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Navegando DEGEO - Artigos publicados em periódicos por Autor "Albertão, Gilberto Athayde"
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Item The Cretaceous-Tertiary boundary in the context of impact geology and sedimentary record : an analytical review of 10 years of research in Brazil.(2000) Martins Júnior, Paulo Pereira; Albertão, Gilberto Athayde; Hadad, Renato MoreiraThe question of the Cretaceous-Tertiary (K-T) boundary is here considered in a more wide sense, considering its importance for Impact Geology. The first two sub-principles of uniformitarianism can be seen as similar to the actualist principle and can be both merged with catastrophism as a renewed view of geosciences [as two principles in dialectical opposition for working with regime x rupture processes in Earth Sciences]. Examples from Brazilian basins, especially Pernambuco-Paraiba (PE-PB) basin, are considered with their face value for the study of the K-T boundary. Most of their characteristics also give support to Impact Geology Theory. It is also considered the importance of the initial works on the Brazilian K-T sedimentary boundaries (in a Impact Geology context), which begun 10 years ago giving support to present time trends of researches. At present with the actual state of knowledge in Geosciences it is no longer possible to consider the Earth System as a closed one (Albertão 1991). It is obvious that Earth is an open system subjected to any sort of interactions with other corpses and fields within the Cosmos as many geological and biological evidences indicate everywhere.Item The K-T boundary in Brazilian marginal sedimentary basins and related spherules.(2004) Albertão, Gilberto Athayde; Grassi, Alexandre de Azevedo; Marini, François; Martins, Paulo Pereira; Martins Júnior, Paulo Pereira; Ros, Luiz Fernando deDuring the last 10 years some important results have been reached after extensive research performed on some Brazilian basins relating to the Cretaceous-Tertiary Boundary (KTB) matter. This paper presents some of these results mainly focused on the spherule content of the sediments. The preliminary analysis carried out without strong constraints have not revealed any distinguishing and typical characteristics known for the KTB. These geochemical analysis were performed on ditch samples, from subsurface data, submitted to statistical tests such as factor and discriminant analysis. The result of the factor analysis indicated general trends in the concentration of chemical elements while the discriminant analysis showed a very clear discontinuity of the chemical data between the Cretaceous and Tertiary periods. The first occurrence of spherules was found in sediments from the KTB of Pernambuco-Paraíba Basin (PE-PB). Despite other impact-derived characteristics present in this sedimentary section these spherules do not show any direct evidence of an impact origin. On the other hand, the study of microspherules recovered from a drilling core of Campos Basin has probably revealed the first documented occurrence of tektites in South America.