Type section: Exposure in Walche's cut on Illinois Central Railroad, 3 miles (4.83 km) northeast of Scottsburg and 3,500 ft (1066.8 m) west of Claxton in southwest corner of 19-H-21, 6,400 ft (1950.7 m) from south line and 8,600 ft (2621.3 m) from east line of H-21, Princeton East quadrangle, Caldwell County, Kentucky (Swann, 1963, p. 39).
History of usage:
Named: The Walche Limestone Member of the Menard Formation was named by Swann, (1963, p. 38).
In Indiana, the Walche Limestone Member is a light- to dark-gray limestone; in places the limestone is dolomitic or may contain quartz grains in silt and sand sizes (Droste and Keller, 1995). The limestone may contain thin interbeds of shale and it produces a characteristic geophysical log trace (Droste and Keller, 1995, fig. 4). The Walche ranges in thickness from 4 to 20 ft (1.2 to 6.1 m), however, it is commonly 6 to 12 ft (1.8 to 3.7 m) thick (Droste and Keller, 1995).
The basal contact of the Walche is conformable with the underlying Waltersburg Formation (Droste and Keller, 1995).
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 featuers in Indiana.
Major tectonic features that affect bedrock geology 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.
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.
Swann, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.
For additional information, contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: September 1, 2011