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.This is part of the following larger work.Online Links:
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:
This is a Vector data set. It contains the following vector data types (SDTS terminology):
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.
Sequential unique whole numbers that are automatically generated.
Coordinates defining the features.
| Value | Definition |
|---|---|
| shelly sand | This 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/gravel | This 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 - mottled | Sections 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 inlet | This 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 wave | Two 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. |
| sand | This 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. |
| oyster | Areas 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 |
| mud | The 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/oyster | Oyster beds that have developed on top of dredge-spoil material. |
| dredge | These 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. |
| Value | Definition |
|---|---|
| O | Oyster |
| Do | Dredge material/oyster |
| D | Dredge material |
| Shg | Shell/gravel |
| Shs | shelly sand |
| S | Sand |
| St | Sand - tidal inlet |
| Ssw | Sand - sand wave |
| SMm | Sandy mud - mottled |
| M | Mud |
| Shg | Shell/gravel |
| SMm | Sandy Mud-Mottled |
| St | Sand - Tidal Inlet |
| Ssw | Sand-sand wave |
| S | Sand |
| O | Oyster |
| M | Mud |
| Dmo | Dredge Material/Oyster |
| Dm | Dredge Material |
Positive real numbers that are automatically generated.
508-548-8700 x2266 (voice)
508-457-2310 (FAX)
dtwichell@usgs.gov
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.
Person who carried out this activity:
508-548-8700 x2266 (voice)
508-457-2310 (FAX)
dtwichell@usgs.gov
Person who carried out this activity:
508-548-8700 x2348 (voice)
508-457-2310 (FAX)
bandrews@usgs.gov
Person who carried out this activity:
508-548-8700 x2348 (voice)
508-457-2310 (FAX)
bandrews@usgs.gov
Person who carried out this activity:
508-548-8700 x 2348 (voice)
508-457-2310 (FAX)
bandrews@usgs.gov
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.
Interpreted facies were qualitatively compared to ground truth data collected for NOAA in 1999. No quantitative comparison was conducted.
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.
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.
508-548-8700 x2348 (voice)
508-457-2310 (FAX)
bandrews@usgs.gov
Downloadable Data
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.
| Data format: | Shapefile contains interpretation of the surficial geology of the study area in format SHP (version ArcGIS 9.2) ESRI polygon shapefile Size: 30 |
|---|---|
| Network links: |
<http://pubs.usgs.gov/of/2006/1381/GIS/shapefiles/SurficialGeology.zip> |
| Media you can order: |
DVD-ROM
(Density 4.75
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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.
508-548-8700 x2348 (voice)
508-457-2310 (FAX)
bandrews@usgs.gov
