EGU2020-718
https://doi.org/10.5194/egusphere-egu2020-718
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Eccentricity forcing of Saharan climate drives fluvial strath terrace formation in the High Atlas

Jesse Zondervan1, Martin Stokes1, Matt Telfer1, Sarah Boulton1, Jan-Pieter Buylaert2,3, Mayank Jain2, Andrew Murray3, Alaeddine Belfoul4, Anne Mather1, Nawfal Taleb4, and Madeleine Hann5
Jesse Zondervan et al.
  • 1University of Plymouth, School of Geography, Earth & Environmental Sciences, United Kingdom (jesse.zondervan@plymouth.ac.uk)
  • 2Center for Nuclear Technologies, Technical University of Denmark, Roskilde, Denmark
  • 3Nordic Laboratory for Luminescence Dating, Department of Geoscience, University of Aarhus, Roskilde, Denmark
  • 4Structural Geology and Thematic Mapping Laboratory, Earth Sciences Department, Ibn Zohr University, Agadir, Morocco
  • 5Geography, School of Environment, Education and Development, The University of Manchester, Manchester, United Kingdom

River strath terraces reflect changes in lateral and vertical erosion rates within mountain valleys related to changes in the sediment to water discharge ratio. In contrast to the formation of terraces in high latitude glaciated catchments, little is known about the timing and mechanisms of river valley aggradation and incision in response to climate in low latitude, non-glaciated arid regions. To investigate the timing of river strath terrace formation in North-West Africa, we developed and applied a new approach to OSL dose rate correction of gravels. We sampled terraces in the M’Goun catchment crossing the thrust front and a thrust-sheet-top basin of the south-central High Atlas in Morocco, totalling 23 dated samples. Strath surfaces are elevated 10 to 40 m above the modern river plain, depending on local valley and bedrock configuration, and are overlain by 2 to 10 m of fluvial conglomerates. Burial ages of conglomerates in the first strath terrace level span from 180 to 60 ka, with widespread abandonment and incision post 60 ka throughout the catchment. This timing coincides with an eccentricity-driven decrease in African summer insolation and a decrease in the fluvial signature of Saharan dust recorded in an offshore Atlantic sediment core. We propose enhanced precipitation from the African summer monsoon during high insolation periods led to increased sediment yield and aggradation in the southern High Atlas, whilst low insolation and dry periods led to sediment-starved incision. To our knowledge, the M’Goun river terrace record is the most detailed record of long-term landscape evolution in response to climate fluctuations in northwest Africa to date.

How to cite: Zondervan, J., Stokes, M., Telfer, M., Boulton, S., Buylaert, J.-P., Jain, M., Murray, A., Belfoul, A., Mather, A., Taleb, N., and Hann, M.: Eccentricity forcing of Saharan climate drives fluvial strath terrace formation in the High Atlas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-718, https://doi.org/10.5194/egusphere-egu2020-718, 2019

Display materials

Display file