Abstract
The U.S. Geological Survey, the National Oceanic and Atmospheric Administration (NOAA), and the Connecticut Department
of Environmental Protection are mapping the sea floor in coastal areas of the northeastern United States. As part of the project, more
than 100 square kilometers of multibeam-echosounder data, 23 sediment samples, bottom video, and 86 still photographs were
obtained from an area in Long Island Sound north of Duck Pond Point, New York, in the study area of NOAA survey H11999. This
report delineates the sediment types and sea-floor features found within this area in order to better understand the sea-floor
processes occurring in this part of Long Island Sound. The sea floor in the study area is dominated by ubiquitous sand-wave
fields and three northeast-southwest trending bathymetric depressions. Barchanoid and transverse sand waves, including
sinusoidal, bifurcating, arced, and straight-crested morphologies, are variably present. Asymmetrical sand-wave profiles indicate
a westward to southwestward direction of sediment transport in most of the study area; current ripples and megaripples on the
stoss slopes of the sand waves indicate transport is ongoing. The majority of the sediment on the sea floor is sand, although
bouldery, gravelly, and muddy sediments are also present. Gray, cohesive mud crops out on the walls of some of the scour
depressions associated with the troughs of large sand waves. Clasts of the muddy sediment scattered on the sea floor around
the depressions demonstrate the intensity of the scour and suggest erosion of the underlying distal deltaic sediments.
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First posted February 22, 2012
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