Age:

Mississippian

Type designation:

Type area: The Blue River Group was named by Gray, Jenkins, and Weidman (1960, p. 48) for the Blue River in Washington, Harrison, and Crawford Counties, Indiana. Many excellent exposures are in the valley walls of the Blue River from about 2.5 miles (4.0 km) northeast of Fredericksburg, Washington County, to the Ohio River (Carr, 1986).

History of usage:

Revised: Droste and Carpenter (1990) divided the Blue River Group both in the subsurface and in outcrop, into (ascending order) the St. Louis, Ste. Genevieve, and Paoli Limestones. They (1990) reduced the rank of the Aux Vases and Renault, formations in the subsurface, to that of members of Paoli Limestone, replacing the Popcorn and Shetlerville Members of previous surface usage.

Description:

The Blue River Group is formed largely of carbonate rocks but has significant amounts of gypsum, anhydrite, shale, chert, and calcareous sandstone (Carr, 1986).

The combined thickness of the constituent formations is 540 ft (165 m) in southern Crawford and Harrison Counties (Carr and others, 1978, p. 12); about 400 ft (122 m) in northwestern Orange County (Gray, Jenkins, and Weidman, 1960, p. 48); and 240 ft (73 m) in southern Monroe County (Malott, 1952, p. 57). The Blue River Group thickens southward from more than 250 ft (76.2 m) in Clay and Putnam Counties to more than 850 ft (259.1 m) in Posey County (Droste and Carpenter, 1990, p. 9, fig. 5.).

Distribution: The Blue River Group crops out in an area extending from the Ohio River in Harrison County to Parke and Vermillion Counties (Droste and Carpenter, 1990, fig. 1). The outcrop belt has approximately county width in Harrison County, narrows sharply northward in Orange and Lawrence Counties, and gradually diminishes northward to its termination, where it is overlapped by Pennsylvanian rocks (Carr, 1986).

Boundaries:

The Blue River Group rests conformably on the Sanders Group and is overlain, generally conformably but with local disconformity, by rocks of the West Baden Group (Carr, 1986). North of Owen County the Mansfield Formation of Pennsylvanian age disconformably overlaps successively older Blue River rocks northward (Carr, 1986).

Correlations:

The group has no exact named equivalent in neighboring states, but it is equivalent to the section extending from the St. Louis Limestone through the Cedar Bluff Group of Illinois usage (Swann, 1963). It spans the Valmeyeran-Chesterian boundary as that boundary is generally recognized (Carr, 1986).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Blue River Group
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Blue River Group
Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: Blue River Group

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

Mbr

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:

Carr, D. D., 1986, Blue River Group, 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. 16–17.

Carr, D. D., Leininger, R. K., and Golde, M. V., 1978, Crushed stone resources of the Blue River Group (Mississippian) of Indiana: Indiana Geological Survey Bulletin 52, 225 p.

Droste, J. B., and Carpenter, G. L., 1990, Subsurface stratigraphy of the Blue River Group (Mississippian) in Indiana: Indiana Geological Survey Bulletin 62, 45 p.

Gray, H. H., Jenkins, R. D., and Weidman, R. M., 1960, Geology of the Huron area, south-central Indiana: Indiana Geological Survey Bulletin 20, 78 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.

Malott, C. A., 1952, Stratigraphy of the Ste. Genevieve and Chester formations of southern Indiana: Ann Arbor, Michigan, Edwards Letter Shop, 105 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.