Rock magnetic record of core SG-3 since 1 Ma in the western Qaidam Basin and its paleoclimate implications for the NE Tibetan Plateau
Abstract Quaternary saline lake deposits are well formed and widely distributed in the Qaidam Basin, on the northeastern Tibetan Plateau, NW China. Studying these lacustrine salt mineral deposits in closed lakes would improve our understanding of tectonic deformation, Asian interior aridification and monsoon climate associated with global cooling and Tibetan Plateau uplift. Previous paleoclimate records in the Qaidam Basin are mostly documented by geochemical proxies, pollen spectra and sedimentary characteristics, however, supportive evidence from the rock magnetic index of sediments with salt deposits in the basin has not been well studied. Here, we present a continuous, high-resolution 1.0 Myr rock magnetic record from the well-dated drill core SG-3 with typical saline lake deposits in the western Qaidam Basin. The results show that deposits with low magnetic susceptibility (χ) are caused by low contents of magnetic minerals with single-domain (SD) grains, but those with high χ have relatively high contents of magnetic minerals with SD and pseudo-single-domain (PSD) grains. In full consideration of the sedimentary environments, weathering and erosion associated with the tectonic uplift of the northeastern Tibetan Plateau and the global climate since the middle Pleistocene, we propose that χ variations in the closed lake are influenced by the input of debris and regional precipitation. Combing the χ changes with pollen and grain size records, we demonstrate that the drying process in central Asia since 1 Ma, with obvious aridification increases at 0.6 Ma and 0.13 Ma, has been mainly induced by the uplift of the Tibetan Plateau under global cooling.