THE SALTVILLE AND GREAT SMOKY FAULTS: MESOFABRICS, MICROFABRICS, AND EMPLACEMENT CONDITIONS

The Saltville thrust fault extends from Georgia to Virginia, and is one of the largest thrust faults in the Appalachian foreland fold thrust belt. The area studied is located along I-275 at Sharp Gap in northwestern Knoxville, TN. The Saltville fault at Sharp Gap consists of Rome Formation rocks thrust over an Upper Knox Group horse. Complex deformation is exposed at I-275 and on the frontage road (northeast of I-275), with the near-horizontal Saltville frontage-road sheet broken through by the more steeply dipping segment (45-55 degrees) during the last stages of movement. A horse of Knox above the Middle Ordovician footwall rocks thins dramatically to the NW. Samples collected from the I-275 locality consist primarily of carbonate gouge derived mostly from footwall Knox Dolomite. Meso and microscopic analysis within the fault zone reveal conditions during formation and emplacement of the fault. Abundant tectonic stylolites and very fine-grained gouge characterize the footwall and fault zone rocks suggesting abundant fluid was present during deformation. Crosscutting relationships between tectonic stylolites and layering in gouge reveal relative timing that suggests an emplacement chronology of the Saltville fault. Ultracatalasite (>90% matrix), cataclasite (50-70% matrix), stylolites, static recrystallization, veins, and extensional and contractional faults associated with the Saltville fault at both micro and hand specimen scale suggest fluctuating pore fluid pressure. The fluctuating pore fluid pressure is suggested by cyclic deformation such as crosscutting cataclasite layers and increased stylolite and vein density. Comparison with Great Smoky fault (GSf) gouge from a small exposure in Tuckaleechee Cove reveals similar conditions during emplacement. Both the Saltville and GSf were emplaced at near-surface temperatures with movement enhanced by abundant fluids.