THE CRETACEOUS-TERTIARY TRANSITION: A UNIQUE PALEOENVIRONMENTAL PERSPECTIVE ON THE NEW JERSEY COASTAL PLAIN

Buck’s Pit, located near Perrinville, Monmouth County, NJ, is an age equivalent up dip site of upper Maastrichtian and Danian shallow marine strata deposited in shoreface to inner shelf environments. The pit exposes the Red Bank, Tinton and Hornerstown Formations representing a transgressive systems tract (quartz sand (Red Bank) to muddy sand (Tinton) to glauconitic sand (Hornerstown)). Our observations differ markedly from down dip sites in Monmouth County and indicate an overall shallower marine depositional environment. Unlike the glauconitic rich Tinton Formation in other areas such as the Manasquan River Basin (Landman et al. 2007), the Tinton Formation has very little glauconite at Bucks Pit. There is a concentration of fossils within the top 40 cm of the Tinton Formation that continues into the base of the Hornerstown Formation similar to that of the Pinna Layer described by Landman et al. at the Manasquan, although differing quite dramatically in faunal constituents. Unlike the Pinna Layer, some of the most common constituents of the uppermost Tinton Formation at Bucks Pit consist of Cyprimeria sp. and Trigonia eufalensis. Various species of Crassatella sp. and Cucullaea sp. are also common. Overall, shallow subtidal bivalves make up the majority of the fauna, most of which are infaunal filter feeders suggesting sedimentation was episodic at best. Gastropods make up the rest of the specimens. Cephalopods such as Discoscaphites iris and Eubaculites latecarinatus and E. carinatus, common at the Manasquan Basin, are glaringly absent at Bucks Pit. All collected fossils are molds and casts, many without visible ornamentation and have undergone clay replacement, often preserving an organic wrinkled shell and being heavily distorted. This preservation is unique to Bucks Pit in the New Jersey Coastal Plain and differs markedly from either the Pinna Layer or MFL (Main Fossiliferous Layer) common at other New Jersey K/T boundary sites. The shallower depths indicated by the sedimentology, the lack of ammonites, and the restricted yet abundant fauna may be indicative of a local bay type setting.