The 40-nmi voyage from Site 1076 to Site 1077 was accomplished at an average speed of 12.5 kt. As the vessel slowly approached the location using Global Positioning System coordinates, the beacon was deployed at 0534 hr on 29 August. Following an unsuccessful attempt at a mudline core from 2385.0 meters below rig floor (mbrf), the bit was positioned at 2387.0 mbrf, where Hole 1077A was spudded at 1210 hr on 29 August. The seafloor depth was established at 2380 (mbsl) by drill-pipe measurement (DPM). Advanced hydraulic piston corer (APC) Cores 175-1077A-1H through 22H were taken from 0 to 204.5 meters below seafloor (mbsf; Table 1; also see the expanded coring summary table on CD-ROM, back pocket, this volume), with 204.5 m cored and 209.5 m recovered (102.2% recovery). Cores were oriented starting with Core 4H. The Adara heat-flow shoe was deployed at Cores 5H (43.0 mbsf), 7H (62.0 mbsf), 10H (90.5 mbsf), and 13H (119.0 mbsf). Headspace analysis of the cores indicates the presence of biogenic methane with insignificant amounts of ethane (<10 ppm) and no discernible amounts of heavier hydrocarbons. The methane concentration peaked at 57 mbsf (54,717 ppm) and gradually tapered off with depth with another peak at 152 mbsf (44, 860 ppm). Although some of the core exuded a mild sulfurous smell, concentrations of hydrogen sulfide were always <1 ppm and could not be measured.
Hole 1077A was logged with a limited suite of sensors to identify and locate the presence of gas hydrate in the sediments and to provide data for core-log integration. After a "go-devil" was pumped down the pipe to ensure the proper operation of the lockable float valve, the drill pipe was tripped to 63.5 mbsf, the top drive was picked up, and the bit was placed at 79.0 mbsf. The logging tool included the spectral gamma-ray, long-spacing sonic, phasor dual-induction, and the Lamont-Doherty high-resolution temperature Sondes and was deployed at 0725 hr on 30 August. The tool logged Hole 1077A at 400 m/hr from 202 to 79 mbsf. By 1115 hr on 30 August, the logging equipment was rigged down, and the top drive was set back as the drill string was pulled to the surface. The bit cleared the seafloor at 1130 hr on 30 August, ending operations at Hole 1077A.
The vessel was offset 20 m to the west, and Hole 1077B was spudded at 1235 hr on 30 August. The seafloor depth was established at 2381.4 meters below sea level (mbsl) by drill-pipe measurement (DPM). APC Cores 175-1077B-1H through 22H were taken from 0 to 205.1 mbsf (Table 1), with 205.1 m cored and 212.7 m recovered (103.6% recovery). The drill string was pulled back with the bit clearing the seafloor at 0455 hr on 31 August, thereby ending operations at Hole 1077B.
The vessel was offset 20 m to the west, and Hole 1077C was spudded with the APC at 0550 hr on 31 August. The seafloor depth was estimated from recovery to be at 2385.2 mbsl. Three APC cores were taken to a depth of 22.8 mbsf when operating time on site expired. Core recovery was only 72.2% of the cored interval because of the loss of watery sediments during the core retrieval process. The drill string was pulled out of the hole and cleared the seafloor at 0720 hr on 31 August, thereby ending operations at Site 1077. By 1206 hr on 31 August, the drilling equipment was secured and the vessel was under way to Lobito, Angola, for a scheduled arrival at 0700 hr on 2 September to take the Angolan scientific observer on board.