CONIACIAN - SANTONIAN SEQUENCE STRATIGRAPHY OF THE KURE BEACH AND ELIZABETHTOWN CORES, SOUTHEASTERN NORTH CAROLINA COASTAL PLAIN, USA

Sequence stratigraphy is a method used to divide the sedimentary record into discrete packages, typically bounded by unconformities or bedding planes between conformable but laterally persistent strata. Each package is interpreted to represent a cyclic change in sea-level and/or sediment supply. To define stratigraphic sequences and to document sea level changes that occurred during Coniacian and Santonian time in the southeast Atlantic Coastal Plain, two cores from the Coastal Plain of North Carolina are being analyzed for lithostratigraphy, and biostratigraphy. Four geologic formations are the main focus of this investigation: Collins Creek, Pleasant Creek, Cape Fear and Shepherd Grove. The Collins Creek Formation varies from sediments formed in restricted marine and shallow marine to middle neritic depositional environments. The Pleasant Creek Formation overlies the Collins Creek and represents a middle to outer neritic depositional environment as indicated by the presence of calcareous microfossils. The Cape Fear Formation formed in a fluvial depositional environment and is the nonmarine updip lateral equivalent of the marine Pleasant Creek Formation. The Shepherd Grove Formation overlies the Pleasant Creek/Cape Fear Formations and represents a shallow marine to middle neritic environment. Grain size analyses have been performed for 88 samples from the Kure Beach core and 46 samples from the Elizabethtown core using ½ phi intervals and sand-sized particles have been separated from silt/clay particles using a #230 sieve. Silt and clay ratios are being determined using a sedigraph. The percent of calcium carbonate correlates well with gamma ray geophysical logs, and both show good correlation with lithologic breaks throughout the Coniacian and Santonian in spite of differing environments of deposition from down-dip to up-dip. Planktic/benthic foraminiferal ratios will be used to determine paleo-water depth for selected intervals within these formations. Preliminary results for sand, silt and clay percentages, and interpretation of the lithology, respective depositional environments, and depositional sequences will be presented for the first time in this session.