Plio-Quaternary Stepwise Aridification of the Asian Inland: Multi-Proxy Records from a 938.5m Drill Core in the Western Qaidam Basin, NE Tibet Plateau

The Qaidam Basin is a largest closed basin in the northeastern Tibetan Plateau which is now under hyperarid climate. A 938.5 m-long core was drilled in the Qahansilatu depression in the western Qaidam Basin with an average core recovery rate of 95%. It consists of lacustrine grayish mudstone and siltstones with upperward increasing interbedded salt layers. High resolution paleomagnetic and OSL-U/Th dating of the core determine the core formed between 2.77 Na and 0.1 Ma. Detailed examinations of lithofacies, evaporative minerals, carbon and oxygen isotopes, grain size, bioproductivity and redox conditions collectively reveal that the climate was dry since 2.77Ma and became intensively dried at about 2.5 Ma, 2.2 Ma, 1.6 Ma, 1.2 Ma, 0.9 Ma, 0.6 Ma and 0.1 Ma. Accompanying this stepwise aridifications is the phased shrinkage of the paleo-Qaidam lake from the semi-deep brackish lake in early stage via shallow brackish lake and perennial saline lake to playa saline lake in late stage and completely dried out at the end. Episodic global cooling and tectonic uplift of the NE Tibetan Plateau are possible forcing.