Geomorphological features of the Keriya River valley and the early-middle Pleistocene great lake of the Tarim basin

The present geomorphological features of the Keriya River valley are the results of evolution since 1.09 Ma BP and record the surface processes controlled by combined structural and climatic effects. Geomorphologically, the valley may be divided notably into the early-stage broad valley and the late-stage narrow and small deep-incised valley from the Wugeyeke River—a tributary of the Keriya River flowing out of the piedmont of the Kunlun Mountains—to the Kangsulake River of the main branch of the Keriya River. During the past five decades, the mean annual runoff has been ~734.5 million m3, and the mean annual runoff in the early broad valley development stage is estimated to be more than 14.69 billion m3. It reveals that at that time the runoff of the Keriya River was by far higher than the present observation values, which suggests that the water from the upstream and regional precipitation were much more than nowadays, and that the paleoclimate and paleoenvironment of the Tarim basin were utterly different from the desert environment of the present Tarim basin. The mudflow deposits observed in the Xiyu conglomerate along the Qira River in the adjacent area suggest that there was substantial seasonal flood in the West Kunlun Mountains in the early Pleistocene and slightly earlier, when the valley of the Keriya River was much broader. Therefore it is thought that a “great lake” should exist in the Tarim basin in the early-mid Pleistocene