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doi:10.2204/iodp.proc.342.109.2014

Operations

All times are local ship time (UTC – 2.5). See Table T1 for coring summary.

Hole U1408A summary

• Latitude: 41°26.2985′N
• Longitude: 49°47.1483′W
• Water depth below sea level (m): 3021.6
• Date started: 2045 h, 11 July 2012
• Date finished: 1045 h, 13 July 2012
• Time on hole (days): 1.6
• Seafloor depth (m drilling depth below rig floor [DRF]): 3033.2
• Seafloor depth est. method: mudline core
• Rig floor to sea level (m): 11.64
• Penetration depth (m drilling depth below seafloor [DSF]): 246.5
• Cored interval (m): 246.5
• Recovered length (m): 243.92
• Recovery (%): 99
• Total cores (number): 27
• APC cores (number): 20
• Extended core barrel (XCB) cores (number): 7
• Drilling system: 11 inch APC/XCB bit with 136.00 m bottom-hole assembly (BHA)
• Objective: core from seafloor to ~250 m DSF or until science objectives are met
• Result: target reached; objectives met

Hole U1408B summary

• Latitude: 41°26.2989′N
• Longitude: 49°47.1361′W
• Water depth below sea level (m): 3022.1
• Date started: 1045 h, 13 July 2012
• Date finished: 1700 h, 14 July 2012
• Time on hole (days): 1.3
• Seafloor depth (m DRF): 3033.8
• Seafloor depth est. method: mudline core
• Rig floor to sea level (m): 11.69
• Penetration depth (m DSF): 217.5
• Cored interval (m): 214.5
• Recovered length (m): 224.09
• Recovery (%): 104
• Drilled interval (m): 3
• Drilled interval (number): 1
• Total cores (number): 25
• APC cores (number): 17
• XCB cores (number): 8
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: core from seafloor to ~220 m DSF
• Result: target reached; objectives met

Hole U1408C summary

• Latitude: 41°26.2878′N
• Longitude: 49°47.1345′W
• Water depth below sea level (m): 3022.5
• Date started: 1700 h, 14 July 2012
• Date finished: 0715 h, 16 July 2012
• Time on hole (days): 1.6
• Seafloor depth (m DRF): 3034.2
• Seafloor depth est. method: mudline core
• Rig floor to sea level (m): 11.71
• Penetration depth (m DSF): 187.5
• Cored interval (m): 184.5
• Recovered length (m): 181.52
• Recovery (%): 98
• Drilled interval (m): 3
• Drilled interval (number): 1
• Total cores (number): 22
• APC cores (number): 18
• XCB cores (number): 4
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: repeat cored sequence from Hole U1408B
• Result: target reached; objectives met

Description

The vessel arrived at Site U1408 after a 1.46 nmi dynamic positioning move from Site U1407, which took 1.75 h at 0.83 kt. The vessel stabilized over Site U1408 at 2045 h on 11 July 2012. The plan for Site U1408 called for drilling three holes to ~250 m DSF. Holes U1408A, U1408B, and U1408C were successfully cored to 246.5, 217.5, and 187.5 m DSF, respectively. The total time spent at Site U1408 was 106.5 h (4.4 days).

Hole U1408A coring

A mudline core of 4.3 m determined seafloor depth at 3033.2 m DRF (3021.6 mbsl). Hole U1408A was spudded at 2335 h on 11 July, and Cores 342-U1408A-1H through 20H were retrieved using nonmagnetic core barrels and the FlexIT core orientation tool. Core 14H experienced the first partial stroke, and the APC was advanced by recovery to the APC total depth of 182.9 m DSF. The XCB was deployed for Cores 21X through 27X to a final depth of 246.5 m DSF. The seafloor was cleared at 1045 h on 13 July, ending Hole U1408A. Overall core recovery for Hole U1408A was 243.92 m for the 246.5 m interval cored (99.0% recovery). The total time spent on Hole U1408A was 38.00 h.

Hole U1408B coring

The vessel was offset 20 m east. Hole U1408B was spudded at 1230 h on 13 July, and the 6.74 m long mudline core established the seafloor at 3033.8 m DRF (3022.1 mbsl). Cores 342-U1408B-1H through 18H were retrieved using nonmagnetic core barrels and the FlexIT core orientation tool. A 3 m long interval (25.7–28.7 m DSF) was drilled without recovery to optimize coverage of coring gaps in Hole U1408A. Coring was slowed when the FlexIT tool housing sheared at the overshot connection above the core barrel three times in the APC section of Hole U1408B. Total advance including the drilled interval with the APC was 154.5 m. The XCB was deployed for Cores 19X through 26X to a final depth of 217.5 m DSF. The seafloor was cleared at 1700 h on 14 July, ending Hole U1408B. The recovery for Hole U1408B was 224.09 m over the 214.5 m cored (104.5% recovery). The total time spent on Hole U1408B was 30.25 h.

Hole U1408C coring

The vessel was offset 20 m south, and Hole U1408C was spudded at 1905 h on 14 July. Cores 342-U1408C-1H through 19H (0–165.1 m DSF) were retrieved using nonmagnetic core barrels. Core orientation was performed with Cores 6H through 8H. A 3 m long interval (8.8–11.8 m DSF) was drilled without recovery to optimize coverage of coring gaps in the previous holes. Again, the FlexIT tool was held responsible for mechanical trouble, including one mechanical shear at the overshot and one mechanical shear of the APC shear pins. During APC operations, an intermittent electrical fault developed, and coring operations were suspended for 6.5 h while the problem was located and fixed. The XCB was deployed for Cores 20X through 23X to a final depth of 187.5 m DSF. The drill string was pulled to the surface and the drill floor was secured at 0715 h on 16 July, ending Hole U1408C. The vessel began the transit to Site U1409. The recovery for Hole U1408C was 181.52 m over the 184.5 m cored (98.4% recovery). The total time spent on Hole U1408C was 38.25 h.

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