USING GIS, LIDAR AND CORE TO MAP COASTAL PLAIN TERRACES, PALEOSHORELINES, SURFICIAL STRATIGRAPHIC UNITS, AND SHALLOW AQUIFERS IN THE VICINITY OF THE CROATAN NATIONAL FOREST, NEUSE RIVER BASIN, NORTH CAROLINA

A preliminary map of Quaternary surficial stratigraphic units, based on interpretations of geomorphic features from LIDAR elevation data, and geologic cores is presented for a sector of the Croatan National Forest in the Neuse River Basin, North Carolina. The Croatan and adjacent Hofmann State Forests are located on the south side of the Neuse Estuary, near the boundary between the middle and lower Coastal Plain. This region includes a series of terraces, < 15 m above mean sea level (MSL), and intervening paleoshorelines with Pleistocene highstand elevations of about 9 m and 4.6 m above MSL.

North of the Neuse River, the Suffolk Scarp forms the Arapaho Ridge, a prominent paleobarrier island complex that may have formed at a highstand of about 9 m (local shoreface toe at 6 m). On the south side of the Neuse, the projected axis of the Arapaho Ridge into the Croatan Forest is marked by a sandy shoal complex that lacks a steep shoreface. A second, older paleobarrier, the Reelsboro Barrier (highstand elevation also 9 m), occurs on both sides of the Neuse estuary, landward of the projected Arapaho Ridge. Dubar and others (1974) provided a generalized map of the geomorphology of the Croatan area, and a cross section along the Neuse River's outcrops in which they defined the Yorktown (Pliocene), James City (early Pleistocene), and Flanner Beach (mid? Pleistocene) Formations, and the late Pleistocene “Cherry Point” unit.

Here we build on previous work by further defining the geomorphic map units using LIDAR (Light Detection and Ranging), a remote sensing technique that provides high-resolution elevation data with a vertical accuracy of +/- 25 cm per 1 m x 1 m tile. Cross section profiles were oriented either perpendicular to the axis of the Neuse River Basin or followed the basin boundary. In cores (<67 m deep, spacing < 3 km), we defined facies, surficial units, subcrops, aquifers and confining units. Surficial stratigraphic units, defined from both landscape position, or landform, and facies attributes, are then correlated with an established stratigraphic model for southeastern Virginia (see Mixon and others, 1989; Johnson and Berquist, 1989).