EAST-WEST LINEAMENTS OF THE SOUTHERN APPALACHIAN PIEDMONT AND BLUE RIDGE

The southern Appalachian Piedmont and Blue Ridge are dominated by northeast trending lineations created during the three major orogenies that created the Appalachian mountains. However, a detailed analysis of LIDAR data shows that there is also a more subtle E-W lineation scattered throughout western North and South Carolina. Two E-W lineations were previously identified on an outcrop scale: an early pre-Alleghenian E-W fracture set in the Blue Ridge to Valley and Ridge provinces and an E-W fracture system associated with strike-slip faulting in the Triassic in the Piedmont and Coastal Plain (Bartholomew & Whitaker, 2010; Bartholomew et al., 2009). Other authors have noted large-scale E-W lineations and joints associated with the Swannanoa Lineament and the Laurel Creek Lineament (Hill, 2018). Some authors suggest that these lineaments are associated with steeply dipping reverse faults associated with Miocene block rejuvenation of the Southern Appalachians (Hill, 2018). However, given the steepness of the faults, it is likely that the E-W fracture zones existed prior to the Miocene. So which tectonic event created the E-W lineation that trends oblique to all other regional tectonic lineations and are they related to inherited structures from the Iaptean rifting?

We used Global Mapper, GIS, the 3DEP LIDAR data from the USGS, and geologic maps from the USGS and State Geologic Surveys to conduct initial analyses on the lineaments. Two approaches were used: large-scale mapping of locations of E-W lineations and small-scale mapping to determine age relationships. Both techniques began with visual analysis of lidar data under various filters and variables to assess areas of interest. For the large-scale mapping we subdivide the region into sections with obvious E-W lineations and areas without, comparison with Iaptean rifting maps suggest that present day E-W lineations appear to be more prevalent where pre-Taconic ~E-W rifting transforms were numerous. Age relationships are determined based on cross-cutting relationships within sections where the E-W fabric is dominant and where it appears to interact/be superseded by northeast-trending fabrics. A comparison with geologic maps will clarify any existing rock type and terrane relationships.