Geologic units in Arapahoe county, Colorado

Mineral Resources On-Line Spatial Data

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

Includes Broadway and Louviers Alluviums

Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 5 % of this area

Lithology: sandstone

Laramie Fm (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 10 % of this area

Shale, claystone, sandstone, and major coal beds

Pierre Shale--Upper unit (Phanerozoic | Mesozoic | Cretaceous) at surface, covers 13 % of this area

Lithology: shale

Denver and Arapahoe Fms (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 0.1 % of this area

Sandstone, mudstone, claystone, and conglomerate; Denver is characterized by andesitic materials

Denver Fm or lower part of Dawson Arkose (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) at surface, covers 21 % of this area

Arkosic sandstone, shale, mudstone, conglomerate, and local coal beds

Eolian deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 27 % of this area

Includes dune sand and silt and Peoria Loess

White River Fm or Group (Phanerozoic | Cenozoic | Tertiary) at surface, covers 2 % of this area

East: Ashy claystone and sandstone. Includes Castle Rock Conglomerate in region southeast of Denver. Northwest: Ashy claystone in North Park

Older gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 1 % of this area

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

Upper part of Dawson Arkose (Phanerozoic | Cenozoic | Tertiary) at surface, covers 10 % of this area

Arkosic sandstone, conglomerate, and shale. Includes Green Mountain Conglomerate south of Golden

Modern alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 8 % of this area

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium