Geologic units in Mason county, Illinois

Carbondale Formation (Pennsylvanian) at surface, covers 53 % of this area: Carbondale Formation
Lithology: shale; limestone; clay or mud; sandstone; coal; black shale
Middle Valmeyeran (Salem, Warsaw, Borden, Springville; includes thin Mvl and Mk in south and east) Series (Mississippian) at surface, covers 27 % of this area: Middle Valmeyeran (Salem, Warsaw, Borden, Springville; includes thin Mvl and Mk in south and east) Series
Lithology: limestone; siltstone; shale
Spoon Formation (Pennsylvanian) at surface, covers 15 % of this area: Spoon (includes Pa in northeast)
Lithology: shale; sandstone; clay or mud; limestone; coal; black shale
Upper Valmeyeran (Aux Vases, Ste. Genevieve, St. Louis) Series (Mississippian) at surface, covers 2 % of this area: Upper Valmeyeran (Aux Vases, Ste. Genevieve, St. Louis) Series
Lithology: limestone; sandstone; dolostone (dolomite); sedimentary breccia; chert
Lower Valmeyeran (Keokuk-Sedalia) Series (Mississippian) at surface, covers 2 % of this area: Lower Valmeyeran (Keokuk-Sedalia) Series
Lithology: limestone; shale