Abstract:
The New Jersey continental margin provides a natural laboratory to study passive margin stratigraphic architecture. Onshore drilling (ODP Legs 150X and 174AX) has investigated Cretaceous through Miocene sequence development. Offshore (outer shelf and slope) drilling (ODP Legs 150 and 174A) has targeted the complimentary Eocene through Pleistocene sequences in a basinal setting. Seismic profiles connecting the onshore and offshore drillsites reveal onlap, downlap, and offlap geometries that define depositional sequences of Oligocene through Pleistocene age. A seismic grid collected on cruise 0698 of the R/V Cape Hatteras shows 6 sequence boundaries that have been correlated to lower Miocene sequence boundaries defined by facies successions in boreholes at Island Beach, Atlantic City, and Cape May, NJ (Leg 150X). A borehole drilled at Ocean View, NJ in Sept-Oct 1999 (ODP Leg 174AX) offers additional data to substantiate the correlation of the seismic sequence boundaries; preliminary identification at Ocean View, augmented by a sonic log and associated synthetic seismogram, allows correlation with the CH0698 sequences that are defined by seismic geometries and can be traced on lower resolution seismic data to slope boreholes. Lower Miocene clinoform fronts associated with sequence boundaries m5, m5.2, m5.4 and m5.5/m5.6 all dip SE; by contrast, m6 (Miocene-Oligocene boundary) dips SSE and intersects the modern coastline near the Leg 150X Cape May borehole. The CH0698 data reveal the following characteristics of lower Miocene sequences. Onlap and downlap geometries define thin lowstand deposits resting on sequence boundaries at the toes of several clinoforms. Transgressive deposits are evident above the lowstand sediments seaward of several clinoform inflection points (CIPs), but they thin to below seismic resolution in a shoreward direction. The maximum flooding surface topping the transgressive unit is typically incised seaward of the CIP. Finally, highstand deposits, defined by prograding geometries of various degrees, are well imaged throughout much of the study area.