Geoelectric study in the southwestern end of the Sierra de San Luis: Insights into the broken foreland in the Pampean flat-slab segment

Abstract

The southwestern end of the Sierra de San Luis, located within the Argentinian Pampean flat-slab segment, presents a complex tectonic architecture associated with intraplate deformation in a broken foreland setting. In this study, we use vertical electrical soundings (VES) to investigate the subsurface features in a particular sector of this region, aiming to characterize the geometry and depth of sedimentary basins and the underlying crystalline basement. Twenty-six VES were acquired using a Wenner configuration, reaching up to 316 m in depth. The geoelectrical models reveal three main resistivity domains: a high-resistivity crystalline basement (>500 Ωm), a low-resistivity clastic unit (LRCU; <29 Ωm), and a high-resistivity clastic unit (HRCU; 80–300 Ωm). These resistivity patterns, supported by surface geology and stratigraphic data, allow for the delineation of major tectonic blocks and depocenters. The results highlight a markedly heterogeneous basement topography controlled by N-S reverse and NW-SE oblique extensional faults. Lateral variations in sediment thickness and fault geometries indicate significant control from inherited basement eopalezoic anisotropies, including ductile shear zones and magmatic fabrics. This study provides new geophysical evidence for the segmentation of the foreland in the Sierra de San Luis and underscores the importance of integrating electrical methods in regions affected by thick-skinned tectonics. The findings have implications for neotectonic activity, structural evolution, and groundwater dynamics in intraplate settings.