CENOZOIC PLATE-TECTONICS AND BASIN EVOLUTION IN INDONESIA

SE Asia comprises a complex array of Cenozoic basins. The chronostratigraphic evolution of these basins may be understood within the plate tectonic evolution of SE Asia. The relative motions of India, Australia, the Pacific and Eurasia provide the boundary conditions for this evolution. Indian collision and indentation destroyed a subducting northern Tethyan margin and led to major clockwise rotation of SE Asia. The South China Sea continental shelf developed after collapse of the West Pacific subducting margin. Crustal extension led to sea floor spreading and the formation of the Reed Bank Terrane and, at its trailing edge, the South China Sea. Sumatran basins opened due to back arc extension in the Eocene. Closure of a marginal ocean basin resulted in a major contractional event in the Late Oligocene. The Gulf of Thailand basins and Andaman Sea opened in response to rotation of Indochina and oblique convergence at the precursor to the Sunda trench. Inversion of the southern end of these basins and uplift in Borneo coincided with the collision of the Reed Bank Terrane with Borneo. Opening of the Makassar Straits, Kutei, Tarakan and Barito basins occurred during the Eocene. Inversion of these basins was a result of the collision of Australia and Australian derived microplates in the Late Miocene/Pliocene. Pliocene fold and thrust belt and foreland basin formation in New Guinea was a result of oblique arc collision. Basin evolution of SE Asia is not a result of major lateral extrusion in front of the Indian indenter. The major effect of this collision is in terms of the clockwise rotation of Indochina and extension along the Sumatran active margin.