Pennsylvanian System

Type section and use of name: The name Silverwood was applied by Alexander (1943, p. 143) to a well-developed cyclothem and limestone exposed near Silverwood, Fountain County, Ind., about a quarter of a mile (0.4 km) north of Indiana 234 on the east side of Coal Creek. This exposure in the SE¼NW¼ sec. 36, T. 18 N., R. 9 W., was mistakenly cited by Alexander as in the NE¼SW¼ sec. 36, T. 18 N., R. 8 W. Hutchison (1970 1976, p. 19, 50) assigned the limestone member rank in the Staunton Formation and designated the above exposure as the type section, although he, too, listed incorrect locations, the NE¼SW¼ sec. 36, T. 18 N., R. 8 W., in 1970 and the NE¼SW¼ sec. 36, T. 18 N., R. 9 W., in 1976.

Description: The Silverwood Limestone Member consists of three benches. The upper bench at the type section is dark-blue fossiliferous limestone, which is 0.2 foot (0.06 m) thick and has distinctive cone-in-cone structure. The middle bench is a calcareous fossiliferous shale, 0.75 foot (0.23 m) thick, and the lower and more persistent bench is dark-gray fossiliferous limestone, 0.3 foot (0.09 m) thick (Alexander, 1943).

Correlation: The Silverwood Cyclothem, according to Alexander (1943), extends as far north as Fall Creek in north-central Warren County and includes Coal II of Parke and Clay Counties as defined by Ashley (1909). In Fountain County, however, the Silverwood Limestone Member lies about 50 feet (15 m) above Coal II, and it correlates with one or more of a group of marine zones in the middle part of the Staunton Formation (Hutchison, 1961). This zone can be traced along the outcrop and in the subsurface from Warren County to the Ohio River.

The Silverwood has been correlated with the Stonefort Limestone Member of Illinois (Peppers and Popp, 1979, p. 71).