Geologic units in Peoria county, Illinois

Spoon Formation (Pennsylvanian) at surface, covers 0.2 % of this area: Spoon (includes Pa in northeast)
Lithology: shale; sandstone; clay or mud; limestone; coal; black shale
Modesto Formation (Pennsylvanian) at surface, covers 31 % of this area: Modesto Formation
Lithology: shale; sandstone; limestone; clay or mud; coal; black shale
Carbondale Formation (Pennsylvanian) at surface, covers 69 % of this area: Carbondale Formation
Lithology: shale; limestone; clay or mud; sandstone; coal; black shale