寒武纪早期是地球生命演化史上最重要的阶段之一，期间发生了著名的寒武纪生命大爆发，以及两次全球性的生物灭绝事件。目前国内外学者主要聚焦于寒武纪生命大爆发的研究，而对第四期生物灭绝事件的重视程度远远不够。实际上，生物灭绝事件的研究是对生物繁盛和辐射的反证，对于认清寒武纪时期生命兴衰的主要控制因素至关重要，因此相关工作亟待推进。下扬子地区发育有两个连续的第四阶钻井剖面，为系统开展古环境特征和生物事件成因的研究提供了极好的素材。本项目拟通过系统的古生物和稳定同位素地层学工作建立地层时代框架；之后运用多种地球化学手段查明第四期海水氧化还原条件的演化过程；最后对第四期古环境演化和生物事件之间的相关性进行全面分析和深入讨论。项目研究结果能够清晰地揭示寒武纪第四期下扬子地区海水氧化还原条件的时空变化，并推进对生物演化事件成因等问题的认识，具有重要的研究价值和科学意义。

Early Cambrian is one of the most important stages in the geological history of biological evolution on earth, during which the “Cambrian explosion” and two global extinction events occurred. Current research of lower Cambrian strata has been focused on the “Cambrian explosion”, yet very limited attention has been paid to the extinction events during Cambrian Stage 4. In fact, a combination of research on biological radiation and extinction events is essential to understand what controlled the biological flourishment and depression during early Cambrian. Therefore, to construct a complete picture of the palaeoenvironmental and biological evolution during early Cambrian, it is urgent to expand global research on Cambrian Stage 4. Recently, two continuous drilling profiles of Stage 4 have been found in the Lower Yangtze Platform, which provide an excellent opportunity for systematic studies on palaeoenvironmental evolution and the origin of biological events during Stage 4. In this project, we plan to carry out systematic studies of palaeontology stratigraphy and stable isotope chemostratigrapy so as to construct a clear stratigraphic framework of the drilling profiles. Based on the stratigraphic framework, we will figure out the evolution of redox conditions in the ocean during Stage 4 with multiple geochemical proxies. Finally, a detailed discussion of the relationship between palaeoenvironmental evolution and biological events will be presented. The results of this project can reveal the temporal and spatial variation of redox conditions in the ocean, and lead to a better understanding of the cause of biological radiation and extinction events during Cambrian Stage 4.