Division of sedimentary facies and sequence stratigraphy of the foreland basin in the Longmen mountain area, Sichuan

The NE-trending Mesozoic and Cenozoic continental strata crop out on a wide range of scales in the Wenchuan-Dujiangyan-Chongzhou-Dayi zone of the Longmen mountain area, Sichuan.The sedimentary facies in these places were once explored by the author during the surveying of the 1:50000 Sanjiang Sheet and Wanjiaping Sheet from 1997 to 1999.These sedimentary facies may be assigned, in terms of sediment filling sequence, depositional bounding surface, facies transformational surface and isochronous surface, to alluval fan facies, fluvial facies, lacustrine facies and delta facies. Six tectonic sequences are also recognized and discussed in detail.