Rio Grande Rise

Together with the Walvis Ridge off Africa, the Rio Grande Rise forms a V-shaped structure of mirrored hotspot tracks or seamount chains across the northern South Atlantic.

[5] The Rio Grande Rise separates the Santos and Campos Basins and is composed of western and eastern areas, which have different geological backgrounds.

The disappearance of these differences during the Maastritchtian indicates a reorganisation of oceanic circulation patterns that lead to a global homogenisation of intermediate and deep waters.

[8] The origin of modern circulation of cold, deep water — known as the "Big Flush" — is associated with Early Eocene (55 to 40 Ma) geological events; tectonism that resulted in the opening of the north-east Atlantic and fracture zones that developed in the subsiding Rio Grande Rise, which allowed cold water from the Antarctic Weddell Sea to flow northward into the North Atlantic.

40 Ma, the generation of cold bottom water in the Antarctic resulted in the formation of psychrospheric fauna, which today live in temperatures below 10 °C (50 °F), in the Atlantic and Tethys.

The Rio Grande Rise separates the Brazil (north) and Argentine Basins (south) and is separated from the Vema Sill and Santos Plain (west) by the Vema Channel and from the Mid-Atlantic Ridge by the Hunter Channel (east). [ 1 ]