首页|Neogene integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas
Neogene integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas
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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 C4 plant expansion event based on carbon isotope changes comes from the southern margin of the Tibetan Plateau,but in sharp contrast,δ13C indicates that there was still no clear or significant C4 plant signal on the northern margin of the Tibetan Plateau until the end of the Neogene.The δ18O analysis shows that there were several major climate change events in the Cenozoic,especially in the Late Miocene at about 7 Ma,when positive drift of δ18O indicates that the northern and southern sides of the Tibetan Plateau were changing to drier environments.The strong uplift of the Tibetan Plateau in the Late Miocene strengthened the thermal contrast between sea and land,which strengthened monsoon circulation and led to the expansion of C4 vegetation in South Asia.However,the East Asian summer monsoon,which can bring atmospheric precipitation and a climate suitable for C4 plants to northern China,was not enough to affect the northern Tibetan Plateau.The Tibetan Plateau on the whole rose to an altitude of about 3000 m in the Miocene,becoming a barrier to mammalian migration;it reached its modem altitude of more than 4000 m in the Pliocene,thus forming a cryosphere environment,which led to the emergence of ancestral types of the Ice Age fauna.
Tao DENG、Xiaomin FANG、Qiang LI、Shiqi WANG、Feixiang WU、Sukuan HOU、Jiao MA、Qigao JIANGZUO、Danhui SUN、Yan ZHENG、Qinqin SHI、Boyang SUN、Lu LI
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Key Laboratory of Vertebrate Evolution and Human Origins,Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences,Beijing 100044,China
CAS Center for Excellence in Life and Paleoenvironment,Beijing 100044,China
University of Chinese Academy of Sciences,Beijing 100049,China
CAS Center for Excellence in Tibetan Plateau Earth Sciences and Key Laboratory of Continental Collision and Plateau Uplift,Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101,China
Key Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China
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Second Comprehensive Scientific Expedition on the Tibetan Plateau中国科学院战略规划重点项目中国科学院战略规划重点项目国家自然科学基金国家自然科学基金
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