华南不同相区早三叠世史密斯-斯帕斯界线事件过程中海洋碳-硫循环及其对事件的响应

The Smithian-Spathian boundary Event is the most significant biological, environmental and climatic event in the Early Triassic, thus important for the studies of the co-evolutions between environmental changes and biological evolution after the end-Permian mass extinction. However, studies around the event is still lacking to date, and properties of the marine environmental changes and their relationships to the biological and climatic changes is still unclear. Our proposed study aims to investigate the Smithian-Spathian boundary Event at different sedimentary facies in South China. Firstly, sampling in high resulution at several relatively better studied Smithian-Spathian boundary sections (e.g., Lichuan, Hubei; Qingyan, Guizhou; Jiarong, Guizhou; West Pingdingshan, Chaohu) in South China. Better preserved samples were chosen and analyses of the inorganic carbon (δ13Ccarb) and sulfur isotope of carbonate associated sulfate (δ34SCAS) were carried out. Then, we reconstructed δ13Ccarb-δ34SCAS profiles of different sedimentary facies coupled with previous published geochemical data, and discussed carbon-sulfur cycling models during the Smithian-Spathian boundary Event. The timing, processes and amplitudes of marine circulation were discussed. We also discussed the reaction of environmental changes to the biological evolution, and coupling relationship between biology and environment. The present work will provide critical geochemical information for the studies of the mechanisms of the biological recovery during the Early Triassic.

史密斯-斯帕斯界线事件是早三叠世最显著的一次生物、环境与气候事件，是探讨二叠纪末生物大灭绝后地球环境和生物协同演变过程的重要研究对象。目前国内外针对该事件的研究尚在起步阶段，事件过程中海洋环境变化的具体过程以及其与生物演化和气候变化的耦合关系仍不清楚。本项目拟在华南不同相区系统开展下三叠统史密斯-斯帕斯界线事件的研究。在研究程度较高的湖北利川、贵州青岩、贵州甲戎和安徽巢湖平顶山等下三叠统剖面中的史密斯-斯帕斯界线附近进行高分辨率的全岩样品采集。选取受成岩改造较小且较“纯净”的碳酸盐岩开展无机碳同位素和碳酸盐晶格硫同位素的测试分析研究，结合前人已发表的数据，重建华南不同相区史密斯-斯帕斯界线事件过程中碳-硫同位素演化曲线、海洋碳-硫循环模式，探讨海洋环流的时间、过程及幅度；揭示海洋环境变化对早三叠世生物复苏的影响及其生物与环境耦合关系。为早三叠世生物复苏机制的研究提供更多新的地球化学信息。

史密斯-斯帕斯亚期是早三叠世生物、环境、气候演变的关键时期。本研究重点关注史密斯极热事件和史密斯-斯帕斯降温事件过程中海洋碳-硫循环过程，及其对生物环境事件的响应过程。通过对华南不同相区系列剖面（平顶山西剖面、甲戎剖面、大峡口剖面、建始剖面、齐跃山剖面）以及克什米尔地区Guryul Ravine剖面和日本Kamura剖面碳-硫同位素研究，建立了这一时期全球多地不同相区高分辨率的碳-硫同位素演变曲线。不仅厘定了史密斯极热事件以及史密斯-斯帕斯界线降温事件的时限，而且在此基础上探究了两次事件期间海洋环流模式以及海洋缺氧过程，及其与生物演化的关系。通过系列研究，显示史密斯极热事件期间全球海洋环流减弱、海洋生产力降低且缺氧加剧，史密斯-斯帕斯降温事件期间全球海洋环流增强、海洋生产力提高且缺氧减弱。极热事件可能导致了这一时期牙形石和菊石动物的小型灭绝，而史密斯-斯帕斯降温事件后海洋环境的改善促进了更高等海洋生物的出现。本研究详细论述了史密斯-斯帕斯之交生物-环境-气候之间的协同演变关系，为早三叠世生态系统复苏过程的研究提供了关键数据。