Little Bear Soil

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Lithostratigraphy: Tuscaloosa Formation >>Little Bear Soil
Chronostratigraphy: Mesozoic Erathem >>Cretaceous System

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 John C. Frye


Original description

The Little Bear Soil (Mellen, 1937, p. 8-20), a soil locally preserved at the base of the Cretaceous System.


Named for Little Bear Creek, Tishomingo County, Mississippi.

Other names


Type section

Type location

It is well exposed along the Post Creek Cutoff in Pulaski County (cen. 2, 15S-2E), where it is 7 feet thick, rests on the St. Louis Limestone, and is overlain by gravel of the Tuscaloosa Formation.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Little Bear Soil is included in the lower part of the Tuscaloosa Formation.

Extent and thickness

Isolated remnants have been found throughout the eastern part of the Mississippi Embayment.


It is the only soil-stratigraphic unit that has been named in Illinois in pre-Quaternary strata (Pryor and Ross, 1962; Ross, 1963). It consists of remnants of an iron-rich residual soil developed on Paleozoic rocks. In Illinois it consists of red and brown clays with lenses and nodules of brown to black limonite and, generally, a few angular chert pebbles.




Well log characteristics


Age and correlation

The Little Bear Soil was developed during early Cretaceous time, after the erosional truncation of the Paleozoic rocks by the sub-Cretaceous unconformity.

Environments of deposition

Economic importance



MELLEN, F. F., 1937, Little Bear residuum: Mississippi Geological Survey Bulletin 34, 36 p.
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.
ROSS, C. A., 1963, Structural framework of southernmost Illinois: Illinois State Geological Survey Circular 351, 27 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation