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Geologic units in Colorado (state in United States)

Additional scientific data in this geographic area

Eolian deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 12 % of this area

Includes dune sand and silt and Peoria Loess

Lithology: dune sand; silt; loess

Ogallala Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 4 % of this area

Loose to well-cemented sand and gravel

Lithology: sandstone; conglomerate

Gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 4 % of this area

Includes Broadway and Louviers Alluviums

Lithology: gravel; alluvium

Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 3 % of this area

Intertongues complexly with units overlying Mesaverde Group or Formation; lower part consists of a calcareous Niobrara equivalent and Frontier Sandstone and Mowry Shale Members; in areas where the Frontier and Mowry Members (Kmfm), or these and the Dakota Sandstone (Kfd) are distinguished, map unit (Km) consists of shale above Frontier Member

Lithology: shale; sandstone

Older gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 3 % of this area

Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest

Lithology: gravel; alluvium

Modern alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 3 % of this area

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

Felsic and hornblendic gneisses, either separate or interlayered (Proterozoic | Paleoproterozoic) at surface, covers 3 % of this area

Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks

Dakota Sandstone and Purgatoire Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 3 % of this area

Sandstone and shale

Lithology: sandstone; shale

Biotitic gneiss, schist, and migmatite (Proterozoic | Paleoproterozoic) at surface, covers 3 % of this area

Locally contains minor hornblende gneiss, calc-silicate rock, quartzite, and marble. Derived principally from sedimentary rocks

Granitic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 2 % of this area

Includes Boulder Creek -M.Y. AGE GROUP (AGE 1650-1730 M.Y.)--Includes Boulder Creek, Cross Creek, Denny Creek, Kroenke, Browns Pass, Powderhorn, Pitts Meadow, Bakers Bridge, and Tenmile Granites, Quartz Monzonites, or Granodiorites;

Unclassified surficial deposits and underlying Alamosa Fm in San Luis Valley (Phanerozoic | Cenozoic | Tertiary Quaternary) at surface, covers 2 % of this area

Alamosa Fm: gravel, sand, silt

Lithology: alluvium

Glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 2 % of this area

Includes some unclassified glacial deposits

Lithology: glacial drift

Pierre Shale--Upper unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Lithology: shale

Carlile Shale, Greenhorn Limestone, and Graneros Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Lithology: shale; limestone

Browns Park Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 2 % of this area

Sandstone and siltstone; west of Park Range

Lithology: sandstone; siltstone

Granitic rocks of 1400-m.y. age group (Proterozoic | Mesoproterozoic) at surface, covers 2 % of this area

Includes Silver Plume, Sherman, Cripple Creek, St. Kevin, Vernal Mesa, Curecanti, Eolus, and Trimble Granites or Quartz Monzonites; also, San Isabel Granite of Boyer (1962) and unnamed granitic rocks

White River Fm or Group (Phanerozoic | Cenozoic | Tertiary) at surface, covers 2 % of this area

East: Ashy claystone and sandstone. Includes Castle Rock Conglomerate in region southeast of Denver. Northwest: Ashy claystone in North Park

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

Locally includes talus, rock-glacier, and thick colluvial deposits

Lithology: landslide; talus; colluvium

Ash-flow tuff of main volcanic sequence (Phanerozoic | Cenozoic | Tertiary) at surface, covers 2 % of this area

Includes many named units

Lithology: ash-flow tuff

Niobrara Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1 % of this area

Calcareous shale and limestone

Lithology: shale; limestone

Pierre Shale, undivided (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1 % of this area

Lithology: shale

Dakota Sandstone and Burro Canyon Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1 % of this area

Sandstone, shale, and conglomerate. In northwest and west-central: Lower Cretaceous. In southwest: Lower and Upper Cretaceous.

Denver Fm or lower part of Dawson Arkose (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 1 % of this area

Arkosic sandstone, shale, mudstone, conglomerate, and local coal beds

Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary) at surface, covers 1 % of this area

Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences

Uinta Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 1 % of this area

Sandstone and siltstone; in Piceance basin. Formerly Evacuation Creek Member of Green River Fm

Lithology: sandstone; siltstone

Pierre Shale--Middle unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1 % of this area

In Boulder-Fort Collins area, contains Richard, Larimer, Rocky Ridge, Terry, and Hygiene Sandstone Members; elsewhere shale between zones of Baculites reesidei and B. scotti

Lithology: shale; sandstone

Laramie Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1.0 % of this area

Shale, claystone, sandstone, and major coal beds

Lithology: shale; claystone; sandstone; coal

Coalmont Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 1.0 % of this area

Arkosic sandstone, conglomerate, and shale; coal in lower part; in North Park

Williams Fork Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 1.0 % of this area

Sandstone, shale, and major coal beds

Lithology: sandstone; shale; coal

Wasatch Fm (including Fort Union equivalent at base) and Ohio Creek Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.9 % of this area

Claystone, mudstone, sandstone, and conglomerate

Middle Tertiary intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.9 % of this area

Intermediate to felsic compositions

Rocks of Pikes Peak Batholith (1000-m.y. age group) (Proterozoic | Mesoproterozoic) at surface, covers 0.9 % of this area

Includes Pikes Peak, Mount Rosa, Windy Point, and Redskin Granites and unnamed rocks

Morrison Fm, Summerville Fm, and Entrada Sandstone (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.8 % of this area

Summerville Fm: Shale and siltstone

Lithology: mudstone; sandstone

Pierre Shale--Lower unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.8 % of this area

Sharon Springs Member (organic-rich shale and numerous bentonite beds) in lower part

Lithology: shale; bentonite

Wasatch Fm--Cathedral Bluffs Tongue (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.8 % of this area

Claystone, mudstone, and sandstone; in Sand Wash basin

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.7 % of this area

Includes several named units

Maroon Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.7 % of this area

Arkosic sandstone, siltstone, conglomerate, and local limestone

Green River Fm--Lower Part (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.6 % of this area

Shale, sandstone, marlstone, and limestone in Anvil Points, Garden Gulch, and Douglas Creek Members; in Piceance basin

Lithology: mudstone; shale; sandstone

Raton Fm (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.6 % of this area

Arkosic sandstone, siltstone, and shale; contains major coal deposits in Raton Basin

Lithology: sandstone; mudstone; coal

Kayenta Fm, Wingate Sandstone, and Chinle Fm (Phanerozoic | Mesozoic | Triassic) at surface, covers 0.6 % of this area

Kayenta Fm: red siltstone, shale, and sandstone. Chinle Fm: red siltstone and sandstone

Lithology: sandstone; siltstone; shale

Mesaverde Fm, undivided (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.6 % of this area

In northwest and west-central: Major coal beds in lower part; Rollins Sandstone Member at base in Delta, Gunnison, and Pitkin Counties. In southwest: sandstone and shale.

Lithology: sandstone; shale; coal

Upper part of Dawson Arkose (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.6 % of this area

Arkosic sandstone, conglomerate, and shale. Includes Green Mountain Conglomerate south of Golden

Santa Fe Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.6 % of this area

Siltstone, sandstone, and conglomerate

Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.5 % of this area

Lithology: sandstone

Cliff House Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.5 % of this area

Lithology: sandstone

Intra-ash flow andesitic lavas (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.5 % of this area

Lithology: andesite

Wasatch Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.5 % of this area

Claystone, shale, and sandstone

Lithology: claystone; shale; sandstone

Lewis Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.4 % of this area

Lithology: shale

Colorado Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.4 % of this area

Consists of Niobrara Formation (Kn) and either Benton Shale or Carlile, Greenhorn, and Graneros Fms (Kcg)

Lithology: shale; limestone

Minturn Fm in west-central and south-central and other units (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.4 % of this area

Arkosic sandstone, conglomerate, shale, and limestone. Includes Madera Fm and Sharpsdale Fm of Chronic (1958) in Sangre de Cristo Range and Gothic Fm of Langenheim (1952) in Elk Mountains. Other units of Middle Pennsylvanian age.

Granitic rocks of 1400- and 1700-m.y. age groups, undivided, or, in Taylor River region, rocks with characteristics of Xg but U-Th-Pb zircon ages of Yg (Proterozoic | Paleoproterozoic Mesoproterozoic) at surface, covers 0.4 % of this area

Granitic rocks of 1400- and 1700-m.y. age groups, undivided, or, in Taylor River region, rocks with characteristics of Xg but U-Th-Pb zircon ages of Yg

Lithology: granitoid

San Jose Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.4 % of this area

Siltstone, shale, and sandstone

Lithology: siltstone; shale; sandstone

Green River Fm--Parachute Creek Member (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.4 % of this area

Parachute Creek Member--Oil shale, marlstone, and siltstone; in Piceance basin

Lithology: mudstone; shale; oil shale

Iles Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.4 % of this area

Sandstone and shale. Trout Creek Sandstone Member at top; coal beds in upper half

Lithology: sandstone; shale; coal

Uinta Mountain Group (Proterozoic | Mesoproterozoic) at surface, covers 0.4 % of this area

Quartzite, conglomerate, and shale

Eagle Valley Fm - evaporitic facies (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.4 % of this area

Gypsum, siltstone, and shale; salt present in deep borings. Intertongues with Minturn and Lower Maroon Fms. Diapiric structure in many places

Lithology: siltstone; shale; evaporite

Pictured Cliffs Sandstone and Lewis Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.4 % of this area

Lithology: sandstone; shale

Animas Fm (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.4 % of this area

Arkosic sandstone, shale, and conglomerate; contains abundant volcanic materials; Upper Cretaceous volcaniclastic McDermott Member at base

Laramide intrusive rocks (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.4 % of this area

Mainly intermediate to felsic compositions; some mafic

Lithology: granitoid

Morrison, Wanakah, and Entrada Fms (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.3 % of this area

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous) at surface, covers 0.3 % of this area

Lithology: limestone; quartzite

Minturn and Belden Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.3 % of this area

Cutler Fm (Phanerozoic | Paleozoic | Permian) at surface, covers 0.3 % of this area

Arkosic sandstone, siltstone, and conglomerate

Intra-ash flow quartz latitic lavas (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % of this area

Lithology: quartz latite

Green River Fm--Laney Member (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % of this area

Claystone, oil shale, and sandstone; in Sand Wash basin

Rico and Hermosa Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.3 % of this area

Arkosic sandstone, conglomerate, shale, and limestone. Includes at base in some areas siltstone and shale of Molas Fm or Larsen Quartzite

Bridger Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % of this area

Claystone and mudstone; in Sand Wash basin

Lithology: mudstone; claystone

Poison Canyon Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % of this area

Arkosic conglomerate, sandstone, and shale

Weber Sandstone and Maroon Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.3 % of this area

Dry Union Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % of this area

Siltstone, sandstone, and conglomerate. Includes Wagontongue Fm (Miocene) in South Park

Troublesome Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % of this area

Sandstone and siltstone; in Middle Park

Lithology: sandstone; siltstone

Sangre de Cristo Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.3 % of this area

Arkosic conglomerate, sandstone, and siltstone

Dakota Sandstone or Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.3 % of this area

Lithology: sandstone

Fort Union Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Shale, sandstone, and local coal beds

Lithology: shale; sandstone; coal

Oligocene sedimentary rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Northwest: includes Duchesne River Fm (sandstone and shale; includes some rocks of Eocene age) and Bishop Conglomerate near Utah border. South-central: includes Florissant Lake Beds (tuffaceous shale and tuff) and Antero Fm (lime

Volcanic rocks in northwestern Colorado (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Mainly of intermediate compositions

Morgan Fm and Round Valley Limestone (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.2 % of this area

Morgan Fm: limestone, sandstone, and shale. In far northwest.

Lithology: limestone; sandstone; shale

Cuchara Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Sandstone and shale

Lithology: sandstone; shale

Hunter Canyon Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.2 % of this area

Sandstone and shale

Lithology: sandstone; shale

Huerfano Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Shale and sandstone. Includes Farisita Conglomerate in northwestern Huerfano County

Older glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.2 % of this area

Lithology: glacial drift

Mesaverde Group or Fm--Upper part (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.2 % of this area

In Moffat and Rio Blanco Counties, sandstone, shale, and coal beds above Sego Sandstone. Along Grand Hogback south of Colorado River, sandstone and shale above coal-bearing sequence

Lithology: sandstone; shale; coal

Leadville Limestone, Gilman Sandstone, Dyer Dolomite, and Parting Fm (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian) at surface, covers 0.2 % of this area

Parting Fm: quartzite and shale.

Weber Sandstone (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.2 % of this area

Lithology: sandstone

Dakota, Morrison, and Sundance Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers 0.2 % of this area

Lithology: sandstone; mudstone

Mount Garfield Fm and Sego Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.2 % of this area

Sandstone and shale; major coal beds in lower part of Mount Garfield

Lithology: sandstone; shale; coal

Laramie Fm and Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.2 % of this area

Lithology: sandstone; mudstone; coal

Glen Canyon Group and Chinle Fm (Phanerozoic | Mesozoic | Triassic Jurassic) at surface, covers 0.2 % of this area

In southwest, Glen Canyon Group consists of Navajo Sandstone, Kayenta Fm (red siltstone, shale, and sandstone) and Wingate Sandstone; Chinle is red siltstone

Lithology: sandstone; siltstone; shale

Morrison, Ralston Creek, and Entrada (or Exeter) Fms (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.2 % of this area

Lithology: mudstone; sandstone

Green River Fm--Tipton Tongue (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Claystone and oil shale; in Sand Wash basin. In extreme northwest includes rocks of Wilkins Peak Member

Lithology: claystone; oil shale

Fountain Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.2 % of this area

Arkosic sandstone and conglomerate

Lithology: sandstone; conglomerate

Denver and Arapahoe Fms (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.2 % of this area

Sandstone, mudstone, claystone, and conglomerate; Denver is characterized by andesitic materials

Vermejo Fm and Trinidad Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.2 % of this area

Shale, sandstone, and major coal beds; sandstone

Lithology: sandstone; shale; coal

North Park Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area

Sandstone, siltstone, and conglomerate; in North Park and Laramie basin

State Bridge Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers 0.2 % of this area

Red and orange siltstone and sandstone

Lithology: siltstone; sandstone

Chinle And State Bridge Fms (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers 0.2 % of this area

Red siltstone and sandstone

Lithology: siltstone; sandstone

Belden Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.1 % of this area

Shale, limestone, and sandstone. Includes Kerber Fm in south-central

Lithology: shale; limestone; sandstone

Ingleside Fm and Fountain Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.1 % of this area

Ingleside Fm: Limestone and calcareous sandstone. Fountain Fm: arkosic sandstone and conglomerate

Los Pinos Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.1 % of this area

Volcaniclastic conglomerate interbedded with basalt flows of Hinsdale Fm (Tbb) on east flank of San Juan Mountains. Grades laterally into Santa Fe Fm of San Luis Valley

Mafic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers 0.1 % of this area

Gabbro and mafic diorite and monzonite

Lithology: gabbro; diorite; monzonite

Evaporitic facies of Minturn And Belden Fms in South Park and southward (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.1 % of this area

Gypsum, siltstone, and shale

Lithology: siltstone; shale; evaporite

Frontier Sandstone and Mowry Shale Members of Mancos Shale, and Dakota Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.1 % of this area

Locally includes, at base, Burro Canyon Fm (shale and sandstone) or, in western Moffat County, Cedar Mountain Fm (conglomerate and shale)

South Park Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.1 % of this area

Arkosic sandstone and shale, volcaniclastic conglomerate, and andesite flows and breccia

Dakota, Burro Canyon, Morrison, and Junction Creek Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers 0.1 % of this area

Burro Canyon is locally absent

Lithology: sandstone; mudstone; shale

Dockum Group (Phanerozoic | Mesozoic | Triassic) at surface, covers 0.1 % of this area

Red sandstone, siltstone, and local limestone

Glen Canyon Sandstone (Phanerozoic | Mesozoic | Triassic Jurassic) at surface, covers 0.1 % of this area

In northwest

Lithology: sandstone

Leadville Limestone, Williams Canyon Limestone, and one or more of: Fremont Limestone, Harding Sandstone, and Manitou Limestone (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian(?) Carboniferous Mississippia) at surface, covers 0.1 % of this area

Lithology: limestone; sandstone

Morrison Fm (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.1 % of this area

Variegated claystone, mudstone, sandstone, and local beds of limestone

Pierre Shale (Kp), Niobrara (Kn), and Carlile, Greenhorn, and Graneros (Kcg) Fms, undivided (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 0.1 % of this area

Lithology: shale; limestone

Morrison, Curtis, and Entrada Fms (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.1 % of this area

In extreme southwestern Moffat County, includes thin wedge of Carmel Fm (red siltstone and sandstone) beneath Entrada

Lithology: mudstone; sandstone

Jelm, Lykins, Lyons, and Satanka Fms (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Red siltstone, shale, and sandstone

Sego Sandstone, Buck Tongue of Mancos Shale, and Castlegate Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Lithology: sandstone; shale

Moenkopi Fm and Cutler Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Red siltstone and sandstone

Lithology: siltstone; sandstone

Nacimiento Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Shale and sandstone

Lithology: shale; sandstone

Kirtland Shale and Fruitland Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Shale, sandstone, and major coal beds

Lithology: shale; sandstone; coal

Madison Limestone (Phanerozoic | Paleozoic | Carboniferous Mississippian) at surface, covers < 0.1 % of this area

Upper part includes equivalents of Upper Mississippian Doughnut and Humbug Fms (shale, limestone, and sandstone)

Lithology: limestone; shale; sandstone

Ancient alluvium (Phanerozoic | Cenozoic | Tertiary Quaternary) at surface, covers < 0.1 % of this area

In isolated patches that may not all be of the same age

Lithology: alluvium

Dolores Fm (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Red siltstone, shale, sandstone, and limestone-pellet conglomerate

Morrison, Curtis, Entrada, and Glen Canyon Fms (Phanerozoic | Mesozoic | Triassic Jurassic) at surface, covers < 0.1 % of this area

Curtis is absent along Grand Hogback

Lithology: mudstone; sandstone

Green River Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Marlstone, sandstone, and oil shale

Lithology: mudstone; shale; sandstone

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

South-central: Arkosic sand and bouldery gravel of Echo Park Alluvium. Southwest: includes Telluride Conglomerate and Blanco Basin Fm (arkosic mudstone, sandstone, and conglomerate)

Uncompahgre Fm (Proterozoic | Paleoproterozoic Mesoproterozoic) at surface, covers < 0.1 % of this area

Quartzite, slate, and phyllite

Lithology: quartzite; slate; phyllite

Green River Fm--Luman Tongue (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Carbonaceous shale and marlstone; in Sand Wash basin

Lithology: shale; mudstone

Leadville, Gilman, Dyer, Parting, and Sawatch Fms in west-central and south-central. Leadville Limestone, Ouray Limestone, Elbert Fm, and Ignacio Quartzite in far southwest (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous) at surface, covers < 0.1 % of this area

Elbert Fm: shale and sandstone.

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

Ash-flow tuff of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lithology: ash-flow tuff

Triassic and Permian rocks (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Red siltstone, shale, and sandstone. Includes various combinations of Nugget, Jelm, Popo Agie, Chugwater, Red Peak, Forelle, Satanka, and Goose Egg Fms near Wyoming border

Lithology: siltstone; shale; sandstone

Wall Mountain Tuff (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Early ash-flow tuff of Sawatch Range provenance

Lithology: ash-flow tuff

Arikaree Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Sandstone; contains abundant volcanically derived material

Wingate Sandstone and Chinle Fm (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Bouldery gravel on old erosion surfaces in Front Range and Never Summer Mountains (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lithology: gravel

Mesozoic rocks (Lower Phanerozoic | Mesozoic | Cretaceous-Triassic) at surface, covers < 0.1 % of this area

Mainly Lower Cretaceous, Jurassic, and Triassic Fms

Lithology: clastic

Madison Limestone and Lodore Fm (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous) at surface, covers < 0.1 % of this area

Chinle Fm (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Red siltstone, sandstone, and limestone-pellet conglomerate

Upper Tertiary intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Intermediate to felsic compositions

Eagle Valley Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers < 0.1 % of this area

Siltstone, shale, and local gypsum

Lithology: siltstone; shale; evaporite

Mancos Shale--Juana Lopez Member (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Calcareous sandstone; a thin but persistent unit distinguished only locally

Lithology: sandstone; shale

Dakota and Morrison Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers < 0.1 % of this area

Lithology: sandstone; mudstone; shale

Chinle, Moenkopi, and Park City Fms (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Red and gray siltstone, shale, and sandstone

Lithology: siltstone; shale; sandstone

Quartzite, conglomerate, and interlayered mica schist (Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area

Quartzite, conglomerate, and interlayered mica schist

Intrusive rocks (Phanerozoic | Paleozoic | Cambrian) at surface, covers < 0.1 % of this area

Alkalic and mafic intrusive rocks in small plutons, and diabase dikes

Lithology: diabase

One or more Ordovician fms (Phanerozoic | Paleozoic | Ordovician) at surface, covers < 0.1 % of this area

Fremont Limestone, Harding Sandstone, and Manitou Limestone

Lithology: limestone; sandstone

Menefee Fm and Point Lookout Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

sandstone, shale, and coal; sandstone

Lithology: sandstone; shale; coal

Hermosa Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers < 0.1 % of this area

Arkosic sandstone, conglomerate, shale, and limestone; gypsum and salt in Paradox Member present in salt anticlines near Utah border

Rhyolitic intrusive rocks and flows of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lithology: rhyolite

Manitou Limestone and Sawatch Quartzite in Southern Front Range and Wet Mountains. One or more Ordovician Fms (Fremont Limestone, Harding Sandstone, and Manitou Dolomite), Dotsero Fm, Peerless Fm, and Sawatch Quartzite in west-ce (Phanerozoic | Paleozoic | Cambrian Ordovician) at surface, covers < 0.1 % of this area

Dotsero Fm: Dolomite, in White River plateau only. Peerless Fm: sandstone and dolomite.

Morrison Fm and Junction Creek Sandstone (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

In Gunnison River area east of wedgeout of all units of Wanakah Fm (Jmw) except the Junction Creek Member

Lithology: mudstone; sandstone

Morrison Fm and Entrada Sandstone (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Lithology: mudstone; sandstone

lower part of Green River Fm and Wasatch Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Shale and sandstone

Lithology: shale; sandstone

Lykins Fm and Lyons Sandstone (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Mancos Shale--Frontier Sandstone and Mowry Shale Members (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Frontier Sandstone and Mowry Shale Members and intervening shale zone

Lithology: sandstone; shale

Windy Gap Member of Middle Park Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Andesitic breccia and conglomerate

Lodore Fm (Phanerozoic | Paleozoic | Cambrian) at surface, covers < 0.1 % of this area

Sandstone, shale, and conglomerate

Chugwater Fm (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Red sandstone, siltstone, shale, and local limestone and gypsum

Park City Fm (Phanerozoic | Paleozoic | Permian) at surface, covers < 0.1 % of this area

Calcareous siltstone and sandstone

Lithology: siltstone; sandstone

Casper Fm and Lower part of Fountain Fm (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers < 0.1 % of this area

Casper Fm: sandstone

Lithology: sandstone; conglomerate

Lykins Lyons and Fountain Fms (Phanerozoic | Paleozoic Mesozoic | Carboniferous Pennsylvanian Permian(?) Triassic) at surface, covers < 0.1 % of this area

Red siltstone, sandstone, and conglomerate

Upper Permian rocks, undivided (Phanerozoic | Paleozoic | Permian) at surface, covers < 0.1 % of this area

Siltstone, dolomite, and sandstone; in southeast

Chinle and Chugwater Fms (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Older eolian deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Includes Loveland Loess

Lithology: dune sand; silt; loess

Mesozoic and Paleozoic rocks (Phanerozoic | Paleozoic Mesozoic | Carboniferous Pennsylvanian) at surface, covers < 0.1 % of this area

Mainly as in Mesozoic unit (MZ) plus Permian and Pennsylvanian Fms

Lithology: clastic

Morrison Fm and Sundance Fm (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Sundance Fm: Sandstone, shale, claystone, and limestone

Mesaverde Group or Fm--Lower part (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Sandstone, shale, and major coal beds

Lithology: sandstone; shale; coal

Morrison, Entrada, and Chinle Fms (Phanerozoic | Mesozoic | Triassic Jurassic) at surface, covers < 0.1 % of this area

Along southern Grand Hogback, Chinle is represented only by basal Gartra Sandstone Member

Lithology: mudstone; sandstone

Morrison and Ralston Creek Fms (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Ralston Creek Fm: Claystone, sandstone, limestone, and gypsum

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.

Moenkopi Fm (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Red siltstone, mudstone, sandstone, and local gypsum

Morrison Fm and Wanakah Fm (Junction Creek Sandstone Member at or near top; Pony Express Limestone Member at base) (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Wanakah Fm: Sandstone, shale, limestone, and local gypsum

Basalt flows (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Lithology: basalt

Dolores Fm and Cutler Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Red siltstone, sandstone, and conglomerate

Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian) at surface, covers < 0.1 % of this area

Locally includes Peerless Fm

Telluride conglomerate of Eocene prevolcanic sedimentary rocks (Te) and Cimarron Ridge Fm (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers < 0.1 % of this area

In northwestern San Juan Mountains. Cimarron Ridge Fm: volcanic breccia and conglomerate.

Dakota, Burro Canyon, Morrison, and Wanakah Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers < 0.1 % of this area

Alkalic and mafic rocks in small plutons, and diabase and gabbro dikes (Proterozoic | Mesoproterozoic) at surface, covers < 0.1 % of this area

Alkalic and mafic rocks in small plutons, and diabase and gabbro dikes

Lithology: granitoid; diabase; gabbro

Loess (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

eolian silts

Lithology: silt

Lykins Fm (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers < 0.1 % of this area

Red siltstone, shale, and limestone

Lithology: siltstone; shale; limestone

Basaltic flows in Denver Fm near Golden (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lithology: basalt

San Jose Formation (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

San Jose Formation; Eocene, San Juan Basin

Basaltic intrusive rocks related to basalt flows (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

In dikes and plugs

Lithology: basalt

Parting, Fremont, and Harding Fms (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian) at surface, covers < 0.1 % of this area

Morrison Fm and Curtis Fm (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Morrison Fm: Variegated claystone, mudstone, sandstone, and local beds of limestone. Curtis Fm: glauconitic sandstone and limestone

Metasedimentary and metavolcanic rocks (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % 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.

Sherman Granite (Proterozoic | Mesoproterozoic (1415-1435 Ma)) at surface, covers < 0.1 % of this area

SHERMAN GRANITE (AGE 1,415 TO 1,435 Ma)--In Medicine Bow and Laramie Mountains.

Lithology: granite

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

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

White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene (31-35 Ma)) at surface, covers < 0.1 % of this area

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

Cretaceous (1) sedimentary rocks in southeastern Utah (Cretaceous) at surface, covers < 0.1 % of this area

Lithology: sandstone; shale

Cliff House Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Cliff House Sandstone; transgressive marine sandstone; Campanian

Lithology: sandstone; shale

Ogallala Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area

massive to cross-bedded, generally arkosic sand, silt and gravel, locally cemented with calcium carbonate; also contains limestone, volcanic ash, diatomaceous marl, opaline sandstone and bentonitic clay

Animas Formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers < 0.1 % of this area

Animas Formation; in northeast San Juan Basin

Lithology: clay or mud; tuff; clastic

Wasatch Formation (SW) (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % 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.

Casper and Fountain Formations (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle Pennsylvanian-Late Permian) at surface, covers < 0.1 % 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

Dakota Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Dakota Group of east-central and northeast New Mexico; in ascending order, Mesa Rica Sandstone, Pajarito Shale, and Romeroville Sandstone; includes the underlying Tucumcari Shale in Tucumcari area and Glencairn Formation in Union County. Encompasses both Upper and Lower Cretaceous rocks

Cretaceous (3) sedimentary rocks in Uinta Mountains-Uinta Basin region (Late Cretaceous) at surface, covers < 0.1 % of this area

Lithology: sandstone; shale; coal

basalt and andesite flows, Neogene (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Basalt and andesite flows; Neogene. Includes flows interbedded with Santa Fe and Gila Groups

Lithology: basalt; andesite

Cloverly, Morrison, and Sundance Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers < 0.1 % 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.

Granitic rocks (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area

GRANITIC ROCKS OF 1,700-Ma AGE GROUP.

Lithology: granitoid

Upper Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene-Late) at surface, covers < 0.1 % 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.

Williams Canyon Limestone, Manitou Limestone, and Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian) at surface, covers < 0.1 % of this area

Lithology: limestone; quartzite

Gravel, pediment, and fan deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % 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.

Quaternary eolian deposits (Quaternary) at surface, covers < 0.1 % of this area

Lithology: eolian

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

Lewis Shale; marine shale and mudstone

Alluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

unconsolidated sand, silt, clay, and gravel

Lithology: gravel; sand; silt; clay or mud

Red Creek Quartzite (Archean) at surface, covers < 0.1 % of this area

Metaquartzite, amphibolite, and mica schist. Present only in small area at Utah border in Uinta Mountains

Triassic and Jurassic sedimentary rocks in southeastern Utah (Early Jurassic) at surface, covers < 0.1 % of this area

Pictured Cliffs Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Pictured Cliffs Sandstone; prominent cliff-forming marine sandstone

Lithology: sandstone; mudstone

Pennsylvanian sedimentary rocks in Uinta Mountains-Uinta Basin region (Pennsylvanian) at surface, covers < 0.1 % of this area

Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % 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.

Quaternary alluvium and colluvium (Quaternary) at surface, covers < 0.1 % of this area

Lithology: alluvium; colluvium

Dune Sand (Phanerozoic | Cenozoic | Quaternary | Pleistocene) at surface, covers < 0.1 % of this area

CIMARRON- Fine- to medium-grained sand 0 to 40 feet thick. TEXAS- Fine to coarse windblown sand. Maximum thickness about 30 feet. BEAVER- Fine to coarse, round to sub-round, windblown sand consisting mostly of quartz grains. 0-50 feet thick

Lithology: sand

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

thin bedded gray to brownish gray shale; contains concretions, selenite crystals, thin beds of bentonite and locally chalky beds.

Lithology: shale

Dune Sand (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

unconsolidated dune sand

Lithology: sand

Alluvium and Colluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

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

Lithology: alluvium; colluvium

Kirtland and Fruitland Formations (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Kirtland and Fruitland Formations; coal-bearing, coal primarily in the Fruitland; Campanian to Maastrichtian

Lithology: sandstone; mudstone; coal

Tertiary (3) sedimentary rocks in Uinta Mountains-Uinta Basin region (Middle Eocene to Early Oligocene) at surface, covers < 0.1 % of this area

landslide deposits and colluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Landslide deposits and colluvium

Lithology: landslide; colluvium

Mesaverde Formation (N) or Mesaverde Group (S) (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % 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.

Tertiary (1) sedimentary rocks in Uinta Mountains-Unita Basin region (Early to Middle Eocene) at surface, covers < 0.1 % of this area

Mesaverde Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Mesaverde Group includes the Gallup Sandstone, Crevasse Canyon Formation, Point Lookout Sandstone, Menefee Formation, and Cliff House Sandstone

Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Mancos Shale; divided into Upper and Lower parts by Gallup Sandstone

Jurassic (1) sedimentary rocks in southeastern Utah (Middle to Late Jurassic) at surface, covers < 0.1 % of this area

Jurassic (2) sedimentary rocks in southeastern Utah (Late Jurassic) at surface, covers < 0.1 % of this area

Poison Canyon Formation (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Poison Canyon Formation; Paleocene, Raton Basin

Lithology: sandstone

Tertiary (4) sedimentary rocks in Uinta Mountains-Uinta Basin region (Oligocene) at surface, covers < 0.1 % of this area

Lithology: conglomerate

Dakota Sandstone (Phanerozoic | Mesozoic | Cretaceous-Early ) at surface, covers < 0.1 % of this area

CIMARRON- Buff to light-brown, fine- to medium-grained, thin bedded to massive sandstone with interbedded shales.

Lithology: sandstone; shale

Older Quaternary alluvial deposits (Quaternary) at surface, covers < 0.1 % of this area

Lithology: alluvium

Cretaceous (2) sedimentary rocks in southeastern Utah (Late Cretaceous) at surface, covers < 0.1 % of this area

Lithology: shale; sandstone; limestone

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

CIMARRON- Varicolored fine-grained sandstone, limestone, dolomite, shale, and conglomerate 0 to 470 +/- feet thick.

Morrison Formation and upper San Rafael Group (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Morrison Formation and upper San Rafael Group

Glacial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

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

Lithology: glacial drift

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

Lower Oligocene and Eocene volcanic rocks, undifferentiated; dominantly intermediate composition, with interbedded volcaniclastic rocks; (31-44 Ma)

Mississippian (1) carbonate rocks in Uinta Mountains-Uinta Basin region (Mississippian) at surface, covers < 0.1 % of this area

Lithology: limestone

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

Tertiary intrusive rocks; undifferentiated

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.

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

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.

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.

Chugwater and Goose Egg Formations (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early(?) Triassic-Middle(?) Triassic-Late) at surface, covers < 0.1 % 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.

Older Precambrian metamorphic rocks in southeastern Utah (Precambrian) at surface, covers < 0.1 % of this area

Raton Formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers < 0.1 % of this area

Raton Formation; in Raton Basin; unit contains conformable K/T boundary

alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Alluvium; upper and middle Quaternary

Lithology: alluvium

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

Menefee Formation; mudstone, shale, and sandstone; coal-bearing

Morrison Formation (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Morrison Formation; Upper Jurassic nonmarine rocks present only in northern one-third of state

Dakota Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Dakota Sandstone; includes Oak Canyon, Cubero, and Paguate Tongues plus Clay Mesa Tongue of Mancos Shale; Cenomanian

Entrada Sandstone (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Entrada Sandstone, Middle Jurassic; Callovian

Lithology: sandstone

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

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

Quaternary landslides (Quaternary) at surface, covers < 0.1 % of this area

Lithology: landslide

Dockum Group (Phanerozoic | Mesozoic | Triassic-Late ) at surface, covers < 0.1 % of this area

CIMARRON- Upper shale unit: Varicolored siltstone or claystone, conglomerate, fine-grained sandstone, and limestone. Lower sandstone unit: Varicolored, fine- to coarse-grained sandstone with some clay and interbedded shale.

Triassic (2) sedimentary rocks in southeastern Utah (Late Triassic) at surface, covers < 0.1 % of this area

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

Ogallala Formation, alluvial and eolian deposits, and petrocalcic soils of the southern High Plains; Lower Pliocene to middle Miocene (locally includes unit Qoa)

Lithology: alluvium; eolian; carbonate

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

Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers < 0.1 % 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

Ogallala Formation (Phanerozoic | Cenozoic | Tertiary | Pliocene) at surface, covers < 0.1 % of this area

CIMARRON- Generally semiconsolidated clay, silt, sand, gravel, and caliche 0 to 400 feet thick. BEAVER- Interbedded sand, siltstone, clay, gravel lenses, and thin limestone. Caliche common near surface but occurrence is not limited to the surface. Caliche accounts for most of the white color in the Ogallala. Other colors generally light tan or buff but locally may be pastel shades of almost any color. The Laverne and Rexroad Formations of Pliocene age and the Meade Group and Odee (of local usage) and other formations of Pleistocene age occur locally and are included with the Ogallala Formation, 0-700 feet thick. WOODWARD- Gravel, sand, silt, clay, caliche, and limestone, locally cemented with calcium carbonate. Generally light-tan to gray to white. Thickness ranges up to 400 feet and probably averages 150 feet. CLINTON- Gray to light-brown, fine- to medium-grained sand with some, clay, silt, gravel, volcanic ash, and caliche beds; locally cemented by calcium carbonate. Thickness ranges from 0 to about 320 feet. The formation thins eastward.

Greenhorn Limestone and Graneros Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Greenhorn FM- thin bedded gray, chalky limestone and calcareous shale. Graneros Shale- fissile, noncalcareous, gray shale locally contains sandstone and siltstone beds.

Permian (1) sedimentary rocks in southeastern Utah (Pennsylvanian to Early Permian) at surface, covers < 0.1 % of this area

Cambrian quartzite in Uinta Mountains-Uinta Basin area (Early to Middle Cambrian) at surface, covers < 0.1 % of this area

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

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

Jurassic (2) sedimentary rocks in Uinta Mountains-Uinta Basin region (Late Jurassic) at surface, covers < 0.1 % of this area

Cretaceous (1) sedimentary rocks in Uinta Mountains-Uinta Basin region (Cretaceous) at surface, covers < 0.1 % of this area

Lithology: sandstone; shale

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

chalky shale with bentonite and thick chalk beds, dark gray fissile shale containing septarian concretions, and fine-grained sandstone.

Lithology: shale; limestone; sandstone

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

CIMARRON- Kiowa Shale Member: Gray to black fossiliferous shale with sandstone in the upper part. Thickness ranges from 0 to 50 +/- feet. Cheyenne Sandstone Member: Massive, white to buff, fine- to medium-grained sandstone, containing some conglomerate in the lower part, from 0 to 120 +/- feet thick.

Chinle Group (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Chinle Group; Upper Triassic; includes Moenkopi Formation (Middle Triassic) at base in many areas; in eastern part of state the following five formations are mapped:

Cretaceous (2) sedimentary rocks in Uinta Mountains-Uinta Basin region (Late Cretaceous) at surface, covers < 0.1 % of this area

Lithology: shale; sandstone

Jurassic (1) sedimentary rocks in Uinta Mountains-Uinta Basin region (Middle to Late Jurassic) at surface, covers < 0.1 % of this area

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

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

sedimentary units, Palogene (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Paleogene sedimentary units; includes Baca, Galisteo, El Rito, Blanco Basin, Love Ranch, Lobo, Sanders Canyon, Skunk Ranch, Timberlake, and Cub Mountain Formations

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

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

Lithology: shale; sandstone

Green River Formation: Wilkins Peak Member (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers < 0.1 % 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.

silicic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lower Oligocene silicic pyroclastic rocks (ash-flow tuffs); includes Hell's Mesa, Kneeling Nun, lower part of Bell Top Formation, Caballo Blanco, Datil Well, Leyba Well, Rock House Canyon, Blue Canyon, Sugarlump and Tadpole Ridge Tuffs, the tuffs of the Organ cauldron, Treasure Mountain Tuff (now known as Chiquito Peak Tuff), Bluff Creek Tuff, Oak Creek Tuff, tuff of Steins Mountain, tuff of Black Bill Canyon, tuff of Farr Ranch, Woodhaul Canyon, Gillespie and Box Canyon Tuffs, Cooney Tuff, and other volcanic and interbedded fluvial and pumiceous units; (31-36.5 Ma)

Graneros Shale and Greenhorn Formation (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Graneros Shale and Greenhorn Formation; limited to northeastern area; lower Turonian and Cenomanian

Lithology: shale; limestone

piedmont alluvial deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Piedmont alluvial deposits: upper and middle Quaternary; includes deposits of higher gradient tributaries bordering major stream valleys, alluvial veneers of the piedmont slope, and alluvial fans

Lithology: alluvium