Age:

Mississippian

Type designation:

Type section: In a roadside ditch and stripping above an abandoned quarry on the west slope of Cave Hill about 4 miles (6.4 km) northeast of Rudement, SE¼SW¼NW¼ sec. 3, T. 10 S., R. 7 E., Rudement quadrangle, Saline County, Illinois (Swann, 1963, p. 43).

History of usage:

Named: Cave Hill Member of Kinkaid Limestone (Swann, 1963, p. 42).

Extended: Droste and Keller (1995, p. 14) adopted the name “Cave Hill Shale Member” for use in the subsurface of Indiana. They recognized the unit in Posey and Gibson Counties and a small area in southern Spencer County.

Description:

In Indiana, the Cave Hill Shale Member generally has three distinctive divisions as outlined by Droste and Keller (1995, p. 14). The lower part of the unit is composed of medium- and dark-gray shale that is silty and calcareous. The middle part of the Cave Hill shows the greatest variability with interbeds of dark silty to sandy shale, light- to dark-gray shaly limestone, and fine-grained silty sandstone. The upper part of the Cave Hill contains medium- and dark-gray shale below and interbedded green and red to maroon shale above. The Cave Hill is 80 to 100 ft (24.4 to 30.5 m) thick where it underlies the Goreville Limestone Member of the Kinkaid Limestone (Droste and Keller, 1995).

Distribution: Droste and Keller (1995, fig. 16) mapped the Cave Hill Shale Member in Gibson, Posey, and Spencer Counties in the subsurface in southwestern Indiana.

Boundaries:

The Cave Hill Shale Member overlies the Negli Creek Limestone Member of the Kinkaid Limestone conformably (Droste and Keller, 1995). The contact of the Cave Hill with the overlying Goreville Limestone Member of the Kinkaid Limestone is conformable (Droste and Keller, 1995). In areas where the Goreville is absent, the Cave Hill is unconformably overlain by Pennsylvanian rocks (Droste and Keller, 1995, fig. 16).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Buffalo Wallow Group
Formation: Kinkaid Limestone
Member: Cave Hill Shale Member

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

Mkch

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:

Droste, J. B., and Keller, S. J., 1995, Subsurface stratigraphy and distribution of oil fields of the Buffalo Wallow Group (Mississippian) in Indiana: Indiana Geological Survey Bulletin 63, 24 p.

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.

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.