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IODP Expedition 371

Tasman Frontier Subduction Initiation and Paleogene Climate


Daily Science Report for 20 September 2017

Location: Hole U1511B (37°33.6656′S, 160°18.9379′E, water depth 4847 m)

Cores U1511B-34R through 41R penetrated from 432.2 to 508.8 m and recovered 45.6 m (60%). At 1600 h coring was suspended due to excessive heave and the drill string was raised ~37 m above the bottom of the hole (472 m), while maintaining circulation and rotation in the hole. For the rest of the day we waited for the weather to improve to a level where it is possible to maintain weight on the bit.

Cores U1511B-25R through 30R consist of greenish gray to brown diatomite with variable clay content. Cores 31R through 37R consist of reddish brown and greenish gray claystone with rare siliceous microfossils. Millimeter-sized native copper occurs in several green intervals. All cores are severely fractured and biscuited by RCB coring.

Cores 33R to 37R were tentatively placed in the early Eocene using benthic foraminifera. Core 38R is barren of microfossils. Few nannofossils were found in Cores 39R to 41R, indicating a middle Paleocene age.


Daily Science Report for 19 September 2017

Location: Hole U1511B (37°33.6665′S, 160°18.9379′E, water depth 4847 m)

Cores U1511B-15R to 33R penetrated from 249.9 to 432.2 m and recovered 154.7 m (85%).

Cores U1511B-10R to 24R consist of varying proportions of clay and biosilica (in decreasing abundance: diatoms, radiolarians, and sponge spicules). Rare rhodochrosite concretions, infilled burrows, and dark blebs were observed from Core 16R downhole. Cores are moderately to severely fractured by RCB coring.

Cores 15R to 32R are barren of calcareous microfossils, but radiolaria are abundant. Cores 10R to 21R (209–313 m) are upper to middle Eocene based on radiolarian biostratigraphy.​ Excellent paleomagnetic results were obtained from 250 m to 300 m, straddling Chron C17r to Chron C20n (38–43 Ma).​


Daily Science Report for 18 September 2017

Location: Hole U1511A (37°33.6665′S, 160°18.9380′E, water depth 4847 m)

We were waiting for the weather to improve until 0145 h, with the drill string suspended just above the seafloor. At 0200 h we began washing down in Hole U1511B (i.e., drilling without coring and without a center bit installed) to 19.8 m, near the total depth of Hole U1511A (26.6 m). We resumed coring from 0215 h to 1015 h, and Cores 2R to 7R penetrated from 19.8 to 77.2 m and recovered 30.4 m (53%). At 1015 h we deployed a center bit and drilled without coring from 77.2 to 192.2 m to accelerate penetration and reach the target depth in the time remaining for operations on Expedition 371. At 1500 h we resumed coring and Cores 9R to 14R penetrated from 192.2 to 240.3 m and recovered 36.8 m (64%).

Cores U1511B-2R to 9R consist of clay, except in Section U1511B-7R-7, where clay with nannofossils was encountered. Cores 2R to 4R are Pliocene to Miocene, and Core 6R is possibly Miocene based on planktic foraminifera. Core 9R has an early Oligocene age based on calcareous nannofossils. Core 11R has a middle to late Eocene age based on benthic foraminifera. No age could be assigned to Cores 10R and 12R through 14R, but siliceous microfossils are abundant.​​


Daily Science Report for 17 September 2017

Location: Hole U1511A (37°33.6665′S, 160°18.9380′E, water depth 4847 m)

Drill pipe assembly was completed and at 0245 h a wiper “pig” was pumped through the pipe to clean out potential debris. RCB coring in Hole U1511A began at 0425 h. After retrieving Core 3R at 0810 h we had to pull the drill string clear of the seafloor due to excessive heave and wind. Cores 1R through 3R penetrated from 0 to 26.6 m and recovered 7.9 m (30%). From 0845 h to midnight we were waiting for the weather to improve.

Cores U1511A-1R to 3R consist of brown clay. The cores are barren of calcareous nannofossils and radiolaria, but scarce planktic foraminifera indicate a late Pliocene to late Miocene age​.​


Daily Science Report for 16 September 2017

Location:
• Transit to Site U1511 (proposed Site TASS-2A)
• Hole U1511A (37°33.6665′S, 164°18.9380′E, water depth 4847 m)

The ship arrived at Site U1511 at 1248 h and switched to dynamic positioning mode. The rig floor was ready for operations at 1334 h and by 1645 h an RCB bottom-hole assembly was made up and deployed. Drill pipe assembly began and by midnight the bit reached 4097 m below the rig floor, or 761 m above the seafloor.

The scientists completed final measurements of Site U1510 materials and worked on final reports for Site U1509 and draft reports for Site U1510.​


Daily Science Report for 15 September 2017

Location:
• Hole U1510B (36°19.7392′S, 164°33.5347′E, water depth 1239 m)
• Transit to Site U1511 (proposed Site TASS-2A)

At 0215 h we completed APC coring in Hole U1510B. Cores 3H through 7H penetrated from 18.8 to 66.3 m and recovered 46.0 m (97%). The drill pipe was retrieved and the rig floor secured at 0815 h, ending operations at Site U1510. The thrusters were raised and at 0842 h the ship began the transit to Site U1511 (proposed Site TASS-2A). By midnight we had completed 120 nmi of the ~216 nmi transit. Expected arrival is at 1200 h on 16 September.

Cores U1510A-47X to 49X consist of nannofossil chalk interbedded with tuffaceous sandstone, tuffaceous siltstone, and claystone with volcanic ash, with sporadic occurrences of chert beds. Cores 50X to 52X are nannofossil chalk with subtle variations in clay content in 52X. Cores are severely “biscuited” due to drilling disturbance. Cores U1510B-1H to 7H consist of nannofossil ooze with 10%–50% foraminifers and abundant bioclasts in Cores 4H to 5H.​​​


Daily Science Report for 14 September 2017

Location:
• Hole U1510A (36°19.7385′S, 164°33.5220′E, water depth 1238 m)
• Hole U1510B (36°19.7392′S, 164°33.5347′E, water depth 1239 m)

At 1930 h we completed XCB coring in Hole U1510A. Cores 36X through 52X penetrated from 320.7 to 483.4 m and recovered 77.7 m (48%). The drill pipe was retrieved from Hole U1510A and the ship was offset 20 m to the east, ending Hole U1510A at 2145 h. APC coring in Hole U1510B was initiated at 2300 h and the first two Cores 1H and 2H penetrated from 0 to 18.8 m and recovered 18.7 m (99%).

Cores U1510A-22X to 46X consist of nannofossil chalk with clay and bioclasts, interlayered with cherty limestone of centimeter-scale thickness at meter-scale intervals. From Core 36X downhole, cherty limestone frequency decreases, core recovery increases, and white nannofossil chalk with foraminifers is the dominant lithology. In Core 46X, organic rich claystone overlying a 30 cm thick tuffaceous sand layer was encountered. Cores 36X to 52X are middle to early Eocene in age.


Daily Science Report for 13 September 2017

Location: Hole U1510A (36°19.7385′S, 164°33.5220′E, water depth 1238 m)

Cores U1510A-9H through 17H penetrated from 71.5 to 150.5 m and recovered 76.3 m (97%). APC cores were oriented down to Core 15H, and temperature measurements were taken with the APCT3 while cutting cores 10H, 13H, and 17H. At 0645 h, a hard surface was encountered, corresponding to a major seismic sequence boundary. We switched to XCB coring and Cores 18X through 35X penetrated from 150.5 to 320.7 m, recovering 30.5 m (18%). Recovery was seriously compromised by frequent chert layers.

Cores U1510A-1H to 16H consist of white homogeneous nannofossil ooze with varying amounts of foraminifera, in places with beds of white foraminiferal ooze. Cores U1510A-17H to 20X consist of light gray clayey nannofossil chalk with foraminifera and decimeter-thick intervals of light grey cherty limestone. These XCB cores are severely affected by drilling disturbance.​ P-wave velocity values for Cores 1H through 20X are unexpectedly low, rarely exceeding 1600 m/s.​


Daily Science Report for 12 September 2017

Location:
• Transit to Site U1510 (proposed Site LHRS-3A)
• Hole U1510A (36°19.7385′S, 164°33.5220′E, water depth 1238 m)

We arrived at Site U1510 at 0918 h, ending the 380 nmi transit from the waiting on weather location. Dynamic positioning was established and an APC/XCB bottom-hole assembly was made up. After a pause in operations from 1330–1515 h to repair the clamping valve on the iron roughneck, we resumed lowing the drill string to the seafloor and initiated Hole U1510A at 1915 h. By midnight we had cut Cores U1510A-1H through 8H from 0 to 71.5 m, with a recovery of 71.6 m (100%). Cores U1510A-1H through 7H consist of foraminiferal ooze of Pleistocene to Pliocene age.


Daily Science Report for 11 September 2017

Location: Transit to proposed Site LHRS-3A

We continued the transit to proposed Site LHRS-3A, completing 193 nmi today for a total of 292 nmi traveled since we left the waiting on weather location. The total transit distance is 380 nmi. Expected arrival at Site U1510 (proposed Site LHRS-3A) is 1100 h on 12 September.​


Daily Science Report for 10 September 2017

Location:
• Waiting on weather location (30°0.2416′S, 164°25.8056′E)
• Transit to proposed Site LHRS-3A

We waited on weather in dynamic positioning mode ~380 nmi north of proposed Site LHRS-3A until 0730 h, when the ship began transiting south. By the end of the day we completed 99 nmi. Expected arrival at Site U1510 (proposed Site LHRS-3A) is 1600 h on 12 September.​


Daily Science Report for 9 September 2017

Location: Waiting on weather location (30°0.2416′S, 164°25.8056′E)

We were waiting in dynamic positioning mode ~380 nmi north of proposed Site LHRS-3A for weather to improve. Expected departure from our waiting location is 10 September and expected arrival at Site U1510 (proposed Site LHRS-3A) is 12 September.

Scientists worked on Site U1509 draft reports.​


Daily Science Report for 8 September 2017

Location:
• Underway to waiting on weather location
• Waiting on weather location (34°39.1312′S, 165°49.6599′E, water depth 2913 m)

We sailed north, then west, for a total transit of 316 nmi. At 2145 h the ship established dynamic positioning mode to wait on the severe weather at proposed Site LHRS-3A to pass. The waiting on weather location is 379 nmi north of proposed Site LHRS-3A, our next planned drill site.

Scientists worked on finalizing Site U1508 report revisions and Site U1509 draft reports.​


Daily Science Report for 7 September 2017

Location:
• Hole U1509A (34°39.1312′S, 165°49.6599′E, water depth 2913 m)
• Underway ~200 nmi north of remaining proposed drilling area, waiting on weather

In preparation for logging Hole U1508A, the rotary shifting tool (RTS) was deployed to trigger the mechanical bit release (MBR) and drop the bit at the bottom of the hole (0045 h). The reverse RST was deployed to shift the MBR sleeve back into the circulation position (0145 h). Next, the hole was displaced with 214 barrels of 10.5 ppg mud and the end of the drill string was set at a logging depth of 81 m (0530 h). The modified triple combo logging tool string was rigged up when at 0645 h the operational decision was made to stop logging operations based on ship heave exceeding 3.0 m. The drill string was retrieved and the rig secured for transit by 1400 h. After recovering the seafloor positioning beacon and retrieving positioning thrusters and hydrophones at 1630 h, the ship began the ~200 nmi transit to the north to avoid severe weather, forecast for the remaining proposed drilling areas on 9–10 September.

Scientists worked on finalizing Site U1508 report revisions and Site U1509 draft reports.​


Daily Science Report for 6 September 2017

Location: Hole U1509A (34°39.1312′S, 165°49.6599′E, water depth 2913 m)

Cores U1509A-63R through 74R penetrated from 575.8–690.7 m and recovered 86.7 m (75%). This concluded coring in Hole U1509A, with the last core on deck at 2345 h. Total recovery in Hole U1509A was 462.9 m (67%). The plan is to release the bit at the bottom of the hole and log the hole with the modified triple combo wireline tool string.

Cores U1509A-49R to 62R consist of gray to dark gray claystone with minor abundance of nannofossils and silt. Several centimeter-thick seams of large (>1 mm) pyrite crystals occupy some fractures. Bedding and planar burrows are typically tilted up to 30°, and the core material is generally fractured by drilling throughout. ​Nannofossil biostratigraphy determined an early Paleocene age for Cores 63R to 66R. Cores 67R to 73R are barren of calcareous microfossils and age diagnostic foraminifera.​​


Daily Science Report for 5 September 2017

Location: Hole U1509A (34°39.1312′S, 165°49.6599′E, water depth 2913 m)

Cores U1509A-50R through 62R penetrated from 451.3 to 575.8 m and recovered 88.2 m (71%).

Cores U1509A-44R to 48R were described ahead of Cores 33R to 43R in order to examine the sharp transition from light greenish gray limestone to dark gray, heavily bioturbated calcareous mudstone in Core 44R. Deformation is significant in both lithologies, with beds tilted up to 30°, and common shear zones with scaly fabric in the mudstone. We then returned to describing Cores U1509A-33R to 42R, consisting of light greenish gray nannofossil chalk with biosilica and tilted beds. Core catcher samples of Cores 50R to 62R are middle Paleocene in age.


Daily Science Report for 4 September 2017

Location: Hole U1509A (34°39.1312′S, 165°49.6599′E, water depth 2913 m)

Cores U1509A-34R through 49R penetrated from 298.1 to 451.3 m and recovered 106.7 m (70%).

Cores U1509A-16R to 32R consist of a light greenish gray foraminiferal nannofossil chalk. Bioturbation is heavy in places and includes darker brownish burrows, some with diagenetic halos. Bedding is indicated by green laminae with an average dip of ~30°.​ Based on nannofossil and planktic foraminifera biostratigraphy, the following ages were assigned to cores: middle Eocene (33R to 44R), early Eocene (45R), late Paleocene (46R to 48R), and middle Paleocene (49R).


Daily Science Report for 3 September 2017

Location: Hole U1509A (34°39.1312′S, 165°49.6599′E, water depth 2913 m)

Cores U1509A-4R through 33R penetrated from 19.4 to 298.1 m and recovered 179.3 m (64%).

The dominant lithology in Cores U1509A-2R to 12R is sparsely bioturbated white foraminiferal nannofossil chalk with thin green laminae and dispersed green grains. In Cores 12R to 15R, the lithology changes to a light greenish gray, heavily bioturbated foraminiferal nannofossil chalk, commonly affected by significant soft-sediment deformation.​ Cores 4R to 10R are Miocene, 11R to 28R are Oligocene, and 29R to 32R late Eocene based on nannofossil and planktic foraminifera biostratigraphy. The folded and reworked nature of the sections from Hole U1509A analyzed so far hampers good preservation of the paleomagnetic directions, which is also reflected in the wide distribution of the AMS ellipsoid principal axes measured on the discrete samples.​


Daily Science Report for 2 September 2017

Location:
• Transit to Site U1509 (proposed Site NCTS-2A)
• Hole U1509A (34°39.1312′S, 165°49.6599′E, water depth 2913 m)

We arrived at Site U1509 at 1030 h, completing the last 92 nmi of the 273 nmi transit from Site U1508. After lowering thrusters and hydrophones and establishing dynamic positioning, the rig floor was cleared for operations at 1045 h. While the RCB bottom-hole assembly was being assembled, a seafloor positioning beacon was deployed. The drill string was deployed to just above the seafloor and the top drive was engaged. A “wiper pig” was pumped through the drill pipe in an attempt to remove excessive rust observed during drill string assembly. Hole U1509A was initiated at 2145 h. Cores U1509A-1R through 3R penetrated from the seafloor to 19.4 m and recovered 2.1 m (11%). Cores 1R to 3R are Pleistocene based on nannofossil and planktic foraminifera biostratigraphy.​​


Daily Science Report for 1 September 2017

Location:
• Hole U1508C (34°26.8905′S, 171°20.5889′E, water depth 1609 m)
• Transit to Site U1509 (34°39.1312′S, 165°49.6591′E, water depth 2913 m; proposed Site NCTS-2A)

The logging tools were recovered and cleaned by 0315 h. The drill string was recovered and the end of pipe cleared the rig floor at 0650 h. The positioning beacon was recovered, the rig floor was secured for transit, the thrusters and hydrophones were raised, and the transit to Site U1509 began at 0730 h. By the end of the day we completed 181 nmi of the ~273 nmi transit at an average speed of 11.0 kt. The expected time of arrival at Site U1509 is 1030 h on 2 September.

The scientists completed Site U1508 reports and prepared for presentations.​