TRANSGR_GRD - ESRI ArcRaster grid representing the elevation of the regional transgressive unconformity underlying the inner shelf of Long Bay, South Carolina

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Frequently-anticipated questions:

What does this data set describe?

Title:
TRANSGR_GRD - ESRI ArcRaster grid representing the elevation of the regional transgressive unconformity underlying the inner shelf of Long Bay, South Carolina
Abstract:
In 1999, the USGS, in partnership with the South Carolina Sea Grant Consortium, began a study to investigate processes affecting shoreline change along the northern coast of South Carolina, focusing on the Grand Strand region. Previous work along the U.S. Atlantic coast shows that the structure and composition of older geologic strata located seaward of the coast heavily influences the coastal behavior of areas with limited sediment supply, such as the Grand Strand. By defining this geologic framework and identifying the transport pathways and sinks of sediment, geoscientists are developing conceptual models of the present-day physical processes shaping the South Carolina coast. The primary objectives of this research effort are: 1) to provide a regional synthesis of the shallow geologic framework underlying the coastal upland, shoreface and inner continental shelf, and define its role in coastal evolution and modern beach behavior; 2) to identify and model the physical processes affecting coastal ocean circulation and sediment transport, and to define their role in shaping the modern shoreline; and 3) to identify sediment sources and transport pathways; leading to construction of a regional sediment budget.
  1. How should this data set be cited?

    U.S. Geological Survey, 2007, TRANSGR_GRD - ESRI ArcRaster grid representing the elevation of the regional transgressive unconformity underlying the inner shelf of Long Bay, South Carolina: Open-File 2005-1346.

    Online Links:

    This is part of the following larger work.

    Baldwin, W.E., Denny, J.F., Schwab, W.C., Gayes, P.T., Morton, R.A., and Driscoll, N.W., 2007, Geologic Framework Studies of South Carolina's Long Bay from Little River Inlet to Winyah Bay, 1999-2003; geospatial data release: Open-File Report 2005-1346, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -79.158619
    East_Bounding_Coordinate: -78.514899
    North_Bounding_Coordinate: 33.855993
    South_Bounding_Coordinate: 33.188888

  3. What does it look like?

    <http://pubs.usgs.gov/of/2005/1346/images/transgr_grd.jpg> (JPEG)
    elevation of regional transgressive unconformity underlying the Long Bay inner shelf

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

    Beginning_Date: 1999
    Ending_Date: 2003
    Currentness_Reference: publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: raster digital data

  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 728 x 583 x 1, 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: 17
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -81.00000
      Latitude_of_Projection_Origin: 0.0000000
      False_Easting: 500000.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 100.000
      Ordinates (y-coordinates) are specified to the nearest 100.000
      Planar coordinates are specified in meters

      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Mean lower low water
      Depth_Resolution: 0.5
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview: Elevation of paleochannel unconformities in ESRI GRID format.
    Entity_and_Attribute_Detail_Citation: usgs

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?

  3. To whom should users address questions about the data?

    Wayne Baldwin
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

Why was the data set created?

This data set contains a surface depicting the elevation of the regional transgressive unconformity underlying the inner shelf of Long Bay, offshore of the South Carolina Grand Strand. Chirp seismic data collected with Benthos SIS-1000 and Edgetech SB-512 acquisition systems were processed using SIOSEIS (Scripps Institute of Oceanography) and Seismic Unix (Colorado School of Mines) to produce segy files and jpg images of the profiles. Data were then imported into Landmark SeisWorks, a digital seismic interpretation package, where the sea floor and underlying transgressive surface were interpreted and digitized. The isopach between these horizons was exported at every 50th shot as xyz points, and imported to ArcGIS for interpolation into a 10-m raster grid. The isopach grid was then subtracted from a seafloor bathymetry grid (bathy_grd) to approximate the proper elevation of the transgressive unconformity beneath the sea floor.

How was the data set created?

  1. From what previous works were the data drawn?

    sedthick_grd, v1.0, 2006 (source 1 of 2)
    U.S. Geological Survey, 2007, SEDTHICK_GRD - ESRI ArcRaster representing the isopach of Holocene surficial sediment within the inner shelf of Long Bay, South Carolina: Open-File 225-1346, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Baldwin, W.E., Denny, J.F., Schwab, W.C., Gayes, P.T., Morton, R.A., and Driscoll, N.W., 2007, Geologic Framework Studies of South Carolina's Long Bay from Little River Inlet to Winyah Bay, 1999-2003; geospatial data release: Open-File Report 2005-1346, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: DVD-ROM
    Source_Contribution:
    This data set contains polygons that identify the geologic unit type present in outcrop or subcrop along the Long Bay inner shelf. Polygon areas are based upon digital interpretations of Chirp seismic reflection data and coastal plain boreholes. A polygon outlining the inner shelf study area was erased (ArcGIS Analysis toolbox) in iterations using polygons outlining gridded surfaces of Holocene surficial sediment (sedthick_grd) and paleochannel unconformities (paleoch_grd). Outside of the area covered by the Holocene surficial sediment grid, seismic data indicate surficial sediment cover of < 50 cm. In these areas, paleochannel fills, Cretaceous, and Tertiary units are interpreted to crop out at the sea floor, or subcrop near the surface.

    bathy, v1.0, 2006 (source 2 of 2)
    U.S. Geological Survey, 2007, BATHY - Bathymetry within the inner shelf of Long Bay, South Carolina collected by the USGS, 1999-2003 (Grid): Open-File 2005-1346, U.S. Geological Survey, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Baldwin, W.E., Denny, J.F., Schwab, W.C., Gayes, P.T., Morton, R.A., and Driscoll, N.W., 2007, Geologic Framework Studies of South Carolina's Long Bay from Little River Inlet to Winyah Bay, 1999-2003; geospatial data release: Open-File Report 2005-1346, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    Type_of_Source_Media: DVD-ROM
    Source_Contribution:
    This data set contains polygons that identify the geologic unit type present in outcrop or subcrop along the Long Bay inner shelf. Polygon areas are based upon digital interpretations of Chirp seismic reflection data and coastal plain boreholes. A polygon outlining the inner shelf study area was erased (ArcGIS Analysis toolbox) in iterations using polygons outlining gridded surfaces of Holocene surficial sediment (sedthick_grd) and paleochannel unconformities (paleoch_grd). Outside of the area covered by the Holocene surficial sediment grid, seismic data indicate surficial sediment cover of < 50 cm. In these areas, paleochannel fills, Cretaceous, and Tertiary units are interpreted to crop out at the sea floor, or subcrop near the surface.

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

    Date: 2003 (process 1 of 1)
    The ARCGIS raster calculator was used to subract a grid representing Holocene surficial sediments (sedthick_grd) from the regional seafloor bathymetry grid (bathy_grd) to approximate the proper elevation of the transgressive unconformity beneath the sea floor.

    Person who carried out this activity:

    Wayne Baldwin
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

    Data sources used in this process:
    • sedthick_grd, v1.0, 2006
    • bathy, v1.0, 2006

    Data sources produced in this process:

    • trans_grd

  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 were interpretted from seismic-reflection and bathymetric data at a regional scale of 1:75,000.

  2. How accurate are the geographic locations?

    Interpretations are derived from seismic-reflection and bathymetric data at a regional scale of 1:75000.

  3. How accurate are the heights or depths?

    Seismic data are not corrected for tides. Thickness of Holocene surficial sediments was calculated as the distance between the seafloor and the underlying transgressive surface from interpretation of seismic reflection profiles. An isopach grid of the thickness of Holocene surficial sediments (sedthick_grd) was then subtracted from a gridded surface of seafloor bathymetry (bathy_grd) to generate a grid representing the regional elevation beneath the seafloor.

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

    All interpretations of paleochannel unconformities are present in this data set

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

    No additional checks for topological consistency were performed on the data.

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:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.

  1. Who distributes the data set? (Distributor 1 of 1)

    Wayne Baldwin
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543
    USA

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

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

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Although all data 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 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 materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    These data are available in Environmental Systems Research Institute (ESRI) GRID format. The user must have software capable of importing and processing the data file.

Who wrote the metadata?

Dates:
Last modified: 23-Jan-2007
Metadata author:
Wayne Baldwin
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA 02543-1598
USA

508-548-8700 x2226 (voice)
508-457-2310 (FAX)
jdenny@usgs.gov

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

Generated by mp version 2.9.2 on Fri Mar 09 10:00:23 2007