Sedimentary facies and sequence stratigraphy of Upper Permian Changxing Formation in Pingtang, Guizhou Province

Abstract：Using the basic principles and methods of sedimentology and sequence stratigraphy, combining field measurements with indoor microscopic study, and applying drilling data to correlating data of regional sequence stratigraphy, the authors studied and summarized sedimentary facies characteristics, sequence stratigraphy and lithofacies paleogeography distribution of Upper Permian Changxing Formation in Pingtang, Guizhou Province.. The results demonstrate that three kinds of sedimentary environments exist in Upper Permian Changxing Formation, i.e., open platform, shoal of platform margin and inter-platform basins. The Changxing Formation of the study area can be divided into two third-order sequences of PSQ1 and PSQ2, and both are composed of the transgressive systems tract (TST) and the highstand systems tract (HST), with the thickness of TST larger than that of HST. A comparison with the sedimentary facies and sequence stratigraphy characteristics of adjacent areas indicates that the sedimentary environments of Changxing Formation must have been open platform, shoal of platform margin and deep inter-platform basins in vertical direction. In the eastward transverse direction, there formed the sedimentary belt of shallow-water carbonate platform and deep basin sediments in the area of Anshun to Ganzhai during the PSQ2 period of late Permian. During late Permian, sea began the transgression from south to north.