Motutere Tephra Formation and redefinition of Hinemaiaia Tephra formation, Taupo Volcanic Centre, New Zealand

Abstract

Motutere and Hinemaiaia Tephra Formations are moderately widespread rhyolitic tephras erupted from near the southeast margin of Lake Taupo. The 2 multiple-bedded formations constitute a prolonged eruptive sequence interrupted by a short hiatus. The eruptive sequence comprises a plinian-type eruption of coarse pumice lapilli (Motutere Tephra (new name), volume c. 1 km₃), and further eruptions of a more widespread vitric ash (Hinemaiaia Tephra, volume c. 3 km₃) apparently related to the growth of a rhyolite dome. Isopach data for both tephras place the eruptive vent near the southeast margin of Lake Taupo in the vicinity of Te Rangiita. Bathymetry and geophysical data suggest the presence of a rhyolite dome 2 km offshore and within the vent area.Two unpublished radiocarbon dates of 5370 ± 90 years B.P. (NZ4846A) for Motutere Tephra and 4650 ± 80 years B.P. (NZ4574A) (old T½) for Hinemaiaia Tephra establish the age of these tephras.