The 191-nmi sea voyage between Sites 1230 and 1231 lasted 18.2 hr at an average speed of 10.2 kt. A positioning beacon was deployed over the Global Positioning System coordinates of Deep Sea Drilling Project (DSDP) Site 321 in 4824.9 meters below rig floor (mbrf) water depth (precision depth recorder). Coring operations at Site 1231 are detailed in Table T1.
Hole 1231A was initiated at 0300 hr on 20 March 2002. When Core 201-1231A-1H returned full we could not determine the mudline, so the hole was abandoned. The first core from Hole 1231B (Core 201-1231B-1H) (0.0-3.4 mbsf; recovery = 100%) was initiated by pulling the bit ~5 m above the bit depth of Core 201-1231A-1H. Recovery established the mudline at 4824.0 mbrf. Continuous advanced hydraulic piston coring (APC) through Core 201-1231B-12H (3.4-107.9 mbsf) returned 102% recovery. Based on Leg 34 recovery at this location (Yeats, Hart, et al., 1976), we expected basement penetration at ~124 mbsf, so after a final deployment attempt of the DVTP-P at 107.9 mbsf, we drilled out the interval disturbed by the probe tip (to 109.4 mbsf) and fired Core 201-1231B-13H, which only returned 5 m of core with small chips of basalt in the core catcher. Fearing we had struck basement (some 9.5 m shallower than reported in the coring summary table for Leg 34) we deployed the extended core barrel, which immediately showed indication of hard basement (slow penetration and high, erratic torque). After 2 hr, we had advanced <3 m, so we recovered the core barrel (Core 201-1231B-14X; 114.4-117.3 mbsf), which returned only a few pieces of basalt. Having reached our basement target, we terminated Hole 1231B.
Perfluorocarbon tracer (PFT) was pumped continuously during all coring operations at Site 1231. In addition, fluorescent microspheres were deployed on Cores 201-1231A-1H and 201-1231B-1H, 2H, 6H, 12H, and 14X. The Adara temperature shoe was deployed at the mudline and at 41.4, 60.4, 88.9 and 118.9 mbsf. The DVTP-P tool was deployed after Core 201-1231B-12H at a depth of 107.9 mbsf.
Two cores were recovered to support high-resolution paleoceanographic and paleomagnetic studies (Cores 201-1231C-1H and 2H; 0.0-15.1 mbsf). Because heavy microbiological and geochemical whole-round core sampling depleted a significant part of the recovery at Hole 1231B, we chose to recover a complete section (Cores 201-1231D-1H through 13H and 14X [0.0-121.9 mbsf; recovery = 92%]) at this site in support of shipboard and shore-based solid-phase sampling. The Adara temperature shoe was deployed at 74.3 and 112.3 mbsf in Hole 1231D.
Still in a quandary over the offset between the depth where we encountered basement (~115 mbsf) and where the Leg 34 coring and lithostratigraphic summary reported the basement contact (124.5 mbsf), we noted an interval in the Site 321 lithostratigraphic column that reported 9.5 m (between 96.5 and 106.0 mbsf) as uncored. The sediments above and below this interval in our recovery are similar in appearance to those described in the Leg 34 site report. The time on deck between cores surrounding the reported uncored interval is recorded as 1.5 hr, which was similar to our wireline time in this water depth, suggesting little time was spent on drilling without coring. The operations section of the Site 321 chapter does not report an uncored interval, and the reported depths between mudline depth and basement contact differ by 114.5 m. We can only surmise that there was a recording error in the coring summary table that was accounted for in the lithostratigraphic column as a coring gap, but that the basement contact at Site 321 is at the same depth as at Site 1231.
Our final operation for Leg 201 was recovery of a complete section to sample specific intervals for high-resolution microbiology and geochemistry. Cores 1H through 14H (0.0-119.0 mbsf; recovery = 100%) ended with a final penetration into basement. The Adara temperature shoe was deployed at 98 mbsf. Operations for Leg 201 ended when the bit passed through the rig floor at 1600 hr on 23 March, and we began our ~5-day transit to Valparaiso, Chile. We arrived at the pilot station in Valparaiso at 0716 hr on 29 March and the first line ashore at 1120 hr officially ended Leg 201.