Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS13] Evolution of the Pelagic Realm

Mon. May 23, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Atsushi Matsuoka(Department of Geology, Faculty of Science, Niigata University), Toshiyuki Kurihara(Graduate School of Science and Technology, Niigata University), Yasuhiro Kato(Department of Systems Innovation, Graduate School of Engineering, University of Tokyo), Tetsuji Onoue(Earth and Environmental Sciences, Graduate School of Science and Technology, Kumamoto University), Katsunori Kimoto(Japan Agency for Marine-Earth Science and Technology), Tatsuo Nozaki(Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology), Hayato Ueda(Department of Geology, Niigata University), Kenta Kobayashi(Department of Geology, Faculty of Science, Niigata University), Takashi Hasegawa(Division of Global Environmental Science and Engineering, Graduate School of Natural Science and Technology, Kanazawa University)

5:15 PM - 6:30 PM

[MIS13-P05] Sandstone dikes within pelagic cherts of the Permian Yoshii Group in Southwest Japan and its deformation structure

*Tsuyoshi Ito1, Atsushi Matsuoka2 (1.Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 2.Department of Geology, Faculty of Science, Niigata University)

Keywords:ductile deformation, Permian, radiolaria, pelagic chert, sandstone dike, Akiyoshi terrane

Deformation structure of consolidated cherts would record its diagenetic process. The Akiyoshi terrane, which is a Permian accretionary complex of the Inner Zone of Southwest Japan, contains Permian cherts. However, there are a few studies that have described the deformation structure of the Permian cherts of the Akiyoshi terrane. The Yoshii Group, distributed over west Okayama Prefecture, belongs to the Akiyoshi terrane.
We discovered ductilely- and brittlely-deformed chert blocks within sandstone dikes of the Yoshii Group in the Mihara area. The ductilely-deformed chert blocks and the clay minerals within the sandstone dikes are elongated and have slightly preferred orientation.
Pseudoalbaillella sp. cf. P. longtanensis Sheng et Wang was obtained from a chert bed just below the sandstone dike. Pseudoalbaillella longtanensis is characteristic species of the P. longtanensis Assemblage-Zone corresponding tentatively to the Kungurian (Cisuralian: Lower Permian).
The presence of the ductilely-deformed cherts suggests that the siliceous deposits had yet been unconsolidated when the sandstone dikes intruded. The sandstone dikes might be originated in terrigenous clastic, which is a component of chert-clastic sequences of the Yoshii Group in the Mihara area. The Permian chert had kept unconsolidated more than 10 My in this case.