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Geologic units in Arapahoe county, Colorado

Additional scientific data in this geographic area

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

Includes dune sand and silt and Peoria Loess

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

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

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

Pierre Shale--Upper unit

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

Shale, claystone, sandstone, and major coal beds

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

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

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

Includes Piney Creek Alluvium and younger deposits

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

Fox Hills Sandstone

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

Includes Broadway and Louviers Alluviums

White River Fm or Group (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 (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

Denver and Arapahoe Fms (Tertiary-Cretaceous) at surface, covers 0.1 % of this area

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