| Project/Area Number |
07041081
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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 Institution | Tohoku University |
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Principal Investigator |
OHMOTO Hiroshi Graduate School of Science, Tohoku University, Professor, 大学院・理学研究科, 教授 (60194304)
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| Co-Investigator(Kenkyū-buntansha) |
ONO Shuhei The Pennsylvania State University, USA, 地球科学科, 助手
MOCK Robin L The Pennsylvania State University, USA, 地球科学科, 助手
YAMAGUCHI Kosei The Pennsylvania State University, USA, 地球科学科, 助手
KUMP Lee R The Pennsylvania State University, USA, 地球科学科, 教授
OCHIAI Ei-ichiro Juniata College, USA, 化学科, 教授
MINTER W.E.L University of Cape Town, South Africa, 地質学科, 教授
BARNES Hubert L The Pennsylvania State University, USA, 鉱床学研究所, 教授
NEDACHI Munetomo Kagoshima University, 教養部, 教授 (10107849)
KAKEGAWA Takeshi Graduate School of Science, Tohoku University, 大学院・理学研究科, 助手 (60250669)
HAYASHI Ken-ichiro Graduate School of Science, Tohoku University, 大学院・理学研究科, 助教授 (40124614)
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| Project Period (FY) |
1995 – 1996
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| Keywords | biological evolution / early Earth / environmental change / atmospheric evolution / Precambrian / Cambrian / submarine hydrothermal process / phosphate flux |
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| Research Abstract |
The main objective of this research project was to understand the causes for major biological events in the early Earth, especially the first appearances of eukaryotes around 2 billion years ago and of large marine fauna around 550 million years ago. This objective was mostly pursued from systematic geochemical investigations of organic matter, minerals and rocks in about 1000 rock specimens that were collected during our field surveys in 4 areas : (A) the southern Ontario district, Canada (2.8-1.8 Ga sequence), (B) the Burin Peninsula, Newfoundland, Canada (570-520 Ma sequence), (C) the Normandy district, France (600-500Ma sequence), and (D) the Kaapvaal Craton, South Africa (3.0-2.0 Ga sequence).
Our investigations have resulted in the following major findings :
(1). According to a currently popular theory, the first major division of biological species (Eukaryotes, Bacteria, and Eubacteria) were caused by a dramatic rise of the atmosphericO_2 around 2.0 billion years ago. However, we
… More
have discovered various lines of geochemical evidence suggesting that the major division of biological species and the development of an oxic atmosphere had already taken place by 3.0 billion years ago.
(2). "The great biological explosion" of around 550 million years ago was probably caused by the global changes in the ocean water chemistry (e.g., an increase in the phosphate flux) and climate.
(3). The major changes in the ocean water chemistyr that affected the biological activity in ocean through geologic time were probably caused by the changes in the geographical configuration of continents (e.g., breaking of super continents) and in submarine hydrothermal activity in mid ocean ridges. These changes were in turn caused by changes in the convective patterns in the mantle.
Some of the results from our investigations have already been presented at national and international scientific meetings (about 25 presentations). Five papers have been published (or in press) in major international journals, and about 20 more papers related to this project are in preparation. Less
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