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Estimated Mean Water Residence Time (Δ~ (18) O) of Karstic Springs and Karst System Development

Author(s): Th. Herold; F. Zwahlen; S. M. Bernasconi; P. Jordan

Linked Author(s): Jordan Joseph Grados Panduro

Keywords: Nticline; Tectonic; Stable Isotopes; Karst springs; Residence times; Paleogeomorphological evolution

Abstract: The Weissenstein Anticline is located 100 km northwest of Bern, in the south-east part of the Folded Jura (Switzerland). The anticline contains two large aquifers, the Dogger limestone and the Malm limestone. The two aquifers are separated by impermeable layers. The anticline is hydrogeologically bounded by the Weissensteintunnel in the west and the Oensingen gorge in the east. Geometric modelling and the results of the multiple tracer experiments showed that pre-and synorogenic faults strongly influence the pattern and interconnection of karst systems. During the folding of the anticline, the erosion started at preferential locations which were connected to preexisting fault systems. Thus we suspect a paleogeomorphologic pattern which influenced the development of limestone fracture systems in present day karst systems. To test this hypothesis, the largest karst springs in the Weissenstein Anticline were continuously measured for discharge, temperature and conductivity for several years. In addition, weekly samples of spring waters and the daily precipitation were measured for stable Isotpes (18O) to determine annual variations. As demonstrated in this paper, with the Malm karst spring database, it was possible to estimate, as the first step, the mean residence time of the spring water. The water from individual sampling points showed characteristic differences in residence time along the valley from east to west. Given the spring water residence times we believe that maturity of karstic features in the Weissenstein Anticline increases from east to west as a result of the structure’s geological and paleo-geomorphological evolution.


Year: 1999

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