Mio-Pliocene piracy, relict landscape and drainage reorganization in the Namcha Barwa syntaxis zone of eastern Himalaya

Abstract

The presence of unique elevated low relief relict landscape in the transient Dibang catchment, at the orographic edge of Tibet-Himalaya in the tectonically active Namcha Barwa syntaxial zone, is modelled to understand evolving regional landscape, drainage reorganization and tectonics. This elevated low relief landscape represents a Mio-Pliocene abandoned paleo-channel of the Yarlung river, which was captured by the headward eroding Siang river owing to >600 m base level advantage. The river capture caused isolation of the Dibang river, which evolved as a transient parched catchment since 3–6 Ma after loss of ~17 times drainage area and 4–17 times discharge. The drainage area and discharge gained by the Siang river triggered enormous incision causing aneurysm leading to the accelerated growth of the Tsangpo gorge and affected regional tectonics. This paleo-drainage reorganization is reflected in the Mio-Pliocene sedimentation pattern in the southern Tibet-Himalaya and foreland basins.