The Eocene-Oligocene Transition (EOT) marks a turning point from the Eocene greenhouse paleoclimate to near-modern icehouse conditions. This ~790 kyr long interval is associated with major shifts in geochemical and sedimentological proxies, biological extinctions, and evolutionary turnovers, in both the marine and continental realms. These various archives provide strong evidence for a rapid global cooling, an oceanic reorganization, and the onset of a continental-scale icesheet over Antarctica. The two main causes invoked for this climatic turnover, for which underlying mechanisms and precise timings are still debated, are the decrease of greenhouse gases concentrations in the atmosphere, and the opening of the Southern Ocean gateways. At the time, the opening of these gateways could have led to the thermal isolation of Antarctica through the onset of the Antarctic Circumpolar Current. Investigating the EOT most-likely holds keys to the understanding of Earth’s climate, its interactions with ice-masses, greenhouse gases, and climatic thresholds. The Upper Rhine Graben (URG) is a complex intra-continental rift that is part of the European Cenozoic Rift System. With its first sediments dating back to the Lutetian, it provides a great window of investigation into late Eocene to Oligocene times in western Europe, and as such a great opportunity to investigate the impact of the EOT on continental landscapes, depositional environments, and ecosystems. Previous studies allow a broad view into the evolution of climate through the various geological formations and sub-basins of the URG, but the EOT has not yet been directly investigated in detail in this area. Critical questions remain unanswered: Is the EOT continuously recorded in the URG? What were its impacts on continental environments? Great uncertainties remain in the chronostratigraphy of the URG, preventing precise documentation of this event in the geological record. This presentation will go through the methods being used to tackle these problematics.
Emile Simon1, Hendrik Vogel2, Mathieu Schuster1
1Université de Strasbourg, CNRS, ENGEES, Institut Terre et Environnement de Strasbourg, UMR 7063, 5 rue Descartes, Strasbourg F-67084, France.; 2Institute of Geological Sciences & Oeschger Centre for Climate Change Research, University of Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland.