Bulletin of the Geological Society of Malaysia, Volume 19, April 1986, pp. 153 – 164
Jabatan Geologi, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia
Abstract: The older continental part of Southeast Asia is a composite of four tectonic blocks, the SIBUMASU Block (comprising the Shan States of Burma, northwest Thailand, Peninsular Burma and Thailand, western Malaya and Sumatra and possibly extending northwards into Tibet and western China), the MANABOR Block (comprising eastern Malaya, Natuna and southwest Borneo), the Indochina Block (comprising eastern Thailand, Laos, Vietnam southwest of the Song Ma-Song Da suture zone and Kampuchea) and the South China Block (comprising northeast Vietnam and South China).
The South China and Indochina Blocks probably rifted from eastern Gondwana in Late Devonian-Early Carboniferous times and appear to have sutured to each other by the Middle Carboniferous. Stratigraphical, palaeomagnetic, faunal and floral data indicate that South China lay in low equatorial latitudes during the Carboniferous and Permian. The Indochina Block must therefore have occupied similar palaeolatitudes in the Middle and Late Carboniferous and Permian.
The presence of extensive Carbo-Permian glacial marine diamictites, Carbo-Permian faunas with Australian biogeographic affinities and recent palaeomagnetic evidence indicates that the SIBUMASU Block (rotated approximately 180°) lay adjacent to the northwest Australian part of Gondwanaland in the Carboniferous and early Permian. The rifting of SIBUMASU from Gondwana probably began in the Late Devonian-Early Carboniferous but the main separation probably occurred in late Lower Permian times. Accretion of SIBUMASU to the Indochina/South China Blocks was probably completed by the Middle Permian.
The MANABOR Block had sutured to SIBUMASU by the Late Triassic but the actual timing of accretion may have been as early as Lower Carboniferous.