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doi:10.2204/iodp.proc.342.108.2014

Operations

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

Hole U1407A summary

• Latitude: 41°25.4993′N
• Longitude: 49°48.7987′W
• Water depth below sea level (m): 3073.13
• Date started: 0800 h, 7 July 2012
• Date finished: 1005 h, 9 July 2012
• Time on hole (days): 2.1
• Seafloor depth (m drilling depth below rig floor [DRF]): 3084.7
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.57
• Penetration depth (m drilling depth below seafloor [DSF]): 308.7
• Cored interval (m): 308.7
• Recovered length (m): 205.64
• Recovery (%): 67
• Total cores (number): 35
• APC cores (number): 15
• Extended core barrel (XCB) cores (number): 20
• 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 exceeded; objectives met

Hole U1407B summary

• Latitude: 41°25.4990′N
• Longitude: 9°48.7840′W
• Water depth below sea level (m): 3073.5
• Date started: 1005 h, 9 July 2012
• Date finished: 1340 h, 10 July 2012
• Time on hole (days): 1.1
• Seafloor depth (m DRF): 3085.1
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.63
• Penetration depth (m DSF): 276.3
• Cored interval (m): 241.3
• Recovered length (m): 234.54
• Recovery (%): 97
• Drilled interval (m): 35
• Drilled interval (number): 2
• Total cores (number): 26
• APC cores (number): 10
• XCB cores (number): 16
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: core from seafloor to ~270 m DSF
• Result: target reached; objectives met

Hole U1407C summary

• Latitude: 41°25.5000′N
• Longitude: 49°48.8137′W
• Water depth below sea level (m): 3075.2
• Date started: 1340 h, 10 July 2012
• Date finished: 1915 h, 12 July 2012
• Time on hole (days): 1.2
• Seafloor depth (m DRF): 3086.8
• Seafloor depth estimation method: mudline core
• Rig floor to sea level (m): 11.64
• Penetration depth (m DSF): 261.6
• Cored interval (m): 237.6
• Recovered length (m): 244.36
• Recovery (%): 103
• Drilled interval (m): 24
• Drilled interval (number): 2
• Total cores (number): 27
• APC cores (number): 10
• XCB cores (number): 17
• Drilling system: 11 inch APC/XCB bit with 136.00 m BHA
• Objective: repeat cored sequence from Hole U1407B
• Result: target reached; objectives met

Description

After a 120 nmi, 11 h transit from Site U1406 at a speed of 10.9 kt, the vessel arrived at Site U1407 at 0800 h on 7 July 2012. The plan for Site U1407 called for drilling three holes to a depth of ~250 m DSF. Holes U1407A, U1407B, and U1407C were successfully cored to 308.7, 276.3, and 261.6 m DSF, respectively, without any significant problems. Recovery was mediocre in the first hole because of weather but improved in the second and third holes. Overall recovery for Site U1407 was 86.9%. The total time spent at Site U1407 was 107.25 h (4.5 days).

Hole U1407A coring

The second attempt at a mudline core recovered 6.81 m, establishing Hole U1407A at 1655 h on 7 July at a seafloor depth of 3084.7 m DRF (3073.1 mbsl). Cores 342-U1407A-1H through 15H were retrieved using nonmagnetic core barrels and the FlexIT core orientation tool. The first partial stroke was experienced with Core 11H, and the APC was advanced by recovery to Core 15H (121.9 m DSF). The XCB was deployed for Cores 16X through 35X to a final depth of 308.7 m DSF. The seafloor was cleared at 1005 h on 9 July, ending Hole U1407A. Overall core recovery for Hole U1407A was 205.64 m for the 308.7 m cored (66.6% recovery). This relatively low APC recovery can most likely be attributed to the high heave and large pitch and roll of the vessel during coring operations as well as low recovery in cherts and reef sediment. The total time spent on Hole U1407A was 50.00 h.

Hole U1407B coring

The vessel was offset 20 m east. Hole U1407B was spudded at 1200 h on 9 July, and an 8.4 m mudline core established the seafloor at 3085.1 m DRF (3073.5 mbsl). Cores 342-U1407B-1H through 11H were recovered using nonmagnetic core barrels and the FlexIT core orientation tool. A 3 m interval (27.4–30.4 m DSF) was drilled without coring in an attempt to cover a coring gap in Hole U1407A. Based on the poor recovery of an interval of chert layers in Hole U1407A, the interval from 95 to 127 m DSF was drilled without coring using the XCB. Cores 13X through 28X were then recovered to a final depth of 276.3 m DSF. The seafloor was cleared at 1340 h on 10 July, ending Hole U1407B. The recovery for Hole U1407B was 234.54 m over the 241.3 m cored (97% recovery). The total time spent on Hole U1407B was 27.75 h.

Hole U1407C coring

The vessel was offset 40 m west. Hole U1407C was spudded at 1510 h on 10 July, and a 7.7 m mudline core established the seafloor at 3086.8 m DRF (3075.2 mbsl). Cores 342-U1407C-1H through 11H (0–93.0 m DSF) were recovered using nonmagnetic core barrels. No core orientation was performed in Hole U1407C. A 3 m interval was drilled without coring to optimize core overlap in multiple holes. Once again, a 21 m interval (96–117 m DSF) was drilled without coring through the chert layers using the XCB. Cores 13X through 29X were then recovered to a final depth of 261.6 m DSF. The seafloor was cleared at 1805 h on 11 July. The drill string was pulled up to 2792 m DRF, and the rig was secured for a dynamic positioning move to the next site at 1915 h on 11 July, ending Hole U1407C. Overall recovery for Hole U1407C was 244.4 m from the 237.6 m interval cored (103% recovery). The total time spent on Hole U1407C was 29.5 h.

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