2019-09-252019-09-252013REIS, Luiza Santos. Sedimentação em áreas de manguezal sujeitas ao regime de Macromaré, Bragança (PA). Orientador: Pedro Walfir Martins e Souza Filho. 2013. 70 f. Trabalho de Curso (Bacharelado em Oceanografia) - Faculdade de Oceanografia, Instituto de Geociências, Universidade Federal do Pará, Belém, 2013. Disponível em: https://bdm.ufpa.br/jspui/handle/prefix/2114. Acesso em:.https://bdm.ufpa.br/jspui/handle/prefix/2114The mangrove ecosystem strongly influences the hydrodynamics, geomorphology and sedimentology of tidal flat environments. These environments are located in coastal areas of flat topography, may have alternating sequences of sand and mud, deposits formed by lateral migration of tidal channels and wide that ranging mainly due to tidal amplitudes, higher in regions subject to the macrotidal regime (greater than 4 m). And the benthic, detritus organisms and vegetation play an important role in tidal flat environment, being responsible for the degradation of organic matter and sediment trapping, respectively. It is in this context that is embedded the study area, located in the Bragança Coastal Plain featuring a progradation muddy plain with 25 km long, vegetated by mangrove and developed over the last 2,000 years. This study aims to investigate the pattern of sedimentation, through recognition of the grain size, quantification of organic matter and estimate rates of sediment accumulation. To this end, four cores were collected manually, using PVC tubing which were introduced vertically into the substrate, with up to approximately 60 cm depth. In addition, samples were taken using vertical trays acrylic been used for radiographic X-rays. Later, the cores were transversely sliced and divided into intervals of 1 and 2 cm for holding the sieve analysis, calculation of sedimentation rates and elimination of organic matter. The four cores (FDT-1, FG-1, FDO-2 and FDE-1), in general, showed significant levels of sandy sediments at the base (20%) and an increase in finer fraction (<0.062 mm) toward the top (>80%), being predominantly silt-clay, showing a decrease in energy from the environment, which may have been promoted by the migration of the channels or the colonization of mangrove vegetation. The FDT-1 located in the vegetated (Avicennia forest) presented from top to bottom the lower organic matter content (OM) (<5%), which is due to the action of roots and benthic organisms that facilitate the entry of oxygen into the sediment and consequently the oxidation of sedimentary organic material. In other cores, the content of OM fluctuated significantly (2-10%) over the same; this trait was due to changes in the proportions of sand, silt and clay, which allowed us to observe a strong relationship between the muddy sediments and organic material. This significant variation in the content of fine sediments and organic matter strongly affected the 210Pb activity; exhibit unstable profiles and impossible to calculate the sedimentation rates, with FDT-1 exception which showed a rate equal to 0.59 cm / yr. The excess of this radionuclide in the sediment reflect a large accumulation of modern sediment and a strong relationship between 210Pb activity, fine sediments and organic matter. Thereby, the collected cores demonstrate considerable control of topography, vegetation and marine influence on sedimentation in mangrove. Factors such as microbial activity, bioturbation, detritivore fauna abundance, flood frequency, plant species composition, grain-size and rate of accumulation of sediments, acting on the organic material and depending on the nature of the mechanism, favors the transport, decomposition or preservation this material onto the muddy substrate. The difficulty in estimating the rate of accumulation in this study, makes necessary to use an alternative technique such as use of radionuclide Cs-137, which is applied to areas with high rates of accumulation, such as Bragança Coastal Plain.Acesso AbertoSedimentologiaManguezalTaxa de sedimentaçãoNordeste ParaenseCNPQ::CIENCIAS EXATAS E DA TERRA::OCEANOGRAFIATrabalho de Curso - Graduação - Monografia