Evaluation of structural controls in the evolution of the São Francisco River delta using geophysical methods

Abstract

The São Francisco River delta is a Quaternary sandy plain built on a structural low of the Sergipe-Alagoas Basin, known as the São Francisco Low. The inner limit of the São Francisco River delta is defined by rectilinear cliffs between the delta plain and the Barreiras Formation, which coincide with important faults of the Sergipe-Alagoas structural basin. Thus, based on a theoretical background that indicates the existence of structural control over the formation and evolution of delta systems in general, it is possible that the Sergipe-Alagoas Basin structure has influenced the delta. This relationship can be inferred using adequate methodology. The present work consists in the use of the seismic geophysical method, integrated with the geological information of the area, having as main objective the evaluation of the existing structural controls on the formation and evolution of the São Francisco delta. The interpretation of a 3D seismic data allowed the individualization of five geological units, as well as the faults that cut them. The seismic data analysis yielded isopach maps of the region in relation to depth. The presence of a set of faults that directly affect the sedimentation in the region was identified through the joint analysis of all generated and pre-existing information. The data analysis and a previous knowledge regarding the geology of this area indicate that the faults observed are related to a tectonic reactivation of the study area.