GEOLOGY FOR A CHANGING COAST: THE NORTH CAROLINA COOPERATIVE

A cooperative project to map the regional coastal sedimentary system of northern North Carolina was begun in 1999 by the USGS, North Carolina Geological Survey, East Carolina University, and other academic collaborators. The overall objectives of this project are: 1) use sea-floor and coastal mapping techniques to provide a regional synthesis of the geologic framework of the estuaries, barrier islands, and inner shelf; 2) to develop a series of isopach maps of sediment deposits and surface distribution patterns to assess potential offshore aggregate resources by; 3) use shoreline change data, topographic mapping surveys, and core hole data to compare conceptual models of inner-shelf sediment transport with barrier island behavior; 4) identify sediment transport patterns and investigate the role oceanographic processes and antecedent geology play in controlling coastal evolution and modern behavior of the barrier-island system; 5) make these mapping products, data, and interpretations available to collaborators and stakeholders such as the National Park Service, Fish and Wildlife Service, the Army Corps of Engineers, and State agencies; and 6) identify and conduct studies to further understand the processes controlling sediment flux within the coastal system.

The primary study area includes the coastal and estuarine system from the Virginia state line to Cape Lookout, extending ~250 km alongshore and ~10 km offshore. The mapping products serve as baseline geologic framework information; these efforts will inform future physical oceanographic and/or sediment transport processes investigations that will be part of a second phase of the cooperative program. Initial results suggest that the underlying geologic framework of Quaternary sediments determines the availability and distribution of sediment in this coastal system and controls the geomorphology of the overall barrier island system. For example, sediment-rich coastal segments have wide, accretionary barriers dominated by beach ridges, while sediment-starved coastal segments have narrow, washover-dominated barriers. Sediment-rich barriers are related to underlying trunk stream valley-fills or interfluvial headlands; sediment-starved barriers are related primarily to tributary stream valley-fills along the flanks of paleo-drainage basins.