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

Published online by Cambridge University Press:  01 May 1998

K. DAVIDEK ,
E. LANDING ,
S. A. BOWRING ,
S. R. WESTROP ,
A. W. A. RUSHTON ,
R. A. FORTEY  and
J. M. ADRAIN
K. DAVIDEK
Affiliation:
Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
E. LANDING
Affiliation:
New York State Geological Survey, The State Education Department, Albany, NY 12230, USA
S. A. BOWRING
Affiliation:
Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
S. R. WESTROP
Affiliation:
Department of Earth Sciences, Brock University, St. Catharines, ON K1A 0E8, Canada
A. W. A. RUSHTON
Affiliation:
Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK Formerly British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
R. A. FORTEY
Affiliation:
Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
J. M. ADRAIN
Affiliation:
Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Abstract

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.

Type
Research Article
Information
Geological Magazine , Volume 135 , Issue 3 , May 1998 , pp. 303 - 309
Copyright
© 1998 Cambridge University Press

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