A REVISED HISTORY OF CENOZOIC ACCRETIONS FOR THE EURASIAN MARGIN

New age data obtained in the Wharton Basin offshore Indonesia during the 2008 IFM-GEOMAR CHRISP (Christmas Island Seamount Province) research cruise, indicating the presence of Jurassic seafloor, necessitated a revision of the plate tectonic model for the early Indian Ocean. Compared to previous models our revised reconstructions involve a greater western extent for Argoland/West Burma and also a reduced extent of Greater Indian crust (Gascoyne block), as a promontory of continental crust north of the Wallaby-Zenith Fracture Zone, separated from Greater India by about 50 km of oceanic crust. An implication of our revised model is that Argoland/West Burma block accreted to the Eurasian and Southeast Asia margin c. 60-65 Ma, with an earlier collision event likely if an intra-oceanic arc was present. This event may coincide with a major regional angular unconformity in the Lhasa terrane dated c. 69 Ma. Some researchers also refer to an additional and not widely recognized suture zone within the Lhasa terrane, but the terrane itself is linked to the closure of the Bangong suture, which was traditionally considered a Jurassic event, though recent studies along the Bangong suture indicate oceanic conditions were prevalent until at least the mid Cretaceous. In our model, the Gascoyne block reaches Sumatra c. 50 Ma, supported by the emplacement of granitic batholiths in Sumatra at this time, while an arbitrary northeastern extent of Greater India reaches the Eurasian margin c. 35 Ma, with earlier collisions likely depending on the configuration of the southern Eurasian margin, overall complying with the activation of the Alaio-Shan/ Red River fault resulting from strike-slip motion through Central Burma from about 30 Ma. Seismic tomography supports onshore geological evidence that, preceding Greater India, an intra-oceanic arc was accreted to the Eurasian margin. The timing of our continental collisions has been modeled in context with the position of this oceanic arc.