The Shan–Thai orSibumasu Terrane is a mass of continental crust extending from Tibet into Southeast Asia sharing a similar geological history. The Shan–Thai Terrane rifted from Australia in the Permian and collided with the Indochina terrane in the Triassic.[1] It extends from Malaysia, through peninsular Thailand, Myanmar, West Yunnan, to Lhasa.[2]
Shan–Thai is c. 4,000 km (2,500 mi) long and bounded by the Indochina terrane to the east and the South China terrane to the north. It is one of a series of continental blocks or terranes that were rifted off eastern Gondwana during the Ordovician (495 to 443Ma), long before the formation of Pangaea. Today these blocks form south-east Asia but the different timing of their journeys has given them distinct geologic histories.[3]
Shan–Thai was an archipelago on the Paleo-Tethys Ocean spread over several latitudes. It can therefore be subdivided into several portions with different palaeo-geographical histories. The internal "Thai" elements, bordering the Indochina block, are of Cathaysian type and characterised by palaeo-tropical warm-water facies. The external "Shan" part has Gondwanan cold-water facies whilst the central "Sibumasu" part is transitional between the other two. The internal parts of Shan–Thai merged with Laurasia 265Ma when the Nan-Uttaradit suture closed.[4] Oceanic basins separated the other elements of Shan–Thai until the Late Triassic–Early Jurassic Late Indochina Orogeny.[5]
The collision between India and Eurasia during the Oligocene and Miocene resulted in clockwise rotation of south-west Asia, severe deformation of south-east Asia, and the extrusion of Shan–Thai and Indochina blocks. These two blocks are still crisscrossed by the faults from this collision.[6]
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