EVOLUTION OF A DELTA, BROWNS COVE, LAKE WYLIE, NC

During the year 2007, the southeastern United States experienced a severe drought and as a result, the impoundments along the Catawba River, including Lake Wylie, reached record low levels. In Browns Cove, one of the coves of Lake Wylie, the delta at the outlet of Beaverdam Creek was subaerially exposed. This allowed the UNC Charlotte sedimentology class of fall 2007 to extract 5 cores ranging in length from 140 to 288 centimeters from the delta. The cores were extracted from the northern section of the delta using a Livingstone coring system. The cores were sedimentologically logged and five recurring sedimentary facies identified. The logs of the cores were stratigraphically correlated in order to interpret the depositional history of the delta. A key factor in the stratigraphic analysis is the variation in grain size within and between cores. We found that during the 80 year history of Browns Cove, the delta sequence records two transgressions and two regressions. The initial transgression was likely due to the rising water level of Lake Wylie in response to construction of the Lake Wylie dam in 1924. That transgressive sequence was followed by a regressive sequence which is interpreted as the product of progradation of the delta into Browns Cove. Aerial photographs indicate that the outlet of Beaverdam Creek was located on the northern flank of the delta from 1938-1956. Later aerial photographs from 1968-1983 indicate that the main outlet for Beaverdam Creek avulsed to the south side of the delta, away from the coring sites. This likely resulted in a drop in sediment supply accompanied by compaction on the northern section of the delta. This was likely the cause for the second transgressive sequence. Recent aerial photographs (2007) indicate the presence of a crevasse splay channel supplying sediment to the northern flank of the delta. This crevasse splay channel is likely responsible for the second regressive sequence. The relatively high sedimentation rate (~2.5 centimeters per year) for the Browns Cove delta is a product of high sediment supply due to rapid development in the Beaverdam Creek watershed.