BIOSTRATIGRAPHY AND PALEOECOLOGY OF THE VINCENTOWN, MANASQUAN, AND SHARK RIVER FORMATIONS OF NORTHERN KENT COUNTY, DELAWARE

The Vincentown, Manasquan, and Shark River Formations are three marine units deposited during the Paleocene and Eocene in the Middle Atlantic Coastal Plain. This study analyzes the lithostratigraphy, planktonic foraminiferal biostratigraphy, and benthic foraminiferal evidence for paleoenvironmental interpretation from three core holes in Kent County, Delaware at Woodland Beach (Hd25-07) and Smyrna (Hc35-25, Hc34-51). Previous studies of the Paleocene-Eocene section in Maryland-Delaware-New Jersey have found a regional trend in lithofacies characterized by an upper Paleocene section composed of siliciclastic and carbonate sands updip and finer clastics downdip overlain by a lower-middle Eocene section with a more consistent fine-grained character.

The Rancocas aquifer, within the upper Paleocene Vincentown Formation, is an important groundwater resource in Delaware. This interval is also important in New Jersey (the Vincentown Formation and aquifer) and in Maryland (the Aquia Formation and aquifer). The Vincentown Formation changes in lithology and thickness in these cores from northwest to southeast, transitioning from a thick interval of clean, permeable Rancocas aquifer sands into a thinner zone of less permeable, sandy muds and muddy sands. However, this facies change has not been well constrained by previous studies. The Vincentown is overlain in these cores by finer-grained Eocene units, the Manasquan Formation and the Shark River Formation. The Marlboro Clay, which was deposited during the Paleocene-Eocene boundary, is not present at these sites, suggesting an unconformity.

Planktonic foraminifera from these coreholes permit evaluation of preliminary biostratigraphic correlations to published sites in New Jersey and Maryland. Benthic foraminifera from the Vincentown Formation allow for evaluation of the preliminary lithofacies interpretation of a southeastward deepening of depositional environments on the continental shelf. Changes in benthic foraminifera between the Vincentown Formation and the finer-grained Eocene units allow for a comparison to the preliminary lithofacies interpretation of deepening in the Eocene. The results of this project are expected to help better understand the regional Paleocene aquifer system and the overlying Eocene units.