title: Abrupt response of chemical weathering to Late Quaternary hydroclimate changes in northeast Africa.
abstract: Chemical weathering of silicate rocks on continents acts as a major sink for atmospheric carbon dioxide and has played an important role in the evolution of the Earth's climate. However, the magnitude and the nature of the links between weathering and climate are still under debate. In particular, the timescale over which chemical weathering may respond to climate change is yet to be constrained at the continental scale. Here we reconstruct the relationships between rainfall and chemical weathering in northeast Africa for the last 32,000 years. Using lithium isotopes and other geochemical proxies in the clay-size fraction of a marine sediment core from the Eastern Mediterranean Sea, we show that chemical weathering in the Nile Basin fluctuated in parallel with the monsoon-related climatic evolution of northeast Africa. We also evidence strongly reduced mineral alteration during centennial-scale regional drought episodes. Our findings indicate that silicate weathering may respond as quickly as physical erosion to abrupt hydroclimate reorganization on continents. Consequently, we anticipate that the forthcoming hydrological disturbances predicted for northeast Africa may have a major impact on chemical weathering patterns and soil resources in this region.
authors.affiliation: Université Cote d'Azur, CNRS, Observatoire de la Côte d'Azur, IRD, Geoazur, 250 rueAlbert Einstein, Sophia Antipolis 06560 Valbonne, France.|Laboratoire Océanographique de Villefranche sur Mer (LOV, OOV), CNRS, UPMC Univ Paris 06, 181 chemin du Lazaret, 06230, Villefranche sur Mer, France.
authors.forename: Luc
authors.initials: L
authors.lastname: Bastian
authors.affiliation: Université Cote d'Azur, CNRS, Observatoire de la Côte d'Azur, IRD, Geoazur, 250 rueAlbert Einstein, Sophia Antipolis 06560 Valbonne, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Revel
authors.affiliation: IFREMER, Unité de Recherche Géosciences Marines, 29280 Plouzané, France.|Department of Earth Sciences - Royal Museum for Central Africa, Leuvensesteenweg, 13, B-3080 Tervuren, Belgium.
authors.forename: Germain
authors.initials: G
authors.lastname: Bayon
authors.affiliation: Laboratoire Océanographique de Villefranche sur Mer (LOV, OOV), CNRS, UPMC Univ Paris 06, 181 chemin du Lazaret, 06230, Villefranche sur Mer, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Dufour
authors.affiliation: Laboratoire Océanographique de Villefranche sur Mer (LOV, OOV), CNRS, UPMC Univ Paris 06, 181 chemin du Lazaret, 06230, Villefranche sur Mer, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vigier