|Location of the Rio Grande Rise and the MarineE-Tech |
project research area (red box).
|A typical example of a ferromanganese crust: the dark layer, |
deposited on a sedimentary rock substrate
The RGR is the largest bathymetric feature on the oceanic part of the South American plate and is located about 2000 km west of the Mid-Atlantic Ridge. The RGR is divided into a number of sub-regions and is intersected by a major north-west south-east-trending submarine graben structure. The current expedition focuses on a small area on the western side of the RGR, investigating the 25 km wide graben and its adjacent Fe-Mn crust covered plateaus. The origin of the RGR is the subject of continued debate. It is an aseismic, volcanic oceanic plateau that is likely to have formed on or close to the Mid-Atlantic Ridge, and may have a common origin with the Walvis Ridge, which extends off the coast of Africa. Basalt ages suggests these deep-sea plateaus principally formed between 89 and 78 million years ago.