Recent deep drilling in eastern Kentucky is adding much new subsurface information, making possible a reinterpretation of this portion of the Interior Plateau region. The present study is a preliminary report on the subsurface stratigraphy and structure of that region, including 6 newly made geologic cross sections and 8 isopachous maps of various stratigraphic groups or series. Three matters in particular are reported. 1) There is a newly discovered Lower Cambrian coastal declivity which may be a fault scarp or a steep coastwise cliff that is responsible for an abrupt thickening of Early Cambrian deposits on its SE. side. Apparently it does not affect sediments of Dresbachian age. 2) As they appear to have quite different thickness-distribution patterns, rocks commonly called Mt. Simon-Eau Claire, or Lamotte-Bonneterre (the group known as Dresbachian) should be separated from overlying sediments and not regarded as Upper Cambrian. In this paper they are placed in the late Middle Cambrian. 3) There is a broad low concealed arch extending from N.-central Ohio southward into eastern Kentucky, on top of which all Beekmantown strata have been removed by pre-Chazy erosion that also cut deeply into the Upper Cambrian below the Beekmantown. This arch, here named the Waverly arch, lies about 60 miles E. of the Cincinnati anticline which was apparently absent in pre-Trenton time. Many paleogeographic and structural relations hitherto assigned to the Cincinnati arch during pre-Trenton epochs are attributed now to the Waverly arch. If these and other preliminary observations are substantiated as is confidently expected, considerable revision is required of various subsurface interpretations previously held for this region.

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