A new 14C age for the Oruanui (Wairakei) eruption, New Zealand

Abstract

The Oruanui eruption was the largest known outburst of Taupo volcano, New Zealand, and is among the larger Quaternary eruptions documented. The eruption deposits are variously known as the Oruanui, Wairakei, Kawakawa Tephra, or Aokautere Ash formations, and represent a bulk volume probably exceeding 500 km3. Four new 14C age determinations on carbonized vegetation in the non-welded Oruanui ignimbrite are combined to give a conventional age of 22590±230 yr b.p. Compared with the previously accepted figure of 20000 yr b.p., this new age resolves the anomaly of apparently older 14C ages being obtained from a demonstrably younger New Zealand deposit, and strengthens correlation of this eruption with an Antarctic ice-core acid anomaly. The trace of this eruption has great potential as a time-plane marker in the Antarctic just prior to the last glacial maximum. The close similarity in ages between the Oruanui and a comparable sized eruption (Ito/Aira-Tn) in Japan suggests that this period of activity may represent the best chance of resolving any linkages between large-scale explosive silicic volcanism and climate changes.