Thursday December 5th at 11am room1129 by Guillaume Paris
Abstract : The carbon and oxygen cycles have controlled the composition of the ocean-atmosphere system throughout Earth’s history. They are linked through widely studied processes: photosynthesis and oxidation of organic matter, as well as carbonate precipitation coupled with weathering. The third process, less well characterized, is the formation and burial of pyrite, which releases oxygen and CO2 on geological timescales and its counter-flux, the oxidation of pyrite at the surface of continents, which disrupts weathering and lead to atmospheric oxygen consumption.
I will present my contributions to our understanding of the sulfur cycle. I will first introduce how anaytical developments for measuring sulfur isotope ratios by MC-ICPMS helped improve our understanding of the modern sulfur cycle and to refine the use of carbonate associated sulfate as an archive for past sulfur isotope ratios of seawater. Additionally, I will present my contribution to the investigation of of biomineralization, and how to extract multiple paleoenvironmental signals from carbonate rocks. Not only can we now reliably reconstruct past sulfur isotope ratios of seawater from carbonates, but we can also use isotopes to unpack the various steps of diagenetic alteration and thus collect key information about the activity of microorganisms in deep ocean sediments.