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doi:10.2204/iodp.proc.342.112.2014

Operations

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

Hole U1411A summary

• Latitude: 41°37.0992′N
• Longitude: 48°59.9990′W
• Water depth below sea level (m): 3298.8
• Date started: 1115 h, 25 July 2012
• Date finished: 2320 h, 25 July 2012
• Time on hole (days): 0.5
• Seafloor depth (m drilling depth below rig floor [DRF]): 3310.6
• Seafloor depth estimation method: adopted from Hole U1411B
• Rig floor to sea level (m): 11.78
• Penetration depth (m drilling depth below seafloor [DSF]): 9.5
• Cored interval (m): 9.5
• Recovered length (m): 9.87
• Recovery (%): 104
• Total cores (number): 1
• APC cores (number): 1
• Drilling system: 11 inch advanced piston corer (APC)/extended core barrel (XCB) bit with 136.00 m bottom-hole assembly (BHA)
• Objective: core from seafloor to ~250 meters below seafloor (mbsf) or until science objectives are met
• Result: missed mudline; abandoned Hole U1411A and began Hole U1411B

Hole U1411B summary

• Latitude: 41°37.0993′N
• Longitude: 48°59.9839′W
• Water depth below sea level (m): 3298.8
• Date started: 2320 h, 25 July 2012
• Date finished: 1310 h, 27 July 2012
• Time on hole (days): 1.6
• Seafloor depth (m DRF): 3310.6
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.81
• Penetration depth (m DSF): 254.2
• Cored interval (m): 254.2
• Recovered length (m): 233.94
• Recovery (%): 92
• Total cores (number): 28
• APC cores (number): 20
• XCB cores (number): 8
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: core from seafloor to ~250 mbsf
• Result: target reached; objectives achieved

Hole U1411C summary

• Latitude: 41°37.0890′N
• Longitude: 48°59.9856′W
• Water depth below sea level (m): 3300.18
• Date started: 1310 h, 27 July 2012
• Date finished: 0500 h, 29 July 2012
• Time on hole (days): 1.7
• Seafloor depth (m DRF): 3312.0
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.82
• Penetration depth (m DSF): 223.9
• Cored interval (m): 133.1
• Recovered length (m): 118.62
• Recovery (%): 89
• Drilled interval (m): 90.8
• Drilled interval (number): 1
• Total cores (number): 16
• APC cores (number): 8
• XCB cores (number): 8
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: core from seafloor to ~250 mbsf
• Result: objectives changed after starting hole to advance the hole by drilling to ~100 m DSF and then resume coring operations; at 223.9 mbsf, a medical emergency terminated coring operations

Description

The vessel arrived at Site U1411 at 1115 h on 25 July 2012 after a 19.0 nmi transit from Site U1410 that took 2.0 h at 9.5 kt. The plan for Site U1411 called for three holes to a depth of ~250 m DSF. The first core for Hole U1411A failed to capture the mudline, and the hole was terminated after Core 342-U1411A-1H. The second hole was successfully cored to 254.2 m DSF. The third hole was APC-cored to 9.2 m DSF, advanced by drilling 90.8 m, and then cored to a total depth of 223.9 m DSF. Because of a medical emergency, the decision was made to terminate coring operations rather than coring a further, last hole at this site. Overall recovery for Site U1411 was 91.3%. The total time spent at Site U1411 was 89.75 h (3.7 days).

Hole U1411A coring

After arriving at Site U1411, a short test was performed during the BHA to determine if the APC core barrel was in fact landing on the landing seat in the BHA. During the test, it was discovered that the core barrel was landing prematurely in the modified top sub. It was suspected that premature landing of the APC core barrel on the top sub was responsible for occasional premature partial shearing of APC pins when the FlexIT core orientation tool was deployed during earlier drilling operations. The modified top sub was changed out and the test was performed again to the satisfaction of all concerned.

The remainder of the drill string was tripped to just above mudline and Hole U1411A was spudded at 2320 h on 25 July. Core 342-U1411A-1H was 9.87 m long and therefore did not recover the mudline. Without confirmation of the mudline, it was decided to abandon Hole U1411A. The seafloor and water depths for Hole U1411A were adopted from Hole U1411B (seafloor at 3310.6 m DRF; 3298.8 mbsl). The seafloor was cleared at 2320 h on 25 July, ending Hole U1411A. Overall core recovery for Hole U1411A was 9.87 m for the 9.5 m interval recovered (103.9% recovery). The total time spent on Hole U1411A was 12.00 h.

Hole U1411B coring

The vessel was offset 20 m east. Hole U1411B was spudded at 0035 h on 26 July and recovered a 0.93 m long mudline core, establishing seafloor depth at 3310.6 m DRF (3298.8 mbsl). Cores 342-U1411B-1H through 20H were recovered to 177.4 m DSF using nonmagnetic core barrels and the FlexIt core orientation tool. The XCB was deployed for Cores 21X through 28X to a final depth of 254.2 m DSF. The seafloor was cleared at 1310 h on 27 July, ending Hole U1411B. The recovery for Hole U1411B was 233.94 m over the 254.2 m cored (92.0% recovery). The total time spent on Hole U1411B was 38.00 h.

Hole U1411C coring

The vessel was offset 20 m south. Hole U1411C was spudded at 1505 h on 27 July and recovered a 3.2 m long mudline core, establishing the seafloor depth at 3312.0 m DRF (3300.18 mbsl). Cores 342-U1411C-1H through 2H were recovered to 9.2 m DSF. After Core 2H, the hole was advanced by drilling without coring from 9.2 to 100.0 m DSF in order to save operational time for deeper objectives. After the drilling advance, APC coring continued with Cores 4H through 9H (100.0–152.2 m DSF). All APC cores were oriented with the FlexIt core orientation tool and recovered using nonmagnetic core barrels. The XCB was deployed for Cores 10X through 17X to a final depth of 223.9 m DSF. After recovery of Core 17X, a medical emergency terminated operations. The seafloor was cleared and the vessel was secured for transit at 0500 h on 29 July, ending Hole U1411C. The recovery for Hole U1411C was 118.62 m over the 133.1 m cored (89.1% recovery). The total time spent on Hole U1411C was 39.75 h.

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