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| Detailed Reference Information |
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Misi, A. and Veizer, J. (1998). Neoproterozoic carbonate sequences of the Una Group, Irece Basin, Brazil: chemostratigraphy, age and correlations. Precambrian Research 89(1-2): 87-100. doi: 10.1016/S0301-9268(97)00073-9. |
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The Una Group, Irec (e) over cap Basin (Bahia state) is correlative with the better known Bambui Group of the S (a) over tilde o Francisco Basin (Minas Gerais state); these basins are remnants of widespread carbonate platform that covers > 300000 km(2) of the S (a) over tilde o Francisco Craton in Brazil. The Irec (e) over cap 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 Sr-87/Sr-86 ratios ranging between 0.70745 and 0.71776, and delta(13)C values ranging between -4.4 and +9.4 parts per thousand PDB. The carbonates also contain beds and nodules of barite and gypsum with highly positive delta(34)S values (+25.2 to +32.8 parts per thousand CDT). The 'best preserved' carbonate samples selected on the basis of their Mn and Sr concentrations as well as their ratios, yield Sr-87/Sr-86 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 S (a) over tilde o Francisco Basin. (C) 1998 Elsevier Science B.V. |
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Keywords
brazil, chemostratigraphy, correlations, isotope stratigraphy, neoproterozoic, upper proterozoic successions, isotopic variations, precambrian carbonates, east greenland, bambui group, stratigraphy, geochemistry, diagenesis, seawater, sulfur |
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Publisher
Elsevier Science
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The Netherlands
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