OPERATIONS

The 94-nmi voyage to Site 1233 (proposed Site SEPAC-19A) was accomplished in 10 hr at an average speed of 9.4 kt. The vessel was on station at 0945 hr on 12 April 2002.

Prior to our arrival on site, the maximum approved penetration at Site SEPAC-19A was 80 mbsf, based on the maximum penetration of Parasound seismic records obtained by the Sonne in 1995. On approach to the site, the JOIDES Resolution's 3.5-kHz precision depth recorder (PDR) was able to record seismic reflectors to a depth of 110 mbsf. A request to drill to that depth was made to, and approved by, Ocean Drilling Program/Texas A&M University (ODP/TAMU) headquarters.

Hole 1233A

Hole 1233A was initiated with the advanced piston corer (APC) at 1350 hr on 12 April. The first attempt at a mudline core with the APC from 851 meters below rig floor (mbrf) (Core 1H) resulted in a full core barrel (9.9 m; recovery = 105%) that was not suitable for calculating the seafloor depth. This was the only core from Hole 1233A (Table T1).

Hole 1233B

The bit was raised 7 m, and Hole 1233B was initiated from 844.0 mbrf at 1340 hr on 12 April. The seafloor depth calculated from the recovery of the initial core was 848.5 mbrf, 7.9 m shallower than the corrected PDR depth estimate.

Piston coring advanced without incident to 109.5 mbsf. The interval from 5 to 14.5 mbsf was drilled without coring. The cores were oriented starting with Core 2H. Downhole temperature measurements were taken with the APC temperature (APCT) tool (Table T1). Of the 100.0 m cored, 102.0 m was recovered (recovery = 102%) (Table T1). The bit was pulled free of the seafloor at 2200 hr on 12 April.

Hole 1233C

The vessel was offset 10 m southeast of Hole 1233B. Before Core 1H was shot, a bottom water temperature measurement was taken with the APCT tool. In order to obtain a stratigraphic overlap with the previous hole, the bit was positioned at a depth of 847 mbrf. Hole 1232C was initiated with the APC at 2305 hr on 12 April. The seafloor depth calculated from the recovery of the mudline core was 848.7 mbrf. Piston coring advanced to 116.3 mbsf and recovered 121.8 m of core (recovery = 105%) (Table T1). Cores were oriented starting with Core 3H. Downhole temperature measurements were obtained with the APCT tool (Table T1). The combined downhole temperature measurements taken in Holes 1233B and 1233C yielded a temperature gradient of ~4.5C/100 m. The bit was pulled free of the seafloor at 0745 hr on 13 April.

Hole 1233D

The vessel was offset 10 m southeast of Hole 1233C. In order to obtain a stratigraphic overlap with the previous holes, the bit was positioned at a depth of 841 mbrf. Hole 1233D was initiated with the APC at 0810 hr on 13 April. A seafloor depth of 850.2 mbrf was calculated from the recovery of the mudline core. Piston coring advanced to the depth of 112.3 mbsf. The interval from 43.8 to 45.8 mbsf was drilled without coring to maintain the desired offset in regard to the cores recovered in the previous holes. A total of 110.3 m was cored and 114.9 m recovered (recovery = 104%) (Table T1). Cores were oriented starting with Core 4H. The bit was pulled free of the seafloor at 1715 hr on 13 April.

Hole 1233E

The vessel was offset 10 m southeast of Hole 1233D. The objective for this last hole was to improve the stratigraphic coverage by filling gaps in the core logging data. The bit was placed at 848 mbrf. Hole 1233E was initiated with the APC at 1750 hr on 13 April. A depth of 849.1 mbrf was calculated for the seafloor from the recovery of the mudline core. Piston coring advanced to the target depth of 101.5 mbsf. The interval from 55.9 to 82.5 mbsf was drilled without coring. The cored interval was 74.9 m with 73.7 m recovered (recovery = 98%) (Table T1). Cores were oriented starting with Core 3H.

The vessel was secured for transit. Because of the calm environment, the bottom-hole assembly was not disassembled. The two stands of drill collars were set back in the derrick, and the nonmagnetic and seal bore drill collars were laid down. The 24-hr transit to the next site began at 0400 hr on 14 April.

NEXT