| State | Michigan |
|---|---|
| Name | Michigan Formation |
| Geologic age | Mississippian |
| Lithologic constituents |
Major
Sedimentary > Clastic > Mudstone > Shale (Bed)
Minor
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed)
Incidental
Sedimentary > Carbonate > Dolostone (Bed)
Sedimentary > Chemical > Evaporite > Gypsum (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Chemical > Evaporite > Anhydrite (Bed)
|
| Comments | Secondary unit description from USGS Geologic Names lexicon (ref. MI016): Unit, which is mostly shale, is Osagean and Meramecian in age and conformably overlies the Marshall Sandstone. Underlies the Meramecian Bayport Limestone. Michigan Formation reaches its maximum thickness of 152 m in Missaukee Co. to the north of the central basin area. Thicknesses of 91 to 122 m are more typical. Although generally composed of greenish gray and dark gray shale, this formation is lithologically variable and includes discontinuous beds of sandstone, limestone, dolostone, gypsum, and anhydrite. One of these carbonate beds, called the "Brown Lime," is a 3- to 6-m thick dolostone that can be traced in the subsurface across much of the basin. |
| References | Milstein, Randall L. (compiler), 1987, Bedrock geology of southern Michigan: Geological Survey Division, Michigan Dept. of Natural Resources, scale 1:500,000.USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/https://ngmdb.usgs.gov/Geolex/search |
| NGMDB product | |
| Counties | Allegan - Arenac - Barry - Calhoun - Crawford - Eaton - Genesee - Gladwin - Grand Traverse - Huron - Ingham - Ionia - Iosco - Jackson - Kalkaska - Kent - Lake - Lapeer - Livingston - Manistee - Mason - Missaukee - Muskegon - Newaygo - Oakland - Oceana - Ogemaw - Oscoda - Ottawa - Roscommon - Sanilac - Shiawassee - Tuscola - Washtenaw - Wexford |