IODP Expeditions 367 and 368

South China Sea Rifted Margin

Daily Science Report for 31 May 2017

Location: Hole U1505C (alternate Site SCSII-3D, 18°55.0570′N, 115°51.5491′E, water depth 2917.4 mbsl)

Science Update: Cores U1505C-35F to 47F penetrated from 258.8 m to HLAPC refusal at 317 m, recovering 57.2 m (98%). We then switched to the XCB coring system, and Cores U1501C-48X to 52X penetrated from 317 to 365.2 m, recovering 48.7 m (101%).

Cores U1505C-18H to 43F consist of interbedded foraminifera-rich nannofossil ooze with clay, nannofossil ooze with clay, and clay rich nannofossil ooze with foraminifera, and rare silty layers. Bioturbation ranges from moderate to heavy. Drilling disturbance (flow-in) has been observed in the bottom 1–3 sections of most split cores after Core U1505C-19H. The sedimentary succession recovered so far extends to the early Miocene. Scientists are collecting Site U1505 data and beginning to submit Site U1504 reports.

Daily Science Report for 30 May 2017

Location: Hole U1505C (alternate Site SCSII-3D, 18°55.0566′N, 115°51.5382′E, water depth 2916.6 mbsl)

Science Update: APC Cores U1505C-11H to 34F extended the hole from 93.7 to 258.8 m, recovering 167.9 m (102%). Cores U1505C-16H, and 19H to 23H were only partial strokes, and Cores 21H to 23H (from 188.7 to 207.1 m) were advanced by recovery (7.83, 3.36, and 3.95 m, respectively). At that point we switched to the half-length APC (HLAPC) system to continue deepening the hole.

Cores U1505C-5H to 17H consist of foraminifera-rich nannofossil ooze with clay. The color of the sediment is predominantly dark greenish gray with alternating gray and brown layers. A middle Miocene age has been determined for the base of Core U1505C-34H based on biostratigraphic markers. We held meetings to discuss strategies for postexpedition research planning across the two South China Sea expeditions. Scientists are collecting and measuring data from Site U1505 and preparing the Site U1504 reports.

Daily Science Report for 29 May 2017

Location:
Hole U1505A (alternate Site SCSII-3D, 18°55.0560′N, 115°51.5369′E, water depth 2916.6 mbsl)
Hole U1505B (alternate Site SCSII-3D, 18°55.0562′N, 115°51.5370′E, water depth 2918.6 mbsl)
Hole U1505C (alternate Site SCSII-3D, 18°55.0570′N, 115°51.5491′E, water depth 2917.4 mbsl)

Science Update: The day started while lowering the drill string with an APC/XCB bottom-hole assembly to the seafloor to start APC coring at Site U1505. At 0545 h, before we reached bottom, we conducted required routine rig servicing (drill line slip and cut), and lowered the camera system to observe the end of the pipe tag the seafloor and establish the water depth (2916.6 m). The camera was pulled back to surface. Hole U1505A was started at 1130 h, but Core 1H misfired (failed shear pins) and only recovered 0.3 m of sediment. The cause of the error is believed to have been the shear pins that are used to contain the core barrel before it is pressurized and fired. They likely failed before the core barrel got to the bottom. Without offsetting the ship, and with the bit at 2922 mbsl, we started coring in Hole U1505B and Core 1H penetrated 3 m into the seafloor, recovering 3.23 m of core (107%). With a good mudline core, we terminated Hole U1505B, offset the ship 20 m to the east, and with the bit at 2916.5 m, Hole U1505C was started at 1340 h. Core U1505C-1H penetrated 8 m with a recovery of 100%, establishing a seafloor depth of 2917.4 m. By midnight, Cores U1505C-2H through 10H had penetrated to 93.7 m and recovered 98.2 m (105%).

Cores U1505C-1H to 4H contain greenish gray and dark greenish gray nannofossil-rich clay with biogenic silica intercalated with nannofossil ooze. An 8 cm thick pinkish gray ash layer occurs in Core 3H. Calcareous nannofossil biostratigraphy provides an estimated age of 4.37 Ma for the base of Core U1505-10H. The Co-Chief Scientists presented the scientific objectives and operations plan for Site U1505. Scientists are collecting and measuring data from Site U1505 and preparing the Site U1504 reports.

Daily Science Report for 28 May 2017

Location:
Hole U1504A (alternate Site SCSII-27A, 18°50.9199′N, 116°14.5293′E, water depth 2816.6 mbsl)
In transit to Site U1505
Site U1505 (alternate Site SCSII-3D, 18°55.0566′N, 115°51.5382′E, water depth 2916.6 mbsl)

Science Update: RCB coring continued in Hole U1504A from 152.6 to 163.3 m (Cores U1504A-19R to 20R; recovery 17%) while experiencing erratic torque and strong overpull. A wiper trip to 133 m and back to bottom was conducted, and drilling continued, advancing another 2.2 m in 2.5 h with significant torque and overpull. Having already sampled firm basement (primary target for the site), with increasingly poor hole conditions and low recovery, the decision was made to recover one last core and terminate the hole. Core U1504A-21R arrived on the rig floor at 1000 h (0.45 m; 20% recovery). The drill string was recovered, ending operations in Hole U1504A. Total recovery for Hole U1504A was 32%. The rig floor was secured for transit and the thrusters were raised by 1900 h. The 22 nmi voyage to Site U1505 (alternate Site SCSII-3D) was completed at 2112 h.

Site SCSII-3D is an alternate for Site U1501 (proposed Site SCSII-41A). The objectives at Site U1505 are to recover a complete sedimentary succession from the early Miocene to Holocene that can supplement the material sampled at Site U1501 for postcruise paleoceanographic and paleoclimatological studies. The last ~3 h of the day were spent preparing the rig floor for coring operations in Hole U1505A.

Cores U1504A-13R to 21R were described today. Cores 13R and 15R contain clast-supported limestone with coral fragments, mollusk shells and large benthic foraminfera, and a few minor clasts of basement rocks. Cores 16R to 21R contain highly deformed epidote chlorite schist. Review of Sites U1502 and U1503 reports and research planning presentations are in progress.

Daily Science Report for 27 May 2017

Location: Hole U1504A (alternate Site SCSII-27A, 18°50.9199′N, 116°14.5293′E, water depth 2816.6 mbsl)

Science Update: The underwater camera survey confirmed that the seafloor was free of obstructions at Site U1504 (alternate Site SCSII-27A). The sea bottom then was tagged with the RCB bit, determining a water depth of 2816.6 m for Hole U1504A. The hole was started at 0145 h and by midnight we had rotary cored from the seafloor to 152.6 m (Cores U1504A-1R to 18R). Total core recovery for this interval was 51.58 m (33%), and varied from less than 4% in Cores U1504A-1R, 2R, 13R, and 14R, to more than 79% in Cores U1504A-11R, 13R, and 15R. Cores U1504A-1R to 12R were described today—they consist of nannofossil and foraminifera oozes with varying amounts of clay. The color of the sediment ranges from dark greenish gray to light brownish gray. An early Miocene age has been assigned to the base of this succession. Review of Site U1502 reports and research planning presentations are in progress.

Daily Science Report for 26 May 2017

Location:
Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)
In transit to Site U1504
Arrived at Site U1504 (alternate Site SCSII-27A, 18°50.9208′N, 116°14.5293′E, water depth 2816.6 mbsl)

Science Update: Following the underwater camera survey of the Hole U1503A reentry cone, the drill string and the positioning beacon were recovered, and the rig floor was secured for transit. The thrusters were raised, and the vessel was underway to Site U1504 (alternate Site SCSII-27A) by 0930 h. The 42 nmi transit was completed at 1400 h and the JOIDES Resolution was positioned over the site coordinates to start operations at Site U1504. A new RCB bit (C-7) was made up, and the drill string was lowered to 1709 mbsl, when the pipe spinner on the iron roughneck failed. The spinner was replaced and the drill string was lowered to the bottom by 2200 h. The subsea camera was deployed soon after, and a survey of the seafloor was conducted to confirm it was free of obstructions. Review of Site U1502 reports and research planning presentations are in progress.

Daily Science Report for 25 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: After successfully completing the replacement of the forward Elmagco brake of the drawworks at 0600 h, we continued lowering the drill pipe to the seafloor; however, as the bit descended from 1220 to 3821 mbsl, the newly replaced low clutch diaphragm failed. Faced with the new situation, and knowing that (1) after this clutch diaphragm was replaced we would have only one more spare onboard, and (2) with an inoperable low clutch, it would not be possible to lift the drill string from depth due to heavy load, the Co-Chief Scientists, Expedition Project Manager, Operations Superintendent, and key Siem Offshore staff met to discuss operations at Site U1503. It was decided to stop operations at this site in favor of conducting operations at alternate Sites SCSII-27A and SCSII-3D, where the shallower water depth would allow for a limited use of the low clutch. Once the clutch was replaced, the underwater camera was deployed to the seafloor to inspect and document the condition of the reentry cone in Hole U1503A for future drilling. The top of the cone appeared to be one to two meters below the seafloor, but it was clearly visible and free of sediment. Review of Site U1502 reports and presentations on future research planning themes are in progress.

Daily Science Report for 24 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: Repairs of the drawworks brake system continued throughout the entire day. By midnight, the new forward Elmagco brake was placed back into position, and the crew had connected the electrical components and the water drainage. Shaft alignment procedures were in progress. We continue reviewing the Site U1502 reports.

Daily Science Report for 23 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: At 0530 h this morning while lowering the RCB BHA and bit to the seafloor for rotary drilling/coring in Hole U1503A, a shrieking noise was detected coming out of the drawworks brake system. All operations were stopped, and the rig mechanic was called to inspect the hardware. It was determined that the aft shaft bearing on the forward Elmagco brake had failed. With the brake inoperable, the drill string was hung off the rotary table. Fortunately, a replacement brake unit was onboard and the sea was calm. Therefore, with the bit at 1221 mbsl, the crew initiated repairs. The forward brake was disconnected from the drawworks, and all nonessential equipment was removed from the rigfloor, including the elevator handlers. Following this, the broken 28,000 lb (12.7 MT) brake unit was carefully moved out to the rig floor. The hub was removed for use on the new installation, and the old brake was lifted and lowered to the main deck. The replacement unit was then lifted and moved onto the rig floor by 2100 h. The lifting operation would not have been possible if the sea weren’t calm. Repairs are expected to continue for most of the day tomorrow. Scientists are revising and finalizing the Site U1502 reports.

Daily Science Report for 22 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: This morning we successfully completed the drilling of the 992 m long 10.75 inch casing string into the seafloor at 0915 h. We pulled the bit up to 976 mbsf, recovered the subsea camera system at 1115 h, then continued to recover the drill string, until the bit was back onboard at 2230 h. The last 1.5 h of the day were spent flushing and storing away the mud motor and underreamer, and reinstalling the upper guide horn in the moonpool area. At our noon crossover, the scientific party received a presentation on the scientific objectives at Site U1503 and an update on the operations plan based on the latest approval by EPSP to RCB core from 990 to 1060 m, then to drill ahead to 1360 m, and finally to RCB core from 1360 m to our target depth of ~1800 m. Review of the Site U1502 reports continues.

Daily Science Report for 21 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: The crew successfully completed the replacement of the clutch diaphragm of the drawworks at 0415 h. Then they continued to lower the drill string from 2379 to 3856 mbsl. As the drill pipe was lowered to the seafloor, they stopped every 25 stands to fill the pipe with seawater to equalize the pipe’s inside pressure with that of the surrounding water. At 0745 h, with the bit at 3856 mbsl, they deployed the underwater camera to inspect the reentry cone assembly and reenter the hole. Hole U1503A was reentered at 1005 h and the rig crew worked the 10¾ inch casing downhole to 908.2 m by midnight. We held a meeting to discuss the scientific results from Site U1502, and the scientists submitted all the site reports to the Co-Chief Scientists and Expedition Project Manager for review.

Daily Science Report for 20 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: At 2300 h a tugboat (M/V Taikoo) arrived on site and delivered the critical spares for the drawworks clutch. The transfer was completed by 2330 h and the rigfloor crew began repairs immediately. Scientists began to submit the Site U1502 reports.

Daily Science Report for 19 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: Drilling and coring operations are on standstill until the replacement parts (low clutch diaphragms) are delivered to the ship on Saturday night, 20 May. Scientists continue writing up the Site U1502 reports.

Daily Science Report for 18 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: We completed assembling the stinger and latched it into the casing hanger. We then lowered the casing and the drill string to 2378.7 mbsl, where we had to stop because their combined weight (430,000 lb) was too high to continue their deployment without using the low clutch of the drawworks. At this point there is nothing more that can be done on the rigfloor until the replacement parts (low clutch diaphragms) are delivered to the ship. Scientists continue writing up the Site U1502 reports.

Daily Science Report for 17 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: The assembling of the 989 m long casing was completed and the casing was hung off the moonpool doors at 1830 h. Following this, the mud motor and underreamer were assembled and function-tested in the moonpool, and the rig crew started to assemble the rest of the drill string that will be used to drill the casing in Hole U1503A. Scientists continue collecting, analyzing, and writing up the data from Site U1502. At 1100 h, we held the science summary meeting for Site U1502 with the participation of the Expedition 367 scientists.

Daily Science Report for 16 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: By 0100 h, the tricone bit had extended Hole U1503A from 864.5 to 902.8 m when the mechanic detected a leak in the drawworks clutch diaphragm that had been replaced earlier in the expedition. Consequently, the decision was made to recover the drill string before the clutch completely failed. The bit was pulled back to 97.6 m inside the hole by 0430 h. A 13 ft wide reentry cone was launched from the moonpool, free-falling all the way down to the seafloor. Following, the subsea camera was deployed to the sea bottom to inspect the landing of the reentry system and confirm that it had landed in the correct position, which it had. Then the bit was pulled up to just above the internal aperture of the reentry cone, which was tagged at 3867.7 m below sea level. Before retrieving the underwater camera system, we conducted required routine rig servicing, which consisted of slipping and cutting 215 ft of drilling line. The subsea camera was brought back onboard at 1045 h, and we continued to recover the drill string until the bit cleared the rotary table at 1655 h. The rest of the day was spent making up the 10.75 inch casing string. Spare diaphragms to repair the drawworks clutch are scheduled to arrive in Hong Kong on 18 May, then be delivered to the ship by boat. While waiting for these to arrive, assembly of the casing string and the stinger will continue as planned. Scientists are documenting the Site U1502 data in the site reports and preparing presentations for tomorrow’s science summary meeting.

Daily Science Report for 15 May 2017

Location: Hole U1503A (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E; water depth 3867.7 mbsl)

Science Update: We spent the day drilling ahead with a 14.75 inch tricone bit in Hole U1503A, deepening the hole from 203.1 to 864.5 m with an average rate of penetration of 49 m/h. We have accumulated 15.8 h on the bit. We plan to drill ahead to 1000 m then install a reentry system and a 10.75 inch casing to ~990 m in the same hole. Scientists are analyzing and documenting the Site U1502 data and preparing presentations for the crossover meeting.

Daily Science Report for 14 May 2017

Location:
Hole U1502B (proposed Site SCSII-17A, 18°27.8798′N, 116°13.8409′E)
In transit
Arrived at Site U1503 (proposed Site SCSII-9B, 18°8.6298′N, 116°18.8460′E, water depth 3873 mbsl)

Science Update: Following the recovery of the drill string from Hole U1502B, the rig floor was secured, the thrusters were raised, and the short journey to the next site began. We arrived at Site U1503 (scientific prospectus Site SCSII-9B) at 1000 h, but we were unable to position the JOIDES Resolution over the site coordinates until ~1130 h because a research vessel (R/V Shiyan 2) operated by the South China Sea Institute of Oceanology, Chinese Academy of Sciences, was deploying an ocean bottom seismometer (OBS) at the same location as part of a seismic survey the ship was conducting in the area. Following the departure of the research vessel, the JOIDES Resolution lowered the thrusters and a seafloor positioning sonar beacon was deployed as the ship was positioned over the site coordinates. A precision depth recorder (PDR) water depth of 3873.1 m was established and rigging preparations began on the drill floor. A 14.75 inch bottom-hole assembly (BHA) was made up and the drill string was lowered to the seafloor. Hole U1503A was spudded at 2000 h, and by midnight we had drilled without recovery to 191.8 m. Our plan is to continue drilling to 1000 m, then install a reentry system and 10.75 inch casing to ~990 m in Hole U1503A.