996 resultados para Sedimentació fluvial


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Este trabalho teve como objetivo principal analisar a dinâmica geomorfológica, bem como a apropriação humana do relevo, mediante a interpretação de forma integrada dos documentos cartográficos elaborados a partir de técnicas da cartografia morfométrica, geomorfológica e de uso da terra, de forma a subsidiar ações vinculadas ao planejamento ambiental da Bacia do Ribeirão Tijuco Preto (SP). Sob os auspícios da abordagem sistêmica, a partir de uma visão integrada e complexa dos sistemas geomorfológicos, propôs-se a quantificar os atributos das formas de relevo, representando-os cartográficamente com a elaboração das Cartas Morfométricas de Declividade ou Clinográfica (De Biase, 1970 e 1992), de Dissecação Horizontal (Spiridonov, 1981 e adaptações de Mauro et. al.,1991), de Dissecação Vertical (Spiridonov, 1981) e de Energia do Relevo (Mendes, 1993). Também, contemplou-se a cartografia geomorfológica de detalhe, com a elaboração da Carta Geomorfológica (Tricart, 1965), bem como o mapeamento do uso da terra, expresso na Carta de Uso da Terra (Ceron e Diniz, 1966). De forma geral, a análise dos Produtos Cartográficos elaborados, permitiu constatar que a Bacia do Ribeirão Tijuco Preto vem sofrendo o desencadeamento de processos erosivos variados. Tais processos estão associados a uma conjunção de condicionantes, que podem ser apontados pelas variadas condições morfométricas do terreno, o clima quente e úmido reinante, as diferentes litologias aflorantes, a tipologia dos solos, bem como, e, de maneira veemente, a intervenção humana. O condicionante antrópico está majoritariamente representado pela monocultura canavieira e pela urbanização, sendo agentes cruciais no desencadeamento dos processos erosivos existentes e na interferência direta na dinâmica do escoamento fluvial da Bacia do Ribeirão Tijuco Preto.

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STRATIGRAPHIC SUCCESSION OF ALAGOAS STAGE ON SERRA DO TONÃ, TUCANO BASIN (BAHIA). Located in northeast of Bahia, serra do Tonã is a NS elongated plateau that standsout in the flattened relief of Tucano Basin. The stratigraphic succession belongs to the Aptian post-rift sequence of this basin. Based on facies analysis, vertical stratigraphic profiles and satelite images interpretation, three stacked stratigraphic units were recognized: (1) lower carbonate unit, composed by laminated limestones and breccias, 5 m thick, correlated with Camadas Batateira of Arripe Basin; (2) intermediate siliciclastic unit, 100m thick and made of sandstones exhibiting finning upward cycles, overlaid by mudstones and sandstones wich sedimentary structures suggest action of tidal currents and (3) upper carbonate unit, composed by laminated limestones, 2-10 m thick, related with Santana Formation, that record lacustrine environment with possible marine influence. Paleocurrent analysis indicates proviniance from north and paleoflows towards south, similar to the Aptian fluvial facies of Araripe Basin, showing that both basins integrated the same continental paleodrainage

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The thermoluminescence intensity as a function of gamma-ray dose of the 325 degreesC peak, in quartz grains extracted from sea sediments and from fluvial aeolic dunes, is studied. It is found that the response curve at low doses has a concavity directed opposite to that of quartz grains extracted from archaeological potteries. To explain this behavior a model is proposed here based on oxygen vacancies and [AlO4/h](0) centers. The experimentally observed ESR intensity of E-I'-centers as a function of radiation dose can also be explained by this model.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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This scientific research aimed at to analyse the susceptibility to debris flow of the watershed of Ribeirão do Roque (SP), focusing on the upstream areas of OSBRA pipeline. This is because, mass flow can cause damage to pipes, mainly due to conditioning hydro erosion of the land in the drainage crossings, including the undermining the banks of streams. Firstly, It was conducted a literature review, aiming to identify and understand the principal characteristics and conditions of debris flow. Secondly, the physical and anthropic factors and their respective weights of influence were selected and used to determine the mass flow susceptibility. It was selected the following physical factors: type and thickness of rocks, soil and unconsolidated materials; textural density; amplitude relief; relief slope; shaped valley; and shape of slopes. Such factors are present in the physiographic subdivision map of the study area. In addition, the anthropic attributes correspond to the classes contained in the land use map. Therefore, the physical and anthropic factors were integrated through the multi-criteria analysis in a GIS environment, generating a total susceptibility map of debris flow on the scale 1:50,000. The results showed that a significative part of the study area was classified as average susceptibility. However, it was identified areas with high susceptibility in the region in which the pipe cross the Ribeirão do Roque. Moreover, at which point the river presents a closed valley and a meander shape, without a fluvial plain that would be useful to attenuate the development of the process. Consequently, if a mass flow begins in any of these most susceptible regions located upstream of the pipe, the chances that the process develops by the river and causes the excavations of his bed are quite large. However, the pipelines cross these critical areas directly on the rock (diabase), which provides additional protection against possible ...

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)