EVIDENCE FOR MESOZOIC-RECENT DEFORMATION ALONG AND ACROSS PALEOZOIC TERRANE BOUNDARIES : SOUTHWESTERN VIRGINIA AND NORTHERN NORTH CAROLINA BLUE RIDGE AND PIEDMONT

Until very recently, Paleozoic terrane boundaries in the Southern Appalachian Blue Ridge and Piedmont were considered major landscape forming features that had remained relatively static except for passive erosion and progressive exhumation since the end of the Alleghanian Orogeny some 300 MA before the present. A series of recent seismic events felt here in the NC and VA Blue Ridge and Piedmont combined with some recent research in the Danville and Dan River Triassic Basins stimulated a detailed review of modern geological and geophysical maps as well as structural, geochronology and thermal and metamorphic history studies published by geologic journals, state geologic surveys, Virginia and Carolina Geological Field Conference Guidebooks . It turns out there is ample field evidence for post- Triassic deformation along Terrane boundaries. Preliminary results of the study suggests clockwise rotation of “dormant” Paleozoic and Triassic fault zones through the late Mesozoic and Cenozoic into alignment with a major left-lateral transform zone that developed in the Bay of Biscay Aulacogen, transferring strain progressively across the North Atlantic Basin . Most of the on- shore deformation seems to be concentrated along old rifts in the extended crust east of the old Laurentian continental margin and along north- to west- directed fracture zones across the old Laurentian basement.