Historical:Lusk Shale Member
M. E. Hopkins and J. A. Simon
The Lusk Shale Member of the Caseyville Formation (Weller, 1940, p. 36), is named for Lusk Creek in Pope County.
The type section consists of exposures along the creek north of Waltersburg (12, 13S-6E).
Extent and Thickness
The thickness of the Lusk varies from zero to over 200 feet.
The Lusk Shale member is the basal unit of the Pennsylvanian System in southeastern Illinois.
The member is composed of various amounts of silty shale, siltstone, and sandstone. Quartz pebbles are common to abundant in some sandstone units as much as 25 feet or more thick, and these units are similar to the Battery Rock and Pounds Sandstone Members. Other sandstone units as much as 50 feet thick are fine grained. The Lusk contains a few thin, unnamed, nonpersistent coal seams and a few zones with marine fossils, most of them fragmentary. In general, all the Pennsylvanian rocks in southern Illinois below the Battery Rock Sandstone are assigned to either the Lusk Shale or the Wayside Sandstone.
WELLER, J. M., 1940, Geology and oil possibilities of extreme southern Illinois: Illinois State Geological Survey Report of Investigations 71, 71 p.
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