IODP Expedition 375

Hikurangi Subduction Margin

Daily Science Report for 4 May 2018

Location: In transit to Auckland, New Zealand

Science Results: We continued our transit to Auckland throughout the day covering 176 nmi at an average speed of 7.3 kt.

We anticipate arriving at the Auckland pilot station at 0600 h tomorrow.

We backed up the database and finalized the Site U1520 reports, the Site U1526 reports, and the Preliminary Report.

Daily Science Report for 3 May 2018

Location:
• Hole U1526B (39°1.3146′S, 179°14.7481′E, water depth 2888 m; proposed Site HSM-08A)
• In transit to Auckland

Science Results: Core 5X advanced from 32.5 to 33.5 m and recovered 0.61 m (61%). Coring for Site U1526 and Expedition 375 ended at 0150 h. We started raising the drill string at 0300 h and the rig floor was secure for transit at 1155 h. Our 315 nmi transit to Auckland began at 1230 h, and we expect to arrive at the Auckland pilot station around 0600 h on May 5.

Cores 2H and 3H consist of greenish gray mud with foraminifer-rich silt layers and ash beds. Within Core 4H, lithologies change rapidly from greenish gray mud to nannofossil-rich light green calcareous mudstone, to light pink nannofossil-rich ooze, to shell-rich sand, and finally to volcaniclastic conglomerate with shells. The boundary between the ooze and the sand is characterized by a 20 cm interval rich in manganese concretions. Core 5X consists of a matrix-supported conglomerate with variably altered basalt clasts. The sand-sized matrix is composed of shell and basalt fragments. Section U1526B-4H-4 is probably early Late Cretaceous (~94–100 Ma).

We continued reviewing the scientific results from Hole U1520D with presentations on biostratigraphy, paleomagnetism, geochemistry, and core-log-seismic integration. We completed personal sampling and circulated a list with all proposed Expedition 372/375 manuscripts. Finally, we uploaded all description data into the LIMS database, started cleaning the laboratories, and worked on the Site U1520 reports, the Site U1526 reports, and the Preliminary Report.

Daily Science Report for 2 May 2018

Location:
• Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)
• Hole U1526B (39°1.3146′S, 179°14.7481′E, water depth 2888 m; proposed Site HSM-08A)

Science Results: Cores U1520D-66X to 67X advanced from 625.1 to 642.3 m and recovered 8.09 m (47%). Following the completion of coring at Hole U1520D, the drill string was raised ~800 m in preparation for transiting in dynamic positioning mode back to Tūranganui Knoll Site U1526.

Following an 8 h transit, the ship arrived at the coordinates of Hole U1526B at 1830 h (20 m to the west–northwest from Hole U1526A). Our objective here is to recover the sediments in the upper 30 m that comprise the hemipelagic apron covering the volcaniclastic sequence we cored in Hole U1526A. The drill string was lowered to 2932 m below seafloor, and Hole U1526B was started at 2015 h. Cores 1H to 4H advanced from 0 to 32.5 m and recovered 30.95 m (95%).

Cores U1520D-64X to 67X consist of light greenish gray marl with ash layers. Planktonic foraminifers indicate that Samples 66X-CC and 67X-CC are late Miocene.

Core U1526B-1H consists of greenish gray mud with foraminifer-rich silt and ash layers. Planktonic foraminifers indicate that Sample U1526B-1H-1, 0–6 cm, is possibly Holocene (<0.009 Ma), and Samples 1H-CC through 3H-CC are middle to early Pleistocene (0.52–2.17 Ma).

We started reviewing the scientific results from Hole U1520D with presentations on lithostratigraphy, structural geology, and physical properties, and are working on the Site U1520 reports and the Preliminary Report.

Daily Science Report for 1 May 2018

Location: Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)

Science Results: Cores U1520D-57X to 65X advanced from 558.1 to 625.1 m and recovered 17.35 m (26%). Once we reach ~650 m, we will return to Tūranganui Knoll Site U1526 to APC core the top 30 m of sediments, which were not recovered sufficiently with RCB coring. We hope to achieve this last objective during deteriorating weather conditions over the next 1–2 d.

Cores 56X to 63X consist of light greenish gray marl with ash layers. Severe drilling disturbance and slight bioturbation occur throughout. We also observe rare convoluted, variegated marls containing reworked marl clasts and dispersed pumice and basalt clasts as well as soft sediment deformation. Planktonic foraminifers indicate that Sample 60X-CC is Miocene/Pliocene and Samples 61X-CC and 65X-CC are late Miocene.

We continued our coordination of postcruise research plans and proposed manuscripts.

Daily Science Report for 30 April 2018

Location: Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)

Science Results: We waited on weather until 1315 h (21.25 h in total from the previous day). We spent the next ~6 h cleaning the hole of cuttings and performed a minor clutch repair. Core U1520D-56X advanced from 548.5 to 558.1 m and recovered 0.48 m (5%). Our target depth in this hole is ~650 m.

We continued our coordination of postcruise research plans and proposed manuscripts.

Daily Science Report for 29 April 2018

Location: Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)

Science Results: Cores U1520D-50X to 55X advanced from 500.7 to 548.5 m and recovered 18.28 m (38%). Due to increasing sea state and heave, we stopped coring at 1600 h and raised the drill bit ~250 m above the bottom of the hole. Waiting on weather continued until midnight. We will resume coring to ~650 m when weather improves.

Cores 45X to 50X consist of alternating siltstone and greenish gray mudstone layers. Starting with Core 51X, the lithology changes into light greenish gray siltstone interbedded with light pink ash layers. From Section 51X-1, 66 cm, to Core 55X we also observe convoluted marl layers with dispersed basalt clasts and soft sediment deformation. Planktonic foraminifers indicate that Sample U1519D-53X-CC is middle to late Pleistocene (0.62–2.17 Ma), Sample 54X-CC is early Pleistocene (2.37–2.40 Ma), and Sample 55X-CC is late Pliocene (2.98–3.53 Ma), with hiatuses present between these samples.

We continued working on postcruise research plans and proposed manuscripts.

Daily Science Report for 28 April 2018

Location: Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)

Science Results: Cores U1520D-40X to 49X advanced from 414.4 to 500.7 m and recovered 29.35 m (34%). Our target depth in this hole is ~650 m.

Cores U1520D-35X to 45X consist of alternating siltstone and greenish gray mudstone with a few intercalated whitish tephra layers. Siltstones exhibit parallel and cross lamination and become thinner and less abundant with depth. Slight bioturbation and some drilling disturbance are observed. Planktonic foraminifers indicate that Sample 49X-CC is middle to early Pleistocene (0.62–2.17 Ma).

We finished reviewing the scientific results from Site U1526 with presentations on paleomagnetism, geochemistry, and core-seismic integration, and we are working on the reports.

Daily Science Report for 27 April 2018

Location: Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)

Science Results: Cores U1520D-30F to 39X advanced from 243.5 to 414.4 m and recovered 31.77 m (42%). Within this interval, we drilled without coring from 270.8 to 366.6 m.

Cores U1520D-17H to 30F contain alternating silt and greenish gray mud layers with interspersed ash layers up to 1 m thick. Starting with Core 31X the lithology changes to alternating siltstone and greenish gray mudstone. Silts and siltstones generally exhibit parallel and cross lamination. Slight bioturbation occurs throughout the formation. Planktonic foraminifers indicate that Samples 35X-CC through 40X-CC are middle Pleistocene (0.54–0.62 Ma).

We started reviewing the scientific results from Site U1526 with presentations on lithostratigraphy, structural geology, biostratigraphy, and physical properties.

Daily Science Report for 26 April 2018

Location: Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)

Science Results: Cores U1520D-14H to 29F advanced from 120.0 to 243.5 m and recovered 88.24 m (95%). Within this interval, we drilled without coring from 189.3–220.0 m. Formation temperature measurements were taken with the APCT-3 temperature tool for Cores 16H, 19F, 23F, and 27F.

Cores U1520D-3H to 12H contain layers of alternating dark gray silt to fine sand and greenish gray mud. Starting with Core 13H, there is a change to alternating light gray silt and light greenish gray mud layers. Planktonic foraminifers and calcareous nannofossils indicate that Core 30F is middle to late Pleistocene (<0.54 Ma).

The Expedition Project Manager gave a presentation on the scientific and logistical tasks we need to accomplish during the last 10 d of the expedition.

Daily Science Report for 25 April 2018

Location: Hole U1520D (38°58.1475′S, 179°7.8991′E, water depth 3520 m; proposed Site HSM-05A)

Science Results: Coring resumed at Site U1520 to recover the shallow input sediments. Hole U1520C was previously cored on 3–8 April from 646 to 1054.1 m. We assembled an advanced piston corer/extended core barrel (APC/XCB) bottom-hole assembly, and Hole U1520D was started at 0850 h. Cores 1H to 13H advanced from 0 to 120.0 m and recovered 108.1 m (90%). Formation temperature measurements were taken with the APCT-3 temperature tool for Cores 4H, 7H, 10H, and 13H. The APCT-3 shoe deployed with Core 10H cracked when it encountered a sand layer and the tool was flooded.

Cores U1520D-1H to 3H consist of alternating dark gray silt and greenish gray mud in the upper part, changing into alternating dark gray sand beds and greenish gray mud in the lower part. Few ash layers are interbedded in the background lithology. Planktonic foraminifers and calcareous nannofossils indicate that Core 17H is Pleistocene (<0.54 Ma).

We completed our review of the scientific results from Site U1519 and we are working on the reports.

Daily Science Report for 24 April 2018

Location:
• Hole U1526A (39°1.3204′S, 179°14.7594′E, water depth 2890 m; proposed Site HSM-08A)
• Site U1520 (38°58.1475′S, 179°7.8993′E; proposed Site HSM-05A)

Science Results: Coring was completed in Hole U1526A. Cores 10R to 14R advanced from 59.5 to 83.6 m and recovered 9.69 m (40%). Our next objective is to core the shallower sediments we drilled through at Site U1520 earlier in the expedition. We started retrieving the drill string while at the same time moving toward nearby Site U1520 in dynamic positioning mode. The transit took ~6 h and we arrived at the specified coordinates of Hole U1520D at 2305 h.

Cores U1526A-6R to 14R consist of a clast-supported volcaniclastic conglomerate with clasts of basalts and volcaniclastic sandstones. Formerly free pore space is filled with cement. Longer basalt fragments up to tens of centimeters long, with various amounts of vesicles and alteration, are intermixed in the conglomerate.

Daily Science Report for 23 April 2018

Location: Hole U1526A (39°1.3204′S, 179°14.7594′E, water depth 2890 m; proposed Site HSM-08A)

Science Results: Hole U1526A was started at 0150 h. Cores 1R to 9R advanced from 0 to 59.5 m and recovered 19.57 m (33%).

Cores U1519E-7H to 13H are composed of alternating mud and silt with severe drilling disturbance.

Cores U1526A-1R to 2R contain light green nannofossil-rich calcareous mud. Core 3R is composed of light pink to whitish nannofossil-rich ooze. Cores 1R to 3R are severely disturbed by rotary drilling. Core 4R is composed of a volcaniclastic conglomerate. Core 5R is composed of a volcaniclastic conglomerate with interspersed basalt clasts with varying amounts of vesicles and alteration.

Planktonic foraminifer and calcareous nannofossils from Hole U1526A indicate that Sample 3R-1W, 56 cm (19.96 mbsf) is middle Pleistocene (<0.62 Ma) and Sample 3R-CC (21.09 mbsf) is late Miocene (<5.44 Ma). Foraminifers or calcareous nannofossil were not recovered from the conglomerate in Sample 4R-CC.

Daily Science Report for 22 April 2018

Location:
• Hole U1519E (38°43.6572′S, 178°36.8949′E, water depth 1000 m; proposed Site HSM-01A)
• Site U1526 (39°1.3204′S, 179°14.7594′E, water depth 2888 m; proposed Site HSM-08A)

Science Results: Coring was completed in Hole U1519E. Cores 6H to 13F advanced from 40.1 to 85.8 m and recovered 48.51 m (106%). Formation temperature measurements were taken with the APCT-3 temperature tool for Cores 4H–8H, 9F, 11F, and 13F. The drill string was recovered at 1215 h and the rig floor was secured for transit.

The vessel started the 34.5 nmi transit to Site U1526 (proposed Site HSM-08A) at 1312 h and arrived at 1700 h. Our objective at Site U1526 is to sample a shallow section of the Tūranganui Knoll, which represents one component of the material entering the Hikurangi subduction zone. Upon arrival, a rotary core barrel bottom-hole assembly was assembled and lowered to the seafloor. At midnight, the drill bit had reached 2873 m below rig floor.

Description continued on Hole U1519C–U1519E sediments. Cores U1519C-25R to 26R are composed of greenish gray mudstone showing clear evidence of soft-sediment deformation, including convolute laminae, dismembered bedding, and clasts of mudstone supported by a mudstone matrix. Cores U1519D-1H and U1519E-1H contain light-greenish gray mud and two ash layers each up to 100 cm thick. Cores U1519D-2H to 3H and Cores U1519E-2H to 6H consist of alternating mud and silt with severe drilling disturbance.

Planktonic foraminifers from Hole U1519E suggest Sample U1519E-1H-CC (4.5 mbsf) is possibly Holocene (<0.009 Ma), and Samples 2H-CC through 13F-CC (14.00–85.78 mbsf) are late to middle Pleistocene (0.009–0.54 Ma).

Scientists attended a seminar on the geologic setting of Site U1526 (proposed Site HSM-08A).

Daily Science Report for 21 April 2018

Location:
• Hole U1519C (38°43.6483′S, 178°36.8773′E, water depth 1000 m; proposed Site HSM-01A)
• Hole U1519D (38°43.6516′S, 178°36.8831′E, water depth 1000 m)
• Hole U1519E (38°43.6572′S, 178°36.8949′E, water depth 1000 m)

Science Results: Coring continued in Hole U1519C. Cores 24R to 26R advanced from 614.0 to 640.0 m and recovered 11.46 m (44%). The drill string was recovered at 0815 h, and the rotary core barrel (RCB) bottom-hole assembly (BHA) was put away.

The next objective was to collect in situ temperature measurements and high-resolution whole-round samples for pore water geochemical analyses. An advanced piston corer (APC) BHA was assembled and the drill string was lowered to the seafloor. The vessel was offset 10 m at a heading of 122°, and Hole U1519D was started at 1505 h. Cores 1H to 3H advanced from 0 to 23.2 m and recovered 23.64 m (101%).

Because sand made it difficult to collect in situ temperature measurements and resulted in a partial stroke with Core U1519D-3H, we decided to start a new hole. The vessel was offset 20 m at a heading of 122°, and Hole U1519E was started at 1845 h. Cores 1H to 5H advanced from 0 to 40.1 m and recovered 40.47 m (101%). APC coring is planned to ~80 m before moving to proposed Site HSM-08A.

Cores U1519C-17R to 19R are composed of dark greenish-gray sandy mudstone with normally graded beds of fine sand. From Section 19R-2 to Core 24R, we observe intercalated, contorted beds with flow banding and dispersed rounded mudstone clasts.

Daily Science Report for 20 April 2018

Location: Hole U1519C (38°43.6483′S, 178°36.8773′E, water depth 1000 m; proposed Site HSM-01A)

Science Results: Drilling without core recovery continued to 518.4 m in Hole U1519C until 0730 h. Core 131 corresponds to the drilled interval 288.4–518.4 m. The center bit was removed and Cores 14R to 23R advanced from 518.4 to 614.0 m and recovered 72.2 m (76%).

Cores U1519C-14R to 16R are composed of dark greenish-gray mudstone and fine sandstone. The sandstone is present as interbedded, few to several cm-thick, contorted and normally graded layers. Bioturbation and drilling disturbance are minor. Calcareous nannofossils and planktonic foraminifers indicate that Core 22R is younger than 1.73 Ma and Core 26R is younger than 2.17 Ma.

Daily Science Report for 19 April 2018

Location: Hole U1519C (38°43.6483'S, 178°36.8773'E, water depth 1000 m; proposed Site HSM-01A)

Science Results: Drilling without core recovery continued to 108 m in Hole U1519C until 0600 h. The center bit was removed and Cores 2R to 7R advanced from 108.0 to 163.6 m and recovered 11.67 m (21%). This interval brackets the top pressure screen deployed with the ACORK observatory. The center bit was redeployed and we drilled without core recovery from 163.6 to 250.0 m. The center bit was removed and Cores 9R to 12R advanced from 250.0 to 288.4 m and recovered 23.84 m (62%). This interval brackets the bottom pressure screen deployed with the ACORK observatory. Recovery over this entire interval was 35.51 m (38%). Cores 11 and 81 correspond to the drilled intervals 0–108.0 m and 163.6–250.0 m. The center bit was redeployed so we could drill without core recovery from 288.4 to 520 m. At midnight, the bit had reached 413.1 m. The last coring target at this hole is the interval from 520 to 640 m.

Cores U1519C-2R to 5R are composed of mudstone with variable amounts of silt that are severely disturbed by drilling. Cores 6R and 7R had almost no recovery. Cores 9R to 12R have the same lithology with a few sand pods present and are also heavily disturbed by drilling. In the lowermost part of Core 12R the mudstone becomes siltier and lighter in color. Preliminary biostratigraphic results suggest Cores 2R to 12R are late Pleistocene (<0.54 Ma). Benthic foraminifers suggest deposition was in water depths <200 m.

Scientists attended a seminar on the geologic setting of Site U1519 and the LWD data collected during Expedition 372.

Daily Science Report for 18 April 2018

Location:
Hole U1519B (38°43.6426′S, 178°36.8655′E, water depth 1000 m; proposed Site HSM-01A)
Hole U1519C (38°43.6483′S, 178°36.8773′E, water depth 1000 m)

Science Results: We continued lowering the CORK-II assembly to the seafloor. The subsea camera was deployed and the CORK-II entered the ACORK funnel at 0120 h. The CORK-II wellhead was lowered to ~20 m above the ACORK and was kept there while we deployed the instrument string. At 0230 h, we started assembling the 268 m long instrument string, which consists of one segment of Spectra rope with 15 miniature temperature loggers, one weak link and one sinker bar at the bottom, and a top plug. The top plug was connected to the Schlumberger wireline with the Electrical Release System (ERS), and the instrument string was lowered slowly to the seafloor inside the drill pipe connected to the running tool. Once the top plug latched inside the CORK-II wellhead at 0530 h, the ERS mechanism was activated, releasing the instrument string. The CORK-II then landed inside the ACORK funnel at 0700 h, and was released from the running tool at 0735 h, completing the observatory installation. Following a brief visual survey of the wellhead, the camera and running tool bottom-hole assembly (BHA) were recovered at 1100 h.

The next objective at Site U1519 is to core sediments in the intervals surrounding the ACORK pressure screens (around 124 and 264 m), in the underlying Miocene section, and finally in the uppermost ~100 m for temperature measurements. In preparation for coring, we assembled a rotary core barrel (RCB) BHA. The drill string was lowered to the seafloor and the vessel was offset 20 m at a heading of 122°. Hole U1519C was started at 1640 h and drilling without core recovery reached 96 m at midnight.

Science seminars were presented on ocean bottom seismometers and pressure gauges deployed at the Hikurangi and Nankai margins and a precruise heat flow transect conducted over our drill sites.

Daily Science Report for 17 April 2018

Location: Hole U1519B (38°43.6426′S, 178°36.8655′E, water depth 1000 m; proposed Site HSM-01A)

Science Results: We finished cleaning Hole U1519B of cuttings and recovered the drill string at 0315 h. Next, we assembled a bottom-hole assembly (BHA) with a bridge plug to seal the bottom of the ACORK casing. The drill string was lowered to the seafloor and the subsea camera was deployed to aid with the reentry. Hole U1519B was reentered at 0755 h. The end of the drill string was positioned at 277 m inside the ACORK casing and the bridge plug was activated until the packer was set at 1135 h. After the bridge plug BHA was recovered at 1455 h, we started assembling the 269 m long CORK-II casing string, which consists of 20 full joints and four pup joints of 4½ inch casing, four 6¾ inch drill collars, and a bull nose. The CORK-II body and casing string were deployed with a J running tool and the entire assembly had reached 271 m below rig floor at midnight.

The Expedition Project Manager gave a presentation on publication obligations and moratorium guidelines.

Daily Science Report for 16 April 2018

Location: Hole U1519B (38°43.6426′S, 178°36.8655′E, water depth 1000 m; proposed Site HSM-01A)

Science Results: We continued deploying the ACORK casing string in Hole U1519B, and the ACORK landed in the reentry cone on the seafloor at 0635 h. Once the ACORK had been released (0715 h), we recovered the subsea camera and deployed a free-fall funnel (FFF) at 0845 h. The subsea camera was redeployed to verify that the FFF had landed correctly on top of the ACORK wellhead. The drill string with the mudmotor, underreamer, and drill bit was recovered at 1605 h, and the bottom-hole assembly (BHA) was cleaned with water. In preparation for deploying a bridge plug at the bottom of the ACORK casing, the drill string was deployed with a 9⅞ inch drill bit BHA. Hole U1519B was reentered at 2100 h with the aid of the subsea camera, and we proceeded to clean the hole of cuttings down to 267 m.

The science party continued reviewing the scientific results from Hole U1520C with a presentation on the core-log-seismic integration of Expedition 375 core and wireline logging data, Expedition 372 logging-while-drilling data, and precruise seismic data.

Daily Science Report for 15 April 2018

Location: Hole U1519B (38°43.6426′S, 178°36.8655′E, water depth 1000 m; proposed Site HSM-01A)

Science Results: The hydraulic release tool (HRT) was assembled and stored in the derrick at 0115 h. Next, we assembled a 279 m long ACORK casing string, consisting of 22 joints of 10¾ inch casing, two casing joints with 2 m tall screens for pressure measurements, and an umbilical secured on the outside of the casing to connect the two screens to pressure loggers on the wellhead. As the casing string was assembled from the bottom up, the umbilical was connected to the bottom and top screen, intended to be deployed at 264 and 124 m below seafloor, respectively. The casing string was completed at 1245 h and landed in the moonpool. Next, we assembled the drilling assembly needed to help get the casing into the predrilled hole. The drilling assembly is composed of a 9⅞ inch drill bit, an underreamer with its arms set to 14 inch to clear any obstacles in the predrilled hole, and a mud motor to rotate the bit and underreamer in isolation from the ACORK casing. The underreamer arms were tested and the drilling assembly was completed and landed inside the casing by 1645 h. The pressure umbilical terminations were made on the ACORK wellhead at 1930 h, and the wellhead was submerged for 10 min with the valves in the open position to purge the lines of air. The wellhead was then brought back to the surface to set the valves to their deployment (closed) position, and the wellhead was submerged for the last time. The entire assembly with the HRT running tool, the ACORK wellhead, casing, and umbilicals, and the drilling assembly was lowered to the seafloor between 2000 and 2130 h. The subsea camera was then deployed to assist with the reentry. Hole U1519B was reentered at 2310 h, and at midnight the drill bit had reached 33 m below seafloor.

The science party continued reviewing the scientific results from Hole U1520C with presentations on biostratigraphy and paleomagnetism.

Daily Science Report for 14 April 2018

Location: Hole U1519B (38°43.6426′S, 178°36.8655′E, water depth 1003 m; proposed Site HSM-01A)

Science Results: Hole U1519B was started at 0105 h and reached a total depth of 285.1 m at 1630 h. A 30-barrel mud sweep was circulated to clean the hole of cuttings and the bit was raised to 71 m below the seafloor. At 1845 h, the reentry cone and its base were released from the moonpool and allowed to fall to the seafloor, and the subsea camera was deployed to check that the reentry cone had landed properly. The subsea camera was brought to the surface at 2015 h and we continued to recover the drill string until the bit cleared the rig floor at 2225 h. Next, we started assembling the hydraulic release tool (HRT) that will be used to deploy the first stage of the observatory.

The science party continued reviewing the scientific results from Hole U1520C with a presentation on geochemistry.

Daily Science Report for 13 April 2018

Location: Site U1519 (38°43.6427′S, 178°36.8657′E; proposed Site HSM-01A)

Science Results: Following an 18 h transit, we arrived at Site U1519 at 1810 h. Operations at this site include installing an observatory to 280 m that will collect temperature and pressure data, and coring a portion of the sedimentary section. Hole U1519A was drilled during Expedition 372 for logging-while-drilling measurements. Upon arrival, we moved the base of the reentry cone that will be used for the observatory installation to the moonpool. Next, we started assembling a bottom-hole assembly with a 14¾ inch drill bit, which will be used to predrill the observatory hole. By midnight, the drill bit was at 972 m below rig floor.

The science party continued reviewing the scientific results from Hole U1520C with a presentation on physical properties.

Daily Science Report for 12 April 2018

Location: Bay of Plenty (37°18.20′S, 176°44.66′E; waiting on weather)

Science Results: We stayed in the Bay of Plenty, waiting on weather to improve at our drill sites. At 2357 h, we raised the thrusters and started our transit to Site U1519. We expect to arrive at the site between 1700 h and 2300 h tomorrow depending on the winds and sea state we encounter on the east side of New Zealand.

The science party started reviewing the scientific results from Hole U1520C with presentations on lithostratigraphy and structural geology.

Daily Science Report for 11 April 2018

Location: Bay of Plenty (37.303°S, 176.744°E; waiting on weather)

Science Results: We arrived at the Bay of Plenty at 1054 h, covering the remaining 54 nmi at a speed of 5 kt due to the strong winds and high sea state. We will stay here until the severe weather over our drill sites improves; we anticipate departing for Site U1519 at midnight on 13 April. Scientists continued working on the Site U1520 reports. Science seminars were presented on the frictional behavior of input sediments to the Hikurangi Trench and fault thermal maturity experiments on the previous day.

Daily Science Report for 10 April 2018

Location: In transit to the Bay of Plenty

Science Results: The drill string was recovered at 0010 h, ending operations at Hole U1520C. At 0118 h we started our transit north to the Bay of Plenty to wait for the weather to improve, covering 150 nmi at a speed of 6.6 kt.

Scientists are working on the Site U1520 reports.