CONTRIBUIÇÃO À CRONOESTRATIGRAFIA DAS FORMAÇÕES CABOCLO, BEBEDOURO E SALITRE NA CHAPADA DIAMANTINA (BA) PELOS MÉTODOS Rb-Sr E K-Ar

M. H. F. MACEDO, M. G. BONHOMME

Resumo


The Rb-Sr and K-Ar dates obtained on whole-rock and fine fractions of the Caboclo, Bebedouro and Salitre Formatíons allowed the establishment of a chronostratigraphy for the sedimentary cover of the São Francisco Craton in the Northeast region of Brazil. For the Caboclo Formation, one compilation of the data shows that the formation suffered a late diagenetíc event at 958 ± 38 Ma. The Bebedouro Formation is represented by an isotopic diagram of difficult interpretation. As the Rb-Sr and K-Ar dates are in agreement, an age between 930 to 900 Ma can be regarded as the age or late diagenesis. The Salitre Formation is a carbonate layer. Cationic resins have been used to dissolve the carbonate fraction, which is necessary in order to extract the clay fraction of such a rock. An age of 767 ± 18 Ma. was obtained and it was attributed to an early diagenesis. The dates define à chronology which is in conformity with the stratigraphic succession.

Texto completo:

PDF

Apontamentos

  • Não há apontamentos.