Our transit from Site 1225 to Site 1226 was by way of Puerto Isidro Ayora, Santa Cruz Island, in the Galapagos archipelago, Ecuador. We laid over at anchorage for 4.5 hr to clear customs as an ODP employee disembarked for compassionate leave. The 1258-nmi transit from Site 1225 to the Galapagos required 117 hr at an average speed of 10.8 kt. We made the 155-nmi transit from the Galapagos to Site 1226 in 13 hr at an average speed of 11.9 kt, arriving on the Global Positioning System coordinates of previously occupied Site 846 at 1100 hr on 19 February. A summary of Site 1226 coring operations is listed in Table T1.
The positioning beacon for Site 1226 was deployed at 1203 hr on 19 February. A pipe trip positioned the bit at 3308 meters below rig floor (mbrf), and a bottom-water temperature was recorded with the Adara APC temperature tool. Core 1H returned full and did not establish a mudline depth, so Hole 1226A was abandoned.
After raising the bit to 3303 mbsf, Core 1H recovered 4.4 m of sediment, establishing the mudline at 3308.1 meters below rig floor. Continuous APC coring from Core 1H through 29H (0.0-271.9 mbsf) returned 105% recovery. Slow drill over after Core 29H prompted us to change to XCB coring, which continued through Core 41X (271.9-378.0 mbsf) (average recovery = 91%). Core 42P, cut with the pressure coring sampler (PCS) (378.0-380.0 mbsf) recovered a full 1-m core as well as ~40 cm in the barrel beneath the pressure chamber. XCB coring continued with Cores 43X through 47X (380.0-421.4 mbsf) (recovery = 74%). Hole 1226B was terminated after coring ~1.5 m into basement.
In addition to the mudline temperature recording before Core 2H, downhole operations in Hole 1226B included Adara tool measurements on Cores 5H, 7H, 10H, 13H, 16H, and 21H (42.4, 61.4, 89.9, 118.4, 146.9, and 194.4 mbsf, respectively). The APC-Methane (APC-M) tool was run continuously on Cores 5H through 29H (32.9-271.9 mbsf) but stopped recording data after Core 10H. No reason for this interruption in recording could be determined. The Tensor APC orientation tool was used continuously on Cores 3H through 29H. The DVTP was deployed at 262.4, 310.0, and 358.4 mbsf, and the DVTP-P was deployed at 241.9 mbsf. A single logging run with the triple combination (triple combo) tool string was completed in Hole 1226B by 1100 hr on 23 February. PFT was pumped continually for microbiological contamination testing. Fluorescent microspheres were also deployed on Cores 2H, 5H, 12H, 22H, 34X, 40X, 43X, 46X, and 47X. Operations in Hole 1226B were terminated at 1045 hr on 23 February.
Hole 1226 was a mudline core dedicated to physical properties sampling. Core 1H (0.0-7.9 mbsf; recovery = 100%) was spudded 20 m north of Hole 1226B, and after recovery the hole was abandoned.
After another offset of 20 m north, Core 1H (0.0-7.6 mbsf; recovery = 100%) was intended to initiate a second attempt at deep penetration, but upon recovery we discovered that the upper 3 m of the core was surrounded by water in the core liner and the core appeared to be either slightly under gauge or at least soupy. As an intact mudline core was required for dense interstitial water and microbiological sampling, we deemed this core inappropriate and abandoned Hole 1226D. Fluorescent microspheres and continuous PFT were used on Core 1H.
In planning this expedition, we recognized that time on site would be a critical parameter if we were to complete all our scientific objectives. Our operations plan included the option of spot coring intervals of interest in order to conserve valuable operations time. For Hole 1226E, we determined that intervals of particular interest were the upper 100 m of the section, the top of the interval where XCB coring returned poor material for interstitial water and microbiological sampling (250-320 mbsf), and the lower 40 m of the section (380-420 mbsf). Continuous APC coring from 0.0 to 112.1 mbsf (Cores 1H through 12H) returned an average of 105% recovery.
The interval between 114 and 250 mbsf was then drilled without coring. Continuous APC coring from 250 to 326 mbsf required drilling over the bit but returned superb intact cores. The interval between 326 and 378 mbsf was also drilled without coring. At 378 mbsf, the PCS was run at the same depth as deployed in Hole 1226B to test a different bit configuration (polycrystalline diamond [PDC] vs. carbide). A nearly full core barrel was recovered (Core 21P), but a piece of chert was jammed in the throat of the tool, preventing recovery under pressure. Four XCB cores (Cores 22X through 25X) (380.0-418.4 mbsf; recovery = 76%) ended operations in this hole.
In order to evaluate the downhole temperature gradient, additional Adara temperature measurements were performed at 45.6, 74.1, and 112.1 mbsf in Hole 1226E. To complete the temperature profile in this hole, the DVTP was deployed at 307 and 400 mbsf and an in situ pressure measurement was attempted with the DVTP-P at 326 mbsf. PFT was pumped continually for microbiological contamination testing, and fluorescent microspheres were deployed on Cores 1H, 15H, and 16H as part of our contamination testing protocol. The APC-M tool was deployed on Cores 5H through 12H. Operations at Site 1226 concluded when the bit passed through the rig floor at 1615 hr on 25 February, and we began our transit to Site 1227.