Today is Saturday 10th of April and we are in the lee of Tierra del Fuego heading into an early afternoon arrival in PA on Sunday. The last week of
science operations took us from the Palmer Deep, to Andvord Bay/Paradise Harbor, and the Southern Gerlache Strait. We achieved nearly all of our primary science objectives and tackled some secondary targets as well. All the science staff are very pleased with the success of our field program and the tremendous support provided by ASA and ECO personnel.
We began the week with jumbo piston core operations in the Palmer Deep; we rigged the giant core with 50í of barrel and targeted a small isolated depocenter identified from the multibeam swath imagery. Operations went as planned and we recovered 13.5 m of core, a new length record for conventional piston cores on the Antarctic shelf. Kasten and multi-cores were also collected. The core provided a higher resolution record than previous ODP or USAP cores in the Palmer Deep region. We finished the Palmer Deep survey with completion of the biological grab stations directed by Patrick Reynolds. The survey was completed in the early hours of the 5th of April and the remaining time was spent filling in gaps in the multibeam survey of the Palmer Deep. We put into Palmer Station at around 8:00 AM on Monday, April 5th for the transfer of personnel and minor cargo operations. Ship personnel took advantage of the opportunity to visit the base and all returned by 11:30 for the 12:00 noon departure.
We transited to the Andvord Bay/Paradise Harbor area via the scenic Neptune Passage and Flandres Bay, adding to the swath mapping of the Bismark and Gerlache Straits initiated during NBP99-02. We arrived over the Andvord Drift late on the 5th of April and conducted kasten and multi-core operations over a jumbo piston core site. After some delay in setting up the jumbo piston core an 80 inch barrel was rigged (the longest possible) and we recovered 19.34 m of core, another new record core length. The core proved to contain a remarkable record of paleoenviornmental change for the Andvord Bay region and clearly has stratigraphic corollaries with the Palmer Deep record further south. Maximum pull-out tension was never in excess of 15,000 lbs. and the system proved itself in true glacial marine sediments, rich in ice rafted debris. The core site was only a few kms from tidewater glaciers. We finished the Andvord Bay multi-beam survey that day with a transit into the fjord and then completed a very successful biological dredge in Andvord Bay. We began core operations in Paradise Harbor late on the 6th of April. Two kasten cores were successfully acquired in Paradise Harbor and two bottom grabs. We selected a site for our third Jumbo Piston Core based upon poorly defined Bathy2000 3.5 kHz imagery. The core was rigged for 50í and we penetrated a rather thin glacial marine unit and then till, so recovery was only 3.7 m. The core barrel was also bent and caused some difficulty in core recovery.
A few hours of down time were spent in the morning hours in Paradise Harbor before we exited via the Aguirre Channel. Our goal was to finish two grab stations in channel areas. These channels feed into the Andvord Bay and were found to consist of (ice rafted) gravel deposits.
We also completed the swath mapping in a timely fashion. This was completed and we exited the area late in the afternoon heading toward a secondary objective in the Southern Gerlache Strait. We once again added to the swath map of the Gerlache begun during 99-02 and completed a reconnaissance survey of a potential core site between the Neumayer Channel and Boyd Strait. The Bathy2000 3.5 kHz system revealed a large sediment drift within the central channel of the Gerlache Strait. We completed a site survey with crossing lines, and began a coring program at approximately 9:30PM. First a kasten core was recovered and then we rigged for an 80 Jumbo Core.
The Jumbo Core was deployed in wind and driving snow, but sea state was minimal. The core hit bottom at around midnight and was successfully brought on board just after 1:00 AM. We recovered over 20 m of core, another core length record. The core stratigraphy revealed the highest resolution hemipelagic record for the region to date, and much will be learned by the detailed study of this core. At approximately 3:00 AM all deck operations were secured and we headed up the Gerlache on our way home. Multi-beam and Bathy200 data were collected by our team across the shelf, and transit data through the Drake were recorded for S. Cande.
Eugene W. Domack
Professor of Geology