Sulfur cycle, carbon and oxygen through the ages, from rivers to sedimentary carbonates
Abstract :
The carbon and oxygen cycles have controlled the composition of the ocean-atmosphere system throughout Earth’s history. They are linked by widely studied processes: (1) photosynthesis and its associated opposed flux, the oxidation of organic matter, and (2) carbonate precipitation coupled with weathering and its counter-flux, reversed weathering. The third flux/counter flux, 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.
This memoire presents how I helped develop measurements of sulfur isotope ratios in rivers to improve our understanding of the modern carbon, oxygen and sulfur cycles and how I improved the use of carbonate associated sulfate as an archive for past sulfur isotope ratios of seawater. Additionally, I contributed to a better understanding of biomineralization, and paved the way 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. Collectively, my work has enhanced our understanding of the relationships between past and modern sulfur, carbon and oxygen cycles.
The members of the jury are:
Rapporteurices :
Adina Paytan, Prof. (UCSC)
Vincent Balter, DR (LGL-TPE),
Magali Ader, Prof. (IPGP)
Examinateurices
Vincent Busigny, Prof. (IPGP)
Emmanuelle Pucéat, Prof. (UBFC)
Edward Tipper, Prof. (Cambridge)
Christian France-Lanord, DR (CRPG)