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Geologic units in Wyoming (state in United States)

[Additional scientific data in this geographic area]

Cloverly and Morrison Formations (N,S) or Cloverly Formation, Inyan Kara Group, and Morrison Formation (Phanerozoic | Mesozoic | Jurassic-Late Cretaceous-Early) at surface, covers 1 % 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.
Lithology: sandstone; claystone; conglomerate; limestone
White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene (31-35 Ma)) at surface, covers 2 % of this area
WHITE RIVER FORMATION (AGE 31 TO 35 Ma)--White to pale-pink blocky tuffaceous claystone and lenticular arkosic conglomerate.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/volcanic
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.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; mixed clastic/volcanic; coal
Wayan and Smiths Formations (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers < 0.1 % of this area
WAYAN AND SMITHS FORMATIONS. WAYAN FORMATION--Variegated mudstone, siltstone, and sandstone. SMITHS FORMATION--Ferruginous black shale and tan to brown sandstone.
Lithology: mudstone; sandstone
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.
Lithology: sandstone; shale; mixed clastic/volcanic
Chugwater and Goose Egg Formations (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early(?) Triassic-Middle(?) Triassic-Late) at surface, covers 0.6 % of this area
CHUGWATER AND GOOSE EGG FORMATIONS (north Wyoming). CHUGWATER FORMATION--Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming. GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone; CHUGWATER FORMATION OR GROUP (south Wyoming)--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. GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone.
Lithology: siltstone; sandstone; shale; conglomerate; evaporite; dolostone (dolomite); limestone
Madison Limestone or Group (S) (Phanerozoic | Paleozoic | Carboniferous Mississippian-Early Mississippian-Middle(?) Mississippian-Late) at surface, covers 0.3 % 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).
Lithology: limestone; dolostone (dolomite)
Chugwater and Dinwoody Formations (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late) at surface, covers 0.4 % 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.
Lithology: mudstone; limestone; evaporite
Metasedimentary rocks (Archean) at surface, covers 0.2 % 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.
Lithology: metasedimentary rock
Pahasapa and Englewood Limestones (Phanerozoic | Paleozoic | Devonian-Late Carboniferous Mississippian-Early) at surface, covers < 0.1 % of this area
PAHASAPA AND ENGLEWOOD LIMESTONES. PAHASAPA LIMESTONE--Gray massive dolomitic limestone. ENGLEWOOD LIMESTONE--Pink slabby dolomitic limestone.
Lithology: limestone
Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.8 % 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.
Lithology: shale; sandstone; mixed clastic/volcanic
Oldest gneiss complex (Archean) at surface, covers 1 % 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.
Lithology: granitic gneiss; migmatite; metamorphic rock
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
Granitic rocks (Archean) at surface, covers 2 % 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 1 % 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.
Lithology: limestone; dolostone (dolomite); mudstone
Minnekahta Limestone and Opeche Shale (Phanerozoic | Paleozoic | Permian) at surface, covers 0.2 % of this area
MINNEKAHTA LIMESTONE AND OPECHE SHALE. 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.
Lithology: limestone; shale
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 0.3 % 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).
Lithology: limestone; sandstone; shale; conglomerate; dolostone (dolomite)
Green River Formation: Wilkins Peak Member (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.2 % of this area
GREEN RIVER FORMATION Wilkins Peak Member (age about 49 Ma)--Green, brown, and gray tuffaceous sandstone, shale, and marlstone; contains evaporites in subsurface sections.
Lithology: fine-grained mixed clastic; mixed clastic/carbonate; mixed clastic/volcanic; evaporite
Gravel, pediment, and fan deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 3 % 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.
Lithology: unconsolidated deposit
Volcanic Conglomerate (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
VOLCANIC CONGLOMERATE--Dark-brown to black conglomerate, poorly bedded, composed chiefly of basalt clasts in a basaltic tuff matrix.
Lithology: conglomerate; mixed clastic/volcanic
Gannett Group (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.3 % of this area
GANNETT GROUP--Red sandy mudstone, sandstone, and chert-pebble conglomerate; thin limestone and dark-gray shale in upper part, more conglomeratic in lower part. Includes Smoot Formation (red mudstone and siltstone), Draney Limestone, Bechler Conglomerate, Peterson Limestone, and Ephraim Conglomerate. Upper Jurassic fossils have been reported from the Ephraim.
Lithology: mudstone; sandstone; conglomerate; limestone
Cody Shale (Phanerozoic | Mesozoic | Cretaceous-Late (78-83 Ma)) at surface, covers 3 % 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
Terrace gravel (Phanerozoic | Cenozoic | Tertiary Quaternary | Pliocene Pleistocene) at surface, covers < 0.1 % of this area
TERRACE GRAVEL (PLEISTOCENE AND/OR PLIOCENE)--Partly consolidated gravel above and flanking some major streams.
Lithology: gravel
Mesaverde Formation (N) or Mesaverde Group (S) (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 1 % 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.
Lithology: sandstone; shale; coal; conglomerate
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 2 % of this area
FORT UNION FORMATION Tullock Member--Soft gray sandstone, gray and brown carbonaceous shale, and thin coal beds.
Lithology: sandstone; shale; coal
Lower Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene-Early) at surface, covers < 0.1 % of this area
LOWER MIOCENE ROCKS--Northwest Wyoming (Bighorn Mountains): Gray soft poorly bedded to massive sandstone; Central Wyoming: Tuffaceous sandstone, siltstone, and white marl.
Lithology: sandstone; siltstone
Cloverly, Morrison, and Sundance Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers 0.3 % 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.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; limestone; mixed clastic/volcanic; conglomerate
Quartz diorite (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area
QUARTZ DIORITE. Sierra Madre--Encampment River Granodiorite 4; age 1,800 Ma. Medicine Bow Mountains--Keystone Quartz Diorite 5. Hartville uplift--Diorite of Twin Hills 6.
Lithology: quartz diorite
Wagon Bed Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (45-49 Ma)) at surface, covers 0.5 % 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.
Lithology: claystone; conglomerate; sandstone
Bighorn Dolomite (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late) at surface, covers < 0.1 % of this area
BIGHORN DOLOMITE--Light-gray massive siliceous dolomite in northern Yellowstone area. Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone in Thrust belt and northern Wyoming.
Lithology: dolostone (dolomite)
Sherman Granite (Proterozoic | Mesoproterozoic (1415-1435 Ma)) at surface, covers 0.4 % of this area
SHERMAN GRANITE (AGE 1,415 TO 1,435 Ma)--In Medicine Bow and Laramie Mountains.
Lithology: granite
Sage Junction, Quealy, Cokeville, THomas Fork, and Smiths Formations (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.1 % of this area
SAGE JUNCTION, QUEALY, COKEVILLE, THOMAS FORK, AND SMITHS FORMATIONS. SAGE JUNCTION FORMATION--Gray and tan siltstone and sandstone. QUEALY FORMATION--Variegated mudstone and tan sandstone. COKEVILLE FORMATION--Tan sandstone, claystone, limestone, bentonite, and coal. THOMAS FORK FORMATION--Variegated mudstone and gray sandstone. SMITHS FORMATION--Ferruginous black shale and tan to brown sandstone.
Lithology: mudstone; sandstone; limestone; bentonite; coal
Alluvium and Colluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 7 % of this area
ALLUVIUM AND COLLUVIUM--Clay, silt, sand, and gravel in flood plains, fans, terraces, and slopes.
Lithology: alluvium; colluvium
Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers 2 % 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.
Lithology: sandstone; conglomerate; claystone
Undivided surficial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 1.0 % of this area
UNDIVIDED SURFICIAL DEPOSITS--Mostly alluvium, colluvium, and glacial and landslide deposits. Primarily in Yellowstone area and Bighorn Mountains.
Lithology: alluvium; colluvium; glacial drift; landslide
Peridotite intrusive rocks (Archean) at surface, covers < 0.1 % of this area
PERIDOTITE INTRUSIVE ROCKS--In Laramie Mountains.
Lithology: peridotite
Medicine Bow Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.1 % of this area
MEDICINE BOW FORMATION--Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.
Lithology: sandstone; shale; coal
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
Hanna Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 0.4 % of this area
HANNA FORMATION--Brown and gray sandstone, shale, conglomerate, and coal; giant quartzite boulders near Medicine Bow Mountains.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; conglomerate; coal
White River Formation--Chadron Member (Phanerozoic | Cenozoic | Tertiary | Oligocene ) at surface, covers 0.3 % of this area
WHITE RIVER FORMATION Chadron Member--Light-gray to dark-red tuffaceous claystone, sandstone, and lenticular conglomerate.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/volcanic
Pennsylvanian, undifferentiated (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers < 0.1 % of this area
Pennsylvanian, undifferentiated: in western Montana is mainly the Quadrant quartzite but includes limestone and other rocks of Pennsylvanian age so far as present data permit. Farther east other formations of Pennsylvanian or possible Pennsylvanian age are included.
Lithology: sandstone; mudstone; carbonate; conglomerate; chert
Madison Limestone and Bighorn Dolomite (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late(?) Silurian(?) Devonian(?) Carboniferous Mississippian-Early(?) Mississippian-Middle(?) Mississippian-Late) at surface, covers < 0.1 % of this area
MADISON LIMESTONE AND BIGHORN DOLOMITE. MADISON LIMESTONE OR GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). BIGHORN DOLOMITE--Light-gray massive siliceous dolomite.
Lithology: limestone; dolostone (dolomite)
Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.3 % of this area
FOX HILLS SANDSTONE--Light-colored sandstone and gray sandy shale containing marine fossils.
Lithology: sandstone; shale
Lance Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 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.
Lithology: sandstone; shale; conglomerate; coal
Alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area
Clay to boulder-size clasts with locally abundant organic material. Thickness up to 75 ft (23m).
Lithology: clay or mud; silt; sand; gravel
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
Frontier Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 1 % 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
Tertiary (1) sedimentary rocks in Salt Lake City-Coalville-Randolph region (Late Paleocene to Early Eocene) at surface, covers < 0.1 % of this area
Lithology: mudstone; conglomerate; limestone
Madison Group (Phanerozoic | Paleozoic | Devonian Carboniferous Mississippian) at surface, covers < 0.1 % of this area
Includes: Pahasapa Limestone (Mississippian)-White, light-gray to tan, fine- to medium-crystalline limestone and dolomite containing brown to gray chert. Solution features including collapse breccia, sinkholes, and caves are prevalent. Thickness 300-630 ft (91-192 m). Englewood Formation (Mississippian to Dovonian)- Pink, lavender to light-gray, thin- to medium-bedded, finely crystalline, argillaceous, dolomitic limestone. Thickness 30-63 ft (9-19 m).
Lithology: limestone; dolostone (dolomite); chert
Green River Formation: Laney Member (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 3 % of this area
GREEN RIVER FORMATION Laney Member (age probably about 45 Ma)--Oil shale and marlstone.
Lithology: oil shale; mixed clastic/carbonate
Goose Egg Formation (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early) at surface, covers 0.2 % of this area
GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone.
Lithology: mudstone; carbonate; evaporite; dolostone (dolomite)
Intrusive and extrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Miocene Pliocene) at surface, covers < 0.1 % of this area
INTRUSIVE AND EXTRUSIVE IGNEOUS ROCKS--Composition ranges from hornblende monzonite to basalt. In Yellowstone area includes andesite and basalt of Emerald Lake (age about 2 Ma), rhyolite of Broad Creek, Pliocene Junction Butte Basalt, and gravel of Mount Everts. Age of basalt on Crescent Mountain 3.6 Ma.
Lithology: granitoid; basalt
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 < 0.1 % 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).
Lithology: limestone; dolostone (dolomite); shale; sandstone; siltstone
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.
Lithology: plutonic rock (phaneritic)
Huckleberry Ridge Tuff of Yellowstone Group (Phanerozoic | Cenozoic | Tertiary | Pliocene) at surface, covers 0.2 % of this area
HUCKLEBERRY RIDGE TUFF OF YELLOWSTONE GROUP (AGE SLIGHTLY MORE THAN 2 Ma)--Lavender to gray-brown welded rhyolite tuff.
Lithology: rhyolite; tuff
Cloverly, Morrison, Sundance, and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers 0.2 % 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.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; carbonate; mixed clastic/volcanic; conglomerate; dolostone (dolomite); evaporite
Sundance and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers 0.7 % 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.
Lithology: sandstone; shale; dolostone (dolomite); evaporite
Hell Creek formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene) at surface, covers < 0.1 % of this area
Hell Creek formation: somber-gray sandstone and greenish shaly clay and mudstone containing dinosaur bones; a few thin lignite and subbituminous coal beds.
Lithology: sandstone; mudstone; coal
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.
Lithology: conglomerate; sandstone; claystone
Dune sand and loess (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 2 % 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
Upper Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene-Late) at surface, covers 3 % 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.
Lithology: sandstone; claystone; conglomerate; siltstone; limestone
Wind River Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 3 % 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.
Lithology: claystone; siltstone; sandstone; coal
Bacon Ridge Sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
BACON RIDGE SANDSTONE--Gray to tan marine sandstone and thick coal beds; gold-bearing quartzite conglomerate in lower part.
Lithology: sandstone; coal; conglomerate
Absaroka Volcanic Supergroup: Hominy Peak Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
ABSAROKA VOLCANIC SUPERGROUP--HOMINY PEAK FORMATION (AGE ABOUT 49 Ma)--Mafic volcaniclastic conglomerate and tuff; sparse claystone in upper part; gold-bearing quartzite conglomerate at base.
Lithology: mixed clastic/volcanic; coarse-grained mixed clastic; fine-grained mixed clastic
Green River Formation: Wilkins Peak Member and Tipton Shale member or Tongue (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.3 % of this area
GREEN RIVER FORMATION Wilkins Peak Member (age about 49 Ma) (green, brown, and gray tuffaceous sandstone, shale, and marlstone; contains evaporites in subsurface sections) and Tipton Shale Member or Tongue (oil shale and marlstone).
Lithology: mixed clastic/carbonate; fine-grained mixed clastic; mixed clastic/volcanic; evaporite; oil shale
Willwood Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 2 % of this area
WILLWOOD FORMATION--Variegated claystone, shale, and sandstone; some lenticular gold-bearing quartzite conglomerate.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; conglomerate
Green River Formation: Tipton Shale Member or Tongue (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.3 % of this area
GREEN RIVER FORMATION Tipton Shale Member or Tongue--Oil shale and marlstone.
Lithology: oil shale; mixed clastic/carbonate
Fox Hills Sandstone and Bearpaw Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
FOX HILLS SANDSTONE AND BEARPAW SHALE. FOX HILLS SANDSTONE (Kfh)--Light-colored sandstone and gray sandy shale containing marine fossils. BEARPAW SHALE--Dark-greenish-gray shale containing thin gray sandstone partings.
Lithology: sandstone; shale
Quaternary alluvium and colluvium (Quaternary) at surface, covers < 0.1 % of this area
Lithology: alluvium; colluvium
Granite gneiss (Archean) at surface, covers 1.0 % 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
Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Tepee Trail Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma)) at surface, covers 0.3 % 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.
Lithology: mixed clastic/volcanic; medium-grained mixed clastic
Conglomerate (Phanerozoic | Cenozoic | Tertiary Quaternary | Miocene Pliocene(?) Pleistocene) at surface, covers < 0.1 % of this area
CONGLOMERATE--Northwest Wyoming (Jackson Hole) (Pleistocene or Pliocene)--Paleozoic clasts, chiefly of Madison Limestone, in a lithified carbonate matrix; Central (Medicine Bow Mountains) and east Wyoming (east of Laramie Mountains) (Pleistocene to Miocene)--Giant granite boulders in an arkose matrix.
Lithology: conglomerate
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 0.3 % of this area
FORT UNION FORMATION Tongue River (Tftr) and Lebo (Tfl) Members.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; coal
Niobrara Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.3 % of this area
NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale.
Lithology: limestone; fine-grained mixed clastic
Glacial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 2 % of this area
GLACIAL DEPOSITS--Till and outwash of sand, gravel, and boulders.
Lithology: glacial drift
Shooting Iron Formation (Phanerozoic | Cenozoic | Tertiary | Pliocene) at surface, covers < 0.1 % of this area
SHOOTING IRON FORMATION--Greenish-gray to pink tuffaceous lacustrine and fluviatile claystone and siltstone, fine-grained sandstone, and conglomerate.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/volcanic
Indian Meadows Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % 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.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; carbonate; conglomerate
Carlile Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Dark-gray to black, silty to sandy shale with several zones of septarian, fossiliferous, carbonate concertions. Contains up to three sandstone beds near the middle of the formation and sandy calcareous marl at the base. Thickness 345-620 ft (105-189 m).
Lithology: shale; sandstone; limestone
Salt Lake Formation (Phanerozoic | Cenozoic | Tertiary | Miocene Pliocene) at surface, covers < 0.1 % of this area
SALT LAKE FORMATION--White, gray, and green limy tuff, siltstone, sandstone, and conglomerate.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/carbonate; mixed clastic/volcanic
Phosphoria, Wells, and Amsden Formations (TB), Phosphoria Formation and related rocks, Quadrant Sandstone, and Amsden Formation (Y), or Phosphoria Formation and related rocks, Tensleep Sandstone, and Amsden Formation (N) (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian) at surface, covers 0.1 % of this area
PHOSPHORIA, WELLS, AND AMSDEN FORMATIONS (Thrust Belt). PHOSPHORIA FORMATION--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. WELLS FORMATION--Gray limestone interbedded with yellow limy sandstone. AMSDEN FORMATION--Red and gray cherty limestone and shale, sandstone, and conglomerate. PHOSPHORIA FORMATION AND RELATED ROCKS, QUADRANT SANDSTONE, AND AMSDEN FORMATION (Yellowstone). PHOSPHORIA FORMATION AND RELATED ROCKS--Brown sandstone and dolomite, cherty phosphatic and glauconitic dolomite, phosphatic sandstone and dolomite, and greenish-gray to black shale. Intertonguing equivalent is Shedhorn Sandstone. QUADRANT SANDSTONE--Light-gray sandstone. AMSDEN FORMATION--Red and green dolomitic shale, siltstone, and sandstone. PHOSPHORIA FORMATION AND RELATED ROCKS, TENSLEEP SANDSTONE, AND AMSDEN FORMATION (north Wyoming). PHOSPHORIA FORMATION AND RELATED ROCKS--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 (primarlily cherty dolomite, limestone, and phosphatic gray shale) and Shedhorn Sandstone. 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.
Lithology: sandstone; limestone; shale; dolostone (dolomite); phosphorite; siltstone; chert; conglomerate
Camp Davis Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area
CAMP DAVIS FORMATION--Upper 5,000 ft chiefly red conglomerate and red claystone; underlain by white tuff, limestone, claystone, and basal gray conglomerate.
Lithology: conglomerate; claystone
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
Bishop Conglomerate (Phanerozoic | Cenozoic | Tertiary | Oligocene ) at surface, covers 0.1 % of this area
BISHOP CONGLOMERATE--Clasts of red quartzite, gray chert, and limestone in a gray to white tuffaceous sandstone matrix.
Lithology: conglomerate
Thermopolis shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers < 0.1 % of this area
Thermopolis shale: dark-gray shale with some sandstone. The subsurface consists of Muddy sandstone member or Newcastle sandstone member at top, Skull Creek shale member in middle, and Fall River sandstone or First Cat Creek sand of drillers at base.
Lithology: mudstone; sandstone; bentonite
Steele Shale and Niobrara Formations (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
STEELE SHALE (Ks) AND NIOBRARA FORMATIONS (Kn). STEELE SHALE (AGE ABOUT 78 TO 82 Ma)--Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone. NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale.
Lithology: shale; mixed clastic/volcanic; mixed clastic/carbonate; sandstone
Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Blue-gray to dark-gray, fissile to blocky shale with persistent beds of bentonite, black organic shale, or light-brown chalky shale. Contains minor sandstone, conglomerate, and abundant carbonate and ferruginous concretions. Thickness 1,000-2,700 ft (305-823 m).
Lithology: shale; clay or mud; sandstone; conglomerate
White River Formation--Upper conglomerate member (Phanerozoic | Cenozoic | Tertiary | Oligocene ) at surface, covers 0.4 % of this area
WHITE RIVER FORMATION Upper conglomerate member--Light-gray soft conglomeratic tuffaceous sandstone and conglomerate of Precambrian clasts.
Lithology: medium-grained mixed clastic; conglomerate; mixed clastic/volcanic
Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers 0.3 % of this area
WASATCH FORMATION La Barge and Chappo Members--Red, gray, and brown mudstone and conglomerate and yellow sandstone. La Barge Member tongues out to north at about T. 35 N. Lower part of Chappo is Paleocene.
Lithology: mudstone; conglomerate; sandstone
Playa lake and other lacustrine deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 0.3 % of this area
PLAYA LAKE AND OTHER LACUSTRINE DEPOSITS--Chiefly clay, silt, and fine sand. Includes travertine deposits.
Lithology: playa; lake or marine deposit (non-glacial)
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
Ordovician, undifferentiated (Phanerozoic | Paleozoic | Ordovician) at surface, covers < 0.1 % of this area
Ordovician, undifferentiated: Mainly Bighorn dolomite; near Idaho, Kinnikinic quartzite.
Lithology: dolostone (dolomite); arenite; medium-grained mixed clastic; limestone; chert
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
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
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
Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.5 % 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--Wiggins Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-47 Ma)) at surface, covers 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.
Lithology: mixed clastic/volcanic
Aspen Shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.2 % of this area
ASPEN SHALE--Light- to dark-gray siliceous tuffaceous shale and siltstone, thin bentonite beds, and quartzitic sandstone.
Lithology: mudstone; mixed clastic/volcanic; sandstone
Arikaree Group (Phanerozoic | Cenozoic | Tertiary | Oligocene Miocene) at surface, covers < 0.1 % of this area
Consists mainly of gray, fine, loose to compact sand that has layers of hard, fine-grained dark-gray concretions which vary from few in to 15 in and often have tabular form. Includes a large amount of volcanic ash mixed in with the sand. Contains a number of channels filled with coarse conglomerate along ridge south of North Platte River. About 500 ft thick.
Lithology: sand; volcanic ash; conglomerate
Metasedimentary and metavolcanic rocks (Archean) at surface, covers 0.3 % 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.
Lithology: metasedimentary rock; metavolcanic rock
Mowry Shale, Newcastle Sandstone, and Skull Creek Shale (Phanerozoic | Mesozoic | Cretaceous-Early ) at surface, covers < 0.1 % of this area
Mowry Shale- Black to gray, siliceous, fissile shale and siltstone containing bentonite layers, and sparse sandstone dikes and sills. Thickness 125-250 ft (38-76 m). Newcastle Sandstone- Gray, light-brown to yellow, discontinuously distributed siltstone, claystone, sandy shale, and fine-grained sandstone. Thickness up to 290 ft (88 m). Skull Creek Shale- Dark-gray to blueish-gray shale containing ferruginous, and carbonate concretions. Thickness 150-275 ft (46-84 m).
Lithology: shale; siltstone; sandstone; claystone
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 0.8 % 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.
Lithology: limestone; dolostone (dolomite); shale; sandstone
Teewinot Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area
TEEWINOT FORMATION (AGE ABOUT 9 Ma)--White lacustrine clay, tuff, and limestone. In thrust belt includes conglomerate.
Lithology: mixed clastic/carbonate; mixed clastic/volcanic; fine-grained mixed clastic; conglomerate
Basal part of Cody shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Basal part of Cody shale: gray and dark-gray shale with some sandstone beds; in north end of Big Horn Basin includes the Telegraph Creek formation.
Lithology: shale; sandstone
Conglomerate of Sublette Range (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % of this area
CONGLOMERATE OF SUBLETTE RANGE (EOCENE AND PALEOCENE)--Locally derived indurated angular conglomerate.
Lithology: conglomerate
Meeteetse Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.1 % of this area
MEETEETSE FORMATION (AGE ABOUT 73 Ma)--Chalky-white to gray sandstone, yellow, green, and dark-gray bentonitic claystone, white tuff, and thin coal beds.
Lithology: sandstone; claystone; mixed clastic/volcanic; coal
Minnekahta Limestone and Opeche Shale (Phanerozoic | Paleozoic | Permian) at surface, covers < 0.1 % of this area
Minnekahta Limestone-Purple to gray, finely crystalline, thin- to medium-bedded limestone with varying amounts of red shale. Thickness 30-50 ft (9-15 m). Opeche Shale- Red siltstone, argillaceous sandstone and shale interbedded with caliche layers. Thickness 85-130 ft (26-40 m).
Lithology: siltstone; sandstone; shale; limestone
Mississippian, undifferentiated (Phanerozoic | Paleozoic | Carboniferous Mississippian) at surface, covers < 0.1 % of this area
Mississippian, undifferentiated: sandstone, shale, and limestone, in part dolomitic, with chert nodules, some quartzite; includes Big Snowy group in central part of State, Madison group in central and southwestern parts; and Hannan and Brazer limestones in the northwestern part; may include small amounts of Pennsylvanian rocks in areas where stratigraphic studies are incomplete.
Lithology: carbonate; fine-grained mixed clastic; medium-grained mixed clastic; chert
Metasedimentary rocks: Deep Lake Group (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area
METASEDIMENTARY ROCKS--In Medicine Bow Mountains and Sierra Madre. Deep Lake Group 3--Quartzite, diamictite, pelitic schist, and quartz-pebble conglomerate.
Lithology: metasedimentary rock
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 2 % of this area
FORT UNION FORMATION Lebo Member--Dark-gray clay shale and concretionary sandstone.
Lithology: shale; sandstone
Older Quaternary alluvial deposits (Quaternary) at surface, covers < 0.1 % of this area
Lithology: alluvium
Tensleep Sandstone and Amsden Formation (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian) at surface, covers 1 % 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
Landslide deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 1 % of this area
LANDSLIDE DEPOSITS--Locally includes intermixed landslide and glacial deposits, talus, and rock-glacier deposits.
Lithology: landslide; glacial drift
Absaroka Volcanic Supergroup: Sunlight Group (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
ABSAROKA VOLCANIC SUPERGROUP: SUNLIGHT GROUP--including Trout Peak Trachyandesite, Wapiti Formation (andesitic volcaniclastic rocks), Crescent Hill Basalt, and Mount Wallace Formation (felsic and mafic volcaniclastic rocks).
Lithology: intermediate volcanic rock; basalt; felsic volcanic rock
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.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; coarse-grained mixed clastic; coal
Colorado shale (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers < 0.1 % of this area
Colorado shale: dark-gray shale and siltstone with many concretions and sandy units. Includes equivalents of Fall River, Skull Creek, Newcastle, Mowry, Belle Fourche, Greenhorn, Carlile, and Niobrara formations, and locally Telegraph Creek formation. In the less well-known areas beds of other ages may have been included.
Lithology: fine-grained mixed clastic
Lance Formation, Fox Hills Sandstone, Meeteetse Formation, Bearpaw and Lewis Shales (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % 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.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; mixed clastic/volcanic; coal
Tatman Formatin (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
TATMAN FORMATION--Drab nontuffaceous claystone, oil shale, lignite, and sandstone.
Lithology: fine-grained mixed clastic; oil shale; coal
Crooks Gap Conglomerate (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % 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
Phosphoria Formation (Phanerozoic | Paleozoic | Permian) at surface, covers 0.4 % 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.
Lithology: shale; phosphorite; sandstone; chert; dolostone (dolomite)
Green River and Wasatch Formations (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.4 % of this area
GREEN RIVER AND WASATCH FORMATIONS -- in Thrust Belt: GREEN RIVER FORMATION--Buff laminated marlstone and limestone, brown oil shale, and siltstone. Includes Angelo and Fossil Butte Members. WASATCH FORMATION--Variegated mudstone and sandstone. Includes Tunp and Bullpen Members, other tongues and unnamed members, and main body (variegated red to gray, brown, and gray mudstone and sandstone; conglomerate lenses); in southwest Wyoming -- GREEN RIVER FORMATION--Oil shale, light-colored tuffaceous marlstone, and sandstone. WASATCH FORMATION--Drab to variegated claystone and siltstone, carbonaceous shale and coal, buff sandstone, arkose, and conglomerate. In northwestern part of Green River Basin is thick arkosic light-yellowish-tan sandstone intertonguing with pale-green to gray claystone and shale.
Lithology: mudstone; sandstone; oil shale; limestone; coal; conglomerate
Newcastle Sandstone and Skull Creek Shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.4 % of this area
NEWCASTLE SANDSTONE AND SKULL CREEK SHALE. NEWCASTLE SANDSTONE--Gray sandstone and sandy shale containing some bentonite and coal. SKULL CREEK SHALE--Black soft fissile shale.
Lithology: sandstone; shale; bentonite; coal
Lower Miocene and Upper Oligocene rocks, or Rocks equivalent to Upper and Lower Miocene AND White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene-Late Miocene-Early(?) Miocene-Middle(?) Miocene-Late) at surface, covers 3 % of this area
LOWER MIOCENE AND UPPER OLIGOCENE ROCKS--Light-colored soft porous sandstone and underlying white tuffaceous claystone and siltstone. Arikaree Formation in Denver Basin; ROCKS EQUIVALENT TO UPPER AND LOWER MIOCENE ROCKS AND WHITE RIVER FORMATION--Light-colored sandstone, white tuffaceous blocky claystone, and siltstone. Black Hills.
Lithology: fine-grained mixed clastic; mixed clastic/volcanic
Chugwater Formation (N, NE), or Chugwater Formation or Group (S) (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late) at surface, covers 0.3 % 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.
Lithology: siltstone; shale; sandstone; limestone; conglomerate
Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.9 % of this area
PIERRE SHALE (AGE 72 TO 78 Ma)--Dark-gray concretionary marine shale; contains several bentonite beds.
Lithology: shale; mixed clastic/volcanic
Spearfish Formation (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area
Red sandy shale, siltstone, sandstone, and minor limestone. Interbedded with abundant gypsum. Thickness 328-559 ft (100-170 m).
Lithology: shale; siltstone; sandstone; evaporite; limestone
Steele Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.6 % of this area
STEELE SHALE (AGE ABOUT 78 TO 82 Ma)--Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone.
Lithology: shale; mixed clastic/volcanic; sandstone
Fowkes Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
FOWKES FORMATION--Light-colored tuffaceous sandstone and siltstone, locally conglomeratic. Locally designated by some as Norwood Tuff.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/volcanic
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.
Lithology: dacite; felsic volcanic rock
Gravel, sand, and silt; Quaternary; alluvium (Quaternary) at surface, covers < 0.1 % of this area
Quaternary alluvium; may contain some glacial deposits and colluvium in uplands
Lithology: alluvium; alluvial terrace; floodplain; alluvial fan; colluvium
White River Group (Phanerozoic | Cenozoic | Tertiary | Oligocene) at surface, covers < 0.1 % of this area
Clay, some claystone, silt and siltstone. Predominantly greenish gray and volcaniclastic. Other occurrences are greenish gray to white and bentonitic. Local channel sandstone at base. Aprox thickness 195 ft.
Lithology: clay or mud; claystone; silt; siltstone
Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.6 % of this area
WASATCH FORMATION Cathedral Bluffs Tongue--Variegated claystone and lenticular sandstone; conglomeratic near south margin of Wind River Range.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic
Evanston Formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene) at surface, covers < 0.1 % of this area
EVANSTON FORMATION--Gray siltstone, sparse red sandstone, and lignite beds.
Lithology: siltstone; sandstone; coal
Oligocene and (or) Upper and Middle Eocene rocks (Phanerozoic | Cenozoic | Tertiary | Eocene Oligocene) at surface, covers 0.2 % of this area
OLIGOCENE AND (OR) UPPER AND MIDDLE EOCENE ROCKS--Light-gray tuff, arkosic sandstone, and lenticular conglomerate.
Lithology: mixed clastic/volcanic; medium-grained mixed clastic
Adaville Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
ADAVILLE FORMATION--Gray sandstone, siltstone, and carbonaceous claystone; conglomeratic in upper part; coal-bearing in lower part.
Lithology: sandstone; fine-grained mixed clastic; conglomerate; coal
Laramide Anorthosite Complex--anorthosite and norite (Proterozoic | Mesoproterozoic) at surface, covers 0.3 % of this area
LARAMIE ANORTHOSITE COMPLEX--Anorthosite and norite. In Laramie Mountains.
Lithology: anorthosite; norite
Granodiorite of the Louis Lake Pluton (Archean) at surface, covers 0.3 % of this area
GRANODIORITE OF THE LOUIS LAKE PLUTON (AGE 2,640 Ma)--Equigranular; locally gneissic.
Lithology: granodiorite
Ferris Formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene) at surface, covers 0.1 % of this area
FERRIS FORMATION--Brown and gray sandstone and shale; sparse carbonaceous shale and coal beds; thin lenses of pebble conglomerate.
Lithology: sandstone; shale; coal; conglomerate
Tertiary (2) sedimentary rocks in Salt Lake City-Coalville-Randolph region (Eocene) at surface, covers < 0.1 % of this area
Lithology: fine-grained mixed clastic; conglomerate; tuff; limestone
Wasatch formation (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Wasatch formation: Light-colored massive sandstone; drab-colored shale and coal in southeastern Montana; and variegated, dominantly red beds of clay and sandstone in north-central Montana.
Lithology: sandstone; shale; coal; claystone
Granitic rocks (Proterozoic | Paleoproterozoic ) at surface, covers 0.1 % of this area
GRANITIC ROCKS OF 1,700-Ma AGE GROUP.
Lithology: granitoid
Belle Fourche Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Dark-gray to black bentonitic shale containing minor limestone lenses, bentonite layers, fossiliferous calcarenite, and large, ferruginous, carbonate concretions. Thickness 150-350 ft (46-107 m).
Lithology: shale; limestone; clay or mud
Greenhorn Formation and Belle Fourche and Mowry Shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.5 % of this area
GREENHORN FORMATION AND BELLE FOURCHE AND MOWRY (Kmr) SHALE. GREENHORN FORMATION--Light-colored limestone, marl, and limy sandstone interbedded with gray concretionary shale. BELLE FOURCHE SHALE--Black soft bentonitic concretionary shale. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds.
Lithology: mixed clastic/carbonate; fine-grained mixed clastic; mixed clastic/volcanic
Rhyolite flows, tuff, and intrusive igneous rocks (Phanerozoic | Cenozoic | Quaternary | Pleistocene) at surface, covers 1 % of this area
RHYOLITE FLOWS, TUFF, AND INTRUSIVE IGNEOUS ROCKS--Includes Plateau Rhyolite (age about 0.07 Ma) and interlayered sediments, Mount Jackson Rhyolite (age 0.6 to about 1 Ma), Lewis Canyon Rhyolite (age about 0.9 Ma); and Lava Creek Tuff of Yellowstone Group (age 0.6 to about 1 Ma).
Lithology: rhyolite; lava flow; tuff; plutonic rock (phaneritic)
Pierre shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Pierre shale: dark-gray clay shale with calcareous and ferruginous concretions and sandy members.
Lithology: shale; sandstone; bentonite
Intrusive and extrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
INTRUSIVE AND EXTRUSIVE IGNEOUS ROCKS (CHIEFLY EOCENE; AGE OF INTRUSIVES ABOUT 53 TO 55 Ma)--Incorporates masses of Mississippian through Cambrian formations. Confined to Black Hills.
Lithology: plutonic rock (phaneritic); volcanic rock (aphanitic)
Devonian sedimentary rocks in Salt Lake City-Coalville-Randolph region (Devonian) at surface, covers < 0.1 % of this area
Lithology: dolostone (dolomite); sandstone
Tertiary (1) sedimentary rocks in Uinta Mountains-Unita Basin region (Early to Middle Eocene) at surface, covers < 0.1 % of this area
Lithology: fine-grained mixed clastic; limestone; coal
Conant Creek Tuff (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area
CONANT CREEK TUFF (AGE ABOUT 5.8 Ma)--Lavender rhyolite welded tuff.
Lithology: rhyolite; welded tuff
Niobrara Formation and Carlile Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.1 % of this area
NIOBRARA FORMATION (Kn) AND CARLILE SHALE (Kcl). NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale. CARLILE SHALE--Dark-gray sandy shale; Sage Breaks Member at top; Turner Sandy Member in middle.
Lithology: shale; fine-grained mixed clastic; limestone
Bear River Formation (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.1 % of this area
BEAR RIVER FORMATION--Black shale, fine-grained brown sandstone, thin limestone, and bentonite beds.
Lithology: shale; sandstone; limestone; bentonite
Bug Formation (Phanerozoic | Cenozoic | Tertiary Quaternary | Pliocene Pleistocene) at surface, covers < 0.1 % of this area
BUG FORMATION (PLEISTOCENE OR PLIOCENE)--Lacustrine white marl, claystone, sandstone, conglomerate, and tuff; generally radioactive.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/carbonate; mixed clastic/volcanic
Cambrian, undifferentiated (Phanerozoic | Paleozoic | Cambrian) at surface, covers < 0.1 % of this area
Cambrian, undifferentiated: comprises Deadwood formation, in south-central Montana, and Red Lion formation, Dry Creek shale, Hasmark formation, Pilgrim limestone, Silver Hill formation, Park shale, Meagher limestone, Wolsey shale, Flathead quartzite, and other units. In a few places quartzite of Cambrian age may be mapped with the Belt series or quartzite of Belt age with the Cambrian rocks.
Lithology: carbonate; mudstone; sandstone; conglomerate
Green River Formation: Fontenelle Tongue or Member [NONE ON MAP] (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.7 % of this area
WASATCH AND GREEN RIVER FORMATIONS: New Fork Tongue (dull-red and green mudstone, brown sandstone, and thin limestone beds, merging southward in T. 23 N. with other units) of Wasatch and Fontenelle Tongue or Member (oil shale, marlstone, limestone, and siltstone; occurs along Green and New Fork Rivers and on west side of Green River Basin from T. 33 N. south to and lensing out in T. 17 N.) of Green River.
Lithology: fine-grained mixed clastic; mixed clastic/carbonate; oil shale
Stump Formation, Preuss Sandstone or Redbeds, and Twin Creek Limestone (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers 0.4 % of this area
STUMP FORMATION, PREUSS SANDSTONE or REDBEDS, and TWIN CREEK LIMESTONE. STUMP FORMATION--Glauconitic siltstone, sandstone, and limestone. PREUSS SANDSTONE OR REDBEDS--Purple, maroon, and reddish-gray sandy siltstone and claystone; contains salt and gypsum in thick beds in some subsurface sections. TWIN CREEK LIMESTONE--Greenish-gray shaly limestone and limy siltstone. Includes Gypsum Spring Member.
Lithology: fine-grained mixed clastic; limestone; sandstone; evaporite
Alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area
Alluvium: mainly valley fill consisting of silt, sand, and gravel; includes some terrace deposits and glacial drift of Pleistocene age in some areas; locally includes hot spring tufa. The older part of the alluvium, where present, is probably of Pliocene age.
Lithology: alluvium; glacial drift; carbonate
Wasatch Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 8 % of this area
WASATCH FORMATION -- in Thrust belt: Main body--Variegated red to gray, brown, and gray mudstone and sandstone; conglomeratic lenses; in southwest Wyoming--Drab to variegated claystone and siltstone, carbonaceous shale and coal, buff sandstone, arkose, and conglomerate. In northwestern part of Green River Basin is thick arkosic light-yellowish-tan sandstone intertonguing with pale-green to gray claystone and shale; in east Wyoming--Drab sandstone and drab to variegated claystone; numerous coal beds in lower part.
Lithology: mudstone; sandstone; conglomerate; coal
Terrace deposits (Phanerozoic | Cenozoic | Tertiary Quaternary) at surface, covers < 0.1 % of this area
Terrace deposits: gravel, sand, and silt of terrace remnants.
Lithology: alluvial terrace
Coralline Limestone, sandstone, siltstone, shale, chert, and phosphorite; Mississippianshallow marine inner continental-shelf deposits; east-central Idaho, central Idaho (Mississippian ) at surface, covers < 0.1 % of this area
Mississippian shallow-water coralline limestone interval of southern Idaho.
Lithology: limestone; sandstone; siltstone; shale; chert; phosphorite
White River Formation--Brule Member (Phanerozoic | Cenozoic | Tertiary | Oligocene ) at surface, covers 0.4 % of this area
WHITE RIVER FORMATION Brule Member--Pale-pink to white blocky tuffaceous claystone and lenticular sandstone. Locally includes the Upper Conglomerate Member (Twru).
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/volcanic
Absaroka Volcanic Supergroup: Washburn Group (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.3 % of this area
ABSAROKA VOLCANIC SUPERGROUP--WASHBURN GROUP: includes Sepulcher Formation (andesitic and dacitic volcaniclastic rocks), Lamar River Formation (andesitic lava and volcaniclastic rocks), and Cathedral Cliffs Formation (light-colored andesitic volcaniclastic rocks).
Lithology: mixed clastic/volcanic; intermediate volcanic rock; felsic volcanic rock
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
Hartville Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early Pennsylvanian-Middle(?) Pennsylvanian-Late(?) Permian) at surface, covers 0.2 % of this area
HARTVILLE FORMATION--Red and white sandstone underlain by gray dolomite and limestone, red shale, and red and gray sandstone. Lowermost unit may be Late Mississippian in age.
Lithology: sandstone; carbonate; shale
Triassic, undifferentiated (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area
Triassic, undifferentiated: conglomerate, sandstone, shale, and impure limestone belonging to the Dinwoody and Thaynes formations and other units of Triassic age, and the Chugwater of Triassic and Permian age.
Lithology: fine-grained mixed clastic; limestone; medium-grained mixed clastic
Mowry Shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers < 0.1 % of this area
MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds.
Lithology: shale; bentonite
Limestone, sandstone, dolostone, and chert; Permian to Pennsylvanian marine epicontinental-basin deposits; southeastern Idaho; (Early Permian to Early Pennsylvanian) at surface, covers < 0.1 % of this area
Lower Permian to Lower Pennsylvanian chert, limestone, and sandstone of southern Idaho; subdivisions are (Ps, and PNs).
Lithology: limestone; sandstone; dolostone (dolomite); chert; siltstone; shale
Oldest gneiss complex (Archean) at surface, covers < 0.1 % 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.
Lithology: granitic gneiss; migmatite
Eagle sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Eagle sandstone: sandstone and shaly sandstone with lignite beds in basal part of upper unit (Keu). The Virgelle sandstone member (Kvi) at base is distinguished where possible. Near Yellowstone National Park rocks incorrectly called Laramide in early reports and now regarded as roughly equivalent to the Eagle sandstone are tentatively mapped as Eagle sandstone.
Lithology: sandstone; mudstone; coal
Hoback Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers < 0.1 % of this area
HOBACK FORMATION--Interbedded drab and gray sandstone and claystone. Locally contains thick red and gray conglomerate.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; conglomerate
Bridger Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 2 % of this area
BRIDGER FORMATION--Greenish-gray, olive-drab, and white tuffaceous sandstone and claystone; lenticular marlstone and conglomerate.
Lithology: fine-grained mixed clastic; mixed clastic/volcanic; mixed clastic/carbonate
Quartz monzonite of northern Yellowstone (Archean) at surface, covers < 0.1 % of this area
QUARTZ MONZONITE OF NORTHERN YELLOWSTONE (AGE 2,740 Ma).
Lithology: quartz monzonite
Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.1 % of this area
WASATCH FORMATION Niland Tongue--Brown sandstone, carbonaceous shale, and coal.
Lithology: sandstone; shale; coal
Ankareh Formation, Thaynes Limestone, Woodside Shale, and Dinwoody Formation (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late) at surface, covers 0.3 % of this area
ANKAREH FORMATION, THAYNES LIMESTONE, WOODSIDE SHALE, AND DINWOODY FORMATION. ANKAREH FORMATION--Red and maroon shale and purple limestone. THAYNES LIMESTONE--Gray limestone and limy siltstone. WOODSIDE SHALE--Red siltstone and shale. DINWOODY FORMATION--Gray to olive-drab dolomitic siltstone.
Lithology: mixed clastic/carbonate; fine-grained mixed clastic
Absaroka Volcanic Supergroup: Sunlight Group--Trout Peak Trachyandesite (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.2 % of this area
ABSAROKA VOLCANIC SUPERGROUP: SUNLIGHT GROUP--Trout Peak Trachyandesite.
Lithology: trachyandesite
Wasatch Fm--Cathedral Bluffs Tongue (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Claystone, mudstone, and sandstone; in Sand Wash basin
Lithology: claystone; mudstone; sandstone
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.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; coal
Middle and Lower Eocene Rocks (Phanerozoic | Cenozoic | Tertiary | Eocene-Early Eocene-Middle) at surface, covers < 0.1 % 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.
Lithology: mixed clastic/volcanic; fine-grained mixed clastic; medium-grained mixed clastic
Greenhorn Formation and Belle Fourche Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
GREENHORN FORMATION AND BELLE FOURCHE SHALE. GREENHORN FORMATION--Light-colored limestone, marl, and limy sandstone interbedded with gray concretionary shale. BELLE FOURCHE SHALE--Black soft bentonitic concretionary shale. CARLILE SHALE--Dark-gray sandy shale; Sage Breaks Member at top; Turner Sandy Member in middle.
Lithology: mixed clastic/carbonate; fine-grained mixed clastic; mixed clastic/volcanic; medium-grained mixed clastic
Jelm and Chugwater Formations, Forelle Limestone, and Satanka Shale (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early) at surface, covers < 0.1 % of this area
JELM AND CHUGWATER FORMATIONS, FORELLE LIMESTONE, AND SATANKA SHALE. CHUGWATER FORMATION OR GROUP--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. FORELLE LIMESTONE--Thin-bedded limestone. Locally is a member of the Goose Egg Formation. SATANKA SHALE--Red shale.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/carbonate; evaporite
Niobrara formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Niobrara formation: chiefly calcareous shale with limestone concretions; many thin bentonite beds locally.
Lithology: shale; bentonite
Morrison Formation, Unkpapa Sandstone, Sundance Formation, and Gypsum Spring Formation (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers < 0.1 % of this area
Morrison Formation (Late Jurassic)- Light-gray to green and variegatedred, brown, yellow, or lavender, silceous claystone, shale, and siltstone containing interbedded sandstone and fresh-water limestone lenses. Thickness up to 150 ft (46 m). Unkpapa Sandstone (Late Jurassic)- White, massive to thin-bedded, fine-grained, argillaceous sandstone. May be variegated to banded red, yellow, brown, or lavender. Thickness up to 267 ft (81 m). Sundance Formation (Late to Middle Jurassic)- Greenish-gray, yellow, tan, red to orange, and white, variegated, interbedded, fine- to coarse-grained sandstone, siltstone, clay, and limestone. Thickness 250-350 ft (76-107 m). Gypsum Springs Formation (Middle Jusassic)- Massive white gypsum and minor maroon siltstone and shale. Thickness up to 40 ft (12 m).
Lithology: sandstone; siltstone; claystone; clay or mud; shale; limestone; evaporite
Plutonic rocks (Archean) at surface, covers 0.7 % of this area
PLUTONIC ROCKS. Wind River Range--Largely granite gneiss; contains diorite and quartz diorite facies. Bighorn Mountains--Quartz diorite to quartz monzonite. Age 2,900+ Ma.
Lithology: granitoid
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 1 % of this area
FORT UNION FORMATION Tongue River Member--Thick beds of yellow sandstone interbedded with gray and black shale and many coal beds.
Lithology: sandstone; shale; coal
Judith River formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Judith River formation: light-colored sandstone at top; lower third somber-gray siltstone and sandy shale; greenish-gray clay and some lignite beds; includes the Parkman sandstone member of south-central Montana.
Lithology: sandstone; mudstone; coal
Ogallala Group or Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area
Silt, sand, sandstone, gravel and conglomerate. Predominantly interfingered fine- to coarse grained, poorly sorted, arkosic, fluvial deposits of light-gray, light-olive-gray, and grayish-green calcareous silt and sand, and locally poorly consolidated conglomerate, sandstone, and siltstone.
Lithology: mudstone; sandstone; volcanic ash
Cody Shale and Frontier Formation (N, S) (Phanerozoic | Mesozoic | Cretaceous-Late (78-83 Ma)) at surface, covers < 0.1 % of this area
CODY SHALE AND FRONTIER FORMATION north and south Wyoming. CODY SHALE (AGE 78 TO 83 Ma) (Kc2)--Dull-gray shale, gray siltstone, and fine-grained gray sandstone. FRONTIER FORMATION (Kf2)--Gray sandstone and sandy shale.
Lithology: mudstone; sandstone
Sohare Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
SOHARE FORMATION--Lenticular gray and brown sandstone and shale; thin coal beds.
Lithology: sandstone; shale; coal
Pass Peak Formation and Equivalents (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.2 % of this area
PASS PEAK FORMATION AND EQUIVALENTS--Includes Lookout Mountain Conglomerate Member of Wasatch Formation. On the south side of Gros Ventre Range consists of gold-bearing quartzite conglomerate; intertongues southward with sandstone and claystone of main body of Wasatch Formation.
Lithology: conglomerate; medium-grained mixed clastic; fine-grained mixed clastic
Siltstone, evaporites, and redbeds; Late Jurassic Cordilleran retroarc-foreland-basin deposits; southeastern Idaho (Late Jurassic) at surface, covers < 0.1 % of this area
Upper Jurassic shallow-marine to non-marine sediments; glauconitic and variegated sandstone, siltstone and oolitic limestone of eastern Idaho.
Lithology: siltstone; shale; sandstone; limestone; evaporite
Shale, limestone, and sandstone; Triassic marine to non-marine epicontinental deposits (subunits are TRl and TRu) (Triassic) at surface, covers < 0.1 % of this area
Triassic shallow-marine to non-marine sediments of eastern Idaho; subdivisions are (TRu and TRl).
Lithology: shale; limestone; sandstone; chert; conglomerate
Mesaverde Group, Ericson Sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.1 % of this area
MESAVERDE GROUP (SOUTH WYOMING). Rock Springs uplift. Ericson Sandstone--White massive sandstone; lenticular chert-grit conglomerate in upper part.
Lithology: sandstone; conglomerate
Metabasalt (Archean(?) Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area
Dark-green amphibolite and amphibolite schist. Thickness of individual flows 50-200 ft (15-61 m).
Lithology: amphibolite; schist
Wasatch Formation (E) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
WASATCH FORMATION Kingsbury Conglomerate Member--Conglomerate of Paleozoic clasts, interbedded with drab sandstone and variegated claystone.
Lithology: conglomerate; medium-grained mixed clastic; fine-grained mixed clastic
Hillard Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % of this area
HILLIARD SHALE--Dark-gray to tan claystone, siltstone, and sandy shale.
Lithology: mudstone
Kootenai formation and associated rocks (Phanerozoic | Mesozoic | Jurassic Cretaceous-Early) at surface, covers < 0.1 % of this area
Kootenai formation and associated rocks: conglomerate, sandstone, shale, and mudstone; purplish and green beds are common; mainly the Kootenai; in southern Montana includes strata that have been mapped as Cloverly formation. Includes Second Cat Creek and Third Cat Creek sands of drillers in central part of State; Sunburst sand of drillers in north-central part; and Cut Bank sand of drillers in western part. As here mapped, may locally include thin units of Jurassic age.
Lithology: medium-grained mixed clastic; mudstone; limestone
Conglomerate of Roaring Creek (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % of this area
CONGLOMERATE OF ROARING CREEK (EOCENE OR PALEOCENE; OLDER THAN MAIN PART OF WASATCH FORMATION)--Red and gray conglomerate containing clasts of Mesozoic, Paleozoic, and Precambrian rocks.
Lithology: conglomerate
Carlile Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
CARLILE SHALE--Dark-gray sandy shale; Sage Breaks Member at top; Turner Sandy Member in middle.
Lithology: shale; fine-grained mixed clastic
Red Conglomerate on top of Hoback and Wyoming Ranges (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area
RED CONGLOMERATE ON TOP OF HOBACK AND WYOMING RANGES (MIOCENE?; MAY BE AS OLD AS EOCENE)--Locally derived clasts of Mesozoic and Paleozoic rocks in a red clay and sand matrix.
Lithology: conglomerate
Mesaverde Group, Almond Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % of this area
MESAVERDE GROUP (SOUTH WYOMING). Rock Springs uplift. Almond Formation--White and brown soft sandstone, gray sandy shale, coal, and carbonaceous shale.
Lithology: sandstone; shale; coal
Nugget Sandstone, Ankareh Formation, Thaynes Limestone, Woodside Shale, and Dinwoody Formation (TB), or Nugget Sandstone and Chugwater and Dinwoody Formations (N) (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late(?) Triassic(?) Jurassic(?)) at surface, covers 0.2 % of this area
NUGGET SANDSTONE, ANKAREH FORMATION, THAYNES LIMESTONE, WOODSIDE SHALE, and DINWOODY FORMATION (Thrust Belt). NUGGET SANDSTONE--Buff to pink crossbedded well-sized and well-sorted quartz sandstone and quartzite; locally has oil and copper-silver-zinc mineralization. ANKAREH FORMATION--Red and maroon shale and purple limestone. THAYNES LIMESTONE--Gray limestone and limy siltstone. WOODSIDE SHALE--Red siltstone and shale. DINWOODY FORMATION--Gray to olive-drab dolomitic siltstone. NUGGET SANDSTONE AND CHUGWATER AND DINWOODY FORMATIONS (north Wyoming). NUGGET SANDSTONE--Gray to dull-red, crossbedded quartz sandstone. CHUGWATER FORMATION--Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming. DINWOODY FORMATION--Olive-drab hard dolomitic thin-bedded siltstone.
Lithology: siltstone; sandstone; shale; limestone
Clastic debris; Quaternary colluvium, fanglomerate, talus, and glacial deposits; upland-valley margins (Quaternary) at surface, covers < 0.1 % of this area
Quaternary colluvium, fanglomerate, and talus plus some glacial debris in upland valleys.
Lithology: alluvium; glacial drift; colluvium
Kootenai and Morrison Formations and Ellis Group (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers < 0.1 % of this area
KOOTENAI AND MORRISON FORMATIONS AND ELLIS GROUP. KOOTENAI FORMATION--Rusty thin-bedded sandstone, grayish-red soft claystone, white limestone, and chert-pebble conglomerate. MORRISON FORMATION in northern Yellowstone area--Variegated silty claystone and fine-grained sandstone. ELLIS GROUP includes SWIFT, RIERDON, and SAWTOOTH FORMATIONS. Swift Formation--Calcareous glauconitic sandstone and sandy limestone. Rierdon Formation--Mudstone, siltstone, shale, and basal limestone. Sawtooth Formation--Red beds and limestone.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; limestone; conglomerate
Wasatch Formation (E) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
WASATCH FORMATION Moncrief Member--Conglomerate of Precambrian clasts, interbedded with drab sandstone and claystone.
Lithology: conglomerate
Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers 2 % 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.
Lithology: sandstone; fine-grained mixed clastic; conglomerate
Fort Union formation (Phanerozoic | Cenozoic | Tertiary Cretaceous-Late | Paleocene) at surface, covers < 0.1 % of this area
Fort Union formation: Clay shale, siltstone, and sandstone; local lenses of impure limestone, and numerous lignitic beds; contains Tertiary plant and animal fossils but no dinosaurs; base generally placed at the lowest of the succession of lignite beds within it; includes the Tongue River member, Lebo shale member, and Tullock member.
Lithology: shale; siltstone; sandstone; coal; limestone
Fox Hills Sandstone and Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % 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
Shear zone (Archean) at surface, covers < 0.1 % of this area
Lithology: tectonite
Ogallala Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Loose to well-cemented sand and gravel
Lithology: sandstone; conglomerate
Alkalic extrusive and intrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
ALKALIC INTRUSIVE AND EXTRUSIVE IGNEOUS ROCKS (AGE ABOUT 44 Ma)--Light- to greenish-gray porphyry.
Lithology: alkalic intrusive rock; alkalic volcanic rock
Jurassic, undifferentiated (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area
Jurassic, undifferentiated: calcareous shale and sandstone; includes the Morrison formation, the Ellis group, Sundance formation, and other rocks of Jurassic age.
Lithology: fine-grained mixed clastic; limestone; evaporite
Laramide Anorthosite Complex--pyroxene and hornblende syenite (Proterozoic | Mesoproterozoic) at surface, covers < 0.1 % of this area
LARAMIE ANORTHOSITE COMPLEX--Pyroxene and hornblende syenite--Age 1,435 Ma. In Laramie Mountains.
Lithology: anorthosite
Sohare Formation and Bacon Ridge Sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
SOHARE FORMATION AND BACON RIDGE SANDSTONE. SOHARE FORMATION (Kso)--Lenticular gray and brown sandstone and shale; thin coal beds. BACON RIDGE SANDSTONE (Kb)--Gray to tan marine sandstone and thick coal beds; gold-bearing quartzite conglomerate in lower part.
Lithology: sandstone; coal; shale; conglomerate
Tertiary volcanic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Tertiary volcanic rocks: Flows and associated pyroclastic deposits, with subordinate amounts of intercalated sedimentary beds and lignite. The volcanic material is mostly latite, quartz latite, and andesite but includes some rhyolite and basalt. The distinction between Tertiary and pre-Tertiary volcanic rocks was not made in some of the reports used in the complilation. Hence in the less well-known areas some pre-Tertiary volcanic rocks may be included.
Lithology: volcanic rock (aphanitic); mixed clastic/volcanic; coal
Mississippian (1) carbonate rocks in Salt Lake City-Coalville-Randolph region (Mississippian) at surface, covers < 0.1 % of this area
Lithology: limestone
Casper Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle Pennsylvanian-Late Permian) at surface, covers 0.1 % of this area
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.
Lithology: sandstone; limestone
Permian, undifferentiated (Phanerozoic | Paleozoic | Permian) at surface, covers < 0.1 % of this area
Permian, undifferentiated: chert, sandstone, limestone, quartzite, and shale with rock phosphate mostly at base; mainly Phosphoria formation
Lithology: fine-grained mixed clastic; carbonate; chert; phosphorite; black shale; oil shale
Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Two Ocean and Langford Formations (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma)) at surface, covers 0.6 % 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.
Lithology: mixed clastic/volcanic; intermediate volcanic rock
Colter Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area
COLTER FORMATION--Dull-green and gray tuff, volcanic conglomerate, and sandstone.
Lithology: mixed clastic/volcanic; tuff; sandstone
Washakie Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (43-44 Ma)) at surface, covers 0.5 % of this area
WASHAKIE FORMATION (AGE ABOUT 43 TO 44 Ma)--Gray, green, tan, and dull-red tuffaceous arkosic sandstone and claystone.
Lithology: medium-grained mixed clastic; mixed clastic/volcanic
Belle Fourche shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Belle Fourche shale: dark blue-gray siliceous shale with many calcareous and ferruginous concretions and intercalated thin layers of bentonite.
Lithology: shale; bentonite; sandstone
Absaroka Volcanic Supergroup: Sunlight Group--Wapiti Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.9 % of this area
ABSAROKA VOLCANIC SUPERGROUP: SUNLIGHT GROUP--Wapiti Formation: andesitic volcaniclastic rocks.
Lithology: mixed clastic/volcanic; intermediate volcanic rock
Metagraywacke (Archean(?) Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area
Gray, siliceous mica schist and impure quartzite. Thickness undetermined.
Lithology: schist; quartzite
Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Aycross Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma)) at surface, covers 0.3 % 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.
Lithology: mixed clastic/volcanic; fine-grained mixed clastic; conglomerate
Whitewood Limestone, Winnipeg Formation, and Deadwood Formation (Phanerozoic | Paleozoic | Cambrian Ordovician) at surface, covers < 0.1 % of this area
Whitewood Limestone (Ordovician)- Mottled, tan, gray to lavender, fine- to medium-crystalline, sparsely fossiliferous limestone and dolomite. Thickness up to 70 ft (21 m). Winnipeg Formation (Ordovician)- Grat and light-green, fissile shale, and tan, calcareous siltstone, sandy shale, and limestone lenses. Thickness up to 110 ft (34 m). Deadwood Formation (Ordovician to Cambrian)- Variegated, yellow to red, brown, gray, and green, glauconitic, conglomerate, sandstone, shale, dolomitic limestone, and dolomite. Thickness 4-400 ft (1-122 m).
Lithology: conglomerate; shale; limestone; dolostone (dolomite); siltstone
Green River Fm--Laney Member (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Claystone, oil shale, and sandstone; in Sand Wash basin
Lithology: claystone; oil shale; sandstone
Granitic rocks (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area
GRANITIC ROCKS OF 2,000-Ma AGE GROUP. Medicine Bow Mountains--Gaps Intrusion 3 (granitic). Hartville uplift--Granite and quartz monzonite of Flattop Butte 6; age 2,150+/- Ma.
Lithology: granitoid
Frontier formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Frontier formation: mainly gray sandy shale; locally Torchlight sandstone member constitutes upper third and thinner Peay sandstone member is at base; contains some thick beds of bentonite.
Lithology: medium-grained mixed clastic; bentonite
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.
Lithology: sedimentary rock; clastic; mixed clastic/volcanic; mixed clastic/carbonate
Basalt flows and intrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area
BASALT FLOWS AND INTRUSIVE IGNEOUS ROCKS (AGE ABOUT 11 Ma).
Lithology: basalt
Guernsey Formation (Phanerozoic | Paleozoic | Devonian-Late Carboniferous Mississippian-Early) at surface, covers < 0.1 % of this area
GUERNSEY FORMATION--Blue-gray massive cherty limestone and dolomite. Locally includes unnamed dolomite and sandstone of Devonian and Cambrian(?) age.
Lithology: limestone; dolostone (dolomite); sandstone
Wasatch Formation (TB) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.2 % of this area
WASATCH FORMATION Diamictite and sandstone--Diamictite grades laterally into other members of the formation.
Lithology: clastic; medium-grained mixed clastic; fine-grained mixed clastic
Spearfish Formation (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early(?) Triassic-Middle(?) Triassic-Late) at surface, covers 0.3 % of this area
SPEARFISH FORMATION--Red shale, red siltstone, and white gypsum beds; gypsum beds especially abundant near base.
Lithology: mudstone; evaporite
Inyan Kara Group (Phanerozoic | Mesozoic | Cretaceous-Early ) at surface, covers < 0.1 % of this area
Includes: Fall River Formation- Variegated brown, red, gray to purple, calcareous, well-sorted, fine-grained sandstone, siltstone, and shale containing mica flakes. Thickness 100-200 ft (30-61 m). Lakota Formation- Yellow, brown, red-brown, gray to black silty shale, pebble conglomerate, and massive to thin-bedded, cross-bedded sandstone. Locally interbedded with fresh-water limestone and bituminous coal beds. Thickness 35-500 ft (11-152 m).
Lithology: shale; sandstone; conglomerate; siltstone; limestone; coal
Trachytic Intrusive Rocks (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % of this area
Tan to reddish-brown, iron-stained stocks, laccoliths, sills, and dikes of trachyte, quartz trachyte, and alkalic rhyolite. Contains phenocrysts of sanidine, orrthoclase, anorthoclase, aegirine-augite and biotite in a finely crystalline orthoclase-quartz biotite groundmass.
Lithology: trachyte; trachyte; rhyolite
Mowry shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers < 0.1 % of this area
Mowry shale: chiefly light-gray silicified shale and claystone with minor amounts of sandy shale and sandstone; contains some thick beds of bentonite.
Lithology: fine-grained mixed clastic; bentonite
Metasedimentary rocks: Libby Creek Group (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area
METASEDIMENTARY ROCKS--In Medicine Bow Mountains and Sierra Madre. Libby Creek Group 3--Pelitic schist, amphibole schist, quartzite, diamictite, quartz-pebble conglomerate, and marble.
Lithology: metasedimentary rock
Metasedimentary and metavolcanic rocks (Proterozoic | Paleoproterozoic ) at surface, covers 0.4 % of this area
METASEDIMENTARY AND METAVOLCANIC ROCKS. Sierra Madre--Granite gneiss, felsic gneiss, amphibolite, and metavolcanic rocks. Medicine Bow Mountains--Granite gneiss, felsic gneiss, amphibolite, and hornblende gneiss. Laramie Mountains--Pelitic schist, marble, granite gneiss, layered amphibolite, and felsic gneiss. Black Hills--Pelitic schist; includes minor amounts of granite and amphibolite.
Lithology: metasedimentary rock; metavolcanic rock
Niobrara Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
White to dark gray argillaceous chalk, marl, and shale. Weathers yellow to orange. Contains thin, laterally continuous bentonite beds, chalky carbonaceous shale, minor sand, and small concretions. Thickness 160-225 ft (49-69 m).
Lithology: limestone; limestone; shale; clay or mud; sand
Open Water (Holocene) at surface, covers < 0.1 % of this area
Lakes and streams
Lithology: water
Sandstone and Conglomerate (Phanerozoic | Cenozoic | Tertiary | Oligocene Miocene) at surface, covers < 0.1 % of this area
SANDSTONE AND CONGLOMERATE--Gray hard coarse-grained sandstone and conglomerate.
Lithology: sandstone; conglomerate
Absaroka Volcanic Supergroup: Thoroughfare Creek and Sunlight Groups (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)--Light-colored volcaniclastic strata, andesite lava flows, and dark-brown breccia AND SUNLIGHT GROUP--including Trout Peak Trachyandesite, Wapiti Formation (andesitic volcaniclastic rocks), Crescent Hill Basalt, and Mount Wallace Formation (felsic and mafic volcaniclastic rocks).
Lithology: andesite; pyroclastic; trachyandesite; basalt; felsic volcanic rock
Forelle Limestone and Satanka Shale (Phanerozoic | Paleozoic | Permian) at surface, covers < 0.1 % of this area
FORELLE LIMESTONE AND SATANKA SHALE. FORELLE LIMESTONE--Thin-bedded limestone. Locally is a member of the Goose Egg Formation. SATANKA SHALE--Red shale .
Lithology: limestone; shale
Claggett formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Claggett formation: chiefly dark-gray shale with iron-stained concretions; locally sandstone present; numerous bentonite beds near base.
Lithology: shale; sandstone; bentonite
Ice Point Conglomerate (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
ICE POINT CONGLOMERATE--Reddish-brown conglomerate, chiefly of Paleozoic rock fragments.
Lithology: conglomerate
Blind Bull Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.1 % of this area
BLIND BULL FORMATION--Gray to tan conglomeratic sandstone, siltstone, claystone, coal, and bentonite.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; coal; mixed clastic/volcanic
Gypsum Spring Formation, Nugget Sandstone, and Chugwater Formation (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late(?) Jurassic-Early(?) Jurassic-Middle(?) Jurassic-Late) at surface, covers < 0.1 % of this area
GYPSUM SPRING FORMATION, NUGGET SANDSTONE, AND CHUGWATER FORMATION. 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. CHUGWATER FORMATION--Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming.
Lithology: fine-grained mixed clastic; carbonate; dolostone (dolomite); evaporite
Devonian, undifferentiated (Phanerozoic | Paleozoic | Devonian) at surface, covers < 0.1 % of this area
Devonian, undifferentiated: comprises Three Forks formation consisting of carbonaceous and calcareous shale with some sandstone and limestone, Jefferson limestone, and unnamed units of Devonian age.
Lithology: carbonate; fine-grained mixed clastic; conglomerate; sedimentary breccia; evaporite
Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Mostly medium to dark-gray, brownish-gray, and black, fissle clay shale. Locally grades to thin beds of calcareous, silty shale or claystone, marl, shaly sandstone, and sandy shale. Locally contains thin seams of gypsum and sparse selenite crystals. Approx. max thickness 1970 ft.
Lithology: shale; evaporite
Mafic intrusive rocks (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area
MAFIC INTRUSIVE ROCKS. Sierra Madre--Gabbro of Elkhorn Mountain; age 1,800 Ma. Medicine Bow Mountains--Mullen Creek 5 and Lake Owens 7 Mafic Complexes; older than 1,700 Ma.
Lithology: gabbroid
Laketown Dolomite (Phanerozoic | Paleozoic | Silurian) at surface, covers < 0.1 % of this area
LAKETOWN DOLOMITE--Light-gray thick-bedded finely crystalline dolomite.
Lithology: dolostone (dolomite)
Mafic intrusive rocks (Archean) at surface, covers < 0.1 % of this area
MAFIC INTRUSIVE ROCKS.
Lithology: plutonic rock (phaneritic)
Pre-Belt gneiss, schist, and related rocks (Archean Proterozoic(?) preCambrian-Proterozoic(?) preCambrian(?) Phanerozoic | Paleozoic(?) Mesozoic(?) Cenozoic | Cambrian(?) Ordovician(?) Silurian(?) Devonian(?) Carboniferous(?) Permian(?) Triassic(?) Jurassic(?) Cretaceous(?) Tertiary) at surface, covers < 0.1 % of this area
Pre-Belt gneiss, schist, and related rocks: comprises all the rocks older than the Belt series except the Stillwater complex. These include the Cherry Creek group, consisting of interlaminated gneiss, schist, marble, and quartzite; and the Pony series of Tansley and others, consisting of gneiss and schist of both sedimentary and igneous origin. Recent work has resulted in the distinction of small masses of granitic and injected rocks now regarded as resulting from intrusion in Cretaceous or Tertiary time. Other such masses may have escaped recognition.
Lithology: metamorphic rock; plutonic rock (phaneritic)
Intrusive igneous rocks (Phanerozoic | Mesozoic | Cretaceous(?)) at surface, covers < 0.1 % of this area
INTRUSIVE IGNEOUS ROCKS--Gray to buff monzonite porphyry. Beartooth Mountains.
Lithology: plutonic rock (phaneritic)
Casper and Fountain Formations (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle Pennsylvanian-Late Permian) at surface, covers 0.2 % of this area
CASPER AND FOUNTAIN FORMATIONS. 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. FOUNTAIN FORMATION--Arkose and red sandstone.
Lithology: sandstone; limestone
Dacite and quartz latite intrusive and extrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
DACITE AND QUARTZ LATITE INTRUSIVE AND EXTRUSIVE IGNEOUS ROCKS (AGE ABOUT 44 Ma)--Light-gray porphyritic rock.
Lithology: dacite; quartz latite
Heart Lake Conglomerate (Phanerozoic | Cenozoic | Tertiary | Pliocene) at surface, covers < 0.1 % of this area
HEART LAKE CONGLOMERATE--Abundant gray limestone and dolomite clasts and sparse rhyolite and quartzite clasts in a talc and clay matrix.
Lithology: conglomerate
Telegraph Creek formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Telegraph Creek formation: buff mainly soft, fissile sandy shale with subordinate amounts of concretionary sandstone.
Lithology: mudstone; sandstone
Eolian Deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area
(loess and sand dune) Silt to medium-grained sand. Deposited as sand sheets and barchan, linear, and dome-like dunes and as veneer on uplands. Thickness up to 300 ft (91m).
Lithology: silt; sand
Minnelusa Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers < 0.1 % of this area
Variegated, yellow to red, gray to brown, pink to purple, and black, interbedded sandstone, siltstone, shale, limestone, dolomite, calcarenite, chert and brecciated beds. Thickness 394-1,175 ft (120-358 m).
Lithology: sandstone; siltstone; shale; limestone; dolostone (dolomite); chert
Bearpaw shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Bearpaw shale: Dark-gray and brownish clay shale; thick units of nonfissile bentonitic shale; calcareous and ferruginous concretions throughout; contains some thick bentonite beds.
Lithology: shale; sandstone; bentonite
Tertiary (1) sedimentary rocks in Logan-Huntsville Allochthon (Late Cretaceous to Early Eocene) at surface, covers < 0.1 % of this area
Lithology: conglomerate; medium-grained mixed clastic
Minnelusa Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early Pennsylvanian-Middle(?) Pennsylvanian-Late(?) Permian) at surface, covers 0.2 % of this area
MINNELUSA FORMATION--Buff and red limy sandstone; some thin limestone beds, solution breccias, and gypsum.
Lithology: sandstone; limestone; evaporite
Sundance and Gypsum Spring Formations and Nugget Sandstone (Phanerozoic | Mesozoic | Triassic(?) Jurassic(?) Jurassic-Early(?) Jurassic-Middle(?) Jurassic-Late) at surface, covers < 0.1 % 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.
Lithology: sandstone; shale; dolostone (dolomite); evaporite
Sandstone, siltstone, shale, limestone, and coal ; Early Cretaceous Cordilleran retroarc-foreland-basin deposits; southeastern Idaho (Early Cretaceous) at surface, covers < 0.1 % of this area
Lower Cretaceous shale, siltstone, red-bed sandstone and fresh-water limestone.
Lithology: sandstone; siltstone; shale; limestone; coal
Alkalic extrusive and intrusive igneous rocks (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area
ALKALIC EXTRUSIVE AND INTRUSIVE IGNEOUS ROCKS (AGE 1.25 Ma)--Leucite- and nepheline-rich flows, scoria, and necks.
Lithology: alkalic volcanic rock; alkalic intrusive rock
Mesaverde Group, Blair Formation. (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % of this area
MESAVERDE GROUP (SOUTH WYOMING). Rock Springs uplift. Blair Formation--Drab-yellow and brown sandstone and sandy shale.
Lithology: sandstone; shale
Landslide Creek Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
LANDSLIDE CREEK FORMATION--Greenish-gray bentonitic tuffaceous sandstone and conglomerate.
Lithology: sandstone; conglomerate; mixed clastic/volcanic
Rhyolite ignimbrites; Early Pleistocene felsic volcanics; Yellowstone Plateau (Early Pleistocene) at surface, covers < 0.1 % of this area
Lower Pleistocene silicic volcanic units of the Island Park-Yellowstone area.
Lithology: rhyolite; ignimbrite
Cloverly, Morrison, Sundance, and Gypsum Spring Formations and Nugget Sandstone (Phanerozoic | Mesozoic | Triassic(?) Jurassic(?) Cretaceous-Early) at surface, covers < 0.1 % 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.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; carbonate; dolostone (dolomite)
Fox Hills Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Consists of fossiliferous, gray, ferruginous and yellowish fine-grained sandstone, arenaceous clays and a few interbeds of gray to brown sandy shale and coal totaling 172 ft thick at that section. Estimated thickness 500 ft.
Lithology: sandstone; clay or mud; shale; coal
Gypsum Spring Formation and Nugget Sandstone (Phanerozoic | Mesozoic | Triassic-Early Triassic-Middle(?) Triassic-Late(?) Jurassic-Early(?) Jurassic-Middle(?) Jurassic-Late) at surface, covers < 0.1 % 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.
Lithology: sandstone; fine-grained mixed clastic; dolostone (dolomite); evaporite
Mesaverde Group, Rock Springs Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % of this area
MESAVERDE GROUP (SOUTH WYOMING). Rock Springs uplift. Rock Springs Formation--White to brown sandstone, shale, and claystone; numerous coal beds.
Lithology: sandstone; mudstone; coal
Green River Formation: Luman Tongue (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.1 % of this area
GREEN RIVER FORMATION Luman Tongue--Oil shale, carbonaceous shale, and sandstone.
Lithology: fine-grained mixed clastic; oil shale
Crandall Conglomerate (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
CRANDALL CONGLOMERATE--Nonvolcanic conglomerate containing clasts of Lower Paleozoic rocks.
Lithology: conglomerate
Wasatch Fm--Niland Tongue (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Mudstone, sandstone, and carbonaceous shale; in Sand Wash basin
Lithology: mudstone; sandstone; shale
Baxter Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.2 % of this area
BAXTER SHALE--Gray to black soft sandy shale and shaly sandstone.
Lithology: shale; sandstone
Greenhorn Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Gray shale, mudstone, marl, calcarenite, and shaley limestone grading upward into light-gray to tan, alternating marl and thin-bedded, fossiliferous limestone. Thickness 225-315 ft (69-96 m).
Lithology: shale; mudstone; limestone
Three Forks and Jefferson Formations and Bighorn Dolomite (Y) or Three Forks, Jefferson, and Beartooth Butte Formations and Bighorn Dolomite (N) (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late(?) Silurian(?) Devonian-Early(?) Devonian-Middle(?) Devonian-Late) at surface, covers < 0.1 % of this area
THREE FORKS, JEFFERSON, AND BEARTOOTH BUTTE FORMATIONS AND BIGHORN DOLOMITE (Yellowstone). THREE FORKS FORMATION--Pink, yellow, and green dolomitic siltstone and shale. JEFFERSON FORMATION--Massive siliceous dolomite. BEARTOOTH BUTTE FORMATION--Red sandstone, limy siltstone, and limestone. Occurs only in the Beartooth Mountains. BIGHORN DOLOMITE--Light-gray massive siliceous dolomite. THREE FORKS, JEFFERSON, AND BEARTOOTH BUTTE FORMATIONS AND BIGHORN DOLOMITE (north Wyoming). THREE FORKS FORMATION--Yellow and greenish-gray shale and dolomitic siltstone. JEFFERSON FORMATION--Fetid brown dolomite and limestone. BEARTOOTH BUTTE FORMATION--Red sandstone, limy siltstone, and limestone. Occurs only in the Beartooth Mountains. BIGHORN DOLOMITE--Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone.
Lithology: carbonate; mudstone; sandstone
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers < 0.1 % of this area
FORT UNION FORMATION Lebo (Tfl) and Tullock (Fft) Members.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; coal
Niobrara and Frontier Formations, and Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers < 0.1 % of this area
NIOBRARA (Kn) AND FRONTIER (Kf) FORMATIONS, AND MOWRY (Kmr) AND THERMOPOLIS SHALES. NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale. FRONTIER FORMATION--Gray sandstone and sandy shale. 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.
Lithology: sandstone; shale; mixed clastic/carbonate; mixed clastic/volcanic
Madison Limestone, Darby or Three Forks, Jefferson, and Beartooth Butte Formations, and Bighorn Dolomite (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late(?) Silurian(?) Devonian(?) Carboniferous Mississippian-Early(?) Mississippian-Middle(?) Mississippian-Late) at surface, covers < 0.1 % of this area
MADISON LIMESTONE, DARBY or THREE FORKS, JEFFERSON, AND BEARTOOTH BUTTE FORMATION. 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. THREE FORKS FORMATION--Yellow and greenish-gray shale and dolomitic siltstone. JEFFERSON FORMATION--Fetid brown dolomite and limestone. BEARTOOTH BUTTE FORMATION--Red sandstone, limy siltstone, and limestone. Occurs only in the Beartooth Mountains.
Lithology: carbonate; mudstone; sandstone
Wind River Formation and Indian Meadows Formations (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % 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.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; carbonate; conglomerate
Terrace Deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area
Clay to boulder-size clasts deposited as pediments, paleochannels, and terrace fills of former flood plains. Thickness up to 75 ft (23m).
Lithology: clay or mud; silt; sand; gravel
White River Fm or Group (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
East: Ashy claystone and sandstone. Includes Castle Rock Conglomerate in region southeast of Denver. Northwest: Ashy claystone in North Park
Lithology: sandstone; claystone; conglomerate
Greenhorn formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Greenhorn formation: mainly light-gray marl and calcareous shale.
Lithology: mudstone; limestone; bentonite
Browns Park Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Sandstone and siltstone; west of Park Range
Lithology: sandstone; siltstone
Everts Formation, Eagle Sandstone, and Telegraph Creek Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
EVERTS FORMATION, EAGLE SANDSTONE, AND TELEGRAPH CREEK FORMATION--Massive to thin-bedded sandstone, mudstone, and shale.
Lithology: sandstone; mudstone
Sandstone, conglomerate, siltstone, tuff, claystone, limestone, and diatomite; Pliocene tuffaceous alluvial and lacustrine deposits; Snake River Plain and vicinity, southeastern Idaho (Pliocene ) at surface, covers < 0.1 % of this area
Pliocene stream and lake deposits; may be due to volcanic and block-faulting events.
Lithology: sandstone; conglomerate; siltstone; tuff; claystone; shale; limestone
Coalmont Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % of this area
COALMONT FORMATION (EOCENE AND PALEOCENE)--Tan to gray arkosic micaceous soft sandstone, claystone, and locally derived conglomerate.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; conglomerate
Pennsylvanian and Permian sedimentary rocks in Salt Lake City-Coalville-Randolph region (Pennsylvanian to Permian) at surface, covers < 0.1 % of this area
Lithology: orthoquartzite; limestone
Lennep sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Lennep sandstone: mainly dark-brown andesitic sandstone with intercalated shale; locally contains thin coal beds.
Lithology: sandstone; mudstone; coal
Granitic conglomerate above or in upper part of Wasatch Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % of this area
GRANITIC CONGLOMERATE ABOVE OR IN UPPER PART OF WASATCH FORMATION--Giant granite boulders in arkosic sandstone matrix. Occurs along west margin of Wind River Range.
Lithology: conglomerate
Carlile shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
Carlile shale: dark-gray shale with calcareous and ferruginous concretions; middle part commonly sandy
Lithology: shale
Wasatch Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Claystone, shale, and sandstone
Lithology: claystone; shale; sandstone
Green River Fm--Tipton Tongue (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area
Claystone and oil shale; in Sand Wash basin. In extreme northwest includes rocks of Wilkins Peak Member
Lithology: claystone; oil shale

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