International Geologiical Congress - Oslo 2008


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SES-05 Dynamics of complex intracontinental basins


High-resolution isotope stratigraphy: Preliminary data from the Devonian Parana Basin


Egberto Pereira, Rio de Janeiro State University (Brazil)
Maria Suzana Pessoa de Souza, Rio de Janeiro State University (Brazil)
René Rodrigues, Rio de Janeiro State University (Brazil)


Samples of shales / siltstones of the Devonian Parana Basin were investigated for δ 13Corg. The isotope study was based on the analysis of the organic matter content in sedimentary rock sections from the northwest and southeast regions of the Parana Basin. The Parana Basin is an intracratonic basin situated at the southern portion of Brazil, consisting basically of Paleozoic and Mesozoic detritic sedimentary rocks and covered by extensive basaltic flows of Jurassic-Cretaceous age related to the opening of the South Atlantic Ocean. The sections focus on the Pragian - Emsian and Givetian ? Frasnian stage boundaries. The Devonian sediments were deposited on lower shoreface / offshore conditions in an intracratonic ramp basin. During the Pragian and up to the Emsian interval cold water conditions prevailed in the basin. The Devonian sediments reveal a progressive and continuous transgression for this time interval. In reaction to this mechanism the presence of offshore facies are the most frequent in the Pragian up to the Emsian section. During the Givetian interval the climate condition changed and it became warmer during the Frasnian interval. In that period of time (Givetian - Frasnian boundary), the transgression reached its maximum expansion. After that expansion the regression conditions were more frequent in the basin and more regressive facies were preserved. These events are well documented by the δ13Corg and TOC (Total Organic Carbon) excursions, which permit a high-resolution subdivision of the Devonian record.


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