Understanding the drivers of the Phanerozoic strontium isotope record

The strontium isotope ratio of ⁸⁷Sr/⁸⁶Sr is one of the best-defined tracers of Earth’s evolving surface environment over the Eon of macroscopic life, due to the long residence time of Sr in the ocean. If offers tantalising clues about past CO₂ emissions and the rate of continental weathering, which are vital considerations for understanding Earth’s changing surface temperature, climate, and atmospheric oxygen abundance. However, the Sr isotope ratio has strong regional lithological control, with mafic and felsic rocks having dramatically different isotopic compositions, which limits any simple analysis of Sr ratios over Phanerozoic timescales. We present an update to the SCION Earth Evolution Model, which allows it to track the spatial distribution of lithologies and Sr compositions over deep time, enabling regional-scale Sr isotope inputs to be assessed in the context of wider Earth system evolution. We use this to explore to what degree we currently understand the Phanerozoic Sr record, and how it can be used as a proxy to validate or falsify theories about long-term climate change and oxygen levels.