[B-CG07] Phanerozoic biodiversity change: radiation and extinction

[BCG07-05] Permian Panthalassan Sr budget change

*Tomomi Kani¹, Yukio Isozaki², Keiji Misawa³, Akira Ishikawa⁴, Shigekazu Yoneda⁵ (1.Department of Earth and Environmental Sciences, Kumamoto University, 2.The University of Tokyo, 3.National Institute of Polar Research, 4.Tokyo Institute of Technology, 5.National Museum of Nature and Science )

Keywords: δ88Sr, 87Sr/86Sr, carbonate, seawater

The radiogenic Sr isotopic composition (⁸⁷Sr/⁸⁶Sr) of the Phanerozoic seawater has been fluctuated according to global tectonics and/or climate change. The major Sr fluxes to drive ⁸⁷Sr/⁸⁶Sr in seawater are three-fold; i.e., weathering of highly radiogenic continental silicates, non-radiogenic submarine hydrothermal fluid, and weathering of less radiogenic carbonates and basalts from island arc/oceanic island. During the Phanerozic, seawater ⁸⁷Sr/⁸⁶Sr changed most dramatically around the Middle/Late Permian boundary marked by a major mass extinction. Stable Sr isotope (δ⁸⁸Sr) in seawater is recently recognized as an useful proxy for estimating ancientburial/dissolution of marine carbonate. The δ⁸⁸Sr values were consistently low in the Middle Permian and began to increase during the Late Permian. The timing of thistrend change across the G-LB corresponds to that of ⁸⁷Sr/⁸⁶Sr. This significant change of ocean Sr budget in the Phanerozoic might be explained by increase/decrease of carbonate weathering on continental shelves with respect to the long-term cooling/warming associated with global sea level change.