Leg 201 began at 0830 hr on 27 January 2002, when the first line was passed ashore at Berth 4 of the 10th Avenue Terminal in San Diego, California. Routine port call activities were accompanied by the loading of several boxes of equipment and supplies dedicated to the microbiological and geochemical objectives of Leg 201. In addition, the new radioisotope facility was brought on board (see "Rate and Biogeochemical Process Measurements" in "Procedures and Protocols" in "Microbiology" in the "Explanatory Notes" chapter). Site 1225 coring operations are described in Table T1.
After completing port call activities, the last line was cast off at 0800 hr on 1 February. The pilot and three harbor marshals were discharged at 0910 hr just off Point Loma, and the vessel assumed full speed for the voyage to the first site of Leg 201. Because of excellent weather and a favorable current, the 1835-nmi voyage to Site 1225 was accomplished in just 6.6 days at an average speed of 11.7 kt. This led to arrival on site nearly a full day earlier than scheduled.
The vessel arrived on the Global Positioning System coordinates for Site 1225 on 7 February at 2115 hr, and we commenced lowering thrusters and hydrophones. After switching into dynamic positioning mode, a positioning beacon was deployed at 2242 hr.
The bottom-hole assembly for Site 1225 consisted of a new Rock Bit Industries 11
-in C-3 extended core barrel (XCB) bit, five 8
-in drill collars plus the nonmagnetic collar used with the Tensor tool core orientation system, and the seal bore drill collar used with the advanced hydraulic piston corer (APC), XCB, and pressure coring system (PCS).
While tripping the pipe, a precision depth recorder reading was taken using the 3.5-kHz recorder. The site-corrected reading of 3755 m was adjusted for the distance to the rig floor dual elevator stool to 3773.4 meters below rig floor (mbrf). The APC core barrel was deployed on the aft wireline, and the bit was positioned at 3767.0 mbrf. Bottom-water temperature was measured with the APC temperature tool (Adara tool). We initiated Hole 1225A at 0840 hr on 8 February. Upon recovery, Core 1H contained 4.30 m of core, establishing a drill pipe-measured seafloor depth of 3772.2 mbrf. All cores recovered from Hole 1225A were extracted from the drill pipe and transferred as expeditiously as possible to the catwalk to minimize core warming (see "Core Handling and Sampling" in "Introduction and Background" in "Microbiology" in the "Explanatory Notes" chapter).
APC coring continued without incident through Core 19H to a depth of 175.3 mbsf. Core 20H gave a positive full stroke indication; however, because of a 70-kilopound (klb) overpull, the barrel had to be freed by drilling down and over the end of the APC shoe (drill over). Cores 21H and 22H continued with a normal full-stroke pressure bleed off and required only 30 klb of overpull for extraction from the formation.
Tensor core orientation was initiated with Core 4H and continued through Core 33H. Adara temperature measurements were recorded before recovery of Cores 5H (42.3 mbsf), 7H (61.3 mbsf), 9H (80.3 mbsf), and 14H (127.8 mbsf). All measurements were successful except the one from 42.3 mbsf. Failure of this run was attributed to a tool software fault. The APC-Methane (APC-M) tool was installed in the coring system prior to Core 5H and was run on each core barrel through Core 14H. The tool worked well initially but stopped collecting data after Core 8H. This failure was thought to be the result of a power interruption that caused the tool to stop logging data.
After Core 22H (203.8 mbsf), we ran the first of three deployments of the DVTP. After recovering the DVTP, we drilled without coring through the disturbed interval (nominally 1.5 m) to a depth of 205.3 mbsf. We followed the successful temperature probe wireline run with deployment of the new Davis-Villinger Temperature-Pressure Probe (DVTP-P). The first deployment with this tool was unsuccessful, apparently as a result of a clogged filter.
APC coring continued through Core 27H to a depth of 243.3 mbsf. All coring runs except 27H achieved full stroke of the piston. Each extraction attempt from Core 23H through 27H required >80 klb overpull, so in each case we employed the drill-over technique to facilitate core barrel recovery. Although the driller indicated we did not achieve a full stroke on Core 27H, we opted to drill ahead to a full-stroke length to keep our sampling strategy consistent. A second DVTP wireline run after Core 27H suffered an electronic failure, due to a broken thermistor bulkhead, and did not record a temperature.
Because of the incomplete stroke on Core 27H, we switched to the XCB coring system. Core 28X returned empty. Core 29P was cut using the newly modified PCS. This tool was being tested for possible use on the Peru margin sites of Leg 201 and also for Leg 204. Core 29P advanced a total of 2.0 m. Upon recovery, the pressurized chamber was 100% full; the tool recovered 1.0 m of core under 1200 psi pressure. Another 41 cm of unpressurized core was recovered in the bit extender below the ball valve.
In deference to the poor recovery with the XCB and in light of the soft sediment recovered in the bottom of the PCS core barrel, we opted to attempt to deepen the hole with the hydraulic piston core system. Cores 30H through 33H all required drill over after 80 klb overpull failed to release the barrels from the formation. In addition, Core 30H indicated only partial stroke but returned full recovery. After Core 33H, we ran a second deployment of the DVTP-P. The pressure measurement again failed, and a postdeployment inspection located an internal leak in the pressure transducer line. After drilling down 1.5 m to remove the sediment disturbed by the pressure probe, this was followed by a third DVTP temperature measurement, which was successful.
With basaltic basement projected at a depth of ~318 mbsf, a final APC core (Core 34H) was recovered after drilling over the shoe because of excessive overpull. Subsequently, we deployed an XCB core barrel hoping to obtain ~1.0 m of basement rock. After contacting basement at ~318.6 mbsf, the driller advanced another 1.0 m in 15 min. Basement was readily identifiable because of an abrupt increase in drilling torque and a significantly reduced rate of penetration. Upon recovery, the XCB core barrel contained 7.25 m of sediment, with two cobbles of basalt embedded in sediment packed in the core catcher. Rather than deploy another barrel (since we had already drilled >1 m into basement without recovering the sediment/basalt interface), we chose to conclude coring operations for this hole at 1930 hr on 10 February.
A wiper trip to 80 mbsf followed, sweeping the hole with a 20-bbl sepiolite mud pill. We displaced the hole with 130 bbl of sepiolite in preparation for logging and encountered only 2 m of fill in the bottom of the hole. A single wireline run with the triple combination (triple combo) tool string was completed by 1045 hr on 11 February, and the bit cleared the seafloor at 1110 hr on 11 February, ending Hole 1225A.
In support of the microbiological contamination testing protocol, Whirl-Pak bags containing full-concentration fluorescent microspheres (see "Fluorescent Microparticle Tracer" in "Procedures and Protocols" in "Microbiology" in the "Explanatory Notes" chapter) were deployed with Cores 2H, 12H, 17H, 22H, and, possibly, 34H. In addition, perfluorocarbon tracer (PFT) was pumped continuously during coring operations. The rate and quantity of tracer was automatically controlled using an input signal from the Tru-Vu rig instrumentation system (see House et al., this volume).
We offset 10 m north of Hole 1225A and spudded Hole 1225B at 1240 hr on 11 February. Subsequent recovery of APC Core 1H was 8.96 m, establishing a seafloor depth of 3771.0 mbrf. Hole 1225B consisted of a single APC core to provide samples for high-resolution physical property measurements. Hole 1225B ended with the recovery of Core 1H at 1315 hr on 11 February.
After offsetting another 10 m north, Hole 1225C was spudded at 1355 hr on 11 February. Recovery of Core 1H was 8.83 m, establishing a seafloor depth of 3771.2 mbrf.
APC coring continued without incident through Core 15H (141.8 mbsf). Core 16H required 10 min to drill over after 80 klb of overpull failed to extract the barrel from the formation. Coring continued using the drill-over technique with all barrels stroking fully through Core 25H. Drill-over time ranged from 20 to 30 min.
APC coring resumed with Core 26H and continued through Core 31H (293.8 mbsf). Cores 26H, 27H, 29H, and 30H indicated partial stroke but returned full recovery. Cores 28H and 31H were recovered after indicating that a full stroke had been achieved. Tensor core orientation was initiated with Core 3H and continued through Core 31H.
Core 32P was cut using the PCS and an auger-style bit. As with the first test conducted in Hole 1225A, coring advanced a total of 2.0 m (to a depth of 295.8 mbsf), even though the pressure core chamber was only designed to hold 1.0 m of core. Upon recovery, the pressurized chamber was once again 100% full. This time the tool recovered 1.0 m of core under 4800 psi pressure. There was no core recovered in the bit extender below the ball valve on this deployment.
After completing the second PCS test, Core 33H indicated a full stroke, but our attempts to drill over the bit were thwarted by a bent core barrel. This resulted in a pipe trip, terminating Hole 1225C at a total depth of 305.3 mbsf, 13.3 m short of the basement objective. Microspheres were deployed with Core 1H, and PFT was pumped continuously during coring operations. By 1930 hr on 13 February, all thrusters and hydrophones had been raised and the ship was secured for transit. Weather and sea state during the occupation of Site 1225 ranged from good to excellent. We experienced no operational difficulties that could be attributed to the environment.
