Geologic units in Phillips county, Kansas

Loess (Holocene to Pleistocene) at surface, covers 52 % of this area

eolian silts

Niobrara Chalk (Late Cretaceous) at surface, covers 18 % of this area

Interbedded, soft, light-gray calcareous shale and chalk

Ogallala Formation (Miocene) at surface, covers 16 % 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

Alluvium (Holocene to Pleistocene) at surface, covers 14 % of this area

unconsolidated sand, silt, clay, and gravel

Carlile Shale (Late Cretaceous) at surface, covers 0.4 % of this area

Chalky shale with bentonite and thick chalk beds, dark gray fissile shale containing septarian concretions, and fine-grained sandstone.

Ogallala Group or Formation (Miocene) at surface, covers < 0.1 % 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.

Pierre Shale (Late Cretaceous) 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.

Niobrara Formation (Late Cretaceous) at surface, covers < 0.1 % of this area

Argillaceous chalk, limestone and shale. Chalk is medium gray to white, interbedded with thin layers of chalky shale; contains many fossil clams, oysters, and formanifera. Limestone is light gray to medium gray and yellowish gray, interbedded with medium-gray chalky shale; also contains fossil clams, oysters, and formanifera. Bedding plans commonly marked by thin layers of gypsum and locally a thin bed of red flint occurs at top of unit. Approx. max thickness 570 ft.