Mineral Resources
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Geology
by state
Michigan geologic units
Geologic units in Iosco county, Michigan
Michigan Formation
(Mississippian)
at surface, covers 41 % of this area
Michigan Formation
Marshall Sandstone
(Mississippian)
at surface, covers 33 % of this area
Marshall Sandstone
Coldwater Shale
(Mississippian)
at surface, covers 26 % of this area
Coldwater Shale