PALEOCENE-EOCENE PALYNOLOGY AND STRATIGRAPHIC CORRELATION ACROSS A NEARSHORE-TO-OFFSHORE TRANSITION IN THE SUBSURFACE OF CENTRAL DELAWARE (U.S. MID-ATLANTIC COASTAL PLAIN)

Lithologic observations and dinoflagellate cysts from three coreholes (Blackbird, Smyrna, and Woodland Beach) provide biostratigraphic and paleoceanographic information on Paleocene and Eocene deposits of the Delaware Coastal Plain. Three formations were identified at these sites: the Vincentown, Manasquan, and Shark River Formations. The Marlboro Clay, a unit associated with the Paleocene-Eocene Thermal Maximum (PETM), does not appear to exist between the Vincentown and Manasquan Formations despite its presence in cores from neighboring states. The Vincentown Formation is a Paleocene unit that, in places, includes the regionally important Rancocas/Aquia aquifer. Vincentown core lithologies change from clean permeable sands up-dip to silty sand and sandy silt downdip, supporting the hypothesis that the formation transitions from nearshore to offshore in the study area. No Marlboro Clay lithologies are present above the Vincentown strata and typical Apectodinium-dominated PETM dinocyst assemblages were not identified. The overlying Manasquan Formation is the lowest Eocene unit, characterized predominantly by silt and clay with a glauconite sand bed at the base. The Eocene Shark River Formation consists of interbedded clayey silts and sands with a basal muddy glauconite sand. Dinoflagellate biostratigraphy suggests that the Vincentown Formation is upper Paleocene, the Manasquan Formation lower Eocene, and the Shark River Formation is lower Eocene. Key taxa in determining age include Areoligera gippingensis, Cribroperidinium giuseppei, and Stenodinium meckelfeldense. These results are generally consistent with calcareous nannofossils and foraminifera found in some of the same cores, with the difference being the recognition of middle Eocene microfossils in the upper part of the Shark River Formation. Assemblages in the Vincentown Formation suggest a transition from a shallow coastal setting at the up-dip Blackbird site to a neritic or outer marine setting at the other two more downdip sites. The assemblages in the Manasquan Formation suggest neritic, open marine conditions, changing upward to a more coastal inner neritic setting in the Shark River Formation.