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UTIG NewsNPB-9507 Weekly Cruise Report #1
RVIB Nathaniel B. Palmer
28 October - 2 November 1995
Punta Arenas, Chile
The scientific party members from the University of Texas at Austin left Austin on the
23rd of October. We rendevoused with Richard Von Herzen of the Woods Hole Oceanographic
Institution, Scott Borg of the National Science Foundation, Amelia Shevenell of Hamilton
College, and Steve Stevenoski of Wisconsin Rapids High School in Miami. We were met in
Santiago by the Agunsa agency personel and stayed in the Hotel Monte Carlo in Santiago.
While in Santiago, Scott Borg and I visited Sergio Barrientos and Emilio Vera of the
Geophysics Department of the University of Chile. On the 25th of October we met Dr. Marta
Ghidella of the Argentine Antarctic Program and Rick Pearce of Innovative Transducers Inc.
(Ft. Worth, TX) at the Santiago Airport and flew to Punta Arenas. Most of the scientific
party stayed at the Hotel Jose Noreiga in Punta Arenas. We settled in aboard the ship on
the 26th but found that the ship had not been fueled while at the pier and that one ASA
employee would not arrive until the 27th. Consequently, rather than sailing on the 27th as
scheduled we did not depart the fuel pier until the morning of the 28th.
Drake Passage
We left the Straits of Magellan and sailed around the eastern tip of Tierra del Fuego. At
0805 on the 29 October 1995, we dropped a pressure gauge for Wentworth of Texas A&M.
It, in conjunction with another instrument to be dropped near Elephant Island and some
British instruments, will be used to determine flow rate and volume of water through Drake
Passage. Total time on station was about 1.5 hours. We then proceeded along the
continental margin on the southern side of Tierra del Fuego. We ran along at water depths
varying between 1000 m and 3000 m. This was the first real trial of the new, improved
Seabeam 2112. I am happy to say the system works well. We continued on course across the
Shackleton Fracture Zone Ridge that extends from South America to the Antarctic Peninsula.
We crossed the flat trench at a depth of ~4300 m and then turned northwest for a short
survey, ran up the continental margin of South America, and found the southern corner of
South America where the contours come to an angle of 50 degrees. We then headed down the
start of the Shackleton Ridge using the Geosat gravity maps of David Sandwell. The ridge
has one major offset at about 66-degrees 30-minutes W which we aniticipated from the
Geosat gravity data. We then were able to follow the ridge without any problems all the
way across the Drake. In the northern part of the ridge, it does not match the published
position very well but with the new Seabeam system, it was quite easy to follow across. We
did one additional quick survey of the intersection of the abandoned spreading center in
the Scotia Sea with the Shackleton Ridge. Originally we had planned to deploy the new ITI
streamer and balance it in our work area in the Southwest Scotia Sea but the wind was up
to 30 kts and the seas were building so it was decided to postpone the streamer party
until later. We turned and ran south along the east side of Bridgman Island, neatly
imaging two of the small volcanic cones that Randy Keller and I dredged on our NBP9301
cruise. We then turned south around the southern edge of Bridgman Island and headed west
into King George Basin.
Bransfield Basin
An initial lowering of the
Oregon State vent detection (ZAPS) sled was made in the eastern end of King George Basin.
We then turned southwest and began to profile the Central Bransfield Basin. The detail of
the Seabeam image is astounding. We have a beautiful image of the submarine volcano just
off Maxwell Bay, King George Island. We then returned to the eastern end of the King
George Basin and made a second ZAPS sled lowering after which we made a second survey to
the southwest. We picked up numerous small volcanic features, all of which seem to be
lineated and parallel along about four lines. The lineation of these features is truly
remarkable. After additional lowerings of the ZAPS sled and the CTD rosette we have now
proceeded to the Eastern Bransfield Basin where we are in the process of running a Seabeam
survey towards Clarence Island.
Larry Lawver and the Shipboard Scientific Party