Geologic units in Ouray county, Colorado

Additional scientific data in this geographic area

Dakota Sandstone and Burro Canyon Fm (Cretaceous) at surface, covers 23 % of this area

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

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Tertiary) at surface, covers 20 % of this area

Includes several named units

Mancos Shale (Cretaceous) at surface, covers 19 % 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)

Landslide deposits (Quaternary) at surface, covers 14 % of this area

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

Intra-ash flow andesitic lavas (Tertiary) at surface, covers 4 % of this area

Intra-ash flow andesitic lavas

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 3 % 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

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

Includes many named units

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

Includes Piney Creek Alluvium and younger deposits

Morrison Fm, Summerville Fm, and Entrada Sandstone (Jurassic) at surface, covers 2 % of this area

Summerville Fm: Shale and siltstone

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

Includes Broadway and Louviers Alluviums

Dolores Fm and Cutler Fm (Triassic-Permian) at surface, covers 1 % of this area

Red siltstone, sandstone, and conglomerate

Laramide intrusive rocks (Tertiary-Cretaceous) at surface, covers 1 % of this area

Mainly intermediate to felsic compositions; some mafic

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

Morrison, Wanakah, and Entrada Fms

Glacial drift (Quaternary) at surface, covers 1.0 % of this area

Includes some unclassified glacial deposits

Middle Tertiary intrusive rocks (Tertiary) at surface, covers 0.8 % of this area

Intermediate to felsic compositions

Telluride conglomerate of Eocene prevolcanic sedimentary rocks (Te) and Cimarron Ridge Fm (Tertiary-Cretaceous) at surface, covers 0.6 % of this area

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

Morrison Fm (Jurassic) at surface, covers 0.6 % of this area

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

Older glacial drift (Quaternary) at surface, covers 0.6 % of this area

Older glacial drift

Uncompahgre Fm (Early-Middle Proterozoic) at surface, covers 0.5 % of this area

Quartzite, slate, and phyllite

Eocene prevolcanic sedimentary rocks (Tertiary) at surface, covers 0.5 % 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)

Hermosa Fm (Pennsylvanian) at surface, covers 0.4 % of this area

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

Leadville Limestone, Gilman Sandstone, Dyer Dolomite, and Parting Fm (Devonian-Ordivician) at surface, covers 0.3 % of this area

Parting Fm: quartzite and shale.

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