Geologic units in Albany county, Wyoming

Alluvium and Colluvium (Pleistocene-Holocene) at surface, covers 15 % of this area

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

Granite gneiss (Late Archean) at surface, covers 9 % of this area

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

Granitic rocks of 2,600-Ma Age Group (Late Archean) at surface, covers 8 % 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.

Sherman Granite (Middle Proterozoic) at surface, covers 7 % of this area

In Medicine Bow and Laramie Mountains.

Gravel, pediment, and fan deposits (Pleistocene-Holocene) at surface, covers 6 % of this area

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

Laramide Anorthosite Complex--anorthosite and norite (Middle Proterozoic) at surface, covers 6 % of this area

Anorthosite and norite. In Laramie Mountains.

Metasedimentary and metavolcanic rocks (Early Proterozoic) at surface, covers 4 % 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.

Wind River Formation (Eocene) at surface, covers 4 % 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.

Steele Shale (Upper Cretaceous) at surface, covers 4 % of this area

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

Casper and Fountain Formations (Upper and Middle Pennsylvanian-Permian) at surface, covers 4 % 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. Fountain Formation - Arkose and red sandstone.

Wagon Bed Formation (Eocene) at surface, covers 3 % 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.

Chugwater Formation or Group (Lower Triassic-Upper Triassic) at surface, covers 3 % 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 2 % 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.

Niobrara Formation (Late Cretaceous) at surface, covers 2 % of this area

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

Wells and Amsden Formations, Casper Formation, and Madison Limestone (Upper Mississippian-Permian) at surface, covers 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).

Cloverly, Morrison, and Sundance Formations (Middle Jurassic-Lower Cretaceous) at surface, covers 2 % 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.

Lewis Shale (Upper Cretaceous) at surface, covers 2 % of this area

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

White River Formation (Oligocene) at surface, covers 2 % of this area

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

Laramide Anorthosite Complex--pyroxene and hornblende syenite (Middle Proterozoic) at surface, covers 2 % of this area

Pyroxene and hornblende syenite--Age 1,435 Ma. In Laramie Mountains.

Mesaverde Formation or Mesaverde Group (Upper Cretaceous) 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.

Upper Miocene Rocks (Upper Miocene) at surface, covers 1 % 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.

Mowry and Thermopolis Shales (Lower Cretaceous) at surface, covers 1 % 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.

Hanna Formation (Paleocene) at surface, covers 1 % of this area

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

Goose Egg Formation (Permian-Lower Triassic) at surface, covers 1.0 % of this area

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

Metamorphosed mafic and ultramafic rocks (Late Archean) at surface, covers 0.9 % 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.

Glacial deposits (Pleistocene-Holocene) at surface, covers 0.8 % of this area

Till and outwash of sand, gravel, and boulders.

Casper Formation (Upper and Middle Pennsylvanian-Permian) at surface, covers 0.8 % of this area

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.

Quartz diorite (Early Proterozoic) at surface, covers 0.7 % 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.

Cloverly and Morrison Formations or Inyan Kara Group (Upper Jurassic-Lower Cretaceous) at surface, covers 0.7 % 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.

Mafic intrusive rocks (Early Proterozoic) at surface, covers 0.6 % 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.

Forelle Limestone and Satanka Shale (Permian) at surface, covers 0.5 % of this area

Forelle Limestone - Thin-bedded limestone. Locally is a member of the Goose Egg Formation. Satanka Shale - Red shale.

Metasedimentary rocks - Libby Creek Group (Early Proterozoic) at surface, covers 0.3 % 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.

Metasedimentary and metavolcanic rocks (Middle Archean-Late Archaen) at surface, covers 0.3 % 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.

Granitic rocks of 1,700-Ma Age Group (Early Proterozoic) at surface, covers 0.3 % of this area

Granitic rocks of 1,700-Ma Group

Jelm and Chugwater Formations, Forelle Limestone, and Satanka Shale (Permian-Lower Triassic) at surface, covers 0.3 % of this area

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. Forelle Limestone - Thin-bedded limestone. Locally is a member of the Goose Egg Formation. Satanka Shale - Red shale.

Landslide deposits (Pleistocene-Holocene) at surface, covers 0.3 % of this area

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

Sundance Formation (Middle Jurassic-Upper Jurassic) at surface, covers 0.2 % of this area

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

Metasedimentary rocks (Late Archean) at surface, covers 0.2 % 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.

White River Formation - Upper conglomerate member (Oligocene) at surface, covers 0.2 % of this area

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

Chugwater and Goose Egg Formations (Permian-Upper Triassic) at surface, covers 0.2 % 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.

Medicine Bow Formation (Upper Cretaceous) at surface, covers 0.2 % of this area

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

Lower Miocene and Upper Oligocene rocks or rocks equivalent to Upper and Lower Miocene rocks and White River Formation (Upper Oligocene-Upper Miocene) at surface, covers 0.2 % 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.

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

In Laramie Mountains.

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.

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.

Frontier Formation and Mowry and Thermopolis Shales (Lower Cretaceous-Upper Cretaceous) at surface, covers 0.1 % 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.

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.

Shear zone (Archean) at surface, covers < 0.1 % of this area

Shear zone

Dune sand and loess (Pleistocene-Holocene) at surface, covers < 0.1 % of this area

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

Madison Limestone or Group (Lower Mississippian-Upper Mississippian) at surface, covers < 0.1 % of this area

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

Metasedimentary rocks - Deep Lake Group (Early Proterozoic) at surface, covers < 0.1 % of this area

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

Terrace gravel (Pliocene-Pleistocene) at surface, covers < 0.1 % of this area

Partly consolidated gravel above and flanking some major streams.