We made the 745-nmi transit between Sites 1226 and 1227 in 63.7 hr at an average speed of 11.7 kt, arriving on location at ~0800 hr on 28 February. Because our drilling target was a small sediment pond, we decided to conduct a brief 3.5-kHz survey in a west-east then north-south cross pattern centered on our projected site coordinates to confirm our position (Fig. F1). On the first west-east limb of our survey (based on coordinates reported on the first page of the Leg 112 Initial Reports volume Site 684 report [Shipboard Scientific Party, 1988]), we were concerned that the seafloor depth indicated by the survey was significantly shallower than the reported depths at Site 684 (~250 m as opposed to 426 m). In addition, the survey showed no evidence of sediment cover. At this point, we noticed a 3-nmi discrepancy between the coordinates reported in the Leg 112 Initial Reports volume and the site survey navigation track for Site 684 presented later in the chapter. The ODP Drilling Services Department operations report for Leg 112 records coordinates that agree with the Site 684 site survey data, so we moved our survey location center to these coordinates. The water depth at our new survey location agreed with the water depth reported in the Leg 112 Initial Reports volume, and our survey indicated the presence of a sediment pond, although the limited penetration of the 3.5-kHz signal below the seafloor did not allow us to estimate the sediment thickness. Based on our survey data, we selected a position 50 m north of the Site 684 survey coordinates to begin coring operations at Site 1227. Prior to initiating coring, we affected a personnel and equipment transfer via a Peruvian Navy helicopter. Coring operations at Site 1227 are summarized in Table T1.
Operations in this hole began with deployment of the Water Sampling Temperature Probe (WSTP) to collect a bottom-water sample and a near-mudline water temperature. Upon recovery of the WSTP, we noticed the probe tip had mud impacted in the water sample ports, suggesting that either the tool had embedded below the mudline or the interface between the seafloor and sediment column was turbid. Core 1H established the mudline at 438.9 mbrf. While planning for shallow-water drilling at all of the Peru margin sites, we recognized that the drill crew could deliver cores to the core laboratory at a much faster rate than the cores could be processed, owing to the high-resolution geochemistry we required and the core handling requirements for microbiological sampling. To account for protracted laboratory handling times, we initiated a protocol of slowing core recovery, which required continual communication between the various processing laboratories and the rig floor. In short, coring operations were held in stasis by the drilling crew until word was received from both the chemistry and microbiology processing groups that they were approaching the end of a sample handling program. The rig floor crew would then respond with immediate deployment of the next core barrel. This routine prevented cores from piling up in the laboratories, enhancing our chances of meeting our science objectives.
The first five advanced hydraulic piston coring (APC) cores (Cores 1H through 5H) (0.0-43.6 mbsf) returned 105% recovery. Hydrogen sulfide monitoring registered measurable quantities of hydrogen sulfide on core surfaces beginning with Core 2H, and levels rose to as high as 25 ppm in the first few cores. Hydrogen sulfide core handling protocols were initiated after Core 2H. It is important to note that the core handling procedures dictated by safety have a potential impact on science objectives because they may slow delivery of samples to the microbiology and geochemistry laboratories. Consequently, biogeochemical and microbiological samples were processed as rapidly as possible while adhering to hydrogen sulfide safety protocols. In addition, hydrogen sulfide was continuously monitored in all laboratories. Core flow through the physical property and description laboratories was radically slowed because even after perforating the cores, residue of as much as several parts per million of hydrogen sulfide was detectable in core sections several hours after recovery.
Recovery began to deteriorate after Core 5H, as the next several APC barrels (Cores 6H through 8H; 43.6-72.1 mbsf) returned an average of 40%. Through this interval, recovery ranged from as little as 4% to as much as ~70%. In addition, starting with Core 8H we were required to drill over the APC shoe when we encountered elevated tension when trying to extract core barrels via wireline (overpull). However, we chose to continue to attempt APC coring to as deep as possible, since the extended core barrel (XCB) cores we had recovered from previous sites were so disturbed and XCB coring during Leg 112 had experienced such poor recovery (average = <15% at this location). After Core 8H and continuing through the bottom of the hole (Cores 9H through 18H; 72.1-151.1 mbsf) recovery improved to average of 60%, which allowed us much improved core recovery and quality as compared to operations during Leg 112. Hole 1227A was terminated after impacting a hard layer at 151 mbsf in Core 18H.
Several downhole tool measurements were accommodated by our slowed recovery pace in Hole 1227A. The Adara temperature shoe was deployed on Core 4H. Because the core liner from Core 4H shattered, possibly as a result of the measurement protocol, we abandoned Adara tool measurements in lieu of DVTP runs for the remainder of the hole. The DVTP was deployed at 81.6 and 110.1 mbsf, and the DVTP-P was deployed at 132.1 mbsf. Both the PCS and the FPC were deployed between 128 and 132 mbsf, but neither run was particularly successful, as the only material recovered was a handful of pebbles and shell hash. The APC-M tool was deployed on Cores 4H and 5H. The WSTP was deployed once each above Holes 1227A and 1227D with failure on the first run and success on the second run.
Holes 1227B, 1227C, and 1227E were all three-core holes (mudline plus two subsequent penetrations) dedicated to shipboard and shore-based high-resolution sampling. Hole 1227D was drilled to provide high-resolution microbiological and geochemistry sampling and to attempt to improve recovery rates in certain intervals cored in Hole 1227A. Our target depth for this hole was to reach the interval at ~70 mbsf, where recovery improved while APC coring in Hole 1227A. Cores 201-1227D-1H through 5H (0.0-45.5 mbsf) returned 96% recovery. Core 201-1227D-6H (45.5-55.0 mbsf) was nearly full (recovery = 96%), but a shattered core liner resulted in severe core disturbance in the lower two-thirds of the core. Core 201-1227D-7H also returned with a shattered core liner and only a handful of pebbles and shell hash. In addition, the end of the APC cutting shoe showed evidence of impact with a hard ground. Coring operations were terminated in Hole 1227D when Core 201-1227D-8H (64.5-74 mbsf) delivered an incomplete stroke and returned only 1.7 m of core. The APC-M tool was deployed on Cores 201-1227D-1H through 7H.
After recovering three cores from Hole 1227E (Cores 201-1227E-1H through 3H) (0.0-25.9 mbsf; recovery = 101%) that were not split and that were end-capped without acetone but with tape, we deployed the FPC. This strategy allowed a test of the FPC in an interval where we were confident that the lithology contained more abundant clay and less abundant sand and pebbles. Operations at Site 1227 concluded when the bit passed through the rig floor at 0245 hr on 3 March, and we began a short transit to Site 1228.