Hydrochemical properties of deep carbonate aquifers, SW-German Molasse Basin

Abstract

The Upper Jurassic (Malm) limestone and the middle Triassic Muschelkalk limestone are the major thermal aquifers in the southwest German alpine foreland. The aquifers are of interest for production of geothermal energy and for balneological purposes. The hydrochemical properties of the two aquifers differ in several aspects. The total amounts of dissolved solids (TDS) are much higher within the Upper Muschelkalk aquifer than within the Upper Jurassic. Water composition data reflect the origin and hydrochemical evolution of deep water. Rocks and their minerals control the chemical signature of the water. With increasing depth, the total of dissolved solids increases. In both aquifers, the water evolve to a NaCl-dominated fluid regardless of the aquifer rock. The salinity of the aquifers has different sources. In the case of the Upper Muschelkalk it is linked to deep circulation-systems, while the hydrochemical properties in the Upper Jurassic developed due to changing overburden and hydraulic potential