ETUDE DES DIAPIRS EN ALSACE ET BADEN‐WURTEMBERG PAR LA METHODE DU RECTANGLE DE RESISTIVITE*

Abstract

AbstractThe study of tectonics of salt and of diapirs in particular is an important problem in the mining field as well as in that of petroleum exploration. This paper describes surveys that were carried out, using the method of the rectangle of resistivities.After stating the principle of the method, the way it is carried out and its advantages, three examples are discussed: two in the Alsace plain (Hettenschlag‐Oberentzen and Blodelsheim), the third in Baden‐Wurtemberg (Weinstetten‐Heitersheim). Geological conditions are practically the same (resistive alluvia, very conductive marls and resistive salt series); the depth at which the top of the salt was found varied from 100 meters to more than 1000 meters. Maps of resistivities (with current electrode spacing of 6000 meters) and graphs of a few electrical soundings are presented, together with the results obtained under the form of isobath maps of the top of the salt series.The surveys lasted 26 months and covered 171 square kilometers. The work presented corresponds to three sections totalling 93 square kilometers and was chosen because of the diversity of the tectonics. Four drill holes have been carried out since then and have confirmed the results quite well.The method may be extended to the survey of the tectonics of a salt series or of a resistive substratum, for instance a limestone formation, that are deeper than the above cases (2000 meters or more), using current electrode spacing of 20 kilometers. Surveys of this type have already been realized in the field.