Shan–Thai terrane

The Shan–Thai or Sibumasu terrane was a microcontinent which extended from Lhasa (Tibet) West Yunnan, Myanmar, West Thailand, much of Malaysia and Sumatra. It was an archipelago with landmasses which shared a similar geological history. The Shan–Thai terrane rifted from Australian plate part of Gondwana in the Permian. It collided with the Indochina and South China terranes almost simultaneously in the Middle Triassic.

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. Today Shan-Thai and Indochina form mainland Southeast Asia (the Indochinese Peninsula) but with original palaeo-geographic positions may have been different and their geologic histories also differ.

Its Early Ordovician faunas show affinity with North China-Korea-Australia part of Gondwana on the palaeo-equator, but its Late Ordovician fossils and sedimentary facies have affinity with the South China block. Fortey & Cocks (1998) suggest that North and South China might not have been far as previously proposed and that Sibumasu, which was most similar to South China, may have moved away from North China/Australia towards South China and came to be close to it over the Ordovician.

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-geographic 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. Oceanic basins separated the other elements of Shan–Thai until the Late Triassic–Early Jurassic Late Indochina Orogeny.

The collision between the Indian plate and the Eurasian plate during the Oligocene and Miocene resulted in clockwise rotation of southwest Asia, severe deformation of southeast Asia, and the extrusion of Shan–Thai and Indochina blocks. These two blocks are still crisscrossed by the faults from this collision.

See also

References

Notes
  1. ↑ 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."
  2. ↑ Fortey & Cocks 1998, Introduction, pp. 43-44
  3. ↑ 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."
  4. ↑ Fortey & Cocks 1998, Introduction, pp. 43-44
  5. ↑ Fortey & Cocks 1998, Introduction, pp. 43-44
  6. ↑ Hirsch et al. 2006, Abstract; Paleozoic, p. 201
  7. ↑ Hirsch et al. 2006, Late Permian – Triassic, p. 201
  8. ↑ Hirsch et al. 2006, Cenozoic, p. 201
Sources
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  • 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. Archived from the original (PDF) on 2017-11-07. 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". 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. Archived from the original (PDF) on 27 January 2018. Retrieved 5 November 2017.