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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
A three-year time series of mineral dust deposits on the West African margin: Sedimentological and geochemical signatures and implications for interpretation of marine paleo-dust records
Earth and Planetary Science Letters, Volume 364, Year 2013
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Description
Mineral dust deposits in the Northeastern Tropical Atlantic Ocean (NETAO) are an important contribution for reconstructing paleoenvironments and paleoclimates of West Africa. However, the interpretation of the changes in the sedimentological and geochemical characteristics of the dust deposits recorded in the marine sediments from the NETAO remains incomplete. In order to improve our understanding of dust proxies, in particular its mineralogical and geochemical provenance tracers, present-day dust deposition has been monitored at Mbour (~80km south of Dakar) on the Senegalese margin. Here we report a multi-proxy investigation of a unique three-year continuous time series of mineral dust deposits collected at a weekly (or better) temporal resolution over the March 2006-March 2009 period. Mass deposition flux and mean modal grain size display marked but reverse seasonal features, with higher flux during the winter/spring seasons and coarser grain size mode in summer when flux is minimal, reflecting contrasting transport patterns throughout the year. Similarly, clay mineralogy, the illite/kaolinite ratio in particular, shows seasonal fluctuations, manifesting the latitudinal displacement of the contributing domains of provenance in response to the seasonal migration of the ITCZ position and the associated wind systems. Our three-year record also reveals the occurrence of major deposition events superimposed on the seasonal pattern, generally during the winter/spring dry seasons and most frequently during the month of March. Our study shows that these major events, which contribute a large fraction of the total annual deposition flux, all originate from the western Sahara-Sahel (a major area of emission in the region beside the Bodele Depression, stretching from the Mauritanian and Western Saharan coasts to the Hoggar Mountains). Combined with air mass tri-dimensional back-trajectories and satellite images, the mineralogical and Sr-Nd isotopic compositions of these large dust events enable us to identify several mineralogically and geochemically distinct provenance sectors within this vast western area. Unlike the background dust deposits, the 87Sr/86Sr and the εNd isotopic signatures of the major dry events closely match that of the NETAO Late Holocene sediments, supporting the hypothesis that these events account for most of the aeolian terrigenous supply reaching the ocean floor. Although this database needs to be expanded, our results already provide useful constraints for the interpretation of the dust proxies' variations in marine sedimentary archives off Mauritania/Senegal in terms of changes in wind regimes and aridity over West Africa. © 2013 Elsevier B.V.
Authors & Co-Authors
Skonieczny, Charlotte
France, Lille
Université de Lille
Bory, Aloys Jean Mathias
France, Lille
Université de Lille
Bout-Roumazeilles, Viviane
France, Lille
Université de Lille
Abouchami, Wafa
Germany, Mainz
Max Planck Institute for Chemistry
Germany, Munster
University of Münster
Galer, Stephen J.G.
Germany, Mainz
Max Planck Institute for Chemistry
Crosta, X.
France, Pessac
Environnements et Paléoenvironnements Océaniques et Continentaux
Diallo, Aboubacry
Senegal, Dakar
Institut de Recherche Pour le Développement Dakar
Ndiaye, Thierno
Senegal, Dakar
Institut de Recherche Pour le Développement Dakar
Statistics
Citations: 63
Authors: 8
Affiliations: 5
Identifiers
Doi:
10.1016/j.epsl.2012.12.039
ISSN:
0012821X
Research Areas
Environmental
Mental Health
Study Locations
Multi-countries
Mauritania
Senegal