Pennsylvanian System

Type section: The Blue Creek Coal Member, named by Gray, Jenkins, and Weidman (1960, p 25, 71, 72), consists of the coal mined extensively on Coal Mine Ridge at the headwaters of Blue Creek in southeastern Martin County and in northeastern Dubois County, Ind. The type section is in an abandoned strip mine in the SW¼NW¼ sec. 10, T. 1 N., R. 3 W. (Gray, Jenkins, and Weidman, 1960, p. 71-72. (See also Jenkins, 1956, p. 30-31.)

Description and correlation: Near the type section the Blue Creek is divided into two benches. The upper bench, 2.0 feet (0.6 m) thick, is dull banded and slightly fissile to shaly, and the lower bench, 2.8 feet (0.8 m) thick, is bright banded and has blocky to hackly fracture. The roof of the coal is dark-gray carbonaceous ferruginous shale that is 8.0 feet (2.4 m) thick and is overlain by 6.5 feet (2.0 m) of yellow-brown to light-gray sandstone that is carbonaceous, micaceous, and ferruginous. The floor is white fire clay at this location. Sandstone overlies the Blue Creek at a few locations.

The Blue Creek is extremely variable in quality and thickness within short distances. Near Coal Mine Ridge the coal ranges from less than 1.0 foot (0.3 m) to more than 5.0 (1.5 m) in thickness in places it is an economically minable coalbed as described above, but at others it is hardly more coaly than a black fissile shale. In this area the coal lies some 60 to 80 feet (18 to 24 m) below the top of the Mansfield Formation and about 100 feet (30 m) above the Pinnick Coal Member, or its mapped position. The Blue Creek has been mapped or identified throughout Martin County (Hutchison, 1967), Dubois County (Hutchison, 1964), Daviess County (Hutchison, 1971a), and Perry County (Hutchison, 1971b).