Woods Hole Coastal and Marine Science Center

Back-Barrier Geologic Mapping

in cooperation with Stan Riggs (riggss@ecu.edu),

East Carolina University , Greenville, NC

A major component of the USGS-NC cooperative is to map the Quaternary section within the Albemarle - Pamlico estuarine system and associated barrier islands to develop the geologic framework and define the process dynamics. The Albemarle - Pamlico Embayment is a large Quaternary basin with a Holocene stratigraphic record. Previous investigations show a record of non-steady state conditions through the Holocene within the shallow, micro- to nanno-tidal estuarine system and the intimately coupled, wave-dominated barrier-island system.

These investigations established that the post-glacial transgression was frequently interrupted by millennial to centennial small-scale sea-level fluctuations driven by some combination of changes in climatic and oceanographic processes. These fluctuations resulted in multiple erosional and depositional events. Episodes of lowered sea-level caused channel incisement and erosional truncation within the estuarine system and regression of the barrier-island system. Subsequent coastal flooding led to deposition of estuarine sediments within the space and remobilization of the barrier islands. The interrelationship between the underlying paleodrainage framework and availability of sand on the shoreface and inner shelf determines the character of the resultant barrier island. Coastal segments form complex, wide, accretionary barriers dominated by progradational beach ridges and back-barrier dune fields. In comparison, sediment-starved (sand-poor) coastal segments develop simple, narrow overwash barriers. There is a complex relationship between sediment-rich barrier segments, related to trunk stream valleys or interfluvial headlands, and sediment-starved, overwash barrier segments, which are mostly related to tributary stream valley-fills along the flanks of drainage basins. The principal goal of this task is to define the Quaternary geologic framework and evolutionary development of the back-barrier system.

<font size="-1">Project area segments

Figure 1. Project area segments of back-barrier geologic
mapping program: Northeastern North Carolina.
Segment 1 to be completed in 2001;
Segment 2 - 2002; Segment 3 - 2003; Segment 4 - 2004.

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