[B-CG06] Decoding the history of Earth: From Hadean to the present

[BCG06-14] Deep-sea redox variations in deep-sea Panthalassa during the Pliensbachian-Toarcian Oceanic Anoxic Event (Early Jurassic)

*Masayuki Ikeda¹, Rio Miyata¹, Hiroki Kamikura¹, Yuki Nakagawa¹, Yoshimi Kubota², Benjamin Breeden² (1.University of Tokyo, 2.National Museum of Nature and Science )

Keywords:Jurassic, radiolaria, anoxia, euxinia

Recent global warming increased biological production in the tropics is causing anoxia in intermediate and deep waters. Future predictions suggest that planktonic diversity in the tropics will decrease with further warming, but the tipping point is not clear. In this study, we examined the response of marine ecosystems to rapid warming based on the relationship between carbon isotope stratigraphy, pelagic redox and biogenic silica fluxes during the Toarcian hyperthermal event (183 Ma). The results showed that bottom and intermediate waters became anoxic and hypoxic, while they became hypoxic and hypoxic during the Toarcian oceanic anoxic event (T-OAE). In the latter period, the geometric mean grain size of fine-grained strawberry pyrite was less than 5 μm and the euxinic water mass reached the pelagic zone, and thez development of this euxinic water mass may have suppressed radiolarian production due to their toxic environment. The development of this euxinic water mass corresponds to a warm period when the Tethys Sea low-latitude water temperature reaches ~30°C, which may require further constraints on the tipping point.