Geologic units in Kent county, Michigan

Marshall Sandstone (Mississippian) at surface, covers 5 % of this area: Marshall Sandstone
Lithology: sandstone; siltstone
Red beds (Jurassic) at surface, covers 25 % of this area: Red beds
Lithology: shale
Michigan Formation (Mississippian) at surface, covers 31 % of this area: Michigan Formation
Lithology: shale; black shale; sandstone; dolostone (dolomite); limestone; evaporite
Bayport Limestone (Mississippian) at surface, covers 20 % of this area: Bayport Limestone
Lithology: limestone; dolostone (dolomite); sandstone; shale; chert; evaporite
Saginaw Formation (Pennsylvanian) at surface, covers 19 % of this area: Saginaw Formation
Lithology: sandstone; shale; coal; limestone