255 resultados para Geomorphological facies
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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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Mining activities are directly related to changes in natural landscapes. With the objective of analyzing the changes imposed by the geomorphological dynamics of human action in areas of mining clay, two fragments were selected from the basin of Ribeirão Santa Gertrudes / SP, representing denudational and sedimentation processes respectively. This area is within the context of the Ceramic Pole Santa Gertrudes / SP, which besides its importance as a supplier of raw material, is characterized as the largest center of international reference in ceramic tiles on the American continent. Data was collected and analyzed from the perspective of anthropogenic geomorphology supported by general systems theory and uses techniques from evolutionary geomorphological mapping. Thus, geomorphological mapping were produced concerning three scenarios, which date from 1962, 1988 and 2006 in a scale of 1:10.000. These surveys allowed us to infer a detailed investigation of the evolution of changes in topography and hydrology, geomorphology representative of the original (1962), which has characteristics of an earlier phase of earlier existing large mining pits, and its evolution to a anthropogenic geomorphological stage, represented by active disruption scenarios dating from 1988 and 2006. The last two scenarios have analyzed changes in the dimensions of relief features when compared with the original scenario representative of geomorphology, as well as an intense reallocation of surface and subsurface materials, in which human action is highlighted by becoming responsible for sculpting the landscape through the imposition of control mechanisms to natural processes.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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This paper presents an evaluation of the geomorphological implications of urban runoff on the evolution of linear erosion processes in peri-urban areas. The Tucunzinho watershed (São Pedro/SP) case was chosen because it presents linear erosive forms in which the dynamic is associated with urban expansion into fragile areas and implantation of inadequate dissipation devices. The method proposed by the Soil Conservation Service (SCS) was adopted to obtain the Curve Number (CN) and runoff hydrographs of different sectors of the basin. The coverage classification (use and occupancy) was based on analysis of aerial photographs of two periods (1962 and 2006, updated in the field in 2011). The IPHS1 model was used for the simulation and analysis of the hydrological behavior for both the pre-urban occupation and the current occupation. The hydrogeomorphological analysis helped understand the influence of the urban run-off on the erosion dynamics, clearly showing the ineffectiveness of dissipation energy devices in the area, which has a natural susceptibility to erosion due to litho-soil characteristics.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Agronomia (Produção Vegetal) - FCAV
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Pós-graduação em Geografia - FCT
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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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Located in northeastern Brazil, the evolution of Araripe Basin has been associated with the fragmentation of Gondwana and opening of the South Atlantic. The Santana Formation belongs to the post-rift sequence of the basin and is characterized by the presence of laminated limestones in the lower portion (Mb. Crato), evaporite (Ipubi) and siliciclastics (Mb. Romualdo). For better understanding of the Romualdo's stratigraphy, depositional environments and tract of systems, a stratigraphic analysis was made with representative columnar sections of the unit. Sedimentary facies have been described in detail, as well as paleocurrents measured at different stratigraphic levels. It was found that the contact of Mb. Romualdo with the carbonate-evaporite section (Mbs. Crato and Ipubi) is a unconformity, evidenced by residual lags and thin layers of conglomerates above the contact. Above the conglomeratic levels predominate fine sandstones / medium interlayered with calciferous green shales. The percentage of shales increases towards the top, featuring retrogradational stacking culminating in layers of coquinas, excellent stratigraphic mark in the basin. Thin layers of coquins of gastropods comprising equinoids, located on the shale section, present in three sections marine deposits are associated with surfaces ravine. The upper section is characterized by recurrent facies of green shales, sandstones intercalated with sandstones progressively become more frequent towards the top of the unit, featuring the regressive part of the cycle. The sandstones present cross-stratification, often with mud clasts and clay layers in the foresets, and beddings of flaser type and wavy in heterolitic facies, suggesting the action of tidal currents. Paleocurrents measured in the sandstones show gaps with opposite flow directions outlining bipolar standards, which reinforce the interpretation of shallow marine environment influenced by tides during the sedimentation...
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The towns of Castro Alves and Rafael Jambeiro, central-east of Bahia state, are located in the east of São Francisco Craton, in granulite terrains of Salvador-Curaçá Belt, formed in Paleoproterozoic. The region of study contains ortognaisses of Caraíba Complex, metamafic and metaultramafic rocks of São José do Jacuípe Suite, metasedimentary rocks of Tanque Novo-Ipirá Complex, granitoids, pegmatites and alkaline rocks. The study carried out regional and detailed geological mapping in addition to petrographical and geochemical characterization of six areas in the search for targets of feldspar and white diopside, minerals used in ceramic industry. The areas consist of granitic ortognaisses interspersed with lenses of mafic granulite rocks, calc-silicate rock, banded iron formations, paragnaisses, quartzites, and bodies of quartz-feldspar or feldspar pegmatites and alkaline rocks that fill discontinuities. The region of study contains four deformations phases, with a predominance of ductile structures. The foliation Sn has N30E to N70W direction, high angle of dip and is characterized by compositional banding of granoblastic and felsic bands interspersed with nematoblastic or lepidoblastic mafic bands. A mineral or stretching lineation Ln is associated with Sn and has trend of S55E to S72E. The rocks have been suffered a regional metamorphism with granulite facies peak and partial retrogression to greenschist facies. Geochemical studies indicate that the green coloring calc-silicate rocks have lower SiO2, MgO and higher Fe2O3 content compared with white calcssilicate rocks. The alkaline rocks of the studied area have higher Na2O, SiO2 and lower K2O, Fe2O3 content compared with others Paleoproterozoic alkaline rocks of Bahia state. The targets of diopside are associated with white calc-silicate rocks, while the targets of feldspar are associated with paragnaisses, pegmatites and alkaline rocks
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The Areado Group of the Sanfranciscana Basin is a Lower Cretaceous continental sedimentary system that is correlated to the Brazilian Pre-Salt beds. The Aerado Group is composed of Abaeté, Quiricó and Três Barras formations. Paleocurrent data for the Areado Group were previously presented, although not systematically which prevented significative interpretations on the basin paleogeography. This work attempts to systematically evaluate paleocurrent data, aiming to recognize depositional environment and paleogeographic reconstruction, based on the sedimentary facies and paleocurrents measurements along vertical profiles. Fluvial paleocurrents of the Abaeté Formation indicate paleoflows towards NW whereas aeolian palecurrents of the Três Barras Formation show paleowinds towards SW. The depositional systems interpreted for the Areado Group were: braided river, alluvial fan, lacustrine, playa lake, fluvial-deltaic and aeolian. The combined analyses of facies and paleocurrents allowed a reliable paleogeographic reconstruction of the basin, with paleodip towards northwest, paleowinds towards south-southwest and source-area located at southeast. These results indicate that paleowinds were orthogonal to paleostream, but parallel to depositional strike of the basin. The interpreted depositional systems characterize a desert environment during the Abaeté sub-basin times. The association of dunes and wet interdunes followed by large scale dunes and dry interdunes suggests a decrease in humidity towards the top of the Três Barras Formation, with a dry aeolian system onlapping the basement. The observed decrease of humidity in Sanfranciscana Basin may reflect local or regional paleoclimatic changes during the opening of the South Atlantic, but this assumption is only tentative