FORMATION IN MOJIANG, YUNNAN AND ITS GEOLOGICAL SIGNIFICANCE
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Abstract:
It has been controversial for a long time on the tectonic evolution of Ailaoshan Ocean Basin since the fossil and sedimentary records implying a deep-sea environment from late Carboniferous to Permian have not been discovered in the Ailaoshan Suture Zone, which represents the Ailaoshan Ocean Basin. This paper reports the Early Carboniferous and Middle Permian radiolarians discovered from the bottom conglomerate of the Upper Triassic Waigucun Formation in the BaLiu area, Mojiang, Yunnan. Well-preserved radiolarians were recovered from four chert pebbles. In total, 11 genera, 14 species, 7 indeterminate species and 1 gen. et sp. indet. were identified. In these chert pebbles, three of them yield the Early Carboniferous radiolarian Assemblage such as Albaillella deflandrei Gourmelon, Albaillella sinuosa Won and Seo, whereas another pebble contains the Middle Permian radiolarian assemblage including Pseudoalbaillella spp., Quadricaulis scalae Caridroit and De Wever, Cauletella sp. and Ishigaum sp. Thus, it is certain that the sedimentary records, which represent a deep-sea environment in the Ailaoshan Suture Zone in the Early Carboniferous and Middle Permian, do exist. Furthermore, it indicates that the Ailaoshan Ocean Basin might have been closed after the Middle Permian. The Ailaoshan suture zone is the same as the Jinshajiang suture zone, exisiting records of sedimentary strata in the Carboniferous and Permian deep-water ocean basins, further suggested that there are the same evolution history in the Ailaoshan suture zone and the Jinshajiang suture zone. The above results provide significant palaeontological evidence for the evolution of the Ailaoshan Paleo-Tethyan Basin.
