Time to reconsider the enigmatic tail of eastern Paleo-Tethys: New insights from Borneo

• Main Authors: Zhang, Xiao Ran, Chung, Sun-Lin, Ghani, Azman A., Rahmat, Rezal, Hsin, Yi-Ju, Lee, Hao-Yang, Liu, Ping-Ping, Xi, Jinyu
• Format: Article
• Published: Elsevier 2023
• Subjects: GE Environmental Sciences; QE Geology
• Online Access: http://eprints.um.edu.my/38584/

The rise of Tibet and growth of Asia resulted from successive accretion of Gondwana-derived continental frag-ments at the expense of Tethyan oceans, yet how and where the eastern Paleo-Tethys closed in SE Asia remain controversial. Here we report new and synthesized detrital zircon data from Borneo and relevant regions revealing that West and SW Borneo show consistent Precambrian age profiles resembling that of Northern Australia (Kimberley to Pine Creek), but contrasting with those of NW/NE Australia, Bird's Head, and Cathaysia/ Indochina. Considering the questionable suture between West and SW Borneo, we suggest a united Borneo basement that originated from Northern Australia, with a position between Sumatra and Timor. Surprisingly, Borneo lacks NE Australia-sourced ca. 1700-1400 and 400-280 Ma zircons that prevail in Triassic-Jurassic strata of Timor, Babar, and Tanimbar offshore Northern Australia, which may be best explained by pre-Triassic rifting of the Borneo basement from Northern Australia. Combining with recent investigations, we propose a new tectonic scenario involving a Permian separation of Borneo (probably together with Sumatra) from northern Gondwana through opening of the Meso-Tethys Ocean followed by a Triassic docking with Eurasia that closed the eastern Paleo-Tethys. Thus, assembly of Sundaland (continental core of SE Asia) completed in the Late Triassic, rather than Cretaceous as previously thought, and the tail (or the southeasternmost section) of eastern Paleo-Tethys lies within the Kuching zone of Borneo. Our new reconstruction challenges current understanding of Gondwana dispersion and Asian accretion, shedding new light on Asian climate change and biogeographic diversity.