Mapeamento de superfícies de aplanamento no centro-norte da Amazônia
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2020-04-27
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Universidade Federal de Goiás
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The recognition of the different planation surfaces of a region provides a picture of the structure of its relief and helps to understand the distribution of its surface formations. Mapping of planation surfaces traditionally carried out by geomorphologists is subject to strong interference from decision makers and there are few proposals for automated mapping. The manual and analogical methods depend fundamentally on the interpretation of the decision maker and often lack mathematical logic, and may be relative, biased and inaccurate. The structure of the reliefs of the Amazon and its natural resources are still little known by researchers and by Brazilian society and the mapping of their planation surfaces can assist in this task. This thesis has as its study area the center-north of the Amazon, covering parts of the territories of Brazil, Venezuela and Guyana. Thus, the main objective is to contribute to the methodologies for mapping the planation surfaces as a resource for understanding the spatial distribution of surface formations (soils, laterites, alluviums, mineral occurrences). As specific objectives, we sought to a) develop an automated methodology for mapping planation surfaces to tectonically stable areas; b) check if there is a correlation between the distribution of the surfaces of the mapped areas and the distribution of their surface formations; c) relate the mapped surfaces to the surfaces recognized by the literature and their ages. The methodology is divided into the following stages: 1. Elaboration of a mathematical algorithm using geoprocessing techniques to get data base from remote sensing, specifically radar, extracted from images of the PALSAR sensor (Phased Array type L-band Synthetic Aperture Radar), on board the ALOS satellite (Advanced Land Observing Satellite).This stage was carried out for a control area, which has two planation surface that are very clear and still little disturbed by river dissection, located in the municipality of Chapada Gaúcha-MG; 2. Application of the proposed methodology to the central-northern region of the Amazon; 3. Obtaining data on surface formations (soils, sediments, laterites) of the two regions and checking, through geoprocessing, digital cartography and graphical representations, the correlations between surface formations and mapped surfaces. In the control area, reliefs associated with three planation surfaces were identified: first surface, associated with the Velhas surface (the most recent and of lowest altitude), between 685 and 800 m; a second surface, associated with the South American surface (intermediate in age and with a better degree of flattening), between 801 to 881 m; and a third surface, between 882 and 898 m, associated with Post-Gondwana (oldest and represented only by dissected forms located altimetrically above the level of South American surface).The mapped surfaces showed good correlation with the types of surface formations (soils), indicating that the structure of natural landscapes has a direct relationship with the distribution of planation surfaces, considering their flat remnants and the reliefs resulting from their dissection The inconsistencies found can be fundamentally attributed to the incompatibility of scales between the surface map and the soil map available for the studied area. For the central-northern region of the Amazon, the proposed model allowed the identification of five planation surfaces in the strip that extends from the highlands of the border between Brazil, Venezuela and Guyana to the axis of the Amazon River, near the city of Manaus: a summit surface, which was associated with to Gondwana surface, between 855 and 2,745 m; a second surface, between 525 to 854 m, associated to Post-Gondwana; a third surface, between 279 and 524 m, associated to South American; a fourth surface, between 114 and 278 m, associated with to Velhas Precoce surface (Early Velhas surface), and a fifth surface, associated with to Velhas Tardio surface (Late Velhas). For each surface, the remaining flat areas and the dissected areas were mapped. The spatial distribution of geomorphological surfaces showed a good correlation with the spatial distribution of mapped surface formations. In the first three surfaces, young soils predominate, whose presence was attributed to the erosion of surface formations and the rock exposure. The two lower altitude surfaces present a greater diversity of soils, due to the increase of flattened areas under more deficient drainage conditions (Spodosols, Plintossols, Gleisols, Planossols), in addition to Latosols and Acrisols, which are dominant. The mapping proposal presented coherent and unprecedented results on the distribution of planation surfaces in the north-central Amazon, making it possible to infer the distribution of surface formations in the region.
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MANTOVANI, J. R. A. Mapeamento de superfícies de aplanamento no centro-norte da Amazônia. 2020. 146 f. Tese (Doutorado em Geografia) - Universidade Federal de Goiás, Goiânia, 2020.