SPONTANEOUS POTENTIALS AND RESISTIVITY SURVEYS APPLIED TO HYDROGEOLOGY IN A VOLCANIC AREA: CASE HISTORY OF THE CHAÎNE DES PUYS (PUY-DE-DÔME, FRANCE)1

Authors

  • CLAUDE FOURNIER

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    • 2

      United Nations Development Program, P.O. Box 553, Banjul, The Gambia. Formerly: Observatoire de Physique du Globe de Clermont-Ferrand, and Centre Géologique et Géophysique, Université de Sciences et Techniques du Languedoc, Mont-pellier, France.


  • 1

    Received July 1987, revision accepted October 1988.

ABSTRACT

Two geophysical methods [resistivity soundings and spontaneous potentials (SP)] are used to investigate aquifers in the Quaternary volcanic formations of the Chaîne des Puys (France). The interpretation of the resistivity soundings required a specific work of determination of the resistivity of the formations concerned. The basement topography, characterized by axial horst and graben structures and perpendicular palaeovalleys, was revealed. SP was developed experimentally in the field and theoretically. It is shown that the SP anomalies can be considered as double-layer potentials, with their source on the aquifers' interfaces. The most significant of them is the water table, which creates an SP anomaly of similar but inverted form. SP anomalies due to flows in unconfined aquifers, in palaeovalleys, and in volcanic ranges are computed and compared with the observed ones. These two methods have determined the extent and the boundary conditions of the different hydrogeological basins and have determined the major drainage axes and the groundwater flow pattern.

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