[B-CG07] 地球史解読：冥王代から現代まで

[BCG07-08] ペルム紀グアダルピアンーローピンジアン境界を跨ぐ高温燃焼事件とその最後に起きた土壌流出

*海保 邦夫¹、Stephen Grasby²、Zhong-Qiang Chen³ (1.東北大学、2.カナダ地質調査所、3.中国地質大学)

キーワード：燃焼事件、大量絶滅、海洋酸化還元、ペルム紀、土壌流出、火山活動

A major bio-crisis in the Guadalupian−Lopingian transition (Capitanian−Wuchiapingian, middle−late Permian), possibly driven by the volatile eruption of the Emeishan large igneous province (LIP), was marked by the first-order collapse of global metazoan reefs and decline of fusulinid foraminifera, but with only minor impacts on other marine invertebrates (brachiopod, crustacea, other foraminifera). To assess the exact cause of this event, we conducted geochemical analyses of the shallow marine strata at the global stratotype section and point of the Guadalupian−Lopingian (G−L) boundary (GLB) in Laibin, South China, which corresponds to the last step of the Capitanian bio-crises during Emeishan volcanism. Here, we detect evidence for high temperature combustion of organic matter in air spanning the GLB (indicated by enriched coronene) that was terminated by a soil erosion event accompanied with terrestrial vegetation collapse at the mass extinction level (evidenced by enriched dibenzofuran) and a carbon isotope perturbation (a 2.5−3.5‰ negative shift of δ¹³C_carb). Molybdenum data indicates oxic seawater during the combustion event, likely reflecting regression. These findings imply that large volatile volcanic eruptions of the Emeishan LIP may have caused these environmental extreme events and mass extinctions, and that relatively lower magnitude of volcanism related to Emeishan LIP may have led to impacts on terrestrial−nearshore ecosystems.