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doi:10.2204/iodp.proc.303306.106.2006

Operations

The 103 nmi transit from Site U1305 to Site U1306 (LAB7A) took 11.3 h at an average speed of 9.1 kt. Upon arrival at the site coordinates, the thrusters were lowered and the beacon was deployed at 0130 h on 23 October 2004, officially initiating operations at Site U1306.

Hole U1306A

With the bit positioned at 2280.4 meters below rig floor (mbrf) (8 m shallower than the calculated precision depth recorder depth), Hole U1306A was spudded with the advanced piston corer (APC) at 0910 h. Recovery for Core 1H was 8.3 m, suggesting a seafloor depth of 2270.5 meters below sea level (mbsl) (2281.6 mbrf). A total of 33 piston cores were collected to a total depth of 304.3 mbsf, with an average recovery of 101.2% for the cored interval. Core orientation and use of nonmagnetic core barrels are shown in Table T1. Core 16H was only able to advance 0.5 m (141.3–141.8 mbsf), and the interval from 141.8 to 142.8 mbsf was drilled without coring. Core 29H was the only core barrel that required drillover. After achieving the depth objective, coring was halted and the bit was pulled clear of the seafloor at 1550 h on 24 October 2004, ending operations in Hole U1306A.

Hole U1306B

The ship was offset 30 m east of Hole U1306A, and the bit was positioned 4.5 m shallower than at Hole U1306A. Hole U1306B was initiated at 1710 h on 24 October 2004 with recovery of a 1.36 m core (Core 1H), suggesting a seafloor depth of 2273 mbsl (2284.1 mbrf). Piston coring and drilling advanced the hole to a total depth of 309.3 mbsf, with 103.5% average recovery for the cored interval. The interval from 162.8 to 166.8 mbsf was drilled to maintain appropriate stratigraphic offset with Hole U1306A. Four of the last five core barrels had to be drilled over (Cores 29H and 31H–33H). The bit cleared the seafloor at 0330 h on 26 October, concluding operations in Hole U1306B.

Hole U1306C

After offsetting the vessel 30 m to the east, the bit was positioned 2.5 m deeper than in Hole U1306B. Hole U1306C was spudded at 0500 h on 26 October 2004. Based on recovery of the first core (0.96 m), the seafloor depth was estimated to be 2274.8 mbsl. However, it is unlikely that this is a reasonable estimate because the deeper bit position should have produced a longer first core than in Hole U1306B. Piston coring and drilling advanced Hole U1306C to a total depth of 256.0 mbsf. Recovery in the cored section averaged 103.8%. In addition to coring, two intervals were drilled (20.0–24.0 and 223.5–227.5 mbsf) to adjust stratigraphic overlap with the previous holes. Operations officially concluded when the bit cleared the seafloor at 0800 h on 27 October.

Hole U1306D

The ship was offset 30 m east of Hole U1306C, and Hole U1306D was initiated at 0910 h on 27 October 2004. The recovery of the initial core was 7.06 m, suggesting a seafloor depth of 2271.8 mbsl (2282.9 mbrf). Piston coring and drilling advanced the hole to a total depth of 180.0 mbsf, when coring was terminated after necessary stratigraphic overlap was achieved. Average recovery was 100.9% for the cored section. The interval from 83.0 to 85.0 mbsf was drilled to adjust overlap with previous holes.

Our original plan was to depart the Eirik Drift area for proposed Site IRD1A (Site U1308). However, a low-pressure system centered southeast of Newfoundland was moving slowly northeastward and was forecast to pass through the transit area and Site IRD1A location. As a result, we opted to core at nearby alternate Eirik Drift Site LAB8C and wait for a weather window to open that would allow a safe voyage to Site IRD1A. After retrieving the drill string and securing the vessel for transit, we departed Site U1306 at 0830 h on 28 October.

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