Geologic units in Alger county, Michigan

Trenton Limestone (Late Ordovician) at surface, covers 11 % of this area: Trenton Limestone
Lithology: limestone; dolostone (dolomite); shale
Jacobsville Sandstone (Middle Proterozoic) at surface, covers 10 % of this area: Jacobsville Sandstone - Red, brown, and white quartzose sandstone, and minor siltstone, shale and conglomerate
Lithology: sandstone; siltstone; conglomerate; shale
Prairie du Chien Group (Early Ordovician) at surface, covers 28 % of this area: Prairie du Chien Group
Lithology: dolostone (dolomite); sandstone; shale
Trempealeau Formation (Late Cambrian) at surface, covers 22 % of this area: Trempealeau Formation
Lithology: sandstone; shale; dolostone (dolomite)
Utica Shale (Late Ordovician) at surface, covers < 0.1 % of this area: Utica Shale
Lithology: black shale
Munising Formation (Late Cambrian) at surface, covers 13 % of this area: Munising Formation
Lithology: sandstone; shale; conglomerate
Black River Limestone (Late Ordovician) at surface, covers 14 % of this area: Black River Limestone
Lithology: limestone
Collingwood Limestone (Late Ordovician) at surface, covers 0.2 % of this area: Collingwood Limestone
Lithology: limestone; black shale