2 Exotic Terranes in the Southern Appalachians: Evidence from Igneous, Sedimentary, and Metamorphic Rocks

Thursday, 17 March 2005
8:00 AM - 12:10 PM

STRUCTURE AND KINEMATICS OF THE GOLD HILL FAULT ZONE IN SOUTH-CENTRAL NORTH CAROLINA

Paper number: 2-4
Program: THEME SESSIONS
Time: 8:50 AM – 9:10 AM

Authors

Abstract

Detailed mapping at the 1:24 000 scale has been completed along a portion of the Gold Hill fault zone (GHfz) in south-central North Carolina (NC). The GHfz is a first order structure located within the peri-Gondwanan Carolina zone (CZ) that juxtaposes Neoproterozoic metavolcanic rocks of the Charlotte terrane (ChT) and the Carolina terrane (CT). Accretion of the CZ to Laurentia is poorly understood, mainly because Alleghanian shortening has obscured the suture. The GHfz predates Alleghanian deformation and may therefore be related to the docking of the CZ. Ongoing work in central NC indicates the GHfz is a sinistral reverse fault with southeast vergence. Age dating in this region has revealed the zone was active throughout the Paleozoic; however, earliest motion along the GHfz appears to be coeval with a set of Late Ordovician CCW en echelon regional folds. These observations support Late Ordovician accretion of the CZ in a manner compatible with other peri-Gondwanan terranes in the northern Appalachians.

Field work in south-central NC indicates the GHfz is a steep dipping zone of dextral transpression characterized by a wide damage zone in the CT. There the zone trends N60E and it is bounded to the north by the Gold Hill fault (GHf), which is a right lateral reverse fault that places ChT rocks over the CT. Strain in the zone intensifies towards the GHf. Strata in the CT are folded into a series of upright, northeast-plunging, regional folds and are imprinted by a steep dipping axial planar cleavage that strikes roughly parallel to the trace of the GHfz. The Waxhaw granite intrudes the CT and is deformed by the fault zone. Age dates obtained from deformed rocks in the immediate vicinity indicate the GHfz was active during either the mid or late Paleozoic.

Data gathered from the GHfz in south-central NC and northern South Carolina indicate that it is a mid to late Paleozoic dextral shear zone. However, sinistral shear is well documented along the zone in central NC. The simplest explanation is that later dextral shear represents reactivation of the GHfz during the mid to late Paleozoic. Middle to late Paleozoic ages along the zone in other regions of NC support this interpretation. Alternatively, the curved surface trace of the GHfz suggests that dextral shear in south-central NC could be coeval with sinistral shear in central NC.