Type area: The name “Lost River Chert” was given by Elrod (1899, p. 259) to rocks exposed along the dry bed of Lost River in Orange County, Indiana (Carr, 1986).
History of usage:
Elrod (1899) considered the Lost River Chert to be an interformational marker between his Paoli Limestone and his Mitchell Limestone, but Cumings (1922, p. 507) included it in the St. Louis Limestone, as did Woodson (1982) (Carr, 1986). Especially through the work of Malott (1952, for example), the Lost River is now assigned to the lower part of the Ste. Genevieve Limestone and given the rank of bed (Smith, 1970; Carr, 1986).
The Lost River Chert Bed consists of one stratum or more of very fossiliferous and siliceous limestone distributed through a stratigraphic interval as much as 6 ft (1.8 m) thick (Smith, 1970; Carr, 1986). It contains abundant bryozoans and is oolitic in places (Smith, 1970; Carr, 1986). Commonly the chert is bluish gray, but in places it is light brownish gray and blends with the host limestone (Carr, 1986). The bryozoan limestone is differentially silicified, so that weathered surfaces from which the carbonate has been leached have a distinctive aspect (Smith, 1970; Carr, 1986).
The Lost River Chert Bed and the immediately overlying beds contain conodonts of the Apatognathus scalenus-Cavusgnathus Assemblage Zone (Collinson, Rexroad, and Thompson, 1971) and so correlates with the upper part of the St. Louis Limestone of the Mississippi Valley (Carr, 1986).
Regional Indiana usage:
Illinois Basin Margin (COSUNA 12)
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.
Carr, D. D., 1986, Lost River Chert Bed, 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. 82-83.
Collinson, Charles, Rexroad, C. B., and Thompson, T. L., 1971, Conodont zonation of the North American Mississippian: Geological Society of America Memoirs 127, p. 353-394.
Cumings, E. R., 1922, Nomenclature and description of the geological formations of Indiana, in Logan, W. N., Cumings, E. R., Malott, C. A., Visher, S. S., Tucker, W. M., Reeves, J. R., and Legge, H. W., Handbook of Indiana geology: Indiana Department of Conservation Publications 21, pt. 4, p. 403-570.
Elrod, M. N., 1899, The geologic relations of some St. Louis Group caves and sinkholes: Indiana Academy of Science Proceedings for 1898, p. 258-267.
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.
Malott, C. A., 1952, Stratigraphy of the Ste. Genevieve and Chester formations of southern Indiana: Ann Arbor, Michigan, Edwards Letter Shop, 105 p.
McGrain, Preston, 1969, Extension of Lost River Chert across parts of Kentucky: American Association of Petroleum Geologists Bulletin, v. 53, p. 1,506-1,507.
Sable, E. G., and Dever, G. R., Jr., 1990, Mississippian rocks in Kentucky: U.S. Geological Survey Professional Paper, 1503, 125 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.
Smith, N. M., 1970, Lost River Chert Bed, in Shaver, R. H., Burger, A. M., Gates, G. R., Gray, H. H., Hutchison, H. C., Keller, S. J., Patton, J. B., Rexroad, C. B., Smith, N. M., Wayne, W. J., and Wier, C. E., Compendium of rock-unit stratigraphy in Indiana: Indiana Geological Survey Bulletin 43, p. 96-97.
Woodson, F. J., 1982, Uppermost St. Louis Limestone (Mississippian)–the Horse Cave Member in Indiana: Indiana Academy of Science Proceedings, v. 91, p. 419-427.
For additional information, contact:
Nancy Hasenmueller (firstname.lastname@example.org)Date last revised: August 26, 2016