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A Comparison of Radiocarbon and U/Th Ages on Continental Carbonates

Published online by Cambridge University Press:  18 July 2016

J.-C. Fontes ,
J. N. Andrews ,
Christiane Causse  and
Elisabeth Gibert
J.-C. Fontes
Affiliation:
Laboratoire d'Hydrologie et de Géochimie Isotopique, Bâtiment 504, Université de Paris-Sud 91405 Orsay Cedex, France
J. N. Andrews
Affiliation:
Laboratoire d'Hydrologie et de Géochimie Isotopique, Bâtiment 504, Université de Paris-Sud 91405 Orsay Cedex, France
Christiane Causse
Affiliation:
Laboratoire d'Hydrologie et de Géochimie Isotopique, Bâtiment 504, Université de Paris-Sud 91405 Orsay Cedex, France
Elisabeth Gibert
Affiliation:
Laboratoire d'Hydrologie et de Géochimie Isotopique, Bâtiment 504, Université de Paris-Sud 91405 Orsay Cedex, France
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Abstract

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Authigenic micrite from a playa in the northern Sahara has been dated by both the U/Th and 14C methods. The U/Th ages can be a few thousand years greater or less than the 14C ages obtained on the smallest crystals of micrite. The latter are considered to form a reasonable chronology for the Holocene deposits. The deviations of the U/Th ages are explained by quantifiable losses and gains of uranium under changing redox conditions. Under conditions where U is conservative (reduced sediments with low permeability), the U/Th method can provide good chronologies for lacustrine deposits.

Type
II. Applied Isotope Geochemistry
Information
Radiocarbon , Volume 34 , Issue 3: Proceedings of the 14th International Radiocarbon Conference , 1992 , pp. 602 - 610
Copyright
Copyright © The American Journal of Science 

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