Geochemical analysis of extremely fine-grained cryptotephra: new developments and recommended practices

Helen M. Innes*, William Hutchison, Andrea Burke

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Tephrochronology is a powerful tool used to synchronise and date stratigraphic records by accurate and precise geochemical analysis of deposited volcanic glass shards. However, in many distal stratigraphic records (e.g., polar ice cores) tephra shards are often extremely fine-grained (5 μm for electron probe microanalysis (EPMA) to ensure high analytical totals and minimise alkali element loss. Recent method developments have put forward alternative approaches to accurately measure major oxides of small shards: a smaller 3 μm diameter beam, overlapping large (20 μm) beam areas onto supporting epoxy resin, and using scanning electron microscopy with energy dispersive spectrometry (SEM-EDS). However, there has been no direct intercomparison of these alternative techniques, which to date have only been tested on a limited range of glass compositions and tephras that are much larger than the extremely fine-grained material found in distal archives. These issues complicate decision making about the best analytical approach to take when faced with small shards. Here, we provide a new workflow protocol for the analysis of
Original languageEnglish
JournalQuaternary Geochronology
VolumeIn Press
Early online date14 Jun 2024
DOIs
Publication statusE-pub ahead of print - 14 Jun 2024

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