African humid periods triggered the reactivation of a large river system in Western Sahara

Abstract

The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara.

Mapping Palaeohydrography in Deserts: Contribution from Space-Borne Imaging Radar

“…However, the branch of the palaeodrainage network identified using radar represents a fifth of the total length of the Tamanrasett palaeoriver. The palaeochannels detected in radar images are also perfectly aligned with palaeovalleys identified in the Arguin Basin, as well as with the proximal tributaries of the submarine Cap Timiris Canyon system [24]. , palaeochannels detected in PALSAR data (blue lines) and Tamanrasett River valley (dark brown area), after [24].…”

Multi vegetation model evaluation of the Green Sahara climate regime

“…the region of the present-day Sahara desert transitioned to a vegetated state, with lakes and river systems that are not evident today [Hoelzmann et al, 1998;Skonieczny et al, 2015]. This transition was ultimately driven by changes in incident solar insolation caused by variations in Earth's orbit through time.…”

“…This is shown by fossil pollen [Prentice et al, 2000], paleolake levels [Kohfeld and Harrison, 2000], paleohydrological reconstructions [Pachur and Kropelin, 1987;Pachur and Holzmann, 1991;Hoelzmann et al, 1998Hoelzmann et al, , 2001Skonieczny et al, 2015], and archeological evidence [e.g., Dunne et al, 2012;Manning and Timpson, 2014].…”

Humans as Agents in the Termination of the African Humid Period

“…The Nile, Yoa, and Megalake Chad basins were created in ArcGIS 10.1 from the GTOPO30 DEM available from the USGS web data portal (http://earthexplorer.usgs.gov). The Tamanrasett paleodrainage was digitized from Skonieczny et al (2015).…”