扬子地区奥陶纪-志留纪转折期古气候变化

The latest Ordovician was an important interval in the Phanerozoic. During this time, profound climatic, marine environment and biotic changes occurred in which the mass extinction is one of the greatest five ones in Phanerozoic. Climatic change and biological evolution are close related. However, climatic changes and its dynamic mechanism and their relationship with the massive biotic extinction during the Ordo-Silurian transition were not well documented and constrained. In this study, typical sections across the Ordo-Silurian transition in the Yangtze area will be selected, upon which detailed studies in stratigraphy, sedimentology and geochemistry will be carried out. Based on the characteristic proxies for climatic changes, i.e., clay mineralogy, magnetic susceptibility and chemical weathering index, high-resolution climatic changes and its dynamic mechanism and their relationship with the mass extinction will be explored. This study is of important scientific significance for understanding the climatic changes, driving mechanism, atmosphere-ocean-biosphere interactions and the earth''s surface evolution during this important geological period.

晚奥陶世是一个重要的地质转折期，全球气候、海洋环境和生物界面貌都发生了重大的变化，在该时期发生的生物集群绝灭事件是显生宙五大生物绝灭事件之一。气候环境变化与生物演化关系密切。然而目前对奥陶纪-志留纪转折期气候环境变化、动力机制以及与生物绝灭的关系尚缺乏深入研究。本项研究将选择扬子地区上奥陶统-下志留统的典型剖面，对其进行详细地层-沉积学和地球化学等研究，利用气候特征指标（粘土矿物、磁化率和化学风化指数）分析该时期气候环境高分辨的变化过程及动力机制，进而探讨气候环境变化与生物绝灭事件的内在联系。本项研究对于了解重要地质历史时期气候特征、变化机制、大气-海洋-生物圈相互作用特点和地球表层演化具有重要的理论意义。

晚奥陶世是一个重要的地质转折期，全球气候、海洋环境和生物界面貌都发生了重大的变化，在该时期发生的生物集群绝灭事件是显生宙五大生物绝灭事件之一。气候环境变化与生物演化关系密切。然而目前对奥陶纪-志留纪转折期气候环境变化、动力机制以及与生物绝灭的关系尚缺乏深入研究。本项研究选择扬子地区上奥陶统-下志留统的典型剖面，对其进行详细地层-沉积学和地球化学等研究，利用气候特征指标分析该时期气候环境高分辨的变化过程及动力机制，进而探讨气候环境变化与生物绝灭事件的内在联系。研究表明扬子地区五峰组下部和龙马溪组是在温暖湿润的气候环境下形成的。但五峰组上部N.extraordinarius-N.ojsuensis笔石带气候条件不稳定，总体处于寒冷干燥气候，曾短暂转入温暖湿润气候。晚奥陶世两幕生物绝灭事件的时间与气候变化的时间高度吻合，表明气候变化对生物演化起着至关重要的作用。本项研究对于了解重要地质历史时期气候特征、变化机制、大气-海洋-生物圈相互作用特点和地球表层演化具有重要的理论意义。