Isotopic and faciological analysis applied to the characterization of the Barra de Tabatinga Formation - the record of a pleistocene marine transgressive pulse on the eastern coast of Rio Grande do Norte
Transgressive pulse; Pleistocene; Sedimentological analysis; Isotopic analysis; Barra de Tabatinga Formation
This paper represents the integration and interpretation of past data, field geology, with subsequent laboratory analysis, carried out in the coastal region, eastern coast of Rio Grande do Norte, between Baía Formosa and Natal, regarding the stratigraphic record of a marine level pleistocene. The relative variation of the shoreline and its morphological features are directly associated tectonic and paleoclimatic interferences. These variations model the locally acting depositional systems, stacking lithostatigraphic units with single signatures, with respect to lithotype, sedimentary structures, diagenesis, depositional age and crystallization age of the source rock. During the bibliographic survey, we sought to consolidate a transgressive pulse, where it was observed that for the region, the most applied dating, occurred by thermoluminescence (TL), in 210,000 ± 10,000 years, correlated to the peak of the antepenultimate marine transgression of the Brazilian coast. Sedimentological and granulometric evaluations indicate low energy environments of deposition, correlated to intermarine systems, for that were described outcrops, made thin section and granulometer analysis. Sm-Nd isotopic analyzes, including sediments adjacent to the shoreline, were performed objectifying the characterization of isotopic signatures and identification of their probable source areas. The association of relative sea level variations, sedimentological characterization and sediment source, play a fundamental role in the analysis of siliciclastic sedimentary successions, thus allowing the reconstruction of tectonic, stratigraphic and geographic parameters. After the information processing, it was possible to characterize and insert in the regional stratigraphy, Barra de Tabatinga Formation, deposited during a transgressive pleistocene pulse, thus, of genesis different from the above and below units, respectively Barreiras Group and Coastal Eolic Deposits.