Records of the oceanic propagator closure at the southern splay of the Palaeo‐Tethys

Abstract

The Palaeo-Tethys is known to have diverged into several splays throughout East and South-east Asia. Several researchers have widely studied the importance and geometries of the Palaeo-Tethys' branches. Plate reconstruction geometries for the southern Palaeo-Tethys splay suggest that the ocean either connects to the proto-Pacific or dies out. We review and discuss the Late Palaeozoic to the Early Mesozoic lithologies attributed to the Palaeo-Tethys, from the Himalayan Syntaxis in the north to the Bangka and Belitung islands in western Indonesia to the south. Relics of oceanic crust and deep-sea sediments related to the main Palaeo-Tethys Basin can be traced from the South China (Yunnan)-Thailand border to Peninsular Malaysia. A sub-parallel back-arc suture exists in eastern Thailand in the north and vanishes towards the south at the latitude of the Gulf of Thailand. Towards the south of Peninsular Malaysia, the material that constitutes the suture zone of main Palaeo-Tethys is found offshore in the Riau Archipelago, Indonesia, and has been extensively eroded. Thus, we rely on gravity signatures to extrapolate the extension of the structures to the Bangka and Belitung islands, which show only minor serpentine and pillow basalts occurrences along a line that curves towards Borneo. The metamorphic rocks associated with the suture zones range from high grade (gneiss) in Thailand to low grade (mica schist and minor amphibolite) in Peninsular Malaysia. The syn- and post-collisional granitic bodies that form large batholiths in Thailand and Malaysia are comparatively smaller in Indonesia, particularly on Belitung Island, suggesting the lack of large underplating of the Sibumasu crust within the region. We interpret the stratigraphic and tectonic observations of the southern Palaeo-Tethys to support the theory of the southward (present orientation) opening of a propagating oceanic basin from Devonian to Carboniferous, which began to close from the Permian to Triassic period.