GEOLOGIC CROSS SECTION I-I’ THROUGH THE APPALACHIAN BASIN FROM NORTH-CENTRAL KENTUCKY TO SOUTHWESTERN VIRGINIA

Based on data from 19 deep drill holes and numerous geologic quadrangle maps, the U.S. Geological Survey has completed a 280-mile long geologic cross section through the Appalachian Basin from north-central Kentucky to southwestern Virginia. From west to east, the section extends from the eastern margin of the Illinois Basin across the Cincinnati Arch (Jessamine Dome), Grenville Front, Rome Trough, Cumberland Plateau, Pine Mountain thrust fault, and into the Valley and Ridge Province. Paleozoic strata range in thickness from approximately 3,000 ft along the crest of the Cincinnati Arch to approximately 16,000 ft near the Pine Mountain thrust fault. Structural features include basement-involved faults, and thin-skinned structures such as bedding-plane detachment zones, footwall ramps, ramp anticlines, and imbricate thrust faults. Major stratigraphic features include (from top to bottom):

(1) Upper Mississippian and Pennsylvanian siliciclastic strata (e.g., Pennington Group, Breathitt Group) coincident with the Alleghanian orogeny;

(2) Middle and Upper Mississippian predominantly carbonate strata (e.g., Greenbrier Limestone, Newman Limestone), capped by the Kaskaskia-Absaroka regional unconformity;

(3) Middle Devonian to Middle Mississippian siliciclastic strata (e.g., Ohio Shale, Borden Formation) coincident with the Acadian orogeny;

(4) Lower Silurian to Middle Devonian carbonate and evaporitic strata (e.g., Salina Group, Helderberg Group), capped by the Tippecanoe-Kaskaskia regional unconformity;

(5) Upper Ordovician to Lower Silurian siliciclastic strata (e.g., Reedsville Formation, Clinch Sandstone) coincident with the Taconic orogeny;

(6) Middle and Upper Ordovician predominantly carbonate strata (e.g., High Bridge Group, Lexington Limestone);

(7) Lower Cambrian to Lower Ordovician predominately carbonate strata (e.g., Rome Formation, Conasauga Group, Knox Group), capped by the Sauk-Tippecanoe regional unconformity;

(8) Mesoproterozoic to Neoproterozoic rocks (capped by a regional unconformity), ranging from crystalline rocks (Granite-Rhyolite province) and overlying siliciclastic red beds (Middle Run Formation) in the western portion of the cross section to crystalline rocks (Grenville province) in the central and eastern portion of the cross section.