Shan–Thai Terrane

The Shan–Thai or Sibumasu Terrane is a mass of continental crust extending from Tibet into Southeast Asia sharing a similar geological history. The Shan–Thai Terrane rifted from Australia in the Permian and collided with the Indochina terrane in the Triassic.^[1] It extends from Malaysia, through peninsular Thailand, Myanmar, West Yunnan, to Lhasa.^[2]

Shan–Thai is c. 4,000 km (2,500 mi) long and bounded by the Indochina terrane to the east and the South China terrane to the north. It is one of a series of continental blocks or terranes that were rifted off eastern Gondwana during the Ordovician (495 to 443 Ma), long before the formation of Pangaea. Today these blocks form south-east Asia but the different timing of their journeys has given them distinct geologic histories.^[3]

Shan–Thai was an archipelago on the Paleo-Tethys Ocean spread over several latitudes. It can therefore be subdivided into several portions with different palaeo-geographical histories. The internal "Thai" elements, bordering the Indochina block, are of Cathaysian type and characterised by palaeo-tropical warm-water facies. The external "Shan" part has Gondwanan cold-water facies whilst the central "Sibumasu" part is transitional between the other two. The internal parts of Shan–Thai merged with Laurasia 265 Ma when the Nan-Uttaradit suture closed.^[4] Oceanic basins separated the other elements of Shan–Thai until the Late Triassic–Early Jurassic Late Indochina Orogeny.^[5]

The collision between India and Eurasia during the Oligocene and Miocene resulted in clockwise rotation of south-west Asia, severe deformation of south-east Asia, and the extrusion of Shan–Thai and Indochina blocks. These two blocks are still crisscrossed by the faults from this collision.^[6]

References[edit]

Notes

^ Bunopas & Vella 1992: "Thailand consists of Shan–Thai and Indochina Microcontinents or Terranes welded together by the subsequently deformed Nan Suture.... During the Middle Triassic Shan–Thai sutured nearly simultaneously to Indochina and to South China, the continent–continent collision being a part of the Indosinian Orogeny and Indochina tended to underthrust Shan–Thai."
^ Chaodumrong, Xiangdong & Shuzhong 2007: "Permian strate of the Shan-Thai terrance in Thailand consist of the clastic sequence of the Kaeng Krachon Group and the conformably overlying carbonate sequence of the Ratburi Group ...[which] can be traced widely from Malaysia, through peninsular Thailand, Myanmar, West Yunnan, to Lhasa."
^ Fortey & Cocks 1998, Introduction, pp. 43-44
^ Hirsch et al. 2006, Abstract; Paleozoic, p. 201
^ Hirsch et al. 2006, Late Permian – Triassic, p. 201
^ Hirsch et al. 2006, Cenozoic, p. 201

Sources

Bunopas, Sangad; Vella, Paul (November 1992). Geotectonics and Geologic Evolution of Thailand (PDF). National Conference on "Geologic Resources of Thailand: Potential for Future Development". Department of Mineral Resources, Bangkok. pp. 209–229. Archived from the original (PDF) on 28 March 2018. Retrieved 5 November 2017.
Chaodumrong, Pol; Xiangdong, Wang; Shuzhong, Shen (2007). Permian lithostratigraphy of the Shan-Thai terrane in Thailand: revision of the Kaeng Krachan and Ratburi Groups (PDF). GEOTHAI'07 International Conference of Geology of Thailand: Towards Sustainable Development and Sufficiency Economy. Department of Mineral Resources, Bangkok & Nanjing Institute of Geology and Palaeontology, Nanjing. pp. 229–236. Retrieved 5 November 2017.
Fortey, R. A.; Cocks, L. R. M. (1998). "Biogeography and palaeogeography of the Sibumasu terrane in the Ordovician: a review. Biogeography and geological evolution of SE Asia, 43-56" (PDF). In Hall, R.; Holloway, J. D. (eds.). Biogeography and Geological Evolution of SE Asia. Leiden: Backhuys Publishers. doi:10.1002/mmnz.20000760119. ISBN 90-73348-97-8. Retrieved 5 November 2017.
Hirsch, F.; Ishida, K.; Kozai, T.; Meesook, A. (2006). "The welding of Shan-Thai". Geosciences Journal. 10 (3): 195–204. Bibcode:2006GescJ..10..195H. doi:10.1007/BF02910364. S2CID 140133725. Retrieved 5 November 2017.
Metcalfe, I (2011). "Tectonic framework and Phanerozoic evolution of Sundaland" (PDF). Gondwana Research. 19 (1): 3–21. Bibcode:2011GondR..19....3M. doi:10.1016/j.gr.2010.02.016. Retrieved 5 November 2017.
Metcalfe, I. (2013). "Tectonic Evolution of the Malay Peninsula" (PDF). Journal of Asian Earth Sciences. 76: 195–213. Bibcode:2013JAESc..76..195M. doi:10.1016/j.jseaes.2012.12.011. Retrieved 5 November 2017.

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[1] Bunopas & Vella 1992: "Thailand consists of Shan–Thai and Indochina Microcontinents or Terranes welded together by the subsequently deformed Nan Suture.... During the Middle Triassic Shan–Thai sutured nearly simultaneously to Indochina and to South China, the continent–continent collision being a part of the Indosinian Orogeny and Indochina tended to underthrust Shan–Thai."

[2] Chaodumrong, Xiangdong & Shuzhong 2007: "Permian strate of the Shan-Thai terrance in Thailand consist of the clastic sequence of the Kaeng Krachon Group and the conformably overlying carbonate sequence of the Ratburi Group ...[which] can be traced widely from Malaysia, through peninsular Thailand, Myanmar, West Yunnan, to Lhasa."

[3] Fortey & Cocks 1998, Introduction, pp. 43-44

[4] Hirsch et al. 2006, Abstract; Paleozoic, p. 201

[5] Hirsch et al. 2006, Late Permian – Triassic, p. 201

[6] Hirsch et al. 2006, Cenozoic, p. 201

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