shorelines of the Holocene Megalake Chad (Africa, Sahara) investigated with very high resolution satellite imagery (Pléiades) : example of the Goz Kerki paleo-spit

Mathieu Schuster; Claude Roquin; Abderamane Moussa; Jean-François Ghienne; Philippe Duringer; Frédéric Bouchette; Arnaud Durand; Bernard Allenbach

doi:10.52638/rfpt.2014.114

Auteurs-es

Mathieu Schuster Institut de Physique du Globe de Strasbourg, UMR7516, CNRS — Université de Strasbourg/EOST, 1 rue Blessig, 67084 Strasbourg Cedex
Claude Roquin Institut de Physique du Globe de Strasbourg, UMR7516, CNRS — Université de Strasbourg/EOST, 1 rue Blessig, 67084 Strasbourg Cedex
Abderamane Moussa Département de Géologie et Paléontologie, Faculté des Sciences, Université de N'Djamena
Jean-François Ghienne Institut de Physique du Globe de Strasbourg, UMR7516, CNRS — Université de Strasbourg/EOST, 1 rue Blessig, 67084 Strasbourg Cedex
Philippe Duringer Institut de Physique du Globe de Strasbourg, UMR7516, CNRS — Université de Strasbourg/EOST, 1 rue Blessig, 67084 Strasbourg Cedex
Frédéric Bouchette Géosciences-Montpellier CNRS / Université Montpellier II 34095 Montpellier
Arnaud Durand SERTIT, Université de Strasbourg, 300 Boulevard Sébastien Brandt, 67412 Illkirch-Graffenstaden
Bernard Allenbach SERTIT, Université de Strasbourg, 300 Boulevard Sébastien Brandt, 67412 Illkirch-Graffenstaden

DOI :

https://doi.org/10.52638/rfpt.2014.114

Mots-clés :

african humid period, beach ridges, paleo-lake, littoral

Résumé

Megalake Chad (350,000 km²), the largest paleo-lake of the Sahara-Sahel area, is one of the most emblematic marker of the hydroclimatic changes that occurred during the African Humid Period (AHP; ca. 11,500 — 5,000 years BP) in subtropical Africa. From field surveys, the existence of Megalake Chad is well demonstrated by widespread typical lake deposits. However, considering the very large size of this paleo-lake, it is best evidenced and understood from space. Conspicuous paleo-littoral features distributed along hundreds of kilometers are clearly visible on second generation satellite images. These features represent major archives of the Megalake Chad and of the climate during the AHP. This paper is the first attempt to investigate the paleo-littoral of Megalake Chad with very high resolution satellite imagery. A Pléiades scene (images and DEM) is used to characterize the fossil sand spit of the Goz Kerki, which is one of the most representative and best preserved littoral features of Megalake Chad. Thanks to Pléiades stereoscopic images the geomorphology and the lithology of this paleo-spit can now be detailed and the evolution of the paleo-bathymetry of Megalake Chad can be reconstructed. This brings new insights into the paleo-environments and paleo-climates of the Sahara-Sahel region.

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