LATE QUATERNARY SEDIMENTATION OFF NEW-JERSEY - NEW RESULTS USING 3-D SEISMIC PROFILES AND CORES

Regional seismic reflection surveys have delineated a wedge of late Quaternary sediment extending 150 km south from the Hudson apron along the edge of the continental shelf off New Jersey. The bottom of the sediment wedge is defined by a prominent reflector (R), assumed to represent an erosional surface carved during a low-stand of sea level, probably corresponding to the Wisconsinan Maximum glaciation. A 3-D reflection survey of a 5 x 0.5 km area of the southern part of the wedge was carried out in October 1989. Line spacing was 10 m and shot spacing 2.5 m. Navigation achieved position accuracies to < 5 m. A series of cores both within and near the survey area yielded sedimentological and faunal data for ground-truth of the seismic results. The survey shows that the outer shelf sediment wedge has a complex internal structure unrelated to the present seafloor morphology. The sedimentary sequence appears to have been formed by a series of depositional events related to glacial melting and interrupted by at least one erosional episode, marked by a seismic surface that defines a system of meandering channels. Faunal studies of samples from cores indicate that the sediments were deposited at shallower depths than at present, but there is no evidence for deposition in shallower water or closer proximity to land than the modem mid-shelf. It appears that the history of periglacial marine sedimentation which accompanied the post-Wisconsinan deglaciation is no less complex than its continental counterpart.