Late Triassic volcanic activity in South-East Asia: New stratigraphical,geochronological and paleontological evidence from the Luang Prabang Basin (Laos) |
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| Institution: | 1. School of Earth Science and Geological Engineering, Sun Yat-Sen University, Guangzhou 510275, China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;3. Department of Earth Sciences, University of St Andrews, North Street, St Andrews KY169AL, UK;4. Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;5. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;1. Centre for Tectonics Resources and Exploration (TRaX), Department of Earth Sciences, The University of Adelaide, SA 5005, Australia;2. Department of Geological Sciences, Chiang Mai University, 239 Huaykaew Road, Tumbol Suthep Amphur Muang, Chiang Mai 50200, Thailand;3. Western Australian Argon Isotope Facility, Dept of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;4. Centre for Tectonics Resources and Exploration (TRaX), The Australian School of Petroleum, The University of Adelaide, SA 5005, Australia;1. School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou, 510275, China;2. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan, 430074, China;3. Department of Applied Geology, Curtin University, Perth, 6102, Australia;4. School of Geotechnology, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand;1. Universidade de São Paulo, Departamento de Geofísica, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Rua do Matão, 1226-Cidade Universitária, Butantã, 05508-090 São Paulo, SP, Brazil;2. Univ Rennes, CNRS, Géosciences Rennes - UMR 6118, F-35000, Rennes, France;3. Biogéosciences UMR uB/CNRS 6282, Université Bourgogne Franche-Comté, 21000 Dijon, France;4. CASP, West Building, Madingley Rise, Madingley Road, Cambridge CB3 0UD, United Kingdom;5. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, People''s Republic of China |
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| Abstract: | In South-East Asia, sedimentary basins displaying continental Permian and Triassic deposits have been poorly studied. Among these, the Luang Prabang Basin (North Laos) represents a potential key target to constrain the stratigraphic and structural evolutions of South-East Asia. A combined approach involving sedimentology, palaeontology, geochronology and structural analysis, was thus implemented to study the basin. It resulted in a new geological map, in defining new formations, and in proposing a complete revision of the Late Permian to Triassic stratigraphic succession as well as of the structural organization of the basin. Radiometric ages are used to discuss the synchronism of volcanic activity and sedimentation.The Luang Prabang Basin consists of an asymmetric NE-SW syncline with NE-SW thrusts, located at the contact between Late Permian and Late Triassic deposits. The potential stratigraphic gap at the Permian–Triassic boundary is therefore masked by deformation in the basin. The Late Triassic volcaniclastic continental deposits are representative of alluvial plain and fluvial environments. The basin was fed by several sources, varying from volcanic, carbonated to silicic (non-volcanic). U–Pb dating of euhedral zircon grains provided maximum sedimentation ages. The stratigraphic vertical succession of these ages, from ca. 225, ca. 220 to ca. 216 Ma, indicates that a long lasting volcanism was active during sedimentation and illustrates significant variations in sediment preservation rates in continental environments (from ～100 m/Ma to ～3 m/Ma). Anhedral inherited zircon grains gave older ages. A large number of them, at ca. 1870 Ma, imply the reworking of a Proterozoic basement and/or of sediments containing fragments of such a basement. In addition, the Late Triassic (Carnian to Norian) sediments yielded to a new dicynodont skull, attributed to the Kannemeyeriiform group family, from layers dated in between ～225 and ～221 Ma (Carnian). |
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| Keywords: | Luang Prabang Basin Permian Triassic Volcaniclastic continental deposits Kannemeyeriiformes Dicynodont U–Pb geochronology |
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