Benue Trough the Central African Shear Zone and for the volcanic island of St. Helena in the Atlantic ocean. Three periods of magmatic activity (volcanic action) have been identified, 147–106 Ma, 97–81 Ma and 68–49 Ma. The first is prominent in the north of the trough, and contemporary with magmatism in Brazil, probably occurring during a period of crustal extension before the Atlantic started to open. The second is found only in the south of the trough, and may belong to a period when the extension of the Atlantic had slowed down, ending with a period of compression. The third and last
Rockall Basin Cretaceous all being suggested. To date, there has been comparatively little drilling to explore for oil and gas within the Rockall Basin and only two discoveries have been made, Benbecula in the northern UK Rockall (Shell originally Enterprise Oil) and Dooish in the northern Irish Rockall (Shell originally Enterprise Energy Ireland). The discoveries show that, at least locally, there is a working petroleum system. Rights to exploit these resources are disputed between the UK, Ireland, Iceland and Denmark (on behalf of the Faroes). This topic is addressed in Rockall Bank dispute. The Rockall Trough () is a deep-water bathymetric feature