Texture: Surficial Sediment Distribution Interpretation of the Sidescan Sonar Mosaic of NOAA Survey H11045 off Bridgeport, CT.

Title:

Abstract:

The U.S. Geological Survey, in cooperation with the National Oceanic and Atmospheric Administration and the Connecticut Department of Environmental Protection, has produced detailed geologic maps of the sea floor in Long Island Sound, a major East Coast estuary surrounded by the most densely populated region of the United States. These studies have built upon cooperative research with the State of Connecticut that was initiated in 1982. The current phase of this research program is directed toward studies of sea-floor sediment distribution, processes that control sediment distribution, nearshore environmental concerns, and the relation of benthic community structures to the sea-floor geology.

Anthropogenic wastes, toxic chemicals, and changes in land-use patterns resulting from residential, commercial, and recreational development have stressed the environment of the Sound, causing degradation and potential loss of benthic habitats (Koppelman and others, 1976; Long Island Sound Study, 1994). Detailed maps of the sea floor are needed to help evaluate the extent of adverse impacts and to help manage resources wisely in the future. Therefore, in a continuing effort to better understand Long Island Sound, we have constructed and interpreted sidescan sonar mosaics (complete-coverage acoustic images of the sea floor) within specific areas of special interest (Poppe and Polloni, 1998; fig. 1). The mosaic presented herein covers a 190.3 km square area of the sea floor in west-central Long Island Sound off Bridgeport, Connecticut.

The mosaics and their interpretations serve many purposes, including: (1) defining the geological variability of the sea floor, which is one of the primary controls of benthic habitat diversity; (2) improving our understanding of the processes that control the distribution and transport of bottom sediments and the distribution of benthic habitats and associated infaunal community structures; and (3) providing a detailed framework for future research, monitoring, and management activities. The sidescan sonar mosaics also serve as base maps for subsequent sedimentological, geochemical, and biological observations, because precise information on environmental setting is important for selection of sampling sites and for accurate interpretation of point measurements.

Value	Definition
Gravelly sand	Sand containing greater than 10 percent gravel
Sand	Sediment mostly greater than 0.062 mm, but less than 2mm
Silty Sand or Clayey Sand	Sand with significant (greater than 20 percent) mud
Sand Silt Clay	Sediment with significant sand, silt and clay
Clayey Silt or Sandy Silt	Silt with significant clay or sand

Value

Definition

Gravelly sand

Sand containing greater than 10 percent gravel

Sand

Sediment mostly greater than 0.062 mm, but less than 2mm

Silty Sand or Clayey Sand

Sand with significant (greater than 20 percent) mud

Sand Silt Clay

Sediment with significant sand, silt and clay

Clayey Silt or Sandy Silt

Silt with significant clay or sand

Data format:	Six files (texture.shp, texture.shx, texture.dbf, texture.sbn, texture.sbx, texture.avl) in format ArcView (version 3.3) ESRI shapefile Size: 144 KB
Media you can order:	DVD-ROM (Density 650 Mbytes) (format ISO9660)

Data format:

Six files (texture.shp, texture.shx, texture.dbf, texture.sbn, texture.sbx, texture.avl) in format ArcView (version 3.3) ESRI shapefile Size: 144 KB

Media you can order:

DVD-ROM (Density 650 Mbytes) (format ISO9660)

Texture: Surficial Sediment Distribution Interpretation of the Sidescan Sonar Mosaic of NOAA Survey H11045 off Bridgeport, CT.

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