Normal faulting, basin development, and paleoelevation in south Tibet and the evolution of the Tibetan Plateau

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The Tibetan-Himalayan orogen is the result of the ongoing plate convergence between India and Eurasia since the Early Cenozoic. At a late stage of this long-lasting history (i.e. since the mid- to late Miocene), the formation of several N-S trending rift systems dissecting the Tibetan Plateau highlights significant changes in the evolution of the orogen. The relation between the rifts in Tibet and the uplift of the plateau is the key to a better understanding of the geological evolution of the entire orogen. The joint Sino-German cooperation proposed here will focus on this major scientific problem by investigating the tectonic, sedimentological, and paleoelevation history of the Gyirong and Nima-Dingri Rifts, which extend over a distance of more than 300 km through the Lhasa terrane and into the Himalaya. The German group (this proposal) will apply low-temperature thermochronology (i.e. fission track and (U-Th)/He dating) on apatite and zircon along elevation profiles through granitic intrusions, which are exposed in the footwalls of the rift-bounding faults. Thermokinematic modelling of the respective data will allow us to quantify the onset of normal faulting and temporal variations in fault slip along strike of the Gyirong graben and the Nima-Dingri rift system. Our Chinese partners will use sedimentological and magnetostratigraphic analyses to reconstruct the evolution and the depositional environment of the fault-controlled Gyirong basin. On this basis, they will use stable isotope analysis of carbonate from paleosols, authigenic minerals, and fossils to decipher how the paleoelevation of the Gyirong basin has changed through time and how it is related to the activity of the basin-bounding faults. The complementary approaches and results of our two working groups will lead to an improved understanding of the causal relation between rift development, basin formation, and paleoelevation on the Tibetan Plateau and their timing with respect to past climate changes.