Geologic units in Garfield county, Colorado

Wasatch Fm (including Fort Union equivalent at base) and Ohio Creek Fm (Tertiary) at surface, covers 15 % of this area

Claystone, mudstone, sandstone, and conglomerate

Uinta Fm (Tertiary) at surface, covers 10 % of this area

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

Green River Fm--Lower Part (Tertiary) at surface, covers 10 % of this area

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

Green River Fm--Parachute Creek Member (Tertiary) at surface, covers 7 % of this area

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

Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Tertiary) at surface, covers 7 % of this area

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

Landslide deposits (Quaternary) at surface, covers 4 % of this area

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

Hunter Canyon Fm (Cretaceous) at surface, covers 4 % of this area

Sandstone and shale

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-central and south-central (Ordovician-Cambrian) at surface, covers 4 % of this area

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

Belden Fm (Pennsylvanian) at surface, covers 4 % of this area

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

Leadville Limestone, Gilman Sandstone, Dyer Dolomite, and Parting Fm (Devonian-Ordivician) at surface, covers 4 % of this area

Parting Fm: quartzite and shale.

Mancos Shale (Cretaceous) at surface, covers 3 % 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)

Minturn Fm in west-central and south-central and other units (Pennsylvanian) at surface, covers 3 % 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.

Mount Garfield Fm and Sego Sandstone (Cretaceous) at surface, covers 3 % of this area

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

Eagle Valley Fm - evaporitic facies (Pennsylvanian) at surface, covers 2 % of this area

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

Gravels and alluviums (Quaternary) at surface, covers 2 % of this area

Includes Broadway and Louviers Alluviums

Weber Sandstone and Maroon Fm (Permian-Pennsylvanian) at surface, covers 2 % of this area

Weber Sandstone and Maroon Fm

Modern alluvium (Quaternary) at surface, covers 2 % of this area

Includes Piney Creek Alluvium and younger deposits

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

Includes some unclassified glacial deposits

Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Mississippian-Cambrian) at surface, covers 2 % of this area

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

Wasatch Fm (Tertiary) at surface, covers 2 % of this area

Claystone, shale, and sandstone

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

Sandstone, shale, and major coal beds

Mesaverde Group or Fm--Upper part (Cretaceous) at surface, covers 0.9 % 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

Older gravels and alluviums (Quaternary) at surface, covers 0.8 % of this area

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

Browns Park Fm (Tertiary) at surface, covers 0.8 % of this area

Sandstone and siltstone; west of Park Range

Morrison, Curtis, Entrada, and Glen Canyon Fms (Jurassic-Triassic) at surface, covers 0.7 % of this area

Curtis is absent along Grand Hogback

Maroon Fm (Permian-Pennsylvanian) at surface, covers 0.6 % of this area

Arkosic sandstone, siltstone, conglomerate, and local limestone

Ancient alluvium (Quaternary-Tertiary) at surface, covers 0.5 % of this area

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

Frontier Sandstone and Mowry Shale Members of Mancos Shale, and Dakota Sandstone (Cretaceous) at surface, covers 0.5 % of this area

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

Chinle And State Bridge Fms (Triassic-Permian) at surface, covers 0.4 % of this area

Red siltstone and sandstone

Granitic rocks of 1700-m.y. age group (Early Proterozoic) at surface, covers 0.4 % 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; also, unnamed granitic rocks

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

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

Felsic and hornblendic gneisses, either separate or interlayered (Early Proterozoic) at surface, covers 0.4 % of this area

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

Mesaverde Group or Fm--Lower part (Cretaceous) at surface, covers 0.2 % of this area

Sandstone, shale, and major coal beds

Dakota Sandstone or Group (Cretaceous) at surface, covers 0.1 % of this area

Dakota Sandstone or Group

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

Frontier Sandstone and Mowry Shale Members and intervening shale zone

Biotitic gneiss, schist, and migmatite (Early Proterozoic) at surface, covers 0.1 % of this area

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

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

Morrison Fm and Entrada Sandstone

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

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

Minturn and Belden Fms (Pennsylvanian) at surface, covers < 0.1 % of this area

Minturn and Belden Fms

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

Siltstone, shale, and local gypsum

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

In dikes and plugs

Eastern Uinta Basin Members of the Green River Formation (Eocene) at surface, covers < 0.1 % of this area

Eastern Uinta Basin Members of the Green River Formation (Evacuation Creek Mbr, Parachute Creek Mbr (oil shale), Garden Gulch Mbr, and Douglas Creek Mbr.).

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

Mesaverde Group.

Wasatch/Colton Formations and Flagstaff Limestone (Early to Middle Eocene) at surface, covers < 0.1 % of this area

Wasatch/Colton Formations and Flagstaff Limestone.

Morrison, Curtis, and Entrada Fms (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

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

Mancos Shale (Masuk Shale Mbr, Emery Sandstone Mbr, Blue Gate Shale Mbr, Ferron Sandstone Mbr, and Tununk Shale Mbr).

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

Older alluvial deposits