Twichell, D. C., U S Geological Survey, Woods Hole, USA, dtwichell@usgs.gov
Baldwin, W. E., U S Geological Survey, Woods Hole, USA, wbaldwin@usgs.gov
Flocks, J. G., U S Geological Survey, St. Petersburg, USA, jflocks@usgs.gov
Pendleton, E. A., U S Geological Survey, Woods Hole, USA, ependleton@usgs.gov
Miner, M. D., University of New Orleans, New Orleans, USA, mminer@uno.edu
Kulp, M. ., University of New Orleans, New Orleans, USA, mkulp@uno.edu

SUBSURFACE CONTROL ON SEA-FLOOR EROSIONAL PROCESSES OFFSHORE OF THE CHANDELEUR ISLANDS, LA

Semi-circular depressions that coincide with variations in the underlying shallow stratigraphy were found on the offshore side of the Chandeleur Islands. The depressions, which occur in discontinuous patches in a 40-km-long section between Curlew Island and the central part of the northern island chain, were found through use of sidescan sonar, swath bathymetry, and high-resolution seismic data collected in 2006 and 2007 after Hurricane Katrina. The depressions occur in 3-15 m water depths, and have 200-800 m diameters, steep edges, 0.5-1.5 m relief, and a high-backscatter signature on the sidescan. The surrounding sea floor exhibits a low-backscatter signature on the sidescan. Seismic profiles show that depressions are concentrated over and adjacent to an acoustically transparent facies interpreted to be sandy distributary channels, and are less frequent where muddy lagoonal deposits are exposed on the sea floor. This difference suggests that distributary channel deposits are more readily eroded than the surrounding lagoonal deposits. Two possible explanations for the formation of these features are scour caused by the interaction of waves and coastal currents or liquefaction due to loading by storm waves.

Oral presentation

Presentation is given by student: No
Session #:078
Date: 03-06-2008
Time: 16:30

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