| State | Illinois |
|---|---|
| Name | Clayton Formation, Porters Creek Formation, Claiborne Formation, Wilcox Formation |
| Geologic age | Tertiary (Paleocene) to Tertiary (Pliocene) |
| Lithologic constituents | Major
Sedimentary > Clastic > Mudstone > Shale (Bed, Glauconitic)Clayton Fm contains glauconite.
Sedimentary > Clastic > Sandstone (Bed)
|
| Comments | Thickness from stratigraphic column for southern Illinois (south of 40 degrees north latitude), from oldest to youngest: Clayton Fm (0-20’), Porters Creek Fm (0-150’), Claiborne/Wilcox Fms (0-300’). [T is mapped only in southern Illinois.] Clayton and Porters Creek Formations comprise the Midway Group. |
| 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 | Alexander - Pulaski |