Transit from Site 1257 to Site 1258

The 23.5-nmi transit to Site 1258 was made in 2.5 hr at an average speed of 9.4 kt. As the ship settled on the site's coordinates, a positioning beacon was launched, initiating operations at 1815 hr on 22 January 2003.

Hole 1258A

The same rotary core barrel (RCB) bottom-hole assembly (BHA) used at Site 1257 was deployed, tagging the seafloor at 3203.2 meters below rig floor (mbrf) (3192.2 mbsl). Hole 1258A was spudded at 0015 hr on 23 January, coring from 0 to 322.4 mbsf and recovering 34 cores. While recovering Core 34R, the aft wireline parted from the core barrel at 405 mbrf. Fishing the wireline and core barrel required 3 hr. After cutting 1100 m of damaged wireline, the core barrel was reheaded and placed back in service.

Coring in Hole 1258A resumed from 322.4 to 447.5 mbsf, recovering an additional 16 cores for an average recovery of 83.9% (Table T1). With the depth objective achieved, the hole was filled with sepiolite mud for abandonment and the drill string was retracted. We concluded operations in Hole 1258A when the bit cleared the seafloor at 1010 hr on 25 January.

Hole 1258B

The ship was offset 30 m east of Hole 1258A, and Hole 1258B was spudded at 1245 hr on 25 January. An RCB core (Core 1R) was recovered (0–7.1 mbsf), and the hole was drilled ahead 7 m to 14.l mbsf in an attempt to provide better stratigraphic overlap with Hole 1258A. RCB coring resumed from 14.1 to 349.3 mbsf. Poor recovery in Core 37R (1.1%) and high pump pressures suggested the bit was obstructed, so the bit deplugger was deployed. Cores 38R through 41R were taken to 383.8 mbsf, but no recovery in Core 41R and the return of elevated pump pressures indicated the bit was obstructed again. Two separate deployments of the bit deplugger were conducted. After a return to normal pressures, RCB coring resumed from 383.3 to 460.9 mbsf. We collected a total of 57 cores from Hole 1258B (average recovery = 76.3%) (Table T1). With the depth objective achieved, coring was terminated and the hole displaced with 143 bbl of sepiolite mud. The drill string was pulled back, and the bit cleared the seafloor at 1010 hr on 28 January, ending Hole 1258B.

Hole 1258C

The ship was offset 30 m east of Hole 1258B, and Hole 1258C was spudded at 1145 hr on 28 January and drilled ahead to 120 mbsf. RCB coring commenced at 120 mbsf and advanced to 206.1 mbsf, collecting nine cores. We drilled ahead to 245.3 mbsf, where we resumed coring. After low recovery in Cores 10R and 11R, we suspected the bit was obstructed and the deplugger was deployed. After clearing the bit, coring deepened the hole to 274.2 mbsf. Subsequent drilling ahead to 384.8 mbsf was followed by coring to the depth objective of 485.0 mbsf. A total of 34 cores were taken in Hole 1258C (recovery = 74.9%) (Table T1).

In preparation for logging, the hole was swept with 30 bbl of sepiolite mud, which was followed by a wiper trip. Twenty-five meters of fill was noted on the bottom, prompting a second mud sweep. The bit was released, the hole was displaced with 150 bbl of mud, and the drill string was pulled to 100 mbsf for logging.

The first logging run was made with the triple combination (triple combo) tool string, which was deployed to ~485 mbsf and logged to the base of the drill pipe in two passes. Two more passes were made with just the Multi-Sensor Spectral Gamma Ray Tool (MGT) activated. The second logging run included two passes with the Formation MicroScanner (FMS)-sonic tool string from 485 mbsf to the base of the drill string. After completion of the logging operations, the drill string was retrieved, clearing the rig floor at 0750 hr on 1 February, ending operations at Site 1258. After recovery of the beacon and retraction of the thrusters and hydrophones, the ship began the transit to Site 1259.