“Puzzle” of Africa and South America: a unique place testifies to the separation of these continents

When you have fun rotating a globe, this is one of the most fascinating aspects: the almost perfect complementarity between the east coast of South America and the west coast of Africa. This strange “puzzle”, represented by cartographers before it was visualized from space, is actually one of the testimonies of a great event that took place about 140 million years ago…

Even as a result of the breakup of another supercontinent, Pangea, Gondwana began to fragment 180 million years ago into two “pieces”, one of which was torn apart, 40 million years later, to form the two continents that we observe today on either side of the South Atlantic.

Beyond the simple geographic puzzle, several study sites contain geological evidence of this separation, including rocks and fossils. But the authors of a study published in the journal Geological Society, London, Special Publications (April 24, 2024) today reveal the existence of a place that gathers the remains of all stages of this process in one place, especially between -130 million years (Ma) and -70 Ma.

The rest below this ad

The most beautiful gardens photographed by the GEO Community

Lava fields, salt deposits…

This exceptional place is none other than the Namibe Basin, in southern Angola. A region that attracts both geologists and prospectors commissioned by the oil industry, given the hydrocarbon reserves it contains (Agência Angola Press, 2023).

“There are places in, for example, South America where you can see this or that part of the crack, but in Angola everything is gathered in one place”emphasizes Professor Louis L. Jacobs from Southern Methodist University (SMU) in Texas (USA), lead author of the study (press release).

The rest below this ad

Here, lava fields reveal volcanic eruptions, while geological faults indicate where continents have separated. Salt deposits testify to flooding or, on the contrary, evaporation of water. Finally, the oceanic sediments mark the entrance to the “adult” age, so to speak, in the South Atlantic.

…and fossils of marine reptiles

If these different elements had been revealed gradually from 2005, it would have required the more recent contribution of paleontologists to complete the picture. They discovered fossils of large marine reptiles that lived at the end of the Cretaceous: “We were able to document when there was no ocean at all, and when the ocean was cool enough for these reptiles to thrive and have something to eat.”notes Diana P. Vineyard, co-author.

The rest below this ad

A real revolution for the experts concerned. “Prior to this, there was no known place to go and see the surface rocks that really reflected the opening of the South Atlantic, because they are now in the ocean or eroded away.”, says Professor Jacobs. A limitation that therefore forced his peers to collect data using geophysical experiments (seismic data) and taking sediment cores from the seabed.

“It is quite another thing to organize a trip to look at rock formations or outcrops and be able to say: “it was at this time that lava spread from eastern South America”. Or: “it was at this time that the Earth was continuous”, compares Michael J. Polcyn (SMU), co-author of the study. As a guided tour into the planet’s extraordinary past…

The rest below this ad

Image of the Namibe Basin, Angola, where the research team found rocks and fossils of marine reptiles. The different letters correspond to the different stages of the separation of South America and Africa and the subsequent formation of the South Atlantic Ocean. The Geological Society, London, Special Publications