STRUCTURAL AND STRATIGRAPHIC RELATIONSHIPS NEAR THE SOUTHERN TERMINUS OF THE PULASKI FAULT, NORTHEAST TENNESSEE

The Pulaski fault is one of the master thrust faults in the Appalachian Alleghanian fold-thrust belt. Detailed geologic mapping of Cambrian and Ordovician strata in northeastern Tennessee 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 records at least two deformation phases. Geometric and crosscutting relationships along parts of the Pulaski thrust sheet in this study area and in southwestern Virginia suggest hanging wall and possibly some footwall deformation prior to the emplacement of the thrust sheet. The initial deformation in the Pulaski sheet, which consists of northwest-vergent, tight to overturned, pre-faulting macroscopic folds, may be a manifestation of the previously recognized late Mississippian to 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, would therefore be associated with the main (Early Permian) phase of the Alleghanian orogeny. In the study area, these two phases likely represent small changes in orientation during a single event of continued shortening. Type 3 fold interference patterns in the Pulaski thrust sheet here further support this notion. Substantially different facies occur on opposite sides of the fault. Upper Conasauga and Knox Group strata in the Pulaski thrust sheet consist predominantly of limestone and contain few identifiable stratigraphic markers suitable for subdividing the Knox northwest of the fault. Lower Conasauga Group rocks in the thrust sheet are more dolomitic and are interbedded with thin shale units. Geologic mapping during this study has successfully subdivided Honaker Dolomite in parts of the Pulaski thrust sheet by the tracing of the Rogersville Shale. Data suggest that the Pulaski fault was overridden by the thin-skinned Great Smoky fault. 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 foreland fold-thrust belts. Findings here could also improve our understanding of deformation sequences between the southern and central Appalachians.