A LITHOSTRATIGRAPHIC COMPARISON BETWEEN THE CAPE FEAR FORMATION AND AN UNNAMED NON-MARINE UNIT OF THE SOUTHEASTERN ATLANTIC COASTAL PLAIN

North Carolina Coastal Plain stratigraphic units often are difficult to distinguish due to several contributing factors: limited exposure, lithologic similarity between units, lack of mappable surfaces, and scarcity of fossils within non-marine units. Mineralogical and grain-size analyses of samples from the Elizabethtown, Smith Elementary School, and Kure Beach cores are being used to characterize different facies and provide clues to provenance of the Cape Fear Formation and a lithologically similar but slightly older, currently unnamed, non-marine unit. These two units often are separated by a marine unit, but there are locations in the subsurface of the Southeastern Coastal Plain where the Cape Fear formation is in direct contact with the unnamed non-marine unit. In such cases, it is difficult at present to distinguish between them without the aid of palynology. Eighty-three samples were collected and washed on a #230 screen in order to determine percent weight of sand versus silt/clay. X-ray diffraction was performed on the coarse fraction of twenty selected samples to identify mineralogy. These results are being compared with vacuum-impregnated thin-sections of hand samples so that quartz-feldspar-lithic diagrams can be made by point-counting thin-sections from whole-core and outcrop material. The fine fraction is being analyzed to determine clay mineralogy in three phases: untreated, ethylene glycol-treated, and heat treated. Heavy mineral suites are being analyzed to determine the depositional environment of each sample and to distinguish between these units in various core and outcrop locations. Natural gamma ray logs also will be used to correlate mineralogies of each section.