Investigations into the Advancement of Cryptotephra Geochemical Fingerprinting

• Main Author: Hartman, Laura
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2018
• Subjects: Geology; ice core
• Online Access: https://digitalcommons.library.umaine.edu/etd/3015; https://digitalcommons.library.umaine.edu/context/etd/article/4089/viewcontent/Hartman_Final_1.23.19.pdf

The primary purpose of this work is to advance new sample preparation and analytical methods for ice core tephrochronology. When a volcanic source can be accurately identified using volcanic glass particle geochemistry, it may provide a robust time reference for the ice core’s timescale. The presence of an identifiable tephra layer may also suggest atmospheric pathways at the time of deposition, or assist in reconstructing volcanic forcing of climactic state for a specific event. One of the perpetual challenges in ice core based tephrochronological work is measuring the geochemical composition of ultra-fine particles (<10 >μm). Not only is it difficult to extract these particles from ice core samples, but obtaining fully quantitative geochemical measurements is also a challenge because of the very fine grain size. In this work, we attempt to further improve SEM-EDS based tephra measurements to unveil their fullest potential. The first chapter explores the use of recent particle mounting methodological advancements to examine the source of a volcanic horizon in 1450s. This work suggests that the widely accepted source of Kuwae Caldera in Vanuatu is incorrect and will be submitted to Nature Geosciences for publication. The second chapter outlines the results of experiments with testing a recently developed fully quantitative SEM-EDS geochemical measurement protocol developed at the National Institute of Standards and Technology (NIST) called DTSA-II.