Bouchez C. auteur aut IRD Deschamps Pierre auteur aut IRD Goncalves J. auteur aut IRD Hamelin Bruno auteur aut IRD Sylvestre Florence auteur aut IRD Doumnang J.C. auteur aut IRD Nour A.M. auteur aut IRD Goni I.B. auteur aut IRD Favreau Guillaume auteur aut IRD Genthon Pierre auteur aut IRD Seidel J.L. auteur aut IRD text journalArticle eng text/pdf reformatted digital access 36Cl measurements in groundwaters of the deep confined aquifer of the Lake Chad Basin (LCB) were performed in order to constrain groundwater geochemical ages and residence times. Twenty-seven wells were sampled in Nigeria, Niger and Chad in the southern parts of the large (700 000 km2) multilayered aquifer of the LCB. 36Cl/Cl values range between 11±1.10-15 to 148±8.10-15 at/at. The highest ratios are observed near the recharge zone of the Nigerian part of the Continental Terminal aquifer, while the lowest ones are found in wells located near the southern fringe of the present-day lake Chad. Chloride concentrations are low (below 100 mg/l) and not correlated to the 36Cl/Cl values, indicating negligible dissolution of evaporites in most samples. Reliable 36Cl ages can be calculated along the different flow paths investigated, suggesting residence times of the deep groundwaters larger than 300 000 years. These results are consistent with new AMS-14C data below the detection limit but are in contradiction with previous 14C data obtained in the area. specialized DATATION EAU SOUTERRAINE AQUIFERE NAPPE METHODOLOGIE CHIMIE DE L'EAU GEOCHIMIE CHLORE CHLORURE PUITS ECHANTILLONNAGE PALEOENVIRONNEMENT TRACEUR PALEOHYDROLOGIE CONTINENTAL TERMINAL TCHAD TCHAD LAC NIGER NIGERIA ZONE SAHELIENNE 064GEOCHI 062MECEAU04 Millot R. ed. edt IRD Negrel P. ed. edt IRD 13 147-150 2015 1878-5220 International Symposium on Applied Isotope Geochemistry, 11., Orléans (FRA), 2015/09/21-25 https://www.documentation.ird.fr/hor/fdi:010065222 10.1016/j.proeps.2015.07.035 1878-5220 [F B010065222] https://www.documentation.ird.fr/hor/fdi:010065222 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers15-09/010065222.pdf IRD - Base Horizon / Pleins textes 2015-09-17 2020-02-25 fdi:010065222 fre