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SITE 1154

Transit to Site 1154
The 124-nmi transit to Site 1154 took 11.5 hr at an average speed of 11 kt. At 0115 hr on 2 December, the vessel slowed to 6 kt for a SCS and 3.5-kHz survey over the site. These data indicated a similar sediment thickness as we penetrated at Site 1153 (~200 m).

Hole 1154A
After the survey we deployed a beacon on GPS coordinates ~450 m southwest of our prospectus coordinates, closer to the center of a localized sediment pond. Water depth at this site obtained by PDR was 5747.4 m. A nine-collar BHA was made up of a C-7 four-cone rotary bit, a mechanical bit release, a head sub, an outer core barrel, a top sub, a head sub, seven 8 1/4-in drill collars, one tapered drill collar, six 5 1/2-in drill pipes, and one crossover sub.

We spudded Hole 1154A with the RCB at 1235 hr on 2 December. We washed ahead to 233.2 mbsf before we encountered a hard contact, presumed to be igneous basement. Rotary coring advanced the hole from 233.2 to 267.6 mbsf, with an average recovery of 27%. In an effort to increase recovery, we retrieved core barrels after advancing an average of 4.5 m. Plastic bags containing fluorescent microspheres used as microbiological tracers were deployed on Cores 187-1154A-3R, 6R, and 9R.

Coring was terminated at 34.4 m into basement. The total drill string length at this depth was 6015 m, representing a static hook load of 675,000 lb. While advancing Core 9R, the driller noted evidence of deteriorating hole conditions. As we had recovered adequate material to meet our scientific objectives, we decided to abandon Site 1154. On 4 December the bit cleared the seafloor at 1215 hr and cleared the rotary table at 1445 hr. The vessel was under way to the next site by 2130 hr.

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