M. E. Hopkins and J. A. Simon
The Virgilian Series of the Pennsylvanian System (Moore, 1931, correlation chart) is named for Virgil, Greenwood County, Kansas, which lies in the outcrop belt of these rocks.
In Illinois it includes all Pennsylvanian strata above a position a few feet below the coal that occurs just below the Shumway Limestone Member (Willman et al., 1967). It thus includes the upper half of the Mattoon Formation of the McLeansboro Group (fig P-2).
Where marine rocks are found, as they are in Illinois and the Midcontinent Region, the Virgilian includes strata containing fusulinids of the genus Triticites that are more advanced than the subgenus Kansanella found in lower strata. The upper limit is placed just below the first appearance of the Permian genera Pseudoschwagerina and/or Schwagerina, but neither have been found in the Illinois Basin. The spores and plant-compression fossils in Virgilian rocks are not well known.
MOORE, R. C., 1931, Pennsylvanian cycles in the northern Midcontinent region: Illinois State Geological Survey Bulletin 60, p. 247-257.
WILLMAN, H. B., et al., 1967, Geologic map of Illinois: Illinois State Geological Survey.
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