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Guillaume Fontorbe

On long time scales, silicon cycling is closely linked to carbon cycling by chemical weathering of silicate minerals. This process consumes atmospheric carbon dioxide (CO2) and releases essential ions into the terrestrial system. These weathering products are transported to the ocean mostly by riverine transport. In the ocean, photosynthetic siliceous organisms (diatoms) uptake dissolved silica (DSi) in the surrounding waters to form their shells as well as consuming CO2 via photosynthesis. These organisms are responsible for a big part to the “oceanic carbon pump” and couple on short time scales the carbon and silicon cycles. However, little is known about how the silicon cycle and his link to the carbon cycle have evolved through geological times.

My PhD project focuses on the reconstruction of oceanic DSi concentrations during the Paleogene (65.5 to 23Ma). To do that, we measure silicon isotopes ratios in marine siliceous microfossils (diatoms, radiolarians and sponges) from marine sediment cores. The isotopic signature of these organisms can give us an estimation of the variation in oceanic DSi concentration. By coupling these results with a modeling experiment, we will provide insights on processes responsible for long and short term modification of the silicon cycle such as: How does the silicon cycle respond to geological events (changes in weathering intensities, changes in ocean circulation)? What impact do long and short-term changes in global climate have on silicon cycle?

Publications

Retrieved from Lund University's publications database

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Publications

Retrieved from Lund University's publications database

Publications

Retrieved from Lund University's publications database

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Guillaume Fontorbe
E-mail: guillaume [dot] fontorbe [at] geol [dot] lu [dot] se

Postdoctoral fellow

Quaternary Sciences

+46 46 222 01 07

Sölvegatan 12, Lund

16