Pliocene–Pleistocene stepwise drying of Central Asia: Evidence from paleomagnetism and sporopollen record of the deep borehole SG-3 in the western Qaidam Basin, NE Tibetan Plateau

Drying of the Asian interior has generally been linked to Tibetan Plateau uplift, retreat of the Para-Tethys Sea and global cooling. However, lack of detailed aridification records hinders elucidation of how drying is controlled by these factors and to what extent each factor contributes. In this study, a 600 m deep core (SG-3) of lacustrine–playa deposits was obtained from the western Qaidam Basin, NE Tibetan Plateau for pollen analysis. Magnetostratigraphic dating of the core determines its age at ca. 3.1–0.01 Ma. The palynologic compositions show that a steppe to desert vegetation predominates the core. Artemisia-dominated steppe representative of relative warm and wet climate before 2.6 Ma changed to Chenopodiaceae-dominated steppe desert under drier climate conditions between 2.6 Ma and 0.9 Ma, interrupted by a short moister interval of Artemisia-dominated steppe at 1.8–1.2 Ma. From 0.9 Ma to 0.6 Ma, Chenopodiaceae–Ephedraceae desert vegetation started to develop, and since 0.6 Ma, Ephedraceae-dominated desert prevailed. This vegetation change in the western Qaidam Basin suggests a stepwise long-term aridification of the central Asia inland beginning at ca. 2.6 Ma, 1.2 Ma, 0.9 Ma and 0.6 Ma since the late Pliocene, most probably as a response to both long-term global cooling and Tibetan Plateau uplift at those times.