CHEMICAL AND MECHANICAL EROSION IN THE NI GER AND AMAZON BASINS - CLIMATIC AND PALEOCLIMATIC EVOLUTION OF TROPICAL LANDSCAPES

The annual hydrograph separation of the upper Niger basin at Bamako, d etermined from the TDS and TSS concentration variations in the river w aters during the dry period 1990-1992, has been extrapolated to climat ic cycles from arid to perhumid. A dilution factor (F = rainfall/runof f) is introduced, so that the extrapolation from the Niger basin data corresponds to the weathering parameters which characterize, in very h umid environments, three tributaries of the Amazon. The erosion rates of tropical landscapes submitted for 150 Myr are finally reconstituted to major paleoclimatic oscillations. (C) Academie des sciences/Elsevi er, Paris.