Age:

Pennsylvanian

Type designation:

Type area: The name "McLeansboro Formation" was first used by De Wolf (1910, p. 181) for all rocks of Pennsylvanian age above the Herrin (No. 6) Coal of Illinois exposed near McLeansboro, Hamilton County, Illinois (Burger and Wier, 1970, 1986).

History of usage:

The name "McLeansboro" was later (Kosanke, Simon, Wanless, and Willman, 1960, p. 36) used in Illinois with the rank of group for all Pennsylvanian rocks above the Danville (No. 7) Coal (Burger and Wier, 1970, 1986). Wier and Gray (1961) extended the use of this name into Indiana (Burger and Wier, 1970, 1986).

Description:

The McLeansboro Group as recognized in Indiana extends from the top of the Danville Coal Member of the Dugger Formation to the top of the Pennsylvanian sequence. This group consists of, in ascending order, the Shelburn, Patoka, Bond, and Mattoon Formations, but in Indiana it does not include the entire section represented in the type area because of eastward erosional truncation (Burger and Wier, 1970, 1986). The maximum thickness of 770 ft (235 m) is reached in the Mumford Hills in northern Posey County. Shale and sandstone make up more than 90 percent of this sequence, but minor amounts of siltstone, limestone, clay, and coal are present (Burger and Wier, 1970, 1986).

Distribution: In Indiana, the outcrop belt of the McLeansboro Group extends from western Warrick County northward to southwestern Vermillion County (Burger and Wier, 1970, 1986).

Regional Indiana usage:

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

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

*mc

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, McLeansboro 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. 101.

Burger, A. M., and Wier, C. E., 1986, McLeansboro 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. 85–86.

De Wolf, F. W., 1910, Introduction, in De Wolf, F. W., and others, Studies of Illinois coal: Illinois Geological Survey Bulletin 16 (Year Book for 1909), p. 178–181.

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.

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.