IMPROVED AGE ESTIMATES FOR THE WHITE-RIVER AND BRIDGE-RIVER TEPHRAS, WESTERN CANADA

New C-14 ages date the eruptions that produced the White River and Bridge River tephras, two important Holocene marker beds in western Canada. The C-14 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 C-14 ages, is 1147 cai years BP (calibrated years, approximately equivalent to calendric years) or AD 803 (the 2 sigma age range, obtained from the two most precise C-14 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 C-14 age and (ii) the weighted mean of six outer-ring C-14 ages is 2360 cal years BP or 411 BC (2 sigma age range = 2349-2704 cal years BP or 755-400 BC).