Type designation:

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).

Characteristic sections: Carr (1986) noted that the unit is particularly well exposed in Wesley Chapel Gulf (called Elrod Gulf on the French Lick topographic quadrangle map), 0.5 miles (0.8 km) south of Wesley Chapel Church in the SW¼NE¼ sec. 9, T. 2 N., R. 1 W., and near Orangeville in the SE¼ sec. 6, T. 2 N., R. 1 W.

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).

Distribution: Carr (1986) noted that the Lost River Chert Bed is an important stratigraphic marker 15 to 40 ft (4.6 to 12.2 m) above the base of the Fredonia Member and of the Ste. Genevieve Limestone. It is especially persistent in and south of Lawrence County, but northward the bed is mostly absent, although it has been reported as far north as Greencastle, Putnam County (Malott, 1952, p. 8, 23; Smith, 1970; Carr, 1986). Droste and Carpenter (1990) noted that the Lost River Chert Bed had limited recognizable distribution in the subsurface.

McGrain (1969, p. 1,506-1,507; fig. 59) noted the presence of the Lost River Chert Bed in west-central Kentucky to the west of the Cincinnati Arch. He also recognized a possible equivalent to the bed to the east of the Cincinnati Arch in Wayne and Pulaski Counties in southeastern Kentucky and in northern Tennessee. Sable and Dever (1990) reported that the name “Lost River Chert Bed” has been used in west-central, central, and south-central Kentucky and that the unit is locally absent in parts of south-central Kentucky.


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)
Supergroup: none
Group: Blue River Group
Formation: Ste. Genevieve Limestone
Member: Fredonia Member
Bed: Lost River Chert Bed

Misc/Abandoned Names:


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.

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.

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 (
Date last revised: August 26, 2016