PALEOGENE SEQUENCE STRATIGRAPHY AND RELATIONSHIP TO HYDROSTRATIGRAPHY, CRAVEN COUNTY, NORTH CAROLINA

Siliciclastic and carbonate sediments in two Craven County cores (Smith E.S. and Quinn) located 2 km apart provide a record of Upper Cretaceous, Paleogene and Neogene base-level lowering. Depositional sequences are defined from lithology, biostratigraphy and Sr dates, and are correlated to the lithostratigraphy, global coastal onlap cycles (GCOC) and the local hydrostratigraphic framework.

Sediments below the K/T boundary produce nannofossils indicative of Zone CC25a; ⁸⁷Sr/⁸⁶Sr from oysters produce dates between 68.9 and 69.2 Ma indicating correlation to the Maastrichtian Peedee I depositional sequence. Units above the K/T boundary include two Paleocene sequences (Beaufort Formation), two or three Eocene sequences (Castle Hayne Limestone), and two Pleistocene units (James City Formation and an unnamed surficial unit). Mollusk shells from interbedded sand and carbonate (Smith) and glauconitic sand (Quinn) of the oldest Paleocene sequence provide ⁸⁷Sr/⁸⁶Sr dates of 64.2 Ma and 62.5 Ma and 61.3 Ma, respectively. These dates suggest a Danian age and probable correlation to the updip Jericho Run Formation and the TA1.2 GCOC. Mollusk shells from cross-bedded coquina-like grainstones in the younger Paleocene sequence provide ⁸⁷Sr/⁸⁶Sr dates ranging between 56.8 and 60.3 Ma. These dates suggest correlation of the sequence to the updip Moseley Creek Formation and the Thanetian TA2.1 GCOC. The Eocene Castle Hayne Limestone consists of at least two depositional sequences that vary from fine calcarenite to slightly sandy sparite-cemented cross-bedded grainstones. A sharp, burrowed contact overlain by green glauconitic bioclastic sand separates the two sequences. A ⁸⁷Sr/⁸⁶Sr date from the older sequence in the Quinn core of either 41.5 Ma or 47.5 Ma indicates correlation to the TA3.3/3.4 GCOC. ⁸⁷Sr/⁸⁶Sr dates of 38.2 Ma and 38.3 Ma from the upper sequence indicate correlation to the TA4.1 GCOC. The lower Pleistocene James City Formation pinches out before reaching the Smith core.

Fine-grained Cretaceous sediments below the K/T boundary at the Quinn core form part of the Peedee confining unit; at Smith, coarser sediments are part of the Peedee aquifer. These are overlain by an unconfined aquifer that includes the Paleocene through Pleistocene section; Beaufort, Castle Hayne and younger confining units are absent.