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doi:10.2204/iodp.proc.320321.105.2010

Operations

Unless otherwise noted, times are local ship time, which was Hawaii Standard Time (UTC – 10 h) for Site U1333.

Transit to Site U1333

The 176 nmi voyage to Site U1333 took 18.3 h and was accomplished at an average speed of 9.6 kt. The journey required a little more than the allotted time because the speed was adversely affected by having to sail into a 22–26 kt wind and a strong current.

Site U1333

Hole U1333A

At 1400 h on 30 March 2009, the vessel began positioning over the site in dynamic positioning (DP) mode. Once the drilling assembly was deployed, the driller carefully lowered the bit and tagged the seafloor at ~4875 m drilling depth below rig floor (DRF). The bit was raised 10 m, and Hole U1333A was spudded at 1225 h on 31 March. The seafloor depth calculated from the recovery of the first core was 4865.0 m DRF (4853.7 mbsl) (Table T1); however, this depth measurement is questionable because the recovery was a full core (10.05 m).

APC Cores 320-U1333C-1H through 10H were taken from 0 to 95.0 m DSF, and we recovered 104 m (109%) (Table T1). We switched to XCB coring after the core barrel for Core 10H had to be drilled over to free the fully stroked core barrel from the sediment. All APC cores were obtained with nonmagnetic core barrels; the FlexIt orientation tool was not deployed since there were questions about its data reliability.

XCB Cores 11X through 22X penetrated from 95.0 to 184.1 m DSF, and we recovered 77.0 m (87%). Coring ended when we recovered basalt in Core 22X. The drill string was pulled out of the hole and cleared the seafloor at 1155 h on 1 April.

Hole U1333B

The vessel was offset 25 m east of Hole U1333A, and APC coring in Hole U1333B started at 1305 h on 1 April with the bit 5 m shallower than the first hole. We recovered 7.7 m in Core 1H, so the seafloor was established at 4861.8 DRF (4850.5 mbsl).

Based on drilling and coring data from the first hole, the drillers were confident that by drilling over stuck core barrels, the APC could safely be pushed deeper than the 95.0 m penetration that was realized in the first hole. This confidence was justified when APC Cores 1H through 18H were advanced to 162.7 m DSF and we recovered 166.4 m (102%). Nonmagnetic core barrels were used on Cores 1H through 9H, and standard steel core barrels were deployed on all subsequent piston cores. Formation temperature measurements were made with the APCT-3 tool at 26.7, 45.7, 64.7, and 83.7 m DSF (Cores 3H, 5H, 7H, and 9H, respectively). The FlexIt orientation tool was not used. Three stuck core barrels (Cores 13H, 16H, and 17H) required drilling over when they could not be released from the sediment despite 70,000 lb of overpull. Core 18H failed to achieve a full stroke of the core barrel, and no further APC coring was conducted.

Two XCB cores advanced the hole from 162.7 to the final depth of 180.3 m DSF, and we recovered 13.44 m (76%). Coring ended when we recovered basalt in Core 20X. The drill string was pulled out of the hole and cleared the seafloor at 1845 h on 2 April.

Hole U1333C

Hole U1333C was started 25 m east of and 2.75 m shallower than Hole U1333B. Core 320-U1333C-1H was shot at 2000 h on 2 April and we recovered 1.65 m, so the water depth for this hole is 4865.1 m DRF (4853.8 mbsl).

Cores 1H through 21H penetrated from 0 to 163.2 m DSF, and we recovered 176.1 m (108%). Seven core barrels (Cores 13H through 19H) required drilling over to release the barrels from the sediment when the application of 70,000 lb of overpull was not successful. Nonmagnetic core barrels were used on Cores 1H through 13H. Standard steel core barrels were used on all subsequent APC cores. The advancement of four cores was adjusted to maintain the overlap with previous holes: Cores 11H (6.0 m advance), 12H (5.0 m advance), 16H (4.5 m advance), and 19H (4.0 m advance). All other cores advanced the full 9.5 m except for Core 21H, which did not penetrate into the formation at all. We subsequently switched to XCB coring.

XCB Cores 22X through 24X penetrated from 163.0 to 177.0 m DSF, and we recovered 0.87 m (6%). Coring in this hole ended when we recovered basaltic basement in the last core.

Once the seafloor beacon was recovered on board, the drill string recovered on the rig floor, the thrusters raised, and the drilling equipment secured, the vessel departed for the Site U1334 at 1815 h on 4 April.

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