New insights into Holocene eruption episodes from proximal deposit sequences at Mt. Taranaki (Egmont), New Zealand

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• 作者：Rafael Torres-Orozco ; Shane J. Cronin ; Natalia Pardo…
• 关键词：Andesitic volcanoes ; Explosive volcanism ; Proximal lithostratigraphy ; Eruption history ; Volcanic hazards
• 刊名：Bulletin of Volcanology
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：79
• 期：1
• 全文大小：
• 刊物主题：Geology; Geophysics/Geodesy; Mineralogy; Sedimentology;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-0819
• 卷排序：79

文摘

Upper stratovolcano flanks contain the most nuanced depositional record of long eruption episodes, but steep, irregular terrain makes these sequences difficult to correlate and interpret. This necessitates development of a detailed and systematic approach to describing localized depositional facies and relating these to eruptive processes. In this work, the late-Holocene eruption history of Mt. Taranaki/Egmont, New Zealand, was re-assessed based on a study of proximal deposits spanning the 14C-dated age range of ~5.0–0.3 cal ka B.P. Mt. Taranaki is a textbook-example stratovolcano, with geological evidence pointing to sudden switches in scale, type and frequency of eruptions over its ~130 ka history. The proximal stratigraphy presented here almost doubles the number of eruptions recognized from previous soil-stratigraphy studies. A total of 53 lithostratigraphic bed-sets record eruptions of the summit crater and parasitic vents like Fanthams Peak (the latter between ~3.0 and 1.5 cal ka B.P.). At least 12 of the eruptions represented by these bed-sets comprise deposits comparable with or thicker than those of the latest sub-Plinian eruption of AD 1655. The largest eruption episode represented is the 4.6–4.7-cal ka B.P. Kokowai. Contrasting eruption styles were identified, from stable basaltic-andesite eruption columns at Fanthams Peak, to andesitic lava-dome extrusion, blasts and partial collapse of unstable eruption columns at Mt. Taranaki’s summit. The centemetre-scale proximal deposit descriptions were used to identify several previously unknown, smaller eruption events. These details are indispensable for building a comprehensive probabilistic event record and in the development of realistic eruptive scenarios for complex eruption episodes prior to re-awakening of a volcano.