EGU22-1875, updated on 09 Jan 2024
https://doi.org/10.5194/egusphere-egu22-1875
EGU General Assembly 2022
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Do upstream factors control fluvial stratigraphic architecture? Insights through quantitative paleohydrology

Nikhil Sharma1, Jean Vérité2, Alexander C. Whittaker3, François Guillocheau4, Cai Puigdefàbregas5, Miguel Garces6, Luis Valero1, Stephen E. Watkins1, Thierry Adatte7, and Sebastien Castelltort1
Nikhil Sharma et al.
  • 1Department of Earth Sciences, University of Geneva, Geneva, Switzerland (nikhil.sharma@unige.ch)
  • 2LPG - Le Mans, UFR Sciences et Techniques, Université du Maine, Le Mans, France
  • 3Department of Earth Science and Engineering, Imperial College London, London, UK
  • 4Gèosciences Rennes, Université de Rennes 1, Rennes, France
  • 5Department of Earth and Ocean Dynamics, University of Barcelona, Barcelona, Spain
  • 6Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, Barcelona, Spain
  • 7Institute of Earth Sciences (ISTE), University of Lausanne, Lausanne, Switzerland

Studies have long recognised the role of upstream factors such as sediment flux and water discharge variations in determining the equilibrium river profile. This approach has, however, not been tested in the stratigraphic record of ancient fluvial systems. Here we test the hypothesis that upstream factors control fluvial architecture through changes in water discharge and sediment flux. For this purpose, we utilise the Escanilla sediment routing system, an extensively documented source-to-sink river system in the southern Pyrenees, Spain, and of middle-upper Eocene age (ca. 40 Ma). Our focus is on the locality of Olson, at the distal part of the system, where the gullied landscape allows detailed documentation of fluvial stratigraphic architecture. We describe several fining-upward sequences of 35–40-metre thicknesses with a laterally extensive, amalgamated base overlain by a floodplain-dominated interval containing isolated channel bodies. For each amalgamated and non-amalgamated interval, data pertaining to grain size distributions and flow depths were collected. These data sets were used to perform quantitative palaeohydrological analysis based on paleoslope reconstruction, and from this, we estimated palaeoflow velocity, unit and total discharge, and bedload sediment fluxes. We find that the river slope is lower in the amalgamated intervals as discharge and sediment flux increases, while river slope increases in the non-amalgamated interval as the discharge and flux decreases. Given the available magnetostratigraphic constraints, the studied interval is compared to an astronomical reference curve. The depositional sequences reflecting variations in discharge are likely paced by the major component (413 000 yrs) of the Earth orbital eccentricity variations and thus point to climatic effect on sediment production and transport as the main driver of the fluvial sequences rather than autogenic shifts of the distributive fluvial system, or base-level changes.

How to cite: Sharma, N., Vérité, J., Whittaker, A. C., Guillocheau, F., Puigdefàbregas, C., Garces, M., Valero, L., Watkins, S. E., Adatte, T., and Castelltort, S.: Do upstream factors control fluvial stratigraphic architecture? Insights through quantitative paleohydrology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1875, https://doi.org/10.5194/egusphere-egu22-1875, 2022.