Caracterización de los acuíferos jurásicos de la Formación Gijón (Asturias) mediante el uso de isótopos estables (δ 34SSO4, δ 2HH2O y δ 18OH2O)

Abstract

_In certain areas of the Asturian Jurassic basin, the groundwater sulphate concentration in acarbonate aquifer is very high. In order to determine the origin of the sulphate and improve theknowledge of other hydrogeological parameters, a hydrochemical survey was carried out including ananalysis of major cations and anions, stable isotopes of the water molecule (δ2H and δ18O) and δ34Svalues. Water from nine springs were sampled in order to determinate the groundwater composition, aswell as two gypsum samples from Triassic sediments and from gypsum interbedded in the overlyingJurassic sequence to obtain δ34S values. The results suggest that the main source of the sulphates isrelated to dissolution of gypsum from Jurassic sediments. The values obtained from the δ2H and δ18Oanalysis lies a little above the World Meteoric Line and fit well with the local line, as would be expected,given the meteoric origin of the recharge and excludes other origins. The estimated elevations for springrecharge, according to its isotopic composition, have contributed to validate the hydrogeologicalcartography.