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metadata.dc.type: | Artigo de Periódico |
Title: | Neoproterozoic carbonate sequences of the Una Group, Irecê Basin, Brazil: chemostratigraphy, age and correlations |
Other Titles: | Precambrian Research |
Authors: | Misi, Aroldo Veizer, Ján |
metadata.dc.creator: | Misi, Aroldo Veizer, Ján |
Abstract: | The Una Group, Irecê Basin (Bahia state) is correlative with the better known Bambuí Group of the São Francisco Basin (Minas Gerais state); these basins are remnants of widespread carbonate platform that covers > 300 000 km2 of the São Francisco Craton in Brazil. The Irecê area contains a well-controlled stratigraphic succession hosting economic phosphate deposits and sulfide mineralization. Una Group strata comprise a basal siliciclastic sequence, mostly composed of glacial diamictites (Bebedouro Formation), followed by a carbonate succession that is several hundred meters thick, the Salitre Formation. An angular unconformity separates the two units. The carbonates of the Salitre Formation are characterized by 87Sr/86Sr ratios ranging between 0.70745 and 0.71776, and δ13C values ranging between −4.4 and +9.4‰ PDB. The carbonates also contain beds and nodules of barite and gypsum with highly positive δ34S values (+25.2 to +32.8‰ CDT). The ‘best preserved’ carbonate samples selected on the basis of their Mn and Sr concentrations as well as their ratios, yield 87Sr/86Sr values of 0.70745–0.70765. Comparison of these values with the secular strontium isotopic curve for the Neoproterozoic seawater suggests a 600 (to 670) Ma age for the Salitre Formation and for its correlative units in the São Francisco Basin. |
Keywords: | Brazil Chemostratigraphy Correlations Isotope stratigraphy Neoproterozoic |
URI: | http://www.repositorio.ufba.br/ri/handle/ri/8256 |
Issue Date: | 1998 |
Appears in Collections: | Artigo Publicado em Periódico (IGEO) |
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File | Description | Size | Format | |
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Misi.pdf Restricted Access | 2,06 MB | Adobe PDF | View/Open Request a copy |
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