THE TIMING AND SEDIMENTOLOGY OF TERRACES FORMED ALONG BLUE RIDGE ESCARPMENT RIVERS

Fluvial terraces are recognized as indicators of environmental shifts within stream systems including tectonic activity, climate change, and anthropogenic alteration. Our recent geomorphic mapping in drainages along the Blue Ridge Escarpment indicate that at least one terrace is generally present along most streams. However, it is unclear what age these terraces are and what they might indicate about the recent evolution of the escarpment. Here, we examine terraces along the lower portions of the Linville River and compare them with terraces along the nearby Upper Creek. Both drainages are along the escarpment but the Linville drainage includes portions on top of the escarpment as a result of stream capture while Upper Creek drains the escarpment itself. Along the lower Linville River, terraces are fine grained and mantled with cumulic soils indicating slow, steady aggradation via overbank deposition. Radiocarbon ages from soil profiles indicate that aggradation occurred throughout the second half of the Holocene. In contrast, sedimentology of terraces in Upper Creek indicate that they formed as part of a braided river network. Preliminary dating in Upper Creek indicates that basal deposits are as old as the Late Pleistocene. The cause these differences between terraces in the two drainages is somewhat uncertain. However, differences in the geological history of the drainages and the amount of sediment they received from upland (paraglacial) surfaces during the LGM may play a role.