Graduation Year

2023

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Environmental Analysis

Reader 1

Colin Robins

Reader 2

Donald McFarlane

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2023 Cecilia Compton

Abstract

It is clear that the increased effort the scientific, and global community, has put into understanding the earth's climate is both productive and can create solutions. In addition to the positive side of putting more focus on climate-specific research, it is also abundantly clear that the climate is endlessly complex and its history reflects that. While there exist many effective ways to understand certain elements of paleoclimates, isotopic dating, sediments, fossil relics, etc. There also exists evidence of past climates that require a much more involved approach to understanding. Soils are great for determining previous climates as they are somewhat an accumulation of countless factors from the outside environment. The soils found in arid regions specifically are great at preserving this evidence as leaching infrequently and horizons become cemented. In late stage petrocalcic soils the laminar layers can be observed as potential evidence of the environments in these layers entered the soil horizons. The Mormon Mesa area located Northeast of Las Vegas contains multiple exposed profiles of petrocalcic soils horizons samples from this area have been the subject of several previous studies. This study attempts to utilize multiple methods of analysis to confirm and deepen the previous understanding of samples from the Mormon Mesa area. This study utilizes thin sections and billets from archived samples that were either previously prepared or newly cut for this study, specifically (Crandall, 2019; Robins, personal communication). Billets for SEM analysis were trimmed using a diamond tile saw and a lapidary saw. Samples were then studied using Visual (macro-scale) observation, optical light microscopy Nikon Eclipse LV100 transmitted and reflected, polarized, light microscope, portable x-ray fluorescence spectrometry (pXRF), scanning electron microscopy with energy dispersive x-ray spectrometry (SEM-EDS). This combination of methods showed that these samples were consistent with previous studies, where lighter calcium carbonate-rich soils showed larger grain and crystal sizes and darker layers showed complex crystal structures and higher clay concentration. There was evidence of biological factors found mostly in the darker denser layers of the samples.

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