[B-CG09] [EJ] 顕生代生物多様性の変遷：絶滅と多様化

[BCG09-P05] ペルム紀中期後期炭酸塩の放射起源Sr同位体とSr安定同位体変動

*可児 智美¹、磯崎 行雄²、三澤 啓司³、米田 成一⁴ (1.熊本大学大学院先端科学研究部、2.東京大学　、3.極地研究所、4.国立科学博物館)

キーワード：Sr同位体、ペルム紀、炭酸塩

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.