30 Geomorphic Evolution of River Corridors in the Eastern United States from the Pleistocene to the Anthropocene

Saturday, 18 March 2023
1:30 PM - 5:30 PM
Lake Fairfax

MIOCENE FRACTURES AND LANDSCAPE RESPONSE IN THE SPRUCE PINE 7.5-MINUTE QUADRANGLE, WESTERN NORTH CAROLINA

Paper number: 30-10
Program: Theme Sessions
Time: 4:10 PM – 4:30 PM

Authors

Abstract

East-west-, southeast-northwest-, and north-south-trending lineaments within the Blue Ridge Province of western North Carolina separate crustal blocks that record differential uplift throughout the Miocene. East-west oriented lineaments include, from north to south, the Boone, Laurel Creek, and Swannanoa lineaments. 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 a 2005 earthquake. The Spruce Pine 7.5-minute quadrangle includes a portion of the Laurel Creek Lineament. Geologic field mapping of bedrock and fractures within the quadrangle was combined with digital mapping of knickpoints within streams and landslides from 1-m resolution LiDAR data to constrain the orientation of lineament fractures, direction of slip, and the role of these fractures in landscape evolution. Joints and faults throughout the quadrangle are dominantly vertical and strike toward 080˚/260˚. Fault slickenlines, offset rock units, and tension gashes suggest that the block north of the lineament moved up relative to the south block. The elevations of knickpoints, discordant with lithologic contacts and anthropogenic disturbances, on streams that flow south into the lineament ranged from 780 to 1070 m, with a strong cluster (60%) found between elevations of 807-874 m. Streams that flow north into the lineament do not exhibit disequilibrium. This strong cluster found only on the north block, along with kinematic indicators, likely reflects knickpoint retreat associated with uplift of the north block rather than stream capture. Additionally, landslide aspects ranged from 010° to 340°, with elevated frequencies (32% of total landslides) parallel and perpendicular to the strike of the fractures.

Geological Society of America Abstracts with Programs. Vol. 55, No. 2

doi: 10.1130/abs/2023SE-385675

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