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References


derived from Schwab, W.C., Thieler, E.R., Denny, J.F., Danforth, W.W. 2000. Seafloor Sediment Distribution Off Southern Long Island, New York: U.S. Geological Survey Open-File Report 00-243
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FIGURES/MAPS

  Figure 1. Location figure showing the study area and location of late Pleistocene terminal moraines on Long Island, NY.

  Figure 2a. Sidescan-Sonar mosaic of the study area, overlain with 2 meter bathymetric contours (See Figure 1 for location). Light tones depict high backscatter, dark tones areas of low backscatter within the imagery.

  Figure 2b. Sidescan-Sonar mosaic of the study area, showing locations of figures used throughout the text. Light tones depict high backscatter areas, dark tones areas of low backscatter within the image.

  Figure 2c. Sidescan-Sonar mosaic showing location of sediment grab samples collected within the study area. Light tones depict areas of high backscatter, dark tones areas of low backscatter within the image. See Table 1 for sediment texture data.

  Figure 3. Sidescan-sonar image showing outcrop of Cretaceous Strata offshore of Watch Hill, Long Island. High backscatter is represented by light tones, low backscatter is represented by dark tones within the image. See Figure 2b for location.

  Figure 4. Sediment textural data from surface grab samples displayed on Figure 2c (see Table 1 for additional textural data). Samples are divided into three facies based on the sea-floor sediment distribution derived from seismic profiles (Foster and others, 1999). These facies are: a) Modern sediment (red crosses) - sediment reworked from early Holocene estuarine sediment, Pleistocene glaciofluvial sediment, and Cretaceous Coastal Plain Strata; b) Early Holocene/Pleistocene sediment (black crosses) - samples collected from areas where Pleistocene glacioflucial or early Holocene estuarine sediment outcrop; c) Cretaceous sediment lag (blue circles)- sediment reworked in the area of outcropping Cretaceous Coastal Plain Strata off Watch Hill, Long Island (see Figure 3). The sediments are further divided by textural characteristics into: a) coarse-grained lag deposits of Pleistocene sediment and Cretaceous strata; b) Fine-grained early Holocene estuarine sediment; and c) The most mobile sediment based on the textural characteristics of the modern sediment distribution.

  Figure 5. Sidescan-sonar image showing filled paleochannels exposed on the seafloor. These paleochannels are cut into the Pleistocene sedimentary deposit and filled with an early Holocene transgressional sequence. High backscatter is represented by light tones, low backscatter is represented by dark tones within the image. See Figure 2b for location.

  Table 1. Sediment grab samples collected off of the southern Long Island shore.

  Figure 6a. Simrad EM 1000 Echo Sounder backscatter image of the shoreface-attached sand ridges west of Watch Hill. Light tones depict areas of high backscatter, dark tones areas of low backscatter within the image. See Figure 2b for location.

  Figure 6b. Simrad EM 1000 Echo Sounder shaded relief image of the shoreface-attached sand ridges west of Watch Hill. Bathymetric profile from A to B is displayed in the insert. See Figure 2b for location.

  Figure 6c. Simrad EM 1000 Echo Sounder pseudo-color backscatter image of the shoreface-attached sand ridges west of Watch Hill. See Figure 2b for location.
 
  Figure 7. Sidescan-sonar mosaic of the high-backscatter lineaments east of Watch Hill formed by reworking of Pleistocene glaciofluvial and early Holocene estuarine sedimentary deposits exposed at the sea floor. Light tones depict areas of high backscatter, dark tones areas of low backscatter within the image. See Figure 2b for location.

  Figure 8a. Simrad EM 1000 Echo Sounder backscatter image of the sand waves offshore of eastern Long Island. Light tones depict areas of high backscatter, dark tones areas of low backscatter. See Figure 2b for location.

  Figure 8b. Simrad EM 1000 Echo Sounder shaded relief image of the sand waves offshore of eastern Long Island. Bathymetric profile from A to B is displayed in the insert. See Figure 2b for location.

  Figure 8c. Simrad EM 1000 Echo Sounder pseudo-color backscatter image of the sand waves offshore of eastern Long Island. See Figure 2b for location.

  Figure 9(a). Map showing the thickness, in meters of the modern sedimentary deposit based on interpretation of seismic reflection profiles (Foster and others, 1999). Cretaceous Coastal Plain Strata and associated lag deposits, Pleistocene glaciofluvial deposits, and early Holocene estuarine deposits are exposed on (or are close to) the sea floor in areas devoid of this modern sedimentary deposit. Arrows denote landward migration of the barrier island system east of Watch Hill, and west of Fire Island Inlet. The barrier island system between Watch Hill and Fire Island Inlet represents the oldest, most stable part of the system, and has experienced in place submergence over the past ~1000yrs.

  Figure 9(b). Interpretive geologic map of the surficial sediment off of the southern Long Island coast, showing coastal plain strata, Pleistocene glaciofluvial and early Holocene estuarine deposits, and modern sediments.

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