Trapping and Escape of Fine-Grained Sediments: Neuse River Estuary, N.C.by John T. Wells, Univ of North Carolina at Chapel, Hill, Morehead City, United States,
Seok-Yun Kim, Univ of North Carolina at Chapel, Hill, Morehead City, United States,
Abstract: The Neuse River estuary and its receiving basin, Pamlico Sound, are part of a system that comprises large, shallow bodies of water which have little or no free connection with the open sea; a complicated shoreline geometry with different freshwater sources and orientations relative to prevailing winds; and, a low tide range with circulation that is dominated by wind-driven currents. The two accumulation sites for silt-and clay-sized sediments are the fresh-to-brackish estuarine waters associated with riverine sources, and the deep central basin of Pamlico Sound. These two environments, which are lithologically very similar, are separated by a region of fine sand and are controlled by two quite different processes of sedimentation. This paper provides from field measurements an overview of physical processes and sedimentation in the Neuse Estuary-Pamlico Sound system. Results show that sediments are initially trapped in the upper estuary, but eventually move through the system to the open waters of Pamlico Sound. Highest long-term accumulation rates of 1-6 mm/yr are in the lower estuary and may be topographically controlled. Sediments that escape the Neuse River probably undergo many cycles of deposition and resuspension before being incorporated into the sedimentary record of the deep basin, which includes at least 6 m of structureless Holocene mud. Low current speeds and confinement by the Outer Banks barrier islands prevent transport of mud to the shelf, but insufficient input from tributary sources will prevent the basin from ever achieving a sediment-filled state.
Subject Headings: Sediment | Estuaries | Rivers and streams | Basins | Water resources | Ocean currents | Water circulation | Wind engineering | North Carolina
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