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).
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).
Regional Indiana usage:
Illinois Basin (COSUNA 11)
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.
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.
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., 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.
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.].
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 (email@example.com)Date last revised: June 6, 2017