1999 Fiscal Year Final Research Report Summary
Study on the cause of the Earth's greatest mass extinction
| Project/Area Number |
10041113
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| Research Category |
Grant-in-Aid for Scientific Research (A).
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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 |
ISOZAKI Yukio Gen. Sys. Studies, Univ. of Tokyo, Asso. Pro., 大学院・総合文化研究科, 助教授 (90144914)
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| Co-Investigator(Kenkyū-buntansha) |
TAKANO Masao Sch. of Sci., Nagoya Univ., Asso. Prof., 理学部, 助教授 (90262849)
NISHI Hiroshi Soc. & Cult. Stud., Kyushu Univ., Asso. Prof., 大学院・比較社会文化研究科, 助教授 (20192685)
KAWAHATA Hotaka Geol. Surv. of Japan Researcher, 海洋地質部, 研究員
SAKAI Harutaka Sch. of Sci., Kyushu Univ., Prof., 大学院・比較社会文化研究科, 教授 (90183045)
YANO Akira Fac. of Sci., Osaka City Univ., Prof., 理学部, 教授 (40047353)
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| Project Period (FY) |
1998 – 1999
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| Keywords | mass extinction / volcanic ash / permoo-Triaasic boundary / plume winter / drilling / global environmental change / Sichuan China / supercontinent breakup / 中国四川省 |
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| Research Abstract |
This project was aimed to reveal the cause of the Permo-Triassic boundary (ca. 250 million years ago) mass extinction which represents the greatest biospheric catastrophe in the Earth's history. We planned to collect a continuous sedimentary sequence that recorded the secular environmental change around the P-T boundary, particularly by deep-drilling, because it is critical for this study to obtain weathering -free fresh rock samples for geochemnical analyses. Out of 4 candidate sections in South China, the Chaotien section was chosen on the basis of preliminary field research in winter of 1998. We conducted an academic drilling at Chaotien in northern Sicuan province in summer of 1999 and recovered 260 m long drilled core samples. The section along the Jialingian river covers the entire Upper Permian series from top Maokoan to Changhsingian plus the lowest Griesbachian of Lower Triassic. Numerous samples including ammonoid, coral, brachiopod and fusulinid fossils collected from surfac
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e outcrops made the total sample weight ca. 5 tons.
These samples were shipped to Tokyo in Fall of 1999 and are currently under geochemical analyses in various aspects including major element composition, carbon isotope ratio plus rare earth element composition. In Particular, the Scanning X-ray Analyzing Microscope of the Nagoya Univ. is used for recovering visualized images of chemical composition of the samples. As the geochemical analysis has just started, results will be summarized later on.
According to the field research and preliminary indoor analyses, the following new observations were made ; 1) The Chaotien section covers fossiliferous Upper Maokoan, Wuchapingian and Canhsingian plus the lowest Griesbachian on the basis of index fossils, 2) the cored samples are quite fresh, much better than those from the outcrop, 3) This section has many tuff layers whose horizons often correspond to the disappearance horizon of particular fossils. This suggests the "Plume Winter" scenario (proposed by the project leader) that connects plume-induced extraodinarily violent volcanism with the Pangean supercontinent breakup, and with the global environmental change associated with mass extinction across the P-T boundary. Less
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