Chinese scientists reveal the history of height growth in central Valley of Qinghai-Tibet Plateau

2022-05-02 0 By

38 million years ago, the Central Valley of the Qinghai-Tibet Plateau, less than 2,000 meters above sea level, was the “Shangri-La” within the plateau.When did it rise to its present height of more than 4,000 meters?How did it rise?Researchers from the Institute of Qinghai-Tibet Plateau, Chinese Academy of Sciences and other institutions have successfully solved the uplift process of the Central Valley of the Qinghai-Tibet Plateau from 38 million to 29 million years ago through multi-field and multi-means comprehensive research, including tectonic geological evolution, deep dynamics of the lithosphere, paleo-height, paleo-temperature, paleo-vegetation analysis and paleoclimate simulation.The uplifting of the Central Valley is the beginning of the great influence of the Qinghai-Tibet Plateau on the surface environment.The study was published online Feb. 10 in Science Advances.”With the support of the second Qinghai-Tibet Scientific Expedition, this research has broken through the isolation of the circles and the boundaries of disciplines, making a solid step forward in the study of the space-time evolution of all the circles on the Qinghai-Tibet Plateau, and plays an important demonstration role in the scientific research of the Earth system on the Qinghai-Tibet Plateau.”Corresponding author ding Lin, Academician of institute of Tibetan Plateau, Chinese Academy of Sciences.Since 1997, after the collision between the Indian plate and the Eurasian plate, a low-altitude central valley developed between the tall Gangdise orogenic belt and the central watershed orogenic belt, which was completely different from the present landform, and distributed along the present line of Ritu-Geize-Nima-Bangor-Nagqu dingqing from west to east.Since 1997, Ding’s team has been conducting field trips to the Lumpola Basin in the middle of the Central Valley, trying to solve the mystery of the Central Valley uplift.Lumpola Basin, which is located in Bangor County, covers an area of about 3,600 square kilometers and has an altitude of about 4,700 meters. The annual average temperature is about 0℃ and annual precipitation is 400-500 mm. It is a typical alpine monsoon climate, and it is a hot area for studying the uplift history, mechanism and environmental and biological effects of the Qinghai-Tibet Plateau.”We found a total of nine sets of volcanic ash in the basin.Using zircon uranium-lead dating method, the absolute ages of these volcanic ash are determined, and the absolute age frame of the lumpola basin sedimentary strata from 50 to 20 million years ago is established.The lower Niubao Formation was deposited between 50 and 29 million years ago, and the upper Dingqing Formation was deposited between 29 and 20 million years ago.”Dr. Xiong Zhongyu, first author, Institute of Tibetan Plateau, Chinese Academy of Sciences.On the basis of the s framework, the research team and the university of Bristol, paleoclimate simulation team, for the first time in the qinghai-tibet plateau of paleoclimate simulation method to determine the qinghai-tibet plateau central valley rainfall patterns for winter and summer two season bi-model, combined with the rainfall, the surface evapotranspiration and soil water content, reveals the formation of ancient soil calcareous tuberculosis season:The formation time of calcareous nodules in the lower part of niubao Formation is from March to June, while the formation time of calcareous nodules in the upper part of Niubao Formation is limited to two stages: May to June and September.At the same time, the team creatively used the wet-bulb temperature and wet-bulb temperature lapse rate to quantitatively reconstruct the history of land surface height changes in the Lumpola Basin.The results show that about 50 million to 38 million years ago, the Qinghai-Tibet Plateau was characterized by “two mountains sandwich-one basin”, with the Gangdises mountains at an altitude of about 4,500 meters and the Central Watershed Mountains at an altitude of about 4,000 meters, and the Central Valley at an altitude of about 1,700 meters between them.The climate of the Central Valley is warm and humid. The precipitation is dominated by the west wind and the monsoon. Subtropical plants and animals flourish in the Central Valley, which is the “Shangri-La” within the plateau.About 38 million to 29 million years ago, the Central Valley represented by the Lumpola Basin rapidly “grew” into a plateau with an elevation of over 4,000 meters, 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, there has been a significant drop in temperature and precipitation in the central plateau, and a relative strengthening of the southern monsoon.”Climate change has caused the central plateau to change from a warm and humid subtropical ecosystem to a cold and dry alpine ecosystem, with alpine meadows as the main surface vegetation, Xiong said.”Based on the evidence of paleo-height, tectonic activity and magmatism in the region, we believe that the deep geodynamic mechanisms leading to the uplift of the Central Valley are the subduction of the Lhasa mantle, the upwelling of asthenosphere material and the shortening of the upper crust.”At the same time, ding said, the plateau’s growth process, driven by the deep layer interaction of the Qinghai-Tibet Plateau, is the internal driving force of the evolution and chain response of the plateau’s surface layer.Combined with team pilot study, the researchers pointed out that further north of the yarlung zangbo river suture, development as the main body in the plateau from the orogenic belts of time of 38 million years ago to 29 million years ago the late Eocene and Oligocene early, and south of the yarlung zangbo river suture of the Himalayas from 25 million to 15 million years ago in early Miocene to reach the current level.This article is from: Science and Technology Daily Digital News