Paper No. 9-47
Presentation Time: 8:00 AM-12:00 PM
KNICKPOINT ELEVATIONS WITHIN THE SPRUCE PINE 7.5-MINUTE QUADRANGLE, NC: IMPLICATIONS FOR MIOCENE UPLIFT OF THE BLUE RIDGE PROVINCE
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. Relict topography and retreating knickpoints within stream channels that drain into these lineaments suggest the block between the Laurel Creek and Swannanoa lineaments uplifted first, followed by the block south of the Swannanoa Lineament, with the block south of the Boone lineament uplifting most recently. 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. This lineament parallels jointing found throughout the Spruce Pine 7.5-minute quadrangle, which dominantly strike toward 260°. Retreating knickpoints and other disequilibrium features have not been constrained on the block north of this lineament. This study utilized 1-m resolution LiDAR for the Spruce Pine 7.5-minute quadrangle to evaluate knickpoints within streams that drain into the lineament to place the blocks bounded by it into a chronological framework. Stream profiles were created for seven stream systems: Little Bear Creek, Bear Creek, Graveyard Creek, Gouges Creek, Pyatt Creek, Jones Creek, and Beaver Creek. 24 knickpoints discordant with lithologic contacts and anthropogenic disturbances were identified on streams that flow south into the lineament. The elevations of these knickpoints ranged from 780 to 1070 m, averaging 867 m (s.d. 70 m). A strong cluster (60%) of these knickpoints were found between elevations of 807-874 m. This strong cluster in elevation is independent of lithology and likely reflects knickpoint retreat. Streams that flow north into the lineament do not exhibit disequilibrium. These data are consistent with previous research that suggests the block south of the Laurel Creek Lineament records an earlier uplift history and shows that the block north of this lineament likely uplifted concurrently with movement along the Boone Lineament.