| Project/Area Number |
18540450
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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 |
Geology
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| Research Institution | Tohoku University |
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Principal Investigator |
EHIRO Masayuki Tohoku University, Tohoku University, The Tohoku University Museum, Professor (10124554)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Noritoshi Graduate school of Sciences, 大学院・理学研究科, Assistant Professor (60312542)
YAMAKITA Satoshi Miyazaki University, Faculty of Education and Culture, Associate Professor (80210342)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,720,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥420,000)
Fiscal Year 2007: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2006: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Keywords | North Kitakami Belt / cross section of the tectono-stratigraphic unit / Jurassic accretionary complex / Kuzumaki-Kamaishi Subbelt / Akka-Tanohata Subbelt / Carboniferous seamount complex |
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| Research Abstract |
The North Kitakami Belt of Northeast Japan is situated between and links the Taukha-Oshima Belts and South Chichibu Belt. To create a geologic cross section and to elucidate a tectono-stratigraphy and accretion ages of the Jurassic accretionary complexes of the North Kitakami Belt in the Kuzumaki-Akka area, detailed geologic survey and Paleontological investigation were carried out. The key results are as follows:
1) We found that there was Late Carboniferous seamount basalt-limestone complex in the Kuzumaki area, and Late Carboniferous chert in the Akka area, suggesting the birth of oceanic plate constitute the North Kitakami Belt is dating back to the Late Carboniferous.
2) We discovered a deep-sea Permian-Triassic boundary bed (PTB) in the Otori Formation of the Akka area and confirmed a sharp negative sift of 13C value at the basal part of the black organic mudstone bed. This is the first discovery of PTB in Northeast Japan.
3) We elucidated the accretion age of the Otori and Takayashiki Formations as late Bajocian-Bathonian (Middle Jurassic) and Oxfordian (Late Jurassic), respectively.
4) The geologic structure of the Jurassic accretionary complexes in the Akka area is characterized by a broad syncline and anticline of seated units, and the accretionary ages of the units are become young in structurally descending order.
From these data it is concluded that the boundary between the Kuzumaki-Kamaishi Subbelt and Akka-Tanohata Subbelt is extendable to the north running the, central part of the Oshima Belt of Southwest Hokkaido, and based on the similarities in the lithology and oceanic plate stratigraphy, the Otori Formation and its adjacent formations are correlatable with the Kashiwagi Unit and Ohirayama Unit of the Chichibu Belt of Southwest Japan.
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