BASEMUD_SURF: ESRI Binary 75-m Grid of the Base of the Mud Depth Surface of Apalachicola Bay based on Seismic-Reflection Profiles Collected in 2006 from U.S. Geological Survey Cruise 06001 (UTM, Zone 16, WGS84)

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Frequently-anticipated questions:

What does this data set describe?

Title:
BASEMUD_SURF: ESRI Binary 75-m Grid of the Base of the Mud Depth Surface of Apalachicola Bay based on Seismic-Reflection Profiles Collected in 2006 from U.S. Geological Survey Cruise 06001 (UTM, Zone 16, WGS84)
Abstract:
Apalachicola Bay and St. George Sound contain the largest oyster fishery in Florida, and the growth and distribution of the numerous oyster reefs here are the combined product of modern estuarine conditions and the late Holocene evolution of the bay. A suite of geophysical data and cores were collected during a cooperative study by the U.S. Geological Survey, the National Oceanic and Atmospheric Administration Coastal Services Center, and the Apalachicola National Estuarine Research Reserve to refine the geology of the bay floor as well as the bay's Holocene stratigraphy. Sidescan-sonar imagery, bathymetry, high-resolution seismic profiles, and cores show that oyster reefs occupy the crests of sandy shoals that range from 1 to 7 kilometers in length, while most of the remainder of the bay floor is covered by mud. The sandy shoals are the surficial expression of broader sand deposits associated with deltas that advanced southward into the bay between 6,400 and 4,400 years before present. The seismic and core data indicate that the extent of oyster reefs was greatest between 2,400 and 1,200 years before present and has decreased since then due to the continued input of mud to the bay by the Apalachicola River. The association of oyster reefs with the middle to late Holocene sandy delta deposits indicates that the present distribution of oyster beds is controlled in part by the geologic evolution of the estuary. For more information on the surveys involved in this project, see <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2005-001-FA> and <http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2006-001-FA>.
  1. How should this data set be cited?

    Twichell, David C. , and Cross, VeeAnn A. , 2012, BASEMUD_SURF: ESRI Binary 75-m Grid of the Base of the Mud Depth Surface of Apalachicola Bay based on Seismic-Reflection Profiles Collected in 2006 from U.S. Geological Survey Cruise 06001 (UTM, Zone 16, WGS84): Open-File Report 2012-1003, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Cross, V.A., Twichell, D.C., Foster, D.S., and O'Brien, T.F., 2012, Apalachicola Bay Interpreted Seismic Horizons and Updated IRIS Chirp Seismic-Reflection Data: Open-File Report 2012-1003, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -85.096952
    East_Bounding_Coordinate: -84.873700
    North_Bounding_Coordinate: 29.727790
    South_Bounding_Coordinate: 29.598613

  3. What does it look like?

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

    Beginning_Date: 31-May-2006
    Ending_Date: 27-Jun-2006
    Currentness_Reference: ground condition

  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 186 x 285 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: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 75.000000
      Ordinates (y-coordinates) are specified to the nearest 75.000000
      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: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Implicit coordinate

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview: This grid represents thickness values in meters.

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?

Why was the data set created?

This grid represents the interpretation of the base of mud horizon presented as a depth surface. This interpretation is based on seismic-reflection profiles collected in 2006 in Apalachicola Bay. The base of mud surface separates the late Holocene estuarine deposits into two units based on changes in the depositional history of the bay.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    Source_Contribution:
    The seismic data used for the interpretation come from two different seismic systems. The bulk of the data are from the EdgeTech FSSB 424 system pole mounted on the R/V Rafael. These data were logged in SEG-Y format using SBLogger. This system had a 1/4 second fire rate. The remainder of the data, in the shallower areas, were acquired with the USGS IRIS system. IRIS is a remotely operated vehicle that has an EdgeTech FSSB 424 chirp sub-bottom profiling system mounted to it. The seismic data were recorded by JSTAR, a software package developed by EdgeTech. This system had a much faster fire rate, almost 15 times per second. The EdgeTech FSSB 424 is a chirp sub-bottom profiler that operates within a 4-24kHz frequency range. The IRIS vehicle is navigated using Real-Time Kinematic (RTK) GPS. The antenna is mounted directly on the platform to minimize navigational error. The R/V Rafael was also navigated with an RTK GPS system with the navigation antenna approximately 1.5 meters forward of the seismic transducer. This offset was not accounted for.

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

    Date: Nov-2011 (process 1 of 1)
    Using ArcMap 9.2 - Spatial Analyst Toolbar - Raster Calculator subtracted the base of mud isopach from the sea floor to create the base of mud depth surface grid.

    Data sources used in this process:

    • apalach_sf
    • basemudiso

    Data sources produced in this process:

    • basemud_surf

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

    Twichell, D.C., Andrews, B.D., Edmiston, H.L., and Stevenson, W.R., 2007, Geophysical mapping of oyster habitats in a shallow estuary; Apalachicola Bay, Florida: Open-File Report 2006-1381, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    Online Links:

    Twichell, D.C., Pendleton, E.A., Poore, R.Z., Osterman, L.E., and Kelso, K.W., 2009, Vibracore, radiocarbon, microfossil, and grain-size data from Apalachicola Bay, Florida: Open-File Report 2009-1031, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Bergeron, E., Worley, C.R., and O'Brien, T.F., 2007, Progress in the development of shallow-water mapping systems: using an autonomous surface vehicle for shallow-water geophysical studies: Sea Technology v. 48, no. 6, p. 10-15, Compass Publications, Inc., Arlington, VA.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

    The R/V Rafael acquired data recording navigation using a Real Time Kinematic (RTK) GPS at a one second interval. The GPS antenna was mounted over the bathymetric sonar. The seismic pole mount system was on the starboard side and approximately 1.5 meters aft of the bathymetry system. No offset was added to the navigation for the seismic data. For seismic data collected with the IRIS system, an RTK GPS system was also used. The GPS antenna for IRIS was mounted directly over the seismic transducer.

  3. How accurate are the heights or depths?

    For the Rafael seismic system, the transducers were located approximately 1 meter below the water surface. This offset was not adjusted for. For the ASV system, the transducers are barely below the water surface, less than half a meter. This depth is not adjusted for. Although the seismic data were not tide corrected, the depth surfaces are related to a sea-floor surface based largely on swath bathymetry data that was tide corrected to mean lower low water.

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

    All useable seismic-reflection profiles collected in 2006 within Apalachicola Bay were used in the interpretation.

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

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:
The public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.

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

    VeeAnn A. Cross
    U.S. Geological Survey
    Marine Geologist
    Woods Hole Coastal and Marine Science Center
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2251 (voice)
    (508) 457-2310 (FAX)
    vatnipp@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?

    Neither the U.S. government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. 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 as a 32-bit floating point raster in Environmental Systems Research Institute (ESRI) format. To utilize these data, the user must have software capable of viewing or importing an ESRI raster.

Who wrote the metadata?

Dates:
Last modified: 12-Apr-2012
Metadata author:
VeeAnn A. Cross
U.S. Geological Survey
Marine Geologist
Woods Hole Coastal and Marine Science Center
Woods Hole, MA 02543-1598

(508) 548-8700 x2251 (voice)
(508) 457-2310 (FAX)
vatnipp@usgs.gov

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

Generated by mp version 2.9.6 on Wed Apr 18 17:06:53 2012