The age of a Mount St. Helens set Y tephra at Tonquin Pass, British Columbia, previously assumed to be 4300 years BP, is revised to ca. 3400 years BP, based on bracketing 14C dates of 3140 ± 70 (Beta 13558) and 3680 ± 80 years BP (Beta 13559). The implications of this revision for tephrostratigraphy of this area are discussed.

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