Geologic units in Eagle county, Colorado

Additional scientific data in this geographic area

Eagle Valley Fm - evaporitic facies (Pennsylvanian) at surface, covers 12 % of this area

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

Minturn Fm in west-central and south-central and other units (Pennsylvanian) at surface, covers 10 % 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.

Maroon Fm (Permian-Pennsylvanian) at surface, covers 10 % of this area

Arkosic sandstone, siltstone, conglomerate, and local limestone

Biotitic gneiss, schist, and migmatite (Early Proterozoic) at surface, covers 9 % of this area

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

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 5 % of this area

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

State Bridge Fm (Triassic-Permian) at surface, covers 5 % of this area

Red and orange siltstone and sandstone

Pierre Shale, undivided (Cretaceous) at surface, covers 4 % of this area

Pierre Shale, undivided

Glacial drift (Quaternary) at surface, covers 4 % of this area

Includes some unclassified glacial deposits

Granitic rocks of 1700-m.y. age group (Early Proterozoic) at surface, covers 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

Weber Sandstone and Maroon Fm (Permian-Pennsylvanian) at surface, covers 4 % of this area

Weber Sandstone and Maroon Fm

Dakota Sandstone or Group (Cretaceous) at surface, covers 4 % of this area

Dakota Sandstone or Group

Colorado Group (Cretaceous) at surface, covers 3 % of this area

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

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

Includes Broadway and Louviers Alluviums

Chinle And State Bridge Fms (Triassic-Permian) at surface, covers 2 % of this area

Red siltstone and sandstone

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

Belden Fm (Pennsylvanian) at surface, covers 1 % of this area

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

Dakota, Purgatoire, Morrison, Ralston Creek, and Entrada Fms in southeast. Dakota, Morrison, and Entrada Fms in central mountains. Dakota, Burro Canyon, Morrison, Wanakah, and Entrada Fms in Gunnison River area. Dakota, Morrison, Curtis, And Entrada Fm (Cretaceous-Jurassic) at surface, covers 1 % of this area

Dakota, Purgatoire, Morrison, Ralston Creek, and Entrada Fms in southeast. Dakota, Morrison, and Entrada Fms in central mountains. Dakota, Burro Canyon, Morrison, Wanakah, and Entrada Fms in Gunnison River area. Dakota, Morrison, Curtis, And Entrada Fm

Morrison, Curtis, and Entrada Fms (Jurassic) at surface, covers 1 % of this area

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

Mancos Shale (Cretaceous) at surface, covers 1 % 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)

Browns Park Fm (Tertiary) at surface, covers 1 % of this area

Sandstone and siltstone; west of Park Range

Chinle Fm (Triassic) at surface, covers 1 % of this area

Red siltstone, sandstone, and limestone-pellet conglomerate

Minturn and Belden Fms (Pennsylvanian) at surface, covers 0.9 % of this area

Minturn and Belden Fms

Eagle Valley Fm (Pennsylvanian) at surface, covers 0.9 % of this area

Siltstone, shale, and local gypsum

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

Morrison Fm and Entrada Sandstone

Laramide intrusive rocks (Tertiary-Cretaceous) at surface, covers 0.8 % of this area

Mainly intermediate to felsic compositions; some mafic

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

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

Leadville Limestone, Gilman Sandstone, Dyer Dolomite, and Parting Fm (Devonian-Ordivician) at surface, covers 0.4 % of this area

Parting Fm: quartzite and shale.

Older glacial drift (Quaternary) at surface, covers 0.4 % of this area

Older glacial drift

Dakota and Morrison Fms (Cretaceous-Jurassic) at surface, covers 0.3 % of this area

Dakota and Morrison Fms

Felsic and hornblendic gneisses, either separate or interlayered (Early Proterozoic) at surface, covers 0.2 % of this area

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

Morrison Fm (Jurassic) at surface, covers 0.2 % of this area

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

Rhyolitic intrusive rocks and flows of late-volcanic bimodal suite (Tertiary) at surface, covers 0.2 % of this area

Rhyolitic intrusive rocks and flows of late-volcanic bimodal suite

Middle Tertiary intrusive rocks (Tertiary) at surface, covers 0.2 % of this area

Intermediate to felsic compositions

Sawatch Quartzite (Cambrian) at surface, covers 0.1 % of this area

Locally includes Peerless Fm

Modern alluvium (Quaternary) at surface, covers 0.1 % of this area

Includes Piney Creek Alluvium and younger deposits

Older gravels and alluviums (Quaternary) at surface, covers < 0.1 % of this area

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

Granitic rocks of 1400-m.y. age group (Middle Proterozoic) at surface, covers < 0.1 % 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

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

Basalt flows

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

In dikes and plugs