THE PULASKI FAULT IN NE TN AND SW VA: A POSSIBLE RECORDER OF TWO-PHASE ALLEGHANIAN DEFORMATION

The Pulaski is one of the master Alleghanian thrust faults in the Valley and Ridge fold-thrust belt, and is the only major southern Appalachian fault to extend into the central Appalachians around the Roanoke recess in SW VA. Detailed field mapping of Cambrian and Ordovician strata in NE TN revealed key structural and stratigraphic characteristics for distinguishing the Pulaski thrust sheet from its footwall, the Saltville thrust sheet. Unlike most thrust systems in the Valley and Ridge, the Pulaski sheet may exhibit two deformation phases. The initial deformation, consisting of NW vergent, tight to overturned, pre-faulting macroscale folds that are contained within the Pulaski hanging wall, may be a manifestation of the previously recognized late Pennsylvanian Lackawanna phase of the Alleghanian orogeny. Transport of the earlier deformed strata, analogous to deformation sequences that occurred in the Pulaski sheet near the Roanoke recess, and subsequent folding would therefore be associated with the main (Permian) phase of the Alleghanian. The Saltville sheet, in contrast to the Pulaski thrust sheet, contains broad and mostly open folds, typical of buckle folding of the thick Cambro-Ordovician carbonate sequence. Significant changes in stratigraphy are also present on opposite sides of the fault. Upper Conasauga and Knox Groups within the Pulaski sheet consist of more limestone and fewer stratigraphic markers for use in subdividing the Knox northwest of the fault. Lower Conasauga Group rocks within the thrust sheet contain more dolomite and thin traceable to untraceable shale units. These dissimilarities between thrust sheets document key telescoped facies changes that can be used to map the Pulaski fault trace and reconfirm its fundamental character. Our data suggest that the Pulaski fault was overridden by the thin-skinned Great Smoky fault, which marks the westernmost boundary of the Blue Ridge. The kinematic and geometric interrelationships between the Pulaski and other Valley and Ridge faults provide useful insight into the processes of footwall/hanging wall deformation and thrust propagation in thin-skinned foreland fold-thrust belts. Findings here could also improve our understanding of deformation sequences between the central and southern Appalachians.