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Fact Sheet 2011–3026

Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazard Susceptibility Project

Seafloor Erosional Processes Offshore of the Chandeleur Islands, Louisiana

By David C. Twichell and John C. Brock

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The Chandeleur Islands are a chain of barrier islands that lies along the eastern side of the modern Mississippi River Delta plain. The island chain is located near the seaward edge of the relict St. Bernard Delta, the part of the Mississippi Delta that formed between approximately 4,000 and 2,000 years before present and was later abandoned as sedimentation shifted southward. After abandonment of the St. Bernard Delta, deposits were reworked, and the sandy component was shaped into the Chandeleur Islands. With continued subsidence, the islands became separated from their original delta headland sources and presently are isolated from the mainland by the shallow Chandeleur Sound.

Newly acquired geophysical data and vibracores provide an opportunity to better understand the processes that are shaping seafloor morphology (i.e., shape, geometry, and structure of the seafloor) on the inner shelf adjacent to the Chandeleur Islands. The inner shelf offshore of the Chandeleur Islands was mapped in 2006 and 2007 using swath bathymetry, sidescan sonar, and high-resolution seismic-reflection techniques. The detailed results of this study were published in December 2009 (Twichell and others, 2009) as part of a special issue of Geo-Marine Letters that documents early results from the Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazard Susceptibility Project. This study addresses questions and concerns related to limited sand resources along the Louisiana shelf and their implications to long-term relative sea-level rise and storm impacts.

First posted March 14, 2011

For additional information contact:
David C. Twichell
U.S. Geological Survey
Woods Hole Coastal and Marine Science Center
384 Woods Hole Road
Quissett Campus
Woods Hole, MA 02543-1598

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Suggested citation:

Twichell, D.C., and Brock, J.C., 2011, Seafloor erosional processes offshore of the Chandeleur Islands, Louisiana: U.S. Geological Survey Fact Sheet 2011–3026, 2 p.

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