Other ID: 85 Leg 2; FRNL 85-2
Organization(s): USGS, Woods Hole Coastal and Marine Science Center
Location: central Gulf of Mexico, Mississippi fan area, Louisiana, Mississippi, Alabama, Florida, United States, North America, North Atlantic;
Principal Investigator(s): Bonnie McGregor
Affiliate Investigator(s): Neil Kenyon - IOS
Data Type(s): Electro-Magnetic: Magnetics, Location-Elevation: Navigation, Seismics: Air Gun / Water Gun, Seismics: Sub Bottom Profiler, Sonar: Sidescan, Sonar: Single Beam
Scientific Purpose/Goals: The purpose of the cruise was to map the sea floor between the shelf edge and the seaward limit of the EEZ, using the GLORIA system owned and operated by IOS. Leg 2 focused in the central Gulf of Mexico on the Mississippi Fan seaward of Louisiana, Mississippi, Alabama, and Florida.
Start Date: 1985-09-05
Start Port/Location: New Orleans, LA
End Date: 1985-09-29
End Port/Location: Tampa, FL
Equipment Used: 3.5 kHz, Air gun, 10 kHz Bathymetry, GLORIA sidescan, Marine magnetometer, ABC navigation system, Loran-C, Single channel hydrophone
Information to be Derived:
Summary of Activity and Data Gathered: This cruise was very successful. Equipment down time was minimal. The warm surface water temperature continued to limit the GLORIA range necessitating closer line spacing than planned. The presence of the loop current for the last half of the cruise not only provided warm surface water temperatures but also a strong current often approaching 4 knots. The current shear prevented the GLORIA fish from towing parallel to the ship's track, introducing some distortion in the mosaic. In the northeast portion of the Gulf near Desoto Canyon fishing boats with lines set across our proposed track caused a problem requiring several lines to be terminated early. Leg 3A will collect data to cover these data gaps. An additional 8 days will be necessary on Leg 3 to complete the coverage of the Mississippi Fan. The objective of this leg was to map the surface features in the Mississippi Fan area. Although the channel of the Mississippi could be identified on the mid-fan, over much of the fan the channel was obscured by a major submarine slide or slides. Flow patterns were well displayed on the surface and the slide could be mapped to the base of the West Florida Escarpment. Another submarine slide was also present in the Desoto Canyon area. The meandering channel from Desoto Canyon was traced from this slide seaward parallel to the escarpment. Mass wasting appears to be an important process in distributing sediments in the deep water of the central Gulf. The Sigsbee Escarpment was mapped to the east as far as the Mississippi Canyon. Isolated salt diapirs were present to the east of the Mississippi Canyon.
Staff: Ronald C. Circe, John S. Schlee, David Twichell
Notes: Original Center People field contained: Ronald Circe; John Schlee - geologist; Dave Twichell - Data curator.
Lubinski, D.J., and Twichell, David C., 1989, Magnetic and bathymetric data from R/V FARNELLA Cruises FRNL85-1, 85-2, and 85-3 in the U.S. Gulf of Mexico EEZ: 6 URL: http://pubs.er.usgs.gov/publication/ofr89156, download PDF.
Twichell, D., Paskevich, V.F,, 1996, GLORIA sidescan-sonar field data and navigation data collected in the Gulf of Mexico during R/V FARNELLA cruises in 1982 and 1985: URL: http://woodshole.er.usgs.gov/publications/of96-707/OPR96_707/INTRO.HTM.
Twichell, D.C., Cross, VeeAnn A., Paskevich, Valerie F., Hutchinson, Deborah R., Winters, William J., and Hart, Patrick E., 2007, GIS of selected geophysical and core data in the northern Gulf of Mexico continental slope collected by the U.S. Geological Survey: URL: http://pubs.usgs.gov/of/2005/1071/.
Twichell, D.C., McGregor, Bonnie A., and Lubinski, David J., 1989, Seismic-reflection data from R/V FARNELLA Cruises FRNL82-7, FRNL85-1, FRNL85-2, and FRNL85-3A in the U.S. Gulf of Mexico EEZ: U.S. Geological Survey Open-File Report 89-549, 7 p., URL: http://pubs.er.usgs.gov/usgspubs/ofr/ofr89549, download PDF.