Geologic units in Marshall county, Indiana

Antrim Shale (Devonian) at surface, covers 53 % of this area

Black shale; gray shale and limestone in lower part

Ellsworth Shale (Devonian-Mississippian) at surface, covers 38 % of this area

Green shale; some black shale in lower part

Muscatatuck Group (Devonian) at surface, covers 9 % of this area

Limestone and dolomite