SEDIMENTARY ANALYSIS OF CONIACIAN-SANTONIAN SEDIMENTS OF THE KURE BEACH AND ELIZABETHTOWN CORES, SOUTHEASTERN NORTH CAROLINA COASTAL PLAIN, USA

Lithostratigraphy, Sr isotope stratigraphy and biostratigraphy are used to define stratigraphic sequences and to document sea level changes that occurred during the Coniacian to Santonian along the southeast Atlantic Coastal Plain. Two cores from the Coastal Plain of North Carolina were used for this study: Kure Beach (New Hanover County) and Elizabethtown (Bladen County). This study focuses on four geologic formations: Collins Creek, Pleasant Creek, Cape Fear and Shepherd Grove Formations. The Cape Fear formation is the nonmarine updip lateral and temporal equivalent of the downdip marine Pleasant Creek Formation. All of the contacts between these formations are unconformable. Grain size analysis, lithology, mineralogy, and paleontology of each formation was compared and contrasted between the two cores.

Grain size analysis utilized both sieved and sedigraph data, and showed clear bimodality within many of the samples. Percent calcium carbonate curves from the two cores have been correlated with gamma logs, and a clear correlation between changing lithology and carbonate content exists. Samples from the top of the Collins Creek of the Elizabethtown core, show a dominance of fluvial sediments, grading to a marine environment towards to the bottom of the formation. Marine components include trace amounts of glauconite, shell fragments, and calcareous nannofossils that are indicative of Zone CC14. The Pleasant Creek Formation in the Kure Beach core can be subdivided into at least two parasequences at 1,051 ft based on lithology. This formation is clearly marine to marginal marine, having glauconite, shell fragments and microfossils throughout. Calcareous nannofossils place this unit predominantly in Zone CC16. Comparison with the Elizabethtown core, which has only trace amounts of glauconite in the basal Cape Fear/Pleasant Creek, and is barren of marine fossils, suggests that sea level did not extend any further west during the Santonian. The Shepherd Grove Formation in the Kure Beach core has a lower sand content than in Elizabethtown, which shows increased organics. This unit is strongly marine downdip and marginally marine updip and can be placed in Zone CC17. Interpretation of the lithology, respective depositional environments, and depositional sequences are presented for the first time in this session.