Geologic units in Moffat county, Colorado

Browns Park Fm (Tertiary) at surface, covers 17 % of this area

Sandstone and siltstone; west of Park Range

Wasatch Fm (Tertiary) at surface, covers 13 % of this area

Claystone, shale, and sandstone

Wasatch Fm--Cathedral Bluffs Tongue (Tertiary) at surface, covers 11 % of this area

Claystone, mudstone, and sandstone; in Sand Wash basin

Mancos Shale (Cretaceous) at surface, covers 7 % of this area

In northwest and west-central: Intertongues complexly with units of overlying Mesaverde Group or Fm; 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. In Southwest: Lower part contains Juana Lopez Member (Kmj)

Williams Fork Fm (Cretaceous) at surface, covers 6 % of this area

Sandstone, shale, and major coal beds

Uinta Mountain Group (Middle Proterozoic) at surface, covers 5 % of this area

Quartzite, conglomerate, and shale

Green River Fm--Laney Member (Tertiary) at surface, covers 4 % of this area

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

Modern alluvium (Quaternary) at surface, covers 4 % of this area

Includes Piney Creek Alluvium and younger deposits

Bridger Fm (Tertiary) at surface, covers 4 % of this area

Claystone and mudstone; in Sand Wash basin

Fort Union Fm (Tertiary) at surface, covers 3 % of this area

Shale, sandstone, and local coal beds

Morgan Fm and Round Valley Limestone (Pennsylvanian) at surface, covers 3 % of this area

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

Iles Fm (Cretaceous) at surface, covers 3 % of this area

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

Weber Sandstone (Permian-Pennsylvanian) at surface, covers 3 % of this area

Weber Sandstone

Green River Fm--Tipton Tongue (Tertiary) at surface, covers 2 % of this area

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

Glen Canyon Sandstone (Jurassic-Triassic) at surface, covers 2 % of this area

Glen Canyon Sandstone; In northwest

Lewis Shale (Cretaceous) at surface, covers 1 % of this area

Lewis Shale

Madison Limestone (Mississipian) at surface, covers 1 % of this area

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

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

Shale, sandstone, and minor coal beds; Fox Hills equivalent at base

Green River Fm--Luman Tongue (Tertiary) at surface, covers 1 % of this area

Carbonaceous shale and marlstone; in Sand Wash basin

Wasatch Fm--Niland Tongue (Tertiary) at surface, covers 1 % of this area

Mudstone, sandstone, and carbonaceous shale; in Sand Wash basin

Morrison, Curtis, and Entrada Fms (Jurassic) at surface, covers 1.0 % of this area

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

Frontier Sandstone and Mowry Shale Members of Mancos Shale, and Dakota Sandstone (Cretaceous) at surface, covers 0.8 % of this area

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

Green River Fm (Tertiary) at surface, covers 0.8 % of this area

Marlstone, sandstone, and oil shale

Madison Limestone and Lodore Fm (Mississipian-Cambrian) at surface, covers 0.7 % of this area

Madison Limestone and Lodore Fm

Chinle, Moenkopi, and Park City Fms (Triassic-Permian) at surface, covers 0.6 % of this area

Red and gray siltstone, shale, and sandstone

Older gravels and alluviums (Quaternary) at surface, covers 0.5 % of this area

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

Landslide deposits (Quaternary) at surface, covers 0.4 % of this area

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

Mesaverde Group or Fm--Upper part (Cretaceous) at surface, covers 0.4 % 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

Lodore Fm (Cambrian) at surface, covers 0.4 % of this area

Sandstone, shale, and conglomerate

Gravels and alluviums (Quaternary) at surface, covers 0.4 % of this area

Includes Broadway and Louviers Alluviums

Park City Fm (Permian) at surface, covers 0.3 % of this area

Calcareous siltstone and sandstone

Eolian deposits (Quaternary) at surface, covers 0.3 % of this area

Includes dune sand and silt and Peoria Loess

Sego Sandstone, Buck Tongue of Mancos Shale, and Castlegate Sandstone (Cretaceous) at surface, covers 0.3 % of this area

Sego Sandstone, Buck Tongue of Mancos Shale, and Castlegate Sandstone

Moenkopi Fm (Triassic) at surface, covers 0.2 % of this area

Red siltstone, mudstone, sandstone, and local gypsum

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

Mainly of intermediate compositions

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

Curtis is absent along Grand Hogback

Mesaverde Fm, undivided (Cretaceous) at surface, covers 0.1 % 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.

Chinle Fm (Triassic) at surface, covers 0.1 % of this area

Red siltstone, sandstone, and limestone-pellet conglomerate

Green River Fm--Lower Part (Tertiary) at surface, covers < 0.1 % of this area

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

Oligocene sedimentary rocks (Tertiary) at surface, covers < 0.1 % 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 (limestone tuff, tuffaceous sandstone, and conglomerate). Southwest: includes Creede Fm (tuffaceous siltstone, sandstone, conglomerate) and gravels interbedded with volcanic rocks northeast and southeast of Gunnison

Minturn Fm in west-central and south-central and other units (Pennsylvanian) at surface, covers < 0.1 % 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.

Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Tertiary) at surface, covers < 0.1 % of this area

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

Green River Fm--Parachute Creek Member (Tertiary) at surface, covers < 0.1 % of this area

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

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

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

Morrison Fm (Jurassic) at surface, covers < 0.1 % of this area

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

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

Intermediate to felsic compositions

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Mississippian-Cambrian) at surface, covers < 0.1 % of this area

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite

Alluvium and Colluvium (Pleistocene-Holocene) at surface, covers < 0.1 % of this area

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

Uinta Mountain Group (including Red Pine Shale) (Proterozoic Y) at surface, covers < 0.1 % of this area

Uinta Mountain Group (24,000 feet thick along the Green River). Red Pine Shale (950 my).

Morgan Formation and Round Valley Limestone (Pennsylvanian) at surface, covers < 0.1 % of this area

Morgan Formation and Round Valley Limestone.

Red Creek Quartzite (Late 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

Bishop Conglomerate (Oligocene) at surface, covers < 0.1 % of this area

Bishop Conglomerate.

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

Mainly Lower Cretaceous, Jurassic, and Triassic Fms

Miocene Rocks (Miocene) at surface, covers < 0.1 % 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.

Madison Limestone (Mississippian) at surface, covers < 0.1 % of this area

Madison Limestone.

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

Alluvium and colluvium

Green River Formation - Luman Tongue (Eocene) at surface, covers < 0.1 % of this area

Oil shale, carbonaceous shale, and sandstone.

Mesaverde Group (Late Cretaceous) at surface, covers < 0.1 % of this area

Mesaverde Group.

Mesaverde Formation or Mesaverde Group (Upper Cretaceous) 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.

Lodore Sandstone (Early to Middle Cambrian) at surface, covers < 0.1 % of this area

Lodore Sandstone.

Wasatch Formation - Cathedral Bluffs Tongue (Eocene) at surface, covers < 0.1 % of this area

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

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

Older alluvial deposits

Wasatch Formation - Niland Tongue (Eocene) at surface, covers < 0.1 % of this area

Brown sandstone, carbonaceous shale, and coal.

Fort Union Formation (Paleocene) at surface, covers < 0.1 % 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.

Green River Formation - Laney Member (Eocene) at surface, covers < 0.1 % of this area

Oil shale and marlstone.

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

Landslides

Browns Park Formation (Miocene) at surface, covers < 0.1 % of this area

Browns Park Formation.

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

Morrison Formation (Dinosaur National Monument).

Weber Sandstone (Pennsylvanian to Permian) at surface, covers < 0.1 % of this area

Weber Sandstone.

Dakota and Cedar Mountain Formations (Cretaceous) at surface, covers < 0.1 % of this area

Dakota and Cedar Mountain Formations.

Mancos Shale, Frontier Ss, and Mowry Shale (Late Cretaceous) at surface, covers < 0.1 % of this area

Mancos Shale (Hilliard Shale and Blair Formation north of Uinta Mountains), Frontier Ss, and Mowry Shale.

Curtis Fm, Entrada Ss, and Carmel Fm (Middle to Late Jurassic) at surface, covers < 0.1 % of this area

Curtis Fm, Entrada Ss, and Carmel Fm.

Green River Formation - Tipton Shale Member or Tongue (Eocene) at surface, covers < 0.1 % of this area

Oil shale and marlstone.

Park City Formation (Permian) at surface, covers < 0.1 % of this area

Park City Formation.

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

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

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

Basalt flows and intrusive igneous rocks

Green River Formation - Wilkins Peak Member (Eocene) at surface, covers < 0.1 % of this area

Green, brown, and gray tuffaceous sandstone, shale, and marlstone; contains evaporites in subsurface sections.