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Timing and eruptive characteristics of the 349 ka Whakamaru supereruption sequence constrained by high-resolution analysis of tephra sites around New Zealand

^^ Anna Miller^^ 1, Simon Barker1, Colin Wilson1, Kat Holt2, Stephen Piva1

  • Affiliations:  1School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington 6010, New Zealand; 2School of Agriculture and Environment, Massey University, Palmerston North 4410, New Zealand. 

  • Presentation type: Talk

  • Presentation time: Thursday 11:15 - 11:30, Room R380

  • Programme No: 3.11.4

  • Theme 3 > Session 11

Abstract

The Whakamaru supereruption from the central Taupō Volcanic Zone (TVZ), New Zealand, vented >1,500 km3 of rhyolitic magma at ~349 ± 4 ka and is globally one of the largest Quaternary eruptions. The eruptive products include a complex sequence of welded ignimbrites in the central North Island, and tentatively correlated fall deposits of the same age, documented as the Rangitawa or Kohioawa tephras, found throughout New Zealand (including Chatham Island) and in distal marine cores in the Tasman Sea and South Pacific. The inter-relationships and relative timings of these deposits remain poorly constrained but are vital to understanding the nature and potential impacts of this event. Here, we present major and trace element data from Rangitawa/Kohioawa tephra collected from multiple sites at cm-scale resolution to characterise any spatial or temporal variability in glass compositions. Importantly, this work correlates fall deposits preserved in marine, terrestrial and lacustrine environments to one another over proximal, distal, and extremely distal areas. The presence and changing abundance of multiple glass populations in the fall deposits reflects the sequential tapping of multiple magma bodies through the eruption with no time breaks discernible. Extrapolated over multiple sites this approach will build a robust model of how the Whakamaru supereruption evolved, and the nature of ash dispersal across New Zealand and the South Pacific. Further to this work, the climate setting and post-eruptive environmental impacts are being examined through high-resolution pollen analyses at proximal and distal sites with drastic changes in vegetation assemblages observed across the tephra horizon.