EGU2020-14955
https://doi.org/10.5194/egusphere-egu2020-14955
EGU General Assembly 2020
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Jura glacial lakes: a paleoclimatic and paleoenvironmental evolution since the Late Glacial Period.

Brahimsamba Bomou1, Damien Zappa1, Anne-Marie Rachoud-Schneider2, Jean-Nicolas Haas3, Marina Gärtner3, Jorge Spangenberg1, Vincent Bichet4, and Thierry Adatte1
Brahimsamba Bomou et al.
  • 1University of Lausanne, Institute of Earth Sciences, Lausanne, Switzerland (brahimsamba.bomou@unil.ch)
  • 2Musée et Jardins botaniques cantonaux, Av. de Cour 14bis, 1007 Lausanne, Switzerland
  • 3Department of Botany, University of Innsbruck, Sternwartestrasse 15, 6020 Innsbruck, Austria
  • 4Laboratoire Chrono-Environnement, UMR 6249 du CNRS, UFR des Sciences et Techniques, 16 route de Gray, 25030 Besançon, France

During the retreat of a Würm ice sheet, numerous glacial paleolakes took place in the Swiss and French Jura. Two sites were investigated: the Amburnex Valley site (Switzerland), which evolved in well-developed peatland and the Lake Val (France), which is still persisted as a lacustrine system. During the Late Glacial period, both sites were glacial lakes characterized by a significant accumulation of lacustrine sediments.

Using a multiproxy approach, this project aims to reconstruct the paleoclimatic and the paleoenvironmental evolution recorded in lacustrine sediments and peatbog deposits since the last 13’000 years.

The Amburnex core (7m) exhibit a basal morainic deposit from the Würm period, overlain by three meters of lacustrine deposits and four meters of peatland deposits. The Lake Val core (4.5m) consists of the same lithological succession.

A multiproxy approach based on palynological analyses, grain-size analyses, mineralogical analyses (XRD) and geochemical analyses (TOC, Nitrogen, Phosphorus and Mercury contents; major and trace elements; organic carbon isotopes) have been used to characterize the hydrological and climatic fluctuations, the trophic level and the origin of organic matter in order to reconstruct the paleoenvironmental and paleoclimatic evolution of this area.

In the Amburnex site, the Bølling-Allerød, the Younger Dryas and the beginning of the Preboreal period have been recognized by palynological analyses and confirmed by carbon 14 dating. During the Oldest Dryas, oligotrophic conditions took place as suggested by the very low concentrations in nitrogen and organic matter. Then, during the warmer Bølling period, an enrichment in total organic carbon (TOC) associated with a decrease in phosphorus content are observed, implying the development of eutrophic conditions and maybe phosphorus recycling. Later in the Allerød period, low TOC and phosphorus contents, associated with varved carbonate deposits, indicate a return to more oligotrophic conditions. New organic matter enrichments are observed in the interval corresponding to the colder Younger Dryas period. These trends are quite consistent with those observed in the Lake Val and reflect significant changes in runoff and nutrient inputs at least at regional scale.

How to cite: Bomou, B., Zappa, D., Rachoud-Schneider, A.-M., Haas, J.-N., Gärtner, M., Spangenberg, J., Bichet, V., and Adatte, T.: Jura glacial lakes: a paleoclimatic and paleoenvironmental evolution since the Late Glacial Period., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14955, https://doi.org/10.5194/egusphere-egu2020-14955, 2020.