JpGU-AGU Joint Meeting 2020

Presentation information

[E] Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS14] Evolution of Pelagic Realm

convener:Atsushi Matsuoka(Department of Geology, Faculty of Science, Niigata University), Toshiyuki Kurihara(Graduate School of Science and Technology, Niigata University), Tetsuji Onoue(Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University), XIN LI(State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences)

[MIS14-P01] Preservation of Permian–Triassic boundary section in the Jurassic accretionary complex of the Lake Hamana, Central Japan

*Wang Ding1, Kohtaro Ujiie1, Katsuo Sashida1 (1.University of Tsukuba)

Keywords:P–T boundary, black carbonaceous claystone, Lake Hamana

The Permian-Triassic (P–T) boundary has been received extensive attention, because it recorded the largest mass extinction event in Earth’s history. However, the entire P-T section has been rarely preserved in the pelagic sedimentary rocks. We examined the lithostratigraphy and deformation structures of the accreted pelagic rocks in Lake Hamana, Central Japan, based on a detailed field mapping and the radiolarian ages. The constructed lithostratigraphy is composed of Late Permian gray chert, black chert, black claystone with a high carbon content of 4.86%–6.78%, siliceous claystone, black chert, and middle Triassic gray chert, in the ascending order. The symmetry in the lithostratigraphy and the change in the radiolarian ages with respect to black carbonaceous claystone are presumed to represent a deep-sea anoxic event that occurred across the P–T boundary. The P–T boundary black carbonaceous claystone suffered from an intense shear, resulting in blocks of siliceous claystone in the scaly black claystone matrix. In places, the sheared terrigenous rocks composed of sandstone blocks in the mudstone matrix are intercalated into the pelagic rocks, possibly representing complex mélange forming processes during the development of the Jurassic accretionary complex.