Paleoclimate Evolution of the Qinghai-Tibet Plateau since the Cenozoic

Clay mineralogy of sediments of the basins in different locations of the Qinghai-Tibet plateau was investigated to reveal the paleoclimate evolution in Tibet.Our results show that the planetary wind system prevailed over the Paleocene-Eocene in Tibet.A rapid cooling in Qaidam was found in ～36 Ma,prior to the global cooling event by ～2 Ma.In the Oligocene,paleoclimate was warm and dry and the temperature was lower than that of the previous stage.In Miocene-Pliocene period cooling event was found in ～21.5 Ma in Qaidam and Xunhua basins,northeastern Tibet.Climate change in 8-7 Ma occurred in the whole Qinghai-Tibet plateau.In Gyirong,southern Tibet and in Yecheng,western Tibet,smectite occurred in a certain amount in the sediments prior to ～1.8 Ma,indicating that climate was relatively humid in these regions prior to ～1.8 Ma though the climate changed into cool and dry in the Qinghai-Tibet plateau.