Study of the pedological coverage and its relation to the formation and evolution of depressions in the southwest of the municipality of Maracaí (SP)

Author(s)

Grace Bungenstab Alves

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH/SBD)
• Defense date: 2014-12-05

Examining board members

Jose Pereira de Queiroz Neto; Heloísa Ferreira Filizola; Maria Teresa de Nóbrega; Antonio Manoel dos Santos Oliveira; Fábio Soares de Oliveira

• Advisor: Jose Pereira de Queiroz Neto

Abstract

This research investigates the pedological cover to understand genetic processes at work in the formation and evolution of closed depressions in the Três Cantos compartment. The study area is located in the municipality Maracaí-SP (Brazil), at the interfluve between Anhumas and Capivara rivers, both tributaries of the Paranapanema River. The area has closed depressions in the top of local surface, with red-yellow and red soils and iron crust. To achieve our goal we evaluated two toposequences in the Mandacaru depression, as well as regional and local factors that could contribute to the formation and evolution of depressions. The procedures adopted for this research were based on the Structural Analysis of the Pedologic Coverage, proposed by Boulet et al. (1982). The results showed that the pedological processes that dominate are latosolization, hydromorphy and illuviation. The latosolization transforms the iron crust into Latosol in the Brazilian System of Soil Classification (Ferrasols -FAO, 2006). The hydromorphy that attacks the iron crust and Bw horizons resulting in a block structure when dry, and massive when wet combined with the illuviation process that transforms the horizons A and Bt into E result in Argisol in the Brazilian System of Soil Classification (Lixisols FAO, 2006). The latosolization process was the first to transform the iron crust, followed by wet conditions, transforming the iron crust and latosols due to hydromorphy action; consequently, the plateau was deformed. Hydromorphy, therefore, was responsible for initiating depression formation and subsequently the illuviation process contributed to it. Currently these two processes act deepening and widening the depressions. The formation of depressions is related to the geological structure, and these depressions are the initial stage of the areas drainage system, as may be observed in areas where the depressions have been opened, and where the soils are not yet adjusted to the new form of the slope. (AU)