The results of 33 seismic refraction profiles recorded along two lines, one west-east between Punta del Este and the Rio Grande rise and the other southeast-northwest between the Rio Grande rise and Rio de Janeiro, are presented in two structure sections, with continuous seismic reflection profiles recorded parallel with the refraction lines. Plots of magnetic and gravity data recorded along the reflection lines are shown with the seismic data. These data, supplemented by previously reported measurements on the northern Argentine shelf and in the Argentine basin, are compiled in a generalized structure map.

The seismic section across the Uruguayan continental margin is similar to one previously measured eastward of Rio de la Plata. The continental margin south of Rio de Janeiro contains a sediment-filled shelf embayment and a marginal plateau which extends 450 km out to sea. Possible velocity-age correlations are given for the seismic sections.