Dinâmica da paisagem na região do Alto Rio Abaeté, Bacia do Rio São Francisco

• Autor(a) principal: Costa, Fernanda de Oliveira
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5428
• topic: Erosão; Vertentes; Bacia hidrográfica; Erosion; Slope; Watershed; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The Alto Paranaíba fisiographic region, located at western Minas Gerais State, is an important watershed boundary between the São Francisco River and Paraná River. In addition, it was an important scenario of geological and geomorphological activities in the course of its formation and evolution. These activities took place in past geological times, leaving evidences represented by several volcanic rocks of varied chemical and mineralogical composition. These surfaces are uplifted and named the High Paranaíba Arc, which has dendritic drainage controlled by geological structures. This region has the following stratigraphic column: Bambuí Group (pelitic rocks), Areado Group (conglomerates rocks, sandstones, argillite and shales), Mata da Corda Group (extrusive volcanic rocks and sandstones) and the topped detritic laterites. Each rock type has evolved through different ways, developing specific soils. At this context, the present study has the objective of correlating the long term denudational processes that occur on slopes with nowadays landscape morphology at the upper and middle Abaeté River watershed, a São Francisco River sub-watershed, located at this region. This correlation is made by comparing and overlaping thematic maps, at the scale of 1:300.000, which were produced out of NASA SRTM (Shuttle Radar Topographic Mission) 9.3- arc resolution altimetry data, RADAMBRASIL maps and IBGE and ANA databases. These data is processed in ArcGis®, a software by ESRI (Environmental Systems Research Institute). For identifying the denudational relief features, two soil transect are selected for sampling three soil profiles from each one: Latossolo Amarelo Distrófico típico (Oxisol), Plintossolo Pétrico Concrecionário típico (Latheritic Soils), Argissolo Vermelho-Amarelo Distrófico típico (Ultisols). For each profile, are presented the analyses of physicochemical and mineralogical features of each horizon. Some morphometric parameters are calculated for the study-area to help understanding its hydrologic regime and identifying some structural features, which are important to quantify the watershed features. The soil analyses demonstrate a natural low fertility, though other physicochemical features have satisfactory values for mechanized agriculture, as low values for water dispersible clay and high aggregates stability, obtained either via wet and dry measurements. The clay fraction mineralogy shows a preeminence of oxides, that indicates an intense weathering for all the sampled soils. At the table surfaces, the gibbsite is the centerpiece for the aggregates stability due to its granular structure, its high permeability and its high portion of macroaggregates. So, even when soils have more intensive usages, they keep their structure. Besides, the removal of the detritic laterites from the table surfaces boundaries for paving roads allows the ravines to deep, causing the long-term retreat of the scarp. The downhill soil preparing is another ordinary practice in the region. When associated to exposed C-horizon and varied lithological material, this technique initiates intense erosive processes. The correlation of the cartographic data to the field observations demonstrate the necessity of conservationist practices, especially for less developed soil derived from volcanic and Bambuí rocks. In the course of such diversified geology and geomorphology, the present work aimed at assessing the relationship between soils, more specifically, their geomorphological and geological features with the landscape of the upper and medium Abaeté River, a sub-watershed of the São Francisco River.