1997 Fiscal Year Final Research Report Summary
Isotopic anomalies at the Precambrian-Cambrian boundary
| Project/Area Number |
07041094
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Field Research |
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| Research Field |
Geology
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MATSUMOTO Ryo UNIVERSITY OF TOKYO,Graduate School of Sciences, Professor, 大学院・理学系研究科, 教授 (40011762)
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| Co-Investigator(Kenkyū-buntansha) |
ウッシュマンド A. イラン地球科学技術研究所, 所長
UENO Katsumi Tsukuba Univ., Institute of Geoscience, Lecturer, 地球科学系, 講師 (90241786)
KANO Akihiro Hiroshima Uni., Faculty of Science, Assistant, 理学部, 助手 (60231263)
KAKUWA Yoshitaka UNIVERSITY OF TOKYO,Graduate School Arts and Sciences, Assistant, 大学院・総合文化研究科, 助手 (70124667)
HUSHMAND A. Research Institute of Earth Sciences, Director
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| Project Period (FY) |
1995 – 1997
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| Keywords | Precambrian / Cambrian boundary / Cambrian explosion / F / F boundary / Carbon isotope / Rare earth elements / Cerium anomaly / Redox potential |
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| Research Abstract |
This project was originaly intended to elucidate the nature of the Precambrian/Cambrian boundary event. However, the actual field work plans were reorganized and expanded towards the entire Paleozoic sections in the course of the joint study with the Iranian geologist group. Because the P/C boundary event was believed to be characterized only through the comparison with the other Paleozoic boundary events such as F/F boundary and P/T boundary. We have obtained the following major results concerning the chemo-stratigraphy and environmental changes of the Paleozoic world.
1. Negative and positive carbon isotopic anomaly have been recognized just below and bove the P/C boundary. The formaer and the latter are interpreted to correspond to mass extinction of Precambrian fauna and explosive diversification of the Paleozoic type fauna. Moreover, strong positive anomaly was observed in the late Cambrian strata.
2. Moderate negative carbon anomaly in the upper Devonian is probably attributed to the Famenian/Frasnian boundary events.
3. Cyclic changes in carbon isotopic composition recognized in the Carboniferous-Permian may reflect the glacier-interglacier cycles.
4. Chondrite-normalized REEs patterns show interesting secular variations. Strong negative Ce anomaly occurs in the Cambrian explosion intervals whereas the remaining Paleozoic sections show normal pattern, suggesting that the Cambrian explosion was associated with oxygenated ocean while the entire Paleozoic ocean was characrerized by reducing environment.
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[Publications] Matsumoto, r., Zhong Zheng, Kakuwa, Y., Hamdi, B., and Kimura, H.: "Preliminary results of paleomagnetic study on the Cambrian to the Triassic rocks of the Alborz, Northeaast Iran" Jour.Fac.Sci., Univ.of Tokyo, Sec.II. 22. 233-249 (1995)
Description
「研究成果報告書概要(欧文)」より
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