Evidence for the multiphase nature of the India-Asia collision from the Yarlung Tsangpo suture zone, Tibet

Abstract

Recent investigations in southern Tibet enable the testing and refinement of existing models for India-Asia collision. Presently available data indicate that marine deposition continued in the southern central portion of Tibet until at least the end of the Eocene. Subduction-related magmatism continued until the Mid-Oligocene, after which rapid uplift of the plateau was initiated. Mass-wasting of sediments into molasse basins did not commence until the latest Oligocene. The implications are that existing models, based on less-precise age constraints, invoking India-Asia collision at 55 Ma, are either flawed, or collision began at a different time. Recent work has produced sufficient data to allow the recognition of two different collisional events along the suture between India and Asia. Features related to each event require separate interpretation, and no collisional continuum should be assumed. In southern Tibet, a collision between the northern margin of India and a south-facing intra-oceanic island arc occurred at around 55 Ma, whereas continent - continent collision between India and Asia did not occur until at least 20 million years later. © The Geological Society of London 2004.