Holocene tephrochronology in the Northern Cordilleran Volcanic Province, northwestern British Columbia

The Northern Cordilleran Volcanic Province (NCVP) of northwestern British Columbia and southwest Yukon is the most active volcanic region in Canada, including both the most recent eruption in Canada and the only eruption with known fatalities. However, little is known about the Holocene eruptive history of the region, in part due to the remoteness and inaccessibility of the volcanic centres. Here, we investigate the potential for volcanic ash (tephra) to identify Holocene volcanic activity in the NCVP. Major-element geochemistry, morphology, and mineralogy are described from the four previously reported tephra in the region, legacy samples from the University of Alberta tephra collection, and new tephra from lake sediment cores collected along an ∼165 km transect of the Stewart–Cassiar Highway. The sediment cores contained 5–9 newly described tephra for a total of at least 9–13 easily detectable tephras in this region, with a range of composition from basalt to phonolite. Repetition in geochemical signatures and difficulty in chronology results in an inability to confidently determine the number of tephra. Though very little proximal glass geochemical data exist to correlate to, these tephra are suggested to originate from Mount Edziza, Iskut Volcanic Field, and potentially Hoodoo Mountain. The majority of these tephra, some dispersed over ∼200–300 km, likely erupted from Mount Edziza, reinforcing the need for a better understanding of this volcanic complex and its hazards. Further exploration of volcanoes in the NCVP is required to establish proximal geochemistry to confirm the sources of these tephra.