Lower Permian glacially influenced deposits in Phuket and adjacent islands, peninsular Thailand |
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| Authors: | Tianpan Ampaiwan Ken-Ichiro Hisada and Punya Charusiri |
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| Institution: | Chevron Thailand Exploration and Production, SCB Park East Building, 19, Chatuchak, Bangkok 10900, Thailand (email: ),;Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572 Japan, and;Research Unit for Earthquake and Tectonic Geology, Department of Geology, Chulalongkorn University, Bangkok 10330, Thailand |
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| Abstract: | 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. |
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| Keywords: | dropstone structure dump structure Early Permian glaciomarine Gondwana Sibumasu block |
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