Geologic units in Montgomery county, Illinois

Bond Formation (Pennsylvanian (Kasimovian)) at surface, covers 95 % of this area

Bond Formation

Mattoon Formation (Pennsylvanian (Kasimovian)) at surface, covers 3 % of this area

Mattoon Formation.

Shelburn-Patoka Formations undivided (Pennsylvanian (Kasimovian)) at surface, covers 2 % of this area

Shelburn-Patoka Formations undivided.