RIFT TECTONICS IN MADAGASCAR - ITS IMPACT ON GEOMORPHOLOGY AND FLOWS

In Madagascar, evidence of a rift neotectonics oriented north-south is shown and analyzed on microtectonic, kilometric, and regional scales. This phase, reported for the first time, influences significantly the water flow patterns and the following modern processes: directional control of the hydrographic system; local changes in base water levels; development of zones of active erosion and sedimentation; opening and (or) reopening of drainage fractures in karstic systems; typological diversification of some depressions (lowland floodings); hydraulic transfer between surface and subsurface controlled by preferential major axes of underground water drainage.