The hydrogeology of sulfate-bearing soft rocks - a case study: Gipskeuper (Triassic, Grabfeld-Formation)

摘要

In the Southwest German Cuesta, the 150-metre-thick Gipskeuper-Formation (Grabfeld-Formation, Triassic) is dominated by claystones, intercalated with dolostone beds and thin- to massive-bedded sulfate rocks. When in contact with groundwater, the soft claystones experience a reduction of rock strength in several weathering stages. Upon hydration of anhydritic sulfates, the resulting gypsum is also subject to leaching. As both processes are dependent on depth and geomorphological relief, complex aquifer geometries with a high range of hydraulic properties develop. In extreme cases, impermeable, low-permeability and high-permeability zones can be found contiguously within the Gipskeuper. The process of aquifer evolution is described using the example of the Stuttgart basin.