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
Gulf Trough of roughly , material born of erosion began building up more rapidly in the Gulf Trough, due to the uplifting of the Appalachian Mountains to the north, which provided the primary source of siliciclastic material transported south via rivers and streams. By the Early Miocene, the trough was filled, and materials continued to move southward covering and replacing the carbonate-depositing marine environment with sands, silts, and clays; these sediments created the peninsula on which terrestrial flora and fauna could become established. Gulf Trough The Gulf Trough, also known as the Suwanee Straits, is an ancient geologic feature of Florida present