Previous   |    Next

doi:10.2204/iodp.proc.303306.107.2006

Operations

The 28 nmi transit from Site U1306 to U1307 was accomplished in 3.1 h at an average speed of 9.2 kt. At 0824 h on 28 October 2004, the beacon was deployed initiating operations at Site U1307.

Hole U1307A

With the bit at 2586.4 meters below rig floor (mbrf), Hole U1307A was spudded with the APC at 1425 h on 28 October 2004. The recovery of the initial core was 9.48 m, suggesting an estimated seafloor depth of 2575.1 meters below sea level (mbsl) (2586.4 mbrf). Piston coring and drilling advanced the hole to a total depth of 162.6 mbsf, with an average recovery of 102.5% for the cored interval (Table T1). Core 6H was a partial stroke and only advanced 3 m (47.5–50.5 mbsf) before encountering a hard or debris-rich layer. The interval from 50.5 to 52.5 mbsf was drilled without coring to advance the bit beyond this layer. Core 9H also was a partial stroke that recovered only 2.2 m (71.5–73.7 mbsf), which resulted in drilling the interval from 73.7 to 77.7 mbsf to advance the bit beyond the layer. A total of five cores were advanced by recovery (Cores 6H, 9H, 13H, 15H, and 18H). No core barrels had to be drilled over. The bit clogged prior to Core 19H and required the deployment of the bit deplugger and several coring line round trips before the core could be obtained. Because our strategy at this site was to core until a weather window opened to allow a safe transit to Site U1308, the depth objective was limited by the available operational time and the desire to acquire a complete composite section. Operations in Hole U1307A ended when the bit cleared the seafloor at 1155 h on 29 October.

Hole U1307B

The ship was offset 30 m to the northwest, and Hole U1307B was spudded at 1250 h on 29 October 2004. With the bit positioned 4.5 m shallower than at Hole U1307A, we obtained a 4.83 m core, suggesting a seafloor depth of 2575.3 mbsl (2586.6 mbrf). Piston coring advanced the hole to a total depth of 154.6 mbsf, with an average recovery of 101.5% (Table T1). Unlike in Hole U1307A, only one core (Core 17H) was a partial stroke. Coring was terminated when the passing low-pressure system began to affect drilling operations because of excessive heave. The drill string was recovered and the ship was secured for transit. We departed Site U1307 at 1300 h on 30 October to safely navigate behind the storm, as the weather deteriorated to a Force 8 gale with winds gusting to 40 kt and 5.5 m seas.

Top of page   |    Previous   |    Next