R/V Yokosuka “Cruise Report” YK19-07S

Origin of Philippine Sea basins -Tectonic setting leading to subduction initiation of

Izu-Bonin-Mariana arc-

Kita-Daito Basin and Oki-Daito escarpment

May 24, 2019-June 3,2019

Joint Usage/Research Center for Atmosphere and Ocean Science (JURCAOS) Japan Agency for Marine-Earth Science and

Technology (JAMSTEC)

TABLE OF CONTENTS:

List of cruise personnel ......................................................................... .... 1 Acknowledgements ............................................................................... ..... 6 1. Cruise information .................................................................................. 7 2. Research proposal and Science party ........ ....................................... 8 3. Cruise Objectives...................................... .............................................. 8 4. Geological background ..................................... ..................................... 8 5. Operations and data processing information ..................................... . 11 6. Dive results ................................................................... .......................... 11 7. Geophysical Survey ................................................................................ 12 8. Shore-based studies ............................................................................... 12 9. Cruise log ................................................................................................. 14 10. Notice on using ...................................................................................... 16

List of cruise personnel

SCIENCE Dr. Osamu Ishizuka, Chief Scientist Geological Survey of Japan/AIST (also at Japan Agency for Marine-Earth Science and Technology)

Dr. Susumu Umino Kanazawa University

Dr. Rex N. TaylorUniversity of Southampton School of Ocean and Earth Science, NOC, Southampton, SO14 3ZH, UK

Dr. Izumi Sakamoto Tokai University

Dr. Hajime Shimoda Geological Survey of Japan/AIST

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Dr. Kenichiro Tani National Museum of Nature and Science

Ms. Yuka Yokoyama Tokai University

Mr. Sho Yatsuka Tokai University

Mr. Tomoaki WakayamaTokai University

Mr. Ryota Uchiyama Tokai University

Ms. Aimi Suzuki Tokai University

Mr. Ping Tian Yu Kanazawa University

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Ms. Kana Narita National Museum of Nature and Science

Ms. Chinatsu Ogawa National Museum of Nature and Science

Mr. Ryo KimuraNippon Marine Enterprises, Ltd.

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SHIP CREW

Mr. Yoshiyuki Nakamura, Captain Mr. Toshiyo Ohhara, Chief Officer Mr. Saito Takata, 2nd Officer Mr. Tomohiro Yukawa, 3rd Officer Mr. Keisuke Kusumi, Jr.3rd Offucer

Mr. Kazunori Noguchi, Chief Engineer Mr. Wataru Kurose, 1st Engineer Mr. Akira Hanawa, 2nd Engineer Mr. Kenichi Shirakata, Jr.2nd Engineer Mr. Shohei Miyazaki, 3rd Engineer

Mr. Shunsuke Fukagawa, Chief Radio Officer Mr. Ryuji Onikubo, 2nd Radio Officer Mr. Yohei Sugimoto, 3rd Radio Officer

Mr. Masanori Ohata, Boatswain Mr. Yoshiaki Matsuo Quarter Master Mr. Takuya Miyashita Quarter Master Mr. Shinya Ueno Quarter Master Mr. Yudai Yoshimi, Sailor Mr. Tomoki Asakuni, Sailor Mr. Daisuke Yamamoto, Sailor Mr. Taisei Matsuda, Sailor

Mr. Yuji Higashigawa, No1.Oiler Mr. Sota Misago, Oiler Mr. Daiki Sato, Oiler Mr. Shota Shimohata, Oiler Mr. Motohiro Kawano, Assistant Oiler Mr. Sota Itagaki, Assistant Oiler

Mr.Yukihide Chikuba, Chief Steward Mr. Kanjuro Murakami, Steward Mr. Takahiro Abe, Steward Ms. Yuki Shirasaki, Steward Mr. Ryumei Ito, Steward

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SHINKAI OPERATION TEAM Mr. Toshiaki Sakurai, Submersible Operation Manager Mr. Kazuhiro Chiba, Deputy Submersible Operation Manager Mr. Keita Matsumoto, Deputy Submersible Tec. Manager Mr. Mitsuhiro Ueki, 1st Submersible Staff Mr. Hirofumi Ueki Matsumoto, 2nd Submersible Staff Mr. Takuma Onishi, 2nd Submersible Staff Mr. Keigo Suzuki, 2nd Submersible Staff Mr. Ryo Saigo, 2nd Submersible Staff Mr. Yoshikazu Kuramoto, 2nd Submersible Staff Ms. Satsuki Iijima, 2nd Submersible Staff Mr. Naoto Minamino, 2nd Submersible Staff Mr. Mothohiro Matsusaka, 3rd Submersible Staff

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ACKNOWLEDGEMENTS

We are grateful to Captain Yoshiyuki Nakamura and the excellent crew of the Yokosuka, for their outstanding efforts to make this scientific program successful. The Shinkai 6500 operation team manager Toshiaki Sakurai and the Shinkai 6500 team for their outstanding efforts to make this scientific program successful. We also thank JAMSTEC for their support of this project.

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1. Cruise Information ● Cruise ID YK19-07S ● Name of vessel R/V Yokosuka ○ Title of project: Origin of Philippine Sea basins-Tectonic setting leading to subduction

initiation of Izu-Bonin-Mariana arc-● Title of cruise: Origin of Philippine Sea basins -Tectonic setting leading to subduction

initiation of Izu-Bonin-Mariana arc-● Chief Scientist [Affiliation] Osamu Ishizuka (Geological Survey of Japan) ● Cruise period May 24, 2019- June 3, 2019 ● Ports of departure / call / arrival: JAMSTEC to JAMSTEC ● Research area Kita Daito Basin, West Philippine Basin ● Research map

Fig.1 Ship track and dive sites of YK19-07S cruise.

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2. Research Proposal and Science Party

Origin of Philippine Sea basins -Tectonic setting leading to subduction initiation of Izu-Bonin-Mariana arc-

Osamu Ishizuka (GSJ), Kenichiro Tani (NMNS), Gen Shimoda (GSJ), Susumu Umino (Kanazawa Univ.), Izumi Sakamoto, Yuka Yokoyama, Syo Yatsuka (Tokai Univ.), Rex Taylor (Univ. of Southampton), (Tokai Univ.), Yumiko Harigane, Taichi Sato, Chris Conway (GSJ), Yasuhiko Ohara (HODJ) Americus Perez (Kanazawa Univ.) (not in order)

3. Cruise objectives

Robust tectonic reconstruction of the evolving Philippine Sea Plate for the period immediately before and after subduction initiation at ~52 Ma to form the Izu-Bonin-Mariana (IBM) arc is prerequisite to understand cause of subduction initiation (SI) and test competing hypotheses for SI such as spontaneous or induced nucleation. Understanding of nature and origin of overriding and subducting plates is especially important because plate density is a key parameter controlling SI based on numerical modeling (e.g., Leng and Gurnis 2015). There is increasing evidence that multiple geological events related to changing stress fields took place in and around Philippine Sea plate about the time of SI ~52 Ma (Ishizuka et al., 2011). For our understanding of the early IBM arc system to increase, it is important to understand the pattern and tempo of these geological events, particularly the duration and extent of seafloor spreading in the proto arc associated with SI, and its temporal relationship with spreading in the West Philippine Basin (WPB).

The YK19-07S cruise aimed to investigate origin and age of formation of ocean basins in and around the Daito Ridge group. Especially ocean basins which potentially existed in the period of SI to form the IBM arc were the major targets of this cruise, because ocean crust of these basins might be part of overriding plate when subduction of Pacific plate initiated to form IBM arc. Since gravitational instability between the neighboring plates is supposed to be a critical factor for subduction initiation, it is important to understand characteristics (age, origin, crustal structure) of overriding plate to test hypotheses of subduction initiation. Recovery and characterization of igneous crust of these basins will provide crucial information about the possible basement of the IBM arc and critical constraints to evaluate models for subduction initiation along the Pacific margin.

4. Geological background 4.1. Daito Ridge group and Kyushu-Palau Ridge

The Daito Ridges region is a complex array of ridges and basins (Fig. 2). This comprises three remnant arcs: the Amami Plateau, the Daito and Oki-Daito Ridges, and two ocean basins among these ridges (the Kita-Daito and Minami-Daito Basins). The Oki-Daito Ridge (Fig. 2), is WNW–ESE trending ridge characterised by crust ranging

from 20 to 23 km in thickness, based on its seismic velocity structure (Nishizawa et al., 2014), and is supposed to be another Mesozoic remnant arc (Tani et al., 2012). Another important characteristics of the Oki-Daito Ridge is occurrence of extensive escarpment and lineament in NW-SE direction. Seismic experiments show that crustal thickness and seismic velocity

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structure significant change at the NW-SE escarpment along the Oki-Daito Ridge. Oki-Daito Escarpment (ODE) is a major

tectonic lineament in the northern WPB. The trend of abyssal hills of the WPB is discontinuous across this escarpment. WNW-ESE, while trend is close to NNW-SSE to N-S. This implies that the basin north of ODE has different spreading history from other part of the WPB. Hilde and Lee (1984) interpreted magnetic anomaly data of the basin, and insisted that this part of the basin could correspond to the oldest part of the WPB, but Deschamps and Lallemand (2002) considered that interpretation of magnetic anomaly of this part the basin is highly questionable. No reliable age constraints have been obtained from this part of the basin.

4.2. IODP Exp. 351 in the Amami Sankaku Basin (ASB)

IODP Exp. 351 was conducted to recover detailed geological information when subduction initiated as well as basement of Izu-Bonin-Mariana arc (Fig. 2). Drill site of Exp. 351 is located in Amami Sankaku Basin (ASB) which corresponds to the reararc area of Kyushu-Palau Ridge, i.e., reararc of ancient Izu-Bonin-Mariana arc. The Kyushu-Palau Ridge is a remnant arc separated from the IBM arc by backarc spreading of Shikoku and Parece-Vela Basins initiated at c. 25 Ma. West of the drill site is Mesozoic arc terrane of Daito Ridge group. Igneous basement of this drill site could correspond to basement of the Izu-Bonin-Mariana arc.

Fig.2 Map of Philippine Sea Plate with major tectonic features. Survey areas of YK19-07S cruise are shown with red boxes.

Igneous basement of this drill site consists of basaltic lava flows. The ASB basalts and the FAB from the IBM forearc share geochemical characteristics. The ASB basalts have lower Ti/V compared to MORB and most of the younger Philippine Sea ocean crust. This is one of the important geochemical characteristics of FAB, possibly due to melting at higher oxygen fugacity condition than MORB. Primitive mantle normalised spidergrams indicate that basement basalts show significant depletion in LREE and highly-incompatible elements. This characteristics is remarkably similar to that of forearc basalt from IBM arc. Age of the basement basalt was determined by ArAr dating (Ishizuka et al., 2018). Several samples from different level of the basement gave well-defined and consistent ages of Middle Eocene (48.7 Ma). This age of basaltic crust overlaps with the age range of forearc basalt (c. 52-48 Ma) of the IBM arc, i.e., period of seafloor spreading associated with subduction initiation. Based on this age constraints and geochemical similarity of the basement basalts to forearc

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basalts, we proposed tectonic model for the period of subduction initiation of the IBM arc. One of the key feature of this model is, based on the possible wide distribution of “forearc basalt” type magmatism, the area affected by seafloor spreading associated with subduction initiation is supposed to be wider than previously expected, which means spanning from forearc to reararc area of the future IBM arc. In this scenario, most of the IBM arc volcanoes formed on ocean crust which formed at subduction initiation. It is now clear that Mesozoic terrane is supposed to have been the main component of overriding plate, and then rifted prior to the onset of spreading at subduction initiation. In fact, Mesozoic MORB-like basalts and granitic rocks were recovered from the Bonin forearc, and this could correspond to rifted fragments of the Daito Ridges. This means that the overriding plate is not entirely ocean crust as has previously been assumed. Volcanoes of the IBM arc have been established on oceanic crust produced following the onset of subduction, but subduction began between juxtaposed oceanic crust (Pacific Plate) and remnant arc terranes (Daito Ridges). Numerical models for subduction initiation predict that the density contrast of juxtaposing plates is critical in triggering the sinking of the slab through gravitational instability. Remnant arcs in the Daito Ridges have less dense and thicker crust relative to normal oceanic igneous crust, i.e., they are more buoyant. Assuming the downgoing plate was the Pacific Plate, a tectonic setting wherein a plate composed of buoyant Mesozoic remnant arcs faced an oceanic plate is more favourable for subduction initiation than the situation where both plates consist of oceanic crust. This model needs to be tested by detailed reconstruction of Philippine Sea plate at 50 Ma.

4.3 Kita-Daito Basin and Oki-Daito Escarpment -Outcome of MR17-02 and KS-17-15 cruise-

Recent cruises in the Philippine Sea basins recovered basalts from ocean crust along the major tectonic lines such as the Oki-Daito Escarpment (MR17-02 cruise). The dredge sampling recovered basalt clast including some fresh basalt glasses. Geochemical characteristics of the basalts show MORB-like character, which is consistent with the interpretation that the collected basalts are part of upper ocean crust. ArAr dating of fresh glassy basalt returned c. 58 Ma. This age is the oldest age reported from the West Philippine Basin, and older than the age of onset of subduction along the IBM arc at c. 52 Ma. This strongly implies that some part of the Philippine Sea basins such as the West Philippine Basin existed prior to the IBM arc, and these basins could be a part of overriding plate at subduction initiation. Kita-Daito Basin was investigated during the KS-17-15 cruise. The cruise conducted bathymetry survey, seafloor magnetics and dredge sampling. Due to the malfunction of the winch, only the slopes shallower than 5.4 km deep were dredged. Four dredge sites on the slope of bathymetric highs (seamounts and ridges) recovered samples mostly composed of volcanic rocks and trace amount of sedimentary rock and conglomerate. The volcanic rocks are basalt to andesite clasts. Geochemical characteristics of these volcanics strongly implies that these formed possibly in arc setting (i.e., with contribution of slab component) , and not

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part of the ocean crust. These volcanic rocks gave ages of around 44 Ma. This imply that these volcanic rocks formed after the period of subduction initiation of Izu-Bonin-Mariana arc. This further implies that the Kita-Daito Basin formed not by seafloor spreading, but rifting of preexisting crust.

5. Operations and data processing information

Shinkai 6500 dove with payloads that included 2 rock-sampling baskets, with 2 push cores and one scoop sampler. Data and samples from the dives were archived as customary. Brief sample descriptions

are included in Section 6. Samples distributed to the scientific party are listed in Appendix A. Standard data products were provided to the shipboard scientific party.

6. Dive results

Summaries of the results of each dive with representative pictures, track maps, and dive logs are included in the sections below. All dive locations are shown in Fig. 3, and Table 1.

Fig.3 Shinkai6500 dive locations of YK19-07S cruise.

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7. Geophysical Survey

Geophysical survey including bathymetry, magnetic and gravity anomalies have been conducted during the YK19-07S cruise in the West Philippine Basin and Kita-Daito Basin to better characterise the dive site and its geologic and tectonic context. Oki-Daito Escarpment in the northern West Philippine Basin was also investigated to understand seafloor fabric and magnetic lineation of this area, hence mode of spreading and age of this part of the basin.

7.1. Instruments and Measurements

Multi-narrow beam bathymetric data were obtained using a KONGSBERG EM122 (Swath width 120°; 288 beams with its width of 2°), which also provides a backscatter image that will be processed after the cruise. Sub bottom profile data were also obtained along with bathymetric data using EdgeTech 3300-HM. Sound velocity correction was applied using XBT data. Three XBTs were done in the research area.

For magnetic anomaly measurements, a towed proton magnetometer (PM-217, Kawasaki Geological Engineering & Tierra Technica) and onboard three-component magnetometers, a Tierra Technica SFG-1212 system equipped with R/V Yokosuka was used. Processing of magnetic anomaly data will be conducted by shore-based collaborator.

7.2. Data processing Bathymetric data obtained during this cruise have been merged with those from previous

cruises. 100m-mesh data has been produced for both Kita-Daito Basin and Oki-Daito Escarpment areas (Fig. 3).

8. Shore-based studies

A comprehensive work plan for the rock samples was developed by the shipboard scientific party. This work will include major element analyses, trace element analyses, geochronology studies, mineral analyses, petrographic characterization, and stable and radiogenic isotope characterization. The work will be completed at the Geological Survey of Japan/AIST, National museum of nature and science, Kanazawa University, Tokai University, and University of Southampton. Analytical responsibilities include:

Volcanic rocks: Petrological, geochemical and geochronological study on volcanic rocks will be conducted

to reveal age, magmatic processes and geochemical characteristics of magma sources. . •Whole rock chemical composition (XRF, ICP-MS): GSJ •Mineral chemistry: GSJ, Kanazawa •Ar/Ar dating: GSJ •Zircon U-Pb dating: National Museum of Nature and Science •Whole rock radiogenic isotopes (Sr, Nd, Pb, Hf): GSJ, Southampton • Radiogenic isotopic composition of minerals: Southampton •Melt inclusion studies, if applicable: Kanazawa, GSJ •Description of volcanic textures for marginal part of subaqueous volcanic rocks: Tokai

University •Clay-minerals and rock alteration process: Tokai University.

Volcaniclastic rocks •SHRIMP zircon U-Pb dating: National Museum of Nature and Science •LA-ICP-MS zircon trace element analyses: National Museum of Nature and Science

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•LA-ICP-MS analyses on other minerals and glass: GSJ, Kanazawa •XRF and EPMA analysis on relatively fresh clast and glass will be conducted at GSJ.

Sedimentary rocks •Description of sediments and sedimentary rocks: Tokai University •SHRIMP zircon U-Pb dating: National Museum of Nature and Science •LA-ICP-MS zircon trace element analyses: National Museum of Nature and Science •Melt inclusion study of heavy minerals: Kanazawa

Mn-nodules •Paleontological study of core of Mn-oxides

Geophysical data •Bathymetric and magnetic data will be merged with existing data and synthesized at GSJ

and Tokai University.

Other shore-based studies include: •Volcanic and geologic synthesis will be done at GSJ, National Museum of Nature and

Science, Kanazawa University and Tokai University.

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9. YK19-07S Cruise Log Date & Time Note Position/Weather/Wind/Sea condition

2019/05/24 Fri. 8:00 9:00 9:40

16:40

Scientists onboard a vessl Sail out, proceeding to research area from YOKOSUKA JPP Briefing about ship's life and safety Konpira ceremony

2019/05/24　12:00(JST) SAGAMI WAN 34-55.0N, 139-24.0E Fine but Cloudy ESE-2 (Light breeze) 2 (Sea Smooth) 2 (Low Swell Slong) Visibly: 8'

2019/05/25 Sat. 9:00

11:00 13:00 14:00 17:45

Scientist and "SHINKAI 6500"-Team meeting "SHINKAI 6500" Tour Ship Tour "SHINKAI 6500" Tour Scientist meeting

2019/05/25　12:00(JST) South ward off MUROTO 32-30.0N, 134-30.0E Fine but Cloudy WSW-2 (Light breeze) 2 (Sea Smooth) 2 (Low Swell Slong) Visibly: 8'

2019/05/26 Sun. 9:00

15:00 15:15 15:17 15:29 15:38

16:05~16:51 16:53~17:15

17:45 18:22

Briefing about "SHINKAI 6500"-Team operation Meeteing for "SHINKAI 6500" Dive #1545 Arrived at research area (KITA-DAITO Basin) Released XBT (27-50.4N 130-38.1E) Launched towing proton magnetometer Com'ced towing proton magnetometer Carried out MBES mapping survey Carried out eight figure running Scientist meeting Com'ced MBES mapping & Geomagnetic survey

2019/05/26　12:00(JST) East ward off AMAMI-OOSHIMA 28-21.0N, 131-06.0E Fine but Cloudy SE-4 (Moderate breeze) 3 (Sea Slight) 1 (Low Swell Short) Visibly: 8'

2019/05/27 Mon. 4:23 6:51 6:58 8:45 8:51 8:59

10:00 11:49 15:05 17:01 17:21 17:28 18:18 18:27

19:26~19:56 19:45 21:34

"SHINKAI 6500" Dive #1545 Finished MBES mapping & Geomagnetic survey Finished towing proton magnetometer Recovered towing proton magnetometer Hoisted up "SHINKAI 6500" Launched "SHINKAI 6500" "SHINKAI 6500" dove and started operation #1545 Meeteing for "SHINKAI 6500" Dive #1546 "SHINKAI 6500" landed on the sea bottom (D=6500m) "SHINKAI 6500" left the sea bottom (D=5400m) Refloated "SHINKAI 6500" Hoisted up "SHINKAI 6500" Recovered "SHINKAI 6500" Launched towing proton magnetometer Com'ced towing proton magnetometer Carried out MBES mapping survey Scientist meeting Com'ced MBES mapping & Geomagnetic survey

2019/05/27　12:00(JST) West ward KITA-DAITO Basin 27-45.0N, 130-36.0E Overcast SSE-5 (Fresh breeze) 3 (Sea Slight) 1 (Low Swell Short) Visibly: 8'

2019/05/28 Tue. 6:11 6:52 6:59 8:50 8:55 9:03

11:23 15:31 17:11 17:30 17:39 18:20 19:25

"SHINKAI 6500" Dive #1546 Finished MBES mapping & Geomagnetic survey Finished towing proton magnetometer Recovered towing proton magnetometer Hoisted up "SHINKAI 6500" Launched "SHINKAI 6500" "SHINKAI 6500" dove & started operation #1546 "SHINKAI 6500" landed on the sea floor (D=5,729m) "SHINKAI 6500" left the sea bottom (D=4,679m) Refloated "SHINKAI 6500" Hoisted up "SHINKAI 6500" Recovered "SHINKAI 6500" Departured from research area (KITA-DAITO Basin) Scientist meeting

2019/05/28　12:00(JST) West ward KITA-DAITO Basin 27-42.0N, 130-49.0E Overcast South-5 (Fresh breeze) 4 (Sea Moderate) 1 (Low Swell Short) Visibly: 8'

2019/05/29 Wed. 9:00

11:00 17:45

Sampling party Meeteing for "SHINKAI 6500" Dive #1547 Scientist meeting

2019/05/29　12:00(JST) East ward off OKI-DAITO 24-22.0N, 132-52.0E Fine but Cloudy South-3 (Gentle breeze) 2 (Sea Smooth)

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9. YK19-07S Cruise Log Date & Time Note Position/Weather/Wind/Sea condition

1 (Low Swell Short) Visibly: 8'

2019/05/30 Thu. 3:45 5:04

5:31~6:01 8:50 8:57 9:05

10:00 11:43 15:07 17:07 17:24 17:34 18:20 18:27

18:36~18:56 19:45 20:28

"SHINKAI 6500" Dive #1547 Arrived at research area (OKI-DAITO Escarpment) Released XBT (21-35.5N 131-30.4E) Carried out MBES mapping survey Hoisted up "SHINKAI 6500" Launched "SHINKAI 6500" "SHINKAI 6500" dove and started her operation #1547 Meeteing for "SHINKAI 6500" Dive #1548 "SHINKAI 6500" landed on the sea bottom (D=6,320m) "SHINKAI 6500" left the sea bottom (D=5,654m) Refloated "SHINKAI 6500" Hoisted up "SHINKAI 6500" Recovered "SHINKAI 6500" Launched towing proton magnetometer Com'ced towing proton magnetometer Carried out eight figure running Scientist meeting Com'ced MBES mapping & Geomagnetic survey

2019/05/30　12:00(JST) OKI-DAITO Escarpment 21-37.0N, 131-31.0E Fine but Cloudy WSW-3 (Gentle breeze) 2 (Sea Smooth) 1 (Low Swell Short) Visibly: 8'

2019/05/31 Fri. 2:25 5:00

5:28~5:59 6:49 6:58 8:44 8:50 8:59

11:44 15:02 16:56 17:12 17:21 18:00 19:25

"SHINKAI 6500" Dive #1548 Finished MBES mapping & Geomagnetic survey Released XBT (21-47.7N 131-00.9E) Carried out MBES mapping survey Finished towing proton magnetometer Recovered towing proton magnetometer Hoisted up "SHINKAI 6500" Launched "SHINKAI 6500" "SHINKAI 6500" dove & started her operation #1548 "SHINKAI 6500" landed on the sea floor (D=6,140m) "SHINKAI 6500" left the sea bottom (D=5,321m) Refloated "SHINKAI 6500" Hoisted up "SHINKAI 6500" Recovered "SHINKAI 6500" & Finished above operation. Departured from research area (OKI-DAITO Escarpment) Scientist meeting

2019/05/31　12:00(JST) OKI-DAITO Escarpment 21-51.0N, 131-01.0E Fine but Cloudy SW-2 (Light breeze) 1 (Sea Calm Rippled) 1 (Low Swell Short) Visibly: 8'

2019/06/01 Sat. 9:00

13:00 18:00

Sampling party "YKDT" Tour Scientist meeting

2019/06/01　12:00(JST) East ward off KITA-DAITO 25-20.0N, 134-40.0E Fine but Cloudy SSW-3 (Gentle breeze) 2 (Sea Smooth) 1 (Low Swell Short) Visibly: 8'

2019/06/02 Sun. 9:00 9:45

16:00

Seminar to ship's crew & students Group photo Scientist meeting

2019/06/02　12:00(JST) Southwest off HACHIJO-JIMA 31-30.0N , 137-42.0E Rain ESE-5 (Fresh breeze) 4 (Sea Moderate) 1 (Low Swell Short) Visibly: 5'

2019/06/03 Mon. 14:20 15:15

Sent out 1st shore line, arrived at YOKOSUKA JPP Scientists disembarked, then completed voyage YK19-07S

2019/06/03　12:00(JST) South ward off TSURUGISAKI 35-03.5N, 139-40.0E Fine but Cloudy ESE-3 (Gentle breeze) 2 (Sea Smooth) 1 (Low Swell Short) Visibly: 8'

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10. Notice on Using

This cruise report is a preliminary documentation as of the end of cruise. This report is not necessarily corrected even if there is any inaccurate description (i.e. taxonomic classifications). This report is subject to be revised without notice. Some data on this report may be raw or unprocessed. If you are going to use or refer the data on this report, it is recommended to ask the Chief Scientist for latest status. Users of information on this report are requested to submit Publication Report to Cooperative Research System Office.

E-mail: kyodoriyo@aori.u-tokyo.ac.jp

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