Mineralogy of a soils toposequence developed from holocenic material from Jequitaí region - State of Minas Gerais

Abstract

The studied regions are located in the northeast part of the State of Minas Gerais, and are characterizad by several erosional cycles due to the work of the São Francisco river and its tributaries, like Jequitai and das Velhas rivers. A soil toposequence represented by fine soils profiles developed from Quaternary sediments was choosed for this study. Profile 1, a Typic Haplustox, is located in the oldest surface. The other soils are located in the holocenic sediments, the alluvial area of São Francisco river. These are less weathered soils classified as Plinthic Haplustult (Profile 2); Oxic Plintaquult (Profile 3), Fluventic Plinthustult (Profile 4) and Fluventic Argiustoll (Profile 5). Mineralogical analysis was carried out in all soil fractons. Profile 1 has only resistent minerals in the sand fraction, whereas in the other soils plagioclases and micas occurs.These minerals increase in depth and from Profile 2 to Profile 5 (the less weathered soil). Kaolinite is the dominant clay mineral in all the studies soils, mainly in Pedon 1 (the most weathered soil). This mineral decrease in depth and from Profile 1 to Profile 5. In the less weathered soils mica, vermiculite and montmorillonite also occurs.