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• Boron isotopic study on coral for seawater paleo-pH reconstruction

• Tectonics and magmatism of the Okinawa Trough

• Petrology of large caldera in south Kyushu

• Evolution and geochemistry of the West Philippine Basin

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• Petrology and geochemistry of volcanic rocks from the Okinawa Trough and Ryukyu Islands

  1992.03

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Published Papers 【 display / non-display 】

• Penultimate glacial sea surface temperature and hydrologic variability in the tropical South Pacific from 150 ka Tahiti corals

  Asami, R; Felis, T; Shinjo, R; Murayama, M; Iryu, Y

  CLIMATE OF THE PAST ( Climate of the Past )  21 ( 12 ) 2525 - 2539   2025.12 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Abstract. Constraining climate models under extreme boundary conditions of the past on societally-relevant timescales is complicated by a common lack of high-resolution reconstructions of sea surface environmental variability for glacial periods. Here, we present subseasonally-resolved Sr/Ca and oxygen isotope (δ18O) records from well-preserved fossil corals of the penultimate glacial and last glacial periods drilled by Integrated Ocean Drilling Program Expedition 310 “Tahiti Sea Level” in the central tropical South Pacific. The proxy records document the mean and seasonality of sea surface temperature (SST) and seawater δ18O (δ18Osw) at 153 and 148 ka, during Marine Isotope Stage (MIS) 6b, and around 30 ka during MIS 3a. Results show mean SST 2.8–4.0 °C lower than present for MIS 6b, and about 3.8 °C lower for MIS 3a. The MIS 6b SST differences are greater during the austral winter (3.7–4.4 °C lower) than during the austral summer (2.0–3.7 °C lower), indicating a greater SST seasonality relative to today during the penultimate glacial. A reconstructed higher mean δ18Osw for both MIS 6b and MIS 3a (+0.41 ‰ to +0.51 ‰ relative to today) suggest more saline surface waters in the central tropical South Pacific over the entire year. Our coral-based reconstructions of SST and hydrology may indicate a reduced mixed layer depth around Tahiti during the penultimate glacial and last glacial. A potential explanation is a westward-expanded South Pacific subtropical dry area relative to today, probably accompanied by lower activity and/or displacement of the South Pacific Convergence Zone.

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• Tracing young subduction beneath northwest Iran: Insights from cosmogenic <SUP>10</SUP>Be recycling and Sr-Nd-Hf isotopes in late Miocene volcanoes

  Azizi, H; Minami, M; Daneshvar, N; Asahara, Y; Matsuzaki, H; Yamagata, T; Deevsalar, R; Aizawa, M; Shinjo, R

  GEOLOGICAL SOCIETY OF AMERICA BULLETIN ( Geological Society of America )  137 ( 9-10 ) 4413 - 4430   2025.09 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Abstract Late Miocene–Quaternary volcanoes in northwestern Iran, characterized by andesitic to dacitic compositions including adakitic rocks with high Sr/Y and La/Yb ratios, exhibit zircon U-Pb ages ranging from 12 to 2 Ma. The isotopic compositions of whole-rock samples (εNd = +0.1 to +4.4; εHf = +2.8 to +11.8; 87Sr/86Sr &amp;lt; 0.705) indicate that the primary magma originated from partial melting of subcontinental lithospheric mantle. The whole-rock chemistry supports an arc magmatic signature, which is consistent with an active continental margin setting. To investigate sediment recycling, cosmogenic beryllium-10 (10Be) isotopes, with a short half-life (1.39 m.y.), were measured in 40 fresh whole-rock samples. Elevated 10Be concentrations (&amp;gt;106 atoms/g) in certain volcanoes confirm a young metasomatized mantle beneath the northwest Iran block. Variations in 10Be concentrations that increase from the front-arc to the rear-arc magmatic rocks suggest greater incorporation of pelagic sediments (rich in 10Be) away from the trench zone. These findings indicate that late Miocene–Quaternary magmatic activity coincided with or followed the formation of an active margin linked to the subduction of the Khoy-Oshnavieh oceanic branch of the northern Neo-Tethys Ocean beneath northwest Iran. Evidence suggests that this branch remained active until the late Miocene. This study highlights the significant role of subducted terrestrial and pelagic sediments in Pliocene–Quaternary magmatism, as supported by 10Be data. This study underscores the utility of cosmogenic 10Be as a reliable tracer for sediment incorporation in young magmatic systems along active margins, providing insights into the geodynamic processes shaping northwestern Iran.

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• Sedimentary record of submarine gravity‐flow events in the southern Ryukyu forearc during the last 200 000 years: archive of mega‐earthquakes and tsunamis

  Babonneau, N., Ratzov, G., Guerin, C., Richa, M., Lallemand, S., Condomines, M., Bachelery, P., Bosch, D., Hsu, S.-K., Su, C.-C., Shinjo, R., Lin, A., Bassetti, M.-A., Revel, M., Cattaneo, A., he EAGER Scientific Team

  Sedimentology ( Wiley )    2025.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  ABSTRACT Despite high convergence velocity, the southern Ryukyu subduction has relatively low and sparse instrumental seismicity, in contrast with the Yaeyama Islands, hit by huge tsunamis over the last few thousand years. This study explores the potential of deep marine sediments to record past large earthquakes and tsunamis. During the MD214/EAGER cruise (2018), four sediment cores (12 to 23 m long) were collected in the forearc area (south of Yaeyama Islands), which is an efficient trap for gravity‐flow deposits. The chrono‐stratigraphic framework is established with radiocarbon dating, δ¹⁸O stratigraphy, U‐series data and tephra analysis including major/trace elements and Hf‐Pb‐Sr‐Nd isotopes. In the basin floor, bulk sedimentation rates locally exceed 60 cm/ka, while hemipelagic sedimentation rates range from 3 to 8 cm/ka, similar to values derived from U‐series data in recent sediments of the boxcores. Twenty‐four gravity‐flow deposits were identified over the last 20 000 years, a frequency consistent with the past tsunamis recorded in the coastal sediments over the last thousand years, emphasising their interest as archives of earthquakes and major tsunamis. At a regional scale, bulk sedimentation rates fall under 10 cm/ka for 48 large‐scale gravity‐flow deposits over the last 200 000 years. With average recurrence periods about 3500–4000 years, these regional events could be triggered by subduction large earthquakes (M &gt; 7). Finally, four exceptionally large submarine gravity‐flow events (mega‐deposits) of unclear origin have been documented over the last 200 000 years. This work provides an unprecedented time series of major submarine gravity instabilities, probably initiated by great earthquakes on this active subduction. It implies that millennial recurrence periods of great earthquakes must be considered on subduction segments where instrumental seismicity is relatively low and underlines the importance of deep marine sediments in tracing these events.

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• Recent monogenic volcanism in North Central Vietnam: Implications for the regional mantle geodynamics

  Anh Le DucHoang, NguyenHuong Tran ThiRyuichi ShinjoLuong Le, DucNhon Dang HoaiCan, Pham Ngoc

  Vietnam Journal of Earth Sciences ( Vietnam Journal of Earth Sciences )  47 ( 3 ) 1 - 24   2025.07 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Pliocene to Pleistocene monogenic basalt volcanism in North Central Vietnam is typical of the East and Southeast Asian' diffuse igneous province'. Exposed at Khe Sanh (4.5 Ma), Gio Linh (1.5–1.3 Ma), and Con Co Island (0.35 Ma) the Miocene activity marks the southeastern tip of the Red River Shear Zone (RRSZ) and appears to relate to the rifting of the Hue Sub-basin, triggered by the Song Ca-Rao Nay Fault system (SCRNFS). Petrological analysis of primitive samples suggests that their formation occurred via decompression melting of spinel peridotite mantle at temperatures of 1350–1400°C and pressures of 15–29 kbar. The basalts display oceanic island basalt (OIB)-type geochemical signatures, characterized by enrichment in radiogenic isotopes of Sr, Nd, Pb, and Hf. They are relatively high in TiO2 and K2O, and incompatible element concentrations. These suggest a fertile, spinel-peridotite source, influenced by in situ metasomatism and/or the presence of recycled subducted oceanic sediment melt. Given the lack of evidence for mantle plume activity beneath the region, we propose that North Central Vietnamese monogenic volcanism reflects decompression melting of a hotter-than-average (Tp ≈ 1400°C) mantle, triggered by lithospheric stretching (greater than 1.5) within the Red River and Hue Sub-basins. In the context of previous regional studies of east/southeast Asian Cenozoic volcanism, Dupal-like mantle affinity is ascribed to eastward asthenospheric flow from the Neo-Tethyan mantle following its closure due to the India-Eurasia collision in the Tertiary.

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• Can sclerosponge skeletons record ocean acidification?: Boron and carbon isotope ratios (δ11B and δ13C) in Acanthochaetetes wellsi from Okinoerabu Island, southwestern Japan

  Tanaka, K., Shirai, K., Uyeno, D., Shinjo, R.

  GALAXEA, Journal of Coral Reef Studies   27   103 - 107   2025.07 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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Books 【 display / non-display 】

Books 【 display / non-display 】

• Technology-Based Solutions for Sustainable Groundwater Management Challenges, Models, and Strategies

  Christmas Uchiyama, Mattia Sacco, Robert Reinecke, Tiziana Di Lorenzo, Chris Leong, Saurav KC, Ryuichi Shinjo ( Part: Allotment Writing ,  Chapter 22: Imagining the invisible: Codesigning adaptive methodologies for groundwater governance in small islands )

  Elsevier  2025.11

• Wadomari Town's Progress: the town history book of Wadomari, Kagoshima, Japan

  Ryuichi SHINJO ( Part: Allotment Writing )

  2024.05

• 豊臣石垣公開施設整備に伴う発掘調査

  大阪市文化財協会 ( Part: Allotment Writing )

  大阪市文化財協会  2024.03

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• Tungsten isotopic compositions of Ethiopian and Aden Bay basalts and the Samoan ocean island: implications for core-mantle interaction in their source

  鈴木勝彦, 賞雅朝子, 賞雅朝子, 深海雄介, 深海雄介, 飯塚毅, 折橋裕二, 新城竜一, 羽生毅

  日本地球惑星科学連合大会予稿集(Web)   2020   2020

   

  J-GLOBAL

• 現生腕足動物殻の微量金属元素濃度に関する基礎的研究

  西尾拓哉, 高柳栄子, 浅海竜司, 新城竜一, 山本鋼志, 井龍康文

  日本古生物学会年会講演予稿集   2018   29   2018.06

   

  J-GLOBAL

• Groundwater in the Ryukyu limestone aquifer

  Yasumoto Jun, Nozaki Masashi, Nakaya Shinji, Harue Masuda, Hosono Takahiro, Toki Tomohiro, Shinjo Ryuichi

  Abstracts of Annual Meeting of the Geochemical Society of Japan ( GEOCHEMICAL SOCIETY OF JAPAN )  65 ( 0 ) 164   2018

   

  DOI CiNii Research

Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• Changes in Subduction Conditions Revealed by Nd-Hf Isotope Compositions: Cretaceous Volcanic Rocks from Sakhalin and Middle Miocene Volcanic Rocks from the Shimokita Peninsula

  Masataka Aizawa, Satoshi Okamura, Ryuichi SHINJO

  36th MSSJ Hokkaido-area Colloquium  2024.08  -  2024.08 

• 電磁流量計を使用した琉球石灰岩帯水層からの非常に速く局所的な海底地下水湧出の直接測定法の開発

  安元純, 安元剛, 浅井和見, Leong Chris, 飯島真理子, 細野高啓, 新城竜一, 宋科翰, 中屋眞司, 井口亮, Bam Razafindrabe, 谷口真人

  JpGU 2024  2024.05  -  2024.05 

• 電気抵抗トモグラフィーと数値解析を統合した黒島における淡水レンズの賦存形態と地下水流動特性の把握

  南隆正, 安元純, 安元剛・Leong Chris, 飯島真理子, 細野高啓, 新城竜一, SONG KE-HAN, 谷口真人, 高橋昌弘, 三浦豪, 澤野陽介, 田原康博

  JpGU 2024  2024.05  -  2024.05 

• Assessing the Influence of NO3-N in the Seawater on the Composition of Benthic Communities: Utilizing Remote Sensing Techniques

  Pingkan Mayestika Afgatiani, Ryuichi Shinjo, Fitra Annurhutami

  JpGU 2024  2024.05  -  2024.05 

• Chemical and Isotopic Characteristics of Pore Water in Surface Sediments of the Southern Okinawa Trough Back-arc Basin

  JpGU 2024  2024.05  -  2024.05 

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Grant-in-Aid for Scientific Research 【 display / non-display 】

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• Does the distinctive soil composition and distribution in Okinawa Prefecture influence the clinical course of idiopathic interstitial pneumonia?

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2025.04  -  2028.03 

  Direct: 3,500,000 (YEN)  Overheads: 4,550,000 (YEN)  Total: 1,050,000 (YEN)

• Determination of acceptable terrestrial phosphate loads for coral growth: Focusing on accumulated phosphorus

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2023.04  -  2026.03 

  Direct: 3,600,000 (YEN)  Overheads: 4,680,000 (YEN)  Total: 1,080,000 (YEN)

• Eruption prediction of the volcanoes where precursory phenomena are continuing: petrologic approach of eruption materials.

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,300,000 (YEN)  Overheads: 4,290,000 (YEN)  Total: 990,000 (YEN)

• Eruption prediction of the volcanoes where precursory phenomena are continuing: petrologic approach of eruption materials.

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,300,000 (YEN)  Overheads: 4,290,000 (YEN)  Total: 990,000 (YEN)

• Eruption prediction of the volcanoes where precursory phenomena are continuing: petrologic approach of eruption materials.

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,300,000 (YEN)  Overheads: 4,290,000 (YEN)  Total: 990,000 (YEN)

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Social Activity 【 display / non-display 】

• 2024.07

  　

  　

• 2023.07

  　

  　

• 2023.06

  　

  　

• 2022.07

  　

  　

• 2022.05

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  2022.07

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Media Coverage 【 display / non-display 】

Media Coverage 【 display / non-display 】

• 沖永良部島での出前授業：地質学教室  Newspaper, magazine

  南海日日新聞社  南海日日新聞  2023.10

  Author： Other 

• NHK総合1７月１７日 海の日 沖縄やんばる編 〜ギョギョギョ 沖縄やんばるスペシャル〜 取材協力

  NHK  〜ギョギョギョ 沖縄やんばるスペシャル〜  2023.7

  Author： Myself 

• 総合地球環境学研究所、与論島でサンゴの掘削調査 陸と海の関係調べる  Newspaper, magazine

  奄美群島南三島経済新聞  2022.10

  Author： Other 

• SKYMARK Inflight Magazine -SORA NO ASHIATO-

  SKYMARK AIRLINES  SKYMARK Inflight Magazine -SORA NO ASHIATO-  Special issue "Let's go see the sea of Miyakojima"  2022.8

• 地球研、プロジェクションマッピングで“地下水の流れ”可視化 汚染対策支援ツールに  Newspaper, magazine

  日刊工業新聞  日刊工業新聞  2022.7

  Author： Other 

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