Crustal framework of the northwest Paraná Basin, Brazil: Insights from joint modeling of magnetic and gravity data

Abstract

The Transbrasiliano Lineament (TBL) is a major Proterozoic strike-slip shear zone crossing the Paraná Basin, Brazil, yet the relationship between the TBL and basin structures is poorly understood. Magnetic and gravity data are available from the whole northwestern region of the Paraná Basin and provide insights into crustal partitioning and basement geometry. Joint 2D modeling of these data was performed in three strategic sections of the study area. Two smaller sections were constrained by available borehole data and receiver function analysis. Modeling of these sections facilitated modeling of the third, larger NW-SE section, which crosses the basin in an area with significant lack of data. These three sections together form the basis for a preliminary tectonic model of the northern Paraná Basin. The TBL includes strong N30°E-trending gravity and magnetic gradients represented by the Serra Negra fault zone. This structure separates two crustal tectonic domains, the Paranapanema Block to the east, and the Amazon paleocontinent to the west. The tectonic domain northeast of the fault is represented by the Arenópolis Magmatic Arc. The N60°–70°E-trending General Carneiro fault, also reflected in gravity anomalies, forms another important magnetic contact. Our tectonic model shows a region of crustal thinning between the two fault zones, where structures associated with possible reactivation form small Cretaceous basins. The Baliza fault may accommodate significant vertical displacements of Devonian and Carboniferous sections of the Paraná Basin. The main structures revealed in the sections are associated with grabens and horsts, interpreted as reactivated structures that controlled Paraná Basin sedimentation. The northwestern portion of the basin exhibits basement asymmetry caused by dip- and strike-slip faulting along the TBL.