25 resultados para Mountain ranges


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The fission-track method (FTM) in apatite was applied to 45 samples collected in the Serra da Mantiqueira (Mantiqueira mountain range), the Serra do Mar (Mar mountain range), regions next to these mountain ranges and the coastal region between Ubatuba and Santos in the State of São Paulo, Brazil, to study the thermochronology of the South American Platform in southeast Brazil and its influence on Santos and Campos basins. The data presented in this work complement the previously presented data on the same region (Tello Saenz et al., 2003. J. S. Am. Earth Sci. 15, 765-774) with 31 new samples analyzed. The weighted mean of the corrected ages from high Mantiqueira (around 1000 m), (121 +/- 6) Ma, coincides with the South Atlantic opening. The fact that its thermal history starts at a relatively low temperature (similar to 80 degrees C) suggests that the age of similar to 120 Ma would be the formation age of Serra da Mantiqueira due to a rapid pulse, in which tracks had no time to be retained at the closure temperature, that is similar to 120 degrees C. The Serra do Mar presents a more complicated thermal history, with several reactivations indicated by the changes in the slope of its cooling curve. The thermal histories obtained in the regions next to these mountain ranges are compatible with the results mentioned above. The Santos Basin has unconformities that agree with changes in the slope thermal histories of the studied region. (c) 2005 Elsevier Ltd. All rights reserved.

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The description of patterns of variation in any character system within well-defined species is fundamental for understanding lineage diversification and the identification of geographic units that represent opportunities for sustained evolutionary divergence. In this paper, we analyze intraspecific variation in cranial shape in the Pumpkin Toadlet, Brachycephalus ephippium-a miniaturized species composed of isolated populations on the slopes of the mountain ranges of southeastern Brazil. Shape variables were derived using geometric-statistical methods that describe shape change as localized deformations in a spatial framework defined by anatomical landmarks in the cranium of B. ephippium. By statistically weighting differences between landmarks that are not close together (changes at larger geometric scale), cranial variation among geographic samples of B. ephippium appears continuous with no obvious gaps. This pattern of variation is caused by a confounding effect between within-sample allometry and among-sample shape differences. In contrast, by statistically weighting differences between landmarks that are at close spacing (changes at smaller geometric scale), differences in shape within- and among-sample variation are not confounded, and a marked geographic differentiation among population samples of B. ephippium emerges. The observed pattern of geographic differentiation in cranial shape apparently cannot be explained as isolation-by-distance. This study provides the first evidence that the detection of morphological variation or lack thereof, that is, morphological conservatism, may be conditional on the scale of measurement of variation in shape within the methodological formalism of geometric morphometrics.

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The morphological and anatomical leaf and scape differentiation of Leiothrix crassifolia is analysed and classified into seven types (I, II, III, IV, V, VI, Vn). The species has a relatively wide distribution in the campo rupestre of Minas Gerais in Brazil. Variation in the isolated populations on different mountain ranges is complex, does not follow a clear geographical pattern, and defies taxonomic classification. L. nubigena and L. obtusifolia are included in L. crassifolia.

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Seventy-seven rabies virus (RV) isolates originating from Brazilian cattle were genetically characterized. Partial nucleoprotein gene sequences of these isolates were phylogenetically and geographically analyzed. Cattle isolates, which clustered with the vampire bat-related RV group, were further subdivided into nine genetic subgroups. These subgroups were distributed widely in lowland regions, with some subgroups separated from each other by mountain ranges. In addition, separation of the groups in mountainous regions was correlated with altitude. These results indicate that cattle rabies is derived from several regionally-defined variants, which suggests that its geographical distribution is related to that of the vampire bat population.

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The different tectonic stages that occurred at the end of the Proterozoic and during the Phanerozoic have an important bearing on the tectonothermal history of the South American Platform and its consolidation. Geochronological data (U/Pb monazite, Ar-40/Ar-39 whole rock) and apatite fission-track analysis, from Precambrian rocks of the southeastern Brazilian coastline, permit the modeling of a long-term thermal history of the crust and constrain variable denudation rates.Using these data, a temperature-time diagram reflects a period of accelerated exhumation during the end of the Brasiliano Orogeny, followed by long stability and reactivation of the platform during the Rifting Phase of the South Atlantic Ocean.U/Pb zircon and monazite (blocking temperature of ca. 650degreesC) data from a series of igneous bodies suggest that a tangential and transpressional tectonic regime occurred between 625 and 610 Ma. During the following escape tectonics, between 610 and 590 Ma the exhumation process indicates cooling rates of ca. 12degreesC/Ma. Ar-40/Ar-39 biotite ages between 540 and 510 Ma (ca. 300degreesC) and a corrected fission-track age on apatites (100degreesC) of 480 Ma indicate an exhumation event related to block tectonics with huge vertical displacement along shear zones.A long stabilization phase, with low exhumation, and cooling rate around 0.25degreesC/Ma was recorded from the Cambro/Ordovician to the Mesozoic. At 65 Ma an acceleration of the exhumation through denudation and reworking of the South American surface with cooling rate of 1.5degreesC/Ma is observed.The uplift of the Mantiqueira and Serra do Mar mountain ranges along the southeast Brazilian coastline works as a climatic barrier provoking lateral erosional processes causing long-term scarp retreat, combined with intense, but progressive denudation towards the continent. A denudation of 2.5 to 4 km was calculated for such processes. This lateral retreat of escarpments and flexural response can provide important insights regarding marginal isostatic uplift and the evolution of offshore sedimentary basins of southeast Brazil.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Background: Vampire bats are important rabies virus vectors, causing critical problems in both the livestock industry and public health sector in Latin America. In order to assess the epidemiological characteristics of vampire bat-transmitted rabies, the authors conducted phylogenetic and geographical analyses using sequence data of a large number of cattle rabies isolates collected from a wide geographical area in Brazil.Methods: Partial nucleoprotein genes of rabies viruses isolated from 666 cattle and 18 vampire bats between 1987 and 2006 were sequenced and used for phylogenetic analysis. The genetic variants were plotted on topographical maps of Brazil.Results: In this study, 593 samples consisting of 24 genetic variants were analyzed. Regional localization of variants was observed, with the distribution of several variants found to be delimited by mountain ranges which served as geographic boundaries. The geographical distributions of vampire-bat and cattle isolates that were classified as the identical phylogenetic group were found to overlap with high certainty. Most of the samples analyzed in this study were isolated from adjacent areas linked by rivers.Conclusion: This study revealed the existence of several dozen regional variants associated with vampire bats in Brazil, with the distribution patterns of these variants found to be affected by mountain ranges and rivers. These results suggest that epidemiological characteristics of vampire bat-related rabies appear to be associated with the topographical and geographical characteristics of areas where cattle are maintained, and the factors affecting vampire bat ecology.

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This paper presents the gravity survey refinement of the Paraíba do Sul river valley, east region of São Paulo state, by acquisition of 646 gravity stations. Further than the traditional Free-Air and Bouguer corrections, it was necessary to apply the Terrain Correction due the proximity of the Mantiqueira and Mar mountain ranges. An enhanced understanding of Taubaté Basin structural framework was the main objetive of this work. As result, we present the Bouguer Gravity Map of the east region of São Paulo State and the Residual Bouguer Gravity Map generated by Upward Continuation and High-pass filtering. The 2D Gravity Modeling was applied in 4 sections, using bi-dimensional models for the bodies that produced the anomalies (Talwani Method). After integrating the gravity data with the interpretation of 11 seismic sections, it was possible to delineate the Taubate Basin structural framework, which shows an utmost sedimentary thickness of 800 m in the depocenters. It was also interpreted an ultramaphic alkaline plug in the subsurface of Caçapava city.

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The city of Lima has undergone serious changes over the past sixty years. Until the middle of the last century, Lima retained an urban structure similar to that built in the 18th century, during the final decades of its colonial period. This reality began to change with the abrupt onset of migration from the mountain ranges to the coast in 1946. However, rather than changes in its urban plan, Lima underwent a ethnic and social reconfiguration that would bring new color and new cultural and behavioral norms to the Peruvian capital. The arrival of migrants to the city caused a conservative reaction in the local elites, but it also sparked a need for the intelligentsia to develop new ways of thinking about the place of migrants in the space of the city, and on the other hand, to create new representations of the city itself. From being a city isolated from the rest of the country, Lima came to live with a range of cultural and ethnic references. It did so, however, without creating greater opportunities for the integration of the masses within the urban and social logic of the city, thus making clear the separation between the aristocracy and the general populace.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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

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A fauna de Ephemeroptera, Plecoptera e Trichoptera associadas ao folhiço em um riacho do sudeste do Brasil foi estudada com o objetivo de responder às seguintes questões: 1) A riqueza e a composição faunística de EPT difere entre os dois mesohabitats (corredeira-remanso) mesmo quando associadas ao mesmo substrato, folhiço? 2) A similaridade da fauna de EPT entre os dois mesohabitas muda temporalmente? 3) A estrutura funcional de EPT difere entre os dois mesohabitats (corredeira-remanso)? Para responder essas questões, coletas mensais, de novembro de 1999 a junho de 2000, foram feitas no Ribeirão Bocaina com rede D (10 acúmulos de folhas em remanso e 10 em corredeira). A fauna de EPT do Ribeirão Bocaina foi mais diversificada e mais abundante no folhiço em corredeira do que no folhiço em remanso, no entanto, quando a riqueza foi padronizada para o mesmo número de indivíduos essa se tornou similar para as duas condições. A fauna de EPT foi bastante diferente entre os dois mesohabitats, tanto em termos da composição faunística quanto em termos funcionais. Isso provavelmente ocorreu devido às diferenças de velocidade da água, no tempo de residência do folhiço e na taxa de oxigênio da água entre os dois mesohabitats.

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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)