Atlantic South Equatorial Current

The equatorial current region lies between continents that once formed part of West Gondwana. During the Early Cretaceous, South America and Africa began to separate and the South Atlantic took shape. The apparent fit of their coastlines was noticed on early maps and later examined by computer-assisted tectonic reconstructions, although detailed models then include shoreline deformation and internal rifting.

Seafloor spreading propagated northward through several geological segments before reaching the equator. The equatorial segment represents the final phase of this breakup in the South Atlantic. Because the region lies at the equator, magnetic anomalies are poor tools for dating it, but estimates place the opening of the Equatorial Atlantic Gateway between roughly 120 and 96 million years ago. The event also coincided with the end of continental extension in Africa.

The later tropical waters therefore conceal a complex record of rifted margins, fractured ocean floor, and slowly changing deep-water connections. What appears as a single band of warm ocean is underlain by one of the Atlantic's later tectonic openings. The ancient gateway therefore remains visible in the geometry of the later ocean floor.