FORAMINIFERA, PALEOENVIRONMENTS, AND SYSTEMS TRACTS DEVELOPMENT ON THE NJ CONTINENTAL SHELF: KEYS TO GLOBAL SEA LEVEL CHANGE

We evaluate late Miocene-Recent paleoenvironments, paleobathymetry, and depositional facies recovered at two sites drilled by ODP Leg 174A on the New Jersey continental shelf. Based on seismic stratigraphy, previous studies suggested that the N.J. margin sequences are primarily either highstand deposits or lowstand systems tracts. However, benthic foraminiferal biofacies and planktonic foraminiferal abundances proved to be key to deciphering systems tracts development. By integrating foraminiferal, lithologic, and downhole logging evidence within a seismically-defined sequence stratigraphic framework, we show that Pleistocene sequences cored by Leg 174A are characterized by transgressive and highstand deposits, whereas Miocene sequences consist of lowstand, transgressive, and highstand deposits, with repeated flooding surfaces indicating parasequences. We propose that the erosion responsible for the shelf sequence boundaries can be attributed to mean lowerings of base level in response to changes in the mean states of glaciation that marked: 1) the Miocene increase in ice volume and glacioeustatic lowering; 2) the transition to Northern Hemisphere-dominated glaciation; and 3) the transition to the large eustatic fluctuations of the middle-late Pleistocene.