Um novo método de avaliação da correspondência entre lineamentos de superfície e subsuperfície: estudo de caso na bacia potiguar, nordeste do brasil

Abstract

Studies that assess the correspondence between deep structures and their possible expression on the surface visually compare magnetic and relief linear features, overlapping them on thematic maps or evaluating the spatial variability of each one separatelyusing density maps. This work proposes a new method for assessing lineaments, focusingon the quantitative and qualitative expressionof linear features regarding the correspondencebetween surface and subsurface. A region in the northern part of the Borborema Province, Northeastern Brazil, was selected as a test area, including Precambrian basement lands, Mesozoic-Cenozoic portions of the Potiguar Basin, and Cenozoic sedimentary deposits. Magnetic and relief linear featureswere extracted semiautomatically from aeromagnetic data and the SRTM mission, respectively. The operations in a GIS environment made possible to define the convergent lineamentsin the two plans, involving: generation of buffers; the intersection between buffer polygons; segmentation ofpolygons with the same orientation in surface and subsurface; and clipping ofthe original linear featuresaccording to the polygons with the same direction in both planes. Kernel density maps were generated to assess the spatial variability of agreement between the lineaments, integrating the information contained in each plan. There was a strong NE-SW conditioning of the structures, either for sectors with a greater or lesser density of lineaments. Sectors whose linear featureshave a different direction are also grouped in sectors oriented to NE-SW, showing the strong influence of this trend in the structuring of the area. The regions with the lowest density of lineaments were associated with zones that limit sectors with different rates of deformation, accommodating this movement against the current stress field. Portions with higher linear density were related to sectors more prone to neotectonics, involving possible inversion of relief, such as the Serra do Meldome. The multiple correspondencesanalysisreinforced the importance of the NE-SW trend, whose association between the lineaments was the strongestin the data set, followed by NW-SE, which is a direction associated with transfer faultsand truncated by large NE-SW structures, such as the Carnaubais fault. The E-W direction was associated with the events of the opening and expansion of the Atlantic Ocean and is also expressed truncated by NE-SW structures. The N-S trend was unimpressive. A visual correspondencewas noticed between the data from the hydrocarbon producing wells and the areas located at the edges of the sectors with the highest density of concordant lineaments. However, this evaluation requiresmore robust observations, as an aid to a possible replication of the method in other areas with oil exploration.It is proposed to survey additional geophysical and field data to test the correspondences obtained in the present work between portions with a greater or lesser density of concordant lineaments, in addition to the elaboration of a tool that unifies all the processes involved in the method, helping its dissemination and replication in thefield of Geosciences.