Report of Investigations--KGS


This east–west cross section across western Kentucky is one of a network of regional cross sections prepared by the Illinois Basin Consortium that illustrate the structural and stratigraphic framework of the Illinois Basin. The structural cross section uses wireline logs of deep tests, as well as proprietary reflection seismic data, to show the relationship of Paleozoic rocks to each other from the surface to the top of the Precambrian unconformity.

The line of the cross section extends east from the complexly faulted Western Kentucky Fluorspar District across the Moorman Syncline and the underlying Rough Creek Graben to the Cincinnati Arch in central Kentucky. The cross section extends across the northern, deepest part of the asymmetrical Rough Creek Graben. Relatively minor changes in stratigraphic thickness occur within the Paleozoic from the arch west, with a few units pinching out to the east. Extensive post-Paleozoic erosion, however, has rendered the middle and upper part of the Paleozoic section an overall west-thickening wedge that has been further accentuated by the extreme thickening that occurs in the lower part of the section, especially in the Eau Claire Formation, which expands nearly 15 times and to a depth approaching 30,000 ft in the Rough Creek Graben.

As a result of this study, changes in stratigraphic nomenclature are recommended. The recommended changes include raising the Cambrian-Ordovician Knox Group to supergroup status in Kentucky with two groups recognized within it. Southern Illinois and southwestern Indiana formation nomenclature is recommended for the Lower Ordovician Beekmantown Group of western Kentucky; it differs from that in the area of the Cincinnati Arch and eastern Kentucky, where Appalachian formation terminology is recommended together with the Rose Run Formation. Recognition of the Pecatonica Formation eastward from western Kentucky results in the subdivision of the Ordovician High Bridge Group into five lithologic units in central and eastern Kentucky.

Publication Date



Series XII

Report Number

Report of Investigations 13

Digital Object Identifier (DOI)


© 2005 University of Kentucky

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