Morrowan, Atokan, and Desmoinesian Series

Pennsylvanian System

Type locality: The term Raccoon Creek Group was first used by Wier and Gray (1961) in a generalized columnar section and was later proposed by Wier (1961, 1965) for those rocks in the lower part of the Pennsylvanian System that crop out along Raccoon Creek in southern Parke County, Ind., in T. 14 N., Rs. 5, 6, 7, and 8 W., and T.15 N., R. 8 W.

Description: The Raccoon Creek Group consists in ascending order of the Mansfield, Brazil, and Staunton Formations, is overlain by the Carbondale Group, and is underlain by rocks ranging in age from Middle Devonian to Late Mississippian.

Shale and sandstone compose more than 95 percent of the group, and clay, coal, and limestone make up nearly all the rest; small amounts of chert and sedimentary iron ore are in the lower part of the group. Shale is more common than sandstone, and most of it is light-gray to dark-gray shale and soft nonsilty shale to hard silty and sandy shale. A small amount of black fissile shale is also present. The sandstone is mostly fine grained; coarse-grained size is rare. Where the sandstone is present in the subsurface, massive crossbedded sandstone seems to be most common.

The Raccoon Creek Group generally thickens toward the southeast but in some places has thickness variations of more than 300 feet (91 m) because of irregular unconformity on the surface of underlying rocks. It ranges in thickness from less than 100 feet (30 m) in some locations in Parke and Vermillion Counties to more than 1,000 feet (305 m) in Vanderburgh County. It crops out in southwestern Indiana along the easternmost margin of Pennsylvanian rocks.

Correlation: The Raccoon Creek Group correlates with the McCormick Group and the lower part of the Kewanee Group in Illinois and with the Caseyville and Tradewater Formations and the lower part of the Carbondale Formation in western Kentucky.