Previous works used marine magnetic survey data and interpreted magnetic anomalies related to seaward-dipping reflectors (SDRs) as oceanic crust or SDR age constraints in the South Atlantic Ocean. However, we advise against using SDR-related magnetic anomalies to constrain ages because of the mostly low-dipping geometry causing the overlapping of rocks extruded during periods of different polarities. The data are difficult to interpret correctly because of the SDR compositional heterogeneity, sedimentary intercalations, variations in package thickness with different compositions and magnetic polarities, and the absence of a link between the SDR magmatic position and age. SDR-related magnetic anomalies are mainly caused by magnetic susceptibility contrasts rather than remanent magnetism. Due to this complexity, the SDR geometry and variable composition make SDR-related magnetic anomalies challenging to use for age constraints. The Pelotas Basin SDRs age cannot be estimated by magnetostratigraphy, and this method likely cannot constrain the age of any SDR wedge.