Chirp seismic surveying of shallowly buried fluvial systems on the outer New Jersey continental shelf: Mapping channel morphology and internal stratigraphy in 3D

Abstract

The outer New Jersey continental shelf has been the focus of Office of Naval Research-sponsored acoustic studies for more than a decade. As part of this effort, ONR has funded a number of field programs to characterize the geologic history and sedimentary properties of the shallow seabed. We report here on a chirp seismic campaign conducted in 2001, with particular focus on characterizing the morphology and internal stratigraphy of shallowly buried fluvial channel systems that are widespread in this region. These channels were formed during the last glacial lowstand, and then filled and buried by sediments during sea level rise. Mapping the channel morphology in 3D presented a significant challenge. Although coverage (200-m line spacing) was dense, application of standard interpolation techniques resulted in poor representation of channel continuity along sinuous pathways. We developed a technique for transforming the seismic horizon data into a channel-oriented reference frame, wherein the channel is effectively straight and simple interpolation techniques can be used to maintain channel continuity. Seismic units within the channel fill could be discerned based on bounding reflectors and acoustic character and mapped throughout the 3D channel systems. These units provide a record of sea level change and drowned-river estuary development.