Type locality and use of name: The name Seelyville was applied casually by Ashley (1909, p. 31, chart opposite p. 97) to the thick coalbed mined underground at Seelyville in Vigo County, Ind. No specific type section was designated. From 1899 to 1909 this coal had been mistakenly called Coal VI (Ashley, 1899), an error that Ashley later (1909) corrected to Coal III. Fifty years later this coal was formally named the Seelyville Coal Member by Kosanke and others (1960, p. 33), who incorrectly spelled it "Seeleyville" and who (p. 46) designated the type area as the mines near Seelyville, Vigo County, in T. 12 N., Rs. 7 and 8 W.
Description: The Seelyville Coal Member has been reported to be as much as 11 feet (3.4 m) thick and averages 6 feet (1.8 m) in thickness in the northern part of the Indiana coalfield. It is bright banded and highly pyritiferous and is split into three benches of about equal thickness by two thin pyritiferous shale partings (Hutchison, 1960). The roof of the coal is either gray shale that is silty and carbonaceous or brown to gray sandstone that is massive, friable, fine grained, carbonaceous, and micaceous. The floor is generally gray plastic underclay that is shaly in places.
Correlation and nomenclature: The Seelyville is the uppermost member of the Staunton Formation and has been known by various names along its outcrop area, which extends the length of the Indiana coalfield. It has been called the Lower Hanging Rock Coal in Vermillion County, where it was mined with the Colchester Coal Member along the Big Vermillion River northwest of Eugene. In Clay and Vigo Counties it has been called the Staunton Coal from exposures around Staunton, and in Dubois and Pike Counties it has been called the Rock Creek Coal (Fuller and Ashley, 1902, p. 2). Along the outcrop in the latter counties, it is only 2 to 3 feet (0.6 to 0.9 m) thick and has a shale or a sandstone roof.
The Seelyville was correlated with a part of the Abingdon Cyclothem of western Illinois by Alexander (1943). As recognized in Illinois by Hopkins and Simon (197b, p. 186), the Seelyville occurs primarily in Edgar, Clark, and Crawford Counties in the eastern part of the state but is found only in places in southern Illinois between the DeKoven and Colchester Coal Members. There the species of spores found in the Seelyville help to distinguish it from the older DeKoven coal (Peppers, 1970, p. 31-33). Southward in Illinois the Seelyville thins and is split into two benches (Treworgy, 1981, p. 5).