Geologic units in Rush county, Kansas

Carlile Shale (Late Cretaceous) at surface, covers 33 % of this area

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

Loess (Holocene to Pleistocene) at surface, covers 26 % of this area

eolian silts

Greenhorn Limestone and Graneros Shale (Late Cretaceous) at surface, covers 20 % of this area

Greenhorn FM- thin bedded gray, chalky limestone and calcareous shale. Graneros Shale- fissile, noncalcareous, gray shale locally contains sandstone and siltstone beds.

Alluvium (Holocene to Pleistocene) at surface, covers 17 % of this area

unconsolidated sand, silt, clay, and gravel

Ogallala Formation (Miocene) at surface, covers 3 % 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 (Pleistocene) at surface, covers 0.4 % of this area

unconsolidated sand, silt, clay, and gravel

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

Interbedded, soft, light-gray calcareous shale and chalk