Geologic units in Sedgwick county, Colorado

Ogallala Fm (Tertiary) at surface, covers 68 % of this area

Loose to well-cemented sand and gravel

Eolian deposits (Quaternary) at surface, covers 13 % of this area

Includes dune sand and silt and Peoria Loess

White River Fm or Group (Tertiary) at surface, covers 8 % of this area

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

Modern alluvium (Quaternary) at surface, covers 6 % of this area

Includes Piney Creek Alluvium and younger deposits

Gravels and alluviums (Quaternary) at surface, covers 4 % of this area

Includes Broadway and Louviers Alluviums

Ogallala Group or Formation (Miocene) at surface, covers 0.3 % 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.

Arikaree Fm (Tertiary) at surface, covers < 0.1 % of this area

Sandstone; contains abundant volcanically derived material

White River Group (Oligocene) at surface, covers < 0.1 % of this area

Clay, some claystone, silt and siltstone. Predominantly greenish gray and volcaniclastic. Other occurrences are greenish gray to white and bentonitic. Local channel sandstone at base. Aprox thickness 195 ft.