华南早二叠世环境事件及其蜓类有孔虫响应

Late Paleozoic Ice Age is the longest of continuous glaciation in Phanerozoic, and affected almost the whole Gondwana during its acme of Early Permian. In Sakmarian the majority of ice sheets collapsed, indicating the temperature rising, and resulted in a global transgression. The glacial-postglacial transition marks the step of Earth out of an icehouse period into a greenhouse, and therefore is a crucial event in geological history. The transition made significant influence to the low latitude region such as South China. During the transition the continental sea of South China was midst the transgression, although interrupted by the uplifting of Upper Yangtze land and retreated rapidly. The carbonate fossil trace element changed abruptly during late Sakmarian-Artinskian, indicating a rapid environmental transformation. Fusulinid foraminifer is a major component of the Late Paleozoic marine ecosystem in South China and its evolutionary turnover took place in this period. All of these suggest South China has been through a significant environmental transition in Early Permian. However the aiming studies are far less than sufficient. This project will aim at the glacial-postglacial transition period, select the well-preserved, continuous sections of diversified carbonate facies containing abundant fusulinid fossil, and conducted an integrated study combining sedimentology, fusulinid paleontology and evolution and geochemistry. The study is designed to disclose the environmental change and evolutionary responses of fusulinids, which will provide more details for this global transition event.

晚古生代冰期是显生宙持续时间最长的冰期，在早二叠世的高峰期时冰川覆盖几乎整个冈瓦纳大陆。早二叠世Sakmarian期冰川主体开始迅速消融，温度升高，进入冰后期，全球海平面显著上升，地球气候从“冰室”转换至“温室”，是一次重要的环境事件。这次冰期-冰后期的环境转换对处在低纬度的我国华南地区也产生了显著的影响。在这一全球环境转换阶段，华南地区在沉积序列上表现为海侵过程，微量元素发生明显的变化，蜓类有孔虫动物群发生重要更替，都显示了其环境变化与全球可能存在同步性，但对这些现象尚缺乏系统的研究。本项目将在华南地区选择发育良好的、不同碳酸盐相的晚石炭-早二叠世连续剖面，进行沉积学、地球化学、蜓类有孔虫演化特征等的精细研究，对比不同相区的海平面、温度、含氧量等环境因子变化与蜓类有孔虫演化的响应关系，为晚古生代冰期-冰后期转换的重大环境事件提供更为详细的信息。

项目研究目标在于通过对华南二叠纪Asselian-Artinskian期环境变化过程以及蜓类有孔虫的生物学响应的综合与定量研究，厘清晚古生代冰期阶段低纬度地区的环境变化过程，揭示这一环境事件对海洋底栖生物的可能影响。项目通过对晚古生代冰期海洋生物的宏观演化过程、华南早二叠世蜓类的形态演化过程、华南早二叠世沉积环境变化与生物响应等三方面的研究，揭示出冰期阶段蜓类生物发生适应辐射的过程及其特殊的发育机制。. 项目揭示并确立了晚古生代大冰期阶段，海洋生物物种多样性快速升高，在早二叠世达到最高峰，是古生代最大规模的一次海洋生物多样化事件。在多样化事件的最高峰时期，球形䗴有孔虫演化出特殊的复合式异时发育机制，体现出特殊的形态适应。辐射高峰期之后，华南的䗴类出现类群分异，与沉积环境具有高度的对应关系。结合地球化学信号分析与有孔虫动力学实验结果，初步得到早二叠世海洋环境发生突变，蜓类的形态分异则与之响应。. 项目研究中获得的晚古生代大冰期阶段海洋生物宏观演化模式、化石有孔虫地球化学分析方法，为高分辨率生物多样性演化模式的研究、生物与环境协同关系的研究提供了重要基础。生物形态演化研究路径以及机制探索、有孔虫沉积动力学特征，则在生物个体演化、沉积动力学研究上，具有鲜明的独创性，在生物演化、化石沉积与埋藏的研究上可提供重要参照。