Geologic units in Montmorency county, Michigan

Antrim Shale (Late Devonian) at surface, covers 52 % of this area

Antrim Shale

Coldwater Shale (Mississippian) at surface, covers 27 % of this area

Coldwater Shale

Bedford Shale (Late Devonian) at surface, covers 9 % of this area

Bedford Shale

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

Traverse Group

Sunbury Shale (Mississippian-Devonian) at surface, covers 2 % of this area

Sunbury Shale