Gravitational collapse of the Paleozoic thrust stack and later hinterland-directed Alleghanian (?) back thrusting, Inner Piedmont, South Carolina & North Carolina.

The 80th meeting of the Carolina Geological Society was held October 4-6, 2019 in the area of Greenville, SC, and focused on two new aspects of Inner Piedmont tectonic history in South Carolina and nearby North Carolina. Retrograde shear zones and their internal fabrics are interpreted to be the result of top-to-the-south gravitational collapse of the early-mid-Paleozoic thrust stack. The trip visited the Mine Mountain shear zone in Standingstone Mountain quadrangle. Second, later hinterland-directed thrusting, inverting the normal structural stacking sequence of Six Mile thrust sheet paragneisses over Walhalla thrust sheet orthogneisses, is interpreted as the result of back-thrusting associated with an Alleghanian (?) brittle thrust. Several exposures of the back thrusts were visited on Sunday. An alternate Sunday excursion described the hydrologic conditions at the Cliffs at Glassy Community along the Blue Ridge Front.