Poppe, L. J., USGS, Woods Hole, USA, lpoppe@usgs.gov
Ackerman, S. D., Massachusetts CZM, Woods Hole, USA, sackerman@usgs.gov
Williams, S. J., USGS, Woods Hole, USA, jwilliams@usgs.gov
Moser, M. S., NOAA, Norfolk, USA, marc.s.moser@noaa.gov
Stewart, H. F., NOAA, Norfolk, USA, helen.stewart@noaa.gov
Glomb, K. A., NOAA, Norfolk, USA, kimberly.glomb@noaa.gov>


Multibeam and sidescan-sonar data cover 39.9 sq. km of Great Round Shoal Channel, the main passage through shoals at the eastern entrance to Nantucket Sound. These data and verification stations show seabed composition and terrain, provide information on transport and habitat, and are part of a framework for research and management activities along the Massachusetts inner-shelf. Processes of erosion and non-deposition prevail at the western channel entrance, off the southeastern tip of Great Round Shoal, and across the eastern study area. High-energy environments there prevent Holocene deposition and erode finer grained sediments, exposing glacial drift and leaving coarse lag deposits. These conditions are especially apparent off the tip of the shoal where large scour depressions have formed. Elsewhere, sand waves dominate in areas characterized by coarse bedload transport. Barchanoid sand waves, common near the channel axis where Holocene sediments are thinner, align into elongate fields with bedforms that progressively widen and increase in amplitude and complexity eastward. Transverse sand waves with slip faces generally oriented eastward dominate along channel edges where sediment supply is greater. Barchanoid sand wave orientation and transverse sand wave and obstacle mark asymmetry show net transport is predominantly eastward and out of Nantucket Sound. Dataset comparisons with existing charts show the shoal tip has propagated over 0.6 km southeastward since 1954.

Poster presentation

Presentation is given by student: No
Session #:054
Date: 03-06-2008
Time: 17:30 - 19:30

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