STRATIGRAPHY OF A CAMPANIAN FOSSIL ANGIOSPERM FLORAL ASSEMBLAGE FROM THE NEW JERSEY COASTAL PLAIN

An excavated outcrop located at the former Pine Hill sand pit in Monroe Township, NJ, is interpreted as an incised valley fill cut into the prograding, deltaic Campanian Englishtown Formation and may represent a rare Lowstand Systems Tract (LST) preserved within Upper Cretaceous New Jersey Coastal Plain deposits. The upper sequence boundary and the contact with the overlying Marshalltown Formation are correlated with the Haq global sea-level curve as UZA 4.4. This eustatic unconformity approximately dates from 74.5-75 Ma, using ⁸⁷Sr/⁸⁶Sr age analysis (Sugarman et al., 1995; Miller et al., 2004; Hanczaryk and Gallagher, in press). Twelve species of angiosperm plants have been identified from a 0.5 to 1 meter thick lens of fine to medium-grained, moderately well sorted micaceous sand representing the incised channel fill onto the truncated prograding delta Highstand Systems Tract (HST). The plant assemblage indicates a warm subtropical to nearly tropical climate for this time interval at this location (Gallagher et al., 1999). The Englishtown Formation measures here approximately 3-4 meters thick and is bracketed by the underlying massive, carbonaceous Woodbury Clay and the overlying marcasite concretion-bearing silty fissile shale of the basal Marshalltown Formation. The relationship between the underlying Woodbury Clay and the Englishtown is seen to be mostly conformable as evidenced at the adjacent Toto Brothers pit, located less than a quarter mile away, where beds typical of the Woodbury Clay were found intercalated with beds of typical Englishtown Formation fine-medium grained micaceous sand until finally grading into sand, only. The contact with the overlying Marshalltown is abrupt and interpreted as unconformable. Additionally, at the nearby Toto Brothers sand pit, casts of the ichnofossil Ophiomorpha were found to be plentiful, indicating a high-energy littoral or intertidal environment on a sandy coastline – an environment similar to present day New Jersey's shoreline.