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New uppermost Cambrian U–Pb date from Avalonian Wales and age of the Cambrian–Ordovician boundary

  • K. DAVIDEK (a1), E. LANDING (a2), S. A. BOWRING (a1), S. R. WESTROP (a3), A. W. A. RUSHTON (a4) (a5), R. A. FORTEY (a4) and J. M. ADRAIN (a4)...


A crystal-rich volcaniclastic sandstone in the lower Peltura scarabaeoides Zone at Ogof-ddû near Criccieth, North Wales, yields a U–Pb zircon age of 491∓1 Ma. This late Late Cambrian date indicates a remarkably young age for the Cambrian–Ordovician boundary whose age must be less than 491 Ma. Hence the revised duration of the post-Placentian (trilobite-bearing) Cambrian indicates that local trilobite zonations allow a biostratigraphic resolution comparable to that provided by Ordovician graptolites and Mesozoic ammonites.


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Geological Magazine
  • ISSN: 0016-7568
  • EISSN: 1469-5081
  • URL: /core/journals/geological-magazine
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