Charles Collinson and Elwood Atherton
The Blocher Shale (Campbell, 1946, p. 840; Lineback, 1968a, p. 1295-1298), the basal formation in the New Albany Group, is named for Blocher, Scott County, Indiana.
The type section of the Blocher Shale is 1.5 miles northwest of Blocher, Scott County, Indiana, on Highway 50, 1 mile east of the Baltimore and Ohio Railroad. It originally included only the lower 8-10 feet of black shale in the type area, but Lineback (1968a) extended it upward about 6 feet to the base of the Spathiocaris Zone, which is a gray shale more easily traced, and that position is now accepted.
North (1969) correlated it with the Tripp Member of the Lingle Formation, but the conodont fauna suggests that it is equivalent also to higher parts of the Lingle, the Alto Formation, and the earliest Upper Devonian strata (Collinson et al., 1967a).
Extent and Thickness
The Blocher Shale extends from the type locality into eastern Illinois (Workman and Gillette, 1956), where it is as much as 80 feet thick, but it thins out in the central part of the state (fig. D-17)
CAMPBELL, GUY, 1946, New Albany Shale: Geological Society of America Bulletin, v. 57, p. 829-908.
COLLINSON, CHARLES, L. E. BECKER, G. W. JAMES, J. W. KOENIG, and D. H. SWANN, 1967a, Illinois Basin, in International symposium on the Devonian System: Alberta Society of Petroleum Geologists, v. 1, p. 940-962; Illinois State Geological Survey Reprint 1968-G.
LINEBACK, J. A., 1968a, Subdivisions and depositional environments of New Albany Shale (Devonian-Mississippian) in Indiana: American Association of Petroleum Geologists Bulletin, v. 52, p. 1291-1303.
NORTH, W. G., 1969, Middle Devonian strata of southern Illinois: Illinois State Geological Survey Circular 441, 45 p.
WORKMAN, L. E., and TRACEY GILLETTE, 1956, Subsurface stratigraphy of the Kinderhook Series in Illinois: Illinois State Geological Survey Report of Investigations 189, 46 p.
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