CORRELATION OF MAJOR TOPOGRAPHIC LINEAMENTS IN THE NORTH CAROLINA BLUE RIDGE WITH REGIONAL FRACTURE ZONES

Hundreds of E-W and SE-NW-trending topographic lineaments crosscut the SW-NE-trending southern Appalachian orogenic belt, mostly within the Blue Ridge but some in the Valley and Ridge and Piedmont provinces. Although the lineaments have been recognized by previous workers, their origin is unknown. This study focuses on the two longest E-W lineaments in western North Carolina originally described by Hack (1982) as the Swannanoa and Laurel Creek trenches. Visible in satellite imagery and on topographic maps, these features span ~250 km and ~120 km, respectively. The western end of the Swannanoa lineament is at Fontana Lake, south of Great Smoky Mountains National park; continues east through Asheville, NC; and ends at Lake Hickory. The Laurel Creek lineament runs from Hot Springs, NC in the west, through Spruce Pine, NC, and truncates the northern end of the Black Mountains, the highest range in the eastern US. The Swannanoa lineament is not one continuous corridor, but a slightly N-of-E-trending zone of en echelon, E-W-striking trenches. These smaller trenches correspond to Lakes Fontana, James, Rhodhiss, and Hickory and are parallel to the Laurel Creek lineament but slightly shorter in length. Joints in the Swannanoa lineament have a mean strike of 101° (n=1291, 86 outcrops). Within the Laurel Creek lineament, joints have a mean strike of 93° (n=197, 17 outcrops). E-W and SE-NW joint sets are equally common within both lineaments, but the SE-NW joints are the dominant set in the regions between the lineaments. We interpret the SE-NW joints to be a regional set related to late Alleghanian shortening. Paleostress inversion of 16 minor E-W dextral-normal faults within the Swannanoa lineament near Canton, NC, yields a best-fit principal stress tensor with a vertical maximum compressive stress and an east-west minimum compressive stress. The faults and fractures, therefore, appear to have formed in an extensional stress field, which may be related to post-orogenic doming of the southern Appalachians.