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doi:10.2204/iodp.pr.346.2014

Operations

Port call

Expedition 346 began with the first line ashore the Valdez Container Terminal in Valdez, Alaska (USA), at 1120 h on 29 July 2013. The first week of Expedition 346 consisted almost entirely of port call activities. This was the first port of call in Valdez, and operations proceeded very smoothly. In spite of the remote location and logistical challenges, the vessel was resupplied and departed 1 day earlier than scheduled.

The IODP-United States Implementing Organization crew and the expedition Co-Chief Scientists arrived at the ship in Valdez on 29 July after an 8 h bus ride from Anchorage. The ship’s (Siem Offshore) crew arrived the following day. On day three of the port call, the Expedition 346 science party moved aboard, completing the sailing complement for the expedition.

Port call activities included routine resupply of consumables and offloading of the previous expedition’s (IODP Southern Alaska Margin Expedition 341) freight. All Expedition 341 core samples were offloaded to refrigerated containers and dispatched to the IODP Core Repository at Texas A&M University (College Station, Texas). All microbiological samples were offloaded and dispatched to the Expedition 341 scientists’ home institutions by courier. Three empty core liner boxes were also offloaded for disposal. In addition, 2441 sacks/122.1 short tons of barite, 3920 sacks/196.0 short tons of sea gel, and 1872 sacks/88.0 short tons of cement were loaded. Bunkering totals included loading of 115,015 gal marine gas oil by trucks from a local Valdez refinery.

The ship’s crew’s activities included receipt and installation of a replacement standpipe valve, including the required X-ray certification of the high-pressure welds by a technician from Anchorage. In addition, a Schlumberger mechanic came to assist the logging engineer with repairs to the securing system holding the logging winch/transmission in place.

With port call activities completed, the R/V JOIDES Resolution departed for Site U1422 (proposed Site JB-3) with the last line away at 0718 h on 2 August. Departure was 28 h ahead of the scheduled departure time.

The 3556 nmi voyage to Site U1422 lasted 2 weeks at an average speed of ~10.2 kt. During the transit, we crossed two low-pressure cells with their associated strong winds and high seas, which impacted our cruising speed. Average speed over ground during those times was as slow as 7.5 kt. A total of eight time changes took place during the transit, with the clock being turned back 7 h and advanced 1 day to compensate for passage across the International Date Line. In effect, the day of 9 August was lost and the ship time jumped from 8 August directly to 10 August at 2400 h on 8 August. The last time change placed the ship at UTC + 9 h, which was the local time for all Expedition 346 sites as well as Japan and Busan, Korea.

The ship maintained good speed (+11 kt) during the final days of the transit until entering the heavily trafficked Tsugaru Strait south of Hokkaido, Japan. A strong current on the bow reduced the vessel’s speed over ground through the strait to 6.0 kt. This lost time was made up once exiting the strait and turning to a more northerly course, during which an average speed of 11.7 kt was achieved during the last day of the transit.

Site U1422

Five holes were cored at Site U1422 using the APC and nonmagnetic core barrels (Table T1). Two holes were cored to 9.5 m CSF-A (1 core each), one hole to 205.2 m CSF-A, one hole to 141.8 m CSF-A, and one hole to 111.6 m CSF-A. A total of 63 cores were required to obtain 502.6 m of sediment (105.2% recovery). The APCT-3 was deployed four times.

We arrived at Site U1422 at 1448 h on 17 August 2013. Control of the ship was shifted from bridge “cruise” mode to dynamic positioning mode at 1528 h. A strong gale was blowing as the ship arrived on location, which complicated the vessel’s maneuvering over the location coordinates. However, the ship soon steadied over the site’s coordinates, and the rig crew began picking up drill collars and making up the APC/XCB bottom-hole assembly (BHA). All tubular joints were measured and drifted (internal diameter clearance checked) as they were made up into the drill string. By ~0300 h on 18 August, the drill string had been deployed to the seafloor.

Hole U1422A

Operations continued at Site U1422 as the drill string was tripped to a depth of 3425.0 meters below rig floor (mbrf). The top drive was picked up, and the pipe was spaced out for spudding Hole U1422A. A precision depth recorder (PDR) reading for the site established a projected seafloor depth of 3450.4 mbrf. This was 4.4 m deeper than the predicted depth of 3446.0 mbrf for operations at this site. The bit was placed at 3446.4 mbrf, and Hole U1422A was started at 0340 h on the morning of 18 August. When recovered, the core barrel was full (9.96 m), preventing the possibility of determining an accurate seafloor depth. This ended Hole U1422A.

Hole U1422B

The vessel was offset 15 m north of Hole U1422A, and Hole U1422B was spudded at 0515 h with the bit placed at a depth of 3441.4 mbrf. Once again, the barrel was recovered full (9.67 m), necessitating a third attempt to establish mudline.

Hole U1422C

The vessel was offset 30 m south of Hole U1422B, and Hole U1422C was spudded at 0640 h with the bit placed at 3435.4 mbrf. When recovered, the barrel contained 4.64 m of core, establishing a seafloor depth of 3440.3 mbrf. Coring operations continued in this hole using full-length APC core barrels to a depth 125.3 m CSF-A. Core 346-U1422C-14H required 90,000 lb of overpull, indicating that we would need either to drill over future core barrels or switch to the half APC system. Because of the success of the half APC system during the previous expedition (Expedition 341), this was the tool of choice. Very successful half APC coring continued to a total depth of 205.2 m CSF-A. The top drive was set back, and the drill string was pulled clear of the seafloor at 1950 h on 19 August, ending Hole U1422C and beginning Hole U1422D. Total recovery for this hole was 215.78 m (105.2%). A total of 17 half APC cores were recovered. A total of 79.90 m of penetration was achieved with this system, recovering 86.2 m (107.9%). Four successful temperature measurements were taken using the APCT-3 temperature shoe on Cores 4H, 7H, 10H, and 13H at depths of 33.1, 61.6, 87.3, and 115.8 m CSF-A, respectively.

Hole U1422D

The vessel was offset 15 m west of Hole U1422A, and Hole U1422D was spudded at 2120 h on 19 August. The bit was placed 3 m lower (3438.4 mbrf) than it was for Hole U1422C. The mudline core contained 8.14 m of core, establishing a seafloor depth of 3439.8 mbrf. APC operations continued in this hole to 141.8 m CSF-A. At that time, the Co-Chief Scientists decided that spending further time on the hole would not be fruitful because of the increasing amount of turbidites recovered from the section. The top drive was set back, and the drill string was pulled clear of the seafloor at 1235 h on 20 August, ending Hole U1422D and beginning Hole U1422E. A total of 141.8 m of penetration was achieved, recovering 152.83 m (107.8%).

Hole U1422E

The vessel was offset 15 m east of Hole U1422A, and Hole U1422E was spudded at 1320 h on 20 August, establishing a seafloor depth of 3440.0 mbrf. Coring operations continued in this hole, recovering 14 APC cores to 111.6 m CSF-A. Two of these cores (346-U1422E-9H and 10H) were half APC cores in an attempt to recover a turbidite section of the formation where recovery had been problematic. Incomplete stroke on Cores 13H and 14H led to curtailment of coring operations for the site. Total recovery for this hole was 114.34 m (102.5%). The top drive was set back, and the drill string was pulled clear of the seafloor at 0420 h on 21 August. The drill string was recovered back aboard the vessel, the BHA was set back in the derrick, and the vessel was secured for transit. At 1142 h that same day, the vessel got under way for Site U1423. This ended operations at Site U1422.

Site U1423

Three holes were drilled at Site U1423 (proposed Site JB-2) (Table T1). Hole U1423A was cored using the APC to 206.6 m CSF-A. Similarly, Hole U1423B was cored with the APC to 249.1 m CSF-A. Hole U1423C was drilled without coring to 114 m CSF-A. From this depth to 180 m CSF-A, we cut and recovered six cores in a series of alternating drilled and cored intervals with the objective of filling gaps in APC cores recovered from the previous two holes. Real-time stratigraphic correlation indicated that the carefully orchestrated coring operation appeared to be successful. Downhole measurements were carried out in Hole U1423B using a modified version of the paleo-combo tool string and the FMS-sonic tool string. A total of 56 cores were required to obtain 502.6 m of sediment (105.2% recovery).

Transit from Site U1422

The transit to Site U1423 was very short, and the 125 nmi distance was covered uneventfully in 12 h at an average speed of 10.4 kt. The sea passage ended at 2342 h on 21 August 2013. The vessel was maneuvered over the location coordinates, control of the vessel was turned over to dynamic positioning control at 0030 h on 22 August, and a seafloor positioning beacon was deployed at 0215 h the same day.

Hole U1423A

Operations in Hole U1423 started on 22 August. The same three-stand APC/XCB BHA used at the previous site was deployed, and the drill string was lowered to 1774 mbrf. After picking up the top drive and spacing out the drill string, an APC core barrel was deployed at 0530 h on 22 August. The bit was positioned at 1784.4 mbrf for the mudline core; however, the driller was unable to pressure up the drill string. Suspecting that the shear pins had prematurely failed during deployment, the barrel was recovered to the rig floor, where it was discovered empty and with all shear pins sheared. The pins were replaced, and the bit was lowered 10 m to 1794.4 mbrf for a second attempt. Hole U1423A started at 0640 h on 22 August. Core 346-U1423A-1H was recovered with 7.26 m of core, establishing a seafloor depth of 1796.6 mbrf. Cores 1H through 22H were taken from 0 to 206.6 m CSF-A and recovered 212.9 m of core (103%). Four temperature measurements were taken using the APCT-3 temperature shoe on Cores 4H, 7H, 10H, and 13H (35.8, 64.3, 92.8, and 111.8 m CSF-A, respectively). With the top drive left in place, the drill string was pulled clear of the seafloor at 2355 h on 22 August, ending Hole U1423A.

Hole U1423B

The ship was offset 15 m north of Hole U1423A and the bit was positioned at 1791.4 mbrf. Hole U1423B was spudded at 0050 h on 23 August. Core 346-U1423B-1H was recovered with 4 m of core, establishing a seafloor depth of 1797 mbrf. Cores 1H through 28H extended to 249 m CSF-A and recovered 250 m of core (100%). The recovery amount was negatively impacted because of zero recovery for Core 18H (151.6–158.1 m CSF-A), the result of a space-out error on the rig floor, resulting in an inadvertent drilling of hole that was to be cored on the next core. APC overpull (using full-length core barrels) varied between 60,000 and 80,000 lb between 142 and 249 m CSF-A (Cores 17H through 28H), with the exception of Core 27H (230.1–239.6 mbrf), when overpull reached 100,000 lb. The last core on deck was recovered at 1530 h on 23 August. To prepare for downhole logging, the hole was circulated clean, the logging tools were moved forward to the rig floor, the top drive was set back, and the drill string was pulled to a logging depth of 80.0 mbrf. The paleo-combo tool string was deployed and recorded spectral gamma ray, caliper, magnetic susceptibility, resistivity, and lithologic density logs. The second string consisted of the FMS-sonic tool string, which recorded resistivity images of the borehole, sonic velocities, and NGR data over the entire interval. Both logging tool strings were able to reach total hole depth. The logging tools were then rigged down, and the drill string was pulled clear of the seafloor at 0515 h on 24 August. This marked the end of Hole U1423B.

Hole U1423C

The ship was offset 15 m south of Hole U1423A, and Hole U1423C was spudded at 0655 h on 24 August. The operations plan for this hole was altered to save time and allow for recovering a few gaps in the stratigraphic record remaining after coring Holes U1423A and U1423B. The hole was drilled without coring (using an XCB center bit) to 114 m CSF-A. APC coring commenced, recovering six cores interspersed with appropriate drilled intervals to properly space out the core breaks and cover the areas of interest. Hole U1423C was terminated at 180.5 m CSF-A. After setting back the top drive, the bit cleared the seafloor at 1700 h and was back on the rig floor at 2040 h on 24 August. The positioning beacon was recovered aboard at 1756 h while tripping the drill string. After breaking out the bit and nonmagnetic drill collar, the rig floor was secured for transit, thrusters/hydrophones were raised, and the sea passage to Site U1424 began at 2136 h on 24 August.

Site U1424

Three holes were drilled at Site U1424 (proposed Site JB-1) (Table T1). Hole U1424A was cored using the APC to 158.8 m CSF-A. Similarly, Hole U1424B was cored with the APC to 154.7 m CSF-A, and Hole U1424C was cored to only 63.9 m CSF-A. A total of 41 cores obtained 380.68 m of sediment (101% recovery).

Transit from Site U1423

The transit to Site U1424 was very short. The 98.5 nmi distance was covered in just 10 h at an average speed of 9.9 kt. The sea passage ended at 0738 h on 25 August 2013. The vessel was maneuvered over the location coordinates and turned over to dynamic positioning control. By 0815 h the vessel was stabilized for rig floor operations to begin at Site U1424.

Hole U1424A

The drill string was tripped to the seafloor, and the bit was positioned at 2806 mbrf for the mudline core. However, this core barrel was recovered empty. The bit was repositioned at 2816 mbrf for the second attempt, and Hole U1424A was spudded at 1525 h on 25 August. Based upon recovery from the first core, a seafloor depth of 2818.7 mbrf was established. APC coring continued with 17 cores recovered to 158.8 m CSF-A. With the top drive left in place, the drill string was pulled clear of the seafloor at 0645 h on 22 August, ending Hole U1424A. Coring recovered 161 m of sediment (101%). One temperature measurement was taken using the APCT-3 temperature shoe on Core 346-U1423A-4H at 35.3 m CSF-A. This measurement fell exactly on the temperature gradient established during Leg 127 when this site was first cored (Site 794). Therefore, no additional temperature measurements were made at this site.

Hole U1424B

The ship was offset 15 m north of Hole U1424A, and Hole U1424B was started at 0740 h on 26 August. Recovery from Core 346-U1423B-1H established a seafloor depth of 2819.8 mbrf. APC coring continued uneventfully with 17 cores recovered to 154.7 m CSF-A. The bit cleared the seafloor at 2035 h on 26 August, ending Hole U1424B. Coring recovered 155.3 m of sediment (100%).

Hole U1424C

The ship was offset 15 m south of Hole U1424A, and Hole U1424C was spudded at 2125 h on 26 August. The operations plan for this hole was amended to conserve valuable operating time. Cores 346-U1424C-1H through 3H were taken for postexpedition OSL dating, and Cores 4H through 6H were taken for high-resolution geochemical analyses. Hole U1424C was started with the bit positioned at the same depth as it was for Hole U1424A (2416 mbrf). APC coring extended from the seafloor to 63.9 m CSF-A. OSL sampling involved special core handling procedures, and Hole U1424C was intentionally planned to be cored during the night to minimize the cores exposure to light. Cores 1H through 3H were cut in sequence into 1.5 m whole-round sections directly on the drill floor as the core was pulled out of the core barrel and placed into opaque aluminum-lined pouches, labeled, sealed, and stored in the refrigerated core storage. The drill string was pulled out of the hole, clearing the seafloor at 0320 h on 27 August, and was back on the rig floor at 0815 h on 27 August. The rig floor was secured for transit, thrusters were raised, and the sea passage to Site U1425 began at 0854 h on 27 August.

Site U1425

Site U1425 (proposed Site YR-1) was occupied at two different times during Expedition 346, first following operations at Site U1424 on 28 August 2013 and then ~3 weeks later after revisiting Site U1427 on 24 September (see below) to acquire additional material for postcruise studies. The return to Sites U1425 and U1427 was possible because all scientific and operations objectives were met ~5 days before the end of the expedition; therefore, the remaining time available was spent reoccupying these two important sites drilled earlier in the expedition. We drilled Hole U1425E during the revisit.

Four holes were cored at Site U1425 using the full and half APC and the XCB (Table T1). Hole U1425A was cored to 9.5 m CSF-A (one core), Hole U1425B was cored to 407.2 m CSF-A, Hole U1425C was cored to 25 m CSF-A, and Hole U1425D was cored to 431 m CSF-A. A total of 135 cores obtained 502.6 m of sediment (105.2% recovery). The APCT-3 was deployed four times.

Transit from Site U1424

The 180 nmi distance between Sites U1424 and U1425 was covered in 17.6 h at an average speed of 10.2 kt. The sea passage ended at 0230 h on 28 August. The vessel was maneuvered over the location coordinates, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 0300 h, the vessel was stabilized for rig floor operations to begin.

Hole U1425A

A three-stand APC/XCB BHA was assembled, and the drill string was run to bottom. After picking up the top drive and spacing out the drill string to 1911.4 mbrf (6 m above the observed seafloor depth on the ship’s PDR), an APC core barrel was deployed. The first core barrel was recovered empty. The bit was repositioned 10 m lower at 1901.4 mbrf for the second attempt. Hole U1425A was started at 0905 h on 28 August. This time, however, the core barrel was recovered full, once again missing a reliable seafloor determination.

Hole U1425B

The ship was offset 15 m north, a new APC core barrel was deployed, and the bit was positioned at 1918.4 mbrf. Hole U1425B was spudded at 1005 h on 28 August, establishing a seafloor depth of 1919.1 mbrf. APC/XCB coring continued to a final depth of 407.2 m CSF-A, the scientific target depth for this site. The coring operation in Hole U1425B consisted of 28 full APC cores, 23 half APC cores, and 10 XCB cores. We recovered 397.25 m of core (98%). Three successful temperature measurements were taken using the APCT-3 temperature shoe on Cores 346-U1425B-4H, 7H, and 10H (37.3, 65.8, and 94.3 m CSF-A, respectively). The hole was circulated clean, the logging tools were moved forward to the rig floor, the top drive was set back, and the drill string was pulled to a logging depth of 80 mbrf. At 1115 h on 30 August, preparations for wireline logging were initiated. The paleo-combo tool string was deployed to the bottom of the hole and recorded spectral gamma ray, caliper, magnetic susceptibility, resistivity, and lithologic density logs. The second string consisted of the FMS-sonic tool string, which recorded resistivity images of the borehole, sonic velocities, and NGR data. The FMS-sonic string reached 396.0 m CSF-A, 11.2 m off the bottom of the hole (407 m CSF-A). The logging tools were rigged down, and the drill string was pulled clear of the seafloor at 0200 h on 31 August.

Hole U1425C

After offsetting the ship 15 m south of Hole U1425A, Hole U1425C was spudded at 0355 h on 31 August. Core 346-U1425C-1H recovered 5.95 m, establishing a seafloor depth of 1918.9 mbrf. This core was followed by two additional full-length APC cores to 25 m CSF-A. Because these cores were for OSL sampling, they were handled per the protocols established at Site U1424, taking care to shield the core from any natural or artificial light as much as possible. The drill string was pulled clear of the seafloor at 0540 h on 31 August, ending Hole U1425C operations.

Hole U1425D

The ship was offset 15 m west of Hole U1425A and Hole U1425D was spudded at 0605 h on 31 August. Core 346-U1425D-1H established a seafloor depth of 1919.6 mbrf. Coring continued to a final depth of 431 m CSF-A, alternating between the full and half APC and the XCB core barrels. The coring effort consisted of 26 full APC cores, 40 half APC cores, and 4 XCB cores. Core recovery totaled 417.5 m (98%). Recovery percentages are biased in the last few cores in Hole U1425D because both the XCB and half APC systems were pushed into dolomite and siliceous claystone horizons that neither coring system was designed to handle. Despite the poor recovery in the last few cores, the coring effort was scientifically successful, obtaining a dateable cored section for the last half APC core recovered (Core 72H). The top drive was set back and the drill string was recovered back aboard the ship. The positioning beacon was recovered during the pipe trip and was back aboard after lunch on 2 September. The BHA was set back in the derrick, and the vessel was secured for transit to Site U1426, ending (temporarily) operations at Site U1425.

Return to Site U1425

We returned to Site U1425 after completing an additional hole at Site U1427. The 212 nmi distance between these two sites was covered in 19.5 h at an average speed of 10.9 kt. The sea passage ended at 1430 h on 24 September. The vessel was maneuvered over the location coordinates, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 1500 h, the JOIDES Resolution was stabilized and rig floor operations began.

Hole U1425E

Deployment of a positioning beacon was deemed unnecessary for this hole because the weather was good, the water depth was <2000 m, and the anticipated penetration depth was only ~100 m CSF-A. Nonetheless, a Falmouth Scientific positioning beacon (model BAP-547; SN1022, 14 KHz, 208 dB) was kept on standby in case it was required.

As at Site U1427, this hole was to provide extra core material for future sampling needs and postexpedition studies. The APC/XCB BHA was assembled, and the drill string was run to bottom. The ship was positioned 15 m east of Hole U1425A. The top drive was picked up, and the pipe was spaced out, positioning the bit at a depth of 1913.4 mbrf. The first barrel was recovered empty (water core), so the bit was lowered 3.0 m to 1916.4 mbrf, and the process was repeated. Hole U1425E was ultimately spudded at 1945 h on 24 September. The first core barrel recovered 5.69 m of core, establishing a seafloor depth of 1920.2 mbrf. APC coring continued using full-length nonmagnetic core barrels through Core 346-U1425E-13H to a total depth of 113.1 m CSF-A. Total recovery for Hole U1425E was 107.75 m (95%). A total of 13 cores were recovered in this hole, all using full-length nonmagnetic core barrels.

The top drive was set back, and the drill string was pulled clear of the seafloor at 0435 h on 25 September. All drill collars were laid out to the forward pipe rack, and the bit was clear of the rotary table by 0910 h. The bit and bit sub were removed, and the outer barrel coring system was disassembled. The rig floor was secured for transit by 0950 h. Thrusters were raised, and the sea passage to Busan was initiated at 1012 h on 25 September, successfully ending all coring operations of Expedition 346.

Site U1426

Four holes were cored at Site U1426 (proposed Site YB-2) using the full and half APC and the XCB (Table T1; Fig. F38). Holes U1426A, U1426B, U1426C, and U1426D were cored to 396.7, 34.7, 204.0, and 99.4 m CSF-A and recovered 418.78, 35.82, 211.89, 103.71 m of core, respectively. A total of 95 APC and 2 XCB cores obtained 770.2 m of sediment (104.8% recovery). The APCT-3 was deployed four times.

Transit from Site U1425

The 148 nmi transit to Site U1426 was covered in 13.4 h at an average speed of 11 kt. The sea passage ended at 0636 h on 3 September 2013. The vessel was maneuvered over the location coordinates, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 0715 h, the vessel was stabilized for rig floor operations to begin. A Falmouth Scientific positioning beacon (model BAP-547; SN1028W, 16 KHz, 206 dB) was deployed at 0822 h.

Hole U1426A

A three-stand APC/XCB BHA was assembled, and the drill string was run to the seafloor. After picking up the top drive and spacing out the drill string to a depth of 907.4 mbrf, which was 6.0 m below the depth provided by the PDR, an APC core barrel was deployed. The first core barrel recovered 2.47 m of core, establishing a seafloor depth of 914.4 mbrf. Oriented APC coring continued using full-length nonmagnetic core barrels through Core 346-U1426A-28H at 256.2 m CSF-A. At this depth, the APC was switched to the half APC (4.7 m) system, and coring continued through Core 37H (297.0 m CSF-A), where a solid dolomite layer was encountered. The XCB was picked up and used to cut a 1.0 m core (38X) until breaking through the layer of resistance. Half APC coring resumed from that point and continued through Core 59H (396.7 m CSF-A). The hole was displaced with 160 bbl of 10.5 ppg mud. The top drive was set back, and the drill string was pulled clear of the seafloor at 2330 h on 4 September, ending Hole U1426A. Total recovery for this hole was 418.78 m (105.6%). A total of 29 half APC cores were recovered. Four successful temperature measurements were taken using the APCT-3 temperature shoe at 31.0, 59.5, 88.0, and 116.5 m CSF-A, respectively.

Hole U1426B

The ship was offset 15 m north of Hole U1426A, and the bit was positioned 3 m lower at a depth of 910.4 mbrf. Hole U1426B was spudded at 0045 h on 5 September. Recovery from the first core established a seafloor depth of 913.7 mbrf. APC coring continued with four cores recovered for intensive geochemistry sampling to a depth of 34.7 m CSF-A. By 0215 h, the last core barrel had been laid out and the rig floor prepared for tripping pipe. Because the hole was shallow, the pipe was tripped out of the hole with the top drive in place. The bit cleared the seafloor at 0230 h, officially ending Hole U1426B. Recovered core totaled 35.82 m (103%).

Hole U1426C

The ship was offset 15 m south of Hole U1426A. The top drive was picked up, the bit was positioned at 911.4 mbrf, and Hole U1426C was spudded at 0250 h on 5 September. The mudline core established a seafloor depth of 914.4 mbrf. APC coring continued through Core 346-U1426C-15H to 128.3 m CSF-A. XCB Core 16X cut through a hard dolomite layer, allowing the continuation of APC coring. Full-length core barrels were used through Core 24H to 206 m CSF-A. The hole was plugged and abandoned with 80 bbl of 10.5 ppg mud. The drill string was pulled with the top drive to 895 mbrf, clearing the seafloor at 1425 h. This ended Hole U1426C. Total recovery for this hole was 211.9 m (103.9%). There were no half APC cores from this hole.

Hole U1426D

The ship was offset 15 m west of Hole U1426A. The top drive was picked up, and the bit was positioned at 909.4 mbrf. Hole U1426D was spudded at 1500 h on 5 September. The sediment/water interface was recovered in Core 1H, establishing a seafloor depth of 914.4 mbrf. APC coring continued with 11 full-length cores recovered to 99.4 m CSF-A. The hole was plugged and abandoned with 40 bbl of 10.5 ppg mud. The top drive was set back, and the drill string was pulled clear of the seafloor at 2030 h on 5 September. The bit subsequently cleared the rotary table at 2235 h. The rig floor was secured for transit, thrusters were raised, and the sea passage to Site U1427 began at 2342 h on 5 September. Total recovery for this hole was 103.71 m (104.3%). There were no half APC cores taken from this hole.

Site U1427

Site U1427 (proposed Site YB-1) was occupied at two different times during Expedition 346, first following operations at Site U1426 (6 September 2013) and then ~2 weeks later after completing operations at Site U1430 (22 September), to acquire additional material for postcruise studies. A return to Site U1427 was possible because all scientific and operations objectives were met ~5 days before the end of the expedition; therefore, the remaining time available was spent reoccupying two sites drilled earlier in the expedition (Sites U1427 and U1425). Preliminary shipboard scientific results from Holes U1427A and U1427B indicated that this site exhibits a continuous late Pleistocene sedimentary sequence with high sedimentation rates and excellent carbonate preservation, both of which are ideal for high-resolution paleoceanographic studies. Therefore, we drilled Hole U1427C during the revisit.

Three holes were cored at Site U1427 using the full and half APC and the XCB. Hole U1427A was cored to 548.6 m CSF-A (81 cores) with a recovery of 542.59 m (98.9%). Hole U1427B was cored to 405.6 m CSF-A (65 cores) with a recovery of 422.41 m (105%). Hole U1427C was cored to 351.1 m (52 cores) with a recovery of 367.77 m (105%) (Table T1; Fig. F38). Four formation temperature measurements were performed, and downhole wireline log data were obtained to 548.5 m WSF in Hole U1427A.

An exciting aspect of operations at Site U1427 included the acquisition of the deepest continuously recovered APC-cored sequence in DSDP/ODP/IODP history and the deepest piston core, 81H, from 490.4 m CSF-A.

Transit from Site U1426

The 66 nmi distance to Site U1427 was covered in 6 h at an average speed of 11.1 kt. The sea passage ended at 0542 h on 6 September. The vessel was maneuvered over the location coordinates, a wide-angle positioning beacon was deployed, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 0615 h, the vessel was stabilized, and rig floor operations began.

Hole U1427A

A three-stand APC/XCB BHA was assembled, and the drill string was run to bottom. After picking up the top drive and spacing out the drill string to a depth of 329.4 mbrf (6.0 m above PDR depth), an APC core barrel was deployed. The first core barrel recovered 1.79 m of core, establishing a seafloor depth of 337.1 mbrf. Oriented APC coring continued using full-length nonmagnetic core barrels through Core 346-U1427A-25H to 228.7 m CSF-A. The base of Core 25H recovered reworked volcanic sand, and the next core contained volcanic ash. At that point, we switched to the half APC system and continued coring through Core 81H to a depth of 490.4 m CSF-A, making this, as mentioned above, the deepest continuously cored sequence ever recovered with the APC coring system in DSDP/ODP/IODP history. An additional 6 XCB cores were cut to a final total depth of 548.6 m CSF-A. The hole was circulated and displaced with 10.5 ppg weighted mud, the top drive was set back, and the pipe was pulled up to logging depth (80 m WSF). Rig-up for wireline logging began at 0630 h on 8 September. Both the paleo-combo and FMS-sonic tool strings were deployed to 548.5 m WSF, and all wireline logging runs were successful. By 1715 h that same day, the rig floor was rigged down from logging. The pipe was lowered (without the top drive) to 519 m CSF-A, and a 10 bbl (24 m long) 14.5 ppg cement plug was displaced using a circulating head. The drill string was pulled clear of the seafloor at 2020 h on 8 September, ending Hole U1427A and beginning Hole U1427B. Total recovery for this hole was 542.6 m (99%). A total of 56 half APC cores were recovered. Four formation temperature measurements were taken using the APCT-3 temperature shoe at 30.3, 58.8, 87.3, and 115.8 m CSF-A.

Hole U1427B

Once clear of the seafloor, the drill string was thoroughly flushed to remove any remnant cement, and an XCB was deployed to aid in flushing/cleaning the lockable flow valve. The XCB was recovered and the ship was offset 15 m north of Hole U1427A. The bit was placed at a depth of 332.4 mbrf, and an APC core barrel was deployed. Hole U1427B was spudded at 2220 h on 8 September, and the 4.8 m of core recovered from the mudline core established a seafloor depth of 337.1 mbrf. APC coring with full core barrels continued through Core 346-U1427B-6H to 52.3 m CSF-A before a 1.0 m drilled interval was used to correct the core break offsets. APC coring continued through Core 12H to a depth of 100.8 m CSF-A, where a second 1 m advance was made. APC coring resumed, recovering Cores 14H through 28H to 235.8 m CSF-A. This barrel was an incomplete stroke and was very near the interval in Hole U1427A where the APC met refusal. Eight half APC cores were then recovered (Cores 29H through 36H) to a depth of 273.4 m CSF-A. Because the overpull was zero for the previous six cores, we switched back to full APC barrels beginning with Core 37H. However, this core failed to fully penetrate the formation, and coring resumed at that point using the half APC system once again. A 1.0 m advance was made to properly align the core breaks, and coring then continued recovering half APC Cores 39H through 47H to 325.4 m CSF-A. There, another 3 m “drill ahead” advance was made to realign core breaks, which had drifted close to stacking up with the earlier hole. With the exception of a fourth drill ahead of 2 m after Core 52H, half APC coring continued through Core 65H to a total depth of 405.6 m CSF-A. The hole was displaced with 190 bbl of 10.5 ppg mud, and the drill string was pulled clear of the seafloor by 0605 h on 10 September. The bit cleared the rotary table at 0735 h, the positioning beacon was recovered aboard by 0752 h, and by 0830 h the ship was under way for the next drill site (U1428). Total recovery for Hole U1427B was 422.41 m (105%). Of the 61 cores recovered, 32 were half APC cores.

Return to Site U1427

The 182 nmi between Sites U1430 and U1427 were covered in 17.2 h at an average speed of 10.6 kt. The sea passage ended at 0830 h on 22 September. The vessel was maneuvered over the location coordinates, and a Falmouth Scientific positioning beacon (model BAP-547; SN1028W, 16 KHz, 206 dB) was deployed at 0958 h. Thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 0900 h, the vessel was stabilized and rig floor operations began.

Hole U1427C

The APC/XCB BHA was quickly assembled, and the drill string was run to bottom. For this hole, the ship was positioned 15 m south of Hole U1427A. The top drive was picked up and the pipe was spaced out, positioning the bit at a depth of 336 mbrf. Hole U1427C was spudded at 1200 h on 22 September. The first core barrel recovered 8.05 m of core, establishing a seafloor depth of 337.5 mbrf. APC coring continued using full-length nonmagnetic core barrels through Core 346-U1427C-10H to 93.5 m CSF-A. A single half APC core was then taken (Core 11H) to adjust the core break offset. APC coring then continued using full barrels through Core 25H to 224.2 m CSF-A. Coring continued from that point using the half APC through Core 52H to a total depth of 351.1 m CSF-A. The hole was displaced with 140 bbl of 10.5 ppg weighted mud, the top drive was set back, and the drill string was pulled clear of the seafloor at 1710 h on 23 September. The bit was clear of the rotary table by 1815 h. During the pipe trip, the positioning beacon was recovered at 1739 h. The bit and bit sub were removed, and the rig floor was secured for transit by 1845 h. Thrusters and hydrophones were pulled, and the sea voyage to the next site was initiated at 1900 h on 23 September. Total recovery for Hole U1427C was 367.77 m (105%). Of the total 52 cores recovered, 25 were full APC cores and 27 were half APC cores. There were no cores cut using the XCB.

Sites U1428 and U1429

Two holes were cored at primary Site U1428 (proposed Site ECS-1B), and three holes were cored at alternate Site U1429 (alternate Site ECS-1C) using the full and half APC and the XCB. At both sites, nonmagnetic core barrels were used with the APC system. Only full APC core barrels were oriented. In Hole U1428A, 26 cores extended from the seafloor to 211.5 m CSF-A, including seven drilled intervals (totaling 37.6 m) through thick sand beds. The cored interval in Hole U1428A was 173.9 m, with a recovery of 178.86 m of core (103%) (Table T1; Fig. F38). After completing Hole U1428A, we moved to Site U1429, which was estimated to have higher LSRs and, therefore, an expanded late Pleistocene section.

APC coring at Site U1429 was uneventful. Hole U1429A penetrated to 188.3 m CSF-A, including two drilled intervals totaling 4.1 m. Core recovery for Hole U1429A was 190.3 m (103%). Hole U1429B penetrated to 186.2 m CSF-A, with a recovery of 200.9 m of core (108%). Hole U1429C penetrated to 179.2 m CSF-A, including two drilled intervals totaling 4.9 m. Core recovery for Hole U1429C was 180.7 m (104%).

After completing the three holes at Site U1429, we returned to Site U1428 to drill a second, additional hole that provided material to build a complete spliced section at this site spanning at least the last ~0.3 m.y. and to provide additional material for high-resolution paleoceanographic studies. Hole U1428B was subsequently APC cored to 143.3 m CSF-A (16 cores), with a recovery of 145.85 m (102%).

Transit from Site U1427

The transit to Site U1428 included a short stop offshore at Kitakyushu, Japan, to evacuate a scientist suffering from kidney stones. The 248 nmi transit to the rendezvous coordinates (34°30.0′N, 130°23.0′E) was covered at an average speed of 10.8 kt. The designated rendezvous time was 0800 h on the morning of 11 September 2013. Coordination of the medical evacuation was provided by the Sea Trade and Agency Yokohama and locally by Green Shipping in Moji, Japan. The JOIDES Resolution was on location for the evacuation at 0736 h. The sea-going tug Musashi Maru 2 was alongside by 0752 h. The transfer was completed safely and efficiently by 0754 h. The tug was clear by 0755 h and headed back to shore. The JOIDES Resolution then resumed course for Site U1428. The remaining 228 nmi distance was covered in 21 h at an average speed of 10.9 kt. The sea passage ended at 0500 h on 12 September. The vessel was maneuvered over the location coordinates, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 0530 h on 12 September, the vessel was stabilized and rig floor operations began. A Falmouth Scientific positioning beacon (model BAP-547; SN1028W, 16 KHz, 206 dB) was deployed at 0614 h.

Hole U1428A

A three-stand APC/XCB BHA was assembled, and the drill string was run to bottom. During the pipe trip, the vibration-isolated television (VIT) subsea camera was deployed. The top drive was picked up, and the drill string was spaced out to just above the seafloor. Because of the presence of submarine cables in the vicinity of this site, a camera survey of the seafloor was conducted to ensure that no holes were spudded into a submarine cable. This was considered precautionary only because the closest cables to the drill site should have been nearly 2 nmi away. A box survey was conducted radiating out from the drill site coordinates in 5 m increments. The total outside diameter of the box was 25 m. This ensured that any of the holes spudded within 15 m of Hole U1428A would be well within the preinspected area. The survey was completed at 1200 h, and after returning to zero-zero coordinates, a tag of the seafloor with the drill bit was observed on camera. This established a drill string tag depth of 735.3 mbrf, or 1.6 m shallower than the depth predicted with the PDR. The pipe was then picked up 3 m, placing the bit at 732.3 mbrf, and Hole U1428A was spudded at 1230 h on 12 September. The first core barrel recovered 6.37 m of core, establishing an “official” seafloor depth of 735.4 mbrf. Oriented APC coring continued using full-length nonmagnetic core barrels through Core 346-U1428A-18H to a depth of 150.1 m CSF-A. Half APC coring continued from that point through Core 346-U1428A-32H to a total depth of 211.5 m CSF-A. Because of the large accumulation of sand in the formation, further coring at this site was abandoned. The hole was displaced with 80 bbl of 10.5 ppg weighted mud, and the drill string was pulled clear of the seafloor at 0735 h on 12 September. The bit was clear of the rotary table by 0930 h. The positioning beacon was recovered at 0811 h, and the ship was secured for transit by 0940 h. Thrusters and hydrophones were pulled, and the sea voyage to Site U1429 was initiated at 1024 h on 13 September. Total recovery for Hole U1428A was 178.86 m (103%). There were no half APC cores taken in this hole; however, there were seven drilled intervals totaling 37.6 m. Three successful formation temperature measurements were taken using the APCT-3 temperature shoe at 34.9, 63.4, and 120.4 m CSF-A. A fourth temperature measurement attempted on Core 10H failed because of insertion into sand.

Transit from Site U1428

The transit to Site U1429 included a brief stop while en route to discharge another scientist, this one suffering from a severe case of shingles. The scientist was removed from the JOIDES Resolution by a Japanese Coast Guard helicopter. The transfer was completed safely and efficiently by 1100 h on 13 September. The JOIDES Resolution then resumed full speed for Site U1429. The 228 nmi to Site U1429 was covered in 1.6 h at an average speed of 7.4 kt. The sea passage ended at 1200 h on 13 September. The vessel was maneuvered over the location coordinates, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 1215 h, the JOIDES Resolution was stabilized, and rig floor operations began.

Hole U1429A

A three-stand APC/XCB BHA was assembled, and the drill string was run to bottom. During the pipe trip, the VIT subsea camera was deployed. The top drive was picked up, and the drill string was spaced out to just above the seafloor. As at the previous site, a camera survey of the seafloor was conducted to ensure that no holes were spudded into a submarine cable. As before, a box survey was conducted radiating out from the drill site coordinates in 5 m increments. The total outside diameter of the box was again 25 m. This ensured that any of the holes spudded within 15 m of Hole U1429A would be well within the preinspected area. The survey began at 1735 h and was completed by 1945 h on 13 September. After returning to zero-zero coordinates, a tag of the seafloor with the drill bit was observed on camera. This established a drill string tag depth of 743.6 mbrf, or 2.8 m shallower than the depth predicted with the PDR. The pipe was then picked up 3 m, placing the bit at 740.6 mbrf, and Hole U1429A was spudded at 2045 h on 13 September. The first core barrel recovered 6.4 m of core, establishing an “official” seafloor depth of 743.7 mbrf. Oriented APC coring continued using full-length nonmagnetic core barrels through Core 346-U1429A-23H to 188.3 m CSF-A. As at Site U1428, large accumulations of volcanic sand in the formation prevented coring to the original deeper objectives. This led to the decision to complete three APC holes through the upper section (~200 m CSF-A) and then abandon the site. The hole was displaced with 75 bbl of 10.5 ppg weighted mud, and the drill string was pulled clear of the seafloor at 0900 h on 13 September, ending Hole U1429A and beginning Hole U1429B. Total recovery for this hole was 190.29 m (103%). No half APC cores were taken in this hole; however, there were two drilled intervals totaling 4.1 m to adjust the core breaks. Four successful formation temperature measurements were taken using the APCT-3 temperature shoe at 34.9, 61.1, 89.6, and 116.4 m CSF-A.

Hole U1429B

Because a massive sand horizon was also present at this site, the operations plan was revised to eliminate any deep penetration attempt. Instead, the focus was on obtaining two additional ~200 m holes to thoroughly recover the upper section. Hole U1429B began as the drill string cleared the seafloor. The ship was offset 15 m north of Hole U1429A. The bit was positioned at 736.6 mbrf. An APC core barrel was deployed, and Hole U1429B was spudded at 0935 h on 14 September. The 2.93 m of core recovered established a seafloor depth of 743.2 mbrf. APC coring with full-length core barrels continued through Core 346-U1429B-22H to 186.2 m CSF-A. Partial strokes were experienced on Cores 6H, 18H, and 22H; however, all others were full stroke. Hole U1429B was once again terminated just into the volcanic sand. The hole was displaced with 75 bbl of 10.5 ppg mud, and the drill string was pulled clear of the seafloor at 2210 h on 14 September, ending Hole U1429B. Total recovery for this hole was 200.92 m (108%). Of the 22 cores recovered, all were full-barrel cores. There were no attempted half APC cores.

Hole U1429C

Hole U1429C began as the drill string cleared the seafloor. The ship was offset 15 m south of Hole U1429A. The bit was positioned at 738.6 mbrf. An APC core barrel was deployed, and Hole U1429C was spudded at 2235 h on 14 September. The 4.16 m of core recovered established a seafloor depth of 744.0 mbrf. APC coring with full-length core barrels continued through Core 346-U1429C-24H to 179.2 m CSF-A. Partial strokes were experienced on Cores 6H, 16H, 20H, and 24H; however, all others were full stroke. The hole was once again terminated just into the volcanic sand. Total recovery for Hole U1429C was 180.70 m (103.7%). Of the 22 cores recovered, all were full-barrel cores. There were no attempted half APC cores.

Hole U1429C was displaced with 75 bbl of 10.5 ppg mud, the top drive was set back, and the drill string was pulled clear of the seafloor at 1055 h on 15 September. The pipe was tripped back to the surface, and the BHA racked back in the derrick. Because the move back to Site U1428 was only 4 nmi, the last stand with the bit and outer core barrel components was left hanging on the hook through the rotary table. This saved time and allowed the ship to get under way faster. The positioning beacon was recovered back aboard during the pipe trip at 1142 h. The ship was secured for transit by 1225 h. Thrusters and hydrophones were pulled, and the sea voyage to Site U1428 was initiated at 1242 h on 15 September.

Return to Site U1428

The transit back to Site U1428 was quickly accomplished. The 4.0 nmi distance was covered in just 0.75 h at an average speed of 5.3 kt. The sea passage ended at 1330 h on 15 September. The vessel was maneuvered over the location coordinates, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 1345 h, the JOIDES Resolution was stabilized, and rig floor operations began.

Hole U1428B

Because of the shallow nature of the single hole and short duration on site, a positioning beacon was not deployed to the seabed. The APC/XCB BHA was quickly assembled, and the drill string was run to bottom. The ship was offset 15 m north of Hole U1428A. The top drive was picked up, and the pipe was spaced out, positioning the bit at 728.8 mbrf. Hole U1428B was spudded at 1635 h on 15 September. The first core barrel recovered 2.49 m of core, establishing a seafloor depth of 735.8 mbrf. APC coring continued using full-length nonmagnetic core barrels through Core 346-U1428B-16H to 143.3 m CSF-A. Hole U1428B was displaced with 55 bbl of 10.5 ppg weighted mud, the top drive was set back, and the drill string was pulled clear of the seafloor at 0130 h on 16 September. The bit was clear of the rotary table by 0330 h. The bit and bit sub were removed, and the ship was secured for transit by 0345 h. Thrusters and hydrophones were pulled, and the sea voyage to Site U1430 was initiated at 0418 h on 16 September. Total recovery for this hole was 145.85 m (102%). Of the 16 cores recovered, all were full-barrel cores. There were no attempted half APC cores.

Site U1430

Three holes were cored at Site U1430 using the full and half APC and the XCB. Oriented, nonmagnetic core barrels were used with the full APC system in Hole U1430A. Half APC cores in Hole U1430A were not oriented but used nonmagnetic barrels. A total of 29 APC cores and 3 XCB cores penetrated to 274.4 m CSF-A in Hole U1430A, recovering 258.24 m (94%). In Hole U1430B, 29 APC cores and 8 XCB cores extended from the seafloor to 275 m CSF-A, recovering 259.71 m (94%). In Hole U1430C, 33 APC cores and 1 XCB core penetrated to 250 m CSF-A, recovering 257.02 m (103%). Total core recovery for Site U1430 was 775 m (Table T1; Fig. F38).

Transit from Site U1428

The transit to Site U1430 was slowed somewhat by the effects of the distant tropical storm Man-yi, which passed ~300 nmi to the east of the JOIDES Resolution off the eastern side of Japan. Strong winds (sustained at 36 kt and gusting to 48 kt) caused some heavy seas and a reduced transit speed of 9.0 kt. The 430.5 nmi total distance was ultimately covered in 44.0 h at an average speed of 9.8 kt. The sea passage ended at 0018 h on 18 September 2013. The vessel was maneuvered over the location coordinates, thrusters were lowered into position, and the vessel was turned over to dynamic positioning control. By 0100 h, the JOIDES Resolution was stabilized, and rig floor operations began.

Hole U1430A

A Falmouth Scientific positioning beacon (model BAP-547; SN1028W, 16 KHz, 206 dB) was deployed at 0123 h on 18 September. A three-stand APC/XCB BHA was assembled, and the drill string was run to bottom. The top drive was picked up, and the bit was positioned at 1077.7 mbrf, 3.0 m above the PDR depth. Hole U1430A was spudded at 0445 h on 18 September. The first core barrel recovered 3.58 m of sediment, establishing a seafloor depth of 1083.6 mbrf. Oriented APC coring continued using full-length nonmagnetic core barrels through Core 346-U1430A-25H to 230.7 m CSF-A. Half APC coring with nonmagnetic core barrels continued through Core 29H to 249.5 m CSF-A, where refusal was reached in acoustic basement. The XCB was then used to advance the hole to 274.5 m CSF-A (Cores 30X through 32X). XCB coring was problematic because of the nature of the interbedded hard/soft layering of the formation. Based on poor recovery and slow penetration rates with the XCB, the decision was made to stop coring in this hole. Hole U1430A was circulated and displaced with 114 bbl of 10.5 ppg heavy mud, and the drill string was pulled clear of the seafloor at 0220 h on 19 September, ending the hole. Total recovery for Hole U1430A was 258.24 m (94%); however, core recovery with the XCB system was only 1.12 m of the 24.9 m advanced (4.5%). Four successful formation temperature measurements were taken using the APCT-3 temperature shoe at 32.1, 60.6, 89.1, and 117.6 m CSF-A.

Hole U1430B

The ship was offset 15 m north of Hole U1430A. The bit was positioned at 1081.7 mbrf. An APC core barrel was deployed, and Hole U1430B was spudded at 0330 h on 19 September. The 8.27 m of core recovered established a seafloor depth of 1082.9 mbrf. APC coring with full-length core barrels continued through Core 346-U1430B-25H to 234.6 m CSF-A. This was followed by the half APC system for Cores 26H through 28H to 246.0 m CSF-A. At that point, we switched to XCB and recovered Cores 29X through 36X to 274.1 m CSF-A. One final half APC core (37H) advanced the hole to a total depth of 275.0 m CSF-A. The hole was displaced with 114 bbl of 10.5 ppg mud, the top drive was set back, and the drill string was pulled up to a logging depth of 79.1 m WSF. Rig-up for wireline logging began at 0215 h on 20 September. Because of the shallow hole depth and to maximize the logging data acquired, the triple combination tool string was split into two shorter tool strings. All logging runs reached within a few meters of total hole depth, and all wireline logging runs were considered successful. By 1530 h, the rig floor was rigged down from logging, and the drill string was pulled clear of the seafloor at 1550 h on 20 September, ending Hole U1430B. Total recovery for Hole U1430B was 259.71 m (94%). A total of 25 full APC cores and 4 half APC cores were recovered. As in Hole U1430A, recovery with the XCB remained poor. Eight XCB cores were attempted, penetrating 28.1 m and recovering only 5.94 m (21%).

Hole U1430C

Hole U1430C began as the drill string cleared the seafloor. The ship was offset 15 m south of Hole U1430A. The bit was positioned at 1079.7 mbrf. An APC core barrel was deployed, and Hole U1430C was spudded at 1645 h on 20 September. The 4.78 m of core recovered established a seafloor depth of 1084.4 mbrf. Oriented APC coring continued using full-length nonmagnetic core barrels through Core 346-U1430C-26H to 227.3 m CSF-A. A single XCB barrel (Core 27X) was deployed to drill through a hard layer, penetrating 1.5 m. This core recovered 0.05 m of dolomite fragments. Half APC coring with nonmagnetic core barrels continued, recovering Cores 28H through 34H to 250.0 m CSF-A. The hole was displaced with 100 bbl of 10.5 ppg weighted mud, the top drive was set back, and the drill string was pulled clear of the seafloor at 1215 h on 21 September. The bit was clear of the rotary table, the bit and bit sub were removed, and the rig floor was secured for transit by 1500 h. Thrusters and hydrophones were pulled, and the sea voyage to the next site was initiated at 1518 h on 21 September. Total recovery for Hole U1430C was 257.02 m (103%). Of the 34 cores recovered, 26 were full APC cores, 7 were half APC-cores, and 1 was an XCB core.

Return to Sites U1427 and U1425

Because of excellent success throughout the expedition with high core recovery stratigraphic correlation, and operations and enjoying the benefit of highly advantageous weather, we had the unusual opportunity to return to several of the previously occupied Expedition 346 sites for additional coring. After extensive discussions with the shipboard science party, technical support staff, and operations superintendent, it was deemed most appropriate to return to Sites U1427 and U1425. The order in which we returned to the two sites was dictated by scientific priority, the most efficient use of transit times, and consideration of end of expedition requirements. The science party and Sample Allocation Committee anticipated that there will be many sample requests for those two sites and that additional coring there would be highly beneficial. For details about the return to these two sites (and operations in Holes U1427C and U1425E, respectively), please refer to the operations sections describing those sites.

Transit from Site U1425 to Busan, Korea

The transit to Busan was completed without incident. The vessel arrived at the Busan pilot station at 0600 h on 27 September. The Asian Monsoon Expedition 346 officially ended 24 h early with the first line ashore at 0651 h on 27 September.

It seems only fitting that on this research voyage, which is the last of this phase of IODP, that we draw attention to the fact that this expedition set the record for the most amount of core recovered during any single research cruise by IODP. That the recovery of 6135 m of sediment occurred during only ~6 weeks of drilling operations makes this accomplishment even more remarkable. In combination with the record achieved of acquiring the deepest piston core (and deepest continually piston cored sequence at Site U1427), these achievements speak of the commitment to excellence, teamwork, and, to be direct, impressively hard work of men and women dedicated to the pursuit of scientific knowledge about Planet Earth.

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