Historical:Cave Hill Shale Member
Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Cave Hill Shale Member of the Kinkaid Formation (Swann, 1963, p. 42-43), the middle member, is named for Cave Hill, Saline County.
The type section of the Cave Hill Shale Member is on Cave Hill, Saline County, on the west slope of the hill (SE SW NW 5, 10S-7E).
Extent and Thickness
The Cave Hill Shale is 108 feet thick in the type section, but is over-thickened 25-30 feet by tectonic squeezing. It is a limestone-shale unit about 65 feet thick in the northern area, thickening southward to a little more than 90 feet in the south. The proportion of limestone increases southward, and in the southern area the shale is largely limited to the top and bottom few feet (fig. M-1C).
The upper shale, about 15 feet thick, consists of calcareous, dark gray and greenish gray shale at the top and red and green shale below. The red shale makes a fairly extensive marker bed. The middle limestone part contains a variety of carbonate rocks, mainly light brownish gray lithographic limestone, dark shaly limestone, and buff dolomite. The interbedded shale is mainly dark gray, but locally some is very dark gray or black. The basal shale, about 15 feet thick, consists of dark gray shale and locally some black shale. The lower third of the Cave Hill commonly includes some silty shale, a little gray to dark gray and green siltstone, and, in places, more or less shaly sandstone.
SWANN, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.
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