LATE HOLOCENE GEOLOGIC AND MORPHODYNAMIC RESPONSE TO SEA-LEVEL RISE IN A BACK BARRIER LAGOON: PRELIMINARY FINDINGS

Coastal evolution is an increasingly important area of study, especially with the projected rise in sea level, increase in storm intensity, and population increases along the nation’s coasts. In order to predict how the coastal environment will respond to these changes detailed studies of the Holocene evolution of coastal systems are extremely important. This study uses geophysics, sedimentology, and foraminiferal data collected from vibracores, as well as hydrodynamic modeling using Delft3D software, to characterize the Holocene evolution of a shallow lagoonal system, Currituck Sound, North Carolina.

Vibracore locations were chosen based on interpretations of chirp and boomer seismic data. Areas that were interpreted as paleo-fluvial channels, tidal channels, beach ridges, and ravinement surfaces were targeted for coring. Thirteen vibracores display a variety of lithofacies from clean quartz sands to highly organic muds. Most cores display a quartz sand unit at the bottom of the core and a slightly sandy mud at the top of the core demonstrating a decrease in energy over time, most likely a result of inlet closures. Rooted horizons in a slightly muddy, very fine sand AMS C-14 dated to ca. 3680-3620 cal yr BP and 2810-2500 cal yr BP are present in two cores indicating periods of subaerial exposure followed by rapid ravinement and then deposition of an estuarine facies consisting of slightly sandy muds and oyster bioherms at ca. 1260-1200 cal yr BP. Foraminiferal data will help refine paleoenvironmental interpretations.

Geological data are being compared to Delft3D hydrodynamic models of the system, which incorporate varying degrees of inlet activity, to enhance our understanding of changes in tidal amplitudes, current magnitudes, and flow patterns in Currituck Sound during the late Holocene.