Phases of Evaporite Deposition In the Largest European Foredeep Basin (Miocene Carpathian Foredeep Basin)

The Carpathian Foredeep Basin, a part of the Central Paratethys, stretches for more than 1300 km from the Danube in Vienna (Austria) through Czech Republic, southern Poland, West Ukraine and Romania to the NW part of Bulgaria. It is asymmetric and is filled with predominantly clastic deposits of Miocene age as much as 6 km thick in the Carpathian front in Ukraine. It is hosting rock salt mined in southern Poland since the 13th century (mines: Wieliczka and Bochnia) and potash deposits mined in Ukraine since 19th century. All these mines are located near the front of the overthrusted Carpathian nappes, and because of such a geological location, the stratigraphic section is likely repeated. For example, the Stebnyk potash deposit is part of the Vorotyshcha Suite composed of three members: lower salt-bearing, middle terrigenous and upper salt-bearing ones, with a total thickness more than 2000 m due to intensive folding and overthrust tectonics: the normal total thickness of potash deposits in Stebnyk is 100 – 125 m. The age of the Vorotyshcha Suite is the Early Miocene Eggenburgian (ca. 19.0 Ma). The lithostratigraphical and chronostratigraphical position of another potash deposit (Kalush) is subject to controversies. The potash-bearing sequence consists of interbedded salt claystones, breccias, potash and rock salt, up to 500 m thick; the unfolded thickness of the potash complex is 38.5 m. Geochemical arguments and radiometric data suggest that the Kalush evaporites can be Karpatian in age (Lower Miocene; ca. 16.8 Ma). The mined rock salt deposits are Badenian in age (Middle Miocene, ca. 13.3 Ma). Unfolded thickness of the halite-bearing sequence, consisting of rock salt with intercalations of claystones and minor Ca-sulfates, is 30 – 100 m. Halite deposits occur near the Carpathian Overthrust, and elsewhere in the Carpathian Foredeep Basin coeval sulfate deposits (10 – 60 m thick) occur.