Sexton Creek Limestone

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Lithostratigraphy: Hunton Limestone Megagroup >>Sexton Creek Limestone
Chronostratigraphy: Paleozoic Erathem >>Silurian System >>Alexandrian Series
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 Elwood Atherton

Name

Original description

Derivation

The Sexton Creek Limestone named for exposures in the Mississippi River bluff at the mouth of Sexton Creek in Alexander County (SW 27, 14S-3W) where it is about 40 feet thick.

Other names

History/background

Type section

Type location

The Sexton Creek Limestone is best exposed 4 miles northeast of Sexton Creek, just north of the mouth of Dongola Hollow (SW SE NW 12, 14S-3W).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Sexton Creek Limestone (Savage, 1909, p. 518; Ulrich, 1911) overlies the Edgewood Formation in southern Illinois (fig. S-6). The Sexton Creek was originally defined to include higher strata, now differentiated as the St. Clair Limestone, but was restricted to its present boundaries by Ulrich (1911). The Sexton Creek locally truncates the Edgewood Limestone to rest directly on the Girardeau Limestone. The Sexton Creek and its contact with the Edgewood Limestone are exposed in a roadcut a quarter of a mile southeast of Gale (NE NE NW 4, 15S-3W) (Pryor and Ross, 1962).

Extent and thickness

Lithology

The formation is a thin-bedded, fine-grained, cherty, gray limestone. The upper part is thicker bedded and is mottled red. In the areas where it is relatively thick, the Sexton Creek commonly contains persistent bands of black chert nodules.

Core(s)

Photograph(s)

Contacts

Well log characteristics

Fossils

Age and correlation

The formation is correlated with the Kankakee Formation in northern Illinois on the basis of its fossils, although the faunal zones that mark the top and bottom of the Kankakee Formation have not been found in the Sexton Creek. The Sexton Creek is approximately equivalent to the Brassfield Limestone in Indiana and Kentucky.

Environments of deposition

Economic importance

Remarks

References

PRYOR, W. A., and C. A. ROSS, 1962, Geology of the Illinois parts of the Cairo, La Center, and Thebes Quadrangles: Illinois State Geological Survey Circular 332, 39 p.
SAVAGE, T. E., 1909, Ordovician and Silurian formations in Alexander County, Illinois: American Journal of Science, v. 28, p. 509-519.
ULRICH, E. O., 1911, Revision of the Paleozoic systems: Geological Society of America Bulletin, v. 22, p. 281-680.

ISGS Codes

Stratigraphic Code Geo Unit Designation
6940
Ssx