,1 312% 1 M M; The Structure of the Olympic Mountains, Washington— Analysis of a Subduction Zone By R. W. TABOR and W. M. CADY GEOLOGICAL SURVEY PROFESSIONAL PAPER 1033 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1978 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Tabor, Rowland W. The structure of the Olympic Mountains, Washington. Geological Survey Professional Paper 1033 Bibliography: p. 24-25. 1. Geology—Washington (State)—Olympic Mountains. 1. Cady, Wallace Martin, 1912- joint author. 11. Title. 111. Series: United States Geological Survey Professional Paper 1033 QE176.038T3 557.97’94 76-606187 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock No. 024-001-03079-9 CONTENTS Page Page Abstract ____________________________________________________ 1 Structural geology of the eastern core—Continued Introduction ________________________________________________ 1 Tectonic fabric—Continued Summary of regional geology ____________________________ 1 Pencil structures ____________________________________ 10 Procedure and acknowledgments ________________________ 3 Stretched clast lineations ____________________________ 12 Structural geology of the eastern core ________________________ 3 Major structural terranes ________________________________ 12 Overview of the structure ________________________________ 3 Multiple folding ________________________________________ 14 Major rock units ____________________________________ 3 Early folding—formation of the core units ____________ 14 Faults bounding the core ____________________________ 5 Late folding and doming—formation of the pencils ____ 19 Significance of top directions ________________________ 5 Summary of the deformation ____________________________ 22 Tectonic versus soft-sediment slump structure ________ 7 Plate margin tectonics __________________________________ 23 Tectonic fabric __________________________________________ 7 References cited ____________________________________________ 24 Cleavage __________________________________________ 7 Supplemental information ___________________________________ 28 Folds ______________________________________________ 10 Frequency diagrams for subdomains ______________________ 28 Computerized structural diagram program ________________ 36 ILLUSTRATIONS Page FIGURE 1. Sketch map showing major geologic terranes of the Olympic Peninsula __________________________________________ 2 2. Geologic map of the eastern core ______________________________________________________________________________ 4 3. Sketch map showing major folds and faults on the Olympic Peninsula ____________________________________________ 6 4—8. Photographs showing: 4. Beds sheared off by cleavage in zone of disruption, Hurricane Ridge fault zone south of Mount Angeles ____ 7 5. Block of undisrupted thin-bedded sandstone and slate in broken formation, western Olympic lithic assemblage 8 6. Shear fold in thin-bedded sandstone with slate core, southwest of Mount Olympus ________________________ 8 7. Sheared-off sandstone bed in weakly developed slate, south side Mount Appleton __________________________ 8 8. Sketches showing beds in sandstone and slate disrupted by cleavage ______________________________________ 9 9—15. Photographs showing: 9. Blocks and lenses of sandstone in contorted slate matrix, southeast of Muncaster Mountain ________________ 9 10. Tectonic lenses of sandstone in phyllite, southwest side Mount Barnes ____________________________________ 9 11. Small blocks of sandstone in slate, east of Mount Christie ________________________________________________ 11 12. Disrupted beds and tectonic lenses in slate, west side Mount Olympus ____________________________________ 12 13. Recumbent fold juxtaposed by faulting with inclined fold, northwest of Grand Pass ________________________ 12 14. Sharply hinged fold in sandstone with slate interbeds, northeast shoulder McCartney Peak ________________ 12 15. Fold with rounded hinge in sandstone with siltstone laminations, north side Mount Cameron ______________ 12 16. Sketch showing folded isoclinal fold northwest of Mount Olympus ________________________________________ 12 17. Large overturned drag fold on Mount Anderson ________________________________________________________ 13 18—23. Photographs showing: 18. Folds in cleavage, phyllite, south ridge Mount Norton __________________________________________________ 14 19. Pencil structures in limestone northeast of Grand Pass __________________________________________________ 14 20. Pencil structures in slate, northwest McCartney Peak __________________________________________________ 14 21. Large pencils in slate and siltstone at high angle to bedding and fold axis, north of Mount Cameron ________ 15 22. Crude pencils parallel to axial plane of fold northeast of Grand Pass ______________________________________ 15 23. Lineated granule conglomerate, east of Ludden Peak ____________________________________________________ 15 24—32. Sketches showing: 24. Pencil lineations in the eastern core ____________________________________________________________________ 16 25. Domains and subdomains eastern core __________________________________________________________________ 17 26. Principal structural elements for each subdomain ______________________________________________________ 18 27. Development of eastern core by folding, faulting, and shear folding ______________________________________ 19 28. Ninety-five poles to bedding in volcanic rocks in the Crescent Formation __________________________________ 19 29. Summary diagrams, structural elements in Domain West ________________________________________________ 20 30. Summary diagrams, structural elements in Domain East ________________________________________________ 21 31. Intersection of principal shear cleavage, late stage deformation with girdle of early fold axes and constructed kinematic axis _ _ ___________________________________________________________________________________ 22 32. Generalized section through Olympic Mountains at plate margin ________________________________________ 23 33. Computer form for structural data ______________________________________________________________________ 37 34. Computer output for structural program ________________________________________________________________ 38 IH IV TABLE CONTENTS TABLES Page 1. Probable ages for units in the eastern core and adjacent peripheral rocks on the Olympic Peninsula ________________ 5 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON— ANALYSIS OF A SUBDUCTION ZONE By R. W. TABOR and W. M. CADY ABSTRACT Long thin packets of structurally disrupted rocks in the eastern core of the Olympic Mountains mostly top eastward, but the overall age of the rocks decreases westward, suggesting early folding around subhorizontal axes with imbricate thrusting or imbricate thrusting alone. Continued east-west compression overturned beds eastward, bend- ing the packets into an arc within the horseshoe bend of the Crescent Formation, a foldlike structure that formed as the core rocks were imbricated or was extant from the original arcuate distribution of basaltic seamounts. In the western part of the eastern core, second- ary structures (B elements) (mostly small-scale folds) developed par- allel to the steep axis of the fold of the basaltic horseshoe; in the southern part of the core, the rock packets were sheared off beneath the basalts on the south limb of the horseshoe bend. Later shear folding on a cleavage fan oriented parallel to a north-northwest- trending subhorizontal kinematic axis rotated B elements (folds) formed earlier, producing widespread late pencil structures, in part centripetal to the basaltic horseshoe, where the late cleavage inter- sected earlier deformed bedding and cleavage. This late folding pro- duced a domelike structure extended asymmetrically eastward. The complex structure of the core rocks is consistent with current models of accretionary prisms in subduction zones and developed its form as the thick mass of volcanic rocks of the Crescent Formation to the east resisted the eastward movement of the accreted sedimentary prism. INTRODUCTION The marked horseshoe outcrop pattern of the Eocene basalts on the Olympic Peninsula has long fascinated geologists. Weaver (1937, pl. 2) was the first to recog- nize this pattern; in his interpretation, the peninsula was traversed by a large east-southeast-trending anti- cline, a concept that has persisted to the present. The rocks in the core of this fold were thought to be mostly pre-Tertiary (Weaver, 1937, p. 17—18), probably Cre- taceous (Danner, 1955, p. 24-27). The structural com- plexity of the mountainous core became apparent as small areas were investigated in detail (compare McMichael, 1946; Banner, 1948; Harvey, 1959; Lind- quist, 1961; Hawkins, 1967; Miller, 1967). Park (1950) and Walter Warren (written commun., 1955) cited evi- dence that core rocks included younger strata and an- ticipated some of the structural complexities described here. We began systematic mapping of the mountainous core in 1961 (Cady, Tabor, MacLeod, and Sorenson, 1972; Cady, Sorenson, and McLeod, 1972; Tabor and others, 1972; Tabor, 1975; Tabor and Cady, 1978). Our study and unpublished work of the US. Geological Survey done earlier by Walter Warren, Charles Park, and others indicates that: the mountainous core of the range is mostly, if not all, Tertiary in age; much of the core is about the same age or younger than the partly encircling Eocene basalts; the rocks are highly de- formed, having been thickened by imbricate faulting, and, in the eastern part, underwent multiple shear folding. Deformation probably took place in an ac- cretionary prism during underthrusting of the conti- nent by an oceanic plate. In this report we describe and analyze the mega- scopic and macroscopic structures in homogeneous do- mains and subdomains of the mountainous core and develop a tectonic model for their formation. SUMMARY OF REGIONAL GEOLOGY Two major geologic terranes dominate the Olympic Peninsula. Surrounding the mountainous core on three sides is a horseshoelike belt of early and middle Eocene, mostly oceanic, basalt, the Crescent Formation of Brown, Gower and Snavely (1960, fig. 1). Overlying the basalt on the north, east, and south are upper Eocene to Miocene and minor Pliocene marine sedi- mentary rocks. The peripheral sedimentary rocks are fossiliferous and, though folded and faulted, are in general stratigraphically continuous. Within the arms of the basaltic horseshoe, the core consists of two major terranes. The western core of Eocene to Miocene rocks is nonslaty and at least locally includes coherent areas of rocks that are for the most part stratigraphically continuous. Complex folds and faults are common, and some areas are so totally disrupted that the rocks have the aspect of melange (Weissenborn and Snavely, 1968, p. F8—F9; Koch, 1968; Stewart, 1970; Rau, 1973, 1975; Tabor and Cady, 1978). The slaty rocks of the eastern core are Eocene to 1 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON .ESmEEwn— 39.520 0:... we 3:953 ofiofiwm SFSIA HEDGE vague—o 32m ~ _ noao_e>uu.=o>> mo m2< mmmkmfioflv. cm or o . / o, , z , / J z / C , / mmjzz on or o 5528:: v.35: u».:»:® :aam Inl 33:00 :otmEhom «coumouo 0.: m0 3.00.. 03333 ocuuom 0528 can ram 330.. ocooom 5.00.. 2803.0 “Em ocooom .3an $.09. 0:332 ammoo mac—m Ban: 0» ucooom 83°.— ocooom mo 93.5 :EE :3? 8.00.. 2.80:2 083E 3 05302.0 Saab mvmoom A_ or > 1 3 1 » .9150 4) VF .omomfi STRUCTURAL GEOLOGY OF THE EASTERN CORE 5 TABLE 1.—Probable ages of units in the eastern core and adjacent peripheral rocks on the Olympic Peninsula Unit Age Fossil evidence and reference Early and Crescent Formation Many microfossils, some megafossils, and associated middle Eocene coccoliths (Ran, 1964, .G&G4; sedimentary rocks. and ossibly Tabor and others, 197 ; Cady, late ocene. 1972; PD. Snavely, Jr., N.S. MacLeod, and JR Pearl, written commun., 1974). Core units Needles—Gray Wolf Late Eocene ,,,,,, Some microfossils, a few megafossils lithic assemblage. (Cady and MacLeod, 1963; Cady, Tabor, MacLeod and Sorenson, 1972). Grand Valley Tertiary ,,,,,,,,,, Very sparse microfossils (Tabor and lithic assemblage. others, 1972). Elwha lithic Early and middle Very sparse microfossils (Tabor and Eocene. Late Eocene to early Oligocene. assemblage. Western Olympic lithic assemblage. others, 1972). Lithologic continuity with fossilif- erous rocks to west and northwest (Gower, 1960; R.J. Stewart, written commun., 1970; Harvey, 1959, . 4&46; PD. Snavely, Jr., .8. MacLeod, and J.E. Pearl, written commun., 1974). moved far, for the general lithology of the surrounding terrane is the same as that of local rocks containing the fossils. On the basis of whole-rock potassium-argon ages, re- gional metamorphism culminated in the growth of new minerals about 29 million years ago. A later episode of fault brecciation and quartz veining (along faults dur- ing uplift?) took place about 17 million years ago (Tabor, 1972). FAULTS BOUNDING THE CORE The highly disrupted core rocks appear to be sepa- rated from the peripheral rocks by anastomosing steeply dipping faults that we interpret to be thrust faults (figs. 2, 3). Some of these faults are between units of contrasting rock types; one such fault, the Hurricane Ridge fault, separates micaceous lithic t0 feldspathic subquartzose sandstone of the Needles— Gray Wolf lithic assemblage in the core from volcanic- rich lithic subquartzose sandstone associated with the Crescent Formation. Shearing associated with the Hurricane Ridge fault is well exposed on the Hurricane Ridge Road (fig. 4), on Mueller Creek northeast of Gray Wolf Ridge, and along a logging road up Boulder Creek east of Mount Stone. An unnamed westward extension of the Hurricane Ridge fault separates the Crescent Formation from relatively undeformed sandstone and shale north of the western core. This extension is a moderately dipping thrust fault that has moved the Crescent Formation over younger sedimentary rocks similar to peripheral rocks that lie stratigraphically above the Crescent Formation to the north (P. D. Snavely, Jr., N. S. Macleod and J. E. Pearl, written commun., 1972). The continuation of the Hurricane Ridge fault in the southern Olympic Mountains separates rocks of less contrasting lithology. Mica is common in both periph- eral sedimentary rocks and in core units (Tabor and Cady, 1978), but the fault can be traced along slaty tectonic-breccia zones such as in Slate Creek near Staircase and northwest of Capitol Peak, near the head of the Wynoochee River. Most of the rocks in the southeastern core area are intensely sheared; neither core units nor bounding faults can be traced far in them. To the south near Lake Quinault, the faults that bound the core units probably merge through this zone of intense deformations to form a fault zone at the base of the peripheral rocks (fig. 3). The southern fault zone is critical to the interpreta- tion of structure here. The faults shown on the map tend to truncate southeast- to south-trending struc- tures and lithologic units. This tendency is especially evident west of Mount Stone (fig. 2), where a prominent shear zone northwest of the high basalt ridge forming Mount Stone and other peaks truncates major core units. On the northern side of the core, where units and structures tend to curve around parallel to the periph- eral basaltic horseshoe, the recognition of tectonic truncation is more difficult, except farther west where fossils are more abundant. The extension of faulting southwest of Lake Quinault is speculative because the area is completely covered by glacial deposits. By analogy to the faulted contact between the highly deformed core rocks and the less deformed peripheral rocks elsewhere and in- terpretation of drill-core data and aeromagnetic sur- veys (P. D. Snavely, written commun., 1976), a fault or complex of faults probably extends southwestward to the coast. The Calawah fault zone (Gower, 1960) along the north margin of the western core cuts only core rocks where it is best exposed east of Sappho as a wide zone of sheared argillite set with many blocks of sandstone, conglomerate, and basaltic volcanic rocks. Westward from near Sappho, the probable extension of the Calawah fault separates highly deformed core rocks from peripheral rocks (P. D. Snavely, Jr., N. S. Mac- Leod, and J. E. Pearl, written commun., 1974). East- ward, the Calawah fault appears to splay to the south- east into several faults separating the slaty units of the eastern core. SIGNIFICANCE OF TOP DIRECTIONS Of great significance to the structural interpretation of the Olympic Mountains is the distribution of bed- ding tops. In the peripheral rocks, sedimentary beds and the pillow basalts of the Crescent Formation gen- erally top away from the core, although locally there THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON 1 24° 1 23° Cape o F latterv Port \ Angeles M 0 Se uim W \ q 0 7 < 5 A Mt Anderson A \ 50‘J1 / // % LAKE QUINAULT A V 4 {n A r ‘__\ \I V r v Z <44; V< r A>VV4L A< > > < > V v A Tahola rvz‘d" A474r ’\ L:74V4> >AL 4A7" A' “‘4: 2* h ’V 1 l 0 10 20 MILES 0 10 20 KILOMETERS EXPLANATION " V A W—V‘Lv- —'-- L " r~< ‘ Basaltic rocks of the Crescent Formation + Syncfine Showing direction ofplunge + Anticline Showing direction ofplunge High-angle fault Folded thrust fault Dashed where inferred Queried where uncertain. Sawteeth on upper plate _H— 45% Large-scale drag fold Overturned anticline Showing plunge of axis Showing direction of dip of lim bs FIGURE 3.—Major folds and faults on the Olympic Peninsula. Geology modified from Tabor and Cady (1978). STRUCTURAL GEOLOGY OF THE EASTERN CORE 7 FIGURE 4.— Beds sheared off by weakly developed cleavage in zone of disruption marking the Hurricane Ridge fault zone, Hurricane Ridge Road, south of Mount Angeles. are a few folds (fig. 3). Within the rocks of the eastern core, about 23 percent of the beds measured yielded top data such as graded beds, ripple marks, load casts, and pillows in basalt. Of the known tops, about 70 percent face north, east, and southeastward, away from the core. If each lithic assemblage or structural unit is con- sidered separately, about the same proportion of tops faces away from the core. This suggests that the core rocks are older coreward or westward, but the best paleontologic evidence indicates that in general the rocks are as young or younger westward and axially to the horseshoe, with one possible age reversal in the Elwha lithic assemblage (table 1). This enigmatic rela- tion supports the interpretation that the major rock units are separated by faults (Tabor and others, 1970), as indicated by the penetrative deformation within the units and local severe disruption at their margins. TECTONIC VERSUS SOF'I‘~SEDIMENT SLUMP STRUCTURES Many of the structures of highly disrupted beds found in rocks of the Olympic core could have origi- nated through soft-sediment slumping. We did not find specific evidence to identify olistrostromes, although it is likely that they were common in the original depo- sitional environment. The slaty cleavage and recrys— tallization, closely associated with the folding, indicate that most of the structures in the eastern core are closely related to the metamorphism of the core rocks and are therefore tectonic. TECTONIC FABRIC CLEAVAGE Cleavage is the dominant structural element of the 8 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON eastern core. It is less pronounced in rocks of the north- eastern part, Where bedding is relatively consistent and continuous; southwestward, beds are increasingly disrupted by cleavage. In the most disrupted areas, bedding and other sedimentary features are preserved in isolated blocks in the sheared matrix of slate and siltstone (fig. 5). We have not made a distinction between shear cleavage and fracture cleavage in this analysis, but most cleavage is parallel to axial planes of folds (fig. 6) and many folds are highly attenuated. The hinges of folds are commonly sheared off by movement along cleavage (fig. 7), and, in some areas, thin beds of sandstone are alined in a crisscross pattern (fig. 8A), suggesting that all hinges have been sheared off; the beds are realined roughly parallel to the cleav- age. Sandstone lenses and large blocks of thinly bedded sandstone and slate may display divergent beds or folded beds, truncated by the cleavage in slate or phyl- lite enveloping the sandstone (figs. 6, 8B) or folds and beds may be in total chaos (fig. 8C). The scale of disruption of bedding by movement along cleavage ranges from outcrop dimensions (figs. 9, 10, 11) to entire mountainsides (figs. 5, 12), although its prominence may well be dependent on the bedding and lithologic features of the original rocks. In outcrops of slate, where bedding is visible in siltstone lamina- tions, isoclinal folding is commonly evident, and the beds are not disrupted on an outcrop scale. In very thick beds of sandstone and slate, disruption is recog- FIGURE 5.—-Block of undisrupted thin-bedded sandstone and slate (foreground) in broken formation in the western Olympic lithic assemblage. Tightly appressed isoclinal folds are found in some thin-bedded blocks like this one. Subdomain 17, southwest side of Mount Olympus. nizable only at map scale (fig. 2). The most severe dis- ruption is found in thinly bedded sandstone and slate where each outcrop bears many small tectonic lenses (compare fig. 11). Where the rock is strongly sheared, it is commonly crisscrossed by many curving cleavages and studded with blocks and lenses (fig. 9). Whereas pelitic rocks through the area of this study display fairly well developed slaty cleavage, the cleav— '*. :3???» l,“ 1. FIGURE 6,—Shear fold in thin—bedded sandstone with slate core. Axial-plane cleavage is alined with hammer handle. Note di— vergence ofbedding and cleavage in sandstone and irregular shape of fold. Subdomain 1’7, southwest of Mount Olympus, upper South Fork of the Hoh River. FIGURE 7.—Sheared-off sandstone bed in weakly developed slate. The structure probably began as a clockwise drag fold. North of subdomain 16, south side of Mount Appleton. STRUCTURAL GEOLOGY OF THE EASTERN CORE 9 age in sandstone is more subtle. Development of cleavage or low-rank schistosity in sandstones, as in other rocks, progresses from northeast to southwest, mostly independent of the units mapped (fig. 2). The most highly schistose and more recrystallized rocks occur in the south-central part of the area in subdo- FIGURE 8.—Notebook sketches of disrupted beds in sandstone and slate. A, Crisscross beds in thin-bedded slate; folded beds sheared off and juxtaposed. Subdomain 6, north side of Hurricane Ridge. B, Sandstone blocks and lenses in slate with bedding partially rear- ranged by movement along cleavage. Subdomain 10, northwest of Mount Anderson. C, Parts of folds and beds juxtaposed by move- ment along slaty cleavage. Subdomain 14, east side of Chimney Peak. mains 8 and 10 and the northern parts of subdomains 13 and 14 (see fig. 25). The development of cleavage (schistosity) and new minerals in sandstones can be best seen in thin section. FIGURE 9.—Highly disrupted zone with blocks and lenses of sandstone in contorted slate matrix. Subdomain 13, southeast of Muncaster Mountain. ‘ifl’ w: :- FIGURE 10.—Tectonic lenses of sandstone in phyllite. Subdomain 8, southwest side of Mount Barnes. 10 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON In the initial stages of metamorphism (or diagenesis), elastic irregular haloes and wisps of white mica and chlorite grow around grains of quartz and feldspar. Where penetrative deformation increases, the intersti- tial micas are smeared out into thin layers anastomos- ing between lithic fragments and microaugen of quartz and feldspar. Lithic fragments and plagioclase are re- placed more and more by white mica (and calcite and chlorite). Clastic grains are crushed and lose their identity. As deformation and recrystallization prog- ressed, the micas apparently became more abundant and both quartz and mica more segregated. In the most metamorphosed sandstones, the semischists, a schis- tose mica fabric prevails with rare augen of quartz and plagioclase-bearing relict Clastic textures (see Tabor, 1972, p. 1812). FOLDS Folds of outcrop scale are common throughout the area, although hinges are hard to find and many folds are revealed only by opposing tops of beds. Folds in thinly bedded rocks most commonly have sharp hinges and are open to tightly appressed (figs. 13, 14). Fold hinges in thick-bedded sandstones are more rounded (fig. 15). Pelitic material appears to have been highly mobile. FIGURE 11.—Small tectonic blocks of sandstone in slate. The cleav- age runs left to right and the rock has fractured parallel to a quartz vein (parallel to plane of photo) which has weathered differ- entially, leaving quartz caps on the sandstone clasts. Subdomain 14, east of Mount Christie, head of Buckinghorse Creek. In folds with tightly appressed limbs, the core material is almost totally squeezed out. Folded folds are common (fig. 16), and the juxtaposition of fold hinges along shears (or small faults) make a chaotic terrane (fig. 13). The prevalence of axial-plane cleavage and flowage of material into the crest of similar folds indicates that most folding is shear folding. Very few large folds greater than outcrop scale have been found in core rocks; they appear to be more com- mon in peripheral rocks and in rocks of the western core (fig. 3). A large fold, of drag—fold form and measur- ing several kilometers across the limbs, crops out west of Mount Constance (fig. 2) in subdomain 12 (see sec- tion at end of text “Frequency Diagrams for Subdo- mains”); a poorly developed draglike fold lies east of Steeple Rock in subdomain 1, and a moderately large fold is exposed on the ridge of Mount Anderson (fig. 17). As very few individual folds or structures can be re- lated to particular phases of folding by style or orienta- tion, we do not know how these large-scale folds fit into the tectonic sequence. The shapes of the fold and steeply plunging axes suggest that they are simply large versions of the small folds. Folds in cleavage are numerous in subdomains 8 and 10 (fig. 25) and southward. The larger cleavage folds are cylindrical and open (fig. 18). A later cleavage par- allels axial planes of folds in the early cleavage. Small crinkle folds on cleavage surfaces are especially prom- inent in subdomain 10. The fold axes of the crinkles tend to parallel larger fold axes in cleavages and pencil structures (see below and fig. 30). Locally crinkle folds are folded. Conventional structural analysis depends heavily on field recognition of the relative ages of folds by their style, superposition, or orientation. We were unable to recognize various generations of folds or other struc- tures by style. That the Olympic core rocks have been subjected to several episodes of folding is shown by crinkle folds, folds in cleavage, and a few isolated folded folds and by cleavage girdles, axial-place gir- dles, and fold-axis girdles in most plots of the struc- tural elements (see section at end of text "Frequency Diagrams for Subdomains”). PENCIL STRUCTURES The most eye-catching, consistently oriented, and characteristic structures in the eastern core of the Olympic Mountains are thin slivers of rock or pencils, formed by the intersections of either two or more cleavages or cleavage and bedding. The pencils range in length from a few centimeters to 1 or 2 m (figs. 19, 20, 21). They are prominent in slate but also occur in sandstone, where they are blockier and less perfectly formed. STRUCTURAL GEOLOGY OF THE EASTERN CORE 11 FIGURE 12.—Disrupted beds and tectonic lenses ofsandstone in slate. Subdomain 17y west side of Mount Olympus. In many outcrops, especially in the western and northeastern parts of the eastern core, pencil struc— tures lie in the bedding; in the central part, especially where several generations of cleavage occur, pencils do not lie in bedding (figs. 19, 21, 22) but stand almost perpendicular to fold axes or the crests of folds. These pencils athwart fold axes are clearly formed by two cleavages and are probably later formed than their as- sociated folds. Because of their consistent orientation (homogeneity) relative to other structures, pencils ap- pear to be late-formed structures, but we observed a few outcrops where pencils are folded with the cleav- age. The orientations of pencils plotted in figure 24 are direct measurements of pencil bearings and plunge. We found that plotting intersecting cleavage and bed- ding, especially where they intersect in a small angle, gave unreliable pencil orientations. A small error in the measurement of two nearly parallel planes leads to a very large error in orientation of their intersection. The strong maximum of pencil orientations (fig. 30C) is produced partly by the large amount of data collected in the axial region of the eastern core where pencils are particularly well formed. FIGURE 13.—Recumbent fold (left) juxtaposed by faulting with in- clined fold (right). Subdomain 5, northwest of Grand Pass. 12 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON S’I‘RIITCHFD CLAST LIN liATlONS In subdomains 3, 8, 9, 10, and 14, foliated sand- stones, especially those of the Elwha lithic assemblage, commonly show a strong linear fabric of uniformly dis- tributed slate chips, 1—2 mm long. Foliated granule conglomerates display a similar lineation (fig. 23). These lineations tend to parallel pencils (fig. 30C) in the same area. MAJOR STRUCTURAL TERRANES We selected two major structural domains and 19 subdomains (fig. 25) on the basis of pencil orientation because it is the most consistent structural element (fig. 24). Although some of the subdomains roughly coincide with the major core units, most are unrecog- nizable in the field. The boundary between the princi- pal domains, Domain West and Domain East, is recog- nizable in the field by opposing dips and plunges. FIGURE 14.—Sharply hinged fold in thick-bedded sandstone with thin slate interbeds. Axial plane cleavage and a second cleavage form pencil structure in the slate beds. Subdomain 5, northeast shoulder of McCartney Peak. FIGURE 15.—Fold with rounded hinge in sandstone with dark siltstone laminations. Fold is partially sheared off along right limb. Subdomain 5, north side of Mount Cameron. FIGURE 16.—Sketch of folded isoclinal fold in slate bed. Subdomain 16, northwest of Mount Olympus. STRUCTURAL GEOLOGY Planar structures east of the boundary dip west and southwest, and most pencils plunge westward. In con- trast, planar structures west of the boundary dip to the east and northeast, and pencils plunge eastward (fig. 26). Many structures along the boundary have steep to vertical dips. Pencils in subdomains 1 and 2 (east of the boundary) actually plunge south to southeast, but the direction of plunge rotates smoothly and becomes dom- inantly westward approaching the center of Domain East. Subdomains 16, 8, and 10 best illustrate the progressive change from east to west dip of bedding and cleavage and from east to west plunge of pencils and other linear structures. OF THE EASTERN CORE 13 Subdomains 1 and 2 extend beyond the core into the peripheral rocks. In subdomain 1, only 18 percent of the data fall outside the core, and these are mostly bedding. In subdomain 2, about 50 percent of the data come from the peripheral rocks; for that reason, we broke subdomain 2 into two small domains, 2A and 2B, separated by the Hurricane Ridge fault. Except for cleavage, not present in most of the peripheral rocks in subdomain 2A, structural elements do not suggest that the peripheral rocks of this area have undergone a structural history highly different from the adjoining core rocks. As will be shown, the difference is mostly one of intensity of deformation. FIGURE 17.—Large overturned drag fold on Mount Anderson viewed from the south, subdomain 14. Data on the tops of beds show the folding although most of the hinges are sheared off. Sketch shows probable shape of the fold, axis plunges about 45° S. 35°W. 14 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON Elements of the structure are summarized for each subdomain in figure 26. The near-coplanar orientation of all the structures (note the near parallelism of prin- cipal beds, cleavage, and axial planes in most sub- FIGURE 18.—-Folds in cleavage. Traces of (younger) axial-plane cleavage in these folds can be seen to left and below hammer han- dle. Phyllite in subdomain 10, south ridge of Mount Norton. FIGURE 19.—Pencil structures in red limestone. Pencils parallel to wooden pencil; bedding strikes from left to right and dips steeply away from plane of photograph. Subdomain 7, northeast of Grand Pass. domains) is to be expected in rocks where cleavage dominates. MULTIPLE FOLDING EARLY FOLD]N(}#l-‘()Rl\l.v\'l‘l().\' OF 'l‘llli (KORE UNITS The arcuate structural packets of broken formations that make up the eastern core of the Olympic Mountains probably formed when the depositional se- quence (fig. 27A) was folded and faulted (fig. 27B, C). A scheme of this sort, though highly simplified, can be used to explain both the distribution of rocks of various ages in the eastern core units and the overturning of beds away from the core. In figure 27C, the west-facing limbs of the major folds are shown sheared off. The style of folding and sense of yielding in the early stages of the deformation (fig. 27B) are suggested by struc- tures in the western core, where folds are overturned westward (Stewart, 1970, pl. 1; Rau, 1975), and on the northwestern peninsula, where the Crescent Forma- FIGURE 20.—Pencil structures in slate. Subdomain 5, northwest of McCartney Peak. STRUCTURAL GEOLOGY OF THE EASTERN CORE tion is thrust over younger rocks (P. D. Snavely, Jr., written commun, 1976; fig. 3). Eastward underthrust- ing without large-scale folding could also account for is 1; FIGURE 21.——Large pencils in slate and siltstone at high angle to steep bedding and fold axis. Subdomain 5, ridge north of Mount Cameron. FIGURE 22.—Crude pencils parallel to axial plane of a fold but roughly perpendicular to bedding and a nearly horizontal fold axis. Subdomain 5, northwest of Grand Pass. 15 the structures in the eastern core. Considerable disrup- tion of bedding probably took place in this early stage of large-scale folding and or thrusting. The formations were broken. Horizontal fold axes or other B lineations formed at this stage are not evident in the eastern core. As we will show, early fold axes have been rotated by later shear folding. The arcuate bend of the core units did form in this early stage, for the bend controls the orien- tation of later-formed structures, and the bend indi- cates that the basaltic horseshoe was forming or al- ready extant. This horseshoe could have formed during this early stage of deformation, or, as an initial reen- trant formed by the arcuate distribution of several vol- canic seamounts (see Cady, 1975, p. 575), it could have been enhanced as the rocks of the core, predominantly sedimentary, were pressed into and against the more rigid basalt. The similarity of structural fabric in the peripheral rocks (subdomains 2A and 2B) adjacent to the main fault separating core rocks from peripheral rocks is to be expected in this scheme (see discussion of “Major Structural Terranes”). Although the rigid mass of basalts protected the peripheral rocks from being highly deformed, they were acted upon by the same forces. The entire eastern core has the aspect of a large steeply plunging fold sheared off on the south side. Al- though there is no independent way of showing that FIGURE 23.—Lineated granule conglomerate. Subdomain 9, east of Ludden Peak. 16 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON 123°15’ 47°45' 2% 4 MlLES 4 K! LOMETERS EXPLANATION “ ” ' o—45° 4s-79° 80-90° "PA" Bearing and plunge of pencils Crescent Formation Contact Fault Domain boundary FIGURE 24.—Pencil lineations in the eastern core. 47°45‘ — STRUCTURAL GEOLOGY OF THE EASTERN CORE 123°15’ [ 8 MILES we—H 8 Kl LOMETERS l FIGURE 25.—Domains and subdomains in the eastern core. 17 18 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON the peripheral rocks have been folded into the horse- ward (fig. 28). In Domain East, the B elements (fig. 30) shoe configuration (see Cady, 1975, p. 578), a pole dia- do not in any way parallel this “fold.” In Domain West, gram of bedding attitudes in the basaltic horseshoe the B lineation and B axes of beds and cleavage (fig. 29) crudely defines a ,8 fold axis that plunges steeply east- generally correspond to this axis, suggesting that at fold axes or pencils Principal bedding plane Principal cleavage plotted from maxima FIGURE 26.—Summary of principal structural elements for each subdomain. Data from section at end of text "Frequency Diagrams for Subdomains.” STRUCTURAL GEOLOGY OF THE EASTERN CORE WEST Oligocene h/ // Upper Eocene / Q3 Lower and middle Eocene ,__‘ A. Depositional sequence prior to folding. 8. Early folding and position of faults. W0, E. and NG denote the western Olympic. Elwha and Needles — Gray Wolf lithic assem blages. respectively. Oligocene / \ Lfinper Eocene\ C. After early folding and faulting, major core units established. P - P' is form llne to show later deformation in D. Crescent Formation D. After shear folding, doming, and erosion occurred. Deforma- tion of P — P' exaggerated for illustration. FIGURE 27.—Development of the eastern core by folding, faulting, and shear folding. Diagram is simplified because deformation and deposition may have gone on at the same time and may have been episodic. 19 some stage in the deformation the basaltic horseshoe either influenced structures in Domain West or devel- oped with them. The southern fault zone must have developed in this stage, for structures parallel to it are rearranged by later cleavage (see below) and it seems to be a part of the horseshoe fold. Although some of the major rock units are truncated by the fault zone, others curve around sharply to the southwest to parallel the south- ern arm of the horseshoe. On an outcrop scale, north- to northeast-trending bedding is broken and rotated by shear movement along later northwest-trending cleav- age; bedding maxima (fig. 26) reflect the rearranged bedding even though the gross lithologic units curve around to the southwest. Subdomain 18 contains ele- ments of both the fault zone and later northwest- trending cleavage. LATE FOLDING AND DOMING—FORMATION OF THE PENCILS Summary diagrams for Domain East (fig. 30) indi- cate considerable complexity, but the data reveal major features of the structure not as well shown in the sub- domains. In Domain East, there is considerable scatter of orientations, especially of bedding, cleavage, and axial planes, a pattern to be expected in multiple fold- ing. From the field evidence, we have assumed that rocks were deformed predominantly by shear folding, FIGURE 28.—Ninety-five poles to bedding in volcanic rocks in the Crescent Formation within lower 1—3 km of main part of basal- tic horseshoe. Overturned beds, mostly in northeast part of hor- seshoe, were left out. Contours at 1, 2.1, 4.2, 5.3, and 7.4 percent per 1 percent area plotted by hand. 20 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON and we have not considered flexural slip in the follow- ing analysis. In figure 31A a selected maximum for the summary cleavage s-pole diagram (fig. 303) is plotted as a principal cleavage orientation that approximately coincides with the partial girdle in the summary dia- gram for pencils (fig. 30C). This principal cleavage orientation is well represented by cleavage s-pole max- ima in subdomains 1, 2B, 4, 5, 6, 7, 9, and 11. In south- ern subdomains 13 and 15, few cleavages correspond to this orientation. Cleavage of the principal orientation is probably one of the principal planes bounding the late—formed pen— cils, hence is itself late formed. It intersects earlier planar structures of diverse orientation (mostly earlier formed cleavage and subparallel bedding which are isoclinally folded as well as partially bent around into the arc of the basaltic horseshoe; see strikes of bedding and cleavage in fig. 26). The summary fold—axis girdle (fig. 30E) intersects the principle cleavage in projection at a (fig. 31A). Most fold axes represent bedding-plane folds that probably formed in the earlier stage in the deformation. They have been rotated in a plane that defines the girdle (great circle) of figure 30E. Fold-axis maxima near a may indicate that the late shear folds are in part isoclinal. Ideally, the late shear folding, if isoclinal, rotates earlier formed fold axes into the a direction. Intersection (1 represents a west-plunging line (kinematic a) that parallels the direction of move- ment during the latest stage in shear folding (Weiss, 1959, p. 100—103). The latest movement in Domain East, then, was in general east-west direction on shear planes (cleavage) dipping southwest. The b kinematic axis for this late shear folding should lie in the cleav- age, 90° from a (fig. 31A). Axes of crinkle folds and folds in cleavage (fig. 301) tend to lie in the synoptic fold-axis girdle, indicating 209 poles to bedding with contours at 1, 2, 3, and 5 percent per 1 per— cent area cent area 25 poles to axial planes of folds in bedding 199 poles to cleavage with contours at 1, 2,3, and 5 percent per 1 per— 156 pencils with contours at 1, 2, 6, 10, and 13 percent per 1 percent area. In— cludes 26 pencils from area north of subdomain 16 29 fold axes of folds in bedding FIGURE 29.—Summary diagrams for structural elements in Domain West. STRUCTURAL GEOLOGY OF THE EASTERN CORE 21 lllliL 2,337 poles to bedding with contours 1,716 poles to cleavage with contours 1,104 pencils with contours at 1, 2, 3, at 0.1, 0.5,1.0, 1.5, 2.0, and 2.5 per— at 0.1, 0.5, 1.5, 2.5, and 3.5 percent 4, and 5 percent per 1 percent area cent per 1 percent area per 1 percent area 331 poles to axial planes of folds in 401 fold axes of folds in bedding 40 poles to axial planes of folds in bedding with contours at 0.3, 1, 2, with contours at 0.2, 1, 2, and cleavage with contours at 3, 5,10, 3, and 4 percent per 1 percent area 2.5 percent per 1 percent area and 13 percent per 1 percent area 66 fold axes of folds in cleavage with 16 long axes of stretched slate 81 crinkle folds in cleavage of contours at 2, 3, and 5 percent per chips in sandstone and pebbles phvllite and slate 1 percent area in conglomerate FIGURE 30.—Summary diagrams for structural elements in Domain East. 22 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON that they too are earlier formed B structures. As they themselves formed after cleavage had formed, they in- dicate multiple shear folding prior to the last stage of shear folding under consideration here. Although stretched-clast lineation (fig. 30H) usually coincides with the a direction, probably indicating extension in the east—west direction, the small amount of data, espe- cially in subdomains to the northeast, precludes recog- nition of a possible girdle. If the long axis of the clasts lay in the plane containing the fold axes, some clasts at least would have to parallel earlier formed B elements. Summary diagrams for Domain West display a fair monoclinic symmetry with a steeply dipping north- east-striking symmetry plane (fig. 29). They are not so amenable to the same analysis as Domain East be- cause they contain much less data and the pencil girdle is less discrete (fig. 290), making identification of a late cleavage less certain. The summary pencil diagram (fig. 290) contains data from the area north of subdo- main 16 (figs. 24, and 25), where pencil structure is poorly defined. This area was not otherwise included in the analysis, partly because of sparsity of well- developed cleavage, but the pencils help define a par- tial girdle. There is considerable continuity in pencil structures across the eastern core, suggesting they all formed by the same process. The fan of cleavage from east to west suggests that the pencils formed together in the latest stage of deformation and that, on the west, steeply eastward-dipping late cleavage and earlier planar Selected O/ cleavage maxima Fold‘axis E maXIma structures controlled pencil formation. By analogy to the features discussed for Domain East, then, a weak girdle of early-formed fold axes (fig. 29E) intersects a principal cleavage plane near a possible pencil girdle at a (fig. 313). At 90° from a in the cleavage is the b axis of the late shear folding. It is subhorizontal and trends north northwest; its proximity to the theoretical b axis for Domain East shows the results of the analysis for the two domains to be consistent. In Do- main West, the a movement direction is roughly paral- lel to the monoclinic symmetry plane of the total struc— tural fabric, as is required by the symmetry. The late shear folding is present in both major do— mains. The direction of yielding, based on the orienta- tion of a, was steeply up and westward in Domain West and more gently up and eastward in Domain East. The analysis of only two major domains has generalized kinematic direction a into two directions, whereas ac- tually it probably is distributed in a fan from west to east, radiating upward from a sub-horizontal north- northwest—trending b axis. We picture a mushrooming dome, with fan of cleavage, extended asymmetrically to the east (fig. 27D). SUMMARY OF THE DEFORMATION By our analysis, deformation of the rocks of the Olympic Mountains can be summarized as four episodes: (1) The thick sequence of lower Tertiary sandstone and shales with thin interbeds of pillow basalt (fig. Probable location", of fold axis girdle;\/zg ‘ '. \ -_ \'. Approximate location of a OSelected cleavage maxima FIGURE 31.—Intersection (a) of the principal shear cleavage of the late stage of deformation with girdle of early fold axes and constructed b kinematic axis. A, Domain east. B, Domain west. STRUCTURAL GEOLOGY OF THE EASTERN CORE 23 27A) was isoclinally folded along roughly northwest- southeast trending axes, then faulted, imbricated, and overturned westward (fig. 273). Imbricate faulting without major folding would also produce the pattern seen today. Rocks may not have been highly lithified during early stages of deformation, but cleavage could have developed very early (Moore and Geigle, 1974, p. 509). The folding and imbrication may well have begun before deposition of Oligocene rocks. (2) Continued deformation under east—west compres- sion pressed the core rocks into an arc of basaltic rocks that was forming in response to deformation or was already extant from the initial distribution of sea- mounts. The easternmost core rocks were bent into the horseshoe fold on the north but were mostly sheared off below the basalt on the south and southeast along the southern fault zone. (3) Deformation continued, and as the pile of sedimentary rocks, now thoroughly lithified, became even more constrained by the basaltic horseshoe, which may have ceased yielding, the core rocks yielded upward and outward by shear folding (fig. 27D). An overall mushroomlike dome, highly asymmetric to the east and northeast, developed with a fan of cleavage. The conspicuous pencil structures formed where the new cleavage intersected older, deformed bedding and cleavage. In much of Domain East, the sense of shear in this last stage of deformation was opposite that of the earlier stages. Any one of the east-dipping shear planes in the eastern core that had undergone east- ward underthrusting in the early stages of deformation was now bent over eastward, and movement continued as eastward overthrusting. There is no way to tell from data in the eastern core if the deformation process was continuous or sporadic, although Tertiary unconformities on the west (Snavely and Pearl, 1975) suggest distinct episodes of deforma- tion. (4) The final uplift of the Olympic Mountains could well have been isostatic because of the thickened pile of sedimentary rocks. This uplift would increase the over- turning of structures on the east, especially if there was considerable differential uplift in the center of the range as suggested by uplift to higher elevations of rocks of the highest metamorphic grade (see Tabor, 1972, p. 1811). PLATE MARGIN TECTONICS The sedimentary history and style of deformation in the western core led Stewart (1970, p. 66) to propose plate margin deformation in the Olympic Mountains. The severe disruption of the eastern core rocks and the overall progression of ages from oldest to youngest westward, even though tops indicate eastward young- ing, is strong evidence for subduction (Maxwell, 1974, p. 1195). Recent studies of trench deposits have devel- oped a scenario of deformation that in part at least fits the history of deformation in the Olympic core rocks (see Grow, 1973, fig. 6; Karig and Sharman, 1975, figs. 2, 7; Moore and Karig, 1976, p. 1266—1267). A gen— eralized section (fig. 32) based on a figure from Karig and Sharman (1975, p. 3791) illustrates how Olympic core rocks may have been emplaced in the accretionary prism. The absence of blueschist-facies rocks and ul- tramafic rocks is evidence that Olympic rocks were ac- creted high in the subduction zone, not dragged down the descending slab or mixed with mantle material. There is no exact analogy between Olympic rocks and typical island—arc systems because massive ac- cumulations of submarine basalt similar to the prob- able seamounts of the Crescent Formation (Snavely and Wagner, 1963, p. 3—5; Lyttle and Clarke, 1975) close to the continental margin (see Cady, 1975, p. 57 9—580) have not been reported elsewhere. In the al- ternative model proposed by Glassley (1974, p. 792) and Glassley, Lyttle, and Clarke (1976), oceanic basalt of a ridge or intraplate seamount occurring in the lower part of the Crescent Formation is juxtaposed by faulting with Hawaiian Island-type basalt of the upper part of the Crescent Formation. This interpretation implies that at least the lower part of the Crescent Formation was partially subducted in the early stages of deformation. Whatever the origin of the basalt, its great mass provided a resistant bulwark to the sub- ducted sediments. The deformation history of the east- ern core, beginning with imbricate underthrusting and ending with mushroom-like shear folding, is appropri- ate for an accreted mass of sediments pushed against a rigid mass. The less intensely deformed peripheral sedimentary rocks accumulated back (east) of the sub- ducted part of the accretionary prism, protected from severe deformation by the rigid horseshoe of basalt. This summary of deformation simplifies a very com- plex process. There may have been considerable over- lap of each stage. Deformation of lower and middle WEST EAST |<——Olympic core rocks fiperipheral rocks—ti ' nar r'sm k—Accretlo y D I *4 Crescent k—SUBDUCTION ZONE Formation \ .N \ FIGURE 32.—Generalized section through Olympic Mountains at plate margin. Modified from Karig and Sharman (1975). 24 Eocene rocks of the eastern core may well have begun while upper Eocene and Oligocene rocks were still being deposited to the west. Underthrusting and im- brication in the western core may have continued while late—stage shear folding and doming progressed in the eastern core. We believe that this study has successfully analyzed the very complex deformation of an exposed subduction zone, mainly owing to the large amount of data and the availability of computers and programs to handle it. Broken formations and melanges elsewhere that ap- pear inordinately complex structurally may yield a coherent deformational scheme through statistical structural analysis. REFERENCES CITED Brown, R. D., Jr., Gower, H. D., and Snavely, P. D., Jr., 1960, Geol- ogy of the Port Angeles—Lake Crescent area, Clallam County, Washington: US. Geol. Survey Oil and Gas Inv. Map OM‘203, scale 1262,500. Cady, W. M., and MacLeod, N. S., 1963, Geological Survey research 1963—Summary of investigations: U.S. Geol. Survey Prof. Paper 475—A, p. A96. Cady, W. M., Tabor, R. W., MacLeod, N. S., and Sorensen, M. L., 1972, Geology of the Tyler Peak quadrangle, Washington: US. Geol. Survey Geol. Quad. Map GQ«970, scale 1:62,500. Cady, W. M., Sorensen, M. L., and MacLeod, N. S., 1972, Geology of the Brothers quadrangle, Washington: US. Geol. Survey Geol. Quad. Map GQ—969, scale 1:62,500. Cady, W. M., 1975, Tectonic setting of the Tertiary volcanic rocks of the Olympic Peninsula, Washington: US. Geol. Survey Jour. Research, v. 3, no. 5, p. 573—582. Cheney, E. S., and Stewart, R. J., 1975, Subducted graywacke in the Olympic Mountains, USA—implications for the origin of Ar- chaean sodic gneisses: Nature, v. 258, p. 60—61. Cowan, D. S., 1974, Deformation and metamorphism of the Francis- can subduction zone complex northwest of Pacheco Pass, California: Geol. Soc. America Bull., v. 85, p. 1623—1634. Crook, K. A., 1960, Classification of arenites: Am. Jour. Sci., v. 258, p. 419—428. Danner, W. R., 1948, A contribution to the geology of the Olympic Mountains, Washington: Washington Univ., Seattle, M.S. thesis, 67 p. 1955, Geology of Olympic National Park: Seattle, Olympic National History Assoc, Univ. Washington Press, 68 p. Glassley, W. E., 1974, Geochemistry and tectonics of the Crescent volcanic rocks, Olympic Peninsula, Washington: Geol. Soc. America Bull., v. 85, p. 785—794, Glassley, William, Lyttle, N. A., and Clarke, D. B., 1976, New analyses of Eocene basalt from Olympic Peninsula, Wash- ington—Discussion and reply: Geol. Soc. America Bull., v. 87, p. 1200—1204. Gower, H. D., 1960, Geologic map of the Pysht quadrangle, Washing- ton: U.S. Geol. Survey Geol. Quad. Map GQ—129, scale 1:62,500. Grow, J. A., 1973, Crustal and upper mantle structure of the central Aleutian arc: Geol. Soc. America Bull., V. 84, p. 2169—2191. Harvey, J. L., 1959, Geologic reconnaissance, S. W. Olympic Penin- sula: Washington Univ., Seattle, M.S. thesis, 53 p. Hawkins, J. W., Jr., 1967, Prehnite-pumpellyite facies metamorph- ism of a graywacke-shale series, Mount Olympus, Washington: Am. Jour. Sci., v. 265, p. 798—818. THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON Hsii, K. J., 1968, Principles of melanges and their bearing on the Franciscan-Knoxville paradox: Geol. Soc. America Bull., v. 79, p. 1063—1074. 1969, Preliminary report and geologic guide to Franciscan melanges of the Morro Bay—San Simeon area, California: California Div. Mines and Geology Spec. Pub. 35, 46 p. Karig, D. E., and Sharman, G. F., 3d, 1975, Subduction and accretion in trenches: Geol. Soc. America Bull., v. 86, p. 377—389. Koch, A. J., 1968, Petrology of the “Hoh Formation” of Tertiary age in the vicinity of the Raft River, western Washington: Washing- ton Univ., Seattle, M.S. thesis, 41 p. Lindquist, J. W., 1961, Geology and paleontology of the fork area, Dungeness and Greywolf River, Clallam County, Washington: Washington Univ., Seattle, M.S. thesis, 185 p. Lyttle, N. A., and Clarke, D. B., 1975, New analyses of Eocene basalt from the Olympic Peninsula, Washington: Geol. Soc. America Bull., v. 86, p. 421-427. McKee, Bates, 1972, Cascadia—The geologic evolution of the Pacific Northwest: New York, McGraw-Hill Book Co., 394 p. McMichael, L. B., 1946, Geology of the northeastern Olympic Penin- sula, Washington: Washington Univ., Seattle, M.S. thesis, 33 p. Maxwell, J. C., 1974, Anatomy of an orogen: Geol. Soc. America Bull. V. 85, p. 1195»1204. Miller, M. S., 1967, The bedrock geology of the southeast quarter of Mount Steel quadrangle, Washington: Washington Univ., Seattle, M.S. thesis, 78 p. Moore, J. C., and Geigle, J. E., 1974, Slaty cleavage—incipient occur- rences in the deep sea: Science, v. 183, p. 509—510. Moore, J. C., and Karig, D. E., 1976, Sedimentology, structural geol~ ogy, and tectonics of the Shikoku subduction zone, southwestern Japan: Geol. Soc. America Bull., v. 87, p. 1259—1268. Muecke, G. K., and Charlesworth, H. A. K., 1966, Jointing in folded cardium sandstones along the Bow River, Alberta: Canadian Jour. Earth Sci., v. 3, p. 579—596. Page, B. M., 1966, Geology of the Coast Ranges of California, in Bailey, E. H., ed., Geology of northern California: California Div. Mines and Geol. Bull. 190, 508 p. Park, C. F., Jr., 1950, Structure in the volcanic rocks of the Olympic Peninsula, Washington: Geol. Soc. America Bull., v. 61, no. 12, pt. 2, p. 1529. Rau, W. W., 1964, Foraminifera from the northern Olympic Penin- sula Washington: US. Geol. Survey Prof, Paper 374—G, 33 p. 1973, Geology of the Washington coast between Point Gren- ville and the Hoh River: Washington Dept. Natural Resources Bull. 66, 58 p. 197 5, Geologic map of the Destruction Island and Taholah quadrangles, Washington: Washington Geologic and Earth Re- sources Div. Map GM 13, scale 1:62,500. Snavely, P. D., Jr., and Wagner, H. C., 1963, Tertiary geologic his- tory of western Oregon and Washington: Washington Div. Mines and Geology Rept. Inv. 22, 25 p. Snavely, P. B., Jr., and Pearl, J. E., 1975, Geological Survey research 1975—Summary of investigations: U.S. Geol. Survey Prof. Paper 975, p. 128. Stewart, R. J., 1970, Petrology, metamorphism, and structural rela- tions of graywackes in the western Olympic Peninsula, Wash- ington: Stanford Univ., Stanford, Ph.D. Thesis, 129 p. 1971, Structural framework of the western Olympic Penin- sula, Washington: Geol. Soc. America Abs. with Programs, v. 3, no. 2, p. 229. Suppe, John, 1973, Geology of the Leech Lake Mountain—Ball Mountain region, California: California Univ. Pubs. Geol. Sci., v. 107, 82 p. Tabor, R. W., 1971, Origin of ridge-top depressions by large-scale creep in the Olympic Mountains, Washington: Geol. Soc. REFERENCES CITED 25 America Bu11., V. 82, p. 1811—1822. 1972, Age of the Olympic metamorphism, Washington—K-Ar dating of low-grade metamorphic rocks: Geol. Soc. America Bull., v. 83, p. 1805—1816. 1975, Geologic guide to Olympic National Park: Seattle, Univ. Washington Press, 144 p. Tabor, R. W., Cady, W. M., and Yeats, R. S., 1970, Broken formations and thrust faulting in the northeastern Olympic Mountains, Washington: Geol. Soc. America Abs. with Programs, v. 2, no. 2, p. 152. Tabor, R. W., Yeats, R. S., and Sorensen, M. L., 1972, Geologic map of the Mount Angeles quadrangle, Washington: U.S. Geol. Survey Geol. Quad. Map GQ—958, scale 1:62,500. Tabor, R. W., and Cady, W. M., 1978, Geologic map of the Olympic Peninsula: U.S. Geol. Survey Map 1—994, scale 1:125,000. Weaver, C. E., 1937, Tertiary stratigraphy of western Washington and northeastern Oregon: Washington Univ. Pub. in Geology, v. 4, 266 p. Weiss, L. E., 1959, Geometry of superposed folding: Geol. Soc. America Bull, v. 70, p. 91—106. Weissenborn, A. E., and Snavely, P. D., Jr., 1968, Summary report on the geology and mineral resources of the Flattery Rocks, Quil- layute Needles, and Copalis National Wildlife Refuges: U.S. Geol. Survey Bull. 1260—F, 16 p. 1. R ._R,:_ L SUPPLEMENTAL INFORMATION 28 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON SUPPLEMENTAL INFORMATION FREQUENCY DIAGRAMS FOR SUBDOMAINS Frequency diagrams for subdomains shown on figures 25 and 26. Contours drawn by hand on percentages calculated and plotted by computer to nearest whole number; contours shown to lower right of each diagram. All percentages calculated per one percent area. Data not contoured if less than 40 points. 29 SUPPLEMENTAL INFORMATION A: mwcfln .EXu 0w afloa w “A; $xw 20* FF A: 3.55 Ex.» 9 3.0a NF 2; max.“ 30» mp A: mwcfla it.» Ow no.2... mw ”3 «38 20+ ON m__u:aa ww m:o:wa hm «cwoaa NP K .m .m .w ..2_ocon mm mmn>m2o op mgon mp 0323.0 3 3.0a C. «:8th h .m .m .P 63520 3 38a 2. «:8th w :v N .F ”anon 3 no.0.“ mow Emu :m I mm EmEoBam ucmuhoa w .v .N .F ”flown Ow 3.0.”. was Sat =m I w2u OH 3.0a m3. A: mmcfla _m_Xm Ow «6.2. N A: $38 20* m m__ocon mm 33>me op 3.0a mm «:3th w :v ~Hm .9 Rows cu 3.0a .vn 8% __m 1 a 53255 232 op mo_oa m2o Ow mo_on 3: ”:50th m K .m .m .p “mums Ow aflon Nov 382% mummy men 1 S 525an U302“; mwmv ammo l m EmEoEJm ucoohoa : K .v .N ”muwn Ow mm_ou m1 3% __m I m 5,835 33 SUPPLEMENTAL INFORMATION A+v mmcma _m_xw cu moan w: ® 23 3mm mucaumcoo 2i mocma Exm op “Eon n 3 max—w 30+ _. ours... «mo>>© (u. 09:: ummw @an m< 3 #38 v.8 «N mac} ummm - (L 09:... ~33 Eon m< TV mwcfln _m_xm cu 3.9; m_. ~ .3 3:8 .23 mm _. ® ~55th Np . p .m 9 3:28. E mzocmn m #56th NF . m .w .m Essa me “:8th w .w .m .N .p $3.;wa 3. 3:5 mm wcwoLwQ or .w .V N $393.0 3 ”20a om «smegma or .w .m .F “mmmm>mm_o cu mw_0n_ mm «c0030 w .m .m .p “mums Ow mm_oa hm mum—u :m I. mp EmEOUnam #53th w .m .1 .N .F ”mums op m2oa Vnr mam—u :m I S 52538 ucwoLwa 0—. K .m ._. 3an Op mw_on mn 5% __m I : EmEoEzw THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON 34 At $53 Exw Ow mo_on w 2; moxm mEOw O— A+v mmcma _w_xw ca mw_oa m XL «38 EC», m “cwuLmQ N_. K .N .6953 F53 op 3.0a 5v ucwuhwa or .m N .6me 30+ mm m:o:ua mu mzucon. m 2.60th Z. .w .v .N 3.5.3520 3 3.9.. m? E82 3 .5 K .m d .F “mmm>mo_o on «Eon VA acmema or .NF .w .v .» umzucmn MK unmoLma w .w :v ‘N .F ..wmm>mw.o 0w 3.0a mmw “>50th m .m .N ”mnmn ou m2oa mm Emu :m I E 52535 uchEQ or .0 .V .N ._. ”muwn Ow 3.00. .v: Emu Sun I m, EmEoBsm acmoaa m :V .N .F .‘mUmn 0w 3.0a nor 3% __m I 3 55033 35 SUPPLEMENTAL INFORMATION A1 9.53 338 :3 «.98 30+ N A: mwcfln .EXN Ow 3.0a m: "3 £38 30w hr azucoa mm m=ocmn hm ucwewa w :v .m .F “mmwm>mm_o op 3.0a hh wcwohwa or K .m .— wamm>m20 cu 3.0a K wcwogma w .m .v .N .6an Ga m20Q on Sat :m I M: 5.53% «:8th n .v N .F “muwn cw aflon Pw 8% __m I C 59833 36 THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON COMPUTERIZED STRUCTURAL DIAGRAM PROGRAM In order to handle the large amounts of complex structural data obtained while mapping the Olympic Mountains, we established a two-part computer program in Fortran IV. The first part allows stor- age of the structural data on punchcards with provisions to select the data by type and geographic location (subdomain). The second part of the program prepares a pole-density orientation diagram from the selected data. The computer program for pole-density orientation diagrams was made at the University of Alberta by Muecke and Charlesworth (1966). Our orientation program deck is a duplicate of the Canadian deck, lent to us by Dr. Charlesworth. Ming K0, of the U.S.G.S. Computer Center, modified the Canadian program for our needs. The storage of data was facilitated by the use of forms (fig. 33) that we filled out in the field. Any type of line or plane can be entered on the form and treated by the program. We measured dips to the nearest 5", strikes to the nearest 2°. Before the data were entered on punch cards, station coordinates were punched by use of a coor- dinatograph. The program allows subdomains to be selected by coordinates and (or) indicated stations. If coordinates are used, each subdomain is outlined as nearly as possible by two rectangles, specified by their southwest and northeast corners. Stations can be added or subtracted individually to fill in irregular subdomains. Because the Olympic rocks are particularly prone to sliding and slumping (see Tabor, 1971), we included an option of select data on the basis of field observation of reliability, a somewhat subjective judgment. We found that the results for all data and for only the best data were about the same. Most subdomains were run with all the data. The following summary of the pole-density orientation program is modified from a description of the program by H. A. K. Charlesworth (written commun., 1967). The program counts out points on the reference sphere, not on their projection in the equatorial plane. The pole densities obtained are then projected onto the equatorial plane and faithfully reflect the true pole densities. The computer converts the strike, dip, and direction of a plane to the bearing and plunge of the normal to the plane. All the bearings and plunges are then changed into direction cosines of unit length. The counting out of the poles in the reference sphere is accom- plished by the use of a circular cone with semivertical angle, the value of which is determined by the percentage of the total area of the projection that the counter is required to cover. The percentage of the total area counted and the number of counting locations are chosen such that the counting cones overlap so as to assure that all points on the sphere are counted. At the same time, the counting area is kept small in order to obtain the best possible definition of any differences in the densities of the points. The number of data readings in each data set falling within the counting cone at each counting locality is converted into the percent— age of the total number of points processed. In order to facilitate a simple output format for a line printer, the counting locations were chosen to form a regular grid and projected from the lower hemisphere of the reference sphere onto the equato- rial plane by equal—area projection (fig. 343). For the convenience of accurate contouring, these locations were augmented by 14 ad- ditional points near the periphery ofthe projection. We contoured the printed densities by hand; a subprogram that plots the projections of the pole intersections (fig. 34A) was especially useful in subdomains with small amounts of data. In keeping with the spirit established by Muecke and Charles- worth, we maintain a program card deck with our modifications (data retrieval and plotting subroutine), available for loan and dupli- cation. Address inquiries to R. W. Tabor, US. Geological Survey, 345 Middlefield Road, Menlo Park, Calif. 94025. 37 SUPPLEMENTAL INFORMATION v a 9:9. J £2 Eon 25: its. 3: So an: :3: :uo .52. c 3 IE» 4 mm mmVnupaocmm nuns m u m .mumv 19:53:? (8m 5.5m xoasafioollfim “559m 3 3 Nu : A :2 u HHUCQA m —V on mm at oxvhm H v >mu~u 9 a. C o— :v 9i: H v S muom RN moan mNNEEm—ECE . fin. _:o_ X mwumcfiunooo .22 :0. monomVnN .mum H uwnED: uawwh ooh wmcn~ — THE STRUCTURE OF THE OLYMPIC MOUNTAINS, WASHINGTON 38 dam: z: vegagcoo d2“ 3:8ng H .8.” mmmmgoflom 5 Saw macaw mo 83 3:3th ,m .% amohmm: 05 3 mama wigs“: mo 8&5; an mm unwfiwszm 533:0 .mmonwa o2 Sm 333° hog—o5 4x .355 3 59a 3263 $3ng .Emgmoa #93356 Sm 335° Easmfioolfim "EDGE m|__Uan. me_|_ omw V a? 3n9V‘é 35 Crustal Structure of the Western United States By CLAUS PRODEI—IL GEOLOGICAL SURVEY PROFESSIONAL PAPER 1034 A reinterpretation of seismic-refraction measurements made from 1961 to 1963 and a comparison with the crustal structure of central Europe 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 Prodehl, C. 1936- Crustal structure of the Western United States. (Geological Survey professional paper ; 1034) Includes bibliographical references. Supt. of Docs. no.: I 19.1621034 1. Geology—The West. 2. Earth—Crust. 3. Seismic refraction method. 4. Geology—Central Europe. I. Title. II. Series: United States. Geological Survey. Professional paper ; 1034. QE79.P76 551.1’3’0978 79-607072 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock Number 024-001-03214-7 CONTENTS Page Page Abstract —-— 1 Analysis of seismic-refraction profiles—Continued Introduction — 2 Coast Ranges of California 35 Acknowledgments -— 2 San Francisco to Santa Monica Bay —————————— 35 Geophysical fieldwork 3 Other profiles from Santa Monica Bay ————————— 36 Procedure of interpretation —— 3 Transverse profiles from San Francisco and San Record sections —— 3 Luis Obispo — 38 Principles of observed traveltime diagrams ——————— 5 Colorado Plateau ——.—— 38 Calculation of the velocity-depth function Middle Rocky Mountains — 40 from the traveltime diagram —————————————— 7 Results and discussion ———————————————————— 42 Analysis of seismic-refraction profiles —————————————— 13 Basic data —— 42 Basin and Range province — 14 Crustal structure 43 Delta, Utah, to Fallon, Nev —————————————— 14 Discussion 46 Boise, Idaho, to Lake Mead. Nev ——————————— 18 Comparison with seismic-refraction studies in Profiles in the southern Basin and Range central Europe ____ 51 province ——————————————————————— 23 Traveltime diagram — 52 Other profiles from NTS ———— 27 Basic data— 55 Sierra Nevada —— ——— 29 Crustal structure -— 56 Shasta Lake to China Lake —————————————— 29 References cited ————————————————————4——— 59 Other profiles in the Sierra Nevada —————————— 32 Supplemental tables —— 63 ILLUSTRATIONS [Plates are in pocket] Page PLATE 1. Location of shotpoints and recording units, and fence diagram showing crustal structure under California and Nevada and adjacent areas. [Includes figs. 2 and 87.] 2. Record sections of seismic profiles. [Sheet 1 includes figs. 10, 11. 13-24, 26—31, 35. 41-44, 46; sheet 2 includes figs 47—49, 51—60, 64—67, 69—75. and 77—80.] 3. Crustal cross sections. [Includes figs. 12, 25. 36-40. 45, 50, 61—63, 68, 76, and 81.] FIGURE 1. Map showing physical divisions of the Western United States and location of seismic profiles ———————— 4 2. Map showing location of shotpoints and recording units on the reinterpreted profiles ———————————— Plate 1 3. Typical seismic record— —— 5 4. Simplified geologic map of the Western United States —— 6 5. Basic traveltime diagram 7 6. Diagrams illustrating principles of observation and their inversion into velocity-depth functions ——————— 9 7. Diagram showing z/A versus V ( T/A) with velocity gradient d V/dz being parameter ————————————— 1 1 8. Diagrams showing examples of velocity-depth functions 12 9. Record section of the profile from Delta to SHOAL — 15 10. Record section of the profile from Eureka to Fallon Plate 2 1 1. Record section of the profile from Fallon to Eureka Plate 2 12. Crustal cross section from San Francisco, Calif, to Delta, Utah -— — Plate 3 13—24. Record sections of the profiles: 13. From Boise to Elko Plate 2 14. From Strike Reservoir to Boise Plate 2 15. From Strike Reservoir to Elko Plate 2 16. From Mountain City to Boise Plate 2 17. From Mountain City to Eureka Plate 2 18. From Elko to Boise— Plate 2 19. From Elko to Eureka Plate 2 20. From Eureka to Mountain City —— Plate 2 21. From Eureka to Lake Mead — Plate 2 22. From Hiko to Eureka Plate 2 23. From Hiko to Lake Mead —— —— ————- Plate 2 24. From Lake Mead to Eureka —— Plate 2 Crustal cross section from Boise, Idaho, to Lake Mead, Nev Plate 3 25. III IV FIGURES 26—31. 32. 33. 34. 35. 36—40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51-59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69—75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. CONTENTS Record sections of the profiles: Page 26. From Lake Mead to Mono Lake —————————————————————————————————— Plate 2 27. From Lake Mead to Santa Monica Bay —————————————————————————————— Plate 2 28. From NTS to Kingman —————————————————————————————————————— Plate 2 29. From Kingman to NTS —————————————————————————————————————— Plate 2 30. From N TS to Ludlow ——————————————————————————————————————— Plate 2 31. From Ludlow to N TS ——————————————————————————————————————— Plate 2 Reduced traveltime graph of the profile from Ludlow to Mojave —————————————————————— 24 Reduced traveltime graph of the profile from Barstow to Ludlow —————————————————————— 24 Reduced traveltime graph of the profile from Barstow to Mojave —————————————————————— 24 Record section of the profile from Mojave to Ludlow ———————————————————————————— Plate 2 Crustal cross sections: 36. From Lake Mead, Nev., to Mono Lake, Calif ———————————————————————————— Plate 3 37. From Lake Mead, Nev., to Santa Monica Bay ——————————————————————————— Plate 3 38. From NTS to Kingman, Ariz ——————————————————————————————————— Plate 3 39. From Eureka, Nev., to Ludlow, Calif ——————————————————————————————— Plate 3 40. From Mojave to Ludlow, Calif —————————————————————————————————— Plate 3 Record section of the profile from NTS to Navajo Lake ——————————————————————————— Plate 2 Record section of the profile from Navajo Lake to NTS ——————————————————————————— Plate 2 Record section of the profile from N TS to Elko ——————————————————————————————— Plate 2 Record section of the profile from NTS to San Luis Obispo ————————————————————————— Plate 2 Crustal cross section from San Luis Obispo, Calif., to Navajo Lake, Utah —————————————————— Plate 3 Record section of the profile from Shasta Lake to Mono Lake ———————————————————————— Plate 2 Record section of the profile from Mono Lake to Shasta Lake ———————————————————————— Plate 2 Record section of the profile from Mono Lake to China Lake ———————————————————————— Plate 2 Record section of the profile from China Lake to Mono Lake ———————————————————————— Plate 2 Crustal cross section from Shasta Lake to China Lake, Calif ———————————————————————— Plate 3 Record sections of the profiles: 51. From China Lake northwest ——————————————————————————————————— Plate 2 52. From China Lake west —————————————————————————————————————— Plate 2 53. From China Lake to Santa Monica Bay —————————————————————————————— Plate 2 54. From Mono Lake to Santa Monica Bay —————————————————————————————— Plate 2 55. From Fallon to San Francisco —————————————————————————————————— Plate 2 56. From Fallon to Mono Lake ———————————————————————————————————— Plate 2 57. From Mono Lake to Fallon ———————————————————————————————————— Plate 2 58. From Fallon to China Lake ———————————————————————————————————— Plate 2 59. From Mono Lake to Lake Mead —————————————————————————————————— Plate 2 Record section of fan observations from Mono Lake at 230 km distance ——————————————————— Plate 2 Crustal cross section from China Lake, Calif, toward northwest —————————————————————— Plate 3 Crustal cross section from Fallon, Nev., to Santa Monica Bay, Calif, crossing China Lake —————————— Plate 3 Crustal cross section from‘Fallon, Nev. to Santa Monica Bay, Calif, crossing Mono Lake —————————— Plate 3 Record section of the profile from San Francisco to Camp Roberts ————————————————————— Plate 2 Record section of the profile from Camp Roberts to San Francisco ————————————————————— Plate 2 Record section of the profile from Camp Roberts to Santa Monica Bay ——————————————————— Plate 2 Record section of the profile from Santa Monica Bay to Camp Roberts ——————————————————— Plate 2 Crustal cross section from San Francisco to Santa Monica Bay, Calif ———————————————————— Plate 3 Record sections of the profiles: 69. From Santa Monica Bay to Mono Lake —————————————————————————————— Plate 2 70. From Santa Monica Bay to China Lake —————————————————————————————— Plate 2 71. From Santa Monica Bay to Lake Mead —————————————————————————————— Plate 2 72. From San Francisco to Fallon —— —— ——— ——————————————— Plate 2 73. From San Luis Obispo to NTS — ———-— —— — ————————————— Plate 2 74. From Hanksville to Chinle ———————————————————————————————————— Plate 2 75. From Chinle to Hanksville ———————————————————————————————————— Plate 2 Crustal cross section from Hanksville, Utah, to Chinle, Ariz. ———————————————————————— Plate 3 Record section of the profile from American Falls Reservoir to Flaming Gorge Reservoir —————————— Plate 2 Record section of the profile from Flaming Gorge Reservoir to American Falls Reservoir —————————— Plate 2 Record section of the profile from Bear Lake to American Falls Reservoir —————————————————— Plate 2 Record section of the profile from Bear Lake to Flaming Gorge Reservoir —————————————————— Plate 2 Crustal cross section from American Falls Reservoir, Idaho, to Flaming Gorge Reservoir, Utah ——————— Plate 3 Contour map of the crossover distance Ad for California and Nevada and adjacent areas ——————————— 45 Contour map of the “critical” distance Ac for California and Nevada and adjacent areas ——————————— 45 Contour map of the reduced traveltime To — TM for California and Nevada and adjacent areas ———————— 45 Contour map of the average P" velocity for California and Nevada and adjacent areas ———————————— 47 Record section of the profile from SHOAL to Delta ————————————————————————————— 48 FIGURE CONTENTS Page 87. Fence diagram showing the crustal structure under California and Nevada and adjacent areas ——————— Plate 1 88. Contour map of total crustal thickness under California and Nevada and adjacent areas ——————————— 47 89. Contour map of the velocity umc) at the depth of strongest velocity gradient 2(Ac) in the crust-mantle transi- tion zone California and Nevada and adjacent areas __________________________ 47 90. Bouguer gravity anomaly map of the area of investigation ————————————————————————— 47 91. Graph showing relation between grade of metamorphism and density of the B'undner Schiefer ———————— 51 92. Index map of seismic-refraction profiles in the Alps and their vicinity ———-—————————————————_‘__ 52 93. Record sections of three profiles in central EurOpe ————————————————————————————— 53 94. Contour maps of the parameters Ad. AC, and t: for the Alps ————————————————————————— 54 95. Contour map of total crustal thickness under central Europe ———————————————————————— 56 96. Fence diagram showing the crustal structure under the Alps ———————————————————————— 58 TAB LE S Page TABLE 1. Location of shotpoints — ——-—— ____________________ 5 2—53. Velocity-depth functions of the profiles from: 2. Delta to SHOAL ____________________________________________ 16 3. Eureka to Fallon ____________________________________________ 17 4. Fallon to Eureka ____________________________________________ 17 5. Boise to Elko _____________________________________________ 19 6. Strike Reservoir to Elko ———————————————————————————————————————— 20 7. Mountain City to Boise ———————————————————————————————————————— 20 8. Mountain City to Eureka ________________________________________ 20 9. Elko to Boise — ———— —— __ _ _____ 20 10. Elko to Eureka ——————————— _ ________________ 21 11. Eureka to Mountain City ————————————— —— —_ __-_ 21 12. Eureka to Lake Mead ————————————————————————————————————————— 21 13. Lake Mead to Eureka ———— ———— ___________ 22 14. Lake Mead to Mono Lake _______________________________________ 25 15. Lake Mead to Santa Monica Bay ____________________________________ 25 16. N TS to Kingman ——————————————————————————————————————————— 25 17. Kingman to NTS ——————————————————————————————————————————— 2 5 18. NTS to Ludlow ———————————————————————————————————————————— 25 19. Ludlow to N TS ———————————————————————————————————————————— 26 20. Ludlow to Mojave ——————————————————————————————————————————— 26 21. Barstow to Ludlow __________________________________________ 26 22. Barstow to Mojave __________________________________________ 26 23. Mojave to Ludlow ——— __________________ 26 24. NTS to Navajo Lake ————— _ __________________ 28 25. Navajo Lake to NTS ———— —— _— ________________ 28 26. NTS to Elko — —— __________________ 28 27. NTS to San Luis Obispo —————————————————— ____ __ ___ 28 28. Shasta Lake to Mono Lake ————————— _— __ _____________ 31 29. Mono Lake to Shasta Lake —— ——— ___________ 31 30. Mono Lake to China Lake ___________________ 31 31. China Lake to Mono Lake —— ____________________ 31 32. China Lake to northwest ———————————————————————————————————————— 32 33. China Lake to Santa Monica Bay ____________________________________ 33 34. Mono Lake to Santa Monica Bay ____________________________________ 33 35. Fallon to San Francisco ——————————— _ _ ____________ 33 36. Fallon to Mono Lake -——— —— __ ____ __ ___ 34 37. Mono Lake to Fallon __________________________________________ 34 38. Fallon to China Lake ———————————— —_ _._ ____ 34 39. Mono Lake to Lake Mead _______________________________________ 35 40. San Francisco to Camp ROberts ____________________________________ 36 41. Camp Roberts to San Francisco ——————— ——— —_ ____________ 37 42. Camp Roberts to Santa Monica Bay — __ ______________ 37 43. Santa Monica Bay to Camp Roberts __________________________________ 37 44. Santa Monica Bay to Mono Lake/China Lake ______________________________ 37 45. Santa Monica Bay to Lake Mead ____________________________________ 38 46. San Francisco to Fallon ________________________________________ 39 47. San Luis Obispo to NTS ________________________________________ 39 48. Hanksville to Chinle ————————————— __ ____________ 40 V VI CONTENTS TABLES 2—53. Velocityvdepth functions of the profiles from—Continued Page 49. Chinle to Hanksville -— 40 50. American Falls Reservoir to Flaming Gorge Reservoir 41 51. Flaming Gorge Reservoir to American Falls Reservoir — ———- 41 52. Bear Lake to American Falls Reservoir —— 42 53. Bear Lake to Flaming Gorge Reservoir 42 54. Average Pn velocities, based on curve d, and velocities MAC) at the depth 2(Ac) —————————————————— 44 55—107. Data for the record section of the profile from: 55. Eureka to Fallon —— —— 64 56. Fallon to Eureka ————————————————— 64 57. Boise to Elko 64 58. Strike Reservoir to Boise —— 64 59. Strike Reservoir to Elko 64 60. Mountain City to Boise — 65 61. Mountain City to Eureka ———— 65 62. Elko to Boise — —— 65 63. Elko to Eureka ————————————— -—-— —— — 65 64. Eureka to Mountain City — —— 66 65. Eureka to Lake Mead 66 66. Hiko to Eureka — 66 67. Hiko to Lake Mead —— —— 66 68. Lake Mead to Eureka —— 66 69. Lake Mead to Mono Lake ————————————— —-— 66 70. Lake Mead to Santa Monica Bay — 67 71. Kingman to NTS —- 67 72. NTS to Ludlow ——- 67 73. Ludlow to NTS —— 67 74. Mojave to Ludlow ——-—-— — 67 75. NTS to Navajo Lake —— —————————————— 67 76. Navajo Lake to NTS 68 77. N’I‘S to Elko — —— ———— 68 78. NTS to San Luis Obispo 68 79. Shasta Lake to Mono Lake 68 80. Mono Lake to Shasta Lake — 69 81. Mono Lake to China Lake ' -——— 69 82. China Lake to Mono Lake —— 69 83. China Lake to northwest ——— 69 84. China Lake to west — ‘ —— 69 85. China Lake to Santa Monica Bay — -— 69 86. Mono Lake to Santa Monica Bay ——————————————————— 7O 87. Fallon to San Francisco 70 88. Fallon to Mono Lake — -—— —— 70 89. Mono Lake to Fallon 70 90. Fallon to China Lake 70 91. Mono Lake to Lake Mead —— 70 92. Mono Lake at 230 km (fan observations) — 71 93. San Francisco to Camp Roberts 71 94. Camp Roberts to San Francisco 71 95. Camp Roberts to Santa Monica Bay 71 96. Santa Monica Bay to Camp Roberts —— 71 97. Santa Monica Bay to Mono Lake 71 98. Santa Monica Bay to China Lake — 72 99. Santa Monica Bay to Lake Mead —— 72 100. San Francisco to Fallon 72 101. San Luis Obispo to NTS 72 102. Hanksville to Chinle 73 103. Chinle to Hanksville 73 104. American Falls Reservoir to Flaming Gorge Reservoir 73 105. Flaming Gorge Reservoir to American Falls Reservoir 73 106. Bear Lake to American Falls Reservoir -— 74 107. Bear Lake to Flaming Gorge Reservoir 74 108. Corrections applied to record sections —— 75 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES BY CLAUS PRODEHL ABSTRACT A network of 64 seismic-refraction profiles recorded by the US. Geological Survey in Nevada and California and adjacent areas in Idaho, Wyoming, Utah, and Arizona from 1961 to 1963 was rein- terpreted. The investigation was concentrated on the Basin and Range province and the Sierra Nevada. Two recording lines extended into the western Snake River Plain of Idaho and the southern Cascade Range in California. Other profiles were recorded in the Coast Ranges of California, in the Colorado Plateau, and in the Middle Rocky Mountains. A basic traveltime diagram for P waves can be derived from record sections compiled for the profiles. The first arrivals generally aline on two traveltime curves. The first one (curve a) can be traced to distances of 100—150 km, yields velocities of 5.9—6.3 km/s, and is correlated with the basement. The second one (curve d) is observed mainly at distances greater than 150—200 km, yields velocities of 7.6—8.2 km/s, and is correlated with the top of the upper mantle. One or two dominant phases can be correlated in secondary arrivals by traveltime curves over distances of 50-200 km; their velocity decreases with increasing distance. The most significant one (curve c) is observed between distances of 80 and 200 km from the shotpoint and is correlated with the crust- mantle boundary zone. An approximation method was used for the depth calculations. The method does not require sharp discontinuities and takes into account steady velocity gradients. A test for the existence of low- velocity zones within the crust was made on each profile. A velo- city-depth function was calculated for each profile, and the results of profiles along lines were combined to form crustal cross sections represented by contour lines of equal velocity. Basement velocities between 5.9 and 6.2 km/s were recorded on the profiles in the Basin and Range province, whereas velocities of 6.6—7.0 km/s result from the first arrivals at relatively small distances on the profiles in the adjacent Snake River Plain. A velo- city inversion within the upper crust is present on many profiles; the velocity in this inversion zone decreases from about 6.2 to 6.1 or 6.0 km/s, most markedly in the profiles terminating at Lake Mead. Two dominant phases characterized by large amplitudes can be correlated in secondary arrivals on the profiles in the north and east parts of the Basin and Range province. These phases are interpreted as reflected phases from transition zones in which the velocity gradients are very steep. One of these phases is reflected from an intermediate boundary zone between the upper and lower crust and the other from the transition zone between the crust and upper mantle. On the profiles in the southern part of the Basin and Range province, however, the phase correlated with an inter- mediate boundary zone disappears, and only one phase remains, indicating that a lower crust there is not distinct but rather is part of a thick transition zone between a crust with a low mean velocity of 6.2 km/s and the upper mantle. Upper-mantle velocities based on first arrivals at distances greater than 130 km generally do not exceed 7.8—7.9 km/s, except on profiles recorded in the Mojave Desert. No first arrivals representing upper-mantle velocities were recorded in the Snake River Plain from chemical explosions. Traveltime curves for the southern part of the Basin and Range province are similar to the ones recorded in the Sierra Nevada. However, the secondary arrivals were less prominent, and P,l arrivals were not recorded on some of the profiles. A low-velocity zone is not present under the central Sierra Nevada but was found at depths 6-10 km under the nearby Lassen Peak National Park area. The mean crustal velocity is higher in the Sierra Nevada than in the Basin and Range province. The velocity in the Sierra increases gradually from 6.2 to 6.6 km/s between depths of 5 and 35 km. The transition zone between crust and mantle is as much as 10 km thick in the Sierra Nevada, and its base rises from 42 to 33 km in depth toward the south. A fairly sharp crust-mantle boundary was found under the Coast Ranges of California west of the San Andreas fault. The average crustal velocity between 10 and 24 km depth there is 6.3—6.4 km/s, and the total crustal thickness is'about 26 km beneath the central Coast Ranges but is greater under the Transverse Ranges. An intermediate boundary zone within the crust as well as the crust-mantle transition zone can be clearly distinguished from secondary arrivals on the profiles in the Colorado Plateau and in the Middle Rocky Mountains. A low-velocity zone within the crust is apparently present under the Middle Rocky Mountains at a depth of approximately 17 km. The velocity in this zone decreases from 6.4 to 5.8 km/s. Some basic parameters can be measured on the traveltime curves that may yield objective information on general crustal structure. These parameters were plotted on contour maps. The distance Ad at which the P" traveltime curve d crosses the distance axis and the “critical” distance Ac at which the refracted P,l traveltime curve d is tangent to the reflected curve c, which is correlated with the crust-mantle transition zone, represent to a first approximation the variation of the total crustal thickness. High values of the reduced traveltime Tc at the distance of critical reflection at the crust-mantle boundary indicate that the crust contains material with relatively low P-wave velocities. The upper- mantle velocity does not exceed 8.0 km/s under the Great Basin and Range province, the Sierra Nevada, or the Colorado Plateau. The lowest upper mantle velocity (7.6 km/s) was found under central and southern Utah. The upper mantle velocity was found to be 8.0 km/s or slightly higher only under the Coast Ranges of California, the Mojave Desert, and the Middle Rocky Mountains. A fence diagram constructed from the seismic-refraction lines represents the 15 crustal cross sections by contour lines of equal velocity. The contour map of the depth of strongest velocity gradient represents a map of the total crustal thickness. The crust is generally thinner under the Basin and Range province, which has an average thickness of 32—34 km, than under the surrounding 1 2 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES Sierra Nevada, Snake River Plain, Middle Rocky Mountains, and Colorado Plateau, where crustal thicknesses exceed 40 km. Mini- mums of crustal thickness were found south of the line from Kingman, Ariz., to Barstow, Calif, (28 km) and under the Coast Ranges of central California (24—26 km). With a few exceptions, the results reported by other authors who studied the same data were confirmed in this study. In some areas, however, velocity inversions in the upper crust were found that have not been reported by previous authors. There is a general correspondence between crustal structure as derived from explosion seismology and Bouguer gravity anomalies, except in the Basin and Range province, in which only regional gravity dif- ferences can be explained by differences in crustal structure, whereas the general low gravity there must be attributed to an anomalous upper mantle. The present results support a previous interpretation for the upper 20 km of the Sierra Nevada crust but differ for the lower part of the Sierra crust, which seems to have lower velocities than previously reported. Upper crustal silicic material is probably absent under the southern Cascade Mountains and the western Snake River Plain. The average composition of the crust in the Basin and Range province must be fairly silicic to account for the seismic velocities, but in the northern part of the province an increasing proportion of mafic mantle material within the lower crust is indicated by the higher crustal velocities. This is true also for the western Snake River Plain. The velocity inversions within the upper crust may be explained by an increase of temperature with depth, which may have stronger influence on velocity than the increase of pressure or grade of metamorphism with depth. The reinterpretation presented in this report is based on the principles that were used by other seismologists in the Alps and southern Germany. The principal results for central Europe are presented for a comparison of crustal structure of the Western United States and central Europe. The basic traveltime graph in central Europe is generally the same as that found for the Western United States. Contour maps of the parameters Ad, AC, and Tc represent approximately the general configuration of the crust of the Alps, all three parameters increasing toward the main Alpine axis. The total crust and crust-mantle transition zone are thickest under the main axis of the Alps. A 10-km-thick low-velocity zone exists in the crust between depths of 10 and 30 km, where the velocity decreases from 6.0—6.2 to 5.5—5.6 km/s. The velocity inver- sion is less marked outside of the Alps. INTRODUCTION During the past 10 years, many studies have used explosion seismology to examine the structure of the Earth’s crust. Summaries of most of the results in Europe and North America have been published, for example by Steinhart and Meyer (1961), Kos- minskaya and Riznichenko (1964), Pakiser and Stein- hart (1964), James and Steinhart (1966), Morelli, Bellemo, Finetti, and de Visintini (1967), Closs (1969), Healy and Warren (1969), Kosminskaya, Belyaevsky, and Volvosky (1969), and Sollogub (1969). Detailed experiments have resulted in a huge amount ‘of seis- mic data, and the methods used and the results ob- tained by many different authors are heterogeneous; nevertheless, these experiments have also shown that crustal structure does vary from area to area. The US. Geological Survey began a detailed study of crustal and upper mantle structure in the Western United States by explosion seismology in April 1960 (Stuart and others, 1964). From 1961 to 1963, 64 pro- files were recorded, mainly in California and Nevada, but also in adjacent areas of Idaho, Wyoming, Utah, and Arizona. From 31 shotpoints, 255 chemical explo- sions, varying in size from less than 1,000 to 20,000 lb, and several underground explosions of nuclear devices at the Nevada Test Site (N TS) served as seis- mic energy sources. Most profiles were reversed; the average profile length was 300-400 km. Recordings were made at approximately 2,700 individual sites along the profiles. Results concerning the structure of crust and upper mantle in the Western United States have been previously summarized by Pakiser (1963, 1965), Stuart, Roller, Jackson, and Mangan (1964), and Pakiser and Robinson (1966a, b). This report presents a model of the crustal struc- ture under the Western United States as derived from seismic-refraction measurements and compares this model with one of the crustal structure under the Alps and central Europe (see also Prodehl, 1970a, b). Detailed comparison of the crust of the Western United States and the Alps requires a comparable model for both regions. For this reason, I have rein- terpreted many of the seismograms that were recorded in the Western United States by the US. Geological Survey from 1961 to 1963 using the same interpretive principles that were used for the con- struction of the Alpine model by Choudhury, Giese, and de Visintini (1971). ACKNOWLEDGMENTS This study was made possible by a grant from the Deutsche Forschungsgemeinschaft (German Research Association) and my succeeding appointment as a Visiting Scientist at the US. Geological Survey in Menlo Park, Calif, while on leave from Geophysikali- - sches Institut der Universita't, Karlsruhe, Germany. Fieldwork was supported by the Advanced Research Projects Agency, Department of Defense, as part of VELA UNIFORM, under ARPA Order No. 193. I am indebted to the staff of the US. Geological Survey for discussion, advice, and help, especially to L.C. Pa- kiser, J .H. Healy, S.W. Stewart, and W. Hamilton for review and detailed discussion; J .P. Eaton, W.H. Jackson, J.C. Roller, D.J. Stuart, and SW. Stewart for unpublished reports, record sections, and com- puter programs; and Ray Eis for drafting the many drawings. I am also indebted to Prof. Peter Giese, Freie Uni- versita't, Berlin, Germany for detailed discussions INTRODUCTION 3 and for figures 91—96. Prof. Stephan Mueller, Univer- sita't Karlsruhe, Germany (now at ETH Ziirich, Swit- zerland), and Prof. Mark Landisman, University of Texas, Dallas, made available record sections they compiled of the Mojave-Ludlow profile from the US. Geological Survey. GEOPHYSICAL FIELDWORK The network of shotpoints and recording stations at which seismograms analyzed in this report were re- corded extends from eastern Utah to the Pacific coast and from southern California to central Idaho (fig. 1; pl. 1; table 1). Except for the nuclear tests, seismic energy was generated by chemical explosions fired in the Pacific Ocean, in lakes, or in drill holes. Ocean shots ranged from 2,000 to 6,000 lb and were placed on the sea- floor. The charges in lakes ranged from 2,000 to 10,000 lb and were placed on the lake bottoms. At all the other shotpoints, the charges were fired in drill holes and ranged in size from 250 to 20,000 lb (Roller and Gibbs, 1964). Details of the shot procedure were discussed by Jackson, Stewart, and Pakiser (1963). Usually 10 recording units were used in the field pro- grams. Each unit recorded with an array of six verti- cal- and two horizontal-component seismometers having natural frequencies of 1 or 2 Hz. Where ter- rain permitted, the vertical-component seismometers are placed at one-half-km-intervals to form a 21/2-km spread that was oriented as far as possible in line with the direction to the shotpoint. The output of the six vertical-component seismometers was recorded on a frequency-modulated magnetic tape system at two levels of amplification separated by 30 dB. In addi- tion, output of the vertical- and horizontal-component seismometers was recorded by an oscillograph on photographic paper at two levels of amplification sep- arated by 15 dB. The paper speed of the recording units was usually 21/2 inches per second, but in some instances, especially for the recording of some nuclear tests, the speed was changed to 1% inches per second. On a typical record (fig. 3), traces 1-6 and 9—14 show the low-gain and high-gain traces of the six vertical-component seismometers, and traces 7 —8 and 15-16 show the lbw-gain and high-gain traces of the two horizontal-component seismometers. The pro- file was timed by recording the output of broadcast station WWV (trace 19), a calibrated chronometer (trace 20), and when possible, the shot instant trans- mitted by radio from the shotpoint (trace 17). A detailed description of the instrumentation used and the procedure of recordings is given by Warrick, Hoover, Jackson, Pakiser, and Roller (1961) and J ack- son, Stewart, and- Pakiser (1963). The average spacing of the recording units on profiles recorded from chemical explosions was about 10 km, but in a few in- stances the units were closer together. The westernmost profiles were recorded in the Coast Ranges of California, partly parallel to and partly across the geologic structures. In the Sierra Nevada, which is separated from the Coast Ranges by the Great Valley of central California, several pro- files were recorded parallel to and across the geologic structures. One of these profiles extends into the southern Cascade Range north of the Sierra Nevada. The main part of the investigation was concentrated in the Basin and Range province of Nevada and adja- cent areas in southern California, northwestern Ari- zona, and western Utah. One profile extends into the western Snake River Plain of southern Idaho. In the Middle Rocky Mountains, which border the Snake River Plain and the Great Basin of the Basin and Range province to the east, one profile system was recorded. From the profiles observed in the Colorado Plateau, only one line recorded in 1963 is included in this report. Figure 4 is a simplified geologic map of the area covered by seismic profiles. More details of this fieldwork can be obtained from unpublished re- ports such as those by Cooper, Strozier, and Martina (1962), Frankovitch, Cooper, and Forbes (1962), Healy and others (1962), Roller and Gibbs (1964), Roller, Jackson, Cooper, and Martina (1963), and Roller, Strozier, Jackson, and Healy (1963), from which many of the data such as distances and coordinates were taken for the present investigation. PROCEDURE OF INTERPRETATION RECORD SECTIONS One of the most difficult tasks in interpreting seis- mic-refraction measurements is the correlation of the different wave groups from seismogram to seismo- gram along the profile. The correlation of later arrivals is especially delicate. To facilitate this correlation, all seismograms along a profile were arranged into a record section according to their distance from shot- point and reduced traveltimes. Because the present study is confined to the investigation of com- pressional (P) waves propagating in the crust and uppermost mantle, 6 km/s is a suitable reduction velo- city. The reduced traveltirne (7—) is defined as the observed traveltime (T) minus distance (A) divided by reduction velocity (V,): T = T — A/V, = T — A/6. Record sections were drawn by hand for 52 profiles (see, for example, fig. 10 and table 55). Because of the array length of 2.0-2.5 km at nearly every recording site, it was possible to draw more than one seismic CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES 100 200 ~30° I 300 kw l 31: PLATEAPS 105° SN N1d l ——_‘__ I——— __~_ —§ FIGURE 1.—Physical divisions of the Western United States and location of seismic profiles. After the map of the physical divi sions of the United States by Fenneman and Johnson (1946). M. D.. Mojave Desert; 0. V., Owens Valley; D. V.. Death Valley; L. P., Lassen Peak National Park. Shotpoints are listed in table 1. trace per seismogram. In most instances the traces fig. 3). The high-gain traces (9 and 14) were used if the recorded nearest to and most distant from the shot— peak-to-peak amplitude of the most prominent phase point at each station were used (traces 1, 6, 9, and 14, on the original record did not exceed 4 cm. For INTRODUCTION 5 TABLE l.—Location of shotpoints m Altitude No. Shotpoint N. lat W. long (m) 1 San Francisco ————————————— 37 D36. 08' 122 "41.55' Sea level 2 Camp Roberts ————————————— 35 °47. 38' 120 °49.98' 208 3 San Luis Obis o ———————————— 35°07. 60’ 120°47.10’ Sea level 4 Santa Monica ay ——————————— 84 000. 06' 118°33.28' Sea level 5 Shasta Lake —————————————— 40°46.17' 122°13.92’ 314 6 Mono Lake ——————————————— 37 059. 00’ 119 °07.60' 1.950 7 Independence ————————————— 36°44 79’ 118°l5.72' 1,655 8 China Lake ——————————————— 35 °47. 00' 117 °44.96’ 677 9 Fallon ————————————————— 39°31. 43' 118°52.48' 1.220 10 SHOAL ———————————————— 39°12.02' 118°22.82' 1,740 11 Boise —————————————————— 43°34.70' 115°58.95' 931 12 Strike Reservoir ———————————— 42°55.29' 115 °53.70' 748 13 Mountain City ————————————— 41°50.24' 115°53.70' 1,683 14 Elko —————————————————— 40°46.23’ 115°40.97' 1,625 15 Eureka ————————————————— 39 °30.82 115°39.00' 1,806 16 Delta —————————————————— 39°40.55 112°35.55' 1,150 17 Lida Junction ————————————— 37 020.96 117 "29.54' 1,658 18 Lathrop Wells ————————————— 36°37.18' 116°13.76' 951 19 Nevada Test Site (NTS)‘ ———————— 37 °O7 116°02' 1,400 20 Hike —————————————————— 37°54. 20' 115°13.80’ 1,538 21 Navajo Lake —————————————— 37°32. 53' 112°47.55’ 2,912 22 Lake Mead ——————————————— 36 °05. 28' 114°47.96' 369 23 Mojave ————————————————— 35 °03. 02' 118 °00.33' 786 24 Barstow ———————————————— 34 °58.34' 117°04.23' 755 25 Ludlow ————————————————— 34 °49.36' 116 ”11.02' 396 26 Kingman ———————————————— 35°19.36' 114°03.92' 1,180 27 American Falls Reservoir ———————— 42 “50. 14’ 112 °48.66’ 1,360 28 Bear Lake ——————————————— 41°56. 35' 111°17.10' 1,820 29 Flaming Gorge Reservoir ———————— 40 056. 77' 109 °38.43' 1,730 30 Hanksvill e ——————————————— 38°21. 99' 110°55.64' 1,430 31 Chinle ————————————————— 35 °55. 64' 109 °34A4’ 1,830 ‘Approximate center of location of the NTS shots used in this report. ( “(d '1‘ V \LJ/JNVJ FIGURE 3.—Typical seismic record. Seismic signals: Nos. 1—6 and 9—14: low- and high-gain traces of six vertical-component seis- mometers; Nos. 7—8 and 15—16: low- and high-gain traces of two horizontal-component seismometers. The two levels are sepa- rated by 15 dB. Timing signals: No. 19: broadcast station WWV; No. 20: calibrated chronometer; No. 17: shot instant if possible. seismograms with weak first arrivals and secondary phases with extremely high amplitudes, the low-gain traces (1 and 6) were used together with a high-gain trace from near the middle of the record. The last col- umn of the tables 55—107 shows which traces of each record were used for the corresponding record section. No corrections were made to eliminate the influence on a recording site of near-surface low-velocity sediments, because little is known about the thickness and seismic velocities of these sediments. For one profile (Delta-SHOAL) an unpublished record section prepared by SW. Stewart and RR. Ste- venson was available. The analog records for this pro- file were digitized and the digitized records plotted by computer into a record section. The record section for the profile NTS-Kingman was compiled by Diment, Stewart, and Roller (1961). PRINCIPLES or THE OBSERVED TRAVELTIME DIAGRAMS Most previous interpretations of the profiles studied were based on the assumption that the Earth’s crust consists of layers that are characterized by constant velocities and are separated from each other by sharp discontinuities. As Stuart, Roller, Jackson, and Mangan (1964) pointed out, first-arrival times for most profiles were approximated by a two— or three-segment straight-line traveltime curve. These segments repre- sent the arrival times of compressional waves that have been refracted at velocity interfaces in the upper crust (Pg), in the lower crust (P), and beneath the Mohorovicic discontinuity (M-discontinuity) (Pa). Large-amplitude reflected phases that arrived at times appropriate for reflections from the top of the upper mantle (PMP) and from the top of a lower crustal layer (P1P) (Healy and Warren, 1969) were also found. N 0 at- tempt was made in these studies to determine whether or not low-velocity layers exist within the crust. In the present investigation, no assumption was made concerning the character of correlated phases (re- fraction, reflection, or other). The method of depth cal- culation used does not require sharp discontinuities, but takes into account steady velocity gradients. Also, the possibility of low-velocity crustal zones was in- vestigated. Careful study of the record sections show- ed that within the Western United States, similar phases can be found that fit into a basic traveltime diagram. On any profile, one or more traveltime branches may be missing, but a generalized traveltime diagram can be drawn (fig. 5). In this report only the structure of the Earth’s crust is investigated systema- tically. Phases concerning local sedimentary sequences or upper mantle structure are not investigated in detail. Phases that are present only sporadically on a few profiles are not considered here. At distances of up to 100—150 km from the shot- point, a traveltime curve, a, can be observed in the first arrivals. This phase can be correlated with the base- ment rocks. Usually the first arrivals aline on a contin- uous convex-upward curve that starts at the origin of the traveltime diagram. However, delays often occur, especially in the Basin and Range province, owing to sediments that cover the basement and whose thick- ness varies from station to station. With increasing distance the amplitudes of wave group a get smaller and gradually die out, usually between 100 and 150 km. A prominent phase, c, characterized by large amp- litudes, was recorded in the later arrivals on all profiles between 70 and 240 km from the shotpoint (fig. 9). Traveltime curve c is concave upward with respect to the distance axis. Most authors who have worked on seismic-refraction profiles in the Western United States denote these arrivals by PMP and interpret them as P waves reflected from the Mohoroviéié dis- continuity. On the assumption of a monotonic velocity CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES EXPLANATION I:| Terrestrial basin fill of Tertiary and Quaternary age Marine deposits of Tertiary age E Miogeosynclinal deposits and shelf deposits of Paleozoic and Mesozoic age C] Eugeosynclinal deposits of Paleozoic and Mesozoic age Terrestrial volcanic rocks of Tertiary and Quaternary age Granitic and other intrusive rocks of Mesozoic and Tertiary age Ultramafic rocks Precambrian rocks Platform deposits overlying basement rocks of Precambrian age FIGURE 4.—Simplified geologic map of the Western United States. After King ( 1967). INTRODUCTION 7 TIME,IN SECONDS DISTANCE, IN KILOMETERS FIGURE 5.—Basic traveltime diagram. The numbers on both axes indicate approximate values. The curves can be shifted as much as 30—50 km and up to i2—3 seconds. increase with increasing depth, Bullen (1963), Officer (1958), Giese (1966), and others have shown that the corresponding traveltime curve becomes retrograde where the velocity increases very quickly within a cer- tain depth range, forming the type of traveltime curve that is observed as c or PMP on the seismic-refraction profiles. The velocity measured by the reciprocal slope of such a traveltime curve decreases with increasing distance from about 7.2-8.0 km/s to 6.2—6.6 km/s. Traveltime curve 0 therefore is explained as a strong increase in velocity at the base of the crust. Phase d is observed in first arrivals at distances greater than about 130—200 km, depending on crustal thickness and velocity (for example, fig. 9). The exten- sion of traveltime curve d as a secondary arrival toward smaller distances ends where it becomes tangent to curve c. The measured velocities at that point are 7.4 km/s or more. Phase d can usually be re- cognized only where it occurs as a first arrival, how- ever. The waves represented by d penetrate the upper mantle. This phase is usally called P,, if its velocity is greater than 7.6 km/s. Another phase, represented by traveltime curve b, is present on many profiles (for example, fig. 9). On some seismograms it is as prominent as phase c. This travel- time curve is also concave upward with regard to the distance axis, and it is interpreted as a retrograde curve reflecting a fairly strong increase in the velocity between the upper and lower crust. However, although very well observed in some areas, this phase is very weak (for example, fig. 11) or does not seem to exist in others. In some areas where the phase b is very well ex- pressed, a forerunning phase, d(b), can be observed (for example, figs. 9, 17). The traveltime curve d(b) is tangent to curve b in a manner analogous to the curves 0 and d. All of these phases can usually be correlated over 10 km in distance or more. On some profiles, additional phases between traveltime curves a and b can be corre- lated. These curves have nearly the same velocity as the most distant end of curve a and also of curve b. These curves were named a—b by Giese (1966) (for ex- ample, fig. 10). If the velocity is assumed to increase monotonically with depth but with variable velocity gradients, the corresponding traveltime diagram should be a contin- uous system with cusps (triplications) corresponding to depths where the velocity gradients are very strong. However, many traveltime curves cannot be combined to form a closed system, even under the assumption that some phases are missing, owing to a lack of energy or too wide spacing of the recording units. Rather, the extension of the curves a and b or d(b) and c toward greater distances sometimes results in parallel segments that cannot be combined to form continuous cusps, because b or c is delayed for frac- tions of a second or more with respect to a or d(b). One explanation for this delay is the existence of a velocity- inversion zone with increasing depth. The arrangement of traveltime curves described above was first described in detail by Giese (1966) in a systematic investigation of 12 profiles in southern Germany and the Alps. These seismic-refraction pro- files in central Europe as interpreted by Giese (1966) and by Choudhury, Giese, and de Visintini (1971) are compared in this report with the seismic-refraction profiles in the Western United States. CALCULATION OF THE VELOCITY-DEPTH FUNCTION FROM THE TRAVELTIME DIAGRAM As shown above, a consistent arrangement of the dif- ferent traveltime segments, T(A), exists for all profiles. For the determination of the corresponding velocity- depth function, V(z), several methods can be applied. The simplest case is that the correlated traveltime curves are straight line segments. Under the assump- tion that the Earth’s crust consists of layers with cons- tant velocities separated by discontinuities at which 8 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES the velocity increases discontinuously from V, to Vm, formulas have been developed to calculate depth and dip of the corresponding layers (for example, Bullen, 1963; Officer, 1958; Perrier, 1973; Steinhart and Meyer, 1961). However, as has been shown, usually the arrivals correlated do not aline along straight line segments. Curved segments can occur in first as well as in later arrivals. When later arrivals are fitted by concave traveltime curves, they can be interpreted as reflection from first-order discontinuities (T2, A2 method). All these methods assume constant-velocity layers with first order discontinuities. A more general method for inversion of traveltime data into depth values is offered by the Wiechert- Herglotz method (Giese, 1963). This method can be ap- plied for the determination of the complete velocity- depth function when the traveltime curve, T(A), starts at the origin (T=0, A =0) and forms a continuous func- tion including cusps and when the derivative, dA/dT, increases continuously along the traveltime curve. Then the depth, z, at which the velocity reaches the value V(A1) is obtained by the following equation: Vl—A—‘l dA, A < A1. (1) 1 A1 _1 = _ h z ni cos ( ) However, an exact solution is not possible if the travel- time curves cannot be combined into a continuous function, because then the conditions of integration are no longer fulfilled. This is the case for many pro- files discussed herein. Instead of a continuous system, interruptions occur within the traveltime diagram. Such an interruption can have several causes (fig. 6A): a. A discontinuity of first order exists. The distance of point B is infinite (neglecting the curvature of the Earth). In this case the traveltime curve BC is a true reflection hyperbola. b. The profile is too short; one part of the cusp is located beyond the maximum recording distance. c. A velocity inversion exists within the crust. d. The connection of the different traveltime segments is open, because only short segments of traveltime curves can be correlated clearly. This may be the case, for instance, when two cusps are inter- fering. In each case, the determination of V(z) is no longer unique. In order to get information on crustal struc- ture, some simplification must be introduced. Assum- ing first-order discontinuities, for example, different methods have been proposed. For instance, the T’, A” method can be applied on the “reversed” segments — “reversed” meaning those parts of the traveltime- curve system where the velocity, V(A), decreases with increasing A (for example, reflection hyperbolas). The application of this method, however, is satisfactory for T(A) values in the critical and subcritical range only but not in the supercritical range (Stewart, 1968b). Because the seismic-refraction profiles recorded for crustal studies show mainly the supercritical part, a more general method should be applied. Fuchs and Landisman (1966) and Mueller and Landisman (1966) use an indirect method to calculate the velocity-depth function for the case of interrupted traveltime curves. Starting from a rough model, they try to correct this model by trial and error until the best fit is reached between observed and theoretical traveltimes. Any model that fulfills the conditions of flat-layering is possible. Usually discontinuous velocity increases are assumed. Giese (1966) has proposed an approximation method to calculate rapidly the velocity-depth distribution di- rectly from any given traveltime-curve system. The method assumes also homogeneity in the horizontal direction but takes especially into account the ex- istence of finite velocity gradients, meaning that the velocity is not constant but may increase continuously with increasing depth. Also, the possible existence of velocity inversions is recognized in this method. The crustal models in this paper for the different parts of the Western United States are based on Giese’s method exclusively (fig. 6). This method was used for the reinterpretation of the data shown below for several reasons. Firstly, the method allows a quick determination of deep structure from traveltime data. FIGURE 6.—Diagrams illustrating principles of observations and their inversion into velocity-depth functions based on a method after Giese (1966). A, Examples of disconnected traveltime curves and the corresponding velocity-depth functions: (a) First-order discontinuity. The corresponding traveltime curve is a hyperbola BC, but the distance of point B is infinite. (b) Second-order discontinuity. The distance range of observations is insufficient. (0) Velocity inversion. (d) Interference of two cusps causing uncertainties in the correlation of phases. B, Ray path in a homogeneous (full lines) and an inhomogeneous layer (dashed lines) and the corresponding velocity-depth functions. C, Presentation of V(zmu) (full lines) for (a) d V/dzmax = 0, (b), dV/dzmax < 0 and (c) d V/dzmax > 0 and the corresponding velocity-depth functions V(z) (dashed lines). D, The possible solutions of velocity-depth functions from a given traveltime diagram are located between the curves V(zmax) and V(zmin). E, Sketch demonstrating the position of points A and B of a travel- time diagram necessary for the direct determination of the max- imum thickness dzmax and the average velocity V; of a low- velocity zone, that is, the range between the depths correspond- ing to the rays emerging at A(A) and A(B). F, Sketch for the estimation of the average velocity 17,- within a depth range 62 for which V(z) cannot be calculated directly. INTRODUCTION Secondly, the ability to account for the existence of velocity-gradient zones and of zones with velocity in- versions within the crust is of great importance for the reinterpretation. The inclination of reversed traveltime curves usually differs considerably from the inclina- 9 tion of a traveltime curve interpreted as a reflection from a sharp discontinuity within the crust. Finally, because the comparison of the crustal structure of the Western United States with that of central Europe is one of the aims of the reinterpretation presented here, (a) {b} (C) (d) T B T T T / i// | // / /‘/ I; I I I / i I | | |———> l————-—) V A V A V A VA ‘ I I\ \ \ Z Z Z Z A 5 6 7 8[km/s] o . . v A VoVV(Z) .i T .if \\ 10 a 2:“.‘1 \ zmaxe‘Q \ "O\ Q\ N}¢ z ‘ 20 o iii; \\ z \xzmin \\ \ 3\\\\\ B 30 NIEE zmax '4: (a) (b) (c) 49"]: 5 6 7 8[km/s]6 7 8[km/s]5 6 7 8[km/s] o o o ‘ ' v ‘ v E v I , D 10 i 10 ‘| 10 I. I I 20 I 20 ‘ 20 " I I‘ ~\ I \\ 30 z ,— -——3c 7"“1” 30 \ [km] 4c I ' 40 ‘~. 2 l ‘V [km] [km] C I \ V 0 Nu) - A—[ I: II T :5 I: a: I_: B l' .L \ c:z Z A Z c f dz +15—2+ f dz =_z_ o V(z) vi B V(z) w E F 10 the same methods should be used for the interpreta- tion of seismic-refraction measurements in both areas. In Europe, Giese’s method was applied in many seismic-refraction investigations carried out in western Germany, the Alps, Italy, and elsewhere, as will be discussed in some detail in the last section. Therefore it is essential to apply the same method to as many profiles in the Western United States as possi- ble, if a valid comparison of structures is to be realized. Cross sections are compiled on the basis of velocity- depth functions calculated for each profile (for exam- ple, fig. 12). Though the depth calculations are made under the assumption that no horizontal changes oc- cur, the resulting velocity-contour lines actually dip and rise. Dips less than 5° can be neglected, however, because the uncertainty in arrival times in the records is greater than errors in depth calculation caused by dips less than 5° (Peter Giese, written commun., 1975). For some examples presented here, velocity-depth calculations have been made by the author using other methods, including the computation of synthetic seis- mograms, in order to prove the reliability of the models obtained by Giese’s method. The resulting models do not differ in essential parts; rather, slight deviations in models occur at depths where the velocity gradient is weak or where the error of velocity distribution is rather large owing to uncertainties in the correlation of the corresponding phases. The greatest relative dif- ference occurred in profiles whose corresponding velocity-depth functions contain zones with marked velocity reversals. It turned out that the approximate determination of the velocity within such low-velocity zones leads to slightly different values from those ob- tained with other methods. However, in the following section only the models are presented that were obtain- ed with the method of Giese, even if there are some dis- crepancies with the depth determinations using other methods. The approximation method by Giese will be de- scribed in detail below, following description and dis- cussions published by Giese (1966), Bram and Giese (1968), and Perrier (1973). For all following discus- sions, the term “normal” traveltime curves or segments will be used for the cases in which the re- cording distance increases with increasing depth of penetration of the corresponding wave, approximated by a curved ray path. The term “reversed” traveltime curve or segment will be used when the recording distance decreases with decreasing angle of incidence. Assuming a two-layered model consisting of homo- geneous upper and lower layers characterized by the respective velocities V0 and V, for the wave reflected from the discontinuity between upper and lower layer, the following equations are valid: CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES A2 2 T2 _ = ._ 2 (2)+z (V02) () and dT From these equations the following relation can be deduced: - _A_ ‘ l T _dA _ 1 2 A dT ’ which allows us to determine exactly the depth of the reflecting horizon. This depth determination can be used also when the overburden is inhomogeneous, in which V0 corresponds to an average velocity equal to the average velocity, u_, of a ray that traverses the up- per medium perpendicular to the layers of the upper medium: 3 = (4) 17 = (5) f2 dz/( )2 dz/V(z) ), 0 0 Continuously refracted waves (called by some authors diving waves or “Tauchwellen”) can be regarded as the critical case of reflected waves, their angle of apparent reflection being 90 ° (curved ray path O—Q—Q in fig. 6B). The principle of Fermat requires that the calculated depth value be greater than the real depth (Dix, 1955), and for each value of dA/dT = V (velocity at the point of maximum penetration of the corresponding ray) the following relation is valid: A TdA S max = ' M Z 2 AdT (4a) J obert and Perrier (1974) demonstrated with the aid of the “Schwarz’sche Ungleichung” that .zmax is really the maximum depth to which the corresponding ray can penetrate. By equation 4a, 2mx can easily be calculated for all points of normal and reversed travel- time curves. For normal traveltime curves, the quantity dV/dzmax derived from the curve V = V(zmu) is always positive. For reverse segments three cases are possible (fig. 60): (a) d V/dzmax = 0: The mean velocity is independent of the angle of incidence. The overburden is homogen- eous. The T”, A2 method can be used. (b) dV/dzmax < 0: The overburden is not homogen- eous. and the velocity increases sharply within the cor- responding depth range. (c) dV/dzmax > 0: The velocity gradient, dV/dz, is also positive; a transition zone exists. INTRODUCTION 1 1 By this very simple method it is possible to tell if the corresponding boundary zone is a discontinuity or a broader transition zone. For the case of correlated traveltime segments sepa- rated from each other, a minimum depth can also be determined using the integral of Wiechert-Herglotz for the traveltime segments known: zmin = l(IA1 cosh‘I VIA") dA + n 0 WA) WA") dz, V(A) A3 Azf cosh ‘1 WA») IA" + . .. + A,..1cosh‘l V(A) dA) ,Zmin < 2(V). (6) 2min can be calculated for all points of the normal and reversed traveltime segments. After the correlation of traveltime curves is fixed, the unknown velocity-depth function, V(z), must be located between the two limiting functions of zmx and am. It must be asumed that the velocity gradient, dV/dz, changes linearly between zmm and zmax. Figure 6D shows an example of a velocity-depth function that was calculated after the method described below. For the selection of the most probable velocity-depth relation, the solutions that show a negative gradient must be rejected. Furthermore, one can reduce the number of possible solutions by taking other data into account. As mentioned above, the velocity gradient, dV/dz, has an important influence on the determin- ation of the velocity-depth function, V(z). Having this in mind, Giese (1966) assumed several velocity-depth distributions that characterize reasonable crustal models. V ranging from 5 to 8.2 km/s. From these models he calculated the corresponding traveltime curves and plotted the values z/A versus V(T/A) (fig. 7). As can be seen in figure 7, all points belonging to the same velocity gradient can be approximately re- presented by a curve in which the scatter of points is much greater for small velocity gradients than for large ones. With increasing velocity gradient. the curves approach the limiting curve, which is valid for an infinite velocity gradient (d V/dz -* °° ) and is iden- tical with zmax. In order to approach the real solution it is sufficient to start with the determination of zmax by equation 4a, where T, A, and (3?: V are read from the traveltime diagram, and to deduce for each point of the curve V(zmax) thus obtained the corresponding velocity gra- dient dV/dzmax. Using this gradient as the new I>|N 0.3 0.2 0.1 V-T 0 1.0 1.1 1.2 1.3 1.4 1.5 FIGURE 7.——Diagram showing z/A versus V(T/A) with velocity gradient, dV/dz, being parameter. After Giese (1966). parameter, the diagram of figure 7 gives now a new depth, 2, for each point (T, A, V). From the resulting new function, V(z), again the velocity gradient can be determined for each point (T, A, V) and the correspond- ing depth obtained. This procedure is repeated three or four times until the curve V(z) does not change signi- ficantly. A specific solution results from this procedure because the diagram of figure 6 is constructed on the base of velocities that are probable within the Earth’s crust. Figure 8 shows examples of three profiles in the Western United States demonstrating the three possi- ble cases of reversed traveltime curves as discussed above. The open circles show the calculated values of Zmax using equation 4a, and the full circles show the cor- rected values using the iteration process described above. Giese has also empirically deduced the following equation, which allows us to approach the solution: (7) where CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES v v v 5 6 7 8 km/s 5 6 7 8 km/s 5 6 7 8 km/s o o o k \' \. \.\.‘ \.\ \ "\ .\o \- 1o 1o ‘; 1o ‘ '-. i "x 1 '~. .....~.. 20 ‘ 20 r 20 ' ‘. z. ‘. .‘-3—t—8-‘ .‘. .R 0 ° l) ° \ : . o \ a 30 ° \ 30 n ‘ ‘ 30 \‘ : \ \ . . . , 0 ° ° | Q \ i 40 4o 40 ‘. km km km \‘ o \ 000 ‘\‘ Z Z Z c .0 A B C FIGURE 8.—Velocity-depth functions calculated by the approxima- tion method after Giese (1966). Open circles represent the calculation of Zmax, the first approximation. Full circles show the result after the last approximation step; the slope of the short lines through points is equal to the velocity gradient, d V/dz. A, Calculated from the traveltime diagram of the profile San Luis Obispo—NTS (fig. 73; table 47): dV/dzmax < 0, dV/dz -> where a = (V — V1) is the mean gradient (V, — velocity at the surface) and [3 = d V/dz is the local velocity gra- dient at the depth 2. Giese (1966) has estimated the error on the depth determination when using equation (7): (a) The error in the determination of A can be neglected. (b) The error in d V is d_z Z TdV 2A (3V — 1) A where A/T = 6 km/s, VT/A = 1.2, and dV = 0.1 km/s. It results in 1 dz _ 0.1 — 0.04 = 4% 2.4 Z (c) The error in dT is 00. B, Calculated from the traveltime diagram of the profile Fal- lon—China Lake (fig. 58; table 38): dV/dzmax < 0 and > 0. C, Calculated from the traveltime diagram of the profile American Falls—Flaming Gorge (fig. 77; table 50): dV/dzmax >0, dV/dz > 0. The values for zmax are only presented for the part concerning curve c. All velocity-depth functions are cut off for velocities less than 5 km/s. VdT 2A (I-V— 1) A where V = 7 km/s, A=140 km, dT = 0.05 s (accuracy of traveltime determination from a record section), and VT/A=1.2; dz 2 ’ 0.006 = 0.6% (d) The error in d ( if} ) is ——1—. dm z 4(1+—) [3 where: =1andd(%)0.2; df _ 03 =0.025 =2.5%. 2 Given the inaccuracy of the values chosen above, an average error of 5 percent may result. The error deter- mination shown here requires that the correlation be ANALYSIS OF SEISMIC-REFRACTION PROFILES 13 certain. The total error in the determination of the depth, 2, depends on the gradient, d V/dz, at the point of maximum penetration of the corresponding ray. If the gradient is strong (>0.1 km/s/km), the error is about 3 percent. It increases to 5—10 percent for smaller gradients (between 0.01 and 0.1 km/s/km). When the segments of the traveltime diagram are in- terrupted, only parts of the complete function V(z) can be determined, whereas between these determinable parts of V(z), velocity inversions may be present. It is possible to determine the maximum thickness, zmax, and the mean velocity, 17,- (see fig. GB) for those depth ranges not determinable from the traveltime diagram if the coordinates of points A and B, as well as the ap- parent velocity, VAB, at these points, can be deter- mined. Then the following equations can be applied: 6A 6T _1 (8) dzmax — 3 6A VA,B) . Vi - (LA ' VAB . (9) 6T with dA=AWW—NN, dT=7W)—NNJM _ déE)-dA_(Al A,B — dT — dT With these equations a homogeneous low-velocity zone is assumed. dz,“ax is the upper limit for the thickness of the low-velocity zones; its lower limit is equal to zero. In most cases, however, the points A and B cannot be defined precisely. Nevertheless it is possible to estimate the average velocity, W, with such a depth range, for which V(z) is not determined, by the follow- ing expression (fig. 6F): A 3::2— Ei—ICd—z (10) V,- W o V(z) B V(z), where W = 72: V 22 (A/2)2. ‘11) Giese has proposed the following procedure to estimate the average velocity for the undetermined depth ranges: Having calculated for a point (A, T, V) the corresponding depth, 2, by equation (5) one can determine the mean velocity, LE, for a ray traversing the Earth’s crust perpendicularly, that is, travelling perpendicular to the lines of equal velocity. Assuming that the path for other rays that do not travel perpen- dicularly is a straight line, that is, neglecting Snellius’ law, the average velocity, 17V, along this way is the same as that for LZ. 17V can be determined by equation 11. In reality according to the principle of Fermat, the traveltime along the straight line is greater than the traveltime along the actual curved ray path (see ray paths O-Q—Q in fig. GB). In consequence (according to equation 11) the calculated average velocity, W, based on the observed traveltime, T, is greater than 171: W 2 17., (12) the equal sign being valid for rays travelling perpen- dicular to the lines V = constant, or for a homogeneous overburden. As described above, for a point (A, T, V), the depth, 3, and the average velocity, W, can be determined. The determination of the average velocity, 171, however, is not immediately possible if the function V(z) can only be determined piecewise, as is true for most cases. Therefore, in a first step, a linear interpolation across the missing parts of V(z) is made and the integral :7, = z/(gzdz/Wz» (5a) is calculated (for instance, graphically, as indicated in figure 6F by the dotted part of V(z) and 1/V(z)). Com- monly, the resulting values for (Z are greater than W, in contradiction to equation 12. This contradiction can be avoided by introducing velocity inversions, 7, within the indeterminate parts 62 of V(z) and recalcu- lating the integral 5a until the relation in equation 12 is fulfilled. Of course, only an average value can be estimated for the corresponding depth ranges. For the determination of W (equation 11) it is recommended to use a ray characterized by the relation A/z < 4/1. (13) The condition is fulfilled mostly by critical rays. ANALYSIS OF SEISMIC-REFRACTION PROFILES The profiles recorded from each shotpoint in the dif- ferent azimuths were analyzed in detail. A record sec- tion is presented for each profile. With two exceptions (Delta-SHOAL and NTS-Kingman), tables present the following data for each section: the distance of the least and most distant seismometers from the shot- point (traces 1 and 6, and 9 and 14, respectively, of fig. 3) at each recording site, coordinates and elevation of one of the seismometers along each spread, and the numbers of the traces (according to fig. 3) included in 14 the corresponding record section. The velocity-depth functions calculated for each profile and listed in tables are shown in figures that summarize the results of all profiles along a recording line (for example, fig. 12). The numbers given in parentheses after the shotpoint names refer to the shotpoint numbers listed in table 1. The discussion that follows is arranged according to the geologic setting of the profiles. The three profiles recorded in the Snake River Plain between Boise, Idaho, and Mountain City, Nev., are included in the description of the profiles in the Basin and Range province. The profiles from Shasta Lake, Mono Lake, and China Lake, Calif., and the profiles from Fallon, N ev., to the south and southwest are combined in the discussion of the Sierra Nevada. The different travel- time curves are named a, a—b, b. d(b), c, and d following the notation of figure 5. The respective depth ranges calculated for each segment are named by the same let- ters. BASIN AND RANGE PROVINCE The following brief summary of the main geologic features of the Basin and Range province is based on Eardley (1962), Gilluly (1963), Hamilton and Myers (1966), Nolan (1943), Osmond (1960), Roberts (1968), and Thompson (1959). The broad Great Basin of the Basin and Range province in Nevada and western Utah is bordered on the west by the Sierra Nevada and on the east by the Wasatch Mountains. The north-trending ranges stand 500—1,200 m above the alluvial floors of flanking basins. Ranges and basins cover about equal areas in most of the province north of the 35th parallel. The blocks are typically between 10 and 20 km wide and are bounded on one or both sides by normal faults. The mountains are composed principally of sedimentary rocks of Paleozoic age, volcanic rocks of Tertiary age, and continental deposits and volcanic rocks of Pliocene and Pleistocene age. The individual ranges have com- plex internal structures, including folds (some over- turned), overthrusts, granitic intrusions, and high- angle faults with vertical and horizontal components of movement. Basin-and-range faulting began during Miocene time and still continues. The baSin-and-range faults are not alined with the earlier Precambrian and Laramide structures. According to Hamilton and Myers (1966) and Thompson and Talwani (1964), the geometry of the tilted normal-fault blocks requires regional extension as the basic cause of faulting. Hamilton and Myers (1966) estimated the total _ Cenozoic crustal extension indicated by the faults to be at'least 100 km, and possible as much as 300 km in the north, the larger value representing nearly half the pre- sent width of the province. CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES DELTA, UTAH, TO FALLON, NEV. The recording line extending from Delta, Utah (16), through Eureka, Nev. (15), to Fallon, Nev. (9), crosses the central part of the Great Basin transverse to the structure of the basins and ranges. The line was con- tinued west from Fallon to San Francisco (1) across the Sierra Nevada, the Great Valley, and the Coast Ranges (discussed in the next sections). Reversed observations were carried out between Fallon and Eureka; both pro- files were recorded in 1961. The distance between the two shotpoints is 275.3 km. Eaton (1963) has reported on the entire line from Eureka to San Francisco. In 1963, records were made alOng a 400-km-long line from Delta, Utah, to the nuclear shotpoint SHOAL (10) 55 km southeast of Fallon, passing Eureka 263.2 km from Delta. Only two stations were occupied beyond 280 km from Delta. This line was not reversed from Eureka, but it was possible to record with nine stations spread over the entire line between 150 and 550 km east of SHOAL. However, the stations on this profile are about 50 km apart, a separation too great to allow a detailed crustal study. Both profiles, Delta-SHOAL and SHOAL-Delta, were discussed by Eaton, Healy, Jackson, and Pakiser (1964). The record section of the profile Delta-SHOAL (S.W. Stewart and RR. Steven- son, written commun., 1967) is shown in figure 9, and the record sections and corresponding tables for the profiles Eureka-Fallon and Fallon-Eureka are presented in figures 10 and 11 (pl. 2) and tables 55 and 56. The record section of the profile Delta-SHOAL figure 5. First arrivals between 30 and 90 km from the shotpoint form the traveltime curve a. A gentle curve seems to be a better representation of a than a straight line. The first arrivals at 30 km and between 70 and 80 km from Delta probably are delayed by sedimentary basin fills. According to laboratory measurements on granite (Birch, 1958) and seismic-refraction results of profiles made in the Bohemian massif in southern Ger- many (Giese, 1963, 1966), it is reasonable to expect a velocity gradient within approximately the upper 5 km of the basement in which the velocity increases from 5.0 km/s or less to about 5.85 km/s, resulting in a cur- vature of the traveltime curve a at short distances. Where sediments cover the basement, however, the curvature due to the gradient in the upper part of the basement is hidden and commonly cannot be recognized. Between 50 and 80 km from the shotpoint, a second strong phase can be recognized in later arrivals after the first wave group a; this phase is identified as curve b. It is interpreted as a retrograde curve, and it can be traced in secondary arrivals as far as'125 km from the 15 ANALYSIS OF SEISMIC-REFRACTION PROFILES Soism .auE30wO .m.D dew—.265 dd tam fimbam .>>.m *3 803.55 nofioom .mfioifiomfi E veins m. 83... come we 93 23 am :oEEnmwo wfiunonmwtoo 2a. .3329 0.8 EEMoEmEm :23 ac m8“: 958 A $33 “Eu 6: 329 .H Baum 8 .802 35039? 23 9.:an 2.55:: 9.9 .8: Al_ l l l ‘L l l\l\ l l x 4 50 g 100 A(km) 150 50 g 100 A(km) 150 BARSTOW-LUDLOW 9 BARSTOW-MOJAVE < g 8 W .1 E E 2 W FIGURES 32—34.—Reduced traveltime graphs of the profiles from Ludlow (25) to Mojave (23), Barstow (24) to Ludlow (25), and Barstow (24) to Mojave (23). ANALYSIS OF SEISMIC-REFRACTION PROFILES 25 beneath the Mojave Desert seems therefore to be equal to or greater than 8.0 km/s, confirming the result ob- tained on the profiles between Ludlow and NTS. The upper mantle velocity is consistently less than 8.0 km/s elsewhere in the Basin and Range province. The details of the depth calculations for the profiles described in this section are given in tables 14—23, and the corresponding velocity-depth functions are shown in figures 36—40 (pl. 3). The crustal cross sections were obtained in the same way as were those for the line Delta-Fallon (see fig. 12). Intersections with other seismic refraction lines yielded additional information for the lines of equal velocity. The total crustal thickness decreases along the lines TABLE 14.— Velocity-depth function of the profile from Lake Mead(22) to Mono Lake(6) TABLE 16.— Velocity-depth function of the profile from NTS(19) to ngman(26') Gradient. Distance, A Traveltime. T Velocity, V Depth, 2 dV/dz Curve (km) (sh (km/5) 1km) (km/s/km) a 0 0 5.16 0 20 3.60 5.91 2.1 40 6.90 6.10 3.6 60 10.16 6.17 5.0 80 13.38 6.21 6.1 100 16.60 6.22 6.4 a—b 150 25.22 6.38 18.0 0.075 210 34.64 6.34 17.0 .01 c 90 17.80 7.57 30.7 .80 100 19.09 7.33 30.4 .70 120 21.90 6.98 29.8 .30 140 24.86 6.74 28.7 .15 160 27.87 6.60 27.6 .075 180 30.87 6.50 26.2 .04 210 35.50 6.42 24.0 .02 230 38.62 6.40 23.0 .01 d 90 17.68 7.93 31.6 .35 180 28.80 8.06 33.7 .015 z = 30.7 km: E: 6.30 km/s, E = 6.12 km/s, V = 6.0 km/s for z = 6.5—163 km and 18.1— 22.9 km. TABLE 17.— Velocity-depth function of the profile from Kingman(26) Gradient, Distance, A Traveltime. T Velocity, V Depth, 2 dV/dz Curve [kml (sh (km/sh (kml {km/s/kml a 0 0 4.43 0 20 3.79 5.94 3.1 40 7.09 6.07 4.1 70 12.03 6.10 5.0 a—b 60 12.06 6.30 14.4 0.20 100 18.46 6.23 13.4 .01 c 90 18.36 7.61 33.5 >200 100 19.68 7.41 33.4 2.00 110 21.04 7.25 33.3 .75 130 23.79 7.01 32.8 .30 150 26.65 6.80 31.9 .175 170 29.62 6.65 30.9 .10 190 32.68 6.51 29.2 .075 220 37.31 6.40 27.4 .04 240 40.44 6.35 26.2 .03 290 48.27 6.30 24.4 .01 d 150 26.20 7.72 35.0 .04 190 31.37 7.80 37.0 .02 230 36.45 7.85 40.0 .015 z = 33.5 km: 17: 6.17 km/s.127 = 6.11 km/s. V = 6.0 km/s forz = 5.1~13.3 km and l4.5~ 24.3 km. TABLE 15.— Velocity-depth function of the profile from Lake Mead(22) to Santa Monica Bay(4) Gradient, Distance. A Traveltime. T Velocity, V Depth, 2 dV/dz Curve (km) is) {km/s) 1km) (km/s/kml a 0 0 4.40 O 20 3.88 5.81 3.1 40 7.19 6.09 4.8 60 10.47 6.11 5.3 90 15.38 6.12 6.0 a—b] 40 7.94 6.13 8.0 0.05 70 12.84 6.12 7.3 .005 a-b2 70 13.47 6.19 14.0 .125 110 19.96 6.15 13.2 .01 c 70 15.03 7.90 28.9 5.00 80 16.30 7.60 28.8 1.00 100 19.00 7.10 28.3 .50 120 21.95 6.80 27.6 .20 140 24.96 6.55 26.3 .125 160 28.07 6.38 24.5 .06 180 31.21 6.30 22.8 .03 200 34.41 6.26 20.4 .01 to NTS(19) Gradient, Distance, A Traveltime, T Velocity, V Depth, 2 dV/dz Curve (km) Isl (km/sh (kml (km/s/km) a 0 0 5.58 0 30 5.37 5.68 1.5 60 10.38 6.13 6.0 90 15.27 6.14 6.6 120 20.15 6.15 7.1 0‘!” 130 21.97 6.20 9.9 0.01 (.1er 160 27.23 6.34 16.5 .01 c 90 17.40 7.34 27.7 .50 100 18.76 7.08 27.2 .40 120 21.69 6.70 26.0 .22 140 24.72 6.53 25.0 .10 180 30.91 6.42 23.4 .025 220 37.13 6.38 21.0 .008 d 100 18.62 7.71 29.0 .125 120 21.19 7.80 30.2 .05 140 23.74 7.86 31.4 .035 160 26.30 7.90 32.8 .025 z = 27.7 km: E = 6.27 km/s.u_1 = 6.07 km/s, V = 6.0 km/s forz = 7.2—9.8 km. 10.0~16.4 km. 16.6—20.9 km. TABLE 18.— Velocity-depth function of the profile from NTS(19) to Ludlow(25) Gradient. Distance, A Traveltime, T Velocity, V Depth. 2 dV/dz Curve (kml is! (km/s) 1km! (km/s/km) a 0 0 5.00 O 60 10.36 6.01 4.4 80 13.67 6.06 5.9 100 16.96 6.10 7.2 u—b 80 14.53 6.13 11.5 0.035 90 16.17 6.10 10.0 .01 c 100 19.83 7.80 35.5 1.00 110 21.12 7.58 35.2 .40 130 23.84 7.20 34.2 .25 150 26.66 6.88 32.2 .125 170 29.58 6.62 29.5 0.75 190 32.69 6.40 25.9 .04 220 37.40 6.20 20.7 .03 260 43.89 6.13 18.0 .01 z = 28.9 km: 14': 6.07 km/s,1? = 6.04 km/s, V = 6.0 km/s for z = (3.1—7.2 km,8.1—13.1km, 14.1—20.3 km. z = 35.5 km: E = 6.23 km/s, E = 6.18 km/s, V = 6.0 km/s for z = 7.3—9.9 km and 11.6— 17.9 km. 26 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 19.— Velocity-depth function of the profile from Ludlowf25) to TABLE 22.— Velocity-dep th function of the profile from Barstow(24) NTS(19) to Mojave(23) Gradient, Gradient, Distance. A Traveltime, T Velocity. V Depth, 2 dV/dz Distance, A Traveltime. T Velocity, V Depth. 2 dV/dz Curve (km) (S (km/s) lkmb (km/s/kmb Curve (km) (51 (km/s) (km) (km/s/km| a 0 0 3.97 0 a 0 0 4.93 0 30 5.82 5.99 5.0 20 3.73 5.60 1.9 60 10.80 6.05 6.1 40 7.30 5.71 3.3 90 15.73 6.10 7.8 60 10.66 6.17 7.9 110 19.00 6.11 8.2 80 13.87 6.23 9.1 a~b1 80 14.29 6.15 9.7 0.02 a—b1 60 10.97 6.25 9.4 0.03 41—172 70 13.50 6.31 14.6 .10 a—b2 50 10.14 6.48 13.0 .20 110 19.36 6.25 13.7 .01 60 11.71 6.33 11.5 .03 c 80 15.86 7.85 28.3 .50 c 80 16.41 7.80 30.0 2.00 90 17.18 7.45 27.6 .45 90 17.71 7.51 29.8 .70 100 18.51 7.18 27.0 .36 100 19.04 7.29 29.4 40 120 21.35 6.80 25.6 .175 120 21.81 6.92 28.0 15 140 24.41 6.53 23.4 .075 140 24.74 6.64 25.3 05 160 27.56 6.37 20.7 .03 190 32.29 6.33 19.2 .01 z = 27.5 km: E = 6.03 km/s, 13 = 6.14 km/s. TABLE 20.— Velocity-depth function of the profile from Ludlow(25) to Mo;aue(23) Gradient, Distance, A Traveltime. T Velocity, V Depth. 2 dV/dz Curve {km} (s) [km/s) {km} (km/s/km) u 0 0 3.60 0 20 4.22 5.71 4.0 40 7.59 6.11 6.3 , 60 10.85 6.16 7.1 80 14.09 6.18 7.8 100 17.33 6.19 8.6 2*!) 80 14.17 6.32 12.7 0.10 120 20.56 6.27 11.9 .01 c 80 16.30 7.80 30.8 00 100 18.98 \ 7.40 30.7 1.00 120 21.74 7.12 30.4 .30 140 24.54 6.92 29.6 .14 160 27.44 6.70 28.0 .085 180 30.47 6.54 26.2 .06 200 33.56 6.42 23.6 .04 230 38.27 6.34 20.2 .01 d 90 17.53 8.11 31.0 .20 140 23.60 8.21 32.0 .025 z = 30.3 km: E: 6.04 km/s. 173 = 6.13 km/s. TABLE 21.— Velocity-depth function of the profile from Barstow(24) to Ludlowf25) Gradient. Distance, A Traveltime. T Velocity, V Depth. z d V/dz Curve (kmi 1s) (km/s) (km) 1km/s/kml a 0 0 4.66 0 20 3.89 5.51 2.3 40 7.46 5.74 4.4 60 10.78 6.21 8.5 a—b 70 13.05 6.41 14.7 0.21 80 14.61 6.33 14.1 .075 100 17.81 6.25 11.9 .01 c 70 14.81 8.00 28.6 2.00 80 16.09 7.63 28.4 1.00 100 18.77 7.27 28.2 .30 120 21.58 6.91 25.9 .075 140 24.54 6.58 20.5 .05 d 80 15.94 8.21 29.0 .20 140 23.21 8.25 29.6 .02 z = 28.6 km: E: 6.18 km/s.13 = 6.10 km/s, V 5 6.1 km/s forz = 8.7—ll.8 km and 14.8—17.9 km, and V = 6.48 km/s at z = 18.0 km. z = 30.0 km: 17 = 6.22 km/s, (T = 6.09 km/s. V = 6.1 km/s for z = 9.5—11.4 km and 13.1— 233 km, and V = 6.58 km/s at z = 24.0 km. TABLE 23.— Velocity-depth function of the profile from Mojave(23) to Ludlow(25) Gradient. Distance, A Traveltime. T Velocity. V Depth, z dV/dz Curve (km; (st {km/st (km) {km/s/km) a 0 0 4.19 0 20 3.93 5.79 3.3 40 7.29 6.12 5.4 60 10.50 6.25 7.0 80 13.69 6.27 7.6 a-b 80 14.17 6.32 12.7 0.10 120 20.56 6.27 11.9 .01 c 80 16.30 7.80 308 0° 100 18.98 7.40 30.7 1.00 120 21.74 7.12 30.4 .30 140 24.54 6.92 29.6 .14 160 27.44 6.70 28.0 .085 180 30.47 6.54 26.2 06 200 33.56 6.42 23.6 04 230 38.27 6.34 20.2 01 d 90 17.46 8.00 31.1 30 130 22.43 8.05 31.8 04 z = 30.8 km: E = 6.16 km/s. E = 6.19 km/s. from N TS to Kingman from 31 to 28 km and from NTS to Ludlow from 35 to 28 km. On the profiles Lake Mead-Mono Lake and Lake Mead-Santa Monica Bay, the crustal thickness at Lake Mead changes from 33 km for the northern profile to 29 km for the southern one. Comparison of u— and W (tables 14-19) shows that except for the profile Ludlow-N TS (table 19), velocity inversions are evident within the upper crust. The con- dition 17 - 1.005 < W can be fulfilled for all profiles by assuming an average velocity of 6.0 km/s for the depth range between the depth points calculated from the most distant end of curve a and curve c, and by assum- ing that within this low-velocity material there are ex- tended areas with higher P-wave velocity as indicated by curves a-b between a and c. With this assumption the upper crust is 18—24 km thick, and a distinct lower crust does not exist; rather, the lower crust is a transi- tion zone between crustal and upper mantle material. ANALYSIS OF SEISMIC-REFRACTION PROFILES 27 Another solution could be obtained by assuming that a low-velocity zone exists only between the depth ranges corresponding to a and a—b. The lower limit of the low-velocity zone is the greatest depth range a—b if more than one a—b curve exists. In this solution, the velocity inversion above a-b should be strong, and an average velocity of 5.8 km/s would be required. Several scattered arrivals between curves a and c suggest several additional short a-b branches for which no depth calculations were made. These short branches weaken the assumption of an extensive low-velocity zone, and so the first solution seems more probable. The velocity-depth functions for the line between Ludlow and Mojave are presented in figure 40 and tables 20-23. Whereas the curves a from the shotpoint at Ludlow indicate a basin filled with about 2 km of sediments, the curves (1 of the profiles from Barstow and Mojave indicate an increase of the velocity with depth from less than 5 km/s to 6.20-6.25 km/s. This in- crease is due mainly to a gradual increase in the veloci- ty of the basement rocks. On the basis of phase c, the total crustal thickness between Ludlow and Mojave ranges from 29 to 31 km. As the comparison of 17 and 17V shows, the P-wave velocity seems to decrease to 6.1 km/s at a depth range between 9 and 18 or 24 km in the vicinity of Barstow. Within this zone there may be material with higher velocity (up to 6.4-6.5 km/s), but the correlation of the corresponding phases in the record sections is ambiguous. Comparison with the results published by Diment, Stewart, and Roller (1961) and Roller (1964) for the line NTS-Kingman and by Gibbs and Roller (1966) for the line NTS-Ludlow shows total crustal thicknesses close to those obtained here; the base of the crust rises from 3—34 km south of NTS to 27 km at King- man and Ludlow. The average velocity in the crust, according to Diment, Stewart, and Roller (1961) and Roller (1964), corresponds to the velocity distribution found here. The average velocity reported by Gibbs and Roller (1966) is higher than that obtained here; no traveltime curve corresponding to 6.8 km/s could be found in the present study. Rather, the first arrivals between 120 and 145 km are interpreted here as P" arrivals that can be correlated up to a distance of 150 km, whereas the first arrivals beyond 150 km are delayed for 0.3 second to form a traveltime curve approximately parallel to curve d. A similar feature is found on the profile Kingman-NTS at 175 km, as re- ported by Roller (1964). Johnson (1965) and Roller and Healy (1963) presented evidence for traveltime curves with a velocity of 7.0 km/s for the profiles Lake Mead-Mono Lake and Lake Mead-Santa Monica Bay. However, these traveltime curves are based on weak secondary arrivals and could not be confirmed in the present reinterpretation. Although the average velocity distribution in the crust determined by the above authors is somewhat higher than that obtained in this paper, their resulting total crustal thicknesses agree fairly well with those reported here. OTHER PROFILES FROM NTS In addition to the profiles discussed above, three other profiles from NTS are included in this paper: NTS to Navajo Lake, Utah; NTS to Elko, Nev.; and NTS to San Luis Obispo, Calif. The profile to Navajo Lake was extended to a distance of about 1,000 km into the Great Plains of Colorado. Initial results for this profile were published by Ryall and Stuart (1963). In this report, only the recordings up to a distance of 400 km were reinterpreted (fig. 41, pl. 2; table 75). On this line, the shotpoint at Navajo Lake is located approximately at the border between the Basin and Range province and the Colorado Plateau, 290 km from NTS. Three drill-hole shots were recorded to a distance of 250 km from Navajo Lake toward N TS (fig. 42, pl. 2; table 76). The profile from NTS to Eureka and Elko was also extended to a dis- tance of 1,000 km into northern Idaho, crossing the Basin and Range province, the western Snake River Plain, and the Idaho batholith. It was interpreted by Pakiser and Hill (1963) and Hill and Pakiser (1966, 1967). In this report, only the recordings up to a dis- tance of 440 km from NTS are included (fig. 43, pl. 2; table 77). The first part of this profile, to Eureka at a distance of 270 km from NTS, was not reversed. North of Eureka, some of the same recording sites were used from the shotpoints of the line from Boise to Eureka. The profile from NTS to San Luis Obispo crosses the Basin and Range province, the Sierra Nevada, the Great Valley of California, and the Coast Ranges of California. It was “reversed” from San Luis Obispo by offshore shots in the Pacific Ocean at a distance of 480 km from NTS. Similar to the “reversed” profiles between Lake Mead and Mono Lake or Lake Mead and Santa Monica Bay, the observations from the shotpoints at both NTS and San Luis Obispo were not really reversed because the interval distance is too large to provide a common reversed subsurface path along the M-discontinuity. In this report, the profile from NTS (fig. 44, pl. 2; table 78) is analyzed only with regard to the crustal structure under the Basin and Range province. The profile enters the Sierra Nevada at a distance of 190 km from NTS. The first four shots recorded along this profile were chem- ical explosions; the other recordings were obtained from underground explosions of nuclear devices. On the profiles from NTS to Navajo Lake and N TS 28 to Elko, no stations were recorded between the respective 0—55 and 0-70 km distance, and so the deter- mination of curve a is based on only a few records at distances less than 120 or 130 km from NTS. The delay at the first two stations on the profile be- tween N TS and San Luis Obispo at distances of 5 km and 25 km from the shotpoint northeast of NTS is the result of sedimentary covers in Emigrant Valley and Yucca Flat. It is generally assumed that the velo- city increases gradually within the uppermost few kil- ometers of the basement. If the nearby stations are not located on basement rocks, the convex-upward curvature of curve a within the first 30 km cannot be recognized in the first arrivals. Because of wider spacing of recording stations on these profiles and gaps of several tens of kilometers, the correlation of phases between a and c is more doubtful than on other profiles. Only on the profile NTS-San Luis Obispo and on the reverse profile N av- ajo Lake-NTS are there enough indications to permit the correlation of wave group b. On all profiles, how- ever, phase 0 can be correlated confidently. Phase d is strong only on the profiles NTS-Elko and NTS- Navajo Lake. It is recognizable on the profile NTS- San Luis Obispo only at distances beyond 250 km, which may result partly from the energy released at NTS. On the profile Navajo Lake-NTS there are only weak indications for phase d. Tables 24—27 show the computed results. The trend of curve c at distances beyond 200 km on the profiles NTS-Elko, NTS-Navajo Lake, and NTS- Ludlow is similar to that found on the line Boise-Lake Mead. From north to south, the velocity correspond- ing to the slope of curve 0 at 250 km decreases from 6.30 to 6.15 km/s. Whereas curve c crosses the distance axis on the profile NTS-Elko at 250 km, this distance increases to 320 km on the profile NTS-Nav- ajo Lake. Curve 0 does not cross the distance axis on TABLE 24.—Velocity-depth function of the profile from NTSIIQ) to Navajo Lake(21) Gradient. Distance. A Traveltime, T Velocity. V Depth, 2 dV/dz Curve (km) {sh [km/st 1km) (km/s/kml a 0 0 4.52 0 50 9.43 5.92 6.9 80 14.47 5.98 8.3 100 17.81 6.02 9.8 130 22.76 6.09 12.2 c 90 18.09 7.70 32.1 0.80 100 19.41 7.40 31.7 .50 120 22.14 7.04 31.0 .30 140 25.01 6.76 29.8 .18 160 28.06 6.56 28.7 .15 180 31.18 6.43 27.8 .15 200 34.31 6.35 27.2 .10 240 40.62 6.30 26.4 .04 300 50.16 6.28 25.2 .01 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES the profile NTS-Ludlow. Figure 39 (pl. 3) shows the combined crustal cross sections of the lines Ludlow- NTS and NTS-Elko, In addition, the results of inter- pretation of the profile Eureka-Lake Mead were pro- jected on the line Eureka-N TS. As is indicated by the TABLE 25.— Velocity-depth function of the profile from Navajo Lake(21) to NTS(19) Gradient, Distance, A Traveltime, T Velocity. V Depth. z dV/dz Curve (km) (s) {km/s) 1kml (km/s/km) a O 0 3.19 0 20 4.51 5.71 4.6 40 7.88 6.04 6.4 70 12.78 6.17 8.5 b 60 12.55 6.37 15.2 0.10 90 17.28 6.30 14.0 .01 c 100 20.23 7.80 36.6 1.00 110 21.55 7.62 36.4 .42 120 22.85 7.44 36.0 .30 140 25.53 7.07 34.1 .15 160 28.41 6.75 31.5 .075 180 31.46 6.52 28.2 .035 210 36.16 6.40 24.0 .01 z = 36.4 km: E: 6.07 km/s, E = 6.12 km/s. TABLE 26.— Velocity-depth function of the profile from NTS(19) to Elkof14) Gradient, Distance. A Traveltime, T Velocity. V Depth. z dV/dz Curve (kml (sl (km/sh (km) (km/s/km) a 0 0 5.04 0 80 13.86 6.01 6.5 100 17.19 6.03 7.4 120 20.50 6.05 8.3 c 100 18.90 7.60 31.4 0.50 120 21.62 7.15 30.1 .25 140 24.48 6.80 28.0 .15 160 27.51 6.55 25.4 .075 180 30.57 6.38 22.3 .04 220 36.90 6.30 19.6 .01 z = 31.4 km: E: 6.19 km/s.13 = 6.25 km/s. TABLE 27.— Velocity-depth function of the profile from NTS(19) to San Luis 0bispo(3} Gradient, Distance. A Traveltime, T Velocity, V Depth. 2 dV/dz Curve (kml ls) (km/5| (km) (km/s/kml a 0 0 3.57 0 30 6.20 5.72 5.2 60 11.33 5.87 6.8 90 16.42 5.96 9.3 120 21.43 6.02 11.6 155 27.45 6.11 15.1 b 90 17.12 6.23 18.2 0.15 120 21.95 6.18 17.3 .025 c 100 20.20 7.65 36.1 5.00 120 22.91 7.24 36.0 1.00 140 25.71 7.03 35.7 .30 160 28.60 6.84 35.0 .175 180 31.5.6 6.67 34.0 12 200 34.59 6.55 32.8 .08 220 37.67 6.46 31.4 .05 240 40.77 6.38 29.3 .03 270 45.47 6.30 25.6 .015 z = 32.1 km: E = 5.99 km/s, 17} = 6.11 km/s. z = 36.1 km: E = 5.92 km/s, E = 6.11km/s. ANALYSIS OF SEISMIC-REFRACTION PROFILES crustal cross section of the line Navajo Lake-San Luis Obispo in figure 45 (pl. 3), the velocity decrease in the upper crust from 6.15 to 6.0 km/s south of' NTS is not evident beneath NTS. The average velocity at depths of 18 km is about 6.1 km/s south of Eureka but may be somewhat higher north of NTS. The average crustal velocity increases also from NTS to the east. West of Navajo Lake, at the border of the Colorado Plateau, the velocity increases to nearly 6.4 km/s at a depth of 15 km and is about constant to a depth of 24 km. The total crustal thickness reported by Pakiser and Hill (1963) for the profile NTS-Elko is 28 km without and 31 km with an intermediate layer in the lower crust (velocity 6.7 km/s). In later publications, Hill and Pakiser (1966, 1967) reported a 29-km crustal thickness 100 km north of N TS under the assumption that an intermediate layer exists with a velocity of 6.7 km/s at a depth of 20 km beneath an upper crustal layer with a velocity of 6.0 km/s. The average velocity obtained in this paper corresponds roughly to the average velocity of Hill and Pakiser, although the velocity distribution differs significantly between depths of 8 and 26 km. No evidence was found for an intermediate layer separated from the upper crust by a discontinuity but rather for a continuous increase of velocity from 6.0 km/s at 7 km to 7.6 km/s at the base of the crust at 31 km depth. The velocity gra- dient also increases gradually at depths greater than 20 km. The increasing thickness of the crust from NTS toward Eureka reported by Hill and Pakiser is confirmed here. The total crustal thickness of 25—26 km reported by Ryall and Stuart (1963) under NTS is sig- nificantly less than that reported here (32 km east of NTS). However, the increasing thickness to 42 km to the east reported by Ryall and Stuart under the west- ern part of the Colorado Plateau is confirmed here by the results of the profile from Navajo Lake to NTS, with 36 km crustal thickness, and by the line from Hanksville (30) to Chinle (31), with 42-43 km crustal thickness. The apparent P,. velocities reported by the above authors for the profile NTS-Elko as well as the NTS-Navajo Lake correspond to the values reported in this paper. THE SIERRA NEVADA The Sierra Nevada (figs. 1, 4) is bounded by the Great Basin of the Basin and Range province on the east, the Great Valley of central California on the west, and the Cascade Range on the north. The gener- al features of Sierra Nevada geology that follow are based mainly on Bateman and Wahrhaftig (1966), Bate- man and Eaton (1967), Bateman (1968), and Pakiser, 29 Kane, and Jackson (1964). The Sierra Nevada is a strongly asymmetrical mountain range with a gentle western slope and a high and steep eastern escarp- ment, a huge block formed by westward tilting and profound late Cenozoic faulting on the east. Most of the southern and the northeastern parts of the Sierra Nevada are composed of plutonic rocks of the Sierra Nevada batholith of Mesozoic age. In the north half of the range, the batholith is flanked on the west by the western metamorphic belt composed of strongly deformed and metamorphosed sedimentary and vol- canic rocks of Paleozoic and Mesozoic ages. Farther south, scattered remnants of metamorphic rock are found in the western foothills and also along the crest in the east-central Sierra Nevada (Kistler and Bateman, 1966; Rinehart and Ross, 1964). These rocks are overlapped on the west by sedimentary rocks of the Great Valley and discontinuously over- lain on the north by Cenozoic volcanic sheets that ex- tend southward from the Cascade Range. The great eastern escarpment was created in Pliocene and Pleis- tocene times. The main faulting may represent col- lapse of the Owens Valley block in the crest of a broad arch (Bateman, 1968). The Sierra Nevada con- stitutes the west flank of this arch, and the desert ranges as far east as Death Valley constitute the faulted east flank. The Cascade Range, in which one line was partly recorded, is a volcanic mountain range that extends north through Oregon and Washington from the Sierra Nevada in northeastern California (fig. 1). According to Macdonald (1966) and Macdonald and Gay (1968), the older part of the range (the Western Cascades) consists of early and middle Tertiary basalt, andesite, and dacite. The High Cascades to the east were built by eruptions of basaltic to rhyolitic lava during Pliocene and Qua- ternary time. Andesites are the predominant rocks of the High Cascades. The most recently active volcano, Lassen Peak, erupted last in 1915. SHASTA LAKE TO CHINA LAKE The line extending from Shasta Lake (5) through Mono Lake to China Lake (8) yielded the most reliable data on the crustal structure under the Sierra Nevada. The northernmost 100-km segment of the profile, between Shasta Lake and Mono Lake, is located in the southern Cascade Mountains near Las- sen Volcanic National Park. South of Mono Lake (409.0 km south of Shasta Lake and 273.3 km north of China Lake) the recording sites were located immedi- ately east of the eastern escarpment of the Sierra Nevada (fig. 1). Previous investigations of Mono Basin and Owens Valley (for example, Pakiser and 30 others, 1964) make possible estimation of the influ- ence that sediments and near-surface structures have on the broader seismic observations. This influence seems to be relatively small. The Mono Lake shot- point was located in the western part of the lake just outside the deepest part of the Mono Basin structure (Pakiser, 1970). A depth to basement of 1.1 km was calculated for this shotpoint. Most of the recording sites up to 212 km south of Mono Lake were located directly on the granitic basement rocks or at places where the thickness of overlying sediments seems to be rather small. Between Mono Lake and China Lake, an interme- diate shotpoint was located at Independence, 157.2 km south of Mono Lake and 116.4 km north of China Lake. Figures 46—49 (pl. 2) and tables 79—82 present the record sections and corresponding data for the profiles from Shasta Lake, Mono Lake, and China Lake. Although the line between Mono Lake and China Lake was recorded east of the crest of the Sier- ra Nevada, the Bouguer gravity anomaly and geolo- gic evidence suggest that the Sierra Nevada block is tilted toward the west and that the recording line fol- lows closely the deep crustal axis of the Sierra Nevada. The profiles were observed in 1962 and first interpreted by Eaton (1966). Because the northernmost part of the profile from Shasta Lake to Mono Lake was located in the south- ern Cascade Mountains, the first part of the record section (fig. 46) differs significantly from the other record sections of this line. Traveltime curve a shows a relatively steep slope that defines a velocity of 6.5—6.6 km/s at distances beyond 50 km. Curve (1 crosses the distance axis about 75 km from the Shas- ta Lake shotpoint. Secondary arrivals between 110 and 150 km define a traveltime curve a’ parallel to curve a. This curve can be traced farther in weak first arrivals up to a distance of 175 km. Whereas this first part of the profile Shasta Lake-Mono Lake yields information on the crustal structure under the south- ernmost Cascade Mountains, the phases recorded at greater distances yield information on the Sierra Nevada. This explains the fact that the velocity indi- cated by curves a—b and b is slightly lower than that recorded at distances to 175 km. Phases b and c are not very clear but nevertheless can be traced with fair reliability between about 210 and 300 km. Pn arrivals were well recorded beyond 210 km, yielding an apparent upper mantle velocity of about 7.9 km/s. However, the point of critical distance can only be es- timated because of the absence of corresponding ar- rivals in the appropriate distance range. This zone of weak arrivals is probably due to the change of crustal CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES structure along the geologic boundary between the Sierra Nevada and Cascade Mountains. The resulting velocity-depth function (table 28; fig. 50, pl. 3) conse- quently must be considered as reflecting two geologic units: The upper part (to a depth of 17—18 km) is related to the Cascade Mountains, and the lower part is related to the Sierra Nevada. Comparison of the average velocities 17 and W suggests a velocity inver- sion from 6.55 to 6.0 km/s at depths below 7.5 km. However, the curve a’ suggests that zones with high- er velocity material probably exist within the low- velocity zone. On the other profiles of the line from Shasta Lake to China Lake (figs. 47 —49), the reciprocal slope of the traveltime curve a yields velocities corresponding to typical values for granitic rocks and to the location of the recording sites on or near rocks of the Sierra Nevada batholith. On the profile from Mono Lake to Shasta Lake, curve a can be traced to distances as great as 170 km, suggesting a gradual increase of velocity within the crust to 6.38 km/s at a depth of 17 km. This increase in velocity with depth was not found between Mono Lake and China Lake, along which line the resulting velocity at 160-170 km dis- tance is about 6.1 km/s. A rather easily correlated curve a—b can be seen in secondary arrivals, and the record sections also support the existence of curve b, indicating a slight increase in velocity to 6.4—6.5 km/s at a depth of 21—24 km within the crust. Curve c can be traced between 80 and 300 km on all profiles. However, the arrivals defining curve c are not as dominant as they are on most profiles in the Basin and Range province. P,, arrivals are generally very weak on the profile from Mono Lake to Shasta Lake; at many stations the first part of the P, phase is either delayed or cannot be detected. The determin- ation of the apparent upper mantle velocity is there- fore uncertain. No P" arrivals could be found on the profile from Mono Lake to China Lake. The first ar- rivals at 160—170 km distance from China Lake are probably P" arrivals having an apparent velocity of 7.8 km/s when these arrivals are connected by a straight line with curve c at 80 km distance. The comparison of the average velocities LT and 17V shows that the condition 17 - 1.005 < W is fulfilled for the profiles from Mono Lake and that no decrease of velocity within the crust is evident (tables 29, 30). However, the profile from China Lake to Mono Lake indicates that the velocity in the upper crust does not exceed 6.1 km/s at depths above approximately 20 km (table 31). Figure 50 shows the computed velocity-depth func- tions (tables 28—31) and a crustal cross section along ANALYSIS OF SEISMIC-REFRACTION PROFILES 31 TABLE 28.—Velocity-depth function of the profile from Shasta TABLE 30.— Velocity-depth function of the profile from Mono Lake(5) to Mono Lake/6) Lake(6) to China Lake(8) Gradient. Gradient.) Distance. A Traveltime, ’1‘ Velocity. V Depth, 2 dV/dz Distance. A Traveltime. T Velocity, V Depth. 2 dV/dz Curve (km) (S) (km/s) 1km) (km/s/km) Curve (km) (s) (km/s) lkm) (km/s/km) a 0 0 4.98 0 a 0 0 3.45 0 20 3.89 5.59 2.3 20 4.34 5.66 4.1 40 7.14 6.45 6.3 40 7.79 5.86 5.5 60 10.20 6.55 7.7 60 11.17 5.96 7.1 90 16.11 6.11 10.5 a 140 22.81 6.55 10.8 0.005 aeb 90 16.58 6.30 17.0 0.15 arb 210 34.26 6.48 13.7 .02 170 30.91 6.26 15.6 .005 b 180 30.37 6.55 26.4 .05 b 120 21.79 6.44 23.3 .20 220 36.47 6.52 25.0 .02 140 24.89 6.40 23.4 .075 280 45.69 6.50 22.4 .005 170 29.59 6.36 22.8 .025 200 34.31 6.32 21.0 .01 c 140 25.73 7.54 40.3 .35 160 28.46 7.22 39.8 .225 c 110 22.03 7.86 40.1 1.00 180 31.25 7.03 38.9 .15 120 23.30 7.70 39.9 .40 200 34.13 6.87 37.6 .10 140 25.92 7.38 39.2 .25 220 37.07 6.73 35.9 .065 160 28.62 7.10 38.0 .15 240 41.10 6.64 34.2 .045 130 31.50 6.85 36.3 .10 260 43.16 6.59 33.0 .03 200 34.47 6.66 34.2 .075 280 46.23 6.57 32.4 .02 220 37.56 6.54 31.9 .035 320 52.33 6.55 31.4 .01 240 40.65 6.47 30.0 .025 280 46.87 6.42 28.0 .01 d 140 25.70 7.60 41.0 .30 $1138 3%? 3;: 2;: ;g§5 z = 40.1 km: E = 6.09 km/s, :7 = 6.18 km/s. 340 51.20 7.90 48.0 .008 z = 40.8 km: E = 6.43 km/s, 13‘: 6.29 km/s, V = 6.0 km/s for z = 7.8—10.6 km and 11.07 18'6 km' TABLE 31.—Velocity-depth function of the profile from China Lake(8) to Mono Lake(6) TABLE 29.— Velocity-depth function of the profile from Mono Gradient. Distance. A Traveltime, T Velocity, V Depth. 2 dV/dz Lake(6) to ShaSta Lake(5) Curve (km) (S) (km/s) (km) (km/s/km) Gradient. a 0 0 4.48 0 Distance. A Traveltime. T Velocity, V Depth. 2 dV/dz i8 32; 2%? 23 k k / . . . 5. Curve ( m) (s) ( m 5) (km) (km/s/km) 60 11,08 594 7.6 30 14.41 6.04 9.2 a 0 0 3.57 0 110 19.36 6.06 9.9 30 6.19 5.76 5.4 60 11.27 6.14 9.1 avb 30 14.60 6.03 10.6 0.02 90 16.11 6.22 10.7 120 20.92 6.26 12.1 b 100 18.55 6.43 21.2 .30 150 25,68 6.34 15.6 130 23.26 6.40 20.8 .035 170 28.82 6.40 17.9 170 29.50 6.38 19.9 .01 a—b 130 22.75 6.44 20.7 0.06 c 90 18.53 7.60 33.5 2.00 180 30,54 6,40 19,2 ,0] 110 21.25 7.20 33.3 .75 120 22.63 7.06 33.0 .50 b 140 24.89 6.55 25.2 .075 140 25152 6.85 32.2 .175 170 29.47 6.51 244 .025 160 28.49 6.71 31.2 .075 190 32.54 6.49 22.6 .01 180 31.47 6.61 29.2 03 200 34.51 6.54 25.2 01 c 130 24.67 7.65 41.6 .50 _ 140 25,97 7,44 411 ,50 z = 33.5 km: u = 6.08 km/s, [F = 6.06 km/s. V = 6.1 km/s for z = 11549.8 km. 160 28.78 7.14 40.5 .30 180 31.65 6.96 39.9 .20 200 34.52 6.84 39.2 .125 240 40.42 6.68 37.2 .05 . _ , 318 3:23 322 3:3 gf8 reg1ona1 Bouguer grav1ty, suggesting that upper z = 41.6 km: E = 6.15 km/s,17 = 6.26 km/s. the line from Shasta Lake through Mono Lake to China Lake. As discussed above, at a depth of 7.5 km a low-velocity zone was found in the area southeast of Shasta Lake in which the velocity decreases from 6.55 km/s to 6.0 km/s. This part of the profile is located on volcanic material that consists mainly of pyroxene andesites and basaltic andesites (Pakiser, 1964) having the observed high velocity of 6.5-6.6 km/s near the surface (see also Eaton, 1966). A similar velocity was found beneath the Snake River Plain at relatively shallow depth in an area of high crustal material may be absent there. The more recent eruptions of Lassen Peak and the observed local gravity low in that area (Pakiser, 1964) suggest a low-velocity zone below 7 km there. Whether the seismic low-velocity zone is confined to the area of Lassen Volcanic National Park only or is a general feature of the Cascade Mountains cannot be decided on the basis of the available seismic-refrac- tion data. The average velocity within the upper 20 km decreases under the Sierra Nevada from the northwest toward the southeast, as is suggested by the 6.2- and 6.4-km/s contour lines. The average velocity below 20 km depth is 6.4-6.6 km/s to a depth of approximately 33-35 km under Mono Lake and 30 32 km northwest of China Lake. At this depth, the velocity begins to increase to 7.6—7 .8 km/s at the base of the crust. The total computed crustal thickness is 41—43 km in the middle part of the line and decreases to 33 km toward the southeast. On the basis of the velocity estimated from curve c at distances beyond 200 km, there does not seem to be a thick layer with 6.9 km/s average velocity under the Sierra Nevada, as interpreted by Eaton (1966); rather, the average velo- city does not seem to exceed 6.6 km/s to a depth of 30—35 km. Consequently, the crustal thickness obtained herein is less than that reported by Eaton in 1966 but agrees well with that reported by Eaton in 1963. Mikumo (1965) also reported a crustal thickness of 43 km under the central Sierra Nevada, assuming an average crustal velocity of 6.3 km/s. OTHER PROFILES IN THE SIERRA NEVADA In addition to the line extending from Shasta Lake through Mono Lake to China Lake, several other pro- files were recorded from shots at Mono Lake and China Lake. Three profiles were recorded from Fallon toward the west and south. Eaton (1963) reported on the profiles recorded from Fallon, and Johnson (1965) reported on the profile from Mono Lake to Lake Mead. The other profiles interpreted herein have not been previously published. Figures 51-59 (pl. 2) and tables 83—91 present the record sections and corresponding data for all profiles discussed in this section. Figure 60 (pl. 2) and table 92 present a record section and data for fan observations that were recorded approximately 230 km from Mono Lake between the profiles from Mono Lake to China Lake and Mono Lake to Lake Mead (azimuths 119° to 152°). A corresponding record of the profile from Mono Lake to Santa Monica Bay (azimuth 166°) is also included. Recording sites for shots from China Lake were ir- regularly distributed in a pattern that can be approxi- mated by three profiles. Only seven recordings were obtained along the profile from China Lake (fig. 51; table 83) to a distance of 175 km to the northwest. Although the spacing along this profile is very large, the four most distant stations show clearly the phase 0 in later arrivals. No P" arrivals were recorded be- cause the profile was too short. The velocity-depth function calculated from curves a and c is shown in table 32 and figure 61 (pl. 3), together with an ap- proximate crustal cross section based on this profile only. Like the profile from China Lake to Mono Lake, the total crustal thickness beneath this profile is 33 km, and a low-velocity zone is interpreted to exist be- tween depth of 13 and 23 km in which the velocity de- creases from 6.26 to 6.0 km/s. CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES The record section for the profile from China Lake to the west is shown in figure 52 (see also table 84). Only four usable stations between 140 and 245 km distance were recorded toward San Luis Obispo. These stations were west of the Sierra Nevada in the Great Valley and the Coast Ranges of California. On the basis of data in Hackel (1966), the stations in the Great Valley at distances of 140 and 165 km were located over 3 km and 6 km, respectively, of sedimen- tary rocks, and on the basis of data in Payne (1967), one station in the Carrizo Plain area of the Coast Ranges (distance 205 km) was located over sediments more than 2 km thick. Correcting the reduced travel- time (T — A/6) by 1.0 s for 3-km- and 1.5 s for 6-km- thick sediments on the basis of data from Eaton (1963) causes later arrivals to aline on a curve yield- ing an apparent velocity of 6.5 km/s at 140 km and 6.1 km/s at 245 km distance. However, because avail- able observations are insufficient, no depth calculations were made. The profile from China Lake to Santa Monica Bay (fig. 53; table 85) was recorded along the southeastern edge of the Sierra Nevada. To the south it crosses the western Mojave Desert near Mojave. The first arriv- als at distances of 14 and 23 km were delayed for more than one-half second, probably owing to a thick sedimentary cover in the basin at China Lake. At the end of the profile near Santa Monica Bay, good P,, arrivals can be recognized, and fairly well correlated secondary arrivals permit the tracing of phases b and c. The total crustal thickness calculated for this profile (table 33; fig. 62, pl. 3) is 31 km, and the comparison of the average velocities LT and W indicates that low-velocity material with a velocity of 6.1 km/s extends to a depth of about 12 km south of China Lake. The 444.9-km-long profile from Mono Lake to Santa Monica Bay (fig. 54; table 86) crosses the Sierra Nev- ada, but it was recorded in adequate detail only TABLE 32,—Velocity-depth function of the profile from China Lake(8) to northwest Gradient, Distance, A Traveltime. T Velocity, V Depth. 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 4.15 0 30 5.78 5.95 4.7 70 12.41 6.05 6.3 100 17.36 6.13 9.2 110 18.97 6.21 11.1 120 20.58 6.26 12.7 c 110 21.28 7.35 33.2 0.30 i 120 22.67 7.04 32.1 .25 140 25.59 6.75 30.4 .10 160 28.58 6.55 28.0 .04 180 31.65 6.40 23.5 .015 z = 33.2 km: E = 6.13 km/s, E = 6.04 km/s. V = 6.0 km/s for z = 12.8-23.4 km. ANALYSIS OF SEISMIC-REFRACTION PROFILES TABLE 33.— Velocity-depth function of the profile from China Lake(8) to Santa Monica Bay(4) Gradient. Distance. A Traveltime. T Velocity. V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 3.84 0 20 4.09 5.83 3.8 40 7.42 6.05 5.2 60 10.71 6.08 5.9 80 13.99 6.10 6.6 100 17.27 6.11 7.2 b 60 11.77 6.26 13.7 0.30 80 14.97 6.21 13.2 .03 100 18.21 6.19 12.6 .01 c 80 16.76 7.84 31.1 2.00 90 18.06 7.54 30.8 .65 100 19.40 7.29 30.4 .45 120 22.13 6.85 29.3 .30 140 25.25 6.58 27.9 .125 160 28.34 6.41 26.1 .075 180 31.46 6.32 24.5 .03 210 36.25 6.26 21.4 .01 z = 31.1 km: E = 6.03 km/s. LT) = 6.05 km/s, V = 6.1 km/s for z = 7.3A12.5 km. TABLE 34.—— Velocity-depth function of the profile from Mono Lake(6) to Santa Monica Bay(4) Gradient, Distance, A Traveltime. T Velocity, V Depth. 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 4.23 0 20 4.10 5.51 3.1 40 7.54 5.90 5.3 90 15.84 6.12 9.2 140 23.95 6.22 13.4 c 190 32.39 6.98 37.0 0.08 200 33.85 6.81 34.8 .075 220 36.87 6.59 31.2 .05 240 39.95 6.46 28.9 .05 280 46.16 6.35 25.5 .02 320 52.49 6.30 21.8 .01 z = 37.0 km: E = 6.17 km/s, w = 6.30 km/s. beyond 190 km from Mono Lake. Only two records were available between 50 and 190 kin. Because of the lack of observations up to.190 km, only curves a and c can be determined. Curve c is well defined be- tween 190 and 300 km from Mono Lake; however, the continuation of curve c toward smaller distances is doubtful. P,. arrivals could not be identified. The cal- culated velocity-depth function (table 34; fig. 63, pl. 3) shows a gradual velocity increase with depth from 6.3 km/s at 22 km to about 7.0 km/s at 37 km, assuming a velocity gradient of 0.08 km/s/km at that depth as determined from other similar profiles. A low-velocity zone within the crust is not evident. The profile from Fallon to San Francisco (fig. 55; table 87) crosses the Sierra Nevada between Lake Tahoe and Sacramento at distances between 90 and 220 km from Fallon. The stations east of Lake Tahoe were located in the Basin and Range province, and the stations beyond 220 km were located in the Great Valley of California. In addition to curve a, curve b can be traced between 80 and 125 km and indicates a 33 velocity increase from 6.2 to 6.4 km/s between depths of 14 and 18 km. Curve c was reliably determined be- tween 80 and 230 km. Curve d is tangent to c at 110 km and can be traced to 230 km. The apparent velo- city defined by curve d is 7.7—7.8 km/s. From curve c, a velocity increasing with depth from 6.45 km/s at 21 km to 7.90 km/s at 35 km was derived. The center part of figure 12 shows the velo- city-depth function of this profile (table 35) and the resulting crustal cross section from Fallon to the west. Additional velocity-depth data are available at the intersection with the line from Shasta Lake to Mono Lake. From east to west, the cross section shows a gradual thickening of the crust from the Basin‘ and Range province near Fallon into the Sierra Nevada, which corresponds with Eaton’s (1963) inter- pretation. The decrease of crustal thickness west of the intersection with the line from Shasta Lake to Mono Lake is not based on seismic observations. According to the considerations of Eaton (1963), however, it is assumed that the crustal thickness under the Great Valley of California is close to that found under the Coast Ranges. The profiles from Fallon and Mono Lake extend into the Basin and Range province immediately east of the Sierra Nevada, where the crust seems to be similar to that in the Sierra Nevada. The most distant stations of the profile from Fallon to Mono Lake (fig. 56, pl. 2; table 88) are located be- yond a distance of 180 km south of Mono Lake in the Sierra Nevada. Because of lack of observations be- tween 90 and 145 km, only the phases a (0—90 km), c (90—295 km), and d (290-350 km) can be correlated. Phase d at a distance of 90 km seems to mark ap- proximately the critical distance because it fits the extrapolated curves c and d at their point of tan- TABLE 35.—Velocity-depth function of the profile from Fallon(9) to San Franciscofl) Gradient, Distance, A Traveltime, T Velocity. V Depth, z dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 3.39 0 20 4.40 5.73 4.3 40 7.73 6.04 5.9 60 11.04 6.06 6.5 90 15.97 6.10 7.9 b 90 16.60 6.44 18.5 0.20 100 18.17 6.35 17.9 .10 120 21.35 6.21 13.8 .01 c 100 19.39 7.90 34.7 .40 110 20.64 7.64 34.1 .42 120 21.99 7.40 33.5 .30 140 24.81 7.06 32.0 .15 160 27.67 6.80 30.2 .09 180 30.67 6.60 27.2 .04 200 33.72 6.46 20.8 .01 z = 34.1 km: E = 6.05 km/s. 1? = 6.27 km/‘s. 34 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES gency. Pu arrivals that could be confidently identified were not recorded at distances less than 290 km; the apparent P" velocity beyond 290 km is 7 .5—7.6 km/s. The reverse profile from Mono Lake to Fallon (fig. 57; table 89) was recorded at only eight stations. Curve (1 suggests a gradual velocity increase with depth. However, because there are no stations between 0 and 45 km and only a few stations beyond that distance, the possibility cannot be excluded that the first arrivals were delayed by sediments in such a way that a velocity gradient is erroneously suggest- ed. Therefore, the slope based on the two stations be- tween 15 and 55 km may not yield a true velocity. The position of curve c on the profile from Fallon to Mono Lake contains some arrivals of phase c that also seem to be delayed on this profile. The results of the depth calculations for the profiles between Fallon and Mono Lake are presented in tables 36 and 37 and shown in figure 63 with the results from the line from Mono Lake to Santa Monica Bay. Crustal thick- ness increases from 31 km south of Fallon to 33 km west of Walker Lake to 41 km at Mono Lake. Eaton (1963) reported a similar increase in thickness along this line. The thickness obtained on the line from Shasta Lake to China Lake is supported by the pro- file from Mono Lake to Santa Monica Bay, where a velocity of 7.0 km/s was found at a depth of 37 km. Farther south, the profile extending northwest from China Lake contains some information that can be used to construct the crustal cross section in figure 63. This profile shows that the crust thins under the southern part of the Sierra Nevada. The dotted lines in the cross section of figure 63 for distances greater than 150 km south of Mono Lake show the suggested trend of the lines of equal velocity for the area where no seismic information was available. The first part of the profile from Fallon to China Lake (fig. 58; table 90) is largely composed of the TABLE 36.—Velocity-depth function of the profile from Fallon(9) to same stations as the profile from Fallon to Mono Lake. Phase a can be traced up to distances of 90—100 km, but the first arrivals beyond 100 km seem to cor- relate well with later arrivals at shorter distances (curve a—b). For only a short distance range, but clearly correlatable, phase b indicates a velocity in- crease from 6.2 to 6.3 km/s at depths of 16—18 km (table 38). Curve c is expressed by very strong se- condary arrivals between 135 and 220 km, and it can be correlated over the entire distance range from 85 to 355 km. Pn arrivals seem to be delayed between 180 and 220 km. An 8-km-thick transition zone from lower crust to upper mantle between depths of 24 and 32 km was calculated (fig. 62). Results of the two re- cording lines from Fallon through China Lake to Santa Monica Bay were combined to form a crustal cross section (fig. 62). The reversed part of the line from Fallon to China Lake is based on’ the results of the profiles from Independence and China Lake along the line from Shasta Lake to China Lake (fig. 50). TABLE 37.— Velocity-depth function of the profile from Mono Lake(6) to Fallon(9) Mono Lake(6) Gradient. Distance, A Traveltime. T Velocity, V Depth, 2 (IV/dz Curve (km) (5) (kms) (km) (km/s/km) a 0 0 3.43 0 20 4.45 5.43 3.9 40 7.91 5.97 6.6 60 11.20 6.14 8.6 90 16.04 6.24 10.6 L‘ 100 19.37 7.60 32.3 0.40 110 20.72 7.27 31.5 .40 120 22.12 7.04 30.5 .28 140 25.00 6.76 29.8 .18 160 28.03 6.59 28.6 .10 180 31.10 6.44 26.4 .05 200 34.23 6.33 22.6 .02 Gradient, Distance. A Traveltime, T Velocity. V Depth, 2 dV/dz Curve (km) (s) (kmis) (km) (km/s/km) u 0 0 5.09 0 20 3.31 5.39 1.4 40 7.48 5.49 2.6 60 11.10 5.63 5.1 80 14.55 5.95 9.8 110 19.49 6.13 13.2 r- 90 18.25 7.90 33.7 1.00 100 19.54 7.65 33.5 .50 120 22.22 7.24 32.2 .20 140 24.93 6.86 29.7 .10 160 27.98 6.52 26.1 .05 130 31.11 6.30 20.9 .02 z 2 33.7 km: E : 6.1:1kmrs. (T : 6.16 km/s. TABLE 38.— Velocity-depth function of the profile from Fallon(9) to China Lake(8) Gradient. Distance, A 'l‘raveltime. T Velocity. V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 3.56 0 20 4.45 5.42 3.9 40 7.91 5.96 6.6 60 11.21 6.09 8.1 90 16.11 6.15 9.8 u h 110 19.72 6.15 10.8 0.005 b 100 18.49 6.30 18.5 .10 120 21.66 6.25 17.7 .03 140 24.85 6.22 16.1 .01 (' 90 18.04 7.90 32.7 .60 100 19.34 7.52 31.9 .50 120 22.04 7.10 30.7 .30 140 24.90 6.79 29.4 .14 160 27.89 6.55 27.2 .085 180 31.00 6.40 25.2 .05 200 34.16 6.33 23.5 .025 230 38.92 6 30 22.1 .01 z = 32.3 km: E = 6.00 km/s. E = 6.15 km/s. z = 32.7 km: E = 5.98 km/s, L? = 6.17 km/s. ANALYSIS OF SEISMIC-REFRACTION PROFILES The final profile east of the Sierra Nevada was re- corded from Mono Lake to Lake Mead, 439 km to the southeast. On this profile (fig. 59; table 91), correlation of phase b is uncertain. Phase 0 can be recognized up to a distance of 320 km, but the point of critical reflection at a distance of 110 km was not as confidently determined as on other profiles. The P” arrivals form two parallel branches; weak first arriv- als were followed by strong arrivals one-half second later. The general delay of P" between 270 and 310 km seems to be explainable by a section of thick sedi- ments overlying the basement rocks, whereas at dis- tances greater than 310 km the energy was too weak to produce good P" arrivals. The measured apparent velocity of P" is 8.0 km/s. ‘ The calculated velocity-depth function (table 39; fig. 36) for the profile from Mono Lake to Lake Mead includes a velocity increase from 6.15 km/s to 6.4 km/s at a depth of 12—17 km. The average crustal velocity is 6.4 km/s below 17 km. Velocity increases gradually between 28 km and the base of the crust at a depth of 37 km. Crustal thickness decreases from 41 km under Mono Lake to 37 km under the Inyo Mountains (fig. 36) and is uniform toward the south- east to the intersection with the line from Ludlow to NTS (see also fig. 39). The average velocity in the upper 25 km of the crust decreases east of the Inyo Mountains, in agreement with the other profiles from NTS and Lake Mead. Johnson (1965) found a layer with a velocity of 7.1 km/s, which is reinterpreted here as a 7—8-km-thick transition zone in which the velocity increases gradually from 6.5 to 7.8 km/s. The characteristics of the arrivals correlated by curves 0 and d change from the Sierra Nevada to the Basin and Range province, as revealed by observations ap- proximately 230 km from Mono Lake (fig. 60; table TABLE 39.—-Velocity-depth function of the profile from Mono Lake(6) to Lake Mead(22) Gradient, Distance, A Traveltime, T Velocity, V Depth, 2 dV/dz Curve (km) (s) (kmfls) (km) (km/s/km) a 0 0 4.02 0 £10 6.05 5.68 4.7 60 11.09 6.06 7.9 90 16.01 6.11 9.1 110 19.28 6.13 9.9 130 22.54 6.15 11.0 150 25.79 6.16 11.6 b 70 13.91 6.38 16.9 0.20 110 20.19 6.33 16.5 .02 c 120 22.71 7.70 37.3 25 130 24.03 7.30 35.4 20 140 25.45 6.98 33.6 18 160 28.42 6.62 31.2 15 180 31.49 6.50 30.0 08 210 36.13 6.41 28.1 03 230 39.27 6.38 24.9 01 z = 37.3 km: E = 6.14 km/s, (T = 6.22 km/s. 35 92). The amplitudes of the P,, phase decrease with increasing crustal thickness westward toward the Sierra Nevada, and the arrivals gradually disappear at an azimuth of 146°. The early arrival of phase c at 166° shows that this phase approaches the distance axis at 225 km. The slope of curve 0 decreases with decreasing azimuth to define a velocity at a distance of 220—240 km and azimuth of 166° at 6.6 km/s de- creasing to 6.4 km/s at 119°. COAST RANGES OF CALIFORNIA The Sierra Nevada is bordered on the west by the Great Valley of central California, a nearly flat allu- vial plain 750 km long and about 80 km wide on the average. In structure it is a large, elongate, north- west-trending, asymmetric trough with a wide and stable eastern shelf underlain by the buried west-dip- ping Sierran slope and a narrow western flank formed by the steeply upturned edges of the basin sediments (Hackel, 1966). Hamilton (1969) regards the Great Valley sedimentary rocks as continental shelf depos- its and partly, in their westernmost parts, as contin- ental slope deposits of Mesozoic age. The Coast Ranges, farther west, are a series of ridges and valleys that generally trend northwest near and subparallel to the Pacific Coast. The Coast. Ranges are still undergoing folding and warping, and several fault zones are seismically active (Crowell, 1968; Page, 1966). According to Eaton (1967, 1968), earthquakes occur along the San Andreas fault only at depths no greater than 15 km. Two entirely different core complexes, one the Jurassic and Creta- ceous eugeosynclinal assemblage called the Francis- can Formation (Bailey and others, 1964) and the other the block consisting of Cretaceous granitic in- trusions and older metamorphic rocks, lie side by side and are separated from each other by the San Andreas fault system in central California. Hamilton (1969, p. 2419) suggested that “the undated platform- facies meta-sedimentary rocks, intruded by Creta- ceous batholiths and exposed in small areas of the central Coast Ranges west of the San Andreas fault (Compton, 1966), perhaps lay near the southeastern California (Pre-cambrian basement) complexes in Cretaceous time***” and were displaced about 500 km north-northwestward by the right-lateral San Andreas and other faults. SAN FRANCISCO TO SANTA MONICA BAY The profiles recorded in 1961 from San Francisco through Camp Roberts to Santa Monica Bay trend parallel to the geologic features of the Coast Ranges of California. The recording sites were located near 36 the coastline west of the San Andreas fault zone on granitic intrusions, metamorphic rocks, or covering sediments. The line is about 550 km long with the fol- lowing distances between shotpoints: San Francisco—Camp Roberts, 260.8 km, and Camp Roberts—Santa Monica Bay, 287.6 km. The maximum recording distance was 320 km. Figures 64—67 (pl.2) and tables 93-96 present the record sections and cor- responding tables for the profiles. Near San Francisco and Santa Monica Bay, offshore shots were deton- ated; near Camp Roberts, the shots were fired in . drill holes. The line was first interpreted by Healy (1963). In 1967, the US. Geological Survey carried out a detailed seismic investigation of the crust be- tween San Francisco and San Luis Obispo. Two lines, each about 200 km long, were recorded from several shotpoints alined parallel to and on both sides of the San Andreas fault zone (see fig. 82 for locations of shotpoints). A preliminary interpretation of these ob- servations was published by Stewart (1968a). In this report, only the profiles recorded in 1961 are included, but main phases on the record sections of these profiles were correlated by visually comparing them with the data of 1967. In agreement with the results of Healy (1963) and Stewart (1968a), traveltime curves for phase a of all four profiles along the line from San Francisco to Santa Monica Bay show a velocity slightly higher than 6.0 km/s beyond distances of 60 km. In contrast, Eaton (1963) and Stewart (1968a) found the velocity within the Franciscan basement rocks east of San Andreas fault zone to range from 3.3 km/s near the surface of 5.7 km/s at depths of several kilometers. Secondary arrivals were weak on the profile from San Francisco to Camp Roberts (fig. 64), and so curve c can be traced only between 65 and 130 km. However, clear P,. arrivals were recorded beyond 190 km, yielding an apparent velocity of 8.0 km/s. The correlation of phase b on the profiles from Camp Roberts (figs. 65, 66) and the resulting depth calcula- tion are uncertain. Secondary arrivals corresponding to curve c were stronger from the Camp Roberts shots. P" arrivals can be identified and correlated, yielding average velocities of 7.9—8.1 km/s to the northwest and 7.9 km/s to the southeast. The weak- ness of the phases of curve c from the San Francisco shotpoint is in agreement with the profiles recorded in 1967 west of the San Andreas fault, whereas on some profiles recorded on Franciscan basement east of the San Andreas fault a very clear phase can be recognized as curve c. On the profile from Santa Monica Bay to Camp Roberts (fig. 67), secondary ar- rivals can be correlated relatively well between 50 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES and 110 km. The corresponding velocity-depth calcu- lation for these arrivals indicates a velocity increase from 6.32 to 6.45 km/s at depths of 15—17 km. The record section of this profile shows prominent phases that can be correlated to form curves 0 and d. Curve d defines an apparent velocity of 8.3 km/s. The resulting velocity-depth functions and the crustal cross section (fig. 68, pl. 3; tables 40—43) show that there is a sharp, nearly discontinuous boundary between crust and mantle under the Coast Ranges of central California at which the velocity increases within a depth range of 2 km from 6.6—6.8 to 7.8-8.0 km/s. The crust there is about 26 km thick. Toward the south, under the Transverse Ranges between Santa Barbara and Los Angeles, the crust thickens to 36 km, and the transition zone between crust and mantle thickens to about 6 km. A distinct intermed- iate boundary does not seem to be present within the crust; the average velocity between depths of 10 and 24 km is 63—64 km/s. The velocity-depth model proposed by Healy (1963) has an average crustal velocity of 6.1 km/s. This value is approximately that proposed in this report. The total crustal thickness presented by Healy and in this paper is about the same. OTHER PROFILES FROM SANTA MONICA BAY In addition to the profile from Santa Monica Bay to Camp Roberts, three other profiles were recorded from Santa Monica Bay: to the north toward Mono Lake (fig. 69, pl. 2; table 97), to the north-northeast toward China Lake (fig. 70, pl. 2; table 98), and to the northeast toward Lake Mead (fig. 71, pl. 2; table 99). Results for the profile from Santa Monica Bay to Lake Mead were published by Roller and Healy (1963). The two profiles from Santa Monica Bay to Mono Lake and China Lake actually constitute a single profile because the recording locations of which TABLE 40.— Velocity-depth function of the profile from San Franciscofl) to Camp Roberts(2) G radient, Distance. A Traveltime, T Velocity, V Depth. z dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 3,79 0 20 4.46 5.11 3.2 40 8.19 5.60 6.2 60 11.60 6.04 9.9 80 14.85 6.24 12.5 c 70 14.50 7.78 26.2 1.00 80 15.79 7.28 25.5 .75 100 18.60 6.90 24.7 .20 120 21.56 6.62 22.0 .04 d 80 15.68 7.96 27.0 .20 100 18.22 8.00 27.4 .05 z = 26.2 km: E = 5.93 km/S. E = 6.03 km/s. ANALYSIS OF SEISMIC-REFRACTION PROFILES 37 TABLE 41.~— Velocity-depth function of the profile from Camp Roberts(2) to San Francisco/1) Gradient. Distance. A Traveltime, T Velocity, V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 2.85 0 20 4.80 5.64 5.0 40 8.16 6.07 7.2 60 11.38 6.34 9.8 80 14.51 6.38 10.7 b 70 13.65 6.39 11.7 .01 c 70 14.48 7.80 26.5 1.00 80 15.80 7.41 26.1 .70 100 18.52 6.90 25.3 .40 120 21.51 6.60 24.4 .20 140 24.56 6.50 23.9 .10 160 27.66 6.44 23.1 .04 180 30.77 6.42 22.5 .025 210 35.44 6.40 21.4 .01 d 100 18.24 7.98 27.5 .06 160 25.76 8.05 30.2 .015 210 31.81 8.10 34.0 .01 z = 26.5 km: E = 5.82 km/s, 13 = 6.06 km/s. TABLE 42.—Velocity-depth function of the profile from Camp Roberts(2) to Santa Monica Bay(4) Gradient. Distance, A Traveltime, T Velocity. V Depth. 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 3.49 O 20 4.30 5.66 4.1 40 7.76 5.89 5.7 60 11.09 6.15 8.5 80 14.28 6.26 10.2 b 150 25.86 6.27 15.5 0.01 c 70 14.46 7.70 25.7 .70 80 15.80 7.20 25.0 .70 100 18.71 6.70 24.1 .35 120 21.75 6.47 23.3 .15 140 24.89 6.37 22.4 .05 160 28.04 6.34 21.6 .025 200 34.32 6.33 21.4 .01 d 100 18.33 7.80 26.5 .05 140 23.52 7.85 28.0 .02 230 34.93 7.90 31.0 .007 z = 25.7 km: E = 5.90 km/s, E = 6.01 km/s. TABLE 43.— Velocity-depth function of the profile from Santa Monica Bay(4) to Camp Roberts(2) Gradient, Distance. A Traveltime. T Velocity. V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 3.97 0 30 6.45 5.51 5.3 60 11.44 6.21 9.8 90 16.25 6.26 11.2 120 21.02 6.30 12.7 b 60 12.69 6.45 17.3 0.50 80 15.79 6.35 16.6 .04 100 18.95 6.32 15.2 .01 c 100 19.86 8.00 36.1 .40 110 21.14 7.67 35.2 .30 120 22.43 7.40 34.3 .25 140 25.10 6.99 32.1 .15 160 27.98 6.69 29.9 .10 180 31.07 6.55 28.4 .05 200 34.16 6.50 27.2 .028 240 40.33 6.47 25.6 .01 d 110 21.00 8.10 36.6 .18 140 24.64 8.19 38.0 .06 200 31.90 8.25 40.0 .02 they are formed are almost identical up to a dis- tance of 200 km. Many stations up to 110 km were located so that their records have been plotted in both record sections (figs. 69, 70). Therefore, the traveltime curves for the profile to Mono Lake do not differ from those on the profile to China Lake. Fur- thermore, the curve parallel to curve d beyond 240 km has the same position on both record sections. The velocity-depth calculations are therefore identical (table 44; figs. 62, 63). However, the arrivals between 40 and 130 km that form a cusp with curve a seem to be restricted to the profile to Mono Lake, which crosses the central Sierra Nevada, whereas only curve a can be correlated on the profile to China Lake, which crosses the western Mojave Desert. The traveltime diagram for the profile from Santa Monica Bay to Lake Mead (fig. 71) is very similar to those of the other profiles from Santa Monica Bay. The large delay of curve a on all three profiles results from the thick accumulation of sedimentary rocks in the Los Angeles basin. These rocks may be 2 km thick or more under the area crossed by the profiles from the base- ment map by Yerkes, McCulloch, Schoellhamer, and Vedder (1965). The velocity determined from the curves a for the basement rocks exceeds 6 km/s. On the basis of curve b, the velocity increases at depths be- tween 17 and 20 km from 6.3—6.4 to about 6.5 km/s. The total crustal thickness is 34-34 km under the Transverse Ranges north of Los Angeles. The velocity gradient increases below depths of about 30 km (table 45; left part of fig. 37). There are no seismic data avail- able that yield direct information about the boundary zone between the Transverse Ranges and the Mojave TABLE 44.—Velocity-depth function of the profile from Santa Monica Bay(4) to Mono Lake(6)/China Lake(8) Gradient. Distance. A Traveltime, T Velocity, V Depth. 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 2.78 0 30 6.71 5.71 6.1 60 11.81 5.95 8.5 90 16.75 6.12 11.5 100 18.39 6.15 12.3 Santa Monica Bay to Mono Lake only: 40 8.71 6.29 12.8 80 14.96 6.41 13.8 120 21.20 6.42 14.3 b . 70 14.75 6.54 19.9 0.25 90 17.83 6.43 18.5 .03 c 90 18.75 8.00 36.6 >500 100 20.07 7.72 36.5 2.00 120 22.71 7.46 36.2 .40 140 25.37 7.26 35.6 .15 160 28.15 7.08 33.9 .05 180 31.00 6.92 29.9 .02 d 100 19.95 8.04 36.7 .25 180 29.88 8.06 37.0 .02 z = 36.1 km: E = 6.07 km/s, I? = 6.21 kaS. z = 36.6 km: E = 5.99 km/s, LT} = 6.19 km/s. 38 TABLE 45.— Velocity-depth function of the profile from Santa Monica Bay(4) to Lake Mead(22) Gradient, Distance, A Traveltime, T Velocity, V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/’s/km) a 0 0 2.74 0 30 6.35 6.14 6.1 60 11.21 6.18 7.0 90 16.06 6.185 7.4 110 19.29 6.19 7.6 l) 60 13.08 6.44 18.0 0.40 80 16.18 6.36 17.4 .04 100 19.35 6.30 16.0 .01 t 90 18.78 7.84 34.4 .55 100 20.09 7.49 33.9 .70 120 22.83 7.07 33.0 .30 140 25.71 6.84 31.7 .10 160 28.68 6.70 30.0 .04 200 34.70 6.59 26.4 .01 d 200 32.56 7.911 35.4 .01 z = 34.4 km: E = 5.97 km/‘s, L? = 6.03 km/‘s. Desert. However, the two areas are separated by the San Andreas fault zone (Dibblee, 1967), so it seems likely that the crust thins to the north and northeast within a small distance as shown in the crustal cross sections and as also suggested by Roller and Healy (1963). TRANSVERSE PROFILES FROM SAN FRANCISCO AND SAN LUIS OBISPO The two profiles from San Francisco to Fallon and San Luis Obispo to NTS cross the Coast Ranges, the Great Valley, and the Sierra Nevada transverse to their trends. Only a few recording stations from these shotpoints were located east of the Sierra Nevada. These profiles were especially difficult to interpret be- cause of the poorly known influence of the thick sedi- ments in the Great Valley and because of the struc- tural complexity of the features that the profiles cross. If the thickness and velocity of the sediments were known, the traveltimes of the arrivals at stations in the Great Valley could be corrected. By using the map of central California showing thickness of sedimentary rocks in the Great Valley after C. A. Repenning (Hackel, 1966) and a graph for traveltime delays in sediments published by Eaton (1963, fig. 4), the records of the stations in the Great Valley were shifted in the record sections with respect to the time axis to make approximate corrections. Both the uncorrected (a) and the corrected (b) record sections are shown in figures 72 and 73 (pl. 2). Tables 100 and 101 present the corresponding data, and table 108 lists the correc- tions made. The uncertainties involved in such a cor- rection were discussed in detail by Eaton (1963). On the west side of the Great Valley, where the sediments reach a thickness of 10 km or even more, the station corrections may be large. The interpretation is further CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES complicated because the profiles cross the granitic basement west of and the Franciscan basement east of the San Andreas fault zone. Therefore it is not possible confidently to define basement velocities from these profiles. Nevertheless, the transition zone between crust and mantle seems to be fairly well defined by curve 0. Curve d can be well correlated up to 220 km on the pro- file from San Luis Obispo to N TS, but it is not clearly established in the first part of the profile from San Francisco to Fallon. P" arrivals can be correlated at distances beyond 270 km where they are delayed 1.2 and 2.7 seconds with respect to curve d on the first part of these profiles. This suggests a sharply thicken- ing crust under the foothills of the Sierra Nevada. The velocity-depth functions (tables 46, 47; figs. 12 and 45, pl. 3) give average crustal models for the Coast Ranges in central California that agree with that ob- tained for the line from San Francisco to Santa Monica Bay. These results also agree with the model obtained by Eaton (1963, 1966) for the profile from San Francis- co to Fallon. Eaton also made a preliminary analysis of the profile from San Luis Obispo to N TS and proposed a slightly thicker crust under San Luis Obispo than under San Francisco. COLORADO PLATEAU The network of profiles recorded in 1961-63 in the Basin and Range province, Sierra Nevada, and Coast Ranges of California is fairly dense, but only a few pro- files were recorded in the Colorado Plateau and the Middle Rocky Mountains. The Colorado Plateau is bounded by the Basin and Range province on the south and west, the Middle Rocky Mountains on the north, and the Southern Rocky Mountains on the east. It is a region of large plateaus, escarpments, and canyons; the plateaus reach heights of 3,000—3,600 m. The char- acteristic structures are broad uplifts and intervening basins. Wide areas of nearly flat-lying rocks are sepa- rated by abrupt monoclinal flexures. Several clusters of laccolithic intrusions form mountain ranges in Utah. Volcanic fields are present around the periphery of the Colorado Plateau. The Colorado Plateau can be regard- ed as stable compared with the complex deformational features of the adjacent provinces, but it has been tec- tonically active compared with the great stable shield areas (Eardley, 1962; King, 1959). A reversed seismic-refraction profile was recorded in the central part of the Colorado Plateau between Hanksville, Utah, and Chinle, Ariz. The distance be- tween the shotpoints is 296.2 km. No recording site was occupied south of Chinle, but six sites were install- ed north of Hanksville to distances of 50 km from ANALYSIS OF SEISMIC-REFRACTION PROFILES TABLE 46.— Velocity-depth function of the profile from San Franciscofl) to FallonIQ) Gradient, Distance, ./_\. Traveltime, 7' Velocity, V Depth. 2 dV/dz Curve (km) (s) (kmxs) (km) (km/51km) a 0 0 4.98 0 30 5.50 5.73 2.8 60 10.55 6.19 7.5 90 15.39 6.22 8.5 110 18.59 6.31 11.3 90 15.48 6.55 14.2 50 9.51 6.80 14.3 90 15.35 6.90 15.5 120 19.68 6.97 17.4 150 23.96 7.05 19.8 C 170 26.78 7.12 22.2 40 9.41 7.87 22.9 (1 70 13.20 7.95 23.2 90 15.71 8.00 24.0 2 = 23.6 km: E = 6.30 kms, 17- = 6.44 kmrs. TABLE 47,—Velocity-depth function of the profile from San Luis Obispofl?) to NTSIIQ) Gradient, Distance. A Traveltime. T Velocity, V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 3.57 0 30 6.01 5.89 5.1 60 10.99 6.13 7.7 90 15.78 6.39 12.0 110 18.90 6.41 12.6 c 60 13.12 7.70 24.6 5.00 70 14.43 7.28 24.5 5.00 80 15.80 7.04 24.2 2.00 100 18.71 6.75 24.0 .20 120 21.72 6.60 22.8 05 140 24.78 6.52 19.2 .01 160 27.85 6.50 17.0 .005 d 100 18.18 7.96 25.7 .04 120 20.70 8.00 27.1 .027 210 30.56 8.10 34.8 .015 z = 24.6 km: E = 5.90 km/s, (T = 5.92 kme. Hanksville and 358 km from Chinle. The line crosses the eastward extension of the profile from NTS to Navajo Lake about 80 km south of Hanksville and 195 km east of Navajo Lake. The shotpoints of Hanksville and Chinle were both located in structural basins. The recording line crosses the east flank of the intrusive Henry Mountains, the Monument uplift, and the Comb monocline south of the Colorado River. A detailed de- scription and interpretation of this survey was pub- lished by Roller (1965). In addition to the line, an ex- tensive survey between Hanksville and Chinle was car- ried out in 1964 in central Arizona. Two profiles in the 1964 survey were located in the southern part of the Colorado Plateau (position of shotpoints is shown in fig. 82). These seismic-refraction measurements were analyzed in detail by Warren (1969). In this report, on- ly the 1963 survey is discussed in detail. The record sections of the two profiles to 100 km (figs. 74 and 75, pl. 2; tables 102, 103) permit correla- tion only of curve a. The delays of the first arrivals on 39 the profile from Hanksville to Chinle between 10 and 50 km were caused by low-velocity sedimentary rocks in the basin in which the stations were located. Increasing depth of the top of the Chinle Formation (Triassic) to about 1 km below the surface in the area south of Hanksville is indicated by the Tectonic Map of the United States (Cohee, 1962). The Basement Rock Map of the United States (Bailey and Muehlberger, 1968) shows a depth to Precambrian basement in this area of as much as 3 km. The first ar- rivals forming curve a on the reverse profile from Chinle to Hanksville confirm that the basement is shal- lower near Chinle, as indicated by the cited maps. Ear- ly first arrivals on this profile at distances of 100—160 km can be combined to form a cusp with the first arriv- als at shorter distances and some fairly strong later ar- rivals, yielding a rapid velocity increase from 6.1 to 6.3 km/s at a depth of 6—7 km. Such first arrivals beyond 100 km were not found on the profile extending south from Hanksville. On this profile, first arrivals at dis- tances of 110—170 km were delayed with respect to curve a, probably because the stations were located in large structural basins (Roller, 1965). Phase a—b can be identified on the profiles from both Chinle and Hanksville up to 180 km. This phase can be correlated with well-defined arrivals at distances of 280—300 km on the profile from Hanksville to Chinle. Curve b can be correlated on both profiles at distances beyond 110 km. Some arrivals at smaller distances suggest that curve b may be traced backward toward the shotpoints to distances of less than 110 km. Curve 0 is defined by clear secondary arrivals beyond 110 km. The fact that the curve d is tangent to curve c at a distance of 140-150 km indicates that the part of curve c nearest the shotpoint has to be interpreted as a reflected phase. This reflected phase seems to be recognizable beyond a distance of 60-70 km. Curve d is well deter- mined by first arrivals at distances beyond 220 km. The apparent velocity of the P, phase defined by this curve is 7.6 km/s up to a distance of 300 km and in- creases to 7.8 km/s north of Hanksville. Curve d crosses the distance axis at a distance of 210 km. This is a large distance compared with the corre- sponding crossover distances on the profiles in the Basin and Range province and is in agreement with the position of the P,. curve on a profile recorded southeast from Sunrise, Ariz., 45 km south of Chinle (Warren, 1969). Several phases can be recognized at distances beyond 210 km. These arrivals, however, are scattered, which complicates the correlation of the different phases. This is especially true for the profile from Chinle to Hanksville. Some of the secondary arrivals may belong to a traveltime curve that is parallel to 40 curve d (see for example Prodehl, 1965). Curve c seems to be the most reliable correlation, whereas the exten- sion of curves b and a-b on the profile from Hanksville beyond the intersection with curve c is not clear. Tables 48 and 49 show the calculated velocity-depth relations, and figure 76 (pl. 3) shows the velocity-depth functions and the resulting crustal cross section for the Hanksville-Chinle profile. The velocity gradient at 25—29 km depth derived from curve b is large. The velocity increases from 64-65 km/s to 6.65-6.75 km/s within a small depth range that corresponds to the in- termediate boundary found by Roller (1965) at a slight- ly greater depth. This zone dips downward from south to north, also in agreement with Roller’s result. How- ever, the velocity increase is not very large, and the velocity difference of 0.2 km/s between neighboring lines of equal velocity does not permit recognition of this zone in the crustal cross section of figure 76. At depths greater than 31-35 km, the velocity increases gradually from about 6.8 to about 7.6 km/s at the base of the crust at a depth of 42—43 km. As shown by R01- ler, the transition zone between crust and mantle (indi- cated by merging velocity lines in fig. 76) dips downward from north to south, revealing that the thickness of the crust as a whole as well as the lower part of the crust increases toward the south. A similar crustal model was proposed by Warren (1969) for the southern part of the Colorado Plateau on the basis of his interpretation of the profile between Sunrise and the Tonto Forest Seismological Observatory near Pay- son, Ariz. MIDDLE ROCKY MOUNTAINS The Rocky Mountains face the Great Plains to the east and are divided into three major parts (King, 1959): the Northern Rocky Mountains extending from Idaho and western Montana into Canada, the Middle Rocky Mountains in Wyoming and adjacent states, and the Southern Rocky Mountains in Colorado and adjacent states (fig. 1). Only a few seismic-refraction lines have been recorded in the Rocky Mountains. The University of Wisconsin, in cooperation with other institutions, completed a detailed seismic-refraction survey in Montana in 1962 (Steinhart and Meyer, 1961; Pakiser and Steinhart, 1964). In 1963, a seismic- refraction line was recorded in the Middle Rocky Mountains between American Falls Reservoir (27) in Idaho and Flaming Gorge Reservoir (29) in Utah. Some seismic refraction surveys were carried out in the Southern Rocky Mountains and the adjacent Great Plains of Colorado in 1961, 1964, and 1965 (Jackson and others, 1963; Jackson and Pakiser, 1965; Healy and Warren, 1969; Prodehl and Pakiser, 1979). Fur- thermore, in 1972 a seismic refraction profile was re- CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 48.—— Velocity-depth function of the profile from Hanksville(30) to Chinle(31) Gradient, Distance, A Traveltime, T Velocity. V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 4.90 0 20 3.70 5.82 2.4 40 7.06 6.03 4.0 60 10.35 6.08 4.9 80 13.63 6.11 5.9 11—!) 140 24.29 6.48 23.1 0.15 160 27.39 6.41 22.4 .07 200 33.60 6.30 20.5 .04 240 39.94 6.22 17.1 .04 280 46.45 6.17 15.7 .01 b 130 23.34 6.75 29.1 .50 140 24.82 6.71 28.9 .20 160 27.84 6.60 28.2 .10 200 33.90 6.53 27.0 .028 240 40.05 6.50 25.2 .01 c 140 25.81 7.60 42.0 .50 160 28.50 7.35 41.5 .25 180 31.18 7.17 40.5 .15 200 33.98 7.03 39.2 .075 220 36.84 6.93 37.4 .04 260 42.66 6.82 34.3 .02 300 48.56 6.76 30.4 .01 z = 42.0 km: E = 6.31 km/s, IF = 6.33 km/s. TABLE 49.— Velocity-depth function of the profile from Chinle(31) to Hanksvtlle(30) Gradient, Distance. A Traveltime. T Velocity. V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 4.39 0 20 3.75 6.00 3.2 50 8.71 6.06 4.0 70 12.01 6.07 4.6 90 15.30 6.09 5.3 110 18.58 6.10 6.2 30 5.57 6.24 6.5 70 11.93 6.29 7.1 110 18.28 6.30 7.7 150 24.63 6.305 8.3 a—b 160 26.73 6.33 14.4 0.01 b 130 23.08 6.64 27.4 >5.00 150 26.13 6.57 27.2 .15 180 30.71 6.50 26.6 .075 220 36.81 6.44 25.5 .03 280 46.11 6.40 21.6 .005 c 160 28.24 7.60 43.3 24 170 29.55 7.41 42.5 22 180 30.93 7.27 41.8 19 200 33.74 7.08 40.8 15 220 36.59 6.97 39.7 09 240 39.47 6.89 38.4 05 280 45.31 6.80 35.2 02 z = 43.3 km: E = 6.37 km/s, 13 = 6.44 km/s. corded from Bingham, Utah, to the northeast, crossing the Basin and Range province and the Middle Rocky Mountains (Braile and others, 1974). This. report presents only the seismic-refraction line recorded in 1963 in the Middle Rocky Mountains be- tween American Falls Reservoir in Idaho and Flaming Gorge Reservoir in Utah. The Middle Rocky Moun- tains in this area “consist of ranges of miogeosynclinal Paleozoic and Mesozoic sediments which have been thrown down into closely packed folds and thrust slices without exposing any Precambrian basement. ANALYSIS OF SEISMIC-REFRACTION PROFILES 41 Their structures trend *** northeastward into Idaho and Montana and southward into the Wasatch and other ranges of Utah***” (King, 1959). The recording line extends from the southeast edge of the Snake River Plain southeastward across the southeastern Idaho-western Wyoming overthrust belt (Rubey and Hubbert, 1959) and acrosss the southwest- ern part of the Green River Basin to the north flank of the Uinta Mountains (Willden, 1965). It is 336.6 km long, with an intermediate shotpoint at Bear Lake (28), 176.2 km northwest of Flaming Gorge Reservoir and 160.3 km southeast of American Falls Reservoir. Shots from the shotpoints at the ends of the line were recorded along the entire line (figs. 77 and 78, pl. 2; tables 104, 105), whereas the profiles from Bear Lake were recorded only to a distance of 150 km toward the northwest (fig. 79, pl. 2; table 106) and to a distance of 115 km toward the southeast (fig. 80, pl. 2; table 107). The recording length of not more than 150 km was too short to obtain any reliable information about the base of the crust and the upper mantle. Willden (1965) first interpreted these profiles. The shotpoint at Flaming Gorge Reservoir and the two stations nearest to it were located on the northeast slope of the Uinta Mountains over Permian rocks (Hansen, 1965). Seismic stations were located in the Green River Basin at distances up to 100 km from Flaming Gorge Reservoir. The Precambrian surface there is more than 8,000 m below the surface (Bradley, 1964; Bailey and Muehlberger, 1968). The thick section of sedimentary rocks in the Green River Basin accounts for the delays of curve a on the profile from Flaming Gorge (fig. 78) and of curve d at distances greater than 220 km on the reverse profile from American Falls (fig. 77). , In addition to the first arrivals, secondary arrivals on all four profiles can be correlated by curves a—b and b. These curves are interpreted as retrograde curves similar to those on other profiles. On the profile from Flaming Gorge to American Falls (fig. 78), curve a-b forms a cusp with curve a, and this relation may also be true for the reverse profile from American Falls (fig. 77 ). The cusping does not seem to be the case for the profiles from Bear Lake, however (fig. 79—80). Curves c and d can only be identified on the profiles from Ameri- can Falls and Flaming Gorge at distances beyond 1 15 km. Phase 0 is prominent between 1 10 and 220 km, but the correlation on this phase becomes questionable at greater distances. Curve d is well defined on recordings from both American Falls and Flaming Gorge. On the profile from American Falls (fig. 77), there is evidence for a traveltime curve that is parallel to curve d. This phase is similar to a phase found on the profiles in the Colorado Plateau. The average velocity measured on curve d is about 8.05 km/s from American Falls and 7.95 km/s from Flaming Gorge, indicating that the up- per mantle velocity is 8.0 km/s. ' The corresponding velocity-depth functions (tables 50-53) and the resulting crustal cross section (fig. 81, pl. 3) show that the basement under the Green River Basin is more than 8 km below the surface. The top of the Chinle Formation (Triassic) is approximately 4 km below the surface, according to the Tectonic Map of the United States (Cohee, 1962). The basement dips northwest near the American Falls shotpoint, in ac- cord with the northwest dip of the Tertiary rocks that TABLE 50.— Velocity-depth function of the profile from American Falls Reservoir(27) to Flaming Gorge Reservoir(29) Gradient. Distance, A Traveltime. T Velocity. V Depth. 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 5.00 0 30 5.61 5.57 2.5 60 10.86 5.85 6.1 90 15.90 6.01 9.1 120 20.87 6.05 10.5 a~b 80 15.15 6.48 18.4 1.00 110 19.82 6.33 17.6 .04 140 24.59 6.27 15.8 .01 b 100 18.78 6.80 25.2 .35 120 21.75 6.66 24.2 .06 140 24.77 6.56 19.5 .01 C 140 25.66 8.00 45.2 .40 150 26.91 7.81 44.7 .40 170 29.53 7.56 43.8 .20 190 32.21 7.33 42.4 .125 210 34.97 7.12 40.6 .09 230 37.83 6.97 38.4 .05 250 40.74 6.89 36.5 .03 270 43.65 6.85 34.3 .02 300 48.02 6.83 33.0 .01 z = 45.2 km: E: 6.41 km/S. (T = 6.49 km/s; z = 25.2 km: E: 5.98 km/s, 17) = 5.96 km/s, V = 5.8 km/s for z = 18.5-19.4 km. TABLE 51.— Velocity-depth function of the profile from Flaming Gorge Reservoir(29/ to American Falls Reservoir(27) Distance. A Traveltime, T Velocity. V Depth, 2 G radiant, d V/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 O 4.16 0 30 6.49 5.45 5.2 60 11.54 6.12 9.8 90 16.38 6.21 11.5 a—b 130 22.82 6.25 13.2 50 10.23 6.49 14.2 90 16.38 6.52 14.7 130 22.52 6.57 17.1 150 25.54 6.62 18.9 b 110 20.46 6.80 24.6 0.075 130 23.45 6.64 19.7 .01 c 130 23.96 7.94 41.0 .30 150 26.52 7.48 39.3 .20 170 29.26 7.16 37.6 .15 190 32.14 6.97 36.3 .10 210 35.03 6.90 35.2 .045 240 39.40 6.85 33.4 .024 280 45.27 6.82 31.4 .01 z = 41.0 km: E: 6.30 km/s, (F = 6.41 km/s; z = 24.6 km: E = 5.85 km/s. L3 = 5.89 km/s. 42 TABLE 52.—-Velocity-depth function of the profile from Bear Lake(28) to American Falls Reservoir(27) G radiant, Distance, A Traveltime, T Velocity, V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/s/km) a 0 0 4.25 0 10 2.17 5.05 1.2 30 5.64 5.98 4.4 50 8.96 6.05 5.4 a—b 70 13.23 6.40 15.8 1.00 90 16.37 6.34 15.3 .05 110 19.54 6.26 13.1 .01 b 90 16.95 6.62 21.4 .30 110 19.99 6.51 20.9 .075 120 21.53 6.43 19.3 .03 z = 21.4 km: E = 5.97 km/s,1§ = 5.88 km/s, V = 5.8 km/s for z = 15.9—19.2 km. TABLE 53.—Velocity-depth function of the profile from Bear Lakel28) to Flaming Gorge Reservoir(29) Gradient, Distance, A Traveltime, T Velocity, V Depth, 2 dV/dz Curve (km) (s) (km/s) (km) (km/srkm) a 0 O 4.41 0 20 3.90 5.73 2.9 30 5.60 5.96 4.0 a-b 70 12.93 6.34 14.2 1.00 80 14.51 6.28 14.0 .20 100 17.71 6.23 13.1 .025 110 19.31 6.22 12.6 .015 b 60 12.47 6.86 18.8 1.00 80 15.42 6.71 18.3 .05 110 19.92 6.64 16.8 .01 z = 18.8 km: E = 5.96 km/s. IF = 5.88 km/s, V = 5.8 km/‘s for z = 1437167 km. are exposed southeast of the reservoir (Carr and Trim- ble, 1963). The base of the crust in this area is at a depth of more than 40 km, dipping from about 41 km under the Green River Basin to about 45 km under the Middle Rocky Mountains and a wedge of the Basin and Range province northwest of Bear Lake. According to travel- time curves a—b and b, there are two depth ranges within the crust where the velocity gradient is relative- ly large, increasing downward by about 0.2 km/s/km. The zone corresponding to phase a—b dips from 13 km near Flaming Gorge to 18 km near American Falls, whereas the zone corresponding to phase b is located at about 25 km depth at both ends of the line, rising to' 14—16 km under the Middle Rocky Mountains near Bear Lake. A zone with a velocity inversion must be assumed between zones a-b and b to satisfy the com- parison of the average velocities 17 and W (tables 50, 52, 53). This zone of velocity inversion, in which the velocity decreases from 6.3—6.5 km/s to 5.8 km/s (average value), is evident on the profiles from Bear Lake, but it is probably not present near Flaming Gorge. It is thin in the vicinity of American Falls. The CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES velocity inversion on the profile from American Falls is based only on curve b; the velocity comparison based on curve c indicates that no inversion is present. The assumed velocity of 5.8 km/s in the velocity-inversion zone is an average value. The details of the velocity- depth function within this zone cannot be determined. The profile from Bingham, Utah, to the northeast crosses the line from American Falls Reservoir to Flaming Gorge Reservoir close to Bear Lake. The crus- tal structure obtained by Braile, Smith, Keller, Welch, and Meyer (1974) for the profile from Bingham at the intersection of both lines is in good agreement with the structure beneath Bear Lake as shown in figure 81. RESULTS AND DISCUSSION BASIC DATA The record sections of the profiles recorded by the US. Geological Survey from 1961 to 1963 and of a pro- file published by Diment, Stewart, and Roller (1961) (fig. 38) in the area of investigation show that the traveltime curves fit into a basic traveltime diagram (fig. 5). In addition to curves a and d, which are based on first arrivals, a strong phase 0 is the most evident feature in nearly all record sections. Because phases corresponding to curves a, c, and d exist on all profiles within the area of investigation, we should look for parameters that use these curves to give objective information on the general features of crustal structure before determining detailed velocity- depth relations. In the Alps and western Germany, Choudhury, Giese, and de Visintini (1971), Giese (1970), and Giese and Stein (1971) successfully mapped typical parameters from the basic traveltime diagrams (see also Giese and others, 1976). The distance Ad at which the traveltime curve d (Pu) crosses the distance axis is one parameter that does not contain subjective elements of interpretation. Other objective parameters are the so-called “critical” distance A, at which curve d is tangent to curve c, and the corresponding reduced traveltime 7—} = T, — Ac/6. These parameters were mapped for the area of investi- gation. Ad and A. were plotted at half their values (figs. 82, 83). To a first approximation, both maps represent the variation of total crustal thickness. Under the Basin and Range province, the crust is thinner than under the surrounding provinces to the west, north, and east, and it is evident that crustal thickness decreases south of the line from China Lake to Lake Mead. The inclusion of the P,, data from a 1964 crustal study in Arizona (Warren, 1969) in the contour map of the crossover distance Ad confirms that the crust thickens from the Basin and Range province eastward into the Colorado Plateau. The P,. traveltime curve for RESULTS AND DISCUSSION the eastern Basin and Range province (Berg and others, 1960) was also included in the map of Ad, pro- viding evidence that the crustal thickness minimum under central Nevada extends into northwestern Utah. Both A, and Ad maps indicate a thick crust under the Middle Rocky Mountains, the Colorado Plateau, and the Sierra Nevada, whereas the thickening of the crust under the Snake River Plain is shown by the map of the “critical” distance A. only, because no P,, arrivals were found here. The thick crust under the Sierra Nevada is not restricted to the Sierra Nevada but also extends eastward into the ranges east of Owens Valley and southward into the Transverse Ranges north of Los Angeles. Additional data for the Coast Ranges of central California were made available by SW. Stewart (1968a; written commun., 1969) for inclusion in the map of the crossover distance Ad. In the Coast Ranges a thin crust that thins from east to west is indicated. The reduced traveltime T, at the critical distance was corrected by using the reduced Pg traveltime to eli- minate the traveltime delays caused by sedimentary layers. The resulting time difference, 7‘, — T”, was plotted at the distance AC/2 (fig. 84). Large values indi- cate that the crust contains material of relatively low P-wave velocities, that the crust is relatively thick, or both. The map shows two maximums, one in central Nevada near Eureka and the other extending across southern Nevada into the southern Sierra Nevada and toward the Transverse Ranges of California. Small values of 7"c — T0,, were found on the profiles in the Middle Rocky Mountains, the Colorado Plateau, and the Coast Ranges of central California. Comparison of this map with the results of the analysis of the seismic- refraction profiles leads to the conclusion that large values of To — TM are characteristic of areas of rela- tively low crustal P—wave velocities and relatively thin crust. The low-velocity zone found under the Middle Rocky Mountains (fig. 81), however, is not indicated in the contour map of TI, -— T“. This is probably because values To - Tu were available in this area only for the profiles from the shotpoints of American Falls and Flaming Gorge, where evidence for a velocity inversion was weak or lacking. Because of the lack of data, no conclusions can be drawn concerning the low-velocity zone under the southern Cascade Mountains. The contour map of average P, velocity (fig. 85; table 54) is based on curve d. The velocity gradient in the up- per mantle is very small because curve d is a nearly straight line on most traveltime curves. The resulting velocity values are strongly influenced by horizontal velocity gradients and also by dip on the M-discontinu- ity. To obtain approximately true velocities, therefore, an average value of the velocity from curve d was used 43 for reversed profiles and plotted at the middle of the corresponding two shotpoints. However, in un- reversed profiles, and in profiles for which the subsur- face refracted path along the M-discontinuity was not reversed, some effects of variations in dip of the M-discontinuity probably remain. The P,, velocities found for the Western United States are generally less than 8.0 km/s, ranging be- tween 7.6 and 7.9 km/s. Only beneath the Coast Ranges of California, in southern California, and in the Middle Rocky Mountains were P,, velocities of 8 km/s and higher obtained. The lowest P,, velocity (7 .6 km/s) was found in Utah. The 7.6 km/s contour extends across the eastern part of the Great Basin into the Colorado Plateau. The low velocity found on the un- reversed profile from Delta to SHOAL (table 54) is sup- ported to some extend by the profile from SHOAL to Delta (fig. 86), for which Eaton, Healy, Jackson, and Pakiser (1964) reported apparent velocities for first ar- rivals of 8.1 km/s between 240 and 410 km and 7.6 km/s between 410 and 547 km, suggesting that the true velocity west of Delta (16) may not exceed 7.6 km/s. The variations of apparent velocity along this profile, however, clearly indicate variations in dip of the M-discontinuity. Berg, Cook, Narans, and Dolan (1960)'reported a velocity of 7.6 km/s from unreversed traveltime data in the eastern part of the Basin and Range province. N o subcrustal velocity can be given for the Snake River Plain because of the lack of P,, ar- rivals on the corresponding profiles. Recordings in the Snake River Plain from nuclear explosions at NTS, however, suggest that the P,, velocity in the Snake River Plain is about 7 .9 km/s (Hill and Pakiser, 1966, 1967). CRUSTAL STRUCTURE The results of the velocity-depth determinations along 15 lines were compiled in a fence diagram (fig. 87, pl. 1). For a clearer presentation, the cross section bas- ed on the profile extending northwest from China Lake (fig. 61) was omitted. The fence diagram was con- structed to be viewed from the southwest, approxi- mately parallel to a line from Los Angeles to Salt Lake City. The diagram shows lines of equal velocity with a contour interval of 0.2 km/s. The equal-velocity con- tours are dashed in areas where velocity data were esti- mated because of lack of observations, for example in the Great Valley of California, the western flank of the Sierra Nevada, and the line from N TS through Navajo Lake to Colorado (see figs. 12, 45, 63). A distinct lower crustal layer or zone is present under the northern part of the Basin and Range pro- vince (see also figs. 12, 25); velocity increases from 6.4-6.6 to 7.0 km/s in a narrow depth range between 44 the upper and lower crustal zones. This transition zone from upper to lower crust was not found under the southern part of the Basin and Range province (see also figs. 25, 36—40, 45). In the southern part of the province, low P—wave velocities are found in the upper 20 km of the crust. Near Lake Mead and N TS, material with P—wave velocities of 6.0—6.1 km/s seems to exist at even greater depths. Under the Sierra Nevada (central part of the line be- tween Shasta Lake and China Lake) and east of Mono Lake (see also figs. 12, 36, 50, 61-63), the velocity in- creases steadily with increasing depth between 10 and 35 km from 6.2 to 6.6 km/s. Near China Lake, however, the velocity distribution is different; low-velocity material (6.1 km/s) extends to depths of 20 km, and the base of the crust rises from 42 km at Mono Lake to 33 km depth at China Lake. Toward Shasta Lake in the southern Cascade Mountains, the 6.4-km/s velocity contour rises to about a depth of 7 km, and it is under- lain by a velocity inversion in which the velocity de- creases to 6.0 km/s (see also fig. 50). Under the Coast Ranges west of the San Andreas fault system in central California, the crust is only 24—25 km thick and has uniform velocity increase with depth from 6.2 to 6.8 km/s between depths of 10 and 25 km. The velocity increases at the base of the crust from 6.8 to 8.0 km/s within a depth range of only 2—3 km (see also fig. 68). A fairly uniform velocity increase with depth was also found under the Colorado Plateau. The velocity in- creases smoothly from 6.1—6.2 to 6.7 —6.8 km/s between depths of 7 and 33 km, and the base of the crust is at a depth of 42—43 km (see also fig. 76). Under the western Snake River Plain, a distinct lower crust with velocities of 6.8—7.0 km/s extends from 11—17 km to a depth of about 35 km (see also fig. 25). Under the Middle Rockly Mountains, velocities of 6.8—7.0 km/s were also found between depths of 20 and 40 km, indicating a distinct and rather homogeneous lower crust that in its lower part joins the transition zone between crust and mantle. In the upper crust of the Middle Rocky Mountains, a narrow velocity inver- sion zone in which velocity decreases with depth from 6.4 to 5.8 km/s was found at a depth of about 17 km (see also fig. 81). The base of the crust as interpreted by the conven- tions discussed above is generally not a sharp discon- tinuity but rather a transition zone, the thickness of which varies between 2 and 10 km and in which the velocity increases gradually from 6.6-7.0 km/s to about 7.8 km/s. This transition zone is about 10 km thick under the Sierra Nevada, the Middle Rocky Mountains, and the Colorado Plateau and is relatively CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 54.—Average Pn velocities, based on curve (I, and velocities v (Ac) at the depth 2 (Ac) Average P" velocity Velocity v (AC) (Curve (1) [km/s) k Profile ( m/s) I)elLa116| L0 SHOALUO) ——————————————— ‘7 :3- 7 8 7777777777 7 24 l- urekall ) to F allole) ————————— l-allonl9) to Eurekall 5) 7 Boisell l) to Elkoll4) ~V SLrikellZ) to Elkol14)—-7 — —7.77 Mountain Cityllil) to Boisellll 77777777777777777777777777 7.91 Mountain CILyllilHo Eurekallfy) 77777777777 I7,678.0 —————————— 7.48 l'llkoll4)LoBoiselll) 77777777777777777777 (7.9) ———————————— 7.75 l‘ilkoll4) Io l‘IurekallSI 7777777777777777777777777777777 7.74 l‘IurekaIlS) Lo Mountain Cityllil) 77777777777 7.9 ~~~~~~~~~~~~~ 7.90 Eureka) 1 3) to Lake MeadlZZ) ————————————— . Lake MeadlZZ) to Eureka) 15) —————————————— ‘ .‘ Lake Meadl22| to Mono Lakelb') 7777777777777 . Lake McadlZZ) to Santa Monica Hayl4) 77777777 . N'l‘SllQ) to Kingmaanfi) 77777777 N'l‘Sll9) to LudlowlZB) iiiiiiiiiiiiiiii .‘ Ludlowl25) Lo NTSIIS) ————————————————— . NTSllQHo\avajnLakIlZl) 7777777777777777 . Na\ajo Lakcl‘Zl) Lo .\ [5119) 777777777777777 \"‘ZISH9)Lquo¢I4) 77777777777777777 761A<290km) ______ 7.60 8. 0 lA> 290 km) ———————— NTSHB) Lo San Luis ()bispol'd) 777777777777 8 01A > 260 km) —————— 7.65 ludlowZéI to \lojavelZLi) 77777777777777 ‘81 8 25 ‘ Barstow124) L0 Ludlowl25) 7777777777 __ I) 25 ,,,,,,,,,, goo Barsmwl‘zm L0 Moj Ivuz‘ i) ——————————— -#—__)7 9) iiiiiiiiiiii 7_ 8O MOJaHlZiHU I udlothS) 777777777777777 0 777777777777 7 30 Shasta Lake)?» to Mono Lakelfi) 77777777777 7 9 )A > 210 km) ______ 7 54 Mono Lakelli) to Shasta LakelS) 77777777777 9) ____________ 7 55 Mono Laketéi) L0 China Lakel8) __________________________ 7 86 China Lakelh‘) w Mono Lakelb’) 7777777777777 )78) ____________ 750 China Lakel8) to northwest ——————— China Lakel8) to Santa Monica BayMl \lonol ake(6) Io Santa Monica Baymi l- allonl9) to San l‘ ranciscoll) iiiiiiiiiiiii ‘7. 777. 8 Fallonl‘a) to Mono I aktlb‘) 77777777777777 ‘7 ) 7 6 (A > 290 km)————7. 60 Mono Lakel6) to Fallonl9) 77777777777777 8. 5 ———————————— 7. 90 l‘ allonl9) to China Lakel8) 7777777777777777 ‘7. 6— 7. 8 —————————— 7. 90 Mono I ake16) to Lake Meadl22) —————————————— 8. 0 777777777777 7. 70 San 1‘ ram iscol l) to Camp Robertle) ————————— 8. 0 {A > 190 km) 777777 7 78 ( amp RobertSIZI to San l-rancIscoll) ——~ 7'7. 9 8.1 7777777777 7.80 Camp llohertle) to Santa Monica Bay I4) 77777777 7. 9 777777777777 7.70 Santa Monica Haj/)4) to Camp RobertsIZI 7777777 8. 8 7, Santa Monica llayH) to Mom) lakelti) __________ 8 0 77777777777777 8 00 Santa Monica Bayl4) to China Lakel8) ' ' Santa Monica Bayl4) to Lake Meadl22) 777777777 "1.9—8.1 7777777777 784 San Franciscolll to Fallonl9| —-~7~-~ v—~A7777718.0)(A < 120 km) 77777 7.87 San Luis ()bispolll) to NTSHQ) ————————————— ‘7.8—8.2 (A < 220 km) —A -— 7 . 7 0 Hanksvillcl30) to Chinlecil) 777777777777777 7.6 ———————————— 7.60 (‘hinlelll ]) to HanksvillcflIU) 777777777777777 7677.8 —————————— 7.60 American Falls licsl27) Lo Flaming Gorge lieslzill 77,, 8.05 ——————————— 8.00 Flaming (iorge Resl29) to American Falls Re5127) 77* 7.95 ——————————— 7.94 Velocity increases with increasing distance. FIGURES 82—84.-—FIGURE 82, Crossover distance Ad for California and Nevada and adjacent areas between d(P,.) and U = 6 km/s (A-axis, see fig. 5). Contour interval is 20 km. Values shown by crosses are plotted at half the distance Ad from the correspon- ding shotpoint. Full circles, shotpoints according to figure 1 and table 1. Open squares, shotpoints of other seismic-refraction surveys, the P,l traveltime curves of which are included. To a first approximation the map represents the variation of total crustal thickness. FIGURE 83, “Critical" distance Ac for California and Nevada and adjacent areas. Contour interval is 20 km. Values shown by crosses are plotted at half the distance Ac from the shotpoint. To a first approximation the map represents the variation of total crustal thickness. FIGURE 84, Reduced traveltime Tc — TM in California and Nevada and adjacent areas. The reduced traveltime To of the wave group c at the “critical” distance Ac is corrected by the corresponding traveltime TM of the wave group a(Pg) at the same distance. The contour interval is 1 second. The values shown by crosses are plotted at half the critical distance Ac from the corresponding shotpoint. High values indicate that the medium of wave propagation contains material with relatively low P-wave velocities. RESULTS AND DISCUSSION thin under the Basin and Range province, the western Snake River Plain, and the Coast Ranges of California (fig. 87 ). Most previous authors (for example, Pakiser, 45 1963) have interpreted the base of the crust (M-discon— tinuity) as a relatively sharp discontinuity. The transition zone between crust and mantle is CONTOUR MAP CONTOUR MAP I) 1l5° CROSS'OVER' REDUCED TIME "\ DISTANCE AT Ac' T-A/6 Ad(1"=0) T [ (s) \\ I \ VLOA -1 0 135-200 km 0 -100 200 km L____l__l FIGURE 82 , CONTOUR MAP If 115° \ 1io° CRITICAL DISTANCE \ I T—A/e { .117 l (s) I i . ,40\l 7'20 123 X130 I\\\\ 11 "TL - T. “'1 \ o 100 200m WW4" 128x ,' _|\ \ / x \ I \ \ l x. I l | l / / X141 \ / | _7./___ __.—[ x150 \ ) . \ 70 J _ 35o FIGURE 83 FIGURE 84 46 characterized by increasing velocities and increasing velocity gradients. The depth to the strongest velocity gradient is defined in this report as the base of the crust in drawing a contour map of crustal thickness. The uncertainty of the depth of the maximum velocity gradient in the crust-mantle transition zone is small (about 3—5 percent). Figure 88 shows the map of the depth of the strongest velocity gradient, 2(AC), for the area of investigation. It represents a contour map of the total crustal thickness. The dashed contour lines in the Great Valley and the western flank of the Sierra Nevada in California and the eastern Basin and Range province in Utah were based on very few data points and were extrapolated into areas not traversed by profiles. , The crust is generally thinner under the Basin and Range province than under the surrounding provinces, as is also suggested by the contour maps of the para- meters Ad and Ac. The average thickness in the Basin and Range province is 32—34 km, with minimum thick- ness of 29—30 km near Fallon, Nev., and Delta, Utah. South of Eureka, Nev., the crust thickens to 37—38 km between Eureka and Navajo Lake. Farther south, the crust thins to 31-32 km near Hiko and in the area north and east of N TS, reaching a minimum thickness of 28 km between Kingman, Ariz., and Ludlow, Calif. As suggested by the contour maps of Ac and A d, the crust is relatively thick east of the Sierra Nevada be- tween Mono Lake and China Lake and thins south- ward to 29—31 km under the Mojave Desert. Under the Sierra Nevada, the total crustal thickness is 42—43 km between Shasta Lake and Mono Lake, thinning toward the south to 33 km northwest of China Lake. Under the Transverse Ranges north of Los Angeles, a crustal thickness of 36—37 km was in- ferred, whereas the crust under the Coast Ranges of central California between San Luis Obispo and San Francisco is only 24—26 km thick. From the Basin and Range province, the base of the crust dips downward to the east under the Colorado Plateau, where it reaches a depth of 42-43 km between Hanksville, Utah, and Chinle, Ariz. The crust is thick under the Middle Rockly Mountains, reaching a maxi- mum thickness of 45 km between American Falls Re- servoir and Bear Lake. The nature of the transition from the Basin and Range province to the Middle Rocky Mountains can only be suggested. According to an interpretation of Berg, Cook, Narans, and Dolan (1960), the top of a layer with a velocity of 7.59 km/s was found at a depth of 25 km in northwestern Utah. This layer is probably the same as that bounded by the base of the crust at a depth of 29 km west of Delta, Utah (figs. 12, 87, and 88). These results suggest that the crust is very thin under northwestern Utah and CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES thickens abruptly toward the northeast under the Mid- dle Rocky Mountains and adjacent provinces in Idaho and Wyoming. The interpretation of the profile from Bingham, Utah, to the northeast (Braile and others, 1974) confirms this suggestion. The crust is 40—44 km thick under the Snake River Plain between Boise and Mountain City, with a probable maximum thickness south of Strike Reser- voir. In addition to the depth at which the velocity gra- dient reaches its maximum value (fig. 88), the velocity v(Ac) corresponding to this depth was mapped (fig. 89 and right column of table 54). As the comparison of this map with the map of the P" velocity (fig. 85) shows, the velocity v(AC) cannot be identified with the velocity within the uppermost mantle. For some areas, significantly lower velocity values were compiled in figure 89 than in the contour map of the P,. velocity (fig. 85). These differences may be explained by a de- creasing velocity gradient below the depth of strongest velocity gradient. DISCUSSION From published interpretations available a few years ago, Hamilton and Pakiser (1965) published a crustal cross section across the United States along the 37th ; parallel. Pakiser and Zietz (1965) published a cross sec- tion along a transcontinental aeromagnetic profile. As part of the Transcontinental Geophysical Survey of the US. Upper Mantle Project, Warren (1968a, b, c, d) reviewed and compiled more recent interpretations of seismic profiles in the United States between lats 35 ° and 39 ° N. in the form of a fence diagram. A two-layer crust convention with constant velocities within the layers was used for most of the profiles (see also Healy and Warren, 1969, figs. 1—4). The crustal thicknesses shown by Warren, with few exceptions, do not differ FIGURES 85, and 88-90.—Average P" velocity for California and Nevada and adjacent areas, based on curve d (see table 54). For the construction of the contour lines, for reversed profiles an average value was used, for profiles where the P" velocity in- creases with increasing distance the lowest well-defined value was used. FIGURE 88.—Total crustal thickness under California and Nevada and adjacent areas. The contour lines show the depth of strongest velocity gradient, z(Ac), in the transition zone be- tween crust and mantlelin the westernUnited States.Contour in- terval is 2 km. Dashed contour lines indicate uncertain results. Values shown by crosses are plotted at half the critical distance from the corresponding shotpoint. FIGURE 89.—Velocity MAC) at the depth of strongest velocity gradient 2(Ac) in the crust-mantle transition zone. Values are plotted at half the critical distance from the corresponding shot- point (see table 54). FIGURE 90.—-Bouguer gravity anomaly map of the area of in- vestigation. Contour interval is 50 mgal. From the Bouguer gravity anomaly map of the United States (Am. Geophys. Union, 1964). RESULTS AND DISCUSSION 47 significantly from the results shown in figures 87 with the map of Pakiser and Zietz (1965, fig. 2) show- and 88. ing the variations in crustal thickness, mean crustal The fact that no distinct lower crust was found under velocity, and upper mantle velocity. According to the southern Basin and Range province is compatible these authors, the mean crustal velocity is less than I VELOCITY V(Ac) 115° AT DEPTH 2(Ac) T—A/G (fl AVERAGE Pn VELOCITY I441mg) km T-A/S FIGURE 85 FIGURE 89 CONTOUR MAP / ”'50 Ho" BOUGUER GRAVITY DEPTH 2(Ac) '1 ANOMALY MAP T—A/ 6 mgal +50 0 -50 -100 — 150 -200 —250 FIGURE 88 FIGURE 90 48‘ CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES 6 T-A /6 (sec) PROFILE SHOAL-DELTA W \ \ FIGURE 86.—Record section of the profile from SHOAL (10) to Delta (16). 6.2 km/s in the main part of the Basin and Range province, and this is consistent with the present inter- pretation. The increase in mean crustal velocity to 6.2—6.5 km/s shown by Pakiser and Zietz toward the north, east, and west of the central Basin and Range province is compatible with the presence of a distinct lower cmst of higher average velocity under the north- ern part of the Basin and Range province and the nearly uniform velocity increase with depth under the Colorado Plateau and the Sierra Nevada. Under the Snake River Plain, the mean crustal velocity is greater than 6.5 km/s because of the shallow depth to the top of the lower crust. Whereas the P,, velocity in most parts of the world is usually equal to or greater than 8.0 km/s (see for exam- ple Closs, 1969; Healy and Warren, 1969; Kosmin- skaya and others, 1969; Sollogub, 1969), the P" veloc- ity in the Western United States is less than 8.0 km/s in most areas, ranging between 7.6 and 7.9 km/s. Similar values have been reported for profiles in Japan and the Kuril Islands (Kosminskaya and Riznichenko, 1964; James and Steinhart, 1966; Research Group for Explosion Seismology, 1966). The Pn-velocity values re- ported here are in general agreement with those of pre- vious investigations (Pakiser, 1963; Pakiser and Stein- hart, 1964; Stuart and others, 1964; Pakiser and Zietz, 1965‘; James and Steinhart, 1966; Herrin, 1969), except for the higher velocity for the Mojave Desert in southern California reported here. The velocity of 8.0-8.1 km/s shown by Herrin (1969) for southern Utah was not con- firmed by the results of interpretation of the lines from the N TS to Navajo Lake and Hanksville to Chinle, where apparent velocities of 7.7 —7.9 and 7 .6—7.8 km/s were found (table 54). Some previous authors (for example, Berg and others, 1960) have suggested that the discontinuity at a depth of 24-25 km at which the velocity changes from less than 6.5 to about 7.6 km/s overlies a deeper discontinuity at which the velocity increases to more than 8 km/s. James and Steinhart (1966) noted that no such discontinuity has ever been reported for profiles wholly within the Basin and Range province. In com- paring the record sections of all profiles investigated by the author, it can be seen that the traveltime curves 0 and d (fig. 5) are similar on all profiles throughout the Western United States; the distance to the point of cri- RESULTS AND DISCUSSION tical reflection, Ac, (fig. 83) and the crossover distance, Ad, (fig. 82) increase or decrease as crustal thicknesss increases or decreases (fig. 88). The boundary zone de- rived from these curves and identified with the M-dis- continuity seems to be well defined throughout the area of investigation (fig. 87). Comparison of crustal structure with the Bouguer gravity map of the study area (fig. 90) shows a general agreement between crustal structure (fig. 87, 88) and Bouguer gravity for areas outside the Basin and Range province. The gravity high of the Coast Ranges of Cali- fornia corresponds to a thin crust. Gravity lows of the Colorado Plateau, the Middle Rocky Mountains, and the Sierra Nevada, including the area east of Owens Valley, correspond to a thick crust. The gravity highs under the Snake River Plain and the southern Cascade Mountains in the vicinity of Shasta Lake correspond to a thin upper and a thick lower crust with high P—wave velocities. The local gravity low in the Lassen Peak area of California interpreted by Pakiser (1964) is in agreement with the seismic low-velocity zone. The thinning of the crust in the southern Basin and Range province from north to south is expressed by increas- ing gravity. However, there does not generally seem to be a correlation between gravity and the thinning of the crust from the Sierra Nevada toward the Basin and Range province. The generally low gravity in the Basin and Range province is probably caused by lower densi- ty of the upper mantle in this area of P,, velocity less than 8 km/s and heat flow of 2 “cal/cmZ/s or more (Lee: and Uyeda, 1965). Johnson (1976) derived a velocity structure for P waves in the upper mantle under the Basin and Range province from dT/dA measurements from the array at the Tonto Forest Seismological Observatory in Arizona. Johnson’s structure includes a low-velocity zone at a depth of 60—160 km in which the velocity decreases from 7.8—7.9 km/s to 7.6-7.7 km/s. Similar conclusions were reached by Green and Hales (1968) and Archambeau, Flinn, and Lambert (1969). The main part of the gravity low in the Basin and Range pro- vince obviously has its origin in a low-density upper mantle, although some of the anomalies can be explain- ed as differences in crustal structure. Relative gravity highs near Fallon and in northwestern Utah can be associated with the fact that the crust is thinner in these places than it is along the line from Mountain Ci- ty to Lake Mead. The fact that a dense lower crust is well defined north of Eureka and decreases in thickness and distinctness toward the south cor- responds with a slight decrease in gravity from Eureka toward the south. The thick crust between Eureka and Navajo Lake and the decrease in crustal thickness 49 toward the south is roughly in agreement with the gravity minimum in central Nevada and southwestern Utah and the general gravity increase toward the south. That some form of regional isostatic compensa- tion exists within the Basin and Range province was suggested by Mabey (1960), who noted the correlation between low Bouguer anomaly values and high regional topography. These areas also coincide fairly well with the areas where a relatively thick crust is found. From gravity data, Thompson and Talwani (1964) computed models of crustal structure from the Pacific Basin to central Nevada. The depth (about 22 km) that they find for the upper mantle under the Coast Ranges of California corresponds approximately to the results reported by Eaton (1963) and Healy (1963) and in this report. The depth of the upper mantle under the Sierra Nevada reported by Thompson and Talwani (maxi- mum depth of 34 km), however, differs significantly from the depth determinations by seismic-refraction data (Eaton, 1963, 1966; Prodehl, 1970a, b; this report). Thompson and Talwani's depth to the upper mantle of 27—28 km east of the Sierra Nevada near Fal- lon, Nev., and the increasing crustal thickness east of Fallon correspond to the results in this report. As the seismic-refraction results show, the thick crust under the Sierra Nevada is not restricted to the area of the Sierra Nevada but extends eastward from Owens Valley to the western part of the Basin and Range province. This fact underlines the statement (Bateman and others, 1963, p. D6) that “the eastern limit of the synclinorium” that is occupied by the Sierra Nevada batholith “is probably marked by a belt of Precambrian and Cambrian rocks that extends from the White Mountains (southeast of Mono Lake) south- eastward into the Death Valley region***.” Hunt and Mabey (1966) and Hall (1971) suggest that the Sierra Nevada batholith extends to the Panamint Range at the western edge of Death Valley. East of the southern part of the Owens Valley, however, the batholith “is broken into'numerous large and small basin-and-range blocks***” (Hamilton and Myers, 1967, p. 025). The present result for the Sierra Nevada obtained from the recording line from Shasta Lake to China Lake agrees with Eaton’s (1966) result from the upper crust down to about 20 km. According to Hamilton and Myers (1967), the Sierra Nevada batholith extends no deeper than 10 km. They interpreted the underlying high-velocity (6.4 km/s) rocks as metasomatized schist and gneiss. Bateman and Eaton (1967, p. 1413) corre- lated the downward increase in P—wave velocity in the upper crust from 6.0 km/s to 6.4 km/s to a “downward increase in the proportion of diorite, quartz-diorite, and 50 calcic granodiorite or their gneiss equivalents relative to quartz monzonite and granite***.” The thick layer of Bateman and Eaton with a velocity of 6.9 km/s below 25 km was not confirmed by our investigation, which indicates that the velocity does not exceed 6.6 km/s down to a depth of about 35 km. This result ap- pears to agree with Hamilton and Myers (1967, p. C20), who stated that “the eastern part of the Sierra Nevada batholith consists largely of light-colored quartz mon- zonite and granodiorite***” and that “Mesozoic meta- volcanic rocks are mostly dacite and quartz latite***. " They concluded, “the lower crust is richer in potassium and is less mafic***” than the upper crust. Unfortun- ately, the available seismic data are inadequate to determine the crustal structure beneath the western part of the Sierra Nevada where, according to Hamilton and Myers, the lower crust is expected to be more mafic. Under the southern Cascade Mountains of northern California, upper crustal silicic material is probably thin or absent, as is indicated by volcanic surface material consisting mainly of pyroxene andesites and basaltic andesites and also by higher seismic velocities of 6.5—6.6 km/s at a depth of only 7 km. Hamilton and Myers (1966, p. 540) assumed that “the southern Cas- cades consist of a surface pile of relatively light volcan- ic and plutonic rocks, 6—10 km thick, resting on a dense basaltic crust***.”, On the basis of seismic data, Hamilton (1969, p. 2421) suggested that “the meta- morphic terrane of the northwestern Sierra Nevada is truncated against new volcanic crust at the north end of the range***.” The velocity inversion from 6.6 to about 6.0 km/s observed between depths of 8 and 17 km occurs in the area of a gravity low (Pakiser, 1964) and may be re- stricted to the area of Lassen Volcanic National Park. The gravity low and the velocity inversion might also be explained as a buried silicic batholith, a thick sedimen- tary sequence, a low-density thermally expanded body of rock, or “a volcano-tectonic depression filled with volcanic material of low-average density***” (Pakiser, 1964, p. 617). The average composition of the crust in the Basin and Range province is fairly silicic, as has been sug- gested by Pakiser and Robinson (1966a, b). The veloc- ity-depth functions obtained for the province may sug- gest a petrographic interpretation for the upper crust similar to that proposed of Giese (1966, 1968) for the Bohemian massif in southern Germany. The travel- time curve a represents mainly Precambrian plutonic rocks (Hamilton and Pakiser, 1965), the velocity of which may increase with increasing depth according to , increasing metamorphism. Birch (1958) and Hughes and Maurette (1956, 1957) CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES suggested that the increase of pressure with depth is the most important influence on velocity within the up- per 5 km of the crust. This was demonstrated by Giese, who interpreted several seismic-refraction lines that were located entirely on basement rocks (Giese, 1963, 1966). At depths below 5 km, however, temperature also has a significant influence on velocity, as experi- ments in laboratories have shown. Temperature effects may partly explain the decrease of velocity with depth in the upper part of the crust that has been observed on many profiles in the Basin and Range province. Another possible explanation of the origin of a velo- city inversion with increasing depth is given by Giese (1966), following Bederke (1962), who observed that, with increasing metamorphism, the density of schists (demonstrated by experiments on rocks of the Bfindner Schiefer, fig. 91) increases to 3—3.2 g/cma. But at higher grades of metamorphism, the density may de- crease to 2.8 g/cm3. Consequently, by applying the velocity-density relation of Woollard (1959), for exam- ple, the velocity decreases with depth also. Finally, with granitization, the density decreases still more and may be as low as 2.60—2.65 g/cma. Figure 91 shows the results of Bederke (1962, figs. 3, 4) and Giese (1966, fig. H3; 1). According to Winkler (1967), melting begins in terranes of high-grade metamorphism if quartz- feldspar-mica gneisses and water are present at the surprisingly low temperature of 650°—700°C, indepen- dently of the amount of water available. Giese (1968) infers that anatexis has the greatest influence on veloc- ity inversion. In the part of the Western United States covered by this report, however, velocity inversions due to anatexis probably can be excluded because the inversions are not very strong. The low-velocity zone in the crust of the Middle Rocky Mountains may be correlated with decreasing density because of increas- ing temperature and (or) increasing metamorphism (Bederke, 1962). The narrow depth range in which the velocity inversion is evident suggests that anatexis is not involved. Hamilton and Myers (1966, 1968) suggested that the northern part of the Basin and Range province has undergone a total crustal extension of between 50 and 300 km, accompanied by rebuilding of the crust by sur- face volcanism and intrusion at depth. Pakiser and Zietz (1965) suggested a similar process of crustal thickening. According to Hamilton and Myers (1968, p. 343), “both the width of the province and the propor- tion of Cenozoic volcanic and sedimentary rocks within it increase northward in the province***.” These inter- pretations are in good agreement with the geophysical definition of a distinct lower crust beneath the north- ern Basin and Range province, whereas the transition COMPARISON WITH SEISMIC-REFRACTION STUDIES IN CENTRAL EUROPE bei 3 k bar und 0°C 2,2 6,2 6,5 7,0 7,5 (km/s) 2,4 2,6 2,8 3,0 3,2(g/cm3) | | | | I Chloritoid- Schiefer Granat- Biotit- Schiefer fiaTHathE‘_ Disthen— Glimmer- Staurolith- Andalusit- | CoEErTF—_ I Sillimanit- Cordierit- Gneis (- Granit lllllllll NOIiVSIlINVHS FIGURE 91.—Relation between grade of metamorphism and density of the Biindner Schiefer (after Bederke, 1962, figs. 3, 4, with supplements by Giese, 1966, fig. H3; 1). The velocity scale, drawn by aid of the density-velocity curve by Woollard (1959), is plotted without marks to demonstrate that the cor- relation is not precise. zone between upper and lower crust disappears toward 51 Great Basin. The average velocity for the lower part of the crust increases from 6.4 to 6.8 km/s along the line from Eureka to Delta and from Eureka to Mountain City, which may indicate an increasing proportion of new mantle material within the lower crust under the northern Basin and Range province toward the east and north. This interpretation of the lower crust under the northern Basin and Range province is particularly ap- propriate for the western Snake River Plain. Hill and Pakiser (1966, 1967) pointed out that high-velocity material is found at shallow depths beneath the Snake River Plain. They concluded that the Snake River Plain is a rift through the continental crust filled with basaltic material from the mantle, produced, according to Hamilton and Myers (1966), by the northwestward shift of the Idaho batholith. The mafic material has a velocity of 6.8 km/s or more. The transition zone at a depth of about 40 km may mark a phase boundary rather than a chemical change in material. A similar relation may hold for the southern Cascade Mountains, which were traversed by only a small part of the profile from Shasta Lake to Mono Lake. The composition of the low-velocity anomalous upper mantle‘in the Basin and Range province remains unknown. During recent years, it has been thought that pressure-temperature conditions at the M-discontinuity are incompatible with those for the basalt-eclogite transition and that the petrologic considerations are also unfavorable to the hypothesis that the M-discontinuity represents the basalt-eclogite transition. However, Ito and Kennedy (1969) have shown recently that the basalt-eclogite transition seems to occur in two fairly sharp steps, from basalt to garnet granulite and from garnet granu- lite to eclogite, at pressures that are equivalent to depths in the lower crust and uppermost mantle and that the “two-step transitions are expected to produce sharp seismic discontinuities in the lower crust and up- per mantle***.” These results, therefore, restore the basalt-eclogite hypothesis for the M-discontinuity as a tenable. one. Alternatively, the anomalous upper man- tle may be ‘ ‘grossly heterogeneous, consisting primarily of peridotite, but with large lenses or blocks of basaltic to intermediate and perhaps even silicic material distributed through it***” (L.C. Pakiser, written com- mun., 1970). COMPARISON WITH SEISMIC-REFRACTION STUDIES IN CENTRAL EUROPE At the same time as the intensive seismic investiga- tion of the Western United States was made, a syste- matic seismic investigation of the crust and upper the south. Material with low P-wave velocities extends to greater depths beneath the southern part of the mantle was made in the Alps and adjacent areas. The 52 measurements were coordinated by the Sub-Commis- sion for Explosions in Southern and Western Europe of the European Seismological Commission, and they were carried out by many geophysical institutions from several European countries. About 40 profiles from 12 shotpoints covered the Alps (fig. 92). The total number of recording points was approximately 1,500. Explosions in small lakes, boreholes, and tunnels, and commercial quarry blasts were used as energy sources for the seismic experiments. A detailed list of publica- tions resulting from these studies was published by Morelli, Bellemo, Finetti, and de Visintini (1967). In order to collect the most important data and to elaborate the general features of the alpine crustal structure, a working group was elected, the synthesis of which was first published in 1967 (Choudhury and others, 1971; Giese and others, 1976). In the following sections, the main results of this in- vestigation are summarized to provide background for a comparison of the crustal structure of the Western United States and central Europe. Figure 92 shows an POSITION MAP CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES index map of the seismic-refraction profiles recorded in the Alps and vicinity. THE TRAVELTIME DIAGRAM Record sections were prepared for most profiles shown in figure 92 in the same manner as those de- scribed in this paper. Figure 93 shows three typical record sections: the profile from Eschenlohe to Bohmischbruck in the Bavarian Molasse Basin outside the Alps, the profile from Eschenlohe to Lago Lagorai extending across the eastern Alps from north to south, and the profile from Lago Lagorai toward the east in the southern Alps. In a detailed investigation of several profiles in central Europe, Giese (1966) pointed out that a basic traveltime diagram of the type shown in figure 5 can be used to represent all seismic-refraction profiles in central Europe. These traveltime curves are designated a, a-b, b, c, and d, as in this report. Giese (1966) noted a difference in the shape of curve a depending on the type of basement rocks. On profiles FIGURE 92.—-Index map of seismic-refraction profiles in the Alps and their vicinity. Shotpoints: ES, Eschenlohe; LB, Lago Bianco; LG, Lenggries; LL, Lago Lagorai; LN, Lac Négre; LR, Lac Rond; LV, Levone; MB, Monte Bavarione; MC, Mont Cenis; ML, Mont Lozere; RE, Le Revest; R0, Roselend; SC, Ste. Cécile d‘Andorge; TO, Tb'lz. Double lines, reverse profiles. Single lines, recorded in one direction only. Dotted region: Alps, Apennines, and Dinarides (Tertiary age). Area marked with X: Crystalline areas of Varis- can age. 53 COMPARISON WITH SEISMIC-REFRACTION STUDIES IN CENTRAL EUROPE .:.3 .ma $2 .986. mag. 523:8 9: E 3988 2:: Each“ BE. .umwwlfiuomfifi 095 .D .2.wa .mw .33 685 ”H H .mc .33 Emcee 5385. finenwhfio: E 33. 5398 as”. $398 2%on 2:. guano: oMmQIwnoEosowm .m .Aam .NNG .me .83 .mmwmg mamas mafiaambo :wgvaom 25 «3838 Emam mama—02 :mtgam 2: 938.8 @503 of. .xusgnnomwnfimlwnoiuaomm 6. .onoEm 135:8 E 8:on we nosoom Eouoxldm ”:50an mmws 50:5 ._. ,. - W W m . W W H. _ . W W . W M W . x .s m m n u m u u a a a am a can nmuzuuu u m «nu-mm- u mu n a unmade .muéulvxzn- w; m|_ .EOLL \ \ Ex o I; W\ IIIW\ nI II III: I: o N . . N M c w «WIN .. u w. 3., 96 W. n W has 0—! m | I | \lv mom. o n 5883888889 as u 9 handgun £8 a 8 8 83 w 3.: a 9 8 5 a n... _ ._<:ow no mwzfi mzoioww mmomu (zomm? xuammeZT REFERENCES CITED 59 REFERENCES CITED American Geophysical Union, 1964, Bouguer gravity anomaly map of the United States, exclusive of Alaska and Hawaii; pre- pared by a special committee for the geophysical and geologi- cal study of the continents, G. P. Woollard, chm., and the U.S. Geological Survey, H. R. Joesting, coordinator: U.S. Geol. Survey Spec. Map, 2 sheets, scale 1:2,500,000. Ansorge, J., 1968, Die Struktur der Erdkruste an der Westflanke der Zone von Ivrea [The structure of the earth‘s crust at the western flank of the zone of Ivrea]: Schweizer. Mineralog. u. Petrog. Mitt., v. 48, p. 247—254. Archambeau, C. B., Flinn, E. A., and Lambert, D. G., 1969, Fine structure of the upper mantle: Jour. Geophys. Research, v. 74, p. 5825—5865. Bailey, E. H., Irwin, W. P., and Jones, D. L., 1964, Franciscan and related rocks, and their significance in the geology of western California: California Div. Mines Bull. 183, 177 p. Bailey, R. W., and Muehlberger, W. R., 1968, Basement rock map of the United States, exclusive of Alaska and Hawaii: US. Geol. Survey Spec. Map, 2 sheets, scale 1:2,500,000. Bamford, D., 1973, Refraction data in western Germany—A time- term interpretation: Zeitschr. Geophysik, v. 39, p. 907-927. Bateman, P. C.. 1968, Geologic structure and history of Sierra N e- vada: UMR (Univ. Missouri, Rolla) Jour., v. 1, p. 121—131. Bateman, P. 0., Clark, L. D., Huber, N. K., Moore, J. G., and Rine hart, C. D., 1963, The Sierra Nevada batholith—A synthesis of recent work across the central part: U.S. Geol. Survey Prof. Paper 414—D, 46 p. Bateman, P. C., and Eaton, J. P., 1967, Sierra Nevada batholith: Science, v. 158, p. 1407-1416. Bateman, P. C., and Wahrhaftig, Clyde, 1966, Geology of the Sierra Nevada, in Bailey, E. H., ed., Geology of northern California: California Div. Mines Bull. 190, p. 107—172. Bederke, E., 1962, Altersgliederung und Dichteverteilung im kri- stallinen Grundgebirge,[Age classification and density distri- bution within the crystalline basement]: Geol. Rundschau, v. 52, p. 1-12. Berg, J. W., Cook, K. L., Narans, H. D., and Dolan, W. M., 1960, Seismic investigation of crustal structure in the eastern part of the Basin and Range province: Seismol. Soc. America Bull., v. 50, p. 511—535. Birch. F., 1958, Interpretation of the seismic structure of the crust in the light of experimental studies of wave velocities in rocks, in Benioff, H., Ewing, Maurice, Howell, B. F., and Press, F., eds., Contributions in geophysics in honor of B. Gutenberg: London—New York, Pergamon Press, p. 158-170. Bradley, W. H., 1964, Geology of Green River formation and asso- ciated Eocene rocks in southwestern Wyoming and adjacent parts of Colorado and Utah: US. Geol. Survey Prof. Paper 496-A, 86 p. Braile, L. W., Smith, R. B., Keller, G. R., Welch, R. M., and Meyer, R. P., 1974, Crustal structure across the Wasatch Front from detailed seismic refraction studies: J our. Geophys. Research, v. 79, p. 2669-2677. Bram, K., and Giese, Peter, 1968, Die Geschwindigkeitsverteilung der P-Welle in der Erdkruste im Raum Augsburg (Siid- Deutschland)—Ergebnisse und Vergleich zweier seismischer Messungen [The velocity distribution of the P-wave within the Earth’s crust in the area of Augsburg (southern Ger- many)—Results and comparison of two seismic measure- ments]: Zeitschr. Geophysik, v. 34, p. 611~626. Bullen, K. E., 1963, An introduction to the theory of seismology [3d' ed.]: Cambridge, Cambridge Univ. Press, 381 p. Carr, W. J., and Trimble, D. E., 1963, Geology of the American Falls quadrangle, Idaho: US. Geol. Survey Bull. 1121-G, 44 p. Choudhury, M., Giese, Peter, and de Visintini, G., 1971, Crustal structure of the Alps: Some general features from explosion seismology: Boll. Geofisica Teor. ed Appl., v. 13, p. 211—240. Closs, H., 1966, Der Unterg'rund der Alpen im Lichte neuerer geo- physikalischer Untersuchungen [The deep structure of the Alps in light of recent geophysical investigation]: Erdol u. Kohle, v. 19, p. 81-88. 1969, Explosion seismic studies in western Europe, in Hart, P. J ., ed., The earth’s crust and upper mantle: Am. Geophys. Union Mon. 13, p. 178—188. Cohee, G. V., chm., 1962, Tectonic map of the United States, exclu- sive of Alaska and Hawaii; prepared by a joint committee of the US. Geological Survey and the American Association of Petroleum Geologists: U.S. Geol. Survey Spec. Map, 2 sheets, scale 1:2,500,000. Compton, R. R., 1966, Granitic and metamorphic rocks of the Sali- nian block, California Coast Range, in Bailey, E. H., ed., Geo- logy of northern California: California Div. Mines Bull. 190, p. 277—288. Cooper, J. F., Strozier, O. A., and Martina, B. A., 1962, Field opera~ tions and shotpoint refraction survey of 1962 crustal studies program, western United States: United Electrodynamics, Inc., United Geophysical Corp., rept., 56 p. Crowell, J. C., 1968, The California Coast Ranges: UMR 1Univ. Mis- souri, Rolla) Jour., v. 1, p. 133—156. Dibblee, T. W., 1967, Areal geology of the western Mojave Desert, California: US. Geol. Survey Prof. Paper 522, 153 p. Dirnent, W. H., Stewart, S. W., and Roller, J. C., 1961, Crustal struc- ture from the Nevada Test Site to Kingman, Arizona, from seismic and gravity observations: J our. Geophys. Research, v. 66, p. 201—214. Dix, C. H., 1955, Seismic velocities from surface measurements: Geophysics, v. 20, p. 17—26. Eardley, A. J ., 1962, Structural geology of North America [2d ed.]: New York, Harper and Bros., 624 p. Eaton, J. P., 1963, Crustal structure from San Francisco, California, to Eureka, Nevada, from seismic-refraction measurements: Jour. Geophys. Research, v. 68, p. 5789—5806. 1966, Crustal structure in northern and central California from seismic evidence, in Bailey, E. H., ed., Geology of north- ern California: California Div. Mines Bull. 190, p. 419—426. 1967, Instrumental seismic studies, in Brown, R. D., and others, The Parkfield-Cholame, California, earthquakes of June-August 1966: US. Geol. Survey Prof. Paper 579, p. 57—65. _ 1968, Spatial distribution of aftershocks of the June 27, 1966, Parkfield-Cholame earthquake in the San Andreas fault zone, in Dickinson, W. R., and Grantz, A., eds., Proceedings of Conference on Geologic Problems of San Andreas fault system: Stanford, Calif, Stanford Univ. School of Earth Sci- ences, p. 84. Eaton, J. P., Healy, J. H., Jackson, W. H., and Pakiser, L. C., 1964, Upper mantle velocity and crustal structure in the eastern Basin and Range province, determined from SHOAL and chemical explosions near Delta, Utah [abs]: Seismol. Soc. America, 1964 Ann. Mtg., Prog., p. 30—31. Edel, J. B., Fuchs, K., Gelbke, C., and Prodehl, Claus, 1975, Deep structure of the southern Rhinegraben area from seismic-re- fraction investigations: Zeitschr. Geophysik, v. 41, p. 333— 356. 60 Fenneman, N. M., and Johnson, D. W., 1946, Physical divisions of the United States: US. Geol. Survey Map, scale 1:7,000,000. Frankovitch, C. J., Cooper, J. F., and Forbes, C. B., 1962, Seismic studies of the crustal structure, California-Nevada region (1961): United Electrodynamics, Inc., United Geophysical Corp., rept., 72 p. Fuchs, K., and Landisman, M., 1966, Detailed crustal investigation along a north-south section through the central part of west- ern Germany, in Steinhart, J. S., and Smith, T. J., eds., The earth beneath the continents: Am. Geophys. Union Mon. 10, p. 433—452. Fuchs, K., Mueller, 8., Peterschmitt, E., Rothe, J. P., Stein, A., and Strobach, K., 1963, Krustenstruktur der Westalpen nach re- fraktionsseimischen Messungen [Crustal structure of the Western Alps from seismic-refraction measurements]: Ger- Iands Beitr. Geophysik, v. 72, p. 149—169. German Research Group for Explosion Seismology, 1964, Crustal structure in western Germany: Zeitschr. Geophysik, v. 30, p. 209—234. Gibbs, J. F., and Roller, J. C., 1966, Crustal structure determined by seismic-refraction measurements between the Nevada Test Site and Ludlow, California, in Geological Survey re- search 1966: U.S. Geol. Survey Prof. Paper 550-D, p. D125— D131. Giese, Peter, 1963, Die Geschwindigkeitsverteilung im obersten Bereich des Kristallins, abgeleitet aus Refraktionsbeobach- tungen auf dem Profil Biihmischbruck-E schenlohe [The velo- city distribution in the uppermost part of the basement, derived from refraction measurements on the profile Boh- mischbruck-Eschenlohe]: Zeitschr. Geophysik, v. 29, p. 197- 214. _ 1966, Versuch einer Gliederung der Erdkruste im n'ordlichen Alpenvorland, in den Ostalpen und in Teilen der Westalpen mit Hilfe charakteristischer Refraktions-Laufzeitkurven, sowie eine geologische Deutung [Towards a classification of the Earth's crust in the northern Alpine foreland, in the East- ern Alps, and in parts of the Western Alps, using characteris- tic refraction-traveltime curves, as well as a geological inter- pretation]: Habil. Schrift, Math. N aturwiss. Fak. Freie Univ. Berlin, 143 p. (republished 1968: Inst. Meteorol. und Geo- physik FU Berlin, Geophys. Abh., 1/2, 214 p.) __ 1968, Die Struktur der Erdkruste im Bereich der Ivrea-Zone [The structure of the Earth's crust in the area of the Ivrea zone]: Schweizer. Mineralog. u. Petrog. Mitt., v. 48, p. 261- 284. __ 1970, The structure of the Earth’s crust in central Europe: European Seismol. Comm., 10th General Assembly (Lenin- grad 1968), Proc. Acad. Sci. USSR, Moscow, p. 387—403. Giese, Peter, Giinther, K., and Reutter, K. J ., 1968 11970) Verglei- chende geologische und geophysikalische Betrachtungen der Westalpen und des Nordapennins [Comparing geological and geophysical considerations of the Western Alps and the Northern Appenine]: Zeitschr. Deutsch. geol. Gesell., v. 120, p. 152—196. Giese, Peter, Morelli, C., Prodehl, Claus, and Vecchia, 0., 1971, Crust and upper mantle beneath the southern part of the zone of Ivrea: European Seismol. Comm., 12th General As- sembly (Luxembourg 1970), Proc., Obs. Royal de Belgique, Comm. Sér. A. no. 13, Sér. Geophys. no. 101, p. 182—183. Giese, Peter, Prodehl, Claus, and Behnke, C., 19673, Ergebnisse refraktionsseismischer Messungen 1965 zwischen Franzb'si- schem Zentralmassiv und den Westalpen [Results of seismic- refraction measurements 1965 between the French Massif Central and the Western Alps]: Zeitschr. Geophysik, v. 33, p. 215—261. CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES Giese, Peter, Prodehl, Claus, and de Visintini, G., 1967b, Ergebnisse refraktionsseismischer Messungen im Grenzbereich Alpen/ Apennin und im Nordapennin [abs.] [Results of seismic-re- fraction measurements in the border area Alps/Apennines and in the Northern Apennines]: Zeitschr. Deutsch. geol. Gesell., v. 119, Hauptversammlung. Giese, Peter, Prodehl, Claus, and Stein, A., eds., 1976, Explosion seismology in central Europe—Data and results: Berlin-Hei- delberg-New York, Springer-Verlag, 429 p. Giese, Peter, and Stein, A., 1971, Versuch einer einheitlichen Aus- wertung tiefenseismischer Messungen aus dem Bereich zwi- schen der Nordsee und den Alpen [Toward a unified interpre- tation of deep-seismic sounding measurements of the area be— tween the North Sea and the Alps]: Zeitschr. Geophysik, v. 37, p. 237—272. Gilluly, J., 1963, The tectonic evolution of the western United States: Quart. Jour. [London] Geol. Soc., v. 119, p. 133-174. Green, R. W. E., and Hales, A. L., 1968, The traveltimes of P-waves to 30° in the central United States and upper mantle struc- ture: Seismol. Soc. America Bull., v. 58, p. 267-289. Hackel, 0., 1966, Summary of the geology of the Great Valley, in Bailey, E. H., ed., Geology of northern California: California Div. Mines Bull. 190, p. 217—252. Hall, W. E., 1971, Geology of the Panamint Butte quadrangle, Inyo County, California: US. Geol. Survey Bull. 1299, 67 p. Hamilton, W., 1969, Mesozoic California and the underflow of Paci- fic mantle: Geol. Soc. America Bull., v. 80, p. 2409—2430. Hamilton, W., and Myers, W. B., 1966, Cenozoic tectonics of the western United States: Rev. Geophysics, v. 4, p. 509—549. 1967, The nature of batholiths: U.S. Geol. Survey Prof. Pa- per 554—C, 30 p. 1968, Cenozoic tectonic relationships between the western United States and the Pacific Basin, in Dickinson, W. R., and Grantz, A., eds., Proceedings of Conference on Geologic Prob- lems of San Andreas fault system: Stanford, Calif, School of Earth Sciences, p. 342-357. Hamilton, W., and Pakiser, L. C., 1965, Geologic and crustal cross section of the United States along the 37th parallel: U.S. Geol. Survey Misc. Geol. Inv. Map 1—448. Hansen, W. R., 1965, Geology of the Flaming Gorge area, Utah- ColoradoWyoming: U.S. Geol. Survey Prof. Paper 490, 196 p. Healy, J. H., 1963, Crustal structure along the coast of California from seismic-refraction measurements: Jour. Geophys. Re— search, v. 68, p. 5777—5787. Healy, J. H., Cooper, J. F., Eaton, J. P., Forbes, C. B., Frankovitch, C. J., Roller, J. C., and Stewart, S. W., 1962, Crustal studies in western United States, part IV: Study of seismic propaga- tion paths and regional traveltimes in the California-Nevada region: U.S. Geol. Survey Report, Denver, Colo., 103 p. Healy, J. H., and Warren, D. H., 1969, Explosion seismic studies in North America, in Hart, P. J., ed., The earth’s crust and up- per mantle: Am. Geophys. Union Mon. 13, p. 208—220. Herrin, E., 1969, Regional variations of P-wave velocity in the upper mantle beneath North America, in Hart, P. J ., ed., The earth’s crust and upper mantle: Am. Geophys. Union Mon. ' 13, p. 242—246. Hill, D. P., 1963, Gravity and crustal structure in the western Snake River Plain, Idaho: J our. Geophys. Research, v. 68, p. 5807- 5819. Hill, D. P., and Pakiser, L. C., 1966, Crustal structure between the Nevada Test Site and Boise, Idaho, from seismic refraction measurements, in Steinhart, J. S., and Smith, T. J ., eds., The earth beneath the continents: Am. Geophys. Union Mon. 10, p. 391—419. )1—‘Y REFERENCES CITED 6] 1967, Seismic-refraction study of crustal structure between the Nevada Test Site and Boise, Idaho: Geol. Soc. America Bull., v. 78, p. 685-704. Hirn, A., Steinmetz, L., Kind, R., and Fuchs, K., 1973, Long range profiles in western Europe: II. Fine structure of the lower lithosphere in France (southern Bretagne): Zeitschr. Geo- physik, v. 39, p. 363—384. Hughes, D. S., and Maurette, C., 1956, Variation of elastic wave velocities in granites with pressure and temperature: Geo- physics, v. 21, p. 277—284. 1957, Variation of elastic wave velocities in basic igneous rocks with pressure and temperature: Geophysics, v. 22, p. 23-31. Hunt, C. B., and Mabey, D. R., 1966. Stratigraphy and structure, Death Valley, California: US. Geol. Survey Prof. Paper 494—A, 62 p. Ito, K., and Kennedy, G. C., 1969, The fine structure of the basalt- eclogite transition [abs]: Geol. Soc. America and associated societies, Annual Meeting, Atlantic City, N.J., 1969, part 7, Abs. with Program, p. 113. Jackson, W. H., and Pakiser, L. C., 1965, Seismic study of crustal structure in the southern Rocky Mountains, in Geological Survey research: U.S. Geol. Survey Prof. Paper 525—D, p. D85-D92. Jackson, W. H., Stewart, S. W., and Pakiser, L. C., 1963, Crustal structure in eastern Colorado from seismic-refraction meas- urements: Jour. Geophys. Research, v. 68, p. 5767—5776. James, D. E., and Steinhart, S. W., 1966, Structure beneath conti- nents: A critical review of explosion studies 1960—1965, in Steinhart, J. S., and Smith, T. J ., eds., The earth beneath the continents: Am Geophys. Union Mon. 10, p. 293—333. J obert, G., and Perrier, G., 1974, Demonstration de 2(V) < zmax, in Coulomb, J ., and J obert, G., eds., Traité de Géophysique in- terne, Complements et erratum de Tome I in Tome II: Paris, Masson et Cie. Johnson, L. R., 1965, Crustal structure between Lake Mead, Ne- ada, and Mono Lake, California: J our. Geophys. Research, v. 70, p. 2863—2872. 1967, Array measurements of P velocities in the upper man- tle: Jour. Geophys. Research, v. 72, p. 6309—6325. King, P. B., 1959, The evolution of North America: Princeton, N.J., Princeton Univ. Press, 189 p. 1967, Tectonic features: National Atlas, Sheet no. 70, US. Geol. Survey, scale 1:7,500,000. Kistler, R. W., and Bateman, P. C., 1966, Stratigraphy and struc- ture of the Dinkey Creek roof pendant in the central Sierra Nevada, California: US. Geol. Survey Prof. Paper 524—8, 14 p. Kosminskaya, I. P., and Riznichenko, Y. V., 1964, Seismic studies of the earth's crust in Eurasia, in Odishaw, H., ed., Research in Geophysics, v. 2, Solid earth and interface phenomena, chap. 4: Cambridge, Mass, Massachusetts Inst. Technology Press, p. 81—122. Kosminskaya, I. P., Belyaevsky, N. A., and Volvovsky, I. S., 1969, Explosion seismology in the USSR, in Hart, P. J., ed., The earth’s crust and upper mantle: Am. Geophys. Union Mon. 13, p. 195—208. Lee, W. H. K., and Uyeda, S., 1965, Review of heat flow data, in Lee, W. H. K., ed., Terrestrial heat flow: Am. Geophys. Union Mon. 8, p. 87—190. Mabey, D. R., 1960, Regional gravity survey of part of the Basin and Range province, in Short papers in the geological sci— ences 1960: US. Geol. Survey Prof. Paper 400-B, p. B283— B285. Macdonald, G. A., 1966, Geology of the Cascade Range and Modoc Plateau, in Bailey, E. H., ed., Geology of northern California: California Div. Mines Bull. 190, p. 65—96. Macdonald, G. A., and Gay, T. E., 1968, Geology of the Cascade Range: California Div. Mines Mineral Inf. Ser., v. 21, p. 108— 1 11. Meissner, R., 1967, Zum Aufbau der Erdkruste. Ergebnisse der Weitwinkelmessungen im bayerischen Molassebecken [Struc- ture of the Earth's crust. Results of wide-angle measure- ments in the Bavarian Molasse Basin]: Gerlands Beitr. Geo- physik, v. 76, p. 211-254, 295—314. Meissner, R., and Berckhemer, H., 1967, Seismic-refraction meas- urements in the northern Rhinegraben, in Rothé, J. P., and Sauer, K., eds., The Rhinegraben progress report 1967: Abh. geol. Landesamt Baden-Wiirttemberg, Freiburg, Heft 6— Mém. Serv. Carte Geol. Alsace et Lorraine, Strasbourg, no. 26, p. 105-107. Mikumo, T., 1965, Crustal structure in central California in relation to the Sierra Nevada: Seismol. Soc. America Bull., v. 55, p. 65—84. Morelli, C., Bellemo, S., Finetti, 1., and de Visintini, G., 1967, Pre- liminary depth contour maps of the Conrad and Moho discon- tinuities in Europe: Boll. Geofisica Teor. ed Appl., v. 9, p. 142—157. Mueller, 8., and Landisman, M., 1966, Seismic studies of the earth‘s crust in continents. 1: Evidence for a low-velocity zone in the upper part of the lithosphere: Geophys. J our., v. 10, p. 525— 538. Mueller, 8., Peterschmitt, E., Fuchs, K., and Ansorge, J ., 1967, The rift structure of the crust and upper mantle beneath the Rhinegraben, in Rothe, J. P., and Sauer, K., eds., The Rhinegraben Progress Report 1967: Abh. Geol. Landesamt Baden-Wiirttemberg, Freiburg, Heft 6—Mém Serv. Carte Geol. Alsace et Lorraine, Strasbourg, no. 26, p. 108-112. Nolan, T. B., 1943, The Basin and Range province in Utah, Nevada, and California: US. Geol. Survey Prof. Paper 197—D, p. D141—D196. Officer, C. B., 1958, Introduction to the theory of sound transmis- sion: McGraw-Hill, New York, 284 p. Osmond, J. C., 1960, Tectonic history of the Basin and Range prov- ince in Utah and Nevada: Mining Engineering, v. 217, p. 251-265. - Page, B. M., 1966, Geology of the Coast Ranges of California, in Bailey, E. H., ed., Geology of northern California: California Div. Mines Bull. 190, p. 255-275. Pakiser, L. C., 1963, Structure of the crust and upper mantle in the western United States: Jour. Geophys. Research, v. 68, p. 5747-5756. 1964, Gravity, volcanism, and crustal structure in the south- ern Cascade Range, California: Geol. Soc. America Bull., v. 75, p. 611—620. 1965, The basalt-eclogite transformation and crustal struc- ture in the Western United States, in Geological Survey re- search 1965: US. Geol. Survey Prof. Paper 525-3, 8 p. 1970, Structure of Mono Basin, California: Jour. Geophys. Research, v. 75, p. 4077—4080. Pakiser, L. C., and Hill, D. P., 1963, Crustal structure in Nevada and southern Idaho from nuclear explosions: J our. Geophys. Re- search, v. 68, p. 5757—5766. Pakiser, L. C., Kane, M. F., and Jackson, W. H., 1964, Structural geology and volcanism of Owens Valley region, California—— A geophysical study: U.S. Geol. Survey Prof. Paper 438, 68 p. , Pakiser, L. C., and Robinson, R., 1966a, Composition and evolution of the continental crust as suggested by seismic observa- tions: Tectonophysics, v. 3, p. 547—557. 62 1966b, Composition of the continental crust as estimated from seismic observations, in Steinhart, J. S., and Smith, T. J ., eds., The earth beneath the continents: Am. Geophys. Union Mon. 10, p. 620—626. Pakiser, L. C., and Steinhart, J. S., 1964, Explosion seismology in the western hemisphere, in Odishaw, H., ed., Research in Geo- physics, v. 2, Solid earth and interface phenomena, chap. 5: Cambridge, Mass., Massachusetts Inst. Technology Press, p. 123—147. Pakiser, L. C., and Zietz, Isidore, 1965, Transcontinental crustal and upper mantle structure: Rev. Geophysics, v. 3, p. 505— 520. Payne, M. P., 1967, San Andreas fault cross sections: Am. Assoc. Petroleum Geologists, Pacific Sec. Perrier, G., 1973, La croute terrestre, in Coulomb, J., and Jobert, G., eds., Traite de geophysique interne, v. I: Sismologie et pesanteur: Paris, Masson et Cie., p. 229-281. Prodehl, Claus, 1965, Struktur der tieferen Erdkruste in Siidbayern und la'ngs eines Querprofiles durch die Ostalpen, abgeleitet aus refraktionsseismischen Messungen bis 1964 [Structure of the deep crust in Southern Bavaria and along a traversing profile through the Eastern Alps, derived from seismic-re- fraction measurements to 1964]: Boll. Geofisica Teor. ed Appl., v. 7, p. 35—88. 1970a, Seismic refraction study of crustal structure in the western United States: Geol. Soc. America Bull., v. 81, p. 2629—2646. 1970b, Crustal structure of the western United States from seismic-refraction measurements in comparison with central European results: Zeitschr. Geophysik, v. 36, 477—500. Prodehl, Claus, and Pakiser, L. C., 1979, Crustal structure of the Southern Rocky Mountains from seismic measurements: Geol. Soc. America Bull., v. 89 [in press]. Research Group for Explosion Seismology, 1966, Explosion seismo— logical research in Japan, in Steinhart, J. S., and Smith, T. J., eds., The earth beneath the continents: Am. Geophys. Union Mon. 10, p. 334—348. Rhinegraben Research Group for Explosion Seismology, 1974, The 1972 seismic refraction experiment in the Rhinegraben— First results, in Illies, H., and Fuchs, K., eds., Approaches to taphrogenesis: Stuttgart, Schweizerbart, p. 122—137. Rinehart, C. D., and Ross, D. C., 1964, Geology and mineral deposits of the Mount Morrison quadrangle, Sierra Nevada, Califor- ’ nia: U.S. Geol. Survey Prof. Paper 385, 106 p. Roberts, R. J., 1968, Tectonic framework of the Great Basin: UMR (Univ. Missouri, Rolla) Jour., v. 1, p. 101-119. Roller, J. C., 1964, Crustal structure in the vicinity of Las Vegas, Nevada, from seismic and gravity observations, in Geological Survey research 1964: US. Geol. Survey Prof. Paper 475-D, p. D108—D111. 1965, Crustal structure in the eastern Colorado Plateaus province from seismic-refraction measurements: Seismol. Soc. America Bull., v. 55, p. 107—119. Roller, J . C., and Gibbs, J. F., 1964, Chemical explosions detonated by the US. Geological Survey from July 1961 to July 1964: US. Geol. Survey CS [Crustal Studies] Tech. Letter No. 24, Denver, 0010., 13 p. Roller, J. C., and Healy, J. H., 1963, Seismic-refraction measure- ments of crustal structure between Santa Monica Bay and Lake Mead: Jour. Geophys. Research, v. 68, p. 5837—5849. Roller, J. C., Jackson, W. H., Cooper, J. F., and Martina, B. A., 1963, Crustal structure in the western United States; Study of seismic propagation paths and regional traveltimes in the California—Nevada region: U.S. Geol. Survey CS [Crustal Studies] Tech. Letter No. 9, Denver, 0010., 57 p. Roller, J. C., Strozier, O. R, Jackson, W. H., and Healy, J. H., 1963, CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES Preliminary report on seismic-refraction studies of crustal structure in the western, central, and southern United States: US. Geol. Survey CS [Crustal Studies] Tech. Letter No. 14, Denver, 0010., 55 p. Rubey, W. W., and Hubbert, M. K., 1959, Overthrust belt in geo- synclinal area of western Wyoming in light of fluid-pressure hypothesis: Geol. Soc. America Bull., v. 70, p. 167-206. Ryall, A., and Stuart, D. J ., 1963, Traveltimes and amplitudes from nuclear explosions, Nevada Test Site to Ordway, Colorado: Jour. Geophys. Research, v. 68, p. 5821—5835. Sollogub, V. B., 1969, Seismic crustal studies in southeastern Eu- rope, in Hart, P. J ., ed., The earth's crust and upper mantle: Am. Geophys. Union Mon. 13, p. 189—195. Steinhart, J. S., and Meyer, R. P., 1961, Explosion studies of conti- nental structure: Carnegie Inst. Washington Pub. 622, 409 p. Stewart, S. W., 1968a, Preliminary comparison of seismic travel- times and inferred crustal structure adjacent to the San An- dreas fault in the Diablo and Gabilan Ranges of central Cali- fornia, in Dickinson, W. R., and Grantz, A., eds., Proceedings of Conference on Geologic Problems of San Andreas Fault System: Stanford Univ., Stanford, Calif, School of Earth Sci- ences, p. 218—230. 1968b, Crustal structure in Missouri by seismic-refraction methods: Seismol. Soc. America Bull., v. 58, p. 291—323. Stuart, D. J., Roller, J. C., Jackson, W. H., and Mangan, G. B., 1964, Seismic propagation paths, regional traveltimes, and crustal structure in the western United States: Geophysics, v. 29, p. 178—187. Thompson, G. A., 1959, Gravity measurements between Hazen and Austin, Nevada, a study of Basin-Range structure: J our. Geophys. Research, v. 64, p. 217-230. Thompson, G. A., and Talwani, M., 1964, Crustal structure from Pa- cific basin to central Nevada: J our. Geophys. Research, v. 69, p. 4813—4837. Warren, D. H., 1968a, Transcontinental geophysical survey (35 °— 39 ° N.) seismic refraction profiles of the crust and upper man- tle from 112° W. longitude to the coast of California: US. Geol. Survey Misc. Geol. Inv. Map I—532—D, scale 1:1,000,000. _ 1968b, Transcontinental geophysical survey (35° — 39°N.) seismic refraction profiles of the crust and upper mantle from 100° to 112° W. longitude: U.S. Geol. Survey Misc. Geol. Inv. Map I—533—D, scale 1:1,000,000. 1968c, Transcontinental geophysical survey (35° — 39 °N.) seismic refraction profiles of the crust and upper mantle from 87° to 100° W. longitude: U.S. Geol. Survey Misc. Geol. Inv. Map -534—D, scale 1:1,000,000. _ 1968d, Transcontinental geophysical survey (35° — 39° N] seismic refraction profiles of the crust and upper mantle from 74° to 87° W. longitude: U.S. Geol. Survey Misc. Geol. Inv. Map I—535-D, scale 1:1,000,000. 1969, A seismic-refraction survey of crustal structure in cen- tral Arizona: Geol. Soc. America Bull. v. 80, p. 257—282. Warrick, R. E., Hoover, D. B., Jackson, W. H., Pakiser, L. C., and Roller, J. C., 1961, The specification and testing of a seismic- refraction system for crustal studies: Geophysics, v. 26, p. 820—824. Willden, Ronald, 1965, Seismic-refraction measurements of crustal structure between American Falls Reservoir, Idaho, and Flaming Gorge Reservoir, Utah: US. Geol. Survey Prof. Paper 525—C, p. C44—C50. Winkler, H. G. F., 1967, Petrogenesis of metamorphic rocks [2d ed]: Berlin-New York, Springer-Verlag, 237 p. ' Woollard, G. P., 1959, Crustal structure from gravity and seismic measurements: J our. Geophys. Research, v. 64, p. 1521—1544. Yerkes, R. F., McCulloh, T. H., Schoellhamer, J. E., and Vedder, J. G., 1965, Geology of the Los Angeles basin, California—An introduction: U.S. Geol. Survey Prof. Paper 420—A, 57 p. 4)- 4'v — —’ TABLES 55—108 Tables 55-107 show the data for the corresponding record sections. The first column identifies the recording station. The second column shows the distance from the shotpoint referring to the location of the closest and most distant seismometer of the corresponding spread, that is. traces 1. 6. 9. and 14 (fig. 3). The coordinates and the elevation in columns 4-6 are given for the seismometer, the trace number of which is shown in column 3. Column 7 shows the traces according to figure 3 that are included in the corresponding record section, the first number referring to the seismometer of the corresponding spread closest to the shotpoint. the last number to the seismometer most distant from the shotpoint. Table 108 lists the corrections applied to some profiles. 64 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 55.—Data for the record-section of the profile from Eureka/I5) TABLE 57.—Data for the record-section of the profile from Boise(11) to Fallon(9) (fig. 10) to Elko(14) (fig. 13) Trace N 0. Trace No. Distance of coordi- Coordinates Traces Distance of coordi- Coordinates Traces (km) mates and —__ Elevation included (km) notes and _.___._ Elevation included Station (traces 1. 6) elevation Lat Long (feet) in section Station (traces 1. 6) elevation Lat long (feetl in section S—4 ————— 1.2 - 3.7 1 39°36.00' 115°37.70' 6.050 3 J—l—————— 7.03- 7.84 l 43°32.25’ 115°54.96' 2.6 J43——— -- 18.6 21.1 6 39°31.39' 115°53.90' 6.800 4 R—l — —— 13.41- 15.37 1 43°27.58’ 115°57114' 2.5 Q— — 26.4 - 28.9 1 39°34.54' 115°59.90' 5.970 1 L—1 — —— 28.82— 31.11 1 43°20.52’ 115°50.15’ 1.5 T— - 38.7 , 41.2 1 39°36.12’ 116°08.87’ 6.050 1.6 S—l — —— 33.55— 36.02 1 43°1662’ 115°57.35’ 2.6 I—4 — 42.4 — 44.9 1 39°36.41' 116°09.94' 6.020 5 132—1 — —— 42.77— 45.19 1 43°11.72' 115°55.77’ 3.4 P—3 — 56.6 — 58.9 6 39°31.42’ 116°21.46’ 3.6 H-1 — -— 54.83— 57 34 1 43°05.10' 115°57.96' 3.5 Q-8 — 61.5 — 63.9 6 39°30190’ 116°24.40’ 6.200 2.5 I—l—— —— 70.39— 72 87 1 42°57.24' 115°50.10’ 2.5 P— - 77.8 ~ 80.3 6 39“26.20’ 116°35.10’ 6.500 1.6 K-1 — —- 75.76— 76 76 1 42°53.92' 115°54.42’ 1.6 J-12 — 83.5 A 85.5 1 39°33.65’ 116°38.50’ 6.450 1 T—l — —— 87.60— 89.89 1 42°47.44' 115°55.97’ 1.5 [~10 — 84.1 , 86.1 1 39°33.65’ 116°38.50' 6.450 4 P—l — —-—103.59~105.92 1 42°39.40' 115°47.35' 2.6 J— — 98.6 —101.1 6 39°23.84’ 116°49.00’ 5.820 1.11.6 I—2—— ——107.42—109.51 1 42°37.26' 115°47.81' 3.950 2.6 K— —106.4 —1089 6 39°23.84’ 116°54.08’ 5.740 1 R—2 — ——i15.13—117.56 i 42°32.52’ 115°58.61' 4.830 1.6 K— —108.9 41112 1 39°24.44' 116°55.3’ 6.000 1.11.6 L—2 — ——125.68—128.02 1 42°26.82' 115°58.78' 5.310 1.5 J—9— —117.7 ~119 6 1 39°28.71' ll7°01.75’ 7.200 1.11.6 S—Z — ‘——139.417141.83 1 42°19.50’ 115°53.79' 5.400 1.11.6 H—9 —125.1 v1276 3 39°36.02’ 117°09.28' 5.775 2.6 H—2 — ——143.19—145.74 1 42°17.46’ 115°53.73' 5.200 1.12.6 1— —130.6 —133 0 1 39°25.95' 117°10.50' 5.760 1.11.6 1—2—— ——157.64—160.12 1 42°09.75’ 115°51.18' 5.800 1.11.6 H—8 —139.7 —142 2 3 39°28.41' 117°18.16' 6.050 2.6 K—2 — ——169.38—170.59 1 42°03.42’ 115°50.67' 5.700 1.11.5 J- —153.4 —155 9 3 39°31.51’ 117°27.58' 6.250 9 T—2 — ——176.9l—178.94 1 41°59.33’ 115°50.95' 6.650 9.12.6 I—9———— —153.0 4155 2 3 39°21.20' 117°25.46' 6.100 6 Q-2 — ——182.99—184.34 1 41°56.00’ 115°51.94' 6.500 12 K— ~157.0 ~158 0 3 39°33.24' 117°30.0' 6.000 1 P72 — ——184.41—186.57 l 41 °55.20' 115°52.87’ 64.50 2.12.6 1- —159.6 —1621 3 39°22.47' 117°31.10' 6.100 2.6 R—3 — ——196.28—197.80 1 41°48.77' 115°53.25' 6.250 1.12.6 S~ —164.0' —166 1 3 39°22.08' 117°34.02’ 6.300 1.6 5-3 - -——200.88—203.21 l 41 °46.52' 115°47.69’ 6.500 1.12 L— 2 ——— —179.6 —182 0 3 39 °29.7’ 117° 46.3’ 5.300 1.5 J-3—— ——203.73—205.99 1 41°44.96' 115°47.98’ 6.540 1.11.6 K—11——— —l82.5 —185 0 3 39 ”31.79’ 117°48.70’ 5.300 4 L—3 — ——208.91—211.07 1 41 ”42.19’ 115°47.35' 6.370 1.11.5 H-11——— —185.0 —1865 3 39°32.20’ 117°50.1’ 5.400 1.5 H—3 — ——221.29—223.47 1 41 ”35.42’ 115°48.60' 6.380 1.11.6 S—ll ——— -207.1 ~2095 3 39°32.46’ 118°05.78' 4.000 9.13 [-3 —— ——233.64—236.12 1 41°28.73’ 115°48.75' 1.12.6 S—10A —— —215.9 42168 1 39°13.77’ 118°07.71' 6.000 9.14 [(—3 — ——244.87—247.35 1 41 “22.94’ 115°43.39' 1.12.6 Q—11——— ~236.0 —238 4 1 39°16.38’ 118°24.45’ 4.300 9.13.14 T-3 — ——254.44—256.72 1 41 °17.55' 115°46.98' 1.12.6 K-10——- —240.4 ~242 4 3 39°32102' 118°29.22' 3.900 10.14 P—S —- ——260.15—262.02 1 41 °14.52' 115°45.75' 5.800 1.12.6 H—lOA —— ~246.7 ~248 9 1 39°03.78' 118 “28.53' 9.13 Q-3 ————— 31187-31399 1 40°46180' 115°40.42' 5.320 10.12.14 P-ll ——— —264.3 —266 8 1 39°40.90' 118°46.51' 3.900 9.13 P—lO —-—— —274.1 —276.5 1 39°31.97' 118°50.64' 4.020 10.13 ¥_10A ————278.2 —280.7 1 39°03.24' 118°50.91’ 4.400 9.14 T h —10A ————3i2.4 -3i4,9 1 39°09.15' 119°16.50' 4.600 9.11.12.14 ABLE 58.—Data r re r .s ' r ‘ R—ll ————— 315.5 -318,0 6 39°39.02' 119°20.31' 4.400 10.13 . f0 t e . CO d ection Of thep Ofile from Strike Reservozr(12) to Botse(11) (fig. 14) Trace No. Disktance of coordic-i Coordinates E1 Traces . . ( m) nates an _.____. evation included TABLE 56-—Data for the record-sectzon Of the profile Fallon(9) Station (traces 1. 6) elevation Lat Long (feet! in section to Eureka(15) (fig. 11) 1—1 —————— 5.13— 6.08 6 42°57.24' 115°50.10' 1.5 H—1 . 19.06 6 43°05.10' 115°57.96' 1.3.6 Trace No. Q—l 6 43°11.72' 115°55.77' 2.12.14 Distance of coordi- Coordinates Traces 3—1 6 43°16.62' 115°57.35’ 1.3.5 (km! mates and _. Elevation included L—l 6 43 °20.52’ 115°50.15’ 2.4.6 Station (traces 1. 61 elevation Lat Long (feet) in section 8—1 6 43 °27.58' 115°57.14' 1.4.6 1—1 6 43°32.25’ 114°54.96' 1.3.6 P—7 — — 1.4 6 39°31.97’ 118°50.64' 4.020 6 H-18—— — 10.1 — 12.2 6 39232.30 118°44.14' 3.940 1.5 I47———— — 24.2 — 25.8 6 39°15 . 3’ 118°34.44’ 3,900 2.6 ' ' ‘ J_.,___ _ 26.2 _ 2&7 1 39.32.92. 118534.89. 3,900 2.6 TABLE 59.—Data for the record-section of the profile from Stnke K—7 —— — 323 ~ 343 4 39°32.02' 118°29.22’ 3.900 1.5 ' ‘ H—l —— — 32.7 — 34.9 1 39°23.29' 118°32142' 4.050 1.6 Reservozra2) t0 Elko(14)(fig 15) Q-S —— — 48.9 — 51.2 1 39°16.38' 118°24.45’ 4.500 1.6 [-18 —— — 59.7 ~ 61.9 1 39°32.15' 118°10.80' 4.150 2.6 T N 13-8 — — 65.7 — 68.1 4 39°32.46' 118°05.78' 4.000 6.2 . {80911;} C d' K—18—— — 67.7 - 69.2 i 39°33.00' 118°O5.20' 4.150 1 ”Stance 0 C00 1' °°r "mes . Traces _ __ _ _ o . o . [kml nates and __ Elevation included H 8 89.8 91.3 4 39 32.20 117 50.10 5.400 5 S . . 1 . K—8 __ _ 900 _ 92.5 4 39631.79. 117648.70: 5300 175 tation (traces 1. 6) elevation Lat Long (feet( in section L—18 —— — 93.8 — 96.0 4 39°29.70' 1130;3'30, 5.300 2.5 'K-6 — -—118.4 -119.4 4 39533.24' 11 ° . 0' 6.000 2.6 K_1 _____ 2_—,2_ 4.80 1 42.5332. 115054.42. 1— -- -120.0 4225 4 39°31-51' 117°27-53' 61250 2'6 T—i ————— 14.86— 17.12 1 42°47.44' 115°55.97' 1.2.6 J-8——- —143.4 -l459 4 39°36.57' 117°12.50' 5.750 1.11.6 p_1 _____ 30.67- 32.88 1 4203940 115047351 1'5 H-6 —- —146.6 —1491 4 39°3602' 117°09.28' 5.775 2.6 J_2 ______ 343+ 36.32 1 42.3726. 115.47 81. 3950 1'5 J—6——— —156.7 ~1587 6 39°2871' 117°01.75' 7.200 1.11.6 R_2 _____ 42_69_ 45.13 1 42.3252. 115.5816... 4'830 1'5 K—5 — —166.3 -1686 6 39°24.44' 116°55.30' 6.000 1 .9 L_2 _____ 53_17_ 55.39 1 4202632. “5.58.78. 5'31.) 1'5 .i—5—— —117.6 -1799 i 39°23.84’ 116°49.00' 5.820 1. 1.6 8—2 _____ 662$ 68.65 1 42.1950. 115.5379. 5'40.) 1'6 s-18 — —190.0 —1919 6 39°33.64’ 116°38.49’ 6.440 10.6 H_2 _____ 70.0.“ 7259 1 42.17.46. 115053.73. 5'2...) 3'6 P—5 — —197.1 —1996 1 39°26.20’ 116°35.10’ 6.500 1.11.6 1-2 ______ 84‘38_ 86.87 1 42.09.75. 115051.18. 5'80.) 1'116 P-4 — —212.5 —2149 6 39°31.26’ 116°22.28’ 6.120 1.6 K4 _____ 9612- 97.29 1 42.0342. 115.5057. 53,00 1'5 ' T-18 - —234»4 -236 6 1 39 “36112 116°03-84’ 6-040 9-13 T—2 ————— 10367—10572 1 41°59.3a' 115°5o.95' 6:650 9:6 J-3-- -256-7 -259 2 1 39:31-39, 115253-90: 6300 9-12 Q-2 ————— 109.79—111.18 1 41°56.00’ 115°51.94' 6.500 11 K-3 - -272-8 -2751 6 39 35.80 115 40-40, 5,860 9-14 P—2 ————— 11125—11342 1 41°55.20' 115°52.87’ 6.450 11 H-3 - ~282-2 -284 4 1 39°36-36’ 115°34-75 6300 1014 R—3 ————— 123.15—124.63 1 41°48.77’ 115°53.25' 6 250 16 [-3--- -294-5 -297 0 4 39°36~41' 115°26-22’ 6.100 10'” s—a ————— 12758-12933 1 41°46.52’ 115°47.69’ 6:500 1:6 K-4 - -301-3 -3038 4 39:34-84: 115221-14: 61100 11 J—3 —————— 13044-13271 1 41°4496' 115°47.98' 6.540 2.6 Q-4 - -318-4 -320-9 4 39037-23. 115909-22. 6-400 11 L—3 ————— 13561-13777 1 41°4219' 115°47.35' 6.370 1.5 1-4 ------ 328-8 -331-1 4 39 37-57 115 02-06 6,300 11 H—3 ————— 14803—15023 1 41°35.42' 115°48.60’ 6.380 1.11.6 1— 16039-16286 1 41°28.73' 115°48.75’ 2.12.6 K—a ————— 17155-17404 1 41°22.94' 115°43.39' 1.11.6 T—3 ————— 181.18—183.45 1 41°17.55' 115°46.98’ 1.12.6 P-3 ————— 18687-18875 1 41°14.52' 115°45.75' 5.800 1.12.6 Q—a ————— 23857-24069 1 40°46.80’ 115°4o.42' 5.320 10.1 .14 TABLE 60.—Data for the record-section of the profile from Mountain City(13) to Boise(11) (fig. 16) TABLES 55—108 65 TABLE 62.—Data for the record-section of the profile from Elko(14) to Boise(11) (fig. 18) Trace No, Trace No. Distance of coordi— Coordinates Traces Distance of coordi- Coordinates Traces (km) mates and Elevation included (km) mates and _ Elevation included Station (traces 1. 6D elevation Lat Long (feet) in section Station (traces 1. 61 elevation [.at Long (feet) in section Q-3 —————— 7.24— 9.46 6 41°55.23’ 115°52.81' 6.550 2.6 Q~2 77777 1061‘ 13.10 1 40°52.29' 115°45.78' 5.440 6.2 T—5 ~— 15.23— 17.40 6 41°59133' 115°50.95' 6.650 1.5 $72 — —— 19.63~ 22.15 6 40°57.78' 115°45.10' 2.6 K—5 — 24.35— 24,91 6 42°03142' 115°50.67' 5.700 1.6 L—2 — —— 32.09~ 34.42 1 41°03.00’ 115°51.57' 6.100 5.1 [—5— ~ 33.93— 36.43 6 42°09.75' 115°51.18' 5.600 1.6 R—2 — —— 36.45— 38.22 1 41°06.63’ ll5°45.18' 6.500 5.1 H—5 —— 47.96— 50.54 6 42°17.46' 115°53.73' 5.200 1.6 P—3 — —— 51.01— 52.79 6 41°14.52' 115°45175' 5.800 2.6 3—5 — 5193— 54.32 6 42°19.50' 115°53,79' 5.400 1.6 T—3 — —— 56.25— 58.58 6 41 “17.55' 115°46.98' 1.6 L—5 —~ 65.82— 68.22 6 42°26.82' 115°58.78' 5.310 2.6 [(—3 — —— 65.53— 68.03 6 41°22194' 115°43139' 1.11.6 R—5 — 76.32- 78.71 6 42°32.52' ll5°58.61' 4.830 1.6 1—3—— —— 76.86— 79.41 6 41°28173' 115°48.75' 2.5 J—5— — 85.28- 87.57 6 42°37.26' 115°47.81' 3.950 2.6 H»3 — —— 89.55— 91.67 6 41°35142' 115°48.60' 6.380 1.3.5 P—4 — 89.12— 91.58 6 42°39.40' 115°47.35' 1.6 L»3 -‘ ~‘101.79»103.96 6 41°42.19' 115°47.35' 6.370 2.12.6 T>4 —103.79—106.09 6 42°47.44' 115°55.97’ 2.12.6 J—3 ——106.88—109.15 6 41°44196' 115“47.98' 6.540 1.6 K~4 —116.93~118.05 6 42°53,92' 115°54.42' 2.11.6 S—3 # ——109.66—111.99 6 41°46.52' 115°47.69' 6.500 11.6 1-4— —121.79-124.29 6 42°57,24' 115°50.10' 2.12.5 R—3 — ——115.38—117.02 6 41°48.77' 115°53.25' 6.250 2.6 114 —136.35—138.66 6 43°05,10' 115°57.96' 2.11.6 Q—3 — ——126.54—128179 6 41°55.23' 115°52.81' 6.550 9.12 Q—4 —148.61-151.02 6 43°11.72' 115°55.77' 9.11.14 Q—4 — ——128.80—130.05 6 41 °56.00' 115°51.94' 6.500 3.14 S—4 —157.674160.15 6 43°16.62' 115°57.35' 9.11.13 T—4 - ——134.04»136.02 6 41°59.33' 115°50.95' 6.650 2.12.6 L—4 —164.874167.36 6 43°20.52’ 115°50.15' 2.12.6 K—4 — —-—142.274143.52 6 42°03.42’ 115°50.67' 5.700 1.11.6 R—4 —178.807180.43 6 43°27.58' 115°57.14' 1.12.6 1—4 —' ~~152.78v155.25 6 42°09.75' 115°51.18' 5.800 1.12.6 J—4 —————— 18703—18902 6 43°32.25' 115°54.96' 1.11.6 P—4 — ——160.08—162.80 6 42°13.74' 115°52.68' 1.11.6 H—4 — ——167.26—169.80 6 42 °17.46’ 115°53.73' 5.200 2.5 8—4 — ——171.13—173.57 6 42°19,50' 115°53.79' 5.400 2.12.6 L—4 — ——185.42-187.84 6 42 °26.82' 115°58.78' 5.310 2.13 R~4 — ——195.91—198.27 6 42°32,52' 115°58.61' 4.830 2.14 .é—4—— ——203,57—205.75 6 42 °37.26' 115°47.81' 3.950 2.4 TABLE 61.—Data for the record-section of the profile from Mountain an: _ "321333333 2 2:033:22. “£42232 3;: - ‘ 75 — 7—236.147237.11 6 42°53192' 115°54.42' 9.14 Clty(13) t0 Eurekaa5) (fig 17) 115__._ ——240.35A242.85 6 42 “57.24' 115°50.10' 10.13 H75 — 7—255.647258.15 6 43°05.10' 115°57196' 9,13 s-s — W—276.85-279.32 6 43°16.62' 115°57135' 9,12,14 _ Trace N9- , 1,5 — 7—28341428591 6 43°20.52' 115°50.15' 1.11.5 Distance of word; Coordinates E] Traci; R75 — 7—297151-299 53 6 43°27 58’ 115°57 14' 9 1 14 ( mi nates an —_ evation inc u _______ ,- ' o ' 1 o‘ ' . ‘ ‘ Station (traces 1. 6) elevation Lat Long (feet( in section J 5 306'02 307'9‘5 6 43 3225 “5 5496 9111.5 R—3 ————— 2.65— 4.52 6 41°48.77' 115°53.25' 6.250 5.2 S—6 —— — 10.73— 12.12 1 41°46.52' 115°47.69’ 6.500 3.6 J—3——— — 12.49— 14.40 1 41°44.96' 115°47.98' 6.540 3.6 L-6 —— — 17.19— 19.51 1 41°42.19' 115°47.35' 6.370 10.13 _ . ' ‘ H_6 __ _ 28.15% 30,18 1 “035.42, “5048.60, 6380 9.14 TABLE 63. Data for the record secno'n of the profile from Elko(14) I—6————— — 40.26- 42.82 1 41°28,73' 115°48.75' 9.6 to Eurekal15) (fig- 19) K—6 —— — 52.39— 54.71 1 41°22.94' 115°43139' 9,13 T—6 —— —- 61.09— 63.43 1 41°17.55' 115°46198' 9.14 P-6 —— — 66.90— 68.65 1 41°14.52' 115°45.75' 5,800 1.14 Trace No. R-2 —— — 81.45— 83.22 1 41°06163' 115°45.18’ 6.500 2.5 i 11 e {C rdi- - L-2 —— — 87.33» 33.70 1 4(1) mggg 112051.17 6.100 1.2 13353.)“ gateosoand C______°°’d'"ms Elevation $111314 S-2 —— — 97.7 —1 . 6 l 4 °5 . ' °45.10' 2. ' ‘ ' ' Q—2 __ —107.69—110.00 1 40052.29, 115°45.78' 5,440 213 Station (traces 1. 61 elevatlon Lat Long (feet) 1n section Q—6 ——- —116.747120 75 1 40°46.80' 115°40.42' 5,320 2.12.6 ‘ I—2—--— —130.96~133 40 1 40°39.77' 115°4423' 1,11.6 1—2 —————— 12.81— 14.76 1 40°39.77' 115°44.23' 1,5 K—2 —— —141.62-144 18 1 40°34.35' 115°40.05' 5,700 1,11.6 K—2 ————— 22.03- 24.56 1 40 °34.35’ 115°40.05' 5.700 1.6 T—2 ——-— —145.76—148.16 1 40°31.77' 115°43.80' 5.400 3.5 T-2 ————— 27.06- 29.52 1 40 “31.77' 115°43.80' 5.400 1.6 P—2 —— —148.99—151.30 1 40°30.05' 115°43.30' 5.400 2.5 13-2 ————— 3013- 32-35 1 40°30.05' 115°43~30' 5.400 2.5 T—l ——— —157.61—157.89 1 40°25.25' 115°41.41' 5,440 6 T~1 ————— 38.33— 38.93 6 40°25.25' 115°41.41' 5.440 6.1 R-l ——— —158.20-160.55 1 40°25.14' 115°42.16' 5,420 1.11.6 R~1 ————— 39.07- 41.52 1 40°25.14' 115°42.16' 5.420 3.6 J-1———— —169.64—172.ll 1 40°19.09' 115°40.10' 5.860 1.12.6 J~1 —————— 50.24- 52.71 1 40°1909' 115°40.10' 5.860 1.6 L—l ——— —178,38—180 76 1 40°14.15' 115°41.25' 5.910 1.11.6 L~1 ————— 59.19— 61.60 1 4004.25’ 115°41.25' 5.910 1.11.6 s-1 ——— —-188.72-19122 1 40°08.60' 115°4180' 6.100 2.12.6 S-1 —————— 69.65— 72.17 1 40°08.60’ 115°4l.80' 6.100 2.5 Q—1 ——— —197.05—199 53 1 40°04.10' 115°4154' 6,100 2.13 Q~1 ————— 77.97- 80.45 6 40°04.10' 115°41.54' 6.100 5.12.2 H-1 —— —207.74—210 12 1 39°58.35' 115°40180' 6.150 1.11.6 H~1 ————— 88-61- 91-02 1 39°58.35' 115°40.80' 6.150 2.12.6 I—1——— —216.78—219 l7 1 39°53.56' 115°39.11’ 6.140 2.12.6 1-1 —————— 97.51- 99.85 1 39°53.56’ 115°39.11' 6.140 1.11.6 K—l ——— —229.78—232.26 1 39°46.44' 115°40.13’ 5.920 1.11.6 K-l ————— 110-66413.” 1 39°46144' 115°40.13' 5.920 1.12.6 P—l ————— 247.47—249.84 1 38°36.85' 115°40.11’ 5.920 9.12.14 P71 ————— 128-40-130-72 1 39°36-85' 115°40.11' 5.920 1.12.6 66 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 64.—Data for the record-section of the profile from Eureka(15) TABLE 67.—Data for the record-section of the profile from Hiho(20) to Mountain City(13) (fig. 20) to Lake Mead(22) (fig. 23) Trace No. Trace No. Distance of coordi- Coordinates Traces Distance of coordi- Coordinates Traces (km) mates and —. Elevation included (km) nates and .— Elevation included Station (traces 1. 6) elevation Lat Long (feet) in section Station (traces 1. 6) elevation Lat Long (feet) in section P—5 ————— 8.89— 11.27 6 39°36.85' 115°40.11'~ 5,920 1.6 K42 5.19— 8.23 1 37°51.15' 115°12.69' 10.5 K—5 ————— 26.46— 28.95 6 39°46.44' 115°4o.13' 5,920 1.6 T—2 16.87— 19.22 1 37°46.13' 115°08.55’ 9.14 1—5 —————— 39.77— 42.08 6 39°53.56’ 115°39.11' 6.140 2.6 P-2 23.85; 25.27 1 37°41.55' 115°10.75' 9,12 H—5 ————— 48.61~ 51.01 6 39°58.35’ 115°40.80' 6.150 1.6 Q~1 38.22— 40.66 1 37°33.69’ 115°1381' 11.14 Q—5 ————— 59.21- 61.69 6 40°04.10' 115°41.54' 6.100 9.5 S~1 42.20— 44.25 1 37°31.82' 115°08.32' 9.12 S—5 ————— 67.51- 70.03 6 40°08.60’ 115°41.80’ 6.100 9.5 L—l 56.06— 58.60 1 37°24.85' 115°04.40' 9.11.14 L-5 ————— 78.04— 80.43 1 40°14.25' 115°41.25' 5,910 6.12.1 H—l 65.63— 67.55 1 37°19.77' 115°03.12' 9.12.14 J—5 86.87— 89.34 6 40°19.09' 115°4o.10' 5.860 1.12.6 I—1——~ 76.90— 78.99 6 37°12.65' 115°12.23' 14.11.9 R-5 ————— 9823-10062 1 40°25.14' 115°42.16' 5.420 6.13.2 K-l 84.385 86.12 1 37°08.81' 115°08.21’ 2.11.6 P—6 ————— 10749-10978 6 40°30.05' 115°43.30' 5,400 1.11.5 T—1 96.69— 98.86 1 37°01.93' 115°14.10' 2,5 T—6 ————— 110.58—113.00 6 40°31.77' 115°43.80' 5.400 2.12.6 P71 ————— 10340—10490 1 36°59.98' 114°56.85' 9,13 §<—6 — ———115.07-117.58 6 40°34.35' 115°40.05' 5.700 2.6 —6—— ————125.4l—l27.81 6 40°39.77' 115°44.23' 2.6 -. . . H—G _ ——-—138.52—140.80 6 40°46.83’ 11504340 5900 1,125 TABLE 68.—Data for the record-section of the profile from Lake Q—6 — ~——148.81-151.08 6 40°52.29' 115°45.78' 5.440 10.12.14 - S-6 — ——158.'I5—161.16 6 40°57.78' 115°45.10' 9.11.5 Mead(22) to Eureka(15) (fig. 24) L—6 — ——169.14-171.52 6 41°03.00' 115°51.57' 6.100 1.4.6 R—6 — ——175.75—177.53 6 41°06.63' 115°45.18’ 6.500 1.4.14 P—7 — ——190.27—192.15 6 41°14.52' 115°45.75' 5,800 2.12.6 , Trace N9. , T~7 — ——195.58—197.85 6 41°17.55' 115°46.98' 1.12.6 DIStance ofcoordl- Coordmates , Traces K~7 - ——205.08—207.59 6 41°22.94' 115°43.39' 1.11.6 (km) mates {and Elevation {"61“de I-7 —— —-—216.17—218.65 6 41°28.73’ 115°48.75' 9.10.11 Station (traces l. 6) elevation Lat Long (feet) 1n section so — ———228.82—231.00 6 41°35.42' 115°48.60’ 6.380 9.12.14 —7 — —-241.28—243.42 6 41°42.19' 115°47.35' 6.370 1.11.5 a 1 o . J—7—— ~~246.32—248.58 6 41°44.96' 115°47.98’ 6.540 9.13 £47 —"‘_: 3%: 42(1):; ‘15 3343;; “1232} (‘5'? S—7 — ——249.10—251.45 6 41°46.52' 115°47.69' 6.500 11.14 1‘ __ 53'90_ “'73 6 3663468, 11494505 1'14 R—7 — ——254.54—256.10 6 41°48.77’ 115°53.25' 6.250 10,5 ‘ “‘ _ ' ' a ' . o ‘ . ' Q—7 ————— 265 73—267 93 6 41°55 23' 115°52 81' 6550 914 “'7 __ ‘ 58'82‘ 5°03 6 36 3733 “4 51'68 1'6 ‘ ‘ ' ‘ ' ' L—7 —— e 74.929 76.44 6 36°46.61' 114°48.09' 1.5 $77 *A — 78.145 80.09 6 36°48.49' 114°51.49' 1.6 Q77 ~e — 88.905 91.20 6 36°54.37' 114°53.72' 3.6 . . P»8 —— —100.357102.03 6 36°59.98' 114°56.85’ 1.6 TABLE 65.—Data for the record-sermon of the profile from Eureka(15) E33 __ $368—$131) g glogéjgi 11255;;g‘1’. 3:2 ' IA ——— —127.50—129 74 6 37°1265‘ 115°12.23' 1.5 to Lake Mead(22) (fig. 2“ H—8 —— ~137.59—13961 6 37°19.77' 115°03.12' 1.11.6 L—8 —— 44664—14919 6 37°24.85’ 115°04.40' 1.12.6 S~8 -— 7160.88-162 90 6 37°31.82’ 115°08.32’ 3.13.6 . Trace N94 . Q78 —— 7165.06—167 98 1 37°33.69’ 115°l3.81' 5.11.1 D‘S‘ance “WW" Cmrdmaws . Traces P~9 —— 47990-18125 6 37°41.55‘ 115°10.75' 1.12.6 . 1km) "8‘95?“ Elevamn .mC‘Ud9d r79 —— 48690—18902 6 37°46.13' 115°08.55’ 1.12.6 Stat1on (traces l. 6) elevat1on Lat Long (feet) 1n sect1on K-9 __ 7196.88-19923 6 37 651.151 “561269, 1.6 179——— 28011—21064 6 37°56.74' 115°17.11‘ 1.11.6 _ _ __ , _ . 39°27, . .. _ 51 H59 ,, 213975216 56 6 38°00.67' 115°12.72‘ 1.12.6 {if _ __ 1332.. 1:23 1 39023.33: ”2433,33 E1’55“ L—9 —— —226.50~229 13 6 38°06.99' 115°16.77' 1.12.6 1—4—— —— 19.32— 21.76 1 39°20.38' 115°38.86' 10.14 3-9 -- 43616—13335: 6 38°11}?! 115°19'50' $va __ ___.-_ 01‘, —9—— 244—‘4‘ .. if _ __ 333; 233: i 3301323, {(23323 3:}: P—10 -2 256 99-259 40 6 38°2326' 115°19.33' 1.11.6 p_4 _ __ 47.97_ 50.33 1 39905031 “50351;? 9'13 T510 ,‘ —266.69—267.97 6 38°28.62' 115°l4.25' 1.11.5 J_10 _ __ 76.13— 78.79 1 38°49.68' 115°38.10' 9'13 K~101~ —278.015279.99 6 38°32.53' 115"31.88' 1.12.6 H—3 _ __ 89.97- 91.74 1 38943.171 115°26.55' 9'11‘14 1710 —— —289.04—29l.39 6 38°39.30' 115°29.40' 1.12.6 Q_10_ __ 96.20- 98.52 1 38°39.36' 11592949 1.12.6 H—lO ————— 29581—29765 6 38°43.17' 115°‘26.55v 1.12.6 L—10 — —-—-108.34—110.51 1 38°32.53’ 115°31.88’ 2.12.6 ' R—lo — ——120.45—122.20 1 38°25.83' 115°34.20' .11,6 . . p_3 _ _128_19_130_59 1 3802326. 115419331 $3.12 TABLE 69,—Data for the record-section of the profile from Lake 3120 _ __}gg:§3_}iigé 1 38 1833 “5 39-73 {fig Mead(22) to Mono Lake(6) (fig. 26) S—2 — —-—l48.86—150.40 1 38°11.82' 115°19.50' 1.11.6 L—2 — ——158.40—161.03 1 38°06.99' 115°16.77’ 1.11.6 H—2 — ——171.08—l73.65 1 38°00.67’ 115°12.72' 1.11.6 . Trace N9 I--2 —— ——176.93—179.45 1 37 “56.74’ 115 °17.11' 9.14 Distance of word!" Coordinates . Traces K—2 — ——188.31—l90.65 1 37°51.15' 115°12.69’ 1.11.5 , (km) flares {and Elevation mcluded T—2 _ ——198.67—200.85 1 37 043.13' 115°08.55’ 1'11‘5 Stat1on (traces l. 6) elevatwn Lat Long (feet) in sect1on P—2 — ——206.28—207.63 1 37°41.55' 115°10.75' 1.11.5 3:11 — :"gég-gg‘ggggg } $335153: 112111631 )3}; T4; ————— 24.01~ 26.35 1 36°12.59' 11501.19 1.860 9.13 — " ‘ ' ' ., - . - , ' S—6 — 29.79— 32.26 1 36°13.56' 115°05.00' 1.900 1.6 L—l — ——238.43—240.97 1 37 24.85 115°04.40 10.12.14 Q_6 _ 37 78“ 4019 1 3661346. “501104. 2200 15 H—l — —-—-248.0l—249.97 1 37°19.77' 115°03.12' 9.12.14 P_6 _ 5045, 52'62 1 36015;”. “51.1693. 2'600 1'6 I—1—— ~—258.58—260.76 6 37°12.65’ 115°12.23' 12.10.9 L—6 _ 6088- 63‘33 1 3642337. 115.7155. 2'840 2'6 K—l — ——-266.53—268.l4 1 37°08.81' 115°08.21’ 9.14 1—6— ’ 68'0. , 70'“ 1 3602933, ”5022'”. 3'350 3'6 T—1 — ——277.83—279.86 1 37°01.93' 115°14.10' 10,13 KG 7 69'75, “'09 1 3602.86, 11562967. 2'880 1'6 P—1 ————— 28575—28730 1 36 °59.98’ 114°56.85' 9 14 ' ' ' . ' , ' ‘ . 1+6 7 77.70- 79.92 1 36°30.12 115°29.82 3.200 9.13 T—5 — 88.62- 90.58 6 36°27.41' 115°40.45' 5.150 13.9 s-5 40334710574 1 36°34.65' 115°46.7l' 3.900 9.14 Q—5 —109.02—111 49 5 36 °32.76' 115°52.40' 3.960 14.1 12-5 —115.92—116 19 6 36°33.12' 115°57.35' 4,000 14 _ _ 5 - ~ L—5 —131.28-133 23 1 36 °33.14' 116°08.64' 2.600 9.6 TABLE 66. Data for the record sectloh of the profile from H1ho(20) K—5 “39.71442 16 6 36.32.57. 116°15.00’ 2.500 14710 to Eureka(15) (fig. 22) 1—5— 449.994.52.49 1 36°34.20’ 116°21.60’ 2.500 1.6 T—4 ————— 16030—16250 1 36°36.69' 116°29.40’ 2.500 1.12.14 S—4 169.07~171.27 1 36°39.44' 116°3281' 2.520 1.11.6 N. 6:: ‘13823‘13l'22 1 223-3 3333 . .- . . _ — . — . ° . ' 11 °40.4 ' 4.4 .3.6 3353333 ——°° 53339 1 32:22-91 112222.32: 192 Stat1on (traces l. 6) elevat1on Lat Long (feet) in sect1on I—4 _ —224.17—226 21 1 37°03.81' 116°59.55' 4.300 11,” T-3 23313—235 18 1 37°08.80’ 117°03.02' 4.100 1.11.6 I—2 —————— 4.34— 6.65 6 37°56.74' 115°17.11' 9.14 S—3 —240.77—243 37 1 37°12.80‘ 117°06.09’ 4.000 1.14 H 2 ————— 9.51— 12.09 6 38°00.67’ 115°12.72' 1.14 , P—3 —252.68—255.36 1 37°15.15' 117°13.70' 6.000 9.14 L—2 ————— 21.40» 24.03 6 38°06.99 115°16.77' 9.10.14 L—10 —263.40—263.70 1 37°18.77' ll7°19.69' 6.400 10 S—2 ————— 32.23— 33.61 6 38°11.82 11509.50 9.12.14 K53 ~275.62—278.06 6 37°19.44' ll7°28.49' 5.600 6.12.2 P—3 ————— 51.91— 54.34 ‘ 6 38°23.26 115°19.33' 9.11.14 1~3— 1 37°17.55' 117°31.72' 4.510 12 T-3 ————— 62.16— 63.68 6 38°28.62 115°14.25' 9.13 S—2 1 37°19.66' 117°33.48' 5.500 9.12 K—3 ————— 73.83- 75.61 6 38°3253 115°31.88' 9.14 T—2 1 37°22.43' 117°36.26’ 7.100 9.14 I~3 —————— 84.15- 86.44 6 38°39.30' 115°29.40' 9.12.14 Q-a 1 37°26.99' 117°42.10' 6.000 9.13 H-3 ————— 90.71- 92.45 1 38°43.17’ 115°26.55' 6.11.1 P—2 —307.56—310.17 1 37°27.07' 117'1793' 5.300 9.14 L—2 —311.93—314.46 1 37°28.24' 117°50.50' 5.140 10.14 K—2 ————— 325.99~328.03 1 37°33.04' 117°58.08' 5.120 10.14 TABLES 55-108 67 TABLE 70.—Data for the record-sectzon of the profile from Lake TABLE 73.—Data for the record~sectwn of the profile from Mead(22) to Santa Monica Bay(4) (fig. 27) Ludlow(25) to NTS(19)(fig. 31) Trace N 0, Trace N 0. Distance of coordi- Coordinates Traces Distance of coordi- Coordinates Traces km) nates and ____._. Elevation included (km) nates and Elevation included Station (traces 1, 6) elevation Lat Long (feet) in section Station (traces l. 6) elevation Lat Long (feet) in section T—l 2.0 — 4.4 l 36°04.66' 114°49.68’ 1.470 2,6 P—4 ————— 3.00— 5.48 6 34°52.29' 116°11.56' 1,370 1,6 S-l — 17.7 — 20.2 6 35°58.93' 114°59.04' 2.330 1.6 L—4 ————— 13.48— 15.98 6 34°58.00' 116°11.09' 1,370 1.6 R—1 22.8 — 25.2 1 36°01.82' 115°02.86' 2.000 1,6 K—4 ————— 32.48» 34.78 6 35°07.78' 116°06.38' 970 1,6 Q—l — —— 35.4 1 35°58.23' 115°11.09' 2,500 1 T—4 ————— 36.80- 39.11 6 35°10.17' 116°06.40' 970 1.6 P—1 — 50.0 — 52.2 6 35°50.24' 115°15.71' 3,030 6,3 Q—4 ————— 39.51— 41.08 6 35°11.40' 116°07.61' 970 6 L—1 —- 602 — 62.7 1 35°46.32' 115°20.60' 2,930 1,5 R—4 ————— 51.70- 53.98 6 35°18.12' 116°04.91' 910 1,6 K—l — 65.2 — 67.7 1 35°44.70’ 115°23.24' 2,930 4.6 J—4 —————— 58.82— 60.30 6 35°21.74' 116°06.29' 910 1.6 J-1——— — 75.9 v 78.3 1 35°41.94' 115°29.58' 3,170 1.6 S—4 ————— 66.40— 68.47 6 35°26.36' 116°09.19' 760 1.5 1~1——— — 88.9 — 91.1 1 35°38.30' 115°36.68' 3,470 1.6 H—4 ————— 75.91— 78.31 6 35°31.71' 116°10.72' 760 1.6 H-1 — 98.8 —101.3 1 35°33.25' 115°40.75' 3,600 2.5 1—4 —————— 85.11— 87.07 6 35°36.35' 116°14.75' 760 1,6 T—2 —106.7 409.2 6 35°31.85' 115°48.10' 3,500 2.4 P~5 ————— 93.73— 96.20 6 35°4l.10' 116°17.64' 510 3.14 S-2 —118.9 7121.3 6 35°24.94' 115°53.18' 3,470 2.6 L—5 ————— 105.87»108.13 6 35°47.68' 116°05.77' 2.290 1.5 Q-2 — 140.0 —142.5 6 35°23.47' 116°07.44' 930 1,5 K—5 ————— 110.24—112.46 6 35°50.14' 116°08.39' 2.030 2.6 P—2 —149.9 -1513 6 35°22.98' 116°14.43' 1,400 2,14 T—5 ————— 12085—12324 6 35°55.89' 116°15.87' 1.520 1.5 L—2 —163.1 —165.6 6 35°15.70' 116°19.44' 1,970 10.13 Q—5 — ———132.12—134.60 6 36°02.15' 116°11.40' 3.150 1.5 J-2— -—174.3 —176.7 6 35°05.46' 116°19.16' 1,330 10.14 R—5 - ———140.90~143.38 6 36°06.90’ 116°10.90‘ 2.740 1.12.6 1—2— —183.3 —185.8 6 35°05.36' 116°26.80' 1.900 1,11.6 J—5—— ———150.15—152.25 6 36°11.66’ 116°08.02' 2.590 2.6 T-3 ——209.0 —2ll.3 6 35°02.22' 116°45.80' 1,730 1,4 S—5 — ———157.38—159.75 6 36"15.75’ 116°10.08' 2.590 2.12.6 H-2 ——211.5 —213.4 6 35°01.58' 116°45.80‘ 1.770 2,12.6 H—5 — ———166.96—169.28 6 36°20.67' 116°02.97‘ 3.050 1.12,14 S—3 —226.8 >229.2 6 34°59.86' 116°56.85' 2,670 1,6 I—5—— ———176.05—178.51 6 36°25.74' 116°04.26' 3.400 2.12.6 R-3 —223.2 —235.7 6 34°55.33' ll6°58.38' 2,330 9,14 P-6 — ———184.32—186.70 6 36°30.30' 116°08.34' 2.540 1.11.14 Q—3 —247.3 —249.8 6 34°49.02' 117°04.32' 2.600 9,14 L—6 — ———197.80-199.93 6 36°37.26' 116°02.64' 3.300 1.13 P—3 -—259.1 —261.5 6 34°49.72’ 117°13.44' 2.630 9.14 K—6 -— ————201.15—202.54 6 36°38.80' 116°05.70' 3.860 1 .6 L—3 —268.8 —271.2 1 34°45.68' 117°18.00' 2.630 14.9 R~6 —— —»—211.89—213.81 6 36°44.70' 116°01.11' 3.450 10.14 K—3 —-277.5 —279.7 6 34°42.02’ 117°22.28' 2.730 9.13 T—6 — ——-228.59-230.99 6 36°54.27' ll6°10.37' 4.780 10.13 J—3— —283.9 -286.4 6 34°39.21' 117°25.26' 2.770 11,14 J—6— ———241.70—244.16 6 37°01.30' 116°04.97' 4.170 9,14 l—3— —293.3 -295.8 1 34°37.06’ 117°29.60' 2830 9.14 1—6— ———249.59—252.09 6 37 °05.64' 116°07.12' 4,470 9,13 H—3 ————— 303.7 -306.1 6 34°37.73' 117°39.60' 2900 10.14 H—6 ————— 25764425974 1 37 °08.59' 116°04.93' 4.520 9,12 TABLE 71.—Data for the record-section of the profile from ngman(26) to NTS(19) (fig. 29) TABLE 74.—Data for the record-section of the profile from Trace No. Mo;ave(23) to Ludlow(25) (fig. 35) Distance of coordi- Coordinates Traces (km) nates and Elevation included Station (traces 1, 6) elevation Lat Long (feet) in section Trace N 9. Distance of coordi‘;l Coordinates El Traces (km) nates an evation included 5'2 ————— 7-13' 3-71 6 35°22.28' 114°06-99' 1-6 Station r 1. el va i n Lat Lon f et in sec ' Q-2 —— — 14.27— 15.31 6 35°24.44' 114°11.90' 1.5 1‘ aces 6’ e L 0 g le ' ”on P-2 —— — 29.23- 31.13 6 35°32.75' 114°16.39' 9.14 H—2 —— — 35.47— 37.29 6 35°33.65' 114°21.31' 1 .14 L—l ————— 9.77— 12.13 6 35°05.24' 117°52.82’ 5,900 2.6 K—Z —— — 45.89— 48.35 6 35°39.23' 114°24.70' 9,14 P-l — —— 19.68— 22.16 6 35°04.33' 117°45.84' 6.000 1.6 I—2——— — 56.52— 58.88 6 35°44.60' 114°27.67' 9.13 1-2—— —— 30.15— 32.52 6 35°03.45' 117°38.95’ 2,540 2,6 S—l —— — 78.80- 81.30 6 35°54.16' 114°36.82' 1,5 S-2 —— 48.74— 51.21 6 35°01.61' 117°26.70' 2,430 2,6 Q—l —— — 87.59- 90.00 6 35°57.95’ 114°40.25' 1,5 J—2—— —— 58.49— 61.11 6 34°58.86' 117°20.48' 2,200 1,6 H-l —— — 95.92— 97.59 6 36°01.74’ 114°42.46’ 9,14 R—2 — —— 69.34— 71.36 6 34°57.49’ 117°13.91' 2.170 1,6 K-4 __. —101.94—103.83 6 36°02.l4’ 114°43_49' 9,14 Q—2 — —— 77.14— 79.59 6 34°57.95' 117°08.38' 2.170 9.13 p-4 __ —106.16—108.19 6 36°04.65’ 114°49,33' 1,11,e T—2 — —— 87.95- 89.88 6 34°55.85' 117°01.91' 2,400 l,ll.6 T—l —— —120.76—121.69 6 36°08.82' 114°57.16' 1,12,6 K—2 — ~— 9841—10080 6 34°55.5l' 116°54.72' 2.100 1,4 K-1 .._ '—125.59-127.99 6 36°14.57' 114°55,14' 1,11,5 L—2 — ——109,50~111.79 6 34°57.25' 116°47.19' 2.400 2.6 1—1 ——— —135.18-137.29 6 36°18.25' 114°59.42’ 9,11 p-2 -— -—-124.21~126.74 6 34 °59.53' 116°37.l7' 1.770 9.14 Q_4 __ _141_05-143,48 6 36°13.91' 115°11,63’ 1,11,14 1—3——- ——128.29»130.75 6 34°53.65' 116°35.18' 1.800 9.12 5.4 .._ -151,44-153 so 6 36°18.60' 115°15,59' 9,13 H—3 — ——140.21—142.14 6 34°53.75' 116°27.62' 2,300 9.14 T—3 —— —163.55-165 80 6 36 °26,39' 115°17‘08' 9 S—3 — ——150.04—152.l7 6 34 °47.94’ 116°22.10' 2,200 9.14 5-3 __ —164.34-166 24 6 36 °31,5o' 115°09.86' 10,14 J—3—— ——163.25—165.32 6 34 °50.49' 116°12.82’ 1,540 9.14 1,4 __ —171.26—17370 6 397322 115°22.43' 9,14 R-3 — ——l70.50—17l.79 6 34°48.48' 116°08.91' 1.340 9.13 Q_3 __ —186.18—187 81 e 36°39.56’ 115°20.5s' 10,13 Q—3 — ——184.75—186.83 6 34°37.80’ 116°01.65’ 1,280 9.14 P—3 _ —196 75—198 92 6 36°48.73’ 115°17.65' 9,14 'I‘-3 — ——190.85—193.40 6 34°36.25' 115°57,71' 1.100 9.12 [,3 .__ _205.15_2o7.53 6 36°54.37' 115°17,54' 9,14 K—3 — ——207.25—209.49 6 34°40.91’ 115°45.51' 2.600 9.13 [(—3 __ —223.57—226.37 6 37°09’ 115°12.0' 1,14 L—3 — —-214.12—216.59 6 34°39.58' 115°41,10' 2.100 9.14 J—4—— —249.66—251 17 9,13 P43 ————— 227.10~229.64 6 34°4l.09' 115°32.01' 2.300 9,14 1—4 —— —256.76-258 60 6 37 °03.00' 115°59.72' 9.14 H-3 —- —262.54-264 48 6 36°54.4‘ 115°17.7' 9.11.14 R-4 —— —265.52-267.80 6 37°08.65’ 116°01.18' 9,13 T-4 ————— 27720—27941 6 37°11.45’ 116°09.00' 10.13 TABLE 72.—Data for the record-section of the profile from NTS(19) to Ludlow(25) (fig. 30) Trace No. Distance of coordi- Coordinates Traces (km) nates and Elevation included Station (traces 1, 6) elevation Lat Long (feet) in section R—55 —— — 66.29- 68.75 1 36°31.80' 116°08.50' 2,590 11 K—55 —— — 84.17— 86.74 1 36°23.50' 116°18.08' 2,240 2.6 Q—55 —— —103.23—105 36 6 36°10.50' 116°07.17' 2,590 6 P—55 —— —129.72—132 05 1 35°58.03' 116°16.13' 1.520 1.5 J—52 —- —140.25—142 28 1 35°47.53' 116°05.70' 2.290 2.6 J—55 —-— —147.40—149 70 1 35°47.70' 116°05.82' 2.290 2.6 K—52 —— —154.85—157 25 1 35°40.60' 116°17.93' 510 2.6 P—52 —— —169.85—172.29 1 35°31.75' 116°10.78' 760 2.6 J—51 —— —186.71—188.50 1 35°21.75' 116°06.30' 910 2.4 1—52 —- —207.89—209 96 1 35°10.97' 116°07.05' 970 1.4 1—51 —— -208.25—210 65 6 35°08.80’ 116°06.38' 970 6 S—52 ——- 214.87—21718 6 35°07.20' 116°07.28' 1.120 5.1 T—52 —— 232.51—235 00 1 34°57.80' 116°11.10' 1.370 1.5 L—51 -—- —246.89—249 02 1 34°49.36’ 116°11.02' 1,320 10,6 P—51 ——— —264.29—266 42 1 34 “39.85’ 116 °09.00' 1.930 9.4 S—56 ————— 31517—31736 1 34°11.96’ 115°57.60’ 1,730 10.6 TABLE 75.—Data for the record-section of the profile from NTS(19) to Navajo Lake(21) (fig. 41) Trace No. Distance of coordi- Coordinates Traces (km) nates and .——._.— Elevation included Station (traces 1. 6) elevation Lat Long (feet) in section 1-28 ————— 52.6 — 54.7 1 37°22.70' 115°31.95' 4.400 1.6 J-26 ————— 86.0 — 88.5 1 37°16.55' 115°06.35' 3.400 9.12 J-28 ————— 103.6 —106.1 1 37°19.75' 114°53.75' 4.600 9.14 Q—28 ————— 123.1 424.8 1 37°14.65' 114°39.25' 3.900 1.6 L-28 ————— 132.1 —134.2 1 37°18.20' 114°34.45’ 4.000 2.5 Q—26 ————— 171.6 —174.1 1 37°32.40' 114°11.85‘ 5.400 1.6 P-28 ————— 187.1 -189.0 1 37°37.55' 114°01.00' 6.000 1.5 1—23 ————— 20460-20464 1 37°49.80' 113°56.35' 5.700 9 S—26 ————— 222.6 —224.8 1 37°25.10' 113°34.10' 6.000 9,13 1—24 ———255.0 -257.5 1 37°36.10' 113°14.03' 5.500 10.13 J—24 —-——298.8 -300.9 6 37“52.90' 112°46.95' 5.780 9.14 S-28 — ———319.6 -322.1 1 37°37.65' 112°28.85' 7.000 1.6 L—24 —— ———356.3 -358.8 1 37°37.45' 112°04.50' 6.400 9.12 T-28 — -———387.9 -389.9 1 37°45.70' 111°43.45' 6,500 10,14 Q-24 ————— 409.1 —411.6 1 37°44.88' 111°29.48' 6.000 9.13 68 TABLE 76.—Data for the record-section of the profile from Navajo CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES Lake(21) to NTS(19) (fig. 42) TABLE 78.—Data for the record-section of the profile from NTS(19) to San Luis 0bispo(3) (fig. 44)) Trace No. Distance of coordi- Coordinates Distance Coordinates Traces (km) nates and (km) included Station {traces l. 6) elevation Lat Long Station (traces 1. 6) Long in section 1L2 ————— 248‘ 3.38 6 37°31.66’ 112°49.57’ L73 ————— 2.70 5.15 115°57.52' .4 H~2 —— ~ 15.087 16.39 6 37 “30,97' 112°58.50’ L~2 ————— 24.60~ 26,83 116°05.77' .11.14 R—2 —— a 23.57- 25.80 6 37°32.16' 113°05.06' K—3 ————— 36.00— 38.49 116°12.12’ .4.14 J—2——— ~ 3486— 37.46 6 37°33.45' 113°12.96' S—3 ————— 77.40— 79.93 116°41.87' .4 T—2 —— — 40.35— 42.79 6 37°28.94' 113°16.24’ R~3 ————— 78.50— 80.97 116°41.95’ S-2 —~ — 55.94— 58.26 6 37 °33.51‘ 113°27,09' T73 ————— 89.95~ 92.50 116°47.94' .11.6 K71 ~— — 67.01» 69.42 6 37°31.35’ 113°34.65’ P73 ————— 10652—10900 116°57.47' .5 Q71 7— — 71.52- 74.04 6 37°24.96' 113°3687’ T72 ————— 1254042742 117°11.40' .12.2 172 ~v~ — 85.00— 86.73 6 37°31.00' 113°46.39‘ L5 —————— 13296—13450 117°16.80' L~1 7.7 — 94.77— 96.70 6 37 029.80' 113°53.09' J—3— ———A134.487136,50 ll7°12.85’ .l2.6 P—l —— —104.15~105.91 6 37°37.20' 113°59.25' S—2 ———157.577159.60 117°27.40' .14 H71 w~ —116.39—118.65 6 37°32.70' 114°08.10' I—3— ——-~—158.04~159.60 117°16.79' R71 ._ —125.68~127.37 6 37°29.22‘ 114°13189' Q—29 w~~172.74—174.90 117°48,75' 9.11 J71~—— —143,76~144 80 6 37°28.34‘ 114°25,67’ Q~30 ———174.2l—176.58 117°49.58' 11.14 T—l —— 715513456 97 6 37°19,80’ 114°32.76' R—2 ———183.83—185.80 117°42.14' 14.10 K—3 —— —-167.567169 35 6 37°26,88' 114942.23' K~5 ———189.13—191.10 117°52.00' 10.13 Q—S —— wl76.47~178 71 l 37°26.97' 114°48.60' JAZA ——194.06—196.10 117°48.76' 10.12 [—3—— —186.15~188 63 6 37°25.93' 114°55.25' L74 ~ ——195.90—198.41 117°46.71’ 12.9 L—3 —— *195.04—197 .34 6 37°22.95' 115°00.84' Qv2 — ——199.50—201.97 ll7°52.10’ 10.13 P—S —— —203.45—205 79 6 37°20.76' 115°06.30' 1'2—— ~208.50—21101 117°56.42’ 9.14 H—3 —— —214.277216 77 6 37°21.26' 115°13.85' P—2 A—212,65—214.65 118°01.33' 9 R~3 v~ —230.18—230.31 6 37°25.35' 115°23.53’ K—4 k—213.04—215.00 117°52.00' 10.14 J73 —————— 23685—23932 6 37 “23.25' 115°29.44’ J-29 ~—219.62—221.86 118°06.65’ 9.12.14 T—3 ————— 248.16—25054 6 37 °20.90' 115°36.80' Q—3 —~221,58—223.60 118°02.12' 13 L—29 —-—255.27—257.50 118°40.30' 9.11.14 15— ——272.15—274.65 118°47.70' 9.13 1-4 — ——275.00—276.46 118°40.64' 10.14 L—30 — ~—281.38—283.69 118°53.09' 9.11.13 P45 ~ ——290.29—292.50 118°57.80’ 10.13 TABLE 77.—Data for the record-sectwn of the profile from NTS(19) 5'29 ——g%~§?-ggg-?g 3333433, £1,014}? to Elko(14) (fig. 43) 9—37 ——335.42—337.43 119°22.40' 9.13 J—30 ————— 35167—35420 119°27.90' 9.14 PA ~365.95—367.15 119 “41.60' 9.14 We N°- 163 ““““ 3333132333 118323181 3’1” . f r ._ . _ __ _ _ . _ ”1‘53“ 3553311 ——°° "2136-23312 63:22-23? 3-}: Station [traces 1. Si elevation Lat ong R— ——455.34-457.85 120033.50, ‘ T— ————— 475.46A 477.01 120°51.20' P—33 —— — 68.037 70.30 1 37°43.17' 115°53.22’ 1.5 J— — 97.74—100 27 1 37°59.90' 115°59.50’ 1.11.6 T—33 —— —116.32—118 61 1 38°09.78’ 115°55.83' 1.4. 3 3— 2 {333123-136 g i 33%??? 1120325132. $151.6 TABLE 7 9.—Data for the record-section of the profile from Shasta S— ~186145—18904 1 38°46.24’ 115°38.87’ 9.14 ‘ . P— —205.95—208 46 1 39°02.93' 115°45.00’ 9.13 Lake(5) t0 Mono Lake(6) (fig 46) L— —215.80—218 29 1 39°02.93' 115°45.00' 1.11.5 Q—38 —— —235.02—237.31 1 39°14.4' 115°41.0' 2.12.5 1—33 —— —248.45~250 88 1 39°20.90' 115°47.52' 1.11.5 . . Q— —256.947259 42 1 39°20.90' 115°47.52' 1 .14 Dmance Coordinates 3810:; 62—44 —— —262.09—264 58 1 39°2o.90' 115°47.52' 2.14 _ (km’ L F” u . P—38 —— —276.56—278 75 1 39°36.25' 115°45.44' 1.6 3mm" “races 1. 6) °“8 1“ 590m“ J— —301.89~304 37 1 39°55.24' 115°44.31’ 9.13 J—38 —— —327.72~330 25 l 40°04.1' 115°47.0' 1.11.6 1_4 ______ 10.80- 13.05 1 122°07‘21' 1 P— —367.817370 05 6 40 °30.05' 115°43.30' 9.12 H—4 _ 20.28- 22.61 6 122 °13_11' 6 T— —370.717373 17 6 40°31.77' ll5°43.80' 9.14 8—4 _ 33.14, 3511 1 122901.75, 1'6 K—45 —— —375.93—378 36 6 40°34.35' 115°40.05' 1.6 J_4_ 39.9% 42.22 6 121453.91, 1 T— —381.08—383 34 1 40°38.30' 115°43.51' 9.13 [H 50_57_ 5269 1 121.5019, L6 L45 ——— «385.62—387 89 6 40°39.77' 115°44.23' 9.13 Q_4 _ 58.3} 60.81 1 121 ”6159, 1 '14 P— ~394.20—396 64 6 40 “38.30' 115°43.51' 1.6 T_4 _ 7060- 72.78 1 121.4301, 1,6 H-45——- —398.66—401 01 6 40 °46.83' 115°43.40' 9.14 K_4 _ 80.48» 82.20 1 121.4115, 1'5 Q—45 ——— —408.75—410 87 6 40°52.29' 115°45.78’ 2.6 L_4 _ 92_02_ 94.35 1 12103064. 1‘6 S—45 ——— —418.77—421.07 6 40°57.78’ 115°45.10' 9.5 p_4 4004940210 1 121°25.60’ 1,6 L—45 ————— 42795—43027 6 41°03.00’ 115°51.57' 1.6 1_3_ _1o7_71_110_00 1 121021731 2.6 R—45 ————— 43565—43742 6 41 °06.63’ 115°45.18' 1.6 5—3 _____ 1263142189 1 121171656. 9‘14 J—3 13706—13925 1 121°10.11' 1.6 R—3 ————— 15032—152.” l 121 ”06.30' 1.6 T—3 —169.33—170 33 1 120°56.89' 1.6 K—3 —174.83—176 57 l 120 °51.60' 1.6 L—3 —184.09—185 99 1 120 ”49.57' 2.6 P—3 —197.89—199 33 1 120 “41.79’ 9.14 I-2 — —208.48—209 64 1 120 “39.12’ 9.14 H~2 —214.47—216 10 1 120°34.63' 9.14 8—2 —228.96—230 69 1 120°31.78' 9.14 J-2— —235,77—237 24 1 120°24.18’ 9.14 R—2 —249.43-250 72 1 120°22.50' 9.14 Q—2 —255.87-258 06 l 120°24108’ 9.14 K—2 -—279.054281 15 l 120°02.60' 9.14 L—2 ~287.20—289 29 1 120°01.30' 9.14 Hvl —316.96-318 56 1 119°42.32' 9.13 8—1 —322.86—325 04 1 119°42.22' 10.13 J-1— —336.99—338 67 1 119°32.70' 9.14 R-1 —346.56—348 20 1 119°29.30' 9.14 K—l —376.60—378 28 1 119°19.40’ 9.14 L—l —385.82—387.74 1 119°13.12’ 10.14 P—1 ————— 40310-40552 1 119°03.22' 9.13 TABLES 55-108 ' 69 TABLE 80.—Data for the record-sectton of the profile from Mono TABLE 82.—Data for the record-section of the profile from Chma Lake(6) to Shasta Lake(5) (fig. 47) Lake(8) to Mono Lake(6) (fig. 49) Trace No. Trace No. Distance of coordi- Coordinates Traces Distance of cocrdi- Coordinates Traces (km) nates and __ Elevation included (km) nates and __ Elevation included Station (traces l, 6) elevation Lat Long (feet) in section Station (traces 1, 6) elevation Lat Long (feet) in section P—8 ————— 13.46— 14.76 6 38°06.19’ 119°03.22' 6,640 1.6 J—l —————— 3.63- 4.66 6 35°47,98’ 117°47.81' 2270 1,6 L—8 ————— 22.54- 24.91 6 38°11.74' 119°13.12' 6,800 1.6 P—1 ————— 5.88— 8.23 1 35°44.10' 117°43.36' 2,190 1.5 K—8 ————— 30.93- 32.74 6 38°14.04' 119°19.40' 6,800 1,6 K—1 ————— 15.55— 16.99 6 35°51.61' 117°54.72' 3,400 1.5 T—8 ————— 45.03- 46.76 1 38°19.40’ 119°26.50' 7,600 1,6 H—l ————— 25.89- 26.27 6 35°59.24' 117°53.82' 3,360 2.5 R-8 ————— 61.63— 63.58 6 38°28.80’ 119°29.30' 6,400 1,6 L—l ————— 32.45— 34.24 6 36°05.19’ 117°49.22' 5.000 1,2,3,5,6 .I-8 —————— 71.38— 73.35 1 38°32.10' 119°32.74' 7,500 1 T—l ————— 45.43— 47.84 6 36°11.89’ 117°53.64' 4,400 4 T—IA ————— 76.01- 77.78 1 38°37.80’ 119°24.76' 1,6 I—1 —————— 53.82- 56.22 6 36°15.15' 117°59.09' 3,710 1,3,6 S—8 ————— 84.20— 86.41 6 38"36.91’ 119°42.22' 6,400 2,6 R—1 ————— 62.67— 63.71 6 36°20.39' 117°55.40' 3,660 1,3,6 H—8 ————— 91.24- 92.91 6 38°41.12’ 119°42.32' 6,800 6 Q-1 ————— 76.91— 79.02 6 36°29.33' 117°52.15' 3,620 2.6 L—1A 96.10- 97.99 1 38°39.97’ 119°48.14' 6,000 1,6 S—1 ————— 82.54— 84.84 6 36°29.76' 118°05.45' 6,000 1,6 1—8— 101.26—10306 1 38°39.09‘ 119°54.90' 7,800 2,6 P—2 6 36°35.67' 118°06.87’ 4,650 9,14 P-9 — —108.21-110.66 1 38°44.36' 119°54.50' 7,800 1.6 J—2— 6 36°40.58' 118°07.20’ 4,200 1,6 L—9 ————— 119.67—121.76 6 38°49.46' 120°01.30’ 6,400 1.6 L-2 6 36°4352' 118°10.04’ 4,200 4 P—lA ————— 12803—13003 1 38°53.55' 120°01.74' 6,600 1.6 K—2 6 36°48.37' 118°05.39' 3,840 1,5 T—9 ————— 150.46—151.45 1 38°54.23' 120°23.50' 5,600 1,6 H-2 ————— 11951—12124 6 36°47.00‘ 118°17.39' 5.800 1,6 R-9 ————— 158.65—159.81 6 39°02.23' 120°22.50' 6,200 1,6 T-2 ————— 12338—12599 1 36°51.94' 118°05.25' 5.600 3 J-9 —————— 17171—17319 6 39°10.76’ 120°24.18' 5.800 9,6 1-2 —————— 13621—13861 6 36°58.15’ 118°14.09' 3.840 9.6 S—9 ————— 178.45-180.27 6 39°10.61‘ 120°31.78’ 6.400 2,6 R—2 ————— 14577—14823 6 37°03.12' 118°16.00’ 4.300 1.5 H-2 ————— 19285-19448 6 39°18.95’ 120°34.63' 6,000 9,6 Q—2 ————— 15831-16028 6 37°09.22' 118°18.87' 4.200 9.14 1-9 ______ 19945—20054 1 390143.23 120139.43 4,300 2 P—3 ————— 165.49—167.96 6 37°12.99' 118°21.14' 4.050 1,5 P—1o ————— 209.63-21106 6 3925.99 120°41.79' 6,000 1,6 S—2 ————— 16749—16972 6 37°12.00‘ 118°27.80' 9.900 6 L-10 ————— 22297—22489 6 39°30.64' 120°49.57' 5,700 1.5 L—3 ————— 18372—18583 6 37°18.46' 118°36.51' 7.700 1,14 K-10 ————— 23239—23414 6 39°35.90' 120°51.60’ 5,000 1,6 K-3 ————— 19101—19290 6 37°23.32' 118°34.58' 5.200 1.6 T— 10 ————— 238.76—239.69 6 39 °36.30' 120 °56.89' 4,600 2,5 T-3 ————— 20540-20133 6 37 ”30.76' 118 °37.61' 6.400 1.5 Q—10 ————— 24857-25044 1 39 °4o.58' 121 °00,01' 5.500 1,4 Q—3 ————— 20666-20808 6 37 °31.41' 118 ”3804' 6.300 6 R—10 ————— 256.88-258.76 6 39 °43.62' 121°06.30' 5.300 1,6 R—3 ————— 23110-23354 6 37 °43.12' 118°46.60' 6.840 11.14 J—lo ————— 269.71-271.90 6 39°50.51’ 121°10.11' 5,600 1,14 J-3 —————— 23437-23621 6 37°40-76' 118°57.08' 7.900 1.5 S—10 ————— 281.11-282.71 6 39°53.91’ 121°16.56' 4,800 2,6 S-3 ————— 242-86-245-20 6 37 °46-34' 118°56‘74’ 7,400 9.13 1—10 ————— 29899-30128 6 40°01.75' 121°24.73' 6,700 1,6 H—3 ————— 25258—25499 6 37°52.12' 118°56.97’ 7.700 10.13 P—ll ————— 306.31—308.50 6 40°06.36' 12l°25.60’ 5,900 9,14 1—3 —————— 26053—26291 1 37°53.34' 119°02.46' 7.000 1.4 L—11 ————— 31461-31694 6 40°09.03' 121°30.64‘ 5,200 9,14 K-ll ————— 32730—32914 6 40°10.61' 121°41.15' 3,600 1,6 Q—11 ————— 34815—35014 6 40°22.10' 121°46.69' 3,000 1,13 , . , R-11 ————— 356.28—358.40 6 40°25.69’ 121°50.19' 2,900 9.14 TABLE 83.—Data for the record-sectwn of the profile from Chma I-11 ————— 396.61—398.79 6 40°43.34' 122°07.21' 1,400 1.6 . Lake(8) to northwest (fig. 51) TABLE 81.—Data for the record-sectwn of the profile from Mono Trace No. ' - Distance of coordi~ Coordinates 'h'aces Lake(6) to Chlna Lake(B) (fig' 48) (km) nates and __ Elevation included Station (traces 1, 6) elevation Lat Long (feet) in section Trace No. Distance “worm. Cmmmaces Traces S—6 ——————— 16.3— 18.4 1 35°5o.51' 117°54.33' 3.500 1,6 (km) “ms and Elevation included J—s ——————— 27.1- 29.5 1 35°52.58' 118°01.17' 6.700 1.6 Station (traces 1, 6) elevation Lat Long (feet) in section 41—2 ——————— 667' 68:0 1 35 °56~76' “$2856, 3300 “'10 1—6 ——————— 104.8—107.2 1 36°11.30' 118°47.76' 1.450 2.6 P-6 ——————— 114.1—116.4 6 36°19.92' 118°50.45' 3,600 1,6 1—12 ————— 10.78— 12.90 1 37°54.71') 119°02.62’ 7.000 2.6 L7 ——————— 131.1—132.1 1 36°29.48' 118°54.89' 1,200 1 H—12 ————— 20.12- 22.29 1 37°52.12' 118°56.97’ 7.700 1,6 1—8 ——————— 132.0—133.8 1 36°36.55' 118°48.35' 7,200 1,5 S—12 ————— 28.32— 30.58 1 37°46-34' 118°56.74' 7.400 1.6 P—8 ——————— 172.5-174.7 1 36°54.14' 119°07.30' 1,200 9,14 J—12 ————— 37.10- 38.62 6 37°39.58' 118°57.94' 7.900 3.6 R-12 ————— 42.57— 44.96 1 37°43.12' 118°46.60’ 6,840 9,14 3-12 ————— 67.01— 69 27 1 37°3(1)A(1)' 118°38.04' 6,300 9,13 - 2 ————— 6. - 70 2 6 37°3 .1 ' 118°3 .1 ' ,4 0 . . K)” _____ 833; 83§4 1 3732332. 1193253 2280 313 TABLE 84.—Data for the record-sectzon of the profile from Chma L-12 ————— 87.83- 89.84 1 37°18.46' 118°36.51' 7,700 1,6 ' s-7 ————— 10484—10720 1 37°12.00' 118°27.80’ 9,900 9,4 Lake(8) to west (fig. 52) P—12 ————— 1o9.18-111.48 1 37°12.99' 118°21.14' 4,050 10.14 Q—7 ————— 116.74—118.18 1 37°09.22' 118°18.87' 4,200 1,4 R—7 ————— 12832—13077 6 37 °01.92‘ 118°15.25’ 4.300 5 . Trace N9~ . I-7 —————— 13745-13957 1 36 “58.15' 118°14.09' 3.840 9.14 Dmmnce 0‘ word“ 000mm” . Tram H—7 ————— 15227—15413 1 36°47.00' 118°17.39' 5,800 9,14 . 1km) mites 9nd —- Elevatlon éncluded K—7 _____ 159.68—161.90 1 36 048-37' 118005.39' 3340 1,6 Station (traces 1, 6) elevation Lat Long (feet) 1n section 11.4 6 36°43.12’ 118°11.57' 4,200 5 -7 1 36°40~58' 118°07-20’ ”00 9-14 K—3 —————— 137.8-140.3 1 35°2520' 119°12.17' 350 11,14 P-7 - ~ 1 36°35-67, 118°06-37, 4-650 2’13 P-3 ——————— 164.4—166.9 1 35°21.36' 119°29.11’ 360 9,14 S—6 ————— 188.93-191.23 1 36 °29.76 118°05.45 6,000 1,6 s—3 _______ 20544079 1 3551756. ”9055.39. 1925 1 12 6 Q-6 ----- 19990-20133 1 36°29-33’ 117°52-15' 3-620 1 R—3 ——————— 2426-2434 6 35 °03.76' 120°17.19' 750 1'1 14 R—6 ————— 211.41-211.86 1 36°20.39’ 117°55.40' 3,660 1.6 ' I—6 —————— 21724—21968 1 36°15.15’ 117°59.09' 3,710 11,14 g—e ————— meg—228.? 1 36°11.89‘ 117°53.64' 4.430 1.6 —13 ————— 227. —230. 5 6 36°09.67' 117°53.31' 4,6 0 14 _ _ - - - L—6 _____ 24046442.” 1 36005.19, “7049.22, 5000 2 TABLE 85. Data for the record sectton of the profile from Chma H—6 ————— 24708-24776 1 35°59.24‘ 117°53.82' 3,360 11 Lake (8) to Santa Momca Bay(4) (fig. 53) K—6 ————— 259.29-261.58 1 35 °51.66’ 117°54.72' 3,400 9,6 J-6 —————— 269.77—272.21 1 35°47.98' 117°47.81' 2,270 9,14 :6 ————— 27916-22315,? 1 35 °44.10' 117°4(3).36' 2,1343% 90'13 Trace N0 -13 ————— 294.11— . 5 1 35°36.38’ 117°4 .15' 2, ,12,14 Distance ofcoordi; Coordinates hm e . a . I— 3 ————— 30845-91074 1 35 24.63 117 49.23 2,500 2.5 (km) news and Elevation included Station (traces l, 6) elevation Lat Long (feet) in section 54 ——————— 12.3- 14.7 1 35°40.98' 117°45.47' 2,350 1.6 T—s ——————— 21.4— 23.8 1 35°36.45' 117°5o.15' 2,700 1.6 Q-2 ——————— 48.6- 50.8 1 35°32.99' 118°12.32‘ 3,850 9,14 Q-1 ——————— 60.6- 63 o 6 35 °21.82’ 118°13.00' 4,000 9.14 1-1 ——————— 76.1- 78.4 1 35°09.11' 118°03.37’ 2,550 9.12 S-5 ——————— 991-1012 6 35°01.06’ 118°20.90’ 4,050 1,6 13- ——————— 1322-1345 6 34°49.01' 118°38.50’ 3.000 10.14 R- 1 34°33.54' 118°29.24' 1.730 2.6 K— 1 34°33.59' 118°34.36' 1.400 1 ,14 K— 6 34°26.90' 118°39.15' 1.400 9.14 I- 6 34°18.81' 118°36.45' 1,750 9.14 1—5 ——————— 2073-2093 6 34°02.82' 118°38.30' 400 9,12 70 TABLE 86.—Data for the record-section of the profile from Mono Lake(6) to Santa Monica Bay(4) (fig. 54) CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 89.—Data for the record-section of the profile from Mono Lake(6) to Fallon(9) (fig. 57) Trace No. Distance Coordinates Distance of coordi- Coordinates Traces [kml Elevation [km] nates and Elevation included Station (traces 1. 6] Long (feet) Station (traces 1. GD elevation Lat Long (feet! in section 1—3 ——————— 3.2- 52 1 119°05.99' 6.480 1.3.6 1—2 ——————— 47.3— 49.8 1 38°22.22’ 118°54.10' 6.000 1.5 K»3 — 10.94 134 1 119°06.01' 7.120 9.11.14 K—z —— 54.4— 56.9 6 38°28.00' 118°54.75’ 6.400 1.6 L—3— — 20.57 227 1 119°03.37' 7.740 10.14 L—2— —— 83.4— 85.3 1 38°43.52' 118°58.50' 4.730 11.14 .1—3— — 40.4— 413 1 118°59.71’ 8.400 3.6 P—2— ——113.4—115.4 1 38°58.80' 118°50.50’ 4.200 10.13 s—3— — 94.07 96.3 6 118°36.05’ 8.400 2.5 Q~2— ——124.6—127.0 6 39°06.70' 118°53.20’ 4.300 1.5 Q—3— —133.8—141.1 1 118°57.80' 6.500 2.4 T—2— ——143.2—144.6 6 39°10.06' 118°50.90' 4.050 1.6 P—3— —187.8—189.8 6 118°47.20' 3.600 1.6 s-2— -—173.0-175.5 1 39°31.65' 118°51.35' 4.000 12.14 11-1 ~ 198242005 6 113°41.00' 6.200 2.6 J—2 ——————— 178.3—180.6 1 39°34.46' 118°50.47' 3.960 1.6 1~1 — —218.4—220.0 6 118°32.45' 6.800 2.5 .1—1 — —224.6—226.2 1 118°32.40' 4.800 2.6 K-l —240.5~242.3 6 118°26.90' 3.200 9.14 . . L_1__ _259,4_231,e 1 11802505 2.760 1.5 TABLE 90.—Data for the record-sectwn of the profile from PAl—— —271.1-273.3 1 118°15.95’ 2.920 9.14 ~ - Q—1—— —288.3-290.0 1 118°20.78’ 6.500 1.6 Fallon(9) to Chma Lake(8) (fig. 58) R—1—— —300.0—3o2.2 6 118°23.45’ 3.100 1.6 8—1 —— —318.8—321.2 6 118°27.20’ 4.000 9.5 T—1 ——————— 366.9—368.9 6 118°43.80’ 3.600 9.14 Trace No. Distance of coordi- Coordinates Traces km nates and . Elevation included Station (traces 1. 61 elevation Lat Long (feet) in section TABLE 87.—Data for the record-section of the profile from . . J-19 —————— 4.0— 6.2 6 39°34.46' 118°50.47' 3.960 1.6 Fallonl9) to San Franciscan) (fig. 55) R—9—— —— 10.67 13.0 6 3925.30 118°48.00’ 3.960 2 R—10 — —— 18.7~ 20.9 1 39°22.00' 118°47.70' 3.930 1.6 T—19 — —— 285 1 39°16.06' 118°50.90' 1 1-1—10 — 38.2— 40.5 6 3909.66 118°49.35' 4.800 1.6 Distance Coordinates Q—19 - 45.7 1 39°06.70’ 118°53.20' 1 (km Elevation P~19 — -— 58.4— 60.5 6 38°58.80' 118°50.50’ 4.500 1.6 Station (traces 1. 6, Long [feet] 1-9 —— —— 67.7— 70.2 1 38°55.32' 118°45.88’ 4.100 9.12 1-10 — —— 82.0— 842 6 38°4823' 118°41.03’ 4.250 2.6 S410 — —— 97.0— 994 6 38°38.76' 118°38.65’ 4.200 1.5 K-15 —————— 6.6- 8.7 6 118°58.00' 4.030 1.6 S~9— ——100.9—103.2 1 38°38.04' 118°38.00' 4.130 2.6 L—15 —— — 17.6— 19.9 1 119°02.65' 4.200 1.6 P—9— ——109.7—112.2 6 38°34.00’ 118°27.40’ 4.450 2.6 H-15 —— — 33.4— 34.8 1 119°12.45' 4.200 3.1 P-lO — ——133.94136.3 6 38°19.28’ 118°33.20’ 5.700 1.6 H5 —— — 48.9— 51.2 1 119°21‘90' 4.250 1.5 1—14 — ——159.0~161.0 6 33°04.10' 118°46.46' 6.900 2.6 J—15 — — 62.‘ — 64.5 1 119°30.85’ 4.360 1.6 —14 — ——165.1-167.4 1 38°02.32' 118°45.50' 7.120 2.6 P-15 — — 65.1~ 67.6 6 1193420 4.350 10.13 K-14 — ——176.17178.6 1 37°56.66’ 118°56.66’ 6.540 9.14 Q-15 — — 8140- 83-1 6 119°42-05' 4.700 1.14 J—14 — —186.1—1886 1 37°51.80’ 118°34.80’ 6.440 2.6 P~17 —— — 94.2- 96.6 1 119°48.85' 5.000 1.11.5 T—14 — —210.9-211.9 1 37°37.90' 118°39.35’ 7.520 9 R—ls —— — 94.6- 97.0 1 119°47.10' 4.700 14 K—13 — -—210.1—212.3 1 37°39.25' 118°34.90’ 6.750 4.14 8—15 — —106-3—1081 6 119°54.50' 7.200 12 P—14 — ——213.1~215.5 6 37°37.04' 118°24.09’ 4.540 2.6 K—17 —— —114.8-116 5 6 119°57.60' 6.500 1.12.6 Q—12 — ——216.2-220.6 1 37°34.38' 118°33.90' 6.700 1.11.5 1—17 — —120.0-1209 1 119°55.35' 7.300 1.11.6 T713 — ——219.9—222.1 1 37°33.28’ 118°39.30' 6.560 1 T—15 — —120.9-122 1 1 120°02.75’ 6,400 5 R—13 — ——254.1—256.4 6 37°13.45' 118°36.08’ 8.500 9.12.14 L—17 — —122.9—1250 6 120°03‘60' 7.200 2.5 T—12 — ——261.3—263.0 1 37°12.34' 118°21.00' 4.050 10.13 K-16 —— —140.0—1415 6.640 1 14 8—11 — ——271.1-273.5 6 37°05.94' 118°19.10' 5.400 9.14 L-16 — —152.1-154 2 6 120°24-00' 5.400 91 K—12 — ——305.6-308.0 6 36°49.13’ 118°05.38' 4.400 9.13 H-16 —— —157~5-159 9 6 120°28‘44j 47920 9, J—13 — ——327.3—329.7 1 36°37.22’ 118°04.85’ 3.760 13.10 [-16 - —172.0-174 2 6 120°35-60, 3,450 1, K—ll — ——331.5—333.9 6 36°37.00’ 118°00.50’ 3.680 11 J—16 — 4856—1880 1 120°42~60 2,100 2, J—12 — ——334.5—337.0 1 36°34.36’ 118°05.85' 4.620 9.12.14 P516 — ~1973-1993 6 120°50-45j 1.200 1, s-13 — ——390.2—392.6 1 36°11.05' 117°53.55‘ 4.600 9.14 Q-16 — —212-1-214 3 1 120°59‘20, 600 9. J—11 — ——391.7~394.1 6 36°03.68' 117°52.90' 4.200 9 R46 — —226-0-227 5 1 121°07-47, 170 9 s-12 — ——397.2~399.7 1 36°01.68’ 117°54.45' 3.340 10.12 8-16 — 4352-237 3 1 121°11-62 100 2 Q—ll —————— 4419—4444 1 35°38.44' 117°49.32' 2.500 10.13 J—18 — —246.3—2493 1 121°18.15’ 50 9 Q47 — ~269.9—2721 1 121°32.45' 0 1. T~17 —— —291.7-293.7 6 121°41.35' 220 1. P48 ------ 2933-2961 1 121°48-20’ 100 1 TABLE 91.—Data for the record-section of the profile from Mono TABLE 88.—Data for the record-section of the profile from Lake(6} to Lake Mead(22) (fig. 59) Trace No. Fallon(9) to Mono Lake(6) (fig. 56) Distance of coordi- Coordinates Traces (km) mates and Elevation included Station (traces 1. 6) elevation Lat Long (feet) in section 13‘5”“ Cw’dmms . S— 1 A 10.37 6 37 °56.20' 119 °01.47 ' 3.6 . “m“ _=L' Elevation K—l 41.80 6 37 °56.34' 118°3926' 6.530 2.5 3mm" ("8665 1' 6) (mg “88” P—l 52.49 6 37 "4800' 118°34.60' 6.500 1.6 Q-2 62.05 6 37°44.10' 118°29.70' 2.5 _ ______ _ a . T—l 71.21 6 37°41.36’ 118°24.46' 2.5 %_l39___ _ 13:3 133 2 333.3%; 3:323 :2 s—1 . 81.19 6 37°35.53' 118°20.87' 5.000 2.5 “40 __ _ 18} 20.9 1 118,447.70, 3930 16 K—2 ——110.87~112.82 6 37°33.04' 117°58.03' 5.120 2.6 T49 __ _ 8.5 1 11835090 ‘ 1' L—2 —-124.24—126.77 6 37°28.24( 117°50.50' 5.140 1.6 H_10__ _ 38} 405 6 11864935 4.800 1.6 P—2 . 131.13 6 37°27.07' 117°47.93' 5.300 1.6 Q_19 __ _ 5.7 1 118653201 1 T~2 -—148.09 150.37 6 37°22.43' . 117°36.26' 7.100 2.6 P_19 __ _ 58+ 60 5 6 “805050. 4500 16 8—2 - ———154.32—156.39 6 37°19.66' 117°33.48’ 5.500 2.6 H‘" — 1‘6 ' 1' {4‘33" "1232312313 2 33333? {$331133 $233 3'5 (15_113__ 427514322 (15 3303333. 3138 1': P—3 — ——183.53—186.20 6 37°15.15' 117°13.70' 5.600 1.11.5 H_11__ 45054530 6 119413.151 6'800 5'1 T—3 — ——203.64—205.61 6 37°08.80' 117°03.02' 4.100 1 .5 Q_9___ 458.5460 5 6 11900238. 6'640 1'5 [—4 —— ——212.45-214.51 6 37°03.81’ 116°59.55’ 4.300 9.12.14 1—20 __ _173 6,175 6 1 119505 99. 6'480 1'6 K—4 — ——226.53—229.02 6 36°57.12’ 116°53.06’ 4.380 2.12.6 Q_13 __ 4813,1836 1 119415324. 9'840 2' L—4 ~ —-236.43-238.57 6 36°55.81' 116°46.56' 9.13 K,” __ _183_1_185 6 1 11940601, 7'040 9 P—4 — ——246.95—249.03 6 36°52.99’ 116°40.46’ 4.400 9.13 1,20 __ 491.2493 4 1 11930337. 7'760 1' Q4 - —-256.33—258.32 6 36°48.80’ 116°36.28' 3.300 9.13 J_20 ,_ _209 9_212 2 1 118359 77, 8'400 9' S4 — ——269.53—271 93 6 36 °39.44' 116°32.81’ 2.520 9.12.14 s-20 __ —254:1-2566 6 118°36:08’ 8'500 1' T-4 — —278.98—281 40 6 36°36.69' 116°29.40' 2.500 9.12 p_13 __ _291_8_294 3 1 11990730. I'm, 9" 1—5 —— ——288.97—291.22 6 36°34.20' 116°21.60' 2.500 1.11.5 p_12 __ _307_7_3097 6 11835335, 6‘200 10 K—5 — ——298.60—301.11 6 36°32.57' 116°15.00' 2.500 10.13 ]_13 __ —321.0—323 5 1 11834835, 7'200 1 L—5 — ——306.90—308.56 6 36°33.14' 116°08.64' 2.600 10.12 T_20 __ _345.4_347'6 6 118°52.65' I'm) 9 P—5 — ——322.53-323.00 1 36°34.32' 115°56.81’ ,4.000 14.9 13—20 ______ 356 $3585 6 118047 20, 3'600 9 Q—5 _ _ _- 327.26»329.72 6 36°32.76’ 115°52.40' 3.960 9.11.13 ' ' s-5 — —‘332.99—335.42 6 36°34.65' 115°46.71' 3.900 9.11.13 T75 H ~—343.25—350.13 6 36°27.41' 115°40.45' 5.150 9.12 H—5 ————— 36126—36332 6 36°30.45' 115°27.90' 1,14 VVAWfi .4,V,‘_ 4 fi‘!‘ ‘ ’ “‘1— ,. TABLES 55—108 TABLE 92.—Data for the record section offan observations from Mono Lakelb‘l at 230 km distance (fig. 60) 71 TABLE 95.—Data for the record-section of the profile from Camp Roberts(2) to Santa Monica Bay(4) (fig. 66) Trace No. Trace Trace N o. Azimuth Distance of coordi- Coordinates included Distance of coordi- Coordinates Traces (epicenter (km) nates and Elevation in (km) nates and Elevation included Station to station) (traces 1. 6) elevation Lat Long (feet) section Station (traces 1. 6) elevation Lat Long (feet) in section 23643—23857 6 36°55.81' 116°55.8l' 13 H—3 —————— 4.4— 6.8 1 35°46.81' 120°47.10' 700 1.3.14 23616—23730 1 36°45.23' 116°56.10' 3800 3 1— —— — 15.4— 17.6 6 35°40.05' 120°43.50' 900 1.6 23383—23561 6 36°34.26' 117°08.59' 400 14 K—3 — — 42.9- 45.4 1 35°31.40' 120°29.34' 1.6 24870—25053 1 36°25.71' 117°06.55' 5.600 9 L—3—— — 59.3- 61.8 6 35°26.31’ 120°18.15' 1.550 1.4.6 . 24040—24182 1 36°22.69' 117°17.01' 4.800 3 P—3—— -— 72.5— 75.0 1 35°21.08’ 120°14.38' 2.250 1.6 Q—13 ———140.3 23758—24003 1 36°20.15' 117°25.13' 1.550 1 Q—3—— —— 94.2— 96.7 6 35°13.51' 120°01.25' 2.000 1.4.6 R—13 YA—143.1 22136—22362 1 36 “23.26' 117°37.85' 4.900 9 R-3—-— —-102.9—105.4 6 35°09.34' 119°58.06' 2.750 4 J—13 ———146.4 21962—22209 1 36°20.14' 117°45.45' 4.700 9 S—3—— ——121.9—124.4 1 35”01.69' 119°51.86' 1.500 10.13 S—13 v— 151.4 22799723025 6 36°09.67' 117°53.31' 4,600 14 T-3—— —132.8—135.2 1 34557.38' 119°46.98' 2.200 1.4 JilAA—~166.5 224.71~226.20 1 36°00.86' 118°32.40' 4.800 6 H-4 — —149.5—152.0 1 34“50.35' 119°40.15' 10.14 1-4 -— 159.9-162.4 1 34 °47.21' 119°34.17' 9.12 J-4 —— 175.8—178.3 6 34 ”42.26' 119°23.37' 3,500 9.13 E—4 — —194.3—196.5 1 34°34.22’ 119°16.67' 3.700 10.14 ‘ . . —4—— —202.1-204.6 1 34°32.20' 119°13.39' 3.400 9.14 TABLE 93.—Data for the record-section of the profile from San p_4__ 415.5418.) 1 34°26”, “9.07.05. 9.14 ' ' Q—4—— —232.9-235.0 6 34°19.36' 118°58.50’ 700 10,13 Franciscan) to Camp ROberts(2) (fig' 64) R-4—— —249.7—251.3 6 34513.51' 118°50.55’ 1.000 10.14 S—4——— —264.3—266.4 1 34°08.17' 118°43.55' 750 10.14 T—4 ——————— 2671—2691 6 34°04.40' 118°45.18' 2 000 11.14 Trace No. Distance of coordi- Coordinates Traces (km) nates and Elevation included Station (traces l. 6) elevation Lat Long (feet) in section H—6 —————— 25.4— 27.9 1 37 °34.54' 122°24.40‘ 350 1.6 1—4 -_ — 33.1— 35.6 1 37°24.18' 122°24.22’ 200 ‘ 9.14 J—G —— — 45.7— 47.7 6 37°19.52’ 122°16.75’ 750 1.6 K-4 —— ~~ 64.2- 66.2 6 37°14.00' 122°06.18’ 2.14 L—4—— ~ 70.7— 72.7 6 37°06.64' 122°08.75’ 2.6 P-6—— —- 82.9— 84.9 1 37 °01.52' 122 °05.73’ 1.150 1.6 Q—6—— — 96.9— 98.8 6 36°59.30’ 121 “53.00’ 200 2.6 R—6—— —108.5—111.0 6 36°53.76’ 121 °48.95' 10.11 S‘6—— —111.7—1141 1 36°52.46' 121°49.30' 25 9.12.14 T—6—— —126.8—1293 6 36°43.18' 121 °44.43’ 20 10.14 H—5 —137.7~140 O 6 36°38.36’ 121°40.37’ 40 10.12.14 J—5 ———- —161.4—163 9 6 36°29.04' 121°29.20’ 150 2,4,6 K-6 —l76.8—1792 6 36°23.50’ 121°21.95' 150 9.12.14 L-6—— —194.l—1964 1 36°15.58' 121 D17.65' 550 1.12.6 P-5— —208.3—210 2 6 36°09.56’ 121°09.90' 900 9.13 Q~5— —217.0—219 3 1 36 °05.78’ 121°08.85' 1.000 10.14 R-5—— —227.4—229 5 1 36 °01.42’ 121°04.05’ 1.500 9.6 S-5—— —-240.5—243 0 1 35°56.66' 120°57.30’ 1.100 9.14 L5 — —-275.l-277.4 1 35°40.80’ 120°44.89’ 900 10.13 K~5 —303.5—305.5 1 35 °31.40' 120 D29.34’ 9.12.14 L-5 ——————— 3192—3216 6 35°26.30’ 120°18.ll’ 1.760 11.14 TABLE 94.—Data for the record-section of the profile from Camp Roberts(2) to San Franciscan} (fig. 65) Trace No. Distance of coordi- Coordinates Traces (km) nates and Elevation included Station (traces l. 6) elevation Lat Long (feet) in section T—2 ——————— 6.5— 8.7 l 35 r’50.90' 120°50.85' 500 1.6 S—2— —— 17.6— 20.1 6 35 °56.66' 120°57.30' 1,100 1.6 R—2— ~——— 312- 33.3 6 36°01.42' 121°04.05' 1.500 2.6 Q—2— —- 41.9— 44.2 6 36°05.78' 121°08.85' 1,000 1.6 P-2— —-— 51.5v 53.8 1 36°09.22' 121°ll.36' 800 1,6 L—l — —— 66.5— 68.8 1 36 ”15.58' 121°17.65' 550 5.1 K-l —— 82.1— 84.6 1 36°23.50’ 121°21.95’ 150 9.11.14 J—2— —-— 93.6— 95.1 1 36°22.98' 121°34.45’ 1.550 1.6 1—2 —— —— 99.2—101.5 1 36°23.72' 121538.70' 800 1.6 I—l — ——104.6—106.8 l 36°32.42' 121°32.35' 90 9,14 H—2 —-120.6—123.0 1 36°38.36' 121°40.37' 9.11.13 T—l— ———131.4—133.9 1 36°43.18' 121°44.43' 20 9.13 S~1-— ——l49.4—151.8 6 36°52.46' 121°49.30' 25 14.9 Q—l— ——‘163.5—165.4 1 36°59.30' 121°53.00' 200 1.5 P-l— ——175.7—177.7 6 37°01.52' 122°05.78' 1.150 9,14 L—2— ——187.9-189.9 1 37°06.64' 122°08.82' 1 .13 K—2 ——196.4—198.4 1 37°14.00' 122°06.18' 10,13 J—l — ——214.97217.1 1 37°19.52’ 122°16.75' 750 9.14 1'1—1 —————— 240.4»2429 6 37 °34.54' 122 °24.40' 350 10.12.14 TABLE 96.—Data for the record-section of the profile from Santa Monica(4) to Camp Roberts(2) (fig. 67) Trace No. Distance of coordi- Coordinates Traces (km) nates and Elevation included Station (traces 1. 6) elevation Lat Long (feet) in section T—10 —————— 19.1- 21.1 1 34°04.40' 118°45.18' 2.000 1.5 S—10 —————— 19.5— 21.6 6 34°08.17' 118°43.45' 750 2.6 R—10 —————— 36.3- 37.9 6 34°13.51’ 118°50.55' 1.000 6.1 Q—lO —————— 52.6v 54.7 1 34°19.36’ 118°58.50' 700 2.6 P—10 —————— 69.2» 71.7 6 34°26.88' 119°07.05' 1,6 L»10 —————— 83.07 85.5 1 34°32.20' 119°13.39' 3.400 6.12.1 K—10 —————— 90.5— 92.7 6 34°35.22’ 119°16.67’ 3.700 3.14 J-10 —————— 109.6—112.1 1 34°42.26' 119°23.37’ 3.500 2.5 1—10 —————— 125.171276 6 34°47.21' 119°34.17' 1.5 11-10 —————— 135.8—1383 6 34°50.35' 119°40.15' 9.13 T—9 ——————— 1523—1547 6 34°57.38' 119°46.98’ 2.200 1.6 S—9 ——————— 1631—1656 6 35°01.69' 119°51.86' 1.500 2.14 R—9 ——————— 1822-1847 1 35°09.34' 119°58.06' 2.750 11.14 Q—9 ——————— 1900-1925 1 35°13.51' 120°01.25' 2.000 9.14 P—9 ——————— 212.6—215.1 6 35°21.08' 120°14.38' 2.250 9.14 L—9 ——————— 2259—2284 6 35°26.31' 120°18.15' 1.550 13.9 K—9 —————— 2421-2446 6 35°31.40‘ 120°29.34' 9,14 J—9 ——————— 260.4—262.6 6 35°36.94' 120°37.30' 900 13.9 1—9 ——————— 271.2~273.4 1 35°40.05' 120°43.50' 900 9.13 H-9 —————— 281.3—283.7 6 35°46.81’ 120°47.10' 700 9.14 TABLE 97 .—Data for the record-section of the profile from Santa Monica Bay(4) to Mono Lake(6) (fig. 69) Trace No. Distance of coordi- Coordinates Traces (km) nates and Elevation included Station (traces 1. 6) elevation Lat Long (feet) in section [—3 ——————— 35.0— 36.3 1 34°18.82' 118°36.45’ 1.750 2.6 K—5 — — 50.4— 51.4 6 34 °26.90' 118°39.15' 1.000 13.10 K—3 — — 60.0— 62.0 6 34 °33.59' 118°34.36' 1.400 1 R—5—— — 60.7— 62.2 1 34°33.54' 118°29.24' 1.750 6.1 T-ll — — 76.3— 78.2 1 34 °40.42' 118°43.80' 3.600 1.12.6 R—3—— — 90.8— 93.3 1 34 °49.01' 118°38.50’ 3.000 1.6 R—2—— — 94.0— 96.5 1 34°50.32' 118°23.70' 2.650 9.14 8—5 ——— —111.8—114.3 6 35°01.06’ 118°20.90' 4.050 1.1.1.6 S—11 —— —126.7—1291 1 35°08.42' 118°27.25' 4.000 10.12.14 R—ll —— —147.7—1499 1 35°19.54' 118°23.45’ 3.100 9.14 Q—2——-— —154.3—156 8 1 35°21.82' 118°13.00’ 3.950 10.14 Q-ll — —161.1—1629 6 35°27.58’ 118°20.78' 6,500 9.12.14 S-3 —— —168.6—171 1 1 35 °32.62’ 118°30.50' 3.360 5.2 Q—3—— —172.2—174 7 6 35°32.99' 118°12.32' 3,700 9.14 P—11 — —181.4—183 7 6 35°38.38' 118°15.95' 2.900 9.14 J—4 ——— —185.5-185 9 1 35°40.25' 118°22.70' 2.500 13 L—11 — —188.3—190 6 6 35 ”42.96’ 118°25.05' 2.600 9.12 J—2 —— —203.0-205 2 6 35 °50.94' 118°27.00' 3,050 10.12.14 J-3 —— —215.8—217 7 1 35°56.76' 118°28.53' 8.600 9.12 J—ll —— —221.7—223 3 6 36°00.86' 118°32.40' 4.800 11.14 1-11 — —228.2—229 7 1 36 °03.46’ 118°32.45' 6.800 10.14 I-6 ——— —243.6—245 9 1 36°11.30' 118°47.76' 1.500 10.14 H-ll — —245.3—247 6 1 36°12.60' 118°41.00’ 6.400 12 P—6—— —255.3—257 8 6 36°18.96' 118°50.37’ 3.600 9.14 1-7 —— —278.2—2799 1 36°29.48' 118°54.89’ 1.200 9.14 1-8 -— —290.3—292 8 1 36 °36.55’ 118 °48.35' 7,200 10.12 P—8—— —323.4—325 9 6 36°54.14’ 119°07.30' 1.150 9.11 T-7—— ——353.7—3560 6 37°12.33' 118°21.00’ 4,020 9.11.13 R-8—— —357.5—359 8 1 37°13.45' 118°36.08' 8.600 .12 T—8—-— —392.2-394 4 6 37 °33.30' 118 °39.32’ 6.560 10 Q—7—— -394.0-396.4 6 37 “34.38' 118°33.90‘ 6.700 9.14 Q—S ——————— 4396-4421 1 37°55.31' 119°15.24' 9.950 10 72 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 98.—Data for the record-section of the profile from Santa Monica Bay(4) to China Lake(8) (fig. 70) TABLE 100.—Data for the record-section of the profile from San Francisco(1) to Fallon(9) (fig. 72) Trace No. Trace No. Distance of coordi- Coordinates Traces Distance of coordi- Coordinates Traces (km) mates and Elevation included (km) mates and Elevation included Station (traces 1 . 6) elevation Lat Long (feet) in section Station (traces 1, 61 elevation Lat Long (feetl in section 1—3 ——————— 35.0- 36 3 1 34 ”18.82' 118°36.45' 1.750 2.6 S—4 ——————— 23.6- 26.1 6 37 l’46.06' 122 °28.90' 150 11.14 K—5 —————— 50.4— 51 4 6 34 °26.90' 118°39.15' 1.000 13.10 Q—4 ——————— 50.7- 52.7 1 37 "55.97' 122 °17.80' 550 2.6 K—3 —————— 60.0- 62 0 6 34 °33.59' 118°34.36' 1.400 1 T—4 ——————— 58.9— 60.5 1 37 °55.44' 122 °09.70' 900 2.6 R-5 ——————— 60.7- 62 2 1 34 °33.54' 118°29.24' 1.750 6.1 J-4 ——————— 66.2— 68.2 1 37 °59.00' 122°06.90' 250 10.13 K-2 —————— 80.8— 83.2 1 34 °42.22' 118°19.40' 2.500 9.14 H—4 —————— 92.2— 94.3 1 38 °06.62' 121°51.80' 0 9.12 R-2 ——————— 94.0— 96.5 1 34°50.32' 118°23.70' 2,650 9,14 T—3 ——————— 107.7-109.7 1 38 °09.52' 121 °41.35' 220 1.11.5 S-5 ——————— 111.8-114.3 6 35°01.06' 118°20.90' 4.050 1.11.6 J-3 ——————— 119.1-121.5 6 38°11.80' 121°32.00' 0 9.11.14 1—2 ——————— 133.0-135.4 6 35°09.11' 118°03.37' 2.600 9.14 Q—3 ——————— 122.5-124.7 6 38°16.24' 121 °32.45' 0 2 P—l ——————— 153.2-155.7 1 35°18.75' 118°01.71' 2.520 9.13 S—3 ——————— 125.9-128.4 1 38°18.06' 121 °33.90' 0 1.6 Q—2 ——————— 154.3-156.8 1 35°21.82' 118°13.00' 3.950 14 T-2 ——————— 147.1—149.4 6 38°21.42’ 121 °27.15' 10 1.5 3—3 ——————— 172.2-174.7 6 35°32.99' 118°12.32' 3.700 9.14 S—2 ——————— 158.0—160.1 6 38°25.40' 121°11.62' 100 1 .14 —6 ——————— 187.5—189.9 6 35°36.42' 117°50.17' 2.750 1.11.6 R—2 ——————— 167.8-169.4 6 38°28.51' 121°07.47' 170 9.14 Q-l ——————— 191.3—193.8 6 35°38.43' 117°49.31' 2.500 9.11 Q—2 181.1—183.3 6 38°33.30' 120°59.20' 600 10.13 Q-5 ——————— 195.2—197.4 6 35°44.54' 118°06.75' 3.400 9.12 P—2 194.7—196.7 1 38 °35.32' 120°50.45' 1.200 9.13 S-2 ——————— l97.9—200.2 6 35 °40.98' 117°45.47' 2.350 9.12.14 J-2 — ————— 205.8—208.2 6 38 °38.06' 120 °42.60' 2.100 9.14 1 35 °52.58' 118°01.17' 6.600 9.14 1—2 ——————— 221.3—223.5 1 38 ”42.64' 120°35.60' 3.450 9.12.13 6 36°01.68' 117°54.45' 3.6 H—2 —————— 232.2—234.6 1 38°48‘22' 120°28.44' 4.920 12.14 J—l ——————— 236.6-2390 1 36 l’03.68' 117°52.19' 4.100 9.11.14 L—2 ——————— 241.0—243.0 1 38 °48.18' 120 °24.00' 5.400 10.13 J-6 ——————— 281.1-283.5 6 36°31.74' 118°05.60' 5.200 9.11.14 ' K—2 —————— 2518—2533 6.640 9.13 J—7 ——————— 285.9-288.3 6 36 “34.36' 118°05.85' 4.630 9.12 L-3 ——————— 270.3—272.4 1 38 °52.48’ 120 °03.60' 7.200 9.14 J—8 ——————— 2937-2953 1 36°37.22' 118°04.85' 3.770 9.14 1-3 ——————— 276.3—277.2 6 38°46.46’ 119°55.35' 7.300 9.13 K-6 —————— 305.2—307.1 1 36 °44.04' 118°09.95' 3.920 10.13 K-3 —————— 279.2—280.8 6 38 °54.10' 119°57‘60' 6.500 14.9 K-7 —————— 315.4—317.8 1 36°49.13' 118°05.38' 4.400. 10.13 P—3 ——————— 2986—3010 6 39°05.44‘ 119°48.85' 5.000 9.11.14 TABLE 99.—Data for the record-section of the profile from Santa TABLE 1 01 .—Data for the record-section of the profile from San Monwa Bay(4) to Lake Mead(22) (fig. 71) Luis Obl5p0(3) to N TS (1 9) (fig. 73) Trace N 0. Trace No. Distance of coordi- Coordinates Traces Distance of coordi- Coordinates Traces (km) nates and Elevation included (km nates and Elevation included Station (traces 1 . 6) elevation Lat Long (feet) in section Station (traces 1. 6) elevation Lat Long (feet) in section H-14 —————— 7.0- 8.7 1 34°02.68' 118°29.95' 300 1.6 [(-3 ————— 20.53- 22.90 1 35 °13.62' 120°35.74' 500 1.6 1-14 —————— 13.7- 15.3 1 34°06.16' 118°28.38' 1.270 1.6 S—3 ————— 36.78— 38.79 1 35 °21.29' 120°29.51' 2.000 1.5 J-14 —————— 26.1- 28.4 1 34 °08.83' 118°19.89' 570 2.14 8-3 ————— 41.85— 44.24 1 35 °20.30' 120 “24.27' 2.000 9.2.6 K-14 —————— 36.2- 38.4 1 34 °09.64' 118°12.68' 770 1.6 -3 ————— 48.62— 50.56 1 35 °21.92' 120 °20.22' 1.400 1.5 14-14 —————— 41.7- 43.1 1 34°13.40' 118°11.36' 2.000 9.14 K—3 ————— 52.47— 54.24 1 35°21.07’ 120°16.66' 2.000 2.6 P-14 —————— 50.5- 52.6 1 34°15.54' 118°06.15' 4.670 1.6 L—3 ————— 73.81- 76.30 1 35°27.83' 120°05.13' 2.000 1.11.5 Q—l4 —————— 64.9— 67.3 6 34 °20.60’ 117°58.90' , 6.1 T—3 —————— 84.6— 86.6 1 1.500 1.6 R-14 —————— 75.1- 76.9 6 34°25.58’ 117°55.17' 4.970 5.1 P-3 ————— 88.70- 91.29 1 35°34.63' 119°58.73' 1.000 1.6 S-14 —————— 86.7- 88.6 1 34 °28.54' 117°48.40' 3.700 2.6 1-3 —————— 99.98—102.41 1 35 °38.55' 119°52i96’ 600 1.5 T—14 —————— 90.8- 93.3 6 34 “31.50' 117°43.65' 3.230 1.12.6 R ————— 103.48—105.85 1 35°37.31‘ 119°49.20' 500 1.6 . 0.7 1 34 °37.73' ll7°39.60' 2.900 2.12.6 T 1 35 °38.65' 119°43.26' 300 1.3.5 . 9.2 6 34 °37.06' 117°29.60' 2.830 1.11.6 L l 35 °41.13' 119°34.53' 235 1.4.6 . 9.7 1 34°39.21' 117°25.26' 2.770 1.12.6 J- 1 35°39.29' 119°29.40' 240 1.4.6 . 4.6 1 34 °45.68' 117°18.00' 2.630 9.14 H-4 ————— 141.48-143.74 1 35 °42.65’ 119°24.02' 250 3 . 4.3 1 34°49.72' 117°13.44' 2.630 9.13 R-2 ————— 141.95-144.08 1 35°46.18' 119°26.00' 230 1.14 . 5.8 1 34°49.02' 117 °04.32' 2.600 9.14 Q—2 ————— 154.57-156.82 1 35 “48.73' 119°18.15' 250 1.5 R—13 —————— 177.7-180.2 l 34 °55.33' 116°58.38' 2.330 10.14 S—2 ————— 16410-16620 1 35 °54.36' 119°14.85' 270 1.6 S—13 —————— 184.4-186.8 1 34 °59.86' 116°56.85' 2.670 10.13 T—4 ————— 174.53—176.73 1 35 °52.61' 119°05.65' 500 1.6 H-12 —————— 199.9-201.8 6 35°01.58' 116°45.80' 1.770 14.12 S—4 ————— 191.46—193.78 1 35 °54.63' 118°54.28' 1.000 2.6 T-13 —————— 202.0-204.3 1 35 °02.22' 116°45.80' 1.730 9.14 P—2 ————— 19108—19933 1 36“01.53' 118°54.58' 1.000 1.11.6 J-l2 —————— 2280-2305 1 35 °05.36' 116°26.80' 1.900 1.11.6 J—4 —————— 20129—20364 1 36 ”05.95' 118°54.57' 1.300 1.5 I-12 —————— 239.8-242.2 1 35 °05.46' 116°19.16' 1.330 11.13 Q-4 ————— 22058-22265 1 36 °09.82' 118°42.42' 3.000 2,4,6 L-12 —————— 247.7-250.2 1 35°15.70' 116°19.44' 1.970 10.13 1-2 —————— 22426-22459 6 36°11.28’ 118°40.38' 3,000 6 P-12 —————— 261.6-263.6 1 35°22.98' 116°14.43' 1.400 9.11.14 P-4 ————— 23306-23461 1 36°07.45' 118°31.25' 7.500 1,6 Q-12 —————— 270.9-273.4 1 35 °23.47' 116°07.44' 930 .14 K—4 ————— 255.28-255.37 1 36 °02.42' 118°12.00' 7.500 1.3 R-12 —————— 2743-2768 1 35°23.77' 116°04.92' 1.470 11.14 K—2 ————— 28781-29006 1 36°12.14' 117°53.55' 4.500 1.12.5 S-12 —————— 2905-2929 1 35 °24.94' 115°53.18' 3.470 10.14 I—1 —————— 28983-29226 6 36°20.57' 117°55.16' 3,600 3.6 T-12 —————— 303.9-306.4 1 35 “31.85' 115°48.10' 3.500 11 Q-l ————— 29867-30106 1 36 °23.36' 117°52.10' 3.600 1.4 L-2 ————— 303.10-30336 1 36°19.91' 117°46.70‘ 4.700 2.5 J—l —————— 30429-30635 6 36°27.15' 117°48.75' 4.000 5 R—l ————— 314.73-316.70 1 36°29.24' 117°43.77' 5.000 2.5 S-l ————— 341.15-342.90 6 36 °36.84' 117°27.40' 5.000 4.5 TABLES 55—108 73 k TABLE 102.—Data for the record-section of the profile from TABLE 104—Data for the record section of the profile from Amencan . Hanksutlle(30) to Chmle(31) (fig. 74) Falls Reseruozr(27) to Flammg Gorge Reservotr(29) (fig. 77) 1 Trace N 0. Trace No. 1 Distance of coordi- Coordinates Traces Distance of coordi- Coordinates Traces ' (km) nates and Elevation included {kml nates and Elevation included Station {traces 1. 61 elevation Lat Long {feet) in section Station {traces 1. 61 elevation Lat Long {feet} in section K—2 ————— 0.15‘ 2.44 1 38°21.97' 110°55.54' 4.930 1.6 T-l ————— 12.30— 12.94 1 42 °48.40' 112°39.95' 4,570 9,14 L—2 — 9.95— 12.38 1 38°17.28' 110°52.34’ 5.230 1.6 J-l —————— 30.90— 32.58 1 42 °45.09' 112°27.06' 6.700 2.6 P—2 —— 24.08- 26.37 1 38°12.18' 110°44.79' 5.670 1.14 I~1 —————— 34.97— 36.55 1 42°42.48' 112°25.23' 5.700 1,6 Q—2 — 32.09~ 34.09 1 38°11.77' 110°37.86' 5.300 10.14 H-l ————— 48.61- 50.67 1 42°39.18' 112°16.29' 5.380 1.6 S—2 — 39.80— 42.02 1 38°04.58' 110°39.62' 5,970 9.14 K-l ————— 58.99- 60.39 1 42°35.88’ 112°10.02’ 4.980 1.6 T—3 — 48.62— 50.62 6 37°59.00' 110°36.85' 5.470 6.12.1 L-l ————— 67.507 68.75 1 42°31.74’ 112°06.00’ 5.800 1.6 r R-3 — 63.24- 65.33 1 37°54.60’ 110°27.82’ 4.400 1.14 T—2 ————— 80.81— 82.75 1 42°23.61' 112°01.74' 5.280 2.6 J‘3— — 71.14— 73.43 1 37°49.82' 110°28.98' 3.900 9.13 J~2 —————— 10123—10283 1 42 °22.74' 111°44.61' 5,180 2,6 l [—3— — 79.65— 81.53 1 37°48.79' 110°20.95' 5.130 1,14 1-4 —————— 111.23—113.49 1 42°18.84' 111°39.36' 6.100 2.6 H-3 — 34- 94. 6 1 37°43.80' 110°15.00' 5.270 1.14 H—2 ————— 116.50—118.71 1 42°07.77' 111°45.81' 5.180 9.14 K—3 —101 27—103 69 1 37°39_90' 110°11.40' 5.070 10.14 K—2 ————— 13013—13222 1 42°11.52' 111°29.28’ 6.600 1.6 L—3 —113 77—115 75 6 37 °30.00' 110°14.16' 6.000 14.129 L-2 ————— 13706-13833 1 42°05.19' 111°29.22' 7.520 2.6 P—3 —117 87-119 72 l 37°27.66' 110°11.25' 5.330 9,1 P-2 ————— 151.14—152.94 1 42°06.21' 111°15.72' 6.100 10.14 S—3 —141.20—143 06 6 37 °20.34' 109 °57.00' 7.200 1 .12,9 Q-2 ————— 158.54»159.36 l 41 °58.05' 111°16.20' 6.100 9.13 T—4 —149.32—151.73 1 37°16.26' 109 °56.58' 5.670 1.6 T-3 ““““ 17358-13035 1 41°50‘28' 111°07-08' 6.400 1.6 R—4 —161.26—162.63 1 37 °07.47' 109 °58.68' 5.670 1.12.6 R~3 ~~~~~ 18861—19098 1 41 “46.32' 111°02.07' 6.500 1.6 . J—4—— —169.96—171.29 1 37 °03.08' 109 “54.65' 5.030 1.12.6 l~3 —————— 21002—21150 1 41 “47.36' 110°41.50’ 7.020 9.14 1-4 —— —180.10-182.37 1 36 ”58.68' 109 °52.25' 5.070 2.12.6 H-3 ————— 22066-22288 1 41 °43.26' 110 ”35.97' 6.700 1.14 b K—4 ————— 19769—19971 1 36 “47.43' 109 °53.07' 5.530 2.11.6 L~3 ————— 23866—23931 1 41 °34.14' 110°28.86' 6.600 9,14 S—4 ————— 23764-23984 1 36 °30.15' 109°36.36’ 5.670 1.12.6 P-3 ————— 24734—24979 1 41°28-02' 110°27~36' 61700 9114 H44 -257.05~259.59 6 36°18.24' 109°36.45' 5.800 6.12.1 Q‘3 ————— 25811—26058 1 41 °24400' 110°21-75' 6.870 9.14 L-4 —276.84—279.26 1 36 ”07.00' 109 °34.78' 5.670 1.3.6 5'3 ————— 27280-27513 1 41 °22<26' 110°10.08v 6.650 9.14 P—4 ————— 293.41—295.58 1 35 °57.25' 109°34.54' 6.330 9.11.14 P—4 ————— 279.26-281.75 1 41°20.04' 110°06.51’ 7.020 9.14 R—4 ————— 28906—29142 1 41 “08.10’ 110°10.71' 7.450 1.11.6 J_4 ______ 298.69—301.03{?1 1 41 °15.75'{?) 109°53.31'{?) 6.800 1.12.6 Q-4 ————— 30808—31033 1 41 °10.14' 109 °50.58' 7.170 1.11.6 {(111 ————— 3;8.3.g—§gggg 1 41 °81.65' 109°52.56' 7.120 9.14 . . - ————— 5.4 — . 1 41° 3.54' 109°4l.70‘ 6.970 2.6 TABLE 103.—Data for the record-sectzon of the profile from s-4 ————— 33534-33611 6 40°55.14' 109°41.76' 6.200 14 Chznle(31) to Hanksvtlle(30) (fig 75) L 4 336.17 336.57 1 40 55.95 109 40.06 6.150 5 Trace 1:110. Distance of coor i- Coordinates Traces _ _ ' ‘ ‘ ‘km’ "aces and Elevation included TABLE 105. Data for the recorti section of the profile frorn Flaming Station {traces 1, 6) elevation Lat Long (feet) in section Gorge Reservozr(29) to Amencan Falls Reservotr(27) (fig. 78) P—3 ————— 0.65— 2.98 6 35°57.25' 109°34.54’ 6.370 1.6 ' P—4 — 3.22— 5.62 6 35 °58.67' 109°34.71' 6.200 4 . “a“ N9- , H—4 — 6.73— 8.72 6 36 °oo.15' 109°36.13' 6.070 1.6 Distance 0‘ cwrd" C°°rdmaws . Traces R-4 — 12.14— 14.60 6 36°03.37’ 109°36.43' 6.000 1.6 , ‘kml ““95 hind Elevam“ Endu‘iéd L—3 _ 18.51- 21.01 6 36°07.00' 109°34.78' 51570 1.6 Station {traces 1. 61 elevation Lat Long {feet{ in section ¥—3 — 39.37— 41.90 6 36°18.24' 109°36.45' 5,800 1.6 -4 — 48.35- 50.71 6 36°22.77’ 109°39.33' 5,600 1.6 _ _____ _ a ' ° ' P 63 — 61.65- 63.89 6 36°30.15' 109°3636' 5.670 1.6 1512 _____ 3‘33 fig 2 28.22%. igg.fi§’;2g, $33 {2 s—4 — 68.07- 69.82 6 36°32.85' 109°42.33' 5.700 9.14 K_4 _____ 10_98_ 131,4 6 41.0354. 109.4110. 6:970 1:6 7 Q-3 — 8042‘ 82-58 6 36°37'20' 109°5025' 5.370 1-6 H-4 ————— 19.38— 21.76 6 41°01.65’ 109°5246' 7.120 2.6 K-4 — 86.36- 88.97 6 36°41.88: 109°50.85' 5.270 1.6 Q_4 _____ 28.25' 3004 6 41°10'14' 109°50.58' 7_170 1.6 K'3 — 7'57‘ 9975 6 36°47~43. 109°53-07, 5530 L13 .1—4 —————— 39.04- 40.84(?) 6 41°15.75'{?) 109°53.31'{71 6.800 1.6 1—4— ——113.18—114.52 6 36°56.79 109°37.52 4.970 9.6 R4 _____ 47_77_ 4936 6 41.08.10. 110010.71. 7 450 16 ’ 1-3 - ~117.33—119.59 1 36 °58.68' 109°52.25' 5.070 14.9 p_4 _____ 55.96— 58.30 6 41°20_04' 110°06.51' 7.020 16 J—3—— ~128.3_3-130.19 6 37 °03.08' 109 °54.65' 5.030 1.12.6 s_3 _____ 62.37- 64.70 6 41°22.26' 110121003 6,650 16 R—3 -—136.93—137.69 6 37°07.47' 109°58.68’ 5.670 1.12.6 Q_3 _____ 76_33_ 7&8. 6 41.2400. 110.21%. 6'870 1'6 T—3 —150.65-152.72 6 37°16.26' 109°5658' 5.670 1.11.6 p-51 _____ 87.1% 89.58 6 41.2802, 110.2736, 6'700 1'6 s-2 —160.15—162.23 6 37°20.34' 109°57.00' 7.200 1.12.6 L_3 _____ 9839. 98,72 6 41°34.14' 110°28.86' 6600 1'13 7 P—2 —178.80-180.99 6 37 “27.66' 110°11.25' 5.330 1.11.6 K_3 _____ 109.364.1159 6 41.3738. 110.3750. 6'970 1'5 L—2 —182.57—184 27 6 37°30.00' 110°14.16' 6.000 1.11.6 - _ ____ _ o . o r ' ' , , 1'1 3 115.69 117.69 6 41 43.26 110 35.97 6,700 1.12.6 1‘4 498-153—200 52 6 37 °39-90 110°11~40 5.070 2,125 1—3 —— ——126.65—128.47 6 41 °47.36' 110°41.50' 7 020 1 116 h i‘l-22 —g?g.?g-2g3 93 2 3;°4g.88' 110°15.00' 5.270 1.4.6 p_1 __135.30_137‘42 ‘ 1'6 ' — — — . —2 4 3 °4 .7 ' 110°2o.95' 5.130 1.12.6 _ __ __ - o . o . ' . We «a 4226112623 2 21424; 119.337.: 2133 12.1.6 * R-2 —233.67-235 96 6 37 °54.60: 110°27.82' 4.400 1.12.6 T—3 ~156.27—158.37 6 41050.28' 111 007.081 6:400 2:6 T'2 ’246-26'245 49 5 37:59-00. 110°36-35, 5-470 1-6 s-2 — -——166.29—168.12 6 41°55.47' 111°1o.53' 7.020 1.11.6 Q—l —-266.29—268 77 6 38 11.77 110°37.86 5,300 1.11.6 13-2 _ ——184.62—186.65 6 4260621: 111 015.721 6100 1 116 P—1 —270.65-273 23 6 38°12.18' 110 “4.79, 5.670 1.11.6 L—2 _ ——198.29-199.50 6 4200519! 111029 22' 7.520 1’4 ' L-l —283.87-286 27 6 38°17.28' 110°52.34' 5.230 1.11.6 K—2 _ __205‘20_207 10 6 42011.52! 111029.28! 6.600 1.6 K—l —296.15—298 08 6 38°21.97' 110°55.54' 4.930 10.6 H—2 _ ——218.40—220l59 6 42.30177. 111°45‘81v 5,180 9'4 ‘. ”—1 —3°2-15—304 59 6 33°27”? 110°53-38' 41570 1-12'6 1—2 — ——224.28-226.46 6 42°18.84’ 111°39'36' 6100 1013 1—1———— —310.51—311 30 6 38°30.59' 110°55.20' 5.170 9,6 J_2_ ___234 72-236 65 6 42422 74: 111044‘61’ 5,180 10'12 J—1———— —323.22-324 96 6 38°38.26' 110°54.48' 6.250 10,14 R_2 _ ——247:56-249:27 6 42°23:81' 111055.471 6.100 2 1‘4 . R—l ————— 328.33—330.11 6 38:41.47: 110°52.15: 6,900 9.14 T-2 _ ——253.81—255.74 6 42 °23.61' 112001:74I 5:280 1:6 T—l ————— 33664733859 6 38 47.78 110°48.45 7.100 1.11.6 L71 _ __268.23_269.76 6 42.31.74. 112.0600. 5,800 1.116 K—1 - ——277.11—278.90 6 42 °35.88' 112°10.02' 4.980 1.6 . H—l — ——287.67—289.40 6 42 ”39.18' 112°16.29' 5,380 9.14 1—1 —— ——300.71—302.70 6 42 °42.4B' 112°25.23' 5,700 9.14 T—l ————— 32522—32585 6 42 “48.40' 112°39.95' 4,570 9.14 CRUSTAL STRUCTURE OF THE WESTERN UNITED STATES TABLE 106.—Data for the record-section of the profile from Bear Lake(28) to American Falls Reservoir(27) (fig. 79) Trace No. Distance of coordi- Coordinates Traces 1km) mates and included Station {traces 1, 61 elevation Lat Long in section P-2 ————— 16.18— 1835 6 42°06.21' 111°15.72’ 9,14 L—2 ————— 22.49— 23 40 6 42°05.19' 111°29.22' 1.5 K-2 _____ 31.417 32 73 6 42°11.52' 111°29.28' 1.6 H 2 ————— 42.81— 44 91 6 42°07.77' 111°45.81' 1.6 1-2 —————— 49.76— 51 72 6 42°18.84' 111°39.36' 2.12.6 T—2 ————— 77.62— 79.54 6 42°23.61’ 112°01.74' 1.5 L—l ————— 92.27‘ 93.91 6 42°31.74’ 112°06.00' 2.6 K—l ————— 101.29—103.20 6 42°35.88' 112°10.02' 9.14 H-l ————— 111.99—113.60 6 42°39.18' 112°16.29' 1.6 1—1 —————— 12466-12671 6 42 ”42.48' 112°25.23' 1.6 J-l —————— 12968—13161 6 42°45.09' 112°27.06’ 9.14 T—l ————— 149.07—149.77 6 42 °48.40' 112°39.95’ 9.6 TABLE 107,—Data for the record-section of the profile from Bear Lake(28) to Flaming Gorge Reservoir(29) (fig. 80) Trace N0. Distance of coordi- Coordinates Traces 1km) names and included Station (traces 1. 61 elevation Lat Long in section S—2 ————— 9.23— 10.33 6 41°55.47' 111°10.53' 6.1 T—3 ————— 17.84— 19.96 1 41 °50.28' 111°07.08' 1.6 [(—3 ————— 27.88— 30.27 6 41°46.32' 111°02.07' 6.3.1 J—3 —————— 36.35— 37.18 1 41°46.44' 110°53.73' 2.6 1—3 —————— 52.00— 52.92 1 41°47.36' 110°41.50' 1.6 H—3 ————— 61.89— 64.25 6 41°43.26' 110°35.97' 6.1 K—3 ————— 65.15— 67.43 1 41°37.38’ 110°37.50' 1.5 L—3 ————— 78.50— 79.40 1 41°34.14' 110°28.86' 1.11.5 P—3 ————— 86.67— 89.11 1 41°28.02' 110°27.36’ 9.6 Q43 ————— 97.41— 99.88 1 41 ”24.00’ 110°21.75' 1.12.6 S—3 ————— 112.43—114.74 1 41°22.26‘ 110°10.08' 1.12.6 TABLE 108.—Correctwns applzed to record sections Thickness of Time delay Distance sediments, assumed applied Figure (kml (ml (S) 52 137.8—140.3 3.000 1.0 164.4-1663 6.000 1.5 205.4‘2073 >2.000 1.0 72 92.2— 94.3 4.000 1.20 107.7-109.7? 5.000? ——— 119.1—121.5 4.500 1.30 l22.5~124.7 4,000 1.20 1259—1284 3.800 1.20 147.1-149.4 1.400 .60 158.0—160.1 800 .35 167.8~169.4 500 .20 73 89.0— 91.5 1.000 .40 996—1021 2.500 .90 103.5~105.9 3.500 1.10 112.1—114.4 4.500 1.30 125.6—127.9 5.500 1.45 131.0—133.5 5.000 1.40 141.0—143.2 4.000 1.20 153.5—155.7 3.000 1.00 1633—1654 1.500 .60 173.571759 500 .20 GPO 689-035 L_ UNITED STATES DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 1034 GEOLOGICAL SURVEY PLATE 1 I I I .. I ,I l I I I I C .' I I I | EXPLANATION 125° 3‘ ,- 120° I K x ~ I 1103’ " IL, I American Falls I - ___________________________________ I . Reservoir I 20 * Shotpoints (see table 1): I Reservoir l Recording units along the following lines: OREGON I I I . I _____ o 0 American Falls-Flaming Gorge, : .. . , Bear l Hanksville—Chinle, _ _ I :d Lake I ,- WYOMING Boise-Lake Mead, T " ‘ \ - — ‘ :' O ;‘ - Shasta Lake-China Lake, “ ‘ x _ _ . - . . x — — _ _ ______ . _ L _ ,.' San Francisco-Santa Monica Bay, ~ ~ _ ____________ _ __ —— —— '—— __ . .‘ - - ' I Mountain13 Q ________ I .L . . ." MOJave Ludlow, I City ,. ’ o ~~~~~~ l O _ I . I _ ; I 0'. A A Santa Monica Bay-Lake Mead, I _________ 0 ' ,1 O . San Luis Obispo-NTS-Colorado, - .. I I Flammg Gorge San Francisco-Fallon-Delta; : ‘ I l‘ l Reservoir ' \K I I . . ‘.‘ __ _ ’— —' - I V ' L_:'_,A-;:::=—---° ‘ '7" v v Eureka-NTS-Ludlow, Shasta 5* ' 2 Vv I H ‘ Fallon-China Lake—Santa Monica Bay; Lake — J Ix I. V 14 ELKO ‘3 ,‘ .71.. W I ______________________ “ ~~~~~~~~ I D Fallon-MonoLake-Santa Monica Bay, I ;' Q ) I % I I‘.‘ ' " Mono Lake-Lake Mead; —4 ° ' ' 0 0 W, o ’0 I : I I; NTS-Kingman, “ ‘ ,A ‘~ I v. } China Lake-NW, " x ma a e- ; 'o I 5 + I , ' _ Ch' L k w o 71 O ' . . 0.. I. 9 A A NEVADA . ' % A *Delta ‘ Q Mono Lake: fan at 220 km distance 0. I Fallon n“ M A M A A M: WAQ AA AAAAS Imé %m 16 .. I I A AA % A Aét A AA A A 15 A A A I full symbol: recorded from the shotpoints at both sides _ . . 5 AA A EV *SHOAL A M V Eureka | . £A @317 10 E o I open symbol: recorded from one shotpoint only I, g :' '6 A v o I UTAH CALIFORNIA 5. A“ 6\ . § I o (A V [A recorded from NTS only) '.‘ A‘IA 00: “3 0. I 8 I. A 5 0 K ‘x v _ _ _ _ State boundaries A AA :- . \ 2‘ . V . . I — A‘% X: 3. Vi \7 v 00 O I ........... . approximate boundary of the physical f A |' Mano . {3 V . divisions after Fenneman and Johnson San Francisco Lake 6 V‘ .' H I ’. (1946) (see fig. 1) ............................... 1 Cl 8 \ V fi 20 1C0 Ir 0 E? A .0 . \ 0 A A A . 1. dxtw 9a \ - v ° IA 2‘ A A g3 i Lida o. g AA AA AEA *Navajo _ 0‘ l * Junctlon AAA AAA AA I A Lake .. 0% \ D. D A A% A AA .' o . ° \ -' A 113m . — — '— — - . [I I. \ .A D k . . x x Independence . \ I; o x DD *0? A \ $9 A I . A 0\ alhrop Wells I “r “ N: A O \ *V§ * “3 A \II 8. % I TBA A O o I — g Ea g-‘no Ge 0 Y v Dag, g '. 0 Camp ”3 ‘AA Sb OED I _ . Roberts A A I ‘ 1? g 31 ‘32 i‘ 4‘ A '3 U:. W" 8 v \ Chinle I Afl v : "‘ China V7 NEW A E; . . o A D U 0 Lake 5 A MEXICO AA ‘ A A I . O 7 AA . — 35° A . A u ‘3 ,v AA% A ARIZONA I - 23 I o_ Obispo 3 ______ 4’,“ ’5. it o . . Barstow A ‘ A V + I 35 Mojave O . . V ....... | \fi A ‘24 ' ' ‘25 ““““ *l‘u. V [A 0 Ludlow I U: ‘ A V00 0. . I o 100 200 km E, AA I _ lllllll|lllllll|lllll a [5Ax ... AA """""" A -------------- A 1210 4Santa Monica Bay V 1 10° I ’ I I I I I I l I I wt.- o$ Imagéayk fl 053°“ A? / /’ \ \7 0’2) Illlllllll 0' 0 Depth ARIZONA ,Aom I." I 1.... I IIIIII...“ 'I autumn.“ «trauma: / I "I" 'IIIIIIIIIIIIIIIII... ”lull-Ii? / ,’ \ ' II ~. \ \ ."lllrn‘" Ia» // \ \ \ \ " ‘4!" \ .II'"l'"""'II'""""":W WWII-“Ill: \\ \ \ \\ , ,, , x \ . ,, CALIFORNIA \ W In. I \ W / A \ // / ./ 7% / _,../ é / // I /.—/‘_/' % // i /"’” \ // % /,-/ ’ —’ ' <0 a .— -/- 6‘ / / ./ O . / /. / /" /" / /.- , III"""""'IIIIIII|"""""IIIIII-nu“Inn... _/ I / .‘M -'/ / in, /'./ / 'I .- // @ “'Iufii}; / / 6:90 $ N //K5\o o$ O t 55 \ ”k :50 it Interior—Geological Survey, Reston, Va.—1979~G77079 The diagram is viewed from an angle of 45° from the Pacific Ocean toward the northeast, approximately parallel to the line The contour interval of the lines of equal velocity is 0.2 km/s. Velocity lines less than 5 km/s are not shown. Dashed lines from Los Angeles to Salt Lake City. The depth Z is exaggerated 2:1 versus the horizontal direction y (SW to NE). The indicate uncertain results. The depth scales under the shotpoints are divided into 10 km intervals. The shotpoints are num- scale of the surface altitude above sea level corresponds to the scale of the depth 2. The cross sections are drawn along the bered according to figure 1 and table 1. lines shown in figures 12, 25, 36—40, 45, 50, 62—63, 68, 76, and 81. FIGURE 87.— Fence diagram showing the crustal structure under California and Nevada and adjacent areas from seismic—refraction measurements. LOCATION OF SHOTPOIN TS AND RECORDING UNITS, AND FENCE DIAGRAM SHOWING CRUSTAL STRUCTURE UNDER CALIFORNIA AND NEVADA AND ADJACENT AREAS PROFESSIONAL PAPER 1034 PLATE 2 (SHEET 2 OF 2) 32. . Q .. .gQQQQQQQQ; . Q. 5 .. .s gifieeeeig 5s 5% . . . . Q, $§§§i§3§kfi$fi IHHIIIII . .:...Q\..._Q .3»? I . interpretation. (b) Corrected (see fig. 72). Corrections applied are listed in table 108. FIGURE 73.~Record section of the profile from San Luis Obispo (3) to NTS (19). Data in table 101. (a) Not corrected, without II?:>ES§ 2.....§¥£A.Q.(I...QZ.Q§§.3.€§>§.. 2Q.SQ..§ 2t< I E. $88.88; Data in table 103. FIGURE 74.—Record section of the profile from Hanksville (30) to Chinle (31). Data in table 102. FIGURE 75.7Record section of the profile from Chinle (31) to Hanksville (30). Q 52 \, r g5§<§§flfiw®a§ ... .. . Q...§QQ§QQQQ.iiQQQzQE... , . C ES? s. .I ..(.III .. .>;........\ Data in: table 104. FIGURE 77.—Record section of the profile from American Falls Reservoir (27) to Flaming Gorge Reservoir (29). 245 2495; £$§§§a§s§§§§<§ a: :3?§.§3§.§i .. 0% Eggs? §.Q§.e.sQQ;QQQ.§.Q§a...<....§, c E . . >QQ . . Q FQQQ . ..Q. ”Fig .9 e23 Ema m .. Q A(km) I I II NW BEAR LAKE-FLAMING GORGE SE Q2 {€22 §X§Z Ewe. IIIIIIHI. mg Q _ _>/Ii R E 7 A E W $ w . .3-.. Is a . W ,2 ,...II. E PB E 0 /Q Wfiéiiyrlfi S m H 6 6 4 2 O 2 4 4 4 6 6 4 2 0 4. 4 I 6 6) 4 2 _ 2 4 0 2 4 G 8 / \W . . . / I / c . _ . E _ I 2 A__ u A m A u s F ( ll _ O — l\ T T I T .m 0 .5 mm 9.5 022.74 A O 0 iIIMIII ; IIIIIII. t IIIZI . nits .ISII IIIIIII.IIIII .0 .4 3 .m: 0 W yam «920$ \»S?.>I a. .. z). , s / (4). Data in table 95. (2). Data in table 96. CAMP ROBERTS-SANTA MONICA BAY SANTA MONICA BAY -CAMP ROBERTS PROFILE PROFILE FIGURE 66.— Record section of the profile from Camp Roberts (2) to Santa Monica Bay FIGURE 67.—Record section of the profile from Santa Monica Bay (4) to Camp Roberts PROFILE SANTA MONICA BAY - MONO LAKE FIGURE 69.4Record section of the profile from Santa Monica Bay (4) to Mono Lake (6). Data in table 97. uxaj «2on D 2 EEQQQERI a§3% a. 2»? 16° III II III 1 SANTA MONICA BAY-CHINA LAKE PROFILE .—Record section of the profile from Santa Monica Bay (4) to China Lake (8). T-A/6 (sec) .§<.KIS31EIBXMI 1r?»)\(I/>\( III xix)? §QXU$ E89. SS??? 2 s . >\\/I\/\I\/h\/IIP{IAI\I)IIK\I\I p x I . 4 .1. s...)>\<;€ _.)I. I.1,3.,..I. SANTA MONICA BAY-LAKE MEAD PROFILE FIGURE 78.—Record section of the profile from Flaming Gorge Reservoir (29) to American Falls Reservoir (27). .5 {I1 .1) I IIZESXII)» I 3%. 45.89.922.18.saw/szzK/aigtnflufldnatx. t». . (Ix/\IIIII/Bitzli III . giggiwig ‘ zso mg. II.I II.III.I.. mI 3.1))?”(5 I... I I» I I I40 3?‘ SAN FRANCISCO - FALLON SAN FRANCISCO - FALLON PROFILE PROFILE SW SW corrected, without interpretation. (b) Corrected: Records of the stations in the Great Valley were shifted along the time axis to eliminate traveltime delays in sedimentary rocks in the valley. Corrections applied are listed in table 108. FIGURE 71.4Record section of the profile from Santa Monica Bay (4) to Lake Mead (22). Data in table 99. 316151t>t<$§ : i1 Iii<<§zz§5 .i. . was 1....) It.)\rs>>7>\s)>_ SIIII IIIIIIII5<1<$ igvég. I I Q Q IOO >§§>«irt§<<§>?IIII L K2? QIII Q MONO LAKE FALLON 93.1.. . III Fallon (9). Data in table 89. PROFILE FALLON PROFILE MONO LAKE - -2 -4 -6 -4 FIGURE 57.—Record section of the profile from Mono Lake (6) to FIGURE 56.—Record section of the profile from Fallon (9) to Mono Lake (6). Data in table 88. T-A/G (sec) mxaj lffi 5:65.; A . $.35 Q » >8 .Q\$aQ/\>.r§i<2 . D . we; Q9... Q... o . 1, Q4; Z ..>)>2>>><§.Q >722: ) 83$) 0 . IS IE§PSJx>5§II§iZf 300 13(ka NW Atkm) 230 RECORD SECTIONS OF S .III. mu.Q..QQ._Q....§:§§w§..§?§.§ PROFILE MONO LAKE-CHINA LAKE PROFILE MONO LAKE-SHASTA LAKE .—Record section of the profile from Mono Lake (6) to Shasta Lake (5). Data in table 80. :Eéé: II m §e%§.QQQQQQ../II ideas? % cw 6 4 9.. O J. 4. "w l I A u ._. u FIGURE 47 mx<1_ 0202 IV Wu FIGURE 48.—Record section of the profile from Mono Lake (6) to China Lake (8). Data ir table 81. . «13/ .Ix/x Data in table 82. PROFILE CHINA LAKE - MONO LAKE Record section of the profile from China Lake (8) to Mono Lake (6). .QQ..£..s.....Z.}Q.QQQ‘.QQ..Q.QBEQQKeéFQQ.....,.;.... II Gr T-A/S (sec) FIGURE 49. T S E .\}.IEW. H_E FKO OA M RL EPA I.W .. 4% emu A“ —_I( c Em A (km) I PROFILE CH INA LAKE-NORTHWEST II I I‘ .I I I IOO‘I so I II II northwest. Data in table 83. I SE FIGURE 51.vRecord section of the profile China Lake (8) 8 9 b b a t .m a t a D W 0 S 7 S E R U 4 G _ I F .L 9 b b a t n .1 a t a D \..I 2 2 ( d a e M e k a L 0 t ) 6 ( e k a L 0 n m 5 Q3384-» m 0 fl 6 are. a \. erxyEQES/i fl f 0 r P e m f 0 n 0 .U c e S d r 0 C e R _ 9. 5 E R U IIIIII ........ 6 G 5 . I F lewngAW/gxgnuégwaVhflhui "ML-v m 0 m f . . a d W m4m A pooi 6km. .htba aim r 0 P I n I niw m a n .tfli C I. 0 T 6D u m S 5L 0 Q E Mam. . W 0 .1 . _ CW w . EE 6) ., LK Rood . I b _(e FA .610. 2k Q 0L sum 0 DH B EPA Ma m N n I ..I -I I Uit 0 2 4 H Gwnm _ _ I C F . Gm «920:. 524m . .\ 0), \ aw LQ, LG? \ Q Q iéig. fir \ . _ EQEEQQEEQQQQQQQQQQQQQ. _rIII time delays caused by sedimentary fill in the along the time axis for eliminating travel- Great Valley (140 and 175 km) and the Carrizo Plain (205 km). Corrections ap- (b) Corrected: The records were shifted plied are listed in table 108. Record section of the profile from China Lake (8) to Santa Monica Bay (4). Data in table 85. CHINA LAKE-SANTA MONICA BAY PROFILE E NN —4 FIGURE 53. RefififipfiewéufirfiafifaIII I. 11......II. I. I M B A rIv N O M QAIH N A S _ PROFILE MONO LAKE 2 ‘41 -6 -2. -2 FIGURE 64.—Record section of the profile from San Francisco (1) to Camp Roberts (2). Data in table 93. -4 FIGURE 65.—Record section of the profile from Camp Roberts (2) to San Francisco T-A/S (uc) FALLON - SAN FRANCISCO PROFILE NE FIGURE 54.—Record section of the profile from Mono Lake (6) to Santa Monica Bay (4). Data in table 86. FIGURE 55.—Record section of the profile from Fallon (9) to San Francisco (1). Data in table 87. —4 -s UNITED STATES DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 1034 Pacific Transverse Ocean Ranges W Mojave-Ludlow Ludiow-NIS. E SANTA MONICA BAY LAKE MEAD 3000 (mi Basin and Range Province 20 40 Depth (km) I I , 400 300 200 IOO 0 Distance (km) Velocity (km/s) Depth (km) FIGURE 37.7Crustal cross section from Lake Mead, Nev, (22), to Santa Monica Bay, Calif. (4). Explanation same as figure 12. Mono Lake-Santa Monica San Luis Obispo-NTS. Fallon—S Monica Boy I CHINA LAKE SE E 20 L L L_L / / 20 x L 74— ‘: 7g 1; 40 km/s 40 8 60 I 60 200 IOO 0 Distance (km) Velocity (km/s) E 8 6 4O :5 .C E a) o FIGURE 61.—Crusta1 cross section from China Lake, Calif. (8), toward northwest. Explanation same as figure 12. Depth (km) Depth (km) GEOLOGICAL SURVEY PLATE 3 Basin and Range Province Basin and Range Province Basin and Range Province Sierra Nevada Mojave Desert Tgansverse gagific k - L dl . _ _ , , an es 0 an NIE/I/He a U W SE Elk L k M d S.Luis 0b.'N0V°I° Lake 8‘ Monica Bay Lake Mead San Francisco-Eureka Mono Lake-Lake Mead San LUIS Obispo-NIS. Moiave-Ludlow g o- a e ea NTS LAKE MEAD KINGMAN N | I Mono Lake-Lake Mead 3 N I INDEPENDENCE CHINA LAKE S Imo EUREKA ms, FALLON I I I SANTA MONICA BAY .. (m) 3000 . O I I LUDLOW 0 (m) s' A 3000 '13 E (m) 3' F .................. j 20 O A % L 6 E 20 e: fig 20 L 5 NEVADA f: Q 40 E :I f 40 760 E 40 D 8 so 60 Distance (km) 0 |00 200 300 400 500 600 700 . 60 . VGIOCIW (km/SI 500 400 300 200 I00 0 9'59"” (:m} 0 Distance (km) Velocity I m s; 4 6 8 ---- E Velocity (km/s) 6 4 5 8 ii A L 20 ,L E a E V a 5 5 40 a E Taumw‘ “ , + 35. FIGURE 38.—Crustal cross section from Nevada Test Site (19) 8 '1“; u. {sum to Kingman, Ariz. (26). Explanation same as figure 12. 40 FIGURE 62.—Crustal cross section from Fallon, Nev. (9), to Santa Monica Bay, Calif. (4), crossing China Lake (8). The part “I V" " ' . , _ . between Independence (7) and China Lake is identical with the corresponding part of the crustal cross section from Shasta V ......... In: ___________ I .. FIGURE 39.—Crustal cross section from Eureszi, Nev.1(215), to Ludlow, Calif. (25). Explanation same as Lake (5) to China Lake (fig. 50). Further explanations on figure 12_ ””'" ' Basin and Range Province 13“” ' M°l°ve Dese” ' ‘ ' ransv rse Ran e acifc Sam Monica Bay _ Lake Mead N Basm and Range PrOVInce Sierra Nevada T e g OPcean P 'f' C 1 G I 8' Santa Monica Bay-Mono Lake 8 F _ E k Sh t L k Ch L k NTS _ San Luis Obispo aCI IC OCIS rea Ierra - - I an ranCIsco- ure 0 as a a e— inc (1 e ‘ " ' . Ocean Ranges Valley Nevada 805'” 0’“ R‘mge va'me W MOJAVE BARSTOW LUDLOW E I I China Luke-NW China Lake —w 5 Elko- Lake Mead E 3000 FALLON MONO LAKE I SANTA MONICA BAY W Shasta Lake-Mono Lake DELTA O(m) 33830 SAN FRANCISCO I FALLON I , 0 3000 I 3880 E . — (m)o 20 x \‘f‘ 20 a ,5 L ’E‘ L L L L r 20 \LA ' E — § 2 i E f 7§~-~in\. \ - x 7— i _ _=_ E 20 4O 3 W I 20— aging-2% a 40 —=; —40 E _ 40 ' ' 8 40— 300 200 I00 0 60 | l l I l l 60 — Distance (km) 0 IOO 200 300 400 500 600 700 60 I | I I I 60 Velocity (km/s) Distance (km) IOOO 900 800 700 600 ' 500 0 O4 6 88 6 4 Velocity (km/s) Distance (km) E 4 6 8 8 6 4 6 8 Velocity (km/s) 55 E ' ' ' TI /' “\' ' ' O4 ‘5 8 E :5 20 A a) E 20 a -' ‘= E D E K / \ TE- 20 FIGURE 40:Crustal cross section from Mojave (23) to Ludlow, Calif. (25). Explanation same as figure 12. D 40 40 (D FIGURE 63.—Crustal cross section from Fallon, Nev. (9) to Santa Monica Bay, Calif. (4), crossing Mono Lake (6). The crustal Q 40 structure under the Sierra Nevada, south of Mono Lake, is uncertain owing to the lack of observations (dashed lines). Further . . . explanations in figure 12. FIGURE l2.*Crustal cross section from San Francisco, Calif. (1), to Delta, Utah depth versus horizontal distance 2:1. At each shotpoint the depth 2 = 0 corres- POCIfIC COOST Great Sierra - - (16). Numbers behind the shotpoints refer to figures 1 and 2 (pl. 1) and table 1. ponds to the respective surface altitude above sea level. In the corresponding Ocean Ranges Valley Nevada Basm and Range Provmce COIorOdO PIOIECIUS Contour interval of lines of equal velocity in the crustal cross section (upper velocity-depth functions (lower part), the position of the velocity 4 km/s correlates Mono Lake-Santa Monica Boy NW COOSI Ranges Transverse SE 1part) is 0.2 km/s. Velocity contour: lower than 5 km/s were omitted. Dashed with the position of the shotpoint in the crustal cross section. Increasing velocity is C R berts Santa M ' B I Mono Lake — China Lake Eureka I Ludlow s L . Obi N15 Ranges ines indicate uncertain results. SUI ace altitude versus depth is exaggerated 311, plotted to the left or right according to the direction of the profile (west or east). amp 0 ' onlcu 0y China Lake—NW Mono Lake _ Lake Mead Eureka _ Lake Mead _ , I an Uls SpO - . . . Hankswlle-Chin e SAN LUIS OBISPO NTS NAVAJO LAKE I SAN FRANCISCO CAMP ROBERTS l SANTA MONICA BAY | I E 3000 F’ I I 13000 Snake River Plain Basm and Range Provmce 3 _ 000 A - N Fallonl-Delta N.T.S.-Navajo Lake NIS-Klingman 3 ("”0 5E, 20~ 20 BOISE STRIKE MT. CITY ELKO EUREKA LAKE MEAD E .5 - 3000 I I I I I 3000 5 20 3 40 _ 40 (m) 0 (m) I D _ .._ _ Q I I I I I CD 40 60 60 E 20 Q 600 500 400 300 200 loo 0 :35 0 I Distance (km) 5 40 1000 900 800 700 600 500 400 300 200 IOO 0 8 WWW (km/5) 8 3 Distance (km) 04 6 4 6 0 Velocity (km/s) E 60 I I i I I 60 4 6 8 if 0 IOO 200 300 400 500 A 5 20 Distance (km) E E Velocity (km/s) V 20 " 3 4 6 8 8 6 4 6 8 8 6 4 :2. FIGUREggOC tl t' f S F ' (1)t S tM ' B C1'f(4) E I t' f' 12 A - i ‘ , l: : .:/: I * = . : . . . . . I a) .— rus a cross sec ion rom an ranc1sco 0 an a onica ay, a 1 . . xp aria ion same as igure . s I’ ‘\ m \ F D 7T“ e .0 I E 20 20 '1 20 \ /... 20 \I if 20 20 FIGURE 45.~Crustal cross section from San Luis Obispo, Calif. (3) to Navajo Lake, . of the results of the line from Hanksville (30) to Chinle (31) (see fig. 76). Further Colorado Plateaus 8 - )\ I K Utah (21). The line was extrapolated beyond Navajo Lake (dashed lines) on the baSis explanation see figure 12. N.T.S.-Co|orado 40 4O 40 4O 40 HANKSVILLE CHINLE FIGURE 25.—Crustal cross section from Boise, Idaho (11), to Lake Mead, Nev. (22). Explanation same as figure 12. Cascade Mountains Sierra Nevada NNW I ISSE NW Fallon-S.Monica Bay 3%))0 . . - - - ~ .. O Basm and Ron e Provmce Sun FranCIsco Fallon I San LuIs ObIspo N.T.s A g . , SHASTA LAKE MONO LAKE INDEPENDENCE CHINA LAKE SE E / NTS -San Luis Obispo l x 20 2 Shasta-China NTS-Kingman 3000 v —/ O NNW I Fallon-China Lake NTS-Ludlow SSE ( ) f MONO LAKE LAKE MEAD m 0 Q 7\ 3000 D (m) E km/s A :5 60 ' I 60 E _: 300 200 IOO O +— . E 20 a Distance (km) a.) . E Q Velocny (km/s) 8 40 O A 8 800 700 600 500 . 400 300 200 IOO 0 E Distance (km) 3.5 60 60 - .r: 500 400 300 200 I00 0 VeIoCIty (km /s) a Distance (km) A 8 6 4 6 8 8 Velocity (km/s) E :5 FIGURE 76.—Crustal cross section from Hanksville, Utah (30) to A f Chinle, Ariz. (31). Explanation same as figure 12. 5‘ e O n o a l - 1;; Snake River Basm and Range Middle Wyoming Basm 8 Plain Province Rocky Mountains FIGURE 50.—Crustal cross section from Shasta Lake (5) to China Lake, Calif. (8). Explanation same as figure 12. FIGURE 36.7Crustal cross section from Lake Mead, Nev. (22), tO Mono Lake, Calif. (6). Explanation NAIR/AERICAN FALLS BEAR LAKE FLAMING GORGE same asfigure 12. Sierra Nevada SE 3000 7/" __L_7—‘ImEI:n:IEI_II_IJD [58]?ng 60 I ' I 60 400 300 200 I00 0 Distance (km) Velocity (km/s) 4 6 8 7 4 7 8 6 4 0 .\ - . - / \1 . . . . . o 20 ....\. : """\ 20 ...... K 1'” 20 / 40 K 40 j 40 FIGURE 81.~Crustal cross section from American Falls Reservoir, Idaho (27), to Flaming Gorge Reservoir, Utah (29). Short dotted lines between 15 and 20 km depth between the velocity lines 6.4 and 6.6 km/ s indicate the approximate boundaries of a low-velocity zone (shaded) in which the velocity decreases to 5.8 km/s. Further explanations see figure 12. CRUSTAL CROSS SECTIONS firlnterior— Geological Survey, Reston, Va.71979AG77O79 PROFESSIONAL PAPER 1034 PLATE 2 (SHEET 1 OF 2) 260 Aikm) Data in table 74. MOJAVE - LUDLOW NTS - NAVAJO LAKE PROFILE FIGURE 41.—Record section of the profile from NTS (19) to Navajo Lake (21). Data in table 75. FIGURE 35.—Record section of the profile from Mojave (23) to Ludlow (25). T-A/G (sec) Data in table 76. 5'0 PROFILE NTS - ELKO S T N _ E K A L w AVM A N PROFILE FIGURE 42.—Record section of the profile from Navajo Lake (21) t0 NTS (19). FIGURE 43.—Record section of the profile from NTS (19) to Elko (14). Data in table 77. T-A/G (sec) E Emmo £3 z85}. It/Z Eigigfijfigfifiiw n was. (IIIIIMIII\II III gee/xéaeiéxxééas §§§§§§EIIII 3/? II»?\ I>x<§I 0 AIka \It/>\{I/>I\/St/\I<)\/\/)I/\ «I Q<<<§II> W 5 4. f,...(i,.x>\<>.,\Aves/.2; 3x)? I II....,.. .3... 3...... 1...} . .,» I INK.) fit/\IQEgQIII IN E ... Whflé.§£&&fi§wéwflwmu IIIIII/IIII VIP ‘2 PROFILE NTS - SAN LUIS OBISPO EN E -4 -e IIIIII Va.~1979~G77079 s .. 400 Atkm) filnterior~Geological Survey, Reston < I \EgIIIII E K A I. O N O M . E K A L A T S A H S E H. F O R P NW FIGURE 44.wRecord section of the profile from NTS (19) to San Luis Obispo (3). Data in table 78. LAKE MEAD-SANTA MONICA BAY LA-KE MEAD- MONO LAKE ESE PROFILE PROFILE FIGURE 26.— Record section of the profile from Lake Mead (22) to Mono Lake (6). Data in table 69. FIGURE 27.—Record section of the profile from Lake Mead (22) to Santa Monica Bay (4). Data in table 70. o -2 -4 é a III 3 £5 _°._, o.—. , fig. 8). 00 3 300 m u A '250 DISTANCE A IN KILOMETERS .200I mg 388% ' v50 m§§§§ L _\ \ ' I00 50 The correlation shown here differs from that published by Diment and others. PROFILE NTS-KINGMAN PROFILE KINGMAN - NTS SE 8 +6 4 2 O + + + mozoomm z" wx<|u._. FIGURE 28.—Rec0rd section of the profile from NTS (19) to Kingman (26) (Diment and others, 1961 -4 FIGURE 29.—Record section of the profile from Kingman (26) to NTS (19). Data in table 71. ID If”) T-A/6 (sec) .1 . _ \ .. mi....>...§§§.§€é...3\§ 50 PROFILE NTS - LUDLOW N FIGURE 30,—Re(ord section of the profile from NTS (19) to Ludlow (25). Data in table 72. -4 -4' -6 FIGURE 46.—Record section of the profile from Shasta Lake (5) to Mono Lake (6). Data in table 79. .mHz m g ,:»QR,:>3?)<>3..ch>r>z3>>§)§II II 1.32 I 538.33 32435;.sz MOUNTAIN CITY - EUREKA Data in table 61. PROFILE ELKO - BOISE PROFILE -2 -4 -2 -4 FIGURE 18.—Reeord section of the profile from Elko (14) to Boise (11). Data in table 62. FIGURE 17.—Record section of the profile from Mountain City (13) to Eureka (15). I EIIIs‘II II I III I 1.333.. E $2»??? ma iziiéaézEzéégiIII £51333§§t$fl ”ix/3:23? ., I. 13ft. 11.1.3). I. ,7 . I II I I éfi>§§§<< c .3 .3 §I.I..I§Xz.%nfiwzsfl nsIz\.S/.{<\?3\<€A§>\,IK<>> IIIEESZERKI -2 PROFILE HIKO-LAKE MEAD FIGURE 23.—Record section of the pro— file from Hiko (20) to Lake Mead (22). Data in table 67. Jifzzitr é/IIII I FSIJHIIIII I IIIEIJ‘EZ, (2. III (I PROFILE HIKO - EUREKA FIGURE 22. 7 Record section of the profile from Hiko (20) to Eureka (15). Data in table 66. (292333; I 3 I I 13W.» ,, w. IttitvéLImIIIIIIIII L -4 FIGURE 31.3Record section of the profile from Ludlow (25) to NTS (19). Data in table 73. IEEFQDI . . 3,. .. ., _ _ 3...... 33.3 .....EIII RECORD SECTIONS OF SEISMIC PROFILES ?§.3>5>3. . I .3 _ I\ I LAKE MEAD-EUREKA PROFILE 4 2 0 COLORADO NEW MEXICO 35° - WYOMING ARIZONA A ,mu I6 AAM‘ B‘Mim + AAA AA A "ELKCI 5 1 '__7 I. A Bars: ”'5. vi...a.n.mene NEVADA A ‘9 AA AA‘ I 2'0“ OREGON éiguafifififiiagu LIIIIH I I -2 IN B hm r I 25" ~40“ UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY seismogram are plotted (see table 55). PROFILE EUREKA-FALLON FIGURE 10.—Record section of the profile from Eureka (15) to Fallon (9). Two or three traces of each -4 -s .9 III .I 59.3.». bkufik¢vaI \ III 50 m3 III 3.333006. I .—Record section of the 2 PROFILE STRIKE-BOISE FIGURE 14 (12) to Boise (11). Data in table profile from Strike Reservoir 58. T-A/s S (no) \2<;>\;>;>\}>\$><§I SIII I 522323;??? >>>>I<(I>\>ZZ§ Eisfiégiasjgg ”Wiggifi. . . _. PROFILE BOISE-ELKO PROFILE FALLON - EUREKA ..EEEFEKEEL -a -4 FIGURE 11.—Record section of the profile from Fallon (9) t0 Eureka (15). Data in table 56. -4 m FIGURE 13.3Record section of the profile from Boise (11) to Elko (14). Data in table 57. The corresponding calibration at the top of each trace is marked in microvolts. figggg n MR Ii.(3.3c...3..{/>\..< .3.>3>,3Ir\:(... <3 ( g Ix)>>>\{<../ » \J) té Eggwgfiéxéfi m 9% 22§QSE3>§33 I (2%; we a? \Atkm) I ‘E'ao FIGURE 15.vRecord section of the profile from Strike Reservoir (12) to Elko (14). f. (IIIII PROFILE STRIKE -ELKO é... Q Egg? » -2 -4 FIGURE 24.7Record section of the profile from Lake Mead (22) to Eureka (15). Data in table 68. Data in table 59. m5). (36.8.32..sz aziiaif Boise (11). Data in table 60. MOUNTAIN CITY — BOISE PROFILE misu Ifizraay<>r9< moav Nouvuaaavxa wouuaA 'QMEqS '(OLBL) 13193 UJOJ; 9J9 0p910|03 UJBISBM U[8U01Spues OIBAEN SEEM-3 WO‘I I)! 008 OCT O 001 : SEEING“)! 09 017 US DZ 01 0 sumo suwn walsea Btu 'uoueompow 3111!: u1!M‘(Z'Id'015L)eu59H L % fi- H L—. .—. .—« E ,009 ~ -. , I I! * 74 i , g 7‘ 1009 pue Aung Luau 919 ugseg JaAga JapMOd am u! sumep eoepnsqng SE‘IIW 008 001 0 Got 00000091 '531913 pellun - 33m 09 m; 09 oz m 0 '1x31 u! l elqel u! pals” 319 mm p 130111 'saamos Auem tum; paudwog 000 000 9:1 EjVOS Aeluns lemfioloag 'S'n we]; ages : m ozm cam 0W ‘ ‘29“ 090‘ cm; £01 050: 01 1 '00“ — mm 88 0001 at I ——W « ll AWL»; L4 7 g ‘ i z ‘ )0 0i” 02” " £38 0‘ ‘ x , z 3 i 1 I g g ; . i ' ! _ 2‘ m ”9” am ' o - ‘ . z a I ““““““ ‘ ““““““ 3 ~ . ‘ D ‘ r _____________________________ - ‘ ' ***** -; L : i : l f7 175 _ i “:7“ « ,,,,,,,,,, i ' 3 §—~~r’7\'”~« ’0091 _ m1 uopewmjgdoxusow 10091 T 1' _ “WT """"""""" "I .' f _ t i 33‘ ‘ 5 _ uoneuuog gdoxueow §~ C'~£:L~- -~- ,sz'ez ‘ \ , .' g ,7 : f m ‘ ‘ + \\ 3 Egg}; (,4, i ,oooz — 3002 .5 W“ ..... .... . : f 7 : 1 ‘ N “Tm—m...» “35; er :3 5 . ; o9s: : , . ‘ g 9? u ; ; i 3 _ uonewmj need pau 3h,“ g ~ at h: ,r ; ; [0092— “1 ' ,oogz : L“\ . . A i oh; 5‘ ; 7 _ _ 1 B ‘ g . , — , _ _ , , , ““MFWw‘ L.~».»»\.‘+—u~-m./.._...P I . _ V H , , , L , , . . ,7: , , » ,7 _ , ‘A , , ”‘r—«w- ’“"'"l_«,..-_ ,’> \ ‘ - ~‘ ', g.L..m...—n~.~i , g / mi ? “f“ “" ‘ 10008 — ‘ . , _ '~. ‘ , ' ‘ * , ‘ . . ,_ , g ' ”53*“ “mm“ W "23 “5’9 ‘ ,0008 w :3 . =9. » xi, / 095 A _ , ‘ , ‘ s, 3 9‘1 7 g - . , auoaspues 1a56n~ ‘2 ‘3 i ‘ f / 7 A ', War ”“49““? , ‘ ‘ ‘ 4 ,7 _ 7 _ _ _ _ 7. ‘ . < 4- - « "'7 “- I! 1009€~ ‘ .» ' , " " » 7 ‘ . ; , 7 7 , . ‘ ‘ ‘ n ' . " 9' ' ‘ 7 ‘ .0098 L~:’ / ‘ ‘ .. \\ - - y A!" —-— ‘ \ L11. 5 Z Jf‘ ...... 7 ‘7 o g AOUUV 9W SL‘Z uOllEUJJOfi UOSHJOW ' ' uoneuuod uoquow 777 ’000V 17w 9w LW mw uw LM - - > % zz/v\ zn m - - an em .g;.,:..m.r- «4—»«7 _ * 8, . ‘ 1“ 31> g a: S 0 £13. » » ‘ffi _\ _ ‘ _ VNVLNOIAI DNIIAIOAAA ‘ E {)NIWOAAA HVLI] ‘ g (g S i i ‘ m: 313% $93. 7%) 1 . ‘ , Ln. C) 2 D Z w _ f / 7:; 8g HLHON E; g; Hmos J..J« ~ , - i O L; , )2, v ‘ LL 8LM am 41 w ff ..... l (W)! 9m) saw 021 moav ‘ I / {”7777}? \ * +3 , .......... m iOClVHO rID 055 % Ii Pymfiwfifimbféfflfll OGVHO'IOC) ‘HIOAHEISEIH NOLSTVH 0.1. ‘DNIWOAM ‘SV'IDDOCI OOIXEIW MEIN 3.1.1.09 HOOlEld Ol ‘va ‘XOO'INOD ‘ ” _. v. 7 /0 I 10 ,0 :0 i ,. .4“, mar ‘‘‘‘ “ xb/A’g‘ _____ ’ 029 x iflDBV Nouvaasavxa wouaaA ewm % 7‘? \1/ “F ---------- ,09 SHHHW01I>I 09 017 02 OZ 0L 0 109 90l X inOHV NUUVHSBQVX?! 1V3|1H3A 5 , «, a ,_ 3 >017 . suaflwmm 09 017 as oz [11 0 V’L‘dewuww v ,3‘ " 1‘ I5 «001 saw 09 017 09 oz 01 o AJUL 1009 W ‘l ' 1 ’ ' l ' 7’ um 0“” 1009 x a» ,./ “‘3 09L sanw 09 or 08 oz 0L 0 ' ' I [DEL \ x “z; , IDUZ IUOZ IOOOL IOOUL f, ‘ ,092 1092 .-- , «a (pad) uoneuuod suDM‘l w; uogewmj gdoxuaow _ 715’ 1009 ,008 41091 “/0091. 3 1095 m3 ..... 1098 A Z83 £33 023 SL3 89M msr Jeqwaw euolspues E g L17/V\ asp Jaqmaw sumspues U0!19LUJO;1 uosguow ||!H APUEM g D m ,UOOZ _10002 0Z9 SSungs quuea z E E a OGVHOTOO {)NIWOAAA 917M ‘ ‘3 u g E S ‘ ‘ O _ HinOS HLHON '0093 Z _ ,0092 1‘ V m a I (W)l 828) SEHIW 1703 anEIV 7] 2 E E: _ , cat» ,(I (I ,0009 :17: ‘0009 a? , I 1 , g _ ....... g A1095 —/0099 3 . V ’ 7+: uoueuuo} uosmow 7 77 77 77 7 7 77 77 7 7 77 7777 77 77 7 77 77 7 7 ‘ m fl OLWN 7 7 ( “V 91001 ogssemr uongJow-eJd \fi‘ _ “ ,00017 2 E fl 3? fluent 6 OlV 6V 2 2 VZWN 2 E a E 880 ngN OOIXHW AAEIN VNOZIHV Z Z VNOZIHV HVLII 8V ‘9‘ lSVEl iSElM IL (W)! 229) 831m 868 moav ’1‘ O O _ ‘1’ 097 5' VLOXVG H1003 ‘STIIH XOV'IH :IO ALINIOIA OJ. ‘HVLH ‘HSVM NHOHXODH ‘3 ,0 ,0 777“ 7 OlZ >< inoav NOILVHBEJEJVXE wauuaA . . _ . . . ‘ SHEBWOTI)! 09 017 09 DZ UL 0 m .. 01v _ | u IIJII 'I’fi I" sauw 09 av 09 oz 01 0 \ {fiuo suogoag—mguuowooun z—p uo saquad 11an v v v _ ‘\ Aluo suogoag—pmuoo alqeuuowog ___*_ 1009 _ 009 ' Aluo suogoaS—finuuowooun 7 . ‘ . _ uogoas }0 aun V V 0817 . . ' f .. ~ 08? , mgod [ouuoo 3012an snoauenaosgux JELHO .10 ‘papaI ’ '7 » . ' 7 7 ' 7 -[o:) 10 pa/uasqo mam saquad uaqo axeqm Amenoq 17. , a; V - . v . f. . '~ . .‘ $128 10 [go 10} panpp aloH 17L© 7.; ‘, " 77 ._ * xaqumu v 7777;0L7 . 1 ‘ _~ ; » " pue 31918 Aq 1an u; I a[qe1 u; pawl—slugod [ouuog IUUUL— ,OOOL . U17m o 0901 JUL 08 ' 06‘? as am“ ”0‘ w m m m 00” om azu {:11 est NOILVNV1dXEI 085 ° ° om ALIWHOdNOONn Z—l’ HHL HEIAO XLLOEIHICI SMOOH‘V ,OOQLV [OOSL I: ‘. H H H H‘FI '(BSBL) fileqpues pue '(LSBL) SloueH '(zgel) uosmed 1995” Meg 8831mm” 003 00‘ 0 0‘” ‘(sssmsmbpmw '(BVBLMSIPEHPU9'31950H'19UD199 an“... '(GtBL) If H a- H l—-i H H E ueqqog um; paAgJap 319 euewow u! suun ammoafi ;0 ”Ounqumg SE‘HW 002 001 O 001 OUO'OOO'SIL '331918 peuun '1er, U! L Slqel U! pals” 819 HONM }0 180w 'SBOJHOS New ”’0” PGWUJOO 000 000 SW HTVOS Aa/uns |ealfio|039 '31} mm} 3329 . 11 uoueuuoj need pea oLOl oZOi 0801 JUL Jim 0901 °Lxm 080! IUUUZ 81 euoxsemn emaw ' ' ‘ 77 7 7 7 7 7, 77 7 7 7 a ‘ 7 7 C 7‘ V . V V ' ~ 7 7 . ' 7 , . /UUDZ OODL ‘ ' , oZLL 'Kluo 23m neamld 013210103 u[* Jaqwaw SUI-Ids umsdrig) ’ ' ‘ ' - ‘ ' ' ' ‘“ otssem a I d ‘ uo saw! as; ( . F IPPJ’W 1-19 a 1 .1 )1 D UIML 6r “H Buuds umsdAg 5!. uoueuuog HSIJJBGdS 35“”? sfiuudsgsmrig ‘ - 1 Jews a use ”301 UQquUQDaId (DISSEJHP BIPPIW) 996I lSIanJON }O UOHQLUIOd UOSSSN JG": SS name-4 301 310206 anSuo 52 Sun; ““““ 8’1 ‘ [ed 1 q M ' H [0092 A1092 anSuol slafiood puesnoql , _ , 7 , , ,, , , , , Aqw >191 _ uopeuuozj uosguow med Jame—I 313s 1 I auo Ur; S g qu Bung sum 0 % €9M‘817M 179M Msr uoueuuoj aoue‘puns LEM-99M 09M—69M LLO 83 MS,- 60 Zlg ( . 2 1’11" SIPPJN) 15p 8 3 9d U VLOXVCI qu HS JSIEMPSH 'U 2 4o Jaqwaw auozspues ”gH ApugM rln g ”(New au0133u1r1 pequgg 1-19 d 16 E HLHOS GNU/“0177““ ‘ 3 DNIWOAAA OCIVHOrIOO OCIVHO'IOO HVlfl "J g M071 1703 m cm ued Jaddn 2’ E anfiuol MOIIOH ppnp lSVSHiHON g E .LSEIMHiflOS ue ‘a I L17 (ogsseul lamo'l p M {ppm} uogeuuog gdoxuaow mi JaunBLU papueg H M (W)! 868) SE‘IIW 999 moav fir, :nsseu ‘ ( . . 1) mad uonewuod sum/Y1 léL 112d 13 d d0 1 H , , _, 9 sseu ‘ i g g a (a; ..L)119d UOREUHOJ qsweeds Jaqwaw snOJaflsd/sg NVIangoaad (31532111 IBMO'I) uogeuuog Apoomu; G Jaqwaw mum 3102031ch cu Jam (3158 ‘ J“ 071) uogeuuod Head 1363 (ogssemp aIppgw) uogeuuod [aweg (3135211 auolsaux; mos 1‘) 71 [V xaqwaw afipug Aamaq DISSERL 13M0”[ uenpuI pue 112d JQMO'I (95591“? 91PPIW) 9U°15PUQS QPQHUH Pug ueplaualo (3155ng .L Jaddn) Med ‘auolspues uymunow mox) (aalPPEIN Jaqwaw mag P38 (315991“? aIPPIW) auolsawn OllEPOJ. n _ (3159911 .L Jaddn) mad ‘uogeuuod Lupf’ 7 77 I i auo1spueg x3313 uouounp 1 (9!5 put; ‘uogeuuog qeqeueM aq; sapnpu; ‘opexopg u; fsauolspueg ; ‘ ‘ ‘ seal Jam0'1) suogeuuod fipoomuyq pue Head peg ‘apgspoom sfiugds M03 pug Hnlfi pug uogeuuo :1 allwawums 3H1 sapnp SNIWOAM 11.2mm Ol OHVCII X3383 dWOlS ‘sau/ieql pue (31599”.1. Jam0'1 pue laddn) 119d ‘uogeuuog anF-wuv mi -u; ‘oogxaw maN pue euozuv uI—SfiDOJ ogssemp alppgw JafiunoA J ‘0 ’0 8 HJ. - 318 VI ('6~w[>) AJJWHOJNOOND 9—11 [Hz >< iflOGV NOILVHEIEJEJVXB ‘IVIJIiHHA W - z 0 uogeuno; (3599an alPPIW) uogeLuJod sumo " ' saaflwmlx 0'9 917 0'8 0| 0L aq; }o sued Japlo pue Jaqwaw 159103 pagmad aq; JIo 112d Jamo’l — f 0"] 0'8 0'2 81 ' (agssemp alppgw) uogeuuod anyuamums ”SSW-L 83M 09 0 uogpuuo; aq; Iaddfl j ueguxeg 7 J0 sued Jafiunofl pue Jaqwaw 15310:; pagmad sq; }0 mad laddn Jaquxaw auolspues sSupdg uo/iueg pue n1 1009 — ueuoN _ sypox lualeAgnba xaqwew £31qu laneag apeypo1s pue Slaquxaw dwmeugqs pue ‘aung xouuow 153103 pagmad _ sxaqwaw uaInH pue 512*] ‘anng augd—ued a[pp1w L _ Jaqwaw “308 IMO Jaqmaw aquspueS HalnH r _ ('fi‘wOI—L) AlIWHOdNOONn o—r , Jaqulaw 211.1129 (angsseul I L _ IOUOL Jaqwaw )IQ'I laddn UOISSHDSI 000 mm Pamow Iaqwaw sung and Olgggggrv ea: - (ogssemf a1pp1w) 112d ‘uogeuuod aouepung 3‘55“”? — xaqwaw auo1sms 231qu Jamoj Slaqwaw ypoxapqg pue ‘qogg ‘afipgg Mapunog—ued lamO’I « » 7 Jaqwaw au01s11gg ('fi'ws—a) ALIWHOdNODNn I-l’ fl laqulaw nooxapqg (ogssepl Jaddn) uogeuuod alugqg ~ 7 [ODSL — JaqLuaw luyod >pog Jaqwaw LPEH uemoreg ('A‘UII) ALIWHOiNOONn z—r _ (agssepl laddn) ued ‘auo1spues 3125mm jaquxaw 235ng Mepunog 7 7 ‘ mad laddn (3199ng .L Jaddn) 112d ‘auo1spueg ugmunow m013 Jaqwaw uofiugo UOJJEM - xaqwaw x3313 sdgg _ (ogssepl Jaddn) wed ‘uogeuuod ullap Iaqwaw 319313 spaa—I 18 we mm ulfi ‘ODUZ H Q N G 1 g xaqwaw x3913 ageug) ueguoqwg _ .13 we (is suofi Q N "EA 1 (ogssemp alppgw) ued ‘aumsawn x9313 ugml ogssemp - Jaqwaw Jaddn “PPM A (ogssemp ampgw) auozspueg ssnaxd 6998 9 (DESSQRL Iaddn) uogeuuod agfiv OdOd 119d Jam0'1 OISSVHQP 4 ’ “098mm5‘3 otssem a I ed ‘auos ue d , ~ [OOSZ (31552111 .xaddm ued hogan-10:1 qamxuv ( . P lPPJAI) 11 1 P S umJS 009g (ogssemp alppgw) uogeuuod Jadgd — uvamoneg (757m I>> AlIWHOdNODNn EH7 91 euozsemn emaIV_ o o , , ' 7 (dogsseul Jaddn) uolleuuod aneuaow (3753217117 9IPPIW) u geuu :1 qloolmes 7 [‘— _ ‘ oyssem a 1 uogeuuo uo .131 - (DESSQLLL Jaddn) 119d auolspues 3198mm ( P [PP W) :1 P 78 7/L-Jl . 10008 — 10008 ((PISSEIIL laddn) Uoneuuod remade); (vi-wt) AlIWHOdNODND v—I’ _ , xaqwaw apqs lalempaa 1559p ue ogssem auo l ; (9’ 1‘ p P) lspueg OIQAQN (ogssemp Jaddn) 119d ‘uogeuuod aouepung UE’IPJOJXO - 77777 ,» ~ (ued) . . u 112d Jaddn ogssemp ('fl‘mz>) Mmgoanoann s—r S1 uoueuuoa usweads 3195mm pug ‘uogguuo :1 9111869» ‘BUOISPUES ofeAQN JO SlUGI (DISSEmP Jaddn) 119d ‘3U019PUPS <1me 13‘1de uelfipuawng - f M. - _ -eAInba sapnpUI—(DESSE’IJLL Pue ogssemf) au01spues uofiueg uaIQ (355me aIPPIW pue Jaddn) uogeuuod LII/“S 9! “0139mm emaw 6 d (5-1119) Auwuomomn x ,0099 ' ,ODSS (galssegl Jaddn) Jaqwaw 5 UR S [138 snoaowaao 112d Jaddn Jaqwaw auowpueg IIIH (Spugm . (ogssemp xaddn) ued ‘uogeuuod aouepuns nVSiV‘Id oavao‘loo NHEILSEIMHLHON oavamoo 'IVULNEIO-HLHON . va NHHHLHON GNV VJ.O)|V(] HLHON (EDISSQRL PUB (13155911111) QUOISPUQS 1655nN OGVHO1OO CINV HVJ.” NHSLSVEIHLHON GNV 'VLONVCI HanS DNIWOAM NHELSSMHLDOS VNVLNOW (3135(2an Jaddn) uogeuuod uoswow ’QNIWOAM NHELSVEI 'OHVGI NHEIiSVSI-LLHOS CINV 'IVHiNED , ‘ ’ I 0’? (DISSEJnf alpww) auolspues Cleo BIdI-Llal £00779 UORBLU—lod UOSEJJOW 0, $41? LZM uoueuuoj uosumw 93“ I DO ‘ ‘ (snoaomaxf) JaMOj) alexawolfiuog ulgelng 9)] ”9“)“ Eng 3 g g ‘ ‘ :4 o ‘ a (ogsswnp alppgw) uogewjod Supdg umsdflg ‘. ‘ 31UIH UEAPUQ (I93 ~d ‘1796U uopuo'UO 5131303 [93!501039 aqmqpaugap 291235an 3 E z SOL .... “WOGDL (91063121313 I39/‘1‘0'1 pue cla/V‘O'I xaddn) auolSPUeS 9103190 p)| uo paseq am salewusa 551235 }0 ‘sasaqluaxed u; umoqs samuuo;uo:>un }o suoyemq] 6 M a E ONIWOM OHVGI 0 [1x31 u; z an91 u; paquosap axe snun 38010me isva g E J-S3M Z SLINQ :10 L811 SLINO :lO NOLLV'IEIHHOO IL“ (W)! 8L9) SEI‘IIW 999 moav 8”“ fl] _ 1V V I 2-1le V9801 HEIdVd ”IVNOISSEHOHCI AHAHDS 'IVOIOO'IOEIE) HOIHHLNI Ell-LL :IO .LNEIWLHVCIEICI SELLVLS CIELLINQ 4575 M v.1035A in: um “ ‘&);.4FM£~ wigwu mu ‘5 u A“? Stratigraphic Relations of the Navajo Sandstone to Middle Jurassic Formations, Southern Utah and Northern Arizona By FRED PETERSON and G. N. PIPIRINGOS UNCONFORMITIES, CORRELATION, AND NOMENCLATURE OF SOME TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES GEOLOGICAL SURVEY PROFESSIONAL PAPER1035-B A reexamination of the stratigraphy of formations that lie on the Navajo Sandstone UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON21979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Peterson, Fred. Stratigraphic relations of the NavajoSandstone to Middle Jurassic formations, southern Utah and northern Arizona. (Geological Survey Professional Paper 1035—B) (Unconformities, correlation, and nomenclature of some Triassic and Jurassic rocks, western interior United States) ‘ Bibliography: p. 42 Supt. of Docs. no.: 119.16 1035—B 1. Geology, Stratigraphic—Jurassic. 2. Geology—Utah. 3. Geology—Arizona. I. Pipiringos, George Nicholas, 1918— joint author. 11. Title III. Series. lV. Series; United States Geological Survey Professional Paper l035—B. QE681.P42 551.7’6 77—60832] For sale by the Superintendent of Documents, US. Government Printing Office Washington, DC. 20402 Stock Number 024—001—03198—1 CONTENTS Page Abstract ................................................ B1 San Rafael Group—Continued Introduction and acknowledgments ....................... 2 Carmel Formation —Continued Glen Canyon Group ...................................... 4 Upper member .................................. Navajo Sandstone ................................... 4 Page Sandstone ..................................... San Rafael Group ........................................ 6 Harris Wash Tongue ............................. Temple Cap Sandstone ............................... 6 Thousand Pockets Tongue ....................... Sinawava Member ............................... 8 Entrada Sandstone .................................. White Throne Member ........................... 9 Age and correlation ...................................... Carmel Formation ................................... 10 Glen Canyon Group .................................. Limestone member .............................. 11 San Rafael Group .................................... JUdd HOHOW Tongue ----------------------------- 11 Name and location of measured sections ................... Banded member ................................. 13 . . Measured sections ....................................... Gypsxferous member ............................. 14 Winsor Member ................................. 14 References cited ........................................ ILLUSTRATIONS FIGURE 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. Index map of southern Utah and northern Arizona ............................................................ Restored section from Zion Canyon, Utah, to Red Rock, Arizona ................................................ Photograph of typical exposures of Navajo Sandstone and Temple Cap Sandstone in Zion Canyon, Utah ........... Photograph showing typical exposures of Navajo Sandstone in Glen Canyon near Page, Arizona .................. Photograph of authigenic chert nodules in limestone bed of Navajo Sandstone ................................... Photograph of authigenic chert in sandstone bed of Navajo Sandstone .......................................... Photograph showing principal reference section of Temple Cap Sandstone and type section of Sinawava and White Throne Members ....................................................................................... Stratigraphic section from Gunlock to Johnson Canyon. Utah .................................................. Photograph showing thin Temple Cap Sandstone at Johnson Canyon, Utah ..................................... Restored section from Gunlock, Utah, to Cummings Mesa, Arizona ............................................. . Restored section from Kodachrome Flat, Utah, to Cow Springs, Arizona ........................................ Photograph showing good exposures of banded member of Carmel Formation near Mount Carmel Junction, Utah ..... Photograph showing interfingering of banded member of Carmel Formation and lower part of Thousand Pockets Tongue of the Page Sandstone ........................................................................... Photograph of the Thousand Pockets Tongue of the Page Sandstone and gypsiferous member of the Carmel Formation ............................................................................................. Photograph of reference section of Carmel Formation and Page Sandstone at Pine Creek near Escalante, Utah ..... Photograph showing typical exposure of upper member of Carmel Formation at Warm Creek ..................... Photograph of good exposures of lower part of upper member of Carmel Formation southeast of Escalante, Utah . . . Photograph showing type section of Page Sandstone near Page, Arizona ........................................ Photograph showing evenly distributed small angular chert pebbles at base of Page Sandstone .................... Photograph of Glen Canyon at Crossing of the Fathers showing conspicuous notch or bench at contact of Page Sandstone and Navajo Sandstone ........................................................................ Photograph showing angular chert pebbles embedded in basal stratum of Page Sandstone ........................ Photograph of fossil joint crevice at top of Navajo Sandstone .................................................. Photograph showing plan view of fossil joint crevices at top of Navajo Sandstone ................................ Photograph showing conspicuous difference in colors of Navajo and Page Sandstones at Thousand Pockets ........ Photograph of Glen Canyon near Last Chance Creek showing color difference and topographic expression of Page Sandstone and Navajo Sandstone ........................................................................ Photograph of small nodules in uppermost part of Navajo Sandstone near Page, Arizona ......................... Photograph showing buried hill of Navajo Sandstone on northeast side of Kaiparowits Plateau .................... Photograph of small buried ledge of Navajo Sandstone preserved beneath Page Sandstone on northeast side of Kaiparowits Plateau .................................................................................... Photograph showing type section of Harris Wash Tongue of Page Sandstone .................................... Diagram showing correlation of formations in Glen Canyon Group with European time-stratigraphic units ......... Chart showing correlation of rocks at selected sections in southwestern Utah and north-central Arizona with a section in southeastern Idaho, western Wyoming, and north-central Utah ................................... III Page 317 20 27 29 30 31 31 35 36 38 42 Page B2 3 004mm 11 12 13 14 15 16 18 20 21 22 23 24 25 26 27 27 28 29 30 31 32 33 35 UNCONFORMITIES, CORRELATION, AND NOMENCLATURE OF SOME TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES STRATIGRAPHIC RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC F ORMATIONS, SOUTHERN UTAH AND NORTHERN ARIZONA By FRED PETERSON and G. N. PIPIRINGOS ABSTRACT Stratigraphic studies in southern Utah and northern Arizona in- dicate that the Navajo Sandstone does not intertongue with the overlying Middle Jurassic Carmel Formation. Two crossbedded sandstone bodies previously thought to be tongues of the Navajo in the Carmel are, instead, entirely separate from the Navajo. In addi- tion, a regional unconformity is present at the base of the Carmel and equivalent formations. Thus, the Navajo is a predominantly crossbedded sandstone formation at the top of the Glen Canyon Group that does not intertongue with the Carmel Formation. Early Jurassic palynomorphs were discovered in the Moenave Formation, which is at the base of the Glen Canyon Group in southwestern Utah and northwestern Arizona. These fossils in- dicate that the Moenave as well as the overlying Kayenta and Nava- jo Formations most likely are Early Jurassic in age and that con- siderably more of the Glen Canyon Group is Early Jurassic than had been thought before. However, the US. Geological Survey still considers the Navajo Triassic(?) and Jurassic in age pending further study of these plant fossils. The Temple Cap Sandstone of southwestern Utah was formerly considered a member at the top of the Navajo Sandstone, but it is here given formation rank and included as the oldest formation in the San Rafael Group where it lies beneath the Carmel Formation. The Temple Cap is here divided into two newly named members: the Sinawava Member and the White Throne Member. The Sinawava, at the base of the formation, is flat bedded and consists of sand- stone, silty sandstone, and mudstone, whereas the overlying White Throne Member consists of crossbedded sandstone. The White Throne grades westward into the Sinawava in the vicinity of the Hurricane Cliffs and west of the Hurricane Cliffs the Sinawava is the only member present. Contrary to previous reports, the White Throne is not a tongue of the Navajo; instead. the White Throne Member is separated from the Navajo by the Sinawava Member and neither member merges with the Navajo. In addition, the lower contact of the Sinawava, termed the J -1 surface, may be an uncon- formity, because it is a laterally continuous surface marked by broad irregularities that may have been caused by erosional pro- cesses. This surface is correlative with a similar surface in northeastern Utah and adjacent parts of Idaho and Wyoming that is considered an unconformity. The Temple Cap is unfossiliferous, but it is assigned an early Middle Jurassic age on the basis of cor- relation with the fossiliferous Gypsum Spring Member of the Twin Creek Limestone in north-central Utah. A regional erosion surface termed the J -2 unconformity bevels out the Temple Cap Sandstone in southwestern Utah and the Navajo Sandstone in southeastern Utah and northeastern Arizona. This surface is marked by a thin layer of small chert pebbles that are lag concentrates of chert nodules or pebbles derived from the underly- ing formations. Although it is widespread and occurs throughout most of the Western Interior, the J -2 unconformity probably was formed during a brief erosion interval in early Middle Jurassic time. The Middle Jurassic Carmel Formation of the San Rafael Group lies on the J -2 unconformity in southwestern Utah. In this area, the Carmel contains, in ascending order, the limestone member, banded member, gypsiferous member, and Winsor Member. East of Can- nonville, Utah, the equivalent of the limestone member is termed the Judd Hollow Tongue of the Carmel and southwest of Cannon- ville the banded member grades eastward into the Thousand Pockets Tongue of the Page Sandstone. Owing to facies changes east of the Paunsaugunt fault, strata that are equivalent to the gyp- siferous member and Winsor Member farther west are termed the upper member of the Carmel Formation. Some of the crossbedded sandstone beds in south-central Utah and north-central Arizona that were included in the upper part of the Navajo Sandstone were found to be separated from the underly- ing Navajo by the J -2 unconformity. These beds comprise a discrete mappable unit and, accordingly, they are here removed from the Navajo, assigned formation rank, and named the Page Sandstone. The western part of the Page is divided into two westward-thinning tongues by the eastward-thinning Judd Hollow Tongue of the Carmel Formation. The lower tongue is here named the Harris Wash Tongue of the Page Sandstone; the upper tongue of the Page is the Thousand Pockets Tongue which was formerly considered a tongue of the Navajo Sandstone. The Page is laterally equivalent to the limestone and banded members of the Carmel Formation of southwestern Utah. Based on these relationships. the Page is here assigned a Middle Jurassic age and is placed in the San Rafael Group. The upper member of the Carmel Formation lies conformably on the Page Sandstone in south-central Utah, but, progressing southeastward from this area, strata included in the lower part of the upper member interfinger with and gradually replace the Page. Farther southeast in north-central and northeastern Arizona, the lower beds of the upper member completely replace the Page so that the upper member rests directly on the Navajo Sandstone and is B1 B2 separated from the Navajo by the J -2 unconformity. Where it rests on the Thousand Pockets Tongue Of the Page Sandstone, the upper member is equivalent to the gypsiferous member and Winsor Member of the Carmel of southwestern Utah; where it rests directly on the Navajo, the upper member probably is equivalent in age to most of the Carmel of southwestern Utah. These correlations in- dicate that the upper member of the Carmel Formation is Middle Jurassic in age. INTRODUCTION AND ACKNOWLEDGMENTS Stratigraphic studies on the Colorado Plateau over the past several decades yielded an anomalous stratigraphic relationship between the Navajo Sand- stone and the overlying Carmel Formation. In southeastern Utah and northeastern Arizona, an un- conformity separates the Navajo and Carmel, yet in southwestern Utah the upper Navajo and lower Carmel were thought to intertongue. Although this was explained as westward dying-out Of the unconfor- mity, recent fieldwork between the Hurricane Cliffs TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES and the Kaiparowits Plateau (fig. 1) led to the discovery that the Navajo and Carmel do not inter- tongue and that the unconformity in southeastern Utah and northeastern Arizona does continue westward into southwestern Utah (fig. 2). Because of these findings, the stratigraphic relations of the N ava- jo Sandstone to the Carmel Formation must be reinter- preted. Because the stratigraphic relations determined by this study are so different from those published by Thompson and Stokes (1970), and because of am- biguities in their report, we do not use the names that they proposed for members of the Carmel Formation and Entrada Sandstone. Instead, we feel that the infor- mal names suggested by Cashion (1967) are adequate. Considerable emphasis in this study was placed on stratigraphic markers including marker surfaces and key beds or marker zones with distinctive lithologies or bedding characteristics. We used these markers to trace formation boundaries as well as member boun- daries through areas where similar rock types are jux- II4° 113° 112° 111° 110° 109° r-—————L_ _ T _ J. _ _ _ I _ _ _ 1,- _ __I «I ’2 38., __ ' I GARFIELD 93>" 4; 8 K I _ ' IRON j vs) 3° 0. ’52 3 36‘ I r 4» 1 (2‘6 00‘? 46 VJ; I'J ' Bodante 9'4 6a a), l Cad“ CW. l 33 O 9; "6 9’. l :7/ .__ ,_ ' ' 3334 v / g/////////; I I l Cannonvile ' 5 36 //////// 0 WASHINGTON q —_ ___ 0': — , _ _ , 6’ D -11872' 6‘,” O E a: I ‘7 2‘ ~ S) SAN JUAN ARIZONA '< G‘m'mk ‘5 22 I0 I h .0 a . 9 10 ‘Q . Q. 40 f I I—l :3 5 sam.6 . ‘ . . 11 12 .31'15 93,0 .23 Kaiparowits 41 RIM O 7 ‘ ° 14'\ 2‘ ‘ Plateau 42 .1 90" Q < SaInO $96 a? Mount Johnson ' ' 50" | George : Carmd 25 29 . 3 37° —— EH- __ U __ Juncfion_ C:nyon _ .26 -_ 28, 31 ‘3 x/_Navajo Mountain _ UTAH _ I __ Lu 0 .,, ,9,- ' "2 32 ' Cummings ARIZONA z M °' 0° .0 Mesa trail Whitmore 5' Page . ' 7OD‘m‘em‘” . 44 TsaI I I4 I Pom! 3 ‘ . . Kayenh Red I O ' < 3 g Slum o Rockl 0 z MOJAVE £3 *3) s o L- § “- Square , 1. 3 I 5 z °<< 3 Butte 45 I I w | l g S 33 Cow a?» I IE 2 S . I \é} | Z Q P/ I. I I ll f’cOLOWDO NAVAJO ”Ac”; I / COCONINO a l | I 36°- ? ‘ i I l I ‘ I I I I 0 50 100 I50 KILOMEIERS I_ l I I FIGURE 1.—Index map of southern Utah and northern Arizona showing location of measured sections and localities mentioned in the text. The names of the sections are listed below, and the locations are given in detail at the end of the report. 1. Pine Creek 9. Potato Hollow 17. Little Bull Valley 25. East Cove 33. Upper Valley 41. Fiftymile Point 2. Page 10. Meadow Creek 18. Averett Canyon 26. Judd Hollow 34. Seep Flat 42. Navajo Point 3. Harris Wash 11. Mount Carmel Junction 19. Sheep Creek 27. Sand Valley 35. Twentyfive Mile Wash 43. Little Arch Canyon 4. Zion Canyon (Observation PointI 12. Kanab Creek 20. Kodachrome Flat 28. Gunsight Butte 36. Early Weed Bench 44. Tsai Skizzi 5. Gunlock 13. Brown Canyon 21. The Gut 29. Kane Wash 37. Cat Pasture 45. Square Butte 6. Diamond Valley 14. Johnson Canyon 22. Goodwater Seep 30. Cummings Mesa NW 38. Big Hollow Wash 46. Cow Springs 7. Cottonwood Canyon 15. Carly Knoll 23. Hackberry Canyon 31. West Canyon 39. Hurricane Wash 47. Dinnehotso 8. Danish Ranch 16. Lick Wash 24. West Cove 32. Cummings Mesa Trail 40. Cave Point 48. Little Rock RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA B3 —‘VWest East g Zion Canyon 24 Sand Valley Dinnehobo Red Rock 0 .. 48 ‘9 27 45 _ 47 K—1 3 Wm ’°""""°"s fl ‘5 . \ Entrada Sandstone and g Carmel Formation younger Jurassic formations tn \ (;\ / J—1 Temple Cap Sandstone Navajo Glen Canyon Group :3 mo KlOMEI'ERS K Page Sandstone Sandstone 0 Y I FIGURE 2.—Restored section of the Glen Canyon Group and lower part of the San Rafael Group showing continuity of J-0 and J -2 uncon- formities from northeastern Arizona to southwestern Utah. Stratigraphic relations in Glen Canyon Group after Harshbarger, Repenning, and Irwin (1957), Wilson {1965), and R. B. O’Sullivan (oral commun., 1970). Unconformity or probable unconformity shown by wavy line; J-0, J -1, J -2, and K-l designate unconformities in Pipiringos and O'Sullivan (1978). taposed and where the contacts had not been recogniz- ed before. The result is a clearer picture than had been obtained before of the relationship between the Navajo Sandstone and younger formations. Furthermore, our findings are consistent with the stratigraphic framework of Lower and Middle Jurassic strata as cur- rently understood in other parts of the Western In- terior of the United States. Owing to stratigraphic complexities, some of the units cannot be discussed in a simple oldest-to- youngest fashion. On the following pages we describe the Navajo Sandstone as it occurs throughout the region, followed by descriptions of the Temple Cap and Carmel Formations in southwestern Utah, where the type localities of these two formations are located. We then discuss the Carmel and Page Formations in south-central and southeastern Utah and adjoining parts of Arizona, where these rocks are equivalent or nearly equivalent in age to the type Carmel of southwestern Utah. Following this is a brief descrip- tion of the Entrada Sandstone, which lies on the Carmel throughout most of the region. Finally, we discuss the age of these formations in light of correla- tions to well-dated units in other regions and in light of recent paleontological discoveries. The basic framework of this study consists of a net- work of 21 measured sections of the Temple Cap Sand- stone, about 100 complete or partial measured sections of the Carmel Formation, about 1 10 measured sections of the Page Sandstone, and 45 measured sections of the Entrada Sandstone. In addition, the logs from 13 drill holes were also used. This was supplemented by tracing the units laterally wherever possible, aided by the stratigraphic markers noted earlier, and by map- ping in the Kaiparowits Plateau by W. E. Bowers, E. V. Stephens, H. A. Waldrop, H. D. Zeller, and Fred Peterson. The writers acknowledge with gratitude the helpful comments and constructive criticism offered by W. E. Bowers, P. E. Soister, E. V. Stephens, H. A. Waldrop, and H. D. Zeller during the course of the Kaiparowits mapping project, which has been in progress since 1963. Other members of the US. Geological Survey who have given freely from their knowledge of the stratigraphy of the Triassic and Jurassic Systems of the United States include W. B. Cashion, L. C. Craig, M. W. Green, R. W. Imlay, R. B. O’Sullivan, C. E. Turner-Peterson, and D. G. Wyant. The palynomorphs were identified by Bruce Cornet of Gulf Research and Development Company, Houston, Texas, who has made extensive studies of the palynology of Upper Triassic and Lower Jurassic rocks of the eastern United States. Capable assistance in the field was given by B. E. Barnum, P. C. Birkhahn, J. D. Craig, C. B4 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES J. Flynn, G. W. Horton, B. E. Law, R. A. Lehtola, O. L. Ligon, Jr., and R. L. Sutton. Mapping was done in the Kaiparowits Plateau at the scale of 1:24,000 by plane table and alidade aided by aerial photos flown in 1951, 1958, and 1966. In the part of Glen Canyon now covered by Lake Powell, the study was augmented by photos in the files of the US. Geological Survey that were taken by T. H. O’Sullivan with the Wheeler Survey in the 1870’s and by N. W. Bass, E. C. LaRue, H. D. Miser, and R. C. Moore with various US. Geological Survey parties in the 1920’s. The sections were measured using a Brunton compass and steel tape or using an Abney level and 5-foot Jacob staff. Measurements were made in the English system and later converted to metric. Colors in the lithologic descriptions follow those in a rock color chart of God- dard and others (1963), but the number and letter code in that chart is not given because it implies a greater accuracy than is possible to achieve in the field. Bed- ding classification and terminology generally follow that of McKee and Weir (1953), and grain size is ex- pressed in terms of the Modified Wentworth Grade Scale suggested by Dunbar and Rodgers (1957, p. 161). Sorting and mean grain size were estimated in the field with a hand lens, aided by comparison with 16 sieve analyses made by R. F. Gantnier on samples from the Page, Carmel, and Entrada Formations. In addition, 63 thin sections were prepared by M. E. Johnson from samples of each of the formations. The term silty sandstone is used for moderately to poorly sorted very fine grained sandstone or coarse siltstone that is poorly to moderately cemented and generally weathers to form a slope. The term mudstone is used for a nonfissile or poorly fissile rock composed mainly of clay-size particles but also containing a significant fraction of silt and sand-size grains. Shale, while present, is for the most part included with the mudstone because it is minor, inconspicuous, and generally difficult to distinguish from the mudstone except at perfect exposures. This report is a byproduct of a comprehensive pro- gram of the US. Geological Survey to evaluate and classify mineral lands in the public domain. GLEN CANYON GROUP The name Glen Canyon Group was first used by Baker and others (1927) for typical exposures in Glen Canyon, where it included, in ascending order, the Wingate Sandstone, rocks now known as the Kayenta Formation but at that time thought to be the Todilto Formation, and the Navajo Sandstone. Later, Williams (1954) named the Moenave Formation and assigned it to the group, where, in general, it is con- sidered an equivalent to parts of the Wingate Sand- stone and Kayenta Formation (fig. 2). Previous workers considered the Glen Canyon Group Triassic and Jurassic in age and thought that the systemic boundary was near the top of the group, in the Navajo Sandstone. However, recent paleontological and stratigraphic discoveries, strongly suggest that the group is largely Early Jurassic in age and that the systemic boundary is at or near the base of the group, either at the base of the Lukachukai Member of the Wingate Sandstone or at the base of the Moenave For- mation where the Lukachukai is absent. The Navajo Sandstone is the only formation in the group that is considered in detail here although a discussion of the age of the entire group is given in later paragraphs. NAVAJO SANDSTONE The Navajo Sandstone (Gregory, 1917) is a thick, cliff-forming, crossbedded sandstone formation that underlies a large part of southern Utah and northeastern Arizona. The colorful and spectacular sheer cliffs, deep canyons, and impressive spires, pro- montories, and monoliths that have been eroded in this formation are responsible for much of the scenic beau- ty of Zion National Park, Glen Canyon, and the Navajo Indian Reservation (figs. 3, 4). For the most part, the Navajo has two contrasting colors—various shades of red in the lower part and various shades of light gray in the upper part—but considerable variation occurs within these colors. The boundary between the red and white parts may be sharp or gradational, but in most places the color change bears little if any relation to bedding features and cuts directly across the stratification. In addition, one or the other of these col- ored zones may be missing, so that in places (for exam- ple, west of Zion Canyon) the formation is almost en- tirely moderate reddish orange or, as in parts of the Circle Cliffs area, it is entirely very light gray to very pale orange. Most of the Navajo consists of quartzose sandstone that is well sorted and fine to medium grained, although at several places along the base of some of the crossbedding sets there are scattered well-rounded coarse and very coarse grains of quartz and black or gray chert. The principal bedding types are high-angle, large-scale crossbedding in tabular-planar, wedge- planar, or trough-shaped sets generally 6—15 m thick, although one set 34 m thick was measured in Glen Can- yon near the mouth of the San Juan River. Minor but conspicuous lenses of interbedded sand- stone, mudstone, and cherty limestone or dolomite (Pipiringos and O’Sullivan. 1975), comprise about 2-3 percent of the Navajo in south-central Utah and north- central Arizona, but they are rare in southwestern Utah. The lenses contain fine-grained, moderately RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA B5 FIGURE 3.—View of typical exposures of the Navajo Sandstone (J‘fi n) and Temple Cap Sandstone in Zion Canyon, Utah. The narrow slot- like inner gorge of Zion Canyon is in the red lower part of the Navajo and the wider upper part of the canyon is in the white part of the Navajo. The red Sinawava Member of the Temple Cap (Jtcs) weathers to form a narrow, tree-covered shelf above the white cliffs of the Navajo and below the white crossbedded sandstone cliff of the White Throne Member of the Temple Cap (Jtcw). The limestone member of the Carmel Formation (Jcls) forms another tree-covered slope above the Temple Cap. The Temple Cap is about 52 m thick. View is north- northwest from Observation Point in Zion National Park, Washington County, Utah. sorted, laminated to very thin bedded, moderate- reddish-brown to grayish-red—purple sandstone and sil- ty sandstone interbedded with laminated dark-reddish- brown mudstone and light-gray cherty limestone or dolomite (fig. 5). Most of the lenses are less than 3 m thick and 300 m wide, although Davidson (1967, p. 37) found several in the Circle Cliffs area that could be traced for 16—24 km. Although chert nodules are a minor constituent of the Navajo, they are especially significant because they were the most likely source of the chert pebbles that were incorporated in the basal part of some of the formations that lie on the Navajo. Two types of chert are present and both are of authigenic origin. Authigenic chert nodules in the limestone beds of the interbedded sandstone, mudstone, and limestone lenses are microcrystalline and range in color from medium gray to grayish red or pale brown. Most of these nodules are white or very light gray on the periphery (fig. 5). The other type of authigenic chert oc- curs as highly irregular masses as much as 0.3 m long that are present in the crossbedded sandstone, general- ly along the base of crossbedding sets or in some of the areas where slumping of the crossbedded sandstone oc- curred, as well as in the flat-bedded sandstone lenses that also contain thin limestone beds (fig. 6). For the most part, these irregular masses are color zoned from grayish red on the interior to white or very light gray on the outside, and the texture is either colloform or, less commonly, microcrystalline. The greatest thickness of the Navajo known to the writers is 677 m, measured in Zion National Park by Wilson (1965, p. 42). The formation thins eastward and is beveled out near the Arizona-New Mexico and Utah- Colorado State lines by the J-2 unconformity at the base of the overlying Middle Jurassic formations (fig. 2). The lower contact is sharp or gradational, and inter- fingering of the lower part with the Kayenta Forma- tion has been recorded by Wilson (1965) in southwestern Utah and by Harshbarger, Repenning, B6 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE 4.—View of typical exposures of red crossbedded Navajo Sandstone in Glen Canyon about 10 km northeast of Page, Ariz. In general, a bench is stripped back on top of the Navajo (JR n); this stripped bench is apparent on either side of the canyon at the foot of the smooth rounded bluffs of Page Sandstone (J p). Some Holocene polygonal joint crevices (j) similar to fossil joint crevices preserved beneath the Page Sandstone (figs. 22, 23) are well exposed in the light-colored area to the right above the canyon walls. For scale, the Page Sandstone is about 38 and 46 m thick, respectively, on the right and left sides of the canyon, which is about 134 m deep in the middle of the photo. Warm Creek Canyon in foreground, Navajo Mountain forms the broad asymmetrical dome on the skyline. Jcau, upper member of Carmel Formation; -Je, Entrada Sandstone; Jr, sandstone at Romana Mesa; Jms. Salt Wash Member of Morrison Formation. View is toward east in the NE1/4 sec. 12, T. 44 S., R. 4 E., Kane County, Utah. Photo by T. H. O'Sullivan (Wheeler Survey). 1873. and Irwin (1957) in southeastern Utah and northeast- ern Arizona. SAN RAFAEL GROUP The San Rafael Group was named by Gilluly and Reeside (1928, p. 73) for strata in the San Rafael Swell of Central Utah that include, in ascending order, the Carmel, Entrada, Curtis, and Summerville Forma- tions. Later workers added the Todilto Limestone and Bluff Sandstone to the group (Harshbarger and others, 1957, p. 32). The Todilto and Bluff are present near the Four Corners and farther south, but they are not described in this report. Two additional formations, the Temple Cap Sandstone (formerly a member of the Navajo Sandstone) and the Page Sandstone (formerly an unnamed part of the Navajo), are also assigned to the San Rafael Group in this report. Along with the Carmel Formation, these are the only formations in the group that are considered in detail here. Paleon- tological evidence and regional stratigraphic relations indicate that the group is Middle Jurassic in age (R. W. Imlay, oral commun., 1976). TEMPLE CAP SANDSTONE The Temple Cap Sandstone is presently known to oc- cur only in southwestern Utah, where it forms a distinct stratigraphic unit between the Navajo Sand- stone and the Carmel Formation (fig. 3). The formation was considered an informal member of the Carmel by Baker, Dane, and Reeside (1936, p. 22). It was con- RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA B7 FIGURE 5,—Authigenic chert nodules in limestone bed of Navajo Sandstone. Several of the nodules are color zoned from medium gray or grayish red in the middle to very light gray or white on the periphery. Weathering of beds such as this probably produced many of the detrital chert pebbles that were incorporated in the basal stratum of the Page Sandstone. East side of Dangling Rope Canyon about 6.4 km southwest of Navajo Point, Kane County, Utah. sidered a formal member of the Navajo Sandstone by Grater (1948) and later a more detailed description was published by Gregory (1950a, p. 89). Workers since 1961 (Lewis and others, 1961) thought that the Temple Cap graded into the Navajo east of Mount Carmel Junction, Utah, but recent field examination of that area indicates that these formations do not intergrade. Because the Temple Cap is a separate mappable unit that can be distinguished from the Navajo and Carmel Formations, and because the Temple Cap is more close- ly related temporally, and to some extent lithological- ly, to other formations in the San Rafael Group, the Temple Cap is here raised to formation rank, removed from the Glen Canyon Group, and included in the San Rafael Group. The type locality of the Temple Cap (Gregory, 1950a, p. 89) is at the top of East and West Temples in Zion National Park, where the formation is only accessible by means of mountaineering techniques or with a helicopter. For this reason, a more accessible section measured about 500 m northeast of Observation Point, at the top of Zion Canyon (fig. 7), is here proposed as a principal reference section. This section also serves as the type section of two new members that are here named the Sinawava Member and the White Throne Member. The principal reference section is typical of B8 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE 6.—Authigenic chert in sandstone bed of Navajo Sand- stone. Although these nodules and small blebs are in a flat-bedded sandstone lens, similar but larger nodules also occur in the crossbedded sandstone of the Navajo. Note the extreme angulari- ty and the tiny fingers that extend from the nodules out into the sandstone. West side of West Canyon tributary to Glen Canyon about 4 km southeast of Gregory Butte in the SW% sec. 23, T. 43 S., R. 61/2 E., San Juan County, Utah. the formation in the Zion Canyon section of Zion Na- tional Park and farther east. West of Zion Canyon the White Throne Member grades into a predominantly flat bedded redbed facies that is included in the Sinawava Member. The Temple Cap thins irregularly eastward along the principal line of outcrops from a maximum of 113.4 m near Gunlock, Utah, to its wedgeout near Johnson Can- yon (fig. 8). SINAWAVA MEMBER The Sinawava (pronounced Si-na’-wa-va, meaning Wolf-god in the Paiute language according to Wood- bury, 1950, p. 112) Member of the Temple Cap Sand- stone takes its name from the Temple of Sinawava in Zion Canyon (Gregory, 1950a, fig. 98) about 1 km northwest of the type section, which is 500 m northeast of Observation Point (fig. 7). At the type sec- tion and throughout the area east of the Hurricane Cliffs, the member is a slope-forming unit composed of interbedded sandstone, silty sandstone, and mudstone. West of the Hurricane Cliffs, the topographic character and lithologic composition re- main the same but several beds of gypsum are also pre- sent. West of Mount Carmel Junction the Sinawava is moderate reddish brown to dark reddish brown and it forms a conspicuous dark-red slope between the lighter colored cliffs of the underlying Navajo Sandstone and the overlying White Throne Member of the Temple Cap. East of Mount Carmel Junction the Sinawava grades to very light gray or very pale orange and the color difference between the overlying and underlying rocks is not as conspicuous. Here, the member must be recognized and traced solely on the basis of its slope- forming character and lithologic composition. The Sinawava Member thins irregularly eastward from 6.1 m at the type section near Observation Point to 2.4 m at Johnson Canyon about 27 km east of Mount Carmel Junction, where it is overlain by the thin wedge edge of the White Throne Member (fig. 9). East of Johnson Canyon the Sinawava apparently is truncated by the J -2 unconformity at the base of the overlying Carmel Formation (fig. 8), but this area is heavily covered by soil, windblown sand, and vegeta- tion; and the relationships at the wedgeout of the Sinawava could not be examined. West of the type sec- tion, near Observation Point, the Sinawava thickens ir- regularly to as much as 113.4 m, owing primarily to in- terfingering and westward replacement of beds in the White Throne Member, as shown in figure 8. As a result of this facies change, the White Throne is mis- sing west of the Hurricane Cliffs, and the Sinawava is the only member of the Temple Cap that is present. The Sinawava Member consists of interbedded slope-forming sandstone, silty sandstone, mudstone, and scarce gypsum. The sandstone and silty sandstone beds are very fine to fine grained, poorly to moderately sorted, and are predominantly moderate reddish brown, although several beds are light gray to very light gray. Scattered throughout several of these beds are well-rounded coarse and very coarse grains or very fine pebbles of black, gray, light-brown, green, orange, or red chert. The scattered coarse grains and small peb- bles are fairly common in the western part of the Sinawava; they were found as far east as section 9 at Potato Hollow, which is about 7.2 km northwest of the type section above Zion Canyon. At Cottonwood Canyon (sec. 7, fig. 8), scattered angular light-gray chert pebbles up to 13 mm long are locally present in a thin sandstone bed at the base of the member. The chert is similar to the authigenic chert that occurs in nodules in the underlying Navajo Sandstone. Mudstone in the member is laminated to very thin bed- ded and dark reddish brown or yellowish gray. Very light gray gypsum is also present west of the Hur- ricane Cliffs, where it occurs in several beds as much as 2 m thick that are laminated to very thin bedded or composed of nodular gypsum aggregates. As many as eight thin beds of very dusky purple or yellowish-gray bentonite as much as 0.6 m thick occur in the middle of the member west of the Hurricane Cliffs. The basal contact of the Sinawava, named the J-1 surface by Pipiringos and O’Sullivan (1978), is a clearly defined and continuous surface that is easy to recognize because it separates markedly different RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS. UTAH AND ARIZONA B9 FIGURE 7 .—Principal reference section of Temple Cap Sandstone and type section of the Sinawava and White Throne Members above Zion Canyon, Utah. 4, principal reference section, Temple Cap Sandstone is 55.8 m thick; (J ‘E n), Navajo Sandstone; Jtcs, Sinawava Member of Temple Cap Sandstone; Jtcw, White Throne Member of Temple Cap; JCIS, limestone member of Carmel Formation. View is toward the northeast from Observation Point in Zion National Park. lithologies. The abrupt change in rock types at this contact, the lateral continuity of this surface, the broad irregular form of this surface with respect to the upper contact of the Temple Cap (fig. 8), the local presence of small angular chert pebbles on it that pro- bably were derived from the underlying Navajo Sand- stone, and the extensive bleaching at the top of the underlying Navajo Sandstone east of Zion Canyon, suggest that the J-1 surface at the base of the Sinawava is an unconformity. However, none of these features can be considered as conclusive evidence that the J -1 surface is indeed an unconformity, and it could also be that this surface merely marks an abrupt and Widespread change in depositional environments. WHITE THRONE MEMBER The White Throne Member takes its name from the Great White Throne in Zion Canyon, which is about 2 km south of the type section about 500 m northeast of Observation Point (fig. 7). The member is a con- spicuous cliff-forming unit (fig. 3) composed of fine- grained well-sorted crossbedded sandstone. The crossbedding is the high-angle tabular-planar or wedge-planar type in sets as much as 6 min thickness. Locally, the sandstone contains small irregular blebs less than 1 cm wide of very light gray authigenic chert along the base of some of the crossbedding sets. At the type section in Zion Canyon and farther east, the member is very light gray to very pale orange, but Hurricane Cliffs Limestone member of Carmel Formation ' ' \ -~ \ (lower part) I . . \ Limestone \ unit \. \—\ \\\ \ Basal unit ? ... Sinawava Member ’I ITIITTT} Fl Temple .-. Cap 7 p _ Sandstone :'. NW Navajo Sandstone EXPLANATION I Varbusshadesofred H Variousshadesoigray Crossbedded sandstone a limestone Flat-bedded sandstone Gypsum Mudstone Covaed Partly covered E [I] E TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES East Zion Mount Johnson Canyon Camel Canyon Junction 0 20 KlLOMETERS 0 E Mixed red and gray J v: | :— UTAH ‘L .. _ I—rf . 0 50 KM . Line of I ”“9““ M ”ebb” _1 ”said“ _ “I- 0 Rounded vay coarse grains : ) T l and very fine pebbles /J ARIZONA I I | —< Bentonite f f I I J FIGURE 8.—Stratigraphic section from Gunlock to Johnson Canyon, Utah, showing relations of Temple Cap Sandstone to Navajo Sand- stone and Carmel Formation. Unconformity shown by wavy line. J-l, J-2, unconformities of Pipiringos and O'Sullivan (1978). west of Zion Canyon the color grades to moderate red- dish orange. The White Throne is 49.7 m thick at the type section, and it thins eastward to Johnson Canyon (figs. 8, 9), where it is beveled out by the J -2 unconfor- mity at the base of the overlying Carmel Formation. West of Zion Canyon the White Throne grades into the Sinawava Member (fig. 8). East of Mount Carmel Junction the lower contact generally is well exposed and it is a fairly sharp and planar surface (fig. 9). West of Mount Carmel Junction the contact generally is poorly exposed, but in the few places where it is visible it is vertically gradational through a thin transition zone about 1 m thick that consists of laminated to very thin bedded and small- to medium-scale crossbedded sandstone. Probably because of similar lithologic characteristics, many workers thought that the crossbedded sandstone of the White Throne Member was a tongue of the Navajo Sandstone that merged with that formation just east of Mount Carmel Junc- tion (Lewis and others, 1961, p. 1439; Wright and Dickey, 1963a, p. E65, and 1963b; Wilson, 1965, p. 42; Thompson and Stokes, 1970, p. 6). However. the flat- bedded Sinawava Member does not pinch out and the crossbedded White Throne Member does not merge with the crossbedded Navajo anywhere east of Mount Carmel Junction. Instead, the Sinawava continues on east to Johnson Canyon where the stratigraphic rela- tions indicate that the entire Temple Cap Sandstone is beveled out (figs. 8, 10). Thus, the White Throne Member is an eastward-thinning wedge, separated from the Navajo Sandstone by the Sinawava Member, and does not merge with the Navajo Sandstone. CARMEL FORMATION The Carmel Formation (Gregory and Moore, 1931; Cashion, 1967) is a generally eastward thinning limestone, gypsum, and redbed unit that is present RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA FIGURE 9.—Thin Temple Cap Sandstone at Johnson Canyon about 27 km east of Mount Carmel Junction, Utah. The flat-bedded Sinawava Member (Jtcs) forms a notch beneath the crossbedded White Throne Member (Jtcw), which forms a conspicuous ledge beneath the rubble-covered slopes of the limestone member of the Carmel Formation (Jcls). The Temple Cap is 3.7 m thick here. J'fi n, Navajo Sandstone. West side of Johnson Canyon in the NW1/4 sec. 26, T. 41 S., R. 5 W., Kane County, Utah. throughout southern Utah and northeastern Arizona. At the type locality near Mount Carmel Junction, Utah, the formation consists of four members, which are (from oldest to youngest) the limestone member, banded member, gypsiferous member, and Winsor Member. A somewhat different nomenclature is used farther east in south-central Utah, where several significant facies or nomenclatural changes occur: the limestone member is termed the Judd Hollow Tongue of the Carmel east of Cannonville, Utah, and the Judd Hollow grades farther east into the Page Sandstone; the banded member grades eastward into the Thou- sand Pockets Tongue of the Page Sandstone; the gyp- siferous member grades into the lowest part of the up- per member of the Carmel; and the Winsor Member grades into the middle and upper parts of the upper member of the Carmel. LIMESTONE MEMBER The limestone member of the Carmel Formation (Cashion, 1967) is composed of two units: a lower, thin, slope-forming mudstone and sandstone unit and an up- per, thick, cliff-and-slope-forming limestone and shale unit (fig. 13). At the type locality of the Carmel near Mount Carmel Junction, the lower unit is about 5.5 m thick and consists of moderate-reddish-brown, very light gray, or very pale orange, very fine to fine- grained, poorly to moderately sorted sandstone and sil- ty sandstone interbedded with laminated to very thin bedded mudstone or shale. Locally scattered along the base are coarse and very coarse grains or very fine peb- B11 bles of chert and green mudstone pellets or chips. The upper unit is 66.1 m thick and contains very light gray to very pale orange, laminated to thin-bedded, microcrystalline to fine-grained, fossiliferous limestone interbedded in the middle with yellowish- gray calcareous shale and scarce moderate-reddish- brown mudstone. Several beds of light-olive-gray oolitic limestone commonly occur in about the lower third of the upper unit. About 1 1 km southwest of Can- nonville, Utah, the middle part of the upper unit con- tains as many as four beds of light-gray gypsum as much as 0.3 m thick. The limestone member is 71.6 m thick at the type locality of the Carmel near Mount Carmel Junction and it thickens westward to 191.1 m near Danish Ranch in southwestern Utah (sec. 8, fig. 10). It thins eastward to 34.4 m at the Paria River near Cannon- ville, where rocks equivalent to this member are term- ed the Judd Hollow Tongue of the Carmel Formation. The lower contact is described with the lower contact of the Judd Hollow Tongue. JUDD HOLLOW TONGUE East of the Paria River near Cannonville, Utah, strata equivalent to the limestone member have been named the Judd Hollow Tongue of the Carmel Formation (Phoenix, 1963, p. 33). The Judd Hollow is 34.4 m thick near Cannonville (sec. 20, fig. 10), where it consists of essentially the same lithologies as the limestone member farther west; but east of the Paria River the limestone beds thin and pinch out into laminated to thin-bedded, moderate-reddish-brown sandstone, silty sandstone, and mudstone (Wright and Dickey, 1963a, p. E66). Although the upper 0.3 m of the Judd Hollow at the Paria River near Cannonville consists of red mudstone that correlates with the lowermost part of the banded member farther west, by far the greater part of the Judd Hollow correlates with the limestone member. For all practical purposes, one may consider the Judd Hollow the eastern equivalent of the limestone member. The Judd Hollow Tongue is about 9.9 m thick at the type locality in Judd Hollow on the south side of the Kaiparowits Plateau about 27 km northwest of Page, Ariz. (fig. 10, sec. 26). Here, it consists mainly of sand- stone and siltstone, although it also contains one thin bed of silty limestone about 0.3 m thick (Phoenix, 1963, p. 69, sec. 3, unit 3). Several kilometers southeast of this locality these beds grade into crossbedded sand- stone strata that are included in the Page Sandstone (fig. 10). A similar facies change occurs on the north side of the Kaiparowits Plateau about 34 km southeast of Escalante, Utah (fig. 11). The lower contact of the limestone member is a sharply defined, continuous and planar surface that B12 TRIASSIC AND JURASSIC ROCKS. WESTERN INTERIOR UNITED STATES West East .gmnson Paunsaugunt Mount 3W0" fault Wes1 Cove Gunlock Carmel l Cummings . 16 I l Junction K—1 Mesa I 13 "4 I trail Zion ‘\ Canyon 12 \ 3 9 4 ‘° 5 K 1 Cretaceous 10 11 ch 6 \ ”W Carme| Formation Carmel Formation ”a? g 51] KILUMETEHS ’6’ r: 8 EXPLANA110N % U % Carmel Formation Sandstone, medium to large-scale crossbedded “E; Jcau Upper member :_ chh Judd Hollow Tongue ch Wirsor Member E Sandstone, flat—bedded to medium-sale cross— ch Gypsflerous member bedded; includes mudstone and scarce gypsum Job Banded member Jcls Linestone member Sandstone, mudstone, and gypsum I Temple Cap Sandstone Jtcw While Throne Manber V ——‘ J16 Sinawava Member ”A Limestone, includes some mudstone J Judi” | i l Jp Page Sandstone thp Thousand Pockets Tongue V , ARIZONA I \ Gyps ' W “N0 5 as” l l l Jphw Harris Wash Tongue \\\\\ um‘ includes m he and m M FIGURE 10.—Restored section from Gunlock, Utah, to Cummings Mesa. Ariz., showing correlations and dominant lithologies in the Temple Cap, Carmel, and Page Formations. Unconformity shown by wavy line. J -1, J -2, K-l, unconformities of Pipiringos and O’Sullivan (1978). Dashed lines indicate correlation of beds or minor units below member rank. bevels out the Temple Cap Sandstone in southwestern Utah (figs. 8, 10). This surface is named the J -2 uncon- formity by Pipiringos and O’Sullivan (1978). The con- tact is marked by local concentrations of whatever hard and resistant coarser grains and small pebbles or authigenic chert blebs and nodules are present in the underlying rocks. Where the limestone member lies on the White Throne Member of the Temple Cap Sand- stone, or where the limestone member and Judd Hollow Tongue lie on the Navajo Sandstone, the lowest bed of the limestone member or Judd Hollow Tongue contains scattered or locally concentrated coarse and very coarse grains and very fine pebbles of subangular to angular, very pale orange, grayish-pink, or very light gray chert that probably were derived from authigenic chert blebs or nodules in the underly- ing rocks. Where underlain by the Sinawava Member of the Temple Cap Sandstone in southwestern Utah, the lowest bed of the limestone member contains scat- tered or locally concentrated coarse and very coarse grains and very fine pebbles of well-rounded, red, black, light-gray, light-brown, green, or orange chert. Evidently the coarser grains and small pebbles were derived from the eroded parts of the underlying forma- tions and locally concentrated in lag deposits during the earliest stage of deposition of the limestone member or Judd Hollow Tongue. Where the Judd Hollow rests on the Harris Wash Tongue of the Page Sandstone, the contact is conformable and either sharp and planar or vertically gradational through a transi- tion zone about 1 m thick of laminated to very thin bedded or small- to medium-scale crossbedded sand- stone. Angular chert pebbles were not found at the contact with the Harris Wash Tongue, although local- RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA B13 Southwest Northeast } Northwest Southeast Cannonvlle METERS 150 20 Escalante 33 Early Weed 100 Bench Navajo 50 Carmel Pornt Cummings Cow Formation I Mesa Springs 39 tralrl 0 38 4° 41 42 43 32 44 45 46 S ngte .53“- , \ Entrada Sandstone act; one .. . zzzb J Carmel rmel Z cau Formation F°"ma"°" .2 , ,. .. . , . ,, , ,,,,, ‘« -==5: 1’ m Navajo Sandstone \J_2 Page Sandstone Navajo Sandstone \J 2 0 50 KlOMEIERS l___—___J EXPLANATION F Sandstone, medium to large—scale crossbedded I JI— 1 UTAH ( P _ | Carmel onnation I Jcau Upper member ‘:| Sandstone, flat-bedded to medium-scale cross- [_“1_‘_1_I_30 —f 0 50 KM I Jog Wm member bedded; includes mudstone and scarce gypsum l 37 J L—1 chh Judd II I] Tongue Sandstone, mudstone, and gypsum I -—17--— 44 —l-_—I 7 . . I I I JP Page Sandstone M Lmestone, Includes some mudstone J 1 Line 01" 46 I I thp Thousand Pockets Tongue V . ' - section Jphw Hans Wash Tongue A\\\ Gypsum, includes some mudstone and limestone ( ARIZONA I l FIGURE 11.—Restored section from Kodachrome Flat near Cannonville, Utah, to Cow Springs, Ariz., showing correlations and dominant Iithologies in the Page Sandstone and Carmel Formation. Unconformity shown by wavy line. J-2, unconformity named by Pipiringos and O'Sullivan (1978). Dashed lines indicate correlation of beds or minor units below member rank. 1y, as at measured section 27 in Sand Valley, coarse and very coarse sand grains are scattered in the basal stratum of the Judd Hollow just above the Harris Wash Tongue. BANDED MEMBER The banded member of the Carmel Formation (Cashion, 1967) is a slope-forming sandstone unit that was mistaken for the Entrada Sandstone by early workers (Baker and others, 1936; Gregory, 1948, 1950a, b) and later shown to be part of the Carmel For- mation by Wright and Dickey (1963a, b). At the type locality of the Carmel, near Mount Carmel Junction, it is composed of very fine to fine-grained, poorly to moderately sorted, moderate-reddish—brown, light-red, and very light gray sandstone (fig. 12). The stratification is very thin to thin bedded and small to medium scale, low and high angle, tabular planar crossbedded in sets less than a meter thick. Scattered well-rounded pebbles of chert, quartzite, tuf- faceous sandstone, and microcrystalline or porphyritic igneous rocks as much as 1.5 cm long locally occur in the member. West of Mount Carmel Junction, Gregory (1950b, p. 89) noted that the member contains two beds of white gypsum 0.3 m thick and a bed of con- glomerate 3 m thick composed of chert and quartzite pebbles as much as 2.5 cm in diameter. About 11 km southwest of Cannonville, Utah, a bed of light-gray gypsum, 7.3 m thick, is present at the base of the member. In general, the banded member thins southeastward across southwestern Utah. It is as much as 68.3 m thick about 30 km northwest of Mount Carmel J unc- tion (Gregory, 1950b, p. 89) and is 51.2 m thick at Mount Carmel Junction (Gregory, 1950a, p. 127; Cashion, 1967, p. J3). In the outcrop belt between Johnson Canyon and Cannonville, Utah, the member grades laterally into the Thousand Pockets Tongue of the Page Sandstone. Contrary to Thompson and Stokes (1970, p. 6), we could not find evidence of a regional unconformity between the banded member (their Crystal Creek Member) and the Thousand Pockets Tongue. The best place where interfingering of these units can be examined is in the canyon of Willis B14 FIGURE 12.—Good exposures of banded member of Carmel Forma- tion near Mount Carmel Junction, Utah. The member consists of interbedded red to white. flat-bedded and crossbedded sandstone and silty sandstone and red mudstone that locally contains sandstone-filled mudcracks. Uppermost rounded gray ledge is basal part of gypsiferous member of Carmel Formation. View is northeast about 0.5 km northwest of Mount Carmel Junction, Kane County, Utah. Creek about 10 km southwest of Cannonville, Utah (fig. 13). The lower contact of the banded member is a sharp and planar surface at the top of the highest limestone bed of the limestone member. Some interfingering of the lowest beds of the banded member and the highest beds of the limestone member may occur in the area west of the Paria River near Cannonville, but the ex- posures are too poor to determine this accurately. GYPSIFEROUS MEMBER The gypsiferous member of the Carmel Formation (Cashion, 1967) tends to form cliffs where exposed to rapid erosional processes (fig. 14), but for the most part it forms a slope that is covered by soil and vegetation. TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES At the type locality of the Carmel and at many other places, the lower half or two-thirds of the member con- sists of white to very light gray gypsum that is laminated to thin bedded or is composed of nodular gypsum aggregates. One or two thin beds of light-gray limestone or yellowish-gray mudstone also occur local- ly in this part of the member, although they are not common. In places, the basal 0.3—1.0 m consists of light-olive-gray to yellowish-gray mudstone that local- ly contains mudchip conglomerate composed of fragments 2—5 cm long of mudstone similar to that in the underlying banded member. The upper half or third of the gypsiferous member contains light-gray, yellowish-gray, or moderate-reddish-brown, laminated to thin-bedded, gypsiferous sandstone, silty sand- stone, or mudstone, and pale-olive to light-gray, laminated, locally fossiliferous limestone. It was once thought that the member correlated with the Curtis Formation of central Utah (Gregory, 1950a, b, 1951) but later, Wright and Dickey (1963a) demonstrated that it is older than the Curtis. The gypsiferous member is 15.2 m thick at Mount Carmel Junction and it thickens irregularly westward to as much as 41.8 m near Kanarraville, Utah, about 50 km northwest of Mount Carmel Junction (Gregory, 1950b, p. 85). It has not been found or reported west of the Hurricane Cliffs, where, presumably, it was remov- ed by erosion prior to deposition of Cretaceous rocks. The member thins eastward, largely by interfingering with the lower beds of the upper member of the Carmel, and pinches out about 11 km southeast of Can- nonville, Utah, and near Escalante, Utah (figs. 10, 11). The lower contact is sharp and generally planar, although several centimeters of relief occur on the sur- face in places. The contact was chosen at the base of the lowest gypsum, limestone, or mudchip con- glomerate bed in the gypsiferous member. Although the local mudchip conglomerate at the base suggests an unconformity, we could find no evidence that any appreciable regional erosion or nondeposition occurred prior to deposition of the member. About 15 km northeast of Page, Ariz., interfingering occurs along the lateral continuation of this surface between the Page Sandstone and the overlying upper member of the Carmel Formation (fig. 10). Elsewhere in the Western Interior, Imlay (1967, p. 20, 45) found evidence of erosion at about the same stratigraphic position at the base of the Watton Canyon Member of the Twin Creek Limestone. WINSOR MEMBER The Winsor originally was considered a separate for- mation at the top of the Jurassic System in southwestern Utah by Gregory (1950a, b). Later, Wright and Dickey (1963a, b), who did not use the term RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS. UTAH AND ARIZONA Bl5 Winsor, included these rocks in the Carmel and cor- related them with strata farther east and northeast in south-central Utah that long had been considered part of the Carmel Formation. Based on the correlations established by Wright and Dickey, Cashion (1967) reviewed the nomenclature of the Carmel Formation, reduced the Winsor to member rank, and included it as the youngest member in the Carmel Formation west of the Paunsaugunt fault, which is about 50 km northeast of Mount Carmel Junction (fig. 10). Cashion’s FIGURE 13.—lnterfingering of banded member of Carmel Formation (Job) and lower part of Thousand Pockets longue of Page Sand- stone (J ptp) about 10 km southwest of Cannonville, Utah. Progressing from left to right (northwest to southeast) the upper contact of the banded member is lowered as indicated owing to pinching out of thin red mudstone marker beds (a and b on photo) at the top of the member. To the right, the top of a local buildup of very thickly crossbedded sandstone in the lower part of the Thousand Pockets Tongue is outlined by dots; near the center of the view, this sandstone unit grades northwestward (left) into flat-bedded sandstone that is included in the banded member (Jcb). Truncation of the crossbedding in the sandstone buildup by the onlapping strata above it is interpreted as a local diastem rather than as part of a regional unconformity such as suggested by Thompson and Stokes (1970. p. 6). For scale, the Thousand Pockets Tongue and handed member together are about 30 m thick in the middle of the photo. J E n, Navajo Sandstone; J cls. limestone member of the Carmel Formation; dotted line and C (in JCIS), approximate contact between basal and limestone units; 09, Quaternary gravels; dashed lines indicate formation or member contacts, dotted lines indicate correlation of units within the member: J -2. unconformity named by Pipiringos and O'Sullivan (1978). Looking north-northeast across Willis Creek Canyon in the NE‘ASE‘A sec. 23, T. 38 S., R. 3 W., Kane County, Utah. B16 nomenclature and recommendations are followed in this report, although it is recognized that the upper part of the Winsor is slightly younger farther northeast near the Paunsaugunt fault than it is at the type locality in Winsor Cove near Mount Carmel J unc- tion. The type locality of the member is in Winsor Cove (Gregory, 1950b, p. 42) about 3 km north of Mount Carmel Junction, Utah, where it is a poorly indurated sandstone unit that weathers to form broad slopes TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES largely covered with soil and vegetation. The color of the member varies considerably, from moderate or dark reddish brown and grayish pink to very pale orange and very light gray. The upper 15 m or more is very light gray to pale orange near Mount Carmel Junction as well as farther northeast, where it is overlain by the Dakota Sandstone of Cretaceous age. The thick light-colored zone is consistently present at the top of the member and is thought to result from bleaching by solutions that percolated into the FIGURE 14,—The Thousand Pockets Tongue of the Page Sandstone (J pip) and gypsiferous member of the Carmel Formation (ch) in Aver- ett Canyon about 9 km southwest of Cannonville, Utah. The Thousand Pockets is grayish orange and forms the light-colored slope above the red slopes of the banded member of the Carmel (Jcb). The gypsiferous member consists of a cliff-forming white gypsum bed about 10 In thick overlain by a platy slope-forming grayish-yellow—green unit of interbedded mudstone and gypsum about 3.7 m thick. A thin limestone marker bed (ls) capping the ridge is included in the upper member member of the Carmel (Jcau), rather than with the gypsi- ferous member as had been done by previous workers. The locality is about 1.1 km northwest of the locality shown in figure 13 where the banded member grades southeastward into the lower part of the Thousand Pockets Tongue. Thus, the part of the banded member visible here is a facies of the lower part of the Thousand Pockets farther southeast. Looking northeast in the NW% sec. 23, T. 38 S., R. 3 W., Kane County, Utah. RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA member during the erosion interval that preceded depositon of the Dakota. The Winsor consists mostly of very fine to medium- grained, poorly to moderately sorted, friable sand- stone, pebbly sandstone, and silty sandstone. The stratification is predominantly very thin to thick bed- ded, although a significant fraction consists of small- to medium-scale, low- and high-angle, tabular-planar or wedge-planar cross-strata. Sets of large-scale, high- angle crossbedding are present but not common. The Winsor also contains several thin beds of laminated to very thin bedded, dark-reddish-brown or yellowish- gray mudstone, but because of poor exposures these beds usually are not noticed. Averitt (1962, p. 22—23) measured a section near Cedar City, Utah, that in- cludes approximately 10—15 percent mudstone, sug- gesting that more mudstone is present than is general- ly apparent or that the amount of mudstone varies significantly from place to place. Gregory (1950b, p. 41) noted that the member contains several thin lenses of limestone and gypsiferous shale northwest of Win- sor Cove in southeastern Iron County, Utah. Scattered throughout the sandstone beds of the Winsor or locally concentrated in lenses up to about 0.6 m thick are rounded and subrounded pebbles of gray, green, or black chert, red to light-purple tuffaceous sandstone, gray or green quartzite, gray sandstone, dark-gray silicified tuff, and aphanitic or porphyritic igneous rocks as much as 5 cm in diameter. In addition, Gregory (1950a, p. 98) found sharply angular pebbles of limestone and rhyolite in the member. The Winsor ranges in thickness from 54.9 to 97.2 m west of Mount Carmel Junction according to Gregory (1950a) and Averitt (1962). It has not been found west of the Hurricane Cliffs, where it was apparently bevel- ed out by the unconformity at the base of the Cretaceous System. The Winsor thickens northeast of Mount Carmel Junction and reaches its maximum thickness of 204.2 m near Carly Knoll, about 15 km west of the Paunsaugunt fault (fig. 10). In this area the Winsor is composed of rocks similar to those at the type locality, but facies changes occur east of the Paunsaugunt fault and equivalent beds are included in the upper member of the Carmel Formation. The lower contact of the Winsor is conformable and either sharp or gradational; it is placed at the top of the highest gypsum or limestone bed in the gypsiferous member of the Carmel. UPPER MEMBER East of the Paunsaugunt fault, strata at the top of the Carmel are informally named the upper member of the Carmel Formation. 'IVvo different facies of this member are recognized in south-central Utah, and easi- B17 ' ly reached reference sections for each of these facies are given at the end of this report. The Pine Creek reference section is 5 km north of Escalante, Utah, where the member consists primarily of limestone in the lower part and interbedded sandstone, mudstone, and gypsum in the upper part (fig. 15). The Page, Ariz., reference section is 5 km north of Glen Canyon Dam, where the member consists primarily of sandstone and less abundant mudstone. An important limestone marker bed is in the lower part of the upper member east of the Paunsaugunt fault. Just east of the fault it is about 4.9 m thick and consists of light-gray, laminated to very thin bedded limestone that lies about 47.2 m above the base of the upper member. In this area, Thompson and Stokes (1970, fig. 3) included the marker bed in the gyp- siferous member (their Paria River Member of the Carmel Formation), but they miscorrelated the bed with thin limestone beds at the top of the gypsiferous member near Mount Carmel Junction. We do not in- clude the marker bed in the gypsiferous member because the bed pinches out southwestward near the Paunsaugunt fault and is not present at the type locali- ty of the Carmel Formation, and because the marker bed is stratigraphically higher than any part of the gypsiferous member at the type locality of the Carmel. The limestone marker bed extends east of the Paun- saugunt fault into parts of the Kaiparowits Plateau. Between Cannonville and Escalante, Utah, in the sub- surface, well logs show that several other limestone beds occur beneath the marker bed. In the exposures near Escalante, the marker bed is at the top of a se- quence of beds 31.4 m thick at the base of the upper member of the Carmel Formation. This sequence con- sists of light-gray to yellowish-gray, very thin to thin- bedded limestone interbedded with about 35 percent of dark-reddish-brown or scarce grayish-yellow-green, laminated to very thin bedded mudstone (fig. 11). About 20 km southeast of Escalante the limestone beds beneath the marker bed grade into red sandstone, silty sandstone, and mudstone; and the marker bed can be traced farther southeast along the foot of the Straight Cliffs to about 72 km southeast of Escalante, where it also grades into red sandstone, silty sand- stone, and mudstone (fig. 11). The marker bed can be traced underground by means of well logs to the part of Glen Canyon that lies just north of Page, Ariz. (fig. 10). In this area it is as much as 4.3 m thick and lies about 5.5—12.5 m above the base of the upper member of the Carmel Formation (Peter- son and Waldrop, 1965, p. 52; Peterson, 1973, colum- nar section; Section 2a, unit 7, at end of this report). At its southeasternmost extent along the Straight Cliffs and in Glen Canyon north and northeast of Page, Ariz., B18 the marker bed is moderate orange pink to light gray, laminated to very thin bedded limestone. Locally, it has peculiar straight lines on the bedding surfaces that intersect at right angles. These lines resemble linear markings on some maps and prompted Young (1964) to name it “maprock.” Gypsum is another rock type in the upper member that serves to distinguish it from the Winsor Member. a, TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES Near Cannonville, Utah, as many as five beds of gyp- sum occur in a marker zone as much as 17.1 m thick at the top of the upper member. This zone is composed of interbedded sandstone, silty sandstone, mudstone, and gypsum; and it is a valuable unit to use in tracing out the upper contact of the member. The sandstone and silty sandstone is red or, less commonly, white, very fine to fine grained, moderately to poorly sorted, FIGURE 15.—Reference section of Carmel Formation and Page Sandstone at Pine Creek near Escalante, Utah. View is toward northwest across valley of Pine Creek. 1, reference section; JTm. Navajo Sandstone; Jphw, Harris Wash Tongue of Page Sandstone; chh, Judd Hollow Tongue of Carmel Formation; thp, Thousand Pockets Tongue of Page Sandstone including red marker bed shown by m; Jcau, upper member of Carmel Formation including limestone-bearing part shown by Is and gypsum-bearing part shown by gyp; Je, Entrada Sandstone; Jm, Morrison Formation. For scale. section from top of Navajo Sandstone to base of Entrada Sandstone is 162.5 m thick. RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA and very thin to thin bedded. The mudstone is red or, less commonly, grayish yellow green and laminated to very thin bedded. The gypsum is white, light gray, and grayish yellow green and laminated to very thin bed- ded in strata as much as 1.2 m thick. The marker zone commonly weathers to slabby cliffs or to slopes lit- tered with gypsum fragments. Southwest of Cannon- ville, Utah, the gypsum beds pinch out but the zone can be recognized in this area because it consists of the red lithologies noted above, interbedded with several thin beds of hard, white, fine-grained calcareous sand- stone about 0.3 m thick. This zone persists southwestward past the Paunsaugunt fault, where it is at the top of the Winsor Member of the Carmel; and it was traced as far southwest as Carly Knoll about 35 km northeast of Mount Carmel Junction, where it is beveled out by the unconformity at the base of the Dakota Sandstone (fig. 10). Northeast of Cannonville, gypsum occurs in the part of the upper member that lies above the limestone marker bed. Near Escalante, this part of the member contains approximately 12 beds of gypsum as much as 3.0 m thick. The gypsum beds thin and pinch out southeast of Escalante and Cannonville, and they are not present in Glen Canyon or farther southeast. The upper member consists of a predominantly red- bed facies in Glen Canyon and the region farther southeast, where it has been informally called the reservation “facies” of the Carmel (O’Sullivan and Craig, 1973, p. 79). The Page, Ariz., reference section given at the end of this report is reasonably represen- tative of this facies, although it contains less mudstone than is usually found in this facies, and the limestone marker bed is not present in this facies southeast of Glen Canyon. A typical view of the redbed facies of the upper member is shown in figure 16. Other than the limestone marker bed that is locally present near Page, the upper member consists of in- terbedded moderate-reddish—brown or scarce white sandstone, silty sandstone, and dark-reddish—brown mudstone in the eastern part of the Kaiparowits Plateau, Glen Canyon, and the region farther southeast (fig. 17). The sandstone and silty sandstone consist of coarse silt to fine-grained sand and they are poorly to moderately sorted. Scattered small pebbles like those described in the Winsor Member also occur in the upper member as far east as Kane Wash in Glen Canyon (sec. 29, fig. 10). The stratification includes laminated to thick bedding or crossbedding in sets that generally are small to medium scale low angle and tabular planar or wedge planar. Locally the sandstone contains one or several sets of large-scale high-angle tabular-planar crossbedding. At the excellent ex- posures along US. Highway 89 near West Cove (sec. B19 24, fig. 10), large-scale crossbedding occurs in the mid- dle of the member in a conspicuous very light gray cliff-forming sandstone unit 40.2 m thick that can be mistaken from the Entrada Sandstone. Intraforma- tional slumps, faults, and breccia pipes are locally pre- sent in the upper member just east of the Paria River near Cannonville, Utah. The greatest known thickness of the upper member is 205.1 m at Bull Valley about 13 km southwest of Cannonville, Utah (sec. 17, fig. 10). It thins to about 113.4 m at the reference section of the Carmel at Pine Creek, near Escalante, Utah, and to about 77.7 m at the other reference section near Page, Ariz. The thin- nest section that was measured is 38.1 m near Navajo Point about 48 km northeast of Page. The contact of the upper member with the underly- ing gypsiferous member of the Carmel is sharp or gradational, and it is placed at the top of the highest gypsum or limestone bed of the gypsiferous member. Where the gypsiferous member pinches out, the con- tact with the underlying Page Sandstone generally is sharp, and it is placed at the top of the highest crossbedded sandstone of the Page and at the base of the lowest flat-bedded sandstone, silty sandstone, or mudstone of the upper member. Southeast of Glen Canyon where the upper member rests directly on the Navajo Sandstone, the contact is sharp, and it is plac- ed at the top of the highest crossbedded Navajo Sand- stone and at the base of the lowest flat-bedded sand- stone or silty sandstone that contains scattered small, angular chert pebbles. The contact with the Navajo is the same J -2 unconformity that separates the limestone member of the Carmel from the Temple Cap Sandstone farther west in southwestern Utah (figs. 10, 1 1), but the contact of the upper member with the Page Sandstone is not an unconformity. Interfingering of the lower approximately 3 m of the upper member with the upper part of the Page Sand- stone was found at one locality in Glen Canyon about 14 km northeast of Page, Ariz., demonstrating that this contact is not an unconformity (fig. 10). Correla- tions 45 km southeast of Escalante, Utah, in the Early Weed Bench area (fig. 11), suggest that the lowermost beds of the upper member are time-equivalent to the Judd Hollow Tongue of the Carmel Formation and the Thousand Pockets Tongue of the Page Sandstone. In this area the Judd Hollow Tongue grades southeastward into sandstone that is included in the Page Sandstone because it is crossbedded, but it can be distinguished and traced because it is considerably darker (very dark red to very dusky red) than the rest of the crossbedded sandstone in the Page. This darker bed was traced southeast along the north side of Early Weed Bench to section 36 (fig. 11), where the overlying B20 TRIASSIC AND JURASSIC ROCKS. WESTERN INTERIOR UNITED STATES FIGURE 16.—Typical exposures of ledges and broad slopes in the upper member of the Carmel Formation (Jcau) at canyon of Warm Creek in southern part of Kaiparowits Plateau. The small cliffs in the member are sandstone whereas the slopes are underlain by interbedded sandstone, silty sandstone, and mudstone similar to the strata described in the reference section of the Carmel at Page approximately 7 km southwest of here (measured section 2a). The upper member is predominantly red, and it contrasts markedly in color and topograph- ic expression with the Entrada Sandstone (Je), sandstone at Romana Mesa (Jr), and Salt Wash Member of the Morrison Formation (Jms) on walls of Romana Mesa in the distance. The buildings and associated structures are an abandoned depot that was built about 1910—1911 and used as part of an ambitious project to haul coal out of the Kaiparowits Plateau and down the Colorado River to Lees Ferry, Ariz., for use in gold-mining endeavors by C. H. Spencer (Gregory and Moore, 1931, p. 148; Crampton, 1964, p. 142). The buildings and most of the Carmel Formation here are now covered by the waters of Lake Powell. Photo by R. C. Moore, 1921, in the NW1/4 sec. 35, T. 43 S., R. 4 E., Kane County, Utah. crossbedded sandstone, equivalent to the Thousand Pockets Tongue, thins and pinches out and the hard, dark-colored, crossbedded sandstone, equivalent to the Judd Hollow, is overlain directly by the upper member of the Carmel. Farther southeast, a transition zone ap- proximately 6.6 m thick at the base of the upper member consists of very thin to thin-bedded and small- to medium-scale crossbedded sandstone that probably correlates with the Judd Hollow and possibly with the Thousand Pockets Tongue farther northwest. A hard, dark-colored, crossbedded sandstone facies of the Judd Hollow Tongue also is present on the south side of the Kaiparowits Plateau (fig. 24), but this unit grades eastward into crossbedded strata that are in- distinguishable from the enclosing Page Sandstone. PAGE SANDSTONE The Page Sandstone is here named for a cliff-forming crossbedded, red or light-gray sandstone formation in south-central Utah and north-central Arizona. Rocks now assigned to the Page were considered part of the Navajo Sandstone by previous workers, but recent work indicates that the Page is younger than the Nava- jo; and they are separated by a regional erosion surface termed the J -2 unconformity by Pipiringos and O’Sulli'van (1978). The Page is included in the San Ra- fael Group because: (1) it is separated from the Glen Canyon Group by the J -2 unconformity, (2) it is younger than the Temple Cap Sandstone, which is also included in the San Rafael Group, (3) it is the same age as the lower part of the Carmel Formation of the San RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA FIGURE 17.—Good exposures of interbedded lithologies in lower part of upper member of Carmel Formation (Jcau) about 50 km southeast of Escalante, Utah. The cliff is about 15 m high and contains, in ascending order, a thin basal stratum of light-red sandstone overlain by laminated red mudstone and gray gypsum; irregularly thin bedded to thick bedded red sandstone, silty sand— sandstone, and mudstone in the middle; and a capping bed of white sandstone. The irregular, lenticular, and somewhat con- torted bedding in the middle is fairly common in the member. The pack in the lower right rests on the uppermost part of the Page Sandstone (J p). Looking southeast across a small tributary of Big Hollow Wash in the SEA sec. 8, T. 39 S.. R. 7 E., Kane County, Utah. Rafael Group, and (4) for simplicity of stratigraphic classification. The Page Sandstone is 55.8 m thick at the type sec- tion near Page, Ariz. (section 2b at end of this report), and it attains its greatest known thickness of 88.7 m about 18 km farther south. It pinches out about 40 km southeast of Page and on the northwest flank of Nava- jo Mountain about 50 km east of Page. Progressing northwestward from the type locality, the Page is split into two tongues by the southeastward-thinning Judd Hollow Tongue of the Carmel Formation. The lower of these tongues is here named the Harris Wash Tongue of the Page Sandstone and the upper tongue is the Thousand Pockets Tongue. The Thousand Pockets was B21 named by Phoenix (1963), who assigned it to the Nava- jo Sandstone, but it is reassigned here to the Page Sandstone. The type section of the Page Sandstone is on the northwest side of Manson Mesa on which the town of Page, Ariz., is situated, and it is about 1 km northeast of Glen Canyon Dam (fig. 18). At this locality the for- mation consists largely of moderate—reddish—brown, moderate-reddish-orange, and locally very light gray or grayish-pink sandstone that is fine grained and well sorted. The crossbedding is predominantly large scale and of low- or high-angle, tabular-planar, and wedge- planar types. The crossbedding sets range in thickness from 1 m to about 6 m, although locally near Escalante, Utah, sets as much as 18.3 m thick occur. In places the sandstone includes several thin beds as much as 0.3 m thick of laminated to Very thin bedded, very fine to fine-grained, moderately sorted, moderate- reddish-brown sandstone. A small but important constituent of the Page Sand- stone is small angular pebbles of chert. These have microcrystalline or colloform texture and are white to very pale orange, although less commonly they are moderate red to moderate reddish orange. At the type locality the pebbles are less than 5 mm long (fig. 19), but throughout most of the region the maximum size is about 1.3 cm. Locally, the pebbles are as much as 6.4 cm long, and at one locality about 24 'km east of Escalante, Utah, a cobble 25 cm long and about 3.8 cm in diameter was found. The pebbles generally occur scattered along the basal contact or in the basal 15 cm of the formation. They have also been found higher in the formation at several localities, where they occur scattered along some of the bedding surfaces; but they are consistently larger and more abundant at the base of the formation. The basal contact of the Page Sandstone is a sharply defined and continuous surface that is characterized in most places by a thin layer of scattered angular chert pebbles. It is generally expressed topographically as a bench about a meter to a kilometer wide stripped back on the top of the Navajo (figs. 4 and 18) or as a promi- nent incised notch in the cliffs of Glen Canyon (fig. 20). This surface is considered an unconformity because it has features associated with it that indicate extensive weathering or erosion, and because it truncates underlying formations. The unconformity occurs throughout much of the Western Interior of the United States where it was described by Pipiringos (1967, 1968) and Pipiringos and O’Sullivan (1975). The sur- face was formerly known as the chert pebble unconfor- mity, but more recently it was named the J -2 unconfor- mity by Pipiringos and O’Sullivan (1978). Discovery of this unconformity in southwestern Utah is especially B22 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE 18.—Type section of Page Sandstone near Page, Ariz. The stripped surface in the foreground at the base of the Page (J p) is a typical topographic feature marking the top of the Navajo Sandstone (JTz n). 2b, type measured section; the Page is 55.8 m thick. Jcau, upper member of Carmel Formation. View is southeast toward northwest side of Manson Mesa. significant because it serves to demonstrate that the Navajo Sandstone and Carmel Formation do not inter- finger as had been thought by previous workers. The scattered angular chert pebbles such as shown in figures 19 and 21 generally are the most reliable feature to use in locating the basal contact of the Page Sandstone. These pebbles have the same color and tex- ture as the authigenic chert that occurs as irregular nodules in the underlying Navajo Sandstone, sug- gesting that the pebbles originally came from that for- mation. Also, the angularity of the pebbles indicates a nearby source that could only be the Navajo. Consider- ing the widespread distribution of the Navajo throughout most of southern Utah and northern Arizona in Early Jurassic time (Baker and others, 1936, p. 47), it would take an extraordinary set of sedimentary processes to bring a similar suite of peb- bles into the region from localities outside the limits of the Navajo Sandstone without rounding the pebbles considerably and without incorporating other rock types into the pebble suite. The evenly distributed angular pebbles in a thin layer on the unconformity are similar to deflation-lag gravels in modern deserts where the angularity of the pebbles is caused by split- ting from insolation (Glennie, 1970, p. 16—21; Walker and Harms, 1972, p. 284—287). Similar but smaller detrital chert pebbles locally occur at higher stratigraphic levels in the Page but they have not been found in the Navajo. Thus, the lowest level of detrital chert pebbles usually is the best criterion to use in locating the basal contact of the Page Sandstone. Another feature commonly found at the lower con- RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE J URASSIC FORMATION S, UTAH AND ARIZONA tact of the Page Sandstone is downward-tapering sandstone-filled crevices that probably mark fossil joints. In many places where the strata can be viewed in a vertical section, the contact is indented about every 3—15 m with crevices up to 15 cm wide at the top, which extend down as much as 1.8 m into the Navajo Sandstone (fig. 22). The sandstone that fills the crevices is vertically continuous‘with the sandstone in the overlying strata of the Page Sandstone. Angular chert pebbles, so commonly found elsewhere along this surface, also occur in some of these crevices. On horizontal surfaces where the Page is stripped off and the crevices can be examined in plan view, the linear or sinuous trend of isolated crevices can be traced for 15 m or more, and abundant swarms of crevices are inter- connected to form polygons 1.5—3.0 min diameter (fig. 23). The crevices are similar to presentday linear, sinuous, and polygonal joints that weather out of the Navajo Sandstone. For this reason it is thought that the crevices formed by weathering along ancient joints in the Navajo prior to deposition of the Page Sand- stone and were filled with sand during the earliest stages of deposition of the Page. Small sandstone-filled crevices locally occur at the base of some of the thin flat-bedded sandstone units higher in the Page Sandstone. They are generally smaller than those at the top of the Navajo, being several centimeters wide at the top and pinching out about 0.3—0.6 m into the underlying sandstone. These probably are ancient joint crevices or shrinkage cracks that formed during brief periods when sand deposition ceased and the surface became sufficiently lithified to allow them to form. Because these fossil joint crevices or shrinkage cracks occur within the Page but have not been found below the upper surface of the Navajo, the lowest level of these crevices is another important feature that marks the basal contact of the Page Sand- stone. The uppermost part of the Navajo has an irregular light-colored or bleached zone at many localities that is also helpful in locating the basal contact of the Page Sandstone (figs. 24 and 25). In general, the bleached zone is very light gray to grayish pink, but locally it is only a slightly grayer shade of red than the unaltered strata. The top of the zone coincides with the upper contact of the Navajo, whereas the lower boundary of the zone may be gradational or sharp, and in many places it cuts across the cross-laminae in the forma- tion. The thickness of the bleached zone varies con- siderably, from less than a meter to about 300 m, and in the Waterpocket Fold and Circle Cliffs areas the zone extends throughout the Navajo (Smith and others, 1963; Davidson, 1967). The light-colored zone probably was caused by fluids that seeped down into B23 the Navajo and bleached the upper part of it during the erosion interval that produced the J-2 unconformity. Similar bleached zones occur beneath many of the other Jurassic as well as Cretaceous unconformities in the region, especially where the underlying beds are porous and permeable and where the erosion surface had been exposed to subaerial weathering processes. Locally, the basal stratum of the Page Sandstone contains light-colored reworked or residual deposits derived from the underlying Navajo Sandstone. These beds generally are less than 0.3 m thick and consist of very thin but irregularly bedded sandstone that is similar in color and texture to the sandstone in the bleached zone at the top of the Navajo. This similarity of color and texture as well as the lack of current- produced bedding structures suggests that the sand in these beds came from the bleached zone at the top of FIGURE 19.—Evenly distributed small angular chert pebbles at base of Page Sandstone at the type section near Page, Ariz. The pebbles are as much as 5 mm long, and most are white to very pale orange, although some are moderate red or moderate reddish orange. Scarce pebbles locally occur higher in the Page, but they have not been found below it in the Navajo Sandstone. Thus, the lowest level of detrital chert pebbles marks the lower contact of the Page Sandstone. The pick head (scaled in inches) rests on the uppermost part of the Navajo Sandstone and the surface was brushed clean of all loose detritus before the photo was taken. TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES B24 4%: 63m «A .0 .m .3 SSE .ASD c3560 52:. gm :m w .m :m mv .E .3 .03 X32. 2: 5 $2558: mniooq doEwESm 83:02 23 mo 53:82 5:35 :am .mE... H82 anmfiom as macamvnam E, .xomfi E wém anon“ mm accumufiwm wwum 2: 630m Sm doSmESm $530 2: we :32 an E biota :usom 2.15 we 83.5w BE. downs 0.8 msoswfiua 98:? Eat 8 8.8 :33 scam .m an :85 96mm we 5:2: £233 8m 285258 823 £2 3 83m 29350 .32 3 £25 33m cage—co .83 2833mm “Erasm— mfi tam uwam of “o mama 2: 5253 5:3 983 23130830 5 258 disamuwm 23 3 9:30 maosofimnoofi unakofiom .383 somuufiuom 38.80 93 mo .8382: San: SE. .3 W3 encumcnuw omm>wz «Eu 3 3 mucumvnmm mMmm «0 83:8 .3 :25: .8 :30: 303328 MESS? mhmfium 93 «o mammmoho an com—ED $5 $98“ 33 >1.om $5.2m RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA the Navajo, mainly through weathering in place with little lateral transportation or admixture of new sedi- ment from other sources. Small sandstone nodules cemented mainly with silica commonly occur in the upper part of the bleached zone of the Navajo where it is overlain by the Page Sandstone (fig. 26). The nodules are about 1.3—2.5 cm in diameter and they are the same light-gray or light- red color as the enclosing sandstone in the bleached zone. The cementing material is mainly silica although weak effervescence with dilute hydrochloric acid sug- gests that a small quantity of calcite cement also is present. Bedding laminae pass directly through the nodules, indicating that they formed by precipitation of the cementing material in the intergranular pore spaces after deposition of the Navajo, and similarity of the color of the sandstone in them to that of the enclos- ing bleached zone suggests that they formed at the same time as that zone or slightly later. Both the bleached zone and the small nodules in the upper part of the Navajo are readily identified on many outcrops, and they are additional guides to locating the basal contact of the Page Sandstone. A moderate amount of local erosional relief on the top of the Navajo is indicated by buried hills of Navajo FIGURE 21.—Angular chert pebbles embedded in basal stratum of Page Sandstone. The angularity of the pebbles, indicating a near- by source, and position high on the flank of the buried hill of Navajo Sandstone shown in figure 27, indicate that they could only have come from the top of that hill. Presumably the hill was originally capped with a cherty limestone bed similar to the one in the Navajo Sandstone shown in figure 5, and the pebbles were derived from it by weathering processes early in the deposi- tional history of the Page Sandstone. Scale on pick head is in inches; the surface to the right of the pick was brushed clean of all loose detritus before the photo was taken. Cave Point area in the NWV4 sec. 35, T. 40 S., R. 8 E., Kane County, Utah. B25 Sandstone preserved beneath the Page Sandstone or upper member of the Carmel Formation (fig. 27). Thus far, four of these hills have been found in the eastern part of the Kaiparowits Plateau about 40—50 km northeast of Page, Ariz., and about 70—80 km southeast of Escalante, Utah. The hills are as much as 11.3 m high, and they extend up to or slightly above the top of the surrounding Page Sandstone, so that they are directly overlain by the upper member of the Carmel Formation. In cross section they are about 150—460 m wide. Chert pebbles along the unconformity are larger (as much as 6.4 cm long) and more abundant on the crest or flanks of these bills (fig. 21), suggesting that they were originally capped with a protective bed of cherty limestone in the Navajo that was the source of the pebbles. The cherty limestone bed shown in figure 5 is the capping stratum of one of these buried hills in Dangling Rope Canyon about 50 km northeast of Page, Ariz. No alinement of the hills could be deter- mined; instead, they seem to be randomly distributed erosional remnants whose preservation was determin- ed solely by the presence of a resistant cherty limestone bed in the Navajo Sandstone. Smaller erosional irregularities occur at the top of the Navajo, where they are preserved beneath the Page Sandstone. These include small knolls, cliffs, and overhanging ledges 0.3—1.0 m high, such as are shown in figure 28. Small shallow depressions as much as 1 m deep and 3—6 m wide were also found on this surface, but they are not considered fluvial channels because they do not contain deposits typical of fluvial deposi- tion. Indeed, no strata containing bedding or textural features typical of fluvial deposits were found in either the Navajo or Page Sandstone. The buried hills and small-scale erosional irregularities at the top of the Navajo indicate that it was fairly well lithified when the Page sediments were being deposited, and the relatively greater degree of lithification of the Navajo apparently has been maintained throughout geologic time in most places. Eastward or southeastward regional beveling of older rocks by the J -2 unconformity at the base of the Carmel or Page Formation is indicated by eastward truncation of the Temple Cap Sandstone in southwestern Utah (figs. 8, 10), southeastward trunca- tion of the Navajo Sandstone in northeastern Arizona and southwestern Colorado (fig. 2; Harshbarger and others, 1957, p. 21, 33; Shawe and others, 1968, p. A38—A41), and eastward truncation of older forma- tions in west-central Colorado (Craig and Dickey, 1956, p. 97). Similar southeastward regional beveling of older formations by the J-2 unconformity has been well documented in south-central Wyoming (Pipiringos, 1968, p. D3), where this unconformity is at the base of the Sundance Formation. TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE 22.—Fossil joint crevice at top of Navajo Sandstone. The Page Sandstone (J p) fills the crevice down about 1.2 m to the level of the base of the pick and the fracture extends down 0.6 In more to about the level of the middle of the pack where a narrow vertical bleached zone is present in the Navajo Sandstone (J‘fi n). Although not apparent, several small angular chert pebbles are present in the part of the Page Sandstone that fills the crevice. Looking east and up on the east side of Dangling Rope Canyon about 6.4 km southwest of Navajo Point in the SEA sec. 30, T. 32 S., R. 8 E., Kane County, Utah. RELATIONS OF THE NAVAJO SANDSTON E TO MIDDLE J URASSIC FORMATIONS, UTAH AND ARIZONA B27 FIGURE 23.—Plan view of fossil joint crevices at top of Navajo Sandstone (J3 n). The polygonal distribution of the ancient crevices filled with Page Sandstone (J p) is similar to the polygonal distribution of modern joint crevices in the Navajo and suggests a similar origin. Northwest side of Manson Mesa at type section of Page Sandstone near town of Page, Ariz. HARRIS WASH TONGUE The Harris Wash Tongue of the Page Sandstone is here proposed for a westward-thinning unit of crossbedded sandstone at the base of the Page Sand- stone. The tongue takes its name from the type section in a small tributary to Harris Wash about 20 km southeast of Escalante, Utah (fig. 29). It weathers to form a cliff that in places may be vertically continuous with the sheer cliff at the top of the Navajo Sandstone, but more commonly it is set back slightly (03—30 In) from the Navajo cliff. The Harris Wash Tongue thins irregularly westward in the western part of the Kaiparowits Plateau and along the Waterpocket monocline about 50—80 km far- ther north. It reaches a maximum thickness of about 36.6 m on the northeast side of the Kaiparowits Plateau about 45 km southeast of Escalante, Utah. Near Escalante, the tongue is only 4.6 m thick, and, judging from the rate of westward regional thinning, it FIGURE 24.—-Conspicuous difference in colors of Navajo and Page Sandstones at Thousand Pockets about 8 km west of Page, Ariz. The J -2 unconformity marked by small angular chert pebbles is at the base of the darker Page Sandstone (J p; actually moderate reddish brown), which lies on the nearly white discolored zone at the top of the Navajo Sandstone (J'fi n). The discoloration is attributed to bleaching prior to deposition of the Page, probably by fluids that seeped into the Navajo during the erosion interval that produced the unconformity. The cuesta is capped by a thin, hard, very dark red crossbedded sandstone unit in the Page that correlates with the Judd Hollow Tongue of the Carmel Formation about 8 km farther northwest. For scale, the part of the Page Sandstone visible in the cuesta is about 21.3 m thick. View is northwest in the SW1/Ja sec. 24, T. 41 N., R. 7 E., Coconino County, Ariz. TRIASSIC AND J URASSIC ROCKS, WESTERN INTERIOR UNITED STATES B28 .32 .8: 3 .o .m 3 SEE .625 .5550 .33. 55 :m w d ..m mv .9 .mm 68 KHZ one :... amokfiuogfiuo: 9:384 4mg: Satan “Em :02:an 8m o:3m~u:am 3.2»:m 3... gen: 3?: E 85388: 829:8 208 3m domaufihom £51.82 ac 89:82 :83 3am .me ”:82 gufiom an 0:32.55 5. £02» E 5.3 uses: mm Saginaw awam .038 :Pm demuwfiuoh 3:580 93 mo :3 23 am am 3:528 :25m 234 we 88.5w SE. 28:8 :m 2 «$20 8:25 ”.25 w: :938 23:35 £2 3 mica 83m 82300 .33 8:82:55 322m 23 a: flu? 285.. 0:... 58:3 8:3 :85 053882qu a :23 8 22383 u: 93 «fish 23 «a 8:88 8:282 23 a: 893 3 3:83 89$ :8: 2338 38 3 :ofiafihom 3:580 23 mo 83:55 :23: 25. .8“: use a: 5:3 ”EH—m .8 :30: a mm: H: was? :938 on» :m 6:: :2 «o 033m 8x3: 3333 a m: :95 2.5 .E #3 u:3mv:am 0.73:2 93 a 3 Saginaw wmwm we ”238298 oEQuuMoQB v5» 8:285. :28 WEBB? :85 8:25 :93 :8: :9350 :26 820: 3:; Ida mangm RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE J URASSIC FORMATIONS, UTAH AND ARIZONA FIGURE 26.—Small nodules in uppermost part of Navajo Sandstone near Page, Ariz. The nodules are about 1.3—2.5 cm in diameter and are cemented mainly with silica in the form of a spherical shell. They commonly occur in the bleached or discolored zone at the top of the Navajo. Type section of Page Sandstone on northwest side of Manson Mesa near Glen Canyon Dam, Coconino County, Ariz. pinches out underground about 5—10 km west of there. The Harris Wash is as much as 26.8 m thick on the south side of the Kaiparowits Plateau about 21 km northwest of Page, Ariz. It thins irregularly westward from there and pinches out near the East Kaibab monocline about 45 km northwest of Page. Because the younger Thousand Pockets Tongue thins and pin- ches out northward in the Carmel Formation along the Waterpocket Fold, the Harris Wash probably is the only part of the Page Sandstone that is present in the San Rafael Swell 1 10-190 km north of the Kaiparowits Plateau (Pipiringos and O’Sullivan, 1975). Subsurface configuration of the tongue cannot be determined ac- curately owing to the similar response of it and the Navajo Sandstone on the various geophysical well- logging devices. The Harris Wash Tongue consists predominantly of crossbedded sandstone like most of the other parts of the Page Sandstone. The sandstone is very fine to fine grained and moderately well sorted to well sorted, and 329 the color ranges from very light gray to moderate red- dish brown or grayish red. Bedding generally consists of tabular-planar to wedge-planar sets of small- to large-scale cross-stratification as much as 10.7 m thick. Some interfingering with the Judd Hollow Tongue of the Carmel Formation occurs in the western- most extent of the Harris Wash. In this area the crossbedding tends to occur in thinner sets less than about a meter thick, and several very thin to thin- bedded and ripple cross-laminated strata are also pre- sent. Scattered along the base of the Harris Wash are the same angular chert pebbles, generally less than 13 mm long, that occur so commonly along the base of the main body of the Page. The basal contact is the J -2 un- conformity that was described more thoroughly in the preceding discussion of the Page Sandstone. THOUSAND POCKETS TONGUE The Thousand Pockets Tongue of the Page Sand- stone is a cliff-forming sandstone unit that is only pre- sent in south-central Utah and a small part of north- central Arizona about 24 km west of Page, Ariz. (figs. 13, 14, 15). It lies beneath the gypsiferous member or upper member of the Carmel Formation and it is underlain by the Judd Hollow Tongue, limestone member, or banded member of the Carmel. The Thou- sand Pockets was formerly considered a tongue of the Navajo Sandstone by Phoenix (1963), Wright and Dickey (1963a), and Thompson and Stokes (1970), but it is here designated as a tongue of the Page Sand- stone. The greatest known thickness of the Thousand Pockets is 76.8 m, measured by J. C. Wright and D. D. Dickey (Phoenix, 1963, p. 65—66) in southern Utah about 42 km northwest of Page, Ariz. The tongue pin- ches out farther northwest along a northeast-trending line that passes 2 km southeast of Cannonville, Utah. The tongue also pinches out northward along the Waterpocket Fold and in the subsurface just northeast of that flexure. The Thousand Pockets Tongue is composed chiefly of crossbedded sandstone that is identical in most aspects to that of the main body of the Page Sand- stone. However, the color of the tongue is somewhat more varied than the main body of the Page, ranging from moderate reddish brown, moderate pink, and very light gray throughout most of the region to grayish orange in the area south and southwest of Can- nonville, Utah. For the most part, the tongue consists of fine-grained, well-sorted, crossbedded sandstone like that described at the type section of the Page. In its northwesternmost parts where it interfingers with the banded member of the Carmel Formation, the Thou- sand Pockets grades into very thin to thick-bedded, B30 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE 27.—Buried hill of Navajo Sandstone on northeast side of Kaiparowits Plateau. Page Sandstone (J D) is 11.3 and 7.0 m thick, re- spectively, on left and right sides of the buried hill of Navajo Sandstone (J‘fi n), and the upper member of the Carmel Formation (Jcau) rests directly on the crest of the hill in the center of the view. Abundant and relatively large angular chert pebbles occur on the crest and flanks of this hill (fig. 21), suggesting that it was originally capped with a cherty limestone bed of the Navajo. This hill and three other buried hills that have been found in the region indicate that a moderate amount of erosional relief was present on top of the Navajo before and during deposition of the Page-Note the distinctly lighter color of the Navajo compared to the Page. Cave Point area, looking northwest in the N W1/4 sec. 35, T. 40 S., R. 8 E., Kane County, Utah. grayish-orange sandstone, and only one or two sets of medium- to large-scale tabular-planar or wedge-planar crossbedding are present (figs. 13, 14). Throughout most of the region east of Cannonville, Utah, a conspicuous notch-forming red sandstone or silty sandstone marker bed is present in the middle of the Thousand Pockets Tongue (fig. 15). This bed is as much as 3.7 m thick and is composed of very fine to fine-grained, moderately sorted, very thin to thin- bedded sandstone and silty sandstone. Although the marker bed has a lensoid shape in the outcrop belts around the Kaiparowits Plateau (figs. 10, 11), its lithologic similarity to the handed and upper members of the Carmel Formation suggests that it may be a thin tongue of either or both of these members. The basal contact of the Thousand Pockets Tongue generally is sharp and planar, although in the northwesternmost parts of the tongue the lower con- tact locally is gradational. Contrary to Thompson and Stokes (1970), no evidence was found that this surface is an unconformity. ENTRADA SANDSTONE The Entrada Sandstone was named by Gilluly and Reeside (1928) for exposures at Entrada Point in the northeastern part of the San Rafael Swell of central Utah. Subsequent workers, notably Wright and Dickey (1963b), correlated the formation southward in- to the Kaiparowits Plateau of south-central Utah. In the Kaiparowits Plateau the Entrada is divided into three members (Peterson, 1973; Zeller, 1973), of which only the lower member is considered here. The lower member of the Entrada is approximately 107 —152 m thick and consists of two facies. Southeast of a line that passes roughly through Cannonville and Escalante, Utah, it consists predominantly of a crossbedded sandstone facies; northwest of that line it consists of a generally flat bedded silty sandstone facies. The crossbedded southeastern facies is compos- ed of very fine to fine-grained, moderately to well- sorted, moderate-reddish-orange, cliff-forming sand- stone (figs. 16, 25, 29). The bedding consists of tabular- planar and wedge-planar sets of medium- to large- scale, low- and high-angle cross-strata. The flat-bedded northwestern facies is moderate reddish orange and composed of coarse siltstone and fine—grained, moderately to poorly sorted, slope-forming silty sand- stone (fig. 15). The bedding in this facies ranges from very thin bedded to very thick bedded. The lower contact of the southeastern facies is sharp and is placed at the top of the highest thin-bedded silty sandstone or mudstone of the underlying upper member of the Carmel Formation. Interfingering of the lower 1.8 m of the Entrada with the upper part of the Carmel was found in the Kane Wash area about 23 km northeast of Page, Ariz. The lower contact of the northwestern facies is somewhat more difficult to pick owing to lithologic similarity of the Entrada and RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA FIGURE 28.—Small buried ledge of Navajo Sandstone (JTz n) pre- served beneath Page Sandstone (J p) on northeast side of Kaiparo- wits Plateau. Small angular white chert pebbles are scattered along the J -2 unconformity just left of the pick. This ledge, and similar features occurring elsewhere in the region, indicate that the top of the Navajo was not beveled to a planar surface prior to deposition of the Page. Pick is scaled in inches. West side of Hurricane Wash at measured section 39, Kane County, Utah. underlying Carmel. Southwest of Cannonville, the con- tact is placed at the top of the highest gypsum or mudstone bed of the Carmel or at the top of the highest thin, white, hard, calcareous sandstone bed in the marker zone at the top of the upper member or Winsor Member of the Carmel. Some interfingering of the En- trada and the Carmel probably occurs in this area, but it could not be documented owing to the large amount of soil and vegetation cover. Near Escalante, the con- tact is placed at the top of a thin purple mudstone or bentonite marker bed. Where this bed cannot be recognized, owing to soil cover, the contact is at the top of the highest gypsum bed in the Carmel. AGE AND CORRELATION GLEN CANYON GROUP Although the Glen Canyon Group lies between well- dated Upper Triassic and Middle Jurassic strata, the paleontological evidence previously obtained from it was not sufficiently diagnostic to determine where the B31 Triassic-Jurassic boundary is Within the group. New findings strongly suggest that most of the group is Early Jurassic in age and that the systemic boundary is considerably lower than had been thought by previous workers (Lewis and others, 1963; Galton, 1971). Because the newly discovered fossils are still be- ing studied, previous age assignments of formations and members in the group are retained by the US. Geological Survey until a more thorough evaluation of the fossils can be published. The new paleontological evidence that the group is entirely Early Jurassic in age in southwestern Utah and northwestern Arizona comes from the recent discovery of Early Jurassic palynomorphs in the Whitmore Point Member of the Moenave Formation. The fossils came from samples collected by C. E. Turner-Peterson and Fred Peterson from the lower part of the Whitmore Point Member at Whitmore Point, Ariz., about 32 km southwest of Kanab, Utah (fig. 1). The palynomorphs were identified by Bruce Cornet of Gulf Research and Development Company. He stated (written commun., 197 6): The samples are strongly dominated by species of Corollina, which make up about 95 to 99 percent of the assemblage. The domi- nant species is Corollina torosus (Reissinger) Klaus; C. murphyi Cor- net and Traverse, and C. meyeriana (Klaus) Venkatachala and G6c- za’n are also present, but are rare. Other rare species include: Granulatisporites infirmus (Balme) Cornet and Traverse, Todisporites rotundiformis (Malyavkina) Pocock. Cycadopites spp., and possibly Podocarpidites sp. Preservation is good. Tetrads of Corollina are common and in- dicate little abrasion during transport. In addition, one of the samples contains “ghosts" of possible reworked Triassic bisaccates, such as Pityosporites and Abiespollenites, which are normally characteristic of the Chinle Formation. The difference in preserva- tion between these “ghosts" and the indigenous palynoflora is con- siderable. The strong dominance of the palynoflorules by species of Cor- ollina is characteristic of the Liassic (Lower Jurassic) Series. In ad- dition, comparison with palynoflorules obtained from the Portland Formation at the top of the Newark Group in the Hartford basin of the Connecticut Valley in the eastern United States (Cornet, Traverse. and McDonald, 1973; Cornet and Traverse, 1975) sug- gests a further refinement in the age. Within the Portland Forma- tion there is a trend from almost entirely non-striate to 28 percent pseudostriate forms of Corollimz torosus in the lower part of the for- mation to 17—43 percent striate and pseudostriate forms in the upper-lower to lower-middle part and to about 35-7 6 percent striate and pseudostriate forms in the middle part of the Portland. If such a trend reflects major regional climatic changes and evolution in North America, then the composition of the Whitmore Point palynoflorules, with 35—42 percent striate and pseudostriate forms of C. torosus, suggests correlation with the upper-lower to lower- middle part of the Portland Formation, which is late Sinemurian to early Pliensbachian in age. Recently, Bruce Cornet (oral commun., 1977) ten- tatively identified three other palynomorphs from the Whitmore Point Member that support these age deter- minations; they are Corollina cf. C. itunensis (Pocock), Chasmatosporites cf. C. apertus (Rogalska) Nilsson, B32 and cf. Callialasporites. As presently understood, the oldest known occurrence of these fossils is from the Liassic (Lower Jurassic) Series. C. itunensis ranges down into middle Liassic strata whereas C. apertus ranges further down into basal Liassic rocks. In most areas, Callialasporites is found in middle Liassic and younger strata although it has been found in lower Liassic beds in Spain; it has been reported from upper- most Triassic (Rhaetian) beds in North Africa but the identification from this area is questioned. Thus, the oldest presently known age of these fossils suggests a middle Liassic (middle Early Jurassic) age for the TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES Whitmore Point Member of the Moenave Formation. Because the underlying Dinosaur Canyon Sandstone Member and the overlying Springdale Sandstone Member of the Moenave are closely related and not separated from the Whitmore Point by unconfor- mities, all three members and the entire Moenave For- mation probably fall in the Lower Jurassic Series (fig. 30). It should be noted that subsequent to his most re- cent publication dealing with the Early Jurassic age of the Portland Formation (Cornet and Traverse, 1975), Bruce Cornet is now able to place the Triassic-Jurassic FIGURE 29.—Type section of Harris Wash Tongue of Page Sandstone. View is toward the west in Halfway Hollow near its junction with Harris Wash, about 20 km southeast of Escalante. Utah. 3, type measured section; the tongue is 18.3 m thick. Although not apparent from this distance, fossil joint crevices and small angular chert pebbles are well exposed to left of where the man (arrow) is standing. (J'fi n), Navajo Sandstone; Jphw, Harris Wash Tongue of Page Sandstone; chh, Judd Hollow Tongue of Carmel Formation. RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA B33 Southwestem Utah and Stage northwestern Arizona System Series Toarcian Navajo Sandstone Northeastern Arizona and northwestern New Mexico Pliensbachian Kayenta Formation Whitmore Point Member Jurassic (part) Lower Jurassic Dinosaur Canyon Ss Mbr Sinemurian Hettangian Triassic (part) Upper Triassic Springdale Sandstone Member Chinle Formation Formation Lukachukai Member of Wingate Sandstone Rock Point Member of Wingate Sandstone FIGURE 30.-Diagram showing correlation of formations in the Glen Canyon Group (Wingate Sandstone, Moenave Formation, Kayenta Formation, and Navajo Sandstone) with European time-stratigraphic units, based on new fossils found in the Whitmore Point Mem- ber of the Moenave Formation. These age assignments are considered tentative and have not been formally adopted by the US. Geological Survey. Unconformity indicated by shaded area. boundary more accurately in the Newark and Hartford-Deerfield basins of Pennsylvania—New Jersey and Connecticut-Massachusetts respectively. According to Bruce Cornet (written commun., 1976): The new palynological discoveries, as yet unpublished, indicate that the systemic boundary lies about 20—25 meters (64—80 ft) below the oldest basalt flow in the Newark basin. The basalt flows and in- terbedded sedimentary rocks of the Newark basin correlate approx- imately with the basalt flows and interbedded sedimentary rocks of the Talcott Formation in the Hartford basin and with the Deerfield Basalt and overlying lower Turners Falls Sandstone of the Deerfield basin. This is based on palynoflorules, as well as on fish faunas (P. E. Olsen, oral commun., 1976), although the oldest flow in the Newark basin is probably slightly older than the oldest flow in the Talcott Formation of the Hartford basin and the Deerfield Basalt of the Deerfield basin. Thus. the Talcott Formation is early Liassic in age and the younger Portland Formation is middle and late Liassic in age. These findings indicate that the Portland Formation clearly is of Liassic age, and that a Liassic age is cer- tainly indicated for the Glen Canyon Group (above the Rock Point Member of the Wingate Sandstone) which correlates with the Portland. In addition to the palynomorphs, reevaluation of the vertebrates also supports correlation of the Glen Canyon Group above the Rock Point Member of the Wingate with the Portland Formation of the eastern United States (Walker, 1968; Galton, 1971, Olsen and Galton, 1977). Based on the fossils and correlations, we consider the Kayenta Formation and Navajo Sand- stone Early Jurassic in age. Since the palynoflorules from the Moenave Formation indicate a late Sinemurian to early Pliensbachian age, and the oldest beds of the San Rafael Group are early Baj ocian in age (earliest Middle Jurassic), the Kayenta and Navajo probably were deposited during the Pliensbachian and Toarcian Ages of the Early Jurassic Epoch (fig. 30). Throughout much of the Colorado Plateau east of southwestern Utah and northwestern Arizona, beds older than the Moenave Formation are present at the base of the Glen Canyon Group. In this area, the Wingate Sandstone lies beneath the Moenave or Kayenta Formation (fig. 2). The Wingate is divided in- to two members: the Lukachukai Member at the top is widespread and occurs throughout much of the Col- orado Plateau, whereas the underlying Rock Point Member is more restricted in distribution and occurs primarily in northeastern Arizona and northwestern New Mexico (Harshbarger and others, 1957). Where the Lukachukai is the basal member of the Wingate, B34 most workers agree that it is separated from the underlying Chinle Formation by an unconformity (Wilson, 1974), termed the J-0 unconformity by Pipir- ingos and O’Sullivan (1978). Thaden, Trites, and Fin- nell (1964, p. 69—70) reported intertonguing of the Lukachukai and Chinle at two places in the White Canyon area of southeastern Utah, but the beds were walked out at these localities and it was found that the intertonguing does not exist. Because the Lower Jurassic Moenave Formation interfingers with the up- permost beds of the Lukachukai Member (Har- shbarger and others, 1957), we place the systemic boundary at the J -0 unconformity at the base of the Lukachukai, and this suggests an Early Jurassic age for the Lukachukai Member of the Wingate Sandstone. Interfingering with the basal beds of the Moenave For- mation indicates that the Lukachukai Member of the Wingate is only slightly older than the Moenave, and that the Lukachukai Member probably is early Sinemurian in age (fig. 30). Interfingering of the Lukachukai and Rock Point Members of the Wingate Sandstone has been reported in northeastern Arizona and northwestern New Mex- ico (Harshbarger and others, 1957; Wilson, 1974), but it could not be confirmed by field investigations. This contact was examined by M. W. Green, R. B. O’Sullivan, Fred Peterson, and G. N. Pipiringos and it was found that interfingering of these members cannot be demonstrated. Instead of interfingering, we suggest that the same J-O unconformity that separates the Lukachukai Member of the Wingate from the Upper Triassic Chinle Formation in other areas separates the Lukachukai and Rock Point Members of the Wingate in northeastern Arizona and northwestern New Mex- ico. Because the Rock Point Member contains phytosaur teeth which indicate a Late Triassic age (Harshbarger and others, 1957, p. 10), we place the Triassic-Jurassic boundary at the top of the Rock Point Member (fig. 30) and we suggest a Late Triassic and Early Jurassic age for the Wingate Sandstone wherever it contains the Rock Point Member. In southeastern Utah and southwestern Colorado, where the Rock Point Member is not present, the Wingate Sandstone consists solely of the Lukachukai Member. In these areas, the Wingate, like the Lukachukai Member, is considered Early Jurassic in age. These suggestions of new age assignments for units in the Glen Canyon Group also affect other un- fossiliferous units that correlate with the group and cannot be dated by other means. The Aztec Sandstone of southern Nevada and southeastern California is a correlative of the Navajo Sandstone (McKee and others, 1956; Wilson and Stewart, 1967), which we now consider Early Jurassic in age. For this reason, the TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES Aztec Sandstone probably is Early Jurassic in age. The Glen Canyon Sandstone and Nugget Sandstone of southwestern Wyoming, northern Utah, and northwestern Colorado also correlate with the Glen Canyon Group (excluding the Rock Point Member of the Wingate Sandstone; Poole and Stewart, 1964). For this reason we consider the Glen Canyon Sandstone and Nugget Sandstone Early Jurassic in age. As noted earlier, these age designations are considered tentative by the US. Geological Survey and have not been for- mally adopted by the US. Geological Survey. Correlation with western Nevada formations can be inferred from the age of the formations, but it is not known if the correlative strata were physically con- nected across eastern Nevada at the time of deposi- tion. The Boyer Ranch Formation of western Nevada (Speed and Jones, 1969) has been correlated with the Navajo Sandstone, primarily because both formations consist largely of highly mature quartz sandstone, but this correlation is contradicted by the different ages of these formations. Speed (1976) indicated that the Boyer Ranch probably is late Toarcian and (or) Bajo- cian, which is younger than the probable Pliensbachian-early Toarcian age of the Navajo (fig. 30). We suggest that the Boyer Ranch probably cor- relates with the Temple Cap Sandstone and (or) the limestone member of the Carmel Formation, and that the Middle Jurassic extrusive rocks that lie on the Boyer Ranch may be closely related in time to the peb- bles and cobbles of volcanic material in the Middle Jurassic banded member and Winsor Member of the Carmel Formation. The age designations adopted in this report suggest that the Glen Canyon Group (ex- cluding the Rock Point Member of the Wingate Sand- stone) correlates with the Sinemurian, Pliensbachian, and Toarcian parts of the Sunrise and Dunlap Forma- tions of western Nevada. Although the new paleontological evidence indicates changes in age assignments of units in the Glen Canyon Group and correlative strata, we do not believe it is appropriate to make definitive age changes until the new fossils can be described more thoroughly in a separate publication. For this reason, we are not changing the age assignments adopted earlier by the US. Geological Survey (Lewis and others, 1961) for units in the Glen Canyon Group and correlative strata. Thus, the ages presently assigned to the formations discussed previously remain as follows: Formation Age Aztec Sandstone .......... Triassic(?) and Jurassic Glen Canyon Sandstone. . . . Late Triassic and Early Jurassic Wingate Sandstone ........ Late Triassic Kayenta Formation ........ Late Triassic(?) Navajo Sandstone ......... Triassic(?) and Jurassic Moenave Formation ....... Late Triassic(?) RELATIONS OF THE NAVAJO SANDSTON E TO MIDDLE J URASSIC FORMATIONS, UTAH AND ARIZONA SAN RAFAEL GROUP Although the San Rafael Group is largely un- fossih'ferous, a Middle Jurassic age can be assigned to it on the basis of fossils in parts of the Carmel Forma- tion and by regional correlations to more fossiliferous strata in the northern part of the Western Interior of the United States. This report only deals with the age of stratigraphic units in the lower part of the group; younger beds are covered in reports by Imlay (1952, 1957, 1979). The Temple Cap Sandstone is unfossiliferous and, therefore, must be dated by correlation with forma- tions whose ages are known. No other rock units on the Colorado Plateau are known to be equivalent in age to the Temple Cap Sandstone, and the nearest unit with which it can be correlated is the Gypsum Spring Member of the Twin Creek Limestone farther north in northern Utah, southeastern Idaho, and western Wyoming (called the Gypsum Spring Formation in B35 south-central Wyoming). The Temple Cap and Gyp- sum Spring are thought to correlate because: (1) the upper contact of both is the J -2 unconformity and both units are beveled out in a similar manner by this un- conformity, (2) the lower contact of the Gypsum Spring is the J -1 surface that occurs at the base of the Temple Cap, and (3) both contain similar lithologies, although the Temple Cap does not contain the fossiliferous limestone that occurs in the Gypsum Spring. Inasmuch as paleontological evidence in- dicates the Gypsum Spring is early and early middle Bajocian in age, according to R. W. Imlay (written commun., 1974), the Temple Cap is also assigned an early and early middle Bajocian age here (fig. 31). The limestone member of the Carmel Formation is fairly fossiliferous in southwestern Utah: the faunule obtained from it consists mostly of pelecypods, but also includes gastropods, echinoids, worm tubes, and colonial corals (Imlay, 1964). According to Imlay (oral O g 3 9 Southeastern Idaho, Section II Section I Section 2 Section46 E 5 Stage 3' western Wyoming, and Mount Carmel Junction, Pine Creek, Page, Cow Springs, 9, <0 0:, north—central Utah Utah Utah Arizona Arizona 0 A i 1: :9 a Entrada Entrada Callovian 5 "‘ Preuss Sandstone Entrada Sandstone Sandstone Sandstone (part) ._ E -1 Giraffe Creek Member G bea _ m- n - 99:; 999“... "9 ”99:; o - mem r mem r g L Creek Member Winsor Member of of 3 Carmel , . Carmel c Formation Limestoner-tbearing Formation U r 2 Watton Canyon Member 9 Gypsiferous member pa ppe . 9° - member Bathonlan :9 a E of 2 S E Carmel A ‘5 Formation A 1: . - Thousand Pockets Ton ue E a 5 g Boundary Ridge Member 3 Banded member of Page Sandstoneg 3 Z 3 '5‘ ii Page -§ '§ " i o Sandstone Q I- a l- 9- : ._ 0 . Judd Hollow Tongue 3 1 : Rich Member . a 2 g E Li m em on e member of Carmel Formation E 3 " Sliderock Member Harris Wash T0n9ue E _ of Page Sandstone 2 Bajocian E E . . White Throne g Gypsum Spring Member Cap Member 3 Sandstone Sinawava Member .2 3 E ... 3 t '2 S O V . 3 Navajo Sandstone (part) Navajo Sandstone (part) N3V8l° Sandstone Navajo Sandstone 3 (part) (part) FIGURE 31.—Correlation of rocks at selected sections in southwestern Utah and north-central Arizona with a section in southeastern Idaho. western Wyoming. and north-central Utah (Imlay. 1967, and written commun., 1975). Unconformities indicated by shaded areas. BB6 commun., 1974), the fossils indicate that the limestone member is late-middle and late Baj ocian in age (fig. 31) and that it correlates with the Sliderock and Rich Members of the Twin Creek Limestone in the Wyoming-Idaho-Utah area. Carmel strata above the limestone member are un- fossiliferous or, in the case of the gypsiferous member, contain a depauperate and nondiagnostic fauna. Based on a regional synthesis and similar stratigraphic posi- tion, the present writers agree with Imlay’s (1967) cor- relation of the banded and gypsiferous members of the Carmel with the Boundary Ridge and Watton Canyon Members, respectively, of the Twin Creek Limestone as well as correlation of the Winsor Member of the Carmel with the Leeds Creek and Giraffe Creek Members of the Twin Creek. Inasmuch as Imlay (writ- ten commun., 1974) has placed the Bathonian- Callovian boundary at the base of the Giraffe Creek Member of the Twin Creek or equivalent strata, these correlations indicate that the banded and gypsiferous members and the lower part of the Winsor Member are Bathonian in age and the uppermost part of the Win- sor Member is early Callovian in age (fig. 31). The stratigraphic relations in south-central Utah in- dicate that the Judd Hollow Tongue of the Carmel cor- relates with the limestone member farther west, thus indicating a late-middle and late Bajocian age for the Judd Hollow. Because the Page Sandstone is laterally equivalent to the Judd Hollow Tongue and banded member of the Carmel Formation, the Page also is late- middle Baj ocian to early-middle Bathonian (Middle Jurassic) in age. Accordingly, the Harris Wash Tongue of the Page is late-middle and late Bajocian in age because it lies beneath but in normal depositional con- tact with the Judd Hollow Tongue of the Carmel, and the Thousand Pockets Tongue of the Page is early to early-middle Bathonian in age because it is laterally equivalent to the banded member of the Carmel as shown diagrammatically on figure 31. Although the upper member of the Carmel is middle Bathonian to early Callovian in age near Cannonville and Escalante, Utah, where it correlates with the gyp- siferous member and Winsor Member of the Carmel, the lowermost part of the upper member is older far- ther southeast, where it interfingers with the upper- most beds of the Page Sandstone northeast of Page, Ariz. (fig. 10). In Glen Canyon, roughly 50 km northeast of Page, Ariz., and farther southeast, wherever it lies directly on the Navajo Sandstone, the upper member is late Bajocian, Bathonian, and early Callovian in age (fig. 31). TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES According to Imlay (1967, p. 20), the entire Entrada Sandstone is late-early and middle Callovian in age. NAME AND LOCATION OF MEASURED SECTIONS Accurate locations of measured sections are given wherever possible, but, in general, the locations of measured sections of formations in the Glen Canyon Group are only approximately known. Sections of for- mations in the Glen Canyon Group are included with the nearest section of formations in the San Rafael Group to avoid repetition. References are given where measured by persons other than the writers. No. Name Location and reference 1. Pine Creek SW1/2 sec. 29, SEA sec. 30, T. 34 S., R. 3 E., Garfield County, Utah. 2. Page Sec. 2a: SW‘/4 sec. 1, SE1/4 sec. 2, T. 41 N., R. 8 E.; Sec. 2b: NWI/a sec. 19, T. 41 N., R. 9 E., Coconino County, Ariz. NW1/4 sec. 35, T. 35 S., R. 4 E.; SE1/4 sec. 22, NE1/4 sec. 26, T. 36 S., R. 4 E., Gar- field County, Utah. NW1/4 sec. 2, T. 41 S., R. 10 W., Wash- ington County, Utah. Glen Canyon Group measured nearby in Zion Can- yon by Wilson (1965, p. 32, 38, sec. 2). NW1/4 sec. 32, T. 40 S., R. 17 W., Wash- ington County, Utah. About sec. 2, T. 41 S., R. 16 W., Wash- ington County, Utah (Reeside and Bassler, 1922, p. 77, sec. 21). NE1/4 sec. 11, T. 41 S., R. 15 W., Wash- ington County, Utah (J. C. Wright, unpub. data). NEW sec. 34, T. 40 S., R. 14 W., Wash- ington County, Utah. NW1/4 sec. 20, T. 40 S., R. 10 W., Wash- ington County, Utah. Sec. 7, T. 41 S., R. 8 W.; El/z sec. 13, SW1/4 sec. 16, T. 41 S., R. 9 W., Kane County, Utah. Secs. 12, 13, 24, 25, T. 41 S., R. 8 W., Kane County, Utah; Carmel Forma- tion from Gregory and Moore (1931, p.73—74) modified by Gregory (1950a, p. 126—127, sec. 13) and Cashion (1967). Temple Cap Sandstone measured in NE1/4 sec. 36, T. 41 S., R. 8 W. by Fred Peterson in 1970. Glen Canyon Group measured about 8 km west of Kanab by Wilson (1965, p. 32, 38, sec. 3). NW1/4 sec. 16, T. 41 S., R. 6 W., Kane County, Utah. NW1/4 sec. 32, T. 40 S., R. 5 W.; SE1/4 sec. 7, Nl/z sec. 19, NEW: sec. 21, T. 41 S., R. 5 W., Kane County, Utah. NW1/4 sec. 26, T. 41 S., R. 5 W., Kane County, Utah. 3. Harris Wash 4. Zion Canyon 5. Gunlock 6. Diamond Valley 7. Cottonwood Canyon 8. Danish Ranch 9. Potato Hollow 10. Meadow Creek 11. Mount Carmel Junction 12. Kanab Creek 13. Brown Canyon 14. Johnson Canyon No. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE J URASSIC FORMATIONS, UTAH AND ARIZONA Name Carly Knoll Lick Wash Little Bull Valley Averett Canyon Sheep Creek Kodachrome Flat The Gut Goodwater Seep Hackberry Canyon West Cove East Cove Judd Hollow Sand Valley 28. Gunsight Butte Location and reference WV: sec. 30, center of sec. 31, T. 40 S., R. 4 W.; SE1/4 sec. 21, T. 40 S., R. 4V2 W.; SW1/4 sec. 3, SE1/4 sec. 4, T. 41 S., R. 4% W., Kane County, Utah. SW1/4 sec. 30, T. 39 S., R. 3 W.; NE1/4 sec. 1. T. 40 S., R. 4 W., Kane County, Utah. SE1/4, NW1/4 sec. 19,SE1/4 sec. 20, NEVA sec. 28, T. 38 S., R. 3 W., Kane County, Utah. NE1/4 sec. 23, T. 38 S., R. 3 W., Kane County, Utah. Center of sec. 24, T. 38 S., R. 3 W., Kane County, Utah. E‘/2 sec. 3, WV: sec. 14, SEA sec. 15, SW1/4 sec. 20, SW1/4 sec. 21, El/z sec. 22, T. 38 S., R. 2 W., Kane County, Utah. SE1/4 sec. 12, T. 39 S., R. 1 W., Kane County, Utah. SEl/4 sec. 11, T. 40 S., R. 1 W., Kane County, Utah (J. C. Wright, unpub. data). SE1/4 sec. 9, T. 41 S., R. 1 W., Kane County, Utah (J. C. Wright, unpub. data). SW1/4 sec. 19, T. 42 S., R. 1 W.; SE1/4 sec. 25, T. 42 S., R. 2 W., Kane County, Utah. NE‘A sec. 15, T. 43 S., R. 1 W., Kane County, Utah. Phoenix, 1963, sec. 2, p. 64-66, modi- fied. Center of W‘/2 sec. 36, T. 43 S., R. 1 E., Kane County, Utah. Note: According to Phoenix (1963, p. 67), the type section of the Judd Hollow Tongue and Thousand Pockets Tongue is about 1 km northeast of this locality. However, judging from the distribution of outcrops in the area, and a photo of the locality in the orig- inal report (Phoenix, 1963, p. 32, fig. 12), the type sections probably were measured here. Remeasured by Fred Peterson in 1970. SE1/4 sec. 33, SW% sec. 34, T. 42 N., R. 7 E., Coconino County, Ariz. Navajo Sandstone measured about 29.9 km northwest of Lees Ferry by Phoe- nix (1963, p. 30). Kayenta and Moenave Formations measured in the NE1/4 sec. 19, T. 40 N., R. 8 E., Coconino County, Ariz. by Phoenix (1963, p. 79—80, sec. 7). Wingate Sandstone probably measured in same area as Kayenta Formation by Wilson (1965. p. 38). SW1/4 sec. 23, T. 43 S., R. 5 E., Kane County; WV: sec. 12, T. 44 S., R. 5 E., San Juan County, Utah. - No. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. Name Kane Wash B37 Location and reference NE1/4 sec. 13, T. 43 S., R. 5 E.; NW‘A sec. 18, T. 43 S., R. 6 E., Kane County, Utah. D. D. Dickey and others (unpub. data). Cummings Mesa NW Measured at north end of west finger of West Canyon Cummings Mesa trail Upper Valley Seep Flat Twentyfive Mile Wash Early Weed Bench Cat Pasture Big Hollow Wash Hurricane Wash Cave Point Fiftymile Point Navajo Point Little Arch Canyon Tsai Skizzi Square Butte Cow Springs Dinnehotso Red Rock Cummings Mesa, about 5.5 km N. 55° E. and 6.9 km N. 62° E. of Gregory Butte, San Juan County, Utah. Measured 9.2 km S. 55° E. of Gregory Butte, San Juan County, Utah, and 10.9 km S. 55° E. of Gregory Butte, Coconino County, Ariz. Measured on southeast side of Cum- mings Mesa about 10.5 km N. 6° E. of High Point Rock, Coconino County, Ariz. Well: California Company, No. 1 unit, SW1/4NW1/4 sec. 12, T. 36 S., R. 1 E., Garfield County, Utah. SW1/4 sec. 33, T. 36 S., R. 5 E.; N% sec. 4, T. 37 S., R. 5 E., Garfield County. Utah. Wl/z sec. 30, T. 37 S., R. 6 E., Garfield County, Utah. NW‘ASE‘A sec. 1, T. 38 S., R. 6 E., Kane County, Utah. NE1/4 sec. 26, NE1/4 sec. 27, T. 38 S., R. 6 E., Kane County, Utah. Center of N V: sec. 7, SW% sec. 10, T. 39 S., R. 7 E., Kane County, Utah. NEVA sec. 26, T. 39 S., R. 7 E., Kane County, Utah. SW1/4 sec. 26, T. 40 S., R. 8 E.; NEl/4 sec. 2, T. 41 S., R. 8 E., Kane County, Utah. NW‘A sec. 14, T. 41 S., R. 81/2 E., Kane County, Utah. SEl/4 sec. 12, T. 42 S., R. 8 E., Kane County, Utah. Measured at north end of east finger of Cummings Mesa, about 8 km S. 5° W., of Navajo Point, San Juan County, Utah. Measured on northwest side of Tsai Skizzi Rock, a prominent isolated butte about 33.8 km S. 68° E. of Page, Coconino County, Ariz. Measured in small tributary canyon to Potato Canyon about 1 km east and southeast of Square Butte and about 22.5 km N. 22° W. of Cow Springs Trading Post, Coconino County, Ariz. Measured about 2.1 km east of Cow Springs Trading Post, Coconino Coun- ty, Ariz. Near Dinnehotso, Apache County, Ariz. Harshbarger and others (1957, p. 65, sec. 6; plates 2 and 3). Near Red Rock, Apache County. Ariz. Harshbarger and others (1957, pl. 2). B38 MEASURED SECTIONS Section 1.—Reference section of Carmel Formation and Page Sandstone at Pine Creek [Measured on west side of valley of Pine Creek about 4.8 km north of Escalante in the NWSW'ASW‘A sec. 29. EwSE‘ASE‘A sec. 30, T. 34 S., R. 3 E. (projected), County, Utah] Entrada Sandstone (part): Lower member (part): 42. Sandstone, silty, moderate-reddish-orange, coarse silt size to very fine grained, moderately to poorly sorted, very thin to thick bedded; lower contact sharp and nearly planar; forms slopes ..................................... Carmel Formation: Upper member: 41. Marker bed: mudstone, grayish-purple, laminated to very thin bedded, probably a ben- tonite bed; forms slope ...................... 40. Sandstone, moderate-reddish-brown, very fine grained, moderately sorted; some ripple cross- lamination apparent; forms slight ledge ...... Mudstone, dark-reddish-brown, laminated to very thin bedded; forms slope ............... Sandstone, moderate-reddish-brown, very fine grained, moderately sorted, irregularly very thin bedded and ripple cross-laminated; forms ledge ...................................... Sandstone, silty, moderate-reddish-brown, coarse silt to very fine grained, moderately to poorly sorted; bedding not apparent; forms slope ...................................... Gypsum, mainly light gray but includes some moderate-reddish-brown and grayish-yellow- green, laminated to very thin bedded, locally contorted; forms ledge ...................... Sandstone, like unit 37 ....................... Mudstone, grayish-purple, some grayish-yellow- green; forms slope .......................... Sandstone, light-gray at top to moderate- reddish-brown at base, mottled in middle, very fine grained, moderately sorted, very thin bed- ded; forms slope ............................ Gypsum, like unit 36; 1.8 m above base is 0.9-m bed of moderate-reddish-brown, slope-forming, silty sandstone ............................ Sandstone, like unit 37 ....................... Gypsum, like unit 36 ......................... Mudstone, grayish-brown, dark-reddish-brown, and grayish-yellow-green; 1.5 m above base is 0.6-m bed of gypsum like unit 36; forms slope . Gypsum, like unit 36; includes about 20 percent dark-reddish-brown mudstone; badly con- torted; forms cliff .......................... Gypsum, like unit 36 but badly contorted; about 0.9 m above base is 0.9-m bed of dark-reddish- brown mudstone; poorly exposed; forms slope Mudstone, dark-reddish-brown, irregularly lam- inated to very thin bedded; includes about 30 percent moderate-reddish—brown silty sand- stone; 6.7 m above base is 0.6 m of gypsum like unit 36; overlain by 1.2 m of laminated gray limestone and 0.9 m of grayish-yellow-green mudstone. The gypsum and limestone form a slight ledge; the remainder forms a slope ..... 39. 38. 37. 36. 35. 34. 33. 32. 31. 30. 29. 28. 27. 26. Garfield Thickness meters co to O 0.3 1.8 0.5 0.3 0.6 0.3 0.5 0.3 4.0 3.4 1.5 1.2 4.6 3.0 3.0 14.6 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES Section 1.—Reference section of Carmel Formation and Page Sand- stone at Pine Creek—Continued Carmel Formation—Continued Upper member—Continued 25. Partly covered slope; some light-gray gypsum and very light gray limestone weathering out on the slope ................................ Gypsum, like unit 36; includes about 30 percent dark-reddish-brown mudstone; generally forms slope although several gypsum beds form ledges ................................ 24. 23. Sandstone, very light gray, very fine grained, moderately sorted, very thin bedded; forms slope ...................................... Partly covered slope, mainly dark reddish brown mudstone and some moderate-reddish-brown silty sandstone ............................ 22. 21. Gypsum, like unit 36; exposed as a series of small hills and knobs that extend along the partly covered floor of a small gully .......... 20. Partly covered slope, mainly dark reddish brown mudstone ................................. Marker bed: limestone, yellowish-gray, micro- crystalline to very fine grained, very thin to thin-bedded, locally very low angle, small-scale crossbedded; top 15 cm contains several poorly preserved pelecypods identified as Pronoella uintahensis Imlay by R. W. Imlay (written commun., 1969); weathers to slabby cliffs and forms a small hogback ...................... 19. 18. Partly covered slope, mainly dark reddish brown mudstone grading to grayish-yellow-green in upper 0.9 m above base, suggesting a thin limestone bed at top ........................ Limestone, light-gray, microcrystalline, very thin bedded; forms flaggy cliffs .............. 17. 16. Partly covered slope, mainly dark reddish brown mudstone ................................. Partly covered slope, mainly yellowish gray, very thin bedded limestone includes some grayish-yellow mudstone; lower contact ap- parently planar ............................ 15. Thick ness meters 1.5 8.5 5.8 17.2 1.5 7.6 15.2 5.2 6.7 3.4 0.9 Total upper member of Carmel Formation . 113.4 Page Sandstone Thousand Pockets Tongue: 14. Sandstone, very light gray to pale-yellowish- orange at top, fine-grained, well-sorted; consists of tabular-planar and wedge-planar sets of large-scale low- and high-angle cross-strata; basal 0.6 m locally slumped; forms smooth cliff 13. Marker bed: sandstone, moderate-reddish-brown, very fine grained, moderately sorted, irregularly very thin to thin-bedded; forms slope ......... 12. Sandstone, light-gray, very fine grained, moder- ately sorted, very thin to thin-bedded; forms cliff ....................................... 5.5 3.0 2.0 RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA Section 1.—Reference section of Carmel Formation and Page Sand- stone at Pine Creek—Continued Thick ness meters Page Sandstone—Continued Thousand Pockets Tongue—Continued 11. Sandstone, moderate-reddish-brown; grades to light-gray and pale-yellowish-orange at top; very fine grained, well-sorted. Consists of tabular-planar and wedgeplanar sets of large- scale, low-and high-angle, cross-strata; lower 9.6 m is irregularly very thin bedded; basal contact placed at sharp change in lithology; forms smooth cliff ................................ 1 1.3 Total Thousand Pockets Tongue of Page Sandstone ........................... 21.9 Carmel Formation: Judd Hollow Tongue: 10. Partly covered slope, mainly dark reddish brown mudstone; includes some moderate—reddish- brown silty sandstone; top 15 cm is grayish- purple bentonite; bedding not apparent ....... 5.2 9. Limestone, yellowish-gray, very fine grained, sil- ty and sandy, ripple cross-laminated; forms flaggy cliff ................................. 3.0 8. Interbedded unit: sandstone (about 50 percent), moderate-reddish-brown, fine-grained, moderately sorted; mudstone (about 40 percent), dark-reddish-brown; and limestone, moderate-reddish-brown; very thin to thin- bedded; about 3 m above base is 0.3-m bed of grayish-purple mudstone; forms slope ........ 8.4 7. Limestone, very pale orange, very fine grained, sandy and silty, irregularly very thin bedded; forms flaggy ledge .......................... 1.4 6. Sandstone, light-gray to grayish-orange, fine- grained, irregularly laminated to very thin bed- ded; forms slope ............................ 1.4 5. Sandstone, light-gray, fine-grained, moderately to well-sorted, laminated to small-scale very low angle crossbedded; forms ledge .............. 0.5 4. Sandstone, light-gray to grayish-orange, fine- grained, moderately sorted, irregularly laminated to very thin bedded; forms notch or slope ...................................... 0.6 3. Sandstone, light-gray, stained moderate- yellowish-brown, very fine grained, moderately sorted, irregularly very thin bedded; contains several slumped beds; lower contact sharp and planar; forms flaggy cliff .................... 2.0 Total Judd Hollow Tongue of Carmel Form— ation ................................ 26.6 Page Sandstone: Harris Wash Tongue: 2. Sandstone, light-gray, some moderate-reddish- brown, fine— to medium-grained, well-sorted; bedding consists of tabular-planar and trough- shaped sets of large-scale low- and high-angle cross-strata; scarce angular very fine to fine pebbles of pale-brown to grayish-red chert scat- tered along base; lower contact sharp and planar; regional studies indicate it is. an uncon- formity; forms cliff; base locally forms slight overhang .................................. 4.6 Total Harris Wash Tongue of Page Sand- stone ................................ 4.6 B39 Section 1.—Reference section of Carmel Formation and Page Sand- stone at Pine Creek—Continued Thickness Unconformity. me 2278 Navajo Sandstone (part): 1. Sandstone, light-gray, fine-grained, well-sorted; consists of tabular—planar and wedge-planar sets of large-scale low- and high-angle cross- strata; forms blocky cliffs ................... 30.5+ Total measured Navajo Sandstone ....... 30.5 Section 20.. —Reference section of Carmel Formation (upper member) at Page [Measured near paved road on west side of valley of Wahweap Creek about 5 km north of Hayden Visitor Center at Glen Canyon Dam in the SW'ASWI/a sec. 1, SE‘ASEV. sec. 2, T. 41 N., R. 8 E., Coconino County, Ariz.] Entrada Sandstone (part): 24. Sandstone, very light gray, fine-grained. moder- ately to well-sorted; bedding consists of trough-shaped sets of medium- to large-scale high-angle cross-strata; lower contact sharp, planar, and conformable; top eroded; forms small irregular cliffs and knobby slopes ...... 6.1 Total measured Entrada Sandstone ...... 6.1 Carmel Formation: Upper member: 23. Sandstone, silty, grayish-yellow-green, coarse silt to very fine grained, moderately to poorly sorted, irregularly very thin bedded; forms slope ...................................... 0.3 22. Mudstone, dark-reddish-brown, sandy, lamin- ated to very thin bedded; contains several sandstone and silty sandstone beds, which are moderate reddish brown, coarse silt to very fine grained, moderately to poorly sorted, very thin to thin bedded; 9.1 m above base is 0.9-m bed of very thin bedded white sandstone overlain by 15 cm of grayish-purple mudstone; 8.5 m above base is 0.3 m of very thin bedded white sandstone overlain by 15 cm of grayish- purple mudstone; 0.9 m above base is 15 cm of grayish-purple bentonite; forms slope ........ 13.5 21. Sandstone, moderate-reddish-brown; top 0.3 m is white, fine-grained, moderately sorted; con- tains scattered very coarse grains, irregularly very thin to thin bedded; 3.7 m above base is thin lens of dark-reddish-brown mudstone as much as 0.3 m thick; forms slopes with slabby cliff in middle .............................. 5.5 20. Sandstone, moderate-reddish—brown, very fine grained, moderately sorted, irregularly very thin to thin-bedded; includes many laminae or very thin beds of silty sandstone or mudstone; 8.5 m above base is 5 cm of dark-reddish—brown mudstone; 7.3 m above base is 0.9 m of white crossbedded sandstone; 6.7 m above base is 15 cm zone with scattered very fine to fine peb- bles; forms slabby slopes at base and slabby cliffs at top ................................ 9.4 19. Sandstone, moderate-reddish-brown, fine- grained, moderately sorted, contains scattered very fine pebbles; laminated to very thin bed- ded; 1.2 and 1.5 m above base are two 7-mm- thick laminae of grayish-purple mudstone; forms slope with slabby cliff at top ........... 4.9 B40 Section 2a —Reference section of Carmel Formation (upper member) at Page—Continued Carmel Formation~Continued Upper member—Continued Thickness meters 18. Sandstone, moderate-reddish-brown, very fine grained, moderately sorted; several beds con- tain scattered very fine pebbles; bedding is laminated to very thin bedded or consists of tabular-planar sets of small- to medium-scale, low-angle cross—strata; includes minor dark- reddish-brown mudstone; forms a series of slabby to blocky ledges ..................... 6.7 17.1nterbedded sandstone and mudstone; sand- stone, grayish-purple, fine-grained, moderately sorted; mudstone, dark-reddish-brown to grayish-purple, very thin to thin-bedded; forms slope ................................ 1.5 16. Sandstone, very light gray, fine-grained, mod- erately sorted; bedding is indistinct; forms ledge ...................................... 0.6 15. Sandstone, moderate-reddish-brown, fine- grained. moderately sorted; contains scattered very fine pebbles. very thin bedded; forms slope ...................................... 0.3 14. Sandstone, pebbly, moderate-reddish-brown, fine-grained, poorly sorted; contains scattered very fine to fine pebbles and thin conglomerate lenses, irregularly very thin bedded; forms slope ...................................... 0.3 13. Sandstone, like unit 15 ....................... 0.9 12. Sandstone, moderate-reddish-brown, fine- grained, moderately sorted; contains scattered very fine pebbles, very thin bedded; slight ledge caps cliff ............................. 0.9 11. Sandstone. moderate-reddish-brown, fine- grained, well-sorted; consists of a tabular- planar set of large-scale high-angle cross- strata; forms smooth cliff ................... 4.6 10. Sandstone, moderate-reddish-brown, fine- grained, moderately sorted; contains scattered very fine pebbles laminated to very thin bed- ded; top 0.9 m includes several very thin beds of darkreddish-brown mudstone, some of which have sandstone-filled mudcracks; 5.5 m above base is 0.3-m bed of dark-reddish-brown shale containing sandstone-filled mudcracks, overlain by 2.1-m sandstone bed that is locally crossbedded and contains scarce scattered mudchips; 4.3 m above base is 0.3-m bed of dark-reddish-brown shale; 0.9 m above base is 2.5-cm bed of dark-reddish-brown shale; generally forms slabby to blocky cliffs but in- cludes several slopes ....................... 8.8 9. Sandstone, moderate-reddish-brown, very fine grained, moderately sorted, very thin bedded; includes several very thin beds of dark- reddish-brown mudstone; forms slope ........ 0.5 8. Sandstone, moderate-reddish-brown, fine- grained. moderately sorted; contains scattered coarse and very coarse grains; bedding is laminated to very thin bedded or consists of scarce tabular-planar sets of medium-scale high-angle cross-strata; includes scarce very thin beds of dark-reddish-brown shale and TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES Section 2a ——Reference section of Carmel Formation (upper member) at Page—Continued Carmel Formation—Continued Upper member—Continued Thickness meters mudstone; forms slabby to blocky ledges and slopes ..................................... 7.9 . Marker bed: limestone, grayish-pink to mod- erate-pink. microcrystalline, laminated but in- cludes scarce ripple cross-laminae; locally has abundant straight lines that intersect at right angles on several bedding surfaces (“maprock" of Young, 1964); forms platy ledge ........... 0.6 q 6. Sandstone, silty, moderate-reddish-brown, very dark red in thin irregular zone in middle, coarse silt to very fine grained, moderately to poorly sorted, very thin bedded; forms slope . . 0.6 5. Sandstone, moderate-reddish-brown, fine- grained, moderately sorted; contains scarce scattered very fine pebbles, irregularly laminated to thin-bedded; includes scarce very thin beds of dark-reddish-brown mudstone; forms flaggy ledges and slopes .............. 5.3 4. Sandstone, moderate-reddish-brown, fine- grained, moderately sorted; contains scattered very coarse grains; very thin bedded; includes some very fine grained silty sandstone; forms flaggy slope ............................... 2.6 3. Sandstone, like unit 4, but forms ledge ......... 0.8 2. Sandstone, silty, moderate-reddish-brown, coarse silt to fine-grained, moderately to poor- ly sorted, very thin to thin-bedded; includes several very thin beds of dark-reddish-brown mudstone; lower contact sharp, nearly planar with less than 0.3 m of relief locally; forms slope ...................................... 1.2 Total upper member of Carmel Form- ation ................................ Page Sandstone (part): 1. Sandstone, moderate-pink, fine-grained, well- sorted; consists of tabular-planar and wedge- planar sets of large-scale low- and high-angle cross-strata; forms smooth slopes and cliffs . . 30.0+ Total measured Page Sandstone ......... Section 2b.—Type section of Page Sandstone [Measured on northwest side of Manson Mesa and the town of Page in the SWV‘NW‘A sec. 19, T. 41 N.. R. 9 E., (projected), Coconino County, Ariz. Base of section is about 914 m east-northeast from Glen Canyon Dam and line of section trends due east up small cleft in cliffs to VABM 4103, Antelope] Thickness meters Carmel Formation (part): Upper member (part): 9. Sandstone, dark-reddish-brown, fine-grained, moderately sorted; contains scattered very fine pebbles, very thin bedded to thin bedded; includes some sandy mudstone; forms ledges and slopes ................................. 8. Mudstone, dark-reddish—brown, sandy, lamin- ated to very thin bedded; forms slope ........ 2.0 6.0+ RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA Section 2b.—Type section of Page Sandstone—Continued Carmel Formation—Continued Upper member—Continued Thickness meters 7. Sandstone, very light gray to grayish-pink, fine-grained, moderately sorted, irregularly very thin to thin-bedded, lower contact sharp and planar; generally covered by soil; forms slight ledge where exposed .................. 0.2 Total measured upper member of Carmel Formation ........................... 8.2 Page Sandstone: 6. Sandstone, moderate-reddish-orange to moder- ate-reddish-brown; grades to very light gray or grayish pink at top, fine grained, well sorted; scarce coarse grains occur at base of several cross-bedding sets; bedding consists of tabular-planar sets of medium- to large-scale, . low- and high-angle cross-strata; forms smooth slopes or cliff rounded at top ................ 39.1 5. Sandstone, dark-reddish-brown, fine-grained, moderately sorted, irregularly very thin bed- ded; fossil joints at base extend about 0.6 m in- to underlying beds; forms local small bench or slight notch ............................... 0.3 4. Sandstone, same as unit 6; grades to grayish red at top where small calcite or silica- cemented sandstone nodules occur; forms smooth steep slopes or cliff ................. 7.9 3. Sandstone, dark-reddish—brown, fine-grained, moderately sorted, irregularly very thin bed- ded; forms local small bench or slight notch . . . 0.3 2. Sandstone, moderate-reddish-orange to moder- ate-reddish-brown, fine-grained, well-sorted; scarce coarse grains occur at base of several crossbedding sets; bedding consists of tabular- planar sets of medium- to large-scale, low- and high-angle cross-strata; scattered along base are abundant angular very fine to fine pebbles of white to very pale orange chert or scarce red chert; fossil joints at base extend down about 1 m into Navajo Sandstone; lower contact sharp and planar except at fossil joints; regional studies indicate an unconformity; forms smooth rounded cliffs ...................... 8.2 Total Page Sandstone .................. 55.8 Unconformity. Navajo Sandstone (part): 1. Sandstone, pale-reddish-brown; grades down to moderate reddish brown, fine grained, well sorted; bedding consists of tabular-planar sets of medium- to large-scale, low- and high-angle cross-strata; small silica- and calcite-cemented sandstone nodules occur in upper 4.6 111; forms smooth sheer cliffs in Glen Canyon but above the canyon has irregular bench a kilometer or more wide, stripped back on top ............. 15.2+ Total measured Navajo Sandstone ....... 15.2 B41 Section 3. —Type section of Harris Wash Tongue of Page Sandstone [Measured on west side of Halfway Hollow about 0.8 km from junction with Harris Wash, about 20 km southeast of Escalante, Utah, in the NE‘ASEVANE‘A sec. 26, T. 36 S., R. 4 E.. Garfield County, Utah] Carmel Formation 1part): Judd Hollow Tongue (part): 5. Mudstone, dark-reddish-brown, laminated to very thin bedded; upper part involved in in- traformational folds; forms slope ............ 4. Sandstone, moderate-reddish-brown and gray- ish-red; top meter mottled with grayish pink; fine grained, moderately to well sorted, ir- regularly laminated to very thin bedded; in- cludes some small- to medium-scale, low-angle, wedge-planar cross-strata; forms slabby cliff . 6.9 Total measured Judd Hollow Tongue of Carmel Formation .................... 7 5 Thick ness meters 0.6+ Page Sandstone (part): Harris Wash Tongue: 3. Sandstone, moderate-reddish-brown and gray- ish-pink; grading upward to dominantly grayish pink, fine grained, well sorted; consists of tabular-planar and wedge-planar sets of medium- and large-scale, low- and high-angle cross-strata; top 15 cm is a set of low-angle, wedge-planar cross-strata; beneath that is a set of large-scale, high-angle cross-strata about 10.7 m thick; forms smooth cliff ....... 2. Sandstone, moderate-reddish-brown; includes some that is grayish pink and very light gray, fine grained, moderately sorted, laminated to very thin bedded and ripple cross laminated; scattered along base are angular very fine peb- bles of white to very pale orange chert; fossil joints extend down as much as 1.2 m into the Navajo Sandstone; basal contact sharp and planar except at fossil joints; regional studies indicate it is an unconformity; forms smooth cliffs, locally stripped back slightly at base . . . 0.3 Total Harris Wash Tongue of Page Sand- stone ................................ 18.3 18.0 Unconformity. Navajo Sandstone (part): 1. Sandstone, grayish-pink to moderate-reddish- brown, fine-grained, well-sorted; consists of tabular-planar and wedge-planar sets of medium- to large-scale, low- and high-angle cross-strata; forms smooth cliff ............. 6.1+ Total measured Navajo Sandstone ....... 6.0 Section 4.—Principal reference section of Temple Cap Sandstone, type section of Sinawava and White Throne Members [Measured at top of Zion Canyon about 500 m northeast of Observation Point in the NW‘ANW‘A sec. 2, T. 41 S., R. 10 W. (projected), Zion National Park. Washington County, Utah] Thick ness Carmel Formation (part): M 2 e 978 Limestone member (part): Limestone unit (part): 10. Limestone, very pale orange, microcrystal- line to very fine grained, thin- to thick- bedded, locally laminated to very thin bed- ded; forms slabby ledges; top eroded, only lower part present ...................... 12.2+ Total measured limestone unit ....... 12.2 B42 Section 4,—Principal reference section of Temple Cap Sandstone, type section of Sinawava and White Throne Members—Continued Carmel Formation—Continued Limestone member—Continued Basal unit: 9. Interbedded mudstone and sandstone; mudstone, dark-reddish-brown, laminated to very thin bedded; sandstone and silty sandstone, moderate-reddish-brown to grayish-pink, coarse silt, to fine-grained, moderately sorted, very thin bedded; con- tains some pink limestone near top; forms a slope, generally partly concealed by thin veneer of talus of soil ................... Thickness meters 6.0 8. Sandstone, moderate-reddish-brown, medi- um-grained; contains scattered rounded coarse grains of black, gray, or brown chert and red or clear quartz, and angular very coarse grains and very fine pebbles of white or pink chert, irregularly very thin to thin bedded; lower contact sharp and planar; regional studies indicate it is an un- conformity; forms flaggy ledge .......... Total basal unit .................... Total measured limestone member of Carmel Formation ................ 18.6 Temple Cap Sandstone: White Throne Member: 7. Sandstone, yellowish-gray grading down to very light gray and very pale orange, fine-grained, well-sorted: consists of trough and tabular- planar sets of large-scale, low- and high-angle cross-strata; forms smooth cliff ............. 26.5 6. Sandstone, grayish-yellow to pale-yellowish- orange, very fine to fine-grained, scattered very coarse grains, moderately sorted; con- sists of tabular-planar and wedge-planar sets of medium-scale, low-angle cross-strata; forms irregular cliff; locally has a, small shoulder at top ....................................... 4.0 5. Sandstone, grayish-yellow to pale-yellowish- orange, very fine to medium-grained; scattered coarse grains, moderately sorted, very thin bedded; includes tabular-planar sets of small- scale, low-angle cross-strata in lower 15 cm; forms cliff ................................. 0.6 4. Sandstone, very light gray and some moderate- reddish-brown, mottled, fine-grained, moderately to well-sorted; consists of trough- shaped sets of medium- to large-scale low- and high-angle cross-strata; lower contact grada- tional; unit varies in thickness owing to in- traformational folds or slumps at or near the base; forms cliff ............................ Total White Throne Member ............ ._. 9° 0': a; S9 q Sinawava Member: 3. Interbedded sandstone, silty sandstone, and mudstone; sandstone and silty sandstone, moderate-reddish-brown, coarse silt to very fine grained: scattered coarse grains, moderately to poorly sorted, laminated to very thin bedded; mudstone, dark-reddish-brown, laminated to very thin bedded, more abundant near base of unit; unit varies in thickness ow- ing to intraformational folds or slumps near top, largely concealed by talus and soil cover; forms slope ................................ 5.8 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES Section 4. —Principal reference section of Temple Cap Sandstone, type section of Sinawava and White Throne Members—Continued Temple Cap Sandstone—Continued Sinawava Member—Continued 2. Sandstone, very light gray to moderate-red- dish-brown, mottled, very fine to fine-grained, scattered coarse and scarce very coarse grains, moderately to poorly sorted, irregular very thin bedding, basal contact sharp, nearly planar, but locally has about 15 cm relief; Thickness meters forms slope or slight ledge .................. 0.3 Total Sinawava Member ................ 6.1 Total Temple Cap Sandstone ............ 55.8 Navajo Sandstone (part): 1. Sandstone, white to very light gray, fine-grain- ed, well-sorted; consists of tabular-planar and wedge-planar sets of largescale, low- and high- angle cross-strata; forms smooth cliff ........ 15.2 Total measured Navajo Sandstone ....... 15.2 REFERENCES CITED Averitt, Paul, 1962, Geology and coal resources of the Cedar Moun- tain quadrangle, Iron County, Utah: U.S. Geol. Survey Prof. Paper 389, 72 p. Baker, A. A., Dobbin, C. E., McKnight, E. T., and Reeside, J. B., Jr., 1927, Notes on the stratigraphy of the Moab region, Utah: Am. Assoc. Petroleum Geologists Bull., v. 11, no. 8, p. 785—808. Baker, A. A., Dane, C. H., and Reeside, J. B., Jr., 1936, Correlation of the Jurassic formations of parts of Utah, Arizona, New Mex- ico, and Colorado: US. Geol. Survey Prof. Paper 183, 66 p. Cashion, W. B., 1967, Carmel Formation of the Zion Park region, southwestern Utah—A review: U.S. Geol. Survey Bull. 1244—J, p. J 1—J 9. Cornet, Bruce, Traverse, Alfred, and McDonald, N. G., 1973, Fossil spores, pollen, and fishes from Connecticut indicate Early Jurassic age for part of the Newark Group: Science, v. 182, p. 1243—4247. Cornet, Bruce, and Traverse, Alfred, 1975, Palynological contribu- tions to the chronology and stratigraphy of the Hartford basin in Connecticut and Massachusetts: Geoscience and Man, v. 11. p. 1—33. Craig, L. C., and Dickey, D. D., 1956, Jurassic strata of southeastern Colorado, in J. A. Peterson, ed., Geology and economic deposits of east-central Utah: Intermountain Assoc. Petroleum Geologists Guidebook, 7th Ann. Field Conf., p. 93—104. Crampton, C. G., 1964, Standing up country—The canyon lands of Utah and Arizona: New York, Alfred A. Knopf, Utah Universi- ty Press, 191 p. Davidson, E. S., 1967, Geology of the Circle Cliffs area, Garfield and Kane Counties, Utah: US. Geol. Survey Bull. 1229, 149 p. Dunbar, C. 0., and Rodgers, John, 1957, Principles of stratigraphy: New York, John Wiley and Sons, 356 p. Galton, P. M., 1971, The prosauropod dinosaur Ammosaurus, the crocodile Protosuchus, and their bearing on the age of the Nava- jo Sandstone of northeastern Arizona: Jour. Paleontology, v. 45, no. 5, p. 781—795. Gilluly, James, and Reeside, J. B., J r., 1928, Sedimentary rocks of the San Rafael Swell and some adjacent areas in eastern Utah: US. Geol. Survey Prof. Paper 150—D, p. 61—110. Glennie, K. W., 1970, Desert sedimentary environments: New York, Elsevier, 222 p. Goddard, E. N., chm., and others, 1963 reprint, Rock-color chart: New York, Geol. Soc. America, 6 p. Grater, R. K., 1948, Some features of the Navajo Formation in Zion National Park, Utah: Am. Jour. Sci., v. 246, no. 5, p. 311—318. Gregory, H. E., 1917, Geology of the Navajo country—a reconnai- ssance of parts of Arizona, New Mexico, and Utah: US. Geol. Survey Prof. Paper 93, 161 p. _ 1948, Geology and geography of central Kane County, Utah: RELATIONS OF THE NAVAJO SANDSTONE TO MIDDLE JURASSIC FORMATIONS, UTAH AND ARIZONA Geol. Soc. America Bull., v. 59, no. 3, p. 211—247. 1950a, Geology and geography of the Zion [National] Park region, Utah and Arizona: U.S. Geol. Survey Prof. Paper 220, 200 p. 1950b, Geology of eastern Iron County, Utah: Utah Geol. Mineralog. Survey Bull. 37, 153 p. 1951, The geology and geography of the Paunsaugunt region, Utah: U.S. Geol. Survey Prof. Paper 226, 116 p. Gregory, H. E., and Moore, R. C., 1931, The Kaiparowits region, a geographic and geologic reconnaissance of parts of Utah and Arizona: U.S. Geol. Survey Prof. Paper 164, 161 p. Harshbarger, J. W., Repenning, C. A., and Irwin, J. H., 1957, Strati- graphy of the uppermost Triassic and the Jurassic rocks of the Navajo country [Colorado Plateau]: U.S. Geol. Survey Prof. Paper 291, 74 p. Imlay, R. W., 1952, Correlation of the Jurassic formations of North America, exclusive of Canada: Geol. Soc. America Bull., v. 63, no. 9, p. 953—992. 1957, Paleoecology of Jurassic seas in the Western Interior of the United States, in H. S. Ladd, ed., Paleoecology: Geol. Soc. America Mem. 67, v. 2, p. 469—504. 1964, Marine Jurassic pelecypods from central and southern Utah: U.S. Geol. Survey Prof. Paper 483-C, p. 01—042. 1967 , Twin Creek Limestone (Jurassic) in the Western Interi- or of the United States: U.S. Geol. Survey Prof. Paper 540, 105 p. 1979, Jurassic paleobiogeography of conterminous United States and adjacent areas in its continental setting: U.S. Geol. Survey Prof. Paper 1062. (In press.) Lewis, G. E., Irwin, J. H., and Wilson, R. F., 1961, Age of the Glen Canyon Group (Triassic and Jurassic) on the Colorado Plateau: Geol. Soc. America Bull., v. 72, no. 9, p. 1437—1440. McKee, E. D., and Weir, G. W., 1953, Terminology for stratification and cross-stratification in sedimentary rocks: Geol. Soc. America Bull., v.64, no. 4, p. 381-389. McKee. E. D., Oriel, S. S., Swanson, V. W., MacLachlan, M. E., MacLachlan, J. C., Ketner, K. B., Goldsmith, J. W., Bell, R. Y., and Jameson, D. J ., 1956, Paleotectonic maps of the Jurassic System: U.S. Geol. Survey Misc. Geol. Inv. Map I—175, 6 p. Olsen, P. E., and Galton, P. M., 1977, Triassic-Jurassic tetrapod extinctions: are they real?: Science, v. 197, p. 983—986. O’Sullivan, R. B., and Craig, L. C., 1973, Jurassic rocks of northeast Arizona and adjacent areas, in New Mexico Geol. Soc. 24th Ann. Field Conf. Guidebook of Monument Valley and Vicinity, Arizona and Utah: p. 79—85. Peterson, Fred, 1973, Geologic map of the southwest quarter of the Gunsight Butte quadrangle, Kane and San Juan Counties, Utah, and Coconino County, Arizona: U.S. Geol. Survey Misc. Field Studies Map MF—306. Peterson, Fred, and Waldrop, H. A., 1965, Jurassic and Cretaceous stratigraphy of south-central Kaiparowits Plateau, Utah, in Geology and resources of south-central Utah—Resources for power: Utah Geol. Soc. Guidebook to Geology of Utah, no. 19, p. 47—69. Peterson, Fred, and Barnum, B. E., 1973, Geologic map of the south- west quarter of the Cummings Mesa quadrangle, Kane and San Juan Counties, Utah, and Coconino County, Arizona: U.S. Geol. Survey Misc. Geol. Inv. Map I—759. Phoenix, D. A., 1963, Geology of the Lees Ferry area, Coconino County, Arizona: U.S. Geol. Survey Bull. 1 137, 86 p. Pipiringos, G. N., 1967, Jurassic and Triassic of Wyoming and southern Rockies [abs]: Am. Assoc. Petroleum Geologists Bull., v. 51, no. 9, p. 1904-1905. 1968, Correlation and nomenclature of some Triassic and Jurassic rocks in south-central Wyoming: U.S. Geol. Survey Prof. Paper 594—D, p. D1-D26. Pipiringos, G. N ., and O'Sullivan, R. B., 1975, Chert pebble uncon- formity at the top of the Navajo Sandstone in southeastern Utah, in J. E. Fassett, ed., Canyonlands Country: Four Corners Geol. Soc. Guidebook, 8th Field Conf., p. 149-156. B43 1978, Principal unconformities in Triassic and Jurassic rocks, Western Interior United States—A preliminary survey: U.S. Geol. Survey Prof. Paper 1035-A, 29 p. Poole, F. G., and Stewart, J. H., 1964, Chinle Formation and Glen Canyon Sandstone in northeastern Utah and northwestern Col- orado: U.S. Geol. Survey Prof. Paper 501—D, p. D30-D39. Reeside, J. B., J r., and Bassler, Harvey, 1922, Stratigraphic section in southwestern Utah and northwestern Arizona: U.S. Geol. Survey Prof. Paper 129—D, p. 53-77. Shawe, D. R., Simmons, G. C., and Archbold, N. L., 1968, Strati- graphy of Slick Rock district and vicinity, San Miguel and Dolores Counties, Colorado: U.S. Geol. Survey Prof. Paper 576—A, p. A1—A108[1969]. Smith, J. F., Jr., Huff, L. C., Hinrichs, E. N., and Leudke, R. G., 1963, Geology of the Capitol Reef area, Wayne and Garfield Counties, Utah: U.S. Geol. Survey Prof. Paper 363, 102 p. Speed, R. C., 1976, Geologic map of the Humboldt Lopolith and surrounding terrane, Nevada: Geol. Soc. America, Map MC—14. Speed, R. C., and Jones, T. A., 1969, Synorogenic quartz sandstone in the Jurassic mobile belt of western Nevada: Boyer Ranch Formation: Geol. Soc. America Bull., v. 80, no. 12, p. 2551—2584. Thaden, R. E., ’I‘rites, A. F., J r., and Finnell, T. L., 1964, Geology and ore deposits of the White Canyon area, San Juan and Garfield Counties, Utah: U.S. Geol. Survey Bull. 1125, 166 p. Thompson, A. E., and Stokes, W. L., 1970, Stratigraphy of the San Rafael Group, southwest and south-central Utah: Utah Geol. Mineralog. Survey Bull. 87, 50 p. (replacement copy issued May 1971). Walker, A. D., 1968, Protosuchus, Proterochampsa, and the origin of phytosaurs and crocodiles: Geological Magazine, v. 105, no. 1, p. 1—14. Walker, T. R., and Harms, J. C., 1972, Eolian origin of flagstone beds, Lyons Sandstone (Permian), type area, Boulder County, Col- orado: The Mountain Geologist, v. 9, nos. 2—3, p. 279—288. Williams, G. A., 1954, Stratigraphic studies: U.S. Atomic Energy Comm, Trace Element Investigations Report TEI-440, p. 30-35. Wilson, R. F., 1965, Triassic and Jurassic strata of southwestern Utah, in Geology and resources of south-central Utah—Resources for power: Utah Geol. Soc. Guidebook to Geology of Utah, no. 19, p. 31—46. 1967, Whitmore Point, a new member of the Moenave Form- ation in Utah and Arizona: Plateau, v. 40, no. 1, p. 29—40. 1974, Mesozoic stratigraphy of northeastern Arizona; in T.N.V. Karlstrom, Swann, G. A., and Eastwood, R. L., eds., Geology of northern Arizona with notes on archaeology and paleoclimate, Part 1, Regional Studies: Northern Arizona University, Museum of Northern Arizona, and U.S. Geol. Survey, p. 192—207. Wilson, R. F., and Stewart, J. H., 1967, Correlation of Upper Triassic and Triassic(?) formations between southwestern Utah and southern Nevada: U.S. Geol. Survey Bull. 1244—D, p. D1-D20. Woodbury, A. M., 1950, A history of southern Utah and its national parks: Utah State Hist. Soc. Quart., v. 12, nos. 3—4, p. 111—223 [J uly—October 1944, revised and reprinted 1950]. Wright, J. C., and Dickey, D. D., 1963a, Relations of the Navajo and Carmel Formations in southwest Utah and adjoining Arizona, in Geological Survey research 1962, Short papers in geology, hydrology, and topography: U.S. Geol. Survey Prof. Paper 450-13, p. E63—E67. _ 1963b, Block diagram of the San Rafael Group and under- lying strata in Utah and part of Colorado: U.S. Geol. Survey Oil and Gas Inv. Chart OC—63. Young, R. G., 1964, An unusual sedimentary structure from the Carmel Formation: Jour. Sed. Petrology, v. 34, no. 4, p. 883—886. Zeller, H. D., 1973, Geologic map and coal resources of the Dave Canyon quadrangle, Garfield County. Utah: U.S. Geol. Survey Coal Map C—59. "U.s. GOVERNMENT PRINTING o:=s=um== lQ‘IQ—fl.£77.noc 1:: Lithology and Subdivisions of the Jurassic Stump Formation in Southeastern Idaho and Adjoining Areas By GEORGE N. PIPIRINGOS and RALPH W. IMLAY UNCONFORMITIES, CORRELATION, AND NOMENCLATURE OF SOME TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES GEOLOGICAL SURVEY PROFESSIONAL PAPER 1035-C Marked rapid lateral changes in lithology, fossil content, and thickness of the Stump Formation are due principally to erosion associated with the Cretaceous (K) and Jurassic (]-4) unconformities UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. AN DRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Pipiringos, George Nicholas, 1 918— Lithology and subdivisions of the Jurassic stump formation in southeastern Idaho and adjoining areas. (Unconformities, correlation, and nomenclature of some Triassic and Jurassic rocks, western interior United States) (Geological Survey Professional Paper 1035—C) Bibliography: p. 25 1. Geology, Stratigraphic—Jurassic. 2. Geology—Idaho. 3. Geology—The West. 4. Petrology—Idaho. 5. Petrology—The West. I. Imlay, Ralph Willard, 1908— joint author. II. Title. III. Series. IV. Series: United States Geological Survey Professional Paper 1035—C. QE681.P49 551.7’6 78—1687 For sale by the Superintendent of Documents, US. Government Printing Office Washington, DC. 20402 Stock Number 024—001—03150—7 CONTENTS Page Abstract .................................................................................................................................... C1 Introduction ................................................................................. l Stump Formation ........................................................................... 1 Curtis Member ................................................................................. 3 Redwater Member ............................................................................... 9 Unconformities ................................................................................................................ 13 Stratigraphic sections ............................................................................... 15 References cited ............................................................................................................................ 25 ILLUSTRATIONS Page FIGURE 1. Index map of the Western United States. showing distribution of Stump Formation ....................................................... C2 2. Index map of southeastern Idaho. western Wyoming. and northern Utah. showing location of measured sections of the Stump Formation ....................................................................................................................................................... 4 3. Index map of southeastern Idaho and adjoining areas showing approximate margin ofthe Redwater Member ofthe Stump Formation ................................................................................................................................................................... 6 4. Columnar sections of the Stump Formation from Wolverine Canyon. Idaho to Watton Canyon. Utah .......................... 7 5. Columnar sections of the Stump Formation from Blacktail Creek. Idaho to Telephone Creek. Wyoming ....................... 8 6. Columnar sections of the Stump Formation from Sheep Creek. Wyoming to Peoa. Utah ............................................... 9 7-16. Photographs showing: 7. Contact of the Stump Formation with the Preuss Sandstone at Indian Camp Hollow (loc. 3. fig. 5) .................. 11 8. Stump Formation at McCoy Creek (Ice. 4. fig. 5) ....................................................................................... 12 9. Sandstone unit of the Curtis Member at the start of Corral Creek trail (loc. 5. fig. 5) ............... 13 10. Type area of the Stump Formation ............................................................................................. 14 11. Contact of the Stump Formation with the Preuss Sandstone at Stump Creek (loc. 8. fig. 4) ........... . 15 12. Ephraim Conglomerate. Stump Formation and Preuss Sandstone at Telephone Creek section (loc. 9. fig. 5) ..... 16 13. Ephraim Conglomerate. Stump Formation. Preuss Sandstone. and Twin Creek Limestone nearjunction ol‘Shecp Creek with Greys River (Ice. 10. fig. 6) ..................................................... 17 14. Bedding features typical of the Curtis Member. sandstone unit of the Stump Formation ..................................... 18 15. Stump Formation on old US. Highway 30 near Evanston, Wyoming (10c. 17. fig. 6) .......................................... 20 16. Near view of contacts shown in figure ISB ............................................................................................................ 22 TABLE Page TABLE 1. Thicknesses of the Stump Formation and its subdivisions ................................................................................................. C10 III UNCONFORMITIES, CORRELATION, AND NOMENCLATURE OF SOME TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES LITHOLOGY AND SUBDIVISIONS OF THE JURASSIC STUMP FORMATION IN SOUTHEASTERN IDAHO AND ADJOINING AREAS By GEORGE N. PIPIRINGOS and RALPH W. IMLAY ABSTRACT The Stump Formation (called Stump Sandstone in previous reports) comprises the latest marine Jurassic beds nearthe Idaho-Wyoming border and adjoining parts of Utah, and it is divisible into two members. The lowest member is nearly identical with the Curtis Formation of Utah, and the upper member closely resembles and contains the same fossils as the sandy facies of the Redwater Shale Member of the Sundance Formation of Wyoming. The Stump Formation is herein divided from about the Salt Lake City area north through the Wyoming-Idaho thrust belt and east in the Uinta Mountains as far as northwest Colorado into the Middle Jurassic Curtis Member, which is reduced in stratigraphic rank in these areas from formation, and the Upper Jurassic Redwater Member, which is newly assigned to the Stump in these areas. The stratigraphic and geographic relations of the two members show that they were deposited in different seas that covered different areas, that erosion occurred before and after Redwater deposition. and that variations in the thicknesses ofthe members are in part depositional but are due principally to truncation of stratigraphic units directly under the Cretaceous (K) and Jurassic (J-4) unconformities. INTRODUCTION This report discusses the lithologic characteristics, sub- divisions, area] distribution, ages, and correlations of the latest marine Jurassic beds, called the Stump Formation, as exposed along the Wyoming—Idaho border and nearby in northern Utah. One principal and two supplementary reference sections are herewith established, and I8 stratigraphic sections are described, based on field studies by the writers in 1975 and 1976. The regionaldistribution of the Middle and Upper Jurassic Stump Formation in the Western United States, shown in figure I, is nearly the same as that of the Middle Jurassic Twin Creek Limestone as shown by Imlay (1967, p. 54). Locations of measured stratigraphic sections as well as localities mentioned in the text are shown in figures I, 2, and 3. Stratigraphic sections described at the end of the report are shown graphically in figures 4, 5, and 6. Localities in figure 4 lie west and localities in figures 5 and 6 lie east of the line representing the approximate western margin of the Redwater Member of the Stump Formation shown in figure 3. Figures 7 through 16 are representative of the lithologic features and general appearance of the Stump Formation throughout the study area. Thickness of the Stump Formation and its various subdivisions are summarized in table 1 from measured sections described in the section entitled “Stratigraphic sections.” STUMP FORMATION The term Stump Formation includes the latest Jurassic marine sandstone, limestone, sandy shale, siltstone, and claystone overlying the red Middle Jurassic Preuss Sandstone in westernmost Wyoming, southeastern Idaho, and adjoining parts of northern Utah. Stump Formation is used in place of Stump Sandstone because sandstone is not the predominant rock type in all sections and because several other kinds of sedimentary rocks are present in most sections. The formation occurs in an area extending from the Blackfoot Mountains southeast of Idaho Falls eastward to the Hoback Range and Wyoming Range in western Wyom- ing and extending from the Snake River Range southward at least as far as Woodruff and Peoa in north-central Utah (fig. 2). Its distribution coincides mainly with a belt of overthrusting that extends along the Wyoming-Idaho border southward into north-central Utah, but it occurs also in the Uinta Mountains in northeastern Utah east of the Cl C2 TRlASSlC AND JURASSlC ROCKS. WESTERN INTERIOR UNITED STATES 0 128° 124° 120° 116° 112° 108° 104° 100° 96° 48 I I I I I T a \ \ \ 7 [\\ \ \ \ 46 ° \ I’ I \ ~ ~CMADA “ / l T ‘ \ ~ - _ l T ‘ ~ — ~ _ _ I \ 7 _ __I — I \K'I MO I, ‘ 44 ° NT \ ‘ \ > ,’ ANA I NORTH DAKOTA I )1 C} l I , l \ 7 L. ,f.\\ morn—“~4— \ I ”‘M \ ~ — \ _ <1 Redwater Shale Member \ II DAHO l /',< Sundance Formation | SOUTH DAKOTA ! 40° '— \ I — ~ — - _ - -_. r v—K ( x, 38 ° \ NEBRASKA , _l l , .\ , l————--—--- / Type I - 36K / camshfggtgnl I I (1 COLORADO I L \\ I l KANSAS ‘\ _ / “\~I~\ ' \ ‘J _ ~ \ 34°\ \ I l “\—— .1.______ \. I I; —-—- 1 § — -I \ ARIZONA I I I — 2’ I NEW MEXICO I I OKLAHOMA 32° \ I ' I 1 ' L \ I I .n\ T I W x \\ 1 I “MA «f,- 30° \ ”’6? I ' I \ T oo\\ I __ _ ‘ I EXAS ‘ \ § _L ‘1 T \ k\ - - ‘ ‘ " _ I I \ l l 0 500 1000 KILOMETERS L l l l L 1 FIGURE 1.—~ Distribution of Stump Formation (patterned) and location of type area, locality, and section, respectively, of Stump Formation. Curtis Formation, and Redwater Shale Member of Sundance Formation, Western United States. overthrust belt. The formation ranges in thickness from 28 m to at least 120 m and thins from Idaho irregularly eastward and northward (table 1). Lithologically, the Stump Forma— tion consists Of a variety of marine sedimentary rocks that apparently change markedly within relatively short dis- tances, as described by Mansfield and Roundy (1916, p. 76, 81); Mansfield (1927, p. 99-101; 1952, p. 38); Gardner(l944); Thomas and Krueger (1946, p. 1269, 1276, 1278, 1285); Rubey (1958, 1973); Oriel (1963); Cressman(l964, p. 52, 53); Staatz and Albee (1963, 1966); Pampeyan and others(l967), Albee (1968); Schroeder (1969); and Rubey, Oriel, and Tracey (1975, p. 5). These irregular lateral variations in facies and thickness in the Stump Formation have hitherto been perplexing. In places the Stump resembles only the Curtis Formation ofthe San Rafael Swell in east—central Utah; in other places the UNCONFORMITIES, CORRELATION. AND NOMENCLATURE C3 Stump mainly resembles the Redwater Member of the Sundance Formation of Wyoming. Elsewhere, as in the western part of the Uinta Mountains, the Stump Formation, as used by Thomas and Krueger(l946, stratigraphic sections 1, 2, 3, p. 12764285), resembles both the typical Curtis Formation and the Redwater Member. It is now recognized (I) that the lower part of the Stump Formation throughout the Uinta Mountains is identical with the Curtis Formation of the San Rafael Swell and (2) that the upper part of the Stump is closely similar to the Redwater Member of the Sundance Formation farther to the north and to the east in Wyoming and northern Colorado (fig. I). Furthermore, in the eastern part of the Uinta Mountains, the Curtis Formation, as used by Thomas and Krueger (I946, stratigraphic sections 4, 5, 6, p. 1276, 1287-I290), is identical with the Stump of the western Uintas, and likewise includes two members of which only the lower is equivalent to the type Curtis Formation. It seems best, therefore, to extend the name Stump Formation to all of the Uinta Mountains. Similarly, the Stump Formation along the Idaho- Wyoming border includes beds in its lower part that are nearly identical with the Curtis Formation, and it includes beds in its upper part that closely resemble the silty to sandy facies of the Redwater Member ofthe Sundance Formation. As these lithologic subdivisions are not very thick, the Stump is at present the practical unit for mapping purposes, and accordingly it is herein retained as a formation that is divided into the Curtis Member below and the Redwater Member above. At most places, the Stump Formation rests with apparent conformity on reddish beds of the Preuss Sandstone. Locally, however, that contact is very sharp, as at Blacktail Canyon, Indian Camp Hollow (fig. 7), McCoy Creek (fig. 8), Shale Creek, and on old U.S. Highway 30 (abandoned) east of Evanston, Wyo. The contact is gradational within several centimeters at Telephone Hollow and La Barge Creek and is gradational within about a meter at Sheep Creek near Greys River. In some places, the contact is marked only by an upward color change from red to gray and may even show intertonguing as at Corral Creek (fig. 9) and Fish Creek. In other places, as at Indian Camp Hollow, McCoy Creek, and Shale Creek, the contact is marked also by a slightly irregular surface and by an abrupt upward change from fine-grained red sandstone to hard, thin- to medium—bedded gray sandstone. The regional characteristics of the Preuss Sandstone have been discussed by Mansfield (I927, p. 98, 99) and Imlay (I952, p. 1735, I739). The Stump Formation within the area of extensive thrust faulting in western Wyoming is overlain sharply and unconformably by continental beds of Early Cretaceous or locally younger ages (Mansfield, 1927, p. 101). In the Uinta Mountains the Stump is overlain by Upper Jurassic beds that have been assigned to the continental Morrison Formation and by unnamed Lower Cretaceous beds (Stokes, 1944, p. 969; 1955, p. 84; Hansen, 1965, p. 85, 86). CURTIS MEMBER The Curtis Member of the Stump Formation attains thicknesses of 76-l 13 m in the area between Stump Peak and Fish Creek but thins irregularly northward toward the Snake River, and it thins considerably eastward in western Wyoming to as little as 9 m in the Wyoming Range (table I). Its lithologic and stratigraphic resemblance to the Curtis Formation ofthe San Rafael Swell shows that its equivalents extend considerably farther south in Utah than does the overlying Redwater Member whose southernmost ex- posures are in the Uinta Mountains. The Curtis Member consists of two lithologic units. the lower dominantly sandstone and the upper chiefly clay shale. (See figs. 4 and 5.) The lower or sandstone unit is generally ledgy or cliff forming (figs. 7, 8, 9), ranges in thickness from 6-77 m, thins northward and eastward, and is characterized by glauconitic, thin- to thick-bedded sandstone interbedded with some sandy siltstone and silty shale. Most of the sandstone beds are fine to very fine grained, but some are medium grained and many are silty. Ripple marks are common and some low-angle crossbedding is present. Predominant colors are greenish gray to brownish gray, but locally some beds are red and resemble sandstone in the Preuss Sandstone (loc. 12, fig. 4; loo. 5, figs. 6, 9). Many bedding interfaces are characterized by tracks and furrowed trails, by round to flat shale pebble impressions, by a few cubical salt casts as large as 6 mm, and locally by marine bivalves such Meleagrine/la, Ostrea, and Camptonectes. At Watton Canyon (loc. I6, fig. 2) chert and shale pebbles and fragments of Pentac'rinus are common. This also is true of conglomeratic beds near the base of the Curtis in the San Rafael Swell and in the Uinta Mountains. The upper or shale unit of the Curtis Member varies considerably and irregularly in thickness from 35 m at Fish Creek (10c. 12, fig. 4) and possibly 73 m east of Evanston (loc. 17, fig. 6) to a feather edge from these places both eastward and southward (figs. 4, 5, 6). The unit thins northward slightly and eastward considerably from exposures on Stump Creek and Fish Creek. The unit forms the top part of the Stump Formation at Wolverine Canyon (section I), Stump Peak (section 7), and Fish Creek (section 12), but is absent at places where the Redwater Member is thickest in the Wyoming Range, as at Telephone Creek section (section 9), Shale Creek (section II), and La Barge Creek (section 14). It has an apparent thickness of 73 m east of Evanston (section 17), but in that section the beds are vertical, rest sharply on the red Preuss Sandstone instead of on the lower sandstone unit of the Curtis, and consist mostly of soft claystone that could easily be duplicated in part by folding or faulting. The lower 11 m, containing some sandy beds at bottom and top, could conceivably be equivalent to the lower sandstone unit. Against such a possibility is the fact that a ledgy to cliff-forming sandstone is present at the base of the Stump Formation in every section along or near the Idaho-Wyoming border. TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES C4 mow... . :oficgm . co>cmo cotm>> . =__._ to“. . v.35 wmhmm w... . :9»ch gum . x85 5E . :35 295 . 3090 nwwcw . x85 2053.8. . 3090 9:35 . xmwm aEBw . x090 aaocF . =25. x85 .28 3090 >002). 30:0... 950 can... x690 =m§o£m :9»ch wctm>_o>> wZOFomw n+0 mus—<2 mcwwmvmmhw FFFPPf—FFF L____J .Jdcviéuicorxoo «~20 u=wzqun~ M\NG wvo Telephonell/ Rh)“ I Hollow r/‘~ 24.6 «o», 9./ 85:5 .48“. Beam :09: a U 32“: )..M.... I -l-uIJN./.l:||1|-|.-._|-ll-|-|-||.l.I- .\ _ aw z<=czfi .@ _ we _ I _. Rom“ .W _ w I __ E a mmEEm game .7528 __E8_m r o 53.... 3%;3 yfl/@ 32.2.. 9:8 :29: Busm—ZZOm C5 UNCONFORMITIES, CORRELATION. AND NOMENCLATURE .53: 52:5: «Em .MEEPAB 5833 65:: 523258 E :oszhoL 955m 2: go 3288 8:53:— wo :EEQOAIN 55c.“— —1 _ _ _ _ _ _ 2555.5. 8? 8 a L: K: uzmmzoaa II I\ )xxd _ semé .fl 9:: SPmk\ a)? r-\./"\' I x ! l L x can it i, 13 I ‘rv’ ‘\ , l i i \/ i [’41. \\./ K r i |\_/ /'\ ; i N 'Heba° i >’ i“ 5 A / ‘ , \ . . g n \x / r < \ l‘ quanna l oVemd I . 1. ‘ /\ I i ,‘ “x l i i t P -~~~ . \i ! : k, a x? i 1 ! l} \i i Jimmy” i ! / 'Mutksl'lotlw !’ i i ‘09 _ I ‘.‘ (,4 , i . t /\ ‘ I ' ' _. I. 4/ W i oThBfle L“ I I Ii i l 0 .‘B 100 KlDMEIERS i I 1 l l I l FIGURE 3.AApproximate margin of the Redwater Member of the Stump Formation (long-dashed line), southeastern Idaho and adjoining areas, based on lithology, unconformities, and occurrences of belemnites and ammonites. X, localities representing both Redwater and Curtis Members: +, localities representing only the Curtis Member. UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C7 About 240 kilometers (0 Ephraim WOLNIEHINE ® SALT Wasatch Frn. WATTON Conglomerate A VON (Lower Cretaceous) CANYON (Eocene) CANYON Shale unit Curtis Member Stump Formation [Middle Jurassic) Sandstone unit (Middle Jurassic) Preuss Sandstone |:| EXPLANATION Conglomerate Sandy clay shale Sandstone Silty clay shale Shaly sandstone Limy clay shale Limy sandstone Limestone 0=Oo|itie COLOR “I... X=Glauconitic SYMBOLS Psi—i: C=Crinoid _ Siltstone Sandy limestone E=E°h'"°'d PALE P=Pelecypod RED E R=Ripple marks BROWNISH T=Trai|s RED Clay shale or Shaly limestone - claystone . e . Limestone concretlon Chert nodule E D Covered interval 42D Gypsum nodule 0 50 KILOMETERS —50 FIGURE 4.—Columnar sections of the Stump Formation from Wolverine Canyon, Idaho, to Watton Canyon, Utah. Unconformities are represented by solid lines and presumably conformable contacts by dashed lines. *, fault contact. (See description of bed 6 in Wolverine Canyon section.) The shale unit of the Curtis Member consists mostly of limy, greenish-gray to olive-green, soft, flaky to fissile claystone that contains some very thin platy sandstone beds, some fossiliferous, oolitic limestone slabs, and many large, flat, lenticular yellowish-gray limestone concretions that weather nearly white. The limestone slabs contain oysters and crinoid stems, and the bedding surfaces of the thin sandstone beds bear tracks and trails. The base of the shale unit makes an abrupt but conformable contact with the underlying sandstone unit. C8 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES About 100 kilometers ® ® ® @ © BLACKTAIL INDIAN CAMP CORRAL CREEK TINCUP HOLLOW TRAIL @ TELEPHONE CREEK Ephraim Congl- (Lower Cretaceous) CREEK CREEK l J :::::::::l Redwater Member (Upper Jurassrc) Sandstone unit Stump Formation Shale unit Curtis Member (Middle Jurassic) Sandstone unit Preuss Sandstone H (Middle Jurassic) EXPLANATION O a - Conglomerate Silty clay shale :1; n ‘1? : 54 o :1 :1: Clay shale or claystone . e . Limestone concretion Limy clav shale E L' estone § Sandy limestone D Covered interval A Chert pebble O=Oo|itic X=Glauconitic A=Ammonite B=Belemnite C=Crinoid E=Echinoid P=Pe|ecypod R=Ripple marks T=Trails xl=SaIt crystal casts COLOR SYMBOLS PALE OR GRAYISH RED BROWNISH RED 50 KlLOMETERS FIGURE 5.—Columnar sections of the Stump Formation from Blacktail Canyon, Idaho, to Telephone Hollow, Wyo. Unconformities are represented by solid lines and presumably conformable contacts by dashed lines. The shale unit is correlated with part of the Curtis Formation of Utah because (I) it is conformable with the underlying sandstone unit but unconformable with the overlying Redwater; (2) nearly identical greenish-gray shale that contains light-gray limestone concretions occurs in the upper part ofthe Curtis Formation at Monks Hollow about 30 km southeast of Provo, Utah (Baker, 1947); and (3) similar greenish-gray flaky shale occurs in both the upper UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C9 About 258 kilometers LA BAHGE CREEE SHEEP ® @ FORT H|LL ® EVANSTON Ephraim Conglomerate (Lower Cretaceous) Sandstone unit (Upper Jurassic) Redwater Member Stump Formation Shale unit “furtlijs Shale unit em er d t (Middle sanunsitme Jurassrc) U Preuss Sandstone (Middle Jurassic) EXPLANATION Sand hale tn clay '< i}. I, hale < n a < in Sandstone Lim l a" '“L " E f“: Shaly sandstone Limestone —._' .‘I . . . __ ;1[DAHQ§ Limy sandstone Sandy limestone (IUTAH) o t t i Siltstone Tuff Clay shale or Bentonite ‘ cla stone .1 ,7 '\I (' _ _ __ _ _ _ 7 \K 'A' Partly covered “"' “one 1 -~“' a clay shale 0 50 KlLOMETERS Limestone concretion or nodule I [l Covered interval A Chert pebble / / //// .///// /// ///I/ ' / / ///// / // 1Reported by Thomas and /// Krueger (1946. p. 1282) —0 0=Oolitic COLOR X=Glauconitic — SYMBOLS A=Ammonite B=Belemnite P=Pelecypod R=Ripple marks W=Carbonizad wood PALE RED — BROWNISH RED fragments FIGURE 6.—Columnar sections ofthe Stump Formation from Sheep Creek. Wyo.. to Peoa. Utah.Unconformities are represented by solid lines and presumably conformable contacts by dashed lines. Queried where correlation is in question. and lower parts of the Curtis Formation at its type locality on the San Rafael Swell (Gilluly, 1929, p. 107, 108; Gilluly and Reeside, I928, p. 79, 101). The Curtis Member of the Stump Formation is assigned to the middle Callovian because (I) it unconformably underlies the Redwater Member of early to early middle Oxfordian age and (2) it overlies the Preuss Sandstone, which grades downward into beds of early Callovian age at the top of the Twin Creek Limestone. REDWATER MEMBER The Redwater Member of the Stump Formation is much less extensive than the Curtis Member. In southeastern Idaho the Redwater Member crops out north of the Snake River in the Snake River Range and in the southern part of the Teton Range. South of the Snake River in Idaho it crops out in the Caribou Range in a belt from 19 to 24 km wide that extends from the Fall Creek area southeastward toward Thayne, Wyo. Its southernmost occurrence is in the Caribou Range. Belemnites have been reported from the top of the Stump Formation about 4 km southwest of Thayne on Smith Canyon and 2 km west of the forest boundary in the SE% sec. l0, T. 6 S.. R. 46 F... Idaho (US. Geological Survey Mesozoic loc. 12120). This occurrence needs confir- mation because the Stump Formation is not shown at that location by Mansfield (I927, pl. 5). In western Wyoming the Redwater Member is present in the mountains bordering Greys River as well as farther east in the Wyoming and Hoback Ranges, but it has not been recorded from the west side of the Salt River Range. C10 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES TABLE 1.7 . Thickm’sses ofthe Stump Formation and its subdivisions [Thicknesses in meters, totals rounded; A, absent , queried where uncertain; C, covered; U, unknown] Stump Redwater Member Curtis Member Formation Numbered localities Sandstone Shale Total Shale Sandstone Total Total unit unit thickness unit unit thickness thickness 1. Wolverine Canyon---- A A O 19.8+ 44.2 64+ 64+ 2. Blacktail Creek ————— 34 A 34 24.4 22.8 47 81 3. Indian Camp Hollow—— 18+ A 18+ 21 24 45 63+ 4. McCoy Creek ————————— 45.7 1.8 48 10.6 21.3 32 79 5. Corral Creek Trail-- C C U 7.3-+ 55.4 63+ 63+ 6. Tincup Creek -------- 45.4 A 45 23.6 31.1 55 100 7. Stump Peak —————————— A A 0 15.2 61 76 76 8. Stump Creek ————————— A A O 30.5 69.2 100 100 9. Telephone Creek ————— 54.5 A 55 A 11.3 11 66 10. Sheep Creek --------- 29.9 4 34 2.7 6.1 9 43 11. Shale Creek ————————— 13.4 4 17 A 14.3 14 32 12 Fish Creek —————————— A A O 35 77.7 113 113 13. Salt Canyon --------- A A O A 41.1 41 41 14. La Barge Creek —————— 11.3 5.6 17 A 11.1 11 28 15. Fort Hill ——————————— 23 3 26 l 10 11 37 16. Watton Canyon ——————— A A 0 A 76 76 76 17. Evanston ———————————— 4.6 10.7 15 73.1 A? 73 88 18. Peoa ———————————————— 14.3 11.3 25 29.3 12.5 42 67 The Redwater Member ranges irregularly in thickness from about 15 to 55 m. At some places its uppermost beds are covered, and total thicknesses cannot be determined; for instance, at Blacktail Canyon, Indian Camp Hollow, Tincup Creek, and west of Fort Hill. Nonetheless, the available data suggest that the Redwater Member thins southward along the Wyoming Range in western Wyoming. Along the Idaho-Wyoming border and southward as far as Peoa, Utah, the Redwater Member consists of two lithologic units. The lower or shale unit is 2-11 m thick and consists of yellowish-gray to brown glauconitic chunky siltstone or claystone that is locally finely. sandy and generally contains belemnites. Except for one occurrence at McCoy Creek (section 4) in Idaho, the lower shale unit has been definitely identified mainly on the flanks of the Wyoming Range in western Wyoming and in areas to the south near Evanston, Wyo., and Peoa, Utah. At Shale Creek (section 14) and La Barge Creek (section 15), the lower shale unit rests sharply on the sandstone unit of the Curtis Member and contains belemnites at its base, associated with many small, worn specimens of Gryphaea nebrascensis (Meek and Hayden). West of Fort Hill (section 16), the chunky lower shale unit of the Redwater Member contains belemnites but no gryphaeas and rests sharply on the flaky clay-shale unit of the Curtis Member. In addition to occurrences of Gryphaea at Shale Creek and La Barge Creek, small, worn specimens of Gryphaea Formation at the following US. Geological Survey Mesozoic localities: 16024. Basal part of Redwater Member on creek of Telephone Hollow 2 km above mouth of Deadman Creek, Afton quadrangle, Wyoming. 16047. Unknown position in Redwater Member on White Creek 1 km upstream from bench mark 6758 and 91.4 m below waterfall SW. cor. NE'A sec. 30, T. 35 N., R. 117 W., Bedford quadrangle, Wyoming. 17897. Basal part of Redwater Member 1.2 km northwest of McCoy Creek, near center NWIA sec. 6, T. 3 S., R. 46 E., Alpine quadrangle, Idaho. 18183. From shale 9.1 m below top of Stump Formation near center of north line of NW'A sec. 25, T. 35., R. 45 E., Poker Peak quadrangle, Idaho. 18185. From 36.6 to 61 m above base of Stump Formation, NWIA sec. 1, T. 4 S., R. 45 E., Tincup Mountain quadrangle, Idaho. 18187. From 61 to 71.6 m above base of Stump Formation, NE'A sec. 1, T. 4 S., R. 45 E., Irwin quadrangle, Idaho. Fossils from Mesozoic fossil localities 16024 and 17897 include the ammonite Cardioceras and are definitely from the basal part of the Redwater Member. Those from locality 18185 are probably from the basal part of the Redwater Member if the members are similar in thickness to those at McCoy Creek about 9.6 km to the north. If so, the collection nebrascensis occur together with belemnites in the Stump from locality 18187 was probably collected about 10.7 m UNCONFORMITIES, CORRELATION, AND NOMENCLATURE Cll FIGURE 7.7Contact of the Stump Formation with the Preuss Sandstone at Indian Camp Hollow (10c. 3, fig. 5). A, thin—and medium—bedded ledgy cliff—forming appearance typical of the sandstone unit ofthe Curtis Member. Contact dashed where inferred. Lower cliffis about l2 m high. B, sharp, slightly channeling contact of the Stump with the Preuss. Hammer is about 28 centimeters long. In both views: I, Curtis Member, sandstone unit; 2; Preuss Sandstone. above the base of the Redwater Member. Apparently only the fossils from locality 18183 were collected high in the formation, but the reported occurrence in shale at that position seems peculiar and needs confirmation. In addition, the fOSsils of Gryphaea nebrascensis in the Stump Forma- tion of the Jackson quadrangle, Wyoming, as reported by Wanless, Belknap, and Foster (1955, p. 51,52), are probably also in the basal or lower part of the Redwater Member C12 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE 8.77 Stump Formation at McCoy Creek (loc. 4, fig. 5). A. units: I, Redwater Member, sandstone unit; 2. shale unit; 3. Curtis Member. shale unit; 4, sandstone unit; 5, Preuss Sandstone. Lower cliff is about IO m high. 8. near view of contact between 4. Curtis Member. sandstone unit, and 5, Preuss Sandstone. The contact shows relief of about 3 cm. Hammer is about 28 cm long UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C13 FIGURE 9.——Sandstone unit of the Curtis Member at the start of Corral Creek trail (Ice. 5, fig. 5; vehicle parked on trail). Arrow points to Preuss-like red beds within the Curtis Member suggesting local intertonguing with the Preuss. (I) Preuss Sandstone: (2) Curtis Member, sandstone unit; (3) Curtis Member, basal part of shale unit. Redwater Member is present on ridge to the right but not visible in photograph. because they occur in gray limestone that underlies massive ridge-forming, green, glauconitic sandstone and overlies softer, greenish sandy shale and sandstone. The worn appearance of these gryphaeas, their preserva- tion mostly as parts of the umbonal area, their occurrence mainly at or near the base of the Redwater Member, and their absence in the underlying Curtis Member indicate that they were derived from the Leeds Creek Member ofthe Twin Creek Limestone, which contains many well-preserved, unworn, and much larger specimens of Gryphaea nebrascensis. Evidently they were derived from that member during an interval of erosion after deposition of the Curtis Member. The upper or sandstone unit of the Redwater Member consists mostly of ledgy to cliff-forming sandstone that is thin to thick bedded, crossbedded, highly glauconitic, calcareous, gray to greenish gray or locally nearly white. Most sequences contain interbeds of sandy siltstone or soft, clayey siltstone partings. Sandy oolitic limestone beds are present locally. Chert pebbles are present in some sections in various parts of the member. Belemnites and bivalves are fairly common, and ammonites occur locally. This unit differs from the cliff-forming sandstone unit at the base of the Curtis Member in that it has more fossils, contains ammonites and belemnites, has claystone and siltstone beds that weather chunky instead of flaky or fissile, contains few trace fossils, has glauconite grains that com- monly are larger than associated sand grains instead of the same general size. and lacks clay-pebble imprints or small cubical-shaped casts or imprints of salt crystals. The upper sandstone unit of the Redwater Member rests conformably on the lower chunky shale unit ofthe Redwater Member where present, or sharply on the shale unit or the sandstone unit of the Curtis Member. A disconformable relationship with the Curtis Member is indicated by the sharpness of the contact, by a marked lithologic change, and by the absence ofthe upper shale unit ofthe Curtis Member at some places(sections 12, l4,and 15). The upper sandstone unit of the Redwater Member throughout most of the overthrust belt is overlain sharply and unconformably by red siltstone or conglomerates of the Lower Cretaceous Ephraim Conglomerate. In the Uinta Mountains it is overlain unconformably by the Upper Jurassic Morrison Formation. The Redwater Member of the Stump Formation is correlated with the Redwater Shale Member of the Sun- dance Formation because it likewise contains belemnites in abundance from bottom to top, and it likewise contains Cardioceras. That genus occurs near the base ofthe member west of Fort Hill (section 16) and on the creek of Telephone Hollow (section 12), and in the lower part ofthe upper third of the member at McCoy Creek (section 4). The basal part of the Redwater Member on the creek of Telephone Hollow also contains Vaugom'a quadrangularis (Hall and Whitfield) and 0xytoma wyomingensis (Stanton) along with Cardioceras and belemnites. In addition, the stratigraphical- ly highest exposures of the member on McCoy Creek contain Oxytoma wyomingensis (Whitfield). The pelecypods occur in the Redwater Shale Member of the Sundance Formation as far east as the Black Hills and in the Middle and Upper Jurassic Swift Formation of Montana. The presence of Cardioceras shows that the Redwater Member of the Stump Formation is of early to early middle Oxfordian age. UNCONFORMITIES The lower contact of the Ephraim Conglomerate is an unconformity throughout the study area. The lower contact of the Redwater Member of the Stump is also an unconfor- mity. The nature of the contact between the Curtis Member of the Stump and the Preuss Sandstone, however, is C14 TRlASSlC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE 10.7Type area of the Stump Formation. A, southwestward View ofan overturned but well—exposed section ofthe Stump Formation designated the principal reference section (loc. 7, fig. 4). A northwestward view of this locality was illustrated and described by Mansfield and Roundy (l9l6, p. 82. pl. 13a) as “a typical exposure ofthe Stump sandstone.” 1. Curtis Member, sandstone unit; 2, Curtis Member, shale unit; 3, Ephraim Conglomerate. B, northeastward View of Stump Peak (arrow) on ridge held up by the sandstone unit of the Curtis Member. 1, Ephraim Conglomerate; 2, Curtis Member, sandstone unit; 3, Preuss Sandstone; 4, Twin Creek Limestone undivided, consisting principally of the Leeds Creek Member. North Fork of Stump Creek is in lower right of photograph. Contacts dashed where inferred. UNCONFORMITIES. CORRELATION, AND NOMENCLATURE C15 FIGURE 11.7Contact of the Stump Formation with the Preuss Sandstone at Stump Creek (Ice. 8, fig. 4). I. Stump Formation. sandstone unit; 2. Preuss Sandstone. uncertain. The contact is sharp and probably unconfor- mable at localities 2, 3, 4, 8, ll, 16, and 17; it is concealed at localities l, 6, 7, and 18; it is conformable at localities 9, l3, l4, and 15; and perhaps the Curtis Member and Preuss intertongue at localities 5, 10, and 12. Marked differences in lithologic characteristics, fossils, and thicknesses occur within relatively short distances in the Stump Formation as now mapped. These differences are attributable primarily to truncation of units beneath the unconformities at the base of the Ephraim Conglomerate and at the base of the Redwater Member of the Stump Formation. (See figs. 4, 5, and 6.) The unconformities at the base of the Ephraim, at the base of the Redwater, and at the base ofthe Curtis, where present, have been designated the K, .1-4, and J—3 unconformities, respectively, by Pipiringos and O’Sullivan (1978). The unconformity at the base of the Ephraim Con- glomerate probably represents at least part of the late Tithonian; the one at the base of the Redwater Member represents most of the late Callovian; and the unconformity that is at least locally present at the base of the Curtis Member may represent a small part of the middle Callovian. The latest time represented by the unconformity at the base of the Redwater Member is dated accurately by the presence of ammonites ofearly Oxfordian age in the lower part ofthat member. STRATIGRAPHIC SECTIONS The Stump Formation was named after a sandstone sequence on Stump Peak in the Freedom quadrangle, Idaho, by Mansfield and Roundy (1916, p. 76, 81), who did not designate a type section. That sandstone forms a ridge that extends southeastward for 5 km through the peak. Near the northwest end of the ridge, an overturned sequence (loc. 7) is 'well exposed (fig. 10A). Approximately 1.6 km to the southeast at Stump Peak (NE% NW% sec. 16, T. 6 S., R. 45 E.), the sequence of beds in the Stump Formation is the same and is in normal superposition, but it is less well exposed. About 2 km farther southeast, in the SE'ANW‘A sec. 22, outcrops are even poorer, and, in addition, much of the upper part of the Stump Formation is missing owing either to erosion or to faulting (fig. 103). The sequence near the northwest end of the ridge (10c. 7) is the best exposed and the most accessible within the type area. Furthermore, locality 7 was illustrated by Mansfield and Roundy (1916, pl. 13A), who stated that it shows a typical exposure of the Stump Formation. For these reasons, it is here selected as the principal reference section for the Stump Formation. In addition, lithologically similar and better exposed reference sections also designated in this report that are readily accessible by car are to the southeast at Stump Creek (section 8), Crow Creek, and Fish Creek (section 12). The C16 TRIASSIC AND JURASSIC ROCKS. WESTERN INTERIOR UNITED STATES FIGURE l2.~Ephraim Conglomerate, Stump Formation, and Preuss Sandstone at Telephone Creek section (loo. 9, fig. 5). l, Ephraim Conglomerate; 2, Redwater Member, sandstone unit; 3, Curtis Member, sandstone unit; 4, Preuss Sandstone. section on the north side of Crow Creek (SE%NW% sec. 17, T. 3l N., R. 119 W., Crow Creek quadrangle, Lincoln County, Wyo.) differs from that on Stump Creek by the presence of thin beds of oolitic limestone that contain crinoid columnals and the pelecypod Camptonectes. Such limestone beds occur within a claystone unit at the very top of the formation as well as 18.2-21.3 m lower. All these sections from Stump Peak southward along the Idaho-Wyoming border, as well as at Watton Canyon, Utah, are represented only by lithologies closely similar to those in the Curtis Formation of northern Utah, and they do not contain any units that are lithologically or faunally com- parable with the Redwater Member of the Sundance Formation. Well-exposed and easily accessible sections for the Redwater Member of the Stump Formation are at McCoy Creek (section 4), Telephone Creek (section 9), Sheep Creek (section 10), Shale Creek (section 11), and La Barge Creek (section 14). In the descriptions that follow, the crossbedding noted in the sandstone beds of the Redwater Member seems to be of the medium-angle, trough cross-stratified type, occurring in sets 0.5—2 m thick. The crossbedding in the sandstone beds of the Curtis Member is exclusively low angle, trough cross stratified in sets 3-l0 cm thick. In general the Redwater Member was deposited by currents of lower velocities than the currents that deposited the Curtis Member. Indications of the position of unconformities in the stratigraphic descriptions have been omitted in order to shorten the descriptions; for the most part insertion of the word unconformity is repetitive and unnecessary. In figures 4, 5, and 6, the unconformities are shown by solid lines and conformable contacts by dashed lines. For similar reasons the thicknesses of individual stratigraphic units are omitted in figures 4 and 6 but are summarized in table 1. Formation and member thicknesses in text and in table I, originally measured in feet, were converted to meters and rounded. UNCONFORMITIES, CORRELATION. AND NOMENCLATURE C17 FIGURE 13.—Ephraim Conglomerate, Stump Formation, Preuss Sandstone, and Twin Creek Limestone nearjunction of Sheep Creek with Greys River (loc. 10, fig. 6). 1, Ephraim Conglomerate; 2, Redwater Member, sandstone unit; 3, Curtis Member, shale and sandstone units undivided; 4, Preuss Sandstone; 5, Twin Creek Limestone undivided. Section 1.—Wolverine Canyon [Stump Formation on north side of Wolverine Canyon in E%NE%NE% sec. 28, T. l S.. R. 39 E.. Ammon quadrangle, Bingham County. ldaho] Thlt'km’s‘x (Im’lt’m) Ephraim Conglomerate (incomplete): 6. Mostly covered; base concealed; soil is grayish red; reported by Mansfield (1952, p. 63, pl. 1) to be in fault contact with underlying Stump Formation 3+ Stump Formation: Curtis Member (incomplete): Shale unit (incomplete): 5. Clay shale, limy, gray; contains lenticular flattened limestone concretions ....................................... 152+ 4. Oolite slabs and thin limy siltstone and shale beds, sandy, gray, glauconitic; contains oysters, crinoid stems, echinoid spines, Camptonectes interbedded with some gray shale; unit makes slope ................................................................. 4.6 Sandstone unit: 3. Sandstone, very fine grained, flaggy, mostly gray, ripple-marked; bears many tracks and trails; contains many layers of olive-gray clay shale; basal meter contains slabs of oolite that bear crinoid columnals and oyster fragments .......... 21.3 2. Sandstone, ledgy to cliff-forming, thin- to medium-bedded, medium- to fine-grained, brownish-gray, glauconitic; some low-angle crossbedding, ripple-marked, some tracks and trails present; a thin oolite bed at top contains Section 1.—Wolverine CanyonvContinued Thickness (me/err) Stump Formation—Continued Curtis Member (incomplete)#Continued Sandstone unitiContinued crinoid columnals and oyster fragments, base of unit concealed ................................................... 22.9 Partial thickness of Stump Formation ..... 64+ 1. Covered interval, probably partly Preuss Sandstone ................................ 4.6 Preuss Sandstone (lmlay, 1952, p. 1740) ................. Section 2.—Blackmil Creek [Stump Formation on west side of Fall Creekjust south of Blacktail Canyon in NE'fl. sec. 34, T. 1N., R. 42 E., Conant Valley and Commissary Ridge quadrangles, Bonneville County. ldaho] Ephraim Conglomerate (incomplete): 5. Partly covered pale-red sandy siltstone with a bed of light~gray limestone at the base; basal contact concealed makes slope; limestone makes ledge 9+ Stump Formation: Redwater Member: Sandstone unit: 4. Mostly covered. Some siltstone and silty sandstone, ripple-marked, gray, base not exposed ............ 4.6 3. Sandstone, thin- to medium—bedded, crossbedded, glauconitic, ledgy at base, some shaly beds, some ‘7 C18 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE l4.—Bedding features typical of the Curtis Member, sandstone unit of the Stump Formation. Exposure is on east side of US. Highway 89 about 400 m south of the Fish Creek stratigraphic section (10c. 12, fig. 4). Hammer is about 28 cm long. Section 2.—Blacktail Creek—Continued Thickness (meters) Stump FormationfiContinued Redwater Member—Continued Sandstone unit—Continued oolitic beds, brownish-gray; contains belcmnites, oysters, crinoid fragments, and some small chert pebbles ............................................................. 24.4 Thickness of Redwater Member ............... 34 Curtis Member: Shale unit: 2. Mostly covered clay shale, silty, medium-gray; contains thin oolitic limestone beds near base, just above a bed of olive~green clay shale about 1 meter thick that rests sharply on underlying unit; uppermost meter may belong to Redwater Member ........................................................... 24.4 Sandstone unit: 1. Sandstone, thick— to thin-bedded, ledgy; some platy shale; glauconitic, ripple marked, slightly crossbedded; bears trails and some cubical salt Section 2.—Blacktail Creek—Continued Thickness (meters) Stump Formation—Continued Curtis Member~Continued Sandstone unitfiContinued crystal casts. Rests fairly sharply on the underly- ing red siltstone ................................................ 22.8 Thickness of Curtis Member .................... 47 Thickness of Stump Formation .................. 81 Preuss Sandstone (lmlay, this report) .............................................. 146 Section 3.—Indian Camp Hollow [Stump Formation on ridge south of Indian Camp Hollow, about |.6 km west of Fall Creek in SEV. sec. 13, T. l N., R. 42 E., Conant Valley quadrangle, Bonneville County, ldaho. See figure 7] Ephraim Conglomerate (covered). Stump Formation (incomplete): Redwater Member (incomplete): Sandstone unit (incomplete): 3. Sandstone and sandy limestone, medium— to thin-bedded, speckled, highly glauconitic, UNCONFORMlTlES, CORRELATION, AND NOMENCLATURE Section 3.—Indian Camp Hollow—Continued Thickness (meters) Stump Formation (incomplete)—Continued Redwater Member (incomplete)~Continued Sandstone unit (incomplete)—Continued grayish-yellow, forms low ledge. Basal 4 m contains some chert pebbles. belemnites, Pinna, Gervillia, Camptonectes, and many oysters. Ex- act contact with underlying shale not observed. Estimated exposed thickness ............................ 18+ Curtis Member: Shale unit: 2. Clay shale. calcareous, soft, gray, flaky. contains some large. flat, yellowish-white limestone con- cretions ............................................................ 21 Sandstone unit: 1. Sandstone, cliff-forming, gray, mostly thick bedded to massive, some thin-bedded sandstone in mid- dle fourth, upper 9 m is oolitic and contains many oysters and echinoid spines. Upper contact with clay shale is sharp and has a relief of about 7 cm. Lower contact with red shaly siltstone at top of Preuss Sandstone is very sharp ........................ 24 Thickness of Curtis Member .................... E Partial thickness of Stump Formation ..... _63_+ Preuss Sandstone (Vine, 1959, p. 260) ............................................. [—29 Section 4. —McC0y Creek [Stump Formation on north side of McCoy Creek near center of E'ASW'A sec. 6. T. 3 S., R. 46 E., Alpine quadrangle. Bonneville County, Idaho. See figure 8] Ephraim Conglomerate (incomplete): 8. Conglomerate, gray, clasts mostly black and white chert ................................................................. 3+ Stump Formation: Redwater Member: Sandstone unit: 7. Sandstone, gray, fine-grained, calcareous, oolitic. mostly thick bedded, ledgy; approximately the upper 5 is covered. Ammonites and belemnites found about 10 m below the highest exposure of the sandstone unit about 15 m below the lowest exposure of the Ephraim Conglomerate .......... 45.7 Shale unit: 6. Siltstone, clayey, chunky. gray, glauconitic; upper 1.2 in well exposed; contact with Curtis Member is covered ......................................................... 1.8 Thickness of Redwater Member ............... 48 Curtis Member: Shale unit: 5. Clay shale. calcareous, soft. flaky to fissile. con- taining large. flat. yellowish-white limestone concretions and some thin, platy sandstone beds; top 0.6 m covered ........................................... Sandstone unit: 4. Sandstone, greenish-gray to brownish-gray, fine-grained, glauconitic, ripple-marked, thin- to medium—bedded; contains trails and salt-crystal casts; cliff forming ........................................... 6.0 3. Sandstone, shaly, glauconitic, forms recess in cliff 4.6 10.6 C19 Section 4.—Mz-C0y Creek—Continued Thickness (meters) Stump Formation—Continued Redwater MemberiContinued Sandstone unit—Continued 2. Sandstone as at top of unit, basal contact very sharp. shows local relief of about 3 cm ........... 10.7 Thickness of Curtis Member .................... 32 Thickness of Stump Formation ................ 79 Preuss Sandstone (incomplete): l. Sandstone. thin-bedded. very fine grained. grayish-red and calcareous ............................... Section 5.~ (urral Creek 7rai/ [Stump Formation at beginning of Corral Creek trail on north side 01 Tineup Creek in SE corner sec. 10. T. 5 S. R. 45 E.. Freedom quadrangle. Caribou County. Idaho. See figure 9] Ephraim Conglomerate (not examined). Stump Formation (incomplete): Redwater Member (not exposed near road). Curtis Member (incomplete): Shale unit (incomplete): 9. Shale, fissile, soft. gray; contains a few thin beds of sandstone ......................................................... 7.3+ Sandstone unit: 8. Sandstone. thick-bedded. gray ............................. 3.0 7. Siltstone and sandstone, reddish-brown .............. 4.6 6. Sandstone. thick- to medium-bedded, gray ......... 8.2 5. Sandstone, thin-bedded. gray .............................. 4.6 4. Sandstone. thick- to medium-bedded, gray ......... 13.7 3. Siltstone and sandstone. thin-bedded, dull- brownish-red .................................................... 3.0 2. Sandstone, thick- to medium-bedded. gray 13.7 1. Covered 4.6 Partial thickness of Stump Formation ..63+ Preuss Sandstone (not examined). Section 6.—Tincup Creek [Stump Formation on Tincup Creek on south side ofldaho Highway 34. about 3.2 km northwest of Freedom in NE%SW'/4 sec. 9, T. 5 5.. R. 46 E.. Freedom quadrangle. Ca'ihou County, Idaho (Miinslicld. 1927. pl. 5)] Ephraim Conglomerate (base concealed). Stump Formation: Redwater Member: Sandstone unit: 7. Sandstone. thick— to thin-bedded, glauconitic, gray; some oolitic beds; contains some belemnites near middle; uppermost part is covered ................... 45.4 Curtis Member: Shale unit: 6. Shale, olive-green, flaky to fissile ........................ 1.2 5. Covered (probably underlain by soft shale) ......... 17.4 4. Shale, finely fissile to platy, olive-green; weathers yellowish; bears tracks and trails; contains medium-gray limestone concretions ................. 5 Sandstone unit: medium- to 3. Sandstone. thin-bedded, gray. ripple-marked ................................................... 6.1 2. Siltstone and sandstone, red to gray, resembles Preuss Sandstone ............................................. 2.1 C20 TRIASSIC AND JURASSIC ROCKS. WESTERN INTERIOR UNITED STATES FIGURE 15.~Stump Formation on old US. Highway 30 near Evanston, Wyo. (loo. [7. fig. 6). A. westward view of entire section. B, l. Ephraim Conglomerate; 2. Redwater Member, sandstone unit; 3. shale unit; Section 6.—Tincup Creek—Continued Thickness (meters) Stump Formation~Continued Redwater Member~Continued Sandstone unitiContinued I. Sandstone. thick- to medium-bedded, gray. ripple-marked; basal beds not exposed ............ 22.9 Thickness Curtis Member .............. 55 Thickness of Stump Formation ................ 100 Preuss Sandstone (not examined). Section 7.—Stump Peak [Principal reference section: Stump Formation on peak, about 1.6 km northwest ol‘Stump Peak. near center of NEV; sec. 7, T. 6 S.. R. 45 E.. Freedom quadrangle. Caribou County. Idaho. Strata are overturned. dip 25° W. See figure l0] Ephraim Conglomerate (incomplete): 3. Siltstone, pale-red, sandy 3+ Stump Formation: Curtis Member: Shale unit: 2. Claystone, limy, sandy near base, contains gray limestone concretions, soft, gray, makes slope . 15.2 Section 7. ~Stump Peak—Continued Th it'kness (meterx) Stump Formation—Continued Curtis Member—Continued Sandstone unit: I. Sandstone, thin- to medium-bedded, and sandy shale, gray, ripple-marked; bears tracks and trails; makes cliffs and ledges ........................... 61.0 Thickness of Stump Formation ................ 76 Preuss Sandstone eroded from top of peak. Section 8.~Stump Creek [Reference section: Stump Formation on north side of Stump Creek about 3.2 km west ot‘Auburn. Wyo.. in E'/3NW% see. 26, T. 7 S.. R. 46 E., Freedom quadrangle, Caribou County, Idaho. See figure ll] Ephraim Conglomerate (incomplete): 4. Siltstone. pale-red, sandy Stump Formation: Curtis Member: Shale unit: 3. Claystone, soft, with thin interbeds of platy, ripple-marked sandstone that bear trails, and UNCONFORMITIES. CORRELATION, AND NOMENCLATURE C21 northward view ofupper part ofthe Redwater Member in contact with conglomeratic beds in the lower part ofthe Ephraim Conglomerate. 4, Curtis Member, shale unit; 5, Preuss Sandstone. Arrow points to hammer for scale. Section 8.—Stump CreekfiContinued Thick ness (meters) Stump Formation~Continued Curtis Member—Continued Shale unit—Continued shaly limestone; contains light—gray limestone concretions and some fossiliferous oolitic slabs found as float on claystone .............................. 30.5 Sandstone unit: 2. Sandstone, thick- to thin-bedded, cliff—forming at base; becomes shaly upward; contact with Preuss poorly exposed but appears to be moderately sharp ................................................................ 69.2 Thickness of Stump Formation ................ 100 Preuss Sandstone (incomplete): l. Sandstone, thin-bedded, very fine grained, grayish-red, calcareous, locally contains gypsum and chert nodules, makes ledgy slope Section 9.—Telephone Creek [Reference section: Stump Formation nn west side of creek ofTelephone Hollow about 0.8 km north of Deadman Creek. near center of SE'A sec. 29, T 25 N., R. ”6 W., Alton quadrangle, Lincoln County, Wyo. See figure l2] Thickness (meters) Ephraim Conglomerate (incomplete): 6, Sandstone, gray to pinkish-gray .......................... 3+ Stump Formation: Redwater Member: Sandstone unit: 5. Covered ............................................................... 18.3 4. Sandstone, massive, cliff-forming, glauconitic, gray .......................................................................... 11.3 3. Sandstone, silty, shaly to thin-bedded, gray ........ 9.l 2. Sandstone, medium- to thick—bedded, cliff- forming, glauconitic, yellowish-gray, some crossbedding; contains belemnites, oysters, and Camptonectes; rests sharply on underlying unit 15 8 Thickness of Redwater Member 55 C22 TRlASSlC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES FIGURE l6.—Near View of contacts shown in figure 158. The hammer is on the lowest bed in the Ephraim Conglomerate. Note minor channeling at contact. The hammer is about 33 centimeters long. I, Ephraim Conglomerate; 2, Redwater Member of Stump Formation, sandstone unit; 3, Redwater Member, shale unit. Section 9.—Teleph0ne Creek—Continued Thickness (meters) Stump Formation~Continued Curtis Member: Sandstone unit: 1. Sandstone, silty sandstone, yellowish-gray, shaly to thin—bedded. ripple-marked; has irregular wavy bedding; grades downward into red Preuss Sandstone ......................... Thickness of Stump Formation ................ 66 ll Preuss Sandstone (not examined). Section 10.~Sheep Creek [Stump Formation near intersection of Sheep Creek and Greys River in WV; sec. 4, T. 33 N.. R. ”6 W.. Afton quadrangle, Lincoln County, Wyn. See figure l3] Ephraim Conglomerate (incomplete): 8. Claystone, soft. red and green; contains nodules of limestone; probably of Early Cretaceous age 3 + Stump Formation: Redwater Member: Section 10.—Sheep Creek—Continued 'I'hir'km’xt (mt'lorx) Stump Formation—Continued Redwater Member—~Continued Sandstone unit: 7. Sandstone thin- to medium-bedded, very fine grain- ed; greenish-gray; contains furrowed trails; grades into underlying beds; forms low cliffs 13.7 6. Limestone, thick-bedded, oolitic, glauconitic, san- dy, yellowish-gray; contains a few thin beds; belemnites and Camptonez'tes present .. 9.8 5. Siltstone,'sandy, massive, medium-gray. nontissll ; makes slope ...................................................... 6.4 Shale unit ('2): 4. Limestone, sandy. and limy sandstone, fine-grain— ed, cliff-forming, medium— to dark-gray, glauconitic; some oolitic beds containing oysters in topmost 0.3 m; belemnites present at basal contact and higher; rests sharply on underlying unit .................................................................. __4_.0_ Thickness of Redwater Member ............... 34 UNCONFORMlTlES, CORRELATION, AND NOMENCLATURE Section 10. —Sheep Creek—Continued Thickness (meters) Stump FormationiContinued Curtis Member: Shale unit: 3. Shale, fissile; weathers into pencil-like flakes; some very thin platy sandstone interbeds, medium-gray; rests conformably on thin beds of green tuff ......................................................... 2.7 Sandstone unit: 2. Sandstone and siltstone, red ................................ 2.4 l. Sandstone, silty, and sandy siltstone, gray .......... _3_7 Thickness of Curtis Member ................. _9_ Thickness of Stump Formation ............ i Preuss Sandstone (not examined). Section 11.—Shale Creek [Stump Formation on ridge west ofShale Creek. and north of East Fork ol'Greys River about 0.4 km east of itsjunction with the West Fork of Greys River. NE% sec. 20,T. 30 N.. R. | 16 W., Afton quadrangle. Lincoln County, Wyo.] Ephraim Conglomerate (not examined). Stump Formation: Redwater Member: Sandstone unit: 4. Sandstone, cliff-forming, medium- to thin-bedded, greenish-gray, glauconitic; contains one bed of bentonite about 4.9 m above base; Meleagrinella and Kallirhynchia common in lower part ........ 13.4 Shale unit: 3. Siltstone, soft, brown, clayey at base; contains many belemnites and small, worn specimens of Gryphaea nebrascensis (Meek and Hayden). One bentonite bed occurs 30 cm below top ............. fl Thickness of Redwater Member ............... L7— Curtis Member: Sandstone unit: 2. Sandstone, cliff-forming, medium- to thin-bedded, wavy—bedded. ripple-marked, yellowish-gray; rests sharply on underlying unit ....................... L3 Thickness of Stump Formation ................ 32 Preuss Sandstone (incomplete): 1. Sandstone, red, thin-bedded; makes steep ledgy slope ................................................................. 3+ Section I2.—Fish Creek [Stump Formation near Fish Creek along US. Highway 89 about9.6 km south omeoot in SE% sec. 32. T. 30 N.. R. “8 W., and EIA sec. 5, T. 29 N., R. H8 W., Afton quadrangle. Lincoln County, Wyo. See figure l4] Ephraim Conglomerate (incomplete): 8. Siltstone, pale-red, sandy, partly covered ............ i Stump Formation: Curtis Member: Shale unit: 7. Clay shale, fissile, limy, gray; contains lenticular concretions ranging from several cm to more than a meter in length. At base is a gray oolitic bed, 5-l3 cm thick, that contains crinoid stems and oysters ....................................................... 27.4 6. Clay shale, as above; contains limestone con- cretions as much as 20 cm in length. At base is a gray, slightly sandy, oolitic bed from 15 to 20 cm thick that contains oysters and crinoid fragments 7.6 C23 Section 12. —Fish Creek—Continued Writ/mam (mu/em) Stump Formation—Continued Curtis Member - Continued Sandstone unit: 5. Sandstone, shaly to very thin bedded; some clay shale and some silty clay shale. gray; bears ripple marks and many tracks and trails .................... 13.7 4. Shale, sandy, gray, green, and red, ripple-marked; bears tracks and trails ...................................... 15.2 3. Siltstone, red. about 3 m thick; becomes reddish gray in top 1.6 m; barren of tracks and trails; resembles the Preuss Sandstone ....................... 4.6 2. Shale, sandy, and shaly sandstone, gray to greenish-gray, ripple-marked: contains a few reddish zones ................................................... 24.4 I. Sandstone, medium- to thin-bedded to shaly, very fine grained, gray, slightly glauconitic; ripple-marked; forms low cliffs; lower 0.9-1.2 m covered ........................................ fl Thickness of Stump Formation ................ l 13 Preuss Sandstone (not examined). Section l3.—Salt Canyon [Stump Formation on west side of Salt Canyon south of Packstring Creek. SW%SE% sec. 27. T. 29 N.. R. ||9 W., Salt Flat quadrangle. Lincoln County. Wyo.] Ephraim Conglomerate (incomplete); 4. Siltstone, pale-red, sandy, clayey ......................... 3+ Stump Formation: Curtis Member: Sandstone unit: 3. Sandstone, gray and greenish-gray, fine- to medium-grained, limy, thin-bedded, ripple-marked; bears many tracks and trails; contains many clayey siltstone partings; makes ledgy slope ....................................................... 2. Sandstone, gray and greenish-gray. very fine to fine-grained, medium-bedded. ripple-marked; makes ridge ................................. .. 10.6 Thickness of Stump Formation ..... Preuss Sandstone (Mansfield, 1927, p. 99) ...................................... 396 Section l4.—La Barge Creek [Stump Formation on ridge north of La Barge Creek in north-central part of sec. 17. T. 27 N.. R. 15 W.. Coal Creek quadrangle. Sublette County. Wyo.] Ephraim Conglomerate (incomplete): 5. Basal part consists of l m of sandy limestone underlain by 1.1 m of bright-green shaly sandstone that rests sharply on underlying unit _2+_ Stump Formation: Redwater Member: Sandstone unit: 4. Sandstone, calcareous, glauconitic, massive, cliff-forming, mostly light gray to brownish-gray; basal 1.8 m weathers white, fragments of car- bonized wood common throughout ................. ll.3 C24 Section 14.—La Barge Creek—Continued Thickness (me/em) Stump Formation~Continued Redwater Membeerontinued Shale unit: 3. Shale. silty to finely sandy. gray; bears two thin beds of bentonite: basal part contains belemnites and worn fragments of Gryphaea nehrasrensis ( Meek and Hayden) .................................................... Thickness of Redwater Member ............... Curtis Member: Sandstone unit: 2. Sandstone. thin~ to medium-bedded. light—gray: forms top of low cliff ....................................... I. Sandstone. shaly and sandy siltstone. light-gray: some beds as much as 2.5 cm thick; wavy bedding common: grades downward gradually into red sandstone at top of Preuss Sandstone ............. Thickness of Curtis Member .................... Thickness of Stump Formation ................ Preuss Sandstone (lmlay. I950. p. 41) ............................................. Section l5.—Fort Hill [Stump Formation on ridge west of Dutch George Creek and about 3.2 km west-northwest Hill in NW'ANE'ASE'A sec. 3. T. 25 N.. R. IIS W., Fort Hill quadrangle. Lincoln County. Ephraim Conglomerate (covered. soil is grayish red). Stump Formation: Redwater Member: Sandstone unit: 5. Sandstone. medium- to thin-bedded. flaggy, white; some soft siltstone partings; upper contact covered ............................................................. 4. Sandstone and sandy coquinoid limestone. medium- to thin-bedded, greenish-gray, highly glauconitic; some partings of soft siltstone; some beds as much as 0.6 m thick; contains ammonites and belemnites in basal bed ............................. Shale unit: 3. Claystone, chunky. Iimy. alternating with blocks of chunky limestone, yellowish-gray; contains belemnites in basal 15 cm ................................ I7 co 9. b.) 2 00 (1| N of Forl Wyo.] 4 3 Thickness of Redwater Member ............... 26 Curtis Member: Shale unit: 2. Clay shale, flaky, olive-green; contains limestone concretions. Upper contact with Redwater Member is marked by concretionary blocks that bear oysters ...................................................... Sandstone unit: I. Sandstone, cliff-forming, yellowish-gray, thick~ to thin—bedded. some shaly interbeds. medium- to fine—grained, ripple-marked; wavy bedding com- mon; thicker beds contain much glauconite. Contact with red Preuss Sandstone as exposed on road 1.6 km north of measured section is marked by 15-30 cm of white bentonite ........... Thickness of Curtis Member .................... Thickness of Stump Formation ................ Preuss Sandstone (not examined). TRIASSIC AND JURASSIC ROCKS. WESTERN INTERIOR UNITED STATES Section l6.—Walron Canyon [Stump Formation on north side of Walton Canyon near center WV: sec. 26. 'I'. 9 N.. R. 5 E.. Meachum Ridge quadrangle. Rich County. Utah] Thickness (melerx) Wasatch Formation (incomplete): 2. lnterbedded brownish-red sandy clay shale. siltstone. and sandy claystone .......................... 3+ Stump Formation: Curtis Member: Sandstone unit: I. Sandstone. greenish-gray. coarse-grained to con- glomeratic, thick- to medium-bedded. with thin sandy claystone partings. Pentar'rinus columnals are common throughout: lower part makes ridge; basal contact poorly exposed ........................... Total thickness of Stump Formation ........ o o Preuss Sandstone (not examined). Section l7.—Evanston [Stump Formation on north side ofold U.S. Highway 30 (abandoned) in NW 'ASW'ASW'A sec. I8. T. I5 N., R. ”X W.. about |7.6 km east of Evanston. Guild Hollow quadrangle. Uinta County. Wyo. See figures I5 and I6] Ephraim Conglomerate (incomplete): ll. Basal conglomerate stands vertically and forms a high cliff A ll' 5- O Stump Formation: Redwater Member: Sandstone unit: 10. Sandstone. medium-bedded. medium-grained, cross bedded, highly glauconitic. grayish-yellow; contains some brown chert pebbles and the fossils Meleagrinella and Lop/1a. Contact with Ephraim Conglomerate is sharp and channeled 9. Sandstone, fine-grained. silty. shaly, to very thin bedded. soft, grayish—yellow, glauconitic. A sandstone bed, about 0.3 m thick. is 1.5 m above base and contains carbonized wood fragments Shale unit: 8. Clay shale, chunky, dark-yellowish-gray, mostly covered; a belemnite found 2.4 m above probable base of Redwater Member ............................... 10.7 Thickness of Redwater Member ............... 15 Curtis Member: Shale unit: 7. Clay shale, flaky. greenish-gray, mostly covered . 15.3 6. Clay shale, flaky, greenish-gray; some beds of platy, fine-grained sandstone 12-25 mm thick ............ 45.7 5. Sandstone, Iimy, very thin bedded. wavy-bedded, yellowish-gray. estimated thickness .................. 1.8 4. Clay shale. flaky. soft greenish-gray .................... 8.2 3. Limestone, sandy, thin- to medium-bedded, very fine grained, mostly medium gray; some greenish-gray partings ...................................... 0.9 2. Shale, flaky, rests sharply on underlying unit 1.2 Thickness of Curtis Member ................. 73 Thickness of Stump Formation ............ 88 Preuss Sandstone (incomplete): I. Sandstone, pale-red. fine-grained, thin-bedded; makes soft slope ............................................... 5+ UNCONFORMITIES. CORRELATION, AND NOMENCLATURE Section 18,—Peoa [Stump Formation northwest of Peoa in SE'ASW'A sec. II. T. l S.. R. 5 E.. Kamas quadrangle. Summit County. Utah] Thickness (meters) Ephraim Conglomerate (incomplete): 8. Interbedded red and green claystone and gray limestone .......................................................... 3+ Stump Formation: Redwater Member: Sandstone unit: 7. Sandstone, cliff-forming, medium-bedded. greenish-gray; upper 1.2 m consists of sandy limestone and bears fragments of oysters and other bivalves ................................................... 9.7 6. Siltstone. sandy. greenish-gray ............................. 4.6 , Shale unit: 5. Clayey to finely sandy siltstone, greenish-gray; one bentonite bed at top; base not exposed ........... 6.7 4. Covered (probably contains contact between Redwater and Curtis Members) ....................... 3 Thickness of Redwater Member ........... i Curtis Member: Shale unit (incomplete): 3. Clay shale. flaky; gray top not exposed ............... 29.3 Sandstone unit: 2. Sandstone. platy, thin- to medium-bedded, cross- bedded. wavy-bedded, medium-grained, yellowish-gray; basal contact poorly exposed .. 12. Thickness of Curtis Member .................... (F (It Thickness of Stump Formation ................ llgllgl Preuss Sandstone: l. Sandstone and siltstone, grayish-red; makes slope (Thomas and Krueger, 1946, p. 1282) .............. 365 REFERENCES CITED Albee, H. F., 1968, Geologic map of the Munger Mountain quadrangle, \ Teton and Lincoln Counties, Wyoming: U.S. Geol. Survey Geol. ' Quad. Map GQ-705. Baker, A. A., 1947, Stratigraphy of the Wasatch Mountains in the vicinity of Provo, Utah: U.S. Geol. Survey Oil and Gas Inv. Prelim. Chart 30. Cressman, E. R., 1964, Geology of the Georgetown Canyon-Snowdrift Mountain area, southeastern Idaho: U.S. Geol. Survey Bull. 1153, 105 p. ‘ Gardner, L. S., 1944, Phosphate deposits of the Teton Basin area, Idaho " and Wyoming: U.S. Geol. Survey Bull. 944-A, p. 1-36. Gilluly, James, 1929, Geology and oil and gas prospects of part of the San Rafael Swell, Utah: U.S. Geol. Survey Bull. 806-C, p. 69-130. Gilluly, James, and Reeside, J. B., Jr., 1928, Sedimentary rocks of the San Rafael Swell and some adjacent areas in eastern Utah: U.S. Geol. Survey Prof. Paper ISO-D, p. 61-110. Hansen, W. R., 1965, Geology of the Flaming Gorge area, Utah—Colorado-Wyoming: U.S. Geol. Survey Prof. Paper 490, 196 p. C25 Imlay, R. W., 1950, Jurassic rocks in the mountains along the west side of the Green River Basin, in Wyoming Geol. Assoc. Guidebook 5th Ann. Field Conf., Southwest Wyoming, 1950: p. 37—48. 1952, Marine origin of Preuss sandstone of Idaho, Wyoming, and Utah: Am. Assoc. Petroleum Geologists Bull., v. 36, no. 9, p. 1735-1753. 1967, Twin Creek Limestone (Jurassic) in the western interior of the United States: U.S. Geol. Survey Prof. Paper 540, 105 p. Mansfield, G. R., 1927, Geography, geology, and mineral resources of part of southeastern Idaho, with Descriptions of Carboniferous and Triassic fossils, by G. H. Girty: U.S. Geol. Survey Prof. Paper 152,453 1952, Geography, geology, and mineral resources ofthe Ammon and Paradise Valley quadrangles, Idaho: U.S. Geol. Survey Prof. Paper 238, 92 p. [1953]. Mansfield, G. R., and Roundy, P. V., 1916, Revision of the Beckwith and Bear River formations of southeastern Idaho: U.S. Geol. Survey Prof. Paper 98-G, p. 75-84. Oriel, S. S., 1963, Preliminary geologic map of the Fort Hill quadrangle, Lincoln County, Wyoming: U.S. Geol. Survey Oil and Gas Inv. Map OM-212. Pampeyan, E. H.. Schroeder, M. L., Schell, E. M., and Cressman, E. R., 1967, Geologic map of the Driggs quadrangle, Bonneville and Teton Counties, Idaho, and Teton County, Wyoming: U.S. Geol. Survey Mineral Inv. Field Studies Map MF-300. Pipiringos, G. N., and O’Sullivan, R. B. 1978, Principal unconformities in Triassic and Jurassic rocks, western interior United States—a preliminary survey: U.S. Geol. Survey Prof. Paper 1035-A. 29 p. (in press). Rubey, W. W., 1958, Geology of the Bedford quadrangle, Wyoming: U.S. Geol. Survey Geol. Quad. Map GQ-109. I973, Geologic map of the Afton quadrangle and part of the Big Piney quadrangle, Lincoln and Sublette Counties, Wyoming: U.S. Geol. Survey Misc. Geol. Inv. Map 1-686. Rubey, W. W., Oriel, S. S., and Tracey, J. 1., Jr., 1975, Geology ofthe Sage and Kemmerer 15-minute quadrangles, Lincoln County, Wyoming: U.S. Geol. Survey Prof. Paper 855, 18 p. Schroeder, M. L., 1969, Geologic map ofthe Teton Pass quadrangle, Teton County, Wyoming: US. Geol. Survey Geol. Quad. Map GQ-793. Staatz, M. H., and Albee, H. F., 1963, Preliminary geologic map of the Garns Mountain SE quadrangle, Bonneville and Teton Counties, Idaho: U.S. Geol. Survey Mineral Inv. Field Studies Map MF-262. 1966, Geology of the Garns Mountain quadrangle, Bonneville, Madison, and Teton Counties, Idaho: U.S. Geol. Survey Bull. 1205, 122 p. Stokes, W. L., 1944, Morrison Formation and related deposits in and adjacent to the Colorado Plateau: Geol. Soc. American Bull., v.55, no. 8, p. 951-992. 1955, Non-marine Late Jurassic and Early Cretaceous For- mations, in Wyoming Geol. Assoc. Guidebook 10th Ann. Field Conf., 1955: p. 80-84. Thomas, H. D., and Krueger, M. L., 1946, Late Paleozoic and early Mesozoic stratigraphy of Uinta Mountains, Utah: Am. Assoc. Petroleum Geologists Bull., v. 30, no. 8, p. 1255-1293. Vine, J. D., 1959, Geology and uranium deposits in carbonaceous rocks of the Fall Creek area, Bonneville County, Idaho: U.S. Geol. Survey Bull. 1055-1, p. 255-294 [1960]. Wanless, H. R., Belknap, R. L., and Foster, H. L., 1955, Paleozoic and Mesozoic rocks of Gros Ventre, Teton, Hoback, and Snake River Ranges, Wyoming: Geol. Soc. America Mem. 63, 90 p.