PRELIMINARY STRATIGRAPHIC ANALYSIS OF QUATERNARY LITHOFACIES IN THE OUTER COASTAL PLAIN, NORTHEASTERN NORTH CAROLINA

The North Carolina Geological Survey (NCGS) recently collected a series of rotasonic cores along a NE-SW trending, 65-kilometer transect in a portion of the Albemarle Embayment of the outer Coastal Plain of northeastern North Carolina from Swanquarter to the Alligator River. The objective was to sample the entire Quaternary section at each location. These cores are a subset of 28 core holes drilled for a research program that is intended to provide a thorough basis for characterizing the Quaternary geologic framework of northeastern N.C. Based on interpretations of other cores analyzed in the project, as well as regional stratigraphic and geophysical data, the cores contain mainly Pleistocene sediments above a Tertiary “basement” that is considered to have been penetrated by each core. Preliminary sedimentological and stratigraphic analysis of these cores shows high lithologic variability. The Pleistocene section consists of mixed siliciclastic/bioclastic sediments. Bioclastic materials are absent in the upper portions (shallower than 10-15m) of the two northernmost cores (MLD-03 and MLD-06). The contact between bioclastic and siliciclastic sediments in these cores appears to represent a significant stratigraphic break, perhaps due in part to subaerial exposure. In contrast, the upper portions of the three southernmost cores, (MLD-05, MLD-01, and MLD-04) are characterized by abundant bioclastic materials present as stacked, graded shell gravels and shelly sands. The gravels and sands are underlain by sandy mud containing little bioclastic material. Tertiary sediments are likely represented by very fine grained, slightly sandy, blue-green mud at the base of the northernmost cores and by extensive, muddy shell gravels, often dominated by turritellid gastropods, in the southern cores. Integration with other project data such as amino acid racemization (AAR) and radiocarbon age estimates, as well as biostratigraphic and geophysical data, will facilitate interpretation of the regional stratigraphic framework.