Plate tectonic evolution of the Western Pacific-Indian ocean region

An interpretative model for the plate tectonic evolution of the Western Pacific-Indian Ocean region is illustrated by a series of map reconstructions for selected time slices from Late Permian to Late Miocene. The reconstructions are based on marine magnetic anomalies, information from deep sea drill holes, and regional geology. The maps show that consolidation of continental pieces from Gondwanaland formed the core area of China and Southeast Asia during the Indosinian orogeny near end Triassic time. Subsequently, a number of continental fragments such as Central Iran, Afghanistan, Lhasa (southern Tibet), and India were added during the Alpine orogeny. A major change in plate boundaries and motions about 50 m.y.B.P. resulted in interaction between Southeast Asia, Australia, and the Pacific plates, leading to the complex configuration of island arcs, marginal basins, and continental fragments that characterize the present Western Pacific region. A number of problems remain to be solved such as the precise position of Indosinian sutures and their subduction polarities, the precise timing of the collisions, the amount of strikeslip movement of various portions of China and Southeast Asia resulting from the collision and northward drive of India, and the plate tectonic evolution of the complex arc assemblage that forms the present Philippine archipelago.