An SMU-led analysis workforce has discovered that historical rocks and fossils from long-extinct marine reptiles in Angola clearly present a key a part of Earth’s previous — the splitting of South America and Africa and the next formation of the South Atlantic Ocean.
With their simply visualized “jigsaw-puzzle match,” it has lengthy been recognized that the western coast of Africa and the japanese coast of South America as soon as nestled collectively within the supercontinent Gondwana — which broke off from the bigger landmass of Pangea.
The analysis workforce says the southern coast of Angola, the place they dug up the samples, arguably gives probably the most full geological report ever recorded on land of the 2 continents shifting aside and the opening of the South Atlantic Ocean. Rocks and fossils discovered date again from 130 million years in the past to 71 million years.
“There are locations which you can go to in South America, for example, the place you possibly can see this a part of the cut up or that a part of it, however in Angola, it is all specified by one place,” stated Louis L. Jacobs, SMU professor emeritus of Earth Sciences and president of ISEM. Jacobs is the lead writer of a examine printed in The Geological Society, London, Particular Publications.
“Earlier than this, there was not a spot recognized to go and see the rocks on the floor that basically mirrored the opening of the South Atlantic Ocean, as a result of they’re now within the ocean or eroded away,” Jacobs stated.
Angola rocks and fossils inform the entire story
Africa and South America began to separate round 140 million years in the past, inflicting gashes in Earth’s crust known as rifts to open up alongside pre-existing weaknesses. Because the tectonic plates beneath South America and Africa moved aside, magma from the Earth’s mantle rose to the floor, creating a brand new oceanic crust and pushing the continents away from one another. And ultimately, the South Atlantic Ocean crammed the void between these two newly-formed continents.
Scientists have beforehand discovered proof of those occasions via geophysics and nicely cores drilled via the ocean flooring.
However these tell-tale indicators have by no means been present in one place, or been so clearly seen for anybody to see, stated examine co-author Michael J. Polcyn, analysis affiliate within the Huffington Division of Earth Sciences and senior analysis fellow, ISEM at SMU.
“It is one factor for a geophysicist to have the ability to take a look at seismic knowledge and make inferences from that,” he stated. “It is fairly one other factor to have the ability to take a college subject journey out to the rock formations, or outcrops, and say that is when the lava was spreading from japanese South America. Or this was when it was a steady land.”
Basically, Angola presents the chance for somebody to simply stroll via every part of this geologically important chapter in Earth’s historical past.
“That provides Angola main bragging rights,” Jacobs stated.
Jacobs, Polcyn and Diana P. Winery — who’s a analysis affiliate at SMU — labored with a global workforce of paleontologists, geologists and others to research each the rock formations they present in eight totally different areas on the coast and the fossils inside them.
Fieldwork in Angola’s Namibe Province started in 2005. At the moment, the analysis workforce acknowledged explicit kinds of sediments, which gave them an excellent indication of what the western coast of Africa had been like at numerous levels tens of millions of years in the past. As an example, fields of lava revealed volcanic outpourings, and faults or breaks confirmed the place the continents had been being rifted aside. Sediments and salt deposits confirmed ocean flooding and evaporation, whereas overlying oceanic sediments and marine reptiles confirmed completion of the South Atlantic Ocean.
Paleontologists, in the meantime, found fossils in Angola from massive marine reptiles that had lived late through the Cretaceous Interval, proper after the Atlantic Ocean was accomplished and whereas it grew wider.
By bringing collectively specialists from a variety of fields, “we had been in a position to doc when there was no ocean in any respect, to when there was a recent sufficient ocean for these reptiles to thrive and have sufficient to eat,” Winery stated.
Most of the historical fossils are presently on show on the Smithsonian’s Nationwide Museum of Pure Historical past “Sea Monsters Unearthed: Life in Angola’s Historical Seas” exhibit, which was co-produced with SMU — a nationally-ranked Dallas-based personal college.
Angolan researchers — Nair de Sousa, a geoscientist and power advisor on the African Round Enterprise Alliance, and Pedro Claude Nsungani, a geology professor on the Universidade Agostinho Neto — additionally performed a key function on this analysis.
