TRACKING EARTH’S REDOX EVOLUTION USING MULTI-NON-TRADITIONAL STABLE ISOTOPE SYSTEMS

The reduction/oxidation (redox) potential of Earth’s near-surface environment is intimately linked to life evolution. Poor understanding of Archean, Proterozoic, and early Phanerozoic ocean-atmosphere oxygen evolution hinders distinguishing whether biotic evolution was driven by environmental factors or by other factors such as genetics or ecology. Redox sensitive metal isotope systems (e.g. Fe, Mo, U, Cr, etc.) can potentially track contemporaneous environmental oxygen levels based on the fact that modern redox reactions are observed to induce distinguishable isotopic fingerprints.

We will present records of multi-proxies (U-Cr-Mo) in ancient sedimentary rocks (iron formations and organic-rich shales) and use statistical approaches to infer their paleoredox implications. Specifically, we will synthesize the evidence of the onset of biological oxygen production in the Mesoarchean, of potentially fluctuating oxygen levels during the Proterozoic and its implications for animal evolution, and of rising early Phanerozoic oxygen levels linked to plant life evolution and animal body size shifts.