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Home , Bridger Formation, Browns Park Formation, Eotitanops, Geology of Wyoming, Green River Formation, Hyopsodus

Geology of Green Formation and associated rocks in south­ western and adjacent parts of and By W. H. BRADLEY

THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 496-A

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 DEPARTMENT OF THE INTERIOR

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY

Thomas B. Nolan, Director

The U.S. Geological Survey Library has cataloged this publication as follows: Bradley, Wilmot Hyde, 1899- Geology of and associated Eocene rocks in southwestern Wyoming and adjacent parts of Colo­ rado and Utah. Washington, U.S. Govt. Print. Off., 1964. iv, 86 p. illus., maps (3 fold. col. in pocket) diagrs., tables. 30 em. (U.S. Geological Survey. Professional Paper 496-A.) Bibliography: p. 81-84. 1. Geology-Wyoming-Green River Formation. 2. Geology, Strati- graphic-Eocene. (Series)

For sale by the Superintendent of Docu.ments, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS

Page Page A1 Stratigraphy-Continued IntroductionAbstract------~------______2 -Continued Orientation and purpose ______2 Stratigraphic units-Continued Location and extent of the area ______3 Cathedral Bluffs Tongue ______A26 Earlier geologic surveys ______4 New Fork Tongue~------27 Field work ______:.. ______5 Green River Formation ______-- __ 28 Acknowledgments ______5 Definition and age ______------_-- 28 Topography and drainage ______6 Stratigraphic units ______--- __ _ 28 Luman Tongue ______Geologic structure ______~ ______9 28 Major structural units ______9 Tipton Tongue and Tipton Member_ 31 Fontenelle Tongue ______Faults------10 34 Wind River ______11 Member ______35 Uinta fault and Uinta flexure ______11 Laney Shale Member ______-- __ ---_-- 43 Henrys Fork fault ______12 Battle Spring Formation ______48 Continental fault ______13 ______------48 Faulted zone south of Washakie Basin ______13 Definition and age ______----_------__ _ 48 Miscellaneous faults ______14 Clastic sediment ______49 Interpretation of the structure ______14 Pyroclastic sediment_------49 Pre-Tertiary deformation ______14 Stratigraphic units ______50 Early Eocene deformation ______15 White layers ______- ______- _-- 50 Faunal zones ______Post-Eocene-pre-(?) deformation ______16 54 Post-Miocene deformation ______16 Washakie Basin ______-- __ ----- _-- 54 Structural effect of original dip and compaction ______16 ______---- ___ --_-- 54 Depositional dip ______16 Undifferentiated Eocene formations ______54 Gravitational compaction ______17 Bishop ______-- __ .:.- _-- _-- 55 Regional effect ______17 , Miocene, and formations ______56 Local effects of gravitational compaction ______17 Undifferentiated Oligocene and Miocene ____ ---- 56 Stratigraphy ______18 ______- 56 General relations between the Eocene formations __ _ 18 Split Rock Formation ______-- ___ ------57 Lfthologic terms used ______19 Igneousrocks------~­ 57 Wasatch For~ation ______20 Measured sections of the Green River, Wasatch, and ])efinition and age ______20 Bridger Formations ______---_-- 58 References ______Stratigraphic units ______20 81 Index ______Niland Tongue ______23 83

ILLUSTRATIONS

(Plates are in pocket]

PLATE 1. Geologic map of part of southwestern Wyoming and adjacent States. 2. Geologic map of the area around Green River, Wyo., showing distribution of the members of the Green River Formation and the underlying Wasatch Formation. 3. Reconnaissance geologic map and structure sections of the Phil Pico Mountain area in northern Utah and extreme southern Wyoming.

Page FIGURE 1. Index maP------A3 2. Map showing Great Divide Basin perched on Continental Divide______8 3. Henrys Fork fault on east flank of Phil Pico Mountain------12 4. Tertiary-pre-Tertiary relationships at south end of Phil Fico Mountain ______'______13 5. Shore features of Gosiute on island of rocks------18 6. Diagram showing the relations of the Green River Formation to the enclosing Wasatch and Bridger Formations_ 18 III IV CONTENTS Page FIGURE 7. Banded gray and red mudstone near the top of the Wasatch Formation __ ------A21 8. White tuff in the Niland Tongue of the Wasatch Formation______25 9. Typical exposure of the Tipton Shale Member of the Green River Formation______34 10. Map showing Gosiute Lake's hydrographic basin and areal extent at several stages______-36 11. Photograph showing and the Wilkins Peak Member of the Green River Formation______37 12. Contact between the Wilkins Peak and Laney Shale Members of the Green River Formation______38 13. Crystal molds of an unknown salt from the Wilkins Peak Member of the Green River Formation______39 14. Characteristic exposure of the Laney Shale Member of the Green River Formation______46 15. Tuffaceous lens near the base of the Laney Shale Member of the Green River Formation______47 16. Sketch showing extreme differential compaction around thick tuffaceous sandstone lens______48 17. Characteristic exposure of the Bridger Formation in Twin Buttes------,------49 18. White bench-forming tuff layers in mudstone of the Bridger Formation______51 19. Map showing outcrops of white layers in the Bridger Formation______52 20. Petrified log with bark from the Bridger Formation ______,______53

TABLES

Page TABLE 1. Pollens, spores, and found in the Luman Tongue of the Green River Formation______A30 2. Chemical analyses of carbonate-rich tuffs from the Tipton Shale Member of the Green River Formation______33 3. Boreholes in the Green River Basin drilled to explore for or for oil or gas______41 4. Chemical analyses of two tuffs from the Wilkins Peak Member of the Green River Formation______43 5. Chemical analysis of typical dolomitic organic marlstone from the lower part of the Laney Shale Member______44 6. Chemical analyses of a rhyolitic and an andesitic tuff from the upper and middle parts 'of the Laney Shale Member_ 47 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

GEOLOGY OF GREEN RIVER FORMATION AND ASSOCIATED EOCENE ROCKS IN SOUTHWEST­ ERN WYOMING AND ADJACENT PARTS OF COLORADO AND UTAH

By w. H. BRADLEY

ABSTRACT Most of the Eocene rocks belong to three formations-Wasatch, Discussed in this report is the geology of the Eocene rocks in an Green River, and Bridger. The Green River Formation is of area of about 17,000 square miles. The purpose of the report lacustrine origin and has the form of a great lens, or pile of lenses, is to provide the geologic foundation necessary to understand within an enormous volume of fluviatile sediments. The fluvia­ unci reconstruct the conditions under· which the Green River, tile sediments have been divided into the Wasatch and Bridger Wasatch, nncl Bridger Formations came into being and to pro­ Formations. Though the Bridger Formation is predominantly vide a matrix in which geochemists and mineralogists studying fluviatile, it contains a considerable number of thin extensive parts of the area can set up their models. The report is .based layers of lacustrine sediments. Most of the Wasatch Formation hugely on the author's own fieldwork, which began in the early underlies the Green River Formation, and most of the Bridger 1920's, but it also brings together the findings of many other Formation overlies it; but locally around the margins, the geologists who have worked in the area. Bridger rests directly on the Wasatch. The green River inter­ Four huge structural units dominate the area. The first two fingers and intertongues with both fluviatile formations. Three nrc the Green River and Washakie Basins, each of which is a tongues of the .Wasatch, as well as the main body of the formation, hll'ge synclinal basin. These nrc separated by the third unit, nn have been defined and mapped. The Green River Formation anticlinal uplift of comparable size known ns the Rock Springs has been subdivided into three members and three tongues, all uplift. A fourth large unit, the Great Divide Basin, is perched of which have been mapped. The Bridger Formation has not on the Continental Divide; it is not only n structural unit but been subdivided, but it contains several thin extensive zones also n shallow topographic basin having centripetal drainage. called white layers, which have been mapped only in part. Large faults, flexures, and subsidiary faults bound the south­ Along the mountainward margins of basins are conglomeratic ern margins of the Green River and Washakie Basins and form piedmont deposits, which are equivalent to part or all of several part of the northern boundary of the Great Divide Basin. The of-these Eocene formations or their members and tongues. One Rock Springs uplift is cut by numerous faults that trend north­ of these conglomeratic deposits has been defined as a formation eastward. The many faults and minor flexures in the Great and mapped. The others arc designated Eocene undifferentiated Divide Basin show that its structure is complex and more diver­ and have been mapped only locally. sified thnn that of the other three major features. Gosiute Lake, in which the Green River Formation was de­ All the mountain rnnges-Uinta, Wind River, Wyoming, posited, changed considerably and repeatedly in size and char­ and others-in the aren studied were in existence at the beginning acteristics during the Green River ; but it had three major of the Eocene Epoch, as were also the Rock Springs uplift and stages, each of which corresponds to a member of the Green several other anticlinal bulges now buried under Tertiary River Formation. During the first , the lake was a large sediments. fresh-water lake that had an outlet. The Tipton Shale Member Downwarping of the floors of these basins which began early and the Luman, Tipton, and Fontenelle Tongues were formed in the Tertiary, apparently continued more or less intermittently during this stage. After their formation the climate became more all through the Eocene and was primarily responsible for the con­ arid, and the lake shrank, so that ·it occupied only part of the tinuous sedimentation of the Wasatch, Green River, Bridger, Green River Basin, at times only a small part of it, and had no Uinta Formations. The low stream gradients between this outl'et. During this the second stage the middle, or Wilkins region and the apparently prevented the margins of these Peak Member, was deposited. Becn,usc Gosiute Lake had no basins from being cut downward. outlet during this entire second stage, enormous quantities of Uplift of the marginal mountains, or deformation in the form salts accumulated also. At least 25 beds of trona [NazCOa of faulting or gentle warping of the sedimentary rocks, occurred NaJ-IC03.2H20] ranging in maximum thickness from about 3 feet during the early Eocene, sometime between the end of the Eocene to about 38 feet, and in area from a few hundred to more than 725 and the beginning of the Miocene, and sometime after the square miles, have been found in this member. These beds consti­ Miocene. tute a great economic resource and in 1963 were being mined by ]<'luviatile and lacustrine rocks of Eocene age cropout over two different companies. Comparable volumes of shortite [Naz

most of the area and occupy large parts of the Green River, C03.2CaC03] also occur in the Wilkins Peak Member; but this Washakie, and Great Divide Basins. Upper rocks mineral, \\·hich is unique to the Green River Formation, occurs arc exposed in the Rock Springs uplift. mostly as single crystals or aggregates of crystals rather than Al A2 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS as solid beds. Common salt (N aCl) is distributed unevenly focused an intensive commercial interest· on a large through several of the trona beds and is abundant in the thick part of southwestern Wyoming. Also, discoveries of salt beds in the southern part of the Green River Basin. Along with these saline minerals are other saline minerals and a growing new, or rare, and exotic authigenic minerals in the number of new or unusual authigenic minerals-silicates, Green River Formation have attracted to that forma­ borosilicates, fluorides, phosphates, oxides, and complex carbo­ tion the attention of increasing numbers of mineralo­ nates. Minerals containing the sulfate radical are extremely gists, geochemists, and geologists. My own interest rare. was drawn to this area in the early 1920's when my At the end of the second stage, the climate became humid again, and Gosiute Lake expanded to its maximum size (about imagination was sparked by the possibility of recon­ 15,000 sq mi). In this large fresh-water lake, which had an structing a satisfying picture of the ancient great lake outlet, the uppermost member of the Green River Formation, in which the Green River Formation accumulated. the Laney Shale Member, was deposited. Such a reconstruction seemed within reach from what Gosiute Lake came into existence because the basin floor was even then known of the formation's extensive warped downward and continued, apparently at rather short intervals, to warp downward at a rate greater than the rate at exposures, variety of rock types, and content of re­ which sediments accumulated. But at the end of the Laney markable . Perhaps rriost significant was the stage, sedimentation evidently won out, for the lake became fact that the lake beds and their enclosing formations filled and so vanished. Smaller and much shorter lived , have been little. disturbed by post-Eocene geologic however, repeatedly formed in the central parts of the Green events. River and Washakie Basins during the following Bridger epoch.' In the Washakie Basin deposition of the post-Bridger Uinta The purpose of this report is to provide the geologic Formation apparently continued until about the end of the foundation necessary to understand and reconstruct Eocene Epoch. This formation is not known to be present else­ the conditions under which the Green River, Wasatch, where in the area. and Bridger Formations came into being; to provide a Volcanic activity began early in the Green River epoch and matrix in which geochemists and mineralogists can set increased in frequency and intensity at least until the end of the Eocene. Most tuff beds in the lower parts of the Green River up their models; and, finally, to provide a framework Formation are thin and rather widely spaced, but strati­ that may be useful to those interested in exploring graphically upward they increase in number a.nd thickness; further for additional mineral or mineral-fuel resources. the upper part of the Bridger Formation is dominantly tuffaceous. This report, which covers about 17,000 square miles, The tuffs range from highly siliceous rhyolitic types to andesitic. is focused on the geology of the Eocene formations in In general, the less siliceous tuffs are thicker. Crystal and lithic tuffs are common from the basal part of the Laney Shale Member southwestern Wyoming and small adjacent parts of on up through the section. Colorado and Utah; but it also touches on all the Volcanism was again active during the Oligocene and Miocene. Tertiary history and formations, including the Pliocene Formations of these ages consist largely of volcanic ash. flows of the leucite-rich rock, wyomingite. It does not A long interval of erosion followed the deposition of the deal with the geology. Eocene rocks. Still later, the extensive erosion surfaces cut on the Eocene and earlier formations were covered with a sheet of The report is based mainly on n1y own fieldwork, gravel known as the Bishop Conglomerate, whose exact age is which began in the early twenties and has continued not known. During or after the deposition of the conglomerate intermittently ever .gince. But the report also brings and later rocks, the area was gently deformed and locally faulted. together the findings of many other geologists who have In some of the down-faulted areas and on some of the erosion worked in the area in increasing numbers as the search surfaces, a few hundred to more than 1,000 feet of beds of Miocene, and probably also Oligocene, age are still preserved. for natural gas, petroleum, and sodium salts has The Miocene formations include the Browns Park 11nd Split increased in intensity. Rock Formations, but the beds of Oligocene age have not been This account of the geology is the first of a series of adequately defined and in this area have been locally grouped closely related papers. The second paper, on the into an unnamed unit of Oligocene and Miocene ages. paleoecology of the Wasatch and Bridger Formations Most of these Oligocene and Miocene beds were deeply eroded for a long interval of time after their deposition. of southwest Wyoming will be an effort to reconstruct Late in the Pliocene, a small amount of the highly distinctive the physical environment in which these two thick and lava, wyomingite, flowed out from several vents at the north end extensive fluviatile formations came into being. The of the Rock Springs uplift and from one vent a few miles north third paper, on the paleolimnology of the Green River of the town of Green River. A potassium-argon age determina­ Formation in Sweetwater and adjacent counties in tion on the phlogopite mica from this leucite-rich lava gives the age as about 1.25 million . Wyoming, Colorado, and Utah, will be an effort to reconstruct as fully as possible not only the various INTRODUCTION stages of Gosiute Lake in which the Green River Formation accumulated but also the Eocene climate ORIENTATION AND PURPOSE and the composition of the streams and the lake water; Successive discoveries of natural gas, petroleum, and the depth, circulation, and stratification of the lake; enormous deposits of sodium carbonate (trona) have the aquatic environment and rates of accumulation of EOCENE ROCKS, WYOMING-COLORADO-UTAH A3 the various kinds of sedhnents; and the trophic history LOCATION AND EXTENT OF THE AREA of the lake. The third paper of the series also will The area discussed in this report is mostly in south­ include a discussion of the organic constituents of the western Wyoming but extends a little way into northern sediments and a consideration of the energy regimen. Utah and northwestern Colorado. (See fig. 1.) In This third chapter will draw much frorn the first two Wyoming it includes nearly all of Sweetwater County chn.pters and depends heavily on them. and part of five adjacent counties-Uinta, Lincoln, A fourth paper dealing more comprehensively with Sublette, Fremont, and Carbon. In Utah it includes the Wilkins Peak Member of the Green River Forma­ a narrow strip along the north edge of Daggett and tion is being prepared jointly with Prof. Hans Eugster Summit counties. That part of the area in Colorado of the Johns Hopkins University and the U.S. Geo­ is in Moffat County. The total area is nearly 17,000 logical Survey. This paper will discuss the origin of square miles, all of which lies within the Wyoming the carbonates, sodium salts, and trona beds and will Basin physiographic province except a narrow strip in attempt to give, in part at least, an explanation of the northern Utah and northwestern Colorado. remarkable suite of authigenic minerals. The two largest towns, Rock Springs and Green

110" 108" 106" 104"

44·---

I I 41° _l

50 0 50 100 150 MILES

FIGURE 1.-Locatlon of the area discussed in this report. A4 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

River, are. near the geographic center of the area on In 1945, · I published a preliminary geologic map the Union Pacific Railroad and U.S. Highway 30. At (Bradley, 1945) of the Washakie Basin that included the west edge of the area is Kemmerer, which is on the a brief description of the stratigraphy and structure of Oregon Short Line of the Union Pacific. the area. W. T. Nightingale (1930) presented an argument for EARLIER GEOLOGIC SURVEYS including a thick section of carbonaceous beds in the In this sketch of previous geologic surveys, no attempt basin of Vermilion Creek in the Green River Forma­ has been made to summarize the results of all the tion instead of in the uppermost part of the Wasatch as geologic work that has been done in this area. Only Sears and· Bradley (1924) had done. Reconnaissance those reports are cited here that are accompanied by maps showing the areal geology and structural features geologic maps of parts of the area described in this of the were published in 1937 by report. Scientific papers and reports treating pertinent Forrester (pis. 3, 4). Nace, then of the Wyoming phases of the Tertiary geology are referred to at appro­ Geological Survey, published in 1939 a detailed map priate places in the text. of a small but critical area around Oregon Buttes and Many years ago, that part of the area south of lat from there northward to the outcrops of metamorphic 41 °45' N. was mapped by Powell (1876), Hague and rocks along Sweetwater River. The intertonguing Emmons (1877), and King (1878); that part north relationships between the Green River and Wasatch of this parallel was explored and mapped by Peale and Formations in the vicinity of La Barge, Wyo., were Endlich (1879). In these early surveys the Tertiary mapped n,nd described by Donavan (1950). The area rocks were divided into the Wasatch, Green River, and studied by Donavan and a larger area west of it were Bridger Formations, but the maps showing the areal mapped in more detail in 1957 by Stephen S. Oriel of distribution of these units are of little value today. the U.S. Geological Survey. Oriel generously sent n1e l\1any years later, Veatch (1907) and Schultz (1914) (written communication, Aug. 16, 1957) a copy of his mapped in considerable detail a strip a little more field map showing the various tongues of the Wasatch than 30 miles wide west of the Green River Basin. and Green River Formations in the La Barge and In 1907 and 1908 Schultz (1909, pl. 14; 1910, pl. 14) Fontenelle Creeks area. His information has been mapped the Cretaceous and Tertiary rocks of the incorporated in the geologic map (pl. 1) of the present Rock Springs uplift and some of the adjacent country. report. Later he (Schultz, 1920, pl. 1) 1nade a reconnaissance In 1955 McGrew and Berman (1955; also McGrew survey of the area south and southeast of the Rock and others 1959, p. 121-129) published a geologic n1ap Springs uplift and combined in one map all the data of a small but critical area between Big and Little obtained. Gale (1907) mapped a small area along Sandy Creeks (north of Farson, Wyo.). This mapping the Wyoming-Utah boundary in the vicinity of Henrys and the vertebrate fossils collected there demonstrated Fork in 1907. Schultz (1918), in outlining the phos­ the age relationships of the faults in that part of the phate resources of northern Utah in 1914, made a Green River Basin and established the Bridger age of reconnaissance map of the Uinta l\1ountains. In 1918 the thick tuffs north of the faults. George Pipiringos Winchester (1923, pl. 18) mapped the outcrop of the (1962) of the U.S. Geological Survey made a significant principal zone of the Green River Formation contribution to our knowledge and understanding of the along the Green River southward from the mouth of Green River and related formations in the Great Divide Currant Creek nearly to the Utah State line. A few Basin and along the north side of the Washakie Basin. years later Sears (1924b, pl. 35) mapped in detail an Among other things, he discovered another tongue of area in northwestern Colorado and southern Wyoming, the Green River Formation below the Tipton Tongue and in the following , 1923, I (Bradley, 1926, pl. and separated from it by a unnamed tongue of the 58) mapped a small area in the vicinity of Steamboat Wasatch For1nation. His Inap is included on plate 1 l\1ountain. Two other reports (Bradley, 1935, fig. 1; in somewhat generalized form, and his report is referred 1936, pl. 34) dealing with special features of the area to many times later ih this paper. A small part of have been published by me since the fieldwork on this Harold Masursky's (1962, pl. 1) map which adjoins project was begun in 1928. The first of these reports contains a map of a folded and faulted zone along the Pipiringos' map on the east, is also includ.ed. Ander­ southern margin of Washakie Basin, whereas the other man (1955) pubiished a geologic map of a rather large contains a map showing the geomorphic features super­ area around Manila, Utah, and gave a good account of posed on a generalized geolOgic map of the southern the tectonic history, especially of the relations between part of the Green River and Washakie Basins and part the Uinta and Henrys Fork faults. Hansen and Bo­ of the Uinta Mountains and adjoining areas to the east. nilla (1954, 1956) and Hansen (1961 a, b) also added EOCENE ROCKS, WYOMING-COLORADO-UTAH A5

fippreciably to our knowledge of the orogenic history mapping done specifically for this report is not um­ of the southern 1nargin of the Green River Basin. form for all parts of the area. In the years 1957-59 the geologic mapping was FIELDWORK revised or remapped using the aid of high-altitude The fieldwork upon which this report is based was aerial photographs, new topographic maps of the Army begun in 1928. In that year, 4~ months was spent Map Service, and photogeologic methods. R. J. mapping and measuring sections in the Green River Hackman, of the Geological Survey made a photo­ Bn,sin. l\1r. Joseph Jacoby was engaged for 1 week to geologic map of the vicinity of Green River, Wyo., serve as rodman. A few days was spent in the area in and Wilkins Peak (pl. 2) which was based on his own 1929 revising the mapping of the post-Eocene beds in field sketching. He also made a photogeologic map the Valley of Sweetwater River. During 1930 about of most of Hiawatha Basin (pl. 1) based on field 4 months wn.s spent in the field mapping the erosion sketching by Dwight Taylor, of the Survey, and me. surfaces and the bedrock geology along the north flank Hackman remapped on aerial photographs all the Green of the Uinta Mountains and in the southern part of the River-Bridger boundary in Washakie Basin, on the Green River Bn.sin, and about 1 week was spent with basis of my field observations. J. D. Love, of the C. W. Gilmore, of the U.S. N ationn.l Museum, and his Survey, and I resketched on the Army Map Service pn.rty, who were collecting vertebrate fossils from the 1:250,000 topographic base the Green River-Bridger Bridger Formation. Ln.ter that summer, planetn.ble boundary in the northeastern part of the Green River maps were mn.de of two areas to show the location and Basin and the upper and lower boundaries of the strn,tigraphic position of the principal quarries from Tipton Shale Member of the Green River Formation which vertebrate fossils had been ta,ken. In 1933 south from Wilkins Peak to the north spurs of Little Frfink S. Parker, then of the U.S. Geological Survey, and Mountain. I spent 2 months mapping the rock formations along The Wilkins Peak-Laney Shale Members boundary the east and south sides of the Washakie Basin. from a few miles south of Wilkins Peak southward N en.rly all the mapping was done by triangulation, nearly to the Utah State line has recently been re­ using pln.netables n.nd geologist's alidades, on n, scale mapped on new topographic base maps by W. C. of 1:500,000 or approximately 8 miles to the inch in Culbertson, of the U.S. Geological Survey. His the Green River Basin and 1:250,000 in the Washakie mapping is much superior to my own rapid recon­ Basin. In the Green River Basin the mapping was naissance mapping. My sketching of this boundary done almost wholly from the primary triangulation (pl. 1) places the contact too high; so the result.ing points established by topographic engineers of the pattern is more complex than it should be. Geological Survey. As nearly all these points are on A large subjective element is involved in portraying pro.rninent n.nd easily recognized features that have the areal extent of the Bridger Formation because in n. wide range of visibility, it was necessary to establish most places its lithology grades gradually into the only a minor amount of secondary control. Primary lithology of the underlying Green River Formation. triftngulation established by topographic engineers of No claim for accuracy, or even consistency, can be the Geological Survey and by the Coast and Geodetic made for this boundary as mapped. On the other Survey was availa,ble along the east side of the Washftkie hand, the greater part of the data on other boundaries Basin, but secondary control had to be established taken from published reports (see index n1ap, fig. 1) n.long the southern margin of the basin. A narrow was based on rather detailed surveys and is corre­ strip in northern Utah was nutpped on topographic spondingly more accurate than much of the new infor­ maps (l\1n,rsh Peak, Gilbert Peak, and Hayden Peak mation. These maps required very little adjustment qw1d1·angles) published by the Survey. The drainage, to fit the new topographic base maps. Nevertheless, lt1nd net, t1nd cultural features shown on plate 1 were some of the information taken from two published tftken from the Army Map Service (U.S. Army Corps reports (Schultz, 1918; 1920, pl. 1) was based on rapid of Engineers) 1:250,000 topographic maps (Rock reconnaissance surveys that apparently were less well controlled than the mapping done specifically for this Springs NK 12-9, and parts of Rawlins NK 13-7, project during 1928 and in succeeding years. Verm1l NK 12-12, Ni( 12-11, Ogden NK 12-8, Preston NK 12-5, and Lander NK 12-6). ACKNOWLEDGMENTS The geologic map (pl. 1) is a composite of new and I am grateful to many of my colleagues of the U.S. published information and was recompiled in 1956 Geological Survey who, over the years, have been and adjusted to the Army Map Service 1:250,000 generous with ideas, suggestions, and criticisms. I am topographic maps. The accuracy of the geologic especially grateful to J. D. Love for assistance in the A6 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS field and for many discussions with him on problems the north end of the basin, the Green River Formation relating to the . Few people are makes only a low, and in places poorly defined, escarp­ as conversant with so many aspects of the geology of a ment that faces northeastward and northward. whole State as he is with the geology of Wyoming. I Along the Green River from the northwest corner of am grateful also to Steven S. Oriel for permission to the Green River Basin as far south as LaBarge Creek, use his hitherto unpublished geologic map of the north­ the escarpment made by the Green River and Wasatch western part of the Green River Basin and for many Formations is 100-300 feet high. From LaBarge Creek helpful discussions. I wish to express my thanks to south, the greater part of the western margin of the Dwight Taylor and George Pipiringos for assistance in basin consists of two rather low and irregular escn.rpmehts the field and for helpful discussions about interpreta­ that are roughly parallel and several miles apart. These tions of the stratigraphy and paleoecology. two escarpments are formed respectively by two units This report benefited materially in the manuscript of the Green River Formation, separated by a soft unit stage from the thorough and constructive criticisms of of the Wasn.tch Formation. South of the main line of J. D. Love and W. C. Culbertson, both of the Survey. the Union Pacific Railroad the lower escarpment van­ For their generous help I am particularly grateful. ishes, but the upper one becomes higher and forms a conspicuous bluff that rises nearly 1,000 feet above the TOPOGRAPHY AND DRAINAGE valley to the west in the vicinity of Piedmont. Near The topography of the region can be considered in the southwest corner of the basin, just a few miles north four major units, each of which is rather well defined. of the Wyoming-Utah ·boundn.ry, the upper escarpment These are the Green River Basin, 1 the Rock Springs merges with the high gravel-capped erosion surface that uplift, the Washakie Basin, and the Great Divide slopes northward from Elizabeth Mountain. Basin. (See pl. 1.) All these owe their form to the From the vicinity of Elizabeth Mountain eastward structure of the rocks. The Great Divide Basin, as its across the south end of the basin nearly as far· as Phil name implies, is a topographic depression literally Pico Mountain, broad remnants of several gravel-capped perched on the Continental Divide. (See fig. 2.) erosion surfaces slope gently northward from the Uinta Green River Basin, the largest of the four units, oc­ Mountains. At the Wyoming-Utah boundary these cupies nearly all the western half of the area. Out­ highest terraces have an altitude of about 9,500 feet ward-facing escarpments of the Green River and above level. East of the remnants of this high Wasatch Formations mark the margin of this basin erosion surface, beds of undifferentiated Eocene deposits, everywhere except for about 40 miles along the south equivalent in pn.rt to the Bridger, Green River, and end of the basin between Phil Pico Mountain and Wasatch Formations, make a southward-facing escarp­ Elizabeth Mountain. There the Tertiary rocks are ment whose height gradually in.creases from less than obscured by broad remnants of gravel-covered erosion 100 feet to 700 or 800 feet on the southwest flank of surfaces that slope gently away form the Uinta Moun­ Little Mountain. tains and extend far out into the basin. As thus de­ Within the Green River Basin, and in a very broad fined, the Green River Basin is a roughly rectangular way concentric with its rim, is another escarpment area a little more than 100 miles long from north to that faces outward. This escarpment is. formed by south and about 60 miles wide. the Bridger Formation. In most places it is several At the southeast corner of the basin, where Little miles from the crest line of the marginal escarpment Mountain rises to a maximum altitude of about 9,100 made by the Green River Formation, and in most feet, the escarpment of the Green River and Wasatch places it is a low, irregular, and rather inconspicuous Formations is about 1,000 feet high. From Little feature. A considerable part of the basin enclosed by Mountain northward along the east side of the basin, this secondary escarpment is nearly level or gently rolling. the height of the escarpment diminishes, so that where At various altitudes along n1ost of the streams, terraces it is crossed by the Union Pacific Railroad it is about have been formed. Some of the lowest terraces are 500 feet high. For about 30 miles north from the rail­ very broad, notably those along Big Sandy and Little road, the escarpment is a conspicuous bluff 400-500 feet Sandy Creeks in the northern part of the basin and high which is known as White Mountain. Beyond that along Blacks Fork, Smiths Fork, and other streams the escarpment becomes lower and loses its identify as in the southern part of the basin. Much of this a distinctive topographic feature in the northeastern nearly level land in both parts of the basin is irrigated part of the basin. Northwestward and westward across and under cultivation. Elsewhere, the surface of Green River Basin is either barren of vegetation or • In this and subsequent reports I shall use the name Green River Basin rather the usual growth of shrubs and annuals character­ than Bridger Basin on the basis of the persuasive arguments recently marshalled by J.D. Love (196lb). istic of the semiarid high plateaus. EOCENE ROCKS, WYOMING-COLORADO-UTAH A7

Despite the large area of nearly level land in the rising in height as it does so. A few miles west of the Green River Basin, a considerable part is characterized head of Powder Wash the westward-facing escarpment by badlands. In general, the relief in the badlands that forms the western margin of Washakie Basin also is low, though, locally, buttes with intricately sculp­ is low, but from that locality it swings southwestward, tured sides rise 100-200 feet above the surrounding and its crest rises until it reaches an altitude of 8,120 country. But in the southern part of the basin, feet above sea level at Lookout l\1ountain. along the northern margins of the high gravel-capped Around most of Washakie Basin the back slopes of erosion surfaces and beneath outlying remnants of the outward-facing escarpments slope gently inward but these surffices, the badlands have a relief of 1,200-1,500 are interrupted by low discontinuous escarpments and feet. In this locality the badlands have a most ridges made by the comparatively soft rocks in the striking aspect. (See fig. 17.) upper part of the Green River Formation and the lower Just east of the Green River Basin is the Rock part of the Bridger Formation. The basin floor is a Springs uplift, a large elliptical anticlinal uplift that desolate waste of badlands and broad expanses of exposes Upper Cretaceous rocks at the surface. Ero­ gravel-covered pediment that supports but a sparse sion has removed the somewhat resistn,nt sandstone growth of low vegetation. The relief in the badlands is beds from almost all the highest part of this uplift and prevailingly low, but, locally, long irregular escarpments has cut down into the soft shale in the central part to of badlands rise several hundred feet above the general form a large depression, known as Baxter Basin. level .of the basin floor. In the northern part of the Ln,rge parts of the floor of this basin are nearly flat basin, a large badland mountain known as Haystack and almost featureless. A few of these flats have 1.\tfountain rises to an altitude of more than 7,600 feet shallow closed depressions, which in wet weather above sea level. Haystack Mountain is a conspicuous cont11in playa lakes. Badlands characterize the re­ landmark visible from all parts of Washakie Basin. mainder of Baxter Basin and contrast sharply with The Great Divide Basin, the fourth of the major the smooth level parts. Above the general altitude topographic units of the area, has much less dearly of the basin floor (6,300-6,600 ft above sea level), the defined margins than the others. It lies north and enclosing rim of rough sandstone hogbacks rises 600-800 northeast of Washakie Basin and is a very shallow feet or more. Southward from , depression nearly 100 miles long from east to west and a brofid remnfints of a high gravel-covered erosion little more than 50 miles wide. This basin is remarkable surfn.ce rise gradually toward the Uinta Mountains. in that it has interior drainage and is literally perched An firm. of this bench extends westward into the edge on the Continental Divide. (See fig. 2.) At Oregon of the Green River Basin on the divide north of Sage Buttes, approximately 50 miles north by east from Rock Creek. Springs, the Continental Divide splits, one branch W fiShfikie Basin lies southeast of the Rock Springs running south a little way, then irregularly southeast uplift. It is somewhat smaller than the Green River to the northern tip of Washakie Basin, thence generally Bfisin but is more sharply defined. Like the Green eastward some 30 miles beyond the east edge of the River Bn.sin, its form is determined by the structure of geologic map (pl. 1). The other branch runs sinuously the rocks. On all sides the beds dip inward toward the eastward from Oregon Butt.es for about 70 miles and center. As the rocks of the Green River Fonnation are then swings southeast and south to complete the considerably more resistant to erosion than those of the encirclement of the basin about 20 miles south by west overlying or underlying formations, their uptilted edges of Rawlins. nearly everywhere form the crest and upper part of a Only the western half of the Great Divide Basin bold outwn,rd-fn.cing escn.rpment which encircles the lies within the area described in this report. Its basin. Along the northern margin of the basin, this margins are defined by the divides at the heads of the rim rises 600-700 feet above the country to the north streams draining into the basin. (See fig. 2.) In a n.nd is known as the Laney Rim. Southward the escarp­ rough way 'these divides coincide with the margins of ment increases in height, and locn.lly on each side of the the adjacent basins and mountain uplifts, though in bfisin its crest stn,nds about 1,000 feet above the sur­ some places the streams having exterior drainage have rounding terrain. Along the southwestern nutrgin of cut headward through the rin1s of upturned rocks that the bfisin, the rim is known as the Kinney Rim. The encircle the adjacent basins. Flat-lying or gently southwn,rd-fn,cing escarpment that mn,kes the southern warped beds of gray and reddish-gray mudstone and margin is broken in mfiny places and is generally lower. sandstone belonging to the Wasatch Formation under... Near the head of Powder Wash, just south of the lie much of the west end of the basin. Overlying or Wyoming-Colorado boundary, where the escarpment intertonguing with the Wasatch are buff tongues of is low, it tw·ns southeastward and then southward, the Green River Formation. From mudstone beds of A8 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

10 10 20 30 40 MILES

FIGURE 2.-The Great Divide Basin-a closed drainage basin perched on the Continental Divide. the Wasatch, a thin soil cover has formed which and are nearly barren of perennial plants; others, retains the colors of the mudstone. As a consequence, more particularly the smaller ones, support a dense large tracts of this basin are gray or drab, but a large growth of greasewood. area in the western part is dull red or reddish brown. Another conspicuous feature is the strip of large From this prevailing red color of the soil, that area active sand dunes that extends eastward about 45 has long been known as the . Emmons miles from the north end of the Rock Springs uplift (1877) was one of the .first to use this name, but he out into the northern part of the Red Desert. Most applied it also to a part of the Washakie Basin. of the dunes in the western half of the strip are com­ In general, the land surface in the Great Divide pound and irregular; but, in general, they are asym­ Basin, whose altitude above sea level ranges from metric, and their steep faces are directed eastward. 6,500 to 7,000 feet, is nearly flat and monotonous, These dunes differ from one another as much in size though here and there isolated buttes or groups of as in form. Some of the largest are as much as 100 buttes rise as conspicuous features. Shallow panlike feet high. The dunes in the eastern half of the strip depressions are also significant. These depressions, have the crescentic form typical of barchans. This which are characteristic not only of this basin but of strip of active dunes is superimposed on a broader a large a~ea in southern Wyoming, are elliptical or strip of low dunes that are fixed by a thick growth of rounded in plan and range in size from about 100 yards sage brush and rabbit brush. Less active parts of the to severf!,l miles across. Some of them contain playas live dunes in places support a pure stand of Indian EOCENE ROCKS, WYOMING-COLORADO-UTAH A9 turnip (Psoralia sp.). At one place-locally known canyons. Similarly, the majority of the long streams u.s Flodden Field-nen.r the north end of the Rock in this area have entrenched themselves more or less Springs uplift, numerous hollows between the sand deeply in courses that were determined in very few hills contn.in smn.ll ponds. places by the attitude of the rocks. On the other hand, North and south of the Rock Springs uplift are two the smaller streams throughout the area are rather well smn.ll n1n.sses of high land that are somewhat isolated adjusted to the structure of the rocks. from the major topographic units just described. The The courses of Blacks Fork and its tributaries in highland north of the uplift slopes northward from the Green River Basin and of Bitter Creek and most Sten,mboat Mountain, whose highest point is a little of its tributaries in the Rock Springs uplift are note­ more than 8,600 feet ttbove sea level. A few miles worthy because they flow northward for many miles north of Stettmboat Mountain the high badland bluffs and then swing arc:mnd to more southerly courses known as Oregon Buttes also rise to an altitude of before joining the master stream, the Green River. ttbout 8,600 feet above sea level. Between Steamboat Other smaller streams in the Green River Basin have l'v1ountain and Oregon Buttes the northward-sloping a similar habit. A discussion of the drainage pattern surfttce is deeply dissected. · and drainage changes in this part of the area has been The highland south of the Rock Springs uplift is published elsewhere (Bradley, 1936, p. 187-190, 199). nlso deeply dissected. It slopes rather abruptly north­ The drainage of Great Divide Basin has no outlet eastward from three high points-Diamond Peak, to the sea. Nearly all the streams in the basin are Bishop Mountain, and Pine Mountain. Diamond intermittent, short, and irregular and are directed Peak rises 9,710 feet above sea level, and Bishop and toward the large playas in the center of the basin. Pine l\1ountains are only a little lower. A few streams, however, end in smaller playas that are The Green River and its tributaries drain all that perched ~:m the sides of the basin remote from the p11rt of the area described in this report except the center. About midway in their courses, some of the Great Divide Basin and a narrow strip of country larger streams have intrenched themselves as much as north of it which is drained by the Sweetwater River, 15 feet. Many of the stream courses contain small an ultimate contributor to the l\1ississippi. "alkali slicks" and, in places, especially near such high l\1ost of the tributaries of the Green River that have parts of the rim as Steamboat Mountain and Oregon their headwaters in the mountains bordering the Green Buttes, springs of good water. River Basin are perennial streams. A few of these, North of the Great Divide Basin on the Atlantic such as New Fork River, Blacks Fork, Hams Fork, side of the Continental Divide is a narrow strip of and Big Sandy River, are fairly large streams. Trib­ country drained by the Sweetwater River, a tributary utttries that do not rise in· the bordering mountains of the North Platte. The Sweetwater River gets vir­ tne all intermittent except for a few of the longer streams tually all its water from a few streams that rise in the such as Bitter Creek, which rises in Washakie Basin '"'-ind River Range. The drainage basin of the Sweet­ ttnd flows ttcross the Rock Springs uplift, and Salt Wells water has been so narrowed by headward erosion of Creek in the Rock Springs uplift. the streams on either side that its lateral tributaries Nearly everywhere the courses of the and la.rge are all short and intermittent. Some streams end in strettms are unrelttted to the structure of the rocks. "alkali slicks" before ever reaching the river. The Green River enters Green River Basin through a GEOLOGIC STRUCTURE canyon from the north, crosses the basin diagonally, and then leaves the basin on the south through a deep MAJOR STRUCTURAL UNITS canyon cut normal to the strike of the hard rocks that The part of Wyoming considered in this report con­ mttke the north flank of the Uinttt l\1ountains. Never­ tains four maJor structural units. The first two are theless, the westward tilt of the rocks along that reach Green River and Washakie Basins, each of which is a of the river from the Union Pncific Railron,d south large shallow synclinal basin. These are separated by nearly to the Wyoming-Utah boundary nppnrently the third unit, an anticlinal uplift of comparable size ctwsed the river to shift somewhat to the west n,s it known as the Rock Springs uplift. The fourth unit, cut downward; for, in general, the west side of the vnJley Great Divide Basin, lies northeast of the Rock Springs is precipitous, whereas the east side rises more gradually uplift. n1ong dip slopes. Bitter Creek and some of its tribu­ The Green River Basin is underlain by rocks of the taries, notably Salt Wells Creek, cross the ri~n of the '\\T asatch, Green River, and Bridger Formations. In Rock Springs uplift nearly at right nngles to the strike the central part of the basin, the rocks are virtually of the hogbacks. At each place where these strenms flat or are inclined at angles that exceed 1}~ 0 at only cross the rim, they have cut deep and rather narrow a few places. In a rather narrow strip around the AlO THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

margin of the basin, however, the bedo are tilted more described rather fully in three other reports-Schultz steeply: along the east rim they dip westward at (1909, 1910) and Sears {1926). angles ranging from 3 ° to 12 °, along the northern The major axes of these three major structural fea­ margin they dip 1 °-1}~ 0 southward, and on the west tures-Green River Basin, Rock Springs uplift, and side they dip eastward toward the axis of the basin at Washakie Basin-trend northward and are roughly angles of 2°-8°. parallel to the strike of the folded pre-Tertiary rocks Along the southern margin of Green River Basin, the both west and east of the area discussed in this report. structure is more complex. At Little Mountain the vVest of the Green River Basin the pre-Tertiary rocks rocks dip basinward a little more than 3°, but west­ are sharply folded. Seismic surveys and drilling have ward the inclination steepens, and where the basal beds shown that between these sharply folded pre-Tertiary of the Green River Formation cross the Green River rocks and the less steeply folded pre-Tertiary rocks in they dip about 35 ° northward. A few miles farther the Rock Springs uplift there are folds of intermediate west in the vicinity of Linwood, Utah, beds strati­ form which are now concealed beneath the Tertiary graphically a little lower are overturned and dip steeply beds of the Green River Basin. Presumably the axes to the south. These steep dips, however, are due to of these folds in pre-Tertiary rocks are essentially drag along a large fault that trends roughly parallel to parallel to the strike of the folded belt west of the the basin rim. A few hundred yards north of this Green River Basin and to the major axis of the Rock fault, which is known as the Henrys Fork fault, the Springs uplift. . structure of the Tertiary rocks is comparable with that Pipiringos (1962, p. A41-A74, pl. 1) described in along other parts of the basin rim, for the beds dip detail the structure of part of the Great Divide Basin. northward at angles ranging from 1° to 15°. The structure of the remainder of the western half is The structure of vVashakie Basin is like that of the well known from the development of a considerable Green River Basin. Like the Green River Basin also, number of oil and gas fields, notably the Patrick Draw the Washakie Basin is underlain by rocks of the field (Burton, 1961, p. 276-279), the Arch unit (Lawson Wasatch, Green River, and Bridger Formations; beds and Crowson, 1961), the Table Rock field (Mees, of Uinta age overlie the .Bridger, and the still younger Copen, and McGill, 1961), and the Desert Springs Browns Park Formation makes up a part of the com­ field (May, 1961). Other similar fields are the West plex southern margin. In the large central area the Desert Springs and Sand· Butte fields. Data from all rocks lie nearly flat, but around the edges they are these plus surface dips on the Wasatch Formation tilted up. Along the north and east sides, the beds reveal a rather gentle eastward slope of the beds into dip about 3 °-5 ° toward the center of the basin. Along the Great Divide Basin. The Wamsutter arch, first the west and southwest sides, they dip basinward at recognized by Schultz (1920, pl. 1) and now well angles ranging from 8° to 15°. The southern margin known, extends westward and southwestward from the of the Washakie Basin is defined by a zone of folds northern part of the Washakie Basin into the Rock and faults that extends westward from the town of Springs uplift and makes a structural southern bound­ Baggs, Wyo., to. the Kinney Rim, which forms the ary for the Great Divide Basin. western boundary of the basin. Most of the folds are rather gentle, having dips that range from 3° to 7°; FAULTS though locally, as in the vicinity of Baggs, the beds Most of the faults that cut the Tertiary rocks in this dip as much as 16°. Locally also along the faults, part of Wyon1ing are localized along. the margins of beds are flexed by drag. This faulted zone along the major uplifts of pre-Tertiary rocks. The one notable southern margin of the Washakie Basin has been de­ exception is the zone of faults along the southern scribed more fully in another paper. (Bradley, 1935.) margin of the Washakie Basin. The largest faults are The Rock Springs anticlinal uplift is formed of Upper along the north flank of the Uinta Mountains and the Cretaceous shale and sandstone units that belong to south flank of the Wind River Mountains, though ·near the southeast end of the the Baxter Shale and the overlying . another large fault displaces the Tertiary beds north of The axis of the uplift plunges northward and south­ Continental Peak and Oregon Buttes. This fault and ward from a high central part; and, in consequence, associated smaller faults extend northwestward from the uplift has, in plan, a crudely elliptical outline. there to Big Sandy Creek (T. 29 ~., R. 106 W.). The arch is asymmetric toward the west, on which Numerous faults cut the pre-Tertiary rocks of the flank the beds dip about 12 ° westward. On the east Rock Springs uplift. Some of these extend out into flank the beds dip 5° or 6 ° eastward. The structure the Tertiary rocks. At the north end o.f the uplift is a and stratigraphy of the Rock Springs uplift have been small group of faults in a locality where only Tertiary EOCENE ROCKS, WYOMING-COLORADO-UTAH All rocks are exposed. Along the west side of the Green ward where the fault trace makes an arc convex away River Bnsin, only one fn.ult cutting the Tertiary rocks from the mountt1ins. Observations at additional places, wns found. It is just west. of Piedmont in Uinta however, may show that this suggested generalization County. is not valid. WIND RIVER THRUST FAULT Hansen and Bonilla (1954, p. 15-18), since my This very large thrust fnult bounds the south flank reconnaissance mapping, added substantially to our of the vY ind River l\1ountains. The fault extends far knowledge and understanding of this great fault. back under the front of the range and dips at moderate They discussed various aspects of the Uinta fault rather angles. Although the fault is almost everywhere fully. One summary statement (p. 18) of theirs is concealed, much is known about it from exploratory quoted as particularly pertinent. drilling and frorn geophysical surveys. (See Berg, Where Tertiary rocks are involved in the faulting (just west 1961.) I lu1ve nothing from my own experience to add and east of Clay Basin) they display very little deformation to published interpretations of this major feature. despite their low competence and despite strong overturning in the immediately underlying Cretaceous rocks. It appears, UINTA PAUI... T AND UINTA l''LEXURE therefore, that at least two distinct periods of thrusting have The Uintn. fault coincides with a large and steep occurred on the Uinta fault, that the first and greatest move­ ment followed sharp OYerturning and rupture before Tertiary monocliHnl flexure thnt defines the northern front of time, and that the second moYement in Tertiary time and along the Uint11 rnnge for more than 100 miles. The fault the already established thrust plane, simply sheat;ed the Tertiary itself extends from Diamond Peak, in the extreme rocks without first flexing them or subsequently dragging them. northwest corner of Colorado, westwn.rd along the These same geologists (p. 14-15, 25) presented a good north fln.nk of the Uinta Mountains into Utah at least case for lateral displacement along the Uinta and as­ ns fa.r as Burnt Fork (south of T. 3 N., R. 16 E., sociated faults, saying that the displacement increases S.I.... l\1., Summit County, Utah). Westward beyond eastward as the throw on the Uinta fault increases. Burnt Fork the flexure apparently is not faulted, This lateral movement offsets fold axes that are roughly though the beds are steeply inclined and in p~aces are normal to the trend of the Uinta fault. According to nearly verticnl. Lamentably little precise information Hansen and Bonilla's map, fold axes north of the fault is available on this structure despite its long familia.rity have been moved as much as 7 miles west of their to geologists through the stereograms and text of counterparts south of the fault. _ Powell's report (1876, p. 177-179, 205-207). In a Powell (1876, p. 205) estimated the maximum dis­ reconnaissance survey of the Uinta l\1ountains, Schultz placement on the Uinta fault as about 23,000 feet. (1918, pl. 5) nutpped the Uintt1 fault fr01n its east This figure apparently includes displaceme~t due to the end westward net1rly to the west boundary of Daggett Uinta flexure also. According to n1y scattered obser­ County, Uta.h. l\1y own reconnaissance geologic map­ vations along the fault, the maximum displacement on ping in northern Utah between the longitudes of l\1anila the fault itself is approximately 13,700 feet in T. 3 N ., and Beaver Creek (T. 3 N., R. 15 E., S.L.M.) extended R. 23 E., S.L.M. There the stratigraphic interval the trace of the Uinta fault and flexure and yielded between the two sides of the fault is approximately the information from which the map shown on plate 1 12,300 feet. wt1S drawn. Westward from the vicinity of Phil Pico The Uinta fault evidently cuts the Uinta flexure at l\1ountain ('r. 3 N., R. 18 E., S.L.M.), Forrester least as far west as sec. 4, 'T. 2 N., R. 16 E., S.L.M., (1937, p. 645-646) evidently mapped as the westward Summit County, Utah, for there the fault cuts off the extension of the Uinta fault a different fault fron1 the Weber Sandstone. (See pl. 3.) It was not clear to one I mapped and refer to in this report u.s the Uinta me whether or not the fault is present a mile farther fault. His mapping of the geology around Phil Pico west (sees. 31 and 32, T. 3 N., R. 16 E.) where con­ l\1ountain and from there westwn.rd to Beaver Creek O'lomeratic undifferentin,ted Tertiary beds (at this par­ differs so much from mine that it is impossible to ~icular ph-tee evidently equivalent to the Bridg~r For­ reconcile the two maps. mation) abut the nearly vertical wall of Carbomferous The trt1Ce of the Uinta fault is decidely sinuous. . The relations are similarly obscure where In many ph1ces the plane of the fault is nearly or quite of limestone crosses the West vertical, but in other places it dips either southward Fork of Beaver Creek 3 miles farther west. or northward. On the basis of the limited observations now in hand, it appears that the fault plane is nearly For reasons that are not wholly clear to me, Ander­ vertical where the fault trace is essentially straight, man (1955, p. 132) believed that the Uinta fault does dips northward where the fault trace n1akes an arc not extend this far west. His interpr.etation was that convex toward the Uinta Mountains, a.nd dips south- the fault dies out just a few miles west of Sheep Creek A12 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

(in about sec. 8, T. 2 N., R. 19 E., S.L.M., Daggett remainder is overlapped unconformably by the relatively gently County, Utah)-that is, almost 18 miles farther east. dipping upper part of the Green River Formation. The angular discordance is present only where the Green River Formation HENRYS FORK FAULT laps highest onto the flanks of the Uinta Mountains at Phil The Henrys Fork fault extends from the Green River Pico Mountain and disappears rapidly northward. (T. 3 N., R. 21 E., S.L.M.) westward about 20 miles to My own interpretation of the geology of Phil Pico Phil Pico Mountain (T. 3 N., R. 18 E ., S.L.M.), where Mountain differs somewhat from Anderman's. Al­ it dies out. Throughout the greater part of its length though I did not recognize an within the it is a steep reverse fault, and the beds on its north or Green River Formation, I think its presence in that area downthrown side are steeply upturned or overturned in is plausible. Moreover, I think he was probably right the drag zone. Near its west end, however, it becomes in thinking that all or most of the conglomeratic mass a normal fault. of Phil Pico Mountain is a correlative of the Green The trace of this fault is gently curved except at two River Formation. Certainly many of the finer grained places in the valley of Henrys Fork JUSt north of the beds in the lower part have a distinctly Green River Wyoming-Utah boundary where it makes two abrupt aspect. However, because in my mapping of the con­ bends that are nearly at right angles to the general glomeratic facies there and farther west I was generally trend of the fault. At the southernmost of these bends, unable to discriminate between the vYasatch, Green the strike of the fault changes within a remarkably River, and Bridger Formations, I prefer to use the short distance from N. 40° E. toN. 80° W. (See pl. 3.) indefinite Tertiary undifferentiated. Contrary to The throw of the Henrys Fork fault can not be readily Anderman's interpretation, I believe that the Henrys determined, but it is Judged to be about 2,000 feet. Fork fault dies out in the conglomerates that makeup Anderman (1955, p. 132), however, estimated the throw Phil Pico Mountain, because I was not able to find any as about 12,000 feet on the east side of Phil Pico displacement or distortion of the conglomeratic beds Mountain. He also said (p. 131) that on the east on the west side of the mountain, whereas on the east flank of Phil Pico 1!Lountain there is "* * * an angular flank the upturned beds along the trace of the fault discordance of approximately 60° * * *" within the Green River Formation and in this same vicinity. He are conspicuous. (See fig. 3.) Indeed, the dip on these added: upturned beds decreases westward toward the top * * * a portion of the lower part of the formation is overridden of the mountain, and there it agrees approximately along the H enrys Fork fault by the , and the with the gentle northward dip that prevails throughout

FJGURE 3.-Part of the east fl ank of Phil Pico Mountain showing upturned conglomeratic beds of the Tertiary undifferentiated along the trace of the llenrys Fork fault. EOCENE ROCKS, WYOMING-COLORADO-UTAH Al3 the conglomeratic beds of the northern part of the the l\1iocene Split Rock Formation (Love, 1961a, p. mountain. 124; written communication, l\tfay 1962) down on the An unusunJ feature of the geology of Phil Pico north against the Wasatch Formation, but along its Mountain is the nearly level bench or platform of western part it brings the Bridger Formation down 1'riassic and J urn,ssic rocks upon which rest the north­ against the Wasatch and Green River Formations. ward-dipping conglomeratic Tertiary rocks that make In most places along the trace of this fault the rocks up the mountain. (See fig. 4 and structure sections, on both sides are flexed rather abruptly, so that close pl. 3.) This pln,tform apparently extends westward to the fault plane they dip 20°-48° northward. Nace beyond Phil Pi co l\1ountain; for in the valley of Birch (1939, p. 46, pl. 1), who mapped the eastern part of Creek, the (Jurassic) cr.ops out at the fault in considerable detail, found that it was cut nearly the s11me nltitude as it does at the east base of by many smaller cross faults and subparallel slices, the mountain. (See pl. 3.) The form of this platform especially in the vicinity of Continental Peak. At a suggests tha_t it may be a pre-Tertia1~y erosional place about 7 miles northwest of Oregon Buttes, N ace feature, perhaps a pediment. The northern edge of (p. 45-46) estimated that the Continental fault has a the pln,tform mn,y be an erosional scarp or, as it ap­ throw of 1,450-1,830 feet. Berman (McGrew and parently coincides with the trn,ce of the Henrys Fork Berman, 1955) mapped the western part of the fault, fault, n, fault scarp. If it is a fault scarp, as Anderman between Little and Big Sandy Creeks, and found that (1955, p. 131 and map) believed, it probably represents it was offset there also by transverse faults. pre-Green River movement along the Henrys Fork In the area mapped by Bermn,n, the Bridger contains fn,ult, because the 'I'ertiary beds there do not appear a large amount of light-gray to white tuff and, at the to me to have been disturbed by faulting. top, clay that resembles altered tuff. This sequence is overlain disconformably by a coarse poorly sorted conglomerate which Berman correlated (p. 109) with N ace's. Beaver Divide Conglomerate. I am not familiar with the Beaver Divide Conglomerate on Beaver Divide, but the conglomerate Berman mapped looks a good deal like a conglomerate that occurs in the upper parts of both Oregon Buttes and Continental Peak; indeed, it caps Continental Peak, which is

FJOUin; 4.-l!'iolrl sketch of tho west side of Phil Pico Mountain at its south end about 200 feet lower than Oregon Buttes. In Oregon showing the upturned 'l'ertlary conglomeratic beds (Tu) resting with angular Buttes this conglomerate is about 55 feet thick and discordance against the steeply dipping pre-Tertiary rocks. (Pre-T). consists predominantly of from the east end of the Wind River Range in a matrix of coarse white sand. The two structure sections in figure 4 show my This conglomerate and the overlying tuffaceous beds concept of the structure east and west of' Phil Pico presumably belong to the White River(?) Formation, l\1ountain. 'rhe crude notebook sketch reproduced which is of Oligocene age. on plate 3 shows the unconformable overlap of the Nace (1939, p. 46) estimated the throw of the Con­ Tertiary beds on the more steeply dipping tinental fault a few miles northwest of Oregon Buttes rocks. as 1,450-1,830 feet. Powell (1876, p. 177) referred to the Henrys Fork South of this fault, in T. 27 N., R. 101 W., is a sharp fn,ult as the Fln.ming Gorge Branch of the Uinta fault flexure that extends northwestward from Oregon Buttes and indicated that it was an abrupt flexure between the nearly to the Continental fault. It bends the beds of Green River and the rivers junction with the Uinta the Wasatch Formation down more than 250 feet on fn,ult a few miles en,st of Flaming Gorge. I was unable the south side.· The displacen1ent, which is opposite to find this flexui·e or any trace of the fault east of the to that of the Continental fault, diminishes northwest­ Green River, where the fault apparently goes into a ward. thick body of soft Upper Cretaceous shale. FAULTED ZONE SOUTH OF WASHAKIE BASIN CONTINENTAl.. FAULT The faults of this belt fall into. two broad groups, In the northern part of the area discussed in this according to their general direction of strike. The report, a fault which N ace (1939, p. 45-46) ca.Iled the faults of the dominant group strike generally westward; Continentn1 fn,ult extends from sec. 26, T. 29 N., R. those of the other group strike more nearly northward or 106 lvV., Sublette County, southeastward nearly 55 northwestward. The faults of the first group are miles. It is a normal fault whose plane is steeply apparently older, as they are cut by faults of the second inclined to the north. Along its eastern part it brings group. l\1oreover, the faults of the second group cut 732-705 0--1>4-2 Al4 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS beds of the Browns Park Formation, whereas the Mountains and its southeastward extension. The other faults in most places do not. However, some of northern margin is made up of the , the larger east-west faults were apparently active the Wind River Range, and the Granite Mountains. during the second stage of faulting, because locally It is less simple to measure the north-south dimension, they cut the Browns Park Formation. The mapping but it almost everywhere exceeds 100 miles. A roughly of the faults in this belt was materially improved by triangular extension of this basin runs far up between R. J. Hackman of the U.S. Geological Survey whore­ the Wind River and Wyoming ranges, and . another mapped the whole Washakie Basin photogeologically. rather irregular triangular extension runs equally far His photogeologic mapping is incorporated in the southeastward into northwestern Colorado. Neither of geologic map, plate 1. these extensions from the otherwise roughly rectangular MISCELLANEOUS FAULTS basin are given much consideration in this report, partly None of the numerous faults that cut· the pre­ because the Colorado area has been treated fully in a Tertiary rocks were studied as a part of this project. report by Sears (1924b, p. 292-295) and partly because A small group of faults that cut the Tertiary rocks at my acquaintance with the area in the angle between the the north end of the Rock Springs uplift were described Wind River and Wyoming ranges is inadequate. Only briefly in an earlier publication (Bradley, 1926, p. 123). the elliptical Rock Springs uplift near the center of this They are evidently related to the structure of the Rock great intermontane basin destroys its simplicity. Springs uplift. All t_he surrounding mountain ranges and uplifts The short normal fault near Piedmont, in Uinta named above were in existence at the beginning of the County, Wyo."(Tps. 14 and 15 N., R. 117 W.), trends Eocene Epoch, though the Uinta and Wind River a little east of north and passes just west of Piedmont. ranges were not as high as they later became. Pre­ It drops parts of the Wasatch and Green River Forma­ sumably, the floor of this great intermontane basin tions down on the west. The displacement, which is was not flat but had bulges and depressions. One of moderate, was not measured. Apparently 1nost of the these was the pre-Tertiary on which was later faults in the and its southward exten­ developed the Church Buttes gas field (Fidlar, 1950, sion are of pre-Eocene age, though Tracey, Oriel, and p. 87). The Church Buttes anticline is in the south­ Rubey (1961, p. B149) mentioned post-Wasatch normal · western part of the Green River Basin. According faulting. One of these large overthrust faults, the also to Fidlar (1950), seismic data indicate that on·e of Darby fault of Schultz (1914, p. 84-85), disappears the deep parts of the structural basin is in the southern beneath the Tertiary beds in the southwest part of part near the flank of the Uinta Range. The deepest T. 26 N., R. 113 W., a few miles south of LaBarge part, however, now seems to be along the front of Mountain. the Wind River Range not. far from the great thrust fault along which the ra.nge rose. (See especially INTERPRETATION OF THE STRUCTURE Berg, 1961.) There the celebrated Pacific Creek test PRE-TERTIARY DEFORMATION well had to penetrate approximately 20,000 feet to The following interpretation of the structural features reach either the Upper Cretaceous Frontier Sandstone just described will be focused on the Tertiary history of (Fidlar, 1950, p. 86) or, as some think, the Lower deformation to gain a better understanding of events, Cretaceous Muddy Sandstone (Jenkins, 1955, p. 154). particularly during the Eocene Epoch, that affected in The history and development of the basins in this any way the physical environment within which the large area are treated rather fully in a comprehensive Wasatch, Green River, and Bridger Formations were paper by Love (1960) on the sedimentation deposited. This is a necessary foundation to any con­ and crustal movement in Wyoming. According to sideration of the paleolimnology of the ancient Green Love, the Green River, Great Divide, and Washakie River lake and to a consideration of the paleoecology Basins have been downwarp areas since long before the of the enclosing Wasatch and Bridger Forn1ations. Cenozoic Era. In each of these basins the Accordingly, very little attention will be given to surface is today more than 20,000 feet below sea level. pre-Tertiary structural features. The configuration of these deep basins is shown in a Essentially, what we shall be concerned with is a general way on the Tectonic Map of the United States very large intermontane basin-one that extends (Cohee, 1962). roughly 150 miles eastward from the Wyoming Range The Rock Springs uplift was arched up by the end and its southward extension to the flanks of the Elkhead of the Cretaceous into a low dome whose flanks dipped Mountains in Colorado, the Sierra Madre, and the away from the axis at angles estimated to be about Rawlins uplift and its northward extension. The 1 ° or 2 °. This dip on the flanks of the ancestral Rock southern margin of this basin is defined by the Uinta Springs anticline is inferred from the fact that the lowest EOCENE ROCKS, WYOMING-COLORADO-UTAH A15 beds of the vVnsatch exposed around the flanks of the lift, however, did not reach its present structural relief uplift now dip only 1° or 2° less steeply than the Upper until somewhat later in the Tertiary, certainly not until Cretn.cous rocks; and as the Wasatch sediments were after deposition of the Bridger Formation. presumitbly deposited as virtually horizontal beds, The mountain ranges and hills that resulted from the Upper Cretaceous rocks rnust at that time have these major pre-Tertiary structural changes favored been inclined only 1° or 2°. According to these in­ sedimentation in the basins adjacent to the mountain ferred dips, the dome has a structural relief of 1,000- ranges. 2,500 feet, assuming its present outcrop width. It Apparently the downwarping of the floors of these surely had a broader base than this and consequently basins, 'Yhich began early in the Tertiary or before, must have stood higher. This dmne persisted as a continued more or less uniformly all through the Eocene topographic feature long enough to allow all of the and was primarily responsible for the continuous Ln.nce (Ln.rnxnie of Schultz, 1920), , Almond·. sedimentation of the Wasatch, Green River, Bridger; conl group n.nd Ericson Sandstone of the l\1esaverde and Uinta Formations. Thus, the Tertiary deposits (I-Iltle, 1.950, p. 55; :Hansen a:nd Bonilla, 1954, p. 24; described in this report owe not only their beginning Roehler, 1961, p. 96) to be eroded from large areas of but their full th:ckness to these major structural events. the steep west and southwest . flanks of the dome. The low stream gradients between this region and the l\1uch of this erosion must have occurred before the ocean apparently prevented the margins of these basins lowest part of the Wasatch Formation (of Schultz; from being cut downward. includes the Fort Union) was deposited, EARLY EOCENE DEFORMATION because the Wasatch overlaps the basset edges of these eroded formn.tions and members. Probably only Fort About the middle, or perhaps early, early Eocene, Union is involved in this overlap, as Roehler (1961, the forces which by the end of the Cretaceous had p. 96) reported that the Wasatch and Fort Union are folded the pre-Tertiary rocks sharply in the Wyoming conformable on both flanks of the uplift and that there Range and n1ore moderately a little way eastward is an angular discordn.nce between the Fort Union and acted again in essentially the same direction. This activity raised the mountains considerably, as is indi­ Upper Cretaceous rocks that ranges frmn 3 o to more than 8°. cated by great masses of coarse conglomerate in the On the other hand, Pipiringos (1962, p. A26) re­ middle and upper parts of the Wasatch Formation ported an unconfoflnity between the Wasatch and Fort along the north flank of the Uinta Mountains. Union, at least on the southeast flank of the Rock Subsurface data from sec. 30, T. 27 N., R. 100 W., Springs uplift near Bitter Creek station (T. 18 N., reveal several thousand feet of conglomeratic beds in R. 99 W.). He did not say, however, whether this un­ the Wasatch Formation (J. D. Love, written commu­ confol'lnity involves angular discordance or not. nication, May 1962). A comparable, though smaller, Hansen and Bonilla (1954, p. 10) reported that their conglomeratic mass occurs in the Wasatch For1nation Fort Union(?) Formation along the flank of the Uinta near the Wind River Mountains (T. 27 N., R. 102 W.) l\1ountains rests on the Ericson Sandstone of the and suggests that the Wind River Range was also l\1esaverde with an unconforn1ity that ranges "* * * uplifted then. Hansen and Bonilla (1954, p. 25-26) fr01n near concordance to great angularity." Never­ sununar,ized briefly these events in the orogeny of the theless, the Rock Springs· uplift persisted as a topo­ Uintas: graphic feature while 1nuch of the Fort Union (though Whatever the mechanics of the first uplift, it is clear that the according to Roehler, 1961, p. 98, it was thinned over uplift was strong and that deep erosion preceded deposition of the arch) and much of the Wasatch Formation were the earliest Tertiary beds. Despite strong uplift and deep dissection, however, the height of the range at this time probably deposited and while the greater part, and possibly all, was not great; judging from the lithology of the Fort Union(?) of the Green River Forn1ation was deposited. Evidence formation and the lower part of the Wasatch formation, erosion that the Rock Springs uplift existed as a topographic kept pace with ·uplift. By Fort Union(?) time erosion had feature is found in the distribution of the saline facies penetrated at least 8,500 feet, and possibly considerably deeper of the Green River Formation in the eastern part of into the pre-Tertiary cover of the range. By Wasatch time the range was eroded to its pre- core in the eastern the Green River Basin. Within a few miles east of the part of the area where the Uinta Mountain group became town of Green River, this thick saline facies changes exposed. into the shoal-water nonsaline facies that makes up During Wasatch time the range again began to rise. Coarse White Mountain, which is the escarpment facing the orogenic deposits about midway in the Wasatch section suggest west flank of the Rock Springs uplift. The significance a nearby source higher than the present Uintas. of this change in facies of the Green River Formation is These 1novements are also recorded by an angular discussed 1nore fully on p. A40. The Rock Springs up- unconformity in the Wasatch which both Powell A16 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

(1876, p. 164) and Sears (1924b,· p. 305-3'06) described (See Bradley, 1936, p. 170-179.) The data are i~ade­ in the vicinity of Vermilion Creek, Colo. The effects quate, however, to evaluate this erosion interval in of this early Tertiary deformation may have been terms of geologic epochs; consequently, the post-Eocene. restricted to the flanks of the mountain ranges and the deformation cannot be dated more closely than post­ margins of the adjacent basins, but they may also Eocene-pre-Miocene(?).

have included a slight deepening of the basins. Surely POST-MIOCENE DEFORMATION the increased height of the mountains had a marked Post-Browns Park (Miocene(?)) faulting and folding effect on the characteristics of the sediments and must along the margins of Browns Park near the Utah­ also have had a perceptible effect on the climate of the Colorado boundary, near Diamond Peak, and in the basin. Evidence· that compressive forces acted probably a valley of Vermilion Creek in Moffat County, Colo., have been discussed by Sears (1924a, p. 284-304). little later in the Eocene was presented by Anderman Post-Browns Park deformation in the fault zone along (1955, p. 131), who noted a local angular unconformity within the Green River Formation in the vicinity of the southern margin of the Washakie Basin and in other Manila, Utah. My own evidence for renewed tec­ localities along the Uinta Mountain front was also tonic activity at that time is restricted to a single discussed in my report (1936, p. 179-190) on the geo­ locality on the western margin of the Green River morphic history of a large part of the region considered Basin. There a narrow down fold just west of a in the present report. nubbin of Jurassic rocks (T. 22 N., Rs., 114 and 115 The post-Miocene faulting north and northeast of the W.) sank considerably while beds belonging to a Rock Springs uplift has been mentioned by McGrew tongue of the Wasatch Formation were being deposited. and Berman (1955, p. 109) and by Love (196la, p. This tongue of Wasatch lithology overlies a basal tongue 133-134). Presumably the faulting there occurred of the Green River Formation and underlies the main during the same epoch as that in the southern part of body of the Green River Formation, and as the Green the area. River Formation is of middle Eocene age, the defor­ STRUCTURAL EFFECT OF ORIGINAL DIP AND mation is closely dated. The geology of this small COMPACTION area is discussed more fully below. Some part of the gentle basinward dip of the rocks POST-EOCENE-PRE-MIOCENE(?) DEFORMATION that border the area considered in this report probably At some indefinite time after the Bridger Formation was caused not by the tectonic forces that defor1ned was deposited in the Green River Basin and before these older rocks but by the conbined effect of the the Bishop Conglomerate (Miocene(?)) was deposited, compaction of the Tertiary deposits and their original compressive forces accentuated the Rock Springs uplift basinward dip. This hypothesis can be tested by and steepened the dips locally to as much as 13 o. considering how these factors operate and then making Without departing from its original depositional dip, rough quantitative estimates of their probable magni­ the Bishop Conglomerate bevels the tilted Bridger and tudes. The compaction accentuates the original or Green River Formations and the more steeply inclined depositional dip by lowering the beds in the deep parts Upper Cretaceous rocks of the Rock Springs uplift. of the basin below the level at wl?-ich they were deposited The extensive erosion surface on which the Bishop The effect of the changes due to depositional dip will be Conglomerate was deposited indicates qualitatively that the post-Eocene deformation must have occurred considered first. appreciably earlier than the cutting of this erosion DEPOSITIONAL DIP surface. In the Green River Basin this extensive surface It is evident that the fluviatile beds had an original .bevels beds high in the Bridger Formation, and farther east it cuts progressively lower in the Tertiary; at Pine or depositional dip toward the center of each original Mountain and Diamond Peak (near the junction of structural basin which was about equal to the gradient Wyoming, Colorado, and Utah) it bevels rocks· that of the streams that deposited then1. But as these belong to a tongue of the Wasatch Formation which beds are predominantly fine grained, the original dip overlies the basal unit of the Green River Formation. probably did not exceed 1 or 2 feet per mile except in a These formations, therefore, must have been deformed rather narrow belt adjacent to the mountains. Thus long enough prior to the deposition of the Bishop Con­ the depositional dip of the fluviatile rocks of the Green glomerate to permit the removal of several thousand River Great Divide and Washakie Basins is a real but ' ' feet of beds over a large area and to allow for the reduc­ minor factor in accounting for the present basinward tion of the terrain to a remarkably smooth surface. inclination of the beds. The depositional dip of the EOCENE ROCKS, WYOMING-COLORADO-UTAH A17

lncustl'ine beds, which are generally even finer grained, were deposited. The beds of the Green River and wns pl'obnbly negligible. Wasatch Formations that now rest against the flanks of these hills dip away on all sides at angles ranging GRAVITATIONAL COMPACTION from 1° to 8 ° steeper than the general regional dip of REGIONAL l!:FFECT that locality. Within about 1 mile east of these Compaction can increase the depositional dip of buried hills, the dips flatten to angles of 2 ° or 3 °. sediments regionally nnd locnlly. Discussion of the These relations between locally steepened dips and effect of locnl difre .. entinl compaction will be deferred buried hills were observed at several places along the until the probnble mngnitude of the regional effect is west border of the Green River Bn.sin, but they are examined. Consider a column of Tertiary rocks in particularly well shown in sees. 5, 6, 7, and 8, T. 22 the centml pnrt of the Green River Bnsin. They are N., R. 114 W., and in sees. 1, 2, 11 and 12, T. 22 N., pl'edominantly fine grained and, therefore, capable of R. 115 W. considera.ble compaction. As each successive bed In many places the dips of the Tertiary beds steepen is deposited, those below are incrensingly compacted. markedly as they approach and overlap onto a surface Actunlly the rate of compnction decrenses ns fine­ of steeply dipping pre-Tertiary rock. This is espe­ gl'ained sediments are compacted; becnuse the original cially well shown in sees. 2 and 11, T. 22 N, R. 115 W., wlttel' must be squeezed out thl'ough more nnd. more where. the F.ontenelle Tongue of .the .Green River constl'icted pol'e capillnries (Terznghi, "1925n). As the Formation laps up against the dip slopes of the Beck­ l'n,te of accumulation of such fine-gn1ined mnterinl is with Formation. There the dips in the sandy beds ve1·y slow, howevel', it is likely that compnction about of the Green River Formation steepen 5°-10° within keeps pace with sedimentntion. Tn such a column of a few tens of feet of the Beckwith Formation. In sediments where compnction hns virtunlly ceased, this little area and, indeed, in other similar overlap both the thickness of It unit layer and its areas, the beds of the Green River and Wasatch decl'ease downwnl'd, but not at a uniform rnte. Formations genen1lly tend to blanket a steep pre­ Using dntn published by Athy (1930) nnd Hedberg Tertiary surface and to assume its same direction of (1936), I made a rough analysis of the probable maxi­ slope. Actually the angular discordance is con1monly mum compnctibility of the column of Eocene sediments large; nevertheless, the marked steepening close to the in the Gl'een River Basin, from which it appears that contact is conspicuous. Whether this steepening is difrerential compaction between the mnrginal and all due to differential compaction, I have some doubts. centra] parts of the Green River Basin may account It seems more probable that both abnormally high for a.bout 1° of the observed bnsinward dip. Depo­ initial dips and some subsequent deformation are sitionnl dip plus dip due to differential compaction might involved. account for the observed bnsinwnrd dips of 1 °-J?6° Differential compaction and other related features along the northern mnrgin of the Green River Basin, are also well shown in sees. 19 and 30, T. 22 N., R. but it is very impl'obable that the bnsinwm·d dips of 114 W. Here, small islands in the ancient Green 2°-8° along the western mn.rgin and 3°-12° observed River lake provided local sources of sediments. As a nJong the enstern margin of the Green River Basin result, the beds of the Green River Formation adjacent could be explained in this way. Dips steeper than to the foriner islands are somewhat coarser grained 0 n.bout 1U , thel'efore, must have been produced by and locally are even conglomeratic. Because these downwarping of the basin floors. coarse-grained facies grade abruptly into fine-grained sediments and were less compactible than the fine­ r ... OCAT... l

0 50 100 Feet

FIGURE 5.-Field sketch of shore features of Gosiute Lake on the crest of a hill of Jurassic limestone (Twin Creek Formation) in sec. 6, T. 22 N., R. 114 W ., Lincoln County, Wyo. The domelike forms at the left represent an algal reef, which rests on a coarse beach sand. Right of center is a small patch of angular limestone gravel that laps up on a limestone nubbin. These beach features formed when the limestone hill was a very small island near the western margin of Gosiute Lake. vicinity of the town of Green River. Beneath and the margin, all three formations become conglomeratic between some of these sandstone lenses, units of fine­ and are inseparable. grained sediments have been compressed to about one­ During the Green River epoch, fluvin,tile sediments fifth of their original thickness. (See fig. 16.) Such continued to accumulate around the margins of the features result in part from differential compaction and basin in a belt that narrowed when the lake expanded in part from differences in depth of the original tuff­ and widened when . the lake contnwted. The lake filled channels and from a conspicuous feature of the fluctuated repeatedly, and some of the changes were landscape for many miles along the cliffs in this locality. large. As a result of the continual shift of the shore­ (Seefigs. 11, 15.) line, the body of lacustrine sediments that Jnnlms up the Green River Formation interfingers or, on a larger STRATIGRAPHY scale, intertongues with fluviatile sediments of the san1e GENERAL RELATIONS BETWEEN THE EOCENE age but, by reason of its different lithology, belongs to FORMATIONS a different formatimi-either the Wasatch or the The greater part of this report deals with three Bridger. Actually, this interfingering of the two kinds Eocene formations (Green River, Bridger, and Wasatch) of deposits is common and is on a wide range of scales­ which are defined wholly by their lithology. In the some to be measured laterally in tens of feet, others to broadest and simplest terms, the Green River Forma­ be measured in tens of miles. Only those tongues or tion is a huge lens of fine-grained generally calcareous wedges of sediments that can be measured in miles of sedimentary rock embedded in a thick body of some­ lateral extent lutve been mapped and given strati­ what sandy mudstone that fills a large intermontane graphic names. The stratigntphic relations between basin (fig. 6). The body of mudstone is divided into these tongues and members of the Green River and the Wasatch Formation below the Green River and the Wasatch Formations are shown schematically in Bridger Formation above. In most of the basin the figure 6. The geographic distribution of these units three formations are readily separable because each has is indicated by their outcrop p~tttern on the geologic a distinctive lithology, though the boundary between map (pls. 1, 2). the Green River and Bridger is nearly everywhere Bridger and Wasatch time, on the other hand, are gradational and is uncertain in detail. Locally at the defined by distincti,·e vertebrate faunas, and Green margin of the basin the Bridger overlies the Wasatch Ri,·er time is defined by a distincti,·e flora. without a stratigraphic break. At other places along Students of both the vertebrate remttins and the fossil

Tb E

_l_b______Tb Tw Tw Tgl

Twnf Tgw Twc

Tw

FIGURE 6.-Diagramatic section showing the relations of the members and tongues of the Green River Formation to the tongues and main bodies of the enclosing Wasatch and Bridger Formations. Tb, Bridger Formation; Tgl, Laney Shale Member of Green Hivcr Formation; Twnf, New Fork Tongue of Wasatch Formation; Tgw, Wilkins Peak Member of Green River Formation; Twc, Cathedral Bluffs Tongue of Wasatch Formation; Tgf, Fontenelle 'l'ongue of Green Hiver Formation; Tgt, Tipton Tongue and Tipton Shale Member of Green River Formation; Twn, Niland Tongue of Wasatch Formation; Tglu, Luman Tongue of Green River Formation; Tw, Wasatch Formation. EOCENE ROCKS, WYOMING-COLORADO-UTAH A19 flora hn.ve long recognized thn.t Green River time is in of the characteristic structure. This structure, or fissility, may part equivalent to Bridger time and in part equivalent be defined as the capacity of clayey strata for splitting into somewhat uneven flakes, thin chips, and wedgelikc fragments to vV n.sn.tch time. approximately parallel to the bedding. Fissility is typically This thumbnail sketch of the relations between the developed in most of the clay rocks of finer texture and in Eocene formn.tions is intended only to orient the various unsorted mixtures, such as silty clay, sandy clay, and problem. 'fhe details of the stratigrn.phy n.nd correln.­ mud, and is commonly most conspicuous on weathered surfaces. tions n.re considered more fully in the following pn.ges. Although the term "shale" defines the size of the LITHOLOGIC TERMS USED constituent particles of the rock only within a general The descriptive terms n.pplied to sedimentary rocks range, it must imply that a large proportion of the generally ln.ck precision, n.nd n. few of them have a particles are thin and fln.kelike, otherwise the rock variety of mennings, th~ extremes of . which differ would not be fissile. These flaky pn.rticles may have widely. Because of this uncertainty, the terms used been deposited in that form, or they mn.y ha,·e grown in an earlier report (Bradley, 1931, p. 6-8) were defined within the sediments during compaction n.nd solidifica· and discussed rather fully. For convenience, those tion. The chu.rn.cteristic shn.pe, therefore, mn.y be definitions are sumnutrized here and the terms are used original or secondn.ry. Consequently, shnly is used again in this report. here to modify such rock names as mn.rlstone and Claystone and siltstone n.re both massive fine-grained mudstone to indicate that t-hey have either ·a slight or rocks defined by the size of the predominant grains. apparent fissility yet lack sufficient fissility to be According to Wentworth's classification (1 922), which regarded as shale. is followed for these rocks, the division between clay "Papery shale" is a term used here to designate and silt is at 0.004 mm (millimeter) and that between certain shnly orgn.nic mnrlstones that have a marked silt n.nd very fine sand, 0.0625 mm. Although the name tendency to split nlong orgn.nic-rich huninae. 11 claystone" is not intended to imply any particuln.r In genern.l, fissility becomes apparent only on weath­ minerology, it is likely that most of the crystnlline ered surfaces. Fissility may be, and commonly is, lacking or wholly obscure in the completely fresh rocks grains less thn.n n.bout 0.004 mm in diameter belono-b to the general group of clay minerals or the closely related that one sees in drill cores or in mines. Judged by hydromicas. But these clay minerals and hydromicas such fresh rocks, the Green River Formation would be are not by n.ny men.ns restricted in. size and may be of regarded as predominantly mn.ssive marlstone and such dimensions as to be properly classified as silt or mudstone. even as sand. 'I'he adjectives 11 clayey" and "silty" The term "tuff" is used in this report to mean any imply an appreciable content of either clay- or silt-sized bed that consists largely of volcanic ash, whether the particles. volcanic constituents have been much altered or not. Virtually all the tuffs in the Green River Formation ~1udstone is also a fine-grained massive rock, but it consists of an indefinite mixture of clay- silt- and were deposited in n, lake. Those in the Bridger and ' ' sn.nd-sized grains, and therefore the tenn is more post-Eocene formations were deposited in shallow lakes general than" claystone" or" siltstone." Consequently, or were more or less extensively reworked by streams. the adjective "n1uddy" signifies a rock that has an Oil shale is a fine-grained sedimentary r.ock contain­ admixture of enough particles smaller than fine sand ing organic matter which was derived chiefly from to change its general aspect. aquatic organisms, waxy spores, and pollen grains; Marl and madstone are used as defined by which is only slightly soluble in ordinary petroleum Rosen busch (1 923): solvents; and of which a large proportion is distillable into a liquid similar to petroleum. Despite the name, Marl and dolomitic marl are intimate mi.xtures of crystalline , occasionally of dolomite, with clayey substances whose most rich beds of oil shale in the Green River Fonna­ character is not well known. In such mechanical mixtures the tion cannot be regarded strictly as shale. Instead, individual constituents vary between the widest limits and they are dolomitic marlstones rich in orgn.nic matter. indeed, they show transition forms between limeston~ and Nevertheless, a few are shaly. On the other hand, dolomite on the one hand and clays and on the other. many low-grade oil-s~ale beds are papery slw.le. By The hn ..rder vn.rieties of mn.rl he cn.lled mn.rlstone. Soft low grade is meant any oil shale that will yield less mn.rlstone thu.t hn.s n. chalky texture is referred to as than 10 ,gallons o'f oil per ton of ro.ck. This division chn.lky rnnrlstone. between low- and high-grade oil shale is arbitrary and Shn.le is regarded as a structural term coordinate is adopted merely as a convenience in exposition. I with slate, as advocated by Lewis (1924), who wrote: have used it here in the same sense that I used it It implies no particular composition except so far as certain in earlier reports. materials of fine texture lend themselves to the development W. C. Culbertson of the U.S. Geological Survey, in A20 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS criticizing this manuscript, reminded me . that color The late Roland W. Brown, of the U.S. Geological should be mentioned as a significant criterion in rec­ Survey, told me that he collected fossil plants and ognizing oil shale in the field. All oil-shale beds of the of Paleocene age from a thick section of Green River Formation are some shade of brown, sandstone and mudstone beds just west of Rock though some of the richest beds are almost black; Springs, on the south side of Bitter Creek, in the se­ generally those that are· this dark have a light-gray or quence of beds that Schultz included in his Wasntch. even bluish-gray bloom on weathered surfaces. In the upper part of the Wasntch, ns here defined, are three tongues that interfinger with the lower part WASAT"CH FORMATION of the Green River Formation. These tongues have DEFINITION AND AGE been mapped and named. Little study was given to The Wasatch Formation of early Eocene age is a the main body of the Wasatch Formation, but it con­ thick body of fluviatile sediments that is widely ex­ tains at least one large sandstone unit, several con­ posed in the area. It was named by Hayden (1869, glomeratic facies, and several possible lacustrine lenses p. 90) for exposures in Echo and Weber Canyons, or facies that could be mapped. .Separating the lower Utah. In a later report (1871) he noted that these part of the Wasatch from the Fort Union is doubtless beds, which are conglomeratic in Echo and Weber possible, but the boundary would require rather Canyons, grade eastward into variegated sandy clays critical study. and· sandstones. In the area treated· in this report, Along the west side of the Green River Basin, I variegated sandy mudstone is the predominant rock have distinguished only the mnin body of the Wasatch type in the Wasatch; though local facies are charac­ Formation and one tongue of the Wasatch, the New terized by sandstone, carbonaceous shale, , or Fork Tongue. As in other parts of the area covered conglomerate. STRATIGRAPHIC UNITS in this report, my investigation was restricted mostly to the upper parts of the main body of the Wasatch­ The Wasatch is treated in this report as one forma-. approximately equivalent to what Veatch (1907, tion, though it includes at its base the Fort Union p. 87-96) called the Knight Formation. Steven S. Formation of Paleocene age. For the purposes of this Oriel, of the U.S. Geological Survey, redefined (unpub. report this will not make a great deal of difference, data) and divided the Wasatch into two members and because we shall be concerned primarily with the upper two tongues. The two members of what I hnve shown half of what is here called Wasatch. Wasatch, as (pl. 1) simply as Wasatch are the Chappo l\1ember at used here, is apparently equivalent to the main body the base, which is of Paleocene age and perhaps in of the Wasatch Formation as used by Oriel (1961), though his two members were not identified. Swain part also of Eocene age, and the unconformably over­ (1957) reported 1,530-1,750 feet of Fort Union about lying La Barge Member, which consists chiefly of red 10 miles north of Baggs, Wyo. The lower part of and variegated mudstone and muddy sandstone. The these beds contains an early Paleocene flora and a two tongues of the Wa~atch are the New Fork Tongue middle Paleocene fauna. Swain also reported that (used in this report, pl. 1) and a higher tongue which the Fort Union there rested conformably on the under­ Oriel (1961, p. B152) referred to simply as upper tongue. lying Lance but was overlain along an angular discord­ I think that this upper tongue probably is restricted ance by the Wasatch Formation. The approximate to the northwestern part of the Green River Basin. boundary between theW asatch and Fort Union is shown In the same paper Oriel (1961) listed seven genera of on the "Geologic :rvlap of Wyoming" (Love, Weitz, and vertebrate fossils collected from his Chappo Member Hose, 1955), though the small indefinite area of Fort and referred b:v C. L. Gazin, of the U.S. National Union shown on the west flank of the Rock Springs l\1useum to the Paleocene. Oriel listed also a number uplift is probably much too short. Additional mapping ' of the Fort Union is much needed in that area. of freshwater clams and snails and land snails collected According to Pipiringos (1962, p. A26), from the Chappo l\1ember. These were studied by D. W. Taylor, of the U.S. Geological Survey, who "* * * the upper part of Schultz' 'Wasatch' is about 1,400 feet thick and is separated from the lower part by an unconformity. reported that the land snails, which in places were The beds below the unconformity (the lower part of Schultz' numerous, have Eocene affinities but that the fresh­ 'Wasatch') are about l,lOO feet thick, contain plants of Paleocene water forms have Paleocene affinities. Few new age, and rest unconformably on the of age." vertebrate fossils or mollusks were ·found in the over­ The locality he described is along the southeast flank lying La Barge l\1ember of the 'Vn,sn,tch. This member of the Rock Springs uplift near Bitter Creek station on is considered tts of middle(?) ~tnd late early Eocene a

FIGURE 7.-Banded gray and red mudstone close to the lop of the Wasatch Formation in the valley of Red Creek in sec. 24, T. 13 N., R. 104 W., Sweetwater County, Wyo. The flat top of Little Mountain ~hows on the skyline at the right and Richards Peak shows to the left of center in the distance.

Pipiringos (1962, p. A14) applied the name Red tonguing relationship with adjacent formations. The Desert Tongue to that part of' the Wasatch lying Red Desert Tongue is equivalent to what I am calling between the and the base of the the main body of the Wasatch in this report. Future lowest tongue (Luman) of the Green River Formation. work may show that the Red Desert Tongue of Pipirin­ He reported that this part of the Wasatch is about 1,000 gos and my main body of the Wasatch are actually feet thick on the east flank of the Rock Springs uplift equivalents of Veatch's Knight formation. Gazin and there rests unconformably on the Fort Union. Ver­ (1959, p. 134) indicated this correlation on ·the basis of tebrate fossils he collected in sec. 12, T. 23 N., R. 100 his extensive studies of the Rocky Mountain Tertiary W., indicate an earliest Eocene (Graybull and Sand formations and their vertebrate faunas. Schultz (1 920, Coulee) age for the beds near the base of his Red Desert p. 29) referred to this part of the Wasatch simply as the Tongue. Pipiringos ~lso listed (p. A15) other fossil Wasatch Formation, inasmuch as he regarded the vertebrates and found near the top of the Cathedral Bluffs as a member of the Green River Wasatch in the Great Divide Basin which indicate an Formation. Sears and I (1924, p. 98- 99) later expressed early Eocene age. The fossil plants he found were the concept that the Cathedral Bluffs should be determined as of Eocene age. thought of as a tongue of the Wasatch Formation. McGrew and Roehler (1960), reported vertebrate Over the greater part of the area covered by this fossils from the Wasatch on the west flank of the Rock report, the main body of the Wasatch consists pre­ Springs uplift (sees. 7, 8, and 17, T. 18 N., R. 105 W.) dominantly of sandy gray mudstone in which lenses and that also indicate a early Eocene (Graybull) age. From irregular beds of sandstone are fairly common and beds above those in whi~h these fossils were found, locally are plentiful. The mudstone of most parts of they reported additional vertebrate fossils that suggest the area is only streaked with red bands, but, locally, a Lysite age. layers of red mudstone and claystone are so numerous In this report I have not used the name Red Desert that the formation appears to be predominantly red­ Tongue because over almost the whole large area for example in the area southwest of the Rock Springs covered by the map (pl. 1) the Wasatch, below the uplift. (See fig. 7.) Southeast of the Rock Springs lowest Green River tongue, does not have an inter- uplift in the basin of Vermilion Creek, however, the A22 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Wasatch is prevailingly gray, even including the sand­ north of Rock Springs (T. 19 N., .R. 105 W.), where stones. The name "Red Desert" as used within the the thickness is 1,780 feet; along Salt Wells Creek (Tps. Great Divide Basin, north of Washakie Basin, takes 13 and 14 N., Rs. 103 and 104 W.), where the thick­ its name from the reddish soil derived from the few red ness is 2,565 feet; and in the western part ofT. 14 N., mudstone layers in the Wasatch. R. 101 W., where the thickness is 3,000 feet. All these Carbonaceous shale and lenticular beds of subbitumi­ sections, except perhaps Nightingale's, it should be nous coal are rather common in the upper 3,000 feet of understood, include an unknown amount of Paleocene the main body of the Wasatch. In the basin of V er­ rocks at the base. milion Creek, southeast of the Rock Springs uplift, Although the main body of the Wasatch is regarded and in the Great Divide Basin, coal beds and car­ as a single , significant departures bonaceous shale are locally common. In a few places from the usual lithology were observed in several parts these coal beds have been mined for domestic use. of the area. These changes evidently reflect local en­ The in the central part of the Great Divide vironments at the time the formation was deposited, Basin have been studied by Pipiringos (1962, p. A41- though some may reflect tectonic changes. A59), who gave analyses as well as a great deal of At several places along the north flank of the Uinta information on the distribution and thickness of the Mountains, the Wasatch contains thick units of coarse individual beds. Nearly .all these coal .beds centain conglomerate. One of the most notable of these is the from 0.001 to 0.003 percent . Locally, how­ conglomerate that makes up Richards Peak, just ever, parts of these beds contain no uranium, whereas north of the Wyoming-Utah boundary in the southern in other places parts of beds contain as much as 0.026 parts of T. 12 N., Rs. 105 and 106 W. This con­ percent. glomerate is in the upper part of the Wasatch Forma­ The sandstone lenses and beds scattered through the tion, is approximately 2,700 feet thick, and makes a thick body of Wasatch mudstone range widely in tex­ high ridge several miles long. Pebbles, cobbles, and ture, color, and structure. Fine- to medium-grained boulders of limestone predominate, but those of red buff massive to crossbedded sandstone lenses are rather quartzite are almost equally abundant. The lime­ common around the Rock Springs uplift. Gray car­ stone evidently was derived from the Carboniferous bonaceous medium-grained sandston~ beds and rusty limestone hogbacks along the north flank of the Uinta brown crossbedded lenses are also common in the same Range. Indeed, some of the boulders contain. Penn­ locality. These three types of sandstone may have sylvanian fossils (James S. Williams, oral comnlunica­ been derived from Upper Cretaceous rocks eroded from tion, 1931). The red quartzite plainly came from the the Rock Springs uplift, for they resemble the Upper great mass of red quartzite that makes up· the central Cretaceous sandstones and many of the false beds in part of the Uinta Range and that is known as the the cross bedded Wasatch sandstones dip away from Uinta Mountain Group. Pebbles ·and cobbles of the flanks of the uplift. Sandstone beds and lenses in white quartzite and hornblende schist quite as plainly the main body of the Wasatch in other parts of the came from the Red Creek Quartzite, whose only outcrops area range in texture from that of fine sand to con­ are in that part of the Uinta Range just a few miles glomerate and in color from buff to dark rusty brown, south and southeast of Richards Peak. All the kinds of from dark red through pink to white, and from light rock found are fresh and range in shape from angular gray to nearly black, depending upon the quantities of to fairly well rounded. They have an extreme range dark minerals and carbonaceous material. in diameter from about half an inch to more than 5 feet, The main body of the Wasatch Formation differs in but m·ost of the conglomerate is rather well sorted and thickness from place to place because it was laid down and consists of pebbles 1-2 inches in diameter. Locally, upon an uneven surface. Along the Wyoming-Utah however, thick lenses consist chiefly of cobbles that are boundary near Richards Peak (T. 12 N., Rs. 105 and 4-8 inches across. A matrix of coarse buff sand 106 W.), the Wasatch is approximately 7,000 feet thick, fills the interstices of the conglomerate. The con­ but how much of this should be assigned to the Fort glomerate here has been tilted, so that it dips 23 ° Union is unknown. About 35 miles southeast of Rich­ northward, and as a result of differential movement ards Peak, in the vicinity of Vermilion Creek, Nightin­ during the tilting, many of othe cobbles and boulders gale (1930, p. 1021) measured the thickness of the main have been sheared. body (his Lower Wasatch or Hiawatha 1/fember) of the Below the conglomeratic facies, the Wasatch Forma­ Wasatch Formation as 4,500 feet. Sections of the part tion consists of sandy mudstone that contains only a of the Wasatch exposed around the Rock Springs uplift few widely spaced lenses of sandstone. Above the were measured at the following localities: About 3 miles conglomeratic facies is a considerable thickness of red EOCENE ROCKS, WYOMING-COLORADO-UTAH A23

nnd gray bnnded snndy mudstone thnt contains many nre characteristically ill-sorted mixtures of mud, sand, ~hort itTegulnr lenses of conglomeratic sandstone. cobbles, and boulders. This bnnded unit is overlnin by it thinner unit of The occurrence of these coarse conglomeratic facies flnky cnrbonaceous shnle that contains thin layers of along the north flank of the Uinta lVlountnins nt approxi­ lignite, shell marl, sandy gray clay, and persistent, mately the same stratigraphic position in the main body regulnr thin beds of sandstone. As mentioned nbove, of the Wasatch suggests that they were produced by the whole formntion nt this plnce is npproximately tectonic changes in the regimen of the streams draining 7,000 feet thick. the adjacent parts of the Uinta Range. No other A few miles east of Richards Penk is Tepee l\1ouutnin, evidence, however, of uplift of the eastern part of the a lnrge sprawling feature made up of a similnr con­ range was recognized in the vVasntch Formation of that glomeratic facies of the vVasatch. This conglomeratic locality. mass extends nbout 10 miles along the strike. The In working out the tectonic history of the area, it is rocks nre not well exposed, but uppnrently the con­ probably significant that the vVasatch along the western glomerate merges southeastward into mudstone in side of the Green River Bnsin does not eontain these T. 3 N., R. 25 E., S.L.l\1., Daggett County, Utah. large conglomeratic fa.cies except locally in the vicinity A thin zone of course-grained conglomerate was found of La Barge a.nd Fontenelle creeks (Steven S. Oriel, ia the Wasatch n, few miles northwest. of Oregon Buttes written conununicn.tion, 1957). These ··western con­ (T. 27 N., R. 102 vV., Fremont County, 'Vyo.). This glomerates, unlike those along the Uinta l\1ountains, conglomerntic facies makes a ruther large strike ridge are poorly sorted and have a. muddy matrix. that extends west from the base of Oregon Buttes. A red sa.ndstone facies n1a.kes up the middle part of The beds consist of wholly unsorted material that ranges the main body of the Wasatch Formation in the valley in size from conrse sand to boulders ns much as 13 feet between the Rock Springs uplift and the escarpment of across. l\1ost of the large boulders are of granite and the Green River Forma.tion that makes the. eastern are rounded or subangular; the smaller pieces, of rim of the Green River Basin. This fa.cies extends schist, are angular. Southward and in both directions northwestward nea.rly to the Union Pacific Railroad. along strike, this conglomerate grades iQto mudstone Where best exposed (T. 16 N., R. 105 vV.), this san~­ that is typical of most of the Wasatch exposed in this stone unit is several hundred feet thick and forms a area. high rocky ridge whose cliffs and slopes resemble· ex­ Along the eastern and northeastern margins of the posures of the red quartzite of the Uinta l\1ountain Great Divide Basin, Pipiringos (1962, p. A34-A35) and Group. The sandstone in the Wasatch, however, is Masursky (1962, p. B10-B14) described a great fan of softer and more friable and is more irregularly bedded. course-grained to pebbly arkosic sandstone (the Battle It is a coarse-grained crossbedded sandstone that ranges Spring Formation) that interfingers westward and in color from brick red to a rather dull purplish red. southwestward with all of the subdivisions of the Locally it is gravelly or even conglomeratic. H. W. Wasatch and Green River Formations except the Roehler of the Mountain States Fuel Supply Co. (oral Laney Shale Member of the Green River. This great communication, Aug. 1963) interpreted this red sand­ bulk of arkose was derived from the Granite l\1ountains, stone facies as a sand mass derived from the Upper which lie northeast of the area shown on the geologic Cretaceous sandstone formations of the Rock Springs nutp, plate 1. (See, however, fig. 10.) Uplift, which were arched up along the Wamsutter The coarse conglomerates in the main body of the Arch during middle Wasatch time. The axis of the Wn,satch were evidently deposited by vigorous streams Wamsutter Arch extends from the vicinity of \i\1am­ that emerged from either the Uintn, Wind River, or sutter, Wyo., southwestward diagonally across the Granite l\1ountnins onto an nggrnding alluvial plain. central part of the Rock Springs Uplift, whose axis The nbundnnce of rather well rounded cobbles and runs generally north-south. The fact that this great boulders of unweathered rock suggests that the streams sandstone lens dies out into mudstone both southward were nctively cutting in mountnins of considerable and northward lends strong support to Roehler's height. Furthermore, in the thick conglomerate at interpretation. Richards Peak the small qun.ntity of muddy sediment, NILAND TONGUE the moderately good sorting of thick units of the Pipiringos (1962, p. A24-A29) separated from the conglomerate, nnd the matrix of conrse snnd suggest lower part of what I had n1apped near Wamsutter that the streams, in that locality nt lenst, hnd a rather (Bradley, 1945) in 1933 as Tipton Tongue of the Green uniform flow and were not subject to recurrent tor­ River Formation an additional tongue of the Wasatch rentinl floods. Deposits produced by torrential floods Formation, the Niland Tongue. He mapped this A24 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS tongue northward and northwestward fron1 the north mapped them from there southward into Colorado. rim of the 'Vashakie Basin out into the Great Divide This work is discussed rnore fully on pages A29 and A30 Basin where it passes beneath the Tipton Tongue of the under the subheading "Lun1an Tongue." Green River Formation. (See pl. 1.) Northeastward In the basin of Ver1nilion Creek, southwest of the Niland Tongue grades laterally into the coarse­ Washakie Basin, the Niland is nearly everywhere less grained arkosic sandstone of the Battle Spring Forma­ than 100 feet thick and contuins several units of brown tion. flaky shale that rese1nbles the shale in the underlying At its type locality (T. 24 N., Rs. 95 and 96 vV.) the and overlying tongues of the Green River Formation. Niland Tongue of the Wasatch Formation is about 400 The remainder of the Niland Toague in that ttrea, feet thick and consists of characteristic Wasatch however, is characteristic of the Niland farther north. lithology-that is, predominantly gray mudstone and The most distinctive aspect of the Niland in this part gray to nearly white lenticular sandstone beds. Inter­ of the area is a nearly white very lenticular tuff. bedded with these are thinner beds of carbonaceous (See fig. 8.) This is a crystal tuff that consists ahuost shale and coal beds. wholly of small sharply angular crystals of quttrtz and Pipiringos reported fossil plants and mollusks from feldspar. the middle part of the Niland which indicate an. early Along the southeastern edge of the basin of Venuilion Eocene age. lVIcGrew and Roehler (1960, p. 158) Creek the Niland thickens rather rapidly and assumes reported finding a rather large vertebrate fauna in the a wholly Wasatch aspect. Along the west side of this Niland along the northwestern margin of \i\7 ashakie basin the Niland Tongue thins to about 65 feet in Basin (sec. 8, T. 18 N., R. 98 W.). They characterized sec. 4, T. 12, N., R. 101 W., and pinches out entirely this fauna as a typical Lost Cabin fauna. between there and Canyon Creek (sec. 18, T. 12 N., Eastward the Niland grades into the Battle Spring R. 101 VV.), about 3 miles farther southwest. Formation and loses its identity. Northwestward it Around the northeastern margin of the Washakie becomes the uppermost part of the main body of the Basin, the Niland contains near its top a rather remark­ Wasatch because the Luman Tongue of the Green able canneloid subbituminous coal bed. This coal bed, River Fonnation disappears in that direction. In the which is 6 feet thick, can be traced at least 4 rniles along vicinity of Steamboat Mountain, near the north end the outcrop. .M.icroscopic examination of thin sections of the Rock Springs uplift, neither the Luman nor the of the coal shows that it contains a considerable quan­ Niland Tongue can be identified. Pipiringos and I tity of pollen and leaf-cuticle residues, which give it a traced the Niland and Luman Tongues 6-8 miles canneloid aspect. The most unusual feature, however, southward along the east side of the Washakie Basin is the occurrence in its joint cracks and along bedding and 10-15 miles southward along the west side of the planes of the rare minerals tschermigite, an arnmonium

Basin. The boundarie3 of these tongues are shown alum [(NH4)Al(S04)z+ 12H20], and ammoniojarosite accurately around the north end of Washakie Basin [NH4Fe3 (S04)z(OH) 6]. Also present is the rare mineral 2 where Pipiringos mapped them (sees. 6 and 7, T. 19 melanterite [Fe+ S04·7H20]. The tscherrnigite is rather N., R. 94 W., and Tps. 19' N., Rs. 95 and 96 W.). plentiful, and the ammoniojarosite is cmnmon but less Southwestward from there I had sketched these abundant than the tschermigite. E. T. Erickson of boundaries on aerial photographs. In 1958 J. D. the U.S. Geological Survey published (1922) an analysis Love of the Survey revised my boundaries in the field of the tschermigite and a description of the tscher­ and adjusted them to the topography of the Anny migite and anunoniojarosite. At that time it was the Map Service 1:250,000 rnap. Around the north­ first recorded occurrence of tscher1nigite in the United eastern part of the Washakie Basin I have sketched, States and the first record of mnmonica.l jarosite. without control, the boundaries of the Niland and Since then both tschermigite and armnoniojttrosite Luman Tongues southeastward until they die out. have been reported from southern Utah (Shannon, (See pl. 1.) The base of the Luman Tongue, however, 1927). was mapped by planetable and telescopic alidade· in The canneloid coal has been mined for lomtl use, 1933, at which time I regarded it as the base of the Tipton Tongue of the Green River Formation. and one tunnel about 150 feet long in sec. 7, T. 19 N., In the faU of 1957, Dwight Taylor and I identified R. 94 W., has been ruined out to rnake a rather ln,rge the Niland Tongue of the Wasatch and the Luman room. A sample taken from the working face in this Tongue of the Green River on the west side of Washakie room has the following analysis, which was n1ade by Basin (sees. 14, 15, 23, 24, T. 15 N., R. 101 W.) and the U.S. Bureau of Mines. EOCEN E ROCKS, WYOMIN G- COLORADO- UTAH A25

FIGURE 8.- White crYs tal tuff about 22 feet t hick in the upper part of the N iland Tongue of the Wasatch Formation close to the SW cor. sec. 4, T. 12 N., R. 101 W ., Sweetwater Coun ty, Wyo. The man is standing on t he base of the tuiT, which is lent icular along the strike. At this place the Niland is about 65 feet thick.

Analysis of canneloid coal from the Niland Tongue of the Wasatch site in the coal, as the tschermigite was rather carefully Formation picked from the sample before analysis. [D ata in weight percent] As M oisture Pipiringos (1962, p. A59) mentioned that this canne­ receive d and ash fr ee Moisture ______loid coal bed thins rather abruptly westward along the 9. 9 north rim of the Washakie Basin. He discussed Volatile matter______45. 0 52. 5 Fixed carbon ______40. 7 47. 5 briefly other coals in the Niland farther north in the Ash ______4. 4 Great Divide Basin. At three localities in Tps. 24 N ., Rs. 95 and 96 W., 100. 0 100. 0 Pipiringos (1962, p. A12) collected fossil plants from

}lydrogen ______4. 5 3. 9 the Niland Tongue which Roland W. Brown of the C arbon------~------51. 8 60. 4 U.S. Geological Survey identified as of Eocene age. Nitrogen ______1. 9 2. 3 Pipiringos (1962, p . A12) also collected ostracodes Oxygen ______33. 8 29. 2 from T. 24 N., R. 95 W., which were identified by R. E . Sulphur ______3. 6 4. 2 Ash ______P eck of the University of Missouri. Peck expressed 4. 4 the opinion that they represented a Paleocene or early 100. 0 100. 0 Eocene age. W . C. Culbertson, of the U.S. Geological Survey, The analysis shows that this coal has a much lower showed in the field (Aug. 1963) that either the Niland ash and moisture content than do the other Wasatch Tongue of the " rasatch Formation, or its homotaxial coals, analyzed for Pipiringos (1962 , p . A44- A45). equivalent, extends for several tens of miles along the This coal also contains somewhat more nitrogen and east side of the Green River Basin from the east flank sulfur than is found in most subbituminous coals. of Little Mountain northward almost to the south Presumably the high contents of nitrogen and sulfur flank of Wilkins Peak. Along this escarpment the are accounted for by smae amounts of ammoniojaro- Niland Tongue, or its equivalent, is about 200 feet A26 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

thick and has much the same lithology as the underly­ 1,300 feet. At Pine Butte (T. 16 N., R. 100 W.), ing main body of the Wasatch Formation. This Schultz gave the thickness as 740 feet. But as Love tongue of the Wasatch is separated from the main body illustrated (written communication, 1964), subsurface of the Wasatch by a thin tongue or, lens, of brownish­ data from only about 9 miles farther southeast (sec. buff lacustrine beds, which is evidently the homotaxial 35, T. 15 N., R. 99 W.) show that the Cathedral equivalent, or perhaps was once the actual extension, Bluff thickens to about 2,340 feet. Indeed, Love's of the Luman Tongue of the Green River Formation. figure shows that in several wells within the Washakie

CATHEDRAL BLUFFS TONGUE Basin the Cathedral Bluffs is about this thick but thins markedly, both east and west, toward the outcrops The Cathedral Bluffs Tongue of the· Wasatch Forma­ around the margins. On the northeast side of Washakie tion encircles the greater part of Washakie Basin. Basin, east of Barrel Spring (in T. 17 N., Rs. 93 and 94 Southeast (Tps. 12 and 13 N., R. 93 W., Carbon W., Carbon County, Wyo.), the Cathedral Bluffs is County, Wyo.) of Washakie Basin, wher~ the Tipton only 115 feet thick. Tongue of the Green River Formation dies out, the Vertebrate fossils are rare in the Cathedral Bluffs Cathedral Bluffs Tongue becomes part of the main Tongue, but Morris (1954, p. 195-199) collected a body of the Wasatch Formation. The Cathedral surprisingly large number of bones at four localities Bluffs Tongue is also exposed north of the Rock along the northeast side of the Washakie Basin (T. Springs uplift. From that locality it has been traced 15 N., R. 93 W. toT. 19 N., R. 95 W.). He regarded eastward as far as T. 26 N ., R. 95 W ., where it loses its (p. 199) these as indicative of middle Eocene age identity in the Battle Spring Formation of Pipiringos ("* * * between Lost Cabin level and Bridger B, (1962, p. A32). Westward it thins and fingers out into perhaps being represented by the rarely fossiliferous its stratigraphic and time equivalent, the Wilkins sediments of Bridger A * * *"). Gazin (1959) later Peak Member of the Green River Formation in T. 24 reviewed Morris' collection and expressed the belief N., R. 104 W., Sweetwater County, Wyo. (Bradley, that it represents Lost Cabin level of the Wasatch. 1926, pl. 59). The relations between the Wasatch and Morris observed that most of the fossils from the Green River Formations and the history of the ter­ Cathedral Bluffs Tongue are smaller mamtnals, notably minology have been discussed in two earlier reports and , and suggested that the (Sears and Bradley, 1924; Bradley, 1926, p. 122-125), biocoenose is representative of a forest environment. but in those reports the Wilkins Peak Member of the Gazin (1959, p. 135) revised Morris' faunal list to Green River Formation was regarded as the Laney include the following rather diverse kinds of vertebrates: Shale Member. The Cathedral Bluffs Tongue consists predominantly Marsupalia: , 2 sp. of gray mudstone that is banded with pink and red Insectivora: layers. In the steep badland slopes that characterize N otharctus, sp. this unit, the red clay washes down over the gray, : giving the impression that red mudstone and claystone ? latidens Marsh make up the greater part of the unit. Bands of red : Absarokius witteri Morris are less numerous near the mountains in both the Rodentia: northern and southern parts of the area. Near the paramyid mountains also, lenses and beds of buff, brown, and : . greenish-gray sandstone are rather common; but Viverravus cf. V. lutosus Gazin farther out in the basin, sandstone layers are less Didyntictus cf. D. altidens Cope Condylartha: numerous, and, though lenticular, they are generally sp. somewhat thinner. Locally thin beds of algal limestone Perissodactyla: are interbec;lded with the sandy mudstone. To the east Cf. sp. (T. 26 N., R. 96 W.) in the area mapped by Pipiringos, sp. the Cathedral Bluffs Tongue becomes sandy and con­ Hyrachyus cf. H. modestus Leidy Artiodactyla: · glomeratic; still farther east it merges with the Battle Cf. H exacodus sp. Spring Formation. North of the Rock Springs uplift (sec. 21, T. ~4 N., A maximum thickness of 1,750 feet was given by R. 101 W.) I found numerous fragments of turtle bones Nightingale (1930, p. 1021) for the Cathedral Bluffs near the base of the Cathedral Bluffs Tongue. near its southwestern limit along Kinney Rim in McGrew and Roehler (1960, p. 158) reported further northwestern Colorado, and Pipiringos (1962, p. A32) on vertebrate fossils found in the Cathedral Bluffs estimated the thickness west of Lost Creek as 1,100- Tongue. EOCENE ROCKS, WYOMING-COLORADO-UTAH A27

To the west of Dad, Wyo., in the upper part of the Cathedral places containing an abundance of well-rounded gray Bluffs, a single rodent tooth was found by McGrew which was to black chert pebbles, make up a large percentage of identified by R. W. Wilson (personal communication) as Sciuravus the tongue. A particularly sandy facies of this unit nitidw~ Marsh, a probable Bridger form. In sec. 30, T. 25 N., H.. 101 W., a rodent fauna was found above the Tipton and below is exposed along Hams Fork on the main road between the Laney which H. E. Wood (personal communication) believed Kemmerer and Opal. About 7 miles farther north, to be more or less intermediate between Lostcabinian and Bridg­ however, where the main road from Kemmerer north erian. From the evidence available it appears that the Cathedral to Big Piney crosses the New Fork Tongue, the tongue Bluffs is certainly in part typical Lost Cabin (if it can be assumed contains little sandstone and is prevailingly red. that New Fork and Cathedral Bluffs are time equivalents) but that it may transgress the time boundary between Lostcabinian Superficia~ly the New Fork Tongue resembles the more and Bridgerian. somber phases of the Beckwith Formation of Late The time equivalence of Cathedral Bluffs and New Fork Jurassic and Cretaceous age, which it overlaps in many Tongues of the Wasatch is discussed below. places and from which it probably was in large part derived. NEW FORK TONGUE The New Fork Tongue of the Wasatch Formation Another tongue of the Wasatch Formation extends is 235 feet thick in sec. 31, T. 28 N., R. 112 W., and is for about 100 miles along the west side of the Green approximately 380 feet thick along the main line of the River Basin. (See pl. 1.) Like the Cathedral Bluffs Union Pacific Railroad just west of Carter (T. 17 N., Tongue, it is separated from the main body of the Rs. 115 and 116 W.). Southward from the vicinity of Wasatch Formation by a thin basal tongue of the Green Carter it thickens at the expense of the underlying River Formation. Where this tongue of the Green tongue of the Green River Formation. River Formation thins and loses its identity to the north Gazin (1952, p. 13) suggested that the fossil verte­ (T. 29 N., R. 110 W.) and to the south (T. 14 N., R. brates in the New Fork Tongue of the Wasatch Forma­ 118 W.), the tongue of the Wasatch Formation becomes tion represent the upper stage of the Lost Cabin a part of the main body of the Wasatch. Donavan () age. The · fauna is characterized by (1950, p. 64) mapped this tongue for a few miles along chamense, Cope, Hyrachyus spp., and the east side of Green River (T. 30 N., R. 109 W., south­ Bathyops1's. Lambdotlierium popoagicum Cope, is the west to the northeastern part ofT. 28 N., R. 111 W.) most abundant found, but· the fauna .also and named it the New Fork Tongue of the Wasatch includes such typical Wasatchian forms as , Formation from its exposures in the buttes"* * * over­ Meniscotherium, Esthonyx, and Ambloctvnus cf. A. looking the Green River-New Fork River junction." major Denison. Morris (1954, p. 199) observed that Donovan mapped his New Fork Tongue ofthe Wasatch "* * * in spite of the relatively large number of only to the northeastern part of T. 28 N., R. 111 W. isolated teeth found, none of the genera, with the ex­ (about 14 miles northeast of La Barge), whereas, accord­ ception of Hyrachyus and Hyopsodus, listed as occurring ing to my interpretation, this tongue extends some 80 in the New Fork, have been identified in the Cathedral miles farther southwest into T. 14 N., R. 118 W. (See Bluffs Tongue." He then went on to make the very pl. 1.) StephenS. Oriel, of the U.S. Geological Survey, interesting, though tentative, suggestion that the New told me (written communication, 1957) that Donavan Fork Tongue is equivalent to at least part of the Tipton apparently had regarded red mudstones as an essential Tongue of the Green River Formation-that is, that element of the New Fork Tongue and had terminated the New Fork Tongue of the Wasatch on the west side the unit where the reds graded southeastward into of Green River Basin may be, in part, older thari the greenish-gray to light-gray mudstone and gray, tan, Cathedral Bluffs Tongue of the Wasatch east of the and brown sa.ndstone. Rock Springs uplift. Prof. Paul 0. McGrew (oral Through the generosity of Mr. Oriel, I am able to communication, 1957) of the University of Wyoming, after studying the vertebrate faunas from these forma­ include on the geologic map (pl. 1) his hitherto unpub­ tions in various parts of the Green River and Washakie lished detailed mapping of the margin of the Green Basins, also believed that there is a fair basis for be­ River Basin (north from lat. 42° N. to La Barge Creek lieving that the New Fork Tongue is somewhat older and thence northward along the east side of the Green than the Cathedral Bluffs Tongue. Indeed, MeGrew River to the northern part ofT. 28 N., R. 111 W.). and Roehler (1960, p. 158) Throughout most of its length the New Fork Tongue * * * found a small but diagnostic fauna in the Tipton Tongue consists largely of gray sandy mudstone that is banded of the Green River Formation in sec. 30, T. 25 N., R. 101 W. with thin layers of pink to. maroon mudstone or clay. The fauna is of Lost Cabin age (late early Eocene) with Cyno­ dontomys, Hyracotherium, and Lambdotherium. The Tipton Irregular beds and lenses of coarse-grained crossbedded Tongue at this locality was described by Bradley (1926) as gray to dark-greenish-gray sandstone, however, in representing a near-shore facies. A28 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Apart from this evidence from the vertebrate fossils, southwest can be resolved only by more detailed I believe that there is good reason for thinking that mapping along the northern rnargin of the Green the New Fork and Cathedral Bluffs Tongues of the River Basin. Wasatch Formation are essentially contemporaneous. The paleoecology of the Wasatch u.nd Bridger Each is a wedge of fluviatile sediment that grew Fonnations will be discussed in a subsequent report. basinward from the mountains contemporaneously as GREEN RIVER FORMATION the lake in which the Green River Formation was DEFINITION AND AGE deposited shrank to the small size it was during the Wilkins Peak stage. If these thick and extensive The Green River Formation of middle Eocene age wedges of fluviatile sediment were not contempo­ was named by Hayden (1869, p. 90) for the exposures raneous, we must suppose that the floor of the lake along Green River west of Rock Springs. In a report basin was so deeply depressed that the whole lake published 10 years earlier, Engelmann (1858, p. 70) (during its low stage) was shifted to one side of the referred to "the tertiary Green river1 formation" in the western part of the Green River Basin. But in an basin while a great ~edge of fluviatile sediment formed on the opposite side. Then the first wedge of fluviatile earlier part of that report (p. 46-4 7) it is clear from his sediment must have been warped downward to become good descriptions of the lithology that he meant to the bed of the lake while a second wedge of fluviatile inch1de in this term what we now think of as part of the sediment grew in from the opposite side of the basin. Wasatch Forn1ation, the Green River Formation, and And, finally, the axis of the lake basin must have the Bridger Formation. Light-gray, brown, or buff returned to its original position near the geographic dolomitic madstone and shale of lacustrine origin· that center of the Green River Basin. The vertical con­ may contain organic matter characterize the Green tinuity of moderately shoal-water lacustrine sediment River Formation. Oil shale, beds of dolomitic nlarl­ stone and shale thickly studded with salt-crystal molds, (Wilkins Peak ~1ember of the Green River Formation) along the east side of the Green River Basin argues oolitic limestone and bedded algal deposits, beds of against this complex interpretati_on. volcanic ash, and limy sandstone or sandy madstone Gazin (1959), after collecting additional fossils and characterize various facies of the fonnation. Locally, fossil , plants, gastropods, pelecypods, ostracodes, studying the fossils ~1orris collected frorn the Cathedral Bluffs Tongue, concluded that the Fontenelle Tongue and fly larvae are com.mon. , , and of the Green River Formation and the New Fork reptilian bones have been found locally in the shore Tongue of the Wasatch. Formation on the west side facies of the formation. of the Green River Basin are equivalent, respectively, STRATIGRAPHIC UNITS to the Tipton Tongue of the Green River and the LUMAN TONGUE Cathedral Bluffs of the Wasatch Formation east of The Luman Tongue of the Green River Formation the Green River Basin. was named by Pipiringos (1962, p. A14-A24) for a Oriel (1961) found in the Fontenelle Creek-La Barge section consisting of low-grade oil shale, fossiliferous Creek area (Fort Hill quadrangle) still another tongue muscovitic calcareous sandstone, siltstone, mudstone, of Wasatch lithology roughly 100 feet above the base and a few thin coal beds that is excellently exposed on of the Laney Shale Member of the Green River Forma­ the south slope of Luman Butte (sec. 34, T. 24 N., R. tion. This tongue of the Wasatch, which he calls 97 W.). The Luman Tongue overlies the main body of the upper tongue, is about 90 feet thick along Fontenelle the Wasatch Formation and underlies the Niland Creek and consists largely of gray to brown muddy Tongue of the Wasatch Forn1ation. sandstone and greenish-gray mudstone, but it includes The Luman Tongue crops out in two belts; one also a little soft platy madstone. It grades eastward extends from the vicinity of Luman Butte southeast­ within a few miles into typical Laney Shale ~1ember ward to the center ofT. 22 N., R. 94 W., and the other lithology. · curves around the north end and down the west side of In my reconnaissance mapping (1928) across the the Washakie Basin into northwestern Colorado. As north end of the Green River Basin, I sketched in, noted on page A23 of this report, Pipiringos separated very roughly, a tongue of Wasatch lithology in the the Luman Tongue of the Green River Formation and lower part of the Laney Shale ~1ember of the Green the Niland Tongue of the Wasatch from the lower part River Formation. As mapped, this Wasatch tongue of what I had mapped (Bradley, 1945) as the Tipton extends southward from the southern part of T. 29 Tongue along the northeastern quadrant of the Wa­ N., R. 108 W., to the south-central part of T. 28 N., shakie Basin. Consequently, the base of the Luman R. 110 W. The relationship of this tongue to the has been mapped a.long the east side of Washakie upper tongue of Wasatch mapped by Oriel farther Basin into the southwestern part ofT. 17 N., R. 92 W., EOCENE ROCKS, "WYOl\HNG-COLORADO-UTAH A29

where it gro.des into lithology indistinguishable from logical Survey, and I identified the Luman Tongue of tho.t of the Wasatch. Pipirit1gos (\\Tittcn comnnmica­ the Green River For1nation and the Niland Tongue of tion, 1958) told me that Prof. Don Blackstone of the the 'Vasatch Formation n,t a site about halfway down University of Wyoming ha.d traced the remnants of the the west side of 'Vashakie Basin (sees. 14, 15, and 23, Luman Tongue a few miles farther southeastwa.rd than T. 15 N., R. 101 "V .) . At this locality, both these I hod into sec. 6, T. 16 W., R. 92 W. Also nccording tongues and the overlying Tiptol'l Tongue of the Green to Pipiringos, Bta.ckstone reported thn.t in tracing the River Formation are strikingly similar in lithology and Niland Tongue of the Wasatch southeastward from the thickness to what they are along Bitter Creek (T. 17 vicinity of Wamsutter, it gradually ~-icquired a Green N., R. 98 W.), about 18 miles northeast around the River a.spect and lost its identity in sec. 10, T. 17 N ., edge of ~Vashakie Basin, where Pipiringos and I iden­ R. 93 W. The upper boundary of the Luna1n and tified them in 1956. Nila.ncl Tongues have been roughed in without control Taylor and I sketched the boundaries of the Luman on my map (pl. 1) to connect these two terminal and Niland Tongues of the Green River and 'Vasatch localities with the boundaries mapped by Pipiringos in Formations, respectively, on aerial photographs at the NEX sec. 6, T. 19 N., R. 94 W. Pipiringos (1962, many places in and arou.nd the basin of Vermilion pl. 1) mapped the Luman and Niland Tongues from Creek, known as Hiawatha Basin. Subsequently, sec. 6, T. 19 N., R. 94 W., across the northern edge of R. J. Hackman, of the U.S. Geological Survey, had Washakie Bo.sin to sec. 19, T. 19 N., R. 96 W. I have cliapositives made from these photographs and made a projected these boundnries (pl. 1) southwestward with photogeologic map showing the outcrop pattern of the help of neriol photographs until they connect (in the these tongues of the Green River and Wasatch For­ western part of T. 17 N ., R. 99 W.) with the photo­ mations in all of Hiawatha Basin and northward along geologic mapping clone for me in 1957 by Robert J. the west side of vVashakie Basin to the western part of Hackman. This sketching was kindly checked and T. 17 N., R. 99 '"'· His map has been incorporated revised for me by J. D. Love of the Survey while we in the geologic map (pl. 1) of this report. were in the field in October 1958. Love adjusted these Not shown on plate 1 of this report is a thin tongue, bounda.ries to the 1:250,000 topogrttphic base of the or lens, of brownish-buff lacustrine beds, which is evi­ Army l\1np Service. dently the homotaxial equivalent or perhaps was on~e The Luman Tongue of the Green River Formation the actual extension, of the Luman Tongue; this tongue is 180 feet thick at Lun1an Butte but thickens east­ crops out along part of the east side of the Green River ward to 270 feet in the eastern part of T. 23 N., R. 95 Basin from the east flank of Little l\1ountain northward W. It also thickens eastward along the Union Pacific nearly to the south flank of Wilkins Peak. This unit Railroad from about 200 feet at Tipton Station (N~ has been mapped by W. C. Culbertson, of the U.S. sec. 18, T. 19 N., R. 96 W.) to about 390 feet at Frewen Geological Survey. Culbertson called n1y attention to Station, about 11 miles farther east. this unit in August 1963 while we were in the field In the central part of the area mapped by Pipiringos together. (see area 6 on index map, pl. 1), he reported (1962, p. Both the Luman and the Niland Tongues change A20) ""' "' "' several constituent tongues of low-grade oil southward from about the n1idpoint of the western rin1 shale separated by sandstone and siltstone beds. The of Washakie Basin (T. 15 N., R. 101 W.). The Luman three most conspicuous and persistent tongues were thickens to about 470 feet in the western part ofT. 13 mapped separately * * *." At the base of the lowest N., R. 101 W., nnd becornes cnrbonnceous and sandy; oil-shale tongue is a highly distinctive bed of nearly the Niland Tongue thins to less thnn 50 feet and black concretionary limestone that weathers to pastel becomes somewhat shaly. Westward nJong· the north shades of lavender, pink, yellow, buff, and l;>rown. slope of Pine l\1ountain, where the exposures are not This unit rests, in most of the area, directly on the adequate to identify the units, the Niland extends an highest coal bed in the main body of the 'Vasatch unknown distance. Southwn,rd nlong the west side of Formation and is a very useful horizon marker. The Hiawatha Basin, the Niland thins from about 65 feet two stratigraphically higher oil-shale zones each thicken thick in sec. 6, T. 12 N., R. 101 W., to 0 just a little

I eastward and conJesce in to one body of oil shale in_ the north of Canyon Creek (sec. 18, '1'. 12 N., R. 101 W.). '" enstern part ofT. 23 N., R. 95 ,iV. Along the Union In this nrea the Luman Tongue is overln,in by the Pacific Railroad all three oil-shale tongues thicken Tipton Tongue, which it there closely resmnbles. en,stward from Tipton Station and coalesce in the Along the enst side of Hiawathn, Basin, the Niland vicinity of Frewen Statio.n to form one body of low­ thickens southward and must be several hundred feet grade oil shale about 390 feet thick. thick east of Vermilion Creek in the southern part of In the fall of 1957 Dwight Taylor, of .. the U.S. Geo- T. 11 N., R. 100 W., Moffat County, Colo. The 7"&2-765 0--64-3 A30 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Luman Tongue of the Green River remains thick plants grow. Depths beyond rooted plants mean, (400-500 ft) throughout Hiawatha Basin. according to Ruttner (1953, p. l57), depths probably On the geologic map (pl. I) the Luman Tongue is greater than 25-30 feet. In samples of sandy carbo­ shown extending westward along the north flank of naceous shale which I collected-one (D-1178B) Pine l\1ountain as far as the western part of T. 13 N., from about the middle of the Luman Tongue (sec. 18, R. 103 W. J. D. Love, of the U.S. Geological Survey, T. 12 N., R. 100 W., Moffat County, Colo.) and one mapped the westernmost 6 miles of this extension and (D-117SA) from a bed' near the top (sec. 8, T.' 13 generously gave me his map to incorporate in my m11p, N., R. 101 W., Sweetwater County, Wyo.)-Estella plate 1. This extension along the north flank of Pine B. Leopold of the Survey identified the microscopic Mountain is significant because it suggests that the planktonic alga Pediastrum sp. and the pollen grains Luman and Niland Tongues may once have connected and spores listed in table 1. with the apparent Luman and Niland Tongues that In a sample of black shale collected from a bed about crop out of the east flank of Little l\1ountain and extend 50 feet above the base of the Luman Tongue (sec. 20, northward nearly to the south flank of Wilkins Peak. The gap between known Luman and Niland north of TABLE I.-Pollens, spores, and algae found in the Luman Tongue Pine Mountain and the inferred Luman and Niland of the Green River Formation on the east flank of Little l\1ountain is roughly 10 miles. (Identified by E. B. Leopold. Numbers refer to the number of specimens found) The Luman(?) on Little l\1ountain is about 40 feet USGS Loc. thick and thins gradually n.;>rthward until it disappears Flora D-1178B D-1178A a little south of Wilkins Peak. Cf. Pinus______1 1 Cf. Cycas______1 In Hiawatha Basin the Luman Tongue contains many 10 Ephedra cf. torreyana S. Watson______2 1 layers of sandy shell marl, and along the east side of Cunninghamia or Sequoia______1 0 Vermilion Creek (T. 11 N., R. 100 W., Moffat County, Colo.) it consists predominantly of shell marl. Accord­ TotaL______5 12 ing to Dwight Taylor, the most numerous forms are the snails Goniobasis sp. and Viviparus:sp. and the fresh­ Dicotyledons: Unidentified______14 37 water clam "Unio" sp. These beds also contain Betulacae______3 11 numerous ostracodes. In most. parts of Hiawatha Platycarya ______·______3 15 Basin the Luman contains thin layers of subbitumi­ Cf. Engelhardtia______0 3 nous coal, and, locally, a few of these layers are thick Pterocarya_ ·- ______3 1 J uglandaceae______0 enough to have been mined for domestic use. Along 2 Velkova______0 5 the southern edge of Hiawatha Basin the Luman grades Cf. M orus ______0 1 rather rapidly into either sandstone and then conglom­ Ulmaceae______0 1 erate, as at Sugar Loaf Butte (sec. 15, T. 11 N., R. 101 Carya______0 1 W., Moffat County, Colo.), or into gray sandy mud­ Tilia______1 3 stone typical of the Wasatch Formation. At irregular Cf. Galium______1 0 and rather widely spaced intervals the Luman in TotaL______25 80 Hiawatha Basin and northward around the rim of Washakie Basin contains very persistent beds of sand­ Monocotyledons: stone that are thin bedded and ripple bedded. These Unidentified ______0 18 Nymphae ceae ______beds range in thickness from a few inches to a few feet. 2 3 Potomogeton ______0 1 Channel sandstone lenses occur also, but they are rare. Gramineae ______0 4 About 75 feet above the base of the Luman in T. 12 N., R. 101 W., the late R. W. Brown of the Survey TotaL ______------2 26 and I collected fossil plants which he identified as Potomageton sp. and Nymphaea sp. In a zone of nearly Spores: Unidentified ______2 16 black shale about 50 feet above the base of the Luman Cf. Schizaceae ______0 1 farther south (sec. 20, T. 11 N., R. 100 W.), Dwight Taylor and I collected shells of a minute snail, which Total ______2 17 he identified as Valvata sp., and a tiny clam, which he recognized as Sphaerium sp. These two forms, Algae: Pediastrum ______- 4 1 according to Taylor (oral communication, 1957), are Chrysophyta ______characteristic of, .but not restricted to, the muddy bottoms of lakes beyond the depth where rooted aquatic TotaL------5 2 EOCENE ROCKS~ WYOMING-COLORADO-UTAH A31

T. 11 N., R. 100 W., I\1offat County, Colo.), I\1iss tion on the Union Pacific Railroad, Roehler (unpub. Leopold also found well-preserved "* * * pollen of data) has redefined the Tipton Tongue. As redefined, Platyca1·ya and a few structurally good remains of a the upper body of light-colored n1arlstone and algal Pediastrum of the P. duplex type" (written cOlnmunica­ beds are excluded and are assigned to the Wilkins Peak tion, 1958). I\1Iember. Pipiringos (1962, p. A29-A31) defined the The minute planktonic fresh-water alga Pediastrum upper part of the Tipton as that part extending upward apparently has a remarkably resistant cell wall, for it from the base of the lowest very extensive algal-ball occurs as a fossil in great abundance in certain kinds of bed, which he mapped (1962, pl. 1). Consequently, carbonaceous sediments (Wilson and Hoff1neister, 1953; from his map it is ensy to tell the distribution of the Cookson, 1953). Wilson and Hoffmeister found four Tipton Tongue and the Wilkins Peak I\1ember of the clearly distinct species of Pediastntm in a "" Green River Formtttion. formation of Smnatra, and the individuals were in­ That which is now defined as Tipton Tongue in the credibly well· preserved. I\1iss Cookson (1953) found type locality, around much of Washakie Basin, and Pediastntm in "Cainozoic deposits" of Australia. far up into the Great Divide Basin, is tan to grayish Professor Wilson later told me (written communica­ brown and is made up largely of soft papery low-grade tion, 1953) that he had subsequently found Pedia­ oil shale, but it also contains a few thin brownish fine­ strum in the Oligocene of Texas and Venezuela. grained limy sandstone beds and layers of concretionary

TIPTON TONGUE AND TIPTON SHALE MEMBER sandy limestone that if3 either crowded with gastropod shells or is oolitic. The Tipton Tongue of the Green River Formation Southwest of Washakie Basin, where one end of the encircles the greater part of the Washakie Basin as a Tipton Tongue loses its identity by grading in to great horse shoe, with the open end at the south. Wasatch lithology, sandstone beds become thicker and (See pl. 1.) In this area the Tipton Tongue is entirely much more plentiful in the Tipton, and beds of greenish­ detached fr01n the main body of the Green River Forma­ gray shale and gray mudstone replace much of the tion; but farther northwest, around the north end of the papery shale. Detailed sections measured along Shell Rock Springs uplift where the Cathedral Bluffs Tongue Creek in sees. 27 and 28, T. 12 N., R. 99 W., Moffa.t of the Wasatch dies out (T. 24 N., R. 104 W.), the County, Colo., where the Tipton is 388 feet thick, and Tipton Tongue joins the main body of the Green River in sec. 3, T. 10 N., R. 100 W., where it is 227 fe>et Formation and fron1 there southward .along the east thick, are given in an earlier report (Sears and Bradley, side of the Green River Basin becomes the Tipton 1924, p. 101-103) .. It should be pointed out thut Shale I\1ember of the Green River Formation. This these two sections doubtless also contain an u·pp er intertonguing relation between the Green River and part tha.t should be regarded as the Wilkins Pen.k Wasatch Formations and the history of the strati­ Member. Additional fieldwork, however, will prob­ graphic nomenclature have been discussed in two earlier ably be needed to determine how much of each section reports by J. D. Sears and me (Sears and Bradley, should be regarded as belonging to the Tipton Tongue 1924; Bradley, 1926, p. 122-125). and how much to the Wilkins Peak Member. Around the Washakie Basin the Tipton Tongue con­ About midway along the west side of Washakie sists chiefly of rather soft brown papery organic shale Basin, at Pine Butte, in sees. 5 and 6, T. 15 N., R. and low-grade oil shale, but interbedded with the papery 100 W ., the Tipton is 350 feet thick (Schultz, A. R., shale are somewhat harder beds of gray flaky marlstone unpub. data). Roughly the upper 200 feet of this and thin regular beds of brown limy sandstone. belongs to the Wilkins Peak Member. The Tipton Throughout the greater part of its extent-around the maintains a thickness of about 160 feet around the Washakie Basin and through the northern part of the north end of Washakie Basin and well down the east Great Divide Basin-the Tipton Tongue as mapped by side, but south )of Dad (sec. 32, T. 16 N., R. 92 W ., me (pl. 1) and as mapped by Pipiringos (1962, pl. 1) Carbon County, Wyo.) it thins gradually. East of includes in its upper part 100-200 feet of beds now Flat Top Mountain in sec. 3, T. 14 N., R. 92 lV ., the known to belong to the Wilkins Peak Member of the Tipton is between 110 and 120 feet thick. About Green River Formation. The recognition of these beds 2}~ miles northwest of Baggs the Tipton is 75 feet thick as Wilkins Peak rests on much detailed geologic and consists almost wholly of papery shale which, near mapping by H. W. Roehler, (unpub. data). As a con­ the base and top of the tongue, is· smnewhat carbo­ sequence of having first identified the Wilkins Peak naceous. I\1uch of the southwn,rd thinning of the Member along the north flank of Pine Mountain and Tipton between Dad and Baggs takes place by gradual then along the west side of the Washakie Basin, and lateral transition of the uppermost Tipton beds into having traced it northward to and beyond Tipton Sta- lithology characteristic of the Cathedral Bluffs Tongue A32 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

of the Wasatch; but the Tipton thins southward also, crossbedded lenses. Fishbone fragments are rather at least to some extent, by small-scale intertonguing common in the Tipton of that locality, as are also with the underlying Wasatch. Westward from the gastropod and pelecypod shells. In this part of the \'icinity of Baggs. the Tipton maintains a thickness of area the Tipton ranges in thickness from 179 feet in about 75 feet, but it becomes carbonaceous, then sandy T. 24 N., R. 100 W., to 87 feet in T. 24 N., R. 103 W. and carbonaceous, and finally loses its identity near The various facies changes in the '"ripton of this pa.rt the junction of Red and Sand Creeks in sec. 4, T·. 12 of the area have been discussed in an earlier report N., R. 93 W. (Bradley, 1926), which also contains six detailed One other distinctive detail of the Tipton on the sections of the Tipton. east side of Washakie Basin is the local sandstone The Tipton Tongue becomes the Tipton Shale ~1ern­ facies about 7 miles north of Baggs. At this place the ber of the Green River Formation near the north end Tipton consists predominantly of regular beds of light­ of the Rock Springs uplift by the southward transition gray well-sorted crossbedded sandstone. ~1ttny other of the Cathedral Bluffs Tongue of the Wasatch Forma.­ sandstone beds, however, are brown and n1uddy. Near tion into the Wilkins Peak Member of the Green River the top of the Tipton the sandstone beds contain an Formation. The Tipton Shale ~1ember crops out for abundance of gastropod (Viviparus?) shell molds and a more than 65 miles along the east side of the Green few beds of algal deposits. North and south of this River Basin from T. 24, R. 104 W., to Little ~1ountain locality the Tipton consists almost wholly of papery in T. 13 N., R. 106 W. Buff papery low-grnde oil shale. Apparently this local sandstone facies repre­ shnle chnracterizes most of the member in this pnrt of sents the locus of a strearn that entered the ancient the area, but the lithology changes gradunlly from plnce Gosiute Lake basin from the east or southeast. to place and evidently reflects differences in environ­ In the northern part of the Great Divide Basin where ment determined by the topogrnphy and drninage of the Pipiringos (1962, p. A29) mapped the Tipton Tongue low hills of the Rock Springs uplift a few miles to the of the Green River Formation, the Tipton has very east and by streams coming into the nren from the much the same characteristics as it does around the northwest. In general, the deepest part of the lake north rim of the Washakie Basin. Pipiringos observed persisted in that part of the basin west or southwest of the same distinction between the upper and lower parts Rock Springs. There the beds of the Tip ton are all and, indeed, mapped the boundary between them using fine grained, and most are brown flaky shale, ostracode the top of the "lo'Yest zone of algal balls" as the base shale, and low-grade oil shale. Well-preserved fossil of the upper part of the Tipton. }Ie gave (p. A30) the fish are fairly common in the lower part of the member, total thickness of the Tipton as 280 feet in sees. 9 and and beds of moderately rich oil shale make up a con­ 16, T. 24 N., R. 95 W. At that same place the lower siderable thickness in the upper part. No mud cracks part of the Tipton is 180 feet thick. were observed. North and south of this locality, mud Eastward from Tps. 24, 25, and 26 N., R. 94 W.,· cracks and layers of ripple-bedded sandstone become Pipiringos (p. A30-A31) described the lateral gradation increasingly plentiful; fewer of the beds are papery and of much of the Tipton Tongue into the coarse arkosic they contain less organic matter. Indeed, subsurface sandstone of his Battle Spring Formation. This grada­ information indicates that in a large area northwest of tion occurs by intertonguing and also by surprisingly the town of Green River, the Tipton and its equivalent rapid lateral change from brown papery low-grade oil beds consist largely of a near-shore sandy facies similar shale into the coarse-grained pinkish gray arkose. to the Tipton north of the Rock Springs uplift. Westward from the western part of Pipringos's area Detailed stratigraphic sections of the Tipton Shale (west edge of Tps. 24, 25, and 26 N., R. 97 W.) the ~1ember along the eastern margin of the Green River Tipton Tongue maintains essentially the same charac­ Basin are given later in the report under the heading, teristics as described above, though'' algal deposits, "~1easured sections." ostracode marl, oolite, and madstone beds become Thin regular and persistent lu,yers of ,·olcanic ash somewhat more prevalent and the unit thins gradually. are fairly common in the Tipton Shale ~11ember and in North of the Rock Springs uplift, the Tipton is the Tipton Tongue. These range in thickness from characterized by numerous beds of algal deposits, oolite, about half an inch to about 8 inches. They ntnge in and ostracode marl. Some of the ostracode marl con­ color from light gra.y to brown, but most of them are tains so little else besides ostracode shells that it is a buff. coquina. These distinctive types of rock are inter­ A curious feature of ma.ny of these tuffs is that they bedded with flaky low-grade oil shale, platy madstone, have admixed with the ash such .large quantities of gray mudstone, and persistent beds of gray to brown microgranular carbonates predominantly dolomite. sandstone. The sandstone occurs locally as thick From the analyses (given in table 2) of two of these EOCENE ROCKS., WYOMING-COLORADO-UTAH A33 cn.rbormte-rich tufl's, the following percentages of considerations suggest that the earbonu,te pnrticles enrbon~tte minemls were cn.lculated: precipitated out of the lake water and accumulated

Samples simultaneously with the accumulation of the u.sh 1 f .\1 iuerals (percent) (percent) particles on the lake bottom. In other words, there Dolomite _____ ·______66. 50 72. 76 seems to have been a dependent reln.tionship between Calcite ______13. 06 10. 19 the newly fallen volcanic n.sh and the precipitation of Sideri tc _____ .:. ______3. 11 these dolomite and calcite particles. l\1oreover, the bottom and top surfaces of these beds n,re very sharply Total carbonates ______82. 67 82. 95 defined, which suggests also that rapid deposition of 1. Smne field No. 11-58; laboratory No. F-2399. the carbonate particles begn,n and ended n.bruptly, 2. Sample field No. 12-58; laboratory No. F:...2400. as though the rapidity of their deposition had been According to ttrl X-ray difrnwtion analysis kindly determined by the accumulating volcanic ash. mnde for me by Brian Skinner of the U.S. Geological Throughout its extent, the base of the Tipton Shale· Sun·ey, the carbonn,tes dolomite and cn.lcite in sample ~1ember is sharply defined. The basal bed, or beds, ll-58 are essentially pure species. .He stnted in his range from about 1 to about 7 feet in thickness and report thn.t it The dolomite gi ,·es n, strong X-ray pattern, range from limy sandstone to oolitic limestone and, ex­ and the spn,cing of the (112) plane is 2.892A. The cept in a very few places where the basal bed is very best me~tsurement for stoichiometric dolomite is thin or absent (for example, see p. A65), contain a great 2 .890A." lie commented th~tt, on the basis of one abundance of the snail shells Goniobasis sp. and Vivi­ a.nalysis, one cn.nnot be certain thn,t the small difference parus sp. and the fresh-water clan1 Unio sp. Generally, ( +0.002A) is real If ren1, it would correspond to also, the basal limestone contains numerous ostracodes. n,pproximn,tely 1 percent mole excess CaC03 in the The top of the Tipton is clearly defined for a consider­ dolomite. it The calcite appen.rs to be almost pure able distance north and south of the 1nain line of the CaCOa." Union Pacific Railroad by the overlying limy brown or Inasmuch as the ferrous iron in this sample essentially buff platy sandstone and dolomitic n1arlstone beds in balances the n.v11ilable C02 nJter combining all the the basal part of the Wilkins Peak Member. (See fig. Cn,O n,nd ~1g0 with C02 to form dolomite and calcite 9.) As the Tipton is traced northward toward the it seems reasonable to calculate the remaining C02 Wind River Range or southward toward the Uinta as ferrous carbonate. The small quantity of ferrous carbonate which I calculated for sample ll-58 is TABLE 2.-Chemical analyses of carbonate-rich tuffs from the Tipton Shale Member of the Green Rive1· Fonnation probably siderite. In sample 12-58 the amounts of [Samples from sec. 31, T. 19 N., R. 105 W., Sweetwater County, Wyo. Analyst: CaO, ~1g0, and C02 are in the proper stoichiometric V. C. Smith] proportions to account for dolomite and calcite only. Constituent 1 S Si02------9. 92 10.42 The amount of ferrous iron in this rock (0.09 percent) is AbOa------2. 18 1. 03 negligible. Fe20a------1. 29 2. 04 The cn.rbonate grains in nll these carbonate-rich FeO______.2. 63 . 09 tuffs n.ppear to have accumulated rapidly. They are MgO______14.54 15.91 CaO ______27. 54 27. 83 minute and are conspicuously lighter colored than N azO ______. 29 . 22 those in the underlying and overlying rocks, which KzO ______. 4 7 . 17 shows that they contain much less organic matter, clay, H20+------1. 19 l. 61 and clastic pn.rticles (presumably wind-blown dust). H2o-______. 47 . 52 Ti 0 ______• 08 . 02 These cn.rbonate-rich tuff layers (11-58 and 12-58) 2 contn.in, respectively, 0.25 and 0.44 percent organic P20s------. 14 . 13 M n 0 ______. 10 . 07 rnn.tter, wheren.s most of the shale and marlstone above C0 ______38. 77 39. 32 2 tmd below contain about 6-36 times as n1uch organic Organic matter~------. 25 . 44 matter. Hn.d the carbonate-rich tuff layers accumu­ ln.ted as slowly n.s the adjacent beds, they would hn.ve TotaL______90.86 09.82 lutd cumpn.rn.bly dn.rh: colors owing to the gradun.l n.ceumuln.tion of the same accessory constituents as Powder density______2. 83 2. 78 nre in the adjacent beds. ~101·eover, had the carbonate­ rich tuff lnyers accumulated slowly, the volcanic-ash I Determined by J. J. Fahey. particles would have been concentrated at the bottom 1. Sample field No. 11-58; laboratory No. F-2399. From bed 78 ft above base ot of the layers, but they are not; they are uniformly member. 2. Sample field No. 12-58; laboratory No. F-2400. From bed 5 ft higher in member dispersed through the carbonate particles. These two than bed of sample No. 11-58. A34 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

:FIGU RE 9.- Typical exposure of the Tipton Shale Member (Tgt) of the Green River }' ormation in the NE}~ sec. 23, T. 18 N., R. 106 W., Sweetwater County, Wyo. The base of the Tipton is marked by a thin bard bed that makes a barely discernible line in the bare slope about 25 feet belo w the sharp brea k in the shrubby vegetation. At the top of the Tipton is a rather thick ledge of oil shale, which is here ca pped by a few t hin sandy beds. These sa ndy beds are the basal beds of the overlying Wilkins P eak Member (Twp). The bare slope below the Tipton is made by t he uppermost part of the Wasatch Formation (Tw).

Range, its upper boundary becomes less clearly defined, miles north of Muddy Creek the Fontenelle Tongue particularly in the southern part of the area. Where is approximately 150 feet thick. At its base is a group most clearly defined, the Tipton Shale Member is about of irregularly bedded hard sandy limestone or marl­ 150 feet thick; but as it approaches the shore facies stone beds that contain an abundance of the snail shells near the Uinta Mountains, it gradually thickens. Goniobasis and Viviparus. This basal unit, which re­

FONTENELLE TONGUE sembles the basal unit of the Tipton Shale Member of the Green River on the east side of the Green River A basal tongue of the Green River Formation that is Basin, differs in sandiness from place to place along the the western homolog, and probably the time equivalent, strike and ranges in thickness from 3 to more than 30 of the Tipton Shale Member and Tongue crops out for feet. Above these sandy marlstone beds is soft flaky a little more than 100 miles along the west side of the gray shale that is interbedded with thin but somewhat Green River Basin. (See pl. 1.) Donavan (1950, p. harder marlstone beds. A little of the shale is carbo­ 63-64) mapped this tongue for about 40 miles along the naceous and papery, but most of it is poor in organic Green River (T. 30 N., R. 110 W. , south to T. 24 N., matter of any kind. Near the top of the tongue the R. 114 W.) and named it the Fontenelle Tongue of the shale grades gradually upward into sandstone, which Green River Fprmation. He gave as the type locality in turn grades upward into red sandy mudstone that sec. 13, T. 24 N ., R. 115 W. , about half a mile south forms the basal part of the New Fork Tongue of the of Fontenelle Creek. The Fontenelle Tongue, the Wasatch. Tipton Shale Member, and the Tipton Tongue repre­ Southward from Muddy Creek, however, the Fon­ sent the first great expansion of Gosiute Lake- a stage tenelle Tongue thins by progressive transition of its exceeded in lateral extent only once, and much later, uppermost beds into lithology characteristic of the by the Laney stage, during which the Laney Shale New Fork Tongue of the Wasatch. About 10 miles Member was deposited. farther south, in the northern part of T . 15 N. , R. 117 Along Muddy Creek (T. 17 N ., R. 116 W.) the W., only the basal beds of the Fontenelle T ongue per­ Fontenelle Tongue is about 250 feet thick and consists sist. The unit there is 5- 10 feet thick and consists of predominantly of light-gray rather soft flaky marly marly shale, sandy marlstone, and bedded algal de­ shale. This lithology contrasts sharply with the red posits. This thin remnant of the tongue was traced mudstone of the underlying Wasatch and with the about 12 miles farther south, but it thins still more and green sandstone and mudstone of the overlying New loses its identity 5 or 6 miles southwest of Piedmont Fork Tongue of the Wasatch Formation. About 11 in the southern part ofT. 14 N., R. 118 W. EOCENE ROCKS, WYOMING-COLORADO-UTAH A35

North of Hams Fork, between Kemmerer and Opal, and great abundance of dolomite make it conspicuously the Fontenelle Tongue thins gradually and becomes more unlike the Laney Shale 1fember of the vVashakie sandy. In the vicinity of La Barge Creek and for Basin, unlike any other member of the vVashakie several miles northward along the Green River it is about Basin, and unlike any other 1nember or tongue of the 50 feet thick, according to StevenS. Oriel (1961, p. B151). Green Ri,·er Formation. My other reason for giving It thins rather rapidly near its northern extremity and it a new member name is thn,t my own studies and loses its identity in the northwestern part of T. 29 N., nutpping in 1923 showed plainly that this unit wn,s the R. 110 W., about 6 miles southeast of the town of stratigraphic and time equivalent of the Cathedral Big Piney. Bluffs Tongue of the W tlsatch Formation (Bradley, A pa.rtial section of the Fontenelle Tongue of the 1926, pl. 59), which, of course, underlies the Laney Green River Formation measured on Fontenelle Creek Shale l\1ember at its type locality. approximately 2 miles west of the junction of Fontenelle At the time I defined the WiJkins Peak l\1ember Creek and the Green River is as follows: (1959, p. 1Q72-1075), I believed it was restricted to the

Top. · Ft in Green River Basin. But in 1962 (written cOinmunica­ Sandstone, very fine grained, marly, buff to gray. tion) H. W. Roehler, of the l\1ountain Fuel Supply Co., Groups of finely laminated and banded beds sent me a copy of his geologic map, which showed alternate with beds that are massive and less that the Wilkins Peak l\1einber crops out along the limy. Top 3 ft of unit contains a few thin north and east flanks of Pine l\1ountain and that in crossbedded layers of coarse gray sand, and uppermost layer contains abundance of mud the vicinity of Canyon Creek (southern part of T. 12 lumps______33 0 N., R. 102 W., Sweetwater County, Wyo.) it grades 1\larlstonc, silty, platy; in part coarsely YarYecl abruptly into a sandy, crossbedded conglomerate. and in part crossbeclclecl______10 This conglomerate was formed by a river that must Sandstone, marly, light-gray; in slightly irregular have drained a considerable part of the east end of the beds; contains many mud lumps and a few thin lenses of cross bedded gray sandstone______9 6 Uinta Range. Roehler also showed that typical Sandstone, lenticular, m.edium-grainecl, gray, Wilkins Peak is exposed along the Kinney and Laney crossbecldecl______0 Rims of the Washakie Basin at least as far east as sec. l\'larlstone, buff or brownish-gray; papery at 14, T. 19 N., R. 95 W. (about 3 miles south of Frewen base but progressively harder, more platy, Station on the Union Pacific Railroad). and sanely toward to·P------6 6 Marlstone, carbonaceous and papery at base but In August 1963 I had the opportunity to review grades upward into sanely platy marlstone_ _ _ 0 4 much of Roehler's mapping with him in the field. Sanclston0, soft, muddy, gray, crossbeddecl; base During those 3 or 4 days I ate more crow than has been not exposed______33 0 my lot for many years. In both of these large areas outside ·of the Green Partial thickness, Fontenelle Tongue____ 85 2 River Basin, Schultz (1920, pl. 1) had included the WILKINS PEAK MEMBER Wilkins Peak beds with his Tipton. Unfortunately, The vVilkins Peak ~1ember of the Green River I made the error of accepting Schultz's mapping of the Formation is restricted to the Green River Basin and Tipton-Cathedral Bluffs boundary. is the most conspicuous member in that part of As mentioned earlier, under the heading, "Tipton Wyoming. Schultz (1920) correlated it with his Laney Tongue and Tipton Shale Member," I mentioned the Shale ~1ember, whose type locality is in the Laney fact that Pipiringos (1962, pl. 1) had mapped the lowest Rim along the northern edge of the Washakie Basin. extensive algal-ball zone, which he quite properly (See pl. 1.) All other geologists to 1959 have followed used to define the base of the upper part of the Tipton his usage. One of my reasons for giving this unit a Tongue. Inasmuch as Roehler's mapping now shows new member na.me (Bradley, 1959) stems from the that the "upper part of the Tipton," .as thus defined, is realization that the beds making up the bulk of the in fact a northeastward extension of the Wilkins Peak member were deposited in a lake thn.t represented l\1ember, we can use Pipiringos map (pl. 1) to see how rather low stages of Gosiute Lake. Indeed, probably extensive outcrops of the Wilkins Peak l\1mnber are in for· a significant part of that stage the lake had only the central and northern parts of the Great Divide about one-third the area of its maximum extent and Basin. was essentially restricted to the Green River Basin. The Wilkins Peak Member is named from almost (See fig. 10.) perfect exposures of the whole unit in the north, east, The shrinkage to this low stage gave rise to the and south slopes of Wilkins Peak, which is a conspicuous great abunda.nce of sa.line minerals thn,t are so charac­ peak just south of Bitter Creek, on the main line of the teristic of this unit. Its content of saline minerals Union Pacific Railroad, and U.S. highway 30 about 6 A36 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

GRANITE MOUNT A INS

I I I 1-;:::t::\\f""'

25 0 25 50 75 100 MILES ~~~~-----J__----~----~------~1

FIGURE 10.-Inferred boundary of Gosiute Lake's hydrographic basin, outline of the maximum extent of Gosiute Lake during the Laney stage, and, within that, the average extent of the lake during much of the Wilkins Peak stage. Also shown are the area below which bedded trona is known or inferred and the area (cress hatched) of the island in Gosiute Lake formed by Upper Cretaceous rocks of the ancestral Rock Springs uplift. The loci of large streams that existed during part of the time while the Wasatch and Green River Formations were accumulating are shown by the conglomerate- and sand-patterned areas. miles southeast of the town of Green River in the marlstone. The.se marlstone beds form a bench that southern part of T. 18 N., R. 106 W., Sweetwater caps the cliff of oil shale in the uppermost part of the County. At its type locality the member is about Tipton Shale Member. The top of the Wilkins Peak 900 feet thick. Culbertson (1961) discussed a number Member was taken as the change from light-gray or of key beds, tuffs, and sandy units in the Wilkins white dolomitic marlstone and chippy shale to chalky Peak Member and gave six columnar sections of the buff laminated and varved marlstone, because this member. latter represents a marked deepening and expansion of The Wilkino Peak Member makes up much of the the lake. In most places this change is rather subtle. bare white cliffs and slopes in the vicinity of the town This upper boundary is well exposed in the gulches of Green River and along the east face of White Moun­ on the north side of U.S. Highway 30 a few miles west tain, which marks the east rim of the Green River of the town of Green River. At the 1nouth of the Basin for many miles north of the Union Pacific Rail­ westernmost of these gulches (sec. 9, T. 18 N., R. road. (See fig. 11 and geologic map, pl. 1.) The 107 W.) the boundary is readily accessible. (See fig. picturesque cliffs in the canyon of Green River south 12.) There the upper part of the Wilkins Peak Mem­ of the town of Green River are made up largely of the ber consists of more than 25 feet of gray organic 1narly white' and greenish-gray beds of the Wilkins Peak shale that contains beds and many thin lenses of rich Member, though the overlying sandstone lenses add oil shale overlain by about 10 feet of low-grade papery much to the scenic splendor of that canyon. oil shale and soft flaky or~anic Inarlstone. This upper The base of the Wilkins Peak Member is marked by unit contains several zones or layers of large calcite a group of sandy, dolomitic, crudely bedded layers of molds of radial aggregates of salt crystals. These M 0 () Mz M ;,; 0 () ~ _UJ

~ >-<: 0 ~ 52 0 I () 0 t"' 0 ;,; > t:l 0 I d ~

FIGURE 11.-\"iew northward across the valley of Bitter Creek from the northwest flank of Wilkins Peak (NWJ.< sec. 34, T.18 N., R.106 W., Sweetwater County, Wyo.) showing White Mountain in the dis­ tance and Pilot Butte on the skyline in the center. Pilot Butte is capped with wyomingite lava. In White Mountain, particularly near the right-band margin of the photograph, the upper white and the lower dark halves of the Wilkins Peak Member of the Green River Formation show well. The Tipton Shale Member makes a light band under the Wilkins Peak Member ncar the upper right edge of photo­ graph. The Laney Shale Member, showing as a dark zone overlying the Wilkins Peak Member, is truncated by an erosion surface. In the foreground are beds of the upper white half of the Wilkins Peak Member. A thick dark-olive-brown zone, which mark~ the top of the lower half of the Wilkins Peak Member, is conspicuous in the lower left foreground. Tw, Wasatch Formation; Tgt, Tipton Shale Member; Twp, Wilkins Peak Member; Tgl, Laney Shale :\!ember.

c.:>> '"'-1 A38 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

FIGU RE 12.-Uppermost part of the Wilkins Peak Member and basal part of the Laney Shale Member of the Green River Formation in t he S W HN W ~~ sec. 9, T . 18 N ., R. 107 W., Sweetwater County, Wyo. The man in the ce nter is standing on the thin tuff bed that marks the base of the Laney. The eon tact selected by W. C. Culberston, of the Survey, is the lowest white band in the lower ri ght-hand corner of the photograph. The smooth slope immediately below the tu fT contains e!li p­ soldal molds of radial aggregates of salt crystals thought to have been nahcolite. Below the nahcolite(?) zone (about 6ft thick) are oil shale beds that contain shortito­ crystal molds. The oil-shale and organic-marlstone beds behind and above the man contain no salt-crystal molds. A channel lens of tuffaceous sandstone makes the broken cliff at the top.

strongly suggest molds of nahcolite crystals like those stage of Gosiute Lake, I prefer to place the contact so common in the Green River Formation in the above the highest salt-crystal molds. . The beds below are characterized by an The Wilkins Peak Member has not surely been identi­ abundance of the molds of shortite. Above the zone fied on the west side of the Green River Basin, though containing the nahcolite(?) molds is a tuff bed about Donovan (1950, p. 64- 65) recognized a unit having a 8 inches thick. Resting on the tuff are the thin beds maximum thickness of 121 feet in sec. 29, T. 25 N ., of buff laminated and varved organic madstone that R. 112 W. that has "Laney lithology." He mapped characterize the basal part of the Laney Shale Member this unit and called it the Laney Shale Member of the throughout much of its great lateral extent. These Green River Formation. He noted that south of buff marlstone beds contain no saline minerals. The Fontenelle Creek this unit lost its "Laney" character­ contrast between the gray beds of the Wilkins Peak istics and could not be mapped. One other, and more Member and the buff of the overlying Laney Shale compelling, reason for believing that the featheredge Member is more striking from a distance than it is of the Wilkins Peak Member crops out along the west close to the outcrop. side of the Green River Basin is the fact that, locally, W. C. Culbertson (written communication, 1962) a very few madstone beds contain casts or molds informed me that the contact between these two of salt crystals. Significantly, one of these layers is members, which he mapped in detail over an extensive close to the base of the Laney (sees. 5 and 7, T. 22 N., area south of Wilkins Peal,, is about 26 feet below the R. 114 W.) where one would expect the westernmost one I show in figure 12. I have no quarrel with his edge of the Wilkins Peak Member to crop out. The boundary, which is more readily mappable than mine; salt that gave rise to these salt-crystal casts has not but to be consistent with my own concept that the been identified. (See fig. 13.) saline minerals are characteristic of the Wilkins Peak J. D. Love, of the Survey, added (written communi- EOCENE ROCKS, WYOMING-COLORADO-UTAH A39

cation, 1962) "* * * that a gastropod-bearing limy sandstone here (sec. 5) contains 0.007 percent U and

0.69 percent P 20 5 , which is par for one of the poorer uraniferous phosphate zones in the Wilkins Peak." Along the face of White Mountain the Wilkins Peak Member is made up of two units that differ con­ spicuously in color. The lower part, 430-450 feet thick, is drab to light greenish gray and contains several .distinctive olive-green to brown bands of muddy sand­ stone that can be traced for miles. The upper unit, about 400-500 feet thick, weathers almost chalky white, from which White Mountain gets its name. Why these two units should weather so differently is not clear. Both consist largely of more or less tuffaceous dolomitic mudstone that, on fresh fracture, ranges in color from neutral gray to dark greenish gray. Both units contain thin beds of volcanic ash and beds or groups of beds of marlstone that weather light gray to white, but these do not help to differentiate one unit from the other. Moreover, chemical analyses show that the content of calcium and magnesium carbonates is roughly the same throughout the whole member. D . L . Deardorff, of the Diamond Alkali Co. (unpub. data), working with many cores from exploratory bore FIGURE 13.-Crystal molds of an unknown salt on the bedding plane of a sandy marl­ holes and from surface sections, divided the Wilkins stone from the thin western edge of the Wilkins Peak Member of the Green River Peak Member into upper, middle, and lower units, Formation in sec. 7, T. 22 N., R. 114 W., Lincoln County, Wyo. which are roughly of about the same thickness, though they differ in thickness, lithology, color, and lateral ally westward at angles ranging from 10 o to 18 °. Charac­ extent. teristically, these false beds are laminated, and many According to him, the lowest unit is composed of are current ripple marked and rill. marked. Some of alternate beds of green shaly mudstone and greenish­ the sandy mud slumped under water, so the false beds gray dolomitic mudstone. It contains at least 17 major are considerably contorted. Locally these muddy sand­ extensive trona beds that range in thickness from a few stone units fill shallow channels scoured out of the inches to about 38 feet. Locally, the successive trona underlying beds, and filled channels are numerous beds have an aggregate thickness of about 150 feet. within the sandy beds. The thickest of these beds, Halite occurs in some of these trona beds, but its distri­ which is roughly 400 feet about the base of the Wilkins bution and amount differ from bed to bed and from place Peak Member, ranges in thickness from 30 to a little to place within individual beds. The halite occurs in the more than 50 feet. Below this zone, about 62 feet and trona as disseminated crystals or as aggregates of 152 feet, respectively, are two more similar but some­ crystals and even as lenses or layers. In the southern what thinner muddy sandstone zones. The outcrops part of the Green River Basin, halite predominates over of all three of these are shown on R. J. Hackman's trona in most of the beds. Locally, also, detailed map of the area around Wilkins Peak and the wegscheiderite (Fahey and Yorks, 1963) occurs within town of Green River (pl. 2). On this map these zones the trona. Shortite is abundant through all this unit are lettered A, B, and Din ascending order to correlate except for about 15 feet at the base. with three of the nine grayish-olive-green sandy zones Deardorff's middle unit is much more extensive which William C. Culbertson (1961), of the U.S. areally than either the underlying or overlying unit. Geological Survey, mapped in the area south of that This unit also consists of massive to shaly gray to mapped by Hackman. Culbertson lettered his wnes greenish-gray mudstone that ranges from very fine from A to I, in ascending order. According to Culbert­ grained !Lnd dolomitic to muddy sandstone, ~1nd it contains many of the oliYe-green muddy crossbedded son, these zones can be traced as far south as Sage sandstone zones that are conspicuous on the outcrop. Creek, and they probably could be traced 12- 15 miles These muddy sandstone zones range in thickness from a still farther south. They thicken somewhat south­ few feet to 50 feet and have false bedding that dips gener- ward. It seems clear that most of the material in A40 THE GREEN RIVER ANI) ASSOCIATED TERTIARY FORMATIONS

them was derived from the ancestral Rock Springs this lake repeatedly shrank to relatively small size, uplift. its waters became so concentrated that trona, and According to Deardorff, his middle unit of the Wilkins locally halite, precipitated out. Then it must have Peak ~![ember contains beds of trona, but they are expanded repeatedly to considerably greater size, as thinner and less continuous than those in the unit is shown by the lateral extent of the beds making up below. Few of these are as much as 5 feet thick. this men1ber. We find, then, as would be expected, Shortite is abundant throughout this unit. that this great lens of lacustrine sediment has within Westward and southwn.rd from the central part of it· another comparable, but smaller, lens of saline the basin, this middle unit bec01nes sandy an~ carbo­ sediment-that is, not only trona beds, but also beds of naceous, taking an aspect mo,re like parts of the Fon­ dolomitic mudstone that contain shortite [N a2C03• tenelle Tongue still farther west and parts of the 2CaC03], northupite [N a 2 C0 3 ·~1gC0 3 ·N aCl], halite marginal facies of the Laney Shale Member. These [N aCl], and much smaller amounts of pirssonite

are evidently shallow-water and marshy facies of the [N a2C03·CaC03·3H20], gaylussite [N a2COa·CaC03• Wilkins Peak Member. According to Deardorff, some 5H20], thermonatrite [N a2C03·H20], tychite [2N a2C03 • of the beds of his middle unit crop out along the Green 2MgC03·N a2S04], nahcolite [N aHC03], wegscheiderite River in the vicinity of La Barge and Big Piney. [N a2C03·3N aHC03], and searlesite [N aBSi206·H20]. Deardorff's uppermost unit is the lea~t extensive This internal lens is the saline facies of the Wilkins of the three and is restricted to a rather narrow belt Peak Me1nber. along the eastern margin of the Green River Basin. That part of the member that encloses the saline Evidently that area warped downward into a troughlike facies can be thought of as a fresher water facies, which depression during that last stage of Gosiute Lake. of course has a much greater lateral extent. It also Drill holes show that all along this narrow belt the has a greater vertical range because nonsaline beds rocks of this unit grade westward into carbonaceous both underlie and overlie the beds of the saline facies. muddy sandstone. Like the lower two units, the upper One marginal part of the fresher water facies can unit consists of alternate beds of massive to shaly easily be examined a little way east· of Green River, greenish-gray mudstone and greenish-gray to light-gray Wyo. Just west of the town the 'Vilkins Peak Member dolomitic mudstone and madstone. Thin beds of has enormous numbers of shortite-crystal 1nolds. volcanic ash are fairly common, and many of the mud­ These become less numerous eastward and are absent stone layers are tuffaceous. Shortite is abundant. updip a few miles east of the town. This same Trona beds are numerous but do not have great areal marginal facies then extends far north along White extent; they range in .thickness from a few i;nches to Mountain, though here and there the outcrop cuts about 15 feet. The Stauffer Chemical Co. recently back into the eastern edge of the saline facies. South­ opened a mine (sec. 15, T. 20 N., R. 109 W.) on two ward the outcrop of the Wilkins Peak Member is of these trona beds,· known locally as the Upper Big broader and much more dissected by canyons, so that Island and the Lower Big Island beds. both saline and marginal facies can be found there Deardorff's study of the Wilkins Peak Member and depending on the way the outcrop surface transects its trona beds is valuable for another concept. He the beds. showed that trona deposition began early in the Wilkins At various levels up through this marginal facies of the Peak stage in a restricted depression (roughly 287 sq mi) in the southern part of the Green River Basin Wilkins Peak Member more and less limy beds alternate and then gradually extended northward, the areal with one another rhythmically. The beds in these extent of trona deposition reached a maximum while sequences range in thickness from a few inches to the bed now being mined by the Intermountain Chemi­ several feet, but in any given sequence the pairs of beds cal Co. was being laid down. That bed f\as an esti­ are of roughly the same thickness. One of these mated area of about 725 square miles. Over that sequences will illustrate the phenomenon. extent it ranges from 2 to nearly 20 feet in thickness. Rhythmic sequence cf beds from a zone 85 feet above the base of the The uppermost trona beds formed only in the east­ Wilkins Peak Member in sec. 33, T. 21 N., R. 105 W. central part of the Green River Basin. Marlstone, light-grayish-brown, platy; weathers Ft in Still another useful concept of the Wilkins Peak nearly white; bedding planes mud cracked___ 1 0 Member emerges if one thinks of the unit as a great Mudstone, greenish-drab, rather hard __ :..______3 6 lens of sediment laid down in a closed lake which, Mudstone, light-greenish-gray, limy______1 0 Mudstone, greenish-drab, soft ______- 3 6 like all closed lakes, fluctuated greatly in area and Marl stone, light-grayish-brown, sandy; contains volume during its long history. We know from the mud lumps______1 0 fabulous quantities of bedded trona and halite that as Mudstone, greenish-drab, soft______3 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH A41

Mnrlstone, light-grnyish-brown; weathers nearly Ft in TABLE 3.-Boreholes in the Green River Basin drilled to explore '"hi te ______10 for trona or for oil or gas-Continued Mudstone, greenish-drab, soft ______3 0 Marls tone, light-grayish-brown; weathers nearly 'vhite ______Number Company or owner and well Identification Location 0 on pl. 1 34 ______The more limy mudcracked ·ln.yers are interpreted Mountain Fuel Supply Co. Church SE~~ sec. 16, T. 16 N., R. Buttes 13. 112 W. ns hn.ving formed during fn.lling and low stages of the 35 ______Mountain Fuel Supply Co. Church sec. 28, T. 16 N., R. 112 W. Buttes 8. lake, whereas the greenish mudstone ln.yers are in­ 36 ...... Mountain Fuel Supply Co. Church sec. 29, T. 16 N., R. 112 W. terpreted as having formed during rising and higher Buttes 4. 37 ...... Mountain Fuel Supply Co. Church sec. 20, T 16 N., R. 112 W. stages. In other comparable rhythmic sequences the Buttes 9. 38 ...... Mountain Fuel Supply Co. Church sec. 19, T 16 N., R. 112 W. more limy beds contain salt-crystal molds whereas the Buttes 12. 39 ______Mountain Fuel Supply Co. Church sec. 17, T. 16 N., R. 112 W. intervening beds do not. Buttes 7. 40 .. --.--- Mountain Fuel Supply Co. Church sec. 8, T. 16 N., R. 112 W. The saline facies of the Wilkins Peak Member can be Buttes 1. defined as those beds lying between the stratigraphically 41...... Mountain Fuel Supply Co. Church sec. 6, T. 16 N., R. 112 W. Buttes 10. lowest and highest occurrences of shorti te crystals or 42 ...... Mountain Fuel Supply Co. Church sec 6, T. 16 N'., R. 112 W. Butte 15. their molds. Most of the beds within this bracket 43 ...... Mountain Fuel Supply Co. Church sec 12, T. 16 N., R. 113 W. Buttes 3. contain some saline minerals. The saline minerals 44 ...... Mountain Fuel Supply Co. Church sec. 13 T. 16 N., R. 113 W. Buttes 6. range in abundance from sparsely scattered crystals to 45 .•..... Mountain Fuel Supply Co. Church sec. 34, '1'. 17 N., R. 112 W. Buttes 11. solid beds as much as 38 feet thick. 46 ...... Mountain Fuel Supply Co. Church SEX sec. 22, T. 17 N., R. Although the saline facies has not been mapped, its Buttes 17. 112 w. 47 .•..... Mountain Fuel Supply Co. Church NEX sec. 22, T. 17 N., R. thickness is known from numerous exploratory bore Buttes 2. 112 W. 48 .•..... Mountain Fuel Supply Co. Church SWX sec. 14, T. 17 N., R. holes. (See pl. 1 and table 3.) The saline facies Buttes 18. 112 w. 49 ...... Mountain Fuel Supply Co. Church NEX sec. 14, T. 17 N., R. varies in thickness with the thickness of the Wilkins Buttes 16. 112 w. 50 .•...•. Stauffer Chemical Co. SO 3 .•••••...•..... sec. 6, T. 17 N., R. 110 W. Peak ~1ember. The saline facies, nevertheless, dies 51. •..... Kern County Land Co. 2... ------·----·-- sec. 4, T. 17 N., R. 110 W. out somewhat more rapidly toward the basin margins 52 .••..•. Union Pacific RR Co. 6A .••...... •...•. sec. 15, T. 17 N., R. 110 W. 53 .•..... Diamond Alkali Co. Sturm 2•..•....••••.. sec. 8, T. 17 N., R. 109 W. and is considerably less extensive areally than is the 54 .•...••.•••• do ..•..•.•...... Sturm 1...... sec. 10, T. 17 N., R. 109 W. 55 .•..••••.••. do .•.....•...... ••••.... 5 ...... ••.• sec. 35, T. 17 N., R. 109 w. vVilkins Peak. 56 ....••. Pan American Petroleum Co. Massacre sec. 26, T. 17 N., R. 108 W. Hills 1. TABLE 3.-Boreholes in the Green River Basin drilled to explore 57 ...... Diamond Alkali Co. Reid 2 ••••.....•..... sec. 32, T. 17 N., R. 107 W. for trona or for oil or gas 58 .....•. Perkins 3 .. ------·--·------·- sec. 8, T. 17 N., R. 107 W. [Holes much beyond tho known or Inferred possible outer limits of bedded trona are 59 .....•. Colorado Oil & Gas Rye Grass 1-26 ..•••.. sec. 26, T. 17 N., R. 107 W. 60 .•.•.•• Diamond Alkali Co. McKenna 1...... sec. 6, T. 18 N., R. 106 W. not listed] 61. •.•.•. Mountain Fuel Supply Co. Nightingale sec. 26, T. 18 N., R. 107 W. Number Company or owner and well Identification Location Sodium 1. on pl. 1 62 .....•• Diamond Alkali Co. Butler 1. .•.•.•...••. sec. 12, T. 18 N., R. 108 W. 63 .••..•.....• do ..• ------·-·-----3 ...... •.••. sec. 17, T. 18 N., R. 108 W. 64 ...... Potash Company or America 2 .•..•...... sec. 12, T. 18 ~ .• R. 109 W. L ••••••• Pan American 011 Co. Henrys Fork ______sec. 10, T. 12 N., R. 110 W. · 65 ...... • Allied Chemical Co. Buchanan 1...... sec. 10, T. 18 N., R. 109 W. 2 .•••••.• Northern Natural Gas Co. Great Grizzly __ sec. 10, T. 13 N., R. 112 w. 3 •••.•..• California Co. Spring Branch ______sec. 26, T. 13 N., R. 111 w. 66 ... --.• ___ .. do ... _•.. _._._ .. _Buchanan 2...... _. _. sec. 4, T. 18 N., R. 109 W. 4 •••.••••.•••• do ••••• ~ •.. Frnnklln Wash ______sec. 33, T.13 N., R.109 W. 67 ...... do ....•..•...... Splder Creek L ...... sec. 19, T. 18 N., R. 109 W. 5 •••••••• Barr Smedley 1.------sec. 15, T. 13 N., R. 108 W. 68 .. ----- Potash Company of America L ...... sec. 6, T. 18 N., R. 100 W. 69 .....•. J. R. Simplot Co. Ruby 1..------···--·--- SEX sec. 2, T. 18 N ., R. 6 •••.•••• Palcon 011 Co. Government..------sec. 10, T. 13 N., R. 108 W. 110 w. 7 ••••.•.• William Oruenerwald Currant Creek 4. __ sec. 1, T. 13 N., R. 107 W. iO .....•. Mountain Fuei Supply Co. John Hay NWX sec. 2, T. 18 N., R. fL ••••••• Phillips Petroleum Co. Federal-Hobson ___ sec. 27, T. 13 N., R. 106 W. Jr. 1. 110 W. 0 •••••••. Caulkins Oil Co. 2 (4-0V) ______sec. 9, T. 14 N., R. 106 W. 10 ••...•. California Co. Dry Creek ______sec. 6, T. 14 N., R. 110 W. 71. ....•. Union Pacific RR Co. 1.------··· sec. 3, T. 18 N., R. 110 W. 72.------...•. do .... ------6·------·- sec. 15, '1'. 18 N., R. 110 W. ll ______Pure 011 Co. Butcher Knife Springs 1. .... sec. 21, T. 14 N., R. 113 W. 73 ______Humble 011 and Refining Co. Spider sec. 26, T. 18 N., R. 110 W. 12 ••••.•. l\lountain Fuel Supply Co. Grizzly sec. 35, T. 15 N., R. 113 W. Creek Unit 1-B. Buttes 1. 74 .. ----- Humble 011 and Refining Co. Spider sec. 27, T. 18 N ., R. 110 W. 13 .••.•.• Sohlo-UPRR-Uinta Development Co. sec. 13, T. 15 N., R. 113 W. Creek Unit 2-B. 14 ______UPRRl. 75 ...... Kern County Land Co. 1...... •..••.... NWX sec. 28, '1'. 18 N., R. Park City 011 and Gas Co. 1..------­ sec. 6, T. 15 N., R. 113 W. 110 w. 15 •.••••. lVlax Pray Oovcrnme~t-Akrldge 1. •••.•••. sec. 19, T. 15 N., R. 112 W. 76 .....•...... do ..•...... ••.. 3 ....•.....•.....• SEX sec. 28, T. 18 N., R. 16 .•.•••. Phillips Petroleum Co. Cedar Mtn. L .... sec. 28, T. 15 N., R. 111 W. 110 w. 17 •.•.•.. ~·turta F. Strocck 1. ------·------sec. 14, T. 15 N., R. 111 W. 77 ______..... do ...•...•...... •. .4 ....•...•..•••••• sec. 20, '1'. 18 ~ .• R. 110 W. 18 ••.. :.. Perkins 2 .• ------·--·-···------sec. 32, T. 15 N., R. 109 W. iS ...... do ...... ••... 5 ... ------sec. 21, '1'. 18 N., R. 110 W. Hl...... El Paso Natural Gas Co. (water well) _____ sec. 10, T. 15 N., R. 109 W. i9 ...... Little America-Covey 1 Anderson (water sec. 17, T. 18 N., R. 110 W. 20 ....•.. Sinclair Oil Co. Federal 1. .• ------·---- sec. 6, T. 15 N., R. 108 W. well). 80 ...... J. R. Slmplot Co. Ruby 2...... ••. sec. 4, T. 18 N., R. 110 W. 21. ••••.. Perkins 1. .•. ------·------sec. 32, T. 15 N., R. 108 W. 22 ...... 'l'cxota 011 Co. Post!. •....•...... sec. 18, T. 15 N., R. 107 \\'. 81...... Union Pacific RR Co. 4.... ------sec. 5, T. 18 N., R. 110 W. 23...... Diamond Alkali Co. Reid 1.------sec. 24, T. 16 N., R. 109 W. 82 ...... Stauffer Chemical Co. SO 2.------sec. 2fl, '1'. 18 :-.!., R. 111 W. 24 .•...... do ..••...... Held 3.------sec. 2, T. 16 N., H. 109 \\". 83 ...... do ______so 4.------sec. 10, T. 18 :-.~.,H. 111 w. 25 ...... do ...... Cockercl\2..... : ..... sec. 10, T. 16 ::-.J., H. 109 \\". 84 ...... Diamond Alkali Co. 1...... ------sec. 12, T. 18 :-.!.,H. 112 W. 85 .....•. Union Oil Co. Moxa 1.. ... ------sec. 30, T. 1\1 :-.!., R. 112 W. 20 ...... do •..•...... Orierson 1...... sec. 4, T. 16 N., R. 109 W. 27 ...... do ...... Cockerell 1...... sec. 18, T. 16 N'., R. 109 \\'. 86 ...... Texaco Inc. :\Ioxa 1...... ------·-····--· sec. 22, T. 19 N., R. 112 W. 28 ...... do •.....•...... Finley 2.------sec. 26, T. 10 N., R. 110 \\'. 8i ...... Stauffer Clwmical Co. 1 SO ...•...... sec. 34, T. 19 N., R. 111 W. 29 ...... do ...... Orlerson 2 ...... sec. 2, T. 16 N., R. 110 W. 88 .. ----- Westvaco 4------sec. 27, T. 1!1 N., R. 110 W. 30 ...... do •...•...... Finley 3 •...... sec. 22, T. 16 N., R. 110 \\'. 89 .....•..•... do .... L •... ------·- sec. 26, T. 19 :-.!., R. 110 W. 90 ...... do .... 8...... sec. 29, T. 19 N., R. 110 W. at ...... do ...... Finley 1...... sec. 8, T. 16 N., R. 110 W. 32...... Mountain Fuel Supply Co. Church sec. 4, T. 16 N., R. 112 W. 91...... do .... 2 ...... •.... ------SWX sec. 15, T. 19 ~ .• R. Buttes 5. 110 w. 33...... Mountain Fuel Supply Co. Church NW~~ sec. 16, T. 16 N., R. 92 .....•. Union Pacific RR Co. 2.-----·-·------~ SEX ~rc. 15, T. 19 N., R. Buttes 14. 112 W. 110 w. A42 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

TABLE 3.-Boreholes in the Green River Basin drilled to explore Joseph J. Fahey, of the U.S. Geological Survey, made for trona or for oil or gas-Continued a very thorough study of the saline minerals in the saline .

Number Company or owner and well identification Location facies of the John Hay Jr. 1 well (Fahey, 1962, p. 5-45). on pl. 1 In that study Fahey estimated the abundances of

93 ______Westvaco 3------center sec. 15, T. 19 N., R. several saline minerals, bed by bed, through the whole 110 w. 94 ______Intermountain Chern. Corp. mine ______SE~ sec. 15, T. 19 N., R. thickness of the saline zone, which is there 555 feet thick. 110 w. 95 ______Westvaco 5------sec. 11, T. 19 N., R. 110 W. He estimated that shortite makes up about 10 percent 96.------_____ do ____ 6 ______------_ sec. 9, T. 19 N., R. 110 W. by volume of the whole thickness, and if that percentage sec. 7, T. 19 N., R. 110 W. 9798 ______.•. ______.do._ .9..13. --· ______------_ holds laterally, then there is at least 125 million tons of S~~~\~~c. 1, T. 19 N., R.

99 ______.do._ .12. ______------______SE~ sec. 1, T. 19 N. R. shortite under each square mile of land in that area. 110 \V. ' 100 •. ______.do._ .10. ______SW~NW~ sec. 1, T. 19 N., He found trona at at least 22 levels (either as beds or R. 110 W. scattered crystals) and found that trona aggregates 10L ______do ___ u ______NE~l'\W~ sec.1, T. 19 N. R. llO W. ' about 6.4 percent of the saline zone. Farther south, 102 ______Stauffer Chemical Co. SBI-11______sec. 5, T. 19 N., R. 109 w. 103 ______Westvaco 7 _. _. ------sec. 19, T. 19 N., R. 109 w. trona ma.kes up a much larger percentage of the saline 104 ______Allied Chemical3 Buchanan. ______sec. 29, T.I9 N., R. 109 w. 105 ______Union Pacific RR Co. 3 ______sec. 31, T. 19 N., R. 109 w. zone; but because the saline zone itself thickens south­ 106 ______Diam9nd Alkali Co. 4 ______sec .. 30, T. 19 N., R. 108 w. ward, the relative percentages of trona and shortite may 107 ______do ______2 ______~--- sec. 34, T. 19 N., R. 108 w. not cha.nge much. The detailed data., however, to test this inference are not available. Fahey estimated that Hi=::::~ == :: =~~====~-~=-======~~~~J::f~~-~---- -_- -_- ::---~--~--- -_- ~~~:sec. 6,~~: T. ~: 19 ~g N., ~ :: ·R. ~: 107 ~g~ vV. ~~: IlL _____ P. T. Jenkins Grierson!. ______sec. 4, T. 20 N., R. 107 w. northupite ma.de up about 2.2 percent of the saline zone 112 ______Diamond Alkali Co. Berger L _ ------sec. 28, T. 20 N., R. 108 w. 113 ______Stauffer Chemical Co. SBI 8------sec. 29, T. 20 N., R. 108 w. in the John Hay Jr. 1 well. U~:::::: =====~~:::::::::::::::::~~~ i~::::::::::::: ~~~: ~: ~: ~g ~:: ~: ~g~ ~~: In the saline facies in the central part of the basin, loughlinite (Na20·3Mg0·6Si0 ·8Hz0] (Fahey and others, sec. 18, T. 20 N., R.I08 W. 2 sec. 36, T. 20 N., R. 109 W. 1960) is locally plentiful. This occurs as veinlets and sec. 21i, T. 20 N., R. 109 W. sec. I~. T. 20 N .. R. 109 W. beds a.nd as partial replacements of minerals, especially sec. 12, T. 20 N., R. 109 W. liE~~~ ~=~~ ~~n~~~~~~~~~-~dll ~~~~=~~~~~~~~ northupite. In places the beds are more than 1 foot I2L .... -----do ______SBI 18 ______SW,USE.U sec. 14, T. 20 N., R. 109 W. thick. More generally it is only one of several constitu­ 122 ______----.do ______. ____ SBI 16_ ------___ _ NW,USW.U sec. 14, T. 20 N. R. 109\V. ' ents distributed through the rock. It is fibrous, very 123 ______---- .do ______SBI 17------NW,UNE.U sec.14 T. 20N. R. 109 "r· ' ' fine grained, and has a birefringence comparable to that sec. 11, T. 20 N., R. 109 W. g~= == = =: == == =~~======~~~ ~~======~ ======sec. 10, T. 20 N., R. 109 W. of several clay minerals. Its minute crystals are 126 ______----.do. ______SBI 25.------NE~NE.U sec. 15, T. 20 N., generally parallel and may be oriented along a bounding R.109 w. 127------.do _____ ------____ SBI 19.------___ _ S~~ :~· 15, T. 20 N., R. surface or normal to the surface. In larger veinlets its 128 ______----.do ______mine shafts ______N~~ire.c. 15, T. 20 N., R. fibers are usually. normal to the walls. sec. Iii, T. 20 N., R. 109 W. Only two chemical analyses of rocks in the Wilkins sec. 4, T. 20 N., R. 109 w. g~======~~======~~~ ~i~======Peak Member are included in this report because Fahey (1962, p. 15) has already published 14 complete analyses of rocks selected at fairly regular intervals through the !~=~~~~H~JE~:~jjj~j~mJI! H~m~~~=~=~ ll~ ~ti itti'~ii saline zone of the Hay well core. One of the analyses 136 ______Allied Chemical Co. Paddock 3 sec. 33, T. 20 N., R. 110 w. 0 included in this report is of a tuff about 140 feet above lii::::::140 =====~g:::::::::::::::r;i~g;~~i=H bl Oil 1==~=====- ----· sec.24,T.20N.,R.Il1W.~~~: ~~·l·2~ N~:·l·~~~o,~. the base of the member. The bed is light buff to and Refining Co. Blacks sec. 24, T. 21 N., R. w. ------¥>%w\-n. uo brownish gray and is about 8 inches thick; it is an 14L _____ Union Pacific RR Co. 7 _ sec 29 T 21 N R 109 w excellent marker bed that can be traced for many miles 142 ______Stauffer Chemical Co. s:Bfia··------sec: 32', T·. 21 N:, Ii. 108 w. 24 -_-=_-_- -_-==-_- -_-===== sec. 28, T. 21 N., R. 108 w. along the outcrop. The other analysis given in this ~!~======~~======--=------_-_.SSBHI1 12 sec. 22, T. 21 N., R. 108 W. 145 ______P. T. Jenkins Dymond 1______:: __ :::_: sec. 18, T. 21 N., R. 107 w. report is of a greenish-gray muddy tuff from the upper­ most part of the Wilkins Peak Member. ~!~======~~======~·~~;.~~sr------sec. 3028, T. 22 N., R. 106 W. 148 ______Belco Petroleum Corp. Eden-2::=::::::::~ sec. • T. N., R. 106 W. Culbertson (1961) described and gave accurate strati­ 149______P. T. Jenkins Mver L- sec. F· ~· 22 N., R. 106 w. 150 ______Union Pacific RR Co. 8 _:~======----===------sec. 35,2, T.· 22 N., R. 107now. W. graphic positions of six continuous tuff beds in the 151. _____ Utah Construction and Mining Co I sec. 36, T. 23 N., R. now. Wilkins Peak Member. These are very useful key 152 ______Delco Petroleum Corp. Sandy Bend 1.~=-= sec. 3, T. 23 N., R. 108 w. 153 ______El Paso Natural Gas Co. Simpson Gulch 1 sec. 4, T. 23 N., R. 107 w. beds. The tuff identified by my field number 19-58 154 ______P. T. Jenkins Pittman I - sec 34 T 23 N R 107 w 155.. ____ P. T. Jenkins Pittman 2::::=::::::~:=:::: sec: 34; T: 23 N:: R: 107 w: (see table 4) is Culbertson's lowest tuff bed, which in his area is roughly 125 feet above the base of the mem­ ber. This same bed has been recognized over a large !H~~~=~~ :JaE~mm~m~=~=~=~~:~~~~~~~~=~ ~~ l~~ r*~l?::~~:~:£. area by J. D. Love, who called it the Firehole analcite }~1------P---do ______6 ______sec.l5, T. 23 N., R.10fl w. bed (written communication, 1964) ~ -----· . T. Jenkins Jenkins L ------sec. 31, T. 24 N., R. 106 w. Microscopic examination ~hows that sample 19-58 EOCENE ROCKS,.. WYOMING-COLORADO-UTAH A43 TABLE 4.-Chemical analyses of two tuffs from the Wilkins Peak The other unusual fossiliferous beds are two beds of Member of the Green River Formation oil shale. One of these oil-shale beds is a rather rich [Analyst: June Goldsmith] bed that immediately underlies the trona bed being Con8tituent mined in the Intermountain Chemical Co.'s mine. Si0a------~------60. 58 51. 51 This bed contains many microscopic aquatic Al203 ____ ---- _------16. 57 13. 58 Fe20s------­ 2. 21 5. 31 and parts of them. These are thought' to be Oladocera . 08 . 05 and parts of aquatic . They are being studied FeO------~go ______CaO ______. 27 3. 18 by specialists in such living organisms . 2. 13 5. 52 The other oil shale is a stratum about one-eighth ~a20------­ 9. 51 5. 33 . 50 2. 40 inch thick that is very rich in organic matter and I·II<20------0 2 + ______-____ -- __ --- ______5. 48 2. 98 pyrite. This stratum was found in the core from the fi20------­ . 28 1. 06 John Hay Jr. 1 well at a depth of 1646.5 feet below the 2 . 09 . 18 Ti0 ------­ surface (sec. 2, T. 18 N., R. 110 W., Sweetwater County, . 05 . 13 P20~------~no ______Wyo.) The rock contains a remarkably rich and varied . 02 . 07 C0 ______---- _ -- .. ______- ______microflora of algae and fungi and many pollen grains 2 1. 58 7. 75 SOs------­ . 06 . 31 and some fragments of aquatic insects. This micro­ BaO------. 10 . 04 flora will be described in another paper. Total ______Both these beds of oil shale, and indeed all the beds 99. 51 99. 40 of oil shale in the Wilkins Peak Member, are believed to represent deposits formed when Gosiute Lake was 1. Sample field No. 10-58; laboratory No. E-2382. From bed about 140ft above base of the member In sec. 31, '1'. 10 N., R.105 W., Sweetwater County, Wyo. at a somewhat higher level than when any of the trona 2. Sample field No. 23-58; labomtory No. E-2383. From bed at the top or the mom· ber In sec. 8, '1'. 18 N., H.107 W., Sweetwater County, Wyo. beds formed. These higher stages of the level repre­ sent fresher water stages, though none of them were contains a very large amount of analcime, mostly in high enough to overflow. While these oil-shale beds small euhedral crystals. Tuff sample 23-58 also con­ were forming, the area of the lake fluctuated between tains considerable analcime, but it differs from the other about 1,500 and 4,500 square miles. The micro­ tuff mostly by having a somewhat greater content of organisms apparently grew in the fresher water of the calcium and magnesium carbonates and a relatively epilimnion, which floated on the rather strongly saline large amount of 1(20, which is probably present as hypolimnion. In other words, the lake was chemi­ potassium feldspar. These two samples are rather cally stratified during those stages; and the organic typical of the altered tuffs in the Wilkins Peak Member. matter was preserved in the stagnant, deeper, saline J. D. Love, of the U.S. Geological Survey, made a water. study of about 35 thin but very extensive zones in the A longer report is being prepared jointly by Prof. Wilkins Peak Member that contain detectable to Hans Eugster, of Johns Hopkins University, and the sign.ificant amounts of uranium and abnormally large U.S. Geological Survey on the conditions of deposition amounts of P205 (written communication, 1964). of the Wilkins Peak Member and the origin of its trona These zones, which range in lithology from muddy beds and other salts. A fuller discussion of the paleo­ sandstone through greenish gray claystone to low­ limnology and geochemistry of Gosiute Lake during grade oil shale and madstone, have P20 5 contents the Wilkins Peak stage will be given in that report. rnnging from less than 0.05 to 18.2 percent. These LANEY SHALE MEMBER same rocks contain 0.003-0.15 percent uranium. Schultz (1920, p. 27-28) nan1ed the Laney Shale Fossils are not common in the Wilkins Peak Member Member of the Green River Formation from exposures though in n few beds they are both numerous and re­ along the Laney Rim around the northern part of the mnrknble. Locally nlong vVhite l\1ountain, especially Washakie Basin. The Laney encircles W askakie Basin in sec. 9, T. 18 N., R. 106 W., a number of organic marl­ and extends southward into Moffat County, Colo., stone and low-grade papery oil-shale beds contain a beyond the south line of the geologic map, plate 1. lnrge number of mycetophyllid fly larvae and a smaller Along the east side of the Green River Basin the Laney number of oestrid nnd unidentified fly lnrvae. With makes up the buff to brownish gray hilltops out of some of these larvae are also adult flies and a few adult Hemiptera nnd Coleoptern. On the bedding planes of which large lenses of tuffaceous sandstone jut boldly. one of the madstone units are many adult flies that Around the other side of the Green River Basin the evidently got stuck in the wet mud just after hatching, Laney Shale Member is the thickest and most extensive ns their wings were not fully developed when they were member of the Green River Formation, as is shown on trapped. plate 1. A44 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

The Laney Shale member around the Washakie make up the greater part of the unit though locally soft Basin ranges in thickness from a little less than 400 to chalky varved organic madstone and low-grade papery nearly 1,900 feet and is characterized by buff, chalky oil shale are rather plentiful, especially in the lower to muddy marls tone and brown to light-ash-gray shale. part of the member. Plant remains, particularly Along the west and north sides of this basin the middle palms, and silicified wood are locally common in the part of the Laney contains considerable amounts of platy marlstone. Thin algal-limestone beds and nodu­ low-grade oil shale and a few beds of moderately rich lar masses occur near the margins of the depositional oil shale. Much of the low-grade oil shale is papery, basin. Near the center of the basin the rocks in the and some of it contains the well-prserved remains of lower part of the member .contain more low-grade oil small fish. Most of the thin volcanic-ash layers in the shale than do those in the marginal facies. Locally, Laney of this part of the area have been altered to oil-shale beds of fair quality are found in lenses of sof.t analcime. Along the east and south sides of the fine-grained muddy tuff. Most of the sandy tuff occurs Washakie Basin the shale and marls tone of the Laney as thick lenses which grade laterally into sandy shale are, in general, somewhat softer and muddier than they or soft sandy madstone. In the Green River Basin the are on the west side of the basin. Also, they contain Laney Shale Member is well exposed in the cliffs along much less organic matter, although zones of chalky the north banks of Big Sandy Creek (T. 23 N., R. 109 varved organic madstone and low-grade oil shale make W.) and in cliffs along a tributary to Blacks Fork in up a considerable part of the Laney, particularly along the northwestern part of T. 16 N., R. 108 W. (see fig. the south; faulted side of the basin. 14) and the northeastern part of T. 16 N., R. 109 W., A chemical analysis of a typical varved dolomitic though at neither locality is either the base or the top organic marlstone from the lower part of the Laney exposed. In the vicinity of the town of Green River Shale Member is given in table 5. the Laney is more than 600 feet thick. A nearly complete section of the Laney Shale Member

TABLE 5.-Chemical analysis of typical dolomitic organic marlstone was me11sured about 23 miles south of the town of from the basal part of the Laney Shale Member Green River near Twin Buttes (sec. 8, T. 14 N., R. 108 [Sample collected In S~NEM sec. 8, T. 18 N., R. 107 W., Sweetwater County, W.). The lithologic details of this section are given Wyo. Sample No. 22-58c; lab. No. E-2380. Analyst: V. C. Smith] later in the report under the heading, "Measured Constituent Weight percent Constituent Weight percent Si02------43. 95 H20+------4. 03 sections." AhOa------11.41 H 20 - __ -- ______. 43 North of the Rock Springs uplift and along the Fe20a--- ______1. 88 Ti02------. 23 north side of the Green River Basin the Laney extends FeO______1. 56 P205------. 41 beyond the feather edge of the Wilkins Peak Member MgO______3. 67 Mn 0 ______. 05 and rests either upon the Cathedral Bluffs Tongue, CaO ______11.43 C02------13. 36 Na20------4. 25 the New Fork Tongue, or the main body of the Wasatch K20------2. 38 TotaL ______99. 04 Formation. (See pl. 1.) Along the north and west sides of the Green River H20+ is abnormally high because organic matter, Basin the Laney Shale Member contains a considerably unfortunately, was not determined. Judging from greater proportion of soft shale and mudstone than other comparable analyses for which the organic matter it does elsewhere. The rocks are consistently poor in was subsequently determined, the organic matter in organic matter a·nd locally along the western side of this marls tone probably is about 4 percent. Nearly 30 the basin soft muddy sandstone beds and lenses are percent of this rock consists of carbonates-14.3 per­ rather numerous. Comparatively hard madstone and cent dolomite, 12.63 percent calcite, and 2.45 percent limy shale is interbedded with these soft muddy rocks. Near the southwest corner of the Green River Basin siderite. It is worth noting that the amount of P20 5 in this rock is considerably greater than that found in where the Laney is only 284 feet thick the following most of the analyzed rocks in the Green River Forma­ section was measured: tion, but it is not nearly so great as the amount Love (written communication, 1964) found in his thin Laney Shale Member of the Green River Formation measured east of Piedmont in the northern part of T. 14 N., R. 117 W., uraniferous phosphate zones in the Wilkins Peak Uinta County, Wyo. Member. Ft in The Laney Shale Member in and around the Green Mudstone of the Bridger Formation. River Basin is characterized by brown and buff-colored Marlstone, hard, white; makes a broad bench_-- 2 0 Volcanic ash, pure white, chalky ______- 2 0 rocks that include marlstone, tuff, sandstone, shale, Shale, soft, gray; contains a few layers of less and limestone. Buff coarsely chippy to platy marlstone fissile mudstone and a few thin layers of hard and tuff, and brown iron-stained muddy sandstone marlstone ______24 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH A45

Ft in Marlstone, hard, thin-bedded, platy, light-gray; Ft in Mudstone, brown, soft, massive ______contains an abundance of ostracodes______0 6 3 0 Mudstone, soft, gray, sandy______13 0 Shale, papery, very soft, chocolate-brown; con­ tains small quantity of organic matter except Marlstone, hard, very limy, almost white; con- in uppermost 6 in. which is barren clay ______14 0 tains shells------1 0 Marlstone, nearly white, sandy, massive; con- Sandstone, soft, muddy, dark-olive-gray; bottom tains clay pellets ______2 0 part consists of very coarse sand grains embedded in greenish-gray waxy clay matrix; Thickness, Laney Shale Member ______20 6 becomes fine grained and fissile toward top __ _ 16 0 Marlstone, gray, flecked with white; apparently tuffaceous ______Approximately 2% miles northwest of this locality 1 0 the :Yaney is represented by only two beds, as follows: Mudstone, pale-greenish-gray ______2 0 Marlstone, rather hard and crudely chippy ____ _ 0 6 Thickness (feet) Mudstone, soft, pale-greenish-gray ______12 0 Oolite, brown, sandy, platy-bedded; contains Sandstone, massive, medium- to fine-grained, many ostracodes ______2 dark-graY------2 0 Sandstone, coarse-grained, muddy ocherous_ 5 Marlstone, hard, clayey, dense, light-grayish- buff, very crudely chippy ______2 0 Thickness, Laney Shale Member ___ _ 7 Mudstone, soft, gray, crudely fissile ______6 0 Mudstone, soft, gray, massive; contains one or The Laney Shale Member continues to thin north­ more thin bands of pink mudstone ______25 0 28 29 Marlstone, dense, nearly white, chippy; makes westward and is absent from Tps. and N., Rs. conspicuous bench ______5 0 103-105 W., according to Berman's mapping. (See Limestone, dense, gray; weathers nearly white __ 1 0 McGrew, and Berman, 1955.) There, north of the Mudstone, soft, gray; crudely fissile at base but Continental fault, the Bridger Formation rests directly grades upward into limy shale ______3 6 on the Wasatch Formation. Limestone, gray, regularly bedded ______0 6 Shale, soft, very limy, light-gray; weathers nearly Prof. Paul 0. McGrew, of the University of Wyoming, white ______2 0 showed me (August 1963) a considerable thickness of Marlstone, alternate dense and chalky layers __ _ 1 0 the Green River Formation (apparently Laney) along Mudstone, soft, gray, crudely fissile; contains the Big Sandy River north of the area shown on few thin layers of dense marlstone ____ . ______4 0 plate 1. The Green River Formation at that locality Marlstone, rather chalky, pale-grayish-buff; in part massive, in part crudely chippy ______.. 2 0 was faulted down on the north side of an unmapped Shale, soft, gray; rather poorly developed fis- fault that strikes northwest-southeast. sility ______45 0 ·Locally in shore phases, generally but not everywhere Mudstone and limy shale; unit poorly exposed; near the mountains, the Laney Shale Member contains soft gray mudstone grades into pale-buff limy massive green mudstone beds, thinner zones of car­ shale that contains a few thin mud-cracked marlstone layers______110 o bonaceous shale, and beds and lenses of carbonaceous sandstone. In these beds, particularly the greenish­ Thickness, Laney Shale Member______283 0 gray rnudstone, and turtle bones and -pike scales are abundant. Silicified wood is also common in A section of the Laney Shale Member measured on such associations. In the buff chippy madstone beds the west slope of Steamboat Mountain (sec. 17, T. 23 that characterize this member, impressions of leaves are N., R. 102 W.) was published in an earlier report common and, locally, plentiful. Leaves and fragments (Bradley, 1926, p. 131), though, of course it was there of palms (Sabalites sp.) are by far the most numerous, designated as Morrow Creek Member ~f the Green though leaves of deciduous trees are common in the limy River Formation. shale and madstone of the Laney. Northeastward from the north end of the Rock McGrew (McGrew and Berman 1955, p. 110) Springs uplift the member thins, and on the northeast­ reported finding abundant crocodile, turtle, and gar­ ern slope of Oregon Buttes (sec. 2 T. 26 N., R. 101 W.), ':here the following section was measured, it is only a pike remains and also the small fish in the httle more than 20 feet thick: Laney Shale (then Morrow Creek) Member in Tps. 26 and 27 N., R. 105 W. More significantly, however, Section of the Laney Shale 1\1 ember. of the Green River Formation measured in sec. 2, 'P. 26 N., R. 101 W., Sweetwater County, Wyo. McGrew also found (McGrew and others, 1959, p. Ft in 125-127) an ilnportant collection of mammalian re­ Algal and oolitic limestone, in part silicified; con- mains in this shore facies. Of these remains he says, tains abundance of ostracode shells ______1 0 Marlstone, shaly; has rather thick but regular "* * * none was larger than Hyopsodus lep1'dus Mat­ laminae ______0 6 thew except for Hyrachyus, of which an astragalus was

732-76lS 0-64---4

() A46 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

FIGURE 14.-Characterlstlc exposure of the Laney Shale Member of the Green River Formation in the north bank of a tributary to Blacks Fork in sec. 7, T. 16 N., R. 108 W., Sweetwater County, Wyo. The member here consists predominantly of brownish buff sandy marlstone. Typical sandstone lenses are visible in the upper part of this exposure. found. Insectivores, primates, rodents, and Hyopsodus Tower Sandstone Lentil has been abandoned. He make up the great bulk of the fauna." The list follows: showed that the Tower is not a single sandstone lens as Leptotomus parvus n. sp. McGrew Thisbemys sp. the name suggested but a complex and extensive system Diacodon edenensis McGrew Sciuravus nitidus Marsh of sand-filled channels and beds. Most of these channel gracilis Marsh Hyrachyus sp. sandstones, which are near or at the base of the Laney Omomys carteri Leidy Hyopsodus lepidus Matthew Shale Member, are 50-75 feet thick and 150-300 feet Shoshonius? laurae McGrew Melanosaurus sp. Paramys delicatus ;Leidy wide. (See fig. 15.) In the vicinity of the town of Green River, the sand::tones cap towers which gave rise These mammals, he believed, indicate early Bridgerian to the name Tower Sandstone Lentil (Bradley, 1926, age. He wrote by way of interpretation (McGrew and p. 123). Locally, however, the sandstones are scattered others, 1959, p. 127) of the ecology: "Altogether the through the lower 400 feet of the Laney. These channel evidence suggests a rather extensive, heavily forested sandstones are common as far south as Sage Creek swampland, with numerous braided waterways. The (T. 15 N., R. 106 W.), but south of that they are less occasional beds of calcareous shale containing abundant conspicuous, though sandstone beds become progres­ impressions of the fish Km.ghtia indicate periodic, per­ sively more numerous still farther south near the Uinta haps widespread submergence." With this interpre­ Mountains. Northward from the Union Pacific Rail­ tation I fully agree. The geology indicates that road the channel sandstones become thinner and less Gosiute Lake was shallow and that small fluctuations of numerous and within 10 or 12 miles lose their identity, level produced large lateral shifts of the shoreline. though they may be present as softer sandstone beds. On the basis of a recent study of the Green River Sandstone lenses and beds that may be correlative with Formation by W. C. Culbertson (1962, p. C54-C57), of some of those in the Green River Basin occur along the the Geological Survey, the formal stratigraphic name western rim of Washakie Basin and are responsible for

• EOCENE ROCKS, WYOMING-COLORADO-UTAH A47

clear and unstrained. The phologopitelike biotite and the hornblende suggest an alkalic source, which is not surprising; many of the tuffs in the Green River Formation of Wyoming have the same kind of biotite, and the hornblende is commonly riebeckite. The nearest vents containing this kind of volcanic material are in the , Tps. 32 and 33 N., Rs. 87 and 88 W., Natrona County, Wyo. (Carey, 1954). But as J. D. Love (written communication, May 1962) pointed out, ash from that source probably would have had to oppose the prevailing winds. Accordingly, a source in the volcanic center of the of northwestern Wyoming is perhaps more reasonable. The volcanoes of that area also are known to have been active during the middle and late Eocene (Love, 1939, p. 109-110). Presumably the finer particles of this ash fall were washed or blown farther southward away from the volcanoes and incorporated in the sediments that make up the lower part of the Laney Shale Member of the FIGURE 15.-Tuffaceous sandstone lens close to the base of the Laney Shale Member Green River Formation. of the Green River Formation. Scour into the underlying oil-shale and marlstone Volcanic ash, as has been noted, is abundant in the beds and differential compaction beneath the sandstone lens are visible in the central part of the photograph. This sandstone lens is one of many exposed along upper part of the Laney Shale Member. Most of this U.S. Highway 30 a few miles west of the town of Green River (sec. 9, T. 18 N., R. ash has been considerably altered, but some beds are 107 W.). This group of sandstone lenses and beds was formerly known as the Tower Sandstone Lentil. comparatively little altered. Two of these were selected for chemical analysis (table 6). the topographic relief of Pine and Sand Buttes (T. 15 N., R. 100 W.). TABLE 6.-Chemical analyses of a rhyolitic and an andesitic tuff from the upper and middle parts of the Laney Shale Member Because the channels in which these sandstones and, for comparison, Daly's average compositions of rhyolite and andesite were deposited were cut in fine-grained highly com­ [Analyst: D. F. Powers] pactible sediment, differential compaction has con­ siderably distorted both the original form of the 2 sandstone bodies and the enclosing sediments. (See ------figs. 15, 16.) Si02------76. 56 72. 77 58. 59 59. 59 Al203-- _- _- _- _------9. 39 13. 33 15. 58 17. 31 The actual channels cut in the Laney Shale Member Fe203---- _------2. 15 1. 40 5. 06 3. 33 FeO ______18 1. 02 62 3. 13 have gently sloping sides. Moreover, the part of the ~gO ______53 38 3. 36 2. 75 sand that filled these channels evidently mixed gradu­ Ca 0 ______1. 36 1. 22 3. 87 5. 80 ally with the marly mud, for in many places the base N a20 ______- _- _- _- - 1. 02 3. 34 4. 54 3. 58 K20------4. 52 4. 58 2. 01 2. 04 of the sandstone lens is silty or slightly sandy regu­ H20 + __ ------1. 98 1. 50 2. 23 1. 26 larly laminated more or "less organic madstone. In H2o- ______----- _ 88 ------2. 00 ------Ti02------36 29 66 77 addition, it contains fish remains and locally shows P20s------09 10 22 26 ~no ______subaqueous slumping. This madstone grows more 02 07 03 18 C02- __ ------05 ------38 ------sandy upward to 10-15 feet above the base where 803------63 ------28 ------CL ______- - __------_ it grades into the typical massive or finely banded F ______01 ------06 ------s ______03 ------06 ------sandstone. 01 ------00 ------Much of the sand that makes up these lenses and Ba 0 ______------03 ------09 ------beds is of volcanic origin. The sandstone lenses SubtotaL ______99. 80 ------99. 64 ------apparently represent concentrations of the crystal and Less 02 correction for s and CL ______02 03 ------lithic grains from blankets of volcanic ash. In thin ------sections the volcanic aspect is as apparent as it is TotaL ______99. 78 ------99. 61 ------obscure in the outcrop or even in a hand specimen. 1. Field No. 26-58, lab. No. F- 2798; rhyolite from sec. 9, T. 15 N., R. 100 W., Sweet­ Almost without exception the grains are sharply water County, Wyo. 2. Daly's average rhyolite (Daly, 1933, p. 9). angular, muscovite is absent but a phologopitelike 3. Field No. 36-58, lab. No. F- 2799; andesite from sec. 27, T. 23 N., R. 109 W., Sweet­ water County, Wyo. biotite is common, and the quartz grains are nearly all 4. Daly's average andesite (Daly, 1933, p. 16). A48 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

b

FIGURE 16.-Field sketch (simplified) to sho"' extent of differential compaction around and between tuffaceous sand­ stone lenses in the lower part of the Laney Shale Member. The interval between two rich oil-shale beds at a and b is 61.5 feet, whereas the interval between them at c and d is only 12.4 feet. The beds enclosing these two oil-shale layers consist of papery oil shale. A lens of sandy marlstone fills the depression above c-d. Exposed in the north wall of a small gulch in the SEH sec. 21, T. 18. N., R. 107 W.

Sample 26-58 is exceedingly fine grained and consists Shale Member of the Green River Formation. Pipi­ mostly of partly devitrified shards that are sharp and ringos inferred that the Battle Spring Formation is almost needlelike. Its composition is similar to the about 3,300 feet thick but that it may be even thicker. average composition of 102 rhyolites given by Daly His description (1962, p. A34-A35) of the formation (1933, p. 9). It differs from the average composition follows: most notably by having higher a Si02 content and lower The base of the Battle Spring formation is exposed on the AltO a and N a20 contents. The total iron is nearly the north slope of Flattop Buttes [northern part of T. 26 N ., R. 95 same; though, as might be expected, much more of the W.] and at a point about 10 miles west of Rawlins, Wyoming, in the northwest part ofT. 21 N., R. 89 W.; at both localities iron in the Green River ash is in the ferric state. the Battle Spring formation overlies the Fort Union formation Sample 36-58 is a medium-grained crystal-lithic unconformably. tuff whose micas are somewhat chloritized. Its The Battle Spring formation consists of very coarse-grained to composition is closely similar to the average composition pebbly arkosic sandstone with less amounts of bright green of 87 andesites given by Daly (1933, p. 16). It differs claystone that contains abundant large grains of clear angular quartz. Locally the beds form low rounded bluffs in which the from the average most by having less Al 20a and more cross-bedded nature of the sandstone is clearly visible, elsewhere Na20 and by having somewhat more MgO and less CaO. the sandstone weathers into soft slopes littered with spheriodal Tuffs more or less similar to these are fairly common sandstone concretions that are moderately calcareous and often in the Laney Shale Member, but variants of the an­ contain limonitic centers. The sediments that make up this desitic tuffs make up a greater volume than do the formation appear to have been deposited· in deltaic sheets, the rhyolitic tuffs. source of which appears to have been the Granite Mountains north and northeast of the map area. [See fig. 10.] BATTLE SPRING FORMATION Where the rivers that carried the sediments spilled out into one of the ancient Green River lakes, extensive areas of foreset Pipiringos (1962, p. A34-A35) gave the name Battle beds were formed, which today exhibit dips up to 15 degrees. Spring Formation to a thick sequence of arkosic sand­ No fossils were found in the Battle Spring formation, but the stone in the eastern part of the Great Divide Basin, formations with which it intertongues range in age from earliest Eocene through early middle Eocene. The Battle Spring for­ taking the name "* * * from typical exposures south­ mation seemingly represents a period of continuous deposition west of Battle Spring Flat * * *" (T. 23 N., R 94 during this time. W.) and "* * * southeast of Lost Creek Butte * * *" (eastern part ofT. 23 N., R. 95 W.). The Battle Spring BRIDGER FORMATION Formation, of early and middle Eocene age, intertongues DEFINITION AND AGE with all the subdivisions of the Wasatch and Green The Bridger Formation, of middle and upper(?) River Formations already described except the Laney Eocene age, was named by F. V. Hayden (1873) for EOCENE ROCKS, WYOMING-COLORADO-UTAH A49 badland exposures in the central part of the Green River conspicuous benches in the Bridger badland terrain. Basin along the main line of the Union Pacific Railroad. (See fig. 17 .) Locally these thin layers are silicified. The Bridger Formation occupies large areas in the Carbonaceous sandstone, shale, and clay layers are central parts of the Green River and Washakie Basins rare but apparently are significant, as they represent where it makes a picturesque badland terrain. Outliers swamp sites and a few of them may represent fossil of the Bridger Formation were mapped northeast of the soils. In an excellent description of the Bridger Forma­ Rock Springs uplift. Pipiringos (1962, pl. 1) and Nace tion in the southern part of the Green River Basin, (1939, pl. 1) mapped other outliers of the Bridger along the Koenig (1960, p. 165-168) reported also thin lignitic northern part of the central Great Divide Basin (Tp. 26 and coaly layers in several parts of the formation. N., R. 94-97 W.) , and Sears (1924b) mapped rather large Koenig (p. 168) proposed a volcanic somce for virtually areas of Bridger in Moffat County, Colo. The Bridger all the sediments of the Bridger Formation except the outliers mapped by Pipiringos and Sears (in part) are thin calcareous layers of lacustrine origin. In this, he shown on plate 1 of this report. agrees with Sinclair ( 1906, p. 273). My impression is

CLASTIC SEDIMENT that most of the beds in the Bridger are tuffaceous but also contain a significant percentage of clastic material. The Bridger Formation resembles in many respects the Wasatch Formation, but it contains fewer red beds PYROCLASTIC SEDIMENT and much more volcanic ash. It consists predomi­ One of the most distinctive features of the Bridger nantly of sandy tuffaceous mudstone that ranges in Formation in the Green River Basin is its andesite tuff, color from light neutral gray to rather dark greenish most of which occurs in irregular beds that consist of drab and grayish chocolate brown. Locally some of continguous or overlapping thick crossbedded lenses. the gray mudstone in the uppermost parts of the forma­ The tuff has been altered, and the alteration minerals tion in the Green River Basin is banded with pink, dull have given it surprisingly vivid colors. Because these red, or mauve. Interbedded with the mudstone are colors are so exceptional as rock colors and because beds and lenses of crossbedded gray to brownish-gray they make such conspicuous bands in the gray bad­ medium-grained tuffaceous muddy sandstone. Vol­ land terrain, it seems worthwhile to define two of the canic-ash beds that contain little clastic material are commonest colors with some precision. One of these numerous in the Bridger and locally make up as much colors matches Ridgway's (1912) "deep bluish glau­ as 15-20 percent of the formation. Widely separated cous," which is a mixture of 93 percent primary green thin limestone and madstone layers make extensive and and 7 percent primary blue subdued by the addition of

FIG tiRE 17.-Characterlstic exposure of the Bridger Formation in the northeast slope of Twin Buttes In the southeastern part of the Green River Basin. About 1,400 feet of Bridger is exposed here. The three highest points, all of small area, are each capped by about 50 feet of Bishop Conglomerate. The apparent highest point, near the center of the photograph, is in sec. 21, T. 14 :-<" ., R. 109 \\" .,Sweetwater County, Wyo. The Buckboard Crossing topographic quadrangle map, publish~d in 1959, shows this mass as Black Mountain, a name I never heard used in that locality. According to that map the name Twin Buttes is restricted to two much smaller, but slightly higher, buttes in sees. 6 and 7, T. 13 N., R. 109 W. A 50 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS considerable neutral gray and lightened in tint by the newly fallen ash until their former gradierits were addition of a moderate amount of white. The other reestablished. Other andesitic ash falls, however, common andesite tuff color is a strong green, although were reworked considerably more, as is shown by the Ridgway gave this particular color the name "deep greater admixture of clastic material. In fact, all dull yellow-green (1)." This is a mixture of equal gradations are found between the nearly pure strongly amounts of primary yellow and green subdued by a colored andesite tuff and gray muddy sandstone whose moderate amount of black. The colors of these par-· pyroclastic constituents are obscure or absent. ticular tuffs, of course, change with changing light and Tuffs more alkalic than andesite make up a greater with the moisture content of the rock. Although these percentage of the Bridger Formation than do the an­ are the prevailing hues of the altered andesite tuffs, desite tuffs. l\1ost of these alkalic tuffs are evidently other more sombre hues that grade into dull olive brown rhyolitic, but some appear to represent rocks inter­ are common. mediate between rhyolite and andesite. Johannsen The bluish-gray andesite tuff is a medium-grained (1914, p. 220-221) studied samples collected frmn bone­ sandy rock consisting of angular to subrounded grains bearing beds in the Bridger Formation and reported of more or less devitrified glassy volcanic rock that most of them as dacite, dacite?, and tuffs but called contains an abundance of plagioclase laths and sand­ one "glass tuff." Possibly, chmnical analyses of a size crystals of calcic plagioclase, green to brown series of these tuffs would show a rather c01nplete hornblende, biotite, augite, and a few grains of potash gradation between the dacite and glassy tuff. The feldspar and quartz. Much of the hornblende and son1e rhyolitic tuffs range in color from dull greenish gray to of the plagioclase is idiomorphic. Some of the glassy white (fig. 18) and in texture from that of fine-grained fragments are fairly fresh and contain minute spherical sandstone to clay depending upon the content and bubbles, whereas other fragments have been altered to size of crystal fragments and the degree of alteration. a felt of clay-mineral laths. Most of the biotite has The commonest rhyolitic tuffs consist of a mixture been bleached or converted to a chloritelike mineral. of lumps and shards of pumiceous glass and angular Pore ·spaces are filled in part with calcite but mostly fragments of quartz and potash feldspar. In addition with a bright-bluish-green fibrous and flaky clay mineral to the quartz and potassic feldspar, at least some of that is probably nontronite. which is sanidine, are lesser amounts of biotite, green The deep.,.green andesite tuff is closely similar to the hornblende, and plagioclase (oligoclase and andesine). light-bluish tuff just described, but it contains con­ Zircon and apatite are rare. In some of the tuffs siderably more of the green alteration mineral that is richest in crystal constitutents, biotite is abundant and inferred to be nontronite and a much larger quantity hornblende is common. Unaltered glass in these tuffs of hydrated iron oxide. The green alteration mineral has a refractive index close to 1. 52. forms a tightly adhering film on each crystal or lithic Most of the rhyolitic tuffs are altered; the glass has grain and also fills the pore spaces. · Much of this been devitrified or, in some, altered to a felt of clay­ alteration mineral is brilliant emerald green and mineral flakes. The shard and pumiceous textures, appears to be made up either of felts of flakelike parti­ however, are clearly visible. A few of the rhyolitic cles or of closely spaced fibres. Some of" this material, tuffs that apparently were originally made up mainly however, makes clusters of radiating needles that ·line of minute and delicate glass shards have been altered cavities. In plain light this material is bright bluish to a bentonitic clay. . These tuffs contain only a small green parallel to the elongation and greenish yellow at quantity of very small angular grains of quartz, right angles to the elongation. C. S. Ross of the sanidine, and sodic plagioclase but have an abundance Geological Survey suggested (oral communication, 1931) of dark-brown to black biotite flakes and a moderate that this may be the bluish-green variety of amount of dark-green hornblende. All these crystal known as celadonite. Attempts to isolate this mineral constituents are remarkably fresh. One of these tuff for further tests we:.;e unsuccessful. layers, which weathers to a distinctive pale lavender, The crossbedding and lenticularity of these strongly contains an abundance of well-preserved vertebrate colored tuffs shows that they were reworked by streams; remains. but apparently the reworking was not extensive, for A likely source for most of this volcanic material is the tuffs contain only a small percentage of clastic the great volcanic center in the Absaroka Range in grains such as quartz and rounded grains of calcite and northwestern Wyoming (Love, 1939, p. 109-110). limestone. The large areal extent and the continuity STRATIGRAPHIC UNITS of crossbedded lenses of these andesite tuffs suggest WHITE LAYERS that the ash falls choked the drainage channels and In the southern half of the Green River Basin, a caused the overloaded .. streams to wander widely in the number of rathe1· widely spaced white layers make EOCENE ROCKS, WYOMI TG-COLORADO- UTAH A51

FIGURE 18.-White layers of altered tuff that make persistent benches in gray and greenish-gray mudstone of the Bridger Formation. View southward from sec. 11 , T . 16 N., R. 113 W., Sweetwater County, Wyo. conspicuous features in the landscape and are used by marlstone beds that contain an abundance of flat­ vertebrate paleontologists as key beds to identify the coiled snail shells. boundaries of faunal zones. (See fig. 6.) One of the The Lonetree white layer of Matthew is 440 feet most extensive of these white layers is the one Matthew stratigraphically higher than the Sage Creek white (1909) called the Sage Creek white layer. This unit layer in the Bridger and crops out in the badlands a was mapped over much of the southern Green River few miles north of Lonetree, Uinta County, Wyo. Basin, and its outcrop is shown on plate 1. Near the The outcrops of the Lonetree white layer and another, headwaters of Little Dry Creek (sec. 27, T. 14 N., R. 390 feet still higher, which Matthew called the Upper 115 W .) the Sage Creek white layer consists of two white layer are shown in figure 19. Partial sections beds. of the beds that include the Lonetree white layer and Thickness the Upper white layer measured on the southwest (feet) Marlstone, white, hard, platy.; some bedding planes have slope of Sage Creek Butte a few miles north of Lone­ numerous long stem impressions and a few leaf frag­ tree are as follows: ments; locally contains thin lenses of carbonaceous shale______4 Partial section of the Bridger Formation that includes the Lonetree white layer of Matthew. (Sec. 8, T. 13 N., R. 113 W.) Marlstone, light-brown, hard, platy; has irregular bands Thickness of brown and black chert______5 (feet) Mudstone, pale-greenish-gray ______- _--- 14 TotaL______9 Sandstone, light-gray, medium-grained, muddy, cross- bedded ______2 A nearly identical but more detailed description of Mudstone, light-gray, and sand ______3 the Sage Creek white layer was given by Sinclair Claystone, bro\\·n, soft, waxy ______(1906, p. 280) for the type locality of the Sage Creek Madstone; contains flat-coiled snail shells, gar-pike scales, and crocodile and turtle bones ______- __ -- white layer on Sage Creek. But farther east this Mudstone, light-gray ______. ______------white layer loses its whiteness and in the vicinity of Lonetree white layer: Madstone, white, chalky, alternate Twin Buttes becomes a group of thin platy brown hard and soft layers ______- _--- 6 A52 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

R.114 W. R.113 W.

5 4 6 Sage Creek Butte

12 .I

__ / ...... / .. /· ./ 13 18 16

·~.

··-...___

21

···----... .r-·· ...... _____···~---~

0 2 MILES

FIGURE 19.-Map shows outcrops (shaded) or two or the white layers In the Bridger Formation In the southwestern part or the Green River Basin.

Thickness (feet) Partial section of the Bridger Formation that includes the Upper Rhyolitic tuff, soft, medium-grained; rich in biotite; white layer of Matthew. (Sec. 9, T. 13 N., R. 113 W.) Thickness lenticular but continuous______3 (jut) Mudstone, tuffaceous, biotitic; contains brown clay Mudstone, soft, brownish-gray ______61 pellets______5 Mudstone, dark-brown, and sandy ______Andesite tuff, light-bluish-green, sandy, crossbedded, Mudstone, soft, brown, clayey; contains fresh-water- lenticular but persistent______23 pelecypod shells ______- ______3 EOCENE ROCKS. WYOMING-COLORADO-UTAH A 53

Thickness (feet) Upper white layer: Marlstone, brownish gray on fresh fracture but weathers stark white; contains an abund- ance of fiat-coiled snail shells______1 Mudstone, brownish-gray; contains lenses of granular gray tuff______8 Marlstone, white; contains Viviparus and flat-coiled snail she)ls______~'z Mudstone, soft, brown______12 Tuff, buff, muddy______10 These partial sections were taken from a much longer section of the Bridger measured on the southwest flank of Sage Creek Butte in T. 13 N., R. 113 W. The details of this section are given later in the report under the heading, "Measured sections." Although the white layers closely resemble some of the white rhyolitic glass tuffs of the Bridger, they con­ sist dominantly of microgranular carbonates and clay. The Lonetree white layer contains 66 percent calcite, about 32 percent minute clay flakes, and about 1 per­ cent small angular grains of quartz and potassium feldspar. Small brownish-gray pellets of clay are common in the Lonetree white layer. The abundance of carbonates and the presence of fresh-water-gastropod shells indicate that these white layers were probably deposited in extensive but shallow lakes. Carbonaceous lenses either within or adjacent to the white layers indicate that swampy areas bordered the lakes or at FIG UHE 20.-Petritled log with the bark well preserved. Found in the lower part times replaced them. For some reason these white of the Bridger Formation in sec. 3, T. 26 N., R. 101 W., approximately on the layers, particularly the Lonetree and Upper white boundary between Sweetwater and Fremont Counties, Wyo. layers, contain numerous remains of small animals. Teeth and jaws are particularly common. tion. This gradation takes place by extensive inter­ No study was made of either the Burnt Fork or fingering of the two lithologies from the central parts Cottonwood white layers of Matthew. of the Green River Basin marginward in all directions. At many places, petrified wood is common in the In other words, the Green River Formation is appreci­ Bridger Formation, particularly around Oregon Buttes ably thicker in the central part of the Green River (T. 26 N., R. 101 W.) (See fig. 20.) In that area much Basin and grades laterally o~tward into successively of the wood is encrusted with silicified algal deposits. lower units of the Bridger Formation. (See fig. 6.) Near the mountains, particularly near the Uinta and The top of the formation in the Green River Basin is Wind River Mountains, the Bridger becomes coarse unknown because even where it is thickest (Twin grained and locally conglomeratic. Along the Uinta Buttes) it is truncated by the younger Bishop Con­ Mountains the conglomeratic facies of the Bridger are glomerate. characterized by pebbles and cobbles of Carboniferous The maximum thickness of the Bridger Formation limestone and, near the Wind River Mountains, by is in the southern part of the Green River Basin. In cobbles of hornblende schist and granite. Along the Twin Buttes, shown on some maps as Black Mountain north flank of the Uinta Mountains, not only the (T. 14 N., Rs. 109 and 110 W.), the Bridger is about Bridger but also the underlying Green River and 1,560 feet thick; westward it thickens about 725 feet Wasatch Formations become so conglomeratic that so that in the area west of Sage Creek Butte (north of they lose their identity. On the geologic map (pl. 1) Lonetree, Wyo.) it must be about 2,285 feet thick. these conglomeratic Eocene rocks are shown as Tertiary This 725 feet of westward thickening replaces an undifferentiated. This facies of the Eocene rocks is equivalent amount of the upper part of the Laney Shale discussed later in this report. M ember of the Green River Formation in the vicinity Nearly everywhere the base of the Bridger Formation of Twin Buttes. At the north end of the Rock Springs is uncertain because it grades downward into the top uplift, in Oregon Buttes (T. 26 N., R. 101 W.), the of the Laney Shale Member of the Green River Forma- Bridger is about 480 feet thick. Detailed sections of the A54 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Bridger measured at these two localities are given later In the Washakie Basin the base of the Bridger Forma­ in the report under the heading "Measured sections." tion is marked by a rather conspicuous change from FAUNAL ZONES buff tuffaceous marlstone of the Green River Forma­ For convenience in locating the numerous collections tion to greenish-brown crossbedded medium- to coarse­ of vertebrate fossils stratigraphically, Matthew (1909) grained lenticular sandstone and greenish-gray mud­ divided the Bridger into five zones, beginning with A stone characteristic of the Bridger Formation. The at the base. Simpson (1933) pointed out that these boundary between the Bridger and Green River in subdivisions of the Bridger do not correspond to major the Washakie Basin was located on aerial photographs faunal divisions; zones A and B are each distinctive in the field by J.D. Love and me along the east slope of faunal units, C and D together make a distinctive the Kinny Rim. Subsequently, R. J. Hackman, of the faunal unit, and E contains no identifiable fossils. Survey traced this boundary all around the Washakie Wood (1934) grouped zones A and B together to Basin photogrammetrically. (See pl. 1..) make his Black's Fork Member of the Bridger and UINTA FORMATION zones C and D to make his Twin Buttes Member. Zone E. of Matthew he regarded as Uinta A of the Vertebrate paleontologists report (Wood, 1934) vertebrate paleontologists. These members are de­ younger faunas in the uppermost parts of the Bridger· fined as faunal units analogous to Lysite and Lost like beds in the Washakie Basin and therefore assign Cabin and were intended to obviate the need for such those beds to the Uinta Formation of late Eocene age. cumbersome terms as Bridger C and D. The two Also, according to Simpson (1933), the Bridger Forma­ members proposed by Wood are not distinguishable tion in the Washakie Basin is younger than the Bridger lithologic units though they are separable and mappable in the Green River Basin. The vertebrate paleontolo­ in part of the area, by means of the Sage Creek and gists refer to the lower (perhaps a little less than half) Lonetree white layers. Beyond the limits of these beds in the Washakie Basin that have general Bridger­ white layers the members are recognizable only by like lithology as Washakie A and the upper part as means of their contained faunas. Washakie B. Ac9ording to McGrew (1951, p ..54), The large vertebrate fauna collected by C. W. Gilmore "The fauna from Washakie A is adequate to prove of the U.S. National Museum in the summer of 1930 approximate contemporaneity with the upper faunal will be listed in another report in which the paleocology horizon (Bridger D) of the Green River Basin. The of the Wasatch and Bridger Formation will be, fauna of Washakie B is like that of the lowest faunal discussed. \ horizon (Uinta B) of the Uinta formation." He listed WASHAKIE BASIN (p.· 54) 20 genera of vertebrates from Washakie A and The Bridger Formation in the Washakie Basin is 10 genera from Washakie B. Because of these a.ge rela­ much like that in the Green River Basin except that tions·and because the Uinta Formation was not mapped, the tuff is less conspicuous, probably because it is the rocks above the Green River Formation in the mixed with more clastic sediment, and the upper part Washakie Basin are grouped as· Bridger and Uinta is more conspicuously banded with pink. This pink Formations and are so shown on plate 1. banding is also characteristic of the Bridger Formation The thickest section of the Bridger and Uinta For­ farther south in Moffat County, Colo. mations in the Washakie Basin is exposed on the flanks Gray mudstone and drab grayish-brown lenticular of Haystack Mountain (T. 16 N., R. 95 W.). There sandstone beds that weather into badlands or extensive the basal 50-75 feet of the Bridger is not well exposed, almost featureless benches are characteristic of the but above that about 780 feet of the two formations is Bridger Formation in the Washakie Basin. Some of perfectly exposed. A section measured there is given the mudstone, however, is pale sage green and, where later in the report under the heading, "Measured banded with pink or mauve, makes a colorful landscape. sections.'' More of the sandstones, especially in the northern part UNDIFFERENTIATED EOCENE FORMATIONS of the Washakie Basin, are coarser grained than those in the Green River Basin; indeed, gravel lenses are Along the north flank of the Uinta Mountains from common in the Bridger of Haystack Mountain. There, a place -a few miles west of Manila, Utah (T. 3 N., R. some of the coarse gravelly sandstones are nearly white 19 E.), to the vicinity of Elizabeth Mountain (T. 3 N., and have false beds that dip ste~ply southeast, in­ R. 10 E.), the Wasatch, Green River, and Bridger For­ dicating a source to the northwest. Many of the mations are all so conglomeratic that they cannot be dis­ details of the Bridger and overlying Uinta formation tinguished from one another. Moreover, in this belt, are given later in the report under the heading which is about 50 miles long and almost entirely in Utah, "Measured sections." the exposures are generally poor. Cobbles and boulders EOCENE ROCKS, WYOMING-COLORADO-UTAH A55

of cherty limestone, mostly from the Madison Lime­ extend more than a few miles out into the Green River stone, make up the greater part of this conglomeratic Basin. facies, though red quartzite from the Uinta Mountain Group is locally plentiful. White quartzite is next most BISHOP CONGLOMERATE abundant, and pebbles of black chert are common. The Bishop Conglomerate caps several large erosion On the southwest side of Phil Pico Mountain (T. 3 N., benches or pediments that slope away from the Uinta R. 17 E., Dagget County, Utah) is exposed a facies of Mountains. J'he largest area of Bishop Conglomerate this undifferentiated Eocene sequence, all of which extends over a large area in the southwest quadrant of Anderman (1955, p. 131) assigned to the Green River the Rock Springs uplift. Other extensive benches Formation, that resembles in lithology the Green River capped by this conglomerate are distributed across the Formation 17 or 18 miles farther east in the canyon of southern margin of the Green "River Basin. Isolatetl the Green River (T. 12 N., R. 108 W., Sweetwater remnants are found on high points south of the Rock County, Wyo.). This possible tongue of the Green Springs uplift and as far east as Flat Top Mountain .• River Formation is thin (not measured) and consists of on the eastern rim of the Washakie Basin (T. 14 N., very fine grained buff soft limy sandstone in thin R. 93 W.). regular beds. It is interbedded with gray sandy gravel The Bishop Conglomerate consists almost wholly of and conglomerate, son1e of which contains well-rounded well~rounded cobbles .and. boulders. Inasmuch as the limestone boulders as much as 18 inches in diameter, formation in this area was derived from the high part and is underlain by even coarser bouldery conglomerate. of the Uinta Mountains, boulders and cobbles of red Along the south end of Phil Pico Mountain, these and quartzite from the Uinta Mountain Group are pre­ the overlying beds are turned up so that they dip about dominant. Boulders and cobbles of limestone and 23 ° northward. metamorphic rock, however, are locally common. A mile or two farther west (sees. 34 and 35, T. 3 N., Local sources ~lso contributed material to the Bishop R. 17 E.), the undifferentiated Eocene has an unusual Conglomerate, as around the flanks of Aspen Mountain and local aspect. There the Weber Sandstone of in T. 17 N., R. 104 W. There the Bishop Conglomerate and age makes a prominent consists chiefly of angular fragments of brown sandstone hogback that dips about 60° northward. The Weber and quartzite derived from nearby outcrops of the is a soft friable very fine grained and well-sorted white Upper Cretaceous Blair Formation. This local facies sandstone. It is also markedly crossbedded. The interfingers with the better rounded material derived undifferentiated Eocene laps up against the Weber from the Uinta Mountains. with approximately a 30 ° angular discordance-that is, The origin, geomorphic history, and stratigraphic the· Eocene rocks dip about 30° N. The Eocene rocks position of the Bishop Conglomerate have been dis­ consist of this same white fine-grained sandstone but cussed at some length in another report (Bradley, 1936, contain stringers of rather angular limestone and white p. 172-17 4). Perhaps all that need be added here is sandstone pebbles. Mixed in with these pebbles and that, as I interpret the geology and geomorphology of distributed through the mass of white sandstone are the north flank of the Uinta Mountains, the Bishop a large number of boulders and blocks of Weber Sand­ Conglomerate is older than· the Browns Park Forma­ stone that are as much as 10 feet across. Some are tion and is not to be confused with the basal conglom­ sharply angular and obviously could have moved but erate of the Browns Park Formation, which it closely a few feet from the parent Weber cliff. Others are resembles. Recent studies by Hansen, Kinney, and rounded, but this is expectable for such soft sandstone. Good (1960, p. B257-B259) cast doubt on this con­ A subordinate number of hard well-rounded limestone clusion and show that the geologic history in critical boulders are also found. areas along the north flank of the Uinta Mountains is Another, but much smaller, strip of undifferentiated complex and not yet fully understood. Tertiary rocks was mapped in the vicinity of Vermilion The age of the Bishop Conglomerate is given tenta­ Creek (Tps. 10 and 11 N., Rs. 100 and 101 W., l\1offat tively as Miocene(?), but it may prove to be Oligocene. County, Colo.). In this area the Tertiary rocks consist The key to its age may be contained in the thick mostly of sandy and pebbly gray mudstone and section of white or light gray biotitic tuff, white sand represent only part of the Wasatch and Green River stone, and quartzite that rests on the Bishop Con­ Formations. glomerate and is thick enough to cap the western part I did not measure the thickness of the undifferentiated of Aspen Mountain in the southern part ofT. 17 N., Eocene formations, but along the Uinta Mountain R. 104 W. Southwest of Aspen Mountain the white flank they must aggregate several thousand feet. They tuff makes a small conical butte known as Antelope represent a piedmont facies that probably does not Butte. Near the top of this butte is a bed of soft A 56 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

greenish-gray muddy sandstone in which I found bones same series of beds as those that crop out in a belt of vertebrates, but the bones were so badly len,ched north of Oregon Buttes and Continental Peak. Love and so fragile that I could not collect them. A sig­ (1960, p. 209) suggested that these beds might be of nificant gap in our knowledge of the geologic history Oligocene age, but he was more inelined (oral communi­ of this part of Wyoming might be filled if some verte­ cation, May 1961) to think that they may be late brate paleontologist could find identifiable and datable Miocene or Pliocene. fossils in these tuffaceous beds. Most of the sandstone and quartzite beds in the upper part of this formation weather dark brown, but OLIGOCENE, MIOCENE, AND PLIOCENE FORMATIONS on fresh fracture they are white. They are remarkable Much geologic work.has been done on these younger in that they consist almost wholly of rounded quartz Tertiary rocks by different geologists in different parts grains, though some thin sections show a considerable of the area shown on the geologic map (pl. 1). Be­ number of plagioclase grains. Dark minerals of any cause these rocks are prevailingly white or very light kind are exceedingly rare. In this they resemble the colored, because they are all more or less tuffaceous quartzite beds in the Browns Park Formation, which and sandy, and because diagnostic fossils are difficult I mapped along the southern, faulted margin of the to find in them, a variety of opinions about their Washakie Basin. This absence of dark minerals in identity, geologic age, and correlations have grown up. an otherwise tuffaceous formation is puzzling. Moreover, many uncertainties persist. The following A few days after Love and I found these beds on discussion represents the state of our knowledge as of and around Aspen Mountain, he climbed Black Butte mid-1962. No attempt to exhaust the subject seems (sec. 9, T. 18 N., R. 101 W.) and found that it also appropriate now. was capped by about 200 feet of the same kind of

UNDIFFERENTIATED OLIGOCENE AND MIOCENE white sandstone and also quartzite beds. I have shown these rocks on the map (pl. 1) as undifferentiated Nace (1939, p. 31-35) mapped beds in the upper Miocene and Oligocene. parts of Oregon Buttes and Continental Peak and north of the Continental fault as Oligocene (Chadron). BROWNS PARK FORMATION Many years later J. D. ·Love, of the U.S. Geological The Browns Park Formation, whose type locality, Survey, and Paul 0. McGrew, of the University of Browns Park, is shown in the extreme southern part of Wyoming, reported to me (oral communication, plate 1, consists predominantly of white sandy tuff and May 1957) that vertebrate fossils of Oligocene age white or light-gray tuffaceous sandstone, clean sand­ have been found north of Oregon Buttes and Continen­ stone, and sandy mudstone. Locally it contains thin tal Peak in beds that underlie the Miocene Split Rock layers and lenses of greenish-gray clayey mudstone, and Formation (Love, 1961a). The lithology of both in some rather extensive areas the sandstone is con­ these formations resembles that of the Browns Park spicuously crossbedded. Much of this crossbedding Formation. The beds of Oligocene and Miocene age apparently resulted from wind action, as the false beds were not mapped separately but are included in the are curved and tangen.M'al. At the base of the formation northern part of the band in that area shown on is a coarse conglomerate that in many places resembles plate 1 as Miocene and Oligocene undifferentiated. the Bishop Conglomerate except that it is generally No post-Bridger beds are shown in Oregon Buttes and thinner. In some places, beds of the Browns Park Continental Peak on my map (pl. 1), but they are, Formation above the basal conglomerate overlap older in fact, present. (See section of Bridger Formation rocks, and in such places there is no basal conglomerate in Oregon Buttes in the part of this report titled, or even coarse-grained sandstone. Sears (1924b, p. "Measured sections.") 286) reported a maximum thickness of 1,200 feet for In 1958 Love and I found a thick section (roughly the Browns Park in Moffat County, Colo. (T. 9 N., 1,200 ft) of white tuff, tuffaceous sandstone, and R. 100 W.). quartzite on and around Aspen Mountain (T. 17 N., The Browns Park, of Miocene(?) age, extends as an R. 104 W.). The beds on the south flank of Aspen irregular, discontinuous band from the type locality Mountain and those that cap the mountain are an eastward across the southern part of the geologic map, upward extension of the white beds that make up plate 1. Antelope Butte (just described) and that blanket a The characteristics, distribution, origin, and strati­ considerable area around Aspen Mountain proper. The graphic relations of the Browns Park Formation in the age of these beds is unknown, but I have shown them area coveredby this report have been discussed rather ~~-- on the map (pl. 1) as Miocene and Oligocene undiffer­ fully in several reports (Sears, 1924a, p. 295-296; Sears, entiated on the assumption that they represent the 1924b, p. 284-287; Bradley, 1936, p. 182-184; and EOCENE ROCKS, WYOMING-COLORADO-UTAH A57

Pipiringos, 1962, p. A35-A37). Nevertheless, a signifi­ (1962, p. A35-A37) called Browns Park(?) in the cant addition to our knowledge of the history and dis­ northern part of his area (from the east side of T. 26 N., tribution of the Browns Park Formation was published ·R. 95 W. to the NW. cor. T. 26 N., R. 97 W.), have in 1960 by Hansen, Kinney, n.nd Good (1960). subsequently been redefined by J. D. Love (1961a, Deposits of uraniurn of commercial size n.nd grade I5-I8) as the Split Rock Formation. Most of the area have been discovered within the past few years in the shown along the northeast edge of the geologic map Browns Pn.rk Formn.tion west of Baggs, Y.lyo., and in (pl. 1) ns undifferentiated Oligocene and Miocene the area around the towns of Lay and Maybell in belongs, in fact, to the Split Rock Formation. Moffat County, Colo. On the basis of vertebrate fossils found in this for­ McGrew (1951, p. 54-55) reviewed the vertebrate nlation, it is of early and middle Miocene age (Love, faunas already collected from the Browns Park Forma­ 1961a, p. I24). Indeed, the uppermost part of the tion and collected still others. He concluded that a Split Rock Formation may possibly be of late Miocene middle Miocene nge is very probn.ble. Bectiuse the age. The Split Rock Formation, therefore, is in part at Wyoming Geological Association Guide Books, in least correlative with the Browns Park Formation which he published the results of his study, are not farther south. everywhere available, it seems desirnble to quote IGNEOUS ROCKS pertinent parts (p. 56). of his report: At the north end of the Rock Springs uplift is a The only faunal element that suggests a late·r age, i.e. post rather widely scattered group of buttes capped by one middle Miocene, is the mastodon, Trilophodon fricki, found in or more flows of the leucite-rich lava, wyomingite. In the Browns Park of Colorado. Osborn (1936) considered this addition to the buttes are a few spines of the same kind one of the most primitive proboscidians known from North of rock that obviously are remnants of feeder pipes. America and in the light of the other mammals it must be considered a middle Miocene form. Of other forms from the Similar feeders doubtless exist under. several of the Browns Park all are known from middle Miocene rocks of other buttes. Two low pumice cones on Steamboat Moun­ areas and one, Moropus, is not known from post middle Miocene tain (T. 23 N., R. 102 W.) indicate that it surely was rocks. the site of a vent. The known mammalian fauna from the Browns Park is as Pilot Butte (T. 19 N., R. 106 W.) is an isolated small follows: butte, also capped by wyomingite, that is 20 miles From the Browns Park of Colorado southwest of the other plugs and lava-capped hills. Procyonid Camelid The lava here contains throughout a great number of Bassariscops Gen. undet. fragments and blocks of shale from the underlying Green Mastodont Oreodont Trilophodon Gen. undet. River Formation. These range from half-inch flakes to Chalicotherid Antilocaprid blocks 2X feet long. All are baked to a greenish or Moropus Gen. undet. yellowish gray, some appear to be sintered, and others Rhinocerotid are rounded and contain fused vesicular masses. Never­ Aphelops theless, most of them retain their original bedding. From Saratoga Basin These inclusions of the underlying bedrock are so Mustelid Camelid numerous and so uniformly distributed through the Gen. nov. Gentilocamelus flow that a feeder pipe must make up the core of the butte. In a written communication (lVIay 1962) J. D. Love According to Kemp and Knight (1903), these lavas told me, however, that the nge of the Browns Park consist principally of leucite and phlogopite, together Formntion in the type locnlity itself mny be in doubt, with a small amount of diopside and hornblende, in a and that there may, in fact, be two formations there gray-green glass. The accessory minerals are rutile and instead of one. In the first plnce, he recalled the fact apatite. Schultz and Cross (1912) made a study of that there is an angular unconformity of about 16 ° of these lavas as a possible source of potash. within the Browns Park Formation (Sen.rs, 1924a, These lavas postdate the Bridger epoch and, as they p. 296); and, in the second place, samples from the rest on erosion surfaces not far above the present general type locnJity collected by W. R. Hansen of the Survey terrain and are not known to be overlain by such forma­ contain determined by K. E. Lohman, also tions as the Browns Park, are inferred to be of late of the Survey, to be of Pliocene nge (unpub. data). Tertiary age. Plainly more study is needed in the type locnlity. This inference was verified by Prof. S. S. Goldich, SPLI'l' ROC.K l"OJlMATION then of the University of 11innesota, now with the '.l.'he white, tufraceous, n.ncl sandy beds, which resem­ Geological Survey, who made a potassium-argon age ble the Browns Fork Formation and which Pipiringos determination on the phlogopite mica from two samples A 58 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS of the lava collected in 1958 on Zirkle Butte by Richard Green River Formation-Continued Johnston, then a graduate student at the University of Wilkins Peak Member-Continued Ft in Oil shale, low-grade, flaky _____ ------2 0 Wyoming, now with the Geological Survey. The Sandstone, limy, muddy, fine-grained, samples came, respectively, from SEXSEXNWX sec. 1, ripple-bedded ______------2 0 T. 22 N., R. 103 W., and NEXSEXSEX sec. 15, T. 21 N., Shale, flaky; contains layer of papery R. 102 W., Sweetwater County, Wyo. Goldich found oil shale about 1 ft thick in middle __ 5 0 that the argon contents of these samples are so low that Sandstone, limy, muddy, fine-grained, platy ripple..:bedded ______- ____ - _- 2 6 he was unable to make a satisfactory determination. Shalf', light-gray, sandy, flaky ______3 0 He expressed the opinion (written communication, Oil shale, low-grade, papery to flaky __ _ 2 0 July 15, 1959) that the rocks were, however, probably Shale, light-brown, flaky ______---- __ - 2 6 less than 5 million years old. As a further check on this Sandstone, medium-grained ______- 10 he sent the samples to Dr. Oliver Schaeffer at the Brook­ ShalE>, grayish-brown, soft, flaky; con- tains groups of thin sandstone beds_ 15 0 haven National Laboratory, whose argon apparatus Sandstone, gray, limy, muddy, fine- was geared to the determination of small quantities of grained, ripple-bedded ______----- 2 6 argon. Dr. W. A. Bassett, then of that Laboratory, Oil shale, low-grade, soft, papery ___ _ 1 6 determined the age as about 1.25 X 10 6 years. This Sandstone, limy, muddy, fine-grained, ripple-bedded ______- ______makes the \vyomingite lavas of latest Pliocene age. 2 4 Shale, sandy, platy, thinly laminated_ 1 6 Oil shale, low--grade, bluish-gray, flaky_ 2 0 MEASURED SECTIONS OF THE GREEN RIVER, Sandstone, very limy, muddy, hard, ·WASATCH, AND BRIDGER FORMATIONS platy, ripple-bedded ______2 6 The following abbreviations are used in the measured sections Oil shale, very low-grade, brownish­ given here: buff, soft, papery; contains a few thin c, Unit contains mud cracks; laminae of purplish-gray rich oil shale ______f, Unit contains fossil fish; 1 4 s, Unit contains salt crystal molds. Mudstone, greenish-drab, soft; unit Brackets indicate Culbertson's (1961, p. D172, fig. 348.2) also contains some greenish-gray key sandy-mudstone units. flaky shale ______------24 0 Boldface indicates beds in rhythmic sequence. Sandstone, very limy, muddy, fine- Section of the Laney, Wilkins Peak, and Tipton Shale Members grained, in part shaly ______1 0 of the Green River Formation and part of the Wasatch Formation Oil shale, low-grade, papery; contains in sec. 1, T. 18 N., R. 106 W. thin layers of rich oil shale ______1 6 Green River Formation: Shale, light-brown, flaky ______------4 0 Laney Shale Member: Ft in Oil shale, very low-grade, papery ____ _ 6 Marlstone, buff, chalky to hard, chippy Shale, gray, soft, flaky ______4 0 to platy; interbedded with gray silty Shale, sandy, and thin sandstone beds_ 1 6 shale, a few beds of rich oil shale, and Oil shale, low-grade, buff, papery ____ _ 1 0 buff even-grained cross bedded. to Oil shale, massive; estimated 25 gallons massive crystal tuff in lenses and per ton ______8 irregular beds near the base; these Shale, brownish-gray, soft, flaky; con­ tuffs are poorly exposed here ______500 + tains thin group of thin limy tuff Marlstone, buff, soft, papery; inter- beds near base, Big Island tuff ___ _ 22 6 bedded with sandy shale layers_____ 25 0 Oil shale, medium-grade, papery ____ _ 1 0 Marlstone, buff, chalky, platy______2 6 c Sandstone, limy, fine-grained, platy; 01l shale, low-grade, flaky to papery; interbedded with sandy shale; all grades upward into organic-poor buff ripple bedded; many surfaces mud papery marlstone that contains many cracked; mud lumps common __ 14 0 paper-thin laminae of rich oil shale__ 24 0 Shale, drab to brownish gray, flaky __ _ 4 0 Oil shale, low-grade, bluish-gray, Thickness, Laney Shale Member__ 551 + papery ______2 6 Shale, light-brown to drab, flaky ____ _ 19 0 Wilkins Peak Member: c Sandstone, very limy, hard, platy; a Marlstone, buff, soft, papery; poor in few bedding planes mud cracked __ 1 5 organic matter ______9 0 Shale, brown, soft, flaky; contains con­ Organic marlstone, buff to gray ______1 0 siderable organic matter at base but Sandstone, limy, muddy, fine-grained, progressively less upward ______-- 5 6 platy, ripple-bedded ______2 6 Oil shale, medium-grade, papery ______2 0 Oil shale, low-grade, papery ______0 Shale, greenish-gray, very soft, papery­ 2 0 Sandstone, limy, muddy, fine-grained, Shale, very sandy; alternates with beds ripple-bedded ______2 6 of very limy sandstone and sandy Shale, flaky; in part thin-bedded or- limestone; contains a few mud lumps_ 8 0 ganic marlstone ______7 0 Oil shale, low-grade, flaky to papery-- 8 EOCENE ROCKS, WYOMING-COLORADO-UTAH A59

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in Mudstone, greenish-drab, soft ______9 0 Mudstone, light-gray; contains green- Shale, papery; contains considerable ish-gray lumps; poor fissility ______5 0 organic matter ______1 0 c Marlstone, sandy, platy, ripple-bedded Shale, gray, sandy, soft, flaky- ______2 0 and mud-cracked ______10 c Limestone, sandy, ripple-bedded and Shale, light-grayish-brown; massive but mud-cracked ______5 laminae visible; soft; becomes sandy Sandstone, very limy, moderately fine upward ______2 6 grained, massive but lenticular ____ _ 8 Mudstone, so carbonaceous that it is Shale, light-brown, flaky; considerable nearly black; rich in iron oxide ____ _ 6 organic matter at base but decreases Mudstone, greenish-gray, sandy, hard_ 2 6 upward; unit grades upward into c Sandstone, very limy, muddy, platy, barren sandy shale_------______3 6 ripple-bedded and mud-cracked ____ _ 6 Oil shale; lower third low grade and Mudstone, drab to greenish-gray, soft; papery; middle third rich and mas­ contains streaks of iron oxides ______7 0 sive; top third less rich and flaky Shale, light-chocolate-brown, flaky __ _ 2 0 but contains a few thin lenses of c Sandstone, light-gray, very limy, me­ rich oil shale ______---- __ _ 3 5 dium-grained, iron-stained, ripple- Shale, drab, soft; poorly developed bedded and mud-cracked ______1 0 fissility _ ------______--- _- __ _ 3 0 Shale, light-grayish-brown, soft, flaky_ 8 Sandstone, very limy, fine-grained, Sandstone, very limy, fine-grained, rip- ripple-bedded ______2 ple-bedded ______11 Shale, flaky ______6 Shale, light-brown, soft, flaky ______4 c Sandstone, very limy, fine-grained, Limestone, sandy, hard, platy, ripple- ripple-bedded and mud-cracked ____ _ 2 bedded ______10 Marlstone, organic, chocolate-brown, Shale, light-brown, soft, flaky ______2 0 platy to chiPPY------­ 2 0 Mudstone, drab, limy, very soft ______4 0 Sandstone, very limy, fine-grained, c Marlstone, iight-grayis'h-brown; con­ ripple-bedded ______3 tains many thin siliceous layers that Shale, drab, soft, flaky ______12 0 are mud cracked ______9 0 c Marlstone, sandy, platy, mud-cracked_ 2 Oil shale, flaky to papery; weathers Oil shale, low-grade, papery; contains white; apparent slight gas breccia­ thin lenses of massive rich oil shale __ 1 6 tion; grades upward into buff varved Randstone, very limy, fine-grained, organic marlstone ______------1 6 ripple-bedded ______4 Marlstone, sandy; contains many large Mudstone, greenish-gray, soft ______7 6 mud lumps ______------3 Oil shale, rich; weathers blue; fairly Marlstone, light-grayish-brown; alter­ short lens ______------nates with thin beds of siliceous Oil shale, low-grade, flaky; weathers 1 3 blue gray ______limestone ____ ------1 0 Marlstone, light - brownish - gray; c Sandstone, very limy, fine-grained, weathers white; soft, almost flaky __ 3 0 ripple-bedded and mud-cracked ____ _ 6 Marlstone, light - brownish - gray; Shale, greenish-drab, soft, flaky ______3 6 weathers white; contains many thin c Sandstone, muddy; alternates with thin siliceous limestone beds ____ ------9 0 sandy shale layers; one layer of sandy c Marlstone, sandy; alternates with edgewise conglomerate; mud cracks muddy marlstone layers; some edge­ and ripple marks plentifuL ______6 wise conglomerate; harder layers are ripple bedded and mud cracked; l- Shale, sandy and limy, soft, flaky ____ _ 1 6 inch volcanic ash layer in middle ___ - 4 6 Edgewise conglomerate in limestone =a~ Marlstone, drab or gray, silty, massive_ 3 0 matrix, very sandy ______1 P Shale, light-chocolate-brown, flaky to Limestone, sandy, dense; contains mud papery; contains five thin siliceous lumps ____ ·______--- ____ ------2 ripple-bedded limestone beds ____ --- 2 6 Shale, flaky ______1 0 Mudstone, grayish-green, much iron Mudstone, drab, soft ______6 0 oxide stain; locally contains much c Limestone, white, sandy, hard; weathers carbonaceous stuff ______------2 0 brown; contains many shale frag­ Marlstone, light-grayish-brown, chippy, ments and mud lumps; ripple bedded ripple-bedded ______------3 0 and remarkably persistent ______8 Sandstone, very limy, fine-grained, Marlstone, brownish-buff, rather soft, ripple-bedded ______------2 laminated; weathers white; contains Marlstone, light - grayish - brown, many carbonaceous fragments; alter­ coarsely chi ppy______------8 0 nates with a few thin limy ripple- c Marlstone, very san.~y i ripple marked bedded sandstone beds ______1 6 at top; several layers mud cracked __ 1 3

t' A60 THE GREEN RIVER AND ASSOCIATED TERTIARY- FORMATIONS

Green River Formation--Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in Marlstone, light - yellowish - brown, Mudstone, greenish-gray, sandy. This chalky ______3 unit, together with overlying sand­ Marlstone, sandy, hard ______6 stone, makes up Principal Olive zone Marlstone, light - yellowish - brown, ~~ (D bed of detailed geologic map, chalky ______l 11 5 pl. 2)------0 Marlstone, sandy, hard ______5 Sandstone, light-gray, very limy, mod- Marlstone, light - yellowish - brown, erately fine grained, ripple-bedded chalky ______11 and ripple-marked ______1 0 Madstone, sandy, hard ______2 Mudstone, greenish-gray; nearly pure clay ______Marlstone, light - yellowish - brown, 12 0 chalky ______6 Sandstone, light-gray, very limy, ripple­ Oil shale, low-grade, papery, gas-brec- bedded and ripple-marked; makes ciated ______10 persistent bench ______6 0 Mudstone, grayish-drab, sandy, hard __ 6 0 Mudstone, greenish-gray; not well ex- posed ______Sandstone, limy, fine-grained; al­ 9 0 ternates with sandy platy mudstone_ 4 0 Sandstone, light-gray, very limy, lami­ Mudstone, greenish-drab, sandy, rather nated, ripple-bedded and ripple- marked ______hard; slightly carbonaceous and 6 :S ~ flecked with iron oxide ______7 6 Mudstone, greenish-gray to nearly ;:::> Shale, drab, limy, coarsely chippy; black with carbonaceous matter, soft; small quantity of organic matter ___ _ 4 0 well exposed only near top ______17 0 Mudstone, very dark gray, carbo­ Sandstone, nearly white, very limy, naceous and iron-stained; weathers fine-grained, ripple-bedded ______10 rusty lavender ______6 c Marlstone, sandy, laminated; many Mudstone, greenish-drab ______7 6 layers mud cracked ______0 Marlstone, light-gray, very clayey; be- Sandstone, very muddy, fine-grained; comes more limy upward ______4 0 alternates with thin beds of sandy Oil shale, medium-grade, papery, gas- limy mudstone ______1 0 brecciated ______6 Oil shale, low-grade, coarsely flaky ___ _ 1 3 Marlstone, sandy, hard; full of mud Mudstone, greenish-gray, soft ______2 0 lumps; gently cross bedded ______1 Oil shale, low-grade, papery ______1 0 Marlstone, light-gray, very clayey; be- Mudstone, greenish-gray, soft ______2 0 comes more limy upward_·:.. ______5 0. Shale, flaky to almost papery; contains c Marlstone, silty, hard; many bedding considerable organic matter ______2 0 planes mud cracked; alternates with c Marlstone, nearly white, sandy; platy softer more muddy layers; all bedding; numerous mud-cracked bed- ding planes ______weathers nearly white ______9 0 1 6 Shale, light-gray, soft, flaky ______6 6 Mudstone, greenish-gray, very soft ___ _ 5 0 Sandstone, very muddy, fine-grained; Oil shale, low-grade, papery ______2 0 beds thin and lenticular; alternate Sandstone, very limy, fine-grained, platy; doubtful mudcracks ______with sandy platy layers of mud- 4 stone ______1 Shale, flaky to almost papery; consider- 6 able organic matter ______Mudstone, greenish-drab, hard; weathers 9 6 ash gray ______5 6 Marlstone, light chocolate-brown, Shale, sandy, greenish-drab, hard, coarsely chippy; considerable or- ganic matter ______--- _- 7 0 platY------~------­ 8 Shale, sandy, greenish-drab, hard, c Sandstone, very muddy, very fine­ flaky ______4 0 grained, limy, platy; many bedding Shale, light-greenish-brown, flaky ____ _ 3 0 planes mud cracked ______5 0 Shale, greenish-gray, very soft; poor . Shale, greenish-brown, silty, soft ___ - __ 6 6 fis~lity ______4 0 Sandstone, gray, iron-stained, fine­ c Sandstone, muddy; brownish buff on grained, well-sorted, very micaceous, on fresh surface; weathers dark thinly and smoothly bedded or lami­ reddish brown·; fine grained; very nated; thin beds are ripple-bedded micaceous; ripple bedded and cross­ and whole is crossbedded ______6 0 bedded; some bedding planes mud Mudstone, greenish-gray; grades up­ cracked; along strike and downdip ward into muddy fine-grained sand- stone ______such sandstone lenses grade into 7 0 sandy greenish-drab mudstone ______20 0 Shale, chocolate-brown, coarsely chippy _ 6 EOCENE ROCKS, WYOMING-COLORADO-UTAH A61

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in c Sandstone, limy and muddy, very fine­ Shale, grayish- to greenish-brown, soft, flaky ______grained; many bedding planes mud 19 0 cracked------~------­ 1 0 Marlstone, silty, hard, platy ______8 Mudstone, greenish-gray; grades from Shale, grayish- to greenish-brown, soft, sandy at base to nearly pure clay at flakY------~------32 0 toP------4 6 Tuff, No. 1 of Culbertson, Fire hole Limestone, massive, crystalline ______Y2 analcite of Love; light-gray; strong­ Oil shale, low-grade, papery ______2 0 ly stained with iron oxides; weathers c Marlstone, sandy, crudely platy, mud reddish brown and makes small but cracked------8 easily traceable bench; consists very Oil shale, low-grade, papery; becomes largely of analcite crystals ______4 less rich m organic matter upward __ 5 0 Shale, brown, soft, flaky ______23 0 c Marlstone, sandy, crudely platy; many Marlstone, sandy, platy ______1 0 bedding planes mud cracked. ______3 2 Shale, soft, flaky; contains considerable Shale, flaky to almost papery; organic organic matter ______12 6 matter moderately abundant at base Marlstone, sandy, platy ______4 0 but decreases upward ______5 6 Mudstone, grayish-brown, blocky, soft_ 7 0 c Marlstone; dense and massive at base, Marlstone, sandy, platy _____ ..: ______6 grades upward into platy marlstone; Marlstone, organic, chocolate-brown; several bedding planes mud cracked_ 1 6 weathers gray, soft chippy; makes Mudstone, greemsh-gray, soft ______-- 7 0 earthy slope ______5 0 Shale, light-chocolate-brown, coarsely c Marlstone, sandy; irregular platy bed­ flaky; much organic matter ______2 6 ding; many bedding planes mud cracked ______c Sandstone, muddy, fine-grained, ripple­ 1 0 bedded; many beddmg planes mud Marlstone, organic, and low-grade oil cracked------2 0 shale; oil-shale zones papery; or­ Shale, sandy, flaky; very little lime or ganic madstone massive to chippy __ 16 6 organic matter ______- 6 0 Madstone, light-gray to ocherous buff, Sandstone, greenish-gray, muddy, very · shaly; unit contains two thin zones fine grained, ripple-bedded and cross- of papery low-grade oil shale ______13 0 bedded ______2 6 Madstone, light-gray to buff, silty to Sandstone, light-gray, fine- to coarse­ sandy; rather regular platy bedding_ 8 0 grained, micaceous, ripple-bedded Shale, chocolate-brown; weathers gray, and cross bedded. ____ - __ ------6 0 flaky to chippy ______2 0 Shale, sandy soft. ______----- 11 6 Madstone, buff, sandy; platy bedding_ 2 0 Tuff, No. 2 of Culbertson, very sandy, Madstone, organic; contains thin silt- fine-grained ______8 stone layers ______11 0 Mudstone, greenish-gray ______11 0 c Sandstone. very limy, light-gray to Shale, flaky; contains some organic ocherous buff, platy; wavy bedding, matter ______2 6 in part crossbedded; some beds mud­ Marlstone, gray, sandy, very fine cracked; some beds thinly lami- grained, platy ______6 nated ______8 0 Mudstone, greenish-gray, soft ______- 4 0 Madstone, gray, sandy, very fine Thickness, Wilkins Peak Member_ 833 grained, platy ______1 6 Marlstone, light-brown, clayey, soft, Tipton Shale Member: flaky to blocky ______7 6 Shale, gray, flaky; nearly free of or- c Sandstone, light-gray, limy; many beds ganic matter______4 0 ripple bedded and mud cracked; some Oil shale, low-grade, flaky; contains bedding planes contain numerous several thin short lenses of rich oil mud flakes and lumps ______3 0 shale near base; upper half less rich Shale, brown, soft, clayey, flaky; be- in organic matter and grades upward comes more sandy toward top ______7 0 into chippy marlstone ___ -- ___ ----- 18 0 Sandstone, light-gray to buff, iron­ Oil shale, ·rich, lenticular; contains abundance of pyrrhotite ______----- 3 stained, fine-grained; bedding sug- Oil shale, low-grade, gray, flaky to gested by color banding ______4 almost papery; contains thin pan­ Shale, brown, soft, flaky to blocky ___ _ 7 0 cake-shaped dolomitic limestone con­ Marlstone, light-gray, sandy;· thinly cretions that are poor in organic laminated to platy; locally cross- matter ______- 11 0 bedded ______7 0 Tuff, gray, micaceous, very fine grained. 1

782-765 0-64--5 r A62 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River For.mation-Continued Wasatch Formation: Ft in Tipton Shale Member-Continued Ft in Shale, greenish-gray, very soft, crudely Oil shale; many thin rich beds separated fissile; contains dense limestone con­ by lower-grade flaky oil shale; unit cretions . and zones of very fine contains thin discoid limestone con­ grained carbonaceous sandstone; top cretions; thin rich oil-shale beds few inches more sandy, carbona- contain abundant pyrrhotite crystal ceous, and iron stained ______aggregates ______15 0 3 0 Mudstone, drab; contains zones of very Tuff, reddish-brown, earthy, very fine fine grained greenish-gray sandstone grained ______5 that is nearly unconsolidated ______18 0 Oil shale, low-grade, flaky; contains Sandstvne, gray, virtually unconsoli­ several thin (1-3 in.) layers of rich dated; contains many muscovite oil shale ______1 0 flakes; sand grains in lower part are Oil shale, rich, reddish-brown; massive H o-7'2 mm in diameter; grades grad­ with papery phases; contains many ually upward through finer and finer thin limy concretions ______2 2 sand into soft clayey mudstone at Tuff, s.oft; sandy ______top ______1 17 0 Shale, hard, lumpy and chippy, poor Mudstone, greenish-drab ______35 0 in organic matter ______3 Mudstone, brownish-maroon; weathers pink ______Madstone, dense, platy; wavy bedding_ 4 53 0 Shale, gray, hard, lumpy to chippy; poor in organic matter; contains Partial section, Wasatch Forma- many limy lenses ______9 0 tion______138 Oil shale, low-grade, papery to flaky; contains many short irregular lenses Section of the Green River Formation (Tipton Shale, Wilkins Peak of silty marlstone ______3 6 and Laney Shale 1\11 embers) and the uppermost part of the Wasatch Oil shale, medium-grade, black, massive Formation in sec. 33, T. 21 N., R. 105 W. to papery; weathers gray ______6 Green River Formation: Shale, light - chocolate - brown, soft, Laney Shale Member: Ft in papery ______4 6 Marlstone and limy shale, brownish-to Tuff, white, powdery ______2 yellowish-buff, soft, chippy to flaky; Shale, light-chocolate-brown, papery at intervals of a few tens of feet are to flaky, soft ______53 0 thin irregular medium- to coarse­ Shale, chocolate-brown, rather hard grained dark-brown sandstone beds; and limy, coarsely chippy ______2 0 unit also contains occasional thin f Shale, light-chocolate-brown, papery; hard layers of white porcelanous contains bones and scales of small fish_ 13 0 marlstone which are probab.ly tuff- Limestone, sandy, irregular; platy aceous; whole unit poorly exposed__ 300 0 bedding; almost a coquina of ostracod Tuff, white; fine nodular structure; valves ______5 thin bedded at base, massive in upper f Shale, chocolate-brown, slightly carbo­ part______1 1 naceous, soft, papery; many bedding Shale, brown, soft, papery; weathers surfaces contain bones and scales of brownish-lavender; contains consid­ small fish ______9 0 erable organic matter-some is Limestone, gray, dense, sandy; contains medium-grade oil shale; unit con­ fine tubules ___ . ______() tains many thin platy sandstone beds Shale, gray, flaky ______4 0 near the base, but top 30 ft is vir­ Limestone, sandy; rich in ostracodes __ 1 tually unbroken shale; shale lami­ Shale, blocky to chippy ______6 nated, and much of it is varved; Limestone, brown, sandy persistent; one-quarter-inch bed of analcitized rich in ostracodes ______2 tuff near top______43 0 Shale, chocolate-brown, soft, flaky ___ _ 6 Shale, light-chocolate-brown, flaky to Shell marl, muddy, gray, hard, crudely papery______2 6 bedded; contains great abundance of Oil shale, low-grade, chocolate-brown, Goniobasis and Unio shells ______1 0 flaky to papery; weathers bluish Shale, chocolate-brown, soft, papery __ 2 0 gray______1 3 Shell marl, black, dense; considerable organic matter; contains abundance Thickness, Laney Shale Member_ 348 of broken shells of Goniobasis and Unio ______2 Wilkins Peak Member: Sandstone and sandy shale ______5 0 Thickness, Tipton Shale Member__ 153 7 Shale, gray, sandy; very little organic matter ______1 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH· A63

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in Sandstone, limy, medium-grained, and Marlstone, organic, gray, chippy ___ .__ _ 1 0 sandy shale ______4 6 Shale, greenish-gray, soft, flaky ______2 0 Shale, greenish-brown; weathers light Sandstone, limy, muddy, platy ______1 0 bluish gray; lower part contains Shale, greemsh -gray, soft flaky ______1 6 considerable organic matter but Sandstone, limy, muddy, platy ______5 grades upward into barren sandy Shale, greenish-gray, soft, flaky ______shale ______4 0 14 0 Sandstone, limy, muddy, platy ______3 Tuff, buff, soft, earthy ______1 0 Shale, greenish-gray, soft, flaky ______10 0 Sandstone, limy, medium-grained, c Sandstone, limy, muddy, platy, mud- cracked ______platy; muddy at base ______0 6 Shale, chocolate-brown, flaky; consid- Shale, gray, flaky; virtually no organic matter ______m·able organic matter ______1 6 1 6 s Shale, chocolate-brown flaky, contains Oil shale, medium-grade ______1 great abundance of shortite molds __ 2 0 Shale, light-brown, flaky to chippy ___ _ 0 Shale, chocolate-brown, flaky: consid- Oil shale, rich; weathers nearly papery_ 4 erable organic matter ______1 0 Shale, gray, soft, flaky ______0 Shale, greenish-brown, soft, flaky ____ _ 3 6 Sandstone, very limy, platy, ripple- bedded ______Sandstone, white, medium-grained, 3 sugary-textured; crudely platy and Shale, gray, soft, flaky ______.1 0 ripple bedded; muddy at base ______2 0 Sandstone, very limy, platy, ripple- bedded ______Shale, greenish-gray, sandy, crudely 3 flaky; contains one 8-inch zone that Shale, gray, soft, flaky ______8 contains considerable organic matter_ 8 0 Sandstone, very limy, platy, ripple- bedded ______Oil shale, rich, bluish-black, massive __ 6 3 Shale, greenish-brown, very soft, flaky_ 6 4 Shale, light-chocolate-brown, flaky ___ _ 1 0 Marlstone, brown, soft ______8 Mudstone, greenish-drab, soft______7 0 Sandst-:>ne, limy, and sandy marlstone; Shale, soft, flaky; considerable organic in alternate beds ~ to 2 in. thick; matter; somewhat carbonaceous ___ _ 3 medium fine grained ______3 6 Mudstone, greenish-buff, soft, blocky Marlstone, organic, brown, platy ____ _ 1 0 to ftakY------~----- 4 0 =2 ~ [ Mudstone, greenish-gray, soft; contains Marlstone, silty, coarsely chippy to ::::> a few sandy layers ______14 6 platy __ ~------­ 2 0 Oil shale, low-grade, light-bluish-gray, Sandstone, very limy, muddy, fine- papery to massive __ .. ______3 grained, hard ______3 Marlstone, chocolate-brown, laminated 1 0 Mudstone, greenish-gray, sandy; Mudstone, greenish-drab, clayey, soft_ 15 0 weathers to puffy soiL ______6 0 Marlstone, sandy, platy ______2 Sandstone, limy, fine-grained, ripple- Shale, buff, soft, papery; considerable bedded with oscillation ripples ______3 organic matter______6 Mudstone, greenish-gray, sandy, hard, blocky ______Oil shale, medium-grade, massive to 5 0 nearly papery ______4 Marlstone, nearly white, dense, platy_ 5 Marlstono, light-brown, silty, platy __ _ 0 Shale, chocolate-brown, soft, chippy __ _ 10 Shale, chocolate-brown, soft, flaky to c Sandstone, limy and muddy, fine­ chiPPY------0 grained; wavy bedding; mud cracked 1 0 Sandstone, very. limy, muddy, fine- Shale, light-brownish-gray, soft, flaky_ 6 grained, platy ______10 Sandstone, limy and muddy, fine- Shale, chocolate-brown, soft, flaky to grained; crudely bedded ______2 .chippy ______2 6 Shale, sage-gray, soft, flaky ______3 Marlstone, sandy, platy ______6 Sandstone, limy and muddy, fine- Mudstone, greenish-brown, soft, grained; wavy bedding ______2 lunlPY------8 Shale, sage-gray, soft, flaky ______3 Snndstone, nearly white, very limy and Sandstone, limy and muddy, fine- muddy, fine-grained, platy ______6 grained; wavy bedding ______2 Mudstone, greenish-drab, very soft; Shale, sage-gray, soft, flaky ______4 contains n few harder snndior layers_ 18 0 Sandstone, limy; contains mud lumps __ 2 Shale, chocolate-brown, soft, flaky to Shale, sage-gray, soft, flaky ______1 6 chippy; contains thin groups of platy c Marls tone, light-greenish-gray, silty sandy marlstone layers; some shale and muddy, platy; bedding planes zones contain nearly enough organic mud cracked ______2 matter to be classed as low-grade oil Mudstone, drab, blocky; weathers to smooth slope ______shale-----~------36 0 5 0

~- A64 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in c Marlstone, nearly white; contains layers Oil shale, low-grade, papery ______1 0 of sage-green clayey marlstone; many Marlstone, light-grayish-brown, platy bedding planes mud cracked ______2 3 to chippy; weathers light gray ______1 2 Shale, greenish-gray, clayey, very soft, Mudstone, greenish-gray, hard ______5 flaky ______6 9 0 c Marlstone, light-grayish-brown, platy; Marlstone, light-gray, clayey, hard, weathers nearly white; bedding massive ______8 0 planes mud cracked ______1 0 Marlstone, light-gray~sh-brown, very Mudstone, greenish-drab, rather hard_ soft ______3 6 11 0 Mudstone, greenish-drab, spheroidal to platy ______Mudstone, grayish-brown, very soft __ _ 3 6 1 0 Marlstone, light-grayish-brown; weath­ Mudstone, greenish-drab, soft ______3 6 ers light ash gray, as coarse chips Marlstone, light-grayish-brown, sandy; or plates ______- 1 0 contains mud lumps ______1 0 Mudstone, greenish-gray, sandy, hard_ 10 6 Mudstone, greenish-drab, soft ______3 0 Tuff, white, limy, friable, sandy­ Marlstone, light-grayish-brown; weath- textured, regularly laminated; con- ers nearly white ______10 tains great abundance of biotite; Mudstone, greenish-drab, soft______3 0 makes very persistent ledge ______5 0 Marlstone,light-grayish-brown; weath- Shale; very limy, light-grayish-brown; ers nearly white ______1 0 poor in organic matter ______28 0 Tuff; consists almost wholly of analcite Shale, grayish-buff, soft, flaky ______3 0 crysta~------~ 1 Mudstone, greenish-drab, sandy, hard_ 7 0 Marlstone, light-chocolate-brown, hard, Marlstone, light-chocolate-brown, coarse- massive to platy ______15 3 ly chiPPY------­ 1 6 Mudstone, light-grayish-drab, clayey __ 4 6 Mudstone, greenish-drab, sandy, hard_ 8 0 Marlstone, light-chocolate-brown, hard, c Limesj;one, silty, platy, mud-cracked __ 3 massive to platy ______7 0 Mudstone, greenish-gray; grades up- Mudstone, greenish-drab, clayey, soft_ 5 0 ward into shale ______5 5 Marlstone, light-gray; ranges from Sandstone, limy, hard, fine-grained, massive through coarsely chippy to flaky ______ripple-bedded ______3 0 20 0 Marlstone, light-chocolate-brown, crudely Sandstone, limy and muddy, fine- chippy; weathers ash gray _____ ·____ _ 2 0 grained, platy ______1 Limestone, sandy, fine-grained ______3 Marlstone, brownish-gray, sandy, Marlstone, light-chocolate-brown, crudely coarsely chippy to platy; weathers ash gray______chippy; contains thin sandy layers __ 8 15 6 Limestone, sandy, fine-grained ______1 Oil shale, low-grade, papery ______6 Marlstone, light-chocolate-brown, crude- Marlstone, brownish-gray, sandy, ly c hippy; weathers ash gray ______4 6 coarsely chippy to platy ______10 6 Shale, very .clayey; poor fissility ______2 6 Oil shale, low-grade, papery ______1 0 c Sandstone, very limy, platy-bedded to Marlstone, brownish-gray, sandy, ripple-bedded; uppermost surface coarsely chippy to platy ______6 0 mudcracked ______10 Mudstone, sandy ______3 0 Thickness, Wilkins Peak Member_ 498 Marlstone, light-grayish-brown, crudely platy or chippy; weathers gray __ _ 2 0 Tipton Shale· Member: Oil shale, low-grade, papery; weathers cOil shale, low-grade; contains many lavender ______2 0 closely spaced thin layers of hard Marlstone, light-grayish-brown; crudely mud-cracked marlstone ______14 0 platy or chippy ______1 0 c Marlstone, organic; many bedding Mudstone, chocolate-brown ______2 0 planes mud cracked, especially near Oil shale, low-grade, papery; weathers top of unit; interbedded with thin lavender ______5 layers of papery low-grade oil shale_ 3 0 Marlstone, light-grayish-brown; crudely Oil shale, medium-grade, bluish-gray, platy or chippy; weathers light ash gray ______paperY------~------­ 5 4 5 8 Tuff; made up mostly of small analcite Oil shale, low-grade; papery ______2 2 crystals but also contains biotite, Mudstone, greenish-gray, hard ______7 5 hornblende, quartz and feldspar ___ _ Marlstone, light-grayish-brown, platy Oil shale, medium-grade, bluish-gray, to chippy; weathers light gray ______6 papery ______Mudstone, greenish-gray; contains few 5 thin marlstone layers ______15 0 Limestone, granular; in thin beds ______6 Marlstone, light-grayish-brown, platy Oil shale, medium-grade, bluish-gray, to chippy; weathers light gray ______2 6 papery ______10 EOCENE ROCKS, WYOMING-COLORADO-UTAH A65

Green River Formation-Continued Green River Formation-Continued Tipton Shale Member-Continued Ft in Tipton Shale Member-Continued Ft in Tuff; made up mostly of small analcite c,f Sandstone, limy, platy; contains fish­ crystals but also contains biotite, bone fragments and ·rests on mud- hornblende, quartz, and feldspar ___ _ 1 cracked surface ______3 Oil shale, medium-grade,. bluish-gray, Shale, light-brown, very soft, papery; paperY------11 contains a' few thin harder marlstone Tuff, white, chalky; probably rich in layers; weathers buffish lavender __ _ 16 0 carbonates ______--- __ ------5 Tuff; almost wholly analcite crystals; Oil shale, low-grade; contains thin marl- lenticular ______1 stone layers ______---_------_--- 10 Marlstone, chocolate-brown; in beds Tuff, largely analcite; overlain by % to 2 in. thick that contain a few brecciated chert _____ -- ____ ------2 thin layers of gravelly limy sand­ c Marlstone, sanely, platy; nearly every stone that contains ostracodes and thin bed mud-cracked; intervening mud lumps ______5 6 beds n.re low-grade papery oil shale_ 1 0 Oil shale, low-grade; contains bone Oil shale, medium-grade, bluish-gray, fragments and mud lumps ______1 pn.pery; contains lenses of massive Oil shale, low-grade, bluish-gray, pa­ rich oil shn.le ______2 0 pery; contains lenses of medium- Tuff, soft, powdery; consists largely of .grade massive oil shale ______3 0 very minute n.nalcite crystals ______1 Limestone ____ ------% Note: The characteristic fossiliferous Marlstone, buff, soft, almost papery __ _ 1 0 basal bed is either so thin that it was Tuff; largely analcite; iron stained __ -_ 2 missed or it is absent at this place. c,f Marlstone, organic, buff, hard, banded; Thickness, Tipton Shale Member __ 98 contains a few fishbone fragments; top surface mud cracked ______1 0 Wasatch Formation: Shale, buff, soft, papery; contains Mudstone, drab; lower part very sandy_ 25 0 many ostracodes----~------­ 2 0 Sandston~, light-gray, medium-grained, Ostracode limestone, hard; contains massive to crudely bedded; contains many mud lumps------3 much biotite, suggesting tuff ______1 0 Marlstone, buff, soft, papery ______2 6 Mudstone; sandy at base but becomes Tuff; lower part analcitized ______2 less so upward ______18 0 Marlstone, buff, sof,t, papery ______0 Mudstone, brick-red, clayey ______2 0 Tuff; mostly analcite ______1 Mudstone, drab, clayey ______1 0 Marlstone, buff, shaly, soft, papery; Sandstone, light-gray, muddy; virtually contains some thin harder marlstone unconsolidated ______15 0 layers ______- ____ -----.------4 0 Mudstone, drab, sandy ______11 0 Tuff, mostly analcite crystals; some Sandstone, gray, medium-grained; in crystals as much as 2 mm across; beds about 1 ft thick; this is a stubby upper part of bed dense ______2 lens, evidently a stream-channel Shale, buff, papery_.------­ 1 0 depos~------6 0 Tuff, almost wholly analcite crystals; Mudstone, drab, sandy ______4 0 resembles coarse sandstone ______5 Sandstone, soft, micaceous, medium- Marlstone, buff, very soft; weathers grained ______1 0 papery; contains ostracodes ______2 8 Mudstone, drab; has few thin maroon Tuff; mostly analcite but contains layers ______10 0 much biotite ______5 f Marlstone, soft; very regular lamina­ Partial section, Wasatch Forma- tions; bedding planes contain many tion______94 large thin-shelled ostracodes, a few plant stems, and fishbone fragments __ 3 6 Section of the Green River Formation (Tipton Shale, Wilkins Peak, c Sandstone, ocherous, muddy, medium­ and Laney Shale Members) in sec. 14, T. 23 N., R. 105 W. grained, crudely bedded; contains Green River Formation: many thin beds of .flaky sandy shale Laney Shale Member: Ft in that is ripple bedded; top surface Marlstone and shale, buff; range from mud cracked ______13 0 very soft and flaky to hard and crudely platy; unit contains sand­ f Shale, soft, flaky; contains a few thin stone lenses at 30 and 50 ft above sandy shale layers and fishbone fragments. ______---- base; upper part consists mostly of 5 0 grayish-buff hard chippy to platy f Sandstone, limy, muddy, very fine marlstone that locally contains plant grained, ripple-bedded; contains stems and, especially, palm leaves___ 200 0 great many fish bone fragments ____ _ 6 Marlstone, buff, muddy, massive; con-

"( Shale, brown, sandy, soft, flaky ______4 0 tains many mud lumps______1 0 A66 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River Formation-Continued Green River Formation-Continued Laney Shale Member-Continued Ft in Wilkins Peak Member-Continued Ft in Shale, buff, soft, papery; contains a few Shale, greenish-gray, soft ______5 0 thin hard layers of madstone and a Madstone, organic, platy to papery __ _ 1 0 few beds of papery low-grade oil Shale, drab, soft, flaky ______9 0 shale______30 0 Madstone, organic, papery ______3 0 Tuff, ocherous, soft, fine-grained, Mudstone, greenish- to brownish-gray, massive______1 0 very soft ______2 6 Shale, buff, papery; contains a few thin Madstone, organic, flaky to chippy ___ _ 1 0 hard layers of madstone at rather Mudstone, greenish-gray to brown, very soft ______regular intervals______69 0 10 0 Madstone, organic, flaky to massive__ 1 0 Madstone, organic, coarsely chippy __ _ 1 0 Shale, greenish-gray, soft, flaky; con- Ostracode limestone, sandy; contains tains layers of low-grade papery oil many mud lumps and pebbles ______4 shale at intervals of 5-6 ft in lower Ostracode limestone, nearly white and platy______part______29 0 2 Oolite, nearly white ______2 Thickness, Laney Shale Member__ 331 Algal reef, laminated ______2 Shale, greenish-gray to brown ______2 6 Wilkins Peak Member: c Oolite, platy; contains mud lumps and Shale, greenish-gray, soft, flaky______11 0 is mud cracked ______6 c Sandstone, limy, very fine grained, Sandstone, limy, medium-grained, platy ______platy, mud-cracked ______6 1 Madstone, flaky______2 3 Shale, greenish-gray to brown, soft, flaky ______Mudstone, greenish-gray______1 0 2 6 Madstone, white, hard, lumpy ______0 Shale, greenish-gray, very sandy, mi- Sandstone, limy, muddy, very fine caceous ______3 5 grained, platy______1 0 Shale, gray, papery to flaky; consider- Shale, grayish-brown, soft, flaky ______3 able organic matter ______2 6 Mudstone, carbonaceous and iron- Sandstone, medium- to coarse-grained; stained ______2 gravel streaks ______1 3 Mudstone, greenish-gray, soft______13 0 Gravel, ·limy; contains many mud Marlstone, ash-gray, coarsely lumpy lumps and bone fragments; some of and chippy______4 0 the bone fragments are probably avian ______c Marlstone, light-gray, muddy and 2 sandy, mud-cracked ______6 Shale, sandy, contorted ______8 c Marlstone, nearly white, hard, chippy; Oil shale, rich, dark bluish-gray, mas- top mudcracked______2 6 sive to papery ______1 Mudstone, dark-greenish-gray, soft____ 1 0 Shale, gray, sandy, micaceous, flaky __ 2 3 Marlstone, nearly white, hard, chippy __ 1 0 Sandstone, buff, micaceous, massive; S h a 1 e, Ii g h t- c hoc o I ate-brown, contains many mud lumps ______3 0 soft, papery______2 0 Mudstone, greenish-gray, sandy, hard__ 8 0 Thickness, Wilkins Peak Member_ 148 Marlstone, nearly white, hard, massive_ 1 0 Mudstone, greenish-gray, sandy, hard__ 8 0 Tipton Shale Member (location of contact Sandstone, buff, medium-grained; con- uncertain) : tains mud lumps ______:______3 Algal reef, penicillate ______2 c Marlstone, buff, flaky to coarsely Sandstone, medium-grained, massive; chippy; makes conspicuous band in lenses of graveL ______1 0 nearly white marlstone; mud cracked Shale, sandy, soft, flaky ______13 0 at top______9 0 Sandstone, dark-brown, coarse-grained, Mudstone, greenish-gray, soft______5 0 crossbedded __ -·- ______2 Madstone, organic, buff, papery ______0 Shale, sandy, soft, flaky ______6 Shale, greenish-gray, soft______2 0 Sandstone, limy; contains mud lumps_ 1 Oil shale, low-grade, flaky to papery____ 2 6 Shale, muddy, flaky to almost papery __ 0 Shale, greenish-gray, soft______2 6 Sandstone, limy, fine-grained, mica- Shale, marly and organic; weathers ceous, platy ______3 bluish gray______1 6 Shale, sandy, soft, flaky ______3 6 Shale, greenish-gray, soft______2 6 Sandstone, buff, medium-grained, soft, Shale, marly and organic; weathers massive ______3 0 bluish gray______5 0 Shale, sandy, soft, flaky ______._ 1 0 Shale, greenish-gray, soft______3 0 Sandstone, very limy, dark-brown, Marlstone, organic, papery______2 0 medium-grained ______3 EOCENE ROCKS, WYOMING-COLORADO-UTAH A67

Green River Formation-Continued Section of Green River Formation (Tipton Shale, Wilkins Peak, Tipton Shale Member-Continued Ft in and Laney Shale Members) and the uppermost part of the Shale, sandy, soft, flaky ______1 0 Wasatch Formation measured along Sage Creek in the northern Sandstone, dark-brown, hard, platy ___ _ 6 part of ·T. 15 N., R. 106 W. Sandstone, buff, medium-grained, mas- Green River Formation: sive to crossbedded ______15 0 Laney Shale Member: Ft . in Shale, sandy, soft, flaky .. ______3 0 Tuff, crystal and lithic, buff, muddy, Sandstone, buff, medium-grained, mas- ocherous, medium- to fine-grained, sive ______3 0 ripple bedded and cross bedded______50 0 Shale, sandy, soft, flaky ______6 0 Marlstone, light-gray, chippy; alter­ Sandstone, dark-brown, strongly iron nates with beds of soft ocherous stained; may be tuff ______0 sandstone (or crystal tuff?); unit con­ Shale, sandy, very soft, flaky; contains tains some beds of algal deposits that a few harder platy sandstone beds; have turbinate heads about 1 ft high_ 160 0 locally this unit contains much regu- Sandstone, very limy, buff, medium- larly bedded sandstone ______29 0 grained______6 Sandstone, dark-brown, iron-stained; Algal bed, nodular, discontinuous_____ 6 almost certainly a tuff ______2 Shale·, buff, soft; alternates with buff Shale, very sandy, flaky; thin·platy beds sandy marlstone and_ sandstone of hard medium-grained sandstone at layers______55 0 intervals of a few feet ______50 0 Sandstone, buff, medium-grained, fri- Partial section, Laney Shale Mem- able, crossbedded ______2 6 ber______266 Shale, sandy, soft, flaky ______3 0 Sandstone, buff, micaceous, massive, Wilkins Peak Member: lenticular------______1 0 c Shale, light-gray, soft, flaky; contains Shale, sandy, flaky, somewhat limy __ _ 20 0 many platy layers of sandy marl­ Sandstone, dark-brown, muddy, fine- stone, some of which are mudcracked _ 25 0 grained ______1 5 c Limestone, sandy, platy, mud-cracked_ 4 0 Shale, sandy, soft, flaky ______3 0 Shale, soft; poor fissility _- ______4 6 Sandstone, dark-brown, muddy, soft, c Marlstone, light-gray, sandy, hard, lenticular------______6 platy, mudcracked ____ --- ____ - ___ _ 0 Shale, very sandy, crudely fissile ______6 0 Oil shale, low-grade, gray, flaky ______17 0 Sandstone, dark-brown, muddy, well- c, s Marlstone, platy; salt-crystal molds bedded ______1 0 and niudcracks ______6 Interval concealed ______8 0 Shale, light-gray, soft, flaky ______10 0 Sandstone, dark-brown, muddy, fine- s Marlstone, organic, gray, platy; a few grained, platy------______4 layers of salt-crystal molds ______-_- 11 0 Interval concealed, probably soft sandy Oil shale, rich ______shale ______50 0 Limestone, light-gray, sandy; banded o Sandstone, very limy, strongly iron with dense white porcellanous layers_ 2 5 stained, mud-cracked; probably a c Marlstone, white, platy; contains many tuff------~------2 thin sandstone layers and several Shale, soft, papery ______5 0 shaly zones; shaly zones contain a Oolite, sandy; contains mud lumps ___ _ 3 few thin lenses of rich oil shale; mud- Shale, soft, flaky ______6 0 cracked m arlstone layers ______21 0 Oolite, sandy, fine-grained; contains Sandstone, limy and muddy, gray, mud lumps ______3 crudely platy ______2 0 Shale, soft, flaky; contains some papery [ Mudstone and muddy sandstone; green- low-grade oil shale ______5 0 ish-gray platy ______-- 5 0 Marlstone, muddy, dense ______6 c Marlstone, sandy; alternates with Oil shale, low-grade, papery ______1 6 layers of mudstone that contains Marlstone, grayish-buff, massive ______3 6 many mud lumps; unit contains Ostracode limestone, sandy ______6 several thin lenses of rich oil shale; Sandstone, buff, limy; contains ostra- mud-cracked marlstone ______5 0 codes ______8 Shale, greenish-gray, soft, flaky; few Ostracode limestone, sandy, lenticular_ 5 thin marls tone layers ______-_--- 22 0 s Shale, brown, soft, flaky; shortite Thickness, Tipton shale member __ 255 molds------5 0 Underlain by mudstone of the Wasatch Tuff, No. 3(?) of Culbe!tson, buff, fine- Formation. grained, earthy ______- ______--- 4 A68 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in s Marlstone, shaly, soft; a few large Marlstone, brown, _flaky; weathers gray ___ .:.·- ______shortite molds ______0 1 6 Mudstone, limy, rather hard and Mudstone, light-brown, soft ______2 0 lumpy ______8 0 Limestone, white, sandy, thin-bedded s Marlstone, shaly, soft; many shortite and ripple-bedded ______1 0 molds and molds of interlocking Mudstone, brownish-gray, limy, hard, platy crystals ______5 0 spheroidaL ______5 0 s Marlstone, gray, platy; shortite molds_ 3 6 c, s Limestone, sandy, ripple-bedded; con­ Shale, gray, flaky to platy ______2 6 tains many mud balls; some bedding s Marlstone, gray, platy; abundance of surfaces mud cracked and some have shortite molds ______0 bladed salt-crystal molds ______1 6 Shale, soft; with limy concretionary Algal bed, layered ______2 layers ______3 0 Sandstone and clay-gall layer; Sand­ s Marlstone, gray, hard, platy; small stone is limy; clay galls fill shallow shortite molds ______1 hollows at base of bed ______1 Interval concealed; apparently soft Shale, dark-greenish-gray, clayey, soft; shale or mudstone containing a few layers of carbonaceous clay ______3 0 thin marlstone layers ______17 0 Limestone, white, sandy, thin-bedded; Sandstone, gray, limy, medium-grained, interlaminated with dense translu­ platy ______0 cent carbonate layers; contains many Interval concealed; apparently soft mud lumps and is, in part, ripple bedded ______flaky gray shale and few thin layers 2 6 of marls tone ______30 0 Mudstone, gray, sandy; contains a few Sandstone, gray to buff, ripple-bedded platy ripple-bedded sandstone lay- ers ______and crossbedded; channels into under- 29 6 lying unit about 2ft ______30 0 Marlstone, brown; weathers gray; in c Marlstone, sandy, platy, thin-bedded part ripple bedded; possibly mud cracked ______and laminated; many bedding planes 3 0 r have thin films of mud which are Limestone, very sandy; contains many small mud flakes ______6 ~a~~ :~~~::~e~~~~- ~~~~- ~a~e~~- ~~ 3 0 Mudstone, gray, sandy ______2 0 Mudstone, gray, very sandy, fine- c Marlstone, gray; contains more or­ grained, ripple-bedded ______3 0 ganic matter upward; contains sandy Sandstone, very limy and muddy, layers; many bedding planes mud ripple-bedded ______3 6 cracked ______7 0 ls Limestone, sandy; many layers of inter- Limestone; banded with dense white locking bladed salt-crystal molds ___ _ 1 0 carbonate layers; some beds show Marlstone; bedding planes coated with oscillation ripple marks, others show sand grains ______2 0 feeble current ripples; apparent rain- Mudstone, light-brown, soft______2 0 drop impressions ______4 0 c Limestone, sandy; banded with dense Tuff, white, soft, sugary ______4 white cellular layers that may repre: 7 Mudstone, greenish-gray; contains thin sent salt crusts; mud cracked ______3 6 sandstonE lenses ______38 0 Mudstone, light-brown, soft; contains lenses of olive-brown sandstone ____ _ Limestone, silty; weathers reddish-gray; 18 0 probably tuff ______Sandstone, gray, limy, hard, fine- · 4 Mudstone, greenish-gray ______grained, regularly-bedded __ :. ______2 2 0 Mudstone, greenish-gray, sandy; con­ Marlstone, light-gray, muddy, lumpy_ 3 0 tains lenses of ripple-bedded and c Limestone, white, sugary, layered, n1ud-cracked ______crossbedded sandstone ______18 0 4 0 c, s Limestone, sandy; small quantity of Marlstone, gray, muddy, lumpy ______4 0 bladed salt-crystal molds; mud Tuff, grayish-brown, limy, fine-grained, cracked ______0 dense------~------6 Marlstone, sandy, flaky; contains thin Sandstone, micaceous, medium-grained, sandstone laminae ______4 0 ripple-bedded and cross bedded ______22 0 Mudstone, light-bro.wn, soft ______2 6 :\'[ udstone, slate-gray, very sandy ____ _ 2 0 s Limestone, brownish-buff, sandy, rip­ Sandstone. limy, ripple-bedded; con­ ple-bedded and irregularly bedded; tains buff limy layers that contain contains cyclic recurrence of platy mud lumps ______2 0 salt-crystal molds at 3-3.5-in inter- :\1udstone, slate-gray, very sandy; con- vals near middle ______6 0 tains lenses of sandstone ______22 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH A69

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in Limestone, white, crystalline, granular, Mudstone, greenish-drab, sandy, soft; platY------8 contains lenses of platy sandstone __ _ 8 0 Sandstone, muddy, micaceous, fine­ Sandstone, gray, muddy, fine-grained, grained, ripple-bedded; contains thin-bedded, ripple-bedded and zones of sandy greenish-gray mud- crossbedded; weathers brown; grades stone ______9 0 upward into coarser grained sand­ Mudstone, greenish-gray, sandy ______3 0 stone; unit contains lenses of gray s Sandstone, very limy, ripple-bedded; sundy mudstone ______! __ _ 25 0 contains small salt-crystal molds ___ _ 6 0 . Mudstone, drab ______10 c,s l\1arlstone, light-gray, sandy; thin regu­ Sandstone, muddy, shaly ______2 0. lur beds whose upper surfaces are s Marlstone, light-brown, dense; con- mud cracked and are covered with tains salt-crystal pseudomorphs ____ _ 1 10 molds of bludcd salt crystals; be­ Tuff, No. 2 of Culbertson, silty ______6 tween these thin murlstone beds are Oil shale, low-grade, laminated; con- layers of unidentified white powdery tains plant fragments ______6 material, possibly tuff ______11 0 Sandstone, drab, very muddy, shaly __ _ 16 0 Algal bed, buff, coarsely laminuted ___ _ 4 Mudstone, greenish-gray, sandy ______3 0 Mudstone,. brownish-drab ____ ,___ -·- __ _ 3 0 Madstone, .light-chocolate-brown, .flaky Sandstone, white, extremely limy, to chippy ______3 0 ripple-bedded; bedding surfaces c Sandstone, limy, hard, platy, ripple- pitted as though salt crystals hud bedded and mud cracked ______3 0 once been there ______1 6 Shale, grayish-green, sandy, soft ______- 7 0 Algul bed, buff, coarsely lamiuated ___ _ 5 Marlstone, organic, light-chocolate­ Shale, sandy, soft, pulty ______8 brown, coarsely laminated; weathers Mudstone, greenish-gruy, sundy, ruther gray; a few carbonized plant stems __ 7 6 hard; thin beds of greenish-gruy Mudstone; poorly exposed ______15 0 muddy sandstone muke up about 5 Shale, limy and sandy; alternates with percent of unit; mud lumps and beds of platy organic marlstone ___ _ 8 0 plarit fragments at top ______34 0 Mudstone; contains at least one thin Sandstone, light-gray, very limy, medi- sandy layer______15 0 um-grained, ripple-bedded ______0 Marlstone, sandy, hard, platy ______1 0 M arlstone shaly, soft; interlaminated Shale, brown, soft, papery ______2 6 with sandy zones------2 8 1 6 Mudstone, greenish-gray, sundy ______4 0 Marlstone, gray, sandy, platy------Marlstone organic, sandy, hurd, platy __ 6 Mudstone, greenish-gray, soft ______- 10 6 Mudstone, greenish-gray, sandy ______Marlstone, organic, sandy, hard, platy 4 0 to papery ______Marlstone, organic, sandy, hard, platy_ 1 0 2 0 Mudstone, greenish-gray, sandy ______5 0 Mudstone, greenish-gray, soft _____ --_- 10 0 Sandstone, light-gray, limy, . platy, Marlstone, dark-gray, silty, hard, ripple-bedded ______-- ___ - __ 2 0 crudely bedded ______1 0 Shale, gray, limy, soft, flaky ______7 0 Shale, grayish-brown, soft, flaky _____ - · 8 6 Mudstone, greenish-gray, sandy ______2 6 c Sandstone, very muddy and limy, c Sandstone, buff, very limy, ripple­ shaly to platy; in part ripple bedded; bedded; contains mud lumps and is many bedding planes mud cracked __ 7 0 mud cracked ______2 6 Shale, ash-gray, soft, flaky ______3 6 Mudstone, greenish-gray, sandy; con­ 6 0 tains two zones of platy sandstone Mudstone, sage-gray, hard, spheroidaL lenses ______33 0 c Sandstone, limy and muddy, very fine c Marlstone, organic, hard, platy; top grained, platy; bedding surfaces mud cracked ______surface mud cracked ______1 6 6 0 Oil shale, low-grade, brownish-gray, Mudstone, greenish-gray, clayey-----­ 2 0 paperY------1 0 Marlstone, gray, platy __ ------_-_---- 1 0 Mudstone, greenish-gray, sandy ______3 0 Mudstone, greenish-gray, clayey ______3 6 c Marlstone, sandy, crudely platy; bed- Marlstone, gray, sandy, hard, platy--- 3 0 ding planes mud cracked ______1 0 Mudstone, greenish-gray, clayey ___ --- 10 0 Shale, brown, soft, flaky to papery ____ _ 2 6 Shale, gray, flaky to chippy, hard ____ _ 7 6 c Marlstone, sandy, hard, platy; a few mud cracks ______2 0 c Shale, gray, sandy, interbedded with 0 gray shale; sandy layers mud cracked; Mudstone, greenish-gray, clayey--_--- 12 thin layer of edgewise conglomerate Marlstone, buff, silty, hard, platy____ _ 2 0 12 o· at tOP------~----- 1 0 Mudstone, greenish-gray, clayey------A70 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River Formation-C

Wasatch Formation-Continued Ft in Green River Formation-Continued Sandstone, maroon, medium-grained, Wilkins Peak Member-Continued Ft in massive; mottled light yellow and Marlstone, light-gray, massive to thin- bedded ______grayish vermilion where lenticular; 10 0 sandy marlstone concretions at top __ 7 0 Marls tone, tuffaceous, micaceous ______1 4 Marlstone, gray, dense; weathers buff_ -1 0 s Marlstone, somewhat shaly; contains Mudstone; banded light gray and light great abundance of shortite molds, brick red; clayey ______13 0 especially in upper 6 ft where salt­ Sandstone; mottled light buff and dark crystal molds exceed marlstone in volume ______brick red; muddy; soft; lenticular __ _ 7 0 17 0 Shale, greenish-gray, sandy, soft, flaky_ 0 Marlstone, slate-gray to cream-colored, Mudstone; banded buff, gray, and shalY------~------14 0 reddish-gray; sandy ______5 0 s Shale, gray, soft, flaky; contains great Sandstone, bright-red; grades up into abundance of salt-crystal molds in gray medium- to fine-grained ma- layers and lenses ______4 0 terial; a lens ______3 0 s Marlstone, organic, thin-bedded to Mudstone; mottled sage gray and dark flaky; contains lenses of rich oil shale, brick red; sandy; soft; contains a few · especially at top; shortite molds throughout ______short lenses of buff or reddish-brown 4 0 medium-grained sandstone ______27 0 s Mudstone, gray; great many shortite Sandstone, deep-red, soft, medium­ molds at base but these decrease to grained, massive to crudely bedded; essentially zero at top ______15 0 locally crossbedded ______5 0 s Tuff, marly; contains layers and dis- II,. Sandstone, very muddy; ocherous at persed molds of shortite ______2 3 base, vermilion at top; possibly tuff_ 3 Marlstone, light-gray, massive, prob- Mudstone, gray, soft______~- __ 5 0 ably tuffaceous ______2 0 Sandstone, red, muddy, shaly ______8 s Tuff, white; contains shortite molds at top ______Shale, sandy, soft, flaky ______2 0 3 Shale, nearly black, carbonaceous, s Shale, gray and buff, limy; contains thin ftakY------~------1 0 lenses oT rich oil shale and dispersed Mudstone, gray, soft ______3 0 and layered shortite molds ______15 0 Sandstone, reddish-gray, muddy, very 01l shale, low-grade, brown; contains soft, shaly ______1 0 lenses of rich oil shale ______2 0 Mudstone, gray, soft ______5 0 Tuff, No. 5 of Culbertson, white to Sandstone, reddish-gray, soft, medium­ pinkish-buff; contains marlstone grained; upper part limy and ripple- layers ______10 bedded ______10 0 c, s Marlstone, massive; contains shortite Shale, gray, soft, flaky ______6 0 molds and is mud cracked ______1 10 Sandstone, reddish-brown; soft, medi­ Shale, gray, sandy, flaky to platy ____ _ 5 0 um-grained, crossbedded and cur- Oil shale, low-grade, brown; contains rent-ripple-bedded ______12 0 thin stubby lenses of rich oil shale __ _ 1 10 Sandstone, reddish-gray, very muddy, Edgewise conglomerate composed of r.egularly bedded and ripple-bedded_ 6 0 slightly rounded mudstone pieces in Mudstone, very sandy, crudely fissile; marlstone rna trix ______2 alternates with beds of gray ripple- Shale, greenish-gray, sandy, soft, flaky bedded sandstone ______10 0 to massive ______4 10 Tuff, pinkish-gray, chalky, soft ______3 Partial section, Wasatch Forma- Oil shale, medium-grade, laminated to tion______549 massive ______7 s Mudstone, sage-green; contains abun­ Partial section of the Wilkins Peak Member of the Green River dant shortite molds; contains l-in. Formation in sees. 23, 5, and 8 T. 18 N., R. 107 W. carbonaceous layer about in middle_ 7 3 Green River Formation: Mudstone, light-brownish-buff, limy __ _ 2 3 Wilkins Peak Member: Ft in :a ~ Marlstone, gray; contains layers of Tuff, dark-gray, medium-grained ______4 P white tuff ______.______1 5 Marlstone, chalky, soft, massive to Mudstone, sage-gray, massive to shaly_ 10 2 platy, finely banded ______5 0 s Mudstone, greenish-brown, very sandy, Marlstone, light-gray, massive to thinly ripple-bedded; shortite molds sparse- bedded; contains thin layers of green- ly distributed in top 2ft ______11 2 ish-gray mudstone ______3 0 c, s Oil shale, rich; thin discontinuous lenses Tuff, No. 6 of Culbertson, white, very alternate with layers of shortite molds )... fine grained ______6 and pseudomorphs; mud cracked;· Marlstone, light-gray, massive to shaly_ 1 0 contains some thin micaceous tuff layers ______Tuff, dense ______2 2 8

"f· A72 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in s Marlstone, shaly; contains shortite c,s Shale, soft, flaky; great abundance of molds ______3 10 shortite molds; mud cracked ______1 4 Tuff, sandy and micaceous ______._ 1% s Oil shale, medium-grade, dark-brown, s Marlstone, massive to shaly; scattered massive to flaky; weathers bluish shortite molds and layers of shortite gray; shortite molds and pseudo­ pseudomorphs------~------­ 5 9 morphs abundant; mud cracks very numerous ______Tuff, white, micaceous; contams coarser 3 2 crystal-tuff laminae ______8 s Marlstone, light-gray, rather coarsely s Marlstone, gray, thin, obscure bedding; laminated; shortite molds sparse; alternate layers contain many short­ unit grades upward into greenish- ite molds; contains a few thin lenses gray sandy mudstone ______6 7 of rich oil shale which are studded s Madstone, light-gray, coarsely lami­ with shortite pseudomorphs ______6 0 nated; contains many crudely lentic­ Tuff, white ______ular layers of· salt-crystal molds s Marlstone, gray, massive; shortite that resemble aggregates of north- molds ______1 4 upite and shortite ______2 4 Tuff and marlstone, in alternate thin s Oil shale, rich, dark-brown, varved; beds; shortite molds ______2. _o regularly spaced thin layers of Tuff, No. 4 of Culbertson or Big Island shortite pseudomorphs; bedding dis- tuff, white ______2 torted by subaqueous slumping ____ _ 1 1 s Marlstone, light-gray, massive though Madstone, light-gray, rather coarsely laminated ___ . ______regularly banded; shortite molds 8 abundant ______3 4 Tuff ______~ ~ [ Mudstone, sage-green, sandy, soft ___ _ 14 0 2 s Marlstone, brownish-gray to sage- Section continued about 3 miles east in green; shortite molds abundant_ ___ _ 5 10 sec. 23 Tuff, No.3 of Culbertson, white ______6 Sandstone, fine-grained, platy ______6 s Shale, light-gray, limy; contains few Shale, grayish-buff, coarsely chippy __ _ 6 6 thin beds of low-grade oil shale; shortite s Marlstone, light-brown, hard, platy; shortite pseudomorphs ______and possibly northupite molds and 2 6 pseudomorphs abundant throughout s Marlstone, silty; contains molds of bladed salt crystals ______unit; some crystal molds large and 10 others unusually fine; layers 3 in. thick s Marlstone, light-brown, chippy; shortite pseudomorphs ______of loose salt pseudomorphs at several 6 0 levels ______------61 0 S11ndstone, gray limy, fine-grained, platy_ 3 s Oil shale, rich; weathers blue; bedding Marlstone, light-grayish-buff, chippy __ 0 planes covered with shortite-crystal Oil shale, medium-grade, papery; weathers bluish gray ______molds; gas brecciated ______1 3 4 Sandstone, gray, medium-grained, crudely c,s Shale, light-gray; contains thin layers bedded ______of low-grade oil shale; all except 3 0 Madstone, organic, chocolate-brown; bottom 1 ft contains abundance of weathers gray, chippy ______2 salt-crystal molds; mud cracks very 0 common ______Shale, light-brown, soft, flaky ______2 0 6 6 Mudstone, sage-green, sandy ______15 0 s Oil shale, low-grade, massive to flaky; many shortite molds ______2 6 ~ d M;~~~~~e: __ ~i~-~t~~~~~ __ ~~~~:~ _ -~a-r~~ 8 Interval concealed ______4 0 [ Mudstone, sage-green, sandy ______5 0 s Oil shale, medium-grade, dark-brown; c Shale, light-buff, soft, flaky; contains a weathers bluish gray; shortite molds few thin sandy marlstone layers abundant; gas brecciated ______3 0 that are mud cracked ______3 0 s Mudstone, light-gray, soft, limy; great c Marlstone, silty, platy to chippy; many abundance of salt-crystal molds and bedding planes mud cracked ______1 0 and pseudomorphs, dispersed and in Shale, drab, soft, flaky ______7 0 layers------~------7 4 Sandstone, rather coarse grained; full of s Oil shale, medium-grade, brown; mud lumps and flakes ______% weathers bluish gray; numerous large Shale, limy, sandy, flaky ______3 shortite molds; gas brecciated ______3 0 Sandstone, coarse-grained; full of mud s Oil shale, low-grade, papery; more than lumps and flakes ______2 half of volume made up of shortite Shale, gray, soft; contains thin sandy molds and pseudomorphs ______7 marlstone layers ______0 c .. s Rhale, soft, flaky; shortite molds Edgewise conglomerate; angular and abundant; mud cracked ______1 subangular pieces of marlstone in Analcite layer ______marlstone matrix ______EOCENE ROCKS, WYOMING-COLORADO-UTAH A73

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in c Marlstone, light-buff, very sandy, mud ternate with coarser sandy layers cracked ______which contain sandy pseudomorphs of c, s Shale, marly, hard, platy; contains bladed salt crystals; includes also salt-crystal molds; many layers mud ellipsoidal cavities that suggest nor­ cracked ______2 thupite; many bedding planes mud cracked ______c Marlstone, very sandy; thin regular 2 8 beds; mud cracked ______2 Tuff, ocherous, sandy ______2 s Shale, light-brown, soft, flaky; shortite Oil shale, low-grade, gray, hard, some­ pseudomorphs abundant ______3 what carbonaceous; contains many s Limestone, buff, sandy; alternates with coarse plant stems or leaves that thin layers of soft limy flaky shale; look like rushes; gas brecciated ____ _ 6 limestone layers contain salt-crystal Edgewise conglomerate; clay pebbles molds that suggest northupite and rounded; matrix very limy ______2 molds of interlocking platy salt crys- Mudstone; olive-drab, sandy, soft ____ _ 8 5 tals; makes persistent bench ______5 6 Limestone, white, sandy, hard, platy __ 6 s Clay, buff; contains many salt-crystal Edgewise conglomerate; sandy mud- rnolds ______10 stone pebbles in limeston~ matrix; platy bedding ______Oil shale, low-grade, light-chocolate­ 4 brown, massive; weathers gray; con­ Marlstone, organic; wavy laminations_ 4 tains a few coarse stem impressions __ 10 Mudstone, sage-green, sandy, soft ____ _ 8 9 Sandstone, light-gray, very limy, fine­ Shale, olive-drab, flaky ______1 2 grained, ripple-bedded; has mud Marlstone, light-gray, platy ______7 lumps in lower part ______8 Mudstone, greenish-buff, soft ______12 0 Shale, buff, soft, papery ______3 0 Shale, greenish-drab, soft, flaky; con- s Limestone, light-gray, platy: in thin tains thin marlstone layers ______1 9 beds that alternate with buff limy Oil shale, low-grade, carbonaceous, gas- shale; shortite pseudomorphs ______2 0 brecciated ______10 Shale, buff, soft, papery ______4 0 Marlstone; contains abundance of buff s Clay, buff; a soft earthy mixture of mudstone 11ellets ______2 pseudomorphs of coarse platy bladed Shale, light-brown, flaky ______1 2 salt crystals and sandy and limy Clay, brownish-drab; probably bento­ clay; may represent salt bed ______2 0 nitic, as it contains laminae rich in biotite ______s Sandstone, gray; contains flat shale 8 lumps and salt-crystal molds. ______2 Tuff, dark-gray, sandy; contains much biotite ______Oil shale, medium-grade; alternates 1~ with thin rich oil-shale laminae; c Mudstone, olive-drab, clayey, soft; mud somewhat carbonac.eous ______·------2 cracked at top ______6 6 Edgewise conglomerate; angular and Shale, light-chocolate-brown, soft, flaky subangular clay fragments and clay to papery ______4 0 pellets randomly oriented ______0 s Shale, drab to buff, flaky; contains Marlstone, grayish-buff, sandy ______3 salt crystal molds ______7 0 c Shale, light-chocolate-brown, crudely Limestone, white, sandy, fine-grained, flaky; lamination becomes more platy ______1 0 regular and better defined upward; Mudstone, drab, limy, chippy ______3 6 slightly carbonaceous; mud cracked __ 8 0 Shale, buff, soft, papery; contains Mudstone, sage-green; buff sandy mud- several thin hard sandy marlstone stone lumps throughout ______2 layers ______3 6 Mudstone, drab, soft ______16 0 Sandstone, very limy, light-gray, fine- Shale, light-brown, soft, papery ______1 6 grained, platy ______1 7 Marlstone, sandy, platy; laminated algal bed in middle ______1 0 r.. [ Mudstone, olive-drab, sandy, soft ____ _ 22 9 ~ Mudstone, greenish-gray to brown, Marlstone, gray, sandy, hard, platy __ _ 1 0 sandy, micaceous; contains lenses and s Shale, chocolatP.-brown, soft, flaky; beds of ripple-bedded and cross­ full of shortite pseudomorphs ______2 10 bedded gray to greenish-brown Marlstone, light-gray, sandy, platy ___ _ 6 muddy sandstone; unit is Principal Shale, light-chocolate-brown, flaky; a Olive zone mentioned in text and D few thin fine-grained sandstone bed shown on geologic map (pl. 2) __ 34 0 layers ______9 6 c,s Marlstone, light-gray, very sandy, Partial section, Wilkins Peak ~ember ______hard, platy; in thin beds that al- 545 A74 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Partial section of the Wilkins Peak Member of the Green River Green River Formation-Continued Formation in sec. 9, T. 18 N., R. 106 W. Wilkins Peak Member-Continued Ft in Green River Formation: Ft in Marlstone, light-gray, chalky; perfect Wilkins Peak Member: lamination; may be carbonate-rich s Marlstone, buff, papery; contains layers tuff______1 0 and modules of molds of bladed salt Oil shale, low-grade, gray; contains crystals that suggest nahcolite______3 0 lenses of richer oil shale______1 0 Marlstone, buff, soft, papery; contains Shale, light-brown to gray, soft, flaky__ 13 0 several nearly black volcanic-ash Tuff, cream-colored, soft, micaceous; layers______37 0 a glassy tuff containing many crystal Tuff, No. 6 of Culbertson, andesitic; fragments ______8 in part analcitized ______5 Mudstone, sage-gray, soft______5 0 Marlstone, buff, soft, papery; contains Marlstone, gray, sandy, soft______6 0 a few thin layers of low-grade oil c Sandstone, white, very limy, platy, shale______19 0 mud cracked; may be tuff ______6 Tuff, light-grayish-buff, rather .coarse Shale, greenish-gray, soft______2 6 grained______10 c Sandstone, white, very limy, ripple- Marlstone, light-gray, flaky to papery; bedded and mud-9racked______1 10 contains thin layers of low-grade oil Mudstone, greenish-gray, soft______6 0 shale and some analcitized volcanic s Marls tone, light-gray, soft, shaly; salt- ash______19 0 crystal molds______4 0 c Tuff, white, limy, platy, mud-cracked__ 4 s Shale, rather coarsely fissile; scattered c Marlstone, light-gray, coarsely chippy, shortite pseudomorphs______1 8 mud-cracked______6 0 Mudstone, greenish-gray to brownish­ Tuff, white to buff; mottled______8 gray; contains a few thin sandy lay- Sandstone, white, fine-grained; un- ers that may be analcitized tuffs_____ 20 6 dulating bedding______2 6 c Sandstone, white, very limy, ripple- Marlstone, organic, shaly to platy____ 6 0 bedded and mud-cracked ______8 Limestone, white, sandy, platy______6 Marlstone, organic, light-chocolate­ Marlstone, hard and platy, to papery brown; has fine banding that sng­ low-grade oil shale______2 6 gests varves; many bedding planes Tuff, yellowish-buff______2 have an abundance of oestrid fly c Marlstone, hard chippy to platy; inter- larvae and other smaller fly larvae; bedded with layers of low-grade pa- also, many adult flies that !lppear to pery oil shale; lower part mud cracked_ 6 0 have gotten caught in mud before Tuff, white, very limy, massive ______~ 2 their wings fully developed __ ~______6 0 Marlstone, gray, hard, coarsely fissile c Sandstone, very limy, platy; mud or chippy; upper part contains many cracked------4 6 thin crystalline white limestone Mudstone, greenish-gray, sandy, soft; layers______5 0 contains also some muddy sandstone Sandstone, very limy, light-gray, platy_ 6 beds______3 Marlstone, sandy; grades upward into Sandstone, very limy; in beds 1-1~ sandy shale______4 0 in. thick; muddy at base; clean at Tuff, No. 5 of Culbertson, yellowish- top______2 0 buff, soft, very fine grained______3 Shale, sage-green, soft______12 6 Marlstone, white, sandy, platy______4 0 Oil shale, low-grade,· papery; bedding Marlstone, organic; contains lenses of planes have an abundance of myce­ papery low-grade oil shale______2 0 tophyllid fly larvae, a few oestrid c Limestone, white, sandy, ripple-marked fly larvae, and a few unidentified and mud-cracked______3 0 larvae of medium size; Coleoptera Marlstone, organic, massive but finely and Hemiptera also present but not banded; bedding planes have a few numerous______1 8 mycetophyllid fly larvae and a few Limestone, nearly white, sandy, ripple- seeds______3 6 bedded______1 11 c Limestone, light-gray, sandy, ripple- Mudstone, sage-green, soft______3 0 marked and mud-cracked______10 Oil shale, low-grade, gray, flaky ______5 Marlstone, buff, papery; contains lenses Shale, gray, flaky______2 0 and films of rich oil shale______0 Oil shale, low-grade, dark-brown, Shale, light-grayish-brown, clayey~ soft, flaky; weathers gray ______11 almost waxy; grades upward into Mudstone, light-greenish-gray; a few about 3ft of greenish-gray mudstone_ 14 0 beds muddy sandstone. ______2 8 c Mudstone, greenish-gray. sandy; con­ Marlstone, slightly organic; in thin tains lenses and beds of ripple-bedded beds that aiternate with thin beds micaceous sandstone; mud cracked of white sandy limestone that has neartop______24 0 characteristic undulant bedding_____ 2 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH A75

Green River Formation-Continued Green River Formation-Continued Wilkins Peak Member-Continued Ft in Wilkins Peak Member-Continued Ft in Marlstone, organic, shaly ______10 c Marlstone, white, sandy, crudely platy; Sandstone, limy, fine-grained; may be some layers contain mud lumps; tuff ______3 many layers mud cracked; cracks Mudstone, greenish-gray, sandy ______7 0 commonly filled with sand ______3 0 Oil shale, low-grade, carbonaceous, coarsely fissile ______6 0 [ Li~ee~~~~~~- ~~~~1~- ~-~i~~~- ~~~~=~ ~~~~~e~ Mudstone, gray ______5 0 Marlstone; contains mud lumps ______H Oil shale, medium-grade, papery; lenses Mudstone, sage-gray, soft ______6 0 of rich oil shale ______0 Limestone, white, sandy, platy ______10 Mudstone, greenish-gray, clayey, very Oil shale, low-grade, brown, coarsely soft ______8 0 fissile, carbonaceous ______0 Sandstone, very limy; in beds 2 in. Sandstone, limy, fine-grained, platy __ _ 1 3 thick, ripple bedded ______8 Mudstone, greenish-gray, soft ______20 0 Mudstone, sage-green, soft, almost Shale, grayish-buff; grades upward into fissile ______mudstone ______3 0 5 0 Oil shale, very low grade, carbonaceous, c Limestone, nearly white, sandy, ripple­ papery ______bedded; contains some layers that 3 look like analcitized tuff; mud cracked_ 2 0 Marlstone, sandy; full of rounded and angular mud lumps and curled mud Mudstone, greenish-gray, sandy ______10 0 flakes ______c Limestone, nearly white, sandy, gently 3 ripple bedded, mud-cracked; some c Marlstone, light-grayish-cream-colored, cracks filled wi~h fine sand ______1 3 clayey, crudely chippy to massive; ~ Marlstone, sandy; contains many mud weathers stark white; contains in r upper half many thin platy sandy 1 ~ C!) M ~~:£os~e-, -;r~~~i;h-~-r~~~ -s~~-d-; _- ~ ~ ~ ~ ~ 14 0 marlstone layers that are mud lc Sandstone, very limy, micaceous, cracked; unit typical of much of white lower half of Wilkms Peak muddy; locally mud cracked and Member ______locally ripple bedded ______10 25 6 Mudstone, greenish-gray, sandy ______11 0 c Sandstone, limy, muddy, micaceous; in thin regular platy beds that are mud c Shale, limy, sandy; contains many thin cracked ______1 6 layers of sandstone, some of which Edgewise conglomerate; clay balls and are mud cracked ______-- ______2 6 shale flakes in limy, sandy matrix __ 1 Sandstone, very limy, fine-grained; thin Mudstone, greenish-gray, sandy, mica­ regular beds, some of which are ceous; contains a few widely spaced gently rippled; few layers contain muddy ripple-bedded sandstone mud lumps ______3 0 layers; unit is Principal Olive zone Shale, gray, soft, crudely fissile; con­ mentioned in text and D bed of tains moderate number of hard sandy marlstone layers ______detailed geologic map (pl. 2) of 15 0 area around town of Green River __ _ 51 0 c Oil shale, low-grade, light-brown, some­ what carbona.ceous; grades upward Partial section, Wilkins Peak into platy marlstone that is sparsely Member ______523 mud cracked_. ______1 2 Marlstone, sandy; contains many Partial section of Laney Shale Member in sec. 8, T. 14 N., rounded mud lumps and pieces of R. 108 W. shale ______3 Bridger Formation: Ft in Mudstone, sage-gray; contains one Mudstone, gray; grades up into grayish group of sandy shale beds ______13 0 brown; becomes more sandy upward ____ _ 85 0 Shale, light - grayish - cream - colored, Green River Formation: sandy, limy; contains thin shaly sand- Laney Shale Member: stone layers ______5 0 Marlstone, white, chippy, porcel­ Mudstone, sage-gray, sandy; contains laneous, locally carbonaceous; con- greenish-gray la.yers ______10 0 tains leaf and stem impressions ______1 0 Shale, gray, sandy, micaceous, contains Mudstone, brown, soft, very sandy ___ _ 5 0 thin platy marlstone layers ______3 0 Marlstone, light-gray, chippy ______3 c Marlstone; weathers white, sandy, fissile Shale, light-brown, soft, sandy ______1 0 to chippy; many bedding planes Marlstone, white, hard- ______-_- __ 3 rnud cracked ______10 0 Shale, brown, soft, sandy ______1 1 c Sandstone, limy, fine-grained, gently Marlstone, brown; contains Goniobasis ripple bedded; has partings of clay and Unio? shells_. ______1 2 that are mud cracked, as are some Marlstone, dark-brownish-gray, hard sandstone beds ______3 chiPPY------2 0 A76 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River Formation-Continued Green River Formation-Continued Laney Shale 'Member-Continued Ft in Laney Shale Member-Continued Ft in Marlstone, dark-brown, sandy; con­ Sandstone, dark-gray, shaly, carbo- tains abundant shells of Goniobasis naceous, ripple:.bedded __ ..; ______1 6 and Unio? ______1 0 f Oil shale, black, rich, papery; contains Tuff, light-gray, silty, hard ______3 skeletons of many small fish ______3 Marlstone, buff; banded with many Oil shale, brown, low-grade, papery to 2-5-in.-thick gray tuff layers and a massive ______3 0 few muddy sandstone layers ______16 0 Marlstone, buff to light-brown; alter- Tuff, in thin beds that alternate with nates with thinner beds of papery equally thin claystone layers ______8 0 low-grade oil shale ______5 6 Tuff, gray, silty; in beds about 6 in. Shale, sandy, carbonaceous ______2 0 thick that alternate with coarse sandy Mudstone, chocolate-brown, very soft; tuff beds 1-2 ft thick ______10 0 slightly carbonaceous at top ______4 0 Tuff, light-gray, banded; mixed with a Mudstone, dark-grayish-brown, soft, considerable amount of mud and sandy ______16 0 sand ______25 0 Marlstone, dark- to light-gray, thickly Tuff, light-gray, chippy to platy, hard; laminated; not well exposed ______4 0 fine-grained glassy tuff ______3 0 Oil shale, black papery, rich ______10 Sandstone, grayish-brown, shaly; con­ Section 1"ncomplete; estimated to be per­ tains a few thin platy layers of haps 50ft more of well-bedded marl­ cleanly sorted reddish-brown sand- stone and oil shale. stone ______19 0 Marlstone, buff; almost a coquina of Approximate thickness, Laney ostracode shells but contains also Shale Member______370 some Unio? shells ______8 Sandstone, buff to dark-reddish-brown, Partial section of Laney Shale Member of the Green River Forma­ medium-grained, platy, more or less tion in sections 8, 17, and 18, T. 11,. N., R. 99 W. crossbedded ______12 6 Green River Formation: Marlstone, light-grayish-buff, shaly to Laney Shale Member: Ft in

almost papery; many layers hard __ _ 5 6 0 Tuff, medium-gray to buff; a muddy Sandstone, buff to dark-grayish-brown, crystal tuff containing considerable very fine grained; in beds ~~-2~ ft microgranular calcite in lenticular thick separated by thin carbonaceous beds which alternate with buff chalky claystone layers ______26 0 marls tone and sandy shale (overlying Sandstone, grayish-brown; poorly ex­ this unit is an estimated 300-400 ft posed but contains some lenses of of similar buff marlstone and a few dark-gray biotitic sandy tuff ______60 0 algal beds) ______---- 100+ Claystone, dark-gray, very carbona- Sandstone, fine-grained, shaly; alter­ ceous, hard, brittle ______1 6 nates with beds of hard shaly marl- stone ______Sandstone, white through buff to dark­ 9 0 gray, medium- to coarse-grained, Tuff, gray, massive ______1 0 soft; beds range from a few inches to Marlstone, buff, soft, shaly; poorly exposed ______several feet in thickness ______35 0 117 0 Marlstone, gray, shaly to platy, sandy_ 10 Shale, gray-buff, soft, flaky; alternates Shale, ocherous-brown· to gray; alter­ with similar shale that contains nate sandy and very fine grained somewhat more organic matter; not well exposed ______- 0 earthy carbonaceous layers ______..; 7 0 128 Tuff; bed consists almost wholly of Marlstone, dark-gray, hard, massive clear analcite crystals ______4 to crudely fissile, carbonaceous, lo- Shale, papery; contains some organic cally sandy ______5 0 rna t ter ______10 0 Sandstone, dark-gray, fine-grained; al­ Oil shale, low-grade, papery; top 1-6 in. most unconsolidated but contains a rich oil shale ______few thin hard layers ______6 6 12 0 Marlstone, buff, sandy, soft ______- 11 0 Marlstone, buff; alternate thin soft Tuff, rusty, analcitized ______-- 6 shaly layers and harder sandy layers; Sandstone, limy, sandy, platy; alter- contains several thin layers of tuff __ 10 0 nates with beds of sandy shale ______14 0 Tuff, buff, soft; consists largely of anal- Marlstone, buff, sandy, flaky to coarsely cite ______4 chippy; contains several harder more Marlstone, light-gray to buff, lami­ sandy beds ______25 0 nated; contains a few thin sandy Oil shale, low-grade, light-gray, flaky; layers ______8 0 contains lenses of rich oil shale; also Shale, dark-brown, soft, sandy, car- contains several thin beds of anal- bonaceous ______5 0 citized tuff ______-- 12 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH A77

Green River Formation-Continued Green River Formation-Continued Laney Shale Member-Continued Ft in Laney Shale Member-Continued Ft in Shale, papery, soft; some organic Mudstone, gray, sandy; shaly at top __ 10 rnatter ______5 0 Sandstone, muddy, fine-grained, cross- bedded ______Tuff, black, bituminous, fine-grained; 4 mostly analcite ______1 Mudstone, gray, sandy ______6 Oil shale, low-grade, papery; contains Sandstone, muddy, fine-grained, cross- bedded ______progressively more numerous ~hin 2 0 lenses of rich oil shale upward______11 6 Mudstone, light-gray, sandy; locally Oil shale, rich, black; groups of thin replaced by overlying sandstone ___ _ 1 9 lenses ______------6 Sandstone, muddy, shaly __ ------1 0 f Marlstone, buff, varved; contains rather Shale, gray, very soft, flaky ______2 0 numerous small fossil fish and verte­ Sandstone, muddy, carbonaceous, iron- stained ______brae of larger fish; unit contains also 2 0 several one-fourth-inch beds of anal- Shale, gray, very soft, flaky ______3 0 citized tuff______17 0 Algal bed; large well-formed heads that Marlstone, sandy, coarsely chippy _ _ _ _ 3 0 grew around fiat nuclei______2 0 Shale, papery______1 6 Marlstone, light-brown, varved, papery; c Algal bed, platy; mud on upper surface contains two thin dense massive mud cracked ______-'- ______3 marlstone beds ______'.:. 12 0 .... Marlstone, buff, papery, soft; contains c Marlstone, buff, hard, sandy, platy, one-half-inch bed of analcitized tuff_ 5 0 mud-cracked, in part oolitic ______._ 6 Algal bed ______5 Marlstone, buff, coarsely varved, soft, papery ______Shale, marly, papery ______6 0 7 6 Algal bed; algal rubble at base; lami- Algal bed, hard; made up of low, flat- nated above ______3 tened heads ______3 Limestone, concretionary, dense ______4 Marlstone, light-brown, hard, platy; Mudstone, buff, marly, soft______2 0 alternates with softer shaly marlstone Marls tone, sandy, concretionary, brec- 11 ciated ______beds------6 Marlstone, buff, soft, papery, varved; Shale, low-grade oil shale, papery; somewhat richer in organic matter at grades upward into harder organic 5 6 marls tone ___ :.. ______- _- ___ _ toP------7 0 c Limestone, brown, sandy; contains Oolite, coarse-grained; locally an algal dark-gray limy sandstone layers that deposit ______3 are mud cracked ______---- ______1 0 Marlstone, buff, varved; papery at base Shale, slightly organic, flaky ______8 to massive at top ______11 6 Oil shale, rich, papery to massive ______3 Partial section, Laney Shale Mem- Marlstone, varved, hard, platy ______1 0 ber______567-f- Tuff, mostly analcite but in part coarse- grained ash ______Underlain by gray clayey mudstone of 3 the Cathedral Bluffs Tongue of the Shale, marly, papery ______5 0 Wasatch Formation. Oil shale, rich, papery to massive_~-~­ 4 Algal bed; changes laterally from algal Partial section of the upper part of the Laney Shale Member of the deposit to limy rubble and back to Green River Formation measured on Big Sandy Creek in sec. 24, algal deposit again ______3 T. 23 N., R. 109 W. ;.. Sandstone, brown, muddy, fine-grained_ 2 0 Green River Formation: Mudstone, gray, sandy ______1 0 Laney Shale Member, upper part: Ft in Marlstone; full of mud lumps; contains Mudstone, olive-drab to brownish-drab, some oolite ______10 Shale, sandy and marly ______and soft chippy marls tone; (top of 1 0 unit not more than a few tens of feet Marlstone; contains mud lumps and oolite ______below base of Bridger Formation, 3 which is not exposed here)------10 0 Shale, marly, sandy, organic, papery __ 2 0 1 Algal bed ______Tuff, light-gray, platy; weathers brown_ 2 Mudstone, olive-drab, very soft; has Shale, gray, flaky ______1 platy rusty-brown sandstone bed at top ______Oolite, very fine grained ______4 9 0 Mudstone, gray, sandy ______6 Marlstone, platy, sandy; alternates Sandstone, medium- to fine-grained, with thin beds of limy sandstone ___ _ 1 0 iron-stained, poorly bedded; con- Tuff, white to light-gray __ -_------­ 1~ tains mud lumps ______5 Marlstone, buff, platy, sandy; alter­ Mudstone, gray, flaky ______3 nates with thin beds of limy sand- stone ______Sandstone, medium- to fine-grained, 9 0 iron-stained; contains mud lumps __ _ 1 0 Tuff, white ______8 732-765 0-64--6 A78 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Green River Formation-Continued Green River Formation-Continued Laney Shale Member, upper part-Con. Ft in Laney Shale Member, upper part-Con. Ft in Marlstone, light-buff, platy to flaky __ _ 2 3 Limestone, buff, sandy, iron-stained __ _ 5 Mudstone, olive-drab, massive ______2 6 Mudstone, olive-drab, sandy------___ _ 3 0 Sandstone, buff, limy, platy ______6 Marlstone, buff; beds lYz-5 in. thick Tuff, white ______1~ that are themselves laminated and Tuff; altered to coarse-grained analcite_ 4 that alternate with somewhat thicker Mudstone, greenish-brown; contains beds of papery marly shale ______6 0 harder crossbedcled sand!'ltone layers_ 10 6 Mudstone, greenish-buff, sandy ______4 0 Marlstone, gray to buff, hard, platy to Marls tone, buff, thinly lamina ted ______5 0 chippy; contains two l-in. layers of Sandstone, reddish-brown, limy; thin pure white tuff_------­ 3 0 irregular beds ______Mudstone, olive-drab, sandy, coarse- Marlstone, buff, laminated; mostly grained ______2 4 silicified tuff ______2 7 Mudstone, olive-drab; alternates in Tuff, light-gray; has rusty tubules; glass thin beds with buff to grayish-gray shards very little devitrified ______9 muddy marlstone ______6 Tuff, andesitic, greenish-drab, muddy, Sandstone, gray, irregularly platy; massive; contains many irregular weathers brown ______6 zones of well-rounded mud lumps that Tuff, gray, platy ______3 range in size from tiny pellets to Marlstone, buff; alternates in thin beds about 2 in. in diameter; makes cliff __ 36 0 with limy mudstone ______1 3 Tuff, light-gray to buff ______3~ Partial section, Laney Shale Mem- Sandstone; buff, medium-grai~ed, len­ ber______163 tic~Ilar; alternates in thin layers with NoTE.-Only two of the mudstone beds in this partial section olive-drab mudstone ______1 4 were examined under the microscope; but because both proved Marlstone, buff, flaky; in beds %-4 in. thick ______to be tuffs containing only minor ~mounts of mud, it is quite 4 0 possible that many of the "olive-drab mudstone" beds in this Marlstone, buff, soft, papery to lami­ part of the Green River Formation are also tuffs or, at least, nated; some laminae very rich in tuffaceous mudstone. ostracodes ______2 1 Ostracode limestone; essentially co- quina ______Section of the Bridger Formation and overlying White River(?) 2 Formation at Oregon Buttes in sec. 3, T. 26 N., R. 101 W. Sandstone, buff, very marly, soft, platy_ 5 White River(?) Formation: Ft Marlstone, buff, laminated ______~ __ 2 0 in Tuff, light-gray, dense; ranges in thick- Tuff, light-gray, massive to crossbedded, ness from 2 to 10 in ______6 nodular; composed of glassy shards with Marls tone, buff, massive to flaky ______3 0 small percentage of crystal fragments Tuff, light-gray ______5 except near base where it is darker and Mudstone, greenish-drab, sandy ______4 0 much coarser grained; predominantly Marlstone, buff, massive to flaky, crystal and lithic tuff. (On middle butte lenticular ______2 0 of group is roughly 125 feet more of this same kind of tuff.)______75 Tuff, gray; mixed with considerable 0 mud and sand ______8 Tuff, white, lenticular; ranges in thickness Mudstone, olive-drab, sandy ______4 0 from about 1 in. to more than 3~~ ft; averages about ______Tuff, gray; mostly coarse-grained anal- 6 cite crystals ______1 3 Tuff, light-gray, banded, massive; Marls tone, buff, massive ______2 8 (weathers light orange brown)______24 0 Tuff, light-gray, micaceous ______4 Gravel; pebbles subangular to rounded, Mudstone, olive-drab ______.:. ______2 4 black and green, and range from less than Tuff; lenticular bed ranging in thick- %in. to 1% in.; matrix white, tuffaceous___ 17 0 ness from 4 to 14 in ______8 Conglomerate; presumably Beaver Divide Mudstone, olive-drab, flaky; ranges in Conglomerate of Nace (1939, p. 32-34); thickness from 8 to 18 in ______1 0 matrix white sand (probably tuff); peb­ Tuff, gray, micaceous ______3 bles and cobbles predominantly angular Sandstone, greenish-gray to brown, and consist of black schist (from vicinity muddy; probably tuffaceous ______2 7 of Atlantic City, Wyo.) mixed with some Mudstone, light-gray, muddy, tuffa- quartz and chlorite schist; locally pre­ ceous, soft______3 6 dominantly granitic pebbles and matrix; Sandstone, olive-drab, very muddy, predominant size of material is about probably tuffaceous, massive to cross- ~~-4 in. but boulders as much as 1 ft in bedded ______10 6 diameter are found; locally, parts of con­ Tuff; mostly coarse-grained analcite_ 2 glomerate resemble volcanic-ash mud Tuff, dark-gray, dense ______4 flow______55 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH A79

White River(?) Formation-Continued Ft .in Bridger Formation-Continued in Sandstone, purplish-brown; rather coarse Mudstone, marly; contains much petrified wood ______grained at base where it channels under­ 6 lying bed; fine grained at top where it Oolite, buff, very fine grained, crudely 0 bedded ______contains many mud lumps ______11 2 0 Marlstone, gray, sandy, thin-bedded ______6 Thickness, White River(?) Formation __ 182 Shale, gray, soft, flaky ______4 0 Marlstone, gray, sandy, platy ______6 Bridger Formation: Mudstone, gray, sandy; locally buff muddy Marls tone, cream-color, dense ______3 0 sandstone ______28 0 Mudstone, sage-gray, soft ______15 0 Mudstone, light-brown, soft; lower one- Sandstone, light-brownish-gray, fine-grained, third shaly; upper part massive ______12 0 massive ______--- _____ ------2 0 Marlstone, buff, soft, thinly laminated ____ _ 6 0 Mudstone, gray to brownish-gray, clayey, Sandstone, very muddy, fine-grained, al- soft ______21 0 most unconsolidated; contains many Sandstone, buff, medium-grained, massive __ 9 0 petrified logs, many of which are en- Mudstone, gray, clayey, soft ______7 0 crusted with algal deposits as much as Sandstone, light-gray, muddy, limy, fine- 4 in. thick ______.; ______1 6 grained, massive ______.- ______11 0 Mudstone, greenish-gray, soft ______2 0 _, Sandstone, yellowish-brown, medium- Marlstone, nearly white; contains many grained, crossbedded; lower 5 ft contains ostracodes ______4 great many shale and mud lumps and Mudstone, gray to grayish-buff, clayey to channels into underlying beds of shale; sandY------~------27 0 25 ft above base is another zone of mud Tuff, greenish-gray, silty; contains great lumps; upper part massive and les~ cross- many petrified logs, some of which must bedded ______51 0 have been originally 1-2 ft in diameter __ 2 0 Sandstone, marly, muddy, fine-grained; Sandstone, dark-brown, medium-grained, banded with very thin alternate brownish­ limy; locally contains many small turtle buff and ash-gray laminae: locally,laminae bones ______6 contorted by subaqueous slumping ______19 0 Mudstone, gray to brownish-gray; contains Marlstone, white, silty, laminated ______6 0 several very sandy zones; also contains Shale, thinly laminated, papery; rich in considerable petrified wood near base ___ _ 22 0 ostracode valves; becomes sandy and platy at toP------­ 6 6 Thickness, Bridger Formation ______482 Sandstone, white, marly, fine-grained, mas- sive ______1 6 Section of the Bridger Formation measured on the east slope of Mudstone, gray, drab, and rusty-buff; Twin Buttes (Black Mountain of some maps) in sections 2.1, 22, clayey but contains some zones of. fairly 23 and 24, T. 14 N., R. 109 W. clean fine sand; unit contains many fossil Bridger Formation: Ft in turtles ______-- ______- __ 40 0 Overlain by 75-100 ft of Bishop Con- Sandstone, gray, very muddy; contains glomerate. rows of small brown sandy concretions __ 22 0 Mudstone, sage-gray, clayey to sandy and Mudstone, gray, clayey, soft; fossil turtles in place ______even gravelly; in uppermost part, banded 8 0 dark-greenish-gray tuffaceous beds alter­ Sandstone, brownish-gray, muddy, fine­ nate with gray mudstone beds; greenish grained; brown sandy concretions near bands range in thickness from one-half toP------12 6 in. to 8 in.; upper part also contains Sandstone, gray, limy, muddy, fine-grained; sandstone lenses and beds that are locally contains many large gastropod shells ___ ~_ 6 gravelly and as much as 15 ft thick; Tuff, yellowish-drab, muddy, fine-grained; pebbles are well-rounded black chert and much biotite ______10 0 jasper and some white quartzite and Mudstone, gray, sandy; a few thin platy hard limestone______225 0 sandstone beds near base ______12 0 Mudstone, gray to greenish-gray, sandy; Marlstone, buff to light-gray, sandy, platy; contains some tuffaceous mudstone; fossil contains oolites and ostracodes ______3 0 turtles common throughout unit; some Mudstone, greenish-gray, sandy ______15 0 large turtles are in place and have ··been Mudstone, gray, sandy; contains lens of virtually undisturbed since death______130 0 strongly iron stained medium-grained Mudstone, ash-gray; probably in large part sandstone near top ______45 0 tuff; contains many fossil turtles______15 0 Sandstone, gray, medium- to coarse-grained, Mudstone, sage-gray to greenish-gray; alter­ soft, massive ______3 6 nates with hard muddy sandstone beds Mudstone, gray, sandy, soft ______47 0 6 in. to 4 ft thick and spaced 5-15 ft Algal bed and coarse-grained oolite, dark- apart______105 0 brown, silicified ______.;. ______10 Mudstone, grayish-lavender______- 6 ABO THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Bridger Formation-Continued Ft in Bridger Formation-Continued Ft in Mudstone, light-greenish-gray ______8 Claystone, gray, rather hard ______11 0 Mudstone, light-brick:-red______1 0 Tuff, light-gray, marly, massive ___ ------1 0 Mudstone, light-greenish-gray______2 0 Claystone, gray, rather hard; probably tuf- faceous ______Mudstone, dull-red______12 0 12 0 Mudstone, light-brick-red;· banded with Marlstone, yellowish-gray, hard; lower part some gray ______-----_ 5 0 full of clay flakes and mud lumps; makes Mudstone, light-gray; stained pinkish_____ 8 0 the ·extensive broad bench at the top of Mudstone, light-gray; a few beds of alter- the Sage Creek white layer of Matthew __ 2 0 nate greenish-gray claystone and dull- Tuff, dark-gray, biotitic, massive ______23 0 reddish-gray mudstone near top______40 0 Mudstone, light-gray; locally contains lenses Tuff, greenish-gray, very sandy, biotitic, of medium-grained sandstone; tuffaceous fine-grained______10 0 and biotitic in upper part ______86 0 Tuff, dark-gray, sandy, biotitic______10 0 Mudstone, pistacio-green, clayey; contains Sand, unconsolidated, medium- to coarse­ great number of fossil turtles; also con­ grained; petrified logs common locally; tains remains of gar pike and __ 10 0 smoothly rounded black chert pebbles as Tuff, marly, hard; makes extensive bench __ 1 0 much as 1 in. in diameter rather generally Mudstone, sage-gray, sandy; turtle carapace distributed through this sand; no other fragments __ .. ______16 0 kind of pebble found______25 0 Tuff, dark-greenish-drab, medium-grained, Marlstone, hard, chippy ______1 6 muddy; andesitic volcanic ash reworked Soil?, dark-reddish-brown, carbonaceous, with mud ______15 0 soft, earthy ______6 Marlstone, tuffaceous ______2 0 Oil shale, very low grade, laminated______1 0 Mudstone, brownish-gray, sandy, soft ______15 0 Tuff, yepowish-buff, powdery_____ .., ______3 Marlstone, light-gray to buff, sandy; makes Mudstone, dull-brick-red, carbonaceous, narrow bench ______3 0 earthY------~------1 0 Sandstone, drab, tuffaceous, muddy, biotitic, Claystone, brownish-drab; grades upward fine-grained--~------­ 15 0 to dark gray; very soft______15 0 Sandstone, dark-gray to greenish-brown, Marlstone, brownish-buff, silty; makes biotitic, crossbedded, concretionary; mostly bench______3 0 andesitic volcanic ash ______6 0 Claystone, light-grayish-green, very soft; Mudstone, cream-colored, clayey, soft. ___ _ 3 0 contains several thin ocherous tuff layers; Tuff, greenish-gray, muddy; largely basic contains fossil turtles and carbonized logs. 26 0 volcanic ash ______4 0 Tuff, dark-greenish-gray, biotitic, fine- Claystone, light-pinkish-buff, waxy; prob- grained______3 0 ably derived from glassy volcanic ash ___ _ 7 0 Mudstone, sage-gray; contains 3-ft layer of Chert, dark-brown, almost black; makes ex- soft pale-grayish-green claystone; contains tensive bench __ :.. ______3 many fossil turtles______21 0 Mudstone, gray, clayey, very soft ______4 0 Tuff, light-yellowish-brown, gritty, biotitic_ 2 0 Tuff, andesitic, gray, gritty ______2 0 Tuff, dark-grayish-drab, muddy, biotitic___ 16 6 Mudstone, brownish-gray, sandy, soft ____ _ 12 0 c Marlstone, light-gray to light-yellowish­ Algal bed, finely laminated, in part silicified; brown, thin; platy bedding; some bedding mixed with hard cream-colored dense planes mud cracked; some have plant- marlstone that is coarsely chippy or mas­ stem impressions______1 6 sive; these two rocks together make a Mudstone, brownish-gray, soft; not well broad and extensive bench near base of exposed______, 15 0 Twin Buttes ______-- ______------1 6 Marlstone, brownish-gray, dense, regularly Mudstone, tuffaceous, gray, biotitic; con­ 6 bedded------~------2 tains irregular lenses of coarse-grained Mudstone, gray, clayey, very soft.______60 0 greenish-gray andesitic crystal tuff ______28 0 Mudstone, tuffaceous, and tuff; tuffaceous Marlstone, greenish-gray, hard, platy; mudstone is dark gray with occasional weathers yellowish brown; makes persist- pistacio-green clay layers; interbedded ent bench ______3 6 with tuffaceous mudstone are rough lenses of coarse-grained, greenish-brown ande- Mudstone, gray, clayey; contains many lenses of greenish-gray, cross bedded sitic tuff _____ .______130 0 Mudstone, pale-greenish-gray; fossil turtles sandstone which is largely andesitic crystal tuff ______20 10 very numerous __ ------10 0 Mar~stone, grayish-brown, hard, chippy to Marlstone, light-gray, sandy, thin-bedded; platy______2 6 contains a few small plant fragments_--­ 2 Mudstone, sage-gray, sandy; contains a few Mudstone, gray, very sandy; contains yel­ sandy concretionary masses______88 0 lowish-brown limy concretions __ ------­ 18 0 Chert, dark-brown; weathers yellowish- Tuff, andesitic, dark-greenish-gray, fine­ , brown; contains many stems and fruiting grained, muddy; contains lumps of under- bodies? of Chara ______6 lying greenish-gray mudstone ______---- 5 0 EOCENE ROCKS, WYOMING-COLORADO-UTAH:; A81

Bridger Formation-Continued Ft in Uinta and Bridger Formations-Continued Ft in Mudstone, greenish-gray, sandy, massive; Tuff, nearly white, limy; supports low heads contains irregular masses and lenses of sandy of algal limestone that apparently formed andesitic volcanic ash______4 0 around coarse plant stems; centers now Mudstone, sage-green, in part clayey; con- filled with clear chalcedony stained tains beds of fine-grained dark-gray chrysocollalike blue ______1 0 muddy sandstone that locally contains Mudstone, drab, rather hard ______11 0 botryoidal limy concretions which weather Sandstone, buff, moderately coarse grained, rusty buff ______15 0 muddY------7 0 Mudstone, light-sage-gray, soft ______4 0 Thickness, Bridger Formation______1, 336 Mudstone, gray, sandy ______6 0 Underlain by Laney Shale Member of Green Sandstone, greenish-buff, rather coarse- River Formation. grained, muddy; weathers dark gray; probably in large part tuff ______24 0 Section of the Uinta and Bridger Formations (undifferentiated) on Mudstone, pinkish-gray, sandy; grades up- the east end of Haystack Mountain in sections 5 and 6, T. 16 N., ward into gray ______~ ______5 0 R. 95 W. Tuff, dark-gray, sandy, coarse-grained; ' grades upward into muddy sandstone __ _ Uinta and Bridger Formations (undifferentiated): Ft in 12 0 Sandstone, brown, very coarse grain~d, Marlstone, nearly white; weathers gray to gravelly, crossbedded, lenticular; caps brown; in part algal; heads extend up into overlying tuff ______high, eastern end of Haystack Mountain_ 9 0 4 6 Mudstone, gray, ·sanely; contains gravelly Mudstone, gray, sandy ______..: ______23 0 lenses ______23 0 Mudstone, pinkish-gray; limy concretions __ 2 0 Sandstone, nearly white, very coarse Mudstone, light-gray to greenish-gray, lo- cally sandy ______grained, gravelly, crossbeclded; contains 58 0 pebbles as much as one-half inch in diam­ Mudstone, brownish-gray; makes conspicu- eter; a lens that ranges in thickness from ous band in landscape __ -.- ______5 0 about 5 to 18ft ______5 0 c Sandstone, limy, mud-cracked ______3 Mudstone, brownish-gray, soft ______7 0 Mudstone, ash-gray, very clayey; probably Sandstone, gray, coarse-grained, gravelly, derived from glassy volcanic ash ______20 0 crossbedded; a lens ______10 0 Mudstone, gray, soft; many limy concre- Mudstone, drab to light-gray, sandy; con­ tions------~------15 0 tains a few poorly defined sanely lenses c Sandstone, dark-gray, hard, medium­ and one pink layer ______83 0 grained; weathers brownish-gray; makes Gravel, gray, muddy and sandy; banded conspicuous and extensive bench ______3 0 w~h pink ______12 0 Mudstone, gray, sandy; several sandstone lenses ______Mudstone, greenish-gray; several pink lay­ 42 0 ers; contains lenses of fine-grained muddy Sandstone, gray to brown, muddy, lami- sandstone ______23 0 nated, rippled ______-- ___ ----- 2 6 Gravel, gray, muddy, soft __ ---- ___ - ______11 0 Mudstone, gray to drab; a few thin pink and Mudstone, gray; pink bands; contains sandy mauve bands; becomes more sandy up- layers------17 0 ward; locally unit contains great massive Mudstone, pink or reddish-gray; has barite lenses of dark-brown muddy sandstone__ 115 0 and limy concretions ______3 0 Sandstone, gray to brown, iron-stained, Mudstone, sage-green; gravelly and sandy muddy, lenticular______8 0 at base but grades upward into silty Mudstone, pale-greenish-gray, locally claystone ______30 0 sandy______23 0 Sandstone, gray, muddy, thin-bedded to Sandstone, gray, muddy; contain~ iron- massive; has some iron-stained concre- stained concretions ______-- __ ~\ 11 ----- 20 0 tions ______10 0 Mudstone, gray, sandy ______4 0 Thickness, Uinta and Bridger Formations__ 778 Sandstone, coarse-grained, cross bedded; a Base concealed by sand dunes; estimated to lens ______be 50-7 5 ft lower. 8 0 Mudstone, grayish-drab; contains pale­ REFERENCES green ahd pink layers in upper part; very Anderman, G. S., 1955, Tertiary deformational history of a sandy; makes steep slope ______90 0 portion of the north flank of the Uinta Mountains in the Tuff, andesitic, greenish-brown, coarse­ vicinity of Manila, Utah, in Wyoming Geol. Assoc. Guide­ grained, cross bedded; contains lenses of book, lOth Ann. Field Conf., Green River Basin, 1955: gravel, largely of greenish-gray chert ___ _ 18 0 p. 130-134, and map. ~· Sandstone, dark-brown, very carbonaceous, Athy, L. F., 1930, Density, porosity, and compaction of sedi­ fine-grained, muddy; grades upward into mentary rocks: Am. Assoc. Petroleum Geologists Bull., gray mudstone ______-.- ______4 0 v. 14, p. 13-14. A82 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Berg, Robert R., 1961, Laramide tectonics of the Wind River Fahey, Joseph J., Ross, Macolm, and Axelrod, Joseph M., 1960, Mountains, in Wyoming Geol. Assoc. Guidebook, 16th Loughlinite, a new hydrous sodium magnesium silicate: Ann. Field Conf., Symposium on Late Cretaceous rocks, Am. Mineralogist, v. 45, p. 270-281. Wyoming and adjacent areas, 1961: p. 70-80. Fahey, Joseph J., and Yorks, K. P., 1963, Wegscheiderite, a new Bradley, W. H., 1926, Shore phases of the Green River formation saline mineral from the Green River Formation, Wyoming: in northern Sweetwater County, Wyoming: U.S. Geol. Am. Mineralogist, v. 48, p. 400-403. Survey Prof. Paper 140-b, p. 121-131, pl. 58. Fidlar, M. M., 1950, Structural features of the Green River --- 1931, Origin and microfossils of the oil shale of the Green Basin, in Wyoming Geol. Assoc. Guidebook, 5th Ann. River formation of Colorado and Utah: U.S. Geol. Survey Field Conf., Southwest Wyoming, 1950: p. 86-87. Prof. Paper 168, p. 1-58. Forrester, J. 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Field Conf., Casper area, Wyoming, 1954: p. 32-34. 5th Ann. Field Conf., Southwest Wyoming, 1950: p. 48-58. Cohee, G. V., Chairman, 1962, Tectonic map of the United Hansen, W. R., 1961a, Geologic map of the Willow Creek States, exclusive of Alaska and Hawaii; prepared by a joint Butte quadrangle, Utah-Wyoming: U.S. Geol. Survey committee of the U.S. Geological Survey and the American Misc. Geol. Inv. Map 1-322. Association of Petroleum Geologists: scale 1: 2,500,000. --- 1961b, Geologic map of the Dutch John Mouptain and Cookson, Isabel C., 1953, Records of the occurrence of Botryo­ Goslin Mountain quadrangle, Utah-Wyom~ng: U.S. Geol. coccus braunii, Ped1·astrum and the Hystrichosphaerideae in Survey Misc. Geol. lnv. Map 1-324. Cainozoic deposits of Australia: Natl. Museum Melbourne Hansen, W. R., and Bonilla, M. G., 1!>54, Laramide faulting and Mem. 18, p. 107-123. orogeny on the north flank of the · Uinta Mountains in Culbertson, W. C., 1961, Stratigraphy of the Wilkins Peak eastern Dagget County, Utah: Colorado ·S.ci. Soc. Proc., Member of the Green River formation, Firehole Basin v. 17, no. 1, p. 1-29. " quadrangle, Wyoming: Art. 348, in Geol. Survey Prof. --- 1956, Geology of the Manila quadrangle, Utah-vVyoming: Paper 424-D, p. D170-D173, fig. 348.2. U.S. Geol. Survey Misc. Geol. lnv. Map 1-156. · --- 1962, Tower Sandstone Lentil and Laney Shale Member Hansen, W. R., Kinney, D. M., and Good, J. M., 1960. Distri­ of the Green River formation, Green River area, Wyoming: bution and physiographic significance of the Bro·;wns Park Art. 78, in U.S. Geol. Survey Prof. Paper 450-C, p. C54-C57. Formation, Flaming Gorge and Red Canyon areas, Utah­ Daly, R. A., 1933, Igneous rocks and the depths of the earth: Colorado: Art. 115, in U.S. Geol. Survey Prof. Pap~r 400-B, New York, McGraw-Hill Book Co., p. 9, 16. p. B257-B259. Donovan, J. H., 1950, Intertonguing of Green River and Wa­ Hayden, F. V., 1869, U.S. Geol. and Geog. Survey Terr., 3d Ann. satch formations in part of Sublette and Lincoln Counties, Rept., p. 90. Wyoming, in Wyoming Geol. Assoc. Guidebook, 5th Ann. --- 1871, U.S. Geol. and Geog. Survey Terr., 4th Ann. Field Conf., Southwest Wyoming, 1950: p. 5!>-67. Rept., p. 155-156. .J Emmons, S. F., 1877, 1·n King, Clarence, Report of the geological --- 1873 ed., U.S. Geol. and Geog. Survey Terr., 3d Ann. exploration of the 40th Parallel: Prof. Papers of the En­ Rept., p. 191. gineer Department, U.S. Army, no. 18, v. 2, p. 211. Hedberg, H. D., 1936, Gravitational compaction of clays and Engelmann, Henry, 1858, Preliminary report on the geology : Am. Jour. Sci., 5th ser., v. 31, p. 262-268. of the country between and Camp Floyd, Utah Territory, and southwest of the latter place, along Jenkins, Carl E., 1955, The Pacific Creek deep test, Superior Oil Company No.1 Unit, sec. 27, T. 27 N., R. 103 W., Sublette Captain J. H. Simpson's routes, 1858: U.S. 35th Cong., County, vVyoming, in Wyoming Geol. Assoc. Guidebook, 2d sess., Senate Ex. Doc. 40, p. 45-75. Erickson, E. T., 1922, Tschermigite (ammonium alum) from lOth Ann. Field Conf., Green River Basin, 1955: p. 153-154. ·Wyoming: Washington Acad. Sci. Jour., v. 12, p. 49-54. Johannsen, Albert, 1914, Petrographic analysis of the Bridger, Fahey, Joseph J., 1962, Saline minerals of the Green River Washakie and other Eocene formations of the Rocky Formation, with section on X-ray powder data for saline Mountai~s: Am. Mus. Nat. History Bull., v. 33, p. 209-222. minerals of the Green River Formation, by Mary E. Mrose: Kemp, J. R., and Knight, W. C., 1903, Leucite Hills of Wyoming: U.S. Geol. Survey Prof. Paper 405, 50 p. Geol. Soc. America Bull., v. 14, p. 326. EOCENE ROCKS, WYOMING-COLORADO-UTAH A83

King, Clarence, 1878, U.S. Geol. Explor. 40th Parallel: v. 1, p. Nightingale, W. T., 1930, Geology of Vermilion Creek gas area 444-449, Atlas (folio) maps II and III, 1876. in southwest Wyoming and northwest Colorado: Am. Assoc. Koenig, Karl J., 1960, Bridger Formation in the Bridger Basin, Petroleum Geologists Bull., v. 14, p. 1013-1040. Wyoming, in Wyoming Geol. Assoc. Guidebook, 15th Ann. Oriel, S. S., 1961, Tongues of the Wasatch and Green River Field Conf., Overthrust belt of southwestern w·yoming and Formations, Fort Hill area, Wyoming: Art. 63. in U.S. adjacent areas, 1960: p. 163-168. Geol. Rnrvey Prof. Paper 424-B, p. BU51-BU12. Lawson, Don E., and C'rowson, C. W., 1961, Geology of the Arch Osborn, H. F., 1936, Proboscidea; a monograph of the discovery, unit and adjacent areas, Sweetwater County, \Vyoming, in ·evolution, migration, and of the mastodonts an·d Wyoming Geol. 1\ssoc. Guidebook, 16th Ann. Field Conf., elephants of the world, v. I, Moeritheroidea, Deinotherioidea, Symposium on l~te Cretaceous rocks, ·wyoming and adjacent Mastodontoiclea; edited by Mabel Rice Percy: New York areas, 1961: p. 78Q-789. · Am. Mus. Press, p. 312-315. Lewis, J. V., 1924, Fissility of shale and its relationship to petro­ Peale, A. C., and Endlich, F. M., 1879, Efeventh Ann. Rept., for leum: Geol. Soc. America Bull., v. 35, p. 568. 1877: U.S. Geol. and Geog. Survey Terr., p. 64-154, 511- Love, J. D., 1939, Geology along the southern margin of the 643. Absaroka Range, Wyoming: Geol. Soc. America Spec. Pipiringos, G. N., 1962, Uranium-bearing coal in the central part Paper 20, p. 1-134. of the Great Divide Basin: U.S. Geol. Survey Bull. 1099-A, --- 1960, Cenozoic sedimentation and crustal movement in p. Af-Al03, pl. I. ·wyoming: Am ..Jour. Sci., v. 258-A, p. 204-.214. Powell, J. \-V., 1876, Report on the geology of the eastern portion --- 1961a, Split Rock Formation (Miocene) and Moonstone of the Uinta Mountains: U.S. Geol. and Geog. Survey Formation (Pliocene) in central Wyoming: U.S. Geol. Terr., 2nd div., p. 161-171, 204-210, atlas (folio) map B. Survey Bull. 1121-I, p. Il-I34. Ridgway, Robert, 1912, Color standards and color nomenclature: --- 1961b, Definition of Green River, Great Divide, and Washington, D.C., published by the author. ·washakie Basins, southwestern Wyoming: Am. Assoc. Roehler, H. W., 1961, The late Cretaceous-Tertiary boundary Petroleum Geologists Bull., v. 45, p. 1749-1755. in the Rock Springs uplift, Sweetwater County, Wyoming, in Love, J. D., Weitz, .J. L., and Hose, R. K., 1955, Geologic Map \-Vyoming Geol. Assoc. Guidebook, 16th Ann. Field Conf., · of Wyoming: U.S. Geol. Survey. Symposium on Late Cretaceous rocks, Wyoming and adja­ McGrew, Paul 0., 1951, Tertiary stratigraphy and paleontology cent area, 1961, p. 96-100. of south-central Wyoming, in Wyoming Geol. Assoc. Guide­ Rosenbusch, Harry, 1923, Elements der Gesteinslehre, 4th ed., book, 6th Ann. Field Conf., South-Central Wyoming, 1951: revised by A. Osann: Stuttgart, E. Schweizerbart schen­ p. 54-57. Verlagsbuchandlung, p. 561, 563. McGrew, Paul 0., and Berman, Jack E., 1955, Geology of the Ruttner, Franz, 1953, Fundamentals of limnology, translated by Tabernacle Butte area, Sublette County, Wyoming, in D. G. Frey and F. E. J. Fry: Toronto Univ. Press, 242 p. Wyoming Geol. Assoc. Guidebook, lOth Ann. Field Conf., Schultz, A. R., 1909, The northern part of the Rock Springs coal Green River Basin, 1955: p. 108-111. field, Sweetwater County, Wyoming: U.S. Geol. Survey McGrew,. Paul 0., with the collaboration of Jack E. Berman, Bull. 341, p. 256-28~, pl. 14. Max K. Hecht, John M. Hummel, George Gaylord Simpson, --- 1910, The southern part of the Rock Springs coal field, and Albert E. Wood, 1959, The geology and paleontology Sweetwater County, Wyoming: U.S. Geol. Survey Bull. 381, of the Elk Mountain and Tabernacle Butte area, Wyoming: p. 214-281, pl. 14. Am. Mus. Nat. History Bull., v. 117, p. 121-176. -·-- 1914, Geology and geography of a portion of Lincoln McGrew, P. 0., and Roehler, H. W., 1960, Correlation of Tertiary County, Wyoming: U.S. Geol. Survey Bull. 543, p. 71-89, units in southwestern Wyoming, in Wyoming Geol. Assoc. pl. 1. Guidebook, 15th Ann. Field Conf., Overthrust belt of --- 1918, A geologic reconnaissance of the Uinta Mountains, southwestern Wyoming and adjacent areas, 1960: p. 158. northern Utah, with special reference to phosphate: U.S. Masursky, Harold, 1962, Uranium-bearing coal in the eastern Geol. Survey Bull. 690, pl. 5. part of the Red Desert area: U.S. Geol. Survey Bull. --- 1920, Oil possibilities in and around Baxter Basin, in the 1099-B, p. Bl-Bl9, pl. 1. Rock Springs uplift, Sweetwater County, \-Vyoming: U.S. Matthew, W. D., 1909, The carnivora and insectivore of the Geol. Survey Bull. 702, p. 24-29, pl. 1. Bridger Basin, middle Eocene: Am. Mus. Nat. History Schultz, A. R., and Cross, Whitman, 1912, Potash-bearing rocks Mem. 9, pt. 6, p. 296. of the Leucite Hills, Sweetwater County, Wyoming: U.S. May, B. E., 1961, The desert springs field, in Wyoming Geol. Geol. Survey Bull. 512, p. 5-39. ·.. Assoc. Guidebook, 16th Ann. Field Conf., Symposium on Sears, J. D., 1924a, Relations of the Browns Park Formation and Late Cretaceous rocks, Wyoming and adjacent areas, 1961: the Bishop Conglomerate, and their role in the origin of p. 290-293. Green and Yampa Rivers: Geol. Soc. America Bull., v. 35, Mees, E. C., Copen, J. D., and McGee, J. C., 1961, Table rock p. 279-304. field, Sweetwater County, Wyoming, in Wyoming Geol. --- 1924b, Geology and oil and gas prospects of a part of Assoc. Guidebook, 16th Ann. Field Conf., Symposium on Moffat County, Colorado, and southern Sweetwater County, Late Cretaceous rocks, Wyoming and adjacent areas, 1961: Wyoming: U.S. Geol. Survey Bull. 751-G, p. 269-319, p. 294-300. pl. 35. Morris, W. J., 1954, An Eocene fauna from the Cathedral Bluffs --- 1926, Geology of the Baxter Basin gas field, Sweetwater tongue of the Washakie Basin, Wyoming: Jour. Paleon­ County, Wyoming: U.S. Geol. Survey Bull. 781, p. 13-27. tology, v. 28, p. 195-203. Sears, J. D., and Bradley, W. H., 1924, Relations or the Wasatch Nace, R. L., 1939, Geology of the northwest part of the Red and Green River Formations in northwestern Colorado and Desert, Sweetwater and Fremont Counties, Wyoming: southern Wyoming: U.S. Geol. Survey Prof. Paper 132-F, Wyoming Geol. Survey Bull. 27, p. 1-48, pl. 1. p. 97-103 .. A84 THE GREEN RIVER AND ASSOCIATED TERTIARY FORMATIONS

Shannon, E. V., 1927, Ammoniojarosite, a new mineral of the Tracey, J. 1., Jr., Oriel, S. S. and Rubey, W. W., 1961, Diamictite jarosite group from Utah: Am. Mineralogist, v. 12, p. 424- facies of the Wasatch Formation in the Fossil basin, south­ 426. western Wyoming: Art. 62, in U.S. Geol. Survey Prof. Simpson, G. G., 1933, Glossary and correlation charts of North Paper 424-B, p. B149-B150. American Tertiary mammal-bearing formations: Am. Mus. Veatch, A. C. 1907, Geography and geology of a portion of south­ Nat. History Bull., v. 47, p. 91. western Wyoming: U.S. Geol. Survey Prof. Paper 56, Sinclair, W. J., 1906, Volcanic ash in the Bridger beds of Wyo­ p. 75-105, pl. 3. ming: Am. Mus. Nat. History Bull., v. 22, p. 273-280, pl. 38. Wentworth, C. K., 1922, A scale of grade and class terms for Swain, Barbara W., 1957, Fort Union Formation, west flank of clastic sediments: Jour. Geology, v. 30, p. 380-389. the Sierra Madre, Carbon County, Wyoming: Geol. Soc. America Bull., v. 68, p. 1874. Wilson, L. R., and Hoffmeister, W. S., 1953, Four new species of Terzaghi, Charles, 1925a, Principles of Soil mechanics: Settle­ fossil Pediastrum: Am. Jour. Sci., v. 251, p. 753-760. ment and consolidation of clay: Eng. News-Rec., v. 95, Winchester, D. E., 1923, Oil shale of the Rocky Mountain region: p. 874-876. U.S. Geol. Survey Bull. 729, p. 1-204, pl. 18. --- 1925b, Principles of soil mechanics: Physical differences Wood, H. E., 2d, 1934, Revision of the Hyrachyidae: Am. Mus. between sand and clay: Eng. News-Rec.,· v. 95, p. 912-915. Nat. History Bull., v. 67, p. 241-242. INDEX

(Italic pngo numbers Indicate major references]

A Page E Page K Page Absarokn Rnngc, source or volcanic material. A47, 50 Echo Canyon, type locality or Wastach For­ Kinney Rim ...... ------A 7 Absarokitts witterL...... 26 mation •.•. ------...... A20 Knightia ... __ ... __ ...... 45, 46 A bstrnct•••••••••••.•...... --..... 1 Eotitanops SP------26 L Acknowledgments...... 5 Esthonvx •• ...... ------27 Lambdotherium. .•...... 27 Alknll slicks...... 9 popoagiw m __ ... __ ...... 27 Ambloctontts major...... 27 F Faulted zone south or Washakie Bnsin...... 1~ Laney Rim ...... ------Ammonlojaroslto, In coni...... 24 Laney Shale Member, Green River Formation. 48 Annlclmo •••••...... •...... 43,44 Faulting •. ------. 10 section of ...... 45, 45 Anderman, 0. S., quoted...... 12 Faults, miscellaneous...... 14 Faunal zones, Bridger Formation...... 54 Leaf-cuticle residue .... ------24 Andesite tuff, distinctive mnrkcr bed In Leopold, E. B., fossils identified by...... 30 Bridger Formation...... 49 Fly larvae...... 28, 43 Fontenellc Creek, section on.····------35 quoted ...... ------.. ----.... 31 Antolopo Butte...... 55 Leptotomus parvus ...... ------...... 46 Fontenclle Tongue, Green River Formation.. S& Aphelops...... 57 Lewis, J. V., quoted ...... ------19 partial section or.------·------35 Little Mountain...... n Fossil soils, Bridger Formation...... 49 B Lonetree white layer, composition oL...... 53 Fossils, Browns Park Formation...... 57 section Including...... 51 Bndlnnds, Bnxter Basin ••...... Green River Formation, Fontanelle rormod on Bridger Formation._ ...... • 49, 54 Tongue ...... ____ ...... 34 Loughlinlte ...... ------.-- 42 rormod on Cnthedrnl Bluffs Tongue, Laney Shale Member.------44, 45,46 Love, J. D,. quoted .. ------39 Luman Tongue, Green River Formation----. £8 Wasatch Formation...... 26 Luman Tongue...... 30 Oroon Rivor Basin .•••...... •.... Tipton Shale Member...... 32,33 M Wnshaklo Bnsln...... 7, 54 Tipton Tongue...... 31,32 McGrew, P. 0., quoted ...... _ ...... 45, 46, 54,57 Bassariscops • . • • • • • . • • • • • . • • • . • . • . • . • • . • . • • • • 57 white layers...... 53 McGrew, P. 0., and Roehler, H. W., quoted. 27 Balhvopsis...... •.•••.. 27 Wilkins Peak Member...... 43 Marl, defined ...... ------19 Hnttlo Spring Formation...... 48 Wasatch Formation ...... ------20,21 Marlstone, defined .. ------19 Baxter Dasln...... 7 Cathedral Bluffs Tongue...... 26 Laney Shale Member, Green River For- Bishop Conglomerate...... 16, 53, 65 New Fork Tongue...... 27 mation, analysis...... 44 18,48 Drldgor Formation •••.•...... Niland Tongue...... 24 Measured sections ...... ------. 58 oscnrpments rormod hy...... • 6, 7 1\felanosaums SP------46 partinl sections oL •...... •.....•.. 51,52 G Melanterite, in coaL...... 24 Browns Park Formntlon...... 56 Oar-pike scales ...... 45,51 1'feniscotherinm ...... •.. ------...... --. 27 uranium ln...... 57 Oaylusslte...... •...... •...... 40 chamense ...... ------27 Burled hills...... 17 Gentilocamelus...... 57 Mining, coaL------24 Goldsmith, Juno, analyst...... 43 trona ...... -- .. --. '40, 43 Goniobasis sp ...... 30, 33,34 c 1\foropus. _.. ------·----- · -- 57 Ooslute Lake, deposits In .•...... 34,35 Cathedrnl Bluffs Tongue, Wasatch Formn- Morris, W. J., quoted ... ------­ 27 Granite Mountains, source or arkosic sedi- tlon,...... £6 Mudstone, defined ... ------19 ments •..•...•...... •...... 23,48 Channeling, In Laney Shale Member•••.....• 46,47 Great Divide Basin, Interior drainage...... 9 N Chrvsophyta...... 30 physiographic setting...... Church Buttes anticline, gas field on...... 14 Nahcolite ...... ------.. ----...... ------40 structural setting...... 10 New Fork Tongue Wasatch Formation...... 27 Cladocera...... 43 Green River Basin, physiographic setting.... 6 Niland Tongue, Wasatch Formation...... 28 Clnystone, defined...... 19 structural setting...... 9 Coni, nnalysls oL...... 25 Northupite ..... ------40,42 Green River Formation ...... 18,28 Notharctus gracilis ...... ------. 46 Bridger Formation...... 49 escarpments formed by...... 6, 7 sp. ______...... ______...... 26 Lumnn Tongue, Green River Formation. 28,29 saline facies .. _...... _.... _...... _... 15 Nilnnd Tongue, Wasatch Formation .• 22, 24,25 Nymphaea SP------30 uranium ln...... 22 II 0 Coleoptera...... 43 Halite...... _... _...... 39, 40 Oil shale, defined ...... ------.... ------19 Compnctlon, local effects...... 17 Hansen, W. R., and Bonilla, M. G., quoted •• 11,15 Green River Formation, Laney Shale regional effect...... 17 Haystack Mountain...... ------7 Member ..... ------17,44 fossils...... 26 Hemiptera.------...... 43 Luman Tongue .... ------28,29 Contlncutal fault...... 19 Henrys Fork fault ...... 10,12 Tipton Tongue.------31,32 Crocodile bonos ...... 45,51 Heptodon...... • ...... 27 Wilkins Peak Member ...... 36,43 Oynodontomvs.. ••• • . •• . . • . • . • • . • . • •. .• .... •. . 27 Hexacodus sp ...... ------26 Omomys carteri...... ------46 Hvopsodus.... •• •• • . . .•. •... •.. •...... 27 Oregon Buttes ...... -----.. ---.-.------9 D lepidus. ------45,46 petrified wood near ... --.--.-... -.------53 Darby fault...... 14 sp...... 26 section on ...... ------44 Derormntlon, early Eocene...... 15 Hvrachvus ...... 27,45 Ostracodes.------25, 28, 29, 32, 33, 45 post-Eocene-pre-Miocene('?)...... 16 modesttts .. ------26 p post-Miocono...... 16 sp .....•...... _...... 46 46 pre-Tertiary___ ...... 14 spp____ .---.--...... --.. ------.-.----.- 27 Paramus delicatus ...... ------Depressions, shallow, pnnliko...... 8 Hyracotherium ...... _. _... _...... 27 Pediastrum duplex •.....•....•.••.••.•. ----.-- 31 30 Diacodon edenensis...... 46 sp.------.-----.-.-.. ------26 sp. ·----·································· Dldvmicttts altfdens...... 26 Peratherium •••••••.•• ------········ ------·-- 26 Dip, depositionaL...... 16 Petrified wood ...... 53 See also Compaction. Islands In ancient Green River lake, a local Phil Pico Mountain, erosional platform on .... . 13 Drainage...... 9 source of sediments ...... 17 Physiography of tho area ...... •.....•...... G A85 A86 INDEX

Page Page Page Piedmont, section near______A44 Smith, V. C., analyst______A33,44 Uinta flexure.------· A11 Pilot Butte, wyomingite cap of. ______.___ 57 Soils, fossiL_. ______------_____ ~__ 49 Uinta Forma~ion______54 Pipiringos, G. N., quoted ______20,29,48 Sphaerium SP------. 30 Uinta Range, age of deformation______15 Pirssonite ... -~ ___ . __ ..... ______• ___ .. ___ 40 Split Rock Formation______57 Unconformity, beneath Bishop Conglomerate. 16 Playa lakes .. ·------7, 8, 9 Spores ______------______30 between Wasatch and Fort Union For- Springs ______·______.c ______9 Pollen. _____ .. --. __ .. ---.•. __ .... ______24, 30, 31, 43 mations. ___ ------15, 21 Potamooeton sp ___ ... ---. ______30 Steamboat Mountain, pumice cones on______57 in Green River Formation______16 Powers, D. F., analyst..______47 Stratigraphy, orientation______18 in Wasatch Formation______15 Previous geological investigations______4 See also separate formations. Unio sp ______------29, 33 Upper white layer, section including______52 R T Uranium.------57 Rattlesnake Hills, source of volcanic materiaL 47 in coaL------22 Red Desert______------8, 22 Tepee Mountain·------~------23 in Wilkins Peak Member______43 Terms used in lithologic descriptions______19 References ... ___ ------______81 Richards Peak______22 See also specific lithologic terms. v Thermonatrite ____ ----.------40 Rock Springs, type locality of Green River Valvata sp .••• ------30 Formation near ______c______28 Thisbemys sp_ ------46 Viverravuslutosus______26 Tipton Shale Member, Green .River Formation_ S l Rock Springs anticline. __ .------______14 Viuiparus SP------~--- 29, 32, 33, 34, 53 Tipton Tongue, Green River Formation .. ___ S1 Rock Springs uplift, age of deformation ___ 14,15,16 Trilophodon fricki______57 Volcanic ash, altered to analcime______44 Bridger Formation._.------49 geologic historY------"- 14 Trogosus latidens ______------___ ------26 physiographic setting ______c ______Laney Shale Member ______47,48 structural setting ______.. ______10 Trona ••. ------~--- 2, 39, 40,42 Rodent fossils, paramyid______26 Tschermiglte, in coaL •• ------24 w Rosenbusch, Harry, quoted______19 Tuff, alkalic .. ------50 Wamsutter arch .• ------10,23 andesite, destinctive marker bed in Bridger Wasatch Formation._------18, !0 s · Formation·------~------49 escarpments formed by •• ------6 Sabalites SP------45 andesitic. ____ ------49, 50 Washakie Rasin, physiographic setting______7 analyses ______------______------47 Sage Creek Butte, sections on ______51,52 structural setting_------10 Sage Creek white layer, fossils in______51 carbonate-rich, analyses______33 , type locality of Wasatch For- section of.______51 Tipton Tongue and Tipton Shale mation. __ ------____ ------_-- 20 Member, Green River Formation. 32,33 Saline minerals·------"------.35, 39,40 Wegscheiderite. ------39, 40 Salt crystals, in Wilkins Peak Member ____ 36, 38,40 defined_------______19 White Mountain. __ ------6, 15, 36,39 Sand, of volcanic origin______47 marker bed in Wilkins Peak Member_____ 42 Wilkins Peak Member, Green River Forma- Sand dunes______8 Niland Tongue, Wasatch Eormation______24 tion.·. ____ ------______35 rhyolitic ______------______50 Sciuravus nitidus ______------·------27,46 partial section of __ ... ______• __ •• 40 47 Searlcsite ______·_ _ 40 analyses ______------Wind River Range, ageofdeformation______15 Shale, defined ______------______19 Wilkins Peak Member, Green River For- Wind River thrust_ ___ ------11 papery, defined______19 mation, analyses oL______43 Wood, silicified_------______------__ 45 Turtle bones ______26, 45,51 ------~- 38, 39, 40,42 Wyoming Range, age of deformation __ • _____ ._ 15 Shortite. _------______Tychite. _____ ----- ______40 Shoshonius laurae. ______46 Wyomingite,lucite-rich lava______57 Significance of area studied ______Siltstone, defined______19 u z Skinner, Brian, analyst, quoted._.------33 Uinta fault. ______------_____ 11 ZirkleButte,ageof lavaon______58

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