--> Exhumation of Western Sundaland: a record of the Path of India?

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Exhumation of Western Sundaland: a record of the Path of India?


In South East Asia, the lateral effect of the northward migration of the Indian Plate on the western edge of Sunda Plate is poorly understood. In several sectors along a N-S transect, where deep ductile material has been exhumed, we review and correlate vertical movements and basin development. From the southern Malay Peninsula to the East Himalayan Syntaxis, five major metamorphic domes with similar dynamics and P-T climax conditions are described. The metamorphism occurred between the Late Cretaceous in the Stong Complex (North Malaysia) and the Late Miocene in the Gaoligong Shear Zone (South China). It is characterized by N-S stretching lineation and detachment faulting. Following this high temperature metamorphic and magmatic event, an uplift of older magmatic bodies is recorded through zircon fission tracks which appears to follow a similar N-S trend. Sedimentary basins often developed on the flanks of the metamorphic domes. In Eastern Myanmar, the Late Oligocene to Miocene Upper Pegu Group series were deposited along the Mogok Metamorphic Belt synchronous to the gravitational collapse of the Shan Plateau. As for Western Myanmar, the deposition took place within a similar process leading to the exhumation of the Kampetlet Schists. The earliest dated syn-rift sediments appear as a precursor to a continuous exhumation to upper brittle levels as recorded by apatite fission tracks. Thus, we highlight an identical succession of thermal, uplift, and sedimentary events for each bracket of age considered from the Cretaceous to the Present and correlate it with northward migration of India. We propose in this paper a theoretical model in which the topographic step bounding the thick Indian continental lithosphere scrapped off the base of the Eurasian crust during underplating, resulting in thermal anomalies, uplift and subsidence.