Hydrogeochemistry and strontium isotopes from the Continental Intercalaire and Complex Terminal aquifers in southern Tunisia

The spatial distribution of trace elements of strontium (Sr), barium (Ba), bromide (Br), boron (B) and lithium (Li) was investigated in the deeper confined continental Intercalair (CI) and the underlying confined/unconfined Complex Terminal (CT) aquifers in southern Tunisia. Geochemical analyses and correlation between trace and major elements suggested that dissolution/precipitation of minerals, water rock interaction are the main factors responsible for the occurrence of these elements in the two aquifers. However, in the CI Djerid aquifer, in addition to these factors, the process of basic exchange is generally responsible for the large variation in cation concentration (Ca, Na, and K) and the five trace elements of interest. The Sr2+ has been used along with Li and other hydrogeological information to trace the extent of leakage from the CI to the CT aquifer. Besides, high 87Sr/86Sr and Br/Cl recorded in the Tazrarit CI1 borehole imply that salinity may be derived from a contact with marine facies in the sediment formation.