Dr Terry Isson (University of Waikato) will present his research on ancient global biogeochemical cycles.

Atmospheric CO2 levels are believed to have evolved dramatically over Earth's multi-billion-year evolution, and played a prominent role in sustaining habitable surface conditions. Yet, the mechanisms responsible for sustaining elevated early-Earth CO2 levels remain debated.

Here, we propose that a late Precambrian shift in marine clay authigenesis (and associated CO2 release) could account for this transition. This process would have fostered enhanced carbon recycling within the ocean and atmosphere, rendering a shift in the efficiency of carbon sequestration. The timing of this transition substantiates the idea that the rise of silica secreting organisms played an important role driving one of the most critical environmental transitions in Earth's history.

Further, we will discuss geochemical evidence suggesting that marine siliceous ecosystem decline could have led to sustained early-Triassic warmth in the wake of Earth's most severe mass extinction event. This work highlights the need to better quantify the synergistic effects of environmental change on siliceous organisms and vice versa for a more complete understanding of how life respond to and shape hyperthermal events.

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Zoom link: https://bit.ly/otagogeology