Tectonics and metamorphism of the Tethyan Sedimentary Sequence in SE Tibet: a cross section from Qonggyai to Gyaca

Chiara Montomoli , B. Antolin, Erwin Appel, I. Dunkl, and L. Ding

The proposed transects is located in South Eastern Tibet and offers a very good exposure of the Tethyan Sedimentary Sequence (TSS).

The TSS has been deposited on the northern Indian passive continental margin and it registers the evolution of the Paleo-Tethys sea, from the pre-rift stage (Cambrian – Ordovician) to the final break-up of Gondwana in early Cretaceous and subsequent sedimentation till Eocene.

Along the proposed transect the TSS, made up by a flysch sequence of Middle Triassic to early Jurassic age and crops out for about 100 kilometers along the N-S study section. south of the Yarlung Tsangpo River from Qonggyai in the west until east of Gyaca.

To the North the TSS is delimited from the mélange complex and the Cretaceous clastic rocks by the top-to-the North Renbu-Zedong thrust correlated with the Great Counter Thrust cropping out westward.

To the South the TSS is limited by the north dipping Lunze fault, that divides it from the Jurassic and Cretaceous portion of the sequence (Pan et al., 2004).

The field trip gives the opportunity to observe several sets of ductile and brittle-ductile structures, linked to several deformation phases during the collisional events.