1987 Fiscal Year Final Research Report Summary
Formation of The Nagano Basin and Tilting of The Kato Mountains
| Project/Area Number |
61540552
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
地質学一般
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| Research Institution | Shinshu University |
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Principal Investigator |
AKAHANE Sadayuki Institute of Nature Education in Shiga Heights, College of Education,Shinshu University, 教育学部附属志賀自然教育研究施設, 助教授 (40089090)
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| Project Period (FY) |
1986 – 1987
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| Keywords | analysis of fossil pollen / K-Ar dating / Nagano Basin / Kato Mountains / tilting / 第四系 |
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| Research Abstract |
The chief purpose of the present work is to give the relation to the geological history of the Nagano Basin and the tiltng of the Kato Mountains. The Nagano Basin is a typical Quaternary sedimentary basin in the northern part of the Fossa Magna in Central Japan. Along the western marginal area of this basin ,a tectonic line and many hills are developed to form a border between the Minochi and the Takai tectonic province.
In the western marginal area of the Nagano Basin, there are widely developed marine and lacustrine deposits of early to late Pleistocene age. They are classified into the Minochi,the Toyono,and the Minamigo Formation in ascending order.
The results of analysis of fossil pollen, which is included the Quaternary system in the western marginal area of this basin,provided a good picture of the past vegetational or climatic changes and the sedimentary environment.
K-Ar dating was carried out the volcanic rocks are distributed along the eastern margenal area of the Nagano Basin. The age of the Boderayama Andesite,the Hakoyama Andesite and the Karitayama Andesite are 1.75 + 0.20 Ma, 2.10 + 0.12 Ma and 2.77 + 0.14 Ma respectively.
The topography of the weatern marginal area is divided into three parts ; mountains, hills and plain arranged in series of steps. The formation of such a steplike hills in the western marginal part of this basin implies a nature of the Quaternary tectonic movement on the boundary between the Minochi and the Takai tectonic province. This tectonic movement is caused by tilting of the Takai tectonic province.
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