Hole 991A A 83-km seismic survey was run in 6.8 hr at 6.0 kt over Sites 991, 992, and 993 and the Cape Fear Slide. The ship returned to the Global Positioning System (GPS) coordinates for Site 991, and a Datasonics 354M commandable recall beacon was dropped at 0022 hr on 5 November (for all of Leg 164 the ship was in the U.S. Eastern Time Zone; ship time is therefore equivalent to Greenwich Mean Time [GMT] - 5 hr). Hole 991A was spudded at 0835 hr on 5 November. The water depth was measured as 2567.5 m below sea level (mbsl) based on recovery of the mudline in Core 164-991A-1H. Advanced Piston Cores (APC) 164-991A-1H to 6H were taken from 0 to 56.6 m below seafloor (mbsf), with 58.66 m recovered (103.6% recovery). The cores were relatively dry and well compacted and were not gassy. They contained a minor amount of H2S as follows: 2 ppm in 1H, 10 ppm in 3H, 22 ppm in 5H, and 20 ppm in 6H. There were no gas voids and little extrusion from the liner ends. Coring was halted for 0.5 hr for repairs when the forward core winch had an intermittent electrical control problem that caused it to jump at times. Hole 991A was terminated and the bit was pulled above the seafloor at 1418 hr on 5 November.
Hole 991B The ship was moved 10 m south, and Hole 991B was spudded at 1507 hr on 5 November. The seafloor was assumed to be at 2567.5 mbsl, based on offset Hole 991A. Hole 991B was spudded at 1507 hr on 5 November, and the hole was washed to 10.0 mbsf for the first Pressure Core Sampler (PCS) run. Core 164-991B-1P was taken with the PCS from 10.0 to 11.0 mbsf. A push-in type shoe and basket catcher were used. When retrieved, the PCS ball valve had closed and the pressure chamber held 2550 psi when first checked. The pressure fell slowly to 2270 psi in 2 min. The hydrostatic pressure was calculated at 3804 psi; therefore, some formation pressure was trapped. No core was recovered and it appeared that none entered the PCS catcher. The hole was drilled ahead from 11.0 to 50.0 mbsf, and PCS Core 164-991B-2P was taken from 50.0 to 51.0 mbsf. A push-in type shoe and basket catcher were again used. A 104 cm core of moderately compacted green-gray clay was recovered, but only 64 psi pressure was trapped. The core barrel was jammed full and the basket core catcher was partially broken off. The Fisseler Water Sampler was run for the first time at 51.0 mbsf and recovered 46 ml of water. Hole 991B was terminated and the bit was pulled above the seafloor at 1953 hr on 5 November.
To Operations Site 992
164 Table of Contents