| Project/Area Number |
16540425
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Tohoku University |
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Principal Investigator |
KAIHO Kunio Tohoku University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (00143082)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Tsutomu Muroran Institute of Technology, Dept. Mechanical Systems Engineering, Professor, 機械工学科, 教授 (00302224)
ASANO Shouji Tohoku University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (00089781)
FUJIMAKI Hirokazu Tohoku University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (90133933)
CRAMER Benjamin S. 東北大学, 大学院・理学研究科, 外国人特別研究員
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2006: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | extraterrestrial impact / mass extinction / aerosol / sulfur / Permian / oceanic anoxia / sulfur isotope / biomarker / イリジウム / 暁新世 / 始新世境界 / 温暖化 |
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| Research Abstract |
An extraterrestrial impact can cause significant development of sulfate aerosols in the stratosphere, resulting reduction of the solar radiation reaching to the Earth's surface and mass extinctions. Our numerical calculation of three cases of impact (10 km-diameter comet, 10 km and 20 km diameter asteroids) shows that these impacts can not cause a significant decrease in solar radiation to the Earth's surface. A larger impact or a target concentrated by sulfur is needed for mass extinctions. Our radiative transfer calculation shows that an increase in UV-B radiation would have occurred after several years from the Chicxulub impact and might contribute the mass extinction of terrestrial life at the end of the Cretaceous.
We show that a significant decrease in the ^<34>S/^<32>S ratio of carbonate-associated sulfate occurred simultaneously in South China, Hungary, and Italy at the end of the Permian (251 Ma), coincident with the end-Permian mass extinction. The cause of the abrupt negative shift of ^<34>S/^<32>S in these two distant sites is the injection of light sulfur to the surface ocean from the deep ocean rich in H_2S, or deposits rich in sulfide, or the mantle. Possible direct causes are (1) massive release of H_2S gas from the euxinic surface and intermediate waters (2) an extraterrestrial impact to sulfide-rich sediments or ore deposit, and (3) release of mantle origin sulfur by an impact of >70 km asteroid to the ocean. We also found high values of sulfate sulfur and carbonate carbon isotope ratio in the uppermost Guadalupian followed by a remarkable decrease in δ^<34>S_<sulfate> and δ^<13>_<carb> occurring within the mass extinction horizon (260 Ma) in South China. The decrease suggests degassing of H_2S from a euxinic ocean. The double mass extinction at 260 Ma and 251 Ma would have been caused by massive release of H_2S.
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