Type designation:

Type locality: The name “West Baden” was originally proposed as a group name in 1920 by E. R. Cumings in a letter to Stuart Weller (Cumings, 1922, p. 514; Gray, 1970, 1986). The group is named for West Baden, Orange County, Indiana (Gray, 1970, 1986). The term received no subsequent use, however, until it was revived in a slightly modified sense by Gray, Jenkins, and Weidman (1960, p. 44-48) (Gray, 1970, 1986).

History of usage:

Naming of groups in upper part of Mississippian System in Indiana: Rocks that are now considered to belong to the Chesterian Series in Indiana previously went by a variety of names, most of which originated elsewhere (Gray, 1970, 1986). Among these names are Ferruginous Sandstone, Kaskaskia Limestone, Archimedes Limestone, Pentremital Limestone, and Chester Limestone, most of which were originally used in early reports on the geology of the region surrounding Ste. Genevieve, Missouri, and Chester, Illinois (Gray, 1970, 1986).

Hopkins (1902, 1904) first applied an indigenous name to these rocks in Indiana. He included in his Huron Group, named for a village in southwestern Lawrence County, all rocks from the top of the Mitchell Limestone to the base of the Mansfield Formation (Gray, 1970, 1986). The name Huron was used for a time, but it was preoccupied, and when equivalence to the Chester Group of southern Illinois became clear, Greene (1911, p. 269) suggested that the name Chester be substituted (Gray, 1970, 1986). He then casually and without explanation used the name Solsberry Formation for these rocks (Greene, 1911, p. 275, 281; Gray, 1970, 1986).

As the term “Chester” came into common use and formational names became accepted, subdivision of the series into groups became possible (Gray, 1970, 1986). These subdivisions were called "lower," "middle," and "upper Chester" (Cumings, 1922, p. 408, 515) and were used as groups, sometimes with capital letters, but were commonly not expressly called groups (Gray, 1970, 1986). "Chester" became "Chesterian," a time and time-rock name that is appropriately designated a series or epoch but that is inappropriate as a group name; principally for this reason Gray, Jenkins, and Weidman (1960, p. 44) adapted two group names earlier suggested by Cumings (1922, p. 514), West Baden and Stephensport, to replace with some modification the former usage, lower and middle Chester (Gray, 1986). The Kentucky name Buffalo Wallow was adopted by Gray (1978) in a group sense and in somewhat modified scope for outcropping upper Chesterian rocks (Gray, 1986).


The West Baden consists of, in descending order, the Elwren Formation (the Cypress Formation in the subsurface), Reelsville Limestone, Sample Formation, Beaver Bend Limestone, and Bethel Formation (Gray, 1970, 1986). It consists dominantly of gray to varicolored shale and mudstone and thin-bedded to cross-bedded sandstone; limestone in beds of variable thickness is an important but lesser constituent (Gray, 1962, table 2 and fig. 4; Gray, 1970, 1986). Total thickness along the outcrop ranges from 100 to 140 ft (30 to 43 m) (Gray, 1970, 1986). Known on the surface from Putnam County southward to the Ohio River, the West Baden Group is also recognized in the subsurface from Parke County southwestward (Gray, 1986). Maximum reported subsurface thickness is 260 ft (80 m) in western Gibson County (Sullivan, 1972, p. 11 and pl. 3; Gray, 1970, 1986).

A major feature of the West Baden Group is a southwestward-trending belt about 6 miles (10 km) wide across which the limestones were not deposited and in which sandstone dominates the entire thickness of the group (Sullivan, 1972; Gray, 1970, 1986).


The West Baden overlies the Blue River Group (Valmeyeran and Chesterian) conformably except at a few localities along the clastic belt where basal sandstone of the West Baden Group lies disconformably as deep as 50 ft (15 m) below the normal position of the top of the Blue River Group (Malott, 1952, p. 49; Gray, 1986). The West Baden Group is overlain conformably by the Stephensport Group (Chesterian) or disconformably by the Mansfield Formation (Morrowan) (Gray, 1986).


The West Baden Group correlates with rocks within the lower part of the North American foraminiferal Zone 16s of Mamet and Skipp (1971) and within the Visean Series (V3cs) of European usage. On the basis of its conodont faunas, the West Baden was assigned to the upper part of the Gnathodus bilineatus-Cavusgnathus charactus Assemblage Zone of standard North American usage by Collinson, Rexroad, and Thompson (1971).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: West Baden Group
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: West Baden Group
Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: West Baden Group

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.


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.

Cumings, E. R., 1922, Nomenclature and description of the geological formations of Indiana, in Logan, W. N., Cumings, E. R., Malott, C. A., Visher, S. S., Tucker, W. M., Reeves, J. R., and Legge, H. W., Handbook of Indiana geology: Indiana Department of Conservation Publications 21, pt. 4, p. 403-570.

Gray, H. H., 1962, Outcrop features of the Mansfield Formation in southwestern Indiana: Indiana Geological Survey Report of Progress 26, 40 p.

Gray, H. H., 1970, West Baden Group, 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. 189-190.

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, West Baden Group, 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. 167-168.

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.

Greene, F. C., 1911, The Huron Group in western Monroe and eastern Greene Counties, Indiana: Indiana Academy of Science Proceedings for 1910, p. 269-288.

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.

Hopkins, T. C., 1902, Lower Carboniferous area in Indiana [abs.]: Geological Society of America Bulletin, v. 13, p. 519-521: Science, new ser., v. 15, p. 83.

Hopkins, T. C., 1904, A short description of the topography of Indiana, and of the rocks of the different geological periods to accompany the geological map of the state: Indiana Department of Geology and Natural Resources Annual Report 28, p. 15-77.

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.

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.

Weller, Stuart, 1920, The Chester Series in Illinois: Journal of Geology, v. 28, p. 281-303 and 395-416.

For additional information contact:

Nancy Hasenmueller (
Date last revised: November 22, 2016