GROUND PENETRATING RADAR INVESTIGATIONS OF PALEOSHORELINE FEATURES IN CURRITUCK COUNTY, NORTHEASTERN NORTH CAROLINA: DEFINING THE GEOLOGIC FRAMEWORK AND SEA LEVEL IMPLICATIONS

The shallow subsurface geology of the northeastern North Carolina coastal system is being mapped through a cooperative investigation involving East Carolina University, the U.S. Geological Survey, and the N.C. Geological Survey. Currituck County is the northern most county in northeastern North Carolina. The county is split into two geographic areas, the mainland and the northern Outer Banks. The mainland area is a peninsula that consists of two north-south oriented paleoshorelines ridges that merge at the town of Grandy. Ridges are approximately 5 meters in relief, and were deposited upon a relatively horizontal meter-thick peat layer that lies approximately 1 meter above present sea level and is exposed along eroding bluffs. Objectives of this investigation include; defining the regional stratigraphic framework and depositional environments comprising these paleoshoreline features; determining the age and sea level implications of the two paleoshorelines; and, determining historic rates of shoreline erosion and relation to the antecedent geology. Ground penetrating radar (GPR) data are being used to define the regional geologic framework and for targeting reflectors and facies for vibracoring. High amplitude reflectors correspond to at least two peat layers in the subsurface. Multiple sets of westward-prograding clinoforms, reactivation surfaces and/or paleosols are evident in GPR data, illustrating a complex depositional history for these paleoshorelines. Vibracores have been collected and lithofacies are being correlated to the GPR data. Age-dates of the peat layer and overlying deposits are pending, but we hypothesize that the deposits are late Pleistocene to early Holocene in age. GPR data and results of radiocarbon and optically stimulated luminescence analyses will be presented and will set the stage for determining sea level position, and the origin of these paleoshorelines.