Abstract The Parnaíba cratonic basin is located in the NE of Brazil and its sedimentation started in the Silurian with the Serra Grande Group. Deep reflection seismic data were acquired along a 1400 km-long profile, with 20 s of two-way travel time (TWT) across the basin. Using these data, we were able to interpret and conjecture about the composition complexity level of the crust and mantle from the features presented in the lower crust, Moho reflector and upper mantle. In addition, the presence of basaltic intrusions from the Sardinha and Mosquito formations are mapped as outcrops and magnetic anomalies on the geological map, and by correlating these areas of occurrence with the lack of the Moho in the seismic section may suggest that these igneous bodies, in some way, contribute to the lack of signal seen in parts of the data.