Paleoclimatic reconstructions from paleosols
Nathan Sheldon, Professeur à l’Université du Michigan (USA), est actuellement missionnaire invité à GEOPS.
In contrast to waterlain sediments, soils form in direct contact with the atmosphere, so their elemental and isotopic compositions directly reflect the environmental conditions at the time of their formation. Paleosols (fossil soils) are present in the geologic record for the past 3.5 billion years, and their abundance through time reflects the Wilson Cycle of plate tectonics.
Thus, if we can relate the chemistry of paleosols to climatic factors such as precipitation, temperature, and atmospheric composition then they can provide one of the longest and most detailed records of the evolution of Earth’s surface environments. Using modern soils for calibration, a variety of organic and inorganic geochemical proxies have been developed for both annual and seasonal climatic conditions.
I will discuss how those proxies are derived and then present two vignettes of past climatic change, one from the Quaternary that reflects glacial-interglacial cycling and one that reflects Eocene greenhouse conditions that have been used as a possible analogue for future climate change.
Finally, I will introduce the global Paleo-CO2.org research community effort to reconstruct atmospheric CO2 levels for the past 450 million years using both marine and terrestrial proxies for past CO2 concentrations and discuss ways to get involved for anyone who is interested.
Salle de conférences du bâtiment 504 (2e étage)