Geologic units in Menard county, Illinois

Carbondale Formation (Pennsylvanian (Moscovian to Kasimovian)) at surface, covers 66 % of this area

Carbondale Formation.

Shelburn-Patoka Formations undivided (Pennsylvanian (Kasimovian)) at surface, covers 34 % of this area

Shelburn-Patoka Formations undivided.