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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.

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Polyhalite is a common constituent of many ancient evaporite sequences, especially Permian and Neogene ones, that is related to the Na-K-Mg-CI-S0 4 type of marine brines in those time intervals. There are four polyhalite deposits in the Zechstein of northern Poland, and more than ten polyhalite-bearing areas in the adjacent part of Russia, and they are commonly accompanied by K-Mg chlorides. Most polyhalite occurrences are related to the upper part of the Lower Werra Anhydrite and in most cases, polyhalite deposits are concentrated at the sulfate platform close to its boundary with platform slope, where they can pass horizontally into polyhalite beds occurring in the Oldest Halite. The bromine content in samples of the Oldest Halite ranges from 40 -120 ppm and the composition of fluid inclusions in halite are characteristic of halite precipitated from seawater concentrated to the early and middle stages of halite precipitation. The 8 180 and 8 34S values for sulfates are 10.03%0 -13.50%0 and 10.03%0 -12.14%0, respectively, and the 8 37CI values for halites from -0.1 %0 to +0.4%0 support their marine origin. Bromine distribution in the Oldest Halite and the occurrence of anhydrite intercalations indicate fluctuations of the brine density during the Oldest Halite deposition. The formation of polyhalite was preceded by the syndepositional dehydration of the original gypsum deposit and it appears that the anhydrite was then transformed to polyhalite by reaction with marine brines more evolved than those from which precipitated precursor calcium sulfate minerals. These concentrated brines could have been derived from the evaporation of marine brines and/or inflow of K-and Mg-rich brines that were formed in nearby shallow salt pans occurring in sulfate platform areas and thus sulfate platform areas and adjacent slopes of those platforms were predestined for polyhalite formation.