The 288-nmi voyage to Site 1234 (proposed Site SEPAC-13B) was accomplished in 26.0 hr at an average speed of 11.1 kt. During the early morning hr of 15 April 2002, the captain reduced speed because of heavy fog and the presence of fishing boats in the area. At 0600 hr, the vessel slowed as it approached the location. The 3.5-kHz precision depth recorder (PDR) was used as a final check of the site characteristics, by comparison to precruise survey data. The vessel was on station by 0650 hr on 15 April, and a beacon was deployed.
Hole 1234A was initiated at 1010 hr on 15 April with a shot from 1018.8 meters below rig floor (mbrf). The seafloor depth inferred from the recovery of mudline Core 1H was 1026.6 mbrf, 3.8 m shallower than the corrected PDR depth. Advance piston corer (APC) coring deepened the hole until Core 11H failed to achieve a full stroke at 100.3 meters below seafloor (mbsf). The recovery for the piston-cored interval was 101.1 m, representing an average recovery of 101% (Table T1). Most cores were affected by expanding gas during recovery, resulting in gas voids and growing cores on the catwalk. Holes were drilled into the core liners to relieve some of the gas pressure before cores were processed on the catwalk. Cores were oriented starting with Core 4H. Downhole temperature measurements were taken with the advanced piston corer temperature (APCT) tool (Table T1). Coring continued with the extended core barrel (XCB) system to the target depth of 205.2 mbsf. XCB coring penetrated 104.9 m and recovered 87.94 m. The total results for Hole 1234A were 205.2 m cored and 189.02 m recovered (recovery = 92%) (Table T1). The bit was pulled free of the seafloor at 0145 hr on 16 April.
The vessel was moved 10 m east. Prior to coring, a bottom water temperature measurement was taken with the bit at 1019 mbrf, which, combined with the downhole temperature measurements in Hole 1234A, established a temperature gradient of ~4.2°C/100 m for this site. To obtain the desired stratigraphic overlap with the first hole, the bit was then positioned at 1025 mbrf and Hole 1234B was initiated at 0319 hr. The seafloor depth was 1025.4 mbrf based on the mudline recovered in Core 1H. Piston coring advanced to refusal at 93.8 mbsf. The cores were oriented starting with Core 3H. Of the 93.8 m cored, 97.1 m was recovered. The hole was deepened to 182.4 mbsf with the XCB before coring was completed. The interval from 132.3 to 134.3 mbsf (2 m) was drilled to maintain a stratigraphic overlap with the XCB portion of the first hole. The XCB cored 86.6 m with an average recovery of 84% (Table T1). The results of APC and XCB operations in this hole were 180.4 m cored with an average recovery of 94% (Table T1). The bit was pulled free of the seafloor at 1515 hr on 12 April.
The vessel was offset 10 m east of Hole 1234B. The bit was positioned at a depth of 1027 mbrf in an effort to target remaining coring gaps. Hole 1234C was initiated with the APC at 1548 hr on 16 April. Piston coring advanced to the target depth of 79.1 mbsf. The interval from 39.6 to 41.1 mbsf was drilled. A total of 76.0 m was cored and 76.4 m was recovered (recovery = 101%) (Table T1). The cores were oriented starting with Core 3H. With the completion of this hole, operations at Site 1234 were concluded.
Because the next site was located at ~500 m water depth and only 7 mi east of the present location, it was decided that we would offset the vessel in dynamic positioning mode with the drill string partially deployed and the bit at a depth of 375 mbrf. After the hydrophones were retracted and the beacon was retrieved, the vessel left location at 2300 hr on 16 April.