Chirp seismic reflection data on the New Jersey middle and outer shelf: The geologic response to 40,000 years of sea level change

Abstract

Chirp seismic reflection data have been collected extensively on the New Jersey continental shelf in support of Office of Naval Research (ONR)-sponsored research. This composite data set includes surveys in 2001 and 2002 for the Geoclutter program, and in 2006 for the Shallow Water 06 program. Chirp uses a swept-frequency source (1–15 kHz), matched filtered to provide decimeter vertical accuracy and penetration up to 30 m in coarse-grained sediments. These data have been used to map out the complex shallow stratigraphy of this region, which includes: (1) a regional reflector formed about 40,000 years ago; (2) a layered shelf-edge wedge deposited during sea level fall; (3) fluvial channels formed at lowstand, and later filled with an estuarine sequence during sea level rise; (4) a ravinement surface created by shoreface erosion, which forms a lag of coarse material; and (5) the Holocene sand sheet, formed into sand ridges up to 10 m thick. Modern erosion has exposed many of the older units at or near the seafloor. Seabed sediments along acoustic propagation pathways are therefore highly heterogeneous. Vibracoring is planned for August, 2007. Analysis will include geoacoustic logging and geologic characterization. Preliminary results from these cores will also be presented.