BY

iii iv ACKNOWLEDGEMENTS I extend gratitude to my dissertation advisors, Dr. Zach Sharp and Dr. Peter Fawcett. I am eternally grateful for their guidance, insight, and kindness. Through their mentoring, I have grown as a scientist and as a person. I thank my dissertation committee Dr. David S. Gutzler, Dr. Joseph Galewsky, and Dr. Robert R. Parmenter for invaluable feedback and advice. I would like to express my sincere thanks and gratitude to Viorel Atudorei and fellow researchers in the EPS Stable Isotope Facility for their help and camaraderie. Additional thanks go to Ara Kooser and Mike Spilde for their invaluable assistance with SEM work. I am greatly appreciative of the many friends and colleagues I had the pleasure to work with in the E&PS department. I would like to extend a special thanks to Cindy Jaramillo, and the rest of the front office staff, without whom I would have been lost. I am grateful to the Valles Caldera National Preserve for permission to conduct m