【摘要】 通过对目前全世界元古宙———寒武纪地层中的浮游植物 (疑源类 )的统计 ,发现在新元古代晚期和早、中寒武世相对较短的时间间隔内发生了一系列的微体植物 (疑源类 )辐射和绝灭事件。而这些辐射和绝灭事件又与早期后生生物的辐射、绝灭都有密切的镜像关系。通过对古海洋的δ13 C、87Sr/ 86Sr研究 ,发现元古宙—寒武纪浮游植物 (疑源类 )的辐射演化、绝灭作用与古海洋环境变化有着密切的关系 ,即生物辐射时期 ,δ13 C、　87Sr/ 86Sr呈现高异常 ;生物绝灭时期 ,δ13 C、87Sr/ 86Sr呈现低异常 ;冰期δ13 C呈现明显的负异常。更多还原

【Abstract】 The degradation-resistant organic-walled cell envelopes of acritarchs are the most abundant microfossils in Proterozoic and Cambrian rocks. These microfossils reveal diverse fluctuations that shed light on the nature of the records of primary producers near the Proterozoic/Cambrian boundary. From statistics on known microfossil assemblages in Proterozoic and Cambrian rocks, it is found that the characteristic macrobiotas of the Late Neoproterozoic and the Early, Middle Cambrian blossomed over relatively narrow time ranges. Owing to extinction in the Late Vendian, the number of species decreased to the primary level before the radiation of Neoproterozoic phytoplanktons (acritarchs), followed by the rapid rise of speciation levels in the early Early Cambrian, a quick decrease in the Late Early Cambrian, a rapid rise in the early Middle Cambrian, and extinction in the late Middle Cambrian. Acritarchs were at the base of the marine trophic chain together with bacteria and other protests that are largely unrepresentative in the fossil record. For this reason, the rise of diverse Neoproterozoic and Cambrian protistan planktons must have been essential for early marine metazoan differentiation. Indeed, the patterns of total diversity, speciation, and extinction of Neoproterozoic and Cambrian acritarchs clearly mirror those of contemporaneous marine invertebrate fauna at the genetic level. From δ 13C, 87Sr/ 86Sr values of the Neoproterozoic and Cambrian seas, it is discovered that the patterns of total diversity, speciation, and extinction of Neoproterozoic and Cambrian acritarchs and the evolution of the contemporaneous marine environment are closely related to each other, i.e.,δ 13C, 87Sr/ 86Sr rise during radiation; δ 13C is negative, and 87Sr/ 86Sr decreases during extinction. During the glacial period,δ 13C is obvious negative and 87Sr/ 86Sr decreased evidently.更多还原