| Project/Area Number |
17K05640
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Osaka Prefecture University |
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Principal Investigator |
Itoh Yasuto 大阪府立大学, 理学(系)研究科(研究院), 教授 (20285315)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2019: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2017: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
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| Keywords | 地質学 / テクトニクス / 熱史 / 背弧拡大 / プレート運動 / 収束境界 / 西南日本 / プルアパート堆積盆 / 堆積盆 / インバージョン / 和泉層群 / 地殻変動 / 固体地球物理学 / 層位・古生物学 / 岩石・鉱物・鉱床学 / 地球化学 |
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| Outline of Final Research Achievements |
Generally, gigantic pull-apart basins develop adjacent to arc-bisecting lateral faults. Understanding of their development processes has great importance to unravel the mechanism of material recycling working on convergent margins of the Earth's plates. In the present study, a detailed analysis of thermal history was performed on the Cretaceous marine sediments, which had buried elongate depression near the Median Tectonic Line in southwestern Japan arc. Apatite grains were separated from sandstones cropping out along the Median Tectonic Line, then their radiometric ages were calculated based on the density of fission tracks (FTs) generated by spontaneous nuclear fission of uranium. Moreover, thermal effects were assessed by means of analysis of FT length in crystals. As a result, it has been clarified that a backarc opening event during the Miocene provoked migration of volcanic front on southwest Japan, which resulted in a large diversity of thermal history of the island arc.
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| Academic Significance and Societal Importance of the Research Achievements |
プルアパート堆積盆は、ファンデルタ相海成堆積物によって埋積される。それは、有機物に富む泥質岩と流体を貯留し得る孔隙に富む砂質岩の膨大な互層から成っており、石油や天然ガス等地下資源を胚胎するポテンシャルが高い。また、横ずれ断層の末端がプロパゲートすることによって堆積中心が移動し、多様な古環境変遷の原因となる。しかし詳細な堆積年代を決定することが難しい層相が多く定量的研究が困難と考えられてきた。本研究では、砕屑性アパタイト粒子のフィッショントラック長解析に基づいて、定量的な熱史復元に成功すると同時に、西南日本最大の活断層である中央構造線の運動ヒストリーを解明し、危険度評価に貢献することができた。
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