EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Upstream versus downstream changes in a natural sediment routing system from source to sink

Nikhil Sharma1, Jean Vérité2, Stephen Watkins1, Luis Valero1, Alex Whittaker3, Miguel Garcès4, Cai Puigdefabregas5, François Guillocheau2, Thierry Adatte6, and Sébastien Castelltort1
Nikhil Sharma et al.
  • 1University of Geneva, Department of Earth Sciences, Rue des Maraichers 13, 1205 Geneva, Switzerland (
  • 2Gèosciences Rennes, Campus Beaulieu, Université de Rennes 1, 35042 Rennes cedex, France
  • 3Department of Earth Science and Engineering, Imperial College London, South Kensington, London SW7 2AZ, England
  • 4Department of Stratigraphy, Paleontology and Marine Geosciences, C/ Martí i Franquès, s/n, University of Barcelona, 08028 Barcelona, Spain
  • 5Department of Earth and Ocean Dynamics, University of Barcelona, C/ Martí i Franquès, s/n, 08028 Barcelona, Spain
  • 6Institute of Earth Sciences (ISTE), University of Lausanne, Bâtiment Géopolis, 1015 Lausanne, Switzerland

The Middle Eocene Climatic Optimum (MECO) represents an episode of widespread warming occurring ~40 million years ago. It is characterized by gradual warming over a period of 500,000 years, leading to a rise in ocean temperatures of about 5° C in the mid and high-latitudes (Sluijs et al., 2013). Contrary to the traditional understanding and consensus that accommodation space or downstream factors control stratigraphic architecture in fluvial successions, we test the hypothesis that upstream factors, rather than downstream factors, control fluvial architecture through changes in the median grain size, sediment supply and water discharge with paleoslope being a measurable proxy to quantify these changes. We test our hypothesis utilizing the natural system of the Escanilla sediment routing system, encompassing the Middle Eocene Climatic Optimum. The Escanilla system is an overall prograding system, consisting of 1000 m thick alluvial and fluvial deposits at the southern-margin of the Tremp-Graus Basin in the south/central Pyrenees, Spain. Multiple lateral measurements for grain size distributions and cross-set measurements, flow direction and channel geometry are taken close to the source (Coll de Vent), at an intermediate location (Lascuarre), and at a distal part (Olson) of the system for paleohydraulic reconstructions. Drone flight missions are also undertaken to capture aerial photographs of the field area, which are required for the construction of 3D photogrammetric models. At Olson, alternating sequences of laterally continuous amalgamated channel bodies and several small sequences of vertically stacked isolated channel bodies have been identified. Preliminary results show distinct values of median grain size, dune height, flow depth and paleoslope for the amalgamated and vertically stacked isolated channel sequences across the MECO; the addition of our 3D models provide further insight into the lateral connectivity of the amalgamated units. Our results suggest different paleohydraulic conditions during the deposition of amalgamated and nonamalgamated units. This data will also be supported by numerical simulations carried out to better understand the response of fluvial systems to changes in upstream factors.

How to cite: Sharma, N., Vérité, J., Watkins, S., Valero, L., Whittaker, A., Garcès, M., Puigdefabregas, C., Guillocheau, F., Adatte, T., and Castelltort, S.: Upstream versus downstream changes in a natural sediment routing system from source to sink, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1004,, 2019