Clumped and Intramolecular Isotopic Perspectives on the Behavior of Organic and Inorganic Carbon in the Shallow Crust and Deep Biosphere

Citation

Lloyd, Max Kaufmann (2018) Clumped and Intramolecular Isotopic Perspectives on the Behavior of Organic and Inorganic Carbon in the Shallow Crust and Deep Biosphere. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z96T0JV5. https://resolver.caltech.edu/CaltechTHESIS:01312018-211454203

Abstract

Although the upper crust is the most accessible swath of the subsurface, the geochemical processes therein are challenging to observe. Here, I use site-specific and ‘clumped’ isotope analyses (where multiple rare, heavy isotopes are bound in single molecules) of carbonates and organic solids to explore petrology, brittle tectonics, diagenesis, and biodegradation in the shallow crust. In carbonates, I employ contact aureoles, regional metamorphic terranes, thermal and geochemical models, and high-pressure experiments, to extract nuanced thermal and chemical histories. In the organic realm, I develop new methods to measure the clumped ¹³C – ²H composition of methoxyl groups (R – O – CH₃) from kerogen, lignin, and other complex organic substrates. This work expands the field of clumped isotope geochemistry into the realm of solid compounds, and enables new, site-specific isotopic perspectives on the shallow crustal transformations of organic carbon substrates and the microbial assemblages that live on them.

Thesis Files