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 GeopulseTM, UniboomTM,
MinisparkerTM, 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