Tar Springs Sandstone
Lithostratigraphy: Pope Megagroup >>Tar Springs Sandstone
Chronostratigraphy: Paleozoic Erathem >>Mississippian Subsystem >>Chesterian Series >>Elviran Stage
Allostratigraphy: Kaskaskia Sequence
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.
Elwood Atherton, Charles Collinson, and Jerry A. Lineback
Tar Springs Sandstone (Owen, 1856, p. 174; Butts, 1917, p. 103-105).
Named for Tar Springs, Breckenridge County, Kentucky.
The type section of the Tar Springs Sandstone is an exposure in a cliff at the town of Tar Springs, Breckenridge County, Kentucky, where the sandstone is about 50 feet thick.
Extent and thickness
It is one of the thickest and most persistent sandstone formations of the Chesterian Series. The Tar Springs is 75-130 feet thick for most of its extent in Illinois, thinning to about 50 feet near its northwestern limits (fig. M-43). It is locally more than 150 feet thick, and in the thicker portions the ratio of sandstone to shale is relatively high.
Locally the formation is almost entirely sandstone or almost entirely shale (fig. M-1A). The sandstone is white to light gray, very fine grained to fine grained, locally medium grained, angular, and friable to well cemented. Conglomerate with coarse sand grains and limestone pebbles occurs at the base but is rare. In general, one to three well developed sandstone bodies make up a little more than half the formation. Commonly, a sandstone body occurs at the base of the formation, but sandstones also occur at the middle and at the top. The sandstone bodies in the Tar Springs thicken or thin rapidly, and they have a deltaic distributary pattern similar to that of other Chesterian sandstones (Swann, 1963). The remainder of the formation is shale, siltstone, and shaly sandstone. The shale is dark gray and slightly carbonaceous. The siltstones and some of the thin-bedded sandstones are medium to dark olive gray. Commonly there is 3-15 feet of shale at the base and a little more than that at the top. Thin beds of coal occur locally near the top and middle of the formation, especially near the southern limit.
Well log characteristics
Age and correlation
Environments of deposition
BUTTS, CHARLES, 1917, Descriptions and correlations of the Mississippian formations of western Kentucky, Part I of Mississippian formations of western Kentucky: Kentucky Geological Survey, v. 1, 119 p.
OWEN, D. D., 1856, Report of the geological survey in Kentucky made during the years 1854 and 1855: Kentucky Geological Survey Bulletin, v. I, Series 1, 416 p.
SWANN, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.
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