Revision of the Post-Glacial Explosive Eruption History of Hudson Volcano (Chile) Using Tephrostratigraphy
Abstract
Hudson, a stratovolcano in the southern Andes, is recognised as the source of four large (>1 km3 of tephra) and tens of smaller explosive eruptions in the past 20 kyr, so is one of the most active volcanoes in the region. Analysis of its eruptive history is therefore particularly important for volcanic hazard assessment, investigating the tempo of volcanism, and tephrochronology in Patagonia. However, the characteristics and timing of all but the large eruptions of Hudson are currently poorly constrained. We present a revised post-glacial explosive eruption history of Hudson, from analysis of the matrix glass composition of tephra units in terrestrial sections and a thorough review of the tephrostratigraphy reported in ice, peat, soils, and lake and marine sediments. Most of the Hudson tephra units analysed have a similar glass composition to the others that they are closest to in age, but the narrow composition range we find for most units means that they are generally still distinguishable by careful glass composition analysis. We suggest that the wide composition range of tephra layers attributed to Hudson in a marine sediment core thus indicates that these layers are reworked deposits. Inconsistencies are found in the prior tephrostratigraphy from other sediment cores, emphasising the importance of detailed characterisation of tephra deposits to validate their correlation. From our compilation of published data, we refine eruption age estimates (using Bayesian analysis) and the isopachs and volume estimates for some of the large eruptions. The terrestrial sections analysed reveal previously unrecognised shifts in erupted magma composition, from silicic to mafic after the H2 eruption ( 3.9 cal ka BP), and then to intermediate compositions for the last 1 kyr. This temporal variation in eruptive behaviour is similar to that recently identified at other volcanoes in the southern Andes and suggested to be a response to deglaciation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.V11A2757L
- Keywords:
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- 8455 Tephrochronology;
- VOLCANOLOGY