Climatic evolution of loess on the northeastern margin of the Qinghai-Tibet Plateau and its coupling with plateau uplift

An integrated analysis has been performed of the climatic carriers such as magnetic susceptibility, grain-size, CaCO3 and TOC in the Minhe loess on the northeast margin of the Qinghai-Tibet Platean. The time interval of 1.90 to 0.70 Ma BP for the loess on the northeast edge of the Qinghai-Tibet Platean can be subdivided into seven climatic stages. Climatic analysis of the Minhe loess shows the following: before 1.10 Ma BP (layer L11 of the Minhe loess), the climatic difference was small and the winter monsoon and summer monsoon were not strong, with only weak antagonism, and loess and paleosol were less developed and relatively thin; by contrast, after 1.10 Ma BP, the antagonism between the winter monsoon and summer monsoon was enhanced rapidly, and the climatic difference became pronounced. A comparison between the isotope records of the Minhe loess and other areas and the oxygen-isotope records of deep-sea sediments indicates that paleosol layers S8, S9 and S10 of the Minhe loess correspond separately to deep-sea oxygen stages 21 and 23 and 25 better, while loess layers L9 and L10 and L11 are separately coincident with stages 22 and 24 and 26. The correlation between loess records below loess layer L11 and deep-sea oxygen-isotope records is not very pronounced. In addition, the high-resolution climatic records of the Minhe loess are well coupled with the staged uplift of the Qinghai-Tibet Plateau.