Opening History of the South Atlantic

Ian Davison¹, C. Reeves², and Pedro Baptista^1
1 Earthmoves Ltd, Camberley, Surrey, United Kingdom
² Earthworks, 2611 Delft, Netherlands

A new model is presented for the early opening of the South Atlantic which has two distinct poles of rotation for (a) NE Brazil and (b) Africa NW of the Benue Trough with respect to the rest of Africa. The model allows for opening of the East Brazil Nigeria-South Africa Rift system, without compression along the Equatorial margin, as transcurrent shearing occurred along the Benue Trough. Rifting reached a climax in the Hauterivian- Barremian, but the basins remained underfilled before deposition of the Aptian salt. This resulted in large offsets of up to 2 km in the base salt, and large thickness variations in the salt controlled by the original rift basin geometry. There are at least three separate salt basins in Brazil and three different basins in Africa, which are separated by: basement highs; lows which never dried up; and sub-aerial mid-ocean ridges. The last land bridge between Africa and Brazil was around the Romanche Fracture Zone (and not as previously believed in the Pernambuco-Niger Delta area). The South and North Atlantic Oceans were separated until mid-Albian times, although early shear deformation began in Aptian times along the Romanche Fracture Zone. The opening history will be illustrated with a new animation which will bring detailed ArcView GIS geological data into a 3D spherical plate model fit for the first time.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005