Massive evaporites were deposited in the Central European Paratethys Sea during the Badenian salinity crisis (BSC). The scarcity of absolute age data has hampered a thorough understanding of these salt deposits. Here we present a robust chronology for this catastrophic event by 40Ar/39Ar dating of volcanic tuffs below and within the Badenian salts in southern Poland. The onset of BSC evaporite deposition is dated at 13.81 ± 0.08 Ma and the entire event is estimated to have lasted 200-600 k.y. Correlation to oxygen isotope records shows that the BSC evaporites were just preceded by glacial event Mi-3b, suggesting a causal relationship. The corresponding sea-level fall most likely restricted the open marine connection to the Mediterranean, thereby trapping the salt in the deep Paratethys basins

Fluid inclusions in halite are widely used in research to determine the conditions of sedimentation in salt basins and reconstruct the chemical composition of seawater during a specific geological period. However, previous preliminary studies of the genetic types of inclusions, considered in the present research project, have not received due attention. Consequently, we decided to take into account the main distinguishing features of fluid inclusions in halite, belonging to various genetic types. The ultramicrochemical analysis (UMCA) method is one of the several methods that are used for the quantitative determination of the chemical composition of the primary fluid inclusions in halite. We have upgraded that technique, and that allowed us to reduce the analytical error rates of each component determination. The error rates were calculated in the study of Ca-rich and SO₄-rich types of natural sedimentary brines.

Currently, fluid inclusions in halite have been frequently studied for the purpose of paleoclimate reconstruction. For example, to determine the air temperature in the Middle Miocene (Badenian), we examine single-phase primary fluid inclusions of the bottom halites (chevron and full-faceted) and near-surface (cumulate) halites collected from the salt-bearing deposits of the Carpathian region. Our analyses showed that the temperatures of near-bottom brines varied in ranges from 19.5 to 22.0 °C and 24.0 to 26.0 °C, while the temperatures of the surface brines ranged from 34.0 to 36.0 °C. Based on these data, such as an earlier study of lithology and sedimentary structures of the Badenian rock salts, the crystallization of bottom halite developed in the basin from concentrated and cooled near-surface brines of about 30 m depth. Our results comply with the data on the temperature distribution in the modern Dead Sea.

The geochemical data and the study of fluid inclusions in primary halite are invaluable sources of saline basin information. Most of the previous analyses of salt from the Carpathian area have been obtained by studying the halite samples collected from depths not exceeding 1000 m (i.e., from salt mine outcrops or boreholes). In this article, for the first time, we present the results of samples obtained from a deep well where salt occurs below the frontal orogenic wedge at a depth of ~5000 m. The salt core’s petrological studies showed, quite unexpectedly, the presence of the chevron relics, typical for primary halite. Their geochemical data and fluid inclusion study can be used to reconstruct the environment of the salt sedimentation. The bromine, strontium, and rubidium content values indicated that primary brines were of marine origin, and salts may have undergone partial dissolution and redeposition under lower salinity water inflows. The main ions’ (K, Mg, SO₄) ratios in the fluid inclusions were typical for those of the Badenian brines collected from the Carpathian Foredeep’s eastern part. Compared with modern seawater’s chemical composition, this brine contained a slightly lower content of sulfate ions. This was associated with evolutionary changes occurring in the contents of sulfate ions during the Cenozoic.

Structure and evolution of the Carpathian thrust front between Tarnów and Pilzno (Pogórska Wola area, southern Poland) – results of integrated analysis of seismic and well data

The Middle Miocene (Badenian) evaporites have formed within more or less restricted basins, occupying the Carpathian Foredeep and inner depressions in the East Slovakian Basin of the Carpathians. Their deposition coincided with the increased tectonic activity in the Carpathians, evidenced by volcanic eruptions (widespread volcaniclastics) and frequent earthquakes. These phenomena apparently initiated landslides, submarine slumps and turbidity currents which formed deposits characterized by rapid facies changes and relatively limited lateral continuity. The clastic–evaporitic deposition in the Zbudza area (East Slovakian Basin) was controlled by frequent tectonic and seismic phenomena and high continental clastic supply that produced repeated slump sediments with dominant proximal mass flows and distal flows and diverse salt types (salt/clay rhythmites, finer halite–arenites, coarse halite–rudites). These zones are separated by primary salt units (halite) precipitated in situ from bottom brines during calm periods. The observed cyclicity (I–V cycles) reflects varied tectonic activity of the basin margins, that mechanically remobilized the sediments from marginal salt pans, flats and adjacent uplifts, and could be correlable with cycles in the Wieliczka Formation from Carpathian Foredeep.