Technischer Bericht NTB 92-08

This report presents hydrochemical information for groundwaters from the Muschelkalk, Keuper, Lias, and Dogger aquifers, and constitutes the third and last part of a comprehensive hydrochemical synthesis of groundwaters from aquifers in northern Switzerland and adjacent areas. The data are mainly the results of the Nagra regional and supervisory programme, completed by a number of published analyses from external sources (= "Fremde Analysen"). From these data it was possible to show differences of waters specific to the formations concerned, particularly with the help of the relationships of minor elements and isotopes. Deep groundwaters in the Muschelkalk and Keuper aquifers distinguish themselves by solution of gypsum/anhydrite and halite, sometimes also by cation exchange or solution of mirabilite. In the deep groundwaters of the Lias and Dogger aquifers processes mainly of cation exchange and mixing with marine pore waters define the chemical compositions. Using specific hydrochemical attributes, in some cases it is possible to recognize mixing processes between groundwaters of different aquifers. Thus, it could be shown that the waters in that portion of the Muschelkalk aquifer thrusted over the south rim of the Folded Jura (Baden/Ennetbaden, Windisch/Birmenstorf) contain an important proportion of sodium chloride groundwaters which have ascended via faults from deeper aquifers. In the Muschelkalk of the Tabular Jura there are indications of such hydraulic connections in the area of the northern margin of the Permo-Carboniferous Trough of Northern Switzerland, as well as in the west, where the Tabular Jura is influenced by Rhine Graben tectonics.