Possibility of sequence stratigraphic subdivision of the Zechstein in the Polish Basin

Abstract

Applying the Exxon method for sequence distinction, four depositional sequences can be distinguished in the Polish Zechstein, out of which the first commenced during the deposition of the upper portion of the Rotliegend and the fourth continued up to the lower portion of the Buntsandstein. In our opinion the Exxon approach is not a significant step in understanding the principles controlling the Zechstein basin evolution during the deposition of carbonate and evaporite-dominated, lower and middle parts of the Zechstein. The fourth depositional sequence commences with evaporite deposits of LST, but afterwards a general change of sedimentary regime occurred and the uppermost part of the Zechstein is dominated by terrigenous-evaporite litho-facies. Because it is not possible to distinguish typical depositional sequences in the Zechstein terrigenous-evaporite lithofacies, it was decided to distinguish climatic sequences. Despite of fundamental differences between the origin of climatic and eustatic sequences, they have an important common feature; their boundaries are isochronous.