Geologic units in Saint Clair county, Illinois

Shelburn-Patoka Formations undivided (Pennsylvanian (Kasimovian)) at surface, covers 59 % of this area

Shelburn-Patoka Formations undivided.

Tradewater Formation (Pennsylvanian (Bashkirian to Moscovian)) at surface, covers 14 % of this area

Tradewater Formation

Carbondale Formation (Pennsylvanian (Moscovian to Kasimovian)) at surface, covers 10 % of this area

Carbondale Formation.

Lower Pope Group (Aux Vases Sandstone through Glen Dean Limestone) (Mississippian (Visean)) at surface, covers 7 % of this area

Lower Pope Group (Aux Vases Sandstone through Glen Dean Limestone).

St. Louis Limestone (Mississippian (Visean)) at surface, covers 5 % of this area

St. Louis Limestone.

Ste. Genevieve Limestone (Mississippian (Visean)) at surface, covers 3 % of this area

Ste. Genevieve Limestone.

Warsaw Formation and Salem Limestone (Mississippian (Visean)) at surface, covers 2 % of this area

Warsaw Formation and Salem Limestone in western Illinois.

Bond Formation (Pennsylvanian (Kasimovian)) at surface, covers 0.6 % of this area

Bond Formation

Holocene series (Quaternary-Holocene Series) at surface, covers 0.2 % of this area

Alluvium - clay, silt, sand, and gravel.