泥盆纪晚期F/F生物灭绝事件的Li同位素限定

最新的研究表明海相碳酸盐Li同位素是探讨重大地质事件与古环境变化之间联系的全新手段。申请人团队对二叠/三叠（PTB）剖面的Li同位素调查显示，火山喷发导致的大陆风化作用的剧烈变化是引发史上最大生物大灭绝事件的重要机制。本申请项目拟在此基础上，对我国华南地区纪录泥盆纪晚期F-F生物灭绝事件的海相沉积碳酸盐展开系统的Li同位素地球化学研究，探讨F/F事件发生的机制，深化和推广Li同位素在这一领域的应用，重点获取以下几方面的信息：（1）建立泥盆纪晚期F/F事件发生期间我国华南地区经典沉积地层的Li同位素组成特征剖面；（2）重建事件发生前后一段时间内古海水Li同位素的演化历史；（3）重点考察F/F事件的前后两幕，即上、下Kellwasser事件发生期间，海水Li同位素记录的相关气候、环境和生物演化关系；（4）在此基础上，比较二叠纪末期和泥盆纪晚期生物灭绝事件在环境变化“触发”机制上的可能异同。

Recent studies have demonstrated that lithium isotopic characteristics of ancient seawater could truly record important information for global climate changing process that related to the occurrence of many great geological events like massive extinction. Lithium isotope geochemistry is thus becoming a powerful new tool for exploring the relationship between global climate change and the initialing mechanism of great geological events. A recent study by the applicant’s group revealed that, sedimentary rocks at the Permo–Triassic boundary (PTB) of the Meishan section in South China have extremely light Li isotopic compositions, which reflect the Li isotopic characteristics of ancient seawater in the occurring period of the most severe mass extinction in the history of animal life. Based on the data we suggest that a rapid enhancement of continental weathering that resulted from the extensive eruption of the Siberian Traps might have led to marine eutrophication, anoxia, acidification, and ecological perturbation, ultimately resulting in the end-Permian mass extinction. Based on these new observations we aim to deepen the study with detailed investigations of Li isotopic compositions of marine carbonates in South China that related to the F/F massive extinction event in the late Devonian, aiming to understanding the environmental factors responsible for the event. In particular we are intent to (1) understand the Li isotopic characteristics of marine carbonates relating to the F/F event in South China, (2) reveal the Li isotope evolution trend of ancient seawater in the period just before- and after- the event, (3) understand the correlations between global climate, local environment and massive extinction events that recorded by Li isotopic compositions of seawater for the Upper Kellwasser and the Lower Kellwasser，which represent the two individual stages of the F/F event, and (4) compare the possible difference between the mechanisms that initiated the F/F event and the PTB massive extinction.