Palaeozoic correlations and the Palaeogeography of the Sibumasu (Shan-Thai) Terrane - a brief review

Abstract

Furongian sandstones yield shallow-water trilobite faunas along the length of the Sibumasu Terrane in the four regions of NW Malaysia (Langkawi), southern Thailand (Satun), the Shan States of Myanmar and the Baoshan Block of western Yunnan. These are associated with felsic plutonics, volcanics or volcaniclastics in all four regions. Correlations of Langkawi Island and Satun Province shallow-water carbonates reveal a succession of dominantly molluscan, stromatoporoid-brachiopod faunas which, from conodont evidence, range from the mid-Tremadocian to the Darriwilian, and which have dominantly North China-Australian afinities. A major increase in sea-level in the late Darriwilian led to trilobite-brachiopod faunas with very strong South China afinities. Deep-water conditions of more than 150 m prevailed in the Katian with the deposition of red, stromatolitic limestones with cool/ deep-water trilobite and conodont faunas. This ‘Pa Kae facies’ re-occurs in limestones of Silurian and Devonian age in several areas of Sibumasu. Llandovery graptolitic shales occur along the length of the terrane. Silurian, probably outer shelf, limestones occur in NW Malaysia, the Shan States and Baoshan but have a limited distribution in Thailand. Most Katian to Devonian faunas in NW Malaysia, Thailand and Baoshan show evidence of deep-water deposition which continues into the Mississippian of NW Malaysia and into the Pennsylvanian of Thailand contrasting with the Baoshan Block’s extensive, Devonian to Mississippian shallow-water, coral-rich carbonates. A signiicant mid-Carboniferous to Pennsylvanian depositional gap in the Shan States and Baoshan may be due to regional uplift by the mantle plume that triggered Cisuralian rifting of Sibumasu from Gondwana. Palaeomagnetic results from Baoshan, along with biogeographic evidence and provenance data from Thailand show that Sibumasu was deinitely part of the Australian sector of Gondwana until the Cisuralian and did not experience major deformation until Late Triassic collision with Indochina.

Keywords

• thailand
• malaysia
• yunnan
• ordovician
• devonian
• biostratigraphy
• palaeogeography