Historical:Drury Shale Member
M. E. Hopkins and J. A. Simon
The Drury Shale Member of the Caseyville Formation (Lamar, 1925, p. 91-95) is named for Drury Creek in Jackson County.
The type section consists of exposures along Drury Creek south of Makanda (33, 34, 10S-1W).
The Drury is equivalent to part of the Mansfield Sandstone of Indiana.
Extent and Thickness
The Drury is as much as 100-150 feet thick in places near the type area, but the thickness varies somewhat, partly because of differential erosion prior to deposition of the overlying Pounds Sandstone.
All strata lying between the Battery Rock and Pounds Sandstones are considered equivalent to the Drury, but, for the sake of clarity in classification, the name "Drury" is not used in parts of southeastern Illinois where two other members of the Caseyville Formation - the Sellers Limestone and the Gentry Coal - occur within the Drury interval.
The Drury is a complex unit of sandy or silty shale, siltstone, and lenticular massive sandstone units, and is much like the Lusk Shale. It contains at least two thin, nonpersistent coals. Although rocks of Drury age are present in the subsurface of the southern part of the Illinois Basin, the Battery Rock and Pounds Sandstones cannot generally be differentiated in well logs, which makes it impractical to differentiate the Drury.
LAMAR, J. E., 1925, Geology and mineral resources of the Carbondale Quadrangle: Illinois State Geological Survey Bulletin 48, 172 p.
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