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doi:10.2204/iodp.proc.341.105.2014

Operations

Transit to Site U1419

After a 47 nmi transit from Site U1418 averaging 9.9 kt, the vessel arrived at the third expedition site. The vessel stabilized over Site U1419 at 2118 h (UTC – 8 h) on 9 July 2013, and the positioning beacon was deployed at 2135 h. The position reference was a combination of GPS signals and a single acoustic beacon.

Site U1419

Site U1419 consists of five holes (Table T1), ranging in depth from 98.7 to 193.0 m drillers depth below seafloor (DSF) (Fig. F5). A total of 101 cores were recovered for the site. The interval cored with the advanced piston corer (APC) system was 517.9 m, with 473.0 m recovered (91%). The interval cored with the extended core barrel (XCB) system was 74.4 m, with 14.86 m recovered (20%). The overall recovery for Site U1419 was 82%. Total time spent on Site U1419 was 4.1 days.

Hole U1419A

Hole U1419A was spudded at 0200 h on 10 July 2013. A mudline core (341-U1419A-1H) recovered 7.43 m of sediment, and seafloor was calculated to be at 687.4 meters below sea level (mbsl). Nonmagnetic core barrels and the APC system were used for Cores 1H through 12H. APC coring with wireline continued through Core 20H with the half APC coring system using steel core barrels. Partial APC strokes were recorded on Cores 5H, 8H, 9H, 11H through 13H, 15H, and 17H through 20H. APC core recovery was affected by frequently encountered large clasts. The XCB system was deployed with a soft-formation cutting shoe for Cores 21X through 29X to 193.0 m DSF. Hole U1419A was terminated after Core 29X at 0235 h on 11 July. At the conclusion of coring, the hole was plugged with 85 bbl of 10.5 ppg mud and then abandoned. The top drive was set back, and the drill string was pulled from the hole. A total of 20 APC cores were taken over a 118.6 m interval, with 96.38 m recovered (81%). A total of nine XCB cores were cut over a 74.4 m interval, with 14.86 m recovered (20%). The overall recovery for Hole U1419A was 111.24 m for the 193.0 m cored interval (58%). Total time spent on Hole U1419A was 30.5 h.

Hole U1419B

After clearing the seafloor, the vessel was offset 20 m east of Hole U1419A. Hole U1419B was spudded at 0530 h on 11 July 2013. The mudline core recovered 8.53 m of sediment, and seafloor was calculated to be at 687.1 mbsl. Nonmagnetic core barrels were used and FlexIT orientation was performed for Cores 341-U1418B-1H through 10H. After Core 10H, the half APC system was deployed. The hole was advanced from Core 11H through Core 19H to 114.0 m DSF. A 1 m interval was drilled without coring from 109.6 to 110.6 m DSF. Partial strokes of the coring systems occurred on Cores 6H, 8H through 10H, 13H, 17H, and 19H. APC recovery was affected by frequently encountered large clasts. Coring in Hole U1419B was terminated at 114.0 m DSF at 1740 h on 11 July. The hole was displaced with 48 bbl of 10.5 ppg mud, and the drill string was tripped from the hole with the top drive installed. The seafloor was cleared at 1940 h on 11 July, ending Hole U1419B. A total of 18 APC cores were taken over a 113.0 m interval, with 99.05 m recovered (88%). Total time spent on Hole U1419B was 15.9 h.

Hole U1419C

After clearing the seafloor, the vessel was offset 20 m south of Hole U1419B. The bit was then spaced out and lowered to the first shot depth, and Hole U1419C was spudded at 2100 h on 11 July 2013. An offset water depth of 685.8 mbsl (tide corrected) was used after averaging the tide-corrected water depths from the two previous holes. Hole U1419C was washed down to 2.0 m DSF, and coring with nonmagnetic core barrels took place for Cores 341-U1419C-2H through 11H (2.0–78.7 m DSF). Partial strokes were recorded on Cores 5H, 7H, 9H, 10H, 14H through 17H, and 19H. The Core Barrel–Drill String Acceleration Tool was run on Cores 2H through 10H as an extension on the APC/XCB core barrel between 2020 h on 11 July and 0450 h on 12 July in order to record drill bit acceleration and vibration signals during drilling. However, the tool malfunctioned downhole, and only ~30 min of reasonable data were recorded. Upon recovery, it was discovered that several supporting screws in the tool were broken, and it seems likely that excessive internal vibration led to small cracks in the sensors, producing intermittent tool response. Cores 11H through 20H (78.7–109.1 m DSF) were recovered using the half APC system. APC recovery was affected by frequently encountered large clasts. Hole U1419C was terminated at 1230 h on 12 July. The hole was displaced with 43 bbl of 10.5 ppg mud, and the drill string was tripped from the hole with the top drive installed. The seafloor was cleared at 1425 h on 12 July, ending Hole U1419C. A total of 19 APC cores were taken over a 107.1 m interval, with 100.37 m recovered (94%). Total time spent on Hole U1419C was 18.8 h.

Hole U1419D

After clearing the seafloor, the vessel was offset 40 m west of Hole U1419C. The bit was then spaced out and lowered to the first shot depth, and Hole U1419D was spudded at 1720 h on 12 July 2013. An offset water depth of 687.5 mbsl (tide corrected) was used after averaging the tide-corrected water depths from the first two holes at the site. After spudding Hole U1419D, the hole was washed down to 5.5 m DSF and Cores 341-U1419D-2H through 14H were recovered from 5.5 to 80.1 m DSF. Partial strokes were recorded on Cores 6H, 8H, 9H, 11H, 12H, 14H, 17H, 21H, 23H, and 24H. After Core 14H, the half APC coring system was deployed, and coring continued through Core 24H to 114.2 m DSF. The hole was displaced with 40 bbl of 10.5 ppg mud, and the drill string was tripped from the hole with the top drive installed. The seafloor was cleared at 0810 h on 13 July, ending Hole U1419D. A total of 20 APC cores were taken over a 103.7 m interval, with 105.10 m recovered (101%). Three intervals were drilled without coring, which added up to 10.5 m. Total time spent on Hole U1419D was 17.75 h.

Hole U1419E

After clearing the seafloor, the vessel was offset 20 m north of Hole U1419D. An offset water depth of 685.5 mbsl (tide corrected) was used after averaging the tide-corrected water depths from the first two holes at the site. Hole U1419E was spudded at 0900 h on 13 July 2013 and washed down to 9.0 m DSF. Cores 341-U1419E-2H through 12H were recovered from 9.0 to 69.0 m DSF. Partial strokes were recorded on Cores 4H, 6H, 8H, 9H, 11H, 12H, 18H, and 19H. After Core 12H, the half APC coring system was deployed, and coring continued through Core 19H to 98.7 m DSF. Coring was terminated at 1900 h on 13 July. The hole was displaced with 38 bbl of 10.5 ppg mud, the drill string was tripped back to 46.4 m DSF, and the top drive was set back. The drill string was then tripped back to the surface, and the bottom-hole assembly was set back in the derrick. The bit cleared the rotary table at 2315 h, the drill floor was secured, and the thrusters were secured for transit at 0030 h on 14 July, ending Hole U1419E and Site U1419. A total of 15 APC cores were taken over a 75.5 m interval with 72.1 m recovered (95.5%). Four intervals were drilled without coring, with a combined length of 23.2 m. Total time spent on Hole U1419E was 16.25 h.

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