Geologic units in Piatt county, Illinois

Bond Formation (Pennsylvanian) at surface, covers 45 % of this area: Bond Formation
Lithology: limestone; shale; sandstone; clay or mud; coal; black shale
Mattoon Formation (Pennsylvanian) at surface, covers 32 % of this area: Mattoon Formation
Lithology: shale; sandstone; limestone; coal; black shale
Spoon Formation (Pennsylvanian) at surface, covers 1 % of this area: Spoon (includes Pa in northeast)
Lithology: shale; sandstone; clay or mud; limestone; coal; black shale
Carbondale Formation (Pennsylvanian) at surface, covers 2 % of this area: Carbondale Formation
Lithology: shale; limestone; clay or mud; sandstone; coal; black shale
Upper Devonian (Devonian) at surface, covers < 0.1 % of this area: Upper Devonian
Lithology: shale; black shale; limestone; sandstone
Modesto Formation (Pennsylvanian) at surface, covers 21 % of this area: Modesto Formation
Lithology: shale; sandstone; limestone; clay or mud; coal; black shale