Abstract
Palm swanp formations, the so-called veredas, typically occur in the Brazilian biome known as "Cerrado" (savanna-like vegetation), especially on flattened areas or tablelands (chapadas). The aim of this study was to characterize the mineralogy and micromorphology of soil materials from a representative toposequence of the watershed of the vereda Lagoa do Leandro, located in Minas Novas, state of Minas Gerais, Brazil, on plains in the region of the upper Jequitinhonha valley, emphasizing essential aspects of their genesis and landscape evolution. The toposequence is underlain by rocks of the Macaúbas group and covered with detrital and metamorphic rocks (schists of Proterozoic diamictites). The soil profiles were first pedologically described; samples of the disturbed and undisturbed soils were collected from all horizons for further micromorphological and mineralogical analyses. The mineralogical analysis was mainly based on powder X ray diffractometry (XRD) and micromorphological descriptions of thin sections under a petrographic microscope. The soils from the bottom to the top of this toposequence were classified as: Typic Albaquult (GXbd), Xanthic Haplustox, gray color, here called "Gray Haplustox" ("LAC"), Xanthic Haplustox (LA) and Typic Haplustox (LVA). The clay mineralogy of all soils was found to be dominated by kaolinite. In soil of LA and LVA, the occurrence of goethite, gibbsite, and anatase was evidenced; "LAC" also contained anatase and the GXbd, illite, anatase, and traces of vermiculite. The micromorphological analyses of the LVA, LA and "LAC" soils showed the prevalence of a microaggregate-like or granular microstructure, and aggregate porosity has a stacked/packed structure, which is typical of Oxisols. A massive structure was observed in GXbd material, with the presence of illuviation cutans of clay minerals and iron compounds. Paleogleissolos, which are strongly weathered, due to the action of the excavating fauna , and resulted in the present "LAC". The GXbd at the base of the vereda preserved the physical, mineralogical and micromorphological properties that are typical of a pedogenesis with a strong influence of long dry periods.
Highlights
IntroductionChapadas (highlands) predominate on the Jequitinhonha plateau, in Northeastern Minas Gerais (MG); these are extensive areas of flattened terrain (at about 900 m asl)
Chapadas predominate on the Jequitinhonha plateau, in Northeastern Minas Gerais (MG); these are extensive areas of flattened terrain
Kaolinite was found by the presence of diffraction peaks at basal spacings of 0.722 nm (12.24 °2θ d001) and 0.359 nm (24.74 °2θ d002), which collapsed after heating to 550 oC
Summary
Chapadas (highlands) predominate on the Jequitinhonha plateau, in Northeastern Minas Gerais (MG); these are extensive areas of flattened terrain (at about 900 m asl). The original biome was the Cerrado vegetation and the area was separated by the Jequitinhonha and Araçuaí River and their affluents. Some of these chapadas, which cover over 10,000 ha, are drained by streams with swamps (veredas) at their source. According to Campos (1998), the drainage system of the upper Jequitinhonha valley is immensely important for the soil and landscape evolution because structural, tectonic, and lithological factors induced changes in this environment. Red, Red Yellow, Yellow, and gray-colored Latosols predominate on the chapadas of the upper Jequitinhonha; and Gleysols and Plinthosols are found in the valleys (Ferreira et al, 2010)
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