Brigham Young University Geology Studies

Volume 27, Part 2

CONTENTS

The Kinnikinic Quartzite (Middle Ordovician) in the Type Area, Central Idaho, and a New Reference Section near Arco, Idaho ...... Robert Q. Oaks, Jr., and W. Calvin James

Geology of the Sage Valley 7 W' Quadrangle, Caribou County, Idaho, and Lincoln County, Wyoming ...... J ohn L. Conner

Geology of the Elk Valley Quadrangle, Bear Lake and Caribou Counties, Idaho, and Lincoln County, Wyoming .... J. Floyd Hatch

Geology of the Woodruff Narrows Quadrangle, Utah-Wyoming ...... Valen D. Ott

Geology and Ore Deposits of Mineral Mountain, Washington County, Utah ...... Stuart K. Morris

Conodonts and Biostratigraphy of the Lower Mississippian in Western Utah and Eastern Nevada ...... Gary J. Newman

Relative Age Determination of Quaternary Fault Scarps along the Southern Wasatch, Fish Springs, and House Ranges ...... Lee Piekarski

Geology and Mineral Deposits of the Lodi Hills, Nye County, Nevada ...... R. Blaine Rowley

The Flagstaff Formation: Depositional Environment and Paleoecology of Clastic Deposits near Salina, Utah ...... Steven W. Sperry

Geology of the Sewing Machine Pass Quadrangle, Central Wah Wah Range, Beaver County, Utah ...... Richard F. Wheeler

Publications and Maps of the Geology Department

Cover: Air photo of House Range fault scarp Courtesy of Lpe P~ekarski. A publicatioll of the Department of Geology Brigham Young Unrversiry

Provo, litah 84602

Editors

W. Ket~nethHamblin Cynthia hf. Gardner

Bllghdm Yomg linzwrfzrjv C;eolo~Stud~ei 17 published by rhe department. Geology Stud- 28 LonsIstS of graduate-student and staff rebearch In the department and occastonal paper\ from othe~contr~bucors Stadzesfor St~dmtssupplements the regular i~~esand IS lntetrded as a serles ut qhort papers of general Inrerest whlch ma? serve AS gu~desto the geolog of Utah for beginning students and laymen

ISSN 0068-1016 Distributed November 1980

l t -80600 46504 Geology of the Sage Valley 7 M' Quadrangle, Caribou County, Idaho, and Lincoln County, Wyoming*

JOHN L. CONNER Texaco, Inc. P.O. Box 2420 Tul~a,Oklahoma 74102

ABSTRACT.-T~~Sage Valley Quadrangle straddles the Idaho-Wyoming border continue to study this region, but no well data or geophysical in the central part of the Overthrust Belt. Approximately 5,400 m of primarily information has thus far been published on the Sage Valley sedimentary strata are exposed, including from the Pennsylvanian Wells Forma- tion through the Tertiary Salt Lake Formation. Rocks within the Cretaceous Quadrangle. Gannett Group previously mapped as Ephraim Conglomerate are now known Mansfield (1927, p. 131-72) summarized the structural his- to include Ephraim Conglomerate, Peterson Limestone, Bechler Conglomerate, Draney Limestone, and Smoot Formation. Rocks previously mapped as the Cre- tory of southeastern Idaho and western Wyoming. Armstrong taceous Wayan Formation in the quadrangle are now mapped as Smoot Forma- and Cressman (1963) described the prominent folded Bannock tion and Tygee Member of the Bear River Formation. Overthrust, which was later named the Meade Overthrust by Two major thrust sheets, the Absaroka and Meade Plates, are recognized in Cressman (1964, p. 62). the quadrangle. Six major imbricate thrust faults, including the West Sage Val- ley Branch, the East Sage Valley Branch, the West Tygee Branch, the East Several quadrangles near and adjacent to the Sage Valley Tygee Branch, the West Hardman Branch, and the East Hardman Branch, were Quadrangle have been mapped recently, mostly by the U.S. mapped as well as two minor unnamed thrust faults. Several minor east-west Geological Survey, to define and evaluate deposits of phosphate trending tear faults and normal faults offset the thrust faults, the fold axes, and individual rock units. The Boulder Creek Andcline, the Afton Anticline, the rock. Montgomery and Cheney (1967) mapped the geology of Spring Creek Syncline, an unnamed anticline, and an unnamed syncline are ma- the Stewart Flat 7%-minute quadrangle, adjacent to the west, jor north-south trending folds mappable across the quadrangle and were prob- and Cressman (1964) mapped the geology of the Georgetown ably formed contemporaneously with thrusting. Canyon-Snowdrift Mountain area, which is adjacent to the Only a single deep well has tested the hydrocarbon potential of the quad- rangle; additional tests seem warranted. Phosphate rock from the Phosphoria southwest (fig. 1). In addition, Gulbrandsen, McLaughlin, Formation and other occurrences of materials for construction were evaluated for exploitab~liry.

INTRODUCTION The Sage Valley 7%-minute quadrangle is included in the region mapped by Mansfield and others (Mansfield 1927) dur- ing early investigations of the western phosphate field. The Sage Valley Quadrangle straddles the Idaho-Wyoming border in the central part of the Overthrust Belt and is approximately 35 km northeast of Montpelier, Idaho, and 7 km west of Af- ton, Wyoming (fig. 1). A .8-km-wide strip along the western border of the quadrangle is in the Caribou National Forest, and a 15.5-kmz area in the southeast corner of the mapped area is in the Bridger National Forest. The remainder of the quadrangle is privately owned, and permission to cross private lands must be obtained from local owners. Numerous ranch and U.S. For- est Service dirt roads branch from gravel roads along Crow Creek and along the eastern border of the map area and provide ready access to most of the area. Primitive roads lead into all but the most rugged areas.

Previous Work Geologic studies done in the region prior to 1927 were summarized and updated by Mansfield (1927). He mapped the Crow Creek 15-minute quadrangle on a scale of 1:62,500 as part of his study of the geology of southeastern Idaho. Stratigraphic nomenclature used by him is applicable to most units in the quadrangle. Kummel (1954) more recently described the re- gional Triassic stratigraphy of sou theastern Idaho and adjacent areas. Eyer (1964) also made a significant contribution in his of the rocks of western and south- FIGURE1.-Index map of the Sage Valley Quadrangle in southeastern Idaho and eastern Idaho. Petroleum and phosphate mining companies western Wyoming.

.A thesis p-nrcd ro rhc Dcprtmrnr oiGcology, Brigham Young Univcnlv, in pnrr~alfulfillmcnr of rhc rcquiremcnrr for the degree Masrer of Sclcncr, April 1980. Thcsir chrlrman: Jtmcr L Baer Honkala, and Clabaugh (1956) mapped the Johnson Creek 7%- 2842) later restricted the Wells Format~onto the lower two of minute quadrangle, Cressman and Gulbrandsen (1955) mapped these unlts The Wells Format~onIS used In thls report In th~s the Dry Valley 7%-minute quadrangle; and R~oux,Hite, Dyn~, modified sense, and the two units are referred to as the upper and Gere (1975) mapped the Upper Valley 7%-minute quad- and lower members. Cheney and others (In McKelvey and rangle, all nearby. Other U.S. Geological Survey and private others 1959, p. 12-15) defined the upper unit as the Grandeur sector studies have been published that deal malnly with the Tongue of the Park C~tyFormation, to be discussed later phosphate depos~ts. The Wells Formation crops out in the core of the Boulder Creek Anticline west of Sage Valley (plate 1). Only the upper F~eldMethods member of the Wells Format~oncrops out withln the quad- Fieldwork was done between June and October 1979. Struc- rangle, and it forms a low, tree-covered ridge It IS overlain ap- tural features and contacts were plotted on colored aerial pho- parently conformably by the Grandeur Tongue of the Park tographs (scale 1:15,000) and subsequently transferred to the City Format~on A partial measured section, 238 m thick, con- 1:24,000 scale topographic base map of the Sage Valley 7%- taining only the upper unlts, was measured on the east flank of minute quadrangle (fig. 1). Stratigraphic sections were mea- the antlcllne The measured sectlon consists of light colored, sured using a l>-m tape, a Brunton compass, and an Abney lev- fine-grained sandstone that forms alternating ledges and slopes el. Samples of rocks were taken for later detailed description The sandstone IS composed mainly of quartz grams, usually and fossll analysis. well cemented by sll~ca,though porosities, probably secondary in origin, of up to 15 percent were observed in some unlts The ACKNOWLEDGMENTS matrix of some of the sandstone units is calcareous. Much of The writer wishes to express appreciation to Drs. James L the sandstone 1s brecc~atedand rehealed. It is apparent that the Baer and J Keith Rigby for their time and numerous helpful breccia IS not sedimentary in origin, but resulted from fractur- suggestions pertaining to the geology and the preparation of Ing of the rock, slight rotatlon of the fragments, and recemen- the thesis Marlon Nance, Gary Oberhansley, and Floyd Hatch tatlon. A light gray sandy llmestone unit was observed near the helped w~ththe fieldwork. Special thanks to Dr. Morris Peter- top of the formation. No fossils were observed In exposures of sen for helplng on identificat~onsof the Thaynes fossils. Steve the format~onin the quadrangle Sperry helped with the laboratory work Doug Taylor, Dave The lower one-third of the upper member of the Wells Jenklns, Dick Hill, and Lynn Meibos asslsted with the prepara- Formation IS Middle Pennsylvanian (Desmoinesian), and the tion of the structural contour map. Some drafting was done by upper two-th~rdsare of Permian age. Whether all the Wells personnel of the Gulf Oil Company of Casper, Wyomlng. The Formation of Permian age IS Wolfcamp~anor whether Leon- thesis was partially funded by grants from Conoco, Inc , Mara- ardian rocks are present at the top is unknown These age de- thon 011 Co., and Brigham Young University Department of terminat~ons,reported by Cressman (1964, p 24-29), are based Geology upon fossil collect~onsfrom the Snowdrift Mountain Quad- Gratitude IS expressed to Kent N~eldand his famlly of Af- rangle and surrounding areas ton, Wyoming, and Ray "Pete" Peterson of Cokevllle, Wyom- Subsidence in th~spart of the Cordilleran geosyncllne in ing, for their support during the fieldwork. I espec~allywish to the Early Permian resulted in the shallow-water marlne deposi- thank my parents, Jack and Wilma Conner, for the~rsupport tlon of the sandstone and carbonate rocks of the upper member during the thew work. of the Wells Format~on.Most of the sand grams were derlved from the craton to the east (Cressman 1964, p. 85-87). STRATIGRAPHY Grandeur Tongue oftbe Park Czty Fonnutzon General Statement The Grandeur Tongue is a northward extension of the The Sage Valley Quadrangle contains an exposed strati- Grandeur Member of the Park C~tyFormat~on, named by graph~csequence of sedimentary rocks about 5,400 m thick Cheney and others (in McKelvey and others 1959, p. 12) for (fig. 2). Format~onsof this sequence involved in Upper Cre- Grandeur Peak, Salr Lake County, Utah The rocks assigned to taceous to Paleocene thrust faulting and folding range from the the Grandeur Tongue In the Sage Valley Quadrangle (fig. 2) Middle Pennsylvanian Wells Formation to the Lower Cre- were prev~ouslyincluded in the Wells Format~on,as the cherty taceous Tygee Member of the Bear Rlver Formation The Ter- limestone member, by Richards and Mansfield (1912, p. tiary Salt Lake Formation, a freshwater lacustrine deposit that 689-93). Because of the thinness of the unlt and the absence of covers a major portlon of the low-lying areas of the quadrangle, good exposures within the quadrangle, the Grandeur Tongue was deposited after the thrust faultlng and folding. Younger was not mapped separately but was grouped as a map unlt w~th alluv~um,colluvium, salt, and travertine deposlts are cons~dered the upper member of the Wells Format~on. to be of Quaternary age Igneous rocks have been mapped In The Grandeur Tongue IS exposed on the east flank of the nearby areas but are absent in the quadrangle. Boulder Creek Anticline In sections 19, 20, 29, and 30, T. 8 S, R. 46 E, in the quadrangle but is faulted out at the surface Pennsylvan~anand Perm~anSystems south of sectlon 29 At the type locality, the Grandeur Member Wells Fonnatzon is approximately 80 m thick and conslsts of limestone and dolo- Richards and Mansfield (1912, p. 689-93) proposed the mite, some of which contaln chert nodules and minor cal- name Wells Fonnatzon for an 800-m-thick sequence of sandstone careous sandstone A partial sectlon was measured 1 km west of and limestone that is exposed on the north side of Wells Can- Sage Valley on the north side of Pole Creek (see appendix). yon In the Snowdr~ftMountaln Quadrangle, Idaho. At the The tongue is estimated to be approximately 25 m thlck, al- type locality, the Wells Formation was div~dedby Richards and though only the lower 7 m are exposed. The exposed beds are Mansfield (1912, p. 691) into an upper calcareous sandstone or composed of very finely crystalline, med~umgray dolom~tethat siliceous limestone unit, a m~ddlesandy unit, and a lower sandy weathers to a light gray. Numerous small fractures contaln sec- and cherty llmestone unit. McKelvey and others (1956, p. ondary sparry calc~te.The unlt is most often seen as a float- GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING

SANDSTONE

FAULT FIGURE2.-Generalized stratigraphic column for the Sage Valley Quadrangle. Thicknesses are in meters INNER covered slope with rare ledges. The Grandeur Tongue IS under- ently In normal contact wlth the conformably underlying lain apparently conformably by the upper member of the Wells Grandeur Tongue of the Park City Formation and w~ththe Formation, the lower boundary of the Grandeur Tongue drawn conformably overlying Rex Chert Member of the Phosphoria at the base of the dolomite unit. The upper hitof the Gran- Format~on. deur Tongue is at the shoulder at the bottom of the swale The shaly Meade Peak Member IS not naturally exposed in formed In the conformably overlying Meade Peak Member of the quadrangle but is represented as a covered swale between the Phosphor~aFormation. No fossils were observed in expo- the more resistant Grandeur Tongue and Rex Chert beds. It is sures in this quadrangle. est~mated to be approx~mately 45 m th~ck F~vebulldozer The Grandeur Tongue in southeastern Idaho IS dated as trenches in sections 29 and 32, T 8 S, R. 46 E, offered the only Early Permian (Leonardian) by Williams (in McKelvey and exposures seen dur~ngthe mapping in 1979. The Meade Peak others 1959, p. 36-37) on the basis of brachiopod collections. beds are entirelv faulted out In two of the trenches Where ex- Origin of the Grandeur Tongue is generally discussed in posed in the other trenches, the member consists of inter- McKelvey and others (1959). These rocks, as exposed In the bedded black, oolite-pelletoid phosphate and dark brown to Sage Valley Quadrangle, probably or~ginatedas a bioclast~c black phosphat~c mudstone These l~tholog~essuggest that l~mestoneor calcareous sandstone de~osltedunder fa~rlvshal- these beds are near the top of the member (McKelvey and low-marine cond~tions.Subsequently, they were subjected to a others 1959, p 21; Montgomery and Cheney 1967, p 22). secondary dolomitization. McKelvey (in McKelvey and others, 1959, p. 23-25) sum- marized evidence bearlng on the depositional environment of Phosphona Formation the Meade Peak phosphat~cbeds. He ind~catedthat the sedi- The Phosphor~a Formation was named from Phosphoria ments accumulated under a variety of conditions on the gently Gulch, which is about 4 km north of Meade Peak, in south- shoaling bottom of a large embayment that probably was eastern Idaho (Richards and Mansfield 1912, P 684). At the flooded by cold, phosphare-rich water from the open ocean type locallty in Phosphoria Gulch four members are recog- Rex Cbert and Cherty Shale Members. The Rex Chert Member nized: the basal Meade Peak Phosphatic Shale Member, the of the Phosphoria Format~onwas named by Gale (R~chardsand overlying Rex Chert Member, the unnamed cherty shale mem- Mansfield 1912, p. 684) for Rex Peak In the Crawford Moun- ber, and the uppermost Retort Phosphatic Shale Member. Two tains, Rich County, Utah. The Rex Chert was first described by other members-the lower chert member, laterally continuous R~chardsand Mansfield (1912) in Phosphoria Gulch, ~tstype w~ththe lower beds of the Meade Peak Member, and the Tosi locality, as conslstlng of approximately 45 m of mass~velybed- Chert Member, laterally continuous with the upper part of the ded chert that contains some interbedded limestone near the Retort Member and the cherty shale member-are not present base and some cherty mudstone near the m~ddleand that IS at the type locality but are present in the broader area of char- overlain by approximately 30 m of cherty mudstone in the up- acter~sticdevelopment of the Phosphoria Formation (McKelvey per part of the member. McKelvey (In McKelvey and others and others 1959, p. 20-21.) 1956, p 2847-48) restricted the Rex Chert to the lower 45 m Members mapped in the Sage Valley Quadrangle have a to- of massively bedded chert and basal limestone and proposed the tal combined th~cknessof approximately 120 m and Include, upper 30 m of cherty mudstone as a separate member of the from the bottom up, the Meade Peak Phosphatic Shale Mem- Phosphona Format~on ber, the Rex Chert Member, and the unnamed cherty shale The Rex Chert in the Sage Valley Quadrangle IS In fault member The Rex Chert and cherty shale member are com- contact with the Wells Format~onand the Grandeur Tongue b~nedas a single map unlt (plate 1). Montgomery and Cheney of the Park C~tyFormatlon In sectlon 32, T 8 S, R. 46 E, and (1967, p. 25-26) noted, near the top of the cherty shale mem- sectlon 19, T. 9 S, R. 46 E. Elsewhere, w~thinthe quadrangle, ber In the Stewart Flat Quadrangle, adjacent to the present in the Boulder Creek Anticl~ne,the Rex Chert is In apparent map area on the west (fig. I), mudstone and phosphor~tebeds normal contact wlth the Meade Peak Member of the Phos- that represent tongues of the Retort Phosphat~cShale Member. phoria Formation. The contacts between the Meade Peak, the They were not seen In the Sage Valley Quadrangle e~therbe- Rex Chert, the cherty shale member of the Phosphor~aForma- cause of burial by weathered debris or because of th~ndevel- tlon, and the lower member of the D~nwoodyFormat~on are all opment No fossils were seen in exposures of this formation In apparently conformable. thls quadrangle. The combined thickness of the Rex Chert and cherty shale The Phosphorla Format~onIS probably Leonard~anor Gua- members, as suggested by map pattern, IS approx~mately80 m dalup~anin age, as suggested by work on foss~lcollect~ons from although the th~cknessesobtained from the map are not every- the Phosphoria Formation by Willlams (In McKelvey and where reliable because the upper contact was located in the others 1959, p. 38-41). field by float or by toPograph; - Meade Peak Phosphatzc Shale Member. The Meade Peak Phos- The Rex Chert forms a resistant ledge or cl~ffand consists phatic Shale Member of the Phosphor~aFormation was named mainly of light gray to black chert. The beddlng of the chert by McKelvey and others (1956, p. 2845) for Meade Peak, ranges from even to wavy or lenticular w~thunlts from 3 to Idaho At its type locality In Phosphor~aGulch In Idaho, the 550 cm th~ck.Stylolites are present In many beds The Ilme- Meade Peak Member consists of approximately 60 m of dark, stone and cherty mudstone reported in other areas (McKelvey carbonaceous, phosphatic, and argillaceous rocks. and others 1959, p 21; Montgomery and Cheney 1967, p 22) The Meade Peak beds are In fault contact with the Wells were not observed In thls quadrangle, probably because of Formation and the Grandeur Tongue of the Park City Forma- weather~ng and burla1 by erosional debris. The cherty shale tlon w~thinthe present quadrangle The member may be mlss- member does not crop out In the quadrangle but IS marked by ~ngor covered by Salt Lake Format~on~n places on the east slopes of medium brown so11 and an occas~onalfragment of limb of the Boulder Creek Ant~clinesouth of sectlon 29, T 8 cherty mudstone S, R. 46 E, In the Sage Valley Quadrangle. In sectlons 18, 19, McKelvey (In McKelvey and others 1959, p 26-28) sum- 20, and 29, T. 8 S, R. 46 E, the Meade Peak Member is appar- marlzed various arguments and evidences for the ongln of the GEOLOGY OF THE SAGE VALLEY QU ADRANGLE, IDAHO AND WYOMING I5 Rex Chert. The arguments include that it is silica chemically Dinwoody Formation in the Sage Valley Quadrangle were precipitated directly from sea water, silica derived from volcanic probably deposited under shallow marine conditions. Numer- rocks, or silica produced by accumulation and alteration of ous fragmented fossils were seen in the limestone units. Sedi- spiculites, among other organically precipitated origins. The mentary structures seen in some of the siltier units include present study adds little to the resolution of the argument. cross-bedding, ripple marks, and roll structures, indicating that The cherty mudstone is, in part, a basinward facies of the at least some of the formation was deposited in a fairly high- Rex Chert Member and was probably deposited in somewhat energy environment. deeper water than were the Rex Chert beds. The surface of dep- Lower Member of the Dinwoody Formation. The lower member osition for both members was continuously below wave base of the Dinwoody Formation crops out in sections 17, 18, 20, (McKelvey and others 1959, p. 27-29). and 29, T. 8 S, R. 46 E (plate I), with the best exposures oc- curring on the north side of Smokey Creek Canyon (fig. 3). Triassic System Sheldon and Carswell (in Montgomery and Cheney 1967, p. Dindy Formation 28-29) measured a partial section on the north side of Smokey The Dinwoody Formation was named by Blackwelder (in Creek Canyon in section 18, T. 8 S, R. 46 E, a few hundred feet Condit 1916, p. 263) for Dinwoody Canyon on the north- within the border of the Sage Valley Quadrangle. eastern flank of the Wind River Mountains in Wyoming. The The lower member of the Dinwoody Formation is approx- name Dinwoody Formation was first used in southeastern Idaho imately 280 m thick. It consists mostly of thin-bedded to fissile, by Kummel (1954, p. 167), who assigned it to rocks previously grayish brown, calcareous siltstone and shale that grade upward mapped as Woodside Shale by Mansfield (1927, p. 86-87). into thick-bedded calcareous siltstone and silty limestone. The As originally defined in its type area, the Dinwoody Forma- limestone is gray and fine to medium crystalline, with most tion consisted of approximately 60 m of gray and olive shaly units containing rare to numerous bivalve fragments. The up- siltstone and shale, with thin, brown, pelecypod-bearing lime- per 40 to 60 m of the lower member is thicker bedded and stone beds near the base (Blackwelder 1918, p. 424-26). Newell forms more prominent ledges than the underlying shaly units. and Kummel (1942, p. 941) later restricted the Dinwoody For- Roll structures, cross-bedding, and ripple marks occur in siltier mation in its type area to include only the dominantly silty units in the upper part of the lower member. strata between the underlying Phosphoria Formation and the The base of the member was mapped at the upper limit of top of the resistant siltstones. The formation thus includes cherty float from the Cherty Shale Member of the Phosphoria only the lower half of the original Dinwoody Formation, with Formation because the contact is covered. Cressman (1964, p. a restricted total thickness of approximately 30 m in the type 39) stated that the contact is sharp and conformable, where ex- area. posed, and marked by a thin, nodular phosphorite bed which is The Dinwoody Formation crops out in the study area on the uppermost unit of the Phosphoria Formation. The top of the Boulder Creek Anticline in sections 7, 8, 17, 18, 20, and 29, the lower member of the Dinwoody Formation was mapped at T. 8 S, R. 46 E (plate 1). It is split into an upper and a lower the lower edge of the shale developed in the Woodside Forma- member by a tongue of the Woodside Formation. The two tion. These units appear to be conformable. members have a combined total thickness of approximately 470 m. Upper Member oftbe Dinwoody Formation. The upper member Kummel (1954, p. 182-83) assigned a Lower Triassic (Oto- of the Dinwoody Formation crops out in sections 7, 8, 18, and ceratan-Flemingitan) age, equivalent to the Griesbachian 19, T. 8 S, R. 46 E, of the Sage Valley Quadrangle (plate 1). It through the Dienerian stages of Silberling and Tozer (1968, was calculated to be approximately 180 m thick, based on map p. lo), to the Dinwoody Formation on the basis of ammonite pattern, and contains generally the same rock types as the lower occurrences. member: i.e., grayish brown shale, calcareous siltstone, and silty Kummel (1957) summarized the depositional history and limestone. Shale units are much thinner, and the limestone facies relationships of the Dinwoody Formation. Rocks of the units are thicker bedded and form prominent ledges and ribs in the upper part of the upper member. Siltier beds are commonly cross-bedded. The limestone units are infrequently cross-bedded and usually contain numerous fossil fragments. The apparently conformable contact with the underlying Woodside Formation was mapped at the shoulder at the top of the swale developed in the Woodside Formation. Contact with the overlying A Member of the Thaynes Formation, as defined in this report, is at the base of the Meekoceras-bearing lime- stone of the Thaynes Formation. This contact is apparently conformable.

Wood~iakFormation The Woodside Formation was named by Boutwell (1907, p. 446) after Woodside Gulch in the Park City District of Utah, where it consists of approximately 360 m of fine-grained, dark red shale with minor local beds of siltstone or fine-grained sandstone. Buff, brown, and greenish gray beds also occur but are relatively thin and rare. The Woodside Formation is exposed along the flanks of the Boulder Creek Anticline in sections 7, 17, and 18, T. 8 S, FIGURE3.-Lower Dinwood!, Formation on the north side of Smoke!, Creek Canyon in the Boulder Creek Anticline. Note the small folds super- R. 46 E, of the Sage Valley Quadrangle (plate 1). The forma- imposed on the larger anticline (black line marks a key unit). tion is poorly exposed within the quadrangle and generally 16 J. L. CONNER forms a swale between the more resistant upper and lower some of the light colored limestone units and the well-sorted, members of the Dinwoody Formation. It generally weathers to well-rounded sand grains in the upper Portneuf Limestone a red soil with rare, red, silty shale float. The Woodside Forma- Member. tion is approximately 45 m thick in the mapped quadrangle, Kummel (1954, p. 182-83) assigned a Lower Triassic based on outcrop pattern. The apparently conformable contact (owenitan-~rohun~arGan)age, equivalent to the Smithian with the underlying lower member of the Dinwoody Forma- through Spathian stages of Silberling and Tozer (1968, p. lo), tion was mapped at the lower edge of the swale developed on to the Thaynes Formation on the basis of ammonite the Woodside Formation. The apparently conformable contact occurrences. with the overlying upper member of the Dinwoody Formation A Member. The A Member of the Thaynes Formation crops was mapped at the upper edge of the swale. out on the flanks of the Boulder Creek anticline in sections 6, No fossils were found in the Woodside Formation in the 7, 8, and 17, T. 8 S, R. 46 E (plate 1). It is estimated to be Sage Valley Quadrangle, but the age of the formation is Lower approximately 200 m thick, on the basis of map pattern. The A Triassic by virtue of its intertonguing relationship with the Member consists of weakly, poorly, or nonresistant, poorly ex- Scythian Dinwoody Formation. posed, thin-bedded, black and gray, calcareous mudstone and Kummel (1957) summarized the depositional history and shaly limestone with a 5- to 10-m-thick basal limestone unit, facies relationships of the Woodside Formation and related for- which contains the Meekoceras fauna of Kummel (1954, p. 171), mations. Poor exposure of the Woodside Formation in the and a 50- to 60-m-thick fossiliferous upper limestone unit. The mapped area made additional observations about depositional Meekoceras-bearing limestone exhibits a strong petroliferous environments of the formation impossible. odor when crushed. The basal contact of the Thaynes Forma- tion was mapped at the base of the Meekoceras-bearing lime Thaynes Formation stone (fig. 4). The top of the member was mapped at the top The Thaynes Formation was named by Boutwell (1907, p. of the 50- to 60-m-thick, fossiliferous gray limestone unit that 448) for Thaynes Canyon in the Park City District of Utah. In contains the brachiopod Pugnoides triassicus in its upper part. his study of southeastern Idaho, Mansfield (1927, p. 87) raised Ammonites collected from the lower limestone unit of the the Thaynes to group rank but did not map separate units center of the NWU, section 17, T. 8 S, R. 46 E, in the Sage within the group, which then included, from the bottom up, Valley Quadrangle include: the Ross Fork Limestone, the Fort Hall Formation, and the Meekoceras gracilitatus Portneuf Limestone. Kummel (1943, p. 316) redefined the Meekoceras musbbachanum ( ?) Thaynes as a formation and described several informal members A rctoceras tuberculatum that are roughly correlative to the Ross Fork Limestone and Pseudosageceras multdobatum the Fort Hall Formation. Kummel (1954, p. 171-79) included Prospbingites slossi the overlying Timothy Sandstone as the uppermost member of Mites koeneni the Thaynes Formation. It is in this sense that the formation is used here. Conodonts recovered from the lower limestone at the same lo- Members of the Thaynes Formation mapped in the Sage cation include the following: Valley Quadrangle are the same as those used by Montgomery Neogondolella milleri and Cheney (1967, p. 32-35). The C Member and the Timothy Neogondolella qJp.( ?) Sandstone Member are not exposed in the mapped area. Hadrodontina q. Depositional history and facies of the Thaynes Formation Neorpatboa'us collinsoni were discussed by Kummel (1957). In the Sage Valley Quad- Neospathoa'us sp. (?) rangle, the formation is of marine origin with represented envi- Ellisonia triassica ronments ranging from euxinic basins, indicated by the black Neospathodus waageni limestones, to high-energy, well-oxygenated environments Cypridodella unialata above wave base, indicated by abundant shell fragments in Two unidentified gastropods, one a convolute planispiral species and the other a low-spired conispiral species, were also

FIGURE5.-Nugget Sandstone Un), lower unlt of Portneuf L~mcstoncMember FIGURE4.-Meekoceru~-bearing limestone from the A Member of the Thaynes of the Thavnes Formarlon (T tpl) and the Lancs Tonguc of rhc Ank'irch Formation north of Smokey Creek Canyon. Formation (T al) east of Sage Valley. GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING 17 The upper unit of the Portneuf Limestone consists of me- dium gray to yellowish gray, well-sorted, well-rounded, very fine-grained quartz sandstone. Carbonate and silica matrix is variable in amount. A 3-m-thick, medium gray, sandy lime- stone unit occurs near the base. The upper unit of the Portneuf Limestone is estimated to be approximately 130 m thick, on the basis of map pattern. The upper unit was not assigned to the Timothy Sandstone Member of the Thaynes Formation here because previously published descriptions of sandstone units in the Timothy Sand- stone do not contain limestone beds (Mansfield 1927, p. 91,93; Cressman 1964, p. 42, 44; Kummel 1957, p. 466). Kummel (1954, p. 173) noted several sandstone beds, similar to those of the Timothy Sandstone, in the upper part of the Portneuf Limestone in the Grays Range. The upper unit of the Portneuf Limestone in the Sage Valley Quadrangle, thus, is probably a transition zone between the basinward, more calcareous facies described by Kummel (1954, p. 173) and Cressman (1964, p. 44) as the Portneuf Limestone, and the near- to onshore sand- FIGURE6.-West Tygee Branch of the Meade Overthrust east of Sage Valley stone-conglomerate facies of the Timothy Sandstone. (black line); Jn = Nugget Sandstone, 'E tpl = lower unit of Portneuf Limestone Member of the Thaynes Formation. Lanes Tongue of the Ankareh Formation The Ankareh Formation was named by Boutwell (1907, p. collected. This list does not include all fossils present in the 452) for Ankareh Ridge in the Park City District of Utah and unit, and more work should be done at this locality. Pub- originally included beds now assigned to the Nugget Sand- lications of Kummel and Steele (1962) and Solien (1979) were stone. Boutwell (1912, p. 59) subsequently redefined the Anka- used to identify a majority of the specimens. reh Formation to exclude the Nugget Sandstone. The Ankareh B Member. The B Member of the Thaynes Formation is Formation there consists chiefly of red shale and siltstone, with also exposed on the flanks of the Boulder Creek Anticline in interbedded coarse, very light gray sandstone and rare, thin, fos- sections 7, 8, and 9, T. 8 S, R. 46 E (plate 1). Only the lower siliferous limestone beds. Gale and Richards (1910, p. 479-80) 60 m of the member are exposed in the mapped area, however. introduced the name Ankareh into southeastern Idaho, appar- Montgomery and Cheney (1967, p. 32) estimated the total ently for beds now named the Lanes Tongue of the Ankareh thickness of the member to be approximately 200 m in the ad- Formation. Mansfield (1927, p. 84) abandoned the name Anka- joining Stewart Flat Quadrangle (fig. 1). The member generally reh in southeastern Idaho, however, and included what is now consists of poorly exposed, brownish gray, thinly bedded, cal- the Lanes Tongue in the Thaynes Formation. Kummel (1954, careous siltstone, interbedded with gray and black thin-bedded p. 173) named the red beds in the Thaynes Formation the limestone and shale. The contact with the underlying A Mem- Lanes Tongue of the Ankareh Formation, and that nomencla- ber of the Thaynes Formation is mapped at the top of the re- ture is followed in this report. sistant, gray, Pugnoides-bearing limestone of the A Member. Portneuf Limestone Member. The Portneuf Limestone Mem- The Lanes Tongue is exposed east of Sage Valley in sec- ber of the Thaynes Formation was named by Mansfield (1915, tions 4, 9, 16, 17, and 20, T. 9 S, R. 46 E (plate 1). The Lanes p. 492) for exposures at the head of the Portneuf River in the Tongue is poorly exposed within the quadrangle and forms a Fort Hall Indian Reservation in Idaho. swale between the more resistant upper and lower units of the The Portneuf Limestone Member crops out east of Sage Portneuf Limestone Member of the Thaynes Formation (fig. Valley in sections 4, 8, 9, 16, 17, and 20, T. 9 S, R. 46 E, and 5). The Lanes Tongue generally weathers to a red soil with sections 28, 29, 32, and 33, T. 8 S, R. 46 E (plate 1). It is di- rare, red silty shale float. It is approximately 310 m thick in the vided into an upper and a lower unit by the Lanes Tongue of Sage Valley Quadrangle, on the basis of map pattern. No struc- the Ankareh Formation (fig. 5). Lowest beds of the lower unit ture could be mapped within the unit, and the thickness may are in fault contact with the younger Nugget Sandstone (fig. be exaggerated biiause of structural deformation. The appa;- entlv conformable contact with the underlvine lower unit of 6). Youngest beds of the upper unit have been removed, either , '7 by tectonism or by erosion. the Portneuf Limestone was mapped at the top of the up- The lower unit of the Portneuf Limestone consists of a permost limestone bed in the lower Portneuf unit. Similarly, lower resistant, medium to dark gray, massively bedded, cherty the apparently conformable contact with the overlying upper limestone; a middle sequence of poorly exposed calcareous silt- unit of the Portneuf Limestone was mapped at the base of the stone with interbedded yellowish gray, medium- to coarse- lowermost resistant sandstone bed of the upper Portneuf unit. grained, calcareous sandstone; and-an upper resistant, gray, No fossils were found in the Lanes Tongue of the Ankareh thin- to thick-bedded, bioclastic limestone. No fossils were ob- Formation in the Sage Valley Quadrangle, but its age within served in the lower two units, but a silicified fauna collected in the quadrangle is Lower Triassic by virtue of its intertonguing the upper unit includes numerous specimens, some articulated, with the Scythian Thaynes Formation. of the brachiopod Spiriferina roimdyi, columnals of Pentacrinus whiteii, unidentifiable echinoid spines and fragments, and an Jurass~cSystem unidentified gastropod. The lower unit of the Portneuf Lime- Nugget Sandstone stone is estimated to be approximately 220 m thick, on the The Nugget Sandstone was first described by Veatch (1907, basis of map pattern. p. 56) for a sequence of yellow, pink, and red sandstone beds 18 J L CONNER bounded by the limestone of the Thaynes Formation, below, Nugget Sandstone in Utah and Wyomlng In the Sage Valley and the limestone and shale of the Twin Creek Limestone, Quadrangle, the Nugget was probably depos~tedin close prox- above The formation was named for Nugget Scation on the lmlty to a dune-covered, sandy shoreline. Differentiation of Oregon Short Line Rallway in southwestern Wyoming. Gale subaqueous deposlts from subaer~aldeposits 1s difficult in the and Richards (1910, p. 480) separated the Nugget Sandstone mapped area. from the underlying Ankareh Format~onand were first to ap- ply the name In southeastern Idaho. Mansfield (1920, p 61-62) Twzn Creek Lzmestone restricted the Nugget Sandstone to beds between underlying The Twin Creek Limestone was defined for exposures of rocks now known as the Wood Shale Tongue of the Ankareh marlne limestone, shale, and sandstone along and near Twin Formation and the overlying Twin Creek Limestone, but appar- Creek between Sage and Nugget in western Wyoming by ently included in the top of the formation the red-bed unit Veatch (1907, p. 56). The name was subsequently used in the that was subsequently placed in the Twin Creek Limestone by Sage Creek area by Mansfield (1927, p. 97). Imlay (1950) dl- Imlay (1950, p. 37) The Nugget Sandstone is used in th~sre- vided the formation into seven members that, from bottom to port as restricted by Imlay. top, were called members A-G. Member A was tenamed the The Nugget Sandstone crops out between the East Tygee Gypsum Spring Member by Oriel (1963). Members B-G were and the West Tygee branches of the Made Overthrust, in a renamed, in ascending order, the Sliderock Member, the Rich north-south belt from sections 27 and 28, T. 8 S, R 46 E, to Member, the Boundary Ridge Member, the Watton Canyon sections 20 and 21, T. 9 S, R. 46 E, and In a thrust slice on the Member, the Leeds Creek Member, 2nd the Giraffe Creek Mem- west l~mbof the Spring Creek Syncline from section 10 south- ber by Imla~(1967). The rmdlfied nomenclature of Oriel and ward to sectlon 34, T. 8 S, R. 46 E (place 1). The Buck Moun Imlay is used in this (fig. 2) cam exposures of the Nugget Sandstone rest In fault contact The entire Watton Canyon Member, the upper Part of the above the stratigraphically younger Twin Creek Limestone Boundary Ridge Member, and the lower part of the Leeds and, in turn, are overlain structurally on the west by faulted Creek Member are not exposed in the Sage Valley Quadrangle. lower Portneuf Limestone Member of the Thaynes Formation Undlfferentlated, but probably middle, Twin Creek Limestone (fig. 6) crops out along the Hardman Branch of the Meade Overthrust in sections 2, 3, 2nd 11, T. 9 S, R. 46 E, and section 34, T. 8 S, N~~~ ~~~k ~~~~~~i~,the N~~~~~ sandstone consists mainly of dark to llght red, yellow, and white, fine-gra~ned,cal- R. 46 E (plate l). careous sandstone. It appears falrly homogeneous throughout The Twin Creek Limestone Is 'On- the section, Clay and silt-slze particles vary In amount through- formably the 'reus' and Is disconformabl~under- out the section, but porosity seems minimal Cross-bed sets up lain by the Nugget Sandstone. Hlntze (1973, p 62) indicated to 15 cm high are weathered into relief on the summlt of Buck an unconformlty between the Rich and Boundary Ridge Mountain, but planar laminations are the predominant sedi- in northern Utah, but none was indicated Imlay (1967, mentary structure in other areas of the quadrangle The Buck P. 31' 37)2 was an unconformlty In evidence In the Sage Quadrangle The Twin Creek Limestone Is Mountain section of Nugget Sandstone is estimated to be ap- proximately 350 m thick, on the basis of map pattern. conformable throughout. Gypsum Spnng Member. The Gypsum Spring Member of the On the west limb of the Creek beds Twin Creek Limestone crops out along the Hardman Branch of the Nugget are On the Gypsum of the Made Overthrust in sections 10, 15, 22, and 27, T. 8 S, 'prlng Member of the Twin Creek Limestone but with a R 46 E, and along the East Tygee Branch of the Meade Over- ma1 depositional contact. Lower Nugget beds are covered by thrust in sections and T, s, 46 E, in the studied Salt Lake Formation. Along the Spring Creek Syncl~ne,the quadrangle (plate Nugget Formation is a red to redd~shbrown, blocky, thick-bed- The Gypsum Spring Member Is approximately 70 thick, ded, fine-grained sandstone The top of the formation here was on the basis of map pattern, and consists mainly of soft, red at the 'Ontact of the resistant Nugget Sandstone slltstone and shale with rare Interbeds of yellowish gray lime- with the less resistant red shale and siltstone of the Gypsum stone, In a roadcut In section 9, T, s, R. 46 E, a few green Member of the Twin Creek Limestone. Nugget Sand- and gray mudstone beds are seen within the red units, The stone In this is estimated be a~~roxlmatel~member generally weathers to a swale between the more resist- 230 m thick, on the basis of map pattern. No marker beds were ant N~~~~~ sandstone and Sllderock Member of the Twin seen in e~therthe Buck Mountain section or the Spring Creek Creek Limestone Syncline sectlon to allow correlat~onof the two outcrop belts. Imlay (1967, p 52) reported crlnoid columnals in what he No fossils have been found In the Nugget Sandstone, so its interpreted as a thrust-faulted section of the G~raffeCreek exact age is st111 debated. High ahd Picard (1965, p. 56) found a Member of the Twln Creek Limestone In the SW '/4, section thin conglomerate at the base of the Nugget Sandstone 2nd an 15 T 8 S, R. 46 E, w~thinthe Sage Creek Quadrangle. Absence angular disconformlt~between the Nugget 2nd the underlylng of defin~tlvefoss~l data, plus the litholog~ccharacter~st~cs of the Pop0 Agie Formation and suggested that this represents the un~tand structural style of the area, leads me to reassign these Triassic-Jurassic boundary and the base of the Nugget Sand- beds to the G~~~~~ spring ~~~b~~ (plate 1). stone The upper boundary of Nugget beds 1s a disconformlty Imlay (1967, p 19) ass~gneda m~ddleBajoc~an (Middle Ju- of regional excent (Love 1957, p. 43). Imlay (1967, p 19) con- rassic) age to the Gypsum Spring Member sidered the overlying Gypsum Spring Member of the Twin The Gypsum Spring Member was probably deposited under Creek Limestone to be a middle Baloclan (Middle Jurassic), so shallow-marine to lagoonal condit~ons.The bedded gypsum, the Nugget Sandstone is probably Early Jurassic in south- depos~tedin other areas (Imlay 1967, p. 17-18) but not ob- eastern Idaho served In the present quadrangle, ind~catesa warm and arld ell- Pacht (1977), Kam~s(1977a), and P~card (1977) present mate, and the limestone indicates a more nearly normal marlne the most recent discussions of the orlgin and diagenes~sof the environment. GEOLOGY OF THE SAGE VALLEY QUADRANGLE. IDAHO AND WYOMING 19 Sliderock Member. The Sliderock Member of the Twin Creek Only the lower 70 m of the member is exposed, but the Limestone crops out in the same localities as the Gypsum Stump Creek section, as reported by Imlay (1967, p. 8), sug- Spring Member but is also exposed in section 16, T. 9 S, R. 46 gests that only about the upper 20 m of the member is covered. E, and as a small inlier in the Salt Lake Formation in section The member consists mainly of thin- to thick-bedded, dense, 34, T. 8 S, R. 46 E, and section 3, T. 9 S, R. 46 E, within the gray limestone similar to that of the Leeds Creek Member. quadrangle (plate 1). Near the top of the member in section 10, T. 9 S, R. 46 E, a 5- The member is approximately 60 m thick, on the basis of m-thick, nonresistant, red siltstone forms a band of red soil but map pattern, and consists mainly of tan-weathering, sandy cal- is not exposed. No fossils were seen in this member in the carenite interbedded with some dense, gray limestone. The best mapped. . area. exposures occur in the small inlier, and rocks there consist of Imlay (1967, p. 39) assigned a probable Bathonian (Middle sandy, dense limestone with some beds containing rip-up clasts Jurassic) age to the Boundary Ridge Member. and other beds containing coquinas of the pelecypods Ostrea sp. The Boundary Ridge Member was probably deposited in a (?) and GIyphaea sp. (?). These beds may be lower Rich Mem- shallow marine to littoral or lagoonal environment under cli- ber, but were assigned to the Sliderock Member on the basis of matic conditions similar to those that existed during deposition lithology. Contact with the overlying Rich Member was map- of the Gypsum Spring Member (Imlay 1967, p. 40). ped at the top of the more resistant, thicker-bedded limestone Leeds Creek Member. The Leeds Creek Member of the Twin of the Sliderock Member. The contact with the underlying Creek Limestone crops out in the quadrangle in the core of the Gypsum Spring Member was mapped at the top of the up- Afton Anticline from section 9 southward to section 33, T. 31 permost red bed of that member. Imlay (1967, p. 24) reported N, R. 119 W, and on the west limb of the Spring Creek Syn- the occurrence of the pelecypod GryPhaea planoconvexa fraterna cline in sections 14, 15, and 22, T. 9 S, R. 46 E (plate 1). Imlay, the diagnostic fossil of the Sliderock Member in W '/i, section 10, T. 9 S, R. 46 E, in the quadrangle. A partial section of the upper 150 m of the member was Imlay (1967, p. 26) assigned a middle Bajocian (Middle Ju- measured along Spring Creek (see appendix). Cressman (1964, rassic) age to the Sliderock Member. p. 50) suggested a total thickness of approximately 490 m for The Sliderock Member was probably deposited in shallow, the member in outcrops to the west. The Leeds Creek Member warm, marine water of norial salinity,- as suggested by is poorly exposed, medium to dark gray, shaly limestone that weathers to form light colored slopes covered with splintery Gtyphaea and other fossils (Imlay 1967, p. 30). Rich Member. The Rich Member of the Twin Creek Lime- float. In the road metal pits along Spring Creek in section 16, stone crops out in sections 9, 10, 16, and 21, T. 9 S, R. 46 E, in T. 31 N, R. 119 W, medium to thick bedding occurs in the the Sage Valley Quadrangle (plate 1). member (fig. 7), although most exposures are closely jointed The member is approximately 70 m thick, on the basis of and bedding generally could not be determined. map pattern, and consists mostl; of light gray to olive gray, The ~eedsCreek Member grades upward into the Giraffe dense, shaly limestone. Creek Member, but the contact can be closely located at the Imlay (1967, p. 31) assigned the Rich Member a probably top of the splintery limestone of the Leeds Creek Member and late Bajocian (Middle Jurassic) age. below the more resistant sandstone of the overlying Giraffe The Rich Member was probably deposited in a shallow sea Creek Member. No fossils were seen in this member in this of normal salinity, as indicated by the abundant Gryphaea. A quadrangle. fairly high-energy environment is indicated for at least part of Imlay (1967, p. 48-49) assigned a Callovian (lower Upper the time by the fragmented condition of the fossils. Jurassic) age to the Leeds Creek Member. Boundary Ridge Member. The Boundary Ridge Member of The bulk of the Leeds Creek Member was probably rapidly the Twin Creek Limestone crops out in sections 9, 10, 16, and deposited under shallow marine conditions as a soft calcareous 21, T. 9 S, R. 46 E, of the quadrangle (plate 1). mud (Imlay 1967, p. 49-50).

FIGURE7.-kds Creek Member of the Twin Creek Limestone in the gravel pit FIGURE8.-Giraffe Creek Member of the Twin Creek Limestone along the near the mouth of Spring Creek in the core of the Afton Anticline. Spring Creek road ~n the Afton Anticline. 20 J. L. CONNER Giraffe Creek Member. The Giraffe Creek Member of the A section of the Preuss Sandstone was measured on the Twin Creek Limestone crops out in the same general belt paral- north side of Spring Creek, where it consists of 372 m of lel to the Leeds Creek Member. In addition it occurs in two poorly exposed, grayish red to reddish brown, very fine- to fine- tight anticlinal folds in sections 21 and 22, T. 9 S, R. 46 E, in grained, calcareous sandstone (see appendix). The sandstone is the quadrangle (plate 1). probably interbedded with shale and siltstone, but these lith- A section 31 m thick of the Giraffe Creek Member was ologies are not exposed. measured along Spring Creek (see appendix) and consists of A partial but detailed section of the Preuss Sandstone, thin- to thick-bedded, olive gray and greenish gray, very fine- to which jncludes the uppermost 137 m of the formation, was medium-grained, ripple-marked, cross-bedded, calcareous, measured about 0.8 km west of Fairview, Wyoming, along the elauconitic sandstone. The sandstone is interbedded with siltv access road to the Mobil Max Smith #I well (see appendix). (7 to sandy, gray to green, glauconitic limestone, with the sandier Here, the Preuss Sandstone consists of several rhythmic se- units ripple marked and cross-bedded (fig. 8). The member quences of interbedded sandstone and mudstone (fig. 9), in grades upward into the softer red siltstone and sandstone of the which the sandstone beds are progressively thinner from base Preuss Sandstone. The less resistant lower beds of the Preuss to top within each sequence. The sandstone tends to be chan- Sandstone form a swale between the resistant ledee-formine Gi- nel fillines that feather out laterallv. Ri~olemarks and cross- " " " I ,' raffe Creek member and more resistant younger Preuss Sand- bedding are common in the thicker sandstone units, and ball- stone beds. No fossils were seen in this member in the mapped and-piliow structures are less common. The interbedded mud- area. stone is generally brown, calcareous, and ripple marked, and Imlay (1967, p. 52) assigned a Callovian (lower Upper Ju- bedding within these rocks is usually distorted by loading. rassic) age to the Giraffe Creek Member. Green mudstone beds are exposed at the top of several of the

The Giraffe Creek Member was orobablvL i deoositedI under rhythmic sequences. Several minor reverse faults are well ex- shallow-marine to littoral conditions, in a fairly high-energy posed in Preuss outcrops along the Mobil well road (fig. 20). environment suggested by widespread ripple marks and cross- Reverse faults of this nature, that are usually not exposed, may bedding. account for much of the thinning and thickening of the for- mation in other areas, depending upon their number and Preuss Sandstone displacement. The Preuss Sandstone was named by Mansfield and Hodgden and McDonald (1977, p. 57, 58) list two wells Roundy (1916, p. 81) for Preuss Creek, about 18 km northeast drilled approximately 1 km north of the Sage Valley Quad- of Montpelier, Idaho, where it consists mostly of reddish rangle in Tygee Valley, the deepest of which penetrated approx- brown, pale red, and grayish red, calcareous, fine-grained sand- imately 800 m of Preuss and bottomed in probable Twin Creek stone. The sandstone is in 2- to 20-cm-thick beds and is prob- Limestone. The Preuss section consists of interbedded shale and ably interbedded with nonresistant, commonly covered shale. A salt, of which 130 m of strata are salt-bearing. Pure salt beds typical Preuss exposure is a rounded hill covered with red soil range in thickness from 2 to 7 m, for an aggregate thickness in that contains sandstone float and with a few widely spaced the well of 30 m. No salt was detected in the Mobil Max Smith sandstone ledges. The Preuss Sandstone is apparently con-for- #I well, which penetrated a 438-m-thick section of the Preuss mably underlain by the Giraffe Creek Member of the Twin Uan Patterson personal communication 1980). A salt spring, Creek Formation and overlain by the Stump Sandstone. reportedly associated with a salt bed in the Preuss (Mansfield The Preuss Sandstone crops.out on the east and west flanks 1927, p. 339), is located along Crow Creek, south of the Sage of the Spring Creek Syncline, on the nose of the Afton Anti- Valley Quadrangle. No salt was seen in the measured sections cline, and as a small inlier in the Salt Lake Formation in sec- although salt hopper crystal casts and gypsum stringers were tions 15, 21, and 22, T. 9 S, R. 46 E, in the Sage Valley Quad- seen in the section along the Mobil well road (see appendix). rangle (plate 1). Salt in the salt spring of Alkali Flat, in the Sage Valley

FIGURE10.-Stump Sand\r~~nrnol-rh ot rhc (:row Creek r

slo~es.L signed an Aptian age to the Peterson Limestone, Bechler Con- A 129-m-thick section of the Stump Sandstone was mea- glomerate, and ~rane~Limestone. The Smoot Formation sured on the north ade of Spring Creek in section 17, T. 31 N, straddles the Aptian-Albian boundary. R. 119 W, in the Sage Valley Quadrangle (see appendix). The Five sections of the Gannett Group were measured along formation there consists mostly of grayish green, very fine- to the Spring Creek Syncline in the Sage Valley (see appendix) fine-grained, glauconitic, silty, calcareous, quartz sandstone, and Elk Valley Quadrangles for this report, and two were taken with some interbedded grayish green, calcareous, sandy s~lt- from Eyer (1964, p. 112-16) so that thickness, lithologies, and stone. Most of the units are cross-bedded, with some of the other trends wlthin the Gannett Group could be documented cross-bed sets weathering into relief. Some of the unlts are in the Sage Valley and Elk Valley Quadrangles (fig. 11). ripple marked. No fossils were found in the Stump Sandstone Ephrazrn Conglomerate. The Ephralm Conglomerate crops in the Sage Valley Quadrangle out on the east and west limbs of the Spring Creek Syncllne Only the Curtis Member of the Stump Sandstone, as used (plate 1). In the Sage Valley Quadrangle, the Ephraim Forma- by Pipiringos and Imlay (1979, p. C3-C9), is present within the tion generally forms low h~llscovered wlth reddish sod, bur Sage Valley Quadrangle, and it is assigned a middle Callovian with &cas~onal outcrops of ledge-forming sandstone and con- (lower Upper Jurassic) age by Pipiringos and Imlay (1979, p. glomerate that become thicker and more prominent to the C6). The Redwater Member of the Stump Formation 1s present south and west. The contact with the underlying Stump Sand to the north and east of the Sage Valley Quadrangle, and lt is stone has already been discussed. assigned an early to early middle Oxfordian (Upper Jurass~c) Conglomeratic units of the Ephraim conglomerate have a age by Pipiringos and Imlay (1979, p. C13, C15) on the basls of fine- to coarse-gra~ned sandstone matnx, are commonly cross- ammonold collections. bedded, and appear to be lenticular channel fill~ngsthat pinch The fossils seen in other areas (Pipiringos and Imlay 1979) out laterally (fig 12), particularly in the northern part of the suggest a shallow-marine orlgin for the Stump Sandstone. A quadrangle. Conglomerate beds become more laterally contin- - NE %, Sect~on10

YERTiClll K4LE IN METERS

SAGE VALLEY 7h WADRUIGLE-

ELK VALLEY 7%

BECHLER CONGLOMERATE

7 Sectlms 5 81 6 T29N,R I19W.INyo

% F z8

P5 CONGLOMERATE

CONGLOMERATE CONGLOMERATE

FIGURE 11 -Columnar xctlons of rhe Gannetr Group from Srump Creek to the ~outhernborder of thc Elk Valley Quadrangle. Correlation, are shown hv sol~d Ilncs, quericd where renrarlvc GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING 23 rapid facies changes into more argillaceous rocks, it general- ly forms a swale in the middle and southern parts of the quadrangle. In sections 2, 3, 10, and 11, T. 8 S, R. 46 E, on the west limb, and in sections 20, 29, and 32, T. 32 N, R. 119 W, and sections 5 and 6, T. 31 N, R. 119 W, on the east limb of the Spring Creek Syncline, the Peterson Limestone consists of mas- sively bedded, medium to dark gray, cliff-and ledge-forming limestone with rarely exposed interbeds of gray calcareous shale (fig. 11). One sample of limestone from the Peterson had a slight petroliferous odor when crushed. When the same sample was dissolved in hydrochloric acid, droplets of oil were seen on the surface of the liquid. This oil was probably present as kero- gen material within the limestone rather than as petroleum mi- grating into it. Abundant mollusk fragments are seen in some of the limestone units. Here, the contact with the underlying Ephraim Conglomerate was mapped at the base of the lower- most massively bedded limestone. Eyer (1964, p. 112) included a covered interval, approximately 45 m thick, of reddish brown FIGURE12.-Conglomerate and sandstone channel in the lower Ephraim Con- soil with abundant limestone nodules below the massively bed- glomerate along the north side of the Stump Creek road on the east limb ded limestone, thus indicating that the contact is gradational. of the Spring Creek Syncline. The contact with the overlying Bechler Conglomerate was mapped at the top of the uppermost massively bedded uous to the south and west. The largest clasts are cobbles limestone. about 24 cm in diameter, seen in section 7 of figure 11, al- The Peterson Limestone changes character rapidly near the though pebbles ranging from 0.5 to 2.5 cm in diameter are middle of the quadrangle. In sections 15, 22, 27, and 35, T. 8 S, more common. Conglomerate units generally grade upward R. 46 E, and sections 2 and 23, T. 9 S, R. 46 E, on the west into sandstone beds that fill the same channel and are similarly limb, and in sections 7, 18, 19, 29, 30, and 32, T. 31 N, R. 119 cross-bedded. Not all the sandstone units are underlain by con- W, on the east limb of the Spring Creek Syncline, the Peterson glomerate, however. becomes a poorly exposed, reddish and grayish green mudstone

The sandstone and conelomerateD channels are 1~robablv that thins to the south and west. Abundant limestone nodules within and overlain by reddish mudstone, shale, and siltstone occur within the mudstone but become less common toward although these lithologies are rarely exposed, except in deep the south and west (fig. 11). No fossils were seen in these sec- gullies or on steep hillsides. Purplish gray, nodular limestone tions. The contact with the underlying Ephraim Conglomerate float is present on some of the covered mudstone units, prob- in this part of the outcrop belt was mapped at the bottom of ably having weathered out of the mudstone. Such float is later- the swale develo~edin the mudstone-nodular limestone unit. ally persistent. The nodular limestone generally decreases in that here represents the Peterson Limestone. The contact with amount toward the south and west. One sample of the nodular the overlying Bechler Conglomerate was mapped at the top of limestone had a strong petroliferous odor when crushed. the Peterson swale which coincides with uppermost occur- The Ephraim Conglomerate is from 263 to 412 m thick rences of nodular limestone. within the Sage Valley Quadrangle, although section 2 (fig. The Peterson Limestone ranges from 19 to 55 m thick 11) is probably anomalously thick because of undetected reverse within the Sage Valley Quadrangle. It thins toward the south faulting. and west (fig. 11). Eyer (1964, p. 35) discussed the depositional environment Eyer (1964, p. 36) and Holm, James, and Suttner (1977, p. of the Ephraim Conglomerate on a regional basis. In the Sage 67-69) discussed the depositional environments of the Peterson Valley Quadrangle, the Ephraim beds probably represent fluvial Limestone on a regional basis. The massive facies of the Peter- to lacustrine conditions. The red mudstone that contains lime- son Limestone in the Sage Valley Quadrangle probably repre- stone nodules probably represents low-energy, freshwater lacus- sent a shallow (less than 15 m deep), freshwater lacustrine envi- trine conditions that exist part of the time on a delta or on ronment. The gray shales interbedded with the limestone beds coalescing deltas and their submerged extensions. Channels probably represent only a slightly higher-energy environment. filled with sandstone and conglomerate represent the fluvial The red mudstone and nodular limestone of the southern and portion of the delta development. southwestern facies were probably deposited in an argillaceous Ever (1964. D. 11-12) summarized fossil occurrences in the lacustrine to flood~lain environment similar ' to the one in I \- ., I Ephraim Conglomerate. He reported marine fossils from lower which the mudstone and nodular limestone of the Ephraim Ephraim beds, probably from below the lowermost con- Conglomerate were deposited. glomerate unit, and nonmarine fossils from middle and upper Becbler Conglomerate. The Bechler Conglomerate crops out Ephraim beds. Thus, Ephraim beds indicate a transition from a on the east and west limbs of the Spring Creek Syncline (plate marine to a nonmarine environment near the Jurassic-Cre- 1). In the Sage Valley Quadrangle, the Bechler Conglomerate is taceous boundary. No fossils were seen in the Ephraim Con- similar in appearance to the Ephraim Conglomerate and forms glomerate in the Sage Valley Quadrangle in the present study. low hills covered by reddish soil, with occasional outcrops of Peterson Limestone. The Peterson Limestone crops out on the ledge-forming sandstone and conglomerate that become thicker east and west flanks of the Spring Creek Syncline (plate 1). In and more prominent to the south and west. the northern part of the Sage Valley Quadrangle, the limestone Conglomeratic units of the Bechler Conglomerate have a is a prominent ledge- and shoulder-forming unit, but, owing to fine- to ;~arse-~rainedsandstone matrix, are ;ommonly cross- bedded, and appear to be lenticular channel fillings that pinch of map pattern (fig. 2). The contact with the underlying Bech- out laterally, particularly in the northern part of the quad- ler Conglomerate was mapped at the upper edge of red soil and rangle. They become thicker and more continuous to the south sandstone float from the Bechler Conglomerate. The contact and west. A 13-m-thick conglomerate unit near the top of the with the overlying Smoot Formation was mapped at the up-

Bechler beds can be correlated across the quadrangle (fig. 11). permost occurrence of brown soil and gray-. limestone float Clasts are up to 36 cm in diameter in this unit in section 4 of &om the Draney Limestone. figure 11. Clasts in the other conglomerate units are more com- Eyer (1964, p. 37), Holm, James, and Suttner (1977, p. monly 1 to 3 cm in diameter. The conglomerates usually grade 267-269), and Brown and Wilkinson (1979) discussed the dep- upward into a sandstone that is filling the same channel and is ositional environment of the Draney Limestone on a regional similarly cross-bedded though not all the sandstone units are basis. The depositional environment of the Draney Limestone underlain by conglomerate. - was probably~similarto that of the Peterson ~im-estone.The Sandstone and conglomerate channels are probably within Draney beds are laterally more continuous in the Sage Valley and overlain by reddish mudstone, shale, and siltstone. These Quadrangle and contain no red mudstone, unlike the Peterson latter lithologies are rarely exposed, except in deep gullies or on Limestone, which indicates a facies freer of terrigenous stem hillsides. such as in section 11. T. 8 S. R. 46 E. where red material. muistone with greenish blebs crops'out. purplish gray, nodular Smoot Formation. The Smoot Formation crops out along the limestone is present as weathered debris on some of the covered axis of the Spring Creek Syncline between section 11, T. 8 S, R. mudstone units and is probably weathered out of the mudstone 46 E, and section 35, T. 8 S, R. 46 E, in the Sage Valley Quad- units. These calcareous mudstones form laterally persistent rangle (plate 1). The Smoot beds form low hills covered by red units. The nodular limestone occurs in more horizons in the soil and generally erode to a low area between the more resis- Bechler Conglomerate than in the Ephraim Conglomerate, and tant Draney Limestone outcrops on either limb of the Spring limestone also appears to be more abundant in the Bechler beds Creek Syncline. The Smoot Formation probably consists of although it deckases in amount to the south and west, paral- nonresistant, calcareous, red mudstone and siltstone although leling the limestone distribution in the Ephraim Conglomerate. outcrops are rare. No fossils were found in Smoot rocks within Complete sections of the Bechler Conglomerate range in the mapped area. thickness from 472 m to 524 m within the Sage Valley Quad- The Smoot Formation is approximately 100 m thick in the rangle. South of Crow Creek, uppermost units of the Bechler Sage Valley Quadrangle. Contact with the underlying Draney are lost to erosion, so a formation thickness could not be ob- Limestone has been discussed previously. The contact with the tained (fig. 11). overlying Tygee Member of the Bear River Formation was The depositional environment of the Bechler Conglomerate mapped at the top of the red siltstone of the Smoot Formation was probably similar to that of the Ephraim Conglomerate. and the base of the black shale of the Tygee Member. Most of the Bechler units within the Sage Valley Quadrangle Eyer (1964, p. 37-39) discussed the regional depositional were deposited in a lower-energy environment than was the environment of the Smoot Formation. He collected nonmarine Ephraim Conglomerate, as suggested by the more abundant fossils in the lower part of the Smoot Formation and brackish- nodular limestone units and the less-common, finer-grained water to marine faunas from the middle and upper Smoot beds, conglomeratic units. There were periods of deposition in thus implying a significant environmental change near the Al- higher-energy environments, however, than any documented by bian-Aptian boundary. The mudstone and siltstone are thought the Ephraim Beds within the quadrangle because of the larger to represent a beach-mudflat environment, similar to the phys- clasts and broader extent of two conglomerate units within the ical environment seen in the modern Bear Lake, Idaho, area. Bechler outcrops (fig. 11). Dranq, Limestone. The Draney Limestone crops out along Tygee Member of the Bear River Formation the axis of the Spring Creek Syncline north of Crow Creek but The Tygee Member of the Bear River Formation crops out is not present south of Crow Creek because of erosion (plate along the axis of the Spring Creek Syncline in section 14, T. 8 1). In the Sage Valley Quadrangle, the Draney Limestone S, R. 46 E, in the Sage Valley Quadrangle (plate 1). The Tygee forms low hills covered by grayish brown soil and abundant light gray limestone float. It is less resistant than the Peterson Limestone and forms low ridges rather than prominent ledges. The Draney Limestone consists of poorly exposed, massive, gray-. limestone beds in the lower part and thin-bedded lime- stone interbedded with gray ca~carebusmudstone in the upper part. The thin-bedded limestone and mudstone weather and cover the underlying units. The limestone beds are generally fossiliferous, with some beds made up almost entirely of oriented gastropods and bivalve fragments. Most of the fossils show signs of transport. Oil droplets were noted as residues when two Draney Limestone samples were dissolved in hydro- chloric acid. One of the samples contained carbon (?) flecks that would not centrifuge out. These shows are probably from keroeen" de~ositswithin the limestone and not from 1~etroleum migrating into the formation. A few fragments of uniden- tifiable silicified wood were found as float weathered out of the formation in section 14, T. 8 S, R. 46 E. The Draney Limestone has a maximum thickness of ap- FIGLIRE13 -Black shale unit <~trlic Tvgcc Xlcmher ot the Hc.~rRlvcr Forni.~tl,m proximately 55 m in the Sage Valley Quadrangle, on the basis '11 tlic Icntcr of rhc Spr~ng('rcck S\.n~ltric GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING 25

FIGURE16.-Fucoidal markings in the sandstone unit of the Tygee Member of the Bear River Formation in the center of the Spring Creek Syncl~ne.

Member forms a knoll above the less resistant red mudstone of the Smoot Formation. Only the lowermost 45 m of the Tygee Member are present within the quadrangle; the remainder has been removed by erosion. The Tygee Member can be divided into two units in the mapped area. The lower unit is a weakly resistant, dark brown to black, very thinly bedded shale that breaks into small pencil- like fragments at the outcrop (fig. 13). No fossils were found in this dark shale unit which is approximately 40 m thick and is overlain by the upper unit-a 5-m-thick layer of quartz sand- stone. The sandstone is grayish yellow, calcareous, poorly sort- ed, medium to coarse grained, cross-bedded (fig. 14), and ripple marked. Vertical burrows (fig. 15) and fucoidal markings (fig. 16) occur in several beds. The contact between the two units is sharp, but no unconformity is suggested. Eyer (1964, p. 40) assigned an Albian (Lower Cretaceous) age to the Tygee Member of the Bear River Formation. The dark shale of the Tygee Member was probably depos- ited under brackish to normal-marine conditions in a lower- FIGURE14.-Cross-Mding in the sandstone "nit ,$ the Tygee Member of the energy environment. The dark color indicates reducing condi- Bear River Formation at the center of the Spring Creek Syncline. tions, but no other environmental indicators were found. The sandstone was probably, deposited. above wave base in fairly shallow, well-oxygenated water-possibly a fluvial environment. The organisms that produced the fucoidal markings were prob- ably restricted to fairly shallow water. The cross-bedding and ripple marks indicate a fairly high-energy environment. Kamis (1977b) discusses the petrology and reservoir capabilities of the Tygee Member.

Tertiary System Salt Lake Formation The white and light gray tuff, marl, sandstone, and con- glomerate exposed in Sage Valley, Tygee Valley, and along the west flank of Star Valley were assigned to the Salt Lake Forma- tion by Mansfield (1927, p. llo), and this terminology is fol- lowed in this report. The Salt Lake Formation overlies older rocks and structures with angular unconformity. The formation is easily eroded and forms low hills covered with light colored soil and occasional float fragments consisting of rounded pebbles or cobbles origi- nally derived from other formations. The formation is poorly FIGURE15.-Vertical burrows in the sandstone unit of the Tygee Member of the Bear River Formation at the center of the Spring Creek Syncline (quarter exposed, and, although Cressman (1964, p. 57) divided it into for scale). an upper and a lower member, such a division was not made in 26 J, L. CONNER the Sage Valley Quadrangle. The best exposures of the forma- W, from approximately 5 to 25 m below the original ground tion occur in section 8, T. 8 S, R. 46 E, on the north ridges surface. Several organic-rich layers were also noted. Tarlike above the deeper stream valleys. Here the Salt Lake Formation blebs, some having a petroliferous odor, were scattered, appar- dips approximately 15" to the east and consists of locally de- ently irregularly and in varying amounts, in some of the rived, subrounded to rounded pebbles and cobbles, probably coarser-grained units. from the Thaynes Formation. They are cemented by a light col- ored marl that sometimes makes up over 80 percent of the rock Travertine volume. The formation ranges up to 300 m in thickness within Small patches of travertine are associated with active the Sage Valley Quadrangle. No fossils were found in the Salt springs on the west side of Sage Valley in the NE '/4 of section Lake Formation in the mapped area. 18, T. 9 S, R. 46 E. Other small patches of travertine also occur Mansfield (1927, p. 111-12) assigned a Pliocene (?) age to along Sage Creek in section 20, T. 9 S, R. 46 E, some associated the Salt Lake Formation in the Slug Creek Quadrangle, Idaho. with active springs, others not. The travertine is generally Cressman (1964, p. 57-58) summarized previously published white, gray, or buff, very porous, and forms low mounds, fossil data that indicate an age of Oligocene to Pleistocene for ledges, or coatings over colluvium or older rocks. No fossils the formation southwest of the Sage Valley Quadrangle. were found in the travertine in the Sage Valley Quadrangle al- Eardley (1944, p. 845-46) recognized that when intermountain though Mansfield (1927, p. 113) reported local occurrences of valleys west of the Wasatch become better known stratigraphi- gastropods and casts of grass stems in the calcareous deposits. cally, the Salt Lake Formation may be found to include several distinct units within the Tertiary that may be separated by con- Salt siderable time gaps. A saline spring is present in Alkali Flat in the SE '/4 of sec- The fossils listed by Cressman (1964, p. 57-58) indicate a tion 16, T. 8 S, R. 46 E, of the Sage Valley Quadrangle (fig. freshwater environment, probably lacustrine, although there 17). The salt forms white encrustations on the ground near the was probably some fluvial influence as indicated by the pebbles spring and along the outflow course. Mansfield (1927, p. and cobbles present in the float. 338-40) reported the chemical content of the salt from nearby saline springs as nearly pure sodium chloride, which is probably Quaternary System also true for the spring in Alkali Flat. The salt was recovered in Colluvium and Alluvium the late 1800s, mostly for local use, by boiling the water off in Colluvium areas mapped within the Sage Valley Quad- large pans. The origin of the salt was previously discussed in rangle consist mostly of poorly sorted, nonstratified rock debris the Preuss Sandstone section. forming hill wash and talus that covers the lower slopes of many hills. In many places, it merges with fluviatile deposits STRUCTURE and forms alluvial fans that may have considerable extent, such General Statement as those in Sage Valley. Areas mapped as alluvium consist Rocks are exposed in the Sage Valley Quadrangle in a series mostly of poorly sorted, somewhat stratified gravel, sand, silt, of north-south-trending arcuate belts that are concave to the and clay. The term is restricted to floodplains and sites of active east. The Meade Overthrust Fault zone (fig. 18) is recognized accumulation of sediments by water movement. in the western and central parts of the quadrangle, where it The contact between the colluvium and the alluvium is lo- forms a series of six major branches that generally follow the cally gradational, but the colluvium generally has more topo- graphic relief than the alluvium and has been dissected to a greater degree by running water. The Quaternary cover is prob- ably not over 50 m thick at any point within the mapped area. Unidentified vertebrate remains, some possibly Pliocene in age, were found in the gravel pit in section 28, T. 32 N, R. 119

FIGURE 17.-Salt Spring in Alkali Flat. The logs lining the pit were uscd to keep the spring open when it was used commcrciallv product salt. FIGURE IX.-M:lp of the m:tior thrust fault zones in wutheartcrn Idaho :~nd Note the salt encrustations. western Wyoming (modified after Rlack\rone 1077). GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING 27

FIGURE19.-Generalized structural conrour map of the Sage Valley Quadrangle. Contours are on top of the Nugget Sandstone in the Absaroka Plare easr of the East Sage Valley Branch and on top of the Meade Pak Phosphatic Shale Member of the Phosphoria Formation in rhe Meade Plate west of the East Sage Valley Branch. Inferred contours are dashed (contour interval = 500 feet). NNER strike of the rock units. Two minor thrust faults were also fault ranges to no more than a few hundred meters at max- found, and several more minor thrust faults are probably pres- imum near the central part of its trace. The minimum dip of ent but remain undetected beneath the unconsolidated cover. the fault plane is approximately 20°, with the dip of the beds Rocks exposed on the upper, or Meade Plate, are almost ex- becoming vertical to overturned near the terminal points. The clusively Paleozoic through Lower Jurassic in age. Rocks ex- East Hardman Branch of the fault was probably formed by im- posed on the lower, or Absaroka Plate, are middle Jurassic brication within the footwall. through Lower Cretaceous in age. Rocks on both the upper The West Hardman Branch of the Meade Overthrust, and lower plates have been compressed into a series of asym- named here, generally parallels the East Hardman Branch, metric, north-south-trending folds (fig. 19). Numerous small though near the north and south borders of the quadrangle, east-west-trending tear faults and normal faults, which were the fault swings slightly more toward the west (plate 1). The probably formed contemporaneously with thrust faulting, off- northern and southern limits of this branch and the remaining set the folds and thrust faults. major branches could not be determined, but their termi- The model for the thrust faulting and deformation is sim- nations are probably beyond the Sage Valley Quadrangle. The ilar to one proposed by Dahlstrom (1970) for the Canadian West Hardman Branch is probably the frontal edge of the Rocky Mountains. The mechanism for thrusting is thought to Meade Plate (plate 1, sections A-A' and B-B'). Its stratigraphic be gravity sliding, as proposed by Rubey and Hubbert (1959). and structural displacements have been discussed previously. Lowell (1977) postulated underthrusting as the mechanism for The fault plane dips between 20° and 45' near the surface. the development of the thrust faults, but this hypothesis has The East Tygee Branch of the Meade Overthrust, named not been widely accepted. Further detail of thrust fault devel- by Mansfield (1927, p. 152), is exposed only in sections 9, 10, opment in Idaho and Wyoming is described in a paper by and 16, T. 9 S, R. 46 E, in the Sage Valley Quadrangle, where Armstrong and Oriel (1965). it faults older Nugget Sandstone over younger Twin Creek Limestone (plate 1). Its trace is covered by Salt Lake Formation Thrust Faults in the rest of the quadrangle, but evidence of its presence is The Meade Overthrust Fault zone, formerly the Bannock indicated by the salt spring in Alkali Flat. The East Tygee Overthrust of Richards and Mansfield (1912), consists of six Branch is a fairly high-angle fault, with dips approaching 70' major branches and is the major zone recognized in the Sage W. at some locations at the surface, but it rapidly flattens west- Valley Quadrangle. Figure 18 shows the position of the Meade ward in the subsurface (plate 1, sections A-A' and B-B'). Struc- Overthrust relative to the other overthrust zones in western tural displacement could not be accurately calculated, but is Wyoming and southeastern Idaho. The glide plane for the sole probably not more than a few hundred meters. The East Tygee of the Meade Overthrust is within the Twin Creek Limestone Branch was probably formed by imbrication of the overriding (Cressman 1964, p. 68-69) until the thrusts ramp sharply up- plate. ward through the Jurassic and Cretaceous sections (plate 1, sec- The West Tygee Branch of the Meade Overthrust, named tion A-A' and B-B'). The horizontal displacement of the east by Mansfield (1927, p. 152), is exposed in sections 4, 9, 16, 17, ern edge of the Meade Plate is approximately 29 to 32 km and 20, T. 9 S, R. 46 E, in the Sage Valley Quadrangle, where (Cressman 1964, p. 76), and the stratigraphic displacement is the fault places older Thaynes Formation over younger Nugget approximately 3,600 to 4,500 m. Initial movement of the Sandstone (plate 1; fig. 6). The fault is covered by Salt Lake Meade Overthrust Fault, complemented by movement of the Formation in the remainder of the quadrangle. The dip of the Crawford Overthrust Fault, is documented by deposition of fault plane of the West Tygee Branch is approximately 70' most of the Echo Canyon Conglomerate (Blackstone 1977, p. near the surface but rapidly flattens westward in the subsurface 381) which has been dated as Upper Cretaceous (Olson 1977, (plate 1, sections A-A' and B-B'). Structural displacement is ap- p. 93). The age of thrusting in the Sage Valley Quadrangle can proximately 300 m where the fault is best exposed. The West be determined only as post-Tygee Member of the Bear River Formation (Lower Cretaceous) and pre-Salt Lake Formation (Pliocene [?I).The faulting was probably a relatively cold event as indicated by the absence of major metamorphic zones. Steep dips near the trace of the thrust faults are generally interpreted as drag features related to movement of the fault. The East Hardman Branch of the Meade Overthrust is named here. The fault enters the Sage Valley Quadrangle ap- proximately 1 km east of the Draney ranch, along the west limb of the Spring Creek Syncline (plate 1). It parallels the Spring Creek Syncline along Hardman Hollow, crosses Crow Creek, and exits the quadrangle near the Idaho-Wyoming bor- der. In sections 22 and 28, T. 8 S, R. 46 E, it splits and rejoins, forming a second small imbricate slice or horse. The fault ter- minates to the south in an anticline approximately 1 km south of the Sage Valley Quadrangle (Floyd Hatch personal commu- nication 1980). To the north, it is thought to terminate just north of the quadrangle border in a similar fold because of an anomalously thick section of Ephraim Conglomerate (fig. 11, section 2) measured just within the border of the quadrangle and the more normal thicknesses of Ephraim Conglomerate measured just north of the quadrangle (fig. 11, section 1; FIGURE 20.-M~nor thrust fault in the Pteuss Sandstone along the Mobil well Mansfield 1927, p. 102-3). Structural displacement along the road. Note the drag folds (arrows show relat~vedisplacement). GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING 29 Tygee Branch was probably formed by imbrication of the over- riding plate. The trace of the East Sage Valley Branch of the Meade Overthrust, named here, is not exposed in the Sage Valley Quadrangle, but is covered by Salt Lake Formation and Qua- ternary deposits (plate 1). It is exposed just south of the quad- rangle border, however, where older Dinwoody Formation is faulted over younger Thaynes Formation (Floyd Hatch person- al communication 1980). Position of the fault within the quad- rangle is inferred to account for the close juxtaposition of the upper unit of the Portneuf Limestone and the Dinwoody and Paleozoic formations in section 29, T. 8 S, R. 46 E (plate 1). There is not enough space to allow for a normal sequence be- tween the outcrops. The dip of the fault plane is probably steep near the surface, but it, too, probably flattens out rapidly at depth. Structural displacement along the fault is estimated to be approximately 1000 m within the Sage Valley Quadrangle. The East Sage Valley Branch was probably formed by imbrica- tion of the overriding plate. The West Sane Vallev Branch of the Made Overthrust. named here, is eiposed along the west side of Sage valley; FIGURE 21.-Tight folds in the Twin Creek Limestone in the road metal pit where older Paleozoic units are thrust over younger Paleozoic between Hardman Hollow and Poison Creek along the Crow Creek road. units (plate 1). This branch probably offsets the Lower Din- woody Formation north of Sage Valley, but the trace could not can be traced into the Stewart Flat Quadrangle (Montgomery be accurately located there because of poor exposure. The dip and Cheney 1969, p. 38). The Draney Creek Fault is indicated of the fault plane is 70' to 80' at the surface, but it also prob- by the apparent offset of the Meekoceras-bearing limestone of ably flattens rapidly in the subsurface (plate 1, sections A-A' the Thaynes Formation. The fault has an approximate struc- and B-B'). Structural displacement along the fault is estimated tural displacement of 150 m. These normal faults apparently do to be approximately 200 m in the Sage Valley Quadrangle. The not offset the Salt Lake Formation and thus may be related to West Sage Valley Branch was probably formed by imbrication thrusting. It is possible that they are basin-and-range normal of the overriding plate. faults, but no north-south-trending normal faults were found Two minor thrust faults were mapped east of the East in the quadrangle, which would be expected in a basin-and- Hardman Branch along the west limb of the Spring Creek Syn- range structural environment. cline in the Absaroka Plate. Several small thrust faults havine (7 displacements of approximately 2 to 3 m were found in the Folds Preuss Sandstone along the Mobil well road (fig. 20). More are The Afton Anticline (fig. 22) is the easternmost fold in the probably present in rocks of the Spring Creek Syncline but Sage Valley Quadrangle (plate 1; fig. 19). The structure trends were concealed. These faults were probably formed by imbrica- generally north-south, plunging northward at approximately lo tion of the footwall. (18 m/km) until near the middle of the quadrangle, beyond Steep and overturned dips near the thrust fault traces are where it plunges steeply, at approximately 15' (268 m/km), interpreted as fault drag features. Minor brecciation and no and terminates in section 5, T. 31 N, R. 119 W. The Leeds metamorphic zones were found. A series of tight folds in the Creek Member of the Twin Creek Limestone is the oldest unit Twin Creek Limestone along Crow Creek (fig. 21) are associ- exposed in the Afton Anticline in the Sage Valley Quadrangle. ated with the West Hardman Branch of the Meade Overthrust. A cross-section through the Afton Anticline by Long (1960, p. 188) shows that the anticline probably does not continue deep- Tear Faults and Normal Faults er than the plane of the Absaroka Overthrust Fault, and is, Numerous tear faults were mapped in the Sage Valley therefore, not a fold formed in the Absaroka Plate by faulting Quadrangle (plate I), most with mappable traces not over 1 and folding within the underlying thrust sheet or sheets. km long with no displacements in excess of a few meters. More The Spring Creek Syncline extends beyond the northern are present but have little displacement, and many were prob- and southern borders of the Sage Valley Quadrangle (fig. 23) ably undetected. Most such faults are oblique to tangential to and has a maximum width of approximately 5 km near the the principal structural grain, trending generally east-west, and northern edge of the quadrangle (plate 1). The syncline does offset thrust faults, fold axes, and individual beds. A tear fault not appear to plunge in either direction within the quadrangle. may be present along Crow Creek to account for the offset of Rock units remain at a fairly constant elevation within the the Peterson Limestone on the west limb of the Spring Creek trough. Several minor synclines and anticlines are present on Syncline. The tear faults were probably formed contempo- the flanks of the Spring Creek Syncline but are probably only raneously with thrusting, which permitted differential move- shallow structures (plate 1, sections A-A' and B-B') formed by ment related to differential stresses between components within local wrinkling at the time of movement of the Meade Plate. the thrust sheet. None of the tear faults seem to offset the Salt The western limb of the Spring Creek Syncline is overturned Lake Formation. throughout most of its exposure in the Sage Valley Quad- Several east-west-trending normal faults were mapped in rangle. That overturning is probably also related to movement the Sage Valley Quadrangle (plate 1). Most have traces less along the Meade Overthrust. The youngest rocks preserved than 1 km long, and most have vertical displacements of less within the Spring Creek Syncline are in the Tygee Member of than 10 m. The largest of these is the Draney Creek Fault that the Bear River Formation. The depth to which the syncline 30 J. L. CONNER persists is unknown, but it may be a fold within the Absaroka mation. The syncline plunges approximately 1" (18 m/km) to Plate that was formed by deformation and movement of the the north. The syncline was probably formed by the movement plate or plates underlying the Absaroka Plate. of the Made Plate and does not continue below the plane of A north-south-trending anticline, with no surface expres- the Made Fault. sion is indicated beneath the Made fault zone, in cross-sections The Boulder Creek Anticline is a north-south-trending fold A-A' and B-B' (plate 1) and figure 19. It is probably an exten- exposed along the western edge of the Sage Valley Quadrangle sion of the Pinnacle Creek Anticline, which is present in the (plate 1; fig. 19). North of section 30, T. 8 S, R. 46 E, the Elk Valley Quadrangle (Floyd Hatch personal communication anticline splits, with one branch trending toward the northwest 1980). The fold is in Twin Creek Limestone and Nugget Sand- and the other continuing to the north. The anticline plunges stone, two of the important reservoir rocks in the overthrust approximately 2' to 3' (36 m/km to 54 m/km) to the north. belt. The anticline may persist at depth, and seismic studies Several minor synclines and anticlines are present on the flanks would help determine its extent and closure. The anticline may of the Boulder Creek Anticline (fig. 3; plate I), but most are be a fold within the Absaroka Plate that was formed by move- probably shallow structures. The eastern limb of the anticline is ment and deformation of the plate underlying the Absaroka overturned in places, which may be a function of fault drag cre- Plate, although the crest of the anticline has been deformed by ated by movement along the West Sage Valley Branch of the movement of the Meade Plate. Meade Overthrust zone. The oldest rocks exposed in the anti- All the folds described previously are on the Absaroka Plate cline in the Sage Valley Quadrangle are upper Wells Forma- in the Sage Valley Quadrangle. The folds described next are on tion. The Boulder Creek Anticline is interpreted to be a fold in the overlying Meade Plate, with some originating as folds con- the Meade Plate formed by deformation and movement of the trolled by deformation of the Absaroka or deeper plates. Absaroka or deeper plate. The oldest unit contained within the An unnamed north-south-trending syncline was mapped on anticline on the Made Plate in the Sage Valley Quadrangle is the east side of Sage Valley, in sections 29 and 33, T. 8 S, R. 46 the Mississippian Madison Limestone, which rests on Jurassic E, and sections 4, 8, 9, and 17, T. 9 S, R. 46 E (plate 1). The Twin Creek Limestone (plate 1, sections A-A' and B-B'). syncline flattens and terminates to the south. Its western flank is overturned in the middle of section 4 and is buried beneath GEOLOGIC HISTORY the Salt Lake Formation from section 29, north. Youngest An area comprising western Wyoming and southeastern rocks exposed in the syncline are in the Triassic Thaynes For- Idaho was the site of deposition within part of the Cordilleran

It. *\-,( ~.

FIGURE 22.-Afton Anricllne. Looking north across the Crow Creek road from the easrern edge of rhe Sage Valley Quadrangle. GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING 3 1

FIGURE23.-Spring Creek Syncline. Looking north into the Auburn Quadrangle from near the north edge of the Sage Valley Quadrangle. miogeosyncline of approximately 7,900 m of primarily sedimen- tions. The origin of the Triassic rocks of southeastern Idaho tary rocks from the Cambrian through the Late Triassic or and western Wyoming has been discussed by Kummel (1957). Early Jurassic (Cressman 1964, p. 85). Early rocks had basically The environment of deposition of the Jurassic formations an eastern source, but beginning in the Late Triassic or Early has been discussed by Imlay (1957) and Hileman (1973, p. Jurassic, most of the sediments were derived from uplifts in the 71-100). The Nugget Sandstone is partially eolian and partially miogeosyncline, to the west, north, and south (Hileman 1973, littoral in character in the Sage Valley Quadrangle. Marine p. 71-78), changing the depositional area to an exogeosyncline. regressions are marked by the Nugget Sandstone, the Gypsum An exposed sequence of sedimentary rocks 5,400 m thick de- Spring Member, and the red beds of the Boundary Ridge Mem- tails the depositional record from the Upper Pennsylvanian to ber of the Twin Creek Limestone, and the tidal flat-lagoonal the Early Cretaceous in the Sage Valley Quadrangle. environment of the Preuss Sandstone. Transgressions are The Paleozoic and Triassic rocks are exclusively marine and marked by deposition of the Sliderock Member through the are generally widespread deposits. The phosphate and chert of limestone units of the Boundary Ridge Member of the Twin the Phosphoria Formation indicate periods of deep, quiet water Creek Limestone, deposition of the Watton Canyon through with a minimum of carbonate deposition. The black shales in- the Giraffe Creek Members of the Twin Creek Limestone, and dicate less deep environments of deposition for the Thaynes deposition of the Stump Sandstone. The Leeds Creek and Gi- and Dinwoody Formations. All were probably formed under re- raffe Creek Members of the Twin Creek Limestone contain the ducing conditions in a deep basin. The limestone and sand- earliest sediments in the Sage Valley Quadrangle derived from stone units generally contain sedimentary structures indicative uplifts in the geosyncline to the west (Hileman 1973, p. 79). of a higher-energy environment, often above wave base. The The Cretaceous-Jurassic boundary marks the change from a Lanes Tongue of the Ankareh Formation and the Woodside marine environment to a freshwater lacustrine environment Formation signal regressions of marine water; and continental (Eyer 1964, p. 11-12). The Smoot Formation marks the change deposits are the dominant lithologies. The limestone present back to brackish-normal marine conditions. Deposition of the above each of the continental deposits indicates a transgression sandstone of the lower Cretaceous Tygee Member of the Bear of the sea and a return to more nearly normal marine condi- River Formation, the youngest prethrusting rock unit pre- INNER

served in the Sage Valley Quadrangle, was probably initiated by have all been met In the Sage Valley Quadrangle Other struc- an orogenic pulse to the west (Eyer 1969, p. 1387). Th~sdeposi- tural and stratigraphic traps may also be present within the tion took place In a shallow foredeep in front of the area being quadrangle uplifted on the west (Blackstone 1977, p. 369). Depos~tionof the conglomerates of the Gannett Group and later Cretaceous and Tertiary formations seems to colncide with movement of Water thrust plates that began to develop and slide from an uplift to The major perennial streams within the Sage Valley Quad- the west (Blackstone 1977, p. 381). Thrust faultlng continued rangle are Crow Creek, Sage Creek, South Sage Creek, Draney into the Tertiary, but apparently ended prior to deposition of Creek, and Pole Creek. Several other small unnamed streams the Pliocene (?)Salt Lake Formation. flow e~therall year or parts of the year, depending upon the The present ranges and basins of the mapped area were de- precipitation of the previous winter. Numerous springs exist fined by warping or normal faulting in middle Tertiary time throughout the quadrangle and are used primarily for watering (Cressman 1964, p. 89). Lakes were formed in the basins, and livestock and some irngat~on.Pole Creek and Sage Creek are the Salt Lake Formation was subsequently deposited. Deposi- used for the Irrigation of Sage Valley, and water 1s diverted tion of the Salt Lake Formation may have continued Into the from Crow Creek for some Irrigation Considerable groundwa- Pleistocene. Some volcanic mater~al1s present in the tuffaceous ter potential 1s present w~thinthe quadrangle, but abundant member of the Salt Lake Formation of Cressman (1964, p. 57), surface water has limited its development. but none was recognized in the Sage Valley Quadrangle. Nor- mal faulting continued after deposit~onof the Salt Lake Forma- Salt tion, and the area is still seismically actlve (Smith and Sbar Salt from the saline spring in Alkali Flat (fig. 17) was for- 1974). merly produced for local use by boiling off the water in large Mansfield (1927, p 11-20) discussed the physiographic de- pans (Mansfield 1927, p. 339). No salt 1s produced in the quad- velopment of southeastern Idaho and western Wyoming and rangle at the present, and the sallne spring has been part~ally distinguished a number of erosional surfaces that are Tert~ary developed Into a salt lick for livestock. and Quaternary in age. Little can be added to Mansfield's dis- cusslon by this study of the Sage Valley Quadrangle. Other Mlneral Depos~ts ECONOMIC GEOLOGY A gravel p~tis currently in product~onin sectlon 28, T. 32, Phosphate N, R 119 W, in the Sage Valley Quadrangle. The material is

As mentioned in the section on the Phos~horia1 Formation. unconsolidated sand and gravel from a Quaternary colluv~alde- a series of five test trenches have been dug on the west side of posit and is used primarily for fill material. Two road metal pits Sage Valley. Three of these contain exposures of phosphate are found along Spring Creek and another along the Crow rock characteristic of the Made Peak Phosphatic Shale Member Creek road between Hardman Hollow and Poison Creek. All of the Phosphoria Formation whereas the other two do not. three produce fractured rock from the pencilly llmestone of the South of section 29, T. 8 S, R. 46 E, in the Sage Valley Quad Twin Creek Limestone which was apparently used for the surf- rangle, phosphate occurrences are probably not economic be- acing of the unpaved roads In the area. The road material pro- cause of the11 limited size and the amount of overburden to be duced from these pits, while sultable for gravel on the unpaved removed. North of section 29, however, a complete sectlon of roads, IS too soft for use as road metal on heavily traveled, the Meade Peak Phosphanc Shale Member is present and will paved roads H~gherquallty road metal could be produced by be economic ~f a method of transport were brought Into the crushlng the conglomerate-sandstone rocks in the Cretaceous area or the mill proposed by the J. R. S~mplotCompany is con- units or some of the dense llmestone and sandstone present In structed. No mlning of phosphate has taken place to date with- some of the Paleozoic, Triassic, and Jurassic unlts. in the Sage Valley Quadrangle. Some of the Twin Creek Llmestone units, some of the Cre- taceous limestone units, and possibly the Portneuf Llmestone Member of the Thaynes Format~on,though ~t may be too SI- Petroleum liceous, could be used to manufacture Portland cement if the Several hydrocarbon test wells have been drilled around the population and industry develop in southeastern Idaho and Sage Valley Quadrangle (Hodgen and McDonald 1977, p. western Wyomlng to make it economically feas~ble(Mansfield 50-51), but none have produced hydrocarbons in economic 1927, p. 331-332) The travertine deposits could be a source of quantity In 1979, Mobil Oil Company drilled the Max Smith h~gh-gradelime (Mansfield 1927, p. 332) though the deposits #I well In the SE % of the SW %, sectlon 5, T. 31 N, R. 119 in the Sage Valley Quadrangle are probably too small to be W, in the Sage Valley Quadrangle. Th~swell was plugged and economlc abandoned after reaching a depth of 4,136 m, bottoming In the Wells Format~on. Source beds. such as the Thavnes Formation and the Phos- SUMMARY phoria Formation, and reservoir beds, such as the Nugget Sand- As a result of this study, the structure and strat~graphyof stone and the Twin Creek Limestone, are In close proximity to the Sage Valley Quadrangle are delineated In much greater de- each other withln the Sage Valley Quadrangle Two anticl~nal tail than before. A rev~sed strat~graphic nomenclature for structures, the Boulder Creek Anticline and the unnamed anti- southeastern Idaho and western Wyomlng was successfully ap- cline shown In cross sectlons A-A' and B-B' of plate 1 and fig- p11ed in the mapped area, clarifying some inconsistencies pres- ure 19, should be tested for hydrocarbon accumulat~on.The ent In previously publ~shedworks. SIX major imbr~catethrust amount of closure on the structures could be determined from faults related to the Meade Overthrust fault zone were recog- selsmlc data. The requirements of structure, source beds, and nized In the Sage Valley Quadrangle, lncludlng the prev~ously reservoir beds necessary for the accumulation of hydrocarbons undetected East Sage Valley Branch of the Meade Overthrust GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING

A number of minor thrust faults, prevlouslv undetected, were tanon, masslve bedded, chert quantlty , . also identified. Increases to masslve bedded at the top of the unlr, ledge At least two folding events are evident: the first is related 4 Sandstone light gray, weathers redd~sh 3 8 47 8 to compression at the &me of movement of the Meade Over- brown to gray, fine gralned, calcareous, thrust Fault, and the second is associated with movement of sl~ghtlyfnable, up to 15% porosity In the Absaroka Overthrust Fault or younger overthrust faults cross-bedded portions, flecks of mafic which deformed the Absaroka Plate as well as the Meade Plate materials, masslve bedded, ledge 3 Sandstone medium gray, weathers light 7 9 44 0 The anticllnal structures were grossly evaluated for hydro- gray, very fine gralned, very well ce- carbon potential. Occurrences of potentially economlc phos- mented by slllca, sl~ghtlycalcareous, phate were noted in the quadrangle, as well as occurrences of masslve bedded, shoulder several ocher materials for construction. 2 Sandstone. white to light gray, weathers 13 7 36 1 Several subjects could be pursued to improve the under- brown~shgray, slightly calcareous, very fine gralned, well cemented, well sorted, standing of rocks in the Sage Valley Quadrangle: (1) detailed masslve bedded, shoulder paleontological studies of the Meekoceras-bearing limestone of 1 Covered brown soil Sect~onsend at an 22 4 22 4 the Thaynes Formation in the mapped area would be useful in unknown locat~onIn the upper mem- establishing a correlation between this and other units In the ber, Wells Formaoon - western United States, (2) detailed petrographic and envlron- Partla1 th~cknessof the upper member, 238 3 mental studies of the Paleozoic and Mesozoic formations in the Wells Formarlon - mapped area to better define hydrocarbon occurrences and drill- Total section th~ckness 245 0 able prospects, and (3) a detalled seismic program to further Sectton 2 delineate deeper structures with hydrocarbon reservoir potential Parr~alsectlon of Twln Creek L~mestone,measured on the north side of in the Sage Valley Quadrangle. Spnng Creek, SE M, sectlon 17, and SW M, sectlon 16, T 31 N, R 119 W, Lincoln County, Wyomlng

APPENDIX Th~ckness(melers) Measured Sect~ons Cumulattue Spctzon 1 Unzt No Unzt Sectzon G~raffeCreek Member Partla1 sectlon of Grandeur Tongue of the Park C~tyFormanon and Wells Format~on,measured on the north s~deof Pole Creek, 1 0 km west of Sage Val- 11 Sandstone alternating bands of 11ght 20 7 181 0 ley, SW M, secnon 31, T 8 S, R 46 E, Canbou County, Idaho brown, thlnly lammated sandstone and gray~shgreen thickly bedded sandstone, Thzdness (meters) cross-lam~nated,calcareous, glaucon~t~c, Cumulatzue r~pplemarked, flaggy, fisslle, some bur- Unrt No. Unzt Sectzon rowing traces, cl~ffContact w~thover- Bottom of the Meade Peak Member of the lying Preuss Sandstone located at d~s- Phosphorla Format~on,an unexposed Inter- appearance of red so11 val-top of Grandeur Tongue of the Park C~ty 10 Sandstone hghr green, weathers l~ghr 1 1 160 3 Format~on brownish green, fine gralned, masslve, calcareous, glaucon~t~c,blocky, friable, 13 Covered unknown cl~mb~ngnpples showing current direc- 12 Dolomlre medlum gray, weathers l~ghr 6 7 245 0 tlon from south to north, 1 cm thtck gray, very fine crystalline, blocky, ledge - lnterbeds of s~ltstone,cl~ff Part~al th~ckness of the Grandeur 6 7 9 Llmesrone medium gray, weathers tan. 7 1 159 2 Tongue of the Park C~tyFormat~on very fine crystall~ne, thlnly lamlnated w~thcross lamlnat~ons,very sandy, thin Wells Format~on,upper member to thick bedded, flaggy to blocky, inter- 11 Sandstone light tann~shgray, weathers 35 9 238 3 beds of l~ghtgray, calcareous, poorly tan, calcareous, fine gralned, porous, consol~datedclaystone, cl~ff fnable, blocky, masslve bedded, parr~ally 8 Sandstone l~ghtbrown, very frne 2 > 152 1 covered, slope gralned, thln bedded w~thpoorly ex- posed cross-beds, calcareous, blocky to 10 Lmestone (') l~ghtto rnedlum gray, 13 0 202 4 flaggy, cliff -. weathers 11ght gray, massive bedded, sandy, vugs up to I 3 cm across com- Total th~cknessof Glraffe Creek Member 31 4 pose up to 5% of the volume, ledge Leeds Creek Member 9 Covered brown so11 42 1 1894 7 Llmestone medium to l~ghtgray, 8 7 149 6 weathers lrght brown, very fine crystal- 8 Sandstone yellow~sh wh~te,weathers 31 6 147 3 line, very finely lamlnated to rhlnly l~ghtyellow~sh gray, fine gralned, well bedded, shaly In thln lamlnat~ons,very sorted, sl~ghrly fr~able, calcareous, silty, some very fine sand grains, np- porous, massive bedded, slope pled, cl~ff 7 Sandstone l~ghtgray, weathers rann~sh 198 115 7 6 Llmestone partially covered, 11ghr to 6.8 1409 brown, very fine gralned, hard, cal- med~umgray, weathers to l~ghtgray. careous, masslvc bedded, shoulder. very silty to very shaly, very thlnly lami- nated, rippled, flaggy, rare 5-cm-th~ck 6 Sandstone llght gray, weathers brown- 27 6 95 9 beds of I~ghtbrown, calcareous slit- ~shred, very fine gralned, well ce- stone, shoulder mented, calcareous, masslve bedded, 5 L~mestone part~allycovered, hght gray, 36 9 134 1 ledge-former gradlng to cl~ff-formerthe weathers l~ghtbrown~sh gray, shaly, last 5 8 m finely laminated, shoulder 5 Sandstone medlum gray, weathers llght 20 5 68 3 4 Lmestone part~allycovered medium to 20.2 97 2 gray, very fine gra~ned,very well ce- dark gray, weathers med~umgray, shaly, mented, vugs up to 2 > cm across con- l~chograph~c,needlel~ke when broken, tainlng calc~te,fractured w~thno onen- shoulder 34 J L CONNER

3 Lmestone similar to unlt 5 9 8 77 0 marks, rare rh~n~nrerbeds of brown, sll- 2 Lmestone s~milarto unlt 4 58 0 67 2 ty, calcareous mudstone, sandstone feathers out laterally 1 Covered float s~mllarto units 4 and > 9 2 9 2 Base of member not exposed Tluckness Sandsrone (40%) and mudstone (60%) of Leeds Creek Member est~matedto be slmllar to unit 48 488 m (Cressman 1964) - Sandsrone pale red, very fine grained. Total rh~cknessof exposed Leeds Creek Memk 149 6 very rhlck bedded, cross-bedded, r~pple marks, some thlck Interbeds of brown, Total sect~onth~ckness 181 0 very thlnly bedded mudsrone slmllar to unlr 48, quartz-filled vugs to 5 cm In Sectron 3 d~ameterIn top sandstone Secr~onof Preuss Sandstone measured on the west s~deof Spring Creek, SE Sandsrone (80%) and mudsrone (20%) %, sectlon 17, T 31 N, R 119 W, L~ncolnCounty, Wyoming similar to unlr 48, sandstone thlck bed- ded Thzcknes~(rnerer~) Curnulatrue Sandstone (50%) and mudstone (50%) Unrt No Unrt Sectrun s~mllarto un1r 48, three 3-cm.thlck In. 7 terbeds of graylsh yellow~sh green, ml- Covered red sod, sandsrone floar, gray- 91 8 3720 caceous mudstone ~shred, weathers prnkrsh gray, fine to med~umgrained, med~umgrained sand Sandstone (90%) and mudstone (10%) decreasing, moderately sorted. In- wm~larto unlt 48 dlstlnctly lammared, calcareous Contact Sandstone slmllar to unlt 47 w~thoverlying Stump Sandstone lo- Sandstone (70%) and mudstone (30%) cated at d~sappearanceof red so11 srmrlar to unrt 48 Covered red sod, sandstone float slm- Sandstone pale red, very fine gra~ned, llar to unit 7, med~um-grarnedsand in- very rh~ckbedded, cross-bedded, some creasing th~nInterbeds of brown, s~lty,cal- Covered red sod, sandstone float, gray- careous mudsrone, sandstone feathers ~shred, weathers light brown~sh red, out laterally very fine to fine gra~ned,s~lty, well sort- Sandstone (70%) and mudstone (30%) ed, thlnly lammared, calcareous slmllar to unlr 48 Sandstone gray~sh red, weathers light Sandstone (80%) and mudstone (20%) redd~sh brown, very fine to fine s~milarto unit 48, some rare, green gra~ned,dry, well sorred, rhlnly 1am1- mudstone blebs In the brown mud- nated, calcareous, shoulder stone, 15 cm thick gray~sh yellow~sh Covered red soil, sandstone float, gray- green mudsrone at top of unit ~shred, weathers brown~shred. fine Sandstone (80%) and mudsrone (20%) gralned, sllty, well sorted, calcareous, s~m~larto unlt 37, 25 cm th~ckpale th~nlylaminated green~shyellow mudstone at top of Sandsrone redd~sh brown, weathers unit light brownish red, very fine gralned. Sandsrone pale yellow~sh brown, verv calcareous, well sorted, blocky, shoul- fine gralned, calcareous, sllry, thlck bed- der ded, cross-bedded Covered red sod, sandsrone floar, gray- Sandsrone (60%) and mudsrone (40%) ~shbrown, weathers brown to brown s~m~larto unlr 48, some rare gray~sh red, very fine to flne gralned, cross yellow~shgreen mudstone bleba In the lamrnated w~th some lam~nat~ons brown mudstone weathering Into rel~ef In the fine gralned unlts, moderately sorted, sllry In Sandsrone pale yellowish brown, very part Contact with underlying Tw~n fine gralned. calcareous, allry, thlck bed- Creek L~mestone located at d~s- ded, crosebedded appearance of wh~teso11 Sandsrone (50%) and mudstone (50%) Total th~cknessof Preuss Sandstone s~mllarto unlt 48 Sandstone (60%) and mudsrone (40%) Sectron 4 similar to unlt 37, 20-cm-thlck moder- Part~alszctlon of Preuss Sandstone measured along Mob11 well road 8 km ate grcen~sh yellow, weathers gray~sh west of Fa~rv~ew,Wyomlng, NW )A, sectlon 9, and SW M, sectlon 4, T 31 N, yellow, mudsrone at top of unlt R 119 W, L~ncolnCounty, Wyomlng Sandstone l~ghtbrown~sh gray, very fine gralned, some cross-bedd~ng,rhln Thrckner~(rneter~) Interbeds of brown, a~lrv,calcareous Curnulatrue mudstone Unrt No Unrt Sectrun Sandstone (60%) and mudstone (40%) 49 Covered red so11 Contact w~thover- 57 7 137 2 s~mllar to unlt 48. 50-cm-th~cksand- lylng Stump Sandstone located at base stone at base of unrt of composltlon of green, glauconrr~c sandstone of slmllar to unlr 30 Smmp Mudsrone moderarr brown, spllnren.. 48 Sandstone (40%) and mudstone (60%) 16 79 5 calcareous, r~ppledIn upper and lower sandsrone mottled moderate brown n) parts, massive and s~ltyIn m~ddlepart, pale red, fine gralned, calcareous, very secondary gypsum stringers. d~s- arg~llaceous, sllty, med~um bedded, continuous 5-cm.th~ckgreen mudsrone mudstone, moderate brown, calcareous, at top of unit splintery, very thrnly bedded, nppled, Sandsrone s~mllarto unit 30 some med~um-gra~nedsand Sandsrone (40%) and mudstone (60%) 47 Sandstone pale red, very fine grained, 1 4 77 9 slmllar to unlr 37. 31-cm-thick green very thick bedded, cross-bedded, r~pple mudstone on top of unlt GEOLOGY OF THE SAGE VALLEY QUADRANGLE, IDAHO AND WYOMING

Sandsrone (40%) and mudstone (60%) 3 Sandstone mottled graylsh red to pale 6 19 s~mllarto unlt 37, 8-cm-th~ckgreen red, very fine grained, very arg~llaceous, mudstone on top of unlt calcareous, masslve Sandstone l~ghrbrown~sh gray, very 2 Sandstone (70%) and mudsrone (30%) 7 13 fine gralned, some cross-bedd~ng, thln s~mllarto unlt 48 Interbeds of brown, sllty, calcareous mudsrone, some green mudstone Inter- 1 Sandstone graylsh oranglsh plnk, very 6 6 beds, 5-cm-thtck green mudstone on fine gralned, calcareous, masslve argll- top of unlt laceous Base of unlt not exposed - Sandstone (70%) and mudstone (30%) Total thickness of exposed Preuss Sand- 137 2 l~ghtbrownlsh gray sandstone, s~mllar stone sectlon Base of formarlon not ex- to unlt 37 except thicker beddlng posed Sandsrone (70%) and mudstone (30%) slmllar to unlr 37, salt hopper crystal casts, mud ch~ps,8-cm-thlck green Secr~onof Stump Sandstone measured on the west side of Spnng Creek, mudstone at top of unrr NW 1/4, sectlon 17, T 31 N, R 119 W, Lincoln County, Wyomlng Mudstone s~m~larto unlt 28 Thzckness (meters) Sandstone (90%) and mudstone (10%) Cumulatzve slmllar to unlr 48 Unrt No Unrr Sec~ron Sandstone (50%) and mudstone (50%) 14 Sandstone and sllrstone alternatrng s~mllarto unlt 37 except In 50-cm-thlck slopes and ledges up to 1 5 m In thick- unlts, 15-cm-thlck green mudstone at ness, sandstone-gray to greenlsh gray, top of unlt weathers l~ghtbrown~sh gray, fine Sandstone (50%) and mudsrone (50%) gralned, sl~ghtlycalcareous, cross laml- s~m~larto unlr 19, 10-cm-thlck gray~sh nared, blocky, ledge, s~ltstone-med~um yellow~sh green mudsrone at top of gray, fnable, very calcareous, thlnly unlt. lam~nated,flaggy, slope Contact w~th Sandstone (40%) and mudstone (60%) overlyrng Ephra~mConglomerate lo- s~mllarto unlt 48, rare, secondary, vertl- cated at disappearance of green so11 cal gypsum stringers 13 Sandstone medlum gray, weathers llghr Sandstone mottled moderate brown to gray~shgreen, very fine gralned, cal- pale red, fine gralned, calcareous, very careous, sllty, glaucon~t~c,sllry, finely arg~llaceous, s~lry, med~um bedded, lamlnated w~th cross-lam~nat~ons, some thln Interbeds of moderate brown poorly preserved rlpple marks, flaggy, mudstone, sandstone feathers out later- ledge ally 12 Sandstone 11ght graylsh brown, weath- Sandstone (50) and mudstone (50) ers l~ghtbrown, very fine gralned, thin slm~larto unlr 37, cross-bedded sand- Iamlnared, w~thcross-lam~nar~ons, cal- stone, 23-cm-rhlck graylsh yellow~sh careous, fisslle, silty, slope green mudstone at top of unlt 11 Sandstone 11ght gray~shgreen, weathers Sandstone slmllar to unlt 16, fr~able 11ght brownlsh gray, thlnly laminated Sandstone (40%) and mudsrone (60%). w~rhcross-lam~nat~ons, calcareous, very slmllar to unlr 37, 5-cm-th~ckgray~sh fine gralned, beds of blocky mater~alto yellow~sh green mudstone on top of 60 cm rh~ck,slope unlt 10 Sandstone alternatlng massive and Sandstone mottled moderate brown to rhlnly lamlnated units up to 30 cm pale red, very fine to fine gralned, cal- thlck, masslve unlrs slmllar to unlt 5, careous, very arg~llaceous,masslve thlnly lam~natedunlts slmllar to unit 9, Mudsrone lower '/, gray~sh yellow~sh form alternatlng ledges and slopes green, upper % moderate brown, splln- 9 Sandstone gray~shgreen, weathers l~ght tery, calcareous green, very fine to fine gralned, laml- Sandstone (60%) and mudstone (40%) nated w~rhcross-lamlnanon sets to 5 s~mllarto unlt 48 cm In he~ghr,calcareous, glaucon~t~c, Sandstone s~mllarto unlr 16 sllty, poorly preserved r~pplemarks, flaggy, alternatlng slopes and ledges Sandstone (85%) and mudstone (15%) slmllar to unlt 48, oranglsh plnk sand- 8 Sandstone medlum gray, weathers gray- stone ~shbrown, thlnly lamlnated, wlth cross- Sandstone (95%) and mudstone (5%) Iamlnat~onsets to 8 cm In he~ghr,very s~mllarto unlt 48, very fine-gralned fine to fine gralned, calcareous, glauco- nlrlc, sllty, flaggy, ledge sandstone Mudsrone moderate brown, spllnrery, 7 Sandstone med~umgray, weathers gray- very thlnly lam~nated,sllty, calcareous, ~shbrown, thlnly lamlnated wlth cross- some fine-gra~nedsand, bimodal npples lam~nat~onsto 30 cm In he~ght,cal- lnd~carlngE-W current dlrect~onw~th careous, trough cross-lam~nat~ons,cur- water motlon toward east the pre- rent dlrectlons N-S, flaggy, ledge dominant dlrect~on,3-cm-thlck graylsh 6 Sandstone l~ghtgreen, weathers gray~sh yellow~shgreen mudstone at top of green, rhlnly lammated w~thcross-lam- unlt natlons to 5 cm In he~ght,sandy, cal- Sandstone pale red, very fine gralned, careous, flaggy, glauconlr~c,ledge very arg~llaceous, npple marks, np-up 5 Sandstone med~umgray. weathers gray- clasts, calcareous, masslve at base be- ~shbrown, thlnly lammated w~thcross- coming lamlnared toward top of unlt lamlnat~onsto 30 cm In he~ghr,trough Sandstone (60%) and mudstone (40%) cross-lam~naoons,calcareous, very fine slmllar to unlt 48 to fine gralned, flaggy, ledge 36 J. L. CONNER

4 Sandstone: light grayish green, weathers 3.7 14.9 Sandscone: light gray, weathers light grayish green, very fine grained, cal. gray brown, medium to coarse grained. careous, glauconiric, rhinly laminated poorly sorted, massive, blocky, very cal- with cross-laminations to > cm in careous, porous, less than l% pebbles, height, flaggy, ledge. interbedded with lighr to medium gray, 3 Sandstone: medium gray, weathers light 1.4 11.2 medium-sized sandsrone In units up to grayish brown, fine grained, very cal- 50 cm thick, shoulder. careous, thinly laminated with poorly Covered: alternating bands of red and preserved cross-laminations, flaggy, gray soil. ledge. Sandstone: lighr gray, weathers light 2 Sandstone: dark gray, weathers to gray- 4.9 9.8 grayish brown, salt and pepper, medium ish olive, medium grained, cross-bedded to coarse grained, massive, blocky, very in sets up to 8 cm in height with some calcareous, porous, less than 1% pebbles, weathering into relief, very calcareous, ledge Contact with underlying Peter- poorly sorted, ripple marks, tight, ledge. son Limestone located at disappearance 1 Covered: olive brown soil. Contact 4.9 4.9 of white limestone float. with the underlying Preuss Sandstone Total thickness of Bechler Conglomerate located at appearance of red soil. - Pert:son Limestone Total thickness of Stump Sandstone 128.9 20 Covered: brown soil, limestone float. Section 6 19 Limestone: medium gray, weathers lighr gray, massive, blocky, micro- Partial section of Gannetr Group (Ephraim Conglomerate, Peterson Lime- crystalline, abundant fossil debris but stone, Bechler Conglomerare) measured .8 km east of the Draney Ranch, NE few whole shells, ledge Ih, section 10, and W Ih, secrion 11, R. 46 E, T. 8 S, Caribou County, Idaho (section 2 of fig. 11). Limestone: similar to unlr 19, weathers light brown. Thickness (meters) Limestone- med~um gray, weathers Cumulative lighr gray, masslve, mlcrocrystalline, Unit No. Unif Section blocky, abundant fossil debris but few Bechler Conglomerate whole shells, ledge. Contact with un- derlying Ephraim Conglomerate located 35 Covered: red soil. Contact with over- at top of purplish gray sandstone unit. lying Draney Limestone located at dis Total thickness of Peterson L~mestone appearance of red soil and appearance of gray soil and limestone float. raim Conglomerate 34 Limestone: medium gray to medium Sandstone: light to medium purplish purple, weathers to light gray, nodular, gray, weathers light purplish gray, very massive, slope. Probably interbedded fine grained, slightly calcareous, mas- with red mudstones and siltstones. sive, blocky, shoulder. 33 Sandstone: light gray, weathers lighr Covered: red soil. gray, fine to coarse grained, angular to Sandstone: light gray, weathers medium subangular, poorly sorted, less than 1% gray, salt and pepper, medium to coarse pebbles, calcareous, forms lenticular grained, calcareous, poorly sorted, cross- bodies interbedded wirh red soil, ledge. bedded, blocky, porous, 10% pebbles to 32 Covered: red soil. 1.4 cm in diamerer, lenticular shape- possibly a channel, cliff, 31 Sandstone: medium gray with purple tint, weathers light to medium gray, Covered: red soil, red and gray sand- fine grained, calcareous, ledge. stone float. 30 Covered: reddish gray soil. Sandsrone: light gray, weathers medium purplish gray, salt and pepper, fine to 29 Conglomerate: light to medium gray, medium grained, calcareous, poorly weathers medium gray, up to 50% peb- sorted, blocky, ledge, fines upward, in- bles that are up to 5 cm in diameter, terbedded with dark red sandstone. coarse-grained sand matrix, subangular weathers medium grayish red, fine to angular, poorly sorted, calcareous grained, massive, some conglomerate very porous, friable, forms lenticular lenses wirh pebble to 1.4 cm in dlame- bodies-some lenticular interbeds of rer, red sandstone drops our in lowc fine-grained sand, ledge. 6 m. 28 Sandstone: interbedded red and me- Covered: red soil, reddish gray, fine- dium gray, medium to coarse grained, grained sandstone float. calcareous, cross-bedded, ledge, gray sandstone decreaxs upward. Sandstone: dark gray, weathers l~ght brownish gray w~thred tint, fine 27 Covered: red soil. grained, calcareous, shoulder, Inter- 26 Sandstone: grayish red, weathers grayish bedded with dark red sandsrone, weath- reddish brown, medium grained, cal- ers medium grayish red, fine grained, careous, rare interbeds of medium gray massive, some conglomerare lenses with sandstone, weathers light brown, occa- pebbles to 1.4 cm In diameter sional purple tint, medium grained, cal- Sandstone: medium purplish gray. careous, up to 60 cm thick, ledge. weathers medium purplish gray, fine 25 Covered: red soil. grained, massive, cross-bedded, blocky, cliff. 24 Sandstone: light to medium red, weath- ers redd~sh grayish brown, medium Covered: limestone and conglomerate float grained, poorly sorred, calcareous, inter- Limestone: medium gray, weathers beds of medium gray, medium-grained light to med~umgray, purple tint, mas- sandstone up to 30 cm thick, ledge. sive, nodular, shoulder. GEOLOGY OF THE SAGE VALLEY QUADRANGL, IDAHO AND WYOMlNG

6 Covered red sod, gray l~mestone,red 22 Sandstone redd~sh gray, weathers red- sandstone, and conglomerate float. d~shgray, very fine to med~umgralned, 5 Sandstone dark red, weathers med~um poorly sorted, graded beddlng In part, gray~shred, fine gralned, rnasslve, some some conglomerate lenses w~thchert conglomerate lenses w~thpebbles to 14 pebbles to 1 4 cm In d~ameter,con- cm In d~ameter,ledge glomerate fines upward, ledge 4 Covered red soil w~thred sandstone float 21 Covered red sod, l~mestonefloat slm- llar In descnprion to that of unlt 14 3 Sandstone dark red, weathers med~um grayish red, fine gralned, masslve, some 20 Sandstone slmllar to unlr 22 conglomerate lenses w~thpebbles to 14 19 Sandstone similar to unlt 21 cm In d~ameter,ledge 18 Covered red so11 2 Conglomerate medlum gray, 20% peb- 17 Llmestone med~um purplish gray, bles to 2 cm In diameter, med~um- weathers l~ghtgray, nodular, Inter- gralned sandstone matnx, salt and pep- bedded red shales may form over 50% per, hard, ledge of the unlt, part~allycovered, l~mestones 1 Covered, red so~l,red conglomerate and form shoulders, shales form slopes gray sandstone float Contact w~thun- derlylng Stump Sandsrone located at 16 Covered: red so~l,I~mestone float nm- appearance of green, glaucon~t~csand- llar description to that of unit 14 stone float and ollve so11 15 Sandstone reddish gray, weathers red- Total th~ckness of Ephralm Con- d~shgray, very fine to medlum gralned, glomerate-about 90 m roo thlck be- poorly sorted, graded beddlng at base, cause of repetition of units by faultlng ledge Contact w~thunderlying Peter- son Llmestone located at top of nodular Total secnon th~ckness limestone unit Total th~cknessof Bechler Conglomerate Partial sectlon of Gannett Group (Ephra~mConglomerate, Peterson L~me- Peterson Llmestone stone, Bechler Conglomerate) measured 2 6 km west of Falrvlew, Wyoming, W 14 Llmestone, med~um purpl~sh gray, M sectlon 8 and E Lh, section 7, T 31 N, R 119 W, Lncoln County, Wyom- weathers light purpl~shgray, nodular, Ing (sect~on3 of fig 11) Interbedded red shales may form up to 90% of the unlt, partially covered, Thrckness (meters) slope. Contact w~thunderly~ng Eph- Cumulaaue ra~mConglomerate located at base of Unrt No. Unzt Sectron nodular llmestone unlr Bechler Conglomerate Total th~cknessof Peterson L~mestone 34 Sandstone Ilght graylsh brown, weath- Ephralm Conglomerate ers l~ghtbrownlsh gray, fine gralned, 13 Covered red so11 fnable, cross-bedded, masslve, ~solated pebbles to 14 cm In d~ameter,ledge 12 Sandstone redd~sh gray, weathers red- Contact w~thoverlying Draney Lme- dish gray, very fine to medlum gralned, stone located at base of gray, fosslll- poorly sorted, graded beddlng at base, ferous llmestone some conglomerate lenses w~thchert pebbles to 1.4 cm In diameter finlng 33 Covered red so11 upward, ledge 32 Sandstone l~ghtgray~sh brown, weath- 11 Covered red soil, nodular Ilmestone ers l~ghrbrownlsh gray, fine gralned, float near m~ddleof unlt fnable, crossbedded, masslve, Isolated pebbles to 14 cm In d~ameter,ledge 10 Sandstone redd~sh gray, weathers red- dish gray, very fine to med~umgralned, 31 Covered red so11 poorly sorted, graded beddlng at base, 30 Sandstone l~ghtgray~sh brown, weath- ledge ers l~ghrbrown~sh gray, fine gralned, 9 Sandstone redd~sh gray, weathers red- fnable, crossbedded, masslve, Isolated d~shgray, very fine to medlum gralned, pebbles to 1 4 cm In d~ameter,ledge poorly sorted, graded beddlng at base 29 Covered red soil, limestone float slm- some conglomerate lenses w~thchert dar to unlt 16 pebbles to 14 cm In d~ameterfinlng 28 Sandstone reddlsh gray, weathers red- upward, ledge dish gray, very fine to med~umgralned, poorly sorted, some conglomerate lenses 8 Covered red soil, llmestone float slm- llar to un~t6 but 1s purple on a fresh w~thchert pebbles to 1 4 cm In d~ame- ter, conglomerate decreases upward, surface ledge 7 Sandstone l~ghtgray, weathers med~um 27 Covered, reddlsh brown sod redd~sh gray, very fine grained, t~ght, masslve, cross-bedded, cl~ff 26 Covered red sod, red sandstone float slmllar to unlt 10 6 Llmestone. med~um gray, weathers 11ght gray, some purple tint, mlcro- 25 Conglomerate l~ghtplnk, masslve, crystall~ne,nodular, shoulder. quartzite, chert, and llmestone cobbles to 20 cm In d~ameter,lnterbeds of red- 5 Covered red soil d~shgray, very fine- to med~um-gn~ned 4 Sandsrone med~um redd~sh gray, sandstone beds to 1 m th~ck,cliff weathers rnedlum gray~shred, medlum 24 Covered red soil, llmestone float near gralned, 5% chert pebbles to 5 cm In base of unlt diameter, cliff 23 Sandstone redd~sh gray, weathers red- 3 Covered red so11 d~shgray, very fine to med~umgralned. 2 Sandstone light gray, weathers med~um poorly sorted, graded beddlng at base, gray, salt and pepper, 25% chert pebbles ledge to 2 cm In d~ameter,cl~ff J L CONNER

1 Covered red so11 Contact wlth under- 23 2 23 3 Peterson Llmesrone lying Stump Sandsrone located at ap- 11 Llmestone med~um to dark gray. 150 277 9 pearance of ol~vebrown sandstone floar weathers l~ghtgray, m~crocrysralllne, and so11 - nodular, part~ally covered by a redd~sh Total th~cknessof Ephralm Conglomerate 3336 brown soll-poss~bly the nodular I~me- Total secrlon th~ckness 836 7 stones are Interbedded w~thred slit- stones, shales and mudstones, slope Sectron 8 Contact w~rhunderlylng Ephralm Con- Parr~alsectlon of Gannett Group (Ephra~mConglomerate, Peterson L~me- glomerate located at base of nodular stone, Bechler Conglomerate) measured 08 km north of Flrsr Creek, a west l~mestoneunlt - flowlng rnbutary of Spnng Creek, NW 'A,scction 5, T 30 N, R 119 W, Lln- Toral th~cknessof Peterson Llmestone 15 0 coln County, Wyom~ng(sect~on 4 of fig 11) > > ' Ephra~mConglomerate 10 Sandstone s~m~larto unlr 13 23 2 262 9 Unlt No. 9 Covered 72 2397 Sect~onends at an unknown locat~onIn the up- 8 Sandstone 11ght redd~sh gray, fine to 24 5 232 5 per part of the Bechler Formarlon on the Sprlng med~um gralned, partly calcareous, Creek Syncllne axls cross-bedded, a few conglomerate lenses, Bechler Conglomerate th~ckbedded, ledge 27 Conglomerate redd~shbrown, weathers 12 8 690 9 7 Sandstone s~m~larto unlt 13 318 2080 brown~shred, chert cobbles to 20 3 cm 6 Covered 144 1762 across and I~mestone boulders to 35 6 cm across, masslve bedded, cl~ff 5 Llmestone med~um brown~sh gray, 11 8 161 8 weathers l~ghrblush gray, very fine 26 Covered red so11 87 1 678 I crystalline, calc~te stnngers, s~l~ceous, 25 Conglomerate reddish brown, weathers 6 1 591 0 masslve bedded, part~ally covered, brown~sh red, chert and llmestone peb- shoulder bles to 7 6 cm across, masslve bedded. cliff 4 Sandstone l~ghrgray, weathers l~ght 23 5 150 0 redd~shgray, calcareous, fine to me- 24 Covered redd~shbrown so11 w~rhsand- 132 3 584 9 d~umgralned w~th5% chert pebbles stone, conglomerate, and l~mestone whlch may be up to .6 cm across, cross- float In the upper 30 2 m Spnng Creek bedded, ledge was crossed In the Interval and beds may be covered by the valley shoulders 3 Sandsrone slmllar to unlt 4 w~thI~me- 17 6 126 5 and floor stone float 23 Sandstone brown~sh red, very fine 96 452 6 2 Covered some l~mestonefloat 76 3 1089 gralned, calcareous, s~lty,med~um bed- 1 Sandstone l~ghtgraylsh wh~te,weathers 32 6 32 6 ded, some llmestone float IS found In l~ghrgray, hard, fine gralned, sll~ceous this untt, shoulder cement, nonporous, masslve bedded, 22 Sandstone slm~larto unlt 23 w~rhout 32 4 443 0 ledge Contact w~thunderlylng Stump the l~mestonefloat Sandstone located at change In sand- stone float color from 11ght gray~sh 21 Sandsrone l~ghtredd~sh brown, wearh- 8 1 410 6 wh~teto llght ol~vebrown ers graylsh brown, calcareous ('), cross- - bedded, contalns conglomerate lenses Toral th~cknessof Ephra~mConglomerate w~thchert fragments to 1 3 cm across at Total sectlon rh~ckness 690 9 the base, masslve bedded, ledge 20 Shale- dark brown, weathers redd~sh 200 402 5 REFERENCES CITED brown, sllty, thin bedded, unlt contalns llmestone float, slope Armsrrong, F C, and Cressman, E R, 1969, The Bannock thrust zone, south. eastern Idaho US Geolog~calSurvey Profess~onalPaper 374.J. p 1-22 19 Shale slmllar to unlt 20 w~thno Ilme- 8 5 382 5 Armsrrong, F C, and Onel, S S. 1965, Tecton~cdevelopment of the Idaho- stone float Wyomlng thrust belt Amer~can Assoc~atlonof Petroleum Geolog~sts 18 Sandsrone smllar to unlt 21, sandstone 15 1 374 0 Bulletln, v 49, p 1847-66 w~thconglomerate lenses near the base Blackstone, D L, 1977, The Overthmsr Belt sal~enrof the Cordilleran fold and a 1 5-cm sandstone ledge between belt, western Wyoming, southeastern Idaho, and northeastern Utah 13 7 and I5 2 m Wyoming Geolog~calAssoc~atron Gu~debook, 29th Annual Field Confer- Sandstone s~m~larto unit 21 14 5 3589 en&, p 367-84 - Sandstone 11ght gray~shwh~te, weathers 5 2 344 4 Blackwelder, E , 1918, New geolog~calformat~ons In western Wyomlng Wash- gny~shred, fine gralned, sl~ghtlycal- lngton Academy of Sc~encesJournal, v 8, p 417-26 careous unlt contalns llmesrone float, Boutwell, J M , 1907, Srrar~graphyand structure of the Park C~rymlnlng d~s. tnct, Urah Journal of Geology, v 15, p 434-58 Slope , 1912, Geology and ore depos~rsof the Park C~cydlsrr~cr, Utah Sandstone slm~larto unlt 16 w~thout 19 5 339.2 US Geolog~calSurvey Profess~onalPaper 77, 231p the llmesrone float Brown. 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