| A transect of multi-frequency, high resolution acoustic images calibrated by surficial samples across the New Jersey shelf (20 to 150 m water depths) resolves the shallow stratigraphic record of the Wisconsinan cycle of glaciation and global eustatic sea level change. Simrad (95 kHz) swath bathymetry and sidescan images, overlapping chirp sonar (1–15 kHz), 2D/3D Huntec (1–3.5 kHz) single channel seismic and 3.5 kHz echosounder surveys, and sediment samples comprise the transect data. The following observed stratigraphic features have been interpreted in light of the well-constrained pattern of shoreline migration, ca. 120 ka to Present: (1) During early and mid-Wisconsinan regression, a gravel-rich outwash plain covered the exposed shelf, and a marine unconformity, “R”, formed on the sediment-starved middle and outer shelf. (2) About 35 ka, a muddy, marine outer shelf wedge was deposited above “R”. (3) During the last glacial maximum (LGM), ca. 22 ka, the fluvial style on the exposed shelf changed from a high-energy outwash plain to a lower-energy system of N-S oriented, dendritic channels. (4) Two observed suites of iceberg keel marks suggest that icebergs grounded on the outer shelf during, or soon after, the LGM. (5) A transgressive ravinement surface above “Channels”, which I have named “T”, marks the migration of the shore-zone across the shelf during the latest Pleistocene and Holocene transgression, ca. 22 ka to Present. (6) The mid-shelf wedge, a prograded sediment lobe above “T”, was deposited in shallow water ca. 11.5 to 8 ka, perhaps as a result of the collapse of glacial Lake Hackensack in northern New Jersey. The mid-shelf scarp, previously interpreted as a Holocene paleo-shore, is the depositional edge of the mid-shelf wedge. (7) Shelf currents have reworked the modern New Jersey seascape into a complex array of superimposed relict and active bedforms. Features older than the LGM have no seafloor expression on this shelf; there is poor correlation between shallowly buried stratigraphy and modern bathymetry. |
