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doi:10.2204/iodp.proc.329.104.2011

Operations

Transit to Site U1366

After a 48.85 h transit from Site U1365, covering 494 nmi and averaging 10.1 kt, the speed was reduced and thrusters and hydrophones were lowered. Speed was less than expected because two of the propulsion motors on the starboard shaft were offline with failed field coils. Dynamic positioning was initiated over Site U1366 at 2215 h on 29 October 2010. The position reference was a combination of GPS signals. No acoustic beacon was deployed, but a beacon remained on standby in the event of loss of GPS satellite coverage. Although automatic input into the dynamic positioning system was not possible, it was possible to manually hold the vessel in position to clear the seafloor with the bottom-hole assembly, if necessary.

All times in this section are given in local ship time unless otherwise noted. For most of the expedition, local time was Universal Time Coordinated –10 h.

Site U1366

Six holes were drilled or cored at this site (Table T1). The first hole was a washdown hole drilled with the center bit in order to establish the sediment depth. The next five holes were cored and drilled with the advanced piston corer (APC) system. Perfluorocarbon tracer (PFT) was continuously injected into the drilling fluid for all coring of Holes U1366B–U1366F. The advanced piston corer temperature tool was not deployed because the sediment thickness was only ~20 m. APC system recovery for Site U1366 was 100.6%. Extended core barrel (XCB) recovery was 0%. A total of 14 cores were attempted after coring 97.9 m. The total length of core recovered from this site was 96.45 m, for a recovery of 98.5%.

Hole U1366A

Rig floor operations commenced at 2215 h on 29 October 2010. The trip to the seafloor was uneventful. The top drive was picked up, and the drill string was spaced out and spudded at 0815 h. The PFT pump was turned on to distribute PFT evenly throughout the fluid in the drill string. The washdown hole was drilled to determine depth of basement. Mudline was established at 5146.0 meters below rig floor (mbrf) by tagging with the bit. After drilling down, basement was established at 17.8 meters below seafloor (mbsf). The bit was pulled back, clearing the seafloor at 0845 h and ending Hole U1366A.

Hole U1366B

After clearing the seafloor, the center bit was pulled by wireline, the vessel was offset 20 m west, and the drill string was spaced out to spud Hole U1366B. After making up the first APC core barrel, the core barrel was run to bottom on the wireline and Hole U1366B was spudded at 1045 h on 30 October. Seafloor depth was established with a mudline core at 5141.8 mbrf. APC coring continued to 17.2 mbsf. Two cores were taken with a total recovery of 17.31 m (100.6% recovery). After Core 329-U1366B-2H, the bit was tripped back to just above the seafloor, ending Hole U1366B at 1300 h on 30 October.

Hole U1366C

Hole U1366C began at 1300 h when the APC assembly cleared the seafloor after completing Hole U1366B. After offsetting the vessel 20 m north, Hole U1366C was spudded at 1345 h on 30 October and advanced with the APC system to 25 mbsf before encountering basement. Seafloor was established at 5140.5 mbrf. Three cores were taken with a total recovery of 25.42 m (101.7% recovery). The drill string was then tripped to just above the mudline, clearing the seafloor at 1715 h on 30 October and ending Hole U1366C.

Hole U1366D

Hole U1366D began at 1715 h when the APC assembly cleared the seafloor after completing Hole U1366C. After offsetting the vessel 20 m east, Hole U1366D was spudded at 1800 h on 30 October and advanced with the APC system for three cores to 18.9 mbsf, with an 18.86 m recovery (99.8% recovery). Seafloor was established at 5137.1 mbrf. After APC refusal, an XCB system was deployed and advanced 2 m into the formation without any recovery. After the last core, the drill string was tripped to just above the mudline, clearing the seafloor at 2330 h on 30 October and ending Hole U1366D.

Hole U1366E

After clearing the seafloor, the vessel was offset 40 m west and the drill string was spaced out to spud Hole U1366E. After making up the first APC core barrel, the core barrel was run to bottom on the wireline and Hole U1366E was spudded at 0015 h on 31 October. Seafloor depth was established with a mudline core at 5138.8 mbrf. APC coring consisted of a single mudline core to 4.7 mbsf. One core was taken with a total recovery of 4.71 m (100.2% recovery). Core 329-U1366E-1H was recovered with a shattered liner and was not acceptable for microbiology. Hole U1366E ended with the first APC core at 0015 h on 31 October.

Hole U1366F

Hole U1366F began at 0015 h after the mudline core of Hole U1366E was completed. After offsetting the vessel 20 m west, Hole U1366F was spudded at 0130 h on 31 October and advanced with the APC coring system for four cores to 30.1 mbsf with a 30.15 m recovery. Overall recovery in Hole U1366F was 100.2%. After the last core, the drill string was tripped to surface and all drilling equipment was secured at 1815 h on 31 October, ending Hole U1366F and beginning the 1019 nmi transit to the next site.