Modeling continental collisions on geological timescales
Adina E. Pusok
The Himalayas and the adjacent Tibetan Plateau represent the largest region of elevated topography and anomalously thick crust on Earth. Understanding the formation and evolution of the region has been the focus of many tectonic and numerical models. While some of these models (i.e. thin sheet model) have successfully illustrated some of the basic physics of continental collision, none can simultaneously represent active processes such as subduction, underthrusting, channel flow or extrusion, for which fully 3D models are required.
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Here, we employed the 3D code LaMEM to investigate the role that subduction, continental collision and indentation play on lithosphere dynamics at convergent margins, and the implications they have for the Asian tectonics.
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Our model setup resembles a simplified tectonic map of the India-Asia collision zone and we performed a large number of 3D simulations to analyse the dynamics and the conditions under which large topographic plateaus, such as the Tibetan Plateau can form in an integrated model.
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Despite the complex dynamics and the great variation in slab shape across the subduction-collision zone (which are consistent with tomographic observations), we note that slab-pull alone is insufficient to generate high topography in the upper plate.
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Moreover, several studies suggested that external forces (i.e. ridge push, plume push or slab suction) must be important in order to sustain the on-going convergence of India towards Eurasia.
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We show that external forcing and the presence of strong blocks such as the Tarim Basin within the Asian lithosphere are necessary to create and shape anomalously high topographic fronts and plateaus, analogous to the Himalayas and the Tibetan Plateau.
