IODP Expedition 349

South China Sea Tectonics

Daily Science Report for 28 February 2014

LOCATION: Hole U1432B (18°21.0831′N, 116°23.4503′E; water depth 3829 m)

SCIENCE UPDATE: We completed drilling the hole for the 10.75 inch casing at 2215 h, cleaned the hole in preparation for casing, and then began to pull out of the hole. We originally planned to drill to 900 mbsf, but decided to stop at 800 mbsf based on the slow rate of penetration and low torque on the drill string, which suggested we had drilled into a very firm and consolidated section ideal for setting casing.

We finished the Site U1431 final science meeting, with presentations and discussions covering the interstitial water geochemistry, microbiology, physical properties, and downhole measurements results. The scientists also prepared presentations for the upcoming Hole U1432C science results meeting.

Daily Science Report for 27 February 2014

LOCATION: Hole U1432B (18°21.1062′N, 116°23.4512′E; water depth 3829 m)

SCIENCE UPDATE: After making up the bottom-hole assembly with a 14.75 inch tri-cone bit with four stands of drill collars, we reentered the hole to drill out the cement and then began drilling the section for the 10.75 inch casing. At the end of the day we were at 296.9 mbsf, with a target depth of ~900 mbsf.

We held a science meeting to present the final results from Site U1431, concentrating on the core description results (lithostratigraphy, igneous petrology, and structural geology), as well as the chronostratigraphy for the site. The scientists also continued revising the Site U1431 reports.

Daily Science Report for 26 February 2014

LOCATION: Hole U1432B (18°21.1062′N, 116°23.4512′E; water depth 3829 m)

SCIENCE UPDATE: We reentered Hole U1432B with the 239 m of 16 inch casing at 0500 h and lowered it into the hole. By 1500 h, the casing had been fully installed, the casing hanger latched into the re-entry cone, and the casing running tool released. The casing was then cemented into place. After flushing the drill pipe to remove remaining cement, we began to trip out of the hole to rig up for drilling a 14.75 inch hole to ~900 mbsf for the 10.75 inch casing string.

The Operations Superintendent gave a ship tour to the other half of the science party. The scientists also continued to work on reports and prepared presentations for the final Site U1431 science meeting.

Daily Science Report for 25 February 2014

LOCATION: Hole U1432B (18°21.1062′N, 116°23.4512′E; water depth 3829 m)

SCIENCE UPDATE: The drill crew prepared the 16 inch casing hanger and ~240 m of 16 inch casing, hanging it off below the moonpool. Once the casing was assembled, they prepared the bottom-hole assembly and casing running tool and deployed the casing string through the moonpool, lowering it toward the seafloor.

The scientists worked to revise the Site U1431 report and site summary. They also began writing up results from Hole U1432C. During the day, the Operations Superintendent gave a ship tour to about half of the science party.

Daily Science Report for 24 February 2014

LOCATION: Hole U1432B (18°21.1062′N, 116°23.4512′E; water depth 3829 m)

SCIENCE UPDATE: We finished drilling down to 250 mbsf in Hole U1432B at 0640 h. The hole was conditioned for running the 16 inch casing by pumping two high viscosity sweeps and then displacing the hole with 10.5 ppg mud. The bottom-hole assembly was tripped to the rig floor and preparations began for running the 16 inch casing.

Cores U1432C-11H and ‑12H were split and described. These cores are very similar to the rest of Hole U1432C, consisting of greenish gray clay interbedded with silt and silty clay turbidite layers.

Daily Science Report for 23 February 2014

LOCATION: Hole U1432B (18°21.1062′N, 116°23.4512′E; water depth 3829 m)

SCIENCE UPDATE: After tripping pipe out of Hole U1432C, the vessel moved back to the Hole U1432B location. The pipe was tripped to the surface and we assembled a bottom-hole assembly with an 18.5 inch bit and 22 inch underreamer and lowered it back down to the seafloor. The subsea camera system was deployed for reentry and the bit reentered Hole U1432B at 1944 h. We plan to finish drilling the 22 inch hole to 250 mbsf for the 16 inch casing.

Cores U1432C-3H through ‑10H were split and described. The cores consist primarily of greenish gray clay and clay with silt. The silt beds, which are interpreted as turbidites, typically have sharp bases and fine upward. Some intervals of clay are color banded, with the lighter colored layers composed of clay with nannofossils. Discrete ash layers are found sporadically throughout the section. A thick (>2 m) dark gray sand interval occurs in the base of Core U1432C-6H and top of Core U1432C-7H. Many of the cores show some drilling disturbance due to suck in. The Brunhes/Matuyama boundary (0.781 Ma) occurs in Core U1432C-12H, which hones the age for the base of the hole based on biostratigraphy (1.0–0.6 Ma). This preliminary age model suggests very high sedimentation rates (>100 m/m.y.) at this site. Geochemistry results indicate that the sulfate/methane transition occurs at around 80–90 mbsf, which is also consistent with these high sedimentation rates.

Daily Science Report for 22 February 2014

LOCATION: Hole U1432C (18°21.0831′N, 116°23.4504′E; water depth 3829.1 m)

SCIENCE UPDATE: After the first coring attempt retrieved only water, we successfully spudded Hole U1432C at 0555 h, recovering 7.95 m of sediment. The next two cores (U1432C-2H and ‑3H) recovered only 6.25 m (66%) and 7.04 m (74%), respectively; the high heave conditions contributed to this. Recovery improved in Core U1432C-4H (101%), indicating that we had penetrated deeply enough for heave to have less influence. Cores U1432C-1H to ‑12H (0–109.93 mbsf) were recovered by late afternoon, at which point we decided to abandon the hole because heave conditions had improved enough to return to casing operations in Hole U1432B. Overall, Hole U1432C recovered 88.74 m of sediment (81% recovery).

We took temperature measurements on Cores U1432C-5H, ‑7H, ‑9H, and ‑11H, which indicate a temperature gradient of approximately 89°C/km, much higher than Hole U1431D (~15°C/km), but similar to that of nearby Ocean Drilling Program Hole 1148A (83°C/km). Biostratigraphy indicates that the entire sequence cored at Hole U1432C is less than ~1 Ma. Radiolarians are particularly abundant in the top of the hole. Cores U1432C-1H and ‑2H (0–14.15 mbsf) were split and described. The core consists of dark greenish gray clay and clay with silt. Graded, sharp-based clay with silt intervals are interpreted as turbidites. The very top of Core U1432C-1H consists of reddish brown silty clay that contains foraminifers and radiolarians.

Daily Science Report for 21 February 2014

LOCATION: Hole U1432C (18°21.0831′N, 116°23.4504′E; water depth 3829.1 m)

SCIENCE UPDATE: We began drilling the 22 inch hole for the 16 inch casing string at Hole U1432B; however, bad weather and high heave conditions caused us to suspend these operations after reaching 160 mbsf. While pulling out of the hole, we discussed options and ultimately decided to offset the ship and core an APC/XCB hole while we wait for heave conditions to improve. With the prospect of coring section that we didn’t plan to recover at this site, the scientists finalized sample requests during the day. We also held three science talks, learning about scientific exploration of the deep oceans from Co-Chief Scientist Jian Lin, study of the deep biosphere by microbiologist Rick Colwell, and initial results from a recent oceanographic survey to a seamount in the South China Sea by Xin Su (paleontologist).

Daily Science Report for 20 February 2014

LOCATION: Hole U1432B (18°21.1062′N, 116°23.4512′E [final]; water depth 3829 m)

SCIENCE UPDATE: After the casing running tool was tripped back to the rig floor, the drillers made up the bottom-hole assembly (BHA) with a 22 inch underreamer and an 18.5 inch bit to drill the hole for the 16 inch casing. The BHA was tripped back to the seafloor and successfully reentered Hole U1432B at 2005 h. After retrieving the undersea video camera used for the reentry, drilling of the 22 inch hole to 250 mbsf commenced.

The scientists submitted site summaries and reports for Site U1431, and also continued revising methods sections for the expedition. We held three science talks during the day, learning more about magnetic anomalies in the South China Sea (SCS) from Anne Briais (physical properties specialist), how to reconstruct the development of rivers in Southeast Asia based on stratigraphic records from Peter Clift (sedimentologist), and insights into rifting of the Southwest Sub-basin of the SCS based on 3D modeling experiments from Weiwei Ding (structural geologist).

Daily Science Report for 19 February 2014

LOCATION: Hole U1432B (18°21.1066′N, 116°23.4511′E; water depth 3829 m)

SCIENCE UPDATE: Hole U1432B was spudded and the 20 inch casing successfully jetted in to 57.1 mbsf. We then deployed the camera system to observe the casing running tool disengage from the reentry and casing system. After retrieving the camera system, we began to trip out of the hole. Our next step is to drill the next section of hole for the 16 inch casing.

The scientists continued to work on the Site U1431 reports and started taking samples for post-expedition research from the remainder of the sedimentary section at Hole U1431E. At the crossover science meeting, we discussed a schedule of events for the next week while casing is being run. Scientists signed up to give 15-minute science talks during the crossover meetings. We also scheduled several ship tours for the scientists that will be led by the Operations Superintendent.

Daily Science Report for 18 February 2014

LOCATION: Hole U1432B (18°21.1066′N, 116°23.4511′E; water depth 3829 m)

SCIENCE UPDATE: After the pipe was tripped back to the surface following the jet-in test, the drillers began preparing the 20 inch casing string and reentry cone. Once the reentry cone was moved into position over the moonpool, the casing hanger and 20 inch casing string were lowered through it and latched in. The entire assembly was picked up with the casing running tool, lowered through the moonpool, and started the trip down to the seafloor.

The lab groups continued to write up results for Site U1431, with two groups submitting a first draft by the end of the day. During the daily crossover meeting, the Staff Scientist gave an overview of the operational plans for deploying the casing and reentry structure in Hole U1432B. The technical staff laid out the remainder of the sedimentary sections from Hole U1431E for the scientists to place stickers for post-expedition research sampling.

Daily Science Report for 17 February 2014

LOCATION: Hole U1432A (18°21.1051′N, 116°23.4504′E, water depth 3829 m)

SCIENCE UPDATE: As our Site U1432 objectives require deep penetration to ~1930 mbsf, we plan to install a reentry and casing system to enhance our ability to core and log deeply. Our first task was to conduct a jet-in test to determine the length of 20 inch casing that will be installed with a seafloor reentry cone. After arriving on site, the drill crew prepared the jet-in assembly with an 18.5 inch bit and then began lowering to the seafloor. As the bit neared the seafloor, the vibration-isolated television (VIT) camera was deployed to observe the bit tag the seafloor, which established a water depth for this hole of 3829 m. The camera system was retrieved and the jet-in test conducted to 62 mbsf. We then began tripping pipe back to the surface to begin preparations for installation of the 20 inch casing and reentry system.

In the labs, some additional work continues on the cores from Hole U1431E. The petrologists defined two lithologic units for the basalt recovered in the hole, yielding a total of eleven lithologic units (nine sedimentary and two igneous) for Site U1431. Additional biostratigraphic work on samples taken from the interflow clay unit recovered between basalts has produced moderately preserved radiolarians that indicate an age of 15–17.5 Ma for that interval. Scientists also continue to work on site reports for Site U1431. We held a scientific objectives meeting in preparation for coring and logging at Site U1432 (proposed site SCS-6A), which led to a good discussion about the nature of the basement rocks we expect to encounter.

Daily Science Report for 16 February 2014

LOCATION: Site U1432 (18°21.1051′N, 116°23.4504′E, water depth 3836 m)

SCIENCE UPDATE: After the pipe was tripped back to the surface and the drill floor secured at 0600 h, we began our transit to Site U1432 (proposed site SCS-6A), arriving shortly before midnight. The primary objective at this site is to core into basement to date the timing of initiation of seafloor spreading in the South China Sea.

In the labs, scientists continued running discrete samples from Hole U1431E for paleomagnetics, physical properties, and geochemical analyses. The scientists also continued writing site reports for Site U1431.

Daily Science Report for 15 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

SCIENCE UPDATE: We continued logging operations at Hole U1431E throughout the day. The first logging tool string, the modified triple combo, was unable to pass an obstruction at 463.7 mbsf. After logging the upper part of the hole with the triple combo, the FMS-sonic tool string was then made up and run in the hole down to 410 mbsf, where it also encountered an obstruction. Two passes were completed with the FMS-sonic tool string above 410 mbsf. Following the completion of logging operations, we began tripping pipe back to the surface. Although we were unable to log below ~464 mbsf, these logs provide valuable information since we did not core the upper part of Hole U1431E. The upper section was APC/XCB cored in the adjacent Hole U1431D.

We held a science meeting in the morning to share initial results from the sediment section (~600 to 900 mbsf) of Hole U1431E. The sedimentologists have defined a total of eight lithologic units for Site U1431. The biostratigraphers and paleomagnetists continue to converge on an age model for the site; results amongst the groups are generally in good agreement, with only a few intervals where refinement is needed. During the day, the petrologists and structural geologists completed the remainder of the macroscopic descriptions for Hole U1431E. They continue to describe thin sections as the samples become available. ICP-AES measurements will be completed on the remainder of the sediment and rock samples in the next couple of days; afterward, the ICP-AES will be switched over for measurement of the rhizon and IW pore water samples. Initial results indicate that we have cored two geochemically distinct basalts.

Daily Science Report for 14 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

SCIENCE UPDATE: We completed coring operations at Hole U1431E with the retrieval of Core U1431E-50R (1001.10–1007.89 mbsf) to the rigfloor at 0910 h. The core consists of basalt with 82% recovery. We then began preparations for logging operations, which included dropping the bit in the bottom of the hole and then pulling up to 650 mbsf to displace the upper portion of the hole with heavy (11.4 ppg) mud in an attempt to stabilize the sandy intervals from 450–600 mbsf. At the end of the day we were running in the hole with the first tool string, a modified triple combo composed of downhole tools that measure borehole fluid temperature, natural gamma radiation, porosity, density, electrical resistivity, and magnetic susceptibility.

In the labs, the remainder of the cores (U1431E-45R to ‑50R) were split and described by the igneous petrologists and structural geologists. The basalts are massive and vary from relatively fresh to altered. Sampling for shipboard analyses will continue for one more day, with final results expected in 3 to 4 days. The biostratigraphers and paleomagnetists continue to collect data to generate a final chronostratigraphic framework for the site. ICP-AES measurements continue, with the first results from the upper part of the basalts expected tomorrow.

Daily Science Report for 13 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

Coring continued throughout the day, with Cores U1431E-46R through ‑49R (972.0–996.44 mbsf) cut and recovered. After Core U1431E-47R was retrieved, we spent some time cleaning the hole, including a wiper trip up to ~863 mbsf to allow loose material to fall in. We found approximately 20 m of fill in the hole while running back in, at which point we dropped a core barrel to collect this loose material while working the pipe back to bottom. This core (U1431E-48G) is a “ghost” core and came back with less than a meter of rubbly basalt that had fallen into the hole from above. After recovering the ghost core, RCB coring continued. Average recovery for the three RCB cores recovered during the day was 45% (this average does not include the material retrieved by the ghost core).

Cores U1431E-39R to ‑44R were split and described by the petrologists and structural geologists. Initial observations indicate that we have cored through approximately 6 or 7 flow units, with unit boundaries demarcated by very fine-grained or glassy textures. The basalts are very homogeneous and show varying degrees of alteration. Some appear to be quite fresh, which will be important for post-expedition geochemical studies. The structural geologists have noted veins and fractures, with most of the fractures appearing to have formed during cooling of the flows. Core U1431E-45R was split and then described by the sedimentologists. The sediments in this core consist of yellowish brown claystone with variable amounts of ash and dark gray basalt clasts. Physical properties, paleomagnetic, and geochemical measurements on discrete samples continue. Initial physical properties measurements on the whole round cores show a distinct change in natural gamma radiation and density measurements between the sedimentary rocks and basalts in Hole U1431E.

Daily Science Report for 12 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

Cores U1431E-41R through ‑45R (923.50–966.36 mbsf) were cut and recovered during the day. Recovery varied from 6% to 95% over the five cores, with an average recovery of 48%. Cores U1431E-41R through ‑44R consist of both altered and relatively fresh basalts; however, Core U1431E-45R recovered more than 3.5 m of sediment and only two small intervals of basalt. The two cores recovered below that consist entirely of basalt. Initial examination of sediment in Section U1431E-45R-CC found very rare calcareous nannofossils characteristic of the Miocene.

Cores U1431E-32R to ‑36R were split and described by the sedimentologists. Cores U1431E-32R through ‑35R consist of dark greenish gray to greenish gray sandstone, siltstone, and claystone, with finer lithologies dominating. The sandstones are fine- to medium-grained, parallel laminated, and generally fining upward. The claystones are heavily bioturbated, with abundant Chondrites burrows. Core U1431E-36R consists of various colored claystone, including shades of gray, green, and brown. The bottom 30 cm of the core consists of basalt. Paleomagnetics results on these cores indicate an age of <12.8 Ma at the base of the sediment section, consistent with biostratigraphic results.

Cores U1431E-37R and ‑38R were split and the petrologists and structural geologists have begun detailed description of the basalts in these cores. The initial characterization indicates that we have cored through basalt flows that consist of massive basalts exhibiting varying degrees of alteration. Examination of thin sections indicates that some intervals contain unaltered olivine.

Daily Science Report for 11 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

SCIENCE UPDATE: Coring continued in Hole U1431E, with Cores U1431E-35R through ‑40R (874.90–917.91 mbsf) cut and recovered during the day. A distinct change to very fine-grained sediments occurs in Core U1431E-36R, with pieces of basalt recovered in the core catcher. Cores collected below U1431E-36R contain basalt. Two of the basalt cores were split and sampled for thin section and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analyses to fast track the results, which should distinguish between the nearby seamounts (ocean island type) or the relict spreading center (mid-ocean ridge type) as the source of these basalts.

Cores U1431-25R to ‑31R were split and described. These cores consist of massive volcaniclastic breccias and sandstone, siltstones, and claystones. The breccias are typically black to greenish black and clast-supported, with clasts composed of several different types of basalt and pumice. Sandstones are typically dark gray to dark greenish gray, fining upward, and often with parallel bedding and cross bedding. The claystones are often bioturbated, although some intervals consist of finely laminated alternating claystones and siltstones. These lithologies continue to yield good paleomagnetics records, which, when combined with biostratigraphic results, should yield a robust chronostratigraphic framework for the hole. Results from physical properties measurements on discrete samples from these lithologies show highly variable P-wave velocities through this section.

Daily Science Report for 10 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

SCIENCE UPDATE: Cores U1431E-24R through ‑34R (768.20–873.81 mbsf) were cut and retrieved. Recovery over much of this interval is excellent (75%), with three full core barrels and another five with recovery >80%. Lithology based on initial examination of the core-catcher and whole round core pieces is similar to that from previous cores in this hole: volcaniclastics interbedded with mudstones. Calcareous microfossils are rare and poorly preserved in these lithologies, although targeted sampling within the working half sections after the core is split has yielded better assemblages than the core-catcher samples. The rocks at the base of the cored interval are younger than 12.8 Ma based on calcareous nannofossil biostratigraphy.

Cores U1431E-14R through ‑24R were split and described. The cores are a mixture of volcaniclastic breccias and sandstones, together with claystone, siltstone, and sandstone. The volcaniclastic deposits are usually massive and ungraded, with clasts composed of various types of basalt, pumice, and mudstone. The clay- and siltstones show a variety of different features. Some are parallel or cross-laminated, whereas others are highly bioturbated. Burrows are common throughout most cores. Some of the coarser-grained units are cross-bedded. These RCB cores yield much better paleomagnetics results than the XCB cores from Hole U1431D. A well-defined reversal near the base of Core U1431E-13R is dated to ~10 Ma and is consistent with the biostratigraphy for that interval. Preparation of samples for thin section and geochemical analyses is ongoing.

Daily Science Report for 9 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

SCIENCE UPDATE: Coring at Hole U1431E continued throughout the day, with Cores U1431E-14R through ‑23R (671.20–762.4 mbsf) cut and recovered. Recovery over this interval was variable, ranging from 18% to 103%, with an overall average recovery of 62%. Foraminifera through this section are very rare and poorly preserved. Calcareous nannofossils are also poorly preserved, but somewhat more abundant, and indicate an age of early Late Miocene for the base of the interval cored.

Cores U1431E-7R through ‑13R were split and described by the sedimentologists and igneous petrologists, whereas structural geology descriptions are ongoing. These cores are dominated by dark greenish gray to greenish black volcanic breccia and volcanic sandstone that are usually massive, ungraded, and poorly sorted. A few intervals of volcanic sand show parallel and cross laminations. Clasts are composed of several different types of basalt, as well as claystones and siltstones. Most clasts are granule size or smaller, but pebble- and boulder-sized clasts occur in some sections. Core U1431E-12R also contains a heavily bioturbated greenish gray calcareous siltstone. We have begun sampling for shipboard analyses (paleomagnetics, thin sections, and geochemistry) after the noon crossover meeting so that all core describers, geochemists, and paleomagnetists can discuss where to take these samples.

Daily Science Report for 8 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

SCIENCE UPDATE: The spot core from 507.0–516.7 mbsf in Hole U1431E failed to recover any sediment, so we continued to wash down to 575.0 mbsf, where continuous coring of Hole U1431E commenced. Cores U1431E-4R through ‑13R (575.0–669.99 mbsf) were collected by the end of the day. Cores U1431E-4R to ‑6R also recovered no sediment, much like the correlative interval in Hole U1431D. From a depth of 603.3 mbsf, Cores U1431E-7R through ‑13R returned very hard, strongly lithified volcaniclastics, with an average core recovery of 58%. Microfossils are very sparse and poorly preserved in these sediments; however, initial analysis indicates an age of Late Miocene, younger than approximately 8.3 Ma. Although none of the cores were split during the day, characterization of the whole-round pieces indicates that the cores are primarily dark greenish gray volcanic breccia and volcanic sands.

Daily Science Report for 7 February 2014

LOCATION: Hole U1431E (15°22.5380′N, 116°59.9903′E, water depth 4240 m)

SCIENCE UPDATE: Hole U1431E was spudded at 0650 h and washed down to 507 mbsf. At midnight we were just preparing to take a spot core from 507–516.7 mbsf. Throughout the day, the remainder of the cores from Hole U1431D (U1431D-44X to ‑67X) were split and described. Cores U1431D-44X through ‑48X are similar in lithology to the cores described yesterday. The dominant lithologies are dark greenish gray clay and light greenish gray nannofossil ooze. The presence of coarser sediment (silt and fine sand) increases downhole. Cores U1431D-49X to ‑51X failed to recover any sediment. Below this interval, core recovery is generally very poor to the bottom of the hole. Lithologies are varied throughout and consist of clay, mudstone, and claystone in varying shades of gray to dark greenish gray, interbedded with silts, sands, and sandstones. Volcanic ash is present in some parts of this interval. Drilling disturbance is moderate to heavy throughout.

We held our first scientific results meeting for Site U1431, with each lab group presenting preliminary results for Holes U1431A through U1431D. In addition to continuing analyses on Hole U1431D, the scientists have started to write-up their results for these holes. The core describers defined lithologic units after the remainder of the cores were split and described. The biostratigraphers continue to review some samples and the paleomagnetists continue to measure discrete samples to better refine the age model. Moisture and density samples have been analyzed down to ~250 mbsf. Grain density shows little variation over this interval, whereas porosity decreases with depth as expected. Initial carbon analysis indicates that there is very little total carbon in the top ~100 mbsf.

Daily Science Report for 6 February 2014

LOCATION: Hole U1431D (15°22.5379′N, 117°00.0022′E, water depth 4241 m)

SCIENCE UPDATE: After the core barrel failed while collecting Core U1431D-67X at 614 mbsf, we abandoned the hole and prepared to offset to Hole U1431E. After discussion with the Co-Chiefs, we will take one to three spot cores starting at ~505 mbsf in Hole U1431E in an attempt to recover some material over an interval with very poor recovery in Hole U1431D. We will then begin continuous coring at ~575 mbsf.

Cores U1431D-34X to U1431D-43X were split and described. The dominant lithologies through this interval are dark greenish gray clay and greenish gray nannofossil ooze. The clays are usually heavily bioturbated, whereas the nannofossil oozes show graded bedding and increased bioturbation toward the top. These sediments are heavily biscuited due to XCB coring disturbance. Sandy silt and clayey sand also occur sporadically throughout the interval and also tend to be heavily affected by drilling disturbance. All physical properties measurements on the Hole U1431D whole-round sections have been completed. We have begun preparing sediment samples from this hole for inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis.

Daily Science Report for 5 February 2014

LOCATION: Hole U1431D (15°22.5379′N, 117°00.0022′E, water depth 4241 m)

SCIENCE UPDATE: Cores U1431D-55X to ‑67X (497.90–614.40 mbsf) were cut and recovered using the XCB coring system. Upon retrieval of Core U1431D-67X, we discovered that the XCB core barrel had failed, leaving the cutting shoe and other steel core barrel parts in the hole. As a result, we abandoned Hole U1431D and will offset to spud Hole U1431E, where we will wash down to ~600 mbsf using the RCB coring system and then continue coring to our basement objective. Core recovery was very poor over the interval cored on Wednesday, with six empty core barrels and several others with <5% recovery. Overall, average recovery for the 13 cores collected was 10%. Sediments recovered in the core catchers primarily consist of volcanic sands. Calcareous microfossils are generally poorly preserved and indicate an age of Late Miocene for the interval cored.

Cores U1431D-22X to ‑33X were split and described. The dominant lithologies through this interval are dark greenish gray clay and nannofossil-rich clay, with occasional alternating dark and light bands. Silty intervals occur sporadically, but are thinner and less frequent than above. Graded carbonate-rich units occur in the bottom few cores. Bioturbation is slight to heavy throughout, with heavily burrowed intervals in some sections. Sand and gravel sized pyrite concretions are present in Core U1431D-25X. Demagnetization of the cores has not effectively removed the drill string overprint through this interval, yielding poor paleomagnetics results from the archive section halves; however, measurements on the discrete samples are promising. Physical properties and geochemistry measurements are ongoing.

Daily Science Report for 4 February 2014

LOCATION: Hole U1431D (15°22.5379′N, 117°00.0022′E, water depth 4241 m)

SCIENCE UPDATE: Cores U1431D-44X to ‑54X (388.50–489.39 mbsf) were cut and recovered with the XCB coring system. Core recovery has been much poorer through this interval than in the horizons above, with three empty core barrels (U1431D-49X to ‑51X) and only 12% recovery in two cores near the base of the cored interval (U1431D-52X and ‑54X). Overall, total recovery for the 11 cores averaged 43%. Analysis of the lithology in the core catchers indicates that this interval is very sandy, which may account for the poor recovery. Biostratigraphic analysis indicates that this interval is Late Miocene in age.

Cores U1431D-14H through ‑21X were split and described. The dominant lithology throughout this interval is dark greenish gray clay, with occasional interbeds of gray nannofossil-rich clay. Coarser grained silty to silty clay layers typically 2–5 cm thick occur sporadically and are interpreted as turbidite deposits. Two foraminifer-rich sands and a volcanic ash layer occur in the upper part of the section. Bioturbation is generally slight to moderate in the clays. Analysis of sediment samples for total carbon has begun for the upper part of the hole.

Daily Science Report for 3 February 2014

LOCATION: Hole U1431D (15°22.5379′N, 117°00.0022′E, water depth 4241 m)

SCIENCE UPDATE: Cores U1431D-28X through ‑43X (245.70–392.35 mbsf) were collected with the XCB coring system. Recovery was excellent (100%) for some of the cores (U1431D-28X, ‑29X, ‑31X, ‑32X, ‑34X, ‑39X, and ‑43X); however, recovery was significantly lower for the others. Overall, the average recovery for the 16 cores collected was 80%. Biostratigraphy indicates that these cores are latest Miocene to earliest Pliocene in age.

Cores U1431D-6H through ‑13H were split and described. The predominant lithology remains dark gray to greenish gray silty clay to clay. Fining upwards turbidite deposits are common in Cores U1431D-6H through ‑9H and occur occasionally below. Volcanic ash occurs sporadically throughout this interval. Cores U1431D-7H and ‑8H contain decimeter- to meter-thick fine sand intervals. The soupy nature of portions of these intervals suggests coring disturbance homogenized the deposits. Paleomagnetics results indicate that the Brunhes/Matuyama boundary (0.781 Ma) occurs in Core U1431D-7H, which is consistent with biostratigraphic results. Discrete physical properties measurements (moisture and density) for the upper part of the hole are now complete.

Daily Science Report for 2 February 2014

LOCATION: Hole U1431D (15°22.5379′N, 117°00.0022′E, water depth 4241 m)

SCIENCE UPDATE: Coring continued in Hole U1431D, with Cores U1431D-13H through ‑19H (107.7–168.9 mbsf) taken using the Advanced Piston Corer (APC) system with 100% recovery. At 168.9 mbsf, we switched to the Extended Core Barrel (XCB) system and collected Cores U1431D-20X through ‑27X (168.9–245.7 mbsf) by the end of the day. Recovery was excellent with the XCB system, averaging 101% for most of the interval, although Core U1431D-26X came back empty. Biostratigraphic analysis through Core U1431D-24X indicates an age of early Pliocene. Methane concentrations remain very low (<3 ppm) throughout the cored interval. Alkalinity measured on pore waters shows a decreasing trend downhole. Temperature measurements conducted on Cores U1431D-4H, ‑7H, ‑10H, and ‑13H, yielding an average geothermal gradient of ~14.5°C/km.

The Section Half Measurement Gantry (SHMG), which measures shear strength and compressional P-wave in the x- and z-direction, was down for a few hours in the afternoon, which slowed the flow of core through the labs. Initially we halted splitting of additional core, but after about one hour splitting resumed so that the core describers could continue descriptions on the archive halves. The working halves were wrapped and stored until the system was fixed by late afternoon. At that time, shipboard sampling resumed and Core U1431D-4H was on the sampling table at midnight.

Cores U1431D-2H through ‑5H were described and the sediment consists of dark gray silty clay with volcanic ash layers. Turbidites are common throughout, some with foraminiferal sands at the base. Much of the sediment is slightly to heavily bioturbated. Calcareous microfossils are abundant throughout; however, radiolarians are only found from the top of the hole through Core U1431D-4H.

Daily Science Report for 1 February 2014

LOCATION: Hole U1431D (15°22.5379′N, 117°00.0022′E, water depth 4241 m)

SCIENCE UPDATE: The first core arrived on deck at 0105 h, marking the start of coring operations for our expedition. Hole U1431A consists of three cores (U1431A-1H through ‑3H) from 0–28.4 m below seafloor (mbsf), with 28.39 m of sediment recovered (100%). This hole was cored primarily for pore-water sampling (rhizones and interstitial water whole rounds), as well as whole rounds for optically stimulated luminescence (OSL) dating. Hole U1431B consisted of two cores (U1431B-1H to ‑2H) collected from 0–17.0 mbsf, with 17.16 m of sediment recovered (101%). This hole was primarily cored for whole round microbiology sampling. The first core of Hole U1431C came back very disturbed with a split core liner. Although we took a second core, we ultimately decided to abandon Hole U1431C. This hole penetrated to 14.2 mbsf, recovering 14.45 m of sediment (102%). After offsetting the ship, Hole U1431D was spudded. The first core of this hole produced a clean mudline and coring continued through Core U1431D-12H (0–107.7 mbsf) by the end of the day.

Sediments from Holes U1431A, U1431B, U1431C, and the top of U1431D primarily consist of dark gray silty clay with volcanic ash layers. Fining upward sequences indicate the presence of turbidite deposits ranging in thickness from 15 to 30 cm, some containing foraminifer sands. Foraminifera, calcareous nannofossil, and radiolarian biostratigraphy indicate that all sediment collected at Holes U1431A, U1431B, and U1431C is late Pleistocene in age. Samples through Core U1431D-10H indicate a progression from late to middle Pleistocene ages, although reworking is common, especially in the turbidites. Radiolarians are absent below the uppermost two cores. Methane gas measurements show very low values (2–5 ppm). Other geochemistry, paleomagnetic, and physical properties measurements are ongoing.