著者

佐沢 豪 Legrand Julien 矢部 淳 指田 勝男 上松 佐知子

出版者

一般社団法人 日本地質学会

雑誌

日本地質学会学術大会講演要旨 第124年学術大会(2017愛媛) (ISSN:13483935)

巻号頁・発行日

pp.233, 2017 (Released:2018-03-30)

著者

大関 仁智 清水 紀和 上松 佐知子 指田 勝男

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.130, no.3, pp.311-329, 2021-06-25 (Released:2021-07-20)

参考文献数

69

被引用文献数

2

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Zircons in Cretaceous sandstones have recently been the focus of a new provenance analysis technique. Microfossil-bearing clasts in conglomerate are also used in this analysis; however, there are few reports on clasts, including microfossils, which are mainly found in the vicinity of Shikoku and Hokuriku districts. Although the Ishido Formation, Sanchu Group, in the Kanto Mountains, is considered to be Barremian in age based on the occurrences of ammonoids, interbedded with conglomeratic beds, there have been no reports of microfossil-bearing clasts from this bed. To confirm whether each fore-arc basin in the whole of southwest Japan had a common hinterland during the Late Mesozoic, microfossils are extracted from gravels in the Ishido Formation to examine their ages. As a result of acidic treatment, Permian and Triassic radiolarians and Triassic conodonts are obtained from eight chert and siliceous mudstone pebbles of the Ishido Formation. On the basis of their lithofacies and ages, these pebbles of this formation are likely to derive from the Chichibu Belt, which constitutes a large part of the Kanto Mountains. These results indicate that, in the Early Cretaceous period, not only granitic rocks but also Jurassic accretionary complexes were exposed as hinterlands of each fore-arc basin in the Shikoku and Kanto districts. Moreover, based on previous reports on the zircon spectra in Cretaceous sandstones and microfossil-bearing clasts in the conglomerates, hinterlands, such as granitic rocks and Jurassic accretionary complexes, of each fore-arc basin in the whole of southwest Japan including the Kanto district, as well as Kyushu and Shikoku districts, indicate common exposure and denudation histories.

著者

歌川 史哲 指田 勝男 上松 佐知子 髙津 翔平

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.123, no.11, pp.969-976, 2017-11-15 (Released:2018-02-23)

参考文献数

15

被引用文献数

1

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The Neogene Chikura Group, which is widely exposed in the southeastern part of Minamiboso City, Chiba Prefecture, Japan, is made up of a thick sequence of marine sedimentary rocks deposited in a middle to upper bathyal environment. The group comprises (in ascending order) the Shirahama, Shiramazu, Mera and Hata formations. The upper Pliocene Shirahama Formation is composed mainly of red-brown volcaniclastic sandstone and the Nojimazaki Conglomerate Member. This member comprises volcaniclastic conglomerate with granules to boulders of basalt and andesite, and is characterized by pebbles of andesite, basalt, granodiorite, gabbro, sandstone, siltstone, greenish tuff, and chert. We obtained Anisian and Ladinian (Middle Triassic) radiolarians from chert pebbles, and Bajocian to Callovian (Middle Jurassic) radiolarians from a siliceous siltstone pebble. These Mesozoic pebbles were probably derived from a Mesozoic accretionary complex (present-day Kanto District) in the northwestern part of Boso Peninsula.

著者

上松 佐知子 鎌田 祥仁

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.124, no.12, pp.951-965, 2018-12-15 (Released:2019-03-15)

参考文献数

179

被引用文献数

2

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本論文では放散虫とコノドント化石に関する過去25年間の研究成果を振り返る.放散虫生層序学分野では,中期古生代から中生代までの多くのデータが蓄積されると共に,化石帯の分解能が大きく向上した.コノドント化石は90年代以降,特にペルム系と三畳系の各階境界を定義する国際的な示準化石として重要性が増している.今後は放散虫とコノドント生層序の相互較正,更に生層序と年代測定学的尺度との対比を積極的に行っていく必要がある.生物学的研究については,放散虫の系統解析や生体飼育に関して我が国から多くの研究が発信され,知見が蓄積された.また付加体地域からは三畳紀コノドントの良質な標本が多数報告され,コノドントの古生物学的研究に貢献している.今後はこれらの研究を更に発展させると共に,微化石研究の一般への普及および次世代を担う若手研究者を育成していくことが重要である.