Isotopic Proxies for Microbial and Environmental Change: Insights from Hydrogen Isotopes and the

Abstract

iii This thesis would not have been possible without the generous help and support from many individuals and organizations. Specifically I would like to thank my advisors John Grotzinger and Alex Sessions, who have been pillars of support and guidance throughout this process. I would also like to acknowledge my current and former committee members Woody Fischer, Tim Lyons, Victoria Orphan, and Joe Kirschvink. In addition, I would like to thank the many other GPS professors that have contributed to my interests and background though classes and field trips including John Eiler, Jess Adkins, Jared Leadbetter, George Rossman, and Ken Farley. I thankful for the editing prowess of Mitchell Barklage and Morgan Raven who were subjected to first drafts of parts of this thesis. Funding is a critical to modern science as well, which indebts me to the NSF GRFP, Petroleum Development Oman, the Gordon and Virginia Eaton Fellowship, and the Agouron Institute for their generous financial support. Many people contributed directly and indirectly to the works presented here. I would like to acknowledge the additional coauthors on these manuscripts, John Spear