Died out at the end of Permian or extended into the Triassic? – The tale of the albaillellarians (radiolarians) and detrital zircons of the Nanpihe bridge section in the Changning-Menglian belt, Western Yunnan, China

Radiolarians of the albaillellarian group, Albaillella triangularis, Albaillella yaoi, Albaillella lauta, Albaillella protolevis, Albaillella levis, and Neoalbaillella optima, are identified from the Nanpihe bridge section of the Changning-Menglian belt in western Yunnan, China. They can be correlated to those from the Neoalbaillella optima Zone of the Upper Permian in Japan and South China. Genera Albaillella and Neoalbaillella, which have been considered as indices of the Upper Permian, are normally believed to have vanished at the Permian-Triassic (P/T) boundary. Nevertheless, detrital zircons from five radiolarian-bearing beds of the Nanpihe bridge section yielded unimodal UPb ages indicative of Early-Middle Triassic (i.e., 241 Ma, 243 Ma, 245 Ma, 247 Ma, and 249 Ma). The exquisite preservation of delicate skeletal structures of radiolarians, their occurrence within the matrix of cherts rather than in clasts, and the absence of fossils of other ages exclude the possibility of reworking. These results indicate that the albaillellarians identified in the studied section, which were previously believed to have gone extinct during the end-Permian mass extinction, could survive into the Triassic.