Abstract:
Spatialized Morphological Analysis is a new method of detecting faults which uses the morphometric relief data (slope, aspect, elevation) taken from a precise Digital Elevation Model by a computer program. This program, taking the principles of the evolution of relief into account (rock type, climate, chronology), allows the statistical identification of morphometric standards for each type of morphology and the extraction of anomalies to these standards. Some of these anomalies, after a processing of spatial classification, are considered as tectonic tracks. The actual existence of faults, corresponding with anomalies, is verified by classical methods of structural geology. By a better localisation and geometrical definition of faults, this method can allow the optimization of hydrodynamical studies of cracked aquifers, and in case of calcareous ones, a spatial approach to karstification. This method is applied to the north of France chalky aquifer, where, associated with detailed hydrogeological records, it allowed the identification of rapid transfers of groundwater at the level of faults. Even so, exokarstic phenomena are uncommon in this area. Some chemical and textural particularities of Quaternary chalk cover may be the cause of rainwater inhibition, and it is possible that the karstic responses observed are due to considerable mechanical dissolution in the saturated area where tectonic activity (neotectonic faults have been observed) creates environments of preferential flow. (C) Elsevier, Paris