Abstract

In person.

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Organic carbon burial is one of the major pathways by which carbon is removed from Earth’s ocean-atmosphere system, and is a principal process in the determination of Earth’s atmospheric composition and climate. Studies of modern sediments suggest that much of the organic carbon buried in margin-proximal marine basins, which host a major fraction of the global organic carbon burial flux, is preserved through physical protection afforded by the close association of buried organic carbon with reactive and high-surface-area minerals. However, the dominant mechanisms of organic carbon preservation deeper in Earth history remain the subject of scientific debate. Here, I will present new mineralogical, sedimentological, and geochemical data from the organic-rich marginal marine sediments of the Miocene Monterey Formation, CA, USA , which demonstrate that most of the organic carbon preserved in Monterey Formation shales is intimately associated with a suite of clay and zeolite minerals. Furthermore, these data suggest that many of the organic-associated minerals in the Monterey Formation are most-parsimoniously derived from the alteration of volcanic ash, pointing to a previously underappreciated role for volcanic ash flux in modulating the protection-based preservation of organic carbon. Finally, I will briefly discuss the environments, depositional settings, and time periods in which volcanic ash flux to sedimentary deposystems may have significantly impacted organic carbon preservation and burial throughout Earth history