The India-Eurasia collision alone set up a series of chain reactions and caused the formation and destruction of sedimentary basins within the domain of the collision belt. Changes in the rate and angle of convergence between the India and Eurasia plates reflect different stages of tectonic development in Southeast Asia. For example, extrusion of the Indochina block induced the consumption of the pre-existing proto-South China Sea along northeastern Kalimantan and led to the eventual opening of the South China Sea along the South China margin. Subsequent motions of the Sino-Burma-Thailand, Malay Peninsula, Sumatra, and Kalimantan blocks have produced a succession of basins stretching from north Sumatra to central Thailand and on to the Natuna area. We present reconstructions of the Southeast Asia region at 60 Ma, 50 Ma, 40 Ma, 30 Ma, 20 Ma, 15 Ma, 10 Ma, and 5 Ma. It is clear, from the reconstructions, that the impact between Greater India and Southeast Asia took place in the northwestern part of Southeast Asia. The duration for the impact was probably from the Middle Eocene to Early Miocene. This timing is in good agreement with the dating of the main Red River Fault motion (Wu et al., 1989; Schärer et al., 1990). Since the impact between Greater India and Southeast Asia was basically west of the Burma block, there is no reason to assume that the Sumatra, Malay Peninsula, and Kalimantan should extrude to the southeast first along the left-laterally displaced Mae Ping and Three Pagodas fault zones as suggested by Peltzer and Tapponnier (1988). If the opening of the central Thailand basins, the Gulf of Thailand, and the Malay Basin are taken into consideration, a dextral megashear zone is required to compensate the relative motion between Indochina and the Malay Peninsula. This dextral megashear zone might even extend into western Kalimantan and serve as a boundary between the Indochina block and Kalimantan.
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