Re-Examination of Sand Ridges on the Middle and Outer New Jersey Shelf Based on Combined Analysis of Multibeam Bathymetry and Backscatter, Seafloor Grab Samples and Chirp Seismic Data

  1. Michael Z. Li3,
  2. Christopher R. Sherwood4 and
  3. Philip R. Hill5
  1. John A. Goff1 and
  2. Laurie Schuur Duncan2

Published Online: 3 JAN 2013

DOI: 10.1002/9781118311172.ch6

Sediments, Morphology and Sedimentary Processes on Continental Shelves: Advances in Technologies, Research, and Applications

Sediments, Morphology and Sedimentary Processes on Continental Shelves: Advances in Technologies, Research, and Applications

How to Cite

Goff, J. A. and Duncan, L. S. (2012) Re-Examination of Sand Ridges on the Middle and Outer New Jersey Shelf Based on Combined Analysis of Multibeam Bathymetry and Backscatter, Seafloor Grab Samples and Chirp Seismic Data, in Sediments, Morphology and Sedimentary Processes on Continental Shelves: Advances in Technologies, Research, and Applications (eds M. Z. Li, C. R. Sherwood and P. R. Hill), John Wiley & Sons, Ltd, Chichester, West Sussex, UK. doi: 10.1002/9781118311172.ch6

Editor Information

  1. 3

    Geological Survey of Canada (Atlantic), Natural Resources Canada, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, B2Y 4A2 Canada

  2. 4

    U. S. Geological Survey, Woods Hole, MA 02543-1598 USA

  3. 5

    Natural Resources Canada, Sidney, BC, Canada V8L 4B2

Author Information

  1. 1

    Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, JJ Pickle Research Campus, Bldg. 196 (ROC), 10100 Burnet Rd. (R2200), Austin, TX 78758-4445, USA

  2. 2

    Jackson School of Geosciences, University of Texas at Austin, 1 University Station, C9000, Austin, TX 78712-0254

Publication History

  1. Published Online: 3 JAN 2013
  2. Published Print: 26 JAN 2012

ISBN Information

Print ISBN: 9781444350821

Online ISBN: 9781118311172

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Keywords:

  • sand ridges;
  • bedform evolution;
  • New Jersey shelf;
  • chirp;
  • grain size;
  • bathymetry;
  • backscatter

Summary

The New Jersey middle and outer continental shelf has been the focus of intensive geophysical and geological investigation over the last decade. Field programs during that time included two swath mapping cruises, three chirp seismic expeditions, two grab sampling efforts and coring. Following the initial swath mapping work in 1996, Goff et al. (1999) published an analysis of seabed morphology and backscatter in this region, with particular focus on sand ridges. These large, pervasive bedforms are ∼1-12 m high, spaced ∼1-5 km apart and ∼2-20 km long, and are oriented oblique to the shoreline. Formed initially in the shoreface, subsequent sea-level rise has brought them into deeper water environments, where they may continue to be modified or may become inactive in response to less vigorous bottom currents. The analysis of Goff et al. (1999) suggested that sand ridges in mid-shelf water depths (∼20-50 m) of their survey area are still being modified in a lee/stoss relationship (erosion on the stoss side, deposition on the lee side) to a modern-day, predominantly westerly bottom current. This orientation represents a switch of the stoss side from the shoreward flank during formative near shore conditions to the seaward flank in the present. This hypothesis made specific predictions about the seabed texture and internal structure of the sand ridges that can now be tested with more recently-collected grab sample and chirp seismic data. However, these predictions are not fully supported by the new observations. On the other hand, neither do the observations support the primary alternative hypothesis that the ridges are presently inactive, or “moribund”. Rather, these mid-shelf ridges appear to be modified by erosion on their seaward flanks without consequent deposition on the shoreward flanks. In outer shelf water depths (∼50-120 m), Goff et al. (1999) concluded that sand ridges are moribund, but modified at basins and flanks by recent and/or modern erosion. The newer textural and seismic data presented here support this conclusion.