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Mineral Resources > Online Spatial Data > Geology > by state > Colorado Geology

Geologic units in Dolores county, Colorado

[Additional scientific data in this geographic area]

Glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.3 % of this area

Includes some unclassified glacial deposits

Lithology: glacial drift

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Includes several named units

Lithology: andesite; tuff; volcanic breccia (agglomerate)

Morrison Fm (Phanerozoic | Mesozoic | Jurassic) at surface, covers 0.5 % of this area

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

Lithology: mudstone; sandstone; limestone

Dakota Sandstone and Burro Canyon Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 34 % of this area

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

Lithology: sandstone; shale; conglomerate

Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 26 % 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 Frontie

Lithology: shale; sandstone

Dolores Fm (Phanerozoic | Mesozoic | Triassic) at surface, covers 3 % of this area

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

Lithology: siltstone; shale; sandstone; conglomerate

Middle Tertiary intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 1 % of this area

Intermediate to felsic compositions

Lithology: plutonic rock (phanerit

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

Quartzite, slate, and phyllite

Lithology: quartzite; slate; phyllite

Glen Canyon Group and Chinle Fm (Phanerozoic | Mesozoic | Triassic Jurassic) at surface, covers 0.7 % 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

Dakota Sandstone or Group (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Lithology: sandstone

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

Lithology: eolian

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

Lithology: shale; sandstone; conglomerate

Cutler Fm (Phanerozoic | Paleozoic | Permian) at surface, covers 4 % of this area

Arkosic sandstone, siltstone, and conglomerate

Lithology: sandstone; siltstone; conglomerate

Landslide deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.5 % of this area

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

Lithology: landslide; talus; colluvium

Morrison, Wanakah, and Entrada Fms (Phanerozoic | Mesozoic | Jurassic) at surface, covers 9 % of this area

Lithology: mudstone; sandstone; limestone

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

Lithology: alluvium; colluvium

Morrison Fm, Summerville Fm, and Entrada Sandstone (Phanerozoic | Mesozoic | Jurassic) at surface, covers 4 % of this area

Summerville Fm: Shale and siltstone

Lithology: mudstone; sandstone

Eolian deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 10 % of this area

Includes dune sand and silt and Peoria Loess

Lithology: dune sand; silt; loess

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

Lithology: sandstone; shale

Modern alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.3 % of this area

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

Rico and Hermosa Fms (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers 0.8 % of this area

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

Lithology: sandstone; conglomerate; shale; limestone; mudstone

Eocene prevolcanic sedimentary rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % 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)

Lithology: sandstone; conglomerate; mudstone

Laramide intrusive rocks (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.5 % of this area

Mainly intermediate to felsic compositions; some mafic

Lithology: granitoid

Mesaverde Fm, undivided (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 3 % 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 Tertiary intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.1 % of this area

Intermediate to felsic compositions

Lithology: plutonic rock (phanerit