Géophysique des sols et des formations superficielles : abstracts et résumés étendus

The tropical soils systems cover more than 1/3 of the emerged earth. The knowledge of the shallow structures is crucial for the understanding of global pedological functioning of soils. Multifrequency radar and pole-pole multi-electrode DC resistivity surveys were conducted here along the 950 meters long main traverse of Nsimi watershed to delineate the main pedological horizons. The results of pole-pole survey are interpreted using RES2DINV software, which allows a rapid 2-D inversion. The resulting image shows the main structures from shallow depth to more than 80 meters deep. Features like major fault, bedrock topography or altered zones are clearly defined. In order to image the shallower part of the section, the radar and a more detailed electrical section are presented together and compared to dense pedological observations available on this traverse. In the first ten meters, the main radar reflectors at 25 MHz and iso-resistivity curves correlate themselves. This allows to give precise indications to the pedologist who can locate more accurately observation pits or borehole investigations as well as to give precise geometrical limits to pedo-hydrogeologic models. (Résumé d'auteur)