Gunter Sandstone

Lithostratigraphy: Knox Dolomite Megagroup >>Prairie du Chien Group >>Gunter Sandstone
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Canadian Series >>Trempealeauan Stage
Allostratigraphy: Sauk 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

Name

Original description

Gunter Sandstone (Ball and Smith, 1903, p. 26).

Derivation

Named for the now abandoned Gunter post office in Miller County, central Missouri, where it is 2.5-18 feet thick in exposures along the Osage River.

Extent and thickness

It is absent in outcrops of lower Prairie du Chien strata in Lee and Ogle Counties, Illinois. In subsurface, the Gunter is commonly a few to 20 feet thick and has a widespread but patchy distribution (fig. O-9). It is continuous and 10-25 feet thick between the centers of La Salle and McLean Counties in north-central Illinois.

Fig. O-9 -- Thickness of the Oneota Dolomite and the Gunter Sandstone.

Lithology

The Gunter consists of medium- to fine-grained, moderately sorted, subrounded quartz grains. It contains thin beds of light gray, fine-grained dolomite and small amounts of green shale. Sharp contacts and irregular distribution of the sandstone suggest unconformities at its top and bottom.

Age and correlation

The Gunter is tentatively correlated with the Rose Run Sandstone at the base of the upper Knox in eastern Ohio and eastern Kentucky.

References

BALL, S. H., and A. F. SMITH, 1903, Geology of Miller County: Missouri Bureau of Geology and Mines (2), v. 1, 207 p.

ISGS Codes

Stratigraphic Code	Geo Unit Designation
8480	Os