Multi-stranded intraplate shear zone revealed by combined morphostructural and ERT imaging: Insights from the Serrote fault system, Brazil

Intraplate strike-slip deformation in continental interiors commonly reactivates inherited basement fabrics, and has been widely documented in the Paraná Basin. However, the internal fault-zone architecture and subsurface connectivity of these systems remain poorly constrained, limiting the understanding of how deformation is partitioned among fault strands and transferred at depth. We address this gap by integrating detailed morphostructural mapping with twenty high-resolution electrical resistivity tomography (ERT) profiles to characterize the three-dimensional geometry and kinematic evolution of the Serrote fault system, located within the central Paraná Basin of southeastern Brazil. Surface structural data reveal steep NW–SE-trending faults with alternating downthrow directions, R- and R′-type shears, calcite-filled veins, breccias and shale smear, documenting repeated brittle reactivation under dextral transtension. ERT imaging resolves vertically persistent low-resistivity corridors that widen, diverge and bifurcate at depth, delineating negative flower structures and a several-hundred-meter-wide shear corridor that contrasts sharply with earlier interpretations of a simple normal-fault–bounded graben. The correspondence between surface structures and subsurface conductive bodies demonstrates that deformation is accommodated not along discrete planar faults, but across a distributed network of interconnected strands and rotated blocks. These results highlight the first-order role of Brasiliano basement anisotropies in focusing strain, controlling fault linkage, and governing hydraulic compartmentalization within intraplate shear systems. By combining structural and geoelectrical datasets, this study provides a refined framework for interpreting the mechanics of a multi-stranded transtensional shear zone in stable continental interiors and offers a transferable approach for resolving fault-zone architecture in intraplate domains worldwide. • Transtensional strain is distributed across a wide, multi-stranded shear corridor. • ERT imaging resolves vertically persistent, segmented fault cores beyond surface mapping. • Negative flower structures and rotated blocks reveal complex internal deformation. • Precambrian basement fabrics exert first-order control on fault architecture and linkage. • Integrated structural–ERT approach refines the characterization of intraplate shear zones.