Walnut Grove Limestone Member
Lithostratigraphy: Hunton Limestone Megagroup >>Lingle Formation >>Walnut Grove Limestone Member
Chronostratigraphy: Paleozoic Erathem >>Devonian System >>Middle Devonian Series
Allostratigraphy: Kaskaskia Sequence
Willman, H. B., Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, and Jack A. Simon, 1975, Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.
Charles Collinson and Elwood Atherton
The Walnut Grove Limestone Member of the Lingle Formation (North, 1969, p. 29-30).
Named for Walnut Grove Church, Union County, 1 mile southeast of the type section.
The type section of the Walnut Grove Member is an outcrop near the head of a small tributary of Clear Creek (SE SE SW 22, 11S-2W), where the member is 29 feet thick.
The Walnut Grove Limestone Member is the uppermost member of the Lingle Formation.
Extent and thickness
The Walnut Grove occurs only in and near the outcrop area in Jackson, Union, and Alexander Counties (fig. D-15), and its maximum thickness is about 50 feet.
The Walnut Grove Member is cherty, very silty, glauconitic, spore-bearing, fine-grained, fossiliferous limestone locally interbedded with very dark brown, calcareous shale. The Rendleman Oolite Bed near the base is a distinctive key bed.
Well log characteristics
Fossils include crinoids, corals, brachiopods, and sporangites.
Age and correlation
Environments of deposition
NORTH, W. G., 1969, Middle Devonian strata of southern Illinois: Illinois State Geological Survey Circular 441, 45 p.
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