JpGU-AGU Joint Meeting 2017

Presentation information

[EJ] Poster

B (Biogeosciences) » B-CG Complex & General

[B-CG09] [EJ] Phanerozoic biodiversity change: Extinction and diversification

Tue. May 23, 2017 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall HALL7)

convener:Yukio Isozaki(Department of Earth Science and Astronomy, Multi-disciplinary Sciences - General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo), Yusuke Sawaki(The University of Tokyo)

[BCG09-P05] Stable and radiogenic strontium isotope variation (δ88Sr, 87Sr/86Sr) in Middle-Upper Permian mid-oceanic paleo-atoll carbonates

*Tomomi Kani1, Yukio Isozaki2, Keiji Misawa3, Shigekazu Yoneda4 (1.Division of Natural Science, Kumamoto University, 2.The University of Tokyo, 3.National Institute of Polar Research, 4.National Museum of Nature and Science)

Keywords:Sr isotope, Permian, carbonate

Stable strontium isotope ratios (δ88Sr) of the Capitanian (late Guadalupian) to Wuchiapingian (early Lopingian) carbonates were measured by TIMS, by correcting isotope fractionation during mass spectrometry with 87Sr-84Sr double spike. The studied carbonate section at Akasaka (Japan) in the Jurassic accretionary complex was originally deposited on a mid-Panthalassan paleo-seamount, which recorded a unique interval with extremely low 87Sr/86Sr values (the Permian minimum for ca. 5 m.y. throughout the entire Capitanian). We also analyzed the Wuchiapingian section at Lianshan in S. China, which was deposited on the shallow shelf. Both in δ88Sr and radiogenic 87Sr/86Sr ratios, low values remained throughout the Guadalupian, whereas they increased rapidly in the Wujiapingian. The newly obtained δ88Sr profile of Middle-Late Permian seawater positively correlated with that of 87Sr/86Sr ratio. As seawater δ88Sr could sensitively reflect marine carbonate flux at the ocean floor, this correlation suggests that the valance between the Sr carbonate burial flux and Sr carbonate dissolution flux has changed sharply across the Guadalupian-Lopingian boundary. The Capitanian minimum and the following rapid increase in seawater 87Sr/86Sr likely reflected a major change in continental flux, probably reflecting the rapid deglaciation together with enhanced erosion/weathering of continental crusts on a global scale.