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

Geologic units in Yuma county, Colorado

Eolian deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 65 % of this area

Includes dune sand and silt and Peoria Loess

Lithology: dune sand; silt; loess

Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

thin bedded gray to brownish gray shale; contains concretions, selenite crystals, thin beds of bentonite and locally chalky beds.

Lithology: shale

Ogallala Group or Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers 0.2 % of this area

Silt, sand, sandstone, gravel and conglomerate. Predominantly interfingered fine- to coarse grained, poorly sorted, arkosic, fluvial deposits of light-gray, light-olive-gray, and grayish-green calcareous silt and sand, and locally poorly consolidated conglomerate, sandstone, and siltstone.

Lithology: mudstone; sandstone; volcanic ash

Modern alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 3 % of this area

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Mostly medium to dark-gray, brownish-gray, and black, fissle clay shale. Locally grades to thin beds of calcareous, silty shale or claystone, marl, shaly sandstone, and sandy shale. Locally contains thin seams of gypsum and sparse selenite crystals. Approx. max thickness 1970 ft.

Lithology: shale; evaporite

Ogallala Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 31 % of this area

Loose to well-cemented sand and gravel

Lithology: sandstone; conglomerate

Loess (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 0.1 % of this area

eolian silts

Lithology: silt

Pierre Shale--Upper unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 2 % of this area

Lithology: shale

Ogallala Formation (Phanerozoic | Cenozoic | Tertiary | Miocene) at surface, covers < 0.1 % of this area

massive to cross-bedded, generally arkosic sand, silt and gravel, locally cemented with calcium carbonate; also contains limestone, volcanic ash, diatomaceous marl, opaline sandstone and bentonitic clay

Lithology: arkose; limestone; volcanic ash; carbonate; sandstone; claystone

Alluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area

unconsolidated sand, silt, clay, and gravel

Lithology: gravel; sand; silt; clay or mud