Heterogeneity of folding in Zechstein (Upper Permian) salt formations in the Kłodawa Salt Structure, central Poland

Abstract

Analysis of folds carried out in the Kłodawa Salt Structure (central Poland) showed that the Upper Permian (Zechstein) siliciclastic-evaporitic bed sequence is heterogeneously folded, which resulted from differences in competence of rocks and from bed stratigraphy. Rock salt and potash-rich complexes of each Zechstein cycle are internally folded and contain multiple sheath folds, interpreted as the early sheath folds, originated during lateral flow of salt. These folds are superposed by upright sheath folds inside thick PZ1-PZ2 rock salt complexes. The lack of superposed folds in younger Zechstein salt complexes (PZ3-PZ4) and unconformities between the PZ1-PZ2 and PZ3-PZ4 beds imply that rock salt beds were internally folded prior to diapirism, independently in each salt bed. Two oldest rock salt beds welded during lateral flow and were folded together into upright sheath folds during the upward flow of salt. These superposed folds clustered into subordinary diapirs and pierced through the younger deposits. The latter sunk in salt masses and formed large-scale synclinoria, consisting of beds with fossil early tectonic and sedimentary structures.