The upper Palaeozoic pebbly mudstone facies of peninsular Thailand and western Malaysia — Continental margin deposits of Palaeoeurasia

Abstract

The Phuket Group in Peninsular Thailand and the Singha Formation in NW Malaysia are of Devonian to Lower Permian age. These approximately 3000 m thick strata, which are part of the »SE-Asian pebbly mudstone belt« stretching from Southern Tibet to Sumatra, have been interpreted as continental margin deposits (Mitchell et al. 1970). In contrast, recent papers (Bunopas et al. 1978,Stauffer 1983) propose a glaciomarine origin. These authors follow the scenario that parts of mainland SE Asia (Shan-Thai Craton) rifted away from Gondwana during the Lower Carboniferous and collided with Eurasia during the Late Triassic after crossing the Tethys Ocean under clockwise rotation of more than 180 degrees. In this paper the arguments of these authors will be discussed and a sedimentological description will be given which shows that the pebbly mudstones are not glaciomarine sediments, but rather of continental margin origin. The investigations on Phuket and Langkawi Islands, when compared with newest results from Central and North Thailand, clearly show that the »Shan-Thai Craton« was a part of, or closely connected with Palaeoeurasia (Indosinia) during Carboniferous and Permian times (comp.Helmcke 1985). The pebbly mudstones were deposited on the southern continental margin of this continent (northern margin of Tethys).