Structural Patterns in the Southern Appalachians: Evidence for a Gravity Slide Mechanism for Alleghanian Deformation

Age relations of major Southern Appalachian structural blocks, as determined at their intersections, indicate that the older faults of the Alleghanian deformation are to the west and the younger ones are to the east toward the supposed direction of the deforming forces. This break-back pattern of deformation is also a characteristic of faulting within each of the blocks. From this it is concluded that the final deformation of the Southern Appalachians did not result from a push from the east, but rather took place when the Alleghanian thrust sheet moved westward above decollement as a gravity slide, crumpled at the toe, and then was faulted in sequence from west to east. The gravity sliding can be related to vertical uplift of an infrastructural Inner Piedmont mobile thermal core.