OXYGEN AND SULFUR ISOTOPE COMPOSITIONS AS INDICATORS OF THE ORIGIN OF MESOZOIC AND CENOZOIC EVAPORITES FROM SPAIN

The general investigation of oxygen and sulphur isotope compositions of the main evaporitic formations of Mesozoic and Cenozoic ages from Spain, for primary purposes, had to differentiate between marine and continental sulphate evaporites. Furthermore, the isotope data would also make it possible to determine the source of sulphate of the continental evaporites. The delta-values measured for the marine evaporites of Spain of Triassic, Lias, Cretaceous and Eocene age, are in good agreement with the general oxygen and sulphur isotopic curves of the oceanic sulphate. The continental evaporites deposited in the Ebro, Tajo, Calatayud and Teruel basins, since Paleocene up to Miocene times, exhibit wide ranges of delta-values both through time and space. The main source of sulphate reworked by continental waters was Triassic evaporitic sulphate, although another one was locally Cretaceous evaporite. In addition, in continental formations the local conditions of drainage and of in situ bacterial activity acted to modify the isotope composition of the sulphate source, thus imprinting specificity of the isotopic signature of each basin.