IGNIS
Degonia Formation

Age:

Mississippian

Type designation:

Type locality: The Degonia Sandstone was named by Stuart Weller (1920, p. 403-405; 1920, p. 216) for exposures of massive cliff-forming cross-bedded sandstone and thin-bedded ripple-marked sandstone in Degonia Township, Jackson County, Illinois (Gray, 1970, 1986).

History of usage:

Revised name: In an early study of outcropping upper Chesterian rocks in Indiana, Malott (1925) named a thin sandstone unit the Mount Pleasant Sandstone (Gray, 1986). Approximate equivalence of this sandstone to the Degonia was later recognized by Malott (1931, p. 222) "after he had made a study of the Chester formations in southern Illinois" (Malott, 1952, p. 6; Gray, 1970, 1986). No other documentation was ever given, but the name “Degonia” was used in a few later papers (for example, Malott and Esarey, 1940; Malott, Esarey, and Bieberman, 1948; Gray, 1970, 1986). The lithologic character, thickness, and nature of the boundaries of this unit were never made clear (Gray, 1986).

Revised extent: In a review of outcropping upper Chesterian rocks in southern Indiana, Gray (1978) discussed the evolution of nomenclature and concluded that a return to the original concept and name, Mount Pleasant, was advisable for surface usage (Gray, 1986).

Assignment: For Indiana usage Gray (1986, p. 35) assigned the Degonia to the Buffalo Wallow Group.

Revised name: Because the Degonia in Indiana contains a mixture of shale and sandstone, Droste and Keller (1995) designated the unit the “Degonia Formation.”

Description:

The dominant lithology of the Degonia Formation is medium- to dark-gray shale; light to dark shades of red and green shales are found in the upper part of the formation in many areas in Indiana (Droste and Keller, 1995). Thin beds of light-gray and light-brown, very fine grained sandstone are present in numerous places. The maximum thickness of sandstone is 60 ft (18 m) in a restricted area in western Posey County (Droste and Keller, 1995). The Degonia Formation ranges from less than 10 ft (3 m) near the area of outcrop to a maximum thickness of 68 ft (21 m) in western Posey County (Droste and Keller, 1995).

Distribution: The Degonia Formation, now restricted to subsurface use, is known from Perry County westward to Posey County and thence northward to Gibson County (Droste and Keller, 1995, fig. 14).

Boundaries:

The Degonia Formation overlies the Clore Limestone and is overlain by the Kinkaid Limestone, but over much of the area of its occurrence, pre-Pennsylvanian erosion has removed the Kinkaid, so that the Degonia is overlain by the Pennsylvanian Mansfield Formation (Morrowan) (Gray, 1986).

Regional Indiana usage:

Illinois Basin (COSUNA 11)
Supergroup: none
Group: Buffalo Wallow Group
Formation: Degonia Formation

Misc/Abandoned Names:

None

Geologic Map Unit Designation:

Md

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.)

Map showing the COSUNA areas (heavy black line) that approximate regional bedrock outcrop patterns and major structural features in Indiana, and the COSUNA numbers (large bold font) for these areas. The COSUNA boundaries are limited to state and county boundaries that facilitate coding.

COSUNA areas and numbers that approximate regional bedrock outcrop patterns and major structural features in Indiana.

Map showing major tectonic features that affect bedrock geology in Indiana.

Major tectonic features that affect bedrock geology in Indiana.

References:

Droste, J. B., and Keller, S. J., 1995, Subsurface stratigraphy and distribution of oil fields of the Buffalo Wallow Group (Mississippian) in Indiana: Indiana Geological Survey Bulletin 63, 24 p.

Gray, H. H., 1970, Degonia Sandstone, 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. 42-43.

Gray, H. H., 1978, Buffalo Wallow Group upper Chesterian (Mississippian) of southern Indiana: Indiana Geological Survey Occasional Paper 25, 28 p.

Gray, H. H., 1986, Degonia Sandstone, 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. 35.

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., 1925, The upper Chester of Indiana: Indiana Academy of Science Proceedings, v. 34, p. 103-132.

Malott, C. A., 1931, Geologic structure in the Indian and Trinity Springs locality, Martin County, Indiana: Indiana Academy of Science Proceedings, v. 40, p. 217-231.

Malott, C. A., 1952, Stratigraphy of the Ste. Genevieve and Chester formations of southern Indiana: Ann Arbor, Michigan, Edwards Letter Shop, 105 p.

Malott, C. A., and Esarey, R. E., 1940, Outcrop of the Chester Series of southern Indiana: Indiana-Kentucky Geological Society, May 18, 1940, 9 p. [mimeo.].

Malott, C. A., Esarey, R. E., and Bieberman, D. F., 1948, Upper and Middle Mississippian formations of southern Indiana: Indiana Division of Geology Field Conference Guidebook 2, 27 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.

Weller, Stuart, 1920, The Chester Series in Illinois: Journal of Geology, v. 28, p. 281-303 and 395-416.

Weller, Stuart, 1920, The geology of Hardin County and the adjoining part of Pope County: Illinois State Geological Survey Bulletin 41, 416 p.



For additional information contact:

Nancy Hasenmueller (hasenmue@indiana.edu)
Date last revised: November 22, 2016

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