THE OHIO JOURNAL OF SCIENCE VOL. 63 NOVEMBER, 1963 No. 6 STRATIGRAPHY OF THE GREEN RIVER FORMATION IN THE BRIDGER BASIN, WYOMING1 DANIEL A. TEXTORIS Department of Geology, University of Illinois, Urbana, Illinois INTRODUCTION This paper presents the results of a subsurface-surface stratigraphic study of the lacustrine Green River Formation and related strata in the Bridger Basin of southwestern Wyoming. Although the Green River Formation has been mapped in some detail, and several geologists have worked on the shore and near-shore facies in areas bordering the basin, no detailed subsurface study of the formation has so far appeared. The Diamond Alkali Co. No. 3 well was chosen as a type well since it displayed all the surface stratigraphic units in core or cuttings, and electric log. Surface sections and other wells were then correlated with it. PREVIOUS STUDIES Reconnaissance studies of the Green River Formation in the Bridger Basin began with the Territorial Surveys of Powell, Hayden, and King from 1868 to 1878. No detailed stratigraphic work was attempted until Schultz (1920) mapped the Rock Springs Uplift and adjacent areas. Green River nomenclature was ex- panded or revised by Sears and Bradley (1924), Bradley (1926, 1959, 1961), Donavan (1950), Deardorff (1959), and Culbertson (1962). Several geologists have studied the shore and near-shore phases of the Green River Formation. Donavan (1950) and Oriel (1961) worked on the northwest outcrop, McGrew and Berman (1955) in the north, and Bradley (1926) in the northeast. Sears and Bradley (1924), Anderman (1955), Deardorff (1959), Millice (1959), and Culbertson (1961) studied the relationships in the southeastern part of the basin. Love et al. (1955), Blackstone (1955), and Bradley (1961) have published geologic maps of the area. Important contributions by Bradley on varves, origin of oil shale, the Green River climate, and other topics have been published. Since the discovery of the evaporite mineral shortite (Na2CO3-2CaCO3) by Fahey (1939), many papers and abstracts have appeared dealing with the descrip- tion and genesis of the unique mineral assemblage of the Green River Formation. Complete bibliographies may be found in Milton and Eugster (1959) and Fahey (1962). Winchester (1923) and Deardorff (1959) have reported on some of the oil shales along the eastern outcrop. Love (1955) and Love and Milton (1959) described several uraniferous zones. LOCATION AND GEOLOGIC SETTING The Bridger Basin is located in the extreme southwestern part of Wyoming, and extends a few miles into northeastern Utah (fig. 1). It is essentially triangular xAdapted from part of a thesis presented in partial fulfillment of the requirements for the degree Master of Science in the Graduate School of The Ohio State University, 1960. THE OHIO JOURNAL OF SCIENCE 63(6): 241, November, 1963. 242 DANIEL A. TEXTORIS Vol. 63 in shape, with the east-west trending Uinta Mountains at the base. The western leg of the triangle consists of the Wyoming Range and the hogbacks formed by The Darby and Absaroka overthrusts. The Rock Springs Uplift and the Wind River Mountains form the eastern boundary, and the Gros Ventre Mountains are at the apex of the triangle. This study is concerned with the southern two- thirds of the basin, in which the Green River Formation was deposited. The Early and Middle Eocene Green River Formation lies nearly everywhere on the Early Eocene Wasatch Formation, but in some areas overlaps pre-Wasatch rocks. Much of the Green River Formation is overlain by the Middle or Late(?) FIGURE 1. Index map of the Bridger Basin showing the locations of surface sections and wells, lines of cross sections, and general geology of the Bridger Basin and surrounding areas. The geology is modified after Love et al. (1955), Blackstone (1955), and Bradley (1961). No. 6 GREEN RIVER FORMATION 243 Eocene Bridger Formation. The highlands that surround the basin are composed of crystalline and sedimentary rocks which range in age from Precambrian to Paleocene. The Bridger Basin is both a topographic and a structural basin, and the Green River Formation dips gently basinward and forms conspicuous escarp- ments along most of its outcrop. The southern, western, and northern outcrops are essentially marginal deposits denoting the original areal extent of the Green River beds, whereas the eastern outcrop is erosional and exposes typical lacustrine rock. STRATIGRAPHY Nomenclature The Green River Formation was named by Hayden (1873), from outcrops in the vicinity of the town of Green River, Wyoming. The name was applied to thinly laminated chalky shales of lacustrine origin. Three years later, Powell (1876) divided the formation into the Upper and Lower Groups, with his Tower Sandstone forming the base of the Upper Group. Since then, the nomenclature has undergone extensive revision (fig. 2). HISTORY OF NOMENCLATURE HAYDEN POWELL SCHULTZ BRADLEY DONAVAN BRADLEY DEARDORFF 1873 876 1920 1926 1950 1959 1959 THIS REPORT EAST EAST EAST EAST NORTHEAST NORTHWEST N. W. S WEST EAST NORTHEAST SOUTHEAST N.W. a WEST EAST NORTHEAST BRIDGER BRIOGER BRIDGER BRIOGER BRIDGER BRIDGER FORMATION BRIDGER FORMATION BRIDGER FORMATION GROUP FORMATION FORMATION FORMATION . MORROW LANEY LANEY R PLANT . PLANT MORROW MORROW LANEY CREEK BEDS BEDS G SHALE R UPPE SANDSTONE SS. LENTIL SS LENTIL SS. LENTIL LANEY SH. LANEY / \ LANEY \ WILKINS \ SHALE \ PEAK PEAK / R GREEN a MBR./ \MBR. \ MBR. MBR. / BEDS \ MBR. 3 UNIT MBR./ , LACUSTRINE LANEY /CATHE- MB GREEN NEW\ NEW\ /CATHE- CATHE\ K /CATHE- FACIES / DRAL < MIDDLE LOWER SHALE FORK\ FORK\ PEAK / DRAL SILTSTONE SHALES OF DRAL\ / DRAL / BLUFFS TONGUE\ / BLUFFS TONGUE CATHEDRAL TONGUE\ BLUFFS\ / BLUFFS GREEN MEMBER / TONGUE MEMBER PEA / TONGUE S BLUFFS OF THE \ OF THE \ GN.-GRAY TONGUE\ z / TONGUE RIVER WASATCH \ WASATCm OF THE OF THE \ LOWER OF THE RED BEDS SHALE WASATCH FM FM. \ WASATCH FM WASATCH \ WASATCH FM GROUP MEMBER BEDS * UNIT WILKIN SHALE SHALE SHALE SHALE SHALE TONGUE MEMBER TONGUE TONGUE TONGUE MEMBER MEMBER MEMBER MEMBER MEMBER TONGUE WA3ATCH BITTER GREEK WASATCH KNIGHT WASATCH WASATCH FORMATION WASATCH FORMATION GROUP GROUP FORMATION FORMATION FORMATION FIGURE 2. Chart showing the history of nomenclature for the Green River Formation in the Bridger Basin. The terminology used in this report is essentially that of Bradley, Donavan, and Deardorff. However, I do not believe that the name Fontenelle is necessary to designate a mere continuation of the Tipton on the west side of the basin. The only difference between the two is that the unit becomes more clastic to the west and northwest as it approaches a source area. The Tipton Tongue of Bradley (1926) displays exactly the same characteristics in the northeast as it approaches the Wind River Mountains. I also believe that the name New Fork should be abandoned in favor of the name Cathedral Bluffs. The "New Fork Tongue" is essentially equivalent to the Cathedral Bluffs Tongue to the northeast, and has a similar genesis and lithology. The two are probably contiguous in the sub- surface in the northern part of the basin. The only difference is that the New Fork is somewhat discontinuous, thinner, and the sediments had their source in the northwest and wTest rather than in the northeast. The three Wilkins Peak subdivisions of Deardorff (1959) are simply called units. The lower and upper units may be the only two represented in the northern 244 DANIEL A. TEXTORIS Vol. 63 FIGURE 3. Type well of the Green River Formation, Bridger Basin. Diamond Alkali Co. No. 3. See Textoris (1960) for complete cutting and core description. No. 6 GREEN RIVER FORMATION 245 part of the basin, and the lower and perhaps the middle units are the only two present in the western part. The Tower Sandstone Lentil has been retained in this report for convenience although Culbertson (1962) suggested abandonment. The Tower is not one continuous unit either horizontally or vertically, although Tower-like sandstones TABLE 1 Names and locations of surface sections, Bridget Basin, Wyoming Reference letter Name Location Reference A Big Piney Northern part of After Donavan (1950, PI. 11) 28N 111W B Hams Fork 29, 30, 32, 21N Measured by Bates and Textoris. See 114W Textoris (1960, Appendix II) for description C Piedmont 2, 3, 14N 117W Measured by Bates. See Textoris (1960, 35 16N 116W Appendix II) for description D Currant 3, 5, 6, 14N 106W After Deardorff (1959) Creek 33, 34 15N 107W E White 3 21N 105W Measured by Deardorff and Textoris. See Mountain Textoris (1960, Appendix II) for description F Leucite NW part 24N After Bradley (1926, PI. LIX) Mountain 103W G Alkali Central part After Bradley (1926, PI. LIX) Brook 25N 102W TABLE 2 Names and locations of wells, Bridger Basin, Wy Reference number Name Location Reference 1 Diamond Alkali, 3 8 18N 108W Type well. See Textoris (1960, Appen- dix I) for detailed cutting and core description. 2 Diamond Alkali, 6 18N 106W McKenna 1 3 Diamond Alkali, 1 12 18N 112W 4 California 6 14N HOW Dry Creek 1 5 Diamond Alkali, 24 16N 109W Reid 1 6 Diamond Alkali, 32 17N 107W Reid 2 7 Diamond Alkali, 12 18N 108W Butler 1 8 Diamond Alkali, 28 20N 108W Berger 1 9 General Petroleum, 9 24N 109W Lithology from the American Strati- Buckhorn 62-A-9 graphic Company 10 Carter, Opal 1 34 22N 112W Lithology from the American Strati- graphic Company 11 Mountain Fuel, 14 17N 112W Lithology from the American Strati- Church Buttes 18 graphic Company 12 Diamond Alkali, 26 16N HOW Findley 2 246 DANIEL A. TEXTORIS Vol. 63 do occur only in the lower 400 ft of the Laney Shale Member. Indeed, the beds are not quartzose but tuffaceous sandstones or even crystal tuffs (Bradley, 1959). Certainly, the bodies of sandstone are lenticular and not one lentil, but the beds are very conspicuous in the vicinity of the town of Green River and here I believe the name can be applied.