Evolution of the western Sichuan basin and its superimposed characteristics,China

The western Sichuan basin is located in the eastern margin of Songpan-Ganze tectonic zone of Tibetan Plateau.Since Sinian,the western Sichuan basin has been involved into two evolution histories,including the basin evolutions of both marine facies and terrestrial facies.The development for the terrestrial facies basin of the western Sichuan basin has very close relationship with the formation and evolution of Songpan-Ganze tectonic zone and Longmenshan orogenic belt.Since Late Triassic,the western Sichuan basin has experienced the coupling of basin and range,as well as the coupling of basin and mountain with Songpan-Ganze tectonic zone and Longmenshan orogenic belt,which resulted in the complex superimposed basin strata with multiple evolution histories.Different basin characteristics and types have been shown in different geological times.In summary,there are four different basin evolution developments,consisting of stable craton marine facies basin(Sinian-Mid Triassic),alternate marine and terrestrial facies downfaulted basin(Xujiahe FM I-Xujiahe FM III of Upper Triassic),terrestrial depressed basin(Xujiahe FM IV of Upper Triassic-Mid of Jurassic),and foreland basin(Upper Jurassic-present),which contributes to the superimposed strata features of the western Sichuan basin with four evolution periods.