Document Type

Dissertation/Thesis

Degree Name

Bachelor of Science (B.S.) in Geology and University Honors

First Advisor

John Bershaw

Abstract

Stable isotopes from ancient water have been used extensively to reconstruct paleoclimates and paleoenvironments (e.g. Bershaw et al., 2010, Cyr et al., 2005, Fan et al., 2017, Quade et al., 2011, Rowley and Garzione, 2007). Volcanic glass found in ash tuffs have been shown to preserve hydrogen (H) isotopes from meteoric water at the time of deposition (Cassel and Breecker, 2017) making it a useful paleowater proxy (e.g. Canavan et al., 2014, Cassel et al., B2009, Friedman et al., 2013, Saylor and Horton, 2014). Carlson (2018) showed differences in δD between two different preparation methods in volcanic glass analysis and suggests that strict grain size filtering and hydrofluoric acid (HF) treatment produce the most reliable results, similar to Cassel and Breecker (2017) findings. Samples were deemed reliable if they contained >99% glass without bubbles. Glass shards with bubbles are less dense and described as pumiceous. Though preparation methods recommend removing pumiceous shards, it is not clear how they affect isotopic results, if at all. I investigate this by comparing pumiceous textures, water concentration, and δD values of different glass samples. Based on the results of this pilot I conclude that; 1) δD and wt. % water are not affected by apparent porosity, 2) The Cassel and Breecker (2017) method effectively removes hydrogen contamination, even in previously discarded pumiceous samples where corrosion is extensive, suggesting pumiceous glass shards can also be used for paleoenvironmental reconstruction. Future work should confirm these results with a more extensive dataset.

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