Southeastern Section–56th Annual Meeting (29–30 March 2007)

Paper No. 19
Presentation Time: 3:20 PM


THIELER, E. Robert, Coastal and Marine Geology Program, U.S. Geological Survey, Woods Hole Science Center, 384 Woods Hole Road, Woods Hole, MA 02543 and ASHTON, Andrew, Geology and Geophysics, Woods Hole Oceanographic Institution, MS 22, Woods Hole, MA 02543,

The origin and evolution of the Carolina Capes (Hatteras, Lookout, Fear, and Romain) have been discussed and debated for decades. The formation of these capes has been attributed to Gulf Stream eddies, location of rivers, antecedent geology, and self-organization due to high-wave-angle instabilities in alongshore sediment transport, among other mechanisms. It is generally agreed that at least these four capes have existed through much or all of the Holocene transgression. Geologic and morphologic data suggest that another cuspate foreland may have existed on the continental shelf between Cape Hatteras and Cape Lookout. A group of 5-8 lobate, en echelon bedforms, similar to the distal lobes of the modern cape-associated shoals, are present on the mid- and outer-shelf about 20 km offshore of Ocracoke Inlet in 25-33 m water depth. The bedforms are up to 5 m high, spaced several hundred meters apart, and the crests extend along the shelf for 12-20 km. The suggested cape would likely have formed during the early Holocene transgression of the shelf. It is possible that fluvio-deltaic sediments from the Tar/Pamlico/Neuse drainage may have set the stage for the initial development of this cape, similar to the mechanism proposed by Hoyt and Henry (1971). Available sea-level data suggest that this shelf sector was not flooded until after ~11,000 cal yr BP. Numerical modeling provides insight into the spatial and temporal scale of cape evolution in this setting, suggesting that the high-wave-angle instability in shoreline shape may be responsible for cape formation and evolution, including the subsequent capture of the suggested cape. Seismic, lithologic, and chronologic data from the continental shelf and modern barrier system, coupled with the model results, suggest the cape was probably captured in the mid-Holocene as the shoreline evolved into its present four-cape configuration.