Age:

Pennsylvanian

Type designation:

Type area: The name “Petersburg,” taken from Petersburg, Pike County, Indiana, by Fuller and Ashley (1902, p. 2), was used for a coal in that area and for a formation consisting of the rocks between the bases of the Petersburg and Millersburg Coals (Burger and Wier, 1970; Burger, Wier, and Eggert, 1986).

Reference section: The reference section is part of the core from Indiana Geological Survey drill hole (SDH) 81 (Indiana Geological Survey Petroleum Database Management System No. 155352) that was drilled 4 miles (6.5 km) northeast of Petersburg in the NE¼NE¼NE¼ sec. 7, T. 1 N., R. 7 W. (Burger and Wier, 1970; Burger, Wier, and Eggert, 1986).

Reference boundary: A designated reference core from SDH 306 (Indiana Geological Survey Petroleum Database Management System No. 115871) contains the boundary between the Petersburg and Linton Formations at 83.3 ft (25.3 m) (Hasenmueller and Ault, 1991, p. 6). The drill hole is located in the SE¼NE¼NW¼ sec. 2, T. 2 S., R. 7 W., near the type section of the Survant Coal Member of the Linton Formation in Pike County, Indiana (Hasenmueller and Ault, 1991, fig. 1).

History of usage:

This name was extended by Cumings (1922, p. 529) to include "the interval from the disconformity over Coal lV to the disconformity over Coal VII," but the formation was restricted by Wier (1950, 1952), so that the Petersburg now consists only of the rocks between the top of the Survant Coal Member of the Linton Formation and the top of the Springfield Coal Member of the Petersburg Formation (Burger and Wier, 1970; Burger, Wier, and Eggert, 1986). In some places in the Warrick County area where the Folsomville Member is present but the upper split of the Springfield coal is absent, the Folsomville marks the top of the Petersburg (Eggert, 1982; Burger, Wier, and Eggert, 1986).

Description:

Four named members of the Petersburg, the Houchin Creek Coal, Stendal Limestone, Folsomville, and Springfield Coal Members, and unnamed beds of shale, siltstone, sandstone, and underclay make up the formation (Burger, Wier, and Eggert, 1986). Although the thickness of the Petersburg has been reported to range from 70 to 190 ft (21 to 58 m), the interval between the Springfield and Houchin Creek coals ranges from less than 40 ft (12 m) to more than 120 ft (37 m) in thickness and consists of prodelta shales, coarsening-upward bay-fill sequences of shale and fine-grained sandstone, and fining-upward fluvial sandstone (Eggert, 1983, 1984; Eggert and Adams, 1985; Burger, Wier, and Eggert, 1986). Thin rock intervals between the Springfield and Houchin Creek coals tend to parallel channels contemporaneous with the Springfield coal and tend to underlie thick Springfield coal (Burger, Wier, and Eggert, 1986).

Correlations:

The Petersburg Formation is correlative with the middle part of the Carbondale Formation of Illinois and Kentucky (Burger, Wier, and Eggert, 1986; The Tri-State Committee on Correlation of the Pennsylvanian System in the Illinois Basin, 2001).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Carbondale Group
Formation: Petersburg Formation
Illinois Basin Margin (COSUNA 12)
Supergroup: none
Group: Carbondale Group
Formation: Petersburg Formation

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

*pb

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:

Burger, A. M., and Wier, C. E., 1970, Petersburg 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. 132–133.

Burger, A. M., Wier, C. E., and Eggert, D. L., 1986, Petersburg 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. 112–113.

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.

Eggert, D. L., 1982, A fluvial channel contemporaneous with deposition of the Springfield Coal Member (V), Petersburg Formation, northern Warrick County, Indiana: Indiana Geological Survey Special Report 28, 20 p.

Eggert, D. L., 1983, Thickness and quality of Springfield Coal Member, Gibson County, Indiana, as a function of differential compaction of precursor sediments [abs.]: American Association of Petroleum Geologists Bulletin, v. 67, p. 1,455.

Eggert, D. L., 1984, The Leslie Cemetery and Francisco distributary fluvial channels in the Petersburg Formation (Pennsylvanian) of Gibson County, Indiana, U.S.A., in Rahmani, R. A., and Flores, R. M., eds., Sedimentology of coal and coal-bearing sequences: International Association of Sedimentologists Special Publication 7, p. 309–315.

Eggert, D. L., and Adams, S. C., 1985, Distribution of fluvial channel systems contemporaneous with the Springfield Coal Member (Middle Pennsylvanian) in southwestern Indiana: Ninth International Congress of Carboniferous Stratigraphy and Geology Compte rendu, v. 4, p. 342–348.

Fuller, M. L., and Ashley, G. H., 1902, Description of the Ditney quadrangle: U.S. Geological Survey Geologic Atlas, Folio 84, 8 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.

Hasenmueller, W. A., and Ault, C. H., 1991, Reference core and correlation of key beds in the Petersburg and Linton Formations (Pennsylvanian) in Indiana: Indiana Geological Survey Occasional Paper 57, 8 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., 1952, Geology and mineral deposits of the Jasonville quadrangle, Indiana: Indiana Geological Survey Bulletin 6, 34 p.