OPERATIONS

SITE 1076
(Proposed Site LCB-4)

Hole 1076A
The 64-nmi voyage from Site 1075 to Site 1076 was accomplished at an average speed of 11.4 kt. As the vessel slowly approached the location using global positioning system (GPS) coordinates, the beacon was deployed at 2338 hr on 26 August. At 0440 hr on 27 August, the bit was positioned at 1411.0 mbrf, where Hole 1076A was spudded at 0440 hr on 27 August. The seafloor depth was established at 1415.7 mbrf DPM. APC Cores 175-1076-1H through 22H were taken from 0 to 204.3 mbsf, with 204.3 m cored and 217.5 m recovered (106.3% recovery). Cores were oriented starting with 3H. The Adara temperature tool heat-flow shoe was deployed at Cores 3H (23.8 mbsf), 5H (42.8 mbsf), 8H (71.3 mbsf), and 11H (99.8 mbsf). The calculated heat-flow gradient is 44.7šC/km. Headspace analysis of the cores indicate the presence of biogenic methane with minute amounts of ethane (less than 28 ppm) and no discernable amounts of heavier hydrocarbons. The methane concentration peaked at 66 mbsf (69,000 ppm) and gradually tapered off with depth. Although some of the core exuded a mild sulphurous smell, any concentration of H2S was below 1 ppm and could not be measured. The drill string was pulled back with the bit clearing the seafloor at 1830 hr on 27 August, ending Hole 1076A.

Hole 1076B
The vessel was offset 10 m to the east, and Hole 1076B was spudded at 1908 hr on 27 August. The seafloor depth was established at 1413.6 mbrf by DPM. After seven APC cores (0-60.9 mbsf), the hole was abandoned because no core was recovered in Cores 1076B-5H, 6H, and 7H. It was assumed that the bit had reentered the previous hole in the section after recovering Core 4H. The drill string was pulled out of the hole and cleared the seafloor at 2250 hr on 27 August, ending Hole 1076B.

Hole 1076C
The vessel was offset 20 m to the east, and Hole 1076C was spudded at 2325 hr on 27 August. APC Cores 1076C-1H through 22H were taken from 0 to 203.1 mbsf, with 203.1 m cored and 216.8 m recovered (106.8% recovery). Cores were oriented starting with 4H. The drill string was pulled out of the hole with the bit clearing the seafloor at 1155 hr on 28 August.

Hole 1076D
The vessel was offset another 20 m to the east where the fourth and final hole of the site was spudded with the APC at 1230 hr on 28 August. The seafloor depth was established at 1412.5 mbrf by DPM. APC Cores 1076D-1H through 12H were taken from 0 to 113.5 mbsf, with 113.5 m recovered (104.3%). The hole was aborted before the initial depth objective because of time constraints. The bit cleared the seafloor at 2030 hr on 28 August. While the drill string was being secured, the beacon was released and recovered at 2100 hr on 29 August, ending operations at Site 1076.


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