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doi:10.2204/iodp.proc.320321.106.2010

Operations

Transit to Site U1334

The 410 nmi voyage from Site U1333 to Site U1334 took 40.8 h and was accomplished at an average speed of 10.1 kt. During the transit the ship's clocks were advanced 1 h, resetting local ship time to more closely follow the earlier rising sun as we migrated eastward to each site. Times for Site U1334 are given in ship local time (UTC – 9 h).

Site U1334

Hole U1334A

Once the vessel approached the coordinates of the new location, the captain slowed the vessel and maneuvered the vessel over the site. We were positioning over the new location by 1222 h on 6 April 2009. After assembling the drill string and lowering it to the seafloor, we attempted to spud the new site with the bit positioned 10 m shallower than the corrected depth of 4798.4 m drilling depth below rig floor (DRF) (4787.0 mbsl) from the precision depth recorder (PDR). We recovered only water, so the bit was lowered to 4798 m DRF for a second attempt. This was successful, and Hole U1334A was spudded with the APC at 0030 h on 7 April. The mudline recovered in Core 1H was used to establish the seafloor depth as 4799.3 m DRF (4787.9 mbsl) (Table T1). This depth was within 1 m of the corrected PDR depth.

APC Cores 1H through 22H were taken from 0 to 206.9 m DSF, and we recovered 212.39 m (103%) (Table T1). APC coring was terminated when Core 22H did not stroke fully and required 80,000 lb to release it from the formation. Nonmagnetic core barrels were used on Cores 1H through 16H; standard steel core barrels were used on Cores 17H through 22H.

XCB Cores 23X through 32X were taken from 206.9 to 285.5 m DSF, and we recovered 77.99 m (99%). Coring was terminated when we recovered basalt in Core 32X. The total cored interval for Hole U1334A was 285.5 m, and we recovered 288.83 m (102%). The drill string was pulled out of the hole and cleared the seafloor at 2150 h on 8 April.

Hole U1334B

The ship was offset 25 m west of Hole U1334A, and we spudded Hole U1334B at 2330 h on 8 April 2009 with the bit 5 m deeper than at the first hole. APC Cores 1H through 22H were taken from 3.7 to 210.7 m DSF, and we recovered 218.43 m (105%). Nonmagnetic core barrels were used on Cores 1H through 15H, and standard steel barrels were used on Cores 16H through 22H. Downhole temperature measurements were obtained at 32.2, 49.2, 68.2, 87.2, and 106.2 m DSF (Cores 3H, 5H, 7H, 9H, and 11H, respectively). Core 5H was advanced 7.5 m to maintain an ~5 m vertical offset with Hole U1334A.

XCB Cores 23X through 31X were taken from 207.0 to 281.7 m DSF, and we recovered 76.84 m (103%). We stopped coring when we recovered basalt in Core 31X. We pulled the drill string out of the hole and the bit cleared the seafloor at 1840 h on 10 April.

Hole U1334C

After the ship was offset 25 m west of Hole U1334B, Hole U1334C was spudded at 2020 h on 10 April 2009 with the bit 3 m deeper than Hole U1334A. APC Cores 1H through 22H penetrated from 0 to 209.0 m DSF, and we recovered 213.0 m (102%). Nonmagnetic core barrels were used on Cores 1H through 15H; Cores 16H through 22H used standard steel barrels. We had to drillover Cores 19H, 21H, and 22H to release them from the formation. We then switched to XCB coring. Cores 23X through 33X were taken from 209.0 to 280.7 m DSF, and we recovered 72.9 m (102%). Core 26X was advanced by 6 m to maintain stratigraphic overlap with the first two holes. Coring finished when limestone including basalt clasts was recovered in the last core. Cores from Hole U1334C successfully covered the stratigraphic gaps in the first two holes.

Our final operations planned for Hole U1334C were to conduct two downhole logging runs. We circulated the hole with 50 bbl of attapulgite mud and then displaced the hole with 100 bbl of attapulgite mud. We raised the bit up to 95 m DSF and rigged up for logging. The first tool string was assembled and deployed into the pipe at 1930 h on 12 April. While lowering the logging tool string into the hole, the transmission on the logging winch failed when the tool was ~1700 m below the rig floor. We started to manually retrieve the tool string using T-bar clamps, air tuggers, and the starboard crane. After recovering ~550 m of wireline and spooling it back onto the logging winch drum, we decided to retrieve the remaining logging wireline by spooling the logging wireline onto the core winch drum. The logging tool was back on the rig floor at ~1200 h on 13 April. No more logging could be conducted during Expedition 320.

We started pulling the drill string out of the hole and the bit cleared the seafloor at 1225 h on 13 April. After the drill string was recovered and the thrusters retracted, we began the transit for Site U1335 at 2200 h on 13 April.

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