Cenozoic plate tectonic reconstructions of SE Asia

Abstract

A new plate tectonic model for the Tertiary is proposed, based on the integration of new palaeomagnetic data from east Indonesia recording Philippine Sea plate motion, recent revisions of the history of the South China Sea, and previously available geological and palaeomagnetic data from SE Asia. Early Neogene counter-clockwise rotation of Borneo is interpreted to have closed a proto-South China Sea suggesting a strike-slip boundary in NW Borneo before the Neogene. This rotation suggests that the West Philippine Sea, Celebes Sea and Makassar Strait formed a single basin which opened in the late Paleogene, and widened eastwards. At c. 25 Ma a major collision, that of Australia with a Philippine Sea plate arc, trapped Indian Ocean lithosphere which later became the Molucca Sea plate. The collision caused clockwise rotation of the Philippine Sea plate, initiated the Sorong Fault system, and then eliminated the Molucca Sea by subduction on its east and west sides. The effects of collision propagated westwards through the region resulting in the initiation of new plate boundaries marked by regional unconformities. The arrival of the Sulawesi ophiolite, which collided with west Sulawesi in the late Oligocene, was the earliest event in collision between Sulawesi and the Bird’s Head microcontinent. Continental crust was thrust beneath Sulawesi in the early Miocene, and the Tukang Besi and Sula platforms were sliced in turn from the microcontinent, transferred to the west-moving Philippine Sea/Molucca Sea plate for a few million years, and finally accreted to Sulawesi. Reconstructing the Molucca Sea and Bird’s Head microcontinent suggests that most of the Banda Sea has a late Neogene extensional origin. Collision between the Philippine arc and the Eurasian continental margin in Taiwan at c. 5 Ma is the key to present regional tectonics.