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UTIG News
At the end of last week we
were heading east into the eastern Bransfield Basin, east of Bridgeman Island. We turned
the ship to a course of 050 degrees and ran straight down the axis of a rather knobby
ridge that stretched about 30 km in a straight line and attains a height of about 1000 m
from a surrounding seafloor of 2 to 2.5 km. We surveyed the axis of the eastern Bransfield
Basin towards Clarence Island where we turned and ran a parallel course to the southwest.
We ran over a potential ZAPS sled station and surveyed a bit more. We then took a station
and proceeded to a deep spot at the end of the 30 km ridge. We next steamed out of
Bransfield Basin passing between Elephant and Clarence Islands where we launched the
second Whitworth buoy at 60 degrees 50'S, 54 degrees 04'W. We found a nice flat spot
at just about 1000 m northwest of the eastern end of Elephant Island. We then turned onto
a course of 330 degrees heading into the Scotia Sea while we deployed the seismic streamer
and balanced it by attaching 0.8 pound lead sheets every other hydrophone. There are 5
hydrophones per channel and 48 channels. 
The streamer, which looks like a bright yellow garden hose with phone
lumps every 5 m, has a 1.2 km active section. The streamer towed just below the surface
with the weight that we put on it. There are six active bird locations although the one
second one from the ship does not respond to commands. Unfortunately, by the time we got
the streamer balanced and were about to bring it back in to put birds on, the weather had
blown up to 35 kts and we were forced to postpone the streamer test. We then tried to
Seabeam across the possible new plate boundary and got blown off the water when the winds
went up to 45 kts. Most everyone on the ship was adamant about returning to the relative
calm of Bransfield Strait. 
By 1500z on the 5th of November, we had returned to the eastern Bransfield Basin and
proceeded to take ZAPS sled stations 9 and 10. We then returned to the central Bransfield
Basin steaming past Bridgeman Island once again. We were headed for a high heat flow
location found on a 1989 R/V Polar Duke cruise. When we approached the site, we
found the area covered in heavy pack ice. As time was now running out for our rendezvous
with R/V Polar Duke on the 9th, we felt we needed to test the seismic streamer
before Rick Pearce of ITI left the ship. Consequently we headed back north of Bridgeman
Island in hopes of getting to the relatively ice-free waters of the eastern Bransfield
Basin. We then began to deploy the streamer with birds and then the airguns. With our
normal luck the weather began to deteriorate abruptly. We started with six SSI GI guns in
the water towed as two bundles of three each. Immediately after getting underway with the
guns firing it was obvious that the ship's crab angle would cause the port gun bundle to
rub against the new streamer. The port guns were pulled and since one of the starboard
guns was leaking and had been shut down, it made little sense to continue seismic work
since we were not collecting quality data. It is safe to say that the streamer appears to
be quiet and to work well. Alas, we have not been able to collect any real data with it
because of weather. So, we once again passed Bridgeman Island and headed southwest for
station work near the previously identified zone of high heatflow where we made ZAPS and
rosette lowerings and acquired a core.
Sediment Coring
The coring device used is a modified Kastenlot corer, a three-meter long stainless steel
barrel with a square cross-section. Operatedby Amelia Shevenell, a Hamilton College
undergraduate representative of sedimentologist Eugene Domack, and University of Texas
foraminiferal micropaleontologist Ben Sloan, the device is designed to preserve the
sediment-water interface. The initial lowering of the device failed to retrieve any
sediment, most likely because the half-ton instrument was too light for the heavy aft
winch line on which it was lowered. A second lowering on the starboard winch penetrated
the sea bottom, but a flapper stuck in the open position and allowed the sample to slide
out as the tool was lifted from the water. Following modification of the catcher by ASA
marine tech Robert Kane, a third penetration returned with a full three meters of mud from
1,960 meters water. The mud was described by Shevenell and Sloan as very soft, weakly
stratified olive-gray hemipelagic mud with occasional interbedded black layers inferred to
be rich in heavy minerals, possibly manganese and/or sulfides. The two photographed the
core and took samples at ten centimeter intervals for sedimentological and foraminiferal
analyses. Sloan extracted small subsamples of the top ten centimeters at one-centimeter
intervals to be used to evaluate the microhabitats of foraminifera living in the mud near
the sea bottom.
Rendezvous
We continued our Seabeam
mapping of the region and met R/V Polar Duke at about 0100 local on the eighth. I
had allotted 3 hours for the rendezvous, which began on calm, moonlit waters. The
computer technicians from our ship went over for emergency TLC for the Duke's
systems. Steve Stevenoski, our high school teacher went over as well to find out how
others work under far more trying conditions. The scientific party of the Duke as
well as Al Hickey, their MPC, visited the Palmer. About two hours into the
rendezvous, the winds kicked up to almost 20 kts and the transfer party returned cold and
wet. The air tempature was down to -4 degrees C. After the transfer we continued surveying
and returned to the Great Wall where we undertook our first ZAPS drift.
Hydrothermal Work
Work on Project S-060
(Hydrothermal Survey of Bransfield Strait) went exceedingly well. We have carried out 19
lowerings of the ZAPS instrument package and 7 rosette casts. These stations were
distributed along the axis of the rift between 54 degrees 30'W to 59 degrees 00'W. This
area includes the eastern basin and the majority of the central basin. Water samples were
collected for radon gas, helium isotopes, manganese, and rare earth elements. Both
filtered and unfiltered samples were collected. Radon is being measured on the ship; the
other analyses will be carried out in shore-based laboratories. In addition manganese
profiles are being determined routinely with a flow-through chemical sensor on the ZAPS
sled. CTD information from the instrument package and rosette are well matched. This
combined data set provides us with the best possible coverage.
Hydrography across this area is complex, especially in intermediate waters where there are
well developed temperature and salinity maxima and a dissolved oxygen minimum. Several
water masses are present and the proportions of these waters vary across the study area.
This information will add considerably to what we know about circulation in the Strait and
communication of the waters here with other areas.
We have detected signals indicative of hydrothermal activity in several areas, including both basins. At one of these locations in the central basin our exploration has advanced to the site survey stage. Along a ridge of pillow basalts in the central basin known as the "great wall" we detected a hydrothermal plume that has a turbidity signal comparable to that observed at the TAG mound on the Mid-Atlantic Ridge. This plume is the first clear evidence of high-temperature, black smoker vents in the Bransfield Strait. More detailed work at this site is planned for later in the project.
Lawver, Klinkhammer, and the Shipboard Scientific Party