Geologic units in Porter county, Indiana

Ellsworth Shale (Devonian-Mississippian) at surface, covers 64 % of this area

Green shale; some black shale in lower part

Antrim Shale (Devonian) at surface, covers 33 % of this area

Black shale; gray shale and limestone in lower part

Muscatatuck Group (Devonian) at surface, covers 3 % of this area

Limestone and dolomite