Age:

Pennsylvanian

Type designation:

Type locality: The name “Hymera Coal Member” of the Dugger Formation was proposed by Wier in an unpublished manuscript for exposures near Hymera, Sullivan County, Indiana (Burger, 1970), but was first published by Wier and Powell (1967) (Burger, 1986).

Reference section: Because natural exposures near Hymera are rare because of stripping operations, a reference section was designated in the NE¼NW¼NE¼ sec. 10, T. 8 N., R. 8 W. (Burger, 1970, 1986).

History of usage:

This unit had previously been designated as Coal VI in Sullivan County, Indiana, by Ashley (1899, p. 839-915; 1909, p. 56) (Burger, 1970, 1986).

In Gibson, Pike, and Warrick Counties the Hymera has been called the Lower Millersburg Coal (Burger, 1970, 1986).

Description:

The Hymera Coal Member is a bright-banded coal, which ranges from 0.5 to 11.0 ft (0.2 to 3.4 m) in thickness (Burger, 1970, 1986). The coal contains numerous small shale and pyrite partings; two of them, lying in the upper part of the coal, can be traced throughout Sullivan County and northern Knox County (Burger, 1970, 1986). In northwestern Knox County one shale and pyrite parting thickens, so that the coal is split into two benches (Burger, 1970, 1986). The Hymera coal, which contains a characteristic spore content composed almost entirely of the genera Laevigatosporites and Lycospora (Guennel, 1952, p. 29), is overlain in most places by a dark-gray to gray silty shale or fine-grained sandstone (Burger, 1970, 1986).

Distribution: The Hymera Coal Member is traceable from its type area southward to southern Knox County and northward to southern Vigo County (Burger, 1970, 1986). It is not present in northern Vigo County or in Vermillion County (Burger, 1970, 1986). It thins abruptly in southern Knox County but is present in Gibson, Pike, and Warrick Counties.

Correlations:

The Hymera is probably correlative with the Jamestown Coal Member in southern Illinois and with the Paradise Coal (W. Ky. No. 12) in Kentucky (Burger, 1970, 1986).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Carbondale Group
Formation: Dugger Formation
Member: Hymera Coal Member

Misc/Abandoned Names:

Coal VI, Hymera Coal Member (VI), Lower Millersburg Coal

Geologic Map Unit Designation:

*dhy

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:

Ashley, G. H., 1899, The coal deposits of Indiana: Indiana Department of Geology and Natural Resources Annual Report 23, p. 1–1,573.

Ashley, G. H., 1909, Supplementary report to the report of 1898 on the coal deposits of Indiana: Indiana Department of Geology and Natural Resources Annual Report 33, p. 13–150.

Burger, A. M., 1970, Hymera Coal Member (VI), 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. 74–75.

Burger, A. M., 1986, Hymera Coal 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. 61–62.

Guennel, G. K., 1952, Fossil spores of the Alleghenian coals in Indiana: Indiana Geological Survey Report of Progress 4, 40 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.

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 Powell, R. L., 1967, Distribution, structure, and mined areas of coals in Knox County, Indiana: Indiana Geological Survey Preliminary Coal Map No. 12, scale 1:126,720.