SURFICIALGEOLOGY - Interpretation of the Surficial Geology of Apalachicola Bay and St. George Sound, Florida

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Frequently-anticipated questions:


What does this data set describe?

Title:
SURFICIALGEOLOGY - Interpretation of the Surficial Geology of Apalachicola Bay and St. George Sound, Florida
Abstract:
These data were collected under a cooperative mapping program between the U.S. Geological Survey (USGS), the National Oceanic and Atmospheric Administration Coastal Services Center (NOAA\CSC), and the Apalachicola National Estuarine Research Reserve (NERR). The primary objectives of this program were to collect marine geophysical data to develop a suite of seafloor maps to better define the extent of oyster habitats, the overall seafloor geology of the bay and provide updated information for management of this resource. In addition to their value for management of the bay's oyster resources, the maps also provide a geologic framework for scientific research and the public.
High-resolution bathymetry, backscatter intensity, and seismic profile data were collected over 230 square kilometers of the floor of the bay. The study focused on the Apalachicola Bay and Western St. George Sound portions of the estuary in mostly in depths > 2.0 meters.
  1. How should this data set be cited?

    U.S. Geological Survey, 2007, SURFICIALGEOLOGY - Interpretation of the Surficial Geology of Apalachicola Bay and St. George Sound, Florida: Open-File Report 2006-1381, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Twichell, David C. , Andrews, Brian D. , Edmiston, H. Lee , and Stevenson, William R. , 2006, 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, Massachusetts.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -85.096005
    East_Bounding_Coordinate: -84.755168
    North_Bounding_Coordinate: 29.783119
    South_Bounding_Coordinate: 29.601303

  3. What does it look like?

    <http://pubs.usgs.gov/of/2006/1381/GIS/thumbnails/SurficialGeology.jpg> (JPEG)
    JPEG image of SurficialGeology shapefile

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

    Currentness_Reference: publication date

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

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

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

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • G-polygon (179)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees.

      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:
      Altitude_System_Definition:

  7. How does the data set describe geographic features?

    SurficialGeology
    Surficial geology of the Apalachicola Bay and St. George Sound Survey areas (Source: USGS)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    FACIES
    Interpreted seafloor facies (Source: USGS)

    ValueDefinition
    shelly sandThis sea floor type is characterized by a moderate to high backscatter signature on the sidescan imagery. Sediment samples from these areas recovered a mix of sand and shell hash (NOAA, Coastal Services Center, 1999). The shelly sand facies is found in three settings. First, it is found fringing parts of many of the oyster bars. Specifically, this facies is found along the eastern sides of Porter's, Platform, and St. Vincent Bars, it is found along both sides of Hotel and Norman's Bars, and occurs in patches around and between many of the smaller oyster bars. Second, this facies covers some shoal areas where there is no evidence of oysters. The shoal off Cedar Point and two areas west of St. Vincent Bar are examples of such areas. The third setting is the floor of troughs where strong tidal currents actively rework the sea floor. One of these troughs extends eastward along the southern side of the bay from West Pass, and another extends west into Apalachicola Bay from the shallow gap between Cat and East Hole Bars. In these areas, the shelly sand probably represents a lag deposit associated with active reworking by strong tidal currents. The shelly sand facies covers 16.33 km2 of the study area.
    shell/gravelThis sea floor type was only identified in a small, relatively deep depression south of Cat Point. This facies has a high-backscatter return, and in this area bottom samples recovered shell hash and some gravel. This shell and gravel appears to be a lag deposit resulting from the strong tidal currents in this area. This facies covers 0.69 km2
    sandy mud - mottledSections of the estuary floor have a moderate-to-low backscatter signature that is interrupted by small high-backscatter patches that are mostly 5-15 m in diameter. This mottled sea floor occurs in narrow bands along parts of the southern side of the survey area in St George Sound, and in some larger patches in the western part of Apalachicola Bay on Higgins Shoal and along both flanks of a second low-relief ridge west of St. Vincent Bar. Sediment samples form these mottled areas are sandy mud. The origin of the mottled pattern is unknown. This facies covers 2.60 km2.
    sand - tidal inletThis sea floor type refers to the flood tidal delta deposit shoreward of Government Cut, the manmade inlet that separates St. George Island from Little St. George Island. The surface of this feature is rippled, and inferred to be primarily of sand composition. West Pass does not have a flood tidal delta on its shoreward side. The flood tidal delta shoreward of Government Cut occupies 0.23 km2.
    sand - sand waveTwo patches of sand waves were identified in the eastern part of St. George Sound where the sea floor is primarily sand. These sand waves have 50-150 m wavelengths, 0.5-0.8 m heights, and crests that trend northwest. Many of the sand waves are asymmetrical with their steep sides facing to the west. The asymmetry of these bedforms suggests a net westward migration. Sand waves cover 1.39 km2 of the survey area.
    sandThis sea floor type refers to clean sand containing no more than small amounts of mud and shell hash. It covers most of the floor of the eastern part of St. George Sound, a large part of the floor of Apalachicola Bay west of St. Vincent Bar, and discontinuous sections of the southern edge of Apalachicola Bay. This facies covers 52.21 km2 of the study area.
    oysterAreas inferred to be covered by oysters show as high backscatter on the sidescan-sonar imagery, coincide with shoal areas on the bathymetry, and bottom observations show living oysters on a shelly sand sea floor. Oyster beds cover 21.91 km2 of the study area
    mudThe mud facies covers the largest part of the study area. It appears on the sidescan-sonar imagery as low backscatter, and samples are comprised of at least 70% silt plus clay. The mud facies covers 134 km2 of the study area; an area that includes much of the floor of Apalachicola Bay and the western part of St. George Sound. It occurs mostly in sections of the study area where water depths are deeper than 2 m.
    dredge/oysterOyster beds that have developed on top of dredge-spoil material.
    dredgeThese manmade deposits have the same origin as the dredge material/oyster areas however these deposits have a moderate backscatter surface and are inferred to not be covered with oysters. Areas classified as Dredge material cover 0.78 km2 and are found in the eastern part of St. George Sound, and along the western side of the section of the Intracoastal Waterway that trends northward to the mouth of the Apalachicola River.

    Name
    Place names for known oyster bars (Source: Florida Dept. of Environmental Protection (FLDEP).)

    Abrev
    Abbreviation of Facies attribute for map labels (Source: USGS)

    ValueDefinition
    OOyster
    DoDredge material/oyster
    DDredge material
    ShgShell/gravel
    Shsshelly sand
    SSand
    StSand - tidal inlet
    SswSand - sand wave
    SMmSandy mud - mottled
    MMud
    ShgShell/gravel
    SMmSandy Mud-Mottled
    StSand - Tidal Inlet
    SswSand-sand wave
    SSand
    OOyster
    MMud
    DmoDredge Material/Oyster
    DmDredge Material

    SHAPE_Leng
    Length in meters. (Source: ESRI)

    SHAPE_Area
    Area of feature in meters squared. (Source: ESRI)

    Positive real numbers that are automatically generated.


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?

    David Twichell
    U.S. Geological Survey
    Oceanographer
    Woods Hole Science Center
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2266 (voice)
    508-457-2310 (FAX)
    dtwichell@usgs.gov


Why was the data set created?

This shapefile provides a high-resolution interpretation of the surficial geology of Apalachicola Bay, and western part of St. George Sound, Florida. The interpretation is based on the sidescan sonar imagery, the bathymetry, available sediment sample information, and seafloor observations.


How was the data set created?

  1. From what previous works were the data drawn?

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

    Date: 21-Dec-2006 (process 1 of 4)
    This data layer was digitized from visual interpretations using ArcView 3.3. Shapefile was digitized at a zoom scale of 1:5000 or greater. Each polygon was digitized and given one of 11 attributes to describe the general composition of that unit.

    Person who carried out this activity:

    David Twichell
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1589
    USA

    508-548-8700 x2266 (voice)
    508-457-2310 (FAX)
    dtwichell@usgs.gov

    Date: 02-Jan-2007 (process 2 of 4)
    Completed shapefile was imported to a polygon feature class. Topological rules were built to identify and fix any gaps or overlaps between adjacent polygons.

    Person who carried out this activity:

    Brian Andrews
    U.S. Geological Survey
    Geographer
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2348 (voice)
    508-457-2310 (FAX)
    bandrews@usgs.gov

    Date: 25-Jan-2007 (process 3 of 4)
    Resulting feature class was visually reviewed to identify and edit any polygons that did not extend to the border of the sidescan sonar.

    Person who carried out this activity:

    Brian Andrews
    U.S. Geological Survey
    Geographer
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2348 (voice)
    508-457-2310 (FAX)
    bandrews@usgs.gov

    Date: Jul-2007 (process 4 of 4)
    Exported feature class from personal geodatabase to a shapefile and projected to geographic.

    Person who carried out this activity:

    Brian Andrews
    U.S. Geological Survey
    Geographer
    384 Woods Hole Road
    Woods Hole, MA 02543-1598

    508-548-8700 x 2348 (voice)
    508-457-2310 (FAX)
    bandrews@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?

    The accuracy of this interpretive data layer is dependent on the level of detail of the source material and interpretation procedures for capturing that source. The primary limiting factor for the level of detail of the source is the scale of the remotely sensed data, and positional accuracy, distribution and total number of surficial samples available for the area. The map scale or remotely sensed image resolution determines the level of content that may be extracted from a given source during digitization.

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

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

    Interpreted facies were qualitatively compared to ground truth data collected for NOAA in 1999. No quantitative comparison was conducted.

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

    Topology was created for these polygons to identify/verify/and fix the following rules:
    1) Polygons must not have gaps. All data gaps less than 15 m across were automatically fixed. A total of 5 errors were identified and fixed
    2) Polygons must not overlap. No errors were found.


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:
These data should not be used at map scales less than 1:30,000, for which it is not intended.
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)

    Brian Andrews
    U.S. Geological Survey, Woods Hole Science Center
    Geographer
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598
    USA

    508-548-8700 x2348 (voice)
    508-457-2310 (FAX)
    bandrews@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 this data set has been used by the U.S. Geological Survey (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?

    The data are available in Environmental Systems Research Institute (ESRI) shapefile format. The user must have ArcGIS or ArcView 3.3 or greater software to read and process the data file. In lieu of ArcView or ArcGIS, the user may utilize another GIS application package capable of importing data. A free data viewer, ArcExplorer, capable of displaying the data is available from ESRI at www.esri.com.


Who wrote the metadata?

Dates:
Last modified: 27-Aug-2007
Metadata author:
U.S. Geological Survey
c/o Brian Andrews
Geographer
384 Woods Hole Rd.
Woods Hole, MA 02543-1598
USA

508-548-8700 x2348 (voice)
508-457-2310 (FAX)
bandrews@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 Mon Aug 27 12:27:27 2007