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Home , Carlile Shale, Chugwater Formation, Fort Union Formation, Frontier Formation, Horn Mountains, Phosphoria Formation

MONTANA BUREAU OF MINES AND GEOLOGY GEOLOGIC MAP SERIES NO. 58 A Department of Tech of The University of Montana Prepared in Cooperation with the U.S. Geological Survey and the U.S. Department of Energy National Technology Office Bridger 30' x 60' Quadrangle, Lopez 2000

Ktf CORRELATION OF MAP UNITS DESCRIPTION OF MAP UNITS Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Ktf Alluvium (Holocene): Gravel, sand, silt, and clay along Bearpaw (Upper ): Dark-gray shale, Kootenai Formation (Lower Cretaceous): Mostly reddish- Ktf Ktf Ktf Ktf Ktf Qtu Qal active channels of rivers, creeks, and tributaries. Most fissile, commonly weathering dark brownish-gray. brown, olive-gray, and dusky-purple bentonitic mudstones Ktf Holocene sediment in tributaries draining areas underlain by Brownish-gray calcareous and nodules are with interbedded, lenticular, fine- to coarse-grained Ktf Cretaceous , and shale bedrock is sand, silt, common, middle part of formation contains numerous , thin zones of light-gray nodular Ktf Qc Qaf Qls and clay. thin mostly greenish-gray beds; thin, silicified, are common in the upper part. remains Ktf Ktf hematite-stained sandstone beds common near the top. present locally. Locally thick, lenticular, fluvial, fine-grained Ktf Ktf Colluvium (Holocene and ): Locally derived The thickness is 200 to 800 feet, thinning to the west. sandstone, the Greybull Sandstone, is present at top. Ktf Ktf Qat slope-wash deposits mainly of sand, silt, and clay. Usually The basal Pryor Conglomerate Member is brown Ktf thin veneer concealing bedrock, but locally as thick as Judith River Formation (Upper Cretaceous): Interbedded conglomerate and pebbly coarse-grained sandstone, 20 Ktf 30 feet. Commonly grades into Qal. Locally contains well- brownish-gray sandy shale and light-brown to pale to 60 feet thick. The total thickness of the Kootenai Ktf Ktf Ktf A' Qafo Pleistocene rounded cobbles derived from alluvial terrace gravel. yellowish-brown argillaceous, very fine to fine-grained Formation is 200 to 250 feet. Ktf Qat4 lenticular sandstone in beds generally up to 10 feet thick, Ktf Ktf Alluvial fan deposits (Holocene and Pleistocene): but locally a massive cliff-forming sandstone, resembling (Upper ): Variegated, mainly Ktf Ktf Gravel, sand, silt, and clay deposited in fans being formed those in the Eagle Sandstone, occurs at the base and is greenish-gray and pale reddish-brown mudstone. Very Ktf Qst Qp by modern streams along major valley margins. Display commonly correlated with the Parkman Sandstone. fine to fine-grained, quartzose, calcareous, cross-bedded Ktf Ktf QTls QTtu QTpg characteristic fan-shaped map pattern and convex upward Sandstones friable to moderately well indurated, cross- sandstones are commonly present at about mid-section, Ktf profile. Typically grade upstream into Qal. Thicknesses bedded, and burrowed to bioturbated and support growths 5 to 10 feet thick but locally can be as much as 30 feet Ktf Ktf range from very thin at toes to as much as 50 feet at of pine trees. Greenish-gray and pale maroon-gray thick. Fossil dinosaur remains common. Upper contact Ktf heads of fans. mudstones and easily eroded sandstones occur near the placed at the base of the Pryor Conglomerate. The basal Tst3 top of the formation. The thickness is variable because contact is placed at the top of fossiliferous limy sandstone Ktf Ktf Unconformity Older alluvial fan deposits (Pleistocene?): Deposits of the lenticularity of the sandstones and eastward regional and coquina of the underlying Swift Formation. Thickness Ktf TERTIARY Ktf Ktf similar to Qaf but overlain by Qaf and are erosionally thinning; in this area it is 250 to 350 feet. is 300 to 350 feet. Ktf Ktf Tftr dissected; occur only along the southwest margin of the Ktf Pryor Mountains. Claggett Shale (Upper Cretaceous): Brownish-gray fissile Ktf Ktf Tfle —ELLIS GROUP undivided (Jurassic) — Ktf shale with minor interbeds of light brownish-gray very Calcareous tufa (Holocene): Very light-gray, vuggy argillaceous sandstone. Also includes thin bentonite beds. Ktf Tft Qtu Swift Formation (Upper Jurassic): Interbedded medium- Ktf Ktf Ktf limestone, being deposited by Blue Water Spring in T. 6 Light brownish-gray to light-brown, calcareous concretions Ktf gray shale, limestone and limy sandstone, fossiliferous. Unconformity S., R. 24 E., sections 4 and 9. Plant material commonly common, often fossiliferous. The upper contact is Ktf Ktf incorporated. Thickness unknown but probably 10 to 20 gradational and conformable and is placed at the change Brownish-gray, fossiliferous, very sandy limestone occurs Ktf Kl feet thick. to ledge-forming sandstones of the Judith River Formation. at the top of the formation and commonly has brownish- gray coquina at the top. About 100 feet thick. Ktf Ktf Kb Thickness of the formation ranges from 100 to 300 feet, Landslide deposits (Holocene and Pleistocene): thinning westward and southward toward the Ktf Rierdon Formation (Upper Jurassic): Mostly pale Ktf Kjr Unconsolidated mixture of soil and blocks of bedrock border. Ktf Ktf greenish-gray very fossiliferous shale with minor Ktf Ktf transported down steep slopes by mass wasting; locally Ktf Kcl consist of internally cohesive, rotated slump blocks. Eagle Sandstone (Upper Cretaceous): Light brownish- interbeddded brownish gray limestone. Typically poorly Ktf Characteristic hummocky surface with concentric swales gray to very pale, orange very fine to fine-grained, cross- exposed, forming smooth slopes littered with , Ke and ridges near downslope limits. Can occur where slope bedded sandstone, burrowed to bioturbated in part. Locally including oysters (Gryphaea and Ostrea), belemnites and moisture content produce unstable conditions. Many contains calcareous, light-brown sandstone concretions (Pachyteuthis), and fragments (Pentacrinus). A Ktc Upper small landslides and some with only minor downslope as much as 15 feet in diameter. As many as four sandstone laminated sandstone about mid-section, 10 to 20 feet Cretaceous thick, containing fish fossils, is present locally at the Kn displacement (Colton, 1995, written communication) are intervals 10 to 50 feet thick can be present with intervening not shown because of bedrock emphasis of this map. sandy as thick as 50 feet. beds present near southern end of the Pryor Mountains. The Rierdon is about 150 feet thick. Kca CRETACEOUS the top of the formation were mined in the Fromberg- Ktf Pediment surface deposits (Pleistocene): Deposits of Bridger area. Thickness ranges from 100 to 350 feet, Kgr sand, silt, and clay mixed with cobble-size clasts of locally thinning to the south and west. Piper Formation (): Interbedded medium derived sandstone on pedimented flat surface immediately gray, and pale reddish-gray, thin-bedded limestone and Kf east of Elk Basin oil field in the southwestern part of the Telegraph Creek Formation (Upper Cretaceous): medium-gray shale. Includes thin, interbedded gypsum. quadrangle. Pediment surface truncates steeply dipping Brownish-gray to medium dark-gray shale and sandy Forms ledge below smooth slopes of the Rierdon shales. Ktf Kbf Fort Union beds. The surface is at the same elevation as shale, with thin, interbedded sandstone. Dusky-red Thickness 75 to 150 feet. Ktf Km the ancestral Shoshone River terrace (Qst) located about concretions common near base. Sandstone beds thicker six miles to the east and is thought to be similar in age and more abundant upward, grading into Eagle Sandstone. (Lower ): Interbedded moderate reddish-brown, fine-grained sandstone, siltstone, Ktf (about 1.4 m.y.). Upper contact is placed at the base of the first cliff-forming Ktf sandstone of the Eagle Sandstone. Zone of dusky-red and mudstone. Thin light-gray limestone bed is present Unconformity Lower Landslide deposits (Pleistocene and Pliocene?): concretions occurs just above the base of the Telegraph near the top, and gypsum beds are common in lower Cretaceous part; locally gypsum thickens to about 10 feet. Typically, Kk Unconsolidated mixture of soil and blocks of local bedrock Creek. Maximum thickness about 150 feet. along the flanks of the Pryor Mountains uplift. Much of strike valleys develop at the base of the Chugwater above Unconformity surface form is obliterated by later erosion. Niobrara Shale (Upper Cretaceous): Olive-gray and dark resistant rocks of the Phosphoria and Tensleep formations. Thickness is 450 to 600 feet. Jm brownish-gray, fissile shale with abundant, thin bentonite Pediment gravel deposits (Pleistocene and Pliocene?): beds. Upper half calcareous, containing few very thin Unconformity Upper Angular and subangular, coarse gravel derived from local bentonite beds, and contains thin beds of very calcareous, (): Light-gray limestone, Jurassic sandstone and quartzite, commonly grayish-pink, cherty. Ktf Js JURASSIC bedrock, mostly limestone, forming smooth surfaces laminated sandstone, siltstone, and sandy limestone near sloping away from the Pryor and Big Horn mountains. the top. Concretions medium light-gray to pale yellowish- Locally a reddish-brown variety of , known as Dry Ktf Je Jr These deposits are assumed older than Qpg because brown and from a few inches to two feet in diameter Head Agate, has been mined and collected for lapidary they are at much higher altitudes and are slightly dissected. commonly present. Inoceramus prisms common. Upper purposes. Phosphoria is a very thin remnant, mapped Ktf Jp Middle Thicknesses 10 to 30 feet. contact placed at change from calcareous shales to non- separately where scale allows, but otherwise included Jurassic with the Tensleep Formation. Thickness 10 to 50 feet. Unconformity calcareous shales of Telegraph Creek. Basal contact is Lower TRIASSIC QTtu Calcareous tufa (Pleistocene and Pliocene?): Light-gray placed below ledge-forming zone of closely spaced, Triassic and grayish-pink, vuggy, limestone spring deposits with fossiliferous gray septarian concretions with veins brown (): Very light-brown to very pale-orange sandstone, fine grained, well sorted, Pp plant material commonly incorporated, occurs only at . About 700 feet thick. Permian PERMIAN Blue Water Spring, T. 6 S., R. 24 E., section 9. Inactive well rounded, cross-bedded. Locally contains thin Unconformity deposit about 100 feet higher in altitude than Qtu. limestone beds, locally cherty near the top, and locally (Upper Cretaceous): Dark-gray to dark silicified to form quartzite. About 200 feet thick. Pennsylvanian PENNSYLVANIAN Thicknesses 10 to 20 feet. bluish-gray fissile shale. Interval about mid-section contains laminae and thin beds of argillaceous, platy, light brownish- Upper Amsden Formation (Lower Pennsylvanian and Upper ALLUVIAL TERRACE GRAVELS gray to light olive-gray sandstone that locally supports ): Interbedded grayish-pink to light-red Ktf Mississippian growth of pine trees, but otherwise surface exposures Unconformity MISSISSIPPIAN Alluvial gravels, terrace levels 1-3 undivided (Holocene mudstone, limestone, and siltstone. are Middle are nearly bare of soil and vegetation. Septarian nodules Mm and Pleistocene?): Gravel, sand, silt, and clay underlying commonly cherty. Unconformably overlies karst surface Mississippian terraces about 20 to 200 feet above present elevation of and concretions common, ranging from light-gray to dark- Ktf developed on limestone of the Madison Group. Unconformity modern streams and rivers. Equivalent to Qat1-Qat3, yellowish-orange. Basal contact placed above last Characteristically produces pink stain on underlying cliffs calcareous shale in the underlying Greenhorn Formation. Dj Upper mapped on the Billings quadrangle to the north (Lopez, of Madison Group. Thickness ranges from 140 to 300 Ktf Devonian 1996). About 250 to 300 feet thick. feet; locally, tectonically thinned to only a few feet along Unconformity the margins of Pryor Mountains uplift. Ktf Middle Greenhorn Formation (Upper Cretaceous): Shale, dark Ob Alluvial gravel, terrace level 4 (Pleistocene): Gravel Kgr Ordovician underlying terraces 200 to 300 feet above present altitude bluish-gray, calcareous, fossiliferous. Typically poorly Amsden Formation and Tensleep Sandstone Ktf Unconformity of Yellowstone River. These terraces locally exhibit relatively exposed, but forms very light brownish-gray soil upon undivided (Pennsylvanian and Upper Mississippian): Middle & Upper steep gradient toward the Yellowstone River valley and weathering. Locally, the lower contact is marked by zone Units mapped together where Amsden has been Cambrian may actually include several levels of terraces that are of closely spaced, gray, calcareous, septarian concretions tectonically thinned as described above. Unconformity difficult to distinguish. Cobble- and pebble-size clasts are at the base of the Greenhorn. Upper contact marked by Ktf Ag Archean mainly granite, granitic gneiss, schist, and quartzite. change to non-calcareous shale. About 75 feet thick. Madison Group undivided (Middle Mississippian): Thickness as much as 20 feet. Limestone and dolomitic limestone, light-gray to light Frontier Formation (Upper Cretaceous): Light brownish- brownish-gray. Thick bedded to massive in the upper part gray, fine-grained, thick-bedded to massive sandstone. Ktf (Mission Canyon Limestone) and thin bedded to thick ALLUVIAL TERRACES OF THE ANCESTRAL Interbedded with dark-gray, fissile shale. Occurs south of bedded in the lower part (Lodgepole Limestone). Also SHOSHONE RIVER Fromberg. Interfingers with the upper part of the Belle contains thin, interbedded gray shales. Fossiliferous and Ancestral Shoshone River gravel, terrace level 1 Fourche Shale and thickens to the south; near the cherty beds are present throughout. Collapse features MAP SYMBOLS (Pleistocene): Gravel and sand underlying terraces about Wyoming border, it replaces the entire Belle Fourche and caves (Campbell, 1978) are common at the upper 400 feet above present altitude of Pryor Creek in its lower section, where it reaches a thickness of about 350 feet. karst surface. Collapse features often contain pale-red reaches. But because of the much steeper gradient of breccia and host low-grade deposits. The upper present day Pryor Creek, this terrace, near the Pryor Belle Fourche Shale (Upper Cretaceous): Shale, dark- massive beds of very pure limestone are quarried in the Contact: Dashed where approximately located, Mountains, is below the level of Pryor Creek. Transported gray, fissile, containing several thick bentonite beds in dotted where concealed southwest part of the Pryor Mountains for industrial uses by the ancestral Shoshone River that flowed through lower part. Thin sandstone bed commonly containing and lime production. Thickness of the Madison is 800 to Pryor Gap (Mackin, 1937). Commonly calcite cemented small chert pebbles, and zone of very dusky-purple to 1,000 feet. near base. Clasts are mainly cobbles and pebbles of glossy grayish-black, ironstone concretions near base. Ktf Fault: Dashed where approximately located, dotted dark-colored andesitic rocks (Absaroka Volcanics), and Light-gray, brownish-gray concretions about 6 in. to 1 foot where concealed, queried where uncertain, bar Jefferson Formation (Upper Devonian): Dolomitic lesser amounts limestone and quartzite. Age estimated in diameter and large (up to four feet in diameter) light- limestone, light brownish-gray, fetid, poorly exposed, and ball on downthrown side. Arrows along fault to be about 1.4 m.y. (Reheis, 1985). Ten to 50 feet thick brown to dark yellowish-orange concretions are trace indicate relative strike-slip displacement. typically occurs as float above Bighorn Dolomite. In other in map area. characteristic. North of Fromberg, the Frontier is absent, areas of Montana, the Jefferson is overlain by the Three Several faults have been reactivated at different but the zone is represented by a salt-and-pepper times and show vertical and strike-slip Forks Formation, which is absent in the Pryor Mountains Ancestral Shoshone River(?) gravel, terrace level 3 sandstone present in the upper part of the Belle Fourche (Sandberg, 1961, 1965). In Punch Bowl Creek on the displacements (Pliocene): Gravel and sand underlying terrace about 200 that is fine- to medium-grained. Contact with Greenhorn Ktf east side of the Pryor Mountains, a thin section of feet above the upgradient projection of Tst2. (Tst1 and marked by abrupt change to very calcareous shale. Beartooth Butte Formation (Lower Devonian), which Tst2 are not present on the Bridger quadrangle but are Thickness is 350 to 400 feet. consists of pale reddish-brown siltstone and limestone Reverse fault: Open teeth on upthrown block present to the north on the Billings quadrangle [Lopez, and dolomite conglomerate and breccia, is present below 1996]). Gravel consists of rounded and weathered cobbles (Upper Cretaceous): Interbedded, siliceous, the Jefferson (Blackstone, 1975). The Beartooth Butte of limestone, quartzite, sandstone, and about 10% of very fine- to fine-grained sandstone, siltstone, and shale. Formation is mapped with the Jefferson. Total thickness andesitic volcanic clasts. May represent a period of Sandstones and siltstones mostly light-gray to medium- of the Jefferson is about 250 feet. accelerated down-cutting of Ancestral Shoshone River gray, with silvery sheen. Locally, some sandstone beds Ktf Slump block scarp: Hachures indicate direction are highly silicified, resulting in very hard quartzite. Shales of block movement through the sequence of sedimentary rocks of Bighorn Dolomite (Middle Ordovician): Dolomite and Ktf age in Pryor Gap. are fissile, and mainly medium dark-gray. Bentonite beds dolomitic limestone, very light-gray to very pale-orange, common, 1 to 4 feet thick, including prominent beds at lower part massive, thin to thick bedded in upper part. base and near top. Fish scales on bedding planes of Has characteristic pock-marked surface due to differential Horizontal beds BEDROCK MAP UNITS sandstones and siltstones are characteristic of the weathering. Forms cliffs in lower reaches of deep canyons. —— formation. Thin, coarse lag deposit containing fish bones, About 500 feet thick. fish teeth, and chert pebbles near the middle of the Ktf Member, Fort Union Formation 32 Strike and dip of inclined beds (Paleocene): Gray to grayish-yellow, fine- to medium- section. Upper contact of Mowry marked by thick bentonite Cambrian Sedimentary rocks undivided (Middle and grained sandstone, cross-bedded. Interbedded with above the highest fish scale-bearing sandstone. Basal Upper Cambrian): Light-red sandstone and quartzite, brownish-gray carbonaceous shale and siltstone and contact placed at change from dark-gray fissile greenish-gray shale and sandy shale, gray thin-bedded to characteristic silvery sandstone 75 Strike and dip of overturned beds minor thin coal beds. Sandstones ledge forming, commonly limestone and greenish-gray flat-pebble limestone support growths of pine trees. Thickness 500 to 700 feet. and siltstone of the Mowry containing fish scales. Thickness conglomerate. Includes the Flathead Quartzite, Gros about 250 feet. Ventre Formation, and Gallatin Limestone of Wyoming Anticline: Showing trace of axial plane and Lebo Member, Fort Union Formation (Paleocene): terminology or Flathead, Wolsey, Meagher, Park, and Predominantly dark-gray to olive shale, locally yellowish- Thermopolis Shale and Fall River Sandstone Pilgrim of Montana terminology. Thickness is 700 to direction of plunge; dashed where approximately Ktf undivided (Lower Cretaceous): Upper 50 feet shale, located, dotted where concealed gray claystone, thin, interbedded sandstones and siltstone, 800 feet. yellowish-gray. Typically forms smooth grassy slopes dark-gray fissile, with few thin bentonite beds. Interval below the Tongue River Member. Thickness 200 to 250 below this is dark-gray to brownish-gray and olive-gray, Granitic gneiss and schist (Archean): Pale to moderate feet. fissile shale with thin interbeds and laminae of olive-gray red gneissic granite, medium dark-gray quartzo-feldspathic Syncline: Showing trace of axial plane and direction and light olive-gray, argillaceous sandstone. Common gneiss, biotite-hornblende schist, quartzite, and aplite of plunge; dotted where concealed Tullock Member, Fort Union Formation (Paleocene): bentonite beds and zones of iridescent very dusky-purple and mafic dikes. Locally cut by veins. Yellowish-gray, fine- to medium-grained, ledge-forming to grayish-black, ironstone concretions. The Fall River Ktf sandstone, cross-bedded in part. Interbedded with gray Sandstone underlies the Thermopolis Shale and is an upward-coarsening sequence of interbedded medium Overturned syncline: Showing trace of axial plane to greenish-gray claystone, siltstone, and minor Ktf carbonaceous shale. Supports growths of pine trees. dark-gray, fissile shale and fine-grained, quartzose, light and direction of dip of bedding; dashed where brownish-gray to moderate yellowish-brown sandstone. approximately located, dotted where concealed About 400 feet thick. Ktf Sandstone coarsens and beds thicken slightly up section, (Upper Cretaceous): Interbedded light commonly rippled, burrowed to bioturbated, and moderately to heavily limonite and hematite stained. Total Monocline: Showing axial plane trace of anticlinal brownish-gray, cliff and ledge-forming, fine-grained, thick- bedded to massive sandstone, medium-gray fissile shale, thickness of the Thermopolis and Fall River combined is flexure; dashed where approximately located, 600 to 700 feet. Ktf dotted where concealed; shorter arrow on more and a few thin beds of coal. Sandstone beds support steeply dipping limb growths of pine trees. Total thickness of the formation is about 350 feet.

W Water

Ktf A INDEX OF PREVIOUS GEOLOGIC MAPPING REFERENCES Topographic layer from USGS Bridger 1:100,000 scale quad 109°00' 108°00' Andrews, D.A., Pierce, W.G., and Eargle, D.H., 1947, Geologic Izett, G.A., and Wilcox, R.E., 1982, Map showing localities and KILOMETERS 1 0 1 2 3 4 5678 9 10 11 12 13 14 15 16 17 18 19 20 SCALE 1:100 000 1000 0 5000 10 000 15 000 20 000 METERS map of the Big Horn Basin, Wyoming and Montana, showing inferred distributions of the Huckleberry Ridge, Mesa Falls, and 1 CENTIMETER ON THE MAP REPRESENTS 1 KILOMETER ON THE GROUND 45°30' terrace deposits and physiographic features: U.S. Geological Lava Creek ash beds (Perlette Family Ash Beds) of Pliocene and MILES 1 0 1 23456789101112 13 CONTOUR INTERVAL 20 METERS 5000 0 10 000 20 000 30 000 40 000 50 000 60 000 70 000 FEET Survey Oil and Gas Investigations Preliminary Map 71, Pleistocene age in western and southern Canada: Washington, D.C., U.S. Government Printing Office, scale U.S. Geological Survey Miscellaneous Investigations Series Map 1:125,000. I-1325, scale 1:4,000,000. Cross Section A–A' Blackstone, D.L., 1974a, Preliminary geologic map of the Deep Knappen, R.S., and Moulton, G.F., 1931, Geology and mineral Creek SW quadrangle, Big Horn County, Montana: Montana resources of parts of Carbon, Big Horn, Yellowstone, and Stillwater Scale (Vertical and Horizontal) 1:100,000 Bureau of Mines and Geology Open-File Report MBMG 62, counties: U.S. Geological Survey Bulletin 822-A, 70 p., pl. 1, scale Thin surficial deposits not shown scale 1:24,000. 1:125,000. ______, 1974b, Preliminary geologic map of the Deep Lopez, D.A., 1995, Field guide to the northern Pryor-Bighorn QTls Landslide deposit Creek SE quadrangle, Big Horn County, Montana: Montana structural block, south central Montana: Montana Bureau of Mines Bureau of Mines and Geology Open-File Report MBMG 63, and Geology Open-File Report 330, 26 p. QTpg Pediment gravel 10 scale 1:24,000. 5 3 4 ______, 1996, Structural geology of the northern Pryor-Bighorn Kcgr Carlile Shale & Greenhorn Formation* ______, 1974c, Preliminary geologic map of the Castle uplift, south central Montana [abs]: American Association of Southwest A A' Northeast Rocks quadrangle, Big Horn County, Montana: Montana Bureau Petroleum Geologists Bulletin, v. 80, p. 974–975. 3000 Dj 3000 Kbm Belle Fourche & Mowry Shales* of Mines and Geology Open-File Report MBMG 64, scale Mm Ob 1:24,000. Mackin, J.H., 1937, Erosional history of the Big Horn Basin, Mm KJkm Ktf Thermopolis Shale & Fall River Sandstone Wyoming: Geological Society of America Bulletin, v. 48, p. 813–894. t QTls Je 2000 Ma t Ma s 2000 8 12 6 2 ______, 1974d, Preliminary geologic map of the Big Ice KJkm Je c c Je QTpg c t t c c KJkm Kootenai & Morrison Formations* Cave quadrangle, Big Horn County, Montana: Montana Bureau McConnell, D.A., 1994, Fixed-hinge, basement-involved fault- t Je KJkm Ktf Kbm Kcgr of Mines and Geology Open-File Report MBMG 65, scale propagation folds, Wyoming: Geological Society of America Bulletin, 1000 Ag 1000 Meters Je Ellis Group, undivided 1:24,000. v. 48, p. 813–894. Meters s c Chugwater Formation ______, 1974e, Preliminary geologic map of the Bear Reheis, M.C., 1985, Evidence for Quaternary tectonism in the Mean Mean Canyon quadrangle, Big Horn County, Montana: Montana Bureau northern , Wyoming and Montana: Geology, v. 13, p. Sea Level Sea Level t Tensleep Sandstone Ag 7911 of Mines and Geology Open-File Report MBMG 66, scale 364–367. 45°00' 1:24,000. 1000 1000 Ma Amsden Formation Richards, P.W., 1955, Geology of the Bighorn Canyon-Hardin area, ______, 1974f, Preliminary geologic map of the Bowler Montana and Wyoming: U.S. Geological Survey Bulletin 1026, 93 Mm Madison Group, undivided Andrews, D.A., Pierce, W.G., ______, 1974h 10 quadrangle, Big Horn County, Montana: Montana Bureau of p., scale 1:62,500. 2000 2000 and Eargle, D.H., 1947 Mines and Geology Open-File Report MBMG 67, scale 1:24,000. Dj Jefferson Formation ______, 1974i Richards, P.W., and Rogers, C.P., 1951, Geology of the Hardin 2 Blackstone, D.L., 1975 11 ______, 1974g, Preliminary geologic map of the Red area, Big Horn and Yellowstone counties, Montana: U.S. Geological Ob Bighorn Dolomite Pryor Mountain quadrangle, Big Horn County, Montana: Montana Survey Oil and Gas Investigations Map OM-111, sheet 1, scale s ______, 1974a ______, 1974j Bureau of Mines and Geology Open-File Report MBMG 68, 1:62,500. Cambrian sedimentary rocks, undivided 3 12 scale 1:24,000. Ag Sandberg, C.A., 1961, Distribution and thickness of Devonian Rocks Granitic gneiss, hornblende schist, and biotite schist ______, 1974h, Preliminary geologic map of the Section in and in central Montana and north-central Wyoming: 4 ______, 1974b Knappen, R.S., and Moulton, G.F., 1931 * Units combined on cross section only House Draw quadrangle, Big Horn County, Montana: Montana U.S. Geological Survey Bulletin 1112-D, 127 p. Bureau of Mines and Geology Open-File Report MBMG 69, Geologic Map of the ______, 1974c Richards, P.W., 1955 5 scale 1:24,000. ______, 1965, Nomenclature and correlation of lithologic subdivisions of the Jefferson and Three Forks formations of southern ______, 1974i, Preliminary geologic map of the Mystery Montana and northern Wyoming: U.S. Geological Survey Bulletin ______, 1974d 6 Stewart, J.C. , 1974 Cave quadrangle, Big Horn County, Montana: Montana Bureau 1194-N, 18 p. of Mines and Geology Open-File Report MBMG 70, scale MN Adjacent 30' x 60' maps ______, 1974e Thom, W.T., Jr., Hall, G.M., Wegemann, C.H., 1:24,000. Stewart, J.C., 1974, Geology of the Dryhead-Garvin basin, Big Bridger 30' x 60' Quadrangle, Montana 7 GN and Moulton, G.F., 1935 Horn and Carbon counties, Montana: Montana Bureau of Mines ______, 1974j, Preliminary geologic map of the Indian and Geology Special Publication 17, scale 1:62,500. ______, 1974f Zimmerman, E.A., 1960 Spring quadrangle, Big Horn County, Montana: Montana Bureau Big Timber Billings Hardin 8 14° of Mines and Geology Open-File Report MBMG 71, scale Thom, W.T., Jr., Hall, G.M., Wegemann, C.H., and Moulton, G.F., 1°47' 1:24,000. 1935, Geology of Big Horn County and the Crow Indian Reservation, by ______, 1974g 9 Montana: U.S. Geological Survey Bulletin 856, 200 p. ______, 1975, Geology of the East Pryor Mountain Red Lodge Bridger Lodge quadrangle, Carbon County, Montana: Montana Bureau of Mines Zimmerman, E.A., 1960, Geology of the Bluewater Springs area, Maps may be obtained from David A. Lopez Grass and Geology Special Publication 69, scale 1:24,000. Carbon County, Montana: U.S. Geological Survey Water-Supply Publications Office Paper 1779-J, 24 p. Montana Bureau of Mines and Geology UTM grid convergence (GN) Campbell, N.P., 1978, Caves of Montana: Montana Bureau of 1300 West Park Street, Butte, Montana 59701-8997 and 1989 magnetic declination 2000 Cody Burgess Mines and Geology Bulletin 105, 169 p. Phone: (406) 496-4167 or (406) 496-4174 (MN) Powell Junction Fax: (406) 496-4451 at center of map Location http://mbmgsun.mtech.edu Diagram is approximate