The Study on Sedimentary Facies of Changlongshan Formation of Neoproterozoic Era in Huailai, Hebei

Changlongshan format ion of N aproteroziic Era in Huailai Hebei is consists of rnainly a sedimentary assoriation of clastic rock with rich macroalgal forssils (Churaia). Studying the sedimentary environment will have an important significane to the ecology of rnacrtalgal organisrns and paleogeography evolution. Three sedimentary facies are tidal flat, shallowshelf and beach facies, which are established through the analysis lithofaies and the study geochernistry in the section. Therefore the sedimentary medel is raised on the basis of sedimentary facies analysis. The Changlongshan formation shows the cyclical accumulation of the three sedimentary facies, and consisting of two sedimentary equences of clastic rock. The evolution feature in the lower of sedimentary Sequences is from the tidal flat facies to shallow shelf facies,then back to beach system. The upper directly develope into the shallow shelf facies, then tobeah facies. The Chudria formed mainly in the offehore shale subfacies of the shallow shelf facies. Cimprehensive analysis shows that sedimentary environrnent of Changlongshan formation is the littoral and neritic sea controled by the tidal, sea wave and river.