|Name||Clayton Formation, Porters Creek Formation, Claiborne Formation, Wilcox Formation|
|Geologic age||Tertiary (Paleocene) to Tertiary (Pliocene)|
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.|
Kolata, D.R., comp., 2005, Bedrock Geology of Illinois: Champaign, Ill., Illinois State Geological Survey, Illinois Map Series 14, scale 1:500,000.
|Counties||Alexander - Pulaski|