Formation and evolution of the Tethys in the Tibetan Plateau

Abstract

The Tibetan Plateau is closely related to the evolution of Tethys, and it constitutes the main scope of the eastern Tethys. According to current data from regional tectonic studies and sedimentary records, Tethys in Tibetan Plateau can be divided into three different stages, namely, Neo-Tethys, Paleo-Tethys, and Proto-Tethys, representing the Tethys in Mesozoic-Cenozoic, Late Paleozoic and Early Paleozoic, respectively. Furthermore, they correspond to three zones in the Tibetan Plateau, namely the northern Tethyan, the central Tethyan region and the southern Tethyan region, respectively. The Proto-Tethys lies in Kunlun and Qilian Mountains in the northern Tethyan region, represented by the Fifth Suture Zone as its remnant. It had been formed in Sinian and closed in Ordovician and Silurian. It was the earliest Tethyan ocean known up to now. The Paleo-Tethys lies in Hoh Xil-Bayan Har in the central of Tibet Tethyan, represented by the Third and Fourth Suture Zones. It initiated as a back-arc basin in Ordovician and eventually formed as a basin typical oceanic crust in Carboniferous and Permian due to its continuous back-arc breaking and spreading. The Paleo-Tethys ocean still existed until the end of the Triassic. The Neo-Tethys lies in the southern Tethyan region, represented by the Yarlung Zangbo Suture Zone. It initiated on the shelf in the northern part of Gondwanaland at the end of Permian and the beginning of Triassic and formed in Mesozoic and Cenozoic. It began to subduct northward and was consumed very soon at the end of Jurassic, however, the main oceanic basin, which is represented by the Yarlung Zangbo Suture Zone and named Neo-Tethys, didn't consume until Early-Mid Eocene. It is obvious that the Tethyan ocean moved southward step by step according to the space distribution pattern of major Tethyan oceans in different periods. The evolution of Tethys, combined with the characteristics of terranes and distribution pattern of biogeography, also indicates the plate tectonic model that the Tibetan Plateau was formed by the continuous rifting of Gondwanaland and the accretion of the Eurasia.