Geology-Geomorphology-Pedology relationship associated with oxisols genesis of the West of Minas Gerais

Abstract

Oxisols and ferralsols have been studied by pedologists in the tropical region. Many of these studies report the development of oxisols in elevated flat area, such as plateaus, and in planing surfaces of different ages and on different geological substrates. However, one aspect remains contradictory in most of these studies: excessive focus on the control section (2 m) in soils that sometimes reach several meters thick until contact with saprolite or rock. If they are so thick soils, why neglect the pedogenesis records in most of the soil profile? Generalizations such as polygenetic, polycyclic and reworked source materials are frequent in the latossolic language, but little it was ordered and hierarchized in the understanding of latosolization process and its relation with the relief evolution and the paleoenvironmental variations. In view of this, this work will try to understand these relations in one of the main regions of occurrence of oxisols: Central Brazil. There are the objectives of a) to clarify the Geology-Geomorphology-Pedology relationship, elaborating a model with attention to possible neotectonic influences in the formation of elevated almost flat surfaces and of valleys constituted by different landforms; b) to identify and characterize the distribution of hardened ferruginous nodules, ferricretes and other reliquial pedological features to relate them to the relief evolution; c) to identify the origin of the material of origin of the oxisols and their homogeneity along the soil profile; d) to try to relate and hierarchize the features that indicate possible stages of latosolization in soils developed in different positions in the landscape; f) to reconstruct the quaternary paleoenvironmental changes and to analyze their influence in the recent sculpture of the landscape and the oxisols genesis; and g) to describe and quantify the bioturbation (roots + fauna) along the soil profile. The study areas comprise the regions of Alto Paranaíba and Unaí, located in the west of the State of Minas Gerais (Brazil). The Geomorphology of these areas is represented by almost flat surfaces very well expressed and locally highly dissected and the Geology predominantly contemplates metasedimentary rocks and other rocks of higher degree of metamorphism, often described in geological maps as partially covered by ferruginous clastic and lateritic sediments. Points to open deep trenches and/or road cut will be selected from the geomorphological interpretation, a preexisting geological map and field incursions in the Quebra Anzol River Valley (Alto Paranaíba) and the Rio Preto Valley (Unaí). The selected soil profiles will be described and soil samples beyond the control section will be collected for chemical, physical, geochemical, mineralogical, micromorphological, isotopic analyzes, and hardened ferruginous nodules and ferricretes for morphological, geochemical, mineralogical and chronological analyses. From this set of results it is expected to understand the genesis of these soils in a surface continuum to saprolite and its relation with the landscape in which they develop. (AU)