Panama debate fueled by zircon dating: Americas connected earlier than thought

Smithsonian's Panama debate fueled by zircon dating
After the Isthmus of Panama formed, animals and plants could move back and forth between continents, the Great American Biological Interchange. Smithsonian scientists are debating when this happened. Credit: Smithsonian Tropical Research Institute

New evidence published in Science by Smithsonian geologists dates the closure of an ancient seaway at 13 to 15 million years ago and challenges accepted theories about the rise of the Isthmus of Panama and its impact on world climate and animal migrations.

A team analyzed zircon grains from rocks representing an ancient sea and riverbeds in northwestern South America. The team was led by Camilo Montes, former director of the Panama Geology Project at the Smithsonian Tropical Research Institute. He is now at the Universidad de los Andes.

The team's new date for closure of the Central American Seaway, from 13 to 15 million years ago, conflicts with the widely accepted 3 million year date for the severing of all connections between the Atlantic and the Pacific, the result of work done by the Panama Paleontology Project, directed by emeritus scientists Jeremy B.C. Jackson and Anthony Coates, also at the Smithsonian Tropical Research Institute.

If a land connection was complete by this earlier date, the rise of the Isthmus of Panama from the sea by tectonic and volcanic action predates the movement of animals between continents known as the Great American Biotic Interchange. The rise of the Isthmus is implicated in major shifts in ocean currents, including the creation of the Gulf Stream that led to warmer temperatures in northern Europe and the formation of a great ice sheet across North America.

"Beds younger than about 13 to 15 million years contain abundant zircon grains with a typically Panamanian age," said Montes. "Older beds do not. We think these zircons were deposited by rivers flowing from the Isthmus of Panama when it docked to South America, nearly 10 million years earlier than the date of 3 million years that is usually given for the connection."

Smithsonian's Panama debate fueled by zircon dating
Before the Isthmus of Panama rose from the sea by tectonic and volcanic action, the Central American Seaway linked the Atlantic to the Pacific as one great ocean. Smithsonian researchers continue to debate when and how that happened. Credit: Smithsonian Tropical Research Institute

The new model sends scientists like the University of Colorado at Boulder's Peter Molnar off to look for other explanations for climate change. Molnar wrote in the journal Paleoceanography, "...let me state that the closing of the Central America Seaway seems to be no more than a bit player in global climate change. Quite likely it is a red herring."

Credit: Camilo Montes, Universidad de Los Andes

"What is left now is to rethink what else could have caused such dramatic global processes nearly 3 million years ago," said Carlos Jaramillo, Smithsonian Tropical Research Institute scientist and member of the research team.

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More information: C. Montes, A. Cardona, C. Jaramillo, A. Pardo, J.C. Silva, V. Valencia, C. Ayala, L.C. Pérez-Angel, L.A. Rodriguez-Parra, V. Ramirez, H. Niño. 2015. Middle Miocene closure of the Central American Seaway. Science. April 10. … 1126/science.aaa2815
Journal information: Science , Paleoceanography

Citation: Panama debate fueled by zircon dating: Americas connected earlier than thought (2015, April 9) retrieved 24 July 2019 from
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Apr 09, 2015
Consider the "climate change" that came about from the closing of the seaway.

Damn world didn't end.

Mankind would be hard pressed to do as much "environmental damage" as that.

Damn world still didn't end.

"Warm Blob" probably didn't act right either.

Apr 09, 2015
Perhaps, like the remarkable Messinian Flood that re-filled Med', it was episodic, with multiple openings and closings. It is a volcanic region, after all, and new marine volcanoes tend to erode. eg Surtsey, which halved in size but may yet equilibrate. Also, 'The eruption that created Surtsey also created a few other small islands along this volcanic chain, such as Jólnir and unnamed other peaks. Most of these eroded away fairly quickly.'

Apr 10, 2015
All articles are interesting to read on some level, but some articles require a lot of side-research just for basic comprehension especially if one is a newcomer to a particular area of research - as I am to the matter of closing the isthmus. But, there's nothing like hearing from the professor himself to skip directly to a basic understanding. Even tone and gestures indicate if something is important in a scientific way or vital to the essential questions he sought to understand. Kudos to the prof for taking the time.

Apr 10, 2015
@Shootist: The problem with climate change isn't that the world would come to an end. It is that it will (already has) damage and hurt people, property and nature. It is a moral and economic problem.

And that we don't understand such changes at times is a scientific problem.

Apr 10, 2015
Our sun, Sol, may be responsible for our confusing highs and lows. I theorized Sol is a magnetar, initially emitting strong energy from the equator which would have sterilized the Earth's surface. Under the ice, life was able to survive. Perhaps an unusually strong burst turned Ice Earth into Earth with life, the Cambrian Explosion. As Sol lost energy, the equatorial emissions lost to polar emissions creating a different and safer solar magnetosphere (see NASA a star with two poles).
Perhaps our extinctions can be traced to the stronger solar equatorial emissions, and life's progression to the weaker polar emissions. Today we have only minor solar equatorial emissions known as a delay magnetic reversal.

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