Geologic units in Saint Clair county, Michigan

Coldwater Shale (Mississippian) at surface, covers 39 % of this area

Coldwater Shale

Bedford Shale (Late Devonian) at surface, covers 18 % of this area

Bedford Shale

Berea Sandstone (Late Devonian) at surface, covers 14 % of this area

Berea Sandstone

Antrim Shale (Late Devonian) at surface, covers 13 % of this area

Antrim Shale

Sunbury Shale (Mississippian-Devonian) at surface, covers 11 % of this area

Sunbury Shale

Marshall Sandstone (Mississippian) at surface, covers 6 % of this area

Marshall Sandstone