DATA COLLECTION AND PROCESSING METHODS FOR CHARACTERIZING THE STRATIGRAPHY OF PLIOCENE-PLEISTOCENE DEPOSITS OF THE NORTH CAROLINA COASTAL PLAIN, FALKLAND 7.5 MINUTE QUADRANGLE

The Atlantic Coastal Plain of eastern NC, mantled by mostly Pliocene and Pleistocene deposits, is difficult to map and stratigraphically characterize because the region is notorious for its low relief, few outcrops, recurring facies, and extensive wetlands cover, even on uplands. A non-traditional method, called three-dimensional (3D) subsurface mapping, is used to define and map surficial geologic units. This method combines geomorphic landscape analysis with targeted subsurface analysis that includes collecting cores along discrete profiles that transect landforms.

Sediment cores (1.75 in diam.) are collected with a Geoprobe Macro-Core MC5 Soil Sampling System. Cores are drilled continuously using the discrete sampling method to obtain undisturbed cores useful for identifying bounding surfaces, describing sedimentary facies, and interpreting the sequence stratigraphic framework. Drilling proceeds incrementally with four-foot runs in plastic tubes. In the field, these core tubes are cleaned, labeled, and cut open. The top of each core is then sliced off with piano wire, creating a flat surface that is washed using a jet of water. A simplified graphic log showing principal grain size and generalized structures is prepared in a cross section field book at 1 cm = 4 ft scale. Field photographs of core runs are taken with a Samsung S7 smartphone before wrapping for transport. Closeup screen shots of the core location in Google Earth using a cell phone are used to obtain approximate coordinates. Finally, research-grade GPS coordinates for core locations are collected using a Trimble GeoXT GPS receiver if the device is available.

In the lab, cores are prepared for high resolution archival photography. Cores are scraped and rewashed to enhance structures and bounding surfaces. Core runs are digitally photographed and post-processed using Adobe DNG Converter, Canon Photostitch, and Adobe Photoshop software to produce photomosaics of each core. The cores are then relogged in detail at 1 in = 1 ft scale using a standardized texture-based graphic logging method. Once complete, the logs are compiled and correlated along cross sections using ArcGIS and Adobe Illustrator software.