CARBON AND OXYGEN STABLE ISOTOPES OF THE MIDDLE MIOCENE BADENIAN GYPSUM-ASSOCIATED LIMESTONES (KUDRYNTSI QUARRY SECTION, WEST UKRAINE): IMPLICATIONS FOR PALEOENVIRONMENTS IN THE CENTRAL PARATETHYS

The Middle Miocene Badenian evaporite deposits in the marginal part of the Carpathian Foredeep Basin are usually overlain by the Late Badenian transgressive deposits (mixed-fossil lithoclastic packstones/grainstones with intercalations of marls, and then coralline algal limestones). At the Kudryntsi Quarry (West Ukraine), siliciclastic series (4 m thick) occurs between the gypsum and the transgressive deposits. The siliciclastic series contains limestone intercalations which are first sparitic and -microsparitic, and then become pelletal. They are barren of marine fauna. The pelletal depositional textures are interpreted as originated in restricted environments. Limestones show a wide range of δ¹³C values (from -1.6‰ to -18.2‰) and δ¹⁸O values (from -0.2‰ to -9.4‰) indicating that the cementation and some recrystallization took place in meteoric-water-dominated fluid but the restriction-controlled trend can be recognized. In turn, the transgressive calcareous deposits contain rich marine fauna. They also show negative carbon and oxygen isotope values (from -4.6‰ to -15.4‰ and from -2.7‰ to -6.5‰, respectively) suggesting the presence of isotopically light, meteoric water rather than only seawater or concentrated, ¹⁸O-rich seawater-derived brines. The average δ¹⁸O values in limestones of Kudryntsi follow restriction-controlled trend, similar to that assumed for the Upper Badenian from Vienna Basin. Much wide ranges of δ¹³C and δ¹⁸O values in Kudryntsi are probably result of considerably more complex recystallization owing to many episodes of dissolution and reprecipitation.