Type locality and description: The Degonia Sandstone was named by Stuart Weller (1920a, p. 403-405 1920b, p. 216) for exposures of massive cliff-forming crossbedded sandstone and thin-bedded ripple-marked sandstone in Degonia Township, Jackson County, Ill. Total thickness of this unit in its type area is as much as 100 feet (30 m). The Degonia Sandstone is a unit in the standard Chesterian section (Swann, 1963, p. 41; Willman and others, 1975, p. 162).
History of name and distribution in Indiana: In an early study of outcropping upper Chesterian rocks in Indiana, Malott (1925) named a thin sandstone unit the Mount Pleasant Sandstone. Approximate equivalence of this sandstone to the Degonia was later recognized by the same author (Malott, 1931, p. 222) "after he had made a study of the Chester formations in southern Illinois" (Malott, 1952, p, 6). 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). The lithologic character, thickness, and nature of the boundaries of this unit were never made clear. (See the discussion of boundary problems under "Tar Springs Formation.")
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. (See also the article on "Mount Pleasant Sandstone Member.") The Degonia Sandstone, now restricted to subsurface use, is uncertainly known from Perry County westward to Posey County and thence northward to Gibson County. It 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 Sandstone is overlain by the Mansfield Formation (Morrowan). Reliable lithologic and thickness data are not available.
For Indiana usage the Degonia Sandstone is here assigned to the Buffalo Wallow Group.