Tectonic And Climatic Evolution Of The Central Northern Tibetan Plateau

Download or read book Tectonic and Climatic Evolution of the Central-northern Tibetan Plateau written by Lin Li and published by . This book was released on 2016 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The uplift history of the Tibetan Plateau serves as key evidence for understanding the dynamic models that build the Plateau and its influence on Cenozoic climate change of East Asia. This dissertation contributes to our knowledge for the growth history of the central and northern Tibetan Plateau through sedimentary analysis of basin sequences, and stable isotope analysis of carbonate rocks and modern surface waters. Field work in the Hoh Xil basin of central Tibet, including facies analysis, paleocurrent reconstruction, detrital zircon provenance analysis, and stable isotope analysis, suggests that a unified Hoh Xil basin, including both the east and west sub-basins, experienced a transition from pre-India-Asia collision foreland basin to post-collision hinterland basin setting at around 50 Ma. The Qiangtang terrane, serving as the main source for sediments deposited in the Hoh Xil basin, experienced significant topographic growth during the Cretaceous time. Far field deformation in the Hoh Xil basin was initiated shortly after India-Asia collision; contractional deformation and concomitant filling of the Hoh Xil hinterland basin provides clues for outward and upward growth of the Tibetan Plateau during Cenozoic time. Work in the western Qaidam basin provides new lithostratigraphy and carbonate stable isotope data that records early-middle Miocene topographic growth of the northern Tibetan Plateau. A hydrological change from restricted sub-basin to open marginal basin around 20 Ma was probably caused by late Oligocene-early Miocene tectonic activity around the Qaidam basinches A major topographic growth in the northern Tibetan Plateau is inferred around 15 Ma based on a negative shift in oxygen isotopic values, sedimentary facies changes from marginal lacustrine to fluvial, and an increase in sedimentation rate. A 13-12 Ma aridification event that was observed over a large area of the northern Plateau was likely caused by continued topographic growth to a critical point to block moisture from entering the northern Tibetan Plateau. To understand the caveats of stable isotope-based paleoaltimetry in the central and northern Tibetan Plateau, a comprehensive data set of 1,315 river water samples (450 newly collected) was compiled. With this large data set, a consistently assumed, but not well-documented prerequisite is demonstrated that river waters are a good substitute for isotopic studies of precipitation on the high Tibetan Plateau on the mean annual scale. The spatial variations of [delta]18O/[delta]D and d-excess values in the plateau margins can be modeled as a Rayleigh distillation process, on which stable isotope-based paleoaltimetry is based. On the contrary, the isotopic values of meteoric waters in the interior of the plateau are controlled by the combined effects of mixing of different moisture sources, contribution of recycled moisture from local surface water evaporation, and sub-cloud evaporation. A Rayleigh distillation model modified by sub-cloud evaporation is provided to simulate the isotopic variations in the western Plateau. This new understanding indicates that stable isotope-based paleoaltimetry is most reliable in the southern margins of the Plateau, and increasingly unreliable toward the northern Plateau. In addition, the contour maps of modern isotopic variations of meteoric waters across the whole Tibetan Plateau also provide validation criteria for isotopic simulations using general circulation models"--Pages v-vi.