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Keywords:

  • Banka Limestone;
  • Changning-Menglian Belt;
  • Doi Chiang Dao Limestone;
  • foraminifers;
  • Inthanon Zone;
  • Lopingian (Late Permian);
  • mid-oceanic Palaeotethys

Abstract

The Changning-Menglian Belt of West Yunnan, SW China and the Inthanon Zone of Northern Thailand are the two best-studied Palaeotethyan collisional belts in Asia. These belts comprise thick pure carbonate successions with basalt at the base, ranging from the Early Carboniferous to the end of the Permian. They are interpreted to have a mid-oceanic build-up origin and have been formed on the top of seamounts and/or oceanic plateaus. The mid-oceanic carbonates in the Inthanon Zone are called the Doi Chiang Dao Limestone and we newly propose in this paper the term Banka Limestone for those in the Changning-Menglian Belt. Foraminiferal faunas from these limestones revealed that they have good Lopingian records of a mid-oceanic shallow-marine domain in the Palaeotethys, and three consecutive foraminiferal zones can be established. The Wuchiapingian is represented by the Codonofusiellakwangsiana Zone comprising four fusuline and 21 non-fusuline foraminiferal genera. The early Changhsingian is distinguished by the Palaeofusulina simplicata/minima Zone, and contains seven fusuline and 27 non-fusuline genera. The succeeding Palaeofusulinasinensis/prisca Zone in the late Changhsingian is characterized by the occurrence of large and advanced Palaeofusulina, and still maintained a high generic diversity with eight fusuline and 36 non-fusuline genera. The Lopingian foraminiferal faunal succession of the mid-oceanic Palaeotethys is essentially similar to those observed in cratonic South China. This is suggestive of a major oceanic part of the Palaeotethys to be included palaeobiogeographically in the Cathaysian Province. The coeval Neotethyan domain also had a high-diversified fauna with the occurrence of six fusuline and nearly 30 non-fusuline genera but lacked Palaeofusulina in Changhsingian time. Panthalassan mid-oceanic build-ups during Lopingian time carried likely lower foraminiferal diversity than those of the Palaeo- and Neotethys. Essentially, Tethyan mid-oceanic carbonate build-ups presumably provided a peculiar habitat suitable for shallow-marine foraminifers in a pelagic equatoro-tropical setting throughout almost the entire Lopingian time. Copyright © 2010 John Wiley & Sons, Ltd.