Preprints
https://doi.org/10.5194/egusphere-2024-163
https://doi.org/10.5194/egusphere-2024-163
23 Jan 2024
 | 23 Jan 2024
Status: this preprint is open for discussion.

Cosmogenic 3He chronology of postglacial lava flows at Mt. Ruapehu, New Zealand

Pedro Doll, Shaun Robert Eaves, Ben Matthew Kennedy, Pierre-Henri Blard, Alexander Robert Lee Nichols, Graham Sloan Leonard, Dougal Bruce Townsend, Jim William Cole, Chris Edward Conway, Sacha Baldwin, Gabriel Fénisse, Laurent Zimmermann, and Bouchaïb Tibari

Abstract. Accurate volcanic hazard assessments rely on a detailed understanding of the timing of past eruptions. While radiometric methods like 40Ar/39Ar or K/Ar are by far the most conventional lava flow dating tools, their low resolution for young (<20 ka) deposits interferes with the development of precise recent effusive chronologies on most volcanoes. Mt. Ruapehu (New Zealand) has produced many lava flows throughout its history, but the precise timing of many recent eruptions remains largely unknown. In this study, we use cosmogenic 3He exposure dating to provide 23 eruption ages of young lava flows at Ruapehu. We then compare our results with existing 40Ar/39Ar and palaeomagnetic constraints, highlighting the value of cosmogenic nuclides exposure dating in refining recent eruptive chronologies. Of the 23 sampled flows, 16 provided robust eruption ages (5–20 % internal 2σ; n≥3) between ca 20 and 8 ka, except for one lava erupted at around 43 ka, and their age distribution indicates that, during the last 20 thousand years, effusive activity at Ruapehu peaked at 17–12 ka and at 9–7.5 ka. Nearly identical eruption ages of lavas located in different flanks of the volcanic edifice suggest concurrent activity from multiple vents during relatively short time intervals (0–2 kyr) at around 13, 10 and 8 ka. We analysed four lavas previously dated by 40Ar/39Ar, two of which yielded eruption ages older than the older limit of the 2σ interval of the radiometric dates, but the good clustering of individual samples from our sites suggests that our results better represent these lava flows’ real eruption ages. Our 3He-based dates show excellent agreement with palaeomagnetic constraints, suggesting that production rate uncertainties are unlikely to impact the accuracy of our eruption ages. This study demonstrates how cosmogenic nuclides dating can provide greater detail on the recent effusive chronology of statovolcanoes, helping to resolve the low resolution and difficulty in applying radiometric dating methods to young lava flows.

Pedro Doll, Shaun Robert Eaves, Ben Matthew Kennedy, Pierre-Henri Blard, Alexander Robert Lee Nichols, Graham Sloan Leonard, Dougal Bruce Townsend, Jim William Cole, Chris Edward Conway, Sacha Baldwin, Gabriel Fénisse, Laurent Zimmermann, and Bouchaïb Tibari

Status: open (until 13 Mar 2024)

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Pedro Doll, Shaun Robert Eaves, Ben Matthew Kennedy, Pierre-Henri Blard, Alexander Robert Lee Nichols, Graham Sloan Leonard, Dougal Bruce Townsend, Jim William Cole, Chris Edward Conway, Sacha Baldwin, Gabriel Fénisse, Laurent Zimmermann, and Bouchaïb Tibari
Pedro Doll, Shaun Robert Eaves, Ben Matthew Kennedy, Pierre-Henri Blard, Alexander Robert Lee Nichols, Graham Sloan Leonard, Dougal Bruce Townsend, Jim William Cole, Chris Edward Conway, Sacha Baldwin, Gabriel Fénisse, Laurent Zimmermann, and Bouchaïb Tibari

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Short summary
In this study, we use cosmogenic-sourced 3He to determine the eruption ages of 23 lava flows at Mt. Ruapehu, New Zealand, and we show how this method can help overcome challenges associated with traditional dating methods in young lavas. Comparison with other methods demonstrates the accuracy of our data, and the method's reliability. The new eruption ages allowed us to identify periods of quasi-simultaneous activity from different volcanic vents during the last 20,000 years.