Walnut Grove Limestone Member

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Lithostratigraphy: Hunton Limestone Megagroup >>Lingle Formation >>Walnut Grove Limestone Member
Chronostratigraphy: Paleozoic Erathem >>Devonian System >>Middle Devonian Series
Allostratigraphy: Kaskaskia Sequence

Primary source

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.

Contributing author(s)

Charles Collinson and Elwood Atherton


Original description

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.

Other names


Type section

Type location

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.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

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

Economic importance



NORTH, W. G., 1969, Middle Devonian strata of southern Illinois: Illinois State Geological Survey Circular 441, 45 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation