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Radiometric age of the Monograptus cyphus graptolite zone in Southeastern Alaska — an estimate of the age of the Ordovician—Silurian boundary

Published online by Cambridge University Press:  01 May 2009

M. A. Lanphere ,
M. Churkin Jr  and
G. D. Eberlein
M. A. Lanphere
Affiliation:
U.S. Geological Survey, Menlo Park, California 94025, U.S.A.
M. Churkin Jr
Affiliation:
U.S. Geological Survey, Menlo Park, California 94025, U.S.A.
G. D. Eberlein
Affiliation:
U.S. Geological Survey, Menlo Park, California 94025, U.S.A.
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Summary

K—Ar age measurements on Esquibel Island, southeastern Alaska yield a minimum age of about 433±3 Ma for the Zone of Monograptus cyphus of the Lower Silurian. An age of approximately 435—437 Ma is estimated for the Ordovician—Silurian boundary.

Type
Articles
Information
Geological Magazine , Volume 114 , Issue 1 , January 1977 , pp. 15 - 24
Copyright
Copyright © Cambridge University Press 1977

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