Age:

Pennsylvanian

Type designation:

Type section: The Excello Shale Member of the Carbondale Formation (Pennsylvanian) was named by Searight and others (1953) for exposures west of Excello in Macon County, Missouri (Hopkins, and Simon, 1975).

Indiana reference cores:

(1 ) Indiana Geological Survey drill hole SDH-306 (Petroleum Database Management System [PDMS] #1155871) at the depth of 21.5 to 26.8 ft (6.5 to 8.2 m) in Pike County, Indiana, was designated as a reference section for the Excello Shale Member by Mastalerz and others (2019).

(2) SDH-366 (PDMS #150359) at the depth of 439.6 to 444.7 ft (134 to 135.5 m) in Vanderburgh County, Indiana, was also designated as a reference section for the horizon by Mastalerz and others (2019).

History of usage:

Nance (1970, p. 77) extended the name “Excello Shale Member of the Carbondale Formation” into Illinois. In Illinois, the unit is composed of black fissile shale that is generally 1 to 3 ft (0.30 to 0.9 m) thick and similar in character to the unit in Missouri (Hopkins, and Simon, p. 189).

In 2019, the name “Excello Shale Member of the Pertersburg Formation” was proposed as a formal name for use in Indiana by Mastalerz and others.

Description:

Hasenmueller and Ault (1991, p. 6) noted in their description of the SDH-306 reference core in Pike County, Indiana, that the interval at a depth of 21.5 to 26.8 ft (6.5 to 8.2 m) was composed of black shale with a few gray silty concretions, two thin vitrain bands, and a few small pyrite nodules and streaks at the base

Mastalerz and others (2019) described the Excello Shale Member in Indiana as a black fissile shale ranging from 1 to 5 ft (0.30 to 1.5 m) thick. They (2019) noted that the unit directly underlies the Stendal Limestone Member of the Petersburg Formation and immediately overlies the Houchin Creek Coal Member of the Petersburg Formation, except locally where 1 to 3 ft (0.30 to 0.9 m) of gray shale separates them.

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Group: Carbondale
Formation: Petersburg
Member: Excello Shale
Illinois Basin Margin (COSUNA 12)
Group: Carbondale
Formation: Petersburg
Member: Excello Shale

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

*pex

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:

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.

Hopkins, M. E., and Simon, J. A., 1975, Pennsylvanian System, in Willman, H. B., Atherton, Elwood, Buschbach, T. C., Collinson, Charles, Frye, J. C., Hopkins, M. E., Lineback, J. A., and Simon, J. A., Handbook of Illinois stratigraphy: Illinois State Geological Survey Bulletin 95, p. 163–201.

Mastalerz, Maria, Ames, P. R., and Drobniak, Agnieszka, 2019, The Survant Coal Member of the Linton Formation (Pennsylvanian) in Indiana–geometry, resources, and properties: Indiana Geological and Water Survey, Indiana Journal of Earth Sciences, v. 1, 25 p., doi: 10.14434/ijes.v1i0.26862 target="_blank">https://doi.org/10.14434/ijes.v1i0.26862.

Nance, R. B., 1970, Limestones and phosphatic rocks from the Summun and Liverpool cyclothems in western Illinois: Illinois State Geological Survey Guidebook Series 8, p. 75–83.

Petroleum Database Management System (PDMS), 2018, Petroleum Database Management System: Indiana Geological and Water Survey website, accessed December 3, 2018, at URL https://igws.Indiana.edu/pdms/WellSearch.cfm.

Searight, W. V., Howe, W. R., Moore, R. C., Jewett, J. M., Condra, G. E., Oakes, M. C., and Branson, C. C., 1953, Classification of the Desmoinesian (Pennsylvanian) of the northern Mid-Continent: American Association of Petroleum Geologists Bulletin, v. 37, p. 2,747–2,749.