HR: 1300h
AN: OS52C-04    [PDF]
TI: Correlation of Underlying, Relict Channels with Gravel Outcrops and Shore-oblique Sandbars in the Nearshore
AU: * Browder, A G
EM: grace@vims.edu
AF: College of William & Mary, VIMS, 1208 Greate Road, Gloucester Point, VA 23062 United States
AU: McNinch, J E
EM: mcninch@vims.edu
AF: College of William & Mary, VIMS, 1208 Greate Road, Gloucester Point, VA 23062 United States
AB: There is growing evidence that framework geology may influence surface sediment characteristics in the nearshore and possibly beach and sandbar morphodynamics. Recent investigations in the surf zone of southern Virginia and the Outer Banks of North Carolina reveal patches of gravel that appear to be part of an underlying substrate. This older substrate, possibly part of a ravinement surface, is characterized by non-sandy fine sediments and gravel. Shore-oblique sandbars are consistently found adjacent to these outcropping gravel patches, and both features have exhibited spatial stability during several years of observation. A research cruise was conducted to determine if there is a correlation between relict channels preserved in the framework geology, and the shore-oblique bars and gravel outcrops that have been observed in these regions. The presence of relict channels was investigated using Chirp seismic in areas where shore-oblique bars have been previously mapped, as well as a control area with no evidence of bars or outcrops. Side scan sonar was employed simultaneously to highlight the precise outcrop locations, while the presence of bars was gleaned from both the Chirp and side scan. Preliminary results indicate the presence of large relict channels at three of the sites, in the vicinity of previously identified bars and outcrops. The fourth site, a control with no bars or outcrops, shows some evidence of small, but poorly defined channels. Analysis is ongoing to spatially correlate the relict channels, transverse bars and gravel outcrops to areas of anomalously high beach erosion.
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 4546 Nearshore processes
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting