Mesozoic plate tectonic reconstructions of the central South Atlantic Ocean: The role of the West and Central African rift system

Abstract

The Mesozoic opening history of the Central, Equatorial and South Atlantic oceans is closely linked in time and space to the development of the Cretaceous rift system in West and Central Africa. Geological and geophysical studies of the West and Central African rift system indicate it to be dominated by a set of sinistral and dextral strike-slip zones diverging from the Gulf of Guinea and terminating as extensional rift basins in Niger and Sudan. Plate tectonic studies of the opening history of the Atlantic basins indicate four stages of development: stage 1, the Jurassic opening of the Central Atlantic, stage 2, the Early Cretaceous (≈ 130-119 Ma) opening of the South Atlantic with rifting propagating deep into Africa via the Benue Trough, stage 3. the opening of the Equatorial Atlantic (119-105 Ma), and stage 4, the linkage of these oceanic basins and development of a single opening mid-oceanic rift system as seen today. The West and Central African rift system continued to develop until the end of the Cretaceous (i.e., into stage 4) when rifting was terminated by a compressional-shear deformation event causing the folding of sediments in the Benue Trough and reactivation of the Central African shear zone and extensional tectonics in the basins of southern Sudan. This event correlates with an important change in the relative opening of the Atlantic basins. During Tertiary-Recent times the West African rift system has not been active. However, during this period domal uplift and volcanism have occurred in central Cameroon and western Sudan and a very active phase of volcanism has occurred within the last 10 Ma along the present-day Cameroon volcanic line. Although these uplift and volcanic events indicate thermal processes in the upper mantle, there is, as yet, no clear link between their development and plate tectonic processes.