Historical:Spar Mountain Sandstone Member
Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Spar Mountain Sandstone Member of the Ste. Genevieve Limestone (Tippie, 1945, p. 1657), which overlies the Fredonia Limestone Member, is named for Spar Mountain, Hardin County.
The type section of the Spar Mountain Sandstone Member is located on Spar Mountain, Hardin County where the section is exposed on the south-facing slope (NE 4, 12S-9E).
Extent and Thickness
In the type section the Spar Mountain is 8-15 feet thick. The Spar Mountain extends throughout most of the area of the Ste. Genevieve (fig. M-22).
In the type locality the Spar Mountain Member consists of light gray to greenish gray, calcareous, glauconitic sandstone or siltstone grading to very sandy limestone. Lenses of similar sandstone and sandy calcarenite occur sporadically at other levels in the Ste. Genevieve, and the Spar Mountain is difficult to differentiate from them in some areas. It is erratic in thickness and has a varied lithology, including beds of dolomite, limestone, sandy limestone, sandstone, and thin shale. In the northern part of its extent, it is as much as 40 feet thick. In the western part of the basin- for example, in western Washington County- the Spar Mountain grades laterally into the Aux Vases Sandstone and is separated from it by vertical cut-off.
TIPPIE, F. E., 1945, Rosiclare-Fredonia contact in and adjacent to Hardin and Pope Counties, Illinois: American Association of Petroleum Geologists Bulletin, v. 29, p. 1654-1663; Illinois State Geological Survey Report of Investigations 112.
|Geo Unit Designation