Tar Springs Formation



Type designation:

Type section: According to Gray (1970, 1986), the original name “Tar Springs Sandstone” is generally attributed to D. D. Owen (1857, p. 85-87). The name is taken from a natural feature in Breckinridge County, Kentucky, near which the unit, as described by Butts (1917, p. 103-105), is 100 to 150 ft (30 to 45 m) thick and consists of massive cliff-forming sandstone, shaly sandstone, and shale (Gray, 1970, 1986).

History of usage:

The name “Tar Springs Sandstone” was first applied in Indiana only to a crossbedded cliff-forming sandstone that is as much as 90 ft (27 m) thick in some places but is absent from others (Malott, 1925, p. 106-108; Gray, 1970, 1986). The same name was later applied to a rather indeterminate unit that includes other rocks as well as the prominent sandstone (Malott, Esarey, and Bieberman, 1948; Gray, 1970, 1986). The unit was designated the Tar Springs Formation by Gray and others (1957, p. 6 and pl. 2), and the lower boundary was established at the top of the main or massive part of the Glen Dean Limestone by Gray, Jenkins, and Weidman (1960, p. 30) (Gray, 1986). As a result of this redefinition, a considerable (but variable) thickness of fossiliferous rocks was excluded from the Glen Dean and included in the Tar Springs see the article "Glen Dean Limestone" for a discussion of the biostratigraphic correlation of these rocks (Gray, 1986). Finally, the upper boundary was fixed at the base of the Vienna Limestone Member of the Branchville Formation and outcrop aspects of the formation were discussed by Gray (1978, p. 5-8) (Gray, 1986).


In Indiana, the Tar Springs Formation is primarily shale, but it also contains scattered thin beds of limestone and massive local lenses of sandstone that on outcrop are differentiated as the Tick Ridge Sandstone Member (Gray, 1986). The formation ranges in thickness from about 70 ft (21 m) in the area of outcrop to more than 150 ft (46 m) in central Posey County and in southwestern Gibson County (Droste and Keller, 1995). Commonly sandstone predominates in those areas where the Tar Springs is as much as 150 ft (46 m) thick (Droste and Keller, 1995).

Distribution: The Tar Springs Formation is recognized on the surface from southwestern Orange County to the Ohio River and is known in the subsurface from central Martin County southwestward (Gray, 1970, 1986).


Although the base of the sandstone member is uneven, in most places the formation overlies the Glen Dean Limestone conformably (Gray, 1970, 1986). See Swann, 1963, p. 37-38, for a discussion of locally disconformable relationships (Gray, 1986).

Where the Vienna Limestone Member is present, it overlies the Tar Springs Formation conformably; where the limestone is depositionally absent, higher Chesterian rocks (Branchville Formation of outcrop usage) overlie the Tar Springs, also apparently conformably, but the distinction is difficult to make (Gray, 1986). Northward, however, these formations are truncated by the Mississippian-Pennsylvanian disconformity, and the Tar Springs is disconformably overlain by the Mansfield Formation (Morrowan) (Gray, 1986).

History of boundary problems and concepts of naming formations in upper part of Chesterian Series: For many years the exact positions of most of the boundaries between formations in the upper part of the Chesterian Series were not well understood (Gray, 1970, 1986). In large part this uncertainty resulted from the fact that no detailed work was done on these rocks for many years following Malott's (1925) pioneering study (Gray, 1970, 1986). In that paper Malott did not recognize the need for including all the rocks in his scheme of formal nomenclature, for he stated (p. 106):

The shale masses count but little in the stratigraphic expression of the upper Chester, and may not be used in the study of the structural details which the region of their occurrence expresses. They are mere fillers or intervals between the outstanding limestone and sandstone units which alone are given names and definite status.

Later, Malott and Esarey (1940, p. 7), in describing the section at Sulphur, stated that "the sandstone above the Vienna . . . is not the Waltersburg," the shale interval between them being only 10 ft (3 m) rather than the more common (as then understood) 50 to 60 ft (15 to 18 m), and ". . . the Tar Springs is poorly represented as a sandstone" (Gray, 1970, 1986). Still later, however, Malott, Esarey, and Bieberman (1948, stops 2-5, pl. 2) apparently recognized the necessity of extending formational names to the entire section; some of the shale intervals were assigned to the limestone formations, however, and some to the sandstones, and it is difficult to determine what philosophy governed the choice (Gray, 1970, 1986).

Boundaries, nomenclature, and lithologic content of outcropping upper Chesterian rocks in southernmost Indiana were reconsidered by Gray (1978).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Buffalo Wallow Group
Formation: Tar Springs Formation
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Buffalo Wallow Group
Formation: Tar Springs Formation

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.)

Map showing the COSUNA areas (heavy black line) that approximate regional bedrock outcrop patterns and major structural features in Indiana, and the COSUNA numbers (large bold font) for these areas. The COSUNA boundaries are limited to state and county boundaries that facilitate coding.

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

Map showing major tectonic features that affect bedrock geology in Indiana.

Major tectonic features that affect bedrock geology in Indiana.


Butts, Charles, 1917, Mississippian formations of western Kentucky: Descriptions and correlations of the Mississippian formations of western Kentucky: Kentucky Geological Survey, ser. 4, v. 5, pt. 1, 119 p.

Droste, J. B., and Keller, S. J., 1995, Subsurface stratigraphy and distribution of oil fields of the Buffalo Wallow Group (Mississippian) in Indiana: Indiana Geological Survey Bulletin 63, 24 p.

Gray, H. H., 1970, Tar Springs Formation, 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. 174-176.

Gray, H. H., 1978, Buffalo Wallow Group upper Chesterian (Mississippian) of southern Indiana: Indiana Geological Survey Occasional Paper 25, 28 p.

Gray, H. H., 1986, Tar Springs Formation, 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. 152-153.

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.

Malott, C. A., 1925, The upper Chester of Indiana: Indiana Academy of Science Proceedings, v. 34, p. 103-132.

Malott, C. A., and Esarey, R. E., 1940, Outcrop of the Chester Series of southern Indiana: Indiana-Kentucky Geological Society, May 18, 1940, 9 p. [mimeo.].

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.

Owen, D. D., 1857, Second report of the geological survey in Kentucky, made during the years 1856 and 1857: Frankfort, Ky., A. G. Hodges, Public Printer, 391 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.

Swann, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.

For additional information contact:

Nancy Hasenmueller (hasenmue@indiana.edu)
Date last revised: June 6, 2017

Generating Your PDF

Your session for the Indiana Geological and Water Survey will expire in 30 minutes. Please refresh your broswer or click here to restart your session timer.