Variation of the kaolinite and gibbsite content at regional and local scale in Latosols of the Brazilian Central Plateau

The mineralogy of the Latosols of the Brazilian Central Plateau remains under discussion in the absence of a clear relationship with their age according to their geomorphic location. The aim of this study was thus to clarify the origin of the kaolinite and gibbsite content variation by studying a regional toposequence and using data from the literature. Chemical composition and soil color were used to discuss mineralogy. The mineralogy of the clay fraction was also investigated using X-ray diagrams. Our results showed that the large variation of kaolinite and gibbsite content can be explained by taking into account both their local and regional location, the variation of the hematite and goethite content remaining limited. The model that is proposed to explain such variation combines a regional component, which is mainly associated to the age of the geomorphic surface and a local component which is mainly associated to the hydraulic conditions along the toposequence.