Linkage between impact event and global environmental changes in the Late Triassic

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K14409
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Chiba Institute of Technology
• Principal Investigator: Sato Honami 千葉工業大学, 次世代海洋資源研究センター, 上席研究員 (20773394)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 隕石衝突 / 環境変動 / 後期三畳紀 / 白金族元素 / オスミウム同位体

Outline of Final Research Achievements

In order to assess environmental changes triggered by a large impact event in the Late Triassic, this study investigated stratigraphic variations in major, trace, and platinum group element (PGE) concentrations and Re-Os isotope records from the Upper Triassic limestone successions in Italy. A PGE-enriched layer are detected in the uppermost Norian, which could be related to influx of extraterrestrial materials into the sediment. Re-Os isotope ratios display a negative shift above PGE-enriched layer. Stratigraphic variations in redox-sensitive elements demonstrate that a transient change of redox state into low oxygen condition after PGE-enriched layer. Their direct causal relationships between the PGE-enriched layer and environmental changes in the western Tethys is not clear. However, these results provided the first sedimentary record of the late Norian impact in deep basinal deposits, which might be used as an important geologic marker.

Free Research Field

地球化学

Academic Significance and Societal Importance of the Research Achievements

本研究により，後期三畳紀に起こった隕石衝突イベントについて，これまでの研究で衝突の影響が検討されてきた遠洋域に加え，大陸縁辺の陸棚環境においても隕石衝突にともなう環境変動を解析することが可能となった．従来．隕石衝突による全球規模での環境変動の解析は白亜紀/古第三紀境界を対象に進められてきたが，本研究の成果を比較することで，衝突した隕石の種類・サイズや衝突地点などによって，どの程度の環境変動を引き起こしたかについての議論が可能となる．隕石衝突が引き起こす環境変動は，流体圏，固体圏，生命圏に関わる重要な問題であり，今後さらに学際領域の広い研究分野へと発展させることができると考えられる.