IODP Expedition 363

Western Pacific Warm Pool

Daily Science Report for 8 December 2016

Location: Dock F3, Port of Guam

Science Update: We finalized the expedition Preliminary Report. The pilot boarded the vessel at 0600 h. Expedition 363 officially ended with the first line ashore at the Port of Guam at 0648 h.

Daily Science Report for 7 December 2016

Location: In transit to Guam

Science Update: We continued our transit to Guam, with an estimated arrival time at the Guam pilot station at 0600 h on 8 December. The scientists finalized all expedition reports. We also held our final science meeting to review what we accomplished during the expedition and synthesize future research. The Staff Scientist also reminded the science party of expedition-related plans following the expedition.

Daily Science Report for 6 December 2016

Location:
Hole U1490C (5°48.9385′N, 142°39.2690′E, water depth 2341.3 mbsl; proposed Site WP-02A)
In transit to Guam

Science Update: We continued to troubleshoot the top drive motor and also secured the vessel for transit. We raised the thrusters and switched to cruise mode to begin our transit to Guam at 0542 h. Our estimated arrival time at the Guam pilot station is 0600 h on 8 December. The scientists continued to work on finalizing all expedition reports and making sure that all data were entered into the database.

Daily Science Report for 5 December 2016

Location: Hole U1490C (5°48.9385′N, 142°39.2690′E, water depth 2341.3 mbsl; proposed Site WP-02A)

Science Update: We continued to core with the advanced piston corer (APC) using orientation and nonmagnetic hardware from 132.0 to 160.5 mbsf (Cores U1490C-17H through 20H). At 0230 h, the shipboard engineers and electricians identified a ground fault in the top drive. We pulled the drill string up to 131.9 mbsf in order to troubleshoot the problem. At ~0645 h, we discovered that the problem would require several days to fix, ending coring in Hole U1490C. This also ended coring operations for the expedition as the last core on deck was originally scheduled for later in the day (2100 h). We pulled the drill string back to the rig floor, clearing the rotary table at 1655 h.

Cores U1490B-31F through 33F were split and described. The sediment is primarily white radiolarian-bearing foraminifer-rich nannofossil ooze. At the base of the described section is ash-rich radiolarian and nannofossil ooze. Several prominent ash layers are also present. The cores from Hole U1490C (1H through 20H) were also split and described. The sediment correlates well with that found in Holes U1490A and U1490B. The uppermost part of the section near the mudline is very pale brown clay-rich foraminifer-rich nannofossil ooze, with siliceous microfossils present in some intervals. Downhole this transitions to light greenish gray clay- and foraminifer-rich nannofossil ooze and then to white clay-bearing foraminifer–nannofossil ooze, which is present to the base of the hole. Greenish and purplish laminae are common through this interval. We finalized all other measurements on the cores and the scientists began to write the reports for Site U1490.

Daily Science Report for 4 December 2016

Location:
Hole U1490B (5°48.9507′N, 142°39.2698′E, water depth 2339.7 mbsl; proposed Site WP-02A)
Hole U1490C (5°48.9385′N, 142°39.2690′E, water depth 2341.3 mbsl; proposed Site WP-02A)

Science Update: After drilling over Core U1490B-25H, we switched to the half-length advanced piston corer (HLAPC) and continued coring to 262.9 mbsf (Core 33F). After having to drill over Core 33F to extract it from the formation, we decided to terminate Hole U1490B with the objective of collecting a third copy of the upper 260 mbsf of Site U1490 to cover core gaps, and then use any remaining time to core as deeply as possible in Hole U1490C. We pulled the drill string to above the seafloor and moved the vessel 20 m south of Hole U1490B. Our first coring attempt missed the mudline, as we were trying for a short core (~2 m) for stratigraphic correlation purposes. We successfully spudded Hole U1490C at 1250 h, with Core U1490C-1H recovering 2.5 m of core, establishing a seafloor depth of 2341.3 mbsl. We continued to core with the advanced piston corer (APC) using orientation and nonmagnetic hardware to 132 mbsf (Core U1490C-16H) by the end of the day. Hole U1490C averaged 103% recovery over this interval.

Cores U1490B-7H through 29F were split and described. The upper part of the succession consists of white clay-bearing foraminifer-nannofossil ooze, with rare foraminifer ooze layers. Greenish and purplish laminae and sulfide specks are common. The amount of clay in the sediment decreases downhole in the upper part of the described interval, with the sediment composition changing to white foraminifer-rich nannofossil ooze. Clay becomes more abundant again in the middle and lower part of the succession, with the sediment dominantly white clay-bearing to clay-rich foraminifer-nannofossil ooze or foraminifer-rich nannofossil ooze. Biosiliceous microfossils (especially radiolarians) are also present in this interval. Biosilica increases downhole, with the sediment becoming radiolarian-bearing foraminifer-rich nannofossil ooze by the base of the described interval. Ash layers are also present.

Daily Science Report for 3 December 2016

Location: Hole U1490B (5°48.9507′N, 142°39.2698′E, water depth 2339.7 mbsl; proposed Site WP-02A)

Science Update: We pulled the drill string out of Hole U1490A and then offset the vessel 20 m east. Hole U1490B was spudded at 0425 h. Core U1490B-1H retrieved 7.51 m of core, establishing a seafloor depth of 2339.7 mbsl. Advanced piston corer (APC) coring with orientation and nonmagnetic hardware continued to 228.0 mbsf (Core U1490B-25H). This included one 2 m interval that was drilled without coring to adjust core gaps for stratigraphic correlation. At the end of the day we were drilling over Core 25H to retrieve it from the formation. Core recovery in Hole U1490B averaged 103%.

Cores U1490A-28H through 43X were split and described. The upper part of the described interval consists of white foraminifer-bearing radiolarian-bearing nannofossil clay. One ash layer is present in this interval. The sediment transitions to white radiolarian-bearing clay-rich chalk. The magnetic susceptibility increases coincident with the increase in clay content of the sediment. Towards the base of the hole, dispersed ash particles become more common and are often associated with better preservation of siliceous microfossils, including radiolarians and sponge spicules. The sediment over this interval alternates between gray and light greenish gray chalk, with varying proportions of clay, foraminifers, radiolarians, and ash. A large chert cobble was found near the base of the hole. Cores U1490B-1H through 6H were also split and described. The uppermost ~75 cm of the hole consists of pink to white radiolarian-bearing foraminifer-rich nannofossil ooze. This transitions to white and light gray clay-bearing foraminifer-rich nannofossil ooze and then to foraminifer-rich nannofossil ooze with rare foraminifer ooze beds that have a sharp basal contact with the underlying nannofossil ooze. Pale yellow and greenish layers are present and sulfide specks are common. At Site U1489, color reflectance (particularly a* and b*) proved to be the best stratigraphic correlation tool over intervals of nannofossil ooze with very low magnetic susceptibility.

Daily Science Report for 2 December 2016

Location: Hole U1490A (5°48.9492′N, 142°39.2599′E, water depth 2341.0 mbsl; proposed Site WP-02A)

Science Update: We continued to core using the advanced piston corer (APC) with orientation and nonmagnetic hardware from 194.2 to 251.2 mbsf (Cores U1490A-22H through 27H). After Cores 25H, 26H, and 27H required drillovers to extract from the formation, we switched to the half-length advanced piston corer (HLAPC) and continued coring to 270.0 mbsf (Cores U1490A-28F through 31F). After drilling over Core 31F, we then switched to the extended core barrel (XCB) coring system and continued coring to 382.9 mbsf (Cores U1490A-32X through 44X). The rate of penetration dropped to nearly zero while cutting Core 43X, so we retrieved the core barrel after only a 5.6 m advance. The cutting shoe on the XCB bit was worn down as a result of encountering chert. We deployed a fresh XCB core barrel for Core 44X, but terminated drilling after advancing only 0.5 m in 45 min and the core barrel was empty upon retrieval. This ended coring operations in Hole U1490A. Core recovery averaged 77% through the XCB section. At the end of the day we were pulling the drill string out of the hole.

Cores U1490A-10H through 27H were split and described. The upper part of the described interval consists of white and light greenish gray foraminifer-rich nannofossil ooze. Purple and green laminae and sulfide minerals are present throughout. The sediment becomes slightly darker towards the middle of the described interval and the lithology transitions to white to light gray clay-bearing foraminifer-rich nannofossil ooze. Near the bottom of the described section, the sediment is white to yellowish/brownish white clay-bearing radiolarian-rich foraminifer-rich nannofossil ooze. A few discrete tephra layers are also present. Carbonate content is very high throughout Hole U1490A, averaging more than 90 wt%. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicate an age near the Oligocene/Miocene boundary at the base of Hole U1490A.

Daily Science Report for 1 December 2016

Location: Hole U1490A (5°48.9492′N, 142°39.2599′E, water depth 2341.0 mbsl; proposed Site WP-02A)

Science Update: After arriving at Site U1490 at midnight, we prepared the advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly and deployed the drill string toward the seafloor. We spudded Hole U1490A at 0655 h. Core U1490A-1H retrieved 4.23 m of sediment, establishing a seafloor depth of 2341.0 mbsl. APC coring with orientation and nonmagnetic hardware continued to 194.2 mbsf (Core U1490A-21H) by the end of the day. We collected downhole formation temperatures using the Advanced Piston Corer Temperature Tool (APCT-3) on Cores 4H, 7H, 10H, 13H, and 16H, with three of the deployments providing good measurements. Core recovery over the cored interval was 104%.

Cores U1490A-1H through 9H were split and described. The uppermost part of the interval consists of very plain brown foraminifer-nannofossil ooze. This transitions to white to light greenish gray foraminifer-rich nannofossil ooze, with occasional discrete intervals of foraminifer ooze. Thin purple and green laminae are present, and yellow burrows and sulfide minerals are abundant. Clay is present in the upper part of the interval. Magnetic susceptibility decreases rapidly from the seafloor, coincident with the decrease in clay content. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicate a late Miocene age for Core U1490A-21H.

Daily Science Report for 30 November 2016

Location:
Hole U1489D (2°7.1761′N, 141°1.6651′E, water depth 3421.5 mbsl; proposed Site WP-04A)
In transit to Site U1490 (proposed Site WP-02A)

Science Update: We continued to pull the drill string back to the vessel after finishing coring in Hole U1489D. The vessel departed for Site U1490 at 0212 h, ending operations at Site U1489. We finished the transit at 2400 h, beginning operations at Site U1490. The scientists worked on the Site U1489 reports and prepared for the science review meeting.

Daily Science Report for 29 November 2016

Location: Hole U1489D (2°7.1761′N, 141°1.6651′E, water depth 3421.5 mbsl; proposed Site WP-04A)

Science Update: We continued drilling without coring in Hole U1489D from 237.4 to 274.0 mbsf. After retrieving the center bit, we cored with the extended core barrel to 385.6 mbsf (Cores U1489D-16X through 27X). We terminated the hole at that depth and began to pull the pipe out of the hole and back to the ship. By the end of the day, the end of the drill pipe was at 423.2 m below rig floor (mbrf). After completing coring operations at Site U1489, we have recovered 6152 m of core, which is the most collected on any single expedition since the start of the second phase of the Integrated Ocean Drilling Program in 2009!

Cores U1489D-9H through 14H were split and described. This interval consists of light greenish gray foraminifer-rich nannofossil clay, grading to clay-bearing foraminifer-nannofossil ooze near the base of the described interval. The sediment is slightly to moderately bioturbated throughout. Pyritized burrows are present, as are sulfide specks and yellowish mottles. Core 14H shows evidence of soft-sediment deformation. Cores U1489D-16X through 27X were also split and described. The upper part of this interval is white foraminifer-bearing clay-rich chalk. Thin greenish and purplish laminae are present throughout and are likely a result of diagenetic alteration. The sediment also shows signs of soft-sediment deformation. Towards the base of the described interval, the sediment becomes yellowish radiolarian-bearing foraminifer-rich chalk. Carbonate content also decreases slightly over this interval.

Daily Science Report for 28 November 2016

Location:
Hole U1489C (2°7.1772′N, 141°1.6746′E, water depth 3423.7 mbsl; proposed Site WP-04A)
Hole U1489D (2°7.1761′N, 141°1.6651′E, water depth 3421.5 mbsl; proposed Site WP-04A)

Science Update: We continued coring with the extended core barrel (XCB) in Hole U1489C, advancing from 269.5 to 385.6 mbsf (Cores U1489C-40X through 42X), where we terminated the hole. Core recovery for those three cores averaged 76%. We then pulled the drill string above the seafloor and offset the vessel 20 m west of Hole U1489C. Hole U1489D was spudded at 0640 h, with Core U1489D-1H recovering 3.69 m of core, establishing a seafloor depth of 3421.5 mbsl. Advanced piston corer (APC) coring with orientation and nonmagnetic hardware continued to 127.7 mbsf (Cores U1489D-1H through 14H). We deployed the Advanced Piston Corer Temperature Tool (APCT-3) on Cores 4H, 7H, 10H, and 13H, as two of the measurements taken in Hole U1489B showed signs of movement and a third measurement had provided a spurious result. We then dropped a center bit to drill ahead without coring to 274 mbsf. By the end of the day, the bit had reached 237.4 mbsf.

Cores U1489C-32X through 42X were split and described. The upper part of the described interval consists of white foraminifer-bearing clay-rich chalk. Bioturbation is slight to moderate, with well-preserved burrows and mottling evident. This transitions to white clay-rich foraminifer-rich chalk. A few coarse (sand-size) layers are present and there is evidence of soft-sediment deformation (folded beds). Siliceous microfossils (especially radiolarians) are also present in the lower part of the described interval. Near the base of the hole there is an abrupt transition from pale yellow foraminifer-bearing radiolarian-rich chalk to white foraminifer chalk. Cores U1489D-1H through 8H were also split and described. The sediment succession correlates well with that seen in Hole U1489C. The uppermost core consists of foraminifer-bearing biosilica-rich clay-rich nannofossil ooze, with the color varying from pale yellow to light greenish gray. Below the first core, the sediment is light greenish gray nannofossil ooze with varying proportions of foraminifers and clay. Sulfide patches and pyritized burrows are occasionally present.

Daily Science Report for 27 November 2016

Location: Hole U1489C (2°7.1772′N, 141°1.6746′E, water depth 3423.7 mbsl; proposed Site WP-04A)

Science Update: We continued advanced piston corer (APC) coring with orientation and nonmagnetic hardware from 184.0 to 269.5 mbsf (Cores U1489C-21H through 29H). When Core 29H required a drillover to extract it from the formation, we decided to switch to the half-length advanced piston corer (HLAPC). We collected Cores U1489C-30F and 31F (269.5–278.9 mbsf); however, Core 30F had a shattered liner that required pumping out and Core 32F required a drillover. Therefore, we switched to the extended core barrel (XCB) coring system and continued coring from 278.9 to 356.5 mbsf (Cores 32X through 39X) by the end of the day. Core recovery over the APC/HLAPC section averaged 99%. Core recovery with the XCB was surprisingly good (average 95%). Although the cores were disturbed by the XCB coring process, the biscuits are usually large, with very little slurry in between.

Cores U1489C-13H through 31F were split and described. The sediment is primarily white clay-bearing foraminifer-rich nannofossil ooze throughout the described interval. Light green and purple laminae are scattered throughout and sulfide patches and pyritized burrows are also present. Towards the base of the described interval, there are short intervals that contain siliceous microfossils (radiolarians, diatoms, and sponge spicules). Much of the examined sequence also displays soft-sediment deformation features, including inclined beds, chaotic bedding, and micro-faults. Carbonate content is ~70 wt% at the top of Site U1489 and increases with depth, reaching values consistently >90 wt% by 150 mbsf. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicate a middle Miocene age at Core U1489C-39X.

Daily Science Report for 26 November 2016

Location: Hole U1489C (2°7.1772′N, 141°1.6746′E, water depth 3423.7 mbsl; proposed Site WP-04A)

Science Update: We offset the vessel 40 m south of Hole U1489B. Hole U1489C was spudded at 0235 h, with Core U1489C-1H retrieving 3.59 m of sediment, establishing a seafloor depth of 3423.7 mbsl. Advanced piston corer (APC) coring with orientation and nonmagnetic hardware continued to 184.0 mbsf (Core U1489C-20H) by the end of the day. Coring proceeded smoothly, with only two issues. The shear pins were prematurely sheared on Core 3H, and the liner of Core 16H was split throughout. Otherwise, we encountered none of the problems that we had during coring of Hole U1489B. Core recovery averaged 101% over the cored interval.

Cores U1489B-13H and 14H were split and described. Core 13H is completely destroyed by drilling disturbance, whereas Core 14H consists of light gray foraminifer-rich nannofossil clay. Cores U1489C-1H through 12H were also split and described. The uppermost part of the first core is composed of light gray diatom-rich clay-rich nannofossil ooze. Below this, the sediment transitions to light greenish gray foraminifer-bearing clay-rich nannofossil ooze and foraminifer-rich clay-rich nannofossil ooze. The sediment is slightly to moderately bioturbated, with occasional pyritized burrows present. A 15 cm thick ash layer is present towards the bottom of the section. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicate that the sediment is late Miocene in age at Core U1489C-20H.

Daily Science Report for 25 November 2016

Location:
Hole U1489A (2°7.1976′N, 141°1.6654′E, water depth 3419.8 mbsl; proposed Site WP-04A)
Hole U1489B (2°7.1984′N, 141°1.6757′E, water depth 3419.5 mbsl; proposed Site WP-04A)

Science Update: We spudded Hole U1489A at 0035 h, retrieving a full barrel. Since we missed the mudline, we terminated coring in that hole. We then offset the vessel 20 m east and spudded Hole U1489B at 0145 h. Core U1489B-1H recovered 5.76 m of sediment, establishing a seafloor depth of 3419.5 mbsl. We continued advanced piston corer (APC) coring with orientation and nonmagnetic hardware to 129.2 mbsf (Core 14H). Core 6H had a split liner. The shear pins for Cores 3H and 8H sheared early due to core barrel movement because of heavy seas; Core 3H was almost entirely disturbed by suck-in, whereas only the top two sections in Core 8H were affected. Beginning at Core 11H, we had trouble with the core barrel coming back empty. Cores 12H and 13H were re-shot from the same depth, recovering full or nearly full barrels; however, the sediment was found to be completely disturbed upon splitting. There were no problems with Core 14H, but when no core was retrieved for Core 15H, we decided to terminate coring in Hole U1489B. While pulling the drill string out of Hole U1489B, we changed out as many components as possible on both core barrels, in case there was a mechanical problem. The pipe cleared the seafloor at 2355 h, ending Hole U1489B.

Cores U1489A-1H and U1489B-1H through 12H were split and described. The uppermost sediment consists of light olive gray clay-rich nannofossil ooze. Siliceous microfossils are present in this interval. Below this, the sediments alternate between light greenish gray clay-bearing foraminifer-rich nannofossil ooze and grayish green foraminifer-rich nannofossil clay. The sediment is moderately bioturbated and some burrows are filled with sulfides. Green laminae are common. One tephra layer is present in the described section. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicate a late Miocene to early Pliocene age for the bottom of Hole U1489B; however, the assemblages are mixed due to significant core disturbance.

Daily Science Report for 24 November 2016

Location:
Hole U1488C (2°2.5793′N, 141°45.2974′E, water depth 2604.0 mbsl; proposed Site WP-03A)
In transit to Site U1489 (proposed Site WP-04A)
Site U1489 (2°7.1976′N, 141°1.6654′E; proposed Site WP-04A)

Science Update: Advanced piston corer (APC) coring with orientation and nonmagnetic hardware continued from 130.8 to 159.3 mbsf (Cores U1488C-15H through 17H). We terminated coring at this depth since we had cored deeper than the interval over which high-resolution interstitial water samples had been taken in Hole U1488A. Core recovery was very poor in Core 17H (3%); however, it was very good over the remainder of the hole (average 102%). We then tripped the pipe back to the ship and prepared the vessel for transit, ending operations at Site U1488 at 1030 h. We arrived at Site U1489 (proposed Site WP-04A) at 1442 h and prepared for coring operations, which included drifting (checking to ensure that the interior was clear) and strapping (measuring) 18 additional stands of 5 inch drill pipe for operations at this deeper water (~3427 mbsl) site. By the end of the day, the pipe had been tripped to near the seafloor and we were preparing to deploy a core barrel.

Cores U1488B-26H through 33H were split and described. The uppermost part of the described section is white foraminifer-rich nannofossil ooze. This transitions to white radiolarian-bearing foraminifer-rich nannofossil ooze, and then to white diatom-rich foraminifer-nannofossil ooze near the bottom of the hole. The sediments are moderately to heavily bioturbated, with numerous faint green, yellowish, and purple-black layers and mottles. A few pyritized burrows are also present. Cores U1488C-1H through 17H were also split and described. The uppermost cores show the most variability, alternating between light greenish gray foraminifer-bearing clay-rich nannofossil ooze and greenish gray foraminifer-rich nannofossil clay. Bioturbation is moderate and greenish layers are present, together with pyritized burrows. Below ~50 mbsf, the sediment transitions to light greenish gray clay-bearing foraminifer-rich nannofossil ooze, with faint green layers and yellowish burrows. Black sulfide patches are common. Near the base of the described section the sediment is foraminifer-bearing nannofossil ooze. Two tephra layers are found in the described section and pyrite nodules are common.

Daily Science Report for 23 November 2016

Location:
Hole U1488B (2°2.5901′N, 141°45.2966′E, water depth 2604.4 mbsl; proposed Site WP-03A)
Hole U1488C (2°2.5793′N, 141°45.2974′E, water depth 2604.0 mbsl; proposed Site WP-03A)

Science Update: We continued oriented advanced piston corer (APC) coring with nonmagnetic hardware in Hole U1488B from 228.9 to 304.9 mbsf (Cores U1488B-26H through 33H). The last three cores (31H through 33H) had to be drilled over to retrieve them from the formation. We terminated coring in Hole U1488B after Core 33H and then pulled the drill string to above the seafloor and offset the vessel 20 m to the south. Hole U1488C was spudded at 1300 h, retrieving 7.27 m of sediment and establishing a seafloor depth of 2604.0 mbsl. Oriented APC coring with nonmagnetic hardware continued to 130.8 mbsf (Core U1488C-14H) by the end of the day. Core recovery averaged 102% in Hole U1488C. Stratigraphic correlation at Site U1486 proved challenging below the top ~50 mbsf, the depth at which the magnetic susceptibility (MS) signal dropped significantly; however, P-wave velocity proved to have a correlatable feature. Since there is no P-wave logger on the Special Task Multisensor Logger (STMSL), which is normally used to collect lower resolution gamma ray attenuation bulk density and MS data rapidly as cores are brought in from the catwalk, we opted to use the Whole-Round Multisensor Logger (WRMSL) as the “fast track” system. Cores were then run on the STMSL at higher resolution after equilibration. This proved successful for monitoring the position of core gaps in near real time, which otherwise would have been almost impossible with the very low magnetic susceptibility data.

Cores U1488B-8H through 25H were split and described. The upper part of the described interval consists of light greenish gray foraminifer-bearing clay-rich nannofossil ooze. Clay content decreases downhole, with the sediment transitioning to light greenish gray foraminifer-rich nannofossil ooze, which becomes white towards the bottom of the described interval. The sediment shows numerous faint thin green and purple-black layers and is moderately bioturbated. Sulfide minerals are abundant, with pyritized burrows particularly common towards the top of the described interval. Total organic carbon content is quite low, with highest values (~0.4–0.7 wt%) near the top of the succession and decreasing downhole.

Daily Science Report for 22 November 2016

Location: Hole U1488B (2°2.5901′N, 141°45.2966′E, water depth 2604.4 mbsl; proposed Site WP-03A)

Science Update: We continued to pull the drill string out of Hole U1488A, clearing the seafloor at 0120 h. We then offset the vessel 20 m to the east and spudded Hole U1488B at 0300 h. Core U1488B-1H retrieved 0.93 m of sediment, establishing a seafloor depth of 2604.4 mbsl. Advanced piston corer (APC) coring with orientation and nonmagnetic hardware continued to 228.9 mbsf (Core 25H) by the end of the day. Core recovery averaged 103%.

Cores U1488A-21H through 35F were split and described. The upper two cores consist of white clay-rich foraminifer-rich nannofossil ooze. Clay content decreases downhole and the lithology changes to foraminifer-bearing nannofossil ooze. Siliceous microfossils are also present, with some intervals of radiolarian-bearing foraminifer-nannofossil ooze. Faint greenish layers and yellowish-black mottles are common throughout the sequence and bioturbation is moderate to heavy. Cores U1488B-1H through 7H were also split and described. The upper ~40 cm of the hole consists of yellowish brown clay-bearing foraminifer-bearing nannofossil ooze, with a color transition to greenish gray below. The remainder of the described succession consists of nannofossil ooze with varying proportions of foraminifers and clay. Diatoms are also sporadically present. Greenish and purple-black mottles are common, as are pyritized burrows. Bioturbation is moderate to heavy throughout. The upper ~50 mbsf of this site has relatively high magnetic susceptibility and the sediments hold a natural remanent magnetization. Magnestic susceptibility drops below this depth and the paleomagnetic signal also deterioriates. The carbonate content is ~65–75 wt% in the upper part of the succession and increases with depth, reaching to ~80–90 wt% by the bottom of Hole U1488A.

Daily Science Report for 21 November 2016

Location: Hole U1488A (2°2.5891′N, 141°45.2864′E, water depth 2603.4 mbsl; proposed Site WP-03A)

Science Update: We continued advanced piston corer (APC) coring with orientation and nonmagnetic hardware from 110.4 to 300.4 mbsf (Cores U1488A-13H through 32H). After drilling over Cores 31H and 32H to retrieve them from the formation, we decided to switch to the half-length advanced piston corer (HLAPC). We cored to 314.5 mbsf (Cores 33F through 35F); however, after two of these cores required drillovers (33F and 35F), we decided to terminate coring operations in Hole U1488A. Core recovery in Hole U1488A averaged 104%. We then began to pull out of the hole to offset the vessel for coring in Hole U1488B. By the end of the day, the bottom of the drill string was at 276.3 mbsf in Hole U1488A.

Cores U1488A-5H through 20H were split and described. The sediment consists of light greenish gray clay-rich foraminifer-nannofossil ooze. The sediment is heavily bioturbated with faint green layers and yellowish-black mottle. Sulfide precipitates are common throughout the sequence. A couple of discrete tephra layers also occur. Siliceous microfossils are present in the uppermost part of the described sequence. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicate a late Miocene age for the bottom of Hole U1488A.

Daily Science Report for 20 November 2016

Location:
In transit to Site U1488 (proposed Site WP-03A)
Hole U1488A (2°2.5891′N, 141°45.2864′E, water depth 2603.4 mbsl; proposed Site WP-03A)

Science Update: We arrived at Site U1488 and switched to dynamic positioning, stabilizing over the site at 0424 h. After deploying the positioning beacon, we made up the advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly and began running the drill string towards the seafloor. Hole U1488A was spudded at 1245 h. Core U1488A-1H recovered 5.89 m of sediment, establishing a seafloor depth of 2603.4 mbsl. We continued APC coring with orientation and nonmagnetic hardware to 110.4 mbsf (Core 12H) by the end of the day. The advanced piston corer temperature tool (APCT-3) was deployed on Cores 4H, 7H, and 10H. We also collected interstitial water (IW) whole-round samples at a rate of one per section over the cored interval. This high-resolution IW sampling will continue to 150 mbsf.

Cores U1488A-1H through 4H were split and described. The uppermost ~50 cm of the sediment consists of pale brown clay-rich foraminifer-rich nannofossil ooze. Below this the lithology alternates between light greenish gray foraminifer-nannofossil ooze and greenish gray clay-rich foraminifer-rich nannofossil ooze. The sediment is moderately to heavily bioturbated and mottled in appearance. A few pumice clasts are present in the upper part of the described section. A pyritized burrow was also found in one core. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicates an early Pliocene age for Core U1488A-12H.

Daily Science Report for 19 November 2016

Location: In transit to Site U1488 (proposed Site WP-03A)

Science Update: We continued our transit to Site U1488 (proposed Site WP-03A), with an estimated arrival time of 0430 h on 20 November. The scientists continued to process remaining cores and samples from Site U1487, while also working on site reports. Cores U1487B-1H through 18F were split and described. These cores correlate well with the section recovered in Hole U1487A. The upper part of the hole is dominated by biogenic material, with ash and volcanic fragment content increasing downhole. The sediment in this interval is primarily olive green to greenish gray clay-bearing foraminifer-rich nannofossil ooze and clay-bearing nannofossil-rich foraminifer ooze. Ash-rich foraminifer ooze becomes common downhole, with significant numbers of discrete ash layers present in each core. The lowermost section of the hole is dominated by volcanic material and ash, and is consequently very dark in color. Nannofossils and foraminifers are a minor component of the sediment in this interval. Similar to Site U1486, the calcium carbonate content is higher in the upper part of the hole (~55–75 wt%) and decreases with depth, reaching values as low as 2 wt% in the lowermost cores.

Daily Science Report for 18 November 2016

Location:
Hole U1487A (2°19.9979′S, 144°49.1627′E, water depth 873.9 mbsl; proposed Site WP-14A)
Hole U1487B (2°19.9975′S, 144°49.1746′E, water depth 873.6 mbsl; proposed Site WP-14A)
In transit to Site U1488 (proposed Site WP-03A)

Science Update: We continued oriented advanced piston corer (APC) coring with nonmagnetic hardware from 120.4 to 144.2 mbsf (Cores U1487A-14H through 16H). Cores 14H and 16H were partial strokes; Core 15H had to be drilled over to extract it from the formation. We decided to terminate coring in Hole U1487A at 144.2 mbsf rather than switch to the half-length APC (HLAPC) as we had reached our age target. Core recovery averaged 103% over those three cores. We then pulled the drill string to above the seafloor and offset the vessel 20 m east of Hole U1487A. We spudded Hole U1487B at 0740 h. Core U1487B-1H recovered 2.71 m of sediment, establishing a seafloor depth of 873.6 mbsl. Oriented APC coring with nonmagnetic hardware continued to 125.5 mbsf (Core U1487B-14H). After a partial stroke on Core 14H, we switched to the HLAPC and continued coring to 144.3 mbsf (Cores 15F through 18F), where we terminated coring. Core recovery for Hole U1487B averaged 103%. We then pulled the drill string back to the vessel and secured the rig for transit at 2210 h, ending operations at Site U1487. At the end of the day, we were underway to Site U1488 (proposed Site WP-03A), with an estimated arrival time of 0430 h on 20 November.

Cores U1486D-15H through 19H were split and described. The sediment is greenish gray ash-rich foraminifer-rich nannofossil clay with numerous discrete ash layers in each core. Cores U1487A-1H through 16H were also split and described. The sediment in this hole can be divided into three sections. The upper part is predominantly biogenic and consists of greenish gray clay-bearing nannofossil-rich ooze and darker nannofossil-bearing ash-rich foraminifer clay. Pteropods and shell fragments are common. Discrete ash layers are present and scoria fragments are scattered throughout the sediment. Below this ash becomes a significant portion of the sediment, although nannofossil and foraminifers are still abundant. Discrete ash layers increase in number downhole, often exceeding 15 ash layers per core. Siliceous microfossils (diatoms and radiolarians) are also present. The lowermost part of the section is dark greenish gray nannofossil-bearing foraminifer-rich ash interbedded with black ash layers. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicates a late Pliocene age for the bottom of the hole.

Daily Science Report for 17 November 2016

Location:
Hole U1486D (2°22.3484′S, 144°36.0690′E, water depth 1334.1 mbsl; proposed Site WP-05A)
In transit to Site U1487 (proposed Site WP-14A)
Hole U1487A (2°19.9979′S, 144°49.1627′E, water depth 873.9 mbsl; proposed Site WP-14A)

Science Update: We continued oriented advanced piston corer (APC) coring with nonmagnetic hardware from 115.2 to 153.2 mbsf (Cores U1486D-14H to 17H). We then drilled ahead without coring 23.8 m to take a final core (U1486D-19H) over an interval that spans a magnetic reversal boundary found in Hole U1486B, but that had fallen within a core gap in Hole U1486C. Core 19H penetrated to 186.5 mbsf, the total depth of Hole U1486D. Core recovery over the bottom part of the hole averaged 104%. We then tripped the drill string back to the vessel and secured the rig floor for transit. We departed Site U1486 at 1018 h for the short sea passage to Site U1487 (proposed Site WP-14A). We arrived on site at 1145 h and prepared for coring operations. Hole U1487A was spudded at 1610 h, recovering 6.4 m of sediment and establishing a seafloor depth of 873.9 mbsl. Oriented APC coring with nonmagnetic hardware continued to 120.4 mbsf (Cores U1487A-1H through 13H) by the end of the day. We took advanced piston corer temperature tool (APCT-3) measurements on Cores 4H, 7H, 10H, and 13H.

Cores U1486C-18H through 23H were split and described. This part of the succession consists of interbedded grayish green foraminifer-rich nannofossil clay and dark gray ash. Numerous (>15) discrete ash layers occur in each core; some of the ash layers have sharp bases. Bioturbation is moderate in the nannofossil clay, but only slight in the ash. Cores U1486D-1H through 14H were also split and described. The upper part of the sequence is primarily light greenish gray foraminifer-rich nannofossil clay, with a few discrete ash layers and common sulfides. Ash layers and scattered ash grains become more abundant downhole. The nannofossil clay transitions to clay-rich foraminifer-rich nannofossil ooze and occasionally even foraminifer ooze in the middle of the described sequence. Towards the bottom, siliceous microfossils (diatoms and radiolarians) are present. Carbonate content is higher in the upper part of the sediment sequence at Site U1486 and decreases downhole, which corresponds to the increase in ash-dominated sediments in the middle and lower parts of the succession.

Daily Science Report for 16 November 2016

Location:
Hole U1486C (2°22.3478′S, 144°36.0798′E, water depth 1334.5 mbsl; proposed Site WP-05A)
Hole U1486D (2°22.3484′S, 144°36.0690′E, water depth 1334.1 mbsl; proposed Site WP-05A)

Science Update: We continued oriented advanced piston corer (APC) coring with nonmagnetic hardware from 115.8–201.3 mbsf (Cores U1486C-15H through 23H), where we terminated coring. Core recovery averaged 88% over this interval, with one core (16H) that had very low recovery (29%). We then pulled the drill string to above the seafloor and offset the vessel 20 m to the west of Hole U1486C. After slipping and cutting the drill line, we spudded Hole U1486D at 1320 h. Core U1486D-1H recovered 1.23 m of sediment, establishing a seafloor depth of 1334.1 mbsl. Oriented APC coring with nonmagnetic hardware proceeded slowly at first in order to confirm that cores were positioned to cover core gaps in Holes U1486B and U1486C. After successfully covering two gaps in the upper part of the hole, coring continued to 115.2 mbsf (Core 13H) by the end of the day with no drilled intervals required. Core recovery averaged 102%.

Cores U1486B-17H through 23H were split and described. The sediment consists of interbedded light gray foraminifer-rich nannofossil clay, gray foraminifer-bearing nannofossil-rich ash, and dark greenish gray ash-bearing foraminifer-bearing nannofossil clay. Glassy ash shards are abundant throughout the sediment and each core contains numerous distinct tephra layers. The sediment at the bottom of the hole contains basalt fragments and the presence of zeolites suggests hydrothermal alteration. The inverse relationship of the interstitial water profiles of Ca²⁺ and Mg²⁺ in Hole U1486B suggest interaction with the underlying basalt. Cores U1486C-1H through 17H were also split and described. The lithologies in these cores correlate well with those from Hole U1486B. The upper part of the succession consists of greenish gray foraminifer-rich nannofossil clay and light greenish gray foraminifer-nannofossil ooze. A few discrete tephra layers are present over this interval. Tephra layers ranging from brown to black increase significantly in number towards the bottom of the described section and are intermixed with background sedimentation consisting of foraminifer-bearing to foraminifer-rich nannofossil clay.

Daily Science Report for 15 November 2016

Location:
Hole U1486B (2°22.3368′S, 144°36.0794′E, water depth 1333.8 mbsl; proposed Site WP-05A)
Hole U1486C (2°22.3478′S, 144°36.0798′E, water depth 1334.5 mbsl; proposed Site WP-05A)

Science Update: We continued oriented advanced piston corer (APC) coring with nonmagnetic hardware from 91.5 to 211.2 mbsf (Cores U1486B-11H through 23H). A final advanced piston corer temperature tool (APCT-3) measurement was taken on Core 13H. We also terminated high-resolution interstitial water sampling at 150 mbsf in Core 17H. Cores 21H and 22H had to be drilled over to extract them from the formation. Core 23H had a full stroke but only recovered 5.67 m of sediment. While drilling out the rat hole, the drill bit stopped advancing at 211.2 mbsf. This, coupled with the low recovery and pebbles of basalt in the core catcher, suggested that we had reached igneous basement. We then terminated coring operations in Hole U1486B. Core recovery over Cores 11H through 23H averaged 101%. After pulling the drilling string to above the seafloor, we offset the vessel 20 m south of Hole U1486B. Hole U1486C was spudded at 1415 h, with Core U1486C-1H recovering 7.34 m of sediment, establishing a seafloor depth of 1334.5 mbsl. We continued oriented APC coring with nonmagnetic hardware to 115.8 mbsf (Core U1486C-14H). Core recovery averaged 87% over this interval. We drilled ahead without coring twice to offset core gaps for stratigraphic correlation purposes.

Cores U1485D-3H through 8H were split and described. These cores consist of dark greenish gray nannofossil-rich silty clay with interbedded silty sand layers. The thickness of the sand layers increases downhole. Bioturbation is moderate to heavy, and sulfide specks and wood fragments are also present. After finishing description for Site U1485 sediment, Cores U1486A-1H and U1486B-1H through 16H were split and described. The upper part of the section is light greenish gray foraminifer-bearing clay-rich nannofossil ooze. Bioturbation is moderate and a sea urchin was found near the top of the cored section. Sulfide is abundant and ash layers are common. Clay and ash content increase downhole, with the primary lithology transitioning to greenish gray foraminifer-rich nannofossil clay. The age at the bottom of Hole U1486B is late Pliocene based on calcareous nannofossil and planktonic foraminifer biostratigraphy.

Daily Science Report for 14 November 2016

Location:
In transit to Site U1486 (proposed Site WP-05A)
Hole U1486A (2°22.3375′S, 144°36.0796′E, water depth 1330.3 mbsl; proposed Site WP-05A)
Hole U1486B (2°22.3368′S, 144°36.0794′E, water depth 1333.8 mbsl; proposed Site WP-05A)

Science Update: We arrived at Site U1486 (proposed Site WP-05A) at 0921 h, and then lowered the thrusters and deployed the positioning beacon. After making up the advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly, we ran the pipe towards the seafloor. Hole U1486A was spudded at 1545 h; however, Core U1486A-1H retrieved a full core barrel, indicating that we missed the mudline. We terminated Hole U1486A and offset the vessel 20 m east. Hole U1486B was started at 1645 h, recovering 5.99 m of sediment and establishing a seafloor depth of 1333.83 mbsl. Oriented APC coring with nonmagnetic hardware continued to 91.5 mbsf (Core U1486B-10H) by the end of the day. Calcareous nannofossil and planktonic foraminifer biostratigraphy indicate an early Pleistocene age at this depth. We took advanced piston corer temperature tool (APCT-3) measurements on Cores 4H, 7H, and 10H. This site is also a target for high-resolution interstitial water measurements, so whole-round samples were taken from the bottom of Sections 1–6 of every core. This will continue to 150 mbsf.

Cores U1485B-26H through 47F were split and described. The upper part of the described section consists of dark greenish gray nannofossil-rich silty clay interbedded with thin sand and silty sand layers. Towards the bottom of the hole, the lithology transitions to dark gray nannofossil silty clay and nannofossil-bearing clay. The coarser grained layers are absent in this part of the section. Pyrite is abundant throughout the hole. Several discrete volcanic ash layers are also present through this section. Carbonate content is generally <15 wt% throughout the sedimentary sequence at Site U1485; however, a short interval with somewhat higher values (~25 wt%) is located just above the transition to dark gray clay. Cores U1485C-1H through 3H and U1485D-1H and 2H were also split and described. The upper part of these holes consists of olive gray foraminifer-bearing nannofossil-rich clay that is heavily bioturbated. A tephra layer is present in both holes within the clay. This sediment transitions to dark greenish gray nannofossil-rich clay intercalated with silty sand layers typically >5 cm thick.

Daily Science Report for 13 November 2016

Location:
Hole U1485B (3°6.1584′S, 142°47.5854′E, water depth 1145.3 mbsl; proposed Site WP-72A)
Hole U1485C (3°6.1697′S, 142°47.5746′E, water depth 1145.8 mbsl; proposed Site WP-72A)
Hole U1485D (3°6.1697′S, 142°47.5854′E, water depth 1144.4 mbsl; proposed Site WP-72A)
In transit to Site U1486 (proposed Site WP-05A)

Science Update: We continued to core in Hole U1485B using the half-length advanced piston corer (HLAPC) from 255.4 to 297.7 mbsf (Cores U1485B-39F through 47F), ending Hole U1485B. Core recovery over this interval was 104%. We pulled the drill string out of the hole and offset the vessel 20 m to the south. Hole U1485C was planned to core the interval where we conducted high-resolution interstitial water sampling in Hole U1485A (through Core U1485A-6H [55 mbsf]). After slipping and cutting the core winch line, we started Hole U1485C at 1045 h. The first core recovered 8.51 m of sediment, establishing a seafloor depth of 1145.8 mbsl. Oriented APC coring continued for two cores (U1485C-2H and 3H) to a depth of 27.5 mbsf. We decided to terminate this hole after stratigraphic correlation indicated that Core 2H repeated much of the section recovered in Core 1H. After pulling the drill string out of the hole, we offset the vessel 20 m to the west of Hole U1485C. Hole U1485D was spudded at 1330 h, recovering 5.94 m of sediment and establishing a seafloor depth of 1144.4 mbsl. Oriented APC coring with nonmagnetic hardware continued to 63.9 mbsf (Core U1485D-8H), with one 1 m drilled interval to ensure core gaps did not align for stratigraphic correlation purposes. We then tripped the pipe out of the hole and up to the drill floor. The positioning beacon was recovered while retrieving the pipe. We secured the rig for transit, raised the thrusters, and departed for Site U1486 (proposed Site WP-05A) at 2330 h, ending operations at Site U1485.

Cores U1485B-1H through 25F were split and described. The uppermost part of the described section consists of interbedded dark greenish gray nannofossil-bearing silty clay and dark gray to very dark greenish gray sand. The sands are variable in thickness, have sharp bases, and some intervals contain abundant shallow water benthic foraminifers. Below the thick sands, the sediment is dark greenish gray nannofossil-bearing silty clay with no coarser material, but abundant pyrite. Sandy silt layers occur near the base of the described section. A few discrete ash layers are present throughout the described interval.

Daily Science Report for 12 November 2016

Location: Hole U1485B (3°6.1584′S, 142°47.5854′E, water depth 1145.3 mbsl; proposed Site WP-72A)

Science Update: We started Hole U1485B at 0010 h, with Core U1485B-1H recovering 1.97 m of sediment, establishing a seafloor depth of 1145.34 mbsl. Oriented advanced piston corer (APC) coring with nonmagnetic hardware continued to 173.5 mbsf (Core 20H). We then switched to the half-length APC (HLAPC) and continued coring to 255.4 mbsf (Cores U1485B-21F through 38F) by the end of the day. One drilled interval advanced the hole by 2 m without coring to avoid alignment of core gaps for stratigraphic correlation. Core recovery averaged 99% in Hole U1485B.

Cores U1485A-15H through 44F were split and described. Thick, dark greenish gray sand layers are abundant in the uppermost part of the described interval. Nannofossil-bearing to nannofossil-rich clay becomes more abundant downcore, with thin (few centimeters to decimeter) sand and silty sand beds interspersed. The base of these beds is sharp. Bioturbation is moderate throughout this interval, which also contains sulfides and wood fragments. Several discrete ash layers also occur. Towards the bottom of the hole, there is a transition from dark greenish gray to dark gray nannofossil clay. Below this depth there are no sand layers. The abundance of foraminifers and nannofossils in the sediment varies, but generally is subordinate to clay and silty clay. A few ash layers are also present through this section. The clay at the bottom of Hole U1485A shows very low magnetic susceptibility relative to the sandier intervals above. Carbonate content is somewhat higher at Site U1485 relative to Site U1484, but is still low (average ~10%).

Daily Science Report for 11 November 2016

Location:
Hole U1485A (3°6.1585′S, 142°47.5750′E, water depth 1144.9 mbsl; proposed Site WP-72A)
Hole U1485B (3°6.1584′S, 142°47.5854′E, water depth 1145.4 mbsl; proposed Site WP-72A)

Science Update: We continued oriented advanced piston corer (APC) coring using nonmagnetic hardware from 159.5 to 188.0 mbsf (Cores U1485A-18H through 20H). Core 20H had to be pumped out of the liner and so we switched to the half-length APC (HLAPC) and continued coring to 296.1 mbsf (Cores 21F through 44F). We reached HLAPC refusal at that depth after Cores 43F and 44F required 40 klbs of overpull to retrieve and the liner at the top of Core 43F was broken. We decided to terminate coring in Hole U1485A rather than switch to the extended core barrel (XCB) system to core only an additional ~29 m (to maximum approved depth of 325 mbsf). Core recovery from Cores U1485A-18H to 44H averaged 106%. We pulled the drill string out of the hole and offset the vessel 20 m to the east of Hole U1485A. At the end of the day we were preparing to spud Hole U1485B.

Cores U1484C-25F through 32F were split and described. The primary lithologies are dark greenish gray nannofossil-rich clay, interspersed with silty sand layers ranging for a few centimeters to a meter or more thick. The silty sand layers usually have sharp bases. Bioturbation is moderate throughout this interval. Cores U1485A-1H through 14H were also split and described. The sediment is primarily dark greenish gray nannofossil-rich clay, with a few thin (1–8 cm thick) silty sand beds scattered throughout. The number of silty sand beds increases downhole. Towards the bottom of the described section, the primary lithology transitions to a foraminifer-bearing nannofossil-rich silty clay. Wood fragments are scattered throughout and bioturbation is moderate. The sediment is very similar to that found at Site U1484 (only ~2 nmi away); however, Site U1485 has slightly higher proportions of finer material (silt and clay) relative to Site U1484, which is more proximal to Papua New Guinea. Calcareous nannofossil biostratigraphy indicates a middle Pleistocene age for the sediment at the bottom of Hole U1485A.

Daily Science Report for 10 November 2016

Location:
Hole U1484C (3°7.9335′S, 142°46.9822′E, water depth 1030.7 mbsl; proposed Site WP-71A)
Transit (using dynamic positioning) to Site U1485 (proposed Site WP-72A)
Hole U1485A (3°6.1585′S, 142°47.5750′E, water depth 1144.9 mbsl; proposed Site WP-72A)

Science Update: Oriented coring with the advanced piston corer (APC) and nonmagnetic hardware continued from 155.2 to 193.2 mbsf (Cores U1484C-23H through 26H). We then switched to the half-length APC (HLAPC) and cored to 221.4 mbsf (Cores 27F through 32F), the total depth of Hole U1484C. Core recovery averaged 104% over the bottom part of Hole U1484C. We pulled the pipe out of the hole to ~55 m above the seafloor and secured the rig floor for transit by 0945 h, which ended operations at Site U1484. We then transited 2 nmi in dynamic positioning mode to Site U1485 (proposed Site WP-72A). After arriving on site at 1110 h, we lowered the pipe to just above the seafloor and prepared for drilling operations. Hole U1485A was started at 1310 h, with the first core recovering 7.58 m of sediment, establishing a seafloor depth of 1144.9 mbsl. Oriented APC coring with nonmagnetic hardware proceeded to 159.5 mbsf (Core U1485A-17H) by the end of the day. Core recovery averaged 103% over Hole U1485A, although Cores 15H through 17H had lower recovery (73%–88%), likely due to unconsolidated sand. We opted not to conduct downhole temperature measurements at this site, since it is located very close to Site U1484.

Cores U1484B-28F to 31F were split and described. Cores 28F and 29F consist primarily of very dark greenish gray nannofossil-rich silty clay, with foraminifers and greenish black sandy silt layers present in the upper part of the interval. Silty sand and sand become abundant towards the bottom of Hole U1484B. Cores U1484C-1H through 24H were also split and described. The cores from Hole U1484C correlate well with the lithologies encountered in Holes U1484A and U1484B. The uppermost part of Hole U1484C consists of dark greenish gray nannofossil-rich clay. Discrete sand and silty sand layers become more abundant below ~10 mbsf. These layers usually show graded bedding and have sharp, irregular bases. Sulfide specks and wood fragments are also common. Thick silty sand and sand beds are more common towards the middle of the described interval. Some sand layers contain abundant shallow water benthic foraminifers. Nannofossil-rich silty clay is more abundant towards the bottom of the described interval, although discrete silty sand and sand layers are still present. Bioturbation is generally slight to moderate throughout the recovered succession.

Daily Science Report for 9 November 2016

Location:
Hole U1484B (3°7.9223′S, 142°46.9809′E, water depth 1030.5 mbsl; proposed Site WP-71A)
Hole U1484C (3°7.9335′S, 142°46.9822′E, water depth 1030.7 mbsl; proposed Site WP-71A)

Science Update: Coring with the advanced piston corer (APC) continued from 180.5 to 190.0 mbsf (Core U1484B-24H), and then we switched to the half-length APC (HLAPC) and penetrated to 222.9 mbsf (Cores 25F to 31F). Core recovery over this interval was 98%. After reaching the total depth of Hole U1484B, we pulled the drill string out of the hole and offset the vessel 20 m to the south. Hole U1484C was spudded at 1010 h and recovered 1.64 m of sediment in the first core, establishing a seafloor depth of 1030.7 mbsl. Oriented APC coring with nonmagnetic hardware continued through 106.1 mbsf (Core U1484C-12H). We then switched to the HLAPC to core through the sands located between ~105 and 130 mbsf. Cores U1484C-13F through 21F penetrated to 145.7 mbsf, with one 2 m drilled interval to offset core gaps for stratigraphic correlation. Coring then proceeded with the full length APC to 155.2 mbsf (Core 22H) by the end of the day. Core recovery averaged 101% through Hole U1484C.

Cores U1484B-4H through 27F were split and described. The uppermost part of the described interval consists of dark greenish gray clay and silty clay with varying proportions of sand and nannofossils. Sand layers are typically 1–11 cm thick and have sharp, irregular bases. Sulfide patches and wood fragments are common. This interval is underlain by thick dark greenish gray sand with common benthic foraminifers. Below the sand, the lithology is primarily dark greenish gray nannofossil-rich silty clay. Foraminifers are common in some intervals. Discrete sand layers are scattered throughout this interval. Several ash layers are also present. Smear slide analysis shows that the sand is primarily composed of glauconite, feldspar, and pyroxene. Calcium carbonate content ranges from ~2 to 15 wt%, with slightly higher values deeper in the section. Total organic carbon content in the uppermost part of the site ranges from about 0.5 to 2.0 wt%.

Daily Science Report for 8 November 2016

Location:
Hole U1484A (3°7.9228′S, 142°46.9699′E, water depth 1030.9 mbsl; proposed Site WP-71A)
Hole U1484B (3°7.9223′S, 142°46.9809′E, water depth 1030.5 mbsl; proposed Site WP-71A)

Science Update: We continued coring with the half-length advanced piston corer (HLAPC) from 209.1 to 223.2 mbsf (Core U1484A-27F). This ended Hole U1484A. We then pulled the pipe out of the hole, offset the vessel 20 m to the east, and spudded Hole U1484B at 0535 h. Core U1484B-1H retrieved 7.88 m of core, establishing a seafloor depth of 1030.5 mbsf. We continued oriented APC coring with nonmagnetic hardware to 104.8 mbsf (Core 12H). We then switched to the HLAPC to attempt to better recover the sand layers that resulted in poor recovery in Hole U1484A. We cored with the HLAPC to 133.0 mbsf (Cores 13F to 18F). This strategy proved successful, yielding an average recovery of 88% over the interval cored with the HLAPC. We then switched back to the full length APC and penetrated to 180.5 mbsf (Core 23H) by the end of the day. Average recovery over all of Hole U1484B was 99%.

Cores U1484A-9H through 27F were split and described. The upper part of the described interval consists of dark greenish gray nannofossil-rich clay and clay-rich silt. Dark gray sand layers of varying thickness are present throughout this interval. These sand layers have sharp, irregular bases. Shell fragments are common. Below this is a thick sand with scattered shell fragments and benthic foraminifers. The lower part of the hole consists of dark greenish gray nannofossil-rich clay, silty clay, and clayey silt. Sand layers are common, and shell and wood fragments also occur. Several ash layers are found in the lower part of the hole. Cores U1484B-1H through 3H were also split and described. These cores are predominantly nannofossil-rich silty clay with some sand layers. Bioturbation is moderate throughout. Nannofossil and foraminifer biostratigraphy indicate a middle Pleistocene age for the bottom of Hole U1484A and magnetostratigraphy constrains the recovered section to the Brunhes Chron.

Daily Science Report for 7 November 2016

Location: Hole U1484A (3°7.9228′S, 142°46.9699′E, water depth 1030.9 mbsl; proposed Site WP-71A)

Science Update: After making up the advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly and spacing it out, we lowered the pipe toward the seafloor. Hole U1484A was spudded at 0520 h. Core U1484A-1H recovered 5.05 m of sediment, establishing a seafloor depth of 1030.90 mbsl. Oriented APC coring with nonmagnetic hardware continued to 195.0 mbsf (Core 21H). Advanced piston corer temperature tool (APCT-3) measurements were taken on Cores 4H, 7H, 10H, and 13H; however, two of the results were questionable and so we opted to take another measurement on Core 16H. Core expansion resulted in a broken liner on Core 8H, and many of the cores extruded out of the top and bottom of the core barrel onto the drill floor upon retrieval. Despite this, recovery was generally very good and the interiors of cores appear to be reasonably undisturbed. Cores 13H and 14H penetrated a liquefied sandy interval, resulting in lower recovery (65% and 50%, respectively). Otherwise, core recovery over the APC interval averaged 102%. As core liners were becoming more difficult to extract from the core barrel due to expansion, we switched to the half-length APC (HLAPC) at 195.0 m, and by the end of the day we had penetrated to 209.1 mbsf (Core 24F).

Cores U1484A-1H through 8H were split and described. The uppermost cores are dark greenish gray silt-rich nannofossil clay to nannofossil-bearing clay, with sand layers 1 to 11 cm thick. Sand becomes more prevalent towards the bottom of the described interval. The cores are moderately bioturbated and foraminifers are scattered on the surface of the split cores. Pieces of wood are also scattered throughout some of the cores. Calcareous microfossils are reasonably abundant and well preserved. Nannofossil biostratigraphy indicates an age of <290 ka at the bottom of the cored interval.

Daily Science Report for 6 November 2016

Location:
In transit to Site U1484 (proposed Site WP-71A)
Site U1484 (3°7.92′S, 142°46.97′E)

Science Update: We arrived at Site U1484 (proposed Site WP-71A) and switched to dynamic positioning control at 2245 h. At the end of the day we were preparing the advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly. The scientists continued to revise site reports throughout the day. The downhole measurements specialist presented the logging results from Site U1482, and then the Co-Chief Scientists introduced the scientific objectives for upcoming Sites U1484 and U1485. Towards the end of the day, two scientists presented research on marine phytoplankton dynamics across the Eocene Oligocene transition and the Eocene warm pool.