Geophysical Investigations of Holocene Sea-Level Change and Barrier Island Formation at Bogue and Shackleford Banks , North Carolina

Posted May 28th, 2010 at 10:28 am.

Stephanie Nebel
Mentor: Dr. Don Barber

Bogue and Shackleford Banks are two barrier islands located on the central North Carolina coast, just southwest of Cape Lookout . Like most East Coast barrier islands, Bogue and Shackleford Banks formed as global sea level rose and inundated the continental shelf at the end of the last ice age. Sediment deposits associated with barrier islands provide a record of regional sea-level history over the last 10,000 years. Local geomorphology and shallow subsurface deposits also document changes in the island configurations on timescales ranging from decades to thousands of years. Documentation of the regional sea-level history contributes to the predictability of future sea-level change associated with global climate change. Furthermore, geomorphologic data on the evolution of barrier islands elucidate the dynamic nature of this type of coastline.

The current project involves collection and interpretation of geophysical data using several remote sensing methods. Seismic reflection profiling (SRP) and side-scan sonar (SSS) are marine remote-sensing techniques, both of which employ sound waves. SRP images sediment layers beneath the seafloor, while SSS maps the surficial characteristics of the seafloor. These techniques provide spatially continuous images of a survey area that can be used to describe both the sediment types and the geometry of sediment layers. When compiled, mapped and interpreted, these geophysical data help constrain the submergence history and changing island geometries over the last several thousand years. Ground-penetrating radar (GPR) is a remote-sensing technique analogous to SRP but employs radio waves instead of sound, and is used to image the shallow subsurface of the emerged (land) part of barrier islands and adjacent coastal deposits. Approximately 100 km of SRP and SSS tracklines were collected by boat along the shoreface and in the backbarrier of Bogue and Shackleford Banks in early May. These offshore data are being mapped, plotted and interpreted in the first part of the summer. In July, adjacent alongshore sites will be profiled using ground-penetrating radar. Together with the GPR data, the SRP data are being used to correlate previously published onshore borehole data and radiocarbon dates (e.g., Heron et al., 1984), and to identify targets for future coring and sampling. Thus far, the preliminary interpretation of the seismic profiles has allowed the identification of several buried former inlet channels. The existence and location of the former inlets indicate that Bogue and Shackleford Banks have had dramatically different configurations as recently as several hundred years ago.

Filed under: 2004,Barber, Dr. Don,Nebel, Stephanie by Ann Dixon

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