Click on figures for larger images

Figure 3. Seismic-reflection profile from line 38 of U.S. Geological Survey cruise 82-3 aboard the Woods Hole Oceanographic Institute research vessel Asterias, with interpretation.

Figure 23. Map showing location of sediment samples collected during U.S. Geological Survey cruises 2010-010, aboard research vessel (RV) Rafael, and 2010-015, aboard U.S. Environmental Protection Agency ocean survey vessel (OSV) Bold, north of Duck Pond Point, New York.

Figure 24. Photograph showing the sea floor at station 999-13 with rippled sand.

Figure 25. Photograph of the sea floor at station 999-6 showing mud clasts scattered on the sea floor.

Figure 26. Photograph of the sea floor at station 999-6 showing an outcrop of gray cohesive mud on the wall of a scour depression.

Sediment Distribution

The majority of the study area has a rippled, sandy sea floor (figs. 23 and 24), with the exception of stations 999-6 and 999-10, which are floored with sand-silt-clay and gravelly sediment, respectively. Most sand in the study area is well sorted and 2 to 3 phi in size. The sediment sample from station 999-6 was made up of gray cohesive mud clasts derived from outcrops of this lithology and coated in sand from the surrounding sea floor (figs. 25 and 26). Despite efforts to remove the sand coating and only analyze the uncontaminated inner section of the clast, some sand remained, which led to the coarser classification of sand-silt-clay. However, a more appropriate classification for these clasts is clayey silt. A seismic-reflection profile collected on the USGS cruise 82-3 aboard the Woods Hole Oceanographic Institute RV Asterias crosses through a nearby scour depression, which reaches into post-glacial marine sediments, likely distal-deltaic deposits (fig. 3; Poppe and others, 2002; Lewis and Needell, 1987). We contend that these clasts are eroded distal deltaic sediments, which have been mapped in the area by Lewis and DiGiacomo-Cohen (2000).

Sediment Data

The sediment grain-size dataset provided here contains information on the collection, description, and texture of sediments at the 23 stations in the study area. The basic structure of the dataset is a flat-file format, a matrix where rows represent individual samples and columns contain sample- and station-specific information. This matrix consists of 42 fields which are defined in the Data Dictionary section below.

In the GIS Data Catalog section, a ZIP file contains the sediment data in three formats (a shapefile, a Microsoft Excel spreadsheet, and a comma-delimited ASCII text file) along with metadata.

Data Dictionary

An integral part of any database is the dictionary that explains the structure and content. It contains a list of the fields and definitions of parameters measured. Data utilization is facilitated by reference to this compilation because it defines abbreviations and lists field names.

LABNO - Unique sample identifier assigned in the laboratory

STATIONID - Sample name or number assigned in the field

PROJECT - Project under which samples were taken or data generated

CRUISEID - Name or number of cruise on which sample was collected or station occupied

PRINCIPAL - Name of principal investigator

LATITUDE - Latitude in decimal degrees (north latitudes are positive values)

LONGITUDE - Longitude in decimal degrees (west longitudes are negative values)

DEPTH_M - Depth of water overlying sediment at the time of sampling, measured by a hull-mounted fathometer, corrected for draft, but not corrected for tides, in meters

T_DEPTH - Top depth of the sample below the sediment-water interface, in centimeters

B_DEPTH - Bottom depth of the sample below the sediment-water interface, in centimeters

DEVICE - Device used to collect the sample

MONTH - Number of calendar month during which the sample was collected

DAY - Calendar day on which the sample was collected

YEAR - Calendar year during which the sample was collected

WEIGHT - Dry weight of sample, in grams

ZGRAVEL - Gravel content in percent dry weight of the sample (particles with nominal diameters greater than 2 millimeters; -1 phi and larger)

ZSAND - Sand content in percent dry weight of the sample (particles with nominal diameters less than 2 millimeters but greater than or equal to 0.0625 millimeter; 0 through 4 phi, inclusive)

ZSILT - Silt content in percent dry weight of the sample (particles with nominal diameters less than 0.0625 millimeter but greater than or equal to 0.004 millimeter; 5 through 8 phi, inclusive)

ZCLAY - Clay content in percent dry weight of the sample (particles with nominal diameters less than 0.004 millimeter; 9 phi and smaller)

SEDCLASS - Sediment description based on a rigorous definition (Shepard, 1954; Schlee, 1973; Poppe, 2004b)

Where for sediments with gravel equal to or greater than 10 percent:

GRAVEL - gravel equal to or greater than 50 percent

GRAVELLY SEDIMENT - gravel equal to or greater than 10 percent, but less than 50 percent

Where for sediments with gravel less than 10 percent:

SAND - sand equal to or greater than 75 percent

SILTY SAND - sand less than 75 percent and equal to or greater than 50 percent, silt is greater than clay, and clay less than 20 percent

CLAYEY SAND - sand less than 75 percent and equal to or greater than 50 percent, clay is greater than silt, and silt less than 20 percent

SILT - silt equal to or greater than 75 percent

SANDY SILT - silt less than 75 percent and equal to or greater than 50 percent, sand is greater than clay, and clay less than 20 percent

CLAYEY SILT - silt less than 75 percent and equal to or greater than 50 percent, clay is greater than sand, and sand less than 20 percent

CLAY - clay equal to or greater than 75 percent

SANDY CLAY - clay less than 75 percent and equal to or greater than 50 percent, sand is greater than silt, and silt less than 20 percent

SILTY CLAY - clay less than 75 percent and equal to or greater than 50 percent, silt is greater than sand, and sand less than 20 percent

SAND SILT CLAY - all of these components greater than 20 percent

MEDIAN - Middle point in the grain-size distribution, in phi units

MEAN - Average value in the grain-size distribution, in phi units

STDDEV - Standard deviation (root mean square of the deviations) of the grain-size distribution, in phi units (that is, sorting)

SKEWNESS - Deviation from symmetrical form of the grain-size distribution

KURTOSIS - Degree of curvature near the mode of the grain-size distribution

PHI_11 - Weight percent of the sample in the 11-phi fraction (nominal diameter of particles greater than or equal to 0.0005 millimeter but less than 0.001 millimeter); fine clay

PHI_10 - Weight percent of the sample in the 10-phi fraction (nominal diameter of particles greater than or equal to 0.001 millimeter but less than 0.002 millimeter); medium clay

PHI_9 - Weight percent of the sample in the 9-phi fraction (nominal diameter of particles greater than or equal to 0.002 millimeter but less than 0.004 millimeter); coarse clay

PHI_8 - Weight percent of the sample in the 8-phi fraction (nominal diameter of particles greater than or equal to 0.004 millimeter but less than 0.008 millimeter); very fine silt

PHI_7 - Weight percent of the sample in the 7-phi fraction (nominal diameter of particles greater than or equal to 0.008 millimeter but less than 0.016 millimeter); fine silt

PHI_6 - Weight percent of the sample in the 6-phi fraction (nominal diameter of particles greater than or equal to 0.016 millimeter but less than 0.031 millimeter); medium silt

PHI_5 - Weight percent of the sample in the 5-phi fraction (nominal diameter of particles greater than or equal to 0.031 millimeter but less than 0.0625 millimeter); coarse silt

PHI_4 - Weight percent of the sample in the 4-phi fraction (nominal diameter of particles greater than or equal to 0.0625 millimeter but less than 0.125 millimeter); very fine sand

PHI_3 - Weight percent of the sample in the 3-phi fraction (nominal diameter of particles greater than or equal to 0.125 millimeter but less than 0.25 millimeter); fine sand

PHI_2 - Weight percent of the sample in the 2-phi fraction (nominal diameter of particles greater than or equal to 0.25 millimeter but less than 0.5 millimeter); medium sand

PHI_1 - Weight percent of the sample in the 1-phi fraction (nominal diameter of particles greater than or equal to 0.5 millimeter but less than 1 millimeter); coarse sand

PHI_0 - Weight percent of the sample in the 0-phi fraction (nominal diameter of particles greater than or equal to 1 millimeter but less than 2 millimeters); very coarse sand

PHIM1 - Weight percent of the sample in the -1-phi fraction (nominal diameter of particles greater than or equal to 2 millimeters but less than 4 millimeters); very fine pebbles (granules)

PHIM2 - Weight percent of the sample in the -2-phi fraction (nominal diameter of particles greater than or equal to 4 millimeters but less than 8 millimeters); fine pebbles

PHIM3 - Weight percent of the sample in the -3-phi fraction (nominal diameter of particles greater than or equal to 8 millimeters but less than 16 millimeters); medium pebbles

PHIM4 - Weight percent of the sample in the -4-phi fraction (nominal diameter of particles greater than or equal to 16 millimeters but less than 32 millimeters); coarse pebbles

PHIM5 - Weight percent of the sample in the -5-phi fraction (nominal diameter of particles greater than or equal to 32 millimeters); very coarse pebbles to boulders