The tectonic evolution of the Transbrasiliano Lineament in northern Parana Basin, Brazil, as inferred from aeromagnetic data

Data from six airborne magnetic surveys were compiled and analyzed to develop a structural interpretation for the Transbrasiliano Lineament in northern Parana Basin, Brazil. Magnetic lineaments, interpreted to reflect geologic contacts and structures at different depths, were illuminated using the matched-filter technique applied to aeromagnetic anomalies. Field-based structural measurements generally support our magnetic analysis. We estimated three primary magnetic zones: (i) a zone of deep magnetic sources at 20 km depth, (ii) an intermediate basement zone at 6 km depth, and (iii) a shallow zone of near-surface geological features at 1.5 km depth. The deepest zone exhibits three major NE trending crustal discontinuities related to the Transbrasiliano Lineament, dividing the region into four geotectonic blocks. Anomalies associated with the intermediate zone indicate directional divergence of subsidiary structures away from the main Transbrasiliano Fault, which strikes N30 degrees E. The shallow magnetic zone includes near-surface post-Brasiliano orogenic granites. Our analysis identified NE trending sigmoidal lineaments around these intrusions, indicating intense zones of deformation associated with probable shear structures. At the shallow depth zone, magnetic anomalies caused by Cretaceous alkaline intrusive bodies and basalts of the Serra Geral Formation are enhanced by the matched-filter method. These igneous bodies are related to extensional NW striking lineaments and seismicity aligned along these lineaments suggests that they currently are reactivated. Prior to flexural subsidence of the Parana Basin, reactivation processes along transcurrent elements of the Transbrasiliano Lineament promoted extensional processes and formed initial Parana Basin depocenters. Cretaceous and more recent sedimentation also correlate with reactivations of NE striking structures.