UNROOFING HISTORY OF THE WEST KUNLUN VIEWED FROM THE PETROGRAPHY OF SANDSTONE AND CONGLOMERATE FROM YECHENG SECTION,XINJIANG

Late Cenozoic foreland basin deposits in Yecheng are composed of Moocene mudstone and sandstone(Wuqia Group),Early Pliocene sandstone with minor gritstone(Artux Formation) and Late Pliocene-Early Pleistocene conglomerate(Xiyu Formation). The Miocene strata are dominated by fine-grained clastic material,indicating a distal source and low gradient slope. Palaeocurrent measurements suggest a northward direction,indicating that the Kunlun area was at low elevation. Deposition of Artux Formation marked the first appearance of gravel and lithic detritus,indicating the uplift of Kunlun. Xiyu Formation is characterized by coarse debris flow deposits,marking the strong uplift of the northern part of Tibetan Plateau and unroofing of the West Kunlun.