ABSTRACT

The Valley and Ridge and eastern Allegheny Plateau from Pennsylvania into Tennessee is subdivided into distinct allochthonous sheets emplaced over an essentially featureless Precambrian basement surface. Sheet development is related to variations in stratigraphic thickness and lithology, as well as regional basement configuration.

Three sheets control central Appalachian structural style. The Massanutten-Blue Ridge sheet is easternmost and is bounded on the west by the (Little) North Mountain-Pulaski fault system. Continuing westward into the plateau, the Martinsburg sheet contains anticlinoria and synclinoria uncut by major thrust faults. Both Massanutten-Blue Ridge and Martinsburg sheets are seated in Upper Ordovician Martinsburg (Reedsville) shales. The underlying Waynesboro sheet is rooted in Lower Cambrian Waynesboro (Rome) shales, and its imbrication has controlled the locations of major anticlinoria and synclinoria in the upper sheet.

Within the southern Appalachians, greater imbrication of the lower sheet and increased thrust fault displacement at longitudinal ramps have destroyed the lateral continuity along strike of the central Appalachian Waynesboro and overlying Martinsburg sheets. There, imbrication to the surface has formed the Saltville sheet, continuous into Alabama, as well as the St.Clair-Narrows, Copper Creek, Cove Mountain, and St. Paul-Honaker sheets.

Southwest of the trend change, the Holston-Stone Mountain sheet adjacent to the Blue Ridge is rooted primarily in Lower and Middle Cambrian strata and is underlain by the Pulaski sheet. In the westernmost sector of this region, the Pine Mountain and Richlands sheets are seated in Devonian shales.

The Pulaski and Massanutten-Blue Ridge sheets, rooted primarily in Upper Ordovician shales, form a continuous structural unit and include Blue Ridge and Piedmont rocks.

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