Alabama Aalps Reef, Northern Gulf of Mexico
Recent USGS mapping shows an extensive deep (~100 m) reef tract occurs on the Mississippi-Alabama outer continental shelf (Figure 1). The tract, known as "The Pinnacles", is apparently part of a sequence of drowned reef complexes along the "40-fathom" shelf edge of the northern Gulf of Mexico (Ludwick and Walton, 1957). It is critical to determine the accurate geomorphology of these deep-reefs because of their importance as benthic habitats for fisheries. The Pinnacles have previously been mapped using a single-beam echo sounder (Ludwick and Walton,1957), sidescan sonar (Laswell et al., 1990), and the TAMU2 towed single-beam sidescan-sonar system (Anonymous, 1999). These existing studies do not provide the quality of geomorphic data necessary for reasonable habitat studies.
Figure 1. Location of USGS 2000 multibeam sonar survey
Geodetically accurate bathymetry maps, coregistered with calibrated acoustic backscatter maps, are critical to delineate benthic biotopes, and are essential to correlate biological community differentiation with the physical environment. In May-June and July of 2000, the U.S Geological Survey mapped the Pinnacles Region using a state-of-the-art multibeam sonar system (Figure 1). This Open File Report publishes the bathymetry and acoustic backscatter data along with FGDC-compliant metadata, images, and a GIS of this survey.
For more information, see the Pinnacles
Area Multibeam Cruise Report, or visit the Pacific
Seafloor Mapping website.
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Anonymous.1999. Northeastern Gulf of Mexico coastal and marine ecosystem program: Ecosystem monitoring, Mississippi/Alabama shelf, 3ed annual interim report. Minerals Management Service. 210p.
Laswell, J.S., Sager, W. W., Schroeder, W. W., Rezak, R., Davis, K.S., and Garrison, E. G., 1990. Mississippi-Alabama Marine Ecosystem study: Atlas of high-resolution geophysical data. Mineral Management Service, OCS Study MMS 90-0045. 40p.
Ludwig, J.C and Walton, W.R., 1957, Shelf-edge calcareous
brominences in northeastern Gulf of Mexico. Bull. Amer. Assoc.
Petroleum Geologists, v. 41, p. 2054-2101.
FGDC Compliant Metadata
The multibeam bathymetry and acoustic backscatter data are
available in two formats; ASCII XYZ and ArcInfo GRID. FGDC
metadata is provided for each format and and is available
in three different forms, FAQ (Frequently Anticipated Questions),
HTML, and text.
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