1. Surficial sediment isopleth maps of sand, silt, and clay, offshore the Isle Dernieres barrier islands, Louisiana Yale Public content 1989. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; For sale by Map Distribution. English. Public. Louisiana, Ship Shoal, and Isles Dernieres Region.