Type locality: The name “Anvil Rock” was used by Owen (1856, p. 45), for a natural feature of sandstone shaped like an anvil near Dekoven, Union County, Kentucky 2,750 ft (0.84 km) from the east line and 1,100 ft (0.34 km) from the south line, N-17, Carter coordinates) (Ault, 1986).
History of usage:
Extended: The name “Anvil Rock Sandstone Member” was adopted for use in Indiana by Ault (1986).
The Anvil Rock sandstone was mapped in Illinois, Kentucky, and Indiana by Hopkins (1958). Unpublished mapping by Curtis H. Ault in Posey County and by Donald L. Eggert in Gibson County indicates that the Anvil Rock is present in these counties as channel fill and also as a thin sheet in many places (Ault, 1986).
The sheet phase of the Anvil Rock sandstone underlies a gray shale below the Universal Limestone Member and overlies a gray shale above the Hymera Coal and Providence Limestone Members, all of the Dugger Formation (Ault, 1986). In Posey County, channels filled with Anvil Rock sandstone have been cut through underlying members of the Dugger to within about 30 ft (9 m) of the Springfield Coal Member (Petersburg Formation) (Ault, 1986).
Part of the Anvil Rock Sandstone Member occupies the same stratigraphic position as the Bridge Junction Sandstone Member mapped by Friedman (1989) in parts of Vigo County, Indiana (Ault, 1986). No direct correlation between the sandstones, however, has yet been shown, although they may be the same sandstone (Ault, 1986).
Regional Indiana usage:
Illinois Basin (COSUNA 11)
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.)
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.
Ault, C. H., 1986, Anvil Rock 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. 6.
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.
Hopkins, M. E., 1958, Geology and petrology of the Anvil Rock Sandstone of southern Illinois: Illinois State Geological Survey Circular 256, 49 p.
Owen, D. D., 1856, Report of the geological survey in Kentucky, made during the years 1854 and 1855: Frankfort, Ky., 416 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.
For additional information, contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: July 28, 2017