Permian tectonic framework and palaeogeography of SE Asia

Abstract

The principal continental lithospheric terranes, now comprising SE Asia and that existed in the Permian, are the South China/Indochina Super Terrane, and the Sibumasu, Simao, West Burma and SW Borneo/Semitau terranes. The Simao Terrane is here regarded a separate terrane, derived from South China by back-arc spreading in the Lower Carboniferous, rather than as an extension of Indochina. The main Palaeo-Tethys ocean in Thailand is identified as being represented by the Chiang Mai and Sra Kaeo sutures, and the eastern boundary of the Sibumasu Terrane is thus interpreted to lie farther west in Thailand than previously inferred. The Nan-Uttaradit Suture is interpreted as representing a marginal back-arc basin, and contiguous with the Ailaoshan and Jinshajiang sutures in SW China. The South China/Indochina Super Terrane, and the Simao Terrane were located within the Palaeo-Tethys in equatorial latitudes during the Permian, where they, together with North China, exhibit Cathaysian floras and faunas. The Sibumasu Terrane was located on the NW Australian margin of Gondwana until the Sakmarian. Major shifts in faunal affinities from Gondwana province faunas to an independent Sibumasu Province and then to assimilation into the Cathaysian Province, records the separation and rapid northward drift of Sibumasu after the Late Sakmarian. The principal Permian palaeogeographic models for the region are assessed for internal consistencies and conflicts.