Tracking the last sea-level cycle: seafloor morphology and shallow stratigraphy of the latest Quaternary New Jersey middle continental shelf
✍ Scribed by Catherine Schuur Duncan; John A. Goff; James A. Austin Jr.; Craig S. Fulthorpe
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 685 KB
- Volume
- 170
- Category
- Article
- ISSN
- 0025-3227
No coin nor oath required. For personal study only.
✦ Synopsis
Sea¯oor geomorphology and sur®cial 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 (t120 kyr B.P. to Present). A NW±SE-oriented corridor on the middle shelf between water depths of ,40 m (the mid-shelf ªpaleo-shoreº) and ,100 m (the Franklin ªpaleoshoreº) encompasses ,500 line-km of 2D Huntec boomer pro®les (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 stratigraphy. Core samples from published studies also provide some chronological and sedimentological constraints on the upper ,5 m of the stratigraphic succession.
The following stratigraphic units and surfaces occur (from bottom to top): (1) ªRº, a high-amplitude re¯ection that separates sediment . , 46.5 kyr old (by AMS 14 C dating) from overlying sediment wedges; (2) the outer shelf wedge, a marine unit up to ,50 m thick that onlaps ªRº; (3) ªChannelsº, a re¯ection sub-parallel to the sea¯oor that incises ªRº, and appears as a dendritic system of channels in map view; (4) ªChannelsº ®ll, the upper portion of which is sampled and known to represent deepeningupward marine sediments ,12.3 kyr in age; (5) the ªTº horizon, a seismically discontinuous surface that caps ªChannelsº ®ll; (6) oblique ridge deposits, coarse-grained shelly units comprised of km-scale, shallow shelf bedforms; and (7) ribbon-¯oored swales, bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into sur®cial 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 ,120 kyr. The morphology of the New Jersey middle shelf shows a discrete sequence of stratigraphic elements, and re¯ects the pulsed episodicity of the last sea-level cycle. ªRº is a complicated marine/ non-marine erosional surface formed during the last regression, while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum Wisconsin lowstand (i.e., marine oxygen isotope stage 3.1). ªChannelsº is a widespread ¯uvial subarial erosion surface formed at the late Wisconsin glacial maximum ,22 kyr B.P. The shoreline migrated back across the mid-shelf corridor non-uniformly during the period represented by ªChannelsº ®ll. Oblique ridges are relict features on the New Jersey middle shelf, while the ribbon-¯oored swales represent modern shelf erosion. There is no systematic relationship between modern sea¯oor morphology and the very shallowly buried stratigraphic succession.