Collaborative Research: Testing Models of Tibetan Plateau Uplift Using Stable Isotope-Based Paleoaltimetry

点击翻译按钮获取中文摘要

The elevation history of the Tibetan Plateau is one of the few direct ways of discriminating among models for the modes of strain accommodation in the India-Asia continent-continent collision system. In addition, the paleo-topographic evolution of the Himalayas and Tibet play important roles in the dynamics of the atmosphere and erosion from this region has been implicated in affecting atmospheric and ocean chemistry. Data constraining the elevation history of the Himalaya and Tibet can play a critical role in determining the degree to which various mechanisms, including crustal subduction, crustal thickening, crust and mantle-lithosphere thickening with subsequent convective removal of the mantle lithosphere, as well as escape and extrusion have contributed to the high elevation and distribution of strain across this region. We present results of our previous investigations of Himalaya and Tibetan paleoaltimetry. An aggressive new program is planned to address additional facets of the paleo-elevation history of the Tibetan Plateau. Our existing data from southern and central Tibet indicate that Tibet and Himalayas had already achieved its current stature in each of those areas at times prior to the oldest samples thus far collected and that each of the areas shows no evidence for changes in elevation associated with convective destabilization of a thickened lithospheric mantle root. This proposal seeks support to specifically focus on older sections in order to determine whether we can capture the actual uplift of various parts of southern and central Tibet, and importantly to determine the pre-collisional topography which is an important boundary condition for all models of crustal mass balance and strain accommodation during the India-Asia collision. Existing interpretation of the pre-collisional Asian margin as an Andean-type margin are often taken to imply that the margin had a pre-collisional topography comparable to the Andes. We propose to explicitly test this hypothesis by extensively sampling the paleosol carbonates interbedded within the Linzizhong Volcanics of Late Cretaceous to Eocene age from numerous preserved sections extending from Oiyug in the west to Markam in the east. In addition, we propose to sample paleosol and lacustrine carbonates from Eocene to Oligocene volcaniclastic and intermontane basin sequences also distributed across southern and central Tibet. The intellectual merits of the project include the potential our research has in identifying the initial age of the development of high topography in the southern Tibetan plateau, as well as providing temporal and spatial paleo-elevation constraints for models of strain accommodation in the Tibetan-Himalayan orogen. The broader impacts of the study include developing a better and more general understanding of continental collisions, and in addition, the cross-cultural exchange of data, research methods, and interpretations regarding the tectonic evolution of Tibet with our Chinese collaborators, as well as the research opportunity the project provides for graduate students at both the University of Chicago and Miami University.