered mi- crothermal climates was low. It is thus evident that microthermal forests have undergone major changes in floristic composition. VEGETATION MEGAFOSSILS All the species in the Seldovia Point flora that are thought to represent trees, shrubs, or vines were probably deciduous. Of the vegetational types de- scribed by Wang (1961) for eastern Asia, only one type—the Mixed Northern Hardwood forest— combines the exclusively broad-leaved deciduous habit with a diversity similar to that of the Seldovia Point assemblage. From the standpoint of foliar physiognomy the Seldovia Point assemblage also compares well with the Mixed Northern Hardwood forest. Only 16 percent of the Seldovia Point species have entire-margined leaves, and in Mixed Northern Hardwood forest the percentage ranges from 9 to 24 (Wolfe, 1979a). Of the various species listed by Wang (1961) as occurring in this forest, almost 20 percent have palmately lobed leaves in comparison with 16 percent for the Seldovia Point assemblage. In floristic composition as well the Seldovia Point assemblage resembles Mixed Northern Hardwood forest, although there are some notable differences. Of the 18 genera listed by Wang (1961, p. 76) as compos- ing the tree stratum of the Mixed Northern Hardwood forest in the northeastern provinces of China, 13 are represented in the Seldovia Point flora. Other Sel- dovia Point tree genera (table 3; Cercidiphyllum, Pterocarya, Fagus) occur in the Mixed Northern Hardwood forest (Fagus zone of many Japanese 12 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA TABLE 3.—Assumed growth habits of Seldovia Point species Trees Cercidiphyllum alaskanum Liquidambar pachyphylla Platanus bendirei Eucommia montana Ulmus knowltoni Ulmus owyheensis Ulmus speciosa Zelkova browni Zelkova ungeri Carya bendirei Cyclocarya ezoana Pterocarya nigella Alnus fairi Alnus healyensis Betula cf. B. sublutea Carpinus seldoviana Ostrya cf. 0. oregoniana Fagus antipofi Fagus aff. F. crenata Quercus furuhjelmi Populus kenaiana Populus sp. Tilia subnobilis Prunus kenaica Cladrastis cf. aniensis Acer ezoanum Acer glabroides Acer grahamensis Acer heterodentatum Nyssa cf. N. knowltoni Kalopanax n-suzukii F raxinus kenaica Glyptostrobus europaeus Metasequoia cf. M. glyptostroboides Ginkgo bibloba Shrubs Celtis sp. Alnus cappsensis Corylus sp. Salix cappsensis Salix hopkinsi Salix picroides Salix seldoviana Hydrangea sp, Crataegus chamisonii Sorbaria hopkinsi Decodon alaskana Alangium mikii Lonicera sp. Vines Cocculus auriculata Pueraria miothunbergiana Vitis seldoviana Terrestrial herbs Dryopteris? sp. Onoclea sensibilis Monocotylophyllum spp. Aquatic herbs Alisma seldouiana Potamogeton alashana Nymphar ebae Hemitrapa borealis botanists) in Japan (Hara, 1959). Further, Wang (1961, p. 77) notes that the shrubs in the Mixed Northern Hardwood forest belong to genera such as Corylus, Crataegus, Sorbaria, and Lonicera, and vines (including Vitis) are present. If only floristic associations were relied upon to de- termine vegetational (and hence climatic) type, the Seldovia Point assemblage would be considered as most probably representing Mixed Mesophytic forest, a conclusion arrived at previously (Wolfe, 1966; Wolfe and Leopold, 1967). The majority of the most closely related extant species are found in this vegetational type (table 4), and several Seldovia Point genera occur only in Mixed Mesophytic forest or in broad-leaved evergreen forests in eastern Asia: Ginkgo, Meta— sequoia, Glyptostrobus, Cocculus, Liquidambar, Carya, Cyclocarya, Cladrastis, and Nyssa. In contrast, of all the Seldovia Point genera, only Sorbaria is pres- ently restricted to cool temperate forests such as the Mixed Northern Hardwood. The physiognomic data, however, clearly indicate that the Seldovia Point as- semblage represents Mixed Northern Hardwood forest. The lack of a closer floristic resemblance be- tween the Seldovia Point assemblage and the extant TABLE 4.—Distribution of most closely related extant species in vegetational types in eastern Asia [Occurrence enclosed in parentheses indicate that the extant Asian species may only be distantly related to Seldovia Point species] Broad- Mixed Broad- Mixed leaved Meso- leaved Northern Ever- phytic Deciduous Hardwood green Ginkgo biloba ,,,,,,,,,,,,,,,,,,,,,,,,,,,, X Metasequoia glyptostroboides _ X? Glyptostrobus pensilis ,,,,,,, A X Coeculus trilobus ,,,,,,,,,,, _ X X Cercidiphyllum japontcam X X X X Ltquidambar formosana _ X Ulmusspp ,,,,,,,,,,,, __(X) (X) (X) (X) Zelkoua serrata _, ___ X X Carya tonkinensts ,1 , X Cyclocurya paliurus ___, _e, X X Pterocarya rhoifolia __,, _____ X X X Alnus hirsuta ,,,,,,,,,,,,,,,,,,,,,,,, X Carpinus cordata ______ , X X X X Corylus spp __ __ (X) (X) (X) (X) Betulaspp_, ”(X) (X) (X) (X) Ostrya spp,,,_ __(X) (X) (X) (X) Fagus crenata X X X Popalus spp __ ______ (X) (X) X Salixsp _______ (X) (X) (X) Tilia nogtlis __v Hydrangea spp A ,,(X) (X) (X) (X) Crataegus spp ,,,,,,,,,,, _ (X) (X) (X) Prunus uaniott ‘_ X Prunus padus ,,,,, X Sorbaria Iindleyana ,,,,,, X Cladrastis wilsoni/platycarp X Paeraria thunbergiana ______ X X X Acer henryii _________________________ >< Acer miyabei _, ,,,,,,,,,,,,,,,,, >< Nyssa spp ,,,,,,,,,,,,,,,, (><) Alangium chtnenszs __ ,,,,,,,,,,,,,,,, X X X Kalopanax pictus ,, X X X X Vitis Spp __________ (X) (X) (X) Fraxlnus hopeiensis X X Lon'wera spp ,,,,,, (X) (X) (X) Total ,,,,,,,,,,,,,,,,,,,,,,,,,,, 13 (10) 13(11) 8 (10) 12 (9) Mixed Northern Hardwood forest of eastern Asia can be explained in terms of the historical development of this forest and the related Mixed Mesophytic forest. As well, the assumptions commonly made concerning present distribution of taxa relative to climate (and hence vegetational type) may not be valid. The inclusion in the Seldovia Point flora of Ginkgo, Metasequoia, Glyptostrobus, Cocculus, Liquidambar, Platanus, Carya, Cyclocarya, Cladrastis, Nyssa, and Alangium indicates a deceptively warm climate if the present distributions of these genera are considered. The resistance to freezing of extant species of many of these genera has, however, been analyzed (Sakai, 1971, 1972; Sakai and Weiser, 1973). Following are listed the results of these investigations in regard to some of the Seldovia Point genera (the temperatures are the highest of the freezing resistances of bud, leaf, or twig): Ginkgo biloba ___________________________ —30°C Glyptostrobus pensilis __________________ ~18° Metasequoia glyptostroboides ____________ —30° Platanus occidentalis ____________________ —20° Liquidambar styraciflua ________________ —25° Liquidambar formosana ,,,,,,,,,,,,,,,, —17° Pterocarya rhoifolia ____________________ ~30° Nyssa sylvatica ,,,,,,,,,,,,,,,,,,,,,,,, -30° Sakai’s data also illustrate the wide variation of freezing resistance from one species to another con- VEGETATION 13 generic species. Again the highest of the three tem- peratures are selected: Acer macrophyllum ____________________ _ —20°C A. mono ______________________________ -25° A. rubrum ____________________________ -30° A. saccharum __________________________ —40° ' Quercus garryana ______________________ — 15° Q. lyrata ______________________________ —20° Q. mongolica __________________________ —30° Q. macrocarpa ________________________ —40° Even within the same species, different geographic races may exhibit considerably different tolerances to freezing (Sakai and Weiser, 1973). We emphasize that the present geographic area occupied by a species may have little or no bearing on the paleoecologic sig- nificance of that species, its ancestors, or other extinct congeneric lineages. Wang (1961, p. 239—246) has noted that today the Mixed Northern Hardwood forest of eastern Asia, al- though containing many genera in common with the Mixed Mesophytic forest, has few species in common with that forest. Despite this specific differentiation, Wang hypothesized that most species now in Mixed Northern Hardwood forest were derived from Mixed Mesophytic lineages during the Tertiary and that, prior to glaciation, Mixed Northern Hardwood forest had more genera and species than now. That the Mixed Northern Hardwood forest was con- siderably richer in the past is fully attested to by the Seldovia Point flora, as well as by assemblages repre- senting the same vegetational type in eastern Asia. Numerous genera are present in these assemblages that no longer participate in Mixed Northern Hardwood forest. This is valid in regard to the east Asian Miocene Mixed Northern Hardwood forest (for example, Alangium, Cyclocarya, Liquidambar), which is the lineal ancestor of the present Mixed Northern Hardwood forest. Wang’s (1961) hypothesis concerning the origin of Mixed Northern Harwood lineages is, however, valid only in regard to the lineages of the West American element (see p. 17) in the Seldovia Point flora— lineages that typically did not become part of the Mixed Northern Hardwood forest in eastern Asia. In the Pacific Northwest, several early and middle Miocene assemblages represent Mixed Mesophytic forest (for example, Latah and equivalents in Washington and adjacent parts of British Columbia and Idaho, Collawash in Oregon), and these as- semblages have several species in common with the Seldovia Point assemblage (table 5). In eastern Asia, however, Mixed Mesophytic forest is probably of a more recent origin than Mixed North- ern Hardwood forest. The early Miocene Aniai-type TABLE 5.—Seldouian dicotyledonous species also occurring in Mixed Mesophytic forest in the early and middle Miocene of the Pacific Northwest Seldovia Point Cocculus auriculata Liquidambar achyphylla Platanus bentllrei Ulmus knowltoni Ulmus owyheensis Ulmus speciosa Zelkova browni Alnus fairi Alnus healyensis Ostrya oregoniana Carya bendirei Pterocarya nigella Populus kenaiana Acer glabroides Acer macrophyllum type Acer heterodentaturn Nyssa knowltoni Other Seldm'ian localities Acer aff. A. pennsylvanicum Acer aff. A. saccharinum ' floras (Tanai, 1961) all represent broad-leaved decidu- ous forest without broad—leaved evergreens; that is, this type of forest is Mixed Northern Hardwood. This is true of assemblages from Kyushu and western Hon- shu, although admittedly these assemblages are small and poorly known. As discussed in the section on paleoclimatology, the vegetational zonation during the early and middle Miocene excluded Mixed Mesophytic forest, but Mixed Northern Hardwood forest occupied a broad area north of latitude 44° N. The first evidence in eastern Asia of Mixed Meso- phytic forest is in the late Miocene. The Mitoku flora from western Honshu (Tanai and Onoe, 1961) is dominantly broad-leaved deciduous but also contains some notophyllous broad-leaved evergreens; this as- semblage thus probably represents Mixed Mesophytic forest. As noted by Tanai and Once (1961, p. 15), some of the Mitoku species are also found in the Aniai-type assemblages, which would indicate the reverse of what Wang (1961) suggested, that is, that some Mixed Mesophytic lineages were derived from Mixed North- ern Hardwood lineages. Some of the Mitoku species also occur in Japanese middle Miocene assemblages that we interpret as rep- resenting Wang’s (1961) Deciduous Broad-leaved forest. Such a pattern of derivation of some Mixed Mesophytic lineages is to be expected as the climate in eastern Asia changed from one favorable to the de- velopment of this forest to one favorable to the de- velopment of Mixed Mesophytic forest (see p. 19). The third major source for Mixed Mesophytic lineages has been from Wang’s Sclerophyllous Broad-leaved Ever- green forest, and these lineages include both broad- leaved evergreen and deciduous plants (as well as conifers such as Cunninghamia). Indeed, today the Mixed Mesophytic and Sclerophyllous Broad—leaved 14 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Evergreen forests of China share many species. Assuming the validity of our paleoclimatological suggestions (p. 19), most species in the Mixed North- ern Hardwood forest of eastern Asia were derived primarily from lineages of Deciduous Broad-leaved forest, although the ultimate origin of the lineages must be in broad—leaved evergreen vegetation; that is, in an area such as Japan, the probable sequence dur- ing the Oligocene climatic deterioration would have been from broad-leaved evergreen forest into Wang’s (1961) lower oak forest, then into Deciduous Broad- leaved forest, and finally into Mixed Northern Hardwood forest. At least part of such a sequence has been demonstrated in the Oligocene of Hokkaido (Tanai, 1970). Lineages that have followed such a pat- tern are exemplified by Acer kushiroanum-A. ezo- anum-A.- miyabei (Tanai, 1972). This pattern is also indicated by the large number of species common to the Yoshioka flora (Decidous Broad-leaved forest) and the isochronous Mixed Northern Hardwood as- semblages such as the Abura (Tanai and Suzuki, 1963) and Upper Dui (Fotianova, 1967). POLLEN Only three samples from the Seldovia Point localities have been analyzed for pollen. The samples from localities 9856 and 9858 are poor, and only 67 and 100 grains, respectively, were counted in these two samples. Locality 9857, however, produced an abundant and well-preserved pollen assemblage, and the percentages (table 6) are based on 300 grains. The pollen assemblage from locality 9858 at Sel- dovia Point is dominated by broad—leaved plants. It is unknown whether the pollen of Alnus came from trees or shrubs or both, but the probable broad-leaved tree pollen (Juglandaceae, Betulaceae other than Alnus, Fagaceae, Liquidambar) in sample 9858 represents 20 percent of the total in contrast to only 6 percent pollen of Pinaceae. The samples from 9856 and 9857, however, have a very small broad-leaved element. Members of Pinaceae account for over half the pollen in both sam- ples. The abundance of Picea and Tsuga is particu- larly significant and gives strong evidence that the forest in this area was dominantly coniferous. Assum— ing that the assemblages from the three localities are approximately isochronous, the data indicate that the area around Seldovia was forested primarily by broad-leaved trees but that in the area of Port Graham the forest was primarily needle leaved, with broad—leaved vegetation confined only to the small valleys. This, in turn, indicates that in the more equable coastal area of southern Alaska, the vegeta— TABLE 6.—Percentages of pollen types in samples from the Seldovia Point beds [x, present but not included in counts] Locality Pollen type 9858 9857 9856 Aff. Cedrus ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, , x H Picea ________________ __ ?l 34 33 Pinus ________________ H 4 1 3 Pseudotsuga/Larix _. W 1 4 T suga ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1 16 22 Taxodiaceae/Cupressaceae ________________ 1 8 1 Salix ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, - x 4 Carya ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, x 1 1 J uglans ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, _ X c- Pterocarya/Cyclocarya ,,,,,,,,,,,,,,,,,,,,,, X 1 6 Alnus ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 45 30 6 Betula ___________________________________________ _ 1 __ Ostrya/Carpinus ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2 3 A- Fagus ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, X 2 ,_ Ulmus/Zelkova ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 4 1 3 Liquidambar ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14 _- 1 Ilex ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1 __ 3 Tilia ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,_ X X Ericales ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, , X A Lonicera ________________________________________ _ __ 1 Indet. dicotyledons ______ _ 12 1 9 Typha ,,,,,,,,,,,,,,,,,,,,,,,,, >< ,_ Indet. monocotyledons 15 _, -_ Osmunda ,,,,,,,,,,,,,,,, X x __ Polypodiaceae _________________________________ _ x X tion was probably dominantly coniferous. The lack of Pinaceae in our megafossil collections is apparently somewhat contradictory. The largest col- lections, however, were made at locality 9858, and the pollen data indicate that Pinaceae were far distant from this locality. In some instances, however, we think that megafossil assemblages can yield a highly distorted picture of the actual vegetation. One exam- ple is the assemblages from the Homerian (late Miocene) part of the Kenai Group. Large collections made in 1962 from the Homerian contained no megafossils of Pinaceae (Wolfe and others, 1966), but the pollen assemblages are dominated by Pinaceae (Wolfe, 1969b) and were interpreted as indicating the presence of a coniferous forest throughout the Cook Inlet area during the late Miocene (Wolfe and Leopold, 1967). Two new localities, first collected in 1967, did produce a diverse and abundant pinaceous flora, thus substantiating the earlier interpretation. A second example is the late Miocene Hidden Lake as— semblage from Oregon (Wolfe, 1969b). Although pol- len of Picea accounts for almost half the pollen, megafossils of Picea represent less than one percent of over 2,000 specimens counted; the association of some 18 species of conifers, however, leaves no reasonable doubt that the vegetation was dominantly coniferous despite the low representation of conifers in the megafossil count. We conclude, therefore, that the pol- len data indicate the dominance of conifers in the Port Graham area during the early and middle Miocene. VEGETATION DISTRIBUTION As discussed previously, the coastal area of south- ern Alaska was probably occupied by coniferous forest. The early and middle Miocene megafossil as- semblages of that area are unknown, so a comparison with the Seldovia Point flora is impossible. In the Wrangell Mountains (fig. 7), however, the late Seldo- vian assemblage represents coniferous forest, attested to by both the dominance of Pinaceae in the pollen assemblage and the diversity of this family in the megafossil assemblage (Wolfe, 1972). The broad- leaved adjuncts to this coniferous forest included Populus, Salix, Pterocarya, Alnus, Betula, Fagus, Ul- mus, Acer (both macrophyllum and saccharinum types), and Lonicera. Presumably the composition of the coastal coniferous forest was similar. A small assemblage at the northern margin of the Kenai basin was collected from beds of the Kenai Group. Because these thin beds on Cache Creek in- clude both Seldovian as well as Homerian floras (Wolfe and others, 1966), the Seldovian beds there are most probably of late Seldovian age. The Cache creek assemblage includes: Metasequoia cf. M. glyptostroboides Cocculus auriculata Cercidiphyllum alaskanum Fagus antipofi P) Nuwok ‘ Northern Coniferous forest \ ‘\ OKougarok \‘x/7 \ ’——_— fl 3 \ fl’ cum“ I — — I ’— ~_—” 0 Sanctuary/ Suntrana Cache Creek Beluga Rivg’ro / 535N149 _ _ — — TuV'NVD I r.— l ’ o ‘. Wran all I 9 .r' / Mixed Northern # f ’ A Hardwood forest (I) ' ,:A‘\~. {I \ Seldovia Point ”4 Coastal V ‘ I Coniferous forest CZ ’, PA CIFIC OCEAN ’ O 100 200 300 MILES ' o " F—H—I—dfiJ ngalslan‘ O 100 200 300 400 KILOMETERS BERING 5/ 8 fl 6,, p ll A m {a} FIGURE 7.—Suggested distribution of vegetational types in Alaska during the late early and early middle Miocene. Approximate ex— tent of land shown by heavy solid line. 15 Quercus furuhjelmi Alnus cappsi Populus kenaiana Salix spp. Acer aff. A. rubrum This assemblage is consistent with the occurrence of Mixed Northern Hardwood forest both to the south (Seldovia Point) and north (Sanctuary and Suntrana) of Cache Creek during the late Seldovian. The Mixed Northern Hardwood forest extended north at least to the central Alaska Range. In the Sanctuary and Suntrana Formations, the following have been found: Metasequoia sp. Cocculus auriculata Ulmus sp. Alnus sp. Fagus antipofi Quercus furhjelmi Carya bendirei Cyclocarya ezoana Pterocarya nigella Populus kenaiana Populus spp. Salix spp. Alangium mikii Additional broad-leaved genera from E. B. Leopold’s (1969, unpub. data) pollen work include Liquidambar, Platanus, Juglans, Eucommia?, Betula, Corylus, Ostrya/Carpinus, Ericales, Malvaceae, Tilia, Rosaceae, Acer, Ilex, Eleagnus, Nyssa, Compositae, and Caprifoliaceae (Lonicera type). The Sanctuary- Suntrana assemblage is similar to the Seldovia Point assemblage from the standpoint of both megafossils and microfossils. We emphasize, however, that warmer elements are fewer in number than in the Seldovia Point assemblage, and in all probability the Sanctuary-Suntrana climate had a lower mean an— nual temperature and a higher mean annual range of temperature. The northern limit of Mixed Northern Hardwood forest in Alaska during the late Seldovian is not known with certainty. A few of the Sanctuary- Suntrana pollen samples are dominated by Picea, thus indicating that the coniferous forest was probably not far to the north. This would place the boundary be- tween the two vegetational types at about lat 64° N. This placement is consistent with the pollen as- semblage from the Noxapaga Formation of Sainsbury (1974) on Seward Peninsula (lat 65° N). The two sam- ples examined are dominated by Pinaceae (Picea, Pinus, Tsuga, Abies, and Larix/Pseudotsuga, in order of decreasing abundance). Except for Betulaceae, none of the broad-leaved genera exceeds one percent; this l6 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA element is, however, moderately diverse and includes F agus, Quercus, Carya, Pterocarya/Cyclocarya, Ulmus, Populus, Salix, and Symphoricarpos. Farther north, the Nuwok pollen assemblage of middle Miocene age (lat 70° N) is almost totally coniferous but has minor amounts of Pterocarya/Cyclocarya and Ulmus. The coastal coniferous forest during the early Miocene was isolated from other coniferous forest. To the southeast, the coniferous forest theoretically gave way to Mixed Northern Hardwood or Mixed Mesophytic forest. To the southwest, coniferous forest was clearly bounded by Mixed Northern Hardwood forest, which has been recorded from Kamchatka (Chelebaeva, 1968). The northern area of coniferous forest probably had a great longitudinal extent. Neogene pollen assemblages from northeastern Siberia (Baranova and others, (1968) are dominated by Pinaceae; it should be noted, however, that all these assemblages have not been independently dated, and their exact placements within the Neogene se- quence are not certainly known. COMMUNITIES Counts of the leaf impressions in terms of abun- dance of individual species were not made; such counts have not yet been proved reliable in indicating . the actual abundance of plants in the original vegeta- tion. The most abundant dicotyledonous tree species in our collections from the Seldovia Point locality are: Fagus antipofi Acer ezoanum Zelkova spp. Alnus spp. Salix spp. Platanus bendirei Quercus furuhjelmi Carpinus seldoviana The above species may well represent the dominant forest species in the vicinity of Seldovia during the early and middle Miocene. We thus envisage the main forest community to have been an association of Fagus- Acer-Zelkova—Quercus-Carpinus-Ulmus. Near Port Graham, the forest association was somewhat differ— ent; there, Fagus and Ulmus are the most common megafossils, Carpinus is absent, and apparently Acer ezoanum was replaced by A. grahamensis. Some of the Seldovia Point species can very clearly be relegated to a streamside element. This assignment is supported not only by the habitats of extant rela- tives but also—and perhaps most significantly—by the abundance of leaves of these species in association on the same slabs. Such species include Salix hop— kinsi, S. cappsensis, S. picroides, S. seldoviana, Platanus bendirei, Decodon alaskana, and Alnus cappsi. The Seldovia Point flora has a strong aquatic ele— ment at locality 9858. Leaves of the extinct Nymphar are particularly common, as are seeds and, to a lesser degree, leaves of Potamogeton. Nuphar (a genus re- lated to Nymphar) and Potamogeton today typically inhabit quiet water, and Nuphar typically lives in lakes. FLORISTICS Traditionally the species composing a fossil flora have been placed into elements, each of which either represents the geographic region where the most closely related extant species are found (for example, East Asian element, East American element) or rep- resents the region where the lineage to which the species belongs putatively originated (for example, Arcto-Tertiary element, Madro-Tertiary element). Both of these approaches to floristic analysis have some validity, despite the fact that particular concepts such as that of the Arcto-Tertiary element have prob- ably been invalidly applied (Wolfe, 1969b, 1972; Tanai, 1971). The areas of origin of the floristic ele— ment in the Seldovia Point flora are particularly sig- nificant to concepts of floristic history because the flora from the Port Graham locality has been one of the fundamental bases for the concept of an Arcto— Tertiary Geoflora, which, in turn, has served as the “type” geoflora for the geofloral concept. We emphasize that the assignment to elements such as East Asian or West American by Chaney (for example, 1959) and his followers was done primarily for paleoclimatic purposes. That is, in west American Tertiary floras, a dominant East American-East Asian element indicated abundant summer precipitation, whereas a dominant West American element indi- cated little summer precipitation. This usage of "ele- ment” has little floristic value and should be aban- doned. To place species such as Liquidambar pachyphylla in an “East American” element is, in View of the his- tory of this lineage, unwarranted. There is no direct relationship between L. pachyphylla and the extant east American L. styraciflua, although the two species may belong to lineages that were derived from a common stock in the Paleogene. L. pachyphylla is a distinctive member of a middle latitude, West Ameri- can element. Similarly, to the same element belongs the type of Cyclocarya found in the Tertiary of the Pacific Northwest, a type that is only distantly related to the extant Asian C. paliurus. Despite the fact that the lineages to which L. pachyphylla and the west American Cyclocarya belong are now extinct, these lineages have the same floristic significance as the Platanus bendirei lineage, which has survived in FLORISTICS l 7 western North America as P. racemosa. Indeed, as pointed out previously (Wolfe, 1969b), several “Madro-Tertiary” lineages are in fact members of this same element. Prior to the Oligocene deterioration of climate (Wolfe and Hopkins, 1967; Wolfe, 1971, 1978), the climates of the Paleogene were characterized by high equability (that is, a low mean annual range of tem- perature). Just as temperate broad-leaved deciduous forests are today absent in the highly equable South- ern Hemisphere temperate regions, it is highly proba- ble that temperate broad-leaved deciduous forests were absent in the Northern Hemisphere during the Eocene and the Oligocene prior to the deterioration (Wolfe, 1978). The Oligocene deterioration was thus characterized not only by a dramatic decline in mean annual temperature but also by a major increase in mean annual range of temperature (Wolfe, 1971). Broad-leaved deciduous forests appeared in a geologi- cally short period of time throughout middle and high latitudes of the Northern Hemisphere. The lineages that composed these forests were derived from two major sources (Wolfe, 1972): (1) lineages that were pres— ent in broad-leaved evergreen forest prior to the deterioration and that were preadapted (or had the genetic capability to adapt rapidly) to climates characterizing broad-leaved deciduous forest and (2) lineages that were present in temperate coniferous forests and that moved downslope during the Oligocene deterioration. During the later Oligocene and Miocene some lineages from broad-leaved ever- green forest also adapted gradually and moved into the broad-leaved deciduous forests (Wolfe, 1972). Terms such as East Asian Element can thus be de- fined relative to the geographic region in which it is thought a given lineage entered broad—leaved decidu- ous forest for the first time. Species such as Liquid- ambar pachyphylla and Carya bendirei, although be- longing to genera that are no longer native to western North America, are consequently considered to belong to the West American Element, because the lineages to which these species belong were present in western North America at middle latitudes prior to the Oligocene deterioration. The significance of the concept of this west Ameri- can, mid-latitude element is considerable to paleo- ecological reconstructions. Just as the tolerances of Carya in eastern Asia are, at least in part, different from the tolerances of Carya in eastern North Amer- ica, so it can be expected that the tolerances of the now extinct west American Carya were also different. This, we think, is at least partly the explanation for the presence of Liquidambar in the Seldovia Point as- semblage; it is also notable that Liquidambar was a conspicuous member of fiuviatile vegetation in the late Miocene upland coniferous forest in the Pacific Northwest, but today none of the surviving members of the genus are associated with Temperate Conifer- ous forest. The Seldovia Point flora has three known floristic elements: East Asian, West American, and Beringian. The Beringian element is composed of those lineages that are thought to have entered into the temperate forests in Alaska and adjacent high-latitude regions. The basis for the assignment to the various floristic elements (table 7) is given in the discussions of the systematic treatments of the various species. Assignment to the various floristic elements is well documented in instances such as Platanus bendirei and less well documented in other instances. It is as- sumed that if a particular lineage appears in a given area immediately following the Oligocene deteriora- tion, that lineage is assigned to that area’s element. TABLE 7.—Analysis ofthe Seldovia Point assemblage in terms of floristic elements Species East Asian West American Beringian Unknown Uryopteris? sp ,,,,,,,,,,,,,,,,,,,,,,, Onaclea sensibilis ________ Glyptostrobus europaeus __ Metasequoia cf. M. _______ glyptoslroboides ________ Ginkgo biloba ,,,,,,,,,,,, Nymphar ebeae __________ Cocculus auriculata ______ Cercidiphyllum alaskanum Liquidambar pachyphylla _ Platanus bendirei ________ Eucummia cf. E. montana Celtzs s ,,,,,,,,,,,,,,,,, Ulmus Ulmus awyheensis ,,,,,,,, Ulmus speciosa __________ A Zellwva browm _ Zelkova ungerz H Fagus antipofi ,,,,, Fagus aff. F. L'renata X X X X XX Quercus furuhjelmi __ Alnus cappsz ____________ Alnus fair: H_ _______ Alnus healyensis ,,,,,,,,, Belula cf. B. sublulea _____ Carpmus seldoviana H Corylus s ,,,,,,,,,,,,, Ostrya cf. 0. oregmiiana Carya bendiret ,,,,,,,,, Cyclocarya ezoana HH Pterocarya mgella ,,,,,,,, Populus kenaiunu HH Populus sp __________ Sulzx Cuppsen ' Salix hop/ems! Sci/ix plt'roidt’s H Salix seldouuaa , Tilia subnobllzs H Hydrangea sp H, Cralaegus chamzsunu H Prunus kenulca ,,,,,,,, Prunus Sp ,,,,,,, Sorbaria hopkmsz ,,,,,, Cladruslzs of C. (miensis Puerarm mmthunbergranu Decodon alaskana _.__ Hemitrapa borealis H Acer emanum __ Acer grahamensis ________ Aeer hetemdenlatum ,,,,, Nyssa cf. N, knuzvltom , Alangmm mzku ___________ Kalopanax n-suzukiz , Vitis seldouiana H Fraxinus kenaica Lomcem Sp Potamngeton alaskana H Monocotylophyllum alaskanum ,,,,,,,, Monocotylophyllum tenuislriatus ,,,,,, IX: X? X XXXX XXXX XXXXX Total ,,,,,,,,,,,,,,,,,,,,,,,,, 14 16 12 16 18 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA For example, Metasequoia is not known in the Alas- kan Eocene, but the early Angoonian assemblages immediately following the deterioration contain abundant Metasequoia, which therefore is assigned to the Beringian element; this genus could equally well be assigned to the other two elements, but there is no need to invoke immigration from another region. The West American element has suffered far more extinction than the remaining two elements. Only three West American lineages in the Seldovia Point flora still survive: Platanus bendirei (P. racemosa), Acer heterodentatum (A. negundo), and A. grahamen- sis (A. macrophyllum). Of the East Asian element, only Cercidiphyllum alaskanum and Decodon alas— kana have definitely become extinct. Of the Beringian element, possibly many lineages yet survive, particu- larly in Alnus and Salix. Today, many boreal species extend southward, par— ticularly in North America, along mountain chains. Similarly, during the late Miocene many species are known from lowland Alaska to the uplands of the Pacific Northwest to the south (Wolfe, 1969b). None of these species are, however, members of the East Asian element as defined in this report; although not yet known in Alaska, Acer scottiae must have had such a distribution and would clearly have been East Asian. Such data emphasize the difficulty of floristic inter— change between midlatitude forests on either side of the Pacific during the Neogene, at least in regard to woody plants. The few West American lineages that probably migrated into eastern Asia during the Miocene are: Pterocarya rhoifolia type—Earliest records of this type are in the middle and late Oligocene of Alaska (Tsadaka Formation). This type appears in the early Mioceneof Japan and Oregon and persisted in the Pacific Northwest through at least the late Miocene. The type of foliage with which the seeds are most fre- quently associated is that assigned to P. nigella, which is thought to be descended from the west Amer- ican P. pugetensis. Acer negundo type—This type extends in North America back to at least the early Oligocene (Mac- Ginitie, 1953) and occurs in many younger as- semblages. The first record in Alaska is in the Sel- dovia Point flora, but the occurrence of this group in Japan in the early to middle Miocene (Tanai, 1961) indicates that the lineage probably migrated through Alaska no later than the early Miocene. The lineage became extinct in Japan but probably survived on the Asian mainland as A. henryi Pax. Cocculus auriculata.—This extinct lineage is thought to be descended from an undescribed species in the Puget Group and is hence West American. The lineage has a Miocene distribution similar to that of A. negundo type but became extinct in North America by the late Miocene. The only East Asian species that probably migrated into middle latitudes of western North America dur- ing the Neogene are: Acer mono type (A. scottiae MacG.).—This type has not yet been found in the Alaskan Tertiary sequence, but the common occurrence of this type in the middle and late Miocene assemblages from the Pacific Northwest indicates that the lineage probably passed through Alaska during the Seldovian. Acer miyabei type—This type has not been previ- ously recorded from the conterminous United States, but seeds from Skull Springs, Oreg, (middle Miocene) and south-central Idaho (middle or late Miocene) probably represent Acer ezoanum. This lineage has a long history in eastern Asia (Tanai, 1972). Excluded from this listing is Acer circinnatum, a species closely allied to A. japonicum, which has an Asian record extending back at least into the early Miocene (Tanai, 1972). No fossil record of this type is known in North America, which is curious in view of the current abundance and widespread occurrence of A. circinnatum in the forests of the Pacific Northwest. We suggest that this is a rare example of long- distance dispersal from Japan to the Pacific North- west during the Pliocene or Quarternary. Neither the West American nor the East Asian element apparently penetrated significantly south- ward in Asia or North America, respectively. Few species are found in the Neogene of both Japan and the Pacific Northwest. We suggest that the northern populations of these two elements were unable to compete successfully with endemic, more southerly populations; that is, while it was apparently easy for many species to spread northward, producing popula- tions better adapted to the more rigorous conditions at higher latitudes, the reverse process was not easy. Possibly these northern populations were genetically less plastic than the southern populations of the same species. Another explanation is the possibility that the midlatitudes of western North America, although clearly having more summer precipitation in the Neogene than now, had an insufficient amount for most East Asian species; the lack of penetration of most West American species into Asia, however, would remain unexplained. We think that the avail- able data support van Steenis’ (1962) suggestion that it is improbable that many species could adapt first to rigorous conditions and then readapt to conditions similar to those of the early member populations of the species. Van Steenis (1962) was particularly referring to the problem of day length (particularly the lack of winter light) relative to floristic interchange over high- PALEOCLIMATOLOGY 1 9 latitude land bridges such as Beringia. We are, how- ever, discussing deciduous species, which are leafless during winter, and thus the relative darkness of the winter is irrelevant. Temperature is not likely to be significant as a barrier to migration, because high- altitude areas at middle latitudes can have the same mean annual and mean annual range of temperature as low-altitude areas at high latitudes. The only major environmental factor that remains is that of day length as related to the phenomenon of photo- periodism. Although we have noted probable excep- tions, we think that the data in this report suggest that generally it is impossible to reverse the trend of photoperiodic specialization in woody deciduous plants. PALEOCLIMATOLOGY Figure 8 shows the distribution of major tempera- ture parameters relative to vegetational types at higher middle to high latitudes of eastern Asia (Wolfe, 1979a). The placement of each climatic station in a given vegetational type follows the maps of Wang (1961), Honda (1928), Hara (1959), and Suslov (1961). That the Seldovia Point assemblage is Mixed North- ern Hardwood forest has been discussed above, in terms of both foliar physiognomy and general floristic affinities. The climatic region now occupied by Mixed North- ern Hardwood forest in eastern Asia is broad. The Sel- dovia Point assemblage is, we think, assignable to the warmer and more equable part of that vegetational type; that is, the Seldovia Point assemblage probably lived at temperatures similar to those of southwestern Hokkaido. In this area, some broad-leaved deciduous plants of a typically more southerly distribution occur: for example, Lindera, Cercidiphyllum, Berchemia, Pterocarya, Schisandra, and Cocculus (Hara, 1959). Analogous genera in the Seldovia Point assemblage are: Cocculus, Cercidiphyllum, Pueraria, Alangium, Platanus, and Liquidambar. 30 T Lu ISTEPPE) D BROAD-LEAVED o g 25 — EVERGREEN “—925 C (D .— 2 Lu 8 2° —>2o°c Ed 0: (D LIDJ > BROAD-LEAVED 215— airings? Mawfi DEC'DUOUS —~ Evergreen RXflwa E ‘L’ ——>13°c 3, + - I; 10 — Portland Dewfiég‘i‘gka 0: Lu n. E u.: |- 62?.Seldovia N°"h°'" _1 5 Point Hardwood < _ D Z . z < Z < 0— ”EJ (TUNDRA) I I I I I I 0 10 20 30 40 50 MEAN ANNUAL RANGE OF TEMPERATURE, IN DEGREES CENTIGRADE FIGURE 8. Temperature parameters of modern vegetational types in eastern Asia and the probable temperature parameters of certain early and middle Miocene assemblages. 20 That the Seldovia Point assemblage had a climate that at least was along the more equable margin of Mixed Northern Hardwood forest is also shown by the fact that coniferous forest was not far distant. Al- though megafossils of Pinaceae have not been col- lected at any of the Seldovia Point localities, the mi- crofossil assemblages contain up to 34 percent Picea pollen, accompanied by a diversity of other pinaceous genera (aff. Cedrus, Picea, Pinus, Tsuga). The samples that have the numerically and taxonomically most abundant representation of Pinaceae are the more southerly localities, indicating that probably the coastal area was occupied by coniferous forest. The temperature regime thus indicated for the Sel- dovia Point assemblage is 6—7°C mean annual tem- perature (see fig. 8); if coniferous forest were not far distant, then a mean annual range of temperature of 26—27°C is indicated. These estimates in turn indicate that mean annual temperature has declined since the middle Miocene by about 3—5°C. As noted previously (Wolfe, 1971), however, the Seldovia Point mean an- nual range of temperature was 9—11°C greater than now; that is, the present climate at Seldovia is consid- erably milder than the middle Miocene climate. There has been almost no change (if anything, perhaps a slight increase) in winter temperatures, but there has been a drastic change in warm month temperatures; the mean temperature of the warmest month has de- clined by about 7—8°C. We suggest that it is this strong decline in summer temperatures during the Neogene that was a major factor in the initiation of widespread glaciation during the later Cenozoic. Today areas such as southern Alaska have a consid- erably lower mean annual range of temperature (that is, have a milder climate) than do areas to the south- west. The same situation appears to have prevailed during the middle Miocene, judging from paleobotani— cal data from Sakhalin and particularly Japan. In Sakhalin, Fotianova’s (1967) analysis of the Upper Dui flora (fig. 9) indicated the total absence of mem- bers of Pinaceae; that is, the assemblage represents a broad-leaved deciduous forest that was geographically not close to coniferous forest. That the Upper Dui as- semblage represents Mixed Northern Hardwood forest is clear from the diversity of lobed leaves (primarily Acer); another similarity to the Seldovia Point as- semblage is in the abundance and diversity of U1- maceae. Although Fotianova (1967) does not list Fagus as a member of the Upper Dui flora, Heer (1978) illustrated many examples of F. antipofi. Floras from other areas of Sakhalin are generally similar to the Upper Dui. The Esutoru, Odasu, Naih- oro, and Kashihi floras (Huzioka, 1949) lack Pinaceae but have a diversity of Ulmaceae, Betulaceae, Aceraceae, and Salicaceae. Among probable trees, MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Populus, Alnus, Ulmus, and Acer are particularly common; Alangium is also well represented. Overall the Upper Dui and other floras from Sakha- lin do not appear to differ vegetationally from the Sel- dovia Point assemblage, except for the apparent ab- sence of members of Pinaceae. The warmer elements present in the Sakhalin middle Miocene flora— Alangium, Leguiminosae—are also represented in the Seldovia Point assemblage. What is known of the middle Miocene flora of Kamchatka (Chelebaeva, 1968) supports the suggestion that mean annual tem- perature during the middle Miocene was almost con- stant from Sakhalin through Kamchatka and into southern Alaska; the same situation prevails today. This interpretation of the paleobotanical data would also indicate—at least for Kamchatka——a decrease in mean annual range of temperature since the middle Miocene. The middle Miocene Yoshioka flora of southwestern Hokkaido was interpreted by Tanai (Tanai and Suzuki, 1963) to be Mixed Mesophytic forest (Cas- tanea zone of many Japanese botanists). Although many of the Yoshioka species occur primarily in this vegetational type in both Japan and central China, it is significant that broad-leaved evergreen plants— typically shrubs but some also scattered trees—occur in Mixed Mesophytic forest (Wang, 1961, p. 98, 100). In the Yoshioka assemblage, in contrast, the broad- leaved evergreen element is represented only by two microphyllous species, Quercus elliptica and Camellia protojaponica. In several respects the Yoshioka assemblage resem- bles what Wang (1961) termed Deciduous Broad- leaved forest; this type of vegetation has been greatly disturbed, and in fact eliminated, in most areas of the Great Plain of North China. In this vegetation, broad— leaved deciduous trees and shrubs predominate, and broad-leaved evergreens are rare. Notable, however, is the occurence in the vegetation of broad-leaved de- ciduous plants that are typical of more southern vege— tational types: Castanea, Gleditschia, Cedrela, Pis— tacia, for example. The mean annual temperatures under which this Deciduous Broad-leaved forest lives, however, are ap- proximately the same as those under which Mixed Mesophytic forest lives, and thus the mean annual temperature suggested for the Yoshioka assemblage by Tanai (IO—14°C; Tanai and Suzuki, 1963) is proba- bly valid. Judging, however, from the diversity of lobed leaves in the Yoshioka (most representingAcer), Mixed Northern Hardwood forest, in which lobed species are common, was not far distant. Indeed, the slightly altitudinally higher Abura flora probably rep- resents this vegetational type (Tanai in Tanai and Suzuki, 1963), and we thus suggest that the mean an- PALE 0C LIMATOLOGY 2 1 12001400 16001700 180° 170° 160° 700 l \ \ \ \ / 60° 160° 170° 180° 50° 170° 40° 160° N, a! HOKKAIDO J Am“ Yoshioka (‘1 < Utto \ C o / 40°— V' Shanwang 1500 KYUSHUQ 0 100 200 300 400 SOOKILOMETERS L._l__J_J_l_l l \ \ 120° 30° 130° 140° FIGURE 9,—Map of northeastern Asia showing location of some middle Miocene assemblages. 22 nual temperature for the Yoshioka assemblage was probably 10— 12°C. The Utto flora of northwestern Honshu was inter- preted to have lived under a mean annual tempera- ture of 15°C but at the same time to have represented broad-leaved deciduous forest (Huzioka, 1963). As analyzed by Huzioka, the forest also included broad- leaved evergreen trees, and the shrub component in- cluded both broad-leaved evergreen and deciduous plants. The evergreen element includes members of Lauraceae and Fagaceae, which account for almost half this element. Comparisons were made with vege- tation in southern Honshu, but in that area the vegetation—except for secondary vegetation—is dom- inantly broad-leaved evergreen. Broad-leaved decidu- ous forests that have a floristic composition highly similar to the Utto assemblage do, however, exist in mainland China. In the southern parts of Shensi and Kansu and adjacent parts of Honan provinces, the forest (lower oak forest of Wang, 1961) is primarily broad-leaved deciduous, but the trees, as well as the shrubs, include both broad-leaved evergreen and de- ciduous types. Evergreen Lauraceae and Fagaceae are particularly notable (Wang, 1961, p. 89—90). The mean annual temperature suggested for the Utto Flora by Huzioka (15°C) is present in the area occupied by the lower oak forest, and this would indi- cate a decline of mean annual temperature of about 4°C since the middle Miocene. The significant point to be made in the above comparison is that in the area occupied by this lower oak forest the mean annual range of temperature is typically higher than the present range at the Utto localities. The change in mean annual range of temperature since the middle Miocene need not have been great (perhaps only 2—3°C), but such a change is consistent with the change indicated by high-latitude floras. Fossil assemblages farther south in Japan have been uniformly compared to the modern Evergreen Sclerophyllous Broad—leaved forest (Tanai, 1961, 1967a, 1972; Matsuo, 1963; Ishida, 1970). These as- semblages typically contain elements indicating somewhat warmer mean annual temperatures during the middle Miocene than now, but estimates of mean annual range of temperature are almost impossible to arrive at. It is clearly possible that this vegetational type lived under a higher mean annual and mean an- nual range of temperature than now exists at the fos- sil localities. Data from these more southerly floras neither contradict nor substantiate the changes in mean annual range of temperature indicated by the more northerly floras. The middle Miocene latitudinal vegetational zonation indicated for eastern Asia indi- cates, however, that there has been a decrease in MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA ’mean annual range of temperature since that time. In western North America at' middle latitudes (fig. 10), most of the known middle Miocene assemblages grew in uplands. These uplands, moreover, are east of the Sierra-Cascade axis, and interpretations of changes in climate since the middle Miocene are greatly complicated by tectonic and altitudinal fac- tors. In the Pacific Northwest, comparisons are best made to climatic data from the region west of the Cas- cade Range. Middle Miocene floras such as the Latah (Knowlton, 1926; Chaney, 1959), Grand Coulee (Berry, 1931), St. Eugene (Hollick, 1927), and Fish Creek (Wolfe, in Peck and others, 1964) represent Mixed Mesophytic forest. These assemblages are dominantly broad- leaved deciduous but contain some notophyllous broad-leaved evergreens (Magnolia, Lauraceae, Ex- bucklandia, Arbutus). These assemblages, however, grew at an altitude perhaps over 500—600 In (Wolfe, 1969a, p. 93). The Latah and similar assemblages lived in a mean annual temperature of 10— 13°C and a mean annual range of temperature of 19—27°C. Com- parisons with data for Cedar Lake (a station on the west side of the Cascades at an altitude of almost 500 m) indicate that since the middle Miocene mean an- nual temperature has declined by at least 1—3°C and that mean annual range of temperature has decreased by 4—12°C. Lowland assemblages of middle Miocene age are still poorly known in the Pacific Northwest. The unde- scribed Wishkaw River assemblage from western Washington and particularly the undescribed Cape Blanco assemblage from southwestern Oregon proba- bly represent Sclerophyllous Broad-leaved Evergreen forest. Notophyllous members of evergreen Fagaceae and Lauraceae are conspicuous elements in these as- semblages. If this vegetation type is represented, then there has probably been a moderate (at least 2—3°C) decline in mean annual temperature since the middle Miocene. In areas lacking major mountains parallel to the coast (such as the middle Miocene Pacific North- west), mean annual range of temperature increases only a few degrees a few hundred kilometers from the coast. It is improbable that mean annual range of temperature in the lowlands during the middle Miocene was more than a few degrees less than that indicated for upland assemblages such as the Latah (19—27°C). If a minimal mean annual range of tem- perature of 15°C is assumed for the Cape Blanco and Wishkaw River climates, then mean annual range of temperature in the coastal areas has lessened since the middle Miocene; mean annual range is today al- most 7°C at Port Orford near Cape Blanco and almost 12°C near Wishkaw River. On Cape Blanco itself mean annual range of temperature is less than 5°C. PALEOCLIMATOLOGY 60° 175° 65° 170° 70“ 165° 160°75° 155° 150° 145° 140°135°130°125. \ W \ \/ / / / / 80, 44> 175°” 0 (f Kougarok + 170°“ ° b \91/ 75. 55° \ 165° 5 Sanctuary/Suntrana Cache Creek + Unga co Island 70° 160° / Wrangem 50° 65° / 155° v6 60° / V 150° ('3 45° \ i m a 55. O / 145° 40 O S“ c U 8 Is \ O gSilltsl' 50° {1'1 > ’2 140° 45' 35° \ 100 O 100 200 300 400 SOOMILES 100 0 100200 300 400 500 KILOMETERS 40° ‘\+Fingerrock \ I 135° 130° 35°125° 120° 115° 110° / / / FIGURE 10.—Northwestern North America showing locafion of some middle Miocene assemblages. 24 The paleobotanical evidence is thus consistent around the North Pacific Basin: mean annual temper- ature has declined since the middle Miocene, although the decline has been greatest at high latitudes. Simi- larly, mean annual range of temperature has de- clined, and the decline has been greatest at high latitudes. Concomitant with the decline in mean an- nual range of temperature, the decline in mean an- nual temperature primarily results in a lowering of summer temperatures; we emphasize again that such a decline in summer temperatures was a major factor in the initiation of late Cenozoic glaciation. Previous analysis of paleoclimates from western North America (Wolfe and Hopkins, 1967; Wolfe, 1971) has indicated that the middle Miocene was warmer than either the earliest or late Miocene, and paleobotanical analyses based on eastern Asian mate- rials are in basic agreement (Tanai and Huzioka, 1967; Tanai, 1967a, 1967b, 1971). The Alaskan data clearly are also in agreement in comparing the ear- liest with the late early to early middle Miocene cli— mates. The vegetation represented by the assemblages from the lower Seldovian of the Cook Inlet region was also probably Mixed Northern Hardwood forest but more depauperate than that of the upper Seldovian. The assemblages of probable early Seldovian age in the Cook Inlet region are Capps Glacier (locs. 9845, 9846, 9937 of Wolfe and others, 1966) and Houston (loc. 9365 of Wolfe and others, 1966). Preliminary de— terminations of the flora from the localities indicate that the following are represented: Glyptostrobus europaeus Metasequoia cf. M. glyptostroboides Keteleeria sp. Chamaecyparis sp. Cercidiphyllum alaskanum Ulmus sp. Quercus furuhjelmi Alnus barnesi Alnus cappsi Alnus fairi Alnus healyensis Carpinus cappsensis Comptonia naumannii Myrica Sp. Pterocarya nigella Populus kenaiana Populus spp. Salix cappsensis Salix picroides Salix spp. MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Hydrangea sp. Crataegus Sp. Sorbaria sp. Spiraea weaveri Cladrastis aff. C. lutea Acer aff. A. pennsylvanicum Acer aff. A. saccharinum Aesculus cf. A. majus Alangium mikii Notable in these assemblages is the diversity of both Betulaceae and Salicaceae, which are also the most abundant megafossils. Just as significant is the lesser diversity in the lower as compared to the upper Seldo- vian flora of Fagaceae, Ulmaceae, Juglandaceae, and Aceraceae. Genera such as Cocculus, Liquidambar, Platanus, and Cyclocarya are absent from the lower Seldovian megafossil assemblages. The most reasonable interpretation of such floristic differences is that the middle Miocene warming documented at middle latitudes allowed the north- ward expansion of some species into southern Alaska. Because the physiognomy of the early Seldovian as- semblages also indicates broad-leaved deciduous forest, it appears that mean annual range of tempera- ture also decreased from the early into the middle Miocene; this suggestion accords with the trend after the middle Miocene. The Homerian (late middle to early late Miocene) assemblages from Alaska, although representing conif- erous forest, do not necessarily indicate that mean annual temperature declined. From figure 8 it can be seen that a change from broad-leaved deciduous to coniferous forest can be the result of a decrease in mean annual range of temperature alone. The rich broad-leaved deciduous tree element that is conspicu- ous even in coniferous assemblages of Seldovian age (for example, Wrangell and Noxapaga assemblages) is absent in the early Homerian megafossil assemblages, and only sparse amounts ofPterocarya/Cyclocarya and Ulmus/Zelkoua occur in some microfossil assemblages. If, as seems probable, broad-leaved trees are better adapted to higher summer heat than are most conifer- ous trees, and if diversity of broad-leaved trees in- creases with overall warmth, then the simplest way to eliminate broad-leaved trees from Alaska following the Seldovian would be to drastically lower summer temperatures and overall heat. Such a lowering is ac- complished by lowering both mean annual and mean annual range of temperature. SYSTEMATICS The preliminary list of the Seldovia Point flora pre- SYSTEMATICS 25 viously published (Wolfe, 1966) differs in several re- spects from that reported here. In order to clarify any differences, the following is presented: Wolfe. 1966 This report Equisetum sp __________________ Not recognized; specimen lost? Dryopteris sp __________________ Dryopteris sp. Onoclea sensibilis ______________ Onoclea sensibilis. Ginkgo biloba __________________ Ginkgo biloba. Glyptostrobus europaeus ________ Glyptostrobus europaeus. Metasequoia glyptostroboides ____ Metasequoia cf. M. glypto- stroboides. Taxodium distichum ____________ Not recognized; probably aber- rant shoots of Glyptostrobus or Metasequoia. Potamogeton sp _________________ Potamogeton alaskanus. Smilax sp ______________________ Alisma seldoviana. Poacites tenuistriatus __________ Monocotylophyllum spp. Cyperacites sp __________________ Monocotylophyllum sp. Populus kenaiana ______________ Populus kenaiana. Populus reniformis ____________ Populus sp. Populus sp. afi". P. ciliata ______ Populus kenaiana. Salix inquirenda ______________ Salix picroides. Salix picroides ________________ Salix picroides. Salix sp ________________________ Salix cappsensis. Carya bendirei ________________ Carya bendirei. Carya sp. aff. C. sessilis ________ Carya bendirei. Pterocarya mixta ______________ Pterocarya nigella. Pterocarya nigella ______________ Pterocarya nigella. Pterocarjya (Cycloptera) sp ______ Cyclocarya ezoana. Alnus cappsi __________________ Alnus cappsi. Alnus healyensis ______________ Alnus healyensis. Alnus fairi ____________________ Alnus fairi. Carpinus seldoviana ____________ Carpinus seldoviana. Fagus antipofi __________________ Fagus antipofi. Fagus sp. cf. F. paleocrenata ____ Fagus aff. F. crenata. Quercus bretzi __________________ Quercus furuhjelmi. Quercus furuhjelmi ____________ Quercus fitruhjelmi. Ulmus longifolia ______________ Ulmus owyheensis. Ulmus newberryi ______________ Ulmus knowltoni. Zelkova oregoniana ____________ Zelkoua browni, Z. ungeri. Nuphar sp _____________________ Nymphar ebae. Cercidiphyllum crenatum ______ Cercidiphyllum alaskanum. Cocculus auriculata ____________ Cocculus auriculata. Hydrangea sp __________________ Hydrangea sp. Liquidambar mioformosana _r__ Liquidambar pachyphylla. Platanus bendirei ______________ Platanus bendirei. Crataegus sp __________________ Crataegus chamisonii. Prunus sp ______________________ Prunus kenaica. Spiraea? andersoni ____________ Not considered; based only on Heer’s illustration. Alchornea? sp __________________ Indeterminate leaf. Mallotus sp ____________________ Pueraria miothunbergiana. Acer ezoanum __________________ Acer ezoanum. Acer fatisiaefolia ______________ Acer ezoanum. Acer macropterum ______________ Acer grahamensis. Acer Sp. all". A. crataegifolium __ Acer heterodentatum. Acer sp. cf. A. subpictum ______ Acer ezoanum fruits. Vitis sp ________________________ Vitis seldoviana. Tilia sp ________________________ Tilia subnobilis. Nyssa sp. cf. N. knowltoni ______ Nyssa cf. N. knowltoni. Hemitrapa borealis ____________ Hemitrapa borealis. Kalopanax sp __________________ Kalopanax acerifolius. Fraxinus sp ____________________ Fraxinus kenaica. Symphoricarpos sp ____________ Decodon alaskana. Family Aspidiaceae Genus Dryopteris Adanson Dryopteris sp. Plate 1, figures 5, 9 Description—A portion of a pinna 3.5 cm long and 1.7 cm wide at the lower part, lanceolate; pinnules ovate, suboppositely pinnatified by shallow but nar- row sinus, nearly entire or having a few teeth on margin; midvein of each pinnule leaving pinna axis at angles of 40 to 50 degrees, somewhat zigzag, forking at the apical part, having 3 or 4 pairs of lateral veins that fade out near the margin without any bifurca- tion. Discussion—A single pinna and its counterpart are fragmentary and sterile, and the generic assignment is uncertain. But these specimens show close re- semblance to the pinnae of some extant Dryopteris in shape of pinnae and venation, such as D. decipiens O. Kuntze and D. tokyoensis (Mats) C. Chr. living in East Asia. Our Alaskan specimens are quite different in venation from D. guyotti (Lesq.) MacG. and D. idahoensis Knowlt., which were described from the middle Tertiary of the conterminous United States. Occurrence—9858 Specimen.—USNM 208348A, B. Genus Onoclea L. Onoclea sensibilisis L. Plate 1, figures 3, 4 Discussion—Several fragmentary pinnae from Sel- dovia Point are undoubtedly referrable to the genus Onoclea by their characteristic venation, which is quite well preserved. Except for the wavy margin of the apical part, they are regularly lobed (each lobe having a rounded apex) but are otherwise entire mar- gined. The pinnae axis bears a single series of low and long areoles on each side. The midvein of each pinnule is thin but distinct and gives off thin secondaries that frequently branch, forming a prolonged reticulation nearly parallel to or at acute angles to the midvein. These characters show that our Alaskan specimens are identical with the modern monotypic species, Onoclea sensibilis L., distributed in northeastern Asia and eastern North America and may represent the pinnae of the middle or proximal parts of the frond. The sterile foliage of Onoclea has frequently been recorded from the Upper Cretaceous and Paleogene of North America, and Brown (1962) gave a new specific name of 0. hesperia to them. As stated previously (Wolfe, 1966), the original specimens of 0. hesperia include both finely serrate and entire margins and are thus separable from the Seldovian specimens. Hypotypes.—USNM 208349, 208350. Occurrence—9858. 26 Family Taxodiaceae Genus Glyptostrabus Endl. Clyptostrobus europaeus (Brong’niart) Heer Plate 1, figure 8 Glyptostrobus europaeus (Brongniart) Heer, 1855, Flora Tertiaria Helvetia, v. 1, p. 51, pl. 19; pl. 20, fig. 1. Discussion—This species is represented only by fragmentary foliage shoots, which have slender leaves. No fossil cone of Glyptostrobus has been col- lected from the Seldovia Point localities. This Eurasian species was widely distributed during the Tertiary, and it is difficult to separate from G. oregonensis Brown of the North American Tertiary only by foliar characters. Cones collected from other Seldovian localities, however, are typical for G. europaeus. Hypotype.—USNM 208351. Occurrence—9858. Genus Metasequm'a Miki Metasequm'a cf. M. glyptostroboides Hu et Cheng Plate 1, figures 2, 6, 7, 10 Metasequoia glyptostroboides Hu et Cheng, 1948, Fan Memorial Inst. Botany Bull., new ser., v. 1, p. 154. Discussion.———Numerous short shoots and pistillate cones of Metasequoia from the Seldovia Point 10— calities are indistinguishable from homologous parts of the extant species. Lacking preservation of epider- mal features, however, we hesitate to place the fossil material in the extant species. The material should not be assigned to M. occidentalis (Newb.) Chan. be- cause the types, as well as other Paleocene shoots of Metasequoia, typically have shorter and blunter nee- dles than in middle to late Tertiary specimens of Metasequoia. Specimens.——USNM 208352—208355. Occurrence.—9856—9858. Family Ginkgoaceae Genus Ginkgo Linnaeus Ginkgo biloba Linnaeus Plate 1, figure 1 Ginkgo biloba Linnaeus, 1771, Linn. Mant., v. 2, p. 313. Discussion—In his extensive review of the geologic history of Ginkgo, Tralau (1968) noted that later Ter- tiary specimens for which epidermal details were known did not differ specifically from the extant species. We think that there is no reasonable basis for excluding later Tertiary material of this genus from the extant species. Hypotype.—USNM 208356. Occurrence.——9857. MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Family Nymphaeaceae Genus Nymphar Ozaki Nymphar ebae (Huzioka) Ozaki Plate 1, figures 11—14 Nymphar ebae (Huzioka) Ozaki, 1978, Yokohama Natl. Univ. Sci. Repts., sec. 2, no. 25, p. 17, pl. 1, figs. 1, 3—5; text-figs. 4B—D, 5A, B. Nuphar ebae Huzioka, 1964, Akita Univ. Mining Coll. Jour., ser. A, v. 3, no. 4, p. 82, pl. 11, fig. 6; ‘pl. 12, figs. 1—3. Supplementary description—Floating leaves ovate to oval in shape, 2.1 to 5.2 cm long and 1.3 to 3.2 cm wide; apex obtuse to rounded; base auriculate with deep sinus; midvein distinct, nearly straight to apex; secondary veins slender, 9 to 15 pairs, irregularly spaced, leaving the midrib at angles of 50 to 70 de- grees, a basal pair more spreading, dichotomizing 3 or 4 times toward the margin and forming series of loops, camptodrome; the intersecondary veins sometimes developing but weak; the tertiary veins thin, forming irregularly large networks which enclose small poly- gonal areoles formed by the fourth order veins; mar- gin entire; petiole rather slender, more than 2 cm long. Discussion—These are the most abundant leaves in our collection, and they are identical in shape and ve- nation to Nymphar ebae, which was described from a lower Miocene flora of Honshu. Hypotypes.—USNM 208357—208360. Occurrence—9858. Family Menispermaceae Genus Cocculus DeCandolle Cocculus auriculata (Heer) Wolfe Plate 2, figure 7 Cocculus auriculata (Heer) Wolfe, 1966, U.S. Geol. Survey Prof. Paper 398—B, p. B24, pl. 7, fig. 1. Hedera auriculata Heer, 1869, Flora Foss. Arctica, v. 2, pt. 2, p. 36, pl. 9, fig. 6. Populus heteromorpha Knowlton, 1926, U.S. Geol. Survey Prof. Paper 140—A, p. 30, pl. 12, figs. 8—10; pl. 13, figs. 1—7; pl. 14, figs. 1—3; pl. 15, figs. 3—5. Berry, 1929, U.S. Geol. Survey Prof. Paper 154, p. 242. Hoffman, 1932, Jour. Geology, v. 40, p. 735. Populus fairii Knowlton, 1926, U.S. Geol. Survey Prof. Paper 140, p. 30, pl. 15, fig. 2; pl. 16, figs. 1—3. Cebatha multiformis Hollick, 1927, New York Bot. Garden Mem., V. 7, p. 406, pl. 38, figs. 1—6; pl. 39, figs. 1—3. Cissampelos dubiosa Hollick, 1927, New York Bot. Garden Mem., v. 7, p. 408, pl. 37, figs. 4—7; pl. 39, fig. 4. Cebatha heteromorpha (Knowlton) Berry, 1931, U.S. Geol. Survey Prof. Paper 170, p. 37. SYSTEMATICS 27 Berry, 1934, US. Geol. Survey Prof. Paper 185, p. 112. LaMotte, 1936 [part], Carnegie Inst. Washington Pub. 455, p. 126 [unfigured specimen 839 only]. Cocculus heteromorpha (Knowlton) Brown, 1946, Washington Acad. Sci. Jour., V. 36, p. 352. Tanai, 1961, Hokkaido Univ. Fac. Sci. Jour., ser. IV, p. 324, pl. 21, fig. 7. Discussion.—This species is one of the most wide- spread plants in the Miocene of the areas bordering the North Pacific, occurring from Honshu north to Alaska and south to northern California. In Alaska, Cocculus auriculata is known only from the Seldovia Point flora and from the Seldovian rocks at Cache Creek and in the Nenana coalfield (Wahrhaftig and others, 1969). The specimen assigned by Becker (1969, pl. 26. figs. 12, 13) to Cocculus heteromorpha is certainly Populus, as indicated by the numerous small teeth and the closely spaced sinuous tertiary veins that are oriented at an acute angle to the secondary veins. In Cocculus auriculata (including the junior synonym C. hetero- morpha), the teeth are few and large, and the tertiary veins are widely spaced and perpendicular to the sec- ondary veins. Cocculus auriculata is clearly related to Paleogene species of the genus such as C. ezoensis Tanai from the Oligocene of Japan. Undescribed material of the same group of Cocculus also occurs commonly in the Eocene Ishikari floras of Hokkaido. C. ezoensis is, however, typically entire margined, although some toothed specimens are known (Tanai, 1970), in contrast to C. auriculata, which in illustrated specimens and mate- rial we have observed always has some teeth. Unde- scribed material from the lower Ravenian of the Puget ’ Group of Washington (loc. 8640 and 9694 of Wolfe, 1968) has numerous teeth, but the areoles are smaller than in C. auriculata and the leaves have small mounds of apparently cutinized material. The small mounds, which are also present in the Paleocene C. flabella (Newb.) Wolfe, indicate a thick leaf and prob- able evergreen habit (Wolfe, 1966), in contrast to the thin leaf and probably deciduous habit of C. au- riculata. Hypotype.—USNM 208369. Occurrence—9856, 9858. Family Cercidiphyllaceae Genus Cercidiphyllum Sieb. et Zucc. Cercidiphyllum alaskanum Wolfe et Tanai, sp. nov. Plate 2, figures 1, 3, 4; plate 11, figures 3, 5 Cercidiphyllum crenatum auct. non (Unger) Brown. Chelebaeva, 1968, Bot. Zhurn., v. 53, p. 744, pl. 4, figs. 1, 2; text-fig. 4a—b. Description.—Leaves simple; lamina symmetrical, wide ovate to very wide ovate; apex obtuse to acute; base cordate; margin simply to doubly crenate, teeth glandular; venation actinodromous; midrib and first two lateral pairs of primary veins of moderate size, two additional pairs of lateral primary veins weak; lateral primary veins markedly curved, irregularly brochidodromous, first lateral pair acrodromous; sec- ondary veins irregularly brochidodromous, diverging at a widely acute angle, uniformly to abruptly curved, branched; intercostal areas between midrib and first lateral pair of primary veins braced by widely and ir- regularly spaced tertiary veins that are approxi- mately perpendicular to primary veins, typically with a composite intersecondary vein; composite intersec- ondary veins typically present in area between first and second pairs of lateral primary veins; fourth order venation irregularly spaced, tending to be orthogonal; fifth order venation forming irregularly polygonal and randomly oriented areoles intruded by irregularly branching freely ending veinlets. Discussion.—Typically orbicular leaves of the Cer- cidiphyllum type were assigned to the European species C. crenata (Unger) R. W. Br. (Brown, 1935, 1939), and most workers have typically followed this practice. Comparison of the Seldovia Point material with topotypic material from the Swiss Tertiary indi- cates a marked difference in ultimate venation, par- ticularly in regard to the size of the areoles. Addition- ally, in the Swiss material the marginal glands are incorporated in the foliar tissue, whereas in the Sel- dovia Point material and the extant C.‘ japonicum Siev. et Zucc. the glands are situated abmedial to the teeth. The Seldovia Point species also has larger areoles than in C. japonicum. Cercidiphyllum alaskanum also has a characteristic pattern in the lateral tertiary venation. The intercos- tal area between the first (from the midrib) lateral primary and the second lateral primary typically is braced by an intersecondary vein extending abme- dially and giving off tertiary braces that extend to the second lateral primary and the most basal secondary of the first lateral primary. In Cercidiphyllum japonicum and in most other fossil material of Cer- cidiphyllum that we have examined, an intersecon- dary is lacking and the bracing is accomplished only by tertiary veins. The only other species of Cer- cidiphyllum that has the type of bracing seen in C. alaskanum is C. eojaponicum Endo ex Tanai, which was originally described from the early Oligocene Fushun beds of Manchuria and later found in approx- imately isochronous beds on Hokkaido (Tanai, 1970). An additional similarity between C. alaskanum and C. eojaponicum is the presence of some doubly crenate teeth (see, for example, Endo, 1968, pl. 15, figs. 3, 4). 28 We have not investigated the areolar size in C. eojaponicum, but this species differs from C. alas- kanum in that the lateral primary and the secondary veins loop well within the margin. The strong similarities between these two species, however, indi- cate that they may be phyletically related. Other material assigned to Cercidiphyllum cre- natum by Brown (1935, 1939) should also be excluded from that species. Material from the Eocene beds at Republic, Wash, for example, has an areolar size comparable to that of the Swiss, material, but the leaf base is never deeply cordate (typically it is broadly rounded) and the teeth are sharp with glands abme- dial to the teeth. We suggest that there is great need for a comprehensive examination and analysis of other material assigned to C. crenatum. Holotype.—USNM 208361A, B. Paratypes.—-USNM 208362, 208363A, B. Occurrence.—9856, 9858. Family Hamamelidaceae Genus Liquidambar L. Liquidambar pachyphylla Knowlton Plate 2, figures 5, 6; plate 3, figures 1—3 Liquidambar pachyphylla Knowlton, 1902, US. Geol. Survey Bull. 204, p. 63, pl. 9, fig. 1. Chaney, 1920, Walker Mus. Contr., v. 2, p. 174, pl. 15, figs. 2, 3. Knowlton, 1926, US. Geol. Survey Prof. Paper 140, p. 42, pl. 22, fig. 7; pl. 29, fig. 1. Brown, 1946, Washington Acad. Sci. Jour., v. 36, p. 352. Chaney and Axelrod, 1959 [part], Carnegie Inst. Washington Pub. 617, p. 181, pl. 35, fig. 5 only. Liquidambar europaeum patulum Knowlton, 1902, US. Geol. Survey Bull. 204, p. 62, pl. 10, fig. 5. Liquidambar acutilobum Chaney, 1920, Walker Mus. Contr., v. 2, p. 175, pl. 15, fig. 4. Arisaema hesperia Knowlton, 1926, US. Geol. Survey Prof. Paper 140, p. 29, pl. 10, fig. 1. Liquidambar europaeum auct. non Al. Braun. Heer, 1869, Flora Fossilis Arctica, V. 2, no. 2, p.25, pl. 2, fig. 7. Lesquereux, 1888, US. Natl. Mus. Proc., v. 11, p. 14. Chaney, 1920, Walker Mus. Contr., v. 2, p. 174. Liquidambar californicum auct. non Lesquereux. Chaney, 1920, Walker Mus. Contr., V. 2, p. 174. Berry, 1929, US. Geol. Survey Prof. Paper 154, p. 250. Berry, 1934, US. Geol. Survey Prof. Paper 185, p. 113. Berry, 1938, Torrey Bot. Club Bull., v. 65, p. 96, text-fig. 3. MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Liquidambar protensum auct. non Unger. Lesquereux, 1888, US. Natl. Mus. Proc., v. 11, p. 13, pl. 8, fig. 3. Knowlton, 1902, US. Geol. Survey Bull. 204, p. 62. Discussion—Early collections from the Seldovia Point locality contained one poorly preserved speci- men of Liquidambar that was three lobed; the speci- men was thus assigned to the typically three-lobed L. mioformosana Tanai et Onoe. Additional specimens obtained in 1967, however, indicated that the Seldovia Point Liquidambar varied from three to five lobed, a condition that is typical for L. pachyphylla (Chaney and Axelrod, 1959, p. 182). Analysis of available specimens of Liquidambar from early and middle Miocene localities in the west- ern United States (Collawash, Latah, Eagle Creek, Mascall) indicates that this species is about evenly di- vided between three- and five-lobed leaves, in contrast to late Miocene leaves of Liquidambar (Faraday, Hid— den Lake, Blue Mountains, Molalla, Weyerhauser), which are almost invariably five lobed (only one three-lobed specimen has been found in late Miocene beds). Additionally, the typical (early and middle Miocene) L. pachyphylla has sharp teeth that have a basal side about three times as long as the apical side, and the areoles are about 06—075 mm in diameter. The late Miocene material has rounded teeth that have a basal side about twice as long or less as the apical side and the areoles are about 1.5—2.1 mm in diameter. These differences are sufficient to exclude the late Miocene material from L. pachyphylla. The present distribution of Liquidambar makes this genus an unlikely member of the Alaskan Neogene flora (see p. 17). The genus, however, was apparently not common. In most pollen samples from the Capps Glacier Seldovian and the Seldovian of the Alaska Range the genus is absent, although the genus is more persistent in the samples from the Suntrana Formation, which is late Seldovian and presumably middle Miocene. The high (14 percent) representation of Liquidambar in the sample from Seldovia Point is the highest we know of in the Alaskan Neogene se- quence. Hypotypes.—USNM 208364—208368. Occurrence.—9856, 9858. Family Platanaceae Genus Platanus Linnaeus Platanus bendirei (Lesquereux) Wolfe Plate 3, figure 4; plate 4, figures 1, 2, 4 Platanus bendirei (Lesquereux) Wolfe, 1964, US. Geol. Survey Prof. Paper 454—N, p. N24, pl. 4, figs. 1, 2, 4. SYSTEMATICS 29 Acer bendirei Lesquereux, 1888 [part], U.S. Natl. Mus. Proc., v. 11, pl. 5, fig. 5; pl. 6, fig. 1; pl. 7, fig. 1. Acer merriami Knowlton, 1902, US. Geol. Survey Bull. 204, p. 74, pl. 14, fig. 7. Platanus youngii Graham, 1963, Am. Jour. Botany, v. 50, p. 925, fig. 12. Graham, 1965, Kent State Univ. Bull., Research Ser. 9, p. 89. Magnolia ingelfieldi auct. non Heer. Lesquereux, 1888, US. Natl. Mus. Proc., v. 11, p. 13. Platanus aceroides auct. non (Goeppert) Heer. Les- quereux, 1888, US. Natl. Mus. Proc., V. 11, p. 19, pl. 5, fig. 7. Knowlton, 1902, US. Geol. Survey Bull. 204, p. 65. Arnold, 1937, Michigan Univ. Mus. Paleontology Contr., v. 5, p. 88, pl. 3, fig. 1. Platanus nobilis auct. non Newberry. Lesquereux, 1888, US. Natl. Mus. Proc., V. 11, p. 19. Knowlton, 1902, US. Geol. Survey Bull. 204, p. 65. Platanus raynoldsii auct. non Newberry. Lesquereux, 1888, US. Nat]. Mus. Proc., V. 11, p. 19. Platanus aspera auct. non Newberry. Berry, 1931, US. Geol. Survey Prof. Paper 170, p. 34. Platanus dissecta auct. non Lesquereux. Berry, 1929, US. Geol. Survey Prof. Paper 154, p. 248, pl. 53, figs. 1, 2; pl. 61. Berry, 1931, US. Geol. Survey Prof. Paper 170, p. 34. Berry, 1934, US. Geol. Survey Prof. Paper 185, p. 111, pl. 21, fig. 2. Arnold, 1937, Michigan Univ. Mus. Paleontology Contr., v. 5, p. 88, pl. 9, figs. 1—3. Brown, 1937.[part], U.S. Geol. Survey Prof. Paper 186, p. 174, pl. 52, fig. 2 only. Brown, 1937, Washington Acad. Sci. Jour., v. 27, p. 515. Chaney and Axelrod, 1959 [part], Carnegie Inst. Washington Pub. 617, p. 182, pl. 36, fig. 3. Graham, 1965 [part], Kent State Univ. Bull., Re- search Ser. 9, p. 88, pl. 13, fig. 1; pl. 14, figs. 1, 5 [“Sucker Creek” occurrences only]. Discussion.—Some workers (for example, Becker, 1969) have applied the epithet dissecta to any three— to five-lobed leaves of Platanus that also have numer- ous teeth. Such a morphological concept for P. dissecta results in the inclusion in this species of several dis— tinctive (and probably in part unrelated) groupings of Platanus. As pointed out previously (Wolfe, 1964, p. N24), the late Miocene P. dissecta has leaves that are typically five lobed and typically without subsidiary teeth between the major teeth, in contrast to the early to middle Miocene P. bendirei, which has typically three-lobed leaves (although five—lobed leaves are also present) that have subsidiary teeth. Moreover, in con- trast to an undescribed species from the later Oligocene of the Pacific Northwest that has several subsidiary teeth between any two adjacent major teeth, P. bendirei typically has only one or two sub- sidiary teeth. On this basis, the Seldovia Point mate- rial is referrable to P. bendirei. The reduction in marginal serrations suggested for the Platanus bendirei lineage led to the Pliocene P. paucidentata Dorf (differing from the next species in having larger areoles) and culminated in the extant P. racemosa Nutt. Thus far this lineage has been found only in North America; the few occurrences of Platanus in the Neogene of Japan represent the P. aceroides complex. Hypotypes.—USNM 208370—208373. Occurrence.—9858. Family Eucommiaceae Genus Eucommia Oliv. Eucommia cf. E. montana Brown Plate 4, figure 6 Eucommia montana Brown, 1940, Washington Acad. Sci. Jour., v. 30, no. 8, p. 349, fig. 3. Discussion.—This specimen, although incomplete, is probably separable from E. montana in size and wing shape. Unfortunately this Alaskan material is carbonized, and the reticulate venation pattern over the seed part, as is characteristic of Eucommia, is not visible. In preserved features, our specimen is closely similar to the samara 0f the modern monotypic E. ul— moides Oliver of central China. No fossil leaves refer- able to Eucommia have been found in the Seldovia Point flora. Specimen.—USNM 208374. Occurrence—9858. Family Ulmaceae Genus Celtis Linn Celtis sp. Plate 4, figure 7 Discussion.—A single, small leaf is, although lack- ing the basal part, referred to the genus Celtis partly on the basis of the pronounced subprimary veins and camptodromous venation. The leaf is similar in gen- eral features to C. kansana Chaney et Elias from the Miocene and Pliocene of the conterminous United States but appears to differ in having apiculate teeth. Specimen.—USNM 208375. Occurrence—9858. 3O MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Genus Ulmus Linnaeus Ulmus knowltom' Tanai et Wolfe Plate 5, figures 1, 2 Ulmus knowltoni Tanai and Wolfe, 1977, US. Geol. Survey Prof. Paper 1026, p. 5, pl. 1C, F, G; pl. 2A, C, H, I, J [see synonymy and discussion]. Discussion.—Two incomplete specimens are re- ferred to U. knowltoni on the basis of a strongly asymmetric cordate base and nearly single blunt teeth. This species is somewhat similar to U. paucidentata H. V. Smith and U. owyheensis H. V. Smith in marginal serrations but differs in shape of the base and in the tertiary branches of the basal sec- ondary vein, which develop only on one side of the base. Hypotypes.—USNM 208376, 208377. Occurrence.—9856. Ulmus owyheensis H. V. Smith Plate 4, figure 8; plate 6, figures 7a, 7b Ulmus owyheensis Smith, 1939, Michigan Acad. Sci, Arts and Letters Papers, v. 24, p. 113, pl. 6, fig. 4. Tanai and Wolfe, 1977, US. Geol. Survey Prof. Paper 1026 p. 6, p1. 2B, D, E, F; pl. 3A [see synonymy and discussion]. Ulmus plurinervis Unger. Heer, 1869, Kongl. Svenska Vet.-Akad. Handl., bd. 8, no. 4, p. 34, pl. 5, fig. 1. Discussion—Our Alaskan specimens are quite iden— tical in shape, venation, and marginal serrations with Ulmus owyheensis H. V. Sm., which was originally described from the Miocene Sucker Creek flora. As discussed elsewhere (Tanai and Wolfe, 1977), the leaves of this species vary in laminar shape from ovate to oval and in basal shape from rounded to broadly rounded. This species, however, is distin- guishable from other Tertiary elms by the following characters: single, apiculate teeth having in many in- stances a minute subsidiary tooth, less unequal and slightly cordate base, irregularly percurrent tertiary veins, and three or four prominent tertiary branches that depart from a basal pair of secondaries and end in the teeth. A single specimen figured as U. pluriner— via from English Bay (Heer, 1869a) is included in U. owyheensis. Hypotypes.—USNM 208376, 208377. Occurrence.—9856, 9858. Ulmus speciosa Newberry ‘ Plate 4, figures 3, 5 Ulmus speciosa Newberry, 1898, US. Geol. Survey Mon. 35, p. 80, pl. 45, figs. 3, 4 (excluding figs. 2, 5—8). Tanai and Wolfe, 1977, US. Geol. Survey Prof. Paper 1026, p. 8, p1. 3C, F [see synonymy and discussion]. Discussion.—Two leaves, although lacking about half the base, match well in their venation and mar— ginal characters Ulmus speciosa, which was recently reinstituted (Tanai and Wolfe, 1977). The primary teeth of our Alaskan specimens typically have two subsidiary teeth of nearly equal size, fed by tertiary branches from the secondaries. The intercostal ter- tiary veins are mostly percurrent, crossing to the sec- ondaries, and enclose irregularly polygonal nets formed by fourth order veins. Hypotypes—USNM 208381, 208382. Occurrence.—9858. Genus Zelkova Spach Zelkova browm' Tanai et Wolfe Plate 5, figures 3, 6, 8a, 8c; plate 6, figure 8 Zelkova browni Tanai and Wolfe, 1977, US. Geol. Survey Prof. Paper 1026, p. 8, pl. 4A, C—G [see synonymy and discussion]. Planera ungeri auct. non Ettingshausen. Heer, 1869, Kongl. Svens. Vet.-Akad. Handl., bd. 8, no. 4, p. 34, pl. 5, fig. 2. Discussion.-——This species was recently established on the basis of well-preserved material from the Miocene Collawash flora of Oregon, because the type specimen of Z. oregoniana was ascertained to belong to Ulmus (Tanai and Wolfe, 1977). Zelkova browni is distinguishable from Z. ungeri in marginal charac- ters: larger and rather bluntly deltoid teeth, some- times with a minute subsidiary tooth. Leaves of this species are highly variable in shape; some have a slightly cordate base and a minute subsidiary tooth on the primary teeth and superficially resemble some leaves of Ulmus owyheensis H. V. Smith. Ulmus owyheensis, however, differs from Z. browni in the serration of basal part of the lamina, the tertiaries branching outward from the basal pair of secondary veins, and the irregularly percurrent intercostal ter- tiary veins. Zelkova browni is similar to the modern Z. carpinifolia Spach of the Caucasus region in foliar shape and marginal serration. A single specimen figured as Planera ungeri from “English Bay” (Heer, 1869a) has the margin of Z. browni, although the lower half of the blade is lack- ing. It is significant in the past distribution of Zelkova that all specimens from the conterminous United States are of the Z. browni type and that this species lived together with the Eurasian species Z. ungeri in Alaska during the Miocene. Hypotypes. —USNM 208384—208388. Occurrence.—9856, 9858. SYSTE MATICS 3 1 Zelkora ungeri Kovats Plate 5, figures 4, 7; plate 6, figures 1, 2, 6 Zelkova ungeri Kovats in Unger, 1852, Iconog'r., p. 42, pl. 20, fig. 19. Kovats, 1856, Fossile Flora von Erdobenye, p. 27, pl. 5, figs. 6, 7. Tanai, 1961, Hokkaido Univ. Fac. Sci. Jour., ser. 4, v. 10, no. 2, p. 322, pl. 18, figs. 1—4, 6—9, 11. Discussion.—A number of our Alaskan specimens are identical with Zelkova ungeri, which is common in the Neogene of Eurasia. These leaves are charac- terized by apiculate, usually single-serrate teeth with somewhat incurved pointing tip. The tertiary veins in the intercostal areas are mostly wavy and typically appear to form irregularly quadragular or pentag- onal meshes due to thick connecting fourth order veins. These marginal and venation characters show that this species is closely related to the modern Z. serrata Mak. from Japan and Z. sinica Schn. from mainland China. As far as we know, Z. ungeri has not been found in the Tertiary of the conterminous United States. Becker (1969) reported a leaf of Z. ungeri from the Beaverhead basin of southern Montana, but his speci- mens appear to be referable to Z. browni in charac- ters of the serrations. Hypotypes.—USNM 208389—208393. Occurrence—9856, 9858. Family Fagaceae Genus Fagus Linn. Fagus antipofi Heer Plate 5, figure 8b; plate 6, figures 3, 4; plate 7, figures 1, 5, 6 Fagus antipofi Heer, in Abich, 1858, Acad. Sci. St. Petersburg Mem., ser. 6, v. 7, p. 572, pl. 8, fig. 2. Heer, 1869, Flora Fossilis Arctica, v. 2, pt. 2, p. 30, pl. 5, fig. 4a; pl. 7, figs. 4—8; pl. 8, fig. 1. Hollick, 1936, US. Geol. Survey Prof. Paper 186, p. 95, pl. 53, figs. 1, 2. Castanea ungeri Heer 1869, Flora Fossilis Arctica, p. 32, pl. 7, figs. 1—3. Fagus macrophylla auct. non Unger. Heer, 1869, Flora Fossilis Arctica, p. 31, pl. 8, fig. 2. Discussion—Leaves referred to Fagus are very common in the Seldovia Point localities; these leaves are generally elliptical to oblong in shape, typically serrate with minute teeth, and have 14 to 26 pairs of secondary veins. Although highly variable in gross shape and size, these Alaskan leaves match well those of Fagus antipofi in venation and marginal characters. The specimen figured as F. macrophylla from the “Eng- lish Bay” locality by Heer (1869a) represents a large leaf of F. antipofi. Heer also described three large- toothed leaves as Castanea ungeri from the same loc- ality; these are included in F. antipofi, because we also collected several leaves having a similar margin. Our material lacks the secondary vein termination near the teeth characteristic of Castanea. In measurements of many of the Seldovia Point specimens, including Heer’s material, the foliar characters of the Alaskan beech such as leaf indices (length to width ratio) is well consistent with measurements of F. antipofi from East Asia, as discussed elsewhere (Tanai, 1973). Hypotypes.—USNM 208394—298399. Occurrence—9856, 9858. Fagus aff. F. crenata Blume Plate 6, figure 5 Discussion.—A single elliptical leaf has, though in- complete, features characteristic of Fagus in venation and margin: the midvein is somewhat zigzag in its upper portion, the secondaries abruptly arise up along the margin, and the margin is sinuately undulate. Judging from the restoration, this leaf probably has less than 13 pairs of secondary veins. All these characters show that this specimen is closely similar to leaves of the extant F. crenata Blume in Japan. While F. crenata has been known to have appeared since the late Pliocene in Japan (Tanai, 1973), this Alaskan fossil beech is, though fragmentary, notewor- thy for the evolutionary history of beech. An undescribed leaf from the Oligocene part of the Kenai Group (Ice. 9884) has a margin of the Fagus crenata type. The number of secondary veins is, how- ever, well over 13, and in this feature the leaf is more similar to leaves of F. antipofi. We tentatively suggest that the lineage to which F. crenata belongs diverged from the F. antipofi line at high latitudes and has since migrated southward. Specimen.—USNM 208400. Occurrence—9856. Genus Quercus Linnaeus Quercus furuhjelmi Heer Plate 7, figures 2—4; plate 8, figures 1—3 Quercus furuhjelmi Heer, 1869, Flora Fossilis Arctica, V. 2, pt. 2, p. 32, pl. 5, fig. 10; pl. 6, figs. 1, 2. ?Hollick, 1936, US. Geol. Survey Prof. Paper 182, p. 98, pl. 55. Quercus pandurata Heer, 1869, Flora Fossilis Arctica, v. 2, pt. 2, p. 33, pl. 6, fig. 6. Populus leucophylla auct. non Unger. Heer, 1869, Flora Fossilis Arctica, v. 2, pt. 2, p. 26, pl. 2, fig. 6. Quercus etymodrys auct. non Unger. Hollick, 1936, US. Geol. Survey Prof. Paper 182, p. 98, pl. 54, figs. 6, 7. 32 Quercus pseudocastanea auct. non Goeppert. Heer, 1869, Flora Fossilis Arctica, V. 2, pt. 2, p. 32, pl. 6, figs. 3—5. Hollick, 1936, US. Geol. Survey Prof. Paper 182, p. 98, pl. 54, figs. 4, 5. Discussion.—The specimen assigned to this species by Hollick (1936, pl. 55) is fragmentary but does have several points of similarity to Quercus furuhjelmi. Hollick’s specimen, however, appears to have consid- erably more secondary veins than in any specimen of Q. furuhjelmi; this apparent difference, as well as the fragmentary nature of the specimen, makes specific assignment to Q. furuhjelmi questionable. The numerous large serrations of these leaves allies Quercus furuhjelmi to the so-called chestnut oaks. The chestnut oaks are, however, an apparently polyphy— 1etic group. The chestnut oaks of eastern Asia (for example, Q. crispula Blume) have been placed in the subgenus Heterobalanus in contrast to the chestnut oaks of eastern North America (for example, Q. prinoides Willd.), which are placed in subgenus Leucobalanus (Trelease, 1924); the one chestnut oak of western North America—Q. sadleriana R. Br.—has been allied to Leucobalanus by some authorities and to Heterobalanus by others. Examination of cleared leaves of almost all species of chestnut oaks does not indicate any fundamental distinction between foliage of these groups, although some species of Hetero- balanus have some aristate teeth, which are absent in Leucobalanus. Some specimens of Q. furuhjelmi also possess some aristate teeth (pl. 8, fig. 3), which indi— cates that this species is probably allied to Heterobalanus. Quercus furuhjelmi is similar to the Korean and Japanese Q. microcrispula Huz., which has been com- pared to both Q. crispula Blume (Huzioka, 1954) and to Q. mongolica Fisch. var. grosseserrata (Blume) R. et W. (Tanai, 1961). In having teeth that are narrowly rounded in the basal part of the lamina and that grade into acute to acute-aristate teeth near the apex, Q. furuhjelmi is distinct from these fossil and extant species. Hypotypes.—USNM 208401—208406. Occurrence—9856, 9858. Family Betulaceae Genus Alnus Linnaeus Alnus cappsi (Hollick) Wolfe Plate 8, figure 5 Alnus cappsi (Hollick) Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B, p. B19, pl. 6, figs. 1, 4; pl. 7, figs. 2, 6; text-fig. 6 [see synonymy]. Crataegus cappsi Hollick, 1936, US. Geol. Survey Prof. Paper 182, p. 86, pl. 49, fig. 3. MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Discussion—The close relationship of Alnus cappsi to the Alaskan Oligocene A. evidens indicates that this lineage is of Beringian origin. Hypotype.—USNM 208407. Occurrence.—9858. Alnus fairi (Knowlton) Wolfe Plate 8, figure 4; plate 9, figure 2 Alnus fairi (Knowlton) Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B, p. B17, pl. 7, fig. 3; text-fig. 3 [see synonymy.] Betula fairii Knowlton, 1926, US. Geol. Survey Prof. Paper 140, p. 33, pl. 17, fig. 4. Discussion.—Although Becker (1973) ignored the transfer of the Latah “Betula” fairii to Alnus, the type of ultimate venation possessed by both the Alaskan and Latah material (see Wolfe, 1966, text-fig. 3) of this species does not occur in Betula. Hypotypes.—USNM 208408, 208409. Occurrence.—9856 (Heer’s material), 9858. Alnus healyensis Wolfe Plate 8, figure 6; plate 9, figure 1 Alnus healyensis Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B, p. B17, pl. 7, fig. 4, text—fig. 4. Artocarpidium alaskanum Hollick, 1936 [part], U.S. Geol. Survey Prof. Paper 182, p. 108, pl. 59, fig. 5. Quercus oregoniana auct. non Knowlton. Hollick, 1936, US. Geol. Survey Prof. Paper 182, p. 103, pl. 50, fig. 5. Alnus relatus auct. non (Knowlton) Brown. Chaney and Axelrod, 1959 [part], Carnegie Inst. Wash- ington Pub. 617, p. 159, pl. 22, fig. 6 only. Discussion.—Alnus healyensis occurs in both the early (Collawash flora) and middle (Latah, Mascall) Miocene in the conterminous United States. In Alaska, this species occurs in the lower (Capps Glacier, Houston, Upper Healy Creek) and upper (Seldovia Point, Sanctuary/Suntrana) Seldovian. A species having, as in A. healyensis, sharp and basally refiexed secondary teeth is represented in the Oligocene Bridge Creek flora of Oregon (Klucking, 1959), and thus A. healyensis is thought to be of West American derivation. The Eocene A. kluckingi Wolfe also has similar but fewer teeth. Hypotypes.—USNM 208410, 208411. Occurrence—9856 (Hollick’s material from Coal Cove), 9858. Genus Betula Linnaeus Betula cf. B. sublutea Tanai et N. Suzuki Plate 9, figure 8 Betula sublutea Tanai and N. Suzuki, 1963, Tertiary floras of Japan, Miocene floras, p. 114, pl. 8, fig. 8; pl. 10, figs. 7—9. SYSTEMATICS 33 Discussion.—A single leaf is referred to Betula on the basis of its shape and marginal serration, par- ticularly on the basis of the apically pointing teeth and secondary veins. It is nearly identical with B. sub- lutea in having rather obtuse teeth and a cordate base, though the detailed venation is not visible. Our Alaskan leaf is different from the finely and sharply serrate B. vera R. W. Br., which was described from the Miocene of Washington. Specimen.—USNM 208413. Occurrence—9858. Genus Carpinus Linnaeus Carpinus seldociana Wolfe Plate 9, figure 7; plate 10, figures 1—3 Carpinus seldoviana Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B, p. B23, pl. 6, fig. 6; text-fig. 11D. Supplementary description.—Involucre obovate in shape, asymmetrically cuneate at base, rounded but abruptly pointed apex, 19 mm long and 9.6 mm wide; palmately three veined, the principal veins leaving the base, entering large teeth; secondary veins thin, diverging at nearly rights angles or obliquely from the principal veins, forming irregular networks with thinner tertiary veins; margin compoundly serrate in the upper half, sparse, minute teeth, excepting the principal three lobes; nutlet not preserved. Discussion.—This species is characterized by leaves having a strongly cordate base and apiculate mar- ginal teeth with aristate tips, thus closely resembling the modern Carpinus cordata Blume living in north- eastern Asia. The intercostal tertiary veins are nearly perpendicular to the secondaries, and typically bifur- cate halfway between the secondaries. The fourth and fifth order veins form quadrangular or pentagonal networks, which are rarely intruded by single branched veinlets. These venation characters also re- semble well those of the extant species. An incomplete involucre is closely similar to those of the extant C. cordata in shape and venation and is included in C. seldoviana. C. seldoviana occurs abundantly at the Seldovia Point locality and rarely at the Port Graham locality. This Alaskan species is probably related to C. subcor— data Nathorst, which is common in the Miocene of Ja- pan. Hypotypes.—USNM 208414—208417. Occurrence—9856, 9858. Genus Corylus Linnaeus Corylus sp. Plate 9, figure 3 Discussion.~ln shape of the teeth, these fragmen- tary leaves are similar to the extant Corylus chinensis Franch. The fossils, however, have areoles about half the size of the areoles of this extant species; in this feature, the fossils are more similar to species such as C. rostrata (Ait.) Pursh. These fossils thus represent a new species, but we consider the present material to be too fragmentary for the basis of a specific concept. One of the two specimens on which Heer (1869a, pl. 10, fig. 2) based his Tilia alaskana represents the same species, but that specimen (as well as the second fragment that is not Corylus) represents less than half a leaf; we, therefore, reject Tilia alaskana Heer (1869, p. 36, pl. 10, figs. 2, 3) under Article 70 of the International Code of Botanical Nomenclature. Specimens.—USNM 208418, 208419. Occurrence.—9856, 9858. Genus Ostrya Scop. Ostrya cf. 0. oregom'ana Chaney Plate 9, figures 4—6 Ostrya oregoniana Chaney, 1927, Carnegie Inst. Washington Pub. 346, p. 106, pl. 9, fig. 12; pl. 10, figs. 1, 4. Discussion—Our involucre specimens of Ostrya vary from elliptical to oval in shape and 7 to 11 in number of primary veins; these are nearly identical with the involucres of 0. oregoniana, which was de- fined by both leaves and involucres. Unfortunately we did not collect any leaves of Ostrya at the Seldovia Point localities. These Alaskan specimens are, there- fore, only tentatively assigned to 0. oregoniana, be- cause of the difficulty of making specific separations in Ostrya on the basis of involucres alone. Specimens.—USNM 208420—208422. Occurrence—9858. Family Juglandaceae Genus Carya Nuttall Carya bendirei (Lesquereux) Chaney et Axelrod Plate 10, figure 7; plate 11, figures 1, 2 Carya bendirei (Lesquereux) Chaney and Axelrod, 1959 [part], Carnegie Inst. Washington Pub. 617, p. 155, pl. 19, figs. 1—5 [not many items synonymized.] Wolfe, 1964, US. Geol. Survey Prof. Paper 454—N, p. N20, pl. 1, fig. 7. Graham, 1965, Kent State Univ. Bull, Research Ser., 9, p. 81, pl. 12, fig. 8. Rhus bendirei Lesquereux, 1888, US. Natl. Mus. Proc., v. 11, p. 15, pl. 9, fig. 2. Salix engelhardti Lesquereux, 1888, US. Natl. Mus. Proc., v. 11, p. 17, pl. 8, fig. 2. H icoria dentata Chaney, 1920, Walker Mus. Contr., v. 2, p. 163, pl. 8, fig. 1. 34 H icoria orientalis Chaney, 1920, Walker Mus. Contr., v. 2, p. 163, pl. 8, fig. 2. Hicoria pecanoides Chaney, 1920, Walker Mus. Contr., V. 2, p. 164, pl. 8, fig. 3. Carya egregia auct. non Juglans egregia Lesquereux. LaMotte, 1936, p. 116, pl. 4, figs. 5, 6; pl. 6, figs. 1, 2. Brown, 1937, US. Geol. Survey Prof. Paper 186, p. 169, pl. 57, fig. 4. Beck, 1938, Mineralogist, V. 6, no. 8, p. 22, text- fig. 3. . Smith, 1939, Michigan Acad. Sci. Papers, v. 24, p. 111, p1.7, fig. 1. Smith, 1941, Am. Midland Naturalist, V. 25, p. 500, pl. 5, fig. 3. Juglans egregia auct. non Lesquereux. Berry, 1931, US. Geol. Survey Prof. Paper 170, p. 35, pl. 11, fig. 3. Ptelea miocenica auct. non Berry. LaMotte, 1936 [part], Carnegie Inst. Washington Pub. 455, p. 133, pl. 11, fig. 4 only. Arbutus matthesii auct. non Chaney. LaMotte, 1936 [part], Carnegie Inst. Washington Pub. 455, p. 140, pl. 14, fig. 3 only. Discussion—Many of the items synonymized under Carya bendirei are rejected by us. For example, the types of Prunus? merriami Knowlton (1902, p. 67) represent Cyclocarya. Additionally, Carya simulata (Knowlt.) R. W. Brown (1937, p. 169) is considered to represent a valid species distinct from C. bendirei. In C. simulata, (1) the secondary veins fork conspicu- ously to give a ladderlike appearance to the secondary external veins and (2) the apical and basal sides of the teeth are equal in length. The Seldovia Point leaflets are assigned to Carya on the basis of (1) finely serrate margin with uniformly spaced and sized teeth, (2) mixed craspedodromous and camptodromous secondary venation, (3) central entry of the teeth by secondary or external secondary veins, (4) fourth rank venation, and (5) typically quadrangular areoles formed by fifth order veins and either lacking veinlets 0r intruded by simple veinlets. Carya is also known from the Neogene of eastern Asia (Hu and Chaney, 1940; Tanai and Suzuki, 1963), but the Asian C. miocathayensis Hu et Chan. is consis— tently camptodromous, has about 25 pairs of second- ary veins, and typically has a narrowly rounded base. In contrast, the Seldovian material—as in mate- rial of C. bendirei from the conterminous United States—has some camptodromous and some cras— pedodromous secondary veins, has fewer (about 12—18) pairs of secondary veins, and has some leaflets with a broadly rounded base. N0 extant species of Carya closely resembles C. bendirei. In members of MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA section Carya, which is exclusively North American, the teeth have a pronouncedly elongated basal side and tend to be pointed apically. In members of section Apocarya, which is disjunct between North America (Mexico and eastern United States) and east Asia (Vietnam and China), the teeth have apical and basal sides of almost equal length and many of the teeth are pointed abmedially. On this basis, C. bendirei is re- ferrable to Apocarya. Hypotypes.—USNM 208423, 208424. Occurrence.——9856, 9858. Genus Cyclocarya Iljinskaja Cyclocarya ezoana (Tanai et N. Suzuki) Wolfe et Tanai, comb. nov. Plate 10, figures 4—6, 8, 9 Pterocarya ezoana Tanai and N. Suzuki, 1963, Ter- tiary Floras Japan, v. 1, p. 110, pl. 6, figs. 2—5, 8, 9, 11; pl. 19, fig. 1; pl. 21, fig. 10. Ishida, 1970 [part], Kyoto Univ. Fac. Sci. Mem., Ser. Geology and Mineralogy, v. 37, no. 1, p. 70, pl. 5, fig. 2 only. Discussion—In establishing this species, Tanai and Suzuki (1963, p. 110) noted the close resemblance to leaflets of the extant Pterocarya paliurus Skan. This extant species, however, is now generally accorded monotypic status as Cyclocarya paliurus (Skan.) Ilj., and we consequently transfer the fossil material to Cyclocarya. As noted by Tanai and Suzuki (1963, p. 110), Cy— clocarya ezoana is readily distinguished from Pter— ocarya asymmetrosa in that the secondary veins bend sharply towards the apex about two—thirds of the dis- tance from the midrib to the margin and in having sharper and more widely spaced teeth. The same criteria also distinguish C. ezoana from P. nigella. Additionally, the areoles of Cyclocarya (including C. ezoana) are about one-half the size of the areoles in Pterocarya. Leaflets similar to the extant Cyclocarya also occur in the Neogene of the conterminous United States (Wolfe, 1959), but the material from the Pacific Northwest is specifically distinct from the Alaskan and Japanese material. In particular, the teeth of the material from the Pacific Northwest are broader, and the areoles are large as in Pterocarya, although in secondary venation and overall shape of the teeth the material is most similar to Cyclocarya. We suggest that the species from the Pacific Northwest represents an extinct lineage of Cyclocarya; the leaflets in the Collawash flora are associated with a fruit of Cy- clocarya. Hypotypes.—USNM 208425—208429. Occurrence—9856, 9858. SYSTEMATICS 35 Genus Pterocarya Kunth Pterocarya nigella (Heer) Wolfe Plate 11, figures 4, 6 Pterocarya nigella (Heer) Wolfe, 1966, US. Geol. Sur- vey Prof. Paper 398—B, p. B15, pl. 3, fig. 3. Juglans nigella Heer, 1869, Flora Fossilis Arctica, v. 2, pt. 2, p. 38, pl. 9, figs. 2—4. Juglans oregoniana Lesquereux, 1878, Harvard Coll. Mus. Comp. Zoology, Mem., V. 6, no. 2, p. 35, pl. 9, fig. 10. Salix varians auct. non Goeppert. Heer, 1869 [part], Flora Fossilis Arctica, V. 2, pt. 2, p. 27, pl. 2, fig. 8 only. Pterocarya mixta auct. non (Knowlton) Brown. Chaney and Axelrod, 1959, Carnegie Inst. Washington Pub. 617, p. 157, pl. 21. figs. 1, 2. Axelrod, 1964, California Univ. Pubs. Geol. Sci., v. 51, p. 115, pl. 10, figs. 8, 9. Discussion.—As noted previously (Wolfe, 1966, p. B15), these leaflets have features that ally them to the extant members of section Platyptera. In particular, leaflets of P. rhoifolia Sieb. et Zucc. are similar to the fossils. The Japanese Neogene P. asymmetrosa Kon’no is also closely similar to P. rhoifolia (Tanai and Suzuki, 1963, p. 110), and probably some material now referred to P. asymmetrosa is conspecific with P. nigella. Other material referred to P. asymmetrosa may, however, be referrable to other species, and we consequently defer a formal synonymy until such time as the Japanese Neogene material of this species is thoroughly reviewed. P. nigella was probably one of the most geographically wide ranging species, occur- ring from Oregon to Alaska and to Honshu. Hypotypes.—USNM 208430, 208431. Occurrence.—9856 (Heer’s material), 9858. Pterocaryu Sp. Plate 11, figure 7 Description—Fruit representing nut with two wings, incomplete in preservation, more than 17 mm wide and 8 mm high; wings linear-oblong in shape, rather thin in texture; alate veins thin, more than 10 in each wing, leaving the nut part, then branching once or twice toward the apical part of wing; nut ovoid, 6 mm high and 3.5 mm wide, pointed at apex; axis of nut parallel to the wing plane. Discussion.—A two-winged nut, though poorly pre- served, is certainly referable to Pterocarya; this specimen is closely similar to the extant P. fraxinifolia Skan. of the Middle East by its shape and the direction of nut axis. This fossil fruit may represent P. nigella, but leaflets of that species are more similar to P. rhoifolia than to P. fraxinifolia. Specimen.—USNM 208432. Occurrence—9856. Family Salicaceae Genus Populus Linnaeus Populus kenaiana Wolfe Plate 11, figure 9; plate 12, figure 1 Populus kenaiana Wolfe, 1966, US. Geol. Survey Prof. Paper, 398—B, p. B12, pl. 3, fig. 1. Vitis crenata Heer, 1869, Flora Fossilis Arctica, v. 2, pt. 2, p. 36, pl. 8, fig. 6. Populus lindgreni Knowlton, U.S. Geol. Survey 18th Ann. Rept., pt. 3, p. 725, pl. 100, fig. 3. Chaney and Axelrod, 1959, Carnegie Inst. Washington Pub. 617, p. 151, pl. 17, figs. 1—3. Vitis heeriana Knowlton and Cockerell, 1919, US. Geol. Survey Bull. 696, p. 648. Discussion.—Although a member of the aspen group of Populus, relationships to extant species ap- pear distant. This or a closely related species occurs in the middle and late Oligocene Alaskan flora; the youngest occurrence of the species in both Alaska and the conterminous United States is late Miocene. Hypotypes.—USNM 42264B, 208433. 0ccurrence.—9856 (Heer’s material), 9858. Papulus Sp. Plate 11, figure 8 Discussion.—This fragmentary specimen has lat- eral primary veins that extend more admedially than apically (as is typical in Populus kenaiana). Although representing a separate species, the material is in- adequate for specific determination. Specimen.—USNM 208434. Occurrence.—9858. Genus Salix Linnaeus Four morphologic types can be differentiated in the Seldovia Point material of Salix. The previously de- scribed S. picroides is characterized by the small, api- cally pointing teeth that may be appressed to the lamina; the tertiary venation is irregular but tends to be percurrent, and the lamina tends to be narrowly oblanceolate. In shape, S. cappsensis is similar to S. picroides, but the former species has large, widely spaced, and basally reflexed teeth and the tertiary ve- nation is more uniformly percurrent. Salix seldoviana has an elliptical shape, but most characteristic are the small, closely spaced, and irregularly shaped teeth. Salix hopkinsi is almost entire margined, has a nar- rowly elliptic shape, and has closely spaced tertiary veins. None of the Seldovia Point species of Salix are known outside of Alaska; the material listed as S. in- quirenda Knowlt. by Wolfe (1966) is now considered to represent S. picroides. Salix seldoviana is similar to 36 MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA some leaves attributed to S. varians Goepp., but leaves of the varians type from the German Miocene do not have a margin as finely serrate as S. sel- doviana. The relationships of the Seldovia Point species of Salix to extant species are not clear. Salix cappsensis is thought to be in the same lineage that gave rise to the extant Alaskan S. richardsonii Hook., and S. picroides has some similarities to the extant S. pseudomonticola Ball (Wolfe, 1966); these suggested relationships, as well as the relationships of S. sel— doviana and S. hopkinsi, require further study, par- ticularly considering the large amount of as yet spe- cifically undetermined material of Salix in the collec- tions from the Homerian and Clamgulchian. This material should provide much information on the re- lationships of the Seldovia Point willows to extant species. Salix cappsensis Wolfe Plate 12, figure 8; plate 13, figures 1, 2, 4; plate 14, figures 3, 4 Salix cappsensis Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B, p. B12, pl. 4, fig. 6. Discussion.—A closely related but undescribed species occurs in Oligocene beds at Kukak Bay; this older species has fewer teeth than Salix cappsensis. As noted previously (Wolfe, 1966), S. cappsensis appears to be ancestral to the Homerian S. chuitensis Wolfe and, in turn, to the extant S. richardsonii Hook. Hypotypes.—USNM 208435—208439. Occurrence.—9858. Salix hopkinsi Wolfe et Tanai, sp. nov. Plate 12, figure 4; plate 13, figures 5, 6 Description.—Leaves simple, venation pinnate; shape narrowly elliptic, apex acute, base acuminate; length 4.5 to 7.0 cm, width 2.0 to 2.8 cm; about seven pairs of secondary veins, irregularly spaced, departing at an angle of 60 to 80 degrees, some slightly decur— rent, bending sharply towards apex, eucamptodrom- ous, approaching margin closely; intersecondaries numerous, gradational with tertiary veins; tertiary veins irregularly spaced, oblique to secondary veins, branching, sinuous; fourth order venation forming a highly irregular reticulum of thinning veins and ap- parently forming areoles; margin entire except for a few irregularly spaced small teeth; petiole incomplete, at least 0.5 cm long. Discussion.—Leaves of Salix from the Homerian appear similar to Salix hopkinsi; whether these younger specimens are conspecific with S. hopkinsi requires further study. We take pleasure in naming this species for David M. Hopkins, who has aided this study in numerous ways. Holotype.—USNM 208440. Paratype.—USNM 208441. Occurrence. —9858. Salix picroides (Heer) Wolfe Plate 12, figures 5—7; plate 13, figures 3, 7 Salix picroides (Heer) Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B p. B14. Juglans picroides Heer, 1869, Flora Fossilis Arctica, v. 2, pt. 2, p. 39, pl. 9, fig. 5. Discussion.—Salix picroides is also represented in collections from the lower Seldovian at Capps Glacier and Houston. In the Nenana coalfield, S. picroides also occurs in both the lower and upper Seldovian. Hypotypes.—USNM 208442—208445. Occurrence—9856 (Heer’s material), 9858. Salix seldociana Wolfe et Tanai, sp. nov. Plate 12, figures 2, 3; plate 14, figure 2 Description.—Leaves simple, pinnately veined; shape elliptical, apex not known, base cuneate; length 8.5 to more than 10 cm, width 5 to 6 cm; about nine pairs of secondary veins, irregularly spaced, departing at an angle of 50 to 70 degrees, eucamptodromous, ap- proaching margin closely; a few short intersecondary veins; tertiary veins oblique to secondary veins, tend— ing to be oriented perpendicular to midrib in outer part of intercostal area, percurrent to branching, somewhat sinuous; fourth order venation forming a reticulation of irregular shape and size; fifth order and ultimate venation indistinct; margin finely serrate, basal side of tooth convex, about twice as long as api- cal side, which is slightly convex to straight; teeth en- tered centrally by branches of secondary veins; petiole incomplete, at least 0.5 cm long. Discussion—The finely serrate margin combined with the few secondary veins and few short intersec- ondary veins separate this species from others found at Seldovia Point. Salix seldoviana does not closely re- semble any other known Alaskan Tertiary Salix. Holotype.——USNM 208446. Paratype.—USNM 208447. Occurrence.—9858. Family Tiliaceae Genus Tilia Linnaeus Tilia subnobilis Huzioka Plate 15, figure 1 Tilia subnobilis Huzioka, 1943, Hokkaido Univ. Fac. Sci. Jour., ser. 4, v. 7, no. 1, p. 125, pl. 22, figs. 2, 3. Tanai, 1961, Hokkaido Univ. Fac. Sci. Jour., v. 11, no. 2, p. 370, pl. 29, fig. 1. SYSTEMATICS 3 7 Discussion—A single leaf is referred to the genus Tilia onrthe basis of its venation and marginal serra- tions with glandular teeth. The tertiary veins are nearly straight or slightly convex and percurrent; the fourth order veins are thin, forming quadrangular or pentagonal meshes that are penetrated by once- or twice-branched veinlets. This Alaskan specimen is re- ferred to T. subnobilis in the oval shape, deeply cor- date base and venation, although the marginal teeth are smaller in the Alaskan leaf. T. subnobilis has been reported from a few localities in the lower and middle Miocene of Hokkaido and Korea. Our specimen shows a slight resemblance in general outline to T. oregona LaMotte from the Bridge Creek flora of Ore— gon (LaMotte, 1935) but differs in venation charac- ters. Hypotype.—USNM 208448. Occurrence—9856. Family Hydrangeaceae Genus Hydrangea Linnaeus Hydrangea sp. Plate 14, figure .1 Discussion.—A single leaf and its counterpart, al- though fragmentary, show characters of the genus Hydrangea in having finely and closely serrate mar— gin and the secondary veins loop well within the mar- gin. Superficially these specimens resemble Prunus el- liptica but differ in the sharply rising secondary veins and marginal looping. This Alaskan specimen is closely similar in venation to an incomplete leaf de- scribed as Ilex insignis Heer from the "English Bay” (Heer, 1869a) locality but differs in the marginal teeth, if his specimen was accurately illustrated. Specimen.—USNM 208449A, B. Occurrence—9858. Family Rosaceae Genus Crataegus Linnaeus Crataegus chamissoni (Heer) Wolfe et Tanai, comb. nov. Plate 14, figures 5. 6 Quercus chamissoni Heer, 1869, Kongl. Svenska Vet.-Akad. Handl., v. 8, p. 33, pl. 6, figs. 7, 8. Discussion—The type specimens of Quercus chamissoni have a cuneate base, irregularly duplicate-dentate teeth, and irregularly spaced sec— ondary veins that enter the teeth that are mixed craspedodromous-camptodromous. The camptodrom- ous secondaries join with the next secondary above or with the intersecondaries. These characters show that Heer’s specimens are not leaves of Quercus but are those of Crataegus. Two incomplete specimens in our collections are re- ferred to Crataegus chamissoni; one specimen is ovate-lanceolate in shape, quite similar to one of the type specimens (Heer, 1869a), pl. 6, fig. 8), while another is obliquely ovate, having well-preserved fine venation. In venation and marginal characters C. chamissoni is similar to the extant C. douglasii Lindl. of western North America, which includes ovate- lanceolate to oval leaves. Hypotypes.-—USNM 208450, 208451. Occurrence.—9856 (Heer’s material), 9858. Genus Prunus Linnaeus Prunus kenaica Wolfe et Tanai, Sp. nov. Plate 15, figures 2, 5 Description.—Leaves elliptic to elliptic-oblong in shape, 10.7 to 17 cm long (estimated) and 4.2 to 5.3 cm wide; base gradually narrowed, broadly cuneate, apex unknown; midrib stout, nearly straight or slightly ar- cuate; secondary veins somewhat slender but distinct, more than 11 pairs, subopposite, somewhat irregu— larly spaced, diverging from the midvein at angles of 40 to 50 degrees in the lower half of blade, at wider angles in the upper, nearly straight and then turning up near the margin, camptodromous, looping dis- tinctly with the next secondary above; tertiaries branching outward from the secondaries also looping well within the margin; fourth order veins branching from the looping tertiaries entering teeth or irregu- larly looping; intercostal tertiaries forming large, ir- regularly polygonal networks that enclose small fourth order nets; veinlets once or twice branching; margin finely serrate with inward-pointed, acute teeth; texture rather thin; petiole missing. Discussion.—Three leaves and their counterparts are referred to the genus Prunus on the basis of their marginal loops and serrations. The fourth and fifth order veinlets show a close similarity to those of many modern cherry leaves. In the conterminous United States no cherry leaves are comparable to this new species. Several fragmentary leaves were described under the name of P. scotti Heer from Paleocene of Greenland (Heer, 1868, 1869b, 1880, 1883) and some show close resemblance in secondary venation and shape, although the finer venation was not figured. Two leaves described as P. scotti from the Mormon Creek flora of southwestern Montana (Becker, 1960) are different in venation from P. kenaica, although somewhat similar in shape. Among extant species our specimens are similar to leaves of P. bicolor Koehne and especially P. vanioti Levl., which live in Szechuan. Holotype.—USNM 208452. Paratype.—USNM 208453. Occurrence. ——9856. 38 Prunus aff. P. padus Linnaeus Plate 14, figure 7 Description.—Leaf incomplete, almost half missing, broadly ovate in general shape, acute or probably acuminate at apex, base unknown; midrib stout, slightly arcuate; secondary veins distinct, about 10 subopposite pairs, irregularly spaced, diverging from the midrib at angles of 40 to 50 degrees in the middle and upper parts of the lamina, higher angles in the lower part, slightly curving upward, then forming dis- tinct, large loops with the next secondary above; some slender intersecondary veins leaving the midvein, nearly parallel to the secondaries, halfway to the margin connecting with the tertiaries; tertiary veins branching from the secondaries near the margin, forming small marginal loops; fourth order veins branching from tertiary vein loops, entering marginal teeth; intercostal tertiaries irregularly percurrent or branching, enclosing quadrangular or pentagonal areoles; areoles intruded by once or twice branching veinlets; margin coarsely duplicate serrate with acute teeth; texture probably thin; petiole missing. Discussion—A single leaf and its counterpart, al- though incomplete, shows venation typical of Prunus and is distinguishable from the P. elliptica in having an ovate shape and coarser marginal serrations. Among the fossil cherry leaves of North America, our specimens are somewhat similar to some leaves of Prunus? merriami Knowlton from the Miocene se— quence of Oregon (Knowlton, 1902, pl. 11, figs. 6, 7 (not figs. 2, 3) ) but are different in the marginal loop- ing of the secondaries. Except for this species, no fossil cherry leaves are comparable to our specimens; these Alaskan specimens are, however, too incomplete to form the basis for a new species. Among extant Prunus, our leaves are most similar to P. padus L. of northeastern Asia. Specimen.—USNM 208454A, B. Occurrence—9858. Genus Sorbaria A. Braun Sorbaria hopkinsi (Wolfe) Wolfe et Tanai, comb. nov. Plate 16, figures 1—2 Spiraea hopkinsi Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B, p. B24, pl. 8, fig. 2. Discussion.—The generic determination of this species was based on comparisons to the extant "Spiraea” lindleyana. This modern species, however, is properly placed in Sorbaria, a small genus of north- east Asian shrubs. Sorbaria has been previously found as fossil in the Eocene of Sakhalin (Borsuk, 1956); an undescribed species has also been found in the late Oligocene rocks of the Alaska Range (Ice. 9749 of Wahrhaftig and MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA others, 1969), and an additional species is known in the early Seldovian Capps Glacier flora. The strati- graphic range of S. hopkinsi is now known to be longer than indicated by Wolfe, Hopkins, and Leopold (1966). This report extends the range downward into the upper Seldovian Stage, and collections made in 1967 from the lower part of the Clamgulchian along Kachemak Bay also includes this species. S. hopkinsi is, however, much more common and widespread in rocks of Homerian age. Hypotypes.—USNM 208455—208458. Occurrence—9858. Family Leguminosae Genus Cladrastis Rafinesque Cladrastis cf. C. am'ensis Huzioka Plate 15, figure 4; plate 16, figures 3, 4 Cladrastis aniensis Huzioka, 1963, Tertiary floras of Japan, Miocene floras, p. 205, pl. 35, figs. 5, 6. Discussion.—Two leaflets, although incomplete, are referred to the genus Cladrastis on the basis of vena- tion characters and are closely similar to C. aniensis Huzioka from the middle Miocene of Japan. Our leaf- lets have a lower angle of departure of the second- ary veins and have two more secondary veins than the type specimens. These differences are not thought to be specifically significant, but we hesitate to refer them to C. aniensis because our specimens are incom- plete. The Alaskan specimens have the fine venation preserved and are closely similar to the modern C. platycarpa (Maxim.) Mak. living in central and west- ern Honshu and Shikoku, Japan. An incomplete flat- tened pod including three seeds is linear in shape and has irregular networks between the dorsal and ven— tral ridges. This pod of Cladrastis is additional evi- dence of the presence of this genus in the Seldovia Point flora. On the basis of well-preserved leaflets, Wolfe (1966) reported Cladrastis from the Homerian flora (loc. 9844 and 9361) and the Capps Glacier flora (loc. 9845). These leaves were described as C. japonica by emend- ing Nyssa japonica Tanai and N. Suzuki from the Miocene Yoshioka flora of Hokkaido (Tanai and Suzuki, 1963) and further by including C. aniensis. However, our further investigations reveal that the type specimens of "Nyssa japonica” are not Cladrastis (although they are also not Nyssa) but that all Alas- kan leaflets described as "C. japonica” are rather simi— lar to the modern C. lutea. This second Alaskan species of Cladrastis is distinguishable from C. anien- sis in shape, number of the secondary veins, and ir- regular, well-developed, percurrent tertiary veins. Ac- cordingly, these Cladrastis leaflets from the Homerian SYSTEMATICS 39 and the Capps Glacier locality should be described as a new species. Specimens.—USNM 208459, 208460. Occurrence—9858. Genus Pueraria DeCandolle Pueraria miothunbergiana Hu et Chaney Plate 15, figure 3 Pueraria miothunbergiana Hu and Chaney, 1938, Palaeont. Sinica, New Ser. A, no. 1, p. 52, pl. 28, fig. 1. Discussion.—A single leaflet and its counterpart compare well with terminal leaflets of the Pueraria in shape and venation characters: both the secondary and tertiary veins branch outward from the secon- daries, gently curve up along the margin, but do not form distinct marginal loops; the intercostal tertiaries are irregularly percurrent and frequently fork once. Our specimens are, although small in size, identical to P. miothunbergiana, which has been reported from the lower and middle Miocene of east Asia. This Alaskan fossil is the first record of the genus Pueraria in North America. Hypotype.—USNM 208461. Occurrence.—9858. Family Lythraceae Genus Decodon J. F. Gmelin Decodon alaskana Wolfe et Tanai, sp. nov. Plate 15, figure 6; plate 16, figures 5, 7, 8. Description.-—Leaves simple; shape oval to linear oval, base acute, apex acute to acuminate; length 5 to more than 10 cm, width 3 to 6 cm; pinnately veined; 12 to 15 pairs of irregularly spaced secondary veins departing from midrib at 80 to 90 degrees, slightly curving, sharply brochidodromous; one or two inter- secondary veins per intercostal area; tertiary venation forming a large, irregular mesh, the veins at a vari- able angle relative to the secondaries; fourth order veins of irregular pattern; a series of marginal loops by branches of the secondary veins irregular in size and tending to be elongated perpendicular to the mid- rib; margin entire. Discussion.—The pronounced series of brochidod- romous loops that form an intramarginal vein readily differentiate Decodon alaskana from other members of the Seldovia Point flora. Such major venation is characteristic of members of Myrtales and allied or— ders (Hickey and Wolfe, 1975). Within most myrta- lean families, the intramarginal vein is a continuous arc, but in the Seldovia Point leaves—as in leaves of the extant D. verticillatus (L.) E11.—the intramargi- nal vein is formed by a series of arcs. Further re- semblances between the fossils and modern leaves of Decodon are in the presence of weak loops abmedial to the intramarginal vein, the presence in some intercos- tal areas of a tertiary vein system that (1) extends di- rectly to the intramarginal vein (intersecondary veins) and giving off right-angle branches to the sec- ondary veins, or (2) extends only a short distance from the midrib, and the presence of a weak fourth order vein system. The fossils differ slightly from modern leaves of Decodon in having a higher proportion of in- tersecondary veins that extend to the intramarginal vein and in having the loops at the margin elongated perpendicular to the midrib (in D. verticillatus the loops are approximately square or are elongated parallel to the midrib). The Seldovia Point specimens of Decodon occur on the same slabs as leaves of Salix. Such an association is to be expected in view of the marsh to swamp habitat of D. verticillatus and many extant species of Salix. Decodon was particularly Widespread in the Neogene of Eurasia (Dorofeyev, 1963; Eyde, 1972), but the Seldovia Point material represents the first occur- rence of the genus as a fossil in North America. The leaf described as Myrtus oregonensis Lesq., however, probably represents Decodon; despite the specific epithet proposed by Lesquereux (1883), the leaf actu- ally came from the late Miocene of California (Condit, 1938). The same or a closely allied species also occurs in the Miocene Collawash flora of Oregon (Wolfe, un- pub. data). Holotype.—USNM 208462. Paratypes.—USNM 208463, 208464. Occurrence—9858. Family Trapellaceae Genus Hemitrapa Miki Hemitrapa borealis (Heer) Miki Hemitrapa borealis (Heer) Miki, 1953, Palaeobotanist, v. 1, p. 349, text-fig. 2 A. Trapa borealis Heer, 1869, Kongl. Svenska Vet.-Akad. Handl., bd. 8, no. 4, p. 38, pl. 8, figs. 9—14. Discussion.—This species was transferred from the genus Trapa by Miki (1953) and is characterized by having two spindle-shape appendages and a well- developed brushy haired apical part. Heer (18693) figured several specimens from the "English Bay” loc- ality, but later collections from this and other Seldo- vian localities have failed to produce additional specimens. Hemitrapa has been described from nu- merous lower and middle Miocene localities of Japan and Sakhalien; the only putative occurrence from the conterminous United States (MacGinitie, 1937) is 40 based on material properly referable to Trapa. Occurrence—9856 (Heer’s material). Family Aceraceae Genus Acer Linnaeus Five species of Acer were originally thought to be represented in the Seldovia Point flora (Wolfe, 1966), but our studies indicate the presence of only four. Other Seldovian localities, however, have produced representatives of two additional species related to the extant A. saccharinum and A. pennsylvanicum (or A. rufinerve). Presumably a species of Acer related to the extant Asian A. mono was also a member of the Sel- dovian flora, because a closely related species (A. scot— tiae) is known from the middle and late Miocene of the Pacific Northwest. Clearly Acer was an important element in the early and middle Miocene flora of Alaska. Acer ezoanum Oishi et Huzioka Plate 17, figures 1—3, 5; plate 19, figures 2, 5 Acer ezoanum Oishi and Huzioka, 1943, Hokkaido Univ. Fac. Sci. Jour., ser. 4, v. 7, p. 89, pl. 10, figs. 1—4; pl. 11, figs. 1—4; pl. 12, fig. 2. Tanai and N. Suzuki, 1969, Hokkaido Univ. Fac. Sci. Jour., ser. 4, V. 10, p. 556, pl. 1, figs. 1, 2; pl. 2, figs. 1, 2; pl. 3, figs. 1—4; pl. 9, figs. 20—25 [see synonymy for references through 1960.]. Tanai, 1961, Hokkaido Univ. Fac. Sci. Jour., ser. 4, V. 11, p. 356, pl. 26, figs. 1, 2, 5. Tanai and N. Suzuki, 1963, Tertiary Floras Ja- pan, V. 1, p. 137. Huzioka, 1964, Akita Univ. Mining Coll. Jour., ser. A, V. 3, no. 4, p. 89, pl. 14, figs. 6—9. Wolfe, 1966, US. Geol. Survey Prof. Paper 398—B, p. B25, pl. 8, fig. 6. Ishida, 1970, Kyoto Univ. Fac. Sci. Mem., Geology and Mineralogy Ser., V. 37, p. 95. Huzioka, 1972, Akita Univ. Mining Coll. Jour., ser. A, v. 5, no. 1, p. 63, pl. 8, fig. 2. Tanai and N. Suzuki, 1972, Hokkaido Univ. Fac. Sci. Jour., ser. 4, V. 15, p. 335, pl. 7, figs. 1—5. Discussion.—A number of leaves are referred to A. ezoanum, which was originally described from the lower Miocene of Hokkaido and Sakhalin. Several winged fruits with expanded seeds are also found from the same locality and are also referred to A. ezoanum. Our Alaskan leaves are more closely related to those of the modern Japanese maple, A. miyabei Maxim., than to any of the North American maples. Leaves of A. ezoanum closely resemble in general appearance those of the modern A. macrophyllum Pursh. but dis- MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA tinctly differ in fine venation. The quadrangular or pentagonal areoles are intruded by simple or once branched veinlets in A. ezoanum as well as in A. miyabei, but the irregularly four-sided areoles are in- truded by twice or more branched veinlets in A. mac- rophyllum. The only other known Alaskan occurrence of Acer ezoanum is a leaf from locality 9848 along Beluga River (Wolfe, 1966). This locality is apparently also of middle Miocene age (see p. 8). Hypotypes.—USNM 208465—208470. Occurrence.—9856 (fruits), 9858 (fruits and leaves). Acer glabroides R. W. Brown Plate 17, figures 7, 8 Acer glabroides Brown, 1937, US. Geol. Survey Prof. Paper 186—J, p. 180, pl. 58, figs. 13—15. Discussion.-—Tw0 samaras are similar to both Brown’s type material and to the extant Acer rubrum. No leaves of the rubrum type have yet been collected from Seldovia Point, but such leaves occur at other Seldovian localities (for example, loc. 9867 on Cache Creek). Hypotypes.—USNM 208471, 208472. Occurrence—9858. Acer grahamensis Knowlton et Cockerell Plate 17, figure 6; plate 18, figure 5; plate 19, figures 1, 4 Acer grahamensis Knowlton and Cockerell, 1919, US. Geol. Survey Bull. 696, p. 50. Acer macropterum Heer, 1869, Flora Fossilis Arctica, V. 2, pt. 2, p. 37, pl. 9, figs. 8, 9 (excluding fig. 7). Discussion.—Two samaras are identical to Acer macropterum in their large size and venation of the wing; this species was originally described from the "English Bay” locality by Heer (1869a). The epithet instituted by Heer is, however, a junior homonym, and Knowlton and Cockerell (in Knowlton, 1919) pro— posed the name A. grahamensis for this material. Al- though our samaras are also incomplete as in the case of Heer’s specimens, one of ours has an elliptical seed and suggests that this species may be related to the extant A. macrophyllum Pursh. living in the western United States. A fragmentary leaf was included in A. macropterum by Heer, but that leaf does not appear to be similar to A. macrophyllum. Two deeply lobed leaves of Acer from Seldovia Point are, although fragmentary, distinctly different in the secondary ve- nation looping and the pattern of fine veinlets from foliage of A. ezoanum; especially the veinlets usually branch more than twice and are closely similar to those of A. macrophyllum. Accordingly, these two in- complete specimens may represent leaves of A. SYSTEMATICS 41 grahamensis. This species is closely similar to A. oregonianum Knowlton from the Miocene of the con- terminous western United States. Chelebaeva (1968) assigned samaras from the middle Miocene of Kam- chatka to Acer cf. grahamensis. Although in features pereserved her specimens are similar to A. grahamen- sis, we concur with Chelebaeva that the lack of seeds attached to the samaras makes the specific determina- tion uncertain. Hypotypes.—USNM 208473—208475. Occurrence—9856, 9858. Acer heterodentatum (Chaney) MacGinitie Plate 16, figure 6; plate 17, figure 4; plate 18, figures 2—4; plate 19, figure 3 Acer heterodentatum (Chaney) MacGinitie, 1953, Car- negie Inst. Washington Pub. 599, p. 140, pl. 57, fig. 3 [see synonymy and discussion]. Discussion—This species is represented by two terminal and several lateral leaflets that show a close resemblance to the modern Acer negundo L. and A. henryi Pax. Leaflets of this type are uncommon in the Tertiary of the conterminous western United States, but fruits of the negundo type have been commonly reported. Our Alaskan leaflets are generally larger than the type specimens: the terminals are 9 to 12 cm (estimated) long and 8 to 9.5 cm wide, and the laterals are 9 to 18 cm long and 3 to 8 cm wide. These leaflets are more closely related in venation to A. negundo than to the East Asiatic A. henryi or A. Cissifolium (Sieb. and Zucc.) K. Koch.: the fourth order veins form irregularly quadrangular or pentagonal meshes, which are intruded by unbranched or once branched veinlets. However, two samaras from the same local- ity closely resemble those of A. cissifolium in their shape and size of seeds. There have been several different opinions regard- ing the specific name for this Tertiary boxelder. As already noted by MacGinitie (1953, p. 141), two types of Rulac crataegifolium and Phyllites bifurcies are too poorly preserved to serve as type specimens, though they resemble the modern boxelder leaflets. Although Rulac crataegifolium was transferred to Acer by LaMotte (1952, p. 53), the new combination in any case is homonymous for the extant A. crataegifolium Sieb. et Zucc. Chaney and Axelrod (1959) nominated “Acer minor,” but the type specimen figured by Knowlton (1902) lacks the seed and is not an adequate name-bearing specimen. Thus we concur with Mac- Ginitie (1953) and accept A. heterodentatum as the oldest valid combination for this species. Hypotypes.—USNM 208476—208481. Occurrence—9858. Family Nyssaceae Genus Nyssa Linnaeus Nyssa cf. N. knowltom' Berry Plate 18, figure, 1 Nyssa knowltoni Berry, 1929, US. Geol. Survey Prof. Paper 154—H, p. 261, pl. 59, fig. 7. Discussion.—One leaf, although fragmentary, is as- signed firmly to Nyssa on the basis of its venatiOn characters and irregularly large teeth. It closely re- sembles the leaves described as N. knowltoni from the Miocene Latah flora of Oregon (Berry, 1929; Brown, 1937) but is too fragmentary for specific determina- tion. Brown (1937) and Chaney and Axelrod (1959) transferred many Tertiary fossil leaves from the west- ern United States resembling the modern N. aquatica to N. hesperia, which was originally defined on the basis of seeds (Berry, 1931). However, as already pointed out by Eyde (1963), it can be difficult to dis- tinquish the modern N. aquatica and N. sylvatica by only external features of the seeds. Furthermore, some leaves of N. sylvatica have large irregularly spaced teeth, similar to those of N. aquatica. Until, therefore, venation characters are thoroughly investi- gated in west American leaves of Nyssa, the synonymy of N. hesperia and N. knowltoni cannot be accepted without scepticism. Specimen.—USNM 208482. Occurrence.—9858. Family Alangiaceae Genus Alangium Lamarck Alangium mikii Wolfe et Tanai, sp. nov. Plate 20, figures 1, 2; plate 21 Marlea aequalifolia (Goeppert) Oishi, 1950, Illust. Catalogue of East Asiatic Fossil Plants, p. 171, pl. 50, fig. 1. Tanai, 1952, Japanese Jour. Geology and Geog- raphy, V. 22, p. 132, pl. 5, fig. 3. Huzioka, 1955, Illust. Fossil Catalogue in Fukui Pref., no. 6, p. 8, pl. 3, figs. 6—8. Alangium aequalifolium (Goeppert) Kryshtfovich and Borsuk, 1939, Problems Palaeont, no.5, p. 390, pl. 5, figs. 1—8; pl. 6, fig. 12. Tanai, 1961, Hokkaido Univ. Fac. Sci. Jour., ser. 4, v. 11, no. 2, p. 371, pl. 30, fig. 1; pl. 31, fig. 9. Huzioka, 1963, Tertiary Floras of Japan, Miocene Floras, p. 212, pl. 38, fig. 9. Matsuo, 1963, Tertiary Floras of Japan, Miocene Floras, p. 242, pl. 52, fig. 6; pl. 53, figs. 3—5 (excluding pl. 53, fig. 1). Huzioka, 1964, Akita Univ. Mining Coll. Jour., ser. A, v. 3, no. 4, p. 96, pl. 17, fig. 1. Huzioka, 1972, Akita Univ. Mining Coll. Jour., ser. A, v. 5, no. 1, p. 70, pl. 14, fig. 4. ?Marlea iragawaense Tanai, 1952, Japanese Jour. 42 Geology and Geography, v. 22, p. 133, pl. 5, fig. 5. Description.——Leaves simple, actinodromous; shape symmetrical to asymmetrical and broadly oval, apex acute, base cordate and typically asymmetrical; length 10 to more than 22 cm, width 10 to more than 22 cm; four or five pairs of lateral primaries, the first pair (from the midrib) paralleling the medial secon- dary veins and extending into the apical half of the lamina, five to seven lateral secondaries on basal side; second lateral pair of primaries paralleling secon- daries of first lateral primary, also with five to seven pairs of lateral secondaries on basal side (these are absent or reduced on smaller side of highly asymmet— rical laminae); third lateral primary veins conspicu- ous only on enlarged side of highly asymmetrical laminae, with three or four lateral secondary veins; medial secondary veins five to seven pairs, departing at an angle of 60 to 70 degrees, straight to broadly curving, brochidodromous, looping close to margin; in- tersecondary veins typically absent; tertiary veins regularly and closely spaced, perpendicular to secon- daries, branched or percurrent, slightly arched abme- dially; fourth order veins numerous, closely spaced, perpendicular to tertiaries, branching acutely; fifth order veins forming a polygonal areolation that is in- truded by profusely branching freely ending veinlets; margin entire; petiole thick, incomplete but more than 3 cm long. Discussion.—Considerable uncertainty and confu- sion exist concerning the nomenclatural and systema— tic position of Alangium—like foliage from the Tertiary of Eurasia. Many Alangium—like leaves have previ- ously been referred to either A. aequifolium (Goepp.) Krysht. et Bors. or A. tiliaefolium (Ung.) Krysht.; both species are based on material from the European Ter— tiary record. Knoblock and Kvacek (1964), however, synonymized these two species and further considered them to represent a sterculiaceous plant, Byttneriophyllum tiliaefolium (A. Braun) Knobl. et Kvac. This reassignment is based on examination of nontype material from Tertiary rocks of Czecho- slovakia, which showed that this material possessed compound trichomes in contrast to the uniformly sim- ple trichomes in extant Alangium. We emphasize that the megascopic characters of the leaves from which Knobloch and Kvacek obtained cuticular material have not been illustrated (Knobloch and Kvacek, 1964, p. 162). In Byttneria, as in most woody Malvales, the fourth and higher order venation is organized into pronouncedly orthogonal patterns (that is, the branching of any particular order is at approximately right angles), and the various orders of venation are well differentiated in size from one another (see Knobloch and Kvacek, 1964, pl. IV). In MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Alangium, the fourth and higher order venation branches at definite acute angles (a Y-shaped pattern predominates in the fourth order venation), and the veins thin so gradually that the fourth and higher order veins are not clearly differentiated in size. Examination of topotypic material of Byttneriophyl- lum tiliaefolium (=Cordia tiliaefolia A. Braun) from Oeningen (material in the US. Geol. Survey collec- tions) substantiates Knoblock and Kvacek’s (1964) opinion. This material has an orthogonal pattern in the fourth and higher order venation. Material from Sotzka, on which Goeppert based Dombeyopsis aequifolia, has not been examined; Goeppert’s (1852) illustrations of this species are inadequate for deter- mination, but, if accurately drawn, the specimen on the same slab assigned to Dombeyopsis grandifolia would also be malvalean because of the predominately orthogonal fourth order venation. The east Asian N eogene leaves reassigned by Knob- loch and Kvacek (1964) to Byttneriophyllum tiliaefolium, however, have intercostal venation of Alangium. These leaves represent the same species as that found at Seldovia Point and the Capps Glacier Seldovian. The Capps Glacier material, moreover, shows that the trichomes are all simple (pl. 20, fig. 2), leaving no reasonable doubt that Alangium is repre— sented. The epithet iragawaense is rejected for these leaves because it is based on poorly preserved mate— rial. We have, therefore, established a new species, A. mikii, to include the Alaskan and east Asian Neogene leaves previously assigned to A. aequifolium. Although Alangium was a conspicuous element in some Paleogene floras in North America (MacGinitie, 1969; Eyde and others, 1969), this is the first vali— dated occurrence for the genus in the Neogene of North America. Pollen of the A. barghoornianum type (Traverse, 1955) has, however, been found in the mid- dle Miocene part of the Kirkwood Formation of New Jersey (Wolfe, unpub. data). A. barghoornianum, A, riparius (MacG.) MacG., and A. mikii all represent the section Marlea. The species of Alangium from the Eocene of Alaska (Wolfe, 1977), however, is a member of the section Alangium. We take pleasure in naming this species in recogni- tion of the contributions of the late Professor Shiguru Miki to the fossil history of the Cornales. Holotype.—USNM 208483. Paratypes.—USNM 208485 (100. (Ice. 9858). Occurrence.—9858, 11091 (Capps Glacier). 11091), 208484 Family Araliaceae Genus Kalopanax Miguel Kalopanax n-suzukii Wolfe et Tanai, sp. nov. Plate 22, figure 4 Kalopanax acerifolium auct. non (Nathorst) Hu and SYSTEMATICS 43 Chaney. Hu and Chaney (nontypic), 1940, Car- negie Inst. Washington Pub. 507, p. 70, pl. 47, figs. 3, 5. Okutsu, 1955, Tohoku Univ. Sci. Repts., ser. 2, v. 26, p. 110, pl. 5, fig. 1. Tanai and Onoe, 1960, Japan Geol. Survey Rept. 187, p. 285, pl. 7, fig. 4. Tanai, 1961, Hokkaido Univ. Fac. Sci. Jour., ser. 4, v. 11, p. 377. Tanai and Suzuki, 1965, Palaeont. Soc. Japan Spec. Paper 10, p. 43, pl. 20, fig. 2. Huzioka and Uemura, 1973, [Tokyo] Natl. Sci. Mus. Bull., v. 16, p. 723, pl. 18, fig. 1. Description—See Hu and Chaney (1940, p. 70— 71). Discussion.—Examination of Nathorst’s type of Acanthopanax acerifolium indicates that these repre- sent Acer and not any genus of Araliaceae. Hu and Chaney’s (1940) Shanwang material, however, does represent Kalopanax and the same species that occurs in the Seldovia Point flora. We accept Hu and Chaney’s (1940) description, but the unavailability of the specimens on which that description was based make it desirable to designate as types specimens that are in existence. We thus designate as holotype Uni— versity of Hokkaido Museum of Paleontology 25727 (figured by Tanai and Suzuki, 1965, pl. 20, fig. 2) and as paratypes 25726 and 25729; all these specimens are from the Shanabuchi locality. Kalopanax is known from several localities in east- ern Asia and is known to range from the early Miocene through the Holocene (Tanai, 1972). The Sel- dovia Point occurrence is the first known in North America. We take pleasure in naming this species for Mr. Nobuo Suzuki, in recognition of his contributions to the Tertiary floras of Japan. Hypotype.—USNM 208486. Occurrence—9856, 9858. Family Vitaceae Genus Vitus Linnaeus Vitis seldociana Wolfe et Tanai, sp. nov. Plate 22, figure 1; plate 23, figures, 1, 3 Description.—Leaves incomplete, pentagonal in general outline, palmately five lobed, broadly cordate at base; midvein thick, nearly straight, giving off more than four pairs of secondaries, which are nearly parallel to the inner primaries; the inner pair of the primaries well defined, making angles of 40 to 60 de- grees with the midvein, giving off about six pairs of secondaries which end in large teeth, the intersecond- ary veins leaving midrib, nearly parallel to the sec- ondaries, camptodromous; the lowest pair of the primaries somewhat slender, nearly at right angles to the midvein, with five or more secondaries; the inter- costal tertiary veins thin but distinct, irregularly per- current, nearly perpendicular to the secondaries; the tertiaries near the margin branching from the secondaries, forming loops with the intersecondaries; fourth and fifth order veins forming quadrangular or pentagonal areoles which are penetrated by once or twice branching veinlets; margin coarsely dentate, with large deltoid teeth; petiole thick, more than 2.2 cm long. Discussion—Several incomplete specimens repre- sent leaves of Vitis on the basis of their marginal den- tation and vein characters. No fossil leaves of Vitis from North America are comparable to our Alaskan materials. Although all the specimens are fragmen- tary the general character of the foliage can be recon- structed. These leaves superficially resemble V. naumanni (Nathorst) Tanai, which was reported from the lower to upper Miocene of Japan, but differ dis- tinctly in having larger teeth and well-defined inter- costal tertiary veins. Vitis seldoviana also superficially resembles V. alia Hall. from the Miocene of British Columbia (Hollick, 1936). The latter species, however, has narrower and more pronounced teeth, and the tertiary veins extend perpendicularly from the midrib; in V. seldoviana, homologous tertiary veins are oriented at an acute angle to the midrib. Holotype.—USNM 208487. Paratypes.—USNM 208488, 208489. Occurrence—9856. Family Oleaceae Genus Fraxinus Linnaeus Fraxinus kenaica Wolfe et Tanai, sp. nov. Plate 24, figures 1—3 Description—Presumably a leaflet; venation pin- nate; shape oval; apex not preserved, base acute; length at least 17 cm, width 9 cm; about 13 pairs of secondary veins, irregularly spaced, departing at an- gles of 7 O to 80 degrees (higher on one side of lamina), slightly curving, irregularly brochidodromous; inter- secondaries numerous, strong; tertiary veins thin, ir- regularly spaced, oblique to more apical secondary veins and orthogonal to more basal secondary veins, branching irregularly; fourth order veins forming a thin reticulum of irregular shape and size; loops abmedial to secondary loops of irregular shape and size, one side formed by veins that extend toward sinuses, these veins either ending in sinuses or ex- tending along apical side of teeth; margin coarsely and irregularly serrate; teeth tending to have convex basal and apical sides; petiolule(?) about 2 cm long. Discussion—The specimen gives no certain indica- 44 tion whether it is a leaf or leaflet, although— assuming the validity of the generic assignment—the lack of an inflated area at the base of the petiolule is consistent with the morphology of terminal leaflets of Fraxinus, which typically are conspicuously stalked and lack an inflated area. Lateral leaflets may also be stalked in Fraxinus but not as elongated as in the fos- sil. The assignment to Fraxinus is based on characters of intercostal and marginal venation. In extant Fraxinus the intercostal areas are typically highly ir— regular in size (that is, the secondaries are very ir- regularly spaced), the tertiary and higher order veins are also inconsistent in spacing, and the areoles, which are formed by sixth order venation, are in— truded by profusely branching veinlets. The secondary veins are consistently camptodromous but give off ex- ternal branches that either bifurcate, sending one branch into the sinus or apically along the margin, or rarely enter the teeth centrally. Fraxinus kenaica appears to be most closely re- lated to the extant F. hopeinsis Tang from northern China. Particularly notable similarities are in the sharpness and large size (for Fraxinus) of the teeth. In this extant species, however, the secondary veins are considerably more apically directed, and there are fewer centrally entered teeth. Holotype.——USNM 208490A, B. Occurrence—9858. Family Caprifoliaceae Genus Lom'cera Linnaeus Lonicera Sp. Plate 25, figure 2 Discussion.—This single specimen has an entire margin except for a single small tooth along the lower left-hand side. The secondary venation forms irregu- larly shaped intercostal areas that contain irregularly spaced branching tertiary veins. Abmedial to the sec- ondary loops is a single series of loops that are also irregular in size and shape. Such features indicate a relationship to certain genera of Caprifoliaceae, but the Seldovia Point specimen is too incomplete and poorly preserved to make generic determination. In characters preserved, this specimen appears con- specific with undescribed leaves from the overlying Homerian assemblages; these younger leaves have the morphology of Lonicera. Specimen.——USNM 208491. Occurrence—9858. Family Alismataceae Genus Alisma Linnaeus Alisma seldoviana Wolfe et Tanai, sp. nov.’ Plate 25, figures 3, 6 Description.—Leaves elliptic-lanceolate in shape, MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA 7.2 to 15 cm (estimated) long and 2.2 to 5.5 cm wide; apex gradually narrowed, somewhat acuminate; base rounded to slightly cordate, sometimes slightly twisted; nine principal veins leaving the very base, acrodromous; midvein stout and thick, nearly straight; two pairs of lateral primaries rather thick, but more slender than the midvein, making initial angles of about 20 to 50 degrees with the midvein, then gently arched, nearly parallel to the margin; outer two pairs of the lateral primaries thinner and more slender than the inner primaries, running along the margin; the tertiaries thin, obliquely transverse to the primaries with the angles of about 40 to 70 de- grees, irregularly spaced; fourth order veins very fine, crossing with the tertiary veins, nearly parallel to the primaries, once or twice bifurcating to form elon- gate reticulation; margin entire; texture thin; petiole missing. Discussion. ——These fossils superficially resemble leaves of Smilax, but in that genus the fourth order venation is randomly reticulate. In Alisma, however, the fourth order veins are, as in the fossils, consist- ently perpendicular to the tertiary veins. Alisma sel— doviana closely resembles the extant A. plantago- aquatica L., a species (or species complex) of wide distribution throughout the Northern Hemisphere. Holotype.—USNM 208492. Paratype.——USNM 208493. Occurrence.-—9858. Family Najadaceae Genus Potamogeton Linnaeus Potamogeton alaskanus Wolfe et Tanai, sp. nov. Plate 22, figures 2, 3; plate 25, figures 1, 7 Description.—Floating leaves variable in size and shape, 0.5 to 3.5 cm wide and 1.4 to 6.5 cm (estimated) long, elliptic to broadly elliptic in shape; base cuneate or rounded; apex incomplete but probably obtuse; petiole rather thick; midvein thick, nearly straight; lateral primary veins, three or four on both sides of midvein, acrodromous; thin and slender lateral sub- primaries running nearly parallel to lateral pri- maries, one or two among each interlateral space; numerous secondary veins very thin, crossing some- what irregularly to the primaries; margin entire. Submerged leaves narrowly linear, 2 or 3 mm wide, more than 5 cm long; base sessile; apex unknown; veins three, lateral veins inconspicuous. Fruits obliquely suborbicular or obovoid, 1.5 to 2 cm long and 1.2 to 2 cm wide; the side flat; dorsal keel prominent, alate, undulate and with sutures; lateral keel low but evident, slightly detate; beak prominent, straight or slightly incurved, 0.8 mm long; apex of seeds pointing slightly above basal end; embryo coiled. REFERENCES CITED 45 Discussion—A number of leaves and fruits referred to Potamogeton occur at the Seldovia Point locality, and it is reasonably supposed that the plant-bearing rocks were mainly deposited in fresh, slowly moving water. Many leaves of Potamogeton have been re- ported from the Tertiary of the conterminous United States, but our Alaskan specimens are not identical with any species described before. P. alaskanus some- what resembles P. hetrophylloides Berry from the Latah flora of eastern Washington (Brown, 1940) but differs in having the lateral subprimary veins. Dorofeyev (1963) described many species ofPotamoge- ton on the basis of fruits from the Miocene of western Siberia, of which species P. alaskanus is most similar to P. tertiarius Dorof. in characters of the dorsal and lateral keels. Holotype.—USNM 208494. Paratypes.—USNM 208495—208497. Occurrence—9856, 9858. Mocotyledonae Incertaesedis Genus Monocotylophyllum Chandler Monocotylophyllum alasktmum (Heer) Wolfe et Tanai, comb. nov. Plate 23, figure 2; plate 25, figure 8 Phragmites alaskana Heer, 1869, Kongl. Svenska Vet-Akad. Handl., v. 8, no. 4, p. 24, pl. 1, fig. 12. Discussion—A number of fragmentary linear leaves with many parallel veins are similar to Phragmites alaskana, which are originally described from the "English Bay” locality. This generic refer- ence may, however, not be valid, because the monocot leaves of Gramineae and other monocotyledonous families are too simply nerved to determine their generic status. Our specimens are from 1.2 to 4 cm in width, but their length is unknown. Hypotypes.~USNM 208498, 208499. Occurrence—9856, 9858. Monocotylophyllmn spp. Plate 25, figures 4, 5 Poacites tenuestriatus Heer, 1869, Kongl. Svenska Vet-Akad. Handl., v. 8, no. 4, p. 24, 11. 1, fig. 12. Discussion—These species are represented by sev- eral fragmentary leaves which are linear with about 17 to 30 mm width and contain numerous indistinct, parallel veins. The genus Poacites has been used for the grass leaves, and it is uncertain whether or not our specimens belong to the Gramineae. Poacites was originally proposed by Schlotheim for the Carbonifer- ous grasslike specimens, but, as pointed out by An- drews (1970), the original specimens are not grass but are lycopod. Specimens.—USNM 208500—208503. Occurrence.—9856, 9858. REFERENCES CITED Andrews, H. N., Jr., 1970, Index of generic names of fossil plants, 1820—1965: US. Geol. Survey Bull. 1300, 354 p. Axelrod, D. I., 1966, The Eocene Copper Basin flora of northeastern Nevada: California Univ. Pubs. Geol. Sci., v. 59, 125 p. Baranova, Iu. P., Biske, S. F., Goncharov, V. F. Kulkova, I. A., and Titkov, A. S., 1968, Cenozoic of the Northeast of the USSR: Akad. Nauk U.S.S.R., Siberian Div., Inst. Geology and Geophysics, Trudy, Issue 38, 125 p. [English translation by L. A. Hutchinson.] Barnes, F. F., 1966, Geology and coal resources of the Beluga- Yentna region, Alaska: US. Geol. Survey Bull. 1202—0, 54 p. Becker, H. F., 1960, The Tertiary Mormon Creek flora from the upper Ruby River basin in southwestern Montana: Palaeonto- graphica, Abt. B, v. 107, p. 83—126. 1961, Oligocene plants from the upper Ruby River Basin, southwestern Montana: Geol. Soc. America Mem. 82, 127 p. 1969, Fossil plants of the Tertiary Beaverhead Basins in southwestern Montana: Palaeontographica, Abt. B, V. 127, 142 1973, The York Ranch flora of the upper Ruby River Basin, southwestern Montana: Palaeontographica, Abt. B, v. 143, 93 p., 40 pls. Berry, E. W., 1929, A revision of the flora of the Latah formation: U.S. Geol. Survey Prof. Paper 154—H, p. 225—265. 1931, A Miocene flora from Grand Coulee, Washington: US. Geol. Survey Paper 170—C, p. 31—42, 3 pls. Borsuk, M. 0., 1956, Paleogene flora of Sakhalin (in Russian): Sci. Invest. Geol. Inst., pt. 12, 88 p. Brown, R. W., 1935, Miocene leaves, fruits, and seeds from Idaho, Oregon, and Washington: Jour. Paleontology, v. 9, no. 7, p. 572—587, pls. 1937, Additions to some fossil floras of the western United States: US. Geol. Survey Prof. Paper 186—J, p. 163—206, pls. 45—63. 1939, Fossil leaves, fruits, and seeds of Cercidiphyllum: Jour. Paleontology, V. 13, p. 485—499. 1940, New species and changes of name in some American fossil floras: Washington Acad. Sci. Jour., v. 30, p. 344—356. 1962, Paleocene flora of the Rocky Mountains and Great Plains: U.S. Geol. Survey Prof. Paper 375, 119 p., 69 pls. Calderwood, K. W., and Fackler, W. C., 1972, Proposed strati- graphic nomenclature for Kenai Group, Cook Inlet basin, Alaska: Am. Assoc. Petroleum Geologists Bull., v. 56, no. 4, p. 739—754. Chaney, R. W., 1936, The succession and distribution of Cenozoic floras around the northern Pacific Basin, in Goodspeed, T. H., ed., Essays in geobotany in honor of William Albert Setchell: Berkeley, Calif, California Univ. Press, p. 55—85. 1952, Conifer dominants in the middle Tertiary of the John Day basin, Oregon: Palaeobotanist, v. 1, p. 105—113. 1959, Miocene floras of the Columbia Plateau, Part 1. Com- position and interpretation:’ Carnegie Inst. Washington Pub. 617, p. 1—134. 1967, Miocene forests of the Pacific basin: Their ancestors and their descendants: Hokkaido Univ., Sapporo, Jubilee Pub. Commemorating Prof. Sasa’s 60th Birthday, p. 209—239. Chaney, R. W., and Axelrod, D. 1., 1959, Miocene floras of the Col- umbia Plateau, Part II. Systematic considerations: Carnegie Inst. Washington Pub. 617, p. 135—237. Chelebaeva, A. I., 1968, Neogenovaya flora reki Levoi Pirozhnikovoi na Kamchatke [The Neogene flora of the River Pirozhnikovoi in Kamchatka]: Akad. Nauk SSSR, Bot. Zhurn., v. 53, p. 737—748, 4 pls. Condit, Carleton, 1938, The San Pablo flora of west—central Califor- 46 nia: Carnegie Inst. Washington Pub. 476, p. 217—268, 7 pls. Dorofeyev, P. I., 1963, Tretichnyye flory Zapadnoy Sibiri [Tertiary floras of western Siberia]: Izd-vo Akad. Nauk SSSR, 346 p. Endo, S., 1968, The flora from the Eocene Woodwardia Formation, Ishikari coal field, Hokkaido, Japan: [Tokyo] Natl. Sci. Mus. Bull., v. 11, no. 4, p. 411—449. Eyde, R. H., 1963, Morphological and paleobotanical studies of the Nyssaceae, I. A survey of the modern species and their fruits: Arnold Arboretum Jour., v. 44, p. 1—59. 1972, Note on geologic histories of flowering plants: Brit- tonia, v. 24, no. 1, p. 111—116. Eyde, R. H., Bartlett, Alexandra, and Barghoorn, E. S., 1969, Fossil record of Alangium: Torrey Bot. Club Bull., v. 96, no. 3, p. 288—314. Fotianova, L. 1., 1967, Special features of the Mid-Miocene flora of Sakhalin: Moscow Univ. Vestnik, no. 3, p. 78—81 (in Russian). English translation by Lydia A. Hutchison, 1968. Goeppert, H. R., 1852, Beitrage zur Tertiarflora Schlesiens: Palaeontographica, Abt. B, v. 2, p. 260—282, pls. 31—38. Hara, H., 1959, Distributional maps of flowering plants in Japan, part 2, An outline of the phytogeography of Japan: Tokyo, Inoue-shoten, 96 p. Heer, Oswald, 1868, Flora fossilis Arctica, v. 1: Zurich, F. Schul- thess, 192 p. 1869a, Flora fossilis alaskana: Kgl. Svenska Vetenskap- sakad. Hand1., v. 8, no. 4, 41 p., 10 pls. 1869b, Contributions to the fossil flora of north Greenland, being a description of the plants collected by Mr. Edward Whymper during the summer of 1867 : Philos. Trans, v. 159, p. 445—488, pls. 39—56. 1878, Fossilen Flora Sibiriens und des Amurlandes: Imp. Acad. Sci. St. Petersbourg, ser. 7, v. 25, no. 6, 58 p. 1880, Nachtrage zur fossilen Flora Gronlands: Kgl. Svenska Vetenskapsakad. Handl., v. 18, no. 2, 17 p. 1883, Den zweiten Theil der fossilen Flora Grénlands: Flora Fossilis Arctica, v. 7, 275 p., pls. 48-110. Hickey, L. J., and Wolfe, J. A., 1974, The bases of angiosperm phylogeny: Vegetative morphology: Missouri Bot. Garden Ann., v. 62, p. 538—589, 21 figs, 2 tables. Hollick, Arthur, 1927, The flora of the Saint Eugene silts, Kootenay Valley, British Columbia: New York Bot. Garden Mem., v. 7, p. 389—464, pls. 29—47. 1930, The Upper Cretaceous floras of Alaska: US. Geol. Sur- vey Prof. Paper 159, 123 p. 1936, The Tertiary floras of Alaska: US. Geol. Survey Prof. Paper 182, 185 p. Honda, 8., 1928, The forest zones of Japan: Tokyo (in Japanese). Hu, H. H., and Chaney, R. W., 1940, A Miocene flora from Shan- tung Province, China, Part I, Introduction and systematic con- siderations: Carnegie Inst. Washington Pub. 507, p. 1-82, pls. 1—50. Huzioka, Kazuo, 1949, Two Daijimaian floral types in the Inner zone of northeastern Japan (in Japanese): Geol. Soc. Japan Jour., v. 55, p. 648—649. 1954, Notes on some Tertiary plants from Tyosen (Korea), IV: Palaeont. Soc. Japan Trans. and Proc., (new series), v. 15, p. 195—200, pl. 25. 1963, The Utto flora in Tertiary floras of Japan, I, Miocene floras: Japan Geol. Survey, p. 153—216, pls. 28—40. 1964, The Aniai flora of Akita Prefecture, and the Aniai-type floras in Honshu, Japan: Akita Univ. Mining Coll. Jour., ser. A, v. 3, no. 4, p. 1—105, 18 pls. Ishida, Shiro, 1970, The Noroshi flora of Note Peninsula, central Japan: Kyoto Univ. Faculty Sci., Mem., Geol. and Mineralogy Ser., v. 37, no. 1, p. 1—112, 22 pls. MIOCENE SELDOVIA POINT FLORA FROM THE KENAI GROUP, ALASKA Kelly, T. E., 1963, Geology and hydrocarbons in Cook Inlet basin, Alaska: Am. Assoc. Petroleum Geologists Mem. 2, p. 278— 296. Klucking, E. P., 1959, The fossil Betulaceae of western North America: California Univ., Berkeley, M.A. thesis, 166 p. Knobloch, Ervin, and Kvacek, Zlatko, 1964, Byttneriophyllum tiliaefolium (A1. Braun) Knoblock et Kvacek in der tertiaren Floren der Nordhalbkugel: Sbornik Geol. Ved., rada P., sv. 5, p. 123~166, 12 pls. Knowlton, F. H., 1894, A review of the fossil flora of Alaska: US. Natl. Mus. Proc., v. 17, p. 207—240, pl. 9. 1902, Fossil flora of the John Day basin, Oregon: US. Geol. Survey Bull. 204, 153 p. 1919, Catalogue of Mesozoic and Cenozoic plants of North America: US. Geol. Survey Bull. 696, 815 p. 1926, Flora of the Latah formation of Spokane, Washington, and Coeur d’Alene, Idaho: US. Geol. Survey Prof. Paper 140—A, p. 17—81. LaMotte, R. S., 1935, The Miocene tilias of western America: Car- negie Inst. Washington Pub. 455, pt. 3, p. 41—48, 3 pls. 1952, Catalogue of the Cenozoic plants of North America through 1950: Geol. Soc. America Mem. 51, 381 p. Leopold, E. B., 1969, Late Cenozoic palynology, in Tschudy, R. H., and Scott, R. A., eds., Aspects of palynology: New York, Wiley, p. 377—438. Lesquereux, Leon, 1883, Contributions to the Miocene flora of Alaska: US. Geol. Survey Terr. Rept., v. 8, p. 257—263. MacGinitie, H. D., 1937, The flora of the Weaverville beds of Trinity County, California: Carnegie Inst. Washington Pub. 465, p. 83—151. 1953, Fossil plants of the Florissant beds, Colorado: Carnegie Inst. Washington Pub. 599, 198 p. 1962, The Kilgore flora: California Univ. Pubs. Geol. Sci., v. 35, no. 2, p. 67— 158. 1969, The Eocene Green River flora of northwestern Colorado and northeastern Utah: California Univ. Pubs. Geol. Sci., v. 83, 140 p. MacNeil, F. S., Wolfe, J. A., Miller, D. J., and Hopkins, D. M., 1961, Correlation of Tertiary formations of Alaska: Am. Assoc. Pet- roleum Geologists Bu11., v. 45, p. 1801— 1809. Martin, G. C., Johnson, B. L., and Grant, U.S., 1915, Geology and ’ mineral resources of Kenai Peninsula: U.S. Geol. Survey Bull. 587, 243 p. Matsuo, Hidekuni, 1963, The Notonakajima flora of Note Penin- sula, in Tertiary floras of Japan, I, Miocene floras: Japan Geol. Survey, p. 219—243, pls. 41~56. Miki, Shigeru, 1953, On the systematic position of Hemitrapa and some other fossil Trapa: Palaeobotanist, v. 1, p. 346—350. Peck, D. L., Griggs, A. B., Schlicker, H. G., Wells, F. G., and Dole, H. M., 1964, Geology of the central and northern parts of the Western Cascade Range in Oregon: US. Geol. Survey Prof. Paper 449, 56 p. Sainsbury, C. L., 1974, Geologic map of the Bendeleben 1:250,000 quadrangle: Anchorage, Alaska, AirSamplex Publ., 32 p. Sakai, Akira, 1971, Freezing resistance of relicts from the Arcto- Tertiary flora: New Phytologist, v. 70, p. 1199—1205. 1972, Freezing resistance of evergreen and broad-leaf trees indigenous to Japan: Japanese Forestry Soc. Jour., v. 54, no. 10, . p. 333—339. Sakai, Akira, and Weiser, C. J., 1973, Freezing resistance of trees in North America with reference to tree regions: Ecology, v. 54, no. 1, p. 1187126. Spurr, J. E., 1900, A reconnaissance in southwestern Alaska in 1898: US. Geol. Survey 20th Ann. Rept., pt. 7, p. 31—268. z" Steenis, C. G. G. J. van, 1962, The land-bridge theory in botany: Blumea, v. 11, p. 235—372. REFERENCES CITED Suslov, S. P., 1961, Physical geogrpahy of Asiatic Russia: San Fran— cisco, W. H. Freeman, 594 p. Takhtajan, Armen, 1969, Flowering plants, origin and dispersal: Washington, DC, Smithsonian Inst. Press, 310 p. Tanai, Toshimasa, 1961, Neogene floral change in Japan: Hokkaido Univ. Faculty Sci. Jour., ser. 4, v. 11, no. 2, p. 119—298, 32 pls. 1967a, Miocene floras and climate in East Asia: Zentr. Geol. Inst. Abh., heft 10, p. 195—205. 1967b, Tertiary floral changes in Japan: Hokkaido Univ., Sapporo, Jubilee Pub. Commemorating Prof. Sasa, 69th Birth- day, p. 317—334. 1970, The Oligocene floras from the Kushiro coal field, Hok- kaido, Japan: Hokkaido Univ. Faculty Sci. Jour., ser. 4, v. 14, no. 4, p. 383—514. 1971, The Miocene Sakipenpetsu flora from Ashibetsu area, central Hokkaido, Japan: [Tokyo] Natl. Sci. Mus. Mem., no . 4, p. 127—172, pls. 4—11. —1972, Tertiary history of vegetation in Japan, in Graham, Alan, ed., Floristics and paleofloristics of Asia and Eastern North America: Amsterdam, Elsevier, p. 235—255. 1973, Evolutionary trend of the genus Fagus around the Northern Pacific basin: Symposium on Origin and Phytogeog- raphy of Angiosperms, Birbal Sahni Inst. Paleobotany, Lucknow, India, Proc,, p. 62—83. Tanai, Toshimasa, and Huzioka, Kazuo, 1967, Climatic implications of Tertiary floras in Japan, in Hatai, Kotora, ed., Tertiary cor- relation and climatic changes in the Pacific: Sendai, Sasaki 00., p. 89—94. Tanai, Toshimasa, and Onoe, Toru, 1961, A Mic-Pliocene flora from the N ingyo-toge area on the border between Tottori and Okayama Prefectures, Japan: Japan Geol. Survey Rept. 187, 62 p., 18 pls. Tanai, Toshimasa, and Suzuki, Nobuo, 63, Miocene floras of south- western Hokkaido, Japan: Tertiary floras of Japan, I, Miocene floras: Japan Geol. Survey, p. 9— 149, 27 pls. 1965, Late Tertiary floras from northeastern Hokkaido, Ja- pan: Palaeont. Soc. Japan. Spec. Paper 10, 117 p., 21 pls. Tanai, Toshimasa, and Wolfe, J. A., 1977, Revisions of Ulmus and Zelkova in the middle and late Tertiary of western United States: US. Geol. Survey Prof. Paper 1026, 11 p. Tralau, Hans, 1968, Evolutionary trends in the genus Ginkgo: Lethaia, v. 1, p. 63—101. Traverse, Alfred, 1955, Pollen analysis of the Brandon lignite of Vermont: U.S. Bur. Mines Rept. Inv. 5151, 107 p. Trelease, William, 1924, The American oaks: Natl. Acad. Sci. Mem., v. 20, 255 p. Triplehorn, D. M., Turner, D. L., and Naeser, C. W., 1977, K-Ar and fission-track dating of ash partings in coal beds from the Kenai Peninsula, Alaska: A revised age for the Homerian Stage- Clamgulchian Stage boundary: Geol. Soc. America Bu11., v. 88, p. 1156—1160. 47 Wahrhaftig, Clyde, Wolfe, J. A., Leopold, E. B., and Lanphere, M. A. 1969, The coal-bearing group in the Nenana coal field, Alaska: US. Geol. Survey Bull. 1274—D, 30 p. Wang, Chi-Wu, 1961, The forests of China: Harvard Univ., Maria Moors Cabot Found, Pub. 5, 313 p. Wolfe, J. A., 1959, Tertiary Juglandaceae of western North Amer- ica: California Univ., Berkeley, M.A. thesis, 110 p. 1964, Miocene floras from Fingerrock Wash, southwestern Nevada: US. Geol. Survey Prof. Paper 454—N, 36 p., 12 pls. 1966, Tertiary plants from the Cook Inlet region, Alaska: US. Geol. Survey Prof. Paper 398—B, 32 p. 1968, Paleogene biostratigraphy of nonmarine rocks in Kings County, Washington: US. Geol. Survey Prof. Paper 571, 33 p., 7 pls. 1969a, Paleogene floras from the Gulf of Alaska region: U.S. Geol. Survey open-file rept., 114 p. 1969b, Neogene floristic and vegetational history of the Pacific Northwest: Madrono, v. 20, no. 3, p. 83—110. 1971, Tertiary climatic fluctuations and methods of analysis of Tertiary floras: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 9, no. 1, p. 27—57. 1972, An interpretation of Alaskan Tertiary floras, in Graham, Alan, ed., Floristics and paleofloristics of Asia and Eastern North America: Amsterdam, Elsevier, p. 201—233. 1973, Fossil forms of Amentiferae: Brittonia, v. 25, p. 334— - 355. +I—1977, Paleogene floras from the Gulf of Alaska region: U.S. k. Geol. Survey Prof. Paper 997, 108 p. \‘ 1978, A paleobotanical interpretation of Tertiary climates in the Northern Hemisphere: Am. Scientist, v. 66, p. 694-703. 1979, Temperature parameters of humid to mesic forests of eastern Asia and relation to forests of other regions of the Northern Hemisphere and Australasia: U.S. Geol. Survey Prof. Paper 1106, 37 p. 1980 , A chronologic framework for the Cenozoic megafossil floras of northwestern North America and its relation to marine geochronology, in Amentrout, J. M., and McDougall, Kristin, eds., Pacific Northwest Cenozoic biostratigraphy: Geol. Soc. America Mem. (in press). Wolfe, J. A., and Hopkins, D. M., 1967, Climatic changes recorded by Tertiary land floras in northwestern North America, in Hatai, Kotora, ed., Tertiary correlation and climatic changes in the Pacific: Pacific Sci. Cong, 11th, Tokyo, Aug—Sept. 1966, Symp. 25, p. 67—76. Wolfe, J. A., Hopkins, D. M. and Leopold, E. B., 1966, Tertiary stratigraphy and paleobotany of the Cook Inlet region, Alaska: US. Geol. Survey Prof. Paper 398—A, 29 p. Wolfe, J. A., and Leopold, E. B., 1967, Neogene and early Quarter- nary vegetation of northwestern North America and northeast- ern Asia, in Hopkins, D. M., ed., The Bering land bridge: Stan- ford, Calif., Stanford Univ. Press, p. 193—206. A Page Abies ............................................ 15 Abura flora .................................... 20 Acer ................................ 15, 16, 20, 40 barghoonianum .......... 42 bendirei .29 chaneyi ..... . .8 circinnatum .................................. 18 cissifolium .................................. 41 crataegifolium ........................... 25, 41 ezoanum ..118, 9, 10, 14, 16, 18, 25, 40; pls. 17, 19 fatisioefolia ................................. 25 glabroides ........................ 10, 40; pl. 17 grahomensis 10, 16, 18, 25, 40; p151 17, 18, 19 henryi .................................. 18, 41 heterodentotum 1.10, 18, 25, 41; pls. 16, 17, 18, 19 japonicum ................................ 18 kushiroanum .............................. 9, 14 macrophyllum ..................... 12, 15, 18, 40 mocropterum ............................. 25, 40 merriami .................................... 29 minor ....................................... 41 miyabei . mono . 1 . negundo . oregonianum ................................. 41 pennsylvanicum ......................... 24, 40 riparius ..................................... 42 rubrum ............................... 13, 15, 40 rufinerue ..................................... 40 saccharinum ....................... 13, 15, 24, 4O scottiae ............... 18, 40 subpictum . .25 sp ....................... 25 Aceraceae .......................... 10, 11, 20, 24,40 acerifolius, Kalopanax ............... 11, 25, 42; pl. 22 oceroides, Platanus ............................... 29 acutilobum, Liquidambar ......................... 28 aequalifalia, Marlea .............................. 41 aequalifolium, Alangium ...................... 41, 42 oequifolio, Dombeyopsis . . . ........ 42 Aesculus majus ........ 24 Age ...................... 7 Alang’iaceae ...................... .1.10, 11,41 Alangium ........................ .12, 13, 19,41 oequalifolium ............................. 41, 42 mileii ............. 8, 10, 15, 22, 24, 41; pls. 20, 21 riporius ..................................... 42 tiliaefolium .................................. 42 Alaska Range ....................... 8, 28 alas/tuna, Decodon .1 ..10, 16, 18, 25, 39; pls. 15, 16 Phragmites .......................... 25 Potomogeton ............... 11, 25, 44; pls. 22, 25 Tilia ...................................... 33 alaskanum, Artocarpidium ........................ 32 Ceridiphyllum ....10, 15, 18, 24, 25,27; p131 2, 11 Monocotylaphyllum ............. 11, 25; pls. 23, 25 Alchorneo Sp ..................................... 25 oleutica, Phyllodoce 1 alia, Vitus ............... Alisma ................ . plantagoaquatica ............................. 44 seldouiana ...................... 11, 25,44; pl. 25 Alismataceae ................................. 11,44 Alnus ............................. 14, 15, 18, 20,32 barnesi .................................. 24 cappsi .............. 8, 10, 15, 16, 24, 25,32; pl. 8 INDEX [Italic page numbers indicate both major references and descriptions] Alnus (continued) Page evidens ...................................... 32 fairi ....................... 10, 24, 25, 32; pl. 8, 9 healyensis ............... 8, 10, 24, 25,32; p11 8, 9 kluckingi .................................... 32 relatus ...................................... 32 sp ............. ..15, 16,; pl. 9 andersoni, Spiraea 1 .25 Aniai flora ...................... 8 aniensis, Cladrastis ..................... 10, 38; pl. 15 antipofi, Fagus .1 . .8, 10, 15, 16, 20, 25, 31; pls. 5, 6, 7 Appcorjya ........................................ 34 aquatica, Nyssa .................................. 41 Araliaceae ................................... 11, 42 Arbutus ......................................... 22 matthesii ..... 1 134 Arisaemo hesperia 11111111 1 .28 Artocarpidium olaskanum . .32 aspera, Platanus 111111111111111111111111111111111 29 Aspidiaceae ................................... 9, 25 osymmetroso, Pteracorya .......................... 35 auriculota, Cocculus 11111 8, 10, 15, 18, 25,26, 27; pl. 2 Hedera ...................................... 26 B Barabara Point ................................. 5, 6 barghoornianum, Acer ................... 142 barnesi, Alnus ........................... 124 Beluga Formation ................................. 5 Beluga River .................................... 40 bendirei, Acer .................................... 29 Caryo ............... 10, 15, 17, 25, 33; pls. 10, 11 Platanus .9, 10, 16, 18, 25,28; pls. 3, 4 Rhus 1 . . ................. 33 Berchemia . 1 119 Betula 111111111 . .15, 32 fairii ................ 32 sublutea ............................ 10, 32; pl. 9 thor .......................................... 8 sp ......................................... pl. 9 Betulaceae .................. 10, 11, 14, 15, 20, 24, 32 bicolor, Prunus . . . . .................... 37 bifurcies, Phyllites 1 . . ............. 41 biloba, Ginkgo ...... . .9, 12, 26; pl. 1 borealis, Hemitrapa 1 . . . 1 .10, 25, 39 Trapo ................ 39 bretzi, Quercus ................................... 25 Bridge Creek flora ................................ 32 browni, Zelkoua ................... 10, 30, 31; p151 5, 6 Byttneriophyllum tiliaefolium ..................... 42 C Cache Creek ..................................... 15 callfornicum, Liquidambar ......... . Camellia protojaponica ........................... 20 camtschalicum, Rhododendron ..................... 9 Cape Blanco, Oreg ............................... 22 Capps Glacier ...... 3, 4, 7,8,24,28,32, 36, 38, 39, 42 cappsensis, Carptnus ............................. 24 Solix ......... 10, 16, 24, 25, 35,36; pls1 12, 13, 14 cappsi, Alnus ......... 8, 10, 15, 16, 24, 25,32; pl. 8 Crataegus .................................. 32 Caprifoliaceae ......................... .11, 15, 44 carpinifolio, Zelkoua .............................. 30 Carpinus ................................. 15, 16, 33 Carpinus (continued! Page cappsensis ................................... 24 cordata ...................................... 33 seldoviana ............... 10, 16, 25,33; p151 9, 10 subcordata ................................... 33 Carya ................................ 12, 16, 17,33 bendirei . egregia ..... .10, 15, 17, 25, 33; pls. 10, 11 ................ 34 miocathayensis . . . .34 sessilis .................... 1 . 125 simulata .......................... 34 5p. ..................................... 8, 12, 25 Castanea ..................................... 20, 31 ungeri ....................................... 31 Cebatha hetermorpha ............................. 26 multiformis ..................... 26 Cedrela .. .............. 20 Cedrus 11111 20 Celtis ........................... 1 .10, 29 kansana ............................ 29 Sp .................................... 29; pl. 4 Cercidiphyllaceae ............................. 10, 27 Cercidiphyllum ............................ 11, 19, 27 alaskanum ....10, 15, 18, 24, 25,27, 28; pls1 2, 11 crenta .................................... 27 crenatum . . .25, 27, 28 eojaponicum . . . .27, 28 joponicum . 1 .27 Chamaecyparis sp ................... 24 chamisonii, Crataegus ............... 10, 25, 37; pl. 14 Quercus 1111111111111111111111111111111111111 37 chaneyi, Acer ..................................... 8 chinensis, Curylus ................................ 33 chuitensis, Salix ................................. 36 Chuitna River 5, 7 ciliata, Populus 1 1 .25 circinnatum, Acer . 1 1 118 Cissampelos dubiosa .............................. 26 cissifolium, Acer ................................. 41 Cladmstis .................................... 12, 38 aniensis ........................... 10, 38; p11 15 japonica ..................................... 38 lutea .................................. 8, 24, 38 platycarpa ....... 38 rafirwsque ...... 38 sp ........ .pls. 15, 16 Clam Gulch ........... . . 1 .5 Coal Cove ....................... 5, 6 Cocculus .............................. 12, 19, 24,26 auriculata .......... 8, 10, 15, 18, 25, 26, 27; p11 2 ezoensis ..................................... 27 flabello ..................................... 27 heteromorpha ................ 27 Collawash flora ......... 30, 32, 34 Communities ............... 16 Comptonia naumannii .................. 1 . .24 Cook Inlet .1, 4, 8, 24 Copper Basin Nevada ............................ 11 cordota, Carpinus ................................ 33 Cardia tiliaefolia ................................. 42 Corylus ................................... 12, 15, 33 chinenszs ....... 33 rostrata . .............. 33 Sp ............. 1.10, 12,33; pl. 9 crataegifolium, Acer ........................... 25, 41 Rulac ....................................... 41 49 50 Page Crataegus .................................. 12, 37 cappsi ................................... 32 chamisonii ..................... 10, 25, 37; pl. 14 douglasii ............... 37 sp ................ .24, 25 crenata, Cercidiphyllum ‘‘‘‘‘‘‘‘ 27 Fagus ............ .10, 25; pl. 6 Vitis ........................ 35 crenatum, Cercidphyllum ................. 25,27, 28 crispula, Quercus ................................. 32 Cunninghamia ............................ 13 Cyclocarya ........................ 12, 13, 16, 24, 34 ezoana ................. .8, 10, 15, 25, 34 paliurus ................. .16, 34 (Cycloptera), Pterocarya . . .25 Cyperacites sp .......... . .25 Cyttneria ...................................... 42 D decipiens, Dryopteris ............................ 25 Decodan ................................. 39 alaskana ..... ..10, I6, 18, 25, 39; pls. 15, 16 uerticillatus ................................. 39 dentata, Hicoria ................................. 33 dissecta, Platanus ................................ 29 distichum, Taxodium ........................... 25 Distribution .................................... 15 Dombeyopsis aequifolia .......................... 42 grandifolia 11111111 . . .42 douglasii, Crastaegus . . . .37 Dryopteris ........ . , 25 decipiens ...................... 25 guyotti . , . . ........................... 25 idahoensis ................................. 25 tokyoensis .................................. 25 sp .................................. 9, 25; pl. 1 dubiosa, Cissampelos ............................. 26 Dui Flora ........................................ 20 E ebae, Nuphar ................................. pl. 1 Nymphar ..................... 8, 10, 25, 26; pl. 1 egregia, Caryn ................................... 34 Juglans ..................................... 34 Eleagnus ,,,,,,,, elliptica, Prunus engelhardti, Salix English Bay ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1, 6, 30 eojaponicum, Cercidiphyllum ................. 27, 28 eotremuloides, Populus ............................. 8 Equisetum sp ................................... 25 Ericales ............... . . .15 Esutoru flora ............ . . .20 etymodrys, Quercus . . ..... 31 Eucammia ................................... 15, 29 montana . . ...................... 10,29; pl. 4 ulmoides .................................. 29 Eucommiaceae ............................... 10, 29 europaeum, Liquidambar ........................ 28 patulum, Liquidambar ....................... 28 europaeus, Glyptostrobus . .9, 24, 25,26; pl. 1 widens, Alnus .......... . . .32 Exbucklandia ......................... 22 ezoana, Cyclocarya .8, 10, 15, 25, 34; pl. 10 Pterocarya ................................... 34 ezoanum, Acer .,,8, 9, 10, 14, 16, 18, 25, 40; pls. 17, 19 ezoensis, Cocculus ................................ 27 F Fagaceae .......................... 10, 14, 22, 24, 31 Fagus ........... 7, 8, 11, 15, 16,20, 31 antipofi .8, 10, 15, 16, 20, 25,31; pls. 5, 6, 7 crenala .......................... 10, 25, 31; pl. 6 macrophylla ................................. 31 palecrenata .................................. 25 sp ..................................... 25; pl. 6 INDEX Page fairii, Alnus ,,,,,,,,,,,,,,,,,,, 10, 24, 25,32; pl. 8, 9 Betula . , . , .................... 32 Populus ...... , .26 fatisiaefolia, Acer . , . .25 Fish Creek flora .................................. 22 flabella, Cocculus ................................. 27 Floristic composition .............................. 9 Floristics ........................................ 16 formosana, Liquidambar .......................... 12 fraxinifolia, Pterocarya ........................... 35 F raxinus iiiiiiiiiiii . .43 hopeinsis ........ , . . .44 kenaica .11, 25, 43; pl, 24 seldoviana ................................... 44 sp ........................................... 25 furuhjelmi, Quercus ...... 8, 10, 15, 16, 24, 25; pl, 7, 8 fusca, Malus ...................................... 9 G gale, Myrica ...... garryana, Quercus . . . . Geologic occurrence .............................. .3 Ginkgo ....................................... 12, 26 biloba ......................... 9, 12, 25,26; pl. 1 Ginkgoaceae ................................... 9, 26 glabroides, Acer ........................ 10, 40; pl. 17 Gleditschia ...................................... 20 glyptostroboides, Metasequoia .9, 12, 15, 24, 25; pl, 1 Glyptostrobus ,,,,,,,, 12, 25, 26 eurpaeus ... 9, 24, 25,26; pl. 1 oregonensis .................................. 26 pensilis ...................................... 12 grahamense, Acer ..................... pls. 17, 18, 19 grahamensis, Acer .................. 10, 16, 18, 25, 40 Grand Coulee flora ............................... 22 grandifolia, Dombeyopsis ......................... 42 grossesermta, Quercus mongolica i . .32 guyatti, Dryopteris ................................ 25 H Hamamelidaceae ............................. 10, 28 Harriet Creek ..................................... 5 Healy Creek Formation ......................... 7, 8 healyensis, Alnus ........... 8, 10, 24, 25,32; pls. 8, 9 Hedera auriculata .............................. 26 heeriana, Vitis ........... . .35 Hemitrapa .... ....... 39 borealis , ..................... 10, 25,39 Hemlock Conglomerate ............................ 4 henryi, Acer .................................. 18, 41 hesperia, Arisaema ............................... 28 Nyssa ....................................... 41 Onoclea ..................................... 25 Heterobalanus .................. ‘ .............. 32 heterodentatum, Acer .10, 18, 25,41; pls. 16, 17, 18, 19 heteromorpha, Cebatha ........................... 26 Cocculus ..................................... 27 Populus ..................................... 26 hetrophylloides, Potamogeton ...................... 45 Hicoria dentata .................................. 33 orientalis .................................... 34 pecanoides . ., ................................. 34 Honshu flora ..... .26, 27 hopeinsis, Fraxinus . . . .......... 44 hoplu'nsi, Salix ..... .10, 16, 35, 36; pls. 12, 13 Sorbaria ........................... 10, 38; pl. 16 Spiraea ...................................... 38 horridum, Oplopanax .............................. 9 Hydrangea ...................................... .37 5p .......................... 10, 24, 25, 37; pl. 14 Hydraugeaceae ............................... 10, 37 I idahoensis, Dryopterzs ............................ 25 1121 ............................................. 15 insignis ..................................... 37 ingelfieldi, Magnolza .............................. 29 Page inquirenda, Salix ................................. 25 insignis, Ilex ..................................... 37 Introduction ...................................... 1 iragawaense ..................................... 42 Marlea ...................................... 41 Ishikari flora .................................... 27 J japonica, Cladrastis .............................. 38 Nyssa ....................................... 38 japonicum, Acer .................................. 18 Cerecidiphyllum .............................. 27 Juglandaceae .......................... 10, 14, 24,33 J uglans ......................................... 15 egregia ...... . . .34 nigella ...... . , .35 aregoniana . . . .35 picroides ..................................... 36 K Kachemak Bay .............................. 2, 5, 38 Kalopanax ....................................... 42 acerifolium .................................. 42 acerifolius ......................... 11, 25; pl. 22 n-suzukii .................................... 42 sp ..................................... Kamchatka . . . , kansana, Celtis . . . Kashihi flora Kenai Peninsula .................................. 1 kenaiana, Populus ...... 8, 10, 15, 24, 25,35; pl. 11, 12 . 10, 25,37 pl. 15 ..11, 25,43; pl. 24 kenaica, Prunus . . . kenaica, F mxinus , Keteleeria sp .................................... 24 Kirkwood Formation ............................ 42 kluckingi, Alnus ................................. 32 knowltoni, Nyssa .................... 10, 25, 41; pl. 18 Ulmus .......................... 10, 25, 30; pl, 5 Kodiak Island ..................................... 6 Kuiu Island .... . .1 Kukak Bay ....... , , .36 kushiroanum, Acer ............................. 9, 14 L Larix ............................................ 15 Lamb flora ............................... 22, 41, 45 Lauraceae ....................................... 22 Leguminosae ................................... . 38 Leucobalonus .................................... 32 leucophylla, Papulus . Linden: .......... lindgreni, Populus . . . . lindleyana, Spiraea ............................... 37 Liquidambar ........ 7, 8, 12, 13, 14, 15, 17, 19, 24,28 acutilobum .................................. 28 califomicum ................................. 28 europaeum ............................ . .28 patulum .......................... . .28 formosana . . .12 mioformosana ...... . .25, 28 pachyphylla .10, 16, 17, 25,28; pls. 2, 3 protensum ................................... 28 straciflua ................................. 12, 16 vachyphylla ................................. 28 Lonicera .................................. 12, 15,44 sp ................................. 11,44;pl. 25 longifilza, Ulmus ................................. 25 lutea, Cladrastis . . . .8, 24, 38 lyrata, Quercus ..... 13 Lythraceae ................................... 10, 39 M maz-rocarpa, Quercus ............................. 13 macrophylla, Fagus macrophyllum, Acer .................... 13, 15, 18, 40 Page macropterum, Acer ........................ 25, 40 Magnolia . . . ..................... 22 ingelfieldz . , . . . .29 . .24 magus, Aesculus ......... Mallotus sp .............. . .25 Malus fusca .................................. 9 Malvaceae .................................. 15 Marlea aequalifolia ........................... I . .41 iragawaense ............................... 41 matthesii, Arbutus ..................... 34 Megafossils .......................... 11 Menispermaceae . . .10, 26 merriami, Acer ........... . . , .29 Prunus ...................... 34, 38 Metasequoia ........................... 12, 18, 25,26 glytostroboides ........ 9, 12, 15, 24, 25, 26; pl. 1 occidentalis ................................. 26 sp ................................... 8, 15; pl. 1 microcrispula, Quercus ........................... 32 mikii, Alangium ...... 8, 10, 15, 22, 24,41; p15. 20, 21 minor, Acer ................................... 41 miocathayensis, Carya , .34 miocenica, Ptelea .......... . . . .34 mioformosana, Liquidambar ................... 25, 28 miothunbergiana, Pueraria .............. 10, 25; pl, 15 mixta, Pterocarya ............................. 25, 35 miyabei, Acer ............................. 14, 18, 40 mongolica, Quercus ............................... 13 grosseserrata, Quercus ........................ 32 mono, Acer ............... .13, 18, 40 Monocotylophyllum .............. 25 alaskanum ...... .11,25; p15. 23, 25 sp ................................. 11, 25; pl. 25 montana, Eucommza ..................... 10, 29; pl. 4 Mormon Creek flora .............................. 37 multiformis, Cebatha ............................. 26 Myrica gale ............................... 9 sp ................................ 24 Myrtus oregonensis ............................... 39 N Naihoro flora .................................... 20 Najadaceae ...................................... 4 4 naumanni, Comptania ............................ 24 Vitus ........................................ 43 negundo, Acer ................................ 18, 41 .3, 7, 8, 27, 36 , .25 Nenana coalfield . . newberryi, Ulmus nigella, Juglans ................................ 34 Pterocarya ...... 8, 10, 15, 18, 24, 25, 34, 35; pl. 11 nobilis, Platanus ................................. 29 North Pacific Basin .............................. 24 Noxapaga Formation ............................. 15 n—suzukii, Kalopanax ............................. 42 Nuphar ... ......................... 16, 26 ebae .. ..pl. 1 sp ...... . .25 Nymphaea ............ 26 Nymphaeaceae ............................. 8, 10,26 Nymphar ............................... 6, 11, 16,26 ebae ................................ 8, 10, 25,26 Nyssa ................................. 12, 15, 38,41 aquatica . . hesperia japonica . . knowltoni ...................... 10,25, 41; pl. 18 syluatica ................................. 12, 41 sp .................................... 25; pl. 18 Nyssaceae .................................... 10, 41 O occidentalis, Metasequaia ........ Platanus ............. . . Odasu flora ...................................... 20 Oleaceae ..................................... 11, 43 Onoclea ........................................ 25 hesperia ..................................... 25 senibilis ............................. 9,25; pl. 1 INDEX Page Oplopanax horridum .............................. 9 oregomz, Tilia .............. . .37 oregonensis, Glyptostrobus . .26 Myrtus ...................................... 39 oregoniana, J uglans .......................... 35 Ostrya .............................. 10, 33; pl. 9 Quercus ..................................... 32 Zelkova ........ . .......................... 2 5, 30 oregonianum, Acer ............................... 41 orientalis, Hicoria . . . ...... 34 Ostrya .............. 15, 33 oregoniana 10 33; pl. 9 sp .......... . . . .pl, 9 owyheensis, Ulmus ................. 10, 25, 30; pl. 4, 6 P pachyphylla, Liquidambar . . .10, 16, 17, 25, 28; pl. 2, 3 padus, Prunus ................................ 10, 38 Paleoclimatology . . . , paleocrenata, Fagus paliurus, Cyclocarya Pberacarya ...... pandurata, Quercus ............ . patulum, Liquidambar europaeum ................. 28 paucidentata, Platanus ........................... 29 Ulmus ....................................... 30 pecanoides, Hicoria ............................... 34 pennsyluanicum, Acer . ................. 24, 40 pensilis, Glyptostrobus , ...................... 12 Phragmites alaskana . .25 Phyllodoce aleutica .......... 9 Picea ............... . 14 15 20 picroides, Juglans ................................ 36 Salix ............ 10, 16, 24, 25, 35, 36; p15. 12, 13 Pinaceae .............................. 14, 15, 16, 20 Pinus ........................................ 15, 20 Pistacia ......................... 20 Planera ungeri ................................... 30 plantagoaquatica, Alisma . . . .44 Platanaceae ......................... 10, 28 Platanus ........... .12, 15, 18, 19, 24, 28 aceroides .................................... 29 aspera ....................................... 29 bendirei ............. 9, 10, 16, 18, 25,28; p15. 3, 4 dissecta ...................................... 29 nobilis . . . ...................... 29 occidentalis ...................... 12 paucidentata . . ......... 29 racemosa ....... 17, 18, 29 raynoldsii ............... 29 youngii ...................................... 29 platycarpa, Cladrastis ............................ 38 Platyptera ....................................... 35 plurineruis, Ulmus ............................... 30 Poacites .................................. 25 tenuistriatus ........................ 25 Point Pogibshi . . .6 Pollen ....................... . ............ 14 Populus ...................... .15, 16, 20, 27,35 Ciliata ....................................... 25 eotremuloides ................................. 8 fairii ........................................ 26 heteromorplw ................................ 26 kenaiana ..... .8, 10, 15, 24, 25, 35; pl. 11, 12 leucaphylla .31 lindgreni ..... .35 reniformis .................................. 25 trichocarpa .................................. 9 Sp ....................... 10, 15,24, 25,35,121. 11 Port Graham ......................... 5, 7, 14, 16, 33 Potamogeton ............................... 6, 16, 44 alaskana ................... 11, 25,44; pls. 22, 25 hetrophylloides .. .................... 45 tertiarius ....... .45 sp ............ . . .25 Potamogetonaceae ................................ ll prinoides, Quercus ............................... 32 proteasum, Liquidambar .......................... 28 51 Page Prunus ......................................... 37 bicolor . . , ............................... 37 elliptica . . . ......... 37, 38 kenaica . . .10, 25, 37; pl. 15 merriami . . ........... 34, 38 padus ................................... 10, 38 scotti ........................................ 37 vanioti ...................................... 37 sp .................................... 25; pl. 14 pseudomonticola, Salix ........................... 36 Pseudotsuga ..................................... 15 Pseudocastanea, Quercus . . . .32 Ptelea miocenica ............................ 34 Pterocarya ........ .11, 15, 16, 19, 24, 34, 35 asymmetrosa ................................. 35 ezoana ....................................... 34 fraxinifolia .................................. 35 mixta .................................... 25, 35 nigella ......... 8, 10, 15, 18, 24, 25, 34, 35; pl. 11 paliurus ..................................... 34 pugetensis ......... 18 rhoifolia ...... . .12, 18, 35 (Cycloptera) sp ....... 25 sp ........................... . . . 35 Pueraria ................................ 19, 39 miothunbergiana ................ 10, 25, 39; pl. 15 Puget Group ................................. 18, 27 pugetensis, Pterocarya ............................ 18 Phyllites bifurcies ................................ 41 Q Quercus .................................. 16, 31 , 37 bretzi ,,,,,,,, . , .25 chamissoni . . .37 crispula ..................................... 32 elliptica ..................................... 20 etymodrys ................................... 31 furuhjelmi ....... 8, 10, 15, 16, 24, 25, 31; pls. 7, 8 ganyana .................................... 13 lyrata ....................................... 13 macrocarpa . . .13 microcrispula . .32 mongolica ....... . . .13 grosseserrata ........ . , .32 oregoniana .............. . . .32 pandurata ................................... 31 prinoides .................................... 32 pseudocastanea ............................... 32 sadleriana ................................... 32 R racemosa, Platanus ........................... 17, 18 raynoldsii, Platanus .............................. 29 References cited .................................. 4 5 relatus, Alnus .................................... 32 reniformis, Populus ............................... 25 Rhododendron camtschaticum ...................... 9 rhoifolia, Pterocarya ....................... 12, 18, 35 Rhus bendirei ................ 33 richardsonii, Salix .36 riparius, Alangium . . , ........ 42 Rosaceae ................................. 10, 15, 37 rostrate, Corylus ................................. 33 rubrum, Acer ............................. 13, 15, 40 rufunerve, Acer .................................. 40 Rulac cratoegifolium ............................. 41 S saccharinum, Acer ..................... 13, 15, 24, 40 sadleriana, Quercus .............................. 32 St, Eugene flora .................................. 22 Salicaceae ............................. 10, 20, 24,35 Salix .............................. 15, 16, 18,35, 39 cappsensis .. 10, 16, 24, 25, 35, 36; pl. 12, 13, 14 chuitensis .................................... 36 engelhardti .................................. 33 52 Salix (continued) Page hopkinsi ................ 10, 16, 35,36; pls. 12, 13 inquirenda , .. . ,,,,,,,,,,,,, 25, 35 picroides ........ 10, 16, 24, 25, 35, 36; pls. 12, 13 pseudamonticola .......................... 36 richardsonii .............................. 36 seldouiana .............. 10, 16, 35, 36; pls, 12, 14 various ................................. 35, 36 Sp ............................. 8, 15, 16, 24, 25 Sanctuary Formation ................... . .7, 8, 15 Schisandra ............ 19 scotti, Prunus scottiae, Acer ................ 18, 40 seldaviana, Alisma .................. 11, 25, 44; pl. 25 Carpinus ................ 10, 16, 25,32; pls. 9, 10 F raxinus .................................... 44 Salix 1111111111111111111 10, 16, 35, 36; p15. 12, 14 Vitis .......................... 11, 25; pls. 22, 23 sensibilis, Orwclea ........................ 9, 26'; pl. 1 serrata, Zelkoua . . . 1111111 31 sessilis, Caryn 11111 . . .25 Seward Peninsula . . . .15 simulata, Carya .................................. 34 sinica, Zelkova ................................... 31 Skull Springs, Oreg .............................. 18 Smilax .......................................... 44 sp .................................. 25 Sorbaria ................................. 12, 38 hopkinsi .10, 38; pl 16 sp .................. 24 speciasu, Ulmus .. . . , .10, 30; pl. 4 Spiraea andersani ................................ 25 hopkinsi ..................................... 38 lindleyana ................................... 38 weaveri ...................................... 24 Sterling Formation .................... . . .5 stynwiflua, Liquidambar ............. . .12, 16 subcordata, Carpinus ,,,,,,,,,,,,,, 33 sublutea, Betula subnobilis, Tilia . . . ,.10, 32;]71, 9 .10, 25; pl. 15 subpictum, Acer .................................. 25 Sucker Creek flora ............................... 30 Suntrana Formation ..................... 7, 8, 15, 28 sylvatica, Nyssa ............................... 12, 41 INDEX Page Symphoricarpos .................................. 16 sp ........................................... 25 Systematics .................................... 24 T Taxodiaceae .......... Taxodium distichum . . . tenuistriatus, Poacites ............................ 25 tertiarius, Potamogeton ........................... 45 thar, Betula ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 8 Tilia .................................... 7, 8, 15, 36 alaskana .................................... 33 aregona ...................................... 37 subnobilis ........... ,.10, 25, 36; pl, 15 sp ........................... 25 Tiliaceae .......... 10, 11, 36 tiliaefolia, Cordia .............. 42 tiliaefolium, Alangium . . .......... 42 Byttneriophyllum ............................. 42 tokyoensis, Dryopteris ............................. 25 Trapa ........................................... 39 borealis ...................................... 39 Trapaceae ................. .10, 1 1 Trapellaceae ,,,,,,,,,,,,,, , 39 trichocarpa, Populus . . ,,,,,,,,, 9 Tsuga ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14, 15, 20 Tyonek Formation .............................. 4, 5 U Ulmaceae .......................... 10, 11, 20, 24,29 ulmoides, Eucommia ............................. 29 Ulmus ..................... 7, 8, 10, 15, 16, 20, 24,30 knawltoni ........... 10, 25, 30; pl. 5 longifolia ................ 25 newberryi .. ................. 25 owyheensis .................... 10, 25, 30; pl. 4, 6 paucidentata ................................. 30 plurinervis ................................... 30 speciosa ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 10, 30; pl. 4 ,8, 10, 15, 20, 24; pl. 5 ungeri, Castanea» ................................. 31 ungeri, Castanea (continued) Page Planera ...................................... 30 Zelkoua ....... .10, 25, 30, 31; pls. 5, 6 Upper Healy Creek . . ......... 32 Utto flora ........................................ 22 V vanioti, Prunus .................................. 37 uarians, Salix Vegetation ,,,,,,,,,,,,,,, i ....................... 1 1 verticillatus, Decodon ............................. 39 Vitidaceae ................................... 11, 43 Vitis ......................................... 12, 43 alia ............... 43 crenata .......... 35 heeriana . ,,,,, 35 naumanni ........................... 43 seldoviana .......... 11, 25, 43; pl. 22, 23 sp ........................................... 25 W weaveri, Spiraea ................................. 24 West Foreland Formation ....................... 3, 4 Wishkaw River, Wash ............................ 22 Wrangell Mountains ............................. 15 Y Yakataga District . Yoshioka flora youngii, Platanus Yukon River ...................................... 1 Z Zelkoua ................................... 16, 24, 30 browni .................... 10, 25, 30, 31; pl. 5, 6 carpinifolia ................... 30 oregoniana 25, 30 serrata . .,31 sinica . . ................................. 31 ungeri ., .............. 10, 25, 30,31; pls. 5, 6 sp ........................................... 16 PLATES 1—25 [Contact photographs of the plates in this report are available, at cost, from U.S. Geological Survey Library, Federal Center, Denver, Colorado 80225] PLATE 1 [All figures natural size unless otherwise stated] FIGURE 1. Ginkgo biloba Linnaeus. (p. 26 ). Hypotype, USNM 208356; loc. 9857. 2, 6, 7, 10. Metasequoia sp. cf. M. glyptostroboides Hu et Cheng. (p. 26 ). 2, 10. USNM 208352, 208355; 10c. 9858. 6, 7. USNM 208353, 208354; loc. 9857. 3, 4. Onoclea sensibilis Linnaeus. (p. 25 ). 3, 4. Hypotypes USNM 208349, 208350; Ice. 9858. 5, 9. Dryopteris sp. (p. 25 ). USNM 208348A, B; Ice. 9858. 8. Glyptostrobus europaeus (Brongniart) Heer. (p. 26). x2. Hypotype, USNM 208351; Ice. 9858. 11—14. Nymphar ebae (Huzioka) Ozaki (p. 26). Hypotypes, USNM 208357~208360; Ice. 9858. Fig. 13, X2. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE] 12 FILICALES, CONIFERALES, MAGNOLIIDAE PLATE 2 [All figures natural size unless otherwise stated] FIGURES 1—4. Cercidiphyllum alaskanum Wolfe et Tanai. (p 27 ). 1, 4. Holotype, USNM 208361A, B; 10c. 9856. 2. Paratype, USNM 208362; 100. 9858. 3. Showing fine veinlets (enlargement of holotype specimen). 5, 6. Liquidambar pachyphylla Knowlton. (p. 28 ). 5, 6. Hypotypes USNM 208364, 208365; Ice. 9858, 7. Cocculus auriculata (Heer) Wolfe. (p. 26). Hypotype USNM 208369; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE 2 HAMAMELIDIDAE, RAN UN C ULIDAE PLATE .3 [All natural size] FIGURE 1—3. Liquidambar pachyphylla Knowlton. (p. 28 ). Hypotypes USNM 208366—208368; 10c. 9858. 4. Platanus bendirei (Lesquereux) Wolfe. (p. 28 ). vaotype USNM 208370; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER [105 PLATE3 - 4 HAMAMELIDIDAE FIGURES 1, 2, 4. 3, 5. 6. PLATE 4 [All natural size] Platanus bendirei (Lesquereux) Wolfe. (p. 28 ). Hypotypes USNM 208371—208373; 10c. 9858. Ulmus speciosa Newberry. (p. 30 ). Hypotypes USNM 208381, 208382; 100. 9858. Eucommia cf. E. montana R. W. Brown. (p. 29 USNM 208374; Ice. 9858. Celtis sp. (p. 29 ). USNM 208375; Ice. 9858. Ulmus owyheensis H. V. Smith. (p. 30 ). Hypotype USNM 208376; Ice. 9858. v GEOLOGICAL SURVEY PROFESSIONAL PAPER [105 PLATE4 HAMAMELIDIDA E FIGURES 1, 2. 3, 6, 8a, 8c. 4, 7. 5. 8b. PLATE 5 [All figures natural size unless otherwise stated] Ulmus knowltoni Tanai et Wolfe. (p. 30 ). Hypotypes USNM 208376, 208377”, 10c. 9856. Zelkova browni Tanai et Wolfe. (p. 30 )l 3, 6. Hypotypes USNM 208384—208385; 10c. 9858. Ba, Ba. Hypotypes USNM 208386—208388; Ice. 9856. Zelkova ungeri Kovats. (p. 31 ). Hypotypes USNM 208389, 208390; loc. 9858. Ulmus sp. USNM 208383; Ice. 9856. Fagus antipofi Heer, (pl 31 ). Hypotype, USNM 208394; Ice. 9856. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATES HAMAMELIDIDAE PLATE 6 [All figures natural size] FIGURES 1, 2, 6. Zelkova ungeri Kovats. (p. 31 ). Hypotypes, USNM 208391, 208392, 208393; Ice. 9858. 3, 4. Fagus antipofi Heer. (p. 31 ). Hypotypes USNM 208395, 208396; Ice. 9858. 5. Fagus sp. aff. F. crenata Blume. (p. 31 ). Hypotype USNM 208400; loc. 9856. 7a, 7b. Ulmus owyheensis H. V. Smith. (p. 30 ). Hypotypes USNM 208377A, 208377B; 10c. 9856. 8. Zelkova browni Tanai et Wolfe. (p. 30 ). Hypotype USNM 208388; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE 6 HAMAMELIDIDAE PLATE 7 IAll figures natural size! FIGURES 1, 5, 6. Fagus antipofi Heer. (p. 31 ). Hypotypes USNM 208397, 208398, 208399; 100. 9858. 2~4. Quercus furuhjelmi Heer. (p. 31 ). Hypotypes USNM 208401, 208402, 208403 100. 9858. PROFESSIONAL PAPER 1105 PLATE 7 GEOLOGICAL SURVEY 4 HAMAME L IDIDA PLATE 8 [All figures natural size] Figures 1—3. Quercus fur’uhjelmi Heer. (p. 31 ). Hypotypes USNM 208404, 208405, 208406; Ice. 9858. 4. Alnus fairi (Knowlton) Wolfe. (p. 32 ). Hypotype USNM 208408; 10c. 9858. 5. Alnus cappsi (Hollick) Wolfe. (p. 32 ). Hypotype USNM 208407; 10c. 9858. 6. Alnus healyensis Wolfe. (p. 32 ). Hypotype USNM 208410; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE8 I?” , ,_ V 5. ‘ ' b) HAMAMELIDIDAE FIGURE PLATE 9 [All figures natural size unless otherwise stated] Alnus healyensis Wolfe. (p. 32 ). Hypotype USNM 208411; Ice. 9858. Alnus fairi (Knowlton) Wolfe. (p. 32 ). Hypotype USNM 208409; Ice. 9858. Corylus sp. (p. 33 ). USNM 208419; Ice. 9858. Ostrya sp. cf. 0. oregoniana Chaney. (p. 33 ). USNM 208420—208422; Ice. 9858. X2. Carpinus seldoviana Wolfe. (p. 33 ). Hypotype USNM 208414; 10c. 9858. Betula sp. cf. B. sublutea Tanai et N. Suzuki. (p. :12). USNM 208413; Ice. 9858. Alnus sp. USNM 208412; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE9 HAMAME L [DIDAE PLATE 10 [All figures natural size unless otherwise stated] FIGURE 1—3. Carpinus seldouiana Wolfe. (p. 33). Hypotypes USNM 208415, 208416, 208417; Ice. 9858. (fig. 3, x2). 4—6, 8, 9a, 9b. Cyclocarya ezoana (Tanai et N. Suzuki) Wolfe et Tanai. (p. 34 ). 4, 5, 8, 9a, 9b. Hypotypes USNM 208425, 208426, 208427, 208428, 208429; Ice. 9858. (fig. 5, x2; fig . 9, X3). 6. Hypotype USNM 208426; Ice. 9856. 7. Carya bendirei (Lesquereux) Chaney and Axelrod. (p. 33 ). Hypotype USNM 208424; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER [105 PLATE IO HA MAME LIDIDAE PLATE 1 1 [All figures natural size unless otherwise stated] FIGURES 1, 2. Carya bendirei (Lesquereux) Chaney et Axelrod. (p. 33 ). 1, 2. Hypotype USNM 208423; Ice. 9856 (fig. 2, X3). 3, 5. Cercidiphyllum alaskanum Wolfe et Tanai. (p. 27 ). Paratypes USNM 208363A, B; Ice. 9858. 4, 6, 7. Pterocarya nigella (Heer) Wolfe. (p. 35 ). 4, 6. Hypotypes USNM 208430, 208431; 10c. 9858. 7. Hypotype USNM 208432; 100. 9856. X2. 8. Populus sp. (p. 35 ). USNM 208434; Ice. 9858. 9. Populus kenaiana Wolfe. (p. 35 ). Hypotype USNM 208433; 10c. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE 1] "\ HAMAMELIDIDAE, DILLENIIDAE PLATE 12 [All figures natural size unless otherwise stated] FIGURES 1. Populus kenaiana Wolfe. (p. 35 ). Hypotype USNM 42264B; loc. 9858. 2, 3. Salix seldoviana Wolfe et Tanai. (p. 36 ). 2, 3. Holotype USNM 208446; Ice. 9858. Fig, 2, X3. 4. Salix hopkinsi Wolfe et Tanai. (p. 36 ). Holotype USNM 208440; Ice. 9858. 5-7. Salix picroides (Heer) Wolfe. (p. 36 ). 5, 7. Hypotypes USNM 208442, 208443; Ice. 9858. 6. Showing fine venation and margin of USNM 208442 (fig. 5). Ca. X3. 8. Salix cappsensis Wolfe. (p. 36 ). Hypotype USNM 208435; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1 105 PLATE 12 DILLENIIDAE PLATE 13 [All figures natural size unless otherwise stated] FIGURES 1, 2, 4. Salix cappsensis Wolfe. (p. 36 ). 1, 2, 4. Hypotypes USNM 208436, 208437, 208438; Ice. 9858. Fig. 2, X3. 3, 7. Salix picroides (Heer) Wolfe. (p. 36 ). Hypotypes USNM 208444, 208445; Ice. 9858. 5, 6. Salix hopkinsi Wolfe et Tanai. (p. 36 ). 5, 6. Paratypes USNM 208441A, 208441B; Ice. 9858. Fig. 6, X3. PROFESSIONAL PAPER 1105 PLATE l3 GEOLOGICAL SURVEY DILLENIIDAE PLATE 14 [All figures natural size] FIGURES 1. Hydrangea sp. (p. 37 ). USNM 208449A; 100. 9858. 2. Salix seldoviana Wolfe et Tanai. (p. 36). Paratype USNM 208447; 10c. 9858. 3, 4. Salix cappsensis Wolfe. (p. 36 ). Hypotypes USNM 208439A, 208439B; 100. 9858. 5, 6. Crataegus chamissoni (Heer) Wolfe et Tanai‘ (p. 37 ). Hypotypes USNM 208450, 208451; loc. 9858. 7. Prunus sp. (p. 38). USNM 208454A, B; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE [4 DILLENIIDAE, ROSIDAE PLATE 15 [All figures natural size unless otherwise stated] FIGURES 1. Tilia subnobilis'Huzioka. (p. 36). Hypotype USNM 208448; 100. 9856. 2, 5. Prunus kenaica Wolfe et Tanai. (p. 37 ). 2. Holotype USNM 208452; 100. 9856. 5. Paratype USNM 208453; 10c. 9856. 3. Pueraria miothunbergiana Hu et Chaney. (p. 39 ). Hypotype USNM 208461; 10c. 9858. 4. Cladrastis sp. cf. C. aniensis Huzioka. (p. 38 ). Hypotype USNM 208459; Ice. 9858. X2. 6. Decodon alaskana Wolfe et Tanai. (p. 39 ). Paratype USNM 208464; 10c. 9858. PROFESSIONAL PAPER 1105 PLATE 15 GEOLOGICAL SURVEY DILLENIIDAE, ROSIDAE PLATE 16 [All figures natural size unless otherwise stated] FIGURES 1, 2a, b, c. Sorbaria hapkinsi (Wolfe) Wolfe et Tanai. (p. 38 ). Hypotypes USNM 208455«208458; Ice. 9858. 3, 4. Cladrastis sp. cf. C. aniensis Huzioka. (p. 38 ). 3, 4. USNM 208460; Ice. 9858. Fig. 4, X3. 5, 7, 8. Decodon alaskana Wolfe et Tanai. (p. 39 ). 5. Paratype USNM 208463; loc. 9858. 7, 8. Holotype USNM 208462; 100. 9858. Fig. 8, X3. 6. Acer heterodentatum (Chaney) MacGinitie. (p. 41 ). Hypotype USNM 208476; 10c. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE l6 ROSIDAE PLATE 17 [All figures natural size] FIGURES 1—3, 5. Acer ezoanum Oishi et Huzioka. (p. 40 ). Hypotypes USNM 208466, 208467, 208468; Ice. 9858. 4. Acer heterodentatum (Chaney) MacGinitie. (p. 41 ). Hypotype USNM 208477; Ice. 9858‘ 6. Acer grahamensis Knowlton et Cockerell. (p. 40). Hypotype USNM 208473; Ice. 9858. 7, 8. Acer glabroides Brown. (p. 40 ). Hypotypes USNM 2084717 208472; 100. 9858. PROFESSIONAL PAPER [105 PLATE 17 GEOLOGICAL SURVEY R OSIDAE PLATE 18 [All figures natural size] FIGURE 1. Nyssa sp. cf. N. knowltoni Berry. (p. 41 ), USNM 208482; 10c. 9858. 2—4. Acer heterodentatum (Chaney) MacGinitie. (p. 41 ). Hypotypes USNM 208478, 208479, 208480; Ice. 9858. 5. Acer grahamensis Knowlton et Cockerell. (p. 40). Hypotype USNM 208474; 100. 9856. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE l8 ,1, ROSIDAE PLATE 19 [All figures natural size] FIGURES 1, 4. Acer grahamensis Knowlton et Cockerell. (p. 40). Hypotype USNM 208475; Ice. 9856. 2, 5. Acer ezoanum Oishi et Huzioka. (p. 40 ). Hypotypes USNM 208469, 208470; 10c. 9858. 3. Acer heterodentatum (Chaney) McGinitie. (p‘ 41 ). Hypotype USNM 208481; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER [105 PLATE ]9 R OSIDA E PLATE 20 FIGURE 1, 2. Alangium mikii Wolfe et Tanai. (p. 41). 1. Holotype, USNM 208483; 100. 9858. X1. 2. Paratype USNM 208485; loc. 11091 (Capps Glacier), ca. X. GEOLOGICAL SURVEY PROFESSIONAL PAPER [105 PLATE 20 ROSIDAE [Nam site! ' Para‘type WWW; lac. 9858.- ’ GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE 2| R OSIDA E PLATE 22 [All figures natural size] FIGURES 1. Vitis seldoviana Wolfe et Tanai. (p. 43 ). Paratype USNM 208488; Ice. 9856. 2, 3. Potamogeton alaskanus Wolfe et Tanai. (p. 44). 2. Paratype USNM 208495; Ice. 9858 3. Holotype USNM 208494; Ice. 9858. 4. Kalopanax n-suzikii Wolfe et Tanai (p. 42). Hypotype USNM 208486; Ice. 9856. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE 22 ROSIDAE, M ONOC 0 TYLEDONES PLATE 23 [All figures natural size] FIGURES 1, 3. Vitis seldoviana Wolfe et Tanai. (p. 43 ). 1. Paratype USNM 208489; Ice. 9856. 3. Holotype USNM 208487; Ice. 9856. 2. Monocotylophyllum alaskanum (Heer) Wolfe et Tanai. (p. 45 )4 Hypotype USNM 208498; Ice. 9858. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1105 PLATE 23 ROSZDAE, MONOCOTYLEDONES PLATE 24 [All figures natural size unless otherwise stated] FIGURES 1—3. Fraxinus kenaica Wolfe et Tanai. (p. 43 ). Holotype USNM 208490 A, B; Ice. 9858. Fig. 3, X3. GEOLOGICAL SURVEY ‘ PROFESSIONAL PAPER 1105 PLATE 24 1 V R OSIDAE Plate 25 [All figures natural size unless otherwise stated] FIGURES 1. 7. Potamogeton alaskanus Wolfe et Tanai. (p. 44). 2. 3, 6. 1. Paratype USNM 208496; Ice. 9858. 7. Paratype USNM 208497; Ice. 9858. X5. Lonicera sp. (p. 44). USNM 208491; 10c. 9858. Alisma seldoviana Wolfe et Tanai. (p. 44 l. 3. Paratype USNM 208493; 10c. 9858. 6. Holotype USNM 208492; loc. 9858. Monocotylophyllum sp. a. (p. 45 ). USNM 208500, Ice. 9858. Monocotylophyllum sp. a. (p. 45 ). USNM 208503. Ice. 9858. Monocotylophyllum alaskanum (Heer) Wolfe et Tanai. (p. 45 ). Hypotype USNM 208499; Ice. 9858. GEOLOGICAL SURVEY . PROFESSIONAL PAPER 1105 PLATE 25 AS TERIDAE, MONOCOTYLEDONES 4 RETURN EARTH SCIENCES LIBRARY T_O__—> 230 Earth Sciences Bld g. 6 ’2- " Wr— ‘ '-‘ -‘T 003243