Abstract:
The Upper Cretaceous (Santonian-Campanian) sediments of the New Jersey coastal plain subsurface yielded rich planktonic foraminiferal assemblages at certain stratigraphic levels in three wells: Ocean Drilling Program (ODP) Leg 174AX at Bass River and Ancora sites and a United States Geological Survey borehole in Freehold. Relative sea-level fluctuations can be recognized by following the presence or absence and amounts of two groups of planktonic foraminifers, the shallow water and deep water faunas. The former consists of globular-chambered species, while the complicated tests showing keels, heavy ornamentation and elaborated umbilical structures are confined to the latter. The Merchantville (late Santonian) and Marshalltown (early late Campanian) formations, which represent transgressive system tracts, show the richest and most diverse planktonic foraminiferal assemblages. In the highstand system tracts, represented by the Woodbury (early Campanian), lower Englishtown (middle Campanian), Wenonah (late Campanian), and Mount Laurel (late Campanian) respectively, a gradual decrease in the planktonic foraminiferal diversity and richness was observed. Planktonic foraminiferal peaks of lower amplitude are recorded in the proximity of the minor flooding surfaces. A five-fold planktonic foraminiferal zonal framework for the Santonian-Campanian stratigraphic interval is proposed. Paleobathymetry strongly influenced the planktonic foraminiferal distribution and biostratigraphic resolution.