Geologic units in Grand Traverse county, Michigan

Coldwater Shale (Mississippian) at surface, covers 47 % of this area

Coldwater Shale

Ellsworth Shale (Late Devonian) at surface, covers 41 % of this area

Ellsworth Shale

Antrim Shale (Late Devonian) at surface, covers 7 % of this area

Antrim Shale

Marshall Sandstone (Mississippian) at surface, covers 3 % of this area

Marshall Sandstone

Michigan Formation (Mississippian) at surface, covers 2 % of this area

Michigan Formation