Brevard fault zone, southern Appalachians: A medium-angle, dextral, Alleghanian shear zone

The record of Alleghanian movements in the rocks of the Brevard fault zone has been studied by using modern techniques of kinematic analysis. Mylonitic and phyllonitic fabric involves (1) strong subhorizontal stretching lineation trending northeast-southwest, parallel to the fault; (2) mylonitic foliation dipping moderately to the southeast; and (3) a great variety of kinematic indicators suggesting a dextral sense of shear. Both Palmetto and Ben Hill granites, Georgia (ca. 325 Ma), were sheared during this event, the age of which should be younger, probably ca. 310 Ma.

The Brevard zone is usually regarded as a listric thrust fault along which the Piedmont terrains have been displaced toward the northwest onto the Blue Ridge. By contrast, the movement picture resulting from our analysis is compatible only with right-lateral strike-slip faulting along a moderately dipping shear zone several kilometres wide, causing southwestward displacement of the Piedmont relative to the Blue Ridge province, parallel to the Appalachian trend.