Improved age estimates for the White River and Bridge River tephras, western Canada

Abstract

New 14C ages date the eruptions that produced the White River and Bridge River tephras, two important Holocene marker beds in western Canada. The 14C ages were obtained on trees in growth position buried in coarse tephra and a pyroclastic flow near the source vents. The mean calendric age of the White River eruption, based on four 14C ages, is 1147 cal years BP (calibrated years, approximately equivalent to calendric years) or AD 803 (the 2σ age range, obtained from the two most precise 14C ages, is 1014–1256 cal years BP or AD 694–936). The mean age of the Bridge River eruption, determined both from (i) the single most precise outer-ring 14C age and (ii) the weighted mean of six outer-ring 14C ages is 2360 cal years BP or 411 BC (2σ age range = 2349–2704 cal years BP or 755–400 BC).