Geologic units in Carbon county, Wyoming

Additional scientific data in this geographic area

Miocene Rocks (Miocene) at surface, covers 14 % of this area

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.

Alluvium and Colluvium (Pleistocene-Holocene) at surface, covers 8 % of this area

Clay, silt, sand, and gravel in flood plains, fans, terraces, and slopes.

Mesaverde Formation or Mesaverde Group (Upper Cretaceous) at surface, covers 8 % 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.

Steele Shale (Upper Cretaceous) at surface, covers 6 % of this area

Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone.

Upper Miocene Rocks (Upper Miocene) at surface, covers 5 % of this area

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.

Hanna Formation (Paleocene) at surface, covers 5 % of this area

Brown and gray sandstone, shale, conglomerate, and coal; giant quartzite boulders near Medicine Bow Mountains.

Lewis Shale (Upper Cretaceous) at surface, covers 5 % of this area

Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Dune sand and loess (Pleistocene-Holocene) at surface, covers 4 % of this area

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

Granitic rocks of 2,600-Ma Age Group (Late Archean) at surface, covers 3 % of this area

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.

Granite gneiss (Late Archean) at surface, covers 3 % of this area

Layered to massive, locally migmatitic; metasedimentary and metavolcanic rocks locally common. Includes Webb Canyon Gneiss in Teton Range.

Wind River Formation (Eocene) at surface, covers 3 % of this area

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.

Fort Union Formation (Paleocene) at surface, covers 3 % of this area

(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.

Metasedimentary and metavolcanic rocks (Early Proterozoic) at surface, covers 2 % of this area

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.

Wasatch Formation - Cathedral Bluffs Tongue (Eocene) at surface, covers 2 % of this area

Variegated claystone and lenticular sandstone; conglomeratic near south margin of Wind River Range.

Wasatch Formation - Main Body (Paleocene-Eocene) at surface, covers 2 % of this area

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

Gravel, pediment, and fan deposits (Pleistocene-Holocene) at surface, covers 2 % of this area

Mostly locally derived clasts. Includes some glacial deposits along east flank of Wind River Range. Locally includes some Tertiary gravels.

Glacial deposits (Pleistocene-Holocene) at surface, covers 2 % of this area

Till and outwash of sand, gravel, and boulders.

Medicine Bow Formation (Upper Cretaceous) at surface, covers 2 % of this area

Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.

Ferris Formation (Upper Cretaceous-Paleocene) at surface, covers 2 % of this area

Brown and gray sandstone and shale; sparse carbonaceous shale and coal beds; thin lenses of pebble conglomerate.

Niobrara Formation (Late Cretaceous) at surface, covers 1 % of this area

Light-colored limestone and gray to yellow speckled limy shale.

Lance Formation (Upper Cretaceous) at surface, covers 1 % of this area

(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.

Granitic rocks of 1,700-Ma Age Group (Early Proterozoic) at surface, covers 1 % of this area

Granitic rocks of 1,700-Ma Group

Steele Shale and Niobrara Formations (Upper Cretaceous) at surface, covers 1 % of this area

Steele Shale (Ks) - Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone. Niobrara Formation (Kn) - Light-colored limestone and gray to yellow speckled limy shale.

White River Formation - Upper conglomerate member (Oligocene) at surface, covers 1.0 % of this area

Light-gray soft conglomeratic tuffaceous sandstone and conglomerate of Precambrian clasts.

White River Formation (Oligocene) at surface, covers 1.0 % of this area

White to pale-pink blocky tuffaceous claystone and lenticular arkosic conglomerate.

Cloverly, Morrison, and Sundance Formations (Middle Jurassic-Lower Cretaceous) at surface, covers 0.9 % of this area

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 (Js) - Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale.

Metasedimentary rocks - Deep Lake Group (Early Proterozoic) at surface, covers 0.9 % of this area

In Medicine Bow Mountains and Sierra Madre. Deep Lake Group 3--Quartzite, diamictite, pelitic schist, and quartz-pebble conglomerate.

Chugwater Formation or Group (Lower Triassic-Upper Triassic) at surface, covers 0.9 % of this area

Chugwater Formation (North and 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. Chugwater Group or Formation (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.

Frontier Formation (Upper Cretaceous) at surface, covers 0.8 % of this area

(Thrust Belt) - White to brown sandstone and dark-gray shale; oyster coquina in upper part; coal and lignite in lower part. (North and South Wyoming) - Gray sandstone and sandy shale.

Tensleep Sandstone and Amsden Formation (Upper Mississippian-Permian) at surface, covers 0.8 % of this area

Tensleep Sandstone (North Wyoming) - 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 (North Wyoming) - Red and green shale and dolomite; at base is brown sandstone. Tensleep Sandstone (Sorth Wyoming) - White to gray sandstone containing thin limestone and dolomite beds. Amsden Formation (South Wyoming) - Red and green shale and dolomite; at base is persistent red to brown sandstone.

Metasedimentary and metavolcanic rocks (Middle Archean-Late Archaen) at surface, covers 0.8 % of this area

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.

Mafic intrusive rocks (Early Proterozoic) at surface, covers 0.7 % of this area

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.

Green River Formation - Laney Member (Eocene) at surface, covers 0.7 % of this area

Oil shale and marlstone.

Frontier Formation and Mowry and Thermopolis Shales (Lower Cretaceous-Upper Cretaceous) at surface, covers 0.6 % of this area

Frontier Formation (Kf) - Gray sandstone and sandy shale. In Northern Yellowstone area, Yellowish- to medium-gray sandstone; tuffaceous and carbonaceous in lower part. Mowry Shale (Kmr) - Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. Thermopolis Shale - Black soft fissile shale; Muddy Sandstone Member at top.

Goose Egg Formation (Permian-Lower Triassic) at surface, covers 0.6 % of this area

Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone.

Cody Shale (Late Cretaceous) at surface, covers 0.5 % of this area

(Northern Yellowstone area) - Gray to brown shale and siltstone. (North and South Wyoming) - Dull-gray shale, gray siltstone, and fine-grained gray sandstone.

Metasedimentary rocks - Libby Creek Group (Early Proterozoic) at surface, covers 0.5 % of this area

In Medicine Bow Mountains and Sierra Madre. Libby Creek Group 3--Pelitic schist, amphibole schist, quartzite, diamictite, quartz-pebble conglomerate, and marble.

Mowry and Thermopolis Shales (Lower Cretaceous) at surface, covers 0.5 % of this area

Mowry Shale (Kmr) - Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. Thermopolis Shale - Black soft fissile shale; Muddy Sandstone Member at top.

Landslide deposits (Pleistocene-Holocene) at surface, covers 0.5 % of this area

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

Chugwater and Goose Egg Formations (Permian-Upper Triassic) at surface, covers 0.3 % of this area

Chugwater Formation (North 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. Goose Egg Formation - Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone. Chugwater Group or Formation (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.

Green River Formation - Tipton Shale Member or Tongue (Eocene) at surface, covers 0.3 % of this area

Oil shale and marlstone.

Madison Limestone, Darby Formation, Bighorn Dolomite, Gallatin Limestone, Gros Ventre Formation, and Flathead Sandstone, Cambrian rocks, Minnekahta Limestone, Opeche Shale, Minnelusa Formation, Pahasapa and Englewood Limestones, Whitewood Dolomite, and Winnipeg and Deadwood Formations (Cambrian-Permian) at surface, covers 0.2 % of this area

Madison Limestone or Group (North and South Wyoming) - Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). Darby Formation (North Wyoming) - Yellow and greenish-gray shale and dolomitic siltstone underlain by fetid brown dolomite and limestone. Bighorn Dolomite (North Wyoming) - Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. Gallatin Limestone or Group (North Wyoming) - Blue-gray and yellow mottled hard dense limestone. Gros Ventre Formation (North Wyoming) - 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 (North Wyoming) - Dull-red quartzitic sandstone. Cambrian Rocks (South Wyoming) - 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 (Northeast Wyoming) - Gray slabby hard limestone. Locally is a member of the Goose Egg Formation. Opeche Shale (Northeast Wyoming) - Red soft sandy shale. Locally is a member of the Goose Egg Formation. Minnelusa Formation (Northeast Wyoming) - Buff and red limy sandstone; some thin limestone beds, solution breccias, and gypsum. Pahasapa Limestone (Northeast Wyoming) - Gray massive dolomititc limestone. Englewood Limestone (Northeast Wyoming) - Pink slabby dolomitic limestone. Whitewood Dolomite (Northeast Wyoming) - Buff massive fossiliferous dolomite. Winnipeg Formation (Northeast Wyoming) - Pink to yellow siltstone and shale. Deadwood Formation (Northeast Wyoming) - Red and brown quartzitic sandstone. Paleozoic Rocks, undifferentiated (Thrust Belt).

Wagon Bed Formation (Eocene) at surface, covers 0.2 % of this area

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.

Mafic intrusive rocks (Late Archean) at surface, covers 0.2 % of this area

Mafic intrusive rocks

Green River Formation - Luman Tongue (Eocene) at surface, covers 0.2 % of this area

Oil shale, carbonaceous shale, and sandstone.

Madison Limestone or Group (Lower Mississippian-Upper Mississippian) at surface, covers 0.2 % of this area

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

Wells and Amsden Formations, Casper Formation, and Madison Limestone (Upper Mississippian-Permian) at surface, covers 0.2 % of this area

Wells Formation (Thrust Belt) - Gray limestone interbedded with yellow limy sandstone. Amsden Formation (Thrust Belt) - Red and gray cherty limestone and shale, sandstone, and conglomerate. Casper Formation (North and South Wyoming) - 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 (North and South Wyoming) - Includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite).

Metamorphosed mafic and ultramafic rocks (Late Archean) at surface, covers 0.2 % of this area

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.

Shear zone (Archean) at surface, covers 0.2 % of this area

Shear zone

Mesozoic and Paleozoic rocks (Upper Mississippian-Lower Cretaceous) 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 (JTRn) (South) - Gray to dull-red, massive to coarsely crossbedded quartz sandstone.

Cloverly and Morrison Formations or Inyan Kara Group (Upper Jurassic-Lower Cretaceous) at surface, covers 0.1 % of this area

Cloverly Formation (North and South Wyoming) - Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. Cloverly Formation (Northeast Wyoming - Hartville Uplift) - Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. Morrison Formation (North and South Wyoming) - Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. Morrison Formation (Northeast Wyoming) - dully variegated siliceous claystone, nodular white limestone, and gray silty sandstone. Inyan Kara Group (Northeast - Black Hills) - Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. Includes Fall River and Lakota Formations.

Battle Spring Formation (Paleocene-Eocene) at surface, covers < 0.1 % of this area

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.

Coalmont Formation (Paleocene-Eocene) at surface, covers < 0.1 % of this area

Tan to gray arkosic micaceous soft sandstone, claystone, and locally derived conglomerate.

Gallatin Limestone, Gros Ventre Formation and equivalents, Flathead Sandstone, and Cambrian Rocks (Middle Cambrian-Upper Cambrian) at surface, covers < 0.1 % of this area

Gallatin Limestone (North Wyoming) - Blue-gray and yellow mottled hard dense limestone. Gros Ventre Formation (North Wyoming) - 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 (North Wyoming) - 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.

Quartz diorite (Early Proterozoic) at surface, covers < 0.1 % of this area

Sierra Madre--Encampment River Granodiorite 4; age 1,800 Ma. Medicine Bow Mountains--Keystone Quartz Diorite 5. Hartville uplift--Diorite of Twin Hills 6.

Fox Hills Sandstone and Lewis Shale (Upper Cretaceous) at surface, covers < 0.1 % of this area

Fox Hills Sandstone (Kfh) - Light-colored sandstone and gray sandy shale containing marine fossils. Lewis Shale (Kle) - Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.

Sundance Formation (Middle Jurassic-Upper Jurassic) at surface, covers < 0.1 % of this area

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

Fox Hills Sandstone (Upper Cretaceous) at surface, covers < 0.1 % of this area

Light-colored sandstone and gray sandy shale containing marine fossils.

Metasedimentary rocks (Late Archean) at surface, covers < 0.1 % of this area

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.

Sandstone and Conglomerate (Oligocene-Miocene) at surface, covers < 0.1 % of this area

Gray hard coarse-grained sandstone and conglomerate.

Lower Miocene Rocks (Lower Miocene) at surface, covers < 0.1 % of this area

Northwest Wyoming (Bighorn Mountains): Gray soft poorly bedded to massive sandstone; Central Wyoming: Tuffaceous sandstone, siltstone, and white marl.

Conglomerate (Miocene-Pleistocene) at surface, covers < 0.1 % of this area

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.

Basalt flows and intrusive igneous rocks (Miocene) at surface, covers < 0.1 % of this area

Basalt flows and intrusive igneous rocks

Undivided surficial deposits (Pleistocene-Holocene) at surface, covers < 0.1 % of this area

Mostly alluvium, colluvium, and glacial and landslide deposits. Primarily in Yellowstone area and Bighorn Mountains.

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

Chiefly clay, silt, and fine sand. Includes travertine deposits.

Washakie Formation (Eocene) at surface, covers < 0.1 % of this area

Gray, green, tan, and dull-red tuffaceous arkosic sandstone and claystone.

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

In Laramie Mountains.

Cody Shale and Frontier Formation (Late Cretaceous) at surface, covers < 0.1 % of this area

(North and South Wyoming) - Cody Shale (Kc2) - Dull-gray shale, gray siltstone, and fine-grained gray sandstone. Frontier Formation (Kf2) - Gray sandstone and sandy shale.