Geochemical characteristics of the widespread Tahuna Tephra

Abstract

The c. 40 000 yr Tahuna Tephra found throughout the central North Island, New Zealand, and offshore in the Bay of Plenty, is considered to have erupted from the Okataina Volcanic Centre. Its glass and mineral chemistry, eruption temperature, and fO2 are dissimilar to Okataina-sourced Mangaone Subgroup tephra with which it is interbedded in the Bay of Plenty. Instead, Tahuna Tephra displays a compositional affinity to pre-22 000 yr tephra from Taupo Volcanic Centre. A Taupo source is also more consistent with the tephra's thickness and coarseness at Lake Poukawa in southern North Island.