Type section: The altered volcanic ash that was noted by Fettke (1931, p. 8) in the Tioga Gas Field of Pennsylvania was named the Tioga Bentonite by Ebright, Fettke, and Ingham (1949, p. 10) (Droste and Shaver, 1986).
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Regional Indiana usage:
Illinois Basin (COSUNA 11)
Onondaga Indian Nation Bentonite
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.)
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.
For additional information contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: June 14, 2017