2001 Fiscal Year Final Research Report Summary
A study on the environmental catastrophe at the K/T bundary
| Project/Area Number |
11691116
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
固体地球物理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
UATSUI Takafumi Univ. of Tokyo, Graduate School of Frontier Sciences, Professor, 大学院・新領域創成科学研究科, 教授 (80114643)
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| Co-Investigator(Kenkyū-buntansha) |
TAJIKA Eiichi The Univ. of Tokyo, Graduate School of Frontier Sciences, Research Associate, 大学院・理学系研究科, 助手 (70251410)
OJI Tatsuo The Univ. of Tokyo, Graduate School of Frontier Sciences, Associate Professor, 大学院・理学系研究科, 助教授 (50160487)
TADA Ryuji The Univ. of Tokyo, Graduate School of Frontier Sciences, Professor, 大学院・理学系研究科, 教授 (30143366)
TOYODA Kazuhiro Hokkaido Univ., Graduate School of Environmental Earth Science, Associate Professor, 大学院・地球環境科学研究科, 助教授 (10207649)
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| Project Period (FY) |
1999 – 2001
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| Keywords | K / T boundary / Cuba / Tsunami deposits |
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| Research Abstract |
In order to understand the mode and magnitude of K/T boundary impact and its consequences, field surveys were conducted in Cuba where the proximal deep-sea K/T boundary deposits are well exposed. As a result of the field surveys, the following new informations are obtained :
1) The deep-sea K/T boundary deposits, as thick as 700 m, are well exposed in three different geological provinces in western Cuba.
2) The K/T boundary deposits are composed of two units such as a lower calcirudite unit and an upper calcarenite/calcilutite unit.
3) The lower unit is characterized by breccia derived from the shallow platform, and contains shocked quartz and altered vesicular glass. It is considered as a gravity flow deposit triggered by the impact-induced seismic wave.
4) The upper unit is massive and normally graded, and contains abundant pelagic microfossils of various ages. These characteristics are similar to those of a homogenite, a deep sea tsunami deposit. Presence of shocked quartz suggests its relation to the impact.
5) The thickness of the upper unit varies laterally. When its thickness is large, its basal contact is gradational, and its appearance is homogeneous. Whereas when its thickness is small, its basal contact is erosional, and sedimentary structures suggest that the influence of current is present. Moreover, grain composition is distinctly different between the two units. These evidences suggest different origin of the two units.
6) A 2-m-thick sandstone complex with the K/T boundary age is discovered at Moncada, western Cuba. The Ir anomaly is found at its uppermost part. Paleo-current analysis reveals existence of bi-directional flows suggestive of tsunami repetition.
It becomes evident that the impact-induced large landslides followed by large tsunamis had occurred in the paleo-Caribbean basin. The tsunamis had eroded deep-sea sediments to form dense, suspended sediment cloud which finally settled down to form a homogenite within a few weeks after the impact.
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Research Products
(16 results)
