Lower Cherokee Group and Raccoon Creek Group

Lower Cherokee Group in southern, central, and western Iowa includes Kilbourn, Kalo, Floris formations (primarily Atokan-lower Desmoinesian, locally Morrowan at base); Raccoon Creek Group in eastern Iowa includes “Caseyville” and Tradewater formations (primarily Morrowan at most localities; locally includes Atokan-lower Desmoinesian Tradewater Formation in upper part). Primary Lithologies: shale/mudstone, light to dark gray, part silty to sandy; sandstone, very fine to medium grained; siltstone, gray. Secondary Lithologies: carbonaceous shale/mudstone, gray to black; phosphatic black shale; limestone, dense, part fossiliferous, part sandy; coal (beds locally > 2 ft). Minor: sandstone, coarse-grained to granular, part conglomeratic; mudstone, red to pink; limestone concretions (may be septarian); cone-in-cone limestone; siderite/ironstone concretions and pellets; pyrite. Maximum thicknesses Raccoon Creek Group in Muscatine-Scott counties: 230-250 ft (70-75 m). Maximum thicknesses Lower Cherokee Group across outcrop belt: 200-370 ft (60-113 m). Maximum thickness in southwest Iowa subsurface: 650 ft (200 m).
State Iowa
Name Lower Cherokee Group and Raccoon Creek Group
Geologic age Lower-Middle Pennsylvanian; Morrowan-lower Desmoinesian
Lithologic constituents
Major
Sedimentary > Clastic > Siltstone (Bed)gray
Sedimentary > Clastic > Sandstone (Bed)very fine to medium grained; incidental coarse-grained to granular, part conglomeratic
Sedimentary > Clastic > Mudstone > Shale (Bed, Carbonaceous)shale/mudstone, light to dark gray, part silty to sandy; minor carbonaceous shale/mudstone, gray to black; incidental red to pink
Minor
Sedimentary > Carbonate > Limestone (Bed)dense, part fossiliferous, part sandy
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed)phosphatic
Sedimentary > Coal (Bed)
References

Witzke, Brian J., Anderson, Raymond R., and Pope, John P., 2010, Iowa Geological and Water Survey, DNR, Bedrock Geologic Map of Iowa, OFM-2010-1. Scale 1:500,000.

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