Upper Triassic stratigraphic correlation and stratigraphic sequence characteristics in western Sichuan and central Sichuan depression

Abstract：Stratigraphic correlation between Xiangxi Group in central Sichuan depression and Xujiahe Formation in western Sichuan depression remains a problem of much controversy. The stratigraphic correlation becomes more complex and difficult because of the activity, asymmetry and deposition center mobility. The landmark sequence boundaries comparable with each other in the whole depression can be identified by stratigraphic sequence analysis of well logging curve, outcrop section，and seismic reflective characteristics. Lowstand, lacustrine transgressive and highstand systems tracts can be subdivided by the stacking patterns of stratigraphy，changes of lithology， lithofacies and palaeontological data. This paper has built up a stratigraphic sequence framework based on the fourth-order sequence of Upper Triassic in western Sichuan and central Sichuan depression on the basis of stratigraphic sequence correlation in well-tied sections，and put forward a reasonable scheme of stratigraphic correlation between Xiangxi Group and Xujiahe Formation. The results obtained are of great significance in such aspects as the reconstruction of the original lithofacies palaeogeography, the distribution of sedimentation, the accurate prediction of favorable facies belts and the evaluation of hydrocarbon resources.