High-resolution 3D seismic reflection and coring techniques applied to late Quaternary deposits on the New Jersey shelf

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Studies of variable, small-scale features typical of Quaternary glacimarine environments require an interdisciplinary approach: precisely navigated, high-resolution 3D seismic surveys nested within a regional 2D seismic framework and integrated with a precisely navigated coring program designed to sample specific shallow acoustic facies. We illustrate this approach with examples from continuing studies of sediments on the New Jersey continental shelf. Surficial stratigraphy associated with the latest Pleistocene-Holocene deglaciation has been imaged twice in true 3D using the Huntec® DTS system, a deep-towed, high-frequency (500–3500 Hz) boomer source. In both cases, nominal profile spacing was 10 m (2.5 m shot points). Penetration of ~40 ms (~30 m) was achieved. Seismic facies in the upper 5 m have been interpreted using differential GPS-navigated vibra-cores. Accuracy of position of both seismic profiles and core locations approaches 5 m, much smaller than the wavelengths of the geologic features being imaged/sampled. Survey results show multiple, sediment-filled channels buried beneath the modern outer shelf meandering south and southeast, in the general direction of the shelf edge. Channels are typically a few meters deep and 100–200 m across. Lateral continuity between the channeled surfaces within the outer-shelf wedge and the mid-shelf cannot be demonstrated because of later erosion, but both sets of channels incise reflector ‘R’, believed to be a pre-Late Wisconsinan exposure surface. AMS 14C dates on benthic foraminifers from cores show that channels on the midshelf are cut into sediment >45,000 yrs old, and filled with muddy sediment as young as ~12,500 yrs, whereas channels on the outer shelf are filled with coarser, and perhaps older, sediment. Both sets of filled channels are buried beneath a surficial sand layer. The integrated approach described here can remove some uncertainties and considerably ‘sharpen’ the Quaternary stratigraphic picture. Without the perspective obtained from 3D seismic surveys and equally precise sampling, interpretations based on broader regional seismic surveys and spot coring are inevitably constrained by the potential for mismatching shallow acoustic and sedimentary facies.