OPERATIONS

At 0745 hr on Sunday, 13 December 1998, the last line was passed ashore and the ship departed Fremantle, Australia. At 0812 hr the pilot was away and the ship was under way at full speed for the first site of Leg 183. For the first 4 days of the transit (north of 44°S), the ship averaged just under 10 kt. On day 5 of the transit, the wind speed increased, blowing predominantly out of the south or southwest, and the seas/swells continued to build over the next 5 days. As local weather conditions deteriorated and the opposing Antarctic Circumpolar Current strengthened, the transit speed dropped to between 8.8 and 6.9 kt. Winds of 20 kt increased to 40-50 kt over this period, with gusts >50 kt. Swells increased to a maximum of 6 m with superimposed wind-generated seas of up to 4 m. Water temperature dropped from an initial 23° to 3°C, and the air temperature decreased from 21° to 3°C. During the final 1 days of the transit (south of 56°S), the wind changed to the north and the seas abated considerably. Transit speed increased accordingly, averaging >10 kt for much of this period. Seawater and air temperatures continued to drop, however, to 0.6° and 0°C, respectively, and snow flurries increased in frequency during the last 1-2 days of the transit. The 2093-nmi transit from Fremantle, Australia, to Site 1135 was accomplished at an average speed of 8.6 kt. The ship arrived on location for the first drill site on 23 December 1998.

At 1145 hr on 23 December 1998, the beacon was deployed on the precise differential Global Positioning System (GPS) coordinates for Site 1135. Using a C-4 core bit, Hole 1135A was spudded with the rotary core barrel (RCB) at 2145 hr 23 December 1998. A good seafloor tag indication was noted by the driller. The depth to the seafloor was 1566.6 m below sea level.

Continuous wireline coring proceeded in homogeneous white foraminifer-bearing nannofossil ooze interspersed with thin chert layers. Recovery in the upper 190.0 m was just under 60%. Recovery continued to drop, however, as the percentage of chert increased and the ooze graded into chalk. Sepiolite mud sweeps every other core were initiated while cutting Core 183-1135A-49R at 458.9 mbsf. While we installed the sinker bars to retrieve Core 183-1135A-49R, the bit jets plugged. Normal circulating pressures were eventually established after working the pipe off bottom with the sinker bars out. Coring proceeded to a total depth (TD) of 2104.0 m (526.0 mbsf) before the hole collapsed while we attempted to recover Core 183-1135A-55R. This was not surprising because the lowermost portion of the hole from 440.0 to 526.0 mbsf contained abundant chert layers. Recovery through this lowermost part of the section was only 11.4%. Summaries of core numbers, depths, and recovery are given in Tables T1 and T2.

After pulling several stands of pipe with 50,000 lb overpull and 600 A of torque, circulation was regained. A wiper trip to bring the top of the 8-in drill collars to the seafloor was then undertaken. There were no problems during the trip back to bottom until tagging fill at 447.7 mbsf, ~78 m above the original TD. After 2.75 hr of reaming and circulating mud pills, attempts to clean out the hole were abandoned. A decision was made to move to an alternate location where sediment cover on top of basement was estimated to be only ~150 m thick.

During operations at Site 1135, several icebergs were identified on radar and observed visually. At times, four to five icebergs were at distances between 10 and 15 nmi. However, no icebergs posed a threat to the drilling operation.

While the drill string was being recovered, both the primary and backup positioning beacons were released and recovered. The ship was secured for transit to Site 1136, a recently approved alternate ~17 nmi to the east. At 2145 hr on 26 December 1998, we were under way in dynamic positioning (DP) mode for Site 1136.