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大峰帯の礫岩
Conglomerates in the Omine Belt
小坂, 共栄
The Omine Belt, on the western border of the Northern Fossa Magna, is about 65 km long from narth to south, and is from 5 to 7 km wide from east to west. Its Western limit is the Itoigawa-Shizuoka Tectonic Line(I-STL), while the eastern limit is the Otari-Nakayama Fault(O-N Fault). The Belt is one of the important zones of the Northern Fossa Magna region, and its tectonic history is related intimately to that of the I-S TL and of O-N Fault. The Omine Belt is underlain by the Pliocene to early Pleistocene sediments, in which conglomerates and pyroclastic rocks of andesitic to rhyolitic series are characteristic. From the sedimentological studies on the conglomerates the following results are obtained. The most remarkable conglomerates occur at three horizons in the Pliocene-Pleistocene succession, i. e. in the Hosogai Member of the Minamiotari Formation, in the Miasa Formation, and in the Oanayama Member of the Omine Formation. They are polymictic, and contain such various kinds of pebbles as graywacke sandstone, slate, chert, quartz porphyry, granites, metamorphic rocks, serpentinite, and clastic sediments and volcanic rocks from the Tertiary formations nearby. The facies of the conglomerates vary remarkably not only from horizon to horizon but also from place to place within the same horizon. The analytical studies on the pebble compositions of these conglomerates have led the author to the following conclusions. The source areas of the sediments were present not only to the west of the Omine Belt, but also to the east, i. e. in the Tertiary areas. And the analyses suggest that even the areas of the Omine Belt itself had become source areas several times since the early Pliocene time. It suggests that upheaval and erosion repeated one after another since the beginning of the Pliocene, and that the fault movements took place several times during the Pliocene and Pleistocene times.
Article
信州大学理学部紀要 15(1): 31-46(1980)
信州大学理学部
1980-09-30
jpn
departmental bulletin paper
VoR
http://hdl.handle.net/10091/10532
https://soar-ir.repo.nii.ac.jp/records/12171
0583-063X
AA00697923
信州大学理学部紀要
15
1
31
46
https://soar-ir.repo.nii.ac.jp/record/12171/files/Science15-01-04.pdf
application/pdf
849.5 kB
2015-09-28