THE STRATIGRAPHICAL DIVISION AND MIDDLE CAMBRIAN OF THE LOWER CAMBRIAN IN SOUTHERN JILIN PROVINCE

In this paper, ample evidence is presented to deal with the stratigraphic division of the Lower Cambrian at the northern margin of the North China platform. From above downwards its succession of strata is the Mantou Forma- tion, Jianchang Formation, Heigou Formation and Shuidong Formation. They may be correlated with the strata of Longwangmiao, Canglanpu, Qiongzhusi and Meishucun ages in southwestern China. In particular, the discovery of small shelly fossils implies that the lower boundary of the Cambrian should be placed between the Qingouzi Formation of the upper Sinian and the Shui- dong Formation of the Lower Cambrian. The small shelly fossils and trace fossils in the Shuidong Formation may be divided in descending order into two small shelly fossil assemblags and one trace fossil assemblage: （3） the Quadratheca-Hyolithellus-Linevitus assemblage, （2） the Paraglobarilus-Circotheca-Turcutheca assemblage, （1） the Phycodes-Bergaueria assemblage. They correspond to the small shelly fossils in the Badaowan Member and Zhongyicun Member of the Meishucun Stage. This is a new understanding of the lower boundary of the Cambrian of the North China platform, which is marked by the deposition of Meishucun age.