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We collected modern foraminiferal and environmental data from three back-barrier intertidal sites (Currituck Barrier Island, Oregon Inlet, and Pea Island) of the Outer Banks, North Carolina, United States, which have different salinity settings and a wind-driven tidal regime. The foraminiferal assemblages indicate that a vertical zonation of foraminifera occurs, with several significant site-specific variations of assemblages. The intertidal zone can be divided into two elements: first, an agglutinated assemblage that is restricted to the vegetated marsh and is dominated by Ammoboculites crossus, Ammobaculites subeotenulotus, Arenoporrello mexicana, Jadammine macrescens, Miliammina fusca, and Trochammina inflata and, second, a calcareous assemblage that dominates the mudflats and sandflats of the intertidal zone, characterized by Ammonia parkinsoniana, Elphidium excavatum, and Haynesina germanica. We used canonical correspondence analysis and partial canonical correspondence analyses of the foraminiferal and environmental data from the Outer Banks to support the hypothesis that the distribution of foraminifera in the intertidal zone is a direct function of elevation, with the duration and frequency of inundation as the most important factors. Partial canonical correspondence analyses and Monte Carlo permutation tests suggest that all available environmental variables except pH play a significant role in understanding the variations in foraminiferal data. [ABSTRACT FROM AUTHOR]

A comparison of two sections of the Outer Banks, North Carolina, USA (Pea Island and Avon-Buxton areas), reveals the importance of the interplay between oceanic and estuarine shoreline dynamics to long-term changes in barrier island width. From 1852 to 1998, the northern portion of Pea laland experienced an average net increase in width of 431 m (3 m/y); this area experienced low to moderate rates of oceanic shoreline erosion and high rates of back-barrier land accretion via overwash and formation of flood tidal delta islands. In contrast, between 1852 and 1998, the width of the southern portion of Pea Island and the Avon-Buxton area decreased an average of 515 m (4 m/y) and 594 m (4 m /y), respectively, because of high rates of oceanic shoreline erosion and variable changes in estuarine shoreline accretion and erosion. Net gain or net loss of barrier island width is strongly dependent on the natural depositional processes of overwash and flood tide delta formation. Anthropogenic modifications to the barrier island, such as construction of barrier dune ridges, planting of stabilizing vegetation, and urban development, can curtail or even eliminate the natural, self-sustaining processes of overwash and inlet dynamics. [ABSTRACT FROM AUTHOR]

Foraminiferal and sedimentary data, supplemented with geochemical dating and ground-penetrating radar transects, show that the barrier island at Pea Island National Wildlife Refuge just north of Rodanthe, North Carolina, has been dominated by a combination of inlet and overwash processes for at least 1000 years. The stratigraphic record of several vibracores does not preserve every, or even many, overwash events but, instead, is characterized by three to four fining-upward sequences. The last three commence with overwash sand or gravel that is overlain by a variety of finer-grained estuarine, inlet, and marsh deposits. The dynamic nature of this segment of the Outer Banks was muted in the late 1930s by construction of artificial barrier dune ridges, extensive planting of grass and shrubs, and construction of Highway 12 in 1953. Subsequently, the road and barrier dune ridge were rebuilt and relocated several times following storm events. [ABSTRACT FROM AUTHOR]