LATE EOCENE UPLIFT OF THE SOUTHEAST MARGIN OF TIBETAN PLATEAU AND ITS CLIMATE EFFECT

The southeast margin of Tibetan Plateau is located in the intersection parts of the Indian monsoon and East Asia monsoon, and is characterized of high elevation, low relief that was deeply dissected by continental scale rivers, served as a key area to understand the coupling between surface uplift and climate change. However, it is still unclear when this low relief was formed and its effect on the climate change. Here we summarize the recent progress on dating of Cenozoic sedimentary basins and sedimentary structures, and build an updated chronological framework for the Cenozoic sediments in the southeast margin of Tibetan Plateau. The results show that the Paleogene sedimentary successions in the southeast margin of Tibetan Plateau were generally formed in compressional settings and deposited between the Late Eocene-early Oligocene, while the Neogene basins were mostly developed in extensional settings after the Late Miocene; suggesting a big sediment hiatus during the Oligocene-Early Miocene. This suggests that the southeast margin of Tibetan Plateau experienced significant crustal shortening and surface uplift in the Late Eocene, and then widespread regional erosion in the Oligocene-Middle Miocene, forming the high elevation low relief. The lithology and plant fossils in the Cenozoic sediments suggest that the climate became wetter and cooler since the Late Eocene, which is most likely related to the Tibet uplift at this time.