Timing and stepwise transitions of the African Humid Period from geochemical proxies in the Nile deep-sea fan sediments

• Published in: Quaternary science reviews 2020-01, Vol.228, p.106071, Article 106071
• Main Authors: Ménot, Guillemette, Pivot, Sébastien, Bouloubassi, Ioanna, Davtian, Nina, Hennekam, Rick, Bosch, Delphine, Ducassou, Emmanuelle, Bard, Edouard, Migeon, Sébastien, Revel, Marie
• Format: Article
• Language: English
• Subjects: African Humid Period; Clastic εNd; Earth Sciences; Environmental Sciences; GDGT-indices; Nile river; Sciences of the Universe
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2019.106071

Large fluvial systems, such as the Nile River, allow a basin-scale integrated view of climatological and environmental changes. In this study, we reconstructed the Nile discharge history for the last 20 ka using molecular ratios of glycerol dialkyl glycerol tetraethers (GDGTs) and neodymium (Nd) radiogenic isotopes. By characterizing both the organic and inorganic fractions, we assessed the relevance of the GDGT-based proxies in deltaic environments as tracers of terrigenous origin. A large increase in Nile discharge is documented from 14.8 to 8.4 ka BP reflecting enhanced physical erosion and transport processes from the Ethiopian Traps. We confirmed the primary control of insolation on precipitation on North East Africa through the last 20 ka. The centennial time resolution reached on the sedimentary sequence revealed a step-wise onset and termination of the African Humid Period (AHP) starting at 14.8 ka and ending at 8.4 ka BP, respectively. Our centennial-millennial records allowed furthermore pinpointing the abrupt periods of arid conditions corresponding to the Younger Dryas. These data illustrate the linkage between low and high latitude hydrological variability. •Reliability, with qualifications, of brGDGTs as terrigenous flux tracers in deltaic environments.•Diversity of sedimentary settings in the Nile deep-sea fan.•Fluctuations of terrigenous inputs as retraced by εNd and brGDGTs records driven by summer insolation.•Stepwise onset of the AHP at 14.8 ka and early initiation of the AHP termination at 8.5 ka.•Stepwise termination pattern to a modern hydrology state occurred within 4 ka.•Imprint of abrupt “North Atlantic events” such as the Younger Dryas in the Nile sedimentary sequence.