Age:

Pennsylvanian

Type designation:

Type locality: The Staunton Formation was named by Cumings (1922, p. 525) for rocks exposed near Staunton, Clay County, Indiana (Hutchison, 1970; Hutchison and Hasenmueller, 1986).

History of usage:

As defined by Cumings, this formation consisted of the interval from the disconformity above Coal II to the disconformity above Coal IV (Survant Coal Member) and, therefore, also included the Seelyville Coal Member and the Colchester Coal Member (Hutchison, 1970; Hutchison and Hasenmueller, 1986).

As restricted by Wier (1950), however, the Staunton Formation consisted of those rocks in the interval between the disconformity above Coal II and the disconformity above the Seelyville (Hutchison and Hasenmueller, 1986). Still later, the upper boundary of the Staunton was changed to the top of the Seelyville (Wier and Gray, 1961), and the lower boundary was changed to the top of the Minshall Coal Member (Hutchison, 1976, p. 18; Hutchison and Hasenmueller, 1986). The Perth Limestone Member, which formerly belonged to the underlying Brazil Formation, was then reassigned to the Staunton Formation (Hutchison, 1970; Hutchison and Hasenmueller, 1986). In the same report by Hutchison, the poorly defined and miscorrelated Coal II was abandoned as a stratigraphic name (Hutchison, 1970; Hutchison and Hasenmueller, 1986).

As revised by the Tri-State Correlation Committee on Correlation of the Pennsylvanian System in the Illinois Basin (2001), the Staunton includes the rocks from the top of the Minshall (Buffaloville) Coal Member of the underlying Brazil Formation to the base of the Seelyville Coal Member. The upper contact is also the upper boundary of the Raccoon Creek Group (Tri-State Correlation Committee on Correlation of the Pennsylvanian System in the Illinois Basin, 2001).

Description:

The Staunton Formation consists of 75 to 150 ft (23 to 46 m) of sandstone and shale and as many as seven coal beds (Hutchison and Hasenmueller, 1986). These coal beds are generally of little areal extent and variable in quality and thickness (Hutchison, 1970; Hutchison and Hasenmueller, 1986). Three lithologies characterize the roof of the coals: (1) black fissile shale overlain by limestone, (2) gray soft silty or sandy shale and interbedded fossiliferous shale or limestone, and (3) gray massive to shaly hard to friable sandstone (Hutchison, 1970; Hutchison and Hasenmueller, 1986). The floor of the coals is underclay, clay shale, or sandy shale (Hutchison, 1970; Hutchison and Hasenmueller, 1986). The three named members of the Staunton are the Perth, Holland, and Silverwood Limestone Members (Hutchison and Hasenmueller, 1986). The Perth limestone lies at or near the base of the Staunton and the Silverwood and Holland limestones are in the middle part of the formation (Hutchison, 1970; Hutchison and Hasenmueller, 1986).

Correlations:

The Staunton Formation is considered to consist of basal rocks of the Desmoinesian Series in Indiana and is recognizable throughout the Indiana coalfield. Equivalents of the Staunton Formation are the uppermost part of the Tradewater Formation of Illinois and western Kentucky (Tri-State Correlation Committee on Correlation of the Pennsylvanian System in the Illinois Basin, 2001).

According to Shaver and Smith (1974, p. 18) and Shaver (1984), the Atokan-Desmoinesian series boundary should be placed at the base of the Staunton Formation, that is, below the Perth Limestone Member in western Indiana and the limestone next above the Buffaloville Coal Member (Brazil Formation) in southern Indiana (Hutchison and Hasenmueller, 1986). This limestone contains microfaunas characterized by an unidentified species of Fusulinella, F. iowensis, and the ostracod Amphissites centronotus (Hutchison and Hasenmueller, 1986).

Rexroad and others (1998) noted that the Perth Limestone Member of the Staunton Formation in Indiana and the Curlew Limestone Member of the Tradewater Formation in western Kentucky are in the Neognathodus bothrops-N. bassleri Subzone and correlate approximately with the Seville in northwestern Illinois and with the interval between the Lower and Upper Mercer Limestones in Ohio. Rexroad and others (1998) note that in Indiana the base of the Desmoinesian has traditionally been placed slightly below the Perth, and the Perth conodonts are compatible with this age, but Peppers (1996) on the basis of palynological and fusulinid data placed the boundary at the top of the Perth-Curlew-Seville complex.

Bashfort and others (2016) discuss the biostratigraphic, paleobiogeographic, and paleoecologic implications of Middle Pennsylvanian plant fossils collected from four beds in the lowermost Staunton Formation, above the Minshall Coal Member of the uppermost Brazil Formation, in Clay County, Indiana. They note that comparisons with established biozonation schemes yield different ages depending on the regional biostratigraphic framework used.

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Raccoon Creek Group
Formation: Staunton Formation
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Raccoon Creek Group
Formation: Staunton Formation

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

*st

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:

Bashforth, A. R., DiMichele, W. A., Eble, C. F., and Nelson, W. J., 2016, A Middle Pennsylvanian macrofloral assemblage from wetland deposits in Indiana (Illinois Basin)–a taxonomic contribution with biostratigraphic, paleobiogeographic, and paleoecologic implications: Journal of Paleontology, v. 90, no. 4, p. 589–631.

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 Publication No. 21, pt. 4, p. 403–570.

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.

Hutchison, H. C., 1970, Staunton Formation, 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. 170–172.

Hutchison, H. C., 1976, Geology of the Catlin-Mansfield area, Parke and Putnam Counties, Indiana: Indiana Geological Survey Bulletin 54, 57 p.

Hutchison, H. C., and Hasenmueller, W. A., 1986, Staunton Formation, 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. 149–150.

Peppers, R. A., 1996, Palynological correlation of major Pennsylvanian (Middle and Upper Carboniferous) chronostratigraphic boundaries in the Illinois and other coal basins: Geological Society of America Memoir 188, p. 1–111.

Rexroad, C. B., Brown, L. M., Devera, Joe, and Suman, R. J., 1998, Conodont biostratigraphy and paleoecology of the Perth Limestone Member, Staunton Formation (Pennsylvanian) of the Illinois Basin, U.S.A., in Szaniawski, Hubert, ed., Proceedings of the Sixth European Conodont Symposium (ECOS VI): Palaeontologia Polonica, v. 58, p. 247–259.

Shaver, R. H., and Smith, S. G., 1974, Some Pennsylvanian kirkbyacean ostracods of Indiana and midcontinent series terminology: Indiana Geological Survey Report of Progress 31, 59 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.

The Tri-State Committee on Correlation of the Pennsylvanian System in the Illinois Basin, 2001, Toward a more uniform stratigraphic nomenclature for rock units (formations and groups) of the Pennsylvanian System in the Illinois Basin: Indiana Geological Survey, Illinois Basin Consortium Illinois Basin Studies 5, 26 p.

Wier, C. E., 1950, Geology and coal deposits of the Jasonville quadrangle, Clay, Greene, and Sullivan Counties, Indiana: U.S. Geological Survey Coal Investigations Map C 1, scale 1:24,000.

Wier, C. E., and Gray, H. H., 1961, Geologic map of the Indianapolis 1° x 2° quadrangle, Indiana and Illinois, showing bedrock and unconsolidated deposits: Indiana Geological Survey Regional Geologic Map, Indianapolis Sheet, scale 1:250,000.