GEOLOGIC MAP OF THE SOUTHERN HALF OF THE MOUTH OF WILSON AND SOUTHEAST CORNER OF THE GRASSY CREEK 7.5-MINUTE QUADRANGLES, NC-VA: ASHE-BASEMENT CONTACT REVISITED
FF shear zones vary from meters to ~1 km wide and are composed of basement-derived porphyroclastic mylonites with the assemblage chlorite + epidote + garnet + biotite + muscovite + quartz + plagioclase. These shear zones trend NE-SW, dip 45-60o SE with a moderately ESE plunging lineation, and contain top-to-NW kinematic indicators. The GLF trends N 65-70o E, dips moderately SE, and is parallel to the regional foliation in the AMS, basement rocks, and FF shear zones. AMS and basement rocks near the GLF are mylonitic, locally truncated and contain moderately plunging ESE mineral lineation. In the AMS the GLF is marked by mylonitic graphitic phyllite to muscovite schist and quartz pebble metaconglomerate with rare lithic clasts, which could be traced ~500m. Recent Ar/Ar ages (Stokes et al., 2010) from the FF and AMS suggest the faults and related structures developed during a Dev.-Miss. event.
Quaternary terrace deposits of unconsolidated sands, with quartz and lithic pebbles to cobbles occur ~500’ above the present level of the New River. The largest terrace deposit underlies a gentle rolling surface (~7 sq. km) near in Piney Creek, NC and is at least 40 feet thick.