The Paleoelevation History Of Cretaeceous To Cenozoic Terrestrial Basins Of Tibetan Plateau:Insights From Clumped Isotope Thermometry

The Tibetan Plateau is the biggest and newest uplifted topography in the world.The uplift history of the Tibetan Plateau is essential to interpret the geodynamic process and mechanism,and holds significant implications for global/regional paleoclimatic and paleoenvironmental evolution such as the Cenozoic global cooling,the onset of the Asian monsoon,and the Central Asia aridification.However,when and how the Tibetan Plateau was uplifted is remain controversial.To address these issues,we applied the sedimentological methods and clumped isotope thermometer to paleosol carbonate nodules and lacustrine carbonate to reconstruct the Late Cretaceous to Cenozoic topographic evolution of the Tibetan Plateau.The clumped isotope thermometry is a new method to estimate the carbonate form-temperature[T??47?]based on evaluating the degree of the ¹³C-¹⁸O bond ordering in the carbonate lattice.These temperatures thus were used to calculated the paleoelevation based on the temperature lapse rate.In addition,the burial temperatures could also be obtained by applying the clumped isotope thermometry to diagenesis altered samples,which could reflect the burial history according to the geothermal gradient.In this study,we collected paleosol carbonate nodules and lacustrine carbonates from the Liuqu Conglomerate in southern Tibet,the Nima and Lunpola basins in central Tibet,and the Hoh Xil Basin in northern Tibet.Our results suggested that the paleoelevation was>2 km Nima at⁷5 Ma in the Lunpola basins,central Tibet,and the paleoelevation was² km during the Oligocene in the Hoh Xil Basin,northern Tibet.During the latest Paleocene to Eocene,the Liuqu Conglomerate was buried 3.7-4.3 km in depth.The erosion and exhumation of Liuqu Conglomerate was likely caused by the incision of the paleo-Yarlung River.Besides,we also concluded that the Fenghuoshan Group was buried as deeply as 6.8-10.3 km during the Eocene,which indicates that the Fenghuoshan Group was deposited in a foreland basin environment induced by the Tanggula Fault.Taken our results and published paleoaltimetry estimates into account,we concluded that the central Tibet uplifted to² km during the Late Cretaceous and attained today's elevation during the Eocene,while the southern and northern Tibet were not as high as today's elevation until Miocene,which supports the model of outward growth of the Tibetan Plateau.