Rate of sedimentary in the coastal systems and on the souther continental plataform of the state of São Paulo, Brazil
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2000
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INTERNATIONAL GEOLOGICAL CONGRESS, 31st
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Resumo
Analyses of the concentrations of the natural radionuclideos 210Pb and 226 Ra,
scattered in the environment in vestigial amounts in witnesses of the coastal and
occeanic areas provide a historical record of events and make it possible to
estimate the background and variations in the volume of sediments laid down
extensive periods of time. The results of the analyses of the rates of sedimentation
obtained in the coastal systems (Cananeia-Igaupe system) and the souther
continental platform of the state of São Paulo, by means of the calculation of the
210Pb and 226Ra by gama spectrometry, are presented in this study.A detector of
hyperpure Germanium with a low level of bottom radiation and a study of the
phototype of these radionuclideos was used for the analysis of these same
radionuclideos in the marine sediments. The analysis of the 210Pb was undertaken
by means of the gama emission of 47Kev and that of 226Ra by the gama emission
of the Bi (609 Kev). Additionally a sedimentation rate was calculated for purposes
of comparison on the basis of the levels of 137 Cs present in the witnesses, the
biennium 1963/1964 being taken as the maximum pcak of atmospheric emission
by nuclear explosions as from witch time on the atmospheric emission of this
radionuclid diminishes and its rate of deposition on the earth’s crust is considered
constant. The rates of sedimentation obtained for the coastal system show
agreement of the values obtained for 210Pb (5.33mm/yr) with those obtained
through the dating method for 137Cs (5.46mm/yr). The sedimentation rates
obtained for the continental platform correspond to values some five times inferior
to those obtained in the coastal systems.
Como referenciar
TESSLER, M.G.; CUNHA, I.I.L.; SAITO, R.T.; FIGUEIRA, R.C. Rate of sedimentary in the coastal systems and on the souther continental plataform of the state of São Paulo, Brazil. In: INTERNATIONAL GEOLOGICAL CONGRESS, 31st, August 6-17, 2000, Rio de Janeiro, RJ. Abstract... Disponível em: http://repositorio.ipen.br/handle/123456789/25240. Acesso em: 30 Dec 2025.
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