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The caldera-forming eruption of the Aniakchak volcano in the Aleutian Rangeon the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holoceneeruptions worldwide. The resulting ash is found as a visible sediment layerin several Alaskan sites and as a cryptotephra on Newfoundland and Greenland.This large geographic distribution, combined with the fact that the eruptionis relatively well constrained in time using radiocarbon dating of lakesediments and annual layer counts in ice cores, makes it an excellentstratigraphic marker for dating and correlating mid–late Holocene sedimentand paleoclimate records. This study presents the outcome of a targetedsearch for the Aniakchak tephra in a marine sediment core from the ArcticOcean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth inHerald Canyon, western Chukchi Sea. High concentrations of tephra shards,with a geochemical signature matching that of Aniakchak ash, were observedacross a more than 1.5 m long sediment sequence. Since the primary input ofvolcanic ash is through atmospheric transport, and assuming that bioturbationcan account for mixing up to ca. 10 cm of the marine sediment deposited atthe coring site, the broad signal is interpreted as sustained reworking atthe sediment source input. The isochron is therefore placed at the base ofthe sudden increase in tephra concentrations rather than at the maximumconcentration. This interpretation of major reworking is strengthened byanalysis of grain size distribution which points to ice rafting as animportant secondary transport mechanism of volcanic ash. Combined withradiocarbon dates on mollusks in the same sediment core, the volcanic markeris used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the majorinfluence of typically <q>carbon-old</q> Pacific waters, and it agrees well withrecent estimates of ΔR along the northwest Alaskan coast, possiblyindicating stable oceanographic conditions during the second half of theHolocene. Our use of a volcanic absolute age marker to obtain the marinereservoir age offset is the first of its kind in the Arctic Ocean andprovides an important framework for improving chronologies and correlatingmarine sediment archives in this region. Core 2PC has a high sedimentaccumulation rate averaging 200 cm kyr−1 throughout the last4000 years, and the chronology presented here provides a solid base for high-resolution reconstructions of late Holocene climate and ocean variability inthe Chukchi Sea

The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea