SEDIMENTOLOGICAL AND PALEONTOLOGICAL CHANGES ACROSS A LATE CRETACEOUS REGRESSIVE/TRANSGRESSIVE BOUNDARY, ATLANTIC COASTAL PLAIN OF NEW JERSEY

Three detailed stratigraphic sections in the late Cretaceous Winonah/Mt. Laurel and Navesink Formations in Marlboro New Jersey reveal five distinct facies based on lithologic and paleontologic characteristics. Facies 1 and 2, at the base of the section, represent a regressive phase of inner shelf to shoreface sedimentation characterized by a coarsening upward cycle of very fine to moderately coarse micaceous and carbonaceous quartz sands. Facies 3 is characterized by a fining upward sequence of muddy fine to very fine quartz sand with minor amounts of mica and carbonaceous matter and represents shoreline retreat and an initial phase of transgression that is not preserved outside the Raritan Embayment. We interpret this facies as a transitional deposit from inner to mid shelf environment. We attribute its preservation to its proximity to a deltaic front prograding from the north which provided sufficient sediment input to overcome the effects of intial sea level rise associated with the transgression. Facies 4 is a lag horizon characterized by glauconitic quartz sand with a basal pebble and concretion zone. This lag is significantly more glauconitic than the lower facies, and represents a sharp decline in sedimentation rates related to a more offshore depositional environment. Facies 5, the uppermost facies, is characterized by moderately coarse sand composed almost entirely of glauconite, and represents an offshore deep water depositional environment with very slow depositional rates. Facies 1, 2, and 3 contain a shallow water fauna dominated by small bivalves. Facies 5 is dominated by large, deeper water bivalves and belemnites. Facies 4 appears to contain a mix of these two faunas as well as abundant crab claws. These observations suggest that lithologically and paleontologically, the boundary between the Wenonah/ Mt. Laurel and Navesink Formations in northern New Jersey is best considered as the lag horizon of Facies 4.