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
Slyne-Erris Trough Slyne Transfer, interpreted to be a splay of the Great Glen Fault. The Corrib Field is situated in the Northern Slyne Basin. In the Central Slyne the 27/5-1 well proved the presence of Late Permian evaporites including salt, possibly indicating fault activity at this time. The basin is interpreted to have been active particularly during the Triassic and Middle Jurassic periods. The Slyne Basin links the Erris and Porcupine Basins. The Erris Trough or Erris Basin is a half-graben that runs parallel with the Rockall Basin and is separated from it by a horst structure, the Erris Ridge. It is