IMPLICATIONS OF STORM EVENTS AND ANTHROPOGENIC ENVIRONMENTAL MODIFICATION ON THE STRATIGRAPHIC RECORD OF THE NORTH CAROLINA OUTER BANKS, U.S.A

Over the past 70 years, North Carolina's Outer Banks have been greatly modified by human activity. A multidisciplinary study involving foraminiferal, sedimentological, geochemical, geophysical and aerial photographic methodologies on the U.S. Fish and Wildlife Service's Pea Island National Wildlife Refuge has been initiated to investigate the stratigraphic record resulting from the interplay of natural (ocean and estuarine washover events) and anthropogenic processes (fore dune ridge construction, road building and the modification and management of wildlife ponds). Only by characterizing these interrelationships can the record of storm activity be recognized and understood here.

Prior to the late 1930's Pea Island was a barren-sand, washover barrier island, until the fore dune was constructed allowing marsh vegetation to grow. This promoted the deposition of a thin peaty soil containing Trochammina spp. adjacent to ephemeral lakes with extensive algal flats, bounded by a road on the east and by estuarine storm beach ridges on the western edge of the barrier island. Based on several vibracores taken along three transects these thin modern deposits overlie a 40 cm thick sand and gravel layer containing broken marine bivalves which in turn rests in sharp contact on 30 cm of peaty clay (older than 120 years based on Pb-210 dating) containing Trochammina spp. and Miliammina fusca. The clay grades down into well sorted fine sand to 6m depth.

Results show that Holocene transgression resulted in an overwash-dominated barrier island, however this process was stopped about 65 years ago when the barrier dune ridge was constructed. Only in localized erosional hot-spots have washover fans penetrated the barrier dune ridge since that time. In contrast to other studies along the U.S. east coast, marine washover sand has so far proven to be barren of open marine benthic foraminifera, perhaps through mechanical destruction of tests along this extremely high energy tract of coastline. Estuarine washover sand is also barren of foraminifera. Storm-generated washover events from the back-barrier estuarine system appear to be as important in constructing the sedimentological record as washover events from the Atlantic Ocean. The human imprint on the natural record of barrier island processes is great and increasingly so.