PRELIMINARY RESULTS OF GEOLOGIC MAPPING IN THE GREENSBORO, NORTH CAROLINA AREA

The Greensboro, NC area is located along strike to the north of the Gold Hill shear zone (GHSZ) and along strike to the south of the Hyco shear zone (HSZ). Both the GHSZ and HSZ are significant shear zones in the southern Appalachians and determining the nature of these shear zones has significant implications for understanding the evolution of the eastern Laurentian margin during Appalachian orogenesis. Limited detailed geologic mapping studies have been conducted in the Greensboro, NC area. As a result, very little is known about the nature of the GHSZ and HSZ in this area as well as how the lithostratigraphy in this area fits into the regional context of the southern Appalachians.

In order to shed light on the nature of the GHSZ and HSZ in the Greensboro, NC area and better constrain the lithostratigraphy in this area, we have begun a geological mapping project. During our mapping to date we have observed a medium-grained, granitic pluton in the northern part of the area and a suite of coarse to fine, felsic to mafic plutonic igneous rocks in the southern part. Regional geologic maps of the southern Appalachians depict the granitic pluton in the northern part of the area as part of the Late Carboniferous Churchland Plutonic Suite while the suite of felsic to mafic rocks in the southern part of the area are grouped with Neoproterozoic rocks of Peri-Gondwanan origin. Further mapping and petrographic analysis will provide more details on these rocks.

All of the rocks we have observed contain a foliation. The average strike of the foliation is 240^◦-60^◦ and dips steeply (75^◦) either to the northwest or southeast. We have also located a northeast-southwest trending shear zone that deformed both the granitic pluton and the suite of felsic to mafic rocks. In this zone, we have observed two sets of folds. The oldest set consists of tight, upright folds with an average hinge orientation of 232^◦, 30^◦ while the younger set consists of broad, open folds with an average hinge orientation of 300^◦, 50^◦. Also in this zone, we have also observed mineral and stretching lineations that range from sub-horizontal to sub-vertical as well as steeply-dipping faults that offset the tight, upright folds in a left-lateral sense. Further structural and microstructural analyses will provide more details on the characteristics and kinematics of this shear zone.