ROLE OF SEA-LEVEL FLUCTUATION, PALEOTOPOGRAPHY, AND SEDIMENT SUPPLY IN HOLOCENE EVOLUTION OF NORTHEASTERN NORTH CAROLINA BARRIER ISLAND--ESTUARINE SYSTEM

O.H. Pilkey is an important catalyst in coastal systems research. His constant challenges have led to our present understanding of the NC coastal system, which provides the basis for the ongoing USGS-ECU-NCGS NC coastal geology cooperative research program. Program goals are to delineate the geologic framework, develop the detailed evolutionary history, and define the process dynamics driving the rapidly changing, high-energy NE NC coastal system.

Albemarle Embayment is a Quaternary basin on the US Atlantic continental margin with an extensive Holocene record. Integrating sedimentologic, geophysical, and chronostratigraphic data have allowed us to decipher the erosional-depositional geometries of subtle coastal lithofacies characterizing non-steady state conditions of coastal fluctuations within the Holocene record. The general post-glacial, sea-level transgression was frequently interrupted by both millennial- to centennial-scale and decadal- to event-scale sea-level fluctuations driven by changes in climatic and oceanographic processes. Episodes of lowered sea level caused channel incision and erosional truncation of the estuarine and barrier island systems. Subsequent coastal flooding led to deposition within the newly created accommodation space and remobilization of the barrier islands. Interaction between underlying paleotopography, sediment supply, and sea-level fluctuations controlled: 1) formation of accretionary prisms including beach ridges and back-barrier dune fields on sediment-rich barriers, and 2) presence or absence of barriers along sediment-poor segments. In the latter situation the sediment-poor segments evolved from low-stand strandplain beaches perched on the antecedent shoreface, to migrating roll-over barriers with back-barrier estuaries (present situation), to collapsing barrier islands producing open marine embayments (short-term future--decades), and back-stepping barriers on the mainland (long-term future--centuries).