Speaker Bios (Current Season)

October 1st, 2026

  The Ediacaran-Cambrian transition witnessed tumultuous changes in Earth’s tectonics, biosphere, climate, and biogeochemistry, culminating in the evolution and diversification of animals. A key question that remains is whether major changes in the carbon cycle (recorded by profound carbonate carbon isotope excursions) and major steps in animal evolution were related to oxygenation of the ocean-atmosphere system. Here, I present a new perspective on Ediacaran-Cambrian ocean oxygenation from metal isotope geochemistry applied to marine carbonate rocks, particularly the uranium and thallium isotope systems. I also investigate the role of weathering on these Earth system changes using the lithium isotope system. Data will be presented for the Ediacaran Shuram Excursion on multiple continents, as well as the terminal Ediacaran and Ediacaran-Cambrian boundary. Taken together, these metal isotope systems support the view that important Ediacaran-Cambrian evolutionary events were not driven by large-scale ocean-atmosphere oxygenation, but rather by tectonically-driven changes in weathering and the carbonate saturation state of the oceans.