Mississippian System

Type section and description: The Underwood was originally designated as a formation (Campbell, 1946) but was later assigned as a bed to the upper part of the Clegg Creek Member of the New Albany Shale (Lineback, 1968, 1970). The Underwood consists of 0.4 foot (0.1 m) of greenish-gray fossiliferous shale at the type section in the SE¼ sec. 21, T. 2 N., R.7 E., 2 miles (3.2 km) southeast of Underwood in Clark County, Ind. This unit, overlain by the Henryville Bed and underlain by the Falling Run Bed, is of extremely limited extent and cannot be recognized away from the immediate area of the type section.

Correlation: Containing a Kinderhookian conodont and scolecodont fauna, the Underwood is the lowest bed of proved Mississippian age in the New Albany Shale. On the basis of a conodont fauna indicative of the Siphonodella sulcata Assemblage Zone, it is correlated with the lower part of the Hannibal Shale of the upper Mississippi Valley. The conodont fauna is also indicative of the cuI division of the German standard. (See Lineback, 1970, and "Clegg Creek Member, Correlation.")