Late Pleistocene Sequence Stratigraphy of the New Jersey Continental Shelf

John S. Carey, Robert E. Sheridan, Gail M. Ashley

High-resolution reflection profiles over a 25000 km² area off New Jersey illustrate the effects of high amplitude, high frequency eustasy on a slowly subsiding passive margin. Vibracores and USGS AMCOR project drill holes and geophysical well logs provide age and lithologic control for the sequences identified from 1600 km of Geopulse^TM, Uniboom^TM, Minisparker^TM, and air gun profiles. Analysis of the data reveal four depositional sequences controlled by late Quaternary (past 140 ka) sea-level fluctuations of up to 120m that are tentatively correlated with the ^dgr¹⁸O stages. The base of Sequence I is a major unconformity associated with a gravel layer at -80 m in AMCOR 6020, lying at -230 m at the shelf edge and overl in by the Emiliania huxleyi zone indicating a post-Stage 8 age; the unconformity was likely cut during Stage 6 (~140 ka). The highstand tract (HST) of this sequence reaches +5-10m in the Cape May Formation (Stage 5e, ~125 ka). The elevation of lowstand wedge (LSW) sediments in Sequence II indicates a drop in sea level to ~-75 m, possibly during Stage 4 (~75 ka). The overlying HST deposits include a barrier island shoreline indicating sea level at ~-20m. An Astarte shell from this unit produced amino acid ratios consistent with an early Stage 3 age (~ 55 ka). The Sequence III LSW implies a drop in sea level to about -60 m, during which time a paleo-Hudson River cut southward across the shelf. The associated baymouth shoal complex suggests a maximum late Stage 3 (~ 35 ka) transgression to an elevaton of -35 m. Sequence IV is bounded by the Stage 2 (~ 18 ka) lowstand unconformity cut to a deph of ~120m and includes the latest Pleistocene-Holocene transgressive sediments. The elevation of the Stage 2 lowstand deepens northwards because of glacio-isostatic adjustment. High amplitude fluctuations (~120m) such as Sequence I and Sequence IV are more laterally continuous; the record of lower amplitude fluctuations (20-60m) is preserved only on the mid-shelf. Fragmentary preservation of high-order sequences can complicate sequence stratigraphic interpretation.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995