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

Abstract

New I4C 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 I4C ages, is 1147 cal years BP (calibrated years, approximately equivalent to calendric years) or AD 803 (the 2a 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 I4c age and (ii) the weighted mean of six outer-ring I 14C ages is 2360 cal years BP or 411 BC (20 age range = 2349-2704 cal years BP or 755-400 BC).

Stable Isotope Records from Mount Logan, Eclipse Ice Cores and Nearby Jellybean Lake. Water Cycle of the North Pacific Over 2000 Years and Over Five Vertical Kilometres: Sudden Shifts and Tropical Connections

“…Figure 2 shows a comparison between Eclipse and PRCol records. The PRCol record is placed on a time scale using a model, recent accumulation rates and the major ECM (acid) peaks of Katmai, Laki, a large unknown peak at A.D. 1516 and White River (Clausen et al, 1995;Clague et al, 1995;Zheng et al, 1998;Yalcin and Wake, 2003). The unidentified A.D. 1516 event must be "local" because, although it is the largest peak in the last 550 years, it has no prominence in the Eastern Arctic (Clausen et al, 1995;Zheng et al, 1998).…”

“…The White River candidate ECM peak stands out and is within a metre of where it is expected. Thus, it is assigned the age of the most recent large eruption (A.D. 803) that deposited the white ash layer over most of southern Yukon (Clague, 1995). Using the time scale for PRCol described in the text, the six largest PRCol ECM peaks coincide with six large sulfate peaks of the Eclipse core over the 530 years.…”

“…The sediment core chronology is based on 210 Pb, 137 Cs, seven AMS 14 C measurements on identifiable macrofossils and the White River tephra (Clague et al, 1995). A linear interpolation between dated depths was used to determine ages of sediment samples.…”

Topographically controlled grassland soils in the Boreal Cordillera ecozone, northwestern Canada

“…Their characteristic soils are mildly weathered, alkaline, and have dark A horizons and are classified as Melanic Brunisols. A distinctive component of soil parent materials in southern Yukon is the widespread occurrence of a surface veneer of the late Holocene White River tephra (1147 calibrated years BP; Clague et al 1995). In steeply sloping grasslands, much of the tephra veneer has been modified by organic matter accumulation to form Ah horizons that are generally less than 10 cm thick and overlie buried profiles classified as Melanic Brunisols (Strickland et al 2005).…”

The influence of historical forestry practices and climate on the sediment retention function of wetlands.

“…), it was concluded that the tephra originated from the Bridge River eruption ca. 2,410 calendar years ago (Clague et al, 1995). See Appendix C for a microscope image of the glass shards found in the Boswell Lake core.…”