Cape Limestone

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Lithostratigraphy: Cape Limestone
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Cincinnatian Series >>Edenian Stage
Allostratigraphy: Tippecanoe 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)

H. B. Willman and T. C. Buschbach


Original description

The Cape Limestone (Templeton and Willman, in Gutstadt, 1958b, p. 524).


The Cape Limestone, the oldest Cincinnatian formation, is named for Cape Girardeau, Missouri.

Other names

The Cape Limestone was for many years called the Fernvale Limestone.


Type section

Type location

The type section for the Cape Limestone is an exposure on Main Street just north of Broadway in Cape Girardeau, where the formation is 8.5 feet thick, the maximum thickness observed (Templeton and Willman, 1963, p. 134).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Cape Limestone occurs mainly in shallow channels eroded in the top of the Dunleith Formation. In the northern part of the area, it is overlain by the Elgin Shale Member of the Scales Shale, as shown by the presence of the Lower Depauperate Zone above it at Valmeyer. In the southern part of the outcrop area, it is overlain by the Thebes Sandstone Sandstone Member of the Scales.

Extent and thickness

The Cape Limestone has a patchy distribution in the outcrop area in Missouri from St. Louis to Cape Girardeau. It occurs in the southwestern part of Illinois, where Cincinnatian strata deeply truncate the Trentonian Series, but it is exposed only at Valmeyer, Monroe County (SW 3, 3S-11 W), where it is 1.5 feet thick. A few small outcrops formerly occurred near Thebes in Alexander County but are now covered.


The Cape Limestone is a light gray to reddish gray, coarse-grained, fossiliferous calcarenite. It occurs in medium to thick beds with weak shaly partings.




Well log characteristics


The Cape Limestone has a large fauna characterized by brachiopods, particularly Lepidocyclus capax, and crinoids.

Age and correlation

The Cape Limestone is correlated with the Fernvale Limestone in Arkansas and Oklahoma but not with the type Fernvale in Tennessee, which, being Richmondian in age, is much younger.

Environments of deposition

Economic importance



GUTSTADT, A. M., 1958b, Upper Ordovician stratigraphy in Eastern Interior region: American Association of Petroleum Geologists Bulletin, v. 42, p. 513-547.
TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation