Quaternary evolution of the Dunhuang paleolake and its controlling factors in the northeastern Tibetan Plateau

Abstract

Complex interactions between neotectonics, surface uplift, and climatic oscillations have been affecting the landscape and environmental evolution of the northeastern Tibetan Plateau since the late Cenozoic. The Dunhuang Basin, located at the northeastern frontier of the plateau, has undergone intensive deformation and desertification during the Quaternary, recording the coupling between the plateau's northward growth and associated environmental changes. Here we conduct an integrative study on the Quaternary fine-grained lacustrine deposits of the Dunhuang Basin including sedimentary observations, chronological determination, and climatic and provenance analyses. Our results reveal the existence of basin-scale paleolakes with two phases in the Dunhuang Basin during the Quaternary: (1) the paleo-South Lake, with sedimentary ages ranging from ∼1.16 to 0.41 Ma, is mainly exposed to the south of the Sanwei Shan and north of the Altyn Tagh Fault (ATF), and may have a further northward extension across the Sanwei Shan to the Bei Shan; (2) the paleo-West Lake developed later, with sedimentary ages of ∼18–9 ka, is situated to the north of the Sanwei Shan and south of the Bei Shan, and likely continued westwards to Lop Nur. Combining our new data with previous studies, we propose a model of propagating foreland basins to reveal the Quaternary evolution of the Dunhuang paleolake in the context of plateau growth. In this model, the Quaternary transpression of the ATF formed a foreland basin, which controlled the formation of the paleo-South Lake since ∼1.16 Ma. Subsequently, the plateau propagated from the ATF to the Sanwei Shan Fault (SWSF). The northward-thrusting SWSF caused the uplift of its southern wall, which forced the paleo-South Lake to migrate northwards, resulting in its drying up and the formation of the paleo-West Lake since ∼0.41 Ma. Finally, the combination of tectonic uplift and climate caused the drying up of the paleo-West Lake and the formation of the present-day desert landscape after ∼9 ka.