HOLOCENE COASTAL CHANGE IN NORTHEASTERN NORTH CAROLINA

The North Carolina Coastal Geology Cooperative, led by East Carolina University, the US Geological Survey and the NC Geological Survey, has contributed extensive data and led to a new understanding of Holocene coastal evolution in northeastern North Carolina. Geophysical and geochronologic data have provided a spatial and temporal framework within which sedimentological, geomorphological and paleontological data have been interpreted. Foraminifera, in particular, have proven to be a valuable tool for reconstructing Holocene evolution of coastal paleoenvironments.

Rising sea level flooded Last Glacial Maximum (LGM) paleovalleys of the Roanoke, Tar and Neuse rivers, including Pamlico Creek (the precursor to Pamlico Sound) ca. 9,000 yrs BP leading to restricted estuarine conditions. The N-S trending Pamlico Creek drainage basin was separated from a similar basin to the east by a low LGM interstream divide. By ca. 7,000 yrs BP this divide had been flooded, an extensive chain of barrier islands (the early Outer Banks) had formed upon its eastern margin, and muddy estuarine sediments characterized a broadening Pamlico Sound. Long segments of the southern Outer Banks were reduced to subtidal shoals, presumably by hurricane strikes, ca. 4,000 yrs BP and, after being reformed, ca. 1,100 yrs BP, allowing waters derived from the Gulf Stream to advect into the southern part of Pamlico Sound for several centuries on each occasion. The ca. 1,100 yrs BP segmentation of the southern Outer Banks occurred during the Medieval Warm Period, an interval of increased rate of relative sea-level rise and possible increased tropical storms. The barrier islands reformed during the succeeding Little Ice Age (LIA), although the northern Outer Banks were characterized by greater inlet activity relative to present, probably related to increased extra-tropical storm activity during the LIA, until the early 19^th century.

This Holocene record of coastal change, coupled with the prediction of acceleration in 21st century sea-level rise and an increase in tropical storm intensity, suggests that North Carolina’s northeastern coastal system is likely to experience similar dramatic environmental and geomorphic change in the near future.