云南墨江上三叠统歪古村组燧石质砾石中的晚古生代放射虫化石及其地质意义

LATE PALEOZOIC RADIOLARIANS FROM CHERT PEBBLES OF THE UPPER TRIASSIC WAIGUCUN FORMATION IN MOJIANG, YUNNAN AND ITS GEOLOGICAL SIGNIFICANCE

云南哀牢山缝合带由于长期未找到晚石炭世至二叠纪深海环境的化石及沉积地层记录,对哀牢山古特提斯盆地演化历史存在着不同认识。文中报道了采自云南墨江坝留地区上三叠统歪古村组底砾岩中的早石炭世和中二叠世放射虫化石,所有放射虫化石发现于4件燧石质砾石中,共计11属9种和7未定种及1属种未定放射虫。其中,3件砾石含有Albaillella deflandrei Gourmelon,Albaillella sinuosa Won and Seo等早石炭世放射虫化石组合,另1件砾石含有Pseudoalbaillella spp.,Quadricaulis scalae Caridroit and De Wever,Cauletella sp.和Ishigaum sp.等中二叠世放射虫化石组合。由此表明,哀牢山缝合带存在着早石炭世和中二叠世深海盆地沉积地层记录,哀牢山深海盆地应该在中二叠世之后封闭。该成果为探讨哀牢山古特提斯盆地演化提供了放射虫古生物学证据,进而说明哀牢山缝合带与金沙江缝合带一样,也存在石炭纪和二叠纪深水洋盆沉积地层记录,指示其演化历史是相同的。

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.