Origin and age of saline waters in Busko Spa (Southern Poland) determined by isotope, noble gas and hydrochemical methods: evidence of interglacial and pre-Quaternary warm climate recharges

In the Busko and Solec Spas, saline sulphide and sulphate waters are exploited at different depths. The shallow water system in Busko is related to an interglacial or interstadial period shown by the lack of tritium and14C and its δ18O and δD values equal to that of modern water. The noble gas temperatures (NGT) are somewhat lower than the present air temperatures, but the4He and40Ar ages of about 90–480 ka confirm a Pleistocene recharge. The δ18O and δD values of the deep system are much heavier than those of local modern waters, which may mean the recharge of a warm pre-Quaternary climate. The4He,40Ar and21Ne contents and the NGT values confirm the deep system to be recharged at the pre-Quaternary stages of the present hydrologic cycle, i.e. after the sea transgression in the Badenian. High SO42− contents indicate that the Cl− and SO42− in both systems originated from simultaneous leaching of NaCl and gypsum. Other components can be explained by cation exchange between water and Badenian clay minerals in marls (e.g. Ca2+ for Mg2+ and Na+ for K+) and by the decay of marine organic matter supplying Br−, I− and B.