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 can 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, supporting 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 for 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 while 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 environment, weathering and erosion associated with the global climate since the middle Pleistocene, we propose that χ variations in the closed lake are mainly influenced by erosion intensity and precipitation. By combining the χ changes with pollen and grain size records, we infer that the drying process of central Asia since 1 Ma, with intensified aridity at 0.6 Ma and 0.13 Ma, was primarily induced by global cooling.