Age:

Pennsylvanian

Type designation:

Type locality: The name "Carbondale Formation" was first used by Shaw and Savage (1912, p. 6) in a description of rocks exposed near Carbondale in Jackson County, Illinois (Burger and Wier, 1970, 1986).

Type section: A type section consisting of three outcrops in Fulton County, western Illinois, was designated by Kosanke and others (1960, p. 34, 46) in the SE¼NE¼ sec. 1, T. 7 N., R. 4 E. (Glasford quadrangle); the NW¼NE¼NW¼ sec. 20, T. 8 N., R. 3 E. (Canton quadrangle); and the SW cor. Sec. 21, T. 8 N., R. 3 E. (Canton quadrangle).

History of usage:

Assignment: In Indiana, Carbondale rocks were assigned by Fuller and Ashley (1902) to the lower part of the Millersburg Formation, to the Petersburg Formation, and to the upper part of the Brazil Formation and by Cumings (1922, p. 525-529) to the Petersburg Group and the upper part of the Staunton Group (Burger and Wier, 1970, 1986).

Extended: Wier and Gray, (1961) and Burger and Wier (1970) introduced the term “Carbondale Group” in Indiana for the rocks between the top of the Seelyville Coal Member of the Staunton Formation and the top of the Danville Coal Member of the Dugger Formation.

Revised contact: In 2001, the Tri-State Committee on Correlation of the Pennsylvanian System in the Illinois Basin revised the lower boundary of the Carbondale Group in Indiana to the base of the Seelyville Coal Member and placed the Seelyville in the Linton Formation.

Description:

The Carbondale Group includes some laterally persistent limestones and five of Indiana's commercially important coals. Persistent shales and underclays are associated with several of these coals. Most of the thickness of the Carbondale Group consists of variable shales and sandstones. In Indiana the Carbondale Group ranges from 260 to 470 ft (79 to 143 m) in thickness but averages slightly more than 300 ft (91 m) (Burger and Wier, 1970, 1986). It is thickest in central Posey County and generally thins to the north and the east (Burger and Wier, 1970, 1986). Three formations (the Linton, Petersburg, and Dugger Formations) make up the Carbondale Group, which is overlain by the McLeansboro Group and underlain by the Raccoon Creek Group (Burger and Wier, 1970, 1986).

Distribution: The outcrop belt in Indiana extends from Warrick County northward to Vermillion County (Burger and Wier, 1970, 1986).

Correlations:

The Carbondale Group in Indiana is essentially equivalent to the Carbondale Formation in Illinois and western Kentucky except that rock units between the Herrin Coal Member and the Danville Coal Member are placed in the Carbondale Group in Indiana and in the McLeansboro Group in Illinois and Kentucky (Tri-State Committee on Correlation of the Pennsylvanian System in the Illinois Basin, 2001).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Carbondale Group
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Carbondale Group

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

*c

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 features in Indiana.

Major tectonic features that affect bedrock geology in Indiana.

References:

Burger, A. M., and Wier, C. E., 1970, Carbondale 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. 32–33.

Burger, A. M., and Wier, C. E., 1986, Carbondale 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. 27.

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 Publication No. 21, pt. 4, p. 403–570.

Fuller, M. L., and Ashley, G. H., 1902, Description of the Ditney quadrangle: U.S. Geological Survey Geologic Atlas, Folio 84, 8 p.

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

Kosanke, R. M., Simon, J. A., Wanless, H. R., and Willman, H. B., 1960, Classification of the Pennsylvanian strata of Illinois: Illinois State Geological Survey Report of Investigations 214, 84 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.

Shaw, E. W., and Savage, T. E., 1912, Description of the Murphysboro and Herrin quadrangles, Illinois: U.S. Geological Survey Geologic Atlas, Folio 185, 15 p.

The Tri-State Committee on Correlation of the Pennsylvanian System in the Illinois Basin, 2001, Toward a more uniform stratigraphic nomenclature for rock units (formations and groups) of the Pennsylvanian System in the Illinois Basin: Indiana Geological Survey, Illinois Basin Consortium Illinois Basin Studies 5, 26 p.

Wier, C. E., and Gray, H. H., 1961, Geologic map of the Indianapolis 1° x 2° quadrangle, Indiana and Illinois, showing bedrock and unconsolidated deposits: Indiana Geological Survey Regional Geologic Map, Indianapolis Sheet, scale 1:250,000.