Geologic units in Graham county, Kansas

Loess (Holocene to Pleistocene) at surface, covers 57 % of this area

eolian silts

Ogallala Formation (Miocene) at surface, covers 26 % 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

Niobrara Chalk (Late Cretaceous) at surface, covers 10 % of this area

Interbedded, soft, light-gray calcareous shale and chalk

Alluvium (Holocene to Pleistocene) at surface, covers 7 % of this area

unconsolidated sand, silt, clay, and gravel

Dune Sand (Holocene to Pleistocene) at surface, covers 0.4 % of this area

unconsolidated dune sand

Pierre Shale (Late Cretaceous) 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.

Carlile Shale (Late Cretaceous) at surface, covers < 0.1 % of this area

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