LATE HOLOCENE EVOLUTION OF CURRITUCK SOUND, NORTH CAROLINA, USA: ENVIRONMENTAL CHANGE DRIVEN BY SEA-LEVEL RISE, STORMS AND BARRIER ISLAND MORPHOLOGY

Coastal evolution is an increasingly important area of study, especially with the projected rise in sea level, increase in storm intensity, and population increases along the nation’s coasts. In order to predict how the coastal environment will respond to these changes in the future, we need to first understand the evolution of coastal systems in the past. Here we address the late Holocene evolution of Currituck Sound, North Carolina, by examining time periods with different barrier island and inlet configurations interpreted from the core data.

Chirp and Boomer seismic data and 13 vibracores have been used to interpret the Holocene development of this region. The lowermost unit (Unit I) is represented by quartz sand, barren of foraminifera, considered to be the Pleistocene “basement”; supported by an OSL age estimate of 33.7 ka. Overlying the Pleistocene, Unit II consists of slightly muddy sand that fines upward to slightly sandy mud; it is barren of foraminifera, contains rooted horizons in several cores, and is interpreted as a fresh water swamp forest deposit (C-14 ages provide estimates of ca. 4000 to 2800 cal yr BP). Unit III is characterized by slightly sandy mud to mud containing a calcareous foraminiferal assemblage and substantial oyster bioherms; these characteristics indicate a back-barrier estuarine environment with high salinity (ca. 20 to 30) due to open inlets in the barrier islands to the east. Unit III contains C-14 age estimates ranging from ca. 1700 to 500 cal yr BP. The topmost unit (Unit IV) is composed of sediment with variable composition, ranging from clean quartz sand to mud, and contains foraminiferal assemblages that are generally mixed calcareous/agglutinated at the base overlain by entirely agglutinated assemblages. This unit represents the modern (post-1827), mid- to low salinity (less than 10), back-barrier lagoon with no inlets open in the barrier island. To further understand the recent evolution of this system a hydrodynamic model has been implemented which displays a positive correlation between the number of historical (known) inlets and tidal range, corroborating the interpretation of Units III and IV.