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本文对采自云南永善肖滩剖面下寒武统１００余件碳酸盐岩样品的碳氧同位素进行了分析研究。在从灯影组白岩哨段上部至筇竹寺组玉案山段碳酸盐岩碳同位素变化曲线上，梅树村组小歪头山段底部Ｃ值表现出显著负飘移。早寒武世梅树村期，碳同位素值缓慢增大，至大海段达到最大值。在筇竹寺组石岩头段底部，Ｃ值表现为明显负飘移。在玉案山段，碳同位素又开始一个新的正飘移旋回。根据同位素资料，肖滩剖面下寒武统梅树村组小歪头山段至大海段地层相当于前托莫特阶地层，筇竹寺组石岩头段与托莫特阶地层对应，玉案山段与呵特达班阶下部地层对比。小歪头山段底部标志着寒武纪沉积已经开始。
In this paper, the carbon and oxygen isotopes collected from more than 100 samples of the Lower Cambrian carbonate rocks in the Xiaokan section of Yongshan, Yunnan Province were analyzed. On the carbon isotope curve of carbonate rocks from the Upper Baiying Sentinel to the Qushan Formation Carbonate of the Qiangshu Formation, the C value at the bottom of the Xiaoyousuoshan section of Meishu Group shows a significant negative drift. During the Precambrian plum tree period, the carbon isotope value slowly increased to reach the maximum value in the sea. At the bottom of Shitanzhu Section of Qiongzhusi Formation, the C value shows obvious negative drift. In the Yushan section, carbon isotopes begin a new, positive drift cycle. According to the isotopic data, the Xiaowutou section to the Dahai section of the Lower Cambrian plum Shucun Formation in the Xiaotan section corresponds to the former Toomut stratum, and the Shiyan head section of the Qiongzhusi Formation corresponds to the Tomodut stratum. The Jushan Comparisons between the Sections and the Lower Strata Strata. The bottom of the small tilt head marks the beginning of Cambrian sedimentation.