日本地球惑星科学連合2015年大会

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セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS30] 遠洋域の進化

2015年5月26日(火) 18:15 〜 19:30 コンベンションホール (2F)

コンビーナ:*松岡 篤(新潟大学理学部地質科学科)、栗原 敏之(新潟大学大学院自然科学研究科)、加藤 泰浩(東京大学大学院工学系研究科システム創成学専攻)、尾上 哲治(熊本大学大学院自然科学研究科)、木元 克典(独立行政法人海洋研究開発機構)、野崎 達生(海洋研究開発機構地球内部ダイナミクス領域)、植田 勇人(新潟大学理学部地質科学科)、小林 健太(新潟大学理学部地質科学科)、長谷川 卓(金沢大学自然システム学系)

18:15 〜 19:30

[MIS30-P01] 西南日本丹波帯に見られる下部ペルム系遠洋深海相層序の確立

*内田 光哉1高橋 聡1武藤 俊1田代 貴志1鈴木 紀毅2 (1.東京大学大学院理学系研究科地球惑星科学専攻、2.東北大学大学院理学研究科地学専攻)

The Carboniferous and following early Permian are associated with climate changes related to tectonics and glaciations. The development of ice-sheets occurred on the Gondowana continent, which was placed around the southern polar region. Repeated increase and decrease in the volume of such ice sheets have been suggested by the oxygen isotope ratio variations of carbonate fossils (e.g., Chen et al., 2012). According to previous researches, the fluctuation of ice-sheet volume occurs in the time interval of from one million years to several million years. Contemporaneous pelagic deep-sea sediments would provide materials available for the reconstruction of environmental conditions such as oceanic ventilations and biotic productivity, but their records have been poorly known. The delay in the establishment of Carboniferous and lower Permian pelagic deep-sea stratigraphy is the main reason of this problem. The Paleozoic to Mesozoic deep-sea sedimentary rocks including the lower Permian are preserved in Japanese accretionary complexes. Among previous researches, Ishiga et al. (1982) reports one of the best lithologic sections of lower Permian deep-sea. This section is named the Funaeda section, and located in Yagi area, Northwest of Kyoto city. The Funaeda section is composed of grey and red colored bedded chert. Although Ishiga et al. (1982) examined the age diagnostic radiolarian fossils, the Permian biostratigraphy has recently been updated, and therefore more detailed discussion on the age assignment of this section is required.
In this study, detailed field works on the Funaeda section were conducted, and the section was divided the Funaeda section into five subsections, namely Fd-A~E sections. We found conodont fossils from the uppermost and the middle part of the Fd-B section. Some specimens are identified Mesogondolella sp.. Occurrences of these species are limited within the Cisuralian, suggesting that the Fd-B section belongs to the Cisuralian. To observe each stratum in detail, we made polished rock specimens for the Fd-B section. We found periodic variations in the thickness of bedded chert, rock color and lamina preservation. Thickness, rock color, and lamina preservation of the Fd-B section vary every ca.50, 4 and 48 beds, respectively. In this presentation, we will discuss these lithologic features and their relationship with the paleo-environmental conditions at the early Permian pelagic ocean.