Imagine that the level of the oceans is much higher than it is today and that much of today’s Europe is underwater. As a result of the cooling of the climate, the level of oceans decreases by about 60 meters, a closed reservoir with very high salinity is created. The watercourse cuts deep into the land, forming narrow bays and lagoons, and rock mass movements and subsidence cause the seabed to drop steadily.
Under these conditions, about 13.6 million years ago, salt deposits were formed. Slow precipitation of salt deposits takes place – evaporation accompanied by intensive evaporation of water caused by dry climate. The progressing evaporation together with the subsidence of the seabed and the erosion of the coastal parts of the basin meant that more terrigenous material was supplied to the basin along with the sea waters, as a result of which excesses of gangue was deposited within the salt beds.
Saline sedimentation in the Carpathian Foredeep probably lasted at least 200,000 years. Deposits that were formed in the Carpathian Foredeep extend over a length of 300 km and width of 100 km. These also include the Wieliczka deposits, which stretch for 10 km in length, with a width from several hundred metres to 1.5 km.
Source: https://www.wieliczka-saltmine.com/indi ... f-the-mine