Age, Extent and Climatic Significance of the c. 3400 BP Aniakchak Tephra, Western Alaska, USA

Tephra deposits at Whitefish Lake and Cape Espenberg on the northernmost Seward Peninsula of western Alaska were derived from the Aniakchak Caldera on the Alaska Peninsula more than 1500 km to the south. Radiocarbon dates on the climactic, caldera-forming Aniakchak eruption and on proximal and distal tephra indicate the Aniakchak tephra was deposited about 3435 ± 40 BP (3614-3815 cal. BP), and forms an isochronous marker horizon across much of western Alaska. The Aniakchak tephra eruption and several other targe eruptions during the seventeenth century BC may have had widespread effects on climate.