Through comprehensive research in multiple fields and means, such as tectonic geological evolution, deep dynamic processes of the lithosphere, paleothermal temperature, paleogetological analysis and paleoclimate simulation, the scientific research team led by Academician Ding Lin of the Institute of Tibetan Plateau of the Chinese Academy of Sciences quantitatively restored the uplift and demise process of the central valley of the Qinghai-Tibet Plateau from 38 million to 29 million years ago, revealing that the uplift of the central valley is the beginning of the huge impact of the Qinghai-Tibet Plateau on the surface layer environment. On the 10th, the results were published online in the international academic journal Science Advances.
The scientific research team found that after the collision of the Indian plate and the Eurasian plate, a low-altitude central valley completely different from the current landform developed between the tall Ganges orogenic belt and the central watershed orogeny belt, from west to east, along the current Line of Sun-Soil - Gaize - Nyima - Bangor - Nagqu - Dingqing.
Since 1997, the scientific research team has continued to conduct field investigations in the Lumpola Basin in the middle of the Central Valley, found 9 sets of volcanic ash in the Cenozoic strata in the basin, and determined the absolute age of volcanic ash by zircon uranium and lead dating, and established an absolute dating framework for sedimentary strata in the Lunpola Basin from 50 million to 20 million years ago.
The results show that about 50 million to 38 million years ago, the Qinghai-Tibet Plateau presented a geomorphological feature of "two mountains and one basin", with the Ganges Mountains at an altitude of about 4500 meters and the Central Watershed Mountains at an altitude of about 4000 meters, sandwiched between them the central valley at an altitude of about 1700 meters. The climate of the Central Valley is warm and humid, the precipitation is dominated by westerly and monsoon winds, and the sub-heat drives the flourishing of plants, which is the "Shangri-La" in the interior of 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 a warm, humid subtropical ecosystem to a cold, dry alpine ecosystem, with the main surface vegetation being alpine meadows.
The core data of this achievement, the isotopes of calcareous nodule clusters in ancient soils, were analyzed and obtained from the National Key Laboratory of Earth System and Resource Environment on the Qinghai-Tibet Plateau, which is under preparation. In the process of ancient height reconstruction on the Qinghai-Tibet Plateau, there is a lack of directly defined indicators for the formation temperature of calcareous nodules in ancient soils. After four years of technical research, the team experimental technicians independently developed the isotope measurement method of carbonate clusters, and built an isotope pretreatment experimental device for carbonate clusters, which successfully solved the above problems.
Academician Ding Lin, the corresponding author of the paper, introduced that by synthesizing the evidence of paleoal height, tectonic activity and magmatic action in the region, the study further believes 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. 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).