The edge of time : Dating young volcanic ash layers with the 40Ar-39Ar laser probe

Argon-40-argon-39 single-crystal dating of young (5000 to 30,000 years ago) volcanic ash layers erupted from the Mono Craters, California, shows that the method can yield meaningful ages in Holocene tephra. Because of ubiquitous xenocrystic contamination, the data do not form isochrons but plot in w...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1996-11, Vol.274 (5290), p.1176-1178
Main Authors: CHEN, Y, SMITH, P. E, EVENSEN, N. M, YORK, D, LAJOIE, K. R
Format: Article
Language:English
Subjects:
Crystalline rocks
Earth sciences
Earth, ocean, space
Exact sciences and technology
Geochronology
Geological time
Geology
Heat
Igneous and metamorphic rocks petrology, volcanic processes, magmas
Isotope geochemistry. Geochronology
Lasers
Physics
Volcanoes
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Summary:Argon-40-argon-39 single-crystal dating of young (5000 to 30,000 years ago) volcanic ash layers erupted from the Mono Craters, California, shows that the method can yield meaningful ages in Holocene tephra. Because of ubiquitous xenocrystic contamination, the data do not form isochrons but plot in wedge-shaped regions on an argon isotopic diagram. The upper boundary of the region is an isochron matching the 14C-derived age of the eruption. Such contamination-related patterns may be common in dating young materials by the single-crystal method. Argon dating by this method can help refine the time scale of physical and biological evolution over the past 100,000 years.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.274.5290.1176