Relations between Potiguar Rift structural framework and the adjacent basement: analysis of gravity and magnetic data

Abstract

The potential geophysical methods (gravity and magnetic) classically have good responses for the study of tectonic framework of sedimentary basins. In this work, we applied advanced processing techniques for gravity and magnetic data (reduce to pole, matched filter, horizontal gradient and tilt derivative) in order to characterize the geophysical expression of the main structures of the Potiguar Rift and its crystalline basement (NE Brazil). In an attempt to establish the behavior of major crustal blocks of the Borborema Province under the sedimentary package of the Potiguar Basin, eight tectonicgeophysical domains were identified by correlating anomalous patterns of causative sources with geological data available in the literature. Extensive fault systems, which limit the Potiguar Rift, are presented as large positive gravity lineaments. The main shear zones are correlated to expressive elongated anomalies in NE-SW direction and control the boundaries of the crustal blocks of the Borborema Province. The integration of various geophysical maps with the surface geology also allowed to correlate the geophysical expression of these structures and to establish its influence in the rifting processes by which passed the basin, including the NE-SW structural features observed in the regions adjacent to the basin. It was possible to define the presence of these features below the thick sedimentary package, strongly controlling internal architecture of the Potiguar Rift. These results support the hypotheses about the influence of Precambrian structures in the formation of the basin during the rifting in the continental margin of Brazil. Importantly, the inference of NW-SE trending deformation, mostly revealed by magnetic data, contributes to the hypothesis that there has been the spread of E-W tectonic forces that formed the equatorial margin into the continent. Such efforts also influenced the truncation of basement structures, NNW-SSE deformation of the Rio Ceará-Mirim dykes and caused EW lateral drag, which occurs between the Portalegre Shear Zone and the Carnaubais Fault System