Upper crustal structure of the transition zone between Recôncavo and Camamu Basins in Itaparica Island, NE Brazil revealed by 3D inversion of magnetoteluric data

The contact between the Recôncavo and Camamu Basins in Itaparica Island, NE Brazil is marked by the Barra Fault, formed during the separation of the South American and African continents and exhibits a unique geological behaviour. This study aims to understand the transition between the two basins and the sedimentary structure in Itaparica Island. To achieve this, magnetotelluric (MT) data covering the frequency range 10³ to 10⁰ Hz were recorded at 15 stations along a transect and we obtained data from boreholes for model verification. After processing the MT data, 3D resistivity models were generated through nonlinear regularized inversions, considering the full impedance tensor and tipper. The models showed good data fit and a strong correlation with borehole profiles, revealing anomalies and heterogeneities in this portion of the basins. Additionally, the vertical derivative of the resistivity model was used to map relevant structural and stratigraphic boundaries. Comprehensive analysis of the results enabled the identification of possible saline water infiltration zones, indicated post-sedimentary structural adjustments that may have influenced the petroleum system in the region, and provided insights into a shared depression in the early stages of basin development.