Deformation in portions of the distal continental margin to ancestral North America: An example from the westernmost internal zone, central and southern Appalachian Orogen, Virginia

Late Precambrian(?)–early Paleozoic metasedimentary and metavolcanic rocks of the Evington Group crop out in a belt along the eastern flank of the Blue Ridge, Virginia. Near Lynchburg, where the sequence is well preserved, the Evington Group is interpreted as a transitional rift/drift succession of the distal continental margin to ancestral North America, caught up in the internal zone of the southern Appalachian orogen. The initial deformation of the Evington Group involved recumbent folding and nappe thrusting, which emplaced distal facies over proximal facies rocks. A penetrative schistosity, axial planar to the early folds, developed under greenschist facies conditions. Nearly coaxial refolding about upright, NE trending, SE dipping axial surfaces followed, also under greenschist facies, and was contemporaneous with high‐angle reverse faulting vergent westward toward the craton. The age of metamorphism and tectonostratigraphic correlations along strike indicate that these deformations were coincident with arc convergence and collision during the Taconic Orogeny. Transpressional stresses related to NE striking Alleghanian (late Paleozoic) dextral strike‐slip faults outboard of the Evington Group rocks studied here are interpreted by others to have caused domes and basins to form 35 km along strike southwest of Lynchburg in the Roanoke River region. Integration of data collected along strike of the belt from the Roanoke River to Lynchburg indicates that dome formation produced F2 plunge variations NE in the belt of Evington Group rocks. Many orogens developed through continent‐arc collision which proceeded from internal to external zones. Comparison of the Evington Group with rock sequences from tectonostratigraphic settings similar to those in other orogens (e.g., Wopmay Orogen) indicates that they have roughly similar histories of deformation. Recumbent folding and thrust nappe emplacement in the internal zone is an early phase of orogenic evolution and proceeds toward the craton through time. Second‐stage coaxial refolding about upright axial planes may or may not occur or be recorded. Late stage strike‐slip faulting in the internal zone is a common feature of many orogens that may reflect oblique convergence or tectonic escape.