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doi:10.2204/iodp.proc.342.110.2014

Operations

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

Hole U1409A summary

• Latitude: 41°17.7501′N
• Longitude: 49°13.9996′W
• Water depth below sea level (m): 3503.2
• Date started: 1010 h, 16 July 2012
• Date finished: 0550 h, 18 July 2012
• Time on hole (days): 1.8
• Seafloor depth (m drilling depth below rig floor [DRF]): 3514.9
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.70
• Penetration depth (m drilling depth below seafloor [DSF]): 200.1
• Cored interval (m): 200.1
• Recovered length (m): 183.33
• Recovery (%): 92
• Total cores (number): 26
• APC cores (number): 16
• Extended core barrel (XCB) cores (number): 10
• 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: drilling terminated at 200 m penetration because of poor recovery in cherts; objectives met

Hole U1409B summary

• Latitude: 41°17.7493′N
• Longitude: 49°13.9852′W
• Water depth below sea level (m): 3501.0
• Date started: 0550 h, 18 July 2012
• Date finished: 0340 h, 19 July 2012
• Time on hole (days): 0.9
• Seafloor depth (m DRF): 3512.7
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.70
• Penetration depth (m DSF): 170.5
• Cored interval (m): 170.5
• Recovered length (m): 167.09
• Recovery (%): 98
• Total cores (number): 19
• APC cores (number): 14
• XCB cores (number): 5
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: core from seafloor to ~250 m DSF or until science objectives are met
• Result: target shallower than planned; objectives met

Hole U1409C summary

• Latitude: 41°17.7392′N
• Longitude: 49°13.9853′W
• Water depth below sea level (m): 3500.5
• Date started: 0340 h, 19 July 2012
• Date finished: 1515 h, 20 July 2012
• Time on hole (days): 1.5
• Seafloor depth (m DRF): 3512.2
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.75
• Penetration depth (m DSF): 160.8
• Cored interval (m): 160.8
• Recovered length (m): 160.98
• Recovery (%): 100
• Total cores (number): 21
• APC cores (number): 14
• XCB cores (number): 7
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: repeat cored sequence from Hole U1409B
• Result: target reached; objectives met

Description

The vessel arrived at Site U1409 at 1010 h on 16 July 2012 after a 26.3 nmi transit from Site U1408 that took 3.0 h at 8.8 kt. The plan for Site U1409 called for three holes to a depth of ~250 m DSF. In addition, the vibration-isolated television (VIT) camera system was to be deployed and tested for the repairs done after the damage sustained at Site U1403. The test was aborted because of the risks to the camera system from strong ocean currents. Holes U1409A, U1409B, and U1409C were successfully cored to 200.1, 170.5, and 160.8 m DSF, respectively. Overall recovery for Site U1409 was 96.2%. The total time spent at Site U1409 was 101.0 h (4.2 days).

Hole U1409A coring

The pipe trip to the seafloor was interrupted at 2863.3 m DRF to install the VIT with subsea camera system. The plan was to deploy the camera near the seafloor and record the shooting of the APC. After installing the VIT, it was determined that the surface currents posed a serious risk to the equipment, and the VIT frame was pulled back on board. After completing the pipe trip, a 1.07 m long mudline core defined the seafloor depth at 3514.9 m DRF (3503.2 mbsl). Hole U1409A was spudded at 2200 h on 16 July and Cores 342-U1409A-1H through 16H were recovered to 127.0 m DSF using nonmagnetic core barrels and the FlexIT core orientation tool. Core 15H experienced the first partial stroke and the APC was advanced by recovery to Core 16H. The XCB was deployed for Cores 17X through 26X to 200.1 m DSF. The seafloor was cleared at 0550 h on 18 July, ending Hole U1409A. Overall core recovery for Hole U1409A was 183.33 m for the 200.1 m interval cored (91.6% recovery). The total time spent on Hole U1409A was 43.5 h.

Hole U1409B coring

The vessel was offset 20 m east. The mudline recovery was 8.36 m and established the seafloor depth at 3512.7 m DRF (3501.0 mbsl). Hole U1409B was spudded at 0800 h on 18 July and Cores 342-U1409B-1H through 14H were retrieved to 122.5 m DSF using nonmagnetic core barrels and the FlexIT core orientation tool. The XCB was deployed for Cores 15X through 19X to 170.5 m DSF. The seafloor was cleared at 0340 h on 19 July, ending Hole U1409B. The recovery for Hole U1409B was 167.09 m over the 170.5 m cored (98.0% recovery). The total time spent on Hole U1409B was 22.00 h.

Hole U1409C coring

The vessel was offset 20 m south, and Hole U1409C was spudded at 0800 h on 19 July. After the mudline core, which established the seafloor at 3512.2 m DRF (3500.5 mbsl), the wireline blow-out preventer (BOP) was observed to be leaking around one of the bonnets. The top drive had to be set back, and an attempt was made to tighten the leaking connection. The top drive was then reinstalled, and a core barrel was run to bottom to take Core 342-U1409C-2H. The wireline BOP was still leaking, and the top drive had to be set back again. This time the entire BOP bonnet assembly was changed out. The top drive was again reinstalled, and APC coring resumed to Core 14H (124.2 m DSF). Nonmagnetic core barrels were used for all APC cores. Core orientation was not performed on cores from Hole U1409C. XCB coring continued from Core 15X through 21X to the final depth of 160.8 m DSF. The seafloor was cleared at 1315 h on 20 July. The recovery for Hole U1409C was 160.98 m over the 160.8 m cored (100.1% recovery).

The drill string was pulled to ~3200 m DRF and the rig prepared for a transit in dynamic positioning mode to Site U1410. Although the beacon was tracked during its ascent after being released from the seafloor, it was never sighted at the surface because of poor weather conditions and strong surface currents. The drill floor was secured for transit, and the beacon recovery operations concluded at 1515 h on 20 July, ending Hole U1409C. The total time spent on Hole U1409C was 35.50 h.

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