Lanphere et al. (1999) presented new data for the age of the Rockland pumice tuff breccia of Wilson (1961) using the incremental-heating 40Ar/39Ar technique. Their age, ∼610 ka, is ∼200 ka older than zircon fission-track ages obtained on this tuff by Meyer et al. (1980; 1991). Application of new 40Ar/39Ar technologies to tephrochronometry is an important advance that allows more precise dating of widespread tephra layers. Although the new age may be correct, I urge caution in accepting it in place of grain-discrete fission-track dates and other data that suggest a younger...

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