Tephra in Antarctic Ice Cores
Volcanic ash (fine tephra particles), due to their instantaneous geological deposition, are excellent markers for correlating terrestrial, marine, lacustrine and glacial depositional sequences. The composition, size, and shape of tephra particles can provide information about an eruption’s magnitude...
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DigitalCommons@UMaine
2015
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| Online Access: | https://digitalcommons.library.umaine.edu/etd/2381 https://digitalcommons.library.umaine.edu/cgi/viewcontent.cgi?article=3409&context=etd |
| Summary: | Volcanic ash (fine tephra particles), due to their instantaneous geological deposition, are excellent markers for correlating terrestrial, marine, lacustrine and glacial depositional sequences. The composition, size, and shape of tephra particles can provide information about an eruption’s magnitude and timing, as well as about atmospheric circulation patterns and transport mechanisms at the time of the volcanic eruption. This thesis is focused on refining a methodology for extracting tephra particles from polar ice cores and developing analytical protocols for geochemical parameterization ("fingerprinting") of these very fine ash particles. The first chapter summarizes existing tephra mounting techniques and describes new methodology developed during the course of this research. Use of this new sample preparation technique ensures robust capture of ultra fine tephra particles from ice core samples. In addition, uncertainties between EDS from the SEM and WDS measurements from an EPMA for various tephra particle sizes and compositions were estimated. In summary, oxide concentrations above one weight percent for SiO2, Al2O3, FeO, CaO, K2O, and Na2O showed good correspondence between EDS and WDS for rhyolite and basalt material with no observed influence of particle sizes on the measurements. For the P2O5, MgO, MnO, and TiO2 oxides with concentrations in measured tephra samples below one percent, comparison between EDS and WDS methods were not always consistent. These data contribute to developing a quantitative methodological framework that will be used in the future for designing quantitative tephra correlation algorithms for very fine tephra particles. Potentially very small, 1-5 m in size, tephra fragments can be transported for thousands of kilometers in the atmosphere from source volcanic eruptions and provide robust tephrochronological markers for intercontinental correlations of paleoclimate data sets. This chapter is the University of Maine research team’s contribution to the collaborative paper submitted ... |
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