|Geologic age||Mississippian (Tourniaisian to Visean)|
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Carbonate > Limestone (Bed)Limestone can be cherty, also can contain geodes or drusy quartz.
|Comments||Thickness from stratigraphic columns: Chouteau Ls (0-80’) and Borden Sltst (0-650’) in southern Illinois (south of 40 degrees north latitude); Borden Sltst (0-600’) in northern Illinois (north of 40 degrees north latitude). The Borden Sltst is part of the Knobs Group in southern Illinois and part of the Mammoth Cave Group in northern Illinois. In southern Illinois, the Chouteau Ls is portrayed in the stratigraphic column as being below the Meppen Ls (which is in turn overlain by the Borden Sltst); however, note that the Meppen is NOT included in the unit Mb.)|
|Stratigraphic units||Carper Sand, Sonora, Cole|
Kolata, D.R., comp., 2005, Bedrock Geology of Illinois: Champaign, Ill., Illinois State Geological Survey, Illinois Map Series 14, scale 1:500,000.
|Counties||Champaign - Douglas - Ford - Iroquois - Vermilion|