安徽巢湖地区二叠系瓜德鲁普统孤峰组古环境演化

二叠纪瓜德鲁普世是古海洋条件发生重大变化的转折期。瓜德鲁普世古海洋、古环境的演化对古生代底栖无脊椎动物灭绝的影响仍然是个谜。利用元素地球化学,分析瓜德鲁普统孤峰组的陆源碎屑供应、海洋表层水体的初级生产力以及底部水体的氧化还原条件。结果表明:瓜德鲁普世早期和晚期分别发生了一次陆源碎屑输入的高峰期。瓜德鲁普世早期海洋初级生产力最高,中期海水初级生产力较低,而晚期稍有升高。瓜德鲁普世古海水主要为缺氧至硫化环境。瓜德鲁普世早期以贫氧至缺氧环境为主,间歇性出现硫化环境;中晚期则以硫化环境为主,间歇性出现缺氧环境。这些氧化还原环境的演化主要受到水动力条件的影响。瓜德鲁普世深水环境水体的持续缺氧硫化引发浅水台地底部水体的持续贫氧甚至缺氧,造成海洋生态系统变得脆弱,引发生物危机事件。

Paleoenvironmental Evolution in the Guadalupian (Permian) Gufeng Formation in Chaohu Area,Anhui

The Guadalupian(Permian)period was a critical transition of paleo-ocean conditions.The effect of the paleo-ocean and paleo-environmental conditions on the Guadalupian mass extinction of benthic paleo-invertebrates is still a mystery.Here,we analyzed terrestrial detritus input,surface water primary productivity and bottom water redox conditions in the Guadalupian Gufeng Formation via elemental geochemistry.The results show high terrestrial detrital inputs in the Early and Late Guadalupian.The primary marine productivity was the highest in the Early Guadalupian,low in the Middle Guadalupian,and relatively high in the Late Guadalupian.The paleo-water column was mainly anoxic to euxinic in the Guadalupian.The Early Guadalupian was mainly suboxic-anoxic with intermittent euxinic episodes,while the Middle-Late Guadalupian was mainly euxinic with intermittent anoxic episodes.The environmental redox evolution may have controlled mainly by hydrodynamic conditions.The persistent anoxia/euxinia of the deep-water environment in the Guadalupian may have led to persistent suboxia(or even anoxia)of the shallow-platform bottom water,causing vulnerability to the marine ecosystem and eventually biocrisis events.