Congo Submarine Canyon and Fan Valley

Abstract

Seventeen transverse profiles of the inner 460 km of the Congo Canyon and the Congo Fan Valley were made during a 4-day study in June 1972. These profiles show that the canyon is V-shaped with side slopes 400-1,400 m high between the coast and a point 240 km seaward, where the axial depth is about 2,700 m. Farther seaward, the continuation as a fan valley narrows and is bordered by levees a few tens of meters high, and distributaries are found. The latter continue beyond the 4,600-m limits of this study for at least an additional 320 km to depths of 4,900 m. Seismic profiles show that the canyon has been cut through a belt of diapirs--probably derived from evaporites of Early Cretaceous age, and still rising through the several kilometers of subsequent sediments. Highest ide slopes and a major bend in the canyon are present within the belt of diapirs or in the thick sediments that are dammed by the belt. The absence of a broad delta at the mouth of the Congo River, the presence of a possible temporary fill at the head, a steep axial slope near the head, a submerged fan bordering the seaward side of the diapir belt, and levees at depth support the concept of origin of the canyon-fan-valley system largely through erosion and deposition by turbidity currents. Tidal-current scour probably helps to limit the amount of fill in the canyon head.