as on Figs.1 and 2) terrane embraces much of the Malay peninsula, extending northwards into West Thailand and Burma and southwards into western Indonesia (Sumatra). It is bounded to the east by the Uttaradit-Nan to Raub-Bentong sutures, and to the west by what Metcalfe (1992) termed the Shan boundary (also possibly an an- cient suture). Thus it comprises a tract of land some 4000 km long, clearly a continental entity of sufficient size to have acquired its own palae- ogeographic signature. Several major neigh- bouring terranes have been referred to in rela- tion to the history of Sibumasu. These are (Fig.1): the Indochina terrane immediately to the east; the South China terrane, today comprising many of the most populous regions of China south of the Tsinling (Chin Ling) suture; the North China terrane (including the northern part of China and associated regions of Korea); and the Australian continent, which was already constituted in something like its present form, although the Tasman fold-belt to the south (in- cluding New South Wales and much of Victoria) and montane Queensland were mobile belts in the Ordovician.