The building of pericratonic mountain ranges; structural and kinematic constraints applied to GIS-based reconstructions of SE Asia

Southeast Asia represents a valuable playground for studying the mechanisms of supra subduction mountain building. Fast relative plate velocities induce rapid geodynamic changes, so that the parameters for the convergence can be constrained, whereas the recently inactivated systems are still accessible. We make use of the GPS-controlled motion of major plates together with that of smaller units within the deformed belts, to explore the Neogene evolution of SE Asia. We present simplified synthetic sections for the structural control, and used GIS-based reconstructions to support the relative location of the plates and distances between them, so that at a given time, location of units can be confronted to the tectonic observations. Pericratonic mountain ranges are the result of long lasting convergence which was responsible for both the fragmentation of continental landmasses by the opening of marginal basins, and the shortening of these supra subduction units, which ultimately jammed them back against the motherland, or transferred them to the neighbouring plate. Because the obliquity of the convergence generated strain partitioning, new paired trench and strike-slip systems are created, moving blocks further away from the locus of accretion, so that continental or oceanic fragments may be chopped, transported and eventually severely sheared during final docking. We present simplified cross sections of the margins of the SE Asian regions prior and after the accretions of blocks and reconstructions at 2, 4, 6, 10, 15 and 20 Ma.