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Crustal Thickening History of Lhasa Block, Coqin area, south-central Tibet
This project investigates the timing and magnitude of crustal shortening of the Tibetan plateau. Although it has long been recognized that Tibet was the locus of continental collision since the early Mesozoic, the style and intensity of deformation produced by each accretionary event remain poorly documented. To address this issue, we have completed a systematic mapping project of the Coqin area in south-central Tibet, within the Lhasa block. This mapping documented three major thrust systems (the Gugu La, the Shibaluo, and the Emei La) along a 150-km long traverse. Together with earlier studies, our mapping and geochronological results show that southern Tibet experienced little or no N-S shortening during the Cenozoic except along its southernmost margin. In contrast, significant horizontal shortening (~60%), and thus vertical thickening and uplift, occurred during the mid-Cretaceous. An implication of this observation is that a significant portion of Tibet was raised to perhaps 3-4 km elevation prior to the Indo-Asian collision.
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