Type section: The name “Vernon Fork Member” was given by Droste and Shaver (1975, p. 404-406) to the rocks often called the laminated beds, Laminated Zone, chalk beds, or fine-grained dolomite of the Jeffersonville Limestone (Droste and Shaver, 1986). The type area was designated as the area near Vernon and North Vernon along Vernon Fork of the Muscatatuck River, Jennings County, Indiana (Droste and Shaver, 1986). (Butlerville quadrangle).
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Regional Indiana usage:
Illinois Basin (COSUNA 11)
chalk beds, fine-grained dolostone of the Jeffersonville Limestone, laminated beds, Laminated Zone
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 featuers in Indiana.
Major tectonic features that affect bedrock geology in Indiana.
Conkin, J. E., and Conkin, B. M., 1979, Selected glossary of eastern North American Devonian stratigraphy, pyroclastics, bone beds, disconformities, and correlation: Louisville, Ky., University of Louisville Studies in Paleontology and Stratigraphy 9, 32 p.
Droste, J. B., and Shaver, R. H., 1975, The Jeffersonville Limestone (Middle Devonian) of Indiana—stratigraphy, sedimentation, and relation to Silurian reef-bearing rocks: American Association of Petroleum Geologists Bulletin, v. 59, p. 393-412.
Droste, J. B., Shaver, R. H., 1986, Vernon Fork 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. 160-162.
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.
For additional information, contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: August 6, 2013