| State | Illinois |
|---|---|
| Name | Platteville Group |
| Geologic age | Upper Ordovician (Stage 5) |
| Lithologic constituents |
Major
Sedimentary > Carbonate > Dolostone (Bed)Dolomite can be cherty, shaly or argillaceous, or phosphatic.
Sedimentary > Carbonate > Limestone (Bed)Limestone can be cherty, shaly or argillaceous, or phosphatic.
Minor
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)K-bentonite
|
| Comments | Thickness from stratigraphic columns: Pecatonica Fm (0-80’), overlaid (from oldest to youngest) by the Mifflin Fm (0-55’), Grand Detour Fm (0-180’), and Quimbys Mill/Nachusa Fms (0-220’) which together comprise the Plattin Ls (250-625’) in southern Illinois (south of 40 degrees north latitude); and in northern Illinois (north of 40 degrees north latitude), from oldest to youngest, Pecatonica Fm (0-50’), Mifflin Fm (0-30’), Grand Detour Fm (0-180’), Nachusa Fm (0-40’), and Quimbys Mill Fm (0-30’). |
| Stratigraphic units | Deicke K-bentonite Bed |
| References | Kolata, D.R., comp., 2005, Bedrock Geology of Illinois: Champaign, Ill., Illinois State Geological Survey, Illinois Map Series 14, scale 1:500,000. |
| NGMDB product | |
| Counties | Boone - Bureau - Calhoun - Carroll - DeKalb - Grundy - Jo Daviess - Kendall - La Salle - Lee - McHenry - Monroe - Ogle - Pike - Stephenson - Winnebago |