Geophysical data reveal a tectonic indentation and constrain the transition zone between the São Francisco Craton and the Borborema Paleoplates across the Neoproterozoic Sergipano Orogen, beneath the Cretaceous Tucano Basin, NE Brazil.

Geophysical techniques can improve knowledge about the deep structures of collisional orogens. Therefore, magnetotelluric and gravimetric data were combined in this study to enhance the poorly understood subsurface structure of the transition zone from the São Francisco Craton to the Neoproterozoic Sergipano Orogen in northeastern Brazil. The results along a 240-km-long, NE–SW trending geophysical transect revealed two main geoelectric domains beneath the Cretaceous Tucano Basin, which can be linked to two distinct tectonic blocks on the surface. The less resistive SW domain corresponds to the rocks of the Serrinha Block within the São Francisco Craton. In contrast, the more resistive NE domain matches the basement rocks of the northernmost units of the Sergipano Orogen. The results are discussed considering Paleoproterozoic and Neoproterozoic scenarios with different interpretations of the NE domain. Based on the surface geology and additional gravimetric and magnetotelluric data, the best scenario is to consider the NE domain as representing the geoelectric signature of the three northernmost geological domains of the Sergipano Orogen (Macururé, Poço Redondo–Marancó, and Canindé) and that of the Pernambuco–Alagoas Block (PEAL). PEAL collided with the São Francisco paleolithosphere forming the Sergipano Orogen. The NE geoelectric domain can be interpreted as an indenter of the tectonically intruded PEAL beneath the São Francisco paleolithosphere. The new data properly define the northern limit of the São Francisco Craton and explain both indentation structures and contrasting sediment provenance observed in the Sergipano Orogen. [Display omitted] • Geophysical data for the basement of the Cretaceous Tucano Basin, Brazil. • Basement comprises the São Francisco Craton–Sergipano Orogen transition zone. • Magnetotelluric data characterize two blocks: Northeast (NE) and Southwest (SW). • SW Block is the Craton, NE Block is the Sergipano Orogen and Pernambuco-Alagoas block. • Contact between SW and NE blocks dips to SW and was formed by indentation. [ABSTRACT FROM AUTHOR]