Sub-areas in steep rock salt formations – what do we know about the geological composition of North German salt structures?

Abstract. Suitable host rocks for a repository high-level radioactive waste (HLW) in Germany include not only clay and crystalline but also rock salt formations so-called flat steep bedding (StandAG, 2017). Favourable relevant properties of are, e.g. the high heat conductivity, low porosity permeability, its viscoplastic deformation behaviour. Thicker deposits can be attributed to formation approx. 700 structures that have formed under various geological conditions North German Basin (NGB) over last 250 million years. According their shape genesis, are classified as pillows (considered bedding) or diapirs (steep bedding). Out total 74 sub-areas salt, 60 consisting Permian evaporates were identified within first phase site selection procedure (BGE, 2020). At current stage process, conservative approach has been adopted internal structure yet taken into account further classification sub-areas. However, interior consists varying proportions clay, carbonate anhydrite rocks, well potassium salts by progressive evaporation marine brines. Multi-phase tectonics led folding these differently composed layers complex structures. Therefore, detailed knowledge compositions is necessary identify suitable areas designation containment providing zone. As result decades research through extensive potash mining, cavern storage exploration final disposal, represent well-studied Germany. The use different methods multidisciplinary data evaluation comprehensive understanding composition some Systematic studies shown several factors influenced external shapes, sizes, spatial distribution (e.g., Pollok et al., Furthermore, amount varies greatly closely related structure. Since considered process so far, (or sub-areas) certain types with complexity presented. By examining lithofacial composition, structural position basin, it possible narrow down specific NGB. Without acquisition additional this provides important legally demanded assessment overall favourable situation.