A RIVER RAN THROUGH IT: THE GEOLOGIC FRAMEWORK OF THE CONTINENTAL SHELF BETWEEN OREGON INLET AND DUCK, NORTH CAROLINA, USA

Digital seismic profile data collected offshore of the northern Outer Banks, North Carolina were processed and interpreted to delineate principal reflecting horizons and develop a three-dimensional seismic stratigraphic framework for the insular continental shelf between Oregon Inlet and Duck, North Carolina. Interpretation and three-dimensional mapping of seismic data indicated six principal reflecting horizons (designated R₀ through R₅) bounding five seismic stratigraphic units (designated S₁ through S₅) within the upper 60 m of the shelf stratigraphic succession. Three-dimensional mapping of Reflector R₁ demonstrated its origin from fluvial incision of the continental shelf during sea-level lowstands. Fluvial processes responsible for development of Reflector R₁ included erosion, reworking, and re-deposition of sediment such that stratigraphic units S₂ and S₃ were truncated and removed throughout much of the northern half of the study area during development of Unit S₁. Remnants of S₂ and S₃ were found only in interfluvial divides. Vibracores obtained from stratigraphic units indicated both sand-prone and mud-prone deposits. Sand prone sediments were interpreted to represent sediment eroded, reworked, and re-deposited by fluvial processes during shelf emergence whereas mud-prone sediments accumulated as back-filling estuarine facies during transgression and inundation of incised fluvial channels. Knowledge of the three-dimensional subsurface stratigraphic architecture of the continental shelf enhances understanding of the development of continental shelf depositional successions offshore North Carolina. In addition, archiving these data in a geographic information system makes them compatible with other data from the continental shelf and enhances the ability of scientists, resource managers, and decision makers to analyze relationships among different data sets.