Late Cenozoic uplift of the northwestern margin of the Qinghai-Tibet Plateau:Sedimentary evidence from piedmont basins of the West Kunlun Mountains.

The study of Late Cenozoic sedimentary characteristics in the piedmont basins on the north margin of the West Kunlun Mountains shows that various sedimentary sequences developed along the piedmont of the West Kunlun Mountains have similar characteristics in vertical sections. Paleogene deposits consist of gypsum beds, limestone containing lamellibranches and purplish red fine clastic rocks, indicating a quiet marine and paralic sedimentary environment. Continental molasses started deposition from the latest Miocene-earliest Pliocene, indicating an unquiet continental sedimentary environment. The tendency of coarsening-upward of gravels may indicate the accelerated uplift of the West Kunlun. The intervals of almost invariable gravel diameters may mark the intermittency of tectonic movement or stable deposition, indicating a pulsating uplift model. The molasses are mainly composed of sedimentary rocks at the bottom and igneous rocks and metamorphic rocks at the top, indicating acceleration of denudation. According to the features of the molasses, both the volume and intensity of denudation have a tendency of decreasing and weakening from west to east, implying easterly weakening of the tectonic uplift of the West Kunlun during the Late Cenozoic. The conclusion also coincides with the result of morphotectonic research in the area.