Tracking the last sea-level cycle: seafloor morphology and shallow stratigraphy of the latest Quaternary New Jersey middle continental shelf

Seafloor geomorphology and surficial stratigraphy of the New Jersey middle continental shelf provide a detailed record of sea-level change during the last advance and retreat of the Laurentide ice sheet (similar to 120 kyr B. P. to Present). A NW-SE-oriented corridor on the middle shelf between water depths of similar to 40 m (the mid-shelf "paleo-shore") and similar to 100 m (the Franklin "paleo-shore") encompasses similar to 500 line-km of 2D Hu ntec boomer profiles (500-3500 Hz), an embedded 4.6 km(2) 3D volume, and a 490 km(2) swath bathymetry map. We use these data to develop a relative str atigraphy. Core samples from published studies also provide some chronologi cal and sedimentological constraints on the upper <5 m of the stratigraphic succession. The following stratigraphic units and surfaces occur (from bottom to top): (1) "R", a high-amplitude reflection that separates sediment > similar to 4 6.5 kyr old (by AMS C-14 dating) from overlying sediment wedges; (2) the ou ter shelf wedge, a marine unit up to similar to 50 m thick that onlaps "R"; (3) "Channels", a reflection sub-parallel to Be seafloor that incises "R", and appears as a dendritic system of channels in map view; (4) "Channels" fill, the upper portion of which is sampled and known to represent deepenin g upward marine sediments similar to 12.3 kyr in age; (5) the "T" horizon, a seismically discontinuous surface that caps "Channels" fill; (6) oblique ridge deposits, coarse-grained shelly units comprised of km-scale, shallow shelf bedforms; and (7) ribbon-floored swales, bathymetric depressions para llel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits. We interpret this succession of features in light of a global eustatic sea- level curve and the consequent migration of the coastline across the middle shelf during the last similar to 120 kyr. The morphology of the New Jersey middle shelf shows a discrete sequence of stratigraphic elements, and refl ects the pulsed episodicity of the last sea-level cycle. "R" is a complicat ed marine/non-marine erosional surface formed during the last regression, w hile the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum Wisconsin lowstand (i.e., marine oxygen iso tope stage 3.1). "Channels" is a widespread fluvial subarial erosion surfac e formed at the late Wisconsin glacial maximum similar to 22 kyr B.P. The s horeline migrated back across the mid-shelf corridor non-uniformly during t he period represented by "Channels" fill. Oblique ridges are relict feature s on the New Jersey middle shelf, while the ribbon-floored swales represent modern shelf erosion. There is no systematic relationship between modern s eafloor morphology and the very shallowly buried stratigraphic succession. (C) 2000 Elsevier Science B.V. All rights reserved.