Oxygen and sulphur isotope composition of Badenian (Middle Miocene) gypsum deposits in southern Poland: a preliminary study

Abstract

The isotopic studies of primary gypsum facies have been used as a tool for interpreting palaeoenvironments and the sedimentary evolution in the Badenian evaporite basin of southern Poland. The oxygen and sulphur isotope composition of gypsum is homogeneous throughout the section. The average d-values (δ¹⁸O = 12.21‰ and δ³⁴S = 22.21‰) correspond very well to data found for the Messinian (Upper Miocene) primary gypsum in SE Spain, as well as to other Tertiary sulphate evaporites, and thus provide additional arguments for the marine origin of these deposits. For the Badenian gypsum, the relative depletion in δ¹⁸O might reflect a distinct palaeogeographic control on sulphate sedimentation in the northernmost part of Central Paratethys. The results obtained, combined with other geochemical and sedimentological studies, reflect unstable sedimentary conditions in the peripheral part of the basin in the transition from the autochthonous to allochthonous gypsum members. The minor variations of isotope data are due to dissolution-precipitation and/or partial bacterial sulphate reduction.