Type designation:

Type locality: In 1931 Malott (p. 224 and fig. 2) noted that the shale was "called the Indian Springs shale after the outcrop 0.25 miles northwest of the village" of that name in Martin County, Indiana (Gray, 1986).

Reference sections: Gray (1986, p. 62) designated the following two sections as reference sections of the Indian Springs Shale Member.

(1) An exposure in a railroad cut about 3 miles (4 km) east of Shoals in sec. 28, T. 3 N., R. 3 W., Martin County, in which the member is 22 ft (7 m) thick (Gray and others, 1957, p. 16).

(2) A core from Indiana Geological Survey drill hole 48 (Indiana Geological Survey Petroleum Database Management System No.106886) in sec. 32, T. 2 N., R. 2 W., Orange County (Gray, Jenkins, and Weidman, 1960, p. 75-77), in which the member is 32 ft (10 m) thick.

History of usage:

The term “Indian Springs Shale” was proposed (without documentation) in 1920 by Malott and Thompson (p. 522) (Gray, 1986).

Malott, Esarey, and Bieberman (1948, p. 24) included the shale in the Golconda (now Haney) Limestone (Gray, 1986), To clarify the nomenclature of the Golconda Limestone, Gray, Jenkins, and Weidman (1960, p. 39-41) placed the shale in the Big Clifty Formation, where it still resides (Gray, 1986).

Gray (1986, p. 62) recognized formally this shale unit that is widely present on the outcrop in Indiana and adopted the name “Indian Springs Shale Member” for the upper part of the Big Clifty Formation.


The member commonly consists of 3 to 14 ft (1 to 4 m) of gray fossiliferous shale and interbedded thin limestone underlain by 3 to 10 ft (1 to 3 m) of varicolored shale and siltstone (Gray, 1986).

The Indian Springs Shale Member can be recognized almost continuously along the outcrop from Perry County (Gray and Powell, 1965, p. 18) to Greene County (Malott, 1952, p. 66). Although the shale is soft and poorly exposed except in relatively fresh cuts; its place can commonly be noted by such features as a break in slope above the prominent sandstone of the lower Big Clifty and beneath the ledges of the Haney Limestone (Gray, 1986). In most places the member is 11 to 25 ft (3 to 8 m) thick. It is not distinguished in the subsurface (Droste and Keller 1995), where the Big Clifty Formation is mainly shale.

The fauna of the Indian Springs member has been rather thoroughly studied, but little has been published (Gray, 1986). Horowitz (1979) presented from a single site a faunal list of more than 50 species, including notably bryozoans, brachiopods, and crinoids; from the same site Kelly (1984) tabulated an even more diverse fauna, including vertebrate remains (Gray, 1986).


The fauna is consistent with that reported for the upper part of the Fraileys Shale and for the Haney Limestone elsewhere in the Illinois Basin (Gray, 1986).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Stephensport Group
Formation: Big Clifty Formation
Member: Indian Springs Shale Member
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Stephensport Group
Formation: Big Clifty Formation
Member: Indian Springs Shale Member

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.


Droste, J. B., and Keller, S. J., 1995, Subsurface stratigraphy and distribution of oil fields of the Stephensport Group (Mississippian) in Indiana: Indiana Geological Survey Bulletin 64, 21 p.

Gray, H. H., 1986, Indian Springs Shale Member, 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. 62.

Gray, H. H., and Powell, R. L., 1965, Geomorphology and groundwater hydrology of the Mitchell Plain and Crawford Upland in southern Indiana: Indiana Geological Survey Field Conference Guidebook 11, 26 p.

Gray, H. H., Dawson, T. A., McGregor, D. J., Perry, T. G., and Wayne, W. J., 1957, Rocks associated with the Mississippian-Pennsylvanian unconformity in southwestern Indiana: Indiana Geological Survey Field Conference Guidebook 9, 42 p.

Gray, H. H., Jenkins, R. D., and Weidman, R. M., 1960, Geology of the Huron area, south-central Indiana: Indiana Geological Survey Bulletin 20, 78 p.

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.

Horowitz, A. S., ed., 1979, Mississippian rocks—New Albany to Indianapolis, Indiana, via Interstate 64 and Indiana Highway 37: Bloomington, Indiana, Guidebook prepared for Ninth International Congress of Carboniferous Stratigraphy and Geology, Field Trip 7, Day 4, May 20, 1979, 70 p. [mimeo.].

Kelly, S. M., 1984, Paleoeology [sic] and paleontology of the Indian Springs Shale Member, Big Clifty Formation (middle Chesterian) in south-central Indiana: Bloomington, Indiana University, Ph.D. thesis, xix + 343 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.

Malott, C. A., and Thompson, J. D., Jr., 1920, The stratigraphy of the Chester Series of southern Indiana [abs.]: Science, new ser., v. 51, p. 521-522.

Malott, C. A., Esarey, R. E., and Bieberman, D. F., 1948, Upper and Middle Mississippian formations of southern Indiana: Indiana Division of Geology Field Conference Guidebook 2, 27 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.

For additional information contact:

Nancy Hasenmueller (
Date last revised: June 8, 2017