Type designation:

Type section: The Reelsville Limestone was named by Malott (1919, p. 10-11) for exposures of gray, biomicritic, somewhat ferruginous, and locally sandy limestone about 3 ft (1 m) thick near Reelsville, Putnam County, Indiana (Gray, 1970, 1986). Malott (1952, p. 26-27) later designated a type section on the south bluff of Walnut Creek immediately south of Reelsville (Gray, 1970, 1986).


Characteristically the Reelsville Limestone is a single bed of skeletal limestone 2 to 7 ft (0.5 to 2 m) thick, but in some small areas it is as thick as 20 ft (6 m) (Gray, 1986).

Distribution: The somewhat erratic distribution of the Reelsville is best understood by reference to the West Baden clastic belt (see under "Elwren Formation"), an elongate area that extends from Owen and Greene Counties southwestward (Sullivan, 1972; Gray, 1986). In the clastic belt the Beaver Bend and Reelsville Limestones are absent, and much of the West Baden Group is made up of sandstone that is indivisible into formations (Gray, 1986). Along the edges of the belt the limestones are anomalously thick and sandy, apparently the result of dilution by terrigenous clastic material from the belt (Gray, 1986).

North and west of the clastic belt, in an area that includes the type locality as well as the northern part of its outcrop, the Reelsville occurs only in isolated small areas (Gray, 1986). Few outcrops are known, therefore, from Putnam County southward to Lawrence County (Malott, 1952; Gray, 1986). South and east of the clastic belt the Reelsville is more continuous, and in many places two or more limestone beds are recognized in this general stratigraphic position (Gray, 1986). As concluded by Ross (1934) in an outcrop study from Martin County to Crawford County, only the lowermost of these beds is correctly assigned to the Reelsville; the others belong within the overlying Elwren Formation (Gray, 1986).


The Reelsville conformably overlies the Sample Formation and is overlain conformably by the Elwren Formation or disconformably by the Mansfield Formation (Morrowan) (Gray, 1970, 1986).


The Reelsville Limestone was considered by Malott (1931, p. 222) to be equivalent to the lower part of the Paint Creek Formation of southwestern Illinois; it was later shown instead to represent the upper part of the Paint Creek (Swann and Atherton, 1948; Gray, 1970, 1986). The term “Paint Creek” (as the Paint Creek Group) is now restricted to western Illinois use (Atherton and others, 1975, p. 153), and the name “Reelsville” has been adopted with member status for the upper part of the Ridenhower Formation of the standard Chesterian section (Swann, 1963, p. 35; Atherton and others, 1975, p. 155; Gray, 1986). The Reelsville Limestone correlates with rocks within North American foraminiferal Zone 16s of Mamet and Skipp (1971) and within Zone V3cs of the type Visean Series of European usage (Gray, 1986). On the basis of its conodont fauna, the Reelsville has been assigned to the Cavusgnathus charactus-Gnathodus bilineatus Range Zone (Collinson, Rexroad, and Thompson, 1971; Rexroad and Merrill, 1996).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: West Baden Group
Formation: Reelsville Limestone
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: West Baden Group
Formation: Reelsville Limestone

Misc/Abandoned Names:


Geologic Map Unit Designation:


Note: Hansen (1991, p. 52) in Suggestions to authors of the reports of the United States Geological Survey noted that letter symbols for map units are considered to be unique to each geologic map and that adjacent maps do not necessarily need to use the same symbols for the same map unit. Therefore, map unit abbreviations in the Indiana Geologic Names Information System should be regarded simply as recommendations.

COSUNA areas and regional terminology

Names for geologic units vary across Indiana. The Midwestern Basin and Arches Region COSUNA chart (Shaver, 1984) was developed to strategically document such variations in terminology. The geologic map (below left) is derived from this chart and provides an index to the five defined COSUNA regions in Indiana. The regions are generally based on regional bedrock outcrop patterns and major structural features in Indiana. (Click the maps below to view more detailed maps of COSUNA regions and major structural features in Indiana.)

COSUNA areas and numbers that approximate regional bedrock outcrop patterns and major structural featuers in Indiana.

Major tectonic features that affect bedrock geology in Indiana.


Atherton, Elwood, Collinson, Charles, and Lineback, J. A., 1975, Mississippian System, in Willman, H. B., Atherton, Elwood, Buschbach, T. C., Collinson, Charles, Frye, J. C., Hopkins, M. E., Lineback, J. A., and Simon, J. A., Handbook of Illinois stratigraphy: Illinois State Geological Survey Bulletin 95, p. 123-163.

Collinson, Charles, Rexroad, C. B., and Thompson, T. L., 1971, Conodont zonation of the North American Mississippian: Geological Society of America Memoirs 127, p. 353-394.

Gray, H. H., 1970, Reelsville Limestone, in Shaver, R. H., Burger, A. M., Gates, G. R., Gray, H. H., Hutchison, H. C., Keller, S. J., Patton, J. B., Rexroad, C. B., Smith, N. M., Wayne, W. J., and Wier, C. E., Compendium of rock-unit stratigraphy in Indiana: Indiana Geological Survey Bulletin 43, p. 138-139.

Gray, H. H., 1986, Reelsville Limestone, in Shaver, R. H., Ault, C. H., Burger, A. M., Carr, D. D., Droste, J. B., Eggert, D. L., Gray, H. H., Harper, Denver, Hasenmueller, N. R., Hasenmueller, W. A., Horowitz, A. S., Hutchison, H. C., Keith, B. D., Keller, S. J., Patton, J. B., Rexroad, C. B., and Wier, C. E., Compendium of Paleozoic rock-unit stratigraphy in Indiana–a revision: Indiana Geological Survey Bulletin 59, p. 122-123.

Hansen, W. R., 1991, Suggestions to authors of the reports of the United States Geological Survey (7th ed.): Washington, D.C., U.S. Geological Survey, 289 p.

Malott, C. A., 1919, The "American Bottoms" region of eastern Greene County, Indiana–a type unit in southern Indiana physiography: Indiana University Studies, v. 6, no. 40, 61 p.

Malott, C. A., 1931, Geologic structure in the Indian and Trinity Springs locality, Martin County, Indiana: Indiana Academy of Science Proceedings, v. 40, p. 217-231.

Malott, C. A., 1952, Stratigraphy of the Ste. Genevieve and Chester formations of southern Indiana: Ann Arbor, Michigan, Edwards Letter Shop, 105 p.

Mamet, B. L., and Skipp, B. A., 1971, Lower Carboniferous calcareous Foraminifera–preliminary zonation and stratigraphic implications for the Mississippian of North America: Sixieme Congres International de Stratigraphie et de Geologie du Carbonifere Sheffield, 1967, Compte rendu, v. 3, p. 1,129-1,146.

Rexroad, C. B., and Merrill, G. K., 1996, Conodonts from the Reelsville Limestone (Chesterian, Lower Carboniferous) in Indiana and adjacent Kentucky, U.S.A: Geologica et Palaeontologica, v. 30, p. 225-238.

Ross, T. W., 1934, A stratigraphic and petrologic study of the Reelsville Limestone (lower Chester) in south-central Indiana: Bloomington, Indiana University, master's thesis, 68 p.

Shaver, R. H., coordinator, 1984, Midwestern basin and arches region–correlation of stratigraphic units in North America (COSUNA): American Association of Petroleum Geologists Correlation Chart Series.

Sullivan, D. M., 1972, Subsurface stratigraphy of the West Baden Group in Indiana: Indiana Geological Survey Bulletin 47, 31 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.

Swann, D. H., and Atherton, Elwood, 1948, Subsurface correlations of lower Chester strata of the Eastern Interior Basin: Journal of Geology, v. 56, p. 269-287.

For additional information contact:

Nancy Hasenmueller (
Date last revised: April 5, 2017