Japan Geoscience Union Meeting 2023

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H (Human Geosciences ) » H-CG Complex & General

[H-CG22] Earth surface processes related to deposition, erosion and sediment transport

Mon. May 22, 2023 3:30 PM - 5:00 PM 201B (International Conference Hall, Makuhari Messe)

convener:Koji Seike(Geological Survey of Japan, AIST), Masayuki Ikeda(University of Tokyo), Kazuki Kikuchi(Division of Earth and Planetary Sciences, Guraduate School of Science, Kyoto University), Hideko Takayanagi(Institute of Geology and Paleontology, Graduate School of Science, Tohoku University), Chairperson:Masayuki Ikeda(University of Tokyo), Kazuki Kikuchi(Division of Earth and Planetary Sciences, Guraduate School of Science, Kyoto University), Koji Seike(Geological Survey of Japan, AIST)

3:45 PM - 4:00 PM

[HCG22-07] Imprecations for low latitude terrestrial environment from Cretaceous deep-sea chert

*Yuki Nakagawa1, Julien Legrand2, Maximilien Bôle1, Ryosuke Saito3, Hitoshi Hasegawa4, Masayuki Ikeda1 (1.The University of Tokyo, 2.Department of Geosciences, Shizuoka University, 3.Department of Geosphere Sciences, Yamaguchi University, 4.Department of Global Environment and Disaster Prevention, Faculty of Science and Technology, Kochi University)


Keywords:Cretaceous, OAE, Flood sediment

Cretaceous oceanic anoxic event (OAE) was accompanied with large igneous province, which increased atmospheric pCO2 and accelerated continental weathering caused the eutrophication and anoxic ocean. However, how the low-latitude terrestrial environment, which is responsible for most of the continental weathering, changed during the OAE is still unknown. In this study, we attempted sedimentological analyses using Field Emission Electron Probe Micro Analysis (FE-EPMA) for the Aptian deep-sea chert in the Goshikinohama section to estimate the sedimentary environment. Across the Aptian OAE 1a, several silt to very fine sand layers with inverse-grading and normal-grading were identified in some cherts, interpreted as hyperpycnites, possibly derived from oceanic islands because of their mafic composition. Nakagawa et al. (2022) reported terrestrial organic matters from the same interval and suggested that an increased vegetation and intensified hydrological circulation have linked the terrestrial organic matters discharge during OAE 1a with high atmospheric pCO2 level. Recognition of hyperpycnite further support this idea. According to their linear sedimentation rate of 1 mm/kyr, massive flood discharge in low latitude area might have repeated on timescale of several hundreds to thousands years. An increased precipitation at low latitudes may have increased weathering rate through soil erosion and may have been one of the factors that expanded anoxic water mass.