Isotopic data ( super(87)Sr/ super(86)Sr) and hydrological changes during the last 15 000 years on the Andean Altiplano

• Published in: Hydrological sciences journal 2002-04, Vol.47 (2), p.293-306
• Main Authors: Coudrain, A, Loubet, M, Condom, T, Talbi, A, Ribstein, P, Pouyaud, B, Quintanilla, J, Dieulin, C, Dupre, B
• Format: Article
• Language: fre
• Subjects: South America, Andes Mts; South America, Desaguadero R
• ISSN: 0262-6667

At present, the southern basin of the Altiplano (17 degree -22 degree S, 126 000 km super(2)) receives about 39.4 x 10 super(9) m super(3) year super(-1) including 4% of surface runoff from the northern catchment (14 degree -17 degree S) via the Rio Desaguadero. The values of super(87)Sr/ super(86)Sr of present surface flow are distinct for the two catchments. This tracer can thus be used for studying the past and contrasting hydrological conditions of the southern basin. For the arid period from 10 000 to 2000 years BP, the acquired data and the transport modelling of soluble strontium in an aquifer confirm that the levels of precipitation were about 80% of the present amounts and that the inflow from the Desaguadero was insignificant. For the high levels of the palaeolake Tauca, around 15 000 years BP, the hydrological and isotopic data indicate that, for a total inflow estimated at 110 x 10 super(9) m super(3) year super(-1), the northern contribution might have been limited to 5%.Original Abstract: Actuellement, le bassin sud (17 degree -22 degree S, 126 000 km super(2)) de l' Altiplano recoit environ 39.4 x 10 super(9) m super(3) an super(-1) d'eau dont 4% proviennent du bassin nord (14 degree -17 degree S) par le Rio Desaguadero. Le rapport super(87)Sr/ super(86)Sr des ecoulements de surface actuels presentent des valeurs distinctes sur les deux bassins permettant d'utiliser ce traceur pour reconstituer des conditions hydrologiques passees contrastees du bassin sud. Pour la periode aride de 10 000 a 2000 ans BP, les donnees acquises et la modelisation du transport de strontium dans un aquifere renforcent les hypotheses d'une valeur des precipitations de 80% de l'actuel et de l'absence d'alimentation significative du bassin sud par le Rio Desaguadero. Pour les hauts niveaux d'eau de la phase lacustre Tauca, vers 15 000 ans BP, les donnees hydrologiques et isotopiques indiquent que pour une alimentation totale estimee a 110 10 super(9) m super(3) an super(-1) les apports du bassin nord pouvaient etre limites a 5%.