Paper No. 11-14
Presentation Time: 8:00 AM-12:00 PM
GEOLOGY AND BLUE RIDGE ESCARPMENT EVOLUTION ALONG THE WHITEWATER RIVER IN NORTHWESTERN SOUTH CAROLINA AND ADJACENT NORTH CAROLINA
The Blue Ridge Escarpment (BRE), a complex geologic feature that connects the Blue Ridge upland to the lower elevation Piedmont region, has been the focus of much research and speculation about its origin and subsequent erosional history. This research focused on the Whitewater River in northwestern South Carolina and adjacent North Carolina in order to examine how the river has eroded into the Blue Ridge Escarpment and how that relates to overall escarpment evolution. Field studies determined the dominant bedrock to be Toxaway Gneiss, and thin section analysis reveals that the primary mineralogy is microcline (25-30%), plagioclase (20-25%), quartz (20-25%), and biotite (25-30%) with accessory epidote. Whole rock chemistry shows a range of silica content from 64% to 67% weight percent which coincides with quartz abundance seen in thin sections. A total of 14 joints in bedrock were measured with joint orientations striking predominantly EW with near vertical dips. A total of 32 foliations were measured in the Toxaway Gneiss that show that the dominant foliation orientations were striking NE with steep to moderate dips mainly SE. Digital Elevation Models (DEM) analysis gives a catchment basin of 50 km2, which is larger than the adjacent Thompson River watershed. A longitudinal profile created using DEM analysis shows that the river has low gradient in between the two prominent knickpoints, the Upper and Lower Whitewater Falls. According to this analysis, the river is eroding into the escarpment by the propagation of the two major knickpoints, mainly by plucking along joint surfaces. However, potholes and stream-abraded bedrock at the top of both knickpoints demonstrate that abrasion is also a mechanism of river incision.