WAS THE TABLEROCK THRUST SHEET DEFORMED BY SHEATH FOLDING?

The Tablerock thrust sheet (TR) is exposed along the western margin of Grandfather Mountain Window (GMW) in western North Carolina. It is a horse of Chilhowee Group and Shady Dolomite that moved along the Linville Falls fault, where it separates basement and cover rocks inside the window from the overriding Blue Ridge-Piedmont (BR-P) megathrust sheet (Tugaloo terrane). The TR comprises two quartzite units of Lower Cambrian Chilhowee Group separated by a thin layer of blue-gray phyllite, overlain by Shady Dolomite. Trupe et al. recognized significant shearing along the base of the TR, and within the portions near the thick Linville Falls shear zone (LFSZ) in the hanging wall above it. This indicates the TR likely accommodated shear strain generated by the movement of the BR-P megathrust sheet, either in conjunction with, or in addition to the accommodation recorded by the overlying LFSZ. Rocks of the TR are penetratively deformed and contain NW-trending tight to isoclinal meso-scale folds and a prominent NW-trending mineral stretching lineation. This NW-trending fabric also occurs in the thrust sheets above and below the TR, as previously recognized by Bryant and Reed. All tectonic units are overprinted by a NW-vergent/NE-trending crenulation cleavage and larger mesoscopic folds. The lateral relationship between the trends of the mineral lineation and of the fold axes in rocks of the TR suggest the early folds formed as a set of sheath folds during thrusting of the BR-P and/or TR. If so, the TR may have been rotated during transport and by progressive, heterogeneous strain, and NW-trending tight to isoclinal folds may represent parasitic folds on one or more NW-verging macroscopic sheath folds that define the TR.