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Thrusts in the crystalline core of the southern Appalachians formed by both ductile and brittle mechanisms during three or more major Paleozoic deformational-thermal events (Taconic, Acadian, Alleghanian), in contrast to thrusts in the foreland which formed primarily as brittle faults during the Alleghanian. Early prethermal peak thrusts formed in the crystalline core, then were subsequently thermally overprinted and annealed. Thrusts that formed late in a metamorphic-deformational sequence have maintained a planar geometry. Many of these thrusts, such as the Brevard and Towaliga faults, were later reactivated in either the ductile or brittle or both realms, possibly involving both dip-slip and strike-slip motion. The thrusts framing the Pine Mountain and Sauratown Mountains windows formed both pre- and post-thermal peak. The pre-thermal peak Box Ankle thrust in the Pine Mountain window is a structurally lower fault, whereas the window is flanked externally by the post-thermal peak Towaliga (northwest) and Goat Rock (southeast) faults. Conversely, in the Sauratown Mountains the brittle Hanging Rock thrust frames an inner window beneath the older Forbush thrust. Here a downward and outward propagating sequence is suggested for the development of thrusts. North American basement rocks are involved in both the Pine Mountain and Sauratown Mountains windows, and basement and cover behave as a homogeneously coupled mass with respect to strain. Consequently, the only factor that controlled the siting of early thrusts may have been the depth to the ductile-brittle transition zone. The frontal Blue Ridge thrust was the last formed in the Blue Ridge-Piedmont thrust sheet although the Cartersville-Miller Cove thrust is a slightly older Alleghanian thrust than the Great Smoky fault.

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