2022 Fiscal Year Final Research Report
Examination of the oxygen overshoot hypothesis
Project/Area Number |
19K14832
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Research Category |
Grant-in-Aid for Early-Career Scientists
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Allocation Type | Multi-year Fund |
Review Section |
Basic Section 17050:Biogeosciences-related
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Research Institution | National Institute of Advanced Industrial Science and Technology |
Principal Investigator |
Goto Kosuke 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 主任研究員 (30612171)
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Project Period (FY) |
2019-04-01 – 2023-03-31
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Keywords | 大酸化イベント / オーバーシュート仮説 / 原生代前期 / モリブデン同位体 / 大気進化 |
Outline of Final Research Achievements |
To further understand the atmospheric redox conditions during the early Paleoproterozoic, we analyzed Mo isotopic compositions (δ98/95Mo) of ~2.35-Gyr-old clastic sedimentary rocks from the Serpent Formation in the Huronian Supergroup. The δ98/95Mo values of the analyzed samples range between -0.06 and 0.32‰ and are similar to the average Archean upper continental crust δ98/95Mo (+0.03 ± 0.18‰) estimated from Archean and early Paleoproterozoic glacial diamictites (Greaney et al., 2020 EPSL 534, 116083). The unfractionated δ98/95Mo values require limited oxidative weathering of Mo as well as little authigenic Mo enrichment during deposition. Our results, therefore, suggest low atmospheric O2 conditions at ~2.35 Ga and support the oscillations in atmospheric O2 levels after its initial rise at ~2.43 Ga.
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Free Research Field |
古環境学
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Academic Significance and Societal Importance of the Research Achievements |
地球大気の化学組成が地球史を通じてどのように変化してきたのかは、生命の進化と密接に関係している。本研究により、23.5億年前の堆積物の化学分析に基づき、この時代の大気酸素濃度が低かった可能性が明らかとなった。得られた知見は、原生代前期におきた大気酸素濃度上昇イベント(大酸化イベント)と酸素発生型光合成生物や真核生物の進化・出現の関係を理解する一助になると考えられる。
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