The aim of this work is to improve our understanding of the internal structures and dynamics inside mechanically layered evaporite bodies during deformation. A better understanding is needed to improve salt reservoir models, reduce drilling risks and to understand the long-term behavior of complex salt structures. In detail, we address the questions: What is the influence of extreme soft or much harder layers during deformation? What happens during this deformation inside K-Mg salt dominated layers and which structures are formed? Under which conditions (rheology, viscosity contrast, strain rates, stresses, layering, multiphase deformation) can the observed structures be formed? With the synthesis of data from basin to micro scale structures, the salt body evolution, local salt flow, material mixing, stress indicators, strain concentration was analyzed based on existing rheology models and concepts of salt body deformation. Thus, a model of salt deformation inside the Veendam salt pillow in the framework of local tectonics was developed together with a concept of conditions leading to the local extreme accumulation of bischofite. A fine stratigraphic analysis of the bischofite rich ZIII-1b layer was performed with a detailed examination of the existing deformational structures. Based on these results, the deformation of the ZIII-AC stringer was modeled revealing the influence on the internal deformation and the boundary conditions to produce the observed structures. In the first part, the evolution of the Veendam and Slochteren salt pillows at the southern boundary of the Groningen High, northern Netherlands is studied with high-resolution 3D seismic and well data. The internal structure of the two salt pillows shows areas in which the K-Mg salt-rich ZIII 1b layer is much thicker than elsewhere, in combination with a complexly ruptured and folded ZIII Anhydrite - Carbonate stringer. Thickness maps of supra-salt sediments and well data are used to infer the initial depositional architecture of the K-Mg salts and ...