2018 Fiscal Year Final Research Report
Toba "Level 8" Eruption; its impact on Earth's climate, life and human
| Project/Area Number |
16H04067
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | The University of Tokyo |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
吉村 寿紘 国立研究開発法人海洋研究開発機構, 生物地球化学研究分野, 研究員 (90710070)
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| Research Collaborator |
Ota Yuki
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | 火山灰 / トバ火山 |
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| Outline of Final Research Achievements |
We investigated a volcanic ash layer intercalating in a sediment core recovered from the Bay of Bengal, and identified its source and paleoclimatic conditions before and after the volcanic ash layers. Based on major, trance element abundances, and radiogenic isotopic compositions of Sr, Nd and Pb, we identified the ash layer as the Younger Toba Tephra (YTT) that erupted in 74-70 ka. Stratigraphy based on oxygen isotopic composition of planktonic foraminifera strongly supports the idea that the ash layer deposited around 74-70 ka. The sediment that includes YTT is characterized by very high sedimentation rate, that enables to reconstruct climate and ocean changes in high time resolution. We investigated temporal changes in paleo-seasurface temperature (SST) by analyzing alkenone compositions in millimeter scale.
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| Free Research Field |
海洋地質学，古海洋学
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| Academic Significance and Societal Importance of the Research Achievements |
インドネシア・スマトラ島のトバ火山は約7万年前に爆発的な噴火を起こした．その噴火は過去100万年間でも最大級といわれる．その時に噴出した火山灰は南アジア，インド洋，南シナ海と広く分布している．地球深部探査船「ちきゅう」でベンガル湾においてNGHP-02航海が実施され，トバ火山灰らしき火山灰層が回収された．本研究では，その火山灰層の詳細な検討と分析により，新期噴火のものであることを明らかにした．また，その火山灰層が含まれる堆積物は非常に堆積速度が高いため，高時間解像度での気候・海洋変動を記録している．火山灰層の直上，直下の堆積物の詳細な古水温記録を復元したところ，大変興味深い知見が得られた．
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