Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Genevievian Stage (Swann, 1963, p. 20-21) is named for the Ste. Genevieve Limestone.
The type section of the Genevievian Stage is the same of that for the Ste. Genevieve Limestone which is in Ste. Genevieve, Missouri.
It is the only stage at present differentiated in the Valmeyeran Series and covers only the latest part of Valmeyeran time (fig. M-3). It consists of all the strata contemporaneous with the Ste. Genevieve Limestone where its top corresponds with the last occurrence of Platycrinites penicillus. The Platycrinites - Talarocrinus boundary is the basis for the time plane separating the Valmeyeran and Chesterian Series. It falls within the Renault Limestone at the top of the Levias Member. The base of the Genevievian Stage is less well defined, but in the Illinois Basin it is placed at the top of the St. Louis Limestone, which is the base of the Gnathodus bilineatus - Cavusgnathus charactus Zone, somewhat higher than the disappearance of Lithostrotion and Lithostrotionella with large corallites, where it was originally placed.
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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