Lower Permian glacially influenced deposits in Phuket and adjacent islands, peninsular Thailand

It has previously been proposed that the Sibumasu block of Southeast Asia, which contains glaciomarine deposits, became detached from the Gondwana margin during the Early Permian. A combination of facies analysis and the identification of dropstones and dump structures from a Lower Permian diamictite-bearing sequence at Phuket, Thailand, and adjacent islands suggests that the sediments originated as glaciomarine and debris-flow deposits. The Lower Permian diamictite-bearing sequence in the study area corresponds to the Ko Sire and Ko He Formations, both of which consist of three principal lithofacies: diamictite, sandstone, and fine-grained facies. The low-lying Ko Sire Formation is up to 400 m thick and is characterized by laminated mudstone; the presence of dropstones and dump structures associated with Cruziana ichnofacies indicates ice-rafted sedimentation in a glacially influenced offshore area. The Ko Sire Formation is overlain by a diamictite sequence of the Ko He Formation (up to 400 m thick). Poorly and well-stratified diamictites with tabular and lensoidal geometries, in combination with resedimentation textures, indicate that the diamictites within the Ko He Formation are debris-flow deposits. The similar lithology of clasts in the diamictites and dropstones possibly suggests that the debris-flow diamictite was presumably remobilized from pre-existing glacial deposits. The evidence of a glacially influenced offshore environment supports a previously proposed paleogeographic interpretation in which the Sibumasu block was most likely located at the Northwest Australian margin of Gondwana.