Atlantic South Equatorial Current

The equatorial Atlantic gateway opened during the final phase of the breakup between South America and Africa. West Gondwana separated in the Early Cretaceous, and seafloor spreading moved north through the southern and central parts before reaching the equatorial segment. Estimates place the gateway's opening at roughly 120 to 96 million years ago.

Dating is difficult because magnetic anomalies at the equator are less useful, but the event coincided with, or helped end, continental extension in Africa. The later warm waters then move above that long-lived rift system. The Mid-Atlantic Ridge marks the divergent boundary between the South American and African plates, with transform faults breaking its continuity. The equatorial segment lies between about 10 degrees north and the Romanche fracture zone, separating it from the central segment farther south.

Deep-water connections altered as the continental barrier disappeared, and the ocean gradually assumed its present broad intercontinental form. The seafloor preserves traces of volcanic spreading, fracture zones, and basin development beneath the tropical route then followed by ships and surface currents. Over geological time, that opening helped establish the deep connections of the later Atlantic.