Abstract

The Sinian and Cambrian systems within the Yangtze stratigraphic province represent continuous deposits. The Meishucun section in Jinning County, Yunnan Province serves as the stratotype section for the Sinian-Cambrian boundary and is the Chinese candidate for the global stratotype section and point for the Precambrian-Cambrian boundary. The present paper, with the various charts and tables, elaborates on several typical Sinian-Cambrian boundary sections and the distribution of fossils in them. In accordance with the characteristics of biological evolution, three biotas can be recognized for the period from the late Sinian to the Early Cambrian. The first biota appeared in the late Sinian, characterized by the presence of the soft-bodied metazoans; the second biota occurred during the Meishucun Stage of the Early Cambrian, and is characterized by the appearance and prevalence of small shelly fossils from many different phyla; and the third biota came into existence during the Qiongzhusi Stage of the Early Cambrian; it is characterized by the first appearance and prevalence of trilobites. The Meishucun Stage of the Lower Cambrian can be divided into three fossil zones. The Sinian-Cambrian boundary is placed at the base of the first Anabarites-Circotheca-Protohertzina Zone. According to isotopic dating by the Rb-Sr whole-rock isochron technique, the age of the Sinian-Cambrian boundary is inferred to be 610+ or -10 Ma.--Modified journal abstract.

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