Type and reference sections and history of name: The name Velpen Coal was used by Fuller and Ashley (1902) for the coal in Pike County, Ind., now known as the Colchester Coal Member of the Linton Formation. The name Velpen was later used by Weller, Henbest, and Dunbar (1942, p. 32) for the cap rock of this coal and by Cooper (1946, p. 16) and Zangerl and Richardson (1963, p. 28) for the limestone above the coal. The name Velpen was adopted (Wier, 1961, 1965) as a member of the Linton Formation, and its type section was designated in the NEl¼SE¼NE¼ sec. 8, T. 2 S., R. 6 W., half a mile northeast of Velpen in Pike County. A reference section for the Velpen (136.2 to 136.8 feet 41.5 to 41.7 m) was cored in SDH 306 by the Indiana Geological Survey in the SE¼NE¼NW¼ sec. 2, T. 2 S., R. 7 W. (Hasenmueller and Ault, in preparation).
Description: The Velpen Limestone Member is a variable unit, generally tan to black, dense, and argillaceous, containing small crinoid columnals and ranging from 0.1 to 4.5 feet (< 0.1 to 1.4 m) in thickness. The Velpen consists variably of black dense, sparsely fossiliferous limestone, brownish-gray, finely crystalline limestone containing abundant brachiopods and crinoid fragments, calcareous fossiliferous shale, and nonfossiliferous argillaceous siderite. It generally rests on black shale, which separates it from the underlying Colchester Coal Member, and underlies gray or black shale. The Velpen is recognizable in the outcrop wherever the Colchester can be identified. The Velpen may not be recognized in the subsurface on geophysical logs because of its thinness, but its position can usually be inferred from the position of the Colchester, which can be recognized on most logs.
Correlation: The stratigraphic position of the Velpen is identified in Illinois as the Oak Grove Limestone Member of the Carbondale Formation, a zone of limestones and calcareous shales.