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
The Trough Long Knob (1,725 feet) flanks the Trough. Sawmill Ridge ends at the mouth of the Trough at the point where Sawmill Run descends the ridge and joins the river. The communities of Sector and Glebe are located here to the west and east, respectively. The concrete piers of the old bridge that once carried Fleming-Sector Road (County Route 8/3) connecting these two communities are still visible here as well. A typical Trough canoe run ends at the Harmison's Public Access Site below the old bridge and behind The Trough General Store. The Trough is a popular canoeing/kayaking venue, although not