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Geologic units in Fremont county, Wyoming

Additional scientific data in this geographic area

Wind River Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 20 % of this area

WIND RIVER FORMATION Northwest Wyoming (Jackson Hole)--Variegated red and white claystone and siltstone; largely nontuffaceous except near the top; lenticular coal unit in middle. At base locally includes equivalent of Indian Meadows Formation; Central Wyoming--Variegated claystone and sandstone; lenticular conglomerate. Age of tuff at top 49 Ma.

Alluvium and Colluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 12 % of this area

ALLUVIUM AND COLLUVIUM--Clay, silt, sand, and gravel in flood plains, fans, terraces, and slopes.

Lithology: alluvium; colluvium

Cody Shale (Phanerozoic | Mesozoic | Cretaceous-Late (78-83 Ma)) at surface, covers 6 % of this area

CODY SHALE (AGE 78 TO 83 Ma) northern Yellowstone area--Gray to brown shale and siltstone; north and south Wyoming--Dull-gray shale, gray siltstone, and fine-grained gray sandstone.

Lithology: shale; siltstone; sandstone

Gravel, pediment, and fan deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 4 % of this area

GRAVEL, PEDIMENT, AND FAN DEPOSITS--Mostly locally derived clasts. Includes some glacial deposits along east flank of Wind River Range. Locally includes some Tertiary gravels.

Dune sand and loess (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 3 % of this area

DUNE SAND AND LOESS--Includes active and dormant sand dunes. In northwestern Wyoming is chiefly loess (age 12,000-19,000 years).

Lithology: dune sand; loess

Glacial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 3 % of this area

GLACIAL DEPOSITS--Till and outwash of sand, gravel, and boulders.

Lithology: glacial drift

Bighorn Dolomite, Gallatin Limestone, and Gros Ventre Formation (TB), Bighorn Dolomite, Snowy Range Formation, Pilgrim Limestone, Park Shale, Meagher Limestone, Wolsey Shale, and Flathead Sandstone (Y), Bighorn Dolomite, Gallatin Limestone, Gros Ventre Formation, and Flathead Sandstone (N), or Whitewood Dolomite, and WInnipeg and Deadwood Formations (NE) (Phanerozoic | Paleozoic | Cambrian-Middle Cambrian-Furongian(?) Ordovician-Early(?) Ordovician-Middle(?) Ordovician-Late) at surface, covers 3 % of this area

BIGHORN DOLOMITE, GALLATIN LIMESTONE, and GROS VENTRE FORMATION. BIGHORN DOLOMITE (Thrust Belt)--Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. GALLATIN LIMESTONE--Gray and tan limestone. GROS VENTRE FORMATION--Greenish-gray micaceous shale. BIGHORN DOLOMITE, SNOWY RANGE FORMATION, PILGRIM LIMESTONE, PARK SHALE, MEAGHER LIMESTONE, WOLSEY SHALE, AND FLATHEAD SANDSTONE (Yellowstone). BIGHORN DOLOMITE--Light-gray massive siliceous dolomite. SNOWY RANGE FORMATION (Gallatin Group)--Medium-gray limestone and underlying greenish-gray shale. PILGRIM LIMESTONE (Gallatin Group)--Blue-gray and yellow mottled hard limestone. PARK SHALE--Green micaceous soft shale. Upper part may be Late Cambrian. MEAGHER LIMESTONE--Blue-gray and yellow mottled hard limestone. WOLSEY SHALE--Green micaceous soft shale. FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. BIGHORN DOLOMITE, GALLATIN LIMESTONE, GROS VENTRE FORMATION, AND FLATHEAD SANDSTONE (north Wyoming). BIGHORN DOLOMITE--Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. GALLATIN LIMESTONE--Blue-gray and yellow mottled hard dense limestone. GROS VENTRE FORMATION--Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. WHITEWOOD DOLOMITE, AND WINNIPEG AND DEADWOOD FORMATIONS (northeast Wyoming). WHITEWOOD DOLOMITE--Buff massive fossiliferous dolomite. WINNIPEG FORMATION--Pink to yellow siltstone and shale. DEADWOOD FORMATION--Red and brown quartzitic sandstone.

Granodiorite of the Louis Lake Pluton (Archean) at surface, covers 3 % of this area

GRANODIORITE OF THE LOUIS LAKE PLUTON (AGE 2,640 Ma)--Equigranular; locally gneissic.

Lithology: granodiorite

Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers 3 % of this area

MIOCENE ROCKS--Southwest Wyoming: Southern Rock Springs uplift--Pale-green to tan tuffaceous sandstone and claystone of Miocene(?) age. Conglomerate of uncertain correlation locally at base. Saratoga Valley and west and southwest to Colorado--White massive soft tuffaceous sandstone and lesser amounts of white marl; lower part conglomeratic. Underlies North Park Formation in Saratoga Valley. To the west and southwest is called Browns Park Formation. Rawlins area--White massive soft tuffaceous sandstone; Central Wyoming: White soft tuffaceous sandstone. Locally derived conglomerate in upper and lower parts of sequence; in places lower conglomeratic sequence may be of Oligocene age. In Granite Mountains K/Ar age of tuff in lower part of sandstone sequence about 17 Ma and fission-track age of lower conglomerate about 24 Ma.

White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene (31-35 Ma)) at surface, covers 3 % of this area

WHITE RIVER FORMATION (AGE 31 TO 35 Ma)--White to pale-pink blocky tuffaceous claystone and lenticular arkosic conglomerate.

Oldest gneiss complex (Archean) at surface, covers 3 % of this area

OLDEST GNEISS COMPLEX--Chiefly layered granitic gneiss, locally migmatitic. Local masses of quartzite, metagraywacke, iron-formation, and other metasedimentary rocks and amphibolite and felsic gneiss thought to be volcanic; metasedimentary rocks in Beartooth Mountains contain detrital zircon dated at more than 3,400 Ma. Inclusions show evidence of granulite-facies metamorphism prior to 2,800 Ma. Mueller and others (1982) suggest that large areas in Beartooth Mountains were invaded by Late Archean granite (age about 2,800 Ma). Bighorn Mountains--Dates of metamorphism 3,000+ Ma.

Granitic rocks (Archean) at surface, covers 3 % of this area

GRANITIC ROCKS OF 2,600-Ma AGE GROUP. Teton Range--Mount Owen Quartz Monzonite. Age 2,500+/- Ma; may be of Early Proterozoic age. Gros Ventre and Washakie Ranges--Granitic rocks. Yellowstone National Park, Owl Creek, Granite, and Seminoe Mountains, Rawlins uplift, and Medicine Bow Mountains--Granite. Wind River Range--Granodiorite to porphyritic and equigranular granite. Sierra Madre--Granite and granodiorite. Laramie Mountains--Granite, amphibolite, and minor amounts of metasedimentary rocks. Hartville uplift--Granite and quartz monzonite. Black Hills uplift--Granite and minor amounts of metasedimentary rocks.

Lithology: granitoid

Madison Group and Darby Formation (TB, N) or Madison Group and Three Forks and Jefferson Formations (Y) (Phanerozoic | Paleozoic | Devonian-Late Carboniferous Mississippian-Early(?) Mississippian-Middle(?) Mississippian-Late) at surface, covers 2 % of this area

MADISON GROUP AND DARBY FORMATION (Thrust Belt, north Wyoming). MADISON GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). DARBY FORMATION--Yellow and greenish-gray shale and dolomitic siltstone underlain by fetid brown dolomite and limestone. MADISON GROUP AND THREE FORKS AND JEFFERSON FORMATIONS (Yellowstone). MADISON GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). THREE FORKS FORMATION--Pink, yellow, and green dolomitic siltstone and shale. JEFFERSON FORMATION--Massive siliceous dolomite.

Chugwater and Dinwoody Formations (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late) at surface, covers 2 % of this area

CHUGWATER AND DINWOODY FORMATIONS. CHUGWATER FORMATION--Red siltstone and shale. Alcova Limestone Member in upper middle part. Thin gypsum partings near base. DINWOODY FORMATION--Olive-drab hard dolomitic thin-bedded siltstone.

Upper Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene-Late) at surface, covers 2 % of this area

UPPER MIOCENE ROCKS--Southwest Wyoming: South end of Wind River Range--Siliceous, arkosic, and locally radioactive sandstone, claystone, and conglomerate. Fission-track age about 27 Ma. Recent work suggests that part of these deposits may be of Eocene age. Pliocene and Miocene (as originally defined 2) South Pass Formation. Saratoga Valley--White to greenish-gray tuffaceous sandstone, siltstone, and claystone; locally conglomeratic. North Park Formation; Central Wyoming: Arkosic sandstone, conglomerate, and siltstone; some light-colored tuffaceous radioactive claystone and white cherty limestone. North of Sweetwater River in Granite Mountains--Light-colored tuffaceous radioactive claystone, siltstone, sandstone, and arkose. Moonstone Formation; East Wyoming: Light-colored tuffaceous claystone, sandstone, and conglomerate. Ogallala Formation in Denver Basin.

Frontier Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 2 % of this area

FRONTIER FORMATION in thrust belt--White to brown sandstone and dark-gray shale; oyster coquina in upper part; coal and lignite in lower part; in north and south Wyoming--Gray sandstone and sandy shale.

Lithology: sandstone; shale; coal

Metasedimentary rocks (Archean) at surface, covers 2 % of this area

METASEDIMENTARY ROCKS. Wind River Range--Metagraywacke, pelitic schist, metaconglomerate, graphitic schist, and iron-formation; local meta-andesite. At least 2,800 Ma. Seminoe Mountains (southeast end of Granite Mountains)--Pelitic schist, quartzite, and iron-formation. Casper Mountain (northwest extension of Laramie Mountains)--Felsic gneiss, quartzite, and iron-formation. Laramie Mountains--Pelitic schist, iron-formation, quartzite, marble, metaconglomerate, and metagraywacke.

Landslide deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 2 % of this area

LANDSLIDE DEPOSITS--Locally includes intermixed landslide and glacial deposits, talus, and rock-glacier deposits.

Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 2 % of this area

FORT UNION FORMATION northwest, southwest, and central Wyoming--Brown to gray sandstone, gray to black shale, and thin coal beds; east Wyoming--Light-colored massive sandstone, drab shale, and thick coal beds.

Lithology: sandstone; shale; coal

Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 2 % of this area

MOWRY (Kmr) AND THERMOPOLIS SHALES. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.

Tensleep Sandstone and Amsden Formation (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian) at surface, covers 2 % of this area

TENSLEEP SANDSTONE AND AMSDEN FORMATION. North Wyoming: TENSLEEP SANDSTONE--White to gray sandstone containing thin limestone and dolomite beds. Permian fossils have been found in the topmost beds of the Tensleep at some localities in Washakie Range, Owl Creek Mountains, and southern Bighorn Mountains. AMSDEN FORMATION--Red and green shale and dolomite; at base is brown sandstone. South Wyoming: TENSLEEP SANDSTONE AND AMSDEN FORMATION. TENSLEEP SANDSTONE--White to gray sandstone containing thin limestone and dolomite beds. AMSDEN FORMATION--Red and green shale and dolomite; at base is persistent red to brown sandstone.

Lithology: sandstone; carbonate; shale

Wagon Bed Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (45-49 Ma)) at surface, covers 1 % of this area

WAGON BED FORMATION (AGE ABOUT 45 TO 49 Ma)--Southwest and central Wyoming--Green and gray tuffaceous claystone, sandstone, and conglomerate; some uranium-phosphate marlstone and variegated bentonitic claystone. Locally contains oil shale between Wind River and Bighorn Basins; Central Wyoming (west side of Laramie Mountains)--Dull-green siliceous bentonitic claystone and tuff; giant granite boulder conglomerate in tuffaceous matrix.

Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Aycross Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma)) at surface, covers 1 % of this area

ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP (AGE 44 TO 49 Ma) Aycross Formation (age 49 Ma)--Brightly variegated bentonitic claystone and tuffaceous sandstone, grading laterally into greenish-gray sandstone and claystone. In and east of Jackson Hole contains gold-bearing lenticular quartzite conglomerate.

Phosphoria Formation (Phanerozoic | Paleozoic | Permian) at surface, covers 1 % of this area

PHOSPHORIA FORMATION AND RELATED ROCKS--Thrust Belt: Upper part is dark- to light-gray chert and shale with black shale and phosphorite at top; lower part is black shale, phosphorite, and cherty dolomite; north Wyoming: Brown sandstone and dolomite, cherty phosphatic and glauconitic dolomite, phosphatic sandstone and dolomite, and greenish-gray to black shale. Intertonguing equivalents of parts of Phosphoria are Park City Formation (primarily cherty dolomite, limestone, and phosphatic gray shale) and Shedhorn Sandstone.

Granite gneiss (Archean) at surface, covers 1 % of this area

GRANITE GNEISS (AGE 2,600 TO 3,100+ Ma)--Layered to massive, locally migmatitic; metasedimentary and metavolcanic rocks locally common. Includes Webb Canyon Gneiss in Teton Range.

Lithology: granitic gneiss

Mesaverde Formation (N) or Mesaverde Group (S) (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.9 % of this area

MESAVERDE FORMATION (north Wyoming)--Light-colored massive to thin-bedded sandstone, gray sandy shale, and coal beds. In Jackson Hole locally contains gold-bearing quartzite conglomerate. North of North Fork Powder River east of the Bighorn Mountains, consists solely of the Parkman Sandstone Member; MESAVERDE GROUP (SOUTH WYOMING). Includes Almond Formation, Ericson Sandstone, Rock Springs and Blair Formations in Rock Springs uplift; Almond Formation (white and brown soft sandstone, gray sandy shale, coal and carbonaceous shale), Pine Ridge Sandstone (light-gray sandstone and thin coal beds), and Allen Ridge (gray sandstone, shale, and thin coal beds) and Haystack Mountains (gray marine sandstone and shale) Formations in Rawlins uplift; Pine Ridge Sandstone (light-gray sandstone and thin coal beds) and Rock River Formation (soft sandstone and sandy shale) in Laramie Basin.

Battle Spring Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers 0.9 % of this area

BATTLE SPRING FORMATION--Equivalent to, and lithologically similar to locally derived basin-margin conglomerate of Wasatch Formation; merges southward into main body of Wasatch Formation. Lower part is Paleocene.

Lithology: conglomerate

Shear zone (Archean) at surface, covers 0.7 % of this area

Lithology: tectonite

Oldest gneiss complex (Archean) at surface, covers 0.7 % of this area

OLDEST GNEISS COMPLEX--Chiefly layered granitic gneiss, locally migmatitic. Local masses of quartzite, metagraywacke, iron-formation, and other metasedimentary rocks and amphibolite and felsic gneiss thought to be volcanic; metasedimentary rocks in Beartooth Mountains contain detrital zircon dated at more than 3,400 Ma. Inclusions show evidence of granulite-facies metamorphism prior to 2,800 Ma. Mueller and others (1982) suggest that large areas in Beartooth Mountains were invaded by Late Archean granite (age about 2,800 Ma). Wind River Range--Includes large bodies of metagabbro. Overprint pattern indicates area of migmatite related to emplacement of 2,600-Ma granite.

Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers 0.7 % of this area

WASATCH FORMATION Main body--Drab sandstone, drab to variegated claystone and siltstone; locally derived conglomerate around basin margins. Lower part is Paleocene.

Crooks Gap Conglomerate (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.7 % of this area

CROOKS GAP CONGLOMERATE--Giant boulders of granite in arkosic sandstone matrix. Reynolds (1976) considers age of eastern exposures to be Oligocene(?).

Lithology: conglomerate

Metasedimentary and metavolcanic rocks (Archean) at surface, covers 0.6 % of this area

METASEDIMENTARY AND METAVOLCANIC ROCKS--Amphibolite, hornblende gneiss, biotite gneiss, quartzite, iron-formation, metaconglomerate, marble, and pelitic schist; locally preserved textures and structures suggest origin to be sedimentary or volcanic. Older than 2,875 Ma in Teton Range; older than 3,200 Ma in Granite Mountains; older than 2,600 Ma in Medicine Bow Mountains and Sierra Madre, where it is the Late Archean Phantom Lake Metamorphic Suite 3.

Madison Limestone or Group (S) (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early Mississippian-Middle(?) Mississippian-Late) at surface, covers 0.6 % of this area

MADISON LIMESTONE OR GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite).

Bridger Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.5 % of this area

BRIDGER FORMATION--Greenish-gray, olive-drab, and white tuffaceous sandstone and claystone; lenticular marlstone and conglomerate.

Cloverly, Morrison, and Sundance Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers 0.5 % of this area

CLOVERLY, MORRISON, AND SUNDANCE (Js) FORMATIONS. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale.

Wind River Formation and Indian Meadows Formations (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.5 % of this area

WIND RIVER AND INDIAN MEADOWS FORMATIONS. WIND RIVER FORMATION Central Wyoming (Twdr2)--Variegated claystone and sandstone; lenticular conglomerate. Age of tuff at top 49 Ma. INDIAN MEADOWS FORMATION (Twim)--Red to variegated claystone, sandstone, and algal-ball(?) limestone; some beds of large Paleozoic boulders and detachment masses of Paleozoic and Mesozoic rocks.

Gypsum Spring Formation and Nugget Sandstone (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late(?) Jurassic-Early(?) Jurassic-Middle(?) Jurassic-Late) at surface, covers 0.5 % of this area

GYPSUM SPRING FORMATION AND NUGGET SANDSTONE. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N. NUGGET SANDSTONE--gray to dull-red, crossbedded quartz sandstone.

Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Tepee Trail Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma)) at surface, covers 0.4 % of this area

ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP (AGE 44 TO 49 Ma) Tepee Trail Formation (age probably about 48 Ma)--Green and olive-drab hard generally well bedded andesitic conglomerate, sandstone, and claystone.

Cloverly and Morrison Formations (N,S) or Cloverly Formation, Inyan Kara Group, and Morrison Formation (Phanerozoic | Mesozoic | Jurassic-Late Cretaceous-Early) at surface, covers 0.4 % of this area

CLOVERLY FORMATION and MORRISON FORMATION. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable; CLOVERLY FORMATION (Hartville uplift) or INYAN KARA GROUP (Black Hills) and MORRISON FORMATION. CLOVERLY FORMATION--Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. INYAN KARA GROUP--Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. Includes Fall River and Lakota Formations. MORRISON FORMATION, in northeast Wyoming, dully variegated siliceous claystone, nodular white limestone, and gray silty sandstone.

Gallatin Limestone, Gros Ventre Formation and equivalents, and Flathead Sandstone (N) or Cambrian Rocks (S) (Phanerozoic | Paleozoic | Cambrian-Middle Cambrian-Furongian) at surface, covers 0.4 % of this area

GALLATIN LIMESTONE, GROS VENTRE FORMATION and equivalents, and FLATHEAD SANDSTONE (north Wyoming). GALLATIN LIMESTONE--Blue-gray and yellow mottled hard dense limestone. GROS VENTRE FORMATION--Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. CAMBRIAN ROCKS (south Wyoming). South flank of Granite Mountains--Blue-gray and yellow mottled hard dense limestone interbedded with soft green micaceous shale; dull-red quartzitic sandstone at base. On and south of Rawlins uplift--Glauconitic quartzitic sandstone.

Lithology: limestone; sandstone; shale

Indian Meadows Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.3 % of this area

INDIAN MEADOWS FORMATION--Red to variegated claystone, sandstone, and algal-ball(?) limestone; some beds of large Paleozoic boulders and detachment masses of Paleozoic and Mesozoic rocks.

Middle and Lower Eocene Rocks (Phanerozoic | Cenozoic | Tertiary | Eocene-Early Eocene-Middle) at surface, covers 0.2 % of this area

MIDDLE AND LOWER EOCENE ROCKS--Equivalent to Aycross (Ta) and Wind River (Twdr) Formations. AYCROSS FORMATION (ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP)--Brightly variegated bentonitic claystone and tuffaceous sandstone, grading laterally into greenish-gray sandstone and claystone. In and east of Jackson Hole contains gold-bearing lenticular quartzite conglomerate. WIND RIVER FORMATION--Variegated claystone and sandstone; lenticular conglomerate.

Sundance and Gypsum Spring Formations and Nugget Sandstone (Phanerozoic | Mesozoic | Triassic(?) Jurassic(?) Jurassic-Early(?) Jurassic-Middle(?) Jurassic-Late) at surface, covers 0.2 % of this area

SUNDANCE AND GYPSUM SPRING FORMATIONS AND NUGGET SANDSTONE. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N. NUGGET SANDSTONE--gray to dull-red, crossbedded quartz sandstone.

Madison Limestone, Darby Formation, Bighorn Dolomite, Gallatin Limestone, Gros Ventre Formation, and Flathead Sandstone (N), Madison Limestone and Cambrian rocks (S), Minnekahta Limestone, Opeche Shale, Minnelusa Formation, Pahasapa and Englewood Limestones, Whitewood Dolomite, Winnipeg and Deadwood Formations (NE), or Paleozoic, undifferentiated (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous(?) Permian) at surface, covers 0.2 % of this area

MADISON LIMESTONE, DARBY FORMATION, BIGHORN DOLOMITE, GALLATIN LIMESTONE, GROS VENTRE FORMATION, AND FLATHEAD SANDSTONE (north Wyoming). MADISON LIMESTONE OR GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). DARBY FORMATION--Yellow and greenish-gray shale and dolomitic siltstone underlain by fetid brown dolomite and limestone. BIGHORN DOLOMITE--Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. GALLATIN LIMESTONE--Blue-gray and yellow mottled hard dense limestone. GROS VENTRE FORMATION--Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. MADISON LIMESTONE AND CAMBRIAN ROCKS (south Wyoming). MADISON LIMESTONE--Includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). CAMBRIAN ROCKS--On south flank of Granite Mountains, blue-gray and yellow mottled hard dense limestone interbedded with soft green micaceous shale; dull-red quartzitic sandstone at bae. On and south of Rawlins uplift, glauconitic quartzitic sandstone. MINNEKAHTA LIMESTONE, OPECHE SHALE, MINNELUSA FORMATION, PAHASAPA AND ENGLEWOOD LIMESTONES, WHITEWOOD DOLOMITE, AND WINNIPEG AND DEADWOOD FORMATIONS--Various combinations (northeast Wyoming). MINNEKAHTA LIMESTONE--Gray slabby hard limestone. Locally is a member of the Goose Egg Formation. OPECHE SHALE--Red soft sandy shale. Locally is a member of the Goose Egg Formation. MINNELUSA FORMATION--Buff and red limy sandstone; some thin limestone beds, solution breccias, and gypsum. PAHASAPA LIMESTONE--Gray massive dolomititc limestone. ENGLEWOOD LIMESTONE--Pink slabby dolomitic limestone. WHITEWOOD DOLOMITE--Buff massive fossiliferous dolomite. WINNIPEG FORMATION--Pink to yellow siltstone and shale. DEADWOOD FORMATION--Red and brown quartzitic sandstone. PALEOZOIC ROCKS, undifferentiated (Thrust Belt).

Ice Point Conglomerate (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.2 % of this area

ICE POINT CONGLOMERATE--Reddish-brown conglomerate, chiefly of Paleozoic rock fragments.

Lithology: conglomerate

Lance Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % of this area

LANCE FORMATION north Wyoming--Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses; south and northeast Wyoming--Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.

Nugget Sandstone (Phanerozoic | Mesozoic | Triassic(?) Jurassic(?) ) at surface, covers 0.2 % of this area

NUGGET SANDSTONE--Thrust Belt: Buff to pink crossbedded well-sized and well-sorted quartz sandstone and quartzite; locally has oil and copper-silver-zinc mineralization. North Wyoming: Gray to dull-red, crossbedded quartz sandstone.

Lithology: sandstone

Cloverly, Morrison, Sundance, and Gypsum Spring Formations and Nugget Sandstone (Phanerozoic | Mesozoic | Triassic(?) Jurassic(?) Cretaceous-Early) at surface, covers 0.2 % of this area

CLOVERLY, MORRISON, AND SUNDANCE (Js), GYPSUM SPRING FORMATIONS, AND NUGGET SANDSTONE (J@n). CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N. NUGGET SANDSTONE--Gray to dull-red, crossbedded quartz sandstone.

Basalt flows and intrusive igneous rocks (Phanerozoic | Cenozoic | Quaternary | Pleistocene) at surface, covers 0.1 % of this area

BASALT FLOWS AND INTRUSIVE IGNEOUS ROCKS. Yellowstone area--Includes Osprey, Madison River, Swan Lake Flat, and Falls River Basalts, basalts of Mariposa Lake, Undine Falls Basalt, and gravels, sands, silts, and basalts of The Narrows. In and adjacent to Absaroka and Washakie Ranges--Includes basalt of Lava Mountain (age about 0.5 Ma).

Lithology: basalt; gravel; sand; silt

Cloverly, Morrison, Sundance, and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers 0.1 % of this area

CLOVERLY, MORRISON, AND SUNDANCE (Js), AND GYPSUM SPRING FORMATIONS. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N.

Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.1 % of this area

LEWIS SHALE (AGE ABOUT 68 Ma)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Lithology: shale; sandstone

Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Two Ocean and Langford Formations (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma)) at surface, covers 0.1 % of this area

ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP (AGE 44 TO 49 Ma) Two Ocean and Langford Formations (age 47-48 Ma)--Dark-colored andesitic volcaniclastic rocks and flows underlain by light-colored andesitic tuffs and flows. In places may include Trout Peak Trachyandesite of Sunlight Group.

Green River Formation: Laney Member (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.1 % of this area

GREEN RIVER FORMATION Laney Member (age probably about 45 Ma)--Oil shale and marlstone.

Metamorphosed mafic and ultramafic rocks (Archean) at surface, covers 0.1 % of this area

METAMORPHOSED MAFIC AND ULTRAMAFIC ROCKS. Teton Range--Rendezvous Metagabbro; 2,875 Ma or older. Gros Ventre Range--Hornblende gneiss and serpentinite. Wind River Range--Pillowed amphibolite, metagabbro, and ultramafic sills. Wind River Canyon (cutting through Owl Creek Mountains)--Amphibolite and felsic gneiss of volcanic origin. Older than 2,700 Ma. Bighorn and Granite Mountains--Amphibolite. Seminoe Mountains--Amphibolite of volcanic origin, komatiite, and metagabbro. Casper Mountain--Amphibolite and serpentinite. Laramie Mountains--Amphibolite of volcanic origin, komatiite(?), metagabbro, and ultramafic sills.

Lithology: metavolcanic rock

Intrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area

INTRUSIVE IGNEOUS ROCKS--Felsic and mafic igneous bodies; the larger are mainly felsic.

Frontier Formation and Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers < 0.1 % of this area

FRONTIER FORMATION (Kf) AND MOWRY (Kmr) AND THERMOPOLIS SHALES. FRONTIER FORMATION--Gray sandstone and sandy shale. In Northern Yellowstone area, Yellowish- to medium-gray sandstone; tuffaceous and carbonaceous in lower part. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.

Meeteetse Formation and Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

MEETEETSE FORMATION AND LEWIS SHALE. MEETEETSE FORMATION (AGE ABOUT 73 Ma) (Km)--Chalky-white to gray sandstone, yellow, green, and dark-gray bentonitic claystone, white tuff, and thin coal beds. LEWIS SHALE (AGE ABOUT 68 Ma) (Kle)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Playa lake and other lacustrine deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

PLAYA LAKE AND OTHER LACUSTRINE DEPOSITS--Chiefly clay, silt, and fine sand. Includes travertine deposits.

Sundance Formation (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers < 0.1 % of this area

SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale.

Lithology: sandstone; shale

Absaroka Volcanic Supergroup: Thorofare Creek Group--Wiggins Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-47 Ma)) at surface, covers < 0.1 % of this area

ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP Wiggins Formation (age 44-47 Ma)--Light-gray volcanic conglomerate and white tuff, containing clasts of igneous rocks.

Transitional unit between Battle Spring and Wasatch Formations (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area

TRANSITIONAL UNIT BETWEEN BATTLE SPRING AND WASATCH FORMATIONS--Contains interbedded lithologies of Battle Spring (Tbs) and Wasatch (Tw2) Formations.

Mesozoic and Paleozoic rocks (Phanerozoic | Paleozoic Mesozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian(?) Triassic(?) Jurassic(?) Cretaceous-Late) at surface, covers < 0.1 % of this area

MESOZOIC AND PALEOZOIC ROCKS (north Wyoming). Shown in small areas of complex structure. East Flank of Absaroka Range--Dinwoody Formation, Phosphoria Formation and related rocks., Tensleep Sandstone, and Amsden Formation (Lower Triassic through Upper Mississippian). East flank of Bighorn Mountains--Cloverly, Morrison, Sundance, Gypsum Spring, Chugwater and Gypsum Spring Formations (Lower Cretaceous through Permian). MESOZOIC AND PALEOZOIC ROCKS (south Wyoming). Shown in small areas of complex structure. South side of Granite Mountains north of Green Mountain--Nugget Sandstone, Chugwater and Goose Egg Formations, Tensleep Sandstone, and Amsden Formation (Jurassic? through Upper Mississippian). South flank of Ferris Mountains--Nugget Sandstone and Chugwater and Goose Egg Formation (Jurassic? through Permian). Northeast flank of Seminoe Mountians--Cloverly, Morrison, Sundance, Chugwater, and Goose Egg Formations (Lower Cretaceous through Permain). West flank of Sierra Madre--Chugwater, Goose Egg, Casper, and Fountain Formations (Upper Triassic through Middle Pennsylvanian). East Flank of Laramie Mountains--Cloverly, Morrison, Sundance, Chugwater, and Goose Egg Formations, and, east of fault in T. 19 N., Casper Formation (Lower Creatceous through Middle Pennsylvanian). NUGGET SANDSTONE in south--Gray to dull-red, massive to coarsely crossbedded quartz sandstone.

Oligocene and (or) Upper and Middle Eocene rocks (Phanerozoic | Cenozoic | Tertiary | Eocene Oligocene) at surface, covers < 0.1 % of this area

OLIGOCENE AND (OR) UPPER AND MIDDLE EOCENE ROCKS--Light-gray tuff, arkosic sandstone, and lenticular conglomerate.

Fox Hills Sandstone and Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

FOX HILLS SANDSTONE AND LEWIS SHALE. FOX HILLS SANDSTONE (Kfh)--Light-colored sandstone and gray sandy shale containing marine fossils. LEWIS SHALE (AGE ABOUT 68 Ma) (Kle)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Lithology: sandstone; shale

Chugwater Formation (N, NE), or Chugwater Formation or Group (S) (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late) at surface, covers < 0.1 % of this area

CHUGWATER FORMATION (north, northeast Wyoming)--Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming. [None mapped in the NE]; CHUGWATER FORMATION OR GROUP (south Wyomingt)--Red shale and siltstone containing thin gypsum partings near base. Group includes Popo Agie Formation (red shale and red, yellow, and purple siltstone; lenses of lime-pellet conglomerate), Crow Mountain Sandstone (red and gray, thick bedded), Alcova Limestone, and Red Peak Formation (red siltstone and shale). Chugwater Formation includes as members all the units listed above. Includes overlying Jelm Formation in Shirley and Seminoe Mountains and at northern end of Laramie Basin. JELM FORMATION--Red sandstone.

Sundance and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers < 0.1 % of this area

SUNDANCE (Js) AND GYPSUM SPRING FORMATIONS. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N.

Green River Formation: Tipton Shale Member or Tongue (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area

GREEN RIVER FORMATION Tipton Shale Member or Tongue--Oil shale and marlstone.

Devils Basin Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers < 0.1 % of this area

DEVILS BASIN FORMATION--Light-gray sandstone interbedded with green and gray claystone; sparse coal and carbonaceous shale.

Caldwell Canyon volcanics (Phanerozoic | Cenozoic | Tertiary | Miocene Pliocene) at surface, covers < 0.1 % of this area

CALDWELL CANYON VOLCANICS--Dacitic volcanic rocks; obsidian gravel at base.

Pinyon Conglomerate (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene) at surface, covers < 0.1 % of this area

PINYON CONGLOMERATE--Brown gold-bearing quartzite conglomerate interbedded with brown and gray sandstone. Age of basal part about 67 Ma in northeastern Jackson Hole; farther south entire sequence is Paleocene.

Lithology: conglomerate; sandstone

Wells and Amsden Formations (TB), or Casper Formation and Madison Limestone (N, S) (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early Pennsylvanian-Middle(?) Pennsylvanian-Late(?) Permian) at surface, covers < 0.1 % of this area

WELLS AND AMSDEN FORMATIONS (Thrust Belt). WELLS FORMATION--Gray limestone interbedded with yellow limy sandstone. AMSDEN FORMATION--Red and gray cherty limestone and shale, sandstone, and conglomerate. CASPER FORMATION AND MADISON LIMESTONE (north, south Wyoming). CASPER FORMATION--Gray, tan, and red thick-bedded sandstone underlain by interbedded sandstone and pink and gray limestone. May include some Devonian(?) sandstone along east flank of Laramie Mountains. MADISON LIMESTONE--Includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite).

Peridotite intrusive rocks (Archean) at surface, covers < 0.1 % of this area

PERIDOTITE INTRUSIVE ROCKS--In Laramie Mountains.

Lithology: peridotite

Sedimentary Rocks (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene) at surface, covers < 0.1 % of this area

SEDIMENTARY ROCKS--Northern part of Wind River Basin. White-weathering oil-stained sandstone and brown carbonaceous shale.

Lithology: sandstone; shale

Lance Formation, Fox Hills Sandstone, Meeteetse Formation, Bearpaw and Lewis Shales (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

LANCE FORMATION (Kl north), FOX HILLS SANDSTONE (Kfh), MEETEETSE FORMATION (Km), AND BEARPAW AND LEWIS (Kle) SHALES--In the Bighorn Basin consists of Lance, Meeteetse and, in the southeastern part, tongue of Lewis Shale; in the northern part of the Wind River Basin, of Lance, Meeteetse, and Lewis, and, in the southeastern part of the basin, of Lance and Lewis; on the west side of the Powder River Basin north of T. 45 N., of Lance, Fox Hills, and Bearpaw, and, to the south, of Lance, Fox Hills, and Lewis. LANCE FORMATION--Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses. FOX HILLS SANDSTONE--Light-colored sandstone and gray sandy shale containing marine fossils. MEETEETSE FORMATION (AGE ABOUT 73 Ma)--Chalky-white to gray sandstone, yellow, green, and dark-gray bentonitic claystone, white tuff, and thin coal beds. BEARPAW SHALE--Dark-greenish-gray shale containing thin gray sandstone partings. LEWIS SHALE (AGE ABOUT 68 Ma)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Goose Egg Formation (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early) at surface, covers < 0.1 % of this area

GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone.

Harebell Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

HAREBELL FORMATION--Gold-bearing quartzite conglomerate, olive-drab sandstone, and green claystone.