Estudio geoquímico de los sedimentos glaciolacustres de la Massana y Ordino (Andorra, Pirineos Orientales): influjo sedimentario entre lagos de obturación yuxtaglaciar e interpretación paleoambiental

(SPA) El estudio geoquímico se realizó en el marco de un proyecto de arqueología ceramológica (Molera et al., 1997). Para ello se efectuó un muestreo exhaustivo de arcillas glaciolacustres en diversas localidades de la cuenca de la Valira del Nord (20 muestras). El presente trabajo utiliza los avances realizados en la última década en relación con la cronología del glaciarismo en el Principado de Andorra (Turu, 2002; Turu & Planas (2005), Turu et al. 2011), lo que ha permitido mejorar la interpretación paleoambiental del sector NW de Andorra a finales del Pleistoceno superior. (ENG) (Geochemistry analysis from glaciolacustrine sediments from La Massana and Ordino -Andorra, Southeastern Pyrenees-: Paleoenvironmental interpretation of the sedimentary influx between glacially constrained paleolakes) Geochemistry of glaciolacustrine deposits in the Pyrenean range is poorly studied. In that sense we have investigated the fine grained deposits of La Massana-Ordino paleolakes in order to increase the knowledge of such deposits. Chemical comparisons between basement rocks and glaciolacustrine deposits indicate an enrichment of chemical elements like Fe & Al. Because most of the catchment was occupied by glaciers, chemical basament denudation should be linked to glacial erosion in the Upper Pleistocene (UP). Since climatic w eathering cannot be involved, geochemical variations are related to chemical precipitation in the paleolakes waters. In essence UP climate changes drive to changes in the chemical equilibrium that were recorded on glaciolacustrine sediments.