Source: China News Network
Beijing, February 10 (China News Network) -- When did the Qinghai-Tibet Plateau, known as the "roof of the world," take shape? When will the Central Valley disappear? What is its dynamic mechanism? And what kind of historical process has it been?
The latest research of the collision uplift and impact team led by Academician Ding Lin of the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences (Institute of Tibetan Plateau Research of the Chinese Academy of Sciences) gives the answer. Through comprehensive research in multiple fields and means such as tectonic geological evolution, deep lithospheric dynamics, paleothermal temperature, paleogetological analysis and paleoclimate simulation, they quantitatively restored the uplift and demise process of the central valley of the Qinghai-Tibet Plateau 38 million to 29 million years ago, revealing that the uplift of the central valley was the beginning of the huge impact of the Tibetan Plateau on the surface layer environment.
This paper on cracking the mystery of the formation of the roof of the world on the Qinghai-Tibet Plateau was published online by the international academic journal Science Advances on February 10, Beijing time, achieving a solid step in the study of the spatio-temporal evolution of various circles on the Qinghai-Tibet Plateau, which has an important demonstration effect on the scientific research of the Earth system on the Qinghai-Tibet Plateau, and has also become an important result of China's second comprehensive scientific expedition to the Qinghai-Tibet Plateau.
The central valley of the Qinghai-Tibet Plateau was uplifted and died 38 million to 29 million years ago. Photo courtesy of the Institute of Tibetan Plateau, Chinese Academy of Sciences
Nine sets of volcanic ash were found in the Lumpola Basin
According to the Institute of Tibetan Plateau of the Chinese Academy of Sciences, after the collision of the Indian plate and the Eurasian plate, a low-altitude central valley completely different from the current landform was developed between the tall Ganges orogenic Belt and the Central Watershed Orogenic Belt, which extended from west to east along the current Line of Sun-Soil-Jieze-Nyima-Bangor-Nagqu-Dingqing.
In order to solve the mystery of the deep geodynamic mechanism that causes the uplift of the Central Valley and the endogenous driving force of the surface layer of the plateau, Academician Ding Lin led the team to continue to conduct field research in the hot spot of studying the history, mechanism and environmental-biological effects of the uplift of the Qinghai-Tibet Plateau since 1997- the Lunpola Basin in Bangor County in the middle of the Central Valley, and so far 9 sets of volcanic ash have been found in the Cenozoic strata in the basin, and rich animal and plant fossils have been exposed in the strata.
The research team used zircon uranium and lead dating methods to determine the absolute age of volcanic ash and established an absolute dating framework for sedimentary strata in the Lumpola Basin 50 million to 20 million years ago, of which the lower strata are deposited 50 million to 29 million years ago and the upper strata sedimentary age is 29 million to 20 million years ago.
Based on this chronological framework, the research team cooperated with the paleoclimate simulation team of the University of Bristol in the United Kingdom to determine for the first time that the rainfall pattern of the central valley of the Qinghai-Tibet Plateau was a double-peaked pattern in winter and summer, combined with rainfall, surface evapotranspiration and soil moisture content, etc., to reveal the formation season of calcareous tuberculosis in paleosoil. In addition, the research team also creatively used the surface air wet bulb temperature and wet bulb temperature direct reduction rate to quantitatively restore the history of surface height change in the Lunpola Basin.
Academician Ding Lin led the team to conduct a field expedition in the Lumpola Basin. Photo courtesy of the Institute of Tibetan Plateau, Chinese Academy of Sciences
"Two mountains and one basin" uplifts to a plateau of more than 4,000 meters above sea level
Dr. Xiong Zhongyu, the first author of the paper and the Institute of Tibetan Plateau of the Chinese Academy of Sciences, said that the research results show that about 50 million to 38 million years ago, the Qinghai-Tibet Plateau showed the geomorphological characteristics of "two mountains and one basin", the Ganges Mountains are about 4500 meters above sea level, the central watershed mountains are about 4000 meters above sea level, and the central valley with an altitude of about 1700 meters is sandwiched between them. The climate in the Central Valley is warm and humid, with precipitation dominated by westerly and monsoon winds. Su Tao, a co-author of the paper and a researcher at the Xishuangbanna Botanical Garden of the Chinese Academy of Sciences, believes that the sub-heat in the central valley drives the flourishing of plants and is the "Shangri-La" inside the plateau.
About 38 million to 29 million years ago, the central valley represented by the Lunpola Basin rapidly uplifted to a plateau of more than 4,000 meters above sea level, marking the formation of the main part of the Qinghai-Tibet Plateau. With the uplift of the Central Valley and the cooling of the global climate, the temperature in the central part of the plateau has dropped significantly, precipitation has decreased, and the southern monsoon has been relatively enhanced. Climate change has led to the transformation of the central plateau from warm, humid subtropical ecosystems to cold, dry alpine ecosystems, with predominantly surface vegetation evolving into alpine meadows.
The central valley extent of the Tibetan Plateau (white shaded area) and the surface height variation profile, the five-pointed star represents the location of the study site, The Lunpola Basin. Photo courtesy of the Institute of Tibetan Plateau, Chinese Academy of Sciences
The deep circle of the Qinghai-Tibet Plateau drives the plateau growth process
Academician Ding Lin, the corresponding author of the paper, pointed out that the deep geodynamic mechanisms that led to the uplift of the central valley were the dismantling and sinking of the subducting Lhasa mantle, the upwelling of asthenosphere material and the shortening of the upper crust. The plateau growth process, driven by the deep sphere of the Qinghai-Tibet Plateau, is an endogenous driving force for the evolution and chain response of the plateau surface layer (atmosphere, cryosphere/hydrosphere, biosphere and human circle).
Combined with the team's previous research, the latest results further show that the time of the development of the orogenic belt to the plateau north of the Yarlung Zangbo River suture is the late Eocene-Early Oligocene (38 million to 29 million years ago), while the Himalayas south of the Brahmaputra Suture reach the current height in the early Miocene (25 million to 15 million years ago). (End)