Rotation and extension of the crust in SE-Tibet

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Understanding large-scale tectonic processes such as uplift of the Tibetan Plateau is important for reconstructing the palaeoclimatic evolution. The mechanism of plateau formation is highly debated and poorly quantified. We propose a palaeomagnetic study of block rotation patterns and long-wavelength folding, to contribute to a better understanding of the mechanism and timing of major geodynamic processes. Secondary thermomagnetic remanences of low-grade metasediments related to last cooling are used. Dating of remanence acquisition and determination of the remanence character require thermochronologic and geothermometric investigations. For our study we focus on SE-Tibet, a key area of lateral mass transfer around the eastern syntaxis, where only very little work has been done until present. We will include the already existing palaeomagnetic results from the southern plateau and the Himalaya in the western and central part, and also information on recent horizontal displacements from GPS measurements and Quaternary strike-slip rates. Palaeomagnetic results will be used to define the onset of lateral mass transfer and better constrain the duration of the first uplift phase as well as for quantification of lateral mass transfer rates. Additionally, we will investigate the chronology and rates of extension in two graben structures that appear to represent the boundaries between rotating crustal-scale blocks. This will provide independent constraints on the geometry and timing of block rotation patterns, and allow us to better assess the importance of crustal thinning for the plateau's elevation history.