3D RECONSTRUCTION OF ALLEGHANIAN STRUCTURE OF THE APPALACHIAN FORELAND FOLD-THRUST BELT, NW GEORGIA TO SW VIRGINIA AROUND THE TENNESSEE SALIENT

New balanced serial cross sections have been constructed across the Appalachian foreland fold-thrust belt (FFTB) from the Cumberland Plateau into the western Blue Ridge (BR) around the TN salient from NW GA to SW VA. These sections are based on surface geology, well data, and seismic reflection data. The cross sections record the changing character of Alleghanian deformation both along and across the salient. Cross sections were imported into 3DMove to connect major structures and fault surfaces in a 3D reconstruction of the FFTB, and to attempt some 3D balancing. The number of major faults in the Valley and Ridge increases south into TN from VA to a maximum of ten at the narrowest part of the salient, near Knoxville, TN, then decreases again south into GA. The basal detachment through most of the FFTB lies in the Cambrian Rome Fm, though it ramps into shallower units on the west side of the FFTB, and downward into basement east of the Pulaski fault. Restorations suggest that total shortening in the FFTB is close to 60%, greater than the previously estimated 45-55%. From the Saltville fault west, deformation is dominated by imbricate faulting; south of Harriman, TN, a large subsurface detachment fold lies just west of and below the imbricate zone. East of the Saltville fault folding dominates surface deformation, but structure below the Middle Ordovician Tellico-Sevier syncline is much more complex than previously thought. Industry seismic reflection data reveal details of previously unknown imbricate and duplex geometries. The BR-Valley and Ridge transition is marked by a NE-trending set of en echelon duplexes of Cambro-Ordovician Valley and Ridge rocks arching the BR thrust sheet from the GA/TN border (Ducktown antiform) to the Foothills duplex to NE TN and SW VA (Mountain City window) and east into NC (Shooting Creek, Hot Springs, and Grandfather Mountain windows). In the Hot Springs window, an uninterrupted section of rocks from Middle Cambrian to Precambrian Ocoee Supergroup is folded by underlying duplexes. Frontal duplexes are consistently oriented 10-20 degrees west of the trace of the frontal BR thrust. The occurrence and location of the sub-BR duplexes may be influenced by localization of the BR thrusts in basement and Chilhowee Group rocks to the north, versus Chilhowee Group and Ocoee Supergroup rocks to the south.