REGIONAL SIGNIFICANCE OF THE GOLD HILL FAULT ZONE, CAROLINA ZONE OF NORTH CAROLINA

The Gold Hill fault zone (GHfz) is a first-order structure in the western portion of a collection of southern Appalachian peri-Gondwanan terranes termed the Carolina Zone. The timing and nature of accretion of the Carolina Zone to Laurentia is controversial, mainly because the suture has been tectonically buried beneath the zone during Alleghanian shortening. Some workers interpret the accretionary event as Devonian subduction of Laurentia beneath the Carolina Zone, whereas we suggest that it involved Late Ordovician-Silurian subduction of Carolina beneath Laurentia. The GHfz predates Alleghanian shortening and thus may well be related to the accretion of the zone to Laurentia.

The GHfz juxtaposes phyllites and metavolcanics of the Charlotte terrane to the west against slaty volcaniclastic rocks of the Carolina terrane to the east. U-Pb geochronology suggests that the Charlotte terrane strata are pre-615 Ma, whereas the Carolina terrane contains significantly younger Neoproterozoic rocks. The GHfz has traditionally been viewed as a Devonian dextral shear zone, supporting the Devonian model for accretion of the Carolina Zone. However, our recent fieldwork indicates that the zone is a sinistral reverse fault system with southeast vergence and an associated wide damage zone in the footwall Carolina terrane. In addition, the fault both truncates, and is folded by, a CCW en echelon array of upright folds with an axial planar cleavage that has previously been documented to be Late Ordovician in age. Thus, the GHfz appears to be coeval with Late Ordovician folding.

The sinistral-reverse GHfz is the youngest documented pre-Alleghanian structure in the Carolina Zone; consequently we interpret it to reflect the timing and nature of accretion of the zone to Laurentia. Our interpretation is temporally and kinematically compatible with accepted models for the docking of northern Appalachian peri-Gondwanan terranes.