The Cenozoic rock magnetic characteristics of the Dahonggou section in Qaidam Basin and the climate change

This paper has discussed the climate change in northeastern Tibetan Plateau according to the Cenozoic rock magnetic characteristics of the Dahonggou section in Qaidam Basin. Progressive thermal demagnetization of typical samples indicates that the percentage composition of magnetite increases with the strata getting younger. The sediments in Qaidam Basin exhibit a noticeable increase in magnetic susceptibility by 5 stages, which is coincident with the increase in the percentage composition of magnetite. The change of magnetic susceptibility of sediments in Qaidam Basin was closely related to climate change: ①the increase in magnetic susceptibility at about 43Ma resulted from the climate cooling and drying; ② the increase in magnetic susceptibility at 33Ma or so resulted from the global climate cooling; ③ the tectonic uplift of the Tibetan Plateau at about 22Ma resulted in the climate system that controlled China's continental environment change from the planetary system of winds to the monsoon of winds and also caused aridification in Asian inland. Hence the magnetite was preserved and the magnetic susceptibility increased; ④the regional tectonic uplift in northeastern Tibetan Plateau at about 14Ma resulted in the expansion of the western arid region and the intensification of eastern Asian monsoon. Meanwhile, the global ice volume extended. Therefore, the magnetic susceptibility of the sediments in Qaidam Basin rose and the fluctuation range and frequency increased.