Search for evidence of impact in the Paleozoic and Mesozoic bedded cherts in Japan

2016 Fiscal Year Final Research Report

• Project/Area Number: 26707027
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Partial Multi-year Fund
• Research Field: Geology
• Research Institution: Kumamoto University
• Principal Investigator: Onoue Tetsuji 熊本大学, その他の研究科, 准教授 (60404472)
• Research Collaborator: EBIHARA Mitsuru 首都大学東京, 大学院理工学研究科, 教授 ; NOZAKI Tatsuo 海洋研究開発機構, 海底資源研究開発センター, 研究員 ; SATO Honami 海洋研究開発機構, 海底資源研究開発センター, 日本学術振興会特別研究員 ; SUZUKI Katsuhiko 海洋研究開発機構, 海底資源研究開発センター, 研究開発センター長代理 ; YAMASHITA Katsuyuki 岡山大学, 大学院自然科学研究科, 准教授
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 天体衝突 / 三畳紀 / チャート / 絶滅 / 放散虫

Outline of Final Research Achievements

This study investigated the extraterrestrial matter in the Permian to Jurassic bedded chert sequences from the Mino Belt, central Japan. A large impact event was detected in the Upper Triassic bedded cherts using platinum group elements (PGE) and osmium (Os) isotope ratio as a tracer. The relatively flat CI-chondrite normalized patterns of the least mobile PGEs (Ir, Ru, and Rh) and the Ru/Ir ratio determined by linear regression analysis suggest that a chondritic impactor is the source of the PGE anomalies preserved in claystone samples from the study sections. The chondritic impactor of the suggested size (3.3-7.8 km in diameter) implies that a large amount of debris and/or climatically active gasses (e.g., sulfur oxides) would have been released from the impactor, which would have had a marked effect on the environment. An analysis of patterns of radiolarian extinction reveals a high extinction rate in the 1 Myr interval after the impact event.

Free Research Field

層位・古生物学