The preliminary boundary of the West Sichuan foreland basin and orogenic belt and its migration in the central Longmen Mountains,Sichuan,China

Through comprehensive studies of the tectonic deformation and development of the orogenic belt,foreland basin,klippe and combined with the provenance analysis of the foreland basin,the preliminary boundary is determined and the migration process of the West Sichuan foreland basin is reconstructed.The research indicates that the preliminary boundary fault between the West Sichuan foreland basin and the orogenic belt is Maowen fault,and the klippes distributed over the thrust zone in the foreland basin were from the areas between the Maowen fault and the Beichuan-Yingxiu fault.The southeastern extrusion of the Songpan-Ganzi orogenic belt during the Indosinian-Yanshan epoch is responsible for the deformation and thrusting uplift of strata between the Maowen fault and the Beichuan-Yingxiu fault.It resulted in the development of NE trending structure.The exhumation of carbonate rock strata as the foreland basin basement is the potential roots of klippes.With the thrust sheets uplift and progression from NW to SE,the west boundary of the West Sichuan foreland basin migrates gradually from the preliminary Maoxian-Wenchuan fault to the Beichuan-Yingxiu fault,the Peng-Guan fault and the east of the Guankou-Zhangming fault in turn.