Análises isotópica e faciológica aplicadas à caracterização da Formação Barra de Tabatinga - O registro de um pulso transgressivo marinho pleistocênico no litoral oriental do Rio Grande do Norte

Abstract

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 high energy environments of deposition, correlated to intermarine systems, for that were described outcrops, made thin section and grain size 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 processing the information, it was possible to characterize and insert in the regional stratigraphy, the Barra de Tabatinga Formation, deposited during the transgressive Pleistocene pulse, characterized by sandstone with medium to coarse granulometry, and isotopic signature concentrated in the lower Paleoproterzoic (Siderian), different from the units below and above, respectively, Barreiras Group (very heterogeneous granulometry and isotopic signature distributed throughout all Paleoproterozoic) and the Coastal Aeolian Deposits (fine to medium sand granulometry).