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Home , Bighorn Mountains, Black Hills, Catenipora, Cleiothyridina, Composita, Gallatin Range

• Paleozoic Formations Ill the Basin

GEOLOGICAL SURVEY PROFESSIONAL PAPER 495-B

Prepared in cooperation with the Geological Surve_y of Wyoming and the Department of of the University of Wyoming as part of a program of the Department of the Interior for development of the basin

Paleozoic Formations In• the Wyoming

By W. R. KEEFER and]. A. VAN LIEU

GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

GEOLOGICAL SURVEY PROFESSIONAL PAPER 495-B

Prepared in cooperation with the Geological Survey of Wyoming and the Department of Geology of the University of Wyoming as part of a program of the Department of the Interior for development of the Missouri River basin

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1966 DEPARTMENT OF THE INTERIOR

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY

William T. Pecora, Director

For sale by the Superintendent of Documents, Government Printing Office Washington, D.C., 20402 CONTENTS

Page. Page Abstract ______B1 Pennsylvanian rocks-Continued Introduction ______2 Tensleep ______--- _------B40 General geographic and geologic setting ______2 rocks ______- ___ -_------43 General stratigraphic features ______6 l'romenclature ______43 rocks ______7 Park City Formation ______44 Generalfeatures------~------7 Permian and rocks, Goose Egg Formation------49 Flathead Sandstone ______14 Paleozoic structure ______------50 Gros Ventre Formation______15 Economic geology ______- _ ------50 Gallatin ______19 Oil and gas ______- - - - _ ------50 rocks, Bighorn Dolomite ______21 Phosphate rock ______- - - _ ------51 rocks, Darby Formation ______26 Other commodities ______--- _------51 Mississippian rocks, Madison Limestone ______29 References cited ______------51 Pennsylvanian rocks ______35 Index ______57 Amsden Formation ______35

ILLUSTRATIONS

[Plates are in pocket] PLATE 1. Map showing major outcrops and locations of measured sections of Paleozoic rocks in central Wyoming. 2-5. Sections of Paleozoic rocks along Wind River Basin: 2. West side. 3. l'rorth side. 4. South side. 5. East side. 6. Electric and sample logs of Pan American Petroleum Corp. -Arapahoe Tribal 9 at Winkleman . Page FIGURE 1. Index map of Wyoming______B3 2. Map showing major physiographic and structural features in central Wyoming______4 3. Photograph of exposures of upper Paleozoic formations in Dinwoody Canyon______5 4. Aerial view looking north into Wind River Canyon______6 5. Schematic diagram showing facies relations in Cambrian rocks from northern Utah to South Dakota______11 6. Thickness map of Cambrian rocks in central Wyoming______12 7. Photograph showing Cambrian rocks along north side of Warm Spring Creek______13 8. Photograph showing Flathead Sandstone unconformably overlying rocks in Wind River Canyon______15 9. Photograph of Cambrian, Ordovician, Mississippian, and Pennsylvanian strata in Wind RiverCanyon______17 10. Photograph of weathered surface of Bighorn Dolomite______22 11. Thickness map of Bighorn Dolomite in central Wyoming ______-- __ -- 24 12. Thickness map of Darby Formation in central Wyoming______28 13. Chart showing nomenclature of strata, east flank of Wind River Range__ 31 14. Thickness map of Madison Limestone in central Wyoming______32 15. Map showing general distribution of formations underlying Madison Limestone______34 16. Section of lower part of Amsden Formation at Cherry Creek ______---- __ -- 36 17. Thickness map of Tensleep and Amsden Formations in central Wyoming______38 18. Diagram showing approximate intervals of time represented by Mississippian and Pennsylvanian formations ______-_ __ _ 39 19. Photograph of of Tensleep Sandstone in Sinks Canyon______41 20. Map showing distribution of major facies in Permian rocks ______-____ 44 21. Photograph of exposures of Goose Egg Formation at Alcova Dam______45 22. Thickness map of Park City Formation and equivalents in central Wyoming______46 23. Photograph of prominent dip slopes of Park City Formation along east flank of Wind River Range______47

lll IV CONTENTS TABLES

Page TABLE 1. Locations of measured sections and the sources of data used in compilation of this report__ B8 2-8. from: 2. Cambrian formations______16 3. Bighorn I>olomite______25 4. I>arby Formation______29 5. Madison Limestone______33 6. Amsden Formation______39 7. Tensleep Sandstone______42 8. Park City and Goose Egg Formations______48 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

PALEOZOIC FORMATIONS IN THE WIND RIVER BASIN, WYOMING

By W. R. KEEFER and J. A. VAN LIEu

ABSTRACT be Late Ordovician in age, but the Lander Sandstone Member The Wind River Basin, occupying an area of 8,500 square may be Middle Ordovician. miles in central Wyoming, is an extensive structural depression rocks have not been recognized in central Wyoming. bounded on the south by the Mountains, on the west by If ever deposited in the region, they were removed by the , on the north by the Range and before succeeding strata were laid down. Owl Creek and , and on the east by the Casper The Darby Formation of Devonian and earliest Mississippian arch. These features were formed during Laramide deforma­ age has the most limited distribution of any of the Paleozoic tion in Late and early times. Paleozoic units in the area, being confined to the western third of the rocks underlie the basin and crop out along all the mountain basin. The sequence, which has a maximum thickness of 200 flanks except the east. feet, consists chiefly of dolomite in the lower part and of inter­ During Paleozoic time central Wyoming was part of the bedded siltstone, , sandstone, and carbonate rocks in the interior stable shelf region that lay along the east side of the upper. Locally at the top is a dark shale which is part of a Cordilleran geosyncline. Rocks representing all the Paleozoic widespread unit of latest Devonian and earliest Mississippian systems, except possibly the Silurian, were deposited across age that rests uncomformably on older Devonian rocks. the present site of the Wind River Basin during repeated trans­ Mississippian strata are 700 feet thick in the western part of gressions and regressions of epicontinental seas. Because the Wind River Basin, but they thin to 175 feet in the south­ greatest sedimentary accumulation was toward the west, the eastern part. These rocks, predominantly resistant massive to Paleozoic section is thicker and more complete in the western thin-bedded crystalline limestone, are all assigned to the Madi­ part of the basin than in the eastern part. Marked changes son Limestone. Brecciated and cavernous zones and intra­ in the thickness and lithology of nearly all form-ations take formational are present, particularly in the place from west to east, and some units disappear east­ upper part. The formation rests on the Dal"by Formation with ward owing to truncation or nondeposition. Although most apparent conformity toward the west, but eastward it truncates of the strata were deposited under normal marine conditions, successively older formations and rests on the Flathead Sand­ the pattern of .sedimentation was often influenced locally 1by stone in the southeast corner of the basin. The bulk of the slight but significant fluctuations in the base level of deposi­ Madison is Early Mississippian, ·but in the northern and central tion caused by changes in sea level or by tectonic movements. Wind River Range and adjacent Washakie Range it includes Paleozoic formations in the 'Vind River Basin include the about 100 feet of beds that are Late Mississippian. Flathead 'Sandstone, the Gros Ventre Formation,· and the Gal­ The Amsden Formation is divided into a lower sandstone unit, latin Limestone of Cambrian age; the Bighorn Dolomite of called the Darwin Sandstone Member, and an upper unnamed Ordovician age; the Darby Formation of Devonian and earliest unit of interbedded dolomite, shale, sandstone, and limestone. Mississippian age ; the Madison Limestone of Missis·sippian Thicknesses range from 355 feet in the northwestern part of the age; the Amsden Formation and the Tensleep Sandstone of Wind River Basin to zero at the southeast corner. The forma­ Pennsylvanian age; the Park Oity Formation and its equiva­ tion is largely Early to Middle Pennsylvanian, but the Darwin lents of Permian age; and the Goose Egg Formation of Permian Sandstone Member and immediately overlying beds are Late and Triassic age. Subdivision into formations and members Mississippian. The Tensleep Sandstone, a uniformly. massive of formations is based primarily on the classification and to crossbedded cliff-forming sandstone, containing a few thin nomenclature that have been established for the sequence in beds of chert and limestone, is one of the most conspicuous the northern part of the Wind River Range. Paleozoic units. 'Thickness ranges from 200 feet to more than The Cambrian rocks are a well-defined transgressive se­ 600 feet. Most of the formation is Middle Pennsylvanian. At quen~e containing .a basal quartzitic sandstone unit (Flathead), the southeast corner of the basin all Pennsylvanian rocks (mostly a middle predonunantly shale unit ( Gros Ventre), and an Upper Pennsylvanian), as well as some Lower Permian rocks, upper limestone unit (Gallatin). Thicknesses decrease from are included in the Casper Formation. 1,200 feet in the northwestern part of the Wind River Basin Permian rocks are interbedded chert, limestone, dolomite, silt­ to 50 feet at the southeastern corner. The sedimentary pat­ stone, sandstone, and phosphorite in the western two-thirds of tern is one of continuous transgression, beginning in Middle the Wind River Basin, and red beds and , with thin beds Cambrian time and reaching a maximum in Late Cambrian of limestone, in the eastern third. The chert and carbonate time, but the strata ·show that the transgression was inter­ rupted many times 'bY minor retreats of the sea. facies, 150-350 feet thick, is referred to the Park City Formation The Bighorn Dolomite is divided into three members : the and equivalents, and the red-bed facies, 355-380 feet thick, to the Lander Sandstone Member which occurs locally at the base an Goose Egg Formation. The Park City is largely early Late unnamed massive cliff-forming dolomite in the middle and' the Permian, although the basal few feet, in some places separated Leigh Dolomite Member at the top. The formation '300 feet from the overlying beds by an , is Early Permian. thick. in the northwestern part of the basin, thins t~ a wedge The lower 270-300 feet of the Goose Egg is equivalent to the edge m the central part. Most of the Bighorn is considered to Park City, but the remainder intertongues with the Dinwoody B1 B2 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMIN-G

Formation of Early Triassic age. Uppermost Permian rocks ton's earlier classifications and also named and defined hav~ not been recognized in the basin area. several new formations and members of formations, T'he Wind River Basin was remarkably stable throughout the particularly in the lower part of the sequence. The Paleozoic Era. Although considerable time elapsed between deposition of successive formations, there are no recognizable work by Darton and Blackwelder, though since modi­ angular discordances within the entire sequence of Paleozoic fied, has formed the basis for all subsequent studies of rocks. Tectonic movements were limited to broad warping along the Paleozoic rocks in central Wyoming. trends which show little direct relation to structural trends Thomas (1948, 1952, 1957) presented excellent sum­ developed during Laramide deformation. One exception is along maries of the and depositional history of the southeast margin of the basin where an area coinciding roughly with the present-day and parts of the Paleozoic rocks in central Wyoming and adjacent the Granite Mountains was positive intermittently during much regions. of Paleozoic time. Paleozoic rocks, principally the Park City Formation and GENERAL GEOGRAPHIC AND GEOLOGIC SETTING Tensleep Sandstone, are among the most important oil and gas The Wind River Basin includes about 8,500 square reservoirs in the Wind River Basin. Much of the production has been from anticlinal traps along the basin margins, but miles in central Wyoming, occupying most of Fremont conditions favoring stratigraphic entrapment also exist. The County and the western part of Natrona County (fig. Park City contains extensive, though undeveloped, deposits of 1). It is an extensive structural depression bounded low-grade phosphate, especially in the western and northwestern on the south by the Granite Mountains, on the west by parts of the basin. Raw materials for construction use are widespread. Pisolitic iron-bearing red shale occurs in the the Wind River Range, on the north by the Washakie Amsden Formation, and small deposits of radioactive materials Range and Owl Creek and Bighorn Mountains, and on have been reported from Cambrian, Pennsylvanian, and Permian the east by the Casper arch. (See fig. 2.) As thus rocks at a few localities. defined, the outline of the is roughly that of a parallelogram, with a maximum length of INTRODUCTION about 180 miles from northwest to southeast and a max­ Rocks of Paleozoic age underlie most of central imum width of about 75 miles north to south. The Wyoming. Complete sequences are especially well structurally deepest parts are close to the Owl Creek exposed along the margins of the Wind River Basin Mountains and the Oasper arch, which lie along the and in the adjacent mountain ranges. Owing to both r.Lorth and east margins, respectively. The basin and academic and economic interest, these rocks have been adjacent mountains were formed during Laramide de­ studied extensively since the earliest territorial surveya formation in Late Cretaceous and early Tertiary times. in the 1870's. As a result, many basic data on the dis­ Most of the Wind River Basin is also a conspicuous tribution, thickness, lithology, paleontology, and deposi­ topographic depression which has the same western tional history of the various Paleozoic formations have and northern limits as the structural basin, but it is been accumulated. These data, many of which were restricted on the south by the Beaver Divide, a 1,000- obtained by the lT.S. Geological Survey during a pro­ foot erosional escarpment of Tertiary rocks, and on gram of detailed geologic mapping and stratigraphic the east by a series of broad low , sometimes studies in the Wind River Basin, begun in the early called the Hiland Divide, extending north from the 1940's, are summarized in this report. to the south end of the Bighorn Many individuals have thus contributed valuable in­ Mountains. The Hiland Divide separates the Wind formation and ideas to this study; specific contributions River drainage system from that of the Powder and will be cited below. Two of the early investigators, North Platte Rivers to the east; the Beaver Divide however, merit special recognition for their fundamen­ separates the Wind River drainage system from that tal work on the classification and nomenclature of Pale­ of the Sweetwater River to the south. ozoic strata in the Wind River Basin and ajacent areas. The floor of the Wind River Basin, underlain by Darton ( 1906 a, b) mapped the distribution of the flat-lying lower rocks, is a region of low re­ Paleozoic rocks in the Owl Creek and Bighorn Moun­ lief with only a few scattered buttes and mesas rising tains along the north and northeast margins of the to as much as 500 feet above the general landscape. In basin and formally named and defined many of the the nortlnvestern part of the basin, the altitude of the individual formations. Blackwelder, during geological floor is 7,000 feet above sea level, whereas farther to the investigations in central and northwestern Wyoming east and southeast in the central part it is 5,000-5,500 from 1910 to 1913, traced many of the Paleozoic units feet. 'Vith few exceptions, Paleozoic rocks do not crop through the Teton and Gros Ventre Ranges into the out within the basin proper, but they have been pene­ northern Wind River Range along the west edge of the trated in many places near the margins by wells drilled 1Vind River Basin. He (1918) modified some of Dar- for oil and gas. PALEOZOIC FORMATIONS B3

44

I Kemmerer 1 Rawlins II I \ 0 0 0 AL ANYI I I A T E R I I 1 -l 0 I I r--_j c !\ \\ ~ -L--~

---,I li I LARAMIE·. I ~-L'al ramie ___IL_ ®

0 50 100 MILES

FIGURE 1.-.Jndex map of Wyoming showing location of Wind River Basin (stippled).

The Granite Mountains are formed from a large an­ The Wind River Range, culminating in 13,785-foot ticlinal uplift that extends eastward from the south end , is the largest mountain uplift in Wyo­ of the Wind River Range for about 75 miles. The ming. The range trends northwest through the west­ steep flank is to the south and southwest; the gentle central part of the State for about 100 miles and has a north flank coincides with the south margin of the maximum width of a;bout 50 miles. Its west flank, Wind River. The range was folded to mountainous bordering on the Green River Basin, is steep to over­ proportions and deeply eroded during Laramide defor­ turned and broken by eastward-dipping reverse faults mation, but later was almost completely buried by mid­ along which 35,000 feet or more of structural displace­ dle and upper Tertiary sediments. At present, the ment has taken place (Berg, 1961). In contra;st, the range is visible only as a series of prominent granite east flank, with which we are concerned in the present knobs projecting as much as 1,000 feet above a nearly study, is characterized by moderately gentle dip slopes level plain of flat-lying Miocene and Pliocene rocks, on Paleozoic rocks which descend uniformly eastward 6,500-7,000 feet above sea level, upon which the Sweet­ into the Wind River Basin at dips of 10°-20°. The water River drainage is established. Paleozoic rocks structural continuity of the east flank is interrupted in crop out in some places along the flanks of subsidiary a few places by high-angle normal and reverse faults, folds, such as the Rattlesnake Hills and Conant Creek with displacements commonly less than 1,000 feet, and anticline, that project northwestward into the Wind by sharp monoclinal folds. Precambrian crystalline River Basin from the main mass of the range (pl. 1). rocks, chiefly massive granite and granite , form B4 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

the core of the range, and Paleozoic rocks are well ex­ outcrops of Paleozoic rocks occur around the margins posed in a nearly linear outcrop belt along the entire of many individual anticlines. east flank (pl. 1). Complete sections of the Paleozoic The rise abruptly along the rocks may be obse.rved in many steep-walled canyons north edge of the Wind River Basin. This large anti­ which have been cut transverse to the strike of the stJ.'Iata clinal uplift, separating the Wind River Basin from by eastward-flowing tributaries of the Wind River. the to the north, extends nearly east­ (For example, see fig. 3.) west across central Wyoming from the southeast edge The Washakie Range, at the northwest corner of the of the to the southwest end of the Wind River Basin, is a series of faulted folds, in eche­ Bighorn Mountains, a distance of about 80 miles.1 lon, which extends northwest from Black Mountain Rocks on the south flank of the range are steep to over­ (81;2 T. 7 N., R. 4 W., pl. 1) for about 70 miles (Love, turned, and have overriden the north margin of the 1939, p. 5). This extensive uplift was completely Wind River Basin along an extensive system of reverse buried by Eocene and Oligocene pyroclastic rocks of the faults (Keefer, 1965, pl. 4). Strata on the north side of Absaroka Range; it has now been partly exhumed. the range dip gently northward into the Bighorn Basin. The south flank of the Washakie Range, generally Although the range as a whole is elongated nearly east­ steep and broken by northward-dipping reverse faults, west, individual segments in the west half trend is visible in several areas, and the Precambrian rocks obliquely northwestward. Altitudes range from 4,800 exposed in some of the larger folds may represent part of its central core (Keefer, 1957, p. 205); the north 1 That part of the range lying east of was called the by many previous workers, but in recent years it flank is still buried. Altitudes of the exposed parts are has been a more common practice to refer to the entire range as the as much as 10,000 feet above sea level. Discontinuous Owl Creek Mountains.

0 10 20 30 40 50 MILES

FIGURE 2.-l\Iajor physiographic and structural features in central Wyoming. Dashed line indicates approximate outline of Wind River structural basin. 0 01"" I 0<.... 0 0 I Ol r""

t;;j~ 0

~...... 0 6 ~ ~

0~ ~

FIGURE 3.-Exposures on north wall of Din woody Canyon, northern Wind River Ra nge. lied, Chugwater and Dlnwoody Formations; Pp, Park City Formation and equivalents; PI, Tensleep Sa ndstone; IPa, Amsden Forma tion; Mm. Madison Limestone.

to en B6 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING to 6,000 feet above sea level along the south edge to 7,000 slope gently eastward into the . to 9,500 feet along the crest. Complete sequences of Altitudes range generally from 5,500 to 6,000 feet above Paleozoic rocks crop out in many places; the best and sea level. No Paleozoic rocks crop out along the Casper most spectacular exposures are in Wind River Canyon arch, but all or part of the sequence has been penetrated which cuts across the central part of the range (fig. 4). hy drill holes at many localities. Outcrops are present The southwest-plunging end o"f the Bighorn Moun­ to the south, however, along the north edge of Casper tains forms the northeast margin of the Wind River Mountain at the northwest end of the Laramie Moun­ Basin. This part of the range has an extensive core tains (fig. 2). A complete sequence of Paleozoic strata of Precambrian crystalline rocks flanked on the south is also exposed near Alcova Reservoir, at the extreme by Paleozoic strata that dip south about 15 ° (Tourtelot, southeast end of the Wind River Basin. 1953). These Paleozoic rocks have likewise been thrust GENERAL STRATIGRAPHIC FEATURES south over the deep part of the Wind River Basin. The Bighorn Mountains are separated structurally from the During Paleozoic time central Wyoming was part of Owl Creek Mountains to the west by a broad shallow the interior stable shelf region that lay along the east synclinal area underlain for the most part by flat-lying side of the main Cordilleran geosyncline. Rocks rep­ Eocene rocks. resenting parts of all the Paleozoic systems, except The Casper arch is a major, but not deeply eroded, possibly the Silurian, were deposited across the present structural upward whose steep to overturned and site of the ·wind River Basin during numerous trans­ faulted west flank coincides with the east margin of gressions and regressions of epicontinental seas. Be­ the \Vind River structural basin. The arch, which is cause the greatest sedimentary accumulation was to­ underlain chiefly by Upper Cretaceous and ward the west, in the geosynclinal area of southeastern rocks, is characterized by low hills and ridges which Idaho, the Paleozoic sequence is thicker and more com-

FIGURE 4.-Aerial view looking north into Wind River Canyon, central Owl Creek Mountains. and north end of are at bottom of photograph. PPu , Park City, Tensleep, and Amsden Formations; MOu, Madison Limestone und Bighorn Dolomite; £u, Cambrian rocks, undivided ; pCr, Precambrian igneous and metamorphic rocks; f-1, . Boysen normal fault. Faulted com­ plex of Paleozoic und rock~. overlapped by 'l'ertiary rocks, occupies lower hulf of view. Photograph courtesy of P . T. Jenkins and L. P. House. PALEOZOIC FORMATIONS B7 plete in the western part of the Wind River Basin than spread as far ·as the region in northeastern in the eastern part. Marked changes in the thickness Wyoming and western (Thomas, 1957, and lithology of nearly all formations take place from p.4). west to east across the basin, and some units elisa ppear The Cambrian sequence varies greatly in thickness easbvard owing to truncation or nondeposition. and lithology from one place to another. The tripartite The general lithologies, thicknesses, and stratigraphic division of sandstone, shale, and limestone is especially relations of Paleozoic formations around the margins distinct in the mountains along the west side of the Wind of the Wind River Basin and along the flanks of the River Basin; but toward the east the rocks become pro­ adjacent mountain ranges are shown graphically on four gressively more clastic, and many units lose their dis­ correlation charts, plates 2-5. Individual measured tinctiveness owing to changes in facies. Formation surface sections or drilled subsurface sections were boundaries cross time lines and become progressively selected at 26 key localities, the distance between adja­ younger from west to east across the basin area. Thick­ cent sections ranging from 6 to 28 miles (pl. 1). Local­ ness of Cambrian rocks decreases from a maximum of ities and sources of data are listed in table 1; significant about 1,200 feet along the west edge of the basin to only collections are given in tables 2-8. 50 feet in the eastern most part (fig. 6) . The decrease is The stratigraphy is discussed according to the classifi­ due partly to nondeposition and partly to the pro­ cation and nomenclature of strata in the northwestern nounced erosional unconformity at the top of the part of the basin, where the Paleozoic record is most sequence. nearly complete. The rocks there are classified as In the Owl Creek and Bighorn Mountains, Darton follows: (1906a, p. 14-15; 1906b, p. 23-'26) referred all Cambrian Permian: strata to the , a name he had given Park City I!'ormation and equivalents earlier (Darton, 1901, p. 505) to Cambrian rocks in the Pennsylvanian: Black Hills region. In the northwestern Wind River Tensleep Sandstone Range, Eliot Blackwelder (U.S. Geol. Survey, 1918, Amsden Formation Mississippian : unpub. field notes), distinguished three formations cor­ Madison Limestone responding to the three major lithologic subdivisions Devonian and lowermost Mississippian : and employed terms then in current use farther west­ Darby Formation Flathead Sandstone, Gros Ventre Formation, and Galla­ Ordovician : tin Limestone (fig. 7). Blackwelder's classification has Bighorn Dolomite Cambrian: been used subsequently throughout much of the 'Vind Galla tin Limestone River Basin, and is used in this report. Gros Ventre Formation Because of the variations in thickness and lithology, Flathead Sandstone however, alternate systems of classification and nomen­ clature have been proposed for the Cambrian sequence in CAMBRIAN ROCKS some areas of the basin. In the central and eastern GENERAL FEATURES Owl Creek Mountains, for example, Miller ( 1936, p. A well-defined transgressive marine sequence, includ­ 124) applied the name Depass Formation to the lower ing a basal sandstone unit, a middle shale unit, and an part of the Cambrian sequence, and Deiss ( 1938, p. upper limestone unit, was deposited across most of cen­ 1104) applied the na1ne Boysen Formation to the upper tral Wyoming during an eastward advance of the epi­ part. In the southwestern part of the Wind River continental sea in Middle and Late Cambrian time (fig. Basin, Shaw (1957) referred the basal Cambrian unit to 5). The major trend of transgression was interrupted the Flathead Sandstone, but elevated both the Gros repeatedly by minor retreats of the sea. At times cer­ Ventre and Gallatin to group status and separated each tain -areas emerged and were eroded, while adjacent group into several individual formations. Shaw ( 1954) areas were still submerged and receiving sediments; also introduced the name Buck Spring Formation for there is no evidence, however, that the sea withdrew completely from the region between the time that the all Cambrian rocks overlying the Flathead Sandstone initial sediments were laid down in Middle Cambrian in the south-central part of the basin. Additional dis­ time and the close of the period. With each new surge etlssions of the problems in classification and nomen­ the sea encroached farther eastward; by Late Cambrian clature are included below in the descriptions of forma­ time all central Wyoming was inundated, and the sea tions. ttl TABLE 1.-Locations of measured sections and the sources of data used 1·n compilat1:on of this report 00 [An asterisk (*) indicates source is unpublished field notes, U.S Geol. Survey; blank space indicates formation absent]

Section Flathead Gros Ventre Gallatin Bighorn Darby Madison Amsden Tensleep Park City Formation Sandstone I Formation Limestone I Dolomite I Formation Limestone Formation Sandstone and equivalents Sees. 30 and 31, T. 42 N., R. 108 W. Sec. 1, T. 41 N., R. 108 W. Sec. 31, T. 42 N., Sees. 14 and 15, Sees. 9 and 10, Sees. 11 and 14, Warm Spring R. 107 w. T. 41 N., R. 107 W. T. 41 N., R. 107 W. T. 41 N., R. 107 W. Creek Miller (1936, p. 131, 132) Keefer (1957, p. 166-168) Weart (1948) Keefer (1957, p. 170-172) Weart (1948)

Northeastern part, T. 4 N., R. 6 W. Sec. 11, Sec. 12, T. 4 N., R. 6 W. Northeastern part, Sec. 1, Sec. 6, T. 4 N., R. 5 W. T. 4 N., R. 6 W. T. 4 N., R. 6 W. T. 4 N., R. 6 W. Dinwoody 0 Canyon t?:l J. F. Murphy* IJ. F. Murphy' J. F. Murphy* J. F. Mrnphy" I J. F. Murphy* J. F. Murphy* J. F. Murphy* Eliot Blackwelder• Sheldon 0 Eliot Blackwelder* Eliot Blackwelder• Eliot Blackwelder• (1957' pl. 13) ~ 0 Sec. 9, T. 2 N., R. 4 W. Sec. 3, Sec. 2, T. 2 N, R. 4 W. Sec. 35, ~ Bull Lake T.2N.,R.4W. T.3N.,R.4W. Canyon 0 ~ Murphy and others (1956); Murphy and Richmond (1965)

Sec. 1, T. 2 S., R. 3 W. Sec. 5, T. 2 S., R. 2 W. Sees. 4 and 5, T. 2 S., R. 2 W; sees 32 and 33, T. 1 S., R. 2 W. Sec. 22, ~ T. 1 S., R. 2 W I ~ Trout Creek (Not measured) z Planetable traverse by W. R. Keefer Love •nd otho" J. F. Murphy* Love and others (1947, p. 36, 37) t:::t and R. L. Koogle (1947, p. 37) I ~ 1-1< Sec. 4, T. 33 N., R. 101 W. Sec. 4, Sec. 5, Along North Fork Sec. 18, t?:l T. 33 N., R. 101 W. T. 33 N., R. 101 W. Popo Agie River T. 33 N., R. 100 W. ~ Squaw Creek (Not measured) txl Burton (1952) Strickland (1957, Biggs (1951) Burton (1952) King (1947, p. 3o-40) p. 21); Burton (1952)

Sec. 25, Sec. 18, T. 32 N., R. 100 W. Sec. 18, Sec. 20, Sec. 25, ~~ T. 32N., R.101 W. T. 32 N., R. 100 W. T. 32 N., R. 100 W. T. 32 N., R. 100 W. Sinks Canyon (Not measured) Q

Hembree (1949) Strickland (1957, fig. 1) Bigg~ (1951) Hembree (1949) Condit (1924, p. 24) ~ ~ Sec. 24, T. 30 N., R. 100 W. Sec. 6, Sees. 8 and 18, Sec. 9, Sees. 9 and 10, Sees. 11 and 12, ~ IT. 30N.,""'· R.100W.... T. 29 N., R. 98 W. T. 30 N., R. 99 W. 'l.'. 30 N., R. 99 W. T.30N., R.99W. T. 30 N., R. 99 W. Beaver Creek -- Gooldy (1947) Gooldy (1947) Lower part, Shaw Gooldy (1947) Condit (1924, 0~ (1955, p. 61) p. 28, 29) ~ Sees. 27 and 28, T. 29 N., R. 97 W. Sec. 34, T. 29 N., R. 97 W. Sec. 27, T. 29 N., R. 97 W. Sec. 26, 0 Sweetwater T. 29 N., R. 97 W. Canyon I DeLand (1954) Bell (1955) Bell (1955)

Sec. 1, T. 42 N., Northeastern part, Sec. 29, T. 43 N., Sec. 36, T. 43 N., R. 106 W. Sec. 7, Sec. 19, Sec. 18, Sec. 13, R.106W. T. 43 N., R.106 W. R.106W. T. 42 N., R. 105 W. T. 43 N., R. 106 W. T. 42 N., R. 105 W. T. 43 N., R. 107 W. Windy Gap Love (1939, p. 15) W. R. Keefer* Love (1939, p. 16); Love {1939, p. 18-25) Biggs (1951) Love (1939, p. 29) Keefer (1957, p. 174) W. R. Keefer*

Sees. 30 and 31, T. 8 N., R. 2 W.; Sec. 13, T. 7 N., R. 3 W. sees. 4 and 5, T. 42 N., R. 101 W. Circle (Not measured) I Milton (1942)

Sec. 3, I Sec. 9, Sec. 3, Sees. 4 and 20, Sec. 2, Sec. 27, I Sees. 10 and 35, I Sees. 14 and 15, I Sec. 31, T. 6 N., R. 2 E. T. 7 N., R. 2 E. T. 7 N., R. 2 E. T. 7 N., R. 2 E. T. 7 N., R. 1 W. T. 7 N., R. 1 E. T. 7 N., R. 1 E. T. 7 N., R. 1 E. T. 7 N., R. 2 E. Sheep Ridge Phillips (1958) Flanagan (1955) Phillips (1958) Thomas (1948, Phillips (1958) p. 85)

------~~;----~ ~~- -Sees.; and 24, Sec. 24, ------Sees. 24 and 25, I Sec. 25, T. 6 N., R. 3E. I Sec. 36, T. 7 N., R. 3 E. T. 7 N., R. 3 E. T. 6 N., R. 3 E. T. 6 N., R. 3 E. T. 6 N., R. 3 E. T. 6 N., R. 3 E. Blackrock Ridge l------'------'------l Powell (1957) Powell (1957)

------Sec. 4; T. 5 N., R. 6 E. I Sec. 33, Sec. 32, I Sec. 30, I Sec. 19, Sec. 28, Wind River T. 7 N., R. 6 E. T. 7 N., R. 6 E. T. 7 N. R. 6 E. T. 7 N., R. 6 E. T. 42 N., R. 94 W. Canyon ----- Tourtelot and Thompson (1948) Tourtelot and Thompson (1948) Tourtelot (1953)

Sec. 19, T. 40 N., R. 91 W. Sec. 35, Sec. 35, Producers Oil No. 1 Barcklay, Sees. 7 and 8, Eastern T. 41 N., R. 92 W. T. 41 N., R. 92 W. sec. 11, T. 40 N., R. 91 W. T. 40 N., R. 91 W. Owl Creek Mountains . H. A. Tourtelot* Lyon (1956) Lyon (1956) Petroleum Information, Inc., Denver, Tourtelot (1953) Colo.

Sec. 6, Sec. 20, I Sec. 22, Sees. 16 and 21, T. 40 N., R. 90 W. T. 40 N., R. 89 W. T. 40 N., R. 89 W. T. 41 N., R. 89 W. 0~ Badwater (Not measured) ~ ~ H. A. Tourtelot* Tourtelot (1953) 0 ------Sec. 26, T. 39 N., R. 88 W. Sec. 3, T. 40 N., R.l Sec. 21, I Sees. 32 and 33. Sec. 4, 6 86 W.; sec. 34, T. 41 T. 40 N., R. 86 W. T. 40 N., R. 86 W. T. 38 N., R. 87 W. l;lj Deadman Butte N., R. 86 W. ~ ~ H. A. Tourtelot* Woodward (1957, p. 259, 260) Tourtelot (1953) ~ ------1------0 Sec. 36, T. 33 N., R. ~ Sec. 13, T. 32 N., R. 94 W. Sec. 23, T. 32 N., R. 94 W. 94 W.; sec. 31, T. 33 N., R.93W.;sec. 2, Conant Creek T. 32 N., R. 94 W.

VanHouten and Weitz (1956); Shaw (1957, p. 12) V. L. White*

Sinclair-Wyoming Oil Co. No.2, sec. 1, T. 33 N., R. 92 W. Muskrat (Not penetrated) (Not penetrated) E-log study by J. A. Van Lieu

I Sec. 26, T. 33 N., R. 89 W. Sees. 23 and 26, T. 33 N., R. 89 W. East Canyon Creek (Not measured) (Not measured) VanHouten and Weitz (1956); VanHouten and Weitz (1956) J. L. Weitz*

Sec. 24, T. 33 N., R. 88 W. Sec. 24, I Sec. 32, I Sec. 24, Sec. 4, T. 33 N., R. 88 w: T. 33 N., R. 87 W. T. 33 N., R. 88 W. T. 32 N., R. 87 W. Rattlesnake Hills Shaw (1957, p. 12); Bogrett (1951) Bogrett (1951) Thomas (1934, p. 1673, 1674)

tt1 <:0 to._. TABLE 1.-Locations of measured sections and the sources of data used in compilation of this 1·eport-Continued 0

Section Flathead Gros Ventre Gallatin Bighorn Darby Madison Amsden Tensleep p.,k City Fo=•tion Sandstone Formation Limestone Dolomite Formation Limestone Formation Sandstone I and equivalents I I I I I I Atlantic Refining Co. No.1, sec. 9, T. 31 N., R. 84 W. Fish Creek (Not penetrated) E-log study by J.D. Love ------Northwestern Sec. 30, part, T. 29 N., Northwestern part, T. 29 N., R. 83 W. T. 30 N., R. 82 W. R.83W. Alcova 0 Lee (1927, p. 52) Lee (1927, p. 52) Thomas (1934, t_:rj p. 1677) 0 ~ 0 Sec. 5, Sees. 5 and 6, T. 30 N., R. 79 W. Sec. 6, T. 30 N., R. 79 W. T. 30 N., R. 79 W. ~ Bates Creek 0 "':! Harrison (1938) Harrison (1938) Jenkins (1950) 8 Trigood Oil Co. Cheyenne Lease No. 10, sec. 3, T. 37 N., R. 85 W. ~ Notches (Not penetrated) E-log study by J. A. Van Lieu ~ zt::; Pure Oil Co. No.1, sec. 36, T. 37 N., R. 82 W. Pure oil Co. No. 1, sec. 36, T. 37 N., R. 82 W. North Casper l:C 1-4 Creek Casper m I Mountain 1-4 Sims (1948) Sims (1948) Lee (1927, p. 49) Burk and Thomas ~z (1956, p. 5-7) I I ·Q zt_:rj 8 l:C ~

0~

0~ (1) (2) (3) BEAR RIVER WIND RIVER WIND RIVER (4) RANGE, UTAH MOUNTAINS CANYON BLACK HILLS Ordovician rocks Ordovician rocks Deadwood St. Charles Formation Limestone

Nounan Limestone

Bloomington PREDOMINANT FACIES Formation . ~ [§I]. t

0~ Langston z Limestone CJ UJ. Limestone and dolomite

FEET Brigham 500~ Quartzite 50 MILES 0 I APPROXIMATE SCALES

FIGURE 5.-Facies relations in Cambrian rocks from northern Utah to western South Dakota. Sources of data: (1) Stokes (1953), Deiss (1938), S.S. Oriel (oral commun., 1964) ; (2) Keefer (19<57); (3) Tourtelot and Thompson (1948); (4) Darton and Paige (1925).

to t-l t-l .....tt1 t>..J

106° rJ.)oo 109° 108° 10r 44 o ! ~~----' _, p A R K I - I T I I 46 I " ,.!'/"\._,-\, I I w 46 A s H A K I E I I -... ) ..... ·- 1.. N I~ 45 ; 3 , ~ 1 · "

\ 1 T .. 36 , \ \ Soh ~ ~ ~~ v · } 1 "~'\ 1 (h t--r-- .Cl 3_5 r-r--b-,•N .A!Eivert--lf r h.-JL1l? -"'- i I 30 ~ I- " ~ I EXPLANATION r- I ~ -t 0 X I:>< ~ F 1 R 1 E 1 M 1 o 1 ~<1'?:.~~ ~~cfo 1 J_ i 1 1 1 1 I I I I N I IZ' Surface section +-~--+------0 1 1 1 ~ t-- -L> (L_ --?!-- I I I I I R I I B I I 0 I I ~ 0 'U !26 I I ! I C I A ,~ • A ~ I Sl w IE T Tl25 E R I Subsurface section El IW I R1~01 !100 99 98 97 I 96 95 9A 93 92 I 91 I 90 s9 1 88 1 87 1 86 1 8ls I 84 I 83 I s2 I 81 8.0 79 78 0 10 20 30 MILES __j I 1 Dl l l l II I Iu l I I rt·_L__j 42 °

FIGURE 6.--Thickness map of Cambrian rocks in central Wyoming. Interval is 100 feet; isopachs are restored across mountain arches where rocks have been eroded; isopachs are da.shed where control is inad.equate. 0"' '!' 01... 0 0 I ico

~t.".l 0 ~ H 0 6 J:lj

0~ rp.z

FIGURE 7.- Cambrian rocks along Warm Spring Creek, northern Wind River Range. Ob, Bighorn Dolomite. Cg, Gallatin Limestone; Cgo, Open Door Limestone Member, Cgd, type section of the Du Noir Limestone Member. Gros Ventre Formation; Cgvp, Park Shale Member, Cgvd, Death Canyon Limestone Member, Cgvw, Wolsey Shale Member. Cf, Flathead Sandstone. Note grass covered siDpes of Gros Ventre Formation in right background and treeless dip slope of Flathead Sandstone In right middle ground.

l:l:l ~ C;.j B14 GE•OLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

FLATHEAD SANDSTONE to more than 500 feet in the northern part of the Rattle­ Definition snake Hills (pl. 4) . In the latter area the basal con­ The name Flathead Formation was originally pro­ glomerate is as mu ch as 120 feet thick. The eastward posed by Peale ( 1893, p. 20-22) for exposures in Flat­ thickening of the formation is at the expense of the over­ head Pass, southwe;;tern , and included a basal lying Gros Ventre Formation, with which it inter­ quartzite, the Flathead Quartzite, and an upper green fingers. shale sequence designated the "Flathead ." In At the southeast end of the 'Wind River Basin, and in the of northwestern 'Vyoming, adjacent areas along the west side of the Laramie Moun­ Blackwelder ( 1918, p. 417) included the green shale tains, 45-90 feet of coarse-grained quartzitic sandstone in the lower part of his Gros Ventre Formation and re­ (pl. 5) was assigned to the Flathead Sandstone by Shaw stricted the Flathead to the basal quartzitic sandstone. ( 1954). These strata are overlain directly by clastic The formation is now generally accepted in this re­ rocks forming the base of the Mississippian Madison stricted sense, and has been recognized over wide areas Limestone, and Maughan ( 1963, p. C26) suggested the in western and central Wyoming. possibility that the sandstone now placed in the Flat­ Lithology and Thickness head may represent a locally thick sandy facies of the Along the east flank of the Wind River Range the basal part of the Madison Limestone. Flathead Sandstone has an average thickness of about Contact With Precambrian Rocks 200 feet, except at the southeast end where it thickens The Flathead Sandstone unconformably overlies to nearly 350 feet (pl. 2, Sweetwater Canyon section). Precambrian igneous and metamorphic rocks. Tht' The formation is predominantly pink, reddish-brown, contact is generally concealed by forest cover or talus. tan, and gray fine- to coarse-grained sandstone. It is In a few places, however, such as in Wind River Can­ quartzitic for the most part, and contains glauconite yon, the contact is continuously exposed for several hun­ and hematite in many places. Many of the beds are dred yards (fig. 8). The eroded surface of the Precam­ thinly laminated with pink and reddish-brown layers br·ian rocks apparently had some topographic relief; alternating with tan and gray layers. Some crossbed­ this relief probably accounts for some of the local varia­ ding is present. The basal beds of the formation are tions in thickness of the Flathead. commonly conglomeratic and arkosic, containing angu­ "\Vhere the Flathead Sandstone directly overlies mas­ lar fragments of quartz, feldspar, and mica. Granite sive granite and granite gneiss, there is commonly a pebbles as much as 1 inch across are locally disseminated transitional zone of weathered arkose at its base. The in the lowermost strata. The upper beds of the Flat­ weathered zone represents a regolith that was winnowed head are generally softer and are shaly, and have nu­ during the encroachment of the Cambrian sea. merous partings of green and gray-green ·micaceous Contact With the Gros Ventre Formation shale. The Flathead sandstone is overlain conformably Topographically, the Flathead Sandstone usually by the Gros Ventre Formation; laterally the two forms a series of resistant blocky ledges which rise formations interfinger. The formation boundary is abruptly in steep slopes above the basal contact with the usually placed at the top of the uppermost persistent Precambrian crystalline rocks. Outcrops support heavy quartzitic sandstone in the sequence, but in most places gro,vths of trees in most places, but locally prominent the change from quartzitic and, in part, shaly sandstone treeless dip slopes on top of the uppermost resistant below to soft shale and shnJy sandstone above is grada­ sandstone bed (fig. 7) occur. The sandstone commonly tional. The contact is also marked locally by a topo­ breaks into large slabs which slide short distances down graphic change from cliffs below to concave slopes the slopes; small rock slides are numerous along steep above. On electric logs there is an easily recognized dip slopes. shift from the low resistivity and self-potential curves Strata included in the Flathead Sandstone along the of the Gros Ventre to the more expanded curves of the north and south margins of the Wind River Basin are Flathead (pl. o). similar lithologically to those in the Wind River Range. In the Washakie Range and western part of the Owl Age Creek Mounta:ins, thicknesses remain fairly constant at Fe\Y diagnostic fossils have been found in the Flat­ 120- 160 feet, but they increase eastward to 255 feet in head Sandstone in the Wind River Basin (table 2); the Wind River Canyon and to nearly 400 feet in the thus, the part of Cambrian time represented is not pre­ eastern OwI Creek Mountains (pl. 3, Bad water section). cisely known. From regional stratigraphic and paleon­ Along the south edge of the basin the Flathead ranges tologic correlations, Miller ( 1936, p. 142) and Shaw in thickness from 245 feet at the Conant Creek locality (1957, p. 9) <.:onsidered the formation to be early Middle PALEOZOIC FORMATIONS B15

FIGURE 8.- Flathead Sandstone (Cf) unconformably overlying Precambrian rocks (p{;r) along east side of Wind River Canyon, central Owl Creek Mountains.

Cambrian in age. Owing to its transgressive origin, the called the Death Canyon Member by Miller ( 1936, p. sequence is somewhat younger in the eastern part of the 119) and referred to in this report as the Death Canyon b1ts in than in the western part (fig. 5). Limestone Member; and an upper shale and limestone The Flathead Sandstone probably is lithologically unit. These units are readily distinguished in the west­ continuous with the lower part of the Deadwood For­ ern and northwestern parts of the Wind River Basin mation of Late Cambrian and Early Ordovician age in (fig. 7) but not in the central and eastern parts. the Black Hills and the Brigham Quartzite of late Pre­ In th western part of the Wind River Basin, Shaw cambrian and Early (?) and Middle Cambrian age in (1957) raised the Gros Ventre to group rank and, fol­ southeastern Idaho and northern Utah (fig. 5). lowing the terminology of Weed ( 1900) in central Mon­ Conditions of Deposition tana, referred to the upper unit as the Park Shale and The Flathead is a classic example of transgressive to the lower unit as the Wolsey Shale. He (Shaw, 1957, sandstone, representing the initial deposit laid down p. 9-10) retained the Death Canyon Limestone for the during the eastward migration of the Cambrian seas middle unit. Although Shaw's terminology is used in into the interior stable shelf region (fig. 5). Debris this report, it is modified to the extent that the Gros eroded from the adjacent Precambrian terrane accumu­ Ventre is retained as a formation and the three subdivi­ lated chiefly in a shore and near-shore environment. sions are classed as members. Gros Ventre strata are Periodic retreats and readvances of the sea caused inter­ generally poorly exposed and, as a result, are mapped as tonguing of the coarser sediments of the Flathead on the a single unit. east with the finer· grained sediments of the Gros Ventre Lithology and Thickness Formation on the west. In the Warm Spring Creek section at the northwest GROS VENTRE FORMATION end of the Wind River Range (pl. 2) the Gros Ventre Definition Formation is 747 feet thick and contains the threefold The Gros Ventre Formation was named by Black­ division mentioned above. The shale units are com­ welder (1918) from exposures on Doubletop Peak in monly grass covered and good exposures are rare; in the Gros Ventre Range, about 25 miles southwest of contrast the Death Canyon Limestone Member forms the Warm Spring Creek section (pl. 1). The sequence vertical cliffs and is one of the most conspicuous units probably includes the lateral equivalents of the "Flat­ in the Cambrian sequence (fig. 7). head shales" and the lower part of the Gallatin Forma­ The Wolsey Shale Member is 107 feet thick along tion of Peale ( 1893, p. 20-25) in southwestern Montana. Warm Spring Creek and consists of greenish-gray, tan, At the type section, the Gros Ventre Formation can and pink micaceous sandy shale and very fine grained be divided into three distinctive lithologic units: a lower shaly sandstone that is highly glauconitic in most places. shale and shaly sandstone unit; a middle limestone unit The basal part contains some beds similar to those in the B16 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

upper part of the Flathead Sandstone, so that the con­ shale with varying amounts of thin-bedded gray lime­ tact in places is grada:tional. The Death Canyon Lime­ stone that increases in abundance toward the top. The stone Member, 219 feet thick, is charaterized by cliff­ limestone commonly contains beds of flat-pebble con­ forming gray thin-bedded crystalline limestone that is glomerate, consisting of disk-shaped limestone frag­ commonly mottled by inclusions of irregularly shaped ments oriented mostly parallel to the bedding planes tan granular limestone or dolomite masses a fraction of in a dense to granular limestone matrix. The flat peb­ an inch to several inches across. The Park Shale Mem­ bles are particularly conspicuous on weathered surfaces ber consists of 421 feet of soft greenish-gray micaceous that transect the bedding planes.

TABLE 2.- Fossils from Cambrian formations [Generic and specific names are quoted "ithout modification from sources shown]

Collec­ tion Stratigraphic section No. References (pis. 2-5) ------·------1------Warm Spring Creek __ 1 Lingulepis acuminatus ______Miller (1936, p. 132). 2 Cedarina cf. C. alberta, C. victoria, Bynumia sp. indet., M odocia? sp., Denson (1942). Tricrepicephalus? sp., Semicircularia arcuata. 3 Agnostus sp., Linnarssonella sp. cf. L. modesta, L. transversa, Obolus? Miller (1936, p. 132). sp. cf. 0 . zentus. 4 Kingstonia sublettensis, Blountia globosa, B. dunoirensis, B. sp. cf. B. Do. amage, Crepicephalus sp., Cedaria sp. aff. C. prolifica, Arapahoia levis, M aryvillia sp., Agnostus sp. aff. A. tumidosus. 5 Elvinia roemeri, Burnetia'! sp., Eoorthis '! sp. cf. E. iddingsi ______Miller (1936, p. 131). 6 Taenicephalus cordillerensis, Wi lbernia sp., Billings ella coloradoensis, Do. Billingsella? sp. aff. B. striata, Dicellomus sp., Lingulepis acuminata var. meeki, Acroteta microscopica var. tetonensis, lrvingella gibba . 7 Briscoia schucherti, Synthrophia alata, Eoorthis sp. cf. E. iophon ______Do. Dinwoody Canyon ___ _ 1 Obolus sp ______Eliot Blackwelder (U.S. Geol. Survey, unpub. field notes). 2 Abnndant fragments of Late Cambrian trilobites ______Do. 3 Eoorthis qf. E. remnicha __ ------Do. Sweetwater Canyon __ _ 1 Glyphaspis ______Shaw (1957). 2 Bolaspidella? ______Do. 3 Bolaspis, Hyolithes ______Do. 4 Apachia convexa, Burnetia alta, Cliffia latagenae, Deadwoodia duris, Do. Dellea saginata, llousia vacuna?, Iddingsia occidentalis, lrvingella aff. I. fiohri, Xenocheilos cf. X. spineum, Elvinia sp. (Elvinia zone). 5 Taenicephalus cordillerensis ( Taenicephalus zone) ______Do. 6 ldahoia sp., Monocheil1ts'? sp., (Idahoia zone) ______Do. 7 Ellipsocephaloides sp., (I dahoia zone) ______Do. 8 Cranidia B and C of DeLand and Shaw (Trempealeauan) ______DeLand and Shaw (1956, p. 561). Windy Gap ______Billingsella coloradoensis, Eo01·this cf. E. remnicha, Lingulepis acumi­ Love (1939, p. 16). natus, Acroteta microscopica var. tetonensis, Dicellomus cf. D. nanus, Hyolithes? sp., Prozacomps·us sp., I dahoia sp., Prosaukia sp., Chario­ cephalus? sp., M aladia sp. (Ptychaspis-Prosaukia zone). Wind River Canyon __ 1 Scohthus ______Miller (1936, p. 137). 2 Scolithus ______Deiss (1938, p. 1099) . 3 Lingulepis ______Do. 4 Glyphaspis ______Deiss (1938, p. 1097, 1098). 5 Ampahoia spatulata, A. sp. cf. A. typa, Dicellomus nana, Linnarssonella Miller (1936, p. 136); tennesseensis, L. sp. cf. L. modesta. Deiss (1938, p. 1096). 6 Arapahoia spatulata, A. typa, Blountia dunoirensis'? ______Deiss (1938, p. 1906). 7 Crepicephalus tripunctatus, M aryvillia sp. cf. M. ariston, Hyolithes sp __ _ Miller (1936, p. 136). 8 Blountia sp., Kingstonia sp., Tricrepicephalus sp., Aphelaspis sp ______Deiss (1938, p. 1095). 9 Taenicephalus cordillerensis, Saratogia sp., Billings ella coloradoensis ____ _ Miller (1936, p. 136) . 10 Elvinia n. sp., Pterocephalia n. sp ______Deiss (1938, p. 1094) . 11 Dike/acephalus ______- _- _------Deiss (1938, p. 1093). Deadman Butte ______1 Peronopsis?, Hyolithes?, Elrathiella, Westonia cf. W. ella ______Woodward (1957, p. 222). 2 Tricrepicephalus tripunctus, Dicellomus nanus ______Do. Conant Creek ______1 Tricrepicephalus ( Crepicephalus zone) ______Shaw (1957). 2 Billingsella, Eom·this, Glyptotrophia, Linnarssonella, Berkia, Bernia, Van Houten and Weitz Dellea, Parabolinoides (Elvinia zone). (1956); Shaw (1957). 3 Billingsella, Eoorthis, Huenella, Bemaspis, Orygmaspis, Taenicephalus Van Houten and Weitz ( Taenicephalus zone). (1956). Rattlesnake Hills ____ _ 1 Approximate horizon of the type of Westonia dartoni of Walcott ______Shaw (1957). 2 Lingulepis; an undescribed trilobite of pre-Cedaria Middle Cambrian age_ Do. PALEOZOIC FORMATIONS B17

Southeast of \'Tarm Spring Creek, along the east flank In the Owl Creek and southern Bighorn Mountains of the Wind River Range, the thickness of the Gros the Gros Ventre Formation is a nonresistant unit con­ Ventre Formation ranges from a minimum of 300 feet sisting largely of interbedded gray-green and tan glau­ to a maximum of about 760 feet (pl. 2). The three conitic micaceous shale, sandstone,· and siltstone and members can be recognized at least as far southeast as some beds of limestone and flat-pebble conglomerate in Bull Lake Canyon, but farther south the Death Canyon the upper part (fig. 9). Some of the sandstone is hem­ Limestone Member becomes progressively more shaly atitic and red to reddish brown. Thickness ranges from and sandy and loses its identity as a resistant cliff-form­ 150 feet in the eastern part of this region to 575 feet in ing unit. In Sweetwater Canyon at the southeast end of the central and western parts; variations seem to be the range, the Gros Ventre is chiefly interbedded shale largely the result of eastward interfingering with the and sandstone with numerous thin beds of limestone upper part of the Flathead Sandstone (pl. 3). Because and flat-pebble conglomerate in the upper one-third to of this interfingering, Miller ( 1936, p. 123, 124) pro­ one-half of the formation. posed that the Flathead and Gros Ventre be combined The three members of the Gros Ventre Formation are as a single unit and applied the name l,)epass Forma­ al so easily identified in outcrops along the south tion to all Cambrian rocks older than the Gallatin Lime­ side of the Washakie Range where their aggregate stone. Tourtelot and Thompson ( 1948), Tourtelot thickness ranges from 500 to 700 feet. Sufficient ob­ ( 1953), and Woodward ( 1957), however, differentiated servations have not been made in the Circle Ridge area the Flathead and Gros Ventre Formations on the basis (pis. 1, 3) to determine the presence of the Death Can­ of detailed mapping of the Cambrian rocks in this yon Limestone Member, but this unit seems to have dis­ reg10n. appeared by facies change at least as far west as the Along the south margin of the Wind River Basin, exposures near Merritt Pass in the western Owl Creek strata assigned to the Gros Ventre Formation are pre­ Mountains (T. 8 N., R.1 W., pl.1). dominantly reddish-brown and gray fine-grained sand-

FtGuHE 9.- Camllrian, Ordovician, Mississippian, and Pennsylvanian strata exposed a long west wall of Wind River Canyon, central Owl Creek :\Iounta ins. !Pta, Teusleep and Amsden Formations; Mm, Madison Limestone ; Ob, Bighorn Dolomite; Cg, Gallatin Limestone; Cgv, Gros Ventre Formation. B18 GE·OLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

stone, siHstone, and a few thin beds of shale. In the eastward from the point of disappearance of the basal Conant Creek area, beds of gray glauconitic flat-pebble Du Noir limestone member of the Gallatin." Similarly, limestone conglomerate, possibly equivalent to part of along the south margin of the Wind River Basin, east the Death Canyon Limestone Member, are present in of Conant Creek, Shaw (1957) recognized the possi­ the middle of the formation; some of these beds extend bility that the upper part of the Gros Ventre Forma­ as far east as the East Canyon Creek section, but they tion (his Buck Spring Formation) contained some seem to be entirely absent at the north end of the Rattle­ equivalents of the Gallatin Limestone. snake Hills (pl. 4). Thickness of the Gros Ventre For­ An erosional unconformity between the Gros Ventre mation decreases from 512 feet in Sweetwater Canyon Formation and Gallatin Limestone was observed by to 287 feet in the northern Rattlesnake Hills. The de­ Miller (1936, p. 122) in the and by Black­ crease in thickness easbvard is caused by interfingering welder (1918) at the type seotion of the Gros Ventre with the Flathead Sandstone at the base of the forma­ in the Gros Ventre Range in northwestern Wyoming. tion and possibly in part by truncation at the top by the Miller (1936, p. 119) reported an unconformity locally Madison Limestone. The Madison bevels eastward in the vVarm Spring Creek area in the northern Wind across successively older beds in the Cambrian sequence, RiYer Range, and DeLand (1954) described a similar overlaps the entire Gallatin Limestone in the south­ relation between the two formations in the Sweetwater central part of the basin, and rests on the Gros Ventre Canyon area at the south end of the range. Elsewhere Formation at the north end of the Rattlesnake Hills in the '\Vind River Basin the contact seems to be con­ (pl. 4 a.nd fig. 15; Shaw, 1957, p. 12). formable. Inasmuch as the Cambrian rocks overlying the Flat­ In the southeastern part of the basin, strata assigned head in the south-central part of the Wind River Basin, to the Gros Ventre Formation are overlain, and in some and adjacent regions to the south, are atypical of the places completely overlapped, by the Madison Lime­ Gros Ventre Formation farther west and northwest, stone. Shaw (1954) introduced a new name, Buck Spring For­ Age mation, for this red facies. That name, however, has Fossils collected from the Gros Ventre Formation not yet been used widely in the vVind River Basin. (table 2) indicate that over much of the basin area the A well drilled in the North Casper Creek oil field formation is of middle to late Middle Cambrian age. along the east edge of the Wind River Basin (pl. 5) pen­ The Oedaria zone is represented in the upper part of the etrated 205 feet of Cambrian strata between the Madi­ formation; this zone is considered to mark the base of son Limestone and the Flathead Sandstone. This se­ the Upper Cambrian Series (Howell and others, 1944). quence, consisting chiefly of purple and tan to white Strata assigned to the Gros Ventre Formation are glauconitic micaceous siltstone in the lower part and so mew hat younger in the eastern part of the Wind purple and gray glauconitic dolomite in the upper part, River Basin that in the western part. Both in the Rat­ may represent only the Gros Ventre Formation, or it tlesnake Hills and southern Bighorn Mountain areas may also contain some equivalents of the Gallatin Lime­ (pl. 3, 4), east of the wedge edge of the Du Noir Lime­ stone. Farther south, however, at the west end of Cas­ stone Member of the Gallatin Limestone, the strati­ per Mountain, these particular strata are entirely cut graphic and paleontologic relations suggest that the out beneath the Madison Limestone which rests directly upper part of the Gros Ventre is in part the age equiva­ on the Flathead Sandstone. lent of the Du Noir (Shaw, 1957, p. 13; Woodward, Contact With the Gallatin Limestone 1957, p. 223, fig. 4). The base of the Gros Ventre also The contact betw.een the Gros Ventre Formation and becomes younger eastward because of intertonguing the overlying Gallatin Limestone, in those areas where with the Flathead Sandstone (fig. 5). the Du Noir Limestone Member is present at the base Conditions or Deposition of the Gallatin, is marked by a sharp change from grass­ Strata of the Gros Ventre Formation are offshore covered shaly slopes below to cliff-forming limestone deposits that were laid down contemporaneously with above (figs. 7, 9). In subsurface sections there is an the shore and near-shore sediments of the Flathead easily recognized shift in the resistivity curves on elec­ Sandstone as the Cambrian sea continued its eastward tric logs (pl. 6). Where the Du Noir Limestone Mem­ transgression across central Wyoming (fig. 5). The ber is absent or poorly developed, however, the forma­ Death Canyon Limestone Member probably was de­ tion contact is not so readily defined. At the south end posited during a more easterly advance of the sea than of the Bighorn Mountains, ·w·oodward (1957, p. 217) was the overlying Park Shale Member; if so, there may stated that "it is difficult if not impossible to differenti­ have been a limited westward retreat of the shoreline, ate the Gros Ventre from the overlying Gallatin north- or the shoreline may have been nearly stabilized in one PALEOZOIC FORMATIONS Bl9 position, during the early part of the deposition of the have formed as a result of different rates of lithification Park. Later, the sea readvanced and limestone was of thin-bedded strata. The distribution of flat-pebble deposited along with the shale over much of the wind conglomerate. in the Cambrian sequence of the Wind River Basin area. River Basin seems to be very similar to that found else­ Shaw (1957, p. 13) cites evidence that the reddish­ where across the Rocky Mountain foreland region, but brown clastic rocks of the Gros Ventre Formation (his few studies have been made. In a brief discussion Shaw Buck Spring Formation) in the south-central part of (1957, p. 13) suggests that the normal condition for the the basin are partly marine and partly nonmarine. He development of the conglomerate was one of shallow concludes that this area, and the adjacent area to the water with restricted circulation. south, were emergent periodically "either through local ·Glauconite, though absent in most of the Paleozoic uplift to the south of Wyoming or simply by filling of rocks of central Wyoming, is abundant in many of the the sea at a faster rate than the eustatic rise of sea level Cambrian units. Conditions facilitating the develop­ could submerge the sediments." Although the data are ment of glauconite have been summarized by Cloud inconclusive, Shaw (1957, p.13) favors the second inter­ (1955) and Lochman-Balk (1957). These include: (1) pretation, because ( 1) the strata generally lack coarse marine waters of normal salinity, (2) slightly reducing conglomerates and ( 2) the repeated intercalation of environment resulting from decaying organic matter, containing inarticulate suggests (3) ingestion of sediment by bottom-dwelling organisms a very close balance between depositional filling and having low oxygen requirements, ( 4) presence of mica­ marine transgression such as would occur on a low shelv­ ceous minerals (especially biotite) or bottom muds of ing shore. high iron content, and ( 5) slow sedimentation rate to In the western part of the Wind River Basin the Park avoid rapid burial of bottom sediments. Presumably, Shale Member of the Gros Ventre Formation was par­ many of these conditions existed during the deposition tially eroded before the deposition of the Du N oir of much of the Paleozoic succession in this region. Limestone Member of the Gallatin Limestone. Farther However, one important factor seems to set the east, however, sedimentation seems to have been con­ Cambrian apart from the younger rock systems. tinous. The Cambrian seas advanced across an eroded surface The origin of limestone flat-pebble conglomerate beds of Precambrian crystalline rocks which doubtless fur­ has been discussed by several workers. McKee ( 1945, nished a greater supply of micaceous minerals than did · p. 65-70) presents an excellent summary of the different any of the succeeding periods of the Paleozoic. Where views bearing on this subject in connection with his de­ other favorable conditions were met along the slowly tailed studies of the Cambrian rocks of the Grand Can­ submerging shelves, a significant quantity of these yon region. He (McKee, 1945, p. 67-69) observed that minerals was probably converted to glauconite. the flat-pebble conglomerate beds in the canyon region. GALLATIN LIMESTONE are common in regressive deposits, but they do not occur Definition in transgressive deposits, and that they developed ex­ The Gallatin Limestone, the youngest Cambrian for­ clusively along the shoreward margins of the limestone mation in central Wyoming, was named and described facies. Although most previous investigators believed by Peale (1893, p. 22, 23) from exposures in the Gal­ that such conglomerate was formed near shore and in latin Range of southwestern Montana. At the type shallow water (beach or tidal-flat conditions), McKee section it originally included in its lower part limestone (1945, p. 69) concluded that some were formed at least and shale of Middle Cambrian age, which probably con­ 100 miles seaward from the strand line. From the sedi­ stitute the upper part of the Gros Ventre Formation mentary relations, he further concluded that these beds as that unit was later defined by Blackwelder ( 1918), originated at a time when basin sinking ceased or slowed and limestone of Late Cambrian age in its upper part. down to such an extent that sedimentation built up the Inasmuch as the Galla tin Limestone, as used in the bottom, partly above the profile of equilibrium, after Wind River Basin, is not completely representative of which the sea regressed and conglomerate was formed the type Gallatin, Deiss ( 1938, p. 110±) substituted a in favorable localities. new name, Boysen Formation, for all Upper Cambrian Regarding similar deposits in parts of Montana and rocks in the Wind River Canyon area and subdivided Wyoming, Lochman-Balk (1957, p. 145) and Robinson it into the Maurice, Snowy Range, and Grove Creek (1963, p. 20) agree that the flat limestone pebbles formed Members (pl. 3) . The Boysen, although extended west­ largely through fragmentation of previously deposited ward into the Gros Ventre Range by Foster (1947, p. limestone by wave and current action, although Robin­ 154 7) and Wanless and others ( 1955, p. 13), has not son also suggests that some of the conglomerate may gained wide acceptance in central Wyoming. B20 GEOLOGY OF THE WJN:D RIVER BASIN, CENTRAL WYOMING

Along the east flank of the Wind River Range the shale with a minor amount of thin-bedded gray lime­ Gallatin Limestone can be divided into three units: stone. The upper 263 feet of the Open Door is a hard, a thin lower limestone unit, a thin middle shale unit, resistant series of gray thin-bedded to massive limestone and a thick upper limestone unit. 'The basal limestone and a few flat-pebble conglomerate beds. The upper­ was named the Du N oir Member (referred to as the most part of this member is commonly mottled with tan Du N oir Limestone Member in this report) by Miller small irregular masses of granular limestone. Some of ('19'36, p. 124, 125) ; the section along Warm Spring the exposed surfaces weather to a rough pitted surface Creek at the northwest end of the range was desig­ similar to ·the overlying Bighorn Dolomite. nated as the type (fig. 7). Shaw (1957, p. 13-15) The Gallatin Limestone in many places contains classed the Gallatin as a group in this region, raised the cavities filled with red earthy deposits which, where Du N oir to formational status, and named the re­ exposed on the sides of the cliffs, contribute much red mainder the Open Door Limestone (Shaw and DeLand, staining to the outcrops. Because of this, the outcrops, 1955, p. 38) from exposures along the east ·wall of when viewed from a distance, appear to contain much Granite Canyon, just below the topographic feature red material. known as the "Open Door" in the Gros Ventre Range The characteristic lithologies of the two members of in northwestern Wyoming. The Open Door Limestone the Gallatin are readily distinguished in most other sec­ included the thin shale ~unit at the base that was referred tions southeast along the east flank of the Wind River to as the Dry Creek Shale Member by Shaw (1957, p. Range. Contacts between members are not drawn 14) following the redefinition of that unit by Lochman through some of the localities shown on plate 2, but this ( 1950) in central l\fontana. Although Shaw's termi­ is chiefly because of poor exposures and (or) the lack nology is used in this report, it is modified to the extent of adequate observations. The Du Noir Limestone that the Gallatin is retained as a formation, and the Member is 82 feet thick in Sweetwater Canyon at the Open Door and Du N oir are classed as members, because southeast end of the range, which is the maximum ob­ they are generally mapped as one unit. served for this region. The overlying shale unit of the Lithology and Thickness Open Door at the same locality (pl. 2) is only 23 feet The Gallatin Limestone is a resistant sequence that thick and contains a few thin white sandstone and red forms conspicuous cliffs above the shale slopes of the siltstone beds in addition to limestone. Gros Ventre Formation. It forms the lowermost series Shaw (1957, fig. 3) has traced the DuNoir Limestone of ledg0s in many canyons. The formation is 265-365 Member as far east as the Conant Creek area along the feet thick in the Wind River Range. In the Washakie south margin of the Wind River Basin, where he as­ Range, and Owl Creek and southern Bighorn Moun­ signed 110 feet of limestone and sandstone to the unit. tains the minimum thickness is about 235 feet and the Farther east, the limestone wedges out into elastic strata maximum is 455 feet (pl. 3), although Darton ( 1906a, of the Gros Ventre Formation and the member becomes p. 14, pl. IV-b) described a section in OwI Creek Can­ unidentifiable (pl. 4). yon (T. 8 N., R. 3 W.) in which the Bighorn Dolomite The subdivisions of the Gallatin Limestone are easily apparently rests directly on shale of the Gros Ventre recognized in the Washakie Range. The Du N oir Lime­ Formation with no intervening Gallatin. Along the stone Member can be traced eastward along the entire south edge of the Wind River Basin the formation can south side of the Owl Creek Mountains and into the be traced from Sweetwater Canyon eastward only as far southern Bighorn Mountains, but there the limestone as the Conant Creek area, where it is 209 feet thick. disappears because of facies change (Woodward, 19·57, Farther east the Du N oir Limestone Member at the base fig. 4). The Open Door Limestone Member also be­ merges with elastic sediments of the Gros Ventre For­ comes progressively more shaly and sandy eastward mation (pl. 4). In the eastern and southeastern parts (pl. 3). of the basin the Gallatin Limestone is entirely cut out In subsurface sections in the western part of the Wind by the erosional unconformity at the base of the Mad­ River Basin the Gallatin Limestone is easily identified ison Limestone. from electric logs (pl. 6) . Along Warm Spring Creek, at the northwest end of Contact With the Bighorn Dolomite the Wind River Range, the Du Noir Limestone Member An erosional unconformity separates the Gallatin is a prominent 48-foot eliff-forming unit (fig. 7) of gray Limestone from the Bighorn Dolomite. In the Warm thin-bedded highly glauconitic and oolitic limestone Spring Creek area, at the northwest end of the Wind with some flat-pebble conglomerate. The overlying River Range, Miller (1936, p. 131) noted 100 feet of lower shale unit of the Open Door Limestone Member is beds at the top of the Gallatin on Warm Spring Moun­ 54 feet thick and consists chiefly of soft greenish-gray tain (Wlj2 sec. :35, T. 42 N., R. 108 W., pl. 1) that are PALEOZOIC FORMATIONS B21 absent 3 miles farther west. At th'e southeast end of tral and eastern parts. At the beginning of the deposi­ the range, Bell ( 1955) observed that the contact relief tional period represented by the Du N oir Limestone is as much as 3 feet, and that debris from the uppermost Member, the entire region was again submerged and Cambrian rocks is incorporated in the Lander Sand­ carbonate sediments accumulated in the central and stone Member of the Bighorn. In Owl Creek Canyon, western parts of the basin area and clastic sediments at the northwest corner of the Owl Creek Mountains, in the eastern part. The flat-pebble conglomerate in the Gallatin was apparently cut out by pre-Bighorn the upper part of this member, and the shale in the erosion (Darton, 1906a, p. 14). In the Wind River overlying Open Door Limestone Member, suggest that Canyon area, Tourtelot and Thompson (1948) reported regression, and perhaps emergence, took place at this a sharp uneven contact at the top of the Gallatin and time. In Late Cambrian time, which is represented by fragments of limestone locally in the basal 3-5 feet of the upper limestone of the Open Door Limestone Mem­ the overlying Bighorn. In many other places, how­ ber, the sea expanded eastward beyond any of its pre­ ever, the formation contact shows little evidence of the vious limits and extended across at least the northern considerable length of time (Late Cambrian to Middle half of Wyoming and into the Black Hills region. or Late Ordovician) that transpired between the depo­ Cavities filled with red earthy material at some horizons sition of the Gallatin and that of the Bighorn Dolomite. within the Open Door Limestone Member may indicate Both the Gallatin and the Bighorn commonly form that parts of central Wyoming were periodically emer­ cliffs, but the massive character of the Bighorn is gen­ gent during Late Cambrian time. erally in sharp contrast to the more prononnced banded At the end of Cambrian time, or shortly thereafter, appearance of the Gallatin (fig. 9). The formation the sea withdrew completely from central Wyoming and bonndary is easily detected on electric logs (pl. 6). the entire region was exposed to erosion. There is, In the eastern Owl Creek and southern Bighorn however, little evidence of this widespread regression in Mountains and in the Conant Creek area along the the uppermost Cambrian rocks. south edge of the basin, the Gallatin Limestone is over­ lain directly by the :Madison Limestone. ORDOVICIAN ROCKS, BIGHORN DOLOMITE Age Definition Fossils collected in the Wind River Basin and adja­ The Bighorn Dolomite, defined by Darton (1904, p. cent regions (ta!hle 2; Miller, 1936, p. 140, 141; Shaw, 394-396) from typical exposures along the east flank 1957, p. 14, 15) indicate the following zonation for the of the Bighorn Mountains, includes all the rocks of Gallatin Limestone: Du N oir Limestone Member­ Ordovician age in central Wyoming. Because it in­ Oedaria, Orepicephaltus, and possibly Aphelaspis zones; variably forms cliffs, the Bighorn is perhaps the most Open Door Limestone Member- Aphelaspis and El­ conspicuous Paleozoic formation in the mountains along vinia zones in the lower shale unit and Elvinia and the west and north sides of the vVind River Basin (figs. other zones of Late Cambrian and possibly earliest 4, 9). Ordovician age in the upper limestone unit. Thus, the In the type area, Darton (1906b, p. 26, 27) recognized formation is largely, if not wholly, Late Cambrian in three lithologic subdivisions of the Bighorn (which he age. called the Bighorn Limestone) : a lower light-gray Regionally, LochlJlan-Balk and Wilson (1958, p. 334) sandstone, a middle massive buff limestone, and an have described an extensive faunal change between the upper thin-bedded white to gray limestone containing, Aphelaspis and Elvinia zones. They attribute this locally, a red-weathering fossil-rich zone at the top. change to widespread emergence and shallowing of the Later work by Kirk ( 1930, p. 460-46·5) in the southern seas. across much of the North American cratonic and Bighorn and eastern Owl Creek Mountains indicated miogeosynclinal areas. The boundary between these that the basal sandstone is in reality two nnits separated two zones corresponds closely to the contact between by an erosional unconformity. Kirk concluded that (1) the Du Noir and Open Door Limestone Members of the lowermost sandstone, which contains abundant fish the Gallatin. As noted by Shaw (1957, p. 14), and as remains, does not extend south and west of the eastern discussed below, sedimentary features suggest a break end of the Owl Creek Mountains and is the equivalent in sedimentation between these two units in the western of the Middle Ordovician Harding Sandstone of central part of the Wind River Basin. Colorado; and (2) the upper sandstone, which has few, Conditions of Deposition if any, fish remains but a large invertebrate fauna, is Before the Gallatin Limestone was deposited the sea of much wider distribution and forms the base of the had apparently withdrawn from the western part of the Bighorn proper. Thomas (1952, p. '35) and Ross Wind River Basin area, but it had remained in the cen- (1957a, p. 17) concur in this interpretation.

2(}5'-54() 0-&6----4 B22 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

In the Wind River Range the basal sandstone (post­ cliff-forming buff to light-gray massive granular dolo­ Harding Sandstone equivalent) of the Bighorn Dolo­ mite. The lower part is rather limy in places and com­ mite was called the Lander Sandstone Member by Mil­ monly darker gray, but it still retains its granular tex­ ler ( 1930, p. 196) from outcrops along the Middle Popo ture. The dolomite weathers to a very rough pitted sur­ Agie River southwest of Lander (near the Sinks Canyon face (fig. 10) that consists of a randomly branching net­ section shown on pl. 2). The upper thin-bedded dolo­ work of slightly raised ridges a fraction of an inch in mite was referred to the Leigh Dolomite Member by height and width. In Dinwoody Canyon, J. F. Murphy Blackwelder (1918), the name being derived from the (oral commun., 1963) found a conglomerate lens, 1 inch canyon of that name in the Teton Range of northwest­ thick, 11 feet above the base of the massive dolomite, ern Wyoming. The middle massive dolomite has not which contains pebbles of igneous and metasedimentary received formal designation. rocks Vs-1,4 inch across. Farther south, in Bull Lake Lithology and Thickness Canyon, Murphy and others (1956) described beds of T~e Lander Sandstone Member occurs only locally dolomite breccia at the top of the member, and along the east flank of ·the Wind River Range (pl. 2). fillings of thin-bedded dolomite in the upper part. It is a lenticular gray to tan, in part red, fine- to coarse­ Thickness of the middle member ranges from about grained sandstone generally less than 5 feet thick. 230 feet in the central and northern Wind River Range Fragments of the underlying Gallatin Limestone are to only about 15 feet in the southern part. The decrease commonly incorporated in the basal part. Because the in thickness southward is the result of beveling at the member is thin and lenticular and easily concealed by top by Mississippian and (or) Devonian strata, and talus, it may have a wider distribution than is apparent perhaps the result in part of nondeposition. from known outcrops. The Leigh Dolomite Member consists chiefly of white, The unnamed middle member of the Bighorn Dolo­ gray, and pink thin-bedded _to platy dolomite. The mite is a remarkably uniform sequence of very resistant dolomite is dense, porcelaneous, and weathers chalky

FIGURE 10.-Weathered surface of Bighorn Dolomite showing typical "fretwork" pattern. Outcrop along east side of Horse Creek, south­ central Washakie Range. PALEOZOIC FORMATIONS B23

white. It generally forms a conspicuous recessed white The Darby Formation is more easily eroded than the band along the cliff faces. Beds of massive dolomite Bighorn, and generally forms slopes above the massive similar to those in the underlying middle member of dolomite cliffs. the Bighorn are in the upper part of the Leigh at many Where the Bighorn Dolomite is overlain by the Madi­ localities. The member.is 85 feet thick at the northwest son Limestone, the contact is likewise sharp and irreg­ end of the Wind River Range, but thins southward and ular in most places. At the south end of the Wind disappears, owing to the erosional unconformity at the River Range, Bell (1955) observed that a weathered top. surface occurs at the top of the Bighorn and that verti­ The middle and upper members of the Bighorn Dolo­ cal fractures or channels filled with red siltstone extend mite, which have a combined thickness of 210-300 feet, down several feet into the underlying dolomite. Where are readily identified in the Washakie Range; the the basal part of the Madison is dolomitic, however, Lander Sandstone Member is only locally present, but the contact is not always apparent. in some sections it is as much as 7 feet thick. In the Age Circle Ridge area the Bighorn is 260 feet thick, but The Bighorn Dolomite contains sparse poorly pre­ because of the unconformity at the top, it thins progres­ served fossils, including corals, mollusks, and crinoids, sively eastward to a wedge edge 'at the east end of the in the western and northern parts of the Wind River Owl Creek Mountains (fig.11; Thomas, 1952, p. 35), Basin (table 3). Probably the most characteristic form approximately at the east edge of T. 40 N., R. 92 W. is the chain coral 0 atenipora (formerly a subgenus of Sandy beds at the base of the formation in Wind River H alysites). The large.st collections of fossils were ob­ Canyon and in the eastern Owl Creek Mountains prob­ tained by Miller ( 1930) . At the type locality of the ably represent the Lander Sandstone Member rather Lander Sandstone Member (Sinks Canyon section, pl. than the Harding Sandstone equivalent. The Bighorn 2), for example, he (Miller, 1930, p. 198-201) found a Dolomite is not present in the Badwater and Deadman total of 135 different species, mostly mollusks. Along Butte sections in the southern Bighorn Mountains (pl. the southeast edge of the Bighorn Mountains (north­ 3), but it reappears beneath the Madison Limestone a east of the Deadman Butte section shown on pl. 3), few miles farther north and thickens along the east Amsden and Miller ( 1942) collected several species of flank of the range toward the type area. conodonts from both the Harding Sandstone equivalent The Bighorn Dolomite is absent along the east and and the next younger Lander Sandstone Member. south margins of the Wind River Basin (fig. 11), al­ 'There seems little doubt that the Harding Sandstone though in the Conant Creek area the lower part of the equivalent is Middle Ordovician. However, despite the Madison Limestone is a hard ragged-weathering sili­ variety of fossils found in the younger parts of the Big­ ceous dolomite that has been mistaken for the Bighorn. horn Dolomite, including the Lander Sandstone Mem­ Contact With Overlying Rocks ber, agreement has not yet been reached regarding the The Bighorn Dolomite is overlain unconformably exact stages of Ordovician time that are represented by by the Darby Formation in the central and northern the formation. The problems have been discussed in parts of the Wind River and Washakie Ranges, and many papers (for example, Ross, 1957b; Thomas, 1952, western Owl Creek Mountains and by the Madison p. 35; 1948, p. 83; Love, 1939, p. 20). No new informa­ Limestone in the e'astern Owl Creek Mountains (fig. 9) tion for dating the formation was obtained during this and southern Wind River Range. Along Warm Spring investigation ; the main issues are summarized below. Creek in the northern Wind River Range the erosional Darton (1906b, p. 29) considered the upper part of unconformity at the top of the Bighorn is marked by the Bighorn Dolomite in the Bighorn Mountains as earthy beds having layers and cavities filled with calcite Late Ordovician (Richmond) and the lower part as crystals. The upper contact has as much as 20 feet of Middle Ordovician (Trenton), based on fossil identifi­ relief and at one place in the north wall of Warm cations by E. 0. Ulrich. This interpretation prevailed Spring Canyon a large mass of breccia is present in the in central Wyoming until Miller (1930, 1932) found top of the Bighorn Dolomite. As discussed below, this that 25 of the relatively diagnostic species from the breccia may represent a channel filled with Devonian Lander Sandstone Member seem to indicate Middle sediments similar to those that have been found in the Ordovician (Trenton and possibly Black River) age Dinwoody Canyon and Bull Lake Canyon areas. The and 22 Late Ordovician (Richmond) age. He (Miller, contact is generally irregular and shows several feet 1930, p. 203, 204; 1932, p. 203, 209) concluded that the of local relief at many other localities; in some places, appearance of Richmond fossils is sufficient to fix the however, there is little physical evidence of the long age of the lower part of the Bighorn Dolomite (Lander hiatus between the Bighorn and next overlying strata. Sandstone Member) as very Late Ordovician. Suhse- ·to t..,:) ~

r-1,)0° 109° 108° wr I r~- p ~ R K ~ I ·r T I 6 i 4~\ ,.!'-' -''\, ~" . - ! ~ w ~ A s H A K I E I I I I I I I I I I I 45 ~ ) ~ '1'- I // I 4 If 112w! "' !1c 109 4o8 106 105 103 1b2 i'Toi 1--!.o.o 99 98 V97 go; -95 ,Jl3 ;2 90 89 88 87 86 1 84 1 83 1! 82 1 811 8 " 1 • · ~ 1~4' 9~ 91 "~ 1 1 1 I 4 r-- ~ 144 oo P I J , / 4-- - t- -+- - ~' H T S P F lel' G ~ / L-- -- f -? ..._C l 1 1 1 1 1 1 r , 1 r '= J---,..7~ __ ... v .. 1 17 x I ·\ 43 / r--. _;· .. -' . lt..-.. 43 I 1/ I II J I 0 i )( , \ '-!... "' ....---r ../ I ./ lTherm poli~ I • / ~ r I T r ~tt . 18 .....,..J---' ~ /- v ~ 0 TfETOfNj' ~- r·~ ~ --~~v.l\. 42 ,r 1 1 .• ~ 1 0 " ' ,~-- x- L- L., ./ ' V. I l J :~JU I "--- (< bD b ·' ' 'i' "T I I , I 41 '~'- u ~~ T 6 - -~ , L....J' v4')( J~~~- ·- ---, L~ +---+- -i _J __ -->--~ ~ 0 l I ' f 4~- ! "\ X ~ '~ J ~/ ~ ~ l I y ~ ,;-~ ! '-. ' ""~ ll I lo%j f---.. Y.r; 5 4 3 2 R.1 W. R.'fi.E 2 3 / 4 5 6j lv l " 1 t-3 39 \ I ' f -, 39 I " 1 4 1 r x '\1 J I : f ' I ~ 38 T re 1 i \ I ~9o -~ j l.....,---~',.....38 ~ r ~v- '\ I \ 3 I / I 1 I I ' 37 / \ I ,\ X II I l 37 I \ h-ll ~ t::J 3 6 ' ! '\t\. ~- /2 / luJl 3 6 ! I \ I I'\"" I I T / I \ I I IJ I ::0 I 13s I )_~I 1 \ ~ If e ~ ~ 'F.ivert n l t\ I T ,TlJ ~ 35 ~43° t<:l '~ 1\X' T I v I N A T 'if 0 N A -I:> ::0 34 .I j- ~ 1\ s . 34 ; I ~ ' __ ,_ \ ~ J-?._,~'- _/ -rt -~-~- ._J I }- ~ 0 I ~ Ul "_l I \ f\1~ 1 L., " I\ I •1 " i I " ~ Cjsper I ~~ __z 32 7 1 / I 1 l ~J ' xk • l 32 1 '\, 1 1 1 1 I Q I s 13'uI I B L E T ' i""l ..... \ I ) I .1.-- l-- -+- --- J 1 111 11· TIE I r--..-4/' ~---, 1---. __.....1 I I ~ ::0 30 ~ i II ~~l~ ~X I I ~fl I ~ .. ~ ~ ~ ~ ~ l fB~u~:,t~~:.~~:1;~;vf'\ ~ EXPLANATION ' 0 l I I ' _I_L ) I I l------~ -~- -ttnr ~ F R X l;>o z IZ 0 Surface section ~~--+---- -:br!_t~l~- - -11-- -I~ -l-1- ___,i---+_,--+--+--++-+-+--+--+----+---+-----+-+I< 26 c I I A I I I R I I B I I o I IN I !>rl Sf w IE ~ Subsurface• section E / T /w I A !I Tj25 E IR I hclJ2VJ 101 !1 oo I 99 98 97 I 96 95 9-4 u !L3 . 9_2 l 91 90 I " I " I " I " I I " I " I " I " I eo I " I " !J,.l 0 10 20 30 MILES t 4 ll II I ILH 1 I i 1 [ I I I I I I I I I ! 42°

FIGURE H.-Thickness of map of Bighorn Dolomite in central Wyoming. Interval is 100 feet; isopachs are res:tored across mountain arches where rocks have been eroded; isopachs are dashed where control is inadequate. PALEOZOIC FORMATIONS B25

TABLE 3.-Fossils from the Bighorn Dolomite [Generic and specific names are quoted without modification from sources shown]

Collec­ tion Stratigraphic section No. Species References (pls. 2-5)

Dinwoody Canyon____ 4 Catenipora gracilis, Streptelasma aff. S. foerstei, Grewinkia sp., Calapoecia R. J. Ross, Jr., to J. F. sp., Nyctopora sp., Zygospira cf. Z. jupiterensis, Paucicrura sp., Murphy (written com­ Sowerbyella or Thaerodonta sp., Platystrophia sp., Hesperorthis sp., mun., 1955). Cyclendoceras? sp. 5 Streptelasma sp., Euomphalopterus? sp., Fusispira cf. F. injlata, Halysites J. W. Huddle to J. F. gracilis, Drepanodus subrectus, Panderodus gracilis. Murphy (written com­ mun., 1963); Eliot Blackwelder (U.S. Geol. Survey, unpub. field notes) ; identifica­ tion by E. 0. Ulrich. Bull Lake______1 Halysites (Cdtenipora) cf. H. gracilis, "Holophragma" sp.; unidentifiable Murphy and others streptelasmoid coral, brachiopods, and cephalopods. (1956); J. W. Huddle 1a Drepanodus curvatus, Oistodus sp., Panderodus cf. P. gracilis, Cordylodus to J. F. Murphy sp., Ozarkodina sp. A, Ozarkodina sp. B, Ligonodina sp., Trichonodella? (written commun., sp., Belodina compressus, Prioniodina sp. 1963). Sinks Canyon______1 Composite fauna from the Lander Sandstone Member in Sinks Canyon Miller (1932, p. 204-206). and vicinity, collected and described by Miller. The following species are included: Receptaculites, 1; Cyclocrinites, 1; coral, 7; worm, 1; brachiopods, 27; pelecypods, 13; gastropods, 34; cephalopods, 50; trilobites, 1. 2 Composite fauna from the middle massive dolomite and Leigh Dolomite Miller (1932, p. 206, 207). Members in the central Wind River Mountains, collected and described by Miller. Includes Receptaculites arcticus, Streptelasma corniculum, S. robustum, S. sp., Columnaria alveolata, C. halli, Palaeophyllum stokesi, Calapoecia borealis, C. canadensis, Halysites gracilis, Dinorthis? sp., · Rhynchotrema capax, Catazyga cf. C. headi borealis, Maclurina? sp., Liospira? sp., Allumettoceras? sp., Spyroceras rarum, Trochonema umbilicatum. Sweetwater Canyon___ 9 Receptaculites sp., Halysites gracilis, Halysites cf. H. microporus, Bell (1955). Hesperorthis? sp., Resserella tersa?, Rhynchotrema increbescens?, tetracorals indet. Windy Gap______2 Calapoecia sp., Streptelasma sp., Receptaculites sp., Halysites sp_------Love (1939, p. 20); 3 Catazyga sp., abundant crinoid stems ______Keefer (1957; p. 167). quent investigations of North American Ordovician Furthermore, in Ross' opinion ( 1957b, p. 463) "the cephalopods by Flower (1946, 1952) have shown that paleontologic evidence for the Late Ordovician age of forms typical of the Bighorn occur both in rocks of the the [Lander Sandstone Member] is still impressive." Upper Ordovician Series in southern Ohio and northern Duncan ( 1956, p. 220) stated "General investigations of Kentucky and in beds of definite late Middle Ordovician American Ordovician corals have led the writer to be­ age in New York and Ontario. lieve that the relatively diversified and advanced fauna Reporting on more recent fossil discoveries ·at severa] in the lower part of the Bighorn dolomite and equiva­ horizons within the Bighorn Dolomite in the southeast­ lent strata must be indicative of Lat&----pDobably early ern Bighorn Mountains, Hose (1955, p. 45-48, 111, 112) Late-Ordovician age." concluded, from identifications by Josiah Bridge, that Conditions of Deposition the upper part of the basal sandstone (Lander Sand­ The Ordovician sea first invaded central Wyoming stone Member) is Middle Ordovician and the upper two in Middle Ordovician time and deposited sandstone members of the formation are Late Ordovician. Ross equivalent to the Harding Sandstone in a shore and (1957b, p. 468) considered the fossil-rich red-weather­ near-shore marine environment. The original distribu­ ing zone at the top of the formation in the central Big­ tion of this sandstone is not known, but Ross (1957a., p. horn Mountains to be Late Ordovician. Wanless and 18) suggested the possibility that the Harding equiva­ others (1955, p. 15, 16) expressed the opinion, based on lent was deposited across at least part of the Wind the presence of favositid corals, that the Leigh Dolomite River Basin, south and west of its present area of out­ Member in the Teton Range might possibly be of Silu­ crop, and that it was completely removed by later ero­ rian age, though corals of this type are also known in sion and reworking into the next younger Lander Sand­ some places from Upper Ordovician rocks. stone Member. Ross (1957a, p. 17) also pointed out, on From the evidence at hand it seems likely that at the other hand, that the irregular occurrence of the least the upper part of the Bighorn is Late Ordovician. Harding Sandstone equivalent may be due as much to B26 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING irregular original deposition as to any subsequent composition of the dolomite. Darton ( 1906c) believed events. After the deposition of the Harding Sand­ that the raised parts of the network are siliceous and stone equivalent, the region seems to have been raised hence less easily weathered than the surrounding dolo­ above the level of the sea again and to have eroded until mite. Blackwelder ( 1913, p. 615, 624) pointed out that later Middle Ordovician time or until Late Ordovician the rock contains very little silica and concluded that time depending on the age that is assigned to the Lander the network is more likely the result of differential Sandstone Member. weathering of compact fine-grained (more resistant) The deposition of the Lander Sandstone Member dolomite embedded in a matrix of more coarsely crystal­ marked the beginning of widespread marine sedimenta­ line and more porous (less resistant) dolomite. He tion in central Wyoming. Miller (1930, p. 213) (Blackwelder, 1913, p. 624) further concluded that the concluded from faunal evidence that a shallow sea branching structures are of organic origin, possibly cal­ transgressed from the Arctic southeastward into the re­ careous algae whose original organic structures were gion. The source of the sand is not known. It is known obliterated in the process of dolomitization. Ross however, that clastic rocks of Cambrian age were ex­ (1957a, p. 18) cited evidence, on the other hand, that posed in some parts of the region during the transgres­ the structures could not have been secreted by algae sion of the Ordovician sea. The nearest such area, above the ocean floor and suggested that the raised parts along the present southeast margin of the Wind River of the network were either minute solution channels or Basin, could have contributed some of the clastic debris passages of burrowing organisms filled by carbonate in the Lander Sandstone Member. The evidence is in­ mud. conclusive, however, be.cause much of the record was The presence of the small pebbles of· igneous and destroyed by pre-Mississippian erosion. No conclusions metasedimentary rocks in the basal part of the middle can be drawn regarding the irregular distribution and massive dolomite member in Dinwoody Canyon is enig­ thinness of the Lander; there is no evidence of erosion matic; so far as is known this is their only occurrence, or reworking of the sands before the carbonate sedi­ but they could have been easily overlooked in other out­ ments were deposited over them. On the contrary, the crops. The pebbles, though somewhat rounded, show contact between the Lander Sandstone Member and the little sign of having been extensively weathered before overlying massive dolomite appears to be conformable, reaching their ultimate depositional site (J. F. Murphy, and, in many places, gradational (Ross, 1957b, p. 462). oral commun., 1963), indicating, perhaps, that trans­ The thick carbonate sequence that forms the main port had not been for any great distance. There is no body of the Bighorn Dolomite was probably deposited evidence, however, to suggest that any part of the Wind in a warm shallow sea, but far enough from shore so River Range was emergent and being eroded during that very little clastic debris was carried into the main deposition of the Bighorn. Some parts of the Granite area of accumulation. The factors influencing sedimen­ Mountains might possibly have been eroded to the tation must have been constant for a long time, because Precambrian at this time, but these mountains lie 75 the strata over large areas are so uniform in composi­ miles southeast of Din woody Canyon (pl. 1). tion, color, and texture. Little is yet known, however, Much additional study is needed before more reliable about the time or mode of dolomitization. Blackwelder conclusions can be made regarding the origin of the ( 1913) was the first to consider this problem in detail; Bighorn Dolomite. Ross (1957a) summarized some of the more current At the close of Ordovician time the sea withdrew views on the subject. Both investigators conclude that from central Wyoming and a period of erosion ensued, the material was deposited originally as calcium carbon­ possibly lasting through all of the Silurian Period and ate; but, whereas Blackwelder (1913, p. 621, 622) be­ part of the Devonian Period. lieved that the limestone was dolomitized before lithifi­ cation, Ross (1957a, p.19) considered it more likely that DEVONIAN ROCKS, DARBY FORMATION dolomitization took place after lithification had begun. Definition According to Robinson (1963, p. 23, 24), the possibility The name Darby Formation was applied by Black­ that dolomite was deposited directly from sea water welder (1918) to a variable sequence of dolomite and should not be dismissed, even though dolomite is not shale lying between the Madison Limestone and Bighorn being deposited in quantity in modern open seas. Dolomite in northwestern Wyoming. Blackwelder The peculiar branching structures that are so charac­ (p. 420) derived the term from the canyon of Darby teristic of exposed surfaces of the Bighorn Dolomite Creek on the west slope of the Teton Range, but he gave (fig. 10) are clearly the result of differential weathering a 1neasured section from Sheep Mountain on the west related to variations in the physical and (or) chemical slope of the Wind River Range (about 20 miles south of PALEOZOIC FORMATIONS B27 the Warm Spring Creek loc., pl. 1) as the type. He The Darby Formation, as mapped in exposures ex­ considered the Darby to be Devonian and equivalent to tending southeast from Warm Spring Creek to Bull the Three Forks Shale and the upper part of the Jeffer­ Lake, ineludes at the top 5-30 feet of thin-bedded silt­ son Limestone in southwestern Montana as described stone, shale, and silty dolomite. According to Sandberg by Peale (1893, p. 27-32). ( 1963), this unit is in part equivalent to a dark shale In the Wind River Basin the Darby Formation, as unit of latest Devonian and earliest Mississippian age mapped, likewise includes all strata lying between the that is widespread in northern Wyoming and southern Bighorn Dolomite and Madison Limestone. Regional Montana and that overlies all older Devonian strata stratigraphic studies by Andrichuk (1951), Sandberg with marked regional unconformity. In parts of Mon­ (1963, oral commun., 1964), and Sandberg and Mc­ tana these strata were assigned to the basal beds of the Mannis (1964) have shown, however, that this sequence Madison Limestone (Sloss, 1952, p. 66) rather than to is very complex, and that it includes strata correlative the underlying Three Forks Shale. with the Beartooth Butte Formation of Early Devonian In the Bull Lake Canyon and Dinwoody Canyon age, the Maywood and Jefferson Formations of Late areas Murphy and others (1956) reported local channels Devonian age, and a dark shale unit of latest Devonian of sandy to conglomeratic siltstone and dolomite at the .and earliest Mississippian age. base of the Darby that have cut into underlying Big­ Strata assigned to the Darby Formation have the horn Dolomite. Some of the channels contain Early most limited distribution of any of the Paleozoic units Devonian fossils and represent the Beartooth Butte in the Wind River Basin, being restricted to the flanks Formation, whereas others contain early Late Devonian of the northern and central Wind River Range, the fossils and correlate with the Maywood Formation Washakie Range, and western half of the Ow1 Creek (C. A. Sandberg, oral commun., 1964) . The large Mountains (fig. 12). masses of breccia at the top of the Bighorn Dolomite at the Warm Spring Creek locality (see discussion above) Lithology and Thickness may also represent either one or both of these forma­ The Darby Formation is 193 feet thick at the north­ tions, but no fossils have been collected. western end of the Wind River Range, but thins progres­ The Darby Formation has been traced southeast sively southeastward to a wedge edge near Sinks Canyon along the east flank of the Wind River Range as far as (pl. 2). Except in canyon walls, these rocks are poorly Sinks Canyon (pl. 2), where about 20 feet of tan exposed, commonly forming topographic saddles or crystalline dolomite imbedded with large fragments of benches between the resistant Madison Limestone and white medium- to coarse-grained quartzitic sandstone Bighorn Dolomite. Where well exposed, however, they was reported by Strickland (1957, p. 27). Sections form a very distinctive unit because of their contrast along the north edge of the Wind River Basin are simi­ in color and in bedding characteristics with both the lar to those in the Wind River Range; the sequence overlying and underlying strata. becomes more sandy and finally wedges out in the cen­ In the northwestern Wind River Range the Darby tral Owl Creek Mountains (pl. 3). Strickland (1957, consists chiefly of resistant buff, gray, and brown thin­ p. 25) noted that toward the limits of its distribution, to thick-bedded ledgy dolomite in the lower part and the lower part of the sequence seems to be overlapped by greenish-gray and red soft siltstone, shale, and sand­ the upper part. Correlation of the upper stra~as stone interbedded with white, pink, and brown seen in sections near the wedge edges-with the dark limestone and dolomite in the upper part. The most shale unit of the northwestern Wind River Range is yet characteristic beds are dark-brown granular dolomite to be determined. Maughan (1963, p. C26) discussed which emits a strong petroleumlike odor when freshly the possibility, however, that clastic rocks assigned to broken; hence, the term "fetid" is commonly applied to the basal part of the Madison Limestone in the northern them. The granular texture of some beds is so conspic­ Laramie Mountains are in part equivalent to the dark uous that they are often mistaken for sandstone. The shale unit. dolomites are readily distinguished from the carbonate Contact With the Madison Limestone rocks in the Bighorn Dolomite below and the Madison The dark shale unit seems to be transitional with the Limestone above, although some of the lower beds of basal beds of the Madison Limestone in outcrops ex­ the Madison are superficially similar in places. The tending from Bull Lake Canyon northwest to Warm sandstone of the Darby is fine to coarse grained and Spring Creek (C. A. Sandberg, oral commun., 1964) . commonly contains abundant large rounded frosted Farther east and south, where the dark shale unit is grains. Such grains are also scattered through some of absent or poorly developed, an erosional unconformity the dolomite beds. may separate the Madison and Darby Formations, but to ~ (YJ

106° ~10o ,.. 109° 10so 10r 44° I~ 0 p A~ R K - I T I I I ~~c:' .1'./'"'\0j.._ I I w 46 A s H A K I E I _! I r-:·~ ~ / I \ - I N I ....:l I 44 ~ ) ' I I ....:l I • - I I '- I 45 I . 82 81 80 79 78 R 77W (:]111 ijiC .11_09 ~Hl8 "110 106 105 10-i, 103 _ lb.2 101 100 99 98 97 96 gs 91 .)l3 92 91 90 89 88 87 R6 85 84 8 3 1'<1 If '~ 144 I I 4 l !, 1 4--- - f-- ---..J ~rt-- ...... H 0 T ~ p R I N G s I ; l P=l ,, -,..c.H~ ·~ -· ...... I • --f- T I I p.. ~~ 43 I / ~"- ~...... Oc~- ~ :..- . !'-- o. 43 I I J o H N s o N l ~ jJ\ 'lrl' ( I ~ '- /~ - lTheril)Jpohs I • , 8 ~ ~I [), V' X -.....; I I I t < 1?:1 TjETojNI\ !4"- ~ ( \ ( r-7<-7!::"':' ~ I. /j" 4 0 t"' I ~~~ ' \ jD .L Y 1 I 41 ~ ...... _ ) Dub Js~ \ 6 - --- I ~ I 8 ,/ ~~- ~-- ~ -- _ ! " ! ~,\ I , / /) I =-: ...... 0 6 "':! 1 -l I ~' '\{ 5 4_ ~ 2 R I W R 1 E1 2 3 4 5 6} I ~ \ I k \ 4/ l 3 I X ~ '\\:~ )( I I 3 ( "\ I ,. 3 ~ - \ I~~ /3 I 1 ~ 3 7 '\ : '\~'\.X • I 2 I 3 I I I I I I 1 I ' II l I t t I --'r-'r" 1 z \ ,'\ I I I· I I I I '\II I I I I I I 00 t:;:j 1 3 ~ ~ II~-, • 1, n· I I I ; I I I I _N l I I I I t l .wM P:l ~3 ~-~ '1.. •• N \ or. I vert< n 13 { ... 43° A ~ -f- ' ... ~. \ k .,.f r--- __ 1?:1 34 1 ,J ~ 'Y" / s I 3 I P:l Pmedale '~~-- ~\~ ... -z.rf\ _/ -~ -~ ~- ~ I [ l 1 l 1 I I l'\ ~ t::d °Casper 10 33 33 w> n ~~ \ \~ 1, [aLan er l I I I I I i I I I l l 1" I ~ I 32 (;.\. I " ,.z I \ l 1: ~ \ 32 I 'i, I I I l I s 131 U / B I L I E I T I T I E ~ '\ 1,' ~ -r- -,~- -- -,-... t-- / I II ~ 11 / ~ 6--..=f-. r[ ~ 30 l P:l r TT- q-"~f-I--~-[1_~~l~_I_I~fo IIi -r I I I II lBout~r:r~~:a~~~~i~iver I > I t"' I l r-~--1--- r- ~ EXPLANATION I ""' '· -LLJJ--LLLlTJ I ~ L + 0 F R E Ml 0 N T I '>< X 27 e ~z z Surface section ~---~--+--+---1--+--t-·-+--+--ll---1--+---+- ! I I I I I I l I I I I I I II~ ~ 26 c A R B 0 N IP=l ~ • II Sl w IE IW A II Tlzs E l R I Subsurface section Ej T 82 I 81 80 79 7R lwkiL.mJ I j _99 98 97 96 95 94 ~ 93 I 92 I 91 I !tO L 89 I 88 I 87 I 86 I 815 I 84 t 83 Rhw too l T 0 10 20 30 MILES 2 4 I I 1 I i 1 I II 1: 1 1 l I I l -ll 1 T n 42°

FIGURE 12.-Thickness map of Darby Formation in central Wyoming. Based in part on C. A. Sandberg (written commun., 1963). Interval is 100 feet; isopachs are restored across mountain arches where rocks have been eroded; isopachs are dashed where control is inadequate. PALEOZOIC FORMATIONS B29

in most places observations have bee too inadequate the Darby in central Wyoming was deposited fairly to determine the nature of the contact i detail. close to shore and that the sand was blown into the sea. Age Presumably, therefore, a broad landmass extended Fish remains have been found inch nellike deposits across the eastern half of the Wind River Basin area at the base of the Darby Formatio and associated during this part of Late Devonian time. strata in Bull Lake Canyon and near y sections along The sea withdrew from central Wyoming before the the east flank of the Wind River Rang (table 4; Deni­ end of Devonian time, and a period of intense erosion son, 1951, p. 234). These fossils indicate that the lower­ followed. Thus, much of the erosion commonly attrib-­ most channels are Early Devonian in age, whereas the uted to the period immediately preceding the dep­ next overlying ones are early Late Devonian (Sandberg osition of the Madison Limestone may have occurred and McMannis, 1964; C. A. Sandberg, oral commun., instead before the end of the Devonian. In latest De­ 1964). Conodonts from the dark shale unit in Din­ vonian and earliest Mississippian time, the sea woody and Bull Lake Canyons are latest Devonian readvanced and the dark shale unit was laid down (table 4; Klapper, 1958, p. 1083) and t ose from Warm across the truncated edges of rocks ranging in age from Spring Lake are earliest Mississippi (C. A. Sand­ Late Devonian in western and northern Wyoming berg, oral commun., 1964). Most of t e rocks assigned (Sando and Dutro, 1960, p. 123; Sandberg, 1963, p. ~o the Darby Formation are, therefor, Late Devonian C19) to Precambrian in east-central Wyoming (C. A. In age. Sandberg, oral commun., 1963). Sedimentation seems Conditions of Deposition to have been continuous into Madison time in at least No positive record that rocks of Silurian age were de­ the western part of the Wind River Basin area, but the posited in the Wind River Basin area has been found. sea may have withdrawn from the central and eastern However, Silurian strata have been recognized in the parts for a short interval before Madison deposition. northern part of the Powder River Basin (C. A. Sand­ MISSISSIPPIAN ROCKS, MADISON LIMESTONE berg, oral commun., 1963) and also in !isolated patches Definition in southeastern Wyoming (Chronic anld Ferris, 1961) ; thus, Silurian seas may have covered rt least parts of The Madison Limestone was named and described by central Wyoming. Peale ( 1893, p 32) for the in the Three The region was emergent during m4 st of Early and Forks region of southwestern Montana. The age of the Middle Devonian time, although PJ.inor flooding formation in the type area was designated as "Lower occurred in at least the western part of the Wind River Carboniferous." In southeastern Idaho, Mansfield Basin area during the early part of the I eriod. In early (1927, p. 60-71) subdivided the Mississippian rocks into the Madison Limestone at the base and the Brazer Lime­ Late Devonian time the sea advance~ eastward, and perhaps southward, into the region, rst filling only stone (named earlier by Richardson, 1913) at the top; narrow channelways but later covering all the land sur­ the ages were considered to be Early Mississippian and face. However, the sea at this time probably did not Late Mississippian, respectively. extend much beyond the present kno1lrn limits of the The name Madision has long been used to designate Darby Formation (jig. 12). Thomati (1948, p. 84) all the rocks of Mississippian age in central Wyoming concluded, from the abundance of fro ted sand grains (Darton, 1906a, b; Blackwelder, 1918). However, as in the formation in sections near the 11ledge edge, that early as 1918 Branson and Greger (1918) described fos-

1 ~BLE 4.-Fossils from the Darby Formation [Generic and pecific names are quoted without modification from sources shown]

Collec­ tion Stratigraphic section No. Species References (pls. 2-5)

Dinwoody Canyon ___ _ 6 Fish remains_ ------J. F. Murphy (U.S. Geol. survey, unpub. field notes). Bull Lake Canyon ___ _ 2 Bothriolepis pate~; teeth _and scales of unidentifiable crossopterygians __ Do. 3 Apatogr:athu~ ~anans, Htndeoqellr: cf. H. acuta, Icriodus darbyensis, I. Klapper (1958). mehlt, ~Crt4 dU;s sp., Jt!eopnonwdus sp., Ozarkodina regularis, Pal­ matolepts g nt?clymem_ae, P. rug?sa, Polygnathus inornata, P. nodo­ costata, P. trwngulans, P. vannodosa, P. wyomingensis Spathog- nathodus ac ~leatus, S. jugosus. ' B30 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING sils of Late Mississippian age from the upper part of the red staining on many outcrops. Massive to bedded formation in Bull Lake Canyon. The lower approxi­ chert layers as much as 15 feet thick are present at mately 50 feet of this sequence, bearing what was con­ several localities, and chert nodules are abundant sidered to be a Ste. Genevieve fauna, was named the throughout. Caverns are common in the limestone, Sacajawea Formation, and the overlying beds, believed especially in the more granular beds. to be of possible Chester age, were included in the The upper member of the Madison Limestone, about Amsden Formation by C. C. Branson (1937; see fig.13). 100 feet thick, is chiefly thin to massive and irregularly More recently other geologists have attempted to sub­ bedded gray, tan, and yellowish-tan dolomite and lime­ divide the Mississippian sequence in the Wind River stone. Thin beds of red shale and siltstone are locally Basin area; the various classifications, many of which present. The carbonate rocks in some zones are highly follow the terminology established in central Montana fractured, brecciated, and cavernous and contain much (Collier and Cathcart, 1922, p. 173; Sloss, 1952; Easton, red cla;stic material. Conspicuous disconformities also 1962) are shown on figure 13. occur at a few horizons. None of the proposed classifications, however, has The limestone and dolomite vary in lithology and been demonstrated to be wholly satisfactory for geo­ texture; these rocks have been described in some detail logic mapping; many are based on lithologic and (or) by Andrichuk ( 1955) and Flanagan ( 1962) . paleontologic differences that may be easily recognized Thickness of the Mississippian sequence ranges from locally but not regionally. Denson and Morrissey 235 to 535 feet in the southern Wind River Range (pl. 2) ( 1952), for example, separated the Madison on the and from 335 to 635 feet in the Owl Creek and southern basis of insoluble residues, but stated (p. 40) ·that "Divi­ Bighorn Mountains (pl. 3). Along the south edge of sions of the Madison formations are frequently recog­ the Wind River Basin the thickness is 175-400 feet, along nized only with difficul•ty in the field." Therefore, in the east edge it is 245-275 feet (pis. 4, ·5). Madison this report all Mississippian rocks above the dark shale strata generally thin from northwest to southeast across unit of the Darby Formation and below the Amsden central Wyoming (fig.14). Formation are included in the Madison Limestone be­ Lithologies similar to those described above charac­ cause they constitute a natural lithologic unit for geo­ terize the Madison Limestone in other areas around the logic mapping. For convenience in stratigraphic and Wind River Basin. The lower member is everywhere paleontologic discussion, however, the formation has present, although Denson and Morrissey (1952, figs. 7, been divided into upper and lower members. 8) indicated that the basal part (their Lodgepole For­ In the summer of 1964, W. J. Sando collected fossils mation) is absent 1along the south margin. Tourtelot and studied the stratigraphy of the Mississippian rocks and Thompson ( 1948) observed lenses of sandstone at at several localities along the east flank of the Wind the hase of the lower member in the Wind River Canyon River Range. The preliminary results of his work area and, at the southeast edge of the basin, Jenkins were made available to us during the final stages of ( 1950) included about 60 feet of quartzitic sandstone preparation of the present report (W. J. Sando, writ­ and conglomerate at the base. As noted above, these ten commun., 1965) . clastic rocks, as well as those that have been assigned to Lithology and Thickness the underlying Flathead Sandstone, are all included The Madison Limestone includes 600-700 feet of re­ by Maughan ( 1963, p. C26) in the basal part of the sistant cliff-forming carbonate strata in the central and Madison Limestone in the northern Laramie Mountains. northern Wind River Range and adjacent parts of the The distribution of the upper member of the Madison W~ashakie Range. The lower member, 500-600 feet Limestone is more restricted than that of the lower thick, consists mainly of bluish-gray to gray massive to member, owing to post-Madison erosion; its exact limits thin-bedded crystalline limestone and dolomitic lime­ have not yet been worked out in detail. Denson and stone. The limestone is mottled by inclusions of tan Morrissey (1952, fig. 4) showed the upper member to be granular limestone or dolomite similar to those in the present in the Wind River Canyon area, whereas Andri­ Gallatin Limestone and the Death Canyon Limestone chuk ('1955, fig. 5) and Sando (written commun., 1965) Member of the Gros Ventre Formation. At most lo­ do not extend it that far east in the Owl Creek Moun­ calities the basal part contains thin beds of buff gran­ tains. Correlation in the southern Wind River Range ular dolomitic limestone similar to some of the beds in is also in doubt, but the unit may extend as far southeast the upper part of the Darby Formation. The lower as Sinks Canyon, or beyond. East of ~Sweetwater Can­ strata also contain masses of breccia consisting of an­ yon, however, the Amsden Formation seems to rest di­ gular limestone fragments in a red earthy matrix ; rectly on the lower member of the Madison, and the weathering and erosion of the breccia causes conspicuous upper member is absent. 1 Branson and • ! Denson and 1 ~ . I Th1s. report I Branson (1937) I _E3ranson (1 Stnckland (1957~~'1D'is~ey 2)~nd nch u k (1955) Flanagan (1962) l 9412 095

Tensleep Ten sleep Ten sleep Sandstone Sandstone Sandstone ...... ·::·

Upper part c Ten sleep g 0 (Not studied) (Not studied) (Not studied) (Not studied) ~ ~ Sandstone ro ro c ~ E E 0 0 0 ~ Upper LL. LL. I Amsden c c E 0~ Q) Q) 0 "0 "0 LL. (/) (/) ~ E E c 1-4 <( Q) Q <( "0 (/) E <( 6 ~ 1:·;:::;:::.::::. ~ Darwin Darwin

Sandstone 92ft [.:·."<·:-:··.. ·: Sandstone 1-4~ Member Member 0 ~

Lower Amsden (Beds of Beds of possible Chester(?) age Q) Brazer(?) c Upper Chester age) .!!!§I Sacajawea. "Upper" Upper "Upper" 96ft~ Limestone 0. 0. 0. .s member :::l ~ Member :::l Madison :::l unit Madison (/) equivalent 0 0 0 Q) ::?! (5 (5 E Sacajawea Sacajawea (5 .... Formation Formation c Q) c c :.J 0 0. 0 0 c .!!! 0. (/) .!!! 0 "0 =>t------1 :0 "0 .!!! ro (Unnamed ro ro "0 ::?! ::?! Mission Canyon! ::?! ro part) ::?! Lower and Middle and "Middle" and 580 ft Madison Limestone Madison Limestone I Madison Limestone member ~~ ID I Lodgepole Lodgepole lower units "lower" Madison and Miss ion ~ Formations ...J Canyon

FIGURE 13.~Nomenclature of Carboniferous strata, east flank of Wind River Range. Section shown is from Bull Lake Canyon.

to ~ 1-' o; ~ t_..:)

~10° 109° 108° 107° 106 T p A R K - ===F=Z="-, T I ., 44° I .!'-',./)...('\ - I I w 46 A s H A K I E I I ~~-~<.. ~ 1\,J'\~ _u I N I - I I 45 3 ! \. fO'i . 45 I I I C:J 00 ~~~ "' I" '" ''" 115} ,,/ '" .o> '"~ ,,, "' , , " , " <,;;- " ,, ' , , 00 ., " " " ; ., " I " I " I " eo '" H 0 T s p R I N G s f.>Ot144 I I ~4---f---r--IT ~ ,...,. i' ( 'llr.::l i_-- ti- V\ • • / / -- j il&:Ci

~ 43 ·:;;Z~ '~- _., - ~ •v '"-._.~,_ r \ I J o H N s o N ; Po< _;\ X \ ~ "- 1->. 1/_lf'x. e \ "'-rfperm poliill • _jt le J I - . ::S

'--ccrcr-r---- x .A0' " "!'--. ! 1 > 1 ~ T/"T1N I ::.., '" '~c 1x "'--r -c ~ 0 T 1 I ~ " ~ . · t'-. 1\ ~ '""- xr ;~ I I I 41 '"' ....:J( -2t_ ""'t\.\ 6 S:- ~. I 41v ,I _,.__ 1- ·- ·~ -t------~j_;.. b \'" I 11 t r·, f' '' ~ Otj:_'~-:-::-- r- 1- ~-=-- R '-=:t:: A I ~ I1 4o I '\, X 1 '\. . -- ~ 1 4o I "' } J. 1 I \ ~ \ 5 I ·, Y6 5 4 3 'J,? R w R 1 E 2 3 4 5 6_1 • / I 0 -- --r y.. \ , ~ l'%j ~ 1_.... li39 X J) \, \ I lA. ''\. . / 1/ 4 7 I 39 /. 1I '\ 1I '( ~ I ' _/ 1- / r-.... I /' T I>( I ~ ( '1\ v1- 3 J7 ' 7 ,l 38 ~~ _L t:rJ 1\ / I 1 r---1 \ 1 11 37 j 1 'I /'~ \ x v I r/ l 37/ i I I \ T£ :a I ... I \· \ t //'2 c / I / V 1 l 1 1I. z 136 /'' I \ \ v T ~ I II 36 ! . { \ / \ ~~ t::1 ~ ,.,.0 ~-~I j ·\ N. ,- ~Eivert r , ~~Q:)','; r ~'~r, w y \< , v-v- 1'-.:.::, N 1: ~~ liJ'uT B L E r T T 1E i _ \ \ _y ~ • ,,iJ'-- ~~-/ -r-,_,_~~Jk Q 30 X i I 2: 0 7 R 8 L-1 I I I I I AJo~ fl\ I~\ I I/1 ~ I r 17! ! ! ! L~/ !~:1 L~} \* I I ~ EXPLANATION r-I :a I t-<1 0 X -+ II>-< ~ Surface section rz 1-4 i II B I I I IN iI~ ~ • LJ:1~1~r·~:r+i~-J~+~1 m ([I 0 IIP=I Subsurface section Sj W IE ~ IRib.ll.l 101 1100 I 99 E I T lw I A II Tl25 E I R ~ I 'I I r ll X I luo 98 97 I 96 95 I 94 ~ 93 92 I 91 90 ~~A 87 86 8 84 83 82 I 81 I 80 I 79 I 78 IR J7W 0 10 20 30 MILES 1 2 4 I r I ! II 1: 1 I i I l I II I I I I 1420

FIGURE 14.-Thickness map of Madison Limestone in central Wyoming. Interval is 100 ft; isopachs are restored across mountain arches where rocks have been eroded; isopachs are dashed where control is inadequate. PALEOZOIC FORMATIONS B33

Ba.sal Unconformity is readily recognized in most outcrops, and the contact The unconformity at the base of the Madison Lime.­ is also easily identified on electric logs (pl. 6). stone is one of the most prominent in central Wyoming; Age however, as stated above, much of the truncation may The Madison Limestone is sparsely to abundantly have taken place in latest Devonian time, before the fossiliferous in many zones (table 5). Recent paleon­ deposition of the dark shale unit of the Darby Forma­ tologic studies by Sando (written commun., 1965) indi­ tion. The general distribution of various formations cate that the lower member is largely late Early Mis­ that directly underlie the Madison across the region is sissippian (late Osage) in age, and that the upper shown on figure 15. In the western part of the Wind member is early Late Mississippian (early Meramec) River Basin the formation overlies the Darby Forma- in age; thus, the bulk of the formation seems to corre­ 6on with apparent conformity, but eastward it rests on late with the Mission Canyon Limestone of southwest­ successively older beds and, in the southeast part of the ern Montana. Basal strata of the lower member may basin, directly overlies the Cambrian Flathead Sand­ be equivalent in part to the Lodgepole Limestone stone. The contact shows several feet of relief in many (I{inderhook and early Osage); as noted previously, places, and basal strata of the l\tiadison commonly con­ C. A. Sandberg (oral commun., 1964) has observed evi­ tain sandstone and siltstone in which fragments re­ dence that the contact between the Madison and Darby worked from the underlying formations are incorpo­ Formations is transitional in places. Sando found no rated. In the Bates Creek section (pis. 4, 5) the basal fossils to indicate that any of the rocks here assigned quartzitic unit was probably derived principally from to the Madison are as young as latest Mississippian the Flathead Sandstone. (Chester), as had been suggested by Branson (1937). Contact With the Amsden Formation Conditions of Deposition The Madison Limestone is separated from the over­ lying Amsden Formation by a conspicuous erosional In Early Mississippian time the sea may have with­ unconformity. The basal strata of the Amsden, gen­ drawn from all but the western third of the Wind River erally sandstone, were deposited on a very irregular sur­ Basin area; strata as old as the Flathead Sandstone face that shows several feet of local relief. The sand­ were exposed to erosion in the southeastern part. The stone commonly fills cracks which extend down ward sea advanced from the north and northwest at the into the underlying limestone. The sharp lithologic beginning of Madison deposition, and a thick succession change between the Madison and Amsden Formations of carbonate sediments were laid down across the entire

TABLE 5.-Fossils from the Madison Limestone [Generic and specific names are quoted without modification from sources shown] -- Collec- tion Stratigraphic section No. Species References (pls. 2-5)

Dinwoody Canyon ____ 7 Syringopora sp ______- _ -- - _ ------;- - Thomas (1948, fig. 3). Bull Lake Canyon ____ 4 Zaphrentis amsdenensis, Spir~fer pella~nsis, S. shoshone.n~is,. Compos'df! Branson and Greger trimtclea, Eumetria marcyt, Pugnmdes ottumwa, Sptnfenna brownt, (1918,p.312);~urphy Orthotetes kaskaskiensis, Chonetes chesterensis, Tetracamera subcuneata, and others (1956); Phillipsia sp.? Homalophyllites?, Caninophyllum?, Lithostrotion?, Helen Duncan (written Diphyphyllum?. . commun., 1954). Sinks Canyon ______4 Triplophyllites sp., Cyathophyllum sp., Syringopora sp., Dtphyphyllum Biggs, C. A. (1951). sp., Barbouria sp. Beaver Creek ______1 Spirifer cf. S. madisonensis ______- _--- _------Shaw (1955, p. 63). Sweetwater Canyon ___ 10 Syringopora surcularia, Spirifer sp ______- _------Bell (1955). 11 Spirifer madisonensis?, S. centronat1ts, "Orthotetes" sp. indet_ ___ - ____ - Do. Windy Gap ______4 Lithostrotion? sp., Syringopora sp., Diphyphyllum?, Spirifer striatus var. Love (1939, p. 26); madisonensis, Spirifer cf. S. increbescens, S. sp., Composita sp. indet., Keefer (1957, p. 169). crinoid columnals, fenestellid bryozoans. Conant Creek ______4 Spirifer centronatus? ______- __ ------V. L. White (U.S. Geol. Survey, unpub. field notes). Alcova ______1 Camarotoechia aff. C. sappho, C. sp., Spirifer aff. S. keokuk, Spiriferina Lee (1927, p. 52). solidirostris?, Cleiothyridina crassicardinalis. 2 Productus parviformis, Spirifer centronatus, Spiriferina solidirostris, Do. Cleiothyridina crassicardinalis. Bates Creek ______1 Spirifer centronatus, Composita sp. indet______----- _------Jenkins ( 1950) . _____ 1 Spirifer centronatus, Syringopora sur wlaria, Com posit a humilis- - - __ --- Lee (1927, p. 48). B34 GEOLOGY OF THE WIND RIVER BASIN, C'ENTRAL WYOMING

EXPLANATION D Darby Formation and associated strata

Bighorn Dolomite D- Gallatin Limestone

. Gros Ventre~ Formation

0 10 20 MILES I

42° 1 ~------~------~------~ 109° 108° 107° 106°

FIGURE 15.-General distribution of formations underlying Madison Limestone in central Wyoming. Dashed line indicates approximate outline of Wind River structural basin. region. Variations in thickness and type of carbonate fragmental limestone and dolomite in some places facies deposited at any given time or place probably (Andrichuk, 1955, p. 2198). reflect minor tectonic movements and consequent Marine sedimentation also took place during early changes in sea level. In the eastern and southeastern Late Mississippian time in at least the western and parts of the basin, debris from the underlying rocks was northwestern parts of the Wind River Basin area. To reworked into the basal strata of the Madison, but it was what extent the sea may have covered the eastern and spread only a short distance into the main basins of southeastern parts of the basin during this part of the depostion to the north and west. period is not known. If the Late Mississippian sea did Toward the end of the depositional period represented extend into the southeastern part of this region, the by the lower member of the Madison, evaporitic sedi­ sediments deposited were probably thin and hence ments accumulated in south-central Montana. Andri­ destroyed by post-Madison pre-Amsden erosion. chuk (1955, p. 2198) attributed this accumulation to Evaporites accumulated in westernmost Wyoming extreme shoaling conditions which hindered free circu­ (Sando and Dutro, 1960, p. 124; Wanless and others, lation of marine waters. As the circulation became more restricted, particularly in areas of deeper water 1955, p. 28, 29) and in northern Wyoming (Andrichuk, surrounded by shoals, the water became progressively 1955, p. 2204) in Late Mississippian time. These more saline and eventually evaporites were precipi­ deposits do not extend into central Wyoming, but the tated. Conditions did not favor evaporite deposition conspicuous brecciated and cavernous zones in the upper farther south in northern and central Wyoming during member of the Madison Limestone may represent evap­ Early Mississippian time, but shoaling across the major orite beds that were leached during periods of emer­ shelf area is indicated by the presence of oolitic and gence, probably in Late Mississippian time. PALEOZOIC FORMATIONS B35

PENNSYLVANIAN ROCKS Popo Agie River, and the first massive sandstone up­ AMSDEN FORMATION 2 ward in the section is the Tensleep Sandstone. Definition C. C. Branson (1937) later referred the basal part of The Amsden Formation was named and described by the Upper Mississippian sequence (bearing a Ste. Gene­ Darton ( 1904, p. 396) from exposures in the northern vieve fauna.) in the Bull Lake region to the Sacajawea part of the Bighorn Mountains; in it he included all Formation and the overlying limestone of possible the strata lying between the typical blue-gray limestone Chester age to the "lower Amsden." The "upper Ams­ of the Madison and the massive crossbedded sandstone den" (fig. 13), according to Branson, "consists of 80 of the Tensleep. In the type area he described a red feet of sandstone [Darwin Sandstone Member] over- . shale sequence, normally with a basal sandstone, in the lain by 96 feet of limestone, sandstone, and shale." Still lower part of the formation and interbedded limestone later it was proposed (Branson, 1939 ; Branson and and sandy and cherty beds in the upper part. Darton Branson, 1941) that the name Amsden he abandoned in ( 1906a, b) traced these units throughout the Bighorn this region, and that all strata of Pennsylvanian age be and Owl Creek Mountains. Blackwelder (1918) referred to the Tensleep Sandstone. No indication is identified the Amsden Formation in the Gros Ventre given that the authors recognized the Darwin. The Range and northern and central Wind River Range, controversial nature of these proposals has fostered ex­ and named the basal sandstone, which is thick in this tensive investigation and discussion of the Amsden Fo:­ region, the Darwin Sandstone Member from Darwin mation in central Wyoming. Details may be found In Peak in the Gros Ventre Range, about 25 miles south­ many published papers, including Love ( 1939, p. 23, 24; west of the Warm Spring Creek locality (pl. 2). Dar­ 19·54), Thomas ( 1948, p. 86, 87), Burk ( 1954, p. 2-4), ton and Blackwelder believed the formation to be Andrichuk (1955, p. '2178), Shaw and Bell (1955), largely Pennsylvanian, but both suggested that the Keefer (1957, p. 172), Strickland (1957, p. 23-25), and lower· part might be Mississippian. Easton (1962, p. 21, 22), and in unpublished theses by Although the Amsden Formation can be recognized Biggs (1951), Bell (1955), Gorman (1962), and Bearce with certainty throughout most of central Wyoming, (196·3). . an anomalous situation at the southern end of the Wind The problems regarding the age and correlatiOn of River Range has given rise to considerable confusion the Amsden Formation have been compounded because and oontroversy regarding its age and correlation. In the Darwin Sandstone Member is unfossiliferous, be­ 1918, Branson and Greger ( 1918) reported a Late Mis­ cause it is poorly exposed in critical areas in the southern sissippian fauna from red ferruginous shale and sand­ Wind River Range, and because it thins southward and stone overlying the Madison Limestone south of the cannot be identified specifically in the vicinity of Little canyon of the Little Popo Agie River (west edge of T. Popo Agie canyon where Branson and Greger ( 19'18) 31 N., R. 99 W.). They (Branson and ·Greger, 1918) first reported Late Mississippian fossils from the lower referred these beds to the Amsden Formation, but be­ part of the Amsden. In 1955, however, Sh~w and Bell cause the exposures are poor (the fossils were collected (19·55) trenched a section of the controversial red beds from slope wash) , they presented a measured section along Cherry Creek (sec. 19, T. 31 N., R. 99 W.), sou~h of the Upper Mississippian rocks (upper member of of the Little Popo Agie canyon, described the rocks In the Madison Limestone of this report) in Bull Lake detail, and made extensive fossil collections (fig. 16). It Canyon as a lateral equivalent, noting (p. 310) that is apparent from Shaw and Bell~s study t?at the con­ "The iron, sandstone, and shales of the [Amsden in the] troversial section about 70 feet thick, contains Pennsyl­ Popo Agie region do not appear [in Bull Lake Canyon] vanian fossils in ;he upper part and Mississippian fossils and the rock is mainly dolomite and limestone." They in the lower part. However, they (Shaw and Bell, failed to recognize that the prominent sandstone over­ 1955) believed that the Mississippian part correl~ted lying the Upper Mississippian rocks in the Bull Lake temporally with the upper member of the. Madison area was actually the basal sandstone of the Amsden Limestone at Bull Lake, whereas Sando (written com­ (Darwin) rather than the Tensleep Sandstone. This mun. 1965) interpreted the fossils from Cherry Creek miscorrelation probably arose for two reasons: ( 1) the to be 'younger than those at Bull Lake. (See di~ussion red shale beds are not present in Bull Lake Canyon; below of age relations within Amsden Formation.) and (2) the Darwin Sandstone Member is either absent Lithology and Thickness or poorly represented at the locality south of the Little In the northwestern Wind River Range and adjacent

2 Since the preparation of this report, W. J. Sando (written com­ Washakie Range the Amsden Formation ranges in mun., 1965) has collected fossils from the Amsden Formation in the thickness from 210 to 355 feet. The Darwin Sandstone western Wind River Basin which indicate that the lower part is Late :\Iississippian in age ; see discussion of age of Amsden Formation. Member at the base consists of cliff-forming red, gray, B36 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

Composita trinuclea, Composita sp., Linoproductus sp. ident., Spirijer opimus Composita ovata, Composita subtilita, Composita trinuclea, Com­ posita sp. ident.,Eumetria sp. ident., Spirijer opimus, Spirijer sp. ident., Wellerella sp. ident. Composita trinuclea, Composita sp. ident., Dictyoclostus sp. ident., Eumetria sulcata, Linoproductus sp. ident., Spirijer opimus, Spirijer sp. ident., Wellerella osagensis? Composita trinuclea, Composita sp. ident., Eumetria verneuiliana, Eumetria sp. ident., Grijjithides moorei, Linoproductus croneisi, ? Myalina sanctiludov1:ci, "Orthotetes" sp., ? Palaeonoeilo amsdenensis, Productus phillipsi?, "Pustula genevievensis," Spirijer welleri, Spirijer sp. ident. Eumetria verneuiliana, Grijjithides moorei, ? Palaeoneilo amsdenensis, Productus phillipsi?, Spirifer weller·i Eumetria verneuUana, ? Palaeoneilo amsdenens·is, "Schizophoria swallovi,'' Spirijer welleri, "Spirijerina" browni, Torynifer ct. T. setigera

EXPLANATION

[_J0 . Sandstone

Siltstone

Shale

Claystone ~ Amsden Formation ~ Madison Limestone Sandstone lenses

Limestone I Red and maroon strata

FIGURE 16.-Section of lower part of Amsden Formation at Cherry Creek, sec. 19, T. 31 N., R. 99 W. Based on Shaw and Bell (1955, p. 334). PALEOZOIC FORMATIONS B37 and white fine-· to medium-grained crossbedded to mas­ sections it can be separated into a basal gray to buff sive moderately porous and friable sandstone. In sandstone (generally correlated with the Darwin Sand­ lithology and outcrop appearance it is strikingly sim­ stone Member) , a middle red shale and siltstone, and an ilar to the Tensleep Sandstone. Thickness of the Dar~ upper light-gray, buff, and tan cherty limestone and win has a considerable range, from a minimum of about dolomite. In some places in the southern Bighorn 30 feet to a maximum of 170 feet. The range in thick­ Mountains, however, carbonate rocks are scanty, and ness, however, seems to have no uniform trend; it prob~ the tripartite division cannot readily be made. rubly is due chiefly to the irregular erosion surface on Along the south margin of the Wind River Basin the which it was deposited. basal sandstone of the Amsden, also generally referred The upper part of the Amsden Formation is a variable to as the Darwin Sandstone 'Member, is 20'-50 feet thick sequence of dolomite, shale, sandstone, and limestone and is overlain by 80-130 feet of chiefly red and gray ranging in thickness from 180 feet to about 300 feet. shale and siltstone and locally a few thin beds of sand­ Colors most common are red, green, gray, and buff. stone and cherty limestone and dolomite. In the Bates The unit is generally poorly exposed because most of Creek and Casper Mountain sections (pl. 5) , at the the strata are nonresistant, but it produces characteris­ southeast edge of the basin, all Pennsylvanian rocks have tic red, tan, and yellow soils. In many places, directly customarily been included in the lower part of the overlying the Darwin Sandstone Member, is a red shale Casper Formation. Lee ( 19·27, p. 49) correlated 85 about 40 feet thick that contains many hematitic nod­ feet of red shale at the base of the Casper on Casper ules or pisolites. It forms a conspicuous red zone Mountain with the lower red shale of the Amsden For­ along the weathered slopes. Thin beds of sandstone mation. However, it is now known that the lower part occur mostly in the upper part of the formation and are o£ the Pennsylvanian sequence in this area is younger typically fine grained, hard, and quartzitic. The dolo­ than the Amsden (fig. 18) and hence is not equivalent mite and limestone are massive to thin bedded and are in a time-stratigraphic sense. generally cherty. Slight disconformities occur locally Contact With the Tensleep Sandstone within this upper sequence. The contact between the Amsden Formation and the Southeast along the east flank of the Wind River overlying 'Tensleep Sandstone is marked by a sharp Range the Amsden Formation is 120 feet to about 400 change in topography £rom weathered talus-covered feet thick. The Darwin Sandstone Member, averaging slopes below to nearly vertical cliffs above. There is about 75 feet in thickness, can be traced as a relatively little evidence of a sedimentary break between the two well defined unit as far southeast as Canyon Creek, · formations, except locally (for example, Love, 1939, p. directly south of Lander in T. 31 N., R. 100 W. There 28), and in many places the contact is gradational where the member is about 30 feet thick, unconformably over­ thin beds o£ sandstone typical o£ the Tensleep are inter­ lies typical Madison Limestone, and conformably bedded with cherty carbonate beds. Agatston (1954, underlies red ferruginous shale. Farther southeast, in p. 515) proposed that the top of the Amsden be drawn sections from the north rim of Little Popo Agie canyon at the base o£ the lowermost sandstone typical o£ the (T. 31 N., R. 99 W.) to Sweetwater Canyon, strata Tensleep, even though thin carbonate, shale, and sand­ assigned to the lower part of the Amsden Formation are stone beds might be included in the Tensleep. Because chiefly interbedded red shale, siltstone, and sandstone. of the uncertainty of the con tact, the Tensleep and Ams­ A 15- to 30-foot basal sandstone is present in most sec­ den Formations have been mapped as a single unit in tions, but it is generally thin bedded and easily eroded, some regions, particularly in northwestern Wyoming and hence forms a much less distinct unit than the Dar­ (Love ~and others, 1951). For the same reason the two win Sandstone Member farther north. Although formations are combined on the isopach map (fig. 17). many workers have considered this basal sandstone to Age represent the Darwin, specific correlations of the var­ Fossils have not been found in the Darwin 8andstone ious sandstone units are still very uncertain. Member o£ the Amsden Formation, but several zones The upper part of the Amsden Formntion can also above the 'Darwin are fossiliferous, particularly along be traced throughout the central and southeastern parts the east flank o£ the Wind River Range (table 6). Until of the Wind River Range. Toward the southeast end recently, all the £ormation above the Darwin was con­ of the range, however, the sequence contains a higher sidered to be Pennsylvanian (probably Morrow and proportion of sandstone and red beds than it does in the Atoka; fig~ 18) in age ('Burk, 1954, p. 5 ; Shaw and Bell, central and northwestern parts. 1955, p. 335; Shaw, 1955, p. 62; Agatston, 1957, p. 32; The Amsden Formation is 190__,250 feet thick in the Gorman, 1962) . Furthermore, despite the fact that Owl Creek and southern Bighorn Mountains. In most red strata assigned to the lower part o£ the Amsden in td ~

"1.10° 109° 108° 10r 106 :I "' l p A R K - F=f="=-r T F="- I ., 44°

I ~6-c.. -" ,; /'.J"\/'\. \.,. I I w 46N A s H A K I E I I I I 45 ) ) - I _., I \_ I 45 111 J:[]~ 6J l1c 1o9 '1'67 106 105 104' 1o3_ 1b2 101 100 99 9oiii 97 gr; -95 9:\l ,Jl3 92 90 3q 88 87 8" 1 I 84 I 83 ' ' ~ ~108 91 R~ <~<:: w -.... , ....._ 144...... _ • _ 1 1 n ! ~- - t-- -t--..>< - · -~o p-- H C T I' S iP R I N G S t I' 'j. i g I I ll: T~ v / ..,. \ b...... -7'' ~ - - I-- -r """'"~...... __ I I 1 I H t],\ ~ ----.... /X / ( ...... ~~. ~-~ ./'7 • -lT . -1-1-4 ~ : r-.... I J 0 T ~ I ( ._ ...... ·1-. 8 -.... l.ooi ...... r- ' D c 0 TjETOINi ~' x, .. l-soK>-r-...... x t:.:.:=!.z ~ X """ i~ - 42 -t...... -.... ~ ... I }.-n t".l v•; 0 f I 1 ..,- yl ~~ ~: ...... '!'\. ~ ~ ~ ")-./J 1 L i ~('" /")(~X lr>DubJ>i' ..V ~..-~ 6 '...... _ ~~ ~ ~- r-- ·E 00 r::-: '""; -,:::__-,_7\. ~ ----{ _ _ _, 8 - 17 '\. <_ ... v "' 1\-- t~--. ,_:.t,_--::_r- I.- -e- - "' ""--- I ~ 4o / _ 1 """" "'1.7 l 40 X'\ I l_ ~ k - ~ 5 l!i~ "'- 0 1---- ~' \ '--1.6 ""-oS_ 4 3 2 R I W R 1 E.~- 3 4 5 6 f 1 '~ \ 1 ~ ~ J I 39 \ _x1 t"' ..... ~ -- I 39 I i'~" ~ I / '\ I / 4 ~Q ·, 1I 8 ~38 y 'i\ v ;;:._ ..__ r-...... '' "- -r 38 i: \-IJ 1 I I' f----:V \.. I \ / ( • 3 I l ' I \ I ~ lL I ~;;; I / .... • / I \ • I Htoo~ ~~ ' I" A "IOU'" I 37 I "' • iJ ~ 'I\ ~ 2 ' Jill, z 6, \ 1/ \ , 7 v .r = --... l ' I I I t J:J t:1 3s e alij;(ert n / s l\1\ I I I t1 \.{'J \ ~ 3 i ""-...: ::tl r<'' 430 I '-..{ 1\ T i "' A T 'lit 0 '7 , ~r ~ ;> ~ "PmOOall /--'\ L- h,ill r~~ /c_G -/,- ~ ( " ; r'\ 1\., \!'-- -\ I ::tl 1 1 1 00 1 ~ }""f" \ I\ ' °Ca:sper 10 ,- l '~,-~f,i\lf x1 1 TrJ:: \ " I<~ "'I, I 1 ~ ', I I r (;\ K\ kx • \ " l '6, \ '~ ~ ",.I IX 1: -~ 31 j s 1 U r B I L E IT IT IElI \ \ ~vn I 3l.---r- !---+-1 --\t---r~ -~--~~ v ..-'tL 41 I ~ t\ ' ,. I I r ' ~- I I 30 r--1 L--. lA ~ ~ I rl\ f Ti-'I I~ \ko ~ou:tr~~i:a~~~~i~irer I I II -T I If • I m I I ~ EX PLANA TI 0 N r-I J I ~ l I I ·rrjrfffi~ffi-t-~-tprtl~~c-•-+ 0 X -+ 1>-o ~ Surface section I LJ F LRTET~ MJ-OKN~i'ZJ, ~ -1==-Tir I I I I I I I I : : 0 I I I~z I -- I I I A I I I R I I B -+---1:_ --L'·~~ "__ t_t_T c I< ~ N ,~ Subsurface• section ~ IT~~~~~~~~~~~-L~~~~~~~~~~~~~~~~~~~~~~UL~~~~~~_,~~~~80 79 I 78 ~J7: 0 10 20 30 MILES I I 1 42°

FIGURE 17.-Thickness map of Tensleep and Amsden Formations in central Wyoming. Includes Casper Formation in southeastern part of Wind River Basin. Based in part on W. W. Mallory (written commun., 1963). Interval is 100 feet; isopachs are restored across mountain arches where rocks have been eroded; isopachs are dashed where control is inadequate. PA!JEOZOIC FORMATIONS B39 the southern Wind River Range contain Mississippian W. J. Sando (written commun., 1965) has obtained :fossils, many workers believed that the conspicuous ero­ evidence to show that the above reasoning is erroneous; sional unconformity at the base of the Darwin Sand­ fossil collections obtained by him from a locality along stone Memher marked the Pennsylvanian-Mississippian I-Iorse Creek north of Dubois (near Windy Gap sec­ boundary. Such a boundary would correspond to the tion, pl. 3) indicate that the systemic boundary actually widespread unconformity between the two systems in occurs within the red shale sequence above the Darwin. most other regions across the continent (Moore and Sando therefore interprets the Darwin Sandstone Menl­ others,1944,p.663). ber and overlying red shale (at least as much as 73 :ft

AGE WESTERN WYOMING I CENTRAL WYOMING Casper Mountain z - Des Moines Tensleep Sandstone Tensleep Sandstone en en / ::::;) z 0 e5 Atoka /?/ ~ a... Amsden Amsden z Formation Formation 0 Morrow co _, 0:: -? ?~? z z

FIGURE 18.-Schematic diagram showing approximate intervals of time represented by Mississippian and Pennsylvanian formations in central and western Wyoming. Interpreted from data in Thomas and others (195'3), Love (1954), and Agatston (1954).

TABLE 6.-Fossils from the Amsden Formation [Generic and specific names are quoted without modification from sources shown]

Collec- tion Stratigraphic section No. Species References (pls. 2-5)

Dinwoody Canyon ____ 8 Pteria sp., Astartella sp., Entomis sp., Paraparchites? sp ______Eliot Blackwelder (U.S. Geol. Survey, unpub. field notes); identifica- tion by G. H. Girty. Bull Lake Canyon ____ 5 Climacammina sp., Endothyra sp., Bradyina sp., Textrataxis cf. T. mill- Murphy and others sapensis, Fusulinella gephyraea?, Spirifer cf. S. opimus, Spirifer cf. (1956); Henbest (1956, S. rockymontanus, Neospirifer? n. sp., Phricodothyris? sp. indet., p. 61); Love (1954). Composita subtilita, Mesolobus striatus, Antiquatonia n. sp., Mar- ginifera splendens, Punctospirifer? sp. indet., Linoproductus prat- tenianus, Pharkidonotus percarinatus, Plagioglypta? sp. Beaver Creek ______2 Orbiculoidea wyomingensis, Wellerella n. sp., Cancrinella boonensis?, Burk (1954, p. 6-7); modi- Cleiothyridina? sp., Linoproauctus n. sp., L. croneisi, "Marginifera" fied by Shaw (1955, p. ., n. sp., Spir(fer welleri, Allorisma. 63). ,) Composita sp. (not like Composita in the Spirifer welleri zone below it) __ Shaw (1955, p. 63). Sweetwater Canyon ___ 12 Spirifer occidentalis, Composita sp ______- ___ - _-- _------W. G. Bell (1955). Windy Gap ______5 Spirifer "opimus," Linoproductus n. sp., Composita "trinuclea," Bel- Love (1939,p.28);Shaw lerophon sp., Strophostylus? sp. (1955, p. 62). 6 Orthotetes? sp., Dictyoclostus portlockianus, Linoproductus prattenianus, Burk (1954, p. 7-8). Spirifer sp., Composita subtilita var. subtilita, C. subtilita var. trinuclea, C. subtilita var. ovata, C. sp., Cleiothyridina sp., Wellerella osagensis, Allorisma terminale. 7 Fusulinella sp ______------Love (1939, p. 28); Shaw (1955, p. 62). Conant Creek ______5 Chaetetes cf. C. milleporaceous ______- __ Love (1954). East Canyon Creek ___ 1 Allorisma cf. A. terminale ______Do. Alcova ______'l ,) Productus cora, P. hermosanus, Composita subtilita, Parallelodon? sp., Lee (1927, p. 52). Deltopecten? sp., Pteria sp., Plagioglypta? sp., Bellerophon crassus?. 4 Allorisma terminale, Pteria longa?, Deltopecten aviculatnm, Parallelodon? Do. sp., Schizodtts? sp., Pleurophorns? sp., Bellerophon n. sp., Euphemus carbonarius?, aff. N. nana. B40 GEOLOGY OF THE WIND RIVER BASIN, C'ENTRAL WYOMING above the top of the Darwin) to be latest Mississippian lory, 1963, fig. 195.2; Agatston, 1954, fig. 9); in some (Chester) in age, and infers partial or complete corre­ places its Precambrian core was breached. lation with the controversial red-bed sequence at the At the beginning of Amsden deposition a shallow sea base of the Amsden Formation along Cherry Creek in spread across all but the southeastern part of the Wind the southern Wind River Range. As stated above, pre­ River Basin, probably from the west and northwest, vious workers (Branson and Greger, 1918; Morey, 1935; and an extensive deposit of sand was laid down. Be­ Shaw and Bell, 1955) had considered this latter se­ cause much of eastern and southeastern Wyoming was quence to be early Late Mississipian (Meramec) in underlain either by Mississippian carbonate rocks or age and hence equivalent to the upper member of the Precambrian crystalline rocks at this time, the source Madison Limestone at the Bull Lake Canyon locality. of the highly quartzose debris of the Darwin Sandstone Sando (written commun., 1965), on the other hand, con­ Member is not known. W. W. Mallory (oral commun., siders the Late Mississippian faunas in the basal part 1964) suggests that the sand may have come from north of the Amsden at Cherry Creek to be of Chester age and east of Wyoming, but the evidence is not conclusive. and hence younger than the early Law Mississippian Sand deposition was followed by the widespread accu­ (:~1eramec) faunas from the upper member of the Madi­ mulation of red clay and silt that was spread across the son at Bull Lake. It should be noted that studies of shallow shelf areas from sources also as yet unknown. ostracodes from the Mississippian sequence in Illinois Presumably the highly ferruginous clay was derived (for example, Croneis and Funkhouser, 1938, p. 334; from a region in which regolithic soils were being de­ Coryell and Johnson, 1939, p. 214) suggested a Chester veloped, perhaps in some parts of southeastern age for forms similar to those identified by Morey Wyoming where Precambrian rocks are known to have ( 1935) as Meramec from the Cherry Creek locality. been exposed to weathering and erosion at that time. Based on the evidence obtained by Sando (written Fluctuations in sea level, probably in response to commun., 1965), the following conclusions seem war­ minor structural movements within the depositional ranted; ( 1) The Amsden contains strata of both Mis­ area, gave rise to an alternating sequence of limestone, sissippian and Pennsylvanian ages; (2) the basal beds dolomite, shale, and sandstone in the upper part of the of the Amsden are approximately the same age through­ Amsden Formation. Local disconformities within this out the Wind River Range, but are younger than the sequence, especially in the upper part (for example, upper member of the Madison Limestone; and (3) the Agatston, 1957, p. 29; Gorman, 1962), suggest that cer­ upper member of the Madison Limestone was cut out by tain areas were periodically raised above the level of the post-Madison pre-Amsden erosion in the southern Wind sea and briefly eroded; the southeastern part of the basin River Range. In the southern Wind River Range, it area remained emergent. The gradational contact be­ is still a matter-of conjecture whether the Darwin Sand­ tween the Amsden and overlying Tensleep indicates stone Member of the Amsden Formation disappears that there was no significant withdrawal of the sea at by facies change, by nondeposition, or by erosion. Pre­ the close of Amsden time. cise correlation of the various units of the Amsden in TENSLEEP SANDSTONE the Wind River Basin with those of the type section Definition along Amsden Creek in the northern Bighorn:Moun­ The Tensleep Sandstone was defined by Darton tains is also pro~lematic. Gorman (1962) concluded, ( 1904, p. 397) as the thick sandstone overlying the froril a study of fusulinids at the type section, that at Amsden Formation in the southwestern part. of the Big­ least the beds immediately overlying the unfossiliferous horn Mountains. The formation can be traced through­ basal sandstone (generally considered to be a Darwin out central and northwestern Wyoming, although on equivalent) are Pennsylvanian and that the basal sand­ Casper Mountain at the southeastern edge of the Wind stone is probably also Pennsylvanian. River Basin equivalent rocks are included in the lower

Conditions of Deposition part of the Casper Formation (Darton, 1908). Bran­ son (1939) included all the Amsden Formation in the After the Madison Limestone was deposited, central Tensleep Sandstone in the central Wind River Range, Wyoming emerged, and the exposed carbonate rocks but this usage was not widely adopted. were eroded into a very irregular surface. In the cen­ Lithology and Thickness tral and southeastern parts of the Wind River Basin The massive cliff-forming Tensleep Sandstone is one area, erosion cut down into Lower Mississippian strata. of the most distinctive Paleozoic formations in there­ A broad positive area occupied southeastern Wyoming gion (figs. 3, 19). Along the east flank of the Wind and extended as far northwest as the region along the River Range the formation is predominantly buff, tan, southeastern margin of the Wind River Basin (Mal- cream-colored, and white fine-grained massive to cross- PALEOZOIC FORMATION'S B41

FIGURE 19.-Cliff of Tensleep Sandstone along north side of Middle Popo Agie River, Sinks Canyon. Note crossbedding in left half of photograph.

bedded sandstone (fig. 19). Most of the rock is rather 5), all Pennsylvanian rocks are placed in the Casper porous and friable, but some beds are hard and quartz­ Formation (Darton, 1908, p. 418). Sandstone beds itic. Thin irregular beds of chert are common, and generally similar to the Tensleep Sandstone occur in because of the gradational contact with the underlying the middle and upper parts of the Casper, although Amsden, the basal part of the Tensleep may include a these beds are younger. (See fig. 18).

few thin beds of limestone or dolomite. Carbonate COntact With Park City and Equivalent Rocks beds also occur higher in the formation. Many of the outcrops weather brown and rusty brown, and, viewed A conspicuous erosional unconformity separates the from a distance, some appear to be nearly black. Tensleep Sandstone from the overlying Park City For­ Coarse talus generally accumulates at the base of the mation and equivalent rocks of Permian age in nearly cliffs and obscures the lower part of the formation as all exposures around the margins of the Wind River well as much of the underlying Amsden. The Ten­ Basin. The contact is distinctly uneven and shows sleep Sandstone is only about 215 feet thick at the from a few inches to several feet of relief in many northwest end of the range, but it thickens gradually places. The basal beds of the Permian sequence are to more than 600 feet at the southeast end (pl. 2). commonly conglomeratic. Blackwelder (U.S. Geol. The lithology of the Tensleep Sandstone is fairly Survey, unpub. field notes) reported that in the Din­ uniform. Thickness along the north edge ranges from woody Canyon area as much as 37 feet of sandstone at 200 to 440 feet, the thickest sections being in the eastern the top of the Tensleep was cut out underneath the Owl Creek Mountains and the southwestern Bighorn unconformity. The time span represented by the un­ Mountains (pl. 3). Along the south margin of the conformity over much of the basin area includes Late basin the formation is 220- 350 feet thick (pl. 4). Pennsylvanian and earliest Permian times. The con­ In the Bates Creek and Casper Mountain areas (pl. tact is easily defined on electric logs (pl. 6). B42 GE10LOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

Age is Late Pennsylvanian (Missouri and Virgil). In the Fossils have been collected from several different Casper Mountain area the lowermost part of the Casper zones within the Tensleep Sandstone at many scattered Formation may be Middle Pennsylvanian (Agatston, localities in central Wyoming (table 7) . They indi­ 1954, table 5), but fusulinids of Late Pennsylvanian ca:te that most, if not all, of the formation within the age have been found near the base and in the middle Wind River Basin area is Middle Pennsylvanian (Des part of the sequence, and Early Permian (Wolfcamp) Moines) (Love, 1954; Agatston, 1954, p. 529; Hen best, fossils in the upper part (Thomas and others, 1953, fig. 1954; Hoare and Burgess, 1960). Love ( 1954) sug­ 2 and table 2). An interpretation of the regional age gested that in westernmost Wyoming the upper part relations is shown on figure 18.

TABLE 7.-Fossils from the Tensleep Sandstone [Generic and specific names are quoted without modification from sources shown]

Collec­ tion Stratigraphic section No. Species References (pis. 2-5)

Warm Spring Creek___ 8 Derbyia crassa, Linoproductus prattenianus, Dictyoclostus hermosanus, Hoare and Burgess (1960, Spirijer opimus, Neospirijer cameratus, Composita sp., Straparolus p. 711-715). (Euomphalus) cf. S. (E.) plummeri, Dentalium (Plagioglypta) sp., Ameura sp., Millerella? sp., fusiform fusulinid, either Fusulina sp., or Triticites sp. Dinwoody Canyon____ 9 Derbyia? sp., Productus cora, P. scmireticulatus, P . sp., Spirijer rocky­ Eliot Blackwelder (U.S. montanus, Composita subtilita, Aviculipecten sp., Pseudomonotis Geol. Survey, unpub. hawni?, Pleurophorous? sp., Dentalium sp., Euphemus carbonarius, field notes) ; identifica­ Bellerophon percarinatus, Pleurotomaria sp. tion by G. H. Girty; Branson (1939, p. 1210). Trout Creek______1 Calcitornella sp., Climacammina sp., Endothyra sp., Bradyina sp., Fusu­ Henbest (1954, p. 52); lina leei?, Wedekindellina sp. Love (1954). Sinks Canyon______5 Dictyoclostus .~ermosanus, Linoproductus prattenianus, Squamularia per­ Branson (1939, p. 1208). plexa, Composita subtilita. Wind River Canyon__ 12 ldiognathodus sp., Streptognathodus sp., Prioniodus sp., Hindeodella sp., Branson (1939, p. 1207). Helodus sp., Cladodus sp., Fusulina n. sp., Staffella sp. Bates Creek ______2 Fusulinids ______C. E . J enkins (1950). Casper Mountain__ __ _ 2 Triticites kellyensis, projected into section from about 6 miles farther Thomas and others (1953). east.

In the Mayoworth area along the east flank of the (1954, p. 564) suggested that it might have been sup­ Bighorn Mountains, about 40 miles northeast of the plied by uplifts west and south of Wyoming. Thin Deadman Butte section (pl. 1), Verville (1957) beds of limestone, thickening toward the main area of described fusulinids and Rhodes ( 1963) described cono­ carbonate deposition in eastern Wyoming (Agatston, donts, of Wolfcamp age in sandy limestone beds which 1954, p. 564) , were deposited along with the sandstone they assigned to the uppermost part of the Tensleep as the sea advanced and retreated. The only land that Sandstone. According to E. K. Maughan (oral com­ stood above the sea in central Wyoming was in the mun., 1963), however, these strata are lithologically Casper Mountain area, where sedimentation did not similar to, and probably correlate with, the N owood occur until later in late Middle Pennsylv-anian or Late Member of the (McCue, 1953) Pennsylvanian time. In southeastern Wyoming a farther west in the southwestern Bighorn Mountains broad positive area furnished sediment until it was sub­ (pl. 3) and hence form no part of the Tensleep as we merged in Early Permian time ( Agatston, 1954, p. 565). have used it in the Wind River Basin area. If sedimentation occurred in the Wind River Basin, Conditions of Deposition exclusive of the Casper Mountain area, during Late Following the deposition of the Amsden Formation a Pennsylvanian time, all record of it was destroyed by shallow sea remained in central Wyoming, although post-Tensleep erosion. The distribution of thickness some moderately unstable areas were at times raised and facies within the Pennsylvanian sequence (Love, above the base level of deposition, thereby producing 1954; Agatston, 1954), however, suggests that ( 1) much local disconformities within the boundary zone between of central Wyoming was raised above the level of the the Tensleep and Amsden Formations. At the begin­ sea at the beginning of Late Pennsylvania time; (2) the ning of Middle Pennsylvanian (Des Moines) time, sea retreated eastward into eastern Wyoming and west­ quartz detritus was spread across the basin of deposi­ ward toward the major geosynclinal area in south­ tion. The source of the sand is not apparent; Agatston eastern Idaho; and ( 3) detritus eroded from the PALEOZOIC FORMATIONS B43 exposed Tensleep Sandstone was redeposited in basins Phosphoria was then widely accepted in the central and of deposition that flanked the uplift. Marine sedimen­ western parts of the Wind River Basin for the rocks tation continued along the southeast edge of the Wind lying between the Tensleep Sandstone and the Dinwoody River Basin and areas to the east through all Late Formation. Limited use of the name Embar contin­ Pennsylvanian ti,me, ·and in westernmost Wyoming at ued, but the term has long since been considered obsolete least until near the close of that epoch. (Thomas, 1934, p. 1670, 1671) and was abandoned (McKelvey and others, 19·56, p. 2835). PERMIAN ROCKS In 1947 the U.S. Geological Survey began a syste­ NOMENCLATURE matic investigation of the western phosphate field, Rocks of Permian age comprise one of the most com­ which includes western Wyoming, northwestern Utah, plex Paleozoic systems in central Wyoming. Because eastern Idaho, and southwestern Montana. This pro­ it contains extensive phosphate deposits and is one of gram resulted in a comprehensive study and review of the most important reservoirs for oil and gas in the the stratigraphy, nomenclature, and correlation of the region, this system has also been one of the most widely Permian rocks (McKelvey and others, 1956, 1959). It studied. Marked lithologic changes occur from west was proposed that the sequence be divided into three to east across the-Wind River Basin, and many problems major lithologic facies, each being assigned to a differ­ exist in nomenclature and correlation. The regional ent formation; the general distribution of the various relations, summarized below, have been discussed in facies is shown on figure 20. Because considerable in­ detail by Thomas ( 1934), Tourtelot ( 1952), McCue tertonguing occurs between the different rock types, the (1953), McKelvey and others (1956; 1959), and Weich­ individual members of one formation in any given verti­ man (1958). cal section may be directly overlain or underlain by Darton (1906a, p. 17, 18) applied the name Embar members of another formation. (See Dinwoody Can­ Formation to a "prominent series of limestone and chert yon section, pl. 2.) Therefore, for geologic mapping, beds lying between the Tensleep sandstone and the Chug­ it was further proposed that the name of the for­ water red beds" along the north slope of the Owl Creek mation bearing the dominant lithology be given Mountains. The type section is about 6 miles north of preference. the Sheep Ridge section (pis. 1, 2). Darton (1906b, Within the Wind River Basin all the major types p. 35, 36) extended the term into the Bighorn Mountains, of facies are present-chiefly red beds of the Goose Egg but limited it to a lower limestone and shale unit only Formation (see following paragraph) in the eastern and did not include any of the overlying red shale and part; carbonate rocks of the Park City Formation in gypsum. Condit (1916, p. 263), however, recognized the central part; and mudstone, chert, and phosphorite that the marine strata graded eastward from the type of the Phosphoria Formation and variable amounts area into red shales containing many gypsum beds. He of sandstone of the Shedhorn Sandstone in the western ( p. 263) stated "In the Bighorn Mountains * * * the part (fig. 20). The distinction between the red-bed transformation of the Embar beds is so complete that and carbonate rock facies in the eastern third of the they ean only with difficulty be distinguished from the basin is relatively clear cut, but in the western third the overlying red beds composing the Chugwater forma­ separation of facies is often very difficult because of the tion [Triassic]." intricate intertonguing of many different rock types. In an early report on the northern Wind ·River Range, The principal lithology over much of the area, how­ Blackwelder (1911, p. 475) used the name Embar, but ever, is carbonate rock; consequently, the name Park he later (1918) separated the sequence into two forma­ City Formation and equivalents is used in this report tions. The upper unit, consisting of greenish-gray rather than the name Phosphoria Formation which has shale, siltstone, and sandstone now considered to be of been used more commonly in the past. Triassic age, he called the Dinwoody Formation from Thomas ( 1934) studied the intertonguing of lime­ exposures in Dinwoody Canyon. The lower part, pre­ stone with red beds in central and southeastern Wyo­ dominantly limestone, dolomite, chert, and phosphate ming, and named several of the eastward-projecting rock, he referred to the Park City Formation, a name tongues of the Phosphoria Formation. In a later re­ used earlier by Boutwell ( 1907, p. 443) in the Park City port, Burk and Thomas ( 1956) proposed the name district of Utah. Condit (1924, p. 11) con­ Goose Egg Formation for the red shale and gypsum cluded that the beds assigned to the Park City by Black­ sequence containing thin beds of limestone in the ex­ welder were more nearly correlative with the Phosphoria treme southeast corner of the Wind River Basin (fig. Formation as that unit had been defined by Richards 21.). The name was derived from the Goose Egg Post and Mansfield ( 1912) in southeastern Idaho. The Office along Wyoming Highway 220 at the west end B44 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING MONTANA ------, EXPLANATION I I

\ Mudstone, chert, and phosphorite (Phosphoria Formation)

Sandstone (Shedhorn Sandstone)

l J

I Carbonate rock I N f (Park City Formation) __ _]

Red beds (Goose Egg Formation)

I I I L-- -UTAH--~------~~~~l~~ ------_j

0 50 100 MILES

FIGURE 20.-Distribution of major facies in Permian rock·s in central and western Wyoming. Based on McKelvey and others (1959, p. 4).

of Casper Mountain; the type section is shown on plate rock types contain abundant phosphatic grains or pel­ 5. In this report the Goose Egg is extended northward lets, and many fossil shells are highly phosphatic. to include similar strata in the southern Bighorn Similar lithology characterizes the Park City Forma­ Mount,ains. tion toward the southeast end of the Wind River Range, PARK CITY FORMATION except for a gradual increase in limestone and dolomite. Lithology and Thickness Also, little sandstone or basal conglomerate is present In the northern Wind River Range and adjacent at most localities. Detailed descriptions have been pub­ parts of the Washakie Range, the Park City Formation lished by King (1947-1957) and Sheldon (1957), who consists of 150-260 feet (fig. 22) of interbedded chert, separated these r:ocks into several units for convenience limestone, dolomite, siltstone, and very fine grained in evaluating the phosphate deposits. Thickness ranges sa~dstone and a few thin beds of shale and phosphate from about 180 to 325 feet (pl. 2). The upper massive rock. Colors are predominantly tan, gray, and buff; the chert and carbonate units erode to very prominent dip phosphatic beds are dark gray to brown and black. The slopes along the entire east flank of the range (fig. 23). basal beds of the formation, 5-15 feet thick, are com­ The dip slopes are grass covered, but they are conspic­ monly conglomeratic and contain angular fragments of uously devoid of trees in contrast to the underlying white and gray siltstone, sandstone, and crystalline Tensleep Sandstone. quartz, and rounded pebbles and granules of black Along the south margin of the Wind River Basin the chert. The matrix of the conglomerate ranges from Park City can be traced as far east as the Conant Creek pink and gray dense sandy limestone to tan and pink area, where it is :about 350 feet thick (pl. 1). Farther coarse-grained sandstone. Chert occurs in thin beds but east, toward the north end of Rattlesnake Hills, the car­ more commonly as tubular twisted masses in thick­ bonate and chert facies grade into the red-bed facies of bedded limestone and dolomite. The twisted chert the Goose Egg Formation (Weichman, 1958). Thin masses, which are particularly abundant in the upper tongues of limestone project eastward into the red beds, half, are the most characteristic lithologic features of however, and are present throughout the eastern part the formation. Phosphate rock, generally black and of the Wind River Basin (fig. 21; see discussion of oolitic, is in beds only a foot or two thick. Some other Goose Egg Formation) .. ;;' ~ 0 ~..... Q ":: 0 ::0

0~ 2: r/J

FIOURFJ 21.- Exposures of Goose Eg·g Formation (l

t:d ~ to ~ 0)

107" .,J,.1o· 109° 1os• 1 I V : p ~ R K - T T F= ' I 4G ~~ .!'' / \....- f-k _J,.....---:::. 1\ ,· w 46A s H A K I E I I - '0 ;' ;·"- I " . - I ll N I I I ' 45 .~ I ' M- I i 45 I1 1 80 79 78 X I• 1a9 ~iX 8 --«57 •or;t 1o5 1~<1 1.Q.L 1;,, 10• 1a!' 99 98 97 96 fos . 9 4 93_ 92 91 9a 89 88 87 8b' "' 84 83 82 8 "' 1 , 1 '~ li2 wl li1 44 H 0 T S: P I N G S t \ ! 4~ fl- _::_ - t--f__ ~' k 1 i 1 ~'\ 43 II > -/--::~. . A 1\-' x·- ,...... • 4~ - ~~ • J o H N s o N \J I1 \ '0.. ~ ....-_]i,- \ ]T~ erm polis I ·'-:3 1 . . :E T IETojN : 4&. \\ 1>< ---1: · ~;o 42 ::>o-iY'-J.-/ I U< ~ 1 '- ( )·------~~ ~ lr ~ 4< • IX 1 u b I 1'- -\ ,j., b . . \X I X I I 0 I I 41 ...... u / 6 41 r- -- I I t... ..,.:Y ~~ v----.k ~ "-X .::-.._ _ r -+-- ~---r=*--r- - - ~ r------1--~ ~--'- >-< 1 I I i 4~- - ! "' / f ·--~- t\ "r---.. fo- • ~ ~--=- "'1\ ~-)<~ - I "-. \ 0 "'j -- •--~ ~0 ' ~\ ~ 13 4' 2 RW ~IE 2 3 4 56 !' 1A ' '· I (' I I 39 I " X I >-3 3~ 4 X !' \ I v •\ I , ~ 38 < ~ ~ .... ~ --11 10/ 38 ,· X \ I I I I I I ---1 \ I J e '-.. " ·, ;::: I 1 ~ 37 •1 1 ·, / ~ \ ~v 37 i ...... -- --'4: • g, ' I/...-'(' -\ 2 ., / - __.. ' '- ~ T --- / 36 ~ \/r \ _\ ! ll'' IL ~ 35 k-"'-1 J \. • N oiivert<>o °Clsper 33 33 X .) 1 I I \ ., ·r· ,r ~~Lat er V I • • • i r-· 32 X ~ l 1 I I I I er,\ I ~, ( ------· ---\3 2 ! • ~ I ' y_ I I I 31 1---'1 f===f f= ~ s 1 u B \',p_ X •\ \ ... / l1!~- ---t-- • L E T T E I p,... _c / I\ t--~j../ ~ 30 I'~ X f¥ ~II ' + o Bpu nd ~ry of_ Win~. Rli ~ '-"'l I I\ I \j I 1 - . I I i I structural bals1n > .. m t"' _j~- - __j r- ~--\- - EXPLANATION ~ I ~-111~0Ilf~ !; L L "r-~ • 0 ~ X 1 z Surface section 0 H:rn_:JJ:tti l~+t~ll4it R Il IIB Iim I I R I • • s E Ef T w A ! T l25 E Subsurface section 90 : 89 88 I 87 I 86 I 82 I 81 I 8o 79 78 R1b2 ·101 riOO I 99 98 97 I 96 1 95 94 . 93 I 92 I 91 ~~ 3 I I 0 10 20 30 MI LES 2 4 [ I II 1: 1 1

F IGURE 22.-Thickness map O:f Park City Formation and equivalents, in central Wyoming. Interval is 100 feet; isopachs are restored across mountain arches where rocks have been eroded ; isopachs are dashed where control is inadequate. PALEOZOIC FORMATIONS B47

FIG URE 23.- Prominent dip slopes ( "flatirons") of Park City Formation along east fiank of Wind River Runge, near· Fort Washakie. 'l'ree- · covered slopes in middle background are on 'l'ensleep Sandstone.

The Park City Formation is 200- 265 feet thick in Age the Owl Creek Mountains (pl. 3), and consists chiefly The Park City Formation is abundantly fossilifer­ of limestone, dolomite, dolomitic siltstone, and chert. ous, containing a predominance of brachiopods and These beds persist to the east end of the range, but far­ bryozoans (table 8) _ Coquina beds consisting almost ther east, in exposures at the west end of the Bighorn entirely of large specimens of a single fossil species oc­ Mountains, red beds and gypsum (of the Goose Egg cur locally, as do conodonts and fish and shark remains. Formation) are the dominant rock types (Tourtelot, Yochelson (1963) found that each major rock facies 1952, p. 50). At the base of the Permain sequence in has its own characteristic fossil assemblage and stated the southwestern Bighorn Mountains is a thin resist­ that "The nearly complete limitation of each assem­ ant dolomite that unconformably overlies the Tensleep blage to a particular facies is striking." Sandstone and which is, in turn, unconformably over­ Despite the variety and abundance of fossils, specific lain by the lowermost red beds (pl. 3). This dolo­ correlation with the standard reference section of Per­ mite has been referred to as the N owood Member of the mian rocks in West Texas is still somewhat uncertain. Phosphoria Formation by McCue ( 1953). It can be According to Thomas ( 1948, p. 90), the faunas in the traced westward into the Owl Creek Mountains (E. K. Permian rocks of central Wyoming are provincial and Maughan, oral commun., 1963) and probably correlates not well represented in the Texas Permian. The avail­ with the Grandeur Member of the Park City Forma­ able data indicate, however, tha:t most of the Park City tion in the northern Wind River Range (McKelvey correlates with the Word Formation of Guadalupe and others, 1959, p. 12-15) _ (Early and Late Permian) age (Thomas, 1948, p. 90; Contact With the Dinwoody Formation Williams, in McKelvey and others, 1959, p. 39, 40). The The contact between the Park City Formation and basal beds (Nowood or Grandeur Member) are as old the overlying Triassic Dinwoody Formation appears as Leonard and possibly Wolfcamp (Early Permian), to be nearly everywhere conformable, even though a and the uppermost part probably is at least as young as hiatus, possibly representing all Late Permian (Ochoa) late Guadalupe. Fossils of definite Ochoa (Late Per­ time, occurs between the two formations. There is, mian) age have not been recognized. however, a sharp change in lithology at the contact. Conditions of Deposition In contrast to the ledge-forming massive gray and tan At the beginning of Permian time a broad north­ chert, limestone, and dolomite in the upper part of the south-trending highland occupied all the Wind River Park City, the Dinwoody is characterized by slope­ Basin area. Rocks of Middle Pennsylvanian age were forming thin-bedded slabby siltstone and very fine exposed in the central and western parts of the basin, grained sandstone that weather to a distinctive yellow­ some of Late Pennsylvanian age in the eastern part. ish tan in most places. The contact is readily defined The seas lay both east and west of the highland and, in on most electric logs. Wolfcamp time, began to encroach upon it from both B48 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING sides. Possibly by late W olfcamp time the highland mentation took place in deeper waters. Periodically was breached by shallow throughgoing seaways that the sea expanded eastward, and thin but widespread persisted into Leonard time, and a thin deposit of lime­ tongues of limestone were deposited over the westward­ stone was laid down across the northern and western projecting tongues of red shale. In Thomas' opinion parts of the basin. Sand, eroded from the exposed Ten­ (1948, p. 91) the relation between the red beds and the sleep Sandstone, was deposited along the east edge dur­ limestone is one of intertonguing rather than of facies ing Wolfcamp time. Then the seas regressed, at least change, suggesting that the eastward expansion of the from the eastern part of the basin area, and a short pe­ sea was fairly rapid. riod of erosion followed. In late Leonard time, seas The sea may have withdrawn by the end of Guada­ again encroached from either side of the highland, and by Guadalupe time the entire region was flooded. In the lupe time, for there is no positive record that sedimenta­ east the sea remained shallow, and red shale and evap­ tion occurred in the basin area during latest Permian orite sediments accumulated, but toward the west, sedi- time.

TABLE 8.-Fossils from Park City and Goose Egg Formations [Generic and specific names are quoted without modification from sources shown]

Collec­ tion Stratigraphic section No. Species References (pis. 2- 5)

Warm Spring Creek __ 9 Bellerophon sp., Euphemites subpapillosus, Strophostylus sp., Plicato­ Love (1939, p. 34). derbya magna, Punctospirifer pulchra, Neospirifer pseudocameratus, Waagenoconcha montpelierensis, Aulosteges cf. A. hispidus, Pustula nevadensis. 10 Stenopora (3 sp.), Lioclema sp., Phyllopora sp., Rhombopora sp., Meekella Eliot Blackwelder (U.S. sp., Chonetes aff. C. geinitzianus, Aulosteges sp., Spiriferina pulchra, Geol. Survey, unpub. Aviculopecten sp., Pseudomonotis aff. P. hawni, Bellerophon? sp., field notes); identi­ Patella sp., Nautilus sp. fication by G . H. Girty. 11 Orbiculoidea sp ______------Weart (1948). Dinwoody Canyon ___ _ 10 Orbiculoidea sp. indet., fish remains ______-- _------E. L. Yochelson (written commun., 1964). 11 Orbiculoidea (Roemerella) utahensis, Schizodus sp. indet. or Scaphellina Do. sp. indet., Sanguinolites? sp. indet. or Wilkingia? sp indet., fish remains, bryozoans. 12 Orbiculoidea (Roemerella) utahensis, Derbyia magna, Wellerella cf. W. Do. osagensis, Spheno.~teges hispidus, Echinauris subhorridus, Bathymyonia nevadensis, Spiriferina pulchra, Aviculopecten sp. indet., Nucluopsis po­ posiensis, Polidevcia bellistriata, Stutchburia sp. indet., fish remains, abundant bryozoans. 13 Composita subtilita, Chonetes sp. indet. Sphenosteges hispidus, Derbyia Do. magna, Bathymyonia sp. indet., Spiriferina pulchra, Aviculopecten sp. indet., Hustedia phosphoriensis, Nucula pulchella, Cyrtorostia varicostata, Camptonectes? sp. indet., Pseudomonotis sp. indet., Conocardium sp. indet., Schizodus canalis, Stutchburia? sp. indet., Sanguinolites? sp. indet. or W ilkingia sp. indet., Stearoceras? sp. indet., Euphemitopsis subjiapillosus, fish remains, abundant bryozoans. Bull Lake Canyon ___ _ 6 Orbiculoidea sp. indet., Scaphellina concinnus, Schizodus cf. S. wheeleri, E. L. Yochelson (written Euphemites sp. indet., Sanguinolites? sp. indet. or Wilkingia sp. commun., 1964) . indet., Cyrtorostia? sp. indet., fish remains, abundant bryozoans. 7 Orbiculoidea sp. indet., Echinauris sub horrid us, "Liosotella" sp. indct., Do. Bathymyonia nevadensis, Spiriferina pulchra, Muirwoodia multi­ striatus, abundant bryozoans. 8 Composita subtilita, Spiriferina cf. S. kentuckensis, Hustedia phos­ Do. phoriensis. 9 lV ellerella cf. W . osagensis, Sphenosteges sp. indet., Composita subtilita, Do. Derbyia sp. indet., Neospirifer pseudocameratus, "Liosotella" sp. indet., Bathymyonia nevadensis, Muirwoodia multistriatus, Spiriferina pulchra, Hustedia phosphoriensis, Dielasma sp. indet., Myalina cf. M. (M.) wyominyensis, Cyrtorostia varicostata, Aviculopecten cf. A. kaibabensis, Aviculopecten sp. indet., Plagioglypta canna, abundant bryozoans. Trout Creek ______2 Composita subtilita?, Solenomya sp., Pteria sp., Allorisma terminale?, Eliot Blackwelder (U.S. Sanguinolaria? sp., Pleurophorus sp., Pleurophorus aff. P. subcostatus, Geol. Survey, unpub. Astartella? sp., Schizodus? sp., Plagioglypta canna, Patellostium? sp., field notes); identifi­ Pleurotomaria sp. cation by G. H. Girty. Squaw Creek ______1 Orbiculoidea sp ______- - --- __ _ ------King (1947, p . 38- 39). 2 Composita sp., Neospirifer pseudocameratis, Punctospirifer pule her __ - __ - King (1947, p. 32). Sinks Canyon ______6 Orbiculoidea sp., Allorisma sp ______-- -_------Condit (1924, p . 24). Beaver Creek ______4 Orbiculoidea sp ______------Condit (1924, p. 29). PALEOZOIC FORMATIONS B49

TABLE 8.-Fossils from Park City and Goose Egg Formations-Continued [Generic and specific names are quoted without modification from sources shown]

Collec­ tion Stratigraphic section No. Species References (pls. 2-5)

Windy Gap______8 Sphenosteges sp. indet., Composita sp. indet., Derbyia magna, Neospirifer E. L. Yochelson (written pseudocameratus, Echinauris subhorridus, "Liosotella" sp. indet., commun., 1964). Bathymyonia nevadensis, Spiriferina sp. indet., Nucula sp. indet., Polidevcia bellistriata, Schizodus sp. indet. or Scaphellina sp. indet., Sanguinolites? sp. indet. or Wilkingia sp. indet., fish remains, abun­ dant bryozoans. 9 Bathymyonia nevadensis, Derbyia magna, Cyrtorostia varicostata, fish re­ Do. mains, abundant bryozoans. 10 Conularia sp. indet., Orbiculoidea sp. indet., Sphenosteges hispidus, Do. Bathymyonia nevadensis, Derbyia magna, Spiriferina pulchra, Spirifer­ ina cf. S. kentuckensis, Hustedia phosphoriensis, Aviculopecten sp. indet., Schizodus sp. indet. or Scaphellina sp. indet., Sanguinolites? sp. indet. or Wilkingia sp. indet., Costatoria secradiata, Stutchburia? sp. indet., fish remains, abundant bryozoans. Circle Ridge______1 Hustedia phosphoriensis, Spiriferina pulchra, Aviculopecten sp., Pustula Milton (1942). nevadensis, Orbiculoidea sp. Sheep Ridge______1 Plagioglypta, M yalina? ______- _------McCue (1953). 2 Plicatoderbya, Punctospirifer, Batostomella, Aviculopecten, Hustedia, Do. Stenopora?, Pleurotomaria, Horridonia?, Dictyoclostus, Ammodiscus. (Collection obtained from type section of "Embar" Formation.) Wind River Canyon__ 13 Stenopora n. sp., Phyllopora sp., Derbya aff. D. multistriata, Spiriferina Lee (1927, p. 57). pulchra, Solenomya? n. sp., Chaenomya? n. sp., Deltopecten aff. D. vanvleeti, Pseuodmonotis aff. P. sublevis, Pseudomonotis aff. P. hawni, Oxytoma? n. sp., Myalina wyomingensis?, Myalina sp., Schizodus aff. S. deparcus, Schizodus aff. S. subcircularis, S. ferrieri?, Pleurophorus n. sp., Plagioglypta canna, Bellerophon aff. B. crassus, Euphemus? sp., Naticopsis? sp., Omphalotrochus? sp. Rattlesnake Hills___ _ _ 3 Plagioglypta? sp ______-- __ - _- _ ------Thomas (1934, p. 1674). 4 Bryozoans (many species), Punctospirifer pulchra, Punctospirifer aff. P. Thomas (1934, p. 1675). kentuckyensis, Composita cf. C. mexicana, Derbya aff. D. plicatella, Tentaculites sp., Plagioglypta? sp. (small), Myalina sp. (large), Mya­ lina aff. M. perattenuata, Pleurophorus pricei, Pleurophorus (4 sp.), Leda obesa, Cyrtorostra? sp., Aviculopecten sp., Deltopecten vanvleeti, Parallelodon aff. P. tenuistriatus, Edmondia? sp., Schizodus cf. S. wheeleri, Schizodus? sp. (large), Schizodus sp. (small), Pinna peracuta, Euphemus subpapillosus, Bellerophon sp., gastropod (high-spired form), Coelogasteroceras thomasi, Coloceras? sp. Alcova______5 Plagioglypta? sp ______------Thomas (1934, p. 1678). 6 Myalina permiana, Pinna cf. P. peracuta, Pleurophorus sp., gastropods Do. (high-spired form; several species). Bates Creek ______3 Dentalium (Plagioglypta) cf. D. (P.) canna, Pleurophorus occidentalis, Jenkins (1950). gastropods (high-spired form). CasperMountain_____ 3 Pinna paracuta, Schizodus ferrieri, Pteria? sp., Plagioglypta canna_----- Lee (1927, p. 49).

PERMIAN AND TRIASSIC ROCKS, GOOSE EGG Medicine Member is an eastward-projecting tongue FORMATION from the Lower Triassic Dinwoody Formation. Thus, Lithology and Thickness only that part of the Goose Egg Formation lying below At its type locality (Casper Mountain section, pl. 5) the top of the Ervay is considered to be the equivalent the Goose Egg Formation consists of 380 feet of red of the Park City Formation; these strata have a thick­ gypsiferous shale and siltstone interbedded with dis­ ness of 304 feet (pl. 5) . tinctive gray and purple dense platy limestone. The The individual members of the Goose Egg Formation formation can be divided in ascending order into can be traced in subsurface sections northwest along the Opeche Shale, Minnekahta Limestone, Glendo Shale, Casper arch to the south end of the Bighorn Mountains. Forelle Limestone, Difficulty Shale, Ervay, Freezeout In this area they are 355 feet thick; of this thickness Shale, and Little Medicine Members ( Burk and the Park City equivalents comprise 270 feet (pl. 3). Thomas, 1956, p. 6; Maughan, 1964). The red-bed Westward into the Owl Creek Mountains the red beds units range in thickness from 40 to about 100 feet, and and gypsum gradually intertongue with carbonate rocks the limestone beds from 6 to 22 feet. The Minnekahta, and chert of the Park City Formation (pl. 3) and with Forelle, and Ervay Members are eastward-projecting dolomitic siltstone of the Dinwoody Formation. An­ tongues from the Park City Formation, and the Little other member, the N owood Member of the Phosphoria B50 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

For1nation of McCue ( 1953), occurs locally at the base water, but this is still uncertain. The source of the of the Goose Egg in the southwestern Bighorn Moun­ red debris is not known, but it was probably low land­ tains (pl. 3). masses tha.:t lay principally to the east and south of Although typical lithologies of fhe Goose Egg Forma­ Wyoming (Thomas, 1934, p. 1691, 1692). Increase in tion can be observed in exposures at the north end of the depth of water, caused either by eustatic rise in sea R1attlesnake Hills (pl. 4), it is difficult to distinguish level or cessation of uplift in the landmasses, resulted the Forelle Limestone Member, because several thin periodically in the deposition of limestone across the limestone beds occur in the middle part of the formation. entire region. In the eastern part of the basin area, Some of the red-bed units appear to extend westward some arms of the sea became isolated, or circulation along the south margin of the Wind River Basin nearly became restricted, to the extent that evaporites were as far -as the Conant Creek area, but exposures are too deposited. poor in the intervening area to show where individual Sedimentation apparently ceased in central Wyoming tongues wedge out. during latest Permian time, but there is no evidence in Contact With the Chugwater Formation the strata of the Goose Egg Formation to suggest that The Goose Egg Formation is overlain conformably the sea withdrew. by the Triassic Chugwater Formation. Because both PALEOZOIC STRUCTURE formations consist predominantly of red shale and silt­ stone, it is commonly difficult to determine the contact in Throughout the Paleozoic Era the present site of surface sections. According to Burk and Thomas the Wind River Basin was a region of remarkable crust­ (1956, p. 7), the Goose Egg beds are generally darker al sta.bility. Although hiatuses-some of them repre­ red, sandier, more gypsiferous, and somewhat more senting long periods of time-occur between many of resistant than those in the Chugwater. In addition, the formations, no angular discordances within the the Goose Egg contains thin beds of limestone, but the Paleozoic rocks were recognized. The thickness maps lower part of the Chugwater does not. The Goose Egg (figs. 6, 11, 12, 14, 17, and 22) suggest that tectonic Formation generally shows higher resistivity on electric movements were limited to broad upwarping and down­ logs than does the Chugwater; the contact, therefore, warping along trends which, with one exception, show is easily identified in subsurface sections. little direct relation to the structural trends of later Laramide deformation. If some parallelism did exist Age during certain periods, it was only temporary and in The Minnekahta Limestone and Ervay Members hs,ve large part probably coincidental. Commonly the re­ yielded fossils at several localities in the southern and verse is true; Paleozoic "highs" and "lows" correspond southeastern parts of the Wind River Basin (table 8). to Laramide "lows" and "highs," respectively. (Com­ A large assemblage from the Ervay in the Rattlesnake pare isopach maps with fig. 2.) The one exception is Hills indicates correlation with the upper part of the along the southeast margin of the basin, where an area Park City Formation and equivalents of the Wind coinciding roughly with the Laramie Mountains wa'3 River Range (Thomas, 1934, p. 1676). It is concluded, relatively positive during much of Paleozoic time. therefore, that the Goose Egg Formation below the This positive area, which widened south and southeast, top of the Ervay Member is probably Early and early is outlined by thickness lines for both the Cambrian Late Permian. The upper two members of the forma­ and Mississippian strata (figs. 6, 14) ; Ordovician and tion (Freezeout Shale and Little Medicine Members), Devonian rocks, if initially deposited in the area, were on the other hand, are lateral equivalents of the Din­ eroded before successively younger strata were laid ·woody Formation which is considered to be of Early down. One of the most pronounced periods of uplift Triassic age (Newell and Kummel, 1942). There is no was Middle Pennsylvanian (Atoka) time, when the evidence that rocks of latest Pennian age exist in the positive area extended westward and included much region, despite the seeming conformity between the of the region now occupied by the Granite Mountains. Ervay Member and overlying strata. In terms of Pennsylvanian paleogeography, it has been Conditions of Deposition referred to by Mallory ( 1963) as the Pathfinder uplift. While normal marine sedimentation took place in the ECONOMIC GEOLOGY western half of the Wind River Basin during late Early and early Late Permian times, red clastic sediments OIL AND GAS accumulated in the shallow areas of the seas in the east­ Paleozoic rocks are among the most important reser­ ern part. The continuity and uniformity of the red voirs for oil and gas in the Wind River Basin ; they beds suggest that the red beds were deposited under constitute the primary objectives for drilling in many PALEOZOIC FORMATIONS B51 areas. The Park City Formation and equivalents and pereent P205 and the upper zone from 15.2 to 20.2 Tensleep Sandstone are the most prolific, each being percent P 205. productive in about 20 fields (drill data as of Aug. 1, None of the phosphate deposits in the region has yet 1963). The Madison Limestone yields oil and gas in two been exploited. The reserves, mining conditions, and fields, the Amsden Formation (Darwin Sandstone power and transportation facilities are adequate, but Member) in one. Wells drilled to Precambrian rocks the thinness and relative low grade of the phosphate in several of the producing fields have not found signifi­ beds have been the principal deterrents (King, 1947, p. cant amounts of petroleum in Devonian or older rocks. 81). A determination that the Lander deposits are Nearly all production from Paleozoic rocks has been economic undoubtedly would provide an incentive to from anticlinal folds along the basin margins. Condi­ search for additional reserves in the adjacent areas. tions favoring stratigraphic entrapment, such as textural and porosity changes within carbonate strata, OTHER COMMODITIES wedging out of beds beneath unconformities, and The sandstone and carbonate rocks of the Paleozoic changes in facies, exist in certain areas. Many of these formations are readily available for a variety of con­ potential sources, however, have not been adequately struction uses in many areas. None of the strata has studied or explored. The Cottonwood Creek field in the yet been used extensively as building stone. The Flat­ southeastern part of the Bighorn Basin produces from head Sandstone would probably be the best source, be­ a stratigraphic trap formed by the carbonate-to-shale cause of its color, resistance to weathering, and thin facies change within the Park City and Goose Egg For­ bedding. Other thick sandstone units, such as the Ten­ mations (Biggs and Espach, 1960, p. 80), but attempts sleep 'Sandstone and the Darwin Sandstone Member of to locate similar traps in the south-central part of the the Amsden Formation, are more massive, friable, and Wind .River Basin have as yet been unsuccessful. porous. Owing to excessive drilling depths, the Paleozoic rocks Hematite-bearing red shale that occurs above the Dar­ remain virtually untested in the central part of the basin. win Sandstone Member of the Amsden Formation at many localities may prove to be a source of low-grade PHOSPH.A:TE ROCK iron ore. Gruner and Smith ( 1955, p. 31) reported Permian rocks have long been recognized as a poten­ carnotite associated with barite and fluorite in rocks of tial source of phosphate in central and western Cambrian ( ?) age near (sec. 12, T. 'Vyoming (Weeks and Ferrier, 1906; Weeks, 1907; 40 N., R. 107 W.), in the northern part of the Wind Blackwelder, 1911; Condit, 1924). Owing to accessibil­ River Range. Localized radioactive deposits have also ity and proximity to a railroad terminal, the deposits been reported from the Tensleep Sandstone in sec. 31, along the east flank of the Wind River Range near Lan­ T. 31 N., R. 97 W., and from the Phosphoda Formation der have been of particular economic interest. King in sees. 7 and 10, T. 30 N., R. 97 W. (Wilson, 1960, p. 23). (1947) studied the Lander deposits, and, more recently, The extent and potential of the deposits are not known. Sheldon (1957) reported on the phosphate rocks at selected localities in the northwestern part of the range. REFERENCES CITED Phosphate rock is also present in nearly all outcrops of Agatston, R. S., 1954, Pennsylvanian and Lower Permian of the Park City Formation and equivalents in the south­ northern and eastern Wyoming : Am. Assoc. Petroleum western and northern parts of the Wind River Basin, Geologists Bull., v. 38, no. 4, p. 508-583. but these have not been extensively studied. -- 1957, Pennsyl~aniau of the Wind River Basin, in Wyo­ The phosphate-bearing rocks generally form two dis­ ming Geol. Assoc. Guidebook, 12th Ann. Field Conf., 1957: p. 29-33. tinct zones within the Permian sequence along the east Amsden, T. W., and Miller, A. K., 1942, Ordovician conodonts flank of the Wind River Range. These zones have been from the Bighorn Mountains of Wyoming: Jour. Paleontol­ referred to as the "lower phosphate zone" and "upper ogy, v.16, no. 3, p. 301-306. phosphate zone" by Condit (1924) and King (1947) · Andrichuk, J. M., 1951, Regional stratigraphic analysis of and as units B and D by Sheldon ( 1957). Each zone Devonian System in Wyoming, Montana, southern Sas­ occurs as distinct beds of phosphorite, generally less katchewan, and Alberta: Am. Assoc. Petroleum Geologists than 1 foot thick and rarely more than 2 feet thick, and Bull., v. 35, no. 11, p. 2368-2408. as grains or pellets disseminated through shale, sand­ -- 1955, Mississippian stratigraphy and sedimentation in Wyoming and southern Montana : Am. stone, and limestone, with which the phosphorite is Ass·oc. Petroleum Geologists Bull., v. 39, no. 11, p. 2170-2210. interbedded. According to King ( 1947, p. 12), the Bearce, D. N., 1963, The Sacajawea Formation and the Darwin phosphate rock in the Lander area is classed as low to Sandstone in the southeast Wind River Mountains, Wyo­ medium grade; the lower zone ranges from 21.5 to 29.7 ming: Missouri Univ., unpub. masters thesis, 61 p. B52 GEOLOGY OF THE WIND RIVER BASIN, CENTRAL WYOMING

Bell, W. G., 1955, The geology of the southeastern flank of the Dakota and Wyoming: U.S. Geol. •Survey 21st Ann. Rept., Wind River Mountains, Fremont County, Wyoming: Wyo­ pt. 4, 489-599. ming Univ., unpub. Ph.D. dissertation, 204 p. Darton, N.H., 1904, Comparison of the stratigraphy of the Black Berg, R. R., 1961, Laramide tectonics of the Wind River Moun­ Hills, Bighorn Mountains, and Rocky Mountain front range: tains, in Wyoming Geol. Assoc. Guidebook 16th Ann. Field Geol. Soc. America Bull., v.l5, p. 379-448. Conf., 1961 : p. 70-80. --- 1906a, Geology of the Owl Creek Mountains: U.S·. 59th Biggs, C. A., 1951, Stratigraphy of the Amsden formation of Cong., 1st sess., S. Doc. 219, 48 p. the Wind River Range and adjacent areas in northwestern ---1906b, Geology of the Bighorn Mountains: U.S. Geol. Wyoming: Wyoming Univ., unpub. masters thesis, 121 p. Survey Prof. Paper 51, 129 p. Biggs, Paul, and Espach, R. H., 1960, Petroleum and natural gas ---1906c, Fish remains in Ordovician rocks in Bighorn fields in Wyoming: U.S. Bur. Mines Bull. 582, 538 p. Mountains, Wyoming, with a resume of Ordovician geology Blackwelder, Eliot, 1911, A reconnaissance of the phosphate of the Northwest: Geol. Soc. America Bull., v. 17, p. 541- deposits in western Wyoming: U.S. Geol. Survey Bull. 470, 566. p. 452-481. ---1908, Paleozoic and Mesozoic of central "''Yoming : Geol. --- 1913, Origin of the Bighorn dolomite of Wyoming : Geol. Soc. America Bull., v. 19, p. 403-470. Soc. America Bull., v. 24, p. 607--624. Darton, N. H., and Paige, Sidney, 1925, Central Black Hills, --- 1918, New geological formations in western Wyoming: South Dakota: U.S. Geol. Survey ·Geol. Atlas, Folio 219, Washington Acad. Sci. Jour., v. 8, no. 13, p. 417-426. 7 maps. Bogrett, J. W., 1951, Geology of the northwestern end of the Deiss, Charles, 1938, Cambrian formations and sections in part Rattlesnake Hills, Natrona County, Wyoming: Wyoming of Cordilleran trough: Geol. Soc. America Bull., v. 49, no. Univ., unpub. masters thesis, 70 p. 7, p. 1067-1168. Boutwell, J. M., 1907, Stratigraphy and structure of the Park DeLand, C. R., 1954, Cambrian stratigraphy and Upper Cam­ City mining district, Utah: Jour. Geology, v. 15, p. 434-458. brian trilobites of the southwestern flank of the Wind River Branson, C. C., 1937, Stratigraphy and fauna of the Sacajawea Mountains. Wyoming: Wyoming Univ., unpub. masters formation, Mississippian, of Wyoming: Jour. Paleontology, •thesis, 135 p. v.11,no.8,p.650--660. DeLand, C. R., and Shaw, A. B., 1956, Upper Cambrian trilobites --- 1939, Pennsylvanian formations of central Wyoming: from western Wyoming: Jour. Paleontology, v. 30, no. 3, Geol. Soc. America Bull., v. 50, no. 8, p. 1199-1226. p. 542-562. Branson, E. B., and Branson, 0. C., 1941, Geology af the Wind Denison, R. H., 1951, Late Devonian fresh-water fishes from the River 'Mountains, Wyoming: Am. Assoc. Petroleum Geol­ western United States: Fieldiana Geology, v. 1'1, no. 5, ogists Bull., v. 25, no. 1, p. 120-151. p. 221-261. Branson, E. B., and Greger, D. K., 1918, Amsden formation of Denson, M. E., Jr., and Morrissey, N. S., 1952, The Madison the east slope of the Wind River Mountains of "Wyoming group (Mississippian) of the Big Horn and Wind River and its fauna: Geol. Soc. America Bull., v. 29, p. 309-326. Basins, Wyoming, in Wyoming Geol. Assoc. Guidebook, 7th Burk, C. A., 1954, Faunas and ·age of the Amsden formation in Ann. Field Oonf., 1952: p. 37-43. Wyoming: Jour. Paleontology, v. 28, no. 1, p. 1-16. Denson, N. M., 1942, Late Middle Cambrian trilobite faunas and Burk, C. A., and Thomas, H. D., 1956, The Goose Egg formation stratigraphy of Al•berta, Montana, Wyoming, and Utah: ('Permo-Triassic) of eastern Wyoming: Wyoming Geol. Princeton Univ., unpub. Ph.D. dissertation. Survey Rept. Inv. 6, 11 p. Duncan, Helen, 1956, Ordovician and ·Silurian coral faunas of Burton, G. ·C., 1952, Geology of 'Squaw Creek area, Wind River western United States: U.S. Geol. Survey Bull. 1021-F, p. Mountains, Fremont County, Wyoming: Mi·ssouri Univ., 209-236. unpub. master thesis. Easton, W. H., 1962,

Gruner, J. W., and Smith, D. K., Jr., 1955, Annual report for Love, J. D., 1939, Geology along the southern margin of the Aprill, 1954 to March 31, 1955: U.S. Atomic Energy Comm. Absaroka Range, Wyoming: Geol. Soc. America Spec. RME 3020, 37 p. Paper 20, 134 p. Harrison, J. W., 1938, Pennsylvanian stratigraphy of the Lara­ --- 1954, Tentative diagrammatic correlation of Tensleep, mie Range of southeastern Wyoming: Wyoming Univ., Amsden, Casper, and Hartville Formations in Wyoming, in unpub. masters thesis, 85 p. Wyoming Geol. Assoc. Guidebook 9th Ann. Field Conf., Hembree, M. R., 1949, Geology of the Fossil Hill area, Wind 1954 [chart in pocket]. River Mountains, Fremont County, Wyoming: Missouri Love, J. D., Keefer, W. R., Dnnean, D. C., Bergqui~St, H. R., and Univ., unpub. masters thesis. Hose, R. K., 1951, Geologic map of the Spread Creek-Gros Henbest, L. G., 1954, Pennsylvanian Foraminifera in Amsden Ventre River area, Teton County, Wyoming: U.S. Geol. formation and Tensleep sandstone, Montana and Wyoming, Survey Oil and Gas Inv. Map OM-118. in Billings Geol. Soc. Guidebook 5th Ann. Field Conf., 1954: Love, J.D., Tourtelot, H. A., Johnson, C. 0., Thompson, R. M., p.~. Sharke:r, H. H. R., and Zapp, A. D., 1947, Stratigraphic --- 1956, Foraminifera and correlation of the Tensleep sections of Mesozoic rocks in central Wyoming: Wyoming sandstone of Pennsylvanian age in Wyoming, in Wyoming Geol. Survey Bull. 38, 59 p. Geol. Assoc. Guidebook 11th Ann. Field Conf., 1956: p. 58-63. Love, J.D., Weitz, J. L., and Hose, R. K., 1955, Geologic map of Hoare, R. D., and Burgess, J.D., 1960, Fauna from the Tensleep Wyoming: U.S. Geol. Survey. Sandstone in Wyoming: Jour. Paleontology, v. 34, p. 711- Lyon, D. L., 1956, Geology of the north flank, eastern Bridger 716. Range, Hot Springs County, Wyoming: Wyoming Univ., Hose, R. K., 1955, Geology of the Crazy Woman Creek area, unpub. masters thesis, 95 p. Johnson County, Wyoming: U.S. Geol. Survey Bull. 1027-B. McCue, J. J., 1953, Facies changes within the Phosphoria For­ p. 33-118. mation in the southeast portion of the Big Horn Basin, Howell, B. F., and others, 1944, Correlation of the Cambrian Wyoming: Wyoming Univ., unpub. masters thesis, 88 p. formations of [chart 1] : Geol. Soc. America McKee, E. D., 1945, Stratigraphy and ecology of the Grand Bull., v. 55, no. 8, p. 993-1003. Canyon Cambrian, Pt. 1 of Cambrian history of the Grand Jenkins, C. E., 1950, Geology of the Bates Creek-Corral Creek Canyon region : Carnegie Inst. Washington Pub. 563, p. area, Natrona County, Wyoming: Wyoming Univ., unpub. 1-168. masters thesis, 80 p. McKelvey, V. E., Williams, J. S., Sheldon, R. P., Cressman, E. Keefer, W. R., 1957, Geology of the Du Noir area, Fremont R., Cheney, T. M., and Swanson, R. W., 1956, Summary de­ County, Wyoming: U.S. Geol. Survey Prof. Paper 294-E, scription of Phosphoria, Park City, and Shedhorn Forma­ p. 155-221. tions in western phosphate field: Am. Assoc. Petroleum --- 1965, Stratigraphy and geologic history of the upper­ Geologists Bull., v. 40, no. 12, p. 2826--2863. most Cretaceous, Paleocene, and lower Eocene rocks in the McKelvey, V. E., Cressman, E. R., Sheldon, R. P., Cheney, T. M., Wind River Basin, central Wyoming: U.S. Geol. Survey Swanson, R. W., and Williams, J. S., 1959, The Phosphoria, Prof. Paper 495-A, 77 p. Park City, and Shedhorn formations in western phosphate King, R. H., 1947, Phosphate deposits near Lander, Wyoming: field: U.S. Geol. Survey Prof. Paper 313-A, p. 1-46. Wyoming Geol. Survey Bull. 39, 84 p. Mallory, W. ,V., 1963, Pathfinder uplift of Pennsylvanian age in southern Wyoming, in Short papers in geology, hydrology, --- 1957, Stratigraphy of the Phosphoria formation in the and topography: U. S. Geol. Survey Prof. Paper 450-E, p. Wind River Mountains, in Wyoming Geol. Assoc. Guide­ E57-E60. book 12th Ann. Field Conf., 1957 : p. 35-38. Mansfield, G. R., 1927, Geography, geology, and mineral re­ Kirk, Edwin, 1930, The Harding sandstone of Colorado: Am. sources of part of southeastern Idaho, with descriptions of Jour. Sci., 5th ser., v. 20, p. 456--466. Carboniferous and Triassic fossils, by G. H. Girty: U.S. Klapper, Gilbert, 1958, An Upper Devonian conodont fauna from Geol. Survey Prof. Paper 152, 453 p. the Darby formation of the Wind River Mountains, Wyo­ Maughan, E. K., 1963, Mississippian rocks in the Laramie Range, ming: Jour. Paleontology, v. 32, no. 6, p. 1082-1093. Wyoming, and adjacent areas, in Short papers in geology Lee, ,V. T., 1927, Correlation of geologic formations between and hydrology : U.S. Geol. Survey Prof. Paper 475-0, p. east-central Colorado, central Wyoming, and southern Mon­ 023--{)27. tana: U.S. Geol. Survey Prof. Paper 149,80 p. --- 1964, The Goose Egg Formation in the Laramie Range Lochman, Christina, 1950, Status of the Dry Creek Shale of and adjacent parts of southeastern Wyoming, in Geological Survey Research 1964: U.S. Geol. Survey Prof. Paper 501-B, central Montana: Am. Assoc. Petroleum Geologists Bull., p. B53-B60. v.34,no. 11,p.2200-2222. Miller, A. K., 1930, The age and correlation of the Bighorn for­ LPChman-Balk, Christina, 1956, The evo~ution of some Upper mation of northwestern United States: Am. Jour. Sci., 5th Cambrian and Lower Ordovician trilobite families: Jour. ser., v. 20, p. 195-213. Paleontology, v. 30, no. 3, p. 445-462. --- 1932, The cephalopods of the Bighorn formation of the --- 1957, Paleoecology of the Cambrian in Montana and Wind River Mountains of Wyoming: Connecticut Acad. Wyoming, chap. 8 in Ladd, H. S., ed., Paleoecology, v. 2 of Arts and Sci. Trans:, v. 31, p. 193-297. Treatise on marine ecology and paleoecology: Geol. Soc. Miller, B. 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Moore, R. C., chm., and others, 1944, Correlation of Pennsyl­ Shaw, A. B., and Bell, W. G., 1955, Age of the Amsden forma­ vanian formations of North America: Geol. Soc. America tion, Cherry Creek, Wind River Mountains, Wyoming: Am. Bull., v. 55, no. 6, p. 657-706. Assoc. Petroleum Geologists Bull., v. 39, no. 3, p. 333-337. Morey, P. S., 1935, Ostracoda from the Amsden formation of Shaw, A. B., and DeLand, C. R., 1955, Cambrian of southwestern Wyoming: Jour. Paleontology, v. 9, no. 6, p. 474-482. Wyoming, in Wyoming Geol. Assoc. Guidebook lOth Ann. Murphy, J. F., Privrasky, N. C., and Moerlein, G. A., 1956, Field Conf., 1955: p. 3~. Geology of the Sheldon-Little Dome area, Fremont County, Sheldon, R. P., 1957, Physical stratigraphy of the Phosphoria Wyoming: U.S. Geol. Survey Oil and Gas Inv. Map OM-181. formation in northwestern Wyoming: U.S. Geol. Survey Murphy, J. F., and Richmond, G. M., 1965, Geology of the Bull Bull. 1042-E, p.105-185. Lake West quadrangle, Wyoming: U.S. Geol. Survey Sims, F. C., 1948, Geology of the west end of the Laramie Range, Geol. Quad. Map ·GQ-432. Natrona County, Wyoming: Wyoming Univ., unpub. masters Newell, N. D., and Kummel, Bernhard, Jr., 1942, Lower Eo­ thesis, 52 p. ·Triassic stratigraphy, western Wyoming and southeast Sloss, L. L., 1952, Introduction to the Mississippian of the Wil­ Idaho: Geol. Soc. America Bull., v. 53, no. 6, p. 937-996. liston Basin, in Billings Geol. Soc. Guidebook 3d Ann. Peale, A. C., 1893, The Paleozoic section in the vicinity of Three Field Conf., 1952 : p. 65-69. Forks, Mont.,: U.S. Geol. survey Bull. 110, 56 p. Stokes, W. L., 1953, Summary of Paleozoic and Mesozoic stratig­ Phillips, D. P., 1958, Geology of the Sheep Ridge area, Hot raphy [Utah], in Intermountain Assoc. Petroleum Geolo­ Springs and Fremont Counties, Wyoming: Wyoming Univ., gists Guidebook 4th Ann. Field Conf., 1953: p. 14-18. unpub. masters thesis, 135 p. Strickland, J. W., 1957, Summary of Mississippian and Devonian Powell, J. D., 1957, The geology of the Blackrock Ridge area, stratigraphy, Wind River Basin, Wyoming, in Wyoming Hot Springs and Fremont Counties, Wyoming : Wyoming Geol. Assoc. Guidebook 12th Ann. Field Conf., 1957: p. 2Q- Univ., unpub. masters thesis, 118 p. 28. Rhodes, F. H. T., 1963, Conodonts from the topmost Tensleep Thomas, H. D., 1934, Phosphoria and Dinwoody· tongues in Sandstone of the eastern Big Horn Mountains, Wyoming : lower Chugwater of central and southeastern Wyoming: Jour. Paleontology, v. 37, no. 2, p. 401-408. Am. Assoc. Petroleum Geologists Bull., v. 18, no. 12, p. 1655- Richards, R. W., and Mansfield, G. R., 1912, The Bannock over­ 1697. thrust, a major fault in southeastern Idaho and north­ --- 1948, Summary of Paleozoic stratigraphy of the Wind eastern Utah: Jour. Geology, v. 20, p. 681-709. River Basin, Wyoming, in Wyoming Geol. Assoc. Guidebook Richardson, G. B., 1913, The Paleozoic section in northern Utah: 3d Ann. Field Conf., 1948: p. 79-95. Am. Jour. Sci., 4th ser., v. 36, p. 406--416. --- 1952, Cambrian and Ordovician stratigraphy around the Rabinson, G. D., 1963, Geology of the Three Forks quadrangle, southern Bighorn Basin, Wyoming, in Wyoming Geol. Assoc. Montana: U.S. Geol. Survey Prof. Paper 370, 143 p. Guidebook 7th Ann. Field Conf., 1952: p. 32-36. Ross, R. J., Jr., 1957a, Origin of Ordovician units exposed near --- 1957, Geologic history and structure of Wyoming : the Wind River basin, i.n Wyoming Geol. Assoc. Guidebook Wyoming Geol. Survey repr. 18, 11 p. 12th Ann. Field Conf., 1957: p. 17-19. Thomas, H. D., Thompson, M. L., and Harrison, J. W., 1953, --- 1957:b, Ordovician fossils from wells in the Williston Fusulinids of the Casper formation of Wyoming: Wyoming basin, : U.S. Geol. Survey Bull. 10"21-M, p. Geol. Survey Bull. 46, 56 p. 439-510. Tourtelot, H. A., 1952, Marine and evaporite facies of Permian Sandberg, C. 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Weart, R. 0., 1948, Geology of the northern flank of the Wind tion in the southern portion of the Wind River Basin, Wy­ River Mountains, Fremont County, Wyoming: Univ. Syr-a­ oming: Wyoming Univ., unpub. masters thesis, 72 p. cuse, unpub. masters thesis. Wilson, W. H., 1960, Radioactive mineral deposits ·of Wyoming: Weed, W. H., 1900, Geology of the Little Belt Mountains, Mon­ Wyoming Geol. Survey Rept. lnv. 7, 41 p. tana: U.S. Geol. Survey, 20th Ann. Rept., pt. 3, p. 257-461. Woodward, T. C., 1957, Geology of the Deadman Butte area, Weeks, F. B., 1907, Phosphate deposits in western United States: Natrona County, Wyoming: Am. Assoc. •Petroleum Geolo­ U.S. Geol. Survey Bull. 340-K, p. 441-447. gists Bull., v. 41, no. 2, p. 212-262. Weeks, F. B., and Ferrier, ,V. F., 1906, Phosphate deposits in Y·oche1son, E. L., 1963, Paleoecology orf the Permian Phosphoria western United States: U.S. Geol. ·Survey Bull. 31&--P, p. Formation and related rocks, in Short papers in geology 449-462. •and hydrology: U.S. Geol. •Survey Prof. Paper 475_.B, p. Weichman, B. E., 1958, Stratigraphy of the ·Phosphoria Forma- B123--B124.

INDEX

[Italic page numbers indicate major references]

A Page Page Page Absaroka Range ______------B4 Bothriolepis ______-- ______------B29 Condit, D. D., quoted______B43 Acroteta microscopica tetonensis______16 Boysen Formation ___ ------7 Conocardium sp.------48 Agatston, R. S., cited______42 subdivisions ______------______19 Conularia SP------49 Agnostus tumidosus______16 Bradyina SP------_------39,42 Cordilleran geosyncline ------6 sp_ ------16 Branson, E. B., quoted _____ ------35 Cordylodus SP------25 AUorisma ______------______. ______39 Brigham Quartzite______15 Costatoria secradiata------49 terminale __------____ ---- _____ 39,48 Briscoia schucherti- ______------__ . -- 16 Cottonwood Creek oil and gas field ------51 Allumettoceras sp_ ------25 Burnetia alta. __ ------16 CrepicephalUS------21 Ameura sp ____ ------____ 42 Buck Spring Formation ______7, 18,19 tripunctatus ______-- _------16 Ammodiscus ______------49 Building stone, Flathead Sandstone______51 sp. ------______------16 Amsden Formation ____ ------______90,95 Bull Lake______35 wne ------16,21 contact with Tensleep Sandstone______97 Bull Lake Canyon. __ ------22, 23, 27, 29, 30, 1,0 Cyathophyllum SP------33 Darwin Sandstone Member ______95,97,99,1,0 Burk, C. A., cited______43,50 Cyclendoceras ______--- _------25 oil and gas ______------51 Burnetia sp______------16 Cyclocrinites __ ------25 fossils ____ ------95, 97,99 Bynumia sp __ ------16 Cyrtorostia varicostata. ------48,49 Anticline, Conant Creek______3 SP------48 Antiquatonia sp. ------39 c Cyrtorostra SP------49 Apachia convexa. __ ------16 Calapoecia borealis------25 Apatognathus varians _____ ------____ 29 canadensis._------_------___ -- __ - __ ---- 25 D sp______----- ______16 Aphelaspis SP------25 Darby Formation ____ ------S3, S6 zone ______------______21 Calcitornella sp_ ------42 contact with Madison Limestone.______S7 Arapahoia levis ______------______16 Camarotoechia sapphO------33 fossils. ______------S9 spatulata ______------_____ 16 sp_ ------______33 Darton, N.H., quoted______43 typa_ ------_____ 16 Cambrian formations, fossils______16 Darwin Sandstone Member of Amsden For­ Astartella SP------______39, 48 Cambrian rocks.------7 mation.------95, 97,99, 1,0 oil and gas______51 Aulosteges hispidus______48 Camptonectes sp_ ------48 sp_ ------______48 Cancrinella boonensis______39 Deadwood Formation.------7,15 Aviculopecten. ______49 Caninophyllum.------33 Deadwoodia duris------16 kaibabensis ______------__ 48 Carnotite associated with barite and fluorite__ 51 Death Canyon Limestone Member of Gros SP------42, 48,49 Casper arch. __ ------2, 6, 49 Ventre Formation ______---- 15, 17,18 Casper Formation______37, 1,0, 1,1, 1,2 Death Canyon Member of Gros Ventre For- B Casper Mountain ___ ------6, 18, 37, 1,0, 1,1, 42 mation------15 Barbouria sp ______---- ______33 Catazyga headi borealis_------25 DeUea. ------16 Bates Creek ______33, 37,41 sp ______---_____ . ___ -- __ -----_-- __ --__ - 25 saginata. ___ ------16 Bathymyonia nevadensis ______48,49 Catenipora •. -_------23 Deltopecten aviculatum------39 sp ______------48 gracilis ______------25 vanvleeti. _------49 Batostomella ______------______49 Cedaria prolifica.------16 sp_------39 Beartooth Butte Formation______27 wne______------18, 21 Denison, R. H., quoted ______30 Beaver Divide, erosional escarpment of Terti- Cedarina alberta ___ ------16 Dentalium (Plagioglypta) canna ______49 ary rocks _____ ------:e victoria ______------______16 (Plagioglypta) SP------42 Bellerophon crassus______39 Chaetetes milleporaceous------"----- 39 sp.------42 percarinatus ______------42 Chariocephalus SP------16 Depass Formation------7,17 sp_ ------39, 48, 49 Cherry Creek. ____ ------95, 1,0 Derbya multistriata. ___ ------49 Belodina compressus. __ ------____ 25 Chonetes chesterensis. ___ ------33 plicatella ____ _-- __ ------49 Bemaspis ______------______16 geinitzianus ___ _-- _____ ------48 Derbyia crassa. _------42 Berkia .• ------______16 sp ______---_------__ 48 magna ______------48,49 Bernia ____ ------______16 Chugwater Formation ______1,9,50 sp ______------42,48 Bighorn Basin______4 Circle Ridge area ______-- 23 Devonian rocks------S6, 50 Bighorn Dolomite ______------____ :eo, :et Cladodus sp __ ------__ 42 Dicellomus nanus------16 contact with overlying rocks______:es Cleiothyridina crassicardinalis------33 sp ______------16 fossils _____ ------______!BJ, 29, 25 sp ______- _------_ 39 Dictyoclostus ___ ------49 Lander Sandstone Member ______21,!B!B,2S,25 Cliffia latagenae.------16 hermosanus.------42 Leigh Dolomite Member ______22,S5 Climacammina SP------39,42 portlockianus. ___ ------39 Bighorn Limestone______21 Cloud, P. E., Jr., cited______19 Dielasma sp. __ ------48 Bighorn Mountains ____ 6, 7, 17, 18, 21, 23, 25, 30, 35, 37, Coelogasteroceras thomasL------49 Difficulty Shale Member, Goose Egg For- 41, 42, 43, 47 Coloceras sp _____ ------__ 49 mation.------__ _ 49 BiUingseUa______16 Columnaria alveolata______25 Dikelocephalus __ ------16 coloradoensis______16 halli______---- 25 Dinorthis sp. ___ ------25 striata _____ ------______16 Composita humilis. __ ------33 Dinwoody Canyon ______U, 23, 26, !B7, S9, 1,1, 1,3 Blackwelder, Eliot, cited ______7, 26, 41,43 subtilita ______------39, 42, 48 Dinwoody Formation._------43, 1,9, 50 Blountia amage______16 ovata. ______------_ 39 Diphyphyllum ______------33 dunoirensis ___ ------16 trinuclea ______------39 sp ______------33 globosa ______------______16 trinuclea ______------33, 39 Disconformities between Tensleep and Atps- sp------_---- ______16 sp_ ------33, 39, 42, 48,49 den Formations______;,:e BolaspideUa ______------16 Conant Creek ______20, 21,44 Drepanodus curvatus______25 Bolaspis ______------______16 Conant Creek anticline______3 subrectus _____ ------25 B57 B58 INDEX

Page Page, Page Dry Creek Shale Member of Gallatin Lime- Glyphaspis _____ ------Bl6 Leigh Dolomite Member, Bighorn Dolomite_ B22, S6 stone_------B20 Glyptotrophia ______------16 Ligonodina sp ____ ------· ------______25 Du Noir Limestone Member of Gallatin Goose Egg Formation ______49,49 Lingulep£8 ______------_ 16 Limestone ______18, ro, S1 contact with Chugwater Formation______50 acuminatus. ------____ ------______16 Du Noir Member of Gallatin Limestone______20 Difficulty Shale Member.------49 acuminata meeki.______16 Duncan, Helen, quoted______25 Ervay Member ____ ------49 Linnarssonella ______------16 fossils. __ ------50 modesta ______------____ _ 16 E Forelle Limestone Member ______49,50 tennesseensis ______----_ 16 East Canyon Creek______18 fossils __ ------48 transversa______16 Echinauris tubhorridU8------48,49 Freezeout Shale Member------49,50 Linoproductus croneisi. _------39 Edmondia sp ___ ------______49 Glendo Shale Member______49 prattenianus ___ ------39, 42 Ellipsocephaloides sp __ ------16 Little Medicine Member ______49,50 sp __ ------______------______39 Elrathiella ______------__ _ 16 Minnekahta Limestone Member______49 Lioclema SP------_ 48 Elvinia roemeri. ____ ------16 fossils. ___ ------___ 50 Liospira sp ______------_ 25 sp ______------_ 16 Opeche Shale Member_------49 Liostella sp ______------48, 49 zone ______------16, 21 Gorman, D. R., cited______40 Lithostrotion. ------__ ------__ 33 Ember Formation______49 Grandeur Member of Park City Formation.. 47 SP------__ 33 Endothyra sp ___ ------39,42 Granite Mountains______3, 26 Little Medicine Member of Goose Egg For­ Entomis sp __ ------39 Greger, D. K., quoted______35 mation_------49,50 Eocene rocks_------2, 4, 6 Grewinkia sp __ ------25 Lochman-Balk, Christina, cited______19 Eoorthis. ______------__ ------__ _ 16 Gros Ventre Formation ___ ------_ 7, 14,15 Lodgepole Limestone ______---- __ .------_-- 33 iddinosL ______------. _------_ 16 contact with Gallatin Limestone______18 iophon ______------16 Death Canyon Limestone Member---- 15, 17, 18 M remnicha. ____ ------___ ------16 Death Canyon Member______15 McKee, E. D., cited______19 Ervay Member of Goose Egg Formation_____ 49 Park Shale Member ______15,18 Maclurina sp______25 fossils ______------______50 Wolsey Shale Member______15 Madison Limestone. ______14, 18, 20, 23, 27, 29,40 Eumetria marcyL------33 Gros Ventre Range ______------14, 15, 18, 20,35 basal unconformity______33 Euomphalopterus sp_ ------25 Gypsum beds ______------43 contact with Amsden Formation______39 Euphemites subpapillosus______48 fossils ____ ------33, 40 sp_ ------48 H oil and gas. ______------51 Euphemitopsis subpapillosus ______48,49 Halysites. ____ ------23 Maladia sp. ______------16 Euphemus carbonarius------39,42 gracilis. ______----- __ ------25 Mallory, W. W., cited______40 Evaporite beds, Mississippian______94 micro porus. __ ------25 Maroinifera splendens ____ ------39 (Catenipora) gracilis .. ------25 sp ______------_-- 39 F Harding Sandstone of central Colorado______21 Maryvillia ariston______16 Faults ______------_ 3, 4 Helodus sp ______------42 sp ______-- ____ - 16 Flathead Pass------14 Hesperothis sp __ ------__ ------25 Maughan, E. K., cited______42 Flathead Quartzite______14 Hiland Divide______2 Maywood Formation______27 Flathead Sandstone ______7, 14, 16, 17, 18,30,39 Hindeodella acuta------29 Meekella SP------48 building stone ______------51 sp_ ------42 Mesolobus striatus. _____ ------39 contact with Gros Ventre Formation_____ 14 Holophraoma sp. _------25 Millerella sp ______------42 contact with Precambrian rocks______14 Homalophyllites. ___ ------33 Minnekahta Limestone Member of Goose Egg Flathead shales ______14, 15 Horridonia ___ ------49 Formation._------49 Folds ______------3, 4 Horse Creek______39 fossils. __ ------50 Forelle Limestone Member of Goose Egg Housia vacuna______16 Miocene rocks______3 Formation_------49,50 Huenella. _------__ 16 Mission Canyon Limestone._------33 Fossils, Amsden Formation _____ ------95,37,39 Hustedia ___ ------49 Mississippian evaporite beds______94 Bighorn Dolomite ______21, 23,25 phosphoriensis. ------48,49 Mississippian rocks ____ ------29 Cambrian formations______16 Hyolithes._------16 Modocia sp_ ------16 Darby Formation __ ------29 sp ______----___ -----___ _ 16" Monocheilus sp __ ------______----- ___ 16 Ervay Member of Goose Egg Formation.. 50 Morrissey, N. S., quoted______30 Gallatin Limestone______21 I Muirwoodia muUistriatus. ------48 Goose Egg Formation______48 Icriodus darbyens£8______29 Murphy, J. F., cited______22 Madison Limestone ______33,40 mehli. ______------29 Myalina __ ------____ ------49 Minnekahta Limestone Member of Goose sp ______---___ _ 29 perattenuata ______------49 Egg Formation______50 Idahoia sp. ______------16 permiana ______------49 Park City Formation ______47,48 wne ______------_ 16 (Myalina) wyomingensis______48 Tensleep Sandstone______42 Iddingsia occidentaliB------_ 16 sp ______-----__ _ 49 Freezeout Shale Member of Goose Egg For­ Idiognathodus sp_ ------42 mation.------49,50 Introduction ______------____ ----_ 2 N Fusispira injlata______25 Iron ore, hematite-bearing red shale.------51 Naticopsis nana ____ ------39 Fusulina leeL______42 Irvinoella flohrL __ ------16 Nautilus SP------48 sp. ------_____ ------______42 gibba. __ ------___ ------___ _ 16 Neoprioniodus sp __ ------29 Fusulinella gephyraea. __ ------39 Neospirifer cameratus______42 sp ______------____ ------______39 J pseudocameratus.------48,49 Fusulinids______42 Jefferson Limestone______27 sp ______--__ _ _ _ 39 North Casper Creek oil field._------18 G K Nowood Member of Phosphoria Forma- Gallatin Formation of Peale______15 King, R. H., cited______51 tion __ ------42, 47, 49 Gallatin Limestone ______7, 18, 19,22 Kingstonia sublettensis. _------16 Nuctopsis poposiensis. ------48 contact with Bighorn Dolomite______20 sp_ ------___ ------16 Nucula pulchella. __ ------48 Du Noir Limestone Member ______18,20,21 Kirk, Edwin, cited______21 sp ______------______------_ 49 Du Noir Member______20 Nyctopora sp_ ------25 fossils _____ ------21 L Open Door Limestone Member ______20,21 Lander, phosphate deposits __ ------51 0 Gas ______------______50 Lander Sandstone Member, Bighorn Do- Obolus zentus.------16 sp ______16 Geology, economic______50 lomite ____ ------21, 22, 23,25 Glauconite in Cambrian units______19 Laramide deformation______50 OiL_------60 Glendo Shale Member of Goose Egg For- Laramie Mountains______14 Oistodus sp ______------25 mation._------______49 Leda obesa______49 Oligocene rocks------4 INDEX B59

Page· Page. Page, Opeche Shale Member of Goose Egg Forma- Precambrian crystalline rocks. ______B3, 6, 14, 19,40 Spyoceras rarum------B25 tion ____ ------______B49 Previous work ____ ------2 Squamularia perplexa______42 Open Door Limestone Member of Gallatin Prioniodina SP------__ 25 Stajfella sp ______------42 Limestone ______20,21 Prioniodus SP------42 Stearoceras. ______------48 Orbiculoidea wyomingensis______39 Productus cora ______39,42 Stenopora ____ ------_ 49 (Roemerella) utahensis______48 hermosanus ______------39 SP------48 sp ______48, 49 parviformis. __ ------_------33 Straparolus (Euomphalus) plummerL------42 Ordovician rocks._------21, 29,50 semireticulatus ______------______42 Stratigraphy ___ ------6 Orthotetes kaskaskiensis. __ . _------33 sp. ______------42 Streptelasma corniculum._------25 sp_ ------____ ------______. 33, 39 Prosaukia sp ______------_____ 16 foerstet_ __ ------_---- ___ ------25 Orygmaspis ... ______. ______16 Prozacompsus sp ______------16 robustum_ ------25 sp. ______----___ 25 Owl Creek Canyon ______20,21 Pseudomonotis hawni. _------42,48 Owl Creek Mountains ______4, 7, 14, 17, 20, 21, 29,90, sp ______------~------48 Streptognathodus SP------42 35, 37, 41, 43,47 Pteria longa ______------39 Strophostylus sp_ ------39,48 Ozarkodina regularis. ______. ______------29 sp_ ------__ ------___ 39, 48, 49 Structure, Paleowic____ ------60 sp. A------____ 25 Pugnoides ottumwa______33 Stutchburia sp __ ------48, 49 sp. B______25 Punctospirifer __ ------49 Sweetwater Canyon ______18,20 pulchra ______------48 Synthrophia alata __------16 p sp______39 Syringopora surcularia______33 Palaeophyllum stokesL------25 Pustula nevadensis------48,49 sp ______--,------______33 Paleowic rocks ______2, 9, 4, 6 Ptychaspis-Prosaukia zone______16 classification._. ______.------_ 7 T reservoirs for oil and gas______50 R Taenicephalus. _----- ___ -- ______------16 Paleozoic structure.------50 cordillerensis------16 Palmatolepis gonioclymeniae __------29 Radioactive deposits, Phosphoria Formation_ 51 zone _____ ------____ ---- ______16 rugosa ______------.. ------29 Tensleep Sandstone __ ------51 Tensleep Sandstone __ ------95, 97, 40,48 Panderodus gracilis. ______------25 Rattlesnake Hills ___ ------18,50 contact with Park City and equivalent Parabolinoides_ ------16 Receptaculites ______------25 rocks----_------41 Parallelodon tenuistriatus_ ------49 articus ______------25 fossils. __ ------42 sp_ ------_____ ---- ______------__ _ 39 sp______25 oil and gas______51 Paraparchites SP------39 Relief._------____ ------2 radioactive deposits______61 Park City Formation_------49, 44,49 Resserella tersa ______------___ ---- 25 Tentaculites sp _____ ------____ ------49 contact with Dinwoody Formation______47 Rhombopora sp ______------48 Teton Range ______18,25 fossils. ___ ------47, 48 Rhynchotrema capa.t. _------25 Tetracamera subcuneata______33 Grandeur Member______47 increbescens ______------25 Textrataxis millsapensis______39 oil and gas______51 Robinson, G. D., cited______19 Thaerodonta sp_ ------25 phosphate rock______51 Ross, R. J., Jr., cited ______------25,26 Thomas, H. D., cited ______43,47,48,50 Park Shale Member of Gros Ventre Forma- Three Forks Shale. __ ------27 tion ______15,18 s Topography------2, 97 Patella sp ____ - --~------_------___ __ 48 Sacajawea Formation ___ ------30,35 Triassic rocks. __ ------49,49 Patellostium sp ___ ------___ ------48 Sandberg, C. A., cited __ ------27, 29,33 Trichonodella sp __ ------_____ ------25 Pathfinder uplift. __ ------______50 Sando, W. J., cited ______30, 33, 39,40 Pricrepicephalus ______------16 Paucicrura sp. _------___ 25 Sanguinolaria SP------48 tripunctus. ___ ------16 Pennsylvanian rocks __ ------____ 95,47 Sanguinolites sp __ ------48,49 sp _------______---_---- 16 Permian rocks______49 Saratogia sp __ ------16 Triplophyllites ______------33 phosphate rock______51 Scaphellina concinnus______48 sp------33 Peronopsis. __ ------___ .__ 16 sp_ ------48, 49 'llriticites kellyensis ______------42 Pharkidonotus percarinatus ____ ------39 Schizodus canalis. __ ------______48 sp------42 Phillipsia SP------33 ferrieri. ______------__ 49 Trochonema umbilicatum ___ ------25 Phosphate deposits near Lander______51 wheeleri. ___ ------48,49 Phosphate rock, Park City Formation______51 SP------39, 48, 49 u Permian rocks______51 Scolithus. ___ ------16 Phosphoria Formation______49 Semicircularia arcuata __ ------16 Unconformity between, Bighorn Dolomite Nowood Member __ ------42, 47,49 Shaw, A. B., cited._------15, 19,20 and Darby Formation______29 radioactive deposits______51 Shedhorn Sandstone ___ ------49 Bighorn Dolomite and Madison Lime- Phricodothyris sp _____ ------____ ------__ _ 39 Sheep Mountain______26 stone ______------29 Phyllopora. ______------______49 Silurian rocks __ ------______29 Darby Formation and Madison Lime- sp. ------______48 Sinks Canyon ______27,30 stone____ ------27 Pierocephalia n. SP------16 Solenomya sp ___ ------48 Gallatin Limestone and Bighorn Dolo- Pinna peracuta_ ------49 Sowerbyella sp ______------______25 mite ___ ------SO Plagioglypta __------____ ------______49 Spathognthodus aculeatus ___ ------29 Gros Ventre Formation and Gallatin canna ______------______48, 49 jugosus. _------___ __ 29 Limestone______18 sp. ------··------______39, 49 Sphenosteges hispidus __------48,49 Tensleep Sandstone and Park City For- mation ______--- 41 Platystrophia sp ______------______25 sp_ ------.------48, 49 Pleurophorus occidentalis______49 Spirifer centronatus------______33 pricei. ______---______49 keokuk ______------_____ 33 w subcostatus _____ ------______48 madisonensis. _____ ------33 SPP------39, 42, 48,49 occidentalis_ ~ _------______39 Waagenoconcha montpelierensis ___ ------48 Pleurotomaria ______------__ 49 opimus.------___ 39, 42 Warm Spring Canyon______!89 sp_ ------_----- ____ ------______42, 48 pellaensis ___ ------______33 Warm Spring Creek ______15,20,23,27 Plicatoderbya ______------______49 rockymontanus ___ ------______39,42 Warm Spring Lake______!89 magna ______------48 shoshonensis ______------______33 Warm Spring Mountain. __ ------20 Pliocene rocks------______3 wellerL------______39 Washakie Range ______4,14,17,20,29,35,44 Polidevcia bellistriata ______------______49 sp_ ------33, 39 Wedekindellina sp __ ------42 Polygnathus inornata ___ ------29 Spiriferina brownL______33 Wellerella osagensis------39,48 nodocosfata ___ ------______29 kentuckensis __------___ 48,49 sp ___ ------______------39 triangularis ______------______29 pulchra ______------____ 48,49 Westonia. ------16 varinodosa. _------__ ------______29 solidirostris ______------___ 33 dartoni. ______------16 wyomingensis __ --- _------___ 29 sp_ ------___ 49 ella.______16 B60 INDEX

Pagt> Page y Page Wilbernia SP------B16 Wolsey Shale Member of Gros Ventre Forma- Wind River Canyon_------14, 19, 21, SS, 30 tion __ ------B16 Yochelson, E. L., quoted ______B47 Wind River drainage system______2 Woodward, T. C., quoted______18 Wind River Range_ 3, 20, 22, 26, 27, 30, 36, 37, 39, 40, 44 Word Formation______47 z Wind River structural basin, defined______S Windy Gap______39 X Zaphrentis amsdensis __------______33 Wilkingia sp ____ ------______48,49 Xenocheilos spineum______16 Zygospira jupiterensis ______------___ ------25 0

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