The 187-nmi sea voyage between Sites 1229 and 1230 lasted 16.6 hr at a speed of 11.3 kt. We arrived on the Global Positioning System coordinates for Site 685, as recorded in the Leg 112 Initial Reports volume (Shipboard Scientific Party, 1988), just after midnight on 11 March. After a positioning beacon was deployed, the pipe trip to bottom in 5097 m water depth required 11 hr. Coring operations are described in Table T1.
We began operations in Hole 1230A, offset 50 m north of the Site 685 coordinates, with a water sampling temperature probe (WSTP) deployment to collect a water sample. The Adara temperature shoe was included on the core barrel assembly for Core 1H to measure the temperature at the mudline. The first core at Site 1230 (Core 1H) (0.0-4.8 mbsf; recovery = 100%) arrived on deck at 1645 hr on 11 March. Continuous advanced hydraulic piston coring (APC) operations through Core 6H returned an average of 103% recovery. Low levels of hydrogen sulfide were measured with handheld detectors on the first three cores, and hydrogen sulfide safety protocols were observed. Hydrogen sulfide was not detected in cores recovered from below 33 mbsf. Cores recovered from below 33 mbsf all showed evidence of gas expansion, which appeared to increase in severity downhole, so precaution against explosive core liner rupture (perforating the core liners with a handheld drill) was continued through the rest of our coring operation.
The PCS was deployed on Core 7P (52.3 mbsf) and returned a full barrel under pressure. Continuous APC coring followed through Core 15H (to 127.3 mbsf). We were able to advance much farther with piston coring than was achieved during Leg 112 because of technological advancements in APC operations. Recovery in this interval was >100%, despite an apparent less than full stroke on the piston coring system (measured by drill-over depth) due to core expansion. Core 16P (PCS) (127.3-129.3 mbsf) also returned a full core barrel under pressure. Cores 17H through 19H (129.3-156.8 mbsf) returned progressively poorer recovery (recovery = 54%-34%) in expanded cores. Core 20P (156.8-158.8 mbsf) recovered 65 cm of poorly consolidated core under pressure.
Cores 21H through 24H (158.8-196.8 mbsf) suffered incomplete stroke and poor recovery (recovery = 7%-44%), but we continued our strategy of drilling through 9.5-m intervals. Another PCS deployment (Core 25P; 196.8-198.8 mbsf) recovered 18 cm of core under pressure. Four more APC cores (Cores 26H through 29H; 198.8-226.3 mbsf) were also interpreted as incomplete deployments, with the APC shoe coming free after only a meter or so of drill over. The Adara temperature shoe was included on the core barrel assembly for Core 29H and was damaged because of the formation density. These cores returned an average of <1.5 m of core. After deployment of Core 28H, we decided to use a center bit while drilling to the full-stroke depth in order to avoid clogging the bottom-hole assembly. The subsequent Core 29H returned only 0.5 m of core, so to supplement recovery for IW analysis we chose to core to the next APC deployment depth with the extended core barrel (XCB). Only 3.3 m of advancement was possible with Core 30X, which returned 1.78 m of core. Another XCB barrel was deployed to determine if the reason for poor penetration was due to clay buildup on the XCB bit or if the main bit was not capable of further penetration. After cutting though a hard layer (part of which was recovered in the top of Core 31X; 229.6-234.1 mbsf), we decided to continue the approach of APC coring and advancing by recovery, followed by XCB coring of the underlying interval. Two short APC strokes returned <1 m each of core, but Core 35X was nearly full (recovery = 99%) of semisoft sediment. The PCS was deployed as Core 36P (254.6-256.6 mbsf), followed by two XCB cores (Cores 37X and 38X; 256.6-276.8 mbsf). Based on the results of the Core 36P (reduced pressure and gas content compared to shallower deployments), we deployed the pressure core barrel as our final coring tool in Hole 1230A (Core 39P; 276.8-278.8 mbsf).
PFT was pumped continuously during all coring operations at Site 1230 as part of our contamination testing, and fluorescent microspheres were deployed on Cores 1H, 2H, 8H, 38X, and possibly 13H. The DVTP was deployed at 33.3, 79.8, 148.3, 177.8, and 256.6 mbsf; however, only the deployments at 33 and 256 mbsf returned data consistent with a reasonable thermal profile. All other deployments either failed to return any data or provided low temperatures indicative of poor penetration of the probe tip into stiff sediment. The Davis-Villinger Temperature-Pressure Probe (DVTP-P) was deployed at 257.6 mbsf. A wireline logging program consisting of two runs, one with the triple combination (triple combo) tool string and a second with the Formation MicroScanner (FMS)-sonic tool string, completed operations in Hole 1230A. Logging was completed by 2200 hr on 16 March.
After an offset of 20 m north, Hole 1230B was initiated at 2300 hr on 16 March. The interval of 3-11 mbsf was of the most intense interest to shipboard scientists, so we wanted this interval recovered in a single core barrel. Core 1H returned 5.4 m. For Core 2H the bit was lowered to 3 mbsf (based on the recovery from Core 1H). For Janus bookkeeping purposes this required adjusting the bottom depth of Core 1H to 3 mbsf, resulting in an artificial value of 100% recovery for Core 1H. The interval between 3.0 and 5.8 mbsf is represented twice in our recovery. High-density sampling for interstitial water, methane, and microbiological DNA assays effectively depleted all but the first and last sections of Core 2H.
Our operations plan for this hole included three deployments of the PCS to complete the shallow portion of the gas profile initiated in Hole 1230A. Coring continued with Core 3H (12.5-22 mbsf; recovery = 105%) and PCS Core 4P (22.0-24.0 mbsf). APC coring to 71.5 mbsf (Cores 5H through 9H) returned 107% recovery. Core 10P (71.5-73.5 mbsf) returned 99 cm of core under pressure. APC coring to 100 mbsf reached our depth objective for this hole, and coring operations ended with a final deployment of the PCS (Core 14P; 103.0-105.0 mbsf). The DVTP was deployed at 73.5 and 100.0 mbsf, and the DVTP-P was deployed at 101.5 mbsf. The APC-methane (APC-M) tool was deployed continuously from Core 201-1230B-3H to 13H.
Three shallow holes (two APC cores each in Holes 1230C and 1230D and four APC cores in Hole 1230E) were cored to provide samples for dense microbiological sampling (Hole 1230C), paleoceanography and paleomagnetics studies (Hole 1230D), and to ensure that material representing the shallow part of the interval cored at Site 1230 was preserved in the Ocean Drilling Program (ODP) archive (Hole 1230E). Fluorescent microspheres were deployed on Cores 201-1230C-1H and 2H. The Adara tool measured a mudline temperature before Core 201-1230E-1H and a temperature at 32.5 mbsf on Core 201-1230E-4H. The DVTP-P was deployed at 32.5 mbsf. A final PCS deployment was completed at the base of Hole 1230E (34.0-36.0 mbsf). Operations at Site 1230 concluded when the bit passed through the rig floor at 0820 hr on 19 March, and we began our transit to our final site for Leg 201.