Zechstein 1- 3 evaporites of the Gorzów Block (NW Poland)

The Gorzów Block (West Poland) occurs in the transition zone between the PZ1 sulphate platform and the Na2 basin. In contrast to the western part of the Southern Permian Basin where the Z1 halite (Oldest Halite Na1) is normally restricted to the peripheral subbasins located south of the main basin, in Poland it occurs both in the basin centre and in the former basins of the Lower Anhydrite within the marginal sulphate platform complex, where halite sequences are thick and may have originated in a deep-water setting. The Na1 deposits have been considered so far to be LST deposits both in the marginal sulphate platform facies as well as in the basin centre. Brine salinities (and the minerals they precipitate) are controlled by brine residence times in the basin, and these are determined primarily by the absolute and the relative rates of water flow into, and brine flux out of the basin (Kendall, 2010). Thus sea-level rise in the Boreal Sea could have resulted in the increase of the brine residence times in the Zechstein basin and the deposition of more saline evaporites. Consequently, the Oldest Halite in the basin centre in Poland is regarded as the TST deposit