Marine geophysical survey of the NE BRazil and French Guiana continental margin onboard RRS Discovery (D275). The Amazon Cone is a deep-sea fan system that developed on a continental margin approximately 90-100 Myr following a rifting event. Gravity and flexure modelling suggest that the Cone sediments have loaded the margin almost to the limits of its strength. The investigators propose to carry out the first seismic refraction experiment to determine the structure of the crust and mantle that has been deformed by the Cone load. The experiment will provide new constraints on the structure, the nature of the ocean-continental boundary, the thermal and mechanical properties, and the resource potential of deep-water continental margins.