967 resultados para sedimentary rocks


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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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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Temporal, spatial and diel variation in the distribution and abundance of organisms is an inherent property of ecological systems. The present study describes these variations and the composition of decapod larvae from the surface waters of St Paul`s Rocks. The expeditions to the archipelago were carried out in April, August and November 2003, March 2004 and May 2005. Surface plankton samples were collected during the morning and dusk periods, inside the inlet and in increasing distances around the archipelago (similar to 150, 700 and 1500 m). The identification resulted in 51 taxa. Seven species, six genera and larvae of the families Pandalidae and Portunidae were identified for the first time in the area. The mean larval density varied from zero to 150.2 +/- 69.6 individuals 100 m(-3) in the waters surrounding the archipelago and from 1.7 +/- 3.0 to 12,827 +/- 15,073 individuals 100 m(-3) inside the inlet. Significant differences on larval density were verified between months and period of the day, but not among the three sites around the archipelago. Cluster and non-metric multidimensional scaling analysis indicated that the decapod larvae community was divided into benthic and pelagic assemblages. Indicator species analysis (ISA) showed that six Brachyura taxa were good indicators for the inlet, while three sergestids were the main species from the waters around the archipelago. These results suggest that St Paul`s Rocks can be divided into two habitats, based on larval composition, density and diversity values: the inlet and the waters surrounding the archipelago.

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Mangrove structure and distribution is conditioned by geomorphic processes. This paper describes the response of mangroves to sedimentary processes at the Cananeia-Iguape Coastal System on the south coast of Sao Paulo State (Brazil), between latitudes 24 degrees 40`S and 25 degrees 20`S. Within six study areas 41 plots were established along 14 transects. Plot size varied according to stem density from 2mx2m to 20mx20m. Here mangroves are strongly coupled to sedimentary processes, forming discrete architectural elements within particular depositional environments or topographic settings. These sedimentary structures and progradation environments are colonized by Laguncularia racemosa, associated with the smooth cordgrass Spartina alterniflora. Rhizophora mangle occurs typically near creeklets where tidal flooding is more frequent. Where tidal influence is restricted Avicennia schaueriana becomes dominant. Erosive margins are dominated by A. schaueriana or R. mangle. Single linkage cluster analysis yields three groups (A, B and C), with high levels of similarity, providing support to the classification of the data into two broad landform categories: depositional and erosive. Group A includes plots with the least structural development (nominal stem diameter d(n) between 1.05 and 4.61cm). Group B is composed of stems of intermediate diameter (4.99 cm <= d(n) <= 5.63cm). Group C plots have the largest structural development (5.50 cm <= d(n) <= 11.10cm). The structure of mangroves (dominance and structural development) reflects responses to geomorphology and habitat change.

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This paper reports the reconstruction of the contamination history of a large South American industrial coastal area (Santos Estuary, Brazil) using linear alkylbenzenes (LABs). Three sediment cores were dated by (137)Cs Concentrations in surficial layers were comparable to the midrange concentrations reported for coastal sediments worldwide LAB concentrations increased towards the surface. indicating increased waste discharges into the estuary in recent decades. The highest concentration values occurred in the early 1970s, a time of intense industrial activity and marked population growth. The decreased LAB concentration, in the late 1970s was assumed to be the result of the world oil crisis Treatment of industrial effluents, which began in 1984, was represented by decreased LAB levels Microbial degradation of LABs may be more intense in the industrial area sediments. The results show that industrial and domestic waste discharges are a historical problem in the area. (C) 2010 Elsevier Ltd. All rights reserved.