2024-03-28T19:43:01Z
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2022-12-15T03:36:22Z
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四国の第三系久万層群の堆積年代とその意義
四国の第三系久万層群の堆積年代とその意義
Depositional age of the Tertiary Kuma Group, Shikoku, and its significance
成田, 耕一郎
山路, 敦
田上, 高広
栗田, 裕司
小布施, 明子
松岡, 數充
dinoflagellate cysts
fission-track dating
Kuma Group
MTL
Miocene
Eocene
Cenozoic clastic sediments in the Kuma area, Shikoku, southwest Japan, previously designated as the Kuma Group, are here redefined as the Hiwada-toge Formation and the overlying Kuma Group sensu strict, considering a significant time-gap between them. The Hiwada-toge Formation is Early Eocene in age on the basis of dinoflagellate cysts, while the lower part of the Kuma Group s.s. (Sagayama Formation) was dated as late Early Miocene by fission-track dating. Organic microfossil assemblages show that the Hiwada-toge Formation contains marine strata and the lower part of the Kuma Group s.s. (Sagayama Formation) is of non-marine origin. These results provide two geochronological constraints critical to the regional tectonic history. The age of the Hiwada-toge Formation indicates that the Sanbagawa metamorphic rocks came under subaerial erosion by Early Eocene in its provenance area. The relationship between the Median Tectonic Line (M.T.L.) and the northern extension of the Miocene Kuma Group s.s. and its contiguous strata shows that a compresional activity of the M.T.L. occurred during a relatively short period in late Early to Middle Miocene.
日本地質学会
1999-04
jpn
journal article
http://hdl.handle.net/10191/17799
https://niigata-u.repo.nii.ac.jp/records/3226
AN00141768
00167630
地質学雑誌
地質学雑誌
105
4
305
308
https://niigata-u.repo.nii.ac.jp/record/3226/files/ZC_105(4)_305-308.pdf
application/pdf
932.0 kB
2019-07-30