Geologic units in Hancock county, Illinois

Warsaw Formation and Salem Limestone (Mississippian (Visean)) at surface, covers 38 % of this area

Warsaw Formation and Salem Limestone in western Illinois.

St. Louis Limestone (Mississippian (Visean)) at surface, covers 37 % of this area

St. Louis Limestone.

Meppen Limestone, Fern Glen Formation, and Burlington-Keokuk Limestone (Mississippian (Tourniaisian to Visean)) at surface, covers 18 % of this area

Meppen Limestone, Fern Glen Formation, and Burlington-Keokuk Limestone.

Tradewater Formation (Pennsylvanian (Bashkirian to Moscovian)) at surface, covers 5 % of this area

Tradewater Formation

Carbondale Formation (Pennsylvanian (Moscovian to Kasimovian)) at surface, covers 1 % of this area

Carbondale Formation.

Augusta Group (Middle Mississippian, Osagean) at surface, covers 0.2 % of this area

Interval includes Burlington, Keokuk, and Warsaw formations. Upper Warsaw strata locally preserved at top of interval in extreme southeast Iowa are lower Meramecian age . Primary Lithologies: dolomite, part argillaceous to shaly; dolomitic limestone, fossiliferous; fossiliferous limestone (especially crinoidal packstone-grainstone). Secondary Lithologies: glauconitic limestone/dolomite; shale, gray to green-gray, part dolomitic, part silty; chert, nodular to bedded. Minor: quartz crystals, quartz geodes, chalcedony; phosphatic dolomite/limestone (“bone bed”); siltstone, dolomitic. Lithologies noted only in northern Iowa: oolitic limestone; “sublithographic” limestone; dolomite/chert breccia. Interval is erosionally beveled beneath sub-“St. Louis” and sub-Pennsylvanian unconformities. Maximum thicknesses in northern Iowa: 85-105 ft (26-32 m). Maximum thicknesses in southern Iowa: 155-240 ft (47-73 m).

Holocene series (Quaternary-Holocene Series) at surface, covers < 0.1 % of this area

Alluvium - clay, silt, sand, and gravel.