Cenozoic erosional history of the Altyn Tagh Mountains inferred from the sedimentary record of the foreland basin

The Janggalsay basin, Qiemo County, Xinjiang, is located in the northwestern front of the Altyn Tagh Mountains, where Meso-Cenozoic sediments are continuously deposited. The Paleocene to Eocene inside the basin are fluvial sediments; the Oligocene to Miocene are piedmont fluvial brown conglomerates and brown sandstones; the Pliocene is piedmont diluvial conglomerates with mudstones; the lower Pleistocene is all composed of conglomerates. The characteristics of the lithological associations and variation in composition of detritus in sandstone and pebbles in conglomerate reveal the erosional history of the Altyn Tagh Mountains. Paleozoic bimodal volcanic rocks were firstly eroded during the Paleocene to Eocene, and the topographic height difference between the Altyn Tagh Mountains and the Janggalsay basin was small. This difference became large during the late Oligocene to early Miocene, and the Proterozoic basement was exposed subseguently and eroded. The denudation ration increased at the end of the Miocene. The Lower to Middle Proterozoic basement rocks were exhumed to the surface till the Early Pleistocene when the Xiyu Formation began to deposit. Analysis of regional data indicates that the Altyn Tagh Mountains were uplifted by stages and experienced three rapid uplift events in the Cenozoic, i.e. from the terminal Oligocene to early Miocene, in the late Miocene (Ca 8 Ma BP) and early Quaternary.