Folsomville Member



Type designation:

Type section: The name "Folsomville" was used by Eggert (1982, p. 7) for a clastic sequence of sediments as much as 65 ft (20 m) thick that splits the Springfield Coal Member into two or more beds in Gibson and Warrick Counties, Indiana. Type and reference sections were designated in the SW¼NE¼ sec. 7, T. 5 S., R. 7 W., and in the NW¼SW¼ sec. 12, T. 5 S., R. 8 W., in Warrick County, but the type section was stated erroneously. It is in the SW¼SE¼ sec. 7 (Eggert, 1986).


The Folsomville Member consists mostly of dark-gray to black organic shale (rash), tan and brown to gray shale, buff to gray sandstone, and some siltstone beds and vitrain bands (Eggert, 1986). In some areas the Folsomville thickens gradually, but in others it thickens from a few tenths of feet to its maximum thickness within several hundred feet laterally (Eggert, 1986).

Miscellaneous Information: These sediments were derived from the Leslie Cemetery Channel, a minor channel that was contemporaneous with part of the Springfield coal but that was abandoned before termination of peat deposition (Eggert, 1986).


Where the upper split of the Springfield coal is absent, the uppermost bed of the Folsomville Member is the top of the Petersburg Formation (Eggert, 1986).


The Folsomville Member is equivalent to part of the Springfield Coal Member and may be similar in age to part of the Dykersburg Shale Member of Illinois (Eggert, 1986). Willard and others (1995) noted that the plant megafossils from the Folsomville Member indicate dominance by pteridosperms and/or lycopsids. The miospore assemblages are dominated by lycopsid miospores most typically found in mudstones, including Lycospora torquifer and higher than normal abundances of Granasporites medius (Willard and others, 1995).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Carbondale Group
Formation: Petersburg Formation
Member: Folsomville Member

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.

See also:

Springfield Coal Member


Eggert, D. L., 1982, A fluvial channel contemporaneous with deposition of the Springfield Coal Member (V), Petersburg Formation, northern Warrick County, Indiana: Indiana Geological Survey Special Report 28, 20 p.

Eggert, D. L., 1986, Folsomville Member, 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. 47.

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.

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.

Willard, D. A., DiMichele, W. A., Eggert, D. L., Hower, J. C., Rexroad, C. B., and Scott, A. C., 1995, Paleoecology of the Springfield Coal Member (Desmoinesian, Illinois basin) near the Leslie Cemetery paleochannel, southwestern Indiana: International Journal of Coal Geology, v. 27, no. 1, p. 59-98.

For additional information contact:

Nancy Hasenmueller (hasenmue@indiana.edu)
Date last revised: November 22, 2016

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