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doi:10.2204/iodp.proc.323.106.2011

Operations

Four holes were drilled at Site U1342 (Table T1). The first was cored using the advanced piston corer (APC) system to refusal. When refusal was met early, the extended core barrel (XCB) system was deployed to confirm formation material. The XCB recovered 0.5 m of basalt, effectively ending Hole U1342A. The second hole (U1342B) was dedicated to microbiology. Hole U1342C was cored with the APC system to 45.4 m drilling depth below seafloor (DSF), and Hole U1342D was APC cored to 44.0 m DSF. At that point, a center bit was dropped and the hole was drilled ahead 18.6 m to determine if the basalt was continuous. At a drilling break, the XCB system was deployed and used to take 13 cores of hard rock to the total hole depth of 127.7 m DSF. A complete set of site-specific tide tables was provided by the science party for Site U1342. These tables were used to make adjustments relative to initial mudline core and for each successive core in each hole. APC coring totaled 182 m penetrated, with 194.11 m recovered (a core recovery of 106.7%). XCB coring for Site U1342 totaled 66.1 m penetrated, with 41.54 m recovered (62.8% core recovery). The total cored interval was 248.1 m, with 235.65 m of core recovered, for a 95% total core recovery. The time spent at Site U1342 was 33.25 h (1.4 days).

Hole U1342A

Hole U1342A was spudded at 1320 h on 3 August 2009 (all times are ship local time, Universal Time Coordinated [UTC] – 11 h). The first APC barrel recovered 1.8 m of sediment, and an official seafloor depth was established at 829.7 m drilling depth below rig floor (DRF). APC coring continued through Core 323-U1342A-8H to 49.3 m DSF. Coring with the APC system was suspended after two successive short, incomplete strokes of the core barrel and apparent refusal. Three meters of hole was then drilled without coring with the APC/XCB bit, and the XCB system was deployed for a short core (1 m) to identify the material at APC refusal. Basalt was recovered and Hole U1342A was terminated. Overall core recovery for Hole U1342A using the APC coring system was 115.5%, with 56.93 m recovered. Core recovery using the XCB coring system was 46%, with 0.46 m recovered.

Hole U1342B

The vessel was offset 20 m east of Hole U1342A, and Hole U1342B was spudded at 2315 h on 3 August. The barrel recovered 5.33 m of core, and an official seafloor depth was established at 830.4 m DRF. APC coring continued through Core 323-U1342B-5H to 43.3 m DSF.

Hole U1342C

The vessel was offset 20 m east of Hole U1342B, and Hole U1342C was spudded at 0235 h on 4 August. The first APC barrel recovered 7.2 m of core, and an official seafloor depth was established at 830.3 m DRF. APC coring continued through Core 323-U1342C-6H to refusal. Overall core recovery for Hole U1342C using the APC coring system was 103.7%, with 47.06 m recovered.

Hole U1342D

The vessel was offset 20 m east of Hole U1342C, and Hole U1342D was spudded at 0830 h on 4 August. The first APC barrel recovered 6.0 m of core, and an official seafloor depth was established at 829.7 m DRF. APC coring continued through Core 323-U1342D-5H to 44.0 m DSF. On reaching refusal, the center bit was dropped and the hole was drilled ahead 18.6 m to see if there were sediments under the layer of hard rock (basalt). After a drilling break was observed, the XCB coring system was deployed and used successfully to core an additional 65.10 m into the formation. Overall core recovery for Hole U1342D using the APC coring system was 102.9%, with 45.29 m recovered. The XCB coring system recovered 41.08 m, for 63.1% core recovery.

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