Age:

Pennsylvanian

Type designation:

Type locality: Sandstone that crops out at Merom, Sullivan County, Indiana, was first described by John Collett in 1871 (p. 199-200) (Wier, 1970, 1986). He stated that "the stone work of the college edifice at Merom was quarried from massive ledges of the 'Merom Sandstone' north of town. . . ." (Wier, 1970, 1986). The type locality was later designated as being at Merom Bluff in secs. 7 and 18, T. 7 N., R. 10 W. (Wier, 1970).

History of usage:

The Merom Sandstone was assigned member status in the Mattoon Formation by Wier and Gray (1961) (Wier, 1970, 1986).

Description:

The sandstone ranges from 10 to 35 ft (3 to 11 m) in thickness at most exposures and is not known to exceed a thickness of 40 ft (12 m) (Wier, 1970, 1986). The Merom Sandstone Member consists of two distinct lithologies: an upper cross-bedded medium- to coarse-grained sandstone and a lower conglomerate that is gray to brown and composed of a mixture of rounded to subrounded pebbles of limestone, coal, and clay cemented with calcium carbonate (Wier, 1970, 1986). In Indiana, the Merom is recognized only near its type area in Sullivan County and in the Mumford Hills area in Posey County (Wier, 1970, 1986).

Correlations:

The Merom has been incorrectly correlated with numerous outcrops of other units in southern Indiana (Wier, 1970, 1986). Collett (1874, p. 321-338) erroneously called the Inglefield Sandstone Member and some higher sandstones in Knox County the Merom, and Ashley (1899, p. 1,051-1,079) repeated this error (Wier, 1986). Other workers (Logan, 1932; Culbertson, 1932; Malott, 1948; and Friedman, 1954) followed Ashley and mistakenly identified the lnglefield as the Merom in southern Indiana (Wier, 1970, 1986).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: McLeansboro Group
Formation: Mattoon Formation
Member: Merom Sandstone Member

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

*mtm

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.

Collett, John, 1871, Geology of Sullivan County, Indiana, in Cox, E. T., Second report of the Geological Survey of Indiana made during the year 1870, p. 189–240.

Collett, John, 1874, Geology of Knox County: Indiana Geological Survey Annual Report 5, p. 315–382.

Culbertson, J. A., 1932, The paleontology and stratigraphy of the Pennsylvanian strata between Caseyville, Kentucky, and Vincennes, Indiana: Urbana, University of Illinois, Ph.D. thesis, 292 p.

Friedman, S. A., 1954, Distribution, structure, and mined areas of coals in Gibson County, Indiana: Indiana Geological Survey, Preliminary Coal Map No. 4, scale 1:126,720.

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.

Logan, W. N., 1932, The subsurface strata of Indiana: Indiana Department of Conservation Publication No. 108, 790 p.

Malott, C. A., 1948, The geology of the Dicksburg Hills, Knox County, Indiana: Indiana Academy of Science Proceedings, v. 57, p. 125–141.

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., 1970, Merom Sandstone Member, 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. 109–110.

Wier, C. E., 1986, Merom Sandstone 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. 91–92.

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.