An occurrence of Tuhua Tephra in deep‐sea sediments from offshore eastern North Island, New Zealand

Abstract

We identify c. 7000 cal yr BP Tuhua Tephra in a marine sediment core from offshore eastern North Island, New Zealand. Its mineral assemblage includes aegirine, which is diagnostic for the Tuhua (Mayor Island) Volcanic Centre, and electron microprobe analyses of glass shards yield compositions close to published analyses of the tephra onshore, closer to the source. Associated radiocarbon ages on planktonic foraminifera from the core show that its age lies within the range previously determined for the calderaforming event that generated Tuhua Tephra. This occurrence, >380 km southeast of the source, indicates that the dispersal of the ash was bi-directional, and that earlier estimates of this tephra's volume may be conservative.

A continuous 5300-yr Holocene cryptotephrostratigraphic record from northern New Zealand and implications for tephrochronology and volcanic hazard assessment

“…BP. (Lowe, 1988a,b;Stokes and Lowe, 1988;Lowe et al, 1999;Manighetti et al, 2003). Its very high FeO content shows up clearly on the XRF-derived Fe plot obtained from earlier studies at Kopouatai bog (Figure 3, right-hand side).…”

Cryptotephra studies applied to a deep marine sedimentary record in the northern Hikurangi Trough, Aotearoa New Zealand

“…(1) a reworked deposit containing both Whakatane and Tūhua shards or (2) the primary Tūhua deposit with reworked Whakatane glass within. The Whakatane eruption produced a large volume of ejecta (13 km 2 ; Berryman et al, 2022;Froggatt and Lowe, 1990) compared to the Tūhua eruption, which produced much less (1.6 km 2 ; (Kósik et al, 2022) and travelled less distances than the Whakatane tephra (Holt et al, 2011;Manighetti et al, 2003). The larger nature of the Whakatane eruption therefore suggests that it would be better preserved in the marine environment than the Tūhua eruption and would be present with a higher number of shards in a reworked deposit.…”