| Project/Area Number |
07454118
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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 | 一般 |
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| Research Field |
Geology
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| Research Institution | Ibaraki University |
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Principal Investigator |
AMANO Kazuo Ibaraki Univ, ; Dept.of Science ; Professor, 理学部, 教授 (00125791)
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| Project Period (FY) |
1995 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1997: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | South Fossa Magna / tectonics / collision / sedimentation / island arc / backarc / 堆積盆 / 島弧システム / プレートテクトニクス / フィリピン海プレート / 火山弧 / ハイアロクラスタイト / 枕状溶岩 |
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| Research Abstract |
The south Fossa Magna is well known as a zone consisting of islands which belonged to the paleo-Izu-Bonin arc and collided and accreted to the Honshu arc due to the movement of the Philippine Sea plate in a north-west direction. There were four times after 15Ma. The purpose of this study is to clarify the relationship between multiple collision tectonics and sedimentation in the South Fossa Magna. The results are summarized as follows.
(1) The trough-fill sediments related to the collision of the Tanzawa block are mainly composed of turbidite and debrite. They show a trend of change of clast type and upward coarsening sequences reflecting the upheaval movement of the hinterland according to the collision of the Tanzawa block.
(2) The geological features of the Misaka block (second collision) was not well understood. Sedimentological studies clarified that the Misaka block constitutes a set of forearc, volcanic arc and backarc rift zone.
(3) The Kushigatayama block that was thought to be the first collided massif in the South Fossa Magna is mainly composed of re-sedimented hyaloclastite and mass flow deposits. These facts show that the Kushigatayama block must have been a forearc or backarc region.
(4) some of the dykes older than 2Ma, distributed in the area to the north of the Tonoki-Aikawa tectonic line, rotated clockwise about 34 degrees based on paleo-magnetic studies. This indicates that part of the Honshu arc rotated clockwise accompanied by the blocks.
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