Geologic units in Oscoda county, Michigan

Coldwater Shale (Mississippian) at surface, covers 51 % of this area

Coldwater Shale

Marshall Sandstone (Mississippian) at surface, covers 33 % of this area

Marshall Sandstone

Michigan Formation (Mississippian) at surface, covers 15 % of this area

Michigan Formation

Sunbury Shale (Mississippian-Devonian) at surface, covers 0.4 % of this area

Sunbury Shale

Bedford Shale (Late Devonian) at surface, covers 0.4 % of this area

Bedford Shale

Antrim Shale (Late Devonian) at surface, covers 0.3 % of this area

Antrim Shale