The Shan–Thai or Sibumasu terrane is a mass of continental crust extending from Tibet into Southeast Asia sharing a similar geological history.
[1] It extends from Malaysia, through peninsular Thailand, Myanmar, West Yunnan, to Lhasa.
It is one of a series of continental blocks or terranes that were rifted off eastern Gondwana during the Ordovician (495 to 443 Ma), 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.
The internal "Thai" elements, bordering the Indochina block, are of Cathaysian type and characterised by palaeo-tropical warm-water facies.