CHRONOSTRATIGRAPHY AND GEOLOGIC FRAMEWORK OF THE CURRITUCK SAND RIDGES, CURRITUCK COUNTY, NC

The shallow subsurface geology of the northeastern North Carolina coastal system is being mapped through a cooperative study involving East Carolina University, U.S. Geological Survey, N.C. Geological Survey, and University of Delaware. Currituck County is the northeastern most county in North Carolina. The mainland portion of Currituck County is a peninsula that contains two north-south oriented sand ridges; the Land of Promise Ridge (LoP) and the Knotts Island Ridge (KI). These ridges extend for ~55 km, are ~2.5 km in width, and have a maximum relief of ~6 m. Lidar imagery and ground penetrating radar (GPR) suggest that the KI truncates the LoP around the Grandy Township. GPR data defined the regional geologic framework and provided target reflectors and facies for subsequent vibracoring. Twenty vibracores and bore logs have been collected for correlation of lithofacies to the GPR data. In the northern part of the study area, high amplitude GPR reflectors correspond to at least two peat layers in the subsurface that mark the depositional base of these ridges. Peat layers have been recovered in cores and are exposed in eroding bluffs. Overlying the peat layers, multiple sets of westward-prograding clinoforms, reactivation surfaces and/or paleosols are evident in GPR data, cores, and local borrow pits, indicating a significant eolian component to at least the upper 2 to 4 meters of the ridges. In the southern portion of the study area, the eolian component overlies a 2 to 3 meter thick medium- to course-grained crossbedded unit, exhibiting wave ripples, laminated heavy mineral sands, small-scale clinoforms, trough cross-bedding, extensive gently dipping planar beds, and burrow structures, suggestive of shallow marine sedimentation. Ongoing pollen analysis will help determine the paleoclimates. Thirteen optically stimulated luminescence dates located throughout southern Currituck County indicate ages corresponding to Marine Isotope Stage 3 or younger for the above-mentioned units. Radiocarbon ages of the peat are inconclusive.