A Study on Sedimentary Characteristics of Upper Triassic Xujiahe Formation in the Eastern Margin of Sichuan Basin

Based on outcrop data,both stratigraphic and lithological characteristics of Upper Triassic Xujiahe formation in the eastern margin of Sichuan basin are analysised in this paper,and its sedimentary characteristics was summarized,too.Xujiahe formation is dominated by sand-stones with a little silty mudstones,which is believed to be the product of fluvial environment by analysis of sedimentary marks.The braided river deposits are developed in the lower-middle part of this formation including several microfacies such as channel bar,flooding plain,valley depression and valley marsh,etc.The meandering river deposits appear in the top part of this formation,including microfacies such as pointbar and flooding plain,etc.The channelbar sandstone is the main reservoir,meanwhile valley depression and valley marsh is the good site for source rocks accumulation.The mode of sedimentary facies of Xujiahe formaton is put forward in this paper.