MIOCENE LINEAMENTS AND FRACTURES IN THE SPRUCE PINE 7.5-MINUTE QUADRANGLE, WESTERN NORTH CAROLINA, ASSOCIATED WITH TOPOGRAPHIC REJUVENATION OF THE BLUE RIDGE MOUNTAINS

There are multiple linear fracture systems (lineaments) exposed across western North Carolina that are associated with Miocene topographic rejuvenation of the Blue Ridge Mountains. These fracture systems are composed of joints and faults that strike obliquely to the rock units across the region. This obliquity along with previous constraints on the direction of fault motion, knickpoints along stream channels, and paleostress analysis suggests that these fracture systems are not associated with the Paleozoic assembly of Pangea or subsequent rifting, but are in fact likely much younger. Previous research on the Laurel Creek Lineament, which extends from Hot Springs, NC east toward Spruce Pine, NC demonstrated that fractures within this lineament formed from a vertical maximum compressional stress consistent with the focal mechanism from an earthquake in 2005. The fractures have not been mapped on the easternmost portion of the lineament near Spruce Pine. This study included geologic field mapping of rock units and fractures in the Spruce Pine 7.5-minute quadrangle to document fractures, fault offsets, and the direction of fault motion along this part of the lineament. Vertical joints and faults are exposed throughout the entirety of the quadrangle and dominantly strike toward 080/260°, consistent with previous measurements elsewhere along the lineament. These fractures are denser around the topographic lineament that extends through the town of Spruce Pine. The majority of the fractures found in Spruce Pine exhibited no offsets and offsets that were found were centimeters to meters in magnitude. Fault slickenlines and offset soil or rock units suggest that the north block moved up relative to the south block. Previous studies on the Boone Lineament, north of Spruce Pine, showed that the fracture system moved with the south side up. These data indicate that the block of crust between the Boone Lineament and the Laurel Creek Lineament could have been uplifted by these fracture systems, resulting in the high topography around Grandfather Mountain which is within this uplifted block.