Type designation:

Type section: The Ohio Division Geological Survey (DGS) core hole DGS 2627 is located in an American Aggregates Corporation quarry, approximately 1 mile (1.6 km) northeast of the town of Lytle, NE¼ sec. 14, T. 3, R. 5, Waynesville quadrangle, Warren County, Ohio (Shrake and others, 1990, p. 2). The Middle Run Formation was encountered from a depth of 3,458.0 ft (1054.0 m) to the bottom of the core hole at 5,380.0 ft (1639.8 m). The formation is named from the stream that heads near the quarry (Shrake and others, 1990, p. 4).

History of usage:

Named: The Middle Run Formation was named by Shrake and others (1990, p. 4).

Extended: Drahovzal and others (1992) adopted the name “Middle Run Formation” for use in the subsurface of Indiana and Kentucky.


The Middle Run Formation is composed of thick-bedded to massively bedded, red to gray, fine- to medium-grained sandstone with minor red siltstones and shales (Drahovzal and others, 1992). Sedimentary structures include large-scale cross bedding and less abundant ripple cross bedding (Drahovzal and others, 1992).

Distribution: The Middle Run Formation has been recognized from Putnam County in northwestern Ohio to Jessamine County in central Kentucky (Drahovzal and others, 1992, p. 7; fig. 5). The known western limit of the formation is from wells in Fayette and Switzerland Counties in southeastern Indiana (Drahovzal and others, 1992, p. 7; fig. 5).


In southeastern Indiana the Middle Run Formation is unconformably overlain by the Mount Simon Sandstone (Cambrian) (Drahovzal and others, 1992, p. 6; fig. 4).


The Middle Run Formation has been assigned ages of either Cambrian or Precambrian by several authors, including Babcock (1994), Roden-Tice and Shrake (1998), and Santos et al. (2001). Because of its stratigraphic location below the Cambrian strata in Ohio and the presence of an unconformable surface, the unit was initially believed to be older than the Cambrian (Richardson, 2015). Work by Babcock (1994) indicated that the Middle Run has a relative date of no younger than Middle Cambrian based on the trilobite biostratigraphy from the overlying Eau Claire Formation. The Eau Claire is stratigraphically above the Mt. Simon Sandstone and the Middle Run, constraining the age assignment of the Middle Run (Richardson, 2015). Richardson (2015) stated that the exact age of the Middle Run was not known.

Regional Indiana usage:

Cincinnati Arch (COSUNA 13)
Supergroup: none
Group: none
Formation: Middle Run Formation

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.


Babcock, L. E., 1994, Biostratigraphic significance and paleogeographic implications of Cambrian fossils from a deep core, Warren County, Ohio: Journal of Paleontology, v. 68, no. 1, p. 24-30.

Drahovzal, J. A., Harris, D. C., Wickstrom, L. H., Walker, Dan, Baranoski, M. T., Keith, Brian, and Furer, L. C., 1992, The East Continent Rift Basin: a new discovery: Indiana Geological Survey Special Report 52, 25 p.

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.

Richardson, J. G., 2015, Organic microfossils of the Middle Run Formation (Neoproterozoic) of Ohio, U.S.A.: Northeastern Geoscience, v. 33, p. 34-40.

Roden-Tice, M. K., and Shrake, D. L., 1998, Age of the Middle Run Sandstone underlying Warren County, Ohio: Geological Society of America Abstracts with Programs, v. 30, no. 2, p. 69.

Santos, J. O., Potter, P. E., Easton, R. M., Hartmann, L. A., McNaughton, N. J., and Rea, R., 2001, Proterozoic Middle Run Formation of eastern Midwest, USA: a Torridonian equivalent?: Geological Society of America Abstracts with Programs, v. 33, no. 6.; Geological Society of America Web page,, date accessed, November 20, 2015.

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.

Shrake, D. L., Wolfe, P. J., Richard, B. H., Swinford, E. M., Wickstrom, L. H., Potter, P. E., and Sitler, G. W., 1990, Lithologic and geophysical description of a continuously cored hole in Warren County, Ohio, including description of the Middle Run Formation (Precambrian?) And a seismic profile across core site: Ohio Geological Survey Information Circular 56, 11 p.

For additional information contact:

Nancy Hasenmueller (
Date last revised: June 29, 2017