TRANSCURRENT TRANSFER ZONE AND DEXTRAL RELEASING OFFSET: THE NUTBUSH CREEK-LAKE GORDON FAULT SYSTEM IN THE EASTERN NORTH CAROLINA PIEDMONT

In the north-central Piedmont along the NC-VA line, the tectonic boundary between the greenschist facies Carolina terrane suprastructure and the amphibolite facies Raleigh terrane infrastructure coincides with the strain transition between the Alleghanian Nutbush Creek (NBC) fault zone and Lake Gordon (LG) mylonite zone. Horton et al. (1993) and Butler et al. (1995) provided initial fabric and kinematic data for these two strands of the eastern Piedmont fault system in VA, proposing that 1) together with the Hylas zone, they comprise en echelon right-stepping strands of this late Paleozoic fault system, 2) the LG and Hylas zones may be linked by a dextral releasing bend, and 3) the Pennsylvanian Buggs Island granite utilized the NBC-LG releasing offset as an emplacement conduit. While the NBC fault zone was mapped southward in NC along the western flank of the Wake-Warren anticlinorium, the LG mylonite zone was interpreted to truncate against northern portions of the Pennsylvanian Rolesville batholith.

NCGS STATEMAP mapping in the John H. Kerr Dam Quadrangle corroborates earlier fabric and kinematic findings, especially in the Kerr Lake State Recreation Area. There, the 2007 drought provided spectacular outcrops of ductile dextral-slip and ductile-brittle normal-slip deformation superimposed on the Vance County pluton of the Carolina terrane to the west, pelitic schist of the newly defined Warren terrane to the east, and intervening Alleghanian granite mylonitic granitic gneiss and mafic to intermediate gneiss of the Raleigh terrane. These units and associated fabric are mapped south into the Middleburg and Henderson Quadrangles where contact relationships become more problematic. We suggest that 1) pulses of granite intruded syn- and post-kinematically with respect to mylonitic fabric development; 2) some strands of the LG mylonite zone continue southward; 3) the previously mapped position of the NBC fault zone actually is the southern trace of the LG mylonite zone; 4) south of Henderson, the NBC fault zone is farther west than previously mapped, marking the western boundary of the Crabtree terrane (closer to the interpretation of Farrar, 1985), and 5) the western flank of the Wake-Warren anticlinorium in the eastern Piedmont is a regional-scale dextral transfer zone and releasing offset.