A Volcanic Tuff Near the Carboniferous–Permian Boundary, Taiyuan Formation, North China: Radioisotopic Dating and Global Correlation

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A 66 cm thick volcanic ash fall tuff occurring within a thick coal deposit and containing a paleobotanical fossil lagerstätte in the Wuda coal district of North China has been dated as 298.34 ± 0.09 Ma. The fossil flora in the tuff indicates a latest Carboniferous to earliest Permian age and is thus in agreement with the radioisotopic age of earliest Permian, Asselian, age. This bed supplies a well-defined position of the Carboniferous–Permian boundary near the northern edge of the North China Block. The tuff occurs in the top of the Taiyuan Formation and several meters below the base of the Shansi (= Shanxi) Formation. These beds were traditionally considered late Carboniferous to early Permian in age. Our results demonstrate that the Taiyuan Formation is time transgressive and its age has to be revised for the northern part of the North China Block.