Magnetic susceptibility of aeolian sediments deposited since Holocene in the East of Qinghai Lake and its environmental implications

Magnetic susceptibility is an efficient indicator to the intensity of pedogenesis and depositional environment for a loess-palaeosol sequence under the Asian monsoon. However, its paleoclimatic implications still need to be revealed for an aeolian-sand-palaeosol sequence. Within the time framework established by AMS ¹⁴C and OSL dating, we studied the magnetic susceptibility characteristics of the aeolian deposits to the east of the Qinghai Lake. Taking the traditional pedogenetic indicators used in soil sciences as references, we found that the magnetic susceptibility is closely related to the intensity of soil development in the sandy land to the East of Qinghai Lake. The results show that: (1) The highest magnetic susceptibility occurs in the palaeosol layer, followed by the weakly developed palaeosol and the aeolian sand. Compared to χ_lf, χ_fd% is more efficient to reflect environmental changes; (2) The variation in magnetic susceptibility exhibits a positive correlation with pedogenesis, and is positively correlated with the content of clay and silt; (3) On the basis of comprehensive analysis, the climatic change in Qinghai Lake since Holocene could be divided into three main phases as follows: Before 10kaBP, the climate was cold and dry and the weathering process weaker. In the period of 10~8.5 kaBP, the climate turned to warm and wet. Optimum period took place from 8.5 kaBP to 4 kaBP, while the climate was warm and humid and the aeolian activity was weakened and pedogenesis became stronger. The climate was colder and drier between 4 to 1.3 kaBP. There possibly existed an abrupt climate cooling event during 3.1~2.4 kaBP. Since1.3 kaBP, the climate became colder and drier further and similar to the modern climate.