- April 10, 2015
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What if at the end of the Isthmus of Panama is not as important to the history of the planet, although there through much of world trade huge ships passing through a more than centenary channel?
That’s the conclusion of a study by a team of Colombian researchers.
But it is not an economic analysis, but geological.
And downplays not the market value of the isthmus, but its role . in the evolution of Earth’s climate and mammalian development of America
Read also: Five Things changed in the world with the Panama Canal
The study, which has lasted three years, is led by Professor Camille Montes, Department of Geosciences, University of the Andes in Colombia.
And is one of those scientific papers more to give answers raises questions.
End of consensus
The scientific consensus so far was that the isthmus, a piece of land 50km wide, closed about three million years ago.
And to unite North and South America opened a land route for migrating animals to and fro, especially mammals.
Read: The Calm After the shock of North and South America
Among the animals moved from south to north are the armadillo and the porcupine, eg
.
The reverse path did bears and cats, among others.
This is what biologists call the Great American Interchange.
And that biological hypothesis adds an oceanographic because some three million years began glacial cycles, something that experts in the field explained, or explained until now by the division between the Caribbean Sea and the Pacific Ocean caused by the emergence of the Isthmus.
Little geological evidence
From the point of view of geology, however, this story “did not look very good in the field, “said Camilo Montes told the BBC.
And with Agustín Cardona, National University and other academic, embarked since 2012 in the task to confirm or reject this idea.
The existing geological evidence was little and was based on foraminifera, microscopic animals that generate some shells that can be recovered from sediments.
Studying shells, micropaleontologists can determine at what depth there.
And their study showed that about 3 million years ago the foraminiferal appeared on or near the ocean surface, implying that had emerged in the context the formation of the Isthmus.
But for Montes and his colleagues was insufficient evidence.
Between 65 and 39 million years
In 2012 Colombian investigators went to Panama, where they took samples of rocks which were subjected to an analysis to determine when contacted with the surface to emerge from the sea.
“We expected (tests ) we were given very pronounced peaks at three million years, “he said.
“And no, the peaks began to give 35, 40, 12 million years, but never three.”
In other work also in 2012, studied the age of the rocks they collected.
“We realized that the Isthmus of Panama has many rocks that are between the ages of 65 million years and about 39 or 40 million years. “
Panama Signature
The data, however, they were not conclusive, so we decided to analyze samples from riverbeds in the northwestern Colombia, where this country is united with Panama.
There, according to an article published this week by the journal Science , discovered in beds from 13 to 15 million years old could be identified sediment rocks carried to Panama.
How did they do it?
They took zircon grains, a mineral abundant in the earth’s crust, and very durable, making it optimal for determining the age of the rock.
If the zircon was between 65 and 39 million years, then had to come isthmus, brought the “Panamanian firm.”
“We could use that signature, like a fingerprint, to say Panama was when he came and hit the northwestern Colombia, “said Montes.
And its calculation is between 13 and 15 million years, at least ten million earlier than previously thought.
This confirmation back what had been inferred by studying fossils in 2011 during excavations for the Panama Canal expansion
Read. When were you born American Central?
New questions
With the data confirmed, then, remain open questions.
Why Why, if there was a bridge formed over three million years ago, mammals waited ten million years to cross?
The lack of a clear answer makes some biologists resist the hypothesis Montes and his colleagues .
But others have adapted to the idea, because they have data that could not be explained by the hypothesis of the three million years.
One is Christine Bacon, researcher University of Gothenburg, Sweden, who was at the University of the Andes in Colombia.
Bacon told BBC News that information already existed plants that had migrated from South and North America before three million years, as well as salamanders and freshwater fish.
“More scientific publications showing migration of older species and now we have a geological framework that explains appear” he said.
The Oceanographic side is more difficult to explain the phenomenon of onset of glaciations three million years ago without using the isthmus as a cause.
But there are also scientists who are trying to unveil the new mystery.
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