Stratigraphic Framework Maps of the inner-continental shelf within the New York Bight: Holocene Thickness Grid

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Frequently-anticipated questions:

What does this data set describe?
    Title:
    Stratigraphic Framework Maps of the inner-continental shelf within the New York Bight: Holocene Thickness Grid
    Abstract:
    These data orginate from interpretations of seismic reflection profile data. The derivative data are in a grid format and are intended to represent the thickness and distribution of Holocene deposits throughout the inner-continental shelf within the New York Bight. The gridded Holocene thickness is helpful in understanding the stratigraphic evolution of the inner-continental shelf, the regional sediment transport system, and the influence of the inner-shelf framework on coastal processes. The grid showing thickness of Holocene sediment is an important factor in the framework of the coastal region.

  1. How should this data set be cited?
    Denny, Jane F. , Foster, David S. , Schwab, William C. , and Swift, B. Ann , 20010000, Stratigraphic Framework Maps of the inner-continental shelf within the New York Bight: Holocene Thickness Grid: U.S. Geological Survey, Woods Hole, MA.

     

    This is part of the following larger work.
    Schwab, William C., Denny, Jane F., Foster, David S., Lotto, Linda L., Allison, Mead A., Uchupi, Elazar, Swift, B. Ann, Danforth, William W., Thieler, Robert E., and Butman, Bradford, 2002, High-Resolution Quaternary seismic stratigraphy of the New York Bight Continental Shelf: Open-File Report OFR02-152, U.S. Geological Survey, Woods Hole, MA.

     

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -74.06
    East_Bounding_Coordinate: -71.8000
    North_Bounding_Coordinate: 41.2322
    South_Bounding_Coordinate: 40.15
  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 01-May-1995
    Ending_Date: 01-Nov-1998
    Currentness_Reference: ground condition
  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: map
  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Raster data set. It contains the following raster data types:

      • Dimensions 454 x 393, type Grid Cell
    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 18
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -075.000000
      Latitude_of_Projection_Origin: +00.000000
      False_Easting: 500000
      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 200
      Ordinates (y-coordinates) are specified to the nearest 200
      Planar coordinates are specified in Meters

      The horizontal datum used is WGS84.
      The ellipsoid used is WGS84.
      The semi-major axis of the ellipsoid used is 6378137.0000000.
      The flattening of the ellipsoid used is 1/298.26.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 1
      Altitude_Distance_Units: Meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
      Depth_System_Definition:
      Depth_Datum_Name: Mean sea level
      Depth_Resolution: 0.1
      Depth_Distance_Units: Meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?
    This data set resulted from a cooperative with the US Geological Survey and the US Army Corps of Engineers.
  3. To whom should users address questions about the data?
    US Geological Survey
    c/o Jane F. Denny
    Geologist, Seafloor Mapping Group
    384 Woods Hole Road
    Woods Hole, MA 012543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

Why was the data set created?
In 1995, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers (USACE), began a program to generate reconnaissance maps of the sea floor offshore of the New York - New Jersey metropolitan area and within the southern Long Island nearshoe area. Our methods include high-resolution sidescan sonar and subbottom profiling techniques, along with surface grab and vibracore sampling to verify the geophysical interpretations. The goal of the investigation is to provide a regional synthesis of the sea-floor environment, to determine regional-scale availability of sand as a resource for beach nourishment programs, and to investigate the role that inner-shelf morphology and geologic framework have in the evolution of the coastal region within the New York Bight Apex and southern Long Island. Maps derived from interpretation of the subbottom profiles show information on the geometry and distribution of the Quaternary sediments and the underlying coastal-plain unconformity. This seismic stratigraphy yields a regional framework on which explanations of present (and past) sediment movement, dispersal, and erosion processes are based.

How was the data set created?
  1. From what previous works were the data drawn?

    Modern Sand Thickness along nearshore - southern Long Island (source 1 of 2)
    Foster, David S. , 1999, Stratigraphic Framework Maps of the Nearshore Area of Southern Long Island, New York: ridded Elevation of coastal-plain Unconformity: U.S. Geological Survey USGS Open-File Report, U.S. Geological Survey, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: paper products
    Source_Contribution:
    These data were merged with pickes of Holocene thickness within the New York Bight in order to generate a composite Holocene isopach for the region.

    Holocene Thickness (source 2 of 2)
    Lotto, Linda, 20000000, Seismic Stratigraphy and Quaternary Evolution of the New York Bight Inner Continental Shelf: Texas A&M University unpublished MS Thesis, Texas A&M University, College Station, TX.
    Type_of_Source_Media: paper
    Source_Contribution:
    Picks of Holocene Thickness were merged with Holocene thickness within the nearshore off southern Long Island in order to generate a composite Holocene thickness for the New York Bight.

  2. How were the data generated, processed, and modified?

    Date: 2000 (process 1 of 6)
    Processed SEG-Y seismic data and associated shot navigation data acquired in 1998 within the New York Bight Apex were loaded into Landmark Seisworks interpretation software. The reflector at the base of the moderen marine sand was digitized along with the seafloor reflector. The difference in two-way travel time between horizons was calculated and converted to meters using an assumed velocity of 1630 m/s. This represents the thickness of Holocene deposits. The resolution of the CHIRP data was poor in the southeastern portion of the survey area. It was difficult to resolve Holocene deposits; the thickness of the deposit may be beyond the resolution of the system. These data were exported from seisworks to an ASCII format file.

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Date: 2001 (process 2 of 6)
    A Holocene Isopach was generated for a portion of the inner-continental shelf within the New York Bight Apex as part of an MS Degree in 1998 (Source_Information 2). The base of the Holocene was not easily resolved within the CHIRP data, and thus, there were a limited number of 'picks' to the base of the Holocene; limited data from which to generate an isopach. The Holocene Isopach was generated by hand using a 5 meter contour interval. Recently, the USGS has revisited these data in order to refine the existing Holocene Isopach. This original Holocene Isopach was digitized and imported into ArcView. The contours of Holocene thickness were converted into an ArcInfo grid file using the ArcInfo TopoGridTool. The resultant grid was then desampled by extracting grid nodes at five minute intervals along the survey tracklines. The grid was desampled in order to limit any bias in the data introduced by converting the 5 meter isopach contours to a continuous grid; i.e. to aviod imparting a higher resolution to the data than is reasonable. These data were then exported in ASCII format file.

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Date: 1998 (process 3 of 6)
    ASCII point data were merged and imported to Dynamic Graphics Inc., EarthVision surface modelling software. These data were gridded at a 100 meter grid cell size, yielding 1061 rows and 1853 columns grid size. This grid was exported as an ASCII format file.

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Date: 1998 (process 4 of 6)
    The exported ASCII Holocene thickness grid file from EarthVision was edited to create an ASCII grid file suitable for import to ArcView software. The order of rows were flipped, so that the file begins with the lower row, left column and ends with the upper row right column. An ArcView header that descibes the lower left origin of the grid, the grid cell size, the number of rows and columns, and the null value used (-9999).

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Data sources used in this process:
    • sandiso

    Date: 1998 (process 5 of 6)
    The edited ASCII grid file was imported into ArcView software with the 3D Spatial Analyst extension. The file was saved as a Spatial Analyst (ArcInfo raster grid format) grid.

    Person who carried out this activity:

    David S. Foster
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2271 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

    Data sources used in this process:
    • sandiso

    Date: 2000 (process 6 of 6)
    The resultant grid was clipped, using the GRIDCLIP script within ArcView 3.2, to the extents of the 1995 and 1996 surveys. The associated contour data (hand generated during processing step 2) are stored as an ESRI vector shapefile and fall within the 1995 and 1996 survey areas. These contour data are stored in the Geographic Coordinate System (decimal degrees, WGS84 Ellipsoid).

    Person who carried out this activity:

    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?

    These data are derived from 2D seismic reflection profiles that are spaced approximately 300 meters apart in the cross track-direction. Along track samples of the seismic profiles are approximately 1 meter assuming a ship speed of 2 meters/second. The data were downsampled in the along-track direction at an interval of about 30 meters. Thickness of sediment are set to zero where the base of the modern sand is not detected (below the vertical reolution of the seismic system) in the data. The horizontal resolution of the gridded data are constrained by the grid cell size of 100 meters. Horizontal interpolation is inherent in the gridding process.

  2. How accurate are the geographic locations?

    DGPS is assumed to be accurate within 1-2 meters. Standard GPS is assumed accurate within 5-10 meters. 99% of the positional data is DGPS. Unless noted, all GPS/DGPS data is referenced to WGS84 (NAD83). Tow fish (sidescan) position was corrected for layback using acoustic slant range measurements and fish pressure depth measurements, otherwise corrected for layback by manual inputs for slant range and fish depth. Accuracy for slant range varies with distance from the ship and the noise conditions in the water, nominally up to 30 meters is better than 2 meters. Pressure depth is accurate to .1 meter. Manual slant range can use cable out measurements or estimates based on data processing results.

  3. How accurate are the heights or depths?

    Vertical positioning is not necessary to quantify thickness of sediment data. The data are referenced to the distance between the sea floor and the base of the modern sand using an acoustic velocity of 1630 m/s.

  4. Where are the gaps in the data? What is missing?

    The gridded data are limited by horizontal resolution of the grid cell size and spatial distribution of the original point data. Higher resolution data acquisition will likely result in a more detailed representation of sediment distribution and thickness. The data also represent a time interval of the data acquisition. Attributes may and probably do change with time.

  5. How consistent are the relationships among the observations, including topology?

    The gridded data were checked for consistency by plotting the point data over the the grid and comparing point values with grid cell values.

How can someone get a copy of the data set?
Are there legal restrictions on access or use of the data?
Access_Constraints: none
Use_Constraints: none

  1. Who distributes the data set? (Distributor 1 of 1)
    Jane F. Denny
    US Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-457-2311 (voice)
    508-457-2310 (FAX)
    jdenny@usgs.gov

  2. What's the catalog number I need to order this data set?

    hiso

  3. What legal disclaimers am I supposed to read?
    Altough this data set and its lineage have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or it's related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related items. Users must assume responsibility for the proper use of this data. This data should not be used at resolutions for which it is not intended. This data has no been reviewed for conformity with US Geological Survey editorial standards, or the North American Strigraphic code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the US Government.
  4. How can I download or order the data?

Who wrote the metadata?
Dates:
Last modified: 19-Jan-2002
Last Reviewed: 2002

Metadata author:
Jane F. Denny
US Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA 02543
USA

508-457-2311 (voice)
508-457-2310 (FAX)
jdenny@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Generated by mp version 2.7.17 on Fri Apr 12 09:07:37 2002