EGU22-10420
https://doi.org/10.5194/egusphere-egu22-10420
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Intense precipitation during the African Humid Period inferred from east Saharan fossil rivers: Implications for human dispersal   

Abdallah Zaki1, Georgina King2, Negar Haghipour3, Robert Giegengack4, Stephen Watkins1, Sanjeev Gupta5, Mathieu Schuster6, Hossam Khairy7, Salah Ahmed7, Mostafa El-Wakil7, Saleh Eltayeb8, Frédéric Herman2, and Sébastien Castelltort1
Abdallah Zaki et al.
  • 1University of Geneva, Faculty of Science, Earth sciences, Geneva, Switzerland (abdallah.zaki@etu.unige.ch)
  • 2Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland
  • 3Geological Institute, ETH Zürich, Zürich, Switzerland
  • 4Department of Earth & Environmental Science, University of Pennsylvania, Philadelphia, USA
  • 5Department of Earth Sciences and Engineering, Imperial College London, London, UK
  • 6Université de Strasbourg, CNRS, Institut Terre et Environnement de Strasbourg, UMR 7063, 5 rue Descartes, Strasbourg F-67084, France
  • 7Egyptian Mineral Resources Authority (EMRA), Cairo, Egypt
  • 8Department of Geology, University of Aswan, Aswan, Egypt

During Late Quaternary time, the paleoclimate of the eastern Sahara was punctuated by multiple pluvial periods, then dramatically and cyclically transformed to hyperarid conditions, receiving less than 2 mm/yr of precipitation at present. Geologists, climate modelers, and archaeologists, therefore, have used various proxies to reconstruct past climates during that time, a crucial period for human habitation and migration. These reconstructions, however, lack the precipitation pattern during those pluvial periods, which represents a significant control on weighing the hypotheses of human migrations and occupations. Here we reconstruct the chronology and paleohydrology of a set of fossil rivers expressed by ridges in the modern landscape due to differential erosion. Our 14C and Optically Stimulated Luminescence (OSL) ages of sediments preserved in these ancient rivers cluster within the last African Humid Period (AHP; ca. 14.8 – 5.5 ka BP) and hence support more significant fluvial activity during this distinct humid epoch. Based on median grain size (D50), paleochannel geometry, and drainage area, paleohydraulic reconstructions indicate that typical precipitation intensities of 55–80 mm/h occurred during sediment transport events. When combined with previous annual rainfall estimates, we find that such rainfall intensities were likely 3–4 times more frequent during the AHP. These climatic perturbations may have rendered some parts of the Nile River Valley inhospitable for occupation, driving humans to migrate away in the northwest and west of the Nile Valley between 10.2 and 7.2 ka BP. Ultimately, our results, along with the archeological data, tell a tale from the past of the dramatic climatic changes that our planet undergoes, demonstrating the critical role of climate in sustaining human populations. 

 

How to cite: Zaki, A., King, G., Haghipour, N., Giegengack, R., Watkins, S., Gupta, S., Schuster, M., Khairy, H., Ahmed, S., El-Wakil, M., Eltayeb, S., Herman, F., and Castelltort, S.: Intense precipitation during the African Humid Period inferred from east Saharan fossil rivers: Implications for human dispersal   , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10420, https://doi.org/10.5194/egusphere-egu22-10420, 2022.

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