Indus-Yarlung-Tsangpo Suture Zone Concept- A Second Opinion

Abstract

It is believed that Greater India migrated from the southern hemisphere, collided with Gondwanaland, Angaraland and Cathaysia, thereby closing an intervening oceanic Tethys along the Indus-Yarlung-Tsangpo Suture Zone (IYTSZ).The suture zone is placed along the Chaman Fault in the Baluchistan-Afghanistan area in the west, and the Indus-Yarlung-Tsangpo in the north, whereas along the east from Thailand to the western Myanmar, identified as different features almost arbitrarily by various authors. However, the Chaman Fault shows younging southward with a number of breaks in the Baluchistan region and abruptly stops short of the coast, taking a sharp turn to the west. More important, the Indus- Yarlung-Tsangpo Suture Zone terminates at Rinbun to the west-southwest of Lhasa, and passes into Jurassic slates/ granites. The extensive Permo-Carboniferous fluvio-glacial deposits and the presence of Gondwana flora and fauna on either side of the Indus-Yarlung-Tsangpo suture suggest continental continuity from Peninsular India to northern Tibet in the Paleozoic. There was also a continuity of climatic zones from the Indian to the Tibetan side of the platform, atleast from Proterozoic to the Quaternary period. The presence of Triassic Gondwana vertebrates in China, Indochina, Mongolia, and Siberia supports free two-way land routes between India and aforesaid landmasses even in Mesozoic. Therefore, various geological arguments based on observed field data do not support the existence of Indus-Yarlung-Tsangpo Suture Zone as a suture zone of modern plate tectonic concept. Instead, it is better explained as a rift valley formed more than 100 Ma prior to supposed collision because the ophiolite emplacements confined to the north and south by steeply dipping faults.