The PDR indicated a seafloor depth of 3016.8 mbsl (3028.4 mbrf). Based on the correlation between the previous PDR measurements and the drilling depth as determined via drill-pipe measurement, the bit was lowered to 3018.4 mbsl (3030 mbrf). Hole 1176A was spudded at 1305 hr on 26 June. In Core 1H, 7.41 m of sediment was recovered, indicating a seafloor depth determined by drill-pipe measurement of 3020.5 mbsl (3032.1 mbrf). The hole was cored with the APC from the seafloor to 170.6 mbsf (3202.7 mbrf), where the overpull had increased to 60,000 lb while we retrieved Core 19H. A considerable amount of sand was encountered in the hole, and a 6.1 m section of sand (from 115.3 to 121.4 mbsf; 3147.4 to 3153.5 mbrf) was drilled ahead without coring. Nineteen APC cores were taken that penetrated 164.5 m of section and recovered 151.43 m of sediment (92%).
The XCB coring system was then used to core from 170.6 to 449.6 mbsf (3202.7 to 3481.7 mbrf). A total of 29 XCB cores were taken, coring 279.0 m and recovering 74.82 m (27%). Sand was encountered virtually throughout the entire borehole. The scientists decided to terminate the hole because the extensive sands prevented the primary objectives of the hole to be achieved.
The bit was pulled out of the hole and cleared the seafloor at 0745 hr on 29 June. The seafloor positioning beacon was released at 0845 hr and sighted on the surface at 0925 hr. At this time, however, the current was ~2.8 nmi/hr and there were also 15-kt winds, so the beacon was swept away from the ship before it could be recovered. The pipe trip continued and the bit cleared the rotary table at 1345 hr, ending Hole 1176A and operations at Site 1176. Once the bit was back on board, the ship began the transit to Site 1177 in dynamic positioning mode.
Operations Synopsis: Site 1177 | Table of Contents