Neogene integrative stratigraphy, biotas, and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

The remarkable uplift of the Tibetan Plateau in the Neogene had great impacts on the climate and environment of East Asia and even the world. Therefore, establishment of the Neogene stratigraphic framework of the Tibetan Plateau is of great significance to research in various fields of geosciences. Based on marine sediments, the international chronostratigraphic system of the Neogene is divided into six stages in the Miocene and two stages in the Pliocene. Since the beginning of the Cenozoic, the share of terrestrial strata on continents has increased rapidly. By the Neogene, it had far exceeded that of marine strata, and almost all deposits on the Tibetan Plateau and its surrounding areas were terrestrial strata. In China, the Miocene includes five stages and the Pliocene includes two stages. Except for the Tunggurian of the Miocene, which has a lower boundary at 15 Ma, the other stages have the same paleomagnetic definitions and time intervals as the corresponding international marine stages. Mammalian fossils play a very important role in the division and correlation of Cenozoic terrestrial strata, and rodent, carnivore, proboscidean, perissodactyl and artiodactyl fossils are especially important in Neogene terrestrial biostratigraphy. There are many basins with well-exposed strata and abundant mammalian fossils in the Tibetan Plateau. The lower boundary stratotype sections of the Neogene Xiejian and Bahean stages are located respectively in the Xining and Linxia basins, and there are precise paleomagnetic dates in coordination with mammalian fossils. The lower boundary stratotypes of other stages can also be effectively determined in the Tibetan Plateau. Many first appearing mammalian genera in East Asia also appeared in the Tibetan Plateau and its surrounding areas, especially in the Linxia Basin on the northeast margin and in the Siwaliks on the southwest margin. Among them, Prodeinotherium first appeared at the bottom of the Miocene in the Siwaliks, and the earliest Hipparion of the Old World first appeared at the bottom of the Bahean Stage in the Linxia Basin. Carbon and oxygen isotope analysis of enamel and paleosols of Cenozoic sediments and mammal fossils in the Tibetan Plateau and its surrounding areas have been used to reconstruct the climate, environment and vegetation development characteristics, and revealed that these changes were not only related to global change, but also had regional features. Evidence of the Late Miocene C 4 plant expa